1240 GMT February 24, 2020
Experts suggested this could be due to vitamin A — a substance which is found in animal foods and dairy products, according to express.co.uk.
The vitamin boosts cells in the pancreas that produce the blood sugar-regulating hormone insulin, researchers said.
There has previously been no known link between diabetes and vitamin A — which is found in liver, oily fish and cheese — until now.
Dr. Albert Salehi, senior researcher at the Lund University Diabetes Center in Sweden, said that vitamin A is found mainly in offal and dairy products.
The researchers said milk in Sweden is enriched with vitamin A and there appears to be no deficiency in people who eat a varied diet.
However, he said some vegetarians perhaps need to be aware of the problem.
The research team from King's College London and the Oxford Center for Diabetes found the vitamin improves the function of the specialist cells — known as beta cells.
They initially discovered the cells contain a large quantity of a cell surface receptor for vitamin A.
Salehi said, "There are no unnecessary surface receptors in human cells. They all serve a purpose but which, in many cases, is still unknown and because of that they are called 'orphan' receptors.
"When we discovered insulin cells have a cell surface expressed receptor for vitamin A, we thought it was important to find out why and what the purpose is of a cell surface receptor interacting with vitamin A mediating a rapid response to vitamin A."
The researchers believe vitamin A has an important role for the development of beta-cells in the early stages of life — and as people get older.
They worked with insulin cells from mice and non-diabetic and type 2 diabetic donors.
By partially blocking the vitamin A receptor and challenging the cells with sugar, they could see that the cells' ability to secrete insulin deteriorated.
Salehi added, "We saw close to a 30 percent reduction.”
He said impaired cell survival and insulin secretion are key causes of type 2 diabetes and said the same thing could be seen when comparing insulin cells from type 2 diabetics.
Cells from patients were less capable of insulin secretion compared with those from healthy individuals.
The researchers also saw that the beta-cells' resistance to inflammation decreases when vitamin A is not prevalent.
In case of a complete deficiency, the cells die.
The discovery may also be significant for certain types of type 1 diabetes when the beta-cells are not sufficiently developed during the early stages of life.
Salehi said, "In animal experiments it's known newborn mice need vitamin A to develop their beta-cells in a normal way.
"Most likely, the same applies to human beings. Children must absorb a sufficient amount of vitamin A through their diet."
Salehi added that vitamin A would not work as a treatment for diabetes because it is possible to have too much.
However, he said experts are trying to find substances similar to the vitamin A which could activate the newly found receptor.