Masayuki Iki1, Akiko Yura2, Yuki Fujita2, Katsuyasu Kouda3, Junko Tamaki4, Takahiro Tachiki5, Etsuko Kajita5, Hirohisa Iwaki6, Rika Ishizuka7, Jong-Seong Moon8, Nozomi Okamoto9, Norio Kurumatani10. 1. Department of Public Health, Kindai University Faculty of Medicine, 377-2 Oono-higashi, Osaka-Sayama, Osaka 589-8511, Japan. Electronic address: masa@med.kindai.ac.jp. 2. Department of Public Health, Kindai University Faculty of Medicine, 377-2 Oono-higashi, Osaka-Sayama, Osaka 589-8511, Japan. 3. Department of Hygiene and Public Health, Kansai Medical University, 2-5-1 Shin-machi, Hirakata, Osaka 573-1010, Japan. 4. Department of Hygiene and Public Health, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan. 5. Chukyo Gakuin University Faculty of Nursing, 2216 Tokicho, Mizunami, Gifu 509-6192, Japan. 6. Senken Co. Ltd., 1-12-12 Tagacho, Takamatsu, Kagawa 760-0063, Japan. 7. Department of Food and Nutrition, Faculty of Contemporary Human Life Science, Tezukayama University, 3-1-3 Gakuenminami, Nara, Nara 631-8585, Japan. 8. Department of Nursing, Kio University, 4-2-2 Umami-naka, Koryo-cho, Nara 635-0832, Japan. 9. Graduate School of Education, Hyogo University of Teacher Education, 942-1 Shimokume, Kato-City, Hyogo 673-1494, Japan. 10. Nara Medical University School of Medicine, 840 Shijocho, Kashihara, Nara 634-8521, Japan.
Abstract
INTRODUCTION: Cross-sectional studies have shown that patients with type 2 diabetes mellitus (T2DM) have low circulating levels of osteocalcin (OC) and undercarboxylated OC (ucOC). This longitudinal study aimed to examine whether low OC or ucOC levels at baseline are associated with the risk of incident T2DM. METHODS: We examined 1700 community-dwelling Japanese men (≥65 years) after excluding those with history of diseases (other than T2DM) or medications that affect bone and glucose metabolism. T2DM was defined as fasting plasma glucose (FPG) ≥126 mg/dl or glycated hemoglobin A1c (HbA1c) ≥6.5%. Participants without prevalent T2DM at baseline were invited to follow-up surveys 5 and 10 years after baseline. RESULTS: Among the participants, 309 with prevalent T2DM showed significantly lower serum OC and ucOC levels at baseline than those without. After excluding these participants, 46 and 57 participants with incident T2DM were identified in the first and second follow-up surveys, respectively. These participants did not show significantly different OC and ucOC levels at baseline relative to those without T2DM, although their FPG and HbA1c levels at baseline were significantly higher compared to those without incident T2DM. Increase in glycemic indices preceded decrease in OC and ucOC levels. OC and ucOC levels at baseline were not significantly associated with the risk of incident T2DM identified in the follow-up surveys. CONCLUSIONS: OC and ucOC levels at baseline were not significantly associated with the risk of incident T2DM. Our results do not support the findings of animal studies that ucOC is a hormone regulating glucose metabolism.
INTRODUCTION: Cross-sectional studies have shown that patients with type 2 diabetes mellitus (T2DM) have low circulating levels of osteocalcin (OC) and undercarboxylated OC (ucOC). This longitudinal study aimed to examine whether low OC or ucOC levels at baseline are associated with the risk of incident T2DM. METHODS: We examined 1700 community-dwelling Japanese men (≥65 years) after excluding those with history of diseases (other than T2DM) or medications that affect bone and glucose metabolism. T2DM was defined as fasting plasma glucose (FPG) ≥126 mg/dl or glycated hemoglobin A1c (HbA1c) ≥6.5%. Participants without prevalent T2DM at baseline were invited to follow-up surveys 5 and 10 years after baseline. RESULTS: Among the participants, 309 with prevalent T2DM showed significantly lower serum OC and ucOC levels at baseline than those without. After excluding these participants, 46 and 57 participants with incident T2DM were identified in the first and second follow-up surveys, respectively. These participants did not show significantly different OC and ucOC levels at baseline relative to those without T2DM, although their FPG and HbA1c levels at baseline were significantly higher compared to those without incident T2DM. Increase in glycemic indices preceded decrease in OC and ucOC levels. OC and ucOC levels at baseline were not significantly associated with the risk of incident T2DM identified in the follow-up surveys. CONCLUSIONS: OC and ucOC levels at baseline were not significantly associated with the risk of incident T2DM. Our results do not support the findings of animal studies that ucOC is a hormone regulating glucose metabolism.