Insulin secretion in IDDM patients who have undergone successful pancreas-kidney transplantation

An empirical index of insulin sensitivity from short IVGTT: validation against the minimal model and glucose clamp indices in patients with different clinical characteristics

AIMS/HYPOTHESIS

Minimal model analysis for insulin sensitivity has been validated against the glucose clamp and is an accepted method for estimating insulin sensitivity from IVGTT. However minimal model analysis requires a 3 h test and relevant expertise to run the mathematical model. The aim of this study was to suggest a simple predictor of minimal model analysis index using only 1 h IVGTT.

METHODS

We studied participants with different clinical characteristics who underwent 3 h regular (n = 336) or insulin-modified (n = 160) IVGTT, or 1 h IVGTT and euglycaemic-hyperinsulinaemic clamp (n = 247). Measures of insulin sensitivity were insulin sensitivity index estimated by minimal model analysis (S(I)) and the mean glucose infusion rate (clamp) (M). A calculated S(I) (CS(I)) predictor, CS(I) = Alpha X K(G)/(DeltaAUC(INS)/T), was suggested, based on the calculation of the rate of glucose disappearance K(G) and the suprabasal AUC of insulin concentration DeltaAUC(INS) over T = 40 min. For all the participants, alpha was assumed equal to the regression line slope between K(G)/(DeltaAUC(INS)/T) and S(I) in control participants.

RESULTS

CS(I) and S(I) showed high correlation (R(2) = 0.68-0.96) and regression line slopes of approximately one in the majority of groups. CS(I) tended to overestimate S(I) in type 2 diabetic participants, but results were more reliable when CS(I) was computed with insulin-modified rather than regular IVGTT. CS(I) showed behaviours similar to S(I) as regards relationships with BMI, acute insulin response and sex. CS(I) showed good correlation with M (R(2) = 0.82).

CONCLUSIONS/INTERPRETATION

A short test can achieve a good approximation of minimal model analysis and clamp insulin sensitivity. The importance of a method such as CS(I) is that it allows analysis of IVGTT datasets with samples limited to 1 h.

[Hereditary pancreatic cancer]

An inherited predisposition to pancreatic cancer (PC) is prevalent in about 3% of PC cases and is currently believed to occur in three distinct clinical settings, (1) hereditary tumour predisposition syndromes with an increased risk of PC such as Peutz-Jeghers syndrome and familial atypical multiple mole melanoma, (2) hereditary pancreatitis and cystic fibrosis, in which genetically determined early-age changes of the pancreas can predispose to the development of PC, and (3) familial pancreatic cancer syndrome (FPC). According to a recent consensus conference, high-risk individuals from PC-prone families should be enrolled in board-approved, prospective, controlled screening programs at expert centres. Based on the available data, prophylactic pancreatectomy is not indicated, since the underlying causative gene defect of the FPC syndrome is still unknown and the penetrance of PC in other tumour predisposition syndromes is either low or yet undetermined. In case of the diagnosis of a PC or high-grade precursor lesions, a prophylactic extension of the resection can be considered, since patients with hereditary PC often develop multifocal pancreatic lesions.

Prophylaktische Chirurgie des Pankreas

The goal of prophylactic surgery is to prevent malignant growth in patients with hereditary tumor predisposition. The pancreas presents as particularly challenging, due to the difficulty of operation and comparatively high risk of morbidity and even mortality. In addition, partial operative procedures and, more significantly, total resection lead to exocrine pancreas insufficiency and secondary diabetes, with grave consequences for the patient. Hereditary tumor predisposition syndromes that can result in pancreaticoduodenal endocrine tumors (PET) include multiple endocrine neoplasia type 1 syndrome and von Hippel-Lindau syndrome. As penetrance is maximally 70-80% and the 10-year survival rate over 80%, prophylactic pancreatic resection without evidence of a tumor is not indicated. However, prophylactic extension of a resection would be advised, should a PET be diagnosed. Patients predisposed to developing ductal pancreatic carcinoma (PC) are at risk of familial pancreatic cancer syndrome (FPC), hereditary pancreatitis, and other hereditary tumor predisposition syndromes such as Peutz-Jeghers syndrome and familial atypical multiple mole-melanoma syndrome. As the gene defect responsible for FPC has yet to be identified and the penetrance of PC in the other tumor predisposition syndromes is low or unknown, a prophylactic pancreatectomy based on today's knowledge is not indicated. Prophylactic extension of the resection is advisable should PC or high-grade PanIN lesions be diagnosed, as these patients often present with multifocal dysplasia and even carcinoma.