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Background: Insulin resistance is a well-known predictor and risk factor for Type 2 Diabetes Mellitus (T2DM). Higher hematocrit induced by higher insulin resistance affects blood rheology. Objective: This study intended to reveal the association between indices of insulin resistance and hemorheological parameters during a 75 g oral glucose tolerance test (75-g OGTT). Methods: A total of 575 healthy young Japanese participants took 75-g OGTT. We then analyzed the association between insulin resistance indices and hematological parameters. Results: The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) was significantly correlated with hematocrit (Ht), hemoglobin (Hb), Red Blood Cell (RBC), White Blood Cell (WBC), platelet count, lipid parameters, and Body Mass Index (BMI). The Matsuda index was negatively correlated with RBC count, WBC count, platelet count, Total Cholesterol (TC), Low-Density Lipoprotein-Cholesterol (LDL-C), triglyceride (TG), and positively correlated with High-Density Lipoprotein-Cholesterol (HDL-C). The disposition index was negatively correlated with Hb, RBC count, LDL-C, and BMI, while remaining positively correlated with HDL-C. The Homeostasis Model Assessment of beta cell (HOMA- IR ) was positively correlated with WBC count, platelet count, TC, LDL-C, and TG. The insulinogenic index was positively correlated with WBC count, platelet count, and TC. Multiple regression analysis revealed that HOMA-IR was independently associated with TG, and the Matsuda index was independently associated with TG, WBC count, and platelet count. The insulinogenic index was independently associated with WBC count. Conclusion: Cardinal rheological parameters reflected insulin resistance and were released even in the young, healthy Japanese individuals within the physiological range of glycemic control.

Background: Exercise stress promoted cortisol and testosterone secretions that have their own circadian rhythms. It is necessary that the testosterone, cortisol and testosterone/cortisol ratio (T/C ratio) are measured through their rhythms for use in monitoring exercise-induced stress in athletes. Automated measurement has not been applied to salivary testosterone, which requires passive drooling difficult to collect sufficient saliva rapidly. This study aimed to verify whether automated measurements of the testosterone and cortisol concentrations and T/C ratio using saliva collected sequentially can effectively assess exercise intensity differences within circadian rhythms in male athletes.Methods: We investigated the correlations of testosterone and cortisol concentrations measured by electrochemiluminescence immunoassay (ECLIA) between saliva and sera collected from 20 male long-distance runners. We collected the runners' saliva sequentially by passive drooling on two consecutive days involving different intensity trainings in the morning and evening; salivary testosterone and cortisol concentrations were measured by ECLIA. Each exercise intensity was measured by running distances, velocities, Borg scale score and maximum pulse rate during exercise.Results: The salivary testosterone and cortisol concentrations were positively correlated with the respective total serum hormone concentrations. The runners were divided into low-intensity exercise group (n = 8) and high-intensity exercise group (n = 7), in which five runners were excluded because measurable saliva samples could not be obtained due to low volume and high-viscosity. Sequential saliva collection and automated measurements detected the runners' circadian rhythms of testosterone, cortisol and T/C ratio. The rate of change in the salivary cortisol concentrations were significantly higher and that in the T/C ratio was significantly lower in the evening interval training on day 1 in the high-intensity exercise group which had significantly higher running velocity, Borg scale score, and maximum pulse rate values; this relationship was not shown for salivary testosterone.Conclusions: Automated measurements of the salivary cortisol concentration and the T/C ratio reflected different exercise intensities may be useful for creating appropriate exercise programs for athletes. Conversely, the automated measurements of salivary testosterone and T/C ratio, which require passive drooling to collect saliva, may be less suitable for practical use with athletes than the salivary cortisol-only measurement

Background Overtraining syndrome, caused by prolonged excessive stress, results in reduced performance and cortisol responsiveness in athletes. It is necessary to collect saliva samples sequentially within circadian rhythm for assessing exercise stress by measuring cortisol concentrations, and automated cortisol measurements using electrochemiluminescence immunoassay (ECLIA) may be useful for measuring a large number of saliva samples. In this study, we evaluated the appropriate use of cortisol-based exercise stress assessment within the circadian rhythm, which may diagnose and prevent overtraining syndrome in athletes. Methods We collected saliva and sera from 54 healthy participants and analyzed the correlation between salivary cortisol concentrations measured by ECLIA and enzyme-linked immunosorbent assay (ELISA) or serum cortisol analysis. We also collected saliva continuously from 12 female long-distance runners on 2 consecutive days involving different intensities and types of exercise early in the morning and in the afternoon and measured salivary cortisol concentrations using ECLIA. Each exercise intensity of runners was measured by running velocities, Borg Scale score, and rate of change in the pulse rate by exercise. Results ECLIA-based salivary cortisol concentrations correlated positively with those detected by ELISA (ρ = 0.924, p < 0.001) and serum cortisol (ρ = 0.591, p = 0.001). In long-distance runners, circadian rhythm of salivary cortisol, including the peak after waking and the decrease promptly thereafter, were detected on both days by continuous saliva sampling. The rates of change in salivary cortisol concentrations were significantly lower after an early morning exercise than after an afternoon exercise on both days (day 1, p = 0.002, and day 2, p = 0.003). In the early morning exercise, the rate of change in salivary cortisol concentration was significantly higher on day 1 than on day 2 (p = 0.034), similar to a significant difference in running velocities (p = 0.001). Conclusions Our results suggest that automated ECLIA-based salivary cortisol measurements are able to detect the athletes’ circadian rhythm and compare the exercise stress intensities at the same times on different days, even in the early morning, possibly leading to the prevention of overtraining syndrome.