Probiotics Shield Aging Hearts by Cutting Oxidative Stress and Boosting Sirt1

Cardiovascular disease is the leading age-related cause of death, and oxidative stress is a central driver of cardiac aging. As the global population ages, finding accessible, low-risk interventions that can slow heart deterioration is increasingly urgent. The gut-heart axis — the bidirectional communication between gut microbiota and cardiac tissue via metabolites like short-chain fatty acids and bile acids — offers a promising therapeutic target. Gut dysbiosis accelerates with age and contributes to systemic inflammation and oxidative burden, making probiotics an attractive candidate for cardioprotection.

This study from Babol University of Medical Sciences used a well-established D-galactose (D-gal) mouse model of accelerated aging. Male BALB/c mice received daily subcutaneous D-gal injections (100 mg/kg) for eight weeks to induce oxidative cardiac damage, while simultaneously receiving oral supplementation with L. casei (2×10⁹ CFU/mL), B. breve (2×10⁹ CFU/mL), or their combination at the same dose. A saline-plus-probiotic-mix control group confirmed baseline safety. Heart tissue was assessed histologically (H&E and Mallory trichrome staining), biochemically (MDA and GSH levels), and at the gene expression level (Sirt1 via qRT-PCR).

D-gal treatment produced pronounced myocardial pathology: vascular and capillary congestion, immune cell infiltration, interstitial edema, cardiomyocyte hypertrophy and hypochromia, and perivascular fibrosis. All probiotic interventions partially reversed these changes. L. casei monotherapy significantly reduced congestion (p<0.01 vs. D-gal+saline). The combination therapy significantly reduced both inflammation and edema/cardiomyocyte damage scores (p<0.05 and p<0.01, respectively). Cardiac fibrosis, assessed by trichrome staining, was most effectively attenuated by L. casei monotherapy and the combination, while B. breve alone showed only modest anti-fibrotic effects.

Biochemically, D-gal elevated MDA and suppressed GSH in heart tissue — classic markers of oxidative stress. Probiotic treatment, especially the combination, significantly reversed both. Crucially, D-gal also suppressed cardiac Sirt1 mRNA expression; all probiotic groups restored Sirt1 levels, with the combination again showing the greatest upregulation. Sirt1 is a NAD+-dependent deacetylase that regulates cardiac energy metabolism, suppresses cardiomyocyte apoptosis, and confers resistance to hypertrophic and oxidative stresses — making its restoration particularly meaningful for cardiac longevity.

These findings collectively suggest that probiotic supplementation — particularly multi-strain combinations — can meaningfully attenuate age-related cardiac remodeling through antioxidant, anti-inflammatory, and epigenetic (Sirt1) mechanisms. While the study is preclinical, it builds a mechanistic rationale for human trials targeting the gut-heart axis in older adults at cardiovascular risk.