The Epigenetic Legacy of Maternal Protein Restriction: Renal Ptger1 DNA Methylation Changes in Hypertensive Rat Offspring

Nutrient imbalances during gestation are a risk factor for hypertension in offspring. Although the effects of prenatal nutritional deficiency on the development of hypertension and cardiovascular diseases in adulthood have been extensively documented, its underlying mechanisms remain poorly understood. In this study, we aimed to elucidate the precise role and functional significance of epigenetic modifications in the pathogenesis of hypertension. To this end, we integrated methylome and transcriptome data to identify potential salt-sensitive hypertension genes using the kidneys of stroke-prone spontaneously hypertensive rat (SHRSP) pups exposed to a low-protein diet throughout their fetal life. Maternal protein restriction during gestation led to a positive correlation between DNA hypermethylation of the renal prostaglandin E receptor 1 (Ptger1) CpG island and high mRNA expression of Ptger1 in offspring, which is consistently conserved. Furthermore, post-weaning low-protein or high-protein diets modified the Ptger1 DNA hypermethylation caused by fetal malnutrition. Here, we show that this epigenetic variation in Ptger1 is linked to disease susceptibility established during fetal stages and could be reprogrammed by manipulating the postnatal diet. Thus, our findings clarify the developmental origins connecting the maternal nutritional environment and potential epigenetic biomarkers for offspring hypertension. These findings shed light on hypertension prevention and prospective therapeutic strategies.

Predictive ability of postnatal growth failure for adverse feeding-related outcomes in preterm infants: an exploratory study comparing Fenton with INTERGROWTH-21st preterm growth charts

BACKGROUND

Postnatal growth failure (PGF) can impact the short- and long-term health outcomes in preterm infants. However, PGF rates vary according to the way it is defined and the growth chart used to monitor the postnatal growth. Fenton-2013 growth charts which suggest following intrauterine fetal growth compared to INTERGROWTH-21st, one specifically constructed for monitoring preterm extrauterine growth.

OBJECTIVE

Exploratory study to determine the PGF definition at first per oral (PO) that is most predictive of adverse oral feeding-related outcomes in preterm infants.

METHODS

Prospectively collected data of preterm infants 24-32 weeks gestation, who were started on cue-based oral feeds at ≤34 weeks gestation were reviewed. Anthropometric data at first PO (weight, length, and head circumference) were compared according to Fenton and INTERGROWTH-21st growth charts. PGF was defined either as <10th percentile, Z-score change (ZSC) of ≥-1.5 from birth, or ZSC of ≥-2.0. Top-quartile (Q4) of feeding-related outcomes (days from first PO to full PO, post-menstrual age at full PO, days from first PO to discharge, and length of hospital stay) was considered as adverse outcome.

RESULTS

Of the 125 infants included, the median birth gestation and weight were 29.4 weeks and 1235 g, respectively. Incidence of appropriate, small, and large for gestational age was similar at birth by both growth charts. ZSC -1.5 for weight by Fenton was significantly higher at first PO vs. INTERGROWTH-21st (p=.02), while percentile <10th and ZSC -2.0 rates were similar. The PGF definition based on individual anthropometrics at first PO that has the best area under the curve (AUC) for adverse feeding-related outcomes was used to create a combined PGF definition for each growth chart. The AUC for the combined PGF for the Fenton and INTERGROWTH-21st was similar (p>.05) and both have moderate sensitivity and negative predictive value, but have low specificity, positive predictive value, and positive likelihood ratio for adverse feeding-related outcomes.

CONCLUSIONS

The tested definitions of PGF at first PO have only small to moderate predictive ability for adverse feeding-related outcomes in preterm infants.

Effect of Postnatal Nutritional Environment Due to Maternal Diabetes on Beta Cell Mass Programming and Glucose Intolerance Risk in Male and Female Offspring

Besides the fetal period, the suckling period is a critical time window in determining long-term metabolic health. We undertook the present study to elucidate the impact of a diabetic suckling environment alone or associated with an in utero diabetic environment on beta cell mass development and the risk of diabetes in the offspring in the long term. To that end, we have compared two experimental settings. In setting 1, we used Wistar (W) rat newborns resulting from W ovocytes (oW) transferred into diabetic GK rat mothers (pGK). These oW/pGK neonates were then suckled by diabetic GK foster mothers (oW/pGK/sGK model) and compared to oW/pW neonates suckled by normal W foster mothers (oW/pW/sW model). In setting 2, normal W rat newborns were suckled by diabetic GK rat foster mothers (nW/sGK model) or normal W foster mothers (nW/sW model). Our data revealed that the extent of metabolic disorders in term of glucose intolerance and beta cell mass are similar between rats which have been exposed to maternal diabetes both pre- and postnatally (oW/pGK/sGK model) and those which have been exposed only during postnatal life (nW/sW model). In other words, being nurtured by diabetic GK mothers from birth to weaning was sufficient to significantly alter the beta cell mass, glucose-induced insulin secretion and glucose homeostasis of offspring. No synergistic deleterious effects of pre-and postnatal exposure was observed in our setting.

Leanness in postnatally nutritionally programmed rats is associated with increased sensitivity to leptin and a melanocortin receptor agonist and decreased sensitivity to neuropeptide Y

BACKGROUND

Pups of normally nourished dams that are cross-fostered after birth to dams fed a low-protein (8% by weight) diet (postnatal low protein (PLP)) grow slower during the suckling period and remain small and lean throughout adulthood. At weaning, they have increased expression in the arcuate nucleus (ARC) of the hypothalamus of the orexigenic neuropeptide Y (NPY) and decreased expression of pro-opiomelanocortin, the precursor of anorexigenic melanocortins.

OBJECTIVES AND METHODS

We investigated, using third ventricle administration, whether 3-month-old male PLP rats display altered sensitivity to leptin with respect to food intake, NPY and the melanocortin 3/4-receptor agonist MTII, and using in situ hybridization or laser capture microdissection of the ARC followed by RT-PCR, whether the differences observed were associated with changes in the hypothalamic expression of NPY or the leptin receptor, NPY receptors and melanocortin receptors.

RESULTS

PLP rats were smaller and had reduced percentage body fat content and plasma leptin concentration compared with control rats. Leptin (5 μg) reduced food intake over 0-48 h more in PLP than control rats (P<0.05). Submaximal doses of NPY increased the food intake less in PLP rats than in controls, whereas submaximal doses of MTII reduced the food intake more in PLP rats. Maximal responses did not differ between PLP and control rats. Leptin and melanocortin-3 receptor (MC3R) expression were increased in both ARC and ventromedial hypothalamic nuclei in PLP animals compared with the controls. MC4R, NPY Y1R, Y5R and NPY expression were unchanged.

CONCLUSION

Postnatal undernourishment results in food intake in adult rats being more sensitive to reduction by leptin and melanocortins, and less sensitive to stimulation by NPY. We propose that this contributes to increased leptin sensitivity and resistance to obesity. Increased expression of ObRb and MC3R may partly explain these findings but other downstream mechanisms must also be involved.