Functional Assessment of Pancreatic β-Cell Area in Humans

OBJECTIVE β-Cell mass declines progressively during the course of diabetes, and various antidiabetic treatment regimens have been suggested to modulate β-cell mass. However, imaging methods allowing the monitoring of changes in β-cell mass in vivo have not yet become available. We address whether pancreatic β-cell area can be assessed by functional test of insulin secretion in humans. RESEARCH DESIGN AND METHODS A total of 33 patients with chronic pancreatitis (n = 17), benign pancreatic adenomas (n = 13), and tumors of the ampulla of Vater (n = 3) at various stages of glucose tolerance were examined with an oral glucose load before undergoing pancreatic surgery. Indexes of insulin secretion were calculated and compared with the fractional β-cell area of the pancreas. RESULTS β-Cell area was related to fasting glucose concentrations in an inverse linear fashion (r = −0.53, P = 0.0014) and to 120-min postchallenge glycemia in an inverse exponential fashion (r = −0.89). β-Cell area was best predicted by a C-peptide–to–glucose ratio determined 15 min after the glucose drink (r = 0.72, P < 0.0001). However, a fasting C-peptide–to–glucose ratio already yielded a reasonably close correlation (r = 0.63, P < 0.0001). Homeostasis model assessment (HOMA) β-cell function was unrelated to β-cell area. CONCLUSIONS Glucose control is closely related to pancreatic β-cell area in humans. A C-peptide–to–glucose ratio after oral glucose ingestion appears to better predict β-cell area than fasting measures, such as the HOMA index.