The Gut Microbiome, Energy Homeostasis, and Implications for Hypertension

Reutericyclin mitigates risperidone-induced suppression of anaerobic energy expenditure

Recent studies from our laboratory demonstrated that the gut microbial community represents a thermogenic biomass, as cecectomy causes an ∼8% decrease in total energy expenditure (EE) via suppression of anaerobic EE. The composition of the microbial community also dictates the EE of the microbial biomass as treatment with the antipsychotic, risperidone, suppresses anaerobic EE in a microbiome-dependent manner. Finally, we have determined that a specialized metabolite produced by Limosilactobacillus reuteri, reutericyclin (RTC), opposes the weight-gain effects of risperidone. In the present study, we performed comprehensive evaluations of energy balance in female C57BL/6J mice treated with risperidone, RTC, or both, to identify mechanisms by which RTC affects energy balance to mitigate risperidone-induced weight gain. We observed that risperidone suppressed anaerobic EE, and that RTC coadministration ameliorated the anaerobic EE suppression and weight gain induced by risperidone. Because anaerobic EE is dependent on the gut microbiota, we performed 16S and whole genome shotgun sequencing on stool and cecal samples following whole animal calorimetry. Risperidone and RTC treatments reciprocally modified the relative abundance of taxa known to participate in fermentation, especially for the production of short-chain fatty acids, which have been correlated with health and leanness in both humans and mice. Together, our data demonstrate that treatment with RTC positively modulates anaerobic EE, possibly by enhancing fermentation of the gut microbial community, and may represent a novel therapeutic in the treatment of obesity.NEW & NOTEWORTHY The gut microbial community represents a thermogenic biomass. The composition of the microbial community dictates energy expenditure of the microbial biomass and is altered by xenobiotics and bacterial metabolites. This study demonstrates that treatment with reutericyclin positively modulates anaerobic energy expenditure and may represent a novel therapeutic in the treatment of obesity.

Metabolic Flexibility to Predict Lifestyle Interventions Outcomes (MEPHISTO): Protocol for Predictive Validation Study and Randomized Controlled Trial

BACKGROUND

Weight loss is a cornerstone of obesity treatment and diabetes mellitus type 2 (T2D) prevention, but its implementation in clinical practice is limited by its perceived burden and variability in response. Personalizing interventions to increase their success rate is an unmet clinical need.

OBJECTIVE

Identification of predictive factors associated with successful weight loss after sequential exercise in women with obesity.

METHODS

The study will consist of a 2-stage analytical approach, including a predictive validation study and a 2:1 randomized cross-over controlled trial. Women aged 25-45 years with obesity (BMI>30) will be included in the study. The intervention will consist of a progressive protocol of aerobic exercise on a treadmill and a bicycle ergometer. We will measure weight loss in terms of fat mass (FM) and fat-free mass (FFM), metabolic flexibility (MetFlex) as ΔRQ (change in respiratory quotient (VCO2/VO2) between basal and insulin-stimulated state during glucose clamp), insulin sensitivity, glucose tolerance, hemoglobin A1c, microbiome composition, and metabolomic signatures.

RESULTS

Recruitment for the trial began in January 2024. A total of 12 participants were enrolled and randomized. Among them 6 participants have completed the first phase of the A-arm and 6 participants have completed the control period of the B-arm and their intervention is ongoing. Recruitment is ongoing. We expect the preliminary data from this study to be completed in 2026.

CONCLUSIONS

This intervention will investigate whether whole body and gut MetFlex can be further explored and used as ex ante predictors of successful weight loss following exercise intervention, providing proof of concept and paving the way for personalized lifestyle interventions.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06329349; https://clinicaltrials.gov/study/NCT06329349.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/67570.

Targeting inflammation and gut microbiota with antibacterial therapy: Implications for central nervous system health

The complex symbiotic relationship between inflammation, the gut microbiota, and the central nervous system (CNS) has become a pivotal focus of contemporary biomedical research. Inflammation, as a physiological defense mechanism, plays a dual role as both a protective and pathological factor, and is intricately associated with gut microbiota homeostasis, often termed the "second brain." The gutbrain axis (GBA) exemplifies this multifaceted interaction, where gut health exerts significantly regulatory effects on CNS functions. Antibacterial therapies represent both promising and challenging strategies for modulating inflammation and gut microbiota composition to confer CNS benefits. However, while such therapies may exert positive modulatory effects on the gut microbiota, they also carry the potential to disrupt microbial equilibrium, potentially exacerbating neurological dysfunction. Recent advances have provided critical insights into the therapeutic implications of antibacterial interventions; nevertheless, the application of these therapies in the context of CNS health warrants a judicious and evidence-based approach. As research progresses, deeper investigation into the microbial-neural interface is essential to fully realize the potential of therapies targeting inflammation and the gut microbiota for CNS health. Future efforts should focus on refining antibacterial interventions to modulate the gut microbiota while minimizing disruption to microbial balance, thereby reducing risks and enhancing efficacy in CNS-related conditions. In conclusion, despite challenges, a more comprehensive understanding of the GBA, along with precise modulation through targeted antibacterial therapies, offers significant promise for advancing CNS disorder treatment. Continued research in this area will lead to innovative interventions and improved patient outcomes.

Gut Microbiota and Gut-Brain Axis in Hypertension: Implications for Kidney and Cardiovascular Health-A Narrative Review

INTRODUCTION

Arterial hypertension is a major contributor to a wide range of health complications, with cardiac hypertrophy and chronic kidney disease being among the most prevalent. Consequently, novel strategies for the treatment and prevention of hypertension are actively being explored. Recent research has highlighted a potential link between hypertension and the gut-brain axis. A bidirectional communication between the microbiota and the brain via the vagus nerve, enteric nervous system, hypothalamus-pituitary-adrenal axis, secreted short-chain fatty acids, and neurotransmitter metabolism.

MATERIALS AND METHODS

A comprehensive literature search was conducted using databases such as PubMed to identify studies exploring the relationship between gut microbiota and hypertension, along with the effects of dietary interventions and probiotics on blood pressure regulation.

DISCUSSION

Studies in both animal models and human subjects have demonstrated a strong correlation between alterations in gut microbiota composition and the development of hypertension. By influencing blood pressure, the gut microbiota can potentially affect the progression of cardiovascular and kidney disorders. Modulating gut microbiota through dietary interventions and probiotics has shown promise in regulating blood pressure and reducing systemic inflammation, offering a novel approach to managing hypertension. Diets such as the Mediterranean diet, which is rich in polyphenols and omega-3 fatty acids and low in sodium, promote the growth of beneficial gut bacteria that support cardiovascular health. Additionally, probiotics have been found to enhance gut barrier function, reduce inflammation, and modulate the Renin-Angiotensin System, all of which contribute to lowering blood pressure.

CONCLUSIONS

Further research is needed to determine the mechanisms of action of the microbiota in hypertension. The aim of this study was to evaluate the influence of gut microbiota on blood pressure regulation and the progression of hypertension-related complications, such as cardiovascular and kidney disorders.

Exploring the Significance of Gut Microbiota in Diabetes Pathogenesis and Management-A Narrative Review

Type 2 diabetes is a disease with significant health consequences for the individual. Currently, new mechanisms and therapeutic approaches that may affect this disease are being sought. One of them is the association of type 2 diabetes with microbiota. Through the enteric nervous system and the gut-microbiota axis, the microbiota affects the functioning of the body. It has been proven to have a real impact on influencing glucose and lipid metabolism and insulin sensitivity. With dysbiosis, there is increased bacterial translocation through the disrupted intestinal barrier and increased inflammation in the body. In diabetes, the microbiota's composition is altered with, for example, a more abundant class of Betaproteobacteria. The consequences of these disorders are linked to mechanisms involving short-chain fatty acids, branched-chain amino acids, and bacterial lipopolysaccharide, among others. Interventions focusing on the gut microbiota are gaining traction as a promising approach to diabetes management. Studies are currently being conducted on the effects of the supply of probiotics and prebiotics, as well as fecal microbiota transplantation, on the course of diabetes. Further research will allow us to fully develop our knowledge on the subject and possibly best treat and prevent type 2 diabetes.

The association between gut microbiota and resting metabolic rate in overweight/obese women: a case-control study

Purpose

When examining the underlying processes of obesity, evaluation of gut flora and energy homeostasis can be crucial since disruption of the normal gut microbiota community and energy imbalances are significant factors in the development of obesity. Therefore, this study aimed to compare the relative abundance of important obesity modulator gut microbiota (including Firmicutes, Bacteroidetes, Bifidobactrium spp., Lactobacillus spp., Bacteroides fragilis, Faecalibacterium prausnitzii, Akkermansia muciniphila, and Escherichia coli) in fecal samples of normometabilic and hypometabolic overweight/obese individuals.

Methods

This matched case-control study conducted on 36 healthy women aged 18-50 years old. An indirect calorimeter and impedance body analyzer were used to assess resting metabolic rate (RMR) and body composition, respectively. Dietary intake and physical activity were assessed using questionnaires. To determine the abundance of the abovementioned gut microbiota, quantitative polymerase chain reaction (qPCR) method was performed. Moreover, ELISA kits were used to assess leptin, ghrelin, and insulin hormones.

Results

The results highlighted higher load of Firmicutes (p = 0.02), F. prausnitzii (p < 0.001), and B. fragilis (p = 0.02) in the normometabolic individuals compared to the hypometabolic ones. Besides, the positive correlation between the abundance of Firmicutes (β = 7.76 × 10-1, p = 0.01), F. prausnitzii (β = 1.29 × 10-5, p = 0.01), and B. fragilis (β = 4.13 × 10-6, p = 0.04) with the RMR have been shown. Whereas the abundance of Bacteroidetes, A. muciniphila, Lactobacillus spp., Bifidobactrium spp., and E. coli showed no significant difference (p > 0.05) and no significant correlation with the RMR except Lactobacillus spp. (β = 1.73 × 10-4, p = 0.01).

Conclusion

It seems that gut microbiota can be a potential target for refining host energy homeostasis and treating obesity and its consequences.

Updated Progress on Polysaccharides with Anti-Diabetic Effects through the Regulation of Gut Microbiota: Sources, Mechanisms, and Structure-Activity Relationships

Diabetes mellitus (DM) is a common chronic metabolic disease worldwide. The disturbance of the gut microbiota has a complex influence on the development of DM. Polysaccharides are one type of the most important natural components with anti-diabetic effects. Gut microbiota can participate in the fermentation of polysaccharides, and through this, polysaccharides regulate the gut microbiota and improve DM. This review begins by a summary of the sources, anti-diabetic effects and the gut microbiota regulation functions of natural polysaccharides. Then, the mechanisms of polysaccharides in regulating the gut microbiota to exert anti-diabetic effects and the structure-activity relationship are summarized. It is found that polysaccharides from plants, fungi, and marine organisms show great hypoglycemic activities and the gut microbiota regulation functions. The mechanisms mainly include repairing the gut burrier, reshaping gut microbiota composition, changing the metabolites, regulating anti-inflammatory activity and immune function, and regulating the signal pathways. Structural characteristics of polysaccharides, such as monosaccharide composition, molecular weight, and type of glycosidic linkage, show great influence on the anti-diabetic activity of polysaccharides. This review provides a reference for the exploration and development of the anti-diabetic effects of polysaccharides.

The keystone gut species Christensenella minuta boosts gut microbial biomass and voluntary physical activity in mice

The gut bacteria of the family Christensenellaceae are consistently associated with metabolic health, but their role in promoting host health is not fully understood. Here, we explored the effect of Christensenella minuta amendment on voluntary physical activity and the gut microbiome. We inoculated male and female germ-free mice with an obese human donor microbiota together with live or heat-killed C. minuta for 28 days and measured physical activity in respirometry cages. Compared to heat-killed, the live-C. minuta treatment resulted in reduced feed efficiency and higher levels of physical activity, with significantly greater distance traveled for males and higher levels of small movements and resting metabolic rate in females. Sex-specific effects of C. minuta treatment may be in part attributable to different housing conditions for males and females. Amendment with live C. minuta boosted gut microbial biomass in both sexes, immobilizing dietary carbon in the microbiome, and mice with high levels of C. minuta lose more energy in stool. Live C. minuta also reduced within and between-host gut microbial diversity. Overall, our results showed that C. minuta acts as a keystone species: despite low relative abundance, it has a large impact on its ecosystem, from the microbiome to host energy homeostasis.IMPORTANCEThe composition of the human gut microbiome is associated with human health. Within the human gut microbiome, the relative abundance of the bacterial family Christensenellaceae has been shown to correlate with metabolic health and a lean body type. The mechanisms underpinning this effect remain unclear. Here, we show that live C. minuta influences host physical activity and metabolic energy expenditure, accompanied by changes in murine metabolism and the gut microbial community in a sex-dependent manner in comparison to heat-killed C. minuta. Importantly, live C. minuta boosts the biomass of the microbiome in the gut, and a higher level of C. minuta is associated with greater loss of energy in stool. These observations indicate that modulation of activity levels and changes to the microbiome are ways in which the Christensenellaceae can influence host energy homeostasis and health.

Connecting the dots in the associations between diet, obesity, cancer, and microRNAs

The prevalence of obesity has reached pandemic levels worldwide, leading to a lower quality of life and higher health costs. Obesity is a major risk factor for noncommunicable diseases, including cancer, although obesity is one of the major preventable causes of cancer. Lifestyle factors, such as dietary quality and patterns, are also closely related to the onset and development of obesity and cancer. However, the mechanisms underlying the complex association between diet, obesity, and cancer remain unclear. In the past few decades, microRNAs (miRNAs), a class of small non-coding RNAs, have been demonstrated to play critical roles in biological processes such as cell differentiation, proliferation, and metabolism, highlighting their importance in disease development and suppression and as therapeutic targets. miRNA expression levels can be modulated by diet and are involved in cancer and obesity-related diseases. Circulating miRNAs can also mediate cell-to-cell communications. These multiple aspects of miRNAs present challenges in understanding and integrating their mechanism of action. Here, we introduce a general consideration of the associations between diet, obesity, and cancer and review the current knowledge of the molecular functions of miRNA in each context. A comprehensive understanding of the interplay between diet, obesity, and cancer could be valuable for the development of effective preventive and therapeutic strategies in future.

Intestinal Production of Alpha-Glucosidase Inhibitor by Bacillus coagulans Spores

This study examines the possibility of directly producing and utilizing useful substances in the intestines of animals using anaerobic bacteria that can grow in the intestines of animals. A facultative anaerobe producing a large amount of α-glucosidase inhibitor was isolated from hay and identified and named Bacillus coagulans CC. The main compound of α-glucosidase inhibitor produced by Bacillus coagulans CC was identified as 1-deoxynojirimycin. α-glucosidase inhibitor activity was confirmed in the intestinal contents and feces of mice orally administered with spores of this strain, and it was confirmed that this strain could efficiently reach the intestines, proliferate, and produce α-glucosidase inhibitors. As a result of administering Bacillus coagulans CC to mice at 10⁹ cells per 1 kg body weight of spores for 8 weeks, the high-carbohydrate diet and the high-fat diet showed a 5% lower weight gain compared to the non-administrated group. At this point, in the spore-administered group, a decrease was observed in both the visceral and subcutaneous fat layers of the abdomen and thorax in both high-carbohydrate and high-fat diet groups compared to the non-administered group on computed tomography. The results of this study show that α-glucosidase inhibitors produced in the intestine by specific strains can work efficiently.

Associations between Intra-Assessment Resting Metabolic Rate Variability and Health-Related Factors

In humans, the variation in resting metabolic rate (RMR) might be associated with health-related factors, as suggested by previous studies. This study explored whether the intra-assessment RMR variability (expressed as a coefficient of variation (CV; %)) is similar in men and women and if it is similarly associated with diverse health-related factors. The RMR of 107 young, and relatively healthy adults, was assessed using indirect calorimetry. Then, the CV for volumes of oxygen consumption (VO2) and carbon dioxide production (VCO2), respiratory exchange ratio (RER), and resting energy expenditure (REE) were computed as indicators of intra-assessment RMR variability. Body composition, cardiorespiratory fitness (peak VO2 uptake), circulating cardiometabolic risk factors, and heart rate and its variability (HR and HRV) were assessed. Men presented higher CVs for VO2, VCO2, and REE (all p ≤ 0.001) compared to women. Furthermore, in men, the intra-assessment RER variability was associated with vagal-related HRV parameters and with mean HR (standardized β = −0.36, −0.38, and 0.41, respectively; all p < 0.04). In contrast, no associations were observed in women. In conclusion, men exhibited higher variability (CVs for VO2, VCO2, and REE) compared to women. The CV for RER could be a potential marker of cardiometabolic risk in young men.

Role of Gut Microbiome in Cardiovascular Events: A Systematic Review

The gut microbiome helps maintain homeostasis in the body, but what if the gut experiences imbalance? It would lead to dysbiosis - which is involved in multiple diseases, including but not limited to cardiovascular diseases, the most common cause of mortality around the globe. This research paper aims to explain all the possible mechanisms known linking the gut microbiome to the contribution of worsening cardiovascular events. PubMed and Google Scholar were thoroughly explored to learn the role of the gut microbiome in cardiovascular events. A systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to analyze the possible pathways and the metabolites included in the study. Thirteen review articles were selected based on the assessment of multiple systematic reviews (AMSTAR) and the scale for the assessment of non-systematic review articles (SANRA) checklist scores. In this article, we have discussed the role of the gut microbiome in atherosclerosis, hypertension, metabolic disorders such as diabetes and obesity, coronary artery disease, etc. Various pathways to modify the gut microbiome are also discussed, along with the use of probiotics. Finally, we discussed the role of trimethylamine N-oxide (TMAO), a gut microbiome metabolite, as a biomarker for the prognosis of various diseases. This study concluded that the gut microbiome does play a crucial role in the worsening of cardiovascular diseases and the metabolites of which can be used as biomarkers in the prognosis of cardiovascular events.

Variability in energy expenditure is much greater in males than females

In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a cumulative effect if those traits mostly exhibit greater male variation, or a lack of greater male variation if many of them do not. Sex differences in energy expenditure variation have been little explored. We analyzed a large database on energy expenditure in adult humans (1494 males and 3108 females) to investigate whether humans have evolved sex differences in the degree of interindividual variation in energy expenditure. We found that, even when statistically comparing males and females of the same age, height, and body composition, there is much more variation in total, activity, and basal energy expenditure among males. However, with aging, variation in total energy expenditure decreases, and because this happens more rapidly in males, the magnitude of greater male variation, though still large, is attenuated in older age groups. Considerably greater male variation in both total and activity energy expenditure could be explained by greater male variation in levels of daily activity. The considerably greater male variation in basal energy expenditure is remarkable and may be explained, at least in part, by greater male variation in the size of energy-demanding organs. If energy expenditure is a trait that is of indirect interest to females when choosing a sexual partner, this would suggest that energy expenditure is under sexual selection. However, we present a novel energetics model demonstrating that it is also possible that females have been under stabilizing selection pressure for an intermediate basal energy expenditure to maximize energy available for reproduction.

Effects of Fermented Milk Containing Bifidobacterium animalis Subsp. lactis MN-Gup (MN-Gup) and MN-Gup-Based Synbiotics on Obesity Induced by High Fat Diet in Rats

Given the probiotic effects previously found in Bifidobacterium animalis subsp. lactis MN-Gup (MN-Gup) and its great application potential in dairy products, this study aimed to investigate the effects of fermented milk containing MN-Gup or MN-Gup-based synbiotics on high fat diet (HFD)-induced obesity in rats. Galacto-oligosaccharides (GOS) and xylo-oligosaccharides (XOS) were selected as the tested prebiotics in MN-Gup-based synbiotics due to their promotion of MN-Gup growth in vitro. After nine weeks of HFD feeding, the obese rats were intervened with fermented milk containing MN-Gup (MN-Gup FM) or its synbiotics (MN-Gup + GOS FM, MN-Gup + XOS FM) for eight weeks. The results showed that the interventions could alleviate HFD-induced body weight gain, epididymal fat deposition, adipocyte hypertrophy, dyslipidemia and inflammation, but GOS and XOS did not exhibit significant synergies with MN-Gup on those alleviations. Furthermore, the interventions could regulate the HFD-affected gut microbiota and microbial metabolites, as shown by the increases in short chain fatty acids (SCFAs) and alterations in obesity-related bile acids (BAs), which may play important roles in the mechanism underlying the alleviation of obesity. This study revealed the probiotic effects of MN-Gup on alleviating obesity and provided the basis for MN-Gup applications in the future.

Gut microbiota predicts body fat change following a low-energy diet: a PREVIEW intervention study

Background

Low-energy diets (LEDs) comprise commercially formulated food products that provide between 800 and 1200 kcal/day (3.3–5 MJ/day) to aid body weight loss. Recent small-scale studies suggest that LEDs are associated with marked changes in the gut microbiota that may modify the effect of the LED on host metabolism and weight loss. We investigated how the gut microbiota changed during 8 weeks of total meal replacement LED and determined their associations with host response in a sub-analysis of 211 overweight adults with pre-diabetes participating in the large multicentre PREVIEW (PREVention of diabetes through lifestyle intervention and population studies In Europe and around the World) clinical trial.

Methods

Microbial community composition was analysed by Illumina sequencing of the hypervariable V3-V4 regions of the 16S ribosomal RNA (rRNA) gene. Butyrate production capacity was estimated by qPCR targeting the butyryl-CoA:acetate CoA-transferase gene. Bioinformatics and statistical analyses, such as comparison of alpha and beta diversity measures, correlative and differential abundances analysis, were undertaken on the 16S rRNA gene sequences of 211 paired (pre- and post-LED) samples as well as their integration with the clinical, biomedical and dietary datasets for predictive modelling.

Results

The overall composition of the gut microbiota changed markedly and consistently from pre- to post-LED (P = 0.001), along with increased richness and diversity (both P < 0.001). Following the intervention, the relative abundance of several genera previously associated with metabolic improvements (e.g., Akkermansia and Christensenellaceae R-7 group) was significantly increased (P < 0.001), while flagellated Pseudobutyrivibrio, acetogenic Blautia and Bifidobacterium spp. were decreased (all P < 0.001). Butyrate production capacity was reduced (P < 0.001). The changes in microbiota composition and predicted functions were significantly associated with body weight loss (P < 0.05). Baseline gut microbiota features were able to explain ~25% of variation in total body fat change (post–pre-LED).

Conclusions

The gut microbiota and individual taxa were significantly influenced by the LED intervention and correlated with changes in total body fat and body weight in individuals with overweight and pre-diabetes. Despite inter-individual variation, the baseline gut microbiota was a strong predictor of total body fat change during the energy restriction period.

Trial registration

The PREVIEW trial was prospectively registered at ClinicalTrials.gov (NCT01777893) on January 29, 2013.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-022-01053-7.

Perspective: Obesity-an unexplained epidemic

Since 1980, obesity prevalence among US adults has soared from 14% to 42%. The commonly accepted explanation is pervasive overeating: ever-increasing energy intake as the population gains weight, year after year. However, evidence does not support this hypothesis. National data on energy intake and energy availability show increases between 1961 and 2000, during modern industrialization of food; but a plateau or declines thereafter-even as obesity continued rising-and while physical activity modestly increased. Thus, Americans appear to be eating relatively less since 2000, for ever-increasing body sizes, as time has progressed. Although both energy intake and energy availability are measured with error, such errors would have to be new since 2000 and systematically increasing over time for these 2 separate, independent measures. Given the tremendous societal consequences of obesity, and failure to date of energy balance-focused interventions to stem the tide, it is critical for the scientific community to consider and test alternative hypotheses. Growing evidence suggests complex, interrelated biological interactions between food processing (including acellular nutrients, depleted prebiotics, additives), gut microbial composition and function, host metabolic expenditure, and intergenerational transmission of risk (including epigenetics, noncoding RNAs, microbial species). In this paradigm, whereas increasing energy intake may have contributed to rising obesity in earlier years, today pervasive adiposity and its physiologic adaptations have created a biological milieu which interacts with industrialized foods to promote escalating obesity, even with stable energy intake-a self-sustaining, difficult-to-reverse cycle. These scientific hypotheses must be rigorously evaluated, because even partial confirmation would dramatically shift and expand current prevention and treatment strategies. Urgent new investment in research is required. Simultaneously, uncertain evidence on the obesity epidemic's primary drivers does not mean there is no evidence on actions that can help, and existing science must be more rapidly translated and refined into clinical, public health, and policy interventions.

Methods for the Comprehensive in vivo Analysis of Energy Flux, Fluid Homeostasis, Blood Pressure, and Ventilatory Function in Rodents

Cardiovascular disease represents the leading cause of death in the United States, and metabolic diseases such as obesity represent the primary impediment to improving cardiovascular health. Rodent (mouse and rat) models are widely used to model cardiometabolic disease, and as a result, there is increasing interest in the development of accurate and precise methodologies with sufficiently high resolution to dissect mechanisms controlling cardiometabolic physiology in these small organisms. Further, there is great utility in the development of centralized core facilities furnished with high-throughput equipment configurations and staffed with professional content experts to guide investigators and ensure the rigor and reproducibility of experimental endeavors. Here, we outline the array of specialized equipment and approaches that are employed within the Comprehensive Rodent Metabolic Phenotyping Core (CRMPC) and our collaborating laboratories within the Departments of Physiology, Pediatrics, Microbiology & Immunology, and Biomedical Engineering at the Medical College of Wisconsin (MCW), for the detailed mechanistic dissection of cardiometabolic function in mice and rats. We highlight selected methods for the analysis of body composition and fluid compartmentalization, electrolyte accumulation and flux, energy accumulation and flux, physical activity, ingestive behaviors, ventilatory function, blood pressure, heart rate, autonomic function, and assessment and manipulation of the gut microbiota. Further, we include discussion of the advantages and disadvantages of these approaches for their use with rodent models, and considerations for experimental designs using these methods.

Nicotinamide Riboside-Conditioned Microbiota Deflects High-Fat Diet-Induced Weight Gain in Mice

With obesity and type 2 diabetes (T2D) at epidemic levels, we need to understand the complex nature of these diseases to design better therapeutics. The underlying causes of both obesity and T2D are complex, but both are thought to develop, in part, based on contributions from the gut microbiota.

Amelioration of Diabetic Nephropathy by Targeting Autophagy via Rapamycin or Fasting: Relation to Cell Apoptosis/Survival

Autophagy has been demonstrated to have a beneficial effect on diabetic nephropathy (DN). Rapamycin, an inhibitor of mTOR, was shown to stimulate β-cell autophagy. However, its effects on preventing or ameliorating DN is unclear, and its effects are worth studying. As fasting is now an attractive protective strategy, we aim to compare its effect to rapamycin effects on pancreatic and renal cells. Twenty-eight adult male Wistar Albino rats were randomly divided into four groups, using streptozotocin (STZ) to induce diabetes mellitus (DM). Autophagy was induced by two ways; rapamycin or fasting. The extent of autophagy and apoptosis were investigated by measuring the level of LC3B and p53 proteins, respectively, in pancreatic and kidney tissues using Western blotting (WB) technique and imaging the renal cells under transmission electron microscope. The efflux transporter P-glycoprotein was quantified by WB as well. Rapamycin-induced autophagy occurred concurrently with apoptosis. On the other hand, fasting supported P-glycoprotein recovery and renal cell survival together with disabling β-cells apoptosis. In conclusion, this study provides a potential link between rapamycin or fasting for the cross-regulation of apoptosis and autophagy in the setting of cell stress as DN. Unlike rapamycin, fasting enhanced the active expression of ABCB1 efflux protein, providing insights on the potential ameliorative effects of fasting in DN that require further elucidation.

Effects of Totum-63 on glucose homeostasis and postprandial glycemia: a translational study

Global prevalence of type 2 diabetes (T2D) is rising and may affect 700 million people by 2045. Totum-63 is a polyphenol-rich natural composition developed to reduce the risk of T2D. We first investigated the effects of Totum-63 supplementation in high-fat diet (HFD)-fed mice for up to 16 wk and thereafter assessed its safety and efficacy (2.5 g or 5 g per day) in 14 overweight men [mean age 51.5 yr, body mass index (BMI) 27.6 kg·m^-2] for 4 wk. In HFD-fed mice, Totum-63 reduced body weight and fat mass gain, whereas lean mass was unchanged. Moreover, fecal energy excretion was higher in Totum-63-supplemented mice, suggesting a reduction of calorie absorption in the digestive tract. In the gut, metagenomic analyses of fecal microbiota revealed a partial restoration of HFD-induced microbial imbalance, as shown by principal coordinate analysis of microbiota composition. HFD-induced increase in HOMA-IR score was delayed in supplemented mice, and insulin response to an oral glucose tolerance test was significantly reduced, suggesting that Totum-63 may prevent HFD-related impairments in glucose homeostasis. Interestingly, these improvements could be linked to restored insulin signaling in subcutaneous adipose tissue and soleus muscle. In the liver, HFD-induced steatosis was reduced by 40% (as shown by triglyceride content). In the subsequent study in men, Totum-63 (5 g·day^-1) improved glucose and insulin responses to a high-carbohydrate breakfast test (84% kcal carbohydrates). It was well tolerated, with no clinically significant adverse events reported. Collectively, these data suggest that Totum-63 could improve glucose homeostasis in both HFD-fed mice and overweight individuals, presumably through a multitargeted action on different metabolic organs.NEW & NOTEWORTHY Totum-63 is a novel polyphenol-rich natural composition developed to reduce the risk of T2D. Totum-63 showed beneficial effects on glucose homeostasis in HFD-fed mice, presumably through a multitargeted action on different metabolic organs. Totum-63 was well tolerated in humans and improved postprandial glucose and insulin responses to a high-carbohydrate breakfast test.

Recent advances and health implications of dietary fasting regimens on the gut microbiome

Calorie restriction is a primary dietary intervention demonstrated over many decades in cellular and animal models to modulate aging pathways, positively affect age-associated diseases and, in clinical studies, to promote beneficial health outcomes. Because long-term compliance with daily calorie restriction has proven problematic in humans several intermittent fasting regimens, including alternate day fasting and time-restricted feeding, have evolved revealing similar clinical benefits as calorie restriction. Despite significant research on the cellular and physiological mechanisms contributing to, and responsible for, these observed benefits, relatively little research has investigated the impact of these various fasting protocols on the gut microbiome (GM). Reduced external nutrient supply to the gut may beneficially alter the composition and function of a "fed" gut microflora. Indeed, the prevalent, obesogenic Western diet can promote deleterious changes in the GM, signaling intermediates involved in lipid and glucose metabolism, and immune responses in the gastrointestinal tract. This review describes recent preclinical and clinical effects of varying fasting regimens on GM composition and associated physiology. Although the number of preclinical and clinical interventions are limited, significant data thus far suggest fasting interventions impact GM composition and physiology. However, there are considerable heterogeneities of study design, methodological considerations, and practical implications. Ongoing research on the health impact of fasting regimens on GM modulation is warranted.

The Microbiome in Obstructive Sleep Apnea

Recent evidence has highlighted important associations between obstructive sleep apnea and the microbiome. Although the intricacies of the pathophysiologic mechanisms are not well understood, available evidence suggests a bidirectional relationship between OSA and microbiota composition. Sleep fragmentation, intermittent hypoxia, and intermittent hypercapnia all play significant roles in altering the microbiome, and initial evidence has shown that alterations of the microbiota affect sleep patterns. Animal model evidence strongly supports the idea that the microbiome mediates disease states associated with OSA including hypertension, atherosclerosis, and obesity. The majority of evidence focuses on changes in the gut microbiome, which may result from OSA as well as contribute to sleep pattern changes, OSA-related CVD, and obesity. Meanwhile, a developing body of work suggests changes in the upper airway microbiome may be associated with OSA and periodontitis-related oral cavity microbiome changes may have significance in OSA-related CVD. Lastly, while evidence is limited, several studies suggest there may be a role for treatment of OSA and OSA-related comorbidities through alteration of the microbiome with probiotics, prebiotics, and microbiota transplantation. These early animal and human studies begin to characterize the interrelationships of the microbiome and OSA and may lead to new avenues for treatment.

The Emerging World of Microbiome in Autoimmune Disorders: Opportunities and Challenges

Trillions of commensal bacteria colonizing humans (microbiome) have emerged as essential player(s) in human health. The alteration of the same has been linked with diseases including autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, and ankylosing spondylitis. Gut bacteria are separated from the host through a physical barrier such as skin or gut epithelial lining. However, the perturbation in the healthy bacterial community (gut dysbiosis) can compromise gut barrier integrity, resulting in translocation of bacterial contents across the epithelial barrier (leaky gut). Bacterial contents such as lipopolysaccharide and bacterial antigens can induce a systemic inflammatory environment through activation and induction of immune cells. The biggest question in the field is whether inflammation causes gut dysbiosis or dysbiosis leads to disease induction or propagation, i.e., it is inside out or outside in or both. In this review, we first discuss the microbiome profiling studies in various autoimmune disorders, followed by a discussion of potential mechanisms through which microbiome is involved in the pathobiology of diseases. A better understanding of the role of the microbiome in health and disease will help us harness the power of commensal bacteria for the development of novel therapeutic agents to treat autoimmune disorders.

What Is an L-Cell and How Do We Study the Secretory Mechanisms of the L-Cell?

Synthetic glucagon-like peptide-1 (GLP-1) analogues are effective anti-obesity and anti-diabetes drugs. The beneficial actions of GLP-1 go far beyond insulin secretion and appetite, and include cardiovascular benefits and possibly also beneficial effects in neurodegenerative diseases. Considerable reserves of GLP-1 are stored in intestinal endocrine cells that potentially might be mobilized by pharmacological means to improve the body's metabolic state. In recognition of this, the interest in understanding basic L-cell physiology and the mechanisms controlling GLP-1 secretion, has increased considerably. With a view to home in on what an L-cell is, we here present an overview of available data on L-cell development, L-cell peptide expression profiles, peptide production and secretory patterns of L-cells from different parts of the gut. We conclude that L-cells differ markedly depending on their anatomical location, and that the traditional definition of L-cells as a homogeneous population of cells that only produce GLP-1, GLP-2, glicentin and oxyntomodulin is no longer tenable. We suggest to sub-classify L-cells based on their differential peptide contents as well as their differential expression of nutrient sensors, which ultimately determine the secretory responses to different stimuli. A second purpose of this review is to describe and discuss the most frequently used experimental models for functional L-cell studies, highlighting their benefits and limitations. We conclude that no experimental model is perfect and that a comprehensive understanding must be built on results from a combination of models.

Amelioration of high-fat diet-induced obesity and its associated complications by a myricetin derivative-rich fraction from Syzygium malaccense in C57BL/6J mice

Obesity is a driving factor in the onset of metabolic disorders. This study aims to investigate the effects of the myricetin derivative-rich fraction (MD) from Syzygium malaccense leaf extract on high-fat diet (HFD)-induced obesity and its associated complications and its influence on uncoupling protein-1 (UCP-1) and gut microbiota in C57BL/6J mice. Mice were randomly assigned into four groups (n = 6) and given a normal diet (ND) or high-fat diet (HFD) for 10 weeks to induce obesity. The HFD groups (continued with HFD) were administered 50 mg kg-1 MD (treatment), 50 mg kg-1 metformin (positive control) and normal saline (HFD and ND controls) daily for four weeks via oral gavage. The ten-week HFD-feeding resulted in hyperglycemia and elevated urinary oxidative indices. The subsequent MD administration caused significant weight reduction without appetite suppression and amelioration of insulin resistance, steatosis and dyslipidemia. Besides, MD significantly reduced lipid hydroperoxides and protein carbonyls in tissue homogenates and urine and elevated Trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) and reduced glutathione (GSH) and thus, alleviated oxidative stress. The weight reduction was correlated with downregulation of inflammatory markers and the increased UCP-1 level, suggesting weight loss plausibly through thermogenesis. The Akkermansia genus (reflects improved metabolic status) in the HFD50 group was more abundant than that in the HFD group while the non-enzymatic antioxidant markers were strongly associated with UCP-1. In conclusion, MD ameliorates obesity and its related complications possibly via the upregulation of UCP-1 and increased abundance of Akkermansia genus and is promising as a therapeutic agent in the treatment of obesity and its associated metabolic disorders.

Plasmids encode niche-specific traits in Lactobacillaceae

Species belonging to the family Lactobacillaceae are found in highly diverse environments and play an important role in fermented foods and probiotic products. Many of these species have been individually reported to harbour plasmids that encode important genes. In this study, we performed comparative genomic analysis of publicly available data for 512 plasmids from 282 strains represented by 51 species of this family and correlated the genomic features of plasmids with the ecological niches in which these species are found. Two-thirds of the species had at least one plasmid-harbouring strain. Plasmid abundance and GC content were significantly lower in vertebrate-adapted species as compared to nomadic and free-living species. Hierarchical clustering highlighted the distinct nature of plasmids from the nomadic and free-living species than those from the vertebrate-adapted species. EggNOG-assisted functional annotation revealed that genes associated with transposition, conjugation, DNA repair and recombination, exopolysaccharide production, metal ion transport, toxin–antitoxin system, and stress tolerance were significantly enriched on the plasmids of the nomadic and in some cases nomadic and free-living species. On the other hand, genes related to anaerobic metabolism, ABC transporters and the major facilitator superfamily were overrepresented on the plasmids of the vertebrate-adapted species. These genomic signatures correlate with the comparatively nutrient-depleted, stressful and dynamic environments of nomadic and free-living species and nutrient-rich and anaerobic environments of vertebrate-adapted species. Thus, these results indicate the contribution of the plasmids in the adaptation of lactobacilli to their respective habitats. This study also underlines the potential application of these plasmids in improving the technological and probiotic properties of lactic acid bacteria.

Endocannabinoid Receptor-1 and Sympathetic Nervous System Mediate the Beneficial Metabolic Effects of Gastric Bypass

The exact mechanisms underlying the metabolic effects of bariatric surgery remain unclear. Here, we demonstrate, using a combination of direct and indirect calorimetry, an increase in total resting metabolic rate (RMR) and specifically anaerobic RMR after Roux-en-Y gastric bypass (RYGB), but not sleeve gastrectomy (SG). We also show an RYGB-specific increase in splanchnic sympathetic nerve activity and "browning" of visceral mesenteric fat. Consequently, selective splanchnic denervation abolishes all beneficial metabolic outcomes of gastric bypass that involve changes in the endocannabinoid signaling within the small intestine. Furthermore, we demonstrate that administration of rimonabant, an endocannabinoid receptor-1 (CB1) inverse agonist, to obese mice mimics RYGB-specific effects on energy balance and splanchnic nerve activity. On the other hand, arachidonoylethanolamide (AEA), a CB1 agonist, attenuates the weight loss and metabolic signature of this procedure. These findings identify CB1 as a key player in energy regulation post-RYGB via a pathway involving the sympathetic nervous system.

Flexibility Is Costly: Hidden Physiological Damage From Seasonal Phenotypic Transitions in Heterothermic Species

Heterothermy allows organisms to cope with fluctuating environmental conditions. The use of regulated hypometabolism allows seasonal heterothermic species to cope with annual resource shortages and thus to maximize survival during the unfavorable season. This comes with deep physiological remodeling at each seasonal transition to allow the organism to adjust to the changing environment. In the wild, this adaptation is highly beneficial and largely overcomes potential costs. However, researchers recently proposed that it might also generate both ecological and physiological costs for the organism. Here, we propose new perspectives to be considered when analyzing adaptation to seasonality, in particular considering these costs. We propose a list of putative costs, including DNA damage, inflammatory response to fat load, brain and cognitive defects, digestive malfunction and immunodeficiency, that should receive more attention in future research on physiological seasonality. These costs may only be marginal at each transition event but accumulate over time and therefore emerge with age. In this context, studies in captivity, where we have access to aging individuals with limited extrinsic mortality (e.g., predation), could be highly valuable to experimentally assess the costs of physiological flexibility. Finally, we offer new perspectives, which should be included in demographic models, on how the adaptive value of physiological flexibility could be altered in the future in the context of global warming.

Unravelling the health effects of fasting: a long road from obesity treatment to healthy life span increase and improved cognition

In recent years a revival of interest has emerged in the health benefits of intermittent fasting and long-term fasting, as well as of other related nutritional strategies. In addition to meal size and composition a new focus on time and frequency of meals has gained attention. The present review will investigate the effects of the main forms of fasting, activating the metabolic switch from glucose to fat and ketones (G-to-K), starting 12-16 h after cessation or strong reduction of food intake. During fasting the deactivation of mTOR regulated nutrient signalling pathways and activation of the AMP protein kinase trigger cell repair and inhibit anabolic processes. Clinical and animal studies have clearly indicated that modulating diet and meal frequency, as well as application of fasting patterns, e.g. intermittent fasting, periodic fasting, or long-term fasting are part of a new lifestyle approach leading to increased life and health span, enhanced intrinsic defences against oxidative and metabolic stresses, improved cognition, as well as a decrease in cardiovascular risk in both obese and non-obese subjects. Finally, in order to better understand the mechanisms beyond fasting-related changes, human studies as well as non-human models closer to human physiology may offer useful clues.KEY-MESSAGESBiochemical changes during fasting are characterised by a glucose to ketone switch, leading to a rise of ketones, advantageously used for brain energy, with consequent improved cognition.Ketones reduce appetite and help maintain effective fasting.Application of fasting patterns increases healthy life span and defences against oxidative and metabolic stresses.Today's strategies for the use of therapeutic fasting are based on different protocols, generally relying on intermittent fasting, of different duration and calorie intake.Long-term fasting, with durations between 5 and 21 days can be successfully repeated in the course of a year.

Metabolites and Hypertension: Insights into Hypertension as a Metabolic Disorder: 2019 Harriet Dustan Award

For over 100 years, essential hypertension has been researched from different perspectives ranging from genetics, physiology, and immunology to more recent ones encompassing microbiology (microbiota) as a previously underappreciated field of study contributing to the cause of hypertension. Each field of study in isolation has uniquely contributed to a variety of underlying mechanisms of blood pressure regulation. Even so, clinical management of essential hypertension has remained somewhat static. We, therefore, asked if there are any converging lines of evidence from these individual fields that could be amenable for a better clinical prognosis. Accordingly, here we present converging evidence which support the view that metabolic dysfunction underlies essential hypertension.

The influence of wasabi on the gut microbiota of high-carbohydrate, high-fat diet-induced hypertensive Wistar rats

The human gut microbiota plays a critical role in the regulation of adiposity, obesity and metabolic and cardiovascular disease. Wasabi is a pungent spice and its active component, allyl isothiocyanate, improves plasma triacylglycerol, cholesterol and high blood pressure in rodents, but it is unclear if this occurs through alterations to the composition of the microbiota. The aim of this study was to determine the effectiveness of Wasabi japonica stem and rhizome blend on ameliorating cardiovascular disease parameters including plasma sodium concentration, systolic blood pressure (SBP), plasma endothelin-1 and angiotensin II concentrations by altering the gut microbiota in a Wistar rat model of obesity and metabolic syndrome. Rats were randomized to receive a corn starch or high-carbohydrate/high-fat diet for 8 weeks before being allocated to supplementation with wasabi powder (5% (w/w) in food) or not for an additional 8 weeks. At the end of the trial, rats were grouped according to blood pressure status. Wasabi supplementation prevented the development of hypertension and was also associated with significantly increased abundance of Allobaculum, Sutterella, Uncl. S247, Uncl. Coriobacteriaceae and Bifidobacterium. Hypertension was positively correlated with higher abundance of Oscillospira, Uncl. Lachnospiraceae and Uncl. Clostridiales, Uncl. Bacteroidales and Butyricimonas. Oscillospira and Butyricimonas abundances were specifically positively correlated with systolic blood pressure. Overall, the improved host cardiovascular health in diet-induced obese rats supplemented with wasabi powder may involve changes to the gut microbiota composition.

The athletic gut microbiota

The microorganisms in the gastrointestinal tract play a significant role in nutrient uptake, vitamin synthesis, energy harvest, inflammatory modulation, and host immune response, collectively contributing to human health. Important factors such as age, birth method, antibiotic use, and diet have been established as formative factors that shape the gut microbiota. Yet, less described is the role that exercise plays, particularly how associated factors and stressors, such as sport/exercise-specific diet, environment, and their interactions, may influence the gut microbiota. In particular, high-level athletes offer remarkable physiology and metabolism (including muscular strength/power, aerobic capacity, energy expenditure, and heat production) compared to sedentary individuals, and provide unique insight in gut microbiota research. In addition, the gut microbiota with its ability to harvest energy, modulate the immune system, and influence gastrointestinal health, likely plays an important role in athlete health, wellbeing, and sports performance. Therefore, understanding the mechanisms in which the gut microbiota could play in the role of influencing athletic performance is of considerable interest to athletes who work to improve their results in competition as well as reduce recovery time during training. Ultimately this research is expected to extend beyond athletics as understanding optimal fitness has applications for overall health and wellness in larger communities. Therefore, the purpose of this narrative review is to summarize current knowledge of the athletic gut microbiota and the factors that shape it. Exercise, associated dietary factors, and the athletic classification promote a more “health-associated” gut microbiota. Such features include a higher abundance of health-promoting bacterial species, increased microbial diversity, functional metabolic capacity, and microbial-associated metabolites, stimulation of bacterial abundance that can modulate mucosal immunity, and improved gastrointestinal barrier function.

Obesity, kidney dysfunction and hypertension: mechanistic links

Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.

Changes in human gut microbiota composition are linked to the energy metabolic switch during 10 d of Buchinger fasting

Fasting is increasingly popular to manage metabolic and inflammatory diseases. Despite the role that the human gut microbiota plays in health and diseases, little is known about its composition and functional capacity during prolonged fasting when the external nutrient supply is reduced or suppressed. We analysed the effects of a 10-d periodic fasting on the faecal microbiota of fifteen healthy men. Participants fasted according to the peer-reviewed Buchinger fasting guidelines, which involve a daily energy intake of about 1046 kJ (250 kcal) and an enema every 2 d. Serum biochemistry confirmed the metabolic switch from carbohydrates to fatty acids and ketones. Emotional and physical well-being were enhanced. Faecal 16S rRNA gene amplicon sequencing showed that fasting caused a decrease in the abundance of bacteria known to degrade dietary polysaccharides such as Lachnospiraceae and Ruminococcaceae. There was a concomitant increase in Bacteroidetes and Proteobacteria (Escherichia coli and Bilophila wadsworthia), known to use host-derived energy substrates. Changes in taxa abundance were associated with serum glucose and faecal branched-chain amino acids (BCAA), suggesting that fasting-induced changes in the gut microbiota are associated with host energy metabolism. These effects were reversed after 3 months. SCFA levels were unchanged at the end of the fasting. We also monitored intestinal permeability and inflammatory status. IL-6, IL-10, interferon γ and TNFα levels increased when food was reintroduced, suggesting a reactivation of the postprandial immune response. We suggest that changes in the gut microbiota are part of the physiological adaptations to a 10-d periodic fasting, potentially influencing its beneficial health effects.

Comparison of the Effects of High-Fat Diet on Energy Flux in Mice Using Two Multiplexed Metabolic Phenotyping Systems

OBJECTIVE

Multiplexed metabolic phenotyping systems are available from multiple commercial vendors, and each system includes unique design features. Although expert opinion supports strengths and weaknesses of each design, empirical data from carefully controlled studies to test the biological impact of design differences are lacking.

METHODS

Wild-type C57BL/6J mice of both sexes underwent phenotyping in OxyMax (Columbus Instruments International) and Promethion (Sable Systems International) systems located within the same room of a newly constructed animal research facility in a crossover design study. Phenotypes were examined under chow (2920×)-fed conditions and again after 4 weeks of 60% high-fat diet (D12492) feeding.

RESULTS

Food intake, physical activity, and respiratory gas exchange data significantly diverged between systems, depending upon sex of animals and diet supplied. Estimates of energy expenditure based on gas exchange in both systems accounted for a fraction of consumed calories that was greater in males than females.

CONCLUSIONS

Design differences quantitatively impact the assessment of metabolic end points and thus the qualitative interpretation of various interventions. Importantly, current multiplexed systems remain blind to multiple additional end points, including digestive efficiency and selected forms of energy flux (nitrogenous, anaerobic, etc.), that account for a physiologically and/or pathophysiologically significant fraction of total energy flux.

Diet, Gut Microbiota, and Obesity: Links with Host Genetics and Epigenetics and Potential Applications

Diverse evidence suggests that the gut microbiota is involved in the development of obesity and associated comorbidities. It has been reported that the composition of the gut microbiota differs in obese and lean subjects, suggesting that microbiota dysbiosis can contribute to changes in body weight. However, the mechanisms by which the gut microbiota participates in energy homeostasis are unclear. Gut microbiota can be modulated positively or negatively by different lifestyle and dietary factors. Interestingly, complex interactions between genetic background, gut microbiota, and diet have also been reported concerning the risk of developing obesity and metabolic syndrome features. Moreover, microbial metabolites can induce epigenetic modifications (i.e., changes in DNA methylation and micro-RNA expression), with potential implications for health status and susceptibility to obesity. Also, microbial products, such as short-chain fatty acids or membrane proteins, may affect host metabolism by regulating appetite, lipogenesis, gluconeogenesis, inflammation, and other functions. Metabolomic approaches are being used to identify new postbiotics with biological activity in the host, allowing discovery of new targets and tools for incorporation into personalized therapies. This review summarizes the current understanding of the relations between the human gut microbiota and the onset and development of obesity. These scientific insights are paving the way to understanding the complex relation between obesity and microbiota. Among novel approaches, prebiotics, probiotics, postbiotics, and fecal microbiome transplantation could be useful to restore gut dysbiosis.

Influence of dietary protein on Dahl salt-sensitive hypertension: a potential role for gut microbiota

High blood pressure affects 1.39 billion adults across the globe and is the leading preventable cause of death worldwide. Hypertension is a multifaceted disease with known genetic and environmental factors contributing to its progression. Our studies utilizing the Dahl salt-sensitive (SS) rat have demonstrated the remarkable influence of dietary protein and maternal environment on the development of hypertension and renal damage in response to high salt. There is growing interest in the relationship between the microbiome and hypertension, with gut dysbiosis being correlated to a number of pathologies. This review summarizes the current literature regarding the interplay among dietary protein, the gut microbiota, and hypertension. These studies may provide insight into the effects we have observed between diet and hypertension in Dahl SS rats and, we hope, lead to new perspectives where potential dietary interventions or microbiota manipulations could serve as plausible therapies for hypertension.

Natural Products for the Treatment of Autoimmune Arthritis: Their Mechanisms of Action, Targeted Delivery, and Interplay with the Host Microbiome

Rheumatoid arthritis (RA) is a chronic, debilitating illness characterized by painful swelling of the joints, inflammation of the synovial lining of the joints, and damage to cartilage and bone. Several anti-inflammatory and disease-modifying drugs are available for RA therapy. However, the prolonged use of these drugs is associated with severe side effects. Furthermore, these drugs are effective only in a proportion of RA patients. Hence, there is a need to search for new therapeutic agents that are effective yet safe. Interestingly, a variety of herbs and other natural products offer a vast resource for such anti-arthritic agents. We discuss here the basic features of RA pathogenesis; the commonly used animal models of RA; the mainstream drugs used for RA; the use of well-characterized natural products possessing anti-arthritic activity; the application of nanoparticles for efficient delivery of such products; and the interplay between dietary products and the host microbiome for maintenance of health and disease induction. We believe that with several advances in the past decade in the characterization and functional studies of natural products, the stage is set for widespread clinical testing and/or use of these products for the treatment of RA and other diseases.

Proton Pump Inhibitors Increase the Susceptibility of Mice to Oral Infection with Enteropathogenic Bacteria

BACKGROUND AND AIMS

Proton pump inhibitors (PPIs) are among the most frequently prescribed medications. Side effects including an increased risk of intestinal infections have been reported. It is assumed that PPIs can increase susceptibility to enteropathogens; however, the underlying mechanisms are unknown. Here in this study, we explored whether Lansoprazole (Laz), one of the PPIs, increases the susceptibility to enteropathogens, and further investigated the mechanism of it.

METHODS

Mice were administered Laz intraperitoneally once daily and orally infected with Citrobacter rodentium (C. rodentium). The establishment of intestinal infection was assessed by histology and inflammatory cytokine expression levels measured by quantitative PCR. To test whether Laz changes the intestinal environment to influence the susceptibility, intestinal pH, microbiota, metabolites and immune cell distributions were evaluated via pH measurement, 16S rRNA gene sequencing, metabolome, and flow cytometry analyses after Laz administration.

RESULTS

Colitis was induced with less C. rodentium in Laz-treated mice as compared with the controls. We found that increased numbers of C. rodentium could reach the cecum following Laz administration. Laz increased pH in the stomach but not in the intestines. It induced dysbiosis and changed the metabolite content of the small intestine. However, these changes did not lead to alterations of immune cell distribution.

CONCLUSIONS

Laz raised susceptibility to C. rodentium as increased numbers of the pathogen reach the site of infection. Our results suggest that it was due to increased stomach pH which allowed more peroral enteropathogens to pass the stomach, but not because of changes of intestinal environment.

Sleep Apnea Morbidity: A Consequence of Microbial-Immune Cross-Talk?

OSA has emerged as a highly prevalent public health problem that imposes important mid- and long-term consequences, namely cardiovascular, metabolic, cognitive, and cancer-related alterations. OSA is characterized by increased upper airway resistance, alveolar hypoventilation, and recurrent upper airway obstruction during sleep. Recurrent collapse of the upper airway develops with sleep onset and is associated with both intermittent hypoxemia and sleep fragmentation. The microbiome is a vast and complex polymicrobial ecosystem that coexists with the human organism, and it has been identified as playing significant roles in the development of host immunologic phenotypes. In humans and animal models, changes in gut microbial communities occur with lifestyle behaviors, such as smoking, long-distance travel, dietary preferences, physical exercise, and circadian rhythm disturbances. In parallel, diseases previously attributed in part to lifestyle such as obesity, coronary heart disease, depression, and asthma (also associated with OSA) are now claimed as microbiota related. We therefore posit that altered patterns of sleep and oxygenation, as seen in OSA, will promote specific alterations in gut microbiota that in turn will elicit the immunologic alterations that lead to OSA-induced end-organ morbidities. The present article assesses the potential mechanistic links between OSA-induced changes in gut microbiota and its morbid phenotypes.

The 24th Annual Midwest Microbial Pathogenesis Meeting

The 24th Annual Midwest Microbial Pathogenesis Conference (MMPC) was held at the University of Notre Dame from August 25-27, 2017. The conference provided an opportunity for scientists from the Midwest to discuss new advances in microbial pathogenesis, including how pathogens promote disease, and how they interact with each other, the microbiome and the host. This commentary highlights the MMPC history, the topics presented at the conference and the reports in this issue.