β1- and β2-adrenoceptor-mediated thermogenesis and lipid utilization in obese and lean men

The aim of this study was to elucidate the roles of the β1- and the β2-adrenoceptors in thermogenesis and lipid utilization in obesity. The β1-adrenoceptor study was performed in 9 obese and 10 lean men and consisted of 4 30-min periods during which subjects received consecutive infusions of 0, 3, 6, and 9 μg/kg fat-free mass (FFM)-min dobutamine. Energy expenditure, lipid oxidation, and plasma nonesterified fatty acids and glycerol concentrations increased similarly in both groups during β1-adrenergic stimulation. The β2-adrenoceptor study was performed in 10 obese and 11 lean men and involved 3 45-rain periods during which 0, 50, and 100 ng/kg FFM·min salbutamol were given in combination 1.2 μg/kg FFM·min atenolol (bolus, 50 μg/kg FFM). During β2-adrenergic stimulation, the increases in energy expenditure and plasma nonesterified fatty acids and glycerol concentrations were reduced in the obese group. Furthermore, lipid oxidation significantly increased in the normal weight group, but remained similar in the overweight group. In conclusion, these data suggest that β1-adrenoceptor-mediated metabolic processes are similar in both groups, but β2-adrenoceptor-mediated increases in thermogenesis and lipid utilization are impaired in the obese.

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