Denti L, Pasolini G, Sanfelici L, Ablondi F, Freddi M, Benedetti R, Valenti G
Department of Geriatrics, University of Parma, Italy.
Metabolism. 1997 Jul;46(7):826-32. doi: 10.1016/s0026-0495(97)90130-x.
Insulin can inhibit dehydroepiandrosterone (DHEA) biosynthesis in humans, as suggested by several studies performed in induced or spontaneous hyperinsulinemia. The increased insulin resistance documented throughout aging, with its accompanying hyperinsulinemia, may contribute to the age-related decline in DHEA synthesis. The aim of this study was to assess if the aging-related differences in DHEA sulfate (DHEA-S) serum levels can be associated with differences in fasting insulin levels, as well as body composition. Two hundred fifty-two healthy subjects of both sexes aged 19 to 90 years with a body mass index (BMI) less than 30 (mean +/- SD, 23.5 +/- 2.4) were studied DHEA-S and insulin serum levels were determined by a radioimmunologic procedure; body composition was assessed by anthropometry (fat mass percentage [FM%] estimated from four skinfold thicknesses by Durnin and Womersley and Siri equations [FM%-SKF]) and by bioimpedance analysis (BIA) (FM% estimated by equations developed by Segal et al and Deurenberg et al for subjects < and > 62 years, respectively [FM%-BIA]). DHEA-S levels were significantly and inversely related to age in both sexes. No significant aging-related differences were found in fasting insulin levels, although a trend toward an increase was apparent in the women on simple regression analysis. No significant associations were found between DHEA-S and insulin levels. As for body composition, a positive relationship to age was apparent for FM%-SKF, FM%-BIA, and waist to hip ratio (WHR), whereas BMI and phase angle ([PA] a bioelectric parameter considered an index of the ratio between intracellular and extracellular water) were inversely related to age. Fasting insulin levels were positively related to FM% as estimated by both BIA and anthropometry, independently of age in both sexes; in addition, a positive correlation with WHR and with the subscapular to triceps skinfold thickness ratio (SS/TS) was found in men and women, respectively. No significant correlation was apparent between DHEA-S and body composition indices in men, whereas in women a slight negative correlation between DHEA-S and WHR was documented, and was still significant after adjustment for age and fasting insulin. Stepwise multiple regression analysis confirmed that DHEA-S levels are not related to fasting insulin, but are independently related to age and, in women only, to WHR. Our study suggests that the DHEA-S decline due to aging is independent of fasting insulin, at least in healthy, non-obese people. In addition, it is not related to the aging-dependent changes in body composition in terms of FM% and fat-free mass (FFM) percentage (FFM%). Only in women could changes in fat distribution be slightly associated with DHEA-S decline, although such a relation cannot be accounted for by changes in insulin levels.
多项针对诱导性或自发性高胰岛素血症开展的研究表明，胰岛素可抑制人体中脱氢表雄酮（DHEA）的生物合成。在整个衰老过程中出现的胰岛素抵抗增加及其伴随的高胰岛素血症，可能导致与年龄相关的DHEA合成下降。本研究的目的是评估硫酸脱氢表雄酮（DHEA-S）血清水平与衰老相关的差异是否与空腹胰岛素水平以及身体成分的差异有关。对252名年龄在19至90岁之间、体重指数（BMI）小于30（均值±标准差，23.5±2.4）的健康男女受试者进行了研究。通过放射免疫法测定DHEA-S和胰岛素血清水平；通过人体测量法（根据Durnin和Womersley以及Siri公式，由四处皮褶厚度估算脂肪量百分比[FM%] [FM%-SKF]）和生物电阻抗分析（BIA）（分别根据Segal等人和Deurenberg等人针对年龄＜和＞62岁受试者制定的公式估算FM% [FM%-BIA]）评估身体成分。男女两性的DHEA-S水平均与年龄呈显著负相关。空腹胰岛素水平未发现与衰老相关的显著差异，不过在简单回归分析中，女性有升高的趋势。未发现DHEA-S与胰岛素水平之间存在显著关联。至于身体成分，FM%-SKF、FM%-BIA以及腰臀比（WHR）与年龄呈正相关，而BMI和相位角（[PA]，一种生物电参数，被视为细胞内与细胞外水比例的指标）与年龄呈负相关。空腹胰岛素水平与通过BIA和人体测量法估算的FM%呈正相关，且在男女两性中均与年龄无关；此外，男性和女性的空腹胰岛素水平分别与WHR以及肩胛下与肱三头肌皮褶厚度之比（SS/TS）呈正相关。男性中DHEA-S与身体成分指标之间未发现显著相关性，而在女性中，记录到DHEA-S与WHR之间存在轻微负相关，在对年龄和空腹胰岛素进行校正后仍具有显著性。逐步多元回归分析证实，DHEA-S水平与空腹胰岛素无关，但与年龄独立相关，且仅在女性中与WHR相关。我们的研究表明，至少在健康、非肥胖人群中，衰老导致的DHEA-S下降与空腹胰岛素无关。此外，就FM%和去脂体重（FFM）百分比（FFM%）而言，它与身体成分随年龄的变化无关。仅在女性中，脂肪分布的变化可能与DHEA-S下降略有关联，尽管这种关系无法通过胰岛素水平的变化来解释。
