Abstract
The ingestion of excess lipids often produces the accumulation of liver fat. The modulation of diet energy partition affects this process and other metabolic responses, and oestrogens and androgens are implied in this process. Ten-week-old male and female rats were fed with either standard rat chow (SD), SD enriched with coconut oil (high-fat diet, HF), SD enriched with protein (high-protein diet, HP) or a 'cafeteria' diet (CAF) for 1 month. HF and CAF diets provided the same lipid-derived percentage of energy (40 %), HP diet protein energy derived was twice (40 %) that of the SD. Animals were killed under anaesthesia and samples of blood and liver were obtained. Hepatic lipid content showed sex-related differences: TAG accumulation tended to increase in HF and CAF fed males. Cholesterol content was higher only in the CAF males. Plasma oestradiol in HF and HP males was higher than in CAF. Circulating cholesterol was inversely correlated with plasma oestradiol. These changes agreed with the differences in the expression of some enzymes related to lipid and energy metabolism, such as fatty acid synthetase or phosphoglycolate phosphatase. Oestrogen protective effects extend to males with 'normal' diets, that is, not unbalanced by either lipid or protein, but this protection was not enough against the CAF diet. Oestradiol seems to actively modulate the liver core of 2C-3C partition of energy substrates, regulating cholesterol deposition and lactate production.
Highlights
The data obtained using high-fat diets almost invariably result in increased body and liver weights[1], including a variety of alterations in homoeostatic markers, especially overall increased fat deposition, and, markedly in liver, altering glucose and lipid metabolism[2,3]
The animals were randomly divided into four groups (n 6–8 each) for each sex: rat chow, a standard rat chow (SD) mixed with coconut oil, a simplified cafeteria diet[15] or a SD mixed with proteins
The values for cafeteria’ diet (CAF) diet were obtained from the actual consumption data and were like those previously described[17,18]
Summary
The data obtained using high-fat diets almost invariably result in increased body and liver weights[1], including a variety of alterations in homoeostatic markers, especially overall increased fat deposition, and, markedly in liver, altering glucose and lipid metabolism[2,3]. Diets with high-protein content have been promoted, especially in humans, to maintain or increase muscle mass[6], they have been applied to the treatment of obesity and related diseases[7,8] Their actual metabolic effects on energy partition and on general regulation of metabolism are largely unknown[9,10], a situation compounded by the lack of information on amino acid diverse catabolism pathways and by the factors that regulate their utilisation under normal feeding conditions. We assumed that the role of oestrogens and/or androgens would help explain the different responses observed in males and females In this experiment, we used controls which fed essentially the same diet components than the groups with an added burden of protein or lipid. We added a classical and proven obesogenic diet type, cafeteria, which we expected could behave as a ‘wild card’ to help explain the way energy partition was modulated by ‘naturally released’ oestrogen in both female and male rats
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