Eyes can can be used to monitor glucose regulation in the body, researchers say.
By transferring the vital insulin-producing cells from the pancreas to the eye, the latter can serve as a kind of window through which health reports can be obtained from the former, researchers said.
The findings at Karolinska Institutet in Sweden are expected to have a significant impact on diabetes research.
The endocrine part of the pancreas, the Islets of Langerhans, produces and secretes insulin, the hormone that regulates blood sugar levels.
After a meal, the hormone is released into the blood at an amount that is in direct proportion to the amount of food ingested; blood insulin levels therefore vary from one meal to the next and between individuals.
In the case of conditions such as obesity, large amounts of insulin are needed to compensate for the high consumption of food and insensitivity to the hormone.
The greatest obstacle to studying the exact workings of the Islets of Langerhans and how they adapt to individual conditions is their relative inaccessibility, in that they lie deeply embedded in and are distributed throughout the tissue.
Now, however, researchers have found a new way to study the insulin-producing beta-cells: by transferring the Islets of Langerhans to the eye.
"What we've done is made the cells optically accessible by grafting a small number of 'reporter islets' into the eyes of mice, which allows us to monitor the activity of the pancreas just by looking into the eye," said Per-Olof Berggren, professor of experimental endocrinology at the Institutet's Department of Molecular Medicine and Surgery.
"We're now able to really study the insulin-producing beta-cells in detail in a way that wasn't possible before," said Berggren.
The eye may be used, as a kind of reporter reproducing the activity of the pancreas and allowing readings of the status of the pancreas under different conditions in health and disease.
"The Islets of Langerhans can be visualised repeatedly over a period of several months, and our work shows that during this time, functional and morphological changes occur in them that are identical to those occurring in the pancreas," says first author Dr Erwin Ilegems, researcher at the Rolf Luft Centre.
Using the new monitoring system and pharmacological treatment, the researchers have reduced food consumption in obese mice models and thus stopped the enormous growth in beta-cell population. This means that they are now able to individually tweak drug doses.
The study was published in scientific journal PNAS.