In vivo measurement of fluoride effects on glucose homeostasis: an explanation for the decrease in intelligence quotient and insulin resistance induced by fluoride

Abstract

The fluoride ion (F) is a disturbing substance for the glucose-insulinsystem. The effects of F have been studied in various aspects. The chronic intake ofF generates hyperglycaemia with high plasma insulin levels. This effect is observedin several countries where the content of fluoride in drinking water is greater than theupper limit recommended by WHO (1.5 mg/L). The administration of a dose of Fcauses a decrease of insulin levels, which was attributed to a decrease in insulinsecretion through in vitro experiments. However, measurement of insulin secretionin vivo has not been done so far. Moreover, in endemic fluorosis areas children hadlower intelligence quotient (IQ) than children of areas with low F in drinking water.This decrease in IQ has also been observed in rats. In this work, the glucose uptakerate of insulin-independent tissues, insulin secretion, and insulin clearances weremeasured in vivo in rats that received a dose of F. A lower secretion and clearance ofinsulin were found in animals that received F. In addition, a decrease in glucoseuptake rate from insulin-independent tissues was observed. This glucose uptake ismainly the glucose consumed by the nervous system. As a consequence, thisdecrease could be associated with the effect of fluoride on IQ.