Differential GIP/GLP‐1 intestinal cell distribution in diabetics’ yields distinctive rearrangements depending on Roux‐en‐Y biliopancreatic limb length

Individuals with type 2 diabetes have higher density of small intestinal neurotensin-expressing cells

Neurotensin (NT) is a gastro-intestinal hormone involved in several pathways that regulate energy and glucose homeostasis. NT was hypothesized to act in synergy with incretin hormones to potentiate its anti-diabetic effects. Additionally, circulating NT levels were shown to rise after bariatric surgery-induced weight loss. Knowledge of NT-secreting cells distribution along the small intestine and its variation according to diabetes status could provide insights on NT role in mediating type 2 diabetes (T2D) improvement after bariatric surgery. So, our aims were to characterize NT-expressing cell distribution along the human small intestine and to compare the relative density of NT-expressing cells in the small intestine of individuals with and without T2D undergoing bariatric surgery for obesity treatment. Autopsy-derived small intestine fragments (n = 30) were obtained at every 20 cm along the entire intestinal length. Additionally, jejunum biopsies (n = 29) were obtained during elective gastric bypass interventions from patients with (n = 10) or without T2D (n = 18). NT-expressing cells were identified by immunohistochemistry and quantified via computerized morphometric analysis. NT-expressing cell density increased along the human small intestine. NT-expressing cell density was significantly higher from 200 cm distal to the duodenojejunal flexure onward, as well as in subjects with T2D when compared to those without T2D. NT-expressing cell density increases along the human small gut, and a higher density is found in individuals with T2D. This finding suggests a potential role for NT in the mechanisms of disease and T2D improvement observed after bariatric surgery.

Peptide Tyrosine-Tyrosine Triggers GLP-2-Mediated Intestinal Hypertrophy After Roux-en-Y Gastric Bypass

Purpose 

Intestinal remodeling and adaptation of the alimentary limb after Roux-en-Y gastric bypass (RYGB) play an important role in the pathophysiological events that lead to type 2 diabetes mellitus (T2DM) improvement. Intestinal absorptive loop hypertrophy and growth following surgery have been related to GLP-2 secretion by ileal L-cells. The secretion of peptide tyrosine-tyrosine (PYY) enterohormone after a meal has been proposed as a trigger for ileal secretion of GLP-1. Our aim is to determine the role of PYY as a GLP-2 secretion modulator as an adaptation result in the alimentary limb after RYGB.

Method

We used a non-obese euglycemic rodent model. Circulating glucose, insulin, PYY, and GLP-2 were measured in the experimental and control groups. We used four groups: fasting control, Sham-operated, RYGB-operated (RYGB), and RYGB-operated and treated with BIIE0246 (RYGB + BII). BIIE0246 is a NPY2 receptor antagonist in L-cells. Intestinal glucose transporters and GLP-1 and PYY gut expression and hypertrophy were analyzed after 12 weeks of surgery.

Results

RYGB increased PYY3-36 plasma levels in rats with or without BII treatment. A high-insulin response was observed in the RYGB group but not in the control or RYGB + BII groups. BIIE0246 treatment limited plasma GLP-2 levels. In the alimentary intestinal limb, hypertrophy and SGLT1 and GLUT1 expression appeared to be reduced after RYGB compared to controls.

Conclusion

The postprandial ileal PYY secretion is enhanced after RYGB. This increase mediates GLP-2 release through its binding to the Y2 receptor on L-cells. This mechanism plays a role in alimentary limb hypertrophy after surgery.

Graphical abstract

SMALL INTESTINAL L CELL DENSITY IN PATIENTS WITH SEVERE OBESITY AFTER ROUX-EN-Y GASTRIC BYPASS

BACKGROUND:

Enteroendocrine L cells can be found in the entire gastrointestinal tract and their incretins act on glycemic control and metabolic homeostasis. Patients with severe obesity and type 2 diabetes mellitus may have lower density of L cells in the proximal intestine.

AIMS:

This study aimed to analyze the density of L cells in the segments of the small intestine in the late postoperative of Roux-en-Y gastric bypass in diabetic patients with standardization of 60 cm in both loops, alimentary and biliopancreatic.

METHODS:

Immunohistochemistry analysis assays were made from intestinal biopsies in three segments: gastrointestinal anastomosis (GIA= Point A), enteroenteral anastomosis (EEA= Point B= 60 cm distal to the GIA) and 60 cm distal to the enteroenteral anastomosis (Point C).

RESULTS:

A higher density of L cells immunostaining the glucagon-1 peptide was observed in the distal portion (Point C) when compared to the more proximal portions (Points A and B).

CONCLUSIONS:

The concentration of L cells is higher 60 cm distal to enteroenteral anastomosis when comparing to proximal segments and may explain the difference in intestinal lumen sensitization and enterohormonal response after Roux-en-Y gastric bypass.

Daily transient coating of the intestine leads to weight loss and improved glucose tolerance

INTRODUCTION

Roux-en-Y gastric bypass surgery (RYGB) has been shown to be the gold standard treatment for obesity associated type-2-diabetes (T2D), however many T2D patients do not qualify or are reluctant to proceed with surgery due to its potential risks and permanent changes to GI anatomy. We have previously described a novel oral formulation, LuCI, that provides a transient coating of the proximal bowel and mimics the effects of RYGB. Herein, we aim to investigate the outcome of chronic LuCI administration on weight and glucose homeostasis.

METHODS

Sprague-Dawley rats on a high fat diet achieving diet-induced obesity (DIO) received 5 weeks of daily LuCI or normal saline as control (n = 8/group). Daily weights and glucose tolerance were monitored throughout the experiment. At 5 weeks, systemic blood was sampled through a surgically placed jugular vein catheter, before and during an intestinal glucose bolus, to investigate changes in key hormones involved in glucose metabolism. To elucidate the effects of LuCI on nutrient absorption, fecal output and food intake were measured simultaneously with the analysis of homogenized stool samples performed using bomb calorimetry.

RESULTS

At 5 weeks, LuCI animals weighted 8.3% less and had lower fasting glucose levels than Controls (77.6 ± 3.8 mg/dl vs. 99.1 ± 2.7 mg/dl, P < 0.001). LuCI-treated animals had lower baseline insulin and HOMA-IR. Post-prandially, LuCI group had increased GLP-1 and GIP secretion following a glucose challenge. Serum lipid analysis revealed lowered LDL levels highlighting the potential to not only improve glucose control but also modify cardiovascular risk. We then investigated whether LuCI's effect on proximal bowel exclusion may play a role in energy balance. Bomb calorimetry analysis suggested that LuCI reduced calorie absorption with no difference in caloric consumption.

CONCLUSION

We demonstrated that LuCI recapitulates the physical and hormonal changes seen after RYGB and can ameliorate weight gain and improve insulin sensitivity in a DIO rat model. Since LuCI's effect is transient and without systemic absorption, LuCI has the potential to be a novel therapy for overweight or obese T2D patients.

Effect of Roux-en-Y Gastric Bypass with Different Lengths of Biliopancreatic and Alimentary Limbs for Patients with Type 2 Diabetes Mellitus and a BMI < 35 kg/m2: 5-Year Outcomes in Chinese Patients

PURPOSE

There have been no definite conclusions about the biliopancreatic limb (BPL) and alimentary limb (AL) lengths in Roux-en-Y gastric bypass (RYGB) operations for different populations and BMIs. Western scholars have performed many studies on the lengths of the BPL and AL in patients with a BMI ≥ 35 kg/m². However, for diabetic Chinese patients with BMI < 35 kg/m², few people have compared the effects of different BPL and AL lengths on patient prognosis.

PATIENTS AND METHODS

Clinical data were collected prospectively and analyzed retrospectively for 87 patients with type 2 diabetes (T2DM) who underwent RYGB with a BPL of 50 cm and an AL of 50 cm (BPL50/AL50) or with a BPL of 100 cm and an AL of 100 cm (BPL100/AL100) and who were followed up for 5 years.

RESULTS

The cohort included 42 patients in the BPL50/AL50 group and 45 patients in the BPL100/AL100 group. At 5 years, there were significant differences in BMI, total weight loss (TWL%), glycosylated hemoglobin, and homeostasis model assessment insulin resistance between BPL50/AL50 and BPL100/AL100 (P < 0.05). Diabetes remission rate of the BPL100/AL100 group was significantly higher than that of the BPL50/AL50 group. Diabetes remission at 1 year after surgery correlated with the length limb (BPL + AL), duration of diabetes and TWL%. There was no difference in complications between BPL50/AL50 and BPL100/AL100.

CONCLUSIONS

RYGB with BPL100/AL100 is a safe and effective treatment for diabetic patients with a BMI < 35 kg/m² and offers significant improvement in weight loss and glycemic control.

Congenital Glucagon-like Peptide-1 Deficiency in the Pathogenesis of Protracted Diarrhea in Mitchell-Riley Syndrome

CONTEXT

Mitchell-Riley syndrome due to RFX6 gene mutations is characterized by neonatal diabetes and protracted diarrhea. The RFX6 gene encodes a transcription factor involved in enteroendocrine cell differentiation required for beta-cell maturation. In contrast to the pathway by which RFX6 mutations leads to diabetes, the mechanisms underlying protracted diarrhea are unknown.

OBJECTIVE

To assess whether glucagon-like peptide-1 (GLP-1) was involved in the pathogenesis of Mitchell-Riley syndrome protracted diarrhea.

METHODS

Two case report descriptions. in a tertiary pediatric hospital. "Off-label" treatment with liraglutide. We describe 2 children diagnosed with Mitchell-Riley syndrome, presenting neonatal diabetes and protracted diarrhea. Both patients had nearly undetectable GLP-1 plasma levels and absence of GLP-1 immunostaining in distal intestine and rectum. The main outcome was to evaluate whether GLP-1 analogue therapy could improve Mitchell-Riley syndrome protracted diarrhea.

RESULTS

"Off-label" liraglutide treatment, licensed for type 2 diabetes treatment in children, was started as rescue therapy for protracted intractable diarrhea resulting in rapid improvement during the course of 12 months.

CONCLUSION

Congenital GLP-1 deficiency was identified in patients with Mitchell-Riley syndrome. The favorable response to liraglutide further supports GLP-1 involvement in the pathogenesis of protracted diarrhea and its potential therapeutic use.

From Entero-Endocrine Cell Biology to Surgical Interventional Therapies for Type 2 Diabetes

The physiological roles of the enteroendocrine system in relation to energy and glucose homeostasis regulation have been extensively studied in the past few decades. Considerable advances were made that enabled to disclose the potential use of gastro-intestinal (GI) hormones to target obesity and type 2 diabetes (T2D). The recognition of the clinical relevance of these discoveries has led the pharmaceutical industry to design several hormone analogues to either to mitigate physiological defects or target pharmacologically T2D.Amongst several advances, a major breakthrough in the field was the unexpected observation that enteroendocrine system modulation to T2D target could be achieved by surgically induced anatomical rearrangement of the GI tract. These findings resulted from the widespread use of bariatric surgery procedures for obesity treatment, which despite initially devised to induce weight loss by limiting the systemic availably of nutrients, are now well recognized to influence GI hormone dynamics in a manner that is highly dependent on the type of anatomical rearrangement produced.This chapter will focus on enteroendocrine system related mechanisms leading to improved glycemic control in T2D after bariatric surgery interventions.

Does Reconstruction Type After Gastric Resection Matters for Type 2 Diabetes Improvement?

BACKGROUND

Gastrointestinal (GI) surgery involving gastric resection and bypass of intestinal segments was reported to facilitate glucose control in obese patients with type 2 diabetes (T2D).

AIM

Our aim was to assess whether the type of post-gastrectomy GI reconstruction also influences glucose control in T2D patients with BMI below 35 kg/m² submitted to gastrointestinal surgery without bariatric intention.

METHODS

A cohort of T2D Caucasian patients (n = 40) with upper GI malignancy (n = 33) or complicated reflux disease (n = 7) were submitted to either a gastrectomy plus Billroth II (BII) gastrojejunal anastomosis (n = 17), a gastrectomy plus Roux-en-Y gastrojejunostomy (RY) reconstruction (n = 18; subtotal gastrectomy n = 7 and total gastrectomy n = 11), or atypical gastrectomy without reconstruction (no-R) (n = 5). Patients were evaluated before and 2 years after surgery for body weight, Hb1Ac, need of glucose lowering drugs, and presence of diabetes.

RESULTS

Body mass index (BMI) decreased after every surgical procedure when compared to baseline (- 0.9 ± 0.8 kg/m² for BII vs - 4.3 ± 2.6 kg/m² for RY vs - 4.6 ± 2.5 kg/m² for no-R, p < 0.05), which was only significantly different after RY surgeries. Diabetes remission occurred in 5.9% of BII patients, in 27.8% of RY patients, and 0% of no-R patients, while in patients with persistent T2D, the needs for glucose-lowering drugs were significantly also decreased after RY (31.3% BII vs 66.7% RY vs 25% no-R, p = 0.03).

CONCLUSIONS

T2D Caucasian patients undergoing post-gastrectomy GI reconstructions without a bariatric intention experience a significant improvement of T2D, in a magnitude that could be influenced by the technical procedure performed in favor of RY reconstruction. Thus, presence of T2D should be taken into consideration when deciding for the type of post-gastrectomy GI reconstruction.

Acute effect of an amino acid mixture in the rat glycemic profile

Amino acid mixtures (AAM) are protein substitutes used for phenylketonuria treatment, but their metabolic effects have not been well characterized. The objective of this study was to compare the acute glycemic response to free amino acids (free AA) from AAM with the response to intact protein (iProtein). Male Wistar rats (n = 14) were administered by gavage a bolus of free AA (n = 7) or iProtein as albumin (n = 7) containing equivalent amounts of nitrogen. Blood glucose and insulin levels were measured at baseline and 15, 30, 60 and 120 minutes later, when gut GLP-1 content and pancreatic insulin, GLP-1 receptor and Ki67 expression were quantified at 120 minutes time point. After AAM, glucose area under the curve (free AA vs iProtein; P < 0.01), serum insulin levels at 120 minutes (free AA vs iProtein; P < 0.05), colon GLP-1 content (free AA vs iProtein; P < 0.01), pancreatic GLP-1 receptor (free AA vs iProtein; P < 0.01) and insulin expression (free AA vs iProtein; p < 0.01) were significantly lower as compared with iProtein. AAM increased Ki67 expression in pancreatic islets (free AA vs iProtein; P < 0.05). In conclusion, this study demonstrated that acute response to AAM differs from iProtein and is characterized by a lower glucose excursion, along with a decrease in gut GLP-1 and pancreatic GLP-1 receptor and insulin. This data suggests the modulation of glycemia by free AA is mediated by the incretin axis.

Offspring from maternal nutrient restriction in mice show variations in adult glucose metabolism similar to human fetal growth restriction

Fetal growth restriction (FGR) is a pregnancy condition in which fetal growth is suboptimal for gestation, and this population is at increased risk for type 2 diabetes as adults. In humans, maternal malnutrition and placental insufficiency are the most common causes of FGR, and both result in fetal undernutrition. We hypothesized that maternal nutrient restriction (MNR) in mice will cause FGR and alter glucose metabolism in adult offspring. Pregnant CD-1 mice were subjected to MNR (70% of average ad libitum) or control (ad libitum) from E6.5 to birth. Following birth, mice were fostered by mothers on ad libitum feeds. Weight, blood glucose, glucose tolerance and tissue-specific insulin sensitivity were assessed in male offspring. MNR resulted in reduced fetal sizes but caught up to controls by 3 days postnatal age. As adults, glucose intolerance was detected in 19% of male MNR offspring. At 6 months, liver size was reduced (P = 0.01), but pAkt-to-Akt ratios in response to insulin were increased 2.5-fold relative to controls (P = 0.004). These data suggest that MNR causes FGR and long-term glucose intolerance in a population of male offspring similar to human populations. This mouse model can be used to investigate the impacts of FGR on tissues of importance in glucose metabolism.