Trimethylamine N-oxide (TMAO) drives cardiac aging in mice by activating NLRP3-mediated pyroptosis

Cardiac aging is a significant health challenge, often leading to conditions like diastolic dysfunction and cardiac fibrosis, which contribute to heart failure. Current therapeutic strategies primarily manage symptoms, leaving a gap in targeting the fundamental mechanisms of age-related cardiac decline. Trimethylamine N-oxide (TMAO), a gut microbiota-derived metabolite, has emerged as a cardiovascular risk factor, but its direct role and precise molecular mechanisms in the context of cardiac aging have remained largely unexplored. This study aimed to investigate if TMAO contributes to cardiac aging and to elucidate the underlying NLRP3-mediated pyroptosis pathway.

Researchers utilized male C57BL/6J mice, dividing them into four age groups (3, 12, 18, and 24 months) to characterize age-related changes in cardiac function. To test TMAO's role, 8-week-old mice received intraperitoneal injections of TMAO (dose not specified) for 1-3 months. To inhibit TMAO production, 15-month-old mice were given 3,3-dimethyl-1-butanol (DMB, dose not specified) in drinking water for 3 months. Additionally, Gasdermin D (GSDMD) knockout mice were employed to confirm the involvement of pyroptosis. Key measurements included cardiac function, senescence markers, oxidative stress levels, and protein expression of pyroptosis components via assays like ELISA and Western blot.

Plasma TMAO levels progressively increased with age in mice, showing a strong correlation with the upregulation of cardiac senescence markers, the development of diastolic dysfunction, increased cardiac fibrosis, and elevated plasma brain natriuretic peptide levels. TMAO treatment in younger mice significantly accelerated cardiac aging.

Starting from 2 months of TMAO treatment, impairment of cardiac diastolic function and progression of cardiac fibrosis were observed, alongside a notable upregulation of senescence marker proteins. Mechanistically, TMAO was found to promote cardiac oxidative stress and activate the NLRP3-mediated pyroptosis pathway. Crucially, genetic ablation of GSDMD completely abolished TMAO-associated cardiac aging, confirming the central role of pyroptosis. Furthermore, pharmacological inhibition of TMAO production in aged mice successfully attenuated oxidative stress, suppressed NLRP3-mediated pyroptosis activation, and significantly alleviated markers of cardiac aging.