Beta Cell Function
The ability of pancreatic beta cells to produce and secrete insulin in response to glucose. Progressive beta cell decline is the hallmark of type 2 diabetes. GLP-1 receptor agonists may preserve beta cell function by reducing glucose toxicity and stimulating beta cell proliferation, though long-term effects are still being studied.
Technical Context
Beta cell function is assessed by: HOMA-B (fasting insulin and glucose — steady-state index), C-peptide measurement (co-secreted with insulin 1:1 but not extracted by liver — better reflection of insulin secretion than insulin levels), glucose-stimulated insulin secretion (GSIS — insulin response to IV or oral glucose challenge), disposition index (insulin secretion adjusted for insulin sensitivity — the most physiologically meaningful measure), and proinsulin:insulin ratio (elevated in beta cell dysfunction). In T2D, beta cell mass and function progressively decline — at diagnosis, approximately 50% of functional beta cell mass is already lost. GLP-1 RAs may preserve beta cell function through: reducing glucotoxicity and lipotoxicity (improving the metabolic environment), stimulating beta cell proliferation and inhibiting apoptosis (demonstrated in rodent models — human relevance debated), and promoting insulin gene expression and proinsulin processing.