Jones P P, Davy K P, Alexander S, Seals D R
Department of Kinesiology, University of Colorado, Boulder 80309, USA.
Am J Physiol. 1997 Jun;272(6 Pt 1):E976-80. doi: 10.1152/ajpendo.1997.272.6.E976.
Tonic sympathetic nerve activity (SNA) increases with age, but the mechanisms are unknown. There is evidence that SNA is positively related to total and abdominal body fat, which also increase with age. We tested the hypotheses that 1) the elevation in SNA with age is partially accounted for by higher abdominal and/or total body fat and 2) skeletal muscle is a target of the adiposity-related sympathetic effects. Direct microneurographic recordings of skeletal muscle SNA (MSNA) were obtained during supine rest in 16 older (64 +/- 1 yr, means +/- SE) and 16 young (24 +/- 1 yr) adult males. Central body fat was estimated by waist circumference (WC) and fat mass (FM) by hydrostatic weight. MSNA, WC, and FM were higher in the older vs. young males (44 +/- 2 vs. 22 +/- 2 bursts/min, 91 +/- 2 vs. 79 +/- 1 cm, and 19 +/- 2 vs. 9 +/- 1 kg, respectively; all P < 0.0001). Although univariate correlations were high for MSNA and both WC (r = 0.77) and FM (r = 0.75), stepwise multiple regression analysis revealed WC to be the best predictor of MSNA (R2 = 0.60, P < 0.0001), with FM explaining only an additional 2% of the variance (not significant). Statistically covarying for WC reduced but did not eliminate the difference in adjusted age-group means for MSNA (39 +/- 3 vs. 26 +/- 2 bursts/min, P = 0.003). We conclude that 1) the elevated SNA in older adults is partially related to higher body fat, particularly in the abdominal region, and 2) skeletal muscle is a target of the adiposity-related sympathetic effects observed with aging.
静息交感神经活动（SNA）随年龄增长而增加，但其机制尚不清楚。有证据表明，SNA与总体脂肪和腹部脂肪呈正相关，而这两者也随年龄增长而增加。我们检验了以下假设：1）SNA随年龄增长而升高部分是由于腹部和/或总体脂肪增加所致；2）骨骼肌是与肥胖相关的交感神经效应的靶器官。对16名老年（64±1岁，均值±标准误）和16名年轻（24±1岁）成年男性在仰卧休息时进行骨骼肌SNA（MSNA）的直接微神经图记录。通过腰围（WC）估计中心体脂，通过水下称重法估计脂肪量（FM）。老年男性的MSNA、WC和FM均高于年轻男性（分别为44±2次/分钟对22±2次/分钟、91±2厘米对79±1厘米、19±2千克对9±1千克；所有P<0.0001）。虽然MSNA与WC（r=0.77）和FM（r=0.75）的单变量相关性都很高，但逐步多元回归分析显示WC是MSNA的最佳预测指标（R2=0.60，P<0.0001），FM仅额外解释了2%的方差（无显著性）。对WC进行统计学协变量调整后，MSNA的调整年龄组均值差异有所减小，但并未消除（39±3次/分钟对26±2次/分钟，P=0.003）。我们得出结论：1）老年人升高的SNA部分与较高的体脂有关，尤其是腹部区域；2）骨骼肌是衰老过程中观察到的与肥胖相关的交感神经效应的靶器官。
