In this study, we examined the genetic contribution on serum creatinine and eGFR, known parameter of kidney function, and identified the quantitativeloci that contribute to the genetic variations of these parameters. With a family-based model adjusted for age, gender, total cholesterol, serum triglycerides, BMI and waist circumference as covariates, we found 63% and 70% of variations in eGFR and serum creatinine, respectively, are due to genetic component. We further identified four significant loci contributing to the heritability of kidney function parameters: 9p21.1, 9p21.3, 15p26.3 and 16.p13.3.
Our study reported high heritability values for serum creatinine and eGFR using a large multi-generation pedigree adjusted to multiple confounding variables. In type 2 diabetic patients, heritability of GFR was found high as 75% with adjustment of age, sex, mean arterial blood pressure, medications, and glycated hemoglobin(Langefeld et al., 2004). In the Framingham Heart Study, genome wide linkage analysis of 330 nuclear families found heritability of serum creatinine as 29% and 33% for eGFR adjusted for age, gender, BMI, diabetes, systolic BP, hypertension treatment, tobacco use, and HDL cholesterol(Fox et al., 2004). In the Swedish Twins-based study, the heritability of serum creatinine was reported as 19%, creatinine based-eGFR as 18.6% and Cystatin-C-based eGFR as 41.8% (Arpegard et al., 2015). Another United Kingdom twin study reported heritability of creatinine of 37% and eGFR as 63% (Hunter et al., 2002). The differences in reported heritability of serum creatinine and eGFR is attributed to the ethnicity of participants under the study or inclusion of patient population. Altogether, these studies suggest strong genetic component in the variability of serum creatinine and eGFR. This provide insights to find the genes that are associated with these biochemical measures and improve the understanding in the variation of kidney function within a population.
we used a validated genetic model of extended pedigree structure with heritability estimation extended up to 9th degree kinship. We identify QTLs for serum creatinine and eGFR in three chromosomes 9, 15 and 16. Prior genome-wide linkage studies identified various QTLs influencing serum creatinine-based eGFR, but none reported significant LOD scores on chromosomes 9, 15, and 16 (Hunt et al., 2004). In Strong Heart Family study, linkage analysis identified significant association between eGFR and SNPs within SLC6A13 (ch.12p13.33),UBE2Q2 (ch.15q24.2), PIP5K1B (ch19p12), and WDR72 (ch15q21.3)genes(Franceschini et al., 2014). One of the candidate gene in contributing to genetic variability in kidney function is Tyrosine kinase receptor (TEK) that ismainly expressed on endothelial cells and serves as a receptor for angiopoietin-1 (ANGPT1) (Suri et al., 1996). Glomerular capillaries are composed of a fenestrated endothelium and specialised epithelial cells (the podocytes).ANGPT1-induced TEK signalling pathway regulates cell survival, quiescence, proliferation, migration, adhesion, and vascular permeability (Suri et al., 1996).Therefore, the role of angiopoietins is important in glomerular function in healthy and disease state(Gnudi, 2016). ANGPT1is constitutively expressed in podocytes(Satchell et al., 2002) while TEK expression is localised in the endothelium of mouse glomerular capillaries (Yuan, Suri, Yancopoulos, & Woolf, 1999) and podocyte of rat kidneys(Dessapt-Baradez et al., 2014).. Moreover, heterozygous deletion of TEK in mice results in reducedglomerular vasculature(Puri, Partanen, Rossant, & Bernstein, 1999). In human, defects in TEK causes an autosomal dominant form of venous malformation (Fukuhara et al., 2008; Wouters et al., 2010) which manifests with abnormalities in kidney function (Cura, Elmerhi, Suri, Bugnone, & Dalsaso, 2010).