Saturated hydrogen improves lipid metabolism disorders and dysbacteriosis induced by a high-fat diet

Studies have shown that metabolic diseases, such as obesity, are significantly associated with intestinal flora imbalance. The amplification of opportunistic pathogens induced by the glyoxylic acid cycle contributes to intestinal flora imbalance. Promising, though, is that saturated hydrogen can effectively improve the occurrence and development of metabolic diseases, such as obesity. However, the specific mechanism of how saturated hydrogen operates is still not very clear. In this study, after a high-fat diet, the level of total cholesterol, total glyceride, and low-density lipoprotein in the peripheral blood of mice increased, and that of high-density lipoprotein decreased. Intestinal fatty acid metabolism-related gene Apolipoprotein E (ApoE), fatty acid synthase (FAS), intestinal fatty acid-binding protein (I-FAPB), acetyl-CoA carboxylase 1 (ACC1), peroxisome proliferator-activated receptor γ (PPARγ), and stearoyl-CoA desaturase 1 (SCD1) increased significantly. Bacteroides, Bifidobacteria, and Lactobacillus counts in feces decreased considerably, while Enterobacter cloacae increased. The activity of isocitrate lyase in feces increased markedly. Treatment of mice with saturated hydrogen led to decreased total cholesterol, total glyceride, and low-density lipoprotein and increased high-density lipoprotein in the peripheral blood. FAS and I-FAPB gene expression in the small intestine decreased. Bacteroides, Bifidobacteria, and Lactobacillus in feces increased significantly, whereas Enterobacter cloacae decreased. The activity of isocitrate lyase also diminished remarkably. These results suggest that saturated hydrogen could improve intestinal structural integrity and lipid metabolism disorders by inhibiting the glyoxylic acid cycle of the intestinal flora. Impact statement Past studies have shown that hydrogen can improve metabolic disorders, but its mechanism of action remains unclear. It is well known that metabolic diseases, such as obesity, are significantly associated with changes in the intestinal flora. The glyoxylic acid cycle is an essential metabolic pathway in prokaryotes, lower eukaryotes, and plants and could be the portal for mechanisms related to metabolic disorders. Many opportunistic pathogenic bacteria can recycle fatty acids to synthesize sugars and other pathogenic substances using the glyoxylic acid cycle. So, the glyoxylic acid cycle may be involved in intestinal dysbacteriosis under high-fat diet. This study, therefore, seeks to provide the mechanism of how hydrogen improves metabolic diseases and a new basis for the use of hydrogen in the treatment of metabolic disorders.