Early postnatal nutrition and programming of the preterm neonate

Sugaring the pill: ethics and uncertainties in the use of sucrose for newborn infants

Sucrose is widely used for the management of procedural pain in newborn infants, including capillary blood sampling, venepuncture, and vascular cannulation. Multiple randomized controlled trials have demonstrated that sweet-tasting solutions reduce behavioral responses to acute painful stimuli. It has been claimed that sucrose should be a standard of care in neonatal units and that further placebo-controlled trials of sucrose are unnecessary and unethical. However, recently published data cast doubt on the analgesic properties of sucrose. We review this new evidence and analyze the philosophical and ethical questions that it raises, including the "problem of other minds." Sugar may be better understood not as an analgesic, removing or relieving pain, but as a compensating pleasure. There is a need for further research on the mechanism of sucrose's effect on pain behavior and on the long-term effects of sucrose treatment. Such trials will require comparison with placebo or with other interventions. Given uncertainty about the benefit of sucrose, it may be wise to use alternative analgesics or nonpharmacological interventions where these are available and appropriate. Sucrose may not be the answer to procedural pain in newborns.

Lactation and neonatal nutrition: defining and refining the critical questions

This paper resulted from a conference entitled "Lactation and Milk: Defining and refining the critical questions" held at the University of Colorado School of Medicine from January 18-20, 2012. The mission of the conference was to identify unresolved questions and set future goals for research into human milk composition, mammary development and lactation. We first outline the unanswered questions regarding the composition of human milk (Section I) and the mechanisms by which milk components affect neonatal development, growth and health and recommend models for future research. Emerging questions about how milk components affect cognitive development and behavioral phenotype of the offspring are presented in Section II. In Section III we outline the important unanswered questions about regulation of mammary gland development, the heritability of defects, the effects of maternal nutrition, disease, metabolic status, and therapeutic drugs upon the subsequent lactation. Questions surrounding breastfeeding practice are also highlighted. In Section IV we describe the specific nutritional challenges faced by three different populations, namely preterm infants, infants born to obese mothers who may or may not have gestational diabetes, and infants born to undernourished mothers. The recognition that multidisciplinary training is critical to advancing the field led us to formulate specific training recommendations in Section V. Our recommendations for research emphasis are summarized in Section VI. In sum, we present a roadmap for multidisciplinary research into all aspects of human lactation, milk and its role in infant nutrition for the next decade and beyond.

Effect of intrauterine growth retardation on liver and long-term metabolic risk

Intrauterine growth retardation predisposes toward long-term morbidity from type 2 diabetes and cardiovascular disease. To explain this association, the concept of programming was introduced to indicate a process whereby a stimulus or insult at a critical period of development has lasting or lifelong consequences on key endocrine and metabolic pathways. Subtle changes in cell composition of tissues, induced by suboptimal conditions in utero, can influence postnatal physiological functions. There is increasing evidence, suggesting that liver may represent one of the candidate organs targeted by programming, undergoing structural, functional and epigenetic changes following exposure to an unfavorable intrauterine environment. The aim of this review is to provide insights into the molecular mechanisms underlying liver programming that contribute to increase the cardiometabolic risk in subjects with intrauterine growth restriction.

Minireview: Epigenetic programming of diabetes and obesity: animal models

A growing body of evidence suggests that the intrauterine (IU) environment has a significant and lasting effect on the long-term health of the growing fetus and the development of metabolic disease in later life as put forth in the fetal origins of disease hypothesis. Metabolic diseases have been associated with alterations in the epigenome that occur without changes in the DNA sequence, such as cytosine methylation of DNA, histone posttranslational modifications, and micro-RNA. Animal models of epigenetic modifications secondary to an altered IU milieu are an invaluable tool to study the mechanisms that determine the development of metabolic diseases, such as diabetes and obesity. Rodent and nonlitter bearing animals are good models for the study of disease, because they have similar embryology, anatomy, and physiology to humans. Thus, it is feasible to monitor and modify the IU environment of animal models in order to gain insight into the molecular basis of human metabolic disease pathogenesis. In this review, the database of PubMed was searched for articles published between 1999 and 2011. Key words included epigenetic modifications, IU growth retardation, small for gestational age, animal models, metabolic disease, and obesity. The inclusion criteria used to select studies included animal models of epigenetic modifications during fetal and neonatal development associated with adult metabolic syndrome. Experimental manipulations included: changes in the nutritional status of the pregnant female (calorie-restricted, high-fat, or low-protein diets during pregnancy), as well as the father; interference with placenta function, or uterine blood flow, environmental toxin exposure during pregnancy, as well as dietary modifications during the neonatal (lactation) as well as pubertal period. This review article is focused solely on studies in animal models that demonstrate epigenetic changes that are correlated with manifestation of metabolic disease, including diabetes and/or obesity.

Ghrelin and feeding behaviour in preterm infants

The importance of early life events in the development of metabolic diseases is well recognized. Early postnatal environment, including nutrition, is key to future health, and this is particularly true for preterm infants. It is important that these infants receive sufficient nutrients to prevent growth restriction and promote neurodevelopment, while minimizing predisposition to metabolic diseases later in life. Feeding habits are the fundamental elements of nutrition and are influenced by many factors, including personal and familial habits, socioeconomic status, and cultural environment. In the last decades, there has been an important scientific interest toward the comprehension of the molecular and neural mechanisms regulating appetite. In these networks, act many peptide hormones produced in brain or gut, among which ghrelin is important because of its action in the short-term regulation of food intake and the long-term regulation of body weight. Ghrelin stimulates appetite and plays a role in regulating feeding behaviour. Ghrelin levels vary from fetal life through to early adulthood, with the highest levels observed in the very early years. Cord ghrelin levels have been evaluated in term and preterm newborns and high ghrelin levels have been observed in small-for-gestational age newborns and in newborns with intrauterine growth restriction. Moreover, ghrelin has been detected in term and preterm human breast milk, suggesting that it may play a role in the development of neuroendocrine pathways regulating appetite and energy homeostasis in early life. However, more research is required to better define ghrelin's role in breast milk and on feeding behaviour.

Postnatal growth and DNA methylation are associated with differential gene expression of the TACSTD2 gene and childhood fat mass

Rapid postnatal growth is associated with increased risk of childhood adiposity. The aim of this study was to establish whether this pathway is mediated by altered DNA methylation and gene expression. Two distinct cohorts, one preterm (n=121) and one term born (n=6,990), were studied. Exploratory analyses were performed using microarrays to identify differentially expressed genes in whole blood from children defined as "slow" (n=10) compared with "rapid" (n=10) postnatal (term to 12 weeks corrected age) growers. Methylation within the identified TACSTD2 gene was measured in both cohorts, and rs61779296 genotype was determined by Pyrosequencing or imputation and analyzed in relation to body composition at 9-15 years of age. In cohort 1, TACSTD2 expression was inversely correlated with methylation (P=0.016), and both measures were associated with fat mass (expression, P=0.049; methylation, P=0.037). Although associated with gene expression (cohort 1, P=0.008) and methylation (cohort 1, P=2.98×10(-11); cohort 2, P=3.43×10(-15)), rs61779296 was not associated with postnatal growth or fat mass in either cohort following multiple regression analysis. Hence, the lack of association between fat mass and a methylation proxy SNP suggests that reverse causation or confounding may explain the initial association between fat mass and gene regulation. Noncausal methylation patterns may still be useful predictors of later adiposity.

Inclusion and exclusion in nutrigenetics clinical research: ethical and scientific challenges

BACKGROUND/AIMS

There are compelling reasons to ensure the participation of ethnic minorities and populations of all ages worldwide in nutrigenetics clinical research. If findings in such research are valid for some individuals, groups, or communities, and not for others, then ethical questions of justice--and not only issues of methodology and external validity--arise. This paper aims to examine inclusion in nutrigenetics clinical research and its scientific and ethical challenges.

METHODS

In total, 173 publications were identified through a systematic review of clinical studies in nutrigenetics published between 1998 and 2007. Data such as participants' demographics as well as eligibility criteria were extracted.

RESULTS

There is no consistency in the way participants' origins (ancestry, ethnicity, or race) and ages are described in publications. A vast majority of the studies identified was conducted in North America and Europe and focused on 'white' participants. Our results show that pregnant women (and fetuses), minors, and the elderly (≥ 75 years old) remain underrepresented.

CONCLUSION

Representativeness in nutrigenetics research is a challenging ethical and scientific issue. Yet, if nutrigenetics is to benefit whole populations and be used in public and global health agendas, fair representation as well as clear descriptions of participants in publications are crucial.

Epigenetic mechanisms elicited by nutrition in early life

A growing number of studies focusing on the developmental origin of health and disease hypothesis have identified links among early nutrition, epigenetic processes and diseases also in later life. Different epigenetic mechanisms are elicited by dietary factors in early critical developmental ages that are able to affect the susceptibility to several diseases in adulthood. The studies here reviewed suggest that maternal and neonatal diet may have long-lasting effects in the development of non-communicable chronic adulthood diseases, in particular the components of the so-called metabolic syndrome, such as insulin resistance, type 2 diabetes, obesity, dyslipidaemia, hypertension, and CVD. Both maternal under- and over-nutrition may regulate the expression of genes involved in lipid and carbohydrate metabolism. Early postnatal nutrition may also represent a vital determinant of adult health by making an impact on the development and function of gut microbiota. An inadequate gut microbiota composition and function in early life seems to account for the deviant programming of later immunity and overall health status. In this regard probiotics, which have the potential to restore the intestinal microbiota balance, may be effective in preventing the development of chronic immune-mediated diseases. More recently, the epigenetic mechanisms elicited by probiotics through the production of SCFA are hypothesised to be the key to understand how they mediate their numerous health-promoting effects from the gut to the peripheral tissues.