Discipline-specific insulin sensitivity in athletes

Coenzyme Q10 status, glucose parameters, and antioxidative capacity in college athletes

BACKGROUND

Glycemia is related to energy production during exercise. Coenzyme Q10 is an antioxidant that participates in adenosine triphosphate synthesis in mitochondria. The aim of this study was to investigate the level of coenzyme Q10, glucose parameters, and antioxidant capacity in athletes.

METHODS

This study was designed as a cross-sectional study. Well-trained college athletes (n = 43) and age-gender matched healthy subjects (n = 25) were recruited from a college. The levels of glucose parameters, oxidative stress, antioxidant enzymes activity, Trolox equivalent antioxidant capacity (TAC), and coenzyme Q10 status were measured in the present study.

RESULTS

The athletes had a significantly lower level of white blood cells (WBC) coenzyme Q10 than the healthy subjects (0.34 ± 0.24 vs. 0.65 ± 0.43 nmol/g, p < 0.01); however, no significant difference was detected in plasma coenzyme Q10 between the two groups. Regarding the glucose parameters, the athletes had significantly higher values for HbA1c (5.5 ± 0.3 vs. 5.3 ± 0.3%, p < 0.05) and quantitative insulin sensitivity check index (QUICKI, 0.37 ± 0.03 vs. 0.34 ± 0.03, p < 0.05), and lower homeostatic model assessment-insulin resistance (HOMA-IR, 1.5 ± 0.8 vs. 2.9 ± 3.8, p < 0.05) than the healthy subjects. A higher level of TAC was found in the athletes (serum, 5.7 ± 0.3 vs. 5.4 ± 0.2 mM Trolox; erythrocyte, 10.5 ± 0.6 vs. 10.0 ± 0.5 mM Trolox, p < 0.05). In addition, WBC coenzyme Q10 status was significantly correlated with catalase activity (r = 0.56, p < 0.01), GPx activity (r = 0.56, p < 0.01), serum TAC (r = 0.54, p < 0.01), fasting glucose (β = - 1.10, p < 0.01), HbA1c (β = - 0.82, p < 0.01), HOMA-IR (β = - 1.81, p < 0.01), and QUICK (β = 0.08, p < 0.01).

CONCLUSIONS

Athletes may suffer from a marginal coenzyme Q10 deficiency, and the level was related to glycemic control and antioxidant capacity. Further interventional studies are needed to clarify an adequate dose of coenzyme Q10 supplementation in athletes to optimize their coenzyme Q10 status and athletic performance or recovery during exercise.

Insulin sensitivity and β-cell function estimated by HOMA2 model in sprint-trained athletes aged 20-90 years vs endurance runners and untrained participants

There are no studies available that portray insulin sensitivity and β-cell function in ageing sprint-trained athletes. We compared male young and master sprint-trained athletes to endurance-trained and untrained individuals. We hypothesised that ageing sprint-trained athletes would preserve insulin sensitivity and β-cell function at a level similar to that of endurance-trained peers and better than in untrained individuals. We showed the associations between age and parameters derived from the updated Homeostasis Model Assessment (HOMA2 model) in 52 sprint-trained track and field athletes (aged 20-90 years), 85 endurance runners (20-80 years) and 55 untrained individuals (20-70 years). Fasting glucose, fasting insulin, insulin sensitivity and β-cell function were not associated with age in sprint-trained athletes. These variables remained relatively stable across a wide range of age and comparable to those observed in endurance-trained athletes. In contrast, the untrained group showed considerable age-related increase in fasting insulin and β-cell activity and a strong decrease in insulin sensitivity compared to both athletic groups. HOMA2 parameters were significantly related to maximal oxygen in the combined group of participants. In summary, chronic training based on a "sprint model" of physical activity, that contains mixed exercise, seems to be effective in maintaining normal insulin sensitivity with ageing.

Plasma zinc, copper, and serum thyroid hormones and insulin levels after zinc supplementation followed by placebo in competitive athletes

Intense physical activity is associated with biological adaptations involving hormones and trace elements. Zinc supplementation may affect plasma copper concentration, thyroid-stimulating hormone (TSH), thyroid hormones, insulin, and glucose homeostasis, but data in athletes are scarce. The aim of this study was to evaluate in competitive athletes (cyclists, n = 7, 32 ± 8 years) the effect of zinc supplementation (22 mg/day as zinc gluconate) during 30 days, and discontinuation using placebo (maltodextrin) during the following 30 days, on plasma zinc and copper concentrations, serum thyroid hormones, insulin and glucose levels, and HOMA2-IR. Compared to baseline, plasma zinc and Zn:Cu plasma ratio increased, but plasma copper decreased after zinc supplementation (day 30) and discontinuation (day 60) (p < 0.05). Zn supplementation and discontinuation had no effect on TSH, T3, and T4. Fasting serum insulin and HOMA2-IR increased (27% and 47%, respectively) on day 60 compared to baseline (p = 0.03), suggesting a delayed effect of zinc supplementation. Moreover, plasma zinc was positively associated with serum insulin (r = 0.87, p = 0.009) and HOMA2-IR (r = 0.81, p = 0.03) after zinc supplementation (day 30), indicating that supplemental zinc may impair glucose utilization in cyclists.

Exercise in aging: its important role in mortality, obesity and insulin resistance

The prevalence of overweight and obesity has increased dramatically over the last several decades. Obesity and physical inactivity increase the risk for cardiovascular disease, Type 2 diabetes mellitus, hypertension, dyslipidemia and certain cancers. Obesity and low levels of physical fitness are also associated with increased risk of all-cause and cardiovascular mortality. Central and total obesity, insulin resistance and inactivity increase with age. Exercise training and increased fitness promote positive changes in body composition and improve insulin sensitivity. This article will describe the effects of exercise training, both aerobic and resistive, on body composition and obesity as well as review studies investigating the effects of exercise training on glucose metabolism and insulin sensitivity in older adults. Adopting a physically active lifestyle should be emphasized in overweight and obese individuals with insulin resistance to reduce the risk for cardiovascular events in the aging population.