Serum β-glucuronidase activity is inversely associated with plant-food intakes in humans

Abstract

β-Glucuronidase hydrolyzes glucuronide moieties from steroids and xenobiotics, such that circulating glucuronyl conjugates can interact with target tissues. In animal models, dietary constituents can after β-glucuronidase activity. In humans, serum β-glucuronidase activity reflects liver enzyme loss during cell turnover, and thus is a surrogate for hepatic β-glucuronidase. We recruited 83 men and 120 women, who were nonsmokers, 20-40 y of age, with self-reported vegetable and fruit (V&F) intakes of ≤ 2.5 or ≥ 4.5 servings/d. Diet was assessed by 3-d food record and serum carotenoids were measured as biomarkers of V&F intake (e.g., servings V&F vs. α-carotene; r = 0.47, P = 0.0001). Serum β-glucuronidase activity (Modified Sigma Units/L), determined in blood samples collected on two consecutive days from fasting subjects, was higher in men than women (mean ± SEM; 20.4 x 103 ± 1.0 x 103 and 17.0 x 103 ± 0.6 x 103, P = 0.002). β-Glucuronidase activity (adjusted for sex) was inversely associated with intakes of plant protein, fruit, dietary fiber (r = -0.24 to -0.30; P < 0.001), botanical groupings Cucurbitaceae, Rosaceae, and Leguminosae (r = -0.16 to -0.19; P < 0.05), and serum α- and β-carotene and β-cryptoxanthin (r = -0.18 to -0.26; P ≤ 0.01). Activity was not associated with overall vegetable intake. Although these associations are modest, the data suggest that plant foods, particularly constituents of fruits and fiber-containing foods, may influence human β-glucuronidase activity in a potentially favorable direction.