Rethinking Bile Acid Metabolism and Signaling for Type 2 Diabetes Treatment

Reveal the mechanism of hepatic oxidative stress in mice induced by photo-oxidation milk using multi-omics analysis techniques

INTRODUCTION

Photo-oxidation is recognized as a contributor to the deterioration of milk quality, posing potential safety hazards to human health. However, there has been limited investigation into the impact of consuming photo-oxidized milk on health.

OBJECTIVES

This study employs multi-omics analysis techniques to elucidate the mechanisms by which photo-oxidized milk induces oxidative stress in the liver.

METHODS

Mouse model was used to determine the effect of the gavage administration of milk with varying degrees of photo-oxidation on the mouse liver. The damage degree was established by measuring serum markers indicative of oxidative stress, and with a subsequent histopathological examination of liver tissues. In addition, comprehensive metabolome, lipidome, and transcriptome analyses were conducted to elucidate the underlying molecular mechanisms of hepatic damage caused by photo-oxidized milk.

RESULTS

A significant elevation in the oxidative stress levels and the presence of hepatocellular swelling and inflammation subsequent to the gavage administration of photo-oxidized milk to mice. Significant alterations in the levels of metabolites such as lumichrome, all-trans-retinal, L-valine, phosphatidylglycerol, and phosphatidylcholine within the hepatic tissue of mice. Moreover, photo-oxidized milk exerted a pronounced detrimental impact on the glycerophospholipid metabolism of mice liver. The peroxisome proliferator-activated receptors (PPAR) signaling pathway enrichment appreciated in the animals that consumed photo-oxidized milk further supports the substantial negative influence of photo-oxidized milk on hepatic lipid metabolism. Gene set enrichment and interaction analyses revealed that photo-oxidized milk inhibited the cytochrome P450 pathway in mice, while also affecting other pathways associated with cellular stress response and lipid biosynthesis.

CONCLUSION

This comprehensive study provides significant evidence regarding the potential health risks associated with photo-oxidized milk, particularly in terms of hepatic oxidative damage. It establishes a scientific foundation for assessing the safety of such milk and ensuring the quality of dairy products.

Enhancing growth, liver health, and bile acid metabolism of tilapia (Oreochromis niloticus) through combined cholesterol and bile acid supplementation in plant-based diets

The present study aimed to compare the nutritional effects of cholesterol, bile acids, and combination of cholesterol with bile acids in plant-based diets on juvenile genetically improved farmed tilapia (GIFT; Oreochromis niloticus). The isonitrogenous (321 g/kg crude protein) and isolipidic (76 g/kg crude fat) diets (Con diet) were based on plant protein sources, which included corn gluten meal, soybean meal, cottonseed meal and rapeseed meal. The Con diet was supplemented with 12 g/kg cholesterol (CHO diet), 0.2 g/kg bile acids (BAs diet), a combination of 12 g/kg cholesterol and 0.2 g/kg bile acids (CHO-BAs diet), respectively. Each diet was fed to three tanks in an indoor recirculating aquaculture system for 9 weeks. Results showed that compared to the Con group, fish had a higher weight gain rate, hepatosomatic index, and a lower feed conversion ratio in the CHO-BAs group. The highest levels of whole-fish fat and ash were found in the Con group. Serum parameters, including activities of alanine aminotransferase (ALT) and aspartate transaminase (AST), along with levels of glucose (GLU) and triglyceride (TG) except for total cholesterol (TCHO), were lower in the CHO, BAs, and CHO-BAs groups than those in the Con group (P < 0.001). Histological examination revealed that fish in the Con group exhibited severe hepatocyte vacuolization and diminished hepatocyte proliferation. Gene expression analysis indicated that the transcriptional levels of bile acid metabolism-related genes (including fxr, fgf19, bsep) were up-regulated in the CHO-BAs group (P < 0.05), whereas cholesterol metabolism-related genes (acly and hmgcr) were down-regulated in both CHO and CHO-BAs groups (P < 0.001). Moreover, UPLC-MS/MS analysis revealed that the higher taurine-conjugated bile acids (T-BAs), followed by free bile acids (Free-BAs) and glycine (G-BAs) were determined in tilapia bile. Among these, taurochenodeoxycholic bile acid was the predominant bile acid. Dietary bile acids supplementation also increased the proportion of T-BAs (tauro β-muricholic acid and taurodehydrocholic acid) while decreasing Free-BAs in the fish bile. In conclusion, the incorporation of cholesterol with bile acids into plant-based diets can effectively reduce cholesterol uptake, suppress bile acids synthesis, enhance bile acids efflux, and promote hepatocyte proliferation, which is helpful for maintaining the normal liver morphology in tilapia, and thus improving its growth performance.

Small Intestinal Bacterial Overgrowth (SIBO) and Twelve Groups of Related Diseases-Current State of Knowledge

The human gut microbiota creates a complex microbial ecosystem, characterized by its high population density, wide diversity, and complex interactions. Any imbalance of the intestinal microbiome, whether qualitative or quantitative, may have serious consequences for human health, including small intestinal bacterial overgrowth (SIBO). SIBO is defined as an increase in the number of bacteria (103-105 CFU/mL), an alteration in the bacterial composition, or both in the small intestine. The PubMed, Science Direct, Web of Science, EMBASE, and Medline databases were searched for studies on SIBO and related diseases. These diseases were divided into 12 groups: (1) gastrointestinal disorders; (2) autoimmune disease; (3) cardiovascular system disease; (4) metabolic disease; (5) endocrine disorders; (6) nephrological disorders; (7) dermatological diseases; (8) neurological diseases (9); developmental disorders; (10) mental disorders; (11) genetic diseases; and (12) gastrointestinal cancer. The purpose of this comprehensive review is to present the current state of knowledge on the relationships between SIBO and these 12 disease groups, taking into account risk factors and the causal context. This review fills the evidence gap on SIBO and presents a biological-medical approach to the problem, clearly showing the groups and diseases having a proven relationship with SIBO, as well as indicating groups within which research should continue to be expanded.

Impacts of prothioconazole and prothioconazole-desthio on bile acid and glucolipid metabolism: Upregulation of CYP7A1 expression in HepG2 cells

As an efficient triazole fungicide, prothioconazole (PTC) is widely used for the prevention and control of plant fungal pathogens. It was reported that the residues of PTC and prothioconazole-desthio (PTC-d) have been detected in the environment and crops, and the effects of PTC-d may be higher than that of PTC. Currently, PTC and PTC-d have been proven to induce hepatic metabolic disorders. However, their toxic effects on cellular bile acid (BA) and glucolipid metabolism remain unknown. In this study, HepG2 cells were exposed to 1-500 μM of PTC or PTC-d. High concentrations of PTC and PTC-d were found to induce cytotoxicity; thus, subsequent experimental exposure was conducted at concentrations of 10-50 μM. The expression levels of CYP7A1 and TG synthesis-related genes and levels of TG and total BA were observed to increase in HepG2 cells. Molecular docking analysis revealed direct interactions between PTC or PTC-d and CYP7A1 protein. To further investigate the underlying mechanisms, PTC and PTC-d were treated to HepG2 cells in which CYP7A1 expression was knocked down using siCYP7A1. It was observed that PTC and PTC-d affected the BA metabolism process and regulated the glycolipid metabolism process by promoting the expression of CYP7A1. In summary, we comprehensively analyzed the effects and mechanisms of PTC and PTC-d on cellular metabolism in HepG2 cells, providing theoretical data for evaluating the safety and potential risks associated with these substances.

Zhuyu Pill Alleviates Nonalcoholic Fatty Liver Disease by Regulating Bile Acid Metabolism through the Gut-Liver Axis

AIM

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide, but there are currently limited treatment options available. Therefore, it is necessary to research new treatment strategies. Zhuyu Pill (ZYP) is a well-known herbal recipe consisting of Huanglian (Coptidis rhizoma) and Wuzhuyu (Evodiae Fructus) that has been clinically used to treat NAFLD. This study aimed to investigate the impact of ZYP on NAFLD induced by a high-fat diet (HFD) and to identify its potential mechanism.

METHODS

In this investigation, we used ZYP to treat a mouse model of NAFLD induced by an HFD. We conducted various analyses including assessment of serum biochemical indices, histological evaluation, fecal metabonomics analysis, western blot, and quantitative real-time polymerase chain reaction.

RESULTS

ZYP effectively improved blood lipid levels and reduced inflammatory response in HFD mice, while also alleviating liver cell damage and lipid accumulation. Additionally, ZYP influenced the fecal bile acid (BA) metabolism profiles of HFD mice by inhibiting the signal transduction of ileal farnesoid X receptor (FXR) fibroblast growth factor 15 (FGF15), enhancing the expression of cytochrome P450 family 7 subfamily A member 1(CYP7A1), promoting BA synthesis and increasing the metabolic elimination of cholesterol.

CONCLUSION

ZYP shows promise as a potential treatment for alleviating NAFLD by modulating BA metabolism through the FXR-FGF15-CYP7A1 pathway.

Sodium glucose co-transporter 2 (SGLT2) inhibition via dapagliflozin improves diabetic kidney disease (DKD) over time associatied with increasing effect on the gut microbiota in db/db mice

BACKGROUND

The intestinal microbiota disorder gradually aggravates during the progression of diabetes. Dapagliflozin (DAPA) can improve diabetes and diabetic kidney disease(DKD). However, whether the gut microbiota plays a role in the protection of DAPA for DKD remains unclear.

METHODS

To investigate the effects of DAPA on DKD and gut microbiota composition during disease progression, in our study, we performed 16S rRNA gene sequencing on fecal samples from db/m mice (control group), db/db mice (DKD model group), and those treated with DAPA (treat group) at three timepoints of 14weeks\18weeks\22weeks.

RESULTS

We found that DAPA remarkably prevented weight loss and lowered fasting blood glucose in db/db mice during disease progression, eventually delaying the progression of DKD. Intriguingly, the study strongly suggested that there is gradually aggravated dysbacteriosis and increased bile acid during the development of DKD. More importantly, comparisons of relative abundance at the phylum level and partial least squares-discriminant analysis (PLS-DA) plots roughly reflected that the effect of DAPA on modulating the flora of db/db mice increased with time. Specifically, the relative abundance of the dominant Firmicutes and Bacteroidetes was not meaningfully changed among groups at 14 weeks as previous studies described. Interestingly, they were gradually altered in the treat group compared to the model group with a more protracted intervention of 18 weeks and 22 weeks. Furthermore, the decrease of Lactobacillus and the increase of norank_f:Muribaculaceae could account for the differences at the phylum level observed between the treat group and the model group at 18 weeks and 22 weeks.

CONCLUSION

We firstly found that the protective effect of DAPA on DKD may be related to the dynamic improvement of the gut microbiota over time, possibly associated with the impact of DAPA on the bile acid pool and its antioxidation effect.

Show Me What You Have Inside-The Complex Interplay between SIBO and Multiple Medical Conditions-A Systematic Review

The microbiota, as a complex of microorganisms in a particular ecosystem, is part of the wider term-microbiome, which is defined as the set of all genetic content in the microbial community. Imbalanced gut microbiota has a great impact on the homeostasis of the organism. Dysbiosis, as a disturbance in bacterial balance, might trigger or exacerbate the course of different pathologies. Small intestinal bacterial overgrowth (SIBO) is a disorder characterized by differences in quantity, quality, and location of the small intestine microbiota. SIBO underlies symptoms associated with functional gastrointestinal disorders (FGD) as well as may alter the presentation of chronic diseases such as heart failure, diabetes, etc. In recent years there has been growing interest in the influence of SIBO and its impact on the whole human body as well as individual systems. Therefore, we aimed to investigate the co-existence of SIBO with different medical conditions. The PubMed database was searched up to July 2022 and we found 580 original studies; inclusion and exclusion criteria let us identify 112 eligible articles, which are quoted in this paper. The present SIBO diagnostic methods could be divided into two groups-invasive, the gold standard-small intestine aspirate culture, and non-invasive, breath tests (BT). Over the years scientists have explored SIBO and its associations with other diseases. Its role has been confirmed not only in gastroenterology but also in cardiology, endocrinology, neurology, rheumatology, and nephrology. Antibiotic therapy could reduce SIBO occurrence resulting not only in the relief of FGD symptoms but also manifestations of comorbid diseases. Although more research is needed, the link between SIBO and other diseases is an important pathway for scientists to follow.

Dietary regulations for microbiota dysbiosis among post-menopausal women with type 2 diabetes

Type 2 diabetes (T2D) and T2D-associated comorbidities, such as obesity, are serious universally prevalent health issues among post-menopausal women. Menopause is an unavoidable condition characterized by the depletion of estrogen, a gonadotropic hormone responsible for secondary sexual characteristics in women. In addition to sexual dimorphism, estrogen also participates in glucose-lipid homeostasis, and estrogen depletion is associated with insulin resistance in the female body. Estrogen level in the gut also regulates the microbiota composition, and even conjugated estrogen is actively metabolized by the estrobolome to maintain insulin levels. Moreover, post-menopausal gut microbiota is different from the pre-menopausal gut microbiota, as it is less diverse and lacks the mucolytic Akkermansia and short-chain fatty acid (SCFA) producers such as Faecalibacterium and Roseburia. Through various metabolites (SCFAs, secondary bile acid, and serotonin), the gut microbiota plays a significant role in regulating glucose homeostasis, oxidative stress, and T2D-associated pro-inflammatory cytokines (IL-1, IL-6). While gut dysbiosis is common among post-menopausal women, dietary interventions such as probiotics, prebiotics, and synbiotics can ease post-menopausal gut dysbiosis. The objective of this review is to understand the relationship between post-menopausal gut dysbiosis and T2D-associated factors. Additionally, the study also provided dietary recommendations to avoid T2D progression among post-menopausal women.

Metabolites of Gut Microbiota and Possible Implication in Development of Diabetes Mellitus

Diabetes mellitus is characterized by having a disorder of glucose metabolism. The types of diabetes mellitus include type 1 diabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus, and other specific types of diabetes mellitus. Many risk factors contribute to diabetes mellitus mainly including genetics, environment, obesity, and diet. In the recent years, gut microbiota has been shown to be linked to the development of diabetes. It has been reported that the gut microbiota composition of diabetic patients is different from that of healthy people. Although the mechanism behind the abnormality remains to be explored, most hypotheses focus on the inflammation response and leaky gut in relation to the changes in production of endotoxins and metabolites derived from the intestinal flora. Consequently, the above-mentioned abnormalities trigger a series of metabolic changes, gradually leading to development of hyperglycemia, insulin resistance, and diabetes. This review is (i) to summarize the differences in gut microbiota between diabetic patients and healthy people, (ii) to discuss the underlying mechanism(s) by which how lipopolysaccharide, diet, and metabolites of the gut microbiota affect diabetes, and (iii) to provide a new insight in the prevention and treatment of diabetes.

Investigation of dysregulated lipid metabolism in diabetic mice via targeted metabolomics of bile acids in enterohepatic circulation

RATIONALE

The mechanism of lipid metabolism disorder in type 2 diabetes (T2DM) remains unclear. This study aimed to reveal the mechanism underlying dysregulated lipid metabolism in T2DM through bile acid metabolism.

METHODS

A db/db mouse model was employed to investigate the alteration of bile acid profiles in T2DM. Ultrahigh-performance liquid chromatography with tandem mass spectrometry was used to quantify the detailed bile acid levels in each compartment of enterohepatic circulation. The pathological change of mouse liver was assessed by liver histology and serum biochemical assays. The expression level of bile acid-related transporters and synthases was measured with Western blot analysis.

RESULTS

The results showed that T2DM can result in severe liver fat accumulation and liver damage. In addition, compared to the control group, in T2DM mice, bile acid synthesis is reduced, while the level of bile acids is increased at the storage sites and the reabsorption sites, but there are subtle gender differences. Further, the ratio of conjugated bile acids in total bile acid in the liver of T2DM mice increased significantly relative to the control group for both female and male mice.

CONCLUSIONS

In T2DM, bile acid metabolism is disordered in both male and female mice, which could be the underlying mechanism of dysregulated lipid metabolism in T2DM.

Reductions in Intestinal Taurine-Conjugated Bile Acids and Short-Chain Fatty Acid-Producing Bacteria Might be Novel Mechanisms of Type 2 Diabetes Mellitus in Otsuka Long-Evans Tokushima Fatty Rats

BACKGROUND

The pathogenesis of spontaneously diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats, among the best models for human type 2 diabetes mellitus (T2DM), remains poorly defined. Therefore, we investigated the dynamic changes in taurine-conjugated bile acids (T-BAs) and intestinal microbiota during T2DM development in OLETF rats.

METHODS

OLETF rats and corresponding diabetes-resistant Long Evans Tokushima Otsuka (LETO) rats were fed a normal baseline diet. The progress of T2DM was divided into four phases, including normal glycemia-normal insulinemia (baseline), normal glycemia-hyperinsulinemia, impaired glucose tolerance, and DM. Body weight, liver function, blood lipids, fasting plasma glucose, fasting plasma insulin, fasting plasma glucagon-like peptide (GLP)-1 and GLP-2, serum and fecal T-BAs, and gut microbiota were analyzed during the entire course of T2DM development.

RESULTS

There were reductions in fecal T-BAs and short-chain fatty acids (SCFAs)-producing bacteria including Phascolarctobacterium and Lactobacillus in OLETF rats compared with those in LETO rats at baseline, and low levels of fecal T-BAs and SCFAs-producing bacteria were maintained throughout the whole course of the development of T2DM among OLETF rats compared with those in corresponding age-matched LETO rats. Fecal taurine-conjugated chenodeoxycholic acid correlated positively with Phascolarctobacterium. Fecal taurine-conjugated deoxycholic acid correlated positively with Lactobacillus and fasting plasma GLP-1 and inversely with fasting plasma glucose.

CONCLUSION

The fecal BAs profiles and microbiota structure among OLETF rats were different from those of LETO rats during the entire course of T2DM development, indicating that reductions in intestinal T-BAs and specific SCFA-producing bacteria may be potential mechanisms of T2DM in OLETF rats.

Flaxseed Powder Attenuates Non-Alcoholic Steatohepatitis via Modulation of Gut Microbiota and Bile Acid Metabolism through Gut-Liver Axis

Non-alcoholic steatohepatitis (NASH) is gradually becoming one of the most common and health-endangering diseases; therefore, it is very important to prevent the occurrence of NASH and prevent simple non-alcoholic fatty liver (NAFL) from further developing into NASH. We fed mice a high-fat diet (HFD, 60% fat) for 14 weeks to induce NAFL and then fed different doses of flaxseed powder (low (10%), middle (20%), and high (30%)) to the mice for 28 weeks. After the animal experiment, we analyzed fecal bile acid (BA) profiles of the HFD mice, flaxseed-fed (FLA-fed) mice, and control mice with a normal diet (10% fat) using a targeted metabolomics approach, and we analyzed the gut microbiota at the same time. We also investigated the mechanistic role of BAs in NASH and identified whether the altered BAs strongly bind to colonic FXR or TGR5. In the present study, we found that 28-week FLA treatment notably alleviated NASH development in NAFL model mice fed with an HFD, and the beneficial effects may be attributed to the regulation of and improvement in the gut flora- and microbiota-related BAs, which then activate the intestinal FXR-FGF15 and TGR5-NF-κB pathways. Our data indicate that FLA might be a promising functional food for preventing NASH through regulating microbiomes and BAs.

Role of Farnesoid X Receptor in the Pathogenesis of Respiratory Diseases

Farnesoid X receptor (FXR) is a bile acid receptor encoded by the Nr1h4 gene. FXR plays an important role in maintaining the stability of the internal environment and the integrity of many organs, including the liver and intestines. The expression of FXR in nondigestible tissues other than in the liver and small intestine is known as the expression of “nonclassical” bile acid target organs, such as blood vessels and lungs. In recent years, several studies have shown that FXR is widely involved in the pathogenesis of various respiratory diseases, such as chronic obstructive pulmonary disease, bronchial asthma, and idiopathic pulmonary fibrosis. Moreover, a number of works have confirmed that FXR can regulate the bile acid metabolism in the body and exert its anti-inflammatory and antifibrotic effects in the airways and lungs. In addition, FXR may be used as a potential therapeutic target for some respiratory diseases. For example, FXR can regulate the tumor microenvironment by regulating the balance of inflammatory and immune responses in the body to promote the occurrence and development of non-small-cell lung cancer (NSCLC), thereby being considered a potential target for immunotherapy of NSCLC. In this article, we provide an overview of the internal relationship between FXR and respiratory diseases to track the progress that has been achieved thus far in this direction and suggest potential therapeutic prospects of FXR in respiratory diseases.

TGR5 Signaling in Hepatic Metabolic Health

TGR5 is a G protein-coupled bile acid receptor that is increasingly recognized as a key regulator of glucose homeostasis. While the role of TGR5 signaling in immune cells, adipocytes and enteroendocrine L cells in metabolic regulation has been well described and extensively reviewed, the impact of TGR5-mediated effects on hepatic physiology and pathophysiology in metabolic regulation has received less attention. Recent studies suggest that TGR5 signaling contributes to improvements in hepatic insulin signaling and decreased hepatic inflammation, as well as metabolically beneficial improvements in bile acid profile. Additionally, TGR5 signaling has been associated with reduced hepatic steatosis and liver fibrosis, and improved liver function. Despite the beneficial effects of TGR5 signaling on metabolic health, TGR5-mediated gallstone formation and gallbladder filling complicate therapeutic targeting of TGR5 signaling. To this end, there is a growing need to identify cell type-specific effects of hepatic TGR5 signaling to begin to identify and target the downstream effectors of TGR5 signaling. Herein, we describe and integrate recent advances in our understanding of the impact of TGR5 signaling on liver physiology and how its effects on the liver integrate more broadly with whole body glucose regulation.

A Novel Synthetic Interfering Peptide Tat-3L4F Attenuates Olanzapine-Induced Weight Gain Through Disrupting Crosstalk Between Serotonin Receptor 2C and Protein Phosphatase and Tensin Homolog in Rats

BACKGROUND

Accompanied with profound efficacy, atypical antipsychotics (AAPs) contribute to metabolic adverse effects with few effective strategies to attenuate. Serotonin 5-HT2C receptor (HTR2C) plays a critical role in hyperphagia and weight gain induced by AAPs, and expression of phosphatase tensin homolog (PTEN) in the hypothalamus also affects feeding behavior and weight change. Moreover, PTEN has a physical crosstalk between PTEN and a region in the third intracellular loop (3L4F) of the HTR2C. Tat-3L4F has the property to disrupt crosstalk between PTEN and HTR2C. This is the first study to our knowledge to investigate the effect of Tat-3L4F on olanzapine-induced metabolic abnormalities and PTEN/ phosphatidylinositol 3-kinase/protein kinase B expression in the hypothalamus in rats.

METHODS

The effects of Tat-3L4F were investigated through measuring body weight, food intake, and blood glucose. In addition, PTEN/phosphatidylinositol 3-kinase/protein kinase B level in the hypothalamus was detected by immunofluorescence assay and western blot. Metabolites in the liver tissue were detected by liquid chromatography-mass spectrometry and analyzed by multivariate analyses and pairwise comparison.

RESULTS

Our results showed that hyperphagia and weight gain were evident in the olanzapine alone-fed rats but was attenuated after Tat-3L4F treatment. In addition, oral glucose tolerance test indicated blood glucose at 120 minutes was higher in the olanzapine alone-treated group than in groups treated with vehicle and olanzapine + Tat-3L4F (10 μmol kg-1 per day). Furthermore, compared with olanzapine alone treatment, treatment with Tat-3L4F (10 μmol kg-1 per day) significantly inhibited PTEN expression in the hypothalamus. The olanzapine alone-treated group had the highest bile acid level, followed by the olanzapine with Tat-3L4F (1 μmol kg-1) group, olanzapine with Tat-3L4F (10 μmol kg-1) group, and vehicle group.

CONCLUSIONS

Our present results reveal that Tat-3L4F is a potential pharmacological strategy for suppressing hyperphagia and weight gain induced by olanzapine, which acts through disrupting crosstalk between HTR2C and PTEN as a result of PTEN downregulation in the hypothalamus.

A Metabolic Insight Into the Neuroprotective Effect of Jin-Mai-Tong (JMT) Decoction on Diabetic Rats With Peripheral Neuropathy Using Untargeted Metabolomics Strategy

Jin-Mai-Tong (JMT) decoction is a traditional Chinese compound prescription for treating diabetic peripheral neuropathy (DPN). The aim of this study is to investigate the neuroprotective effect of JMT decoction on diabetic rats with peripheral neuropathy and to elucidate the potential mechanism based on a metabolomics approach. Sprague-Dawley (SD) rats were randomly divided into four groups: control group, Streptozotocin (STZ) induced model group, JMT low dose (JMT-L) treated group and JMT high dose (JMT-H) treated group. After 12 weeks of treatment, behavioral changes, small fiber loss, and histopathological damages of sciatic nerves were estimated. Serum samples were collected for untargeted metabolomics analysis based on UPLC/QTOF-MS and multivariate statistics. As a result, JMT treatment at two dosages (13.9 and 27.8 g/kg⋅d) evidently improved the mechanical pain threshold (P < 0.05), increased the intraepidermal nerve fiber density (IENFD) and subepidermal nerve fiber density (SNFD) (P < 0.05), and renovated the demyelination and axonal atrophy of sciatic nerves on DPN rats. Furthermore, metabolomics study revealed that the serum metabolic profiles altered significantly among the control group and the STZ-induced model group. A total of 21 metabolites were identified as potential biomarkers related to the therapeutic effect of JMT decoction. Among them, 16 biomarkers were found in both JMT-H and JMT-L treated groups, while the five others were specific to JMT-H group. These metabolites mainly involved in lipid metabolism, tricarboxylic acid (TCA) cycle, amino acid metabolism, and so on. Besides, correlation analysis indicated that both mechanical pain threshold and distal nerve fiber density were negatively correlated with the serum levels of metabolites from lipid metabolism and TCA cycle. In conclusion, the results demonstrated that JMT decoction has an obvious protective effect against DPN, which could be mediated via ameliorating the metabolic disorders in diabetic rats with peripheral neuropathy.

Mechanism of Dyslipidemia in Obesity-Unique Regulation of Ileal Villus Cell Brush Border Membrane Sodium-Bile Acid Cotransport

In obesity, increased absorption of dietary fat contributes to altered lipid homeostasis. In turn, dyslipidemia of obesity leads to many of the complications of obesity. Bile acids are necessary for the absorption of dietary fat. In the mammalian intestine, apical sodium-dependent bile acid cotransporter (ASBT; SLC10A2) is exclusively responsible for the reabsorption of bile acids in the terminal ileum. In rat and mice models of obesity and importantly in obese humans, ASBT was increased in ileal villus cells. The mechanism of stimulation of ASBT was secondary to an increase in ASBT expression in villus cell brush border membrane. The stimulation of ASBT was not secondary to the altered Na-extruding capacity of villus cells during obesity. Further, increased Farnesoid X receptor (FXR) expression in villus cells during obesity likely mediated the increase in ASBT. Moreover, enhanced FXR expression increased the expression of bile-acid-associated proteins (IBABP and OSTα) that are responsible for handling bile acids absorbed via ASBT in villus cells during obesity. Thus, this study demonstrated that in an epidemic condition, obesity, the dyslipidemia that leads to many of the complications of the condition, may, at least in part, be due to deregulation of intestinal bile acid absorption.

Metabolomics and Lipidomics Profiling Reveals Hypocholesterolemic and Hypolipidemic Effects of Arabinoxylan on Type 2 Diabetic Rats

Type 2 diabetes (T2D) is a pandemic disease chiefly characterized by hyperglycemia. In this study, the combination of serum lipidomic and metabolomic approach was employed to investigate the effect of arabinoxylan on type 2 diabetic rats and identify the critical biomarkers of T2D. Metabolomics analysis revealed that branched-chain amino acids, 12α-hydroxylated bile acids, ketone bodies, and several short- and long-chain acylcarnitines were significantly increased in T2D, whereas lysophosphatidylcholines (LPCs) were significantly decreased. Lipidomics analysis indicated T2D-related dyslipidemia was mainly associated with the increased levels of acetylcarnitine, free fatty acids (FFA), diacylglycerols, triacylglycerols, and cholesteryl esters and the decreased levels of some unsaturated phosphatidylcholines (less than 22 carbons). These variations indicated the disturbed amino acid and lipid metabolism in T2D, and the accumulation of incompletely oxidized lipid species might eventually contribute to impaired insulin action and glucose homeostasis. Arabinoxylan treatment decreased the concentrations of 12α-hydroxylated bile acids, carnitines, and FFAs and increased the levels of LPCs. The improved bile acid and lipid metabolism by arabinoxylan might be involved in the alleviation of hypercholesterolemia and hyperlipidemia in T2D.

Bile-ology: from bench to bedside

Bile acids (BAs) are originally known as detergents essential for the digestion and absorption of lipids. In recent years, extensive research has unveiled new functions of BAs as gut hormones that modulate physiological and pathological processes, including glucose and lipid metabolism, energy expenditure, inflammation, tumorigenesis, cardiovascular disease, and even the central nervous system in addition to cholesterol homeostasis, enterohepatic protection and liver regeneration. BAs are closely linked with gut microbiota which might explain some of their crucial roles in organs. The signaling actions of BAs can also be mediated through specific nuclear receptors and membrane-bound G protein-coupled receptors. Several pharmacological agents or bariatric surgeries have demonstrated efficacious therapeutic effects on metabolic diseases through targeting BA signaling. In this mini-review, we summarize recent advances in bile-ology, focusing on its translational studies.

A Possible Mechanism of Metformin in Improving Insulin Resistance in Diabetic Rat Models

BACKGROUND

Type 2 diabetes has become one of the most common diseases worldwide, causing a serious social burden. As a first-line treatment for diabetes, metformin can effectively improve insulin resistance. It has been reported that 12α-hydroxylated BA (mainly CA) is associated with insulin resistance. The purpose of this study was to analyze the changes in CA and possible signaling mechanisms in diabetic rats after metformin intervention.

METHODS

HepG2 cells were cultured after adding different concentrations of metformin. The cell viability was measured using CCK8 kit, and the expression of FXR, MAFG, and CYP8B1 in cells was detected by WB. The rat models of type 2 diabetes were induced by low-dose streptozotocin by feeding a high-fat diet, and the control rats (CON) were fed on normal food; the diabetic rats (DM) were given a high-fat diet without supplementation with metformin, while the metformin-treated diabetic rats (DM + MET) were given a high-fat diet and supplemented with metformin. Biochemical parameters were detected at the end of the test. Expression levels of FXR, CYP8B1, and MAFG were assessed by WB. Serum CA were measured using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

In HepG2 cells, metformin dose-dependently enhanced the transcriptional activity of FXR and MAFG and inhibited the expression of CYP8B1. Metformin-treated DM rats showed improved glucose and bile acid metabolism. In addition, significantly increased FXR and MAFG and decreased CYP8B1 were observed in DM + MET rats. At the same time, the CA content of metformin-treated rats was lower than that of diabetic rats.

CONCLUSION

Changes in CA synthesis after metformin treatment may be associated with inhibition of CYP8B1. These results may play an important role in improving insulin sensitivity after metformin treatment.

Microbiome and diabetes: Where are we now?

Alterations in the diversity or structure of gut microbiota known as dysbiosis, may affect metabolic activities, resulting in metabolic disorders, such as obesity and diabetes. The development of more sophisticated methods, such as metagenomics sequencing, PCR-denaturing gradient gel electrophoresis, microarrays and fluorescence in situ hybridization, has expanded our knowledge on gut microbiome. Dysbiosis has been related to increased plasma concentrations of gut microbiota-derived lipopolysaccharide (LPS), which triggers the production of a variety of cytokines and the recruitment of inflammatory cells. Metabolomics have demonstrated that butyrate and propionate suppress weight gain in mice with high fat diet-induced obesity, and acetate has been proven to reduce food intake in healthy mice. The role of prebiotics, probiotics, genetically modified bacteria and fecal microbiota transplantation, as potential therapeutic challenges for type 2 diabetes will be discussed in this review.

Scutellariae Radix and Coptidis Rhizoma Improve Glucose and Lipid Metabolism in T2DM Rats via Regulation of the Metabolic Profiling and MAPK/PI3K/Akt Signaling Pathway

Aim Scutellariae Radix (SR) and Coptidis Rhizoma (CR) have often been combined to cure type 2 diabetes mellitus (T2DM) in the clinical practice for over thousands of years, but their compatibility mechanism is not clear. Mitogen-activated protein kinase (MAPK) signaling pathway has been suggested to play a critical role during the process of inflammation, insulin resistance, and T2DM. This study was designed to investigate their compatibility effects on T2DM rats and explore the underlying mechanisms by analyzing the metabolic profiling and MAPK/PI3K/Akt signaling pathway. Methods The compatibility effects of SR and CR were evaluated with T2DM rats induced by a high-fat diet (HFD) along with a low dose of streptozocin (STZ). Ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was performed to discover potential biomarkers. The levels of pro-inflammatory cytokines; biochemical indexes in serum, and the activities of key enzymes related to glycometabolism in liver were assessed by ELISA kits. qPCR was applied to examine mRNA levels of key targets in MAPK and insulin signaling pathways. Protein expressions of p65; p-p65; phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K); phosphorylated-PI3K (p-PI3K); protein kinase B (Akt); phosphorylated Akt (p-Akt) and glucose transporter 2 (Glut2) in liver were investigated by Western blot analysis. Results Remarkably, hyperglycaemia, dyslipidemia, inflammation, and insulin resistance in T2DM were ameliorated after oral administration of SR and CR, particularly their combined extracts. The effects of SR, CR, low dose of combined extracts (LSC) and high dose of combined extracts (HSC) on pro-inflammatory cytokine transcription in T2DM rats showed that the MAPK pathway might account for the phenomenon with down-regulation of MAPK (P38 mitogen-activated protein kinases (P38), extracellular regulated protein kinases (ERK), and c-Jun N-terminal kinase (JNK)) mRNA, and protein reduction in p-P65. While mRNA levels of key targets such as insulin receptor substrate 1 (IRS1), PI3K, Akt2, and Glut2 in the insulin signaling pathway were notably up-modulated, phosphorylations of PI3K, Akt, and expression of Glut2 were markedly enhanced. Moreover, the increased activities of phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase (FBPase), glucose 6-phosphatase (G6Pase), and glycogen phosphorylase (GP) were highly reduced and the decreased activities of glucokinase (GK), phosphofructokinase (PFK), pyruvate kinase (PK), and glycogen synthase (GS) in liver were notably increased after treatment. Further investigation indicated that the metabolic profiles of plasma and urine were clearly improved in T2DM rats. Fourteen potential biomarkers (nine in plasma and five in urine) were identified. After intervention, these biomarkers returned to normal level to some extent. Conclusion The results showed that SR, CR, and combined extract groups were normalized. The effects of combined extracts were more remarkable than single herb treatment. Additionally, this study also showed that the metabonomics method is a promising tool to unravel how traditional Chinese medicines work.