Aim: The associations of serum leptin/soluble leptin receptor (sObR) and leptin resistance with symptoms of depression and anxiety were investigated in patients with type 2 diabetes (T2D).
Methods: We report the results of two cross-sectional studies, performed 2 years apart, that included 216 and 237 T2D patients, respectively. Symptoms of depression and anxiety were assessed with specific questionnaires (Patient Health Questionnaire-9, Center for Epidemiologic Studies Depression Scale, and Generalized Anxiety Disorder-7, respectively). Laboratory data (including leptin and sObR) were collected, and free leptin index (FLI), as an estimate of leptin resistance, was calculated. One hundred forty patients had laboratory data available on both occasions, and were evaluated longitudinally. Simple and multiple correlations between depression/anxiety and parameters of interest were performed.
Results: In both studies, serum leptin levels were higher, whereas resting energy expenditure/leptin ratios were lower in T2D patients with depressive and moderate-severe anxiety symptoms. In the second study, patients with depressive symptoms had higher FLI and lower sObR levels, while those with moderate-severe anxiety only had higher FLI. Depression scores correlated with serum leptin (r = 0.29, [95%CI: 0.14-0.42]; r = 0.32, [95%CI: 0.18-0.45]) and FLI (r = 0.30, [95%CI: 0.15-0.43]; r = 0.32, [95%CI: 0.17-0.45]; P < 0.0001 for all). Multiple regression analyses identified leptin (β = 0.167; t ratio = 1.98) and FLI (β = 2.935, t ratio = 2.44) (P < 0.05 for both) as variables that significantly contributed to depressive symptoms. Depressive symptoms were present in significantly more patients with leptin levels in the highest versus the lowest quartiles on both evaluations (odds ratio: 5.98, 95%CI [1.76-20.32], P < 0.01).
Conclusion: Depressive and moderate-severe anxiety symptoms were associated with high leptin concentrations and leptin resistance in T2D patients.
© 2019 The Authors. Psychiatry and Clinical Neurosciences © 2019 Japanese Society of Psychiatry and Neurology.