Leptin and NGF in saliva of patients with diabetes mellitus type 2: A pilot study

This study aimed to measure salivary levels of leptin and nerve growth factor (NGF) in patients with type 2 diabetes (T2D) and to compare with healthy subjects. In addition, markers previously evaluated in diabetes, including insulin, hepatocyte growth factor (HGF), and monocyte chemoattractant protein-1 (MCP-1), and markers of inflammation interleukin ([IL]-1b, IL-6, IL-8, Tumor necrosis factor alpha [TNF-α]), were also measured in saliva to evaluate possible relationship of these markers with the new analytes evaluated in the study.

Unstimulated whole saliva was collected by passive drooling from a total of 65 individuals (34 controls and 31 with T2D) and used for leptin, NGF, HGF, MCP-1, insulin, IL-1b, IL-6, IL-8, and TNF-α determination.

Salivary leptin was 2.1 higher in T2D than in healthy controls (P<.001), while no statistically significant differences were detected between the two groups in salivary concentrations of NGF. Salivary IL-6, TNF-α, insulin, and MCP-1 were higher in DM in comparison with controls (P<.05 in all cases). Leptin showed positive significant correlations with MCP-1, IL-6, TNF-α, and insulin, while NGF positively correlated with HGF, MCP-1, IL-1 β, IL-6, and TNF-α.

This pilot study indicates that salivary leptin is increased in patients with T2D being positively correlated with insulin and pro-inflammatory cytokines and should be further explored as a non-invasive biomarker of T2D. In addition, salivary NGF was positively correlated with pro-inflammatory cytokines and further studies should be performed to evaluate whether it could be useful to detect diabetic neuropathy in T2D patients.