The Fralin Life Science Research Institute and The Metabolic Phenotyping Core at Virginia Tech supported this work.

Animal studies were performed under an approved protocol by the Institutional Animal Care and use Committee at Virginia Polytechnic Institute and State University.
1. Setup (Time: ~45 min)
<ol>
	<li>Thaw frozen stores of 0.25% Trypsin, Isolation Buffer for Mitochondria (IBM) 1 and IBM2 in a 37 &#176;C water bath.</li>
	<li>Rinse glassware and dissecting instruments in 70% ethanol followed by high purity water.</li>
	<li>Prepare 0.05% trypsin solution from 0.25% trypsin stock by diluting 1 part trypsin in 4 parts IBM1.</li>
	<li>Mix protease and phosphatase inhibitor cocktail with cell lysis buffer (1:100 ratio) in a 1.5 ml microcentrifuge tube with screw cap.</li>
	<li>Aliquot 5 ml (5 ml/mouse) of 0.05% trypsin into a 15 ml plastic tube.</li>
	<li>Set motor driven tissue homogenizer to 80 RPM.</li>
</ol>
2. Isolation of Skeletal Muscle Mitochondria (Time: ~90 min)
<ol>
	<li>Euthanize a mouse by CO2 inhalation, followed by cervical dislocation.</li>
	<li>Remove red muscle from the quadriceps and gastrocnemius muscle, which includes the soleus (~75-100 mg total) as described in the following steps:
	<ol>
		<li>Peel the skin towards the mouse.</li>
		<li>Remove the fat pad over the quadriceps origin point. Cut the quadriceps tendon that is attached to the patella with fine tipped scissors. 
		Note: The quadriceps is identified by its anatomical position on the anterior portion of the proximal femur.</li>
		<li>Slowly snip the aponeurosis between the bone and the quadriceps, while avoiding the femoral artery, to liberate the quadriceps from the bone. Cut the tendon with fine tipped scissors at the origin point on the femur to liberate the quadriceps muscle and place the quadriceps muscle in chilled PBS.</li>
		<li>Remove visible adipose tissue over the quadriceps with scissors. Flip the quadriceps over so that the portion of the muscle that was overlying the femur is facing up. Open the quadriceps muscle with forceps in a fanning motion. Remove the two visible red muscle portions from each lobe with fine tipped scissors and place in a beaker containing 5 ml of chilled IBM1. 
		Note: Quadriceps muscle appear as two lobes with a strip of red muscle located near the lateral edge of each lobe.</li>
		<li>Cut the skin overlying the Achilles tendon with fine tipped scissors and peel the skin toward the mouse. Cut the exposed Achilles tendon and peel the muscle towards the body of the mouse.</li>
		<li>Cut the tendon at the lateral and medial condyles of the femur with fine tipped scissors to liberate the gastrocnemius and place the gastrocnemius attached to its tendons in chilled PBS.</li>
		<li>Flip the gastrocnemius over and peel off the soleus muscle and place into the beaker containing 5 ml of chilled IBM1. Fan open the gastrocnemius. Remove the three visual red muscle portions (two lateral and one medial superficial red strips) with fine tipped scissors and transfer them to the beaker containing 5 ml of chilled IBM1.</li>
	</ol>
	</li>
	<li>Remove another ~75-100 mg of red muscle from the other leg of the mouse (as described in step 2.2) and place into a 1.5 ml microcentrifuge tube with protease and phosphatase inhibitor cocktail and cell lysis buffer (50 mM Tris-HCL, 1 mM EDTA, 150 mM NaCl, 1% Sodium dodecyl sulfate, 0.5% Sodium deoxycholate, 1% Polyoxyethylene (9) nonylphenylether, branched. Immediately flash-freeze this second sample in liquid nitrogen for later use in Western blotting (see step 6.1).</li>
	<li>Place a pre-chilled, flat plastic surface on ice in a large bucket. Pour a drop of IBM1 onto the plastic surface and use tweezers to place all of the sectioned red muscle (step 2.2.4 and 2.2.7) in IBM1 droplet. Mince the muscle tissue for 2 min using 3 single edge razor blades by changing razors every 40 sec.</li>
	<li>Transfer the minced tissue to a new beaker with 5 ml of fresh IBM1 by holding the plastic surface over the beaker and scraping the muscle into the beaker with a razor blade. Take this solution and drain it through a 100 &#181;m cell strainer placed onto a 50 ml conical tube.</li>
	<li>Blot the tissue with a delicate task wiper and then transfer it into 5 ml of the 0.05% trypsin solution. Use tweezers to remove the tissue from the task wiper.</li>
	<li>Incubate the muscle tissue on ice for 30 min in 0.05% trypsin solution.</li>
	<li>Spin the 15 ml conical tube containing trypsin/muscle mixture at 200 x g for 3 min at 4 &#176;C.</li>
	<li>Pour the trypsin supernatant into a waste container and resuspend the pellet with 3 ml of ice cold IBM1. Transfer the tissue to a 45 ml glass homogenizer tube. Rinse the 15 ml conical tube with another 1.5 ml IBM1 to gather any remaining sample and add this to the glass homogenizer tube.</li>
	<li>Place the glass homogenizer tube into a beaker or plastic container filled halfway with ice so the glass homogenizer moves minimally within the beaker.</li>
	<li>Homogenize the tissue/IMB1 mixture with the PTFE pestle attached to a motor driven tissue homogenizer with 10 passes at 80 rpm. Hold the bottom of each pass for ~2 sec.</li>
	<li>Transfer the tissue homogenate to a new 15 ml conical tube and rinse the glass homogenizer tube with 6.5 ml of IBM1. Pour the IBM1 into the 15 ml conical tube containing tissue homogenate.</li>
	<li>Spin the 15 ml conical tube at 700 g for 10 min at 4 &#176;C. Gently pour the supernatant into a glass high strength centrifuge tube and discard the pellet.</li>
	<li>Spin the supernatant from the above step at 8,000 x g for 10 min at 4 &#176;C.</li>
	<li>Remove the IBM1 supernatant and re-suspend the pellet by slowly adding 500 &#181;l&#160;of IBM2. Cut off the end of a pipette tip and gently homogenize the pellet in IBM2 with mixing and stirring motions. Add another 4.5 ml of IBM2 to the mixture after the pellet is fully suspended. 
	Note: Avoid excessive trituration while breaking larger pellet pieces as this may damage the mitochondrial membranes.</li>
	<li>Spin the IBM2/tissue homogenate at 8,000 x g for 10 min at 4 &#176;C. 
	Note: This step may be repeated in a clean high strength centrifuge tube for more accurate protein quantification of isolated mitochondria in Step 4 since residual BSA may contribute to total protein content.</li>
	<li>Remove the supernatant and gently, but completely re-suspend the pellet by adding two 25 &#181;l increments of IBM2 with a pipette tip with its point cut off. Gently stir and mix the pellet after each addition of 25 &#181;l of IBM2. Place this mitochondrial stock on ice.</li>
</ol>
3. Homogenization of Whole Tissue Lysate (Time: ~45 min; Can Be Done During Step 7)
<ol>
	<li>Remove the muscle from that was placed in the liquid nitrogen from step 2.3 and incubate at room temperature until fully thawed.</li>
	<li>Mince the tissue for ~30 sec on ice with fine tipped scissors.</li>
	<li>Add two 100 &#181;l scoops of Zirconium Oxide Beads to the 1.5 ml microcentrifuge tube with screw cap from step 3.2 that contains the minced tissue. Homogenize the tissue in a bead mill tissue homogenizer using two to three 5 min cycles at a speed setting of 4-6 (medium setting).</li>
	<li>Spin the mixture from step 3.3 at 12,000 x g for 10 min at 4 &#176;C. Remove the supernatant using a 1,000 &#181;l pipette tip after the spin and transfer into a 1.5 ml microcentrifuge tube. Discard the pellet and place the supernatant on ice.</li>
</ol>
4. Protein Determination (Time: ~30 min)
<ol>
	<li>Determine the protein concentration of the whole tissue lysate (step 3.4) and mitochondrial stock (step 2.17) using the BCA Protein assay kit according to the manufacturer&#8217;s specifications.</li>
</ol>
5. Mitochondria Membrane Integrity; Citrate Synthase (CS) Activity (Time: ~15 min)
<ol>
	<li>Make two separate 1: 20 dilutions of the mitochondrial stock in high purity water. Add 0.1% of Triton 100-X to one sample and sonicate it at a low setting (765 Watts, amplitude of 2). Leave the other dilution on ice. Return the sample to ice after sonication.</li>
	<li>Perform a citrate synthase assay with both the non-sonicated and sonicated mitochondrial dilutions using a spectrophotometric assay as previously described11,12.</li>
	<li>Determine the percentage of intact mitochondria membranes by using the following equations: 
	(Non-sonicated CS activity &#247; Sonicated CS activity)* 100</li>
</ol>
 
&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; 100- N (percent attained from above)
6. Mitochondria Isolation Quality; Western Blotting (Time: According to Lab Protocol)
<ol>
	<li>Perform Western blotting on the whole tissue lysate and isolated mitochondria as described previously12. 
	Note: Use primary antibodies for GAPDH (1: 1,000 dilution in 5% BSA/TBS-T) and COXIV (1:1,000 dilution in 5% non-fat milk/TBS-T) followed by anti-goat, and rabbit secondary antibodies, respectively (1:10,000).</li>
</ol>
7. Respirometric Assay Run (Time: ~90 min)
<ol>
	<li>Perform desired respirometric assays using microplate based O2 consumption measuring technology as previously described (see companion article and Rogers et al8).</li>
	<li>Determine the respiratory control ratio (RCR) by dividing State 3 by State 4o (RCR) or dividing State 3u by State 4o. Use either the middle (average) point, or the highest (State 3) and lowest rates (State 4o) from the point-to-point traces&#160;when determining RCR.</li>
</ol>

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George Rogers is an employee of Seahorse Bioscience that produces the instrument for which this protocol was modified.

The methods presented herein provide a detailed description of a mitochondrial isolation procedure from minimal quantities (~75-100 mg) of mouse skeletal muscle. This isolation procedure is able to yield high functioning, pure mitochondria (~450 &#181;g) as evidenced by O2 consumption rates, RCR values, maximal citrate synthase activity and protein expression from immunoblotting. Importantly, the mitochondria isolated from this procedure can be used for multiple respirometirc assays with microplate based O2 consumption technology that allows for high throughput.
The isolation of skeletal muscle mitochondria often requires harsh methods to liberate mitochondria from surrounding connective tissue and structural proteins7,16. Consequently, mitochondrial membranes can become disrupted, thus impairing the activity (and thus the accuracy) of mitochondrial O2 consumption during subsequent respirometric assays. By including an additional step of tissue mincing using razor blades after tissue excision to a previously described protocol7, a significantly reduced rotor speed for motor driven homogenization was possible (80 rpm vs. 1,600 rpm). These gentler homogenization and resuspension techniques leads to a high percentage of mitochondria with intact membranes (92.5&#177; 2.0%), as assessed from citrate synthase activity following the isolation procedure. Our findings are consistent with Asmann et al.17, who report between 90-95% intact mitochondrial preparations following isolation from human skeletal muscle. It is important to note that measuring citrate synthase activity is better suited for measuring physical integrity of the mitochondrial membranes and should not be used to assess functional integrity of the isolated mitochondria. On the other hand, O2 consumption assays and determination of RCR from these assays should be used to measure the function of isolated mitochondria1. In addition, RCR can also be used as an indicator of coupled mitochondria. Therefore, the OCR and mitochondrial states within a typical range from the pyruvate/malate assay8, and the high RCR values obtained from a variety of respirometric assays indicates that the mitochondria derived from this protocol are tightly coupled and highly functional.
Isolation of intact and pure&#160;mitochondria has important implications for respirometic assays. The contamination of non-mitochondrial proteins in the final mitochondrial preparation can result in loading unequal quantities of mitochondrial protein to each well during O2 consumption measurements, thus decreasing the accuracy of any comparison among experiments performed using different preparations of mitochondria. Furthermore, contamination of the mitochondrial preparation with other respiring organelles (e.g., peroxisomes) can further decrease the accuracy of O2 consumption measurements. The presence of the inner mitochondrial protein, COXIV, and the absence of a prominent band of the cytosolic (and potentially nuclear) protein, GAPDH, in our isolated mitochondrial preparation following immunoblotting is indicative of little contamination from non-mitochondrial sources during the isolation procedure.
It is important to note that although the isolation of a purified mitochondrial preparation is important with respect to the above mentioned, the maintenance of mitochondrial integrity is of utmost importance in respiration assays. The outer mitochondrial membrane can be easily damaged during the isolation procedure, leading to the escape of cytochrome c into the isolation buffer and thus becoming rate limiting during O2 consumption and ATP synthesis18. Therefore, the integrity of isolated mitochondria can be further assessed by quantifying cytochrome c protein expression in the supernatant of the mitochondrial preparation (step 2.15, prior to resuspension) and in the isolated mitochondria with Western blotting. Cytochrome c should not be present in the mitochondrial preparation supernatant if the mitochondrial membranes are intact following the isolation procedures.
All steps of this protocol are important, however there are three critical steps to this protocol. First, the mincing of red skeletal muscle with three different razor blades (step 2.4) is critical because this step allows for slower rotor speeds during the homogenization step (step 2.11). Second, the performance of many steps on ice or in chilled buffers is critical to maintain the mitochondria in a resting state prior to the microplate based respirometric assays. Finally, the gentle resuspension of the mitochondria pellet into IBM2 is of utmost importance. Gentle mixing maintains mitochondrial integrity, which is crucial for accurate respirometic assays.
Some limitations of this technique are worth mentioning. First, the equipment needed (e.g., ultracentrifuge, motor driven homogenizer, etc.) to perform the isolation procedure can be expensive. In addition, multiple quality control methods are needed to ensure clean and intact mitochondria. However, once the researcher is proficient in the isolation procedure, high quality mitochondria are yielded that can be used in a multitude of measurements including, but not limited to: Western blots, enzymatic assays, RT-PCR, PCR, H2O2 assays, and high throughput microplate respiratory measurements. It is important to note that this isolation procedure has been optimized and modified for small quantities of mouse skeletal muscle and caution should be taken when trying to apply isolation techniques from a given tissue from the same species (and even to the same tissue from different species) to other tissues/species. For optimal results, searching the literature will be the best option when trying to find the best isolation method for the intended tissue/species.

The primary function of mitochondria is to produce ATP from oxidative phosphorylation. However, mitochondria have many other important cellular functions including but not limited to: the production and detoxification of reactive oxygen species, the regulation of cytoplasmic and mitochondrial calcium, organelle trafficking, ionic homeostasis, and involvement in apoptosis1,2. Therefore, it is not surprising that dysfunctional mitochondria play a role in many disease pathologies, such as aging, neurodegenerative diseases, cardiovascular disease, cancer, obesity, and diabetes3,4. Importantly, skeletal muscle mitochondria specifically are involved in many of these pathologies3-5.
Mitochondrial respiration assays using isolated mitochondria allow for the assessment of electron transport chain and oxidative phosphorylation function, and the determination of mechanism(s) of action of drugs and proteins that modulate metabolism. Mitochondrial isolation procedures exist for multiple tissue and cell types for a variety of species6,7. However, these procedures often require large quantities of tissue/cells for a high quality mitochondria yield necessary for classic respirometric assays. 
Microplate based respirometirc assays allow for high throughput measurements using minimal quantities of isolated mitochondria, often just several &#181;g per well8. Therefore, we present a modification of previously published methods7 to allow for high quality mitochondria to be isolated from smaller quantities of mouse skeletal muscle for use in microplate based respirometirc assays. In addition, methods are provided to establish the quality of the mitochondrial isolation preparation and the integrity of the mitochondrial membranes. Given that skeletal muscle mitochondria are involved in many pathological conditions, the measurement of O2 consumption in mechanistically driven studies is becoming more prevalent in biomedical research9,10.

<table><tbody><tr><td>Essentially Fatty</td><td>Sigma Aldrich</td><td>A6003</td><td>N/A</td></tr><tr><td>Acid Free- BSA</td><td></td><td></td><td></td></tr><tr><td>Tris/HCl</td><td>Promega</td><td>H5123</td><td>N/A</td></tr><tr><td>KCL</td><td>Sigma Aldrich</td><td>P9541</td><td>N/A</td></tr><tr><td>Tris Base</td><td>Promega</td><td>H5135</td><td>N/A</td></tr><tr><td>EDTA</td><td>Sigma Aldrich</td><td>E6511</td><td>N/A</td></tr><tr><td>EGTA</td><td>Sigma Aldrich</td><td>E4378</td><td>N/A</td></tr><tr><td>Sucrose</td><td>Sigma Aldrich</td><td>S7903</td><td>N/A</td></tr><tr><td>D-Mannitol</td><td>Sigma Aldrich</td><td>63559</td><td>N/A</td></tr><tr><td>Trypsin-EDTA (0.25%), phenol red</td><td>Thermo Scientific</td><td>25200-056</td><td>N/A</td></tr><tr><td>Sodium Chloride&lt;br/&gt; White Crystals or Crystalline Powder&lt;br/&gt; &amp;ge;99.0 %</td><td>Fisher Scientific</td><td>BP3581</td><td>N/A</td></tr><tr><td>Sodium dodecyl sulfate</td><td>Sigma Aldrich</td><td>L3771&amp;nbsp;</td><td>N/A</td></tr><tr><td>Sodium deoxycholate</td><td>Sigma Aldrich</td><td>D6750&amp;nbsp;</td><td>N/A</td></tr><tr><td>Polyoxyethylene (12) nonylphenyl ether, branched</td><td>Sigma Aldrich</td><td>238651</td><td>N/A</td></tr><tr><td>Single Edge Razor Blades</td><td>Fisher Scientific</td><td>12-640</td><td>N/A</td></tr><tr><td>Falcon- 100 uM Nylon Cell Strainers</td><td>Fisher Scientific</td><td>352360</td><td>N/A</td></tr><tr><td>Halt Protease &amp;amp; Phosphatse Inhibitor Cocktail</td><td>Thermo Scientific</td><td>1861284</td><td>N/A</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>1.5 ml microcentrifuge tubes with screw cap</td><td>Thermo Scientific</td><td>3474</td><td>N/A</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>Zirconium Oxide beads</td><td>Fisher Scientific</td><td>C9012112</td><td>N/A</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>GAPDH antibody (1D4)</td><td>Santa Cruz Biotechnology</td><td>sc-59540</td><td>N/A</td></tr><tr><td>Anti- COXIV antibody</td><td>Cell Signaling</td><td>4844s</td><td>Any mitochondrial inner membrane protein will suffice</td></tr><tr><td>Peroxidase conjugated affinipure Donkey, Anti Rabbit IgG (H+L)</td><td>Jackson ImmunoResearh</td><td>711-035-152</td><td>N/A</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>Peroxidase conjugated affinipure Goat, Anti Mouse IgG (H+L)</td><td>Jackson ImmunoResearh</td><td>115-001-003</td><td>N/A</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>Triton-X100</td><td>Sigma Aldrich</td><td>X100</td><td>N/A</td></tr><tr><td>Pierce BCA Protein Assay Kit&amp;nbsp;</td><td>Thermo Scientific</td><td>23225</td><td>N/A</td></tr><tr><td>Pyruvic Acid, 98%</td><td>Sigma Aldrich</td><td>107360</td><td>Store at 4 &amp;deg;C,pH to 7.4 with KOH prior to use in respirometric assay</td></tr><tr><td>Succinic Acid</td><td>Sigma Aldrich</td><td>S9512</td><td>Store at room temperature, pH to 7.4 with KOH prior to use in respirometric assay</td></tr><tr><td>L(-) Malic Acid, BioXtra, &amp;ge;95%</td><td>Sigma Aldrich</td><td>M6413</td><td>Store at room temperature, to 7.4 with KOH prior to use in respirometric assay</td></tr><tr><td>L-Glutamic acid</td><td>Sigma Aldrich</td><td>G1251</td><td>Store at room temperature, to 7.4 with KOH prior to use in respirometric assay, to 7.4 with KOH prior to use in respirometric assay</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>Palmitoyl L-carnitine chloride</td><td>Sigma Aldrich</td><td>P1645</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Oligomycin A, &amp;ge; 95% (HPLC)</td><td>Sigma Aldrich</td><td>75351</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Carbonyl cyanide 4-(trifluoromethoxy)</td><td>Sigma Aldrich</td><td>C2920</td><td>Store at 2-8 &amp;deg;C</td></tr><tr><td>phenylhydrazone</td><td></td><td></td><td></td></tr><tr><td>&amp;ge;98% (TLC), powder [FCCP]</td><td></td><td></td><td></td></tr><tr><td>Antimycin A from streptomyces sp.</td><td>Sigma Aldrich</td><td>A8674</td><td>Store at -20 &amp;deg;C</td></tr><tr><td>Adenosine 5&amp;prime;-diphosphate monopotassium salt dehydrate [ADP]</td><td>Sigma Aldrich</td><td>A5285</td><td>Store at -20 &amp;deg;C, to 7.4 with KOH prior to use in respirometric assay</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>Rotenone</td><td>Sigma Aldrich</td><td>R8875</td><td>Store at room temperature</td></tr></tbody></table>

isolation of mitochondria from minimal quantities of mouse skeletal muscle for high throughput microplate respiratory measurements

Dysfunctional skeletal muscle mitochondria play a role in altered metabolism observed with aging, obesity and Type II diabetes. Mitochondrial respirometric assays from isolated mitochondrial preparations allow for the assessment of mitochondrial function, as well as determination of the mechanism(s) of action of drugs and proteins that modulate metabolism. Current isolation procedures often require large quantities of tissue to yield high quality mitochondria necessary for respirometric assays. The methods presented herein describe how high quality purified mitochondria (~ 450 &#181;g) can be isolated from minimal quantities (~75-100 mg) of mouse skeletal muscle for use in high throughput respiratory measurements. We determined that our isolation method yields 92.5&#177; 2.0% intact mitochondria by measuring citrate synthase activity spectrophotometrically. In addition, Western blot analysis in isolated mitochondria resulted in the faint expression of the cytosolic protein, GAPDH, and the robust expression of the mitochondrial protein, COXIV. The absence of a prominent GAPDH band in the isolated mitochondria is indicative of little contamination from non-mitochondrial sources during the isolation procedure. Most importantly, the measurement of O2 consumption rate with micro-plate based technology and determining the respiratory control ratio (RCR) for coupled respirometric assays shows highly coupled (RCR; &#62;6 for all assays) and functional mitochondria. In conclusion, the addition of a separate mincing step and significantly reducing motor driven homogenization speed of a previously reported method has allowed the isolation of high quality and purified mitochondria from smaller quantities of mouse skeletal muscle that results in highly coupled mitochondria that respire with high function during microplate based respirometirc assays.

Citrate synthase activity serves as a measure for membrane integrity since citrate synthase is located in the inner mitochondrial membrane, and thus should not be present in suspensions of mitochondria with intact membranes. Figure 1 represents citrate synthase activity in non-sonicated mitochondrial samples compared with sonicated samples from the same isolation. Sonicating the mitochondria results in a statistically significant increase in citrate synthase activity (P &#60;0.01). Importantly, 92.5 &#177; 2.0% of mitochondria were intact following the isolation.
Figure 2 depicts GAPDH and COXIV expression in isolated mitochondria and the whole skeletal muscle tissue lysate. GAPDH is a protein located in the cytosol, but can also be found in the nucleus after translocation, while COXIV is a protein located in the inner mitochondrial membrane. Expression of GAPDH and COXIV are evident in the whole tissue lysate. In the isolated mitochondria, expression of COXIV is observed, while only faint bands of GAPDH are evident. These findings indicate good mitochondrial isolations, with little contamination from non-mitochondrial components during the isolation procedure.
Figure 3 is a representative tracing of O2 consumption rates (OCR) vs. time for a coupling assay (10 mM pyruvate/5 mM malate) performed from mitochondria isolated using this protocol and performed with microplate based O2 consumption technology. Each panel represents O2 consumption in different mitochondrial states as described by Chance and Williams13. The first panel represents basal O2 consumption, or State 2. The second panel, after injection of ADP, represents maximal coupled respiration, or State 3. The third panel, after injection of oligomycin A (an inhibitor of Complex V), represents respiration due to proton leak, or State 4o. The fourth panel, after injection of FCCP, represents maximal uncoupled respiration, or State 3u. Finally, the fifth panel, after injection of Antimycin A, represents the inhibition of oxidative respiration. The respiratory control ratio (RCR), a measure of mitochondrial function1, was calculated by dividing State 3 by State 4o. Table 4 reports the average RCR values for alternative substrate coupling assays that can be performed from the mitochondria yield from this protocol. Importantly, the O2 consumption tracing and the high RCR values represent highly functioning and coupled mitochondria. RCR values reported herein are higher or similar than previously reported using similar isolation protocols in murine skeletal muscle7,14,15, thus accentuating the high quality of the mitochondria isolated during this procedure.
 
<img alt="Figure 2" src="/files/ftp_upload/53217/53217fig2.jpg" />
Figure 1: Citrate Synthase Activity. Citrate synthase enzyme activity as determined spectrophotometrically in non-sonicated and sonicated mitochondria preps. Values are expressed as mean &#177; SEM. **p &#60;0.01. Data represents n = 3 paired biological replicates and expressed relative to mg of protein. 
<img alt="Figure 1" src="/files/ftp_upload/53217/53217fig1.jpg" />
Figure 2: Cytosolic and mitochondrial protein expression in isolated mitochondria and whole tissue lysate. Both isolated mitochondria and whole tissue lysates were immunoblotted with COXIV and GAPDH antibodies. The mitochondrial protein, COXIV, was evident in both samples, however GAPDH was only faintly evident in the isolated mitochondria. The absence of a prominent GAPDH band in the isolated mitochondria is indicative of little contamination from non-mitochondrial sources during the isolation procedure.
<img alt="Figure 3" src="/files/ftp_upload/53217/53217fig3.jpg" /> 
Figure 3: Representative tracing of coupling assay with mitochondria isolated from mouse skeletal muscle. 10 mM Pyruvate/5 mM malate coupled mitochondrial respiration assay tracings as determined by multi-well measurement of O2 consumption. Values are expressed as mean &#177; SD. Mitochondrial protein loaded per well was 2.5 &#181;g. OCR = O2 Consumption Rate; ADP = Adenosine diphosphate; Oligo = Oligomycin A; FCCP = Carbonyl cyanide-4- (trifluoromethoxy) phenylhydrazone; Anti-A = Antimycin A.
<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td rowspan="2">Reagent</td>
			<td>Stock Concentration&#160;</td>
			<td>MW</td>
			<td>Final Volume</td>
			<td>Mass Added</td>
		</tr>
		<tr>
			<td>(M)</td>
			<td>(g/mol)</td>
			<td>(ml)</td>
			<td>(g)</td>
		</tr>
		<tr>
			<td>Tris/HCl, pH 7.4</td>
			<td>2</td>
			<td>157.56</td>
			<td>250</td>
			<td>78.8</td>
		</tr>
		<tr>
			<td>Tris/HCl, pH 7.4</td>
			<td>1</td>
			<td>157.56</td>
			<td>250</td>
			<td>39.39</td>
		</tr>
		<tr>
			<td>KCL</td>
			<td>1</td>
			<td>74.55</td>
			<td>500</td>
			<td>37.28</td>
		</tr>
		<tr>
			<td>Tris Base</td>
			<td>1</td>
			<td>121.14</td>
			<td>100</td>
			<td>12.11</td>
		</tr>
		<tr>
			<td>EDTA, pH 8</td>
			<td>0.5</td>
			<td>416.2</td>
			<td>100 ml (in 1 M Tris Base)</td>
			<td>20.81</td>
		</tr>
		<tr>
			<td>EGTA, pH 7.2</td>
			<td>0.1</td>
			<td>380.35</td>
			<td>100 (in 1 M Tris Base)</td>
			<td>3.801</td>
		</tr>
	</tbody>
</table>
Table 1: Preparation of Stock Solutions.
<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td rowspan="2">Reagent</td>
			<td>Stock Concentration</td>
			<td>Mass Added</td>
			<td rowspan="2">Final Molarity/Percent</td>
		</tr>
		<tr>
			<td>(M)</td>
			<td>(g or ml)</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>-</td>
			<td>11.47 g</td>
			<td>67 mM</td>
		</tr>
		<tr>
			<td>Tris/Hcl, pH 7.4</td>
			<td>2</td>
			<td>12.5 ml</td>
			<td>50 mM</td>
		</tr>
		<tr>
			<td>KCL</td>
			<td>1</td>
			<td>25 ml</td>
			<td>50 mM</td>
		</tr>
		<tr>
			<td>EDTA/Tris Base, pH 8</td>
			<td>0.5</td>
			<td>10 ml</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td>Essentially FA Free BSA</td>
			<td>-</td>
			<td>1 g</td>
			<td>0.20%</td>
		</tr>
		<tr>
			<td colspan="4">pH 7.4, 500 ml: Aliquot 50 ml and freeze</td>
		</tr>
	</tbody>
</table>
Table 2: Preparation of Isolation Buffer for Mitochondria 1 (IBM1).
<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td rowspan="2">Reagent</td>
			<td>Stock Concentration</td>
			<td>Mass Added</td>
			<td rowspan="2">Final Molarity/Percent</td>
		</tr>
		<tr>
			<td>(M)</td>
			<td>(g or ml)</td>
		</tr>
		<tr>
			<td>D-Mannitol</td>
			<td>-</td>
			<td>10.9 g</td>
			<td>200 mM</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>-</td>
			<td>7.188 g</td>
			<td>70 mM</td>
		</tr>
		<tr>
			<td>EGTA/Tris Base</td>
			<td>0.1</td>
			<td>15 ml</td>
			<td>5 mM</td>
		</tr>
		<tr>
			<td>Tris-HCl, pH 7.4</td>
			<td>1</td>
			<td>3 ml</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td colspan="4">&#160;pH 7.4, 300 ml: Aliquot 15 ml and freeze</td>
		</tr>
	</tbody>
</table>
Table 3: Preparation of Isolation Buffer for Mitochondria 2 (IBM2).
<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Substrate Medium</td>
			<td>Final Concentration</td>
			<td>RCR</td>
		</tr>
		<tr>
			<td>Pyruvate/Malate</td>
			<td>10 mM/5 mM</td>
			<td>16.2 &#177; 4.6</td>
		</tr>
		<tr>
			<td>Succinate/Rotenone</td>
			<td>10 mM/2 &#956;M</td>
			<td>10.6 &#177; 3.8</td>
		</tr>
		<tr>
			<td>Palmitoyl L-Carnitine/Malate</td>
			<td>40 &#956;M/1 mM Malate</td>
			<td>6.7 &#177; 0.6</td>
		</tr>
		<tr>
			<td>Glutamate/Malate</td>
			<td>10 mM/10 mM</td>
			<td>8.6 &#177; 0.4</td>
		</tr>
	</tbody>
</table>
Table 4: Respiratory Control Ratios for Coupled Mitochondrial Respiration Assays. Respiratory control ratios as determined by first measuring O2 consumption rates with microplate based respirometric assays, followed by dividing maximal coupled respiration (ADP Stimulated State 3) by respiration due to proton leak (Oligomycin A response State 4o). Values are expressed as mean &#177; SE. Mitochondrial protein loaded per well was 2.5 &#181;g for the pyruvate/malate and succinate/rotenone assays, and 3.5 &#181;g of mitochondrial protein per well for the palmitoyl L-carnitine/malate and glutamate/malate assays.

Watch this Scientific Journal Video about Isolation of Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High Throughput Microplate Respiratory Measurements at JoVE.com

Isolation of Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High Throughput Microplate Respiratory Measurements

Here, we present a modification of a previously reported method that allows for the isolation of high quality and purified mitochondria from smaller quantities of mouse skeletal muscle. This procedure results in highly coupled mitochondria that respire with high function during microplate based respirometirc assays.

Dysfunctional skeletal muscle mitochondria play a role in altered metabolism observed with aging, obesity and Type II diabetes. Mitochondrial ...

isolation-mitochondria-from-minimal-quantities-mouse-skeletal-muscle

Nanyang Technological University

Research

JoVE Journal

Biology

12.7K Views.  Virginia Tech. Here, we present a modification of a previously reported method that allows for the isolation of high quality and purified mitochondria from smaller quantities of mouse skeletal muscle. This procedure results in highly coupled mitochondria that respire with high function during microplate based respirometirc assays.

Video: Isolation of Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High Throughput Microplate Respiratory Measurements

Using Isolated Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High throughput Microplate Respiratory Measurements

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of mitochondrial function in this tissue has become more prevalent. Although many technologies and assays exist that measure mitochondrial respiratory pathways in a variety of cells, tissue and species, there is currently a void in the literature in regards to the compilation of these assays using isolated mitochondria from mouse skeletal muscle for use in microplate based technologies. Importantly, the use of microplate based respirometric assays is growing among mitochondrial biologists as it allows for high throughput measurements using minimal quantities of isolated mitochondria. Therefore, a collection of microplate based respirometric assays were developed that are able to assess mechanistic changes/adaptations in oxygen consumption in a commonly used animal model. The methods presented herein provide step-by-step instructions to perform these assays with an optimal amount of mitochondrial protein and reagents, and high precision as evidenced by the minimal variance across the dynamic range of each assay.

The methods presented provide step-by-step instructions for the performance of a collection of microplate based respirometric assays using isolated mitochondria from minimal quantities of mouse skeletal muscle. These assays are able to measure mechanistic changes/adaptations in mitochondrial oxygen consumption in a commonly used animal model.

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of ...

Developmental Biology

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

Mitochondria are key metabolic and regulatory organelles that determine the energy supply as well as the overall health of the cell. In skeletal muscle, mitochondria exist in a series of complex morphologies, ranging from small oval organelles to a broad, reticulum-like network. Understanding how the mitochondrial reticulum expands and develops in response to diverse stimuli such as alterations in energy demand has long been a topic of research. A key aspect of this growth, or biogenesis, is the import of precursor proteins, originally encoded by the nuclear genome, synthesized in the cytosol, and translocated into various mitochondrial sub-compartments. Mitochondria have developed a sophisticated mechanism for this import process, involving many selective inner and outer membrane channels, known as the protein import machinery (PIM). Import into the mitochondrion is dependent on viable membrane potential and the availability of organelle-derived ATP through oxidative phosphorylation. Therefore its measurement can serve as a measure of organelle health. The PIM also exhibits a high level of adaptive plasticity in skeletal muscle that is tightly coupled to the energy status of the cell. For example, exercise training has been shown to increase import capacity, while muscle disuse reduces it, coincident with changes in markers of mitochondrial content. Although protein import is a critical step in the biogenesis and expansion of mitochondria, the process is not widely studied in skeletal muscle. Thus, this paper outlines how to use isolated and fully functional mitochondria from skeletal muscle to measure protein import capacity in order to promote a greater understanding of the methods involved and an appreciation of the importance of the pathway for organelle turnover in exercise, health, and disease.

Mitochondria are key metabolic organelles that exhibit a high level of phenotypic plasticity in skeletal muscle. The import of proteins from the cytosol is a critical pathway for organelle biogenesis, essential for the expansion of the reticulum and the maintenance of mitochondrial function. Therefore, protein import serves as a barometer of cellular health.

Mitochondria are key metabolic and regulatory organelles that determine the energy supply as well as the overall health of the cell. In skeletal muscle, ...

Biochemistry

Preparation and Respirometric Assessment of Mitochondria Isolated from Skeletal Muscle Tissue Obtained by Percutaneous Needle Biopsy

Respirometric profiling of isolated mitochondria is commonly used to investigate electron transport chain function. We describe a method for obtaining samples of human Vastus lateralis, isolating mitochondria from minimal amounts of skeletal muscle tissue, and plate based respirometric profiling using an extracellular flux (XF) analyzer. Comparison of respirometric profiles obtained using 1.0, 2.5 and 5.0 &#956;g of mitochondria indicate that 1.0 &#956;g is sufficient to measure respiration and that 5.0 &#956;g provides most consistent results based on comparison of standard errors. Western blot analysis of isolated mitochondria for mitochondrial marker COX IV and non-mitochondrial tissue marker GAPDH indicate that there is limited non-mitochondrial contamination using this protocol. The ability to study mitochondrial respirometry in as little as 20 mg of muscle tissue allows users to utilize individual biopsies for multiple study endpoints in clinical research projects.

Methods for biopsy of Vastus lateralis, preparation of purified mitochondria, and respirometric profiling are described. The use of small muscle volume makes this technique suitable for clinical research applications.

Respirometric profiling of isolated mitochondria is commonly used to investigate electron transport chain function. We describe a method for obtaining ...

Medicine

Adult and Embryonic Skeletal Muscle Microexplant Culture and Isolation of Skeletal Muscle Stem Cells

Cultured embryonic and adult skeletal muscle cells have a number of different uses. The micro-dissected explants technique described in this chapter is a robust and reliable method for isolating relatively large numbers of proliferative skeletal muscle cells from juvenile, adult or embryonic muscles as a source of skeletal muscle stem cells. The authors have used micro-dissected explant cultures to analyse the growth characteristics of skeletal muscle cells in wild-type and dystrophic muscles. Each of the components of tissue growth, namely cell survival, proliferation, senescence and differentiation can be analysed separately using the methods described here. The net effect of all components of growth can be established by means of measuring explant outgrowth rates. The micro-explant method can be used to establish primary cultures from a wide range of different muscle types and ages and, as described here, has been adapted by the authors to enable the isolation of embryonic skeletal muscle precursors.
Uniquely, micro-explant cultures have been used to derive clonal (single cell origin) skeletal muscle stem cell (SMSc) lines which can be expanded and used for in vivo transplantation. In vivo transplanted SMSc behave as functional, tissue-specific, satellite cells which contribute to skeletal muscle fibre regeneration but which are also retained (in the satellite cell niche) as a small pool of undifferentiated stem cells which can be re-isolated into culture using the micro-explant method.

The micro-dissected explants technique is a robust and reliable method for isolating proliferative skeletal muscle cells from juvenile, adult or embryonic muscles as a source of skeletal muscle stem cells. Uniquely, these cells have been clonally derived to produce skeletal muscle stem cell lines used for in vivo transplantation.

Cultured embryonic and adult skeletal muscle cells have a number of different uses. The micro-dissected explants technique described in this chapter is a ...

Mitochondrial Isolation from Skeletal Muscle

Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and regulate a number of signaling cascades2,3. Past and current researchers have isolated mitochondria from rat and mice tissues such as liver, brain and heart4,5. In recent years, many researchers have focused on studying mitochondrial function from skeletal muscles.
Here, we describe a method that we have used successfully for the isolation of mitochondria from skeletal muscles 6. Our procedure requires that all buffers and reagents are made fresh and need about 250-500 mg of skeletal muscle. We studied mitochondria isolated from rat and mouse gastrocnemius and diaphragm, and rat extraocular muscles. Mitochondrial protein concentration is measured with the Bradford assay. It is important that mitochondrial samples be kept ice-cold during preparation and that functional studies be performed within a relatively short time (~1 hr). Mitochondrial respiration is measured using polarography with a Clark-type electrode (Oxygraph system) at 37&deg;C7. Calibration of the oxygen electrode is a key step in this protocol and it must be performed daily. Isolated mitochondria (150 &mu;g) are added to 0.5 ml of experimental buffer (EB). State 2 respiration starts with addition of glutamate (5mM) and malate (2.5 mM). Then, adenosine diphosphate (ADP) (150 &mu;M) is added to start state 3. Oligomycin (1 &mu;M), an ATPase synthase blocker, is used to estimate state 4. Lastly, carbonyl cyanide p-[trifluoromethoxy]-phenyl-hydrazone (FCCP, 0.2 &mu;M) is added to measurestate 5, or uncoupled respiration 6. The respiratory control ratio (RCR), the ratio of state 3 to state 4, is calculated after each experiment. An RCR &ge;4 is considered as evidence of a viable mitochondria preparation.
In summary, we present a method for the isolation of viable mitochondria from skeletal muscles that can be used in biochemical (e.g., enzyme activity, immunodetection, proteomics) and functional studies (mitochondrial respiration).

This protocol describes a procedure to study the respiration of mitochondria isolated from skeletal muscles. This method was adapted from Scorrano et al. (2007). The mitochondrial isolation procedure requires about 2 hours. The mitochondrial respiration can be completed in about 1 hour.

Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and ...

Purification of Progenitors from Skeletal Muscle

Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing in a "satellite cell position" between the myofiber plasma membrane and the laminin-rich basement membrane that ensheaths it, are self-renewing cells that are solely committed to the myogenic lineage1,2. We have recently described a second class of vessel associated progenitors that can generate myofibroblasts and white adipocytes, which responds to damage by efficiently entering proliferation and provides trophic support to myogenic cells during tissue regeneration3,4. One of the most trusted assays to determine the developmental and regenerative potential of a given cell population relies on their isolation and transplantation5-7. To this end we have optimized protocols for their purification by flow cytometry from enzymatically dissociated muscle, which we will outline in this article. The populations obtained using this method will contain either myogenic or fibro/adipogenic colony forming cells: no other cell types are capable of expanding in vitro or surviving in vivo delivery. However, when these populations are used immediately after the sort for molecular analysis (e.g qRT-PCR) one must keep in mind that the freshly sorted subsets may contain other contaminant cells that lack the ability of forming colonies or engrafting recipients.

Method for the enzymatic dissociation, surface labeling and purification by flow cytometry of fibro/adipogenic and myogenic progenitors from murine skeletal muscle.

Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing ...

Mitochondrial Isolation from Rodents for High-Quality Bioenergetic Studies

Robust Mitochondrial Isolation from Rodent Cardiac Tissue

Mitochondrial isolation has been practiced for decades, following procedures established by pioneers in the fields of molecular biology and biochemistry to study metabolic impairments and disease. Consistent mitochondrial quality is necessary to properly investigate mitochondrial physiology and bioenergetics; however, many different published isolation methods are available for researchers. Although different experimental strategies require different isolation methods, the basic principles and procedures are similar. This protocol details a method capable of extracting well-coupled mitochondria from a variety of tissue sources, including small animals and cells. The steps outlined include organ dissection, mitochondrial purification, protein quantification, and various quality control checks. The primary quality control metric used to identify high-quality mitochondria is the respiratory control ratio (RCR). The RCR is the ratio of the respiratory rate during oxidative phosphorylation to the rate in the absence of ADP. Alternative metrics are discussed. While high RCR values relative to their tissue source are obtained using this protocol, several steps can be optimized to suit the individual needs of researchers. This procedure is robust and has consistently resulted in isolated mitochondria with above-average RCR values across animal models and tissue sources.

Author Spotlight: Uncovering the Role of Mitochondrial Calcium Phosphate in Heart Failure and Bioenergetics

Bioenergetic and metabolomic studies on mitochondria have revealed their multifaceted role in many diseases, but the isolation methods for these organelles vary. The method detailed here is capable of purifying high-quality mitochondria from multiple tissue sources. Quality is determined by respiratory control ratios and other metrics assessed with high-resolution respirometry.

Mitochondrial isolation has been practiced for decades, following procedures established by pioneers in the fields of molecular biology and biochemistry ...

Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria

The mitochondrial permeability transition pore (mtPTP) is a non specific channel that forms in the inner mitochondrial membrane to transport solutes with a molecular mass smaller than 1.5 kDa. Although the definitive molecular identity of the pore is still under debate, proteins such as cyclophilin D, VDAC and ANT contribute to mtPTP formation. While the involvement of mtPTP opening in cell death is well established1, accumulating evidence indicates that the mtPTP serves a physiologic role during mitochondrial Ca2+ homeostasis2, bioenergetics and redox signaling 3.
mtPTP opening is triggered by matrix Ca2+ but its activity can be modulated by several other factors such as oxidative stress, adenine nucleotide depletion, high concentrations of Pi, mitochondrial membrane depolarization or uncoupling, and long chain fatty acids4. In vitro, mtPTP opening can be achieved by increasing Ca2+ concentration inside the mitochondrial matrix through exogenous additions of Ca2+ (calcium retention capacity). When Ca2+ levels inside mitochondria reach a certain threshold, the mtPTP opens and facilitates Ca2+ release, dissipation of the proton motive force, membrane potential collapse and an increase in mitochondrial matrix volume (swelling) that ultimately leads to the rupture of the outer mitochondrial membrane and irreversible loss of organelle function.
Here we describe a fluorometric assay that allows for a comprehensive characterization of mtPTP opening in isolated mouse heart mitochondria. The assay involves the simultaneous measurement of 3 mitochondrial parameters that are altered when mtPTP opening occurs: mitochondrial Ca2+ handling (uptake and release, as measured by Ca2+ concentration in the assay medium), mitochondrial membrane potential, and mitochondrial volume. The dyes employed for Ca2+ measurement in the assay medium and mitochondrial membrane potential are Fura FF, a membrane impermeant, ratiometric indicator which undergoes a shift in the excitation wavelength in the presence of Ca2+, and JC-1, a cationic, ratiometric indicator which forms green monomers or red aggregates at low and high membrane potential, respectively. Changes in mitochondrial volume are measured by recording light scattering by the mitochondrial suspension. Since high-quality, functional mitochondria are required for the mtPTP opening assay, we also describe the steps necessary to obtain intact, highly coupled and functional isolated heart mitochondria.

A spectrofluorometric protocol for the measurement of the mitochondrial permeability transition pore opening in isolated mouse heart mitochondria is presented here. The assay involves the simultaneous measurement of mitochondria Ca2+ handling, mitochondrial membrane potential and mitochondrial volume. The procedure for obtaining high-quality and functional heart mitochondria is also described.

The mitochondrial permeability transition pore (mtPTP) is a non specific channel that forms in the inner mitochondrial membrane to transport solutes with ...

Isolation of Intact Mitochondria from Skeletal Muscle by Differential Centrifugation for High-resolution Respirometry Measurements

Mitochondria are involved in cellular energy metabolism and use oxygen to produce energy in the form of adenosine triphosphate (ATP). Differential centrifugation at low- and high-speed is commonly used to isolate mitochondria from tissues and cultured cells. Crude mitochondrial fractions obtained by differential centrifugation are used for respirometry measurements. The differential centrifugation technique is based on the separation of organelles according to their size and sedimentation velocity. The isolation of mitochondria is performed immediately after tissue harvesting. The tissue is immersed in an ice-cold homogenization medium, minced using scissors and homogenized in a glass homogenizer with a loose-fitting pestle. The differential centrifugation technique is efficient, fast and inexpensive and the mitochondria obtained by differential centrifugation are pure enough for respirometry assays. Some of the limitations and disadvantages of isolated mitochondria, based on differential centrifugation, are that the mitochondria can be damaged during the homogenization and isolation procedure and that large amounts of the tissue biopsy or cultured cells are required for the mitochondrial isolation.

Here, a quadriceps muscle specimen is taken from an anaesthetized pig and mitochondria are isolated by differential centrifugation. Then, the respiratory rates of mitochondrial respiratory chain complexes I, II and IV are determined using high-resolution respirometry.

Mitochondria are involved in cellular energy metabolism and use oxygen to produce energy in the form of adenosine triphosphate (ATP). Differential ...

Isolation of Mitochondria from Mouse Skeletal Muscle for Respirometric Assays

Most of the cell&#39;s energy is obtained through the degradation of glucose, fatty acids, and amino acids by different pathways that converge on the mitochondrial oxidative phosphorylation (OXPHOS) system, which is regulated in response to cellular demands. The lipid molecule Coenzyme Q (CoQ) is essential in this process by transferring electrons to complex III in the electron transport chain (ETC) through constant oxidation/reduction cycles. Mitochondria status and, ultimately, cellular health can be assessed by measuring ETC oxygen consumption using respirometric assays. These studies are typically performed in established or primary cell lines that have been cultured for several days. In both cases, the respiration parameters obtained may have deviated from normal physiological conditions in&#160;any given organ or tissue.
Additionally, the intrinsic characteristics of cultured single fibers isolated from skeletal muscle impede this type of analysis. This paper presents an updated and detailed protocol for the analysis of respiration in freshly isolated mitochondria from mouse skeletal muscle. We also provide solutions to potential problems that could arise at any step of the process. The method presented here could be applied to compare oxygen consumption rates in diverse transgenic mouse models and study the mitochondrial response to drug treatments or other factors such as aging or sex. This is a feasible method to respond to crucial questions about mitochondrial bioenergetics metabolism and regulation.

Here, we describe a detailed method for mitochondria isolation from mouse skeletal muscle and the subsequent analysis of respiration by Oxygen Consumption Rate (OCR) using microplate-based respirometric assays. This pipeline can be applied to study the effects of multiple environmental or genetic interventions on mitochondrial metabolism.

Most of the cell&#39;s energy is obtained through the degradation of glucose, fatty acids, and amino acids by different pathways that converge on the ...

Isolation of Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High Throughput Microplate Respiratory Measurements

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