Weight-maintaining fat-rich, "prudent," carbohydrate-rich, as well as energy-restricted diets (300 kcal/d) were fed in succession for 7 d to 12 healthy males of ideal body weight under metabolic ward conditions. At the end of each period isolated fat cells were prepared from subcutaneous abdominal adipose tissue and incubated in vitro in the absence or presence of adenosine deaminase, either alone or in combination with various lipolytic or antilipolytic hormones and agents.Variations in total energy intake and dietary composition had characteristic and specific effects on fat cell lipolysis in vitro. High carbohydrate and prudent diets resulted in low rates of nonstimulated glycerol release and impaired insulin action in the presence of adenosine deaminase (320 mU/ml). High-fat and energy restricted diets were characterized by high rates of nonstimulated glycerol release. Sensitivity of antilipolysis to insulin and prostaglandin E2 was 10 to 200 times lower respectively on energy-restricted than on fat-rich diets. The effects of a2-and fl-adrenergic catecholamines and ofN6-phenylisopropyladenosine were not affected by the preceding diets.

The aim of the study was to investigate the complete substitution of imported soybean meal in beef cattle diets and the consequences on performance, meat, and adipose tissue quality. Thirty growing crossbred Limousin bulls, with an initial bodyweight of 164 ± 13 kg and 4.3 ± 0.3 months of age, were fed a grass/maize-silage based diet with little additional concentrate (0.5:0.3:0.2). Concentrates contained either soybean meal (positive control), faba beans, pumpkin seed cake, or spirulina (Arthrospira platensis), resulting in about 226 g crude protein (CP)/kg concentrate dry matter (DM) and 158 g CP/kg total diet DM. A grain-based concentrate providing just 135 g CP/kg concentrate DM and 139 g CP/total diet DM served as a negative control. Bulls of all groups had comparable average daily gains (1.43 ± 0.1 kg) and feed intakes (6.92 ± 0.37 kg). Carcass and meat quality did not differ among groups. The fatty acid profile of meat lipids was hardly affected. These results indicate that soybean meal can be replaced by any of the tested protein sources without impairing performance or meat quality. Importantly, bulls fed the negative control achieved a fattening and slaughter performance comparable to that of the protein-supplemented groups without affecting meat and adipose tissue quality. Thus, the present findings suggest that feeding crossbred bulls a grass/maize-silage based diet does not require additional protein supplementation.

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The effects of two phosphodiesterase inhibitors, e.g. theophylline and D-4-(3-butoxy-4 methoxybenzyl)-2-imidazolidinone (RO-20-1724) on the antilipolytic action of insulin in human adipocytes were investigated. At a concentration of 1 mmol/l (theophylline) and 0.1 mmol/l (RO-20-1724) both inhibitors increased cyclic AMP to a similar extent. However, their effects on insulin action were different. Whereas addition of theophylline abolished the ability of insulin to inhibit lipolysis, insulin was fully functional in depressing glycerol release in the presence of RO-20-1724. The results suggest that the insulin-sensitive phosphodiesterase of human adipocytes may be relatively resistant to RO-20-1724 as has been shown for the enzyme system of 3T3-L1 adipocytes.