The effects of food restriction on maternal endocrine adaptations in pregnant rats.

The aim of this study was to characterize hemodynamic, electrolytic and endocrine alterations produced by food restriction (50%) in pregnant rats for the purpose of evaluating the importance of these parameters on the plasma volume expansion and fetal growth. One hundred seventy six pregnant rats were divided into two groups, a control group (C) with an ad libitum diet and another with a restricted diet (U) (50% by weight of the diet of the control group). On days 5, 10, 15 and 20 of pregnancy, the weight of the mother, water intake, urine output, urine and plasma sodium concentration, plasma potassium concentration, blood pressure and heart rate, osmolality, plasma renin activity (PRA) and vasopressin were recorded. The number and weight of the fetuses were determined on days 15 and 20 of gestation. Food restriction results in inadequate weight gain in the mother and retardation of fetal growth. Water and sodium balance (p< or =0.001) were decreased in U group and basal PRA (p< or =0.001) was increased in U group. Food restriction did not significantly alter urine sodium excretion, plasma osmolality, plasma sodium and potassium values, blood pressure and basal vasopressin values. We conclude that the higher values of PRA, described in food restriction situations during pregnancy, seem to be caused by the adaptation to low sodium intake.

Macronutrients intake of top level cyclists during continuous competition--change in the feeding pattern.

In order to quantify the nutritional status and the feeding pattern of professional cyclists during continuous competition, food intake was accurately measured and recorded using the weighed inventory of food (over three 24 h periods) during all meals in ten top professional cyclists during a real 3 weeks' competition. A 24 h period was defined as the time between the start of one stage and the next start. The 24 h period intake of energy, protein, fat, and carbohydrate was used to discover whether these intakes met requirements for endurance exercise. The average intake of energy and macronutrients was: energy = 23.5 +/- 1.8 MJ/24 h period, carbohydrate = 841.4 +/- 66.2 g/ 24h period; protein = 201.8 +/- 17.7g/24 h period; and fat = 158.6 +/- 16.3 g/24 h period. The carbohydrate, protein and fat contribution to energy was 60.0%, 14.5%, and 25.5% respectively. Fluid intake per 24h period was 3.29 +/- 0.94l (1.26 +/- 0.55 l during the race). Our study shows a similar energy intake in comparison with the only previous study in 1989 but there is a change in the feeding pattern of top level cyclists. A more important role is given to the intake of carbohydrate just after competitions together with an increase in protein intake. Both changes could have a positive effect on performance.

Role of 17-beta-estradiol and progesterone on glucose homeostasis: effects of food restriction (50%) in pregnant and non pregnant rats.

The role of 17-beta-estradiol and progesterone on glucose homeostasis was examined in pregnant and non pregnant rats with or without food restriction (50%). Blood glucose and insulin levels were significantly decreased in food restricted pregnant (PM) compared with control pregnant (PC) and in food restricted non pregnant (M) compared with non pregnant control (C). The plasmatic level of progesterone was similar in PC and PM, while the plasmatic level of 17-beta-estradiol was significantly decreased in PM compared with PC at 15 and 20 days. In spite of food restriction, the changes in the insulin/glucose ratio throughout gestation were similar in PC and PM. A positive and significant relation between 17-beta-estradiol and the level of insulin at day 5 of gestation, and a negative and significant relation between the level of 17-beta-estradiol and level of insulin at day 15 of gestation were found in PC. A negative and significant relation between the levels of progesterone and the levels of insulin at day 5 of gestation, at day 10 this relation is positive and significative, and at day 15 a positive and significant relation exists between levels of 17-beta-estradiol and levels of insulin were found in PM. These results suggest that 17-beta-estradiol acts directly on beta-cells to control insulin secretion. Food restriction does not alter the changes in the sensitivity of tissues to the insulin action, and does modify the action of 17-beta-estradiol and progesterone on beta-cell.