Context Slight elevations in plasma glucose (PG) manifest in advance of diabetes onset, but abnormalities in immunoreactive insulin (IRI), proinsulin (Pro), and adiponectin dynamics during this stage remain poorly understood. Objective The objective of this work is to investigate whether IRI and Pro dynamics become abnormal as glucose tolerance deteriorates from within the normal range toward impaired glucose tolerance (IGT), as well as the relationship between PG, and these dynamics and serum adiponectin levels. Design A cross-sectional study was designed. Setting This study took place at Jichi Medical University in Japan. Participants and Measurements PG, IRI, and Pro levels were determined in 1311 young Japanese individuals (age < 40 years) with normal or IGT before and at 30, 60, and 120 minutes during a 75-g oral glucose tolerance test. Participants were assigned to 4 groups according to glucose tolerance, and then background factors, adiponectin levels, insulin sensitivity (SI), and insulin secretion (β) indexes were determined. Results PG levels as well as IRI and Pro levels 60 and 120 minutes after glucose-loading increased incrementally with deteriorating glucose tolerance. All measures of β and the SI measure index of insulin sensitivity (ISI)-Matsuda decreased incrementally. Serum adiponectin levels were not significantly different among the glucose tolerance groups, but were independently and negatively correlated with fasting glucose. Conclusions Early β decreased and postloading Pro levels became excessive in a progressive manner as glucose tolerance deteriorated from within the normal range toward IGT.

A 54-year-old man had been drinking approximately 1.2 L of soy milk (equivalent to approximately 310 mg of isoflavones) per day for the previous 3 years. He then developed erectile dysfunction and gynecomastia. On an examination in our department in May, blood tests showed low gonadotropin and testosterone levels, indicative of secondary hypogonadism. He stopped drinking soy milk on his own in June of that year. When he was admitted in August, blood tests showed an improved gonadal function. Secondary hypogonadism caused by the excessive intake of isoflavones in soy milk was diagnosed. In men, an excessive intake of isoflavones may cause feminization and secondary hypogonadism.

Background Ghrelin is involved in feeding regulation and energy metabolism and is also known to inhibit insulin secretion (β). However, few clinical studies have demonstrated the relationship between β and ghrelin dynamics. This study tested the hypothesis that, in oral glucose tolerance tests (OGTT), ghrelin dynamics are associated with β. Methods Subjects were 1145 healthy individuals <40 years old who tested normal on the 75‐g OGTT. The following indicators and the ghrelin suppression ratio (GSR) during OGTT were calculated: insulin sensitivity (SI) [1/homoeostasis model assessment of insulin resistance, insulin sensitivity index‐Matsuda and 1/fasting insulin (1/FIRI)]; and β [Stumvoll first‐phase index (Stumvoll‐1), Stumvoll second‐phase index and insulinogenic index]. From nine combinations of SI and β, combinations that produce hyperbolic relationships were identified. Results Stumvoll‐1 and 1/FIRI showed a hyperbolic relationship in nonobese subjects, and the product of Stumvoll‐1 and 1/FIRI was used as the disposition index (DI). When analyzed by BMI quartiles, post‐loading glucose and insulin levels at each time point increased from Q1 (low BMI) through Q4 (high BMI), whereas the DI, ghrelin levels at each time point, and GSR decreased from Q1 to Q4. On multivariate and bivariate analysis, GSR and DI were positive and independent, and fasting ghrelin and FIRI were negatively and independently correlated. Conclusions Ghrelin dynamics were associated with beta cell function in subjects with normal glucose tolerance. Glucose intolerance in obesity may be due not only to insulin resistance but also to impaired beta cell function associated with abnormalities of ghrelin dynamics.

Associations of arterial stiffness with glucose, insulin, and proinsulin dynamics during the oral glucose tolerance test (OGTT) remain under debate. The aim of this study was to investigate whether plasma glucose (PG), insulin, and proinsulin (Pro) contribute to arterial stiffness, measured by pulse wave velocity (PWV), in young Japanese persons. PG, immunoreactive insulin (IRI), and Pro levels were determined in 1193 young Japanese subjects (<40 years of age) with normal glucose tolerance or nondiabetic hyperglycemia before and at 30, 60, and 120 min during a 75-g OGTT. Participants were divided into two groups according to the median PWV. Background factors, PG, IRI, and Pro levels during the OGTT, and insulin sensitivity (SI) indices in each group were compared. Several multiple regression analysis models were used to evaluate factors contributing to PWV. All IRI and Pro levels before and after glucose loading and the area under the curve (AUC) values for IRI and Pro increased with higher PWV. 1/HOMA-IR and ISI-Matsuda as measures of SI decreased with higher PWV. The IRI AUC and Pro level before glucose loading (Pro0) were independently associated with PWV, in addition to male sex, heart rate, and mean blood pressure. The IRI AUC had a stronger relationship with PWV than Pro0. The IRI AUC had an independent relationship with PWV, whereas both SI indices did not. Postloading insulinemia, but not reduced SI, was independently associated with arterial stiffness in young Japanese persons.

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