Effect of high-fat diet on refractive development and ocular biological characteristics in guinea pigs

Objective  To investigate the effect of a high-fat diet on refractive development and ocular biological characteristics in guinea pigs.

Methods  Sixteen 3-week-old SPF healthy male tricolor guinea pigs were selected and randomly assigned to a normal control group and a high-fat diet group using a random number table, with 8 animals in each group. The control group was fed a standard diet for 4 weeks (energy composition: fat 9.1%, carbohydrates 65.2%, protein 25.7%), whereas the high-fat diet group was fed a high-fat diet for 4 weeks (energy composition: fat 45.0%, carbohydrates 35.0%, protein 20.0%). Serum levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein, and low-density lipoprotein (LDL) were measured using an automated biochemical analyzer before dietary intervention and at week 4 after the intervention. The weight of guinea pigs were measured using an animal weight meter. Before the intervention and at weeks 2 and 4 after the intervention, refractive error was measured using a small-animal infrared automated refractometer; axial length was measured using an ophthalmic ultrasound biometer; the corneal curvature radius (CCR) was measured using a keratometer; retinal thickness (RT), choroidal thickness (ChT), and choroidal blood perfusion (ChBP) were measured using full-eye optical coherence tomography. The differences in parameters and changes in refraction and axial length between the two groups at different time points before and after intervention were compared, and the correlation of each parameter was analyzed. All animal experiments were conducted in accordance with the guidelines of the Tianjin Medical Experimental Animal Protection Center. The experimental protocol was approved by the Animal Ethics Committee of Tianjin Eye Hospital (No. YSY-DWLL-2022249).

Results  There were significant overall differences in TC, TG, and LDL between the two groups before and 4 weeks after intervention (TC: F _group=8.21, P<0.001; F _time=36.10, P<0.001. TG: F _group=6.60, P<0.05; F _time=11.71, P<0.01. LDL: F _group=5.73, P<0.05; F _time=20.85, P<0.001). Four weeks after intervention, TC, TG and LDL were higher in the high-fat diet group than in the normal control group, with statistical significance (all P<0.01). There were statistically significant overall differences in refractive power between the two groups before intervention, 2 and 4 weeks after intervention ( F _group=24.97, P<0.001; F _time=96.77, P<0.001). At 2 and 4 weeks after intervention, the refractive power was lower in the high-fat diet group than in the normal control group (both P<0.01). The refractive changes at 2 and 4 weeks after intervention were respectively (-0.77±0.28) and (-1.15±0.19)D in the normal control group and were (-2.26±0.35) and (-2.16±0.21)D in the high-fat diet group, respectively, with statistically significant overall difference ( F _group=22.32, P<0.001). The refractive power changes in the high-fat diet group were significantly greater than those in the normal control group at 2 and 4 weeks after intervention (both P<0.01). There were statistically significant differences in axial length between the two groups before and after intervention ( F _group=15.04, P<0.001; F _time=361.40, P<0.001). Four weeks after intervention, the axial length were greater in the high-fat diet group than in the normal control group ( P<0.001). There were statistically significant overall differences in RT, ChT, and ChBP between the two groups ( F _group=30.63, 17.40, 85.21; all P<0.001). Two weeks after the intervention, RT and ChBP in the high-fat diet group were lower than those in the normal control group (both P<0.01). Four weeks after the intervention, RT, ChT, and ChBP in the high-fat diet group were lower than those in the normal control group (all P<0.01). Correlation analysis showed that there was a significant negative correlation between refraction and axial length ( r=-0.84, P<0.001). ChT were positively correlated with ChBP and ChBP, RT, and ChT were positively correlated with refraction ( r=0.42, 0.56, 0.44, 0.37; all P<0.01).

Conclusions  A high-fat diet increases myopia susceptibility in guinea pigs and is accompanied by axial elongation and significant reductions in RT, ChT, and ChBP.