Low-fat Diet Mice Research Articles

Diet-induced insulin resistance elevates hippocampal glutamate as well as VGLUT1 and GFAP expression in AβPP/PS1 mice.

The symptomologies of Alzheimer's disease (AD) develop over decades suggesting modifiable lifestyle factors may contribute to disease pathogenesis. In humans, hyperinsulinemia associated with type 2 diabetes mellitus increases the risk for developing AD and both diseases share similar age-related etiologies including amyloidogenesis. Since we have demonstrated that soluble Aβ42 elicits glutamate release, we wanted to understand how diet-induced insulin resistance alters hippocampal glutamate dynamics, which are important for memory formation and consolidation. Eight to twelve-week-old C57BL/6J and AβPP/PS1 mice were placed on either a low-fat diet or high-fat diet (HFD) for 8months. A HFD led to significant weight increases as well as impaired insulin sensitivity, glucose tolerance, and learning in both C57BL/6J and AβPP/PS1 mice. AβPP/PS1 low-fat diet mice had elevated hippocampal basal as well as stimulus-evoked glutamate release that was further increased with consumption of a HFD. Immunohistochemistry indicated an increase in vesicular glutamate transporter 1 and glial fibrillary acidic protein density in hippocampal subregions corresponding with this elevated extracellular glutamate. While no differences in hippocampal plaque load were observed, the elevated astrogliotic response surrounding the plaques in AβPP/PS1 HFD mice may have been a compensatory mechanism to control plaque accumulation. These data support that AβPP/PS1 mice have chronically elevated extracellular glutamate that is exacerbated by a HFD and that modifiable lifestyle factors such as obesity-induced insulin resistance can contribute to AD pathogenesis. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* and for *Open Data* because it made the data publicly available. The data can be accessed at https://osf.io/5whvu (figures for data) and https://osf.io/gd5vf (materials and methods). The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Cover Image for this issue: doi: 10.1111/jnc.14490.

Prevention of Lipid Peroxidation-derived Cyclic DNA Adduct and Mutation in High-Fat Diet-induced Hepatocarcinogenesis by Theaphenon E.

Obesity is associated with cancer risk and its link with liver cancer is particularly strong. Obesity causes non-alcoholic fatty liver disease (NAFLD) that could progress to hepatocellular carcinoma (HCC). Chronic inflammation likely plays a key role. We carried out a bioassay in the high-fat diet (HFD)-fed C57BL/6J mice to provide insight into the mechanisms of obesity-related HCC by studying γ-OHPdG, a mutagenic DNA adduct derived from lipid peroxidation. In an 80-week bioassay, mice received a low-fat diet (LFD), high-fat diet (HFD), and HFD with 2% Theaphenon E (TE) (HFD+TE). HFD mice developed a 42% incidence of HCC and LFD mice a 16%. Remarkably, TE, a standardized green tea extract formulation, completely blocked HCC in HFD mice with a 0% incidence. γ-OHPdG measured in the hepatic DNA of mice fed HFD and HFD+TE showed its levels increased during the early stages of NAFLD in HFD mice and the increases were significantly suppressed by TE, correlating with the tumor data. Whole-exome sequencing showed an increased mutation load in the liver tumors of HFD mice with G>A and G>T as the predominant mutations, consistent with the report that γ-OHPdG induces G>A and G>T. Furthermore, the mutation loads were significantly reduced in HFD+TE mice, particularly G>T, the most common mutation in human HCC. These results demonstrate in a relevant model of obesity-induced HCC that γ-OHPdG formation during fatty liver disease may be an initiating event for accumulated mutations that leads to HCC and this process can be effectively inhibited by TE. Cancer Prev Res; 11(10); 665-76. ©2018 AACR.

Cardiac branched-chain amino acid oxidation is reduced during insulin resistance in the heart.

Recent studies have proposed that elevated branched-chain amino acids (BCAAs) may induce insulin resistance (IR) in muscle secondary to increased BCAA oxidation inhibiting glucose oxidation (GO) and fatty acid oxidation (FAO). However, BCAA oxidation rates have not been assessed in muscle IR, and cardiac FAO rates are actually already elevated in obesity-associated IR. We therefore directly examined cardiac BCAA oxidation in mice fed a high-fat diet (HFD) to induce insulin resistance to better understand the role of cardiac BCAA oxidation in cardiac IR. BCAA oxidation, GO, FAO, and glycolysis were measured in isolated working hearts from mice fed either a low-fat diet (LFD) or HFD for 10 wk. Insulin stimulation of cardiac GO and inhibition of FAO were blunted in HFD mice, resulting in a marked increase in FAO contribution to ATP production compared with LFD mice hearts (71.2% vs. 37.1%, respectively). Surprisingly, cardiac BCAA oxidation rate was reduced in HFD compared with LFD mice (33.5 ± 3.4 vs. 56.7 ± 7.1 nmol·min-1·g dry wt-1, respectively, P < 0.05, n = 9/group). In addition, BCAA oxidation contributed ~1% of the ATP production of the heart, and, as a result, alterations in BCAA oxidation could not significantly impact either GO or FAO rates. However, the decrease in BCAA oxidation was accompanied by an increase in BCAA concentration and impaired insulin signaling. These results suggest that cardiac IR is not due to an increase in BCAA oxidation and subsequent inhibition of GO and FAO. Rather, we propose that an inhibition of BCAA oxidation rate contributes to IR by leading to increased BCAA concentration, which negatively impacts insulin signaling.

Dietary supplementation with blueberry partially restores T-cell-mediated function in high-fat-diet-induced obese mice.

Blueberry, rich in antioxidant and anti-inflammatory phytochemicals, has been demonstrated to lower inflammatory status in adipose induced by high-fat diet (HFD) and obesity. The effect of blueberry on systemic immune functions has not been examined. C57BL/6 mice were randomised to one of three diets - low-fat diet (LFD), HFD and HFD plus 4 % (w/w) blueberry (HFD+B) - for 8 or 12 weeks. Ex vivo T-cell mitogens (concanavalin A (Con A); phytohaemagglutinin), T-cell antibody (anti-CD3; anti-CD3/CD28)-stimulated T-cell proliferation and cytokine production were assessed. After 8 weeks, both HFD groups weighed more (>4 g) than the LFD group; after 12 weeks, HFD+B-fed mice weighed more (>6 g) and had 41 % more adipose tissue than HFD-fed mice (P<0·05). After 12 weeks, T-cell proliferation was less in both HFD groups, compared with the LFD group. HFD-associated decrements in T-cell proliferation were partially (10-50 %) prevented by blueberry supplementation. At 12 weeks, splenocytes from HFD mice, but not from HFD+B mice, produced 51 % less IL-4 (CD3/CD28) and 57 % less interferon-γ (Con A) compared with splenocytes from LFD mice (P<0·05). In response to lipopolysaccharide challenge, splenocytes from both HFD groups produced 24-30 % less IL-6 and 27-33 % less TNF-α compared with splenocytes from LFD mice (P<0·05), indicating impaired acute innate immune response. By demonstrating deleterious impacts of HFD feeding on T-cell proliferation and splenocyte immune responses, our results provide insights into how HFD/obesity can disrupt systemic immune function. The protective effects of blueberry suggest that dietary blueberry can buttress T-cell and systemic immune function against HFD-obesity-associated insults.

Abstract B15: The effects of obesity on tumor microenvironment and immunotherapy efficacy

Abstract Immunotherapy is a promising treatment for cancer. Although immune checkpoint blockade treatment is life-saving for some patients, only a minority respond to it. There are no clear data from clinical trials to suggest what risk factors that are common among patients affect immunotherapy treatment efficacy. For example, obesity is a risk factor for at least thirteen different types of cancer, including colon and breast, and one-third of Americans are obese. However, no conclusive studies examining the efficacy of cancer immunotherapies in obese patients have been performed. Furthermore, while many cancer patients are obese, preclinical models of immunotherapy typically use lean mice. Studies have shown that obesity promotes a vastly different immune system compared to a lean state. Obesity promotes an increase in adipose tissue macrophages, which tend to have a proinflammatory “M1” polarization, whereas tumor-associated macrophages (TAMs) have an antiinflammatory “M2” polarization. M1 macrophages create a proinflammatory tumor microenvironment, which is potentially favorable for immunotherapy. However, the characteristics of TAMs in obese subjects are poorly described. One theory is that in obesity, the tumor microenvironment shifts the macrophages from the M1 phenotype towards the TAM M2 phenotype, which would result in a worse response to immune checkpoint blockade. Also, obese individuals have a decreased humoral immune response due to a multitude of factors, including an altered lymphocyte profile, decreased lymphocyte functionality, dysregulated cytokines, and decreased numbers of immune cells, which would also worsen treatment response. A second theory is that obese individuals often have a higher mutational load in their tumors, as is seen in increased genomic instability in obese patients with colon cancer and endometrial cancer. Higher mutational loads correlate with immunogenic tumors and often better responses to immunotherapy treatment. It is not clear how these immunologic and genetic differences in obesity will affect response to immunomodulatory therapies. Therefore, our first goal is to understand obesity's immunologic effects on immunotherapy efficacy. We studied the effects of obesity on the tumor microenvironment using a diet-induced obesity mouse model and immunoresponsive cell line. MC38 colon cancer cells were injected subcutaneously in C57BL/6 mice fed a high-fat or control diet. The tumors were collected three weeks post-injection and processed into single cell suspensions for flow cytometry. Samples were stained for helper T cells, cytotoxic T cells, and macrophages with CD11b and F4/80, where CD206 and CD86 identified M2 and M1 macrophages, respectively. Initial experiments revealed a higher concentration of CD4+ T cells in lean mice. We will further investigate the role of immune cell and cytokine differences in obese states. However, when anti-PD-1 antibodies were intraperitoneally administered to the mice on day 7, 10, and 13 post-MC38 cell injection, the high-fat diet mice tumors had higher concentrations of CD4+ T cells compared to low-fat diet mice tumors. These experiments are being repeated, and we are now using an orthotopic EMT6 breast cancer model as well. The importance of identifying optimal diet-induced obese mouse models that are compatible with immunoresponsive cell lines is imperative to conducting translational research and is a focal objective of the ongoing studies. In later experiments, we have engineered biocompatible nanoparticles that can modulate immune cells and shift the tumor microenvironment using siRNA, potentially improving immunotherapy efficacy in obesity. The nanoparticles will identify the role of macrophages in immunotherapy efficacy. These initial studies will lay the foundation for future research and have important translational implications in improving the efficacy of immunotherapy treatment in obese patients. Citation Format: Stephanie O. Dudzinski, Kathryn E. Beckermann, Todd D. Giorgio, Jeffrey C. Rathmell. The effects of obesity on tumor microenvironment and immunotherapy efficacy [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B15.

Overload Alters Skeletal Muscle Glucose Utilization but not Glucose Uptake or Hypertrophy in Insulin-Resistant Mice

Resistance exercise training/chronic muscle loading induces skeletal muscle hypertrophy and improves systemic glucose homeostasis in individuals with type 2 diabetes. Surprisingly, it is presently unknown if the improvement in glycemic control is due to an increase in muscle glucose uptake. PURPOSE: To determine if chronic muscle loading (overload)-induced muscle glucose uptake is impaired by insulin resistance. METHODS & RESULTS: Male C57BL/6J mice (6 wks old) were fed a low fat diet (LFD) or a 60%kcal high fat diet (HFD) for 12 wks to induce insulin resistance. Plantaris muscle overload was elicited by unilateral ablation of the distal 2/3 of the gastrocnemius and soleus. The contralateral leg was sham-operated. Muscles were weighed 5 days later. Overload increased muscle mass ~40% in both LFD and HFD mice. To assess glucose uptake, muscles were incubated in [3H]-2-deoxyglucose. Overload increased muscle glucose uptake ~80% in both LFD [Sham: 0.52±0.02; Overload: 0.91±0.04 (μmol/g muscle/h)] and HFD mice [Sham: 0.49±0.04; Overload: 0.86±0.09 (μmol/g muscle/h)], showing that overload stimulates glucose uptake independent of insulin resistance. To determine if this effect is due to increased glucose transporter (GLUT) or hexokinase levels, immunoblots were performed. Overload did not alter GLUT4 or hexokinase. In contrast, overload increased GLUT1 ~70%, but only in insulin resistant muscles. Decreased glycogen enhances glucose uptake. To determine if overload lowered glycogen levels, glycogen content was measured using a hexokinase-based reagent. Overload increased muscle glycogen ~26% in LFD (Sham: 29.0±1.6; Overload: 36.1±1.5 nmol/mg muscle), and ~40% in HFD mice (Sham: 31.2 ±2.1; Overload: 42.3±1.7 nmol/mg muscle). To determine if overload-induced glucose uptake is dependent on glucose utilization, muscles were incubated in [5-3H]-glucose to assess glycolytic flux, and immunoblots performed to assess the rate limiting enzyme of the pentose phosphate pathway, glucose-6-phosphate dehydrogenase (G6PD). Overload did not alter muscle glycolytic flux. In contrast overload increased muscle G6PD ~140% in LFD, and ~82% in HFD mice. CONCLUSION: Insulin resistance does not impair overload-induced muscle hypertrophy or glucose uptake, but does alter glucose utilization. SUPPORT: NIH R01 DK103562

Microbiota metabolites derived from tryptophan modulate macrophage inflammation and migration through AMP-activated protein kinase

Abstract It is established that the gut microbiota plays an important role in Non-Alcoholic Fatty Liver Disease (NAFLD) and different bacterial taxa have been correlated to disease. However, the specific metabolites through which the microbiota exert their effects and the target pathways in host cells are not fully understood. We used liquid chromatography-mass spectrometry metabolomics to identify two tryptophan-derived metabolites – tryptamine (TA) and indole-3-acetate (I3A) – that require the microbiota and are depleted in high-fat diet mice compared to low fat diet mice. Both I3A and TA reduced palmitate and LPS induced production of pro-inflammatory cytokines (TNFα, IL-1β and MCP-1) in RAW 264.7 macrophages, as well as inhibited macrophage migration toward the chemokine MCP-1. We identified that both palmitate and LPS reduced levels of p-AMPK and the addition of I3A and TA reversed p-AMPK reduction. Since the p-AMPK activator AICAR reduced palmitate and LPS induced inflammatory cytokine production, we propose that I3A and TA modulate inflammation through modulating p-AMPK levels.

Caffeic acid ameliorates hepatic steatosis and reduces ER stress in high fat diet-induced obese mice by regulating autophagy.

Non-alcoholic fatty liver disease is characterized by high hepatic triacylglycerol contents, which is associated with endoplasmic reticulum (ER) stress and insulin resistance. Caffeic acid (CA) has antioxidant, immunomodulatory, and antiinflammatory effects. We investigated the effects of CA on hepatic steatosis and its mechanism of action. We treated CA (50 µM) with AML12 cells. We categorized mice into three groups as follows: low-fat diet mice (LFD, n = 10), high-fat diet-induced obese mice (HFD, n = 10), and HFD fed with CA (50 mg/kg/d, n = 10) for 10 wk. CA did not cause any cytotoxic effect on AML12 cell line within the range of concentrations tested (0-200 µM). We found that CA (50 µM) treatment in palmitate-treated AML12 hepatocytes reduced lipid accumulation and lipogenesis markers, decreased ER stress, and increased autophagy markers. However, there was no significant difference in lipid droplets of palmitate-treated AML12 hepatocytes and CA-treated autophagy-related protein 7 deficiency AML12 hepatocytes with palmitate. Similarly, CA significantly lowered body and liver weights. Lipid accumulation in the liver decreased in the HFD + CA group compared with the HFD group. Glucose intolerance and insulin sensitivity also were markedly improved in the HFD + CA group. Moreover, the levels of ER stress markers were decreased in the livers of the HFD + CA group. Autophagy markers were increased in the livers of the HFD + CA group. These results suggest that caffeic acid may ameliorate hepatic steatosis and decrease ER stress by increasing autophagy.

Low-Fat Diet With Caloric Restriction Reduces White Matter Microglia Activation During Aging.

Rodent models of both aging and obesity are characterized by inflammation in specific brain regions, notably the corpus callosum, fornix, and hypothalamus. Microglia, the resident macrophages of the central nervous system, are important for brain development, neural support, and homeostasis. However, the effects of diet and lifestyle on microglia during aging are only partly understood. Here, we report alterations in microglia phenotype and functions in different brain regions of mice on a high-fat diet (HFD) or low-fat diet (LFD) during aging and in response to voluntary running wheel exercise. We compared the expression levels of genes involved in immune response, phagocytosis, and metabolism in the hypothalamus of 6-month-old HFD and LFD mice. We also compared the immune response of microglia from HFD or LFD mice to peripheral inflammation induced by intraperitoneal injection of lipopolysaccharide (LPS). Finally, we investigated the effect of diet, physical exercise, and caloric restriction (40% reduction compared to ad libitum intake) on microglia in 24-month-old HFD and LFD mice. Changes in diet caused morphological changes in microglia, but did not change the microglia response to LPS-induced systemic inflammation. Expression of phagocytic markers (i.e., Mac-2/Lgals3, Dectin-1/Clec7a, and CD16/CD32) in the white matter microglia of 24-month-old brain was markedly decreased in calorically restricted LFD mice. In conclusion, LFD resulted in reduced activation of microglia, which might be an underlying mechanism for the protective role of caloric restriction during aging-associated decline.

Curcumin and Salsalate Suppresses Colonic Inflammation and Procarcinogenic Signaling in High-Fat-Fed, Azoxymethane-Treated Mice.

High-fat diets (HFDs) and excess adiposity increase proinflammatory cytokines in the colon, altering gene expression in a manner that promotes the development of colorectal cancer (CRC). Thus, compounds that reduce this biochemical inflammation are potential chemopreventive agents. Curcumin (CUR), a dietary polyphenol, and salsalate (SAL), a non-steroidal anti-inflammatory drug, are both anti-inflammatories. We investigated the inhibitory effects of CUR with or without SAL on inflammatory cytokines and procarcinogenic signaling in azoxymethane (AOM)-treated A/J mice. A sub-tumorigenic AOM dose was chosen to produce a biochemical and molecular procarcinogenic colonic environment without tumors. Mice were fed either a HFD (60% of kilocalories) or low-fat diet (LFD) (10% of kilocalories). One HFD treatment group received 0.2% CUR in the diet; one received 0.2% CUR + 0.15% SAL; and one received 0.4% CUR + 0.3% SAL. The HFD mice developed 30% greater fat mass than the LFD mice (p < 0.05). The colonic concentrations of interleukin-1β (IL-1β) and interleukin-6 (IL-6) in the HFD mice were decreased by 50-69% by the high-dose combination regimen (p < 0.015). Only the combination regimens significantly suppressed phosphorylation of protein kinase B (Akt) and nuclear factor-κB (NF-κB) p65 (p < 0.044). The combination of CUR and SAL reduces the concentration of proinflammatory cytokines and diminishes activation of Akt and NF-κB more effectively than CUR alone, providing a scientific basis for examining whether this combination mitigates the risk of CRC in obese individuals.

Control diet in a high-fat diet study in mice: Regular chow and purified low-fat diet have similar effects on phenotypic, metabolic, and behavioral outcomes

Background: Differences in the composition of control diets may confound outcomes in studies investigating dietary effects.Objective: We compared the effects of two control diets commonly used in mice studies, chow (SD) and a purified low-fat diet (LFD), in relation to a chronic high-fat diet (HFD). We hypothesized that SD and LFD will have similar effects on phenotypic, metabolic, and behavioral outcomes.Methods: Fifty-four 5-week-old male C57BL/6J mice were randomly assigned to one of the three dietary interventions (SD, LFD, or HFD) for 18 weeks. At week 16, mice were tested for behavioral changes. Glucose tolerance testing was conducted at week 17 and terminal blood collection at week 18.Results: SD and LFD mice exhibited no differences in cognitive performance on the Y-maze test and comparable anxiety-like behavior in the open-field and elevated zero maze tests. Significant declines in cognitive function and greater anxiety-like behavior were observed in the HFD group compared to both SD and LFD. Areas under the glucose tolerance curve were similar for SD and LFD, as were levels of high-density lipoprotein, triglycerides, cytokines, and adipocytokines. Only total cholesterol was significantly higher in LFD mice compared to SD mice. All measures were significantly higher in the HFD group.Discussion: Our data demonstrate that young mice develop similar phenotypic, metabolic, and behavioral profiles when fed SD vs. LFD. The two diets may thus be equally appropriate as controls for an HFD, although some studies may want to consider differences in effects on cholesterol levels.

Abstract 1261: Lipid-peroxidation derived DNA damage is prevented in obesity-related hepatocarcinogenesis through CD4+ mediated apoptosis in the livers of mice on a green-tea diet

Abstract Using a C57BL/6J bioassay, we assessed whether formation of a lipid-peroxidation (LPO)-derived DNA adduct would induce mutations during the progression of obesity-induced hepatocarcinogenesis and if its formation could be prevented using a diet infused with Theaphenon E, a mixture of polyphenols extracted from green tea. Obesity is now the leading risk factor for the development of hepatocellular carcinoma in the United States. We have conducted a life-time C57BL/6J tumor bioassay to assess the role of obesity in the formation of γ-hydroxy-1,N2-propanodeoxyguanosine (γ-OHPdG), a promutagenic DNA adduct formed endogenously by LPO. Previously, we have shown γ-OHPdG was detected in FFPE liver tissues of patients with different stages of liver disease, demonstrating that its formation is consistent with LPO in the early stages of liver disease and suggesting that it may be a source of endogenous DNA damage in hepatocarcinogenesis. Tea polyphenols, predominately EGCG, are antioxidants that have been shown to prevent obesity and tumorigenesis. For the bioassay, mice were fed either a high fat, low fat, or high fat 2% TE diet starting at 4 weeks of age. Tissue and blood were collected over the course of 80 weeks at 11 separate time points. Health of the mice was assessed using serum concentrations of ALT and AST, gross morphology and immunohistochemistry of TUNEL, Ki67 and CD4+. In contrast to the high-fat and low-fat diet mice, the TE treated mice maintained a healthy body weight, liver to body weight ratio and low levels of AST and ALT enzymes which are elevated in liver disease. Additionally, the health of the liver appears to be maintained through increased CD4+ mediated apoptosis in TE treated mice as demonstrated through decreased Ki67 expression and TUNEL staining showing increased apoptosis in TE treated mice livers in conjunction with increased CD4+ cells. The CD4+ immune response may, therefore, be targeting cells with mutagenic potential. Similar to the trend indicated by the clinical samples, during hepatocarcinogenesis in the high fat diet mice, adduct levels were increased initially and likely fixed into mutation at later time points, where their levels decreased, as quantified by LC-MS/MS. In contrast, in the TE treated mice, the average γ-OHPdG levels remained consistently low. Further studies incorporating whole exome sequencing of the tumors that were formed during the life-time bioassay will indicate whether γ-OHPdG may contribute to the mutations that occured. In conclusion, our study has shown that a robust immune system response mediated by TE may be an underlying mechanism to combat the DNA adduct-induced DNA damage that may lead to HCC. Citation Format: Heidi Coia, Ning Ma, Marcin Dyba, Fung-Lung Chung. Lipid-peroxidation derived DNA damage is prevented in obesity-related hepatocarcinogenesis through CD4+ mediated apoptosis in the livers of mice on a green-tea diet [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1261. doi:10.1158/1538-7445.AM2017-1261

The lemon balm extract ALS-L1023 inhibits obesity and nonalcoholic fatty liver disease in female ovariectomized mice

Increasing evidence indicates that angiogenesis inhibitors regulate obesity. This study aimed to determine whether the lemon balm extract ALS-L1023 inhibits diet-induced obesity and nonalcoholic fatty liver disease (NAFLD) in female ovariectomized (OVX) mice. OVX mice received a low fat diet (LFD), a high fat diet (HFD) or HFD supplemented with ALS-L1023 (ALS-L1023) for 15 weeks. HFD mice exhibited increases in visceral adipose tissue (VAT) angiogenesis, body weight, VAT mass and VAT inflammation compared with LFD mice. In contrast, all of these effects were reduced in ALS-L1023 mice compared with HFD mice. Serum lipids and liver injury markers were improved in ALS-L1023 mice. Hepatic lipid accumulation, inflammatory cells and collagen levels were lower in ALS-L1023 mice than in HFD mice. ALS-L1023 mice exhibited a tendency to normalize hepatic expression of genes involved in lipid metabolism, inflammation and fibrosis to levels in LFD mice. ALS-L1023 also induced Akt phosphorylation and increased Nrf2 mRNA expression in livers of obese mice. Our results indicate that the angiogenesis inhibitor ALS-L1023 can regulate obesity, hepatic steatosis and fibro-inflammation, in part through improvement of VAT function, in obese OVX mice. These findings suggest that angiogenesis inhibitors may contribute to alleviation of NAFLD in post-menopausal women with obesity.

Depot-specific differences in angiogenic capacity of adipose tissue in differential susceptibility to diet-induced obesity

ObjectiveAdipose tissue (AT) expansion requires AT remodeling, which depends on AT angiogenesis. Modulation of AT angiogenesis could have therapeutic promise for the treatment of obesity. However, it is unclear how the capacity of angiogenesis in each adipose depot is affected by over-nutrition. Therefore, we investigated the angiogenic capacity (AC) of subcutaneous and visceral fats in lean and obese mice. MethodsWe compared the AC of epididymal fat (EF) and inguinal fat (IF) using an angiogenesis assay in diet-induced obese (DIO) mice and diet-resistant (DR) mice fed a high-fat diet (HFD). Furthermore, we compared the expression levels of genes related to angiogenesis, macrophage recruitment, and inflammation using RT-qPCR in the EF and IF of lean mice fed a low-fat diet (LFD), DIO mice, and DR mice fed a HFD. ResultsDIO mice showed a significant increase in the AC of EF only at 22 weeks of age compared to DR mice. The expression levels of genes related to angiogenesis, macrophage recruitment, and inflammation were significantly higher in the EF of DIO mice than in those of LFD mice and DR mice, while expression levels of genes related to macrophages and their recruitment were higher in the IF of DIO mice than in those of LFD and DR mice. Expression of genes related to angiogenesis (including Hif1a, Vegfa, Fgf1, Kdr, and Pecam1), macrophage recruitment, and inflammation (including Emr1, Ccr2, Itgax, Ccl2, Tnf, and Il1b) correlated more strongly with body weight in the EF of HFD-fed obese mice compared to that of IF. ConclusionsThese results suggest depot-specific differences in AT angiogenesis and a potential role in the susceptibility to diet-induced obesity.

High fat diet exacerbates dextran sulfate sodium induced colitis through disturbing mucosal dendritic cell homeostasis

Epidemiological studies have shown that fat rich western diet contributes to the high incidence of inflammatory bowel disease (IBD). Moreover, accumulated data indicated that fat dietary factor might promote the change of the composition and metabolism in commensal flora. But, the exact mechanisms for fatty diet in gut inflammation are not well demonstrated. In this study, we found that high fat diet (HFD) promoted inflammation and exacerbated the disease severity of dextran sulfate sodium (DSS) induced colitis in mice. Compared with low fat diet (LFD)/DSS mice, shorter colon length, more epithelial loss and crypt destruction and more Gr-1+ myeloid inflammatory cells infiltration in colons were observed in HFD/DSS cohorts. Interestingly, such HFD mediated inflammation accompanied with the dys-regulation of hematopoiesis, and more hematopoiesis stem and progenitor cells were detected in colon and spleen. We further analyzed the effects of HFD and DSS treatment on mucosal DC subsets, and found that DSS treatment in LFD mice mainly dramatically increased the percentage of CD11c+CD103−CD11b+ DCs in lamina propria (LP). While, in HFD/DSS mice, HFD pre-treatment not only increased the percentage of CD11c+CD103−CD11b+ DCs, but also decreased CD11c+CD103+CD11b+ in both LP and mesenteric lymph nodes (MLN) in mice with colitis. This disequilibrium of mucosal dendritic cells in HFD/DSS mice may depend on the reduced levels of buytrate and retinoic acid. Thus, this study declared the effects of HFD on gut microenviroment, and further indicated its potential role in the development of DSS induced colitis.

Functional and Molecular Adaptations of Enteroendocrine L-Cells in Male Obese Mice Are Associated With Preservation of Pancreatic α-Cell Function and Prevention of Hyperglycemia.

Glucose homeostasis depends on the coordinated secretion of glucagon, insulin, and Glucagon-like peptide (GLP)-1 by pancreas and intestine. Obesity, which is associated with an increased risk of developing insulin resistance and type 2 diabetes, affects the function of these organs. Here, we investigate the functional and molecular adaptations of proglucagon-producing cells in obese mice to better define their involvement in type 2 diabetes development. We used GLU-Venus transgenic male mice specifically expressing Venus fluorochrome in proglucagon-producing cells. Mice were subjected to 16 weeks of low-fat diet or high-fat diet (HFD) and then subdivided by measuring glycated hemoglobin (HbA1c) in 3 groups: low-fat diet mice and I-HFD (glucose-intolerant) mice with similar HbA1c and H-HFD (hyperglycemic) mice, which exhibited higher HbA1c. At 16 weeks, both HFD groups exhibited similar weight gain, hyperinsulinemia, and insulin resistance. However, I-HFD mice exhibited better glucose tolerance compared with H-HFD mice. I-HFD mice displayed functional and molecular adaptations of enteroendocrine L-cells resulting in increased intestinal GLP-1 biosynthesis and release as well as maintained pancreatic α- and β-cell functions. By contrast, H-HFD mice exhibited dysfunctional L, α- and β-cells with increased β- and L-cell numbers. Administration of the GLP-1R antagonist Exendin9-39 in I-HFD mice led to hyperglycemia and alterations of glucagon secretion without changes in insulin secretion. Our results highlight the cross-talk between islet and intestine endocrine cells and indicate that a compensatory adaptation of L-cell function in obesity plays an important role in preserving glucose homeostasis through the control of pancreatic α-cell functions.

Fibroblast Growth Factor 21 (Fgf21) Gene Expression Is Elevated in the Liver of Mice Fed a High-Carbohydrate Liquid Diet and Attenuated by a Lipid Emulsion but Is Not Upregulated in the Liver of Mice Fed a High-Fat Obesogenic Diet

Background:Fibroblast growth factor 21 (FGF21) is a regulator of carbohydrate and lipid metabolism; however, the regulation of Fgf21 gene expression by diet remains incompletely understood.Objective:We investigated the effect of a high-carbohydrate (HC) liquid diet, with and without supplementation with a lipid emulsion (LE), and of a high-fat diet (HFD) compared with a low-fat diet (LFD) on the regulation of Fgf21 gene expression in the liver of intact mice.Methods:C57BL/6 male mice were fed standard feed pellets (SFPs), a purified HC liquid diet (adequate in calories and protein), or an HC liquid diet containing an LE at either 4% or 13.5% of energy for 5 wk (Expt. 1) or 1 wk (Expt. 2). In Expt. 3, mice were fed a purified LFD (∼10% fat) or HFD (∼60% fat) or were fed an HFD and given access to a running wheel for voluntary exercise for 16 wk.Results:Fgf21 mRNA in liver and FGF21 protein in plasma were increased by 3.5- to 7-fold in HC mice compared with SFP mice (P < 0.001), whereas the LE dose-dependently attenuated the induction of Fgf21 expression (P < 0.05). After 16 wk, hepatic Fgf21 mRNA did not differ between LFD and HFD mice but was dramatically reduced in the HFD+exercise group to <20% of the level in the HFD group (P < 0.0001).Conclusions: In mice, hepatic Fgf21 expression was upregulated by 1 and 5 wk of feeding a lipogenic HC diet but not by 16 wk of feeding an obesogenic HFD, whereas the addition of fat as an LE to the HC formula significantly reduced Fgf21 gene expression and the plasma FGF21 protein concentration. Our results support a strong and reversible response of hepatic Fgf21 expression to shifts in dietary glucose intake.

Weight-reduction through a low-fat diet causes differential expression of circulating microRNAs in obese C57BL/6 mice.

BackgroundTo examine the circulating microRNA (miRNA) expression profile in a mouse model of diet-induced obesity (DIO) with subsequent weight reduction achieved via low-fat diet (LFD) feeding.ResultsEighteen C57BL/6NCrl male mice were divided into three subgroups: (1) control, mice were fed a standard AIN-76A (fat: 11.5 kcal %) diet for 12 weeks; (2) DIO, mice were fed a 58 kcal % high-fat diet (HFD) for 12 weeks; and (3) DIO + LFD, mice were fed a HFD for 8 weeks to induce obesity and then switched to a 10.5 kcal % LFD for 4 weeks. A switch to LFD feeding led to decreases in body weight, adiposity, and blood glucose levels in DIO mice. Microarray analysis of miRNA using The Mouse & Rat miRNA OneArray® v4 system revealed significant alterations in the expression of miRNAs in DIO and DIO + LFD mice. Notably, 23 circulating miRNAs (mmu-miR-16, mmu-let-7i, mmu-miR-26a, mmu-miR-17, mmu-miR-107, mmu-miR-195, mmu-miR-20a, mmu-miR-25, mmu-miR-15b, mmu-miR-15a, mmu-let-7b, mmu-let-7a, mmu-let-7c, mmu-miR-103, mmu-let-7f, mmu-miR-106a, mmu-miR-106b, mmu-miR-93, mmu-miR-23b, mmu-miR-21, mmu-miR-30b, mmu-miR-221, and mmu-miR-19b) were significantly downregulated in DIO mice but upregulated in DIO + LFD mice. Target prediction and function annotation of associated genes revealed that these genes were predominantly involved in metabolic, insulin signaling, and adipocytokine signaling pathways that directly link the pathophysiological changes associated with obesity and weight reduction.ConclusionsThese results imply that obesity-related reductions in the expression of circulating miRNAs could be reversed through changes in metabolism associated with weight reduction achieved through LFD feeding.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1896-3) contains supplementary material, which is available to authorized users.

Influence of High Fat Diet on Macrophage Behavior and Metabolic Processes in Obesity Sensitive and Resistant Mice: Role of Monocyte Chemoattractant Protein 1

PURPOSEAdipose tissue macrophages are thought to be a major player in the dysregulation of metabolic and inflammatory processes associated with high fat diet (HFD)‐induced obesity. Monocyte chemoattractant protein 1 (MCP‐1) is a chemokine that recruits macrophages to adipose tissue (AT) and has been implicated in manifestations associated with obesity. The purpose of this study was to examine the role of MCP‐1 in response to HFD feedings. We used both C57Bl/6 (obesity sensitive) and FVB/N (obesity resistant) mice in order to determine obesity versus HFD effects. A HFD that was designed by our laboratory and is similar to a standard American diet was used given its clinical relevance.METHODSC57Bl/6 and FVB/N wild‐type (WT) and MCP1‐/‐ mice at 4 wks of age were fed either a HFD or a low fat diet (LFD) for 16 wks. Body composition was analyzed monthly and HOMA index was determined at mice sacrifice at 20 wks of age. AT mRNA expression of chemokines, macrophage markers and protein expression of inflammatory markers were measured using qPCR and western blot, respectively. Macrophage infiltration into AT were examined using immunohistochemistry and flow cytometry.RESULTSAs expected, HFD induced obesity and increased insulin resistance (IR) comparably in the obesity sensitive C57Bl/6 WT and MCP1‐/‐ mice. Surprisingly, the HFD MCP1‐/‐ in the supposed diet resistant FVB/N strain exhibited increased obesity and IR whereas the HFD WT mice were not different from LFD mice. AT macrophage accumulation increased in HFD WT groups for both strains, regardless of obesity status. Interestingly, the response in HFD MCP1‐/‐ was dependent on the strain.

Role of thyroid hormone homeostasis in obesity-prone and obesity-resistant mice fed a high-fat diet

BackgroundThe exact mechanism for different propensities to obesity when consuming a high-fat diet (HFD) is largely unknown. Thyroid hormone (TH) is an important modulator of energy homeostasis and body weight. ObjectiveThe present study aimed to find the potential mechanisms of TH in the development of obesity-prone (OP) and obesity-resistant (OR) mice after short-term and long-term HFD feeding. MethodsC57Bl/6 male mice were randomly divided into two groups: a low-fat diet (LFD) group and an HFD group. In the 7th week, HFD-fed mice were classified as OP or OR according to upper and lower tertiles of body weight. Half of the mice were sacrificed at this time point and the remaining mice were kept on feeding and sacrificed in the 27th week. Indirect calorimetry was performed. At harvest, serum was used for ELISA assays and oxidative stress biomarkers determination. Tissues were dissected for deiodinases activity and relative mRNA expression determination, as well as antioxidant capacity evaluation. ResultsIn the 7th week, OP mice showed a significant body weight gain, decreased energy expenditure (EE), normal circulating TH levels, and activated HPT axis, whereas OR mice had normal body weight and maintained T3 levels only through enhancing hepatic D1 activity. In the 27th week, OR mice gained more body weight than LFD mice accompanied by an activation of HPT axis and decreased hepatic deiodination. Genes involved in TH production were down-regulated in OP mice and up-regulated in OR mice. Changes in deiodinases activity and thyroid function were related with redox status in specific tissues. Furthermore, OP mice had more serious hepatic steatosis than OR mice, with up-regulation of T3 target genes (e.g. Srebp1c, Acc1, Fasn) involved in lipid synthesis and down-regulation of Pgc1α, Cyp7a1 and Cpt1α. ConclusionsHPT axis function and deiodinases activity might be involved in different propensities to obesity and the ability of OR mice to resist obesity was limited.