GLUCOSE TRANSPORT REGULATION IN SMALL INTESTINE

小肠中的葡萄糖转运调节

• 批准号: 6116606
• 负责人: DAVID B RHOADS
• 金额: $ 6.7万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6116606
• 关键词: Mammalia; Primates; carbohydrates; diabetes mellitus; pancreas

Intestinal expression of the high-affinity Na+/glucose cotransporter (SGLT1), which is responsible for the absorption of dietary glucose and galactose, exhibits both circadian periodicity in its activity and induction by dietary carbohydrate. Because the daily variation in SGLT1 activity is established by the feeding schedule (whether ad libitum or imposed) and persists in the absence of food, this variation has been described as anticipatory. We provide evidence indicating a genetic basis for this anticipatory rhythm. The normal daily periodicity in SGLT1 expression has been examined in rats maintained in a 12-h photoperiod and allowed free access to chow. SGLT1 mRNA levels varied up to 10-fold, with the maximum abundance occurring near the beginning of the dark phase of the photoperiod and the minimum near the onset of light. SGLT1 transcription also changes, with the rate estimated densitometrically (relative to -tubulin) 6.4 q 1.0 times greater between 1000 h and 1100 h than between 1600 h and 1700 h (n=4; p<.007, 2-tailed t-Test). We cloned the rat SGLT1 proximal promoter region and identified an element for hepatocyte nuclear factor 1 (HNF-1) conserved between rat and human. A probe generated from this element formed different complexes with small intestinal nuclear extracts, depending on when the source animal was killed. Serological tests indicated that HNF-1a was present in all complexes, while HNF-1b was present at 1600 h and 2200 h but not at 0400 h or 1000 h. We propose that exchange of HNF-1 dimerization partners contributes to circadian changes in SGLT1 transcription. This expanded role for HNF-1 implicates this homeoprotein in temporal pattern formation in addition to its canonical role in spatial pattern formation. because we have also observed differential SGLT1 mRNA levels in rhesus monkeys (off-set by approximately one-half day from rats), we suggest that a similar mechanism is present in primates. This study has been accepted for publication by the Journal of Biological Chemistry. An RO1 grant is pending to extend these studies (NIDDK).

肠道表达的高亲和力Na+/葡萄糖协同转运蛋白（SGLT 1），这是负责膳食葡萄糖和半乳糖的吸收，表现出昼夜节律的周期性，其活动和诱导膳食碳水化合物。 由于SGLT 1活性的每日变化是由喂食时间表（无论是随意还是强制）确定的，并且在不进食的情况下持续存在，因此该变化被描述为预期性的。 我们提供的证据表明这种预期节奏的遗传基础。 在保持12小时光周期并允许自由进食的大鼠中检查了SGLT 1表达的正常每日周期性。 SGLT 1 mRNA水平变化高达10倍，最大丰度出现在光周期暗期开始附近，最小丰度出现在光开始附近。 SGLT 1转录也发生变化，1000 h至1100 h之间的速率（相对于微管蛋白）密度估计值为6.4 q，是1600 h至1700 h之间的1.0倍（n=4; p<.007，双尾t检验）。我们克隆了大鼠SGLT 1近端启动子区，并确定了大鼠和人之间保守的肝细胞核因子1（HNF-1）的元件。 由这种元素产生的探针与小肠核提取物形成不同的复合物，这取决于源动物被杀死的时间。 血清学试验表明，HNF-1a在所有复合物中均有表达，HNF-1b在1600 h和2200 h有表达，而在0400 h和1000 h无表达。我们认为HNF-1二聚化伴侣的交换有助于SGLT 1转录的昼夜变化。 HNF-1的这种扩大的作用暗示了这种同源异型蛋白除了在空间模式形成中的典型作用外，还在时间模式形成中起作用。 由于我们也在恒河猴中观察到了不同的SGLT 1 mRNA水平（与大鼠相差约半天），因此我们认为灵长类动物中存在类似的机制。 这项研究已被生物化学杂志接受发表。 正在等待一笔RO 1赠款，以延长这些研究（NIDDK）。