Mechanism of glucose-lowering by metformin in type 2 diabetes: Role of bile acids

Influence of gut bile acid composition on the glucose-lowering effect and safety of metformin

AIMS

This study evaluates how changes in intestinal bile acid composition, induced by cholestyramine, a bile acid sequestrant, affect metformin's pharmacodynamics (PD).

METHODS

An open-label, 2-period 1-sequence crossover study was conducted with healthy male adults. Each period consisted of both before and after metformin treatments. Cholestyramine was administered during the second period to change the bile acid pool. For, PD assessment, an oral glucose tolerance test was conducted at each treatment in both periods. Metformin was administered 3 times during each period, and cholestyramine was administered 3 times per day for 7 days during the second period. Maximum serum glucose concentration, area under the glucose concentration curve and homeostatic model assessment of insulin resistance were calculated. Baseline-corrected PD parameters were derived by subtracting pre-metformin values from post-metformin values. Lipid and panels and bile acid profiles in stool were measured. Adverse events were monitored throughout the study.

RESULTS

Fourteen subjects completed the study. The mean values of 3 PD parameters were all decreased after metformin administration in both periods. Cholestyramine administration led to a further decrease in baseline-corrected PD parameters, significantly reducing the area under the glucose concentration curve by 44.7%. Diarrhoea, the most common adverse event, was reported in 10 subjects during the metformin alone treatment and in 1 subject during the cholestyramine combined treatment (P < .01).

CONCLUSION

Cholestyramine affected the glucose-lowering effect of metformin by the possible change in the bile acid pool in the gut, and metformin-associated diarrhoea was improved by cholestyramine.

Differential effects of imeglimin and metformin on insulin and incretin secretion-An exploratory randomized controlled trial

AIMS

Imeglimin is a new oral anti-diabetic drug with a similar structure to that of metformin; however, unlike metformin, clinical trials indicate that imeglimin elicits its glucose-lowering effect mainly by enhancement of insulin secretion. The comparative effects of the two drugs on incretin secretion remains to be elucidated.

MATERIALS AND METHODS

A single-center, open-label, randomized controlled trial was conducted in patients with type 2 diabetes who were drug-naïve or were on a single oral hypoglycaemic agent (OHA). For patients taking a single OHA, an 8-week washout period was employed before randomization. Participants were randomized to the imeglimin group (IME, 2000 mg/day) or the metformin group (MET, 1000 mg/day), and OGTT was performed before treatment and after 12 and 24 weeks of treatment.

RESULTS

The reduction in HbA1c at 24 weeks was similar in IME and MET. OGTT revealed a comparable decrease in post-challenge blood glucose excursion in both groups, but insulin levels were increased only in IME. Total and active glucagon-like peptide-1 (GLP-1) levels were increased in both IME and MET; however, total and active glucose-dependent insulinotropic peptide (GIP) levels were increased only in IME. Interestingly, while an increase in insulin levels in IME was positively correlated with an increase in GLP-1 at 12 weeks, it was correlated only with an increase in GIP at 24 weeks.

CONCLUSIONS

Unlike metformin, imeglimin enhances GIP secretion as well as GLP-1 secretion, in addition to its direct insulinotropic mechanism of glucose control, emphasizing its potential as a therapeutic option in the treatment of patients with diabetes.

Non-Linear Dose-Response Relationship for Metformin in Japanese Patients With Type 2 Diabetes: Analysis of Irregular Longitudinal Data by Interpretable Machine Learning Models

The dose-response relationship between metformin and change in hemoglobin A1c (HbA1c) shows a maximum at 1500-2000 mg/day in patients with type 2 diabetes (T2D) in the U.S. In Japan, there is little evidence on the HbA1c-lowering effect of high-dose metformin because the maintenance and maximum doses of metformin were raised in 2010. The aim of this study was to investigate whether there is saturation of the dose-response relationship for metformin in Japanese T2D patients. Longitudinal clinical information of T2D patients was extracted from electronic medical records. Supervised machine learning models with random effect were constructed to predict change in HbA1c: generalized linear mixed-effects models (GLMM) with/without a feature selection and combining tree-boosting with Gaussian process and mixed-effects models (GPBoost). GPBoost was interpreted by SHapley Additive exPlanations (SHAP) and partial dependence. GPBoost had better predictive performance than GLMM with/without feature selection: root mean square error was 0.602 (95%CI 0.523-0.684), 0.698 (0.629-0.774) and 0.678 (0.609-0.753), respectively. Interpretation of GPBoost by SHAP and partial dependence suggested that the relationship between the daily dose of metformin and change in HbA1c is non-linear rather than linear, and the HbA1c-lowering effect of metformin reaches a maximum at 1500 mg/day. Interpretation of GPBoost, a non-linear supervised machine-learning algorithm, suggests that there is saturation of the dose-response relationship of metformin in Japanese patients with T2D. This finding may be useful for decision-making in pharmacotherapy for T2D.

Advancements in precision medicine: multi-omics approach for tailored metformin treatment in type 2 diabetes

Metformin has become the frontline treatment in addressing the significant global health challenge of type 2 diabetes due to its proven effectiveness in lowering blood glucose levels. However, the reality is that many patients struggle to achieve their glycemic targets with the medication and the cause behind this variability has not been investigated thoroughly. While genetic factors account for only about a third of this response variability, the potential influence of metabolomics and the gut microbiome on drug efficacy opens new avenues for investigation. This review explores the different molecular signatures to uncover how the complex interplay between genetics, metabolic profiles, and gut microbiota can shape individual responses to metformin. By highlighting the insights from recent studies and identifying knowledge gaps regarding metformin-microbiota interplay, we aim to highlight the path toward more personalized and effective diabetes management strategies and moving beyond the one-size-fits-all approach.

A critical review on diabetes mellitus type 1 and type 2 management approaches: from lifestyle modification to current and novel targets and therapeutic agents

Diabetes mellitus (DM) has emerged as an international health epidemic due to its rapid rise in prevalence. Consequently, scientists and or researchers will continue to find novel, safe, effective, and affordable anti-diabetic medications. The goal of this review is to provide a thorough overview of the role that lifestyle changes play in managing diabetes, as well as the standard medications that are currently being used to treat the condition and the most recent advancements in the development of novel medical treatments that may be used as future interventions for the disease. A literature search was conducted using research databases such as PubMed, Web of Science, Scopus, ScienceDirect, Wiley Online Library, Google Scholar, etc. Data were then abstracted from these publications using words or Phrases like "pathophysiology of diabetes", "Signe and symptoms of diabetes", "types of diabetes", "major risk factors and complication of diabetes", "diagnosis of diabetes", "lifestyle modification for diabetes", "current antidiabetic agents", and "novel drugs and targets for diabetes management" that were published in English and had a strong scientific foundation. Special emphasis was given to the importance of lifestyle modification, as well as current, novel, and emerging/promising drugs and targets helpful for the management of both T1DM and T2DM.

Bile acids, fibroblast growth factor-19, and glucagon-like peptide-1 levels in the long term after bariatric surgery

OBJECTIVES

Glucagon-like peptide-1(GLP-1) is a hormone often measured in the short-term following Roux-en-Y gastric bypass (RYGB) due to its elevation and association with improvement of glucose metabolism. We examined the durability of this effect in patients with type 2 diabetes mellitus (DM) in the long term after RYGB.

METHODS

Obese patients with type 2 DM who had received RYGB 10 years ago (n = 10) were enrolled and a meal tolerance test (MTT) was performed. A matched control group with type 2 DM (n = 5) underwent MTT.

RESULTS

Glucose levels during the MTT did not differ between patients with RYGB and the nonsurgical group. Insulin, C-peptide and GLP-1 levels during MTT were significantly higher in patients with RYGB compared with the nonsurgical group (Area under the curve [AUC] of insulin; 57.4 ± 22.9 vs. 27.7 ± 11.1 mIU/L•hr, P = 0.008; AUC of total GLP-1; 189.4 ± 74.72 vs. 52.13 ± 10.23 pM •hr, P = 0.002), and in particular, peak insulin, C-peptide and GLP-1 levels observed 30-45 min after eating were markedly different from those in the nonsurgical group. Bile acids (BAs) and fibroblast growth factor 19 (FGF-19) levels during MTT were higher in patients with RYGB compared with the nonsurgical group. Peak BAs and FGF-19 levels tended to be higher in the RYGB.

CONCLUSIONS

An enhanced GLP-1 response was noted 10 years after RYGB, strongly suggesting a durability of this effect. BAs and FGF-19 were increased in the RYGB group, but not as much as the pronounced increase in GLP-1 secretion.

Effects of Gossypetin on Glucose Homeostasis in Diet-Induced Pre-Diabetic Rats

Natural flavonoids exert many potential health benefits, including anti-hyperglycaemic effects. However, the effects of gossypetin (GTIN) on glucose homeostasis in pre-diabetes have not yet been investigated. This study examined the effects of GTIN on key markers of glucose homeostasis in a diet-induced pre-diabetic rat model. Pre-diabetes was induced by allowing the animals to feed on a high-fat high-carbohydrate (HFHC) diet supplemented with 15% fructose water for 20 weeks. Following pre-diabetes induction, the pre-diabetic animals were sub-divided into five groups (n = 6), where they were either orally treated with GTIN (15 mg/kg) or metformin (MET) (500 mg/kg), both with and without dietary intervention, over a 12-week period. The results demonstrated that animals in the untreated pre-diabetic (PD) control group exhibited significantly higher fasting and postprandial blood glucose levels, as well as elevated plasma insulin concentrations and increased homeostatic model assessment for insulin resistance (HOMA2-IR) index, relative to the non-pre-diabetic (NPD) group. Similarly, increased caloric intake, body weight and plasma ghrelin levels were observed in the PD control group. Notably, these parameters were significantly reduced in the PD animals receiving GTIN treatment. Additionally, glycogen levels in the liver and skeletal muscle, which were disturbed in the PD control group, showed significant improvement in both GTIN-treated groups. These findings may suggest that GTIN administration, with or without dietary modifications, may offer therapeutic benefits in ameliorating glucose homeostasis disturbances associated with the PD state.

The role of glucagon-like peptide 1 in the postprandial effects of metformin in type 2 diabetes: a randomized crossover trial

AIMS

Although metformin is widely used for treatment of type 2 diabetes (T2D), its glucose-lowering mechanism remains unclear. Using the glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) antagonist exendin(9-39)NH2, we tested the hypothesis that postprandial GLP-1-mediated effects contribute to the glucose-lowering potential of metformin in T2D.

METHODS

In a randomized, placebo-controlled, double-blind, crossover study, 15 individuals with T2D (median HbA1c 50 mmol/mol [6.7%], body mass index 30.1 kg/m2, age 71 years) underwent, in randomized order, 14 days of metformin and placebo treatment, respectively. Each treatment period was preceded by 14 days without any glucose-lowering medicine and concluded by two 4 h mixed meal tests performed in randomized order and separated by >24 h with either continuous intravenous exendin(9-39)NH2 or saline infusion.

RESULTS

Compared to placebo, metformin treatment lowered fasting plasma glucose (mean of differences [MD] 1.4 mmol/L × min [95% CI 0.8-2.0]) as well as postprandial plasma glucose excursions during both saline infusion (MD 186 mmol/L × min [95% CI 64-307]) and exendin(9-39)NH2 infusion (MD 268 mmol/L × min [95% CI 108-427]). The metformin-induced improvement in postprandial glucose tolerance was unaffected by GLP-1R antagonization (MD 82 mmol/L × min [95% CI -6564-170]). Metformin treatment increased fasting plasma GLP-1 (MD 1.7 pmol/L × min [95% CI 0.39-2.9]) but did not affect postprandial GLP-1 responses (MD 820 pmol/L × min [95% CI -1750-111]).

CONCLUSIONS

Using GLP-1R antagonization, we could not detect GLP-1-mediated postprandial glucose-lowering effect of metformin in individuals with T2D. We show that 2 weeks of metformin treatment increases fasting plasma GLP-1, which may contribute to metformin's beneficial effect on fasting plasma glucose in T2D. Trial registration: Clinicaltrials.gov NCT03246451.

Regulating the absorption and excretion of perfluorooctane sulfonate and its alternatives through influencing enterohepatic circulation

Enterohepatic circulation has been reported to play a significant role in the bioaccumulation of PFASs. In this study, the tissue distribution and excretion of PFOS and its alternatives, namely 6:2 and 8:2 fluorotelomer sulfonic acid (FTSA) was investigated using a mouse assay with a focus on role of enterohepatic circulation. Liver was the primarily accumulating organ for PFOS and 8:2 FTSA (33.4 % and 25.8 % of total doses absorbed after 14 days), whereas 65 % of 6:2 FTSA was excreted via urine within 24 h. Peak levels of 8:2 FTSA and PFOS were found in the gallbladder, implying the important role of enterohepatic circulation in PFASs reabsorption. The role of enterohepatic circulation was further evaluated through co-exposure of 8:2 FTSA and PFOS with medicines (namely metformin (MET) and ursodeoxycholic acid (UDCA)). MET reduced accumulation of 8:2 FTSA and PFOS in the liver by 68.6 % and 65.8 %, through down-regulation of bile acid transporter (Asbt) and enhancement of fecal excretion. Conversely, UDCA raised their concentrations by 21.9 % and 34.6 % compared to that exposed solely to PFASs. A strong positive correlation was identified between PFASs serum levels and Asbt expression. This study illuminated PFAS bioaccumulation mechanisms and suggested potential strategies to mitigate the exposure risks.

Impact of the timing of metformin administration on glycaemic and glucagon-like peptide-1 responses to intraduodenal glucose infusion in type 2 diabetes: a double-blind, randomised, placebo-controlled, crossover study

AIMS/HYPOTHESIS

Metformin lowers postprandial glycaemic excursions in individuals with type 2 diabetes by modulating gastrointestinal function, including the stimulation of glucagon-like peptide-1 (GLP-1). The impact of varying the timing of metformin administration on postprandial glucose metabolism is poorly defined. We evaluated the effects of metformin, administered at different intervals before an intraduodenal glucose infusion, on the subsequent glycaemic, insulinaemic and GLP-1 responses in metformin-treated type 2 diabetes.

METHODS

Sixteen participants with type 2 diabetes that was relatively well-controlled by metformin monotherapy were studied on four separate days in a crossover design. On each day, participants were randomised to receive a bolus infusion of metformin (1000 mg in 50 ml 0.9% saline) via a nasoduodenal catheter at t = -60, -30 or 0 min (and saline at the other timepoints) or saline at all timepoints (control), followed by an intraduodenal glucose infusion of 12.56 kJ/min (3 kcal/min) at t = 0-60 min. The treatments were blinded to both participants and investigators involved in the study procedures. Plasma glucose, insulin and total GLP-1 levels were measured every 30 min between t = -60 min and t = 120 min.

RESULTS

There was a treatment-by-time interaction for metformin in reducing plasma glucose levels and increasing plasma GLP-1 and insulin levels (p<0.05 for each). The reduction in plasma glucose levels was greater when metformin was administered at t = -60 or -30 min vs t = 0 min (p<0.05 for each), and the increases in plasma GLP-1 levels were evident only when metformin was administered at t = -60 or -30 min (p<0.05 for each). Although metformin did not influence insulin sensitivity, it enhanced glucose-induced insulin secretion (p<0.05), and the increases in plasma insulin levels were comparable on the 3 days when metformin was given.

CONCLUSIONS/INTERPRETATION

In well-controlled metformin-treated type 2 diabetes, glucose-lowering by metformin is greater when it is given before, rather than with, enteral glucose, and this is associated with a greater GLP-1 response. These observations suggest that administration of metformin before meals may optimise its effect in improving postprandial glycaemic control.

TRIAL REGISTRATION

www.anzctr.org.au ACTRN12621000878875 FUNDING: The study was not funded by a specific research grant.

Comparative assessment of immunogenicity of recombinant insulin Aspart from BioGenomics and its originator NovoRapid® in adult patients with type 2 diabetes mellitus

OBJECTIVES

To assess and compare the immunogenicity of recombinant Insulin Aspart [manufactured by BioGenomics Limited (BGL-ASP)] with its originator NovoRapid® (manufactured by Novo Nordisk) in adult patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

BGL-IA-CTP301 study was a randomized, open label, parallel group, multicenter phase-III clinical study to compare the efficacy and safety of recombinant Insulin Aspart 100 U/mL [manufactured by BioGenomics Limited (BGL-ASP)] with its reference medicinal product (RMP); NovoRapid® [manufactured by Novo Nordisk], in adult patients with Type 2 diabetes mellitus (T2DM). The primary objective of the study was to compare the immunogenicity of BGL-ASP and RMP; NovoRapid® in patient serum samples collected from phase-III clinical study. Immunogenicity was studied as the incidence of patients positive for anti-insulin Aspart (AIA) antibodies, developed against BGL-ASP/RMP at baseline, end of 12 week and end of 24 week of the treatment period. The changes in incidence of patients positive for AIA antibodies post-baseline were also studied to assess and compare the treatment-emergent antibody response (TEAR) between the treatment groups (BGL-ASP and RMP). Statistical evaluation was done by Fisher's exact test to compare the overall incidence of patients positive for AIA antibodies and the TEAR positives observed post-baseline in both the treated groups. An in-vitro neutralizing antibody assay (Nab assay) was also performed to study the effect of AIA antibodies in neutralizing the biological activity/metabolic function of the insulin. The neutralizing potential of AIA was studied by its effect on %glucose uptake. We also evaluated the association between AIA antibody levels and its impact on biological activity by studying the correlation between them.

RESULTS

Analysis of immunogenicity data suggested that the percentage of patients positive for AIA antibodies until week 24 was similar and comparable in both the treatment groups, BGL-ASP and RMP; NovoRapid®. The changes in incidence of patients positive for AIA post-baseline in terms of TEAR positives were also similar and comparable between the treatment groups. The results of the Nab assay with confirmed positive AIA samples from BGL-ASP- and RMP-treated groups did not have any negative impact on %glucose uptake by the cells in Nab assay, confirming the absence of neutralizing antibodies in both the treatment groups. The correlation studies also showed absence of association between AIA antibody levels and percentage glucose uptake in both BGL-ASP and RMP-NovoRapid® treatment groups. CONCLUSIONS: The immunogenicity assessment based on the overall incidence of patients positive for AIA, changes in incidence of patients positive for AIA post-baseline, TEAR rates and absence of neutralizing antibodies, were found to be apparently similar and comparable in both the treatment groups (BGL-ASP and RMP). We conclude from our studies that the immunogenicity of BGL-ASP is similar and comparable to RMP and the observed immunogenicity in terms of anti-insulin Aspart antibody levels had no impact on the biological activity of insulin.

In-depth investigation of the therapeutic effect of Tribulus terrestris L. on type 2 diabetes based on intestinal microbiota and feces metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Tribulus terrestris L. (TT) is extensively documented in the Tibetan medical literature 'Si Bu Yi Dian', has been used to treat diabetes mellitus for more than a thousand years. However, the underlying mechanisms and comprehensive effects of TT on diabetes have yet to be investigated.

AIM OF THE STUDY

The aim of the study was to systemically elucidate the potential mechanisms of TT in treating diabetes mellitus, and further investigate the therapeutic effects of the water extract, small molecular components and saccharides from TT.

MATERIALS AND METHODS

Fecal metabolomics was employed to draw the metabolic profile based on UHPLC-Q-TOF-MS/MS. The V3-V4 hypervariable regions of the bacteria 16S rRNA gene were amplified to explore the structural changes of the intestinal microbiome after TT intervention and to analyze the differential microbiota. The microbial metabolites SCFAs were determined by GC-MS, and the BAs and tryptophan metabolites were quantified by UPLC-TQ-MS. Spearman correlation analysis was carried out to comprehensively investigate the relationship among the endogenous metabolites profile, intestinal microbiota and their metabolites.

RESULTS

TT exhibited remarkably therapeutic effect on T2DM rats, as evidenced by improved glucolipid metabolism and intestinal barrier integrity, ameliorated inflammation and remission in insulin resistance. A total of 24 endogenous biomarkers were screened through fecal metabolomics studies, which were mainly related to tryptophan metabolism, fatty acid metabolism, bile acid metabolism, steroid hormone biosynthesis and arachidonic acid metabolism. Investigations on microbiomics revealed that TT significantly modulated 18 differential bacterial genera and reversed the disordered gut microbial in diabetes rats. Moreover, TT notably altered the content of gut microbiota metabolites, both in serum and fecal samples. Significant correlation among microbial community, metabolites and T2DM-related indicators was revealed.

CONCLUSIONS

The multiple components of TT regulate the metabolic homeostasis of the organism and the balance of intestinal microbiota and its metabolites, which might mediate the anti-diabetic capacity of TT.

Effectiveness and safety of glucagon-like peptide 1 receptor agonists in patients with type 2 diabetes: evidence from a retrospective real-world study

Introduction

Global phase III clinical trials have shown superior hypoglycemic efficacy to insulin and other oral hypoglycemic agents. However, there is a scarcity of real-world data comparing different glucagon-like peptide 1 receptor agonist (GLP-1RA) directly. This study aimed to assess the safety and effectiveness of various GLP-1RA in treating type 2 diabetes mellitus (T2DM) in a real-world clinical setting and identify predictive factors for favorable treatment outcomes.

Methods

This was a retrospective, single-center, real-world study. The changes in HbA1c, fasting plasma glucose (FPG), body weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), and the percentage of participants who achieved HbA1c of <7%, 7%-8%, and ≥ 8% after GLP-1RA treatment was analyzed. The clinical factors that affect the effectiveness of GLP-1RA were analyzed.

Results

At baseline, the 249 participants had a mean baseline HbA1c of 8.7 ± 1.1%. After at least three months of follow-up, the change in HbA1c was -0.89 ± 1.3% from baseline. Dulaglutide exerted a more significant hypoglycemic effect than immediate-release exenatide. The percentage of participants who achieved HbA1c<7% was substantial, from 6.0% at baseline to 28.9%. Average body weight decreased by 2.02 ± 3.8 kg compared to baseline. After GLP-1RA treatment, the reduction in SBP was 2.4 ± 7.1 mmHg from baseline. A shorter duration of diabetes and a higher baseline HbA1c level were more likely to achieve a good response in blood glucose reduction.

Conclusions

This study provided real-world evidence showing that GLP-1RA significantly improved HbA1c, body weight, and SBP. The results can inform the decision-making about GLP-1RA treatment in daily clinical practice.

Paneth cell: The missing link between obesity, MASH and portal hypertension

Obesity is a global health crisis, with its prevalence steadily rising over the past few decades. One concerning consequence of obesity is its association with metabolic associated steatohepatitis [MASH], portal hypertension and liver cirrhosis. Cirrhosis is irreversible, but stages of liver disease before the development of cirrhosis are reversible with appropriate interventions. Studies have brought into light new entities that influences the pathophysiology of portal hypertension. This review provides evidence supporting that, Paneth cells[PCs] in the intestinal epithelium, which remained enigmatic for a century, are the maneuverer of pathophysiology of portal hypertension and obesity. PC dysfunction can cause perturbation of the intestinal microbiota and changes in intestinal permeability, which are the potential triggers of systemic inflammation. Thus, it can offer unique opportunities to understand the pathophysiology of portal hypertension for intervention strategies.

Metformin: The Winding Path from Understanding Its Molecular Mechanisms to Proving Therapeutic Benefits in Neurodegenerative Disorders

Metformin, a widely prescribed medication for type 2 diabetes, has garnered increasing attention for its potential neuroprotective properties due to the growing demand for treatments for Alzheimer's, Parkinson's, and motor neuron diseases. This review synthesizes experimental and clinical studies on metformin's mechanisms of action and potential therapeutic benefits for neurodegenerative disorders. A comprehensive search of electronic databases, including PubMed, MEDLINE, Embase, and Cochrane library, focused on key phrases such as "metformin", "neuroprotection", and "neurodegenerative diseases", with data up to September 2023. Recent research on metformin's glucoregulatory mechanisms reveals new molecular targets, including the activation of the LKB1-AMPK signaling pathway, which is crucial for chronic administration of metformin. The pleiotropic impact may involve other stress kinases that are acutely activated. The precise role of respiratory chain complexes (I and IV), of the mitochondrial targets, or of the lysosomes in metformin effects remains to be established by further research. Research on extrahepatic targets like the gut and microbiota, as well as its antioxidant and immunomodulatory properties, is crucial for understanding neurodegenerative disorders. Experimental data on animal models shows promising results, but clinical studies are inconclusive. Understanding the molecular targets and mechanisms of its effects could help design clinical trials to explore and, hopefully, prove its therapeutic effects in neurodegenerative conditions.

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.

Restoring autophagic function: a case for type 2 diabetes mellitus drug repurposing in Parkinson's disease

Parkinson's disease (PD) is a predominantly idiopathic pathological condition characterized by protein aggregation phenomena, whose main component is alpha-synuclein. Although the main risk factor is ageing, numerous evidence points to the role of type 2 diabetes mellitus (T2DM) as an etiological factor. Systemic alterations classically associated with T2DM like insulin resistance and hyperglycemia modify biological processes such as autophagy and mitochondrial homeostasis. High glucose levels also compromise protein stability through the formation of advanced glycation end products, promoting protein aggregation processes. The ability of antidiabetic drugs to act on pathways impaired in both T2DM and PD suggests that they may represent a useful tool to counteract the neurodegeneration process. Several clinical studies now in advanced stages are looking for confirmation in this regard.

Unveiling the potential pleiotropic effects of metformin in treating COVID-19: a comprehensive review

This review article explores the potential of metformin, a medication commonly used for type 2 diabetes, as an antiviral and anti-inflammatory agent in the context of coronavirus disease 2019 (COVID-19). Metformin has demonstrated inhibitory effects on the growth of SARS-CoV-2 in cell culture models and has shown promising results in reducing viral load and achieving undetectable viral levels in clinical trials. Additionally, metformin exhibits anti-inflammatory properties by reducing the production of pro-inflammatory cytokines and modulating immune cell function, which may help prevent cytokine storms associated with severe COVID-19. The drug's ability to regulate the balance between pro-inflammatory Th17 cells and anti-inflammatory Treg cells suggests its potential in mitigating inflammation and restoring T cell functionality. Furthermore, metformin's modulation of the gut microbiota, particularly changes in bacterial taxa and the production of short-chain fatty acids, may contribute to its therapeutic effects. The interplay between metformin, bile acids, the gut microbiome, glucagon-like peptide-1 secretion, and glycemic control has implications for the management of diabetes and potential interventions in COVID-19. By refreshing the current evidence, this review highlights the potential of metformin as a therapeutic option in the management of COVID-19, while also exploring its effects on the gut microbiome and immunometabolism.

Metformin: update on mechanisms of action and repurposing potential

Currently, metformin is the first-line medication to treat type 2 diabetes mellitus (T2DM) in most guidelines and is used daily by >200 million patients. Surprisingly, the mechanisms underlying its therapeutic action are complex and are still not fully understood. Early evidence highlighted the liver as the major organ involved in the effect of metformin on reducing blood levels of glucose. However, increasing evidence points towards other sites of action that might also have an important role, including the gastrointestinal tract, the gut microbial communities and the tissue-resident immune cells. At the molecular level, it seems that the mechanisms of action vary depending on the dose of metformin used and duration of treatment. Initial studies have shown that metformin targets hepatic mitochondria; however, the identification of a novel target at low concentrations of metformin at the lysosome surface might reveal a new mechanism of action. Based on the efficacy and safety records in T2DM, attention has been given to the repurposing of metformin as part of adjunct therapy for the treatment of cancer, age-related diseases, inflammatory diseases and COVID-19. In this Review, we highlight the latest advances in our understanding of the mechanisms of action of metformin and discuss potential emerging novel therapeutic uses.

The Effect and Safety Assessment of Metformin and DLBS3233 (A Bioactive Fraction of Lagerstroemia speciosa and Cinnamomum burmannii) on Improving Metabolic Parameters in Women with Polycystic Ovary Syndrome

Background

Polycystic ovary syndrome (PCOS) can lead to compensatory hyperinsulinemia with consequent metabolic abnormalities in women. In this study, DLBS3233 and Metformin were used to be tested. DLBS3233 itself is the new insulin-sensitizing drug, a combination-bioactive-fraction derived from two Indonesian herbals, Lagerstroemia speciosa and Cinnamomum burmannii. DLBS3233 alone and in combination with metformin were evaluated for efficacy and safety in insulin-resistant women with polycystic ovary syndrome (PCOS).

Methods

A randomized, double-blind, 3-arm, double-dummy, non-inferiority, and also a controlled clinical study was conducted at the Dr. Kariadi Hospital, Indonesia, between October 2014 and February 2019. The study involved 60 female subjects (with 20 female subjects in each group) that had polycystic ovary syndrome (PCOS).Treatment I consists of one placebo capsule twice per day and one 100 mg DLBS3233 capsule once per day. Treatment II consists of one placebo caplet once per day and one 750 mg Metformin XR caplet twice per day. Treatment III consists of one 750 mg Metformin XR caplet twice per day and one 100 mg DLBS3233 capsule once per day.

Results

In treatment I, the homeostatic model assessment for insulin resistance (HOMA-IR) levels were 3.55, 3.59, and 3.80 at pretest, 3 months, and 6 months after intervention, respectively. In treatment II, the HOMA-IR level were 4.00, 2.21, and 4.40 at pretest, 3 months, and 6 months after intervention respectively. In treatment III, the HOMA-IR levels were 3.30, 2.86, and 3.12 at pretest, 3 months, and 6 months after intervention, respectively. There was no apparent difference existed in the fasting plasma glucose (FPG), high-density lipoprotein (HDL), triglycerides, ferriman-gallwey scores (FGS), and safety assessment on vital signs and laboratory examinations (liver function and renal function) in all groups.

Conclusion

Either DLBS3233 alone or the DLBS3233/Metformin combination showed no significant efficacy and did not negatively affect cardiovascular function, liver and kidney function in PCOS subjects.

ClinicalTrialsgov Identifier

NCT01999686 Date: 3rd of December, 2013.

Striking a gut-liver balance for the antidiabetic effects of metformin

Metformin is the most prescribed drug for the treatment of type 2 diabetes mellitus (T2DM), but its mechanism of action has not yet been completely elucidated. Classically, the liver has been considered the major site of action of metformin. However, over the past few years, advances have unveiled the gut as an additional important target of metformin, which contributes to its glucose-lowering effect through new mechanisms of action. A better understanding of the mechanistic details of metformin action in the gut and the liver and its relevance in patients remains the challenge of present and future research and may impact drug development for the treatment of T2DM. Here, we offer a critical analysis of the current status of metformin-driven multiorgan glucose-lowering effects.

Oral metformin transiently lowers post-prandial glucose response by reducing the apical expression of sodium-glucose co-transporter 1 in enterocytes

Metformin (MET) is the most prescribed antidiabetic drug, but its mechanisms of action remain elusive. Recent data point to the gut as MET's primary target. Here, we explored the effect of MET on the gut glucose transport machinery. Using human enterocytes (Caco-2/TC7 cells) in vitro, we showed that MET transiently reduced the apical density of sodium-glucose transporter 1 (SGLT1) and decreased the absorption of glucose, without changes in the mRNA levels of the transporter. Administered 1 h before a glucose challenge in rats (Wistar, GK), C57BL6 mice and mice pigs, oral MET reduced the post-prandial glucose response (PGR). This effect was abrogated in SGLT1-KO mice. MET also reduced the luminal clearance of 2-(¹⁸F)-fluoro-2-deoxy-D-glucose after oral administration in rats. In conclusion, oral metformin transiently lowers post-prandial glucose response by reducing the apical expression of SGLT1 in enterocytes, which may contribute to the clinical effects of the drug.

The Protective Effect of 11-Keto-β-Boswellic Acid against Diabetic Cardiomyopathy in Rats Entails Activation of AMPK

This study examined the protective effect of 11-keto-β-boswellic acid (AKBA) against streptozotocin (STZ)-induced diabetic cardiomyopathy (DC) in rats and examined the possible mechanisms of action. Male rats were divided into 5 groups (n = 8/each): (1) control, AKBA (10 mg/kg, orally), STZ (65 mg/kg, i.p.), STZ + AKBA (10 mg/kg, orally), and STZ + AKBA + compound C (CC/an AMPK inhibitor, 0.2 mg/kg, i.p.). AKBA improved the structure and the systolic and diastolic functions of the left ventricles (LVs) of STZ rats. It also attenuated the increase in plasma glucose, plasma insulin, and serum and hepatic levels of triglycerides (TGs), cholesterol (CHOL), and free fatty acids (FFAs) in these diabetic rats. AKBA stimulated the ventricular activities of phosphofructokinase (PFK), pyruvate dehydrogenase (PDH), and acetyl CoA carboxylase (ACC); increased levels of malonyl CoA; and reduced levels of carnitine palmitoyltransferase I (CPT1), indicating improvement in glucose and FA oxidation. It also reduced levels of malondialdehyde (MDA); increased mitochondria efficiency and ATP production; stimulated mRNA, total, and nuclear levels of Nrf2; increased levels of glutathione (GSH), heme oxygenase (HO-1), superoxide dismutase (SOD), and catalase (CAT); but reduced the expression and nuclear translocation of NF-κB and levels of tumor-necrosis factor-α (TNF-α) and interleukin-6 (IL-6). These effects were concomitant with increased activities of AMPK in the LVs of the control and STZ-diabetic rats. Treatment with CC abolished all these protective effects of AKBA. In conclusion, AKBA protects against DC in rats, mainly by activating the AMPK-dependent control of insulin release, cardiac metabolism, and antioxidant and anti-inflammatory effects.

A Novel Drug Delivery System: Hyodeoxycholic Acid-Modified Metformin Liposomes for Type 2 Diabetes Treatment

Metformin is a first-line drug for the clinical treatment of type 2 diabetes; however, it always leads to gastrointestinal tolerance, low bioavailability, short half-life, etc. Liposome acts as an excellent delivery system that could reduce drug side effects and promote bioavailability. Hyodeoxycholic acid, a cholesterol-like structure, can regulate glucose homeostasis and reduce the blood glucose levels. As an anti-diabetic active ingredient, hyodeoxycholic acid modifies liposomes to make it overcome the disadvantages of metformin as well as enhance the hypoglycemic effect. By adapting the thin-film dispersion method, three types of liposomes with different proportions of hyodeoxycholic acid and metformin were prepared (HDCA:ME-(0.5:1)-Lips, HDCA:ME-(1:1)-Lips, and HDCA:ME-(2:1)-Lips). Further, the liposomes were characterized, and the anti-type 2 diabetes activity of liposomes was evaluated. The results from this study indicated that three types of liposomes exhibited different characteristics—Excessive hyodeoxycholic acid decreased encapsulation efficiency and drug loading. In the in vivo experiments, liposomes could reduce the fasting blood glucose levels, improve glucose tolerance, regulate oxidative stress markers and protect liver tissue in type 2 diabetic mice. These results indicated that HDCA:ME-(1:1)-Lips was the most effective among the three types of liposomes prepared and showed better effects than metformin. Hyodeoxycholic acid can enhance the hypoglycemic effect of metformin and play a suitable role as an excipient in the liposome.

Microbiota: A potential orchestrator of antidiabetic therapy

The gut microbiota, as a 'new organ' of humans, has been identified to affect many biological processes, including immunity, inflammatory response, gut-brain neural circuits, and energy metabolism. Profound dysbiosis of the gut microbiome could change the metabolic pattern, aggravate systemic inflammation and insulin resistance, and exacerbate metabolic disturbance and the progression of type 2 diabetes (T2D). The aim of this review is to focus on the potential roles and functional mechanisms of gut microbiota in the antidiabetic therapy. In general, antidiabetic drugs (α-glucosidase inhibitor, biguanides, incretin-based agents, and traditional Chinese medicine) induce the alteration of microbial diversity and composition, and the levels of bacterial component and derived metabolites, such as lipopolysaccharide (LPS), short chain fatty acids (SCFAs), bile acids and indoles. The altered microbial metabolites are involved in the regulation of gut barrier, inflammation response, insulin resistance and glucose homeostasis. Furthermore, we summarize the new strategies for antidiabetic treatment based on microbial regulation, such as pro/prebiotics administration and fecal microbiota transplantation, and discuss the need for more basic and clinical researches to evaluate the feasibility and efficacy of the new therapies for diabetes.

Enhancing intestinal barrier efficiency: A novel metabolic diseases therapy

Physiologically, the intestinal barrier plays a crucial role in homeostasis and nutrient absorption and prevents pathogenic entry, harmful metabolites, and endotoxin absorption. Recent advances have highlighted the association between severely damaged intestinal barriers and diabetes, obesity, fatty liver, and cardiovascular diseases. Evidence indicates that an abated intestinal barrier leads to endotoxemia associated with systemic inflammation, insulin resistance, diabetes, and lipid accumulation, accelerating obesity and fatty liver diseases. Nonetheless, the specific mechanism of intestinal barrier damage and the effective improvement of the intestinal barrier remain to be explored. Here, we discuss the crosstalk between changes in the intestinal barrier and metabolic disease. This paper also highlights how to improve the gut barrier from the perspective of natural medicine, gut microbiota remodeling, lifestyle interventions, and bariatric surgery. Finally, potential challenges and prospects for the regulation of the gut barrier-metabolic disease axis are discussed, which may provide theoretical guidance for the treatment of metabolic diseases.

The role and mechanism of the gut microbiota in the development and treatment of diabetic kidney disease

Diabetic kidney disease (DKD) is a common complication in patients with diabetes mellitus (DM). Increasing evidence suggested that the gut microbiota participates in the progression of DKD, which is involved in insulin resistance, renin-angiotensin system (RAS) activation, oxidative stress, inflammation and immunity. Gut microbiota-targeted therapies including dietary fiber, supplementation with probiotics or prebiotics, fecal microbiota transplantation and diabetic agents that modulate the gut microbiota, such as metformin, glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors, and sodium-glucose transporter-2 (SGLT-2) inhibitors. In this review, we summarize the most important findings about the role of the gut microbiota in the pathogenesis of DKD and the application of gut microbiota-targeted therapies.

Mechanism Underlying Metformin Action and Its Potential to Reduce Gastric Cancer Risk

Diabetes mellitus is associated with a high risk of developing gastric cancer (GC). Metformin, which is conventionally used to treat type 2 diabetes, induces AMP-activated protein kinase signaling and suppresses gluconeogenesis. Recent studies have reported that metformin is associated with beneficial effects in cancer prevention and treatment owing to its anti-tumor effects. This makes metformin a potential medication for GC therapy. However, contradicting reports have emerged regarding the efficacy of metformin in reducing the risk of GC. This review summarizes the impact of metformin on mitigating GC risk by analyzing clinical databases. The mechanism underlying the anti-tumor effect of metformin on GC is also discussed.

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.

Interactive Relationships between Intestinal Flora and Bile Acids

The digestive tract is replete with complex and diverse microbial communities that are important for the regulation of multiple pathophysiological processes in humans and animals, particularly those involved in the maintenance of intestinal homeostasis, immunity, inflammation, and tumorigenesis. The diversity of bile acids is a result of the joint efforts of host and intestinal microflora. There is a bidirectional relationship between the microbial community of the intestinal tract and bile acids in that, while the microbial flora tightly modulates the metabolism and synthesis of bile acids, the bile acid pool and composition affect the diversity and the homeostasis of the intestinal flora. Homeostatic imbalances of bile acid and intestinal flora systems may lead to the development of a variety of diseases, such as inflammatory bowel disease (IBD), colorectal cancer (CRC), hepatocellular carcinoma (HCC), type 2 diabetes (T2DM), and polycystic ovary syndrome (PCOS). The interactions between bile acids and intestinal flora may be (in)directly involved in the pathogenesis of these diseases.

Reduced Cytokine Tumour Necrosis Factor by Pharmacological Intervention in a Preclinical Study

Recent preclinical studies in our laboratory have shown that the bile acid profile is altered during diabetes development and such alteration has been linked to the diabetes-associated inflammatory profile. Hence, this study aimed to investigate if the first-line antidiabetic drug metformin will alter the bile acid profile and diabetes-associated inflammation in a murine model of pre-type 2 diabetes. C57 mice were randomly allocated into three equal groups of eight. Group One was given a low-fat diet (LFD), Group Two was given a high-fat diet (HFD), and Group Three was given an HFD and, upon prediabetes confirmation, daily oral metformin for one month. Blood glucose, glycated haemoglobin, drug concentrations in tissues and faeces, and the inflammatory and bile acid profiles were measured. Metformin showed wide tissue distribution and was also present in faeces. The bile acid profile showed significant alteration due to prediabetes, and although metformin did not completely normalize it, it did exert significant effects on both the bile acid and the inflammatory profiles, suggesting a direct and, to some extent, positive impact, particularly on the diabetes-associated inflammatory profile.

Metformin in prediabetes: key mechanisms for the prevention of diabetes and cardiometabolic risks

Today, prediabetes is regarded by the world medical community as early diabetes mellitus. The accumulated research evidence shows that prediabetes is characterized by a spectrum of complications that are similar to those of diabetes mellitus, which means that the deterioration of cardiovascular prognosis starts already at the stage of prediabetes. In the current timeframe, metformin is actually the only drug that is widely prescribed for the treatment of prediabetes to prevent type 2 diabetes mellitus and cardiovascular diseases associated with insulin resistance and hyperinsulinemia. Meanwhile, metabolically unhealthy obesity characterized by hyperinsulinemia and insulin resistance is associated with a significantly unfavourable course of prediabetes, as well as the highest risk of developing both type 2 diabetes mellitus and cardiovascular diseases, development/ progression of chronic kidney disease. The theme of this review is the priority of metformin for the management of the most prognostically unfavourable phenotypes of prediabetes. The review is also devoted to the description of the most significant mechanisms that provide effects of metformin underlying the management of key disorders that determine the unfavourable prognosis of prediabetes. In particular, it sets forth the role of unhealthy nutrition, its effects on the development of imbalance of the composition of gut microbiota, which, in turn, entails a cascade of metabolic disorders underlying the development of metabolic ill health. The review sets forth the key role of metformin as a drug that protects against the development of these disorders. The information presented in this review will be useful to personalize the choice of both the scope and nature of interventions in patients with different phenotypic characteristics.

Serum bile acid response to oral glucose is attenuated in patients with early type 2 diabetes and correlates with 2-hour plasma glucose in individuals without diabetes

AIM

To determine the serum bile acid (BA) response to 75-g oral glucose in individuals without diabetes, and whether this is attenuated in patients with 'early' type 2 diabetes (T2D) and related to the glycaemic response at 2 hours in either group.

METHODS

Forty newly diagnosed, treatment-naïve Han Chinese T2D subjects and 40 age-, gender-, and body mass index-matched controls without T2D ingested a 75-g glucose drink after an overnight fast. Plasma glucose and serum concentrations of total and individual BAs, fibroblast growth factor-19 (FGF-19), total glucagon-like peptide-1 (GLP-1), and insulin, were measured before and 2 hours after oral glucose.

RESULTS

Fasting total BA levels were higher in T2D than control subjects (P < .05). At 2 hours, the BA profile exhibited a shift from baseline in both groups, with increases in conjugated BAs and/or decreases in unconjugated BAs. There were increases in total BA and FGF-19 levels in control (both P < .05), but not T2D, subjects. Plasma glucose concentrations at 2 hours related inversely to serum total BA levels in control subjects (r = -0.42, P = .006). Total GLP-1 and the insulin/glucose ratio were increased at 2 hours in both groups, and the magnitude of the increase was greater in control subjects.

CONCLUSIONS

The serum BA response to a 75-g oral glucose load is attenuated in patients with 'early' T2D, as is the secretion of FGF-19 and GLP-1, while in individuals without T2D it correlates with 2-hour plasma glucose levels. These observations support a role for BAs in the regulation of postprandial glucose metabolism.

Metformin inhibits multiple myeloma serum-induced endothelial cell thrombosis by down-regulating miR-532

OBJECTIVES

Thrombotic complications in multiple myeloma (MM) impairs the quality of life of patients. Metformin has a certain effect on anti-thrombosis, but its role and mechanism in MM-induced thrombosis are still uncovered. Therefore, this study evaluated the effect of metformin on MM-induced thrombosis.

METHODS

Human umbilical vein endothelial cells (HUVECs) were exposed to normal serum (15%), MM serum (15%), metformin (0.01 mmol/L), or MM serum and metformin simultaneously. The expression of tissue factor (TF) in HUVECs was detected by flow cytometry and quantitative real-time PCR (qRT-PCR). QRT-PCR was also used to determine the expressions of endothelial protein C receptor (EPCR) and miR-532. The generation of thrombin and activated protein C was measured by thrombin generation and protein C activation assays. And EPCR, extracellular signal-regulated kinase (ERK) 1/2, p38 mitogen activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathway related protein expressions were detected by western blot.

RESULT

MM serum increased the expressions of TF, EPCR and miR-532, and induced thrombin generation and protein C activation in HUVECs. Based on the MM serum treatment, metformin decreased these expressions and inhibited the thrombin generation and protein C activation in HUVECs. However, miR-532 mimic reversed the effect of metformin and promoted the levels of thrombosis related indicators in HUVECs. Moreover, metformin activated the EPCR, ERK 1/2, p38 MAPK and NF-κB pathways but miR-532 mimic suppressed the activation of pathways.

CONCLUSION

Metformin played an inhibitory effect on MM serum-induced HUVEC thrombosis, suggesting that metformin could serve as a novel antithrombotic approach for MM patients.

Metformin: Expanding the Scope of Application-Starting Earlier than Yesterday, Canceling Later

Today the area of application of metformin is expanding, and a wealth of data point to its benefits in people without carbohydrate metabolism disorders. Already in the population of people leading an unhealthy lifestyle, before the formation of obesity and prediabetes metformin smooths out the adverse effects of a high-fat diet. Being prescribed at this stage, metformin will probably be able to, if not prevent, then significantly reduce the progression of all subsequent metabolic changes. To a large extent, this review will discuss the proofs of the evidence for this. Another recent important change is a removal of a number of restrictions on its use in patients with heart failure, acute coronary syndrome and chronic kidney disease. We will discuss the reasons for these changes and present a new perspective on the role of increasing lactate in metformin therapy.

Biguanide Pharmaceutical Formulations and the Applications of Bile Acid-Based Nano Delivery in Chronic Medical Conditions

Biguanides, particularly the widely prescribed drug metformin, have been marketed for many decades and have well-established absorption profiles. They are commonly administered via the oral route and, despite variation in oral uptake, remain commonly prescribed for diabetes mellitus, typically type 2. Studies over the last decade have focused on the design and development of advanced oral delivery dosage forms using bio nano technologies and novel drug carrier systems. Such studies have demonstrated significantly enhanced delivery and safety of biguanides using nanocapsules. Enhanced delivery and safety have widened the potential applications of biguanides not only in diabetes but also in other disorders. Hence, this review aimed to explore biguanides’ pharmacokinetics, pharmacodynamics, and pharmaceutical applications in diabetes, as well as in other disorders.

New Insights of Anti-Hyperglycemic Agents and Traditional Chinese Medicine on Gut Microbiota in Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a widespread metabolic disease characterized by chronic hyperglycemia. Human microbiota, which is regarded as a “hidden organ”, plays an important role in the initiation and development of T2DM. In addition, anti-hyperglycemic agents and traditional Chinese medicine may affect the composition of gut microbiota and consequently improve glucose metabolism. However, the relationship between gut microbiota, T2DM and anti-hyperglycemic agents or traditional Chinese medicine is poorly understood. In this review, we summarized pre-clinical and clinical studies to elucidate the possible underlying mechanism. Some anti-hyperglycemic agents and traditional Chinese medicine may partly exert hypoglycemic effects by altering the gut microbiota composition in ways that reduce metabolic endotoxemia, maintain the integrity of intestinal mucosal barrier, promote the production of short-chain fatty acids (SCFAs), decrease trimethylamine-N-oxide (TMAO) and regulate bile acid metabolism. In conclusion, gut microbiota may provide some new therapeutic targets for treatment of patients with diabetes mellitus.

Gut microbiota of patients with type 2 diabetes and gastrointestinal intolerance to metformin differs in composition and functionality from tolerant patients

OBJECTIVE

Metformin modifies the gut microbiome in type 2 diabetes and gastrointestinal tolerance to metformin could be mediated by the gut microbiome.

METHODS

We enrolled 35 patients with type 2 diabetes not receiving treatment with metformin due to suspected gastrointestinal intolerance. Metformin was reintroduced at 425 mg, increasing 425 mg every two weeks until reaching 1700 mg per day. According to the occurrence of metformin-related gastrointestinal symptoms, patients were classified into three groups: early intolerance, non-tolerant, and tolerant. Gut microbiota was profiled with 16 S rRNA. This sequencing aimed to determine the differences in the baseline gut microbiota in all groups and prospectively in the tolerant and non-tolerant groups.

RESULTS

The classification resulted in 15 early intolerant, 10 tolerant, and 10 non-tolerant subjects. Early tolerance was characterized by a higher abundance of Subdoligranulum; while Veillonella and Serratia were higher in the non-tolerant group. The tolerant group showed enrichment of Megamonas, Megamonas rupellensis, and Phascolarctobacterium spp; Ruminococcus gnavus was lower in the longitudinal analysis. At the end point Prevotellaceae, Prevotella stercorea, Megamonas funiformis, Bacteroides xylanisolvens, and Blautia producta had a higher relative abundance in the tolerant group compared to the non-tolerant group. Subdoligranulum, Ruminococcus torques_1, Phascolarctobacterium faecium, and Eubacterium were higher in the non-tolerant group. The PICRUSt analysis showed a lower activity of the amino acid biosynthesis pathways and a higher sugar degradation pathway in the intolerant groups.

CONCLUSIONS

Gut microbiota of subjects with gastrointestinal intolerance depicted taxonomic and functional differences compared to tolerant patients, and this changed differently after metformin administration.

Long-term effects of metformin use in gestational diabetes mellitus on offspring health

Metformin is the first-line drug for the treatment of type 2 diabetes mellitus, but its role in gestational diabetes mellitus (GDM) management is not clear. Recent evidence suggests a certain beneficial effect of metformin in the treatment of GDM, but a high treatment failure rate leads to the initiation of additional medications, such as insulin. Moreover, since metformin crosses the placental barrier and reaches a significant level in the fetus, it is likely to influence the fetal metabolic milieu. The evidence indicates the long-term safety in children exposed to metformin in utero except for mild adverse anthropometric profiles. Diligent follow-up of metformin-exposed offspring is warranted from the clinician's point of view.

AMPK Activity: A Primary Target for Diabetes Prevention with Therapeutic Phytochemicals

Diabetes is a metabolic syndrome characterized by inadequate blood glucose control and is associated with reduced quality of life and various complications, significantly shortening life expectancy. Natural phytochemicals found in plants have been traditionally used as medicines for the prevention of chronic diseases including diabetes in East Asia since ancient times. Many of these phytochemicals have been characterized as having few side effects, and scientific research into the mechanisms of action responsible has accumulated mounting evidence for their efficacy. These compounds, which may help to prevent metabolic syndrome disorders including diabetes, act through relevant intracellular signaling pathways. In this review, we examine the anti-diabetic efficacy of several compounds and extracts derived from medicinal plants, with a focus on AMP-activated protein kinase (AMPK) activity.

Mechanism exploration of Gouqi-wentang formula against type 2 diabetes mellitus by phytochemistry and network pharmacology-based analysis and biological validation

BACKGROUND

The Gouqi-wentang formula (GQWTF) is a herbal formula used by Academician Xiao-lin Tong for the clinical treatment of T2DM. GQWTF is beneficial to qi, nourishes Yin, clears heat, and promotes fluid production, but the effective components and their mechanism of action remain unclear.

METHODS

The main components of GQWTF were detected by LC-MS, and the multi-target mechanisms of GQWTF in T2DM were elucidated using network pharmacology analysis, including target prediction, protein-protein interaction network construction and analysis, Gene Ontology (GO) terms, Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway annotation, and other network construction. Finally, the efficacy of the GQWTF was verified using biological experiments.

RESULTS

First, the "herb-channel tropism" network suggested that GQWTF focuses more on treating diseases by recuperating the liver, which is considered as an important insulin-sensitive organ. Subsequently, a total of 16 active ingredients in GQWTF were detected and screened, and their biological targets were predicted. Then, "compound-target" network was constructed, where enrichment analysis of GQWTF targets reflected its potential pharmacological activities. After T2DM-related target identification, 39 cross targets of GQWTF and T2DM were obtained, and 30 key targets highly responsible for the beneficial effect of GQWTF on T2DM were identified by PPI analysis. GO analysis of these key targets showed that many biological processes of GQWTF in treating T2DM are key in the occurrence and development of T2DM, including components related to inflammatory/immune response, insulin, and metabolism. KEGG analysis revealed the regulation of multiple signalling pathways, such as insulin resistance, PPAR signalling pathway, FoxO signalling pathway, Fc epsilon RI signalling pathway, and pathways that influence diabetes primarily by regulating metabolism as well as other T2DM directly related pathways. Furthermore, a "formula-compound-pathway-symptom" network was constructed to represent a global view of GQWTF in the treatment of T2DM.

CONCLUSIONS

This study explored the mechanism of action of GQWTF in T2DM by multi-component and multi-target multi pathways, which could provide a theoretical basis for the development and clinical application of GQWTF.

Current progress in pharmacogenomics of Type 2 diabetes: A systemic overview

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is a prevalent disease with incidences increasing globally at a rapid rate. The goal of T2DM treatment is to control glucose levels and prevent the aggravation of glycemic symptoms.

TREATMENT OPTIONS

T2DM regimen include metformin as the first-line, with sulfonylurea, thiazolidinedione (TZD), GLP-1, DPP4I, and SGLT2 inhibitor as the second-line treatment options. However, even with a multitude of choices, patient-to-patient variability due to pharmacogenomic differences still prevail.

CONCLUSION

This review aims to discuss the responses of the major T2DM medications influenced by pharmacogenomics and investigate improved personalized therapy for T2DM patients.

Metformin treatment for 8 days impacts multiple intestinal parameters in high-fat high-sucrose fed mice

Although the mechanism of action of the antidiabetic drug metformin is still a matter of discussions, it is well accepted that the gut plays an important role. To gain more insights into the mechanisms occurring in the different regions of the intestine, adult male mice were fed a high-fat-high sucrose (HFS) diet for 8 days and treated with metformin by gavage (300 mg/day/kg body weight) during the HFS diet. Metformin counteracted HFS diet-induced overexpression of a network of genes involved in the transport of glucose and fatty acids in the different regions of the small intestine. It also induced beneficial modification of secondary bile acid profile in the caecum, with a reduction of deoxycholic acid and lithocholic acid levels and increased abundance of ursodeoxycholic acid and tauroursodeoxycholic acid, potentially leading to FRX inhibition. In parallel, metformin treatment was associated with specific changes of the microbiota composition in the lumen of the different regions of the intestine. Metformin induced a marked increase in the abundance of Akkermansia muciniphila in the lumen all along the gut and counteracted the effects of HFS diet on the abundances of some bacterial groups generally associated with metabolic disturbances (f-Lachnospiraceae, f-Petostreptococcaceae, g-Clostidium). Therefore, the present work clearly emphasises the role of all the regions of the intestinal tract in the beneficial action of the antidiabetic drug metformin in a prediabetic mouse model.

Effect of traditional Chinese medicine on gut microbiota in adults with type 2 diabetes: A systematic review and meta-analysis

BACKGROUND

Despite advances in research on type 2 diabetes mellitus (T2DM) with the development of science and technology, the pathogenesis and treatment response of T2DM remain unclear. Recent studies have revealed a significant role of the microbiomein the development of T2DM, and studies have found that the gut microbiota may explain the therapeutic effect of traditional Chinese medicine (TCM), a primary branch of alternative and complementary medicine, in the treatment of T2DM. The aim of this study was to systematically review all randomized controlled trials (RCTs) on TCM for gut microbiota to assess the effectiveness and safety of TCM in T2DM patients.

METHODS

All RCTs investigating the effects of TCM interventions on modulating gut microbiota and improving glucose metabolism in the treatment of T2DM adults were included. Meta-analyses were conducted when sufficient data were available, other results were reported narratively. The study protocol was pre-specified, documented, and published in PROSPERO (registration no. CRD42020188043).

RESULTS

Five studies met the eligibility criteria ofthe systematic review. All five studies reported the effects of TCM interventions on the gut microbiota modulation and blood glucose control. There were statistically significant improvements in HbA1c (mean difference [MD]: -0.69%; [95% CI -0.24, -0.14]; p = 0.01, I² = 86%), fasting blood glucose (MD: -0.87 mmol/l; [95% CI -1.26, -0.49]; p < 0.00001, I² = 75%) and 2-h postprandial blood glucose(MD: -0.83mmol/l; [95% CI: -1.01, -0.65]; p < 0.00001, I² = 0%). In addition, there were also statistically significant improvements in homeostasis model assessment of insulin resistance (HOMA-IR) (standardized mean difference [SMD]: -0.99, [95% CI -1.25 to -0.73]; p < 0.00001, I² = 0%) and homeostasis model assessment of β-cell function (HOMA-β) (SMD: 0.54, [95% CI 0.21 to 0.87]; p = 0.001, I² = 0%).There was a significant change in the relative abundance of bacteria in the genera Bacteroides (standardized mean difference [SMD] 0.87%; [95% CI 0.58, 1.16], however, the change in Enterococcus abundance was not statistically significant (SMD: -1.71%; [95% CI: -3.64, 0.23]; p = 0.08) when comparing TCM supplementaltreatment with comparator groups. Other changes in the gut microbiota, including changes in the relative abundances of some probiotics and opportunistic pathogens at various taxon levels, and changes in diversity matrices (α and β), were significant by narrative analysis. However, insufficient evidences were found to support that TCM intervention had an effect on inflammation.

CONCLUSION

TCM had the effect of modulating gut microbiota and improving glucose metabolisms in T2DM patients. Although the results of the included studies are encouraging, further well-conducted studies on TCM interventions targeting the gut microbiota are needed.

Glycoursodeoxycholic acid ameliorates diet-induced metabolic disorders with inhibiting endoplasmic reticulum stress

Recent studies reveal that bile acid metabolite composition and its metabolism are changed in metabolic disorders, such as obesity, type 2 diabetes and metabolic associated fatty liver disease (MAFLD), yet its role and the mechanism remain largely unknown. In the present study, metabolomic analysis of 163 serum and stool samples of our metabolic disease cohort was performed, and we identified glycoursodeoxycholic acid (GUDCA), glycine-conjugated bile acid produced from intestinal bacteria, was decreased in both serum and stool samples from patients with hyperglycemia. RNA-sequencing and quantitative PCR results indicated that GUDCA alleviated endoplasmic reticulum (ER) stress in livers of high fat diet (HFD)-fed mice without alteration of liver metabolism. In vitro, GUDCA reduced palmitic acid induced-ER stress and -apoptosis, as well as stabilized calcium homeostasis. In vivo, GUDCA exerted effects on amelioration of HFD-induced insulin resistance and hepatic steatosis. In parallel, ER stress and apoptosis were decreased in GUDCA-treated mice as compared with vehicle-treated mice in liver. These findings demonstrate that reduced GUDCA is an indicator of hyperglycemia. Supplementation of GUDCA could be an option for the treatment of diet-induced metabolic disorders, including insulin resistance and hepatic steatosis, with inhibiting ER stress.

[Treatment persistence with brand-name vs. generic metformin in monotherapy for type 2 diabetes: real-life retrospective study using the propensity matching score]

OBJECTIVE

To evaluate treatment persistence in patients with polymedicated type 2 diabetes (DM2) receiving new treatment with brand-name vs. generic metformin 850mg in usual clinical practice.

PATIENTS AND METHODS

Observational, retrospective study based on the medical records of patients aged ≥50 years who initiated metformin treatment (brand-name vs. generic) between 01/01/2016 and 31/12/2017. The follow up was two years.

MAIN MEASURES

treatment persistence and clinical consequences (metabolic control [HbA1c] and hospital admissions). Each patient in the brand-name group (reference) was paired with a patient from the generic group using propensity score matching. A Cox proportional risk model was constructed (p<0.05).

RESULTS

863 patients receiving brand-name metformin were matched (ratio 1:1) with patients receiving generic metformin. The median age was 60.8 years (SD: 8.8) years and 52.6% were female. Persistence at 24 months was 8.6% higher for brand-name vs. generic metformin (63.2% vs. 58.2%; p=0.034). The hazard ratio for brand-name metformin was 0.83 (95% CI: 0.71-0.96, p=0.013). During the follow-up there was a greater percentage reduction of HbA1c in the brand-name vs. generic group (-6.8% vs. -4.1%; p=0.013). There was a non-significant 19.1% reduction in hospital admissions in the brand-name vs. generic group (8.9% vs. 11.0%; p=0.148).

CONCLUSIONS

Polymedicated patients who initiated new brand-name metformin treatment for DM2 had greater treatment persistence than those who initiated it with generic metformin and had better metabolic control (percentage reduction in HbA1c).

Gut Microbiome of Indonesian Adults Associated with Obesity and Type 2 Diabetes: A Cross-Sectional Study in an Asian City, Yogyakarta

Indonesia is a developing country facing the national problem of the growing obesity and diabetes in its population due to recent drastic dietary and lifestyle changes. To understand the link between the gut microbiome, diet, and health of Indonesian people, fecal microbiomes and metabolomes of 75 Indonesian adults in Yogyakarta City, including obese people (n = 21), type 2 diabetes (T2D) patients (n = 25), and the controls (n = 29) were characterized together with their dietary and medical records. Variations of microbiomes showed a triangular distribution in the principal component analysis, driven by three dominant bacterial genera, namely Bacteroides, Prevotella, and Romboutsia. The Romboutsia-driven microbiome, characterized by low bacterial diversity and high primary bile acids, was associated with fat-driven obesity. The Bacteroides-driven microbiome, which counteracted Prevotella but was associated with Ruminococcaceae concomitantly increased with high-carbohydrate diets, showed positive correlation with T2D indices but negative correlation with body mass index. Notably, Bacteroides fragilis was increased in T2D patients with a decrease in fecal conjugated bile acids, particularly tauroursodeoxycholic acid (TUDCA), a farnesoid X receptor (FXR) antagonist with anti-diabetic activity, while these features disappeared in patients administered metformin. These results indicate that the gut microbiome status of Indonesian adults is differently associated with obesity and T2D under their varied dietary habits.

The Relationship between the Gut Microbiome and Metformin as a Key for Treating Type 2 Diabetes Mellitus

Metformin is the first-line pharmacotherapy for treating type 2 diabetes mellitus (T2DM); however, its mechanism of modulating glucose metabolism is elusive. Recent advances have identified the gut as a potential target of metformin. As patients with metabolic disorders exhibit dysbiosis, the gut microbiome has garnered interest as a potential target for metabolic disease. Henceforth, studies have focused on unraveling the relationship of metabolic disorders with the human gut microbiome. According to various metagenome studies, gut dysbiosis is evident in T2DM patients. Besides this, alterations in the gut microbiome were also observed in the metformin-treated T2DM patients compared to the non-treated T2DM patients. Thus, several studies on rodents have suggested potential mechanisms interacting with the gut microbiome, including regulation of glucose metabolism, an increase in short-chain fatty acids, strengthening intestinal permeability against lipopolysaccharides, modulating the immune response, and interaction with bile acids. Furthermore, human studies have demonstrated evidence substantiating the hypotheses based on rodent studies. This review discusses the current knowledge of how metformin modulates T2DM with respect to the gut microbiome and discusses the prospect of harnessing this mechanism in treating T2DM.

Role of Bile Acids in the Regulation of Food Intake, and Their Dysregulation in Metabolic Disease

Bile acids are cholesterol-derived metabolites with a well-established role in the digestion and absorption of dietary fat. More recently, the discovery of bile acids as natural ligands for the nuclear farnesoid X receptor (FXR) and membrane Takeda G-protein-coupled receptor 5 (TGR5), and the recognition of the effects of FXR and TGR5 signaling have led to a paradigm shift in knowledge regarding bile acid physiology and metabolic health. Bile acids are now recognized as signaling molecules that orchestrate blood glucose, lipid and energy metabolism. Changes in FXR and/or TGR5 signaling modulates the secretion of gastrointestinal hormones including glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), hepatic gluconeogenesis, glycogen synthesis, energy expenditure, and the composition of the gut microbiome. These effects may contribute to the metabolic benefits of bile acid sequestrants, metformin, and bariatric surgery. This review focuses on the role of bile acids in energy intake and body weight, particularly their effects on gastrointestinal hormone secretion, the changes in obesity and T2D, and their potential relevance to the management of metabolic disorders.

The Cross-talk Relationship between Metformin and Gut Microbiota

Background: Metformin is the first-line oral therapy for type 2 diabetes mellitus. However, its mode of action is poorly defined. There is an increasing awareness regarding the cross talk of gut microbiota and metformin. The current review aimed to assess the bidirectional relationship between metformin and gut microbiota. Methods: Electronic search was conducted in Pub Med and the first 100 articles in Google Scholar published until November 2019. However, only randomized controlled trials on humans published in the English language were included.  The terms “gut microbiota,” “gut flora "and “ metformin” were as keywords to perform the search. Although 124 articles were retrieved, only six met the inclusion criteria of the study. Results: Of the six full texts of randomized controlled trials included in the study, two-thirds were published in Europe, one in the USA, and one in China. Six hundred-thirty five patients were included and the duration of the studies ranged from seven days to six months. The studies concluded that microbiota modulates some metformin actions on plasma glucose; while metformin enhances the abundance of microbiota that positively affect insulin resistance and plasma glucose. Conclusion: The current review showed that microbiota dysbiosis may mediate metformin antidiabetic effects. Whereas metformin shifted the gut microbiota toward the beneficial species ameliorating insulin resistance. The present study might provide insights into a novel therapeutic approach to treat type 2 diabetes mellitus. Key words: gut microbiota, metformin, type 2 diabetes