Ovotoxic Effects of Galactose Involve Attenuation of Follicle-Stimulating Hormone Bioactivity and Up-Regulation of Granulosa Cell p53 Expression

Sayani Banerjee,Sutapa Banerjee,Soma Aditya Bandyopadhyay,Syed N Kabir,Pratip Chakraborty,Piyali Saha,Irina Agoulnik

doi:10.1371/journal.pone.0030709

Sayani Banerjee, Sutapa Banerjee + Show 5 more

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https://doi.org/10.1371/journal.pone.0030709

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Abstract

Clinical evidence suggests an association between galactosaemia and premature ovarian insufficiency (POI); however, the mechanism still remains unresolved. Experimental galactose toxicity in rats produces an array of ovarian dysfunction including ovarian development with deficient follicular reserve and follicular resistance to gonadotrophins that characterize the basic tenets of human POI. The present investigation explores if galactose toxicity in rats attenuates the bioactivity of gonadotrophins or interferes with their receptor competency, and accelerates the rate of follicular atresia. Pregnant rats were fed isocaloric food-pellets supplemented with or without 35% D-galactose from day-3 of gestation and continuing through weaning of the litters. The 35-day old female litters were autopsied. Serum galactose-binding capacity, galactosyltransferase (GalTase) activity, and bioactivity of FSH and LH together with their receptor competency were assessed. Ovarian follicular atresia was evaluated in situ by TUNEL. The in vitro effects of galactose were studied in isolated whole follicles in respect of generation of reactive oxygen species (ROS) and expression of caspase 3, and in isolated granulosa cells in respect of mitochondrial membrane potential, expression of p53, and apoptosis. The rats prenatally exposed to galactose exhibited significantly decreased serum GalTase activity and greater degree of galactose-incorporation capacity of sera proteins. LH biopotency and LH-FSH receptor competency were comparable between the control and study population, but the latter group showed significantly attenuated FSH bioactivity and increased rate of follicular atresia. In culture, galactose increased follicular generation of ROS and expression of caspase 3. In isolated granulosa cells, galactose disrupted mitochondrial membrane potential, stimulated p53 expression, and induced apoptosis in vitro; however co-treatment with either FSH or estradiol significantly prevented galactose-induced granulosa cell p53 expression. We conclude that the ovotoxic effects of galactose involves attenuation of FSH bioactivity that renders the ovary resistant to gonadotrophins leading to increased granulosa cell expression of p53 and follicular atresia.

Highlights

Premature ovarian failure, currently referred to as premature ovarian insufficiency (POI), is a frequent finding in women with galactosaemia [1,2,3]
Serum GalTase activity was assessed in respect of the capacity of serum to catalyse the transfer of radiolabeled galactose from UDP-galactose to ovalbumin
The present study demonstrates that galactose toxicity attenuates FSH bioactivity and exerts direct ovotoxic effects

Summary

Introduction

Currently referred to as premature ovarian insufficiency (POI), is a frequent finding in women with galactosaemia [1,2,3]. Lai et al [16] demonstrated that immature rats fed with high galactose diet exhibited higher expression of Fas and Fas-ligand but lower expression of Xiap and Riap, suggestive of increased apoptotic damage of the ovary. These mechanisms, could not explain the full spectrum of ovarian dysfunction since normal adult mice with optimum follicular reserve exhibited ovarian failure in the form of follicular resistance to gonadotrophins following exposure to high galactose [17]. The precise mechanisms underlying ovotoxic effects of galactose is still far from clear

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