Greater Yield of Subsarcolemmal Mitochondria from Skeletal Muscle of Obese Subjects with No Change in Intrinsic Mitochondrial Function

Whether obesity influences content and functional capacity of skeletal muscle mitochondria (MITO) remains unresolved. In this study, biopsies of vastus lateralis from lean and obese human subjects were used to isolate subsarcolemmal (SS) and intermyofibrillar (IMF) MITO. IMF MITO were liberated using a protease. The SS and IMF were pelleted separately, using differential centrifugation. Skeletal muscle from obese subjects gave higher MITO protein yield, per g wet muscle vs. skeletal muscle from lean subjects in the SS but not in the IMF. There was a trend for higher isolated yields of citrate synthase (CS) activity, a marker for MITO content, in the muscle of obese subjects vs. lean subjects in SS, but not in IMF MITO. O2 consumption (JO) and ATP production rates measured with NAD-linked substrates (malate+pyruvate+glutamate), were not different in obese vs. lean in either SS or IMF MITO expressed either per mg MITO protein or per unit CS activity. The similarities in MITO function observed in SS and IMF ...