Protective effect of astaxanthin on the retinopathy of type 1 diabetic rats

Objective

To investigate the protective effect of astaxanthin on the retinopathy in rats with type 1 diabetes and related mechanism.

Methods

Thirty-six male SPF rats received intraperitoneal injection of 1% streptozotocin (STZ) to prepare type 1 diabetes model.The rats were randomly assigned to the diabetes group, low dose astaxanthin group and high dose astaxanthin group by a random number table.The rats in the low dose astaxanthin group and high dose astaxanthin group received respectively astaxanthin 20 mg/kg and 100 mg/kg by gavage everyday.The rats in the diabetes group received an equal volume of olive oil.Twelve rats received an equal volume of sodium citrate as the control group.Blood glucose and body mass were measured every 2 weeks.After 24 weeks, the retina was digested to make retinal capillary network preparation.The number of pericytes and acelluar strands was compared among the different experimental groups.The relative expressions of anti-inflammatory cytokines in retinal tissue were detected by immunohistochemistry, real-time PCR and Western blot.The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.

Results

Body mass of the rats in the low dose astaxanthin group and high dose astaxanthin group was significantly higher than that in the diabetes group (both at P<0.05). Blood glucose levels in the low dose astaxanthin group and high dose astaxanthin group were significantly lower than that in the diabetes group (both at P<0.05). In the control group, main artery was round, uniform, and strongly stained.The vein was lightly stained and had a large diameter.In the diabetes group, retinal arteriovenous trunk and branches appeared tortuous at a low magnification, with capillary network disorder.The morphology of the capillaries showed pathology in the low dose astaxanthin group and high dose astaxanthin group, but the vascular tortuosity, dilatation and stenosis were reduced in comparison with the diabetes group.The number of pericytes was 466.4±23.2, 207.3±31.7, 298.1±27.1 and 312.2±19.5 among different groups, with a significant difference among them (F=34.420, P=0.047). The number of acelluar strands were 5.2±2.3, 32.9±12.7, 14.5±9.1 and 16.5±3.5 among different groups, with a significant difference among them (F=47.340, P=0.021). The relative expression of IL-6, TNF-α and caspase-3 mRNA in the low dose astaxanthin group was 0.87±0.23, 0.91±0.34 and 1.07±0.15, the relative expression in the high dose astaxanthin group was 0.81±0.31, 0.85±0.39 and 0.95±0.11, which was significantly decreased in comparison with the diabetes group (1.63±0.47, 1.57±0.53 and 1.51±0.32) (all at P<0.05). The relative expression of IL-6, TNF-α and caspase-3 protein in the low dose astaxanthin group was 0.63±0.33, 0.51±0.14 and 0.60±0.13, the relative expression in the high dose astaxanthin group was 0.69±0.22, 0.49±0.15 and 0.57±0.22, which was significantly decreased in comparison with the diabetes group (all at P<0.05).

Conclusions

Astaxanthin may play an important role in protecting pericytes from apoptosis and delaying development and progression of diabetic retinopathy in rats.Additionally, astaxanthin can inhibit release of anti-apoptosis and anti-inflammatory cytokines.