Increased levels of retinol binding protein 4 (RBP4) in serum is associated with insulin resistance. To examine this further, the genomic region of RBP4 was genetically surveyed in Mongolian people, who as a group are suffering from a recent rapid increase in diabetes. The RBP4 gene was screened by DHPLC system, and the PCR fragments which showed heteroduplex peaks in multiple samples were followed by direct sequencing to identify common polymorphisms in 48 Mongolian diabetic samples. Identified single nucleotide polymorphisms (SNPs) were genotyped in 511 control and 281 type 2 diabetes samples. The functions of SNPs in the regulatory region were assessed by reporter gene assay and electrophoretic mobility shift assay. Possible association between functional SNPs and serum RBP4 levels or metabolic parameters was statistically assessed. Nine SNPs were identified in the RBP4 gene. A case-control study revealed that the rare alleles of four SNPs were associated with increased risk of diabetes, even after Bonferroni correction (-803, G > A, P = 0.0054; +5169, C > T, P = 0.0025; +6969, G > C, P = 0.0015; +7542, T > del, P = 0.0015). The -803 G > A SNP influenced the transcription efficiency in a hepatocarcinoma cell line as well as the binding efficiency of hepatocyte nuclear factor 1 alpha to the motif. In addition, the -803 A allele was associated with increased serum RBP4 levels in diabetic patients. We have identified a functional SNP in the RBP4 gene associated with type 2 diabetes in Mongolian people.

Associations between the novel loci and plasma lipid concentrations were generally conserved in the Japanese population, with the exception of NCAN/CILP2/PBX4 and MVK/MMAB.

Retinol‐binding protein 4 (RBP4) is a recently identified adipokine that was involved in insulin resistance. RBP4 is predominantly expressed from the liver in normal metabolic state to transport retinoids throughout the body, but the exact physiological function and the regulatory mechanisms of adipocyte‐derived RBP4 have not been revealed. We conducted the genetic analysis about metabolic parameters in Japanese and Mongolian; the minor allele carriers of regulatory single‐nucleotide polymorphism (SNP −803G>A) showed significantly higher BMI in Japanese men (P = 0.009) and women (P = 0.017), and in Mongolian women (P = 0.009). Relative quantification of RBP4 transcripts in −803GA heterozygotes showed that the minor allele–linked haplotype‐derived mRNA was significantly more abundant than the transcript from major allele. RBP4 promoter assay in 3T3L1 adipocytes revealed that the minor allele increased the promoter activity double to triple and the administration of 9‐cis‐retinoic acid (RA) and 8‐bromo‐cyclic adenosine monophosphate (8‐Br‐cAMP) enhanced the activity. Multiple alignment analysis of human, mouse, rat, and cattle RBP4 promoter suggested conserved seven transcription factor binding motifs. Electrophoretic mobility shift assay showed the −803G>A SNP modulate the affinity against unidentified DNA‐binding factor, which was assumed to be a suppressive factor. These results collectively suggested that the minor allele of RBP4 regulatory SNP enhanced the expression in adipocytes, which may be associated with the adipogenesis.

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Cold-induced autoinflammatory syndrome 1 (CIAS1) gene is a member of the NALP subfamily of the CATERPILLER protein family that is expressed predominantly in peripheral blood leukocytes, which is to regulate apoptosis or inflammation through the activation of NF-jB and caspase. Recent genetic analyses suggested an association between inflammation and oxidative stress-related genes in the development of hypertension. This is the first genetic study indicating an association between the CIAS1 gene and susceptibility to essential hypertension (EH). The frequency of subject with the homozygote of 12 repeat allele was significantly higher in patients with hypertension compared with control subjects (987 cases, 924 controls) (P ¼ 0.030; odds ratio ¼ 1.24) at a novel VNTR polymorphism of CIAS1 intron 4 loci. We also found that the mean of systolic blood pressure of homozygotes of 12 repeat allele was 6.4 mmHg higher than those of homozygotes of non-12 repeat allele in male random population (P ¼ 0.009). The frequency of six SNPs spanning of the CIAS1 gene was not significantly between patients and controls. The real-time PCR analysis showed that among healthy young adults, 12-12 subjects expressed CIAS1 mRNA in peripheral leukocytes significantly more abundantly than homozygote of non-12 repeat alleles subjects (Po0.05). Reporter gene assay of the CIAS1-VNTR in HL60 stimulated by lipopolysaccharides showed that the intronic sequence involving 12 repeat increased the expression of luciferase compared with 9, 7, and 6 repeats.