Effects of Trecadrine®, a β3-adrenergic agonist, on leptin secretion, glucose and lipid metabolism in isolated rat adipocytes

Abstract

OBJECTIVE: Leptin, a hormone produced in adipocytes, is a key signal in the regulation of food intake and energy expenditure. b-Adrenergic agonists have been shown to inhibit leptin gene expression and leptin secretion. The mechanisms underlying the inhibitory effects of b-adrenergic agonists have not been established. In this study, we examined the effects of Trecadrine 1 , a novel b3-adrenergic agonist, on basal and insulin-stimulated leptin secretion in isolated rat adipocytes. Because insulinstimulated glucose metabolism is an important regulator of leptin expression and secretion by the adipocytes, the effects of Trecadrine on indices of adipocyte metabolism were also examined. MEASUREMENTS: Isolated adipocytes were incubated with Trecadrine (10 78 -10 74 M) in the absence or presence of insulin (1.6 nM). Leptin secretion, glucose utilization, lactate production, glucose incorporation into CO 2 and triglyceride, as well as lipolysis (glycerol release) were determined. RESULTS: Trecadrine induced a concentration-dependent inhibition of basal leptin secretion. Trecadrine also decreased insulinstimulated leptin secretion; however, the effect was not as pronounced as in the absence of insulin. Treatment of adipocytes with Trecadrine increased basal glucose utilization and produced a further increase in insulin-stimulated glucose utilization. Basal lactate production was also increased by Trecadrine; however, the proportion (percentage) of glucose carbon released as lactate was unaffected. In the presence of insulin, absolute lactate production was unaffected by Trecadrine at 96 h. However, the percentage of glucose carbon released as lactate was significantly decreased by insulin treatment, and was further decreased by the co-treatment with Trecadrine. Trecadrine induced a dose-dependent increase of the absolute amount of glucose incorporated into triglyceride. However, the percentage of glucose utilized that was incorporated into triglyceride was unaffected by Trecadrine. Trecadrine did not modify the proportion of glucose utilized that was oxidized to CO 2 . Trecadrine increased glycerol release after 96 h of treatment. Glycerol release was negatively correlated with leptin secretion. CONCLUSIONS: These results suggest that alterations of glucose metabolism are not directly involved in the effects of b3-adrenergic agonists to inhibit leptin expression and secretion. The inverse relationship between leptin secretion and the increase of glycerol levels, which is an index of the activation of cAMP-dependent protein kinases, suggests that activation of the cAMP signaling pathway mediates the inhibitory effects of Trecadrine on leptin gene expression and secretion.

Lipoic acid inhibits leptin secretion and Sp1 activity in adipocytes

“…Indeed, leptin secretion has been found to be inversely proportional to the amount of glucose anaerobically metabolized to lactate [40,41,26]. In this context, our data demonstrate that LA significantly increased in a concentration-dependent manner, the percentage of glucose that is metabolized to lactate.…”

Isoproterenol decreases leptin release from rat and human adipose tissue through posttranscriptional mechanisms

“…We (22) previously reported that 24 h of culture with Iso significantly decreased leptin mRNA levels in parallel with the quantity of leptin accumulating in the medium, and others have reported similar results in rat adipose tissue or adipocytes (4,15,19). However, no effects of Iso on leptin mRNA levels were found after 3 h of Iso in the current study.…”

Effects of lipoic acid on lipolysis in 3T3-L1 adipocytes

“…Moreover, it was observed that the administration of Trecadrine, a ␤ -3 adrenergic agonist that stimulates lipolysis ( 42 ), induced a decrease in HSL mRNA levels in abdominal white adipose tissue, whereas an increase in HSL activity was observed ( 43 ). Furthermore, a recent study reported that serum amyloid A stimulated lipolysis in parallel with a reduced HSL protein content.…”