Metformin induces the AP-1 transcription factor network in normal dermal fibroblasts

Abstract

Metformin is a widely-used treatment for type 2 diabetes and is reported to extend health and lifespan as a caloric restriction (CR) mimetic. Although the benefits of metformin are well documented, the impact of this compound on the function and organization of the genome in normal tissues is unclear. To explore this impact, primary human fibroblasts were treated in culture with metformin resulting in a significant decrease in cell proliferation without evidence of cell death. Furthermore, metformin induced repositioning of chromosomes 10 and 18 within the nuclear volume indicating altered genome organization. Transcriptome analyses from RNA sequencing datasets revealed that alteration in growth profiles and chromosome positioning occurred concomitantly with changes in gene expression profiles. We further identified that different concentrations of metformin induced different transcript profiles; however, significant enrichment in the activator protein 1 (AP-1) transcription factor network was common between the different treatments. Comparative analyses revealed that metformin induced divergent changes in the transcriptome than that of rapamycin, another proposed mimetic of CR. Promoter analysis and chromatin immunoprecipitation assays of genes that changed expression in response to metformin revealed enrichment of the transcriptional regulator forkhead box O3a (FOXO3a) in normal human fibroblasts, but not of the predicted serum response factor (SRF). Therefore, we have demonstrated that metformin has significant impacts on genome organization and function in normal human fibroblasts, different from those of rapamycin, with FOXO3a likely playing a role in this response.

Metformin Attenuates ROS via FOXO3 Activation in Immune Cells

“…In a recent study by Gillespie et al it was shown that metformin stimulation results in decreased fibroblast proliferation and increased FOXO3 promotor occupancy. However, pathway analysis of FOXO3 activation and downstream effects were not studied (27). Using Foxo3 -/mice we provide further evidence that the reduction of ROS/RNS levels by metformin at least partly depends on Foxo3 as we observed that metformin reduced basal intracellular ROS/RNS level in WT but not Foxo3 -/mice.…”

Haskap Berry Phenolic Subclasses Differentially Impact Cellular Stress Sensing in Primary and Immortalized Dermal Fibroblasts

“…To evaluate the impact of haskap extracts and fractions on cells, we selected 2DD primary dermal fibroblasts and NB1hT telomerase immortalized dermal fibroblasts based on our previous assessment of the impact of the putative anti-aging compounds rapamycin [17] and metformin [18] as well as the oat specific polyphenolic compound avenanthramide C (AVNC) [19]. Our first aim was to determine if the phenolic extracts and fractions had observable impacts on cell growth in terms of population doubling times.…”

The Nuclear Lamina: Protein Accumulation and Disease

“…Research linking the role of autophagy's impact on cellular and organismal lifespan as well as cellular nutrient and stress-sensing pathways has burgeoned in the last decade. This research has identified a growing list of pharmacological agents as well as diet and dietary compounds that lead to increased autophagy function and clearance of excess cellular protein [156][157][158][159][160][161][162][163][164][165][166][167].…”

“…Furthermore, activation of SIRT1 results in deacetylation of nuclear LC3, enabling relocalization of LC3 to the cytoplasm from the nucleus and promoting autophagy and potentially formation of nucleophagy-associated vesicles. Although there is debate surrounding target specificity of many compounds that target nutrient/energy sensing pathways, there is strong evidence linking increased AMPK and SIRT1 function with compounds such as metformin [158,159,162,[175][176][177] and resveratrol [160,[178][179][180][181][182][183], respectively to increased health and lifespan. The benefits of these compounds is likely through increased autophagy and indicates the potential therapeutic use of these compounds (or similar molecules with higher target specificity) to promote protein accumulation clearance from the lamina.…”