Effect of fasting on the pattern of urinary arsenic excretion

Abstract

Millions of people in some of the poorest regions of the world are exposed to high levels of arsenic through drinking contaminated water. It has been reported that development of cancer caused by arsenic exposure in such populations is dependent on dietary and nutritional factors which can modulate arsenic metabolism. Many people in arsenic exposed regions of Bangladesh and India practice fasting for at least one month every year when they refrain from consumption of food and fluid during daylight hours. How such practices may modulate arsenic metabolism has not been previously investigated. This study investigated this issue by determining total arsenic and its species in urine samples from a group of 29 unexposed volunteers at the beginning of the fasting and at the end of approximately 12 h of fasting period. Inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled with ICP-MS was used to measure the total arsenic and arsenic speciation in the urine samples, respectively. The mean total levels of arsenic at the beginning of fasting (18.3 microg g(-1) creatinine) and at the end of approximately 12 h of fasting (17.7 microg g(-1) creatinine) did not differ significantly (p > 0.05). However, the percentages of urinary arsenic as the methylated arsenic species methylarsonate (MA) were found to be significantly different (p < 0.05) and this species was observed more frequently at the end of fasting, although its overall concentration was similar. There were no significant differences (p > 0.05) in both the concentrations and percentages of other urinary arsenic species detected, namely arsenobetaine (AB) and dimethylarsinate (DMA). Arsenite (As(III)) and arsenate (As(V)) were also analyzed, but were not detected. We conclude that fasting for a period of 12 h results in a significant increase in the percentage of urinary arsenic as MA, and its frequency of detection in the volunteers at the end of the fasting period is almost nine fold higher. This suggests that metabolism of arsenic is altered by fasting.

Human toenails as a biomarker of exposure to elevated environmental arsenic

“…Ammonium nitrate (> 99 %) and aqueous ammonia (Fisher, UK) were used in preparation of the mobile phase for anion exchange chromatography. 10 Toenail samples were washed thoroughly following a slightly modified version of the protocol described by Slotnick et al (2007) 8 , which is comparable to several published methods 5,6,37,38 . Visible exogenous material was firstly removed using plastic forceps and a clean quartz fragment.…”

“…Toenail samples were washed thoroughly following a slightly modified version of the protocol described by Slotnick et al (2007) 8 , which is comparable to several published methods 5, 6,37,38 . Visible exogenous material was firstly removed using plastic forceps and a clean quartz fragment.…”

Groundwater Arsenic Contamination, Its Health Effects and Approach for Mitigation in West Bengal, India and Bangladesh

“…The study concluded that fasting for a period of 12 h results in a significant increase in the percentage of urinary As as methylarsonate. The study also suggested that metabolism of As is changed by fasting (Brima et al 2007). Li et al (2008) reported that the average proportions of inorganic As, MMA and DMA in urine in gestational week-8 were 15, 11, and 74%, respectively, based on their study among 442 women from Matlab PS of Bangladesh.…”

“…The explanation of such high percentage of As (III) in urine was thought to be due to poor methylation capacity of the studied subjects. A recent study investigated the effect of fasting on the pattern of urinary As excretion by determining total and speciated As in urine samples from a group of 29 unexposed volunteers at the beginning of the fasting and at the end of approximately 12 h of fasting period (Brima et al 2007). The study concluded that fasting for a period of 12 h results in a significant increase in the percentage of urinary As as methylarsonate.…”

Rapid screening of arsenic species in urine from exposed human by inductively coupled plasma mass spectrometry with germanium as internal standard

“…[1][2][3][4] Urine is 24 regarded as an important biomarker of arsenic intake. In this regard, a speciation analysis of urine is 25 usually performed by HPLC-ICP-MS. [5][6][7][8][9][10] However, signal drift and matrix effects are observed due 26 to urine matrix, hampering the quantification of such species.…”