Diabetes mellitus and melatonin: Where are we?

Diabetes mellitus (DM) and diabetes-related complications are amongst the leading causes of mortality worldwide. The international diabetes federation (IDF) has estimated 592 million people to suffer from DM by 2035. Hence, finding a novel biomolecule that can effectively aid diabetes management is vital, as other existing drugs have numerous side effects. Melatonin, a pineal hormone having antioxidative and anti-inflammatory properties, has been implicated in circadian dysrhythmia-linked DM. Reduced levels of melatonin and a functional link between melatonin and insulin are implicated in the pathogenesis of type 2 diabetes (T2D). Additionally, genomic studies revealed that rare variants in melatonin receptor 1b (MTNR1B) are also associated with impaired glucose tolerance and increased risk of T2D. Moreover, exogenous melatonin treatment in cell lines, rodent models, and diabetic patients has shown a potent effect in alleviating diabetes and other related complications. This highlights the role of melatonin in glucose homeostasis. However, there are also contradictory reports on the effects of melatonin supplementation. Thus, it is essential to explore if melatonin can be taken from bench to bedside for diabetes management. This review summarizes the therapeutic potential of melatonin in various diabetic models and whether it can be considered a safe drug for managing diabetic complications and diabetic manifestations like oxidative stress, inflammation, ER stress, mitochondrial dysfunction, metabolic dysregulation, etc.

Circulatory Omentin-1 levels but not genetic variants influence the pathophysiology of Type 2 diabetes.

OBJECTIVE: Omentin-1, an anti-inflammatory protein, is secreted by the visceral adipose tissue. Altered levels of Omentin-1 are associated with obesity and Type 2 Diabetes (T2D). Although Omentin-1 is implicated in the insulin signaling pathway, the relationship between the genetic variants of Omentin-1 and T2D is not yet explored. The current study evaluates the association of Omentin-1 polymorphisms (rs2274907 A/T and rs1333062 G/T), its transcript and protein levels, and genotype-phenotype correlation with metabolic parameters and T2D susceptibility. METHODS: Plasma and Peripheral Blood Mononuclear Cells (PBMCs) were separated from venous blood taken from 250 controls and 250 T2D patients recruited from Gujarat, India. Genomic DNA was isolated from PBMCs and genotyping of Omentin-1 variants was performed by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). RNA was isolated from Visceral Adipose Tissue (VAT) samples of 12 controls and 10 patients, and transcript levels of Omentin-1 were assessed by qPCR. Plasma Omentin-1 levels were estimated by ELISA. Fasting Blood Glucose, Body Mass Index (BMI) and plasma lipid profile were considered for the genotype-phenotype correlation analysis. RESULTS: Our study revealed no association of Omentin-1 genetic variants with T2D risk (p > 0.05). However, the AT genotype of Omentin-1 rs2274907 A/T polymorphism was associated with increased BMI (p = 0.0247). Plasma Omentin-1 levels were significantly decreased (p < 0.0001) however, increased VAT Omentin-1 transcript levels (p = 0.0127) were observed in T2D patients. CONCLUSION: Our findings suggest that decreased circulatory Omentin-1 levels could pose a risk towards T2D susceptibility.