A Mouse Model of Metabolic Syndrome; Increase in Visceral Adipose Tissue Precedes the Development of Fatty Liver and Insulin Resistance in High-Fat Diet-Fed Male KK/Ta Mice

Pathophysiological Mechanisms and Clinical Associations of Non-Alcoholic Fatty Pancreas Disease

Non-Alcoholic Fatty Pancreas disease (NAFPD), characterized by fat accumulation in pancreatic tissue, is an emerging clinical entity. However, the clinical associations, the underlying molecular drivers, and the pathophysiological mechanisms of NAFPD have not yet been characterized in detail. The NAFPD spectrum not only includes infiltration and accumulation of fat within and between pancreatic cells but also involves several inflammatory processes, dysregulation of physiological metabolic pathways, and hormonal defects. A deeper understanding of the underlying molecular mechanisms is key to correlate NAFPD with clinical entities including non-alcoholic fatty liver disease, metabolic syndrome, diabetes mellitus, atherosclerosis, as well as pancreatic cancer and pancreatitis. The aim of this review is to examine the pathophysiological mechanisms of NAFPD and to assess the possible causative/predictive risk factors of NAFPD-related clinical syndromes.

Coptis chinensis, and extracts of guava and mulberry leaves present good inhibiting potential on obesity and associated metabolic disorders in high-fat diet obesity mice model

This study aimed to investigate the anti-obesity effects of Coptis chinensis (CC), BALASAN (combinational guava leaf extract and mulberry leaf extract), and CC/BALASAN (CC/BAL) on high-fat diet-induced obese C57BL/6 mice and to explore possible mediating mechanisms in 3T3-L1 pre-adipocytes. Oil red-O stain was used to test the effects of CC, BALASAN, and CC/BAL on the differentiation of 3T3-L1 pre-adipocytes. Additionally, real-time PCR was used to detect the expression of genes involved in adipocyte differentiation and inflammation-related genes in adipose tissue of mice that were fed a high-fat diet. CC, BALASAN, and CC/BAL inhibited the differentiation of 3T3-L1 pre-adipocytes and exhibited excellent inhibitory ability against the expression of PPARγ and RXRα genes associated with adipocyte differentiation. Replenishing mice with a high-fat diet with CC, BALASAN, and CC/BAL reduced body weight gaining and blood glucose and plasma cholesterol levels. CC also effectively reduced liver weight, whereas BALASAN and CC/BAL had no inhibitory effect. In addition, CC effectively inhibited the expression of C/EBP-α in adipose tissue. Interestingly, BALASAN not only inhibited the expression of C/EBP-α, but also that of PPARγ, RXRα, and TNFα. Such data indicated that CC, BALASAN, and CC/BAL may have potentially beneficial effects against obesity and associated metabolic disorders by down-regulating the PPARγ/RXRα pathway.

Effects of different diets used to induce obesity/metabolic syndrome on bladder function in rats

Preclinical and human studies on the relationship between obesity/metabolic syndrome (MetS) and lower urinary tract dysfunction (LUTD) are inconsistent. We compared the temporal effects of feeding four different diets used to induce obesity/MetS, including 60% fructose, 2% cholesterol +10% lard, 30% fructose + 20% lard, or 32.5% lard diet, up to 42 wk, on metabolic parameters and bladder function in male Sprague-Dawley rats. Rats fed a 30% fructose + 20% lard or 32.5% lard diet consumed less food (grams), but only the 32.5% lard diet group took in more calories. Feeding rats a 60% fructose or 30% fructose + 20% lard diet led to glucose intolerance and increased blood pressure. Higher body weight and increased cholesterol levels were observed in the rats maintained on a 2% cholesterol +10% lard diet, whereas exposure to a 32.5% lard diet affected most of the above parameters. Voiding behavior measurement showed that voiding frequency and the total voided volume were lower in the experimental diet groups except for the 30% fructose + 20% lard group. The mean voided volume was lower in the 30% fructose + 20% lard and 32.5% lard groups compared with the control group. Cystometric analysis revealed a decreased bladder capacity, mean voided volume, intermicturition interval, and compliance in the 32.5% lard diet group. In conclusion, experimental diets including 60% fructose, 30% fructose + 20% lard, or 2% cholesterol + 10% lard diet differently affected physiological and metabolic parameters and bladder function to a limited extent, while exposure to a 32.5% lard diet had a greater impact.

Adipose tissue dysfunction and visceral fat are associated with hepatic insulin resistance and severity of NASH even in lean individuals

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is a heterogeneous disorder, but the factors that determine this heterogeneity remain poorly understood. Adipose tissue dysfunction is causally linked to NAFLD since it causes intrahepatic triglyceride (IHTG) accumulation through increased hepatic lipid flow, due to insulin resistance and pro-inflammatory adipokines release. While many studies in NAFLD have looked at total adiposity (i.e. mainly subcutaneous fat, SC-AT), it is still unclear the possible impact of visceral fat (VF). Thus, we investigated how VF versus SC-AT was related to NAFLD severity in lean, overweight and obese individuals versus lean controls.

METHODS

Thirty-two non-diabetic NAFLD with liver biopsy (BMI 21.4-34.7 kg/m² ) and eight lean individuals (BMI 19.6-22.8 kg/m² ) were characterized for fat distribution (VF, SC-AT and IHTG by magnetic resonance imaging), lipolysis and insulin resistance by tracer infusion, free fatty acids (FFAs) and triglyceride (TAG) concentration and composition (by mass spectrometry).

RESULTS

Intrahepatic triglyceride was positively associated with lipolysis, adipose tissue insulin resistance (Adipo-IR), TAG concentrations, and increased saturated/unsaturated FFA ratio. Compared to controls VF was higher in NAFLD (including lean individuals), increased with fibrosis stage and associated with insulin resistance in liver, muscle and adipose tissue, increased lipolysis and decreased adiponectin levels. Collectively, our results suggest that VF accumulation, given its location close to the liver, is one of the major risk factors for NAFLD.

CONCLUSIONS

These findings propose VF as an early indicator of NAFLD progression independently of BMI, which may allow for evidence-based prevention and intervention strategies.

Fish Oil Enriched n-3 Polyunsaturated Fatty Acids Improve Ketogenic Low-Carbohydrate/High-Fat Diet-Caused Dyslipidemia, Excessive Fat Accumulation, and Weight Control in Rats

Low-carbohydrate and high-fat diets have been used for body weight (BW) control, but their adverse effects on lipid profiles have raised concern. Fish oil (FO), rich in omega-3 polyunsaturated fatty acids, has profound effects on lipid metabolism. We hypothesized that FO supplementation might improve the lipid metabolic disturbance elicited by low-carbohydrate and high-fat diets. Male SD rats were randomized into normal control diet (NC), high-fat diet (HF), and low-carbohydrate/high-fat diet (LC) groups in experiment 1, and NC, LC, LC + 5% FO (5CF), and LC + 10% FO diet (10CF) groups in experiment 2. The experimental duration was 11 weeks. In the LC group, a ketotic state was induced, and food intake was decreased; however, it did not result in BW loss compared to either the HF or NC groups. In the 5CF group, rats lost significant BW. Dyslipidemia, perirenal and epididymal fat accumulation, hepatic steatosis, and increases in triglyceride and plasma leptin levels were observed in the LC group but were attenuated by FO supplementation. These findings suggest that a ketogenic low-carbohydrate/high-fat diet with no favorable effect on body weight causes visceral and liver lipid accumulation. FO supplementation not only aids in body weight control but also improves lipid metabolism in low-carbohydrate/high-fat diet-fed rats.

Phenotypic and genotypic changes in obesity and type 2 diabetes of male KK mice with aging

Research into the prevention and treatment of age-related metabolic diseases are important in the present-day situation of the aging population. We propose that an elderly diabetic mouse model may be useful to such research as it exhibits deterioration of glucose and lipid metabolism. Although the KK mouse strain is commonly used as a model of moderate obesity and type 2 diabetes, the utility of this strain as an elderly obese and diabetic model mouse for research into aging remains unclear. The present study aimed to investigate age-related changes of glucose and lipid metabolism in male KK mice fed a standard chow diet. We demonstrate that 40 weeks KK mice exhibit age-related dysfunctions, such as development of insulin resistance associated with pancreatic islet hypertrophy and decreased lipolysis in white adipose tissue (WAT) compared with 15 weeks KK mice. However, aging does not appear to cause mitochondrial dysfunction of brown adipose tissue. Unexpectedly, hyperglycemia, potential glucose uptake in insulin-sensitive organs, hepatic lipid accumulation, hypertrophy of adipocytes, and inflammation in epididymal WAT did not worsen but rather compensated in 40 weeks KK mice. Our data indicate that the use of male KK mice as an elderly obese and diabetic mouse model has some limitations and in order to represent a useful elderly obese and diabetic animal model, it may be necessary to induce deterioration of glucose and lipid metabolism in KK mice through breeding with high-sucrose or high-fat diets.

RYGB Is More Effective than VSG at Protecting Mice from Prolonged High-Fat Diet Exposure: An Occasion to Roll Up Our Sleeves?

PURPOSE

Understanding the effects of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on adipose tissue physiology is important for the treatment of obesity-related metabolic disorders. By using robust mouse models of bariatric surgery that closely resemble those performed in humans, we can compare the effects of RYGB and VSG on adipose physiology in the absence of post-operative confounds such as diet and lifestyle changes.

MATERIALS AND METHODS

RYGB and VSG were compared using a diet-induced mouse model of obesity. High-fat diet (HFD) was administered post-operatively and changes to white and brown adipose tissue were evaluated, along with alterations to weight, glucose homeostasis, dyslipidemia, and insulin sensitivity.

RESULTS

After prolonged exposure to high-fat diet post-operatively, RYGB was effective in achieving sustained weight loss, while VSG unexpectedly accelerated weight gain rates. The resolution of obesity-related comorbidities such as glucose and insulin intolerance, dyslipidemia, and insulin sensitivity was improved after RYGB, but not for VSG. In RYGB, there were improvements to the function and health of white adipose tissue, enhanced brown adipose metabolism, and the browning of subcutaneous white adipose tissue, with no comparable changes seen for these factors after VSG. Some markers of systemic inflammation improved after both RYGB and VSG.

CONCLUSION

There are significantly different effects between RYGB and VSG when HFD is administered post-operatively and robust mouse models of bariatric surgery are used. RYGB resulted in lasting physiological and metabolic changes but VSG showed little difference from that of its sham-operated, DIO counterpart.

Hesperidin ameliorates signs of the metabolic syndrome and cardiac dysfunction via IRS/Akt/GLUT4 signaling pathway in a rat model of diet-induced metabolic syndrome

BACKGROUND

Hesperidin has been reported to have biological activities such as antihypertensive, hypoglycemic, and antioxidant effects. This study investigated whether hesperidin could improve signs of the metabolic syndrome and cardiac function in a high-fat diet (HFD) induced metabolic syndrome (MS) in rats.

METHODS

Male Sprague-Dawley rats were fed HFD and 15% fructose for 16 weeks and treated with hesperidin (15 or 30 mg/kg, based on signs of MS from a preliminary study) or metformin, a positive control agent, (100 mg/kg) for the final four weeks. Cardiac function, blood pressure, fasting blood glucose, oral glucose tolerance, serum insulin, and lipid profiles were measured. Histomorphometrics of left ventricles, epidydimal fat pads and liver were evaluated. Expressions of phosphorylate insulin receptor substrate1(p-IRS1), p-Akt and GLUT4 in cardiac tissue were determined.

RESULTS

Hesperidin and metformin attenuated MS in HFD rats (p < 0.05). The accumulation of visceral fat pads and fatty liver associated with increases in liver lipid contents and liver enzymes were found in MS rats that were alleviated in hesperidin or metformin-treated groups (p < 0.05). Hesperidin and metformin improved cardiac dysfunction and hypertrophy observed in MS rats (p < 0.05). Restoration of the insulin signaling pathway, IRS/Akt/GLUT4 protein expression, was demonstrated in hesperidin and metformin-treated groups (p < 0.05). Hesperidin (30 mg/kg) was more effective than the lower dose.

CONCLUSION

Hesperidin was effective in reducing signs of MS and alterations of LV hypertrophy and function. These beneficial effects on the heart were associated with the restoration of the cardiac insulin signaling pathway in MS rats.

Hepatoprotective Role of Eclipta alba against High Fatty Diet Treated Experimental Models - A Histopathological Study

Background

The hepatic injury due to oxidative stress was ameliorated through administration of an aqueous extract of Eclipta alba leaves and suggested that wedelolactone and demethylwedelolactone were the possible components of Eclipta alba behind the protective effect on liver as well as against liver disorders.

Objective

To study the hepato-protective effects of Eclipta alba on high fatty diet treated experimental models.

Material and methods

A total of 30 adult albino rats of Wistar strain weighing 165-215 grams, from the animal house of the Basaveshwara Medical College, Hospital and Research Centre, Chitradurga, were used for the present study: group 1 included animals fed with normal diet (control); group 2, animals treated with hyperlipidemic diet for eight weeks; group 3, animals treated with hyperlipidemic diet for eight weeks, followed by one week post treatment of Eclipta alba with normal diet; group 4, animals treated with hyperlipidemic diet for eight weeks, followed by two weeks post-treatment of Eclipta alba with normal diet; and group 5, animals treated with hyperlipidemic diet for eight weeks, followed by three weeks posttreatment of Eclipta alba with normal diet.

Results

In animals with high fat diet (30%), we observed the deposition of fat in the form of fat lobules in and around the hepatocytes, mononuclear in filtration in the liver parenchyma, dilation of blood vessels, necrotic foci and damaged hepatocytes.

Conclusion

The components of Eclipta alba like wedelolactone, demethylwedelolactone and saponins reduced fat deposition, mononuclear infiltration, and necrotic foci, and stimulated hepatocyte regeneration in the liver.

Combined treatment of dipeptidyl peptidase-4 inhibitor and exercise training improves lipid profile in KK/Ta mice

NEW FINDINGS

What is the central question of this study? Exercise for type 2 diabetes patients treated with insulin therapy involves the risk of hypoglycaemia. Dipeptidyl peptidase-4 (DPP-4) inhibitors can be effective in combination with exercise because they reduce the incidence of hypoglycaemia. We evaluated the effect of this combination of treatments on hepatic lipid metabolism in diabetic KK/Ta mice. What is the main finding and its importance? The combination of a DPP-4 inhibitor and exercise, which lowers the risk of hypoglycaemia, is useful for improving insulin resistance by inhibiting excess insulin secretion and decreasing hepatic lipid accumulation, validated by downregulated CD36.

ABSTRACT

The role of exercise training in prevention of diabetes and/or dyslipidaemia has been firmly established. Dipeptidyl peptidase-4 (DPP-4) inhibitors improve insulin sensitivity and have attracted attention as therapeutics for hepatic lipid accumulation. The effect of a combination of DPP-4 inhibitor and exercise training on the prevention and treatment of hepatic lipid accumulation is unclear. Here, we investigated whether alogliptin, a DPP-4 inhibitor, enhances the preventive effect of exercise-induced hepatic lipid accumulation in diabetic mice. Balb/c and KK/Ta mice were fed a high-fat diet. Mice were divided into the following five groups: B, Balb/c mice; K, KK/Ta mice; K-A, KK/Ta mice with alogliptin (0.01%); K-Ex, KK/Ta mice with exercise training (3 days week^-1 , 15-20 m min^-1 for 30 min); and K-Ex+A, KK/Ta mice with alogliptin and exercise training (n = 8 or 9 mice per group). After 8 weeks, glucose, insulin and triglyceride concentrations in the blood and triglyceride levels in the liver were significantly lower in the K-Ex+A group than in the K group. The liver expression level of PPAR-γ in the K group was significantly higher than that in the other groups. Additionally, the liver CD36 expression level was significantly lower in the K-Ex+A and B groups than in the K group. Thus, combined therapy of a DPP-4 inhibitor with exercise training was effective against high-fat diet-induced hepatic lipid accumulation in KK/Ta mice. The results of this study provide useful support for the practice of safe exercise therapy even in diabetic patients who require treatment with a DPP-4 inhibitor.

Long-Term Effect of Lactation on Maternal Cardiovascular Function and Adiposity in a Murine Model

OBJECTIVE

Epidemiological studies suggest that lactation is associated with long-term maternal health benefits. To avoid confounders in human studies, we used a previously characterized murine model to investigate the long-term effect of lactation on both cardiovascular function and adiposity.

STUDY DESIGN

After the delivery of the pups, CD-1 female mice were randomly divided into two groups: lactated and nonlactated (NL). Before pregnancy and at 9 months postdelivery, blood pressure was measured using a tail cuff, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were assessed by computed tomography (CT), echocardiography was performed using microultrasound, and cholesterol panels and fasting blood glucose were measured. The data were analyzed using Student's t-test (significance at p < 0.05).

RESULTS

There were no differences in baseline parameters between the two groups. At 9 months postdelivery, the NL group weighed significantly more (p = 0.03) and demonstrated a significantly lower cardiac output (p = 0.05) and ejection fraction (p = 0.03). The mice in the NL group also had higher VAT (p < 0.01) and SAT percentiles (p = 0.03). Fasting glucose (p = 0.01) and low-density lipoprotein (p = 0.01) were significantly higher in the NL group at 9 months.

CONCLUSION

Our results show the benefit of lactation is not just limited to the immediate postpartum period but it also extends into midlife in a murine model.

A high-fat diet induced NMRI mouse model of metabolic syndrome: focus on brain-derived neurotrophic factor (BDNF)

The association of brain-derived neurotrophic factor (BDNF) as a member of neurotrophin family and metabolic syndrome (MetS) has been proposed, however basic evidence necessary to prove (or disprove) this association in non-genetic animal model is rare. Therefore, we investigated the alteration of encephalic BDNF gene expression in a mouse model of high-fat diet (HFD) induced MetS. To translate MetS, male NMRI mice (9 weeks old; N = 13) fed on a HFD including suet powder (37.50%) and granulated sugar (19.85%) while control mice were fed a diet contained suet powder (6.25%) and granulated sugar (49.09%). We monitored the development of MetS by measuring fasting blood sugar (FBS) and lipid (total cholesterol (TC) and triacylglycerol (TGs)) and lipoprotein (high-density lipoprotein cholesterol (HDL-C), very low-density lipoprotein cholesterol (VLDL-C)) profiles, atherogenic index (AI), and somatic indices after 1 and 3 months of dietary interventions. The HFD intake led to increased body weight, liver weight, FBS, TC, and decreased HDL-C as compared to chow diet in mice after first month of dietary intervention. The increased FBS, body weight, abdominal fat mass, TGs, TC, and VLDL-C and decreased HDL-C were observed in HFD-fed mice as compared to those of chow-fed mice at 3th month. The statistical comparison of two HFD groups in two time intervals of 1st and 3th month confirmed that our HFD-induced MetS model was reliable because FBS, TGs and VLDL-C, TC, and AI have been increased significantly during selected time intervals. The AI increased significantly in HFD-fed mice compared to chow-fed mice after 3 months. The AI in HFD-fed mice treated with HFD for 3 months was increased significantly as compared to mice fed HFD for 1 month. Our diet-induced model more closely mimics the changes observed in human MetS and showed that encephalic BDNF gene in mice fed HFD was under-expressed by 0.30 fold with respect to chow-fed mice after 3 months of dietary intervention.

High fat diet feeding induced insulin resistance exacerbates 6-OHDA mediated neurotoxicity and behavioral abnormalities in rats

Some of the clinical reports suggest that insulin resistance could be a risk factor for Parkinson's disease (PD) development, however experimental data is scarce. Our previous work has suggested that insulin resistance could be an important factor that leads to diabetes associated neurodegeneration. In the present study, we evaluated whether insulin resistance is linked to PD pathology or not. For this purpose, we first standardized an animal model which could mimic the co-morbid insulin resistance and PD condition. For development of insulin resistance, we fed the male Wistar rats with high fat diet (HFD) for eight weeks, followed by 6-hydroxydopamine (6-OHDA) administration, a toxin widely used for PD induction, in medial forebrain bundle (MFB) of rats. The 6-OHDA treatment resulted in neuronal damage and loss of striatal dopamine level. This dopamine loss was correlated with impaired performance in behavioral tasks such as rotarod, narrow beam walk test and locomotor activity. Interestingly, we found that exposure to HFD exacerbated the effects of 6-OHDA on striatal dopamine loss and behavioral parameters in rats, indicating that HFD-induced insulin resistance is associated with a diminished capacity of dopaminergic neurons to cope with 6-OHDA mediated neurotoxicity. Based upon these findings, it can be suggested that HFD feeding induced insulin resistance exacerbates the PD pathology.

Effects of Oral Administration of Silymarin in a Juvenile Murine Model of Non-alcoholic Steatohepatitis

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD) in adolescents is challenging the global care system. No therapeutic strategies have been defined so far, and changes in the lifestyle remain the only alternative. In this study, we assessed the protective effects of silymarin in a juvenile non-alcoholic steatohepatitis (NASH) model and the in vitro effects on fat-laden human hepatocytes. C57Bl/6 mice were exposed to HFHC diet immediately after weaning. After eight weeks, animals showed histological signs of NASH. Silymarin was added to the HFHC diet, the treatment continued for additional 12 weeks and the effects on BMI, hepatomegaly, visceral fat, lipid profile, transaminases, HOMA-IR, steatosis, inflammation, fibrosis, oxidative stress, and apoptosis were determined. The switch from HFHC to control diet was used to mimic life style changes. In vitro experiments were performed in parallel in human hepatocytes. HFHC diet supplemented with silymarin showed a significant improvement in glycemia, visceral fat, lipid profile, and liver fibrosis. Moreover, it reduced (both in vitro and in vivo) ALT, hepatic inflammation, oxidative stress, and apoptosis. Lifestyle changes restored the control group parameters. The data presented show the beneficial effects of the oral administration of silymarin in the absence of changes in the dietary habits in a juvenile model of NASH.

Metabolic and Blood Pressure Effects of Walnut Supplementation in a Mouse Model of the Metabolic Syndrome

There is extensive evidence that walnut consumption is protective against cardiovascular disease and diabetes in the healthy population, but the beneficial effects of walnut consumption in individuals with the metabolic syndrome (MetS) remain uncertain. We compared a range of cardio-metabolic traits and related tissue gene expression associated with 21 weeks of dietary walnut supplementation in a mouse model of MetS (MetS-Tg) and wild-type (WT) mice (n = 10 per genotype per diet, equal males and females). Compared to standard diet, walnuts did not significantly alter food consumption or body weight trajectory of either MetS-Tg or WT mice. In MetS-Tg mice, walnuts were associated with reductions in oral glucose area under the curve (gAUC, standard diet 1455 ± 54, walnut 1146 ± 91, p = 0.006) and mean arterial blood pressure (MAP, standard diet 100.6 ± 1.9, walnut 73.2 ± 1.8 mmHg, p < 0.001), with neutral effects on gAUC and MAP in WT mice. However, in MetS-Tg mice, walnuts were also associated with trends for higher plasma cholesterol (standard diet 4.73 ± 0.18, walnut 7.03 ± 1.99 mmol/L, p = 0.140) and triglyceride levels (standard diet 2.4 ± 0.5, walnut 5.4 ± 1.6 mmol/L, p = 0.061), despite lowering cholesterol and having no effect on triglycerides in WT mice. Moreover, in both MetS-Tg and WT mice, walnuts were associated with significantly increased liver expression of genes associated with metabolism (Fabp1, Insr), cell stress (Atf6, Ddit3, Eif2ak3), fibrosis (Hgf, Sp1, Timp1) and inflammation (Tnf, Ptpn22, Pparg). In conclusion, dietary walnuts were associated with modest favourable effects in WT mice, but a combination of beneficial and adverse effects in MetS-Tg mice, and up-regulation of hepatic pro-fibrotic and pro-inflammatory genes in both mouse strains.

Enhanced sensitivity to drugs of abuse and palatable foods following maternal overnutrition

Epidemiological studies have shown an association between maternal overnutrition and increased risk of the progeny for the development of obesity as well as psychiatric disorders. Animal studies have shown results regarding maternal high-fat diet (HFD) and a greater risk of the offspring to develop obesity. However, it still remains unknown whether maternal HFD can program the central reward system in such a way that it will imprint long-term changes that will predispose the offspring to addictive-like behaviors that may lead to obesity. We exposed female dams to either laboratory chow or HFD for a period of 9 weeks: 3 weeks before conception, during gestation and lactation. Offspring born to either control or HFD-exposed dams were examined in behavioral, neurochemical, neuroanatomical, metabolic and positron emission tomography (PET) scan tests. Our results demonstrate that HFD offspring compared with controls consume more alcohol, exhibit increased sensitivity to amphetamine and show greater conditioned place preference to cocaine. In addition, maternal HFD leads to increased preference to sucrose as well as to HFD while leaving the general feeding behavior intact. The hedonic behavioral alterations are accompanied by reduction of striatal dopamine and by increased dopamine 2 receptors in the same brain region as evaluated by post-mortem neurochemical, immunohistochemical as well as PET analyses. Taken together, our data suggest that maternal overnutrition predisposes the offspring to develop hedonic-like behaviors to both drugs of abuse as well as palatable foods and that these types of behaviors may share common neuronal underlying mechanisms that can lead to obesity.

High-fructose diet in pregnancy leads to fetal programming of hypertension, insulin resistance, and obesity in adult offspring

BACKGROUND

Consumption of fructose-rich diets in the United States is on the rise and thought to be associated with obesity and cardiometabolic diseases.

OBJECTIVE

We sought to determine the effects of antenatal exposure to high-fructose diet on offspring's development of metabolic syndrome-like phenotype and other cardiovascular disease risk factors later in life.

STUDY DESIGN

Pregnant C57BL/6J dams were randomly allocated to fructose solution (10% wt/vol, n = 10) or water (n = 10) as the only drinking fluid from day 1 of pregnancy until delivery. After weaning, pups were started on regular chow, and evaluated at 1 year of life. We measured percent visceral adipose tissue and liver fat infiltrates using computed tomography, and blood pressure using CODA nonivasive monitor. Intraperitoneal glucose tolerance testing with corresponding insulin concentrations were obtained. Serum concentrations of glucose, insulin, triglycerides, total cholesterol, leptin, and adiponectin were measured in duplicate using standardized assays. Fasting homeostatic model assessment was also calculated to assess insulin resistance. P values <.05 were considered statistically significant.

RESULTS

Maternal weight, pup number, and average weight at birth were similar between the 2 groups. Male and female fructose group offspring had higher peak glucose and area under the intraperitoneal glucose tolerance testing curve compared with control, and higher mean arterial pressure compared to control. Female fructose group offspring were heavier and had higher percent visceral adipose tissue, liver fat infiltrates, homeostatic model assessment of insulin resistance scores, insulin area under the intraperitoneal glucose tolerance testing curve, and serum concentrations of leptin, and lower concentrations of adiponectin compared to female control offspring. No significant differences in these parameters were noted in male offspring. Serum concentrations of triglycerides or total cholesterol were not different between the 2 groups for either gender.

CONCLUSION

Maternal intake of high fructose leads to fetal programming of adult obesity, hypertension, and metabolic dysfunction, all risk factors for cardiovascular disease. This fetal programming is more pronounced in female offspring. Limiting intake of high fructose-enriched diets in pregnancy may have significant impact on long-term health.

An Animal Model for the Juvenile Non-Alcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis

Non Alcoholic Fatty Liver Disease (NAFLD) and Non-Alcoholic Steatohepatitis (NASH) are the hepatic manifestations of the metabolic syndrome; worrisome is the booming increase in pediatric age. To recreate the full spectrum of juvenile liver pathology and investigate the gender impact, male and female C57Bl/6 mice were fed with high fat diet plus fructose in the drinking water (HFHC) immediately after weaning (equal to 3-years old human), and disease progression followed for 16 weeks, until adults (equal to 30-years old human). 100% of subjects of both genders on HFHC diet developed steatosis in 4weeks, and some degree of fibrosis in 8weeks, with the 86% of males and 15% of females presenting a stage 2 fibrosis at 16weeks. Despite a similar final liver damage both groups, a sex difference in the pathology progression was observed. Alterations in glucose homeostasis, dyslipidemia, hepatomegaly and obese phenotype were evident from the very beginning in males with an increased hepatic inflammatory activity. Conversely, such alterations were present in females only at the end of the HFHC diet (with the exception of insulin resistance and the hepatic inflammatory state). Interestingly, only females showed an altered hepatic redox state. This juvenile model appears a good platform to unravel the underlying gender dependent mechanisms in the progression from NAFLD to NASH, and to characterize novel therapeutic approaches.

Depot-specific effects of treadmill running and rutin on white adipose tissue function in diet-induced obese mice

White adipose tissue (WAT) is a critical organ involved in regulating metabolic homeostasis under obese condition. Strategies that could positively affect WAT function would hold promise for fighting against obesity and its complications. The aim of the present study is to explore the effects of treadmill exercise training and rutin intervention on adipose tissue function from diet-induced obese (DIO) mice and whether fat depot-specific effects existed. In epididymal adipose tissue, high-fat diet (HFD) resulted in reduction in adiponectin mRNA expression, peroxisome proliferator-activated receptors (PPAR)-γ and DsbA-L protein expression, elevation in endoplasmic reticulum (ER) stress markers including 78 kDa glucose-regulated protein (GRP-78), C/EBP homologous protein (CHOP) and p-c-Jun N-terminal kinase (JNK). Isoproterenol-stimulated lipolysis and insulin stimulated Akt phosphorylation ex vivo were blunted from HFD group. The combination of rutin with exercise (HRE) completely restored GRP78 and p-JNK protein expression to normal levels, as well as blunted signaling ex vivo. In inguinal adipose tissue, HFD led to increased adiponectin mRNA expression, PPAR-γ, GRP78, and p-JNK protein expression, and reduction in DsbA-L. HRE is effective for restoring p-JNK, PPAR-γ, and DsbA-L. In conclusion, depot-specific effects may exist in regard to the effects of rutin and exercise on key molecules involved in regulating adipose tissue function (i.e., ER stress markers, PPAR-γ and DsbA-L, adiponectin expression, and secretion, ex vivo catecholamine stimulated lipolysis and insulin stimulated Akt phosphorylation) from DIO mice.

Transforming growth factor-β1 induces cholesterol synthesis by increasing HMG-CoA reductase mRNA expression in keratinocytes

In this study, we investigated the effect of TGF-β1 on cholesterol synthesis in human keratinocytes. TGF-β1 increased the level of cholesterol and the mRNA level of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in human keratinocytes. These results show that TGF-β1 induces cholesterol synthesis by increasing HMG-CoA reductase mRNA expression in human keratinocytes.

Effects of phenolic-rich extracts of Clinacanthus nutans on high fat and high cholesterol diet-induced insulin resistance

BACKGROUND

Clinacanthus nutans is used traditionally in many parts of Asia to improve well-being, but there are limited studies on its efficacy. We explored the potential use of C. nutans for prevention of high fat and high cholesterol diet-(HFHC-) induced insulin resistance in rats.

METHODS

The leaf of C. nutans was extracted using water (AL extract) and methanol (AML extract), and the extracts were fed to rats alongside the HFHC diet for 7 weeks, and compared with simvastatin. Oral glucose tolerance test, and serum insulin, retinol binding protein 4 (RBP4), adiponectin and leptin were measured. Homeostatic model assessment of insulin resistance (HOMA-IR) was computed, while transcriptional regulation of hepatic insulin signaling genes was also assessed.

RESULTS

Glycemic response was higher in the HFHC group compared with the AL and AML groups, which also had lower serum RBP4, fasting glucose, insulin and HOMA-IR. Serum adiponectin levels were higher, while leptin levels were lower in the AML and AL groups compared to the HFHC group. There was upregulation of the Insulin receptor substrate, phosphotidyl inositol-3-phosphate, adiponectin receptor and leptin recetor genes, in comparison with the HFHC group.

CONCLUSIONS

Overall, the results showed that the HFHC diet worsened metabolic indices and induced insulin resistance partly through transcriptional regulation of the insulin signaling genes. C.nutans, on the other hand, attenuated the metabolic effects and transcriptional changes induced by the HFHC diet. The results suggested that C.nutans may be a good source of functional ingredient for the prevention of insulin resistance.

Epigenetic modifications by inhibiting histone deacetylases reverse memory impairment in insulin resistance induced cognitive deficit in mice

Insulin resistance has been reported as a strong risk factor for Alzheimer's disease. However the molecular mechanisms of association between these still remain elusive. Various studies have highlighted the involvement of histone deacetylases (HDACs) in insulin resistance and cognitive deficits. Thus, the present study was designed to investigate the possible neuroprotective role of HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA) in insulin resistance induced cognitive impairment in mice. Mice were subjected to either normal pellet diet (NPD) or high fat diet (HFD) for 8 weeks. HFD fed mice were treated with SAHA at 25 and 50 mg/kg i.p. once daily for 2 weeks. Serum insulin, glucose, triglycerides, total cholesterol and HDL-cholesterol levels were measured. A battery of behavioral parameters was performed to assess cognitive functions. Level of tumour necrosis factor (TNF-α) was measured in hippocampus to assess neuroinflammation. To further explore the molecular mechanisms we measured the histone H3 acetylation and brain derived neurotrophic factor (BDNF) level. HFD fed mice exhibit characteristic features of insulin resistance. These mice also showed a severe deficit in learning and memory along with reduced histone H3 acetylation and BDNF levels. In contrast, the mice treated with SAHA showed significant and dose dependent improvement in insulin resistant condition. These mice also showed improved learning and memory performance. SAHA treatment ameliorates the HFD induced reduction in histone H3 acetylation and BDNF levels. Based upon these results, it could be suggested that HDAC inhibitors exert neuroprotective effects by increasing H3 acetylation and subsequently BDNF level.

Metabolic Syndrome Is Associated with Increased Oxo-Nitrative Stress and Asthma-Like Changes in Lungs

Epidemiological studies have shown an increased obesity-related risk of asthma. In support, obese mice develop airway hyperresponsiveness (AHR). However, it remains unclear whether the increased risk is a consequence of obesity, adipogenic diet, or the metabolic syndrome (MetS). Altered L-arginine and nitric oxide (NO) metabolism is a common feature between asthma and metabolic syndrome that appears independent of body mass. Increased asthma risk resulting from such metabolic changes would have important consequences in global health. Since high-sugar diets can induce MetS, without necessarily causing obesity, studies of their effect on arginine/NO metabolism and airway function could clarify this aspect. We investigated whether normal-weight mice with MetS, due to high-fructose diet, had dysfunctional arginine/NO metabolism and features of asthma. Mice were fed chow-diet, high-fat-diet, or high-fructose-diet for 18 weeks. Only the high-fat-diet group developed obesity or adiposity. Hyperinsulinemia, hyperglycaemia, and hyperlipidaemia were common to both high-fat-diet and high-fructose-diet groups and the high-fructose-diet group additionally developed hypertension. At 18 weeks, airway hyperresponsiveness (AHR) could be seen in obese high-fat-diet mice as well as non-obese high-fructose-diet mice, when compared to standard chow-diet mice. No inflammatory cell infiltrate or goblet cell metaplasia was seen in either high-fat-diet or high-fructose-diet mice. Exhaled NO was reduced in both these groups. This reduction in exhaled NO correlated with reduced arginine bioavailability in lungs. In summary, mice with normal weight but metabolic obesity show reduced arginine bioavailability, reduced NO production, and asthma-like features. Reduced NO related bronchodilation and increased oxo-nitrosative stress may contribute to the pathogenesis.

Galectin-3 deficiency exacerbates hyperglycemia and the endothelial response to diabetes

Background

Diabetes promotes maladaptive changes in the endothelium that lead to its dysfunction and contribute to the vascular pathology of diabetes. We have previously reported the up-regulation of galectin-3, a β-galactoside-binding lectin, in the endothelium and sera of diabetic mice, implicating this molecule in diabetic vasculopathy and suggesting its potential as a biomarker of the disease. Therefore, we sought to assess the role of galectin-3 in the vascular pathology of diabetes.

Methods

Galectin-3 knockout mice (KO) and wild-type mice (WT) were fed either a high-fat diet (HFD) (60 % fat calories) to produce insulin resistant diabetes, or standard chow (12 % fat calories), and their metabolic and endothelial responses were measured. After 8 weeks, the aortic and skeletal muscle endothelia were isolated by fluorescence sorting of CD105⁺/CD45⁻ cells and comprehensive transcriptional analyses were performed. Transcripts differentially dysregulated by HFD in KO endothelium compared to WT were confirmed by semi-quantitative RT-PCR, and protein expression was determined by immunofluorescence of aortic and muscle tissue. Ingenuity® Pathway Analysis was used to identify pathways up-regulated by HFD in the KO, such as the coagulation cascade, and measurements of blood clotting activity were performed to confirm these results.

Results

KO mice demonstrate greater hyperglycemia and impaired glucose tolerance but lower insulin levels on HFD compared to WT. KO mice demonstrate a more robust transcriptional response to HFD in the vascular endothelium compared to WT. Transcripts dysregulated in the KO endothelium after HFD are involved in glucose uptake and insulin signaling, vasoregulation, coagulation, and atherogenesis. One of the most down-regulated transcripts in the endothelium of the KO after HFD was the glucose transporter, Glut4/Slc2a4. GLUT4 immunofluorescence confirmed lower protein abundance in the endothelium and muscle of the HFD-fed KO. Prothrombin time was decreased in the diabetic KO indicating increased coagulation activity.

Conclusions

Galectin-3 deficiency leads to exacerbated metabolic derangement and endothelial dysfunction. The impaired tissue uptake of glucose in KO mice can be attributed to the reduced expression of GLUT4. Enhanced coagulation activity in the diabetic KO suggests a protective role for galectin-3 against thrombosis. These studies demonstrate that galectin-3 deficiency contributes both to the pathogenesis of diabetes and the associated vasculopathy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0230-3) contains supplementary material, which is available to authorized users.

Diet is critical for prolonged glycemic control after short-term insulin treatment in high-fat diet-induced type 2 diabetic male mice

Background

Clinical studies suggest that short-term insulin treatment in new-onset type 2 diabetes (T2DM) can promote prolonged glycemic control. The purpose of this study was to establish an animal model to examine such a “legacy” effect of early insulin therapy (EIT) in long-term glycemic control in new-onset T2DM. The objective of the study was to investigate the role of diet following onset of diabetes in the favorable outcomes of EIT.

Methodology

As such, C57BL6/J male mice were fed a high-fat diet (HFD) for 21 weeks to induce diabetes and then received 4 weeks of daily insulin glargine or sham subcutaneous injections. Subsequently, mice were either kept on the HFD or switched to a low-fat diet (LFD) for 4 additional weeks.

Principal Findings

Mice fed a HFD gained significant fat mass and displayed increased leptin levels, increasing insulin resistance (poor HOMA-IR) and worse glucose tolerance test (GTT) performance in comparison to mice fed a LFD, as expected. Insulin-treated diabetic mice but maintained on the HFD demonstrated even greater weight gain and insulin resistance compared to sham-treated mice. However, insulin-treated mice switched to the LFD exhibited a better HOMA-IR compared to those mice left on a HFD. Further, between the insulin-treated and sham control mice, in spite of similar HOMA-IR values, the insulin-treated mice switched to a LFD following insulin therapy did demonstrate significantly better HOMA-B% values than sham control and insulin-treated HFD mice.

Conclusion/Interpretation

Early insulin treatment in HFD-induced T2DM in C57BL6/J mice was only beneficial in animals that were switched to a LFD after insulin treatment which may explain why a similar legacy effect in humans is achieved clinically in only a portion of cases studied, emphasizing a vital role for diet adherence in diabetes control.

Histone deacetylase inhibitor, trichostatin A, improves learning and memory in high-fat diet-induced cognitive deficits in mice

Metabolic syndrome is increasingly recognized for its effects on cognitive health. Recent studies have highlighted the role of histone deacetylases (HDACs) in metabolic syndrome and cognitive functions. The present study was designed to investigate the possible therapeutic role of a HDAC inhibitor, trichostatin A (TSA), in cognitive impairment associated with metabolic syndrome. To ascertain the mechanisms involved, we fed mice with high-fat diet (HFD) for 4 weeks and examined changes in behavioral and biochemical/oxidative stress markers. Mice subjected to HFD exhibited characteristic features of metabolic disorder, viz., hyperglycemia, hypertriglyceridemia, hypercholesterolemia, and lower high-density lipoprotein (HDL) cholesterol levels. Moreover, these mice showed severe deficits in learning and memory as assessed by the Morris water maze and passive avoidance tasks along with elevated oxidative stress and inflammatory markers in brain homogenates. The observed changes occurred concurrently with reduced brain-derived neurotrophic factor (BDNF). In contrast, the mice treated with the HDAC inhibitor, TSA (0.5 and 1 mg/kg, i.p.), showed a significant and dose-dependent reduction in serum glucose, triglycerides, and total cholesterol along with improvement in HDL-cholesterol levels and learning and memory performance. TSA treatment also results in alleviation of oxidative stress and neuroinflammatory markers. Moreover, TSA significantly augmented the BDNF levels in HFD-fed mice. Thus, based upon these observations, it may be suggested that HDAC inhibition could be a novel therapeutic strategy to combat cognitive impairment associated with metabolic syndrome.

Effect of ursolic acid and Rosiglitazone combination on hepatic lipid accumulation in high fat diet-fed C57BL/6J mice

This study investigated the combined effect of ursolic acid (UA) and Rosiglitazone (RSG) on lipid regulatory genes in high fat diet (HFD)-fed mice. Male C57BL/6J mice were fed either normal diet or HFD for 10 weeks, after which animals in each dietary group were divided into following six groups, (normal diet, normal diet plus UA and RSG, HFD alone, HFD plus UA, HFD plus RSG, and HFD plus UA and RSG), for the next 5 weeks. UA (5mg/kg BW) and RSG (4mg/kg BW) were administered as suspensions directly into the stomach using a gastric tube. At the end of the study (106th day), their liver was analyzed for lipid content. RT-PCR and western blotting methods were used to analyze lipid regulatory genes. HFD-fed mice showed increased activities of hepatic marker enzymes (aspartate aminotransferase and alanine aminotransferase) in plasma and an increased concentration of total cholesterol, triglyceride and free fatty acid in liver. These results were confirmed by upregulated mRNA expression of lipogenic genes such as sterol-regulatory-element-binding protein-1c, fatty acid synthase and acetyl-CoA carboxylase and downregulated mRNA expression of fatty acid oxidative genes such as carnitine palmitoyltransferase-1, acetyl-CoA carboxylase and peroxisome proliferator activated receptor-α in HFD-fed mice. Combined treatment (UA/RSG) significantly reduced the hepatic marker enzyme activities and decreased the lipid accumulation in liver. Furthermore, combination treatment (UA/RSG) down-regulated lipogenic genes and upregulated fatty acid oxidative genes in HFD-fed mice. This study suggests that UA in combination with RSG reduced lipid accumulation in liver.

GLUT4 defects in adipose tissue are early signs of metabolic alterations in Alms1GT/GT, a mouse model for obesity and insulin resistance

Dysregulation of signaling pathways in adipose tissue leading to insulin resistance can contribute to the development of obesity-related metabolic disorders. Alström Syndrome, a recessive ciliopathy, caused by mutations in ALMS1, is characterized by progressive metabolic alterations such as childhood obesity, hyperinsulinemia, and type 2 diabetes. Here we investigated the role of Alms1 disruption in AT expansion and insulin responsiveness in a murine model for Alström Syndrome. A gene trap insertion in Alms1 on the insulin sensitive C57BL6/Ei genetic background leads to early hyperinsulinemia and a progressive increase in body weight. At 6 weeks of age, before the onset of the metabolic disease, the mutant mice had enlarged fat depots with hypertrophic adipocytes, but without signs of inflammation. Expression of lipogenic enzymes was increased. Pre-adipocytes isolated from mutant animals demonstrated normal adipogenic differentiation but gave rise to mature adipocytes with reduced insulin-stimulated glucose uptake. Assessment of whole body glucose homeostasis revealed glucose intolerance. Insulin stimulation resulted in proper AKT phosphorylation in adipose tissue. However, the total amount of glucose transporter 4 (SLC4A2) and its translocation to the plasma membrane were reduced in mutant adipose depots compared to wildtype littermates. Alterations in insulin stimulated trafficking of glucose transporter 4 are an early sign of metabolic dysfunction in Alström mutant mice, providing a possible explanation for the reduced glucose uptake and the compensatory hyperinsulinemia. The metabolic signaling deficits either reside downstream or are independent of AKT activation and suggest a role for ALMS1 in GLUT4 trafficking. Alström mutant mice represent an interesting model for the development of metabolic disease in which adipose tissue with a reduced glucose uptake can expand by de novo lipogenesis to an obese state.

Effect of lactation on maternal postpartum cardiac function and adiposity: a murine model

OBJECTIVE

Lactation is associated with reduction in maternal metabolic disease and hypertension later in life; however, findings in humans may be confounded by socioeconomic factors. We sought to determine the independent contribution of lactation on cardiovascular parameters and adiposity in a murine model.

STUDY DESIGN

Following delivery, CD-1 female mice were randomly divided into 2 groups: lactated (L; nursed pups for 3 weeks, n = 10), and nonlactated (NL; pups were removed after birth, n = 12). Blood pressure (BP) was assessed prepregnancy and at 1 and 2 months' postpartum. Visceral and subcutaneous adipose tissue determined by computed tomography and left ventricular ejection fraction, cardiac output, and the E/A ratio determined by microultrasound were evaluated at 1 and 2 months' postpartum. The results were analyzed using a Student t test (significance at P < .05).

RESULTS

We observed a significantly different maternal BP at 2 months' postpartum with relatively greater BP in NL (systolic BP: NL, 122.2 ± 7.2 vs L, 96.8 ± 9.8 mm Hg; P = .04; diastolic BP: NL, 87.0 ± 6.8 vs L, 65.9 ± 6.2 mm Hg; P = .04). Visceral adipose tissue was significantly increased in NL mice at 1 (22.0 ± 4.1% vs 10.7 ± 1.8%, P = .04) and 2 months' postpartum (22.9 ± 3.5% vs 11.2 ± 2.2%, P = .02), whereas subcutaneous adipose tissue did not differ between the groups. At 2 months' postpartum, ejection fraction (51.8 ± 1.5% vs 60.5 ± 3.8%; P = .04), cardiac output (14.2 ± 1.0 vs 18.0 ± 1.3 mL/min; P = .02) and mitral valve E/A ratio (1.38 ± 0.06 vs 1.82 ± 0.13; P = .04) were significantly lower in NL mice than L mice.

CONCLUSION

Our data provide evidence that interruption of lactation adversely affects postpartum maternal cardiovascular function and adiposity.

Neuroprotective role of Indirubin-3'-monoxime, a GSKβ inhibitor in high fat diet induced cognitive impairment in mice

Recent studies have highlighted that diabetes mellitus (DM) is a strong risk factor for Alzheimer's disease (AD). Insulin resistance and/or hyperinsulinemia is one of the main characteristics of type 2 DM. Numerous epidemiological studies have demonstrated that insulin resistance contributes to AD pathogenesis. However the molecular mechanisms of association between these still remain elusive. Among the various possible mechanisms, the GSK-3β activity has been reported to be impaired in insulin-resistance, type 2 DM and AD. Thus, the present study was designed to explore the neuroprotective role of GSK3 β inhibitor, Indirubin-3'-monoxime (IMX) in insulin resistance induced cognitive impairment. Further, we have explored the possible molecular mechanism involved in cognitive impairment associated with insulin resistance. The mice subjected to high fat diet exhibited characteristic features of insulin resistance viz. increased serum glucose, triglycerides, cholesterol, insulin levels and impaired spatial learning and memory ability along with reduced brain insulin level, elevated oxidative stress and acetylcholinesterase (AChE) activity. The observed changes occurred concurrently with reduced brain derived neurotrophic factor. In contrast, the mice treated with IMX showed a significant reduction in plasma glucose, triglycerides, cholesterol, insulin levels and improvement in learning and memory performance, attenuated the oxidative stress and AChE activity. Moreover, IMX dose dependently augment the brain insulin and BDNF levels in HFD fed mice. Based upon these findings it could be suggested that GSK3 β inhibition could prove to be beneficial in insulin resistance induced cognitive deficit and this neuroprotection could be the result of enhanced BDNF based synaptic plasticity.

The inflammatory profile and liver damage of a sucrose-rich diet in mice

It is still unclear if an isoenergetic, sucrose-rich diet leads to health consequences.

AIMS

To investigate the effects of excessive sucrose within an isoenergetic diet on metabolic parameters in male C57BL/6 mice.

METHODS

Animals were fed a control diet (10% fat, 8% sucrose - SC group), a high-sucrose diet (10% fat, 32% sucrose - HSu group), a high-fat diet (42% fat, 8% sucrose - HF group) or a high-fat/high-sucrose diet (42% fat, 32% sucrose - HF/HSu group) for 8 weeks.

RESULTS

Mice fed HF and HF/HSu diets gained more body mass (BM) and more body adiposity than SC- or Hsu-fed mice. Despite the unchanged BM and adiposity indices, HSu mice presented adipocyte hypertrophy, which was also observed in the HF and HF/HSu groups (P<.0001). The HF, HSu and HF/HSu mice were glucose intolerant and had elevated serum insulin levels (P<.05). The levels of leptin, resistin and monocyte chemotactic protein-1 increased, while the serum adiponectin decreased in the HF, HSu and HF/HSu groups (P<.05). In the adipose tissue, the HF, HSu and HF/HSu groups showed higher levels of leptin expression and lower levels of adiponectin expression in comparison with the SC group (P<.05). Liver steatosis was higher in the HF, HSu and HF/HSu groups than in the SC group (P<.0001). Hepatic cholesterol was higher in the HF and HF/HSu groups, while hepatic TG was higher in the HSu and HF/HSu groups (P<.05). In hepatic tissue, the sterol receptor element-binding protein-1c expression was increased in the HF, HSu and HF/HSu groups, unlike the peroxisome proliferator-activated receptor-alpha expression that decreased in the HF, HSu and HF/HSu groups in comparison with the SC group (P<.05).

CONCLUSION

A sucrose-rich diet does not lead to a state of obesity but has the potential to cause changes in the adipocytes (hypertrophy) as well as glucose intolerance, hyperinsulinemia, hyperlipidemia, hepatic steatosis and increases in the number of inflammatory cytokines. The deleterious effects of a sucrose-rich diet in an animal model, even when the sucrose replaces starch isocalorically in the feed, can have far-reaching consequences for health.

Genistein sensitizes hepatic insulin signaling and modulates lipid regulatory genes through p70 ribosomal S6 kinase-1 inhibition in high-fat-high-fructose diet-fed mice

CONTEXT

Genistein reduces high-calorie diet-induced insulin resistance and fat accumulation in animals, but the mechanism is unresolved.

OBJECTIVE

This study explores whether action of genistein is associated with p70 ribosomal S6 kinase-1 (S6K1) inhibition.

MATERIALS AND METHODS

Adult male mice were fed either normal diet or high-fat-high-fructose diet (HFFD) for 15 days, after which animals in each dietary group were divided into two groups and administered either genistein (1 mg kg(-1) day(-1), p.o.) in 0.5 ml of 30% dimethylsulfoxide (DMSO) or 30% DMSO (0.5 ml) for the next 45 days. At the end of the study, their liver was analyzed for lipid content. Semi-quantitative RT-PCR and western blotting methods were used to analyze lipid regulatory genes and insulin signaling proteins, respectively.

RESULTS

Genistein significantly (p < 0.05) lowered HFFD-induced body and liver weight gain and plasma and hepatic lipid levels. Histology showed a 2.5-fold increase of lipid in HFFD compared to control. Genistein treatment to HFFD-fed animals significantly decreased lipid accumulation (by 40%) compared to HFFD. Insulin-stimulated tyrosine phosphorylation of insulin receptor-β and insulin receptor substrates-1 (IRS-1), IRS-1 associated phospatidylinositol-3kinase (PI3K) and Akt Ser(473) phosphorylation were improved while IRS-1 serine phosphorylation was significantly (p < 0.05) decreased by genistein in HFFD. Significant (p < 0.05) increase in adenosine monophosphate-activated protein kinase (AMPK) Thr(172) phosphorylation and decrease in S6K1 Thr(389) phosphorylation were observed in HFFD-plus genistein compared to HFFD. Genistein downregulated lipogenic genes and upregulated fatty acid oxidative genes in HFFD-fed mice.

CONCLUSION

Genistein improves insulin signaling and attenuates fat accumulation in liver through S6K1 inhibition.

Chronic ethanol consumption increases cardiomyocyte fatty acid uptake and decreases ventricular contractile function in C57BL/6J mice

Alcohol, a major cause of human cardiomyopathy, decreases cardiac contractility in both animals and man. However, key features of alcohol-related human heart disease are not consistently reproduced in animal models. Accordingly, we studied cardiac histology, contractile function, cardiomyocyte long chain fatty acid (LCFA) uptake, and gene expression in male C57BL/6J mice consuming 0, 10, 14, or 18% ethanol in drinking water for 3months. At sacrifice, all EtOH groups had mildly decreased body and increased heart weights, dose-dependent increases in cardiac triglycerides and a marked increase in cardiac fatty acid ethyl esters. [(3)H]-oleic acid uptake kinetics demonstrated increased facilitated cardiomyocyte LCFA uptake, associated with increased expression of genes encoding the LCFA transporters CD36 and Slc27a1 (FATP1) in EtOH-fed animals. Although SCD-1 expression was increased, lipidomic analysis did not indicate significantly increased de novo LCFA synthesis. By echocardiography, ejection fraction (EF) and the related fractional shortening (FS) of left ventricular diameter during systole were reduced and negatively correlated with cardiac triglycerides. Expression of myocardial PGC-1α and multiple downstream target genes in the oxidative phosphorylation pathway, including several in the electron transport and ATP synthase complexes of the inner mitochondrial membrane, were down-regulated. Cardiac ATP was correspondingly reduced. The data suggest that decreased expression of PGC-1α and its target genes result in decreased cardiac ATP levels, which may explain the decrease in myocardial contractile function caused by chronic EtOH intake. This model recapitulates important features of human alcoholic cardiomyopathy and illustrates a potentially important pathophysiologic link between cardiac lipid metabolism and function.

The nutrigenomic investigation of C57BL/6N mice fed a short-term high-fat diet highlights early changes in clock genes expression

Mice fed long-term high-fat diets (HFD) are an established model for human metabolic disorders, such as obesity and diabetes. However, also the effects of short-term HFD feeding should be investigated to understand which are the first events that trigger the onset of a pre-disease condition, the so-called metabolic syndrome, that increases the risk of developing clinical diseases. In this study, C57BL/6N mice were fed a control diet (CTR) or a HFD for 1 (T1) or 2 weeks (T2). Metabolic and histological effects were examined. Cecum transcriptomes of HFD and CTR mice were compared at T2 by microarray analysis. Differentially expressed genes were validated by real-time PCR in the cecum and in the liver. After 2 weeks of diet administration, HFD mice showed an altered expression pattern in only seven genes, four of which are involved in the circadian clock regulatory pathway. Real-time PCR confirmed microarray results of the cecum and revealed the same trend of clock gene expression changes in the liver. These findings suggest that clock genes may play an important role in early controlling gut output systems in response to HFD in mice and that their expression change may also represent an early signaling of the development of an intestinal pro-inflammatory status.

Pioglitazone therapy in mouse offspring exposed to maternal obesity

OBJECTIVE

Pioglitazone (PIO), an antidiabetic drug of the thiazolidinedione family, improves glucose and lipid metabolism in muscle, adipose, and liver tissues via peroxisome proliferator-activated receptor gamma activation. We hypothesize that PIO therapy will improve the metabolic status of offspring exposed to maternal obesity in a mouse model developmentally programmed for metabolic syndrome.

STUDY DESIGN

CD-1 female mice were fed a high-fat diet for 3 months prior to breeding and throughout pregnancy and lactation. The pups were weaned to a standard-fat diet. Offspring were randomly assigned to receive 40 mg/kg of PIO in 0.5% of methyl cellulose or 0.5% methyl cellulose by daily oral gavage for 2 weeks. The pre- and posttreatment total body weights of the pups were recorded. Visceral and subcutaneous adipose tissue were evaluated using microcomputed tomography. Serum analytes were measured. After treatment, minimally invasive microendoscopic fluorescence confocal imaging and intraperitoneal glucose tolerance tests were performed. The data were analyzed using appropriate statistical tests (significance, P < .05).

RESULTS

PIO therapy resulted in lower total body weight and lower visceral adipose tissue gain and increased subcutaneous adipose tissue. PIO significantly lowered triglycerides, insulin levels, and homeostasis model assessment of insulin resistance in males and fasting glucose in females. There was a trend toward larger adipocyte size.

CONCLUSION

Short-term PIO therapy in the offspring of obese mothers attenuates metabolic changes associated with the developmental programming of metabolic syndrome. These novel data suggest a potential role for drugs that activate peroxisome proliferator-activated receptor gamma receptors to prevent metabolic syndrome in the adult offspring at risk to develop metabolic alterations.

Maternal obesity during the preconception and early life periods alters pancreatic development in early and adult life in male mouse offspring

Maternal obesity induced by a high fat (HF) diet may program susceptibility in offspring, altering pancreatic development and causing later development of chronic degenerative diseases, such as obesity and diabetes. Female mice were fed standard chow (SC) or an HF diet for 8 weeks prior to mating and during the gestational and lactational periods. The male offspring were assessed at birth, at 10 days, and at 3 months of age. The body mass (BM) gain was 50% greater before pregnancy and 80% greater during pregnancy in HF dams than SC dams. Dams fed an HF diet showed higher oral glucose tolerance test (OGTT), blood pressure, serum corticosterone, and insulin levels than dams fed SC. At 10 days of age and at 3 mo old the HF offspring showed greater BM and higher blood glucose levels than the SC offspring. The mean diameter of the islets had increased by 37% in the SC offspring and by 155% in the HF offspring at 10 days of age. The islet mass ratio (IM/PM) was 88% greater in the HF offspring at 10 days of age, and 107% greater at 3 mo of age, compared to the values obtained at birth. The HF offspring had a beta cell mass (BCM)/PM ratio 54% lower than SC offspring at birth. However, HF offspring displayed a 146% increase in the BCM/PM ratio at 10 days of age, and 112% increase at 3 months of age than values at birth. A 3 mo of age, the HF offspring showed a greater OGTT and higher levels of than SC offspring. In conclusion, a maternal HF diet consumed during the preconceptional period and throughout the gestational and lactational periods in mice results in dramatic alterations in the pancreata of the offspring.

Spleen-derived interleukin-10 downregulates the severity of high-fat diet-induced non-alcoholic fatty pancreas disease

Obesity is associated with systemic low-grade inflammation and is a risk factor for non-alcoholic fatty pancreas disease (NAFPD), but the molecular mechanisms of these associations are not clear. Interleukin (IL)-10, a potent anti-inflammatory cytokine, is released during acute pancreatitis and is known to limit inflammatory responses by downregulating the release of proinflammatory mediators. The origin of IL-10 that suppresses pancreatitis has not been investigated. Since obesity is known to reduce expression of proinflammatory cytokines in the spleen, we examined whether spleen-derived IL-10 regulates NAFPD caused by high-fat (HF) diet-induced obesity. The following investigations were performed: 1) IL-10 induction from spleen was examined in male mice fed a HF diet; 2) triglyceride content, expression of pro- and anti-inflammatory cytokines and infiltration of M1 and M2 macrophages were determined to evaluate ectopic fat accumulation and inflammatory responses in the pancreas of splenectomy (SPX)-treated mice fed HF diet; 3) exogenous IL-10 was systemically administered to SPX-treated obese mice and the resulting pathogenesis caused by SPX was assessed; and 4) IL-10 knockout (IL-10KO) mice were treated with SPX and ectopic fat deposition and inflammatory conditions in the pancreas were investigated. Obesity impaired the ability of the spleen to synthesize cytokines, including IL-10. SPX aggravated fat accumulation and inflammatory responses in the pancreas of HF diet-induced obese mice and these effects were inhibited by systemic administration of IL-10. Moreover, SPX had little effect on fat deposition and inflammatory responses in the pancreas of IL-10KO mice. Our findings indicate that obesity reduces IL-10 production by the spleen and that spleen-derived IL-10 may protect against the development of NAFPD.

Gluten-free diet reduces adiposity, inflammation and insulin resistance associated with the induction of PPAR-alpha and PPAR-gamma expression

Gluten exclusion (protein complex present in many cereals) has been proposed as an option for the prevention of diseases other than coeliac disease. However, the effects of gluten-free diets on obesity and its mechanisms of action have not been studied. Thus, our objective was to assess whether gluten exclusion can prevent adipose tissue expansion and its consequences. C57BL/6 mice were fed a high-fat diet containing 4.5% gluten (Control) or no gluten (GF). Body weight and adiposity gains, leukocyte rolling and adhesion, macrophage infiltration and cytokine production in adipose tissue were assessed. Blood lipid profiles, glycaemia, insulin resistance and adipokines were measured. Expression of the PPAR-α and γ, lipoprotein lipase (LPL), hormone sensitive lipase (HSL), carnitine palmitoyl acyltransferase-1 (CPT-1), insulin receptor, GLUT-4 and adipokines were assessed in epidydimal fat. Gluten-free animals showed a reduction in body weight gain and adiposity, without changes in food intake or lipid excretion. These results were associated with up-regulation of PPAR-α, LPL, HSL and CPT-1, which are related to lipolysis and fatty acid oxidation. There was an improvement in glucose homeostasis and pro-inflammatory profile-related overexpression of PPAR-γ. Moreover, intravital microscopy showed a lower number of adhered cells in the adipose tissue microvasculature. The overexpression of PPAR-γ is related to the increase of adiponectin and GLUT-4. Our data support the beneficial effects of gluten-free diets in reducing adiposity gain, inflammation and insulin resistance. The data suggests that diet gluten exclusion should be tested as a new dietary approach to prevent the development of obesity and metabolic disorders.

White tea (Camellia sinensis) extract reduces oxidative stress and triacylglycerols in obese mice

White tea is an unfermented tea made from young shoots of Camellia sinensis protected from sunlight to avoid polyphenol degradation. Although its levels of catechins are higher than those of green tea (derived from the same plant), there are no studies addressing the relationship between this tea and obesity associated with oxidative stress.The objective of this study was to evaluate the effect of white tea on obesity and its complications using a diet induced obesity model. Forty male C57BL/6 mice were fed a high-fat diet to induce obesity (Obese group) or the same diet supplemented with 0.5% white tea extract (Obese + WTE) for 8 weeks. Adipose tissue, serum lipid profile, and oxidative stress were studied. White tea supplementation was not able to reduce food intake, body weight, or visceral adiposity. Similarly, there were no changes in cholesterol rich lipoprotein profile between the groups. A reduction in blood triacylglycerols associated with increased cecal lipids was observed in the group fed the diet supplemented with white tea. White tea supplementation also reduced oxidative stress in liver and adipose tissue. In conclusion, white tea extract supplementation (0.5%) does not influence body weight or adiposity in obese mice. Its benefits are restricted to the reduction in oxidative stress associated with obesity and improvement of hypertriacylglycerolemia.

A high-fat diet as a model of fatty liver disease in rats

PURPOSE

The objective of the present study was to analyze the physiological and metabolic changes occurring in rats subjected to high-fat diet for one month.

METHODS

The animals received a modified AIN-93 diet with increased lipid content and decreased carbohydrate content, while the control group received the normal AIN-93 diet.

RESULTS

It was observed that the high-fat diet did not induce weight gain but led to greater gain of hepatic fat compared to control. Biochemical parameters, glycemia, total cholesterol and serum protein did not differ between groups. In parallel, rats receiving the high-fat diet consumed less feed.

CONCLUSION

The development of obesity through high-fat diet is associated with increased energy intake and time of exposure to the diet, while the metabolic syndrome is more associated with the combination of a diet rich in fat and carbohydrates.

Hyperadiponectinemia protects against premature death in metabolic syndrome model mice by inhibiting AKT signaling and chronic inflammation

We previously reported that transgenic (Tg) expression of adiponectin significantly prolonged the lifespan of normal mice. The aim of this study was to elucidate the mechanism involved in the longevity effects of adiponectin using KK/Ta mice, a murine model of metabolic syndrome. We established a Tg line of KK/Ta (Tg-KK/Ta) mice expressing human adiponectin in the liver, and assessed their lifespan. The cause of death was determined by macroscopic and microscopic examinations immediately after death. The expressions of SIRT1, C-reactive protein (CRP), inflammatory cytokines, AMPK, and AKT were measured by quantitative real-time PCR, ELISAs, and/or western blotting. KK/Ta mice had lower serum adiponectin levels and shorter lifespan (57.6±13.9 vs 106.5±18.3 weeks, P<0.0001) than C57BL/6N mice. Tg adiponectin expression significantly extended the lifespan of KK/Ta mice (73.6±16.6 weeks, P<0.001) without affecting body weight, daily food consumption, or plasma glucose levels. Neoplasms were observed in only three of 22 KK/Ta mice that died spontaneously because of tumors. Atherosclerotic lesions were not detected in any mice. SIRT1 levels were not significantly different between KK/Ta and Tg-KK/Ta mice. Gene expressions of Crp, Tnfα, Il6, and Nfκb were increased in KK/Ta mice, but they were significantly attenuated in Tg-KK/Ta mice. Phosphorylated AMPK levels were increased and phosphorylated AKT levels were decreased in Tg-KK/Ta mice. The anti-inflammatory effects of adiponectin, achieved by inhibiting the AKT signaling pathway, may explain how adiponectin slows the accelerated aging process associated with the metabolic syndrome.