Toll-like receptor signaling and serum levels of interferon β and lipopolysaccharide binding protein are related to abdominal obesity: a case-control study between metabolically healthy and metabolically unhealthy obese individuals

Interferon Family Cytokines in Obesity and Insulin Sensitivity

Obesity and its associated complications are global public health concerns. Metabolic disturbances and immune dysregulation cause adipose tissue stress and dysfunction in obese individuals. Immune cell accumulation in the adipose microenvironment is the main cause of insulin resistance and metabolic dysfunction. Infiltrated immune cells, adipocytes, and stromal cells are all involved in the production of proinflammatory cytokines and chemokines in adipose tissues and affect systemic homeostasis. Interferons (IFNs) are a large family of pleiotropic cytokines that play a pivotal role in host antiviral defenses. IFNs are critical immune modulators in response to pathogens, dead cells, and several inflammation-mediated diseases. Several studies have indicated that IFNs are involved in the pathogenesis of obesity. In this review, we discuss the roles of IFN family cytokines in the development of obesity-induced inflammation and insulin resistance.

Anti-inflammatory mechanisms of polyphenols in adipose tissue: role of gut microbiota, intestinal barrier integrity and zinc homeostasis

Obesity is associated with an imbalance of micro-and macro-nutrients, gut dysbiosis, and a "leaky" gut phenomenon. Polyphenols, such as curcumin, resveratrol, and anthocyanins may alleviate the systemic effects of obesity, potentially by improving gut microbiota, intestinal barrier integrity (IBI), and zinc homeostasis. The essential micronutrient zinc plays a crucial role in the regulation of enzymatic processes, including inflammation, maintenance of the microbial ecology, and intestinal barrier integrity. In this review, we focus on IBI- which prevents intestinal lipopolysaccharide (LPS) leakage - as a critical player in polyphenol-mediated protective effects against obesity-associated white adipose tissue (WAT) inflammation. This occurs through mechanisms that block the movement of the bacterial endotoxin LPS across the gut barrier. Available research suggests that polyphenols reduce WAT and systemic inflammation via crosstalk with inflammatory NF-κB, the mammalian target of rapamycin (mTOR) signaling and zinc homeostasis.

Curcumin Reduces Adipose Tissue Inflammation and Alters Gut Microbiota in Diet-Induced Obese Male Mice

SCOPE

Obesity prevalence continues to increase and contribute to metabolic diseases, potentially by driving systemic inflammation. Curcumin is an anti-inflammatory spice with claimed health benefits. However, mechanisms by which curcumin may reduce obesity-associated inflammation are poorly understood; thus, it is hypothesized that benefits of curcumin consumption may occur through reduced white adipose tissue (WAT) inflammation and/or beneficial changes in gut bacteria.

METHODS AND RESULTS

Male B6 mice are fed high-fat diets (HFD, 45% kcal fat) or HFD supplemented with 0.4% (w/w) curcumin (HFC) for 14 weeks. Curcumin supplementation significantly reduces adiposity and total macrophage infiltration in WAT, compared to HFD group, consistent with reduced mRNA levels of M1 (Cd80, Cd38, Cd11c) and M2 (Arginase-1) macrophage markers. Moreover, curcumin supplementation reduces expression of other key pro-inflammatory genes, such as NF-κB p65 subunit (p65), Stat1, Tlr4, and Il6, in WAT (p < 0.05). Using microbial 16S RNA sequencing, it is demonstrated that the relative abundance of the Lactococcus, Parasutterella, and Turicibacter genera are increased in the HFC group versus HFD.

CONCLUSIONS

Curcumin exerts protective metabolic effects in dietary obesity, in part through downregulation of adipose tissue inflammation, which may be mediated by alterations in composition of gut microbiota, and metabolism of curcumin into curcumin-O-glucuronide.

Synbiotic Intervention with an Adlay-Based Prebiotic and Probiotics Improved Diet-Induced Metabolic Disturbance in Mice by Modulation of the Gut Microbiota

Metabolic syndrome and its associated conditions, such as obesity and type 2 diabetes mellitus (T2DM), are a major public health issue in modern societies. Dietary interventions, including microbiota-directed foods which effectively modulate the gut microbiome, may influence the regulation of obesity and associated comorbidities. Although research on probiotics and prebiotics has been conducted extensively in recent years, diets with the use of synbiotics remain relatively unexplored. Here, we investigated the effects of a novel synbiotic intervention, consisting of an adlay seed extrusion cooked (ASEC)-based prebiotic and probiotic (Lactobacillus paracasei and Bacillus coagulans) on metabolic disorders and microbial dysbiosis in high-fat diet (HFD)-induced obese mice. The ASEC-based synbiotic intervention helped improve HFD-induced body weight gain, hyperlipidemia, impaired glucose tolerance, insulin resistance, and inflammation of the adipose and liver tissues. In addition, data from fecal metagenomics indicated that the ASEC-based synbiotic intervention fostered reconstitution of gut bacterial diversity and composition in HFD-induced obese mice. In particular, the ASEC-based synbiotic intervention increased the relative abundance of families Ruminococcaceae and Muribaculaceae and order Bacteroidales and reduced that of families Lactobacillaceae, Erysipelotrichaceae, and Streptococcaceae in HFD-induced obese mice. Collectively, our results suggest that delayed dietary intervention with the novel ASEC-based synbiotic ameliorates HFD-induced obesity, metabolic disorders, and dysbiosis.

Obesity, metabolic health and omics: Current status and future directions

The growing obesity epidemic is becoming a major public health concern, and the associated costs represent a considerable burden on societies. Among the most common complications of severe obesity are the development of hypertension, dyslipidemia, type 2 diabetes, cardiovascular disease, and various types of cancer. Interestingly, some obese individuals have a favorable metabolic profile and appear to be somehow protected from the detrimental effects of excessive adipose tissue accumulation. These individuals remain normoglycemic, insulin sensitive, and hypotensive with proper blood lipid levels, despite their high body mass index and/or waist circumference. Multiple independent observations have led to the concept of the metabolically healthy obese (MHO) phenotype, yet no consensus has been reached to date regarding a universal definition or the main mechanism behind this phenomenon. Recent technological advances and the use of high-throughput analysis techniques have revolutionized different areas of biomedical research. A multi-omics approach, which is used to investigate changes at different molecular levels in an organism or tissue, may provide valuable insights into the interplay between the molecules or pathways and the roles of different factors involved in the mechanisms underlying metabolic health deterioration. The aim of this review is to present the current status regarding the use of omics technologies to investigate the MHO phenotype, as well as the results of targeted analyses conducted in MHO individuals.

Postprandial Endotoxin Transporters LBP and sCD14 Differ in Obese vs. Overweight and Normal Weight Men during Fat-Rich Meal Digestion

Circulating levels of lipopolysaccharide-binding protein (LBP) and soluble cluster of differentiation 14 (sCD14) are recognized as clinical markers of endotoxemia. In obese men, postprandial endotoxemia is modulated by the amount of fat ingested, being higher compared to normal-weight (NW) subjects. Relative variations of LBP/sCD14 ratio in response to overfeeding are also considered important in the inflammation set-up, as measured through IL-6 concentration. We tested the hypothesis that postprandial LBP and sCD14 circulating concentrations differed in obese vs. overweight and NW men after a fat-rich meal. We thus analyzed the postprandial kinetics of LBP and sCD14 in the context of two clinical trials involving postprandial tests in normal-, over-weight and obese men. In the first clinical trial eight NW and 8 obese men ingested breakfasts containing 10 vs. 40 g of fat. In the second clinical trial, 18 healthy men were overfed during 8 weeks. sCD14, LBP and Il-6 were measured in all subjects during 5 h after test meal. Obese men presented a higher fasting and postprandial LBP concentration in plasma than NW men regardless of fat load, while postprandial sCD14 was similar in both groups. Irrespective of the overfeeding treatment, we observed postprandial increase of sCD14 and decrease of LBP before and after OF. In obese individuals receiving a 10 g fat load, whereas IL-6 increased 5h after meal, LBP and sCD14 did not increase. No direct association between the postprandial kinetics of endotoxemia markers sCD14 and LBP and of inflammation in obese men was observed in this study.

The Exercise Training Modulatory Effects on the Obesity-Induced Immunometabolic Dysfunctions

Reduced physical activity rate in people's lifestyle is a global concern associated with the prevalence of health disorders such as obesity and metabolic disturbance. Ample evidence has indicated a critical role of the immune system in the aggravation of obesity. The type, duration, and production of adipose tissue-released mediators may change subsequent inactive lifestyle-induced obesity, leading to the chronic systematic inflammation and monocyte/macrophage (MON/MФ) phenotype polarization. Preliminary adipose tissue expansion can be inhibited by changing the lifestyle. In this context, exercise training is widely recommended due to a definite improvement of energy balance and the potential impacts on the inflammatory signaling cascades. How exercise training affects the immune system has not yet been fully elucidated, because its anti-inflammatory, pro-inflammatory, or even immunosuppressive impacts have been indicated in the literature. A thorough understanding of the mechanisms triggered by exercise can suggest a new approach to combat meta-inflammation-induced metabolic diseases. In this review, we summarized the obesity-induced inflammatory pathways, the roles of MON/MФ polarization in adipose tissue and systemic inflammation, and the underlying inflammatory mechanisms triggered by exercise during obesity.

Lipopolysaccharide and inflammatory cytokines levels decreased after sleeve gastrectomy in Chinese adults with obesity

Obesity is linked to a low-grade systemic inflammation and lipopolysaccharide (LPS) is a key factor. Sleeve gastrectomy (SG) can significantly cause weight loss, but few reports have looked into the changes of LPS and inflammatory cytokines after surgery. To explore the potential short-term impact of SG on LPS and inflammatory cytokines and their relationship to early metabolic changes in obesity. 30 Chinese adults with obesity (BMI 39.37 ± 8.22 kg/m², 25 female) receiving SG were included in this study. Fasting blood samples were collected at baseline and 30 days after SG. Serum LPS markedly reduced from 336.50 (73.54, 500) pg/mL to 5.00 (5.00, 5.24) pg/mL at 1 month after SG (p < 0.05). There was a significant decrease in plasma IL-6, IL-8, and serum CRP after SG (all p < 0.05). Insulin resistance improved remarkably after surgery as displayed by reductions in fasting insulin level (FINS, p < 0.001), and HOMA-IR (p < 0.001). In addition, visceral fat area (VFA) decreased from 209.70 ± 39.96 cm² to 193.28 ± 43.68 cm² after SG (p < 0.001). LPS was positively correlated with FINS (r = 0.391, p = 0.033) and HOMA-IR (r = 0.38, p = 0.038) before SG. Meanwhile, VFA was positively associated with CRP (r = 0.388, p = 0.034) before surgery. When assessing 30-days postoperative changes, a positive correlation was found between the variations of LPS, IL-8 and the reduction of VFA. After multivariate analyses, only the reduced IL-8 level was independently associated with the reduction of VFA (p = 0.015). In conclusion, SG can significantly relieve the inflammation in obesity in the short term and LPS might be an earlier predictor of inflammatory changes after surgery.

Anti-Toll-like receptor 2 antibody inhibits nuclear factor kappa B activation and attenuates cardiac damage in high-fat-feeding rats

Long-time consumption of high-fat food is a direct cause of cardiovascular diseases, and high-fat-related inflammation plays an important role in it. Toll-like receptors (TLRs), especially TLR2 and TLR4, play important roles in high-fat-related inflammation. However, the impact of TLR2 on high-fat-associated cardiovascular complications is still unknown. In this study, we try to investigate the relationship between TLR2 and high-fat-related cardiac injury. SD rats were allocated to either a control group which were fed with normal diet or a high-fat group which were fed with high-fat diet for 5 months. At the last month, rats fed with high-fat diet were intraperitoneally injected with control normal mouse IgG or anti-TLR2 antibody. Heart tissues were collected for further analysis. RT-qPCR and western blot analysis results revealed that TLR2 expression was increased in the heart tissues from rats fed with high-fat diet and anti-TLR2 antibody had no effect on TLR2 expression. However, anti-TLR2 antibody alleviated masson staining area, levels of TGF-β1 and Collagen I mRNA, and decreased TUNEL-positive myocardial cells and caspase-3 activity, suggesting that anti-TLR2 antibody protected cardiac cells against high-fat-induced cardiac fibrosis and cell apoptosis. By using immunohistochemistry, RT-qPCR and ELISA, we found that anti-TLR2 antibody blocked NF-κB activation, inhibited the expression of inflammatory factors such as TNF-α, IL-1β, IL-6 and IL-18 in the heart tissues from rats fed with high-fat diet. These results hinted that anti-TLR2 antibody might exert its protective effect via inhibition of the TLR2/NF-κB/inflammation pathway. Our findings suggest that anti-TLR2 antibody has a preventive function against high-fat-induced deleterious effects in the heart, and anti-TLR2 antibody may be used as an attractive therapeutic option for high-fat-induced cardiac injury.