Effects of duodenal distension on antropyloroduodenal pressures and perception are modified by hyperglycemia

The effect of lactose intolerance on plasma glucose levels and related biochemical parameters

Aim: To determine the effect of lactose intolerance on serum glucose levels and related biochemical parameters in the adult population who refrain from consuming milk and milk products. Material and Method: This retrospective, observational study was conducted in a tertiary care hospital between January 2016 and December 2019 with 296 participants. Plasma glucose, calcium, 25-hydroxyvitamin D3, folate, vitamin B12, thyroid-stimulating hormone (TSH), and ferritin levels were controlled. Patients with positive lactose intolerance test results were accepted as the study group and negative results were accepted as the control group, and data of two groups were compared. Results: Of the total 296 participants 212 (71.7%) were found to have lactose intolerance and 84 (28.3%) were found to be normal. In the lactose intolerant group, blood glucose levels were significantly lower than the control group (5.14±0.53 mmol/L versus 5.47±0.54 mmol/L, p

Interdependency between mechanical parameters and afferent nerve discharge in remodeled diabetic Goto-Kakizaki rat intestine

Background

Gastrointestinal disorders are very common in diabetic patients, but the pathogenesis is still not well understood. Peripheral afferent nerves may be involved due to the complex regulation of gastrointestinal function by the enteric nervous system.

Objective

We aimed to characterize the stimulus–response function of afferent fibers innervating the jejunum in the Goto-Kakizaki (GK) type 2 diabetic rat model. A key question is whether changes in afferent firing arise from remodeled tissue or from adaptive afferent processes.

Design

Seven 32-week-old male GK rats and seven age-matched normal Wistar rats were studied. Firing from mesenteric afferent nerves was recorded in excised jejunal segments of seven GK rats and seven normal Wistar rats during ramp test, stress relaxation test, and creep test. The circumferential stress–strain, spike rate increase ratio (SRIR), and single unit firing rates were calculated for evaluation of interdependency of the mechanical stimulations and the afferent nerve discharge.

Results

Elevated sensitivity to mechanical stimuli was found for diabetic nerve bundles and single unit activity (P<0.05). The stress relaxed less in the diabetic intestinal segment (P<0.05). Linear association between SRIR and the thickness of circumferential muscle layer was found at high stress levels as well as for SRIR and the glucose level.

Conclusion

Altered viscoelastic properties and elevated mechanosensitivity were found in the GK rat intestine. The altered nerve signaling is related to muscle layer remodeling and glucose levels and may contribute to gastrointestinal symptoms experienced by diabetic patients.

Malabsorption, Orocecal Transit Time and Small Intestinal Bacterial Overgrowth in Type 2 Diabetic Patients: A Connection

Type 2 diabetes mellitus consists of dysfunctions characterized by hyperglycemia and resulting from combination of resistance to insulin action and inadequate insulin secretion. Most of diabetic patients report significant gastrointestinal symptoms. Entire GI tract can be affected by diabetes from oral cavity to large bowel and anorectal region. Proteins, carbohydrates, fats, and most fluids are absorbed in small intestine. Malabsorption may occurs when proper absorption of nutrients does not take place due to bacterial overgrowth or altered gut motility. The present study was planned to measure various malabsorption parameters in type 2 diabetic patients. 175 patients and 175 age and sex matched healthy controls attending Endocrinology Clinic in PGI, Chandigarh were enrolled. Lactose intolerance was measured by using non-invasive lactose hydrogen breath test. Urinary d-xylose and fecal fat were estimated using standard methods. Orocecal transit time and small intestinal bacterial overgrowth were measured using non-invasive lactulose and glucose breath test respectively. Out of 175 diabetic patients enrolled, 87 were males while among 175 healthy subjects 88 were males. SIBO was observed in 14.8 % type 2 diabetic patients and in 2.8 % of controls. There was statistically significant increase (p < 0.002) in OCTT in type 2 diabetic patients compared with controls. OCTT was observed to be more delayed (p < 0.003) in patients who were found to have SIBO than in patients without SIBO. Lactose intolerance was observed in 60 % diabetic patients and 39.4 % in controls. Urinary d-xylose levels were also lower in case of diabetic patients but no significant difference was found in 72 h fecal fat excretion among diabetic patients and controls. Urinary d-xylose and lactose intolerance in SIBO positive type 2 diabetic patients was more severe as compared to SIBO negative diabetic patients. From this study we can conclude that delayed OCTT may have led to SIBO which may have instigated the process of malabsorption among type 2 diabetic patients.

Specific hunger- and satiety-induced tuning of guinea pig enteric nerve activity

Although hunger and satiety are mainly centrally regulated, there is convincing evidence that also gastrointestinal motor activity and hormone fluctuations significantly contribute to appetite signalling. In this study, we investigated how motility and enteric nerve activity are set by fasting and feeding. By means of video-imaging, we tested whether peristaltic activity differs in ex vivo preparations from fasted and re-fed guinea pigs. Ca(2+) imaging was used to investigate whether the feeding state directly alters neuronal activity, either occurring spontaneously or evoked by (an)orexigenic signalling molecules. We found that pressure-induced (2 cmH(2)O) peristaltic activity occurs at a higher frequency in ileal segments from re-fed animals (re-fed versus fasted, 6.12 ± 0.22 vs. 4.84 ± 0.52 waves min(-1), P = 0.028), even in vitro hours after death. Myenteric neuronal responses were tuned to the feeding status, since neurons in tissues from re-fed animals remained hyper-responsive to high K(+)-evoked depolarization (P < 0.001) and anorexigenic molecules (P < 0.001), while being less responsive to orexigenic ghrelin (P = 0.013). This illustrates that the feeding status remains ‘imprinted' ex vivo. We were able to reproduce this feeding state-related memory in vitro and found humoral feeding state-related factors to be implicated. Although the molecular link with hyperactivity is not entirely elucidated yet, glucose-dependent pathways are clearly involved in tuning neuronal excitability. We conclude that a bistable memory system that tunes neuronal responses to fasting and re-feeding is present in the enteric nervous system, increasing responses to depolarization and anorexigenic molecules in the re-fed state, while decreasing responses to orexigenic ghrelin. Unlike the hypothalamus, where specific cell populations sensitive to either orexigenic or anorexigenic molecules exist, the enteric feeding state-related memory system is present at the functional level of receptor signalling rather than confined to specific neuron subtypes.

The role of continuous subcutaneous insulin infusion therapy in patients with diabetic gastroparesis

AIMS/OBJECTIVE

To describe the effectiveness of continuous subcutaneous insulin infusion (CSII) in patients with symptomatic diabetic gastroparesis and unstable glycaemic control.

METHODS

Data from 26 patients with symptomatic diabetic gastroparesis and unstable glycaemic control using multiple-dose insulin (MDI) regimens, and subsequently managed with CSII, were analysed.

RESULTS

Following initiation of CSII, the median length of inpatient bed days associated with hospital admissions related to gastroparesis and glycaemic instability was reduced from 8.5 (range 0-144) days patient( -1) year( -1) prior to CSII to 0 (range 0-15) days patient( -1) year( -1). The median HbA(1c) reduction with CSII was 1.8% (22 mmol/mol; p < 0.05). The median capillary blood glucose (CBG) with CSII was significantly lower than with MDI: 7.7 mmol/l (range 3.8-15.4 mmol/l) vs 9.8 mmol/l (range 2.3-27 mmol/l), respectively, p < 0.001. Glycaemic variability with CSII was significantly reduced compared with MDI: CBG CV 0.37 vs CV 0.53, respectively, p < 0.001.

CONCLUSIONS/INTERPRETATION

CSII therapy in patients with diabetic gastroparesis results in significant improvement in glycaemic control and reductions in glycaemic variability and number of hospital inpatient bed days.

Effects of intravenous fructose on gastric emptying and antropyloroduodenal motility in healthy subjects

Gastric emptying (GE) of glucose is regulated closely, not only as a result of inhibitory feedback arising from the small intestine, but also because of the resulting hyperglycemia. Fructose is used widely in the diabetic diet and is known to empty from the stomach slightly faster than glucose but substantially slower than water. The aims of this study were to determine whether intravenous (iv) fructose affects GE and antropyloroduodenal motility and how any effects compare to those induced by iv glucose. Six healthy males (age: 26.7 +/- 3.8 yr) underwent concurrent measurements of GE of a solid meal (100 g ground beef labeled with 20 MBq (99m)Tc-sulfur colloid) and antropyloroduodenal motility on three separate days in randomized order during iv infusion of either fructose (0.5 g/kg), glucose (0.5 g/kg), or isotonic saline for 20 min. GE (scintigraphy), antropyloroduodenal motility (manometry), and blood glucose (glucometer) were measured for 120 min. There was a rise in blood glucose (P < 0.001) after iv glucose (peak 16.4 +/- 0.6 mmol/l) but not after fructose or saline. Intravenous glucose and fructose both slowed GE substantially (P < 0.005 for both), without any significant difference between them. Between t = 0 and 30 min, the number of antral pressure waves was less after both glucose and fructose (P < 0.002 for both) than saline, and there were more isolated pyloric pressure waves during iv glucose (P = 0.003) compared with fructose and saline (P = NS for both) infusions. In conclusion, iv fructose slows GE and modulates gastric motility in healthy subjects, and the magnitude of slowing of GE is comparable to that induced by iv glucose.

Computer simulation of flow and mixing at the duodenal stump after gastric resection

AIM: To investigate the flow and mixing at the duodenal stump after gastric resection, a computer simulation was implemented.

METHODS: Using the finite element method, two different Billroth II procedure cases (A and B) were modeled. Case A was defined with a shorter and almost straight duodenal section, while case B has a much longer and curved duodenal section. Velocity, pressure and food concentration distribution were determined and the numerical results were compared with experimental observations.

RESULTS: The pressure distribution obtained by numerical simulation was in the range of the recorded experimental results. Case A had a more favorable pressure distribution in comparison with case B. However, case B had better performance in terms of food transport because of more continual food distribution, as well as better emptying of the duodenal section.

CONCLUSION: This study offers insight into the transport process within the duodenal stump section after surgical intervention, which can be useful for future patient-specific predictions of a surgical outcome.

Upper gastrointestinal function and glycemic control in diabetes mellitus

Recent evidence has highlighted the impact of glycemic control on the incidence and progression of diabetic micro- and macrovascular complications, and on cardiovascular risk in the non-diabetic population. Postprandial blood glucose concentrations make a major contribution to overall glycemic control, and are determined in part by upper gastrointestinal function. Conversely, poor glycemic control has an acute, reversible effect on gastrointestinal motility. Insights into the mechanisms by which the gut contributes to glycemia have given rise to a number of novel dietary and pharmacological strategies designed to lower postprandial blood glucose concentrations.

Relationships of upper gastrointestinal motor and sensory function with glycemic control

Acute changes in the blood glucose concentration have a major reversible effect on esophageal, gastric, intestinal, gallbladder, and anorectal motility in both healthy subjects and diabetic patients. For example, gastric emptying is slower during hyperglycemia than euglycemia and accelerated during hypoglycemia. Acute hyperglycemia also affects perceptions arising from the gastrointestinal tract and may accordingly, be important in the etiology of gastrointestinal symptoms in diabetes. Elevations in blood glucose that are within the normal postprandial range also affect gastrointestinal motor and sensory function. Upper gastrointestinal motor function is a critical determinant of postprandial blood glucose concentrations by influencing the absorption of ingested nutrients. Interventions that reduce postprandial hyperglycemia, by modulating the rate of gastric emptying, have the potential to become mainstream therapies in the treatment of diabetes.

Effects of cholecystokinin on appetite and pyloric motility during physiological hyperglycemia

Recent studies suggest that the interaction between small intestinal nutrient stimulation and the blood glucose concentration is important in the regulation of gastric motility and appetite. The purpose of this study was to determine whether the effects of cholecystokinin octapeptide (CCK-8) on antropyloric motility and appetite are influenced by changes in the blood glucose concentration within the normal postprandial range. Seven healthy volunteers were studied on 4 separate days. A catheter incorporating a sleeve sensor was positioned across the pylorus, and the blood glucose was stabilized at either 4 mmol/l (2 days) or 8 mmol/l (2 days). After the desired blood glucose had been maintained for 90 min, an intravenous infusion of either CCK-8 (2 ng. kg(-1). min(-1)) or saline (control) was given for 60 min. Thirty minutes after the infusion began, the catheter was removed and subjects drank 400 ml of water with guar gum before being offered a buffet meal. The amount of food consumed (kcal) was quantified. The order of the studies was randomized and single-blinded. There were fewer antral waves at a blood glucose of 8 than at 4 mmol/l during the 90-min period before the infusions (P<0.05) and during the first 30 min of CCK-8 or saline infusion (P = 0.07). CCK-8 suppressed antral waves (P<0.05), stimulated isolated pyloric pressure waves (IPPWs) (P<0.01), and increased basal pyloric pressure (P<0.005) compared with control. During administration of CCK-8, basal pyloric pressure (P<0.01), but not the number of IPPWs, was greater at a blood glucose of 8 mmol/l than at 4 mmol/l. CCK-8 suppressed the energy intake at the buffet meal (P<0.01), with no significant difference between the two blood glucose concentrations. We conclude that the acute effect of exogenous CCK-8 on basal pyloric pressure, but not appetite, is modulated by physiological changes in the blood glucose concentration.

Identification and characterization of glucoresponsive neurons in the enteric nervous system

We tested the hypothesis that a subset of enteric neurons is glucoresponsive and expresses ATP-sensitive K(+) (K(ATP)) channels. The immunoreactivities of the inwardly rectifying K(+) channel 6.2 (Kir6.2) and the sulfonylurea receptor (SUR), now renamed SUR1, subunits of pancreatic beta-cell K(ATP) channels, were detected on cholinergic neurons in the guinea pig ileum, many of which were identified as sensory by their costorage of substance P and/or calbindin. Glucoresponsive neurons were distinguished in the myenteric plexus because of the hyperpolarization and decrease in membrane input resistance that were observed in response to removal of extracellular glucose. The effects of no-glucose were reversed on the reintroduction of glucose or by the K(ATP) channel inhibitor tolbutamide. No reversal of the hyperpolarization was observed when D- mannoheptulose, a hexokinase inhibitor, was present on the reintroduction of glucose. Application of the K(ATP) channel opener diazoxide or the ob gene product leptin mimicked the effect of glucose removal in a reversible manner; moreover, hyperpolarizations evoked by either agent were inhibited by tolbutamide. Glucoresponsive neurons displayed leptin receptor immunoreactivity, which was widespread in both enteric plexuses. Superfusion of diazoxide inhibited fast synaptic activity in myenteric neurons, via activation of presynaptic K(ATP) channels. Diazoxide also produced a decrease in colonic motility. These experiments demonstrate for the first time the presence of glucoresponsive neurons in the gut. We propose that the glucose-induced excitation of these neurons be mediated by inhibition of K(ATP) channels. The results support the idea that enteric K(ATP) channels play a role in glucose-evoked reflexes.

Gastroduodenal motility

Several major themes emerged over the past year in the area of gastroduodenal motility. Mostly, these themes represented extensions of research areas discussed in prior reviews in this series rather than the emergence of completely new concepts. Thus, for example, considerable emphasis has again been placed on regional gastric motor function in dyspepsia and on the role of fundic relaxation and accommodation, in particular. Not surprisingly, basic physiologic research has also shown a keen interest in the regulation of fundic relaxation. One new and exciting development is the recognition of the stomach's role in satiety. The spectrum of gastric motor dysfunction in diabetes mellitus continues to be explored, and the important role of hyperglycemia in regulating gastric function has been further emphasized. More data have been provided on noninvasive alternatives to gastric motor function testing, and several studies have looked at factors that may influence variability in these various tests. There have been few innovations over the past year in the therapeutic arena; rather, the indications and limitations of current therapies have been further developed.