Serum β-Glucuronidase Activity in Response to Fruit and Vegetable Supplementation: A Controlled Feeding Study

Abstract

Background: Fruit and vegetable (F&V) intake may lower the risk of some cancers. One hypothesized, but understudied, chemopreventive mechanism is that plant food constituents inhibit B-glucuronidase, an acid hydrolase that deconjugates glucuronides. Methods: We conducted a crossover feeding trial in 63 healthy women and men ages 20 to 40 years to examine the effect of diet on serum B-glucuronidase activity. Participants were randomized to two 2-week experimental diets with an intervening washout period: a diet high in selected citrus fruit, crucifers, and soy (F&V) and a diet devoid of fruits, vegetables, and soy (basal). Serum B-glucuronidase activity was measured during the preintervention, F&V, and basal periods. Linear mixed models were used to obtain effect estimates and 95% confidence intervals (95% CI).

Dietary and Demographic Correlates of Serum β-Glucuronidase Activity

“…Previously, we conducted a cross-sectional pilot study of 83 men and 120 women (22) and observed weak inverse associations between intakes of plant foods and nutrients and serum β-glucuronidase activity. In a subsequent controlled feeding study, we observed no β-glucuronidase lowering effect from supplementation of 10 servings/d of soy, citrus fruits and cruciferous vegetables (23). With respect to non-dietary factors, β-glucuronidase has been positively associated with males, increased age, and higher BMI; however, results have been based on a few, small-sampled studies (1).…”

“…Participants completed an eligibility questionnaire and because this sample was the basis of recruitment for a subsequent dietary feeding study (23), individuals were excluded for the following reasons: 1) medical history of gastrointestinal, hepatic or renal disorders; 2) current or planned pregnancy or lactation; 3) major dietary and/or weight change (>4.5 kg) in the past year; 4) antibiotic use within the past 3 months; 5) BMI >30 or <18; 6) current use of over-the-counter, recreational and prescription drugs (including oral contraceptives); 7) regular exposure (including occupational) to passive smoke or organic solvents; 8) alcohol intake >2 drinks/day (720 mL beer, 240 mL wine or 90 mL hard liquor); 9) no interest in participating in the subsequent controlled feeding trial of fruits and vegetables; and, 10) exercise regimens that require or result in significant short-term dietary changes. Additionally, participants were asked to discontinue use of all multivitamins and dietary supplements one week before participating in the study.…”

“…We used serum β-glucuronidase because it reflects tissue β-glucuronidase resulting from cell turnover, particularly from the liver (28) which is the main source of this enzyme, and because serum collection requires minimally invasive methods. β-glucuronidase activity from serum was determined using a modification of the Sigma β-glucuronidase procedure (Sigma-Aldrich Company, St. Louis, MO) using methods described in detail previously (23). Briefly, serum was incubated in the presence of phenolpthalein glucuronic acid.…”

The flavonoid quercetin induces acute vasodilator effects in healthy volunteers: Correlation with beta-glucuronidase activity

“…Determination of ˇ-glucuronidase activity ␤-Glucuronidase activity was measured by a colorimetric analysis using phenolphthalein mono-␤-glucuronide as the substrate [29]. Briefly, plasma (50 L) was incubated with 1 mM phenolphthalein glucuronic acid in 0.1 mM sodium phosphate buffer at pH 4.5 for 4 h at 37 • C. At 4 h, the reaction was stopped by adding 0.1 M sodium phosphate buffer pH 11.…”

Electrospray ionization Fourier transform mass spectrometric analysis of intact bikunin glycosaminoglycan from normal human plasma

“…In this case, a small amount of GlcA-terminated chains could be rationalized by decreased β-glucuronidase activity across the pool or in one or more individuals whose plasma was in the pooled sample used in the present study. It has been shown that β-glucuronidase activity varies greatly between healthy individuals due to the different levels of enzyme expression and environmental factors, such as dietary preferences [39, 40]. The reason for the absence of even-number chains in the urinary bikunin GAG could have been an artifact of the analysis: it is virtually impossible to detect a minor component in a mixture of hundred components each of which exhibits multiple charge states and various degrees of Na substitution.…”