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Biomedical subjects

Yoichi Izumi

Publications and source records attributed to Yoichi Izumi.

13 recordsLinked to original sources
PubMed2005

Association study of calcitonin-receptor-like receptor gene in essential hypertension.

BACKGROUND: Plasma adrenomedullin (ADM) concentrations increase in patients with hypertension, renal failure, heart failure, essential pulmonary hypertension, myocardial infarction, endotoxin shock, and many other conditions. The ADM receptor is a complex molecule that consists of calcitonin-receptor-like receptor (CRLR) and receptor activity-modifying protein 2 (RAMP2). Because CRLR determines the binding specificity of ADM, the CRLR gene is thought to be a susceptibility gene of hypertension. However, studies have not yet defined the relationship between the CRLR gene and hypertension. The aim of the present study was to investigate relationships between single-nucleotide polymorphisms (SNP) in the human CRLR gene and essential hypertension (EH) in a Japanese population. METHODS: We selected four SNP in the human CRLR gene (rs3771073, rs696574, rs698590, and rs1528233), and we performed a genetic association study in 209 EH patients and 216 age-matched normotensive (NT) individuals. RESULTS: There was no significant difference in overall distribution of genotypes or alleles of any of the SNP between the EH and NT groups. However, among women, the T allele of the SNP rs696574 (C --> T, in intron 6) was significantly more frequent in EH subjects than in NT subjects (P = .032). CONCLUSION: Our findings suggest that rs696574 can be used as a genetic marker of EH in women.

Adult↗
PubMed2005

White coat hypertension in centenarians.

BACKGROUND: To study white coat (WC) hypertension in centenarians, a cross-sectional surveillance was carried out on Uygurs, a long-lived population in China. METHODS: Twenty-four-hour ambulatory blood pressure (BP) monitoring (ABPM) was performed in 33 centenarians (age range, 100 to 113 years) and compared with 100 elderly subjects (age range, 65 to 70 years). All subjects were clinically healthy and capable of self-care. Subjects had no history, signs, or symptoms of cardiovascular disease and were receiving no medical treatments. Office BP, 24-h mean, daytime and night-time BP, pulse pressure, heart rate, standard deviation (SD), and coefficient of variation (CV) of the same variables were extracted from ABPM. The WC effect was defined as the difference between mean office and daytime BP. RESULTS: Centenarians demonstrated higher prevalence of WC hypertension, compared to elderly group (15% vs. 5%). The WC effect was also greater in centenarians than in elderly subjects, and was more marked for systolic BP than for diastolic BP and heart rate. The WC effect for systolic BP was positively correlated with both SD (r = 0.45, P < .01) and CV (r = 0.55, P < .01) for 24-h systolic BP in centenarians, but not in elderly subjects. CONCLUSIONS: Prevalence of WC hypertension was greater in centenarians than in elderly subjects. The WC effect and BP variation may be increased in centenarians. Previously observed higher BPs seen in very elderly individuals might be explained by the greater impact of WC hypertension.

Aged↗
PubMed2005

Haplotype-based case-control study revealing an association between the adrenomedullin gene and proteinuria in subjects with essential hypertension.

Adrenomedullin (AM) has various physiological actions on the cardiovascular system, including vasodilatation, diuresis, natriuresis, inhibition of aldosterone secretion, and increases of the cardiac output, all of which cause hypotension. Since AM plays a role in the pathophysiology of vascular diseases, genes controlling AM might be involved in the development and etiology of essential hypertension (EH). However, there have been few studies examining the relationship between the AM gene and hypertension. The aims of this study were to genotype some of the genetic markers for the human AM gene in Japanese subjects, and via a haplotype-based case-control study, assess the association between and the AM gene and EH or its risk factors, such as hyperlipidemia, renal damage, and proteinuria. We genotyped 205 EH patients and 210 age-matched normotensive (NT) individuals for two single nucleotide polymorphisms of rs4399321, rs7944706 and a microsatellite polymorphism located approximately 5,400 base pairs downstream of the 3' end of the human AM gene. The overall distribution in each variant and haplotype did not significantly differ between the two groups. However, after dividing the groups into those subjects with and without proteinuria, the haplotype analysis revealed a positive association. In conclusion, a possible mutation linked to the haplotype may indicate a genetic predisposition for proteinuria in EH.

Adrenomedullin↗
PubMed2004

An association study in essential hypertension using functional polymorphisms in lymphotoxin-alpha gene.

BACKGROUND: Lymphotoxin-alpha (LTA), a member of the tumor necrosis factor family, is a cytokine produced by lymphocytes. The substance LTA mediates a wide variety of inflammatory, immunostimulatory, and antiviral responses. In 2002, LTA was identified as a major risk factor for myocardial infarction (MI) in Japanese individuals, in a large-scale case-control study using 92,788 gene-based single-nucleotide polymorphism (SNP) markers in the whole human genome. Essential hypertension (EH) is thought to be a multifactorial disorder involved in endothelial dysfunction and atherosclerosis. Although hypertension is one of the greatest risk factors for MI, there have been no reports estimating the association between EH and LTA. The aim of the present study was to evaluate the association between EH and the LTA gene. METHODS: In the present study, we assessed the association between EH and SNP and haplotypes of the LTA gene in a case-control study of 202 EH patients and 217 age-matched normotensive control subjects. RESULTS: The overall distribution of genotypes for each SNP did not significantly differ between the two groups. Furthermore, the haplotype analysis revealed no association between the EH and normotensive groups. CONCLUSIONS: Polymorphisms of the LTA gene were not associated with EH. This finding suggests differences in genetic backgrounds between EH and MI.

Case-Control Studies↗
PubMed2004

Variable number of tandem repeat of the 5'-flanking region of type-C human natriuretic peptide receptor gene influences blood pressure levels in obesity-associated hypertension.

The gene for natriuretic peptides receptor C (NPRC), which is a candidate susceptibility gene for essential hypertension (EH) or obese hypertension, plays a key role in the regulation of plasma levels and biological effects of natriuretic peptides. The aims of the present study were to find new genetic markers in the 5'-flanking region of the NPRC gene and to assess relationships between variants and phenotypes of EH, including EH in obese patients. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we discovered a novel six-nucleotide repeat polymorphism located 4 base pairs (bp) upstream of the major transcriptional initiation site. We performed association analysis of this variable number of tandem repeat (VNTR) in 242 EH patients and 212 normotensive controls (NT). Although no significant difference in overall frequency of VNTR was found between NT and EH groups, the blood pressure level of EH patients with the 5/6 genotype was significantly higher in obese subjects. This suggests that the VNTR of the 5'-flanking region of the NPRC gene influences blood pressure levels in obesity-associated hypertension.

5' Flanking Region↗
PubMed2003

Leukocyte angiotensin II levels inpatients with essential hypertension:relation to insulin resistance.

Insulin resistance is involved in the pathogenesis of type 2 diabetes, hypertension, and atherosclerosis. Angiotensin (Ang) converting enzyme inhibitors and Ang II type 1 receptor antagonists improve insulin resistance in patients with essential hypertension, which suggest that tissue Ang II is involved in insulin resistance in patients with hypertension. To investigate the participation of tissue Ang II in insulin resistance associated with hypertension, we evaluated the Ang II-generating system in leukocytes and its relation to insulin resistance in patients with essential hypertension. Eighteen patients with essential hypertension participated in this study. Ang II was separated from leukocytes by reversed-phase high-performance liquid chromatography and measured by radioimmunoassay. Insulin resistance was evaluated by determining the steady-state of plasma glucose (SSPG) concentration. The Ang I- and Ang II-generating activities were evaluated in human leukocytes. Human leukocytes have Ang I- and Ang II-generating activities. The Ang II-generating activity was significantly inhibited by pepstatin A. Leukocyte Ang II level does not correlate with BP or plasma Ang II level in patients with essential hypertension. Leukocyte Ang II level strongly correlates with SSPG concentration, and significantly correlates with body mass index and plasma insulin, and with leptin levels in patients with essential hypertension. Leukocyte Ang II may be directly associated with insulin resistance.

Adult↗
PubMed2003

Haplotype analysis of the human renin gene and essential hypertension.

The human renin gene is an attractive candidate for involvement in the underlying cause of essential hypertension (EH). Despite extensive examination, the relation between the renin gene and hypertension remains unclear. The aims of the present study were to discover new genetic markers of EH and to investigate the relations between polymorphisms of the renin gene and EH in the Japanese. Using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method, we isolated 3 novel variants of the renin gene; a single nucleotide polymorphism (SNP) in intron 4 (T+17int4G), a variable number of tandem repeats (VNTR) polymorphism in intron 7, and a missense mutation in exon 9 (G1051A). We performed an association study with these polymorphisms in 212 patients with EH and 209 age-matched normotensive (NT) subjects. The frequency of genotypes VNTR and T+17int4G did not differ significantly between the 2 groups, whereas the overall distribution of G1051A was significantly different between EH and NT. Haplotype analysis revealed that the overall distribution of haplotypes differed significantly between the EH and NT groups. PRA levels in patients with EH with the G/G genotype were significantly higher than in subjects with EH with G/A and A/A genotypes. These data suggest that the missense mutation in exon 9 may affect the enzymatic function of renin and consequently may be involved in the etiology of hypertension.

Adult↗
PubMed2003

A novel variable number of tandem repeat polymorphism of the renin gene and essential hypertension.

The aims of the present study were to find new genetic markers of essential hypertension (EH) and to investigate relationships between EH and polymorphisms of the renin gene. Using single strand conformation polymorphism, we discovered a new variable number of tandem repeat (VNTR) polymorphism in intron 7 that is 18 bp upstream from the boundary with exon 8. Nucleotide sequencing revealed that this VNTR polymorphism is a tandem repeat of the 4-nucleotide sequence TCTG. There were 6 alleles of this VNTR polymorphism, ranging from 7 repeats to 12 repeats. We analyzed the association between EH and this VNTR polymorphism. There was no significant difference in the overall distribution of this VNTR polymorphism between the EH and normotensive subjects. In summary, we discovered a novel VNTR polymorphism in the renin gene, and this polymorphism was not associated with EH.

Adult↗
PubMed2003

Time-series analysis of systolic blood pressure variation in thirty-three Uygur centenarians in China.

The Uygur are reported to have an unusually long life expectancy. The purpose of this research was to perform a time-series analysis of systolic blood pressure (SBP) variations in the Uygur and clarify the role of blood pressure variation (BPV) in their longevity. A cross-sectional survey was carried out in Hotan. We investigated 133 clinically healthy elderly Uygur subjects and divided them into two groups: 1) 33 Uygur centenarians in Hotan (UCH; aged > or = 100 years); and 2) 100 elderly Uygur in Hotan (UEH; aged 65-70 years). Blood pressure (BP) was monitored and analyzed with ambulatory BP monitoring. The frequency domain measures were obtained with the maximum entropy method. The mean 24-h SBP was higher in UCH than in UEH. The ratio of non-dipper type BPV was larger in the UCH than in UEH. The highest power spectral density occurred over a 12-h rather than a 24-h period in both UCH and UEH. Ultradian BPVs were more frequent in UCH than in UEH. The least square-fitting curves demonstrated that the maximum values, minimum values, and mean 24-h SBP values were higher in UCH than in UEH. The higher BP and greater number of ultradian BPVs in UCH may have been due to the greater energy expenditure for maintaining daily activities in this population. Factors such as meals, daytime naps, nocturnal micturition, decreased baroreceptor sensitivity, and arterial sclerosis may also have contributed to the higher ultradian BPVs. In conclusion, BPV in the 12-h is more dominant than in the 24-h in both UCH and UEH. BPVs in the 3-h and 4-h are more frequent in UCH than those in UEH.

Aged↗
PubMed2002

Angiotensin-converting enzyme gene and longevity in the Xin Jiang Uighur autonomous region of China: an association study.

BACKGROUND: Longevity can be regarded as a multifactorial trait that results from an interaction between environmental factors and sets of epistatic alleles that have pleiotropic age-dependent effects. The Hotan district in the Xin Jiang Uighur Autonomous region of China is relatively isolated and is well known for an ethnic group that displays marked longevity. METHODS: We performed a correlation study between the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene and longevity by comparing distributions of the polymorphism between three different ethnic groups in this region. We obtained data from 424 subjects comprising 227 Uighur individuals, 108 Kazakh individuals, and 89 Han individuals. All subjects in the latter two groups ranged in age from 65 to 70 years, whereas the Uighur subjects actually comprised two different age groups: those ranging in age from 59 to 70 years (Uighur older group in Hotan [UOH]) and those ranging in age from 90 to 113 years (Uighur longevity group in Hotan [ULH]). Genomic DNA was extracted from peripheral white blood cells. Polymerase chain reaction was performed to amplify the I/D polymorphic region of the ACE gene. RESULTS: Frequencies of the insertion (I) and deletion (D) alleles were 0.596 (243/408) and 0.404 (165/408) in the Uighur group, 0.606 (130/216) and 0.394 (85/216) in the Kazakh group, and 0.657 (117/178) and 0.343 (61/178) in the Han group. The overall distributions of alleles in these three groups did not differ significantly (chi(2) = 4.6, p =.33). Within the Uighur group, frequency of the D allele was significantly higher in the ULH group (0.448) than in the UOH group (0.355) (p <.04). CONCLUSIONS: This association reflects a genetic influence on differential survival and may point to pleiotropic age-dependent effects on longevity. Our data may help elucidate the relationship between natural longevity and race difference among individuals in the Xin Jiang Uighur Autonomous region of China.

Aged↗
PubMed2002

Ambulatory blood pressure monitoring in Uygur centenarians.

Cross-sectional surveillance was carried out in long-lived Uygur in China to investigate blood pressure (BP) and pulse rate (PR) variation in centenarians. The study group comprised 33 centenarians (age > or = 100 years), 103 longevous subjects (age 90-99 years) and 100 elderly (age 65-70 years) subjects. Office BP was measured, and 24-h noninvasive ambulatory blood pressure monitoring (ABPM) was performed. The office BP was higher and hypertension occurred more frequently in the centenarians than in either the longevous or elderly subjects. Mean 24-h systolic and diastolic BP was higher in the centenarians than in the other 2 groups. However, mean 24-h PR did not differ between them. Day-night differences in systolic BP decreased, and the non-dipper-type BP pattern was common in the centenarians (79.1% vs 68% and 63.6% in longevous and elderly subjects, respectively). Circadian BP was characterized by 3 peaks in longevous subjects and multiple peaks in centenarians. Morning rising and nocturnal dipping of BP were observed in both longevous and elderly subjects. In conclusion, BP in longevous and elderly Uygur was characterized by circadian rhythmicity, but the nocturnal fall in BP was not seen in centenarians. Differences in day-night BP and circadian rhythmicity may decrease with advancing age, especially in centenarians.

Aged↗
PubMed2002

Structure and polymorphisms of the human natriuretic peptide receptor C gene.

Natriuretic peptides (NPs) regulate cardiovascular homeostasis, including natriuresis, diuresis, vasodilation, regulation of endocrine secretion, and inhibition of cellular growth. Atrial natriuretic peptide receptor C (NPRC) has a short cytoplasmic domain that lacks guanylyl cyclase activity. We used information available for the cDNA of human NPRC to amplify products covering all genomic regions of the gene by long polymerase chain reaction (PCR) and thermal asymmetric interlaced (TAIL)-PCR. PCR products were sequenced directly after extraction and purification. The human NPRC gene spans > 65 kb and contains eight exons and seven introns. All of the exon-intron junction sequences contain the GT/AG consensus junction sequence. We then used the PCR-single-strand conformation polymorphism (PCR-SSCP) to identify polymorphisms of the human NPRC gene. All eight exons and neighboring introns were analyzed by PCR-SSCP for 96 subjects, and migration variants were observed for intron 1, exon 2, and exon 5. Direct sequencing of these variants revealed the following sequence differences: a C to T transition in intron 1, an A to C transition in exon 2, and a C to T transition in exon 5. PCR-restriction fragment length polymorphism analysis (PCR-RFLP) was used to evaluate all three variations. We have determined the structural organization and identified polymorphic sites in the human NPRC gene. The results of this study will facilitate further genetic analyses of the human NPRC gene function.

Base Sequence↗