Abstract
Accumulating evidences suggested an association between gut microbiome dysbiosis and impaired glycemic control. Ginsenoside Rb1 (Rb1) is a biologically active substance of ginseng, which serves anti-diabetic effects. However, its working mechanism especially interaction with gut microbes remains elusive in detail. In this study, we investigated the impact of Rb1 oral supplementation on high fat diet (HFD) induced obesity mice, and explored its mechanism in regulating blood glucose. The results showed that higher liver weight and lower cecum weight were observed in HFD fed mice, which was maintained by Rb1 administration. In addition, Rb1 ameliorated HFD induced blood lipid abnormality and improved insulin sensitivity. Several mRNA expressions in the liver were measured by quantitative real-time PCR, of which UCP2, Nr1H4, and Fiaf were reversed by Rb1 treatment. 16S rRNA sequencing analysis indicated that Rb1 significantly altered gut microbiota composition and increased the abundance of mucin-degrading bacterium Akkermansia spp. compared to HFD mice. As suggested via functional prediction, amino acid metabolism was modulated by Rb1 supplementation. Subsequent serum amino acids investigation indicated that several diabetes associated amino acids, like branched-chain amino acids, tryptophan and alanine, were altered in company with Rb1 supplementation. Moreover, correlation analysis firstly implied that the circulation level of alanine was related to Akkermansia spp.. In summary, Rb1 supplementation improved HFD induced insulin resistance in mice, and was associated with profound changes in microbial composition and amino acid metabolism.
Highlights
The prevalence of overweight and obesity is increasing at an alarming rate and is a leading risk factor for diseases such as diabetes, non-alcoholic fatty liver disease (NAFLD), and a plethora of cardiovascular diseases (CVD) (Kusminski, et al, 2016; Yoon et al, 2021)
Contrasted with NC group, impaired glucose control and insulin resistance as well as higher liver TG, serum LDL-c, HDL-c, fasting glucose and free fatty acids were observed in mice fed with high fat diet (HFD) (Figure 2)
Rb1-treated mice reduced serum fasting glucose, LDL-c and free fatty acid but increased HDL-c compared to HFD group (Figures 2B–E)
Summary
The prevalence of overweight and obesity is increasing at an alarming rate and is a leading risk factor for diseases such as diabetes, non-alcoholic fatty liver disease (NAFLD), and a plethora of cardiovascular diseases (CVD) (Kusminski, et al, 2016; Yoon et al, 2021). Some bacterial species like Akkermansia spp. were considered as probiotics and put into great hopes to be developed as new agents for the treatment of metabolic syndrome (Anhe et al, 2015; Plovier et al, 2017; Barcena et al, 2019). Their effects may be mediated partly through the metabolome, such as short chain fatty acid (SCFA), bile acids, amino acids (AAs), trimethylamine N-oxide, and so on. Maintaining BCAAs balance is effective and beneficial to the modulation of metabolic syndrome
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