APP and Alzheimer disease: Further, although plasma concentrations of cytokines IL-1β and IL-6 are significantly increased in cirrhosis patients and plasma IL-6 levels are correlated with Aβ40 levels (a 40 amino acid proteolytic product of APP cleavage that has gained attention as a biomarker correlating with AD), no association is observed by linear regression between IL-6 and Aβ40 levels.