Responses of Lipolysis to Physical Activity in Lean and Overweight Children

Abstract

PURPOSE: This investigation was conducted to determine whether there were differences in lipolytic responses to physical activity between lean (LN) and overweight/obese (OW) children. METHODS: Fifty-four children (EX: 15 LN and 39 OW, age 8-11yr) performed 20 min of aerobic exercise eliciting an average heart rate of 140 beats/min with additional 6 min of warm-up and cool-down 2.5 hours following a standardized breakfast (∼300 kcal), while 22 children (CON: 9 LN and 13 OW, age 8-11 yr) remained rested following breakfast. Microdialysis probes were inserted into the subcutaneous abdominal adipose tissue to monitor interstitial glycerol (lipolysis) and microvascular blood flow. Three one-hour dialysate samples were collected with exercise performed in the second hour (or rest in CON). Two-way (time by intervention group) ANOVAs were separately performed in LN and OW. RESULTS: For interstitial glycerol concentrations in LN, significant effects were a time by intervention group interaction, and main effects for time and intervention group (p<0.05). Interstitial glycerol concentration increased (p<0.05) with exercise and decreased (p<0.05) after exercise in EX (176 ± 22 to 261 ±34 to 220 ± 36 uM), but remained unchanged in CON (114 ± 28 to 122 ± 44 to 119 ± 47 uM). In OW, no statistical difference was found in either interstitial glycerol concentration between EX and CON or over time (EX: 281 ± 30 to 326 ± 65 to 311 ± 35 uM; CON: 204 ± 52 to 254 ± 112 to 229 ± 61 uM). In LN, a time by intervention group interaction was found (p<0.05) in ethanol outflow/inflow (O/I, inversely related to microvascular blood flow). Ethanol O/I increased in EX (0.55 ± 0.04 to 0.64 ± 0.04 to 0.61 ± 0.04, p<0.05) while decreased in CON (0.62 ± 0.06 to 0.57 ± 0.05 to 0.52 ± 0.05, p<0.05). In OW, no statistical difference was found in either ethanol O/I between EX and CON or over time (EX: 0.76 ± 0.02 to 0.74 ± 0.03 to 0.73 ± 0.02; CON: 0.73 ± 0.03 to 0.71 ± 0.04 to 0.70 ± 0.04). CONCLUSIONS: Lipolytic response to acute aerobic exercise is lower in overweight compared to lean children. Greater lipolytic response during exercise in lean children was evident even with a decreased adipose tissue microvascular blood flow during exercise in lean children. Supported by NIH RO1DK071081.