Juana Sánchez

A Physiological Role of Breast Milk Leptin in Body Weight Control in Developing Infants

Objective: Leptin, a hormone that regulates food intake and energy metabolism, is present in breast milk. The aim of this study was to determine whether milk leptin concentration is correlated with maternal circulating leptin and BMI and with body weight gain of infants.

Sex-differential Expression of Metabolism-related Genes in Response to a High-fat Diet

Objective: The aim of this work was to determine the sex‐associated differences in the expression of genes related to lipid metabolism and fuel partitioning in response to a high‐fat (HF) diet in rats, and whether this is linked to the higher tendency of males to suffer from metabolic disorders.

Moderate caloric restriction during gestation results in lower arcuate nucleus NPY- and αMSH-neurons and impairs hypothalamic response to fed/fasting conditions in weaned rats

Aim: We aimed to characterize the developmental programming effects of moderate caloric restriction during early pregnancy on factors involved in hypothalamic control of energy balance.

Moderate Caloric Restriction during Gestation in Rats Alters Adipose Tissue Sympathetic Innervation and Later Adiposity in Offspring

Maternal prenatal undernutrition predisposes offspring to higher adiposity in adulthood. Mechanisms involved in these programming effects, apart from those described in central nervous system development, have not been established. Here we aimed to evaluate whether moderate caloric restriction during early pregnancy in rats affects white adipose tissue (WAT) sympathetic innervation in the offspring, and its relationship with adiposity development. For this purpose, inguinal and retroperitoneal WAT (iWAT and rpWAT, respectively) were analyzed in male and female offspring of control and 20% caloric-restricted (from 1–12 d of pregnancy) (CR) dams. Body weight (BW), the weight, DNA-content, morphological features and the immunoreactive tyrosine hydroxylase and Neuropeptide Y area (TH+ and NPY+ respectively, performed by immunohistochemistry) of both fat depots, were studied at 25 d and 6 m of age, the latter after 2 m exposure to high fat diet. At 6 m of life, CR males but not females, exhibited greater BW, and greater weight and total DNA-content in iWAT, without changes in adipocytes size, suggesting the development of hyperplasia in this depot. However, in rpWAT, CR males but not females, showed larger adipocyte diameter, with no changes in DNA-content, suggesting the development of hypertrophy. These parameters were not different between control and CR animals at the age of 25 d. In iWAT, both at 25 d and 6 m, CR males but not females, showed lower TH+ and NPY+, suggesting lower sympathetic innervation in CR males compared to control males. In rpWAT, at 6 m but not at 25 d, CR males but not females, showed lower TH+ and NPY+. Thus, the effects of caloric restriction during gestation on later adiposity and on the differences in the adult phenotype between internal and subcutaneous fat depots in the male offspring may be associated in part with specific alterations in sympathetic innervation, which may impact on WAT architecture.

Gastric leptin: a putative role in the short-term regulation of food intake

The discovery of the production of leptin by the stomach, in addition to its production by adipose tissue, has initiated new investigation into the possible role of this protein in the digestive physiology, in particular in the short-term control of energy balance. Leptin has been identified in the lower half of the stomach glands both in the pepsinogen granules of chief cells and in the granules of a specific endocrine cell type, suggesting that leptin action is exerted by both exocrine and endocrine pathways. Gastric leptin is sensitive to the nutritional state, being rapidly mobilized in response to food intake following fasting, or after the administration of satiety factors; this suggests a role for this protein in the short-term regulation of feeding, acting in collaboration with satiety peptides such as cholecystokinin. Leptin, produced by gastric cells and by adipocytes, could act on both acute and chronic regulation of feeding behaviour respectively, giving information to the brain on the availability of external (food) and internal (fat depots) energy resources, thus participating in short- and long-term satiation.

Regional differences in the expression of genes involved in lipid metabolism in adipose tissue in response to short- and medium-term fasting and refeeding

The aim of this study was to analyze regional differences in the time-course response to fasting and refeeding in the expression of genes involved in lipid metabolism in retroperitoneal, mesenteric and inguinal adipose tissue. Rats were studied under different feeding conditions: feeding state; after 4, 8 or 24 h of fasting; and after 3 h of refeeding following 8 h of fasting. The expression of lipogenesis-related genes decreased by fasting in adipose tissue, and the retroperitoneal depot showed the fastest response: mRNA levels of peroxisome proliferator-activated receptor gamma 2 (PPARgamma2) decreased after 4 h of fasting and those of sterol regulatory element binding protein 1c (SREBP1c), fatty acid synthase (FAS), GPAT and glucose transporter 4 (GLUT4) decreased after 8 h. In the inguinal depot, mRNA levels of SREBP1c, acetyl-coenzyme A carboxylase alpha, FAS and lipoprotein lipase decreased after 8 h of fasting, while in the mesenteric depot, only GLUT4 and FAS mRNA levels decreased after 8 and 24 h, respectively. Concerning lipolytic and fatty acid oxidation genes, only adipose triglyceride lipase and carnitine palmitoyltransferase 1a expression increased after 24 h of fasting in the retroperitoneal depot. Three hours of refeeding restored the expression of the lipogenic transcription factors PPARgamma2 and SREBP1c in the retroperitoneal depot and of PPARgamma2 in the inguinal depot. This period of refeeding was ineffective in changing the expression of genes related with lipid mobilization and fatty acid oxidation, except hormone-sensitive lipase, whose expression decreased in the mesenteric depot. It is suggested that different regulations of the expression of genes related with lipid metabolism between internal and subcutaneous depots to feeding and fasting conditions are site-specific metabolic features of white adipose tissue.

Gene expression patterns in visceral and subcutaneous adipose depots in rats are linked to their morphologic features.

The aim was to characterize the expression pattern of genes involved in lipid metabolism in internal (retroperitoneal, mesenteric) and subcutaneous (inguinal) adipose tissue depots in rats and their relation with site-specific morphological- and metabolic-features. Gene expression by RT-qPCR, western blot and morphometric analyses were performed. Lipogenesis-related genes (PPARγ2, SREBP1c, ACC1, GPAT, LPL, CD36, GLUT4) showed higher mRNA levels in the retroperitoneal depot versus the mesenteric and the inguinal depots; the expression of PPARgamma;2, ACC1, CD36, and GLUT4 in the mesenteric depot was also higher than in the inguinal depot. HKII was similarly expressed in the retroperitoneal and mesenteric depots and higher than in the inguinal one. The expression of lipolysis-related genes (HSL, ATGL) was higher in the retroperitoneal than in the mesenteric and inguinal depots, while the expression of fatty-acid oxidation-related genes (PPARα, CPT1) was lower in the retroperitoneal depot compared with the mesenteric and the inguinal depots. Thus, a higher expression of lipogenesis- and lipolysis-related genes and lower expression of fatty-acid oxidation-related genes in internal depots (particularly in the retroperitoneal, which also presents the largest adipocyte size) can explain its higher triacylglyceride turnover rates and hence account for the differential behavior of fat depots in physiological situations and its involvement in obesity-linked metabolic disorders.

Induction of NPY/AgRP orexigenic peptide expression in rat hypothalamus is an early event in fasting: relationship with circulating leptin, insulin and glucose.

Hypothalamus is crucial in the control of energy intake and expenditure in mammals, presenting two interconnected populations of neurons producing orexigenic NPY/AgRP (neuropeptide Y; agouti related peptide) and anorexigenic POMC/CART (pro-opiomelanocortin; cocaine and amphetamine regulated transcript) neuropeptides. We aimed to shed more light on the response and sensitivity in the production of these neuropeptides to face nutritional changes, particularly food deprivation, and on the signals that regulate them. Male Wistar rats were fasted for 0, 4, 8 and 24h and refed for 3h after 8h fasting. mRNA levels of gastric and adipose tissue (retroperitoneal, mesenteric and inguinal) leptin, and of hypothalamic NPY, AgRP, POMC, CART, leptin receptor, SOCS3 (suppressor of cytokine signaling 3) and insulin receptor were analyzed. Gastric and circulating leptin, and circulating insulin, glucose and ghrelin were also determined. The only neuropeptide mRNAs that responded (increasing) to the short-term periods of fasting used were those of NPY (transiently) and AgRP, and these changes were accompanied by an increase in leptin receptor mRNA levels and by a decrease in adipose and gastric leptin expression and in the circulating levels of leptin, insulin and glucose, but without changes in circulating ghrelin. The elevation in AgRP and leptin receptor mRNA levels and the drop in circulating leptin were not reverted with refeeding. It is suggested that the induction of expression of the orexigenic molecules in NPY/AgRP neurons is an early event upon fasting, related with changes in leptin, insulin and glucose levels, but with the role of leptin signaling in particular.

Protective effects of leptin during the suckling period against later obesity may be associated with changes in promoter methylation of the hypothalamic pro-opiomelanocortin gene

Leptin supplementation of neonatal rats during the suckling period protects against being overweight in adulthood and ameliorates the control of food intake. This was associated with changes in the expression of hypothalamic genes involved in the central action of leptin: pro-opiomelanocortin (Pomc), leptin receptor (Lepr) and suppressor of cytokine signalling (Socs3). The purpose of the present study was to determine the methylation status within the promoter regions of these genes and to assess whether the observed changes in the expression levels of these genes could be explained by changes in their methylation status. Male rats were treated daily with an oral physiological dose of leptin or vehicle during the suckling period. After weaning, animals were fed with a normal-fat or a high-fat (HF) diet until aged 6 months. DNA was extracted from the hypothalamus and methylation within the promoter regions of the gene panel was measured by pyrosequencing. Pomc promoter methylation increased in control animals fed the HF diet but decreased in leptin-treated animals. In addition, there was a weak negative correlation between DNA methylation and POMC mRNA levels (P = 0·075). There were no changes in the methylation status of the CpG sites studied within the promoter regions of Lepr and Socs3 in response to leptin or HF treatments. This is the first demonstration that leptin treatment during lactation may programme methylation of an appetite-related gene in the hypothalamus of animals fed HF diets, with possible implications for gene expression and protection against the development of obesity.

Sexual dimorphism in the lasting effects of moderate caloric restriction during gestation on energy homeostasis in rats is related with fetal programming of insulin and leptin resistance.

AimWe aimed to characterize the lasting effect of moderate caloric restriction during early pregnancy on offspring energy homeostasis, by focusing on the effects on food intake and body weight as well as on the insulin and leptin systems.MethodsMale and female offspring of 20% caloric restricted dams (from 1 to 12 days of pregnancy) (CR) and from control dams were studied. These animals were fed after weaning with a normal-fat (NF) diet until the age of 4 months, and then moved to a high-fat (HF) diet. Blood parameters were measured under fed and 14-h fasting conditions at different ages (2, 4 and 5 months). Food preferences were also assessed in adult animals.ResultsAccumulated caloric intake from weaning to the age of 5 months was higher in CR animals compared with their controls, and this resulted in higher body weight in adulthood in males, but not in females. Both male and female CR animals already showed higher insulin levels at the age of 2 months, under fed conditions, and higher HOMA-IR from the age of 4 months, compared with their controls. CR male animals, but not females, displayed higher preference for fat-rich food than their controls in adulthood and higher circulating leptin levels when they were under HF diet.ConclusionIt is suggested that hyperinsulinemia may play a role in the etiology of hyperphagia in the offspring of caloric restricted animals during gestation, with different outcomes on body weight depending on the gender, which could be associated with different programming effects on later leptin resistance.