Organophosphates (OP), the most frequently used insecticides worldwide, could induce high blood sugar (hyperglycemia) and glucose intolerance when decomposed by gut bacteria, according to a study published in the open access journal Genome Biology.
Surveying 3080 people in a rural population in India, scientists at Madurai Kamaraj University showed that the prevalence of diabetes in people regularly exposed to OP insecticides was three fold higher (18.3%) than in unexposed people (6.2%), while the prevalence of traditional risk factors like obesity, hypercholesterolemia and physical inactivity in this population was low.
To examine whether chronic exposure to OP may be a risk factor for hyperglycemia, the researchers fed groups of up to ten mice an OP insecticide in drinking water for a period of 180 days, which is the equivalent of 12-15 years of human life. OP-fed mice exhibited a slow and steady increase in blood glucose levels and significantly elevated blood sugar levels after 180 days, as well as impaired glucose intolerance compared to controls.
OP pesticides target the neurotransmitter acetylcholine esterase which acts on the synapses of nervous and muscular systems and causes convulsion, respiratory failure and death of insects and mammals. The researchers were surprised to find no changes in levels of acetylcholine esterase in the blood of OP-fed mice. The discovery prompted them to investigate the role played by the gut microbiota in OP-induced hyperglycemia by transplanting fecal samples from both OP-fed animals and controls in randomly selected mice. The researchers found that mice which received fecal transplants from OP-fed mice exhibited significant glucose intolerance. The authors also noticed changes in the gut microbiota, including higher numbers of OP degrading bacterial enzymes. Degradation of OP produces short chain fatty acids - specifically acetate - which in turn leads to the generation of glucose, elevated blood sugar levels and glucose intolerance, according to the researchers.
Further tests on fasting blood and fecal samples from the human study population suggested similar links between OP degradation and hyperglycemia in humans. Based on these findings, the authors conclude that the effects of chronic exposure to OP pesticides on the gut microbiome may be a risk factor for diabetes. They suggest that the use of OP pesticides should be reconsidered.
Article: Gut microbial degradation of organophosphate insecticides-induces glucose intolerance via gluconeogenesis, Velmurugan et al., Genome Biology, doi: 10.1186/s13059-016-1134-6, published 24 January 2017.