The Impact of Early Postnatal Vitamin A Supplementation on Childhood Obesity Risk ‐ A Study in Rat Model

Abstract

Childhood obesity is a serious medical concern because it is associated with many immediate and long‐term health consequences, including diabetes, hypertension, and cardiovascular disease. However, studies are limited about the effects of early nutritional supplementation on later health outcomes. The objective of the study was to investigate whether early postnatal vitamin A (VA) supplementation alters metabolic functions related to childhood obesity risk later in life, using a rat model. We hypothesized that early‐life VA supplementation in rats is associated with altered expression of genes related to insulin resistance and thermogenesis at neonatal period, with carry‐over effects at prepubescent age. In addition, previously in our laboratory, we showed that the early postnatal treatment with VARA, a retinoid combination of VA and 10% retinoic acid (RA), significantly decreases the expression of retinol‐binding protein 4 (Rbp4) in the liver of neonates as well as adult rats and reduced liver Rbp4 expression is associated with improved glucose tolerance. A defined high‐fat VA‐marginal (HFVAM) diet, which is modified to contain 45 kcal‐% fat and a marginal level of VA (0.35 μg of retinol as retinyl palmitate per gram diet), was fed to Sprague‐Dawley dams from pregnancy until the pups were euthanized at postnatal day (P) 12 or 5 weeks of age. Three doses of VA, VARA, or canola oil as control, were adjusted based on body weight (6 mg VA/kg of body weight) and administered orally to the pups on P0/1, P4, and P10. Plasma and tissues, including liver and adipose tissues, were collected on P12 and 5 weeks of age. Body composition of adolescent rats (5 weeks old) was measured by dual‐energy X‐ray absorptiometry (DEXA) to determine the effects of early VA supplementation on adiposity in prepubertal rats. Total retinoid concentrations in the plasma and tissues were determined by ultra performance liquid chromatography (UPLC). Data were compared to age‐ and sex‐matched normal chow‐fed non‐obese rats as references. There was no significant difference in body weight change between treatment groups, indicating similar growth patterns and successful randomization among pups. The adolescent rats fed a HFVAM diet had significantly higher body fat (%), as compared to rats fed a normal chow diet, but there was no difference in body fat between sexes in each treatment group. The VA‐supplemented HFVAM diet‐fed adolescent rats had significant higher serum total retinol concentration, as compared to normal chow‐fed rats. Both neonatal and adolescent VA‐supplemented rats had increased hepatic retinoid storage, as compared to the oil‐dosed group, suggesting the possibility of “carry‐over” effects of early postnatal VA‐supplementation on metabolic changes later in life. However, no difference was observed in the brown adipose tissue retinoid concentrations between treatment groups in adolescent rats. The relationship between early‐life VA supplementation and metabolic functions related to obesity risk remains to be determined by gene expression analysis.Support or Funding InformationThe project was supported by the Pennsylvania State University Childhood Obesity Training Program funded by USDA National Institute for Food and Agriculture Grant #2011‐67001‐30117 Program A2121.