Maternal protein restriction leads to enhanced hepatic gluconeogenic gene expression in adult male rat offspring due to impaired expression of the liver X receptor

Mitochondrial dysfunction and epigenetics underlying the link between early-life nutrition and non-alcoholic fatty liver disease

Early-life malnutrition plays a critical role in foetal development and predisposes to metabolic diseases later in life, according to the concept of 'developmental programming'. Different types of early nutritional imbalance, including undernutrition, overnutrition and micronutrient deficiency, have been related to long-term metabolic disorders. Accumulating evidence has demonstrated that disturbances in nutrition during the period of preconception, pregnancy and primary infancy can affect mitochondrial function and epigenetic mechanisms. Moreover, even though multiple mechanisms underlying non-alcoholic fatty liver disease (NAFLD) have been described, in the past years, special attention has been given to mitochondrial dysfunction and epigenetic alterations. Mitochondria play a key role in cellular metabolic functions. Dysfunctional mitochondria contribute to oxidative stress, insulin resistance and inflammation. Epigenetic mechanisms have been related to alterations in genes involved in lipid metabolism, fibrogenesis, inflammation and tumorigenesis. In accordance, studies have reported that mitochondrial dysfunction and epigenetics linked to early-life nutrition can be important contributing factors in the pathogenesis of NAFLD. In this review, we summarise the current understanding of the interplay between mitochondrial dysfunction, epigenetics and nutrition during early life, which is relevant to developmental programming of NAFLD.

Normalization of maternal adiponectin in obese pregnant mice prevents programming of impaired glucose metabolism in adult offspring

Infants born to obese mothers have a greater risk for childhood obesity and insulin resistance. However, the underlying biological mechanism remains elusive, which constitutes a significant roadblock for developing specific prevention strategies. Maternal adiponectin levels are lower in obese pregnant women, which is linked with increased placental nutrient transport and fetal overgrowth. We have previously reported that adiponectin supplementation to obese dams during the last four days of pregnancy prevented the development of obesity, glucose intolerance, muscle insulin resistance, and fatty liver in three months old offspring. In the present study, we tested the hypothesis that 6-9-month-old offspring of obese dams show glucose intolerance associated with muscle insulin resistance and mitochondrial dysfunction and that normalization of maternal adiponectin in obese pregnant mice prevents the development of this phenotype in the offspring. Male and female offspring of obese mice exhibited in vivo glucose intolerance and insulin resistance at 6 and 9 months of age. In gastrocnemius muscles ex vivo, male and female offspring of obese dams showed reduced phosphorylation of insulin receptor substrate 1^Tyr-608 , Akt^Thr-308 , and decreased Glut4 plasma membrane translocation upon insulin stimulation. These metabolic abnormalities in offspring born to obese mice were largely prevented by normalization of maternal adiponectin levels in late pregnancy. We provide evidence that low circulating maternal adiponectin is a critical mechanistic link between maternal obesity and the development of metabolic disease in offspring. Strategies aimed at improving maternal adiponectin levels may prevent long-term metabolic dysfunction in offspring of obese mothers.

Human Milk Lipids Induce Important Metabolic and Epigenetic Changes in Neonates

Lipids are a major source of energy during the fetal/neonatal period. Most are received from the mother, transplacentally during the intrauterine period or via maternal milk after birth. However, in addition to the known nutritional roles, lipids are now known to bind a variety of cellular receptors to regulate specific patterns in metabolism and gene expression. The expression of these receptors is regulated by various genetic and environmental stimuli, and ligation can activate positive-feedback loops in the expression and the activity of downstream signaling pathways. The authors summarize the role of lipid ligands, cognate receptors, epigenetic regulation, and downstream signaling.

Maternal Protein Restriction and Post-Weaning High-Fat Feeding Alter Plasma Amino Acid Profiles and Hepatic Gene Expression in Mice Offspring

Maternal undernutrition during pregnancy is closely associated with epigenetic changes in the child, and it affects the development of obesity throughout the child’s life. Here, we investigate the effect of fetal low protein exposure and post-weaning high-fat consumption on plasma amino acid profiles and hepatic gene expression. Mother C57BL/6J mice were fed a 20% (CN) or 9% (LP) casein diet during pregnancy. After birth, the male offspring of both these groups were fed a high-fat diet (HF) from 6 to 32 weeks. At 32 weeks, the final body weight between the two groups remained unchanged, but the LP-HF group showed markedly higher white fat weight and plasma leptin levels. The LP-HF group exhibited a significant increase in the concentrations of isoleucine, leucine, histidine, phenylalanine, serine, and tyrosine. However, no differences were observed in the lipid content in the liver. According to the hepatic gene expression analysis, the LP-HF group significantly upregulated genes involved in the chromatin modification/organization pathways. Thus, maternal low protein and a post-weaning high-fat environment contributed to severe obesity states and changes in gene expression related to hepatic chromatin modification in offspring. These findings provide novel insights for the prevention of lifestyle-related diseases at the early life stage.

Maternal curcumin supplementation ameliorates placental function and fetal growth in mice with intrauterine growth retardation†

Intrauterine growth retardation (IUGR) is a serious reproductive problem in humans. The objective of this study was to investigate the effects of daily maternal curcumin supplementation during pregnancy on placental function and fetal growth in a mouse model of IUGR fed the low-protein (LP) diet. Pregnant mice were divided into four groups: (1) normal protein (19% protein) diet (NP); (2) LP (8% protein) diet; (3) LP diet + 100 mg/kg curcumin (LPL); (4) LP diet +400 mg/kg curcumin (LPH). The results showed that the LP group decreased fetal weight, placental weight, placental efficiency, serum progesterone level, placental glutathione peroxidase activity activity, blood sinusoids area, and antioxidant gene expression of placenta. In addition, in comparison with the NP group, LP diet increased serum corticosterone level, placental malondialdehyde content, and apoptotic index. Daily curcumin administration decreased the placental apoptosis, while it increased placental efficiency, placental redox balance, blood sinusoids area, and antioxidant-related protein expression in fetal liver. The antioxidant gene expression of placenta and fetal liver was normalized to the NP level after curcumin administration. In conclusion, daily curcumin supplementation could improve maternal placental function and fetal growth in mice with IUGR.

The Role of Cellular Stress in Intrauterine Growth Restriction and Postnatal Dysmetabolism

Disruption of the in utero environment can have dire consequences on fetal growth and development. Intrauterine growth restriction (IUGR) is a pathological condition by which the fetus deviates from its expected growth trajectory, resulting in low birth weight and impaired organ function. The developmental origins of health and disease (DOHaD) postulates that IUGR has lifelong consequences on offspring well-being, as human studies have established an inverse relationship between birth weight and long-term metabolic health. While these trends are apparent in epidemiological data, animal studies have been essential in defining the molecular mechanisms that contribute to this relationship. One such mechanism is cellular stress, a prominent underlying cause of the metabolic syndrome. As such, this review considers the role of oxidative stress, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and inflammation in the pathogenesis of metabolic disease in IUGR offspring. In addition, we summarize how uncontrolled cellular stress can lead to programmed cell death within the metabolic organs of IUGR offspring.

Personalized Nutrition Approach in Pregnancy and Early Life to Tackle Childhood and Adult Non-Communicable Diseases

The development of childhood and adult non-communicable diseases (NCD) is associated with environmental factors, starting from intrauterine life. A new theory finds the roots of epigenetic programming in parental gametogenesis, continuing during embryo development, fetal life, and finally in post-natal life. Maternal health status and poor nutrition are widely recognized as implications in the onset of childhood and adult diseases. Early nutrition, particularly breastfeeding, also plays a primary role in affecting the health status of an individual later in life. A poor maternal diet during pregnancy and lack of breastfeeding can cause a nutrient deficiency that affects the gut microbiota, and acts as a cofactor for many pathways, impacting the epigenetic controls and transcription of genes involved in the metabolism, angiogenesis, and other pathways, leading to NCDs in adult life. Both maternal and fetal genetic backgrounds also affect nutrient adsorption and functioning at the cellular level. This review discusses the most recent evidence on maternal nutrition and breastfeeding in the development of NCD, the potentiality of the omics technologies in uncovering the molecular mechanisms underlying it, with the future prospective of applying a personalized nutrition approach to prevent and treat NCD from the beginning of fetal life.

Molecular mechanisms governing offspring metabolic programming in rodent models of in utero stress

The results of different human epidemiological datasets provided the impetus to introduce the now commonly accepted theory coined as 'developmental programming', whereby the presence of a stressor during gestation predisposes the growing fetus to develop diseases, such as metabolic dysfunction in later postnatal life. However, in a clinical setting, human lifespan and inaccessibility to tissue for analysis are major limitations to study the molecular mechanisms governing developmental programming. Subsequently, studies using animal models have proved indispensable to the identification of key molecular pathways and epigenetic mechanisms that are dysregulated in metabolic organs of the fetus and adult programmed due to an adverse gestational environment. Rodents such as mice and rats are the most used experimental animals in the study of developmental programming. This review summarises the molecular pathways and epigenetic mechanisms influencing alterations in metabolic tissues of rodent offspring exposed to in utero stress and subsequently programmed for metabolic dysfunction. By comparing molecular mechanisms in a variety of rodent models of in utero stress, we hope to summarise common themes and pathways governing later metabolic dysfunction in the offspring whilst identifying reasons for incongruencies between models so to inform future work. With the continued use and refinement of such models of developmental programming, the scientific community may gain the knowledge required for the targeted treatment of metabolic diseases that have intrauterine origins.

The Role of Nutrition in the Prevention and Intervention of Type 2 Diabetes

Type 2 diabetes (T2D) is a rapidly growing epidemic, which leads to increased mortality rates and health care costs. Nutrients (namely, carbohydrates, fat, protein, mineral substances, and vitamin), sensing, and management are central to metabolic homeostasis, therefore presenting a leading factor contributing to T2D. Understanding the comprehensive effects and the underlying mechanisms of nutrition in regulating glucose metabolism and the interactions of diet with genetics, epigenetics, and gut microbiota is helpful for developing new strategies to prevent and treat T2D. In this review, we discuss different mechanistic pathways contributing to T2D and then summarize the current researches concerning associations between different nutrients intake and glucose homeostasis. We also explore the possible relationship between nutrients and genetic background, epigenetics, and metagenomics in terms of the susceptibility and treatment of T2D. For the specificity of individual, precision nutrition depends on the person’s genotype, and microbiota is vital to the prevention and intervention of T2D.

Perinatal protein restriction with postnatal catch-up growth leads to elevated p66Shc and mitochondrial dysfunction in the adult rat liver

Epidemiological data suggest an inverse relationship between birth weight and long-term metabolic deficits, which is exacerbated by postnatal catch-up growth. We have previously demonstrated that rat offspring subject to maternal protein restriction (MPR) followed by catch-up growth exhibit impaired hepatic function and ER stress. Given that mitochondrial dysfunction is associated with various metabolic pathologies, we hypothesized that altered expression of p66Shc, a gatekeeper of oxidative stress and mitochondrial function, contributes to the hepatic defects observed in MPR offspring. To test this hypothesis, pregnant Wistar rats were fed a control (20% protein) diet or an isocaloric low protein (8%; LP) diet throughout gestation. Offspring born to control dams received a control diet in postnatal life, while MPR offspring remained on a LP diet (LP1) or received a control diet post weaning (LP2) or at birth (LP3). At four months, LP2 offspring exhibited increased protein abundance of both p66Shc and the cis-trans isomerase PIN1. This was further associated with aberrant markers of oxidative stress (i.e. elevated 4-HNE, SOD1 and SOD2, decreased catalase) and aerobic metabolism (i.e., increased phospho-PDH and LDHa, decreased complex II, citrate synthase and TFAM). We further demonstrated that tunicamycin-induced ER stress in HepG2 cells led to increased p66Shc protein abundance, suggesting that ER stress may underlie the programmed effects observed in vivo. In summary, because these defects are exclusive to adult LP2 offspring, it is possible that a low protein diet during perinatal life, a period of liver plasticity, followed by catch-up growth is detrimental to long-term mitochondrial function.

Obesity during pregnancy results in maternal intestinal inflammation, placental hypoxia, and alters fetal glucose metabolism at mid-gestation

We investigated whether diet-induced changes in the maternal intestinal microbiota were associated with changes in bacterial metabolites and their receptors, intestinal inflammation, and placental inflammation at mid-gestation (E14.5) in female mice fed a control (17% kcal fat, n = 7) or a high-fat diet (HFD 60% kcal fat, n = 9; ad libitum) before and during pregnancy. Maternal diet-induced obesity (mDIO) resulted in a reduction in maternal fecal short-chain fatty acid producing Lachnospiraceae, lower cecal butyrate, intestinal antimicrobial peptide levels, and intestinal SCFA receptor Ffar3, Ffar2 and Hcar2 transcript levels. mDIO increased maternal intestinal pro-inflammatory NFκB activity, colonic CD3⁺ T cell number, and placental inflammation. Maternal obesity was associated with placental hypoxia, increased angiogenesis, and increased transcript levels of glucose and amino acid transporters. Maternal and fetal markers of gluconeogenic capacity were decreased in pregnancies complicated by obesity. We show that mDIO impairs bacterial metabolite signaling pathways in the mother at mid-gestation, which was associated with significant structural changes in placental blood vessels, likely as a result of placental hypoxia. It is likely that maternal intestinal changes contribute to adverse maternal and placental adaptations that, via alterations in fetal hepatic glucose handling, may impart increased risk of metabolic dysfunction in offspring.

Epigenetic Modifications Induced by Nutrients in Early Life Phases: Gender Differences in Metabolic Alteration in Adulthood

Metabolic chronic diseases, also named noncommunicable diseases (NCDs), are considered multifactorial pathologies, which are dramatically increased during the last decades. Noncommunicable diseases such as cardiovascular diseases, obesity, diabetes mellitus, cancers, and chronic respiratory diseases markedly increase morbidity, mortality, and socioeconomic costs. Moreover, NCDs induce several and complex clinical manifestations that lead to a gradual deterioration of health status and quality of life of affected individuals. Multiple factors are involved in the development and progression of these diseases such as sedentary behavior, smoking, pollution, and unhealthy diet. Indeed, nutrition has a pivotal role in maintaining health, and dietary imbalances represent major determinants favoring chronic diseases through metabolic homeostasis alterations. In particular, it appears that specific nutrients and adequate nutrition are important in all periods of life, but they are essential during specific times in early life such as prenatal and postnatal phases. Indeed, epidemiologic and experimental studies report the deleterious effects of an incorrect nutrition on health status several decades later in life. During the last decade, a growing interest on the possible role of epigenetic mechanisms as link between nutritional imbalances and NCDs development has been observed. Finally, because of the pivotal role of the hormones in fat, carbohydrate, and protein metabolism regulation throughout life, it is expected that any hormonal modification of these processes can imbalance metabolism and fat storage. Therefore, a particular interest to several chemicals able to act as endocrine disruptors has been recently developed. In this review, we will provide an overview and discuss the epigenetic role of some specific nutrients and chemicals in the modulation of physiological and pathological mechanisms.

Sex Dependent Dysregulation of Hepatic Glucose Production in Lean Type 2 Diabetic Rats

We have characterized a lean type 2 diabetic rat model by gestational low protein programming. We aimed to identify if the regulation of hepatic glucose production (HGP) via gluconeogenesis and glycogenolysis is affected and if there are any sex differences. Fasting (6-7 months old) type 2 diabetic rats received 2H2O followed by a primed constant rate infusion of [6,6-2H2] glucose. Blood samples were drawn during steady states after 4 h of fasting and following a euglycemic hyperinsulinemic clamp. HGP and the fraction of glucose derived from gluconeogenesis under fasting and euglycemic states were measured from steady state glucose enrichments after the infusion of [6,6-2H2]glucose and 2H2O tracers. Glycogenolysis was determined by calculating the difference between total HGP and gluconeogenesis rates. Hepatic gene expression of enzymes involved in HGP were quantified using qPCR. HGP rates was similar during fasting in both groups and sexes. However, under simulated fed condition, HGP rate was suppressed in controls but not in type 2 diabetic rats. They also showed inefficient HGP suppression in a simulated fed state. Differential analysis showed that suppression of both gluconeogenesis and glycogenolysis under simulated fed state was affected in these low protein programmed type 2 diabetic rats. These effects were greater in females when compared to males. Further, key genes involved in these processes like G6Pase, Pepck, pyruvate carboxylase, and glycogen phosphorylase in liver were dysregulated. Our data shows impaired suppression of HGP via gluconeogenesis and glycogenolysis in type 2 diabetic rats with greater effects on females.

Developmental origins of health and disease: current knowledge and potential mechanisms

Epidemiologic and clinical research has provided a large body of evidence supporting the developmental origins of health and disease (DOHaD), but there has been a relative dearth of mechanistic studies in humans due to the complexity of working with large, longitudinal cohorts. Nonetheless, animal models of undernutrition have provided substantial evidence for the potential epigenetic, metabolic, and endocrine mechanisms behind DOHaD. Furthermore, recent research has explored the interaction between the environment and the gastrointestinal system by investigating how the gut microbial ecology may impact the capacity for nutrient processing and absorption in a manner that may limit growth. This review presents a summary of current research that supports the concept of DOHaD, as well as potential mechanisms and interactions that explain how nutrition in utero and during early childhood influences lifelong health.

Effect of L-arginine supplementation on the hepatic phosphatidylinositol 3-kinase signaling pathway and gluconeogenic enzymes in early intrauterine growth-restricted rats

The present study aimed to investigate the response of the phosphatidylinositol 3-kinase (PI3K) signaling pathway and gluconeogenic enzymes in intrauterine growth-restricted rats to dietary L-arginine (L-Arg) supplementation during the lactation period early in life. Pregnant Sprague-Dawley rats were randomly divided into a control group (CON), an intrauterine growth restriction group (IUGR) and an L-Arg group (LA). The pregnant rats in the CON group were fed a 21% protein diet, and those in the IUGR and LA groups were fed a 10% low protein diet, and all rats were fed a 21% protein diet after delivery. Water was available ad libitum to the pregnant rats during the 21-day lactation period, and the water provided to the LA group included 200 mg/kg/day L-Arg. Blood glucose, serum insulin, homeostasis model of assessment for insulin resistance (HOMA-IR), PI3K and protein kinase B (PKB) protein expression, and phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G-6-Pase) mRNA expression in the offspring rats were measured postnatally at 1, 3 and 8 weeks. No significant difference in blood glucose, serum insulin and HOMA-IR were identified at any time point among the three groups. PI3K and PKB expression was lower in the IUGR group offspring compared with that in the CON group offspring, but both were increased by dietary L-Arg supplementation. PEPCK mRNA and G-6-Pase mRNA expression levels in the offspring of the IUGR group were higher compared with those in the CON group but were downregulated following L-Arg supplementation. These results suggest that dietary L-Arg supplementation during the early lactation period promoted catch-up growth and reversed abnormalities in hepatic insulin signaling and gene expression of gluconeogenic enzymes in IUGR offspring rats.

Guide for Current Nutrigenetic, Nutrigenomic, and Nutriepigenetic Approaches for Precision Nutrition Involving the Prevention and Management of Chronic Diseases Associated with Obesity

Chronic diseases, including obesity, are major causes of morbidity and mortality in most countries. The adverse impacts of obesity and associated comorbidities on health remain a major concern due to the lack of effective interventions for prevention and management. Precision nutrition is an emerging therapeutic approach that takes into account an individual's genetic and epigenetic information, as well as age, gender, or particular physiopathological status. Advances in genomic sciences are contributing to a better understanding of the role of genetic variants and epigenetic signatures as well as gene expression patterns in the development of diverse chronic conditions, and how they may modify therapeutic responses. This knowledge has led to the search for genetic and epigenetic biomarkers to predict the risk of developing chronic diseases and personalizing their prevention and treatment. Additionally, original nutritional interventions based on nutrients and bioactive dietary compounds that can modify epigenetic marks and gene expression have been implemented. Although caution must be exercised, these scientific insights are paving the way for the design of innovative strategies for the control of chronic diseases accompanying obesity. This document provides a number of examples of the huge potential of understanding nutrigenetic, nutrigenomic, and nutriepigenetic roles in precision nutrition.

Gestational Protein Restriction Impairs Glucose Disposal in the Gastrocnemius Muscles of Female Rats

Gestational low-protein (LP) diet causes hyperglycemia and insulin resistance in adult offspring, but the mechanism is not clearly understood. In this study, we explored the role of insulin signaling in gastrocnemius muscles of gestational LP-exposed female offspring. Pregnant rats were fed a control (20% protein) or an isocaloric LP (6%) diet from gestational day 4 until delivery. Normal diet was given to mothers after delivery and to pups after weaning until necropsy. Offspring were euthanized at 4 months, and gastrocnemius muscles were treated with insulin ex vivo for 30 minutes. Messenger RNA and protein levels of molecules involved in insulin signaling were assessed at 4 months. LP females were smaller at birth but showed rapid catchup growth by 4 weeks. Glucose tolerance test in LP offspring at 3 months showed elevated serum glucose levels (P < 0.01; glycemia Δ area under the curve 342 ± 28 in LP vs 155 ± 23 in controls, mmol/L * 120 minutes) without any change in insulin levels. In gastrocnemius muscles, LP rats showed reduced tyrosine phosphorylation of insulin receptor substrate 1 upon insulin stimulation due to the overexpression of tyrosine phosphatase SHP-2, but serine phosphorylation was unaffected. Furthermore, insulin-induced phosphorylation of Akt, glycogen synthase kinase (GSK)-3α, and GSK-3β was diminished in LP rats, and they displayed an increased basal phosphorylation (inactive form) of glycogen synthase. Our study shows that gestational protein restriction causes peripheral insulin resistance by a series of phosphorylation defects in skeletal muscle in a mechanism involving insulin receptor substrate 1, SHP-2, Akt, GSK-3, and glycogen synthase causing dysfunctional GSK-3 signaling and increased stored glycogen, leading to distorted glucose homeostasis.

Maternal Chromium Restriction Leads to Glucose Metabolism Imbalance in Mice Offspring through Insulin Signaling and Wnt Signaling Pathways

An adverse intrauterine environment, induced by a chromium-restricted diet, is a potential cause of metabolic disease in adult life. Up to now, the relative mechanism has not been clear. C57BL female mice were time-mated and fed either a control diet (CD), or a chromium-restricted diet (CR) throughout pregnancy and the lactation period. After weaning, some offspring continued the diet diagram (CD-CD or CR-CR), while other offspring were transferred to another diet diagram (CD-CR or CR-CD). At 32 weeks of age, glucose metabolism parameters were measured, and the liver from CR-CD group and CD-CD group was analyzed using a gene array. Quantitative real-time polymerase chain reaction (qPCR) and Western blot were used to verify the result of the gene array. A maternal chromium-restricted diet resulted in obesity, hyperglycemia, hyperinsulinemia, increased area under the curve (AUC) of glucose in oral glucose tolerance testing and homeostasis model assessment of insulin resistance (HOMA-IR). There were 463 genes that differed significantly (>1.5-fold change, p < 0.05) between CR-CD offspring (264 up-regulated genes, 199 down-regulated genes) and control offspring. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) analysis revealed that the insulin signaling pathway and Wnt signaling pathway were in the center of the gene network. Our study provides the first evidence that maternal chromium deficiency influences glucose metabolism in pups through the regulation of insulin signaling and Wnt signaling pathways.

Oxytocin, a main breastfeeding hormone, prevents hypertension acquired in utero: A therapeutics preview

Hypertension is a major risk factor for ischemic heart disease and stroke, leading causes of morbidity and death worldwide. Intrauterine growth restriction (IUGR), caused by an excess of glucocorticoid exposure to the fetus, produces an imbalance in oxidative stress altering many biochemical and epigenetic gene transcription processes exposing the fetus and neonate to the 'thrifty' phenotype and pervasive polymorphisms appearance damaging health, cognitive, and behavioral processes in later life. OT is a major regulator of oxidative stress radicals that plays a major role in neonatal maturation of the central nervous system and many peripheral tissues expressing oxytocin/oxytocin-receptor (OT/OTR) system in the early postnatal period. OT and OTR are damaged by IUGR and early stress. This review highlights the fact that hypertension is likely to be a legacy of preterm birth due to IUGR and failure to meet nutritional needs in early infancy when fed formula instead of breastfeeding or human milk.

Higher Hepatic miR-29 Expression in Undernourished Male Rats During the Postnatal Period Targets the Long-Term Repression of IGF-1

A nutritional mismatch in postnatal life of low birth weight offspring increases the risk of developing the metabolic syndrome. Moreover, this is associated with decreased hepatic Igf1 expression, leading to impaired growth and metabolism. Previously, we have demonstrated that the timing of nutritional restoration in perinatal life can differentially program hepatic gene expression. Although microRNAs also play an important role in silencing gene expression, to date, the impact of a nutritional mismatch in neonatal life on their long-term expression has not been evaluated. Given the complementarity of miR-29 to the 3' untranslated region of Igf1, we examined how protein restoration in maternal protein restriction rat offspring influences hepatic miR-29 and Igf1 expression in adulthood. Pregnant Wistar rats were designated into 1 of 4 dietary regimes: 20% protein (control), 8% protein during lactation only (LP-Lact), 8% protein during gestation only (LP1) or both (LP2). The steady-state expression of hepatic miR-29 mRNA significantly increased in LP2 offspring at postnatal day 21 and 130, and this was inversely related to hepatic Igf1 mRNA and body weight. Interestingly, this reciprocal association was stronger in LP-Lact offspring at postnatal day 21. Functional relevance of this in vivo relationship was evaluated by transfection of miR-29 mimics in neonatal Clone 9 rat hepatoma cells. Transfection with miR-29 suppressed Igf1 expression by 12 hours. Collectively, these findings implicate that nutritional restoration after weaning (post liver differentiation) in maternal protein restriction rat offspring fails to prevent long-term impaired growth, in part, due to miR-29 suppression of hepatic Igf1 expression.

Nutritional epigenetics with a focus on amino acids: implications for the development and treatment of metabolic syndrome

Recent findings from human and animal studies indicate that maternal undernutrition or overnutrition affects covalent modifications of the fetal genome and its associated histones that can be carried forward to subsequent generations. An adverse outcome of maternal malnutrition is the development of metabolic syndrome, which is defined as a cluster of disorders including obesity, hyperglycemia, hyperinsulinemia, hyperlipidemia, hypertension and insulin resistance. The transgenerational impacts of maternal nutrition are known as fetal programming, which is mediated by stable and heritable alterations of gene expression through covalent modifications of DNA and histones without changes in DNA sequences (namely, epigenetics). The underlying mechanisms include chromatin remodeling, DNA methylation (occurring at the 5'-position of cytosine residues within CpG dinucleotides), histone modifications (acetylation, methylation, phosphorylation, ubiquitination and sumoylation) and expression and activity of small noncoding RNAs. The enzymes catalyzing these reactions include S-adenosylmethionine-dependent DNA and protein methyltransferases, DNA demethylases, histone acetylase (lysine acetyltransferase), general control nonderepressible 5 (GCN5)-related N-acetyltransferase (a superfamily of acetyltransferase) and histone deacetylase. Amino acids (e.g., glycine, histidine, methionine and serine) and vitamins (B6, B12 and folate) play key roles in provision of methyl donors for DNA and protein methylation. Therefore, these nutrients and related metabolic pathways are of interest in dietary treatment of metabolic syndrome. Intervention strategies include targeting epigenetically disturbed metabolic pathways through dietary supplementation with nutrients (particularly functional amino acids and vitamins) to regulate one-carbon-unit metabolism, antioxidative reactions and gene expression, as well as protein methylation and acetylation. These mechanism-based approaches may effectively improve health and well-being of affected offspring.

Developmental regulation of key gluconeogenic molecules in nonhuman primates

Aberrant glucose regulation is common in preterm and full‐term neonates leading to short and long‐term morbidity/mortality; however, glucose metabolism in this population is understudied. The aim of this study was to investigate developmental differences in hepatic gluconeogenic pathways in fetal/newborn baboons. Fifteen fetal baboons were delivered at 125 day (d) gestational age (GA), 140d GA, and 175d GA (term = 185d GA) via cesarean section and sacrificed at birth. Term and healthy adult baboons were used as controls. Protein content and gene expression of key hepatic gluconeogenic molecules were measured: cytosolic and mitochondrial phosphoenolpyruvate carboxykinase (PEPCK‐C and PEPCK‐M), glucose‐6‐phosphatase‐alpha (G6Pase‐α), G6Pase‐β, fructose‐1,6‐bisphosphatase (FBPase), and forkhead box‐O1 (FOXO1). Protein content of PEPCK‐M increased with advancing gestation in fetal baboons (9.6 fold increase from 125d GA to 175d GA, P < 0.001). PEPCK‐C gene expression was consistent with these developmental differences. Phosphorylation of FOXO1 was significantly lower in preterm fetal baboons compared to adults, and gene expression of FOXO1 was lower in all neonates when compared to adults (10% and 62% of adults respectively, P < 0.05). The FOXO1 target gene G6Pase expression was higher in preterm animals compared to term animals. No significant differences were found in G6Pase‐α, G6Pase‐β, FOXO1, and FBPase during fetal development. In conclusion, significant developmental differences are found in hepatic gluconeogenic molecules in fetal and neonatal baboons, which may impact the responses to insulin during the neonatal period. Further studies under insulin‐stimulated conditions are required to understand the physiologic impact of these maturational differences.

Significant developmental differences were found in several hepatic gluconeogenic molecules. In particular, phosphorylated FOXO1 was significantly reduced in the liver of premature fetal baboons compared to adults and may contribute the increased incidence of hyperglycemia seen in prematurity. In addition, PEPCK increased with advancing gestational age and may play a key role in glucose regulation during the newborn period.

DNA methylation: the pivotal interaction between early-life nutrition and glucose metabolism in later life

Traditionally, it has been widely acknowledged that genes together with adult lifestyle factors determine the risk of developing some metabolic diseases such as insulin resistance, obesity and diabetes mellitus in later life. However, there is now substantial evidence that prenatal and early-postnatal nutrition play a critical role in determining susceptibility to these diseases in later life. Maternal nutrition has historically been a key determinant for offspring health, and gestation is the critical time window that can affect the growth and development of offspring. The Developmental Origins of Health and Disease (DOHaD) hypothesis proposes that exposures during early life play a critical role in determining the risk of developing metabolic diseases in adulthood. Currently, there are substantial epidemiological studies and experimental animal models that have demonstrated that nutritional disturbances during the critical periods of early-life development can significantly have an impact on the predisposition to developing some metabolic diseases in later life. The hypothesis that epigenetic mechanisms may link imbalanced early-life nutrition with altered disease risk has been widely accepted in recent years. Epigenetics can be defined as the study of heritable changes in gene expression that do not involve alterations in the DNA sequence. Epigenetic processes play a significant role in regulating tissue-specific gene expression, and hence alterations in these processes may induce long-term changes in gene function and metabolism that persist throughout the life course. The present review focuses on how nutrition in early life can alter the epigenome, produce different phenotypes and alter disease susceptibilities, especially for impaired glucose metabolism.

Effect of maternal protein restriction on liver metabolism in rat offspring

Consequences of gestational protein restriction (GPR) on liver metabolism in rat offspring were investigated. Pregnant dams were divided into groups: normal (NP, 17% casein) or low-protein diet (LP, 6% casein). Livers were collected from 30-day-old offspring (d30) for analysis or isolation of mitochondria. At d30, hepatic and muscle glycogen was increased in LP group. Mitochondrial swelling and oxygen uptake (recorded with a Clark-type electrode) were significantly reduced in NP female and LP pups. Thiobarbituric acid reactive substances production was lower in females (NP or LP), suggesting significant inhibition of lipid peroxidation. Measurement of mitochondrial respiration (states 3 and 4 stimulated by succinate) showed a higher ADP/O ratio in LP pups, particularly females, suggesting higher phosphorylation efficiency. In the 1st month of life, under our experimental conditions, GPR protects liver mitochondria against oxidative stress and females seem to be more resistant or more suitable for survival.

Gestational protein restriction impairs insulin-regulated glucose transport mechanisms in gastrocnemius muscles of adult male offspring

Type II diabetes originates from various genetic and environmental factors. Recent studies showed that an adverse uterine environment such as that caused by a gestational low-protein (LP) diet can cause insulin resistance in adult offspring. The mechanism of insulin resistance induced by gestational protein restriction is not clearly understood. Our aim was to investigate the role of insulin signaling molecules in gastrocnemius muscles of gestational LP diet-exposed male offspring to understand their role in LP-induced insulin resistance. Pregnant Wistar rats were fed a control (20% protein) or isocaloric LP (6%) diet from gestational day 4 until delivery and a normal diet after weaning. Only male offspring were used in this study. Glucose and insulin responses were assessed after a glucose tolerance test. mRNA and protein levels of molecules involved in insulin signaling were assessed at 4 months in gastrocnemius muscles. Muscles were incubated ex vivo with insulin to evaluate insulin-induced phosphorylation of insulin receptor (IR), Insulin receptor substrate-1, Akt, and AS160. LP diet-fed rats gained less weight than controls during pregnancy. Male pups from LP diet-fed mothers were smaller but exhibited catch-up growth. Plasma glucose and insulin levels were elevated in LP offspring when subjected to a glucose tolerance test; however, fasting levels were comparable. LP offspring showed increased expression of IR and AS160 in gastrocnemius muscles. Ex vivo treatment of muscles with insulin showed increased phosphorylation of IR (Tyr972) in controls, but LP rats showed higher basal phosphorylation. Phosphorylation of Insulin receptor substrate-1 (Tyr608, Tyr895, Ser307, and Ser318) and AS160 (Thr642) were defective in LP offspring. Further, glucose transporter type 4 translocation in LP offspring was also impaired. A gestational LP diet leads to insulin resistance in adult offspring by a mechanism involving inefficient insulin-induced IR, Insulin receptor substrate-1, and AS160 phosphorylation and impaired glucose transporter type 4 translocation.

Time window-dependent effect of perinatal maternal protein restriction on insulin sensitivity and energy substrate oxidation in adult male offspring

Epidemiological and experimental evidence suggests that a suboptimal environment during perinatal life programs offspring susceptibility to the development of metabolic syndrome and Type 2 diabetes. We hypothesized that the lasting impact of perinatal protein deprivation on mitochondrial fuel oxidation and insulin sensitivity would depend on the time window of exposure. To improve our understanding of underlying mechanisms, an integrative approach was used, combining the assessment of insulin sensitivity and untargeted mass spectrometry-based metabolomics in the offspring. A hyperinsulinemic-euglycemic clamp was performed in adult male rats born from dams fed a low-protein diet during gestation and/or lactation, and subsequently exposed to a Western diet (WD) for 10 wk. Metabolomics was combined with targeted acylcarnitine profiling and analysis of liver gene expression to identify markers of adaptation to WD that influence the phenotype outcome evaluated by body composition analysis. At adulthood, offspring of protein-restricted dams had impaired insulin secretion when fed a standard diet. Moreover, rats who demonstrated catch-up growth at weaning displayed higher gluconeogenesis and branched-chain amino acid catabolism, and lower fatty acid β-oxidation compared with control rats. Postweaning exposure of intrauterine growth restriction-born rats to a WD exacerbated incomplete fatty acid β-oxidation and excess fat deposition. Control offspring nursed by protein-restricted mothers showed peculiar low-fat accretion through adulthood and preserved insulin sensitivity even after WD-exposure. Altogether, our findings suggest a testable hypothesis about how maternal diet might influence metabolic outcomes (insulin sensitivity) in the next generation such as mitochondrial overload and/or substrate oxidation inflexibility dependent on the time window of perinatal dietary manipulation.

Intrauterine nutrition: long-term consequences for vascular health

There is a growing body of evidence that improper intrauterine nutrition may negatively influence vascular health in later life. Maternal malnutrition may result in intrauterine growth retardation and, in turn, metabolic disorders such as insulin resistance, diabetes, hypertension, and dyslipidemia, and also enhanced risk of atherosclerosis and cardiovascular death in the offspring. Energy and/or protein restriction is the most critical determinant for fetal programming. However, it has also been proposed that intrauterine n-3 fatty acid deficiency may be linked to later higher blood pressure levels and reduced insulin sensitivity. Moreover, it has been shown that inadequate supply of micronutrients such as folate, vitamin B12, vitamin A, iron, magnesium, zinc, and calcium may contribute to impaired vascular health in the progeny. In addition, hypertensive disorders of pregnancy that are linked to impaired placental blood flow and suboptimal fetal nutrition may also contribute to intrauterine growth retardation and aggravated cardiovascular risk in the offspring. On the other hand, maternal overnutrition, which often contributes to obesity and/or diabetes, may result in macrosomia and enhanced cardiometabolic risk in the offspring. Progeny of obese and/or diabetic mothers are relatively more prone to develop obesity, insulin resistance, diabetes, and hypertension. It was demonstrated that they may have permanently enhanced appetites. Their atheromatous lesions are usually more pronounced. It seems that, particularly, a maternal high-fat/junk food diet may be detrimental for vascular health in the offspring. Fetal exposure to excessive levels of saturated fatty and/or n-6 fatty acids, sucrose, fructose and salt, as well as a maternal high glycemic index diet, may also contribute to later enhanced cardiometabolic risk.

Maternal and in utero determinants of type 2 diabetes risk in the young

The global prevalence of diabetes mellitus has reached epidemic proportions. In 2010, it was estimated that 6.4 % of the adult population (285 million) have diabetes. In recent years, the incidence of type 2 diabetes (T2D), a condition traditionally associated with aging, has been steadily increasing among younger individuals. It is now a well-established notion that the early-life period is a critical window of development and that influences during this period can "developmentally prime" the metabolic status of the adult. This review discusses the role of maternal and in utero influences on the developmental priming of T2D risk. Both human epidemiological studies and experimental animal models are beginning to demonstrate that early dietary challenges can accelerate the onset of age-associated metabolic disturbances, including insulin resistance, T2D, obesity, hypertension, and cardiovascular disease. These findings show that poor maternal nutrition can prime a prediabetes phenotype, often manifest as insulin resistance, by very early stages of life. Thus, the maternal diet is a critical determinant of premature T2D risk. While the mechanisms that link early nutrition to age-associated metabolic decline are currently unclear, preliminary findings suggest perturbations in a number of processes involved in cellular aging, such as changes in longevity-associated Sirtuin activity, epigenetic regulation of key metabolic genes, and mitochondrial dysfunction. Preliminary studies show that pharmacological interventions in utero and dietary supplementation in early postnatal life may alleviate insulin resistance and reduce T2D risk. However, further studies are warranted to fully understand the relationship between the early environment and long-term effects on metabolism. Such mechanistic insights will facilitate strategic interventions that prevent accelerated metabolic decline and the premature onset of T2D in the current and future generations.

Fetal and neonatal exposure to nicotine leads to augmented hepatic and circulating triglycerides in adult male offspring due to increased expression of fatty acid synthase

While nicotine replacement therapy is assumed to be a safer alternative to smoking during pregnancy, the long-term consequences for the offspring remain elusive. Animal studies now suggest that maternal nicotine exposure during perinatal life leads to a wide range of adverse outcomes for the offspring including increased adiposity. The focus of this study was to investigate if nicotine exposure during pregnancy and lactation leads to alterations in hepatic triglyceride synthesis. Female Wistar rats were randomly assigned to receive daily subcutaneous injections of saline (vehicle) or nicotine bitartrate (1mg/kg/day) for two weeks prior to mating until weaning. At postnatal day 180 (PND 180), nicotine exposed offspring exhibited significantly elevated levels of circulating and hepatic triglycerides in the male offspring. This was concomitant with increased expression of fatty acid synthase (FAS), the critical hepatic enzyme in de novo triglyceride synthesis. Given that FAS is regulated by the nuclear receptor Liver X receptor (LXRα), we measured LXRα expression in both control and nicotine-exposed offspring. Nicotine exposure during pregnancy and lactation led to an increase in hepatic LXRα protein expression and enriched binding to the putative LXRE element on the FAS promoter in PND 180 male offspring. This was also associated with significantly enhanced acetylation of histone H3 [K9,14] surrounding the FAS promoter, a hallmark of chromatin activation. Collectively, these findings suggest that nicotine exposure during pregnancy and lactation leads to an increase in circulating and hepatic triglycerides long-term via changes in the transcriptional and epigenetic regulation of the hepatic lipogenic pathway.

Nutritional programming of insulin resistance: causes and consequences

Strong evidence indicates that adverse prenatal and early postnatal environments have a significant long-term influence on risk factors that result in insulin resistance, type 2 diabetes (T2D), and cardiovascular disease later in life. Here we discuss current knowledge of how maternal and neonatal nutrition influence early growth and the long-term risk of developing insulin resistance in different organs and at the whole-body level. Accumulating evidence supports a role for epigenetic mechanisms underlying this nutritional programming, consisting of heritable changes that regulate gene expression which in turn shapes the phenotype across generations. Deciphering these molecular mechanisms in key tissues and discovering key biological markers may provide valuable insight towards the development of effective intervention strategies.