Low vitamin A linked to beta cell decline in mice

A new study has found that a lack of vitamin A may be linked to beta cell dysfunction and impaired insulin production in mice.
The study, which appeared in the Endocrine Journal, shows that vitamin A binds to receptors, called GPRC5C, on the surface of beta cells.
A team of researchers at the University of Lund, in Swede, set out to find out why. What they’ve found is that blocking the GPR5C receptors in beta cells from mice hampered their ability to secrete appropriate amounts of insulin.
In a separate study, researchers tested whether knocking down those receptors had similar effects in humans.
They isolated beta cells derived from donors with and without type 2 diabetes and proceeded to block GPR5C receptors, but only partially.
Again, they found that the insulin response for glucose disposal was diminished. They’ve estimated that insulin secretion was reduced by almost 30 per cent.
Upon conducting further analyses, researchers found decreased expression of those GPRC5C receptors in the pancreatic islets from donors with type 2 diabetes.
The activation of the GPRC5C receptors may also turn on genes that control cell death, cell survival and proliferation.
This would explai, in part, why previous research found that vitamin A through these receptors supports the development of fully functional beta cells in newborn mice.
This is further supported by the observation that the reduction in activation of GPRC5C receptors was age-dependent – it was greater in old mice compared to newborn mice.
Researchers also tried making the animals vitamin A deficient without touching the receptors to see how big an impact it had on beta cell function.
Without sufficient vitamin A, their beta cells seemed to be more vulnerable to damage from oxidative stress and inflammation and, in some cases, died.
Beta cells are thought to be highly sensitive to free radicals from oxidative stress and vitamin A is a known antioxidant that may interact with them to limit damage to cells.
The findings suggest that vitamin A, which is naturally found in green vegetables, dairy products and organ meats may be an important dietary factor for functional beta cells.