Prospective observational study and mechanistic evidence showing lipolysis of circulating triglycerides worsens hypertriglyceridemic acute pancreatitis.

Background: While most hypertriglyceridemia is asymptomatic, hypertriglyceridemia-associated acute pancreatitis (HTG-AP) can be more severe than other AP etiologies. The reasons underlying this are unclear. We thus studied whether lipolytic generation of non-esterified fatty acids (NEFA) from circulating triglycerides (TGs) could worsen clinical outcomes.

Methods: Admission serum TGs, NEFA compositions and concentrations were analyzed prospectively in 269 patients with AP. These and demographics, clinical outcomes were compared between HTGAP (TGs >500mg/dL; American Heart Association 2018 guidelines) and other AP etiologies. Serum NEFAs were correlated with the serum triglyceride fatty acids (TGFAs) alone, and with the product of TGFA x serum lipase (NEFA-TGFA x lipase). Studies in mice, rats were done to understand the role of HTG lipolysis in organ failure and to interpret the NEFA-TGFA correlations.

Results: HTG-AP patients had higher serum NEFAs and TGs and more severe AP (19% vs. 7% p<0.03) than other etiologies. Correlations of long-chain unsaturated NEFA with corresponding TGFAs increased with TG concentrations up to 500mg/dL and declined thereafter. However, NEFA-TGFA x lipase correlations got stronger with TGs >500mg/dL. AP, and intravenous lipase infusion in rodents caused lipolysis of circulating TGs to NEFA. This led to multi-system organ failure, which was prevented by pancreatic triglyceride lipase deletion, or lipase inhibition.

Conclusions: HTG-AP is made severe by the NEFAs generated form intravascular lipolysis of circulating TGs. Strategies that prevent TG lipolysis may be effective in improving clinical outcomes of HTG-AP.

Trial registration: Not applicable.

Funding: This project was supported by Grant numbers RO1DK092460, R01DK119646 from the NIDDK, PR191945 under W81XWH-20-1-0400 from the DOD (VPS), and R01AA031257 from the NIAAA (VPS).