Kim Y I, Fawaz K, Knox T, Lee Y M, Norton R, Arora S, Paiva L, Mason J B
Department of Medicine, St Michael's Hospital, and the University of Toronto, Ontario, Canada.
Am J Clin Nutr. 1998 Oct;68(4):866-72. doi: 10.1093/ajcn/68.4.866.
Estimates of habitual dietary folate intake are known to be imprecisely correlated with systemic measures of folate status. Furthermore, measurements of blood folate concentrations may not accurately reflect the concentration of folate in tissues of interest. This issue is important for assessing folate status in the colorectal mucosa because low dietary intake or blood concentrations of folate are associated with an increased risk of colorectal neoplasia.
We examined whether conventional measures of folate in blood and a more sensitive, inverse indicator of systemic folate status, serum homocysteine, accurately reflected folate concentrations in human colonic mucosa obtained by endoscopic biopsy.
In 30 persons with colorectal polyps, blood samples were taken and biopsies of normal rectosigmoid mucosa performed at the time of colonoscopic polypectomy. Serum, red blood cell, and colonic mucosal folate and serum homocysteine concentrations were measured.
Serum and red blood cell folate and serum homocysteine concentrations accurately reflected colonic mucosal folate concentrations; among these, serum homocysteine correlated best with mucosal concentrations. Folate concentrations in the normal rectosigmoid mucosa were significantly lower in persons with adenomatous polyps than in those with hyperplastic polyps (P=0.04). Conventional measures of systemic folate status were not significantly lower in those with adenomas, although serum homocysteine was mildly elevated (P=0.04).
Our data underscore the ability of systemic measures of folate status, particularly serum homocysteine, to reflect folate concentrations in the colonic mucosa. Nevertheless, future studies that examine the ability of folate to modulate colorectal carcinogenesis may benefit from direct measurement of folate in the colon.
已知习惯性膳食叶酸摄入量的估计值与叶酸状态的系统测量值之间的相关性并不精确。此外，血液叶酸浓度的测量可能无法准确反映目标组织中叶酸的浓度。这个问题对于评估结直肠黏膜中的叶酸状态很重要，因为低膳食叶酸摄入量或血液叶酸浓度与结直肠癌发生风险增加有关。
我们研究了血液中常规叶酸测量指标以及一种更敏感的系统性叶酸状态反向指标——血清同型半胱氨酸，是否能准确反映通过内镜活检获得的人结肠黏膜中的叶酸浓度。
在30例患有结肠息肉的患者中，在结肠镜下息肉切除时采集血样并对正常乙状结肠直肠黏膜进行活检。测量血清、红细胞和结肠黏膜中的叶酸以及血清同型半胱氨酸浓度。
血清和红细胞叶酸以及血清同型半胱氨酸浓度准确反映了结肠黏膜叶酸浓度；其中，血清同型半胱氨酸与黏膜浓度的相关性最佳。腺瘤性息肉患者正常乙状结肠直肠黏膜中的叶酸浓度显著低于增生性息肉患者（P = 0.04）。尽管血清同型半胱氨酸轻度升高（P = 0.04），但腺瘤患者的系统性叶酸状态常规测量指标并无显著降低。
我们的数据强调了系统性叶酸状态测量指标，特别是血清同型半胱氨酸，反映结肠黏膜中叶酸浓度的能力。然而，未来研究叶酸调节结直肠癌发生能力时，直接测量结肠中的叶酸可能会有所帮助。
