Role of gut metabolism of adrenal corticosteroids and hypertension: clues gut-cleansing antibiotics give us.

Intestinal bacteria can metabolize sterols, bile acids, steroid hormones, dietary proteins, fiber, foodstuffs, and short chain fatty acids. The metabolic products generated by some of these intestinal bacteria have been linked to a number of systemic diseases including obesity with Type 2 diabetes mellitus, some forms of inflammation, and more recently, systemic hypertension. In this review, we primarily focus on the potential role selected gut bacteria play in metabolizing the endogenous glucocorticoids corticosterone and cortisol. Those generated steroid metabolites, when reabsorbed in the intestine back into the circulation, produce biological effects most notably as inhibitors of 11β-hydroxysteroid dehydrogenase (11β-HSD) types 1 and 2. Inhibition of the dehydrogenase actions of 11β-HSD, particularly in kidney and vascular tissue, allows both corticosterone and cortisol the ability to bind to and activate mineralocorticoid receptors with attended changes in sodium handling and vascular resistance leading to increases in blood pressure. In several animal models of hypertension, administration of gut-cleansing antibiotics results in transient resolution of hypertension and transfer of intestinal contents from a hypertensive animal to a normotensive animal produces hypertension in the recipient. Moreover, fecal samples from hypertensive humans transplanted into germ-free mice resulted in hypertension in the recipient mice. Thus, it appears that the intestinal microbiome may not just be an innocent bystander but certain perturbations in the type and number of bacteria may directly or indirectly affect hypertension and other diseases.