Matched Analysis of Circulating and Adipose Tissue SIRT1 Protein Level in Human Obesity

Background/Objectives: Mammalian sirtuins (SIRTs) are evolutionarily conserved proteins that are epigenetically involved in biological processes such as metabolism and longevity. SIRT1 expression is reduced in metabolic disorders and in complicated diseases such as obesity. However, whether the SIRT1 level in subcutaneous adipose tissue (SAT) matches with its circulating form in obesity is unknown. The aim of our study is to evaluate SIRT1 derived from SAT and plasma of the same subject in individuals with and without obesity to assess whether plasma measurements may provide clinically significant information. Methods: Eleven subjects with obesity (BMI ≥ 30 kg/m²) and six controls without the disease (BMI < 30 kg/m²) were enrolled, and SIRT1 was measured in SAT and plasma by ELISA. Anthropometric parameters, glycemia and transaminases were also assessed. Results: Patients with obesity showed similar levels of SIRT1 in SAT and plasma (1.28 ± 0.45 and 1.9 ± 0.25 ng/mL, respectively, p = 0.243). Patients without obesity showed higher SIRT1 levels in SAT than in plasma (4.19 ± 1.33 and 1.06 ± 0.12 ng/mL, respectively, p = 0.039). An inverse correlation between SAT-derived SIRT1 and BMI was found (r = -0.632, p = 0.007). Conclusions: In this pilot study, our results show that the plasma SIRT1 levels substantially reflect those of SAT in patients with obesity. Given the metabolic role of SIRT1, further comprehensive investigations in larger longitudinal cohorts are needed to support plasma SIRT1 as an eligible diagnostic tool for stratifying metabolic risk associated with fat mass expansion in obesity.