Noninvasive glucose estimation possible by measuring glycated albumin levels in tears, saliva among diabetics

"The measurement is expected to reduce the burden on diabetic people in terms of both cost-effectiveness and invasiveness since it can be conducted noninvasively and not as common as compared with the more invasive finger prick method," the researchers wrote. "In the future, we would like to verify the effect of regular measurement of glycated albumin on glycemic control while considering the clinical cost-effectiveness.

To minimize the risk of diabetic complications, strict glycemic control is critical. Frequent blood glucose measurement by the invasive finger prick method helps achieve strict blood sugar control. HbA1c measurement in hospital outpatients is also helpful for determining glycemic control status. All the described ways are useful but could be more manageable and invasive. Previous studies have reported noninvasive measurement of glucose levels in saliva and tear, but experts have pointed out practical problems such as blood contamination and unreliable measurement accuracy.

To overcome these problems, the investigators considered measuring a biomarker in saliva/tear that could be calculated as a ratio to obtain more accurate values than by direct glucose concentration measurement. They selected glycated albumin as a candidate. The GA level (%) is calculated as the ratio of GA concentration to total albumin and reflects the glycemic control status over the previous two weeks, the same as the blood fructosamine level, and is used in settings where HbA1c determination is unreliable, such as in patients with kidney disease and anaemia or pregnant patients.

Masakazu Aihara, The University of Tokyo, Tokyo, Japan, and colleagues investigated the measurement of glycated albumin levels in saliva and tears, which could be collected noninvasively for developing a noninvasive method for evaluating glycemic control in patients with diabetes mellitus.

For this purpose, the researchers collected saliva and tear samples from 48 participants with diabetes mellitus. Liquid Chromatography-Mass Spectrometry (LC-MS/MS) was used to measure GA levels in the saliva and tear specimens.

The authors reported the following findings:

· GA levels in both saliva and tear samples were significantly correlated with the GA levels in the blood.

· Multiple regression analysis revealed that these correlations were maintained even after adjustments for the age, BMI, and nephropathy stage.

"We showed the GA levels in both saliva and saliva specimens were significantly correlated with those in the blood," the researchers wrote, "the associations remained significant even after adjustments for the age, BMI, and nephropathy stage."

Reference:

Aihara, M., Jinnouchi, H., Yoshida, A., Ijima, H., Sakurai, Y., Hayashi, T., Koizumi, C., Kubota, T., Usami, S., Yamauchi, T., Sakata, T., Kadowaki, T., & Kubota, N. (2023). Evaluation of glycated albumin levels in tears and saliva as a marker in patients with diabetes mellitus. Diabetes Research and Clinical Practice, 110637. https://doi.org/10.1016/j.diabres.2023.110637