Association between maximal oxygen uptake and the heart rate corrected-QT interval in postmenopausal overweight women.

BACKGROUND: Increased aerobic capacity can reduce the incidence of cardiovascular disease and the mortality rate. On the other hand, a prolonged heart rate corrected-QT (QTc) interval is associated with an increased risk of arrhythmias, cardiac sudden death and coronary artery disease. AIMS: The association of the aerobic capacity and coronary risk factors with QTc interval was investigated in postmenopausal overweight women. SUBJECTS AND METHODS: The subjects included 84 postmenopausal overweight women [age: 58.7+/-6.4 years, body mass index (BMI): 27.9+/-3.3] with coronary risk factors. Electrocardiogram (ECG) was recorded with a standard resting 12-lead ECG after more than 5 minutes of rest. The QTc interval was automatically calculated according to Bazett's formula. A multistage graded submaximal exercise test was performed on an electric bicycle ergometer to determine the estimated maximal oxygen uptake (VO(2)max). RESULTS: Single correlation analysis showed the QTc interval to be positively associated with hemoglobin A(1)c (HbA(1)c), fasting glucose, fasting insulin, BMI, waist circumference, serum potassium and the number of coronary risk factors, while negatively correlated with VO(2)max. Stepwise multiple regression analysis demonstrated the strong association of the QTc interval with HbA(1)c and VO(2)max (r(2)=0.244, p<0.0001). In both patients with and without metabolic syndrome (n=15, n=69, respectively), the QTc interval was independently associated with the HbA(1)c (r(2)=0.318, p<0.05, r(2)= 0.115, p<0.05, respectively). CONCLUSIONS: These results suggest that decreased aerobic capacity and glucose intolerance may be independent risk factors for a prolonged QTc interval, while demonstrating no relationship with metabolic syndrome.

Effects of low intensity exercise therapy on early phase insulin secretion in overweight subjects with impaired glucose tolerance and type 2 diabetes mellitus.

This study was designed to evaluate effects of exercise therapy on early phase insulin secretion in overweight subjects with impaired glucose tolerance (IGT) and type 2 diabetes mellitus (DM). The subjects consisted of overweight subjects with normal glucose tolerance (NGT, n=10), IGT (n=10) and DM (n=10) (age: 51.1+/-8.2, 56.3+/-8.8 and 58.5+/-6.2 years, respectively). All of these patients performed exercise therapy at lactate threshold intensity for 12 weeks. Before intervention, area under the glucose curve (AUC(PG)) was higher in DM, IGT and NGT groups, and area under the insulin curve (AUC(IRI)) and the early phase insulin secretion as calculated by insulinogenic index was higher in the NGT group than in either the IGT or DM groups (p<0.05). After exercise therapy, the insulin sensitivity, AUC(PG) and AUC(IRI) improved in three groups (p<0.05, respectively). The insulinogenic index increased in IGT and DM groups (p<0.05, respectively), but the changes in the insulinogenic index showed no significant differences between IGT and DM groups. These results suggest that the ss-cell function in subjects with IGT and DM could therefore improve after exercise therapy. Moreover, AUC(PG), AUC(IRI) and insulin sensitivity were also improved no relation to NGT, IGT and DM.

The possible influence of osteoarthritis of the knee on the accumulation of coronary risk factors in postmenopausal obese women.

OBJECTIVE: This cross-sectional study was designed to clarify the association between osteoarthritis of the knee (OAK) and coronary risk factors in postmenopausal obese women. SUBJECTS: The subjects consisted of 72 postmenopausal obese women (mean age 60.3 ± 7.6 years) with coronary risk factors. They were divided into two groups; including the OAK group and the normal knee (control) group. METHODS: Aerobic capacity was evaluated by maximal oxygen uptake (VO2 max) estimated from the nomogram of Åstrand and Ryhming. Daily activity was measured by a single-axis accelerometer. RESULTS: After adjusting for the age, the OAK group (n = 37) showed significantly higher obesity indices, the number of coronary risk factors, incidence of Metabolic Syndrome, a lower aerobic capacity and a lower daily activity than control group (n = 35). After adjusting for the age, body weight and body mass index, the OAK group with a high waist circumference, a low VO2 max and low mean total energy expenditure showed a significantly higher number of coronary risk factors than the control group with a low waist circumference, high VO2 max and high total energy expenditure. CONCLUSION: These results suggest that OAK was therefore associated with the aerobic capacity, daily activity and Metabolic Syndrome, and it may indirectly influence for the development of the future coronary heart disease in postmenopausal obese women.

Association between silent ST segment depression in exercise electrocardiography and insulin resistance in obese subjects.

OBJECTIVES: This study was designed to clarify the association between ST segment depression in exercise electrocardiography (ECG) and insulin resistance in obese subjects. METHODS: A multistage graded submaximal exercise stress test on the bicycle ergometer was performed under CM5-lead ECG monitoring in 114 obese subjects (39 men and 75 women, mean age 50.9 +/- 12.2 years, mean body mass index 28.6 +/- 3.1 kg/m(2)). RESULTS: In 27 patients showing ST segment depression at the final exercise intensities (abnormal ST), insulin resistance index by homeostasis model assessment (HOMA-IR) was higher and insulin sensitivity index was lower than in the remaining 87 patients with normal ST segment level (normal ST). The abnormal ST group showed significantly higher plasma glucose and serum insulin levels during the oral glucose tolerance test (OGTT) than the normal ST group. The abnormal ST group showed a significantly higher prevalence of hypertension, impaired glucose tolerance and metabolic syndrome than the normal ST group. Multiple logistic regression analysis showed that insulin resistance as evaluated by fasting insulin, sigma insulin during OGTT, HOMA-IR, insulin sensitivity index, the levels of uric acid, fasting glucose, systolic blood pressure and maximal oxygen uptake were independently associated with ST segment depression. CONCLUSIONS: These results suggest that insulin resistance may involve pathological ST depression during exercise, as well as previously reported factors such as hyperglycemia, hyperuricemia, hypertension and lower aerobic capacity.