The Effect of Maternal Starvation on the Metabolic Response to Cold of the Newborn Rabbit

Abstract

Summary: Acute starvation of the pregnant rabbit before delivery leads to lipid mobilization, the circulating concentrations of free fatty acids (FFA) increase, and more fatty acids cross the placenta and are stored as triglyceride in fetal tissues, particularly the liver and adipose tissue. Thus the newborns from these unfed does are born with larger fat stores than normal. In this investigation the responses of newborns of unfed and fed does were compared with respect to aspects of the metabolic responses to birth and subsequent cold exposure. It was found that at 2 hr of age the newborns of unfed does had higher circulating concentrations of FFA and triglycerides. The glucose and glycerol concentrations were similar in the two groups, but after 2 hr of cold exposure the newborns of fed docs had much higher blood concentrations of both glucose and glycerol. In both, a large increase in FFA concentration was seen. The newborns of unfed and fed does had similar minimal metabolic rates, but the maximal rate of heat procluction was greater on average by 15% in the newborns of unfed does over the first 3 days of life. Maternal nutrition immediately before delivery has considerable effect on the circulating concentrations of metabolites and the reponses to cold of the newborn. Speculation: In experimental animals and man it has been shown that maternal blood concentrations of free fatty acids influence the net flux of fatty acids to the fetus. the effect of maternal starvation immediately before birth leads to an increase in fetal lipid stores. Newborns from a starved mother might be expected to respond differently with respect to mobilization of energy reserves when they experience starvation and cold exposure for the first time. Newborn rabbits of unfed does had similar blood concentrations of glucose but higher concentrations of FFa and triglycerides than usual; they also had a better thermogenic responce to cold. In this regard they seem better able to withstand acute cold exposure and starvation. A mother's reluctance to eat immediately before delivery may well benefit her yound and these advantages may be reduced by such measures as intravenous glucose feeding.