SIRT1 mRNA Expression May Be Associated With Energy Expenditure and Insulin Sensitivity

Abstract

Objective: Sirtuin 1 (SIRT1) is implicated in the regulation of mitochondrial function, energy metabolism, and insulin sensitivity in rodents. No studies are available in humans to demonstrate that SIRT1 expression in insulin-sensitive tissues is associated with energy expenditure and insulin sensitivity. Research Design and Methods: Energy expenditure (EE), insulin sensitivity, and SIRT1 mRNA adipose tissue expression (n = 81) were measured by indirect calorimetry, hyperinsulinemic-euglycemic clamp, and quantitative RT-PCR in 247 nondiabetic offspring of type 2 diabetic patients. Results: High EE during the clamp (r = 0.375, P = 2.8 × 10\(^{−9}\)) and high \(\Delta\)EE (EE during the clamp − EE in the fasting state) (r = 0.602, P = 2.5 × 10\(^{−24}\)) were associated with high insulin sensitivity. Adipose tissue SIRT1 mRNA expression was significantly associated with EE (r = 0.289, P = 0.010) and with insulin sensitivity (r = 0.334, P = 0.002) during hyperinsulinemic-euglycemic clamp. Furthermore, SIRT1 mRNA expression correlated significantly with the expression of several genes regulating mitochondrial function and energy metabolism (e.g., peroxisome proliferator–activated receptor \(\gamma\) coactivator-1\(\beta\), estrogen-related receptor \(\alpha\), nuclear respiratory factor-1, and mitochondrial transcription factor A), and with several genes of the respiratory chain (e.g., including NADH dehydrogenase [ubiquinone] 1\(\alpha\) subcomplex 2, cytochrome c, cytochrome c oxidase subunit IV, and ATP synthase). Conclusions: Impaired stimulation of EE by insulin and low SIRT1 expression in insulin-sensitive tissues is likely to reflect impaired regulation of mitochondrial function associated with insulin resistance in humans.