Characterization of a peptide containing the major heparin binding domain of human hepatic lipase.

Human hepatic lipase (hHL) is a cell surface associated enzyme that hydrolyzes triacylglycerols and phospholipids within circulating lipoproteins. We hypothesized that an amino acid sequence mimicking the major heparin binding domain (HBD) of hHL will displace hHL from cell surfaces. To test this hypothesis, we generated a recombinant protein of thioredoxin linked with a cleavable, tagged sequence containing amino acids 442 to 476 of the mature hHL sequence, which contains the major HBD of hHL. The recombinant protein associated with heparin-sepharose, and its peak elution from heparin-sepharose occurred in the presence of 0.5 M NaCl. We cleaved and purified the tagged sequence containing the HBD from the recombinant protein and tested the ability of the peptide to displace full-length hHL from HEK-293 cells. The peptide indeed displaced hHL from cell surfaces, while no significant displacement was observed in the presence of a peptide with a scrambled sequence. Finally, we obtained structural information for the peptide containing the HBD. 1 H- and 15 N-NMR spectra of the peptide indicate the peptide is largely unstructured, although not completely random coil. The addition of heparin to the peptide induced some changes in chemical shift, suggesting changes in peptide structure and/or specific interactions with heparin. Molecular simulations confirm the largely unstructured nature of the isolated peptide, but they also indicate weak tendencies for both α- and ß-structure formation in different parts of the chain. Overall, these data provide a proof-of-principle for the use of mimetic peptides for the displacement of cell surface associated lipases.

Characteristics of Interval Colorectal Cancer: A Canadian Retrospective Population-Level Analysis from Newfoundland and Labrador.

Interval colorectal cancers (I-CRCs) arise during the interval time period between scheduled colonoscopies. Predicting which patients are at risk of I-CRCs remains an elusive undertaking, but evidence would suggest that most I-CRCs arise from lesions missed on index endoscopy. The procedural factors that lead to missed lesions are numerous and lack consensus in the literature. In Canada, the province of Newfoundland and Labrador has the highest incidence of CRCs. In this study our aim was to examine I-CRCs (3-60 months after last colonoscopy) in NL through a population-level analysis covering 67% of the province from 2001-2018. We estimated the I-CRC rate to be up to 9.3%. Median age of I-CRC diagnosis was 67.1 years with an interval time of 2.9 years. About 57% of these tumors occurred proximal to the splenic flexure, with 53% presenting as local disease. No temporal differences were observed in interval time or tumor distribution. On univariate and multivariable logistical regression, risk of right-sided I-CRC did not correlate to the index colonoscopy indication, bowel preparation quality, size of largest polyp removed, colonoscopy completion rate, or stage at presentation. Improvements in synoptic reporting utilization and national registries are needed to identity risk factors and reduce I-CRC frequency.