Research at the Joslin Diabetes Center in Boston showed that four viruses found in fish produce proteins similar to human hormones and react with cells similarly to insulin. The discovery suggests that micro-organisms could play a role in development of diabetes, as well as other autoimmune diseases and cancer.

Insulin, a hormone produced by the pancreas, helps transfer blood glucose into cells where it can be used up for energy. If the human body produces insufficient or no insulin or falls short in insulin sensitivity, all that glucose stays in the blood and does not reach the cells. This leads to the development of a chronic metabolic condition called diabetes mellitus or diabetes for short. Diabetes is the fastest growing chronic disease of our time and scientists around the world are working hard to unravel the metabolic riddle it presents.

A research team from the Joslin Diabetes Center in Boston used bioinformatic tools to identify genetic structures similar to human hormones and regulatory proteins in viruses. Their research was published in the journal PNAS. Four viruses typically isolated from fish showed an uncanny degree of similarity in their genetic code and the group wanted to find out if they could interfere with signaling in mammals. They tested the impact of synthetically produced viral insulin-like peptides (VILPs) on mouse and human cells.

“Our research may help open up a new field that we might call microbial endocrinology,” said Emrah Altindis, Ph.D., a Joslin research fellow and lead author on the research paper. “We show that these viral insulin-like peptides can act on human and rodent cells. With the very large number of microbial peptides to which we are exposed, there is a novel window for host-microbe interactions.”

The experiments uncovered that the VILPs mimicked human hormones and did bind to human insulin receptors as well as the receptors for a similar hormone known as insulin-like growth factor one (IGF-1). In other words, the viral peptides could stimulate all of the signaling pathways inside the cells that were normally triggered by human insulin and IGF-1. Mice injected with the viral peptides exhibited lower levels of blood glucose. Furthermore, analysis of viruses found in the human intestine showed that humans are actually exposed to these viruses. According to researchers, VILPs are members of the insulin “superfamily” and the first characterized viral hormones.

While those four viruses do not normally infect humans, questions arise if consuming fish could expose humans to these a risk of insulin cross-reactivity. The research group will carry out additional experiment in the future to see if the viruses could infect cells or be absorbed through the gut.

“This finding is the tip of an iceberg,” says C. Ronald Kahn, the center’s chief academic officer and senior author on the paper, in a press release. “There are thought to be more than 300,000 viruses that can infect or be carried in mammals, and only 7,500 or so of these, or about 2.5%, have been sequenced. Thus, we certainly expect to find many more viral hormones, including more viral insulin, in the future.”

This research has opened up a new view on the understanding and treatment of disease as well as some questions concerning cancer.

“If these viruses are inside the gut, could the VILPs they produce stimulate the growth of gut cells so that you get polyps or tumors of the gut?” Kahn asks. “Or if they’re absorbed or become infectious, could they infect any organ in the body?”

Learn more about diabetes in the video below:

It is not the first time researchers linked viruses to diabetes. Learn more about it in the video below:

By Andreja Gregoric, MSc