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The Effect of a Reduced-Calorie Diet on alpha-2 Adrenergic Receptor Responsiveness in Abdominal Adipose Tissue in Obese Men During Exercise

Roy R. Estrada¹, Joseph O. Schmelz², David Turbow³ & Edith Neumann³

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1. University of Texas Health Science Center San Antonio, School of Allied Health, Physician Assistant Studies, Institutional Review Board
2. The University of Texas Health Science Center at San Antonio, Institutional Review Board
3. TUI University, College of Health Sciences

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Document Type:

Manuscript

Date:

Received 26 April 2008 04:55 UTC; Posted 28 April 2008

Subjects:

Molecular Cell Biology

Tags:

• Subcutaneous Abdominal Adipose Tissue
• Obesity
• Alpha-2 Adrenergic Receptor

Abstract:

There is at present an imperfect understanding of the effect of diet on availability of inhibitory receptors in fat cells during exercise among obese men.

Objective: The purpose of this study was to determine whether diet results in downregulation of alpha-2 adrenergic receptor (α_2-AR) messenger RNA (mRNA), improving metabolism in exercise in obese men.

Design: One group, pre-test, post-test design.

Measurements: Subcutaneous abdominal adipose tissue was tested for physiologic response, such as changes in catecholamines and other markers of lipolysis measured during periods of exercise, before and after a 12-week diet. Plasma markers of lipolysis/antilipolytic activity (catecholamines [adrenaline and noradrenaline], NEFA, lactate, glucose, hematocrit, or insulin levels) were analyzed at four points in time in order to determine the effect of exercise on α_2-AR and β-AR responsiveness to sympathetic stimulation.

Subjects: Otherwise healthy 18 to 45 year old obese men (defined as a body mass index (BMI) over 33 kg/m²).

Results: The 12-week reduced calorie diet did not result in improved metabolism. Instead, upregulation of alpha-2 adrenergic receptor (α_2-AR) messenger RNA (mRNA) was observed. On average, α_2-AR mRNA levels (ratio of α_2-AR to cyclophilin) in subjects increased by 0.022-0.023 after the diet. The average differences in of α_2-AR mRNA and β-AR mRNA measured before and after diet were both insignificant (M = 0.015) t(4) = -0.911; P > 0.05; (M = 0.0139; t(4) = 0.077; P > 0.05).

Conclusion: The observed direction of change in α_2-AR mRNA levels, when viewed together with the stability of β-AR mRNA levels, suggests that upregulation of α_2-AR rather than downregulation occurred. Downregulation would account for decreased lipolytic activity during exercise, future study is needed.

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This document is licensed to the public under the Creative Commons Attribution 3.0 License

How to cite this document:

Estrada, Roy, Schmelz, Joseph, Turbow, David, and Neumann, Edith. The Effect of a Reduced-Calorie Diet on alpha-2 Adrenergic Receptor Responsiveness in Abdominal Adipose Tissue in Obese Men During Exercise. Available from Nature Precedings <http://hdl.handle.net/10101/npre.2008.1838.1> (2008)

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