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The true prevalence, however, remains uncertain because of a lack of population-based studies and inconsistent criteria to define gastroparesis, including variations in the technique used to quantify gastric emptying (where scintigraphy remains the gold standard method and stable isotope breath tests and ultrasonography represent acceptable alternatives), the desirable blood glucose levels during the emptying measurement, the magnitude of the delay in gastric emptying regarded as abnormal, and whether the presence of gastrointestinal symptoms represents a prerequisite for the diagnosis. [...]in an individual type 2 diabetic patient, the impact of a GLP-1 agonist on postprandial glycemia is likely to be dependent on both the baseline rate of emptying and the choice of GLP-1 agonist.

It is now widely appreciated that gastrointestinal function is central to the regulation of metabolic homeostasis. Following meal ingestion, the delivery of nutrients from the stomach into the small intestine (i.e., gastric emptying) is tightly controlled to optimise their subsequent digestion and absorption. The complex interaction of intraluminal nutrients (and other bioactive compounds, such as bile acids) with the small and large intestine induces the release of an array of gastrointestinal hormones from specialised enteroendocrine cells (EECs) distributed in various regions of the gut, which in turn to regulate gastric emptying, appetite and postprandial glucose metabolism. Stimulation of gastrointestinal hormone secretion, therefore, represents a promising strategy for the management of metabolic disorders, particularly obesity and type 2 diabetes mellitus (T2DM). That EECs are distributed distinctively between the proximal and distal gut suggests that the region of the gut exposed to intraluminal stimuli is of major relevance to the secretion profile of gastrointestinal hormones and associated metabolic responses. This review discusses the process of intestinal digestion and absorption and their impacts on the release of gastrointestinal hormones and the regulation of postprandial metabolism, with an emphasis on the differences between the proximal and distal gut, and implications for the management of obesity and T2DM.

OBJECTIVE: We evaluated whether a whey preload could slow gastric emptying, stimulate incretin hormones, and attenuate postprandial glycemia in type 2 diabetes. RESEARCH DESIGN AND METHODS: Eight type 2 diabetic patients ingested 350 ml beef soup 30 min before a potato meal; 55 g whey was added to either the soup (whey preload) or potato (whey in meal) or no whey was given. RESULTS: Gastric emptying was slowest after the whey preload (P < 0.0005). The incremental area under the blood glucose curve was less after the whey preload and whey in meal than after no whey (P < 0.005). Plasma glucose-dependent insulinotropic polypeptide, insulin, and cholecystokinin concentrations were higher on both whey days than after no whey, whereas glucagon-like peptide 1 was greatest after the whey preload (P < 0.05). CONCLUSIONS: Whey protein consumed before a carbohydrate meal can stimulate insulin and incretin hormone secretion and slow gastric emptying, leading to marked reduction in postprandial glycemia in type 2 diabetes.

It is not known whether glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) levels correlate within individuals, nor whether levels change with age. Previous studies have all been cross-sectional in design. To evaluate longitudinal changes in fasting and glucose-stimulated incretin hormone concentrations in healthy older subjects. Forty-one healthy older subjects had measurements of plasma GLP-1 and GIP while fasting and after a 75-g oral glucose load on two occasions separated by 5.9 ± 0.1 years [mean age at the initial study: 71.2 ± 3.8 (SD) years]. Breath samples were collected to calculate the gastric 50% emptying time (T50). For GLP-1, both fasting concentrations (P < 0.001) and area under the curve 0 to 120 minutes (P = 0.001) were decreased at followup. Fasting GIP was also lower (P = 0.03) at follow up, but there was no change in the area under the curve 0 to 120 minutes (P = 0.26). The gastric emptying T50 was slower at followup (P = 0.008). Neither the change in T50 nor the body mass index at the initial study was a determinant of the change in incretin responses. Between the two study days, fasting GIP (r = 0.72, P < 0.001) correlated well, but not fasting GLP-1 (r = 0.23, P = 0.18). However, both glucose-stimulated GLP-1 (r = 0.50, P = 0.002) and GIP (r = 0.60, P < 0.001) showed correlations between the initial and follow-up studies. Fasting GIP and glucose-stimulated GLP-1 and GIP concentrations correlate within individuals over a follow-up period of ∼5.9 years. Aging is associated with reductions in fasting GLP-1 and GIP, and glucose-stimulated GLP-1, which may predispose to the development of glucose intolerance and type 2 diabetes.

It has been reported that the artificial sweetener, sucralose, stimulates glucose absorption in rodents by enhancing apical availability of the transporter GLUT2. We evaluated whether exposure of the proximal small intestine to sucralose affects glucose absorption and/or the glycaemic response to an intraduodenal (ID) glucose infusion in healthy human subjects. Ten healthy subjects were studied on two separate occasions in a single-blind, randomised order. Each subject received an ID infusion of sucralose (4 mm in 0·9 % saline) or control (0·9 % saline) at 4 ml/min for 150 min (T = − 30 to 120 min). After 30 min (T = 0), glucose (25 %) and its non-metabolised analogue, 3-O-methylglucose (3-OMG; 2·5 %), were co-infused intraduodenally (T = 0–120 min; 4·2 kJ/min (1 kcal/min)). Blood was sampled at frequent intervals. Blood glucose, plasma glucagon-like peptide-1 (GLP-1) and serum 3-OMG concentrations increased during ID glucose/3-OMG infusion (P < 0·005 for each). However, there were no differences in blood glucose, plasma GLP-1 or serum 3-OMG concentrations between sucralose and control infusions. In conclusion, sucralose does not appear to modify the rate of glucose absorption or the glycaemic or incretin response to ID glucose infusion when given acutely in healthy human subjects.

Gastric emptying is a major determinant of postprandial blood glucose, accounting for ~35% of variance in peak glucose in both healthy individuals and those with type 2 diabetes. Gastric emptying is frequently disordered in individuals with diabetes (both abnormally delayed and accelerated). Delayed gastric emptying, i.e. diabetic gastroparesis, may be linked to upper gastrointestinal symptoms for which current treatment remains suboptimal; pharmacological acceleration of delayed emptying is only weakly associated with symptom improvement. Accordingly, the relationship between symptoms and delayed gastric emptying is not simply ‘cause and effect’. In insulin-treated patients, disordered gastric emptying, even when not associated with gastrointestinal symptoms, can cause a mismatch between the onset of insulin action and the availability of absorbed carbohydrate, leading to suboptimal glycaemic control. In patients with type 2 diabetes, interventions that slow gastric emptying, e.g. glucagon-like peptide-1 receptor agonists, reduce postprandial blood glucose. This review focuses on recent insights into the impact of gastric emptying on postprandial blood glucose, effects of diabetes therapy on gastric emptying and the management of disordered gastric emptying in diabetes. In view of the broad relevance of gastric emptying to diabetes management, it is important that future clinical trials evaluating novel therapies that may affect gastric emptying should quantify the latter with an appropriate technique, such as scintigraphy or a stable isotope breath test.

Metformin, the most widely prescribed drug therapy for type 2 diabetes, has pleiotropic benefits, in addition to its capacity to lower elevated blood glucose levels, including mitigation of cardiovascular risk. The mechanisms underlying the latter remain unclear. Mechanistic studies have, hitherto, focused on the direct effects of metformin on the heart and vasculature. It is now appreciated that effects in the gastrointestinal tract are important to glucose-lowering by metformin. Gastrointestinal actions of metformin also have major implications for cardiovascular function. This review summarizes the gastrointestinal mechanisms underlying the action of metformin and their potential relevance to cardiovascular benefits.

Background Gastric emptying (GE), with wide inter-individual but lesser intra-individual variations, is a major determinant of postprandial glycaemia in health and type 2 diabetes (T2D). However, it is uncertain whether GE of a carbohydrate-containing liquid meal is predictive of the glycaemic response to physiological meals, and whether antecedent hyperglycaemia influences GE in T2D. We evaluated the relationships of (i) the glycaemic response to both a glucose drink and mixed meals with GE of a 75 g glucose drink, and (ii) GE of a glucose drink with antecedent glycaemic control, in T2D. Methods Fifty-five treatment-naive Chinese adults with newly diagnosed T2D consumed standardised meals at breakfast, lunch and dinner with continuous interstitial glucose monitoring. On the subsequent day, a 75 g glucose drink containing 150 mg 13 C-acetate was ingested to assess GE (breath test) and plasma glucose response. Serum fructosamine and HbA1c were also measured. Results Plasma glucose incremental area under the curve (iAUC) within 2 hours after oral glucose was related inversely to the gastric half-emptying time (T50) ( r  = −0.34, P  = 0.012). The iAUCs for interstitial glucose within 2 hours after breakfast ( r  = −0.34, P  = 0.012) and dinner ( r  = −0.28, P  = 0.040) were also related inversely to the T50 of oral glucose. The latter, however, was unrelated to antecedent fasting plasma glucose, 24-hour mean interstitial glucose, serum fructosamine, or HbA1c. Conclusions In newly diagnosed, treatment-naive, Chinese with T2D, GE of a 75 g glucose drink predicts the glycaemic response to both a glucose drink and mixed meals, but is not influenced by spontaneous short-, medium- or longer-term elevation in glycaemia.

IntroductionGastrointestinal recovery after surgery is of worldwide significance. Postoperative gastrointestinal dysfunction is multifaceted and known to represent a major source of postoperative morbidity, however, its significance to postoperative care across all surgical procedures is unknown. The complexity of postoperative gastrointestinal recovery is poorly defined within gastrointestinal surgery, and even less so outside this field. To inform the clinical care of surgical patients worldwide, this systematic review and meta-analysis will aim to characterise the duration of postoperative gastrointestinal recovery that can be expected across all surgical procedures and determine the associations between factors that may affect this.Methods and analysisMEDLINE, Embase, Cochrane Library and CINAHL will be searched for studies reporting the time to first postoperative passage of stool after any surgical procedure. We will screen records, extract data and assess risk of bias in duplicate. Forest plots will be constructed for time to postoperative gastrointestinal recovery, as assessed by various outcome measures. Because of potential heterogeneity, a random-effects model will be used throughout the meta-analysis. Funnel plots will be used to test for publication bias. Meta-regressions will be undertaken where the outcome is the mean time to first postoperative passage of stool, with potential predictors and confounders being patient characteristics, postoperative outcomes and surgical factors.Ethics and disseminationThis study will not involve human or animal subjects and, thus, does not require ethics approval. The outcomes will be disseminated via publication in peer-reviewed scientific journal(s) and presentations at scientific conferences.PROSPERO registration numberCRD42021256210.

Australia's bowel cancer prevention guidelines, following a recent revision, are amongst the most complex in the world. Detailed decision tables outline screening or surveillance recommendations for 230 case scenarios alongside cessation recommendations for elderly patients. While these guidelines can help better allocated limited colonoscopy resources, their increasing complexity may limit their adoption and potential benefits. Therefore, tools to support clinicians in navigating these guidelines could be essential for national bowel cancer prevention efforts. Digital applications (DAs) represent a potentially inexpensive and scalable solution, but are yet to be tested for this purpose. To assess whether a DA could increase clinician adherence to Australia's new colorectal cancer screening and surveillance guidelines, and determine whether improved usability correlates with greater conformance to guidelines. As part of a randomised controlled crossover study, we created a clinical vignette quiz to evaluate the efficacy of a DA in comparison to standard resources (SR) for making screening and surveillance decisions. Briefings were provided to study participants which were tailored to their level of familiarity with the guidelines. We measured the adherence of clinicians according to their number of guideline-concordant responses to the scenarios in the quiz using either the DA or the SR. The maximum score was 18, with higher scores indicating improved adherence. We also tested the DA's usability using the System Usability Scale (SUS). Out of 117 participants, 80 were included in the final analysis. Using the SR, the adherence of participants was rated a median score of 10 out of 18 (IQR 7.75 - 13). The participants' adherence improved by 40% (RR 1.4, p <0.001) when using the DA, reaching a median score of 14 out of 18 (IQR 12 - 17). The DA was rated highly for usability with a median score of 90 (IQR 72.5 - 95) and ranked in the 96th percentile of systems. There was a moderate correlation between the usability of the DA and better adherence (rs = 0.4, p < 0.001). No differences between the adherence of specialists and non-specialists were found, either with the SR (10 vs 9, p = 0.465) or the DA (13 vs 15, p = 0.242). There was no significant association between participants who were less adherent with the DA (n=17) and their age (p = 0.064), experience with decision support tools (p = 0.509), or academic involvement with a university (p = 0.389). DAs can significantly improve the adoption of complex Australian bowel cancer prevention guidelines. As screening and surveillance guidelines become increasingly complex and personalised, these tools will be crucial to help clinicians accurately determine the most appropriate recommendations for their patients. Additional research to understand why some practitioners perform worse with DAs is required. Further improvements in application usability may optimise guideline concordance further.