Detection of Hsp60 in saliva and serum from type 2 diabetic and non-diabetic control subjects

There is increasing evidence that mitochondrial dysfunction and oxidative stress may be integral to the pathogenesis of type 2 diabetes mellitus. Heat shock protein (Hsp60) is a mitochondrial stress protein known to be induced under conditions of mitochondrial impairment. Although this intracellular protein is normally found in the mitochondrion, several studies have shown that this protein is also present in systemic circulation. In this study, we report the presence of elevated levels of Hsp60 in both saliva and serum of type 2 diabetic patients compared to non-diabetic controls. Hsp60 was detectable in the saliva of 10% of control and 93% of type 2 diabetic patients. Levels detected were in the range of 3-7 ng/ml in control and 3-75 ng/ml in type 2 diabetic patients. Serum Hsp60 levels in the range of 3-88 ng/ml were detected in 33% of control subjects, and levels in the range of 28-1,043 ng/ml were detected in 100% of type 2 diabetic patients. This is the first reporting of the presence of mitochondrial stress protein in salivary secretions. The serum Hsp60 levels were 16-fold higher compared to those in saliva, and there was a good positive correlation between salivary and serum Hsp60 levels (r=0.55). While the exact mechanisms responsible for the secretion of Hsp60 into biological fluids such as saliva and blood are not yet known. The presence of this molecular marker of mitochondrial stress in saliva offers a non-invasive route to further investigate the biological functions of extracellular Hsp60 in type 2 diabetes mellitus and other conditions.