Intraduodenal Guar Attenuates the Fall in Blood Pressure Induced by Glucose in Healthy Older Adults

Abstract

In healthy older participants, the magnitude of the fall in systolic blood pressure and increase in heart rate induced by intraduodenal glucose are attenuated when the exposure of glucose to the small intestinal mucosa and subsequent glucose absorption is slowed by guar.

Role of 5-hydroxytryptamine mechanisms in mediating the effects of small intestinal glucose on blood pressure and antropyloroduodenal motility in older subjects

“…The dose of granisetron (i.e., 10 g/kg iv) employed was comparable with that given in previous studies (2,22,28) and is the recommended dose for clinical use (2). Enteral glucose induced a gradual fall in systolic and diastolic blood pressure and a rapid increase in heart rate, all of which were comparable with those observed previously (9,31,32). Furthermore, in accordance with previous studies, on the control day, there was a transient increase in duodenal motility within the first 15 min of the commencement of the glucose infusion (42) as well as reductions in the number of antral, and proximal, duodenal, PWs and an increase in the frequency of IPPWs (13).…”

“…The onset of the fall in blood pressure after a meal is almost immediate, with a maximum response at 30 -60 min (16), suggesting a direct relationship between the magnitude of the hypotensive response and the rate of delivery of carbohydrate to the small intestine. This is the case in both healthy older subjects (18,32) and patients with type 2 diabetes (19,36) and has been established by a series of studies by our group. For example, in healthy older subjects when glucose is administered intraduodenally at a rate of 1 kcal/min or 3 kcal/min, the fall in blood pressure and increase in heart rate are substantially greater during the 3 kcal/min infusion (31).…”

“…Using oral glucose loads (18,19,36) and intraduodenal glucose infusions (9,31,32), we have established a relationship between the magnitude of the postprandial fall in blood pressure and rise in heart rate with the rate of nutrient delivery from the stomach to the small intestine in healthy older subjects; these effects were evident within 60 min of ingestion and infusion of glucose. The latter studies excluded the potential effects of gastric emptying/distension on blood pressure; hence, in the current study, we infused glucose directly into the small intestine for a period of 60 min and at a rate (i.e., 3 kcal/min) that has been shown to decrease blood pressure in healthy older subjects (31) and approximates the normal rate of gastric emptying (14).…”

“…There is evidence that 5-HT mechanisms play a role in the regulation of splanchnic blood flow (32,44). For example, in the dog, both low-(4 g⅐kg Ϫ1 ⅐min Ϫ1 ) and higher-(10 g ⅐kg Ϫ1 ⅐min Ϫ1 ) dose 5-HT infusions increase gastrointestinal blood flow (44).…”

Effects of exogenous glucagon-like peptide-1 on blood pressure, heart rate, gastric emptying, mesenteric blood flow and glycaemic responses to oral glucose in older individuals with normal glucose tolerance or type 2 diabetes

“…The magnitude of the effect of GLP-1 on BP was substantial (~10 mmHg difference) and may relate to the slowing of GE, but other mechanisms are likely to be important, particularly as GLP-1 reduces the hypotensive response to intraduodenal glucose [22]. In healthy older individuals, orally [36] and intraduodenally administered [37] guar reduces the hypotensive response to glucose administered via the same routes, and the α-glucosidase inhibitor acarbose has comparable effects on the response to orally [24] and intraduodenally administered [38] sucrose. These observations suggest that the slowing of nutrient absorption from the small intestine is a critical factor.…”