Variations in total energy intake and composition of daily food play an important role in the regulation of metabolic processes and so, in the control of body weight. This study was designed in order to investigate the effect of a high-fat diet on lipolysis in isolated adipocytes. For this purpose, fourteen Wistar rats were divided into two groups and fed either a standard-fat diet or a high-fat diet ad libitum for 7 weeks. Adipocytes were prepared from fat pads by collagenase digestion and incubated in vitro in the absence or presence of various lipolytic agents. Lipolysis was measured by the release of glycerol into the medium during 90 min of incubation. We observed that a high amount of fat in the diet induced an enlargement of adipose tissue, which was accompanied by a reduction of beta-adrenergic agonist-induced lipolysis, that could be due to a loss of beta(1) and beta(3)-adrenoceptor number or to alterations of their coupling to adenylate-cyclase through the guanine nucleotide regulatory protein. New data about regional differences were provided by comparing two adipose locations (subcutaneous and visceral).

No abstract

Rasa Aragonesa lambs were used to evaluate the repartition-ing effects of a β-adrenergic agonist and its withdrawal on nutrient metabolism. One group of animals (T-I) was fed salbutamol at a dose of 2 mg × kg^-1 diet × day^-1 for 38 days, while in another group (T-II) the β-adrenergic agonist was discontinued in the diet 5 days before slaughter on the 43rd day. The semitendinosus muscle protein content increased (p < 0.05), while fat and collagen content decreased (p < 0.05) in the T-I group. These differences were not apparent in the group from which salbutamol was withdrawn. Muscle protein degradation was diminished (p < 0.05) in both treated groups. The serum free fatty acid level was markedly enhanced (p < 0.05) in the T-I group. Total essential amino acid serum levels were reduced (p < 0.05) after the withdrawal period. Ketogen-ic and urea cycle amino acids were reduced (p < 0.05) in the salbutamol-fed T-I group and glycogenic amino acids were diminished (p < 0.05) in the T-II experimental group. The data show that salbutamol is able to increase muscle content at the expense of fat stores in productive animals. However, these repartitioning effects are circumvented by a 5-day period of withdrawal, in which concomitant metabolic changes in lipid and protein turnover and plasma amino acid profiles occur.

No abstract

No abstract