Insulin Sensitivity and Skeletal Muscle Mitochondrial Respiration in Black and White Women With Obesity.

OBJECTIVES

Non-Hispanic Black women (BW) have a greater risk of type 2 diabetes (T2D) and insulin resistance (IR) compared to non-Hispanic White women (WW). The mechanisms leading to these differences are not understood, and it is unclear whether synergistic effects of race and obesity impact disease risk. To understand the interaction of race and weight, hepatic and peripheral IR were compared in WW and BW with and without obesity.

METHODS

Hepatic and peripheral IR were measured by a labeled, hyperinsulinemic-euglycemic clamp in BW (n = 32) and WW (n = 32) with and without obesity. Measurements of body composition, cardiorespiratory fitness, and skeletal muscle (SM) respiration were completed. Data were analyzed by mixed model ANOVA.

RESULTS

Subjects with obesity had greater hepatic and peripheral IR and lower SM respiration (P < .001). Despite 14% greater insulin (P = .066), BW tended to have lower peripheral glucose disposal (Rd; P = .062), which was driven by women without obesity (P = .002). BW had significantly lower glucose production (P = .005), hepatic IR (P = .024), and maximal coupled and uncoupled respiration (P < .001) than WW. Maximal coupled and uncoupled SM mitochondrial respiration was strongly correlated with peripheral and hepatic IR (P < .01).

CONCLUSION

While BW without obesity had lower Rd than WW, race and obesity did not synergistically impact peripheral IR. Paradoxically, WW with obesity had greater hepatic IR compared to BW. Relationships between SM respiration and IR persisted across a range of body weights. These data provide support for therapies in BW, like exercise, that improve SM mitochondrial respiration to reduce IR and T2D risk.