The aim is to examine the effect of metformin in human microvascular endothelial cells exposed to high glucose (HG) concentration and compare them with the effects of other 5' adenosine monophosphate-activated protein kinase (AMPK) modulators under the same condition.

In this experimental study, human microvascular endothelial cells (HMECs) were treated with 15 mM metformin, 1 mM 5-aminoimidazol-4-carboxamideribonucleotide (AICAR) and 10 mM compound C in the presence of 20 mM glucose (hyperglycemic condition). Migration, invasion and proliferation were evaluated as well as the capillary-like structures formation. Moreover, the expression of angiogenic genes was assessed.

Metformin significantly inhibited vessel formation and migration, although it did not change HMECs proliferation and invasion. In addition, metformin significantly reduced collagen formation as evidenced by histological staining. Concomitantly, expression of several genes implicated in angiogenesis and fibrosis, namely TGFß2, VEGFR2, ALK1, JAG1, TIMP2, SMAD5, SMAD6 and SMAD7, was slightly upregulated. Immunostaining for proteins involved in ALK5 receptor signaling, the alternative TGFß signaling pathway, revealed significant differences in SMAD2/3 expression.

Our data showed that metformin prevents vessel assembly in HMECs, probably through an AMPK- independent mechanism. Understanding the molecular mechanisms by which this pharmacological agent affects endothelial dysfunction is of paramount importance and paves the way to its particular use in preventing development of diabetic retinopathy and nephropathy, two processes where angiogenesis is exacerbated.

• AICAR
• AMPK Signaling
• Compound C
• Endothelial Cells
• Metformin

• Maturation
• Stem cell therapy
• Type 1 diabetes mellitus
• β cell

• Maturation
• Stem cell therapy
• Type 1 diabetes mellitus
• β cell

• Computational biology
• Diabetic cardiomyopathy
• Epigenomics
• Glycemic memory
• Type 2 diabetes mellitus
• Whole-genome DNA methylation

Endothelial cells take pivotal roles in the heart and the vascular system and their differentiation, subspecification and function is determined by gene expression. A stable, in vitro cardiac endothelial cell line could provide high cell numbers as needed for many epigenetic analyses and facilitate the understanding of molecular mechanisms involved in endothelial cell biology. To test their suitability for transcriptomic or epigenetic studies, we compared the transcriptome of cultured immortalized mouse cardiac endothelial cells (MCEC) to primary cardiac endothelial cells (pEC). Whole transcriptome comparison of MCEC and pEC showed a correlation of 0.75–0.77. Interestingly, correlation of gene expression declined in endothelial cell-typical genes. In MCEC, we found a broad downregulation of genes that are highly expressed in pEC, including well-described markers of endothelial cell differentiation. Accordingly, systematic analysis revealed a downregulation of genes associated with typical endothelial cell functions in MCEC, while genes related to mitotic cell cycle were upregulated when compared to pEC. In conclusion, the findings from this study suggest that primary cardiac endothelial cells should preferably be used for genome-wide transcriptome or epigenome studies. The suitability of in vitro cell lines for experiments investigating single genes or signaling pathways should be carefully validated before use.

Type 1 diabetes (T1D) is associated with a greater occurrence of cardiovascular pathologies. Vascular dysfunction has been shown at the level of the endothelial layers and failure to maintain a continuous pool of circulating nitric oxide (NO) has been implicated in the progression of poor vascular health. Biochemically, NO can be produced via two distinct yet inter-related pathways that involve an upregulation in the enzymatic activity of nitric oxide synthase (NOS). These pathways can be split into an endogenous oxygen-dependent pathway i.e., the catabolism of the amino acid L-arginine to L-citrulline concurrently yielding NO in the process, and an exogenous oxygen-independent one i.e., the conversion of exogenous inorganic nitrate to nitrite and subsequently NO in a stepwise fashion. Although a body of research has explored the vascular responses to exercise and/or compounds known to stimulate NOS and subsequently NO production, there is little research applying these findings to individuals with T1D, for whom preventative strategies that alleviate or at least temper vascular pathologies are critical foci for long-term risk mitigation. This review addresses the proposed mechanisms responsible for vascular dysfunction, before exploring the potential mechanisms by which exercise, and two supplementary NO donors may provide vascular benefits in T1D.

• cardiovascular disease
• dietary nitrates
• endothelial dysfunction
• nitric oxide
• type 1 diabetes