Effects of Acute Exercise on Plasma Apelin and Blood Glucose in Healthy Young Subjects

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Apelin has been reported to enhance glucose uptake but most studies have examined apelin in diabetics and obese individuals. There are few studies that have reported apelin levels in plasma from apparently healthy individuals. However, no study has examined the acute effects of exercise on apelin and its response to glucose concentration in apparently healthy young subjects. PURPOSE: To determine plasma apelin concentration and its response to blood glucose following two acute exercise bouts and a glucose load. METHODS: Apparently healthy male (N=7) and female (N=5) subjects (22.8 3.0 yrs), nonsmokers and not on any medications that would alter metabolism. Subjects reported at 7-9 A.M. after an overnight fast, rested > 30 min and then completed the three conditions in a randomized order: VO2 max (MX) (6.9 ± 1.1 min); 30-min 70-75% VO2max (SM); and 54g glucose feeding (GF). Blood was drawn at four time points ([1] pre, [2] immediately post ex or 30 min post GF, [3]1 hr post and [4] 24 hrs post) and immediately centrifuged and plasma stored in aliquots at -80°C until assayed. Blood glucose was measured immediately using a glucose meter (Bayer Contour) and plasma apelin (Apelin-12 Elisa, Phoenix Pharmaceuticals) was measured in duplicate. RMANOVA was used to assess differences across time and between conditions. RESULTS: Resting blood glucose (77.1 ± 10.7 mg/dl) was not different across treatments. Apelin at rest was significantly higher for MX (.64 ± .36 ng/ml) compared to GF (.45 ± .22 ng/ml) (p=0.05) but not with SM (.54 ± .36 ng/ml). Blood glucose increased immediately after MX (109.2± 17.8 mg/dl) and GF (106.7± 20.9 mg/dl) p=0.05 and returned to normal 1 hr post treatment. The SM exercise did not alter glucose over time (80 ± 6.6 mg/dl). Apelin was not significantly changed with either MX or SM over time. However, apelin was elevated 1 hr post GF (.58 ± .23 ng/ml) and 24 hr post GF (.58 ± .32 ng/ml) (p=0.03) compared to rest. CONCLUSION: GF elevated apelin concentration both 1hr and 24hr post treatment, however the exercise did not significantly alter apelin. The MX exercise demonstrated a similar increase in glucose compared to the GF but did not alter apelin which suggests that other factors may have influenced the apelin response. We intend to examine the insulin response and insulin sensitivity as it relates to apelin concentration.