Department of Anesthesiology, University of Yamanashi, 1110 Shimokato, Chuo-City, Yamanashi, 409-3898, Japan.
Department of Anesthesiology, University of Tsukuba Hospital, 2-1-1 Amakubo, Tsukuba-City, Ibaraki, 305-8535, Japan.
Sci Rep. 2022 Jun 13;12(1):9793. doi: 10.1038/s41598-022-14092-2.
Insulin exerts positive inotropic effects on cardiac muscle; however, the relationship between cardiac contractility and phosphoinositol-3-kinase/Akt (PI3K/Akt) activation remains unclear. We hypothesized that the positive inotropic effects of insulin are dose-dependent and mediated via the PI3K/Akt pathway in isolated normal rat hearts. The Institutional Animal Investigation Committee approved the use of hearts excised from rats under pentobarbital anesthesia. The hearts were perfused at a constant pressure using the Langendorff technique. After stabilization (baseline), the hearts were randomly divided into the following four insulin (Ins) groups: 1) Ins0 (0 IU/L), 2) Ins0.5 (0.5 IU/L), 3) Ins5 (5 IU/L), and 4) Ins50 (50 IU/L) (n = 8 in each group). To clarify the role of the PI3K/Akt pathway in insulin-dependent inotropic effects, we also treated the insulin groups with the PI3K inhibitor wortmannin (InsW): 5) InsW0 (0 IU/L), 6) InsW0.5 (0.5 IU/L), 7) InsW5 (5 IU/L), and 8) InsW50 (50 IU/L). Hearts were perfused with Krebs-Henseleit buffer solution with or without wortmannin for 10 min, followed by 20 min perfusion with the solution containing each concentration of insulin. The data were recorded as the maximum left ventricular derivative of pressure development (LV dP/dt max). Myocardial p-Akt levels were measured at 3 min, 5 min, and at the end of the perfusion. In the Ins groups, LV dP/dt max in Ins5 and Ins50 increased by 14% and 48%, respectively, 3 min after insulin perfusion compared with the baseline. Tachyphylaxis was observed after 10 min in the Ins5 and Ins50 treatment groups. Wortmannin partially inhibited the positive inotropic effect of insulin; although insulin enhanced p-Akt levels at all time points compared with the control group, this increase was suppressed in the presence of wortmannin. The positive inotropic effect of insulin is dose-dependent and consistent with Akt activation. This effect mediated by high doses of insulin on cardiac tissue was temporary and caused tachyphylaxis, potentially triggered by Akt overactivation, which leads beta 1 deactivation.
胰岛素对心肌具有正性变力作用；然而，心肌收缩力与磷酸肌醇-3-激酶/蛋白激酶 B（PI3K/Akt）激活之间的关系尚不清楚。我们假设胰岛素的正性变力作用是剂量依赖性的，并通过分离的正常大鼠心脏中的 PI3K/Akt 途径介导。机构动物调查委员会批准使用戊巴比妥麻醉下切除的大鼠心脏进行研究。使用 Langendorff 技术以恒压方式对心脏进行灌注。稳定（基线）后，将心脏随机分为以下四个胰岛素（Ins）组：1）Ins0（0 IU/L），2）Ins0.5（0.5 IU/L），3）Ins5（5 IU/L）和 4）Ins50（50 IU/L）（每组 8 只）。为了阐明 PI3K/Akt 途径在胰岛素依赖性变力作用中的作用，我们还用 PI3K 抑制剂渥曼青霉素（InsW）处理胰岛素组：5）InsW0（0 IU/L），6）InsW0.5（0.5 IU/L），7）InsW5（5 IU/L）和 8）InsW50（50 IU/L）。心脏用 Krebs-Henseleit 缓冲液灌注 10 分钟，然后用含有每种胰岛素浓度的溶液灌注 20 分钟。数据记录为左心室压力发展最大导数（LV dP/dt max）。在灌注后 3 分钟、5 分钟和结束时测量心肌 p-Akt 水平。在 Ins 组中，与基线相比，胰岛素灌注后 3 分钟时 Ins5 和 Ins50 组的 LV dP/dt max 分别增加 14%和 48%。Ins5 和 Ins50 处理组在 10 分钟后出现脱敏现象。渥曼青霉素部分抑制了胰岛素的正性变力作用；尽管与对照组相比，胰岛素在所有时间点均增强了 p-Akt 水平，但在存在渥曼青霉素的情况下，这种增加受到抑制。胰岛素的正性变力作用是剂量依赖性的，与 Akt 激活一致。这种作用通过心脏组织中高剂量的胰岛素介导，是暂时的，并导致脱敏，这可能是由 Akt 过度激活引发的，导致β1 失活。
