瘦身蛋白由脂肪組織分泌,在動物的研究,它具有生溫 (thermogensis)、增加身體活動、抑制食慾,進而降低體脂肪之效果。在人體的研究中,血液中的瘦身蛋白隨著體脂肪的多寡而增減。本研究目的以磁共振造影 (magnetic resonance imaging) 來測量三組不同長期規律運動者 (慢跑、游泳、重量訓練,每組各12位) 和一般坐式生活者 (12位受試者) 腹部脂肪體積分佈的差異;各組腹部脂肪體積分佈與瘦身蛋白的關係;各組瘦身蛋白與胰島素、睪固酮的關係。結果發現,在各組體脂肪百分比均未達顯著差異的情況下:各組之間的腹部皮下脂肪體積與腹部脂肪總體積未達顯著差異;在腹部內臟脂肪體積,慢跑組顯著低於控制組與游泳組 (慢跑組 0.40 + 0.27,游泳組0.95 + 0.46,重量訓練組0.66 + 0.26,控制組0.85 + 0.33公升,P< 0.05)。慢跑、游泳、重量訓練與控制組之間血液中瘦身蛋白 (1.64 + 0.62,2.51 + 0.73,2.38 + 1.76,2.30 + 1.80 µg/L)、胰島素 (13.51 + 5.17,17.15 + 4.42,17.22 + 12.93,15.45 + 6.13 ng/ml) 和睪固酮的濃度 (7.05 + 1.63,5.58 + 1.41,6.06 + 1.13,6.16 + 2.34 ng/ml) 均未達顯著差異。各組的瘦身蛋白與腹部皮下脂肪體積與腹部脂肪總體積達顯著相關;在瘦身蛋白與腹部內臟脂肪體積之間關係,當腹部內臟脂肪體積除以腹部脂肪總體積之比值為4組中較小時 (慢跑組0.18,重量訓練組0.21),瘦身蛋白與腹部內臟脂肪體積達顯著相關 (分別為0.89,0.72,P< 0.05);當該項比值為4組中較大時 (游泳組0.26,控制組0.28),瘦身蛋白與腹部內臟脂肪體積未達顯著相關。三組長期規律運動者的瘦身蛋白與胰島素、睪固酮之間沒有顯著相關。結論:長期規律運動有助於維持與降低體脂肪,長期規律慢跑可顯著地降低內臟脂肪體積。由本研究腹部脂肪體積分佈與瘦身蛋白的關係得知:腹部脂肪組織體積是決定瘦身蛋白與腹部脂肪組織關係的因子之一。有關長期規律運動者腹部內臟脂肪體積與腹部脂肪總體積的比值變化和瘦身蛋白的關係,與一般人的比較則須進一步探討。
Leptin is exclusively secreted by adipose tissue. Rodent studies have demonstrated that leptin can affect thermogenesis, increase physical activity, inhibit appetite and decrease body fat. In humans, circulating leptin levels correlate closely with body fat content. Purpose: This study examined the differences in the distribution of abdominal fat among three groups of individuals who engaged in long-term regular exercise (runners, R; swimmers, S; and weight lifters, W; 12 males in each group) and a sedentary group (control, C; 12males). The relationships between abdominal fat distribution, fasting leptin, insulin and testosterone were also studied. Results: There were no significant differences among the four groups in % body fat. (R:9.26 + 2.93,S:12.39 + 2.43,W:9.74 + 4.15,C:11.36 + 3.36%). Also the total abdominal fat volume and abdominal subcutaneous fat volume were not different among groups. However, the visceral fat volume in the R group was significantly lower than the C and S groups (mean + SD, R = 0.40 + 0.27; S = 0.95 + 0.46; W = 0.66 + 0.26; C = 0.85 + 0.33 L, P < 0.05). Fasting serum leptin, insulin, and testosterone did not differ significantly among groups (leptin, R: 1.64 + 0.62, S: 2.51 + 0.73, W: 2.38 + 1.76, C: 2.30 + 1.80 µg/L; insulin, R: 13.51+ 5.17, S: 17.15 + 4.42, W: 17.22 + 12.93, C: 15.45+ 6.13 ng/ml: testosterone, R: 7.05+ 1.63, S: 5.58 + 1.41, W: 6.06+ 1.13, C: 6.16+ 2.34 ng/ml). But leptin was significantly correlated with abdominal total adipose tissue volume and abdominal subcutaneous fat volume for all 4 groups. When the ratio of abdominal visceral fat volume (AVFV) to total abdominal fat volume (TAFV) was smaller (R:0.18, W:0.21), leptin and AVFV were significantly correlated (R = 0.89, W = 0.72, P < 0.05);when the ratio of AVFV to TAFV was larger (S:0.26, C:0.28), leptin and AVFV were not correlated. No significant relationship between leptin and insulin, leptin and testosterone was observed in R, S and W groups. Conclusions: Long-term regular exercise can help to maintain and decrease body fat. Long-term runners have the lowest visceral fat volume. Based on the relationship between leptin and abdominal fat volume distribution, adipose tissue volume is an important factor for correlation with leptin. Further research is needed in order to understand difference between long-term exercisers and sedentary individuals in concerning the ratio of AVFV to TAFV change and leptin.