Growth and Fatty Acid Metabolism in Experimental Intrauterine Growth Retardation: Effect of Postnatal Nutrition in Rat

Abstract

Rats, 3½ to 4 d of age, were used to study weight gain and fatty acid (FA) metabolism as a function of degree of intrauterine growth retardation (IUGR) and of postnatal nutrition. The IUGR, quantified postnatally as mild and severe, was produced by uterine artery ligation on d 17 of gestation, and controls were sham-operated. Food intake was manipulated by varying the litter size; i.e., pup number per dam was 4 or 5 for overfeeding, 8–10 for normal feeding and 13–15 for underfeeding. Fatty acid synthesis rate (FASR) (determined by tritiated water incorporation in FA) and contents were determined in selected organs at 84 to 96 h of age. The initial weights (grams) at 2 to 12 h of age were: 5.88 ± 0.74 (mean ± SD) for controls, 5.18 ± 0.11 for mild IUGR and 4.18 ± 0.24 for severe IUGR. During the first 96 h of life, weight gain was less in underfed control pups while overfeeding resulted in the same weight gain as in normally fed pups. Pups with mild IUGR showed the same effect of under- or overfeeding as control pups. In the severe IUGR groups, weight gains were similar in all three feeding groups. In the carcass, the fatty acid content was reduced as a result of both prenatal and postnatal undernutrition. Although the underfed control group had a high FASR, underfeeding had no effect on the FASR of groups with IUGR. In the liver, the FA content was also lower in the underfed controls and in IUGR groups, without any difference in FASR. Feeding did not influence the FASR of liver. In the brain, the FA synthesis rate of normally fed IUGR pups was significantly greater and was almost twice as high in underfed IUGR pups as in normally fed IUGR pups. This was accompanied by significantly lower FA contents in both normally fed and underfed IUGR pups. It is concluded that in the rat, during the first few days of life, 1) a generous food supply does not augment weight gain, 2) a restricted food supply reduces weight gain in normal and mild IUGR but not in severe IUGR and 3) the reduction fatty acid content in prenatal and postnatal under-nutrition is consistent with the reduction in weight gain.