Effect of long-term dietary manipulation on the aggregation of rat lens crystallins: role of alpha-crystallin chaperone function.
OBJECTIVE
To investigate the effect of food, protein, and vitamin restriction on the susceptibility of lens crystallins to aggregation and chaperone activity of alpha-crystallin.


METHODS
Thirty day old Wistar/NIN rats were maintained on regular rodent diet (C), 50% food restriction (FR), 75% protein restriction (PR), and 50% vitamin restriction (VR) diet for 20 weeks. At the end, alpha-, beta-, and gamma-crystallins were isolated from the lenses of these animals and subjected to in vitro aggregation induced by oxidation, UV irradiation and heat. Aggregation and chaperone activity was assessed by light scattering methods.


RESULTS
Dietary restriction has been shown to extend the mean and maximum life span and retard age-related diseases, including cataract. In this study, we demonstrate that while beta- and gamma-crystallins isolated from FR and PR groups were less susceptible to in vitro induced aggregation, beta- and gamma-crystallins from the VR group were more susceptible, compared to controls. Alpha-crystallin from any of the groups did not shown a considerable amount of aggregation. On the other hand, the chaperone activity of alpha-crystallin from FR and PR groups was not significantly different from controls. However, alpha-crystallin from the VR group demonstrated substantially higher chaperone activity than controls.


CONCLUSIONS
These results indicate that while food and protein restriction appear to lower the susceptibility of beta- and gamma-crystallins towards aggregation, vitamin restriction tends to increase the aggregation. Chaperone activity of alpha-crystallin is affected (improved) by only vitamin restriction.
National Institute of Nutrition (ICMR), Hyderabad, India. geereddy@yahoo.com
G Bhanuprakash
GB
Reddy
P Yadagiri
PY
Reddy
A
A
Vijayalakshmi
M Satish
MS
Kumar
P
P
Suryanarayana
B
B
Sesikeran
D000818:Animals; D001361:Avitaminosis / Q000378:metabolism; D001835:Body Weight; D003459:Crystallins / Q000378:metabolism* / Q000528:radiation effects; D004032:Diet; D018753:Diet, Protein-Restricted; D006358:Hot Temperature; D007908:Lens, Crystalline / Q000502:physiology / Q000528:radiation effects; D008297:Male; D018832:Molecular Chaperones / Q000502:physiology*; D010084:Oxidation-Reduction; D011489:Protein Denaturation; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D014466:Ultraviolet Rays
D003459:Crystallins; D018832:Molecular Chaperones