Increased Serum Hepcidin Levels in Subjects with the Metabolic Syndrome: A Population Study

<div><p>The recent discovery of hepcidin, the key iron regulatory hormone, has changed our view of iron metabolism, which in turn is long known to be linked with insulin resistant states, including type 2 diabetes mellitus and the Metabolic Syndrome (MetS). Serum ferritin levels are often elevated in MetS (Dysmetabolic hyperferritinemia - DHF), and are sometimes associated with a true mild-to-moderate hepatic iron overload (dysmetabolic iron overload syndrome - DIOS). However, the pathophysiological link between iron and MetS remains unclear. This study was aimed to investigate, for the first time, the relationship between MetS and hepcidin at population level. We measured serum hepcidin levels by Mass Spectrometry in 1,391 subjects from the Val Borbera population, and evaluated their relationship with classical MetS features. Hepcidin levels increased significantly and linearly with increasing number of MetS features, paralleling the trend of serum ferritin. In multivariate models adjusted for relevant variables including age, C-Reactive Protein, and the HFE C282Y mutation, ferritin was the only significant independent predictor of hepcidin in males, while in females MetS was also independently associated with hepcidin. Overall, these data indicate that the fundamental iron regulatory feedback is preserved in MetS, i.e. that hepcidin tends to progressively increase in response to the increase of iron stores. Due to recently discovered pleiotropic effects of hepcidin, this may worsen insulin resistance and contribute to the cardiovascular complications of MetS.</p> </div

Biochemical iron parameters in the VB population stratified for presence or absence of MetS.

*<p>variables not normally distributed were log-transformed and expressed as geometric means with 95% CIs.</p

Clinical, anthropometrical, and biochemical data of the VB population.

*<p>variables not normally distributed were log-transformed and expressed as geometric means with 95% CIs.</p

Predictors of hepcidin-25 in males and females, considering MetS as a comprehensive binary (present versus absent) covariate.

*<p>this association remained statistically significant also after adjusting for CRP, C282Y HFE mutation, hemoglobin, uric acid, and creatinine.</p

The <i>SPTA1</i> gene is transcriptionally regulated by <i>TAF3</i>.

<p>(A) Knockdown of <i>TAF3</i> by shRNA and its effect on <i>SPTA1</i> expression in human K562 cells, and in differentiating mouse MEL cells. 4 days after induction. Expression was monitored by qRT-PCR. NS: control scrambled shRNA; <i>TAF3</i>kd1 and <i>TAF3</i> kd2 and anti <i>Taf3</i> shRNAs described in Methods. (B) Chromatin immunoprecipitation analysis of the recruitment of <i>TAF3</i> and <i>TBP</i> to the indicated promoters in K562 cells shows that <i>TAF3</i> is associated with <i>SPTA1</i>. <i>TAF3</i>: ChIP with anti Taf3 Ab; IgG: control chromatin immunoprecipitation with IgG addition. Asterisks indicate a statistical significant difference (*  = <i>P</i><0.05; **  = <i>P</i><0.01) between control and TAF3 knockdown data for MEL and K562 cells, and between specific immunoprecipitations and IgG control immunoprecipitations.</p

Regional association plot and linkage disequilibrium pattern at the TAF3 locus.

<p>(A) Association of genotyped and imputed SNPs. The top imputed SNP (rs11255458) is highlighted in violet, the other SNPs are colored according to their degree of linkage disequilibrium (r²) with rs11255458. The chromosomal positions (NCBI human genome Build 36) of the SNPs are plotted against genomic control-adjusted -log10 p-value. The estimated recombination rates (cM/Mb) from HapMap CEU release 22 are shown as gray lines. (B) The D'-based LD map was build using genotyped and imputed data of the INGI-VB population.</p

rs1887582 replica.

*<p>Illegio-Sauris-Resia.</p

rs1887582 association in general population cohorts.

<p>rs1887582 association in general population cohorts.</p

Sample details.

1<p>All data were analysed using Illumina SNP arrays. 300 refers to the Illumina HumanHap 300 panel, 370 to the Illumina HumanHap 370 Duo/Quad panels, 610 to the Illumina Human 610 Quad panel and 670 to the Illumina Human 670 Quad panel. In order to harmonise the data, the analysis was conducted using only those SNPs present in the HumanHap 300 panel.</p>2<p>Population-based studies.</p>3<p>Population-based studies in isolated populations.</p>4<p>Birth cohort studies.</p>5<p>Case control studies.</p

Three alternative measures of mean homozygosity, with 95% confidence intervals, by population sample.

<p>(A) shows mean F_ROH by population sample. F_ROH is defined as the percentage of the genotyped autosomal genome in ROH measuring at least 1.5 Mb. Mean values of F_ROH per population (with 95% confidence intervals) are: CROATIA-Korčula = 1.27 (1.18, 1.36); CROATIA-Split = 0.65 (0.59, 0.71); CROATIA-Vis = 0.94 (0.87,1.01); EGCUT = 0.56 (0.54, 0.58); ERF = 1.12 (1.04, 1.20); FINRISK = 0.79 (0.77, 0.82); HBCS = 0.63 (0.60, 0.65); H2000 = 0.84 (0.82, 0.86); INGI-CARL = 0.78 (0.65, 0.91); INGI-FVG = 1.49 (1.40, 1.58); INGI-VB = 0.76 (0.71, 0.81); LBC1921 = 0.30 (0.25, 0.35); LBC1936 = 0.26 (0.24, 0.28); MICROS = 0.93 (0.87, 0.99); NFBC1966 = 1.02 (1.00, 1.04); NSPHS = 2.83 (2.64, 3.02); ORCADES = 0.81 (0.75, 0.87); QIMR = 0.22 (0.21, 0.23); RS = 0.29 (0.28, 0.30); SOCCS = 0.30 (0.28, 0.32); YFS = 0.81 (0.79, 0.83). (B) shows mean F_ROHLD by population sample. F_ROHLD is defined as the percentage of the genotyped autosomal genome in ROH measuring at least 1.0 Mb, derived from a panel of independent SNPs. Mean values of F_ROHLD per population (with 95% confidence intervals) are: CROATIA-Korčula = 0.67 (0.61, 0.73); CROATIA-Split = 0.13 (0.11, 0.15); CROATIA-Vis = 0.48 (0.43, 0.53); EGCUT = 0.10 (0.09, 0.10); ERF = 0.53 (0.48, 0.58); FINRISK = 0.21 (0.20, 0.23); HBCS = 0.13 (0.11, 0.14); H2000 = 0.23 (0.22, 0.24); INGI-CARL = 0.44 (0.34, 0.54); INGI-FVG = 0.93 (0.86, 0.99); INGI-VB = 0.41 (037, 0.45); LBC1921 = 0.05 (0.02, 0.09); LBC1936 = 0.02 (0.01, 0.03); MICROS = 0.47 (0.43, 0.51); NFBC1966 = 0.32 (0.31, 0.33); NSPHS = 1.17 (1.07, 1.27); ORCADES = 0.35 (0.31, 0.39); QIMR = 0.013 (0.011, 0.015); RS = 0.04 (0.01, 0.07); SOCCS = 0.03 (0.02, 0.04); YFS = 0.20 (0.19, 0.21). (C) shows mean F_hom by population sample. F_hom is defined as the percentage of genotyped autosomal SNPs that are homozygous. Mean values of F_hom per population (with 95% confidence intervals) are: CROATIA-Korčula = 65.47 (65.43, 65.51); CROATIA-Split = 65.28 (65.25, 65.31); CROATIA-Vis = 65.61 (65.58, 65.64); EGCUT = 65.69 (65.68, 65.70); ERF = 65.32 (65.29, 65.35); FINRISK = 65.25 (65.23, 65.27); HBCS = 65.13 (65.12, 65.14); H2000 = 65.24 (65.23, 65.25); INGI-CARL = 65.20 (65.14, 65.26); INGI-FVG = 65.53 (65.49, 65.57); INGI-VB = 65.18 (65.16, 65.20); LBC1921 = 65.00 (64.97, 65.03); LBC1936 = 65.00 (64.99, 65.01); MICROS = 65.26 (65.23, 65.29); NFBC1966 = 65.27 (65.26, 65.28); NSPHS = 66.09 (66.01, 66.17); ORCADES = 65.37 (65.34, 65.40); QIMR = 64.75 (64.74, 64.76); RS = 65.00 (64.99, 65.01); SOCCS = 64.97 (64.95, 64.99); YFS = 65.26 (65.25, 65.27).</p