Role of cystathionine β-synthase in modulating NO and H₂S signaling under metabolic stress in obesity-driven endothelial dysfunction

: Cystathionine β-synthase (CBS), a hydrogen sulfide (H₂S)-producing enzyme, plays a role in maintaining vascular homeostasis through its dual function of generating H₂S and nitric oxide (NO) within the endothelium. Here, we investigated the role of the CBS/H₂S/NO axis under metabolic stress, using both an in vitro model of lipid overload and an in vivo model of high-fat diet (HFD)-induced obesity. Bovine aortic endothelial cells (BAEC) exposed to sodium palmitate (NaP) exhibited impaired NO signaling, accompanied by increased oxidative stress, as evidenced by elevated reactive oxygen species production and upregulation of Nox4 expression, along with activation of the unfolded protein response, an index of endoplasmic reticulum stress. In parallel, a downregulation of CBS expression and H₂S levels was found. Similarly to NaP, CBS silencing was associated with an impairment in NO signaling, supporting its role in endothelial function. The exogenous source of H2S reversed NaP-induced damage in BAEC. Extending these findings in vivo, HFD-fed mice developed metabolic dysfunction in terms of HOMA, insulin resistance, and hyperlipidaemia. This was associated with disrupted NO signaling and increased H₂S levels in the aorta. The rise in H2S serves as a protective response to oxidative stress induced by HFD. Collectively, these findings demonstrated a crucial role for endothelial CBS in modulating the interplay between H₂S and NO in metabolic stress associated with obesity. Targeting CBS to enhance both H₂S and NO bioavailability can represent a novel therapeutic approach in obesity-related endothelial dysfunction.