Neuroprotective Effect of Hydroxytyrosol in Experimental Diabetic Retinopathy: Relationship with Cardiovascular Biomarkers

Abstract

The aim of the study was to test the neuroprotective effect of hydroxytyrosol (HT) on experimental diabetic retinopathy. Animals were divided in four groups: (1) control nondiabetic rats, (2) streptozotocin-diabetic rats (DR), (3) DR treated with 1 mg/kg/day p.o. HT, and (4) DR treated with 5 mg/kg/day p.o. HT. Treatment with HT was started 7 days before inducing diabetes and was maintained for 2 months. In the DR group, total area occupied by extracellular matrix was increased, area occupied by retinal cells was decreased; both returned to near-control values in DR rats treated with HT. The number of retinal ganglion cells in DR was significantly lower (44%) than in the control group, and this decrease was smaller after HT treatment (34% and 9.1%). Linear regression analysis showed that prostacyclin, platelet aggregation, peroxynitrites, and the dose of 5 mg/kg/day HT significantly influenced retinal ganglion cell count. In conclusion, HT exerted a neuroprotective effect on diabetic retinopathy, and this effect correlated significantly with changes in some cardiovascular biomarkers.

Update on the Effects of Antioxidants on Diabetic Retinopathy: In Vitro Experiments, Animal Studies and Clinical Trials

“…There is an increasing body of evidence about the role of antioxidants in the control of diabetic retinopathy in animal models ( Table 2 ) [ 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , …”

“…In diabetic rats treated with hydroxityroxol, the total retinal thickness and the cellular size were similar to non-diabetic animals. Retinal ganglion cell loss is smaller in rats treated with hydroxytyrosol, compared with non-treated diabetic rats [ 76 ].…”

Antidiabetic Effects of Hydroxytyrosol: In Vitro and In Vivo Evidence

“…In another study, oral administration of HT (5 mg/kg) for 7 days before and 2 months after STZ injection resulted in reductions of diabetic retinopathy symptoms [61]. HT treatment attenuated the hyperglycemia-induced decrease in number of retinal ganglion cells, and increases in retinal thickness and retinal cell size [61].…”

“…In another study, oral administration of HT (5 mg/kg) for 7 days before and 2 months after STZ injection resulted in reductions of diabetic retinopathy symptoms [61]. HT treatment attenuated the hyperglycemia-induced decrease in number of retinal ganglion cells, and increases in retinal thickness and retinal cell size [61]. Administration of HT (77 mg/kg/day) by intragastric gavage for 4 weeks decreased plasma glucose levels and markers of oxidative stress (nitric oxide (NO), malondialdehyde (MDA), while increasing levels of serum SOD and SIRT1 expression in the thoracic aorta and human umbilical vein endothelial cells (HUVEC) (Table 7) [62].…”

Retinoprotective Effect of Wild Olive (Acebuche) Oil-Enriched Diet against Ocular Oxidative Stress Induced by Arterial Hypertension

“…In this sense, the Alienor study, a population study based on eye diseases in the elderly, suggested a protective role for EVOO in AMD [ 22 ], and in vitro studies showed that HT might be one of the actors responsible for this beneficial effect [ 23 , 24 ]. In addition, studies in rats demonstrated the neuroprotective effect of HT in the context of diabetic retinopathy (DR) [ 25 ]. Interestingly, neuroprotective properties of EVOO in DR have also been recently associated with other components of EVOO, such as oleuropein [ 26 ].…”