Kinoshita Akito, Nagata Takuma, Furuya Futoshi, Nishizawa Mikio, Mukai Eri
Medical Physiology and Metabolism Laboratory, Department of Biomedical Sciences, College of Life Sciences, Ritsumeikan University, Shiga, Japan.
Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, Shiga, Japan.
Heliyon. 2023 Mar 23;9(4):e14719. doi: 10.1016/j.heliyon.2023.e14719. eCollection 2023 Apr.
Long-term administration of L. (white-skinned sweet potato, WSSP) has been reported to help manage type 2 diabetes mellitus (T2DM) in humans and animals; however, the mechanisms of blood glucose regulation by WSSP remain unclear. Therefore, we aimed to investigate the acute effects of WSSP on blood glucose homeostasis under normal conditions and the underlying mechanisms. Three fractions of WSSP (≤10, 10-50, and >50 kDa) were obtained via ultracentrifugation. Rats were subjected to an oral glucose tolerance test (OGTT) after a single administration of WSSP. The insulin tolerance test (ITT) and pyruvate tolerance test (PTT) were performed to evaluate insulin sensitivity and gluconeogenesis, respectively. Single WSSP administration markedly reduced blood glucose levels as revealed by the OGTT. Serum insulin levels were not increased by WSSP treatment. Blood glucose levels during ITT were significantly reduced due to WSSP treatment. WSSP treatment activated the phosphorylation of Akt, thereby activating insulin signaling in the skeletal muscles and liver. The ≤10 kDa fraction considerably reduced blood glucose levels per the OGTT and ITT. In contrast, gluconeogenesis in PTT and the expression of key enzymes in hepatocytes were suppressed by the >50 kDa fraction. This study demonstrated that WSSP acutely reduced postprandial blood glucose levels by improving insulin sensitivity in skeletal muscles in normal rats, which was attributed to constituents with a molecular weight of ≤10 kDa. Moreover, WSSP treatment suppressed gluconeogenesis in the liver, for which constituents of >50 kDa were responsible. Thus, WSSP can acutely regulate blood glucose homeostasis via multiple mechanisms. Since postprandial hyperglycemia leads to the onset of T2DM, WSSP, as a functional food, may possess potential active compounds that prevent T2DM.
据报道，长期服用白肉甘薯（WSSP）有助于控制人类和动物的2型糖尿病（T2DM）；然而，WSSP调节血糖的机制仍不清楚。因此，我们旨在研究WSSP在正常条件下对血糖稳态的急性影响及其潜在机制。通过超速离心获得WSSP的三个组分（≤10 kDa、10 - 50 kDa和>50 kDa）。大鼠单次服用WSSP后进行口服葡萄糖耐量试验（OGTT）。分别进行胰岛素耐量试验（ITT）和丙酮酸耐量试验（PTT）以评估胰岛素敏感性和糖异生作用。OGTT结果显示，单次服用WSSP可显著降低血糖水平。WSSP处理并未增加血清胰岛素水平。WSSP处理使ITT期间的血糖水平显著降低。WSSP处理激活了Akt的磷酸化，从而激活了骨骼肌和肝脏中的胰岛素信号通路。≤10 kDa组分根据OGTT和ITT结果可显著降低血糖水平。相比之下，>50 kDa组分抑制了PTT中的糖异生作用以及肝细胞中关键酶的表达。本研究表明，WSSP通过提高正常大鼠骨骼肌中的胰岛素敏感性，急性降低餐后血糖水平，这归因于分子量≤10 kDa的成分。此外，WSSP处理抑制了肝脏中的糖异生作用，这是由>50 kDa的成分所致。因此，WSSP可通过多种机制急性调节血糖稳态。由于餐后高血糖会导致T2DM的发生，WSSP作为一种功能性食品，可能含有预防T2DM的潜在活性化合物。
