有氧運動前攝取咖啡因對糖尿病前期者運動後血糖調控之影響

背景：糖尿病前期為第二類型糖尿病 (type 2 diabetes, T2D) 的高風險族群，透過運動時骨骼肌收縮刺激葡萄糖吸收與維持血糖恆定，是非藥物控制血糖、降低罹患糖尿病的有效方法。然而，咖啡因 (caffeine) 是一項廣泛使用的食品添加物，其不利於血糖控制的效果與運動相反，因此運動前攝取咖啡因對糖尿病前期者運動後血糖調控的影響仍需進一步釐清。目的：探討糖尿病前期者，攝取咖啡因對單次有氧運動後空腹血糖、胰島素、C-胜鍊胰島素 (C-peptide) 及葡萄糖耐受度的影響。方法：招募12名糖尿病前期男性，採雙盲、重複量數及平衡次序設計，所有參與者分別接受咖啡因＋運動 (CE, 3mg/kg) 與安慰劑＋運動 (PE) 兩種處理，運動形式為30分鐘60% VO2max (maximal oxygen uptake) 強度的跑步運動，並於攝取前、攝取後30分鐘/運動前、運動後立即及運動後120分鐘檢測血糖、胰島素及 C-peptide 濃度，另外，運動後立即進行口服葡萄糖耐受度測驗 (oral glucose tolerance test, OGTT)。結果：血糖在處理與時間因子的交互作用未達顯著 (p > .05)，在處理因子主要效果中，CE 處理之平均血糖值顯著高於 PE 處理 (133.87 ± 41.22 vs 127.04 ± 34.17 mg/dl) (p < .05)；而胰島素濃度在處理與時間因子的交互作用則達顯著 (p = .010)，單純主要效果顯示，CE 處理在運動後30及120分鐘顯著高於PE 處理；另外，CE 處理於 OGTT 測驗中血糖與胰島素濃度變化總曲線下面積 (area under the curve, AUC) 亦顯著高於PE 處理 (p < .05)。而 CE 處理與 PE處理間之 C-peptide 濃度則無顯著差異 (p > .05)。結論：糖尿病前期者有氧運動前攝取咖啡因會引發體內血糖、胰島素濃度提升，產生短暫性胰島素敏感度下降反應，因此，從事有氧運動前攝取咖啡因可能不利於糖尿病前期者運動後的血糖調控。

關鍵字

胰島素阻抗；葡萄糖耐受度；空腹血糖

並列摘要

Background: Individuals with prediabetes increase the risk of developing type 2 diabetes. Exercise is potent stimulator of skeletal muscle glucose uptake and thus good for maintaining glucose homeostasis. That could be a conducive method to improve blood glucose regulation and prevent diabetes without medication intake. In contrast to exercise, the ingestion of caffeine is adverse for blood glucose regulation. Therefore, it is still unknown whether such effects of pre-exercise caffeine ingestion on post-exercise glycemia regulation in prediabetes. Purpose: It aimed to investigate the effects of caffeine on fasting glucose, insulin, C-peptide and glucose tolerance responses after acute aerobic exercise in individuals with prediabetes. Method: The study was a double-blinded, randomized and crossover trials design and twelve men with prediabetes will be recruited. Participants randomly underwent two different trials which were caffeine + exercise (CE, 3 mg/kg) and placebo + exercise (PE) one week apart in a counterbalanced and double-blinded design. Participants performed a 30-min running at 60% VO2max (maximal oxygen uptake) 30 min after caffeine / placebo ingestion in both trials. Blood glucose, insulin, and C-peptide concentrations were measured at pre-ingestion, pre-exercise, immediately after and 120 min after exercise. In addition, participants received OGTT immediately after exercise, with blood glucose and insulin measured every 30 min during the tests. Results: The results showed that no significant trial × time interaction was observed in blood glucose (p > .05). Regarding the main values of trial factor, blood glucose, (133.87 ± 41.22 vs 127.04 ± 34.17 mg/dl) in the CE were higher than PE (p < .05). Then, there were statistically significant differences in insulin between trials and time points (p = .010). The simple main effect indicated that insulin of CE at post-exercise 30 and 120 (OGTT 30, 120) were significant higher than the PE. Moreover, there were statistically significant differences (p < .05) in blood glucose and insulin AUC between trials. That in CE was significant higher than the PE trial. In addition, there were no differences in C-peptide between CE and PE trials at all time points. Conclusion: Acute caffeine ingestion could increase blood glucose and insulin post aerobic exercise, it will have a transient negative impact on insulin sensitivity in prediabetes. Thus, caffeine ingestion, though combined with aerobic exercise, might have a negative impact on glycemic control among prediabetes.