Sex and race contribute to variation in mitochondrial function and insulin sensitivity

Objective Insulin sensitivity is lower in African American (AA) versus Caucasian American (CA). We tested the hypothesis that lower insulin sensitivity in AA could be explained by mitochondrial respiratory rates, coupling efficiency, myofiber composition, or H2O2 emission. A secondary aim was to determine whether sex affected the results. Methods AA and CA men and women, 19–45 years, BMI 17–43 kg m2, were assessed for insulin sensitivity (SIClamp) using a euglycemic clamp at 120 mU/m2/min, muscle mitochondrial function using high‐resolution respirometry, H2O2 emission using amplex red, and % myofiber composition. Results SIClamp was greater in CA (p
Present results do not support a role for mitochondrial function or fiber type in determining lower insulin sensitivity in African Americans. The source of lower skeletal‐muscle insulin sensitivity in African Americans remains unclear. Future research could focus on aspects of skeletal muscle composition, such as lipid species, and their association with insulin sensitivity in African Americans.