Newly-found functions of metformin for the prevention and treatment of age-related macular degeneration

Pharmaceutical therapies targeting autophagy for the treatment of age-related macular degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible vision loss in the elderly. Although new therapies have recently emerged, there are currently no ways of preventing the development of the disease. Changes in intracellular recycling processes. Changes in intracellular recycling processes, called autophagy, lead to debris accumulation and cellular dysfunction in AMD models and AMD patients. Drugs that enhance autophagy hold promise as therapies for slowing AMD progression in preclinical models; however, more studies in humans are required. While a definitive cure for AMD will likely hinge on a personalized medicine approach, treatments that enhance autophagy hold promise for slowing vision loss.

Metformin inhibits methylglyoxal-induced retinal pigment epithelial cell death and retinopathy via AMPK-dependent mechanisms: Reversing mitochondrial dysfunction and upregulating glyoxalase 1

Diabetic retinopathy (DR) is a major cause of blindness in adult, and the accumulation of advanced glycation end products (AGEs) is a major pathologic event in DR. Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is a precursor of AGEs. Although the therapeutic potential of metformin for retinopathy disorders has recently been elucidated, possibly through AMPK activation, it remains unknown how metformin directly affects the MGO-induced stress response in retinal pigment epithelial cells. Therefore, in this study, we compared the effects of metformin and the AMPK activator A769662 on MGO-induced DR in mice, as well as evaluated cytotoxicity, mitochondrial dynamic changes and dysfunction in ARPE-19 cells. We found MGO can induce mitochondrial ROS production and mitochondrial membrane potential loss, but reduce cytosolic ROS level in ARPE-19 cells. Although these effects of MGO can be reversed by both metformin and A769662, we demonstrated that reduction of mitochondrial ROS production rather than restoration of cytosolic ROS level contributes to cell protective effects of metformin and A769662. Moreover, MGO inhibits AMPK activity, reduces LC3II accumulation, and suppresses protein and gene expressions of MFN1, PGC-1α and TFAM, leading to mitochondrial fission, inhibition of mitochondrial biogenesis and autophagy. In contrast, these events of MGO were reversed by metformin in an AMPK-dependent manner as evidenced by the effects of compound C and AMPK silencing. In addition, we observed an AMPK-dependent upregulation of glyoxalase 1, a ubiquitous cellular enzyme that participates in the detoxification of MGO. In intravitreal drug-treated mice, we found that AMPK activators can reverse the MGO-induced cotton wool spots, macular edema and retinal damage. Functional, histological and optical coherence tomography analysis support the protective actions of both agents against MGO-elicited retinal damage. Metformin and A769662 via AMPK activation exert a strong protection against MGO-induced retinal pigment epithelial cell death and retinopathy. Therefore, metformin and AMPK activator can be therapeutic agents for DR.

Effects of medications on hypoxia-inducible factor in the retina: A review

Hypoxia-inducible factor (HIF) plays a critical role in the mechanisms that allow cells to adapt to various oxygen levels in the environment. Specifically, HIF-1⍺ has shown to be widely involved in cellular repair, survival, and energy metabolism. HIF-1⍺ has also been found in increased levels in cancer cells, highlighting the importance of balance in the hypoxic response. Promoting HIF-1⍺ activity as a potential therapy for degenerative diseases and inhibiting HIF-1⍺ as a therapy for pathologies with overactive cell proliferation are actively being explored. Digoxin and metformin, HIF-1⍺ inhibitors, and deferoxamine and ⍺-ketoglutarate analogues, HIF-1⍺ activators, are being studied for application in age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. However, these same medications have retinal toxicities that must be assessed before implementation of therapeutic care. Herein, we highlight the duality of therapeutic and toxic potential of HIF-1⍺ that must be carefully assessed prior to its clinical application in retinal disorders.

Age-Related Macular Degeneration: Epidemiology, Pathophysiology, Diagnosis, and Treatment

The greatest global root of irremediable amaurosis in the venerable is age-related macular degeneration (AMD), a complex eye condition. Clinically, AMD is characterized as being in an early stage to late stage and initially affects the macula, which is the center of the retina (advanced AMD). Age-related cellular and metabolic imbalance are made worse by the creation of excessive amounts of free radical species, which causes mitochondrial malfunction. As a result, in AMD-affected eyes, the deprivation of melanocytes, confection, and eventually atrophy within the retinal tissue are caused by the continued proliferation of oxidative stress caused by systemic antioxidant capacity depletion.

In the urbanized, industrialized world, age-related macular degeneration (AMD) is one of the major causes of central vision loss in the older age group. Although several causes and mechanisms for the dysfunction and degeneration of the retinal pigment epithelium (RPE) have previously been identified, the condition’s symptoms are still not fully understood. Etiopathogenesis is still not entirely understood. As a result, the RPE fails, allowing an accumulation of aberrant misfolded proteins, due to the loss of anatomical control over oppression, altered homeostasis, dysfunctional lipid homeostasis, and failure of mitochondria.

Due to the multitude of interconnected processes, numerous complicated therapy combinations will probably be the best option to deliver the best visual outcomes; these combinations will vary depending on the kind and degree of the condition being treated. Undoubtedly, this will lead to the development of customized preventative medications and, hopefully, the revelation of a potential cure. All the mechanisms involved in the etiology of AMD should be continuously probed to create covariates for other contemporaneous or future problems.

Role of the AMPK signalling pathway in the aetiopathogenesis of ocular diseases

BACKGROUND

AMP-activated protein kinase (AMPK) plays a precise role as a master regulator of cellular energy homeostasis. AMPK is activated in response to the signalling cues that exhaust cellular ATP levels such as hypoxia, ischaemia, glucose depletion and heat shock. As a central regulator of both lipid and glucose metabolism, AMPK is considered to be a potential therapeutic target for the treatment of various diseases, including eye disorders.

OBJECTIVE

To review all the shreds of evidence concerning the role of the AMPK signalling pathway in the pathogenesis of ocular diseases.

METHOD

Scientific data search and review of available information evaluating the influence of AMPK signalling on ocular diseases.

RESULTS

Review highlights the significance of AMPK signalling in the aetiopathogenesis of ocular diseases, including cataract, glaucoma, diabetic retinopathy, retinoblastoma, age-related macular degeneration, corneal diseases, etc. The review also provides the information on the AMPK-associated pathways with reference to ocular disease, which includes mitochondrial biogenesis, autophagy and regulation of inflammatory response.

CONCLUSION

The study concludes the role of AMPK in ocular diseases. There is growing interest in the therapeutic utilization of the AMPK pathway for ocular disease treatment. Furthermore, inhibition of AMPK signalling might represent more pertinent strategy than AMPK activation for ocular disease treatment. Such information will guide the development of more effective AMPK modulators for ocular diseases.[Formula: see text].