Cíntia Roehrig

Serum and liver lipids in rats and chicks fed with diets containing different oils.

OBJECTIVES Because dietary fat composition is determinant for serum cholesterol level, which is related to cardiovascular disease, we evaluated the effects of diets containing saturated (coconut oil) or polyunsaturated fatty acids (soybean oil) supplemented or not with dietary cholesterol on serum and liver lipid composition in two animal species. METHODS Male Wistar rats (21 d old) were assigned to one of seven groups and fed with commercial diet or diets containing 5% or 20% soybean oil or 20% coconut oil with or without 1% cholesterol. Chicks were assigned to one of four groups and fed with diets containing 15% soybean oil or 15% coconut oil with or without 1% cholesterol. RESULTS In rats, the accumulations of hepatic cholesterol and triacylglycerols were higher in the group fed 20% soybean oil and 1% cholesterol than in the group fed 20% coconut fat and 1% cholesterol. The highest serum levels of cholesterol and triacylglycerols were observed in the group fed coconut oil and cholesterol, compared with the group fed soybean oil and cholesterol. Triacylglycerol, high-density lipoprotein, and total cholesterol serum levels increased with diet containing coconut oil and cholesterol. In chicks, the highest hepatic cholesterol accumulation occurred in the group fed 15% coconut fat and 1% cholesterol. Total and high-density lipoprotein cholesterol levels increased with diet containing coconut oil and cholesterol, although none of these diets modified serum triacylglycerol levels. CONCLUSIONS The type of experimental animal model and the diet composition influence lipid metabolism.

High Extracellular K+ Levels Stimulate Acetate Oxidation in Brain Slices from Well and Malnourished Rats

We investigated the effect of high (12, 20, and 50 mM) extracellular K+ concentrations ([K+]0) on [U-14C] acetate oxidation to CO2 in cerebral cortex slices of control and perinatal malnourished rats. High [K+]0 increased the acetate oxidation, compared with a medium containing 2.7 mM [K+]0. By investigating the mechanisms involved in this stimulation, it was shown that (i) ouabain (1 mM) and monensin (10 μM) prevented this increase; (ii) in a medium with physiological [K+]0 (2.7 mM), the decreasing of [Na+]0 stimulated acetate oxidation. These results suggest that the stimulatory effect of [K+]0 on acetate oxidation was due to the decreasing of Na1 levels. Considering that malnutrition could alter the activity of Na+,K+-ATPase and/or other pertinent proteins, its effect on acetate oxidation was investigated. The malnutrition, which altered the body and cerebral weight of rats, did not modify the acetate oxidation in any protocol.

Glucose and Lactate Utilization by the Amygdala of Male and Female Rats

Gonadal hormones appear to modulate brain energy metabolism, and morphological and functional sexual differences are found in the amygdaloid complex (AC) of rats. Our aim was to study the CO2 production and lipid synthesis, measured by the rate of L-[U-14C]lactate or D-[U-14C]glucose utilization (in pmol.hr−1.mg−1), by AC slices in vitro of male and female rats. Lactate was more used than glucose as energy substrate (p < 0.01) but no sex-related difference was observed in glucose or lactate oxidation to CO2 (p > 0.05) or on lipid synthesis obtained from both substrates (p > 0.05). In addition, there was no effect of the estrous cycle on lactate oxidation to CO2 by the AC of females (p > 0.05). Based on the present data, it appears that the endogenous normal levels of gonadal hormones are not able to promote sex-related differences in the in vitro glucose or lactate utilization by the AC of rats.