Department of Pharmaceutical Sciences, Taneja College of Pharmacy, University of South Florida, Tampa, FL, USA.
Bone-Muscle Research Center, College of Nursing & Health Innovation, University of Texas-Arlington (UTA), Arlington, TX, USA.
J Cachexia Sarcopenia Muscle. 2022 Apr;13(2):1177-1196. doi: 10.1002/jcsm.12887. Epub 2022 Jan 21.
Nicotinamide phosphoribosyltransferase (Nampt), a key enzyme in NAD salvage pathway is decreased in metabolic diseases, and its precise role in skeletal muscle function is not known. We tested the hypothesis, Nampt activation by P7C3 (3,6-dibromo-α-[(phenylamino)methyl]-9H-carbazol-9-ethanol) ameliorates diabetes and muscle function.
We assessed the functional, morphometric, biochemical, and molecular effects of P7C3 treatment in skeletal muscle of type 2 diabetic (db/db) mice. Nampt mice were utilized to test the specificity of P7C3.
Insulin resistance increased 1.6-fold in diabetic mice compared with wild-type mice and after 4 weeks treatment with P7C3 rescued diabetes (P < 0.05). In the db-P7C3 mice fasting blood glucose levels decreased to 0.96-fold compared with C57Bl/6J wild-type naïve control mice. The insulin and glucose tolerance tests blood glucose levels were decreased to 0.6-fold and 0.54-folds, respectively, at 120 min along with an increase in insulin secretion (1.76-fold) and pancreatic β-cells (3.92-fold) in db-P7C3 mice. The fore-limb and hind-limb grip strengths were increased to 1.13-fold and 1.17-fold, respectively, together with a 14.2-fold increase in voluntary running wheel distance in db-P7C3 mice. P7C3 treatment resulted in a 1.4-fold and 7.1-fold increase in medium-sized and larger-sized myofibres cross-sectional area, with a concomitant 0.5-fold decrease in smaller-sized myofibres of tibialis anterior (TA) muscle. The transmission electron microscopy images also displayed a 1.67-fold increase in myofibre diameter of extensor digitorum longus muscle along with 2.9-fold decrease in mitochondrial area in db-P7C3 mice compared with db-Veh mice. The number of SDH positive myofibres were increased to 1.74-fold in db-P7C3 TA muscles. The gastrocnemius and TA muscles displayed a decrease in slow oxidative myosin heavy chain type1 (MyHC1) myofibres expression (0.46-fold) and immunostaining (6.4-fold), respectively. qPCR analysis displayed a 2.9-fold and 1.3-fold increase in Pdk4 and Cpt1, and 0.55-fold and 0.59-fold decrease in Fgf21 and 16S in db-P7C3 mice. There was also a 3.3-fold and 1.9-fold increase in Fabp1 and CD36 in db-Veh mice. RNA-seq differential gene expression volcano plot displayed 1415 genes to be up-regulated and 1726 genes down-regulated (P < 0.05) in db-P7C3 mice. There was 1.02-fold increase in serum HDL, and 0.9-fold decrease in low-density lipoprotein/very low-density lipoprotein ratio in db-P7C3 mice. Lipid profiling of gastrocnemius muscle displayed a decrease in inflammatory lipid mediators n-6; AA (0.83-fold), and n-3; DHA (0.69-fold) and EPA (0.81-fold), and a 0.66-fold decrease in endocannabinoid 2-AG and 2.0-fold increase in AEA in db-P7C3 mice.
Overall, we demonstrate that P7C3 activates Nampt, improves type 2 diabetes and skeletal muscle function in db/db mice.
烟酰胺磷酸核糖基转移酶（Nampt）是 NAD 补救途径中的关键酶，在代谢疾病中减少，但其在骨骼肌功能中的精确作用尚不清楚。我们测试了这样一个假设，即 P7C3（3,6-二溴-α-[(苯氨基)甲基]-9H-咔唑-9-乙醇）激活 Nampt 可以改善 2 型糖尿病和肌肉功能。
我们评估了 2 型糖尿病（db/db）小鼠骨骼肌中 P7C3 治疗的功能、形态计量学、生化和分子效应。利用 Nampt 小鼠来测试 P7C3 的特异性。
与野生型小鼠相比，糖尿病小鼠的胰岛素抵抗增加了 1.6 倍，经过 4 周的 P7C3 治疗后，糖尿病得到了挽救（P<0.05）。在 db-P7C3 小鼠中，空腹血糖水平与 C57Bl/6J 野生型对照小鼠相比降低了 0.96 倍。胰岛素和葡萄糖耐量试验的血糖水平在 120 分钟时分别降低到 0.6 倍和 0.54 倍，同时胰岛素分泌增加（1.76 倍）和胰岛β细胞增加（3.92 倍）。db-P7C3 小鼠的前肢和后肢握力分别增加到 1.13 倍和 1.17 倍，同时自愿跑步轮距离增加了 14.2 倍。P7C3 治疗导致中大型肌纤维横截面积增加 1.4 倍和 7.1 倍，同时前胫骨肌（TA）的小型肌纤维减少 0.5 倍。电镜图像还显示，与 db-Veh 小鼠相比，db-P7C3 小鼠伸趾长肌的肌纤维直径增加了 1.67 倍，线粒体面积减少了 2.9 倍。TA 肌肉中的 SDH 阳性肌纤维数量增加到 1.74 倍。比目鱼肌和 TA 肌肉的慢肌肌球蛋白重链 1 型（MyHC1）肌纤维表达（0.46 倍）和免疫染色（6.4 倍）分别减少。qPCR 分析显示，db-P7C3 小鼠的 Pdk4 和 Cpt1 分别增加了 2.9 倍和 1.3 倍，Fgf21 和 16S 分别减少了 0.55 倍和 0.59 倍。db-Veh 小鼠的 Fabp1 和 CD36 分别增加了 3.3 倍和 1.9 倍。RNA-seq 差异基因表达火山图显示，db-P7C3 小鼠有 1415 个基因上调和 1726 个基因下调（P<0.05）。db-P7C3 小鼠的血清高密度脂蛋白增加 1.02 倍，低密度脂蛋白/极低密度脂蛋白比值降低 0.9 倍。比目鱼肌的脂质谱显示炎症脂质介质 n-6；AA（0.83 倍）和 n-3；DHA（0.69 倍）和 EPA（0.81 倍）减少，内源性大麻素 2-AG 减少 0.66 倍，AEA 增加 2.0 倍。
总的来说，我们证明了 P7C3 激活了 Nampt，改善了 db/db 小鼠的 2 型糖尿病和骨骼肌功能。
