Microbial and Transcriptomic Profiling Reveals Diet-Related Alterations of Metabolism in Metabolic Disordered Mice

Succinic Acid Improves the Metabolism of High-Fat Diet-Induced Mice and Promotes White Adipose Browning

Succinic acid plays a crucial role as an essential intermediate in the mitochondrial tricarboxylic acid cycle in mitochondria. In recent years, growing evidence has supported the the important role of succinic acid in fat metabolism. Therefore, we aimed to investigate the effects of succinic acid on adipose tissue metabolism and insulin sensitivity in high-fat diet (HFD)-induced obese mice and try to explore its potential mechanism. We found that the addition of succinic acid (40 mM) to drinking water inhibited the hypertrophy of inguinal white adipose tissue (iWAT) in HFD-induced mice. Furthermore, succinic acid supplementation enhanced insulin sensitivity and improved their glucose tolerance in obese mice. Interestingly, succinic acid supplementation improved lipid metabolism in HFD-fed mice, as shown by decreased serum levels of TG, TC, LDL-C, and increased HDL-C. In addition, succinic acid supplementation increased the expression of browning markers and mitochondria-related genes in iWAT. Further studies showed that the addition of succinic acid to drinking water promotes the browning of iWAT by activating the PI3K-AKT/MAPK signaling pathway. These results suggest that succinic acid has the potential to be used as an effective component for dietary intervention and may, therefore, play an important role in ameliorating and preventing obesity and associated metabolic diseases caused by HFD.

Zhi-Kang-Yin formula attenuates high-fat diet-induced metabolic disorders through modulating gut microbiota-bile acids axis in mice

BACKGROUND

Metabolic disorders have become one of the global medical problems. Due to the complexity of its pathogenesis, there is still no effective treatment. Bile acids (BAs) and gut microbiota (GM) have been proved to be closely related to host metabolism, which could be important targets for metabolic disorders. Zhi-Kang-Yin (ZKY) is a traditional Chinese medicine (TCM) formula developed by the research team according to theory of TCM and has been shown to improve metabolism in clinic. However, the underlying mechanisms are unclear.

AIM OF THE STUDY

This study aimed to investigate the potential mechanisms of the beneficial effect of ZKY on metabolism.

METHODS

High-fat diet (HFD)-fed mice were treated with and without ZKY. The glucose and lipid metabolism-related indexes were measured. BA profile, GM composition and hepatic transcriptome were then investigated to analyze the changes of BAs, GM, and hepatic gene expression. Moreover, the relationship between GM and BAs was identified with functional gene quantification and ex vivo fermentation experiment.

RESULTS

ZKY reduced weight gain and lipid levels in both liver and serum, attenuated hepatic steatosis and improved glucose tolerance in HFD-fed mice. BA profile detection showed that ZKY changed the composition of BAs and increased the proportion of unconjugated BAs and non-12-OH BAs. Hepatic transcriptomic analysis revealed fatty acid metabolism and BA biosynthesis related pathways were regulated. In addition, ZKY significantly changed the structure of GM and upregulated the gene copy number of bacterial bile salt hydrolase. Meanwhile, ZKY directly promoted the growth of Bifidobacterium, which is a well-known bile salt hydrolase-producing genus. The ex vivo co-culture experiment with gut microbiota and BAs demonstrated that the changes of BAs profile in ZKY group were mediated by ZKY-shifted GM, which led to increased expression of genes associated with fatty acid degradation in the liver.

CONCLUSION

Our study indicated that the effect of ZKY on improving metabolism is associated with the modulation of GM-BAs axis, especially, by upregulating the abundance of bile salt hydrolase-expression bacteria and increasing the levels of unconjugated BAs. This study indicates that GM-BAs axis might be an important pathway for improving metabolic disorders by ZKY.

Chrysanthemum morifolium Ramat extract and probiotics combination ameliorates metabolic disorders through regulating gut microbiota and PPARα subcellular localization

BACKGROUND

Chrysanthemum morifolium Ramat, a traditional Chinese medicine, has the effects on liver clearing, vision improving, and anti-inflammation. C. morifolium and probiotics have been individually studied for their beneficial effects on metabolic diseases. However, the underlying molecular mechanisms were not completely elucidated. This study aims to elucidate the potential molecular mechanisms of C. morifolium and probiotics combination (CP) on alleviating nonalcoholic fatty liver disease (NAFLD) and the dysregulation of glucose metabolism in high-fat diet (HFD)-fed mice.

METHODS

The therapeutic effect of CP on metabolism was evaluated by liver histology and serum biochemical analysis, as well as glucose tolerance test. The impact of CP on gut microbiota was analyzed by 16S rRNA sequencing and fecal microbiota transplantation. Hepatic transcriptomic analysis was performed with the key genes and proteins validated by RT-qPCR and western blotting. In addition, whole body Pparα knockout (Pparα-/-) mice were used to confirm the CP-mediated pathway.

RESULTS

CP supplementation ameliorated metabolic disorders by reducing body weight and hepatic steatosis, and improving glucose intolerance and insulin resistance in HFD fed mice. CP intervention mitigated the HFD-induced gut microbiota dysbiosis, which contributed at least in part, to the beneficial effect of improving glucose metabolism. In addition, hepatic transcriptomic analysis showed that CP modulated the expression of genes associated with lipid metabolism. CP downregulated the mRNA level of lipid droplet-binding proteins, such as Cidea and Cidec in the liver, leading to more substrates for fatty acid oxidation (FAO). Meanwhile, the expression of CPT1α, the rate-limiting enzyme of FAO, was significantly increased upon CP treatment. Mechanistically, though CP didn't affect the total PPARα level, it promoted the nuclear localization of PPARα, which contributed to the reduced expression of Cidea and Cidec, and increased expression of CPT1α, leading to activated FAO. Moreover, whole body PPARα deficiency abolished the anti-NAFLD effect of CP, suggesting the importance of PPARα in CP-mediated beneficial effect.

CONCLUSION

This study revealed the hypoglycemic and hepatoprotective effect of CP by regulating gut microbiota composition and PPARα subcellular localization, highlighting its potential for therapeutic candidate for metabolic disorders.

High Fat Diet and High Sucrose Intake Divergently Induce Dysregulation of Glucose Homeostasis through Distinct Gut Microbiota-Derived Bile Acid Metabolism in Mice

A high calorie diet such as excessive fat and sucrose intake is always accompanied by impaired glucose homeostasis such as T2DM (type 2 diabetes mellitus). However, it remains unclear how fat and sucrose individually affect host glucose metabolism. In this study, mice were fed with high fat diet (HFD) or 30% sucrose in drinking water (HSD) for 24 weeks, and glucose metabolism, gut microbiota composition, as well as bile acid (BA) profile were investigated. In addition, the functional changes of HFD or HSD-induced gut microbiota were further verified by fecal microbiota transplantation (FMT) and ex vivo culture of gut bacteria with BAs. Our results showed that both HFD and HSD caused dysregulated lipid metabolism, while HFD feeding had a more severe effect on impaired glucose homeostasis, accompanied by reduced hyocholic acid (HCA) levels in all studied tissues. Meanwhile, HFD had a more dramatic influence on composition and function of gut microbiota based on α diversity indices, β diversity analysis, as well as the abundance of secondary BA producers than HSD. In addition, the phenotypes of impaired glucose homeostasis and less formation of HCA caused by HFD can be transferred to recipient mice by FMT. Ex vivo culture with gut bacteria and BAs revealed HFD-altered gut bacteria produced less HCA than HSD, which might closely associate with reduced relative abundance of C7 epimerase-coding bacteria g_norank/unclassified_f_Eggerthellaceae and bile salt hydrolase-producing bacteria Lactobacillus and Bifidobacterium in HFD group. Our findings revealed that the divergent effects of different high-calorie diets on glucose metabolism may be due to the gut microbiota-mediated generation and metabolism of BAs, highlighting the importance of dietary management in T2DM.

Exploring the potential mechanism of Rubus corchorifolius L. fruit polyphenol-rich extract in mitigating non-alcoholic fatty liver disease by integration of metabolomics and transcriptomics profiling

Nonalcoholic fatty liver disease (NAFLD), as the commonest chronic liver disease, is accompanied by liver oxidative stress and inflammatory responses. Herein, the extract obtained from Rubus corchorifolius fruits was purified and characterized for its polyphenol composition. The liver protective effect of the purified R. corchorifolius fruit extract (RCE) on mice with high-fat-diet (HFD)-induced NAFLD were investigated, and the potential mechanisms were explored through the integration of transcriptomics and metabolomics. Results showed that the polyphenolic compounds in RCE mainly included (-)-epigallocatechin, procyanidin B2, keracyanin, vanillin, dihydromyricetin, and ellagic acid. In addition, RCE intervention ameliorated liver and mitochondrial damage, which was evidenced by decreased indices of oxidative stress, liver function markers, and lipid profile levels. The liver metabonomics research revealed that RCE intervention affected the metabolic pathways of metabolites, including linoleic acid metabolism, galactose metabolism, alanine, aspartate and glutamate metabolism, retinol metabolism, glycine, serine and threonine metabolism, tryptophan metabolism, aminoacyl-tRNA biosynthesis, riboflavin metabolism, starch and sucrose metabolism, and arachidonic acid metabolism. Additionally, liver transcriptomics research indicated that pathways like fatty acid degradation, circadian rhythm, valine, leucine and isoleucine degradation, primary bile acid biosynthesis, cytokine-cytokine receptor interaction, adipocytokine signaling pathway, glutathione metabolism, lipid and atherosclerosis were significantly enriched. The transcriptomics and metabolomics analysis demonstrated that RCE intervention had significant modulatory effects on the metabolic pathways associated with glycolipid metabolism. Moreover, RT-PCR results verified that RCE intervention regulated liver mRNA levels associated with the inflammatory response. Therefore, our findings suggest that the intake of RCE might be an effective strategy to alleviate liver damage.