Effects of preweaning nutritional deprivation on basal metabolism and thermoregulatory thermogenesis in the rat

Abstract

1. Nutritional deprivation was induced preweaning in Wistar rats by increasing the litter size to sixteen, while paired litters with only five pups served as controls. The nutritionally deprived pups were rehabilitated after weaning by ad lib. access to an adequate diet.2. The body-weights and body lengths were significantly lower in the nutritionally deprived group and significant differences persisted even after 9 weeks of rehabilitation.3. The body temperature of the nutritionally deprived animals was significantly lower than that of their paired controls, both before and following nutritional rehabilitation, except for a short period after weaning when the nutritionally deprived animals were initially given the diet ad lib. 4.The resting oxygen consumption of the nutritionally deprived animals was comparable to that of the controls when corrected for metabolic body size, both before and after weaning. Noradrenaline-stimulated increase in 0, consumption (non-shivering thermogenesis; NST) was reduced by 50% at weaning in the nutritionally deprived animals and returned to levels comparable to those of controls within a short period of rehabilitation.5. The decrease in NST capacity seen in the nutritionally deprived animals was associated with an inability to thermoregulate when exposed to cold (5"), resulting in death. Cold-induced thermogenesis (CIT) also reappeared soon after nutritional rehabilitation.6. Reduction in metabolic rate, NST and CIT seen in the animals nutritionally deprived preweaning was short-lived and disappeared soon after nutritional rehabilitation. Rapid reversal of these physiological changes indicates that they do not confer any long-term benefit or change in metabolic efficiency and are unlike the changes in body size and growth which do not completely recover following nutritional rehabilitation.

Uncoupling protein‐3 gene expression in skeletal muscle during development is regulated by nutritional factors that alter circulating non‐esterified fatty acids

“…Present data also show that long‐term changes in caloric intake affect the expression of UCP3 mRNA but not of UCP2 mRNA in skeletal muscle. An increased litter size, a well‐established model of nutritional deprivation before weaning [16], resulted in a reduced UCP3 mRNA expression. This behavior is similar to that found in adult rodents exposed to chronic caloric under‐nutrition [22] and contrasts with the up‐regulation of UCP3 mRNA due to fasting.…”

“…In contrast, UCP2 gene expression in skeletal muscle is developmentally regulated but this regulation is insensitive to nutritional changes. In some of the physiological and nutritional situations studied here, there is a correlation between thermogenic activity and UCP3 mRNA expression, as for example in the early postnatal period, when high thermogenesis occurs [23], or in nutritionally deprived pups, which show reduced non-shivering thermogenesis [16]. In these situations, fatty acids would play multiple roles in thermogenesis, they are the most calorigenic oxidation substrates, they promote mitochondrial uncoupling through UCPs and other mitochondrial anion carriers [5] and they regulate UCP3 mRNA synthesis in skeletal muscle.…”

“…Regular chow was replaced by the high-fat diet on day 15 of lactation and pups were studied on day 21. When the e¡ects of fasting were analyzed, pups on days 1, 6, 15 or 21 were separated from their mothers and studied 8,16 or 24 h thereafter. The e¡ects of di¡erent times of fasting were determined in pups from the same litter.…”

“…changes in litter size on the expression of UCP3 mRNA and UCP2 mRNA in developing mice Nutritional deprivation of mice pups was induced by in- creasing the litter size to 16 whereas over-nutrition was induced by reducing the number of pups at birth to only four, according to previously reported studies [16]. On day 15, the body weight of pups from large litters was signi¢cantly lower than pups from regular litters whereas pups from small litters had a higher body weight (see Table 1).…”

Impact of Maternal Food Restriction on Cold-Induced Thermogenesis in the Offspring

“…On the other hand, it has been reported that food restriction imposed throughout the lactation period by increasing the number of pups per litter led the restricted animals to have lower rectal temperature than the controls, although cold-induced thermogenesis is present. These data suggest a possible impairment in the hypothalamic set-point as a consequence of food restriction imposed during the lactation period [18][19][20].…”