A low protein diet during pregnancy provokes a lasting shift of hepatic expression of genes related to cell cycle throughout ontogenesis in a porcine model

The Effect of Dietary Protein Imbalance during Pregnancy on the Growth, Metabolism and Circulatory Metabolome of Neonatal and Weaned Juvenile Porcine Offspring

Protein imbalance during pregnancy affects women in underdeveloped and developing countries and is associated with compromised offspring growth and an increased risk of metabolic diseases in later life. We studied in a porcine model the glucose and urea metabolism, and circulatory hormone and metabolite profile of offspring exposed during gestation, to maternal isoenergetic low-high (LP-HC), high-low (HP-LC) or adequate (AP) protein-carbohydrate ratio diets. At birth, LP-HC were lighter and the plasma acetylcarnitine to free carnitine ratios at 1 day of life was lower compared to AP offspring. Plasma urea concentrations were lower in 1 day old LP-HC offspring than HP-LC. In the juvenile period, increased insulin concentrations were observed in LP-HC and HP-LC offspring compared to AP, as was body weight from HP-LC compared to LP-HC. Plasma triglyceride concentrations were lower in 80 than 1 day old HP-LC offspring, and glucagon concentrations lower in 80 than 1 day old AP and HP-LC offspring. Plasma urea and the ratio of glucagon to insulin were lower in all 80 than 1 day old offspring. Aminoacyl-tRNA, arginine and phenylalanine, tyrosine and tryptophan metabolism, histidine and beta-alanine metabolism differed between 1 and 80 day old AP and HP-LC offspring. Maternal protein imbalance throughout pregnancy did not result in significant consequences in offspring metabolism compared to AP, indicating enormous plasticity by the placenta and developing offspring.

Increased Susceptibility to Obesity and Glucose Intolerance in Adult Female Rats Programmed by High-Protein Diet during Gestation, But Not during Lactation

Fetal and early postnatal nutritional environments contribute to lifelong health. High-protein (HP) intake in early life can increase obesity risk in response to specific feeding conditions after weaning. This study investigated the effects of a maternal HP diet during pregnancy and/or lactation on the metabolic health of offspring. Three groups of dams received a normal-protein (NP, 20E% proteins) diet during gestation and lactation (Control group), an HP diet (55E% proteins) during gestation (HPgest group), or an HP diet during lactation (HPlact group). From weaning until 10 weeks, female pups were exposed to the NP, the HP or the western (W) diet. HPgest pups had more adipocytes (p = 0.009), more subcutaneous adipose tissue (p = 0.04) and increased expression of genes involved in liver fatty acid synthesis at 10 weeks (p < 0.05). HPgest rats also showed higher food intake and adiposity under the W diet compared to the Control and HPlact rats (p ≤ 0.04). The post-weaning HP diet reduced weight (p < 0.0001), food intake (p < 0.0001), adiposity (p < 0.0001) and glucose tolerance (p < 0.0001) compared to the NP and W diets; this effect was enhanced in the HPgest group (p = 0.04). These results show that a maternal HP diet during gestation, but not lactation, leads to a higher susceptibility to obesity and glucose intolerance in female offspring.

Lipid metabolism is associated with developmental epigenetic programming

Maternal diet and metabolism impact fetal development. Epigenetic reprogramming facilitates fetal adaptation to these in utero cues. To determine if maternal metabolite levels impact infant DNA methylation globally and at growth and development genes, we followed a clinical birth cohort of 40 mother-infant dyads. Targeted metabolomics and quantitative DNA methylation were analyzed in 1st trimester maternal plasma (M1) and delivery maternal plasma (M2) as well as infant umbilical cord blood plasma (CB). We found very long chain fatty acids, medium chain acylcarnitines, and histidine were: (1) stable in maternal plasma from pregnancy to delivery, (2) significantly correlated between M1, M2, and CB, and (3) in the top 10% of maternal metabolites correlating with infant DNA methylation, suggesting maternal metabolites associated with infant DNA methylation are tightly controlled. Global DNA methylation was highly correlated across M1, M2, and CB. Thus, circulating maternal lipids are associated with developmental epigenetic programming, which in turn may impact lifelong health and disease risk. Further studies are required to determine the causal link between maternal plasma lipids and infant DNA methylation patterns.

Maternal stress and diet may influence affective behavior and stress-response in offspring via epigenetic regulation of central peptidergic function

It has been shown that maternal stress and malnutrition, or experience of other adverse events, during the perinatal period may alter susceptibility in the adult offspring in a time-of-exposure dependent manner. The mechanism underlying this may be epigenetic in nature. Here, we summarize some recent findings on the effects on gene-regulation following maternal malnutrition, focusing on epigenetic regulation of peptidergic activity. Numerous neuropeptides within the central nervous system are crucial components in regulation of homeostatic energy-balance, as well as affective health (i.e. health events related to affective disorders, psychiatric disorders also referred to as mood disorders). It is becoming evident that expression, and function, of these neuropeptides can be regulated via epigenetic mechanisms during fetal development, thereby contributing to the development of the adult phenotype and, possibly, modulating disease susceptibility. Here, we focus on two such neuropeptides, neuropeptide Y (NPY) and corticotropin-releasing hormone (CRH), both involved in regulation of endocrine function, energy homeostasis, as well as affective health. While a number of published studies indicate the involvement of epigenetic mechanisms in CRH-dependent regulation of the offspring adult phenotype, NPY has been much less studied in this context and needs further work.

Nutritional systems biology of type 2 diabetes

Type 2 diabetes (T2D) has become an increasingly challenging health burden due to its high morbidity, mortality, and heightened prevalence worldwide. Although dietary and nutritional imbalances have long been recognized as key risk factors for T2D, the underlying mechanisms remain unclear. The advent of nutritional systems biology, a field that aims to elucidate the interactions between dietary nutrients and endogenous molecular entities in disease-related tissues, offers unique opportunities to unravel the complex mechanisms underlying the health-modifying capacities of nutritional molecules. The recent revolutionary advances in omics technologies have particularly empowered this incipient field. In this review, we discuss the applications of multi-omics approaches toward a systems-level understanding of how dietary patterns and particular nutrients modulate the risk of T2D. We focus on nutritional studies utilizing transcriptomics, epigenomomics, proteomics, metabolomics, and microbiomics, and integration of diverse omics technologies. We also summarize the potential molecular mechanisms through which nutritional imbalances contribute to T2D pathogenesis based on these studies. Finally, we discuss the remaining challenges of nutritional systems biology and how the field can be optimized to further our understanding of T2D and guide disease management via nutritional interventions.

Methylating micronutrient supplementation during pregnancy influences foetal hepatic gene expression and IGF signalling and increases foetal weight

PURPOSE

Maternal diet during pregnancy impacts foetal growth and development. In particular, dietary levels of methylating micronutrients (methionine, folate, choline, vitamins B6, and B12) interfere with the availability and allocation of methyl groups for methylation reactions, thereby influencing normal transcription. However, the currently recommended methylating micronutrient supplementation regimen is haphazard and arbitrary at best.

METHODS

To investigate the effects of a methylating micronutrient-rich maternal diet, pregnant Pietrain sows were fed either a standard diet (CON) or a diet supplemented with methionine, folate, choline, B6, B12, and zinc (MET). Foetal liver and muscle (M. longissimus dorsi) tissues were collected at 35, 63, and 91 days post-conception. Transcriptional responses to diet were assessed in foetal liver. Altered insulin-like growth factor (IGF) signalling in transcriptome analyses prompted investigation of IGF-2 and insulin-like growth factor binding proteins (IGFBPs) levels in muscle and liver.

RESULTS

Maternal diet enriched with methylating micronutrients was associated with increased foetal weight in late gestation. Hepatic transcriptional patterns also revealed differences in vitamin B6 and folate metabolism between the two diets, suggesting that supplementation was effective. Additionally, shifts in growth-supporting metabolic routes of the lipid and energy metabolism, including IGF signalling, and of cell cycle-related pathways were found to occur in liver tissue in supplemented individuals. Weight differences and modulated IGF pathways were also reflected in the muscle content of IGF-2 (increased in MET) and IGFBP-2 (decreased in MET).

CONCLUSIONS

Maternal dietary challenges provoke stage-dependent and tissue-specific transcriptomic modulations in the liver pointing to molecular routes contributing to the organismal adaptation. Subtle effects on late foetal growth are associated with changes in the IGF signalling mainly in skeletal muscle tissue that is less resilient to dietary stimuli than liver.

Maternal high-protein diet during pregnancy, but not during suckling, induced altered expression of an increasing number of hepatic genes in adult mouse offspring

PURPOSE

Indirect effects of a high-protein maternal diet are not well understood. In this study, we analyzed short-term and sustainable effects of a prenatal versus early postnatal maternal high-protein diet on growth and hepatic gene expression in mouse offspring.

METHODS

Dams were exposed to an isoenergetic high-protein (HP, 40 % w/w) diet during pregnancy or lactation. Growth and hepatic expression profiles of male offspring were evaluated directly after weaning and 150 days after birth. Offspring from two dietary groups, high-protein diet during pregnancy and control diet during lactation (HPC), and control diet during pregnancy and high-protein diet during lactation (CHP), were compared with offspring (CC) from control-fed dams.

RESULTS

Maternal CHP treatment was associated with sustained offspring growth retardation, but decreased numbers of affected hepatic genes in adults compared to weanlings. In contrast, offspring of the HPC group did not show persistent effects on growth parameters, but the number of affected hepatic genes was even increased at adult age. In both dietary groups, however, only a small subset of genes was affected in weanlings as well as in adults.

CONCLUSIONS

We conclude that (1) prenatal and early postnatal maternal HP diet caused persistent, but (2) different effects and partially complementary trends on growth characteristics and on the hepatic transcriptome and associated pathways and that (3) only a small number of genes and associated upstream regulators might be involved in passing early diet-induced imprints to adulthood.

Lipocalin-2 (Lcn2) expression is mediated by maternal nutrition during the development of the fetal liver

The mechanisms by which maternal protein deficiency programs insulin action in the offspring are poorly understood. The interpretation of transcriptomics is complicated by homeostatic adaptations, for example, changes in amino acid metabolism, which are potentially unrelated to the programming mechanism. The fatty acid composition of the maternal diet modulates the programming of insulin action, offering a possible strategy to circumvent these complications. Fetal livers harvested on d21 of gestation from pregnant rats fed high-protein (18 % w/w) and low-protein (9 % w/w) diets prepared with either corn or soya oil were screened with rat genome microarrays. Although a low-protein maternal diet altered the abundance of more than one hundred mRNAs in the fetal liver, only 40 were changed by the fatty acid composition of the diet (P < 0.05). One of these mRNAs was identified as lipocalin-2 (Lcn2). This pattern of differential expression was confirmed by qRT-PCR. The expression of Lcn2 was decreased by low-protein diets when the diet contained soya oil, whereas the effect of protein was much smaller in the group fed diets prepared with corn oil. The decrease in Lcn2 expression produced by soya oil persisted into adult life. Levels of the Lcn2 protein were closely correlated to the mRNA abundance. The results suggest a possible involvement of Lcn2 in the programming of hepatic function.

High- and low-protein gestation diets do not provoke common transcriptional responses representing universal target-pathways in muscle and liver of porcine progeny

AIM

Maternal diets introduce transcriptional changes in the offspring, highlighting the concept of genetic and physiological plasticity. Our previous analyses investigated stage-dependent transcriptional responses to either maternal high or low protein/carbohydrate ratios in either muscle or liver. Foetal programming is proposed to be mediated by a small number of gatekeeper processes, such as cytoskeleton remodelling and cell-cycle regulation. Here, we conducted an overall analysis of a three-dimensional data set aiming to elucidate, whether there are universally targeted pathways of adaptive transcriptional response to different protein/carbohydrate ratios.

METHODS

Microarray analyses were performed on liver and skeletal muscle tissue sampled at 94 days post-conception and 1, 28 and 188 days post-natum from offspring (n = 253) of German Landrace gilts that were fed isoenergetic diets containing low, high or adequate protein.

RESULTS

Cluster analyses revealed a hierarchical influence of tissue, ontogenetic stage and diet on transcript levels. Considering results cumulatively over stages, liver showed only marginal transcriptional differences between the dietary groups, whereas considerable differences appeared in muscle. Considering results cumulatively over tissues, nutrition-responsive transcriptions were observed along ontogenesis. Pathway analyses revealed transcript differences in genes related to tissue remodelling, cell-cycle regulation and mitochondrial function.

CONCLUSION

The factors tissue, stage and diet impact gene expression in a hierarchical order. Porcine liver appeared to be a tissue that was more resilient to nutritional modulation compared with skeletal muscle tissue. Differential modulation between tissues and dietary groups reveal that there are no universal target-pathways of adaptive transcriptional response to different protein diets.

The use of transcriptomics to unveil the role of nutrients in Mammalian liver

Liver is the organ primarily responding to diet, and it is crucial in determining plasma carbohydrate, protein, and lipid levels. In addition, it is mainly responsible for transformation of xenobiotics. For these reasons, it has been a target of transcriptomic analyses. In this review, we have covered the works dealing with the response of mammalian liver to different nutritional stimuli such as fasting/feeding, caloric restriction, dietary carbohydrate, cholesterol, fat, protein, bile acid, salt, vitamin, and oligoelement contents. Quality of fats or proteins has been equally addressed, and has the influence of minor dietary components. Other compounds, not purely nutritional as those represented by alcohol and food additives, have been included due to their relevance in processed food. The influence has been studied not only on mRNA but also on miRNA. The wide scope of the technology clearly reflects that any simple intervention has profound changes in many metabolic parameters and that there is a synergy in response when more compounds are included in the intervention. Standardized arrays to systematically test the same genes in all studies and analyzing data to establish patterns of response are required, particularly for RNA sequencing. Moreover, RNA is a valuable, easy-screening ally but always requires further confirmation.

Common phenotypes and the developmental origins of disease

PURPOSE OF REVIEW

The association between nutrition during pregnancy and the development of metabolic disease in the offspring has been well evidenced in humans and animals. Whilst evidence has accumulated to support various theories linking maternal diet to long-term health, the precise mechanisms of action remain poorly understood. This review summarizes recent advances within the field, focusing on the use of animal models to investigate common phenotypic outcomes.

RECENT FINDINGS

Continued characterization of postnatal phenotypes has highlighted the importance of postnatal diet in unmasking programming effects of prenatal diet. Whilst common phenotypes are observed across models, differences in associated regulatory processes exist dependent upon the dietary exposure used and sex of the offspring. The use of unbiased techniques at developmental stages has identified gene pathways sensitive to maternal diet, potentially explaining the induction of a common phenotype by different nutritional interventions. Evidence has also grown to support the role of epigenetic modification, with an increasing range of targets identified as being sensitive.

SUMMARY

A challenge remains in identifying the direct functional and long-term consequences of changes in gene expression or epigenetic status during development, and to translate these back to human populations.

Perinatal epigenetic determinants of cognitive and metabolic disorders

Multiple cues from the environment of our indirect and immediate ancestors, which often persist throughout the prenatal period and adulthood, are shaping our phenotypes through either direct, parent-to-child influences, or transgenerational inheritance. These effects are due to gene-environment interactions, which are intended to be a predictive tool and a mechanism of quick adaptation to the environment, as compared with genetic variations that are inherited over many generations. In certain circumstances the influences induced by the gene-environment interactions can have deleterious effects upon the health status, in the context of a radical change in the environment that does not fit with the predicted conditions, via epigenetic alterations. Conversely the best fit to the expected environment might have a delayed aging process and a longer life span. This review will touch upon the Developmental Origins of Health and Disease (DoHAD) concept, while discussing recent advances in the understanding of metabolic and cognitive disruptions, with a focus on epigenetic factors, their transgenerational effects, and the consequences they might have upon the onset of chronic disease and premature exitus.

Influence of maternal low protein diet during pregnancy on hepatic gene expression signature in juvenile female porcine offspring

SCOPE

Epidemiological and experimental evidence indicates that maternal nutrition status contributes to long-term changes in the metabolic phenotype of the offspring, a process known as fetal programming.

METHODS AND RESULTS

We have used a swine model (Sus scrofa) to analyze consequences of a maternal low protein diet (about 50% of control) during pregnancy on hepatic lipid metabolism and genome-wide hepatic gene expression profile of juvenile female offspring (mean age 85 days). We found 318 S. scrofa genes to be differentially expressed in the liver at age 85 days. In the low protein offspring group key genes of fatty acid de novo synthesis were downregulated whereas several genes of lipolysis and phospholipid biosynthesis were upregulated. qRT-PCR analysis of selected genes verified microarray data and revealed linear correlations between gene expression levels and slaughter weight. Hepatic cholesterol 7α hydroxylase protein expression tended to be lower in the low protein group. Total lipid and triglyceride content and fatty acid composition of total lipids were not different between groups.

CONCLUSION

A maternal low protein diet during pregnancy induces a distinct hepatic gene expression signature in juvenile female pigs which was not translated into phenotypical changes of liver lipid metabolism.

Transcriptional response of skeletal muscle to a low-protein gestation diet in porcine offspring accumulates in growth- and cell cycle-regulating pathways

Inadequate maternal protein supply during gestation represents an environmental factor that affects physiological signaling pathways with long-term consequences for growth, function, and structure of various tissues. Hypothesizing that the offspring's transcriptome is persistently altered by maternal diets, we used a porcine model to monitor the longitudinal expression changes in muscle to identify pathways relevant to fetal initiation of postnatal growth and development. German Landrace gilts were fed isoenergetic gestational diets containing 6.5% (LP) or 12.1% protein. The longissimus dorsi samples were collected from offspring at 94 days postconception (dpc) and 1, 28, and 188 days postnatum (dpn) for expression profiling. At 94 dpc, 1 dpn, and 28 dpn relatively few transcripts (<130) showed an altered abundance between the dietary groups. In fact, at 94 dpc genes of G2/M checkpoint regulation and mitotic roles of Polo-like kinases showed lowered transcript abundance in LP. At 188 dpn 677 transcripts were altered including those related to oxidative phosphorylation, citrate cycle, fatty acid metabolism (higher abundance in LP) and cell cycle regulation (lower abundance in LP). Correspondingly, transcriptional alterations during pre and postnatal development differed considerably among dietary groups, particularly for genes related to cell cycle regulation (G1/S and G2/M checkpoint regulation; cyclines), growth factor signaling (GH, IGF1, mTOR, RAN, VEGF, INSR), lipid metabolism, energy metabolism, and nucleic acid metabolism. In skeletal muscle, fetal programming related to maternal LP diets disturbed gene expression in growth-related pathways into adulthood. Diet-dependent gene expression may hamper proper development, thereby affecting signaling pathways related to energy utilization.