Comparative effects of glucose and water drinks on blood pressure and cardiac function in older subjects with and without postprandial hypotension

Interoceptive accuracy moderates the response to a glucose load: a test of the predictive coding framework

Recently, interoception and homeostasis have been described in terms of predictive coding and active inference. Afferent signals update prior predictions about the state of the body, and stimulate the autonomic mediation of homeostasis. Performance on tests of interoceptive accuracy (IAc) may indicate an individual's ability to assign precision to interoceptive signals, thus determining the relative influence of ascending signals and the descending prior predictions. Accordingly, individuals with high IAc should be better able to regulate during the postprandial period. One hundred females were allocated to consume glucose, an artificially sweetened drink, water or no drink. Before, and 30 min after a drink, IAc, heart rate (HR) and blood glucose (BG) were measured, and participants rated their hunger, thirst and mood. A higher IAc was related to lower BG levels, a decline in anxiety and a higher HR, after consuming glucose. A higher IAc also resulted in a larger decline in hunger if they consumed either glucose or sucralose. These data support the role of active inference in interoception and homeostasis, and suggest that the ability to attend to interoceptive signals may be critical to the maintenance of physical and emotional health.

Hemodynamic Response to Glucose-Insulin Infusion and Meals during Hemodialysis

Introduction: Intradialytic nutrition may improve nutritional status and reduce mortality in patients on maintenance hemodialysis (HD) but has been associated with adverse events, mainly hemodynamic instability. Some dialysis centers therefore restrict intradialytic meals. In 2 clinical studies, we investigated the effects of intradialytic glucose-insulin infusion (GII) and meal intake on blood pressure (BP), pulse wave velocity (PWV), pulse wave analysis (PWA), and cardiac output (CO). PWA yielded augmentation index standardized with heart rate 75 (AIx@HR75). Methods: In the GII study, 12 nondiabetic HD patients had BP, PWV, PWA, and CO measured during 3 HD sessions: standard HD, HD with glucose infusion, and HD with GII. In the Meal study, 12 nondiabetic patients had BP and PWA measured on 3 study days: meal alone (non-HD), meal and HD, 2 meals and HD. Twelve matched healthy controls completed the non-HD day. Findings: In the GII study, glucose or GII had no additional effects on hemodynamic parameters compared with standard HD. HD resulted in a decrease in systolic BP of 13%, in diastolic BP of 9%, in AIx@HR75 of 17%, and CO of 18%. PWV was reduced by only 5%. In the Meal study, a meal alone did not change BP, whereas the combined influence of HD and meal intake reduced systolic BP with 22% and diastolic BP with 19%. Furthermore, AIx@HR75 decreased by 37% on HD days and by 36% in controls, but was unaffected on non-HD days. Discussion: In the GII study, HD significantly reduced BP, AIx@75, and CO, whereas PWV remained almost constant. No additional effects were observed by concomitant GII during HD. BP reductions seemed larger in the Meal study compared with the GII study. Taken together, HD per se appears as the main discriminant for intradialytic hypotension but in hemodynamically unstable patients the timing and route of nutrition provision should be considered carefully.

Acute Effects of Nutritive and Non-Nutritive Sweeteners on Postprandial Blood Pressure

Postprandial hypotension (PPH) is under-recognised, but common, particularly in the elderly, and is of clear clinical importance due to both the independent association between PPH and an increase in mortality and lack of effective management for this condition. Following health concerns surrounding excessive consumption of sugar, there has been a trend in the use of low- or non-nutritive sweeteners as an alternative. Due to the lack of literature in this area, we conducted a systematic search to identify studies relevant to the effects of different types of sweeteners on postprandial blood pressure (BP). The BP response to ingestion of sweeteners is generally unaffected in healthy young subjects, however in elderly subjects, glucose induces the greatest decrease in postprandial BP, while the response to sucrose is less pronounced. The limited studies investigating other nutritive and non-nutritive sweeteners have demonstrated minimal or no effect on postprandial BP. Dietary modification by replacing high nutritive sweeteners (glucose, fructose, and sucrose) with low nutritive (d-xylose, xylitol, erythritol, maltose, maltodextrin, and tagatose) and non-nutritive sweeteners may be a simple and effective management strategy for PPH.

Comparative effects of glucose and water drinks on blood pressure and cardiac function in older subjects with and without postprandial hypotension

Postprandial hypotension (PPH) occurs frequently and is thought to reflect an inadequate increase in cardiac output to compensate for the rise in splanchnic blood flow after a meal. Gastric distension by water attenuates the postprandial fall in blood pressure (BP). Cardiac hemodynamics (stroke volume (SV), cardiac output (CO), and global longitudinal strain (GLS)) have hitherto not been measured in PPH We sought to determine the comparative effects of water and glucose drinks on cardiac hemodynamics in healthy older subjects and individuals with PPH Eight healthy older subjects (age 71.0 ± 1.7 years) and eight subjects with PPH (age 75.5 ± 1.0 years) consumed a 300 mL drink of either water or 75 g glucose (including 150 mg ¹³C-acetate) in randomized order. BP and heart rate (HR) were measured using an automatic device, SV, CO, and GLS by transthoracic echocardiography and gastric emptying by measurement of ¹³CO₂ In both groups, glucose decreased systolic BP (P < 0.001) and increased HR, SV, and CO (P < 0.05 for all). The fall in systolic BP was greater (P < 0.05), and increase in HR less (P < 0.05), in the PPH group, with no difference in SV or CO Water increased systolic BP (P < 0.05) in subjects with PPH and, in both groups, decreased HR (P < 0.05) without affecting SV, CO, or GLS In subjects with PPH, the hypotensive response to glucose and the pressor response to water were related (R = -0.75, P < 0.05). These observations indicate that, in PPH, the hypotensive response to oral glucose is associated with inadequate compensatory increases in CO and HR, whereas the pressor response to water ingestion is maintained and, possibly, exaggerated.