Maternal and early dietary fatty acid intake: changes in lipid metabolism and liver enzymes in adult rats
2000
Chapman, C. | Morgan, L.M. | Murphy, M.C.
Over the last decade, much evidence has emerged to suggest that alterations in maternal nutrition during pregnancy may irreversibly affect aspects of physiological and biochemical functions in the fetus. This study was designed to determine the mechanisms involved in these alterations. Our hypothesis was that the type of maternal dietary fat received in early life could determine the level of lipoprotein lipase (LPL; EC 3.1.1.34) activity and gene expression which would be maintained into later life. A diet high in (n-3) polyunsaturated fatty acids was predicted to be associated with higher levels of lipoprotein lipase (LPL) activity and expression and lower levels of plasma triglyceride after a high fat meal challenge. Using a 2X2 factorial design, Wistar Albino rats were pair-fed either a fish oil diet (50 g/kg) or a mixed oil diet (50 g/kg) for the last 2 wk of gestation, during lactation and pups were fed these diets until 5 wk of age. After 5 wk, the rats were fed nonpurified diet. The rats were killed at 5 wk (young) or 10 wk (adult) of age after a mixed oil (50 g/kg) test meal. There were significant age effects on plasma triglyceride (P < 0.02), cholesterol (P < 0.001), glucose-dependent insulinotrophic polypeptide (GIP) (P < 0.001) and liver glutathione reductase activity (P < 0.05) which were all higher in the young rats compared to the adults. There were significant effects of diet on triglyceride (P < 0.001), cholesterol (P < 0.001) and LPL mRNA levels (P < 0.001). GIP and triglyceride levels were significantly correlated (r = 0.66; P < 0.001). Omental adipose tissue LPL activity as significantly higher in the fish-oil fed groups compared to the other groups (P < 0.001), whereas Epididymal adipose tissue LPL mRNA was significantly higher in the mixed oil-fed adults compared to the other groups (P < 0.001). The latter result suggested an imprinting effect of fatty acid composition in early life on LPL gene expression. Liver superoxide dismutase activity was affected by age and diet and was higher in the young than in the adults and higher in the fish oil-fed young than in those fed the mixed oil-fed (P < 0.005). Catalase activity was also affected by age (P < 0.001) and diet (P < 0.001), and there was a significant interaction between age and diet (P < 0.001). Catalase activity was higher in rats fed fish oils at both stages of development, suggesting that feeding fish oils to rats in early life raises oxidative stress throughout life. The majority of the significant differences shown were between the age groups and not between the two dietary groups, suggesting that postprandial handling of a standard fat meal is affected more by age than by early dietary fatty acid composition. However, the mechanisms of biological imprinting of fatty acids on LPL expression and on enzymes related to oxidative stress requires more investigation.
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