Nicole Bacarella1, Alistaire Ruggiero2, Ashley T Davis3, Beth Uberseder4, Matthew A Davis5, Deanna P Bracy6, David H Wasserman6, J Mark Cline4, Chrissy Sherrill4, Kylie Kavanagh7. 1. Animal Resources Program, Wake Forest University School of Medicine, Winston-Salem, North Carolina. 2. Molecular Medicine and Translational Science, Wake Forest University School of Medicine, Winston-Salem, North Carolina. 3. Translational Imaging Program, Wake Forest University School of Medicine, Winston-Salem, North Carolina. 4. Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina. 5. Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina. 6. Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee. 7. Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina; College of Health and Medicine, University of Tasmania, Hobart, Australia. Electronic address: kkavanag@wakehealth.edu.
Abstract
PURPOSE: Diabetes mellitus is a delayed effect of radiation exposure in human and nonhuman primates. Diabetes mellitus is characterized by peripheral tissue insulin resistance, and as a result, irradiation exposure may cause important changes in insulin-sensitive tissues such as muscle and adipose. METHODS AND MATERIALS: We prospectively investigated changes in response to irradiation (4 Gy whole body exposure) in 16 male rhesus macaques. We evaluated changes in body composition and glycemic control for 2 years. Insulin responsiveness, lipolysis, inflammation, and fibrosis were evaluated at study end. RESULTS: Irradiated animals accumulate less fat and significantly increased percent glycation of hemoglobin A1c over time, such that 40% of irradiated monkeys had values that define them as diabetic at 2 years. Subcutaneous (SQ) adipose tissue was insulin resistant, as evidenced by reduced phosphorylation of the insulin receptor substrate-1 in response to insulin challenge and had increased basal lipolysis despite comparable insulin exposures to control animals. Irradiated SQ adipose tissue had more macrophage infiltration and adipocytes were larger. The observed hypertrophy was associated with decreased glycemic control and macrophage infiltration correlated with decreased adiponectin, signifying that inflammation is associated with worsening health. No evidence of SQ adipose fibrosis was detected. CONCLUSIONS: Our study is the first to prospectively illustrate that sublethal irradiation exposures directly propagate metabolic disease in the absence of obesity in nonhuman primates and implicate SQ adipose dysfunction as a target tissue.
PURPOSE:Diabetes mellitus is a delayed effect of radiation exposure in human and nonhuman primates. Diabetes mellitus is characterized by peripheral tissue insulin resistance, and as a result, irradiation exposure may cause important changes in insulin-sensitive tissues such as muscle and adipose. METHODS AND MATERIALS: We prospectively investigated changes in response to irradiation (4 Gy whole body exposure) in 16 male rhesus macaques. We evaluated changes in body composition and glycemic control for 2 years. Insulin responsiveness, lipolysis, inflammation, and fibrosis were evaluated at study end. RESULTS: Irradiated animals accumulate less fat and significantly increased percent glycation of hemoglobin A1c over time, such that 40% of irradiated monkeys had values that define them as diabetic at 2 years. Subcutaneous (SQ) adipose tissue was insulin resistant, as evidenced by reduced phosphorylation of the insulin receptor substrate-1 in response to insulin challenge and had increased basal lipolysis despite comparable insulin exposures to control animals. Irradiated SQ adipose tissue had more macrophage infiltration and adipocytes were larger. The observed hypertrophy was associated with decreased glycemic control and macrophage infiltration correlated with decreased adiponectin, signifying that inflammation is associated with worsening health. No evidence of SQ adipose fibrosis was detected. CONCLUSIONS: Our study is the first to prospectively illustrate that sublethal irradiation exposures directly propagate metabolic disease in the absence of obesity in nonhuman primates and implicate SQ adipose dysfunction as a target tissue.
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