Distribution of Pancreatic Polypeptide–secreting Endocrine Cells in Nondiabetic and Diabetic Cases

Impaired glucose tolerance is associated with enhanced postprandial pancreatic polypeptide secretion

BACKGROUND

The purpose of this study is to compare serum pancreatic polypeptide (PP), insulin, C-peptide, and glucagon in different glucose tolerance stages; analyze the influencing factors of PP secretion; and further explore the role of PP in the pathogenesis of diabetes mellitus.

METHODS

Data were collected from 100 subjects from hospital. According to the results of oral glucose tolerance test (OGTT), the subjects were divided into a normal glucose tolerance (NGT) group, an impaired glucose regulation (IGR) group, and a newly diagnosed type 2 diabetes mellitus (T2DM) group. PP and the related parameters were measured, and the area under the curve (AUC) 120 min after OGTT was calculated. AUC_pp (AUC of PP) was used as the dependent variable and the potentially influencing factors were used as the independent variable for multiple linear regression analysis.

RESULTS

Postprandial 60 min PP in the IGR group was higher than those in the NGT group (2973.80 [±547.49] pg·h/mL vs 2663.55 [±594.89] pg·h/mL, p < 0.05). AUC_pp was significantly higher in the IGR group (428.76 pg·h/mL, 95% confidence interval [CI] [41.06 -816.46], p = 0.031) and newly diagnosed T2DM group (404.35 pg·h/mL, 95% CI [5.37-803.33], p = 0.047) than in the NGT group. AUC_pp was negatively correlated with body mass index (BMI) (r = -0.235, p = 0.038) and positively correlated with postprandial 60 min blood glucose (r = 0.370, p = 0.001) and AUC_bg (AUC of blood glucose) (r = 0.323, p = 0.007). Multiple linear regression analysis indicated that there was a linear correlation between BMI, AUC_bg , and AUC_pp (p = 0.004, p = 0.001), and the regression equation was calculated as: AUC_pp  = 6592.272 + 86.275 × AUC_bg -95.291 × BMI (R²  = 12.7%, p < 0.05).

CONCLUSIONS

Compared with NGT subjects, IGR and T2DM patients have an enhanced postprandial PP secretion. In T2DMs, the secretion of PP is mainly affected by BMI and blood glucose.

Mechanisms of Post-Pancreatitis Diabetes Mellitus and Cystic Fibrosis-Related Diabetes: A Review of Preclinical Studies

Anatomical proximity and functional correlations between the exocrine and endocrine pancreas warrant reciprocal effects between the two parts. Inflammatory diseases of the exocrine pancreas, such as acute or chronic pancreatitis, or the presence of cystic fibrosis disrupt endocrine function, resulting in diabetes of the exocrine pancreas. Although novel mechanisms are being increasingly identified, the intra- and intercellular pathways regulating exocrine-endocrine interactions are still not fully understood, making the development of new and more effective therapies difficult. Therefore, this review sought to accumulate current knowledge regarding the pathogenesis of diabetes in acute and chronic pancreatitis, as well as cystic fibrosis.

GPR120 Regulates Pancreatic Polypeptide Secretion From Male Mouse Islets via PLC-Mediated Calcium Mobilization

The free fatty acid receptor G protein-coupled receptor 120 (GPR120) is expressed in pancreatic islets, but its specific cell distribution and function have not been fully established. In this study, a GPR120-IRES-EGFP knockin (KI) mouse was generated to identify GPR120-expressing cells with enhanced green fluorescence proteins (EGFP). EGFP-positive cells collected from KI mouse islets by flow cytometry had a significantly higher expression of pancreatic polypeptide (PP) evidenced by reverse transcriptase (RT)-quantitative polymerase chain reaction (qPCR). Single-cell RT-PCR and immunocytochemical double staining also demonstrated the coexpression of GPR120 with PP in mouse islets. The GPR120-specific agonist TUG-891 significantly increased plasma PP levels in mice. TUG-891 significantly increased PP levels in islet medium in vitro, which was markedly attenuated by GPR120 small interfering RNA treatment. TUG-891-stimulated PP secretion in islets was fully blocked by pretreatment with YM-254890 (a Gq protein inhibitor), U73122 (a phospholipase C inhibitor), or thapsigargin (an inducer of endoplasmic reticulum Ca2+ depletion), respectively. TUG-891 triggered the increase in intracellular free Ca2+ concentrations ([Ca2+]i) in PP cells, which was also eliminated by YM-254890, U73122, or thapsigargin. GPR120 gene expression was significantly reduced in islets of high-fat diet (HFD)-induced obese mice. TUG-891-stimulated PP secretion was also significantly diminished in vivo and in vitro in HFD-induced obese mice compared with that in normal-chow diet control mice. In summary, this study demonstrated that GPR120 is expressed in mouse islet PP cells and GPR120 activation stimulated PP secretion via the Gq/PLC-Ca2+ signaling pathway in normal-chow diet mice but with diminished effects in HFD-induced obese mice.

Metabolic dysfunction and diabetes mellitus during long-term follow-up of severe acute pancreatitis: A case-matched study

BACKGROUND/OBJECTIVES

Endocrine insufficiency following severe acute pancreatitis (SAP) leads to diabetes of the exocrine pancreas, (type 3c diabetes mellitus), however it is not known how this metabolic phenotype differs from that of type 2 diabetes, or how the two subtypes can be differentiated. We sought to determine the prevalence of diabetes following SAP, and to analyse the behaviour of glucose and pancreatic hormones across a 2-h oral glucose tolerance test (OGTT).

METHODS

Twenty-six patients following SAP (mean (range) duration of first SAP episode to study time of 119.3 (14.8-208.9) months) along with 26 matched controls underwent an OGTT with measurement of glucose, insulin, c-peptide, glucagon and pancreatic polypeptide (PP) at fasting/15/90/120min. Beta-cell area was estimated using the 15min c-peptide/glucose ratio, and insulin resistance (IR) using homeostasis model assessment (HOMA) and oral glucose insulin sensitivity (OGIS) models.

RESULTS

The prevalence of diabetes/prediabetes was 54% following SAP (38.5% newly-diagnosed compared to 19.2% newly-diagnosed controls). Estimated beta-cell area and IR did not differ between groups. AUC c-peptide was lower in SAP versus controls. AUC insulin and AUC c-peptide were lower in SAP patients with diabetes versus controls with diabetes; between-group differences were observed at the 90 and 120 min time-points only. Half of new diabetes cases in SAP patients were only identified at the 120min timepoint.

CONCLUSIONS

Diabetes and pre-diabetes occur frequently following SAP and are difficult to distinguish from type 2 diabetes in controls but are characterised by reduced insulin and c-peptide at later stages of an OGTT. Consistent with this observation, most new post SAP diabetes cases were diagnosed by 2-h glucose levels only.

Diabetes mellitus secondary to pancreatic diseases (type 3c): The effect of smoking on the exocrine-endocrine interactions of the pancreas

The present study was conducted to ascertain how cigarette smoke affects the exocrine-endocrine interactions of the human pancreas with diabetes mellitus secondary to pancreatic diseases (type 3c). Blood has been collected from smoking and non-smoking healthy individuals as well as from patients with diagnosed chronic pancreatitis and diabetes type 3c. The concentrations of interleukin-6, endothelin-1 and insulin in the plasma were determined by enzyme-linked immunosorbent assay (ELISA) tests. The activities of amylase and lipase in the serum, as well as the lipid profile, creatinine, uric acid and urea concentrations, were measured using colorimetric methods. Samples of normal pancreatic tissue and chronic pancreatitis were verified histopathologically and then interleukin-6, endothelin-1, insulin and glucagon were localized by immunohistochemical staining using a monoclonal anti-human antibody. The highest levels of interleukin-6 and endothelin-1 and the lowest levels of insulin and glucagon intensity from the immunostaining were observed in smoking patients with diabetes. In all smoking patients with pancreatitis and diabetes, there was a significant elevation in interleukin-6 and endothelin-1 concentration and amylase and lipase activities, hyperlipidaemia and a lower value of estimated glomerular filtration rate and blood urea nitrogen when compared to non-smokers. Our study confirmed that smoking exerts a pro-inflammatory effect and disturbs the exocrine-endocrine interactions of the pancreas.