Disturbed tumor necrosis factor system is linked with lower eGFR and chronic inflammation in hypertension.

BACKGROUND: The relationship between tumor necrosis factor (TNF)-related parameters and cardiorenal metabolic factors is still controversial in clinical hypertension. METHODS: Normotensive men (NT, n=60) and treated stage 2 and 3 essential hypertensive men (HT, n=89) were enrolled in this study. The relationship between TNF-related parameters and cardiorenal metabolic factors was examined in NT and HT, separately. RESULTS: HT showed higher rates of insulin resistance and enhanced chronic inflammation compared with NT. The levels of soluble TNF receptor 1 and 2 were significantly higher in HT than in NT, although TNF-α levels were unexpectedly lower in HT than in NT. Regression analysis indicated that the TNF-related parameters were closely linked with mild renal dysfunction both in NT and HT, and moderately related to chronic inflammation only in HT. HT taking inhibitors of the renin-angiotensin system showed improved insulin resistance, but no difference in the TNF-related parameters. CONCLUSION: These results suggest that the disturbed TNF system is closely linked with chronic inflammation rather than with insulin resistance in HT.

CD36 single nucleotide polymorphism is associated with variation in low-density lipoprotein-cholesterol in young Japanese men.

Macrophages uptake oxidized low-density lipoprotein (LDL) via a scavenger receptor such as CD36 from plasma, and then become foam cells. We examined the association of CD36 gene single nucleotide polymorphisms (SNPs) with certain metabolic characteristics in a young male Japanese population (n = 494). The G allele in a SNP located at +30215 on the 3'-untranslated region (UTR) was significantly correlated with the plasma LDL-cholesterol concentrations (r = 0.13, p <0.01). The difference in LDL-cholesterol concentrations was 10 mg dl(-1) between GG- and AA-genotype carriers (p <0.05). The CD36 gene SNP is a novel maker of the variation in the LDL-cholesterol levels in young Japanese men.

Possible association of tumor necrosis factor receptor 2 gene polymorphism with severe hypertension using the extreme discordant phenotype design.

The tumor necrosis factor (TNF)-alpha pathway has a key role in regulating insulin resistance. TNF receptor 2 (TNFR2) is an emerging candidate gene for insulin resistance in essential hypertension. We examined the association of insulin resistance and enhanced TNF pathway with severe hypertension and the association of a microsatellite polymorphism of the TNFR2 gene with severe hypertension. Male severe essential hypertensive patients (HT) with the onset before 60 years of age and with genetic predispositions to hypertension were consecutively enrolled at our outpatient department (N=92). Normotensive men (NT) over 50 years of age were randomly registered from the participants in the annual health check program (N=78). Patients were selected as HT and NT who met stringent criteria for systolic/diastolic blood pressure (SBP/DBP) levels >or=180 and/or 110 mm Hg and <120/80 mm Hg, respectively. HT revealed significantly higher plasma insulin levels, C-reactive protein (CRP) and soluble fraction of TNFR2 concentrations (sTNFR2) than NT. A microsatellite polymorphism of the CA repeat in intron 4 of the TNFR2 gene was analyzed. The allele frequency of CA16 in HT differed significantly from that in NT (66/184 vs. 36/156, P=0.01 by chi(2) analysis). In HT, the CA16 carriers showed significantly higher SBP and plasma insulin levels and a higher tendency of sTNFR2 than did those without this allele. In NT, CA16 carriers revealed significantly higher sTNFR2 and CRP levels than did the CA16 non-carriers. These results suggest that the TNFR2 gene locus has a potential effect on developing severe hypertension through the augmented TNF pathway and insulin resistance.

Congenic substitution mapping for intracellular Ca2+ in spontaneously hypertensive rats.

BACKGROUND: Intracellular Ca(2+) ([Ca(2+)](i)) may be a factor of importance to hypertension in spontaneously hypertensive rats (SHR). Platelet hyperactivity caused by increased [Ca(2+)](i) may contribute to atherothrombotic cardiovascular events. In a genome scan, we have recently demonstrated that a candidate quantitative trait locus (QTL) for [Ca(2+)](i) in platelets is located near the sarco(endo)plasmic reticulum Ca(2+)-dependent ATPase (Serca) II gene locus on chromosome 12 in backcrossed rats derived from SHR and normotensive Fischer 344 rats (F344). METHODS: Congenic substitution mapping was performed for the chromosomal region including the Serca II gene locus. The segment including the Serca II gene locus was transferred from F344 onto the genetic background of the progenitor SHR. Systolic blood pressure (SBP), platelet aggregation, and ratio of heart weight to body weight (HW/BW) as well as [Ca(2+)](i) responses in platelets were compared between SHR and the congenic strain. RESULTS: Among the parental strains, thrombin-stimulated and thapsigargin-induced peak values of [Ca(2+)](i) in platelets, platelet aggregation, SBP, and HW/BW were significantly greater in SHR than in F344 and F(1) rats. The heterozygous congenic rats for the Serca II gene segment had significantly attenuated [Ca(2+)](i) responses and platelet aggregation compared with SHR. Furthermore, they demonstrated significantly lower SBP and HW/BW. CONCLUSION: Congenic substitution mapping clarified that a chromosomal segment including the Serca II gene locus was responsible for attenuated [Ca(2+)](i) responses and platelet aggregation in the heterozygous congenic rats. Therefore, this chromosomal region may contribute to the development of hypertension and cardiac hypertrophy by augmenting Ca(2+) signaling in SHR.

Quantitative trait loci mapping for intracellular calcium in spontaneously hypertensive rats.

BACKGROUND: Increased intracellular calcium ([Ca2+]i) in platelets is also proposed as an intermediate phenotype for hypertension in spontaneously hypertensive rats (SHR). Increased [Ca2+]i in platelets is hypothesized to contribute to atherothrombotic events. Platelet hyperactivity is frequently associated with cardiovascular disease. METHODS: In a genome scan, we performed the quantitative trait loci (QTL) mapping for [Ca2+]i in back-crossed rats derived from SHR and normotensive Fischer 344 rats, which demonstrated a single major QTL for hypertension on chromosome 1. Thrombin-stimulated [Ca2+]i in Ca2+-free and in Ca2+-containing buffers was measured in platelets using the Fura-2 method. RESULTS: Among the parental strains, systolic blood pressure and thrombin-stimulated [Ca2+]i were significantly greater in SHR than in Fischer 344 and F1 rats. The sarco(endo)plasmic reticulum Ca2+-dependent ATPase II gene locus (Serca2) between D12Mgh5 and D12Mgh6 showed the significant linkage for thrombin-stimulated [Ca2+]i in Ca2+-free and Ca2+-containing buffers. The peak logarithm of the odds scores were 3.6 and 3.3, respectively. These QTL explained 19.8% and 17.4% of the total variances, respectively. D3Mit13 and DXMgh1 showed suggestive linkage for thrombin-stimulated [Ca2+]i in Ca2+-free and in Ca2+-containing buffers, respectively. The peak logarithm of the odds scores were 2.6 and 2.1, respectively. CONCLUSIONS: A significant QTL for [Ca2+]i was mapped near Serca2 on chromosome 12, and suggestive QTL were identified near D3Mit13 and DXMgh1 in a genome scan. Genetic abnormalites in platelet [Ca2+]i may contribute to cardiovascular disease via platelet hyperactivity, independent of blood pressure elevation.

Cellular insulin resistance in Epstein-Barr virus-transformed lymphoblasts from young insulin-resistant Japanese men.

The metabolic syndrome is characterized by a blunted insulin-mediated glucose uptake in various cell types. We compared the glucose uptake characteristics of Epstein-Barr virus (EBV)-transformed lymphoblasts obtained from young men with vs without metabolic and cardiovascular evidence of metabolic syndrome. From a population of 218 men, 20- to 25-year-old, 10 men with a systolic blood pressure (BP) > or =130 mm Hg and family history of hypertension were assigned to a high BP (HBP) group, and 10 with a BP < or =110 mm Hg, and no family history of hypertension was assigned to a low BP (LBP) group. Multiple clinical and metabolic characteristics were examined in both groups and compared. Peripheral lymphocytes from HBP and LBP subjects were EBV-transformed, and the glucose transporter (Glut)-mediated glucose uptake from each group was compared in lymphoblasts. Body mass index, fasting glucose, immunoreactive insulin, insulin resistance index based on a homeostasis model assessment (HOMA-R), and total and low-density lipoprotein cholesterol were significantly higher in the HBP than the LBP subgroup (whole-body insulin resistance). Baseline Glut-mediated and Glut-mediated insulin-stimulated glucose uptake by lymphoblasts from the HBP group were significantly lower than by lymphoblasts from the LBP group (cellular insulin resistance). The net increment in Glut-mediated glucose uptake by insulin was inversely correlated with HOMA-R. In conclusion, cellular insulin resistance in EBV-transformed lymphoblasts is associated with young Japanese subjects with HBP. The net increment in Glut-mediated glucose uptake by insulin in lymphoblasts may be a useful intermediate phenotype to study genetic aspects of the metabolic syndrome.

Linkage disequilibrium grouping of single nucleotide polymorphisms (SNPs) reflecting haplotype phylogeny for efficient selection of tag SNPs.

Single nucleotide polymorphisms (SNPs) have been proposed to be grouped into haplotype blocks harboring a limited number of haplotypes. Within each block, the portion of haplotypes is expected to be tagged by a selected subset of SNPs; however, none of the proposed selection algorithms have been definitive. To address this issue, we developed a tag SNP selection algorithm based on grouping of SNPs by the linkage disequilibrium (LD) coefficient r(2) and examined five genes in three ethnic populations--the Japanese, African Americans, and Caucasians. Additionally, we investigated ethnic diversity by characterizing 979 SNPs distributed throughout the genome. Our algorithm could spare 60% of SNPs required for genotyping and limit the imprecision in allele-frequency estimation of nontag SNPs to 2% on average. We discovered the presence of a mosaic pattern of LD plots within a conventionally inferred haplotype block. This emerged because multiple groups of SNPs with strong intragroup LD were mingled in their physical positions. The pattern of LD plots showed some similarity, but the details of tag SNPs were not entirely concordant among three populations. Consequently, our algorithm utilizing LD grouping allows selection of a more faithful set of tag SNPs than do previous algorithms utilizing haplotype blocks.