High-fat Diet-fed Obese Mice Research Articles

Germinated Soybean Embryo Extract Ameliorates Fatty Liver Injury in High-Fat Diet-Fed Obese Mice.

Soybean is known to have diverse beneficial effects against human diseases, including obesity and its related metabolic disorders. Germinated soybean embryos are enriched with bioactive phytochemicals and known to inhibit diet-induced obesity in mice, but their effect on non-alcoholic fatty liver disease (NAFLD) remains unknown. Here, we germinated soybean embryos for 24 h, and their ethanolic extract (GSEE, 15 and 45 mg/kg) was administered daily to mice fed with a high-fat diet (HFD) for 10 weeks. HFD significantly increased the weight of the body, liver and adipose tissue, as well as serum lipid markers, but soyasaponin Ab-rich GSEE alleviated these changes. Hepatic injury and triglyceride accumulation in HFD-fed mice were attenuated by GSEE via decreased lipid synthesis (SREBP1c) and increased fatty acid oxidation (p-AMPKα, PPARα, PGC1α, and ACOX) and lipid export (MTTP and ApoB). HFD-induced inflammation (TNF-α, IL-6, IL-1β, CD14, F4/80, iNOS, and COX2) was normalized by GSEE in mice livers. In adipose tissue, GSEE downregulated white adipose tissue (WAT) differentiation and lipogenesis (PPARγ, C/EBPα, and FAS) and induced browning genes (PGC1α, PRDM16, CIDEA, and UCP1), which could also beneficially affect the liver via lowering adipose tissue-related circulating lipid levels. Thus, our results suggest that GSEE can prevent HFD-induced NAFLD via inhibition of hepatic inflammation and restoration of lipid metabolisms in both liver and adipose tissue.

Anti-Obesity Effect of Lactobacillus plantarum LB818 Is Associated with Regulation of Gut Microbiota in High-Fat Diet-Fed Obese Mice.

Worldwide, obesity has become a major risk factor associated with health risks such as diabetes, hypertension, hypercholesterolemia, cardiovascular disease, stroke, and certain forms of cancer. In this study, we estimated the anti-obesity effect of the bacterial strain Lactobacillus plantarum LB818 (designated as LB818) using male C57BL/6J mice, which were treated with high-fat diet (HFD) to induce obesity. Next, LB818 (109 colony-forming units [CFU]/mL) was orally administered for 8 weeks. The results showed that feeding HFD+LB818 (109 CFU/mL) ameliorated body weight gain and decreased total body fat by regulating fasting glucose levels in HFD-fed mice. LB818 treatment significantly lowered aspartate aminotransferase, alanine aminotransferase (ALT), total cholesterol (TC), triglyceride (TG), and elevated high-density lipoprotein levels in serum and decreased deposition of fat droplets in liver. LB818 treatment increased the respective abundances of essential bacteria, including Bacteroidetes, Akkermansia, Bifidobacterium, Lactobacillus, and increased the Bacteroidetes:Firmicutes ratio; however, it significantly decreased the levels of Firmicutes. Taken together, this study demonstrates that LB818 is effective in attenuating obesity and hepatic steatosis and regulated gut microbiota in HFD-fed obese mice.

Selenium-enriched Bifidobacterium longum DD98 relieves metabolic alterations and liver injuries associated with obesity in high-fat diet-fed mice

Abstract This study aims to explore the effects of selenium-enriched Bifidobacterium longum DD98 (Se-B. longum DD98) on metabolic alterations and liver injuries associated with obesity in mice fed a high-fat diet (HFD). Mice were randomly divided into nine groups treated with different diets: normal diet, HFD, HFD with sodium selenite, HFD with selenomethionine (SeMet), HFD with B. longum DD98 (BL), HFD with BL + SeMet, and HFD with low, medium, high dose of Se-B. longum DD98. After six weeks, all treatments reduced fasting body weight, improved glucose tolerance and hyperlipidemia symptoms. Se-B. longum DD98 exhibited stronger anti-obesity effects than other treatments. Se-B. longum DD98 balanced hepatic lipid disorder and suppressed liver steatosis. The beneficial effect of Se-B. longum DD98 may be mediated through the regulation of leptin, inflammatory response and oxidative stress. Therefore, Se-B. longum DD98 may prove effective in ameliorating metabolic disorders and liver damages in the development of obesity.

Fruit of Hovenia dulcis Thunb. Induces Nonshivering Thermogenesis through Mitochondrial Biogenesis and Activation by SIRT1 in High-Fat Diet-Fed Obese Mice and Primary Cultured Brown Adipocytes.

Brown adipocytes, which contain abundant mitochondria, use stored energy as fuel during a process named nonshivering thermogenesis. Thus, the pharmacological activation of thermogenesis in brown adipose tissue (BAT) has become a promising target for treating obesity. We investigated the effect of fruit of Hovenial dulcis Thunb. (FHD), a frequently used herbal treatment for liver diseases, on thermogenesis and its mechanism using primary cultured brown adipocytes and BAT of high-fat-diet (HFD)-induced obese mice. Thermogenesis-related factors including UCP1 and PGC1α increased with FHD treatment. FHD also increased mitochondrial biogenesis and activation factors such as nuclear respiratory factor (NRF)1 and oxidative phosphorylation (OXPHOS) complex. Furthermore, FHD increased the intercellular nicotinamide adenine dinucleotide (NAD+) level and sirtuin 1 (SIRT1) activity, which may be responsible for the activation of the thermogenic reaction. Overall, our results suggest that FHD can be a novel option for obesity treatment due to its thermogenic action through mitochondrial biogenesis and activation.

Sesamol Increases Ucp1 Expression in White Adipose Tissues and Stimulates Energy Expenditure in High-Fat Diet-Fed Obese Mice

Sesamol found in sesame oil has been shown to ameliorate obesity by regulating lipid metabolism. However, its effects on energy expenditure and the underlying molecular mechanism have not been clearly elucidated. In this study, we show that sesamol increased the uncoupling protein 1 (Ucp1) expression in adipocytes. The administration of sesamol in high-fat diet (HFD)-fed mice prevented weight gain and improved metabolic derangements. The three-week sesamol treatment of HFD-fed mice, when the body weights were not different between the sesamol and control groups, increased energy expenditure, suggesting that an induced energy expenditure is a primary contributing factor for sesamol’s anti-obese effects. Consistently, sesamol induced the expression of energy-dissipating thermogenic genes, including Ucp1, in white adipose tissues. The microarray analysis showed that sesamol dramatically increased the Nrf2 target genes such as Hmox1 and Atf3 in adipocytes. Moreover, 76% (60/79 genes) of the sesamol-induced genes were also regulated by tert-butylhydroquinone (tBHQ), a known Nrf2 activator. We further verified that sesamol directly activated the Nrf2-mediated transcription. In addition, the Hmox1 and Ucp1 induction by sesamol was compromised in Nrf2-deleted cells, indicating the necessity of Nrf2 in the sesamol-mediated Ucp1 induction. Together, these findings demonstrate the effects of sesamol in inducing Ucp1 and in increasing energy expenditure, further highlighting the use of the Nrf2 activation in stimulating thermogenic adipocytes and in increasing energy expenditure in obesity and its related metabolic diseases.

A phytoestrogen secoisolariciresinol diglucoside induces browning of white adipose tissue and activates non-shivering thermogenesis through AMPK pathway

Secoisolariciresinol diglucoside (SDG) is the main phytoestrogen component of flaxseed known as an antioxidant. Current study focused on the effect of SDG in white adipose tissue (WAT) browning. Browning of WAT is considered as a promising treatment strategy for metabolic diseases. To demonstrate the effect of SDG as an inducer of browning, brown adipocyte markers were investigated in inguinal WAT (iWAT) of high fat diet-fed obese mice and genetically obese db/db mice after SDG administration. SDG increased thermogenic factors such as uncoupling protein 1, peroxisome proliferator-activated receptor gamma coactivator 1 alpha and PR domain containing 16 in iWAT and brown adipose tissue (BAT) of mice. Similar results were shown in beige-induced 3T3-L1 adipocytes and primary cultured brown adipocytes. Furthermore, SDG increased factors of mitochondrial biogenesis and activation. We also observed SDG-induced alteration of AMP-activated protein kinase α (AMPKα). As AMPKα is closely related in the regulation of adipogenesis and thermogenesis, we then evaluated the effect of SDG in AMPKα-inhibited conditions. Genetic or chemical inhibition of AMPKα demonstrated that the role of SDG on browning and thermogenesis was dependent on AMPKα signaling. In conclusion, our data suggest SDG as a potential candidate for improvement of obesity and other metabolic disorders.

Modulation of Gut Microbiota by Fucoxanthin During Alleviation of Obesity in High-Fat Diet-Fed Mice.

Fucoxanthin (Fx), an allenic carotenoid from brown seaweeds or diatoms, has been demonstrated to prevent obesity. Gut dysbiosis and inflammation are two counted important incidence reasons of obesity and related diseases. In this paper, a mouse model induced by high-fat diet (HFD) was used to reveal the role of Fx in modulating intestinal homeostasis and treating obesity. In addition, 16S rRNA sequencing results inferred that Fx alleviated HFD-induced gut microbiota dysbiosis by significantly inhibiting the growth of obesity-/inflammation-related Lachnospiraceae and Erysipelotrichaceae while promoting the growth of Lactobacillus/Lactococcus, Bifidobacterium, and some butyrate-producing bacteria. The correlation analysis showed that some gut microbiota taxa were strongly correlated with obesity phenotypes and the inflammation level. In conclusion, dietary Fx has the potential to alleviate the development of obesity and related symptoms through mediating the composition of gut microbiota as demonstrated in mice. This study provides scientific evidence for the potential effects of Fx on obesity treatment.

Resveratrol reduces obesity in high-fat diet-fed mice via modulating the composition and metabolic function of the gut microbiota

Resveratrol (RSV) is a natural polyphenol with anti-obesity effects. However, the mechanisms of anti-obesity remain unclear due to its low bioavailability. Recent evidence demonstrates that gut microbiota plays a key role in obesity. This spurred us to investigate whether the anti-obesity effects of RSV are related to modulations in the gut microbiota and metabolic functions. Here, RSV significantly improved metabolic phenotype and intestinal oxidative stress in the high-fat diet (HFD)-fed mice. A multi-omics approach was used to systematically profile the microbial signatures at both the phylogenetic and functional levels using 16S rRNA gene sequencing and metagenome. At the phylogenetic level, RSV treatment significantly modulated the gut microbiota composition in HFD-fed mice, characterized with increased Blautia abundance and decreased Desulfovibrio and Lachnospiraceae_NK4A136_group abundance. At the functional level, RSV significantly decreased the enrichment of pathways linked to host metabolic disease and increased the enrichment of pathways involved in the generation of small metabolites. Besides, the fecal microbiota transplantation experiment showed anti-obesity and microbiota-modulating effects similar to those observed in the oral RSV-feeding experiment. Furthermore, metabolomic analysis and antibiotic treatment verified that 4-hydroxyphenylacetic acid (4-HPA) and 3-hydroxyphenylpropionic acid (3-HPP) were the two gut metabolites of RSV, which contribute to improving lipid metabolism in vitro. Moreover, the content of 4-HPA and 3-HPP exhibited strong correlation with the intestinal oxidative state. We concluded that the RSV-mediated alteration of gut microbiota, related gut metabolites and redox state of the intestinal environment contributed to prevention of metabolic syndrome in HFD-fed mice.

Peroxiredoxin 2 deficiency does not affect insulin resistance and oxidative stress in high-fat diet-fed obese mice

Objective To examine if peroxiredoxin 2 (Prx2) deficiency aggravates high-fat diet-induced insulin resistance. Material and methods Insulin sensitivity was measured in Prx2 knockout (KO) and wild-type (WT) littermates using the hyperinsulinemic-euglycemic clamp. Results Whole body glucose turnover, glucose uptake, and levels of glucose transporter 4 (Glut4) protein in the skeletal muscle were found to be lower. This was followed by increased expression of oxidative stress markers in Prx2 KO mice than that in WT mice in the control diet group. Although, a 12-week high-fat diet induced insulin resistance and enhanced oxidative stress in both genotypes, there was no difference between WT and Prx2 KO mice with respect to insulin sensitivity and the level of oxidative stress markers. Accordingly, the levels of phosphorylated Akt and Glut4 were similar between the two genotypes. Conclusion These results suggest that Prx2 does not affect high-fat diet-induced oxidative stress and insulin resistance in mice.

Dietary Silk Peptide Prevents High-Fat Diet-Induced Obesity and Promotes Adipose Browning by Activating AMP-Activated Protein Kinase in Mice.

Obesity is associated with metabolic syndrome and other chronic diseases, and is caused when the energy intake is greater than the energy expenditure. We aimed to determine the mechanism whereby acid-hydrolyzed silk peptide (SP) prevents high-fat diet-induced obesity, and whether it induces browning and fatty acid oxidation (FAO) in white adipose tissue (WAT), using in vivo and ex vivo approaches. We determined the effects of dietary SP in high-fat diet-fed obese mice. The expression of adipose tissue-specific genes was quantified by western blotting, qRT-PCR, and immunofluorescence analysis. We also investigated whether SP directly induces browning in primarily subcutaneous WAT-derived adipocytes. Our findings demonstrate that SP has a browning effect in WAT by upregulating AMP-activated Protein Kinase (AMPK) phosphorylation and uncoupling protein 1 (UCP1) expression. SP also suppresses adipogenesis and promotes FAO, implying that it may have potential as an anti-obesity drug.

Chronic n-3 fatty acid intake enhances insulin response to oral glucose and elevates GLP-1 in high-fat diet-fed obese mice

n-3 polyunsaturated fatty acids (PUFA) can exert beneficial effects on glucose homeostasis, especially in obese rodents. Gut incretin hormones regulate glucose and lipid homeostasis, but their involvement in the above effects is not entirely clear. This study aims to assess the effects of chronic n-3 PUFA administration on the insulin and incretin responses in C57BL/6N obese male mice subjected to oral glucose tolerance test (oGTT) after 8 weeks of feeding a corn-oil-based high-fat diet (cHF). The weight gain and adiposity were partially reduced in mice fed cHF in which some of the corn oil was replaced with n-3 PUFA concentrate containing ∼60% DHA and EPA in a 3 : 1 ratio. In addition, these mice had improved glucose tolerance, which was consistent with an increased insulin response to oral glucose and plasma glucagon-like peptide-1 (GLP-1) levels. While the stimulatory effects of n-3 PUFA on GLP-1 levels could not be attributed to changes in intestinal or plasma dipeptidyl peptidase-4 activity, their beneficial effects on glucose tolerance were abolished when mice were pretreated with the GLP-1 receptor antagonist exendin 9-39. Moreover, chronic n-3 PUFA intake prevented the detrimental effects of cHF feeding on glucose-stimulated insulin secretion in the pancreatic islets. Collectively, our data suggest that n-3 PUFA may modulate postprandial glucose metabolism in obese mice through a GLP-1-based mechanism. The significance of these findings in terms of the effective DHA and EPA ratio of the n-3 PUFA concentrate as well as the effect of n-3 PUFA in humans requires further research.

Metformin treatment of high-fat diet-fed obese male mice restores sperm function and fetal growth, without requiring weight loss.

Male obesity is associated with subfertility and increased disease risk of offspring. It is unknown if effects can be reversed through pharmacological interventions. Five- to 6-week-old C57BL6 male mice were fed control diet (n = 10, CD) or high-fat diet (n = 20, HFD) for 16 weeks. Animals fed with a HFD were then allocated to continuation of HFD (n = 8) or HFD with metformin 28 mg kg−1 day−1 (n = 8) for 6 weeks. Animals fed with CD continued on a CD (n = 9). Males were mated with fertile C57BL6 females for the assessment of pregnancy and fetal growth. Sperm motility, spermatozoa and testicular morphology, sperm-zona pellucida binding, sperm reactive oxygen species (ROS) (intracellular [DCFDA], superoxide [MSR], and oxidative DNA lesions [8OHdG]), and mitochondrial membrane potential (JC1) were assessed. Metformin treatment of HFD males improved glucose tolerance (+12%, P < 0.05) and reduced Homeostatic Model Assessment of Insulin Resistance (HOMA-IR; −36%, P < 0.05). This occurred in the absence of a change in body weight or adiposity. Metformin treatment of HFD-fed males restored testicular morphology (+33%, P < 0.05), sperm motility (+66%, P < 0.05), sperm–zona pellucida binding (+25%, P < 0.05), sperm intracellular ROS concentrations (−32%, P < 0.05), and oxidative DNA lesions (−45%, P < 0.05) to the levels of the CD males. Metformin treatment of HFD fathers increased fetal weights and lengths compared with those born to HFD fathers (+8%, P < 0.05), with fetal lengths restored to those of fetuses of CD males. Short-term metformin treatment in men who are obese could be a potential intervention for the treatment of subfertility, without the need for a reduction in body weight/adiposity.

Roles of leptin in the recovery of muscle and bone by reloading after mechanical unloading in high fat diet-fed obese mice

Muscle and bone masses are elevated by the increased mechanical stress associated with body weight gain in obesity. However, the mechanisms by which obesity affects muscle and bone remain unclear. We herein investigated the roles of obesity and humoral factors from adipose tissue in the recovery phase after reloading from disuse-induced muscle wasting and bone loss using normal diet (ND)- or high fat diet (HFD)-fed mice with hindlimb unloading (HU) and subsequent reloading. Obesity did not affect decreases in trabecular bone mineral density (BMD), muscle mass in the lower leg, or grip strength in HU mice. Obesity significantly increased trabecular BMD, muscle mass in the lower leg, and grip strength in reloading mice over those in reloading mice fed ND. Among the humoral factors in epididymal and subcutaneous adipose tissue, leptin mRNA levels were significantly higher in reloading mice fed HFD than in mice fed ND. Moreover, circulating leptin levels were significantly higher in reloading mice fed HFD than in mice fed ND. Leptin mRNA levels in epididymal adipose tissue or serum leptin levels positively correlated with the increases in trabecular BMD, total muscle mass, and grip strength in reloading mice fed ND and HFD. The present study is the first to demonstrate that obesity enhances the recovery of bone and muscle masses as well as strength decreased by disuse after reloading in mice. Leptin may contribute to the recovery of muscle and bone enhanced by obesity in mice.

Selenoprotein W deficiency does not affect oxidative stress and insulin sensitivity in the skeletal muscle of high-fat diet-fed obese mice.

Selenoprotein W (SelW) is a selenium-containing protein with a redox motif found abundantly in the skeletal muscle of rodents. Previous in vitro studies suggest that SelW plays an antioxidant role; however, relatively few in vivo studies have addressed the antioxidant role of SelW. Since oxidative stress is a causative factor for the development of insulin resistance in obese subjects, we hypothesized that if SelW plays a role as an antioxidant, SelW deficiency could aggravate the oxidative stress and insulin resistance caused by a high-fat diet. SelW deficiency did not affect insulin sensitivity and H2O2 levels in the skeletal muscle of control diet-fed mice. SelW levels in the skeletal muscle were decreased by high-fat diet feeding for 12 wk. High-fat diet induced obesity and insulin resistance and increased the levels of H2O2 and oxidative stress makers, which were not affected by SelW deficiency. High-fat diet feeding increased the expression of antioxidant enzymes; however, SelW deficiency did not affect the expression levels of antioxidants. These results suggest that SelW does not play a protective role against oxidative stress and insulin resistance in the skeletal muscle of high-fat diet-fed obese mice.

Chronic Treatment with α-Lipoic Acid Improves Endothelium-Dependent Vasorelaxation of Aortas in High-Fat Diet-Fed Mice

α-Lipoic acid (ALA) is used as a dietary supplement and known as an anti-oxidant. The present study aimed to examine whether ALA improves endothelial dysfunction in high-fat diet-fed obese mice. After feeding a high-fat diet to Institute of Cancer Research (ICR) mice for 4 weeks, the mice were maintained with a high-fat diet (group HF) or a high-fat diet containing ALA (25 mg/d, group HF + ALA) for an additional 20 weeks. Age-matched normal diet-fed mice were also used (group Normal). Chronic oral treatment with ALA did not affect various plasma parameters or body weights. As compared with the aortas of Normal mice, those from HF mice showed impaired endothelium-dependent relaxation in response to clonidine. However, such an impairment was not observed in the aortas from HF + ALA mice. The plasma levels of thiobarbituric acid reactive substances, an indicator of oxidative stress, were significantly decreased in HF + ALA mice compared with HF mice, confirming the anti-oxidative effects of ALA. In addition, when the impaired clonidine-induced vasorelaxation of aortas from normal mice under high glucose conditions was used as a model of acute oxidative stress, the vasorelaxation responses were improved in the presence of ALA at 100 µM. Our results suggested that the chronic oral administration of ALA improves endothelial dysfunction in high-fat diet-fed obese mice possibly through the reduction in oxidative stress in vivo.

Citrus aurantium L. var. amara Engl. inhibited lipid accumulation in 3T3-L1 cells and Caenorhabditis elegans and prevented obesity in high-fat diet-fed mice

Natural products with anti-obesity effects and few side effects have attracted great attention recently. Citrus aurantium L. var. amara Engl. (CAVA) is popularly consumed as an edible and medicinal resource in China. However, its anti-obesity effects were poorly understood. The anti-obesity effects of CAVA extracts were systematically evaluated using 3T3-L1 cells, Caenorhabditis elegans (C. elegans) and high fat diet (HFD)-fed mice. Flavonoid-rich (EA) extracts with neohesperidin, hesperidin and naringin comprising 32.15%, were isolated from CAVA. EA extracts treatment significantly inhibited differentiation of 3T3-L1 preadipocytes by modulating lipid metabolism-related mediators. EA extracts supplementation also inhibited antioxidant responses in C. elegans by decreasing reactive oxygen species generation and malonaldehyde value, and increasing superoxide dismutase content. EA extracts feeding markedly decreased triglyceride (TG) content, and affected expression of genes involved in lipid and glucose metabolism in wild type C. elegans. TG content in mdt-15 (XA7702) mutants was not decreased by EA extracts administration, suggesting that EA extracts treatment might inhibit lipid accumulation in C. elegans dependent on mdt-15. EA extracts intervention further reduced body weight gain and modulated plasma biochemical parameters in HFD-fed mice. EA extracts treatment prevented HFD-induced epididymal adipose hypertrophy, liver oxidative injuries and steatosis. EA extracts administration also strongly prevented HFD-induced reduction of gut microbial diversity, decreased the Firmicutes-to-Bacteroidetes ratio and the Erysipelotrichaceae abundance, and enhanced the Bifidobacteriace abundance in HFD-fed mice. EA extracts from blossoms of CAVA were excellent antiobesogenic candidates that acted through multiple mechanisms that acted simultaneously.

Acute suppression of insulin resistance-associated hepatic miR-29 in vivo improves glycemic control in adult mice

MicroRNAs (miRNAs) are important posttranscriptional regulators of metabolism and energy homeostasis. Dysregulation of certain miRNAs in the liver has been shown to contribute to the pathogenesis of Type 2 diabetes (T2D), in part by impairing hepatic insulin sensitivity. By small RNA-sequencing analysis, we identified seven hepatic miRNAs (including miR-29b) that are consistently aberrantly expressed across five different rodent models of metabolic dysfunction that share the feature of insulin resistance (IR). We also showed that hepatic miR-29b exhibits persistent dysregulation during disease progression in a rat model of diabetes, UCD-T2DM. Furthermore, we observed that hepatic levels of miR-29 family members are attenuated by interventions known to improve IR in rodent and rhesus macaque models. To examine the function of the miR-29 family in modulating insulin sensitivity, we used locked nucleic acid (LNA) technology and demonstrated that acute in vivo suppression of the miR-29 family in adult mice leads to significant reduction of fasting blood glucose (in both chow-fed lean and high-fat diet-fed obese mice) and improvement in insulin sensitivity (in chow-fed lean mice). We carried out whole transcriptome studies and uncovered candidate mechanisms, including regulation of DNA methyltransferase 3a (Dnmt3a) and the hormone-encoding gene Energy homeostasis associated (Enho). In sum, we showed that IR/T2D is linked to dysregulation of hepatic miR-29b across numerous models and that acute suppression of the miR-29 family in adult mice leads to improved glycemic control. Future studies should investigate the therapeutic utility of miR-29 suppression in different metabolic disease states.Enho; insulin resistance; liver; microRNA-29 (miR-29); UCD-T2DM.

Altered Gut Microbiota Is a Novel Mechanism for the Adverse Effects Induced by Foodborne Titanium Dioxide Nanoparticles in Obese and Non-obese Mice (P21-021-19)

ObjectivesMany food products contain inorganic nanoparticles (NPs), such as titanium dioxide (TiO2) NPs. There is increasing concern about the potential unintended health risks associated with foodborne TiO2 NPs in certain populations, such as the obese. The purpose of this study was to determine the adverse effects of TiO2 NPs in obese individuals, the molecular mechanism involved and the potential role of gut microbiota in mediating the adverse effects. MethodsTwo types of TiO2 (30 nm and E171-Food grade TiO2) were mixed with mouse diet at 0.1 wt% and fed to two populations of mice (high-fat diet-fed obese mice and non-obese mice). Meanwhile, fecal samples from the above groups of mice were collected weekly for transplanting to four groups of mice fed a low-fat diet for 10 weeks. 16 s rRNA gene amplicon sequencing, histological analysis, immunohistochemistry, ELISA and SCFAs analysis were utilized to characterize the composition of the microbiota, inflammation status, and the effects of altered gut microbiota on the inflammation status of the mouse colon. ResultsTiO2 NPs significantly altered the composition of gut microbiota with stronger alterations in the high-fat diet-fed obese mice than the low-fat diet-fed non-obese mice. The abundance of inflammation-related cytokines (e.g., IL-10, IL-12p70, and IL-17) and myeloperoxidase (MPO) in the mouse colonic mucosa were significantly altered by TiO2 NPs to produce an inflammatory state. TiO2 NPs decreased the cecal levels of SCFAs such as butyrate. Moreover, the magnitude of the above alteration was higher in the obese mice than in the non-obese mice. After 10 weeks of microbial transplant, microbiota from the mice consuming a high-fat diet with TiO2 NPs led to an increase of pro-inflammatory cytokines, loss of healthy colonic morphology, and infiltration of immune cells in the colon of the low-fat diet-fed recipient mice, indicating a significant colonic inflammation. ConclusionsTiO2 NPs altered gut microbiota in both obese and non-obese mice, with stronger effects in the obese mice, and the alteration of gut microbiota led to colonic inflammation in the mice. Overall, these findings provided a valuable new perspective on the potential adverse effects and appropriate mechanisms of foodborne TiO2 NPs among populations with different obese status. Funding SourcesUSDA/NIFA competitive grants to Hang Xiao.

Protopanaxadiol alleviates obesity in high-fat diet-fed mice via activation of energy-sensing neuron in the paraventricular nucleus of hypothalamus

Obesity is one of the most important health problems worldwide. Panax ginseng has been reported to exert anti-obesity effect. However, the active constituents and the underlying mechanism remained uncertain. This study uncovered the anti-obesity effect of protopanaxadiol (PPD) and its potential mechanism. To investigate the anti-obesity effect of PPD, high-fat diet induced obesity (DIO) C57BL/6 mice were treated with PPD by both intraperitoneal injection (i.p.) and oral administration. Body weight and food intake were recorded. Energy expenditure was measured by CLAMS metabolic cages. For mechanism study, C-Fos in the hypothalamus of the mice was stained following the intracerebroventricular (i.c.v.) injection of PPD. Our results showed that with both injection and feeding, PPD reduced body weight, inhibited food intake, increased energy expenditure and improved liver damage in DIO mice. Mechanistically, i.c.v. injection of PPD inhibited feeding and increased C-Fos expression in paraventricular nucleus of the hypothalamus (PVH). The results suggest that PPD may reduce body weight of DIO mice via the activation of PVH neurons and PPD is a potential therapeutic candidate for the treatment of obesity.

Macrophage-specific hypoxia-inducible factor-1α deletion suppresses the development of liver tumors in high-fat diet-fed obese and diabetic mice.

Aims/IntroductionChronic inflammation of the liver is often observed with obesity or type 2 diabetes. In these pathological conditions, the immunological cells, such as macrophages, play important roles in the development or growth of liver cancer. Recently, it was reported that hypoxia‐inducible factor‐1α (HIF‐1α) is a key molecule for the acquisition of inflammatory M1 polarity of macrophages. In the present study, we examined the effects of altered macrophage polarity on obesity‐ and diabetes‐associated liver cancer using macrophage‐specific HIF‐1α knockout (KO) mice.Materials and MethodsTo induce liver cancer in the mice, diethylnitrosamine, a chemical carcinogen, was used. Both KO mice and wild‐type littermates were fed either a high‐fat diet (HFD) or normal chow. They were mainly analyzed 6 months after HFD feeding.ResultsDevelopment of liver cancer after HFD feeding was 45% less in KO mice than in wild‐type littermates mice. Phosphorylation of extracellular signal‐regulated kinase 2 was also lower in the liver of KO mice. Those effects of HIF‐1α deletion in macrophages were not observed in normal chow‐fed mice. Furthermore, the size of liver tumors did not differ between KO and wild‐type littermates mice, even those on a HFD. These results suggest that the activation of macrophage HIF‐1α by HFD is involved not in the growth, but in the development of liver cancer with the enhanced oncogenic extracellular signal‐regulated kinase 2 signaling in hepatocytes.ConclusionsThe activation of macrophage HIF‐1α might play important roles in the development of liver cancer associated with diet‐induced obesity and diabetes.