Aspects of Hormonal Regulation of Lipolysis During Exercise: Effects of Chronic β-Receptor Blockade*

Abstract

Exercise-induced lipolysis and hormones possibly involved in the regulation of lipid metabolism in association with exercise (plasma catecholamines, ACTH, HGH, TSH, insulin) were studied in 11 WHO stage 1 to 2 hypertensive men (mean age 37 years) during a 30-min steady-state submaximal (65% of VO2 max) and near-maximal exercise seated on a bicycle ergometer. To assess the contribution of the sympathetic system to the regulation of lipolysis and to define the type of beta-receptors mediating the catecholamine effects on lipolysis, all patients were again studied under identical conditions after a 4-week treatment with the beta-1-beta-2-receptor antagonist pindolol (15 mg daily) and with the beta-1-receptor blocker acebutolol (500 mg daily). Eight patients were even restudied after a 16-month treatment with acebutolol. Plasma glycerol levels increased progressively (P less than 0.001) during exercise reflecting increased exercise-induced lipolysis. The concomitant significant rise of noradrenaline, adrenaline, ACTH, and HGH and the parallel fall in plasma insulin suggest that all these hormones are involved in the adjustment of exercise-induced lipolysis. However, the impaired catecholamine-induced lipolysis under beta-receptor blockade was not accompanied by significant compensatory increases of ACTH, HGH, or TSH or a fall in insulin during exercise. Both beta-receptor antagonists resulted in a similar 27% inhibition of lipolysis confirming that the catecholamine-induced increase of lipolysis is mainly mediated via beta-1-adrenoceptors. After 16 months of treatment with acebutolol, the degree of inhibition of the exercise-induced lipolysis was unchanged. However, FFA were significantly reduced (28%, P less than 0.05) and HGH significantly (100%, P less than 0.05) increased.

Oxygen Uptake and Plasma Catecholamines During Submaximal and Maximal Exercise After Long-Term β-Receptor Blockade

“…On the other hand, previous studies (8,10,11,14,16,20) have shown distinct differences in the effects on carbohydrate metabolism exerted during prolonged exercise by cardioselective and nonselective antagonists, respectively. Since j3 -selective receptor blockers conversely to 131-(32-receptor antagonists lack an inhibitory effect of glycogen breakdown (8,10,11,14,16,20) and affect less the exercise performance with respect to individual muscle fiber composition (17), (3 -selective antagonists appear a prefereble choice for patients taking part in preventive and rehabilitative training programs.…”

Variations of Serum Testosterone Concentrations after Physical Exercises of Different Duration

“…Age characteristics and duration of exercise in each group are presented in Table 1. Introduction The influence of physical exercise on serum hormones and metabolites has been the object of many reports (3,6,8,11,16,17); particulary the behavior of testosterone (17-13-hydroxy-androst-4-en-3-one) has been studied after physical activities varying in type, intensity, and duration (5,7,18).…”

Cardiac Response to Exercise in Health and Disease

“…4,65,102,103 Beta blockers do not reduce plasma catecholamine concentration. More over, the effect of beta antagonists is to blunt cate cholamine action and as a result there may be some accumulation of plasma catecholamine activ ity; [102][103][104][105] hence, when β blockers are immediately withdrawn, patients with coronary artery disease may experience a provocation of angina pectoris owing to the massive release of catecholamine activ ity. The rise in plasma potassium seen with virtually all beta antagonists, to a lesser degree with selective β blockers, 4,105 is as a result of blockade of cate cholamines at cellular receptor sites.…”

“…Finally, in addition to the above meta bolic changes no one β-antagonist is preferentially better in terms of altering serum lipids when exer cise and β-blockers are combined, 109,110 although selective β blockers do not blunt exercise-induced lipolysis as readily as does propanolol. 104,111…”