Inhibitory effect of fluoride on the secretion of insulin

Abstract

The oral administration of sodium fluoride (NaF) (40 mumol/100 body weight [bw]) to fasting rats produced an immediate fall in insulin levels and the consequent increase in glycemia. These phenomena were observed with plasma fluoride concentrations 5-15 microM. Glycemia and insulin returned to normal levels within 4-5 hours, together with the washing out of fluoride from plasma and soft tissues. The insulin secretion of isolated Langerhans islets, perifused with solutions containing 5, 10, or 20 microM fluoride, was found to be significantly inhibited as a function of fluoride levels, both with basal and stimulatory concentrations of glucose. One hour after the intake of 60 mg of NaF, fasting human volunteers showed increased fluoride (5-15 microM) together with a significant fall of plasma insulin levels.

Biochemical and Histopathological Effects of Chronic Fluorosis on Lung Tissues of First Generation Rats

“…Previously it had been reported that chronic fluorosis caused alveolar hemorrhage, congestion, oedema fluid, necrosis of alve- ly increased lipid peroxidation in lung tissues of F1 rats, resulting in the increased olar epithelium distortion of alveolar architecture and bronchiolitis in the lung tissues of rats (23,25). In the present study, in F1 rats, alveolar congestion, descuamation of alveolar epithelium, thickened interalveolar septae were observed.…”

Proteomic Analysis of Gastrocnemius Muscle in Rats with Streptozotocin-Induced Diabetes and Chronically Exposed to Fluoride

“…The development of glucose intolerance depends on both the duration and dose of exposure to F [7], [8]. Oral ingestion of F leads to transient inhibition of insulin secretion in both rats and humans [9]. Impairment of glucose homeostasis occurs when plasma levels of F exceed 5 µM.…”

Effect of Fluoridated Water on Plasma Insulin Levels and Glucose Homeostasis in Rats with Renal Deficiency

“…Results are expressed as mean ± SE. *Significant differences compared to rats with access to drinking water containing 0, 1, and 5 ppm F (ANOVA, Tukey's post hoc test, p<0.05) fluoride intakes ranging between 0.2 and 2 mg/kg body weight, which is 40-4 times lower than the values of intake reported in previous experiments [6,7].…”

“…This effect was observed when plasma fluoride concentration is higher than 5 μM after a single dose of NaF in rats (7.6 mg F/kg body weight) and in humans (60 mg NaF) [6] and also after the administration of drinking water with fluoride 100 ppm to rats for 30 days [7]. The effect appears not to be related to insulin resistance [8], and it disappears when rats have high bone fluoride content, which is consistent with low plasma and tissue fluoride levels [7].…”