D. F. García-Díaz

High fat diet-induced obesity modifies the methylation pattern of leptin promoter in rats.

Leptin is an adipokine involved in body weight and food intake regulation whose promoter region presents CpG islands that could be subject to dynamic methylation. This methylation process could be affected by environmental (e.g. diet) or endogenous (e.g., adipocyte differentiation, inflammation, hypoxia) factors, and could influence adipocyte leptin gene expression. The aim of this article was to study whether a high-energy diet may affect leptin gene promoter methylation in rats. A group of eleven male Wistar rats were assigned into two dietary groups, one fed on a control diet for 11 weeks and the other on a high-fat cafeteria diet. Rats fed a high-energy diet become overweight and hyperleptin emic as compared to the controls. DNA isolated from retroperitoneal adipocytes was treated with bisulfite and a distal portion of leptin promoter (from −694 to −372 bp) including 13 CpG sites was amplified by PCR and sequenced. The studied promoter portion was slightly more methylated in the cafeteria-fed animals, which was statistically significant (p<0.05) for one of the CpG sites (located at the position −443). In obese rats, such methy lation was associated to lower circulating leptin levels, suggesting that this position could be important in the regulation of leptin gene expression, probably by being a target sequence of different transcription factors. Our findings reveal, for the first time, that leptin methylation pattern can be influenced by diet-induced obesity, and suggest that epigenetic mechanisms could be involved in obesity by regulating the expression of important epiobesigenic genes.ResumenLa leptina es una adipoquina implicada en la regulación del peso corporal y la ingesta energética cuya región promotora presenta islas CpG que podrían ser metiladas dinámicamente. Este proceso de metilación podría verse afectado por factores ambientales, como la dieta, o endógenos, como la diferenciación adipocitaria, inflamación o hipoxia, y podría influir en la expresión de leptina por parte de los adipocitos. El objetivo de este artículo es estudiar si una dieta alta en grasa podría afectar a la metilación del promotor de la leptina en ratas. Un grupo de once ratas Wistar macho fue dividido en dos subgrupos, uno alimentado con dieta control durante 11 semanas y el otro con dieta alta en grasa (dieta de cafetería). Las ratas alimentadas con la dieta rica en grasa presentaron sobrepeso e hiperleptinemia. El ADN aislado de los adipocitos retroperitoneales fue tratado con bisulfito y una porción distal del promotor de la leptina (de la base-694 a la — 372), conteniendo 13 sitios CpG, fue amplificada por PCR y secuenciada. Esta región del promotor apareció ligeramente más metilada en los animales alimentados con dieta de cafetería, lo cuál fue especialmente significativo (p <0,05) para uno de los sitios CpG (en la posición-443). En las ratas obesas, la metilación se asoció a una disminución de los niveles de leptina circulante, lo que sugiere que esta posición podría ser importante en la regulación de la expresión génica de esta adipoquina, probablemente por ser una secuencia diana de diferentes factores de trnascripción. Nuestos resultados, por primera vez, ponen de manifiesto que el patrón de metilación del promotor de la leptina puede estar influido por la obesidad inducida por la dieta, y sugieren que los mecanismos epigenéticos podrían estar implicados en la reciente pandemia de obesidad mediante la regulación de la expresión de importantes genes epiobesigénicos.

Weight gain induced by an isocaloric pair-fed high fat diet: A nutriepigenetic study on FASN and NDUFB6 gene promoters

Experimental studies have demonstrated that dietary macronutrient distribution plays an important role in insulin regulation, a risk factor associated to obesity, diabetes and other metabolic disorders. To assess whether the macronutrient composition of the diet could be related to obesity onset by affecting the epigenetic regulation of gene expression, we investigated in rats the metabolic effects of two pair-fed isocaloric diets: control (rich in carbohydrates) and high fat diet (rich in fat; HFD). Compared to controls, HFD induced higher weight gain and adiposity and impaired glucose tolerance, which was accompanied by a slight increase in adiponectin levels and liver steatosis. Epididymal adipose tissue expression of the fatty acid synthase (FASN) gene and NADH dehydrogenase (ubiquinone) 1β-subcomplex 6 (NDUFB6) were significantly reduced in HFD group. These variations in mRNA levels were accompanied by changes in the methylation patterns of several CpG islands located in the promoter region of these genes. However, no correlations were found between gene expression and the methylation status. These results suggest that high fat intake produces overweighted rats independently of total energy intake. These diets could also induce some epigenetic changes in the promoters of key genes that could influence gene expression and may be behind metabolic alterations.

Obesity induced by a pair-fed high fat sucrose diet: methylation and expression pattern of genes related to energy homeostasis

BackgroundThe expression of some genes controlling energy homeostasis could be regulated by epigenetic mechanisms that may play a role in body weight regulation. Thus, it is known that various nutritional factors affect DNA methylation. In order to assess whether the macronutrient composition of the diet could be related to the epigenetic regulation of gene expression and with obesity development, we investigated the effects on methylation and expression patterns of two pair-fed isocaloric diets in rats: control (rich in starch) and HFS (rich in fat and sucrose).ResultsThe pair-fed HFS diet induced higher weight gain and adiposity as compared to the controls as well as liver triglyceride accumulation and oxidative stress. Feeding the HFS diet impaired glucose tolerance and serum triglycerides and cholesterol. Liver glucokinase expression, a key glycolytic gene, remained unaltered, as well as the mRNA values of fatty acid synthase and NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 6 (NDUFB6) in liver and visceral adipocytes, which regulate lipogenesis and mitochondrial oxidative metabolism, respectively. Liver expression of hydroxyacyl-coenzyme A dehydrogenase (HADHB), a key gene of β-oxidation pathway, was higher in the HFS-fed animals. However, the methylation status of CpG islands in HADHB and glucokinase genes remained unchanged after feeding the HFS diet.ConclusionsThese results confirm that the distribution and type of macronutrients (starch vs. sucrose, and percent of fat) influence obesity onset and the associated metabolic complications. HFS diets produce obesity independently of total energy intake, although apparently no epigenetic (DNA methylation) changes accompanied the modifications observed in gene expression.

Influence of dietary macronutrient composition on adiposity and cellularity of different fat depots in Wistar rats.

The aim of this study was to investigate the role of dietary macronutrient content on adiposity parameters and adipocyte hypertrophy/hyperplasia in subcutaneous and visceral fat depots from Wistar rats using combined histological and computational approaches. For this purpose, male Wistar rats were distributed into 4 groups and were assigned to different nutritional interventions: Control group (chow diet); high-fat group, HF (60% E from fat); high-fat-sucrose group, HFS (45% E from fat and 17% from sucrose); and high-sucrose group, HS (42% E from sucrose). At day 35, rats were sacrificed, blood was collected, tissues were weighed and fragments of different fat depots were kept for histological analyses with the new softwareAdiposoft. Rats fed with HF, HFS and HS diets increased significantly body weight and total body fat against Control rats, being metabolic impairments more pronounced on HS rats than in the other groups. Cellularity analyses usingAdiposoft revealed that retroperitoneal adipose tissue is histologically different than mesenteric and subcutaneous ones, in relation to bigger adipocytes. The subcutaneous fat pad was the most sensitive to the diet, presenting adipocyte hypertrophy induced by HF diet and adipocyte hyperplasia induced by HS diet. The mesenteric fat pad had a similar but attenuated response in comparison to the subcutaneous adipose tissue, while retroperitoneal fat pad only presented adipocyte hyperplasia induced by the HS diet intake after 35 days of intervention. These findings provide new insights into the role of macronutrients in the development of hyperplastic obesity, which is characterized by the severity of the clinical features. Finally, a new tool for analyzing histological adipose samples is presented.

Vitamin C inhibits leptin secretion and some glucose/lipid metabolic pathways in primary rat adipocytes

Antioxidant-based treatments are emerging as an interesting approach to possibly counteract obesity fat accumulation complications, since this is accompanied by an increased systemic oxidative stress. The aim of this study was to analyze specific metabolic effects of vitamin C (VC) on epididymal primary rat adipocytes. Cells were isolated and incubated for 72 h in culture medium, in the absence or presence of 1.6 nM insulin, within a range of VC concentrations (5-1000 microM). Glucose- and lipid-related variables as well as the secretion/expression patterns of several obesity-related genes were assessed. It was observed that VC dose dependently inhibited glucose uptake and lactate production, and also reduced glycerol release in both control and insulin-treated cells. Also, VC caused a dramatic concentration-dependent fall in leptin secretion especially in insulin-stimulated cells. In addition, VC (200 microM) induced Cdkn1a and Casp8, partially inhibited Irs3, and together with insulin drastically reduced Gpdh (listed as Gpd1 in the MGI database) gene expressions. Finally, VC and insulin down-regulatory effects were observed on extracellular and intracellular reactive oxygen species production respectively. In summary, this experimental assay describes a specific effect of VC in isolated rat adipocytes on glucose and fat metabolism, and on the secretion/expression of important obesity-related proteins.

Regulation by chronic-mild stress of glucocorticoids, monocyte chemoattractant protein-1 and adiposity in rats fed on a high-fat diet

Stress has been reported as a widespread problem and several studies have linked obesity and inflammation-related diseases. Moreover, the combination of suffering from chronic stress and high energy intake might be related to the onset of some metabolic diseases. To study the possible relationships between stress, inflammatory status and obesity, a chronic-mild stress (CMS) paradigm with a high-fat dietary intake model (Cafeteria diet) was implemented on male Wistar rats for 11 weeks. Stress and dietary intake effects on animal adiposity, serum biochemical as well as glucocorticoids and inflammation markers were all analyzed. As expected, consuming a high-fat diet increased body weight, adiposity and insulin resistance in non-stressed animals. A decrease of total white adipose tissue (WAT) and an increase of fecal glucocorticoids, as well as angiotensinogen, and monocyte chemoattractant protein-1 (MCP-1) expression level in retroperitoneal WAT were found only on control-stressed rats. Regarding the serum MCP-1, a decrease was observed on animals under CMS while being fed Cafeteria diet. Furthermore, 11β-hydroxysteroid dehydrogenase activity, a glucocorticoid and obesity biomarker in the liver, was influenced by high-fat diet intake but not by stress. Finally, statistical analysis showed a strong relation between MCP-1 expression levels in retroperitoneal WAT, fecal corticosterone and total WAT. This trial proved that CMS induced a glucocorticoid-mediated response, which was reduced by the intake of a Cafeteria diet. These findings suggest that a high-fat diet could protect against a stress condition and revealed a different behavior to a stressful environment depending on the nutritional status.

Chronic mild stress induces variations in locomotive behavior and metabolic rates in high fat fed rats

Chronic mild stress (CMS) has been often associated to the pathogenesis of many diseases including obesity. Indeed, visceral obesity has been linked to the development of metabolic syndrome features and constitutes a serious risk factor for cardiovascular diseases and diabetes. In order to study possible mechanistic relationships between stress and the onset of obesity, we developed during 11 weeks a model of high-fat dietary intake (cafeteria diet) together with a CMS regimen in male Wistar rats. During the experimental period, basal metabolism by indirect calorimetry, rectal temperature, food intake, and locomotive markers were specifically analyzed. After 77 days, animals were sacrificed and body, adiposity and plasma biochemical profiles were also examined. As expected, cafeteria diet in unstressed animals induced a significative increase in body weight, adiposity, and insulin resistance markers. Locomotive variables, specifically distance, rearing and meander, were significantly increased by CMS on the first weeks of stress. Moreover, this model of CMS in Wistar rats increased significantly energy expenditure, and apparently interplayed with the dietary treatment on the muscle weight/fat weight ratio. In summary, this chronic stress model did not affected weight gain in control and high fat fed animals, but induced an interaction concerning the metabolic muscle/fat repartitioning.ResumenEl estrés crónico moderado se ha asociado a menudo con la patogénesis de diversas enfermedades, como la obesidad. La obesidad visceral, por su parte, se ha relacionado con el desarrollo de síndrome metabólico, enfermedades cardiovasculares y diabetes. Con el fin de estudiar una posible relación entre el estrés y el establecimiento de obesidad, se analizó durante 11 semanas un modelo de ingesta alta en grasas (dieta de cafetería) junto con un estrés crónico moderado en ratas Wistar macho. Durante este período experimental, se analizó el metabolismo basal por calorimetría indirecta, la temperatura rectal, la ingesta calórica y la actividad motora de los animales. Tras los 77 días, los animales se sacrificaron y se analizaron diversas medidas corporales y de adiposidad, así como el perfil bioquímico de las ratas. Como se esperaba, la dieta de cafetería en animales no estresados indujo un aumento significativo del peso corporal, la adiposidad y los niveles de marcadores de insulino-resistencia. Las medidas de actividad motora, específicamente el movimiento horizontal, vertical y la sinuosidad de movimiento, aumentaron significativamente con el estrés, lo que se observó en las primeras semanas del experimento. Además, estrés crónico moderado en ratas Wistar incrementó significativamente el gasto energético y parece jugar un papel conjunto con el tratamiento con dieta alta en grasa en la modulación del índice peso del músculo/peso de la grasa de los animales. En resumen, este modelo de estrés crónico moderado no afectó significativamente al peso corporal, tanto de los animales controles como de los alimentados con dieta de cafetería, pero indujo una interacción con la alta ingesta de grasa concerniente a la repartición metabólica músculo/grasa.

Ascorbic acid oral treatment modifies lipolytic response and behavioural activity but not glucocorticoid metabolism in cafeteria diet-fed rats.

Aim:  To analyse the effects of vitamin C (VC), a potent dietary antioxidant, oral supplementation on body weight gain, behavioural activity, lipolytic response and glucocorticoid metabolism in the early stages of diet‐induced overweight in rats.

Vitamin C modulates the interaction between adipocytes and macrophages

SCOPE Increased adiposity is related with monocyte infiltration into the adipose tissue that accentuates inflammation. Antioxidant treatments emerge as approaches to counteract this phenomenon. METHODS AND RESULTS Cocultures of differentiated 3T3-L1 adipocytes and RAW264.7 macrophages were incubated for 24-72 h with/without 100 nM insulin and/or 200 μM vitamin C (VC). Nitric oxide (NO) secretion (24 h) was measured. Also, expression (24 h) and secretion (72 h) of MCP-1, leptin and apelin were analyzed. NO secretion was significantly inhibited by insulin and VC only in cocultures. MCP-1 expression/secretion was enhanced in cocultures. Insulin incubation reduced MCP-1 expression in both cultures and VC only in controls. Both treatments inhibited MCP-1 secretion in cocultures. Apelin gene expression was induced in cocultures. Insulin induced apelin mRNA expression, but VC inhibited its expression in cocultures under insulin treatment. Apelin secretion was notably induced by insulin and inhibited by VC in cocultures. Leptin expression was decreased in coculture, while presented no effects by VC. CONCLUSION VC importantly modulates the established pro-inflammatory state in the interaction between adipocytes and macrophages.

A high-sucrose isocaloric pair-fed model induces obesity and impairs NDUFB6 gene function in rat adipose tissue.

Background/Aim: Changes in dietary macronutrient content are involved in altered energy metabolism and obesity development. However, there are controversial views about the obesogenic effects of high-sucrose (HS) diets, which usually lead to obesity and insulin resistance but are sometimes associated with reduced weight gain. The aim of this study was to investigate the effect of consumption of a pair-fed HS diet on weight gain and energy homeostasis in rats, as well as to assess the effects on expression of the NADH dehydrogenase (ubiquinone) 1β subcomplex 6 (NDUFB6) gene in adipose tissue. Methods/Results: Although both dietary groups, i.e. HS and control, were pair-fed (isoenergetic feeding), the HS diet increased adiposity and decreased plasma total and high-density lipoprotein cholesterol levels. While no significant differences were found with regard to serum glucose, insulin, adiponectin, free fatty acids and liver malondialdehyde, a slight increase in serum and liver triglycerides was observed. Interestingly, the gene expression of NDUFB6, an inner mitochondrial membrane protein involved in mitochondrial electron transport, was reduced in epididymal adipose tissue when compared to the control-fed group. Conclusion: These results suggest, apparently for the first time, that high-sugar diets appear to induce mitochondrial dysfunction in adipose tissue, which may be related to greater weight gain and metabolic impairment.