Serial Review J. Clin. Biochem. Nutr., 35, 35–45, 2004

Vitamin E Guest Editor: Etsuo Niki Possibility of Clinical Application of Vitamin E to Prevention

Yoshiji Ohta*

Department of Chemistry, School of Medicine, Fujita Health University, Toyoake 470–1192, Japan

Received 30 October, 2003; Accepted 10 November, 2003

Summary It has been implicated that oxidative stress is involved in the development of aged-related and diabetic in humans and also in cataract development in a variety of in vivo experimental cataract models. Therefore, this article will review the possibility of the clinical application of vitamin E to cataract prevention, based on data concerning the level of vitamin E in normal and cataractous lenses of humans and experimental animals, the relationship between dietary vitamin E intake and the risk of cataracts, the effect of vita- min E supplementation on cataract development in humans, and the effect of oral or parenteral vitamin E treatment or topical vitamin E instillation on cataract development in a variety of in vivo experimental cataract models. These data reported so far may allow us to think of a possibility that vitamin E is clinically applied to cataract development.

Key Words: cataract (humans and experimental animals), oxidative stress, vitamin E, cataract prevention

Cataract treatment in humans is now conducted Introduction by surgical operation, i.e., cataract surgery, and then intraocular lenses are inserted into the cataract sur- Cataract is the major cause of blindness world- gery-operated eyes to recover visual acuity. However, wide. About 40% of the estimated 42 million blind an ideal treatment of cataracts is carried out without people worldwide are blind from cataract [1]. In surgical operation. Namely, cataracts are treated by Japan, the percentage of people possessing cataracts administration of anticataract agents. Although the including early age-related cataracts or senile cata- development of anticataract agents has been attempted racts is 29–32% in the fortieth year of age, 24–54% in several countries, there is nothing definitively in the fiftieth year of age, 43–83% in the sixtieth year effective in the treatment of human cataracts at of age, 60–97% in the seventieth year of age, and 98– present. Much attention has been paid to the in- 100% in the eightieth year or more of age [2]. volvement of oxidative stress in cataract development Although there are several cataract risk factors in in humans and experimental animals. The relation- humans, is one of the major cataract risk ship between vitamin E and cataracts has been stud- factors [2, 3]. In people of middle or advanced age, ied in humans and experimental animals. In this the frequency of cataract formation is higher in dia- review, therefore, I will describe the relationship betes than in non-diabetes and is raised with an between cataracts and oxidative stress, the level of increase in age [4, 5]. vitamin E in normal and cataractous lenses of * To whom correspondence should be addressed. humans and experimental animals, the relationship Tel: 81–562–93–2573 Fax: 81–562–93–4593 between dietary vitamin E intake and the risk of cat- E-mail: [email protected] aracts, the effect of vitamin E supplementation on

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36 Y. Ohta cataract development in humans, and the effect of catalase and GPx activities and GSH and ascorbic oral or parenteral vitamin E treatment or topical acid levels with cataract development have been vitamin E instillation on cataract development in a reported in rabbits administered with a catalase variety of in vivo experimental cataract models, and inhibitor 3-aminotriazole [21, 22], rats with strepto- will discuss whether there is a possibility that vita- zotocin (STZ)-induced diabetes [23, 24], rats fed a min E is clinically applied to cataract prevention. diet high in [25, 26], rats treated with selenite [27], diabetic WBN/Kob rats [28, 29], and Relationship between Cataracts and Oxidative Emory mice, a suitable model for age-related human Stress cataracts [30, 31]. Kubo et al. [32] have shown that hydroxyl radical formation occurs in accordance with Oxidative stress is a state of the imbalance accumulation of , a polyol, converted from between antioxidant defense systems and oxidative galactose via the polyol pathway in the cataractous insult, which is most likely resulted from decreased of galactose-fed rats, and have suggested that levels of antioxidants or increased oxidative insult or hydroxyl radical may play an important role in the both. There are several reports showing that the level early stage of galactose cataract process. Thus, it has of lipid peroxides, which are produced in the peroxi- been implicated that oxidative stress contributes to dation of membrane lipids via reactive oxygen species cataract development in various cataract models of such as superoxide radical, hydroxyl radical, hydro- experimental animals as well as in humans. gen peroxide, and singlet oxygen, is higher in cata- ractous lenses than in clear lenses in humans [6–10] Distribution of Vitamin E in Ocular Lenses and that the level of lens lipid peroxide is further increased in diabetic patients with cataracts [7, 8, Vitamin E is well known to exert an antioxidant 10]. It is known that the concentration of hydrogen action by breaking the chain-reaction of lipid perox- peroxide in aqueous and vitreous humors surround- idation and scavenging reactive oxygen species and a ing the lens is higher in people with cataracts than in membrane-stabilizing action [33, 34]. As to the dis- people without cataracts [7, 11]. It is also known tribution of vitamin E in ocular lenses, Bessems et al. that cataract patients who have high concentrations [35] have reported that, in normal human lenses, the of hydrogen peroxide in the aqueous humor posses content of -tocopherol is slightly higher in the high concentrations of hydrogen peroxide in the lens nucleus than the cortex and that, in nuclear-catarac- and that there is a significant correlation between tous human lenses, the content of -tocopherol is aqueous humor and lens hydrogen peroxide concen- rather higher in the cortex than in the nucleus. Yeum trations in the cataract patients [11]. It has been et al. [36] have also shown in cataractous human reported that hydroxyl radical attack on lens proteins lenses that -tocopherol levels are higher in the epi- may play a role in the development of age-related thelial/cortical layer than in the nuclear layer. Thus, nuclear cataracts [12, 13]. the distribution of vitamin E in human lenses seems The antioxidant defense system in lenses is com- to be altered in response to cataract development. posed of antioxidant enzymes, such as superoxide Hirai et al. [37] have shown that the level of -toco- dismutase (SOD), catalase, and peroxi- pherol in the lens fractions of rabbits is as follows: dase (GPx), (GR) and antioxi- capsule/epitheliumnucleusanterior cortexpos- dants, such as reduced glutathione (GSH), vitamin terior cortex. Nagata et al. [38] have shown that the C or ascorbic acid, and vitamin E [14, 15]. It has highest level of -tocopherol in 1-month-old rat been reported that lens SOD, catalase, GPx, and GR lenses is in the nuclear region followed by the deeper activities and GSH levels are lower in cataractous anterior cortex, the shallow anterior cortex, the shal- patients than in normal individuals [7, 9, 10, 16–20] low posterior cortex, and the equatorial region and and the extents of reduction of lens SOD and GR that the distribution pattern of -tocopherol is simi- activities and GSH levels in cataractous patients are lar in 4- and 12-month-old rat lenses and the level of relative to the severity of cataracts [17, 19, 20]. -tocopherol in the lens fractions of 4- and 12- The relationship between cataracts and oxidative month-old rats is as follows: nucleusdeeper poste- stress has been examined in a variety of in vivo rior cortexdeeper anterior cortexshallow poste- experimental cataract models. An increase in lens rior cortexshallow anterior cortexequator. This lipid peroxide levels and/or decreases in lens SOD, finding indicates that the distribution of vitamin E

J. Clin. Biochem. Nutr.

Vitamin E and Cataract Prevention 37 in ocular lenses is altered with aging. cortex and nucleus of nuclear-cataractous human lenses (55–81 years of age) were compared to those Relationship between Dietary Vitamin E Intake and of normal human lenses (50–86 years of age), there Cataracts in Humans and Experimental Animals was no difference in the nucleus content of -toco- pherol between the cataractous and normal lenses There are several papers on the relationship but the cortex content of the vitamin E was signifi- between vitamin E and cataracts in humans. Leske et cantly higher in the cataractous lenses than in the al. [39] showed a reduced risk of cortical and mixed- normal lenses. Yeum et al. [36] have shown in Amer- type of opacities among persons with high dietary ican people with and without cataracts that the con- vitamin E intakes in the Lens Opacities Case-Con- centration of -tocopherol is higher in cataractous trol Study; in the follow-up study, however, the same lenses (76–81 year of age) than in normal lenses (53– authors could not confirm the association between 60 years of age), while the concentration of -toco- the reduced risk of cortical opacities and higher pherol is lower in the cataractous lenses than in the dietary vitamin E intake but suggested the relation normal lenses. Leiria et al. [50] have shown that of higher dietary vitamin E intake and higher plasma membranes isolated from the lenses of patients with vitamin E levels to a reduced risk of nuclear opacity age-related and diabetic cataracts contain two to progression [40]. Vitale et al. [41] reported that three-fold higher vitamin E than membranes iso- higher levels of plasma -tocopherol were associated lated from normal human lenses, although the cata- with a reduced risk of nuclear opacity and that mid- ractous lens membranes contained higher lipid per- dle levels of plasma -tocopherol were associated oxide than the normal lens membranes. Thus, lens with a reduced risk of cortical opacity, although no vitamin E levels are variable in cataractous human association was observed for high levels of plasma - lenses. tocopherol. In the Beaver Dam Eye Study, Lyle et al. [42] indicated the possibility that nuclear cataracts Lens Vitamin E levels in Cataractous Lenses of may be linked inversely to vitamin E status. How- Experimental Animals ever, no significant associations between higher vita- min E intake and less severe nuclear or cortical opac- In 1986, Hirai et al. [51] reported that although ities were found by Jacques and Chylack [43], vitamin E was present in the lens of 6-week-old rats, Mares-Perlman et al. [44], Gale et al. [45], and Tay- its analogues except for -tocopherol were not lor et al. [46]. Cai et al. [47] showed in vitamin E detected in these lenses and that, in 6-week-old rats deficient rats that vitamin E deficiency caused poste- with STZ-induced diabetes, lens -tocopherol con- rior subcapsular cortical degeneration and/or vacu- tent began to decrease after observation of overt dia- olization at the equatorial region with a increase in betes but before the formation of vacuoles at the lipid peroxide levels and a decrease in SOD activity equatorial region of the lens and the decrease in that in the lenses. Recently, Kojima et al. [48] have content was gradually enhanced with cataract devel- shown in a rat model of prednisolone-induced cata- opment. At the same time, the same authors showed ract that vitamin E deficiency is a subliminal catarac- that although a transient increase in lens lipid perox- togenesis risk factor. ide content occurred before cataract formation, there was no increase in that content during cataract Lens Vitamin E Levels in Cataractous Human development [51]. In the same year, Hirai et al. [52] Lenses showed in another report that, in weanling rats given a diet containing 38% galactose ad libitum, lens - In 1983, Dillon et al. [49] reported that when the tocopherol content began to decrease before the for- content of -tocopherol in normal human lenses mation of vacuoles at the equatorial region of the (60–80 years of age) was compared to that in similar lenses, i.e., at 2-day of feeding, and the decreased - aged caratactous human lenses, the cataractous tocopherol content was maintained at a similar level lenses contained 10% lower -tocopherol than the during cataract development, i.e., at 5- and 7-day of normal lenses, although the difference in that level feeding, although increased lipid peroxide and between the normal and cataractous lenses was not decreased GSH contents were observed in the lens statistically significant. Later, Bessems et al. [35] before cataract formation and during cataract devel- reported that when -tocopherol contents in the opment. Ogino et al. [53] showed in adult rabbits

Vol. 35, No. 1, 2004 38 Y. Ohta with 3-aminotriazole administration that lens vita- stage of early cataracts (suture accentuation) appear- min E content decreased with lens vitamin C deple- ing in the central of the lens, i.e., at 6-month of tion at the onset of cataract formation. Mitton and feeding, and the increased -tocopherol content was Trevithick [54] showed in adult rats with STZ- returned to the level of control rats at a stage of pro- induced diabetes that there was no change in - gressed cataracts reaching the nuclear region of the tocopherol content in the lens at 2 and 4 weeks after lens, i.e., at 8-month of feeding. Thus, lens vitamin diabetes induction, although decreases in GSH and E levels are variable in cataractous lenses of experi- total ascorbic acid contents were observed in the lens mental animals. at 1 week after diabetes induction. It is known that the feature and the development of galactose cata- Effect of Vitamin E Supplementation on Cataract racts are different depending on the age of rats used Development in Humans and the content of galactose in diet [55–57]. Namely, the lens of mature rats (6 weeks old or Teikari et al. [59] reported that when middle aged, more) fed a diet low in galactose has opacities at the Finish smoking men (50–69 years old) were orally anterior and posterior subcapsular regions of the cor- supplied with -tocopherol (50 mg/day) for 5 to 8 tex like in the case of human diabetic cataracts, while years, this vitamin E supplementation did not influ- the lens of immature rats (less than 6 weeks old) fed ence the prevalence and severity of nuclear, cortical, a diet high in the sugar has vacuoles at the equatorial subcapsular cataracts. In the Vitamin E and Cataract region initially and then opacities developing toward Prevention Study, Nadalin et al. [60] showed that the anterior and posterior subcapsular regions of the when Australian women and men (55–80 years old) cortex. It is also known that the speed of cataract were orally supplied with vitamin E (500 IU/day), development is faster in immature rats fed a diet there was a significant association between prior high in galactose than in mature rats fed a diet low vitamin E supplementation and the absence of corti- in the sugar [55–57]. Therefore, we examined cal opacity, after adjusting for age, while there was changes in lens -tocopherol levels with galactose no apparent protective role of prior vitamin E sup- cataract development in young (5-week-old), mature plementation in terms of nuclear opacity and nuclear (12-week-old), and aged (12-month-old) rats given color regardless of the level, regularity or duration of a 25% galactose diet at a fixed dose (15 g/day per vitamin E intake. Olmedilla et al. [61] have shown in animal) [26, 58]. As a result, it was found that 5- elderly Spanish women with age-related cataracts week-, 12-week-, and 12-month-old rats given a that when improvement of visual function is com- 25% galactose diet showed different changes in lens pared between subjects supplied with and without - -tocopherol levels with galactose cataract develop- tocopherol (100 mg/day) for 24 months, this vitamin ment. Namely, in 5-week-old rats given a 25% galac- E supplementation has no beneficial effect on the tose diet over a 45-day period, lens -tocopherol visual performance. However, Seth and Kharb [62] content did not change at 12-day of feeding at which have shown in a random trial of 50 patients (50 years time no vacuole formation occurred at the equatorial or above) with unilateral/bilateral idiopathic imma- region of the lens, but that content was reduced at 18 ture age-related cataracts requiring surgery at least days of feeding at which time vacuoles appeared at a one eye that when cataractous patients are orally part of the equatorial region, and the reduced - supplied with vitamin E (100 mg twice day) for 30 tocopherol content was increased over the level of days, the size of lens opacity in cortical cataractous control rats at 45-day of feeding at which time corti- patients, but not nuclear cataractous patients, receiv- cal cataracts were observed in the lens. In 12-week- ing vitamin E supplementation is significantly de- old rats given a 25% galactose diet over a 15-week creased as compared with placebo patients. The same period, lens -tocopherol content remained reduced authors have also shown in the random trial that this before the formation of vacuoles in the equatorial vitamin E supplementation causes an increase in lens region of the lens, i.e., at 2-week of feeding, and dur- GSH levels in patients with cortical cataracts and an ing cortical cataract development, i.e., at 7- and 15- increase in lens vitamin E levels and a decrease in week of feeding. In 12-month-old rats given a 25% lens lipid peroxide levels in patients with cortical or galactose diet over an 8-month period, lens -toco- nuclear cataracts [62]. Thus, the evaluation of vita- pherol content did not change before cataract forma- min E supplementation in cataract prevention in tion, i.e., at 4-month of feeding, but increased at a humans is not always consistent among studies

J. Clin. Biochem. Nutr. Vitamin E and Cataract Prevention 39

Table 1. In vivo experimental cataract models showing the effectiveness of oral or parenteral vitamin E treatment in cataract prevention. Treatment Cataract model Animal Anticataract Reference effect Route Dose Diabetic cataract Rat Protective Subcutaneous 50 mg/kg/day Ross, W.M. et al. [64] Rat Protective Intramuscular 335 mg/kg/day Hirai, T. et al. [65] Rat Therapeutic Oral 72.6 IU/kg/day Hattori, H. et al. [66] Galactose cataract Rat Protective Oral 15 or 30 mg/kg/day Gupta, P.P. et al. [67] Rat Protective Parenteral 100 mg/kg/day Libondi, T. et al. [69] Rat Protective Intramuscular 100 mg/kg/day Hirai, T. et al. [70] Radiation cataract (-ray) Rat Protective Subcutaneous 100 IU/day/animal Ross, W.M. et al. [71] Radiation cataract (X-ray) Rabbit Protective Parenteral 50 mg/kg/day Libondi, T. et al. [72] Selenite cataract Rat Protective Subcutaneous 2.5 mg/kg/animal Mathew, J.P. et al. [73] 3-Aminotriazole cataract Rabbit Protective Intramuscular 50 mg/kg/day Bhuyan, K.C. et al. [74] Naphthalene cataract Rabbit Protective Oral 15 or 30 mg/kg/day Gupta, P.P. et al. [67] Heredity cataract Emory mouse Protective Intraperitoneal 10 mg/week/animal Varma, S.D. et al. [76] reported so far. vitamin E ophthalmic solution showed a slightly weaker inhibitory effect in topical administration Effect of Vitamin E Treatment on Cataract Devel- than in systemic administration. Nagata et al. [78] opment in Experimental Animals reported that when a 1% vitamin E acetate solution, which was prepared by emulsifying vitamin E acetate In 1950, Charalampous and Hegsted [63] re- with polysorbate 80, a detergent, was instilled to ported that feeding of not only a high fat diet but both eyes of rats with a single oral naphthalene also a fat-free diet containing a high amount of vita- administration 5 times a day everyday for 9 weeks min E retarded cataract formation in rats with and the effect of the instilled vitamin E acetate on alloxan-induced diabetes. Later than 1970, the pre- cataract development was evaluated during the ventive or retarding effect of oral or parenteral vita- instillation period, this vitamin E acetate instillation min E treatment on cataract development has been retarded the progression rather than the formation of studied extensively in a variety of in vivo experimen- naphthalene-induced cataracts. In addition, Nagata tal cataract models [64–76]. Effectiveness of oral or et al. [79] measured the concentrations of deuterium parenteral vitamin E treatment in cataract preven- (D3)-labeled -tocopherol acetate and D3-labeled - tion has been confirmed in a variety of in vivo exper- tocopherol derived from D3-labeled -tocopherol imental cataract models, as shown in Table 1. acetate in the aqueous humor and lens of rats after An ideal treatment of cataractous patients with instilling a 1% D3-labeled -tocopherol acetate solu- vitamin E is the topical instillation of vitamin E as tion prepared with polysorbate 80 into the cul-de-sac an ophthalmic solution to the eyes of the patients of both eyes of the rats at a dose of 5 l/eye 5 times because topical vitamin E instillation is not trouble- a day for successive 1 and 3 weeks. As a result, - some for cataractous patients if the prepared vitamin tocopherol acetate was found to be penetrated into E ophthalmic solution has a low viscosity and is not the aqueous humor and lens of rats by instillation of stimulative and because topical vitamin E instillation the emulsified -tocopherol acetate solution to their makes it possible to deliver administered vitamin E eyes. However, the possibility cannot be excluded to ocular lenses in higher concentrations compared that detergents such as polysorbate 80 to emulsify to systemic vitamin E administration. Kojima et al. vitamin E are harmful to eye tissues. [77] evaluated the efficacy of a 5% vitamin E oph- Hattori et al. [80] prepared vitamin E-containing thalmic solution in its topical and systemic adminis- liposomes, in which tritium-labeled -tocopherol is tration (twice a day) using a new rat steroid-cataract present as a tracer, with dipalmitoylphosphatidylcho- model developed by them and found that topical line (DPPC), dioleoylphosphatidilcholine (DOPC) administration of the vitamin E ophthalmic solution or palmitoleoylphosphatidylcholine (POPC) in small showed a significant inhibition of cataract develop- unilamellar vesicles and examined the transport of ment in the rat steroid-cataract model, although the vitamin E into the lens of mice at 30 min after

Vol. 35, No. 1, 2004 40 Y. Ohta

Fig. 1. Outline of the preparation of vitamin E-containing or vitamin E-free liposomes used an ophthalmic solution. instilling each prepared vitamin E-containing lipo- found in vitamin E-containing liposomes prepared at some suspension to both eyes six times at intervals of the ratio of 7 : 3 for DPPC and DOPC (unpub- 30 min. The highest transport of vitamin E into the lished data). Furthermore, it was found that vitamin lens after topical instillation of vitamin E-containing E-containing liposomes prepared with DPPC and liposomes was found in DOPC liposomes followed DOPC at the ratio of 7 : 3 (w/w) delayed opacifica- by DPPC liposomes and POPC liposomes. The tion in isolated rat lenses treated with xylose [83], same authors showed in rabbits with topical instilla- methylprednisolone [84] or diethylmaleate [85]. tion of vitamin E-containing liposomes prepared Therefore, we prepared vitamin E-containing lipo- with DOPC to their eyes that vitamin E instilled in somes or vitamin E-free liposomes with DPPC and a liposomal form was transported into the lens via DOPC at the ratio of 3 : 7 (w/w) and R,R,R-- the aqueous humor and . Furthermore, Hat- tocopherol as an ophthalmic solution as shown in tori et al. [81] reported that opacification in isolated Fig. 1 and examined whether the prepared vitamin rat lenses incubated in medium containing a high E-containing liposome suspension exerts a therapeu- concentration of was retarded with preven- tic effect on sugar cataracts in 5-week-, 12-week-, tion of vitamin E depletion and increased lipid per- and 12-month-old rats fed a 25% galactose diet at a oxidation by treatment with vitamin E-containing fixed dose (15 g/day per animal) by its topical instil- liposomes prepared with DPPC. Kaneda et al. [82] lation to their both eyes at a dose of 10 l/eye (three also reported that topical instillation of vitamin E- times a day) [86, 87]. As shown in Table 2, daily containing liposomes prepared with DPPC to both instillation of vitamin E-containing liposomes, but eyes of rats fed a 50% galactose diet three times a day not vitamin E-free liposomes, to both eyes of 5- and retarded the progression rather than the formation of 12-week-old rats fed a 25% galactose diet for 4 and sugar cataracts. 9 weeks, respectively, which was started at a stage of We observed that when vitamin E-containing early cataracts, i.e., vacuole formation at the equato- liposomes were prepared with DPPC and DOPC in rial region of the lens, was found to retard the pro- various ratios (w/w) and -tocopherol and then the gression of cortical cataracts appearing after vacuole transport of vitamin E in the prepared vitamin E- formation significantly. As shown in Table 3, daily containing liposomes into isolated rat lenses was instillation of vitamin E-containing liposomes, but examined under osmotic stress induced by a high not vitamin E-free liposomes, to both eyes of 12- concentration of glucose, the highest increase in vita- month-old rats fed a 25% galactose diet for 2 min E in the lens subjected to osmotic stress was months, which was started at a stage of early cata-

J. Clin. Biochem. Nutr. Vitamin E and Cataract Prevention 41

Table 2. Effect of vitamin E-containing liposome instilla- Table 4. Effect of vitamin E-containing liposome instilla- tion on cataract progression in 5-week- and 12- tion on lens -tocopherol levels in 5-week-, 12- week-old rats fed a 25% galactose diet. week-, and 12-month-old rats fed a 25% galac- Lens opacity incidence (%)a tose diet. Treatment period and group 0 I II III IV Lens -tocopherol Treatment period and group (mg/lens) 5-week-old ratsb 5-week-old ratsb 0 week of instillation 0 week of instillation Galactose-fed group 0 100 0 0 0 Control group 10.150.78a 4 weeks of instillation Galactose-fed group 8.130.71* Galactose-fed group 0 15 30 35 20 4 weeks of instillation Liposome (vitamin E) 0 20 35 30 15 Control group 13.751.13 Liposome (vitamin E)* 0 50 30 20 0 Galactose-fed group 17.031.38* 12-week-old ratsc Liposome (vitamin E) 17.342.38* 0 week of instillation Liposome (vitamin E) 13.880.95*,# Galactose-fed group 0 100 0 0 0 12-week-old ratsc 9 weeks of instillation 0 week of instillation Galactose-fed group 0 0 30 45 25 Control group 13.632.88 Liposome (vitamin E) 0 0 50 30 20 Galactose-fed group 7.051.73* Liposome (vitamin E)* 0 25 45 30 0 9 weeks of instillation a Lens opacity incidence was evaluated based on the fol- Control group 13.631.15 lowing severity gradation: grade 0, no opacity; grade I, vacu- Galactose-fed group 10.381.95* oles present at a part of the cortical equator; grade II, vacu- Liposome (vitamin E) 11.131.45* oles present at all parts of the cortical equator; grade III, Liposome (vitamin E) 19.132.63*,# vacuoles and their confluents spreading from the cortical d equator toward the center of the cortex; grade IV, large, 12-month-old rats interconnected opacities covering the whole cortex. b The 0 week of instillation number of 5-week-old rats used in 10–11. c The number of Control group 13.52 2.65 12-week-old rats used is 11–12. * Significantly different Galactose-fed group 7.22 1.76* from the corresponding galactose-fed group at p0.05. 9 weeks of instillation Control group 13.721.15 Galactose-fed group 10.541.98* Liposome (vitamin E) 11.521.35* Table 3. Effect of vitamin E-containing liposome instilla- Liposome (vitamin E) 18.832.65*,# tion on cataract progression in 12-month-old rats a Values are meansS.D. b The number of animals used is fed a 25% galactose diet. 8. c The number of animals used is 8. d The number of ani- Lens opacity incidence (%)a Treatment period and group mals used is 10. * Significantly different from the corre- 0 I II III IV sponding control group at p0.05. # Significantly different 0 week of instillation from the corresponding galactose-fed group at p 0.05. Galactose-fed group 0 100 0 0 0 2 months of instillation Galactose-fed group 0 0 0 70 30 racts, i.e., suture accentuation at the central region of Liposome (vitamin E) 0 0 20 70 10 the lens, was found to retard the progression of cor- Liposome ( vitamin E)* 0 15 30 50 0 tical cataracts significantly. In 5-week-old rats fed a a Lens opacity incidence in each group (10 animals) was 25% galactose diet alone, lens -tocopherol content evaluated based on the following severity gradation: grade 0, showed a significant decrease at the onset of instilla- no opacity; grade I, suture accentuation in the central region; tion and a significant increase at the end of instilla- grade II, cortical opacities present in the peripheral region; tion, but this change in lens -tocopherol content by grade III, cortical opacities covering the entire region which tented to become dense in the posterior subcapsular region galactose feeding was significantly attenuated by rather than in the anterior subcapsular region; grade IV, instillation of vitamin E-containing liposomes, but nuclear opacities in addition to cortical opacities covering the not vitamin E-free liposomes (Table 4). In 12-week- entire region. * Significantly different from the galactose-fed old rats fed a 25% galactose diet alone, a significant group at p0.05. decrease in lens -tocopherol content occurred at the onset and end of vitamin E-containing liposome instillation, but this decrease in lens -tocopherol

Vol. 35, No. 1, 2004 42 Y. Ohta content by galactose feeding was significantly atten- models. Therefore, there seems to be a possibility uated by instillation of vitamin E-containing lipo- that vitamin E is clinically applied to cataract devel- somes, but not vitamin E-free liposomes (Table 4). opment. In 12-month-old rats fed a 25% galactose diet alone, although lens -tocopherol content significantly References increased at the onset of instillation and did not change at the end of instillation, the lens vitamin E [1] Hyman, L.: Epidemiology of in the elderly. Eye, 1, 330–341, 1987. content in the galactose-fed rats was significantly [2] Ibaraki, N.: Epidemiology of cataract. increased by instillation of vitamin E-containing (Ganka), 45, 725–731, 2003. liposomes, but not vitamin E-free liposomes (Table [3] West, S.K. and Valmadrid, C.T.: Epidemiology of risk 4). In addition, it was found that although the lenses factors for age-related cataract. Surv. 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