GLUCOSE INTOLERANCE PREDICTS CARDIORESPIRATORY FITNESS IN A HEALTHY POPULATION

Aerobic capacity or maximum oxygen consumption rate (VO2max) is accepted as the single best indicator of cardiorespiratory fitness. VO2max is also an indicator of metabolic health and known as an all-cause mortality predictor. It is well established that glucose intolerance and insulin resistance in patients with diabetes is associated with decline in cardiorespiratory fitness. However, it is not clear if glucose intolerance is associated with poorer cardiorespiratory fitness in a population without diabetes. Therefore, the purpose of this study was to assess if glucose intolerance measured by oral glucose tolerance test (OGTT) is associated with cardiorespiratory fitness in a population without diabetes.

Fifty one (30 males and 21 females) predominantly Mexican-American adults without diabetes (Age 26.1 ± 5.3 years; BMI 26.7 ± 4.2 kg/m2; fasting blood glucose 92.1 ± 10.0 mg/dL) from the border region of El Paso, TX participated in this study. VO2max was assessed using a standardized graded exercise test protocol on a treadmill with Parvomedics metabolic cart. Glucose tolerance was measured by a 3-hour OGTT preformed after a 12-hour overnight fast. Blood glucose measured at fasting and every 30 minutes after the ingestion of 75g of glucose drink during OGTT and glucose area under the curve was determined to access glucose tolerance. Pearson correlation analysis was performed at 0.05 significance level.

Glucose intolerance measured by glucose area under the curve was negatively correlated with VO2max (r = −0.40, p = 0.006). Additionally, blood glucose level during OGTT test at 120 min (r = −0.43, p = 0.003), 150 min (r = −0.36, p = 0.014), and 180 min (r = −0.32, p = 0.048) were also negatively associated with VO2max. However, fasting blood glucose was not associated with VO2max (r = −0.09, p = 0.56).

Poorer cardiorespiratory fitness is indicated by greater glucose intolerance and a greater surge of glucose level during an OGTT, but not fasting blood glucose in a population without diabetes.