Leptin receptor gene expression and its promoter methylation do not change with age in peripheral blood mononuclear cells
Malgorzata Roszkowska-Gancarz1, Magdalena Owczarz2, Jacek Polosak1, Alina Kurylowicz3 & Monika Puzianowska-Kuznicka1,3
Introduction: Leptin is a protein hormone secreted mainly by adipose tissue. It exerts its function via ubiquitously expressed receptors (LEPR). A number of LEPR isoforms are known. Metabolism of lipids and carbohydrates, that, in part, depends on leptin, might deteriorate with age. Aging is associated with a decrease of the global methylation and with hypermethylation of some promoter-located CpG islands. Such hypermethylation results in transcription inhibition.
Aim: To assess the expression of long, cell membrane-located isoform of LEPR and to analyze LEPR promoter methylation pattern in different age groups.
Materials and methods: Methylation and gene expression were assessed in young (Y, 2237 years old), middle-aged (M, 6070 years old) and long-lived (N, 90102 years old) age groups. Total RNA and the genomic DNA were isolated from peripheral blood mononuclear cells. Gene expression was measured by real-time PCR using β-actin as a reference gene. DNA methylation was analyzed by bisulfate sequencing. Results were analyzed using KruskalWallis ANOVA and U MannWhitney tests.
Results: The expression of long LEPR isoform is similar in all age groups. It did not depend on gender, however, a trend towards significance between young males and females (P=0.09, mean 1.37±1.85 vs 2.13±2.27 expressed in arbitrary units, respectively). 29 potential sites of methylation in the analyzed LEPR promoter fragment were analyzed. Methylation of this fragment is low and does not change with age (2.8, 3.1 and 2.1%, in Y, M and in N groups, respectively).
Conclusions: Expression of long LEPR is stable in peripheral blood mononuclear cells and methylation of the LEPR promoter do not change with age. The LEPR promoter does not undergo age-related hypermethylation in blood mononuclear cells of humans.