Laura Paternain

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.

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.

Postnatal maternal separation modifies the response to an obesogenic diet in adulthood in rats

SUMMARY An early-life adverse environment has been implicated in the susceptibility to different diseases in adulthood, such as mental disorders, diabetes and obesity. We analyzed the effects of a high-fat sucrose (HFS) diet for 35 days in adult female rats that had experienced 180 minutes daily of maternal separation (MS) during lactancy. Changes in the obesity phenotype, biochemical profile, levels of glucocorticoid metabolism biomarkers, and the expression of different obesity- and glucocorticoid-metabolism-related genes were analyzed in periovaric adipose tissue. HFS intake increased body weight, adiposity and serum leptin levels, whereas MS decreased fat pad masses but only in rats fed an HFS diet. MS reduced insulin resistance markers but only in chow-fed rats. Corticosterone and estradiol serum levels did not change in this experimental model. A multiple gene expression analysis revealed that the expression of adiponutrin (Adpn) was increased owing to MS, and an interaction between HFS diet intake and MS was observed in the mRNA levels of leptin (Lep) and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Ppargc1a). These results revealed that early-life stress affects the response to an HFS diet later in life, and that this response can lead to phenotype and transcriptomic changes.

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.

Methyl donor supplementation in rats reverses the deleterious effect of maternal separation on depression-like behaviour

Adverse early life events are associated with altered stress responsiveness and metabolic disturbances in the adult life. Dietary methyl donor supplementation could be able to reverse the negative effects of maternal separation by affecting DNA methylation in the brain. In this study, maternal separation during lactation reduced body weight gain in the female adult offspring without affecting food intake, and altered total and HDL-cholesterol levels. Also, maternal separation induced a cognitive deficit as measured by NORT and an increase in the immobility time in the Porsolt forced swimming test, consistent with increased depression-like behaviour. An 18-week dietary supplementation with methyl donors (choline, betaine, folate and vitamin B12) from postnatal day 60 also reduced body weight without affecting food intake. Some of the deleterious effects induced by maternal separation, such as the abnormal levels of total and HDL-cholesterol, but especially the depression-like behaviour as measured by the Porsolt test, were reversed by methyl donor supplementation. Also, the administration of methyl donors increased total DNA methylation (measured by immunohistochemistry) and affected the expression of insulin receptor in the hippocampus of the adult offspring. However, no changes were observed in the DNA methylation status of insulin receptor and corticotropin-releasing hormone (CRH) promoter regions in the hypothalamus. In summary, methyl donor supplementation reversed some of the deleterious effects of an early life-induced model of depression in rats and altered the DNA methylation profile in the brain.

Liver Proteome Changes Induced by a Short-Term High-Fat Sucrose Diet in Wistar Rats

Background/Aims: The aim of this study was to gain insight into those proteins that might be involved in the early stages of liver fat accumulation as a consequence of a different fat versus simple sugar dietary intake. Methods: Forty-five male Wistar rats were randomly distributed into four dietary groups: a starch-rich control diet (CD; n = 10), a high-fat diet (n = 12), a high-sucrose diet (n = 11), and a high-fat sucrose diet (HFSD; n = 12) for 5 weeks. A comparative analysis by 2D-DIGE and LC-ESI-MS/MS was performed to characterize the liver protein expression profiles due to the three obesogenic diets. Results: Ten out of 17 proteins whose expression levels were altered by >1.25-fold were identified. Four proteins (Hspa8, Hspa9, Ca3, and Cat) were differentially expressed after the HFSD period compared to CD. The heat shock proteins (Hspa8 and Hspa9) resulted significantly downregulated in liver from rats fed HFSD versus CD (p < 0.05). The results were confirmed by Western blot. Conclusions: This descriptive study might be useful for further studies aiming at understanding the mechanisms by which diets rich in both fat and sugar affect the initiation of hepatic steatosis.

Effects of perinatal diet and prenatal stress on the behavioural profile of aged male and female rats

The present work studies whether chronic prenatal stress (PS) influences the long-term sex-dependent neuropsychological status of offspring and the effects of an early dietary intervention in the dam. In addition, dams were fed with either a high-fat sugar diet (HFSD) or methyl donor supplemented diet (MDSD). PS procedure did not affect body weight of the offspring. MDSD induced decreases in body weight both in male and female offspring (1 month) that were still present in aged rats. HFSD induced an increase in body weight both in male and female offspring that did not persist in aged rats. In the Porsolt forced swimming test, only young males showed increases in immobility time that were reversed by MDSD. In old female rats (20 months), PS-induced cognitive impairment in both the novel object recognition test (NORT) and in the Morris water maze that was reversed by MDSD, whereas in old males, cognitive impairments and reversion by MDSD was evident only in the Morris water maze. HFSD induced cognitive impairment in both control and PS old rats, but there was no additive effect of PS and HFSD. It is proposed here that the diversity of symptoms following PS could arise from programming effects in early brain development and that these effects could be modified by dietary intake of the dam.

Metabolomics and Transcriptomics of Metabolic Disorders

The current prevalence of metabolic diseases such as obesity and type 2 diabetes mellitus (T2DM) is increasing not only due to genetic causes, but also because of lifestyle factors such as lack of physical exercise and consumption of high fat and high glycemic index diets, being one of the most serious public health problems around the world. Different omic approaches such as metabolomics or transcriptomics have revolutionized the quantitative analysis of an organism’s state, linking cellular pathways to biological mechanisms, and could be applicable for identifying metabolic markers, which could be useful as diagnostic tools in a personalized healthcare setting. It may also open the door to novel biomarker discovery, disease diagnosis, and novel therapeutic avenues. This review covers the metabolomics and transcriptomic studies analyzing different biomarkers involved in the development of obesity and T2DM.

Contents Vol. 4, 2011

M.C. Archer, Toronto, Qué. A.G. Comuzzie, San Antonio, Tex. R. De Caterina, Chieti D. Corella, Valencia H.-W. Deng, Kansas City, Mo. A. El-Sohemy, Toronto, Qué. L.R. Ferguson, Auckland J. Hebebrand, Essen C. Junien, Paris T. Kadowaki, Tokyo D. Langin, Toulouse F. Leighton, Santiago É. Lévy, Montréal, Qué. J.A. Martínez, Pamplona G.D. Miller, Rosemont, Ill. A.G. Motulsky, Seattle, Wash. J.M. Ordovas, Boston, Mass. T. Rice, St. Louis, Mo. W.H.M. Saris, Maastricht A.P. Simopoulos, Washington, D.C. P. Talmud, London M. Uusitupa, Kuopio A. Velázquez, México City C. Warden, Davis, Calif. International Society of Nutrigenetics/Nutrigenomics (ISNN)