Ob Gene Expression Research Articles

Depletion of the gut microbiota differentially affects the impact of whey protein on high-fat diet-induced obesity and intestinal permeability.

Whey protein isolate (WPI) is considered a dietary solution to obesity. However, the exact mechanism of WPI action is still poorly understood but is probably connected to its beneficial effect on energy balance, adiposity, and metabolism. More recently its ability to modulate the gut microbiota has received increasing attention. Here, we used a microbiota depletion, by antibiotic cocktail (ABX) administration, to investigate if the gut microbiota mediates the physiological and metabolic changes observed during high‐fat diet (HFD)‐WPI consumption. C57BL/6J mice received a HFD containing WPI (HFD‐WPI) or the control non‐whey milk protein casein (HFD‐CAS) for 5 or 10 weeks. HFD‐fed mice supplemented with WPI showed reduced body weight gain, adiposity, Ob gene expression level in the epidydimal adipose tissue (eWAT) and plasma leptin relative to HFD‐CAS‐fed mice, after 5‐ or 10‐weeks intervention both with or without ABX treatment. Following 10‐weeks intervention, ABX and WPI had an additive effect in lowering adiposity and leptin availability. HFD‐WPI‐fed mice showed a decrease in the expression of genes encoding pro‐inflammatory markers (MCP‐1, TNFα and CD68) within the ileum and eWAT, compared to HFD‐CAS‐fed mice, without showing alterations following microbiota depletion. Additionally, WPI supplementation decreased HFD‐induced intestinal permeability disruption in the distal ileum; an effect that was reversed by chronic ABX treatment. In summary, WPI reverses the effects of HFD on metabolic and physiological functions through mainly microbiota‐independent mechanisms. Moreover, we demonstrate a protective effect of WPI on HFD‐induced inflammation and ileal permeability disruption, with the latter being reversed by gut microbiota depletion.

Through fat and thin - a journey with the adipose tissues.

The paper is based on the lecture that I gave on receiving the Nutrition Society's inaugural Gowland Hopkins Award for contributions to Cellular and Molecular Nutrition. It reviews studies on the adipose tissues, brown and white, conducted by the groups that I have led since entering nutrition research in 1975. The initial focus was on exploring metabolic factors that underpin the development of obesity using animal models. This resulted in an interest in non-shivering thermogenesis with brown adipose tissue being identified as the key effector of facultative heat production. Brown fat is less thermogenically active in various obese rodents, and major changes in activity are exhibited under physiological conditions such as lactation and fasting consistent with a general role for the tissue in nutritional energetics. My interests moved to white adipose tissue following the cloning of the Ob gene. Our initial contributions in this area included demonstrating nutritional regulation of Ob gene expression and circulating leptin levels, as well as a regulatory role for the sympathetic nervous system operating through β3-adrenoceptors. My interests subsequently evolved to a wider concern with the endocrine/signalling role of adipose tissue. Inflammation is a characteristic of white fat in obesity with the release of inflammation-related adipokines, and we proposed that hypoxia underlies this inflammatory state. O2-deprivation was shown to have substantial effects on gene expression and cellular function in white adipocytes. The hypoxia studies led to the proposition that O2 should be considered as a critical macronutrient.

Effect of dexamethasone on circulating leptin levels during pregnancy

Background: Leptin, the protein product of the Ob gene, is thought to have a role in signaling safety through hypothalamic pathways. Glucocortisteroids are potent stimulation of both Ob gene expression and circulating Leptin in animals and powerful appetite stimulants in humans. Usage in pregnant women has limits, more for fetal lung maturation.

Effects of dopamine on leptin release and leptin gene (OB) expression in adipocytes from obese and hypertensive patients

BackgroundA reduction of dopaminergic (DAergic) activity with increased prolactin levels has been found in obese and hypertensive patients, suggesting its involvement as a pathophysiological mechanism promoting hypertension. Similarly, leptin action increasing sympathetic activity has been proposed to be involved in mechanisms of hypertension. The aim of this study was to analyze the effects of DA, norepinephrine (NE), and prolactin on leptin release and leptin gene (OB) expression in adipocytes from obese and hypertensive patients.MethodsLeptin release and OB gene expression were analyzed in cultured adipocytes from 16 obese and hypertensive patients treated with DA (0.001, 0.01, 0.1, and 1.0 μmol/L), NE (1.0 μmol/L), insulin (0.1 μmol/L), and prolactin (1.0 μmol/L), and from five nonobese and normotensive controls treated with DA (1 μmol/L), NE (1 μmol/L), insulin (0.1 μmol/L), and prolactin (1.0 μmol/L).ResultsA dose-related reduction of leptin release and OB gene messenger ribonucleic acid expression under different doses of DA was observed in adipocytes from obese hypertensive patients. Whereas prolactin treatment elicited a significant increase of both leptin release and OB gene expression, NE reduced these parameters. Although similar effects of DA and NE were observed in adipocytes from controls, baseline values in controls were reduced to 20% of the value in adipocytes from obese hypertensive patients.ConclusionThese results suggest that DAergic deficiency contributes to metabolic disorders linked to hyperleptinemia in obese and hypertensive patients.

Increased Leptin Response and Inhibition of Apoptosis in Thymocytes of Young Rats Offspring from Protein Deprived Dams during Lactation

We investigated the consequences of mild maternal malnutrition in rat dams, in terms of thymocyte responses and the putative role of leptin. The young progeny of dams submitted to protein deprivation (PD) during lactation showed at 30 days of age lower body and thymus weights, significant alterations in CD4/CD8-defined T cell subsets without modifications in total thymocyte number as well as in proliferative response. Despite, the rats from PD group did not present alterations in leptin circulating levels, the expression of leptin receptor ObRb was enhanced in their thymocytes. This change was accompanied by an increase in leptin signaling response of thymocytes from PD rats, with an increase in JAK2 and STAT3 phosphorylation after leptin stimulation. Thymocytes from PD rats also presented a decreased rate of spontaneous apoptosis when compared to controls. Accordingly, higher expression of anti-apoptotic protein Bcl-2, and lower of pro-apoptotic protein Bax, with no change of pro-apoptotic Bad, and higher pro-caspase 3 content were detected in PD thymocytes. Moreover, thymocytes from PD group exhibited a constitutive higher nuclear content of p65 NF-kB associated to a lower IkB content in the cytoplasm. Finally, although there was no change in ob gene expression in PD thymocytes, a higher mRNA expression for the Ob gene was observed in the thymic microenvironment from PD animals. Taken together, the results show that mild maternal protein deprivation during lactation affects thymic homeostasis, enhancing leptin activity, which in turn protects thymocytes from apoptosis in the young progeny, with possible consequences upon the immune response of these animals in adult life.

Leptin and IL-6 as risk factors for metabolic cardiovascular syndrome in obese prepubertal children

Background: Potential risk factors for cardiovascular diseases (CVD) tend to cluster in childhood and are strongly associated with obesity. The prevalence of obesity in children has increased dramatically over the last 20 years, leading to higher health risk associated with complications such as type 2 diabetes, high blood pressure and cardiovascular disease. Leptin is a hormone produced by the adipocytes to regulate food intake, its circulating levels directly correlate with the amount of body fat and body mass index (BMI). Previous researchers had provided evidence suggesting that ob gene expression is up regulated by some inflammatory cytokines such as IL-6. Aim: The aim of this study is to explore the relationship between serum leptin, and interluikin-6 in order to detect the presence of any impairment of these parameters as risk factors for metabolic cardiovascular syndrome in obese prepubertal children, in an attempt to overcome the increased health risk associated with obesity in children. Subjects and methods: Eighty prepubertal children age range between (5-11) years old were enrolled in this study. Divided according to their weight into two groups: Obese group 50 subjects Lean group 30 aged matched subjects. Circulating serum leptin and IL-6 were measured by ELISA technique. Results: both parameters studied showed a significantly higher values in obese children than in leans. No significant correlations were found to exist between these parameters in both groups. However correlations were much more prominent in obese group compared to lean groups. Conclusion: Obese children exhibited a high prevalence of metabolic syndrome. The children with greater insulin resistance exhibited more risk factors. In the light of these findings intervention measures are necessary in order to prevent excessive weight gain during childhood.

Superinduction of leptin mRNA in mouse hypothalamic neurons

In marked contrast to several other species, including rats and humans, leptin gene expression is undetectable in mouse brain. This unexpected finding may reflect unique energy regulation pathways in the mouse. We investigated possible mechanisms by which leptin (ob) gene expression is suppressed in mouse brain: (a) the possibility that ob mRNA levels might be detectable in vitro through the superinduction of gene expression following protein synthesis inhibition and (b) whether chromatin modification of the ob gene was responsible for this repression. Experiments were conducted on mouse hypothalamic neurons in vitro. Cells were treated with (a) protein synthesis inhibitors: cycloheximide (CHX; 25 µg/ml); puromycin (50 µg/ml); anisomycin (5 µM); (b) trichostatin A (histone deacetylase inhibitor; 500 nM); and (c) 5-aza-2'-deoxycytidine (DNA methylation inhibitor; 5 µM). Following the incubations, cells were harvested for the preparation of RNA and ob mRNA was detected using real-time reverse transcription PCR. Protein synthesis inhibitors induced a rapid increase in ob mRNA levels in mouse hypothalamic neurons in vitro. For example CHX stimulation of ob mRNA was detectable at 60 min after treatment and reached a maximum between 4 and 6 h. A dose-response analysis, with concentrations of CHX of 1, 2, 10, 25, and 50 μg/ml, indicated that CHX was already effective at 1.0 μg/ml, with a maximal effect by 25 μg/ml. In contrast, incubation with trichostatin A and 5-aza-2'-deoxycytidine had no effect and ob mRNA remained undetectable. These data show that leptin gene expression is superinduced in ob-negative mouse hypothalamic neurons following inhibition of protein synthesis. They confirm that the previously reported absence of leptin mRNA in mouse brain is probably because of an active repressive mechanism, although this may not involve chromatin modification.

Monosodium glutamate versus diet induced obesity in pregnant rats and their offspring

We aim at determining the role of monosodium glutamate (MSG) compared with high caloric chow(HCC) in development of obesity in pregnant rats and their offspring. Ninety pregnant rats were divided into 3 groups, control, MSG and HCC fed. We determined energy intake, body weight (BW), abdominal fat, fat to body weight ratio, serum glucose, insulin, leptin, lipid profile, ob and leptin receptor-b gene expressions in pregnant rats and ob and leptin receptor-b gene expressions, serum insulin,glucose, leptin, triacylglycerides (TAG), total lipids (TL) and BW in offspring. Although daily energy intake and BW of MSG treated rats were lower than those of HCC fed rats, their abdominal fat and fat body weight ratio were higher. MSG or HCC increased Ob gene expression, leptin, insulin,LDL, cholesterol, total lipids (TL), glucose and decreased leptin receptor-b gene expression. In offspring of MSG treated rats, BW, serum glucose, insulin, leptin, TAG, TL and Ob gene expression increased and leptin receptor-b gene expression decreased whereas in offspring of HCC fed rats, serum insulin, leptin, Ob and leptin receptor-b gene expression increased but serum glucose, TAG, TL or BW did not change. We conclude that in pregnant rats, MSG, in spite of mild hypophagia, caused severe increase in fat body weight ratio, via leptin resistance, whereas, HCC increased BW and fat body weight ratio, due to hyperphagia with consequent leptin resistance. Moreover, maternal obesity in pregnancy, caused by MSG, has greater impact on offspring metabolism and BW than that induced by HCC.

Effect of Niacin on Hyperleptinemia and <i>Ob</i> Gene mRNA Over-Expression in Adipose Tissue of Dexamethasone Treated Rats

Problem statement: Glucocorticoid-induced ob gene over-expression and resulted hyperleptinemia may lead to adverse consequences especially on cardiovascular system; therefore, the present study was conducted to evaluate the effects of niacin on hyperleptinemia and ob gene over-expression due to dexamethasone administration in rats. Approach: Twenty four adult male rats divided randomly into four equal groups: 1- normal saline (control), 2- dexamathasone 0.125 mg kg-1 day-1, I.M. 3- dexamathasone 0.125 mg kg-1 day-1, I.M. + niacin 200 mg kg-1 day-1, by oral gavages and 4-niacin 200 mg kg-1 day-1, by oral gavages. After two weeks, blood samples were collected from all animals and leptin level assayed in harvested sera by ELISA method. Moreover, inguinal adipose tissue was excised to be examined for ob gene expression using quantitative real-time PCR. Results: Dexamethasone treatment (group 2) increased serum leptin along with its mRNA expression more than 3 folds as compared to control (p<0.001 and p = 0.001 respectively). Although leptin level in rats treated with dexamethasone+niacin was 17.8% lower than group 2; however this decrease was not significant (p>0.05). Concomitant administration of niacin with dexamethasone significantly decreased leptin gene mRNA expression compared to dexamethasone treated rats (p<0.001) and even reversed it to the control level (p>0.05). Niacin alone (group 4) had no effect on serum leptin concentration as well as leptin gene expression in comparison with control group (p>0.05). Conclusion: Niacin slightly ameliorates hyperleptinemia and reverses ob gene mRNA over-expression in adipose tissue of dexamethasone treated rats.

MONOSODIUM GLUTAMATE VERSUS DIET INDUCED OBESITY IN PREGNANT RATS AND THEIR OFFSPRING

Background: We aim at determining the role of monosodium glutamate (MSG) compared with high caloric chow (HCC) in development of obesity in pregnant rats and their offspring. Methods: Ninety pregnant rats were divided into 3 groups, control, MSG and HCC fed. We determined energy intake, body weight (BW), abdominal fat, fat to body weight ratio, serum glucose, insulin, leptin, lipid profile, ob and leptin receptor-b gene expressions in pregnant rats and ob and leptin receptor-b gene expressions, serum insulin, glucose, leptin, triacylglycerides (TAG), total lipids (TL) and BW in offspring. Results: Although daily energy intake and BW of MSG treated rats were lower than those of HCC fed rats, their abdominal fat and fat body weight ratio were higher. MSG or HCC increased Ob gene expression, leptin, insulin, LDL, cholesterol, total lipids (TL), glucose and decreased leptin receptor-b gene expression. In offspring of MSG treated rats, BW, serum glucose, insulin, leptin, TAG, TL and Ob gene expression increased and leptin receptor-b gene expression decreased whereas in offspring of HCC fed rats, serum insulin, leptin, Ob and leptin receptor-b gene expression increased but serum glucose, TAG, TL or BW did not change. Conclusion: We conclude that in pregnant rats, MSG, in spite of mild hypophagia, caused severe increase in fat body weight ratio, via leptin resistance, whereas, HCC increased BW and fat body weight ratio, due to hyperphagia with consequent leptin resistance. Moreover, maternal obesity in pregnancy, caused by MSG, has greater impact on offspring metabolism and BW than that induced by HCC.

Fructose Induced Leptin Dysfunction and Improvement by Quercetin and Rutin in Rats

To investigate the dysfunction of leptin underlying insulin resistance syndrome in fructose-fed rats and improvement by lowing uric acid with natural products quercetin and rutin. Rats were fed with fructose solution for 8 weeks. At week 4, animals received quercetin and rutin, as well as allopurinol. Serum uric acid and insulin levels were measured before and after drug treatment. Leptin levels in serum and hypothalamus, leptin secretion from adipose tissue were used to evaluate the responses of leptin to hyperuricemia and hyperinsulinemia in rats with insulin resistance syndrome. Triglyceride (TG), high dense lipid (HDL) and low dense lipid (LDL) in serum were examined to evaluate dyslipidemia in fructose-fed rats. Fructose consumption significantly increased serum uric acid, insulin and leptin levels in rats, and induced a significant increase of leptin secretion by upregulating ob gene expression in adipose tissue. Quercetin and rutin, as well as allopurinol reduced hyperleptinemia and inhibited leptin secretion from adipose tissue. Moreover, fructose-fed rats exhibited leptin level increase in hypothalamus accompanying dyslipidemia. Quercetin, rutin and allopurinol attenuated fructose-induced dyslipidemia in rats, but failed to improve leptin insufficiency in hypothalamus. These results indicated that fructose consumption might cause hyperleptinemia and leptin insufficiency in the brain, which might be indirectly mediated by hyperinsulinemia and hypertriglyceridemia in rats. Hopouricemic agents quercetin, rutin and allopurinol improved hyperinsulinemia and dyslipidemia, and subsequently regulated leptin dysfunction in fructose-fed rats. This study provided direct evidence that hyperuricemia was associated with hyperleptinemia during fructose consumption, and another pharmacological explanation for lowing uric acid agents to prevent hyperuricemia and leptin dysfunctions in fructose-induced insulin resistance syndrome in rats.

Effect of Saturated and Unsaturated Fatty Acid on Ob Gene and Fatty Acid Synthase Gene Expression in 3T3-L1 Adipocyte

Effect of Saturated and Unsaturated Fatty Acid on Ob Gene and Fatty Acid Synthase Gene Expression in 3T3-L1 Adipocyte

High Circulating Leptin Receptors with Normal Leptin Sensitivity in Liver-specific Insulin Receptor Knock-out (LIRKO) Mice

Liver-specific insulin receptor knock-out (LIRKO) mice display hyperinsulinemia, abnormal glucose metabolism, and progressive liver dysfunction. In addition, circulating leptin levels appear to be increased more than 10-fold. However, food intake, body weight, and adipose mass are not significantly altered in LIRKO mice compared with wild-type littermates. Using a ligand immunofunctional assay, we found that the apparent increase in circulating leptin in LIRKO mice is because of an 80-fold increased serum level of soluble leptin receptor. Gene expression analysis by microarray and real time PCR reveals the liver as the source of soluble leptin receptor in LIRKO mice, with an increase in expression of the short (Ob-Ra), long (Ob-Rb), and soluble (Ob-Re) forms of the leptin receptor. Direct control of leptin receptor expression by insulin could also be demonstrated in isolated hepatocytes from normal mice. Despite the markedly increased levels of leptin receptor in their circulation, LIRKO mice exhibit normal or even enhanced leptin sensitivity, as assessed by their physiological and molecular responses to exogenous leptin administration and their lower base-line hypothalamic levels of SOCS3 mRNA. Thus, insulin signaling in the liver plays an important role in control of leptin receptor expression and shedding. In the LIRKO mouse, this is lost, leading to markedly increased leptin receptors into the circulation. These high levels of circulating leptin receptor bind leptin and likely alter its clearance, but do not inhibit leptin action and may actually potentiate leptin action. In this manner, insulin signaling in liver plays an important role in leptin homeostasis and fine modulation of leptin action.

Anti‐obesity effects of bamboo leaf extracts studied by microarray analysis

The purpose of this study was to understand the molecular basis of the anti-obesity effects of bamboo leaf (Sasa borealis) extracts reported in our previous data. C56Bl/6J mice, fed high fat diets with water or ethanol extracts from the bamboo leaves showed significant loss of their weight and body fat mass compared to control mice. In this study, we conducted oligonucleotide microarray (MOC 38.5K) analysis in adipose tissue taken from the previous study and then classified genes into functional Gene Ontology categories. In particular, we focused here on the genes related to obesity and lipid metabolism and confirmed the results by measuring the serum levels of a selected number of proteins that were differentially expressed. 127 genes were up regulated and 451 genes were down regulated by taking BLW and those genes could be categorized in 49 pathways. By taking BLW, 172 genes were up regulated and 222 genes were down regulated and then those genes could be categorized in 31 pathways. Among the genes changed, one of ob gene expression was confirmed by decrease of serum leptin levels. These results indicate that the bamboo leaf extracts may change several gene expressions including the genes of obesity and lipid metabolism.

Leptin cDNA cloning and its mRNA expression in plateau pikas ( Ochotona curzoniae) from different altitudes on Qinghai-Tibet Plateau

Leptin, an adipocyte-derived hormone, plays an important role in body energy homeostasis. Plateau pika ( Ochotona curzoniae), an endemic and keystone species living only at 3000–5000 m above sea level on Qinghai-Tibet Plateau, is a typically high hypoxia and low temperature tolerant mammal with high resting metabolic rate (RMR), non-shivering thermogenesis (NST), and high ratio of oxygen utilization to cope with harsh plateau environment. To explore the molecular mechanism of ecological acclimation in plateau pika, we first cloned pika leptin cDNA and compared its mRNA expression in different altitudes (3200 and 3900 m) using real-time RT-PCR (Taqman probe) technology. The full-length pika leptin cDNA was 3015 with 504 bp open-reading frame encoding the precursor peptide of 167 amino acids including 21 residues of signal peptide. Pika leptin was 70–72% homologous to that of other species and was of similarly structural characteristics with other species. The pika-specific genetic diversity in leptin sequence occurred at twenty sites. With the increase in altitude, there were larger fat store and high level of ob gene expression in plateau pika. Our results indicated that leptin is sensitive to cold and hypoxia plateau environment and may play one of important roles in pika’s ecological adaptation to harsh plateau environment.

In vivo transcriptional profile analysis reveals RNA splicing and chromatin remodeling as prominent processes for adult neurogenesis

Neural stem cells and neurogenesis persist in the adult mammalian brain subventricular zone (SVZ). Cells born in the rodent SVZ migrate to the olfactory bulb (Ob) where they differentiate into interneurons. To determine the gene expression and functional profile of SVZ neurogenesis, we performed three complementary sets of transcriptional analysis experiments using Affymetrix GeneChips: (1) comparison of adult mouse SVZ and Ob gene expression profiles with those of the striatum, cerebral cortex, and hippocampus; (2) profiling of SVZ stem cells and ependyma isolated by fluorescent-activated cell sorting (FACS); and (3) analysis of gene expression changes during in vivo SVZ regeneration after anti-mitotic treatment. Gene Ontology (GO) analysis of data from these three separate approaches showed that in adult SVZ neurogenesis, RNA splicing and chromatin remodeling are biological processes as statistically significant as cell proliferation, transcription, and neurogenesis. In non-neurogenic brain regions, RNA splicing and chromatin remodeling were not prominent processes. Fourteen mRNA splicing factors including Sf3b1, Sfrs2, Lsm4, and Khdrbs1/Sam68 were detected along with 9 chromatin remodeling genes including Mll, Bmi1, Smarcad1, Baf53a, and Hat1. We validated the transcriptional profile data with Northern blot analysis and in situ hybridization. The data greatly expand the catalogue of cell cycle components, transcription factors, and migration genes for adult SVZ neurogenesis and reveal RNA splicing and chromatin remodeling as prominent biological processes for these germinal cells.

Cloning of the obese gene (ob) of adipose tissue, and differences in ob gene expression with age of piglets

AbstractGenomic RNA was extracted from the subcutaneous adipose tissue of piglets (Duroc×Landrace×Tai-hu) at 1, 14, 28, 42 and 56 days of age, and obese gene (ob) mRNA was amplified using reverse transcriptase-polymerase chain reaction (RT-PCR). A DNA fragment of about 504 bp was obtained and the PCR product was cloned into a pGEM-T vector. The ob gene was isolated and sequenced from the positive clones screened. Sequence analysis suggested that this fragment was a partial sequence of ob cDNA, coding 167 amino acid residues, which constituted the major part of leptin mature protein. The gene homology of the fragment obtained in this study compared to the reported ob cDNA sequence in adipocytes of pig was 99.405%, and amino acid homology was 98.94%. Based on the ob gene clone, we successfully constructed an optimal semi-quantitative RT-PCR method. Using β-actin as the internal control, we investigated the difference of ob gene expression at different ages of piglets. Results showed that ob mRNA levels increased steadily at postnatal days 1–28 (preweaning), peaked at postnatal day 28, when piglets were weaned, and decreased from day 28 to 56.

Possible Role of Triacylglycerol-Rich Lipoproteins in the Down-Regulation of Adipose Obese mRNA Expression in Rats Re-Fed a High-Fat Diet

The large amount of absorbed dietary lipid after feeding a high-fat diet is mainly transported as triacylglycerol (TG)-rich lipoproteins (TRL) in the post-prandial blood and is subsequently distributed to peripheral tissues including adipose and muscle tissues. An in vivo and an in vitro study were conducted to investigate the possible role of post-prandial TRL after high fat feeding in the regulation of obese (ob) gene expression. Adult male Wistar rats were fasted for 48 h and re-fed either a fat-free/high-carbohydrate diet or a high-fat diet for 2, 4, or 8 h and plasma glucose, insulin, TG, and leptin as well as ob mRNA expression in epididymal fat pads were examined. Rats re-fed the high-fat diet had significantly higher plasma TG (p < 0.05) and lower plasma leptin and adipose ob mRNA (p < 0.05) than those fed the fat-free/high-carbohydrate diet; however, plasma glucose and insulin concentrations were not significantly different between the two groups. Plasma lipid analysis found large amount of TRL in rats fed with high-fat diet; however, only very small amount of the TRL was found in rats fed with fat-free/high-carbohydrate diet. We speculated that TRL might involve in regulation of ob gene expression. To further examine the regulation of TRL on ob mRNA expression, differentiated 3T3-L1 adipocytes were treated with TRL collected from rats fed 5 ml soybean oil by gastric intubations. TRL down-regulated ob mRNA not only in a dose and time dependent manner but also in the presence of insulin in 3T3-L1 adipocytes. These results suggest a possible role of TRL in the down-regulation of adipose ob mRNA expression and may account, at least in part, for the previous observations that short-term high fat feeding resulted in lower plasma leptin.

The study on mechanism of appetite regulation in diet-induced obesity resistant rats

To explore the cause of decreasing intake food of diet-induced obesity resistant (DIO-R) rats. Fifty male Sprague-dawley (SD) rats were randomly divided into control group and high-fat group and they were fed with basic diet and high-fat diet respectively for 13 weeks. DIO-R and diet-induced obesity (DIO) rats were selected according to their body weight and the quantity of energy intake, then observing the changes of the total food intake, the level of serum leptin and plasma NPY were determined by radioimmunoassay and the contents of the melanocortin receptor-4 (MCR-4) in brain were determined by Western Blot. The total food intake of DIO-R rats was (1 679.1 +/- 146.8) g. The total food intake of DIO rats was (1 818.4 +/- 148.9) g. The total food intake of DIO-R rats was lower than that of DIO rats (P < 0.05). The level of plasma NPY of DIO-R rats was (795.24 +/- 83.59) ng/L. The level of plasma NPY of DIO rats was (1 007.14 +/- 172.83) ng/L. The level of plasma NPY of DIO-R rats was lower than that of the DIO rats (P < 0.05). The levels of serum leptin of basic, DIO-R and DIO rats was (4.80 +/- 0.75) microg/L, (9.17 +/- 1.19) microg/L and (9.32 +/- 1.04) microg/L. The level of serum leptin of rats in high-fat diet group was increased as compared with the rats in basic diet group, but there was no significant difference between DIO-R and DIO rats (P > 0.05). The levels of brain MCR-4 of basic, DIO-R and DIO rats were (342 +/- 31) mm2, (455 +/- 33) mm2, (355 +/- 30) mm2. High fat diets increased the content of brain MCR-4 in DIO-R rats. DIO-R rats decreased appetite by increasing expression of ob gene to reduce activity of NPY pathway and activate the MCR-4 pathway, and thus inhibit the increase body of weight.

Absence of leptin expression and secretion by human luteinized granulosa cells.

Whether leptin is secreted by the human ovary is not known. The available data on leptin gene (ob gene) expression by human granulosa cells are conflicting. The aim of the present study was first to re-examine the expression of leptin messenger RNA (mRNA) by human granulosa cells and second to investigate if these cells have the ability to secrete leptin in cultures. Human luteinized granulosa cells were obtained from normal women undergoing in vitro fertilisation treatment after ovarian stimulation and follicle aspiration. The expression of ob gene was studied by Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR) both in primary granulosa cells treated immediately after oocyte recovery and in cells cultured up to 24 h under baseline and hormonally stimulated conditions (FSH: 100 ng/ml, LH: 100 ng/ml). ob mRNA transcripts were not detected in luteinized granulosa cells, while they were present in adipose tIssue cDNA. Actin gene expression was detected in all studied samples. Using a sensitive radioimmunoassay (lower limit of detection 0.05 ng/ml), leptin was undetectable in the culture media at all points during the 72 h cultures, while at the same time significant amounts of oestradiol and progesterone were produced particularly after the addition of androstendione (1 microM) to the incubation media. These results demonstrate for the first time that leptin is not secreted by human luteinized granulosa cells in cultures. From a physiological point of view, this may contribute to the development of the optimal follicular environment for oocyte maturation during the preovulatory period.