Metabolic Effects Of High-fat Diet Research Articles

Transfer of modified gut viromes improves symptoms associated with metabolic syndrome in obese male mice

Metabolic syndrome encompasses amongst other conditions like obesity and type-2 diabetes and is associated with gut microbiome (GM) dysbiosis. Fecal microbiota transplantation (FMT) has been explored to treat metabolic syndrome by restoring the GM; however, concerns on accidentally transferring pathogenic microbes remain. As a safer alternative, fecal virome transplantation (FVT, sterile-filtrated feces) has the advantage over FMT in that mainly bacteriophages are transferred. FVT from lean male donors have shown promise in alleviating the metabolic effects of high-fat diet in a preclinical mouse study. However, FVT still carries the risk of eukaryotic viral infections. To address this, recently developed methods are applied for removing or inactivating eukaryotic viruses in the viral component of FVT. Modified FVTs are compared with unmodified FVT and saline in a diet-induced obesity model on male C57BL/6 N mice. Contrasted with obese control, mice administered a modified FVT (nearly depleted for eukaryotic viruses) exhibits enhanced blood glucose clearance but not weight loss. The unmodified FVT improves liver pathology and reduces the proportions of immune cells in the adipose tissue with a non-uniform response. GM analysis suggests that bacteriophage-mediated GM modulation influences outcomes. Optimizing these approaches could lead to the development of safe bacteriophage-based therapies targeting metabolic syndrome through GM restoration.

Obese Skeletal Muscle-Expressed Interferon Regulatory Factor 4 Transcriptionally Regulates Mitochondrial Branched-Chain Aminotransferase Reprogramming Metabolome.

In addition to the significant role in physical activity, skeletal muscle also contributes to health through the storage and use of macronutrients associated with energy homeostasis. However, the mechanisms of regulating integrated metabolism in skeletal muscle are not well-defined. Here, we compared the skeletal muscle transcriptome from obese and lean control subjects in different species (human and mouse) and found that interferon regulatory factor 4 (IRF4), an inflammation-immune transcription factor, conservatively increased in obese subjects. Thus, we investigated whether IRF4 gain of function in the skeletal muscle predisposed to obesity and insulin resistance. Conversely, mice with specific IRF4 loss in skeletal muscle showed protection against the metabolic effects of high-fat diet, increased branched-chain amino acids (BCAA) level of serum and muscle, and reprogrammed metabolome in serum. Mechanistically, IRF4 could transcriptionally upregulate mitochondrial branched-chain aminotransferase (BCATm) expression; subsequently, the enhanced BCATm could counteract the effects caused by IRF4 deletion. Furthermore, we demonstrated that IRF4 ablation in skeletal muscle enhanced mitochondrial activity, BCAA, and fatty acid oxidation in a BCATm-dependent manner. Taken together, these studies, for the first time, established IRF4 as a novel metabolic driver of macronutrients via BCATm in skeletal muscle in terms of diet-induced obesity.

1726-P: Male Mice Lacking Estrogen Receptor Beta Develop Obesity but Are Protected from Diet-Induced Insulin Resistance in Skeletal Muscle

Estrogen has an important role in regulating female metabolism. Whereas the role of estrogen receptor (ER) α on female reproductive system is well defined, the role of ERβ (encoded by Esr2) remains unclear. Here we examined the metabolic effects of high-fat diet (HFD) in male Esr2-/- mice on BALB/c background (n=8∼9). After 6 weeks of HFD, Esr2-/- mice became more obese than wild type (WT) mice (Figure 1; *P<0.05). Surprisingly, metabolic cage study showed significantly increased energy expenditure in Esr2-/- mice, likely resulting from skeletal muscle as lean mass tended to be higher in these mice (Figure 2). We performed a hyperinsulinemic-euglycemic clamp to measure insulin sensitivity in awake mice. Despite being more obese, HFD-fed Esr2-/- mice tended to show increased insulin sensitivity with 20% increases in whole body glucose turnover and glycolysis (Figure 3). This was mostly due to a significant increase (52%) in skeletal muscle glucose uptake in HFD-fed Esr2-/- mice (Figure 4). Interestingly, glucose uptake into brown fat tended to be reduced by 50% in HFD-fed Esr2-/- mice. In conclusion, these results indicate that deletion of Esr2 in male mice increases diet-induced obesity, but selectively prevents muscle insulin resistance. Our findings implicate a potential therapeutic role of estrogen signaling to treat insulin resistance. Disclosure R.H. Friedline: None. H. Noh: None. S. Suk: None. C. Goral: None. K.A. Dunphy: None. A.L. Roberts: None. D.A. Tran: None. L.A. Tauer: None. X. Hu: None. L.H. Kim: None. A.M. Kim: None. D. Jerry: None. J.K. Kim: None. Funding National Institutes of Health (5U2CDK093000)

Differential effects of high-fat diet on glucose tolerance, food intake, and glucocorticoid regulation in male C57BL/6J and BALB/cJ mice

The C57BL/6J strain of laboratory mice is a popular subject for studies of diet-induced obesity and diabetes given its propensity for developing obesity and glucose intolerance when placed on high-fat diet. High-fat diet leads to much lower weight gain in young adult BALB/cJ mice, which appear to be protected from many of the metabolic effects of high-fat diet observed in C57BL/6J mice. In this report, the effects of diet and timing of feeding on body weight, food intake, glucose tolerance, and stress-induced corticosterone and blood glucose responses were assessed in male C57BL/6J and BALB/cJ mice. Lower glucose tolerance was observed in low-fat diet-fed C57BL/6J than BALB/cJ mice at four times sampled across the circadian cycle. Ad libitum high-fat diet increased the amount of daytime eating behavior and led to impaired glucose regulation in C57BL/6J but not BALB/cJ mice. Restricting food availability to either daytime or nighttime did not prevent overall body weight gain, but restricting feeding to nighttime (but not daytime) did prevent the significant increase in perigonadal fat pad mass produced by high-fat diet in C57BL/6J mice. Baseline corticosterone levels at their typical daily peak near onset of daily activity were blunted in both strains of mice after 8 weeks on high-fat diet, without corresponding differences in baseline glucose levels. Restraint stress-induced increases in corticosterone were exaggerated in C57BL/6J mice on high-fat diet, with concomitant increases in blood glucose. Paradoxically, stress-induced corticosterone responses were even more exaggerated in BALB/cJ mice yet with significantly blunted glucose responses compared to C57BL/6J mice, regardless of diet, indicating that corticosterone does not have equivalent glucogenic effects in young adult male BALB/cJ and C57BL/6J mice on high-fat diet. These results document considerable strain differences that may provide means for elucidating the mechanisms involved in diet-induced obesity, while highlighting the need to consider these strain differences when extending the results of mouse studies toward the human condition.

1991-P: Mammary Tumors Increase Diet-Induced Obesity and Insulin Resistance in Female MMTV-PyMT Mice

Diabetes and cancer share multiple risk factors including obesity and insulin resistance, but the potential relationship between these two major diseases is unknown. Here we examined the metabolic effects of high-fat diet (HFD) feeding in female MMTV-PyMT mice, a breast cancer model expressing the polyoma middle T antigen driven by the Mouse Mammary Tumor Virus promoter. Female PyMT and wild type (WT) mice were fed a HFD (55% fat by calories) for 4 weeks starting at 4∼5 weeks of age (n=10-12/group). During HFD, PyMT mice became more obese than WT mice with significant increases in both fat and lean mass (Figure 1; *P<0.05). This was largely due to ∼5% and 30% decreases in energy expenditure and physical activity, respectively, in HFD-PyMT mice (Figure 2). Food intake did not differ between groups. Hyperinsulinemic-euglycemic clamps were performed to measure glucose metabolism in awake mice. HFD-PyMT mice showed increased insulin resistance with ∼25% decreases in glucose infusion rate and whole body glucose turnover compared to HFD-WT mice (Figure 3). Increased insulin resistance was due to significantly reduced glucose uptake in white adipose tissue (Figure 4). In conclusion, these results demonstrate that tumor-bearing female PyMT mice developed increased obesity and insulin resistance after high-fat feeding, and our findings implicate an important relationship between obesity, cancer, and type 2 diabetes. Disclosure H. Noh: None. H. Kang: None. J. Mercado-Matos: None. R.H. Friedline: None. S. Suk: None. X. Hu: None. D.A. Tran: None. L.A. Tauer: None. M. Ko: None. J. Choi: None. T. Luong: None. Y. Tsuchida: None. L.M. Shaw: None. J.K. Kim: None. Funding National Institutes of Health (5U2C-DK093000)

Combined loss of GLP-1R and Y2R does not alter progression of high-fat diet-induced obesity or response to RYGB surgery in mice

ObjectiveUnderstanding the mechanisms underlying the remarkable beneficial effects of gastric bypass surgery is important for the development of non-surgical therapies or less invasive surgeries in the fight against obesity and metabolic disease. Although the intestinal L-cell hormones glucagon-like peptide-1 (GLP-1) and peptide tyrosine–tyrosine (PYY) have attracted the most attention, direct tests in humans and rodents with pharmacological blockade or genetic deletion of either the GLP1-receptor (GLP1R) or the Y2-receptor (Y2R) were unable to confirm their critical roles in the beneficial effects gastric bypass surgery on body weight and glucose homeostasis. However, new awareness of the power of combinatorial therapies in the treatment of metabolic disease would suggest that combined blockade of more than one signaling pathway may be necessary to reverse the beneficial effects of bariatric surgery. MethodsThe metabolic effects of high-fat diet and the ability of Roux-en-Y gastric bypass surgery to lower food intake and body weight, as well as improve glucose handling, was tested in GLP1R and Y2R-double knockout (GLP1RKO/Y2RKO) and C57BL6J wildtype (WT) mice. ResultsGLP1RKO/Y2RKO and WT mice responded similarly for up to 20 weeks on high-fat diet and 16 weeks after RYGB. There were no significant differences in loss of body and liver weight, fat mass, reduced food intake, relative increase in energy expenditure, improved fasting insulin, glucose tolerance, and insulin tolerance between WT and GLP1RKO/Y2RKO mice after RYGB. ConclusionsCombined loss of GLP1R and Y2R-signaling was not able to negate or attenuate the beneficial effects of RYGB on body weight and glucose homeostasis in mice, suggesting that a larger number of signaling pathways is involved or that the critical pathway has not yet been identified.

Metabolic profiling by gas chromatography-mass spectrometry of energy metabolism in high-fat diet-fed obese mice.

A novel, selective and sensitive single-ion monitoring (SIM) gas chromatography-mass spectrometry (GCMS) method was developed and validated for the determination of energy metabolites related to glycolysis, the tricarboxylic acid (TCA) cycle, glutaminolysis, and fatty acid β-oxidation. This assay used N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) containing 1% tert-butyldimethylchlorosilane (TBDMCS) as derivatizing reagent and was highly reproducible, sensitive, specific and robust. The assay was used to analyze liver tissue and serum from C57BL/6N obese mice fed a high-fat diet (HFD) and C57BL/6N mice fed normal chow for 8 weeks. HFD-fed mice serum displayed statistically significantly reduced concentrations of pyruvate, citrate, succinate, fumarate, and 2-oxoglutarate, with an elevated concentration of pantothenic acid. In liver tissue, HFD-fed mice exhibited depressed levels of glycolysis end-products pyruvate and lactate, glutamate, and the TCA cycle intermediates citrate, succinate, fumarate, malate, and oxaloacetate. Pantothenate levels were 3-fold elevated accompanied by a modest increased gene expression of Scl5a6 that encodes the pantothenate transporter SLC5A6. Since both glucose and fatty acids inhibit coenzyme A synthesis from pantothenate, it was concluded that these data were consistent with downregulated fatty acid β-oxidation, glutaminolysis, glycolysis, and TCA cycle activity, due to impaired anaplerosis. The novel SIM GCMS assay provided new insights into metabolic effects of HFD in mice.

The role of sex and body weight on the metabolic effects of high-fat diet in C57BL/6N mice

Background:Metabolic disorders are commonly investigated using knockout and transgenic mouse models on the C57BL/6N genetic background due to its genetic susceptibility to the deleterious metabolic effects of high-fat diet (HFD). There is growing awareness of the need to consider sex in disease progression, but limited attention has been paid to sexual dimorphism in mouse models and its impact in metabolic phenotypes. We assessed the effect of HFD and the impact of sex on metabolic variables in this strain.Methods:We generated a reference data set encompassing glucose tolerance, body composition and plasma chemistry data from 586 C57BL/6N mice fed a standard chow and 733 fed a HFD collected as part of a high-throughput phenotyping pipeline. Linear mixed model regression analysis was used in a dual analysis to assess the effect of HFD as an absolute change in phenotype, but also as a relative change accounting for the potential confounding effect of body weight.Results:HFD had a significant impact on all variables tested with an average absolute effect size of 29%. For the majority of variables (78%), the treatment effect was modified by sex and this was dominated by male-specific or a male stronger effect. On average, there was a 13.2% difference in the effect size between the male and female mice for sexually dimorphic variables. HFD led to a significant body weight phenotype (24% increase), which acts as a confounding effect on the other analysed variables. For 79% of the variables, body weight was found to be a significant source of variation, but even after accounting for this confounding effect, similar HFD-induced phenotypic changes were found to when not accounting for weight.Conclusion:HFD and sex are powerful modifiers of metabolic parameters in C57BL/6N mice. We also demonstrate the value of considering body size as a covariate to obtain a richer understanding of metabolic phenotypes.

Abstract 16039: CX3CR1 And CCR2 Synergistically Modulate Inflammatory but Not Metabolic Effects of High-fat Feeding

Introduction: Obesity is associated with a systemic inflammatory reaction that has been associated with the development of type 2 diabetes and atherosclerosis. Substantial evidence points towards the C-C motif chemokine receptor-2 (CCR2) and fractalkine receptor (CX3CR1) as important modulators of metabolic and inflammatory phenotypes in high fat diet (HFD)-induced obesity, but the synergistic effects of dual targeting of CX3CR1 and CCR2 have not been studied. Hypothesis: CX3CR1 and CCR2 exert synergistic effects in HFD-induced obesity. Methods: C57BL/6J wild type mice (WT), Cx3cr1 -/- , Ccr2 -/- and Cx3cr1 -/- Ccr2 -/- double knockout mice were fed a 45% HFD (D124551, Research Diets), which is known to promote hypertriglyceridemia and insulin resistance, for up to 6 months starting at 12-wks old (n=10-16 male mice per group). Results: WT, Cx3cr1 -/- , Ccr2 -/- , and Cx3cr1 -/- Ccr2 -/- gained weight at a similar rate and developed similar degrees of adiposity and hyperglycemia in response to 45% HFD. All groups demonstrated progressive impairment in glucose tolerance, insulin sensitivity (by Insulin Tolerance Test), and glucose-evoked insulin secretion. A complete blood cell count with differential suggested reduced monocyte count in Ccr2 -/- (22.2 ± 10.1 % of WT, mean±SEM, P<0.05) and Cx3cr1 -/- Ccr2 -/- (10.6 ± 1.9% of WT, P<0.05), but not in Cx3cr1 -/- (82.8 ± 16.3 % of WT, P=0.45), consistent with the impaired monocytosis due to Ccr2 deficiency. FACS analysis showed that in stromal vascular cells from epididymal adipose, % of CD45(+)F4/80(+)CD11c(+)MGL1(-) M1-like macrophage was lower while CD45(+)F4/80(+)MGL1(+)CD11c(-) M2-like macrophage was higher in the Cx3cr1 -/- Ccr2 -/- mice vs. WT mice. In contrast, a single knockout of Cx3cr1 or Ccr2 did not affect macrophage phenotypic switching. Conclusion: A single knockout or double knockout of Cx3cr1 and Ccr2 did not affect weight gain, glucose levels and insulin sensitivity in response to HFD. However, the Cx3cr1 -/- Ccr2 -/- but not the single knockout of Cx3cr1 or Ccr2 mice, showed reduced adipose macrophage activation. The results indicate that CX3CR1 and CCR2 synergistically modulate inflammatory but not metabolic effects of HFD.

The temporal impact of chronic intermittent psychosocial stress on high-fat diet-induced alterations in body weight

Chronic stress and diet can independently or in concert influence the body's homeostasis over time. Thus, it is crucial to investigate the interplay of these parameters to gain insight into the evolution of stress-induced metabolic and eating disorders. C57BL/6J mice were subjected to chronic psychosocial (mixed model of social defeat and overcrowding) stress in combination with either a high- or low-fat diet for three or six weeks. To determine the evolution of stress and dietary effects, changes in body weight, caloric intake and caloric efficiency were determined as well as circulating leptin, insulin, glucose and corticosterone levels and social avoidance behaviour. Exposure to stress for three weeks caused an increase in weight gain, in caloric intake and in caloric efficiency only in mice on a low-fat diet. However, after six weeks, only stressed mice on a high-fat diet displayed a pronounced inhibition of body weight gain, accompanied by reduced caloric intake and caloric efficiency. Stress decreased circulating leptin levels in mice on a low-fat diet after three weeks and in mice on a high-fat diet after three and six weeks of exposure. Plasma levels of insulin and markers of insulin resistance were blunted in mice on high-fat diet following six weeks of stress exposure. Social avoidance following chronic stress was present in all mice after three and six weeks. This study describes the evolution of the chronic effects of social defeat/overcrowding stress in combination with exposure to high- or low-fat diet. Most importantly, we demonstrate that a six week chronic exposure to social defeat stress prevents the metabolic effects of high-fat diet, by inhibiting an increase in weight gain, caloric intake and efficiency and insulin resistance as well as in plasma leptin and insulin levels. This study highlights the importance of considering the chronic aspects of both parameters and their time-dependent interplay.