Native Japanese Men Research Articles

Alteration of gut microbiota by a Westernized lifestyle and its correlation with insulin resistance in non-diabetic Japanese men.

Aims/IntroductionThe severity of insulin resistance is higher in Japanese‐American people with American lifestyles than in native Japanese people with Japanese lifestyles. Recently, the role of gut microbiota in the control of host metabolic homeostasis and organ physiology has been recognized. In addition, gut microbiota alterations have been suggested to contribute to pathogenesis of insulin resistance. The principle aim of the present study was to evaluate the impact of a Westernized lifestyle on the gut microbiota of Japanese‐Americans versus native Japanese, and its correlation with insulin resistance.Materials and MethodsA total of 14 native Japanese men living in Hiroshima, Japan, and 14 Japanese‐American men living in Los Angeles, USA, were included. A 75‐g oral glucose tolerance test was carried out for all participants to assess their glucose tolerance, and normal glucose tolerance was observed. We compared the insulin response with oral glucose load, the Matsuda Index, and the composition of the gut microbiota between the native Japanese and Japanese‐American men.ResultsJapanese‐American men showed higher area under the curve values for serum insulin concentrations during the oral glucose tolerance test and lower Matsuda Index than native Japanese men. Gut microbiota composition of the Japanese‐American men was different; in particular, they showed a relatively lower abundance of Odoribacter than native Japanese men. The ratio between relative abundance of Odoribacter and Matsuda Index was positively correlated between the two groups.ConclusionsOur findings suggest that Westernized lifestyles alter gut microbiota, and its alteration might induce insulin resistance in non‐diabetic Japanese men.

UP-1.122: Common Variants on Human Chromosome 8q24 and the Risk of Prostate Cancer in Native Japanese Men

UP-1.122: Common Variants on Human Chromosome 8q24 and the Risk of Prostate Cancer in Native Japanese Men

Significance of common variants on human chromosome 8q24 in relation to the risk of prostate cancer in native Japanese men

BackgroundCommon variants on human chromosome 8q24, rs1447295 (C/A) and rs6983267 (T/G), have been recently linked to the prevalence of prostate cancer in European and American populations. Here, we evaluated whether the single-nucleotide polymorphisms rs1447295 and rs6983267 were associated with the risk of sporadic prostate cancer as well as latent prostate cancer in a native Japanese population.ResultsWe analyzed genomic DNA samples from 391 sporadic prostate cancer patients, 323 controls who had died from causes unrelated to cancer and 112 Japanese men who were diagnosed as having latent prostate cancer based on autopsy results. The polymorphisms were determined by allelic discrimination using a fluorescent-based TaqMan assay. The A allele of rs1447295 was significantly associated with the risk of sporadic prostate cancer (p = 0.04; age-adjusted OR, 1.34), while the G allele of rs6983267 showed a trend towards being a high-risk allele (p = 0.06; age-adjusted OR, 1.27). No significant difference between these two polymorphisms and the risk of latent prostate cancer was observed in the present Japanese population.ConclusionKnown variants on human chromosome 8q24 may be risk factors for sporadic prostate cancer in native Japanese men.

Polymorphism of cytochrome P450 2B6 and prostate cancer risk: A significant association in a Japanese population

To explore whether Lys262Arg polymorphism of the Cytochrome P450 2B6 (CYP2B6) gene could act as a genetic marker for prostate cancer risk among Japanese men. A total of 350 patients with sporadic prostate cancer and 328 controls were examined. A single nucleotide polymorphism with non-synonymous amino acid change located at Lys262Arg of the CYP2B6 gene was genotyped using a TaqMan assay. The frequency of the Arg/Arg genotype among prostate cancer patients was significantly higher than that among the controls (P = 0.027). The frequency of the G allele of the Lys262Arg polymorphism was also significantly higher in prostate cancer patients than in the controls (30.4% vs 24.8%, P = 0.025). Patients with the Lys/Arg plus Arg/Arg genotypes carried a low Gleason score more frequently than those with the Lys/Lys genotype (P = 0.042). The frequency of the G allele of the Lys262Arg polymorphism was significantly higher in the low Gleason score group than that in the high Gleason score group (34.3% vs 26.8%, P = 0.038). Lys262Arg polymorphism of the CYP2B6 gene may be a genetic marker for evaluating the risk of sporadic prostate cancer in native Japanese men.

Prevalence of metabolic syndrome compared between native Japanese and Japanese-Americans

Metabolic syndrome is a condition characterized by the accumulation of multiple risk factors for atherosclerosis. Japanese-Americans in the U.S. have a more rapid and intense progression of atherosclerosis than native Japanese in Japan due to a westernization of their lifestyle. We investigated the prevalence of metabolic syndrome between 416 native Japanese (194 men and 222 women) in Hiroshima and 574 Japanese-Americans (217 men and 357 women) in Los Angeles, aged 30–89 years. According to the criteria proposed by the Japanese Society of Internal Medicine, the prevalence was 13.9 and 2.7% for native Japanese men and women, and 32.7 and 3.4% for Japanese-American men and women, respectively. According to the IDF or AHA/NHLBI criteria, the prevalence was 20.1 and 6.3%, and 38.7 and 4.5%, or 13.4 and 14.4%, and 30.9 and 27.7%, respectively. Thus, the prevalence of metabolic syndrome in men was significantly higher in Japanese-American than in native Japanese by all the three criteria. However, the prevalence in women was similar between native Japanese and Japanese-American by the Japanese and IDF criteria, whereas it was significantly higher in Japanese-American than in native Japanese by the AHA/NHLBI criteria. This report demonstrates that a westernization of lifestyle can increase the prevalence of metabolic syndrome among Japanese-Americans as compared to native Japanese.

Effects of a westernized lifestyle on the association between fasting serum nonesterified fatty acids and insulin secretion in Japanese men

The effects of the prolonged elevation of nonesterified fatty acid (NEFA) levels on insulin secretion have been controversial and thought to be sex-specific. To investigate the association between a westernized lifestyle and the effects of NEFA on insulin secretion in Japanese men, we examined 67 nondiabetic Japanese-American men and 220 nondiabetic native Japanese men who underwent a 75-g oral glucose tolerance test (OGTT). Most Japanese Americans we surveyed are genetically identical to Japanese living in Japan, but their lifestyle is more westernized. Sets of multiple regression analyses were performed to evaluate the relationship between the sum of the immunoreactive insulin (IRI) levels during the OGTT (ΣIRI) and clinical parameters. Japanese Americans had higher levels of fasting IRI, ΣIRI, and a higher insulin resistance index (homeostasis model assessment for insulin resistance [HOMA-IR]) than native Japanese, whereas there were no significant differences in fasting NEFA and triglyceride levels. A multiple regression analysis adjusted for age, fasting triglycerides, and body mass index (BMI) demonstrated that the fasting NEFA level was an independent determinant of the ΣIRI only in Japanese-American men ( P = .001), but not in native Japanese men ( P = .054). Even when HOMA-IR was included in models instead of BMI, the NEFA level was a significant variable of ΣIRI only in Japanese Americans ( P < .001), and not in native Japanese ( P = .098). In addition, a multiple regression analysis adjusted for age, fasting triglycerides, and BMI demonstrated that the fasting NEFA level was the only independent determinant of ΣC-peptide in Japanese-American men ( P = .041). In conclusion, NEFA seems to be associated with insulin secretion independent of obesity or HOMA-IR. A westernized lifestyle may increase the effects of serum fasting NEFA levels on total insulin secretion after a glucose load in Japanese men.

Prostate cancer in native Japanese and Japanese-American men: Effects of dietary differences on prostatic tissue

Objectives. To investigate the relationship between diet and prostate cancer (CaP) among native Japanese (NJ) and second-generation or third-generation Japanese-American (J-A) men—focusing on the effects of animal fat and soy on prostatic tissues. Methods The subjects were 50 Japanese men undergoing radical prostatectomy, 25 NJ living in Nagoya, Japan and 25 U.S.-born J-A men, living in Los Angeles, California. A priori, the NJ men were believed to be a low-fat, high-soy group and the J-A men, a high-fat, low-soy group. The studies included postoperative measurements of diet (Block questionnaire), body fat (bioimpedance), blood, urine, and prostatic biomarkers in malignant and adjacent normal tissue, using a tissue microarray made from the original paraffin blocks. Results The NJ and J-A men were similar in age (65 to 70 years old; P <0.05), prostate-specific antigen level (7.1 to 8.6 ng/mL), prostate volume (35 to 38 cm 3), and Gleason score (5.6 to 6.6), but their body composition differed. J-A men had more body fat (24% versus 19%), higher serum triglyceride levels (245 versus 106 mg/dL), lower estradiol levels (27 versus 31 ng/mL), and much lower urinary soy-metabolite levels (1:3) than NJ men ( P <0.02). In both NJ and J-A groups, expression of numerous tissue biomarkers separated normal from CaP tissue, including markers for apoptosis (Bcl-2, caspase-3), growth factor receptors (epidermal growth factor receptor), racemase, 5-lipoxygenase, kinase inhibition (p27), and cell proliferation (Ki-67; all P <0.02). Furthermore, within both normal and CaP tissues, caspase-3 and 5-lipoxygenase were expressed more in NJ than in J-A men ( P <0.01). Nuclear morphometry showed that the chromatin in each of the four groups (normal versus CaP, NJ versus J-A) was different (area under the curve 85% to 94%, P <0.01), despite fundamental genetic homogeneity. Conclusions NJ and J-A men, products of similar genetics but differing environments, were shown to have differences in body composition that could influence CaP evolution. The CaP specimens from the NJ and J-A men were histologically similar, but tissue biomarker expression, especially of lipoxygenase and the caspase family, suggested differing mechanisms of carcinogenesis. Differences in nuclear morphometry suggested the additional possibility of gene-nutrient interactions.

Plasma Fibrinogen and Its Correlates in Elderly Japanese Men Living in Japan and Hawaii

Plasma fibrinogen levels were determined using comparable methods for 329 Japanese men in Hiroshima Japan, and 3571 Japanese-American men in Honolulu Hawaii, aged 71–93 years. The age-adjusted mean fibrinogen level in Japanese-American men (307 mg/dl) was significantly higher (p < 0.0001) than in native Japanese men (270 mg/dl). In multiple linear regression models, the fibrinogen level was associated significantly and positively with white blood cell count (WBC) and total cholesterol, and inversely with HDL cholesterol and hematocrit in both study samples. The strongest association with fibrinogen was shown for WBC, and this association was not mediated through cigarette smoking. The observed difference in fibrinogen levels could not be fully explained by WBC, total and HDL cholesterol, triglyceride, hematocrit, body mass index, and diabetes. Some unmeasured environmental or lifestyle variables such as diet and physical activity may be partly responsible for the observed difference in fibrinogen levels between native Japanese men and Japanese-American men in Hawaii.

Serum levels of prostate-specific antigen among Japanese-American and native Japanese men.

Fourfold to sixfold higher prostate cancer rates in Japanese-American men in the United States compared with Japanese men in Japan have been cited to support a role for environmental risk factors in the etiology of the disease. To examine the hypothesis that part or all of the elevated prostate cancer rates in Japanese-American men may reflect more intensive prostate cancer screening in the United States than in Japan, we compared prostate-specific antigen (PSA) levels in community-based samples of serum from men without prostate cancer. Japanese-American men aged 40-85 years and native Japanese men aged 40-89 years with no history of prostate cancer provided sera, respectively, in the United States from March 1990 through March 1992 (n = 237) or in Japan from January 1992 through December 1993 (n = 3522). Age-specific PSA levels were used to estimate the prevalences of undetected prostate cancer in the two populations. Age-specific mean PSA levels were significantly lower in Japanese-Americans than in native Japanese (two-sided P<.001). The prevalence of an elevated PSA level increased with age in both populations and exceeded 5% among men aged 60 years or more. Combined with data on prevalence of detected prostate cancer in the two populations, our data suggest that some 10.0% of Japanese-Americans aged 75 years have prostate cancer, with 31% of that fraction remaining undiagnosed. The corresponding estimates in Japan are a total cancer prevalence of 5.4%, of which 81% has not been detected clinically. The total cancer prevalence ratio 10.0/5.4 = 1.9 (95% confidence interval = 1.5-2.3) in Japanese-American men compared with Japanese men in Japan suggests an increased risk for Japanese-American men, but of less magnitude than the fourfold to sixfold increase indicated by the incidence data.