Role of Pancreatic Exocrine Secretion in Weight Gain After Pancreas Transplantation

Pancreas transplantation is currently the most reliable method for glycemic control in insulin dependent diabetic patients. Outcomes of pancreas transplantation have improved significantly over the years due to improved surgical techniques, medical management and immunosuppression. However, weight gain after pancreas transplantation remains a common problem with associated consequences such as development of type 2 diabetes, coronary artery disease, graft loss, metabolic syndrome and increased risk of cardiovascular death. Excessive weight gain is well known after liver and kidney transplantation; however there are very few studies that have looked at weight gain after pancreas transplantation. In a recent study by Knight et al, 26% of the pancreas transplant recipients had excessive weight gain, defined as more than 30% of their baseline weight by 1-year post transplant. The study focused mainly on the endocrine function of the pancreas, explaining that excessive peripheral insulin circulation post-transplant may explain the weight gain. Other factors like immunosuppression, increased oral intake and potentially reduced activity may also have played a role. However no study has looked at the possible role of exocrine secretion from the new pancreatic allograft, combined with exocrine secretion of the old pancreas, leading to excessive availability of digestive juices like trypsin, chymotrypsin, lipase, amylase, gelatinase, elastase etc. Our hypothesis is that the excessive weight gain after pancreas transplant, which is more than in other solid organ transplants, is driven by the excessive digestive juice leading to improved conversion of available food and nutrient into storable energy and subsequently leading to weight gain. The patient will therefore need to either increase physical activity to avoid weight gain post-transplant or significantly reduce caloric intake. Fecal elastase test (FE-1)-elastase is a proteolytic enzyme produced by pancreatic acinar cells. They bind to bile salt and pass through the gut without degradation. These levels correlate well with the other pancreatic enzyme levels. Fecal elastase concentration (FEC) has been used routinely to screen for pancreatic exocrine insufficiency (PEI). Exocrine pancreatic juice has been a target for the management of obesity lately, with the use of drugs like Orlistat (Xenical) that inhibits pancreatic lipase and therefore interfere with the absorption of fat. If our theory of excessive pancreatic juice availability after pancreas transplant can be proven, it can help guide the targeted use and appropriate dosing of such drugs based on the level of the pancreatic juice as measured by the FEC.