Objectives: We assessed the status of micronutrients and oxidative stress in blood and lens and examined their linkages with lens degeneration in cataract patients.
Methods: For 143 cataract patients (50 to 70 y) and 100 age- and sex-matched controls of low- and high-income groups, oxidative stresses such as as thiobarbituric acid reactive substances (TBARS) and levels of Zn, Fe, Se, Mn, riboflavin, thiamine, vitamin C, vitamin A, beta-carotene, ceruloplasmin, and hemoglobin in plasma were assessed. In extracted cataractous lenses, the ratio of soluble to total proteins (S:T ratio), turbidity, TBARS, and levels of Zn, Fe, Cu, Mn, and Se, were estimated.
Results: Plasma TBARS were higher in cataract patients (40% to 66%) than in controls. Levels of hemoglobin and serum ceruloplasmin and plasma levels of Fe, vitamin C, vitamin A, beta-carotene, thiamine, and riboflavin were subnormal in all patients and lowest in low-income patients. Plasma TBARS were positively associated with turbidity (r = 0.30, P < 0.05) but negatively with hemoglobin and ceruloplasmin (r = -0.31 and -0.34, P < 0.05). Plasma malondialdehyde was correlated positively with plasma Se (r = 0.32, P < 0.01), whereas a negative and highly significant correlation was seen with lens Fe (r = -0.53 P < 0.001). Further, plasma TBARS, lens TBARS, and lens turbidity showed significant correlation with opacity grades obtained on a slit-lamp biomicroscope (r = 0.54, 0.37, and 0.34, P < 0.05). The highest S:T ratio was 0.68, indicating a higher threshold for cataract formation in humans. The S:T ratio was negatively associated with lens Fe (r = -0.38, P < 0.001). Turbidity was negatively correlated with Fe levels (r = -0.24, P < 0.001).
Conclusions: Oxidative stress of the lens had direct influence on the solubility of lens proteins, leading to an increase in the opacity of lens. Plasma TBARS can be used as biomarkers of degeneration in the lens. Nutritional etiology of cataractogenesis may be different in the two socioeconomic classes.