Urinary Recovery of Lactulose Compared to D-xylose Absorption Kinetics in HIV Patients with Diarrhea and Weight Loss

Abstract

Using a kinetic model of D-xylose absorption, wehave previously shown that there is severely impairedabsorption of D-xylose in HIV patients with diarrhea andweight loss. The absorptive defect is characterized by an increased rate constant for nonabsorptiveloss of D-xylose, K_o, and a decreasedabsorptive rate constant, K_a, and isunrelated to histology or the presence of pathogens. Itis not known if there is also abnormal paracellular transport inthese patients. We have extended our observations inthese patients by including a measurement ofparacellular transport, lactulose absorption. Nine HIVpatients with chronic diarrhea, weight loss, and nodetectable intestinal pathogens, two healthy volunteers,and three non-HIV patients with chronic diarrhea (twofunctional and one with scleroderma) were enrolled. Of the nine HIV patients, six had diminishedbioavailability of D-xylose, F (range: 19-52%, normal>70%), and elevated rate constant for nonabsorptiveloss, K (range: 0.54-1.35/hr, normal <0.353/min). Four of the six also had decreasedK_a (range: 0.09-0.36/hr, normal>0.634/min). Only one of these six had increasedlactulose recovery (3.51%, normal <0.5%). Two ofthree patients with normal kinetic parameters of D-xylose absorption had increasedlactulose urinary recovery (1.92%, 2.61%). Inconclusion, lactulose absorption is increased in somepatients with HIV-related diarrhea who have normalD-xylose absorption, suggesting a paracellular mechanismfor diarrhea in some patients with AIDSenteropathy.