The initial overall question to be tested by the collaborative of the Peter Butler laboratory at UCLA and the Mark Atkinson laboratory in Florida was to explore the possibility that the recently described pancreatic duct gland (PDG) compartment of the pancreas might serve as the elusive pancreatic stem cell niche, potentially offering an avenue to promote beta cell regeneration. Both laboratories had previously noted the presence of pancreatic beta cells in long standing type 1 diabetes mellitus (T1DM) and had been interested in the possibility that these were derived from beta cell regeneration rather than simply reflecting beta cell survivors.

The initial studies focused on quantification of the PDG compartment in T1DM with comparison to type 2 diabetes mellitus (T2DM) and non-diabetic controls. Since the primary interest in the PDGs was as a potential source of endocrine cells, we also examined the nPOD immunostained sections for insulin and glucagon to evaluate if the PDGs did indeed contain insulin or glucagon staining cells. During this process it was noted that there some of the nPOD sections had markedly expanded glucagon staining compared to normal controls. Further examination of the possible explanation of this led to the observation that the increased glucagon staining was most prominent in the group of individuals with T2DM treated with GLP-1 based therapy prior to their demise.

Following communication between the collaborating laboratories in Florida and Los Angeles, it became apparent that we had a responsibility to further delineate the unexpected differences between the pancreases of individuals with T2DM treated by GLP-1 based therapy and other therapies. The need for this was further heightened by the finding by the University of Florida group of neuroendocrine tumors expressing glucagon in GLP-1 treated T2DM patients. Further studies by an experienced pancreatic pathologist at UCLA raised concern that there was increased pancreatic dysplasia in the pancreases, and data from nPOD revealed increased overall pancreas replication (by Ki67) and expanded pancreas size. A question arose as to how best to make these observations known. It was decided that it would be preferable to include all the findings that seemed relevant to these observations in a peer-reviewed paper as well as to inform the domestic regulatory agency in charge of drug safety (i.e., the Food and Drug Administration – FDA). After months of rigorous peer review, the work saw publication in May of 2013 in the journal Diabetes. In addition, following notification, the FDA posted a Drug Safety Communication in March 2013 noting that a group studying pancreatic pathology had suggested an increased risk of pancreatitis and pre-cancerous cellular changes in patients with type 2 diabetes treated with incretin mimetics.; however, the FDA could not reach any new conclusions about safety risks of incretin mimetic drugs. A vigorous response was seen from interested pharmaceutical interests including broad based subpoenas to multiple individuals at UCLA. The current work in relation to the nPOD studies is now focused largely on repeating various aspects of the study (e.g., glucagon immunostaining originally preformed by nPOD at the University of Florida now being repeated at UCLA) to establish to what extent the criticism of the studies is valid (in which case the authors will acknowledge this) or if not, then respond with additional findings. Since the initial FDA statement, they have subsequently published a follow up finding together with EMA (European Medicines Agency) in February 2014 in the New England Journal of Medicine. These agencies concluded that, based on current data, a causal association between incretin-based drugs and pancreatitis or pancreatic cancer could not be drawn.

In this regard the University of Florida group is now preparing a publication for peer review supporting the notion that the pancreas mass is indeed increased in individuals treated with GLP-1 based therapy. Moreover, the expansion is most apparent in the head of the pancreas, the region most vulnerable to pancreatic dysplasia.

The ongoing UCLA based studies to re-evaluate the alpha cell hyperplasia in GLP-1 treated individuals previously reported from the nPOD immune staining, has agreed with the conclusion of the prior analysis, that there is alpha cell hyperplasia in the incretin treated cases.

Once the issues of criticism in regards the prior study have been addressed the plan is to revert to the originally intended focus, specifically on the PDG compartment as a potential source of endocrine cell formation in humans.