Major differences in noradrenaline action on lipolysis and blood flow rates in skeletal muscle and adipose tissue in vivo

Abstract

Aims/hypothesis: The regulation of skeletal muscle lipolysis is not fully understood. In the present study, the effects of systemic and local noradrenaline administration on lipolysis and blood flow rates in skeletal muscle and adipose tissue were studied in vivo. Methods: First, circulating noradrenaline levels were raised tenfold by a continuous i.v. infusion (n=12). Glycerol levels (an index of lipolysis) were measured in m. gastrocnemius and in abdominal adipose tissue using microdialysis. -10 −6 mol/l) (n=10). Local blood flow was monitored with the ethanol perfusion technique. Results: With regard to systemic noradrenergic stimulation, no change in fractional release of glycerol (difference between tissue and arterial glycerol) was seen in skeletal muscle. In adipose tissue it transiently increased twofold (p<0.0001), and the rate of appearance of glycerol in plasma showed the same kinetic pattern. Blood flow was reduced by 40% in skeletal muscle (p<0.005) and increased by 50% in adipose tissue (p<0.05). After noradrenaline stimulation in situ, a discrete elevation of skeletal muscle glycerol was registered only at the highest concentration of noradrenaline (10 −6 mol/l) (p<0.05). Adipose tissue glycerol doubled already at the lowest concentration (10 −8 mol/l) (p<0.05). In skeletal muscle a decrease in blood flow was seen at the highest noradrenaline concentrations (p<0.05). Conclusions/interpretation: Lipolysis and blood flow rates are regulated differently in adipose tissue and skeletal muscle. Adipose tissue displays a high, but transient (tachyphylaxia) sensitivity to noradrenaline, leading to stimulation of both lipolysis and blood flow rates. In skeletal muscle, physiological concentrations of noradrenaline decrease blood flow but have no stimulatory effect on lipolysis rates.

Neuroendocrine mechanisms in insulin resistance

“…Increased circulating noradrenaline levels induces lipolysis in adipose tissue, but not in muscle (18,19). However, local administration of catecholamines to the muscle tissue induce muscle lipolysis which is more pronounced after epinephrine than norepinephrine stimulation (20).…”

Efeito da suplementação oral de arginina sobre a secreção de GH e metabolismo de lipídios em ratos Wistar treinados

“…Suas principais funções são: fortes efeitos lipolíticos, pois estimula a lipólise através da oxidação de ácidos graxos dos tecidos adiposos durante restrição calórica e no exercício físico pela ação da enzima lipoproteína lipase, promove alterações na composição corporal e reduz o metabolismo dos carboidratos para manter os níveis da glicose sangüínea (Chromiak & Antonio, 2002;Mauras et al, 2000;Moller, Jorgense, Alberti, Flyvbjerg, & Schmitz, 1990;Quisth et al, 2005).…”

In vivoregulation of rainbow trout lipolysis by catecholamines

“…Therefore, the regulation of fatty acid supply, or lipolysis, affects many fundamental life processes (Clarke et al, 1997;Raclot and Oudart, 1999;Hulbert et al, 2007). In the intact organism, lipolysis is measured as the rate of appearance of glycerol (R a glycerol) (Wolfe, 1992), and it has been thoroughly investigated in mammals, mainly in humans (Klein et al, 1989;Wolfe et al, 1990;Klein et al, 1995;Quisth et al, 2005). Unfortunately, the information available for other vertebrates is restricted to two in vivo studies on birds (Bernard et al, 2002;Vaillancourt and Weber, 2007) and one on fish (Bernard et al, 1999).…”