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Lipid metabolism in the obese Zucker rat. Disposal of an oral [14C]triolein load and lipoprotein lipase activity.

ABSTRACT: Oxidation in vivo of [14C]triolein to 14CO2 was significantly lower in obese (fa/fa) Zucker rats as compared with their lean (+/?) controls. In response to a 24 h starvation period, both lean and obese rats showed an enhanced rate of [14C]triolein oxidation. There were, however, no changes in the rate of intestinal absorption of [14C]triolein between the lean and obese animals. Conversely, the total tissular [14C]lipid accumulation was significantly higher in white adipose tissue, carcass and plasma in the obese animals, whereas that of brown adipose tissue was lower. This was associated with a marked hyperinsulinaemia and hypertriglyceridaemia in the fa/fa animals. Starvation dramatically decreased [14C]lipid accumulation in white adipose tissue of the lean Zucker rats, but had no effect in the obese rats. The lipogenic rate of the obese rats was significantly higher than that of lean rats in liver, white adipose tissue, skeletal muscle and carcass. Lipoprotein lipase activity (per g of tissue) was significantly lower in both white and brown adipose tissue of obese versus lean rats; however, total activity was higher in both tissues. Starvation significantly lowered perigenital-adipose-tissue lipoprotein lipase activity in the lean groups, and had no effect in the obese ones. These results demonstrate that the tissue capacity of exogenous lipid uptake is involved, but cannot be the only factor influencing the maintenance of obesity in these animals. Thus, in the adult fa/fa rat, the large increase in obesity is not solely dependent on a deviation of energy-producing substrate metabolism towards the storage of lipids in white fat. Other factors, such as a low rate of oxidation, a high lipogenic rate and decreased brown-adipose-tissue activity are involved in the perseverance of the obesity syndrome.

SUBMITTER: Lopez-Soriano EJ

PROVIDER: S-EPMC1149961 | biostudies-other | 1991 Mar

REPOSITORIES: biostudies-other

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Project description:Ecdysteroids are a class of steroid hormones occurring in insects, where they are referred as zooecdysteroids, and in plants, where they are termed phytoecdysteroids. While zooecdysteroids in insects regulate important developmental processes, such as embryogenesis, molting (ecdysis), metamorphosis, reproduction, and diapause, phytoecdysteroids provide protection against invertebrate predators by acting as feeding deterrents and by disrupting critical developmental processes of such invertebrates. The ecdysteroids in insects and plants comprise a great number of different analogues, with 20‐hydroxyecdysone, also called ecdysterone, being the quantitatively dominating biologically active analogue in both, insects and plants. Although phytoecdysteroids are effective toxins or antifeedants towards non-adapted herbivorous invertebrate predators, ecdysteroids are apparently non-toxic to mammals and even have been shown to exert a variety of interesting metabolic actions, such as antiobesity, hypoglycemic and protein-anabolic effects. In the present study aimed to test the hypothesis that ecdysterone causes lipid-lowering effects in obese Zucker rats. To test this hypothesis, two groups of obese Zucker rats were fed a nutrient-adequate diet supplemented without or with 0.05% ecdysterone. This ecdysterone concentration was appropriate to achieve a similar dose of ecdysterone per kg body weight BW as applied in other rodent studies, in which ecdysterone caused either hepatic and plasma lipid-lowering effects or antiobesity effects in different rodent models. In order to decipher the potential lipid-lowering actions of ecdysteroids in Zucker rats, measurements of liver and plasma lipid concentrations and hepatic transcriptome analysis was carried out. To further study if ecdysterone is capable of alleviating the strong lipid-synthetic activity in the liver of obese Zucker rats, the study included also two groups of lean Zucker rats which also received either the ecdysterone-supplemented or the non-supplemented diet.

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Lipid metabolism in the obese Zucker rat. Disposal of an oral [14C]triolein load and lipoprotein lipase activity.

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