We investigated the adipogenic effects of high-fat diets with different fat sources, as well as their influence on hypothalamus NPY content (NPY) and plasma corticosterone (Cs) and leptin (Lep) concentrations. In a 6-wk experiment performed in 28 male Wistar rats, high-fat diets (approx 60% of energy as fat) containing sunflower oil (S), rapeseed oil (R), palm oil (P), or lard (L) as the fat source were applied. Carcass composition was analyzed by standard methods; NPY, Cs, and Lep were determined by RIA method. Gas chromatography was applied to measure fatty acid composition of dietary fats. S group had the highest body fat content and Lep and the lowest Cs and NPY, while L rats had high Lep and the highest Cs and NPY. We conclude that the fatty acid composition of dietary fat is of high importance where effects of high fat diets on adiposity, as well as on plasma levels of both hormones and hypothalamus NPY content are concerned.

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Our study aimed at investigating the impact of different levels (increased -10% and high -20%; w/w) and types (sunflower oil, rapeseed oil, cod liver oil, lard) of fat in the diet on the activity of the key enzyme in the corticosterone (Cs) biosynthesis pathway in adrenal cortex i.e. deoxycorticosterone 11β-hydroxylase (11β-OHase) (it was expressed as a percent of conversion of [ 14 C]deoxycorticosterone into [ 14 C]corticosterone during 2 h incubation) and on plasma corticosterone and leptin concentration (measured by RIA method) in rats. 102 male Wistar rats were fed their experimental diets for 3 or 6 weeks. All parameters were found to be significantly affected by dietary fat source. Rats fed the diet containing cod liver oil had the highest 11β-OHase activity, while those fed sunflower oil diet had the lowest. Sunflower and rapeseed oil diets brought about higher plasma leptin concentration than cod liver oil and lard diets. Plasma Cs concentration in rats fed cod liver oil diet was higher than in rats fed other fat diets. Additionally, diets containing 20% of fat caused higher enzyme activity than diets containing 10% of fat. There was no effect of fat level in diet on plasma Cs and leptin concentration. These effects were observed in rats fed for six weeks only for enzyme activity and in rats fed for three weeks for plasma Cs concentration. Moreover, 11β-OHase activity increased after 6 weeks of experiment, plasma Cs level -decreased after the same time.

The influence of meal frequency on change of body weight and protein status, measured by level of amino acid oxidation (decarboxylation) in the postabsorptive state, was studied at a fixed daily protein intake. Growing rats (250g) were fed through gastric canula a feeding solution based on Nutrison Standard supplying 1.6g protein and 266kJ ME daily. This amount was given in either 2 large meals at the beginning and the end, or in 6 smaller meals, or by continuous infusion during entire dark period (10 hrs). After 3 weeks of feeding the mean growth rate of the rats fed continuously was nearly 20% higher than rats fed the same amount in 2 meals. The rats fed 6 meals a day had a growth rate rather similar to the rats fed continuously. The percentile recovery of label as 14CO2 in the breath after an intraperitoneal injection of [1-14C]leucine (4 hrs after last meal) was significantly higher (p.05) for the animals fed continuously (27% sd 2.6) compared to the rats fed 2 meals (21.9% sd 4.0). The value for 6 meal group was intermediate (24.5 sd 1.8). The results indicate that the metabolic utilization of a fixed daily amount of protein is clearly influenced by the way of supply. With respect to the change of body weight and protein status, animals have more benefit of the same amount of protein if the supply is more equable. It is suggested that the difference is caused by metabolic restriction for an adequate utilisation of large meals. Therefore large meals are supposed to cause a waste of amino acids in the postprandial phase. As a consequence amino acid amount that will be stored in the body to be available in the postabsorptive phase will be less.

The aim of the study was to assess if supplementation of high-fat diets with vitamin E influences circulating leptin, adiponectin and corticosterone (Cs) in rats. Forty-eight male rats were divided into 4 groups of 12 rats each, and for 6 weeks fed on 20% (wt/wt)-fat diets. Dietary fat was provided by cod liver oil (CLO), grape seed oil (GO), rape seed oil (RO), or lard (L), enriched with vitamin E (500 mg/kg, +E), or not. Plasma hormone levels were unaffected by vitamin E supplementation. Corticosterone concentrations were, however, higher in RO+E rats compared with non-supplemented RO rats. Fat type had a significant impact on relative plasma adipokine levels, body weight, and body fatness. Specifically, GO and RO exhibited the highest levels of adipokines. Yet, plasma Cs levels did not vary among groups. Our study supports the preventive role of vegetable fats, even if supplied in excess, against adipose tissue deposition and its ramifications in terms of hormone secretion.

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The purpose of the study was to elucidate the relationship between meal frequency and the thermic effect of meal in rats.

Forty-one rats were divided into six groups assigned to one of six diets containing three different fat types (sunflower oil, lard or 50:50 (w/w) blend of sunflower and lard) at one of two levels (5 or 30%) to determine the effect on the corticosterone (Cs) level in the cytosol fraction of the adrenal glands, heart muscle and aorta in rats. Plasma cholesterol concentrations and body composition were also measured.The diet with 5% lard significantly increased adrenal Cs compared with diets with 5% sunflower oil or 5% blend. Marked elevations in Cs level in the aorta were evident in rats fed diets with 5 and 30%o sunflower oil in comparison with rats fed the 5 and 30% blend of lard and sunflower oil. In addition, the Cs level in the aorta in rats fed the diet with 30% sunflower oil was significantly higher than in rats fed the diet with 30% lard. The diet containing 5% sunflower oil markedly elevated the Cs level in rat heart muscle compared with the diet containing a 5% blend of the two fats. Unexpectedly, there were no significant effects of the experimental diets on plasma cholesterol concentrations. Moreover, rats fed diets containing 30% fat had higher body dry matter and fat percentages, but lower protein and ash percentages compared with the rats fed diets containing 5% fat. The percentages of fat, protein and ash in the body were not affected by the type of dietary fat, but rats offered lard diets had a higher percentage of dry matter and fat than rats fed mixed fat diets.