Cardioprotective and hepatoprotective effects of ellagitannins from European oak bark (Quercus petraea L.) extract in rats

Background

Red wine contains many potentially bioactive polyphenols including resveratrol, catechins, anthocyanins and flavonoids as well as tannins derived from oak during maturation. This study examined the effects of a mixture of ellagitannins from oak bark (Quercus petraea L.) on cardiovascular, metabolic and liver changes in high-carbohydrate, high-fat diet–fed rats and in Spontaneously Hypertensive Rats (SHR).

Methods

First, 8-week-old male Wistar rats were divided into four groups and given either cornstarch diet, cornstarch diet + oak bark extract (0.5 mL/kg food), high-carbohydrate, high-fat diet or high-carbohydrate, high-fat diet + oak bark extract (0.5 mL/kg food) for 16 weeks. Oak bark extract was added to the diets for last 8 weeks of the feeding period. Secondly, SHR aged 42 weeks fed on standard chow diet were divided into two groups with and without oak bark extract treatment for 12 weeks (0.5 mL/kg food).

Results

The high-carbohydrate, high-fat diet induced signs of metabolic syndrome along with cardiovascular remodelling and non-alcoholic steatohepatitis. Oak bark extract attenuated the signs of metabolic syndrome in high-carbohydrate, high-fat diet–fed rats and improved the structure and function of the heart and the liver. SHR after oak bark extract treatment for 12 weeks showed lower systolic blood pressure, lower cardiac fibrosis and cardiac stiffness and improved vascular reactivity.

Conclusions

Oak bark extract containing ellagitannins improved cardiovascular, metabolic and liver parameters in these rat models of human disease, suggesting that part of the benefits attributed to red wine may be produced by these ellagitannins.     

Ellagic acid coordinately attenuates Wnt/β-catenin and NF-κB signaling pathways to induce intrinsic apoptosis in an animal model of oral oncogenesis

Purpose

Constitutive activation of the Wnt signaling pathway and its downstream effectors plays a key role in neoplastic transformation. The objective of this study was to investigate the effect of ellagic acid, a plant-derived polyphenol on Wnt/β-catenin signaling and its downstream circuits- NF-κB and mitochondrial apoptosis in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model.

Methods

Hamsters were divided into six groups. The right buccal pouches of animals in groups 1–4 were painted with 0.5% DMBA three times a week for 14 weeks. Animals in groups 2–4 received in addition basal diet containing ellagic acid at a concentration of 0.1, 0.2, and 0.4% in the diet. Group 5 animals were given 0.4% ellagic acid alone. Group 6 animals served as control. The expression of the members of Wnt and NF-κB signaling and intrinsic apoptosis was evaluated by western blot analysis.

Results

Dietary supplementation of 0.4% ellagic acid suppressed the development of HBP carcinomas by preventing the constitutive activation of Wnt pathway through the downregulation of Fz, Dvl-2, GSK-3β and nuclear translocation of β-catenin. Abrogation of Wnt signaling by ellagic acid was also associated with inactivation of NF-κB and modulation of key components of the mitochondrial apoptotic network.

Conclusions

Our findings suggest a functional crosstalk between Wnt and NF-κB signaling pathways in HBP carcinomas that is blocked by ellagic acid supplementation. Dietary ellagic acid that targets the Wnt/β-catenin pathway as well as its downstream signaling mediators is a unique candidate for cancer chemoprevention.     

Differential effects of high-fat-diet rich in lard oil or soybean oil on osteopontin expression and inflammation of adipose tissue in diet-induced obese rats

Purpose

To examine the effect of different dietary fat types on osteopontin (OPN) expressions and inflammation of adipose tissues in diet-induced obese rats.

Methods

Male Sprague–Dawley rats were randomly assigned to one control group fed standard diet (LF, n = 10) and two high-fat diet groups fed isoenergy diet rich in lard or soybean oil (HL or HS, n = 45 each). Diet-induced obese rats in HL and HS group were then subdivided into two groups either continuously fed high-fat diet or switched to low-fat diet for 8 more weeks. Fasting serum glucose, insulin, and OPN concentrations were assayed and QUICKI was calculated; the expression of OPN, IL-6, IL-10, TNF-α, NF-κB, and F4/80 in adipose tissue was determined.

Results

Both high-fat diets lead to comparable development of obesity characterized by insulin resistance and adipose tissue inflammation. Obese rats continuously fed high-fat diet rich in lard oil exhibited the highest fasting serum insulin level and adipose tissue OPN, F4/80, TNF-α, and NF-κB expression level. In both high-fat diet groups, switching to low-fat diet resulted in less intra-abdominal fat mass, decreased expression of F4/80, TNF-α, and NF-κB, while decreased OPN expression was only observed in lard oil fed rats after switching to low-fat diet.

Conclusions

Reducing diet fat or replacing lard oil with soybean oil in high-fat diet alleviates obesity-related inflammation and insulin resistance by attenuating the upregulation of OPN and macrophage infiltration into adipose tissue induced by high-fat diet.     

Differential effects of high-carbohydrate and high-fat diets on hepatic lipogenesis in rats

Purpose

Hepatic fatty acid synthesis is influenced by several nutritional and hormonal factors. In this study, we have investigated the effects of distinct experimental diets enriched in carbohydrate or in fat on hepatic lipogenesis.

Methods

Male Wistar rats were divided into four groups and fed distinct experimental diets enriched in carbohydrates (70 % w/w) or in fat (20 and 35 % w/w). Activity and expression of the mitochondrial citrate carrier and of the cytosolic enzymes acetyl-CoA carboxylase and fatty acid synthetase were analyzed through the study with assessments at 0, 1, 2, 4, and 6 weeks. Liver lipids and plasma levels of lipids, glucose, and insulin were assayed in parallel.

Results

Whereas the high-carbohydrate diet moderately stimulated hepatic lipogenesis, a strong inhibition of this anabolic pathway was found in animals fed high-fat diets. This inhibition was time-dependent and concentration-dependent. Moreover, whereas the high-carbohydrate diet induced an increase in plasma triglycerides, the high-fat diets determined an accumulation of triglycerides in liver. An increase in the plasmatic levels of glucose and insulin was observed in all cases.

Conclusions

The excess of sucrose in the diet is converted into fat that is distributed by bloodstream in the organism in the form of circulating triglycerides. On the other hand, a high amount of dietary fat caused a strong inhibition of lipogenesis and a concomitant increase in the level of hepatic lipids, thereby highlighting, in these conditions, the role of liver as a reservoir of exogenous fat.     

Dietary supplementation with geranylgeraniol suppresses lipopolysaccharide-induced inflammation via inhibition of nuclear factor-κB activation in rats

Purpose

The isoprenoid geranylgeraniol (GGOH) inhibits nuclear factor-kappa B (NF-κB) activation in the liver, yet the mechanism remains unclear. We investigated the modulation and inhibition of lipopolysaccharide (LPS)-induced NF-κB signaling in the liver of rats fed a GGOH-supplemented diet.

Methods

Rats were fed a diet supplemented with or without GGOH for 10 days. Rats were then intraperitoneally injected with 0.5 mg/kg LPS or vehicle (sterilized saline) and fasted for 18 h. Plasma levels of the inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, and the liver damage indicators alanine and aspartate aminotransferases (ALT and AST) were assessed. Liver mRNA and proteins were assayed for changes in NF-κB target genes and signal transduction genes.

Results

Rats fed a high-dose, GGOH-supplemented diet showed significantly lower levels of plasma inflammatory cytokines and ALT and AST activities. In the liver, GGOH significantly suppressed NF-κB activation and mRNA expression of its pro-inflammatory target genes. Furthermore, GGOH supplementation substantially suppressed mRNA expression of signal transducer genes upstream of the IκB kinase complex. Western blotting of liver extracts further demonstrated the substantial decrease in total IL-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6), leading to lower signal transduction and inhibition of NF-κB after LPS.

Conclusion

A 10-day, high-dose, GGOH-supplemented diet was sufficient to inhibit LPS-induced inflammation and activation of NF-κB in rat livers. GGOH significantly modulated NF-κB signaling molecules, inhibiting its signal transduction and activation in the liver, thus protecting against liver damage.     

High-fat diet inhibits PGC-1α suppressive effect on NFκB signaling in hepatocytes

Purpose

The peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) regulates the expression of genes implicated in fatty acid oxidation and oxidative phosphorylation. Its role in liver steatosis is well established, since mice with liver-specific deletion of PGC-1α exhibit lipid accumulation and high-fat diet reduces hepatic PGC-1α expression in mice. In this study, we investigated the role of PGC-1α in the inflammatory changes observed in steatohepatitis induced by high-fat diet.

Methods

C57black/6 mice were fed a high-fat diet containing 30% fat for 10 weeks. After euthanasia, liver morphology was examined by HE staining and inflammation was determined by IL-6, TNF-α, and IL-1β quantification. Liver gene expression of PGC-1 isoforms was evaluated by real-time PCR and p65 NFκB nuclear translocation by Western blotting. HepG2 cells were treated with linoleic acid overload for 72 h to create an in vitro model of steatohepatitis. RNA interference (RNAi) was used to evaluate the involvement of PGC-1α on inflammatory mediators’ production by hepatocytes.

Results

The high-fat diet led to a state of nonalcoholic steatohepatitis, associated with increased deposits of intra-abdominal fat, hyperglycemia and hyperlipidemia. Mice liver also exhibited increased proinflammatory cytokines’ levels, decreased PGC-1α expression, and marked increase in p65 NFκB nuclear translocation. Linoleic acid treated cells also presented increased expression of proinflammatory cytokines and decreased PGC-1α expression. The knockdown of PGC-1α content caused an increase in IL-6 expression and release via enhanced IκBα phosphorylation and subsequent increase of p65 NFκB nuclear translocation.

Conclusion

High-fat diet induces liver inflammation by inhibiting PGC-1α expression and its suppressive effect in NFκB pathway.

     

Epigallocatechin gallate attenuates fibrosis,oxidative stress,and inflammation in non-alcoholic fatty liver disease rat model through TGF/SMAD,PI3 K/Akt/FoxO1, and NF-kappa B pathways

Purpose

To investigate the protective mechanisms of an 85 % pure extract of (?) epigallocatechin gallate (EGCG) in the development of fibrosis, oxidative stress and inflammation in a recently developed dietary-induced animal model of non-alcoholic fatty liver disease (NAFLD).

Methods

Female Sprague–Dawley rats were fed with either normal rat diet or high-fat diet for 8 weeks to develop NAFLD. For both treatments, rats were treated with or without EGCG (50 mg/kg, i.p. injection, 3 times per week). At the end, blood and liver tissue samples were obtained for histology, molecular, and biochemical analyses.

Results

Non-alcoholic fatty liver disease (NAFLD) rats showed significant amount of fatty infiltration, necrosis, fibrosis, and inflammation. This was accompanied by a significant expressional increase in markers for fibrosis, oxidative stress, and inflammation. TGF/SMAD, PI3 K/Akt/FoxO1, and NF-κB pathways were also activated. Treatment with EGCG improved hepatic histology (decreased number of fatty score, necrosis, and inflammatory foci), reduced liver injury (from ~0.5 to ~0.3 of ALT/AST ratio), attenuated hepatic changes including fibrosis (reduction in Sirius Red and synaptophysin-positive stain) with down-regulation in the expressions of key pathological oxidative (e.g. nitrotyrosine formation) and pro-inflammatory markers (e.g. iNOS, COX-2, and TNF-α). EGCG treatment also counteracted the activity of TGF/SMAD, PI3 K/Akt/FoxO1, and NF-κB pathways. Treatment with EGCG did not affect the healthy rats.

Conclusions

Epigallocatechin gallate (EGCG) reduced the severity of liver injury in an experimental model of NAFLD associated with lower concentration of pro-fibrogenic, oxidative stress, and pro-inflammatory mediators partly through modulating the activities of TGF/SMAD, PI3 K/Akt/FoxO1, and NF-κB pathways. Therefore, green tea polyphenols and EGCG are useful supplements in the prevention of NAFLD.     

Effect of dietary fatty acid composition on substrate utilization and body weight maintenance in humans

Background/purpose

Dietary fat content is a primary factor associated with the increase in global obesity rates. There is a delay in achieving fat balance following exposure to a high-fat (HF) diet (≥ 40 % of total energy from fat) and fat balance is closely linked to energy balance. Exercise has been shown to improve this rate of adaptation to a HF diet. Recently, however, the role of dietary fatty acid composition on energy and macronutrient balance has come into question.

Methods

We chose studies that compared monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and saturated fatty acids (SFA). We have reviewed studies that measured diet-induced thermogenesis (DIT), energy expenditure (EE), or fat oxidation (FOx) in response to a HF meal challenge, or long-term dietary intervention comparing these fatty acids.

Results

While single-meal studies show that SFA induce lower DIT and FOx compared to unsaturated fats, the effect of the degree of unsaturation (MUFA vs. PUFA) appears to yet be determined. Long-term dietary interventions also support the notion that unsaturated fats induce greater EE, DIT, and/or FOx versus SFA and that a high MUFA diet induces more weight loss compared to a high SFA diet. Sex and BMI status also affect the metabolic responses to different fatty acids; however, more research in these areas is warranted.

Conclusion

SFA are likely more obesigenic than MUFA, and PUFA. The unsaturated fats appear to be more metabolically beneficial, specifically MUFA ≥ PUFA > SFA, as evidenced by the higher DIT and FOx following HF meals or diets.     

Modulation of the nuclear factor-kappa B (NF-κB) signalling pathway by glutamine in peritoneal macrophages of a murine model of protein malnutrition

Background and aims

Protein malnutrition affects resistance to infection by impairing the inflammatory response, modifying the function of effector cells, such as macrophages. Recent studies have revealed that glutamine—a non-essential amino acid, which could become conditionally essential in some situations like trauma, infection, post-surgery and sepsis—is able to modulate the synthesis of cytokines. The aim of this study was to evaluate the effect of glutamine on the expression of proteins involved in the nuclear factor-kappa B (NF-κB) signalling pathway of peritoneal macrophages from malnourished mice.

Methods

Two-month-old male Balb/c mice were submitted to protein-energy malnutrition (n = 10) with a low-protein diet containing 2 % protein, whereas control mice (n = 10) were fed a 12 % protein-containing diet. The haemogram and analysis of plasma glutamine and corticosterone were evaluated. Peritoneal macrophages were pre-treated in vitro with glutamine (0, 0.6, 2 and 10 mmol/L) for 24 h and then stimulated with 1.25 μg LPS for 30 min, and the synthesis of TNF-α and IL-1α and the expression of proteins related to the NF-κB pathway were evaluated.

Results

Malnourished animals had anaemia, leucopoenia, lower plasma glutamine and increased corticosterone levels. TNF-α production of macrophages stimulated with LPS was significantly lower in cells from malnourished animals when cultivated in supraphysiological (2 and 10 mmol/L) concentrations of glutamine. Further, glutamine has a dose-dependent effect on the activation of macrophages, in both groups, when stimulated with LPS, inducing a decrease in TNF-α and IL-1α production and negatively modulating the NF-κB signalling pathway.

Conclusions

These data lead us to infer that the protein malnutrition state interferes with the activation of macrophages and that higher glutamine concentrations, in vitro, have the capacity to act negatively in the NF-κB signalling pathway.     

Soy protein inhibits inflammation-induced VCAM-1 and inflammatory cytokine induction by inhibiting the NF-κB and AKT signaling pathway in apolipoprotein E–deficient mice

Purpose

Inflammation is a hallmark of many diseases, such as atherosclerosis, autoimmune diseases, obesity, and cancer. Isoflavone-free soy protein diet (SPI^?) has been shown to reduce atherosclerotic lesions in a hyperlipidemic mouse model compared to casein (CAS)-fed mice, despite unchanged serum lipid levels. However, possible mechanisms contributing to the athero-protective effect of soy protein remain unknown. Therefore, we investigated whether and how SPI^? diet inhibits inflammatory responses associated with atherosclerosis.

Methods

Apolipoprotein E knockout (apoE?/?) mice (5-week) were fed CAS or SPI^? diet for 1 or 5 week to determine LPS- and hyperlipidemia-induced acute and chronic inflammatory responses, respectively. Expression of NF-κB-dependent inflammation mediators such as VCAM-1, TNF-α, and MCP-1 were determined in aorta and liver. NF-κB, MAP kinase, and AKT activation was determined to address mechanisms contributing to the anti-inflammatory properties of soy protein/peptides.

Results

Isoflavone-free soy protein diet significantly reduced LPS-induced VCAM-1 mRNA and protein expression in aorta compared to CAS-fed mice. Reduced VCAM-1 expression in SPI^?-fed mice also paralleled attenuated monocyte adhesion to vascular endothelium, a critical and primary processes during inflammation. Notably, VCAM-1 mRNA and protein expression in lesion-prone aortic arch was significantly reduced in apoE?/? mice fed SPI^? for 5 weeks compared with CAS-fed mice. Moreover, dietary SPI^? potently inhibited LPS-induced NF-κB activation and the subsequent upregulation of pro-inflammatory cytokines, including TNF-α, IL-6, IL-1β, and MCP-1. Interestingly, SPI^? inhibited NF-κB-dependent inflammatory responses by targeting I-κB phosphorylation and AKT activation with no effect on MAP kinase pathway. Of the five putative soy peptides, four of the soy peptides inhibited LPS-induced VCAM-1, IL-6, IL-8, and MCP-1 protein expression in human vascular endothelial cells in vitro.

Conclusions

Collectively, our findings suggest that anti-inflammatory properties of component(s) of soy protein/peptides may be a possible mechanism for the prevention of chronic inflammatory diseases such as atherosclerosis.     

Hepatic inflammation induced by high-fructose diet is associated with altered 11βHSD1 expression in the liver of Wistar rats

Purpose

High fructose consumption provokes metabolic perturbations that result in chronic low-grade inflammation and insulin resistance. Glucocorticoids, potent anti-inflammatory hormones, have important role in pathogenesis of diet-induced metabolic disturbances. The aim of this study was to examine the link between glucocorticoid metabolism and inflammation in the liver of fructose-fed rats.

Methods

Fructose-fed male Wistar rats consumed 60 % fructose solution for 9 weeks. Glucocorticoid prereceptor metabolism and signaling were analyzed by measuring the level of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) and hexose-6-phosphate dehydrogenase expression, as well as via determination of intracellular corticosterone concentration, glucocorticoid receptor subcellular distribution and expression of its target gene, phosphoenolpyruvate carboxykinase. Nuclear factor kappa B (NFκB), tumor necrosis factor alpha (TNFα) and the level of inhibitory phosphorylation of insulin receptor substrate-1 (IRS-1) on Ser³⁰⁷ were analyzed as markers of hepatic inflammation. The protein and/or mRNA levels of all examined molecules were assessed by Western blot and/or qPCR.

Results

Fructose-rich diet led to an enhancement of 11βHSD1 protein level in the liver, without affecting intracellular level of corticosterone and downstream glucocorticoid signaling. On the other hand, proinflammatory state was achieved through NFκB activation and increased TNFα expression, while elevated level of inhibitory phosphorylation of IRS-1 was observed as an early hallmark of insulin resistance.

Conclusion

High-fructose diet does not influence hepatic glucocorticoid signaling downstream of the receptor, permitting development of NFκB-driven inflammation. The alteration in 11βHSD1 expression is most likely the consequence of enhanced inflammation, finally leading to disruption of insulin signaling in the rat liver.     

Plantago maxima leaves extract inhibits adipogenic action of a high-fat diet in female Wistar rats

Purpose

The primary objective of this study is to investigate the content of biologically active compounds producing an antioxidant effect in Plantago maxima and their influence on main mechanisms of dietary obesity development.

Methods

Biologically active compounds in P. maxima were tested using paper chromatography. In in vivo experiment, high-fat-fed Wistar rats obtained P. maxima water extract for 3 months. Morphometric parameters, weight gain, serum adipokines, and cytokines, as well as oxidative stress biomarkers in rats’ tissues were evaluated. Gut microflora was also examined.

Results

Plantago maxima leaves used in the experiment contained significant amount of flavonoids, iridoids, phenol carboxylic acids, and tannins and ascorbic acid. Our in vivo experiment data demonstrate that P. maxima water extract prevents excessive adiposity in a diet-induced model. P. maxima consumption reduced serum leptin (twofold), macrophage chemoattractant protein-1 (sevenfold), tumor-necrosis factor-α (25 %), and interleukine-6 (26 %) levels. P. maxima water extract decreased adipose tissue oxidative stress biomarkers in rats fed a high-fat diet. In addition, increased bacterial growth in the diet-induced obesity model was reversed by the P. maxima extract treatment.

Conclusion

Plantago maxima water extract possessed antiadipogenic, antidiabetic, antiinflammatory, antioxidant activity, and normalized gut microflora in a rat model of diet-induced excessive adiposity due to a high content of biologically active compounds.     

Effect of maternal protein restriction during pregnancy and postweaning high-fat feeding on diet-induced thermogenesis in adult mouse offspring

Purpose

Prenatal undernutrition followed by postweaning feeding of a high-fat diet results in obesity in the adult offspring. In this study, we investigated whether diet-induced thermogenesis is altered as a result of such nutritional mismatch.

Methods

Female MF-1 mice were fed a normal protein (NP, 18 % casein) or a protein-restricted (PR, 9 % casein) diet throughout pregnancy and lactation. After weaning, male offspring of both groups were fed either a high-fat diet (HF; 45 % kcal fat) or standard chow (C, 7 % kcal fat) to generate the NP/C, NP/HF, PR/C and PR/HF adult offspring groups (n = 7–11 per group).

Results

PR/C and NP/C offspring have similar body weights at 30 weeks of age. Postweaning HF feeding resulted in significantly heavier NP/HF offspring (P < 0.01), but not in PR/HF offspring, compared with their chow-fed counterparts. However, the PR/HF offspring exhibited greater adiposity (P < 0.01) v the NP/HF group. The NP/HF offspring had increased energy expenditure and increased mRNA expression of uncoupling protein-1 and β-3 adrenergic receptor in the interscapular brown adipose tissue (iBAT) compared with the NP/C mice (both at P < 0.01). No such differences in energy expenditure and iBAT gene expression were observed between the PR/HF and PR/C offspring.

Conclusions

These data suggest that a mismatch between maternal diet during pregnancy and lactation, and the postweaning diet of the offspring, can attenuate diet-induced thermogenesis in the iBAT, resulting in the development of obesity in adulthood.     

Transcriptome analysis of anti-fatty liver action by Campari tomato using a zebrafish diet-induced obesity model

Background

Obesity and osteoporosis, two possibly related conditions, are rapidly expanding health concerns in modern society. Both of them are associated with sedentary life style and nutrition. To investigate the effects of diet-induced obesity and voluntary physical activity we used high resolution micro-computed tomography (μCT) together with peripheral quantitative computed tomography (pQCT) to examine the microstructure of the distal femoral metaphysis in mice.

Methods

Forty 7-week-old male C57BL/6J mice were assigned to 4 groups: control (C), control + running (CR), high-fat diet (HF), and high-fat diet + running (HFR). After a 21-week intervention, all the mice were sacrificed and the left femur dissected for pQCT and μCT measurements.

Results

The mice fed the high-fat diet showed a significant weight gain (over 70% for HF and 60% for HFR), with increased epididymal fat pad mass and impaired insulin sensitivity. These obese mice had significantly higher trabecular connectivity density, volume, number, thickness, area and mass, and smaller trabecular separation. At the whole bone level, they had larger bone circumference and cross-sectional area and higher density-weighted maximal, minimal, and polar moments of inertia. Voluntary wheel running decreased all the cortical bone parameters, but increased the trabecular mineral density, and decreased the pattern factor and structure model index towards a more plate-like structure.

Conclusions

The results suggest that in mice the femur adapts to obesity by improving bone strength both at the whole bone and micro-structural level. Adaptation to running exercise manifests itself in increased trabecular density and improved 3D structure, but in a limited overall bone growth     

Effects of high-fat diet and physical activity on pyruvate dehydrogenase kinase-4 in mouse skeletal muscle

Background

The expression of PDK4 is elevated by diabetes, fasting and other conditions associated with the switch from the utilization of glucose to fatty acids as an energy source. It is previously shown that peroxisome proliferator-activated receptor ?? coactivator 1?? (PGC-1??), a master regulator of energy metabolism, coactivates in cell lines pyruvate dehydrogenase kinase-4 (PDK4) gene expression via the estrogen-related receptor ?? (ERR??). We investigated the effects of long-term high-fat diet and physical activity on the expression of PDK4, PGC-1?? and ERR?? and the amount and function of mitochondria in skeletal muscle.

Methods

Insulin resistance was induced by a high-fat (HF) diet for 19?weeks in C57BL/6?J mice, which were either sedentary or with access to running wheels. The skeletal muscle expression levels of PDK4, PGC-1?? and ERR?? were measured and the quality and quantity of mitochondrial function was assessed.

Results

The HF mice were more insulin-resistant than the low-fat (LF) -fed mice. Upregulation of PDK4 and ERR?? mRNA and protein levels were seen after the HF diet, and when combined with running even more profound effects on the mRNA expression levels were observed. Chronic HF feeding and voluntary running did not have significant effects on PGC-1?? mRNA or protein levels. No remarkable difference was found in the amount or function of mitochondria.

Conclusions

Our results support the view that insulin resistance is not mediated by the decreased qualitative or quantitative properties of mitochondria. Instead, the role of PDK4 should be contemplated as a possible contributor to high-fat diet-induced insulin resistance.     

Changes in cardiac energy metabolic pathways in overweighed rats fed a high-fat diet

Background

Heart produces ATP through long-chain fatty acids beta oxidation.

Purpose

To analyze whether in ventricular myocardium, high-fat diet may modify the expression of proteins associated with energy metabolism before myocardial function was affected.

Methods

Wistar Kyoto rats were divided into two groups: (a) rats fed standard diet (control; n = 6) and (b) rats fed high-fat diet (HFD; n = 6). Proteins from left ventricles were analyzed by two-dimensional electrophoresis, mass spectrometry and Western blotting.

Results

Rats fed with HFD showed higher body weight, insulin, glucose, leptin and total cholesterol plasma levels as compared with those fed with standard diet. However, myocardial functional parameters were not different between them. The protein expression of 3-ketoacyl-CoA thiolase, acyl-CoA hydrolase mitochondrial precursor and enoyl-CoA hydratase, three long-chain fatty acid β-oxidation-related enzymes, and carnitine-O-palmitoyltransferase I was significantly higher in left ventricles from HFD rats. Protein expression of triosephosphate isomerase was higher in left ventricles from HFD rats than in those from control. Two α/β-enolase isotypes and glyceraldehyde-3-phosphate isomerase were significantly increased in HFD rats as compared with control. Pyruvate and lactate contents were similar in HFD and control groups. Expression of proteins associated with Krebs cycle and mitochondrial oxidative phosphorylation was higher in HFD rats.

Conclusions

Expression of proteins involved in left ventricle metabolic energy was enhanced before myocardial functionality was affected in rats fed with HFD. These findings may probably indicate higher cardiac energy requirement due to weight increase by HFD.