The Effects of Aqueous Garlic Extract on TGF-β2 Gene and Protein Expression in Retinal Tissues of Male Diabetic Rats

Retinopathy is one of the most important complications of diabetes mellitus that results from chronic hypeglycemia, oxidative stress and inflammation. Tumor necrosis factor-beta2 (TGF-β2) is an important factor in the inflammation pathway due to hyperglycemia. Garlic is one of the most frequently used plants in Iranian diets that has hypoglycemic and antioxidant propertis. So, this study aimed to examine the effects of aqueous garlic extract on TGF-β2 gene and protein expression in retinal tissues of type 1 diabetic rats.
In this experimental study, 24 male Wistar rats were divided into four groups (n = 6) including control rats, type 1 diabetic rats, type 1 diabetic rats treated with the garlic extract and garlic control. To induce diabets type 1, streptozotocin (STZ, 65 mg/kg) was used. Seven days after the STZ injection, the glucose level was measured by a glucometer. at the end of the treatment period(30 days, gavage of the garlic extract (1mL/100g)), the serum sample was isolated and stored in -20ºC for determination of the glucose level. Also, the rat's eyes were removed and their retial tissues separated quickly and stored in -70ºC for gene expression evaluation and protein assay. To determine the gene expression level, RNA extraction, cDNA synthesis and real-time polymerase chain reaction were performed. The TGF-β2 protein level was also measured by the ELISA kit.
The TGF-β2 mRNA expression was increased 1.37 fold in diabetic rats compared to control rats and decreased 1.96 fold in garlic-treated diabetic rats compared to untreated diabetic rats. The TGF-β2 protein level was increased 3.08 fold in diabetic rats compared to control rats and decreased 2.56 fold in garlic-treated diabetic rats compared to untreated diabetic rats.
Garlic extract significantly decreased the TGF-β2 level in retinal tissues of diabetic rats. The TGF-β2 is an important factor in inflammation and damage to retinal; so, it is logical that garlic consumption can reduce diabetes complications by decreasing this factor.