Sex differences in muscle SIRT1 and SIRT3 and exercise plus weight loss effects on muscle sirtuins

The sirtuins, SIRT1 and SIRT3, are involved in the control of cellular processes to maintain metabolic homeostasis. The purpose of this study was to determine the effects of a 6-month aerobic training + weight loss program and hyperinsulinemia on SIRT1 and SIRT3 expression in skeletal muscle and to compare their expression between men and women. Thirty-five adult men (n = 18) and postmenopausal women (n = 17), (X +/- SEM, age: 61 +/- 1 years, BMI: 31.3 +/- 0.7 kg/m(2)) completed 6 months 3x/week of aerobic exercise and 1x/week dietary instruction to induce weight loss (EX + WL). Participants had a VO(2)max test, vastus lateralis muscle biopsies at baseline and 2 h into a hyperinsulinemic-euglycemic clamp, a total body dual-energy X-ray absorptiometry scan, and abdominal computed tomography scan. Skeletal muscle SIRT1, SIRT3, and PGC1-alpha mRNA expression were quantified by qRT-PCR. Skeletal muscle SIRT1 and SIRT3 mRNA expression are higher in women than men (P < 0.005). Body weight, body fat, and abdominal obesity decreased and VO(2)max and glucose utilization (M) increased after EX + WL (P < 0.001). Basal SIRT1 decreased following EX + WL (P < 0.05). This change in basal SIRT1 was not related to changes in VO(2)max, M or fat mass, nor was it different by gender. Insulin stimulation increased SIRT1 expression (P < 0.001) and PGC1-alpha expression (P < 0.01) following EX + WL (insulin-basal post). Sex differences in the levels of these sirtuins did not affect changes with EX + WL. Skeletal muscle SIRT1 decreases after a long-term combined exercise and weight loss program in middle-aged and older adults.

Automated summary

This study aimed to determine the effects of a 6-month aerobic training + weight loss program and hyperinsulinemia on SIRT1 and SIRT3 expression in skeletal muscle and compare their expression between men and women. The results showed higher mRNA expression of SIRT1 and SIRT3 in women's skeletal muscle. After EX + WL, body weight, body fat, and abdominal obesity decreased, VO(2)max and glucose utilization increased, and basal SIRT1 expression decreased. However, there was no gender difference in the changes of these sirtuins.