Cardio-Metabolic Research Group (CMRG), Department of Physiological Sciences, Stellenbosch University, Stellenbosch 7600, South Africa.
Cardio-Metabolic Research Group (CMRG), Department of Physiological Sciences, Stellenbosch University, Stellenbosch 7600, South Africa.
Life Sci. 2014 Jun 6;105(1-2):31-42. doi: 10.1016/j.lfs.2014.04.009. Epub 2014 Apr 18.
Although acute hyperglycemic (AHG) episodes are linked to lower glucose uptake, underlying mechanisms remain unclear. We hypothesized that AHG triggers reactive oxygen species (ROS) production and increases non-oxidative glucose pathway (NOGP) activation, i.e. stimulation of advanced glycation end products (AGE), polyol pathway (PP), hexosamine biosynthetic pathway (HBP), PKC; thereby decreasing cardiac glucose uptake.
H9c2 cardiomyoblasts were exposed to 25 mM glucose for 24h vs. 5.5mM controls ± modulating agents during the last hour of glucose exposure: a) antioxidant #1 for mitochondrial ROS (250 μM 4-OHCA), b) antioxidant #2 for NADPH oxidase-generated ROS (100 μM DPI), c) NOGP inhibitors - 100 μM aminoguanidine (AGE), 5 μM chelerythrine (PKC); 40 μM DON (HBP); and 10 μM zopolrestat (PP). ROS levels (mitochondrial, intracellular) and glucose uptake were evaluated by flow cytometry.
AHG elevated ROS, activated NOGPs and blunted glucose uptake. Transketolase activity (pentose phosphate pathway [PPP] marker) did not change. Respective 4-OHCA and DPI treatment blunted ROS production, diminished NOGP activation and normalized glucose uptake. NOGP inhibitory studies identified PKCβII as a key downstream player in lowering insulin-mediated glucose uptake. When we employed an agent (benfotiamine) known to shunt flux away from NOGPs (into PPP), it decreased ROS generation and NOGP activation, and restored glucose uptake under AHG conditions.
This study demonstrates that AHG elicits maladaptive events that function in tandem to reduce glucose uptake, and that antioxidant treatment and/or attenuation of NOGP activation (PKC, polyol pathway) may limit the onset of insulin resistance.
尽管急性高血糖（AHG）发作与葡萄糖摄取减少有关，但潜在机制仍不清楚。我们假设 AHG 触发活性氧（ROS）的产生，并增加非氧化葡萄糖途径（NOGP）的激活，即刺激晚期糖基化终产物（AGE）、多元醇途径（PP）、己糖胺生物合成途径（HBP）、蛋白激酶 C（PKC）；从而减少心脏葡萄糖摄取。
将 H9c2 心肌细胞在 25mM 葡萄糖中孵育 24 小时，与 5.5mM 对照相比±葡萄糖暴露最后 1 小时的调节剂：a）线粒体 ROS 的抗氧化剂#1（250μM 4-羟基 CA），b）NADPH 氧化酶产生的 ROS 的抗氧化剂#2（100μM DPI），c）NOGP 抑制剂-100μM 氨基胍（AGE）、5μM 白屈菜红碱（PKC）；40μM DON（HBP）；和 10μM zopolrestat（PP）。通过流式细胞术评估 ROS 水平（线粒体、细胞内）和葡萄糖摄取。
AHG 升高 ROS、激活 NOGP 并抑制葡萄糖摄取。转酮醇酶活性（磷酸戊糖途径[PPP]标志物）没有变化。相应的 4-羟基 CA 和 DPI 处理可阻断 ROS 生成、减少 NOGP 激活并使葡萄糖摄取正常化。NOGP 抑制研究表明 PKCβII 是降低胰岛素介导的葡萄糖摄取的关键下游因子。当我们使用一种已知可将通量从 NOGP 转移（进入 PPP）的试剂（苯磷硫胺）时，它可减少 ROS 生成和 NOGP 激活，并在 AHG 条件下恢复葡萄糖摄取。
本研究表明，AHG 引发的适应性不良事件协同作用以减少葡萄糖摄取，抗氧化剂治疗和/或降低 NOGP 激活（PKC、多元醇途径）可能限制胰岛素抵抗的发生。
