Distribution of Prohormone Convertase-6 Expression in the Gastrointestinal Tract and Effects of a Fasting-Refeeding Regimen and a High-Fat Diet on Ileal Prohormone Convertase-6 Expression

Preforms of gastrointestinal peptide hormones and neuropeptides are processed, in part, by prohormone convertases (PCs) to mature, biologically active peptides. The purpose of this study was to characterize the mRNA levels of PC-6 isoforms, PC-6A and PC-6B, in the gastrointestinal tract and pancreas of the rat, and to investigate the effects of a fasting and refeeding regimen, and a high-fat diet on ileal PC-6A expression. PC-6A mRNA is expressed throughout the entire gastrointestinal tract with the highest levels in the small intestine. Multiple-sized transcripts are present. PC-6B mRNA is expressed in the antrum and fundus of the stomach, in the small intestine, and colon. Ileal PC-6A mRNA expression increases significantly with fasting and then declines with refeeding toward control levels. Increased dietary fat increases PC-6A mRNA levels in the ileum. Since PC-6 is found throughout the entire gastrointestinal tract, it is likely that PC-6 participates in the processing of proforms of gastrointestinal peptides. The two isoforms of PC-6 have different patterns of distribution in the gastrointestinal tract and pancreas, suggesting that they process proforms of different gut peptides.