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Biomedical subjects

Tomohiro Katsuya

Publications and source records attributed to Tomohiro Katsuya.

At least 19 recordsLinked to original sources
PubMed2006

Mutation of the follicle-stimulating hormone receptor gene 5'-untranslated region associated with female hypertension.

Inactivating mutations in the follicle-stimulating hormone receptor (FSHR) gene have been reported to cause hereditary hypergonadotropic ovarian failure. It has been found recently that the FSHR knockout mouse exhibits hypertension. The aim of the present study was to investigate the association between polymorphisms in the human FSHR gene and essential hypertension (EH) by using single nucleotide polymorphisms (SNPs). We selected 5 SNPs in the gene (rs1394205, rs2055571, rs11692782, rs1007541, and rs2268361) and performed 2 genetic case-control studies in different populations. A confirmative case-control study was performed using 1035 EH patients and 1058 age-matched controls. Transcriptional activities were measured with a luciferase assay system. The first case-control study found that the A allele of rs1394205 was significantly higher in EH females (P=0.010). In addition, in the confirmative case-control study, there was a significant difference for this SNP between female normotensive subjects (44.5%) and EH patients (50.7%) (P=0.043). Multiple logistic regression analysis in female subjects also revealed a significant association of subjects with the A allele of rs1394205 with EH (P=0.033), with the odds ratio calculated as 1.68 (95% CI: 1.04 to 2.73). Transcriptional activity of the A allele was 56+/-8% (mean+/-SD) of that observed for the G-type allele (P=0.001). Serum estradiol levels were significantly lower in patients with the A/A genotype than in patients without the A/A genotype (P=0.004). The SNP in the 5'-untranslated region of the FSHR gene affects levels of transcriptional activity and is a susceptibility mutation of EH in women.

5' Untranslated Regions↗
PubMed2006

Deletion of angiotensin-converting enzyme 2 accelerates pressure overload-induced cardiac dysfunction by increasing local angiotensin II.

Angiotensin-converting enzyme 2 (ACE2) is a carboxypeptidase that cleaves angiotensin II to angiotensin 1-7. Recently, it was reported that mice lacking ACE2 (ACE2(-/y) mice) exhibited reduced cardiac contractility. Because mechanical pressure overload activates the cardiac renin-angiotensin system, we used ACE2(-/y) mice to analyze the role of ACE2 in the response to pressure overload. Twelve-week-old ACE2(-/y) mice and wild-type (WT) mice received transverse aortic constriction (TAC) or sham operation. Sham-operated ACE2(-/y) mice exhibited normal cardiac function and had morphologically normal hearts. In response to TAC, ACE2(-/y) mice developed cardiac hypertrophy and dilatation. Furthermore, their hearts displayed decreased cardiac contractility and increased fetal cardiac gene induction, compared with WT mice. In response to chronic pressure overload, ACE2(-/y) mice developed pulmonary congestion and increased incidence of cardiac death compared with WT mice. On a biochemical level, cardiac angiotensin II concentration and activity of mitogen-activated protein (MAP) kinases were markedly increased in ACE2(-/y) mice in response to TAC. Administration of candesartan, an AT1 subtype angiotensin receptor blocker, attenuated the hypertrophic response and suppressed the activation of MAP kinases in ACE2(-/y) mice. Activation of MAP kinases in response to angiotensin II was greater in cardiomyocytes isolated from ACE2(-/y) mice than in those isolated from WT mice. ACE2 plays an important role in dampening the hypertrophic response to pressure overload mediated by angiotensin II. Disruption of this regulatory function may accelerate cardiac hypertrophy and shorten the transition period from compensated hypertrophy to cardiac failure.

Angiotensin II↗
PubMed2006

Beta2-adrenoceptor polymorphisms relate to obesity through blunted leptin-mediated sympathetic activation.

BACKGROUND: Obesity is a growing public health problem. It has been reported that beta2-adrenoceptor polymorphisms are associated with obesity. This study examines the associations of beta2-adrenoceptor polymorphism with relationships between plasma norepinephrine (NE) and leptin to evaluate further the mechanisms of obesity. METHODS: In 329 normotensive (BP <140/90 mm Hg) men with a wide range of BMI (17.0 to 36.5 kg/m2), we measured BMI, total body fat mass, waist-to-hip ratio (W/H), BP, plasma NE, leptin, and the beta2-(Arg16Gly, Gln27Glu) adrenoceptor polymorphisms. The subjects consisted of 206 nonobese (BMI <25 kg/m2) and 123 overweight or obese (BMI >or=25 kg/m2) men. RESULTS: Overweight or obese subjects had a significantly higher frequency of Gly16 and Glu27 alleles compared with nonobese subjects. The subjects carrying Gly16 or Glu27 alleles regardless of BMI had greater total fat mass, W/H and plasma leptin compared with those without the Gly16 or Glu27 alleles, indicating that Gly16 and Glu27 alleles of the beta2-adrenoceptor gene are related to obesity and fat mass. Only in the nonobese subjects who carried the Gly16 and Glu27 alleles was there a high plasma NE level, but similar in overweight or obese subjects. To evaluate leptin-mediated sympathetic activation, we performed linear regression analyses between plasma leptin and NE. In groups with and without the Gly16 or Glu27 alleles, plasma leptin correlated with NE, but the slope in the group carrying the Gly16 or Glu27 allele was significantly lower than that without the Gly16 or Glu27. CONCLUSIONS: The findings demonstrate a strong and significant association of the Gly16 and Glu27 alleles with obesity. Lower slopes between leptin and NE in the subjects carrying these beta2-adrenoceptor polymorphisms indirectly indicate a blunted leptin-mediated sympathetic nerve activity. We propose that the beta2-adrenoceptor polymorphisms related to blunted leptin-mediated sympathetic activation offers further proof for the mechanisms of obesity.

Adult↗
PubMed2005

Beta2- and beta3-adrenergic receptor polymorphisms are related to the onset of weight gain and blood pressure elevation over 5 years.

BACKGROUND: The genes responsible for obesity are candidate genes for obesity-related diseases, such as hypertension. Functional polymorphisms in the beta2- and beta3-adrenergic receptors have been reported to be associated with hypertension and obesity. METHODS AND RESULTS: To longitudinally clarify the relevance to alterations in beta-adrenergic receptor polymorphisms related to weight gain, blood pressure (BP) elevation, and sympathetic nerve activity as measured by plasma norepinephrine level, we studied 160 young, nonobese, normotensive men. Changes in body weight, BP, plasma norepinephrine levels, and beta2-adrenergic (Arg16Gly, Gln27Glu) and beta3-adrenergic (Trp64Arg) receptor polymorphisms were measured periodically over a 5-year period. Weight gain and BP elevation were defined as > or =10% increases from entry levels over 5 years in body mass index or mean BP. The presence of the Gly16 allele of Arg16Gly was associated with a higher frequency of weight gain and BP elevation over the 5-year period. The subjects carrying the Glu27 allele of Gln27Glu and the Trp64 allele of Trp64Arg had a higher frequency of BP elevation. Significantly higher levels of plasma norepinephrine at entry and at year 5 were observed in the subjects with the Gly16 allele of Arg16Gly and the Glu27 allele of Gln27Glu compared with those without the Gly16 or the Glu27 alleles. CONCLUSIONS: These results demonstrate that the Gly16 allele is related to greater weight gain and BP elevation. Additionally, Glu27 and Trp64 alleles are linked to BP elevation. The subjects carrying the beta2-polymorphisms linked to weight gain and BP elevation also have higher plasma norepinephrine levels that are present at entry before weight gain and BP elevation. These findings suggest that beta2-adrenergic receptor polymorphisms in association with a heightened sympathetic nerve activity could predict the future onset of obesity and hypertension, as shown in the 5-year longitudinal study.

Adult↗
PubMed2005

Lys418Asn polymorphism of the alpha2-adrenoceptor gene relates to serum uric acid levels but not to insulin sensitivity.

Hyperuricemia is associated with cardiovascular risk. The present study examines the association between serum uric acid (UA) elevation and the alpha2-, beta2-, and beta3-adrenoceptor polymorphisms. In 219 nonobese, normotensive, normouricemic (serum UA <6.5 mg/dL at entry) men, serum UA, plasma norepinephrine (NE), the homeostasis model assessment of insulin resistance (HOMA-IR), body mass index, total body fat mass, the alpha2A(Lys418Asn)-, beta2(Arg16Gly, Gln27Glu)-, and beta3(Trp64Arg)-adrenoceptor polymorphisms were measured annually over 5 years. Hyperuricemia was defined as a serum UA level of > or =mean+1 SD of 5.0 mg/dL in the participants. At entry, there were 36 subjects who had hyperuricemia and 183 who had normal UA levels. A significant UA elevation for 5 years was defined as an increase in > or =10% in UA levels. There were 82 subjects who had significant UA elevations. The subjects who had hyperuricemia at entry in addition to the subjects who had significant UA elevations over the 5-year period carried a significantly higher frequency of the Asn418 allele of Lys418Asn. Additionally, subjects carrying the Asn418 allele had higher UA and plasma NE and greater elevations in UA over the study period, but HOMA-IR was similar. Insulin resistance at entry and during the study was associated with Arg16Gly polymorphisms but not with Lys418Asn polymorphisms. In conclusion, the Asn418 allele of Lys418Asn is associated with either established hyperuricemia or the progressive elevation of UA over time. This polymorphism was not associated with insulin resistance in nonobese, normotensive individuals. Although hyperuricemia is of known relevance to insulin resistance, it appears to have different genetic determinants from insulin resistance in terms of adrenoceptor polymorphisms.

Adult↗
PubMed2005

Association of hypoadiponectinemia with smoking habit in men.

Adiponectin is emerging as an important molecule in obesity, the metabolic syndrome, and cardiovascular disease. On the other hand, smoking habit is well known to be related to cardiovascular disease and hypertension. To examine the association between adiponectin concentration and smoking habit, we performed an epidemiological survey and an acute exposure test in humans and an experiment in adipocytes to elucidate the mechanism underlying the association between adiponectin and smoking. In the epidemiological study, we enrolled a total of 331 male subjects to examine chronic smoking exposure. Plasma adiponectin was significantly lower (P=0.01) in current smokers (5.3+/-0.3 microg/mL) than in never-smokers (6.5+/-0.4 microg/mL). A significant association between smoking and low adiponectin level was also confirmed in multiple regression analysis including age, body mass index, hypertension, diabetes, hyperlipidemia, and creatinine clearance (never-smokers 6.5+/-0.4 microg/mL; past smokers 5.6+/-0.3 microg/mL; current smokers 5.2+/-0.4 microg/mL; F=4.52; P=0.01). To examine the acute effect of smoking on adiponectin concentration for 12 hours, we measured plasma adiponectin level in 5 male never-smokers before smoking and 3, 6, and 12 hours after smoking, with the result that adiponectin showed a significant decrease after smoking (12 hours; -14.5+/-0.6%; P<0.01). In cultured mouse 3T3-L1 adipocytes, H2O2 and nicotine reduced the mRNA expression and secretion of adiponectin in a dose-dependent manner. Smoking habit is associated with adiponectin concentration in men, and its suppressive effect is mediated in part through direct inhibition of smoking on adiponectin expression in adipocytes.

3T3 Cells↗
PubMed2005

Acute hyperinsulinemia reduces plasma leptin levels in insulin-sensitive Japanese men.

BACKGROUND: Elevated plasma leptin levels have been demonstrated in obesity and hypertension. These conditions are documented as insulin-resistant states with sympathetic overactivity. However, the relation between plasma insulin, leptin levels, and sympathetic nerve activity, especially after meals, has not been established. METHODS: To evaluate the impact of insulin sensitivity and obesity on the response of plasma leptin to acute physiologic insulin elevation, we studied 31 nonobese (body mass index [BMI] < 25 kg/m(2)) and 38 overweight or obese (obese; BMI >/= 25 kg/m(2)) normotensive men. Using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), the subjects were subdivided into insulin-sensitive (HOMA-IR <2.5) and insulin-resistant (HOMA-IR >/=2.5) groups. There were 11 nonobese and 28 obese men who were insulin-resistant. Blood pressure (BP), plasma glucose, insulin, leptin, and norepinephrine (NE) levels were measured before and after 75-g oral glucose loading every 30 min for 120 min. RESULTS: In nonobese subjects, fasting plasma insulin and leptin levels and areas-under-the-curves (AUC) for insulin and leptin were significantly lower in the insulin-sensitive group than in the insulin-resistant group. In the insulin-sensitive group regardless of BMI, plasma leptin levels decreased after glucose loading. Plasma glucose, insulin, NE, and BP levels increased in nonobese insulin-sensitive subjects after glucose loading, whereas in obese insulin-sensitive subjects, plasma NE and BP did not change in response to glucose. In insulin-resistant subjects regardless of BMI, marked elevations in plasma insulin did not cause any change in plasma leptin, NE, and BP levels. CONCLUSION: These results demonstrate that insulin sensitivity and adiposity affect the response of leptin and sympathetic nerve activity to acute postprandial hyperinsulinemia.

Acute Disease↗
PubMed2005

Beta2-adrenoceptor polymorphisms relate to insulin resistance and sympathetic overactivity as early markers of metabolic disease in nonobese, normotensive individuals.

BACKGROUND: The genes responsible for insulin resistance are also candidate genes for insulin resistance-related diseases, such as obesity and hypertension. Functional polymorphisms in the beta2- and beta3-adrenergic receptors have been reported to be associated with diabetes, hypertension, and obesity. To clarify the relevance of the beta-adrenergic receptor polymorphisms to insulin resistance, we studied their association with polymorphisms of beta2 (Arg16Gly, Gln27Glu) and beta3 (Trp64Arg) adrenoceptor genes. METHODS: We studied 155 young, nonobese Japanese men using the homeostasis model assessment of insulin resistance (HOMA-IR) to divide individuals into insulin-sensitive and insulin-resistant groups. Insulin resistance in the participants was defined as HOMA-IR equal to or greater than the average plus 1 SD of 3.1. There were 69 men who were insulin resistant and 86 men who were insulin sensitive. Body mass index (BMI), blood pressure (BP), plasma glucose, insulin, leptin, norepinephrine (NE) levels, and the polymorphisms of Arg16Gly and Gln27Glu of the beta2- and Trp64Arg of the beta3-adrenoceptor polymorphisms were measured in all participants. RESULTS: The insulin-resistant group had higher frequency of the Gly16 allele of Arg16Gly compared with the insulin-sensitive group, whereas the frequencies of genotypes or alleles of Gln27Glu and Trp64Arg were similar. The insulin-resistant group had a higher mean HOMA-IR, fasting insulin, NE, and total fat mass compared with levels in the insulin-sensitive group, but the BMI and leptin levels were similar. The subjects carrying the Gly16 allele of the beta2-adrenoceptor gene had a higher mean HOMA-IR, fasting insulin, NE, body fat mass, and BP than those without the Gly16 allele. CONCLUSIONS: The Gly16 mutation of the beta2-adrenoceptor gene is associated with increased insulin resistance, adiposity, and BP accompanied by higher plasma NE levels early in the metabolic disease in developing obesity. These findings show an important role of beta2-adrenoceptor gene polymorphisms in the association of insulin resistance in hypertension and obesity.

Adult↗
PubMed2005

Rebound weight gain as associated with high plasma norepinephrine levels that are mediated through polymorphisms in the beta2-adrenoceptor.

BACKGROUND: A successful weight loss program is essential treatment for obesity-related diseases, but it is well known that the majority of individuals do not succeed in weight loss maintenance. The present study evaluates hormonal mechanisms and the relationship of beta2-adrenoceptor polymorphisms involved in individuals who regain weight after initially successful weight loss. METHODS: Overweight Japanese men (n = 154) were enrolled in a 24-month weight loss program. Body mass index (BMI), total body fat mass, plasma norepinephrine (NE) and leptin levels, and beta2-adrenoceptor polymorphisms (Arg16Gly, Gln27Glu) were measured every 6 months for the 24-month period. Maintenance of weight loss was defined as significant weight loss (>or=10% reduction) from entry weight at 6 months and maintenance of the weight loss for an additional 18 months. Rebound weight gain was defined as significant weight loss at 6 months but subsequent regain of body weight during the next 18 months. RESULTS: The results showed that 37 subjects maintained weight loss during 24 months, whereas 36 subjects had rebound weight gain. The BMI at entry and calorie intake and physical activity at each period were similar between the two groups. Subjects who maintained weight loss had at entry a significantly lower fat mass and plasma NE levels compared to those with rebound weight gain. Body fat mass, NE, and leptin levels at entry predicted the degree of change in body weight during the 24-month study period. Subjects with rebound weight gain had a significantly higher frequency of the Gly16 allele for the beta2-adrenoceptor polymorphism compared to subjects who had a 24-month maintenance of weight loss. Subjects carrying the Gly16 allele also had significantly higher plasma NE, leptin, and body fat mass levels and a greater waist-to-hip ratio both at entry and throughout the study. CONCLUSIONS: A high initial degree of body fat mass and high plasma NE levels as determined by the Gly16 allele for the beta2-adrenoceptor polymorphisms predict those individuals who will have rebound weight gain after their initial successful weight loss.

Adult↗
PubMed2005

Single nucleotide polymorphisms in the interleukin-6 gene associated with blood pressure and atherosclerosis in a Japanese general population.

It is known that increased plasma levels of inflammatory markers, such as interleukin-6 (IL-6), are associated with atherosclerosis and myocardial infarction. The aim of this study was to reveal the contribution of the single nucleotide polymorphisms (SNPs) of the IL-6 gene on the blood pressure regulation and progression of atherosclerosis in a general Japanese population. In order to evaluate the potential implications of genetic variability of the IL-6 gene, we explored eight SNPs by direct sequencing for the entire coding region and the promoter region in the IL-6 gene and genotyped two SNPs, -636G > C in the promoter region and 1691C > G in intron 3, for a total of 2,421 Japanese subjects (1,162 men and 1,259 women). As a consequence, -636 G > C was significantly associated with systolic blood pressure (SBP) and carotid intima-media thickness (IMT) in women, and 1691C > G showed a relationship with SBP and carotid IMT in men after adjustment for all confounding factors. Although neither SNP had a significant correlation to the prevalence of hypertension, the haplotype frequency analysis indicated that the number of hypertensive men with a G allele at both -636 and 1691 was significantly greater than the number of nonhypertensive men with this combination. Thus, these two SNPs in the promoter region and intron 3 of the IL-6 gene might play a role in the blood pressure regulation and progression of atherosclerosis in the Japanese.

Aged↗
PubMed2004

Hypoadiponectinemia is an independent risk factor for hypertension.

Adiponectin is one of the key molecules in the metabolic syndrome, and its concentration is decreased in obesity, type-2 diabetes, and coronary artery disease. Genetic investigation has revealed that 2 polymorphisms (I164T and G276T) are related to adiponectin concentration and diabetes. To examine whether adiponectin affects hypertension genetically or biologically, we performed a case-control study. A total of 446 diagnosed cases of hypertension (HT) in men and 312 normotensive (NT) men were enrolled in this study. Plasma adiponectin concentration was measured using an enzyme-linked immunosorbent assay system. Single nucleotide polymorphisms were determined by TaqMan polymerase chain reaction method. After adjustment for confounding factors, adiponectin concentration was significantly lower in HT (HT: 5.2+/-0.2 microg/mL; NT: 6.1+/-0.2 microg/mL; P<0.001). Furthermore, multiple regression analysis indicated that hypoadiponectinemia was an independent risk factor for hypertension (P<0.001). Blood pressure was inversely associated with adiponectin concentration in normotensives regardless of insulin resistance. In subjects carrying the TC genotype of the I164T polymorphism, adiponectin concentration was significantly lower (TC: 2.6+/-0.9 microg/mL; TT: 5.5+/-0.1 microg/mL; P<0.01), and most of them had hypertension. In contrast, the G276T polymorphism was not associated with adiponectin concentration or hypertension. In conclusion, hypoadiponectinemia is a marker for predisposition to hypertension in men.

Adiponectin↗