Tomoko Takamiya

Keio University, Edo, Tōkyō, Japan

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Publications (23)78.7 Total impact

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    ABSTRACT: Background: We recently reported that Japanese had higher liver fat at a lower level of BMI compared with non-Hispanic whites (NHW). Objective: We hypothesize that ethnic difference in fat storage capacity contributes to this ethnic difference in liver fat. Design: To examine this, we assessed liver fat among 244 Japanese-American aged 40-49, using regional computed-tomography images, along with metabolic variables. Results: Despite the similar BMI between Japanese-Americans and NHW men, Japanese-Americans had more liver fat (liver to spleen attenuation ratio: 1.03 ± 0.22 for Japanese-Americans, and 1.07 ± 0.15 for NHW men; p < 0.05) and tended to have a greater disposition for fatty liver with an increase in BMI than NHW, indicating a clear difference between the two groups. In addition, liver fat is less in Japanese-Americans compared with Japanese men (1.03 ± 0.22 vs. 1.01 ± 0.16; p < 0.05), despite of a much higher BMI. These ethnic differences support the hypothesis that higher fat storage capacity indeed seems to be associated with less liver fat. In all the groups, liver fat content strongly correlated with triglycerides, homeostasis model assessment-insulin resistance, and C-reactive protein (CRP). Nevertheless, these metabolic variables were worse in Japanese-Americans, despite of less liver fat, compared with Japanese. Moreover, CRP levels were least among Japanese with highest liver fat, and highest among NHW men with least liver fat, despite of a strong positive association between CRP and fatty liver within each population. Conclusions: Fat content in the liver is intermediate for Japanese-Americans compared with Japanese and NHW men, which supports the hypothesis of less fat storage capacity among Japanese, closely linked to ethnic difference in predisposition to fatty liver.
    Obesity Research & Clinical Practice 03/2013; 7(3):e198-e205. · 0.51 Impact Factor
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    ABSTRACT: BACKGROUND: The prevalence of coronary artery calcification (CAC) in Japanese men is lower than in white and Japanese-American men. It is unclear if aortic calcification (AC) strongly linked to smoking is also lower in Japanese men who have many times higher smoking prevalence compared to US men. METHODS: We conducted a population-based study of 903 randomly-selected men aged 40-49years: 310 Japanese men in Kusatsu, Japan, 301 white men in Allegheny County, US, and 292 Japanese men in Hawaii, US (2002-2006). The presence of AC was assessed by electron-beam tomography. AC was defined as Agatston aortic calcium scores (AoCaS) >0 and ≥100. RESULTS: Japanese (35.8%) had significantly less AoCaS>0 compared to both white (68.8%, p<0.001) and Japanese-American (62.3%, p<0.001) but similar AoCaS≥100 (19.4%, 18.3%, 22.6%, respectively, p=0.392). The pack-years of smoking, which was highest in Japanese, was the most important single associate of AC in all populations. Additionally age, low-density-lipoprotein cholesterol (LDL-C), and triglycerides in Japanese; body-mass index (BMI) in white; and BMI, LDL-C, hypertension, diabetes, and lipid medications in Japanese-American were independent associates of AC. The risk of AC using either cut points adjusted for pack-years of smoking and additional risk factors was lower in Japanese compared to both white and Japanese-American. AC and CAC had moderately positive and significant correlations in Japanese (r=0.26), white (r=0.39), and Japanese-American (r=0.45). CONCLUSIONS: The prevalence of AC defined both >0 and ≥100 was significantly lower in Japanese than in white and Japanese-American men after adjusting for cigarette smoking and additional risk factors.
    International journal of cardiology 01/2012; · 6.18 Impact Factor
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    ABSTRACT: Epidemiological studies suggested that n-6 fatty acids, especially linoleic acid (LA), have beneficial effects on CHD, whereas some in vitro studies have suggested that n-6 fatty acids, specifically arachidonic acid (AA), may have harmful effects. We examined the association of serum n-6 fatty acids with plasminogen activator inhibitor-1 (PAI-1). A population-based cross-sectional study recruited 926 randomly selected men aged 40-49 years without CVD during 2002-2006 (310 Caucasian, 313 Japanese and 303 Japanese-American men). Plasma PAI-1 was analysed in free form, both active and latent. Serum fatty acids were measured with gas-capillary liquid chromatography. To examine the association between total n-6 fatty acids (including LA and AA) and PAI-1, multivariate regression models were used. After adjusting for confounders, total n-6 fatty acids, LA and AA, were inversely and significantly associated with PAI-1 levels. These associations were consistent across three populations. Among 915 middle-aged men, serum n-6 fatty acids had significant inverse associations with PAI-1.
    The British journal of nutrition 08/2011; 107(4):567-72. · 3.45 Impact Factor
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    ABSTRACT: D-dimer and von Willebrand factor (vWF) are associated with atherosclerosis. We recently reported that in a post-World War II birth cohort, Japanese men in Japan had lower levels of atherosclerosis than white men in the United States (U.S.). We examined whether the differences in D-dimer and vWF levels are associated with differences in atherosclerosis between the two populations. Population-based samples of 99 Japanese and 100 white American men aged 40-49 years were examined for coronary artery calcification (CAC), carotid intima-media thickness (IMT), D-dimer, vWF, and other factors using a standardized protocol. When compared to white American men,Japanese had similar levels of D-dimer (0.22 +/- 0.28 vs. 0.19 +/- 0.24 microg/L, respectively, P = 0.39) but significantly higher levels of vWF (124.1 +/- 36.6 vs. 91.3 +/- 48.8%, respectively, P < 0.01). Japanese as compared to white American men had significantly lower prevalence of CAC (13.1 vs. 28.0%, P < 0.01, respectively) and significantly lower IMT (0.61 +/- 0.07 vs. 0.66 +/- 0.08 mm, P < 0.01, respectively). Japanese men had a significant positive association of D-dimer with the prevalence of CAC and a negative association of vWF with IMT, whereas white American men did not have any significant associations. In men aged 40-49 years, Japanese as compared to white Americans had similar levels of D-dimer and higher levels of vWF although Japanese had a significantly lower prevalence of CAC and IMT. These haemostatic factors are unlikely to explain the difference in atherosclerosis in these populations.
    Acta cardiologica 08/2010; 65(4):449-56. · 0.61 Impact Factor
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    ABSTRACT: Among Asians, including Japanese, obesity is related to dyslipidemia and insulin resistance at a lower level of body mass index (BMI) compared with non-Hispanic whites (NHW). We hypothesize that this ethnic difference in the relationship between BMI and metabolic risks is partly associated with the ethnic difference in fat distribution, namely, liver fat as well as visceral adipose tissue. To compare liver fat content among Japanese vs NHW men, regional computed tomographic images were taken to measure liver computed tomographic density in population-based samples of 313 Japanese and 288 NHW men aged 40 to 49 years, along with the assessment of metabolic parameters. Liver fat content was higher in Japanese than NHW men (liver to spleen attenuation ratio [lower value means higher liver fat content]: 1.01 +/- 0.16 vs 1.07 +/- 0.15, respectively; P < .01), despite a lower mean BMI in Japanese men (BMI: 23.6 +/- 2.9 vs 27.8 +/- 4.2 kg/m(2), P < .01). Moreover, Japanese men had a greater disposition for fatty liver with a small increase in BMI than NHW (P < .01), whereas both groups had a similar relationship between visceral adipose tissue and BMI. In both groups, liver fat content correlated with triglycerides, homeostasis model assessment of insulin resistance, and C-reactive protein. Liver fat content is higher among Japanese than NHW; and this ethnic difference becomes more robust with a small increase in BMI, suggesting that fatty liver is a sensitive marker for the failure of the adipose tissue to expand to accommodate an increased energy influx, and is associated with similar metabolic risk in Japanese despite lower BMI compared with NHW men.
    Metabolism: clinical and experimental 06/2009; 58(8):1200-7. · 3.10 Impact Factor
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    ABSTRACT: We sought to examine whether marine-derived n-3 fatty acids are associated with less atherosclerosis in Japanese versus white populations in the U.S. Marine-derived n-3 fatty acids at low levels are cardioprotective through their antiarrhythmic effect. A population-based cross-sectional study in 281 Japanese (defined as born and living in Japan), 306 white (defined as white men born and living in the U.S.), and 281 Japanese-American men (defined as Japanese men born and living in the U.S.) ages 40 to 49 years was conducted to assess intima-media thickness (IMT) of the carotid artery, coronary artery calcification (CAC), and serum fatty acids. Japanese men had the lowest levels of atherosclerosis, whereas whites and Japanese Americans had similar levels. Japanese had 2-fold higher levels of marine-derived n-3 fatty acids than whites and Japanese Americans in the U.S. Japanese had significant and nonsignificant inverse associations of marine-derived n-3 fatty acids with IMT and CAC prevalence, respectively. The significant inverse association with IMT remained after adjusting for traditional cardiovascular risk factors. Neither whites nor Japanese Americans had such associations. Significant differences between Japanese and whites in multivariable-adjusted IMT (mean difference 39 mum, 95% confidence interval [CI]: 21 to 57mum, p < 0.001) and CAC prevalence (mean difference 10.7%, 95% CI: 2.9% to 18.4%, p = 0.007) became nonsignificant after we adjusted further for marine-derived n-3 fatty acids (22 mum, 95% CI: -1 to 46 mum, p = 0.065 and 5.0%, 95% CI: -5.3% to 15.4%, p = 0.341, respectively). Very high levels of marine-derived n-3 fatty acids have antiatherogenic properties that are independent of traditional cardiovascular risk factors and may contribute to lower the burden of atherosclerosis in Japanese, a lower burden that is unlikely the result of genetic factors.
    Journal of the American College of Cardiology 08/2008; 52(6):417-24. · 14.09 Impact Factor
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    ABSTRACT: Koreans are recently at higher risk for coronary heart disease than are the Japanese. We aimed to evaluate levels of carotid intima-media thickness (IMT) and coronary risk factors in Korean and Japanese men in the post-World War II birth cohort. We conducted a population-based study of 352 randomly selected healthy men 40 to 49 years of age: 102 Koreans in Ansan City, Gyeonggi-do, Korea and 250 Japanese in Kusatsu City, Shiga, Japan. Imaging carotid IMT by ultrasonography and other procedures were standardized. Analyzing blood samples and reading carotid IMT were performed at the University of Pittsburgh. Despite more favorable or similar features in coronary risk factors as compared to Japanese men, the Korean men had a higher crude IMT level than the Japanese men (mean +/- standard error, 0.655+/-0.008 mm vs 0.616+/-0.005 mm, respectively, p<0.0001). The difference in the levels of carotid IMT significantly remained after adjusting for metabolic and conventional risk factors (0.654+/-0.008 mm vs. 0.616+/-0.005 mm, respectively; p<0.0001). Among men 40 to 49 years of age, Koreans had significantly higher levels of carotid IMT than the Japanese. Factors that underlie the different susceptibility to subclinical atherosclerosis need to be explored.
    Annals of Epidemiology 04/2008; 18(4):310-5. · 2.48 Impact Factor
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    ABSTRACT: In men in the post-World War II birth cohort, that is, men aged 40 to 49 years, whites in the United States had significantly higher levels of intima-media thickness of the carotid arteries (IMT) than the Japanese in Japan (Electron-Beam Tomography and Risk Assessment Among Japanese and US Men in the Post World War II Birth Cohort [ERA JUMP] study). The difference remained after adjusting for traditional risk factors. Primary genetic effects are unlikely, given the degree to which IMT is increased in the Japanese who migrated to the United States. We investigated whether the differences in the distributions of lipoprotein subclasses explain the difference in IMT between the 2 populations. We examined population-based samples of 466 randomly selected men aged 40 to 49 years (215 whites from Allegheny County, Pennsylvania, and 241 Japanese from Kusatsu, Shiga, Japan). Lipoprotein subclasses were determined by nuclear magnetic resonance (NMR) spectroscopy. The whites had significantly higher levels of large very low-density lipoprotein particles and significantly lower levels of large high-density lipoprotein particles than the Japanese, whereas the 2 populations had similar levels of small low-density lipoprotein particles. The 2 populations had similar associations of IMT with NMR lipoproteins. Adjusting for NMR lipoproteins did not attenuate the significant difference in IMT between the 2 populations (0.671 +/- 0.006 mm for the whites and 0.618 +/- 0.006 mm for the Japanese, P = .01, mean +/- SE). Differences in the distributions of NMR lipoproteins between the 2 populations did not explain the higher IMT in the whites.
    Metabolism 03/2008; 57(2):177-82. · 3.10 Impact Factor
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    ABSTRACT: Race-specific data for the association between coronary artery calcification (CAC) and carotid intimal medial thickness (IMT) are limited. We sought to compare black-white specific associations of these two measures. We conducted a population-based study of 379 randomly selected men aged 40-49 years (84 black and 295 white) from Allegheny County, US (2004-2006). Agatston CAC score was evaluated by electron-beam tomography and carotid IMT was evaluated by ultrasonography. Compared to white men, black men had similar prevalence of CAC (p=0.56) and higher total carotid IMT (p<0.001). In black and white men, CAC score had significant positive correlations with total carotid IMT (r=0.47 and r=0.24, respectively, p<0.001 for both) as well as the IMT for the common carotid artery (CCA), internal carotid artery and carotid bulb. The associations of CAC with total and CCA IMT were significantly stronger in black (beta=0.07 and beta=0.05, respectively) than white men (beta=0.03 and beta=0.01, respectively) after adjustment for traditional coronary risk factors (p=0.046 and p=0.036, respectively). In black and white middle aged men, CAC score had significant positive correlations with total and segmental carotid IMT. CAC was more predictive of total and CCA IMT in black than white men independent of coronary risk factors.
    Atherosclerosis 02/2008; 196(2):913-8. · 3.71 Impact Factor
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    ABSTRACT: We have previously reported that the prevalence of coronary artery calcification (CAC) was substantially lower among Japanese than American men despite a less favorable profile of many traditional risk factors in Japanese men. To determine whether lipoprotein-associated phospholipase A2 (Lp-PLA2) levels are related to the difference in the prevalence of CAC between the two populations. A total of 200 men aged 40-49 years were examined: 100 residents in Allegheny County, Pennsylvania, United States, and 100 residents in Kusatsu City, Shiga, Japan. Coronary calcium score (CCS) was evaluated by electron-beam tomography, Lp-PLA2 levels, nuclear magnetic resonance (NMR) lipoprotein subclasses, and other factors were assessed in 2001-2002. Lp-PLA2 levels were higher among American than Japanese men (Mean +/- standard deviation 301.7 +/- 82.6 versus 275.9 +/- 104.7 ng/mL, respectively, p=0.06). Among all Japanese men and those with low density lipoprotein (LDL) cholesterol > or =130 mg/dL, there was an inverse association of the prevalence of CCS>0 with the tertile groups of Lp-PLA2 levels (p=0.08 and p=0.03, respectively). American men did not have any association between CCS>0 with the tertile groups of Lp-PLA2 (p=0.62). Although Lp-PLA2 among both populations correlated positively with LDL and total cholesterol, American and Japanese men had different correlations with NMR lipoprotein subclasses. Reported high odds ratio for CCS>0 among American compared to Japanese men was not reduced after adjusting for Lp-PLA2 levels. Lp-PLA2 may have different mechanisms of action among American and Japanese men. Lp-PLA2 levels can not explain the observed CAC differences between the two populations.
    Journal of Epidemiology 11/2007; 17(6):179-85. · 2.11 Impact Factor
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    ABSTRACT: To investigate the association between fish consumption and early atherosclerosis, we analyzed the relationship between fish consumption and average intima-media thickness (AveIMT) by carotid ultrasound in middle-aged Japanese men. Participants were 250 randomly selected, community-based Japanese men aged 40 to 49 years without a prior history of cardiovascular disease. AveIMT was calculated from the mean of 1-cm lengths of both the right and the left carotid arteries at 8 locations. A lifestyle survey was carried out using a self-administered questionnaire including the frequency of fish intake. There were 147 men in the fewer than 4 times per week fish consumption group and 103 men in the 4 or more times per week group. The mean AveIMT was significantly higher in the low fish consumption group than in the high fish consumption group (0.623+/-0.068 vs 0.605+/-0.065 mm, P=.03). After adjustment for age, waist circumference, pack-years of smoking, alcohol consumption, diabetes, and lipid-lowering medications, the significant difference in the AveIMT between the 2 groups remained. However, after further adjustment for low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and C-reactive protein in the model, the significant difference disappeared. Fish consumption may be protective against early atherosclerosis in middle-aged men, probably through its beneficial effects on inflammation.
    Metabolism 09/2007; 56(8):1060-4. · 3.10 Impact Factor
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    ABSTRACT: Ghrelin, a 28-amino-acid gastric peptide hormone, has an appetite-stimulating effect and controls the energy balance. Serum ghrelin levels inversely correlate with body mass index. Recently, several papers reported the ethnic difference in the ghrelin levels. To our knowledge, however, no studies have compared the serum ghrelin levels between Caucasians in the USA and the Japanese in Japan. We conducted a cross-sectional study of 189 men 40-49 years of age (91 US Caucasians in the U.S. and 98 Japanese in Japan) to examine serum ghrelin levels and metabolic and other factors. Serum ghrelin levels correlated with waist circumferences and lipid profiles among Caucasian Americans and the Japanese. Serum ghrelin levels were significantly higher among Caucasian Americans than among the Japanese (904.5 (632.0, 1132.0) pg/mL, 508.0 (399.0, 1378.3) pg/mL (median and 95% confidence interval), respectively, P < 0.01), although Caucasian Americans were much more obese (BMI: 26.9 +/- 3.3 kg/m(2) versus 23.3 +/- 3.1 kg/m(2) respectively, P < 0.01). The ethnic difference remained after adjusting for metabolic factors, smoking status, and other factors (P < 0.01). We have shown in our population-based study that serum ghrelin levels among men aged 40-49 are significantly higher in Caucasian Americans than in the Japanese in Japan. Reasons for the ethnic difference in the ghrelin levels are largely unknown and warrant further investigation.
    Diabetes Obesity and Metabolism 08/2007; 9(4):591-3. · 5.18 Impact Factor
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    ABSTRACT: Coronary heart disease incidence and mortality remain very low in Japan despite major dietary changes and increases in risk factors that should have resulted in a substantial increase in coronary heart disease rates (Japanese paradox). Primary genetic effects are unlikely, given the substantial increase in coronary heart disease in Japanese migrating to the United States. For men aged 40-49 years, levels of total cholesterol and blood pressure have been similar in Japan and the United States throughout their lifetimes. The authors tested the hypothesis that levels of subclinical atherosclerosis, coronary artery calcification, and intima-media thickness of the carotid artery in men aged 40-49 years are similar in Japan and the United States. They conducted a population-based study of 493 randomly selected men: 250 in Kusatsu City, Shiga, Japan, and 243 White men in Allegheny County, Pennsylvania, in 2002-2005. Compared with the Whites, the Japanese had a less favorable profile regarding many risk factors. The prevalence ratio for the presence of a coronary calcium score of > or =10 for the Japanese compared with the Whites was 0.52 (95% confidence interval: 0.35, 0.76). Mean intima-media thickness was significantly lower in the Japanese (0.616 mm (standard error, 0.005) vs. 0.672 (standard error, 0.005) mm, p < 0.01). Both associations remained significant after adjusting for risk factors. The findings warrant further investigations.
    American Journal of Epidemiology 03/2007; 165(6):617-24. · 4.78 Impact Factor
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    ABSTRACT: Levels of adiponectin are inversely associated with obesity levels. We examined the levels of adiponectin in American (n = 98) and Japanese (n = 92) men aged 40 to 49 years. Contrary to our expectations, the American men had higher levels of adiponectin than the Japanese men (13.3 +/- 5.8 vs 7.3 +/- 4.2 (microg/mL) despite higher levels of obesity. Smaller areas of visceral adipose tissue in American than in Japanese men may have resulted in the higher levels of adiponectin.
    Metabolism 01/2007; 55(12):1561-3. · 3.10 Impact Factor
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    ABSTRACT: Epidemiologic studies have investigated the relation between alcohol intake and coronary calcification, with controversial results. Furthermore, the influence of heavy drinking has not been well elucidated. In the present study, a random sample of community-based Japanese men aged 40 to 49 years without a history of cardiovascular disease (n=245) were examined for coronary artery calcium (CAC) determined by electron-beam computed tomography and drinking status. There was a J-shaped association between alcohol intake and CAC. There was an increase of CAC in heavy drinkers (>or=46 g/day), and participants who were drinking>or=69 g/day showed a significant increase in CAC compared with never drinkers after adjusting for other cardiovascular risk factors.
    The American Journal of Cardiology 08/2006; 98(2):141-4. · 3.21 Impact Factor
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    ABSTRACT: Visceral adipose tissue (VAT) is an independent risk factor for metabolic and cardiovascular disorders. There has been no study that demonstrated different abdominal fat distribution between Asian and Caucasian men. As the Japanese are less obese but more susceptible to metabolic disorders than Caucasians, they may have larger VAT than Caucasians at similar levels of obesity. We compared the abdominal fat distribution of the Japanese (n=239) and Caucasian-American (n=177) men aged 40-49 years in groups stratified by waist circumference in a population-based sample. We obtained computed tomography images and determined areas of VAT and subcutaneous adipose tissue (SAT). We calculated VAT to SAT ratio (VSR). The Japanese men had a larger VAT and VSR in each stratum, despite substantially less obesity overall. In multiethnic studies, difference in abdominal fat distribution should be considered in exploring factors related to obesity.
    International Journal of Obesity 08/2006; 30(7):1163-5. · 5.22 Impact Factor
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    ABSTRACT: Elevated plasma plasminogen activator inhibitor-1 (PAI-1) levels were associated with higher incidence of type II diabetes. Elucidating the determinants of PAI-1 in various ethnicities may help to understand the susceptibility to developing diabetes. The aim of our study was to compare PAI-1 levels between Americans and the Japanese in the post-war generation and to elucidate the determinants of the PAI-1 levels. We conducted a cross-sectional study on a total of 198 men aged 40-49 in the US (Body mass index (BMI): 27.0+/-3.3 kg/m(2)) and Japan (BMI: 23.3+/-3.1 kg/m(2)). Examination included physique measurement (BMI and waist girth), blood analysis (lipid profiles, glucose, insulin, C-reactive protein, and PAI-1), and life-style assessment by self-administered questionnaires. PAI-1 levels were significantly lower in American than in Japanese men, even after adjustment for age, waist girth, cigarette smoking, habitual alcohol drinking, and other factors. In the Americans, waist girth, insulin, and cigarette smoking were significantly associated with PAI-1 levels, while waist girth and triglycerides were significantly associated with PAI-1 levels in the Japanese. PAI-1 levels were significantly lower in American than in Japanese men and the determinants of PAI-1 levels differ for American and Japanese men aged 40-49.
    Diabetes Research and Clinical Practice 06/2006; 72(2):176-82. · 2.74 Impact Factor
  • Atherosclerosis Supplements 01/2006; 7(3):265-265. · 4.33 Impact Factor
  • Atherosclerosis Supplements - ATHEROSCLER SUPPL. 01/2006; 7(3):58-58.
  • Atherosclerosis Supplements - ATHEROSCLER SUPPL. 01/2006; 7(3):260-260.

Publication Stats

308 Citations
78.70 Total Impact Points

Institutions

  • 2013
    • Keio University
      Edo, Tōkyō, Japan
  • 2005–2013
    • University of Pittsburgh
      • • Department of Epidemiology
      • • School of Medicine
      Pittsburgh, Pennsylvania, United States
  • 2006–2008
    • Shiga University of Medical Science
      • • Department of Health Science
      • • Department of Medicine
      Ōtu, Shiga, Japan
  • 2007
    • Kyoto Women's University
      Kioto, Kyōto, Japan