Animal Material and Groups
This study was carried out on 24 adult old female Wistar rats (16 months old) obtained from Selcuk University Experimental Medicine Research and Application Center. The rats were fed ad libitum and kept in 12-h light/dark cycle. The study protocol was approved by the ethics committee of the same center (2019-6). A total of 24 elder female Wistar rats were divided into 4 equal groups as follows:
Group 1, Control Group (n=6): The group fed with standard diet in which no administration was applied.
Group 2, Resveratrol Group (n=6): The group given intraperitoneal (ip) RSV (5 mg/kg/day) for 4 weeks in addition to the normal diet.
Group 3, Diabetes group (n=6): The group in which diabetes was induced by 40 mg/kg of ip Streptozotocin (STZ).
Group 4, Diabetic Resveratrol Group (n=6): The group in which diabetes was induced by ip STZ (40 mg/kg) and then RSV supplemented for 4 weeks (5 mg/kg/day).
Experimental Diabetes
In order to induce experimental diabetes, the rats in groups 3 and 4 were injected ip STZ (Sigma S-0130) of 40 mg/kg. 6 days after the injections, blood glucose levels from the tail vein of the animals were measured using a diagnostic glucose kit. Rats with a blood glucose of 300 mg/dL and above were postulated as diabetic [14].
Resveratrol Application
RSV (R5010-Sigma) applied intraperitoneally to the rats in group 2 and group 4 daily at 5 mg/kg for four weeks.
Biochemical Analysis
Determination of Tissue Malondialdehyde (MDA): Retinal MDA levels were determined using the method of Mihara and Uchiyama [27]. Results are given as nmol/g tissue.
Tissue Glutathione (GSH) Analysis: Retinal GSH levels were measured using Ellman's method [31]. The data obtained were given as mg/gr tissue.
Real Time PCR Analysis
Retinal mRNA levels were determined with a real time PCR system. The change in SIRT-1 expression due to diabetes and resveratrol treatment was measured using a real-time RT-PCR in eye tissue mRNA isolates.
RNA isolation
Total RNA was isolated from retinal tissue (50 mg) using Nucleozol (Macherey-Nagel, Düren, Germany) RNA Isolation Kit according to the manufacturer's instructions. The purity and amount of RNA obtained was measured using a SMA1000 model spectrophotometer (Merinton, China) device. In addition, isolated RNA were run in 1% agarose gel to display specific 18S and 28S RNA bands.
Real-Time Quantitative PCR Analysis
The cDNA was obtained with the Bio-Rad (California, USA) cDNA synthesis kit using 1 µg of RNA of each sample. The cDNA mix, with a total volume of 20 µl, contained 1 µg of RNA, 4 µl of cDNA master buffer, and 1 µl of Reverse transcriptase enzyme. The obtained cDNAs was used for quantitative real-time PCR amplification of the targeted genes and reference gene. The target and reference genes were synthesized in the manufacturer company SENTEGEN (Ankara, Turkey). The bases belonging to these primers are given in table 1.
Table 1. Primers for real-time quantitative PCR
Gene
|
Forward primer
|
Reverse primer
|
SIRT-1
|
CATAGGTTAGGTGGCGAGTATG
|
GTTGGTGGCAACTCTGATAAATG
|
Β-actin
|
TGTGACGTTGACATCCGTAAAG
|
GGCAGTAATCTCCTTCTGCATC
|
Samples were amplified in a volume of 20 μl reaction mix, with a concentration of 1 μl of forward and reverse primers, 10 μl of Lightcycler SYBR Green (Roche Diagnostics, Germany), 5 μl cDNA, nuclease-free water to 20 μl.
For PCR, each sample was tested in triplicate and the results were normalized using the amplification of the same cDNAs using the reference genes-actin calculations with ΔΔCt.
Analysis of the results obtained
Reference and target CT values of each sample obtained using the quantification analysis program of the Biorad connect device were taken. Calculations were made on the Delta CT formula and the results were obtained for statistical analysis.
Statistical Evaluations
Statistical analysis was performed using the SPSS statistical program. Results were defined as mean ± standard deviation. Kruskal-Wallis variance analysis was used for comparison between groups and Mann-Whitney U test was used for p<0.05 level. P<0.05 level was considered statistically significant.