van Asselt D Z, van den Broek W J, Lamers C B, Corstens F H, Hoefnagels W H
Department of Geriatric Medicine, University Hospital Nijmegen, The Netherlands.
J Am Geriatr Soc. 1996 Aug;44(8):949-53. doi: 10.1111/j.1532-5415.1996.tb01866.x.
To study free- and protein-bound cobalamin absorption and the correlation with atrophic gastritis in healthy middle-aged and older subjects.
A cross-sectional study.
Fifty-two healthy subjects, aged 26 to 87 years, apparently free from conditions known to influence the cobalamin status. Middle-aged subjects were defined as those younger than 65 years of age (median age 57 years) and older subjects as those 65 years and older (median age 75 years).
Protein-bound cobalamin absorption was assessed by 48-hour urinary excretion method following oral administration of scrambled egg yolk, labeled in vivo with 57 Co-cobalamin by injecting a hen with 57 Co-cyanocobalamin. The percentage of 57 Co-cobalamin bound to protein was 65%. Free cobalamin absorption was assessed by 48-hour urinary excretion method following oral administration of crystalline 57 Co-cyanocobalamin. Plasma cobalamin, folate and fasting plasma gastrin, and pepsinogen A and C concentrations were determined.
The median urinary excretion of egg yolk 57 Co-cobalamin in middle-aged subjects was 12.3% (25th and 75th percentiles 10.5%-14.5%) compared with 11.7% (25th and 75th percentiles 9.8%-13.6%) in older subjects (P = .283). The median urinary excretion after administration of free 57 Co-cobalamin in middle-aged subjects was 25.7% (25th and 75th percentiles 20.6%-30.7%) compared with 27.9% (25th and 75th percentiles 21.4%-34.5%) in older subjects (P = .694). Neither egg yolk nor free 57 Co-cobalamin excretion correlated with age. A ratio of pepsinogen A to pepsinogen C less than 1.6, indicating atrophic gastritis, was found in 13 subjects. Within the atrophic gastritis group, 11 subjects had a pepsinogen A concentration greater than or equal to 17 micrograms/L, indicating mild to moderate atrophic gastritis, and two subjects had a pepsinogen A concentration less than 17 micrograms/L, indicating severe atrophic gastritis or gastric atrophy. All subjects had normal fasting plasma gastrin concentrations. Free and egg yolk 57 Co-cobalamin excretions were not reduced in the atrophic gastritis group when compared with the non-atrophic gastritis group. Median plasma cobalamin concentration was not significantly lower in older subjects (P = .205). Nonetheless, plasma cobalamin concentration correlated negatively with age (r = -.36; P = .008).
We demonstrated no significant difference in either free or protein-bound cobalamin absorption between healthy middle-aged and older adults. In addition, no alteration in cobalamin absorption was found in subjects identified as having mild to moderate atrophic gastritis. Therefore, based on our results, the high prevalence of low cobalamin levels in older people cannot be explained by either the aging process or mild to moderate atrophic gastritis.
研究健康中老年受试者中游离及蛋白结合钴胺素的吸收情况及其与萎缩性胃炎的相关性。
横断面研究。
52名健康受试者，年龄在26至87岁之间，显然未患已知会影响钴胺素状态的疾病。中年受试者定义为年龄小于65岁（中位年龄57岁），老年受试者定义为年龄65岁及以上（中位年龄75岁）。
通过口服经57钴 - 钴胺素体内标记的炒蛋黄后48小时尿排泄法评估蛋白结合钴胺素的吸收情况，标记方法是给母鸡注射57钴 - 氰钴胺素。与蛋白结合的57钴 - 钴胺素的百分比为65%。通过口服结晶57钴 - 氰钴胺素后48小时尿排泄法评估游离钴胺素的吸收情况。测定血浆钴胺素、叶酸、空腹血浆胃泌素以及胃蛋白酶原A和C的浓度。
中年受试者中蛋黄57钴 - 钴胺素的尿排泄中位数为12.3%（第25和第75百分位数为10.5% - 14.5%），老年受试者为11.7%（第25和第75百分位数为9.8% - 13.6%）（P = 0.283）。中年受试者口服游离57钴 - 钴胺素后的尿排泄中位数为25.7%（第25和第75百分位数为20.6% - 30.7%），老年受试者为27.9%（第25和第75百分位数为21.4% - 34.5%）（P = 0.694）。蛋黄和游离57钴 - 钴胺素的排泄均与年龄无关。13名受试者胃蛋白酶原A与胃蛋白酶原C的比值小于1.6，提示存在萎缩性胃炎。在萎缩性胃炎组中，11名受试者的胃蛋白酶原A浓度大于或等于17微克/升，提示轻度至中度萎缩性胃炎，两名受试者的胃蛋白酶原A浓度小于17微克/升，提示重度萎缩性胃炎或胃萎缩。所有受试者的空腹血浆胃泌素浓度均正常。与非萎缩性胃炎组相比，萎缩性胃炎组中游离及蛋黄57钴 - 钴胺素的排泄未减少。老年受试者的血浆钴胺素中位数浓度无显著降低（P = 0.205）。尽管如此，血浆钴胺素浓度与年龄呈负相关（r = -0.36；P = 0.008）。
我们证明健康中年和老年成年人在游离或蛋白结合钴胺素吸收方面无显著差异。此外，在被确定为患有轻度至中度萎缩性胃炎的受试者中未发现钴胺素吸收改变。因此，基于我们的研究结果，老年人中钴胺素水平低的高患病率不能用衰老过程或轻度至中度萎缩性胃炎来解释。
