Rebalancing glucolipid metabolism and gut microbiome dysbiosis by nitrate-dependent alleviation of high-fat diet-induced obesity

Introduction: High-fat diet (HFD)-induced obesity is accompanied by compromised nitric oxide (NO) signaling and gut microbiome dysregulation. Inorganic dietary nitrate, which acts as a NO donor, exerts beneficial effects on metabolic disorders. Here, we evaluated the effects of dietary nitrate on HFD-induced obesity and provided insights into the underlying mechanism.

Research design and methods: To investigate the preventive effect of dietary nitrate on HFD-induced obesity, C57BL/6 mice were randomly assigned into four groups (n=10/group), including normal control diet group (normal water and chow diet), HFD group (normal water and HFD), HFD+NaNO₃ group (water containing 2 mM NaNO₃ and HFD), and HFD+NaCl group (water containing 2 mM NaCl and HFD). During the experiment, body weight was monitored and glucolipid metabolism was evaluated. The mechanism underlying the effects of nitrate on HFD-induced obesity was investigated by the following: the NO₃ ^--NO₂ ^--NO pathway; endothelial NO synthase (eNOS) and cyclic guanosine monophosphate (cGMP) levels; gut microbiota via 16SRNA analysis.

Results: Dietary nitrate reduced the body weight gain and lipid accumulation in adipose and liver tissues in HFD-fed mice. Hyperlipidemia and insulin resistance caused by HFD were improved in mice supplemented with nitrate. The level of eNOS was upregulated by nitrate in the serum, liver, and inguinal adipose tissue. Nitrate, nitrite, and cGMP levels were decreased in mice fed on HFD but reversed in the HFD+NaNO₃ group. Nitrate also rebalanced the colon microbiota and promoted a normal gut microbiome profile by partially attenuating the impacts of HFD. Bacteroidales S24-7, Alistipes, Lactobacillus, and Ruminococcaceae abundances were altered, and Bacteroidales S24-7 and Alistipes abundances were higher in the HFD+NaNO₃ group than that in the HFD group.

Conclusions: Inorganic dietary nitrate alleviated HFD-induced obesity and ameliorated disrupted glucolipid metabolism via NO₃ ^--NO₂ ^--NO pathway activation and gut microbiome modulation.

Keywords: metabolic disorders; microbiology; nitrate; obesity.