Assessment of exercise-induced stress via automated measurement of salivary cortisol concentrations and the testosterone-to-cortisol ratio: a preliminary study.

In this study, our aim was to validate whether the automated measurement of salivary testosterone and cortisol concentrations and the testosterone-to-cortisol (T/C) ratio, considering their individual circadian rhythms can be used to assess the stress response of male athletes to different exercise intensities accurately and effectively. We measured the salivary testosterone and cortisol concentrations and their respective serum concentrations that were collected from 20 male long-distance runners via passive drooling in the morning and evening for two consecutive days involving different exercise intensities. An electrochemiluminescence immunoassay was performed to evaluate the salivary testosterone and cortisol concentrations. The results showed a positive correlation between the salivary testosterone and cortisol concentrations and their respective serum concentrations. The participants were divided into two groups: with and without interval training. The interval training group showed a significantly higher rate of change in the salivary cortisol concentration and a significantly lower rate of change in the T/C ratio in the evening interval training on day 1 than lower-intensity running on day 2. Our results indicated that the salivary cortisol concentrations and the T/C ratio could distinguish between exercises at different intensities, which may be beneficial for detecting differences in stress responses among athletes.

Age-Related Sex Differences in Glucose Tolerance by 75 g Oral Glucose Tolerance Test in Japanese.

To elucidate the age-related sex difference in glucose tolerance, we conducted 75 g oral glucose tolerance tests in 1156 participants. Participants were divided into four groups, namely, young (22−29) males, young females, middle-aged (>50) males, and middle-aged females. According to the Japanese Clinical Practice Guideline for Diabetes 2019, the prevalence of normal glucose tolerance (NGT) was significantly lower in middle-aged than in young participants. The prevalence of high-normal fasting plasma glucose (FPG) was higher, and NGT was lower in young males (high-normal FPG 15.2%, NGT 82.0%) than young females (high-FPG 3.9%, NGT 94.3%). Combined glucose intolerance (CGI) was higher and NGT was lower in middle-aged males (CGI 10.2%, NGT 25.2%) than in middle-aged females (CGI 3.3%, NGT 39.8%). FPG and body mass index (BMI) were the lowest and Homeostatic model assessment beta cell function (HOMA-ß) was the highest in young females, followed by young males, middle-aged females, and middle-aged males. Multiple linear regression analysis revealed that BMI weakly correlated with HOMA-ß and Matsuda index in all subjects except young females. The superior glucose tolerance in females was apparent in young, but attenuated in middle-aged females. The differences are due to the higher insulin secretion potential and lower BMI in young females.

Konjac Glucomannan Attenuated Triglyceride Metabolism during Rice Gruel Tolerance Test.

In a recent study, we showed that konjac glucomannan (KGM) inhibits rice gruel-induced postprandial increases in plasma glucose and insulin levels. To extend this research, we investigated the effects of KGM addition to rice gruel on pre- and postprandial concentrations of circulating lipoprotein lipase (LPL), glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), hepatic triglyceride lipase (HTGL), free fatty acids (FFA), and triglycerides (TG). A total of 13 Japanese men, without diabetes, dyslipidemia, or gastrointestinal diseases, interchangeably ingested rice gruel containing no KGM (0%G), rice gruel supplemented with 0.4% KGM (0.4%G), and rice gruel supplemented with 0.8% KGM (0.8%G), every Sunday for 3 weeks. Blood samples were obtained at baseline and at 30, 60, and 120 min after ingestion to measure the abovementioned lipid parameters. Lipid parameters showed small, but significant, changes. Significant reductions were found in circulating FFA levels among all participants. Circulating TG levels significantly declined at 30 min and then remained nearly constant in the 0.8%G group but exhibited no significant difference in the 0%G and 0.4%G groups. Although circulating levels of LPL and GPIHBP1 significantly decreased in the 0%G and 0.4%G groups, they increased at 120 min in the 0.8%G group. Participants in the 0%G and 0.4%G groups showed significant decreases in circulating HTGL levels, which was not observed in the 0.8%G group. Our results demonstrate the novel pleiotropic effects of KGM. Supplementation of rice gruel with KGM powder led to TG reduction accompanied by LPL and GPIHBP1 elevation and HTGL stabilization, thereby attenuating TG metabolism.

Significance of serum branched-chain amino acid to tyrosine ratio measurement in athletes with high skeletal muscle mass.

BACKGROUND: Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle. Although branched-chain amino acids (BCAA) play crucial roles in protein metabolism in skeletal muscle, the relationship between skeletal muscle mass and amino acid imbalances caused by the metabolism of BCAA and aromatic amino acids remains unclear. The aim of this study is to test the hypothesis that athletes with high levels of skeletal muscle mass have plasma amino acid imbalances, assessed by serum BCAA to tyrosine ratio (BTR) which can be measured conveniently. METHODS: The study enrolled 111 young Japanese men: 70 wrestling athletes and 41 controls. None of them were under any medications, extreme dietary restrictions or intense exercise regimens. Each participant's body composition, serum concentrations of albumin and rapid turnover proteins including transthyretin and transferrin, BTR, and thyroid function were assessed. RESULTS: Compared to the controls, the athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), and lower serum albumin concentration (p < 0.001) and BTR (p < 0.001). Kruskal-Wallis tests showed that serum albumin concentration and BTR were significantly lower in the participants with higher SMI. Serum albumin concentration and BTR were inversely correlated with SMI by multiple regression analysis (logarithmic albumin, ß = - 0.358, p < 0.001; BTR, ß = - 0.299, p = 0.001). SMI was inversely and transthyretin was positively correlated with serum albumin (SMI, ß = - 0.554, p < 0.001; transthyretin, ß = 0.379, p < 0.001). Serum concentration of free 3,5,3'-triiodothyronine (FT3) was inversely correlated with BTR, and, along with SMI and albumin, was independent predictor of BTR (SMI, ß = - 0.321, p < 0.001; FT3, ß = - 0.253, p = 0.001; logarithmic albumin, ß = 0.261, p = 0.003). However, FT3 was not correlated with SMI or serum albumin. Serum concentrations of rapid turnover proteins were not correlated with BTR. CONCLUSIONS: Increased skeletal muscle mass enhances the circulating amino acid imbalances, and is independently facilitated by thyroid hormones. Serum BTR may be a useful biomarker to assess the hypermetabolic state of wrestling athletes with high levels of skeletal muscle.

Simultaneous capillary electrophoresis of anions and cations in a single injection using an anion exchanger-modified capillary for determination of salivary ions in combination with statistical analyses.

This paper describes the simultaneous capillary electrophoresis (CE) of anions and cations using an anion exchange-modified capillary, which was prepared by chemical coating with a cationic silylating reagent, and its application to saliva analysis. The CE method provides high-throughput (5 min for a single sample injection) analysis by generating a high-velocity electroosmotic flow at pH 3.0-3.5. The detection limits at a signal-to-noise ratio of 3 ranged from 1.2 to 18 µM for anions and 1.0 to 2.7 µM for cations. The relative standard deviations for the migration times and peak areas of analytes (n = 4) ranged from 0.05% to 0.40% and 0.94% to 4.7%, respectively. The CE system was used to analyze 11 common ions in saliva samples collected from long-distance runners and sedentary university students before and after running for a set distance or a set time. Interestingly, the SCN- concentrations decreased in the saliva samples of all 14 athletes and 16 sedentary students after running. Furthermore, when the concentrations of the analyzed ions were compared with that of cortisol as a typical stress marker by multiple regression analysis, SCN- and NO3- in saliva samples from the two subject groups strongly correlated with cortisol levels, as determined by an electrochemiluminescence immunoassay. This study improves our knowledge of both the analytical methodology for CE and statistical methods for identifying common ions that could be used as physical stress markers.

Assessment of exercise-induced stress by automated measurement of salivary cortisol concentrations within the circadian rhythm in Japanese female long-distance runners.

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.

Glucomannan Inhibits Rice Gruel-Induced Increases in Plasma Glucose and Insulin Levels.

OBJECTIVE: Given the association between diabetes suppression and inhibition of diet-induced elevation in glucose and insulin, we investigated the effects of adding glucomannan to rice gruel on pre- and postprandial glucose and insulin concentrations. METHODS: A total of 25 Japanese subjects without a history of diabetes or gastrointestinal disease (all males; aged 37-60 years; body mass index 20.4-31.6) participated in this study. Subjects received a 75-g oral glucose tolerance test (75gOGTT) and rice gruel containing 0, 0.4, or 0.8% of glucomannan. Blood samples were then obtained at preload and at 30, 60, and 120 min after receiving 75 g of glucose or rice gruel with or without glucomannan. RESULTS: After the 75gOGTT, 8 subjects had normal glucose tolerance (NGT), whereas 17 showed a borderline pattern. Moreover, our data showed that greater amounts of glucomannan promoted lesser 30-min postload plasma glucose and insulin levels, with differences being larger in the borderline group than in the NGT group. CONCLUSIONS: Glucomannan dose-dependently inhibited the rice gruel-induced increase in 30-min postprandial plasma glucose and insulin levels. Furthermore, greater inhibitory effects on glucose and insulin elevation were observed in the borderline group than in the NGT group.

Prolonged plasma glucose elevation on oral glucose tolerance test in young healthy Japanese individuals.

AIMS: This study aims to assess insulin secretion and resistance through oral glucose tolerance test (OGTT) among young Japanese individuals. SUBJECTS AND METHODS: We enrolled 595 young healthy Japanese individuals aged 22-29 years. They underwent an OGTT, and their results were divided into 4 groups (I-IV), according to the time at which their plasma glucose concentration declined below the fasting glucose concentration (30, 60 or 120 minutes or never as groups I, II, III and IV, respectively). RESULTS: We classified 575 normal glucose-tolerant subjects into 4 groups (I-IV) with I: 28 (4.9%), II: 120 (20.9%), III: 143 (24.9%) and IV: 284 (49.4%) individuals. The Matsuda, insulinogenic and disposition indices were decreased from groups I to IV. ROC curves of disposition index reflecting the composition of insulin secretion and sensitivity classified the prolonged glucose elevation group (group III + IV) from the rapid glucose lowering group (group II; AUC = 0.847). CONCLUSIONS: Even in a young and healthy Japanese individual within the physiological range of glycaemic control, there is a sequential decrease in insulin sensitivity and secretion.

Association between skeletal muscle mass and serum concentrations of lipoprotein lipase, GPIHBP1, and hepatic triglyceride lipase in young Japanese men.

BACKGROUND: Two important regulators for circulating lipid metabolisms are lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL). In relation to this, glycosylphosphatidylinositol anchored high-density lipoprotein binding protein 1 (GPIHBP1) has been shown to have a vital role in LPL lipolytic processing. However, the relationships between skeletal muscle mass and lipid metabolism, including LPL, GPIHBP1, and HTGL, remain to be elucidated. Demonstration of these relationships may lead to clarification of the metabolic dysfunctions caused by sarcopenia. In this study, these relationships were investigated in young Japanese men who had no age-related factors; participants included wrestling athletes with abundant skeletal muscle. METHODS: A total of 111 young Japanese men who were not taking medications were enrolled; 70 wrestling athletes and 41 control students were included. The participants' body compositions, serum concentrations of lipoprotein, LPL, GPIHBP1 and HTGL and thyroid function test results were determined under conditions of no extreme dietary restrictions and exercises. RESULTS: Compared with the control participants, wrestling athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), higher serum concentrations of LPL (p < 0.001) and GPIHBP1 (p < 0.001), and lower fat mass index (p = 0.024). Kruskal-Wallis tests with Bonferroni multiple comparison tests showed that serum LPL and GPIHBP1 concentrations were significantly higher in the participants with higher SMI. Spearman's correlation analyses showed that SMI was positively correlated with LPL (ρ = 0.341, p < 0.001) and GPIHBP1 (ρ = 0.309, p = 0.001) concentration. The serum concentrations of LPL and GPIHBP1 were also inversely correlated with serum concentrations of triglyceride (LPL, ρ = - 0.198, p = 0.037; GPIHBP1, ρ = - 0.249, p = 0.008). Serum HTGL concentration was positively correlated with serum concentrations of total cholesterol (ρ = 0.308, p = 0.001), low-density lipoprotein-cholesterol (ρ = 0.336, p < 0.001), and free 3,5,3'-triiodothyronine (ρ = 0.260, p = 0.006), but not with SMI. CONCLUSIONS: The results suggest that increased skeletal muscle mass leads to improvements in energy metabolism by promoting triglyceride-rich lipoprotein hydrolysis through the increase in circulating LPL and GPIHBP1.

Vaccination Status and Antibody Titers against Rubella and Measles among Japanese Female College Students Majoring in Childcare between 2015 and 2018.

In 2014, for the protection of medical workers against measles and rubella infection, the Japanese Society for Infection Prevention and Control (JSIPC) recommended either maintaining antibody titers of seroprotective range or two-dose vaccination. JSIPC defined antibody titers into 3 ranges: seroprotective as expected prevention of infection, seronegative as under detection levels, and seropositive as antibody titers ranged between seronegative and seroprotective. This study aimed to explore the association between the number of vaccine doses received and the antibody titers against measles and rubella among Japanese college students majoring in childcare. A total of 841 female students with no history of measles or rubella were serologically screened at the time of college admission between 2015 and 2018. All 841 students had been vaccinated against measles; 738 (87.8%) received two doses of the measles vaccine and 103 (12.2%) received one dose. Likewise, 839 students, except for two, had been vaccinated against rubella; 719 (85.7%) received two doses of the rubella vaccine and 120 (14.3%) received one dose. We thus found that 107 students (12.7%) were seropositive for measles-specific IgG and 731 (86.9%) attained seroprotective titers. By contrast, in case of rubella-specific IgG, only 462 students (55.1%) attained seroprotective titers, and 371 students (44.1%) were seropositive. The two students without receiving rubella vaccination were classified as seronegative. In conclusion, despite that > 85% of students surveyed had received two doses of measles and rubella vaccines, a substantial number of students remain susceptible to measles and especially rubella at the time of college admission.

Fasting serum insulin levels and insulin resistance are associated with blood rheology in Japanese young adults without diabetes.

OBJECTIVES: To evaluate fasting serum insulin levels and insulin resistance, and their association with blood rheology, in Japanese young adults without diabetes. METHODS: Blood samples were analysed and blood rheology was estimated using haematological parameters. Whole blood passage time was measured using a Hitachi MC-FAN(©) microchannel array flow analyser. RESULTS: Out of 151 subjects (mean age, 24.1 ± 1.5 years), fasting serum insulin levels and insulin resistance (using homeostasis model assessment-estimated insulin resistance [HOMA-IR]), were positively correlated with longer whole blood passage times and higher values for haematocrit (Hct), haemoglobin (Hb), fibrinogen, body weight, body mass index (BMI), triglycerides, and low-density lipoprotein cholesterol (LDL-C)/high-density lipoprotein cholesterol (HDL-C) ratio, and were negatively correlated with HDL-C. Whole blood passage time correlated with body weight, BMI, LDL-C/HDL-C ratio, Hct, Hb, white blood cell (WBC) count, platelet count, fibrinogen, fasting serum insulin levels, and HOMA-IR. Multiple regression analysis revealed that whole blood passage time was independently associated with Hct, fibrinogen levels, and WBC count. CONCLUSIONS: Fasting serum insulin levels and insulin resistance were associated with blood rheology, and may influence blood rheology by modulating haematological parameters and lipid parameters in young adults without diabetes.

Use of capillary electrophoresis with dual-opposite end injection for simultaneous analysis of small ions in saliva samples from wrestlers undergoing a weight training program.

Capillary electrophoresis-capacitively coupled contactless conductivity detection (CE-C4D), conducted using an in-house-developed polyvinyl alcohol (PVA)-coated capillary system, was applied for the simultaneous analysis of small anions and cations in saliva samples from wrestlers undergoing a weight training program. Use of the PVA capillary for CE provided good reproducible ion separation with minimization of the electroosmotic flow and suppression of protein adsorption onto the capillary wall. Four cations and eight anions were separated in 12min, using a background electrolyte of 20mM MES/20mM histidine and 18-crown-6 ether (pH 6) at 20kV. The relative standard deviations (n=5) of the migration times and peak areas were <1% and <8%, respectively. The detection limit at a signal-to-noise ratio of 3 ranged from 1.6 to 10µM. Using the optimized CE-C4D system, we investigated the correlations between the concentrations of salivary ions and cortisol, which is commonly used as a stress marker. Analysis of saliva samples from ten wrestlers, who were attempting rapid weight loss before a competition, showed the following trends: (1) all ion concentrations, except for Ca(2+), Na(+), and Cl(-), increased between the first and last days of weight loss; (2) Mg(2+) increased to 166% (from 0.50mM to 1.4mM) between the first and last days of weight loss, being the highest increase of all the ions; and (3) K(+), Mg(2+), NO3(-), and SCN(-) levels were strongly correlated (P<0.05) with cortisol. The CE-C4D rapidly produced useful data on saliva ion contents, with good ion recovery as determined by the standard addition method (89-110%).