Wild-type High-fat Diet Research Articles

9210 Nephron specific ATP6AP2 knockout reduces renal fat accumulation in mice consuming high fat diet

Abstract Disclosure: S.A. Culver: None. J. Balugo: None. M. Jansen: None. T. Harris: None. H.M. Siragy: None. Diet induced obesity causes increased renal fat accumulation in both humans and mice which contributes to obesity related kidney injury. We have previously shown that mice with nephron specific ATP6AP2 knockout (KO) consuming high fat diet (HFD) are resistant to weight gain due to increased urinary excretion of glucose, albumin, and fatty acids. Magnetic resonance imaging (MRI) is a useful imaging modality for quantifying organ fat content in live animals though there are few reports of its use quantifying fat in murine kidney. We hypothesized that nephron specific ATP6AP2 knockout inhibits renal fat accumulation with HFD and that we would be able to detect this using MRI. Eight-week-old male wild type (WT) or inducible nephron specific ATP6AP2 KO mice underwent either induction with oral doxycycline or received sucrose water as controls before being placed on either normal diet (ND) (12% fat) or HFD (45% fat) for 3 months. Mice were then imaged using a 9.4 Tesla Bruker BioSpin MRI to determine both liver and kidney cortex fat content. The mean weight of WT HFD mice was 36.03 g compared to 29.03 g in WT ND controls. ND fed and HFD fed KO mice weighed 22.74 g and 23.03 g respectively. MRI showed significant 67% (p<0.05) increase in liver fat content in WT HFD compared to WT ND fed controls, confirming the ability of our MRI technique to detect expected differences in organ fat content. In renal cortex, MRI detected a 54% (p<0.05) increase in lipid content for WT HFD mice compared to WT ND controls. Nephron specific ATP6AP2 KO on HFD demonstrated reduced renal cortical lipid content by 36% (p<0.05) compared to WT HFD controls. These results indicate that ATP6AP2 KO is associated with reduced renal fat accumulation that is measurable with in vivo MRI. MRI therefore represents a valuable tool for studying renal sequelae of obesity in live murine models. Future investigation should examine whether ATP6AP2 KO prevents renal lipotoxicity and kidney injury in the setting of obesity. Presentation: 6/3/2024

Investigating the Role of Cannabinoid Type 1 Receptors in Vascular Function and Remodeling in a Hypercholesterolemic Mouse Model with Low-Density Lipoprotein-Cannabinoid Type 1 Receptor Double Knockout Animals.

Hypercholesterolemia forms the background of several cardiovascular pathologies. LDL receptor-knockout (LDLR-KO) mice kept on a high-fat diet (HFD) develop high cholesterol levels and atherosclerosis (AS). Cannabinoid type 1 receptors (CB1Rs) induce vasodilation, although their role in cardiovascular pathologies is still controversial. We aimed to reveal the effects of CB1Rs on vascular function and remodeling in hypercholesterolemic AS-prone LDLR-KO mice. Experiments were performed on a newly established LDLR and CB1R double-knockout (KO) mouse model, in which KO and wild-type (WT) mice were kept on an HFD or a control diet (CD) for 5 months. The vascular functions of abdominal aorta rings were tested with wire myography. The vasorelaxation effects of acetylcholine (Ach, 1 nM-1 µM) were obtained after phenylephrine precontraction, which was repeated with inhibitors of nitric oxide synthase (NOS) and cyclooxygenase (COX), Nω-nitro-L-arginine (LNA), and indomethacin (INDO), respectively. Blood pressure was measured with the tail-cuff method. Immunostaining of endothelial NOS (eNOS) was carried out. An HFD significantly elevated the cholesterol levels in the LDLR-KO mice more than in the corresponding WT mice (mean values: 1039 ± 162 mg/dL vs. 91 ± 18 mg/dL), and they were not influenced by the presence of the CB1R gene. However, with the defect of the CB1R gene, damage to the Ach relaxation ability was moderated. The blood pressure was higher in the LDLR-KO mice compared to their WT counterparts (systolic/diastolic values: 110/84 ± 5.8/6.8 vs. 102/80 ± 3.3/2.5 mmHg), which was significantly elevated with an HFD (118/96 ± 1.9/2 vs. 100/77 ± 3.4/3.1 mmHg, p < 0.05) but attenuated in the CB1R-KO HFD mice. The expression of eNOS was depressed in the HFD WT mice compared to those on the CD, but it was augmented if CB1R was knocked out. This newly established double-knockout mouse model provides a tool for studying the involvement of CB1Rs in the development of hypercholesterolemia and atherosclerosis. Our results indicate that knocking out the CB1R gene significantly attenuates vascular damage in hypercholesterolemic mice.

High-fat diet impact on prostate gland from adiponectin knockout mice: Morphometric, metabolic and inflammatory cytokines analyses

AimsObesity is a global public health issue, and some studies have linked it to an increased risk of prostatic diseases. This study aimed to evaluate the effects of a high-fat diet on metabolic parameters and prostate morphology in wild-type (WT) and adiponectin knockout (KO) mice. Main methodsMale WT and KO mice were fed a control diet (CD) or high-fat diet (HFD) for 6 months. Serum metabolic parameters, inflammatory cytokines in epididymal fat tissue, dorsal prostatic lobe morphometry and histopathology were analyzed. Key findingsCD WT and CD KO mice did not exhibit altered metabolic or prostatic parameters. However, HFD WT mice showed altered glucose and insulin tolerance even without excessive weight gain. On the other hand, HFD KO mice developed obesity, with an increase in low-density lipoprotein (11.8 ± 5.1 vs. 31.4 ± 3.6 mg/dL), high-density lipoprotein (73.4 ± 7.4 vs. 103.4 ± 2.5 mg/dL), and total cholesterol levels (126.2 ± 16.1 vs. 294.6 ± 23.2 mg/dL), a decrease in insulin levels (28.7 ± 12.2 vs. 4.6 ± 2.3 μIU/mL), and glucose and insulin resistance. We also observed that HFD KO animals display an increase in inflammatory cytokines, such as IL6, IL1β, and IL1RA. The dorsal prostate from HFD KO animals also presented significant increases in the mast cells (1.9 ± 0,7 vs. 5,3 ± 1.5 cells/field) and Ki67 index (2.91 ± 0.6 vs. 4.7 ± 0.4 %). SignificanceThe above findings highlight the complex interactions between adiponectin, metabolism, malnutrition, and prostate health. Metabolic deregulation combined with adipose inflammation potentially induces a proliferative and inflammatory microenvironment in the prostate gland under conditions of low adiponectin production, potentially impairing prostate morphophysiology in the context of obesity and aging.

GPX4 Over-expression Is Associated with Increased Senescence Burden and Metabolic Dysfunction

Chronic inflammation is a hallmark of obesity, diabetes, and cardiovascular disease (CVD), contributing to morbidity and mortality worldwide. Adipose tissue inflammation is commonly observed in obesity-related diseases and is considered a critical driver of metabolic dysfunction. Cellular senescence, a state of cell cycle arrest, accumulates in adipose tissues in obesity and contributes to tissue inflammation through the production of pro-inflammatory factors known as the SASP (senescence associated secretory phenotype). Novel therapeutics targeting senescent cells have been shown to improve metabolic function in obesity, although the underlying mechanisms of senescent cell accumulation and clearance are not well known. Here, we compared a genetically modified mouse model that overexpresses glutathione peroxidase 4 (GPX4), with wildtype (WT) littermate mice. GPX4 is an antioxidant, selenoenzyme, and a key regulator of ferroptosis, an iron-dependent form of regulated cell death. Previous in vitro studies have shown that activation of ferroptosis through inhibition of GPX4 is associated with a decrease in senescence burden, suggesting that ferroptosis may serve as a novel senolytic pathway. We hypothesized that overexpression of GPX4 in the transgenic (TG) mice will reduce ferroptosis, increase senescence burden, and impair metabolic function compared to WT mice. To determine the effects of ferroptosis on metabolic function, GPX4 WT and TG mice were fed either a 60% high fat diet (HFD) or normal chow (NC) ad libitum for 8-10 weeks. We found higher body, liver, and white adipose tissue (WAT) mass in GPX4 TG compared to WT mice fed NC and HFD (Interaction all p&lt;0.0003, 0.0001, 0.0044, n=8-10/group). After HFD, T cell infiltration in the WAT was higher in GPX4 TG mice compared to WT (Interaction all p&lt;0.0253), and both CD8 and CD4 were significantly different from NC controls, contributing to metabolic dysfunction in these animals (p=0.027,0.207, n=4/group). Mice fed HFD demonstrated increased glucose intolerance compared to NC controls (p=0.029, p=0.0216, n=8-12/group), however, the TG HFD mice were trending towards higher glucose intolerance compared to WT HFD (p=0.17). Compared to NC and HFD fed WT mice, there was increased gene expression for the senescence markers, p16 (all p&lt;0.0041) and p21(all p&lt;0.002), as well as increased expression of SASP factors, CXCL2 (all p&lt;0.0055), TNFa (all p&lt;0.0159), and PAI1 (all p&lt;0.05, n=5-7/group) in the HFD fed TG mice, indicating increased senescence burden in the TG HFD mice. Malondialdehyde (MDA), a byproduct and marker of ferroptosis, was elevated in the HFD fed WT mice (p=0.0002) compared to all other groups, indicating increased ferroptosis. HFD fed TG mice also had increased expression of ferritin (all p&lt;0.0079, n=5/group) compared to all other groups, suggesting resistance to ferroptosis that may contribute to the increased senescence burden in the TG HFD group. Together these data demonstrate that increases in cellular senescence and impairments in metabolic function after HFD are exacerbated by increased GPX4 expression, suggesting that GPX4 may be a novel target to decrease senescence and improve metabolic function through induction of the ferroptosis pathway. Funded in part by awards from National Institute of Health Awards R01 AG 060395, R01 AG048366, T32 HL139451-05, T32 HL007576, R01 AG077751, Nora Eccles Treadwell Foundation (NEFT), and Veteran's Affairs Merit Review Award I01 BX004492. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

LDLR heterozygous deletion reduces hamster testicular cholesterol toxicity via AMPK/Sirt1/PGC-1α pathway

Cholesterol is an important part of the human diet. The relationship and molecular mechanisms between intracellular cholesterol and male infertility are unclear. The purpose of this study was to evaluate the role of low-density lipoprotein receptor (LDLR) in male infertility. Both wild-type (WT) and LDLR heterozygous deletion (LDLR+/-) male Golden Syrian hamsters were fed either a high-fat diet (HFD) or a normal diet (ND). Plasma biochemistry, serum hormone, testicular histopathology, mRNA and protein expression of AMPK/Sirt1/PGC-1α in both testicular tissue and isolated Leydig cells (LCs) were measured. Compared with the ND animals, the WT HFD hamsters developed dyslipidemia at three weeks with lipid droplets deposited in LCs, testosterone decreased at four weeks (0.440 ± 0.264 ng/ml vs. 2.367 ± 1.236 ng/ml), the number of the Sertoli cells decreased (21.578 ± 2.934/one tubule vs. 25.733 ± 3.424/one tubule), the seminiferous epithelium became thinner (0.0813 ± 0.01729 mm vs. 0.0944 ± 0.0138 mm), testicular atrophy and AMPK/Sirt1/PGC-1α pathway downregulated at five weeks. All these changes persisted until the end of the study. LDLR+/- alleviated all of the above changes by downregulating the cellular influx of cholesterol induced by HFD except for higher hyperlipidemia. In summary, excessive intracellular cholesterol inactivates AMPK/Sirt1/PGC-1α pathway firstly in LCs and then in both Sertoli and spermatids. Cholesterol toxicity was LDLR dependent.

P27Kip1 Deficiency Impairs Brown Adipose Tissue Function Favouring Fat Accumulation in Mice.

The aim of this work was to investigate the effect of the whole-body deletion of p27 on the activity of brown adipose tissue and the susceptibility to develop obesity and glucose homeostasis disturbances in mice, especially when subjected to a high fat diet. p27 knockout (p27-/-) and wild type (WT) mice were fed a normal chow diet or a high fat diet (HFD) for 10-weeks. Body weight and composition were assessed. Insulin and glucose tolerance tests and indirect calorimetry assays were performed. Histological analysis of interscapular BAT (iBAT) was carried out, and expression of key genes/proteins involved in BAT function were characterized by qPCR and Western blot. iBAT activity was estimated by 18F-fluorodeoxyglucose (18FDG) uptake with microPET. p27-/- mice were more prone to develop obesity and insulin resistance, exhibiting increased size of all fat depots. p27-/- mice displayed a higher respiratory exchange ratio. iBAT presented larger adipocytes in p27-/- HFD mice, accompanied by downregulation of both Glut1 and uncoupling protein 1 (UCP1) in parallel with defective insulin signalling. Moreover, p27-/- HFD mice exhibited impaired response to cold exposure, characterized by a reduced iBAT 18FDG uptake and difficulty to maintain body temperature when exposed to cold compared to WT HFD mice, suggesting reduced thermogenic capacity. These data suggest that p27 could play a role in BAT activation and in the susceptibility to develop obesity and insulin resistance.

Down-regulation of hepatic CLOCK by PPARα is involved in inhibition of NAFLD.

This work aimed to investigate the role of nuclear factor peroxisome proliferator-activated receptor α (PPARα) in modification of circadian clock and their relevance to development of nonalcoholic fatty liver disease (NAFLD). Both male wild-type (WT) and Pparα-null (KO) mice treated with high-fat diet (HFD) were used to explore the effect of PPARα and lipid diet on the circadian rhythm. WT, KO, and PPARα-humanized (hPPARα) mice were treated with PPARα agonist fenofibrate to reveal the hPPARα dependence of circadian locomotor output cycles kaput (CLOCK) down-regulation. The mouse model and hepatocyte experiments were designed to verify the action of PPARα in down-regulating CLOCK and lipid accumulation in vivo and in vitro. Strongest NAFLD developed in mice fed 45%HFD, and it was inhibited in WT mice. The activity rhythm of WT mice was found to be different from that of the KO mice on normal diet and HFD. The core circadian factor CLOCK was down-regulated by HFD in both WT and KO mice in the liver, not in the hypothalamus. More interestingly, hepatic CLOCK was down-regulated by basal PPARα and activated PPARα in dose dependence of fenofibrate. Accordingly, CLOCK down-regulation dependent of PPARα activity was involved in inhibition of lipid metabolism in hepatocytes. Down-regulation of hepatic CLOCK by basal PPARα contributes to tolerance against development of NAFLD. Inhibition of CLOCK by activated PPARα is involved in inhibition of NAFLD by PPARα agonists. KEY MESSAGES: •PPARα inhibited NAFLD development induced by HFD. •PPARα mediated modifications of circadian rhythm and the hepatic circadian factor CLOCK in NAFLD models. •Down-regulation of hepatic CLOCK by basal PPARα contributed to tolerance against development of NAFLD. •Inhibition of CLOCK by activated PPARα was involved in therapeutic actions against fatty liver diseases by PPARα agonists.

UCP2 KO mice exhibit ameliorated obesity and inflammation induced by high-fat diet feeding

Uncoupling protein 2 (Ucp2) was first introduced as a member of Uncoupling protein family and a regulator of ROS formation; however, its role in adipose tissue is not fully understood. In the present study, we have investigated the role of Ucp2 against high-fat diet (HFD)-induced obesity in epididymal white adipose tissue (eWAT) and browning of inguinal white adipose tissue (iWAT). Diet-induced obesity is closely related to macrophage infiltration and the secretion of pro-inflammatory cytokines. Macrophages surround adipocytes and form a crown-like-structure (CLS). Some reports have suggested that CLS formation requires adipocyte apoptosis. After 12 weeks of HFD challenge, Ucp2 knockout (KO) mice maintained relatively lean phenotypes compared to wild-type (WT) mice. In eWAT, macrophage infiltration, CLS formation, and inflammatory cytokines were reduced in HFD KO mice compared to HFD WT mice. Surprisingly, we found that apoptotic signals were also reduced in the Ucp2 KO mice. Our study suggests that Ucp2 deficiency may prevent diet-induced obesity by regulating adipocyte apoptosis. However, Ucp2 deficiency did not affect the browning capacity of iWAT. [BMB Reports 2022; 55(10): 500-505].

ApoE isoform-dependent effects of xanthohumol on high fat diet-induced cognitive impairments and hippocampal metabolic pathways.

Consumption of a high fat diet (HFD) is linked to metabolic syndrome and cognitive impairments. This is exacerbated in age-related cognitive decline (ACD) and in individuals with a genetic risk for Alzheimer’s disease (AD). Apolipoprotein E (apoE) is involved in cholesterol metabolism. In humans, there are three major isoforms, E2, E3, and E4. Compared to E3, E4 increases ACD and AD risk and vulnerability to the deleterious cognitive effects of a HFD. The plant compound Xanthohumol (XN) had beneficial effects on cognition and metabolism in C57BL/6J wild-type (WT) male mice put on a HFD at 9 weeks of age for 13 weeks. As the effects of XN in the context of a HFD in older WT, E3, and E4 female and male mice are not known, in the current study male and female WT, E3, and E4 mice were fed a HFD alone or a HFD containing 0.07% XN for 10 or 19 weeks, starting at 6 months of age, prior to the beginning of behavioral and cognitive testing. XN showed sex- and ApoE isoform-dependent effects on cognitive performance. XN-treated E4 and WT, but not E3, mice had higher glucose transporter protein levels in the hippocampus and cortex than HFD-treated mice. E3 and E4 mice had higher glucose transporter protein levels in the hippocampus and lower glucose transporter protein levels in the cortex than WT mice. In the standard experiment, regardless of XN treatment, E4 mice had nearly double as high ceramide and sphingomyelin levels than E3 mice and male mice had higher level of glycosylated ceramide than female mice. When the differential effects of HFD in E3 and E4 males were assessed, the arginine and proline metabolism pathway was affected. In the extended exposure experiment, in E3 males XN treatment affected the arginine and proline metabolism and the glycine, serine, and threonine metabolism. Myristic acid levels were decreased in XN-treated E3 males but not E3 females. These data support the therapeutic potential for XN to ameliorate HFD-induced cognitive impairments and highlight the importance of considering sex and ApoE isoform in determining who might most benefit from this dietary supplement.

Gasdermin D Deficiency Does Not Protect Mice from High-Fat Diet-Induced Glucose Intolerance and Adipose Tissue Inflammation.

The adipose tissue NLRP3 inflammasome has recently emerged as a contributor to obesity-related metabolic inflammation. Recent studies have demonstrated that the activation of the NLRP3 inflammasome cleaves gasdermin D (GSDMD) and induces pyroptosis, a proinflammatory programmed cell death. However, whether GSDMD is involved in the regulation of adipose tissue function and the development of obesity-induced metabolic disease remains unknown. The aim of the present study was to investigate the role of GSDMD in adipose tissue inflammation as well as whole-body metabolism using GSDMD-deficient mice fed a high-fat diet (HFD) for 30 weeks. The effects of GSDMD deficiency on adipose tissue, liver, and isolated macrophages from wild-type (WT) and GSDMD knockout (KO) mice were examined. In addition, 3T3-L1 cells were used to examine the expression of GSDMD during adipogenesis. The results demonstrate that although HFD-induced inflammation was partly ameliorated in isolated macrophages and liver, adipose tissue remained unaffected by GSDMD deficiency. Compared with the WT HFD mice, GSDMD KO HFD mice exhibited a mild increase in HFD-induced glucose intolerance with increased systemic and adipose tissue IL-1β levels. Interestingly, GSDMD deficiency caused accumulation of fat mass when challenged with HFD, partly by suppressing the expression of peroxisome proliferator-activated receptor gamma (PPARγ). The expression of GSDMD mRNA and protein was dramatically suppressed during adipocyte differentiation and was inversely correlated with PPARγ expression. Together, these findings indicate that GSDMD is not a prerequisite for HFD-induced adipose tissue inflammation and suggest a noncanonical function of GSDMD in regulation of fat mass through PPARγ.

Tim-1 Deficiency Aggravates High-Fat Diet-Induced Steatohepatitis in Mice.

Non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) is commonly associated with obesity and characterized by excessive lipid accumulation and liver inflammation. The T cell immunoglobulin and mucin domain 1 (Tim-1), also known as hepatitis A virus cellular receptor 1 (Havcr-1) and kidney injury molecule 1 (Kim-1), has been shown to affect innate immunity-driven proinflammatory cascade in liver ischemia-reperfusion injury. However, its contribution to obesity-related NAFLD/NASH remains unknown. Thus, this study was designed to evaluate the role of Tim-1 in obesity-related liver inflammation and injury in wild-type (WT) and Tim-1-deficient (Tim-1-/-) C57BL/6J mice fed a high-fat diet (HFD) for 5-6 months. HFD feeding induced steatosis and upregulated Tim-1 gene expression in the liver of WT mice. Surprisingly, Tim-1-/- mice on HFD diet exhibited an exacerbation of hepatic steatosis, accompanied with an elevation of protein levels of fatty acid translocase CD36 and sterol regulatory element binding protein 1 (SREBP1). Tim-1 deficiency also enhanced HFD-induced liver inflammation and injury, as evidenced by augmented increase in hepatic expression of pro-inflammatory factor lipocalin 2 and elevated serum alanine transaminase (ALT). In addition, gene expression of type I, III and IV collagens and liver fibrosis were greatly enhanced in HFD Tim-1-/- mice compared with HFD WT mice. HFD-induced hepatic expression of YM-1, a specific mouse M2 macrophage marker, was further upregulated by deletion of Tim-1. Together, these results show that Tim-1 deficiency aggravates the effects of HFD diet on lipid accumulation and liver fibrosis, most likely through enhanced infiltration and activation of inflammatory cells.

Knockout of the Endothelin B receptor in adipocytes improves insulin sensitivity and the metabolic profile of male mice fed a High fat Diet

Endothelin-1 (ET-1) is elevated in patients who are overweight and suffer from obesity; however, its contribution to the pathophysiology related to obesity is not fully understood. Obesity is associated with dyslipidemia and insulin resistance, which may in part be mediated adipocyte hypertrophy and dysfunction leading to a reduction in circulating insulin sensitizing adipokines. Pharmacological blockade of ETB receptors improves insulin sensitivity in mice fed a high fat diet for 8 weeks, which is associated with increased Peroxisome proliferator-activated receptor gamma (pparg) levels in visceral adipose and increased circulating adiponectin, suggesting a role for ETB receptor activation on adipocytes in pathophysiology related to obesity. We hypothesized that elevated ET-1 in obesity promotes insulin resistance by reducing adipose pparg leading to a reduction in the secretion of adipokines, such as adiponectin. To test this hypothesis, adipocyte-specific ETB receptor knockout mice (adETBKO) were generated by crossing adiponectin Cre mice with ETB floxed mice. AdETBKO or wild type (WT) littermates were fed either normal diet (NMD) or high fat diet (HFD) for 8 weeks. WT HFD fed mice had significantly higher body weight and fat mass compared to WT NMD, although there was no difference between WT HFD and adETBKO HFD mice. KEGG pathway analysis of differentially expressed genes determined by RNA-Sequencing of gonadal adipose indicated that compared to WT HFD fed mice, adETBKO HFD mice have an attenuation of over 500 genes enriched within insulin signaling and fatty acid metabolism pathways including adiponectin, insulin receptor substrate 1, Glucose transporter 4, fatty acid synthase, and adipolin. In addition, adETBKO HFD mice had significantly improved glucose tolerance (4510±395 vs 6610±582 AUC, p<0.05)and insulin tolerance (-6867±517 vs -2927±584 AUC, p<0.05)compared to insulin resistant HFD fed mice. Plasma adiponectin was reduced by 2-fold in WT HFD compared to WT NMD mice (6.82±0.253 vs 10.8±0.624 ug/ml, p<0.05), and this was attenuated in adETBKO HFD fed mice (6.82±0.253 vs 9.90±0.352 ug/ml, p<0.05). Plasma insulin and leptin levels were significantly increased in WT HFD mice, an effect that was attenuated in adETBKO HFD mice (1.59±0.276 vs 0.809±0.064 ng/ml insulin, p<0.05, 22.6±1.08 vs 16.4±1.52 ng/ml leptin, p<0.05). Blood chemistry analysis showed that adETBKO HFD mice had significantly improved ALT (15.5±1.26 vs 46.5±6.16 U/L, p<0.05), HDL (98.3±3.68 vs 84.6±1.76 mg/dl, p<0.05), LDL (19.6±0.945 vs 29.2±2.63 mg/dl, p<0.05) and NEFA (0.377±0.035 vs 0.751±0.076 mEq/L, p<0.05) levels compared to WT HFD mice. These data indicate that loss of the ETB receptor in adipocytes improves peripheral glucose homeostasis, dyslipidemia and the metabolic/cholesterol profile in mice fed a HFD. Coupled with the transcriptomic profile of visceral adipose tissue in adETBKO HFD mice, which reflects a more insulin sensitive phenotype, these data suggest a role for the adipocyte ETB receptor in the development of insulin resistance exhibited by overweight and obese individuals.

Overexpression of Growth Differentiation Factor 15 Reduces Blood Pressure and Produces Anti‐neuroinflammatory Effects in Mice with Diet‐induced Obesity

The growth differentiation factor 15 (GDF15) is a stress-responsive cytokine, which belongs to the super family of transforming growth factor beta (TGFb). In the past decade, GDF15 has been implicated in multiple biological processes and diseases, including anti-inflammation, anti-obesity and anti-diabetes effects. However, the role of GDF15 in sympathetic regulation of blood pressure has not been reported in the cardiovascular disease state. The purpose of the study was to investigate the effects of GDF15 on the blood pressure and central nervous system neuroinflammatory responses in diet-induced obese mice. NAG-Tg+ transgenic mice (TG) with overexpression of GDF15 and wild-type (WT) littermates were fed on normal chow or high-fat diet (HFD) for 16 weeks. During the experimental period, arterial pressure was recorded by radiotelemetry in conscious mice. WT mice with HFD had higher mean arterial pressure (MAP) compared with the normal diet fed WT mice (WT HFD 110±4 mmHg verse WT 93±4 mmHg). Compared with WT mice with HFD, GDF15 overexpression significantly reduced MAP (TG HFD: 99±3 mmHg verse WT HFD: 110±4 mmHg) accompanied by the decreased urinary norepinephrine excretion and baseline renal sympathetic nerve activity (TG HFD: 38.9±4.1% max verse WT HFD: 61.2±5.6% max). GDF15 TG mice with HFD had lower expressions of pro-inflammatory cytokines interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-a), interleukin 1β (IL-1β), C1q/TNF-related protein-1 (CTRP1) and reduced immune cell infiltration in the hypothalamus and brain stem tissue. A downregulation in GDF15 receptor (GFRAL) expression was detected in brain stem medullary nuclei in WT HFD mice, which was significantly upregulated in GDF15 TG mice with HFD. These data suggest that GDF15 overexpression exerts a potential protective effect on hypertension in obese mice through attenuating sympathetic outflow. The mechanism for this effect involves anti-inflammatory and neuronal protective properties of GDF15 in the central nervous system.

Lrg1 is a Driver of Brown Adipose Tissue Dysfunction in Obesity

Background Energy is stored as lipid within white adipose tissue (WAT) however, over-nutrition can lead to excess WAT, obesity and metabolic disease. Brown adipose tissue (BAT) has a primary role in energy expenditure through futile cycling of the electron transport chain (ETC) to generate heat. BATs heat producing capacity may be a novel approach to treating obesity. Adult humans possess metabolically active BAT, but the onset of obesity can reduce BAT thermogenic activity and mass. Obesity can bring about morphological changes to BAT, causing BAT to resemble WAT in a process termed “whitening”. WAT is a well-known endocrine organ. Specific endocrine signals from WAT could be responsible for reduced BAT activity in obesity. Leucine-rich-α2-glycoprotein 1 (LRG1) is an adipose-associated secretory protein and potential adipokine, with plasma levels positively correlated to body mass index in humans. Hypothesis It is hypothesized that LRG1 is an adipokine which negatively regulates thermogenesis in BAT and contributes to obesity related loss of BAT. Methods Male Lrg1 global knockout (KO) mice or wild type (WT) controls were fed standard chow (STD) or high fat diet (HFD) for 10 weeks. At 18 weeks of age systemic and BAT metabolic characteristics were determined by whole body indirect calorimetry, high-resolution tissue respirometry, quantitative PCR and immunoblots. Results After 10 weeks of HFD feeding Lrg1 KO mice fed STD and HFD had significantly higher percentage of body mass comprised of BAT than WT controls (Figure 1A). Lrg1 KO mice fed HFD had a lower respiratory exchange ratio (RER), indicating a greater use of fat oxidation compared to WT controls (Figure 1B). Mitochondrial respiration was used to measure changes in cellular energy. In response to HFD WT mice exhibit a decrease in mitochondrial respiration through complex 1 of the electron transport chain (ETC) (Figure 2A). The mitochondrial function of Lrg1 KO mice BAT is protected from HFD-induced dysfunction at Complex 1 of the ETC (Figure 2A). Uncoupling protein 1 (UCP1), a key protein involved in thermogenesis, Ucp1 mRNA is significantly increased in the BAT of Lrg1 KO STD and HFD fed mice compared to WT (Figure 2B). Ucp1 mRNA expression increase in Lrg1 KO mice was confirmed by measuring UCP1 protein with an immunoblot (Figure 2C). Conclusion Loss of Lrg1 protects BAT from dysfunction in diet-induced obesity.

Mgll Knockout Mouse Resistance to Diet-Induced Dysmetabolism Is Associated with Altered Gut Microbiota.

Monoglyceride lipase (MGLL) regulates metabolism by catabolizing monoacylglycerols (MAGs), including the endocannabinoid 2-arachidonoyl glycerol (2-AG) and some of its bioactive congeners, to the corresponding free fatty acids. Mgll knockout mice (Mgll−/−) exhibit elevated tissue levels of MAGs in association with resistance to the metabolic and cardiovascular perturbations induced by a high fat diet (HFD). The gut microbiome and its metabolic function are disrupted in obesity in a manner modulated by 2-arachidonoyl glycerol (2-AG’s) main receptors, the cannabinoid CB1 receptors. We therefore hypothesized that Mgll−/− mice have an altered microbiome, that responds differently to diet-induced obesity from that of wild-type (WT) mice. We subjected mice to HFD and assessed changes in the microbiomes after 8 and 22 weeks. As expected, Mgll−/− mice showed decreased adiposity, improved insulin sensitivity, and altered circulating incretin/adipokine levels in response to HFD. Mgll−/− mice on a chow diet exhibited significantly higher levels of Hydrogenoanaerobacterium, Roseburia, and Ruminococcus than WT mice. The relative abundance of the Lactobacillaceae and Coriobacteriaceae and of the Lactobacillus, Enterorhabdus, Clostridium_XlVa, and Falsiporphyromonas genera was significantly altered by HFD in WT but not Mgll−/− mice. Differently abundant families were also associated with changes in circulating adipokine and incretin levels in HFD-fed mice. Some gut microbiota family alterations could be reproduced by supplementing 2-AG or MAGs in culturomics experiments carried out with WT mouse fecal samples. We suggest that the altered microbiome of Mgll−/− mice contributes to their obesity resistant phenotype, and results in part from increased levels of 2-AG and MAGs.

Complement Properdin Regulates the Metabolo-Inflammatory Response to a High Fat Diet.

Background and objectives: Overnutrition leads to a metabolic and inflammatory response that includes the activation of Complement. Properdin is the only amplifier of complement activation and increases the provision of complement activation products. Its absence has previously been shown to lead to increased obesity in mice on a high fat diet. The aim of this study was to determine ways in which properdin contributes to a less pronounced obese phenotype. Materials and Methods: Wild type (WT) and properdin deficient mice (KO) were fed a high-fat diet (HFD) for up to 12 weeks. Results: There was a significant increase in liver triglyceride content in the KO HFD group compared to WT on HFD. WT developed steatosis. KO had an additional inflammatory component (steatohepatitis). Analysis of AKT signalling by phosphorylation array supported a decrease in insulin sensitivity which was greater for KO than WT in liver and kidney. There was a significant decrease of C5L2 in the fat membranes of the KO HFD group compared to the WT HFD group. Circulating microparticles in KO HFD group showed lower presence of C5L2. Expression of the fatty acid transporter CD36 in adipose tissue was increased in KO on HFD and was also significantly increased in plasma of KO HFD mice compared to WT on HFD. CD36 was elevated on microparticles from KO on HFD. Ultrastructural changes consistent with obesity-associated glomerulopathy were observed for both HFD fed genotypes, but tubular strain was greater in KO. Conclusion: Our work demonstrates that complement properdin is a dominant factor in limiting the severity of obesity-associated conditions that impact on liver and kidney. The two receptors, C5L2 and CD36, are downstream of the activity exerted by properdin.

Nox2 dependent redox-regulation of Akt and ERK1/2 to promote left ventricular hypertrophy in dietary obesity of mice

BackgroundA Nox2 containing NADPH oxidase (Nox2) is involved in the global oxidative stress found in dietary obesity and metabolic disorders. However, the effects of high fat diet (HFD) on cardiac Nox2 activation and signaling in left ventricular hypertrophy (LVH) remain unknown. MethodsLeft ventricular (LV) tissues isolated from C57BL/6J wild-type (WT) and Nox2 knockout (Nox2KO) mice (11 months old, n = 6 per group) after 4 months of HFD treatment were used. Cardiomyocyte sizes were measured digitally on LV cross-sections. The levels of cardiac reactive oxygen species (ROS) production was determined using lucigenin-chemiluminescence and in situ dihydroethidium (DHE) fluorescence. The levels of Nox subunit expression and redox signaling were examined by immunoblotting and immunofluorescence. ResultsIn comparison to WT normal chow diet control hearts, WT HFD hearts had 1.8-fold increases in cardiomyocyte size, a sign of cardiac hypertrophy, and this was accompanied with ≥2-fold increase in the levels of ROS production, Nox2 expression and the phosphorylation of Akt and ERK1/2. Increased ROS production measured in HFD heart homogenates was inhibited to control levels by Tiron (a cell membrane permeable O2•−scavenger), diphenyleneiodonium (DPI, a flavohaemoprotein inhibitor) and Nox2 ds-tat (a Nox2 assembly inhibitor). However, all of these abnormalities were significantly reduced or absent in Nox2KO hearts under the same HFD. ConclusionsNox2 activation in response to dietary obesity and metabolic disorders plays a key role in cardiac oxidative stress, aberrant redox signaling and cardiomyocyte hypertrophy. Knockout of Nox2 protects hearts from oxidative damage associated with obesity and metabolic disorders.

Cardiovascular Protection Mediated by the Chemokine CXCL5

One out of every four deaths in the United States can be attributed to heart disease. Atherosclerosis is a prevalent form of cardiovascular disease that describes the narrowing of arteries, leading to the restriction of blood flow. Atherosclerosis is caused in part by the accumulation of lipid‐laden macrophages (foam cells) in the walls of arteries. Determining mechanisms that influence lipid metabolism in macrophages may uncover new approaches to modify the disease process and decrease the disease burden. Recently, our lab identified a genetic link between the expression of the chemokine CXCL5 and atherosclerosis in patients that is consistent with a cardioprotective role for CXCL5. One effect of CXCL5 appears to be in the regulation of reverse cholesterol transporters. We found that exposure to CXCL5 decreases foam cell forming macrophages, suggesting CXCL5 may directly impact lipid metabolism. What is not known is how CXCL5 modifies the pathophysiological response to conditions that contribute to atherosclerosis, such as a high fat diet (HFD). We hypothesized that CXCL5 mediates cardioprotection by altering the physiological response to a HFD, such that, lower levels of CXCL5 will lead to altered lipid handling and predisposition to more severe atherosclerosis. We challenged wild‐type (WT) and CXCL5−/− mice with either a HFD (0.2% cholesterol, 42% calories from fat, N = 17 per genotype), or normal chow (NC, 0% cholesterol, 16% calories from fat, N = 15 per genotype) for 16 w. To determine the effect of the diet on circulating lipid levels, we performed blood lipid analysis after the feeding regimen. Interestingly, HFD did not increase cholesterol levels to the same extent in CXCL5−/− mice as compared to WT mice. Specifically, we found that WT mice had a robust, diet‐dependent increase in both high‐density lipoprotein and low‐density lipoprotein levels (LDL: 59.6 mg/dl vs 11.3 mg/dl and HDL: 118.7 mg/dl vs 68.1 mg/dl in HFD vs NC, respectively), whereas in CXCL5−/− mice, this response was diminished (LDL: 20.6 mg/dl vs 8.8 mg/dl and HDL: 82.6 mg/dl vs 56.8 mg/dl in HFD vs NC, respectively). These results suggest that the genetic depletion of CXCL5 alters lipid handling in vivo. Additionally, white blood cell analysis identified that WT mice responded to the HFD with an increase in the number of lymphocytes (10.3e3 cells/μl vs 5.2e3 cells/μl in HFD WT vs NC WT, p = 0.0224) and basophils (20 cells/μl vs 4.0 cells/μl, p = 0.0038), an effect that was attenuated in KO mice in response to the HFD (p &gt; 0.05). These findings suggest that CXCL5 may modify a specific component in the chronic inflammatory response to the HFD. Unexpectedly, HFD led to a modest decrease in cardiac function in KO mice after 16 w of the HFD compared to WT mice (74% vs 82% ejection fraction in CXCL5−/− vs WT mice, respectively, p = 0.0058). These preliminary findings suggest that CXCL5 plays a multifaceted role in the cardiovascular system’s response to an atherogenic diet. Currently, studies are underway using athero‐prone mice to study the effect of CXCL5 on plaque formation, using the ApoE−/− model. Future directions include treating mice with CXCL5 to study the effects on both the progression and regression of atherosclerosis. If successful, our studies would bring light to a new therapeutic target that could be used to combat cardiovascular disease.

Prolyl endopeptidase gene disruption attenuates high fat diet-induced nonalcoholic fatty liver disease in mice by improving hepatic steatosis and inflammation.

BackgroundProlyl endopeptidase (PREP) is a serine endopeptidase that regulates inflammatory responses. PREP inhibitors can reduce hepatocyte lipid accumulation and may participate in the progression of nonalcoholic fatty liver disease (NAFLD). We investigated whether disruption of PREP regulates hepatic steatosis and inflammation in mice with NAFLD.MethodsWild-type and PREP gene disrupted mice were randomly divided into low-fat diet wild-type (LFD-WT), high-fat diet wild-type (HFD-WT), low-fat diet PREP disruption (LFD-PREPgt), and high-fat diet PREP disruption (HFD-PREPgt) groups. Animals were euthanized at the endpoint of 32 weeks. The NAFLD activity score and number of inflammatory cells were determined by hematoxylin-eosin staining and immunohistochemical staining of liver tissue. The expression levels of inflammation- and lipid metabolism-associated genes in the liver and serum were detected by quantitative reverse transcription PCR, mass spectrometry, or enzyme-linked immunosorbent assay.ResultsThe body weight and epididymal fat tissue index of the HFD-PREPgt mice were significantly decreased compared with that of the HFD-WT mice. Moreover, the NAFLD activity score and liver function were attenuated in the HFD-PREPgt mice. Fat accumulation and the level of expression of mRNAs associated with lipid metabolism and proinflammatory responses were improved in the HFD-PREPgt mice. The number of CD68-positive cells in liver tissue and the serum levels of inflammation-associated factors were significantly decreased in the HFD-PREPgt mice compared with those in the HFD-WT mice. Further mechanistic investigations indicated that the protective effect of PREP disruption on liver inflammation was associated with the suppressed production of matrix metalloproteinases (MMPs) and proline-glycine-proline (PGP) and the inhibition of neutrophil infiltration.ConclusionsLoss of PREP lowers the severity of hepatic steatosis and inflammatory responses in a high-fat diet-induced nonalcoholic steatohepatitis model. PREP inhibition may protect against NAFLD.

Polyphenol-rich green tea extract induces thermogenesis in mice by a mechanism dependent on adiponectin signaling

Adiponectin is downregulated in obesity negatively impacting the thermogenesis and impairing white fat browning. Despite the notable effects of green tea (GT) extract in the enhancement of thermogenesis, if its effects are being mediated by adiponectin has been scarcely explored. For this purpose, we investigated the role of adiponectin in the thermogenic actions of GT extract by using an adiponectin-knockout mice model. Male wild-type (WT) and knockout (AdipoKO) C57Bl/6 mice (3 months) were divided into 6 groups: mice fed a standard diet+gavage with water (SD WT, and SD AdipoKO), high-fat diet (HFD)+gavage with water (HFD WT, and HFD AdipoKO), and HFD + gavage with 500 mg/kg of body weight (BW) of GT extract (HFD + GT WT, and HFD + GT AdipoKO). After 20 weeks of experimentation, mice were euthanized and adipose tissue was properly removed. Our findings indicate that treatment with GT extract reversed complications of obesity in WT mice by decreasing final BW gain, adiposity index, adipocyte size and insulin resistance (IR). However, the action of the GT extract was not effective in reversing those markers in the AdipoKO mice, although GT acts independently in the reversal of IR. GT-treatment induced enhancement in energy expenditure (EE), BAT thermogenesis, and promoted browning phenotype in the subcutaneous WAT (scWAT) of WT mice. On the other hand, the thermogenic program was markedly impaired in BAT and scWAT of AdipoKO mice. Our outcomes unveiled adiponectin as a key direct signal for GT extract inducing adaptive thermogenesis and browning in scWAT.