Early biomarkers identified in a rat model of a healthier phenotype based on early postnatal dietary intervention may predict the response to an obesogenic environment in adulthood

KLB and NOX4 expression levels as potential blood-based transcriptional biomarkers of physical activity in children

Insufficient physical activity (PA) in children is considered one of the major contributors to obesity and cardiometabolic complications later in life. Although regular exercise may contribute to disease prevention and health promotion, reliable early biomarkers are required to objectively discern people performing low PA from those who exercise enough. Here, we aimed to identify potential transcript-based biomarkers through the analysis of a whole-genome microarray in peripheral blood cells (PBC) from physically less active (n = 10) comparing with more active (n = 10) children. A set of genes differentially expressed (p < 0.01, Limma test) in less physically active children were identified, including the down-regulation of genes related to cardiometabolic benefits and improved skeletal function (KLB, NOX4, and SYPL2), and the up-regulation of genes whose elevated expression levels are associated with metabolic complications (IRX5, UBD, and MGP). The analysis of the enriched pathways significantly affected by PA levels were those associated with protein catabolism, skeletal morphogenesis, and wound healing, among others, which may suggest a differential impact of low PA on these processes. Microarray analysis comparing children according to their usual PA has revealed potential PBC transcript-based biomarkers that may be useful in early discerning children expending high sedentary time and its associated negative consequences.

Low protein diet during lactation programs hepatic metabolism in adult male and female rats

The liver is an essential regulator of energy metabolism, and its function can be disrupted by nutritional alterations. Since liver development continues during breastfeeding nutritional challenges during this period predispose patients to diseases throughout life. A maternal protein-restricted (PR) diet during lactation promotes reductions in the body weight, adiposity, and plasma glucose and insulin, leptin resistance and an increase in corticosterone and catecholamines in adult male rat offspring. Here, we investigated hepatic metabolism in the offspring (both sexes) of PR (8% protein diet during lactation) and control (23% protein diet) dams. Both male and female offspring were evaluated at 6 months of age. PR males had no liver steatosis and manifested a reduction in lipids in hepatocytes adjacent to the vasculature. These animals had lower levels of esterified cholesterol in hepatocytes, suggesting higher biliary excretion, unchanged glycolysis and gluconeogenesis, and lower contents of the markers of mitochondrial redox balance and endoplasmic reticulum (ER) stress response and estrogen receptor alpha. PR females showed normal hepatic morphology associated with higher uptake of cholesterol esters, normal glycolysis and gluconeogenesis, and lower ER stress parameters without changes in the key markers of the redox balance. Additionally, these animals had lower content of estrogen receptor alpha and higher content of androgen receptor. The maternal PR diet during lactation did not program hepatic lipid accumulation in the adult progeny. However, several repair homeostasis pathways were altered in males and females, possibly compromising maintenance of normal liver function.

Implementation of a healthy diet to lactating rats attenuates the early detrimental programming effects in the offspring born to obese dams. Putative relationship with milk hormone levels

Lactation is a critical period of development and alterations in milk composition due to maternal diet or status may affect infant growth. We aimed to evaluate in rats whether improving maternal nutrition during lactation attenuates early imprinted adverse metabolic effects in the offspring born to obese dams. Three groups were studied: Control (C) dams, fed with standard diet; Western diet (WD) dams, fed with WD one month prior to gestation and during gestation and lactation; and Reversion (Rev) dams, fed as WD-dams, but moved to a standard diet during lactation. Macronutrient content, insulin, leptin and adiponectin levels were determined in milk. Phenotypic traits and circulating parameters in dams and their offspring were determined throughout lactation. Results showed that, at weaning, WD-dams displayed lower body weight and greater plasma insulin and non-esterified fatty acids levels than C-dams, and signs of hepatic steatosis. Milk from WD-dams showed lower protein content and insulin, leptin, and adiponectin levels during the entire or the late lactation. Rev-dams retained excess body fat content, but milk composition and most circulating parameters were not different from controls at late lactation and showed higher leptin mRNA levels in mammary gland than WD-dams. The offspring of WD-dams, but not that of Rev-dams, displayed higher body weight, adiposity, and circulating leptin and glucose levels than controls at weaning. In conclusion, dietary improvement during lactation prevents early adverse effects in offspring associated with maternal intake of an obesogenic diet, that may be related with the normalization of milk hormone levels.

Myo-Inositol Supplementation in Suckling Rats Protects against Adverse Programming Outcomes on Hypothalamic Structure Caused by Mild Gestational Calorie Restriction, Partially Comparable to Leptin Effects

We studied whether myo-inositol supplementation throughout lactation, alone and combined with leptin, may reverse detrimental effects on hypothalamic structure and function caused by gestational calorie gestation (CR) in rats. Candidate early transcript-based biomarkers of metabolic health in peripheral blood mononuclear cells (PBMC) were also studied. Offspring of dams exposed to 25% gestational CR and supplemented during lactation with physiological doses of leptin (CR-L), myo-inositol (CR-M), the combination (CR-LM), or the vehicle (CR-V) as well as control rats (CON-V) were followed and sacrificed at postnatal day 25. Myo-inositol and the combination increased the number of neurons in arcuate nucleus (ARC) (only in females) and paraventricular nucleus, and myo-inositol (alone) restored the number of αMSH⁺ neurons in ARC. Hypothalamic mRNA levels of Lepr in CR-M and Insr in CR-M and CR-LM males were higher than in CR-V and CON-V, respectively. In PBMC, increased expression levels of Lrp11 and Gls in CR-V were partially normalized in all supplemented groups (but only in males for Gls). Therefore, myo-inositol supplementation throughout lactation, alone and combined with leptin, reverts programmed alterations by fetal undernutrition on hypothalamic structure and gene expression of potential early biomarkers of metabolic health in PBMC, which might be attributed, in part, to increased leptin sensitivity.

Lactation as a programming window for metabolic syndrome

The concept of developmental origins of health and disease (DOHaD) was initially supported by the low birth weight and higher risk of developing cardiovascular disease in adult life, caused by nutrition restriction during foetal development. However, other programming windows have been recognized in the last years, namely lactation, infancy, adolescence and even preconception. Although the concept has been developed in order to study the impact of foetal calorie restriction in adult life, it is now recognized that maternal overweight during programming windows is also harmful to the offspring. This article explores and summarizes the current knowledge about the impact of maternal obesity and obesogenic diets during lactation in the metabolic programming towards the development of metabolic syndrome in the adult life. The impact of maternal obesity and obesogenic diets in milk quality is discussed, including the alterations in specific micro and macronutrients, as well as the impact of such alterations in the development of metabolic syndrome-associated features in the newborn, such as insulin resistance and adiposity. Moreover, the impact of milk quality and formula feeding in infants' gut microbiota, immune system maturation and in the nutrient-sensing mechanisms, namely those related to gut hormones and leptin, are also discussed under the current knowledge.

Association of the PNPLA2, SCD1 and Leptin Expression with Fat Distribution in Liver and Adipose Tissue From Obese Subjects

The expansion of adipose tissue is regulated by insulin and leptin through sterol regulatory element-binding protein-1c (SREBP-1c), up-regulating lipogenesis in tissues by Stearoylcoenzyme A desaturase 1 (SCD1) enzyme, while adipose triglyceride lipase (ATGL) enzyme is key in lipolysis. The research objective was to evaluate the expression of Sterol Regulatory Element Binding Transcription Factor 1 (SREBF1), SCD1, Patatin Like Phospholipase Domain Containing 2 (PNPLA2), and leptin (LEP) genes in hepatic-adipose tissue, and related them with the increment and distribution of fat depots of individuals without insulin resistance. Thirty-eight subjects undergoing elective cholecystectomy with liver and adipose tissue biopsies (subcutaneous-omental) are included. Tissue gene expression was assessed by qPCR and biochemical parameters determined. Individuals are classified according to the body mass index, classified as lean (control group, n=12), overweight (n=11) and obesity (n=15). Abdominal adiposity was determined by anthropometric and histopathological study of the liver. Increased SCD1 expression in omental adipose tissue (p=0.005) and PNPLA2 in liver (p=0.01) were found in the obesity group. PNPLA2 decreased expression in subcutaneous adipose tissue was significant in individuals with abdominal adiposity (p=0.017). Anthropometric parameters positively correlated with liver PNPLA2 and the expression of liver PNPLA2 with serum leptin. SCD1 increased levels may represent lipid storage activity in omental adipose tissue. Liver PNPLA2 increased expression could function as a primary compensatory event of visceral fat deposits associated to the leptin hormone related to the increase of adipose tissue.

Gender-Associated Impact of Early Leucine Supplementation on Adult Predisposition to Obesity in Rats

Early nutrition plays an important role in development and may constitute a relevant contributor to the onset of obesity in adulthood. The aim of this study was to evaluate the long-term impact of maternal leucine (Leu) supplementation during lactation on progeny in rats. A chow diet, supplemented with 2% Leu, was supplied during lactation (21 days) and, from weaning onwards, was replaced by a standard chow diet. Then, at adulthood (6 months of age), this was replaced with hypercaloric diets (either with high-fat (HF) or high-carbohydrate (HC) content), for two months, to induce obesity. Female offspring from Leu-supplemented dams showed higher increases in body weight and in body fat (62%) than their respective controls; whereas males were somehow protected (15% less fat than the corresponding controls). This profile in Leu-females was associated with altered neuronal architecture at the paraventricular nucleus (PVN), involving neuropeptide Y (NPY) fibers and impaired expression of neuropeptides and factors of the mTOR signaling pathway in the hypothalamus. Interestingly, leptin and adiponectin expression in adipose tissue at weaning and at the time before the onset of obesity could be defined as early biomarkers of metabolic disturbance, predisposing towards adult obesity under the appropriate environment.

Offspring predisposition to obesity due to maternal-diet-induced obesity in rats is preventable by dietary normalization before mating

SCOPE

We studied in rats whether the expected detrimental effects in offspring associated to maternal dietary obesity may be reverted by obesogenic diet removal 1 month before mating.

METHODS AND RESULTS

Female rats were fed a cafeteria diet (CD) from days 10 to 100 and then a standard diet (SD) (postcafeteria rats). One month after CD removal, postcafeteria rats and a group of SD-fed female rats (controls) were mated with males. At weaning, offspring were fed SD and followed until 4 months old. CD was effective at inducing obesity in dams. Its removal led to a reduction in body weight, although, after 30 days, rats retained excess body weight and fat than controls. During lactation, postcafeteria dams showed greater body fat, and higher leptin and adiponectin levels in milk than controls. From 2 months of life, offspring of postcafeteria dams displayed lower body weight than controls, with no differences in the percentage of fat, homeostatic model assessment for insulin resistance, or circulating parameters.

CONCLUSION

Removal of CD in obese rats before gestation, although without complete reversion of body weight excess, may prevent the expected detrimental effects in offspring associated to an excess fat accumulation in adulthood and the related metabolic disturbances.

White adipose tissue reference network: a knowledge resource for exploring health-relevant relations

Optimal health is maintained by interaction of multiple intrinsic and environmental factors at different levels of complexity-from molecular, to physiological, to social. Understanding and quantification of these interactions will aid design of successful health interventions. We introduce the reference network concept as a platform for multi-level exploration of biological relations relevant for metabolic health, by integration and mining of biological interactions derived from public resources and context-specific experimental data. A White Adipose Tissue Health Reference Network (WATRefNet) was constructed as a resource for discovery and prioritization of mechanism-based biomarkers for white adipose tissue (WAT) health status and the effect of food and drug compounds on WAT health status. The WATRefNet (6,797 nodes and 32,171 edges) is based on (1) experimental data obtained from 10 studies addressing different adiposity states, (2) seven public knowledge bases of molecular interactions, (3) expert's definitions of five physiologically relevant processes key to WAT health, namely WAT expandability, Oxidative capacity, Metabolic state, Oxidative stress and Tissue inflammation, and (4) a collection of relevant biomarkers of these processes identified by BIOCLAIMS ( http://bioclaims.uib.es ). The WATRefNet comprehends multiple layers of biological complexity as it contains various types of nodes and edges that represent different biological levels and interactions. We have validated the reference network by showing overrepresentation with anti-obesity drug targets, pathology-associated genes and differentially expressed genes from an external disease model dataset. The resulting network has been used to extract subnetworks specific to the above-mentioned expert-defined physiological processes. Each of these process-specific signatures represents a mechanistically supported composite biomarker for assessing and quantifying the effect of interventions on a physiological aspect that determines WAT health status. Following this principle, five anti-diabetic drug interventions and one diet intervention were scored for the match of their expression signature to the five biomarker signatures derived from the WATRefNet. This confirmed previous observations of successful intervention by dietary lifestyle and revealed WAT-specific effects of drug interventions. The WATRefNet represents a sustainable knowledge resource for extraction of relevant relationships such as mechanisms of action, nutrient intervention targets and biomarkers and for assessment of health effects for support of health claims made on food products.