Coordinated regulation of adipose tissue adrenergic- and non-adrenergic-mediated lipolysis during exercise in lean and obese individuals: the effect of exercise training

Abstract

Background and aims: Adipose tissue dysfunction, which includes impairments in (adipose tissue) lipolysis, contributes to insulin resistance. Subcutaneous adipose tissue (SCAT) lipolysis in obesity is characterized by catecholamine resistance and an impaired ANP responsiveness. It remains to be established whether exercise training improves nonadrenergically-mediated lipolysis, next to the adrenergic pathway, in metabolically compromised conditions. The aim of the present study was to investigate the effect of local combined α- and β-adrenergic receptor blockade on SCAT lipolysis in obese insulin sensitive (IS), obese insulin resistant (IR) and age-matched lean IS men. Moreover, obese individuals underwent endurance and resistance exercise training to improve metabolic profile and (non-)adrenergically-mediated SCAT lipolysis. Materials and methods: Abdominal SCAT lipolysis was investigated in 10 obese IS, 10 obese IR and 10 age-matched lean IS men using microdialysis in the presence or absence of local combined α-and β-adrenergic receptor blockade (100 μmol/l phentolamine and 100 μmol/l propranolol) at rest, during 60 min of low-intense (40% VO2max) endurance-type exercise and recovery. Systemic responses were investigated using venous blood sampling. Obese individuals participated in a supervised, endurance and resistance exercise training intervention for 12 weeks (3 sessions/week) after which the microdialysis measurements were repeated in obese IR men. Results: The exercise-induced increase in abdominal SCAT glycerol concentrations (expressed as total area under the curve) was more pronounced in obese IS (81%) and IR (34%) as compared to lean individuals (Pgroup=0.012). Abdominal SCAT lipolysis was significantly reduced (by ~40%, P=0.020) following local combined α-/βadrenoceptor blockade in obese IS individuals only. Despite significant improvements in body composition, physical fitness and exercise-induced changes in circulating free fatty acids, lactate and adrenalin, exercise intervention did not significantly affect (non-)adrenergically-mediated lipolysis in abdominal SCAT of obese IR individuals. Conclusion: Our findings indicate a major contribution of non-adrenergically-mediated lipolysis during exercise in abdominal SCAT of lean and obese individuals. Furthermore, a 12-week exercise training program improved metabolic profile and body composition in obese individuals, but did not affect abdominal SCAT lipolysis. Clinical Trial Registration Number: NCT02418728