Dietary fat source regulates ob gene expression in white adipose tissue of rats under hyperphagic feeding

This work was designed to investigate the effect of different lipid sources on ob gene expression and serum leptin levels in rats with two different feeding protocols: (1) free access to food; or (2) energy-controlled feeding. Male Wistar rats were fed diets containing 40 % energy as fat (olive oil, sunflower oil or beef tallow), for 4 weeks. In Expt 1 rats had free access to food, and in Expt 2 rats were fed a controlled amount of food (16 g/d, equivalent to 300 kJ/d). Insulin and leptin were determined by ELISA and ob mRNA by Northern blot. When rats had free access to food, ob mRNA levels were higher in animals fed either olive oil or sunflower oil than in those fed beef tallow. In marked contrast with feeding ad libitum, no differences were found among dietary fat groups in rats fed energy-controlled diets. When both feeding protocols were compared, free access to food induced an increased expression of ob mRNA in perirenal and/or epididymal adipose tissues from rats fed either olive oil or sunflower oil, but not from rats fed beef tallow. Dietary lipid type did not induce modifications in serum leptin concentrations. A tendency to higher serum leptin levels was observed more in rats with free access to food than in rats fed energy-controlled feeding. No differences were found in insulin levels. Dietary fat type importantly affects ob mRNA expression in rat white adipose tissue under hyperphagic conditions. Further study is needed in order to elucidate the mechanism underlying this effect.     

脂肪特异性蛋白27（Fsp27）基因延缓四氯化碳所致实验大鼠肝纤维化

目的 探讨脂肪特异性蛋白27（Fsp27）基因对活体肝纤维化进程的调节作用.方法 分离原代肝星状细胞（HSCs）,采用PCR技术检测在原代HSCs及活化HSCs中的Fsp27基因表达；构建携带Fsp27目的基因的慢病毒；建立肝纤维化模型；慢病毒转染模型鼠肝脏,对实验大鼠行肝脏病理切片检查,采用ELISA法和放射免疫法分别检测肝脏及血浆纤维蛋白含量.结果 Fsp27基因在原代HSCs及活化HSCs中表达差异有统计学意义（P＜0.01）；成功构建了Fsp27基因的慢病毒载体；成功建立了肝纤维化活体模型；Fsp27基因慢病毒成功转染大鼠肝脏,Fsp27基因减轻了肝脏的纤维化程度.结论 Fsp27基因具有延缓活体肝纤维化进程的作用.     

Gender effects on adrenergic receptor expression and lipolysis in white adipose tissue of rats

OBJECTIVE: To investigate the effects of short-term (15 days) cafeteria-diet feeding on the expression of alpha- and beta-adrenergic receptors (AR) and its association with lipolytic stimulation in isolated retroperitoneal white adipocytes. RESEARCH METHODS AND PROCEDURES: Six female and 6 male Wistar rats (4 weeks old) were fed a cafeteria diet plus standard diet for 15 days. The remaining 12 age- and sex-matched rats received a standard diet only. White retroperitoneal adipose tissue was isolated and used for the determination of both alpha(2) and beta-AR expression and for in vitro studies of lipolytic activity. RESULTS: In female control rats, we found higher lipolytic capacities located at the postreceptor level and a lower alpha(2)/beta(3)-AR ratio than male rats. Cafeteria-diet feeding for 15 days decreased lipolytic activity in both male and female rats and altered the alpha(2A)- and beta(3)-AR protein levels with an increase of alpha(2A)-AR in males and a beta(3)-AR decrease in females. DISCUSSION: Our results indicate that a 15-day cafeteria-diet feeding induced an increase in the alpha(2)/beta(3)-AR balance and impaired adipose tissue lipolytic activity, which was higher in males and may contribute to the development of increased fat mass. The higher functionality of alpha(2)-AR, together with the minor role developed by beta(3)-AR and lower lipolytic capacities located at the postreceptor level in cafeteria-diet-fed male rats compared with female rats, may be responsible for the gender-dependent differences observed in this study.     

Impact of dietary protein on lipid metabolism-related gene expression in porcine adipose tissue

Background

Gamma-oryzanol (OR), a phytosteryl ferulate mixture extracted from rice bran oil, has a wide spectrum of biological activities in particular, it has antioxidant properties.

Methods

The regulatory effect of gamma-oryzanol rich fraction (ORF) extracted and fractionated from rice bran using supercritical fluid extraction (SFE) in comparison with commercially available OR on 14 antioxidant and oxidative stress related genes was determined in rat liver. Rats were subjected to a swimming exercise program for 10 weeks to induce stress and were further treated with either ORF at 125, 250 and 500 mg/kg or OR at 100 mg/kg in emulsion forms for the last 5 weeks of the swimming program being carried out. The GenomeLab Genetic Analysis System (GeXPS) was used to study the multiplex gene expression of the selected genes.

Results

Upon comparison of RNA expression levels between the stressed and untreated group (PC) and the unstressed and untreated group (NC), seven genes were found to be down-regulated, while seven genes were up-regulated in PC group compared to NC group. Further treatment of stressed rats with ORF at different doses and OR resulted in up-regulation of 10 genes and down regulation of four genes compared to the PC group.

Conclusions

Gamma-oryzanol rich fraction showed potential antioxidant activity greater than OR in the regulation of antioxidants and oxidative stress gene markers.     

Regulation of angiopoietin-like protein 4/fasting-induced adipose factor (Angptl4/FIAF) expression in mouse white adipose tissue and 3T3-L1 adipocytes

Angiopoietin-like protein 4 (Angptl4)/FIAF (fasting-induced adipose factor) was first identified as a target for PPAR and to be strongly induced in white adipose tissue (WAT) by fasting. Here we have examined the regulation of the expression and release of this adipokine in mouse WAT and in 3T3-L1 adipocytes. Angptl4/FIAF expression was measured by RT-PCR and real-time PCR; plasma Angptl4/FIAF and release of the protein in cell culture was determined by western blotting. The Angptl4/FIAF gene was expressed in each of the major WAT depots of mice, the mRNA level in WAT being similar to the liver and much higher (>50-fold) than skeletal muscle. Fasting mice (18 h) resulted in a substantial increase in Angptl4/FIAF mRNA in liver and muscle (9.5- and 21-fold, respectively); however, there was no effect of fasting on Angptl4/FIAF mRNA in WAT and the plasma level of Angptl4/FIAF was unchanged. The Angptl4/FIAF gene was expressed in 3T3-L1 adipocytes before and after differentiation, the level increasing post-differentiation; Angptl4/FIAF was released into the culture medium. Insulin, leptin, dexamethasone, noradrenaline, TNFalpha and several IL (IL-1beta, IL-6, IL-10, IL-18) had little effect on Angptl4/FIAF mRNA levels in 3T3-L1 adipocytes. However, a major stimulation of Angptl4/FIAF expression was observed with rosiglitazone and the inflammatory prostaglandins PGD2 and PGJ2. Angptl4/FIAF does not act as an adipose tissue signal of nutritional status, but is markedly induced by fasting in liver and skeletal muscle.     

The sympathetic nervous system in white adipose tissue regulation.

Sympathetic stimulation has long been recognized to mobilise fatty acids from white adipose tissue. However, it is now apparent that adipose tissue is not only concerned with energy storage as fat, but is a major endocrine and secretory organ. This change has resulted from the identification of leptin as a hormone of energy balance secreted by white adipose tissue. The sympathetic system is a key regulator of leptin production in white fat. Sympathomimetic amines, cold exposure or fasting (which lead to sympathetic stimulation of white fat), decrease ob gene expression in the tissue and leptin production. On the other hand, sympathetic blockade often increases circulating leptin and ob gene expression, and it is postulated that the sympathetic system has a tonic inhibitory action on leptin synthesis. In rodents this action is through stimulation of, beta3-adrenoceptors. The adrenal medulla (as opposed to the direct sympathetic innervation) has been thought to play only a minor role in the catecholaminergic regulation of white adipose tissue. However, in rodents responses of the leptin system to adrenergic blockade vary with the method used. Changes in leptin and ob gene expression are considerably less using methods of blockade that only effect the terminal adrenergic innervation, rather than medullary secretions as well. Stimulation of the leptin system increases sympathetic activity and hence metabolic activity in many tissues. As well as leptin, other (but not all) secretions from white adipose tissue are subject to sympathetic regulation. In obesity the sympathetic sensitivity of adipose tissue is reduced and this factor may underlie the dysregulation of leptin production and other adipose tissue secretions.     

Physiological role of adipose tissue: white adipose tissue as an endocrine and secretory organ.

The traditional role attributed to white adipose tissue is energy storage, fatty acids being released when fuel is required. The metabolic role of white fat is, however, complex. For example, the tissue is needed for normal glucose homeostasis and a role in inflammatory processes has been proposed. A radical change in perspective followed the discovery of leptin; this critical hormone in energy balance is produced principally by white fat, giving the tissue an endocrine function. Leptin is one of a number of proteins secreted from white adipocytes, which include angiotensinogen, adipsin, acylation-stimulating protein, adiponectin, retinol-binding protein, tumour neorosis factor a, interleukin 6, plasminogen activator inhibitor-1 and tissue factor. Some of these proteins are inflammatory cytokines, some play a role in lipid metabolism, while others are involved in vascular haemostasis or the complement system. The effects of specific proteins maybe autocrine or paracrine, or the site of action maybe distant from adipose tissue. The most recently described adipocyte secretory proteins are fasting-induced adipose factor, a fibrinogen-angiopoietin-related protein, metallothionein and resistin. Resistin is an adipose tissue-specific factor which is reported to induce insulin resistance, linking diabetes to obesity. Metallothionein is a metal-binding and stress-response protein which may have an antioxidant role. The key challenges in establishing the secretory functions of white fat are to identify the complement of secreted proteins, to establish the role of each secreted protein, and to assess the pathophysiological consequences of changes in adipocyte protein production with alterations in adiposity (obesity, fasting, cachexia). There is already considerable evidence of links between increased production of some adipocyte factors and the metabolic and cardiovascular complications of obesity. In essence, white adipose tissue is a major secretory and endocrine organ involved in a range of functions beyond simple fat storage.     

Hydrogenated fat diet intake during pregnancy and lactation modifies the PAI-1 gene expression in white adipose tissue of offspring in adult life

We examine whether feeding pregnant and lactating rats hydrogenated fats rich in trans fatty acids modifies the plasma lipid profiles and the expression of adipokines involved with insulin resistance and cardiovascular disease in their 90-day-old offspring. Pregnant and lactating Wistar rats were fed with either a control diet (C group) or one enriched with hydrogenated vegetable fat (T group). Upon weaning, the male pups were sorted into four groups: CC, mothers were receiving C and pups were kept on C; CT, mothers were receiving C and pups were fed with T; TT, mothers were receiving T and pups were kept on T; TC, mothers were receiving T and pups were fed with C. Pups' food intake and body weight were quantified weekly and the pups were killed at day 90 of life by decapitation. Blood and carcass as well as retroperitoneal, epididymal, and subcutaneous white adipose tissues were collected. Food intake and body weight were lower in TC and TT, and metabolic efficiency was reduced in TT. Offspring of TT and TC rats had increased white adipose tissue PAI-1 gene expression. Insulin receptor was higher in TT than other groups. Ingestion of hydrogenated vegetable fat by the mother during gestation and lactation could promote deleterious consequences, even after the withdrawal of the causal factor.     

Changes in white adipose tissue metabolism induced by resveratrol in rats

Background

A remarkable range of biological functions have been ascribed to resveratrol. Recently, this polyphenol has been shown to have body fat lowering effects. The aim of the present study was to assess some of the potential underlying mechanisms of action which take place in adipose tissue.

Methods

Sixteen male Sprague-Dawley rats were randomly divided into two groups: control and treated with 30 mg resveratrol/kg body weight/d. All rats were fed an obesogenic diet and after six weeks of treatment white adipose tissues were dissected. Lipoprotein lipase activity was assessed by fluorimetry, acetyl-CoA carboxylase by radiometry, and malic enzyme, glucose-6P-dehydrogenase and fatty acid synthase by spectrophotometry. Gene expression levels of acetyl-CoA carboxylase, fatty acid synthase, lipoprotein lipase, hormone-sensitive lipase, adipose triglyceride lipase, PPAR-gamma, SREBP-1c and perilipin were assessed by Real time RT-PCR. The amount of resveratrol metabolites in adipose tissue was measured by chromatography.

Results

There was no difference in the final body weight of the rats; however, adipose tissues were significantly decreased in the resveratrol-treated group. Resveratrol reduced the activity of lipogenic enzymes, as well as that of heparin-releasable lipoprotein lipase. Moreover, a significant reduction was induced by this polyphenol in hormone-sensitive lipase mRNA levels. No significant changes were observed in other genes. Total amount of resveratrol metabolites in adipose tissue was 2.66 ± 0.55 nmol/g tissue.

Conclusions

It can be proposed that the body fat-lowering effect of resveratrol is mediated, at least in part, by a reduction in fatty acid uptake from circulating triacylglycerols and also in de novo lipogenesis.     

Taurine supplementation associated with exercise increases mitochondrial activity and fatty acid oxidation gene expression in the subcutaneous white adipose tissue of obese women

Taurine supplementation only increased the expression of fat oxidation genes (ACO2 and ACOX1). Exercise increased energy metabolism and the expression of fat oxidation genes in the subcutaneous white adipose tissue. The association between taurine supplementation and exercise promoted additional effects to exercise by increasing energy expenditure, and upregulating mitochondrial respiratory capacity and the expression of genes related to mitochondrial metabolism and fat oxidation in the subcutaneous adipose tissue (scWAT) of obese women.

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Partial genome scale analysis of gene expression in human adipose tissue using DNA array

OBJECTIVE: Large scale analysis of gene expression in adipose tissue provides a basis for the identification of novel candidate genes involved in the pathophysiology of obesity. Our goal was to explore gene expression in human adipose tissue at a partial genome scale using DNA array. RESEARCH METHODS AND PROCEDURES: Labeled cDNA, derived from human adipose tissue poly(A+) RNA, was hybridized to a DNA array containing over 18,000 human expressed sequence-tagged (EST) clones. The results were analyzed by database searches. RESULTS: Homology searches of the 300 EST clones with highest hybridization signals revealed that 145 contained DNA sequences identical to known genes and 79 could be linked to UniGene clusters. Of the 145 identified genes, 136 were nonredundant and subsequently characterized with respect to function and chromosomal localization by searching MEDLINE, UniGene, GeneMap, OMIM, SWISS-PROT, the Genome Database, and the Location Data Base. The identified genes were grouped according to their putative functions; cell/organism defense (9.6%), cell division (5.1%), cell signaling/communication (19.8%), cell structure/motility (12.5%), gene/ protein expression (16.9%), metabolism (16.2%), and unclassified (19.8%). Less than 50% of these genes have previously been reported to be expressed in adipose tissue. The chromosomal localization of 268 genes strongly expressed in adipose tissue showed that their relative abundance was significantly increased on chromosomes 11, 19, and 22 compared to the expected distribution of the same number of random genes. DISCUSSION: Our study resulted in the identification of numerous genes previously not reported to be expressed in adipose tissue. These results suggest that DNA array is a powerful tool in the search for novel regulatory pathways within adipose tissue on a scale that is not possible using conventional methods.     

Peripartal feeding strategy with different n-6:n-3 ratios in sows: effect on gene expression in backfat white adipose tissue postpartum

The aim of this study was to describe the effects of two diets differing in n-6:n-3 ratio and prepartal feeding regime on gene expression of PPARgamma1a/1b, PPARgamma1c/1d, PPARgamma2, PPARgamma coactivator 1A (PPARGC1A), GLUT4, TNFalpha, adiponectin, leptin, leptin receptor (LEPR), fatty acid binding protein 4 (FABP4), lipoprotein lipase (LPL) in sows' white adipose tissue on the first day of lactation. The relationship between mRNA expression of these genes and circulating insulin, leptin and thyroid hormones was also considered. Diets contained a low (supplemented with fish oil; f group) or a high (supplemented with sunflower oil; s group) n-6:n-3 ratio and were provided from 8 (f8, s8) or 3d (f3, s3) before parturition (onset day 8 or 3). A low n-6:n-3 ratio reduced the 1d postpartum expression of PPARgamma2 and PPARGC1A but only when applied from 3 d before parturition. Circulating leptin was negatively correlated with mRNA expression of adiponectin, LEPR and LPL, whereas thyroxine was positively correlated with levels of PPARGC1A. In conclusion, the effect of dietary treatments, e.g. altering the n-6:n-3 ratio, around parturition on the expression of crucial genes in nutrient metabolism can be modulated by the duration of application before parturition.     

Olive oil feeding up-regulates uncoupling protein genes in rat brown adipose tissue and skeletal muscle

BACKGROUND: Some nutrients, such as carotenoids, retinoic acid, and certain types of fatty acids, increase thermogenic capacity. OBJECTIVE: The influence of 4 dietary lipid sources (olive oil, sunflower oil, palm oil, and beef tallow) on the content of uncoupling proteins 1, 2, and 3 (UCP1, UCP2, and UCP3) and their messenger RNA (mRNA) expression in several tissues of rats was compared. DESIGN: Wistar rats were randomly divided into 4 groups and fed ad libitum diets containing 40% of energy as fat. UCP1, UCP2, and UCP3 mRNA and protein were assessed by Northern blot and Western blot, respectively. Oxygen consumption in tissues was measured by polarography. Total-body oxygen consumption was assessed in an open-circuit chamber system. Circulating fuels (fatty acids and glucose) and hormones (triiodothyronine, thyroxine, corticosterone, and insulin) were measured. RESULTS: Olive oil feeding induced the highest UCP1, UCP2, and UCP3 mRNA expression in interscapular brown adipose tissue. An analogous effect was observed in gastrocnemius muscle UCP3 mRNA. No significant differences were observed in perirenal white adipose tissue UCP2 mRNA. Changes in mRNAs were not accompanied by close changes in the protein content of UCPs and were not associated with changes in adipose tissue oxygen consumption. Nevertheless, total-body oxygen consumption was higher in rats fed olive oil than in those fed the other 3 diets. No significant differences were found in body and tissue weights or in serum indexes. CONCLUSION: Olive oil induced an up-regulating effect on UCP mRNA that was probably not mediated by systemic metabolic changes, but rather related to a local effect on interscapular brown adipose tissue and skeletal muscle.