Exogenous H₂S reduces the acetylation levels of mitochondrial respiratory enzymes via regulating the NAD⁺-SIRT3 pathway in cardiac tissues of <i>db/db</i> mice

Abstract

Hydrogen sulfide (H₂S), a gaseous molecule, is involved in modulating multiple physiological functions, such as antioxidant, antihypertension, and the production of polysulfide cysteine. H₂S may inhibit reactive oxygen species generation and ATP production through modulating respiratory chain enzyme activities; however, the mechanism of this effect remains unclear. In this study, <i>db/db</i> mice, neonatal rat cardiomyocytes, and H9c2 cells treated with high glucose, oleate, and palmitate were used as animal and cellular models of type 2 diabetes. The mitochondrial respiratory rate, respiratory chain complex activities, and ATP production were decreased in <i>db/db</i> mice compared with those in <i>db/db</i> mice treated with exogenous H₂S. Liquid chromatography with tandem mass spectrometry analysis showed that the acetylation level of proteins involved in the mitochondrial respiratory chain were increased in the <i>db/db</i> mice hearts compared with those with sodium hydrosulfide (NaHS) treatment. Exogenous H₂S restored the ratio of NAD⁺/NADH, enhanced the expression and activity of sirtuin 3 (SIRT3) and decreased mitochondrial acetylation level in cardiomyocytes under hyperglycemia and hyperlipidemia. As a result of SIRT3 activation, acetylation of the respiratory complexe enzymes NADH dehydrogenase 1 (ND1), ubiquinol cytochrome <i>c</i> reductase core protein 1, and ATP synthase mitochondrial F1 complex assembly factor 1 was reduced, which enhanced the activities of the mitochondrial respiratory chain activity and ATP production. We conclude that exogenous H₂S plays a critical role in improving cardiac mitochondrial function in diabetes by upregulating SIRT3.