Underlying the usual symptoms are raised levels of MG (methylglyoxal), a glucose metabolite that is a by-product of cell activity, say researchers from Heidelberg University Hospital in Germany.
They began to suspect there was something more going on when they noted that diabetics continued to display all their usual symptoms, including diabetic damage to their nerves and kidneys, even when their blood-sugar levels had fallen to within a healthy range.
Diabetics typically have raised levels of MG, and this could be causing the damage rather than the usual suspects of raised glucose and insulin resistance, the researchers say.
The theory has been demonstrated in tests on laboratory rats. When they were given MG with their food, the rats started to develop typical signs of diabetes, including insulin resistance.
The Heidelberg researchers discovered something similar when they carried out tests on fruit flies. When the researchers turned off the enzyme that breaks down MG, the flies quickly started to become insulin-resistant.
While MG levels may indeed be the real root cause of diabetes, the researchers don't yet know why levels rise in the first place.
But if they're right, the supplement L-carnosine could be the solution, says Mark Turner, a professor at Nottingham Trent University. It blocks the formation of molecules that are formed from glucose and fatty acids—which suggests that MG would fall into that category. Early trials support the idea; in one, L-carnosine reduced blood-sugar levels, and prevented complications that are typically associated with diabetes.