Combined Antioxidant Therapy on Oxidative Stress, Mitochondrial Dysfunction Markers in Diabetic Retinopathy

The present study aims to support previous research on antioxidant therapy effects in diabetic retinopathy outcome. The investigators intend to assess 180 patients with diabetic retinopathy in different stages (moderate, severe and proliferative), whom either will be assigned to placebo group or combined antioxidant therapy. Each group will receive the intervention for 12 months. Such intervention consists in taking one tablet (placebo or antioxidant therapy) orally, a day.

At baseline, blood and urine samples will be collected in order to assess metabolic and oxidative stress status, mitochondrial function or dysfunction, liver and kidney function. In addition, fluorescein angiography will be done for the categorization of diabetic retinopathy. After six months and at the end of the intervention, blood and urine measurements as well as angiographies will be done for comparing the outcomes between both groups and correlate oxidative stress status, mitochondrial dysfunction with grade of retinopathy.

Diabetic retinopathy is a diabetes microvascular complication due to an insufficient oxygen supply to its endothelial cells in states of constant hyperglycemia. This entity is classified in two main categories: non-proliferative diabetic retinopathy and proliferative diabetic retinopathy, the latter is characterized for the presence of neovascularization as oppose to the first one.

Oxidative stress has been considered as one of the main factors in the development of diabetic retinopathy. It results from an imbalance between oxidants production and cellular antioxidant defenses, which provokes DNA damage in the mitochondrion altering its capacity to produce ATP (Adenosine Triphosphate) resulting in what is known as mitochondrial dysfunction.

Diabetic retinopathy management merely comprises glycemic, lipemic and blood pressure control. Secondary intervention includes anti-platelet agents, protein-kinase C inhibitors, aldolase reductase inhibitors, laser and vitrectomy. Antioxidant therapy has been used as a co-adjuvant for these interventions, as antioxidant substances that complement action and efficacy of the established treatment for diabetic retinopathy.

Diabetic retinopathy is the principal cause of blindness in persons between 20 and 70 years of age. Its prevalence is, approximately, 25% 5 years after diagnosis.

Which is why the investigators intend to prove if the antioxidant therapy is able to change retinopathy outcomes in oxidative stress, mitochondrial dysfunction and/or grade of retinopathy.

Eligibility Criteria:
Inclusion Criteria:

* Patients with type 2 diabetes with moderate or severe non-proliferative diabetic retinopathy without clinically significant macular edema.
* Patients with type 2 diabetes with proliferative diabetic retinopathy without clinically significant macular edema.
* In current treatment that may include: metformin, glibenclamide, pravastatin, bezafibrate, losartan, nifedipine or captopril.
* HbA1c equal or lower than 9%
* LDL under 190mg/dl, triglycerides under 500mg/dl)
* Blood pressure under 180/110 mmHg
* Non-smoker or inactive for at least 6 months
* Signed informed consent

Exclusion Criteria:

* Antioxidant therapy intake over the last 6 months. Antioxidant dietary intake that surpasses the daily DIR (dietary intake recommendations)
* Patients who require secondary intervention (laser surgery)
* Patients with previous history of myocardial infarction, ictus or severe peripheral vasculopathy
* Patients with pathologies that increase oxidative stress
* Patients with neurodegenerative or carcinogen processes
* Hepatic or renal failure
* Pregnancy
* Patients with hypersensitivity to therapy components
* Other ocular pathologies, such as cataract, glaucoma, corneal dystrophy, macular degeneration among others
* Patients who are currently participating in other clinical trials