Abstract
Measurement of insulin is an important marker for diabetes mellitus and other metabolic processes. Most insulin measurements are made in blood, although insulin has been previously found in saliva. Since we have described several of the proteins in both saliva and nasal mucus we wished to determine if insulin were present in these biological fluids and whether or not their measurements could be used to determine physiological and pathological processes. We measured insulin by colorimetric ELISA in a 96-plate assay in plasma and saliva in the fasted and nonfasted state and in nasal mucus in the nonfasted state in 60 patients with a variety of disease states. In plasma in the fasting state insulin was 17.1 ± 3.8 μIU (mean ± SEM), in saliva, 22.6 ± 1.9; in plasma in the nonfasting state insulin was 29.4 ± 4.4, in saliva 24.7 ± 2.4. In the fasted state, insulin in saliva was 32% higher than in plasma, whereas in the nonfasting state it was 15% higher. In the nonfasting state insulin in nasal mucus was 19.0 ± 2.2 or 35% lower than in plasma and 23% lower than in saliva. In patients with diabetes under biochemical control saliva insulin in fasting state was 62% higher than in plasma and in the nonfasting state it was essentially the same as in plasma. In patients with controlled diabetes in the nonfasted state insulin in nasal mucus was 47% lower than in plasma and 45% lower than in saliva. Relative changes in insulin in plasma, saliva and nasal mucus were also found in thin and obese subjects. These results indicate that insulin is present in both saliva and nasal mucus and physiological changes in this hormone can be measured in these fluids. Use of saliva and nasal mucus to monitor diabetes and other disorders offers noninvasive techniques to obtain data usually found in blood.