Antoni Caimari

The intake of physiological doses of leptin during lactation in rats prevents obesity in later life

Background:There is epidemiological evidence that perinatal nutritional factors may have long-term effects on obesity. Which nutrients or food components are involved in this programming mechanism are unknown. Breast milk contains leptin, a hormone that regulates food intake and energy expenditure, and previous studies in rats have shown that leptin orally administered during lactation exerts anorexigenic effects.Objective:To evaluate whether supplementation with physiological doses of oral leptin during lactation has long-term effects on body weight regulation.Design:A daily oral dose of leptin (equivalent to five times the amount of leptin ingested normally from maternal milk during the suckling period) or the vehicle was given to suckling male rats during lactation. Animals were fed after weaning with a normal fat (NF) or a high-fat (HF) diet. We followed body weight and food intake of animals until the age of 6 months, and measured the size of adipose tissue depots, the thermogenic capacity, the expression of leptin in the stomach and adipose tissues and the expression of two appetite-related peptides (neuropeptide Y (NPY) and proopiomelanocortin (POMC)), leptin receptor (OB-Rb) and suppressor of cytokine signalling 3 (SOCS-3) in the hypothalamus at the age of 6 months.Results:Leptin-treated animals had, in adulthood, lower body weight and fat content and ate fewer calories than their untreated controls. Unlike adipocitary leptin production, adult animals that were leptin-treated during lactation displayed higher gastric leptin production without changes in OB-Rb mRNA levels. In addition, in response to HF diet, leptin-treated animals (contrary to controls) showed lower hypothalamic NPY/POMC mRNA ratio. Hypothalamic OB-Rb mRNA levels decreased in control animals as an effect of HF diet feeding, but remained unchanged in leptin-treated animals; SOCS-3 mRNA levels were lower in leptin-treated animals than in their controls, both under normal or HF diet.Conclusion:The animals that received leptin during lactation become more protected against fat accumulation in adult life and seem to be more sensitive to the short- and long-term regulation of food intake by leptin. Thus, leptin plays an important role in the earlier stages of neonatal life, as a component of breast milk, in the prevention of later obesity.

Peripheral Blood Mononuclear Cells as a Model to Study the Response of Energy Homeostasis-Related Genes to Acute Changes in Feeding Conditions

Peripheral blood mononuclear cells (PBMCs) are readily accessible biological material and a potential tissue source to discover novel biomarkers of response to environmental exposures including nutrition. We analyzed whether PBMCs could reflect molecular changes that take place in response to different feeding conditions in key organs/tissues involved in energy homeostasis. We studied energy balance-related genes whose expression was altered in normoweight (control) rats and in diet-induced (cafeteria) obese rats in response to ad libitum feeding, 14-h fasting, and 6-h refeeding after fasting, using whole-genome microarray analysis. In PBMCs, the expression of the genes central to energy metabolism was altered by the feeding conditions. The number of affected genes was 75 in the control rats, but only 23 in the cafeteria obese rats. Most of these genes play a role in metabolic pathways regulated by nutritional changes, such as lipid metabolism (the metabolic pathway mainly reflected in blood cells), carbohydrate metabolism, central energy metabolism, respiratory chain/mitochondrial ATPase system, and food intake regulation. Importantly, our results showed a similar behavior to that of the mesenteric white adipose tissue. In conclusion, metabolic adaptations to acute changes in feeding conditions are reflected in the expression of genes central to energy homeostasis in PBMCs of normoweight rats, while response is impaired in cafeteria obese animals. The lower number of genes affected in obese animals indicates impaired nutritional regulation. PBMCs appear as a suitable potential model to characterize metabolic adaptations to food intake and body weight maintenance in experimental animals. These findings may also inform the development of future peripheral tissue models in the emerging field of clinical nutrigenomics.

Low doses of grape seed procyanidins reduce adiposity and improve the plasma lipid profile in hamsters.

Objective:Procyanidins are polyphenolic compounds with beneficial effects on health in relation to cardiovascular disease and metabolic syndrome. In this study, we evaluated the potential beneficial effects of low doses of a grape seed procyanidin extract (GSPE) on body weight and fat deposition.Design:Four groups of hamsters were fed either a standard diet (STD) or a high-fat diet (HFD) for 30 days and supplemented with either GSPE at 25 mg per kg of body weight per day (STD-GSPE and HFD-GSPE groups) or vehicle (STD and HFD groups) during the last 15 days of the study.Results:A significant decrease in body weight gain was observed in both GSPE-treated animals at the end of the experiment. GSPE treatment significantly reduced the adiposity index and the weight of all the white adipose tissue depots studied (retroperitoneal (RWAT), mesenteric (MWAT), epididymal (EWAT) and inguinal (IWAT)) in both GSPE-treated groups. GSPE administration reversed the increase in plasma phospholipids induced by the HFD feeding. In the RWAT, GSPE treatment increased the mRNA expression of genes related to β-oxidation and the glycerolipid/free fatty acid (GL/FFA) cycle, mainly in HFD-GSPE animals. In the MWAT, the effects of GSPE at the transcriptional level were not as evident as in the RWAT. Moreover, GSPE treatment induced heparin-releasable lipoprotein lipase activity in the RWAT and MWAT depots. The alterations in the lipid metabolic pathways induced by GSPE were accompanied by lower FFA levels in the plasma and decreased lipid and triglyceride accumulation in the MWAT.Conclusion:The use of GSPE at low doses protects against fat accumulation and improves the plasma lipid profile in hamsters. We suggest that GSPE exerts these effects in part through the activation of both β-oxidation and the GL/FFA cycle, mainly in the RWAT.

Lipidomic and metabolomic analyses reveal potential plasma biomarkers of early atheromatous plaque formation in hamsters

AIMS Atherosclerosis is the main pathological process contributing to cardiovascular disease, with diet being the most important factor involved. Although the lipidome of atheromatous plaque has been studied previously, the use of comparative lipidomics and metabolomics in plasma in early atherogenesis could lead to the discovery of plasma biomarkers that allow not only disease prediction but also measurement of disease progression. METHODS AND RESULTS High-throughput techniques, such as liquid chromatography/mass spectrometry, allowed us to compare the circulating and aortic lipidome and plasma metabolome in order to look for new molecular targets involved in atherogenesis. To achieve this objective, we chose the hamster (Mesocricetus auratus) as the best small animal model for diet-induced early atherosclerosis, because its lipoprotein metabolism is similar to that of humans. The results revealed the existence of several, previously unreported, changes in lipid and amino-acid metabolism, the peroxisome proliferator-activated receptor γ pathway, and oxidative and endoplasmic reticulum stress, also involving cell senescence. Furthermore, as a proof of concept in the modelling of dietary influences in atherogenesis, we have measured the effect of a potential anti-atherogenic polyphenol extract on the reported pathways. Our results support a previously unknown role for taurocholic acid as a potential plasma biomarker of early atheromatous plaque formation. CONCLUSION The use of comparative liquid chromatography/mass spectrometry-based lipidomics and metabolomics allows the discovery of novel pathways in atherogenesis, as well as new potential plasma biomarkers, which could allow us to predict disease in its early stages and measure its progression.

Feeding conditions control the expression of genes involved in sterol metabolism in peripheral blood mononuclear cells of normoweight and diet-induced (cafeteria) obese rats

Peripheral blood mononuclear cells (PBMC) are easily obtainable cells from blood whose gene expression profiles have been proven to be highly robust in distinguishing a disease state from healthy state. Sterol metabolism is of physiological importance, and although its nutritional response in liver has been described, it is poorly studied in PBMC. To examine if PBMC sterol metabolism reflects diet-induced physiological responses, we analysed the whole genome gene expression response of PBMC and focused on sterol metabolism-related genes affected by different feeding conditions (ad libitum feeding, fasting, and refeeding) in normoweight (control) rats and in diet-induced (cafeteria) obese rats. Our results of microarray analysis show that, in control rats, 21 genes involved in sterol metabolism were regulated by the different feeding conditions, whereas in cafeteria-obese rats, only seven genes showed a changed expression. Most of the genes identified were classified into three pathways: sterol biosynthesis, cholesterol transport and uptake and sterol signaling. The expression profile of these genes was similar to that previously described for liver, decreasing in response to fasting conditions and recovering the levels found in fed animals after 6-h-refeeding. In addition, our data and the comparable expression pattern of sterol metabolism-related genes between PBMC and liver suggest similar sterol regulatory element-binding protein-mediated regulatory mechanisms in response to feeding conditions in both tissues. In conclusion, the expression of genes involved in sterol metabolism is highly controlled by feeding conditions in PBMC of control rats, but this control is impaired in cafeteria-obese animals. The pathophysiological significance of this impairment requires further investigation.

Distribution of grape seed flavanols and their metabolites in pregnant rats and their fetuses

SCOPE Polyphenols have been demonstrated to provide health benefits affecting cellular and physiological processes. This study aims to evaluate the bioavailability and distribution of grape seed flavanol compounds during pregnancy and whether fetuses could be exposed to these compounds. METHODS AND RESULTS The distribution of flavanols and their metabolites in rat plasma, liver, white adipose tissue, brain, amniotic fluid, placenta, and fetuses after 1 and 2 h of an acute intake of a grape seed proanthocyanidin extract was examined by LC-ESI-TOF/MS. Flavanols and their metabolites were widely distributed in both pregnant and nonpregnant rat plasma and tissues. In liver, the conjugated forms of flavanols were less available in pregnant than nonpregnant rats. Flavanol metabolites were abundant in maternal placenta but detected at low levels in fetuses and amniotic fluid. CONCLUSION Flavanol metabolization appears to be less active in the liver during pregnancy. Moreover, data indicated that transport across the placenta is not efficient and for flavanols and their metabolites, the placenta seems to act as a barrier. However, these compounds target the fetus and are excreted in the amniotic fluid.

Cocoa Consumption Alters the Global DNA Methylation of Peripheral Leukocytes in Humans with Cardiovascular Disease Risk Factors: A Randomized Controlled Trial

DNA methylation regulates gene expression and can be modified by different bioactive compounds in foods, such as polyphenols. Cocoa is a rich source of polyphenols, but its role in DNA methylation is still unknown. The objective was to assess the effect of cocoa consumption on DNA methylation and to determine whether the enzymes involved in the DNA methylation process participate in the mechanisms by which cocoa exerts these effects in humans. The global DNA methylation levels in the peripheral blood were evaluated in 214 volunteers who were pre-hypertensive, stage-1 hypertensive or hypercholesterolemic. The volunteers were divided into two groups: 110 subjects who consumed cocoa (6 g/d) for two weeks and 104 control subjects. In addition, the peripheral blood mononuclear cells (PBMCs) from six subjects were treated with a cocoa extract to analyze the mRNA levels of the DNA methyltransferases (DNMTs), methylenetetrahydrofolate reductase (MTHFR), and methionine synthase reductase (MTRR) genes. Cocoa consumption significantly reduced the DNA methylation levels (2.991±0.366 vs. 3.909±0.380, p<0.001). Additionally, we found an association between the cocoa effects on DNA methylation and three polymorphisms located in the MTHFR, MTRR, and DNMT3B genes. Furthermore, in PBMCs, the cocoa extract significantly lowered the mRNA levels of the DNMTs, MTHFR, and MTRR. Our study demonstrates for the first time that the consumption of cocoa decreases the global DNA methylation of peripheral leukocytes in humans with cardiovascular risk factors. In vitro experiments with PBMCs suggest that cocoa may exert this effect partially via the down-regulation of DNMTs, MTHFR and MTRR, which are key genes involved in this epigenetic process. Trial Registration Clinicaltrials.gov NCT00511420 and NCT00502047

Slc27a2 expression in peripheral blood mononuclear cells as a molecular marker for overweight development

Background:Peripheral blood mononuclear cells (PBMC) can be collected easily and repeatedly. Their potential use to reflect the individuals biological status is increasingly explored. Obesity is becoming the most common health problem of the 21st century, being dietary intake an important determinant of this pathology and numerous chronic health conditions.Objective:The aim of this study is to identify PBMC genes involved in energy homeostasis, which could be good markers of overweight development.Design:Using whole-genome microarray analysis, we evaluated the gene expression in PBMC of normoweight and diet-induced obese (cafeteria-fed) Wistar rats.Results:Microarray analysis showed 566 genes differentially expressed between normoweight and cafeteria-fed rats. Of these, 35 genes were particularly involved in energy homeostasis. The gene with the biggest fold change was the ‘solute carrier family 27 (fatty acid transporter), member 2’ (slc27a2), which is implicated in lipid biosynthesis and fatty acid degradation. Scl27a2 was 33-fold overexpressed in cafeteria-fed rats compared with normoweight rats. This result was confirmed by quantitative PCR, although the overexpression was smaller (sixfold). Moreover, the increase in slc27a2 expression in PBMC of cafeteria-fed rats from 2 to 6 months of age paralleled the increase in body weight.Conclusion:The progressive overexpression of slc27a2 in PBMC of cafeteria-fed rats as the body weight increases suggests this gene as an early marker of overweight development related to the intake of a hyperlipidic diet.

Effects of a post-weaning cafeteria diet in young rats: metabolic syndrome, reduced activity and low anxiety-like behaviour.

Among adolescents, overweight, obesity and metabolic syndrome are rapidly increasing in recent years as a consequence of unhealthy palatable diets. Animal models of diet-induced obesity have been developed, but little is known about the behavioural patterns produced by the consumption of such diets. The aim of the present study was to determine the behavioural and biochemical effects of a cafeteria diet fed to juvenile male and female rats, as well as to evaluate the possible recovery from these effects by administering standard feeding during the last week of the study. Two groups of male and female rats were fed with either a standard chow diet (ST) or a cafeteria (CAF) diet from weaning and for 8 weeks. A third group of males (CAF withdrawal) was fed with the CAF diet for 7 weeks and the ST in the 8th week. Both males and females developed metabolic syndrome as a consequence of the CAF feeding, showing overweight, higher adiposity and liver weight, increased plasma levels of glucose, insulin and triglycerides, as well as insulin resistance, in comparison with their respective controls. The CAF diet reduced motor activity in all behavioural tests, enhanced exploration, reduced anxiety-like behaviour and increased social interaction; this last effect was more pronounced in females than in males. When compared to animals only fed with a CAF diet, CAF withdrawal increased anxiety in the open field, slightly decreased body weight, and completely recovered the liver weight, insulin sensitivity and the standard levels of glucose, insulin and triglycerides in plasma. In conclusion, a CAF diet fed to young animals for 8 weeks induced obesity and metabolic syndrome, and produced robust behavioural changes in young adult rats, whereas CAF withdrawal in the last week modestly increased anxiety, reversed the metabolic alterations and partially reduced overweight.

Retinol-binding protein 4 and nicotinamide phosphoribosyltransferase/visfatin in rat obesity models.

Retinol-binding protein 4 (RBP4) and nicotinamide phosphoribosyltransferase/visfatin (Nampt/visfatin) are adipocyte-secreted proteins (adipokines) whose relevance to the metabolic syndrome and regulation in obesity remain controversial. Here, we tested the hypothesis that adipose tissue expression and circulating levels of these two adipokines are elevated in obesity by analyzing their changes in both a genetic and a diet-induced model of obesity in the rat (obese FA/ FA Zucker rats and Wistar rats fed a cafeteria diet, respectively). Compared with lean controls, obese FA/ FA rats were hyperleptinemic, hyperinsulinemic, and insulin resistant and had reduced RBP4 serum levels and mRNA levels in adipose depots, unchanged Nampt/visfatin serum levels, and reduced Nampt/visfatin mRNA levels selectively in the inguinal adipose depot. Cafeteria diet-induced obesity resulted in increased fed blood glucose levels, a variable degree of insulin resistance, unchanged serum Nampt/visfatin and RBP4 levels, and reduced mRNA levels of both adipokines in several adipose depots. Hence, increases in RBP4 or Nampt/visfatin do not accompany obesity and insulin resistance in the models examined.