Mahmood S, Dani H M, Mahmood A
Am J Clin Nutr. 1984 Aug;40(2):226-34. doi: 10.1093/ajcn/40.2.226.
The effect of dietary thiamin deficiency has been studied on intestinal functions and chemical composition of brush border membranes in rats. Intestinal uptake of glucose, glycine, alanine, and leucine was significantly stimulated in thiamin deficiency compared to pair-fed control group. Studies with glucose and glycine revealed that stimulation of the absorption process occurs only in the presence of Na+ but not in its absence. Km measured in the presence of 140 mM Na+ for glucose and glycine uptakes was reduced by 56 and 41%, respectively, but Vmax remained unaltered in vitamin deficiency. There was no change in these parameters in Na+-free medium (Km = 31.3 and 23.3 mM; Vmax = 17.2 to 19.7 and 13.5 to 16.4 mumol/10 min/g wet tissue, respectively) under these conditions. The activities of brush border sucrase, lactase, maltase, alkaline phosphatase, and leucine aminopeptidase were reduced by 42 to 66% in thiamin deficiency, compared to pair-fed controls. Kinetic studies with sucrase and alkaline phosphatase evinced that a decrease in Vmax (61 and 64%, respectively) with no change in Km (33.8 and 4.3 mM, respectively) was responsible for observed impairment in the enzyme activities in thiamin deficiency. Microvillus membrane proteins expressed on dry membrane basis were reduced by 20% in thiamin-deficient intestine. There was no difference in membrane sialic acid, cholesterol, phospholipids, and triglycerides fractions under these conditions. It is suggested that thinning of the microvillus membrane may be implicated in observed aberrations of intestinal functions in thiamin-deprived animals.
研究了饮食中硫胺素缺乏对大鼠肠道功能和刷状缘膜化学成分的影响。与配对喂养的对照组相比，硫胺素缺乏组大鼠肠道对葡萄糖、甘氨酸、丙氨酸和亮氨酸的摄取显著增加。对葡萄糖和甘氨酸的研究表明，吸收过程的刺激仅在有Na+存在时发生，而在无Na+时则不发生。在140 mM Na+存在下测量的葡萄糖和甘氨酸摄取的Km分别降低了56%和41%，但在维生素缺乏时Vmax保持不变。在这些条件下，在无Na+培养基中这些参数没有变化（葡萄糖和甘氨酸的Km分别为31.3和23.3 mM；Vmax分别为17.2至19.7和13.5至16.4 μmol/10 min/g湿组织）。与配对喂养的对照组相比，硫胺素缺乏组刷状缘蔗糖酶、乳糖酶、麦芽糖酶、碱性磷酸酶和亮氨酸氨肽酶的活性降低了42%至66%。对蔗糖酶和碱性磷酸酶的动力学研究表明，Vmax分别降低了61%和64%，而Km分别为33.8和4.3 mM不变，这是硫胺素缺乏时观察到的酶活性受损的原因。硫胺素缺乏的肠道中以干膜为基础表达的微绒毛膜蛋白减少了20%。在这些条件下，膜唾液酸、胆固醇、磷脂和甘油三酯组分没有差异。有人认为，微绒毛膜变薄可能与硫胺素缺乏动物中观察到的肠道功能异常有关。
