Delay of diabetic cataract in rats by the antiglycating potential of cumin through modulation of alpha-crystallin chaperone activity

J Nutr Biochem. 2009 Jul;20(7):553-62. doi: 10.1016/j.jnutbio.2008.05.015. Epub 2008 Sep 11.

Abstract

alpha-Crystallin, a molecular chaperone of the eye lens, plays an important role in maintaining the transparency of the lens by preventing the aggregation/inactivation of several proteins and enzymes in addition to its structural role. alpha-Crystallin is a long-lived protein and is susceptible to several posttranslational modifications during aging, more so in certain clinical conditions such as diabetes. Nonenzymatic glycation of lens proteins and decline in the chaperone-like function of alpha-crystallin have been reported in diabetic conditions. Therefore, inhibitors of nonenzymatic protein glycation appear to be a potential target to preserve the chaperone activity of alpha-crystallin and to combat cataract under hyperglycemic conditions. In this study, we investigated the antiglycating potential of cumin in vitro and its ability to modulate the chaperone-like activity of alpha-crystallin vis-à-vis the progression of diabetic cataract in vivo. Aqueous extract of cumin was tested for its antiglycating ability against fructose-induced glycation of goat lens total soluble protein (TSP), alpha-crystallin from goat lens and a nonlenticular protein bovine serum albumin (BSA). The antiglycating potential of cumin was also investigated by feeding streptozotocin (STZ)-induced diabetic rats with diet containing 0.5% cumin powder. The aqueous extract of cumin prevented in vitro glycation of TSP, alpha-crystallin and BSA. Slit lamp examination revealed that supplementation of cumin delayed progression and maturation of STZ-induced cataract in rats. Cumin was effective in preventing glycation of TSP and alpha-crystallin in diabetic lens. Interestingly, feeding of cumin to diabetic rats not only prevented loss of chaperone activity but also attenuated the structural changes of alpha-crystallin in lens. These results indicated that cumin has antiglycating properties that may be attributed to the modulation of chaperone activity of alpha-crystallin, thus delaying cataract in STZ-induced diabetic rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cataract / chemically induced
  • Cataract / diet therapy*
  • Cuminum*
  • Diabetes Mellitus, Experimental / complications*
  • Disease Progression
  • Glycosylation / drug effects
  • Male
  • Molecular Chaperones / metabolism*
  • Phytotherapy*
  • Plant Preparations / pharmacology
  • Plant Preparations / therapeutic use
  • Rats
  • Rats, Wistar
  • alpha-Crystallins / metabolism*

Substances

  • Molecular Chaperones
  • Plant Preparations
  • alpha-Crystallins