Holistic perspective of the role of gut microbes in diabetes mellitus and its management

Probiotics and synbiotics for glycemic control in diabetes: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

The escalating prevalence of diabetes mellitus may benefit from add-on therapeutic approaches. Given the recognized need for an updated synthesis of the literature, this systematic review and meta-analysis aimed to synthesize and critically assess the available randomized controlled trials (RCTs) that investigate the efficacy of probiotics and synbiotics on glycemic control in patients with Type 1 (T1DM) and Type 2 (T2DM) diabetes mellitus.

METHODS

Comprehensive searches were conducted on PubMed, Embase, CINAHL, Scopus, and Web of Science, focusing on adults with T1DM or T2DM. All comparators were deemed eligible. Primary outcomes included changes in glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), and insulin levels. Only RCTs were included, and the Cochrane RoB2 tool assessed the risk of bias. Random-effect models facilitated data analysis, supplemented by sensitivity, subgroup analyses, and meta-regressions.

RESULTS

A total of 537 records were screened, resulting in 41 RCTs for analysis, which comprises 2991 (54% females) patients with diabetes. The meta-analysis revealed statistically significant improvements in HbA1c (standardized mean difference (SMD) = -0.282, 95% CI: [-0.37, -0.19], p < 0.001), FPG (SMD = -0.175, 95% CI: [-0.26, -0.09], p < 0.001), and insulin levels (SMD = -0.273, 95% CI: [-0.35, -0.20], p < 0.001). A medium degree of heterogeneity between studies was found in HbA1c (I2 = 62.5%), FPG (I2 = 71.5%), and insulin levels (I2 = 66.4%) analyses. Subgroup analyses indicated that the efficacy varied based on the type of strains used and the country. Multispecies strains were particularly effective in improving HbA1c levels.

CONCLUSION

The study findings suggest that probiotics and synbiotics may be effective as complementary therapies for managing diabetes. Additionally, the study underscores the need for further tailored research that considers variables such as strain types and geographical factors to deepen the understanding of the role of these interventions in diabetes care.

REVIEW REGISTRATION NUMBER

PROSPERO (CRD42023396348).

Technological Trends Involving Probiotics in the Treatment of Diabetic Neuropathy: A Patent Review (2009-2022)

BACKGROUND

Diabetic neuropathy (DN) causes neuropathic pain, and current treatments are unsatisfactory. Recently studies have demonstrated an assertive correlation between gut microbiota and pain modulation.

OBJECTIVE

Considering the emerging search for new therapies for the control of DN and the growing commercial interest in the probiotics market, this study aimed to provide patents on the use of probiotics in the control of DN.

METHODS

This is a patent prospection performed in the Espacenet Patent database, using the association of keywords and IPC related to probiotics in medical preparations and foods, from 2009 to December 2022.

RESULTS

Results have shown that in 2020, there was a boom in patent filing in the area. Asian countries accounted for more than 50% of all 48 inventions (n = 48), with Japan as the only applicant in 2021. Products being developed in recent years point to effects that may represent an advancement in DN treatment, such as reduced concentration of pro-inflammatory mediators, metabolites and neurotransmitters release, and hypoglycemic potential. All effects were more related to the Lactobacillus and Bifidobacterium genera, associated with more than one property mentioned.

CONCLUSION

The mechanisms attributed to the microorganisms suggest the therapeutic potential of probiotics in the non-pharmacological treatment of pain. New applications for probiotics have resulted from great research interest by academia, but also reflect commercial interests despite the paucity of clinical trials. Thus, the present work supports the evolution of research to explore the benefits of probiotics and their clinical use in DN.

Constipation and cardiovascular disease: A two-sample Mendelian randomization analysis

Background

Although several observational studies have suggested positive associations between constipation and cardiovascular disease (CVD), a solid causal association has not been demonstrated. Therefore, a two-sample Mendelian randomization (MR) study was performed to investigate the causal associations between constipation and CVD.

Methods

Independent genetic variants strongly associated with constipation were obtained from the FinnGen consortium. Summary-level data for CVD, including coronary artery disease (CAD), myocardial infarction (MI), heart failure (HF), atrial fibrillation (AF), stroke, and its subtypes, were collected from a few extensive genome-wide association studies (GWASs). The inverse-variance weighted methods, weighted median, and MR-Egger were used for the MR estimates. The Cochran's Q test, MR-Egger intercept tests, MR-PRESSO, MR Steiger test, leave-one-out analyses, and funnel plot were used in the sensitivity analysis.

Results

Genetically determined constipation was suggestively associated with AF risk (odds ratio (OR), 1.07; 95% confidence interval (CI), 1.01, 1.14; p = 0.016). Constipation and other CVD do not appear to be causally related. It was demonstrated that the results were robust through sensitivity analyses.

Conclusion

This MR study demonstrated suggestive causal associations of constipation on AF, despite no associations achieving a significance value after multiple testing corrections. There was no evidence of an association between constipation and the risk of CAD, MI, HF, stroke, or stroke subtypes.

Gut microbiota, behavior, and nutrition after type 1 diabetes diagnosis: A longitudinal study for supporting data in the metabolic control

Introduction

Type 1 diabetes (T1D) risk involves genetic susceptibility but also epigenetics, environment, and behaviors. Appropriate metabolic control, especially quickly after the diagnosis, is crucial for the patient quality of life.

Methods

This study aimed to produce a quantitative comparison of the behavior, nutrition habits, and gut microbiota composition between the onset and the 1-year follow-up in 35 children with T1D.

Results and discussion

At follow-up, with the metabolic control, many parameters improved significantly, with respect to the onset, such as glycated hemoglobin (-19%), body mass index (BMI), and also nutritional behaviors, such as normal calorie intake (+6%), carbohydrate intake (-12%), extra portion request (-4%), and meals distribution during the day. Moreover, glycated hemoglobin decrement correlated with both total and rapid absorption carbohydrate intake (Spearman's rho = 0.288, 95% CI 0.066-0.510, p = 0.013), showing as the nutritional behavior supported the insulin therapy efficiency. The next-generation sequencing (NGS) analysis of microbiota revealed abundance differences for Ruminococcus bromii and Prevotella copri (higher at onset, p < 0.001) and the genera Succinivibrio and Faecalibacterium (lower at onset, p < 0.001), as a consequence of nutritional behavior, but it was not the only changing driver. The qRT-PCR analysis showed significant variations, in particular for Bacteroidetes and Bifidobacterium spp. (+1.56 log gene copies/g stool at follow-up, p < 0.001). During the year, in 11% of the patients, severe clinical episodes occurred (hypoglycemic or ketoacidosis). The likelihood of a severe hypoglycemic episode was modulated when the Methanobrevibacter smithii amount increased (odds ratio 3.7, 95% CI 1.2-11.4, p = 0.026). Integrated evaluation, including nutritional behavior and microbiota composition, could be considered predictive of the metabolic control management for children cohort with a recent diagnosis of T1D.

Association of abnormal bowel health with major chronic diseases and risk of mortality

PURPOSE

We aimed to explore the association of chronic constipation and diarrhea with major chronic diseases including cancer, cardiovascular disease (CVD), and diabetes, as well as with mortality risk. In addition, we characterized the interrelationship of inflammation with abnormal bowel health, major chronic diseases, and mortality.

METHODS

Demographic characteristics, physical and laboratory examinations were collected from the National Health and Nutrition Examination Survey (NHANES) database 2005-2010. Chronic constipation or diarrhea was diagnosed by the shape and frequency of defecation. The number of samples used for the cancer, CVD, diabetes, and mortality analyses were 11,217, 11,168, 11,555, and 14,316, respectively. Logistic regression was used to analyze the association among abnormal bowel health, major chronic diseases, dietary inflammatory index (DII), and C-reactive protein (CRP). A Cox proportional hazard regression was performed to assess risk of all-cause mortality, and the Fine and Gray models were subsequently employed to calculate the cancer and CVD mortality risks.

RESULTS

There were statistically positive associations of chronic diarrhea or constipation with breast and colon cancer, CVD, risks of all-cause mortality, and CVD mortality. Particularly in participants younger than 60, in addition to the positive correlations of chronic diarrhea with three major chronic diseases and all-cause mortality risk, chronic constipation also contributed to an elevated risk of CVD mortality. With respect to inflammation markers, an increased DII or CRP level was significantly associated with a higher prevalence of abnormal bowel health and major chronic diseases, and a higher mortality risk.

CONCLUSIONS

Participants with abnormal bowel health were more likely linked to breast cancer, colon cancer, CVD, and risks of all-cause and CVD mortality. Moreover, inflammation may have a potential role in associations among abnormal bowel health, major chronic diseases and mortality. However, these findings need to be confirmed by further prospective studies.

The Activity of Prebiotics and Probiotics in Hepatogastrointestinal Disorders and Diseases Associated with Metabolic Syndrome

The components of metabolic syndrome (MetS) and hepatogastrointestinal diseases are widespread worldwide, since many factors associated with lifestyle and diet influence their development and correlation. Due to these growing health problems, it is necessary to search for effective alternatives for prevention or adjuvants in treating them. The positive impact of regulated microbiota on health is known; however, states of dysbiosis are closely related to the development of the conditions mentioned above. Therefore, the role of prebiotics, probiotics, or symbiotic complexes has been extensively evaluated; the results are favorable, showing that they play a crucial role in the regulation of the immune system, the metabolism of carbohydrates and lipids, and the biotransformation of bile acids, as well as the modulation of their central receptors FXR and TGR-5, which also have essential immunomodulatory and metabolic activities. It has also been observed that they can benefit the host by displacing pathogenic species, improving the dysbiosis state in MetS. Current studies have reported that paraprobiotics (dead or inactive probiotics) or postbiotics (metabolites generated by active probiotics) also benefit hepatogastrointestinal health.

Faecal microbiota transplantation is better than probiotics for tissue regeneration of type 2 diabetes mellitus injuries in mice

CONTEXT

Western diet and unhealthy lifestyle have contributed to the continued growth of type 2 diabetes mellitus (T2DM). T2DM is associated with dysbacteriosis, and studies have found that altering the gut microbiota has a positive effect on treatment.

OBJECTIVE

In addition to hyperglycaemia, T2DM often causes damage to multiple organs. However, there are few studies on organ damage from faecal microbiota transplantation (FMT).

MATERIALS AND METHODS

T2DM mice were divided into four groups and were given phosphate buffered saline (PBS) (T2DM group), FMT (FMT group), Lactobacillus (LAB group), and Bifidobacterium (BIO group) by gavage for six weeks, respectively. Mice on a normal diet (control group) were gavaged with PBS for six weeks.

RESULTS

After gavage treatment, FMT, LAB, and BIO groups were similar in lowering glucose, endotoxemia was slightly reduced, and the colonic mucus layer and liver lobules developed towards normal tissue. Surprisingly, we found that the FMT group had unique effects on islet cell regeneration, increased functional β cells, and insulin sensitivity.

DISCUSSION AND CONCLUSION

Lactobacillus has the best glucose-lowering effect, but FMT has obvious advantages in β-cell regeneration, which provides new treatment ideas for tissue damage caused by T2DM.

Is Intestinal Dysbiosis-Associated With Immunosuppressive Therapy a Key Factor in the Pathophysiology of Post-Transplant Diabetes Mellitus?

Post-transplant diabetes mellitus (PTDM) is one of the most common and deleterious comorbidities after solid organ transplantation (SOT). Its incidence varies depending on the organs transplanted and can affect up to 40% of patients. Current research indicates that PTDM shares several common features with type 2 diabetes mellitus (T2DM) in non-transplant populations. However, the pathophysiology of PTDM is still poorly characterized. Therefore, ways should be sought to improve its diagnosis and therapeutic management. A clear correlation has been made between PTDM and the use of immunosuppressants. Moreover, immunosuppressants are known to induce gut microbiota alterations, also called intestinal dysbiosis. Whereas the role of intestinal dysbiosis in the development of T2DM has been well documented, little is known about its impacts on PTDM. Functional alterations associated with intestinal dysbiosis, especially defects in pathways generating physiologically active bacterial metabolites (e.g., short-chain fatty acids, trimethylamine N-oxide, indole and kynurenine) are known to favour several metabolic disorders. This publication aims at discussing the potential role of intestinal dysbiosis and dysregulation of bacterial metabolites associated with immunosuppressive therapy in the occurrence of PTDM.

The Synbiotic Combination of Akkermansia muciniphila and Quercetin Ameliorates Early Obesity and NAFLD through Gut Microbiota Reshaping and Bile Acid Metabolism Modulation

Gut microbiota plays a key role in obesity and non-alcoholic fatty liver disease (NAFLD), so synbiotics could be a therapeutic alternative. We aim to evaluate a nutritional intervention together with the administration of the bacteria Akkermansia muciniphila and the antioxidant quercetin in an in vivo model of early obesity and NAFLD. 21-day-old rats were fed with control or high-fat diet for six weeks. Then, all animals received control diet supplemented with/without quercetin and/or A. muciniphila for three weeks. Gut microbiota, NAFLD-related parameters, circulating bile acids (BAs) and liver gene expression were analyzed. The colonization with A. muciniphila was associated with less body fat, while synbiotic treatment caused a steatosis remission, linked to hepatic lipogenesis modulation. The synbiotic promoted higher abundance of Cyanobacteria and Oscillospira, and lower levels of Actinobacteria, Lactococcus, Lactobacillus and Roseburia. Moreover, it favored elevated unconjugated hydrophilic BAs plasma levels and enhanced hepatic expression of BA synthesis and transport genes. A. muciniphila correlated with circulating BAs and liver lipid and BA metabolism genes, suggesting a role of this bacterium in BA signaling. Beneficial effects of A. muciniphila and quercetin combination are driven by gut microbiota modulation, the shift in BAs and the gut-liver bile flow enhancement.