Days Of High-fat Diet Research Articles

Effect of high-fat diet and morning or evening exercise on lipoprotein subfraction profiles: secondary analysis of a randomised trial

We investigated the effect of a high-fat diet (HFD) on serum lipid subfractions in men with overweight/obesity and determined whether morning or evening exercise affected these lipid profiles. In a three-armed randomised trial, 24 men consumed an HFD for 11 days. One group of participants did not exercise (n = 8, CONTROL), one group trained at 06:30 h (n = 8, EXam), and one group at 18:30 h (n = 8, EXpm) on days 6–10. We assessed the effects of HFD and exercise training on circulating lipoprotein subclass profiles using NMR spectroscopy. Five days of HFD induced substantial perturbations in fasting lipid subfraction profiles, with changes in 31/100 subfraction variables (adjusted p values [q] < 0.05). Exercise training induced a systematic change in lipid subfraction profiles, with little overall difference between EXam and EXpm. Compared with CONTROL, exercise training reduced serum concentrations of > 20% of fasting lipid subfractions. EXpm reduced fasting cholesterol concentrations in three LDL subfractions by ⁓30%, while EXam only reduced concentration in the largest LDL particles by 19% (all q < 0.05). Lipid subfraction profiles changed markedly after 5 days HFD in men with overweight/obesity. Both morning and evening exercise training impacted subfraction profiles compared with no exercise.

CD8+ T cells contribute to diet-induced memory deficits in aged male rats

We have previously shown that short-term (3-day) high fat diet (HFD) consumption induces a neuroinflammatory response and subsequent impairment of long-term memory in aged, but not young adult, male rats. However, the immune cell phenotypes driving this proinflammatory response are not well understood. Previously, we showed that microglia isolated from young and aged rats fed a HFD express similar levels of priming and proinflammatory transcripts, suggesting that additional factors may drive the exaggerated neuroinflammatory response selectively observed in aged HFD-fed rats. It is established that T cells infiltrate both the young and especially the aged central nervous system (CNS) and contribute to immune surveillance of the parenchyma. Thus, we investigated the modulating role of short-term HFD on T cell presence in the CNS in aged rats using bulk RNA sequencing and flow cytometry. RNA sequencing results indicate that aging and HFD altered the expression of genes and signaling pathways associated with T cell signaling, immune cell trafficking, and neuroinflammation. Moreover, flow cytometry data showed that aging alone increased CD4+ and CD8+ T cell presence in the brain and that CD8+, but not CD4+, T cells were further increased in aged rats fed a HFD. Based on these data, we selectively depleted circulating CD8+ T cells via an intravenous injection of an anti-CD8 antibody in aged rats prior to 3 days of HFD to infer the functional role these cells may be playing in long-term memory and neuroinflammation. Results indicate that peripheral depletion of CD8+ T cells lowered hippocampal cytokine levels and prevented the HFD-induced i) increase in brain CD8+ T cells, ii) memory impairment, and iii) alterations in pre- and post-synaptic structures in the hippocampus and amygdala. Together, these data indicate a substantial role for CD8+ T cells in mediating diet-induced memory impairments in aged male rats.

PSUN134 Loss of Glp-1r Signaling in the β-Cell Impairs Adaptive Proliferation and Insulin Secretion

Abstract Type 2 diabetes mellitus is characterized by insulin resistance and loss of pancreatic b-cell mass. b-cells are located in the pancreatic islets and secrete insulin. Though many therapies exist that address insulin resistance and to augment b-cell insulin secretion, there is a critical need to find therapies to preserve b-cell mass in order to decrease the incidence and severity of diabetes. In non-diabetic obesity, an early adaptive response to insulin resistance is increased b-cell proliferation. This compensatory mechanism leads to increased b-cell mass and increased insulin secretion from b-cells. This increase in b-cell mass is seen in as little as 4 days of high fat diet (HFD) feeding in murine models. A promising therapeutic for the preservation of b-cell mass is glucagon-like peptide-1 receptor (Glp-1r) agonists. The ability of GLP-1 to stimulate b-cell proliferation and inhibit apoptosis is largely based on studies using pharmacologic treatment, but the importance of GLP-1 in b-cell mass regulation in normal physiology or pathophysiology has not been well studied. Notably, GLP-1 is secreted from alpha cells in the local islet environment and this paracrine signaling pathway is important for islet function. The goal of this work is to investigate the contribution of b-cell Glp-1r signaling to b-cell mass regulation in the metabolic stress condition of a one-week HFD. We hypothesize that b-cell Glp-1r signaling is necessary for the compensatory mechanisms needed to maintain glucose homeostasis during metabolic stress conditions and that lack of b-cell Glp-1r will lead to decreased proliferation of b-cells. Understanding the role of β-cell Glp-1r signaling in adaptive b-cell mass expansion will allow for development of new strategies to augment β-cell mass in type 2 diabetes. We used a newly generated murine model with a b-cell specific knockout of Glp-1r, where the Ins1-Cre knock-in transgene drives recombination in b-cells. Glp-1r fl/fl mice (WT) and Glp-1r fl/fl – Ins1Cre mice (KO) were fed a HFD for one week. There was a trend toward elevated fasting (171+/-29 mg/dl vs 205+/-36 mg/dl, p=0.0475, n=9) and non-fasting blood glucose (195+/-24 mg/dl vs 216+/-40 mg/dl, p=0.0537, n=18) and impaired glucose tolerance in the KO mice. Notably, we found that insulin secretion in response to intraperitoneal glucose is impaired in KO mice. KO mice have a blunted proliferation response to a 1-week HFD stress, as measured by Ki67 mRNA levels (1.5-fold induction of Ki67 in WT vs. 0.6-fold induction in KO, p=0.0167, n=8-10). b-cell proliferation will also be measured by immunofluorescent image analysis of whole pancreas sections. These data suggest there is a critical role for b-cell Glp-1r signaling in the early proliferative response of b-cells in response to metabolic stress. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Chrysin reduces hypercholesterolemia-mediated atherosclerosis through modulating oxidative stress, microflora, and apoptosis in experimental rats.

Chrysin (Chy) is known for various biological proprieties such as inhibitory effects on inflammation, cancer, oxidative stress, aging, and atherosclerosis. However, the hypolipidemic activity of Chy and its mechanistic action remains unclear in cardiovascular diseases (CVD). In this study, we focused on the hypolipidemic proprieties of Chy in hypercholesterolemia-induced atherosclerosis. Male Wistar rats (150-220 g) were divided into four groups as follows: Group I control was fed with standard laboratory chow. Rats in Group II were fed a high-fat diet (HFD) for 60 days. After 60 days of HFD, Group III rats received Chy (100 mg/kg body weight); Group IV rats received Atorvastatin (Atv; 10mg/kg body weight) for 30 days. Biochemical studies showed Chy, Atv treatment decreased the activities of liver marker enzymes and the levels of Reactive Oxygen Species (ROS) and lipid profile. Gene expression analysis on nuclear factor erythroid 2-related factor 2 (Nrf2) and its regulated genes were significantly reduced in the intestine and increased in the aorta by Chy and Atv. Gut microbial species such as Bacteroidetes, Lactobacillus, Enterococcus, and Clostridium leptum copy numbers were significantly increased by Chy and Atv treatment. In addition, Chy and Atv modulated the expression of inflammatory genes including TLR4, TNFα, NLRP3, and IL-17 in the aorta and intestine compared with hypercholesterolemic control rats. Chy and Atv effectively increased the caspase-3 mRNA expression in the intestine, but these decreased in the aorta. The present study concludes that by reducing oxidative stress and increasing gut microbial colonization, Chy may provide an effective therapeutic approach for the prevention of hypercholesterolemia-mediated atherosclerosis. PRACTICAL APPLICATIONS: Our study focused on a therapeutic model representing the clinical presentation of atherosclerosis in humans. Statins are commonly used in the treatment of cardiovascular complications, patients with hypercholesterolemia face difficulties in the continuation of statin therapy. The reason for statin discontinuation has been associated with toxicological effects. It is necessary to investigate the potentiality of the natural compound as an alternative medicine to statin with fewer side effects. The main theme of our study is to compare the therapeutic potential of Chy and Atv. Chy is a natural bioflavonoid that could be considered as an alternative medicinal compound to statins and to avoid toxicity problems associated with statins. Chy is a bioflavonoid present in Passiflora caerulea (blue passion flower), Oroxylum indicum (Indian trumpet flower), Pelargonium crispum, propolis, and honey. Consuming Chy-rich foods will reduce hypercholesterolemia-mediated cardiovascular complications. Overall, the present studies provided a key to developing bioactive compounds-based foods for CVD patients.

Inherited Metabolic Memory of High‐Fat Diet Impairs Testicular Fatty Acid Content and Sperm Parameters

Exposure to a high-fat diet (HFD) from early-life is associated with a testicular metabolic signature link to abnormal sperm parameters up to two generations after exposure in mice. Hereby, this study describes a testicular lipid signature associate with "inherited metabolic memory" of exposure to HFD, persisting up to two generations in mice. Diet-challenged mice (n = 36) are randomly fed after weaning with standard chow (CTRL); HFD for 200 days or transient HFD (HFDt ) (60 days of HFD + 140 days of standard chow). Subsequent generations (36 mice per generation) are fed with chow diet. Mice are euthanized 200 days post-weaning. Glucose homeostasis, serum hormones, testicular bioenergetics, and antioxidant enzyme activity are evaluated. Testicular lipid-related metabolites and fatty acids are characterized by 1 H-NMR and GC-MS. Sons of HFD display impaired choline metabolism, mitochondrial activity, and antioxidant defenses, while grandsons show a shift in testicular ω3/ω6 ratio towards a pro-inflammatory environment. Grandsons of HFDt raise 3-hydroxybutyrate levels with possible implications to testicular insulin resistance. Sperm counts decrease in grandsons of HFD-exposed mice, regardless of the duration of exposure. HFD-induced "inherited metabolic memory" alters testicular fatty acid metabolism with consequences to sperm parameters up to two generations.

Hippocampal Function Is Impaired by a Short-Term High-Fat Diet in Mice: Increased Blood-Brain Barrier Permeability and Neuroinflammation as Triggering Events.

Worldwide, and especially in Western civilizations, most of the staple diets contain high amounts of fat and refined carbohydrates, leading to an increasing number of obese individuals. In addition to inducing metabolic disorders, energy dense food intake has been suggested to impair brain functions such as cognition and mood control. Here we demonstrate an impaired memory function already 3 days after the start of a high-fat diet (HFD) exposure, and depressive-like behavior, in the tail suspension test, after 5 days. These changes were followed by reduced synaptic density, changes in mitochondrial function and astrocyte activation in the hippocampus. Preceding or coinciding with the behavioral changes, we found an induction of the proinflammatory cytokines TNF-α and IL-6 and an increased permeability of the blood–brain barrier (BBB), in the hippocampus. Finally, in mice treated with a TNF-α inhibitor, the behavioral and BBB alterations caused by HFD-feeding were mitigated suggesting that inflammatory signaling was critical for the changes. In summary, our findings suggest that HFD rapidly triggers hippocampal dysfunction associated with BBB disruption and neuroinflammation, promoting a progressive breakdown of synaptic and metabolic function. In addition to elucidating the link between diet and cognitive function, our results might be relevant for the comprehension of the neurodegenerative process.

The effect of morning vs evening exercise training on glycaemic control and serum metabolites in overweight/obese men: a randomised trial

Aims/hypothesisWe determined whether the time of day of exercise training (morning vs evening) would modulate the effects of consumption of a high-fat diet (HFD) on glycaemic control, whole-body health markers and serum metabolomics.MethodsIn this three-armed parallel-group randomised trial undertaken at a university in Melbourne, Australia, overweight/obese men consumed an HFD (65% of energy from fat) for 11 consecutive days. Participants were recruited via social media and community advertisements. Eligibility criteria for participation were male sex, age 30–45 years, BMI 27.0–35.0 kg/m2 and sedentary lifestyle. The main exclusion criteria were known CVD or type 2 diabetes, taking prescription medications, and shift-work. After 5 days, participants were allocated using a computer random generator to either exercise in the morning (06:30 hours), exercise in the evening (18:30 hours) or no exercise for the subsequent 5 days. Participants and researchers were not blinded to group assignment. Changes in serum metabolites, circulating lipids, cardiorespiratory fitness, BP, and glycaemic control (from continuous glucose monitoring) were compared between groups.ResultsTwenty-five participants were randomised (morning exercise n = 9; evening exercise n = 8; no exercise n = 8) and 24 participants completed the study and were included in analyses (n = 8 per group). Five days of HFD induced marked perturbations in serum metabolites related to lipid and amino acid metabolism. Exercise training had a smaller impact than the HFD on changes in circulating metabolites, and only exercise undertaken in the evening was able to partly reverse some of the HFD-induced changes in metabolomic profiles. Twenty-four-hour glucose concentrations were lower after 5 days of HFD compared with the participants’ habitual diet (5.3 ± 0.4 vs 5.6 ± 0.4 mmol/l, p = 0.001). There were no significant changes in 24 h glucose concentrations for either exercise group but lower nocturnal glucose levels were observed in participants who trained in the evening, compared with when they consumed the HFD alone (4.9 ± 0.4 vs 5.3 ± 0.3 mmol/l, p = 0.04). Compared with the no-exercise group, peak oxygen uptake improved after both morning (estimated effect 1.3 ml min−1 kg−1 [95% CI 0.5, 2.0], p = 0.003) and evening exercise (estimated effect 1.4 ml min−1 kg−1 [95% CI 0.6, 2.2], p = 0.001). Fasting blood glucose, insulin, cholesterol, triacylglycerol and LDL-cholesterol concentrations decreased only in participants allocated to evening exercise training. There were no unintended or adverse effects.Conclusions/interpretationA short-term HFD in overweight/obese men induced substantial alterations in lipid- and amino acid-related serum metabolites. Improvements in cardiorespiratory fitness were similar regardless of the time of day of exercise training. However, improvements in glycaemic control and partial reversal of HFD-induced changes in metabolic profiles were only observed when participants exercise trained in the evening.Trial registrationanzctr.org.au registration no. ACTRN12617000304336.FundingThis study was funded by the Novo Nordisk Foundation (NNF14OC0011493).Graphical abstract

CD11c-MHC2low Macrophages Are a New Inflammatory and Dynamic Subset in Murine Adipose Tissue.

BackgroundThe prevalence of obesity is rising and leads to increased morbidity and mortality. Adipose tissue inflammation, due to accumulation and activation of adipose tissue macrophages (ATMs), is a key driver of this phenomenon. Macrophages are heterogeneous cells, adapting quickly to the microenvironment, resulting in so-called M1 or M2 macrophages. In this study, we describe the dynamics and inflammatory properties of a newly identified ATM subset in obese mice.MethodsLDLR-/- mice received a high fat diet (HFD) for 5 weeks or 16 weeks to induce obesity. Adipose tissues were isolated and immune cell subsets were analyzed with flow cytometry or microarray analysis. Bone marrow transplantation (BMT) using CD45.1 and CD45.2 LDLR-/- mice was performed to determine ATM origin.ResultsUpon HFD, there is a massive increase of ATM subsets in the adipose tissue. CD11c−M2 ATMs could be subdivided based on their MHC2 expression into CD11c−MHC2high ATMs and previously unidentified CD11c−MHC2low ATMs. CD11c−MHC2low ATMs accumulated very rapidly after 10 days of HFD, after which they increased even further with prolonged HFD. Microarray data showed that CD11c−MHC2low ATMs resembled CD11c−MHC2high ATMs in the steady state, but became more inflammatory during development of obesity. In vitro stimulation of bone marrow-derived macrophages with palmitate, abundantly present in HFD, resulted in the induction of the CD11c−MHC2low phenotype.ConclusionsAmong M2 macrophages, a novel pro-inflammatory subset of macrophages was found based on their low level of MHC2 expression. This subset may play a role in the development of adipose tissue inflammation.

Serum endotoxin, gut permeability and skeletal muscle metabolic adaptations following a short term high fat diet in humans

BackgroundOur previous work demonstrated that a short-term high fat diet (HFD) increased fasting serum endotoxin, altered postprandial excursions of serum endotoxin, and led to metabolic and transcriptional responses in skeletal muscle in young, healthy male humans. PurposeThe purpose of the present study was to determine if a short-term high fat diet: 1) increases intestinal permeability and, in turn, fasting endotoxin concentrations and 2) decreases postprandial skeletal muscle fat oxidation. MethodsThirteen normal weight young adult males (BMI 23.1 ± 0.8 kg/m2, age 22.2 ± 0.4 years) were fed a control diet (55% carbohydrate, 30% fat, 9% of which was saturated, 15% protein) for two weeks, followed by 5 days of an isocaloric HFD (30% carbohydrate, 55% fat, 25% of which was saturated, 15% protein, isocaloric to the control diet). Intestinal permeability (via four sugar probe test) was assessed in the fasting state. Both before and after the HFD, a high fat meal challenge (HFM, 820 kcal, 25% carbohydrate, 63% fat, 26% of which was saturated, and 12% protein) was administered. After an overnight fast, blood samples were collected before and every hour for 4 h after the HFM to assess endotoxin, and other serum blood measures. Muscle biopsies were obtained from the vastus lateralis before and 4 h after the HFM in order to assess substrate oxidation (glucose, fatty acid and pyruvate) using radiolabeled techniques. Insulin sensitivity was assessed via intravenous glucose tolerance test. Intestinal permeability, blood samples and muscle biopsies were assessed in the same manner before and following the HFD. Main findingsIntestinal permeability was not affected by HFD (p > 0.05), but fasting endotoxin increased two fold following the HFD (p = 0.04). Glucose oxidation and fatty acid oxidation in skeletal muscle homogenates significantly increased after the HFM before the HFD (+97%, and +106% respectively) but declined after the HFM following 5 days of the HFD (−24% and +16% respectively). Fatty acid suppressibility of pyruvate oxidation increased significantly after the HFM (+32%) but this physiological effect was abolished following 5 days of the HFD (+7%). Insulin sensitivity did not change following the HFD. ConclusionThese findings demonstrate that in healthy young men, consuming an isocaloric HFD for 5 days increases fasting endotoxin, independent of changes in gut permeability. These changes in endotoxin are accompanied by a broad effect on skeletal muscle substrate metabolism including increases in postprandial fat oxidation. Importantly, the latter occurs independent of changes in body weight and whole-body insulin sensitivity.

High-fat Overfeeding Does Not Exacerbate Rapid Changes in Forearm Glucose and Fatty Acid Balance During Immobilization.

Physical inactivity and high-fat overfeeding have been shown to independently induce insulin resistance. Establish the contribution of muscle disuse and lipid availability to the development of inactivity-induced insulin resistance. 20 healthy males underwent 7 days of forearm cast immobilization combined with a fully controlled eucaloric diet (n = 10, age 23 ± 2 yr, body mass index [BMI] 23.8 ± 1.0 kg·m-2) or a high-fat diet (HFD) providing 50% excess energy from fat (high-fat diet, n = 10, age 23 ± 2 yr, BMI 22.4 ± 0.8 kg·m-2). Prior to casting and following 2 and 7 days of immobilization, forearm glucose uptake (FGU) and nonesterified fatty acid (NEFA) balance were assessed using the arterialized venous-deep venous (AV-V) forearm balance method following ingestion of a mixed macronutrient drink. 7 days of HFD increased body weight by 0.9 ± 0.2 kg (P = 0.002), but did not alter fasting, arterialized whole-blood glucose and serum insulin concentrations or the associated homeostatic model assessment of insulin resistance or Matsuda indices. Two and 7 days of forearm immobilization led to a 40 ± 7% and 52 ± 7% decrease in FGU, respectively (P < 0.001), with no difference between day 2 and 7 and no effect of HFD. Forearm NEFA balance tended to increase following 2 and 7 days of immobilization (P = 0.095). Forearm immobilization leads to a rapid and substantial decrease in FGU, which is accompanied by an increase in forearm NEFA balance but is not exacerbated by excess dietary fat intake. Altogether, our data suggest that disuse-induced insulin resistance of glucose metabolism occurs as a physiological adaptation in response to the removal of muscle contraction.

Intermittent fasting improves metabolic flexibility in short-term high-fat diet-fed mice.

Four days of high-fat diet (HFD) feeding are sufficient to induce glucose intolerance and hepatic steatosis in mice. While prolonged HFD-induced metabolic complications are partly mediated by increased food intake during the light (inactive) phase, such a link has not yet been established in short-term HFD-fed mice. Herein, we hypothesized that a short bout of HFD desynchronizes feeding behavior, thereby contributing to glucose intolerance and hepatic steatosis. To this end, 12-wk-old C57BL/6J littermates were fed a HFD for 4 days either ad libitum or intermittently. Intermittent-fed mice were fasted for 8 h during their inactive phase. Initiation of HFD led to an immediate increase in food intake already during the first light phase. Moreover, glucose tolerance was significantly impaired in ad libitum- but not in intermittent HFD-fed mice, indicating that desynchronized feeding behavior contributes to short-term HFD-induced glucose intolerance. Of note, overall food intake was similar between the groups, as was body weight. However, intermittent HFD-fed mice revealed higher fat depot weights. Phosphorylation of hormone sensitivity lipase and free fatty acid release from isolated adipocytes were significantly elevated, suggesting increased lipolysis in intermittent HFD-fed mice. Moreover, hepatic mRNA expression of lipogenetic enzymes and liver triglyceride levels were significantly increased in intermittent HFD-fed mice. Importantly, food deprivation decreased respiratory exchange ratio promptly in intermittent- but not in ad libitum HFD-fed mice. In conclusion, retaining a normal feeding pattern prevented HFD-induced impairment of metabolic flexibility in short-term HFD-fed mice.

A single day of high-fat diet feeding induces lipid accumulation and insulin resistance in brown adipose tissue in mice

Brown adipose tissue (BAT) catabolizes glucose and fatty acids to produce heat and thereby contributes to energy expenditure. Long-term high-fat diet (HFD) feeding results in so-called 'whitening' of BAT characterized by increased lipid deposition, mitochondrial dysfunction, and reduced fat oxidation. The aim of the current study was to unravel the rate and related mechanisms by which HFD induces BAT whitening and insulin resistance. Wild-type mice were fed a HFD for 0, 1, 3, or 7 days. Within 1 day of HFD, BAT weight and lipid content were increased. HFD also immediately reduced insulin-stimulated glucose uptake by BAT, indicating rapid induction of insulin resistance. This was accompanied by a tendency toward a reduced uptake of triglyceride-derived fatty acids by BAT. Mitochondrial mass and Ucp1 expression were unaltered, whereas after 3 days of HFD, markers of mitochondrial dynamics suggested induction of a more fused mitochondrial network. Additionally, HFD also increased macrophage markers in BAT after 3 days of HFD. Counterintuitively, the switch to HFD was accompanied by an acute rise in core body temperature. We showed that a single day of HFD feeding is sufficient to induce the first signs of whitening and insulin resistance in BAT, which reduces the uptake of glucose and triglyceride-derived fatty acids. BAT whitening and insulin resistance are likely sustained by reduced mitochondrial oxidation due to changes in mitochondrial dynamics and macrophage infiltration, respectively. Likely, the switch to HFD swiftly induces thermogenesis in other metabolic organs, which allows attenuation of BAT thermogenesis.

Decrement in resting and insulin-stimulated soleus muscle mitochondrial respiration is an early event in diet-induced obesity in mice.

What is the central question of this study? What are the temporal responses of mitochondrial respiration and mitochondrial responsivity to insulin in soleus muscle fibres from mice during the development of obesity and insulin resistance? What is the main finding and its importance? Short- and long-term feeding with a high-fat diet markedly reduced soleus mitochondrial respiration and mitochondrial responsivity to insulin before any change in glycogen synthesis. Muscle glycogen synthesis and whole-body insulin resistance were present after 14 and 28 days, respectively. Our findings highlight the plasticity of mitochondria during the development of obesity and insulin resistance. Recently, significant attention has been given to the role of muscle mitochondrial function in the development of insulin resistance associated with obesity. Our aim was to investigate temporal alterations in mitochondrial respiration, H2 O2 emission and mitochondrial responsivity to insulin in permeabilized skeletal muscle fibres during the development of obesity in mice. Male Swiss mice (5-6weeks old) were fed with a high-fat diet (60% calories from fat) or standard diet for 7, 14 or 28 days to induce obesity and insulin resistance. Diet-induced obese (DIO) mice presented with reduced glucose tolerance and hyperinsulinaemia after 7days of high-fat diet. After 14days, the expected increase in muscle glycogen content after systemic injection of glucose and insulin was not observed in DIO mice. At 28days, blood glucose decay after insulin injection was significantly impaired. ComplexI (pyruvate+malate) and II (succinate)-linked respiration and oxidative phosphorylation (ADP) were decreased after 7 days of high-fat diet and remained low in DIO mice after 14 and 28 days of treatment. Moreover, mitochondria from DIO mice were incapable of increasing respiratory coupling and ADP responsivity after insulin stimulation in all observed periods. Markers of mitochondrial content were reduced only after 28days of treatment. The mitochondrial H2 O2 emission profile varied during the time course of DIO, with a reduction of H2 O2 emission in the early stages of DIO and an increased emission after 28 days of treatment. Our data demonstrate that DIO promotes transitory alterations in mitochondrial physiology during the early and late stages of insulin resistance related to obesity.

CPT1C in the ventromedial nucleus of the hypothalamus is necessary for brown fat thermogenesis activation in obesity

ObjectiveCarnitine palmitoyltransferase 1C (CPT1C) is implicated in central regulation of energy homeostasis. Our aim was to investigate whether CPT1C in the ventromedial nucleus of the hypothalamus (VMH) is involved in the activation of brown adipose tissue (BAT) thermogenesis in the early stages of diet-induced obesity. MethodsCPT1C KO and wild type (WT) mice were exposed to short-term high-fat (HF) diet feeding or to intracerebroventricular leptin administration and BAT thermogenesis activation was evaluated. Body weight, adiposity, food intake, and leptinemia were also assayed. ResultsUnder 7 days of HF diet, WT mice showed a maximum activation peak of BAT thermogenesis that counteracted obesity development, whereas this activation was impaired in CPT1C KO mice. KO animals evidenced higher body weight, adiposity, hyperleptinemia, ER stress, and disrupted hypothalamic leptin signaling. Leptin-induced BAT thermogenesis was abolished in KO mice. These results indicate an earlier onset leptin resistance in CPT1C KO mice. Since AMPK in the VMH is crucial in the regulation of BAT thermogenesis, we analyzed if CPT1C was a downstream factor of this pathway. Genetic inactivation of AMPK within the VMH was unable to induce BAT thermogenesis and body weight loss in KO mice, indicating that CPT1C is likely downstream AMPK in the central mechanism modulating thermogenesis within the VMH. Quite opposite, the expression of CPT1C in the VMH restored the phenotype. ConclusionCPT1C is necessary for the activation of BAT thermogenesis driven by leptin, HF diet exposure, and AMPK inhibition within the VMH. This study underscores the importance of CPT1C in the activation of BAT thermogenesis to counteract diet-induced obesity.

Evidence against Pathway-Selective Hepatic Insulin Resistance in Mice

Insulin suppresses hepatic glucose production and increases hepatic de novo lipogenesis (DNL). Paradoxically, hepatic DNL remains elevated in insulin-resistant subjects, leading to the hypothesis that hepatic insulin resistance is pathway-selective. Prior studies of DNL in hepatic insulin resistance are complicated by confounders, such as use of markedly unphysiologic animal models or comparison of animals on different diets and thus different availability of DNL precursors. We measured DNL in InsrT1150A knockin (KI) mice, a strain protected from diacylglycerol-mediated hepatic insulin resistance, and in littermate controls. Diets were matched: 60% high fat diet (HFD) with 1% dextrose in drinking water. After two days of fat-feeding, before the development of significant insulin resistance, KI and WT mice displayed similar rates of DNL (KI 24.3% ± 3.6; WT 22.2% ± 3.5). After 9 days of HFD, when WT but not KI mice have developed hepatic insulin resistance, rates of DNL were reduced in WT mice but preserved in KI mice (KI 16.4% ± 2.4; WT 7.4% ± 1.3; P &amp;lt; 0.01). After 4 weeks of HFD, with the development of skeletal muscle resistance, rates of DNL increased in WT mice to reach those observed in KI mice (KI 19.3% ± 2.6; WT 15.9% ± 2.3). Consistent with the insulin-resistant phenotype, Srebp-1c cleavage was reduced in the setting of hepatic insulin resistance in WT mice; this effect was attenuated in KI mice. The Srebp-regulated lipogenic proteins Fasn and Scd1 were both reduced in 9d HFD fed livers regardless of genotype; at 4 weeks, protein abundance remained suppressed in WT mice but was restored in KI mice. Pklr, a protein associated with DNL but not regulated by Srebp, was unaffected by HFD-induced hepatic insulin resistance. Conclusion: Regulation of DNL is subject to lipid-induced hepatic insulin resistance, challenging the selective hepatic insulin resistance hypothesis. Increased DNL seen in insulin resistant subjects may be due to hyperinsulinemia and diversion of substrate from the insulin resistant periphery. Disclosure D.F. Vatner: None. M.C. Petersen: None. X. Li: None. J.C. Rogers: None. G. Cline: None. V. Samuel: None. G.I. Shulman: Advisory Panel; Self; AstraZeneca, Janssen Research &amp; Development, Merck &amp; Co., Inc., Novo Nordisk Inc.. Research Support; Self; Gilead Sciences, Inc..

Inhibition of Adipose Tissue Angiogenesis Prevents Rebound Weight Regain after Calorie Restriction Independent of Hypothalamic Melanocortin System in Obese Mice Fed a High-Fat Diet

Prevention of rebound weight gain after dieting is essential to treat obesity. However, its attempts have been unsuccessful and the underlying mechanism remains unclear. In this study, we sought to investigate the role of adipose tissue (AT) vasculature in rebound weight gain after calorie restriction in obese mice fed a high-fat diet (HFD). Obese mice were randomly assigned to 4 groups including mice fed HFD ad libitum (CON), mice under 40% calorie restriction for 5 weeks (CR), 3 days of HFD ad libitum after CR (CRAL), or CRAL treated with TNP-470, an angiogenesis inhibitor (TNP). We compared parameters of energy balance, AT morphometry and remodeling, and hypothalamic neuropeptides gene expression among the groups. Rebound weight gain and food intake were significantly lower and the level of brown AT UCP-1 gene expression was higher in TNP group than CRAL group. Fat mass was significantly lower in TNP group than CRAL group and it was similar to CR group while lean mass was not different between TNP and CRAL groups. Notably, the CD31-positive area was not different in AT between CON, CR, and CRAL groups, indicating that AT vasculature was maintained independently of nutritional status. However, that tended to be lower in AT of TNP group compared to other groups, implicating that inhibition of AT vasculature might be crucial to suppress rebound weight gain after calorie restriction. Consistently, circulating leptin levels were significantly lower in TNP group than CRAL group. However, the pattern of hypothalamic neuropeptides gene expression was different from the changes in food intake among the groups, suggesting an existence of novel regulatory signals independent of melanocortin system. Taken together, these results suggested a critical role of AT vasculature in regulating rebound weight gain and hyperphagia after calorie restriction independent of hypothalamic melanocortin system. Disclosure H. Lee: None. M. Song: None. N. Ha: None. B. Jin: None. S. Choi: None. D. Kim: None.

Frontline Science: Rapid adipose tissue expansion triggers unique proliferation and lipid accumulation profiles in adipose tissue macrophages.

Obesity-related changes in adipose tissue leukocytes, in particular adipose tissue macrophages (ATMs) and dendritic cells (ATDCs), are implicated in metabolic inflammation, insulin resistance, and altered regulation of adipocyte function. We evaluated stromal cell and white adipose tissue (WAT) expansion dynamics with high fat diet (HFD) feeding for 3-56 days, quantifying ATMs, ATDCs, endothelial cells (ECs), and preadipocytes (PAs) in visceral epididymal WAT and subcutaneous inguinal WAT. To better understand mechanisms of the early response to obesity, we evaluated ATM proliferation and lipid accumulation. ATMs, ATDCs, and ECs increased with rapid WAT expansion, with ATMs derived primarily from a CCR2-independent resident population. WAT expansion stimulated proliferation in resident ATMs and ECs, but not CD11c+ ATMs or ATDCs. ATM proliferation was unperturbed in Csf2- and Rag1-deficient mice with WAT expansion. Additionally, ATM apoptosis decreased with WAT expansion, and proliferation and apoptosis reverted to baseline with weight loss. Adipocytes reached maximal hypertrophy at 28 days of HFD, coinciding with a plateau in resident ATM accumulation and the appearance of lipid-laden CD11c+ ATMs in visceral epididymal WAT. ATM increases were proportional to tissue expansion and adipocyte hypertrophy, supporting adipocyte-mediated regulation of resident ATMs. The appearance of lipid-laden CD11c+ ATMs at peak adipocyte size supports a role in responding to ectopic lipid accumulation within adipose tissue. In contrast, ATDCs increase independently of proliferation and may be derived from circulating precursors. These changes precede and establish the setting in which large-scale adipose tissue infiltration of CD11c+ ATMs, inflammation, and adipose tissue dysfunction contributes to insulin resistance.

Intact glucose uptake despite deteriorating signaling in adipocytes with high-fat feeding.

To capture immediate cellular changes during diet-induced expansion of adipocyte cell volume and number, we characterized mature adipocytes during a short-term high-fat diet (HFD) intervention. Male C57BL6/J mice were fed chow diet, and then switched to HFD for 2, 4, 6 or 14 days. Systemic glucose clearance was assessed by glucose tolerance test. Adipose tissue was dissected for RNA-seq and cell size distribution analysis using coulter counting. Insulin response in isolated adipocytes was monitored by glucose uptake assay and Western blotting, and confocal microscopy was used to assess autophagic activity. Switching to HFD was accompanied by an immediate adipocyte size expansion and onset of systemic insulin resistance already after two days, followed by recruitment of new adipocytes. Despite an initially increased non-stimulated and preserved insulin-stimulated glucose uptake, we observed a decreased phosphorylation of insulin receptor substrate-1 (IRS-1) and protein kinase B (PKB). After 14 days of HFD, both the insulin-stimulated phosphorylation of Akt substrate of 160 kDa (AS160) and glucose uptake was blunted. RNA-seq analysis of adipose tissue revealed transient changes in gene expression at day four, including highly significant upregulation of Trp53inp, previously demonstrated to be involved in autophagy. We confirmed increased autophagy, measured as an increased density of LC3-positive puncta and decreased p62 expression after 14 days of HFD. In conclusion, HFD rapidly induced systemic insulin resistance, whereas insulin-stimulated glucose uptake remained intact throughout 6 days of HFD feeding. We also identified autophagy as an early cellular process that potentially influences adipocyte function upon switching to HFD.

Damages and its mechanism of the blood brain barrier in rats with diabetes mellitus with depression

To investigate the expressions of key proteins type IV collagen (CoIV), zonula occludens-1(ZO-1), α-smooth muscle actin(a-SMA) and the mechanisms of the structural injuries of the blood brain barrier in the hippocampus of diabetic rats with depression. After 14 days of high-fat diet, the rats were treated with streptozotocin (STZ, 38 mg/kg, iv). Then, the animals were randomly divided into 2 groups (n=15):the diabetic group and the diabetes mellitus with depression group. The normal rats were randomly divided into 2 groups(n=15):the control group and the depression group. Diabetic group and control group were kept in normal conditions. The diabetes mellitus with depression group and the depression group were treated with chronic unpredictable stress for 28 days. The levels of blood glucose were detected. The behavior changes of rats were evaluated by open-field test and Morris test. The blood brain barrier morphological changes were observed under the electron microscope. The expressions of CoIV, ZO-1 and a-SMA in rat hippocampal blood-brain barrier were detected by immunocytochemistry. Compared with control group, the level of blood glucose was increased,the number of autonomic activity was decreased, the escape latencies were significantly longer in the Morris water maze test, as well as the space exploration times were shortened in the diabetes mellitus with depression group (P<0.05, P<0.01). The endothelial cells of the hippocampus were blurred, the capillary lumen was narrow, and the peripheral glial cells were edema, the expressions of ZO-1 and a-SMA were decreased(P <0.05), while the expression of CoIV was increased(P <0.05). Compared with diabetic group, the number of autonomic activity in the diabetes mellitus with depression group was significantly decreased (P<0.01), the escape latencies were longer (P<0.05), the blood brain barrier capillary lumen was more narrow and the glial cell terminal edema was more obvious, the expression of a-SMA was decreased(P<0.05). The abnormal expressions of ZO-1, CoIV and -SMA, key proteins in the hippocampal blood brain barrier, may be involved in the mechanisms of structural damages of the blood brain barrier in diabetes mellitus with depression.

Metabolomics in Hind limb and Heart Muscle of a Mouse Model after a High-fat Diet

Objective: Dysregulation of FA metabolism in heart muscle is a major problem associated with the metabolic syndrome. Methods: C57Bl/6 mice were fed for 40 days a high-fat diet (+0.25% cholesterol 45% energy from bovine lard). High Performance Thin Layer Chromatography (HPTLC) was used to measure Triacylglycerol’s (TG) and Free Cholesterol (FCh) in hearts and hind limb muscle of mice. With LC-MS techniques we measured Cholesterol esters (ChE), lysophosphatidyl-cholines (LPC), phosphatidylcholine (PC), sphingomyelin (SPM) and Triacylglycerol’s (TG) in hind limb and heart muscle after 40 days of a fatty diet. Results: This study was designed to give more insight in the lipid composition of the heart muscle in comparison to hind limb muscle. Only in the heart muscle cholesterol esters (ChE) were observed. This was confirmed with LC-MS techniques. Especially the 20:3-ChE are significantly increased in the fatty heart with 1317%. The LC-MS techniques gave no clear picture for Lysophosphatidyl-cholines (LPC), Sphingomyelin (SPM) in hind limb and heart muscle after 40 days of a fatty diet. Only for Phosphatidylcholine (PC) the most remarkable observation was that 36:1-PC rises in heart muscle with 4000%. Twenty-three triglycerides were measured in hind limb muscle but no effect was observed after 40 days of high-fat diet. In contrast, in the heart muscle four types of TG increased dramatically after a 40 days fatty diet ( 54:2-TG (+394%), 54:3-TG (+452%), 56:3-TG (+297%) and 56:5-TG (+213%). Based on Principal Component Analysis with different lipid compounds like LPC, SPM, TG, PC and ChE, a separation can be made for high-fat diet fed animals and control diet fed animals both for hind limb muscle and heart muscle. After elimination of the TG and the ChE and a new PCA run we see that four groups can be clearly separated: Control-heart, Fat-heart, Control-hind limb muscle and Fat-hind limb muscle. Conclusions: These analyses provide potential biomarkers for the diagnosis of diet-induced lipid accumulation in heart and hind-limb muscle tissue.