"Western Diet"-Induced Adipose Inflammation Requires a Complex Gut Microbiota

Inflammation-mediated metabolic regulation in adipose tissue

Chronic inflammation of adipose tissue is a prominent characteristic of many metabolic diseases. Lipid metabolism in adipose tissue is consistently dysregulated during inflammation, which is characterized by substantial infiltration by proinflammatory cells and high cytokine concentrations. Adipose tissue inflammation is caused by a variety of endogenous factors, such as mitochondrial dysfunction, reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, cellular senescence, ceramides biosynthesis and mediators of lipopolysaccharides (LPS) signaling. Additionally, the gut microbiota also plays a crucial role in regulating adipose tissue inflammation. Essentially, adipose tissue inflammation arises from an imbalance in adipocyte metabolism and the regulation of immune cells. Specific inflammatory signals, including nuclear factor-κB (NF-κB) signaling, inflammasome signaling and inflammation-mediated autophagy, have been shown to be involved in the metabolic regulation. The pathogenesis of metabolic diseases characterized by chronic inflammation (obesity, insulin resistance, atherosclerosis and nonalcoholic fatty liver disease [NAFLD]) and recent research regarding potential therapeutic targets for these conditions are also discussed in this review.

Reducing gut microbiome-driven adipose tissue inflammation alleviates metabolic syndrome

BACKGROUND

The gut microbiota contributes to macrophage-mediated inflammation in adipose tissue with consumption of an obesogenic diet, thus driving the development of metabolic syndrome. There is a need to identify and develop interventions that abrogate this condition. The hops-derived prenylated flavonoid xanthohumol (XN) and its semi-synthetic derivative tetrahydroxanthohumol (TXN) attenuate high-fat diet-induced obesity, hepatosteatosis, and metabolic syndrome in C57Bl/6J mice. This coincides with a decrease in pro-inflammatory gene expression in the gut and adipose tissue, together with alterations in the gut microbiota and bile acid composition.

RESULTS

In this study, we integrated and interrogated multi-omics data from different organs with fecal 16S rRNA sequences and systemic metabolic phenotypic data using a Transkingdom Network Analysis. By incorporating cell type information from single-cell RNA-seq data, we discovered TXN attenuates macrophage inflammatory processes in adipose tissue. TXN treatment also reduced levels of inflammation-inducing microbes, such as Oscillibacter valericigenes, that lead to adverse metabolic phenotypes. Furthermore, in vitro validation in macrophage cell lines and in vivo mouse supplementation showed addition of O. valericigenes supernatant induced the expression of metabolic macrophage signature genes that are downregulated by TXN in vivo.

CONCLUSIONS

Our findings establish an important mechanism by which TXN mitigates adverse phenotypic outcomes of diet-induced obesity and metabolic syndrome. TXN primarily reduces the abundance of pro-inflammatory gut microbes that can otherwise promote macrophage-associated inflammation in white adipose tissue. Video Abstract.

The Diversity of Gut Microbiota at Weaning Is Altered in Prolactin Receptor-Null Mice

Maternal milk supports offspring development by providing microbiota, macronutrients, micronutrients, immune factors, and hormones. The hormone prolactin (PRL) is an important milk component with protective effects against metabolic diseases. Because maternal milk regulates microbiota composition and adequate microbiota protect against the development of metabolic diseases, we aimed to investigate whether PRL/PRL receptor signaling regulates gut microbiota composition in newborn mice at weaning. 16SrRNA sequencing of feces and bioinformatics analysis was performed to evaluate gut microbiota in PRL receptor-null mice (Prlr-KO) at weaning (postnatal day 21). The normalized colon and cecal weights were higher and lower, respectively, in the Prlr-KO mice relative to the wild-type mice (Prlr-WT). Relative abundances (Simpson Evenness Index), phylogenetic diversity, and bacterial concentrations were lower in the Prlr-KO mice. Eleven bacteria species out of 470 differed between the Prlr-KO and Prlr-WT mice, with two genera (Anaerotruncus and Lachnospiraceae) related to metabolic disease development being the most common in the Prlr-KO mice. A higher metabolism of terpenoids and polyketides was predicted in the Prlr-KO mice compared to the Prlr-WT mice, and these metabolites had antimicrobial properties and were present in microbe-associated pathogenicity. We concluded that the absence of the PRL receptor altered gut microbiota, resulting in lower abundance and richness, which could contribute to metabolic disease development.

Gut Microbiota and Adipose Tissue Microenvironment Interactions in Obesity

Obesity is an increasingly serious global health problem. Some studies have revealed that the gut microbiota and its metabolites make important contributions to the onset of obesity. The gut microbiota is a dynamic ecosystem composed of diverse microbial communities with key regulatory functions in host metabolism and energy balance. Disruption of the gut microbiota can result in obesity, a chronic metabolic condition characterized by the excessive accumulation of adipose tissue. Host tissues (e.g., adipose, intestinal epithelial, and muscle tissues) can modulate the gut microbiota via microenvironmental interactions that involve hormone and cytokine secretion, changes in nutrient availability, and modifications of the gut environment. The interactions between host tissues and the gut microbiota are complex and bidirectional, with important effects on host health and obesity. This review provides a comprehensive summary of gut microbiota changes associated with obesity, the functional roles of gut microbiota-derived metabolites, and the importance of the complex interactions between the gut microbiota and target tissues in the pathogenesis of obesity. It places particular emphasis on the roles of adipose tissue microenvironment interactions in the onset of obesity.

Study of dietary‑induced progression of psoriasis‑like mice based on gut macrophage polarization

The aim of the present study was to investigate the influence of stimulating food (SF), a Traditional Chinese Medicine term for a high protein, high fat diet, on psoriasis exacerbation. It was hypothesized that SF disposed psoriasis-like aggravation might be related to inflammatory pathways induction via gut dysbiosis. In the present study, mice were fed either an SF or normal diet for 4 weeks. In the last week, their back hair was removed to establish psoriasis-like dermatitis by imiquimod. After sacrifice, blood samples, alimentary tissues and skin lesions were collected and tested by enzyme-linked immunosorbent assay, western blotting, immunohistochemistry and immunofluorescence. Compared with normal diet groups, body weight and blood glucose of SF diet mice were not increased, but they exhibited higher modified Psoriasis Area and Severity Index scores and corresponding epithelial hyperproliferation. Unexpectedly, skin lesions showed abnormal lower protein expressions of Notch and TLR-2/NF-κB p65 signaling pathway, which was attributable to severe skin damage. No difference was observed in the structure and inflammatory cell infiltration of the gut between groups. Instead, macrophage polarization (M1/M2) in the gut of the SF diet group marked by high expression of CD11b (a marker of macrophage, M1) and mild low expression of MRC1 (a marker of macrophage, M2), which resulted in increased TNF-α, decreased IL-10, IL-35, and unchanged IL-17 in serum. Furthermore, serum derived from SF diet mice promoted translocation of NF-κB p65 in HaCaT cells, which indirectly suggested a systemic inflammation. These results suggested that mice fed a continuous SF diet for a time could change gut macrophage polarization, which secretes proinflammatory cytokines into blood circulation. Once transported to skin lesions, these cytokines activate psoriasis tissue resident immune cells and present as psoriasis exacerbation.

Gut microbiome modified by bariatric surgery improves insulin sensitivity and correlates with increased brown fat activity and energy expenditure

Alterations in the microbiome correlate with improved metabolism in patients following bariatric surgery. While fecal microbiota transplantation (FMT) from obese patients into germ-free (GF) mice has suggested a significant role of the gut microbiome in metabolic improvements following bariatric surgery, causality remains to be confirmed. Here, we perform paired FMT from the same obese patients (BMI > 40; four patients), pre- and 1 or 6 months post-Roux-en-Y gastric bypass (RYGB) surgery, into Western diet-fed GF mice. Mice colonized by FMT from patients' post-surgery stool exhibit significant changes in microbiota composition and metabolomic profiles and, most importantly, improved insulin sensitivity compared with pre-RYGB FMT mice. Mechanistically, mice harboring the post-RYGB microbiome show increased brown fat mass and activity and exhibit increased energy expenditure. Moreover, improvements in immune homeostasis within the white adipose tissue are also observed. Altogether, these findings point to a direct role for the gut microbiome in mediating improved metabolic health post-RYGB surgery.

Omega-3-Supplemented Fat Diet Drives Immune Metabolic Response in Visceral Adipose Tissue by Modulating Gut Microbiota in a Mouse Model of Obesity

Obesity is a chronic, relapsing, and multifactorial disease characterized by excessive accumulation of adipose tissue (AT), and is associated with inflammation mainly in white adipose tissue (WAT) and an increase in pro-inflammatory M1 macrophages and other immune cells. This milieu favors the secretion of cytokines and adipokines, contributing to AT dysfunction (ATD) and metabolic dysregulation. Numerous articles link specific changes in the gut microbiota (GM) to the development of obesity and its associated disorders, highlighting the role of diet, particularly fatty acid composition, in modulating the taxonomic profile. The aim of this study was to analyze the effect of a medium-fat-content diet (11%) supplemented with omega-3 fatty acids (D2) on the development of obesity, and on the composition of the GM compared with a control diet with a low fat content (4%) (D1) over a 6-month period. The effect of omega-3 supplementation on metabolic parameters and the modulation of the immunological microenvironment in visceral adipose tissue (VAT) was also evaluated. Six-weeks-old mice were adapted for two weeks and then divided into two groups of eight mice each: a control group D1 and the experimental group D2. Their body weight was recorded at 0, 4, 12, and 24 weeks post-differential feeding and stool samples were simultaneously collected to determine the GM composition. Four mice per group were sacrificed on week 24 and their VAT was taken to determine the immune cells phenotypes (M1 or M2 macrophages) and inflammatory biomarkers. Blood samples were used to determine the glucose, total LDL and HDL cholesterol LDL, HDL and total cholesterol, triglycerides, liver enzymes, leptin, and adiponectin. Body weight measurement showed significant differences at 4 (D1 = 32.0 ± 2.0 g vs. D2 = 36.2 ± 4.5 g, p-value = 0.0339), 12 (D1 = 35.7 ± 4.1 g vs. D2 = 45.3 ± 4.9 g, p-value = 0.0009), and 24 weeks (D1 = 37.5 ± 4.7 g vs. D2 = 47.9 ± 4.7, p-value = 0.0009). The effects of diet on the GM composition changed over time: in the first 12 weeks, α and β diversity differed considerably according to diet and weight increase. In contrast, at 24 weeks, the composition, although still different between groups D1 and D2, showed changes compared with previous samples, suggesting the beneficial effects of omega-3 fatty acids in D2. With regard to metabolic analysis, the results did not reveal relevant changes in biomarkers in accordance with AT studies showing an anti-inflammatory environment and conserved structure and function, which is in contrast to reported findings for pathogenic obesity. In conclusion, the results suggest that the constant and sustained administration of omega-3 fatty acids induced specific changes in GM composition, mainly with increases in Lactobacillus and Ligilactobacillus species, which, in turn, modulated the immune metabolic response of AT in this mouse model of obesity.

Proanthocyanidins: Impact on Gut Microbiota and Intestinal Action Mechanisms in the Prevention and Treatment of Metabolic Syndrome

The metabolic syndrome (MS) is a cluster of risk factors, such as central obesity, hyperglycemia, dyslipidemia, and arterial hypertension, which increase the probability of causing premature mortality. The consumption of high-fat diets (HFD) is a major driver of the rising incidence of MS. In fact, the altered interplay between HFD, microbiome, and the intestinal barrier is being considered as a possible origin of MS. Consumption of proanthocyanidins (PAs) has a beneficial effect against the metabolic disturbances in MS. However, there are no conclusive results in the literature about the efficacy of PAs in improving MS. This review allows a comprehensive validation of the diverse effects of the PAs on the intestinal dysfunction in HFD-induced MS, differentiating between preventive and therapeutic actions. Special emphasis is placed on the impact of PAs on the gut microbiota, providing a system to facilitate comparison between the studies. PAs can modulate the microbiome toward a healthy profile and strength barrier integrity. Nevertheless, to date, published clinical trials to verify preclinical findings are scarce. Finally, the preventive consumption of PAs in MS-associated dysbiosis and intestinal dysfunction induced by HFD seems more successful than the treatment strategy.

Why are western diet and western lifestyle pro-inflammatory risk factors of celiac disease?

The prevalence of celiac disease increased in recent years. In addition to the genetic and immunological factors, it appears that environmental determinants are also involved in the pathophysiology of celiac disease. Gastrointestinal infections impact the development of celiac disease. Current research does not directly confirm the protective effect of natural childbirth and breastfeeding on celiac disease. However, it seems that in genetically predisposed children, the amount of gluten introduced into the diet may have an impact on celiac disease development. Also western lifestyle, including western dietary patterns high in fat, sugar, and gliadin, potentially may increase the risk of celiac disease due to changes in intestinal microbiota, intestinal permeability, or mucosal inflammation. Further research is needed to expand the knowledge of the relationship between environmental factors and the development of celiac disease to define evidence-based preventive interventions against the development of celiac disease. The manuscript summarizes current knowledge on factors predisposing to the development of celiac disease including factors associated with the western lifestyle.

Maternal fiber deprivation alters microbiota in offspring, resulting in low-grade inflammation and predisposition to obesity

Diet, especially fiber content, plays an important role in sustaining a healthy gut microbiota, which promotes intestinal and metabolic health. Another major determinant of microbiota composition is the specific microbes that are acquired early in life, especially maternally. Consequently, we hypothesized that alterations in maternal diet during lactation might lastingly impact the microbiota composition and health status of offspring. Accordingly, we observed that feeding lactating dams low-fiber diets resulted in offspring with lasting microbiota dysbiosis, including reduced taxonomic diversity and increased abundance of Proteobacteria species, despite the offspring consuming a fiber-rich diet. Such microbiota dysbiosis was associated with increased encroachment of bacteria into inner mucus layers, low-grade gut inflammation, and a dramatically exacerbated microbiota-dependent increase in adiposity following exposure to an obesogenic diet. Thus, maternal diet is a critical long-lasting determinant of offspring microbiota composition, impacting gut health and proneness to obesity and its associated disorders.

High-fat diet induces intestinal mucosal barrier dysfunction in ulcerative colitis: emerging mechanisms and dietary intervention perspective

The incidence of ulcerative colitis (UC) is increasing worldwide, but its pathogenesis remains largely unclear. The intestinal mucosa is a barrier that maintains the stability of the body's internal environment, and dysfunction of this barrier leads to the occurrence and aggravation of UC. A high-fat diet (HFD) contains more animal fat and low fiber, and accumulating evidence has shown that long-term intake of an HFD is associated with UC. The mechanism linking an HFD with intestinal mucosal barrier disruption is multifactorial, and it typically involves microbiota dysbiosis and altered metabolism of fatty acids, bile acids, and tryptophan. Dysbiosis-induced metabolic changes can enhance intestinal permeability through multiple pathways. These changes modulate the programmed death of intestinal epithelial cells, inhibit the secretion of goblet cells and Paneth cells, and impair intercellular interactions. Gut metabolites can also induce intestinal immune imbalance by stimulating multiple proinflammatory signaling pathways and decreasing the effect of anti-inflammatory immune cells. In this review, we critically analyze the molecular mechanisms by which an HFD disrupts the intestinal mucosal barrier (IMB) and contributes to the development of UC. We also discuss the application and future direction of dietary intervention in the treatment of the IMB and prevention of UC.

Lactiplantibacillus plantarum DSM20174 Attenuates the Progression of Non-Alcoholic Fatty Liver Disease by Modulating Gut Microbiota, Improving Metabolic Risk Factors, and Attenuating Adipose Inflammation

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease, reaching epidemic proportions worldwide. Targeting the gut-adipose tissue-liver axis by modulating the gut microbiota can be a promising therapeutic approach in NAFLD. Lactiplantibacillus plantarum, a potent lactic-acid-producing bacterium, has been shown to attenuate NAFLD. However, to our knowledge, the possible effect of the Lactiplantibacillus plantarum strain DSM20174 (L.p. DSM20174) on the gut-adipose tissue axis, diminishing inflammatory mediators as fuel for NAFLD progression, is still unknown. Using a NAFLD mouse model fed a high-fat, high-fructose (HFHF) diet for 10 weeks, we show that L.p DSM20174 supplementation of HFHF mice prevented weight gain, improved glucose and lipid homeostasis, and reduced white adipose inflammation and NAFLD progression. Furthermore, 16S rRNA gene sequencing of the faecal microbiota suggested that treatment of HFHF-fed mice with L.p DSM20174 changed the diversity and altered specific bacterial taxa at the levels of family, genus, and species in the gut microbiota. In conclusion, the beneficial effects of L.p DSM20174 in preventing fatty liver progression may be related to modulations in the composition and potential function of gut microbiota associated with lower metabolic risk factors and a reduced M1-like/M2-like ratio of macrophages and proinflammatory cytokine expression in white adipose tissue and liver.

Polyunsaturated fatty acids and metabolic health: novel insights

PURPOSE OF REVIEW

This review aims to discuss the potential roles of omega-3 (ω-3) and omega-6 (ω-6) polyunsaturated fatty acids (PUFAs) in the prevention and treatment of metabolic diseases, to provide the latest evidence from epidemiological and clinical studies, and to highlight novel insights into this field.

RECENT FINDINGS

Higher dietary or circulating ω-3 PUFA levels are related to a lower risk of metabolic syndrome. Novel findings in obesity indicate higher proportions of ω-6 and ω-3 PUFAs, a modulated oxylipin profile and an altered transcriptome in subcutaneous white adipose tissue, that seem resistant to the effects of ω-3 PUFAs compared with what occurs in normal weight individuals. ω-3 PUFAs may improve the blood lipid profile and glycemic outcomes in patients with type 2 diabetes mellitus and reduce liver fat in nonalcoholic fatty liver disease (NAFLD); the findings of several recent meta-analyses support these effects. Genetic background affects inter-individual variability in the insulin sensitivity response to ω-3 PUFA supplementation. ω-3 PUFAs have prebiotic effects, altering the gut microbiota.

SUMMARY

Although evidence for health benefits of ω-3 PUFAs is strong, recent findings suggest a more personalized approach to ω-3 PUFA intake for individuals at high risk for metabolic diseases.

Microbiome complexity shapes metabolism

How does the metabolism of mice with a minimal microbial community compare to that of germ-free and conventionally colonized mice? This Primer explores a study in PLOS Biology which uses a novel isolator-housed metabolic cage system to find out.

Microbiota and adipocyte mitochondrial damage in type 2 diabetes are linked by Mmp12+ macrophages

Microbiota contribute to the induction of type 2 diabetes by high-fat/high-sugar (HFHS) diet, but which organs/pathways are impacted by microbiota remain unknown. Using multiorgan network and transkingdom analyses, we found that microbiota-dependent impairment of OXPHOS/mitochondria in white adipose tissue (WAT) plays a primary role in regulating systemic glucose metabolism. The follow-up analysis established that Mmp12+ macrophages link microbiota-dependent inflammation and OXPHOS damage in WAT. Moreover, the molecular signature of Mmp12+ macrophages in WAT was associated with insulin resistance in obese patients. Next, we tested the functional effects of MMP12 and found that Mmp12 genetic deficiency or MMP12 inhibition improved glucose metabolism in conventional, but not in germ-free mice. MMP12 treatment induced insulin resistance in adipocytes. TLR2-ligands present in Oscillibacter valericigenes bacteria, which are expanded by HFHS, induce Mmp12 in WAT macrophages in a MYD88-ATF3-dependent manner. Thus, HFHS induces Mmp12+ macrophages and MMP12, representing a microbiota-dependent bridge between inflammation and mitochondrial damage in WAT and causing insulin resistance.

Human Microbiome and Its Medical Applications

The commensal microbiome is essential for human health and is involved in many processes in the human body, such as the metabolism process and immune system activation. Emerging evidence implies that specific changes in the microbiome participate in the development of various diseases, including diabetes, liver diseases, tumors, and pathogen infections. Thus, intervention on the microbiome is becoming a novel and effective method to treat such diseases. Synthetic biology empowers researchers to create strains with unique and complex functions, making the use of engineered microbes for clinical applications attainable. The aim of this review is to summarize recent advances about the roles of the microbiome in certain diseases and the underlying mechanisms, as well as the use of engineered microbes in the prevention, detection, and treatment of various diseases.

Adipose Tissue Inflammation and Cardiovascular Disease: An Update

PURPOSE OF REVIEW

The obesity epidemic is on the rise, and while it is well known that obesity is associated with an increase in cardiovascular risk factors such as type 2 diabetes mellitus, hypertension, and obstructive sleep apnea, recent data has highlighted that the degree and type of fat distribution may play a bigger role in the pathogenesis of cardiovascular disease (CVD) than body mass index (BMI) alone. We aim to review updated data on adipose tissue inflammation and distribution and CVD.

RECENT FINDINGS

We review the pathophysiology of inflammation secondary to adipose tissue, the association of obesity-related adipokines and CVD, and the differences and significance of brown versus white adipose tissue. We delve into the clinical manifestations of obesity-related inflammation in CVD. We discuss the available data on heterogeneity of adipose tissue-related inflammation with a focus on subcutaneous versus visceral adipose tissue, the differential pathophysiology, and clinical CVD manifestations of adipose tissue across sex, race, and ethnicity. Finally, we present the available data on lifestyle modification, medical, and surgical therapeutics on reduction of obesity-related inflammation. Obesity leads to a state of chronic inflammation which significantly increases the risk for CVD. More research is needed to develop non-invasive VAT quantification indices such as risk calculators which include variables such as sex, age, race, ethnicity, and VAT concentration, along with other well-known CVD risk factors in order to comprehensively determine risk of CVD in obese patients. Finally, pre-clinical biomarkers such as pro-inflammatory adipokines should be validated to estimate risk of CVD in obese patients.

Diet standardization reduces intra-individual microbiome variation

The human gut microbiota is highly heterogenous between individuals and also exhibits considerable day-to-day variation within individuals. We hypothesized that diet contributed to such inter- and/or intra-individual variance. Hence, we investigated the extent to which diet normalization impacted microbiota heterogeneity. We leveraged the control arm of our recently reported controlled-feeding study in which nine healthy individuals consumed a standardized additive-free diet for 10 days. Diet normalization did not impact inter-individual differences but reduced the extent of intra-individual day-to-day variation in fecal microbiota composition. Such decreased heterogeneity reflected individual-specific enrichment and depletion of an array of taxa microbiota members and was paralleled by a trend toward reduced intra-individual variance in fecal LPS and flagellin, which, collectively, reflect microbiota's pro-inflammatory potential. Yet, the microbiota of some subjects did not change significantly over the course of the study, suggesting heterogeneity in microbiota resilience to dietary stress or that baseline diets of some subjects were perhaps similar to our study's standardized diet. Collectively, our results indicate that short-term diet heterogeneity contributes to day-to-day intra-individual microbiota composition variance.

Cross-Talk Between Gut Microbiota and Adipose Tissues in Obesity and Related Metabolic Diseases

The rapid increase of obesity and associated diseases has become a major global health problem. Adipose tissues are critical for whole-body homeostasis. The gut microbiota has been recognized as a significant environmental factor in the maintenance of energy homeostasis and host immunity. A growing body of evidence suggests that the gut microbiota regulates host metabolism through a close cross-talk with adipose tissues. It modulates energy expenditure and alleviates obesity by promoting energy expenditure, but it also produces specific metabolites and structural components that may act as the central factors in the pathogenesis of inflammation, insulin resistance, and obesity. Understanding the relationship between gut microbiota and adipose tissues may provide potential intervention strategies to treat obesity and associated diseases. In this review, we focus on recent advances in the gut microbiota and its actions on adipose tissues and highlight the joint actions of the gut microbiota and adipose tissue with each other in the regulation of energy metabolism.

Role of the Gut Microbiome in Beta Cell and Adipose Tissue Crosstalk: A Review

In the last decades, obesity has reached epidemic proportions worldwide. Obesity is a chronic disease associated with a wide range of comorbidities, including insulin resistance and type 2 diabetes mellitus (T2D), which results in significant burden of disease and major consequences on health care systems. Of note, intricate interactions, including different signaling pathways, are necessary for the establishment and progression of these two closely related conditions. Altered cell-to-cell communication among the different players implicated in this equation leads to the perpetuation of a vicious circle associated with an increased risk for the development of obesity-related complications, such as T2D, which in turn contributes to the development of cardiovascular disease. In this regard, the dialogue between the adipocyte and pancreatic beta cells has been extensively studied, although some connections are yet to be fully elucidated. In this review, we explore the potential pathological mechanisms linking adipocyte dysfunction and pancreatic beta cell impairment/insulin resistance. In addition, we evaluate the role of emerging actors, such as the gut microbiome, in this complex crosstalk.

Formononetin reshapes the gut microbiota, prevents progression of obesity and improves host metabolism

Formononetin (FMNT) is an isoflavone that has been studied for its anti-hyperglycemic and anti-diabetic effects. However, the effect of FMNT on gut dysbiosis and metabolic complications associated with western-style diet consumption has not been reported yet. This study aimed to investigate how FMNT can reshape the gut microbiota at a specific dosage and ameliorate the symptoms of obesity-related metabolic disorders in both genders. Results indicate that FMNT at 60 mg per kg bodyweight dosage can effectively control body weight, hyperglycemia, and insulin resistance, leptin levels and improve HDL to LDL ratio. FMNT treatment suppressed Porphyromonadaceae (Uncultured Alistipes) and augmented maximum genera from families Lachnospiraceae and Clostridiacea, but at species level, formononetin increased Clostridium aldenense, Clostridiaceae unclassified, Eubacterium plexicaum; acetate and butyrate-producing bacteria. Moreover, formononetin regulated the expression of specific liver miRNA involved in obesity and down-regulated mRNA expression levels of pro-inflammatory cytokines IL-6, IL-22 and TNF-α. Additionally, FMNT maintained intestinal membrane integrity by regulating the expression of Muc-2 and occludin. Our findings indicate that FMNT could be a potential prebiotic that can effectively regulate the gut microbiota, improve host metabolism and systemic inflammation, and prevent deleterious effects of a western-style diet by elevating acetate lactate and lactate butyrate producers.

Fructooligosaccharide ameliorates high-fat induced intrauterine inflammation and improves lipid profile in the hamster offspring

Maternal high-fat diet (HFD) often results in intrauterine and feto-placental inflammation, and increases the risks of fetal programming of metabolic diseases. Intake of prebiotic is reported beneficial. However, its effects on HFD during pregnancy and lactation is not known. We evaluated the maternal intake of fructooligosaccharide (FOS) and its impact on placental inflammation, offspring's adiposity, glucose, and lipid metabolism in their later life. Female Golden Syrian hamsters were fed with a control diet (CD, 26.4 % energy from fat) or HFD (60.7% energy from fat) in the presence or absence of FOS from preconception until lactation. All pups were switched over to CD after lactation and continued until the end. Placental inflammation was upregulated in HFD-fed dam, as measured by a high concentration of hsCRP in the serum and amniotic fluid. Neutrophil infiltration was significantly increased in the decidua through the chorionic layer of the placenta. The expression of pro-inflammatory cytokines such as COX2, NFκβ, IL-8, TGFβ mRNA was increased in the chorioamniotic membrane (P <.05). The HFD/CD hamsters had more adiposity, higher triglyceride, and low HDL at 12 months of age compared to CD/CD (P <.05). However, HFD+FOS/CD-fed hamsters prevented adverse effects such as placental inflammation, neutrophil infiltration, glucose, and lipid profiles in the offspring (P <.05). Anti-inflammatory and lipid-lowering effects of FOS may reduce placental inflammation by lowering neutrophil infiltration and decreasing the production of pro-inflammatory cytokines. Intake of FOS during pregnancy may be beneficial in maintaining lipid metabolism and preventing excess adiposity for mother and their offspring.

Does Modern Lifestyle Favor Neuroimmunometabolic Changes? A Path to Obesity

Factors linked to modern lifestyles, such as physical inactivity, Western diet, and poor sleep quality have been identified as key contributors to the positive energy balance (PEB). PEB rises adipose tissue hypertrophy and dysfunction over the years, affecting cells and tissues that are metabolically critical for energy homeostasis regulation, especially skeletal muscle, hypothalamic-pituitary-adrenal axis, and gut microbiota. It is known that the interaction among lifestyle factors and tissue metabolic dysfunction increases low-grade chronic systemic inflammation, leading to insulin resistance and other adverse metabolic disorders. Although immunometabolic mechanisms are widely discussed in obesity, neuroimmunoendocrine pathways have gained notoriety, as a link to neuroinflammation and central nervous system disorders. Hypothalamic inflammation has been associated with food intake dysregulation, which comprises homeostatic and non-homeostatic mechanisms, promoting eating behavior changes related to the obesity prevalence. The purpose of this review is to provide an updated and integrated perspective on the effects of Western diet, sleep debt, and physical exercise on the regulation of energy homeostasis and low-grade chronic systemic inflammation. Subsequently, we discuss the intersection between systemic inflammation and neuroinflammation and how it can contribute to energy imbalance, favoring obesity. Finally, we propose a model of interactions between systemic inflammation and neuroinflammation, providing new insights into preventive and therapeutic targets for obesity.

Gut Microbiota in Adipose Tissue Dysfunction Induced Cardiovascular Disease: Role as a Metabolic Organ

The gut microbiome has emerged as a key regulator of host metabolism. Accumulating evidence has indicated that the gut microbiota is involved in the development of various human diseases. This association relies on the structure and metabolites of the gut microbiota. The gut microbiota metabolizes the diet ingested by the host into a series of metabolites, including short chain fatty acids, secondary bile acids, trimethylamine N-oxide, and branched-chain amino acids, which affects the physiological processes of the host by activating numerous signaling pathways. In this review, we first summarize the various mechanisms through which the gut microbiota influences adipose tissue dysfunction and metabolic processes that subsequently cause cardiovascular diseases, highlighting the complex interactions between gut microbes, their metabolites, and the metabolic activity of the host. Furthermore, we investigated the current status of clinical therapies for adipose tissue dysfunction directed at the gut microbiota. Finally, we discuss the challenges that remain to be addressed before this field of research can be translated to everyday clinical practice.

Effects of dietary protein on gut development, microbial compositions and mucin expressions in mice

AIMS

Dietary protein, as an important macronutrient, widely participates in host growth and metabolism. In this study, effects of different protein levels (14, 20 and 26%) on the gut development, microbial compositions and mucin expressions were studied in C57BL/6 mice.

METHODS AND RESULTS

The results showed that body weight and the relative weight of stomach and gut were decreased in low-protein diet-fed mice, whereas high-protein diet significantly reduced the villus length and area of jejunum. Goblet cells number in the jejunum was reduced in the low-protein group, which was reversed by dietary a high-protein diet. In addition, high-protein diet notably reduced microbial diversity and changed the microbial compositions at the phylum level, such as Bacteroides, Proteobacteria, Actinomycetes and Deferribacteres. Furthermore, high-protein diet significantly increased mucin2, mucin3 and mucin4 expressions in the jejunum, but downregulated mucin1, mucin2, mucin4 and TFF3 in the ileum, indicating a tissue-dependent manner.

CONCLUSIONS

Together, high-protein diet may impair gut development, microbial balance and mucin system, and a low-protein diet is suggested to promote a healthy lifestyle.

SIGNIFICANCE AND IMPACT OF STUDY

Mucin influenced gut development (villus index and goblet cell number) through remodelling gut microbes, as low and high protein levels resulted in contrary expression levels of mucin in jejunum and ileum.

Colonization with Altered Schaedler Flora Impacts Leukocyte Adhesion in Mesenteric Ischemia-Reperfusion Injury

The microbiota impacts mesenteric ischemia-reperfusion injury, aggravating the interaction of leukocytes with endothelial cells in mesenteric venules. The role of defined gut microbiomes in this life-threatening pathology is unknown. To investigate how a defined model microbiome affects the adhesion of leukocytes in mesenteric ischemia-reperfusion, we took advantage of gnotobiotic isolator technology and transferred altered Schaedler flora (ASF) from C3H/HeNTac to germ-free C57BL/6J mice. We were able to detect all eight bacterial taxa of ASF in fecal samples of colonized C57BL/6J mice by PCR. Applying qRT-PCR for quantification of species-specific 16S rDNA sequences of ASF bacteria, we found a major shift in the abundance of ASF 500, which was greater in C57BL/6J mice relative to the C3H/HeNTac founder breeding pair. Using high-speed epifluorescence intravital microscopy to visualize the venules of the small bowel mesentery, we found that gnotobiotic ASF-colonized mice showed reduced leukocyte adherence, both pre- and post-ischemia. Relative to germ-free mice, the counts of adhering leukocytes were increased pre-ischemia but did not significantly increase in ASF-colonized mice in the post-ischemic state. Collectively, our results suggest a protective role of the minimal microbial consortium ASF in mesenteric ischemia-reperfusion injury.

Upregulation of Anti-Oxidative Stress Response Improves Metabolic Changes in L-Selectin-Deficient Mice but Does Not Prevent NAFLD Progression or Fecal Microbiota Shifts

(1) Background: Non-alcoholic fatty liver disease (NAFLD) is a growing global health problem. NAFLD progression involves a complex interplay of imbalanced inflammatory cell populations and inflammatory signals such as reactive oxygen species and cytokines. These signals can derive from the liver itself but also from adipose tissue or be mediated via changes in the gut microbiome. We analyzed the effects of a simultaneous migration blockade caused by L-selectin-deficiency and an enhancement of the anti-oxidative stress response triggered by hepatocytic Kelch-like ECH-associated protein 1 (Keap1) deletion on NAFLD progression. (2) Methods: L-selectin-deficient mice (Lsel^−/−Keap1^flx/flx) and littermates with selective hepatic Keap1 deletion (Lsel^−/−Keap1^Δhepa) were compared in a 24-week Western-style diet (WD) model. (3) Results: Lsel^−/−Keap1^Δhepa mice exhibited increased expression of erythroid 2-related factor 2 (Nrf2) target genes in the liver, decreased body weight, reduced epidydimal white adipose tissue with decreased immune cell frequencies, and improved glucose response when compared to their Lsel^−/−Keap1^flx/flx littermates. Although WD feeding caused drastic changes in fecal microbiota profiles with decreased microbial diversity, no genotype-dependent shifts were observed. (4) Conclusions: Upregulation of the anti-oxidative stress response improves metabolic changes in L-selectin-deficient mice but does not prevent NAFLD progression and shifts in the gut microbiota.

Ethanol: striking the cardiovascular system by harming the gut microbiota

Ethanol consumption represents a significant public health problem, and excessive ethanol intake is a risk factor for cardiovascular disease (CVD), one of the leading causes of death and disability worldwide. The mechanisms underlying the effects of ethanol on the cardiovascular system are complex and not fully comprehended. The gut microbiota and their metabolites are indispensable symbionts essential for health and homeostasis and therefore, have emerged as potential contributors to ethanol-induced cardiovascular system dysfunction. By mechanisms that are not completely understood, the gut microbiota modulates the immune system and activates several signaling pathways that stimulate inflammatory responses, which in turn, contribute to the development and progression of CVD. This review summarizes preclinical and clinical evidence on the effects of ethanol in the gut microbiota and discusses the mechanisms by which ethanol-induced gut dysbiosis leads to the activation of the immune system and cardiovascular dysfunction. The cross talk between ethanol consumption and the gut microbiota and its implications are detailed. In summary, an imbalance in the symbiotic relationship between the host and the commensal microbiota in a holobiont, as seen with ethanol consumption, may contribute to CVD. Therefore, manipulating the gut microbiota, by using antibiotics, probiotics, prebiotics, and fecal microbiota transplantation might prove a valuable opportunity to prevent/mitigate the deleterious effects of ethanol and improve cardiovascular health and risk prevention.

MyD88 determines the protective effects of fish oil and perilla oil against metabolic disorders and inflammation in adipose tissue from mice fed a high-fat diet

BACKGROUND

The beneficial effects of ω-3 polyunsaturated fatty acids (PUFA) vary between different sources. However, there is a paucity of comparative studies regarding the effects and mechanisms of marine and plant ω-3 PUFA on obesity.

OBJECTIVE

The aim of this study was to evaluate the effects of fish oil (FO) and perilla oil (PO) on glucolipid metabolism, inflammation, and adipokine in mice fed a high-fat (HF) diet in association with the contribution of toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88) pathway.

METHODS

C57BL/6J mice and MyD88-/- mice were randomly divided into 4 groups: normal chow diet, HF diet, HF diet accompanied by daily gavage with either FO or PO. After 4 weeks, blood biochemistries, adipocyte histology, mRNA, and protein expression of MyD88-dependent and -independent pathways of TLR4 signaling in epididymal adipose tissue were measured.

RESULTS

In C57BL/6J mice, there were no statistical differences between FO and PO in decreasing body weight, glucose, insulin, triglyceride, total cholesterol, interleukin-6, and increasing adipocyte counts. FO and PO decreased mRNA and protein expression of TLR4, MyD88, tumor necrosis factor receptor-associated factor 6, inhibitor of nuclear factor kappa B kinase beta and nuclear factor-kappa B p65. In MyD88-/- mice, the beneficial effects of FO and PO on HF diet-induced metabolism abnormalities and inflammation were abolished. FO and PO had no impacts on mRNA and protein expression of receptor-interacting protein-1, interferon regulate factor 3, and nuclear factor-kappa B p65.

CONCLUSION

FO and PO exhibit similar protective effects on metabolic disorders and inflammation through inhibiting TLR4 signaling in a manner dependent on MyD88. These findings highlight plant ω-3 PUFA as an attractive alternative source of marine ω-3 PUFA and reveal a mechanistic insight for preventive benefits of ω-3 PUFA in obesity and related metabolic diseases.

Pediatric nonalcoholic fatty liver disease and the microbiome: Mechanisms contributing to pathogenesis and progression

Nonalcoholic fatty liver disease (NAFLD) is the most common form of pediatric liver disease in the United States, and often associated with obesity and metabolic syndrome. NAFLD comprises a broad spectrum of liver diseases, from hepatic steatosis to steatohepatitis, fibrosis and cirrhosis. Disease progression is considered a multi-modal process of liver injury. The intestinal microbiome has been implicated in several aspects of NAFLD pathophysiology. Pediatric studies associating the intestinal microbiome with NAFLD have been limited in number and complicated by inconsistencies in study design and approach. Nevertheless, they provide support for involvement of the intestinal microbiome in NAFLD development and progression and point to common mechanisms shared by microbiome-associated inflammatory diseases with potential to inform future therapeutic intervention.

Inulin Fermentable Fiber Ameliorates Type I Diabetes via IL22 and Short-Chain Fatty Acids in Experimental Models

BACKGROUND & AIMS

Nourishment of gut microbiota via consumption of fermentable fiber promotes gut health and guards against metabolic syndrome. In contrast, how dietary fiber impacts type 1 diabetes is less clear.

METHODS

To examine impact of dietary fibers on development of type 1 diabetes in the streptozotocin (STZ)-induced and spontaneous non-obese diabetes (NOD) models, mice were fed grain-based chow (GBC) or compositionally defined diets enriched with a fermentable fiber (inulin) or an insoluble fiber (cellulose). Spontaneous (NOD mice) or STZ-induced (wild-type mice) diabetes was monitored.

RESULTS

Relative to GBC, low-fiber diets exacerbated STZ-induced diabetes, whereas diets enriched with inulin, but not cellulose, strongly protected against or treated it. Inulin's restoration of glycemic control prevented loss of adipose depots, while reducing food and water consumption. Inulin normalized pancreatic function and markedly enhanced insulin sensitivity. Such amelioration of diabetes was associated with alterations in gut microbiota composition and was eliminated by antibiotic administration. Pharmacologic blockade of fermentation reduced inulin's beneficial impact on glycemic control, indicating a role for short-chain fatty acids (SCFA). Furthermore, inulin's microbiota-dependent anti-diabetic effect associated with SCFA-independent restoration of interleukin 22, which was necessary and sufficient to ameliorate STZ-induced diabetes. Inulin-enriched diets significantly delayed diabetes in NOD mice.

CONCLUSIONS

Fermentable fiber confers microbiota-dependent increases in SCFA and interleukin 22 that, together, may have potential to prevent and/or treat type 1 diabetes.

Plasmodium chabaudi Infection Alters Intestinal Morphology and Mucosal Innate Immunity in Moderately Malnourished Mice

Plasmodium falciparum is a protozoan parasite which causes malarial disease in humans. Infections commonly occur in sub-Saharan Africa, a region with high rates of inadequate nutrient consumption resulting in malnutrition. The complex relationship between malaria and malnutrition and their effects on gut immunity and physiology are poorly understood. Here, we investigated the effect of malaria infection in the guts of moderately malnourished mice. We utilized a well-established low protein diet that is deficient in zinc and iron to induce moderate malnutrition and investigated mucosal tissue phenotype, permeability, and innate immune response in the gut. We observed that the infected moderately malnourished mice had lower parasite burden at the peak of infection, but damaged mucosal epithelial cells and high levels of FITC-Dextran concentration in the blood serum, indicating increased intestinal permeability. The small intestine in the moderately malnourished mice were also shorter after infection with malaria. This was accompanied with lower numbers of CD11b⁺ macrophages, CD11b⁺CD11c⁺ myeloid cells, and CD11c⁺ dendritic cells in large intestine. Despite the lower number of innate immune cells, macrophages in the moderately malnourished mice were highly activated as determined by MHCII expression and increased IFNγ production in the small intestine. Thus, our data suggest that malaria infection may exacerbate some of the abnormalities in the gut induced by moderate malnutrition.

Microbiota, a New Playground for the Omega-3 Polyunsaturated Fatty Acids in Cardiovascular Diseases

Several cardioprotective mechanisms attributed to Omega-3 polyunsaturated fatty acids (PUFAs) have been studied and widely documented. However, in recent years, studies have supported the concept that the intestinal microbiota can play a much larger role than we had anticipated. Microbiota could contribute to several pathologies, including cardiovascular diseases. Indeed, an imbalance in the microbiota has often been reported in patients with cardiovascular disease and produces low-level inflammation. This inflammation contributes to, more or less, long-term development of cardiovascular diseases. It can also worsen the symptoms and the consequences of these pathologies. According to some studies, omega-3 PUFAs in the diet could restore this imbalance and mitigate its harmful effects on cardiovascular diseases. Many mechanisms are involved and included: (1) a reduction of bacteria producing trimethylamine (TMA); (2) an increase in bacteria producing butyrate, which has anti-inflammatory properties; and (3) a decrease in the production of pro-inflammatory cytokines. Additionally, omega-3 PUFAs would help maintain better integrity in the intestinal barrier, thereby preventing the translocation of intestinal contents into circulation. This review will summarize the effects of omega-3 PUFAs on gut micro-biota and the potential impact on cardiac health.

Pinto beans modulate the gut microbiome, augment MHC II protein, and antimicrobial peptide gene expression in mice fed a normal or western-style diet

The onset of type 2 diabetes in obesity is associated with gut dysbiosis and a failure to confine commensal bacteria and toxins to the gut lumen while prebiotics may prevent these effects. This study evaluated the effects of pinto beans (PB) supplementation on cecal bacteria, short-chain fatty acids (SCFAs), distal ileal antigen presentation marker (major histocompatibility complex [MHC] II) and antimicrobial peptide genes during short-term high-fat, high sucrose (HFS) feeding. Six-week-old, male C57BL/6J mice were randomly assigned to four groups (n=12/group), and fed a control (C) or HFS diet with or without cooked PB (10%, wt/wt) for 30 days. Supplemental PB in both the C and HFS diets decreased the abundance of Tenericutes and the sulfate-reducing bacteria Bilophila. In contrast, PB raised the abundance of taxa within the SCFAs-producing family, Lachnospiraceae, compared to groups without PB. Consequently, fecal butyric acid was significantly higher in PB-supplemented groups compared to C and HFS groups. PB reversed the HFS-induced ablation of the distal ileal STAT3 phosphorylation, and up-regulated antimicrobial peptide genes (Reg3γ and Reg3β). Furthermore, the expression of MHC II protein was elevated in the PB supplemented groups compared to C and HFS. Tenericutes and Bilophilia negatively correlated with activated STAT3 and MHC II proteins. Finally, supplemental PB improved fasting blood glucose, glucose tolerance and suppressed TNFα and inducible nitric oxide synthase mRNA in the visceral adipose tissue. Put together, the beneficial impact of PB supplementation on the gut may be central to its potential to protect against diet-induced inflammation and impaired glucose tolerance.

Amelioration of metabolic syndrome by metformin associates with reduced indices of low-grade inflammation independently of the gut microbiota

Metformin beneficially impacts several aspects of metabolic syndrome including dysglycemia, obesity, and liver dysfunction, thus making it a widely used frontline treatment for early-stage type 2 diabetes, which is associated with these disorders. Several mechanisms of action for metformin have been proposed, including that it acts as an anti-inflammatory agent, possibly as a result of its impact on intestinal microbiota. In accord with this possibility, we observed herein that, in mice with diet-induced metabolic syndrome, metformin impacts the gut microbiota by preventing its encroachment upon the host, a feature of metabolic syndrome in mice and humans. However, the ability of metformin to beneficially impact metabolic syndrome in mice was not markedly altered by reduction or elimination of gut microbiota, achieved by the use of antibiotics or germfree mice. Although reducing or eliminating microbiota by itself suppressed diet-induced dysglycemia, other features of metabolic syndrome including obesity, hepatic steatosis, and low-grade inflammation remained suppressed by metformin in the presence or absence of gut microbiota. These results support a role for anti-inflammatory activity of metformin, irrespective of gut microbiota, in driving some of the beneficial impacts of this drug on metabolic syndrome.