Abstract
The purpose of this preliminary study was to investigate changes in plasma concentrations of zinc-α2-glycoprotein (ZAG), a lipid mobilizing hormone, in obese subjects following Roux-En-Y Gastric Bypass (RYGB) surgery or a very low calorie diet (VLCD). Fasting blood concentrations and anthropometric measurements were measured pre and 12 weeks post intervention. 14 healthy, obese individuals underwent either RYGB (N=6) surgery or a VLCD (N=8). Body composition and fasting plasma ZAG concentrations were measured at baseline (pre) and 12 weeks post intervention (post). At pre-intervention baseline, there was no difference in plasma ZAG between the two intervention groups. Post-intervention, there was a significant overall reduction (F(1,11) = 32.8, p<0.001) in plasma ZAG, which was significant only within the RYGB group from pre to post intervention (33.2 ± 5.7 μg/ml to 26.7 ± 4.8 μg/ml (p<0.015)) and significantly greater than the change within the VLCD group. The change in ZAG was inversely correlated across groups with BMI reduction (r= -0.60, p<0.05), % body fat reduction (r= -0.68, p<0.015), reduction in weight (r= -0.58, p<0.05), and % weight loss (r= -0.70, p<0.05). Overall, subjects who underwent RYGB or VLCD had a significant reduction in plasma ZAG. This reduction was significant within the RYGB group alone, who lost a larger amount of weight than the VLCD group, which suggests that ZAG may have a protective effect during marked weight loss.
Highlights
Over one third of the United States population is obese (BMI >30 kg/m2) [1]
ZAG is secreted by adipocytes [8] in the white adipose tissue (WAT) and utilizes the G-protein coupled β3-adrenoreceptor to activate adenylate cyclase, form cyclic AMP, activate protein kinase A (PKA), and induce lipolysis [9,10]
We examined plasma ZAG concentrations pre and post two weight loss interventions, Roux-en-Y Gastric Bypass (RYGB) or a very low calorie diet (VLCD), and we hypothesized that ZAG would increase with weight loss
Summary
Over one third of the United States population is obese (BMI >30 kg/m2) [1]. Bariatric surgery is a relatively effective long-term treatment for obesity [2] especially Roux-en-Y Gastric Bypass (RYGB) [3]. ZAG shares the same structure as a lipid mobilizing factor [6] that is over-expressed in many different cancer types and has been associated with the rapid weight loss in cancer patients [7]. ZAG is secreted by adipocytes [8] in the white adipose tissue (WAT) and utilizes the G-protein coupled β3-adrenoreceptor to activate adenylate cyclase, form cyclic AMP (cAMP), activate protein kinase A (PKA), and induce lipolysis [9,10]. HSL is regulated through the cAMP pathway and PKA [12]. The up-regulation of HSL results in increased lipolysis. ZAG up-regulates the amount of uncoupling protein 1 (UCP-1) [13] in brown adipose tissue, which may increase lipid utilization to produce heat
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