Impact of Maternal Diabetes Mellitus on the Thermoregulation of the Offspring

Abstract

Maternal diabetes mellitus (DM) can induce metabolic alterations in both newborn and adult offspring. It is believed that inadequate intrauterine conditions can impair thermogenic capacity of the offspring. The objective of the present study was to evaluate the effects of maternal DM on the offspring thermoregulation. DM was induced by streptozotocin injection (60 mg/g) in Wistar EPM-1 female rats. Control animals were injected with an equal volume of citrate buffer solution (pH 4.5). Fifteen days after confirmation of diabetes by glycaemia higher than 250 mg/dl, the rats were mated and the intercourse was confirmed by vaginal smear. Diabetic animals received daily 1 UI of insulin and control animals, an equivalent volume of saline. After delivery, 6 newborn females were randomly assigned to each mother in order to assure equivalent nutritional status during lactation during which body weight of the offspring was recorded daily. At weaning (28th day) the animals were transferred to individual metallic cages kept inside a chamber under a room temperature of 25 degrees C. In the 60th day, half of the offspring was moved to a chamber at 5 degrees C, remaining there until the 90th day. Four experimental groups were thus formed that were the offspring of control or diabetic dams acclimated at 25 degrees C or 5 degrees C. During the whole experimental period body weight and food intake were recorded and during the acclimation period energy balance was determined. When rats were 90 days-old, they were blood sampled and the carcasses prepared for calorimetric determination. At birth, weaning and 90 days of age, animals were killed for quantification of body fat, protein and water. Blood samples were collected and used to determine blood glucose and insulin. Offspring from diabetic dams showed lower body weight than controls throughout the whole experiment. No effect of maternal DM on energy balance of offspring acclimated at 25 degrees C or at 5 degrees C was observed. Nevertheless, as expected, cold induced an increase in energy intake and energy expenditure as well as a reduction in food efficiency, which was characterized by lower body weight and fat gain without change in body protein. Body composition was altered only at birth, when animals from diabetic mothers showed decreased body fat content and increased percentage of water in the carcass. Only at 90 days the rats from diabetic mothers showed higher glycaemia and lower blood insulin levels than controls suggesting delayed effects of maternal DM on the offspring. After weaning, rectal temperature of the animals was measured at 25 degrees C and 5 degrees C during 2 hours at time 0, 30, 60, 90, and 120 minutes. This parameter was determined at weaning and at 45, 60, 75, and 90 days of age. The results showed that the offspring from diabetic mothers not only had a delayed thermogenic capacity as shown by their inability to keep body temperature at 5 degrees C until 90 days. It is, thus, suggested that maternal diabetes mellitus delayed thermoregulation of the offsp...

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