Genetic variations in key inflammatory cytokines exacerbates the risk of diabetic nephropathy by influencing the gene expression

Iqra Hameed; Shariq R Masoodi; Perveez A Malik; Shahnaz A Mir; Khalid Ghazanfar; Bashir A Ganai

doi:10.1016/j.gene.2018.03.095

Genetic variations in key inflammatory cytokines exacerbates the risk of diabetic nephropathy by influencing the gene expression

Gene. 2018 Jun 30:661:51-59. doi: 10.1016/j.gene.2018.03.095. Epub 2018 Mar 29.

Authors

Iqra Hameed¹, Shariq R Masoodi², Perveez A Malik³, Shahnaz A Mir⁴, Khalid Ghazanfar⁵, Bashir A Ganai⁶

Affiliations

¹ Department of Biochemistry, University of Kashmir, Hazratbal Srinagar, India; Department of Biochemistry and Molecular Biology, GK Medical Trust, Srinagar, India.
² Department of Endocrinology and Metabolism, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India; Department of Endocrinology, Diabetes & Nutrition, University of Maryland School of Medicine, Baltimore, MD, USA.
³ Department of Minimal Access Surgery, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India.
⁴ Department of Endocrinology, Government Medical College and Associated Hospital, Srinagar, India.
⁵ Regional Research Institute of Unani Medicine, Srinagar, India.
⁶ Center for Research and Development, University of Kashmir, Srinagar, India. Electronic address: bbcganai@gmail.com.

PMID: 29605608
DOI: 10.1016/j.gene.2018.03.095

Abstract

Background: Diabetic nephropathy is the single strongest predictor of mortality in patients with diabetes. The development of overt nephropathy involves important inter-individual variations, even after adjusting for potential confounding influences of modifiable and non-modifiable risk factors. Genome-wide transcriptome studies have reported the activation of inflammatory signaling pathways and there is mounting indication of the role of genetic factors.

Methods: We screened nine genetic variations in three cytokine genes (TNF-α, IL-6 and IL-β) in 1326 unrelated subjects comprising of healthy controls (n = 464), type 2 diabetics with nephropathy (DN, n = 448) and type 2 diabetes without nephropathy (T2D, n = 414) by sequence-specific amplification. Functional implication of SNPs was elucidated by correlation studies and relative gene expression using Realtime-Quantitative PCR (RT-qPCR).

Results: Individual SNP analysis showed highest association of IL-1β rs16944-TT genotype (OR = 3.51, 95%CI = 2.36-5.21, P = 0.001) and TNF-α rs1800629-AA genotype (OR = 2.75, 95% CI = 1.64-4.59, P = 0.001) with T2D and DN respectively. The haplotype frequency showed significant risk of seven combinations among T2D and four combinations among DN subjects. The highest risk of T2D and DN was associated with GGTGAGTTT (OR = 4.25, 95%CI = 3.3-14.20, P = 0.0016) and GACGACCTT (OR = 21.3, 95%CI = 15.1-28.33, P = 0.026) haplotypes respectively. Relative expression by RT-qPCR showed increased cytokine expression in cases as compared to controls. TNF-α expression was increased by more than four-folds (n-fold = 4.43 ± 1.11) in DN. TNF-α, IL-6 and IL-1β transcript levels were significantly modulated by promoter region SNPs.

Conclusions: The present study implicates a strong association between cytokine TNF-α, IL-6 and IL-1β gene promoter polymorphisms and modulation of transcript levels with susceptibility to nephropathy in diabetes subjects.

Keywords: Cytokines; Gene expression; Haplotypes; Nephropathy; Polymorphism.

MeSH terms

Aged
Case-Control Studies
Cytokines / genetics
Cytokines / metabolism
Diabetes Mellitus, Type 2 / complications
Diabetes Mellitus, Type 2 / genetics
Diabetes Mellitus, Type 2 / metabolism
Diabetic Nephropathies / genetics*
Diabetic Nephropathies / metabolism
Female
Gene Expression Regulation
Genetic Association Studies
Genetic Predisposition to Disease
Humans
Inflammation / genetics*
Inflammation / metabolism
Interleukin-1beta / genetics*
Interleukin-1beta / metabolism
Interleukin-6 / genetics*
Interleukin-6 / metabolism
Male
Middle Aged
Polymorphism, Single Nucleotide*
Promoter Regions, Genetic
Tumor Necrosis Factor-alpha / genetics*
Tumor Necrosis Factor-alpha / metabolism

Substances

Cytokines
IL1B protein, human
IL6 protein, human
Interleukin-1beta
Interleukin-6
Tumor Necrosis Factor-alpha