TYPE 3 AUTOIMMUNE PANCREATITIS: CLINICAL PROFILE AND RESPONSE TO STEROIDS

Diabetes mellitus (DM) and prediabetes are common complications of acute pancreatitis (AP) and have aroused general concern in recent years. The underlying mechanisms need to be addressed. Dedifferentiation of β cells has been proposed as an important factor accounting for type 2 diabetes, but has not been studied in AP yet. Notch signaling is a relatively conservative pathway which regulates the differentiation of pancreatic lineages during embryogenesis, and studies have shown a detrimental role of persistent high Notch activity in β cell identity and function in adult pancreas. In our previous study, we found an unregulated Notch activity in the exocrine and endocrine pancreas of AP mice. We hypothesize that β cell dedifferentiation due to excessive Notch activity in injured pancreas may account for prediabetes and DM following AP.
Objective: The aim of this project was to 1) Explore the existence of β cell dedifferentiation in pancreas of acute necrotizing pancreatitis (ANP) patients and AP mice; 2) Investigate the role of Notch activity in β cell dedifferentiation and endocrine function following AP.
Materials and methods: The pancreatic tissues from ANP patients were obtained for analyses. The murine AP model was induced by six hourly intraperitoneal injection of cerulein (100 μg/kg) dissolved in 0.9% saline for 4 days. Control mice received saline instead. In Notch activation group, Hes1-encoding adeno-associated viruses (AAV) of serotype 8 (AAV8-Hes1) were used to transfect the mice 3 weeks before AP model establishment. In Notch inhibition group, DAPT (50 mg/kg) was administered after last cerulein injection for consecutive 7 days. Intraperitoneal glucose tolerance test were performed at 7, 15 and 30 days post AP model establishment. Mice pancreases were harvested at indicated time points for subsequent analyses.
Results: Pancreatic specimens from ANP patients showed increased β cell dedifferentiation (Aldh1a3+ cells) compared with control pancreas. Upregulated Notch activity in both exocrine pancreas and islets were noticed as indicated by increased Hes1 expression. AP mice showed impaired glucose tolerance compared to control mice. The pancreases of AP mice showed increased Notch activity in both exocrine pancreas and islets compared with control mice, together with increased expression of β cell dedifferentiation markers, Ngn3 and Aldh1a3, and decreased β cell markers, Mafa, Nkx6.1, and Nkx2.2. The Hes1 overexpression in AP mice resulted in even worse glucose tolerance and increased β cell dedifferentiation, while Notch inhibition in AP mice with DAPT led to improved glucose tolerance and decreased β cell dedifferentiation.
Conclusion: β cell dedifferentiation accounts for impaired glucose tolerance following AP. Inhibition of Notch activity reduces β cell dedifferentiation and mitigates glucose intolerance after AP.

Background: Type 3 autoimmune pancreatitis (AIP) is a chronic inflammatory disorder of the pancreas caused by heightened immune activity triggered by immune checkpoint inhibitor therapy (ICI-Rx) employed for advanced malignancies. We describe the clinico-radiological spectrum and response to steroids in type 3 AIP.
Methods: We retrospectively performed a detailed clinical and radiological review of the 248/11,165 (2.2%) adult patients receiving ICI-Rx who developed type 3 AIP (>3-fold serum lipase elevation + pain, absent other etiologies). 110/248 had a normal computerized tomography scan (CT) of the pancreas at the time of first lipase elevation. We selected 48 of these patients that had serial pancreas volumetry before and after onset of type 3 AIP. We examined the impact of steroids on pain and the disease course.
Results: A majority of patients with type 3 AIP are Caucasian women in the seventh decade of life with exposure to PD-1/L1 blockade. Genitourinary cancer is the most common cancer type. At onset, type 3 AIP was asymptomatic in 154 (62%) and painful in 94 (38%). (Table 1) CT showed a mild, acute interstitial pancreatitis in a minority 27/110 (24.5%), less so in asymptomatic patients (8% vs 24%, p=0.01). 1 yr after pancreatitis both groups showed pancreatic volume loss, even when CT at the time of initial injury was normal (figure1). Steroids were given for pain (n=44). In ~80%, the pain lasted a short duration (<14 days) and was mild (visual analog score <3 in 62%) regardless of steroid use. (Table 1) Biochemically, a minority achieved complete and persistent biochemical resolution, more often when ICI-Rx was held (32/89) vs no intervention (13/84, p.003) or vs steroid treatment alone (2/23, p=.01); relapses occurred equally frequently regardless of intervention. Steroids did not impact pancreas volume loss (figure1) or occurrence of diabetes 1-year post-pancreatitis. None of these patients developed pancreatic calcifications.
Conclusions: Type 3 AIP is a unique form of pancreatitis that causes a rapid pancreatic volume loss despite the lack of pain or pancreatitis on CT at onset. Immunosuppression with systemic steroids do not alter the disease progression of this form of chronic pancreatic injury.