Colonic expression of calcium transporter TRPV6 is regulated by dietary sodium butyrate

Dietary fibers have been shown to increase the intestinal absorption of calcium (Ca²⁺) and magnesium (Mg²⁺). However, the mechanisms that explain the enhanced electrolyte absorption remain unknown. Therefore, this study aims to investigate the short-term and long-term effects of 5% (w/w) sodium butyrate (Na-butyrate), an important end-metabolite of bacterial fermentation of dietary fibers, on Ca²⁺ and Mg²⁺ homeostasis in mice. Serum Ca²⁺ levels were only significantly increased in mice treated with Na-butyrate for 1 day. This was associated with a twofold increase in the mRNA expression levels of Trpv6 in the proximal and distal colon. Contrary, Na-butyrate did not affect serum Mg²⁺ concentrations at either of the intervention periods. However, we observed a reduction in urinary Mg²⁺ excretion, although not significantly, after 1 day of treatment. A significant reduction of 2.5-fold in urinary Mg²⁺ excretion was observed after 14 days of treatment. Indeed, 14-day Na-butyrate supplementation increased colonic Trpm7 expression by 1.2-fold compared to control mice. In conclusion, short-term Na-butyrate supplementation increases serum Ca²⁺ levels in mice. This was associated with increased mRNA expression levels of Trpv6 in the colon, suggesting that Na-butyrate regulates the expression of genes involved in active intestinal Ca²⁺ absorption.