Plasma melatonin levels in patients with diabetic retinopathy secondary to type 2 diabetes

Effects of melatonin supplementation on markers of inflammation and oxidative stress in patients with diabetes: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

Diabetes mellitus is a metabolic disorder, in which chronic systemic inflammation and oxidative stress contribute to the progression of this condition and its complications. Melatonin, a hormone known for its potent antioxidant and anti-inflammatory properties, has emerged as a potential therapeutic intervention in diabetes. This review aims to evaluate the effects of melatonin supplementation on markers of oxidative stress and inflammation in diabetic patients.

METHODS

A thorough literature search of databases, including PubMed, Embase, Web of Science, Cochrane Central, CNKI, and Scopus, was conducted through October 2023. We included randomized controlled trials investigating the effects of melatonin on markers of inflammation and oxidative stress, compared to placebo in patients with diabetes. The data was analyzed using the random-effects model and the summary effect size was determined using the standardized mean difference (SMD) with 95% confidence interval (CI).

RESULTS

Fourteen studies with 823 participants were included. Our analysis indicates that melatonin can lead to significant reductions in levels of C-reactive protein (CRP) [SMD = -0.75; 95% CI: -1.37, -0.12; P = 0.018], tumor necrosis factor-alpha (TNF-α) [SMD = -0.40; 95% CI: -0.64, -0.15; P = 0.001], interleukin (IL)-1 [SMD = -0.75; 95% CI: -1.03, -0.47; P < 0.0001], IL-6 [SMD = -0.79; 95% CI: -1.07, -0.51; P < 0.0001], and malondialdehyde (MDA) [SMD = -0.61; 95% CI: -0.80, -0.43; P < 0.0001]. Furthermore, we found a significant increase in levels of total antioxidant capacity (TAC) [SMD = 0.81; 95% CI: 0.12, 1.51; P = 0.021], glutathione (GSH) [SMD = 0.66; 95% CI: 0.28, 1.03; P = 0.001], and superoxide dismutase (SOD) [SMD = 1.69; 95% CI: 0.80, 2.58; P < 0.0001] following melatonin consumption in patients with diabetes.

CONCLUSION

Melatonin supplementation is a promising complementary strategy to attenuate oxidative stress and inflammation in diabetic patients.

Multidimensional sleep health and diabetic retinopathy: Systematic review and meta-analysis

Diabetic retinopathy (DR) is one of the most prevalent microvascular diabetic complications. Poor sleep health and obstructive sleep apnea (OSA) are risk factors for diabetes and poor glycemic control. Recent studies have suggested associations between poor sleep health/OSA and DR. Furthermore, there have been suggestions of melatonin dysregulation in the context of DR. We conducted a systematic review and meta-analysis exploring the associations between multidimensional sleep health (duration, satisfaction, efficiency, timing/regularity and alertness), OSA and melatonin with DR. Forty-two studies were included. Long, but not short sleep, was significantly associated with DR, OR 1.41 (95%CI 1.21, 1.64). Poor sleep satisfaction was also significantly associated with DR, OR 2.04 (1.41, 2.94). Sleep efficiency and alertness were not associated with DR, while the evidence on timing/regularity was scant. Having OSA was significantly associated with having DR, OR 1.34 (1.07, 1.69). Further, those with DR had significantly lower melatonin/melatonin metabolite levels than those without DR, standardized mean difference -0.94 (-1.44, -0.44). We explored whether treating OSA with continuous positive airway pressure (CPAP) led to improvement in DR (five studies). The results were mixed among studies, but potential benefits were observed in some. This review highlights the association between poor multidimensional sleep health and DR.

Melatonin protects retinal tissue damage in streptozotocin-induced aged rats

OBJECTIVES

The aim of this study was to investigate how melatonin administration affects retinal oxidative damage and retinal SIRT1 gene activation in diabetic elderly female rat model.

METHODS

16-months-old female rats were used in the study. A total of 24 rats were divided into 4 groups in equal numbers: Group 1. Control, Group 2. Control + Melatonin, Group 3. Diabetes, Group 4. Diabetes + Melatonin. In group 3 and 4 rats, diabetes was induced by intraperitoneal (IP) injection of streptozotocin. Groups 2 and 4 were given ip melatonin for 4 weeks. SIRT-1 gene expression was determined by PCR method and GSH and MDA levels by ELISA in retinal tissue samples taken from animals sacrificed under general anesthesia.

RESULTS

In our study, the highest retinal SIRT1 expression values were obtained in the diabetes + melatonin (G4) group. The retinal SIRT1 expression values of the diabetes group (G3) were lower than group 4 and higher than the general control (G1) and control + melatonin (G2) groups. Again in our study, the highest retinal MDA values were obtained in the diabetes group (G3). The highest retinal GSH values were obtained in the Diabetes + melatonin group (G4).

CONCLUSION

The results of our study showed that melatonin supplementation has a protective effect on retinal tissue in a diabetic elderly female rat model. This protective effect of melatonin supplementation occurs by increasing both retinal antioxidant activity and retinal SIRT1 gene expression.

Serum disease-specific IgG Fc glycosylation as potential biomarkers for nonproliferative diabetic retinopathy using mass spectrometry

OBJECTIVE

To explore the potential of serum disease-specific immunoglobulin G (DSIgG) glycosylation as a biomarker for the diagnosis of nonproliferative diabetic retinopathy (NPDR).

METHODS

A total of 387 consecutive diabetic patients presenting in an eye clinic without proliferative diabetic retinopathy (DR) were included and divided into those with nondiabetic retinopathy (NDR) (n = 181) and NPDR (n = 206) groups. Serum was collected from all patients for DSIgG separation. The enriched glycopeptides of the tryptic digests of DSIgG were detected using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Patients were randomly divided into discovery and validation sets (1:1). The differences in glycopeptide ratios between the groups were compared by using Student's t-test or the Mann-Whitney U test. The predictive ability of the model was assessed using the area under the receiver operating characteristic curve (AUC).

RESULTS

DSIgG1 G1FN/G0FN, G2N/G2, G2FN/G2N and DSIgG2 G1F/G0F, G1FN/G0FN, G2N/G1N, G2S/G2 were significantly different between NDR and NPDR patients (p < 0.05) in both the discovery and validation sets. The prediction model that was built comprising the seven glycopeptide ratios showed good NPDR prediction performance with an AUC of 0.85 in the discovery set and 0.87 in the validation set.

CONCLUSION

DSIgG Fc N-glycosylation ratios were associated with NPDR and can be used as potential biomarkers for the early diagnosis of DR.

Association Between Diabetic Retinopathy and Insomnia Risk: A Nationwide Population-Based Study

BACKGROUND

Previous studies have suggested a close link between sleep disturbances and diabetic retinopathy (DR). However, to date, no confirmatory findings have been reported. We aimed to explore the risk of insomnia in DR by considering demographic factors and diabetes mellitus (DM)-related variables.

METHODS

A nationwide population-based cohort of 2,206,619 patients with type 2 diabetes from the Korean National Insurance Service Database was followed up for insomnia incidence. DR, non-proliferative DR (NPDR), and proliferative DR (PDR) were defined according to ICD-10 codes. The interactive effects of sex, age, and DM-related variables were analyzed to evaluate their impact on insomnia risk in DR.

RESULTS

Compared with the non-DR group, insomnia risk was increased in the DR [(adjusted hazard ratio (aHR): 1.125, 95% confidence interval (CI):1.108-1.142), NPDR (aHR:1.117, 95% CI:1.099-1.134), and PDR (aHR:1.205, 95% CI: 1.156-1.256), even after controlling for comorbidities, lifestyle factors, and DM-related variables. The men and youngest age groups (<40 years) were most vulnerable to insomnia risk. Sex, age, DM duration, and chronic kidney disease (CKD) status exerted interactive effects with DR status in increasing the insomnia risk. In the PDR group, sex, age, DM duration, insulin therapy status, and CKD status exerted interactive effects that increased the risk of insomnia.

CONCLUSION

Insomnia risk is significantly higher in patients with DR, and clinical attention is warranted.

Effects of Melatonin on Diabetic Neuropathy and Retinopathy

Diabetes mellitus (DM) leads to complications, the majority of which are nephropathy, retinopathy, and neuropathy. Redox imbalance and inflammation are important components of the pathophysiology of these complications. Many studies have been conducted to find a specific treatment for these neural complications, and some of them have investigated the therapeutic potential of melatonin (MEL), an anti-inflammatory agent and powerful antioxidant. In the present article, we review studies published over the past 21 years on the therapeutic efficacy of MEL in the treatment of DM-induced neural complications. Reports suggest that there is a real prospect of using MEL as an adjuvant treatment for hypoglycemic agents. However, analysis shows that there is a wide range of approaches regarding the doses used, duration of treatment, and treatment times in relation to the temporal course of DM. This wide range hinders an objective analysis of advances and prospective vision of the paths to be followed for the unequivocal establishment of parameters to be used in an eventual therapeutic validation of MEL in neural complications of DM.