Mirabegron-induced brown fat activation does not exacerbate atherosclerosis in mice with a functional hepatic ApoE-LDLR pathway

Agonism of β3-Adrenoceptors Inhibits Pathological Retinal Angiogenesis in the Model of Oxygen-Induced Retinopathy

Purpose

In response to hypoxia, sympathetic fibers to the retina activate β-adrenoceptors (β-ARs) that play an important role in the regulation of vascular and neuronal functions. We investigated the role of β3-AR using the mouse model of oxygen-induced retinopathy (OIR).

Methods

Mouse pups were exposed to 75% oxygen at postnatal day 7 (PD7) followed by a return to room air at PD12. The β3-AR preferential agonist BRL37344 was subcutaneously administered once daily at different times after the return to room air. At PD17, the OIR mice underwent flash and pattern electroretinogram. After sacrifice, retinal wholemounts were used for vessel staining or immunohistochemistry for astrocytes, Müller cells, or retinal ganglion cells (RGCs). In retinal homogenates, the levels of markers associated with neovascularization (NV), the blood-retinal barrier (BRB), or astrocytes were determined by western blot, and quantitative reverse-transcription polymerase chain reaction was used to assess β3-AR messenger. Administration of the β3-AR antagonist SR59230A was performed to verify BRL37344 selectivity.

Results

β3-AR expression is upregulated in response to hypoxia, but its increase is prevented by BRL37344, which counteracts NV by inhibiting the pro-angiogenic pathway, activating the anti-angiogenic pathway, recovering BRB-associated markers, triggering nitric oxide production, and favoring revascularization of the central retina through recovered density of astrocytes that ultimately counteracts NV in the midperiphery. Vasculature rescue prevents dysfunctional retinal activity and counteracts OIR-associated retinal ganglion cell loss.

Conclusions

β3-AR has emerged as a crucial intermediary in hypoxia-dependent NV, suggesting a role of β3-AR agonists in the treatment of proliferative retinopathies.

Equisetin protects from atherosclerosis in vivo by binding to STAT3 and inhibiting its activity

Atherosclerosis is a chronic inflammatory vascular disease characterized by lipid metabolism disorder and lipid accumulation. Equisetin (EQST) is a hemiterpene compound isolated from fungus of marine sponge origin, which has antibacterial, anti-inflammatory, lipid-lowering, and weight loss effects. Whether EQST has anti-atherosclerotic activity has not been reported. In this study, we revealed that EQST displayed anti- atherosclerosis effects through inhibiting macrophage inflammatory response, lipid uptake and foam cell formation in vitro, and finally ameliorated high-fat diet (HFD)-induced atherosclerosis in AopE-/- mice in vivo. Mechanistically, EQST directly bound to STAT3 with high-affinity by forming hydrophobic bonds at GLN247 and GLN326 residues, as well as hydrogen bonds at ARG325 and THR346 residues. EQST interacted with STAT3 physically, and functionally inhibited the transcription activity of STAT3, thereby regulating atherosclerosis. Therefore, these results supports EQST as a candidate for developing anti-atherosclerosis therapeutic agent.

Kruppel-like factor 14 ameliorated obesity and related metabolic disorders by promoting adipose tissue browning

Obesity has been identified as a serious and debilitating disease that threatens human health, but the current treatment strategies still have some shortcomings. Exercise and dieting are difficult for many people to adhere to, and a series of surgical risks and pain brought about by volume reduction have made it difficult for the current weight loss effect to meet human expectations. In this study, we first found that mice with overexpression of the transcription factor Kruppel-like factor 14 (KLF14) in subcutaneous adipose tissue gained weight more slowly while consuming a high-fat diet than did control mice, and these mice also showed reduced insulin resistance and liver lipid deposition abnormalities. Mechanistically, the browning of white adipose tissue was promoted in adipose tissue with KLF14 overexpression; therefore, we preliminarily concluded that KLF14 can improve obesity by promoting the browning of white adipose tissue and energy consumption, thus ameliorating obesity and related metabolic disturbances. In summary, our results revealed that KLF14 may promote white adipose tissue browning, thus ameliorating high-fat diet-induced obesity and hepatic steatosis, as well as serum lipid levels and insulin resistance, thereby achieving a positive effect on metabolism.NEW & NOTEWORTHY Our study first explored the role of KLF14 in the development and progression of HFD-induced obesity in male mice. Its beneficial effect on adipose browning and metabolic disorders suggests that KLF14 may provide us a new therapeutic strategy for obesity and related metabolic complications. This health problem is of global concern and needs to be addressed.

Therapeutic Potential for Beta-3 Adrenoreceptor Agonists in Peripheral Arterial Disease and Diabetic Foot Ulcers

Annually, peripheral arterial disease is estimated to cost over USD 21 billion and diabetic foot disease an estimated at USD 9-13 billion. Mirabegron is a TGA-approved beta-3 adrenoreceptor agonist, shown to be safe and effective in the treatment of overactive bladder syndrome by stimulating bladder smooth muscle relaxation. In this review, we discuss the potential use of beta-3 adrenoreceptor agonists as therapeutic agents repurposed for peripheral arterial disease and diabetic foot ulcers. The development of both conditions is underpinned by the upregulation of oxidative stress pathways and consequential inflammation and hypoxia. In oxidative stress, there is an imbalance of reactive oxygen species and nitric oxide. Endothelial nitric oxide synthase becomes uncoupled in disease states, producing superoxide and worsening oxidative stress. Agonist stimulation of the beta-3 adrenoreceptor recouples and activates endothelial nitric oxide synthase, increasing the production of nitric oxide. This reduces circulating reactive oxygen species, thus decreasing redox modification and dysregulation of cellular proteins, causing downstream smooth muscle relaxation, improved endothelial function and increased angiogenesis. These mechanisms lead to endothelial repair in peripheral arterial disease and an enhanced perfusion in hypoxic tissue, which will likely improve the healing of chronic ulcers.