Prebiotic fiber increases hepatic acetyl CoA carboxylase phosphorylation and suppresses glucose-dependent insulinotropic polypeptide secretion more effectively when used with metformin in obese rats

Metformin with Versus without Concomitant Probiotic Therapy in Newly Diagnosed Patients with Type 2 Diabetes or Prediabetes: A Comparative Analysis in Relation to Glycemic Control, Gastrointestinal Side Effects, and Treatment Compliance

BACKGROUND

To evaluate the impact of concomitant use of probiotic BB-12 in metformin-treated patients with type 2 diabetes or prediabetes on glycemic control, metformin-related gastrointestinal side effects, and treatment compliance.

METHODS

A total of 156 patients (mean [standard deviation] age: 50.9 [9.9 years], 74.4% females) with newly diagnosed type 2 diabetes or prediabetes were randomly assigned to receive either metformin alone (n = 84, MET group) or metformin plus Bifidobacterium animalis subsp. lactis (BB-12) probiotic (n = 72, MET-PRO group). Data on body mass index (kg/m2), fasting blood glucose (mg/dL), blood lipids, and glycated hemoglobin (HbA1c) levels were recorded at baseline and at the third month of therapy. Data on gastrointestinal intolerance symptoms and treatment noncompliance were also recorded during post-treatment week 1 to week 4.

RESULTS

MET-PRO versus MET therapy was associated with a significantly higher rate of treatment compliance (91.7% vs 71.4%, P = .001), greater reduction from baseline HbA1c values (0.9 [0.4-1.6] vs 0.4 [0-1.6] %, P < .001) and lower likelihood of gastrointestinal intolerance symptoms, including abdominal pain (P = .031 to <.001), diarrhea (P = .005 to <.001) and bloating (P = .010 to <.001). Noncompliance developed later (at least 15 days after the therapy) in a significantly higher percentage of patients in the MET group (P = .001 for 15-21 days and P = .002 for 22-28 days).

CONCLUSION

In conclusion, the present study proposes the benefit of combining probiotics with metformin in the treatment of patients with T2D or prediabetes in terms of improved glycemic control and treatment adherence rather than correction of dyslipidemia or weight reduction.

Diet-Derived Phytochemicals Targeting Colon Cancer Stem Cells and Microbiota in Colorectal Cancer

Colorectal cancer (CRC) is a fatal disease caused by the uncontrolled propagation and endurance of atypical colon cells. A person's lifestyle and eating pattern have significant impacts on the CRC in a positive and/or negative way. Diet-derived phytochemicals modulate the microbiome as well as targeting colon cancer stem cells (CSCs) that are found to offer significant protective effects against CRC, which were organized in an appropriate spot on the paper. All information on dietary phytochemicals, gut microbiome, CSCs, and their influence on CRC were accessed from the various databases and electronic search engines. The effectiveness of CRC can be reduced using various dietary phytochemicals or modulating microbiome that reduces or inverses the progression of a tumor as well as CSCs, which could be a promising and efficient way to reduce the burden of CRC. Phytochemicals with modulation of gut microbiome continue to be auspicious investigations in CRC through noticeable anti-tumorigenic effects and goals to CSCs, which provides new openings for cancer inhibition and treatment.

Diosgenin and 4-Hydroxyisoleucine from Fenugreek Are Regulators of Genes Involved in Lipid Metabolism in The Human Colorectal Cancer Cell Line SW480

Objective

Diosignin and 4-hydroxy-L-isulosine (4-OH-Ile) are the two active ingredients of Fenugreek (Trigonella foenumgraecum). Thus, in this study, we examined the effects of hydroalcoholic extract of fenugreek seeds (HEFS), diosgenin and 4-OH-Ile on the expression of acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), peroxisome proliferator-activated receptor gamma (PPARγ) and low-density lipoprotein (LDL) receptor (LDLR) which are involved in lipid metabolism in SW480 cell line.

Materials and Methods

In this experimental study, SW480 cells were cultured in RPMI-1640 medium and treated with HEFS, diosignin, 4-OH-Ile or orlistat for 24 and 48 hours. Inhibitory concentration of 20% (IC20) was calculated using MTT method and cells were then pre-treated with the IC20 concentrations for 24 and 48 hours before RNA extraction and cDNA synthesis. Changes in the expression of ACC, FAS, PPARγ and LDLR genes were assayed by employing the real time-polymerase chain reaction (PCR) method.

Results

Our results showed a significant down-regulation in the expression of ACC (P<0.001 and P<0.001 after 24 and 48 hours, respectively) and FAS genes (P<0.001 and P<0.001 after 24 and 48 hours, respectively) in SW480 cells treated with HEFS, diosignin, 4-OH-Ile, or orlistat, but significant up-regulation in the expression of PPARγ (P<0.001 and P<0.001 after 24 and 48 hours, respectively) and LDLR (P=0.005 and P=0.001 after 24 and 48 hours, respectively).

Conclusion

According to the results of the present study, HEFS, diosgenin and 4-OH-Ile up or down-regulate the expression of some predominant genes involved in lipid metabolism pathway, similar to that observed for orlistat. These types of regulatory effects are presumably proper for the treatment of obesity and overweight.

Effects of Non-insulin Anti-hyperglycemic Agents on Gut Microbiota: A Systematic Review on Human and Animal Studies

Background: As growing evidence links gut microbiota with the therapeutic efficacy and side effects of anti-hyperglycemic drugs, this article aims to provide a systematic review of the reciprocal interactions between anti-hyperglycemic drugs and gut microbiota taxa, which underlie the effect of the gut microbiome on diabetic control via bug-host interactions. Method: We followed the PRISMA requirements to perform a systematic review on human vs. animal gut microbiota data in PubMed, SCOPUS, and EMBASE databases, and used Cochrane, ROBIN-I, and SYRCLE tools to assess potential bias risks. The outcomes of assessment were trends on gut microbiota taxa, diversity, and associations with metabolic control (e.g., glucose, lipid) following anti-hyperglycemic treatment. Results: Of 2,804 citations, 64 studies (17/humans; 47/mice) were included. In human studies, seven were randomized trials using metformin or acarbose in obese, pre-diabetes, and type 2 diabetes (T2D) patients. Treatment of pre-diabetes and newly diagnosed T2D patients with metformin or acarbose was associated with decreases in genus of Bacteroides, accompanied by increases in both Bifidobacterium and Lactobacillus. Additionally, T2D patients receiving metformin showed increases in various taxa of the order Enterobacteriales and the species Akkermansia muciniphila. Of seven studies with significant differences in beta-diversity, the incremental specific taxa were associated with the improvement of glucose and lipid profiles. In mice, the effects of metformin on A. muciniphila were similar, but an inverse association with Bacteroides was reported. Animal studies on other anti-hyperglycemic drugs, however, showed substantial variations in results. Conclusions: The changes in specific taxa and β-diversity of gut microbiota were associated with metformin and acarbose in humans while pertinent information for other anti-hyperglycemic drugs could only be obtained in rodent studies. Further human studies on anti-hyperglycemic drugs other than metformin and acarbose are needed to explore gut microbiota's role in their therapeutic efficacies and side effects.

Metformin as Anti-Aging Therapy: Is It for Everyone?

Metformin is the most widely prescribed oral hypoglycemic medication for type 2 diabetes worldwide. Metformin also retards aging in model organisms and reduces the incidence of aging-related diseases such as neurodegenerative disease and cancer in humans. In spite of its widespread use, the mechanisms by which metformin exerts favorable effects on aging remain largely unknown. Further, not all individuals prescribed metformin derive the same benefit and some develop side effects. Before metformin finds its way to mainstay therapy for anti-aging, a more granular understanding of the effects of the drug in humans is needed. This review provides an overview of recent findings from metformin studies in aging and longevity and discusses the use of metformin to combat aging and aging-related diseases.

Relationship between diet/exercise and pharmacotherapy to enhance the GLP-1 levels in type 2 diabetes

The rapid rise in the prevalence of type 2 diabetes mellitus (T2DM) poses a huge healthcare burden across the world. Although there are several antihyperglycaemic agents (AHAs) available including addition of new drug classes to the treatment algorithm, more than 50% of patients with T2DM do not achieve glycaemic targets, suggesting an urgent need for treatment strategies focusing on prevention and progression of T2DM and its long-term complications. Lifestyle changes including implementation of healthy diet and physical activity are cornerstones for the management of T2DM. The positive effects of diet and exercise on incretin hormones such as glucagon-like peptide-1 (GLP-1) have been reported. We hypothesize an IDEP concept (Interaction between Diet/Exercise and Pharmacotherapy) aimed at modifying the diet and lifestyle, along with pharmacotherapy to enhance the GLP-1 levels, would result in good glycaemic control in patients with T2DM. Consuming protein-rich food, avoiding saturated fatty acids and making small changes in eating habits such as eating slowly with longer mastication time can have a positive impact on the GLP-1 secretion and insulin levels. Further the type of physical activity (aerobic/resistance training), intensity of exercise, duration, time and frequency of exercise have shown to improve GLP-1 levels. Apart from AHAs, a few antihypertensive drugs and lipid-lowering drugs have also shown to increase endogenous GLP-1 levels, however, due to quick degradation of GLP-1 by dipeptidyl peptidase-4 (DPP-4) enzyme, treatment with DPP-4 inhibitors would protect GLP-1 from degradation and prolong its activity. Thus, IDEP concept can be a promising treatment strategy, which positively influences the GLP-1 levels and provide additive benefits in terms of improving metabolic parameters in patients with T2DM and slowing the progression of T2DM and its associated complications.

Antiobesity Effect of Flaxseed Polysaccharide via Inducing Satiety due to Leptin Resistance Removal and Promoting Lipid Metabolism through the AMP-Activated Protein Kinase (AMPK) Signaling Pathway

Obesity is a metabolic syndrome worldwide that causes many chronic diseases. Recently, we found an antiobesity effect of flaxseed polysaccharide (FP), but the mechanism remains to be elucidated. In this study, rats were first induced to develop obesity by being fed a high-fat diet. The obese rats were then fed a control diet, AIN-93M (group HFD), or a 10% FP diet (group FPD). The body weight, body fat, adipose tissue and liver sections, serous total triglycerides, levels of fasting blood glucose in serum, serous insulin, inflammatory cytokines in serum, and serous proteins within the leptin-neuropeptide Y (NPY) and AMP-activated protein kinase (AMPK) signaling pathway were determined and analyzed. FP intervention significantly reduced body weight and abdominal fat from 530 ± 16 g and 2.15% ± 0.30% in group HFD to 478 ± 10 g and 1.38% ± 0.48% in group FPD, respectively. This effect was achieved by removing leptin resistance possibly by inhibiting inflammation and recovering satiety through the significant downregulation of NPY and the upregulation of glucagon-like peptide 1. Adiponectin was then significantly upregulated probably via the gut-brain axis and further activated the AMPK signaling pathway to improve lipid metabolism including the improvement of lipolysis and fatty acid oxidation and the suppression of lipogenesis. This is the first report of the proposed antiobesity mechanism of FP, thereby providing a comprehensive understanding of nonstarch polysaccharides and obesity.

Role of prebiotics in regulation of microbiota and prevention of obesity

There is an increasing incidence in non-communicable diseases (NCD) such as obesity, diabetes and metabolic syndrome all over the world, despite of the governmental investments in healthy policies. Some of these diseases represent a high economic burden to individuals and society, demanding urgency in the identification of risk factors and appropriate solutions. Inadequate nutrition habits are an important risk factor for developing these diseases, and the consumption of functional foods such as prebiotics, probiotics, and phenolic compounds may contribute to mitigate them. It has been reported that the consumption of prebiotics can cause positive changes in the intestinal microbiota. The healthy microbiota, consisting mainly of Bifidobacterium and Lactobacillus, ferment prebiotics producing compounds that appear to play a protective role against metabolic diseases. Despite the growing number of publications on the effects of regular consumption of prebiotics in experimental models, additional studies on their effects on humans are needed to bring more subsidies to public health programs. This manuscript aims to review the literature on the possible benefits of ingestion of prebiotics in the control of obesity.

Metformin: old friend, new ways of action-implication of the gut microbiome?

PURPOSE OF REVIEW

Gut dysbiosis was recently associated with the occurrence of type 2 diabetes (T2D). In addition to this finding, an increasing number of studies performed upon the last 5 years have also shown that metformin treatment leads to changes in gut bacterial composition in diabetic patients. This review focuses on the articles describing the effects of metformin on gut homeostasis (including the gut microbiota) and proposes potential mechanisms involved in those effects.

RECENT FINDINGS

Several human and animal studies emphasized that metformin alters the gut microbiota composition by enhancing the growth of some bacteria, such as Akkermansia muciniphila, Escherichia spp. or Lactobacillus and by decreasing the levels of some other ones like Intestinibacter. In-vitro studies also demonstrated a direct action of metformin on the growth of A. muciniphila and Bifidobacterium adolescentis. Moreover, in the intestines, metformin does not only improve the glucose uptake, but it also promotes the short-chain fatty acid (SCFA) production, protects the intestinal barrier and regulates the secretion of gut peptides SUMMARY: It is now clear that gut microbiota participates to the glucose-lowering effects of metformin in the context of diabetes. Further work is now needed to determine the exact mechanisms of action of the drug and to understand by which processes metformin is able to enhance the growth of some bacteria exhibiting beneficial effects for the host.

Phytochemicals That Influence Gut Microbiota as Prophylactics and for the Treatment of Obesity and Inflammatory Diseases

Gut microbiota (GM) plays several crucial roles in host physiology and influences several relevant functions. In more than one respect, it can be said that you “feed your microbiota and are fed by it.” GM diversity is affected by diet and influences metabolic and immune functions of the host's physiology. Consequently, an imbalance of GM, or dysbiosis, may be the cause or at least may lead to the progression of various pathologies such as infectious diseases, gastrointestinal cancers, inflammatory bowel disease, and even obesity and diabetes. Therefore, GM is an appropriate target for nutritional interventions to improve health. For this reason, phytochemicals that can influence GM have recently been studied as adjuvants for the treatment of obesity and inflammatory diseases. Phytochemicals include prebiotics and probiotics, as well as several chemical compounds such as polyphenols and derivatives, carotenoids, and thiosulfates. The largest group of these comprises polyphenols, which can be subclassified into four main groups: flavonoids (including eight subgroups), phenolic acids (such as curcumin), stilbenoids (such as resveratrol), and lignans. Consequently, in this review, we will present, organize, and discuss the most recent evidence indicating a relationship between the effects of different phytochemicals on GM that affect obesity and/or inflammation, focusing on the effect of approximately 40 different phytochemical compounds that have been chemically identified and that constitute some natural reservoir, such as potential prophylactics, as candidates for the treatment of obesity and inflammatory diseases.

Fructo-oligosaccharides and glucose homeostasis: a systematic review and meta-analysis in animal models

The aim of this systematic review was to assess the effect of fructo-oligosaccharide supplementation on glucose homeostasis. The search process was based on the selection of publications listed in the Pubmed-Medline database until April 2016 to identify studies evaluating the impact of short-chain fructo-oligosaccharides or oligofructose on glucose homeostasis. Twenty-nine trials were included in the systematic review and the meta-analysis was performed on twelve of these papers according to the inclusion criteria. Fasting blood concentrations of glucose and insulin were selected as pertinent criteria of glucose homeostasis for the meta-analysis. The consumption of fructo-oligosaccharides decreased fasting blood glycaemia levels, whatever the metabolic status (healthy, obese or diabetic) and diet (low-fat or high-fat) throughout the experiment. This reduction was linear with prebiotic dose (from 0 to 13% of the feed). Fasting insulinaemia also decreased linearly with fructo-oligosaccharide supplementation but the reduction was only significant in rodents fed a low-fat diet. Potential underlying mechanisms include gut bacterial fermentation of fructo-oligosaccharides to short-chain fatty acids (SCFA) and bacterial modulation of bile acids, both interacting with host metabolism.

This systemic review, followed by the meta-analysis, provides evidence that fructo-oligosaccharide supplementation has a significant effect on glucose homeostasis whatever the health status and diet consumed by animals.

Microbiota, metabolome, and immune alterations in obese mice fed a high-fat diet containing type 2 resistant starch

SCOPE

We examined the intestinal and systemic responses to incorporating a type 2 resistant starch (RS) into a high fat diet fed to obese mice.

METHODS AND RESULTS

Diet-induced obese, C57BL/6J male mice were fed an HF diet without or with 20% (by weight) high-amylose maize resistant starch (HF-RS) for 6 weeks. Serum adiponectin levels were higher with RS consumption, but there were no differences in weight gain and adiposity. With HF-RS, the expression levels of ileal TLR2 and Reg3g and cecal occludin, TLR2, TLR4, NOD1 and NOD2 were induced; whereas colonic concentrations of the inflammatory cytokine IL-17A declined. The intestinal, serum, liver, and urinary metabolomes were also altered. HF-RS resulted in lower amino acid concentrations, including lower serum branched chain amino acids, and increased quantities of urinary di/trimethylamine, 3-indoxylsulfate, and phenylacetylglycine. Corresponding to these changes were enrichments in Bacteroidetes (S24-7 family) and certain Firmicutes taxa (Lactobacillales and Erysipelotrichaceae) with the HF-RS diet. Parabacteroides and S24-7 positively associated with cecal maltose concentrations. These taxa and Erysipelotrichaceae, Allobaculum, and Bifidobacterium were directly correlated with uremic metabolites.

CONCLUSION

Consumption of RS modified the intestinal microbiota, stimulated intestinal immunity and endocrine-responses, and modified systemic metabolomes in obese mice consuming an otherwise obesogenic diet.

Significance of Microbiota in Obesity and Metabolic Diseases and the Modulatory Potential by Medicinal Plant and Food Ingredients

Metabolic syndrome is a cluster of three or more metabolic disorders including insulin resistance, obesity, and hyperlipidemia. Obesity has become the epidemic of the twenty-first century with more than 1.6 billion overweight adults. Due to the strong connection between obesity and type 2 diabetes, obesity has received wide attention with subsequent coining of the term "diabesity." Recent studies have identified unique contributions of the immensely diverse gut microbiota in the pathogenesis of obesity and diabetes. Several mechanisms have been proposed including altered glucose and fatty acid metabolism, hepatic fatty acid storage, and modulation of glucagon-like peptide (GLP)-1. Importantly, the relationship between unhealthy diet and a modified gut microbiota composition observed in diabetic or obese subjects has been recognized. Similarly, the role of diet rich in polyphenols and plant polysaccharides in modulating gut bacteria and its impact on diabetes and obesity have been the subject of investigation by several research groups. Gut microbiota are also responsible for the extensive metabolism of polyphenols thus modulating their biological activities. The aim of this review is to shed light on the composition of gut microbes, their health importance and how they can contribute to diseases as well as their modulation by polyphenols and polysaccharides to control obesity and diabetes. In addition, the role of microbiota in improving the oral bioavailability of polyphenols and hence in shaping their antidiabetic and antiobesity activities will be discussed.

Preconception Prebiotic and Sitagliptin Treatment in Obese Rats Affects Pregnancy Outcomes and Offspring Microbiota, Adiposity, and Glycemia

Maternal obesity is associated with increased risk of pregnancy complications and greater risk of obesity in offspring, but studies designed to examine preconception weight loss are limited. The objective of this study was to determine if a combined dietary [oligofructose (OFS)] and pharmacological (sitagliptin) preconception intervention could mitigate poor pregnancy outcomes associated with maternal obesity and improve offspring metabolic health and gut microbiota composition. Diet-induced obese female Sprague-Dawley rats were randomized to one of four intervention groups for 8 weeks: (1) Obese-Control (consumed control diet during intervention); (2) Obese-OFS (10% OFS diet); (3) Obese-S (sitagliptin drug); (4) Obese-OFS + S (combination treatment). Two reference groups were also included: (5) Obese-HFS (untreated obese consumed high fat/sucrose diet throughout study); (6) Lean-Control (lean reference group that were never obese and consumed control diet throughout). Offspring consumed control diet until 11 weeks of age followed by HFS diet until 17 weeks of age. The Obese-OFS + S rats lost weight during the intervention phase whereas the OFS and S treatments attenuated weight gain compared with Obese-HFS (p < 0.05). Gestational weight gain was lowest in Obese-OFS + S rats and highest in Obese-HFS rats (p < 0.05). Prepregnancy intervention did not affect reproductive parameters but did affect pregnancy outcomes including litter size. Male Obese-OFS offspring had significantly lower percent body fat than Obese-HFS at 17 weeks. Female Obese-S and Obese-OFS offspring had significantly lower fasting glucose at 17 weeks compared with Obese-Control and Obese-HFS. Clostridium cluster XI was higher in Obese-HFS and Obese-S dams at birth compared with all other groups. Dams with an adverse pregnancy outcome had significantly lower (p = 0.035) Lactobacillus spp. compared with dams with normal or small litters. At weaning, male offspring of Obese-HFS had higher levels of Methanobrevibacter than all other groups except Obese-S and female Obese-HFS offspring had higher Enterobacteriaceae compared with all other groups. At 11 and 17 weeks of age, Bacteroides/Prevotella spp. was significantly lower in male and female offspring of Obese-HFS dams compared with all other groups except Obese-OFS + S. Modest weight loss induced with a diet-drug combination did not affect maternal fecundity but did have sex-specific effects on offspring adiposity and glycemia that may be linked to changes in offspring microbiota.

Involvement of glucagon-like peptide-1 in the glucose-lowering effect of metformin

Metformin is an oral antihyperglycaemic drug used in the first-line treatment of type 2 diabetes. Metformin's classic and most well-known blood glucose-lowering mechanisms include reduction of hepatic gluconeogenesis and increased peripheral insulin sensitivity. Interestingly, intravenously administered metformin is ineffective and recently, metformin was shown to increase plasma concentrations of the glucose-lowering gut incretin hormone glucagon-like peptide-1 (GLP-1), which may contribute to metformin's glucose-lowering effect in patients with type 2 diabetes. The mechanisms behind metformin-induced increments in GLP-1 levels remain unknown, but it has been hypothesized that metformin stimulates GLP-1 secretion directly and/or indirectly and that metformin prolongs the half-life of GLP-1. Also, it has been suggested that metformin may potentiate the glucose-lowering effects of GLP-1 by increasing target tissue sensitivity to GLP-1. The present article critically reviews the possible mechanisms by which metformin may affect GLP-1 levels and sensitivity and discusses whether such alterations may constitute important and clinically relevant glucose-lowering actions of metformin.

Effect of lactulose-derived oligosaccharides on intestinal microbiota during the shift between media with different energy contents

The microbiological and metabolic changes of an overweight-associated colonic microbiota after reducing in vitro the carbohydrate supply and its supplementation with oligosaccharides derived from lactulose (OsLu) were evaluated using a dynamic simulator of the gastrointestinal tract. The differentiation and stability of the microbial communities within each colon compartment were reached after two weeks of feeding the system with a high energy (HE) medium based on fructose and readily fermentable starches. The effect of reducing the energy content (low-energy medium, LE) and the supplementation with OsLu caused minor variations in bacterial counts, except for Enterobacteriaceae. The LE medium caused an effect on the microbial metabolic activity that was characterized by an absence of net butyrate production and an increase in ammonium content. This shift from fermentative to proteolytic metabolism was not observed when the LE medium was supplemented with OsLu. This oligosaccharide mixture was mainly metabolized in the proximal colonic compartment. The results obtained in this study indicate that the substitution in the diet of easily digestible carbohydrates by OsLu maintains the fermentative functionality of the intestinal microbiota, allowing the net production of butyric acid with potential beneficial effects on health, and avoiding a full transition to proteolytic metabolism profiles.

Metagenome-wide association studies: fine-mining the microbiome

Metagenome-wide association studies (MWAS) have enabled the high-resolution investigation of associations between the human microbiome and several complex diseases, including type 2 diabetes, obesity, liver cirrhosis, colorectal cancer and rheumatoid arthritis. The associations that can be identified by MWAS are not limited to the identification of taxa that are more or less abundant, as is the case with taxonomic approaches, but additionally include the identification of microbial functions that are enriched or depleted. In this Review, we summarize recent findings from MWAS and discuss how these findings might inform the prevention, diagnosis and treatment of human disease in the future. Furthermore, we highlight the need to better characterize the biology of many of the bacteria that are found in the human microbiota as an essential step in understanding how bacterial strains that have been identified by MWAS are associated with disease.

Functional Redundancy-Induced Stability of Gut Microbiota Subjected to Disturbance

The microbiota should be considered as just another component of the human epigenetic landscape. Thus, health is also a reflection of the diversity and composition of gut microbiota and its metabolic status. In defining host health, it remains unclear whether diversity is paramount, or whether greater weight is held by gut microbiota composition or mono- or multiple-functional capacity of the different taxa and the mechanisms involved. A network-biology approach may shed light on the key gut players acting to protect against, or promote, disorders or diseases. This could be achieved by integrating data on total and active species, proteins and molecules, and their association with host response. In this review, we discuss the utilization of top-down and bottom-up approaches, following a functional hierarchy perspective.

Mechanisms Linking the Gut Microbiome and Glucose Metabolism

This review details potential mechanisms linking gut dysbiosis to metabolic dysfunction, including lipopolysaccharide, bile acids, short chain fatty acids, gut hormones, and branched-chain amino acids.

Gut Microbiota and Nonalcoholic Fatty Liver Disease: Insights on Mechanism and Application of Metabolomics

Gut microbiota are intricately involved in the development of obesity-related metabolic diseases such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes, and insulin resistance. In the current review, we discuss the role of gut microbiota in the development of NAFLD by focusing on the mechanisms of gut microbiota-mediated host energy metabolism, insulin resistance, regulation of bile acids and choline metabolism, as well as gut microbiota-targeted therapy. We also discuss the application of a metabolomic approach to characterize gut microbial metabotypes in NAFLD.

Repurposing metformin: an old drug with new tricks in its binding pockets

Improvements in healthcare and nutrition have generated remarkable increases in life expectancy worldwide. This is one of the greatest achievements of the modern world yet it also presents a grave challenge: as more people survive into later life, more also experience the diseases of old age, including type 2 diabetes (T2D), cardiovascular disease (CVD) and cancer. Developing new ways to improve health in the elderly is therefore a top priority for biomedical research. Although our understanding of the molecular basis of these morbidities has advanced rapidly, effective novel treatments are still lacking. Alternative drug development strategies are now being explored, such as the repurposing of existing drugs used to treat other diseases. This can save a considerable amount of time and money since the pharmacokinetics, pharmacodynamics and safety profiles of these drugs are already established, effectively enabling preclinical studies to be bypassed. Metformin is one such drug currently being investigated for novel applications. The present review provides a thorough and detailed account of our current understanding of the molecular pharmacology and signalling mechanisms underlying biguanide-protein interactions. It also focuses on the key role of the microbiota in regulating age-associated morbidities and a potential role for metformin to modulate its function. Research in this area holds the key to solving many of the mysteries of our current understanding of drug action and concerted effects to provide sustained and long-life health.

Impact of Diet Composition in Adult Offspring is Dependent on Maternal Diet during Pregnancy and Lactation in Rats

The Thrifty Phenotype Hypothesis proposes that the fetus takes cues from the maternal environment to predict its postnatal environment. A mismatch between the predicted and actual environments precipitates an increased risk of chronic disease. Our objective was to determine if, following a high fat, high sucrose (HFS) diet challenge in adulthood, re-matching offspring to their maternal gestational diet would improve metabolic health more so than if there was no previous exposure to that diet. Animals re-matched to a high prebiotic fiber diet (HF) had lower body weight and adiposity than animals re-matched to a high protein (HP) or control (C) diet and also had increased levels of the satiety hormones GLP-1 and PYY (p < 0.05). Control animals, whether maintained throughout the study on AIN-93M, or continued on HFS rather than reverting back to AIN-93M, did not differ from each other in body weight or adiposity. Overall, the HF diet was associated with the most beneficial metabolic phenotype (body fat, glucose control, satiety hormones). The HP diet, as per our previous work, had detrimental effects on body weight and adiposity. Findings in control rats suggest that the obesogenic potential of the powdered AIN-93 diet warrants investigation.

Dietary phytic acid prevents fatty liver by reducing expression of hepatic lipogenic enzymes and modulates gut microflora in rats fed a high-sucrose diet

OBJECTIVES

The aim of this study was to investigate the effect of phytic acid (PA) on fatty liver and gut microflora in rats fed a high-sucrose (HSC) diet.

METHODS

Three groups of rats were fed a high-starch (HSR) diet or an HSC diet with or without 1.02% sodium PA for 12 d. We evaluated hepatic weight, total lipids, and triacylglycerol (TG) levels, the activities and expression of hepatic lipogenic enzymes (glucose-6-phosphate dehydrogenase, malic enzyme 1, and fatty acid synthetase), and fecal microflora.

RESULTS

The HSC diet significantly increased hepatic total lipids and TG levels, and the activities and expression of the hepatic lipogenic enzymes compared with the HSR diet. These upregulations were clearly suppressed by dietary PA. Consumption of PA elevated the fecal ratio of Lactobacillus spp. and depressed the ratio of Clostridium cocoides, and suppressed the elevation in the ratio of C. leptum induced by the HSC diet.

CONCLUSION

This work showed that dietary PA ameliorates sucrose-induced fatty liver through reducing the expression of hepatic lipogenesis genes and modulates gut microflora in rats.

Diabetes Mellitus and Increased Tuberculosis Susceptibility: The Role of Short-Chain Fatty Acids

Type 2 diabetes mellitus confers a threefold increased risk for tuberculosis, but the underlying immunological mechanisms are still largely unknown. Possible mediators of this increased susceptibility are short-chain fatty acids, levels of which have been shown to be altered in individuals with diabetes. We examined the influence of physiological concentrations of butyrate on cytokine responses to Mycobacterium tuberculosis (Mtb) in human peripheral blood mononuclear cells (PBMCs). Butyrate decreased Mtb-induced proinflammatory cytokine responses, while it increased production of IL-10. This anti-inflammatory effect was independent of butyrate's well-characterised inhibition of HDAC activity and was not accompanied by changes in Toll-like receptor signalling pathways, the eicosanoid pathway, or cellular metabolism. In contrast blocking IL-10 activity reversed the effects of butyrate on Mtb-induced inflammation. Alteration of the gut microbiota, thereby increasing butyrate concentrations, can reduce insulin resistance and obesity, but further studies are needed to determine how this affects susceptibility to tuberculosis.

Selective novel inverse agonists for human GPR43 augment GLP-1 secretion

GPR43/Free Fatty Acid Receptor 2 (FFAR2) is known to be activated by short-chain fatty acids and be coupled to Gi and Gq family of heterotrimeric G proteins. GPR43 is mainly expressed in neutrophils, adipocytes and enteroendocrine cells, implicated to be involved in inflammation, obesity and type 2 diabetes. However, several groups have reported the contradictory data about the physiological functions of GPR43, so that its roles in vivo remain unclear. Here, we demonstrate that a novel compound of pyrimidinecarboxamide class named as BTI-A-404 is a selective and potent competitive inverse agonist of human GPR43, but not the murine ortholog. Through structure-activity relationship (SAR), we also found active compound named as BTI-A-292. These regulators increased the cyclic AMP level and reduced acetate-induced cytoplasmic Ca(2+) level. Furthermore, we show that they modulated the downstream signaling pathways of GPR43, such as ERK, p38 MAPK, and NF-κB. It was surprising that two compounds augmented the secretion of glucagon-like peptide 1 (GLP-1) in NCI-H716 cell line. Collectively, these novel and specific competitive inhibitors regulate all aspects of GPR43 signaling and the results underscore the therapeutic potential of them.

Gut microbiota manipulation with prebiotics in patients with non-alcoholic fatty liver disease: a randomized controlled trial protocol

Background

Evidence for the role of the gut microbiome in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) is emerging. Strategies to manipulate the gut microbiota towards a healthier community structure are actively being investigated. Based on their ability to favorably modulate the gut microbiota, prebiotics may provide an inexpensive yet effective dietary treatment for NAFLD. Additionally, prebiotics have established benefits for glucose control and potentially weight control, both advantageous in managing fatty liver disease. Our objective is to evaluate the effects of prebiotic supplementation, adjunct to those achieved with diet-induced weight loss, on heptic injury and liver fat, the gut microbiota, inflammation, glucose tolerance, and satiety in patients with NAFLD.

Methods/design

In a double blind, placebo controlled, parallel group study, adults (BMI ≥25) with confirmed NAFLD will be randomized to either a 16 g/d prebiotic supplemented group or isocaloric placebo group for 24 weeks (n = 30/group). All participants will receive individualized dietary counseling sessions with a registered dietitian to achieve 10 % weight loss. Primary outcome measures include change in hepatic injury (fibrosis and inflammation) and liver fat. Secondary outcomes include change in body composition, appetite and dietary adherence, glycemic and insulinemic responses and inflammatory cytokines. Mechanisms related to prebiotic-induced changes in gut microbiota (shot-gun sequencing) and their metabolic by-products (volatile organic compounds) and de novo lipogenesis (using deuterium incorporation) will also be investigated.

Discussion

There are currently no medications or surgical procedures approved for the treatment of NAFLD and weight loss via lifestyle modification remains the cornerstone of current care recommendations. Given that prebiotics target multiple metabolic impairments associated with NAFLD, investigating their ability to modulate the gut microbiota and hepatic health in patients with NAFLD is warranted.

Trial registration

ClinicalTrials.gov (NCT02568605) Registered 30 September 2015

Hyperactive mTORC1 signaling is unaffected by metformin treatment in aged skeletal muscle

INTRODUCTION

Appropriate activation of growth signaling pathways, specifically mammalian target of rapamycin complex 1 (mTORC1), is central to muscle mass and metabolism. The goal of these studies was to examine the effects of metformin on mTORC1 signaling in aged skeletal muscle in an attempt to normalize growth signaling.

METHODS

Aged (23m) and young (3m) male mice were fed a low fat diet without or with 0.5% metformin for up to 8 weeks, then mTORC1-related signaling was examined in the plantar flexor complex.

RESULTS

Metformin had no significant effect on lowering body weight or muscle mass in aged animals, nor altered p70 S6 Kinase 1 (S6K1) and 4E-binding protein 1 (4E-BP1) phosphorylation. However, it significantly (P < 0.05) reduced body weight and lowered S6K1 and rpS6 phosphorylation in the young.

CONCLUSIONS

Collectively, these data suggest metformin is ineffective at normalizing growth signaling in aged skeletal muscle.

Postnatal prebiotic fibre intake mitigates some detrimental metabolic outcomes of early overnutrition in rats

PURPOSE

Overnutrition during early development has been linked to metabolic disease and obesity in adulthood. Interventions to ameliorate this metabolic malprogramming are needed. Our objective was to determine whether prebiotic fibre would reduce weight gain and improve satiety hormone profiles in rats overnourished during the suckling period.

METHODS

Male Sprague-Dawley rats reared in small litter (SL 3 pups) or normal litter (NL 12 pups) were randomized at weaning to AIN-93 (control) or a 10 % oligofructose (OFS) diet for 16 weeks. Body composition, an oral glucose tolerance test for glucose and gut hormones, and gut microbiota were assessed.

RESULTS

At weaning, body weight was higher in SL than in NL rats (P < 0.03). At 19 weeks, body weight was lower with OFS than control (P < 0.04). There was a diet × litter size interaction wherein OFS in SL rats reduced body fat (%) to levels seen in NL rats (P < 0.05). OFS attenuated the glucose response in SL but not in NL rats (P < 0.015). Independent of litter size, OFS decreased total AUC for glucose-dependent insulinotropic polypeptide (P < 0.002) and increased total AUC for peptide YY (P < 0.01) and glucagon-like peptide-1 (P < 0.04) when compared to control. OFS, not litter size, played the predominant role in altering gut microbiota which included increased bifidobacteria and Akkermansia muciniphila with OFS.

CONCLUSIONS

Postnatal consumption of OFS by rats raised in SL was able to attenuate body fat and glycaemia to levels seen in NL rats. OFS appears to influence satiety hormone and gut microbiota response similarly in overnourished and control rats.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

Interactive effects of oligofructose and obesity predisposition on gut hormones and microbiota in diet-induced obese rats

OBJECTIVE

Oligofructose (OFS) is a prebiotic that reduces energy intake and fat mass via changes in gut satiety hormones and microbiota. The effects of OFS may vary depending on predisposition to obesity. The aim of this study was to examine the effect of OFS in diet-induced obese (DIO) and diet-resistant (DR) rats.

METHODS

Adult, male DIO, and DR rats were randomized to: high-fat/high-sucrose (HFS) diet or HFS diet + 10% OFS for 6 weeks. Body composition, food intake, gut microbiota, plasma gut hormones, and cannabinoid CB(1) receptor expression in the nodose ganglia were measured.

RESULTS

OFS reduced body weight, energy intake, and fat mass in both phenotypes (P < 0.05). Select gut microbiota differed in DIO versus DR rats (P < 0.05), the differences being eliminated by OFS. OFS did not modify plasma ghrelin or CB(1) expression in nodose ganglia, but plasma levels of GIP were reduced and PYY were elevated (P < 0.05) by OFS.

CONCLUSIONS

OFS was able to reduce body weight and adiposity in both prone and resistant obese phenotypes. OFS-induced changes in gut microbiota profiles in DIO and DR rats, along with changes in gut hormone levels, likely contribute to the sustained lower body weights.

Worms, bacteria, and micronutrients: an elegant model of our diet

Micronutrients are required in small proportions in a diet to carry out key metabolic roles for biomass and energy production. Humans receive micronutrients either directly from their diet or from gut microbiota that metabolize other nutrients. The nematode Caenorhabditis elegans and its bacterial diet provide a relatively simple and genetically tractable model to study both direct and microbe-mediated effects of micronutrients. Recently, this model has been used to gain insight into the relationship between micronutrients, physiology, and metabolism. In particular, two B-type vitamins, vitamin B12 and folate, have been studied in detail. Here we review how C. elegans and its bacterial diet provide a powerful interspecies systems biology model that facilitates the precise delineation of micronutrient effects and the mechanisms involved.

Postnatal prebiotic fiber intake in offspring exposed to gestational protein restriction has sex-specific effects on insulin resistance and intestinal permeability in rats

Maternal protein restriction (PR) during pregnancy is known to have numerous adverse effects on offspring, including increased adiposity and impaired glucose tolerance later in life. A few studies have shown that this adverse programming can be reversed by dietary or hormonal therapies early in postnatal life. The objective of this study was to determine if a weaning diet high in prebiotic fiber could mitigate some of the negative effects of maternal PR, such as increased adiposity and impaired glucose tolerance. Wistar rats were fed a low- (8%) or normal- (20%) protein diet during pregnancy. Male and female pups were weaned onto control (C; 5% fiber, 20% protein) or high (prebiotic) fiber (HF; 21% wt:wt, 1:1 ratio oligofructose and inulin at 4-10 wk; 10% wt:wt, 1:1 ratio oligofructose and inulin at 10-24 wk; 17.3% protein) diets. At 24 wk of age, glucose tolerance, body composition, satiety hormones, gut microbiota, and markers of intestinal permeability were measured in the offspring. Maternal PR reduced offspring birth weight by 5% and lean mass by 9% compared with the C offspring (P < 0.007). HF-fed offspring had lower body weights and percentage body fat (∼23% in males, ∼19% in females) at 24 wk than did C offspring (P < 0.02). Compared with C pups, pups fed the HF diet had greater cecal Bifidobacterium spp. (>5-fold) and plasma concentrations of the gut trophic hormone glucagon-like peptide 2 (GLP-2) (P < 0.05). In male PR offspring fed the HF diet, insulin resistance measured by the homeostasis model assessment of insulin resistance was reduced by 81% compared with those fed the C diet (P = 0.02). In female PR offspring fed the HF diet, plasma endotoxin was greater and colonic tight junction protein 1 (Tjp1) expression was lower than in those fed the C diet. A high prebiotic fiber weaning diet mitigated increased adiposity and insulin resistance associated with maternal PR, which could improve health and decrease risk of chronic disease in offspring born to malnourished dams. However, the functional importance of sex-specific changes in markers of intestinal barrier function warrants further investigation.

Microbiota and diabetes: an evolving relationship

The gut microbiota affects numerous biological functions throughout the body and its characterisation has become a major research area in biomedicine. Recent studies have suggested that gut bacteria play a fundamental role in diseases such as obesity, diabetes and cardiovascular disease. Data are accumulating in animal models and humans suggesting that obesity and type 2 diabetes (T2D) are associated with a profound dysbiosis. First human metagenome-wide association studies demonstrated highly significant correlations of specific intestinal bacteria, certain bacterial genes and respective metabolic pathways with T2D. Importantly, especially butyrate-producing bacteria such as Roseburia intestinalis and Faecalibacterium prausnitzii concentrations were lower in T2D subjects. This supports the increasing evidence, that butyrate and other short-chain fatty acids are able to exert profound immunometabolic effects. Endotoxaemia, most likely gut-derived has also been observed in patients with metabolic syndrome and T2D and might play a key role in metabolic inflammation. A further hint towards an association between microbiota and T2D has been derived from studies in pregnancy showing that major gut microbial shifts occurring during pregnancy affect host metabolism. Interestingly, certain antidiabetic drugs such as metformin also interfere with the intestinal microbiota. Specific members of the microbiota such as Akkermansia muciniphila might be decreased in diabetes and when administered to murines exerted antidiabetic effects. Therefore, as a 'gut signature' becomes more evident in T2D, a better understanding of the role of the microbiota in diabetes might provide new aspects regarding its pathophysiological relevance and pave the way for new therapeutic principles.

Yellow pea fiber improves glycemia and reduces Clostridium leptum in diet-induced obese rats

Numerous studies have demonstrated the impact of functional fibers on gut microbiota and metabolic health, but some less well-studied fibers and/or fractions of foods known to be high in fiber still warrant examination. The aim of this study was to assess the effect of yellow pea-derived fractions varying in fiber and protein content on metabolic parameters and gut microbiota in diet-induced obese rats. We hypothesized that the yellow pea fiber (PF) fraction would improve glycemia and alter gut microbiota. Rats were randomized to 1 of 5 isoenergetic dietary treatments for 6 weeks: (1) control; (2) oligofructose (OFS); (3) yellow PF; (4) yellow pea flour (PFL); or (5) yellow pea starch (PS). Glycemia, plasma gut hormones, body composition, hepatic triglyceride content, gut microbiota, and messenger RNA expression of genes related to hepatic fat metabolism were examined. Pea flour attenuated weight gain compared with control, PF, and PS (P < .05). Pea flour, PS, and OFS had significantly lower final percent body fat compared with control. Oligofructose but not the pea fraction diets reduced food intake compared with control (P < .05). Pea fiber resulted in lower fasting glucose and glucose area under the curve compared with control. Changes in gut microbiota were fraction specific and included a decrease in Firmicutes (percent) for OFS, PF, and PFL compared with control (P < .05). The Firmicutes/Bacteroidetes ratio was reduced with OFS, PF, and PFL when compared with PS (P < .05). Taken together, this work suggests that yellow pea-derived fractions are able to distinctly modulate metabolic parameters and gut microbiota in obese rats.

Gut microbiota-generated metabolites in animal health and disease

Gut microbiota is found in virtually any metazoan, from invertebrates to vertebrates. It has long been believed that gut microbiota, more specifically, the activity of the microbiome and its metabolic products, directly influence a variety of aspects in metazoan physiology. However, the exact molecular relationship among microbe-derived gut metabolites, host signaling pathways, and host physiology remains to be elucidated. Here we review recent discoveries regarding the molecular links between gut metabolites and host physiology in different invertebrate and vertebrate animal models. We describe the different roles of gut microbiome activity and their metabolites in regulating distinct host physiology and the molecular mechanisms by which gut metabolites cause physiological homeostasis via regulating specific host signaling pathways. Future studies in this direction using different animal models will provide the key concepts to understanding the evolutionarily conserved chemical dialogues between gut microbiota and metazoan cells and also human diseases associated with gut microbiota and metabolites.

Diet effects in gut microbiome and obesity

The 100 trillion microbes in human gut coevolve with the host and exert significant influences on human health. The gut microbial composition presents dynamic changes correlated with various factors including host genotypes, age, and external environment. Effective manipulation of the gut microbiota through diets (both long-term and short-term diet patterns), probiotics and/or prebiotics, and antibiotics has been proved being potential to prevent from metabolic disorders such as obesity in many studies. The dietary regulation exerts influences on microbial metabolism and host immune functions through several pathways, of which may include selectively bacterial fermentation of nutrients, lower intestinal barrier function, overexpression of genes associated with disorders, and disruptions to both innate and adaptive immunity. Discoveries in the interrelationship between diet, intestinal microbiome, and body immune system provide us novel perceptions to the specific action mechanisms and will promote the development of therapeutic approaches for obesity.

Combining sitagliptin/metformin with a functional fiber delays diabetes progression in Zucker rats

Our primary objective was to determine whether administering the viscous and fermentable polysaccharide PolyGlycopleX (PGX) with metformin (MET) or sitagliptin/metformin (S/MET) reduces hyperglycemia in Zucker diabetic fatty (ZDF) rats more so than monotherapy of each. Glucose tolerance, adiposity, satiety hormones and mechanisms related to dipeptidyl peptidase 4 activity, gut microbiota and, hepatic and pancreatic histology were examined. Male ZDF rats (9-10 weeks of age) were randomized to: i) cellulose/vehicle (control, C); ii) PGX (5% wt/wt)/vehicle (PGX); iii) cellulose/metformin (200  mg/kg) (MET); iv) cellulose/S/MET (10  mg/kg+200  mg/kg) (S/MET); v) PGX (5%)+MET (200  mg/kg) (PGX+MET); vi) cellulose/sitagliptin/MET (5%)+(10  mg/kg+200  mg/kg) (PGX+S/MET) for 6 weeks. PGX+MET and PGX+S/MET reduced glycemia compared with C and singular treatments (P=0.001). Weekly fasted and fed blood glucose levels were lower in PGX+MET and PGX+S/MET compared with all other groups at weeks 4, 5, and 6 (P=0.001). HbA1c was lower in PGX+S/MET than C, MET, S/MET, and PGX at week 6 (P=0.001). Fat mass was lower and GLP1 was higher in PGX+S/MET compared with all other groups (P=0.001). β-cell mass was highest and islet degeneration lowest in PGX+S/MET. Hepatic lipidosis was significantly lower in PGX+S/MET compared with PGX or S/MET alone. When combined with PGX, both MET and S/MET markedly reduce glycemia; however, PGX+S/MET appears advantageous over PGX+MET in terms of increased β-cell mass and reduced adiposity. Both combination treatments attenuated diabetes in the obese Zucker rat.

Metformin improves healthspan and lifespan in mice

Metformin is a drug commonly prescribed to treat patients with type 2 diabetes. Here we show that long-term treatment with metformin (0.1% w/w in diet) starting at middle age extends healthspan and lifespan in male mice, while a higher dose (1% w/w) was toxic. Treatment with metformin mimics some of the benefits of calorie restriction, such as improved physical performance, increased insulin sensitivity, and reduced low-density lipoprotein and cholesterol levels without a decrease in caloric intake. At a molecular level, metformin increases AMP-activated protein kinase activity and increases antioxidant protection, resulting in reductions in both oxidative damage accumulation and chronic inflammation. Our results indicate that these actions may contribute to the beneficial effects of metformin on healthspan and lifespan. These findings are in agreement with current epidemiological data and raise the possibility of metformin-based interventions to promote healthy aging.

Non-alcoholic fatty liver disease, diet and gut microbiota

Non-alcoholic fatty liver disease (NAFLD) is a severe liver disease that is increasing in prevalence with the worldwide epidemic of obesity and its related insulin-resistance state. Evidence for the role of the gut microbiota in energy storage and the subsequent development of obesity and some of its related diseases is now well established. More recently, a new role of gut microbiota has emerged in NAFLD. The gut microbiota is involved in gut permeability, low-grade inflammation and immune balance, it modulates dietary choline metabolism, regulates bile acid metabolism and produces endogenous ethanol. All of these factors are molecular mechanisms by which the microbiota can induce NAFLD or its progression toward overt non-alcoholic steatohepatitis. Modification of the gut microbiota composition and/or its biochemical capacity by specific dietary or pharmacological interventions may advantageously affect host metabolism. Large-scale intervention trials, investigating the potential benefit of prebiotics and probiotics in improving cardiometabolic health in high-risk populations, are fervently awaited.

Aging-associated reductions in lipolytic and mitochondrial proteins in mouse adipose tissue are not rescued by metformin treatment

Mitochondrial enzyme expression is reduced in adipose tissue from old mice, yet little is known regarding mechanisms that could be mediating, or interventions that could be used, to reverse these changes. The purpose of this study was to examine the relationship between lipolytic and fatty acid reesterification enzymes, 5' adenosine monophosphate-activated protein kinase and mitochondrial proteins in adipose tissue from young versus old mice. A second aim was to determine whether metformin treatment could rescue the age-associated decline in adipose tissue mitochondrial proteins. Approximately 22-month-old male C57BL/6 mice were fed a diet with or without 0.5% metformin for 8 weeks. Compared with young mice (~11 wk of age), the protein content/phosphorylation of hormone-sensitive lipase, adipose tissue triglyceride lipase, and phosphoenolpyruvate carboxykinase were reduced in old mice. This was paralleled by increases in the plasma nonesterified fatty acid:glycerol ratio and reductions in adipose tissue 5' adenosine monophosphate-activated protein kinase activity and select mitochondrial proteins in old mice. There were no differences in these variables when comparing adipose tissue from young and 6-month-old mice. While metformin improved glucose homeostasis, it did not increase 5' adenosine monophosphate-activated protein kinase phosphorylation or mitochondrial enzymes. Our findings demonstrate a co-ordinated down regulation of lipolytic, reesterification, and mitochondrial enzymes in adipose tissue with aging that is unresponsive to metformin treatment.

Short-chain fructo-oligosaccharides modulate intestinal microbiota and metabolic parameters of humanized gnotobiotic diet induced obesity mice

Prebiotic fibres like short-chain fructo-oligosaccharides (scFOS) are known to selectively modulate the composition of the intestinal microbiota and especially to stimulate Bifidobacteria. In parallel, the involvement of intestinal microbiota in host metabolic regulation has been recently highlighted. The objective of the study was to evaluate the effect of scFOS on the composition of the faecal microbiota and on metabolic parameters in an animal model of diet-induced obesity harbouring a human-type microbiota. Forty eight axenic C57BL/6J mice were inoculated with a sample of faecal human microbiota and randomly assigned to one of 3 diets for 7 weeks: a control diet, a high fat diet (HF, 60% of energy derived from fat)) or an isocaloric HF diet containing 10% of scFOS (HF-scFOS). Mice fed with the two HF gained at least 21% more weight than mice from the control group. Addition of scFOS partially abolished the deposition of fat mass but significantly increased the weight of the caecum. The analysis of the taxonomic composition of the faecal microbiota by FISH technique revealed that the addition of scFOS induced a significant increase of faecal Bifidobacteria and the Clostridium coccoides group whereas it decreased the Clostridium leptum group. In addition to modifying the composition of the faecal microbiota, scFOS most prominently affected the faecal metabolome (e.g. bile acids derivatives, hydroxyl monoenoic fatty acids) as well as urine, plasma hydrophilic and plasma lipid metabolomes. The increase in C. coccoides and the decrease in C. leptum, were highly correlated to these metabolic changes, including insulinaemia, as well as to the weight of the caecum (empty and full) but not the increase in Bifidobacteria. In conclusion scFOS induce profound metabolic changes by modulating the composition and the activity of the intestinal microbiota, that may partly explain their effect on the reduction of insulinaemia.

Worms need microbes too: microbiota, health and aging in Caenorhabditis elegans

Many animal species live in close association with commensal and symbiotic microbes (microbiota). Recent studies have revealed that the status of gastrointestinal tract microbiota can influence nutrition-related syndromes such as obesity and type-2 diabetes, and perhaps aging. These morbidities have a profound impact in terms of individual suffering, and are an increasing economic burden to modern societies. Several theories have been proposed for the influence of microbiota on host metabolism, but these largely remain to be proven. In this article we discuss how microbiota may be manipulated (via pharmacology, diet, or gene manipulation) in order to alter metabolism, immunity, health and aging in the host. The nematode Caenorhabditis elegans in combination with one microbial species is an excellent, defined model system to investigate the mechanisms of host–microbiota interactions, particularly given the combined power of worm and microbial genetics. We also discuss the multifaceted nature of the worm–microbe relationship, which likely encompasses predation, commensalism, pathogenicity and necromeny.

Metformin retards aging in C. elegans by altering microbial folate and methionine metabolism

The biguanide drug metformin is widely prescribed to treat type 2 diabetes and metabolic syndrome, but its mode of action remains uncertain. Metformin also increases lifespan in Caenorhabditis elegans cocultured with Escherichia coli. This bacterium exerts complex nutritional and pathogenic effects on its nematode predator/host that impact health and aging. We report that metformin increases lifespan by altering microbial folate and methionine metabolism. Alterations in metformin-induced longevity by mutation of worm methionine synthase (metr-1) and S-adenosylmethionine synthase (sams-1) imply metformin-induced methionine restriction in the host, consistent with action of this drug as a dietary restriction mimetic. Metformin increases or decreases worm lifespan, depending on E. coli strain metformin sensitivity and glucose concentration. In mammals, the intestinal microbiome influences host metabolism, including development of metabolic disease. Thus, metformin-induced alteration of microbial metabolism could contribute to therapeutic efficacy—and also to its side effects, which include folate deficiency and gastrointestinal upset.

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A maternal high-protein diet predisposes female offspring to increased fat mass in adulthood whereas a prebiotic fibre diet decreases fat mass in rats

The negative effects of malnourishment in utero have been widely explored; the effects of increased maternal macronutrient intake are not known in relation to high fibre, and have been inconclusive with regard to high protein. In the present study, virgin Wistar dams were fed either a control (C), high-protein (40 %, w/w; HP) or high-prebiotic fibre (21·6 %, w/w; HF) diet throughout pregnancy and lactation. Pups consumed the C diet from 3 to 14·5 weeks of age, and then switched to a high-fat/sucrose diet for 8 weeks. A dual-energy X-ray absorptiometry scan and an oral glucose tolerance test were performed and plasma satiety hormones measured. The final body weight and the percentage of body fat were significantly affected by the interaction between maternal diet and offspring sex: weight and fat mass were higher in the female offspring of the HP v. HF dams. No differences in body weight or fat mass were seen in the male offspring. There was a significant sex effect for fasting and total AUC for ghrelin and fasting GIP, with females having higher levels than males. Liver TAG content and plasma NEFA were lower in the offspring of high-prebiotic fibre dams (HF1) than in those of high-protein dams (HP1) and control dams (C1). Intestinal expression of GLUT2 was decreased in HF1 and HP1 v. C1. The maternal HP and HF diets had lasting effects on body fat and hepatic TAG accumulation in the offspring, particularly in females. Whereas the HP diet predisposes to an obese phenotype, the maternal HF diet appears to reduce the susceptibility to obesity following a high-energy diet challenge in adulthood.

Sitagliptin reduces hyperglycemia and increases satiety hormone secretion more effectively when used with a novel polysaccharide in obese Zucker rats

The novel polysaccharide (NPS) PolyGlycopleX (PGX) has been shown to reduce glycemia. Pharmacological treatment with sitagliptin, a dipeptidyl peptidase 4 (DPP4) inhibitor, also reduces glycemia by increasing glucagon-like peptide-1 (GLP-1). Our objective was to determine if using NPS in combination with sitagliptin reduces hyperglycemia in Zucker diabetic fatty (ZDF) rats more so than either treatment alone. Male ZDF rats were randomized to: 1) cellulose/vehicle [control (C)]; 2) NPS (5% wt:wt)/vehicle (NPS); 3) cellulose/sitagliptin [10 mg/(kg · d) (S)]; or 4) NPS (5%) + S [10 mg/(kg · d) (NPS+S)]. Glucose tolerance, adiposity, satiety hormones, and mechanisms related to DPP4 activity and hepatic and pancreatic histology were examined. A clinically relevant reduction in hyperglycemia occurred in the rats treated with NPS+S (P = 0.001) compared with NPS and S alone. Blood glucose, measured weekly in fed and feed-deprived rats and during an oral glucose tolerance test, was lower in the NPS+S group compared with all other groups (all P = 0.001). At wk 6, glycated hemoglobin was lower in the NPS+S group than in the C and S (P = 0.001) and NPS (P = 0.06) groups. PGX (P = 0.001) and S (P = 0.014) contributed to increased lean mass. Active GLP-1 was increased by S (P = 0.001) and GIP was increased by NPS (P = 0.001). Plasma DPP4 activity was lower in the NPS+S and S groups than in the NPS and C groups (P = 0.007). Insulin secretion and β-cell mass was increased with NPS (P < 0.05). NPS alone reduced LDL cholesterol and hepatic steatosis (P < 0.01). Independently, NPS and S improve several metabolic outcomes in ZDF rats, but combined, their ability to markedly reduce glycemia suggests they may be a promising dietary/pharmacological co-therapy for type 2 diabetes management.

Satiety hormone and metabolomic response to an intermittent high energy diet differs in rats consuming long-term diets high in protein or prebiotic fiber

Large differences in the composition of diet between early development and adulthood can have detrimental effects on obesity risk. We examined the effects of an intermittent high fat/sucrose diet (HFS) on satiety hormone and serum metabolite response in disparate diets. Wistar rat pups were fed control (C), high prebiotic fiber (HF) or high protein (HP) diets (weaning to 16 weeks), HFS diet challenged (6 weeks), and finally reverted to their respective C, HF, or HP diet (4 weeks). At conclusion, measurement of body composition and satiety hormones was accompanied by ¹H NMR metabolic profiles in fasted and postprandial states. Metabolomic profiling predicted dietary source with >90% accuracy. The HF group was characterized by lowest body weight and body fat (P < 0.05) and increased satiety hormone levels (glucagon-like peptide 1 and peptide-YY). Regularized modeling confirmed that the HF diet is associated with higher gut hormone secretion that could reflect the known effects of prebiotics on gut microbiota and their fementative end products, the short chain fatty acids. Rats reared on a HF diet appear to experience fewer adverse effects from an intermittent high fat diet in adulthood when rematched to their postnatal diet. Metabolite profiles associated with the diets provide a distinct biochemical signature of their effects.