Satoshi Hirayama1, Atsushi Hori2, Miwa Isshiki3, Akiko Hirayama3, Tsuyoshi Ueno4, Yoshifumi Tamura5, Hideyoshi Kaga6, Hirotaka Watada5, Ryuzo Kawamori5, Takashi Miida7. 1. Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan; Sportology Center, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan. Electronic address: sthiraya@juntendo.ac.jp. 2. Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan; Center for Genomic and Regenerative Medicine, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan. 3. Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan. 4. Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan; Clinical Laboratory, Juntendo Tokyo Koto Geriatric Medical Center, Koto-ku, Tokyo, Japan. 5. Sportology Center, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan; Department of Metabolism & Endocrinology, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan. 6. Department of Metabolism & Endocrinology, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan. 7. Department of Clinical Laboratory Medicine, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan; Sportology Center, Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan.
Abstract
BACKGROUND: Triglyceride (TG) is a tri-ester composed of a glycerol and 3 fatty acids. Degradation of TG in adipose tissue is increased in the fasting state but inhibited in the postprandial state. Although insulin suppresses adipose TG degradation, patients with insulin resistance have high concentrations of insulin and free glycerol (FG) in the fasting state. OBJECTIVE: We examined whether the fasting FG concentration reflects visceral obesity and insulin sensitivity in middle-aged Japanese men. METHODS: We measured the fasting serum FG concentration in 72 males aged 30 to 50 years using a simple enzymatic method. The subjects were divided into tertiles according to their homeostasis model assessment of insulin resistance (HOMA-IR). Besides routine glucose- and lipid-related parameters, we determined insulin sensitivity as the rate of glucose disappearance in a 2-step hyperinsulinemic-euglycemic clamp and the abdominal visceral fat area (VFA) by magnetic resonance imaging. RESULTS: The highest HOMA-IR tertile group had a higher fasting FG concentration than the middle- and lowest-tertile groups (0.077 ± 0.024 vs 0.063 ± 0.017 and 0.061 ± 0.016 mmol/L, P < .05 and P < .01). The FG concentration was positively correlated with VFA (rs = 0.36; P < .01) and the HOMA-IR score (rs = 0.26, P < .05) but negatively correlated with insulin sensitivity (rs = -0.26, P < .05). Multivariate regression analysis revealed that the FG concentration is independently associated with VFA and insulin sensitivity. CONCLUSION: The fasting FG concentration reflects VFA and insulin sensitivity in middle-aged Japanese men. The fasting FG concentration may be a potential surrogate marker of visceral obesity and insulin resistance in outpatients.
BACKGROUND:Triglyceride (TG) is a tri-ester composed of a glycerol and 3 fatty acids. Degradation of TG in adipose tissue is increased in the fasting state but inhibited in the postprandial state. Although insulin suppresses adipose TG degradation, patients with insulin resistance have high concentrations of insulin and free glycerol (FG) in the fasting state. OBJECTIVE: We examined whether the fasting FG concentration reflects visceral obesity and insulin sensitivity in middle-aged Japanese men. METHODS: We measured the fasting serum FG concentration in 72 males aged 30 to 50 years using a simple enzymatic method. The subjects were divided into tertiles according to their homeostasis model assessment of insulin resistance (HOMA-IR). Besides routine glucose- and lipid-related parameters, we determined insulin sensitivity as the rate of glucose disappearance in a 2-step hyperinsulinemic-euglycemic clamp and the abdominal visceral fat area (VFA) by magnetic resonance imaging. RESULTS: The highest HOMA-IR tertile group had a higher fasting FG concentration than the middle- and lowest-tertile groups (0.077 ± 0.024 vs 0.063 ± 0.017 and 0.061 ± 0.016 mmol/L, P < .05 and P < .01). The FG concentration was positively correlated with VFA (rs = 0.36; P < .01) and the HOMA-IR score (rs = 0.26, P < .05) but negatively correlated with insulin sensitivity (rs = -0.26, P < .05). Multivariate regression analysis revealed that the FG concentration is independently associated with VFA and insulin sensitivity. CONCLUSION: The fasting FG concentration reflects VFA and insulin sensitivity in middle-aged Japanese men. The fasting FG concentration may be a potential surrogate marker of visceral obesity and insulin resistance in outpatients.