Indian Write- Ups

Management

Role Of Oxidant Stress in Diabetic Retinopathy

A P S Narang, Department of Biochemistry, et al

Source: Indian Medical Gazette

Introduction

Diabetic Retinopathy is one of the common complications of diabetes. It is clinically significant since it can cause 85 percent of blindness in diabetic patients¹. The prevalence of retinopathy is positively associated with duration of diabetes. A good control of blood sugar may delay its development².

The role of oxidative stress in the pathogenesis of complications of diabetes is being investigated. Free radicals initiating an autocatalytic chain reaction attacks membrane lipids resulting in loss of unsaturated fatty acids and membrane damage3 and cell death. Oxidative stress in hyperglycemia is amplified by metabolic stress. The present study was aimed to compare oxidant stress in diabetic patients with or without retinopathy with that of non diabetic control.

Materials and Methods

Study was conducted on 150 patients aged 40–60 years attending OPD and admitted in Dayanand Medical College and Hospital, Ludhiana. Patients were divided into three groups of 50 each.

Group-I : NIDDM patients with background diabetic retinopathy.
Group-II: NIDDM patients without retinopathy.
Group-III: Non diabetic controls.

All the patients were well matched for age and sex and did not have any other complications of diabetes as they had normal liver and kidney function test. All the patients had blood sugar more then 200 mg/dL at one level (Fasting of PP).Duration of diabetes in both the groups was 5-10 years. The biochemical estimation(Blood sugar, RFT, LFT) were performed on Hitachi 911 Autoanalyser using Boehringer Mannheim kits.

Diognosis of diabetic retinopathy was made on direct ophthalmoscopy. Ophthalmascopic features which put the patients in background diabetic retinopathy included microaneorgsms, dot and blot haemorrhages and hard exudates2. Antioxidant Superoxide Dismutase (SOD) was estimated using kits from Randox Ltd. Ascorbic acid was estimated by 2-6-dichlorophenol indophenol titration method.

Result

The result of fasting blood sugar, S.O.D. and ascorbic acid are presented in Table 1. Blood sugar was singnificantly higher in both the groups of diabetics. S.O.D. was found to be decreased in diabetics as compared to controls (p<0.001). S.O.D. was significantly lower in diabetics with retinopathy when compared to diabetics without retinopathy (p<0.001).

Similarly, ascorbic acid was found to be lower in both groups of diabetics (p<0.001) compared to controls. Among two groups of patients , it was significantly decreased in patients with retinopathy (p<0.001).

Table 1

Levels of fasting Blood sugar, Superoxide Dismutase and Ascorbic Acid in whole blood of patients ( Mean + S.D. )
FBS (mg/dL)		SOD(U/ml)	Ascorbic acid ( mg/L )
Group –I	233.11+94.55	95.08+ 44.42	12.61+2.70
Group – II	200.80+64.96	198.48 + 47.43	16.76 + 3.30
Group – III	107.83+8.25	298.84 + 112.07	20.81 + 2.85

Discussion

Oxidative stress in various diseases can be caused by tissue damage. Baynes4 proposed that increase oxidative stress may result either from overproduction of reactive oxygen radicals or decreased efficiency of defence and scavenger system . Pathogenesis of diabetic complications may be result of oxidative as well as metabolic stress.

Vitamin E and Vitamin C are important component of cell defence against oxidant stress5 as these are required for maintaining levels of enzymatic antioxidant. These levels are significantly lower in diabetics and still decreased in diabetic retinopathy6. In the present study , diabetics have significantly lower levels of SOD and ascorbate as compared to non-diabetics . Significantly decreased levels of SOD and ascorbate were found in diabetic patients with retinopathy than patients of diabetes without retinopathy . This implies oxidative stress as the causative factor in pathogenesis of diabetic retinopathy.

This has been found that higher doses of Vitamin C are associated with reversal of early sign of retinopathy in diabetics7 confirming its protective role in damage of blood vessels.

Summary

Antioxidant status was studied in 100 aged 40-60 years Non Insulin Dependent Diabetes Mellitus (NIDDM) patients with and without retinopathy and result were compared with 50 healthy controls. NIDDM patients were divided in two groups of 50 each. Group I included diabetes with retinopathy and Group II comprised of diabetic without retinopathy. Superoxide dismutase levels and plasma ascorbic acid levels were significantly decresed in diabetics both with and without retinopathy as compared to controls (p<0.001). Significantly low values were found in diabetics with retinopathy. When compared to diabetics without retinopathy. Hyperglycemia and antioxidant deficiency are associated with diabetes with a considerable risk for diabetic retinopathy.

Keywords : Diabetes,retinopathy,SOD,Ascorbic acid .

References

Merimee, T.J.- Diabetic retinopathy , W. Eng. J. Med. 322 (14) :978-983, 1990.
Jack J. Kanski- Diabetic retinopathy In : Clinical ophthalmology. 4th Edn. Butter Worth Heinemann Ltd. pp. 465-479,1999.
Robbins V Cotron R.S. and Kumar V. – In : Robbins pathological basis of disease eds. Prism Book(pvt.)Ltd . W.B. Saunders Co. pp. I-34,1994.
Baynes J.W. – Role of oxidative stress in development of complications in diabetes . Diabetes,40 : 405-412, 1991.
Halliwell B., John M.C. and Gutteridge – The antioxidants of human extracellular fluids . Archives of Biochem. and Biophys.280(1): 1-8, 1990.
Rema M.,Mohan V.,Bhasker V. and Shanmugasundram K.R.–Does oxidant stress play a role in diabetic retinopathy. Indian J. Ophthalmol 43(1): 17-21,1995.
Crary E.J. and McCarty M.F. – Potential clinical applications for high dose nutritional antioxidants. Med. Hypothesis, 13: 74-98, 1984.

Printer Friendly