Background

Obesity and mitochondrial dysfunction are related factors contributing to metabolic disease development, but it is unknown if these relationships differ by sex. We determined whether in vivo and ex vivo bioenergetic indexes are associated with body composition and fat distribution in males and females.

Methods

This pilot study included 34 healthy adults: 19 females, median age 27 y/o and 15 males, median age 31 y/o. Body composition and fat distribution were assessed by dual energy x-ray absorptiometry. Ex vivo mitochondrial function was assessed in isolated monocytes using a Seahorse extracellular flux analyzer based on spare respiratory capacity (SRC). Maximum in vivo ATP synthesis was assessed in the quadriceps using 31P-magnetic resonance spectroscopy based on the phosphocreatine recovery time constant (tPCr) following standardized leg exercise. Lower SRC and higher tPCr values reflect impaired mitochondrial function. Spearman correlations were performed with alpha=0.05.

Results

In males, body fat percent (BF%) and fat mass were inversely correlated with monocyte SRC (r= -0.63; p=0.01 and r= -0.61; p=0.02, respectively). In females, visceral fat (VF) was inversely correlated to SRC (r= -0.54; p=0.03). Skeletal muscle tPCr was positively associated with BF% (r=0.68, p=0.04), fat mass (r=0.7, p=0.04), and VF (r=0.73, p=0.02) in males but was not significantly associated with body composition in females. BF% was inversely associated with ATP maximal production in both males (r= –0.81, p=0.01) and females (r= -0.64, p<0.01). In males, but not females, VF was inversely associated with ATP maximal production (males, r= -0.79, p=0.02).

Conclusions

These novel findings demonstrate differential associations of cellular and muscular mitochondrial function impairment by sex and adipose tissue location. Increased understanding of these relationships may inform interventions that target specific fat depots for men and women to improve mitochondrial energy metabolism and reduce disease risk.