Presence Of High-fat Diet Research Articles

PPARα suppresses growth of hepatocellular carcinoma in a high-fat diet context by reducing neutrophil extracellular trap release

Background & AimsThe role of infiltrating neutrophils in hepatocellular carcinoma (HCC) is modulated by cellular metabolism, specifically lipid homeostasis. Throughout the progression of HCC, alterations in lipid metabolism are intricately linked with various signaling that regulate neutrophil function and the release of neutrophil extracellular traps (NETs). However, the dependence of high-fat diet (HFD) on NETs for regulating the development of HCC and the potential interplay between NETs and other leukocytes remains uncertain. MethodsIn this study, the molecular mechanism of NETs release and the potential improvement of the HCC microenvironment by PPARα agonists were explored through proteomics, metabolomics, tissue microarray, immunofluorescence, flow cytometry, Western blot, and dual-luciferase reporter gene assay (n = 6 per group). ResultsOur study demonstrated a notable inhibition of PPARα signaling in HCC. Furthermore, the disruption of PPARα-mediated lipid metabolism was responsible for the release of NETs. The presence of HFD was observed to induce mitochondrial impairment in neutrophils, leading to the activation of cGAS-STING by oxidized mitochondrial DNA (Ox-mtDNA). Consequently, this activation triggered the release of NETs containing Ox-mtDNA through the enhancement of NLRP3-GSDMD-N in a NF-κB-dependent manner. Moreover, the release of NETs within HCC tissues effectively isolated cytotoxic leukocytes in the outer regions of HCC cells. ConclusionsOur study not only enriched the relationship between lipid metabolism disorders and NETs’ tumor-promoting function, but also provided an important strategic reference for multi-target or combined immunotherapy of HCC. Impact and implicationsWe have identified PPARα and its agonists as therapeutic targets for controlling the neutrophil extracellular traps associated with high lipid metabolism. Results from preclinical models suggest that PPARα can limit mitochondrial oxidative stress, inhibit cGAS-STING-NF-κB signaling, and limit the release of neutrophil extracellular traps, thereby increasing the contact of anti-tumor leukocytes and hepatocellular cancer cells, thereby limiting tumor growth.

Impaired IL-27 signaling aggravates macrophage senescence and sensitizes premature ovarian insufficiency induction by high-fat diet

Premature ovarian insufficiency (POI) critically affects female reproductive health, with obesity being a significant and recognized risk factor. Interleukin-27 (IL-27), known for its role in immune modulation and inflammation, has garnered attention in metabolic syndrome research. Nonetheless, the role of these immunometabolic factors on the initiation of POI remains to be unraveled. Our investigation delves into the influence of impaired IL-27 signaling on POI induction, particularly under the challenge of a high-fat diet (HFD). We analyzed patients' serum profiles and established a correlation of increased serum triglycerides with decreased IL-27 levels in POI cases. Experiments on C57BL/6 mice lacking the IL-27 receptor alpha (Il27ra−/−) revealed that when subjected to HFD, these mice developed hallmark POI symptoms. This includes escalated lipid deposition in both liver and ovarian tissues, increased ovarian macrophages cellular aging, and diminished follicle count, all pointing to compromised ovarian function. These findings unveil a novel pathway wherein impaired IL-27 signaling potentiates the onset of POI in the presence of HFD. Understanding the intricate interplay between IL-27, metabolic alterations, and immune dysregulation sheds light on potential therapeutic avenues for managing POI, offering hope for improved reproductive health outcomes.

Metabolic Responses to High-Fat Feeding and Chronic Psychological Stress Combination.

High-fat diet (HFD) consumption and being exposed to daily psychological stress, common environmental factors in modern lifestyle, play an important role on metabolic disorders such as glucose homeostasis impairment. The aim of this study was to investigate the effects of high-fat diet (HFD) and psychological stress combination on metabolic response to chronic psychological stress in male rats. Male Wistar rats were divided into HFD, and normal diet (ND) groups and then into stress and nonstress subgroups. The diets were applied for 5 weeks, and psychological stress was induced for 7 consecutive days. Then, blood samples were taken to measure glucose, insulin, free fatty acids (FFA), and leptin and corticosterone concentrations. Subsequently, glucose-stimulated insulin release from pancreatic isolated islets was assessed. HFD did not significantly change fasting plasma glucose, insulin and corticosterone levels, whereas increased plasma leptin (7.05 ± 0.33) and FFA (p < 0.01) levels and impaired glucose tolerance. Additionally, HFD and stress combination induced more profound glucose intolerance associated with increased plasma corticosterone (p < 0.01) and leptin (8.63 ± 0.38) levels. However, insulin secretion from isolated islets did not change in the presence of high-fat diet and/or stress. HFD should be considered as an intensified factor of metabolic impairments caused by chronic psychological stress.

Resveratrol relieves HFD-induced insulin resistance in skeletal muscle tissue through antioxidant capacity enhancement and the Nrf2-Keap1 signaling pathway.

Resveratrol has received much attention due to its beneficial effects including antioxidant activity. The purpose of this study was to investigate the therapeutic effects of resveratrol treatment on oxidative stress and insulin resistance in the skeletal muscle of high-fat diet (HFD)-fed animals. A total of 30 six-week-old C57BL/6J mice were randomly allocated to three groups (10 animals in each group): The control group in which mice were fed a normal chow diet (NCD); the HFD group in which mice were fed an HFD for 26 weeks; and the HFD-resveratrol group in which HFD was replaced by a resveratrol supplemented-HFD (400mg/kg diet) after 10 weeks of HFD feeding. At the end of this period, gastrocnemius muscle samples were examined to determine insulin resistance and the oxidative status in the presence of HFD and resveratrol. Resveratrol supplementation in HFD-fed mice reduced body and adipose tissue weight, improved insulin sensitivity, and decreased oxidative stress as indicated by lower malonaldehyde (MDA) levels and higher total antioxidant capacity. The supplement also increased the expression and activity of antioxidative enzymes in gastrocnemius muscle and modulated Nrf2 and Keap1 expression levels. These results suggest that resveratrol is effective in improving the antioxidant defense system of the skeletal muscle in HFD-fed mice, indicating its therapeutic potential to combat diseases associated with insulin resistance and oxidative stress.

Chronic exposure to parabens promotes non-alcoholic fatty liver disease in association with the changes of the gut microbiota and lipid metabolism.

Non-alcoholic fatty liver disease (NAFLD) has become a serious public health issue due to changing dietary patterns and composition. However, the relationship between NAFLD occurrence and food additives, such as preservatives, remains unknown. This study aimed to evaluate the toxicity of parabens, namely methylparaben (MeP) and ethylparaben (EtP), in relation to NAFLD occurrence in mice under different dietary conditions. Exposure to MeP and EtP exacerbated high-fat diet (HFD)-induced obesity, glucose intolerance, higher serum lipid concentrations, and fat accumulation by upregulating genes involved in lipid metabolism. Untargeted metabolomics revealed that arachidonic acid (AA) metabolism was the top enriched pathway upon MeP and EtP exposure in the presence of HFD. 11,12-Epoxyeicosatrienoic acid (11,12-EET) was the most abundant AA metabolite and was significantly reduced upon exposure to MeP or EtP. Moreover, an integrative analysis of differential fecal taxa at the genus level and serum AA metabolites revealed significant associations. In addition, MeP and EtP enhanced lipid accumulation in AML12 cells and HepG2 cells cultured with oleic acid. 11,12-EET supplementation could significantly alleviate lipid accumulation by suppressing the expression of lipid metabolism-related genes and proteins. The present study suggests that chronic exposure to MeP and EtP promoted NAFLD via gut microbiota-dependent AA metabolism. These results highlight the need for reducing oral exposure to synthetic preservatives to improve metabolic disturbance under HFD conditions.

Nutritive/non-nutritive sweeteners and high fat diet contribute to dysregulation of sweet taste receptors and metabolic derangements in oral, intestinal and central nervous tissues.

Overconsumption of non-nutritive sweeteners is associated with obesity, whereas the underlying mechanisms remain controversial. This study aimed to investigate the effects of long-term consumption of nutritive or non-nutritive sweeteners with or without high fat diet on sweet taste receptor expression in nutrient-sensing tissues and energy regulation dependent on sweet-sensing. 50 Male Sprague-Dawley rats (140-160g) were assigned to 10 groups (n = 5/group). All received fructose at 2.5% or 10%, sucralose at 0.01% or 0.015% or water with a normal chow diet or high fat diet for 12weeks. Food and drink intake were monitored daily. Oral glucose tolerance test and intraperitoneal glucose tolerance test were performed at week 10 and 11 respectively. Serum was obtained for measurement of biochemical parameters. Tongue, duodenum, jejunum, ileum, colon and hypothalamus were rapidly removed to assess gene expression. Long-term consumption of sweeteners impaired glucose tolerance, increased calorie intake and body weight. A significant upregulation of sweet taste receptor expression was observed in all the four intestinal segments in groups fed 0.01% sucralose or 0.015% sucralose, most strikingly in the ileum, accompanied by elevated serum glucagon-like peptide-1 levels and up-regulated expression of sodium-dependent glucose cotransporter 1 and glucose transporter 2. A significant down-regulation in the tongue and hypothalamus was observed in groups fed 10% fructose or 0.015% sucralose, with alterations in hypothalamic appetite signals. The presence of high fat diet differentially modulates sweet taste perception in nutrient-sensing tissues. Long-term consumption of whether nutritive sweeteners or non-nutritive sweeteners combined with high fat diet contribute to dysregulation of sweet taste receptor expression in oral, intestinal and central nervous tissues.

Pyrroloquinoline quinone attenuated benzyl butyl phthalate induced metabolic aberration and a hepatic metabolomic analysis

Benzyl butyl phthalate (BBP) has recently been implicated as an obesogen. Our recent study demonstrated that BBP can exacerbate high fat diet (HFD) induced diabesity in male mice. Here, we explored if pyrroloquinoline quinone (PQQ), a natural antioxidant andphytochemical, can attenuate metabolic aberrations induced by HFD or HFD-BBPcombination. C57Bl/6 male and female mice were fed either a chow diet (CD) or HFD with or without BBP (3 mg/kg body weight/day)and/or PQQ (20 mg/kg/day)for 16 weeks. The mice’s body and tissue weight, fasting blood glucose, glucose and insulin tolerance test, and liver metabolites level weremeasured. In HFD-fed male mice, PQQ significantly attenuated the increased body weight, liver weight, fasting blood glucose, and insulin intolerance under BBP exposure.Even though female mice did show some reversal of metabolic characteristics by PQQ, the response was not similar nor consistent with the male population. Amongthe 14 hepatic metabolites that were significantly altered by HFD compared to CD, only three major metabolites (acetyl-L-carnitine, DL-stachytine, and propionylcarnitine) were decreased. These three were shown to have more reduction under BBP exposure in the presence of HFD whereas with addition of PQQ, these metabolites were restored. Pathway analysis and literature search revealed that these metabolites were negatively associated with obesity and were involved in several pathways including beta-oxidation, oxidative stress, and mitochondrial function. Overall,this finding indicated the potential use of PQQ to restore thewide range of aberrant metabolic effectinduced by an obesogen in the presence of a western diet.

0033 Recurrent Circadian Disruption While Minimizing Sleep Loss in Humans Impairs Glucose Tolerance Only in The Presence of High-Fat Diet

Abstract Introduction Nearly 14% of Americans experience chronic circadian disruption due to shift work, increasing their risk of obesity and cardiometabolic disorders. These disorders are also exacerbated by modern eating habits such as frequent snacking and consumption of high-fat foods. Here we used a forced desynchrony protocol to investigate the effect of 3 weeks of recurrent circadian disruption (RCD) with minimal sleep loss on glucose metabolism in humans on a lower or higher fat diet (LFD and HFD, respectively). Methods Six healthy adults (38-69yrs; 3f) participated in a 37-day inpatient protocol with LFD (25–27% fat) and 15.67-hr fasting duration, or HFD (45–50% fat) and 13-hr fasting duration. The protocol included three weeks of RCD consisting of 28-hr “days” with 11.67-hr sleep opportunities (=10hrs/24hr). Glucose and insulin responses to a standardized breakfast were conducted at baseline, at an aligned circadian phase after 2–3 weeks of exposure to RCD, and after 1 week of recovery. Frequent blood samples were assayed for glucose and insulin; the Area-Under-Curve was calculated from start of breakfast through postprandial minute 180. Results Total Sleep Time was similar in Baseline and RCD in both groups. Participants on the LFD showed no change in glucose AUC during RCD compared to Baseline. Insulin AUC was lower during RCD (p=0.0269) and Recovery (p=0.0443) than Baseline. In contrast, participants on the HFD showed a significant increase in glucose AUC during RCD compared to Baseline (p&amp;lt;0.0001); AUC returned to Baseline during Recovery. There was no significant change in insulin AUC on the HFD. Conclusion RCD (in the absence of sleep loss) led to impaired glucose tolerance when combined with HFD, but not when combined with LFD. These results suggest that LFD may be part of healthy strategies for people experiencing RCD. Support Study supported by P01AG009975 and conducted in the Brigham and Women’s Hospital Center for Clinical Investigation, part of Harvard Clinical and Translational Science Center supported by UL1TR001102. Authors supported by a fellowship from the Finnish Cultural Foundation (KMZ); T32HL007901 and F32HL143893 (RKY); T32HL007901 and F32AG051325 (NV); K24HL105664 (EBK); R01HL118601 (FAJLS).

NLRP3 inflammasome via IL-1β regulates PCSK9 secretion.

Background: Both PCSK9 and NLRP3 inflammasome play important roles in atherogenesis. This study was designed to test the hypothesis that NLRP3 inflammasome via IL-1β induces PCSK9 secretion. The inter-twined relationship between NLRP3 inflammasome, IL-1β and PCSK9 may be relevant in atherogenesis.Methods: We studied NLRP3 inflammasome-mediated PCSK9 secretion in mouse peritoneal macrophages and in a variety of tissues, such as liver, kidney and small intestine. Macrophages were derived from wild-type (WT) and a variety of gene deletion mice to define the mechanistic basis of NLRP3 inflammasome -mediated PCSK9 secretion. Additional studies were performed in high-fat diet fed mice.Results: We observed that NLRP3 and its downstream signals ASC, Caspase-1, IL-18, and IL-1β all participate in PCSK9 secretion. IL-1β seems to be more important than IL-18 in the induction of PCSK9 secretion. Further, there appears to be significant involvement of MAPKs in this process. Lastly, we observed that mice fed high fat diet have high expression of NLRP3 and a greater secretion of PCSK9 than mice fed a standard diet, and this increased secretion of PCSK9 in high fat diet-fed mice was attenuated in IL-1β-/- mice.Conclusions: This study based on extensive in vitro and in vivo data provides evidence that NLRP3 inflammasome via IL-1β plays an important role in determining PCSK9 secretion, particularly in the presence of high-fat diet.

SUN-LB009 Epigenetic Changes in Response to Metabolic Modifiers in Late Life: Exercise, High Fat Diet, and Angiotenin1-7 Effects on Metabolic Health and DNA Methylation in Frail Old Mice

Background: Reduced muscle and bone-mass and quality as well as impaired energy homeostasis are seen in both aging and the metabolic syndrome (MetS). We previously showed that exercise and Angiotensin1-7 (A1-7) ameliorate this burden in young rats, but their effect vis-a-vis aging is unknown. Aims: To assess the effects of exercise under normal and high-fat diet (HFD) with or without A1-7 on bone architecture and muscle quality as well as on musculoskeletal and fat epigenetic signatures in aged mice. Methods: 19-months-old-mice receiving HFD or normal-chow (NC) with or without 3-months exercise (treadmill, 6 days/week, 20 min/day or A1-7 (0.6 mcg/kg/d). Bone was evaluated by microCT. Global quantification of the epigenetic modification 5-methyl-or hydroxyl-methyl cytosine (5mC; 5hmc) by LC-MS/MS in white/brown adipose tissue (WAT; BAT) and Gastrocnemius muscle. Results: Old, sedentary mice were metabolically "starved" with low serum glucose and triglycerides. (A) Neither exercise nor high fat diet elicited sustained changes in body weight in old mice. B) Exercise per se rehabilitated glucose, triglycerides levels and muscle quality (enhanced muscle-fiber sectional area), accompanied by reduction in muscle 5mC and in BAT 5hmc (p<0.05). (C) Combination of exercise with A1-7 improved bone geometry and density in NC mice but not during HFD. Combination of A1-7 and exercise led to a reduction in global 5mC levels both in the gastrocnemius muscle and in WAT (p<0.05), thus suggesting that some of the effects maybe induced by changes in methylation patterns. Conclusions: The beneficial effects of A1-7 and exercise in aging skeletal tissue are operative only in NC but not in the presence of HFD. These beneficial effects are accompanied, and indeed, may be partly mediated by reversal of gene silencing as depicted by lesser DNA methylation in skeletal muscle. Finally, this is the first report that exercise can induce epigenetic changes in BAT, independent of changes in body weight. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Different Impacts of Intermittent Hypoxia and Hypercapnia on Atherosclerotic Formation

Obstructive sleep apnea (OSA) is a common disorder characterized by intermittent hypoxia and hypercapnia (IHC) during sleep and has been considered a risk for atherosclerosis. However, the particular role of intermittent hypoxia (IH), intermittent hypercapnia (IC) or their combination (IHC) in inducing or promoting atherosclerosis remains obscure. To dissect the mechanisms involved, we examined atherosclerotic formation in the Aorta, Aortic arch and Pulmonary artery (PA) in pro‐atherogenesis mouse model apolipoprotein E (ApoE) deficient mice, after IHC, IH, or IC exposure on high fat diet (HFD) as compared to room air (RA) groups either under HFD or regular chow (RC). Our data revealed that all HFD‐treated mice exhibited more atherosclerotic lesions than those fed with RC (e.g. Aorta, RA‐HFD 8.1±0.8% vs RA‐RC 1.0±0.3%, p&lt;0.01). 10‐week IHC treatment expedited atherosclerosis in Aorta, Aortic arch and PA as compared to room air controls in the presence of HFD (Aorta, IHC‐HFD 13.8±1.0% vs RA‐HFD 8.1±0.8%, p&lt;0.01; Aortic arch, IHC‐HFD 28.5±1.9% vs RA‐HFD 16.6±2.0%, p&lt;0.01; PA, IHC‐HFD 28.9±2.8% vs RA‐HFD 12.2±1.5%, p&lt;0.01). Furthermore, IHC‐induced atherosclerosis in Aorta was significantly greater than in IC or IH (Aorta, IHC‐HFD 13.8±1.0% vs either IH‐HFD 7.6±0.4%, p&lt;0.01 or IC‐HFD 11.1±0.7%, p&lt;0.05), indicating that the effect of IHC is the result of potential interactions between IC and IH. Interestingly, in the PA, the largest atherosclerotic formation was observed in IH‐treated mice, followed by IHC then IC (PA, IH‐HFD 40.9±2.0% vs either IHC‐HFD 28.9±2.8%, p&lt;0.01 or IC‐HFD 20.1±2.6%, p&lt;0.01), suggesting that (a) IH has a greater effect on the PA than on the Aorta and (b) IC may alleviate IH‐ or IHC‐induced lesion in the PA. Our findings suggest that (1) IH, IC and IHC affect the development of atherosclerosis differently and (2) distinct vasculatures (Aorta and Pulmonary artery) react to IHC, IH, IC differently in atherogenesis.Support or Funding InformationSupported by the National Institutes of Health grant 5 P01 32573 (G.G.H.)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A role for microglia in regulating feeding behaviour and weight

Previous work, including our own, has shown microglia are highly sensitive to dietary influence, becoming activated acutely and long-term in the presence of high-fat diet or early life overfeeding. Here we investigated if microglia have a direct role in regulating satiety and feeding, using a novel rat model of acute conditional microglial knockout. We have developed transgenic rats with a diphtheria toxin receptor (DTR) incorporated into the promoter region of the CX3CR1, expression on microglia and monocytes. The administration of diphtheria toxin (DT) thus selectively ablates microglia and monocytes, with at least 50% ablation of microglia in the brain by 24 h after DT administration and full restoration of normal microglia after 7–14 days, without affecting microglia in wildtype rats. Global acute ablation of microglia resulted in a dramatic reduction in weight gain in the week following DT that was at least partially accounted for by a short-term reduction in food intake. This weight loss and anorexia were not due to overt sickness since exploratory behaviour and circulating cytokines were not affected. The ability of circulating satiety hormones to signal feeding were also not affected since circulating ghrelin and the responses to exogenous ghrelin were normal. Together these findings suggest microglia are important in supporting normal feeding behaviours and weight but the mechanisms by which they do this remain to be determined.

How high-fat diet and high-intensity interval training affect lipid metabolism in the liver and visceral adipose tissue of rats

Lipogenic and lipolytic pathways are tightly regulated by nuclear receptors and binding proteins, such as farnesoid x receptor (FXR) and sterol regulatory element binding protein 1c (SREBP-1c). We designed this research to study the effects of high-intensity interval training (HIIT) and high-fat diet (HFD) on hepatic and adipose FXR and SREBP-1c gene expression beside the plasma levels of lipid profile and insulin. 24 male Wistar rats were randomly divided into normal (~12% fat) and HFD (~56% fat) groups with or without participating in the 8 weeks HIIT protocol. Results from two-way ANOVA and Pearson tests (P&lt;0.05) showed that the HFD rats experienced a larger weight gain correlated with dyslipidemia and hyperinsulinemia, higher hepatic and adipose SREBP-1c expression and lower hepatic FXR expression compared with normal diet fed rats. Although HIIT rats showed higher hepatic FXR and lower hepatic and adipose SREBP-1c expression and lower weight gain compared with untrained rats, plasma lipid profile levels had not any significant difference between trained and untrained rats. Interestingly, hepatic FXR expression was negatively correlated with weight gain and SREBP-1c expression in both tissues while only the hepatic SREBP-1c was positively correlated to insulin levels. In conclusion, HFD-induced dyslipidemia could occur via the activation of the hepatic SREBP-1c pathway under the insulin effect. Although HIIT rats showed lower SREBP-1c correlated to hepatic FXR activation it seems diet is more effective on lipid profile than HIIT. Also, in presence of HFD, HIIT only affects adipose lipolysis.

The innovative “Bio-Oil Spread” prevents metabolic disorders and mediates preconditioning-like cardioprotection in rats

Background and aimsObesity is often associated with an increased cardiovascular risk. The food industry and the associated research activities focus on formulating products that are a perfect mix between an adequate fat content and health. We evaluated whether a diet enriched with Bio-Oil Spread (SD), an olive oil-based innovative food, is cardioprotective in the presence of high-fat diet (HFD)-dependent obesity. Methods and ResultsRats were fed for 16 weeks with normolipidic diet (ND; fat: 6.2%), HFD (fat: 42%), and ND enriched with SD (6.2% of fat + 35.8% of SD). Metabolic and anthropometric parameters were measured. Heart and liver structures were analyzed by histochemical examination. Ischemic susceptibility was evaluated on isolated and Langendorff-perfused cardiac preparations. Signaling was assessed by Western blotting. Compared to ND rats, HFD rats showed increased body weight and abdominal obesity, dyslipidemia, and impaired glucose tolerance. Morphological analyses showed that HFD is associated with heart and liver modifications (hypertrophy and steatosis, respectively), lesser evident in the SD group, together with metabolic and anthropometric alterations. In particular, IGF-1R immunodetection revealed a reduction of hypertrophy in SD heart sections. Notably, SD diet significantly reduced myocardial susceptibility against ischemia/reperfusion (I/R) with respect to HFD through the activation of survival signals (Akt, ERK1/2, and Bcl2). Systolic and diastolic performance was preserved in the SD group. ConclusionsWe suggest that SD may contribute to the prevention of metabolic disorders and cardiovascular alterations typical of severe obesity induced by an HFD, including the increased ischemic susceptibility of the myocardium. Our results pave the way to evaluate the introduction of SD in human alimentary guidelines as a strategy to reduce saturated fat intake.

Cardiac Peroxisome Proliferator‐activated Receptor‐β Activity is Up‐regulated in the Absence of Muscle RING Finger‐3, and Exaggerates High‐fat Diet‐induced Cardiomyopathy

Diabetic cardiomyopathy is characterized by structural and functional alterations leading to cardiac hypertrophy and heart failure. These changes are regulated in part by PPAR signaling and subsequent changes in fatty acid metabolism. We recently identified that mice lacking ubiquitin ligase Muscle RING Finger‐3 (MuRF3‐/‐) have increased cardiac PPAR‐β activity in vivo. We hypothesized that challenging MuRF3‐/‐ mice with a high‐fat diet, where lipids act as PPAR ligands, would enhance the severity of diabetic cardiomyopathy. MuRF3‐/‐ mice and strain‐matched controls were fed a high‐fat diet. Serum insulin and glucose were measured every two weeks. Total cholesterol and serum triglycerides (TG) were measured at baseline and 26 weeks. Echocardiography was performed every three weeks. MuRF3‐/‐ mice have less blood glucose after 26 weeks on high fat diet (HFD) as compared to strain‐matched controls (168.8±6.2 vs. 240.2±15.5 mg/dL, P&lt;0.05) and increased fasting insulin levels relative to controls (4.7±0.3 vs. 3.4±0.2 ng/ml, P&lt;0.05). Knockout mice do not show differences in fasting total cholesterol or serum TG compared to wild‐type mice at any timepoint. By echocardiography, MuRF3‐/‐ mice have depressed fractional shortening at 6 weeks HFD compared to wild‐type mice (43.6±6.1% vs. 49.2±3.5%, P&lt;0.05). Mice lacking MuRF3 demonstrate exaggerated cardiomyopathy in the presence of high‐fat diet. Increased PPAR‐β activity and fatty acid metabolism are known contributors to diabetic cardiomyopathy. Taken together, these findings corroborate a novel role for MuRF3 in protecting against the development of diabetic cardiomyopathy.

Oligofructose protects against arsenic-induced liver injury in a model of environment/obesity interaction

Arsenic (As) tops the ATSDR list of hazardous environmental chemicals and is known to cause liver injury. Although the concentrations of As found in the US water supply are generally too low to directly damage the liver, subhepatotoxic doses of As sensitize the liver to experimental NAFLD. It is now suspected that GI microbiome dysbiosis plays an important role in development of NALFD. Importantly, arsenic has also been shown to alter the microbiome. The purpose of the current study was to test the hypothesis that the prebiotic oligofructose (OFC) protects against enhanced liver injury caused by As in experimental NAFLD. Male C57Bl6/J mice were fed low fat diet (LFD), high fat diet (HFD), or HFD containing oligofructose (OFC) during concomitant exposure to either tap water or As-containing water (4.9ppm as sodium arsenite) for 10weeks. HFD significantly increased body mass and caused fatty liver injury, as characterized by an increased liver weight-to-body weight ratio, histologic changes and transaminases. As observed previously, As enhanced HFD-induced liver damage, which was characterized by enhanced inflammation. OFC supplementation protected against the enhanced liver damage caused by As in the presence of HFD. Interestingly, arsenic, HFD and OFC all caused unique changes to the gut flora. These data support previous findings that low concentrations of As enhance liver damage caused by high fat diet. Furthermore, these results indicate that these effects of arsenic may be mediated, at least in part, by GI tract dysbiosis and that prebiotic supplementation may confer significant protective effects.

Matrix metalloproteinase 9 opposes diet-induced muscle insulin resistance in mice

Increased extracellular matrix (ECM) collagen is a characteristic of muscle insulin resistance. Matrix metalloproteinase (MMP) 9 is a primary enzyme that degrades collagen IV (ColIV). As a component of the basement membrane, ColIV plays a key role in ECM remodelling. We tested the hypotheses that genetic deletion of MMP9 in mice increases muscle ColIV, induces insulin resistance in lean mice and worsens diet-induced muscle insulin resistance. Wild-type (Mmp9(+/+)) and Mmp9-null (Mmp9(-/-)) mice were chow or high-fat (HF) fed for 16 weeks. Insulin action was measured by the hyperinsulinaemic-euglycaemic clamp in conscious weight-matched surgically catheterised mice. Mmp9(-/-) and HF feeding independently increased muscle ColIV. ColIV in HF-fed Mmp9(-/-) mice was further increased. Mmp9(-/-) did not affect fasting insulin or glucose in chow- or HF-fed mice. The glucose infusion rate (GIR), endogenous glucose appearance (EndoRa) and glucose disappearance (Rd) rates, and a muscle glucose metabolic index (Rg), were the same in chow-fed Mmp9(+/+) and Mmp9(-/-) mice. In contrast, HF-fed Mmp9(-/-) mice had decreased GIR, insulin-stimulated increase in Rd and muscle Rg. Insulin-stimulated suppression of EndoRa, however, remained the same in HF-fed Mmp9(-/-) and Mmp9(+/+) mice. Decreased muscle Rg in HF-fed Mmp9(-/-) was associated with decreased muscle capillaries. Despite increased muscle ColIV, genetic deletion of MMP9 does not induce insulin resistance in lean mice. In contrast, this deletion results in a more profound state of insulin resistance, specifically in the skeletal muscle of HF-fed mice. These results highlight the importance of ECM remodelling in determining muscle insulin resistance in the presence of HF diet.

Quantitative Proteomic and Functional Analysis of Liver Mitochondria from High Fat Diet (HFD) Diabetic Mice

Insulin resistance plays a major role in the development of type 2 diabetes and obesity and affects a number of biological processes such as mitochondrial biogenesis. Though mitochondrial dysfunction has been linked to the development of insulin resistance and pathogenesis of type 2 diabetes, the precise mechanism linking the two is not well understood. We used high fat diet (HFD)-induced obesity dependent diabetes mouse models to gain insight into the potential pathways altered with metabolic disease, and carried out quantitative proteomic analysis of liver mitochondria. As previously reported, proteins involved in fatty acid oxidation, branched chain amino acid degradation, tricarboxylic acid cycle, and oxidative phosphorylation were uniformly up-regulated in the liver of HFD fed mice compared with that of normal diet. Further, our studies revealed that retinol metabolism is distinctly down-regulated and the mitochondrial structural proteins-components of mitochondrial inter-membrane space bridging (MIB) complex (Mitofilin, Sam50, and ChChd3), and Tim proteins-essential for protein import, are significantly up-regulated in HFD fed mice. Structural and functional studies on HFD and normal diet liver mitochondria revealed remodeling of HFD mitochondria to a more condensed form with increased respiratory capacity and higher ATP levels compared with normal diet mitochondria. Thus, it is likely that the structural remodeling is essential to accommodate the increased protein content in presence of HFD: the mechanism could be through the MIB complex promoting contact site and crista junction formation and in turn facilitating the lipid and protein uptake.

Dietary conjugated linoleic acid reshapes high fat diet‐induced microbiota and reduces its immunogenicity

The composition of human gut microbiota has shifted over the last century, leading to increased prevalence of autoimmune diseases, such as inflammatory bowel diseases. Shifts in dietary intake to Westernized high fat high carbohydrate diet has influenced this phenomenon. Restoring gut microbiota to a less immunogenic state by altering diet to alleviate gut inflammation is a focus of our research. We hypothesized that supplementing conjugated linoleic acids (CLA), a group of fatty acids with anti‐inflammatory properties, in the presence of high fat diet would result in reshaping the gut microbiota to a less immunogenic state. Mice were fed 18% anhydrous milk fat (AMF) or 18% safflower oil diet with or without CLA for 3 weeks. Microbial 16s rRNA profiles of cecal contents were analyzed via Sanger‐based sequencing. Using wild type spleen‐derived dendritic cells, cecal lysate immunogenicity index was determined by comparing IL‐12p40/IL‐ 10 ratio after culture. Dietary CLA reshaped the enteric microbiota by increasing Firmicutes/Bacteroidetes ratio compared to AMF alone and resulted in decreased δ‐proteobacteria. Lastly, CLA supplementation significantly reduced immunogenicity of cecal lysate. These data suggest dietary CLA supplementation can restore the gut microbiome in the presence of high fat diet and could have positive clinical implications for IBD patients.Grant Funding Source : 5T32DK007074‐38

IL-17A Is Proatherogenic in High-Fat Diet-Induced and Chlamydia pneumoniae Infection-Accelerated Atherosclerosis in Mice

The role of IL-17 in atherogenesis remains controversial. We previously reported that the TLR/MyD88 signaling pathway plays an important role in high-fat diet as well as Chlamydophila pneumoniae infection-mediated acceleration of atherosclerosis in apolipoprotein E-deficient mice. In this study, we investigated the role of the IL-17A in high-fat diet (HFD)- and C. pneumoniae-induced acceleration of atherosclerosis. The aortic sinus plaque and aortic lesion size and lipid composition as well as macrophage accumulation in the lesions were significantly diminished in IL-17A(-/-) mice fed an HFD compared with wild-type (WT) C57BL/6 control mice. As expected, C. pneumoniae infection led to a significant increase in size and lipid content of the atherosclerotic lesions in WT mice. However, IL-17A(-/-) mice developed significantly less acceleration of lesion size following C. pneumoniae infection compared with WT control despite similar levels of blood cholesterol levels. Furthermore, C. pneumoniae infection in WT but not in IL-17A(-/-) mice was associated with significant increases in serum concentrations of IL-12p40, CCL2, IFN-γ, and numbers of macrophages in their plaques. Additionally, in vitro studies suggest that IL-17A activates vascular endothelial cells, which secrete cytokines that in turn enhance foam cell formation in macrophages. Taken together, our data suggest that IL-17A is proatherogenic and that it plays an important role in both diet-induced atherosclerotic lesion development, and C. pneumoniae infection-mediated acceleration of atherosclerotic lesions in the presence of HFD.