Effect of Hypoxia on Circulating Levels of Retina-Specific Messenger RNA in Type 2 Diabetes Mellitus

Continuous positive airway pressure effect on visual acuity in patients with type 2 diabetes and obstructive sleep apnoea: a multicentre randomised controlled trial

We sought to establish whether continuous positive airway pressure (CPAP) for obstructive sleep apnoea (OSA) in people with type 2 diabetes and diabetic macular oedema (DMO) improved visual acuity.We randomly assigned 131 eligible patients aged 30-85 years from 23 UK centres with significant DMO causing visual impairment (LogMAR letters identified ≥39 and ≤78, score 0.92-0.14) plus severe OSA on screening to either usual ophthalmology care (n=67) or usual ophthalmology care plus CPAP (n=64) for 12 months.Mean age of participants was 64 years, 73% male, mean body mass index 35.0 kg·m- 2 Mean 4% oxygen desaturation index was 36 events·h-1 There was no significant difference in the visual acuity at 12 months between the CPAP group and the control group (mean LogMAR 0.33 (95% CI 0.29-0.37) versus 0.31 (95% CI 0.27-0.35); p=0.39), and no significant correlation between change in LogMAR and average CPAP use. The median±sd (range) daily CPAP use was 3.33±2.25 (0-7.93) h at 3 months, 3.19±2.54 (0-8.07) h at 6 months and 3.21±2.70 (0-7.98) h at 12 months.CPAP therapy for OSA did not improve visual acuity in people with type 2 diabetes and DMO compared with usual care alone over 12 months.

Effect of obstructive sleep apnoea on diabetic retinopathy and maculopathy: a systematic review and meta-analysis

AIMS

To summarize the association between obstructive sleep apnoea and diabetic retinopathy and diabetic maculopathy, and to examine the effects of oxygen desaturation index, mean and minimum oxygen saturation and time spent with < 90% oxygen saturation on diabetic retinopathy and diabetic maculopathy.

METHODS

A systematic search was performed for papers published from inception to January 2014 in MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews using indexed terms and free text. Additional searches were carried out for grey literature. Two authors conducted the study selection and quality assessment. Data extraction was performed by the main author and checked by the other authors.

RESULTS

One cohort study and 15 cross-sectional studies were included for narrative synthesis and three for meta-analyses. There was no convincing evidence that obstructive sleep apnoea was associated with diabetic retinopathy, although some evidence suggested that obstructive sleep apnoea was associated with greater severity of diabetic retinopathy and advanced diabetic retinopathy in people with Type 2 diabetes. Only six studies examined the impact of obstructive sleep apnoea on diabetic maculopathy and our narrative review suggests there is an association in Type 2 diabetes. Oxygen desaturation index, mean oxygen saturation or time spent with < 90% oxygen saturation were not associated with diabetic retinopathy, and insufficient evidence was available to draw conclusions on their effects on diabetic maculopathy; however, there was evidence from both narrative synthesis and meta-analysis that minimum oxygen saturation had an impact on diabetic retinopathy (pooled odds ratio 0.91, 95% CI 0.87-0.95; I(2) = 0%).

CONCLUSIONS

There is a need for large cohort studies with long-term follow-up data to examine the long-term effects of obstructive sleep apnoea and other sleep variables on advanced retinal disease in diabetes.

Dietary wolfberry upregulates carotenoid metabolic genes and enhances mitochondrial biogenesis in the retina of db/db diabetic mice

SCOPE

Our aim was to investigate whether dietary wolfberry altered carotenoid metabolic gene expression and enhanced mitochondrial biogenesis in the retina of diabetic mice.

METHODS AND RESULTS

Six-week-old male db/db and wild-type mice were fed the control or wolfberry diets for 8 weeks. At study termination, liver and retinal tissues were collected for analysis by transmission electron microscopy, real-time PCR, immunoprecipitation, Western blot, and HPLC. Wolfberry elevated zeaxanthin and lutein levels in the liver and retinal tissues and stimulated expression of retinal scavenger receptor class B type I, glutathione S-transferase Pi 1, and β,β-carotene 9',10'-oxygenase 2, and induced activation and nuclear enrichment of retinal AMP-activated protein kinase α2 (AMPK-α2). Furthermore, wolfberry attenuated hypoxia and mitochondrial stress as demonstrated by declined expression of hypoxia-inducible factor-1-α, vascular endothelial growth factor, and heat shock protein 60. Wolfberry enhanced retinal mitochondrial biogenesis in diabetic retinas as demonstrated by reversed mitochondrial dispersion in the retinal pigment epithelium, increased mitochondrial copy number, elevated citrate synthase activity, and upregulated expression of peroxisome proliferator-activated receptor γ co-activator 1α, nuclear respiratory factor 1, and mitochondrial transcription factor A.

CONCLUSION

Consumption of dietary wolfberry could be beneficial to retinoprotection through reversal of mitochondrial function in diabetic mice.

Frontiers in preclinical safety biomarkers: microRNAs and messenger RNAs

The measurement of plasma microRNAs (miRNAs) and messenger RNAs (mRNAs) is the most recent effort to identify novel biomarkers in preclinical safety. These genomic markers often display tissue-specific expression, may be released from the tissues into the plasma during toxic events, change early and with high magnitude in tissues and in the blood during specific organ toxicities, and can be measured using multiplex formats. Their validation as biomarkers has been challenged by the technical difficulties. In particular, the concentration of miRNAs in the plasma depends on contamination by miRNAs originating from blood cells and platelets, and the relative fraction of miRNAs in complexes with Argonaute 2, high-density lipoproteins, and in exosomes and microvesicles. In spite of these hurdles, considerable progress has recently been made in assessing the potential value of miRNAs in the clinic, especially in cancer patients and cardiovascular diseases. The future of miRNAs and mRNAs as biomarkers of disease and organ toxicity depends on our ability to characterize their kinetics and to establish robust collection and measurement methods. This review covers the basic biology of miRNAs and the published literature on the use of miRNAs and mRNAs as biomarkers of specific target organ toxicity.

The prevalence of retinopathy in men with Type 2 diabetes and obstructive sleep apnoea

AIMS

To clarify the relationship between obstructive sleep apnoea (OSA) and diabetic retinopathy.

RESEARCH DESIGN AND METHODS

A cohort of 240 men from primary and secondary care previously participated in a study on the prevalence of OSA in Type 2 diabetes and provided anthropometric information, details of their diabetes, had glycated haemoglobin (HbA1c) measured and overnight oximetry performed. They were re-contacted for permission to review their routine screening clinical retinal photographs, which were then scored by a trained grader, providing detailed retinopathy, maculopathy and photocoagulation scores.

RESULTS

One hundred and eighteen men both consented and had retinal photographs available to review. Of these, 24% had OSA, with mean+/-sd 4% oxygen saturation (SaO2) dips/h of 20.9+/-16.6 vs. 2.8+/-2.1 in the non-OSA group. As expected, the OSA group had a significantly higher mean body mass index of 31.9+/-5.2 vs. 28.5+/-5.1 kg/m2 and neck size 44.5+/-3.6 vs. 41.9+/-2.5 cm, but the two groups did not differ significantly in age, diabetes duration, diabetes treatment, HbA1c, smoking history or proportion with known hypertension. Retinopathy and maculopathy scores were significantly worse in the OSA group (P<0.0001). Multiple regression analysis showed only OSA (R2=0.19, P<0.0001) and HbA1c (R2=0.04, P=0.03) to be significant independent predictors of retinopathy. OSA was the only independent significant predictor of the total microaneurysm score (R2=0.21, P=0.004), a detailed retinopathy subclassification. OSA was the only independent significant predictor of maculopathy (R2=0.3, P<0.001).

CONCLUSION

In men with Type 2 diabetes, there is a strong association between retinopathy and OSA, independent of conventional retinopathy risk factors.