High-fat Feeding Research Articles

Growth hormone-releasing hormone deficiency confers extended lifespan and metabolic resilience during high-fat feeding in mid and late life.

Growth hormone-releasing hormone-deficient (GHRH-KO) mice have previously been characterized by lower body weight, disproportionately high body fat accumulation, preferential metabolism of lipids compared to carbohydrates, improved insulin sensitivity, and an extended lifespan. That these mice are long-lived and insulin-sensitive conflicts with the notion that adipose tissue accumulation drives the health detriments associated with obesity (i.e., diabetes), and indicates that GH signaling may be necessary for the development of adverse effects linked to obesity. This prompts investigation into the ultimate effect of diet-induced obesity on the lifespan of these long-lived mice. To this end, we initiated high-fat feeding in mid and late-life in GHRH-KO and wild-type (WT) mice. We carried out extensive lifespan analysis coupled with glucose/insulin tolerance testing and indirect calorimetry to gauge the metabolic effect of high-fat dietary stress through adulthood on these mice. We show that under high-fat diet (HFD) conditions, GHRH-KO mice display extended lifespans relative to WT controls. We also show that GHRH-KO mice are more insulin-sensitive and display less dramatic changes in their metabolism relative to WT mice, with GHRH-KO mice fed HFD displaying respiratory exchange ratios and glucose oxidation rates comparable to control-diet fed GHRH-KO mice, while WT mice fed HFD showed significant reductions in these parameters. Our results indicate that GH deficiency protects against the adverse effects of diet-induced obesity in later life.

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.

Saponins from Allii Macrostemonis Bulbus attenuate atherosclerosis by inhibiting macrophage foam cell formation and inflammation

Allii Macrostemonis Bulbus (AMB) is a traditional Chinese medicine with medicinal and food homology. AMB has various biological activities, including anti-coagulation, lipid-lowering, anti-tumor, and antioxidant effects. Saponins from Allium macrostemonis Bulbus (SAMB), the predominant beneficial compounds, also exhibited lipid-lowering and anti-inflammatory properties. However, the effect of SAMB on atherosclerosis and the underlying mechanisms are still unclear. This study aimed to elucidate the pharmacological impact of SAMB on atherosclerosis. In apolipoprotein E deficiency (ApoE−/−) mice with high-fat diet feeding, oral SAMB administration significantly attenuated inflammation and atherosclerosis plaque formation. The in vitro experiments demonstrated that SAMB effectively suppressed oxidized-LDL-induced foam cell formation by down-regulating CD36 expression, thereby inhibiting lipid endocytosis in bone marrow-derived macrophages. Additionally, SAMB effectively blocked LPS-induced inflammatory response in bone marrow-derived macrophages potentially through modulating the NF-κB/NLRP3 pathway. In conclusion, SAMB exhibits a potential anti-atherosclerotic effect by inhibiting macrophage foam cell formation and inflammation. These findings provide novel insights into potential preventive and therapeutic strategies for the clinical management of atherosclerosis.

AMPK-mediated regulation of endogenous cholesterol synthesis does not affect atherosclerosis in a murine Pcsk9-AAV model

Background and aimsDysregulated cholesterol metabolism is a hallmark of atherosclerotic cardiovascular diseases, yet our understanding of how endogenous cholesterol synthesis affects atherosclerosis is not clear. The energy sensor AMP-activated protein kinase (AMPK) phosphorylates and inhibits the rate-limiting enzyme in the mevalonate pathway HMG-CoA reductase (HMGCR). Recent work demonstrated that when AMPK-HMGCR signaling was compromised in an Apoe-/- model of hypercholesterolemia, atherosclerosis was exacerbated due to elevated hematopoietic stem and progenitor cell mobilization and myelopoiesis. We sought to validate the significance of the AMPK-HMGCR signaling axis in atherosclerosis using a non-germline hypercholesterolemia model with functional ApoE. MethodsMale and female HMGCR S871A knock-in (KI) mice and wild-type (WT) littermate controls were made atherosclerotic by intravenous injection of a gain-of-function Pcsk9D374Y-adeno-associated virus followed by high-fat and high-cholesterol atherogenic western diet feeding for 16 weeks. ResultsAMPK activation suppressed endogenous cholesterol synthesis in primary bone marrow-derived macrophages from WT but not HMGCR KI mice, without changing other parameters of cholesterol regulation. Atherosclerotic plaque area was unchanged between WT and HMGCR KI mice, independent of sex. Correspondingly, there were no phenotypic differences observed in hematopoietic progenitors or differentiated immune cells in the bone marrow, blood, or spleen, and no significant changes in systemic markers of inflammation. When lethally irradiated female mice were transplanted with KI bone marrow, there was similar plaque content relative to WT. ConclusionsGiven previous work, our study demonstrates the importance of preclinical atherosclerosis model comparison and brings into question the importance of AMPK-mediated control of cholesterol synthesis in atherosclerosis.

Reduction of oxidative stress response and protection of liver and renal cell functions by reduced glutathione in lower limb arterial ischemia–reperfusion in New Zealand white rabbits with high triglyceride levels

ObjectiveAcute liver and kidney injury is the most common complication after aortic surgery, which seriously affects the survival and safety of perioperative patients. The presence of chronic preoperative liver and renal insufficiency, presence of preoperative blood inflammation indicators, duration of intraoperative extracorporeal circulation, and volume of red blood cell transfusion are the main influencing factors for acute postoperative liver and kidney injuries. In recent years, with the research progress on oxidative stress, a growing body of evidence has demonstrated that oxidative stress may cause tissue damage after ischemia–reperfusion (IR). However, the impact of the oxidative stress of distal tissues caused by IR on liver and renal cells after arterial surgeries has not yet been elucidated. MethodsNew Zealand white rabbits were used for the experiments and were divided into three groups. Among them, two groups were fed high-fat feed to establish a white rabbit model of hypertriglyceridemia, whereas the control group was provided with ordinary feed. In the experiment, white rabbits were subjected to occlusion of the infrarenal aorta abdominalis to simulate IR of the lower limbs. The effects of high triglyceride levels after the arterial IR of the lower limbs were investigated using the contents of reactive oxygen species (ROS) and malondialdehyde (MDA), a fat metabolite, in ischemic muscle tissues and blood tissues. One of the groups receiving high-fat feed received intervention with reduced glutathione (GSH) before IR of the lower limbs. Pathological studies were performed to identify the expression levels of inflammatory factors and inflammatory cells in liver and renal cells as well as cell apoptosis. The effects of GSH administration before IR on reducing the oxidative stress in adipose tissues and alleviating liver and kidney damage after stress response were investigated. ResultsAfter IR, the increases in ROS and MDA in ischemic muscle tissues and blood tissues were higher in white rabbits with high triglyceride levels than in those that only received ordinary feed or received intervention with GSH. In addition, for white rabbits with high triglyceride levels, the TNF-α expression levels in the liver increased after IR. Moreover, a considerable increase in the expression of TNF-α, IL-6, macrophages, and T lymphocytes were observed in renal cells. A large number of inflammatory cells and the formation of immune complexes were also noted in the glomeruli; in addition, cell apoptosis was promoted. ConclusionThis study showed that high triglyceride levels enhanced the oxidative stress response and increased ROS production in New Zealand white rabbits after arterial IR of the lower limbs. High ROS levels activated the expression of inflammatory factors and inflammatory cells in the liver and kidney, which affected cell functions and promoted apoptosis. At high triglyceride levels, GSH downregulated ROS production in oxidative stress after IR, thereby protecting liver and kidney functions.

Human umbilical cord mesenchymal stem cells alleviate fatty liver ischemia-reperfusion injury by activating autophagy through upregulation of IFNγ.

Liver ischemia-reperfusion injury (IRI) is an important factor affecting the prognosis of liver transplantation, and extended criteria donors (e.g., steatosis donor livers) are considered to be more sensitive to ischemia-reperfusion injury in liver transplantation. Currently, the application of human umbilical cord mesenchymal stem cells (hMSCs) has great promise in the treatment of various injuries in the liver. This study aimed to investigate the therapeutic role and mechanism of hMSCs in fatty liver IRI. After more than 8 weeks of high-fat chow feeding, we constructed a fatty liver mouse model and established ischemic injury of about 70% of the liver. Six hours after IRI, liver injury was significantly alleviated in hMSCs-treated mice, and the expression levels of liver enzyme, inflammatory factor TNF-α, and apoptotic proteins were significantly lower than those of the control group, which were also significant in pathological sections. Transcriptomics analysis showed that IFNγ was significantly upregulated in the hMSCs group. Mechanistically, IFNγ, which activates the MAPK pathway, is a potent agonist that promotes the occurrence of autophagy in hepatocytes to exert a protective function, which was confirmed by in vitro experiments. In summary, hMSCs treatment could slow down IRI in fatty liver by activating autophagy through upregulation of IFNγ, and this effect was partly direct.

Mechanism of Yupingfeng Powder on hepatic insulin resistance in type 2 diabetes mellitus rats by regulating IRS/PI3K/Akt pathway

Based on the insulin receptor substrate(IRS)/phosphoinositide 3-kinase(PI3K)/protein kinase B(Akt) pathway, the intervention effect of Yupingfeng Powder on type 2 diabetes mellitus(T2DM) rats was studied, and the potential mechanism of improving T2DM hepatic insulin resistance was explored. A T2DM rat model was established by feeding with high-fat and high-sugar feed combined with intraperitoneal injection of streptozotocin. Successfully modeled rats were selected and divided into a model group, a positive control group(MET), and a Yupingfeng Powder group. At the same time, a blank group was set up, and corresponding drugs were given by gavage. The model group and blank group were given an equal amount of physiological saline by gavage. During the experiment, body mass and fasting blood glucose were regularly measured, and glucose tolerance and insulin tolerance were measured at the end of the experiment. After the experiment, the levels of blood glucose, insulin, blood lipids, and related liver function indicators were measured; changes in liver pathological damage were observed, levels of liver monoamine oxidase were detected, and qRT-PCR was used to detect mRNA expression levels of IRS/PI3K/Akt pathway related genes. Compared with the model group, the Yupingfeng Powder group had an increase in body weight, a decrease in fasting blood glucose, fasting insulin, and steady-state model evaluation index, a decrease in the area under the curve of glucose tolerance and insulin tolerance tests, a decrease in serum total cholesterol, triglycerides, and low-density lipoprotein cholesterol content, and an increase in high-density lipoprotein cholesterol content. Compared with the model group, the Yupingfeng Powder group showed a decrease in liver monoamine oxidase levels, a decrease in serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and total bilirubin levels, and an increase in total protein and albumin levels. Hematoxylin-eosin(HE) staining showed a reduction in pathological liver cell damage. Compared with the model group, the Yupingfeng Powder group showed a significant increase in the mRNA expression levels of IRS1, PI3K, and Akt in the liver of rats, as well as a significant decrease in the mRNA expression levels of interleukin-6(IL-6) and tumor necrosis factor-α(TNF-α). This indicates that Yupingfeng Powder can regulate the IRS/PI3K/Akt signaling pathway and glucose and lipid metabolism disorders, increase insulin sensitivity, improve hepatic insulin resistance, and thus play a therapeutic role in T2DM.

Single-Cell Landscape and a Macrophage Subset Enhancing Brown Adipocyte Function in Diabetes.

Metabolic dysregulation is a hallmark of type 2 diabetes mellitus (T2DM), in which the abnormalities in brown adipose tissue (BAT) play important roles. However, the cellular composition and function of BAT as well as its pathological significance in diabetes remain incompletely understood. Our objective is to delineate the single-cell landscape of BAT-derived stromal vascular fraction (SVF) and their characteristic alterations in T2DM rats. T2DM was induced in rats by intraperitoneal injection of low-dose streptozotocin and high-fat diet feeding. Single-cell mRNA sequencing was then performed on BAT samples and compared to normal rats to characterize changes in T2DM rats. Subsequently, the importance of key cell subsets in T2DM was elucidated using various functional studies. Almost all cell types in the BAT-derived SVF of T2DM rats exhibited enhanced inflammatory responses, increased angiogenesis, and disordered glucose and lipid metabolism. The multidirectional differentiation potential of adipose tissue-derived stem cells was also reduced. Moreover, macrophages played a pivotal role in intercellular crosstalk of BAT-derived SVF. A novel Rarres2+macrophage subset promoted the differentiation and metabolic function of brown adipocytes via adipose-immune crosstalk. BAT SVF exhibited strong heterogeneity in cellular composition and function and contributed to T2DM as a significant inflammation source, in which a novel macrophage subset was identified that can promote brown adipocyte function.

Investigation on the lipid-lowering effect and mechanism by combining turmeric with hawthorn in C57BL/6 obese mice.

Study on the hypolipidemic effect of turmeric combined with hawthorn on C57BL/6 obese mice and its possible mechanism. C57 mice were fed with 60% high-fat diet for 8 weeks to establish an obesity model, and 4 mice were slaughtered to verify whether the modeling was successful. The successful mice were divided into model group (HFD), positive group (high fat feed group [HFD]+simvastatin group [SIM]), turmeric group (HFD+TUR), hawthorn group (HFD+HAW), and para-medicine group (HFD+para-drug group [DOU]) for 4 weeks by gavage intervention. Different intervention groups had certain lipid-lowering effects, and the para-medicine group showed significant differences (p<0.05, p<0.01, p<0.001) in reducing serum total cholesterol, triglycerides, low-density lipoprotein cholesterol, glutamic acid transaminase (ALT), glutamic acid transaminase (AST), and increasing high-density lipoprotein cholesterol. In the para-medicine group, the protein expression of peroxisome proliferator-activated receptor γ, fatty acid synthase, platelet-reactive protein receptor 36, and CCAAT/enhancer binding protein α were significantly downregulated, and the protein expression of carnitine palmitoyl transferase1 and peroxisome proliferator-activated receptor α protein expression (p<0.01, p<0.001), thus suggesting that turmeric and hawthorn are superior to turmeric and hawthorn alone in enhancing lipid metabolism-related mechanisms. Combined effects of turmeric and hawthorn improve lipid metabolism in mice, protect the liver, and improve the protein expression of liver-related genes. This study can lay the theoretical basis for the future association of medicinal food products and the development of related weight loss products.

Arterial Adventitial Vasa Vasorum Hyperplasia involved in Atherosclerotic Plaque Formation in a Rabbit Model

ObjectiveIt was previously believed that atherosclerotic (AS) plaque starts to develop from the intima and that intraplaque vasa vasorum (VV) hyperplasia promotes adventitial VV (AVV) hyperplasia. However, recent studies have shown that arterial AVV hyperplasia precedes early intimal thickening, suggesting its possible role as an initiating factor of AS. To provide further insight into this process, in this study, we examine the evolution of AAV and VV development in a preclinical model of early AS with longitudinal ultrasound imaging. MethodsModels of early AS were established. Duplex ultrasound scanning and contrast-enhanced ultrasound were performed for diagnosis. Pearson correlation tests were used to analyze the relationships between AVV hyperplasia and VV hyperplasia, or between AVV hyperplasia and intima-media thickness (IMT). ResultsDuring 0–12 wk of high-fat feeding, AVV gradually increased and intima-media thickened gradually in the observation area; in the 2nd wk of high-fat feeding, the observation area showed obvious AVV proliferation; at the 4th wk, the intima-media membrane became thicker; at the 12th wk, early plaque formation and intraplaque VV proliferation were observed. There was a strong positive correlation between AVV proliferation and IMT thickening and a strong negative correlation between AVV proliferation and the change rate of vessel diameter. ConclusionThis study demonstrated that AVV proliferation in the arteries occurred earlier than IMT thickening and was positively correlated with IMT. At present, the indicators of ultrasonic diagnosis of AS, such as IMT, Intraplaque VV, Echo property, all appear in the advanced stage of AS. The AVV may be an innovative diagnostic target for the early stage of AS plaque.

LECT2 Deletion Exacerbates Liver Steatosis and Macrophage Infiltration in a Male Mouse Model of LPS-mediated NASH.

Leukocyte cell-derived chemotaxin 2 (LECT2) is a protein initially isolated as a neutrophil chemotactic factor. We previously found that LECT2 is an obesity-associated hepatokine that senses liver fat and induces skeletal muscle insulin resistance. In addition, hepatocyte-derived LECT2 activates macrophage proinflammatory activity by reinforcing the lipopolysaccharide (LPS)-induced c-Jun N-terminal kinase signaling. Based on these findings, we examined the effect of LECT2 deletion on nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) caused by bacterial translocation. We created the bacterial translocation-mediated NAFLD/NASH model using LECT2 knockout mice (LECT2 KO) with 28 times a low-dose LPS injection under high-fat diet feeding conditions. LECT2 deletion exacerbated steatosis and significantly reduced p38 phosphorylation in the liver. In addition, LECT2 deletion increased macrophage infiltration with decreased M1/M2 ratios. LECT2 might contribute to protecting against lipid accumulation and macrophage activation in the liver under pathological conditions, which might be accomplished via p38 phosphorylation. This study provides novel aspects of LECT2 in the bacterial translocation-mediated NAFLD/NASH model.

Deletion of Nrf2 induced severe oxidative stress and apoptosis in mice model of diabetic bladder dysfunction

The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway has been confirmed as a therapeutic target for type 2 diabetes mellitus (T2DM), however few studies revealed its effect in diabetic bladder dysfunction (DBD). Herein, we reported a Nrf2 deletion diabetic mouse model induced by 8-week high-fat diet feeding combined with streptozocin (STZ) injection in Nrf2 knockout mice. Besides, wild-type mice (WT) were used as control group, wild-type mice with high-fat diet feeding and STZ injection as diabetic group (WT-T2DM), and Nrf2 knockout mice as Nrf2 deletion group (KO). The pathophysiological indexes and bladder morphology showed typical pathological features of diabetic bladder dysfunction in Nrf2 knockout diabetic mouse mice (KO-T2DM). ELISA results showed that advanced glycation end products (AGEs), ROS and malondialdehyde (MDA) levels in bladder was were up-regulated in both WT-T2DM and KO-T2DM group, while superoxide dismutase (SOD) and glutathione (GSH) levels decreased in these two groups. Compared with WT-T2DM group, western blot analysis of the bladder showed down-regulated expression of NQO1 and HO-1 in KO-T2DM group. However, apoptosis, marked by Caspase3 and bax/bcl-2 ratio, was increased in KO-T2DM group. Neurotrophic factor (NGF) was significantly decreased in DBD model, and even much lower in KO-T2DM group. Collectively, our findings demonstrated that deletion of Nrf2 lead to severe oxidative stress, apoptosis, and lower level of neurotrophic factor, and provided the first set of experimental evidence, in a mouse model, to support Nrf2 as a promising target for DBD.

Short-term high-calorie high-fat feeding induces hyperinsulinemia and blunts skeletal muscle microvascular blood flow in healthy humans.

Skeletal muscle microvascular blood flow (MBF) plays an important role in glucose disposal in muscle. Impairments in muscle MBF contribute to insulin resistance and prediabetes. Animal studies show that short-term (3 day) high-fat feeding blunts skeletal muscle MBF before impairing insulin-stimulated glucose disposal. It is not known whether this occurs in humans. We investigated the temporal impact of a 7-day high-calorie high-fat (HCHF) diet intervention (+52% kJ; 41% fat) on fasting and postprandial cardiometabolic outcomes in 14 healthy adults (18-37 yr). Metabolic health and vascular responses to a mixed-meal challenge (MMC) were measured at pre (day 0)-, mid (day 4)- and post (day 8)-intervention. There were no significant differences in body weight, body fat %, fasting blood glucose, and fasting plasma insulin concentrations at pre-, mid- and postintervention. Compared with preintervention there was a significant increase in insulin (but not glucose) total area under the curve in response to the MMC at midintervention (P = 0.041) and at postintervention (P = 0.028). Unlike at pre- and midintervention, at postintervention muscle MBF decreased at 60 min (P = 0.024) and 120 min (P = 0.023) after the MMC. However, macrovascular blood flow was significantly increased from 0 to 60 min (P < 0.001) and 120 min (P < 0.001) after the MMC at pre-, mid- and postintervention. Therefore, short-term HCHF feeding in healthy individuals leads to elevated postprandial insulin but not glucose levels and a blunting of meal-induced skeletal muscle MBF responses but not macrovascular blood flow responses.NEW & NOTEWORTHY This is the first study to investigate skeletal muscle microvascular blood flow (MBF) responses in humans after short-term high-calorie high-fat (HCHF) diet. The main findings were that HCHF diet causes elevated postprandial insulin in healthy individuals within 3 days and blunts meal-induced muscle MBF within 7 days, despite no impairments in postprandial glucose or macrovascular blood flow.

High Fat Feeding Blunts Skeletal Muscle Oxygen Mediated Blood Flow Responses in Healthy and Type 2 Diabetic Rats

Hypothesis: High fat diet feeding impairs microvascular blood flow responses to dynamic changes in local oxygen concentration ([O2]) in Sprague-Dawley (SD) and Zucker Diabetic Sprague-Dawley (ZDSD) rats. Methods: Seven-week-old male SD and ZDSD rats were fed either a standard chow (N = 7 SD, 5 ZDSD) or a high saturated fat diet (N = 8 SD, 6 ZDSD) for 7 weeks. At 14 weeks of age animals were anaesthetized, instrumented for systemic monitoring, and mechanically ventilated. The extensor digitorum longus muscle was blunt dissected and reflected over a gas exchange chamber imbedded in the stage of an inverted microscope. Microvascular blood flow responses to high and low [O2] challenges (7 – 12 %, and 7 – 2 %) and sequential changes in [O2] (7 – 12 – 2 – 7 %) were recorded at baseline and during hyperinsulinemic-euglycemic clamp. Gas conditions within the chamber were set at 7 % for a 1-minute baseline followed by 2 minutes at either 2 or 12 % O2. The 4-minute square wave oscillation consisted of 1 minute at each [O2] (7 – 12 – 2 – 7 %). Hyperinsulinemic-euglycemic clamp was achieved by simultaneous infusion of insulin (2 U/hr/kg) and variable rate of 50 % glucose until euglycemia was reached (5 - 7 mM blood glucose). Analysis of intravital videos was completed using custom MATLAB software. All animal protocols were approved by Memorial University’s Animal Care Committee. Results: Chow fed SD had significantly higher glucose infusion rates compared to high fat fed SD, chow fed ZDSD, and high fat fed ZDSD (28.11 ± 1.807 vs. 25.14 ± 1.18, 24.56 ± 2.78, 24.77 ± 2.43 mg/kg/min, p = 0.0429, 0.0305, 0.0323, respectively). Red blood cell (RBC) saturation significantly increased and decreased in all groups within 4 s following the increase and decrease in [O2], respectively. Chow fed SD had significant decrease in RBC supply rate (SR) in response to 12 % [O2] (10.41 ± 11.31 vs 7.44 ± 8.40 cells/s, p &lt; 0.0001, τ = 15.85 s). In response to low [O2], significant increases in SR were measured in the chow fed SD and ZDSD groups (7.10 ± 8.76 vs 11.65 ± 11.36 cells/s, p &lt; 0.0001, τ = 17.65 s, and 10.86 ± 13.62 vs 13.86 ± 14.69 cells/s, p &lt; 0.0001, τ = 85.74 s, respectively). High fat fed SD and ZDSD had significant increases in RBC SR during 2 % [O2] (8.47 ± 9.75 vs 11.84 ± 12.11 cells/s, p &lt; 0.0001, τ = 68.49 s, and 16.09 ± 18.12 vs 20.73 ± 21.92 cells/s, p &lt; 0.0001, τ = 23.98 s). High fat fed ZDSD had higher, but not significantly different, baseline RBC SR compared to the chow fed ZDSD group. Chow fed SD were the only group to have an increase in RBC SR at low [O2] during hyperinsulinemic-euglycemic clamp (13.80 ± 17.78 vs 18.07 ± 20.25 cells/s, p = 0.0003, τ = 10.88 s). Conclusions: High fat feeding impairs the capillary blood flow response to local increases in [O2] in healthy and high fat fed T2D model rats. Chow fed ZDSD rats had slower capillary blood flow dynamics than the SD control group. Hyperinsulinemic-euglycemic clamp diminishes the O2 mediated blood flow response in 14-week-old SD and ZDSD rats fed a high fat diet. This project was supported by the Canadian Institute of Health Research through a project grant to GMF. Studentships were supported by Memorial University's School of Graduate Studies and the Faculty of Medicine. 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.

Gender Specific Effects of Nr4a1 in Obese Mice

A central aspect of type 2 diabetes disease progression is impaired functional β-cell mass. The hyperglycemic and hyperlipidemic environment present in type 2 diabetes corresponds with impaired beta cell function. The orphan nuclear receptor Nr4a1 is critical for fuel utilization in various tissues, however little is known regarding its function in the β-cell. Nr4a1 expression is decreased in the β-cell of rodent models of type 2 diabetes, as well as in primary human islets from type 2 diabetics. Here we demonstrate sex specific effects of β-cell specific Nr4a1 deletion under high fat chow feeding. While female and male βNr4a1−/− mice were no different than wild type controls when fed a standard chow diet, a clear sex dependent difference is observed when fed a high fat diet. While high fat fed male βNr4a1−/− have improved fasting and non-fasting blood glucose levels and no change in glucose tolerance, high fat fed female βNr4a1−/− mice have impaired glucose tolerance as early as one month after beginning high fat feeding. We also found that βNr4a1−/− female mice have decreased β-cell mass and decreased expression in known targets of Nr4a1 regulation including Eno1 and SDHβ. Our data suggest that Nr4a1 is critical for maintenance of beta cell function, and that loss of Nr4a1 under conditions of obesity and overnutrition in females results in impaired beta cell compensation and function. NIH R15DK124835-01A1. 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.

T cell specific Eomes Deletion Does Not Protect Against High Fat Diet Induced Large Artery Stiffening

We have found that T cells contribute to age-related large artery stiffness. The T-box transcription factor, Eomes is an important regulator of CD8+ (Cytotoxic) T cell differentiation from a naïve to a memory phenotype. We previously reported that these effector memory CD8+ T cells accumulate in the aorta of old mice. We aimed to investigate whether inhibiting CD8+ T cell memory differentiation in mice, specifically through T cell-specific Eomes deletion, would protect these animals from high-fat diet (HFD)-induced large artery stiffness. Mice with a CD8 driven Cre Recombinase were bred with mice with loxp sites surrounding the Eomes gene resulting in wild type (CD8 Eomes+/+) and T cell specific Eomes deleted (CD8 Eomesf/f) mice. Mice were randomly divided into a normal chow (NC) and HFD. Resulting in 8 mice of each genotype and diet. The NC group was given a normal diet containing 4% fat and the HFD group was given a high-fat diet containing 60% fat. At 4-8 months of age, doppler pulse wave velocity was used to assess large artery stiffness. Following euthanasia, aortic T cell phenotype was assessed using flow-cytometry. Group differences were assessed by two-way ANOVA and Tukey’s post-hoc test. Data shown as mean ± SD. Regardless of genotype, HFD had a significant impact on pulse wave velocity (PWV), indicating elevated aortic stiffness. In the HFD group, both CD8 Eomesf/f and CD8 Eomes+/+ mice exhibited higher PWV values (330.08±72.33 cm/s;312.5±53.74 cm/s) compared to their counterparts in the NC group (256.4±63.67 cm/s;259.2±66.36 cm/s, p=0.0172). To determine whether HFD-induced increases in aortic stiffness are accompanied by changes in aortic T cell phenotype, flow cytometric analysis was performed on the aorta. First, we observed, regardless of mouse genotype, HFD had a significant impact on CD4+ (Helper T) naïve cells, resulting in a blunted percentage of these cells. This dietary effect was observed in both CD8 Eomesf/f and CD8 Eomes+/+ mice (NCD CD8 Eomesf/f: 70.92±5.912%; NCD CD8 Eomes+/+ mice: 56.46±20.62%; HFD CD8 Eomesf/f: 47.5±7.865%; HFD CD8 Eomes+/+ mice: 50.58±13.907%; p=0.0206). In contrast, the percentages of CD8+ naïve cells did not display a significant change in response to the high-fat diet (p=0.6303). HFD significantly influenced CD4+ memory cells, resulting in an increase in percentages, regardless of mouse genotype (NCD CD8 Eomesf/f: 29.09± 5.909%; NCD CD8 Eomes+/+ mice: 44.27±19.17%; HFD CD8 Eomesf/f: 52.47±7.875%; HFD CD8 Eomes+/+ mice: 49.44±13.9%; p=0.02). However, HFD did not produce any significant alterations in CD8+ memory cell percentages (p=0.6). These results suggest that contrary to our hypothesis, T cell specific Eomes deletion is not suffcient to protect against diet induced large artery stiffness. However, this may be due to greater proportions of CD4+ memory cells in the aorta with high fat feeding. Funding: AHA 940023, NIH R01AG060395, K01AG061271. 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.

S-Methyl Cysteine Sulfoxide Does Not Ameliorate Weight Gain or Hyperlipidemia in Mice Fed a High-Fat Diet.

Higher intake of cruciferous and allium vegetables is associated with lower cardiometabolic risk. Little research has investigated the cardiometabolic effects of S-methyl cysteine sulfoxide (SMCSO), found abundant in these vegetables. This study hypothesizes that SMCSO will blunt development of metabolic syndrome features in mice fed high-fat feed. Fifty C57BL/6 male mice are randomly assigned to standard-chow, high-fat, or high-fat supplemented with low-SMCSO (43mgkg-1 body weight [BW]day-1), medium-SMCSO (153mgkg-1 BWday-1), or high-SMCSO (256mgkg-1 BWday-1) for 12-weeks. High-fat with SMCSO did not prevent diet-induced obesity, glucose intolerance, or hypercholesterolemia. Mice fed high-fat with SMCSO has higher hepatic lipids than mice fed standard-chow or high-fat alone. Urinary SMCSO increases at 6- and 12-weeks in the low-SMCSO group, before reducing 46% and 28% in the medium- and high-SMCSO groups, respectively, at 12-weeks, suggesting possible tissue saturation. Interestingly, two SMCSO-fed groups consume significantly more feed, without significant weight gain. Due to limitations in measuring consumed feed, caution should be taken interpreting these results. SMCSO (43-256mgkg-1 BWday-1) does not ameliorate metabolic syndrome features in high-fat fed mice. Substantial knowledge gaps remain. Further studies should administer SMCSO separately (i.e., gavage), with metabolic studies exploring tissue levels to better understand its physiological action.

Brown Adipose Tissue-Derived GDF15 Mediates Energy Homeostasis in a Sex-Dependent Manner

Growth differentiation factor 15 (GDF15) is a distant member of the transforming growth factor-β (TGFβ) superfamily that can be expressed in several tissues. Studies have shown that in response to prolonged high-fat feeding and cold stress GDF15 can be induced in brown adipocytes. Importantly, administration of recombinant GDF15 in rodents and non-human primates (Xiong, Y. et al. Long-acting MIC-1/GDF15 molecules to treat obesity: Evidence from mice to monkeys. Sci. Transl. Med. 9, eaan8732 (2017) reduces food intake and body mass. Indeed, we have recently shown that in a model of mitochondrial stress, brown adipose tissue (BAT)-derived GDF15 is required to maintain energy homeostasis and cold-induced thermogenesis in mice. Nonetheless, the role of BAT-derived GDF15 during physiological stress is not known. In the present study, we tested the hypothesis that BAT-derived GDF15 is required to regulate cold-induced thermogenesis and energy homeostasis in high-fat fed mice. To test this hypothesis, we generated mice selectively lacking GDF15 in thermogenic adipocytes (brown and beige) (GDF15 BKO). GDF15 BKO male and female mice had normal body weight, body composition and glucose homeostasis under baseline conditions. In response to 4 hours of cold exposure following fasting, the decline in core body temperature in GDF15 BKO female mice was similar to that observed in their wild type (WT) counterparts. Conversely, GDF15 BKO male mice became hypothermic. Surprisingly, after 12 weeks on a high-fat diet (HFD), GDF15 BKO female mice weighed significantly less and had reduced fat mass relative to their WT controls, while male mice had increased body weight and fat accumulation. Furthermore, resistance to DIO in female mice was associated with increased energy expenditure, while food intake and locomotor activity were unchanged. When ovariectomized, GDF15 BKO females experienced similar weight gain and fat accumulation as WT mice and no longer had increased energy expenditure. Of note, estrogen receptor alpha ( Esr1) expression in BAT was significantly repressed in GDF15 BKO male mice fed high-fat diet but was maintained in female mice relative to their respective WT controls. Taken together, our data suggest that GDF15 expression in BAT is dispensable for thermoregulation in female mice but is required to regulate core body temperature in males. Furthermore, while GDF15 BKO male mice are susceptible, female mice are resistant to DIO via mechanisms likely involving sex hormones and increased resting metabolic rates. NIH DK125405 to R.O.P.; Diabetes Research Training Program funded by the NIH (T32 DK112751) to JJ and by the NIH 1R25GM116686 to L.M.G.P. 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.

The prostaglandin E2 EP3 receptor has disparate effects on islet insulin secretion and content in β-cells in a high-fat diet-induced mouse model of obesity.

Signaling through prostaglandin E2 EP3 receptor (EP3) actively contributes to the β-cell dysfunction of type 2 diabetes (T2D). In T2D models, full-body EP3 knockout mice have a significantly worse metabolic phenotype than wild-type controls due to hyperphagia and severe insulin resistance resulting from loss of EP3 in extra-pancreatic tissues, masking any potential beneficial effects of EP3 loss in the β cell. We hypothesized β-cell-specific EP3 knockout (EP3 βKO) mice would be protected from high-fat diet (HFD)-induced glucose intolerance, phenocopying mice lacking the EP3 effector, Gαz, which is much more limited in its tissue distribution. When fed a HFD for 16 wk, though, EP3 βKO mice were partially, but not fully, protected from glucose intolerance. In addition, exendin-4, an analog of the incretin hormone, glucagon-like peptide 1, more strongly potentiated glucose-stimulated insulin secretion in islets from both control diet- and HFD-fed EP3 βKO mice as compared with wild-type controls, with no effect of β-cell-specific EP3 loss on islet insulin content or markers of replication and survival. However, after 26 wk of diet feeding, islets from both control diet- and HFD-fed EP3 βKO mice secreted significantly less insulin as a percent of content in response to stimulatory glucose, with or without exendin-4, with elevated total insulin content unrelated to markers of β-cell replication and survival, revealing severe β-cell dysfunction. Our results suggest that EP3 serves a critical role in temporally regulating β-cell function along the progression to T2D and that there exist Gαz-independent mechanisms behind its effects.NEW & NOTEWORTHY The EP3 receptor is a strong inhibitor of β-cell function and replication, suggesting it as a potential therapeutic target for the disease. Yet, EP3 has protective roles in extrapancreatic tissues. To address this, we designed β-cell-specific EP3 knockout mice and subjected them to high-fat diet feeding to induce glucose intolerance. The negative metabolic phenotype of full-body knockout mice was ablated, and EP3 loss improved glucose tolerance, with converse effects on islet insulin secretion and content.

Morroniside delays the progression of non-alcoholic steatohepatitis by promoting AMPK-mediated lipophagy

BackgroundNon-alcoholic steatohepatitis (NASH), the inflammatory subtype in the progression of non-alcoholic fatty liver disease, is becoming a serious burden threatening human health, but no approved medication is available to date. Mononoside is a natural active substance derived from Cornus officinalis and has been confirmed to have great potential in regulating lipid metabolism in our previous studies. However, its effect and mechanism to inhibit the progression of NASH remains unclear. PurposeOur work aimed to explore the action of mononoside in delaying the progression of NASH and its regulatory mechanisms from the perspective of regulating lipophagy. Methods and resultsMale C57BL/6 mice were fed with a high-fat and high-fructose diet for 16 weeks to establish a NASH mouse model. After 8 weeks of high-fat and high-fructose feeding, these mice were administrated with different doses of morroniside. H&E staining, ORO staining, Masson staining, RNA-seq, immunoblotting, and immunofluorescence were performed to determine the effects and molecular mechanisms of morroniside in delaying the progression of NASH. In this study, we found that morroniside is effective in attenuating hepatic lipid metabolism disorders and inflammatory response activation, thereby limiting the progression from simple fatty liver to NASH in high-fat and high-fructose diet-fed mice. Mechanistically, we identified AMPK signaling as the key molecular pathway for the positive efficacy of morroniside by transcriptome sequencing. Our results revealed that morroniside maintained hepatic lipid metabolism homeostasis and inhibited NLRP3 inflammasome activation by promoting AMPKα phosphorylation-mediated lipophagy and fatty acid oxidation. Consistent results were observed in palmitic acid-treated cell models. Of particular note, silencing AMPKα both in vivo and in vitro reversed morroniside-induced lipophagy flux enhancement and NLRP3 inflammasome inhibition, emphasizing the critical role of AMPKα activation in the effect of morroniside in inhibiting NASH progression. ConclusionIn summary, the present study provides strong evidence for the first time that morroniside inhibits NASH progression by promoting AMPK-dependent lipophagy and inhibiting NLRP3 inflammasome activation, suggesting that morroniside is expected to be a potential molecular entity for the development of therapeutic drugs for NASH.