The spectrum of pancreatic exocrine and endocrine (beta-cell) function in tropical calcific pancreatitis

Fibrocalculous pancreatic diabetes

Fibrocalculous pancreatic diabetes (FCPD) is a unique form of diabetes reported from tropical countries, associated with both endocrine and exocrine disease of the pancreas. The pre-diabetic phase of the disease is called tropical chronic pancreatitis (TCP). Currently FCPD is classified as a secondary form of diabetes called pancreatic diabetes, because essentially the disease is caused by pancreatic damage. There is an overlap of these subjects with idiopathic, non-alcoholic pancreatitis. This review will cover the etiopathogenesis, diagnosis and management of this clinical condition. FCPD could lead to endocrine dysfunction (diabetes and its complications) as well as exocrine dysfunction, and is associated with a higher risk of pancreatic cancer, for which early detection is important.

A comparative study of the clinical profile of fibrocalculous pancreatic diabetes and type 2 diabetes mellitus

AIMS

The present study aimed to compare the clinical characteristics of patients with fibrocalculous pancreatic diabetes (FCPD) and those with type 2 diabetes mellitus (T2DM) to identify the characteristics distinctive of FCPD.

METHODS

A total of 133 patients with FCPD were compared with 665 patients with T2DM matched for duration of diabetes. Biochemical parameters and microvascular and macrovascular complications were assessed in all patients. Multivariate regression analyses were performed to study the determinants of microvascular and macrovascular complications in both groups.

RESULTS

The mean duration of diabetes was 4.42 ± 5.65 years in the FCPD group and 4.51 ± 3.88 years in the T2DM group. FCPD participants were significantly younger at diagnosis and leaner than patients with T2DM. The FCPD group had higher fasting and postprandial glucose and HbA1c levels than the T2DM group. The FCPD group had significantly lower triglyceride, total cholesterol, low-density lipoprotein cholesterol, serum total calcium, hemoglobin, and serum creatinine values than the T2DM group. The prevalence of coronary artery disease, stroke, and retinopathy was significantly higher in the T2DM patients while the prevalence of distal symmetric polyneuropathy was significantly lower. On multivariate logistic regression analysis, duration of diabetes and HbA1c (OR = 1.17, P = 0 0.04) in FCPD patients and age (OR = 1.04, P < 0 0.001), duration of diabetes (OR = 1.17, P < 0 0.001) and HbA1c (OR = 1.28, P < 0.001) in T2DM patients were associated with microvascular complications.

CONCLUSIONS

There are several differences in the phenotype, biochemical parameters, and prevalence of diabetic complications between patients with FCPD and T2DM. Timely diagnosis may have implications in the follow-up and management of patients.

Emerging concepts in the pathogenesis of diabetes in fibrocalculous pancreatic diabetes

Fibrocalcific pancreatic diabetes (FCPD) is a rare form of diabetes affecting people in the tropics and presenting with unique clinical and radiological features. The onset of diabetes usually follows the first few episodes of abdominal pain and develops by the second or third decade of life. Endocrine and exocrine pancreatic insufficiency, brittle glycemic control, and insulin-requiring, ketosis-resistant diabetes are the novel characteristics of FCPD. The etiopathogenetic mechanisms leading to FCPD remain unknown. Although defects in insulin secretion are the major contributors, growing evidence towards a possible role for insulin resistance and body composition abnormalities have added a new dimension to the disease pathogenesis. Deciphering the key pathogenetic mechanisms may have a profound effect on therapeutic strategies in future studies on FCPD.

Genetic aspects of tropical calcific pancreatitis

Tropical calcific pancreatitis (TCP) is a subtype of chronic pancreatitis which is unique to tropical regions. Patients present at young age with recurrent abdominal pain, nutritional deficiencies, and insulin-requiring diabetes. For a long time, the aetiology of this disorder was poorly understood. Several environmental factors, such as malnutrition or the consumption of toxic food components such as cyanogenic glycosides, were proposed as pathogenic factors. In the last decade, a major impact on the understanding of the aetiology of TCP has come from genetic studies on hereditary and idiopathic chronic pancreatitis. Genetic alterations in at least five genetic loci are clearly associated with chronic pancreatitis in the Western world. These include alterations in genes coding for trypsinogens, the most abundant digestive enzymes (PRSS1 and PRSS2), the trypsin inhibitor (SPINK1) and the trypsin-degrading enzyme, chymotrypsinogen C (CTRC). In addition, alterations in the cystic fibrosis (CFTR) gene are associated with idiopathic pancreatitis. TCP clinically resembles non-alcoholic chronic pancreatitis of Western countries, suggesting that similar genetic defects might also be of importance in this disease entity. Indeed, alterations in at least two genes, SPINK1 and CTRC, are strongly associated with TCP. The current review focuses on the recent developments in the understanding of the genetic basis of inherited pancreatitis, with special emphasis on TCP.

Diabetes mellitus in Tropical Chronic Pancreatitis Is Not Just a Secondary Type of Diabetes

AIMS

In chronic calcific pancreatitis of the tropics, etiology and relationship to developing diabetes mellitus are unknown. Some consider these cases a straightforward secondary type of diabetes, while others suggest selective beta-cell impairment. Testing pancreatic function, we investigated whether selective beta-cell impairment triggers diabetes associated with tropical pancreatitis.

METHODS

At a Bangladeshi research institute, 8 chronic tropical pancreatitis and no diabetes mellitus subjects, 14 fibrocalculous pancreatic diabetics and 27 matched healthy controls underwent arginine (endocrine pancreatic function) and secretin (exocrine pancreatic function assessment) stimulation tests.

RESULTS

All patients with clinically-diagnosed, chronic pancreatitis demonstrated pronounced exocrine pancreatic dysfunction with beta-cell functioning differing significantly between the two groups. Compared to controls, patients having tropical pancreatitis and no diabetes showed normal plasma C-peptide values at baseline and after arginine stimulation, while fibrocalculous pancreatic diabetics demonstrated a typical diabetic pattern for plasma C-peptide levels. In contrast, pancreatic alpha-cell functioning (glucagon response to arginine) was preserved in both pancreatitis groups.

CONCLUSION

A preserved pancreatic alpha-cell function in diabetics with advanced chronic pancreatitis of the tropics supports the concept of two different pathogenic mechanisms, one eliciting chronic pancreatitis and the other selective pancreatic beta-cell impairment and subsequent diabetes mellitus.

Tropical chronic pancreatitis

Tropical chronic pancreatitis (TCP) is a juvenile form of chronic calcific non-alcoholic pancreatitis, seen almost exclusively in the developing countries of the tropical world. The classical triad of TCP consists of abdominal pain, steatorrhoea, and diabetes. When diabetes is present, the condition is called fibrocalculous pancreatic diabetes (FCPD) which is thus a later stage of TCP. Some of the distinctive features of TCP are younger age at onset, presence of large intraductal calculi, more aggressive course of the disease, and a high susceptibility to pancreatic cancer. Pancreatic calculi are the hallmark for the diagnosis of TCP and in non-calcific cases ductal dilation on endoscopic retrograde cholangiopancreatography, computed tomography, or ultrasound helps to identify the disease. Diabetes is usually quite severe and of the insulin requiring type, but ketosis is rare. Microvascular complications of diabetes occur as frequently as in type 2 diabetes but macrovascular complications are uncommon. Pancreatic enzyme supplements are used for relief of abdominal pain and reducing the symptoms related to steatorrhoea. Early diagnosis and better control of the endocrine and exocrine dysfunction could help to ensure better survival and improve the prognosis and quality of life of TCP patients.

Tropical calcific pancreatitis: strong association with SPINK1 trypsin inhibitor mutations

BACKGROUND & AIMS

Tropical calcific pancreatitis (TCP) is a chronic pancreatitis unique to developing countries in tropical regions. The cause of TCP is obscure. Whereas environmental factors, such as protein energy malnutrition and ingestion of cassava, have been implicated, a genetic predisposition to the disease also may be important. In the present study we report on mutations in the serine protease inhibitor, Kazal type 1 (SPINK1) gene in north Indian patients with TCP.

METHODS

We studied 66 unrelated TCP patients (44 men, 49 with diabetes, and 6 with family history of TCP), 25 relatives, and 92 healthy control subjects. Samples were analyzed for SPINK1 variants (-53C>T, L14P, N34S, P55S, and 272T>C) and cationic trypsinogen (PRSS1) variants (A16V, K23R, N29I, and R122H) by melting curve analysis.

RESULTS

Twenty-nine patients (44%) carried the N34S missense mutation, of whom 9 (14%) were homozygotes. In contrast, only 2 (2.2%) control subjects were N34S heterozygotes (prevalence ratio 20.2; 95% confidence interval 5.0-81.8; P < 0.0001 vs. TCP). The severity of pancreatitis did not differ between TCP patients with or without N34S, or among those heterozygous or homozygous for N34S. Among TCP patients with or without diabetes, the frequency of N34S carriers (43% vs. 47%) and N34S homozygotes (14% vs. 12%) was similar.

CONCLUSIONS

TCP is highly associated with the SPINK1 N34S mutation. The high prevalence of N34S in TCP patients with and without diabetes suggests that these 2 subtypes have a similar genetic predisposition. The genetic predisposition to TCP resembles, at least in part, the idiopathic chronic pancreatitis found in industrialized countries.

No abnormalities of reg1 alpha and reg1 beta gene associated with diabetes mellitus

In order to investigate whether there would be any association between abnormalities of either reg1 alpha or reg1 beta gene and diabetes mellitus in man, these two genes were analyzed in 42 patients with type 1 diabetes mellitus, 12 with fibrocalculous pancreatopathy, 37 with type 2 diabetes mellitus, and 22 normal controls, by PCR-SSCP analysis and nucleotide sequencing technique. Polymorphism in the reg1 alpha gene resulted in three mobility patterns in the PCR-SSCP analysis, due to nucleotide constituents at position -10 before exon 1 being either C/C, T/C or T/T. These three mobility patterns were observed in every group of subjects. The analysis of reg1 beta gene showed nucleotide substitutions in exon 4 in one patient, exon 5 in another patient with type 1 diabetes, and in exon 4 and intron 5 in one patient with fibrocalculous pancreatopathy. The nucleotide substitutions in exon 4 in the patient with type 1 diabetes and that with fibrocalculous pancreatopathy occurred at codons 103 and 84 while that in exon 5 in the patient with type 1 diabetes occurred at codon 141, changing the codons from CAT to CAC, GTG to GCG, and ACT to AAT and resulting in H103H silent, V84A and T141N missense mutations, respectively. In conclusion, using PCR-SSCP and nucleotide sequence analyses, we did not find any association between abnormalities of either reg1 alpha or reg1 beta gene with any type of diabetes studied.

Type 1 1/2 diabetes: myth or reality?

The disease process in classical Type 1 diabetes patients (IDDM) is believed to be autoimmune. In contrast, the disease process in classical Type 2 diabetes patients (NIDDM) is not autoimmune and a decreased sensitivity to insulin action is the main abnormality. The clinical distinction of Type 1 diabetes versus Type 2 diabetes is recognized to be imperfect and has limitations. There is a group of individuals (Type 1 1/2 diabetes), who present like typical NIDDM, but have some of the immunological and clinical features of IDDM. We review the current medical literature on Type 1 1/2 diabetes with special reference to its clinical characteristics, natural history and pathophysiology. Since the distinction between these two forms of diabetes may have important therapeutic implications especially with regards to the benefits of insulin therapy in patients with Type 1 1/2 diabetes and because of the need for uniformity in its diagnosis we recommend that both clinical plus biochemical criteria (the presence of ICA and/or GAD Ab, HLA typing and tests to quantify beta cell function) be used to make a diagnosis. Comparative studies in the area of cytokine production, T cell reactivity and autoantibody clustering between classic Type 1 diabetes and Type 1 1/2 diabetes patients are needed as are studies with the animal model of Type 1 1/2 diabetes, Psammomys obesus.

Beta-cell function and insulin sensitivity in tropical calcific pancreatitis from north India

Tropical calcific pancreatitis (TCP) is a variant of chronic pancreatitis, occurring only in developing countries. It frequently leads to diabetes at a young age. To determine the pathogenesis of glucose intolerance, beta-cell function and insulin sensitivity were measured in 11 TCP patients with normal glucose tolerance (TCP-NGT), six TCP patients with mild hyperglycemia [TCP-DM] median fasting plasma glucose, 6.1 mmol/L), and 16 healthy control subjects. The technique of continuous infusion of glucose with model assessment (CIGMA) was used to calculate beta-cell function (%B) and insulin sensitivity (%S), based on plasma glucose and insulin levels achieved after an intravenous infusion of glucose. %S was similar in both groups of TCP patients and controls. In contrast, %B was significantly lower in TCP-DM patients (median, 53; interquartile range, 41 to 62) compared with controls (90; 65 to 143; P < .01) and with TCP-NGT patients (119; 91 to 159; P < .01). TCP-NGT and control subjects had similar beta-cell function. Among patients with TCP, %B negatively correlated with the duration of pancreatitis (r = -.63, P < .05). Our results suggest that patients with TCP develop diabetes due to a diminution in beta-cell function, and that insulin resistance does not play a significant role in its pathogenesis.

Islet amyloid in type 2 (non-insulin-dependent) diabetes

Amyloid deposits are found in pancreatic islets of 90% of type 2 (non-insulin-dependent) diabetic subjects at postmortem. Islet amyloid is formed from islet amyloid polypeptide (IAPP). IAPP is a 37 amino acid peptide which is a normal constituent of beta cells and is co-secreted with insulin in animals and in man. The causative factors for fibrillogenesis of IAPP are unclear, but could be related to the sequence of IAPP and abnormal production of the peptide. The lack of islet amyloid in rodent models of diabetes is due to proline substitutions in the amyloidogenic region of IAPP. Amyloid fibrils are deposited between beta cells and islet capillaries: fibrils in invaginations of the plasma membrane may interfere with membrane signalling and insulin release. Amyloid fibrils are formed within 2 days in culture in islets isolated from transgenic mice expressing the gene for human IAPP, but not in vivo. Overexpression and decreased clearance of human IAPP from islet spaces may be important factors. Progressive deposition of IAPP fibrils combined with the associated reduction in the insulin-secreting beta cells is likely to contribute to deterioration of islet function in the course of type 2 diabetes.

The ketosis-resistance in fibro-calculous-pancreatic-diabetes. 1. Clinical observations and endocrine-metabolic measurements during oral glucose tolerance test

We measured circulating levels of C-peptide, pancreatic glucagon, cortisol, growth hormone and metabolites (glucose, non-esterified fatty acids, glycerol and 3-hydroxybutyrate) in fibro-calculous-pancreatic diabetic (FCPD, n = 28), insulin-dependent diabetic (IDDM, n = 28) and non-diabetic control (n = 27) subjects during an oral glucose tolerance test. There was no difference in the two diabetic groups in age (FCPD 24 +/- 2, IDDM 21 +/- 2 years, mean +/- SEM), BMI (FCPD 16.0 +/- 0.6, IDDM 15.7 +/- 0.4 kg/m2), triceps skinfold thickness (FCPD 8 +/- 1, IDDM 7 +/- 1 mm), glycaemic status (fasting plasma glucose, FCPD 12.5 +/- 1.5, IDDM 14.5 +/- 1.2 mmol/l), fasting plasma C-peptide (FCPD 0.13 +/- 0.03, IDDM 0.08 +/- 0.01 nmol/l), peak plasma C-peptide during OGTT (FCPD 0.36 +/- 0.10, IDDM 0.08 +/- 0.03 nmol/l) and fasting plasma glucagon (FCPD 35 +/- 4, IDDM 37 +/- 4 ng/l). FCPD patients, however, showed lower circulating concentrations of non-esterified fatty acids (0.73 +/- 0.11 mmol/l), glycerol (0.11 +/- 0.02 mmol/l) and 3-hydroxybutyrate (0.15 +/- 0.03 mmol/l) compared to IDDM patients (1.13 +/- 0.14, 0.25 +/- 0.05 and 0.29 +/- 0.08 mmol/l, respectively). This could be due to enhanced sensitivity of adipose tissue lipolysis to the suppressive action of circulating insulin and possibly also to insensitivity of hepatic ketogenesis to glucagon. Our results also demonstrate preservation of alpha-cell function in FCPD patients when beta-cell function is severely diminished, suggesting a more selective beta-cell dysfunction or destruction than hitherto believed.