Excessive Milk Intake as a Risk Factor, Probably Associated with Oxidative Stress, in Experimental Naphthalene-Initiated Cataract in Rats

Abstract

Aim: To determine whether a diet containing excessive amounts of milk aggravates naphthalene-initiated cataracts in a common animal model of age-related human cataract. Methods: Ninety Sprague-Dawley rats were fed a natural diet supplemented with either water (group A), normal amounts of milk (group B), excessive amounts of milk (group C), naphthalene plus water (group D), naphthalene plus normal amounts of milk (group E), naphthalene plus excessive amounts of milk (group F). Cataract development was monitored weekly using a slit lamp and lens gray value analysis. Concentrations of reactive oxygen species (ROS), reduced glutathione (GSH) and malondialdehyde (MDA) in rat lenses were measured to determine the role of oxidative stress in cataract induction. Results: By week 4, the cortical gray value was significantly higher in group F than that in group D, and the cortical gray value was significantly higher in group D than in group A. However, by week 8, no significant differences were observed among groups C, F, B, E and A. ROS concentrations in lenses of rats of groups C and F were slightly higher than in those of groups B, E and A, but ROS concentrations in group F were significantly higher than in the other groups receiving naphthalene (i.e. groups D and E). GSH concentrations in group F were significantly lower than in the other groups. MDA concentrations in group F were significantly higher than in the other groups receiving naphthalene, indicating increased lipid peroxidation induced by naphthalene plus excessive intake of milk. Conclusions: Our results provide quantitative evidence that excessive intake of milk aggravates naphthalene-initiated cataracts, which is probably due to oxidative damage caused by increased ROS.

Is Dietary Milk Intake Associated with Cataract Extraction History in Older Adults? An Analysis from the US Population

“…is notion is consistent with the synergistic effect observed when two cataractogenic factors are introduced simultaneously in an animal model [22]. For example, an investigation of the effect of high milk intake in Sprague-Dawley rats showed that the presence of underlying damage to the lens (e.g., by naphthalene) led to significant susceptibility to injury by excessive milk intake [23]. is notion is also in line with previous clinical observations suggesting that high lactose intake was related to cataract risk in subjects with low activity of galactose-metabolic enzymes, but not when high levels of enzymatic activity were present [24].…”

“…Multiple factors could have played a role. References to data stemming from animal experimentation were common [14,23,25], but these models required notably high intake of lactose (25-70% of total dietary intake) that is unlikely to be applicable to the human diet [5]. Besides, different indicators of milk exposure were historically used to assess this relationship in humans.…”

Association of Age-Related Cataract Risk with High Polygenetic Risk Scores Involved in Galactose-Related Metabolism and Dietary Interactions

“…It remains controversial whether dairy product consumption is a risk factor for cataract formation [33]. An experimental animal study provided quantitative evidence that excessive milk intake aggravates ARC in rats due to oxidative damage caused by increased reactive oxygen species [34]. However, a recent longitudinal epidemiologic study reported no significant association between dairy product consumption and the risk of incident cataracts in 5,860 subjects [35].…”