Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama 35294-3360, USA.
J Clin Endocrinol Metab. 2013 Jul;98(7):E1173-80. doi: 10.1210/jc.2013-1203. Epub 2013 Apr 24.
Animal studies indicate that osteocalcin (OC), particularly the undercarboxylated isoform (unOC), affects insulin sensitivity and secretion, but definitive data from humans are lacking.
The objectives of the study were to determine whether total OC and unOC are independently associated with insulin sensitivity and β-cell response in overweight/obese adults; whether glucose tolerance status affects these associations; and whether the associations are independent of bone formation, as reflected in procollagen type 1 amino propeptide (P1NP).
DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study conducted at a university research center involving 63 overweight/obese adults with normal (n = 39) or impaired fasting glucose (IFG; n = 24).
Serum concentrations of total/undercarboxylated OC and P1NP were assessed by RIA; insulin sensitivity was determined by iv glucose tolerance test (S(I)-IVGTT), liquid meal test (S(I) meal), and homeostasis model assessment of insulin resistance; β-cell response to glucose [basal β-cell response to glucose; dynamic β-cell response to glucose; static β-cell response to glucose; and total β-cell response to glucose] was derived using C-peptide modeling of meal test data; and intraabdominal adipose tissue was measured using computed tomography scanning.
Multiple linear regression, adjusting for intraabdominal adipose tissue and P1NP, revealed that total OC was positively associated with S(I)-iv glucose tolerance test (P < .01) in the total sample. OC was not associated with S(I) meal or homeostasis model assessment of insulin resistance. In participants with IFG, unOC was positively associated with static β-cell response to glucose and total β-cell response to glucose (P < .05), independent of insulin sensitivity.
In overweight/obese individuals, total OC may be associated with skeletal muscle but not hepatic insulin sensitivity. unOC is uniquely associated with β-cell function only in individuals with IFG. Further research is needed to probe the causal inference of these relationships and to determine whether indirect nutrient sensing pathways underlie these associations.
动物研究表明，骨钙素（OC），尤其是非羧化形式（unOC），会影响胰岛素敏感性和分泌，但人体缺乏明确的数据。
本研究旨在确定总 OC 和 unOC 是否与超重/肥胖成年人的胰岛素敏感性和β细胞反应独立相关；葡萄糖耐量状态是否会影响这些关联；以及这些关联是否与骨形成独立，这反映在原胶原 1 氨基端前肽（P1NP）中。
设计、地点和参与者：这是一项在大学研究中心进行的横断面研究，涉及 63 名超重/肥胖成年人，其中正常（n = 39）或空腹血糖受损（IFG；n = 24）。
采用 RIA 检测血清总/非羧化 OC 和 P1NP 浓度；通过静脉葡萄糖耐量试验（S(I)-IVGTT）、液体餐试验（S(I) meal）和稳态模型评估胰岛素抵抗来评估胰岛素敏感性；采用 C 肽模型对餐试验数据进行分析，得出葡萄糖刺激的基础β细胞反应、葡萄糖刺激的动态β细胞反应、葡萄糖刺激的静态β细胞反应和葡萄糖刺激的总β细胞反应；使用计算机断层扫描测量腹腔内脂肪组织。
在总样本中，经腹腔内脂肪组织和 P1NP 调整的多元线性回归显示，总 OC 与 S(I)-iv 葡萄糖耐量试验呈正相关（P <.01）。OC 与 S(I) meal 或稳态模型评估的胰岛素抵抗无关。在 IFG 患者中，unOC 与葡萄糖刺激的静态β细胞反应和葡萄糖刺激的总β细胞反应呈正相关（P <.05），与胰岛素敏感性独立相关。
在超重/肥胖人群中，总 OC 可能与骨骼肌而非肝脏胰岛素敏感性相关。unOC 仅与 IFG 患者的β细胞功能相关。需要进一步研究以探究这些关系的因果推断，并确定是否存在间接的营养感应途径导致这些关联。
