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Insulin resistance is associated with reduced serum adiponectin and increased albuminuria levels. Thus, one would anticipate an inverse relationship between circulating adiponectin and albuminuria. However, several studies have described a 'paradoxical' elevation of serum adiponectin in patients with elevated albuminuria. These findings may have been confounded by the presence of diseases and related treatments known to affect circulating adiponectin and albuminuria. We therefore studied the relationship between circulating adiponectin and albuminuria in the absence of such confounders.To this purpose, the relationship between adiponectin isoforms and albumin:creatinine ratio (ACR) was investigated in a family-based sample of 634 non-diabetic untreated white individuals with normal kidney function. We also investigated whether the two variables share a common genetic background and addressed the specific role of the gene encoding adiponectin on that background by genotyping several ADIPOQ single nucleotide polymorphisms (SNPs).ACR was directly associated with high molecular weight (HMW) adiponectin isoform (p = 0.024). The two variables shared some genetic correlation (ρ(g) = 0.38, p = 0.04). ADIPOQ promoter SNP rs17300539 was associated with HMW adiponectin (p = 4.8 × 10(-5)) and ACR (p =0.0027). The genetic correlation between HMW adiponectin and ACR was no longer significant when SNP rs17300539 was added to the model, thus reinforcing the role of this SNP in determining both traits.Our study shows a positive, independent correlation between HWM adiponectin and ACR. ADIPOQ variability is associated with HMW adiponectin and ACR, and explains some of the common genetic background shared by these traits, thus suggesting that ADIPOQ and HMW adiponectin modulate albuminuria levels.

Keywords Insulinresistance.Population-specificeffect.Resistincirculatinglevels.RETNAdipocytes release a number of peptide hormones, collec-tively known as adipokines, which are essential inregulation of intermediate metabolism, and which maycontribute to the pathogenesis of insulin resistance andrelated disorders [1].Among these is resistin, a 12.5 kDa cysteine-rich proteinthat is secreted also by macrophages [2–4]. Several piecesof evidence suggest that this molecule antagonises insulinaction and fosters inflammation [2–4]. In humans, mostcross-sectional studies have reported that elevated resistinlevels are associated with insulin resistance [5–7] and type2 diabetes [8]. In most [9–11], although not all [12],prospective studies, resistin turned out to be a predictor oftype 2 diabetes and cardiovascular disease. Taken together,these findings highlight the role of serum resistin as anemerging pathogenic factor and a potential therapeutictarget for insulin resistance-related disorders. This latterpossibility is reinforced by the observation that resistinexpression in human adipose tissue is inhibited bythiazolidinediones [13], insulin-sensitising molecules thatare used as oral hypoglycaemic agents in the treatment ofpatients with type 2 diabetes.The mechanisms regulating resistin expression, secretionand circulating levels are still poorly understood. Recentdata clearly indicate that resistin serum levels are undergenetic control [6, 14]. Several single-nucleotide poly-morphisms (SNPs) in the RETN gene coding for resistin,have been associated with serum resistin levels and insulinresistance traits [6 ,8 14–18].Among others, rs1862513 at position g.−420 in theRETN 5′ flanking region has attracted much attention. ThisSNP has been associated with high resistin levels [8, 16],insulin resistance [ 17], obesity [15 , 18] and type 2diabetes [8, 19]. A recent meta-analysis, including morethan 3,500 individuals, has shown that those homozygousfor the G allele at rs1862513 have a 30% increase in theodds of being affected by type 2 diabetes [8]. Along thesame lines, the G allele was predictive of glycaemicdeterioration in a Chinese population followed for 5 years[20]. These associations are supported by functional datademonstrating a stronger activation of the RETN promoterby Sp1 and Sp3 transcription factors in the presence of theG allele [8]. In agreement with these data, the same allelehas been reported to be associated with higher abdominal-fat resistin mRNA levels [21]. Thus, so far, so good forSNP rs1862513.Recently, a fine-mapping analysis of the RETN gene hasbeen carried out in a sample of more than 2,500 individualsof European ancestry [14]. The authors found that alleles at