Effects of tauroursodeoxycholic acid on glucose homeostasis: Potential binding of this bile acid with the insulin receptor

Intestinal flora and bile acid interactions impact the progression of diabetic kidney disease

In recent years, with the rapid development of omics technologies, researchers have shown that interactions between the intestinal flora and bile acids are closely related to the progression of diabetic kidney disease (DKD). By regulating bile acid metabolism and receptor expression, the intestinal flora affects host metabolism, impacts the immune system, and exacerbates kidney injury in DKD patients. To explore interactions among the gut flora, bile acids and DKD, as well as the related mechanisms, in depth, in this paper, we review the existing literature on correlations among the gut flora, bile acids and DKD. This review also summarizes the efficacy of bile acids and their receptors as well as traditional Chinese medicines in the treatment of DKD and highlights the unique advantages of bile acid receptors in DKD treatment. This paper is expected to reveal a new and important potential strategy for the clinical treatment of DKD.

The gut microbiota intervenes in glucose tolerance and inflammation by regulating the biosynthesis of taurodeoxycholic acid and carnosine

Objective

This study aims to investigate the pathogenesis of hyperglycemia and its associated vasculopathy using multiomics analyses in diabetes and impaired glucose tolerance, and validate the mechanism using the cell experiments.

Methods

In this study, we conducted a comprehensive analysis of the metagenomic sequencing data of diabetes to explore the key genera related to its occurrence. Subsequently, participants diagnosed with impaired glucose tolerance (IGT), and healthy subjects, were recruited for fecal and blood sample collection. The dysbiosis of the gut microbiota (GM) and its associated metabolites were analyzed using 16S rDNA sequencing and liquid chromatograph mass spectrometry, respectively. The regulation of gene and protein expression was evaluated through mRNA sequencing and data-independent acquisition technology, respectively. The specific mechanism by which GM dysbiosis affects hyperglycemia and its related vasculopathy was investigated using real-time qPCR, Western blotting, and enzyme-linked immunosorbent assay techniques in HepG2 cells and neutrophils.

Results

Based on the published data, the key alterable genera in the GM associated with diabetes were identified as Blautia, Lactobacillus, Bacteroides, Prevotella, Faecalibacterium, Bifidobacterium, Ruminococcus, Clostridium, and Lachnoclostridium. The related metabolic pathways were identified as cholate degradation and L-histidine biosynthesis. Noteworthy, Blautia and Faecalibacterium displayed similar alterations in patients with IGT compared to those observed in patients with diabetes, and the GM metabolites, tauroursodeoxycholic acid (TUDCA) and carnosine (CARN, a downstream metabolite of histidine and alanine) were both found to be decreased, which in turn regulated the expression of proteins in plasma and mRNAs in neutrophils. Subsequent experiments focused on insulin-like growth factor-binding protein 3 and interleukin-6 due to their impact on blood glucose regulation and associated vascular inflammation. Both proteins were found to be suppressed by TUDCA and CARN in HepG2 cells and neutrophils.

Conclusion

Dysbiosis of the GM occurred throughout the entire progression from IGT to diabetes, characterized by an increase in Blautia and a decrease in Faecalibacterium, leading to reduced levels of TUDCA and CARN, which alleviated their inhibition on the expression of insulin-like growth factor-binding protein 3 and interleukin-6, contributing to the development of hyperglycemia and associated vasculopathy.

Bile acid metabolism in health and ageing-related diseases

Bile acids (BAs) have surpassed their traditional roles as lipid solubilizers and regulators of BA homeostasis to emerge as important signalling molecules. Recent research has revealed a connection between microbial dysbiosis and metabolism disruption of BAs, which in turn impacts ageing-related diseases. The human BAs pool is primarily composed of primary BAs and their conjugates, with a smaller proportion consisting of secondary BAs. These different BAs exert complex effects on health and ageing-related diseases through several key nuclear receptors, such as farnesoid X receptor and Takeda G protein-coupled receptor 5. However, the underlying molecular mechanisms of these effects are still debated. Therefore, the modulation of signalling pathways by regulating synthesis and composition of BAs represents an interesting and novel direction for potential therapies of ageing-related diseases. This review provides an overview of synthesis and transportion of BAs in the healthy body, emphasizing its dependence on microbial community metabolic capacity. Additionally, the review also explores how ageing and ageing-related diseases affect metabolism and composition of BAs. Understanding BA metabolism network and the impact of their nuclear receptors, such as farnesoid X receptor and G protein-coupled receptor 5 agonists, paves the way for developing therapeutic agents for targeting BA metabolism in various ageing-related diseases, such as metabolic disorder, hepatic injury, cardiovascular disease, renal damage and neurodegenerative disease.

Tauroursodeoxycholic Acid (TUDCA) Relieves Streptozotocin (STZ)-Induced Diabetic Rat Model via Modulation of Lipotoxicity, Oxidative Stress, Inflammation, and Apoptosis

Tauroursodeoxycholic acid (TUDCA) is approved for the treatment of liver diseases. However, the antihyperglycemic effects/mechanisms of TUDCA are still less clear. The present study aimed to evaluate the antidiabetic action of TUDCA in streptozotocin (STZ)-induced type 2 diabetes mellitus (T2DM) in rats. Fifteen adult Wistar albino male rats were randomly divided into three groups (n = five in each): control, diabetic (STZ), and STZ+TUDCA. The results showed that TUDCA treatment significantly reduced blood glucose, HbA1c%, and HOMA-IR as well as elevated the insulin levels in diabetic rats. TUDCA therapy increased the incretin GLP-1 concentrations, decreased serum ceramide synthase (CS), improved the serum lipid profile, and restored the glycogen content in the liver and skeletal muscles. Furthermore, serum inflammatory parameters (such as TNF-α, IL-6, IL-1ß, and PGE-2) were substantially reduced with TUDCA treatment. In the pancreas, STZ+TUDCA-treated rats underwent an obvious enhancement of enzymatic (CAT and SOD) and non-enzymatic (GSH) antioxidant defense systems and a marked decrease in markers of the lipid peroxidation rate (MDA) and nitrosative stress (NO) compared to STZ-alone. At the molecular level, TUDCA decreased the pancreatic mRNA levels of iNOS and apoptotic-related factors (p53 and caspase-3). In conclusion, TUDCA may be useful for diabetes management and could be able to counteract diabetic disorders via anti-hyperlipidemic, antioxidant, anti-inflammatory, and anti-apoptotic actions.

Isomers-oriented separation of forty-five plasma bile acids with liquid chromatography-tandem mass spectrometry

Some bile acids (BAs) were considered as biomarkers or have therapeutical effect on metabolic diseases. However, due to the existence of isomers and limitations in sensitivity, simultaneous quantification of multiple BAs remains a challenge. The aim of this study is to establish an accurate and sensitive method for the determination of multiple BAs with similar polarity. A LC-MS/MS analytical method capable of quantifying forty-five BAs simultaneously using nine stable isotope internal standards was developed and fully validated based on key isomers-oriented separation strategy. The method was further applied to analyze plasma samples to describe the dynamic profile of BAs after high glucose intake. The chromatography and mass spectrum conditions were optimized to enable the accurate quantification of forty-five BAs, while ensuring the lower limit of quantification between 0.05-10 ng/mL. The results of system suitability, linearity, dilution integrity, accuracy and precision demonstrated the good quantitative capacity and robustness of the method. A total of thirty-five BAs were quantified in plasma samples from twelve healthy Chinese individuals. The established method featured superior sensitivity and better separation efficiency compared to previous studies. Meanwhile, BAs exhibited correlations with glucose and insulin, suggesting their potential as biomarkers for metabolic disorders.

Research progress on the relationship between bile acid metabolism and type 2 diabetes mellitus

Bile acids, which are steroid molecules originating from cholesterol and synthesized in the liver, play a pivotal role in regulating glucose metabolism and maintaining energy balance. Upon release into the intestine alongside bile, they activate various nuclear and membrane receptors, influencing crucial processes. These bile acids have emerged as significant contributors to managing type 2 diabetes mellitus, a complex clinical syndrome primarily driven by insulin resistance. Bile acids substantially lower blood glucose levels through multiple pathways: BA-FXR-SHP, BA-FXR-FGFR15/19, BA-TGR5-GLP-1, and BA-TGR5-cAMP. They also impact blood glucose regulation by influencing intestinal flora, endoplasmic reticulum stress, and bitter taste receptors. Collectively, these regulatory mechanisms enhance insulin sensitivity, stimulate insulin secretion, and boost energy expenditure. This review aims to comprehensively explore the interplay between bile acid metabolism and T2DM, focusing on primary regulatory pathways. By examining the latest advancements in our understanding of these interactions, we aim to illuminate potential therapeutic strategies and identify areas for future research. Additionally, this review critically assesses current research limitations to contribute to the effective management of T2DM.

The Potential of Bile Acids as Biomarkers for Metabolic Disorders

Bile acids (BAs) are well known to facilitate the absorption of dietary fat and fat-soluble molecules. These unique steroids also function by binding to the ubiquitous cell membranes and nuclear receptors. As chemical signals in gut-liver axis, the presence of metabolic disorders such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus (T2DM), and even tumors have been reported to be closely related to abnormal levels of BAs in the blood and fecal metabolites of patients. Thus, the gut microbiota interacting with BAs and altering BA metabolism are critical in the pathogenesis of numerous chronic diseases. This review intends to summarize the mechanistic links between metabolic disorders and BAs in gut-liver axis, and such stage-specific BA perturbation patterns may provide clues for developing new auxiliary diagnostic means.

Metabolic perturbations in pregnant rats exposed to low-dose perfluorooctanesulfonic acid: An integrated multi-omics analysis

Emerging epidemiological evidence has linked per- and polyfluoroalkyl substances (PFAS) exposure could be linked to the disturbance of gestational glucolipid metabolism, but the toxicological mechanism is unclear, especially when the exposure is at a low level. This study examined the glucolipid metabolic changes in pregnant rats treated with relatively low dose perfluorooctanesulfonic acid (PFOS) through oral gavage during pregnancy [gestational day (GD): 1-18]. We explored the molecular mechanisms underlying the metabolic perturbation. Oral glucose tolerance test (OGTT) and biochemical tests were performed to assess the glucose homeostasis and serum lipid profiles in pregnant Sprague-Dawley (SD) rats randomly assigned to starch, 0.03 and 0.3 mg/kg·bw·d groups. Transcriptome sequencing combined with non-targeted metabolomic assays were further performed to identify differentially altered genes and metabolites in the liver of maternal rats, and to determine their correlation with the maternal metabolic phenotypes. Results of transcriptome showed that differentially expressed genes at 0.03 and 0.3 mg/kg·bw·d PFOS exposure were related to several metabolic pathways, such as peroxisome proliferator-activated receptors (PPARs) signaling, ovarian steroid synthesis, arachidonic acid metabolism, insulin resistance, cholesterol metabolism, unsaturated fatty acid synthesis, bile acid secretion. The untargeted metabolomics identified 164 and 158 differential metabolites in 0.03 and 0.3 mg/kg·bw·d exposure groups, respectively under negative ion mode of Electrospray Ionization (ESI-), which could be enriched in metabolic pathways such as α-linolenic acid metabolism, glycolysis/gluconeogenesis, glycerolipid metabolism, glucagon signaling pathway, glycine, serine and threonine metabolism. Co-enrichment analysis indicated that PFOS exposure may disturb the metabolism pathways of glycerolipid, glycolysis/gluconeogenesis, linoleic acid, steroid biosynthesis, glycine, serine and threonine. The key involved genes included down-regulated Ppp1r3c and Abcd2, and up-regulated Ogdhland Ppp1r3g, and the key metabolites such as increased glycerol 3-phosphate and lactosylceramide were further identified. Both of them were significantly associated with maternal fasting blood glucose (FBG) level. Our findings may provide mechanistic clues for clarifying metabolic toxicity of PFOS in human, especially for susceptible population such as pregnant women.

Effects of Tauroursodeoxycholic Acid and 4-Phenylbutyric Acid on Selenium Distribution in Mice Model with Type 1 Diabetes

The effect of selenium on diabetes is significant. As pharmaceutical chaperones, tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA) can effectively improve the oxidative stress of the endoplasmic reticulum. This study established a mice model with type 1 diabetes (T1D) to evaluate the effects of pharmaceutical chaperones on selenium distribution. Streptozotocin was used to induce Friend virus B-type mice to establish a T1D mice model. Mice were administered with TUDCA or 4-PBA. Selenium levels in different tissues were measured by inductively coupled plasma-mass spectroscopy (ICP-MS). After treatment with TUDCA and 4-PBA, related laboratory findings such as glucose and glycated serum protein were significantly reduced and were closer to normal levels. At 2 weeks, 4-PBA normalized selenium levels in the heart, and 4-PBA and TUDCA maintained the selenium in the liver, kidney, and muscle at normal. At 2 months, 4-PBA and TUDCA maintained the selenium in the heart, liver, and kidney at normal levels. The serum selenium had a positive correlation with zinc and copper in the diabetes group and the control group, while the serum selenium had no significant association with magnesium and calcium at 2 weeks and 2 months. TUDCA and 4-PBA have crucial effects on selenium distribution in diabetic mice, and further research is needed to research their internal mechanisms.

Insights by which TUDCA is a potential therapy against adiposity

Adipose tissue is an organ with metabolic and endocrine activity. White, brown and ectopic adipose tissues have different structure, location, and function. Adipose tissue regulates energy homeostasis, providing energy in nutrient-deficient conditions and storing it in high-supply conditions. To attend to the high demand for energy storage during obesity, the adipose tissue undergoes morphological, functional and molecular changes. Endoplasmic reticulum (ER) stress has been evidenced as a molecular hallmark of metabolic disorders. In this sense, the ER stress inhibitor tauroursodeoxycholic acid (TUDCA), a bile acid conjugated to taurine with chemical chaperone activity, has emerged as a therapeutic strategy to minimize adipose tissue dysfunction and metabolic alterations associated with obesity. In this review, we highlight the effects of TUDCA and receptors TGR5 and FXR on adipose tissue in the setting of obesity. TUDCA has been demonstrated to limit metabolic disturbs associated to obesity by inhibiting ER stress, inflammation, and apoptosis in adipocytes. The beneficial effect of TUDCA on perivascular adipose tissue (PVAT) function and adiponectin release may be related to cardiovascular protection in obesity, although more studies are needed to clarify the mechanisms. Therefore, TUDCA has emerged as a potential therapeutic strategy for obesity and comorbidities.

Tauroursodeoxycholic acid functions as a critical effector mediating insulin sensitization of metformin in obese mice

Metformin is widely used to surmount insulin resistance (IR) and type 2 diabetes. Accumulating evidence suggests that metformin may improve IR through regulating gut microbiota and bile acids. However, the underlying mechanisms remain unclear. Our metabolomic analysis showed that metformin significantly increased the accumulation of tauroursodeoxycholic acid (TUDCA) in intestine and liver from high-fat diet (HFD)-induced IR mice. TUDCA also alleviated IR, and reduced oxidative stress and intestinal inflammation in ob/ob mice. TUDCA blocked KEAP1 to bind with Nrf2, resulting in Nrf2 translocation into nuclear and initiating the transcription of antioxidant genes, which eventually reduced intracellular ROS accumulation and improved insulin signaling. Analysis of gut microbiota further revealed that metformin reduced the relative abundance of Bifidobacterium, which produces bile salt hydrolase (BSH). The reduction in BSH was probably crucial for the accumulation of TUDCA. Metformin also increased the proportion of Akkermanisia muciniphlia in gut microbiota of ob/ob mice via TUDCA. These beneficial effects of metformin in remodeling gut microbiota, reducing oxidative stress and improving insulin sensitivity were partly due to the accumulation of TUDCA, suggesting that TUDCA may be a potential therapy for metabolic syndrome.

Bile acids-gut microbiota crosstalk contributes to the improvement of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) occurs that cannot effectively use the insulin. Insulin Resistance (IR) is a significant characteristic of T2DM which is also an essential treatment target in blood glucose regulation to prevent T2DM and its complications. Bile acids (BAs) are one group of bioactive metabolites synthesized from cholesterol in liver. BAs play an important role in mutualistic symbiosis between host and gut microbiota. It is shown that T2DM is associated with altered bile acid metabolism which can be regulated by gut microbiota. Simultaneously, BAs also reshape gut microbiota and improve IR and T2DM in the bidirectional communications of the gut-liver axis. This article reviewed the findings on the interaction between BAs and gut microbiota in improving T2DM, which focused on gut microbiota and its debinding function and BAs regulated gut microbiota through FXR/TGR5. Meanwhile, BAs and their derivatives that are effective for improving T2DM and other treatments based on bile acid metabolism were also summarized. This review highlighted that BAs play a critical role in the glucose metabolism and may serve as therapeutic targets in T2DM, providing a reference for discovering and screening novel therapeutic drugs.