EFFECTS OF LENGTH AND REGION OF SMALL INTESTINAL GLUCOSE EXPOSURE ON BLOOD PRESSURE, SUPERIOR MESENTERIC ARTERY BLOOD FLOW AND PLASMA NORADRENALINE IN HEALTHY OLDER PARTICIPANTS

Background: A substantial postprandial reduction in blood pressure (BP), triggered by the interaction of nutrients with the small intestine and associated with increases in heart rate (HR) and splanchnic blood flow, occurs frequently in healthy older people. Objective: The aim of this study was to determine whether these responses are influenced by the length and/or region of small intestine exposed to nutrients. Design: Randomized, single blind study. Setting: Clinical research laboratory. Participants: Ten healthy older participants (9M, 1F; age 65 – 79 yr). Intervention: On 3 separate study days, participants were intubated with a small intestinal catheter incorporating two duodenal infusion ports and an aspiration port, as well as an occluding balloon, which was positioned ~ 60 cm beyond the pylorus. Each participant then received a 60 min (t = 0 – 60 min) intraluminal infusion of glucose (3 kcal/min) into either the proximal (< 60 cm “GP”), or the distal (> 70 cm “GD”), or both (i.e. proximal and distal “GPD”), small intestinal segments. Measurements: BP, HR (automated device), superior mesenteric artery (SMA) blood flow (Doppler ultrasound) and plasma noradrenaline (NA). Results: Small intestinal glucose infusion was associated with reductions in systolic (GP: P = 0.004, GD: P = 0.001, GPD: P = 0.001) and diastolic (GP: P = 0.007, GD: P = 0.004, GPD: P = 0.003) BP and increases in HR (GP: P = 0.001, GD: P = 0.001, GPD: P = 0.002) and plasma NA (GP: P = 0.001, GD: P = 0.002, GPD: P = 0.001), without any difference between the three days. Conclusion: In healthy older participants, the effects of small intestinal glucose to decrease BP and increase SMA flow in healthy older participants appear to be independent of the region, or length, of small intestine exposed.

Timing of postexercise carbohydrate-protein supplementation: roles of gastrointestinal blood flow and mucosal cell damage on gastric emptying in humans

It is well known that protein ingestion immediately after exercise greatly stimulates muscle protein synthesis during the postexercise recovery phase. However, immediately after strenuous exercise, the gastrointestinal (GI) mucosa is frequently injured by hypoperfusion in the organ/tissue, possibly resulting in impaired GI function (e.g., gastric emptying; GE). The aim of this study was to examine the effect of GI blood flow on the GE rate. Eight healthy young subjects performed an intermittent supramaximal cycling exercise for 30 min, which consisted of a 120% V̇o2peak for 20 s, followed by 20 W for 40 s. The subjects ingested 300 ml of a nutrient drink containing carbohydrate-protein at either 5 min postexercise in one trial (PE-5) or 30 min postexercise in another trial (PE-30). In the control trial (Con), the subjects ingested the same drink without exercise. The celiac artery blood flow (CABF) and superior mesenteric artery blood flow (SMABF) and GE rate were assessed by ultrasonography. Before drink ingestion in PE-5, CABF significantly decreased from baseline, whereas in PE-30, it returned to baseline. Following drink ingestion in PE-5, CABF did not change from baseline, but it significantly increased in PE-30 and Con. SMABF increased significantly later in PE-5 than in PE-30 and Con. The GE rate was consistently slower in PE-5 than in PE-30 and Con. In conclusion, the CABF response after exercise seems to modulate the subsequent GE rate and SMABF response. NEW & NOTEWORTHY A carbohydrate-protein drink was ingested at either 5 min (i.e., profoundly decreased celiac artery blood flow; CABF) or 30 min (i.e., already recovered CABF) postexercise. In the 5-min postexercise trial, the gastric emptying (GE) rate and superior mesenteric artery blood flow (SMABF) response were slower than those in the 30-min postexercise trial. The GE rate and SMABF response may be altered depending on the postexercise CABF response.