Tragopogon porrifolius improves serum lipid profile and increases short-term satiety in rats

Tragopogon porrifolius (white salsify) is an edible plant commonly used in folk medicine in Lebanon and neighbouring countries. This study investigates the effect of the aqueous extract of the aerial part of T. porrifolius on lipemia and appetite regulation using a rat model. Food intake, abdominal fat percentage, blood lipid profile, liver weight and liver enzymes were assessed following 4 weeks of extract intake via drinking water (50, 100, or 250 mg/kg body weight) in standard high-carbohydrate and high-fat dietary conditions. In a separate study, the short term effect of a preload of T. porrifolius extract on food intake was evaluated. Results showed that consumption of the plant extract for a period of four weeks resulted in a marked improvement of the lipid profile (triglycerides, total cholesterol, LDL and HDL cholesterol). Body weight, food intake and intra-abdominal fat were also lower in animals given the plant extract (100 and 250 mg/kg). In addition, T. porrifolius extract preload produced a dose dependent decrease in food intake observed over 24h. The intake of T. porrifolius aqueous extract therefore improved lipemia and increased satiety in rats with no visible adverse effects.

Delayed physical and neurobehavioral development and increased aggressive and depression-like behaviors in the rat offspring of dams fed a high-fat diet

Early maternal exposure to a high-fat diet (HFD) may influence the brain development of rat offspring and consequently affect physiology and behavior. Thus, in the present study, we investigated the somatic, physical, sensory-motor and neurobehavioral development of the offspring of dams fed an HFD (52% calories from fat, mainly saturated) and the offspring of dams fed a control diet (CD - 14.7% fat) during lactation from the 1st to the 21st postnatal day (P). Maternal body weights were evaluated during lactation. In the progeny, somatic (body weight, head and lengths axes) and physical (ear unfolding, auditory conduit opening, eruption of the incisors and eye opening) development and the consolidation of reflex responses (palm grasp, righting, vibrissa placing, cliff avoidance, negative geotaxis, auditory startle response and free-fall righting) were determined during suckling. Depressive and aggressive behaviors were tested with the forced swimming test (FST) and the "foot-shock" test on days 60 and 110, respectively. The open field test was used to assess motor function. Compared to controls, the HFD-pups exhibited decreases in body weight (P7-P21) and body length (P4-P18), but by days P71 and P95, these pups were overweight. All indicators of physical maturation and the consolidation of the following reflexes, vibrissa placing, auditory startle responses, free-fall righting and negative geotaxis, were delayed in HFD-progeny. In addition, the pups from HFD dam rats also exhibited reduced swimming and climbing times in the FST and increased aggressive behavior. No changes in locomotion were observed. These findings show developmental and neurobehavioral changes in the rat offspring of dams fed the HFD during lactation and suggest possible disruption of physical and sensory-motor maturation and increased susceptibility to depressive and aggressive-like behavior.

Low doses of curcumin protect alcohol-induced liver damage by modulation of the alcohol metabolic pathway, CYP2E1 and AMPK

AIMS

This study investigated the hepatoprotective effects of low doses of curcumin against liver damage induced by chronic alcohol intake and a high-fat diet. We also examined several potential underlying mechanisms including action on alcohol metabolism, antioxidant activity, AMPK level and lipid metabolism.

MAIN METHOD

Alcohol (25% v/v, 5 g/kg body weight) was orally administered once a day for 6 weeks to mice fed a high-fat diet with or without two different doses of curcumin (0.02% and 0.05%, wt/wt).

KEY FINDINGS

Curcumin significantly decreased the plasma aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase and alkaline phosphatase activities (p<0.05) and prevented hepatic steatosis compared with the alcohol control group. Curcumin significantly reversed the alcohol-induced inhibition of the alcohol dehydrogenase, aldehyde dehydrogenase 2 and antioxidant enzyme activities as well as the activation of cytochrome P4502E1 and promotion of lipid peroxidation (p<0.05). Curcumin significantly increased the hepatic total AMPK protein level and concomitantly suppressed the fatty acid synthase and phosphatidate phosphohydrolase activities compared with the alcohol control group (p<0.05). Furthermore, curcumin significantly lowered the plasma leptin, free fatty acids and triglycerides levels and hepatic lipid levels (p<0.05).

SIGNIFICANCE

These findings indicate that low doses of curcumin may protect against liver damage caused by chronic alcohol intake and a high-fat diet partly by modulating the alcohol metabolic enzyme activity, the antioxidant activity and the lipid metabolism. Therefore, curcumin may provide a promising natural therapeutic strategy against liver disease.

Effect of a postnatal high-fat diet exposure on puberty onset, estrous cycle regularity, and kisspeptin expression in female rats

Kisspeptin, encoded by Kiss1, plays a key role in pubertal maturation and reproduction as a positive upstream regulator of the hypothalamic-pituitary-gonadal (HPG) axis. To examine the role of high-fat diet (HFD) on puberty onset, estrous cycle regularity, and kisspeptin expression, female rats were exposed to HFD in distinct postnatal periods. Three groups of rats were exposed to HFD containing 60% energy from fat during the pre-weaning period (postnatal day (PND) 1-16, HFD PND 1-16), post-weaning period (HFD PND 21-34), or during both periods (HFD PND 1-34). Puberty onset, evaluated by vaginal opening, was monitored on days 30-34. Leptin, estradiol (E2), Kiss1 mRNA levels, and number of kisspeptin-immunoreactive cells in the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC) were measured at day 34. Body weight increased only in rats exposed to HFD during post-weaning period, whereas the timing of vaginal opening was unaffected in all three groups. Leptin, Kiss1 mRNA levels, and number of kisspeptin-immunoreactive cells at day 34 were not affected by HFD. Additionally, the estrous cycle regularity was monitored in rats exposed to HFD for 40 days from weaning. Leptin, E2, and Kiss1 mRNA levels in the AVPV and ARC were measured after the HFD exposure. Thirty-three percent of rats exposed to HFD exhibited irregular estrous cycles and a two-fold increase in leptin. By contrast, E2 level and Kiss1 mRNA levels were not affected by the treatment. These data show that postnatal HFD exposure induced irregular estrous cycles, but had no effect on puberty onset or kisspeptin.

Brown adipose tissue blood flow and mass in obesity: a contrast ultrasound study in mice

BACKGROUND

When activated by the sympathetic nervous system, brown adipose tissue (BAT) increases energy expenditure to produce heat. Augmenting BAT mass or increasing BAT activation could potentially be used to decrease obesity. Noninvasive methods to detect and monitor BAT mass are needed. Contrast ultrasound can estimate BAT blood flow and is able to measure the perfused volume of an organ and thus its mass. The objective of this study was to evaluate whether contrast ultrasound could characterize BAT mass in two mouse models of obesity: wild-type mice fed a high-fat diet and mutant db/db mice.

METHODS

Contrast ultrasound of BAT (Definity 2 μL/min; 14-MHz linear probe) was performed before and after stimulation of BAT with norepinephrine (NE). BAT replenishment curves were obtained, and blood flow was estimated by the product of the curve's plateau and slope. Additionally, consecutive two-dimensional images of perfused BAT were acquired at 1-mm intervals after stimulation with NE and used to assess BAT volume and mass.

RESULTS

BAT blood flow increased after NE infusion in all mice studied. Blood flow response to NE was similar in wild-type mice fed either a low-fat diet or a high-fat diet. BAT blood flow was lower in db/db mice than in wild-type mice (P = .02). Contrast ultrasound-derived BAT mass was correlated with BAT mass obtained at necropsy (R(2) = 0.83, P < .001). BAT mass was higher in mice fed a high-fat diet than in those fed a low-fat diet.

CONCLUSIONS

Contrast ultrasound can be used to estimate BAT mass in mice when BAT vascularization is not significantly impaired. This noninvasive technique may potentially allow the serial evaluation of therapies designed to augment BAT mass.

Experimental nonalcoholic fatty liver disease in mice leads to cytochrome p450 2a5 upregulation through nuclear factor erythroid 2-like 2 translocation

Mouse cytochrome P450 2A5 (CYP2A5) is upregulated in various liver diseases and a putative common feature for all of these conditions is altered cellular redox status. Nuclear factor erythroid 2-like 2 (Nrf2) is a transcription factor that is post-translationally regulated by oxidative stress and controls the transcription of protective target genes. In the present study, we have characterized the regulation of CYP2A5 by Nrf2 and evaluated gene expression, protein content and activity of anti-oxidant enzymes in the Nrf2^+/+ and Nrf2^−/− mice model of non-alcoholic fatty liver (NAFLD). After eight weeks of feeding on a high-fat diet, livers from Nrf2^−/− mice showed a substantial increase in macro and microvesicular steatosis and a massive increase in the number of neutrophil polymorphs, compared to livers from wild-type mice treated similarly. Livers of Nrf2^−/− mice on the high-fat diet exhibited more oxidative stress than their wild-type counterparts as assessed by a significant depletion of reduced glutathione that was coupled with increases in malondialdehyde. Furthermore, results in Nrf2-deficient mice showed that CYP2A5 expression was significantly attenuated in the absence of Nrf2, as was found with the conventional target genes of Nrf2. The treatment of wild-type mice with high-fat diet leaded to nuclear accumulation of Nrf2, and co-immunoprecipitation experiments showed that Nrf2 was bound to Cyp2a5. These findings suggest that the high-fat diet induced alteration in cellular redox status and induction of CYP2A5 was modulated through the redox-sensitive transcription Nrf2.

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CYP2A5 up-regulation in response to NAFLD was Nrf2 dependent.

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NAFLD induces oxidant stress.

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A protective role for Nrf2 against hepatic damage by NAFLD was demonstrated.

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NAFLD induces translocation of Nrf2 from the cytoplasm to the nucleus.

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Nrf2 binding to CYP2a5 was shown.

Inhibition of ERK1/2 pathway suppresses adiponectin secretion via accelerating protein degradation by Ubiquitin-proteasome system: relevance to obesity-related adiponectin decline

OBJECTIVE

Predominantly secreted by adipose tissue, adiponectin possesses insulin-sensitizing, anti-atherogenic, anti-inflammatory, and anti-angiogenic properties. Paradoxically, obesity is associated with declined plasma adiponectin levels; however, the underlying mechanisms remain elusive. In this study, we investigated the mechanistic involvement of MEK/ERK1/2 pathway in obesity-related adiponectin decrease.

MATERIALS/METHODS

C57 BL/6 mice exposed to a high-fat diet (HFD) were employed as animal obesity model. Both fully-differentiated 3T3-L1 and mouse primary adipocytes were used in the in vitro experiments.

RESULTS

Obesity and plasma adiponectin decline induced by prolonged HFD exposure were associated with suppressed ERK1/2 activation in adipose tissue. In adipocytes, specific inhibition of MEK/ERK1/2 pathway decreased intracellular and secretory adiponectin levels, whereas adiponectin gene expression was increased, suggesting that MEK/ERK1/2 inhibition may promote adiponectin protein degradation. Cycloheximide (CHX)-chase assay revealed that MEK/ERK1/2 inhibition accelerated adiponectin protein degradation, which was prevented by MG132, a potent proteasome inhibitor. Immunoprecipitation assay showed that intracellular MEK/ERK1/2 activity was negatively associated with ubiquitinated adiponectin protein levels. Consistently, long-term HFD feeing in mice increased ubiquitinated adiponectin levels in the epididymal fat pads.

CONCLUSIONS

Adipose tissue MEK/ERK1/2 activity can differentially regulate adiponectin gene expression and protein abundance and its suppression in obesity may play a mechanistic role in obesity-related plasma adiponectin decline.

Prenatal food restriction induces a hypothalamic-pituitary-adrenocortical axis-associated neuroendocrine metabolic programmed alteration in adult offspring rats

BACKGROUND AND AIMS

Intrauterine growth restriction produces susceptibility to adult metabolic syndrome, which may be caused by the permanent alteration of the hypothalamic-pituitary-adrenocortical (HPA) axis. We aimed to verify that HPA axis-associated neuroendocrine metabolic programming is altered in food-restricted (FR) offspring.

METHODS

Maternal rats were fed a restricted diet from gestational day 11 until full-term delivery, all pups were fed a high-fat diet after weaning and exposed to unpredictable chronic stress (UCS) during postnatal weeks 17-20.

RESULTS

Serum levels of adrenocorticotrophic hormone and corticosterone in adult offspring of the prenatal FR group were lower than the control (CN) rats before UCS but increased significantly after UCS. Serum glucose levels in the FR group were normal before UCS but increased after UCS. Serum insulin levels were significantly decreased in FR males but showed a slight increase in FR females before UCS; however, insulin levels decreased significantly in the FR male and female rats after UCS. Before UCS, serum lipid levels were higher in the FR males but were normal in the FR females; after UCS, FR males had a slight decrease and FR females had an increasing trend in serum lipids levels. Lipid droplets in the hypothalamus, pituitary gland, and livers of the FR group indicated steatosis.

CONCLUSIONS

These results suggest that prenatal food restriction alters HPA axis-associated neuroendocrine metabolism in adult offspring fed a high-fat diet, which may originate from the intrauterine programming and increase the susceptibility to adult metabolic diseases.

Saturated fatty acid palmitate induces extracellular release of histone H3: a possible mechanistic basis for high-fat diet-induced inflammation and thrombosis

Chronic low-grade inflammation is a key contributor to high-fat diet (HFD)-related diseases, such as type 2 diabetes, non-alcoholic steatohepatitis, and atherosclerosis. The inflammation is characterized by infiltration of inflammatory cells, particularly macrophages, into obese adipose tissue. However, the molecular mechanisms by which a HFD induces low-grade inflammation are poorly understood. Here, we show that histone H3, a major protein component of chromatin, is released into the extracellular space when mice are fed a HFD or macrophages are stimulated with the saturated fatty acid palmitate. In a murine macrophage cell line, RAW 264.7, palmitate activated reactive oxygen species (ROS) production and JNK signaling. Inhibitors of these pathways dampened palmitate-induced histone H3 release, suggesting that the extracellular release of histone H3 was mediated, in part, through ROS and JNK signaling. Extracellular histone activated endothelial cells to express the adhesion molecules ICAM-1 and VCAM-1 and the procoagulant molecule tissue factor, which are known to contribute to inflammatory cell recruitment and thrombosis. These results suggest the possible contribution of extracellular histone to the pathogenesis of HFD-induced inflammation and thrombosis.

Mild obesity reduces survival and adiponectin sensitivity in endotoxemic rats

BACKGROUND

Recent meta-analyses have reported that critically ill patients with morbid obesity (body mass index >40 kg/m(2)) have poor outcomes, but the effects and mechanisms of action of mild obesity are still unclear. The purpose of this study was to evaluate the effect of mild obesity using a lard-based, high-fat diet (HFD) on pathologic conditions and the mechanisms of adiponectin action in endotoxemic rats.

MATERIALS AND METHODS

Male Wistar rats underwent HFD feeding for 4 wk and were killed at 0, 1.5, and 6 h after lipopolysaccharide (LPS) injection. Plasma levels of adiponectin, nitric oxide, and interleukin 6; messenger RNA expression of adiponectin receptors (AdipoR1 and AdipoR2) in the liver and the skeletal muscle; blood biochemical test results; and histology of the liver were analyzed.

RESULTS

HFD-fed rats had a lower survival rate (12.8% versus 85.2%) and lower plasma adiponectin levels after LPS injection (P < 0.01). Messenger RNA expression of adiponectin receptors in the liver, but not the skeletal muscle, also decreased in HFD-fed rats (P < 0.05). Tissue injury and oxidative stress in the liver and plasma inflammatory mediator levels increased, and worsened lipid metabolism abnormalities were noted. The findings indicated that HFD decreased the sensitivity of adiponectin and was associated with an increase in oxidative stress and inflammation, which finally resulted in worsened liver injury and poor survival rate after LPS injection.

CONCLUSIONS

Short-term, HFD-induced, mild obesity is harmful to the septic host, reduces adiponectin sensitivity, and could be the cause of worsening pathologic conditions.

Effect of a high-fat diet on glucose/lipid metabolism and GLP-1 secretion in rats with type 2 diabetes after gastric bypass surgery

AIM: To assess the effect of a high-fat diet on glucose/lipid metabolism and glucagon-like peptide-1 (GLP-1) secretion in rats with type 2 diabetes after gastric bypass surgery.

METHODS: Twenty-four SD rats were used to induce type 2 diabetes and then randomly divided into either a control group ( n = 10) or a high-fat diet group ( n = 10). After gastric bypass surgery, the control group and high-fat diet group were fed a normal diet and a high-fat diet for 8 wk, respectively. Food intake, body weight, fasting plasma glucose and the levels of GLP-1 were measured.

RESULTS: The body weight and average food intake first decreased and then gradually increased in both groups. At week 10 after surgery, there was a significant difference in body weight between the control group and high fat diet group (302.4 g ± 34.1 g vs 334.2 g ± 47.5 g, P < 0.05). Fasting plasma glucose gradually decreased after surgery in both groups; however, fasting plasma glucose began to increase with the prolongation of time in the high-fat diet group. At week 8, fasting plasma glucose was higher in the high-fat diet group than in the control group. At week 4 after surgery, insulin level increased and insulin resistance index decreased in both groups. The level of GLP-1 at week 10 after surgery significantly increased in the high-fat diet group compared to the control group (39.33 pmol/L ± 2.77 pmol/L vs 22.69 pmol/L ± 3.87 pmol/L, P < 0.05).

CONCLUSION: Gastric bypass reduces blood glucose in rats with type 2 diabetes. A serious disturbance of carbohydrate metabolism stimulated by a high fat diet was not observed in rats after gastric bypass, and the underlying mechanism may be related to increased secretion of GLP-1.

Antiobesity effects of quercetin-rich onion peel extract on the differentiation of 3T3-L1 preadipocytes and the adipogenesis in high fat-fed rats

The aim of the present study was to examine the effect of quercetin-rich onion peel extract (OPE) on anti-differentiation in 3T3-L1 preadipocytes and the antiobesity in high-fat fed rats. We found that lipid accumulations and TG contents in 3T3-L1 cells were markedly suppressed by OPE. The mRNA levels of activating protein (AP2) were down-regulated and those of carnitine palmitoyl transferase-1 α (CPT-1α) and fatty acid binding protein 4 (FABP4) were up-regulated by 75 and 100 μg/ml OPE. Body weight, retroperitoneal and mesenteric fat weights of SD rats were significantly lower in the 8 week high fat (HF) diet+0.72% OPE group than in the HF group. Peroxisome proliferator-activated receptor (PPAR)γ mRNA levels were down-regulated in the epididymal fat of OPE than those of control and HF, and significant down-regulation of CCAAT/enhancer binding protein (C/EBP)α mRNA levels in OPE was also observed than the control. The mRNA levels of CPT-1α and uncoupling protein-1 (UCP-1) were up-regulated by the OPE, while those of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) were down-regulated in HF and OPE groups compared to control group. These results suggest that quercentin-enriched OPE may have antiobesity effects by suppressing preadipocyte differentiation and inhibiting adipogenesis.

Resveratrol inhibits LXRα-dependent hepatic lipogenesis through novel antioxidant Sestrin2 gene induction

Liver X receptor-α (LXRα), a member of the nuclear receptor superfamily of ligand-activated transcription factors, regulates de novo fatty acid synthesis that leads to stimulate hepatic steatosis. Although, resveratrol has beneficial effects on metabolic disease, it is not known whether resveratrol affects LXRα-dependent lipogenic gene expression. This study investigated the effect of resveratrol in LXRα-mediated lipogenesis and the underlying molecular mechanism. Resveratrol inhibited the ability of LXRα to activate sterol regulatory element binding protein-1c (SREBP-1c) and thereby inhibited target gene expression in hepatocytes. Moreover, resveratrol decreased LXRα-RXRα DNA binding activity and LXRE-luciferase transactivation. Resveratrol is known to activate Sirtuin 1 (Sirt1) and AMP-activated protein kinase (AMPK), although its precise mechanism of action remains controversial. We found that the ability of resveratrol to repress T0901317-induced SREBP-1c expression was not dependent on AMPK and Sirt1. It is well established that hepatic steatosis is associated with antioxidant and redox signaling. Our data showing that expression of Sestrin2 (Sesn2), which is a novel antioxidant gene, was significantly down-regulated in the livers of high-fat diet-fed mice. Moreover, resveratrol up-regulated Sesn2 expression, but not Sesn1 and Sesn3. Sesn2 overexpression repressed LXRα-activated SREBP-1c expression and LXRE-luciferase activity. Finally, Sesn2 knockdown using siRNA abolished the effect of resveratrol in LXRα-induced FAS luciferase gene transactivation. We conclude that resveratrol affects Sesn2 gene induction and contributes to the inhibition of LXRα-mediated hepatic lipogenesis.

Effects of excess dietary iron and fat on glucose and lipid metabolism

PURPOSE

Diets rich in fat and energy are associated with metabolic syndrome (MS). Increased body iron stores have been recognized as a feature of MS. High-fat diets (HFs), excess iron loading and MS are closely associated, but the mechanism linking them has not been clearly defined. We investigated the interaction between dietary fat and dietary Fe in the context of glucose and lipid metabolism in the body.

METHODS

C57BL6/J mice were divided into four groups and fed the modified AIN-93G low-fat diet (LF) and HF with adequate or excess Fe for 7 weeks. The Fe contents were increased by adding carbonyl iron (2% of diet weight) (LF+Fe and HF+Fe).

RESULTS

High iron levels increased blood glucose levels but decreased high-density lipoprotein cholesterol levels. The HF group showed increases in plasma levels of glucose and insulin and insulin resistance. HF+Fe mice showed greater changes. Representative indices of iron status, such hepatic and plasma Fe levels, were not altered further by the HF. However, both the HF and excess iron loading changed the hepatic expression of hepcidin and ferroportin. The LF+Fe, HF and HF+Fe groups showed greater hepatic fat accumulation compared with the LF group. These changes were paralleled by alterations in the levels of enzymes related to hepatic gluconeogenesis and lipid synthesis, which could be due to increases in mitochondrial dysfunction and oxidative stress.

CONCLUSIONS

High-fat diets and iron overload are associated with insulin resistance, modified hepatic lipid and iron metabolism and increased mitochondrial dysfunction and oxidative stress.

Taraxacum official (dandelion) leaf extract alleviates high-fat diet-induced nonalcoholic fatty liver

The purpose of this study is to determine the protective effect of Taraxacum official (dandelion) leaf extract (DLE) on high-fat-diet (HFD)-induced hepatic steatosis, and elucidate the molecular mechanisms behind its effects. To determine the hepatoprotective effect of DLE, we fed C57BL/6 mice with normal chow diet (NCD), high-fat diet (HFD), HFD supplemented with 2g/kg DLE DLE (DL), and HFD supplemented with 5 g/kg DLE (DH). We found that the HFD supplemented by DLE dramatically reduced hepatic lipid accumulation compared to HFD alone. Body and liver weights of the DL and DH groups were significantly lesser than those of the HFD group, and DLE supplementation dramatically suppressed triglyceride (TG), total cholesterol (TC), insulin, fasting glucose level in serum, and Homeostatic Model Assessment Insulin Resistance (HOMA-IR) induced by HFD. In addition, DLE treatment significantly increased activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) in liver and muscle protein. DLE significantly suppressed lipid accumulation in the liver, reduced insulin resistance, and lipid in HFD-fed C57BL/6 mice via the AMPK pathway. These results indicate that the DLE may represent a promising approach for the prevention and treatment of obesity-related nonalcoholic fatty liver disease.

Mitofusin-2 ameliorates high-fat diet-induced insulin resistance in liver of rats

AIM: To investigate the effects of mitofusin-2 (MFN2) on insulin sensitivity and its potential targets in the liver of rats fed with a high-fat diet (HFD).

METHODS: Rats were fed with a control or HFD for 4 or 8 wk, and were then infected with a control or an MFN2 expressing adenovirus once a week for 3 wk starting from the 9^th wk. Blood glucose (BG), plasma insulin and insulin sensitivity of rats were determined at end of the 4^th and 8^th wk, and after treatment with different amounts of MFN2 expressing adenovirus (10⁸, 10⁹ or 10¹⁰ vp/kg body weight). BG levels were measured by Accu-chek Active Meter. Plasma insulin levels were analyzed by using a Rat insulin enzyme-linked immunosorbent assay kit. Insulin resistance was evaluated by measuring the glucose infusion rate (GIR) using a hyperinsulinemic euglycemic clamp technique. The expression or phosphorylation levels of MFN2 and essential molecules in the insulin signaling pathway, such as insulin receptor (INSR), insulin receptor substrate 2 (IRS2), phosphoinositide-3-kinase (PI3K), protein kinase beta (AKT2) and glucose transporter type 2 (GLUT2) was assayed by quantitative real-time polymerase chain reaction and Western-blotting.

RESULTS: After the end of 8 wk, the body weight of rats receiving the normal control diet (ND) and the HFD was not significantly different (P > 0.05). Compared with the ND group, GIR in the HFD group was significantly decreased (P < 0.01), while the levels of BG, triglycerides (TG), total cholesterol (TC) and insulin in the HFD group were significantly higher than those in the ND group (P < 0.05). Expression of MFN2 mRNA and protein in liver of rats was significantly down-regulated in the HFD group (P < 0.01) after 8 wk of HFD feeding. The expression of INSR, IRS2 and GLUT2 were down-regulated markedly (P < 0.01). Although there were no changes in PI3K-P85 and AKT2 expression, their phosphorylation levels were decreased significantly (P < 0.01). After intervention with MFN2 expressing adenovirus for 3 wk, the expression of MFN2 mRNA and protein levels were up-regulated (P < 0.01). There was no difference in body weight of rats between the groups. The levels of BG, TG, TC and insulin in rats were lower than those in the Ad group (P < 0.05), but GIR in rats infected with Ad-MFN2 was significantly increased (P < 0.01), compared with the Ad group. The expression of INSR, IRS2 and GLUT2 was increased, while phosphorylation levels of PI3K-P85 and AKT2 were increased (P < 0.01), compared with the Ad group.

CONCLUSION: HFDs induce insulin resistance, and this can be reversed by MFN2 over-expression targeting the insulin signaling pathway.

Short-term, high fat feeding-induced changes in white adipose tissue gene expression are highly predictive for long-term changes

SCOPE

We aimed to evaluate the predictability of short-term (5 days) changes in epididymal white adipose tissue (eWAT) gene expression for long-term (12 weeks) changes induced by high-fat diet (HFD) feeding.

METHODS AND RESULTS

Mice were fed semisynthetic diets containing 10 (low-fat diet) or 40 (HFD) energy% of fat. Global gene expression in eWAT was analyzed using microarrays and confirmed by quantitative PCR. As expected, HFD feeding resulted in increased body fat accumulation and reduced glucose tolerance after 12 weeks. A total of 4678 transcripts were significantly changed by HFD after 12 weeks and 973 after 5 days, with an overlap of 764 transcripts encoding 549 genes. Of these, 79% were downregulated and 21% were upregulated by HFD, all in the same direction and highly correlated (r(2) = 0.90) between the time points. Pathway analysis showed downregulation of the main identified processes: lipid metabolism, carbohydrate metabolism, and oxidative phosphorylation. Mest (mesoderm-specific transcript) was highly upregulated, confirming its role as an early marker of fat cell expansion.

CONCLUSION

The high predictive value of short-term gene expression changes for long-term effects of high fat feeding is a promising step to establish robust early biomarkers that could shorten animal trials to assess health-promoting food compounds.

Rapid glutamate release in the mediobasal hypothalamus accompanies feeding and is exaggerated by an obesogenic food

The mediobasal hypothalamus (MBH) plays a central role in the regulation of food intake and energy balance. Although the excitatory neurotransmitter glutamate is implicated in energy balance regulation by the MBH, the hypothesis that feeding elicits local glutamate release remains untested. To test this hypothesis, we employed a glutamate biosensor that measures glutamate concentrations at 1-s intervals in conscious, freely behaving rats. Results indicate that feeding is associated with an increase of MBH glutamate concentration that occurs within 1-2 s of oral contact with a food pellet, and the glutamate response to a palatable high-fat pellet is greatly exaggerated relative to chow. In contrast, glutamate responses were not observed during water ingestion or other observed behaviors. These findings indicate that feeding is associated with rapid release of glutamate in the MBH, that this release is exaggerated with an obesogenic food, and that this response is likely stimulated by orosensory factors.

Effects of high-fat diet on the numerical density and number of neuronal cells and the volume of the mouse hypothalamus: a stereological study

It has been demonstrated that the type of diet affects the brain structure and function. Consumption of fat-rich food is one of the most important factors that lead to increase in the prevalence of cardiovascular and neurological diseases. High-fat diet may change the volume and neuronal number or density in the hypothalamus, which is the center of energy control. Therefore, this study was designed to study the effect of high-fat diet on the density and number of neurons, and also the volume of hypothalamus in adult male mice. Forty male mice were divided into the control and experimental groups. The control group were fed with standard and the experimental groups, with high-fat diet for 4 (short-term) or 8 (long-term) weeks. The animals were perfused and brains were immediately removed, post-fixed and cut coronally and serially using cryostat at 30-µm thickness. Every 6th sections were stained by cresyl violet. The numerical density and number of neuron and the volume of hypothalamus were estimated by using unbiased stereological methods. Data analysis showed that both short and long time consumption of high-fat diet decreased the neuronal cell density of the hypothalamus. Interestingly, despite a decrease in the neuronal cell density, long time consumption of high-fat diet could significantly increase the volume of hypothalamus (P<0.05). High fat diet decreased the neuronal cell density and increased the volume of the hypothalamus, but it did not significantly change its total neurons. These changes might be due to an increase in the extracellular space through inflammation or gliosis in the hypothalamus.

Coexistence of hyperlipidemia and acute cerebral ischemia/reperfusion induces severe liver damage in a rat model

AIM: To investigate the correlation of hyperlipemia (HL) and acute cerebral ischemia/reperfusion (I/R) injury on liver damage and its mechanism.

METHODS: Rats were divided into 4 groups: control, HL, I/R and HL+I/R. After the induction of HL via a high-fat diet for 18 wk, middle cerebral artery occlusion was followed by 24 h of reperfusion to capture I/R. Serum alanine transaminase (ALT) and aspartate aminotransferase (AST) were analyzed as part of liver function tests and liver damage was further assessed by histological examination. Hepatocyte apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. The expression of genes related to apoptosis (caspase-3, bcl-2) was assayed by immunohistochemistry and Western blotting. Serum tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) and liver mitochondrial superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and Ca²⁺ levels were measured to determine inflammatory and oxidative/antioxidative status respectively. Microsomal hydroxylase activity of the cytochrome P450 2E1 (CYP2E1)-containing enzyme was measured with aniline as the substrate, and CYP2E1 expression in the liver tissue and microsome was determined by immunohistochemistry and Western blotting respectively.

RESULTS: HL alone induced by high-fat diet for 18 wk resulted in liver damage, indicated by histopathological analysis, and a considerable increase in serum ALT (25.13 ± 16.90 vs 9.56 ± 1.99, P < 0.01) and AST levels (18.01 ± 10.00 vs 11.33 ± 4.17, P < 0.05) compared with control. Moreover, HL alone induced hepatocyte apoptosis, which was determined by increased TUNEL-positive cells (4.47 ± 0.45 vs 1.5 ± 0.22, P < 0.01), higher caspase-3 and lower bcl-2 expression. Interestingly, compared with those in control, HL or I/R groups, massive increases of serum ALT (93.62 ± 24.00 vs 9.56 ± 1.99, 25.13 ± 16.90 or 12.93 ± 6.14, P < 0.01) and AST (82.32 ± 26.92 vs 11.33 ± 4.17, 18.01 ± 10.00 or 14.00 ± 6.19, P < 0.01) levels in HL+I/R group were observed suggesting severe liver damage, which was confirmed by liver histology. In addition, HL combined with I/R also caused significantly increased hepatocyte apoptosis, as evidenced by increased TUNEL-positive cells (6.20 ± 0.29 vs 1.5 ± 0.22, 4.47 ± 0.45 or 1.97 ± 0.47, P < 0.01), elevated expression of caspase-3 and lower expression of bcl-2. Furthermore, when compared to HL or I/R alone, HL plus I/R enhanced serum TNF-α, IL-1, liver mitochondrial MDA and Ca²⁺ levels, suppressed SOD and GSH-Px in liver mitochondria, and markedly up-regulated the activity (11.76 ± 2.36 vs 4.77 ± 2.31 or 3.11 ± 1.35, P < 0.01) and expression (3.24 ± 0.38 vs 1.98 ± 0.88 or 1.72 ± 0.58, P < 0.01) of CYP2E1 in liver.

CONCLUSION: The coexistence of HL and acute cerebral I/R induces severe liver damage, suggesting that cerebral ischemic stroke would exaggerate the damage of liver caused by HL. This effect is possibly due to enhanced CYP2E1 induction which further promotes oxidative damage, inflammation and hepatocyte apoptosis.

Epistatic Control of Mammary Cancer Susceptibility in Mice may Depend on the Dietary Environment

Recent studies have linked a high fat diet to the development of breast cancer, but any genetic basis for this association is poorly understood. We investigated this association with an epistatic analysis of seven cancer traits in a segregating population of mice with metastatic mammary cancer that were fed either a control or a high-fat diet. We used an interval mapping approach with single nucleotide polymorphisms to scan all 19 autosomes, and discovered a number of diet-independent epistatic interactions of quantitative trait loci (QTLs) affecting these traits. More importantly, we also discovered significant epistatic by diet interactions affecting some of the traits that suggested these epistatic effects varied depending on the dietary environment. An analysis of these interactions showed some were due to epistasis that occurred in mice fed only the control diet or only the high-fat diet whereas other interactions were generated by differential effects of epistasis in the two dietary environments. Some of the epistatic QTLs appeared to colocalize with cancer QTLs mapped in other mouse populations and with candidate genes identified from eQTLs previously mapped in this population, but others represented novel modifying loci affecting these cancer traits. It was concluded that these diet-dependent epistatic QTLs contribute to a genetic susceptibility of dietary effects on breast cancer, and their identification may eventually lead to a better understanding that will be needed for the design of more effective treatments for this disease.

Involvement of nuclear factor kappa B in high-fat diet-related pancreatic fibrosis in rats

Background/Aims

High-fat diets contribute to pancreatic fibrogenesis, but the pathogenesis remains unclear. This study investigated the role of nuclear factor kappa B (NF-κB) in high-fat diet-induced pancreatic fibrosis in rats.

Methods

Male Wistar rats were fed a high-fat diet or standard normal chow for 20 weeks. Pancreatic fibrosis was determined by Sirius red staining. Immunohistochemical staining, reverse transcription-polymerase chain reaction and Western blotting were used to identify NF-κB-associated genes or protein expressions.

Results

Inflammation, fat deposition, pancreatic stellate cell activation and fibrosis were observed in the pancreases of the high-fat diet group. NF-κB subunit p65 (NF-κB/p65) expression was localized to the nucleus, and intercellular adhesion molecule 1 (ICAM-1) was over-expressed. Pancreatic gene expression levels of NF-κB/p65, ICAM-1 and tumor necrosis factor α were all elevated significantly in rats fed a high-fat diet compared with control rats. Western blotting also revealed significantly increased levels of ICAM-1 and nuclear NF-κB/p65 in rats fed high-fat diets comparison with control rats.

Conclusions

NF-κB is involved in high-fat diet-related pancreatic fibrosis.

Regulation of lipid disorders by ethanol extracts from Zingiber zerumbet in high-fat diet-induced rats

The aim of this study was to investigate the antihyperlipidaemic effects of the ethanol extract of Zingiber zerumbet (L) Smith (EEZZ). After being fed a high-fat diet (HFD) for 2weeks, rats were dosed orally with EEZZ (100, 200 or 300mg/kg) or fenofibrate (100mg/kg) once daily for 8weeks. EEZZ (300mg/kg/day) produced effects similar to fenofibrate in reducing body weight gain, visceral fat-pad weights and plasma lipid levels. EEZZ caused reductions in hepatic triglyceride and cholesterol content, and lowered hepatic lipid droplet accumulation and the size of epididymal adipocytes. HFD-induced reductions in the hepatic proteins of peroxisome proliferator-activated receptor (PPAR) α, acyl-CoA oxidase (ACO) and cytochrome P450 isoform 4A1 (CYP4A1) were reversed by EEZZ. These results suggest that EEZZ reduced the accumulation of visceral fat and improved hyperlipidaemia in HFD-fed rats by increasing fatty acid oxidation, an effect which is likely to be mediated via up-regulation of hepatic PPARα.

Intake of a high-fat diet alters intestinal flora in rats

AIM: To investigate the possible effect of intake of a high-fat diet on intestinal flora in rats.

METHODS: Twenty Sprague-Dawley rats were randomly divided into two groups: group A and group B. Group A was fed a normal diet, while group B was fed a diet rich in oil and fat. The fecal microbial population was analyzed on days 1, 15 and 30. The rats were killed on day 30 to analyze the small intestinal flora.

RESULTS: Serum total cholesterol (TC) level on day 30 was significantly lower in group A than in group B (1.8186 mmol/L ± 0.39 mmol/L vs 2.6213 mmol/L ± 0.28 mmol/L, P < 0.05). The fecal microbial population changed greatly in Group B: the counts of Lactobacillus acidophilus, Bifidobacterium, and Enterococcus were significantly lower on day 30 than on day 1 (6.1353 ± 0.23 vs 7.0203 ± 0.36, 5.3010 ± 0.23 vs 6.8531 ± 0.30 and 3.3269 ± 0.24 vs 5.4740 ± 0.25, all P < 0.05); the counts of Bacteroides on days 15 and 30 were 7.2339 ± 0.32 and 5.7979 ± 0.40, respectively, showing an "initially increased then decreased]trend (P < 0.05) when compared with that on day 1 (6.4933 ± 0.38). In contrast, the small intestinal flora was relatively stable.

CONCLUSION: High-fat diet intake for 30 days results in great changes in intestinal flora that mainly occur in the colon and are considered to be able to accelerate the development of obesity and hyperlipidemia.

Effects of endurance exercise and high-fat diet on insulin resistance and ceramide contents of skeletal muscle in sprague-dawley rats

Background

We evaluated the effects of endurance exercise and a high-fat diet on insulin resistance and ceramide contents of skeletal muscle in Sprague-Dawley rats.

Methods

We randomly divided 32 rats into four groups: control (CON, n = 8), high fat diet (HF, n = 8), exercise (Ex, 24 m/min for 2 hours, 5 days/wk, n = 8), HF/Ex (n = 8). After 4-week treatments, plasma lipid profiles, glucose and insulin concentrations were measured. The triglycerides (TG), ceramide, and glucose transporter 4 (GLUT-4) contents were measured in the skeletal muscle. The rate of glucose transport was determined under submaximal insulin concentration during the muscle incubation.

Results

Free fatty acid levels were significantly higher in CON and HF than Ex (P = 0.032). Plasma glucose levels in HF were significantly higher than the two Ex groups (P = 0.002), and insulin levels were significantly higher in HF than in other three groups (P = 0.021). Muscular TG concentrations were significantly higher in HF than CON and Ex and also in HF/Ex than Ex, respectively (P = 0.005). Hepatic TG concentrations were significantly higher in HF than other three groups but Ex was significantly lower than HF/Ex (P = 0.000). Muscular ceramide content in HF was significantly greater than that in either Ex or HF/Ex (P = 0.031). GLUT-4 levels in CON and HF were significantly lower than those in Ex and HF/Ex (P = 0.009, P = 0.003). The glucose transport rate in submaximal insulin concentration was lower in CON than in either Ex or HF/Ex (P = 0.043), but not different from HF.

Conclusion

This study suggests that high fat diet for 4 weeks selectively impairs insulin resistance, but not glucose transport rate, GLUT-4 and ceramide content in skeletal muscle per se. However, endurance exercise markedly affects the content of ceramide and insulin resistance in muscle.

Therapeutic effects of diet change on nonalcoholic fatty liver disease

AIM: To investigate the therapeutic effects of diet change on nonalcoholic fatty liver disease (NAFLD) and explore potential mechanisms involved.

METHODS: Eighty Sprague-Dawley male rats were randomly and equally divided into five groups: two normal control groups (NG8 and NG12 groups; fed a normal diet for 8 and 12 weeks, respectively), two high-fat diet groups (HG8 and HG12 groups; fed a high-fat diet for 8 and 12 weeks, respectively), and one diet change group (DG group; fed a high-fat diet for 8 weeks and a normal diet for another 4 weeks). The glucose infusion rate (GIR) was detected by the euglycemic hyperinsulinemic clamp test. The levels of ALT, AST, TG, TC, FFAs, FBS, FIns, TNF-α, SOD and MDA in the serum or liver were tested using a biochemistry automatic analyzer or by radioimmunoassay (RIA). The expression of c-Jun N-terminal protein kinase 1 (JNK1), insulin receptor substrate-1 (IRS-1) and phospho-IRS-1 Ser307 (p-IRS-1Ser307) was detected by Western blot.

RESULTS: Compared with the two matched NG groups, the body weight, liver index, the levels of ALT, AST, TG, TC, FFAs, FIns and TNF-α in the serum and TG, TC, FFAs and MDA in the liver increased (all P < 0.05 or 0.01), the level of SOD in the liver and GIR decreased (t = 4.88 and 7.92, respectively; both P < 0.05), and the expression of JNK1 protein and p-IRS-1Ser307 in the liver was upregulated in the two HG groups (t = 4.39, 5.81; 4.60, and 6.48, respectively). Significant differences were also noted in the above parameters between the HG8 and HG12 groups (all P < 0.05 or 0.01). A positive correlation was found between the expression intensity of JNK1 and insulin resistance (IR). The fatty degeneration of hepatocytes was aggravated in the HG groups with the prolongation of feeding time. In the DG group, all the above parameters were improved but did not return to normal levels as those in the NG groups (all P < 0.05).

CONCLUSION: A rat model of NAFLD and a rat model of NASH are established by feeding rats a high-fat diet for 8 weeks and 12 weeks, respectively. Diet change can improve NAFLD induced by a high fat diet.

Investigation of Ala54Thr polymorphism in intestinal fatty acid binding protein in Han and Mongoloid populations

AIM: To investigate the single nucleotide polymorphism (SNP) at the 54Ala/Thr (A/T) in the intestinal fatty acid binding protein (IFABP) gene in Hans and Mongolians.

METHODS: Polymerase chain reaction (PCR), restriction endonuclease (HhaI) digestion and DNA sequencing technique were performed to detect the IFABP gene polymorphism at the 54Ala/Thr in 208 Mongolians of pastoral area, 150 Mongolians of Zhangjakou city and 190 Hans.

RESULTS: The allelic frequency of 54Thr was 0.51, 0.33, and 0.30, while that of 54Ala was 0.49, 0.67, and 0.70 in Mongolians of pastoral area, Zhangjakou city and 190 Hans, respectively. In comparison with that of Mongolians in urban area and Hans, the allelic frequency of codon 54Thr in Mongolians of pastoral area was significantly increased (χ² = 22.98, P < 0.01; χ² = 34.23, P < 0.01, respectively), however, it was not significantly different between the Mongolians of urban area and Hans.

CONCLUSION: The IFABP gene polymorphism at 54A/T has no correlation with ethnics among Mongolians and Hans, and the high frequency of 54Thr mutant genotype in Mongolians of pastoral area may be associated with high-fat dieting.