Peripancreatic fat necrosis worsens acute pancreatitis independent of pancreatic necrosis via unsaturated fatty acids increased in human pancreatic necrosis collections

Abstract

Background and aims Peripancreatic fat necrosis occurs frequently in necrotising pancreatitis. Distinguishing markers from mediators of severe acute pancreatitis (SAP) is important since targeting mediators may improve outcomes. We evaluated potential agents in human pancreatic necrotic collections (NCs), pseudocysts (PCs) and pancreatic cystic neoplasms and used pancreatic acini, peripheral blood mononuclear cells (PBMC) and an acute pancreatitis (AP) model to determine SAP mediators. Methods We measured acinar and PBMC injury induced by agents increased in NCs and PCs. Outcomes of caerulein pancreatitis were studied in lean rats coadministered interleukin (IL)-1β and keratinocyte chemoattractant/growth-regulated oncogene, triolein alone or with the lipase inhibitor orlistat. Results NCs had higher fatty acids, IL-8 and IL-1β versus other fluids. Lipolysis of unsaturated triglyceride and resulting unsaturated fatty acids (UFA) oleic and linoleic acids induced necro-apoptosis at less than half the concentration in NCs but other agents did not do so at more than two times these concentrations. Cytokine coadministration resulted in higher pancreatic and lung inflammation than caerulein alone, but only triolein coadministration caused peripancreatic fat stranding, higher cytokines, UFAs, multisystem organ failure (MSOF) and mortality in 97% animals, which were prevented by orlistat. Conclusions UFAs, IL-1β and IL-8 are elevated in NCs. However, UFAs generated via peripancreatic fat lipolysis causes worse inflammation and MSOF, converting mild AP to SAP.

Fatty Acid Ethyl Esters Are Less Toxic Than Their Parent Fatty Acids Generated during Acute Pancreatitis

“…As previously published, we noted maximal Ca i increase at 600 mmol/L, which is in the range noted in human pancreatic necrosis collections. 11,32 Consistent with the loss of Jm being associated with triggering cell death, there was a greater increase in the 530/590 emission ratio of JC-1 induced by LA and OA than by LAEE or OAEE (Figure 2, A and B) at equal concentrations. Similarly, LA and OA (Figure 2, C and D) did cause an increase in Ca i , but LAEE and OAEE did not.…”

“…11,12,32 This partly explains the high levels of FAEEs noted in the tissues of alcoholics without pancreatitis and why only a minority of alcoholics may develop pancreatitis 53,54 despite high FAEEs in the pancreas. In contrast, lipolytic FA generation universally exacerbates pancreatitis to a lethal disease in the mechanistically distinct IL-12/IL-18, 11 biliary, 12 rat, 32 and mouse 55 caerulein models. 11,12 Ethanol has diverse effects on AP outcomes in rodents.…”

“…The human necrotic fluid collections contained 1235 AE 412 mmol/L OA, 613 AE 214 mmol/L PA, and 586 AE 185 mmol/L LA. 32 Necrotic cell injury was assessed by LDH leakage, propidium iodide (PI) uptake (both as percentage of total), and adenosine triphosphate (ATP) levels of the pellets at the end of the incubation (4 hours). These were performed with colorimetric, fluorescence, or luminescence assay as described previously.…”

“…To determine the relative toxicities of FAEEs and the parent NEFAs, 300 mmol/L of the most prevalent NEFAs in the human pancreatic necrosis collections 11,20,32 were added at relevant concentrations to acinar cells, and LDH leakage was measured over 4 hours ( Figure 1A). These NEFA concentrations used are within the range of those noted in human pancreatic necrosis collections.…”

“…These NEFA concentrations used are within the range of those noted in human pancreatic necrosis collections. 11,12,32 Although both UFAs (LA and OA) resulted in >50% LDH leakage, their respective EEs (LAEE and OAEE) resulted in significantly less acinar injury. Because UFAs are known to eventually induce acinar necrosis, 11e13 we measured PI uptake and noted a similar pattern ( Figure 1B).…”