Abstract
A number of studies have demonstrated that geophagia can be beneficial and harmful. However, toxicological aspects of this earth, soil, clay eating habit are not fully investigated. In addition, low levels of antioxidants have been observed in pre-eclamptic women. Still, the molecular mechanism implicated oxidative stress in geophagia inducing pre-eclampsia has not been elucidated. Despite its absorbent properties in detoxifying phytotoxin, lowering the incidence of nausea, natural clay still remains toxic for human consumption in normal and long term conditions. Our previous studies have shown the implication of oxidative stress in pre-eclampsia characterized by maternal hypertension. Biomarkers of oxidative stress such as lipid peroxides (LPO), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX) and 8-OHdG correlated with the extent of oxidative stress in pre-eclampsia. Fenton reaction induced by the presence of iron produces a more powerful reactive oxygen species (OH radical) which may contribute to the exacerbation of this status; while, clay eating is believed to protect pregnant women from pre-eclampsia by inhibiting iron uptake from gastrointestinal environment and so reducing the risk of production of OH radical during pregnancy where iron deficiency has been observed, it may be harmful however in iron overload conditions. We have demonstrated that cellular hepato-carcinoma can be indeed induced in rats being iron-loaded by ferrocene supplementation of their diet. Taking into account this possibility, we are postulating that during pre-eclamptic pregnancy, a number of factors including oxidative stress, activated macrophages and activation of xanthine oxidase (XO) can exacerbate this pregnancy complication. In addition, the availability of free iron from soil may as catalytic trace element involve in Harber-Weiss and Fenton reactions producing more ROS/RNS and especially OH radical. We are therefore suggesting that the subsequent activation of the nuclear factor NF-kB by ROS/RNS generated from activated macrophages stimulates the induction of COX-2. This enzymatic induction leading to the expression of inflammatory cytokines could be one of the molecular mechanisms underlying pre-eclamptic conditions. Supplementation of zinc or eating clay containing zinc could overcome such pregnancy complication. Key words: Geophagia, pregnancy, molecular mechanism, oxidative stress, Haber-Weiss and Fenton reactions, superoxide dismutase (SOD), glutathione peroxidase (GPX), OH radical, 8-hydroxyl deoxyguanosine (8-OHdG).
Highlights
According to Coreil et al (2000), geophagia may be stimulated by dietary deficiencies and appears to be ubiquitous
Taking together the above considerations, we suggest that the subsequent activation of the nuclear factor NF-kB by ROS/RNS generated from activated macrophages and activation of xanthine oxidase stimulates the induction of COX-2
Iv) Superoxide dismutase (SOD): Erythrocyte superoxide dismutase (SOD) activity was determined by the method of Arthur and Boyne (1985) using a commercial kit obtained from Randox Laboratories, UK
Summary
According to Coreil et al (2000), geophagia may be stimulated by dietary deficiencies and appears to be ubiquitous. Iron and zinc for example obtained through geophagia or normal diet can lose their beneficial effect if they are absorbed by clay. Their uptake from gastro-intestinal tract can cause iron and zinc deficiencies with subsequent consequences respectively on the erythropoiesis inducing a syndrome hypochromic anemia described by Prasad (1991a; 1991b) and various clinical manifestations such as short stature, delayed sexual maturity, hepatosplenomegaly and delayed bone age reported by Korman (1990). Harmful effect of geophagia in pregnancy has been demonstrated in a large number of studies related to the microbial and parasite infections such as helminthes and the presence in the soil of heavy metals such as arsenic, lead and cadmium (Hunter, 1973; Horner et al, 1991; Corbett et al, 2003; Wigle et al, 2008; Al-Rmalli et al., 2010; Baidoo et al, 2010; Nyanza et al, 2014). One case of fatal soil peritonitis in an African women suffering from geophagia has been reported (Woywodt and Kiss, 2000)
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