Metformin influences the expression of beta-actin in human dermal fibroblasts

Introduction Metformin is a drug used in diabetes mellitus type 2 (T2DM) therapy especially in case of Adipositas as a comorbidity. Furthermore, a molecular and cellular link between T2DM and Alzheimerʼs disease may exist. We showed in previous studies that drugs like Norepinephrine and Atomoxetine influence the circadian rhythm in human dermal fibroblasts (HDF). In this study, we investigate the influence of Metformin on circadian gene expression in HDF.

Methods HDF were obtained via skin biopsy from healthy controls (HC) (2 men, 1 woman; 39.00 ± 17.35 years, mean ± SD; BMI: 26.00 ± 4.38 kg/m², mean ± SD). Cells were cultivated at 37 °C and 5% CO2. All participants completed the Multiple-Choice Word Test (IQ score: HC: 112.33 ± 10.01, mean ± SD), German Morningness-Eveningness-Questionnaire (D-MEQ Score: HC: 50.33 ± 4.51, mean ± SD) and Wender Utah Rating Scale, German short-version (WURSk Score: HC: 13.67 ± 12.22, mean ± SD). HDF were treated with either 0 mM, 2 mM or 20 mM Metformin. Synchronization was induced with 0.1 µM dexamethasone (D) for 2 hours. Sampling was performed every forth hour starting after synchronization for a period of 28 hours. CLOCK, BMAL1, CRY1, PER1/2/3, TAU, APP and Beta-Actin gene expression was measured by qRT-PCR. Rhythmicity analysis was perfomed with CircWaveR software. Statistics were calculated using SPSSR.

Results The middle-aged volunteers showed an overweight BMI and standard range IQ score as well as intermediate chronotype. Furthermore, the WURSk score presented no evidence for ADHD characteristics. Significant circadian oscillations were observed for BMAL1 and CRY1 (CircWave, p > 0.05) for all concentrations. Additionally, TAU expression was rhythmic after 2 mM Metformin.

CLOCK expression was significantly higher for 2 mM Metformin compared to 0 mM (p = 0.019) at ZT0. Moreover, BMAL1 expression differs at ZT8 for 20 mM Metformin compared to 0 mM (p = 0.016). Interestingly, APP expression for 2 mM Metformin is significantly lower at ZT12 (p = 0.006) compared to 20 mM Metformin. Additionally, TAU expression differs between the two metformin concentrations (2 mM and 20 mM) at ZT12 (p = 0.018). Interestingly, Beta-Actin, often used as a housekeeping gene, showed lower expression for 2 mM Metformin at ZT8 (p = 0.034) and ZT12 (p = 0.014) as well as for 20 mM Metformin at ZT8 (p = 0.032) compared to 0 mM.

Conclusion Our preliminary results suggest that Metformin may alter the circadian rhythm in HDF for CLOCK, BMAL1, APP and TAU, as well as Beta-Actin.