Suppression of high-fat-diet-induced obesity in mice by dietary folic acid supplementation is linked to changes in gut microbiota.

PURPOSE: To investigate whether the effects of dietary folic acid supplementation on body weight gain are mediated by gut microbiota in obesity.
METHODS: Male C57 BL/6J conventional (CV) and germ-free (GF) mice both aged three to four weeks were fed a high-fat diet (HD), folic acid-deficient HD (FD-HD), folic acid-supplement HD (FS-HD) and a normal-fat diet (ND) for 25 weeks. Faecal microbiota were analyzed by 16S rRNA high-throughput sequencing, and the mRNA expression of genes was determined by the real-time RT-PCR. Short-chain fatty acids (SCFAs) in faeces and plasma were measured using gas chromatography-mass spectrometry.
RESULTS: In CV mice, HD-induced body weight gain was inhibited by FS-HD, accompanied by declined energy intake, smaller white adipocyte size, and less whitening of brown adipose tissue. Meanwhile, the HD-induced disturbance in the expression of fat and energy metabolism-associated genes (Fas, Atgl, Hsl, Ppar-α, adiponectin, resistin, Ucp2, etc.) in epididymal fat was diminished, and the dysbiosis in faecal microbiota was lessened, by FS-HD. However, in GF mice with HD feeding, dietary folic acid supplementation had almost no effect on body weight gain and the expression of fat- and energy-associated genes. Faecal or plasma SCFA concentrations in CV and GF mice were not altered by either FD-HD or FS-HD feeding.
CONCLUSION: Dietary folic acid supplementation differently affected body weight gain and associated genes' expression under HD feeding between CV and GF mice, suggesting that gut bacteria might partially share the responsibility for beneficial effects of dietary folate on obesity.