TAMIL NADU study Health

A stomach for gut research

In small doses, pesticides are lethal to insects. In larger quantities, they outright kill people and may cause cancer. However, an intriguing study conducted in Tamil Nadu suggests that even in trace doses, insecticides could cause diabetes particularly among agricultural workers who intimately work with them.

According to the team of scientists from Madurai Kamaraj University, this happens because the colony of bacteria that populate our gut — or gut microbiota as they are called — chemically break down the insecticide into short chain fatty acids like acetic acid, increase glucose production in cells, and eventually lead to glucose intolerance and type 2 diabetes.

In probiotics industry

The body is estimated to have about 35 trillion cells and — because there’s still considerably uncertainty — about two to three times as many microbial cells distributed all over and inside the body. The greatest diversity is believed to be within the gastrointestinal tract, home to around 3,000-4,000 species of bacteria, not including viruses and other life forms. Some are harmful and many of them indifferent.

Knowledge that the balance of microbes in the gut can thwart infection already underlies the global probiotics (or beneficial gut bacteria) industry. Mother Dairy, Amul, Danone Yakult and Nestle India are among the leading producers of probiotic functional foods and beverages in India with lactobacilli and bifidobacteria, being among the most popular species employed in developing a range of products such as yoghurt, curd and several dietary supplements.

But now, beyond being a palliative for the stomach upset and reservoir of instinct, piling evidence shows that there is a distinct pattern of microbes — healthy and harmful — found in the gut when stricken by atherosclerosis, obesity, intestinal and even psychological disorders. This could help design new drugs and treatment regimes to tackle complex disorders.

A 2014 report in the journal Nature quoted a trial by Joseph Murray, a gastroenterologist at the Mayo Clinic in Rochester, Minnesota, U.S., where the gut bacterium Prevotella histicola was fed to transgenic mice engineered to have human-like immune systems to suppress the inflammation caused by multiple sclerosis and rheumatoid arthritis. Vedanta Biosciences in Boston, Massachusetts, now acquired by Pfizer Inc, is conducting preclinical trials of a pill containing microbes that suppress gut inflammation

Need for an Indian project

The lead editorial in the latest issue of India’s top science journal, Current Science , warns that if Indian science doesn’t wake up, it could be lose out in the revving, global race to understand the mysteries of the gut. “…Several countries have begun projects such as the Australian Gut Project, American Gut Project, British Gut Project, Initiative in Skin and Oral Microbiome (iMicroCare, China), Canadian Microbiome Initiative, Human MetaGenome Consortium Japan (HMGJ), EU-funded MyNewGut Project, and International Human Microbiome Consortium (IHMC, 12 countries),” note Yogesh Shouche and Shekhar Mande at the National Centre for Cell Science, Pune, “There is sufficient evidence to suggest that genetic as well as microbial composition of the Indian population is distinct… a project of such dimensions requires multi-disciplinary expertise and strong financial support.”

The paucity of gut flora-related research in India marks the Tamil Nadu study as among the few India-centric studies to hint at the gut’s microbial diversity and a possible role in diabetes, that afflicts at least 70 million Indians, according to a 2015 report by the International Diabetes Federation.

Study’s findings

The study, published in this week’s issue of the peer-reviewed Genome Biology , and which surveyed 3,080 people in Vadapalanji panchayat of Madurai district, argues that diabetes in people regularly exposed (defined as those involved in spraying or mixing these chemicals) to organo-phosphatic (OP) insecticides, a mainstay of Indian agriculture, was threefold higher (18.3%) than in unexposed people (6.2%), even when traditional risk factors like obesity, hypercholesterolemia and physical inactivity in this population were low.

Typically, OP targets the nervous and muscular systems and causes convulsion, respiratory failure and death of insects and mammals. However, when small doses of the insecticide were given to mice, the researchers found no significant changes in levels of acetylcholinesterase in their blood.

Raising the levels of OP insecticide administered to the mice and delivering the equivalent of 12-15 years of human life exhibited a slow and steady increase in blood glucose levels in the mice and significantly elevated blood sugar levels after 180 days, as well as impaired glucose intolerance compared to controls.

To test the role of gut flora, the researchers then transplanted faecal matter from the OP-fed mice into the guts of regular mice that then, according to the researchers, exhibited significant glucose intolerance. “Further tests on fasting blood and faecal samples from the human study population suggested similar links between OP degradation and hyperglycemia in humans,” lead author of the study, Dr. G. Velmurugan, now at the University of Florida, Gainsville, U.S., said in a statement accompanying the research paper, “the effects of chronic exposure to OP pesticides on the gut microbiome may be a risk factor for diabetes… the use of OP pesticides should be reconsidered.”

“I think it’s a well-executed and interesting study and to some extent explains why you could see increased incidence of diabetes even in rural India, “ Dr. Shouche, who was not involved in the study, told The Hindu in a phone conversation, “However diabetes has many causative mechanisms so the specific effect of OPs may be small.”

jacob.koshy@thehindu.co.in


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Printable version | May 21, 2022 4:59:12 pm | https://www.thehindu.com/sci-tech/health/A-stomach-for-gut-research/article17109591.ece