Pancreatic immunoreactive somatostatin and diabetes mellitus

Structure and function of the exocrine pancreas in patients with type 1 diabetes

In the last 10 years, several studies have shown that the pancreas of patients with type 1 diabetes (T1D), and even of subjects at risk for T1D, was smaller than the pancreas from healthy subjects. This arose the question of the relationships between the endocrine and exocrine parts of the pancreas in T1D pathogenesis. Our review underlines that histological anomalies of the exocrine pancreas are common in patients with T1D: intralobular and interacinar fibrosis, acinar atrophy, fatty infiltration, leucocytic infiltration, and pancreatic arteriosclerosis are all frequent observations. Moreover, 25% to 75% of adult patients with T1D present with pancreatic exocrine dysfunction. Our review summarizes the putative causal factors for these structural and functional anomalies, including: 1/ alterations of insulin, glucagon, somatostatin and pancreatic polypeptide secretion, 2/ global pancreatic inflammation 3/ autoimmunity targeting the exocrine pancreas, 4/ vascular and neural abnormalities, and 5/ the putative involvement of pancreatic stellate cells. These observations have also given rise to new theories on T1D: the primary event of T1D pathogenesis could be non-specific, e.g bacterial or viral or chemical, resulting in global pancreatic inflammation, which in turn could cause beta-cell predominant destruction by the immune system. Finally, this review emphasizes that it is advisable to evaluate pancreatic exocrine function in patients with T1D presenting with gastro-intestinal complaints, as a clinical trial has shown that pancreatic enzymes replacement therapy can reduce the frequency of hypoglycemia and thus might improve quality of life in subjects with T1D and exocrine failure.

Amelioration of hypoglycemia via somatostatin receptor type 2 antagonism in recurrently hypoglycemic diabetic rats

Selective antagonism of somatostatin receptor type 2 (SSTR2) normalizes glucagon and corticosterone responses to hypoglycemic clamp in diabetic rats. The purpose of this study was to determine whether SSTR2 antagonism (SSTR2a) ameliorates hypoglycemia in response to overinsulinization in diabetic rats previously exposed to recurrent hypoglycemia. Streptozotocin diabetic rats (n = 19), previously subjected to five hypoglycemia events over 3 days, received an insulin bolus (10 units/kg i.v.) plus insulin infusion (50 mU/kg/min i.v.) until hypoglycemia ensued (≤3.9 mmol/L) (experimental day 1 [Expt-D1]). The next day (Expt-D2), rats were allocated to receive either placebo treatment (n = 7) or SSTR2a infusion (3,000 nmol/kg/min i.v., n = 12) 60 min prior to the same insulin regimen. On Expt-D1, all rats developed hypoglycemia by ∼90 min, while on Expt-D2, hypoglycemia was attenuated with SSTR2a treatment (nadir = 3.7 ± 0.3 vs. 2.7 ± 0.3 mmol/L in SSTR2a and controls, P < 0.01). Glucagon response to hypoglycemia on Expt-D2 deteriorated by 20-fold in the placebo group (P < 0.001) but improved in the SSTR2a group (threefold increase in area under the curve [AUC], P < 0.001). Corticosterone response deteriorated in the placebo-treated rats on Expt-D2 but increased twofold in the SSTR2a group. Catecholamine responses were not affected by SSTR2a. Thus, SSTR2 antagonism after recurrent hypoglycemia improves the glucagon and corticosterone responses and largely ameliorates insulin-induced hypoglycemia in diabetic rats.

Pancreatic exocrine dysfunction in maturity-onset diabetes of the young type 3

OBJECTIVE

Exocrine pancreas dysfunction is seen in 10-30% of patients with type 1 and 2 diabetes. We have recently identified a syndrome of diabetes and exocrine pancreas dysfunction attributable to mutations in the carboxyl ester lipase (CEL) gene. We wanted to investigate the prevalence of pancreatic exocrine dysfunction in patients with maturity-onset diabetes of the young type 3 (MODY3).

RESEARCH DESIGN AND METHODS

All 119 patients with MODY3 in the Norwegian MODY Registry were invited to participate, and 70 (60.5%) responded, among whom 63 were adults. Control groups included 140 subjects with type 1 diabetes and 78 nondiabetic control subjects. Pancreatic dysfunction was defined by fecal elastase deficiency. Fecal fat excretion was measured in 25 patients with fecal elastase deficiency. CEL was investigated for sequence changes.

RESULTS

We found a prevalence of fecal elastase deficiency of 12.7% in adult patients with MODY3, compared with 18.6% in patients with type 1 diabetes and 3.8% in nondiabetic control subjects. The six patients with MODY3 with fecal elastase deficiency available for analysis all had increased fecal fat excretion. Fecal elastase decreased with age. Controlled for age, patients with MODY3 still had decreased fecal elastase compared with control subjects. Twelve of 70 patients (17%) had single-base insertions in CEL exon 11. Two of these had fecal elastase deficiency.

CONCLUSIONS

The prevalence of pancreatic exocrine dysfunction was 12.7% in a cohort of 63 adult patients with MODY3, similar to the prevalence among type 1 diabetic patients. Fecal fat excretion was increased in all patients with MODY3 with fecal elastase deficiency who were investigated, underscoring the potential clinical importance of the exocrine dysfunction.

Screening for pancreatic exocrine insufficiency in patients with diabetes mellitus

OBJECTIVES

Fecal elastase 1 (E1) is a relatively sensitive and specific indirect test of pancreatic exocrine function. Despite the high functional reserve of the pancreas, it is recognized that a significant proportion of diabetic patients may also have a deficit of the exocrine function. The aim of this study was to screen patients with diabetes mellitus (DM) for pancreatic exocrine insufficiency.

METHODS

A total of 80 patients were enrolled in this prospective study, including 42 patients with DM and 38 nondiabetic controls. Exclusion criteria were as follows: age >75 yr; alcohol intake >40 g/day; intake of orlistat or acarbose; and history of diarrhea, pancreatitis, GI surgery, immunodeficiency, or cancer. All patients underwent the same study protocol, which included clinical evaluation, determination of fecal E1, plain x-rays of the abdomen, and abdominal ultrasound. An immunoenzymatic method (ScheBoTech, Wettenburg, Germany) was used for E1 determination. Diagnosis of pancreatic insufficiency was established for a fecal E1 <200 microg/g.

RESULTS

The DM and control groups were comparable regarding age (62 +/- 10 yr vs 56 +/- 10 yr), sex (18 men and 24 women vs 15 men and 23 women), and proportion of patients with excess weight (50% vs 42%). Patients had DM diagnosed for 11.5 +/- 8 yr, with structural changes of the pancreas detected on ultrasound in three cases and calcifications in one case. There was no relationship between E1 determination <200 microg/g and the duration or the type of therapy for DM. Fifteen patients (36%) in the DM group had a fecal E1 <200 microg/g, compared with two patients (5%) in the control group (p < 0.05). In the DM group (n = 42), 11 patients with excess weight presented a fecal E1 <200 microg/g, whereas four patients with a BMI <25 presented this result (p < 0.05).

CONCLUSIONS

Pancreatic exocrine insufficiency occurs more frequently in diabetic patients than in controls. Diabetic individuals with excess weight (BMI >25) may be at increased risk for underlying exocrine pancreatic insufficiency.

Dietary sugars and carbohydrate metabolism in type II diabetes

Diabetes, the most common metabolic disease, is responsible for the deaths of over 300,000 Americans annually. The incidence of the disease increases with age and since the U.S. population is graying, prevalence is also increasing. Obesity and family history are strong predictors of diabetes. The etiology of Type II diabetes is heterogeneous. The hyperglycemia of Type II diabetes can result from a variety of metabolic defects including impaired beta cell secretion, receptor deficiencies, or abnormal hepatic production or uptake of glucose. Other glucoregulatory hormones such as glucagon, growth hormone, cortisol, thyroid hormones, somatostatin, and gastric inhibitory polypeptide may contribute to the aberrations of carbohydrate metabolism. Environmental factors including stress, diet, and exercise may also contribute to the disease. Since most diabetics are obese, weight loss should be the first priority in improving status. A variety of diet and exercise regimens may help achieve this goal or even improve glucose control without weight loss. Due to the heterogeneity of the disease individualized treatment must be used to improve status of patients with the various metabolic defects of Type II diabetes.