Adipose Tissue Inflammation In Mice Research Articles

Digested protein from chia seed (Salvia hispanica L) prevents obesity and associated inflammation of adipose tissue in mice fed a high-fat diet

Background and aimOverweight and obesity are associated with the development of several health complications, such as diabetes, cancer, and cardiovascular disease. Chia seed is a rich source of proteins and peptides with potential anti-inflammatory and antioxidant effects. This study aimed to evaluate the effects of digested proteins (DP) from chia seed to prevent adipogenesis and adipose tissue inflammation in mice fed a high-fat diet. Methods and resultsC57Bl/6 black mice were fed a high-fat diet plus DP (400 mg/kg of body/day) for 9 weeks. DP from chia seed reduced levels of plasma total cholesterol (−17.5%), LDL (−42.8%), triacylglycerides (−12.3%), % body fat (−26.98%), and waist circumference (−5.5%) in obese mice (p < 0.05). Furthermore, treatment with DP reduced (p < 0.05) adipocytes area, foci of inflammation, levels of p-NF-κB p65, PPARγ, mRNA SREBP1 (sterol regulatory element-binding transcription), and TNF-α. DP also increased mRNA adiponectin on adipose tissue in animals DP-treated, compared with no-DP-treated animals. However, mRNA LPL and HDL levels were not changed (p > 0.05). The peptides from DP had in silico high interaction with metalloproteinase-2. ConclusionsWhen using this experimental model, DP from chia seed had an anti-inflammatory and anti-adipogenic effect. These results suggest the effectiveness of digested proteins from chia seed against central obesity and its associated inflammation.

Adipocyte-specific deletion of Depdc5 exacerbates insulin resistance and adipose tissue inflammation in mice

The mammalian target of rapamycin complex 1 (mTORC1) is a crucial regulator of adipogenesis and systemic energy metabolism. Its dysregulation leads to a diversity of metabolic diseases, including obesity and type 2 diabetes. DEP-domain containing 5 (DEPDC5) is a critical component of GATOR1 complex that functions as a key inhibitor of mTORC1. So far, its function in adipose tissue remains largely unknown. Herein we evaluated how persistent mTORC1 activation in adipocyte via Depdc5 knockout modulates adiposity in vivo. Our data indicated that adipocyte-specific knockout of Depdc5 in aged mice led to reduced visceral fat, aggravated insulin resistance and enhanced adipose tissue inflammation. Moreover, we found that Depdc5 ablation resulted in upregulation of adipose triglyceride lipase (ATGL) in adipocytes and elevated levels of serum free fatty acids (FFAs). Intriguingly, rapamycin treatment did not reverse insulin resistance but alleviated adipose tissue inflammation caused by Depdc5 deletion. Taken together, our findings revealed that mTORC1 activation caused by Depdc5 deletion promotes lipolysis process and further exacerbates insulin resistance and adipose tissue inflammation in mice.

Chia Seed (Salvia hispanica L.) Digested Total Protein Prevented Adipose Tissue Inflammation and Reduce Obesity Complications in Mice Fed a High-Fat Diet

Abstract Objectives To evaluate the effects of digested total proteins (DTP) from chia seed to prevent adipogenesis and adipose tissue inflammation in mice fed a high-fat diet. Methods C57Bl/6 black mice (n = 44; 8 weeks old) where divided in 4 groups (n = 12 each): negative control (NC; standard diet AIN-93M); positive control (PC; high fat diet- HFD- 60% of lipids); normal diet + DTP (NH; standard diet + 400 mg/kg of body/day of DTP); high-fat diet plus DTP (HFH; HFD + 400 mg/kg of body/day of DTP). After 9 weeks of treatment, the animals were euthanized and the blood and the adipose tissue (total) were collected. Plasma was used to analyze total cholesterol, high-density (HDL) and low-density (LDL) lipoprotein cholesterol, triacylglycerides (TGL), aspartate (AST) and alanine (ALT) aminotransferase levels by colorimetry. Waist circumference was measured by metric tape in the middle portion between the anus and mouth and the quantity of p-p65-NF-κB and PPAR-Y ELISA test. Histomorphometric analysis was determined in adipose tissue staining with hematoxylin/eosin to determined adipocytes area and foci of inflammation by the average of 1000 cells/group. Data were analyzed by ANOVA and post-hoc of Newman-Kews (P &amp;lt; 0.05). The study protocol was approved by the Ethics Committee of the Federal University of Viçosa (Protocol 01/2019). Results DTP from chia seed reduced the plasmatic levels of total cholesterol (−17.5%), LDL (−42.8%), TGL (−12.3%), and waist circumference (−5.5%) in obesity mice DTP-treated (P &amp;lt; 0.05). The treatment with DTP reduced the adipocytes area in HFH group by −15.1% and the foci of inflammation in −78.1% in comparison with PC (P &amp;lt; 0.05). The levels of p-p65-NF-κB in adipose tissue were reduced by DTP in mice fed a HFD in −41.1% (P &amp;lt; 0.05). However, PPAR-γ levels, body fat (%), Lee index, and HDL levels were not changed by DTP (P &amp;gt; 0.05). The levels of AST and ALT were not affected by HFD or DTP (P &amp;gt; 0.05). Conclusions DTP from chia seed had an anti-inflammatory and even an anti-adipogenic effect. These results show the effectiveness of digested proteins from chia seed against obesity and its associated inflammation. Funding Sources CNPq and CAPES (Brazil), and ACES (USA).

SUN-LB101 NRF2 Represses Obesity-Associated Adipose Tissue Inflammation in Mice

Obesity is associated with type 2 diabetes, cardiovascular disease and increased incidence of cancer. Chronic inflammation, mainly emanating from adipose tissue, has been proposed to be one of the links between obesity and these pathologies. Thus, identification of new targets against obesity and especially obesity-induced inflammation is needed urgently. Transcription factor Nrf2 (NF-E2-related-factor-2) plays a central role in cytoprotective responses to oxidative and electrophilic stresses and also exerts anti-inflammatory effects in rodent models of inflammation. However, whether activation of Nrf2 signaling pathway influences obesity-associated inflammation in adipose tissue is not well established. To this end, we generated mice with systemic activation of the Nrf2 pathway (Keap1flox/–), as well as mouse models with tissue-specific Nrf2 pathway activation: adipocyte-specific (Fabp4Cre::Keap1flox/ flox) and myeloid cell-specific (LymCre::Keap1flox/ flox). These mice were exposed to a high-fat diet (HFD) 60% kcal fat regimen for 6-weeks or crossed into the db/db background. Keap1flox/– mice showed a dramatic decrease of the numbers of F4/80-positive macrophages in white adipose tissue (WAT). Interestingly, both Fabp4Cre::Keap1flox/ flox and LymCre::Keap1flox/ flox mice showed suppression of F4/80-positive macrophages in WAT as well, suggesting enhanced Nrf2 signaling in either adipocytes or myeloid cells might contribute to anti-inflammatory effects in WAT under the stress of HFD. Transcript levels of inflammatory markers, especially macrophage F4/80 and Cd68 and the chemokine Ccl2 were decreased in the WAT from Keap1flox/– mice on the standard diet and also in the WAT of Keap1flox/– mice in the db/db background. Pharmacological activation of the Nrf2 pathway by treatment with CDDO-Im also suppressed Ccl2 expression in WAT of HFD fed mice and db/db mice. As CCL2 is a key mediator of macrophage accumulation in adipose tissue, we further studied the potential effect of Nrf2 on the transcriptional regulation of Ccl2 using 3T3-L1 preadipocyte and RAW264.7 macrophage cell lines. Treatment of both lines with the small molecule inducer of Nrf2, diethyl maleate significantly suppressed LPS-induced expression of Ccl2. Analysis using luciferase reporter assay revealed that a Nrf2 binding site in the Ccl2 5’ flanking region from -235 to +85 contributed to gene silencing of Ccl2 by activation of Nrf2. Our findings suggest that the druggable Nrf2 pathway may be an effective target to combat obesity-associated inflammation in adipose tissue and its’ concomitant metabolic disorders. Supported by AMED BINDS JP19am0101001 (MY), 19H05649 (MY), 16KK0195 (AU), NIH R35 CA197222 (TWK), JSPS OT 290125 (YY).

Regular Intake of Pistachio Mitigates the Deleterious Effects of a High Fat-Diet in the Brain of Obese Mice.

Obesity has been associated with neurodegeneration and cognitive dysfunctions. Recent data showed that pistachio consumption is able to prevent and ameliorate dyslipidemia, hepatic steatosis, systemic and adipose tissue inflammation in mice fed a high-fat diet (HFD). The present study investigated the neuroprotective effects of pistachio intake in HFD mice. Three groups of mice were fed a standard diet (STD), HFD, or HFD supplemented with pistachio (HFD-P) for 16 weeks. Metabolic parameters (oxidative stress, apoptosis, and mitochondrial dysfunction) were analyzed by using specific assays and biomarkers. The pistachio diet significantly reduced the serum levels of triglycerides and cholesterol in the HFD model. No difference was observed in the index of insulin resistance between HFD and HFD-P. A higher number of fragmented nuclei were found in HFD cerebral cortex compared to STD and HFD-P. A decrease in reactive oxygen species, singlet oxygen and phosphorylated extracellular signal-regulated kinase, and an increase of superoxide dismutase 2 and heme oxygenase expression were found in the brains of the HFD-P samples compared to HFD. Furthermore, the impaired mitochondrial function found in HFD brain was partially recovered in HFD-P mice. These results suggest that the regular intake of pistachio may be useful in preventing obesity-related neurodegeneration, being able to reduce both metabolic and cellular dysfunctions.

Postbiotics for NOD2 require nonhematopoietic RIPK2 to improve blood glucose and metabolic inflammation in mice.

Defining the host receptors and metabolic consequences of bacterial components can help explain how the microbiome influences metabolic diseases. Bacterial peptidoglycans that activate nucleotide-binding oligomerization domain-containing (NOD)1 worsen glucose control, whereas NOD2 activation improves glycemia. Receptor-interacting serine/threonine-protein kinase 2 (RIPK2) is required for innate immunity instigated by NOD1 and NOD2. The role of RIPK2 in the divergent effects of NOD1 versus NOD2 on blood glucose was unknown. We found that whole body deletion of RIPK2 negated all effects of NOD1 or NOD2 activation on blood glucose during an acute, low level endotoxin challenge in mice. It was known that NOD1 in hematopoietic cells participates in insulin resistance and metabolic inflammation in obese mice. It was unknown if RIPK2 in hematopoietic cells is required for the glucose-lowering and anti-inflammatory effects of NOD2 activation. We hypothesized that RIPK2 in nonhematopoietic cells dictated the glycemic effects of NOD2 activation. We found that whole body deletion of RIPK2 prevented the glucose-lowering effects of repeated NOD2 activation that were evident during a glucose tolerance test (GTT) in high-fat diet (HFD)-fed wild-type (WT) mice. NOD2 activation lowered glucose during a GTT and lowered adipose tissue inflammation in mice with RIPK2 deleted in hematopoietic cells. We conclude that RIPK2 in nonhematopoietic cells mediates the glucose lowering and anti-inflammatory effects of NOD2-activating postbiotics. We propose a model where lipopolysaccharides and NOD1 ligands synergize in hematopoietic cells to promote insulin resistance but NOD2 activation in nonhematopoietic cells promotes RIPK2-dependent immune tolerance and lowering of inflammation and insulin resistance.

α-Mangostin remodels visceral adipose tissue inflammation to ameliorate age-related metabolic disorders in mice.

Low-grade chronic adipose tissue inflammation contributes to the onset and development of aging-related insulin resistance and type 2 diabetes. In the current study, α-mangostin, a xanthone isolated from mangosteen (Garcinia mangostana), was identified to ameliorate lipopolysaccharides-induced acute adipose tissue inflammation in mice, by reducing the expression of pro-inflammatory cytokines and chemokines. In a cohort of young (3 months) and old (18–20 months) mice, α-mangostin mitigated aging-associated adiposity, hyperlipidemia, and insulin resistance. Further study showed that α-mangostin alleviated aging-related adipose tissue inflammation by reducing macrophage content and shifting pro-inflammatory macrophage polarization. Moreover, α-mangostin protected the old mice against liver injury through suppressing the secretion of microRNA-155-5p from macrophages. The above results demonstrated that α-mangostin represents a new scaffold to alleviate adipose tissue inflammation, which might be a novel candidate to treat aging-related metabolic disorders.

Reduced obesity, diabetes, and steatosis upon cinnamon and grape pomace are associated with changes in gut microbiota and markers of gut barrier.

Increasing evidence suggests that polyphenols have a significant potential in the prevention and treatment of risk factors associated with metabolic syndrome. The objective of this study was to assess the metabolic outcomes of two polyphenol-containing extracts from cinnamon bark (CBE) and grape pomace (GPE) on C57BL/6J mice fed a high-fat diet (HFD) for 8 wk. Both CBE and GPE were able to decrease fat mass gain and adipose tissue inflammation in mice fed a HFD without reducing food intake. This was associated with reduced liver steatosis and lower plasma nonesterified fatty acid levels. We also observed a beneficial effect on glucose homeostasis, as evidenced by an improved glucose tolerance and a lower insulin resistance index. These ameliorations of the overall metabolic profile were associated with a significant impact on the microbial composition, which was more profound for the GPE than for the CBE. At the genus level, Peptococcus were decreased in the CBE group. In the GPE-treated group, several key genera that have been previously found to be linked with HFD, metabolic effects, and gut barrier integrity were affected: we observed a decrease of Desulfovibrio, Lactococcus, whereas Allobaculum and Roseburia were increased. In addition, the expression of several antimicrobial peptides and tight junction proteins was increased in response to both CBE and GPE supplementation, indicating an improvement of the gut barrier function. Collectively, these data suggest that CBE and GPE can ameliorate the overall metabolic profile of mice on a high-fat diet, partly by acting on the gut microbiota.

Protein-Tyrosine Phosphatase-1B Mediates Sleep Fragmentation-Induced Insulin Resistance and Visceral Adipose Tissue Inflammation in Mice

Sleep fragmentation (SF) is highly prevalent and has emerged as an important contributing factor to obesity and metabolic syndrome. We hypothesized that SF-induced increases in protein tyrosine phosphatase-1B (PTP-1B) expression and activity underlie increased food intake, inflammation, and leptin and insulin resistance. Wild-type (WT) and ObR-PTP-1b-/- mice (Tg) were exposed to SF and control sleep (SC), and food intake was monitored. WT mice received a PTP-1B inhibitor (RO-7d; Tx) or vehicle (Veh). Upon completion of exposures, systemic insulin and leptin sensitivity tests were performed as well as assessment of visceral white adipose tissue (vWAT) insulin receptor sensitivity and macrophages (ATM) polarity. SF increased food intake in either untreated or Veh-treated WT mice. Leptin-induced hypothalamic STAT3 phosphorylation was decreased, PTP-1B activity was increased, and reduced insulin sensitivity emerged both systemic and in vWAT, with the latter displaying proinflammatory ATM polarity changes. All of the SF-induced effects were abrogated following PTP-1B inhibitor treatment and in Tg mice. SF induces increased food intake, reduced leptin signaling in hypothalamus, systemic insulin resistance, and reduced vWAT insulin sensitivity and inflammation that are mediated by increased PTP-1B activity. Thus, PTP-1B may represent a viable therapeutic target in the context of SF-induced weight gain and metabolic dysfunction.

Faecalibacterium prausnitzii treatment improves hepatic health and reduces adipose tissue inflammation in high-fat fed mice.

Faecalibacterium prausnitzii is considered as one of the most important bacterial indicators of a healthy gut. We studied the effects of oral F. prausnitzii treatment on high-fat fed mice. Compared to the high-fat control mice, F. prausnitzii-treated mice had lower hepatic fat content, aspartate aminotransferase and alanine aminotransferase, and increased fatty acid oxidation and adiponectin signaling in liver. Hepatic lipidomic analyses revealed decreases in several species of triacylglycerols, phospholipids and cholesteryl esters. Adiponectin expression was increased in the visceral adipose tissue, and the subcutaneous and visceral adipose tissues were more insulin sensitive and less inflamed in F. prausnitzii-treated mice. Further, F. prausnitzii treatment increased muscle mass that may be linked to enhanced mitochondrial respiration, modified gut microbiota composition and improved intestinal integrity. Our findings show that F. prausnitzii treatment improves hepatic health, and decreases adipose tissue inflammation in mice and warrant the need for further studies to discover its therapeutic potential.

Inhibition of NET Release Fails to Reduce Adipose Tissue Inflammation in Mice

Obesity-associated diseases such as Type 2 diabetes, liver disease and cardiovascular diseases are profoundly mediated by low-grade chronic inflammation of the adipose tissue. Recently, the importance of neutrophils and neutrophil-derived myeloperoxidase and neutrophil elastase on the induction of insulin resistance has been established. Since neutrophil elastase and myeloperoxidase are critically involved in the release of neutrophil extracellular traps (NETs), we here hypothesized that NETs may be relevant to early adipose tissue inflammation. Thus, we tested the effect of the Peptidyl Arginine Deiminase 4 inhibitor Cl-amidine, a compound preventing histone citrullination and subsequent NET release, in a mouse model of adipose tissue inflammation. C57BL6 mice received a 60% high fat diet for 10 weeks and were treated with either Cl-amidine or vehicle. Flow cytometry of adipose tissue and liver, immunohistological analysis and glucose and insulin tolerance tests were performed to determine the effect of the treatment and diet. Although high fat diet feeding induced insulin resistance no significant effect was observed between the treatment groups. In addition no effect was found in leukocyte infiltration and activation in the adipose tissue and liver. Therefore we concluded that inhibition of neutrophil extracellular trap formation may have no clinical relevance for early obesity-mediated pathogenesis of the adipose tissue and liver.

Berberine Ameliorates Hepatic Steatosis and Suppresses Liver and Adipose Tissue Inflammation in Mice with Diet-induced Obesity.

Increasing evidence demonstrates that berberine (BBR) is beneficial for obesity-associated non-alcoholic fatty liver disease (NAFLD). However, it remains to be elucidated how BBR improves aspects of NAFLD. Here we revealed an AMP-activated protein kinase (AMPK)-independent mechanism for BBR to suppress obesity-associated inflammation and improve hepatic steatosis. In C57BL/6J mice fed a high-fat diet (HFD), treatment with BBR decreased inflammation in both the liver and adipose tissue as indicated by reduction of the phosphorylation state of JNK1 and the mRNA levels of proinflammatory cytokines. BBR treatment also decreased hepatic steatosis, as well as the expression of acetyl-CoA carboxylase and fatty acid synthase. Interestingly, treatment with BBR did not significantly alter the phosphorylation state of AMPK in both the liver and adipose tissue of HFD-fed mice. Consistently, BBR treatment significantly decreased the phosphorylation state of JNK1 in both hepatoma H4IIE cells and mouse primary hepatocytes in both dose-dependent and time-dependent manners, which was independent of AMPK phosphorylation. BBR treatment also caused a decrease in palmitate-induced fat deposition in primary mouse hepatocytes. Taken together, these results suggest that BBR actions on improving aspects of NAFLD are largely attributable to BBR suppression of inflammation, which is independent of AMPK.

Exogenous citrate impairs glucose tolerance and promotes visceral adipose tissue inflammation in mice.

Overweight and obesity have become epidemic worldwide and are linked to sedentary lifestyle and the consumption of processed foods and drinks. Citrate is a metabolite that plays central roles in carbohydrate and lipid metabolism. In addition, citrate is the additive most commonly used by the food industry, and therefore is highly consumed. Extracellular citrate can freely enter the cells via the constitutively expressed plasma membrane citrate transporter. Within the cytosol, citrate is readily metabolised by ATP-citrate lyase into acetyl-CoA - the metabolic precursor of endogenously produced lipids and cholesterol. We therefore hypothesised that the citrate ingested from processed foods and drinks could contribute to increased postprandial fat production and weight gain. To test our hypothesis, we administered citrate to mice through their drinking water with or without sucrose and monitored their weight gain and other metabolic parameters. Our results showed that mice receiving citrate or citrate+sucrose did not show increased weight gain or an increase in the weight of the liver, skeletal muscles or adipose tissues (AT). Moreover, the plasma lipid profiles (TAG, total cholesterol, LDL and HDL) were similar across all groups. However, the group receiving citrate+sucrose showed augmented fasting glycaemia, glucose intolerance and the expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-10) in their AT. Therefore, our results suggest that citrate consumption contributes to increased AT inflammation and altered glucose metabolism, which is indicative of initial insulin resistance. Thus, citrate consumption could be a previously unknown causative agent for the complications associated with obesity.

Catalpol ameliorates high-fat diet-induced insulin resistance and adipose tissue inflammation by suppressing the JNK and NF-κB pathways

Catalpol, a bioactive component from the root of Rehmannia glutinosa, has been shown to possess hypoglycemic effects in type 2 diabetic animal models, however, the underlying mechanisms remain poorly understood. Here we investigated the effect of catalpol on high-fat diet (HFD)-induced insulin resistance and adipose tissue inflammation in mice. Oral administration of catalpol at 100 mg/kg for 4 weeks had no effect on body weight of HFD-induced obese mice, but it significantly improved fasting glucose and insulin levels, glucose tolerance and insulin tolerance. Moreover, macrophage infiltration into adipose tissue was markedly reduced by catalpol. Intriguingly, catalpol also significantly reduced mRNA expressions of M1 pro-inflammatory cytokines, but increased M2 anti-inflammatory gene expressions in adipose tissue. Concurrently, catalpol significantly suppressed the c-Jun NH2-terminal kinase (JNK) and nuclear factor-kappa B (NF-κB) signaling pathways in adipose tissue. Collectively, these results suggest that catalpol may ameliorate HFD-induced insulin resistance in mice by attenuating adipose tissue inflammation and suppressing the JNK and NF-κB pathways, and thus provide important new insights into the underlying mechanisms of the antidiabetic effect of catalpol.

Arginase inhibition ameliorates adipose tissue inflammation in mice with diet-induced obesity

This study examined whether oral administration of an arginase inhibitor regulates adipose tissue macrophage infiltration and inflammation in mice with high fat diet (HFD)-induced obesity. Male C57BL/6 mice (n = 30) were randomly assigned to control (CTL, n = 10), HFD only (n = 10), and HFD with arginase inhibitor Nω-hydroxy-nor-l-arginine (HFD with nor-NOHA, n = 10) groups. Plasma and mRNA levels of cytokines in epididymal adipose tissues (EAT), macrophage infiltration into EAT, and macrophage phenotype polarization were measured in the animals after 12 weeks. Additionally, the effects of nor-NOHA on adipose tissue macrophage infiltration and mRNA expression of cytokines were measured in co-cultured 3T3-L1 adipocytes and RAW 264.7 macrophages. Macrophage infiltration into the adipocytes was significantly suppressed by nor-NOHA treatment in adipocyte/macrophage co-culture system and mice with HFD-induced obesity. Pro-inflammatory cytokines, including monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6), were significantly downregulated, and the anti-inflammatory cytokine IL-10 was significantly upregulated in nor-NOHA-treated co-cultured cells. In the mice with HFD-induced obesity, plasma and mRNA levels of MCP-1 significantly reduced after supplementation with nor-NOHA. In addition, oral supplement of nor-NOHA modified M1/M2 phenotype ratio in the EAT. Oral supplementation of an arginase inhibitor, nor-NOHA, altered M1/M2 macrophage phenotype and macrophage infiltration into HFD-induced obese adipose tissue, thereby improved adipose tissue inflammatory response. These results may indicate that arginase inhibition ameliorates obesity-induced adipose tissue inflammation.

Abstract 485: CD44 Deficiency Protects Against Diet-Induced Obesity and Reduces Adipose Tissue Inflammation in Mice

Natural genetic variation between C57BL/6J AND C3H/HeJ affects susceptibility to atherosclerosis and its related risk factors. Recent studies from our laboratory identified a genetic network of co-expressed genes regulating these traits and our mechanistic studies in macrophages identified CD44 as a critical mediator of the network. We found that perturbation of CD44 dramatically affects the network and has possible pleotropic effects on metabolism. CD44 is associated with altered immune function in mice and has been reported to affect atherosclerosis and diabetes, but the underlying mechanism is unclear. Our current hypothesis that CD44 is a critical mediator of a genetic network altering systemic inflammation associated with metabolic syndrome. Thus, we measured the effects of CD44 deficiency in mice challenged with a high fat diet. Male mice (either C57BL6 wild-type or CD44-/-) were fed a diet high in fat, cholesterol, and sucrose for 7 weeks. While there was no significant difference in final body weight, fat mass accumulation was reduced 30% in CD44-/- mice, relative to wild-type mice. Reduced fat mass could not be attributed to reduced food intake or an increase in energy expenditure as measured by indirect calorimetry. However, we observed altered adipose associated inflammation in epidydimal adipose tissue. We found that expression of macrophage markers F4/80, CD11b, and CD14 were decreased 40-60% and inflammation marker TNF-alpha was reduced 40% in CD44-/- mice, relative to wild-type mice. In conclusion, we demonstrate that mice deficient in CD44 exhibit improved metabolic parameters and adiposity, and this may be related to altered adipose tissue inflammation. We are currently extending these studies to include CD44-/- on a C3H/HeJ genetic background to determine if natural variation in macrophage phenotype modulates CD44’s role in adipose tissue associated inflammation.

Oral administration of the milk casein-derived tripeptide Val-Pro-Pro attenuates high-fat diet-induced adipose tissue inflammation in mice.

Inflammation of adipose tissue triggers the metabolic syndrome, atherosclerosis and CHD. In the present study, we investigated whether the milk casein-derived tripeptide valine-proline-proline (VPP) has an anti-inflammatory effect on the adipose tissue of high-fat diet (HFD)-fed mice. Male C57BL/6J mice (7 weeks of age) were fed ad libitum with either a HFD and plain tap water (HFD group) or a HFD and water containing 0·3 mg VPP/ml (HFD+VPP group) for 10 weeks. The results showed that the expression level of CD18 in the peripheral blood monocytes of the HFD+VPP group was significantly decreased compared with the level observed in those of the HFD group. Activated monocytes and pro-inflammatory macrophages were accumulated in the stromal vascular fractions of the adipose tissue from HFD-fed mice, which were significantly decreased in those supplemented with VPP. The formation of crown-like structures rich in pro-inflammatory macrophages was also significantly reduced in the adipose tissue of mice administered with VPP. Real-time PCR analysis revealed that the expression of monocyte chemoattractant protein-1 and that of the pro-inflammatory cytokine IL-6 in adipose tissue tend to be lower in the HFD+VPP group than in the HFD group. These observations indicate that oral administration of VPP exerts an anti-inflammatory effect on the adipose tissue of HFD-fed mice, which may eventually lead to the primary prevention of chronic inflammation-related diseases.

Dietary trimethylamine N-oxide exacerbates impaired glucose tolerance in mice fed a high fat diet

Trimethylamine N-oxide (TMAO) is an oxidation product of trimethylamine (TMA) and is present in many aquatic foods. Here, we investigated the effects of TMAO on glucose tolerance in high fat diet (HFD)-fed mice. Male C57BL/6 mice were randomly assigned to the control, high fat (HF), and TMAO groups. The HF group was fed a diet containing 25% fat, and the TMAO group was fed the HFD plus 0.2% TMAO for 4 weeks. After 3 weeks of feeding, oral glucose tolerance tests were performed. Dietary TMAO increased fasting insulin levels and homeostasis model assessment-estimated insulin resistance (HOMA-IR) and exacerbated the impaired glucose tolerance in HFD-fed mice. These effects were associated with the expression of genes related to the insulin signal pathway, glycogen synthesis, gluconeogenesis and glucose transport in liver. mRNA levels of the pro-inflammatory cytokine MCP-1 increased significantly and of the anti-inflammatory cytokine IL-10 greatly decreased in adipose tissue. Our results suggest that dietary TMAO exacerbates impaired glucose tolerance, obstructs the hepatic insulin signaling pathway, and causes adipose tissue inflammation in mice fed a high fat diet.

Coinhibitory Suppression of T Cell Activation by CD40 Protects Against Obesity and Adipose Tissue Inflammation in Mice

Costimulatory cascades such as the CD40L-CD40 dyad enhance immune cell activation and inflammation during atherosclerosis. Here, we tested the hypothesis that CD40 directly modulates traits of the metabolic syndrome in diet-induced obesity in mice. To induce the metabolic syndrome, wild-type or CD40(-/-) mice consumed a high-fat diet for 20 weeks. Unexpectedly, CD40(-/-) mice exhibited increased weight gain, impaired insulin secretion, augmented accumulation of inflammatory cells in adipose tissue, and enhanced proinflammatory gene expression. This proinflammatory and adverse metabolic phenotype could be transplanted into wild-type mice by reconstitution with CD40-deficient lymphocytes, indicating a major role for CD40 in T or B cells in this context. Conversely, therapeutic activation of CD40 signaling by the stimulating antibody FGK45 abolished further weight gain during the study, lowered glucose levels, improved insulin sensitivity, and suppressed adipose tissue inflammation. Mechanistically, CD40 activation decreased the expression of proinflammatory cytokines in T cells but not in B cells or macrophages. Finally, repopulation of lymphocyte-free Rag1(-/-) mice with CD40(-/-) T cells provoked dysmetabolism and inflammation, corroborating a protective role of CD40 on T cells in the metabolic syndrome. Finally, levels of soluble CD40 showed a positive association with obesity in humans, suggesting clinical relevance of our findings. We present the surprising finding that CD40 deficiency on T cells aggravates whereas activation of CD40 signaling improves adipose tissue inflammation and its metabolic complications. Therefore, positive modulation of the CD40 pathway might describe a novel therapeutic concept against cardiometabolic disease.

The Inhibitory Effect of Quercetin on Adipose Tissue Inflammation in Mice Fed on a High-fat Diet

The Inhibitory Effect of Quercetin on Adipose Tissue Inflammation in Mice Fed on a High-fat Diet