Early alterations in plasma ghrelin levels in offspring of calorie-restricted rats during gestation may be linked to lower sympathetic drive to the stomach

Identification of blood cell transcriptome-based biomarkers in adulthood predictive of increased risk to develop metabolic disorders using early life intervention rat models

Calorie restriction during gestation in rats has long-lasting adverse effects in the offspring. It induces metabolic syndrome-related alterations, which are partially reversed by leptin supplementation during lactation. We employed these conditions to identify transcript-based nutrient sensitive biomarkers in peripheral blood mononuclear cells (PBMCs) predictive of later adverse metabolic health. The best candidate was validated in humans. Transcriptome analysis of PBMCs from adult male Wistar rats of three experimental groups was performed: offspring of control dams (CON), and offspring of 20% calorie-restricted dams during gestation without (CR) and with leptin supplementation throughout lactation (CR-LEP). The expression of 401 genes was affected by gestational calorie restriction and reversed by leptin. The changes preceded metabolic syndrome-related phenotypic alterations. Of these genes, Npc1 mRNA levels were lower in CR vs CON, and normalized to CON in CR-LEP. In humans, NPC1 mRNA levels in peripheral blood cells (PBCs) were decreased in subjects with mildly impaired metabolic health compared to healthy subjects. Therefore, a set of potential transcript-based biomarkers indicative of a predisposition to metabolic syndrome-related alterations were identified, including NPC1, which was validated in humans. Low NPC1 transcript levels in PBCs are a candidate biomarker of increased risk for impaired metabolic health in humans.

Leptin Intake at Physiological Doses Throughout Lactation in Male Wistar Rats Normalizes the Decreased Density of Tyrosine Hydroxylase-Immunoreactive Fibers in the Stomach Caused by Mild Gestational Calorie Restriction

Introduction: Gestational under nutrition in rats has been shown to decrease expression of sympathetic innervation markers in peripheral tissues of offspring, including the stomach. This has been linked to lower gastric secretion and decreased circulating levels of ghrelin. Considering the critical role of leptin intake during lactation in preventing obesity and reversing adverse developmental programming effects, we aimed to find out whether leptin supplementation may reverse the above mentioned alterations caused by mild gestational calorie restriction. Methods: Three groups of male rats were studied at a juvenile age (25 days old) and during adulthood (3 and 6 months old): the offspring of ad libitum fed dams (controls), the offspring of dams that were diet restricted (20%) from days 1 to 12 of gestation (CR), and CR rats supplemented with a daily oral dose of leptin (equivalent to 5 times the average amount they could receive each day from maternal milk) throughout lactation (CR-Leptin). The density of TyrOH-immunoreactive (TyrOH⁺) fibers and the levels of Tyrosine hydroxylase (TyrOH)-used as potential markers of functional sympathetic innervation-were measured in stomach. Plasma leptin and ghrelin levels were also determined. Results: Twenty five-day-old CR rats, but not CR-Leptin rats, displayed lower density of TyrOH⁺ fibers (-46%) and TyrOH levels (-47%) in stomach compared to controls. Alterations in CR animals were mitigated at 6 months of age, and differences were not significant. Adult CR-Leptin animals showed higher plasma ghrelin levels than CR animals, particularly at 3 months (+16%), and a lower leptin/ghrelin ratio (-28 and -37% at 3 and 6 months, respectively). Conclusion: Leptin intake during lactation is able to reverse the alterations in the density of TyrOH⁺ fibers in the stomach and normalize the increased leptin/ghrelin ratio linked to a mild gestational calorie restriction in rats, supporting the relevance of leptin as an essential nutrient during lactation.

Maternal Calorie Restriction Causing Uteroplacental Insufficiency Differentially Affects Mammalian Placental Glucose and Leucine Transport Molecular Mechanisms

We examined the effect of mild (Mi; ∼25%) and moderate (Mo; ∼50%) maternal calorie restriction (MCR) vs ad libitum-fed controls on placental glucose and leucine transport impacting fetal growth potential. We observed in MiMCR a compensatory increase in transplacental (TP) glucose transport due to increased placental glucose transporter isoform (GLUT)-3 but no change in GLUT1 protein concentrations. This change was paralleled by increased glut3 mRNA and 5-hydroxymethylated cytosines with enhanced recruitment of histone 3 lysine demethylase to the glut3 gene locus. To assess the biologic relevance of placental GLUT1, we also examined glut1 heterozygous null vs wild-type mice and observed no difference in placental GLUT3 and TP or intraplacental glucose and leucine transport. Both MCR states led to a graded decrease in TP and intraplacental leucine transport, with a decline in placental L amino acid transporter isoform 2 (LAT2) concentrations and increased microRNA-149 (targets LAT2) and microRNA-122 (targets GLUT3) expression in MoMCR alone. These changes were accompanied by a step-wise reduction in uterine and umbilical artery Doppler blood flow with decreased fetal left ventricular ejection fraction and fractional shortening. We conclude that MiMCR transactivates placental GLUT3 toward preserving TP glucose transport in the face of reduced leucine transport. This contrasts MoMCR in which a reduction in placental GLUT3 mediated glucose transport with a reciprocal increase in miR-122 expression was encountered. A posttranscriptional reduction in LAT2-mediated leucine transport also occurred with enhanced miR-149 expression. Both MCR states, although not affecting placental GLUT1, resulted in uteroplacental insufficiency and fetal growth restriction with compromised cardiovascular health.

Maternal caloric restriction prior to pregnancy increases the body weight of the second-generation male offspring and shortens their longevity in rats

Maternal undernutrition can affect offspring's physical status and various health parameters that might be transmittable across several generations. Many studies have focused on undernutrition throughout pregnancy, whereas maternal undernutrition prior to pregnancy is not sufficiently studied. The objective of our study was to explore the effects of food restriction prior to and during pregnancy on body weight and longevity of the second generation offspring. Adult female Wistar rats ("F0" generation) were 50% food restricted for one month prior to pregnancy (pre-pregnancy) or during pre-pregnancy and pregnancy. The third group was fed normally (control). The first generation offspring were normally fed until the 6(th) month of age to produce the second generation offspring; namely, the first-generation female rats were mated with male breeders from outside the experiment. The second generation offspring thus obtained were observed until natural death (up to 36 months). Compared to the controls, the second-generation male offspring whose "grandmothers (F0 females)" undernourished only during pre-pregnancy were significantly heavier from the 8(th) month of age, whereas no significant weight difference was found in the male offspring whose "grandmothers" were food-restricted during pre-pregnancy and pregnancy. Shorter lifespan was observed in the second-generation male offspring of "grandmothers" that were food-restricted either during pre-pregnancy or during pre-pregnancy and pregnancy. By contrast, no differences in body weight and lifespan were observed in all second-generation female offspring. In conclusion, maternal caloric restriction prior to pregnancy increases the body weight and shortens the longevity of the second-generation male offspring, indicating the sex-dependent transgenerational effect of maternal caloric restriction.

Leptin intake in suckling rats restores altered T3 levels and markers of adipose tissue sympathetic drive and function caused by gestational calorie restriction

BACKGROUND

Maternal calorie restriction during gestation in rats has been associated with altered white adipose tissue (WAT) sympathetic innervation and function in offspring. Here, we aimed to investigate whether supplementation with oral leptin (a breast milk component) throughout the lactation period may revert the aforementioned adverse programming effects.

METHODS

Three groups of male and female rats were studied at the postnatal day 25: the offspring of control dams, the offspring of 20% calorie-restricted dams during pregnancy (CR) and CR rats supplemented with physiological doses of leptin throughout lactation (CR-Leptin). Tyrosine hydroxylase (TH) levels and its immunoreactive area, and mRNA expression levels of lipid metabolism-related genes and of deiodinase iodothyronine type II (Dio2) were determined in WAT. Triiodothyronine (T3) levels were determined in the blood.

RESULTS

In CR males, leptin treatment restored the decreased TH levels and its immunoreactive area in WAT, and partially normalized expression levels of genes related to lipolysis and fatty acid oxidation (adipose triglyceride lipase, hormone-sensitive lipase, carnitine palmitoyltransferase 1b and peroxisome proliferator-activated receptor gamma coactivator 1-alpha). Leptin treatment also reverted the decreased T3 plasma levels and WAT lipoprotein lipase mRNA levels occurring in CR males and females, and the decreased Dio2 mRNA levels in CR females.

CONCLUSIONS

Leptin supplementation throughout the lactation period reverts the malprogrammed effects on WAT structure and function induced by undernutrition during pregnancy. These findings support the relevance of the intake of leptin during lactation, bearing clear characteristics of essential nutrient, and provide a strategy to treat and/or prevent the programmed trend to obesity acquired by inadequate fetal nutrition.

Blood cell transcriptomic-based early biomarkers of adverse programming effects of gestational calorie restriction and their reversibility by leptin supplementation

The challenge of preventing major chronic diseases requires reliable, early biomarkers. Gestational mild undernutrition in rats is enough to program the offspring to develop later pathologies; the intake of leptin, a breastmilk component, during lactation may reverse these programming effects. We used these models to identify, in peripheral blood mononuclear cells (PBMCs), transcriptomic-based early biomarkers of programmed susceptibility to later disorders, and explored their response to neonatal leptin intake. Microarray analysis was performed in PBMCs from the offspring of control and 20% gestational calorie-restricted dams (CR), and CR-rats supplemented with physiological doses of leptin throughout lactation. Notably, leptin supplementation normalised 218 of the 224 mRNA-levels identified in PBMCs associated to undernutrition during pregnancy. These markers may be useful for early identification and subsequent monitoring of individuals who are at risk of later diseases and would specifically benefit from the intake of appropriate amounts of leptin during lactation.

Exposure to increased levels of estradiol during development can have long-term effects on the response to undernutrition in female rats

OBJECTIVES

Undernutrition during development alters the expression of peptides that control energy expenditure and feeding behavior. Estrogens can also modulate these peptides. Here, we analyze whether the early postnatal administration of estradiol modulates the effects of undernutrition on neuroendocrine parameters in adult female Wistar rats.

METHODS

Control rats were fed a control diet. Undernourished pups were submitted to a restricted diet with half of the undernourished rats receiving 0.4 mg/kg s.c. of estradiol benzoate (EB) from postnatal day (P) 6 until P13. Quantitative real-time polymerase chain reaction was performed to determine expression in the hypothalamus of agouti-related peptide (AgRP), proopiomelanocortin (POMC), neuropeptide Y (NPY), and cocaine- and amphetamine-regulated transcript. Plasma estradiol, testosterone, and adiponectin levels were measured by enzyme-linked immunosorbent assay. Total and acylated ghrelin levels were measured in plasma by radioimmunoassay. Insulin and leptin were measured by mulitplex immunoassays.

RESULTS

Undernourishment decreased body weight, fat mass, plasma leptin and insulin levels, and hypothalamic POMC mRNA levels. An increase in orexigenic signals AgRP and NPY mRNA levels, and in plasma adiponectin levels were found in undernourished animals. Early postnatal treatment with EB to undernourished female rats reversed the effects of undernutrition on adult hypothalamic POMC mRNA levels. In addition, neonatal EB treatment to undernourished females significantly decreased adult plasma testosterone, estradiol, and acylated ghrelin levels.

DISCUSSION

Our results suggest that increased estradiol during a critical period of development has the capacity to modulate the alterations that undernutrition produces on energy metabolism.

Gestational exposure to a viral mimetic poly(i:C) results in long-lasting changes in mitochondrial function by leucocytes in the adult offspring

Maternal immune activation (MIA) is a potential risk factor for autism spectrum disorder (ASD) and schizophrenia (SZ). In rodents, MIA results in changes in cytokine profiles and abnormal behaviors in the offspring that model these neuropsychiatric conditions. Given the central role that mitochondria have in immunity and other metabolic pathways, we hypothesized that MIA will result in a fetal imprinting that leads to postnatal deficits in the bioenergetics of immune cells. To this end, splenocytes from adult offspring exposed gestationally to the viral mimic poly(I:C) were evaluated for mitochondrial outcomes. A significant decrease in mitochondrial ATP production was observed in poly(I:C)-treated mice (45% of controls) mainly attributed to a lower complex I activity. No differences were observed between the two groups in the coupling of electron transport to ATP synthesis, or the oxygen uptake under uncoupling conditions. Concanavalin A- (ConA-) stimulated splenocytes from poly(I:C) animals showed no statistically significant changes in cytokine levels compared to controls. The present study reports for the first time that MIA activation by poly(I:C) at early gestation, which can lead to behavioral impairments in the offspring similar to SZ and ASD, leads to long-lasting effects in the bioenergetics of splenocytes of adult offspring.