Department of Physiology, Fourth Military Medical University, Xi'an, China.
PLoS One. 2010 Apr 9;5(4):e10085. doi: 10.1371/journal.pone.0010085.
This study was designed to evaluate the interaction between aging and obesity on cardiac contractile and intracellular Ca2+ properties.
Cardiomyocytes from young (4-mo) and aging (12- and 18-mo) male lean and the leptin deficient ob/ob obese mice were treated with leptin (0.5, 1.0 and 50 nM) for 4 hrs in vitro. High fat diet (45% calorie from fat) and the leptin receptor mutant db/db obesity models at young and older age were used for comparison. Cardiomyocyte contractile and intracellular Ca2+ properties were evaluated including peak shortening (PS), maximal velocity of shortening/relengthening (+/- dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR(90)), intracellular Ca2+ levels and decay. O2(-) levels were measured by dihydroethidium fluorescence.
Our results revealed reduced survival in ob/ob mice. Aging and obesity reduced PS, +/- dL/dt, intracellular Ca2+ rise, prolonged TR(90) and intracellular Ca2+ decay, enhanced O2(-) production and p(47phox) expression without an additive effect of the two, with the exception of intracellular Ca2+ rise. Western blot analysis exhibited reduced Ob-R expression and STAT-3 phosphorylation in both young and aging ob/ob mice, which was restored by leptin. Aging and obesity reduced phosphorylation of Akt, eNOS and p38 while promoting pJNK and pIkappaB. Low levels of leptin reconciled contractile, intracellular Ca2+ and cell signaling defects as well as O2(-) production and p(47phox) upregulation in young but not aging ob/ob mice. High level of leptin (50 nM) compromised contractile and intracellular Ca2+ response as well as O2(-) production and stress signaling in all groups. High fat diet-induced and db/db obesity displayed somewhat comparable aging-induced mechanical but not leptin response.
Taken together, our data suggest that aging and obesity compromise cardiac contractile function possibly via phosphorylation of Akt, eNOS and stress signaling-associated O2(-) release.
本研究旨在评估衰老和肥胖对心肌收缩和细胞内 Ca2+特性的相互作用。
体外将瘦素（0.5、1.0 和 50 nM）处理年轻（4 个月）和衰老（12 和 18 个月）雄性 lean 及瘦素缺乏 ob/ob 肥胖小鼠的心肌细胞 4 小时。使用高脂肪饮食（45%热量来自脂肪）和瘦素受体突变体 db/db 肥胖模型在年轻和老年时进行比较。评估心肌细胞收缩和细胞内 Ca2+特性，包括峰缩短（PS）、最大缩短/再伸长速度（+/- dL/dt）、PS 时间（TPS）、90%再伸长时间（TR(90)）、细胞内 Ca2+水平和衰减。通过二氢乙啶荧光测量 O2(-)水平。
我们的结果显示 ob/ob 小鼠的存活率降低。衰老和肥胖降低了 PS、+/- dL/dt、细胞内 Ca2+升高、延长了 TR(90)和细胞内 Ca2+衰减、增强了 O2(-)产生和 p(47phox)表达，除了细胞内 Ca2+升高之外，没有叠加效应。Western blot 分析显示，年轻和衰老 ob/ob 小鼠的 Ob-R 表达和 STAT-3 磷酸化减少，瘦素可恢复其表达。衰老和肥胖降低了 Akt、eNOS 和 p38 的磷酸化，同时促进了 pJNK 和 pIkappaB。低水平的瘦素缓解了年轻 ob/ob 小鼠的收缩、细胞内 Ca2+和细胞信号传导缺陷以及 O2(-)产生和 p(47phox)上调，但不能缓解衰老 ob/ob 小鼠的这些缺陷。高水平的瘦素（50 nM）损害了所有组的收缩和细胞内 Ca2+反应以及 O2(-)产生和应激信号。高脂肪饮食诱导的肥胖和 db/db 肥胖显示出与衰老诱导的机械但不是瘦素反应相似的情况。
总之，我们的数据表明衰老和肥胖会损害心肌收缩功能，可能是通过 Akt、eNOS 和应激信号相关的 O2(-)释放的磷酸化。
