Proventive effects of astaxanthin on metabolic cataract and its mechanism in type 1 diabetic rats

Background

The pathogenesis mechanism of diabetic cataract has not been fully elucidated.Researches showed that multiple biological pathways participate in the pathogenesis of diabetic cataract, including oxidative stress.Astaxanthin can inhibit oxidative stress-mediated injury and lipid peroxidation.However, whether astaxanthin has the preventive effects on diabetic cataract is unclear.

Objective

This study was to investigate the preventive effects of astaxanthin on metabolic cataract in type 1 diabetic rats.

Methods

Thirty-eight 6-week-old SPF male SD rats were used in this study, and 1% streptozocin was intraperitoneally injected to establish type 1 diabetic models in 30 rats, and 24 successful models were assigned to diabetic model group, low-dose astaxanthin group and high-dose astaxanthin group.Equal volume of normal saline solution was injected in the same way in 8 rats as the normal control group.Mixture foods containing 50 mg/(kg·day) or 100 mg/(kg·day) astaxanthin with olive oil and fodder were used continuously for 3 months in the rats of low-dose astaxanthin group and high-dose astaxanthin group, respectively, and mixture food of olive oil with fodder was used in the diabetic model group.Only fodder was used in the same way in the rats of the normal control group.The opacification of lens was examined by slit lamp section radiography system and graded on a scale of 1-5.The specimen of lens were prepared for the hematoxylin & eosin stain.The expression and lation of advanced glycosylation end products (AGEs) in the lens was examined using immunochemistry.The contents of oxidative stress-related indicators in the lens, such as AGEs, malonydialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD) and mass fraction of glutathione (GSH), were assayed by ELISA.The experimental process complied with the national standard (Laboratory Animal Requirements of Environment and Housing Facilities [GB14925-2001]).

Results

The blood glucose levels of the rats were significantly higher in the diabetic model group, low-dose astaxanthin group and high-dose astaxanthin group than those in the normal control group at 2, 4, 6, 8, 10 and 12 weeks after modeling (all at P<0.05), while the blood glucose levels of rats were not evidently different between low-dose astaxanthin group and high-dose astaxanthin group at various time points(all at P>0.05). The rat lenses were transparent in the normal control group with scale of grade 1, and serious lens opacification was seen in the rats of the diabatic model group, with the scale of grade 5, while the rat lenses in the low-dose astaxanthin group and high-dose astaxanthin group were in grade 3-4.The contents of AGEs in the lenses were (7.23±0.50)μg/ml and (7.01±0.37)μg/ml, and MDA contents were (1.43 ±0.22)mmol/L and (1.35±0.16)mmol/L in the low-dose astaxanthin group and high-dose astaxanthin group respectively, which were significantly lower than (7.61± 0.45)μg/ml and (1.62±0.42)mmol/L in the normal control group (all at P<0.05). GSH contents in rat lenes were (272.70±12.53)ng/L and (283.52±16.17)ng/L, and SOD concents were (55.45±6.47)μmol/(min·L) and (56.73±5.12)μmol/(min·L), and CAT concents were (2.91±0.41)μmol/(min·L) and (3.02±0.13)μmol/ (min·L) in the low-dose astaxanthin group and high-dose astaxanthin group respectively, which were significantly higher than (241.52±15.13)ng/L, (51.67±5.45)μmol/(min·L) and (2.72±0.27)μmol/(min·L) in the normal control group (all at P<0.05). The GSH concent and SOD concent in rat lens were lower in the low-dose astaxanthin group than that in the high-dose astaxanthin group (both at P<0.05).

Conclusions

Astaxanthin can postpone the pathogenesis and development of diabetic cataract in type 1 diabetic rats by antioxydative stress.