We investigated the effects of oral lactate administration on protein synthesis and degradation factors in rats over 2 h after intake. Seven-week-old male Sprague–Dawley rats were randomly divided into four groups (n = 8/group); their blood plasma levels of lactate, glucose, insulin, and insulin-like growth factor 1 (IGF1) were examined following sacrifice at 0, 30, 60, or 120 min after sodium lactate (2 g/kg) administration. We measured the mRNA expression levels of protein synthesis-related genes (IGF receptor, protein kinase B (Akt), mammalian target of rapamycin (mTOR)) or degradation-related genes (muscle RING-finger protein-1 (MuRF1), atrogin-1) and analyzed the protein expression and phosphorylation (activation) of Akt and mTOR. Post-administration, the plasma lactate concentration increased to 3.2 mmol/L after 60 min. Plasma glucose remained unchanged throughout, while insulin and IGF1 levels decreased after 30 min. The mRNA levels of IGF receptor and mTOR peaked after 60 min, and Akt expression was significantly upregulated from 30 to 120 min. However, MuRF1 and atrogin-1 expression levels were unaffected. Akt protein phosphorylation did not change significantly, whereas mTOR phosphorylation significantly increased after 30 min. Thus, lactate administration increased the mRNA and protein expression of protein-synthesis factors, suggesting that it can potentially promote skeletal muscle synthesis.

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外源乳酸对大鼠骨骼肌IGF1 / Akt / mTOR途径的影响

我们研究了口服乳酸对大鼠摄入后2小时内蛋白质合成和降解因子的影响。将7周大的雄性Sprague–Dawley大鼠随机分为四组（n= 8 /组）；服用乳酸钠（2 g / kg）后0、30、60或120分钟处死后，检查其血浆乳酸，葡萄糖，胰岛素和胰岛素样生长因子1（IGF1）的水平。我们测量了蛋白质合成相关基因（IGF受体，蛋白激酶B（Akt），雷帕霉素的哺乳动物靶标（mTOR））或降解相关基因（肌肉RING-手指蛋白1（MuRF1），atrogin- 1）并分析了Akt和mTOR的蛋白质表达和磷酸化（激活）。给药后，血浆乳酸浓度在60分钟后增加到3.2 mmol / L。血浆葡萄糖在整个过程中保持不变，而胰岛素和IGF1的水平在30分钟后下降。IGF受体和mTOR的mRNA水平在60分钟后达到峰值，而Akt表达在30至120分钟时显着上调。但是，MuRF1和atrogin-1的表达水平不受影响。30分钟后，Akt蛋白的磷酸化没有明显变化，而mTOR磷酸化显着增加。因此，乳酸的施用增加了蛋白质合成因子的mRNA和蛋白质表达，表明它可以潜在地促进骨骼肌的合成。