This work was supported by Adelphi University faculty development grant and grant R15GM113156 from NIGMS awarded to EVC, grant R01GM067862 from NIGMS and grant R01AG027849 from NIA awarded to DMR.

1. Reagents and Solutions
<ol>
	<li>Preparation of fly food and media
	<ol>
		<li>Heat fly ingredients 11% sugar, 2% autolyzed yeast, 5.2% cornmeal, agar 0.79% w/v in water in a hotplate set at 90 &#176;C. Stir regularly until a homogenous slightly dense mixture is obtained. Prepare a final volume of 550 ml of fly food for a total of 100 vials with 5 ml fly food in each.</li>
		<li>Remove from the heating source, stir occasionally until the food cools down to 80 &#176;C and add 0.2% tegosept-methyl 4-hydroxybenzoate dissolved in 95% ethanol.</li>
		<li>Split the food in two equal volumes. Add 1.1 ml of 50 mM rapamycin dissolved in ethanol to one volume and 1.1 ml of ethanol to the other volume. Stir the rapamycin and the ethanol solutions into the food. Be sure that the temperature decreases to 50 &#176;C before adding drugs.</li>
	</ol>
	</li>
	<li>Isolation Buffer
	<ol>
		<li>Prepare 500 ml of Isolation Buffer [225 mM Mannitol, 75 mM Sucrose, 10 mM 3-(N-morpholino) propanesulfonic acid (MOPS) and 1 mM ethylenediaminetetraacetic acid (EDTA) , 2.5 mg/ml bovine serum albumin (BSA)] in water.</li>
		<li>Adjust the pH to 7.2 using sodium hydroxide. The initial pH will be acidic.</li>
		<li>Use sterile filter storage bottles with a 0.22 &#181;m pore size to sterilize solution and store it at 4 &#176;C.</li>
	</ol>
	</li>
	<li>Wash Buffer
	<ol>
		<li>Prepare 500 ml of wash buffer [225 mM Mannitol, 75 mM Sucrose, 10 mM KCl, 10 mM Tris HCl and 5 mM KH2PO4] in water.</li>
		<li>Adjust the pH to 7.2 using sodium hydroxide. The initial pH will be acidic.</li>
		<li>Use sterile filter storage bottles with a 0.22 &#181;m pore size to sterilize solution and store it at 4 &#176;C.</li>
	</ol>
	</li>
</ol>
2. Rearing of the Drosophila Strains
<ol>
	<li>To control larval density during development, place 25 pairs of parents in to a culture bottle and allow them to lay eggs for 48 hr.</li>
	<li>Remove parents after 48 hr to regulate egg density.</li>
	<li>Repeat steps 2.1 and 2.2 using the emerging F1 offspring, so two generations of this density control is achieved.</li>
	<li>To collect adults, anesthetize the flies using carbon dioxide (CO2) and separate by sex.
	<ol>
		<li>Use a single stage regulator to delivered pure CO2 from a high pressured tank at a continuous flow of 5 psi. To avoid static electricity, use plastic tubing to catalyze the CO2 into a 500 ml filtering flask with water.</li>
		<li>Use a rubber stopper with one hole to seal the flask. Use plastic tubing to connect the lateral aperture of the flask to a CO2 pad.</li>
		<li>Place the flies in the pad for no more than 10-15 min. Allow to recover from anesthesia for 24 hr before placing them in experimental conditions.</li>
	</ol>
	</li>
	<li>To generate enough metabolites for mitochondrial enriched fractions, use 300 flies per sample. Here, use females, but gender may differ in other experiments. Transfer 150 flies to a homemade 1 L demography cage. Allow access to 5 ml of fly food in a vial.</li>
	<li>Transfer the remaining 150 flies to another 1 L cage. Do not overpopulate cages with more than 150 flies.</li>
	<li>Use six replicate samples per experimental condition. Since whole animal extracts yield more metabolites, to generate 1 sample of whole animal isolates, transfer 50 female flies to one cage. As for the mitochondrial isolates, use six replicate samples per experimental condition.</li>
	<li>Place cages at 25 &#176;C with cycle of 12 hr light and 12 hr dark.</li>
	<li>Provide fresh food every 2 or 3 days in a vial with 5 ml of food to maintain food quality.</li>
	<li>Maintain flies on food for 10 days. This step is needed for the rapamycin treatment7. Other treatments or conditions will differ.</li>
</ol>
3. Isolation of Mitochondrial Fractions
<ol>
	<li>Dump flies from one cage (150 flies) into a glass-teflon dounce homogenizer filled with 1 ml of chilled isolation buffer.</li>
	<li>Homogenize by moving the pestle up and down for 15 strokes. Keep the mortar on ice to keep mitochondria intact.</li>
	<li>Transfer homogenate to a 1.5 ml tube and centrifuge at 300 x g for 5 min at 4 &#176;C.</li>
	<li>Take the supernatant and centrifuge at 6,000 x g for 10 min at 4 &#176;C to enrich for mitochondria.</li>
	<li>As the supernatant contains the cytosolic fraction, discard the supernatant or use it for alternative experiments. Resuspend the pellet in 300 &#181;l of wash buffer.</li>
	<li>Repeat steps 3.1 - 3.5 for the second cage. Combine the resuspended pellets of both cages in a cryogenic microcentrifuge tube.</li>
	<li>Centrifuge at 6,000 x g for 10 min at 4 &#176;C.</li>
	<li>Discard the supernatant and flash-freeze the pellet in liquid nitrogen.</li>
	<li>Store the mitochondrial enriched fractions at -80 &#176;C or lower temperature.
	<ol>
		<li>Alternatively, for whole animal preparation, place the adults in a cryogenic microcentrifuge tube. Flash-freeze the vial in liquid nitrogen and store adults at -80 &#176;C or lower temperature.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Scheffler, I. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Mitochondria (Scheffler, Mitochondria). , 484 (2007).</li><li>Guarente, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondria--a+nexus+for+aging,+calorie+restriction,+and+sirtuins.">Mitochondria--a nexus for aging, calorie restriction, and sirtuins.</a> Cell. 132 (2), 171-176 (2008).</li><li>Raimundo, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+pathology:+stress+signals+from+the+energy+factory.">Mitochondrial pathology: stress signals from the energy factory.</a> Trends in molecular medicine. 20 (5), 282-292 (2014).</li><li>Embley, T. M., Martin, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eukaryotic+evolution,+changes+and+challenges.">Eukaryotic evolution, changes and challenges.</a> Nature. 440 (7084), 623-630 (2006).</li><li>Lane, N., , <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Power, Sex, Suicide: Mitochondria and the Meaning of Life. 368, (2006).</li><li>Montooth, K. L., Meiklejohn, C. D., Abt, D. N., Rand, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial-nuclear+epistasis+affects+fitness+within+species+but+does+not+contribute+to+fixed+incompatibilities+between+species+of+Drosophila.">Mitochondrial-nuclear epistasis affects fitness within species but does not contribute to fixed incompatibilities between species of Drosophila.</a> Evolution; international journal of organic evolution. 64 (12), 3364-3379 (2010).</li><li>Villa-Cuesta, E., Holmbeck, M. A., Rand, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapamycin+increases+mitochondrial+efficiency+by+mtDNA-dependent+reprogramming+of+mitochondrial+metabolism+in+Drosophila.">Rapamycin increases mitochondrial efficiency by mtDNA-dependent reprogramming of mitochondrial metabolism in Drosophila.</a> Journal of cell science. 127 (Pt 10), 2282-2290 (2014).</li><li>Zhu, C. -. T., Ingelmo, P., Rand, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=G&#215;G&#215;E+for+Lifespan+in+Drosophila:+Mitochondrial,+Nuclear,+and+Dietary+Interactions+that+Modify+Longevity.">G&#215;G&#215;E for Lifespan in Drosophila: Mitochondrial, Nuclear, and Dietary Interactions that Modify Longevity.</a> PLoS genetics. 10 (5), e1004354 (2014).</li><li>Madala, N. E., Piater, L. A., Steenkamp, P. A., Dubery, I. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multivariate+statistical+models+of+metabolomic+data+reveals+different+metabolite+distribution+patterns+in+isonitrosoacetophenone-elicited+Nicotiana+tabacum+and+Sorghum+bicolor+cells.">Multivariate statistical models of metabolomic data reveals different metabolite distribution patterns in isonitrosoacetophenone-elicited Nicotiana tabacum and Sorghum bicolor cells.</a> SpringerPlus. 3, 254 (2014).</li><li>Hogeboom, G. H., Schneider, W. C., Pallade, G. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytochemical+Studies+Of+Mammalian+Tissues+I+.+Isolation+Of+Intact+Mitochondria+From+Rat+Liver+Some+Biochemical+Properties+Of+Mitochondria+And+Submicroscopic+Particulate+Material.">Cytochemical Studies Of Mammalian Tissues I . Isolation Of Intact Mitochondria From Rat Liver Some Biochemical Properties Of Mitochondria And Submicroscopic Particulate Material.</a> Journal of Biological Chemistry. 172, 619-635 (1948).</li><li>Frezza, C., Cipolat, S., Scorrano, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organelle+isolation:+functional+mitochondria+from+mouse+liver,+muscle+and+cultured+fibroblasts.">Organelle isolation: functional mitochondria from mouse liver, muscle and cultured fibroblasts.</a> Nature protocols. 2 (2), 287-295 (2007).</li><li>Corcelli, A., Saponetti, M. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondria+isolated+in+nearly+isotonic+KCl+buffer:+focus+on+cardiolipin+and+organelle+morphology.">Mitochondria isolated in nearly isotonic KCl buffer: focus on cardiolipin and organelle morphology.</a> Biochimica et biophysica acta. 1798 (3), 681-687 (2010).</li><li>Roede, J. R., Park, Y., Li, S., Strobel, F. H., Jones, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detailed+mitochondrial+phenotyping+by+high+resolution+metabolomics.">Detailed mitochondrial phenotyping by high resolution metabolomics.</a> PloS one. 7 (3), e33020 (2012).</li></ol>

The authors have nothing to disclose.

The most critical steps in this protocol are: 1) rearing enough flies in abundant space. It is very important to not overpopulate the demography cages with more than 150 flies each; 2) changing the food of the cages frequently to avoid food competition and nutritional stress; and 3) maintaining all samples at 4 &#176;C to ensure integrity during the isolation of the mitochondrial fraction. It is also recommended to chill the isolation buffer, the wash buffer, and the glass-teflon dounce homogenizer before use. To reduce ...

The goal of this procedure is to develop enriched mitochondrial fractions that yield enough mitochondrial metabolites for metabolomics studies using Drosophila melanogaster. In our experience, metabolomics analysis using whole cellular extraction methods are unable to detect subtle mitochondrial metabolite changes in Drosophila. However, mitochondrial fractioning prior to metabolomics analysis increases the sensitivity to identify mitochondrial metabolite shifts.
Mitochondria are cellular organelles responsible for providing 90% of the energy that cells need for normal function1. In recent years it has been recognized that mitochondria play a much more dynamic role in cellular and organismal function than merely producing adenosine triphosphate(ATP), and are now recognized as hubs for the regulation of metabolic homeostasis2,3. Mitochondria are the result of an endosymbiotic process in which distinct microbial lineages merged ~1.5 billion years ago4. As mitochondria evolved into true organelles, genes from the endosymbiont were incorporated in the emerging nuclear genome. In animals today, approximately 1,500 mitochondrial proteins are nuclear-encoded while 37 genes remain in the mtDNA, 13 of which encode mitochondrial proteins that are subunits of the enzyme complexes of oxidative phosphorylation5. Coordination between mitochondria and nuclear compartments is needed to maintain proper mitochondrial function.
Using the methods described here we were able to detect mitochondrial metabolic changes in Drosophila that result from manipulation of the coordination between mitochondrial and nuclear genomes. We used a strain of Drosophila in which mtDNA from its sister species D. simulans was placed on a single D. melanogaster nuclear background6. This &#8216;disrupted&#8217; mitonuclear genotype was compared to the &#8216;native&#8217;, or co-evolved mitonuclear genotype of D. melanogaster carrying the same nuclear genome with its native D. melanogaster mtDNA. The D. melanogaster and D. simulans mtDNAs differ by ~100 amino acids and &#62;500 synonymous substitutions that affect mitonuclear communication7,8. We generated whole fly extracts and mitochondrial enriched extracts to study metabolite shifts in response to pharmacological stress. Here we show that when using mitochondrial enriched fractions we detect pronounced shifts in mitochondrial metabolites between the native, co-evolved genotype carrying the D. melanogaster mtDNAs and the disrupted genotype carrying D. simulans mtDNA. In contrast, the metabolite changes between these two genotypes are subtle using normal methods that utilize whole fly extract. Therefore, this method provided a path to understand how mtDNAs mediate mitochondrial changes in response to different drugs.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>0.2% tegosept -methyl 4-hydroxybenzoate&#160;</td>
			<td>VWR</td>
			<td>AAA14289</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma-Aldrich</td>
			<td>792799</td>
			<td></td>
		</tr>
		<tr>
			<td>Mannitol</td>
			<td>Sigma-Aldrich</td>
			<td>M4125</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma-Aldrich</td>
			<td>S9378</td>
			<td></td>
		</tr>
		<tr>
			<td>3-(N-morpholino) propanesulfonic acid (MOPS)</td>
			<td>Sigma-Aldrich</td>
			<td>M1254&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid (EDTA)</td>
			<td>Sigma-Aldrich</td>
			<td>38057&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA)</td>
			<td>Sigma-Aldrich</td>
			<td>5470</td>
			<td></td>
		</tr>
		<tr>
			<td>KCL</td>
			<td>Sigma-Aldrich</td>
			<td>P9333</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris HCL&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>RES3098T-B7</td>
			<td></td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>1551139</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 pads to anesthetize flies</td>
			<td>Tritech Research</td>
			<td>MINJ-DROS-FP</td>
			<td></td>
		</tr>
		<tr>
			<td>1 liter cage&#160;</td>
			<td>Web Restaurant Store</td>
			<td>999RD32</td>
			<td></td>
		</tr>
		<tr>
			<td>1 liter cage lid&#160;</td>
			<td>Web Restaurant Store</td>
			<td>999LRD</td>
			<td></td>
		</tr>
		<tr>
			<td>a glass-teflon dounce homogenizer&#160;</td>
			<td>Fisher Scientific</td>
			<td>NC9661231</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Sigma-Aldrich</td>
			<td>S8045</td>
			<td></td>
		</tr>
		<tr>
			<td>rapamycin&#160;</td>
			<td>LC Laboratories&#160;</td>
			<td>R-5000</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-porin</td>
			<td>MitoSciences</td>
			<td>MSA03</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-alpha tubulin</td>
			<td>Developmental Studies Hybridoma Bank</td>
			<td>12G10</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce&#8482; BCA Protein Assay Kit&#160;</td>
			<td>Thermo Scientific&#160;</td>
			<td>23225</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 pad</td>
			<td>Tritech Research, Inc</td>
			<td>MINJ-DROS-FP</td>
			<td></td>
		</tr>
		<tr>
			<td>filter flask</td>
			<td>enasco</td>
			<td>SB08184M</td>
			<td></td>
		</tr>
		<tr>
			<td>rubber stopper</td>
			<td>enasco</td>
			<td>S08512M</td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of mitochondrial enriched fractions for metabolic analysis in drosophila

Since mitochondria play roles in amino acid metabolism, carbohydrate metabolism and fatty acid oxidation, defects in mitochondrial function often compromise the lives of those who suffer from these complex diseases. Detecting mitochondrial metabolic changes is vital to the understanding of mitochondrial disorders and mitochondrial responses to pharmacological agents. Although mitochondrial metabolism is at the core of metabolic regulation, the detection of subtle changes in mitochondrial metabolism may be hindered by the overrepresentation of other cytosolic metabolites obtained using whole organism or whole tissue extractions. 
Here we describe an isolation method that detected pronounced mitochondrial metabolic changes in Drosophila that were distinct between whole-fly and mitochondrial enriched preparations. To illustrate the sensitivity of this method, we used a set of Drosophila harboring genetically diverse mitochondrial DNAs (mtDNA) and exposed them to the drug rapamycin. Using this method we showed that rapamycin modifies mitochondrial metabolism in a mitochondrial-genotype-dependent manner. However, these changes are much more distinct in metabolomics studies when metabolites were extracted from mitochondrial enriched fractions. In contrast, whole tissue extracts only detected metabolic changes mediated by the drug rapamycin independently of mtDNAs.

Using the protocol explained above, we performed metabolomic analysis on mitochondrial enriched fractions and whole animal extracts to test the effect of the drug rapamycin on divergent mtDNAs 7. We delivered 200 &#181;M of rapamycin by dissolving the drug in the fly food. Flies were exposed to rapamycin for 10 days. Metabolites from whole fly extracts and from mitochondrial extracts were obtained by using gas chromatography mass spectrometry (GC/MS) and liquid chromatogra...

Watch this Scientific Journal Video about Preparation of Mitochondrial Enriched Fractions for Metabolic Analysis in Drosophila at JoVE.com

Preparation of Mitochondrial Enriched Fractions for Metabolic Analysis in Drosophila

Mitochondria play central roles in the regulation of metabolism and homeostasis. Subtle changes in mitochondrial metabolism that affect organismal physiology could be difficult to detect in whole organism metabolomics studies. Here we describe an isolation method that enhances the detection of subtle metabolic shifts in Drosophila melanogaster.

Preparation of Mitochondrial Enriched Fractions for Metabolic Analysis in Drosophila

Since mitochondria play roles in amino acid metabolism, carbohydrate metabolism and fatty acid oxidation, defects in mitochondrial function often ...

preparation-mitochondrial-enriched-fractions-for-metabolic-analysis

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9.4K Views.  Adelphi University. Mitochondria play central roles in the regulation of metabolism and homeostasis. Subtle changes in mitochondrial metabolism that affect organismal physiology could be difficult to detect in whole organism metabolomics studies. Here we describe an isolation method that enhances the detection of subtle metabolic shifts in Drosophila melanogaster. 