Evaluation of insulin secretion after pancreas autotransplantation by oral or intravenous glucose challenge

Characterisation of oral and i.v. glucose handling in truncally vagotomised subjects with pyloroplasty

OBJECTIVE

Glucagon-like peptide 1 (GLP1) is rapidly inactivated by dipeptidyl peptidase 4 (DPP4), but may interact with vagal neurons at its site of secretion. We investigated the role of vagal innervation for handling of oral and i.v. glucose.

DESIGN AND METHODS

Truncally vagotomised subjects (n=16) and matched controls (n=10) underwent 50 g-oral glucose tolerance test (OGTT)±vildagliptin, a DPP4 inhibitor (DPP4i) and isoglycaemic i.v. glucose infusion (IIGI), copying the OGTT without DPP4i.

RESULTS

Isoglycaemia was obtained with 25±2 g glucose in vagotomised subjects and 18±2 g in controls (P<0.03); thus, gastrointestinal-mediated glucose disposal (GIGD) - a measure of glucose handling (100%×(glucoseOGTT-glucoseIIGI/glucoseOGTT)) - was reduced in the vagotomised compared with the control group. Peak intact GLP1 concentrations were higher in the vagotomised group. Gastric emptying was faster in vagotomised subjects after OGTT and was unaffected by DPP4i. The early glucose-dependent insulinotropic polypeptide response was higher in vagotomised subjects. Despite this, the incretin effect was equal in both groups. DPP4i enhanced insulin secretion in controls, but had no effect in the vagotomised subjects. Controls suppressed glucagon concentrations similarly, irrespective of the route of glucose administration, whereas vagotomised subjects showed suppression only during IIGI and exhibited hyperglucagonaemia following OGTT. DPP4i further suppressed glucagon secretion in controls and tended to normalise glucagon responses in vagotomised subjects.

CONCLUSIONS

GIGD is diminished, but the incretin effect is unaffected in vagotomised subjects despite higher GLP1 levels. This, together with the small effect of DPP4i, is compatible with the notion that part of the physiological effects of GLP1 involves vagal transmission.

Beneficial effect of FR183998, a Na+/H+ exchanger inhibitor, on porcine pancreas allotransplantation retrieved from non–heart-beating donors

Activation of Na(+)/H(+) exchanger (NHE) may have an important role in the ischemia/reperfusion injury by producing intracellular calcium overload. Recent studies have shown a beneficial effect of an NHE inhibitor on the ischemia/reperfusion injury in the heart. In this study, we examined the effect of FR183998, a potent NHE inhibitor, in porcine pancreas allotransplantation from non-heart-beating Landrace pig donors (NHBDs). The four experimental groups included: untreated with no preservation (group 1; n = 3), treated with no preservation (group 2; n = 5), untreated with preservation (group 3; n = 6), and treated with preservation (group 4; n = 4). The preservation was made in ice-cold University of Wisconsin (UW) solution for 24 hours. The groups treated received 1 mg/kg FR183998 before donor cardiac arrest and 10 mg in the UW solution flush in situ. Serum blood glucose, insulin, and amylase were measured daily. An intravenous glucose tolerance test (IVGTT) was performed on the postoperative day (POD) 7 when pigs were sacrificed for histological examination. Graft survival rates on that day in groups 1,2,3, and 4 were 3 of 3; 5 of 5; 3 of 6; and 4 of 4, respectively. The mean K values of IVGTT in groups 3 and 4 were 0.78 +/- 0.10 and 1.27 +/- 0.16, respectively, which were significantly different (P < .05). Upon histological examination, pancreatic tissue in group 3 showed more severe edema and necrosis than other groups. FR183998 may be considered beneficial for ischemia/reperfusion injury to pancreatic grafts from NHBDs.

Efeitos da ligadura do ducto pancreático e da secção ductal com livre drenagem de secreções para o peritônio sobre as funções endócrina e exócrina do pâncreas: estudo clínico e laboratorial em coelhos

As ressecções pancreáticas seguidas de anastomoses acompanham-se de altas taxas de morbidade, que incluem: surtos de pancreatite e, principalmente, fístulas digestivas. Nos transplantes pancreáticos a drenagem da parte exócrina do enxerto para o intestino ou para a bexiga, além das peculiaridades técnicas, também não é isenta de diversas complicações. Visando evitar ou atenuar tais conseqüências e simplificar a técnica cirúrgica, têm sido usadas outras abordagens para o tratamento ductal do coto/enxerto pancreático, tais como: drenagem livre de secreções para o peritônio, com o ducto pancreático aberto, ligadura ductal e oclusão do ducto com polímeros sintéticos. OBJETIVO: O presente estudo visa avaliar clínica e laboratorialmente as funções endócrina e exócrina do pâncreas de coelhos com o ducto aberto e ligado. MÉTODOS: Foram realizadas 150 operações, divididas em 3 grupos: N - manipulação/controle (n=50), A - grupo aberto (n=50), e L - ligado (n=50). Os momentos de observação foram pré-operatório, dia 0 (dia da operação) e pós-operatório (observação e sacrifício): 7 dias, 14 dias, 28 dias, 90 dias e 180 dias. Os parâmetros analisados foram: estado geral, atividade, controles do peso corporal, ingestão hídrica, ingestão alimentar e dosagens da amilase sangüínea, glicemia, glicose urinária e insulina plasmática. RESULTADOS: Todos os grupos tiveram evolução clínica similar, com bom estado geral, ganho ponderal progressivo e valores normais da ingestão hídrica e ingestão alimentar. Exceto uma significativa elevação da amilase sangüínea nas primeiras 24-48h para os 2 grupos com interferência ductal, não houve qualquer alteração dos níveis basais da glicemia, glicosúria e insulinemia entre os 3 grupos experimentais, em todos os momentos de observação. CONCLUSÃO: À exceção da amilase sangüínea, cujos níveis basais foram significativamente elevados no 1º e 2º dias de pós-operatório, as duas modalidades técnicas de abordagem da secreção exócrina do pâncreas, utilizadas em coelhos, não determinaram quaisquer alterações clínicas, bem como dos níveis basais de glicose sangüínea, glicose urinária e insulina plasmática, durante 6 meses de seguimento.

Reinnervation of syngeneic pancreatico-duodenal grafts in rats

BACKGROUND

Knowledge on the reinnervation of transplanted organs is scarce, and the aim of the study was therefore to evaluate to what degree syngeneic pancreas grafts were reinnervated in rats.

METHODS

Syngeneic pancreatico-duodenal transplantations were performed in normoglycemic Wistar-Furth rats. Native and transplanted pancreas and duodenum were removed 4 or 40 weeks after implantation, and processed for indirect immunofluorescence using antibodies directed against vasoactive intestinal peptide, substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), tyrosine hydroxylase (TH), or the general neuronal marker protein gene product 9.5.

RESULTS

Four weeks after transplantation a moderate to rich number of protein gene product 9.5-positive nerve fibers were found homogeneously distributed through the pancreas, probably representing the intrapancreatic nervous system, because the grafted pancreas lacked both a sympathetic (TH/NPY) and sensory (SP/CGRP) innervation 4 weeks after implantation. In a few of the animals there was a marked increase in SP-immunoreactive nerves (lacking CGRP), most conspicuous in the duodenal portion, both 4 and 40 weeks after transplantation probably secondary to a chronic pancreatitis. The fibers seemed to emanate from intrapancreatic ganglia and possibly also from enteric neurons in adjacent parts of the duodenum. A few scattered vasoactive intestinal peptide-containing nerve fibers probably also emanating from local ganglia could be seen throughout the grafted pancreas both 4 and 40 weeks after transplantation. At 40 weeks after transplantation sympathetic (TH- and NPY-positive) nerve fibers were regularly seen, whereas CGRP-positive nerve fibers were still virtually lacking in the pancreas. To trace the origin of the ingrowing nerve fibers, the tracer True Blue was injected into the grafted pancreas of some rats 38 weeks after transplantation, i.e., 2 weeks before killing. True Blue-labeled nerve cell bodies were numerous in the celiac ganglion (presumably sympathetic nerves) and few in dorsal root ganglia (sensory nerves).

CONCLUSIONS

The data suggest that the transplanted rat pancreas becomes reinnervated by mainly sympathetic nerve fibers.

Pancreas transplantation. An initial experience with systemic and portal drainage of pancreatic allografts

Pancreas transplantation has evolved dramatically since its introduction in 1966. As new centers for transplantation have developed, the evaluation of complications associated with pancreas transplantation has led to advances in surgical technique. Furthermore, surgical alterations of the pancreas resulting from transplantation (systemic release of insulin and denervation) are of unproven consequence on glucose metabolism. Since 1988, the authors have performed 21 transplants (16 combined pancreas/kidney, 3 pancreas alone, which includes 1 retransplantation, 1 pancreas after previous kidney transplant, and 1 "cluster") in 20 patients aged 18 to 49 years; mean, 35 +/- 1 years. Overall patient survival is 95%. Three pancreatic grafts failed within the first year because of technical failure; one additional pancreas was lost to an immunologic event on postoperative day 449, for an overall pancreatic graft survival of 81%. No renal grafts were lost. To evaluate causes of graft failure, demographic data were compared, which included age and sex of the donor and the recipient, operative time, intraoperative blood transfusion, and ischemic time of the graft. No statistically significant differences were found between groups except for ischemic time (11.7 +/- 6.4 hours for the technical success group versus 19.8 +/- 3.7 hours for the technical failure group; p less than 0.05 by unpaired Student's t test). Quadruple immunosuppression was used, which included prednisone, cyclosporine, azathioprine, and antilymphoblast globulin. A mean of 1.2 (range, 0 to 3) rejection episodes per patient occurred. Mean hospital stay was 24 +/- 11 days. Surgical and infectious complications were evaluated by comparing the technical success (TS) group (n = 17) with the technical failure (TF) group. Surgical complications in the TS group revealed a mean of 1.3 episodes per patient, whereas the TF group had 3.7 episodes per patient. The TS also had a reduced incidence of infectious complications compared with the TF (1.7 versus 4.3 episodes per patient). Cytomegalovirus was common in both groups, accounting for 11 infectious episodes, and occurred on a mean postoperative day of 38. Mean postoperative HbA1C levels dropped to 5 +/- 1% from 11 +/- 3%. The authors developed a new technique that incorporates portal drainage of the pancreatic venous effluent in three recipients. Preoperative metabolic studies disclosed a mean fasting glucose of 211 +/- 27 mg/dL and a mean stimulated glucose value of 434 +/- 41 mg/dL for all patients; the mean fasting insulin was 23 +/- 4 microU/mL.(ABSTRACT TRUNCATED AT 400 WORDS)

Surgical alterations of the pancreas and insulin-independent glucose disposal

Systemic drainage of pancreatic venous effluent and denervation of the pancreas that follows pancreatic transplantation has been shown to alter postoperative glucose disposal despite elevated levels of peripheral insulin in response to a glucose challenge. Since an appreciable fraction of postprandial glucose disposal takes place in the absence of insulin (insulin-independent glucose disposal--IIGD), we have investigated potential changes in this aspect of carbohydrate metabolism before and after bladder-drained pancreatic auto-transplantation (PAT/B) as well as partial pancreatectomy (PPx). The hyperglycemic clamp protocol with a background infusion of somatostatin was performed on control (PREOP) dogs as well as PAT/B and PPx animals. The rate of glucose disposal (M Value) during the period of hypoinsulinemia induced by Somatostatin (SST) was measured and reported. Whereas glucose disposal during steady state hyperglycemia was significantly diminished for both PPx and PAT/B in the absence of SST, IIGD was unaltered across all three groups studied. We therefore conclude that surgical alteration of the pancreas results in abnormal glucose disposal during steady state hyperglycemia despite apparently normal to supranormal levels of peripheral insulin, and that alterations in IIGD are not responsible for these differences.

Glucose metabolism after pancreas autotransplantation. The effect of open duct versus urinary bladder drainage technique

Glucose metabolism and insulin secretion after pancreas transplantation may be affected by the technique used for ductal drainage. We evaluated peripheral glucose and insulin levels after oral (oral glucose tolerance test [OGTT]) and sustained stable hyperglycemic challenge (clamp) in dogs who had undergone pancreas autotransplantation with intraperitoneal drainage (PAT) or with urinary bladder to pancreatic duct anastomosis (PAT/B). Both groups had basal glucose values comparable to normal controls; PAT/B animals had fasting hyperinsulinemia. Pancreas autotransplantation animals had an increased integrated glucose response to OGTT and blunted insulin response to hyperglycemic clamp. Urinary bladder to pancreatic duct anastomosis animals had a significantly decreased integrated glucose response to OGTT compared to PAT and an exaggerated insulin response to hyperglycemic challenge, which approximated normal control values by the last 30-minute period of the clamp. Interestingly M values, which approximate glucose metabolized during the hyperglycemic challenge, were depressed in both surgical groups. It is concluded that the technique of bladder drainage allows a 'normalization' of peripheral levels of insulin that is associated with amelioration of an altered glucose response after oral challenge. However the clamp studies show that, despite the improvement in insulin response, an insensitivity may exist to a wide range of endogenous levels after pancreas transplantation.

Glipizide treatment of pancreas autotransplantation: effects on alterations in glucose-insulin relationships

Pancreas transplantation has been proven effective in supplying an endogenous insulin supply in diabetics. However, alterations in glucose metabolism after transplantation suggest a possible "insensitivity" to its action in the periphery. We hypothesized that sulfonylurea treatment of canines who had received segmental pancreas autotransplants would correct these alterations by altering peripheral insulin sensitivity. Glipizide therapy (5 mg p.o. b.i.d.) did appear, in fact, to enhance basal insulin sensitivity by lowering fasting glucose (100 +/- 3 to 81 +/- 11 mg/dl pre-treatment to post-treatment) while not affecting basal insulin levels. However, glipizide therapy was associated with decreased insulin response to challenge by either oral glucose (2 gm/kg) or sustained intravenous hyperglycemia (150 mg/dl above basal). We conclude that our model of pancreas autotransplantation documents alterations in glucose metabolism which are devoid of the effect of immunosuppression. Glipizide treatment appears to affect fasting sensitivity to insulin, but results in a decrement of insulin response to oral or intravenous glucose challenge.

Selective neurohormonal interactions in islet cell secretion in the isolated perfused human pancreas

To investigate the effects of stimulant interactions on alpha- and beta-cell secretions, the differential effects of gastric inhibitory polypeptide (GIP) and cholinergic stimulation (CS) on insulin (IRI) and glucagon (IRG) release were examined during euglycemic, single-pass perfusion in the isolated human pancreas. Pancreata obtained from 12 cadaver organ donors were perfused for 15-min test periods with (a) 1 nM GIP (b) intrinsic CS via bipolar electrical stimulation (10 V, 5 msec, 10 Hz) of the splanchnic neural fibers during simultaneous perfusion with 4 microM phentolamine and 6 microM propranolol, or (c) GIP and CS. The integrated response of IRI and IRG demonstrated that IRI release was stimulated 308 +/- 52 microU/g-min by GIP, 366 +/- 73 microU/g-min by CS, and 560 +/- 50 microU/g-min by GIP and CS (P less than 0.05). IRG release was stimulated 111 +/- 33 pg/g-min by GIP, 34 +/- 12 pg/g-min by CS, and 90 +/- 36 pg/g-min by GIP and CS. Combined hormonal and cholinergic stimulation was additive for IRI release, but not for IRG release. We conclude that the interaction of neural and hormonal islet cell stimuli is cell-type specific. This may result in selective impairment of hormone release after pancreatic denervation.

Pancreatic structure and glucose tolerance in a longitudinal study of experimental pancreatitis-induced diabetes

Chronic pancreatitis is associated with glucose intolerance and resultant pancreatogenic diabetes. Using the canine pancreatic duct-ligated model of pancreatitis, we serially evaluated pancreatic histology and electron microscopy, tolerance to intravenous and oral glucose, and insulin response to glucose loading. Pancreatic duct ligation caused microscopic evidence of acute pancreatitis at 1 week, progressing to acinar loss and fibrosis consistent with chronic pancreatitis at time periods up to 6 months. The islets of Langerhans showed degranulation early and appeared to be structurally preserved late. Calculated K values indicated a progressive significant deterioration in intravenous glucose tolerance, falling significantly from 3.46 +/- 0.23 basally to 1.51 +/- 0.17 at 6 months after duct ligation (p less than 0.0001). Oral glucose tolerance deteriorated significantly, with the integrated glucose response rising from 23.7 +/- 1.2 g/dl.minute basally to 32.3 +/- 2.8 g/dl.minute at 6 months after duct ligation (p less than 0.05). Integrated insulin response to both intravenous and oral glucose deteriorated with pancreatitis. Pancreatitis-induced glucose intolerance is a consistent feature of this duct-ligated model. Glucose intolerance stabilizes between 4 and 6 months after duct ligation and is associated with pancreatic acinar fibrosis and pancreatic endocrine structural preservation. While the mechanism of altered glucose tolerance may involve mechanical, neural, humoral, or vascular events, our data clearly support the conclusion that pancreatic ductal stenosis with resultant pancreatic fibrosis and chronic pancreatitis is associated with abnormal islet responsiveness leading to circulating insulin deficiency and glucose intolerance, despite histologic and ultrastructural evidence of intact islets of Langerhans.

Effect of glipizide on the surgically altered pancreas

Surgical alterations of the pancreas affect peripheral glucose, insulin, and glucagon levels with accompanying changes in carbohydrate metabolism. The sulfonylurea glipizide has been used to treat insulin-deficient states; however, its mechanism is not completely known. We hypothesized that glipizide would correct postoperative changes in glucose handling in a way that would allow more complete understanding of the drug's action. Two surgical groups (Group 1:80 percent proximal pancreatectomy; Group 2: proximal pancreatectomy plus splenocaval diversion) were compared with a healthy control group (Group 3). We have concluded that glipizide may have affected basal insulin sensitivity in the control group and Group 2 animals without affecting insulin secretion in response to oral or intravenous glucose stimulation. Glipizide does not correct the alterations in glucose handling or insulin secretion after reduction in beta-cell mass.

Pancreas transplantation

The number of pancreas transplants being performed and the success rate have continued to increase. Most pancreas transplants have been placed in diabetic recipients of kidney transplants, but application to nonuremic, non-kidney transplant recipients without end-stage disease is increasing. Drainage of pancreatic graft duct into the bladder allows exocrine function to be assessed directly and has led to earlier diagnosis and treatment of rejection episodes. The improvement in graft survival rates has been associated with the use of cyclosporine in combination with other immunosuppressants. The effect that establishment of a euglycemic state by successful pancreas transplantation has on the specific complications of diabetes is just beginning to be discerned but appears to be favorable if the transplant is performed sufficiently early in the course of the disease.