CPT1A and pancreatic insulinoma: In contrast to previous studies performed using in vitro model systems (e.g., perfused pancreata and insulinoma cell lines) that showed an enhancement of GSIS upon inhibition of CPT1 activity (6, 7, 8), we found that male mice with Cpt1a deletion in both exocrine and endocrine tissue were glucose intolerant with reduced GSIS.