Serum Ethylamine Levels as an Indicator of l-Theanine Consumption and the Risk of Type 2 Diabetes in a General Japanese Population: The Hisayama Study.

OBJECTIVE: This study investigated the association between serum ethylamine levels as an indicator of l-theanine consumption and the development of type 2 diabetes in a Japanese community. RESEARCH DESIGN AND METHODS: A total of 2,253 community-dwelling Japanese individuals aged 40-79 years without diabetes were monitored for 7 years. Serum ethylamine levels were divided into quartiles: ≤0.86, 0.87-2.10, 2.11-5.28, and ≥5.29 ng/mL. Kinetic analysis of serum ethylamine concentrations was performed after ingestion of l-theanine-rich green tea products containing 8 mg of l-theanine by 12 healthy volunteers. RESULTS: During follow-up, 282 subjects developed type 2 diabetes. The age- and sex-adjusted cumulative incidence of type 2 diabetes decreased significantly with elevating levels of serum ethylamine (P for trend = 0.04). This association remained unchanged after adjusting for potential confounding factors. The multivariable-adjusted hazard ratio (HR) for type 2 diabetes was significantly lower in the fourth quartile of serum ethylamine than in the first quartile (HR 0.69, 95% CI 0.49-0.98). This trend of decrease in diabetic risk across serum ethylamine levels was more prominent in middle-aged subjects and in subjects with prediabetes, obesity, or insulin resistance. Kinetic analysis estimated that the minimum concentration at the steady state was >5.90 ng/mL in the case of twice-daily ingestion with an interval of 12 h. CONCLUSIONS: Higher serum ethylamine was significantly associated with lower risk of the development of type 2 diabetes in a general Japanese population. The measurement of serum ethylamine concentration would be a useful biomarker for the objective estimation of l-theanine consumption.

Glucosamine-containing supplement improves locomotor functions in subjects with knee pain - a pilot study of gait analysis.

BACKGROUND: Previously, we demonstrated that glucosamine-containing supplementation was effective for improving locomotor functions, especially walking speed. However, the biomechanical mechanism of efficacy has not been elucidated. This study aimed to address this challenge in subjects with knee pain, using a motion capture system. METHODS: An open label study was conducted in 30 Japanese subjects with knee pain. The subjects were administered a daily supplement containing 1,200 mg of glucosamine hydrochloride, 60 mg of chondroitin sulfate, 45 mg of type II collagen peptides, 90 mg of quercetin glycosides, 10 mg of imidazole peptides, 1 mg of proteoglycan, and 5 µg of vitamin D (GCQID). The intervention continued for 16 weeks. Efficacy for locomotor functions involving the knee joint was evaluated mainly using the Japanese Knee Osteoarthritis Measure (JKOM) and the 5-question Geriatric Locomotive Function Scale (GLFS-5). To examine the biomechanical mechanism of efficacy for locomotor functions, motions of subjects in a normal walking state were captured. Gait analysis was conducted and efficacy for gait parameters such as normal walking speed, stride length, cadence, and angle of soles was evaluated. RESULTS: GCQID significantly improved total scores on the JKOM and GLFS-5. In gait analysis, normal walking speed, stride length, and angle of soles at the end of the stance phase were all significantly increased, but cadence did not change significantly during the intervention period. There were significant intercorrelations of changes in normal walking speed, stride length, and angle of soles at the end of the stance phase, and between changes in stride length and total JKOM score. CONCLUSION: A GCQID supplement may increase walking speed through increased stride length and angle of kicking from the ground during steps, which might be mainly associated with alleviated knee pain.

Glucosamine-containing supplement improves locomotor functions in subjects with knee pain: a randomized, double-blind, placebo-controlled study.

BACKGROUND: The aim of this study was to investigate the ability of a glucosamine-containing supplement to improve locomotor functions in subjects with knee pain. METHODS: A randomized, double-blind, placebo-controlled, parallel-group comparative study was conducted for 16 weeks in 100 Japanese subjects (age, 51.8±0.8 years) with knee pain. Subjects were randomly assigned to one of the two supplements containing 1) 1,200 mg of glucosamine hydrochloride, 60 mg of chondroitin sulfate, 45 mg of type II collagen peptides, 90 mg of quercetin glycosides, 10 mg of imidazole peptides, and 5 µg of vitamin D per day (GCQID group, n=50) or 2) a placebo (placebo group, n=50). Japanese Knee Osteoarthritis Measure, visual analog scale score, normal walking speed, and knee-extensor strength were measured to evaluate the effects of the supplement on knee-joint functions and locomotor functions. RESULTS: In subjects eligible for efficacy assessment, there was no significant group × time interaction, and there were improvements in knee-joint functions and locomotor functions in both groups, but there was no significant difference between the groups. In subjects with mild-to-severe knee pain at baseline, knee-extensor strength at week 8 (104.6±5.0% body weight vs 92.3±5.5% body weight, P=0.030) and the change in normal walking speed at week 16 (0.11±0.03 m/s vs 0.05±0.02 m/s, P=0.038) were significantly greater in the GCQID group than in the placebo group. Further subgroup analysis based on Kellgren-Lawrence (K-L) grade showed that normal walking speed at week 16 (1.36±0.05 m/s vs 1.21±0.02 m/s, P<0.05) was significantly greater in the GCQID group than in the placebo group in subjects with K-L grade I. No adverse effect of treatment was identified in the safety assessment. CONCLUSION: In subjects with knee pain, GCQID supplementation was effective for relieving knee pain and improving locomotor functions.

Effect of a dietary supplement containing glucosamine hydrochloride, chondroitin sulfate and quercetin glycosides on symptomatic knee osteoarthritis: a randomized, double-blind, placebo-controlled study.

BACKGROUND: Oral glucosamine and chondroitin sulfate, alone and in combination, have been used worldwide for the treatment of osteoarthritis (OA), but their efficacy is controversial. This clinical study was aimed at investigating the potential of a dietary supplement containing glucosamine and chondroitin sulfate in combination with derivatives of quercetin, a naturally occurring flavonoid, (GCQ supplement) for knee OA care. RESULTS: A randomized, double-blind, placebo-controlled study was conducted in 40 Japanese subjects with symptomatic knee OA. Subjects were randomly assigned to GCQ supplement (1200 mg glucosamine hydrochloride, 60 mg chondroitin sulfate and 45 mg quercetin glycosides per day) or placebo and the treatment and follow-up were continued for 16 weeks. The results of symptomatic efficacy assessment based on Japanese Orthopaedic Association criteria showed that scores for two of the four symptom/function subscales, as well as the aggregate scores, were significantly improved at week 16 or earlier in the GCQ group compared to the placebo group. Moreover, analyses of cartilage metabolism biomarkers showed a trend of improvement in type II collagen synthesis/degradation balance in the GCQ group during follow-up. CONCLUSION: GCQ supplement was thought to be more effective than placebo in decreasing the intensity of knee OA-associated clinical symptoms.