Abstract P174: Sex Differences In The Pro-hypertensive Effect Of Carnitine, The Precursor Of Gut-derived Metabolite TMAO

Abstract

Recent evidence reports sexually divergent mechanisms that differentially drive the severity of hypertension. Our data show that female Dahl Salt-Sensitive (SS) rats are significantly protected from salt-induced hypertension and renal injury and have stark differences in gut microbiota composition compared to males. Gut-derived metabolites are increasingly being recognized as mechanistic links between the gut microbiota and hypertension. One such metabolite is trimethylamine N-oxide (TMAO), which is derived from the bacterial metabolism of carnitine and is gaining notoriety for its role in cardiovascular disease. Metabolomics analysis in high salt-fed SS rats revealed a trend for increased TMAO (1.3-fold, p=0.11) in the serum of males compared to females (n=6). TMAO appears to be specifically derived from gut bacteria since oral antibiotic treatment nearly eliminated circulating TMAO levels in both males and females (99.3% and 88.9% reduction, respectively; p<0.001). Interestingly, antibiotic treatment reduced salt-sensitive hypertension in males but not females. There was also a corresponding increase in the TMAO precursor carnitine (1.9-fold, p<0.01) in the serum of males versus females. Thus, we hypothesized that administration of carnitine (400 mg/kg/day) in the drinking water would exacerbate salt-sensitive hypertension, renal damage, and gut inflammation in male and female SS rats challenged with high salt (4% NaCl). There was a trend for carnitine treatment to exacerbate mean arterial pressure in both males (160±9 vs 146±2 mmHg, n=4-6, p=0.22) and females (155±6 vs 139±2 mmHg, n=2, p=0.14) compared to vehicle. Despite elevated pressure in both sexes, carnitine-treated males exhibited greater increases in albuminuria (340±136 vs 194±29 mg/day, carnitine vs vehicle, p=0.28) than females (55±33 vs 26±5 mg/day). Carnitine treatment also significantly increased the number of CD3+ T cells in the colonic lamina propria (24.3±6.0 vs 2.4±0.5 x 10 6 cells/g tissue, n=5, p<0.05) of male rats compared to vehicle. Together, these data identify gut microbiota-mediated carnitine/TMAO metabolism as a potentially detrimental pathway that promotes greater salt-sensitivity, renal damage, and gut inflammation in males versus females.