Pathophysiology of postprandial hypotension in the elderly - role of "gastric" and "small intestinal" mechanisms

餐后血压下降(称为餐后低血压)是一个重要的临床问题，特别是在老年人中，约50%的养老院居民和约30%的健康老年人会发生这种问题。餐后低血压与跌倒、中风以及死亡率的大幅增加有关。导致餐后血压下降的机制还不是很清楚，尽管胃肠道血流和胃肠激素释放的变化已经牵涉其中。虽然摄入碳水化合物，特别是葡萄糖，已被报道最有效地降低血压，但关于脂肪和蛋白质等其他营养物质的影响，信息不充分和相互矛盾。目前的治疗方法并不理想。我们研究小组的研究表明，进餐后血压的下降与营养物质进入小肠的速度有关，即当胃排空得更快时，血压下降得更快。相比之下，胃扩张可以降低血压的下降。因此，治疗可以针对促进胃扩张和-或减缓营养物质输送到小肠的速度。我们之前的研究没有对餐后肠道血流的变化或胃扩张和小肠机制之间的相互作用进行任何评估，并涉及健康的老年受试者和2型(非胰岛素依赖型)糖尿病患者，而不是已知的餐后低血压患者。我们现在有能力用超声波测量肠道内的血流量。目前申请中提出的研究代表了我们先前工作的合乎逻辑的发展，并对餐后低血压的管理具有重要意义。

A fall in blood pressure after a meal (known as postprandial hypotension) is an important clinical problem, particularly in the elderly, occurring in ~50% of nursing home residents and ~30% of healthy older subjects. Postprandial hypotension is associated with a substantial increase in the incidence of falls, stroke, as well as mortality. The mechanisms responsible for the fall in blood pressure after a meal are not well understood, although changes in gastrointestinal blood flow and the release of gut hormones, have been implicated. While ingestion of carbohydrate, particularly glucose, has been reported to decrease blood pressure most potently, there is inadequate and conflicting information about the effects of other nutrients such as fat and protein. Current therapies are less than optimal. Studies by our research group have established that the fall in blood pressure in response to meals is related to the rate at which nutrients enter the small intestine ie the fall in blood pressure is greater when the stomach empties more quickly. In contrast, gastric distension reduces the fall in blood pressure. Hence, treatment could be directed at facilitating gastric distension and-or slowing the rate of nutrient delivery into the small intestine. Our previous studies have not included any assessment of changes in blood flow to the gut after meals, or of the interaction between gastric distension and small intestinal mechanisms, and have involved healthy older subjects and patients with type 2 (non-insulin dependent) diabetes rather than individuals with known postprandial hypotension. We now have the capacity to measure blood flow in the gut with ultrasound. The studies proposed in the current application represent a logical development from our previous work and have important implications for the management of postprandial hypotension.