Recently, with westernization of diets, patients of lifestyle-related diseases are increasing, resulting in serious medical and social problems. At present, in Japan, the number of diabetic patients is 8,000,000, and the number of diabetic patients plus pre-diabetic patients is 20,000,000. The three main complications of diabetes are retinopathy, nephropathy, and neuropathy. Diabetes is also a cause for arteriosclerosis. Furthermore, diabetes may cause heart diseases and brain diseases.
A person develops diabetes in such a manner that improper diets and life styles, secretion from fat cells due to fatness, or oxidative stress decreases the function of pancreas, causing shortage of insulin that controls a blood glucose level or reducing the effect of insulin. Diabetes has symptoms such as frequent urination and increased amount of urination, and increased thirst. However, such symptoms may not enable patients to realize that they develop diabetes, and most patients know their illness when they are subjected to inspection in hospitals etc. This tells why there are so many “silent” diabetic patients.
At the stage where abnormal symptoms resulting from the complications of diabetes are found in hospitals etc., conditions of the disease have advanced too far, making it difficult to completely cure the disease. In particular, many of the complications of diabetes are difficult to cure, and therefore prevention of diabetes is considered as important like many life-style related diseases. For the prevention, early identification and early determination of therapeutic effect are essential, and there are many inspections for diabetes for this purpose.
When a person undergoes oxidative stress in a situation where blood contains abnormal amounts of carbohydrates and lipids therein, the oxidative stress causes reactions of the carbohydrates and the lipids with protein so that AGEs (Advanced Glycation Endproducts) are produced. AGEs are end products produced via non-enzymatic glycosylation reaction of protein (Miallard reaction). AGEs exhibit yellowish brown color, emit fluorescence, and form crosslink by bonding to nearby proteins.
AGEs are considered to be deposited on and infused into blood vessel walls or to interact with macrophage which is a part of an immune system, to thereby release cytokine that is one type of protein and to cause inflammation, resulting in arteriosclerosis.
In the case of diabetes, as the blood glucose level increases, the amount of AGEs increases. Accordingly, by monitoring AGEs, it is possible to identify diabetes at an early stage or to comprehend the progress of diabetes. One example of a method for screening diabetes mellitus by monitoring AGEs is reported in Patent Literature (PTL) 1.
With the reported method, AGEs are monitored by irradiating the skin of a forearm with excitation light, measuring a fluorescence spectrum from the AGEs bound to skin collagen, and comparing the measured fluorescence spectrum with a predetermined model. Thus, AGEs data is obtained in a non-invasive manner.