Polyphenol-enriched cocoa protects the diabetic retina from glial reaction through the sirtuin pathway

Area of Science:

• Neuroscience
• Biochemistry
• Ophthalmology

Background:

• Cocoa flavonoids are antioxidants with cardiovascular benefits.
• Sirtuins (SIRTs) are sensitive to oxidation, impacting cellular health.
• The effect of cocoa on neurodegeneration, particularly in the retina, is not well understood.

Purpose of the Study:

• To assess the protective effects of cocoa against diabetic retinopathy.
• To investigate the role of the Sirtuin-1 (SIRT1) pathway in cocoa's retinal protection.
• To evaluate cocoa's impact on oxidative stress and related markers in a diabetic retina model.

Main Methods:

• In vitro: Rat Müller cells (rMCs) exposed to high glucose or H2O2, treated with cocoa and SIRT-1 inhibitors/siRNA.
• In vivo: Streptozotocin-induced diabetic rats received varying doses of cocoa polyphenols for 16 weeks.
• Assessed markers included reactive oxygen species (ROS), poly(ADP-ribose) polymerase 1 (PARP-1) activity, NAD(+) levels, SIRT1 activity, acetyl-RelA/p65, glial fibrillary acidic protein (GFAP), and electroretinogram (ERG).

Main Results:

• High glucose/H2O2 increased GFAP and acetyl-RelA/p65, while decreasing SIRT1 activity in rMCs.
• Cocoa treatment reversed these changes, reduced ROS and PARP-1 activity, increased NAD(+), and enhanced SIRT1 activity.
• Diabetic rats showed retinopathy markers and impaired ERG, linked to PARP-1 activation, NAD(+) depletion, and SIRT1 impairment.
• Cocoa polyphenols dose-dependently restored these diabetic-induced alterations in vivo.

Conclusions:

• Cocoa polyphenols protect the retina from diabetic damage by modulating the SIRT1 pathway.
• Cocoa reduces oxidative stress and inflammation in the diabetic retina.
• This study highlights cocoa's potential therapeutic role in managing diabetic retinopathy.