Functional Assessment of Pancreatic β-Cell Area in Humans

Objective: Beta-cell mass declines progressively during the course of diabetes, and various antidiabetic treatment regimens have been suggested to modulate beta-cell mass. However, imaging methods allowing to monitor changes in beta-cell mass in vivo have not yet become available. We addressed whether pancreatic beta-cell area can be assessed by functional test of insulin secretion in humans. Research design and methods: 33 patients with chronic pancreatitis (n = 17), benign pancreatic adenomas (n = 13), and tumours of the ampulla of Vater (n = 3) at various stages of glucose tolerance were examined with an oral glucose load prior to undergoing pancreatic surgery. Indices of insulin secretion were calculated and compared to the fractional beta-cell area of the pancreas. Results: Beta-cell area was related to fasting glucose concentrations in an inverse linear fashion (r = −0.53, p = 0.0014), and to 120 min post-challenge glycaemia in an inverse exponential fashion (r = −0.89). Beta-cell area was best predicted by a C-peptide/glucose ratio determined 15 min after the glucose drink (r = 0.72, p < 0.0001). However, a fasting C-peptide/glucose ratio already yielded a reasonably close correlation (r = 0.63, p < 0.0001). HOMA beta-cell function was unrelated to beta-cell area. Conclusions: Glucose control is closely related to pancreatic beta-cell area in humans. A C-peptide/glucose ratio after oral glucose ingestion appears to better predict beta-cell area than fasting measures, such as the HOMA index.