Effect of hypoxia on circulating levels of retina-specific messenger RNA in type 2 diabetes mellitus.

Previously it was shown that the circulating rhodopsin mRNA level was higher in diabetic retinopathy (DR). Recent evidence suggests that hypoxia may also be associated with DR. The aim of this study was to investigate the effect of oxygen desaturation on circulating retina-specific mRNA in type 2 diabetic patients. Thirty-five type 2 diabetic patients underwent overnight oximetry. Two parameters from oximetry were used to measure oxygen desaturation: the number of times per hour the oxygen saturation decreased by 4% or greater (number of dips/hr) and percentage of sleep time with oxygen saturation (SpO(2)) <90%. Blood samples were collected into PAXgene Blood RNA tubes. Total RNA was extracted from the samples and reverse-transcribed into cDNA, and retina-specific markers were measured by quantitative real time PCR. In patients with >/=5 dips/hr, mRNA values for rhodopsin (P= 0.05) and RPE65 (P= 0.044) were significantly higher than in patients with <5 dips/hr. No change was seen in retinoschisin mRNA expression. In patients with preproliferative or proliferative DR, median levels for rhodopsin mRNA and RPE65 mRNA were 30% and 80% higher and retinoschisin mRNA was lower in patients with >/=5 dips/hr when compared to patients with <5 dips/hr. These results indicate that hypoxia may modulate expression of genes in the retina.