A Mouse Model of Metabolic Syndrome: Insulin Resistance, Fatty Liver and Non-Alcoholic Fatty Pancreas Disease (NAFPD) in C57BL/6 Mice Fed a High Fat Diet

Diet-induced obesity in C57BL/6 mice triggers common features of human metabolic syndrome (MetS). The purpose is to assess the suitability of a diet-induced obesity model for investigating non-alcoholic fatty pancreatic disease (NAFPD), fatty liver and insulin resistance. Adult C57BL/6 mice were fed either high-fat chow (HFC, 60% fat) or standard chow (SC, 10% fat) during a 16-week period. We evaluated in both groups: hepatopancreatic injuries, pancreatic islets size, alpha and beta-cell immunodensities, intraperitoneal insulin tolerance test (IPITT) and oral glucose tolerance test (OGTT). The HFC mice displayed greater mass gain (p<0.0001) and total visceral fat pads (p<0.001). OGTT showed impairment of glucose clearance in HFC mice (p<0.0001). IPITT revealed insulin resistance in HFC mice (p<0.0001). The HFC mice showed larger pancreatic islet size and significantly greater alpha and beta-cell immunodensities than SC mice. Pancreas and liver from HFC were heavier and contained higher fat concentration. In conclusion, C57BL/6 mice fed a high-fat diet develop features of NAFPD. Insulin resistance and ectopic accumulation of hepatic fat are well known to occur in MetS. Additionally, the importance of fat accumulation in the pancreas has been recently highlighted. Therefore, this model could help to elucidate target organ alterations associated with metabolic syndrome

Modulation of cytokines, resistin, and distribution of adipose tissue in C57BL/6 mice by different high-fat diets

AbstractObjectiveTo investigate whether changing the lipid source induces metabolic changes and/or modulates the adipose tissue distribution in mice fed with a high-fat (HF) diet.MethodsC57BL/6 mice were subjected to a 10-wk control diet (10% fat) or an HF diet (60% fat) containing lard (HF-L), olive oil (HF-O), sunflower oil, or canola oil. Food intake and body weight were measured. At euthanasia, blood was collected and adipose tissue was dissected. Serum hormones and cytokines were determined.ResultsThe plasma insulin levels were higher in the HF-L and HF-O groups than in the other three groups (P < 0.0001). The levels of resistin were highest in the HF-L and HF-O groups (P < 0.0001). Leptin expression was also highest in these two groups (P < 0.0001). Of the four groups, interleukin-6 was expressed at the highest level in the HF-L group (P < 0.0005), whereas adiponectin was expressed at the lowest level (P < 0.0001). The accumulation of subcutaneous and visceral adipose tissues was higher in the HF-L group compared with the other groups. This group was hypertrophic because of excess subcutaneous fat and epididymal fat in the adipocytes. However, the ratio of subcutaneous to visceral fat was significantly lower in the HF-L and HF-O groups compared with the other groups.ConclusionIn mice fed fat-rich diets, the level of adipokines, the distribution of adipose tissue, and the metabolism of carbohydrates are more significantly influenced by the lipid content rather than the absolute amount of lipid

Programming of obesity and comorbidities in the progeny: lessons from a model of diet-induced obese parents.

AIM:To determine the impact of paternal obesity, maternal obesity or the combination of two obese parents on markers of adult offspring metabolism, with a focus on body mass (BM), lipid and carbohydrate, components of lipogenesis and beta-oxidation in the liver, sex dimorphism in the offspring that received a SC diet during the postnatal period. MATERIALS AND METHODS:Male and female C57BL/6 mice were fed a high-fat diet (HF; 49% lipids) or standard chow (SC; 17% lipids) for 8 weeks before mating until lactation. The offspring were labeled according to sex, maternal diet (first letters), paternal diet (second letters), and received a SCdiet until 12-weeks of age when they were sacrificed. BM, eating behavior, glucose tolerance, plasma analysis, gene and protein expression of the components of lipogenesis and beta-oxidation in the liver of offspring were evaluated. RESULTS:HF diet-fed mothers and fathers were overweight, hyperglycemic and glucose intolerant and had a deteriorating lipid profile. The adult male and female offspring of HF-mothers were overweight, with an increased adiposity index, hyperphagic, had an impaired glucose metabolism, increased total cholesterol and triacylglycerol levels, increased lipogenesis concomitant with decreased beta-oxidation resulting in liver steatosis. The male and female offspring of HF-father had impaired glucose metabolism, exacerbated lipogenesis without influencing beta-oxidation and enhanced hepatic steatosis. These findings are independent of BM. Male and female offspring of a mother and father that received a HF diet demonstrated these effects most prominently in adult life. CONCLUSION:Paternal obesity leads to alterations in glucose metabolism, increase in components of lipogenesis and liver steatosis. In contrast, maternal obesity leads to overweight and changes in the metabolic profile and liver resulting from activation of hepatic lipogenesis with impaired beta-oxidation. When both parents are obese, the effects observed in the male and female offspring are exacerbated

Offspring data: liver.

<p>(A) Volume densities (Vv) of steatosis (left frame, n = 5 mice per group) and photomicrographs of the liver (right frame, B-I) from male and female offspring at 12-weeks old (HE staining). Data are expressed as the mean and SD (one-way ANOVA and the posthoc test of Holm-Sidak). Same letters represent equal groups with no statistical difference while different letters represent different groups from each other, with statistical difference (<i>P</i><0.05). Photomicrographs: B and C—male and female offspring of SC mother and SC father, respectively (SC-Mo/SC-Fa); D and E—male and female offspring of SC mother and HF father, respectively (SC-Mo/HF-Fa); F and G—male and female offspring of HF mother and SC father, respectively (HF-Mo/SC-Fa); H and I—male and female offspring of HF mother and HF father, respectively (HF-Mo/HF-Fa). Offspring of obese mother or obese father and both obese parents present numerous hepatocytes with fat droplets (arrows).</p

Sampling design and formation of the groups.

<p>(A) Sampling design for the study and (B) Scheme of the experimental groups. The letters M and F represent the male and female offspring, respectively (in A). Circles represent the female sex, and squares represent the male sex (in B). Abbreviations: Standard-chow group (SC); high-fat group (HF); father (Fa); mother (Mo). <u>Groups</u>—Father that received standard chow (SC-Fa); Father that received high-fat diet (HF-Fa); mother that received standard chow (SC-Mo); mother that received high-fat diet (HF-Mo); offspring of SC mother and SC father (SC-Mo/SC-Fa); offspring of SC mother and HF father (SC-Mo/HF-Fa); offspring of HF mother and SC father (HF-Mo/SC-Fa); offspring of HF mother and HF father (HF-Mo/HF-Fa).</p

Molecular analyses in the offspring liver (panel 2).

<p>(A) G6Pase and (B) PEPCK mRNA levels of the male and female offspring at 12-weeks old. Endogenous control beta-actin was used to normalize the expression of the selected genes. Data are expressed as the mean and SD (n = 5 mice per group, one-way ANOVA and the posthoc test of Holm–Sidak). Same letters represent equal groups with no statistical difference while different letters represent different groups from each other, with statistical difference (<i>P</i><0.05), * different from the corresponding counterpart (<i>P</i><0.05). Abbreviations: phosphoenolpyruvate carboxykinase (PEPCK); glucose-6-phosphatase (G6Pase); offspring of SC mother and SC father (SC-Mo/SC-Fa); offspring of SC mother and HF father (SC-Mo/HF-Fa); offspring of HF mother and SC father (HF-Mo/SC-Fa); offspring of HF mother and HF father (HF-Mo/HF-Fa).</p

RT-qPCR primers and respective sequences.

<p>Abbreviations: carnitine palmitoyltransferase I (CPT-1); peroxisome proliferator activator receptor (PPAR)-alpha, sterol regulatory element binding protein (SREBP)-1c; fatty acid synthase (FAS); phosphoenolpyruvate carboxykinase (PEPCK); glucose-6-phosphatase (G6Pase).</p><p>RT-qPCR primers and respective sequences.</p