Effect of postnatal undernutrition on ketone metabolism and its relation to metabolic changes in brain and liver of rats

Insulin secretion in adult rats that had experienced different underfeeding patterns during their development

Four populations of 70-day-old undernourished rats were studied. All rats were submitted to a 65% restriction of food intake as follows: 1) undernutrition of the mother from day 14 of gestation until birth only (fetal period, group F), 2) undernourished during fetal and suckling periods only (group FS), 3) undernourished from day 14 of gestation until day 70 of life (group FSA), and 4) undernourished from day 28 of life until day 70 (group A). Body weight, plasma glucose, glucose tolerance, basal plasma insulin, in vivo glucose-induced insulin secretion, pancreatic insulin content, and in vitro response of isolated islets to glucose and amino acids were investigated. Islet insulin content decreased in all four groups studied, and islet mass was found reduced in group FSA. Glucose tolerance was decreased in group A, and in vitro response of islets decreased in both groups FSA and A. We conclude that two different adaptive processes should be considered: the possible long-term consequences of impaired pancreas development due to inadequate perinatal nutrition and the functional alteration of insulin secretion to undernutrition in adulthood.

Long chain fatty acid deficits in brain myelin sphingolipids of undernourished rat pups

A restricted maternal dietary intake (40% of ad libitum intake) is known to cause myelin deficit that is accompanied by decreased amounts of individual phospholipids and sphingolipids in brain myelin of suckling rats. This communication reports the effects of the same nutritional stress on the fatty acid composition of brain myelin lipids. In myelin of 19-day-old normally fed rats, palmitate (16:0), stearate (18:0) and oleate (18:1) accounted for 80-90% of all fatty acids in phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. Maternal dietary restriction resulted in deficits of total fatty acid content, but did not affect the proportional distribution of individual fatty acids among phospholipids. By contrast, longer chain (22- and 24-carbon) fatty acids accounted for more than half the fatty acid content of myelin cerebroside and sulfatide from the 19-day-old control rat pups. In undernourished rats of that age, proportions of lignocerate (24:0) and nervonate (24:1) in cerebroside and sulfatide were 40-50% lower than those in control rats. This, together with higher proportions of 16:0, 18:0 and 18:1 and a higher ratio of C16-C20 to C22-C24 in undernourished than in control rats, suggests an impairment in fatty acid chain elongation. Ten days of nutritional rehabilitation failed to restore the fatty acid imbalances; however, after an additional 5 days of ad libitum feeding, the experimental and control values were similar. The undernutrition results in hypomyelination, which is characterized by a proportional decrease in lignoceric and nervonic acids of sphingolipids.

Maternal dietary restriction causes myelin and lipid deficits in the brain of offspring

The relationship between brain myelination and nutritional insufficiency in suckling rats whose dams had a restricted dietary intake was studied. The undernourished pups were characterized by body weight and brain weight that were 40-70% and 82-88% that of controls throughout the suckling period. Myelin concentrations, whether expressed as mg protein or as mg myelin dry weight per g wet brain, were 30-40% of normally fed controls. Myelin of undernourished rats contained total lipid, cholesterol, phospholipids, and sphingolipids that were 42, 54, 39, and 48%, respectively of the control counterparts. There was no change in the mole ratio of cholesterol:phospholipids:sphingolipids (i.e., cerebroside + sulfatide) in myelin from undernourished rats. Concentrations of individual phospholipids and sphingolipids were lowered by approximately the same percentage. Despite long-lasting, irreversible stunting of whole-body and brain growth, concentrations of myelin and myelin lipids returned to control levels after nutritional rehabilitation. Since the observed effects are different from those of more commonly used models, the present form of undernutrition may offer a useful system for studying the relationship between myelin lipids and brain development.

Glycemia, ketonemia, and brain enzymes of ketone body utilization in suckling and adult rats undernourished from intrauterine life

The effect of undernutrition from the 16th day of pregnancy up to 70th day of life on blood glucose and ketone bodies and on several brain mitochondrial enzymes related to energy metabolism or biosynthetic function was investigated. Undernutrition in perinatal period was established by means of a food restriction to pregnant rats and, later, to the lactating mother; undernourished postweaned rats received half the diet consumed by the controls. Body and brain weight from undernourished rats was less than controls throughout the entire period studied. Glycemia and ketonemia were also always lower than controls. Cytochrome c oxidase, citrate synthase, 3-hydroxybutyrate dehydrogenase, 3-oxoacid coenzyme A transferase, and acetoacetyl-coenzyme A thiolase activities during the suckling period were in most stages lower than controls; subsequently, activities in undernourished rats reached or surpassed the control values. These results could explain the "catch up" phenomenon in several ultrastructural parameters found by other authors in undernourished postweaned rats.

Activities of enzymes of ketone body metabolism in liver and muscle tissues of suckling rabbits

The concentration of ketone bodies in blood of suckling rabbits during the first 6 days following birth was higher than that found in the adult. In the liver the activities of the enzymes of ketone body synthesis were higher than in the adult during the same period. In the heart and leg muscle the activities of the enzymes of ketone body utilization were lower than those found in the adult. It is suggested that the capacity of the muscles of the developing rabbit to utilize ketone bodies is not greater than that of the adult and ketone bodies produced by the liver could contribute as fuel for oxidation and/or synthesis to the brain of the newborn rabbit.