Wang Xiaoyu, McLennan Susan V, Allen Terri J, Tsoutsman Tatiana, Semsarian Christopher, Twigg Stephen M
The University of Sydney, Australia.
Am J Physiol Cell Physiol. 2009 Dec;297(6):C1490-500. doi: 10.1152/ajpcell.00049.2009. Epub 2009 Jul 22.
Diabetic cardiomyopathy is characterized by interstitial fibrosis and cardiomyocyte hypertrophy and apoptosis. Also known as CCN2, connective tissue growth factor (CTGF) is implicated in the fibrosis; however, whether it contributes to cardiomyocytes changes and adverse effects of high glucose and lipids on these cells remains unknown. Hearts from streptozotocin-induced diabetic rats had elevated CTGF and changes of pathological myocardial hypertrophy, fibrosis, and cardiomyocyte apoptosis. Rat H9c2 cardiomyocytes were then treated with recombinant human (rh)CTGF, high glucose, or the saturated free fatty acid palmitate. Each reagent induced cell hypertrophy, as indicated by the ratio of total protein to cell number, cell size, and gene expression of cardiac hypertrophy marker genes atrial natriuretic peptide (ANP), and alpha-skeletal actin. Each treatment also caused apoptosis measured by increased caspase3/7 activity, apoptotic cells by transferase-mediated dUTP nick end labeling (TUNEL) assay, and lower viable cell number. Further studies showed CTGF mRNA was rapidly induced by high glucose and palmitate in H9c2 cells and in mouse neonatal cardiomyocyte primary cultures. small interfering RNA against CTGF blocked the high glucose and palmitate induction of hypertrophy and apoptosis. In addition, these CTGF effects were through the tyrosine kinase A (TrkA) receptor with tyrosine kinase activity, which has previously been implicated in CTGF signaling: TrkA was phosphorylated by CTGF, and a specific TrkA blocker abrogated CTGF-induced effects on hypertrophy and apoptosis. For the first time in any system, fatty acid is newly identified as a regulator of CTGF, and this work implicates autocrine CTGF as a mediator of adverse effects of high glucose and fatty acids in cardiomyocytes.
糖尿病性心肌病的特征是间质纤维化、心肌细胞肥大和凋亡。结缔组织生长因子（CTGF）也被称为CCN2，与纤维化有关；然而，它是否导致心肌细胞变化以及高糖和高脂对这些细胞的不良影响仍不清楚。链脲佐菌素诱导的糖尿病大鼠心脏中CTGF升高，且存在病理性心肌肥大、纤维化和心肌细胞凋亡的变化。然后用重组人（rh）CTGF、高糖或饱和游离脂肪酸棕榈酸酯处理大鼠H9c2心肌细胞。每种试剂均诱导细胞肥大，这通过总蛋白与细胞数量的比值、细胞大小以及心脏肥大标志物基因心房钠尿肽（ANP）和α-骨骼肌肌动蛋白的基因表达来表明。每种处理还通过半胱天冬酶3/7活性增加、末端脱氧核苷酸转移酶介导的缺口末端标记（TUNEL）法检测凋亡细胞以及活细胞数量降低来导致凋亡。进一步研究表明，高糖和棕榈酸酯可在H9c2细胞和小鼠新生心肌细胞原代培养物中快速诱导CTGF mRNA表达。针对CTGF的小干扰RNA可阻断高糖和棕榈酸酯诱导的肥大和凋亡。此外，这些CTGF效应是通过具有酪氨酸激酶活性的酪氨酸激酶A（TrkA）受体介导的，此前已有研究表明TrkA参与CTGF信号传导：CTGF可使TrkA磷酸化，而一种特异性TrkA阻滞剂可消除CTGF诱导的肥大和凋亡效应。在任何系统中，脂肪酸首次被新鉴定为CTGF的调节剂，这项研究表明自分泌CTGF是高糖和脂肪酸对心肌细胞产生不良影响的介质。
