Type 2 diabetes is associated with the MTNR1B gene, a genetic bridge between circadian rhythm and glucose metabolism, in a Turkish population

A systematic review of variations in circadian rhythm genes and type 2 diabetes

BACKGROUND

Type 2 diabetes is a chronic disease that has severe individual and societal consequences, which is forecast to worsen in the future. A new field of investigation is variations in circadian rhythm genes, in conjunction with diet and sleep variables, associations with, and effects on, type 2 diabetes development.

OBJECTIVE

This systematic review aimed to analyse all current literature regarding circadian rhythm gene variations and type 2 diabetes, and explore their interplay with diet and sleep variables on type 2 diabetes outcomes. This review was registered with PROSPERO (CRD42021259682).

METHODOLOGY

Embase and Pubmed were searched on 6/8/2021/11/8/2021 for studies of all designs, including participants from both sexes, all ethnicities, ages, and geographic locations. Participants with risk alleles/genotypes were compared with the wildtype regarding type 2 diabetes outcomes. Studies risk of bias were scored according to the risk of bias in non-randomised studies - interventions/exposures criteria.

RESULTS

In total, 31 studies were found (association n  =  29/intervention n  =  2) including >600,000 participants from various ethnicities, sexes, and ages. Variations in the melatonin receptor 1B, brain and muscle arnt-like 1 and period circadian regulator (PER) genes were consistently associated with type 2 diabetes outcomes.

CONCLUSIONS

Individuals with variations in melatonin receptor 1B, brain and muscle arnt-like 1 and PER may be at higher risk of type 2 diabetes. Further research is needed regarding other circadian rhythm genes. More longitudinal studies and randomised trials are required before clinical recommendations can be made.

Association of CDKAL1 gene polymorphism (rs10946398) with gestational diabetes mellitus in Pakistani population

BACKGROUND

CDK5 regulatory subunit associated protein 1 like 1 (CDKAL1) encodes a tRNA modifying enzyme involved in the proper protein translation and regulation of insulin production encoded by the CDKL gene. Sequence variations in the CDKAL1 gene lead to the misreading of the Lys codon in proinsulin, resulting in decreased glucose-stimulated proinsulin production. Various polymorphic sequence variants of the CDKAL1 gene such as rs7754840, rs7756992, rs9465871, and rs10946398 are reported to be associated with type 2 diabetes mellitus and gestational diabetes mellitus (GDM) incidence. One of these single nucleotide polymorphisms i.e., rs10946398 has been reported to impact the risk of GDM and its outcomes in pregnant women of different ethnicities i.e., Egypt, Chinese, Korean, Indian, Arab, and Malaysian. Numerous findings have shown that rs10946398 overturns the regulation of CDKAL1 expression, resulting in decreased insulin production and elevated risk of GDM. However, there is no data regarding rs10946398 genotype association with GDM incidence in our population.

METHODOLOGY

In this study, 47 GDM patients and 40 age-matched controls were genotyped for rs10946398 CDKAL1 variant using Tetra primer Amplification Refractory Mutation System Polymerase Chain Reaction (Tetra ARMS-PCR).

RESULTS

Analysis of the results showed the significant association of the C allele of CDKAL1 SNP rs10946398 (χ² = 0.02 p = 0.001) with the risk of GDM development. Conclusively, the results support the role of SNP i.e., rs10946398 of CDKAL1 gene in GDM development in Pakistani female patients. However, future large-scale studies are needed to functionally authenticate the role of variant genotypes in the disease pathogenesis and progression.