Institute for Sport and Health, University College Dublin, Dublin, Ireland.
Food for Health Ireland, University College Dublin, Dublin, Ireland.
Exp Physiol. 2019 Jun;104(6):800-807. doi: 10.1113/EP087356. Epub 2019 Mar 29.
What is the research question? This study used a new experimental model, in which culture medium is conditioned with human serum ex vivo, to investigate nutrient-mediated regulation of GLUT4 translocation in skeletal muscle cells in vitro. What is the main finding and importance? Human serum stimulated GLUT4 translocation, an effect differentially modulated by whether the culture medium was conditioned with serum from fasted subjects or with serum collected after feeding of intact or hydrolysed whey protein. Conditioning cell culture medium with human serum ex vivo represents a new approach to elucidate the effects of ingesting specific nutrients on skeletal muscle cell metabolism.
Individual amino acids, amino acid mixtures and protein hydrolysates stimulate glucose uptake in many experimental models. To replicate better in vitro the dynamic postprandial response to feeding in vivo, in the present study we investigated the effects of culture media conditioned with fasted and postprandial human serum on GLUT4 translocation in L6-GLUT4myc myotubes. Serum samples were collected from healthy male participants (n = 8) at baseline (T0), 60 (T60) and 120 min (T120) after the ingestion of 0.33 g (kg body mass) of intact (WPC) or hydrolysed (WPH) whey protein and an isonitrogenous non-essential amino acid (NEAA) control. L6-GLUT4myc myotubes were starved of serum and amino acids for 1 h before incubation for 1 h in medium containing 1% postprandial human serum, after which GLUT4 translocation was determined via colorimetric assay. Medium conditioned with fasted human serum at concentrations of 5-20% increased cell surface GLUT4myc abundance. Incubation with serum collected after the ingestion of WPH increased cell surface GLUT4myc at T60 relative to T0 [mean (lower, upper 95% confidence interval)]; [1.13 (1.05, 1.22)], whereas WPC [0.98 (0.90, 1.07)] or NEAA [1.02 (0.94, 1.11)] did not. The differential increases in cell surface GLUT4myc abundance were not explained by differences in serum concentrations of total, essential and branched-chain amino acids or insulin, glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP). Using a new ex vivo, in vitro approach, cell culture medium conditioned with postprandial serum after the ingestion of a whey protein hydrolysate increased GLUT4 translocation in skeletal muscle cells.
研究问题是什么？本研究使用了一种新的实验模型，即在体外培养的骨骼肌细胞中，使用经人血清离体条件化的培养基，研究营养物质对 GLUT4 易位的调节作用。主要发现和重要性是什么？人血清刺激 GLUT4 易位，这种作用可通过培养基是否用人空腹时的血清或用人进食完整或水解乳清蛋白后的血清来条件化而不同程度地调节。离体用人血清对细胞培养物进行条件化代表了一种阐明摄入特定营养素对骨骼肌细胞代谢影响的新方法。
在许多实验模型中，单个氨基酸、氨基酸混合物和蛋白质水解物都能刺激葡萄糖摄取。为了更好地模拟体内进食后的餐后动态反应，本研究中我们调查了用空腹和餐后人血清条件化的培养基对 L6-GLUT4myc 肌管中 GLUT4 易位的影响。在摄入 0.33g(kg 体重)完整（WPC）或水解（WPH）乳清蛋白和等氮非必需氨基酸（NEAA）对照物后，从健康男性参与者（n=8）在基线（T0）、60 分钟（T60）和 120 分钟（T120）采集血清样本。L6-GLUT4myc 肌管在孵育 1 小时前用不含血清和氨基酸的培养基饥饿 1 小时，然后用含 1%餐后人血清的培养基孵育 1 小时，之后通过比色法测定 GLUT4 易位。5%-20%浓度的空腹人血清条件培养基增加了细胞表面 GLUT4myc 的丰度。与 T0 相比，WPH 摄入后采集的血清在 T60 时增加了细胞表面 GLUT4myc[平均值（低值，95%置信区间上限）]；[1.13（1.05，1.22)]，而 WPC[0.98（0.90，1.07)]或 NEAA[1.02（0.94，1.11)]则没有。细胞表面 GLUT4myc 丰度的差异增加不能用血清中总氨基酸、必需氨基酸和支链氨基酸或胰岛素、胰高血糖素样肽 1（GLP-1）和胃抑制肽（GIP）的浓度差异来解释。使用新的离体、体外方法，用乳清蛋白水解物摄入后的餐后血清对细胞培养基进行条件化，增加了骨骼肌细胞中的 GLUT4 易位。
