During the evolution of skeletons, terrestrial vertebrates acquired strong bones made of calcium–phosphate. By keeping the extracellular fluid in a supersaturated condition regarding calcium and phosphate ions, they created the bone when and where they wanted simply by providing a cue for precipitation. To secure this strategy, they acquired a novel endocrine system to strictly control the extracellular phosphate concentration. In response to phosphate intake, fibroblast growth factor–23 (FGF23) is secreted from the bone and acts on the kidney through binding to its receptor Klotho to increase urinary phosphate excretion, thereby maintaining phosphate homeostasis. The FGF23–Klotho endocrine system, when disrupted in mice, results in hyperphosphatemia and vascular calcification. Besides, mice lacking Klotho or FGF23 suffer from complex aging-like phenotypes, which are alleviated by placing them on a low- phosphate diet, indicating that phosphate is primarily responsible for the accelerated aging. Phosphate acquires the ability to induce cell damage and inflammation when precipitated with calcium. In the blood, calcium–phosphate crystals are adsorbed by serum protein fetuin-A and prevented from growing into large precipitates. Consequently, nanoparticles that comprised calcium–phosphate crystals and fetuin-A, termed calciprotein particles (CPPs), are generated and dispersed as colloids. CPPs increase in the blood with an increase in serum phosphate and age. Circulating CPP levels correlate positively with vascular stiffness and chronic non-infectious inflammation, raising the possibility that CPPs may be an endogenous pro-aging factor. Terrestrial vertebrates with the bone made of calcium– phosphate may be destined to age due to calcium–phosphate in the blood.

Japanese Americans include Japanese individuals migrating from Japan to the United States (first-generation Japanese Americans [JA-1]) and their offspring (second- or later-generation Japanese Americans [JA-2]). Although Japanese Americans share their genetic predisposition with the Japanese, their lifestyles have been westernized rapidly and extensively. We conducted a medical survey for atherosclerosis among Japanese Americans living in Hawaii and Los Angeles and native Japanese living in Hiroshima for 50 years since 1970 (the Hawaii–Los Angeles–Hiroshima Study) and obtained the following results:

(1) In the 1990s, a westernized lifestyle induced hyperlipidemia among Japanese Americans, and based on the evaluation of the carotid artery intima-media wall thickness (IMT), atherosclerosis was apparently more advanced in Japanese Americans than in native Japanese. In addition, the advancement of atherosclerosis corresponded to the degree of westernization of lifestyles in JA-1 and JA-2.

(2) In the 2010s, the serum total cholesterol and low-density lipoprotein cholesterol levels in native Japanese were significantly higher than those in Japanese Americans, and the difference in the progression of carotid artery IMT was smaller between native Japanese and Japanese Americans.

(3) Maintaining a healthy Japanese lifestyle since childhood may suppress future worsening of risk factors for atherosclerosis (such as obesity and diabetes mellitus) and contribute to atherosclerosis prevention in the Japanese.

Aim: To examine the association between long-term exposure to suspended particulate matter (SPM) and cardiovascular mortality in Japan after controlling for known major confounding factors among a large middle and elderly cohort study in Ibaraki Prefecture, Japan.

Methods: We followed 91,808 residents (men 34%) who undertook a national health check-up at age 40–79 years for 17 years (1993–2010). Two different exposure indices were adopted: baseline SPM concentration (in the year 1990) and average SPM concentration for the first (average of 1990 and 1995) and the second half (average of 2005 to 2009) of the study period. Sex-specific adjusted risk ratios (RRs) for cardiovascular mortality were calculated using general mixed Poisson regression models after adjusting the age, BMI, history of diabetes mellitus and hypertension, creatinine, glutamic pyruvic transaminase, total cholesterol, high-density lipoprotein cholesterol, smoking, alcohol, and temperature. The variation between seven medical administration areas was also taken into account as a random effect.

Results: Baseline SPM concentration was associated with an increased risk of mortality from all cardiovascular diseases, coronary artery disease, and stroke. The adjusted RRs (95% confidence interval [CI]) per 10 µg/m³ increase in SPM concentration for all cardiovascular mortality were 1.147 (1.014–1.300) for men and 1.097 (0.985–1.222) for women. The point estimate of RR was highest for non-hemorrhagic stroke in men (1.248 [0.991–1.571]), although CI overlapped the unity. The RRs seemed slightly lower in the second half than in the first half, though the CIs widened in the second half.

Conclusion: Our results suggest that long-term exposure to SPM is associated with an increased risk of all cardiovascular mortality for men in Ibaraki, Japan.

Aim: The association between atrial fibrillation (AF) and risk of stroke mortality among men and women without traditional cerebrocardiovascular risk factors (TCVRFs) is unclear. This study aimed to determine whether AF was a risk factor for stroke and total cardiovascular disease mortality among individuals without TCVRFs.

Methods: A total of 90,629 Japanese subjects from the Ibaraki Prefectural Health Study aged 40–79 years, with and without TCVRFs, were studied from 1993 to 2013. Hazard ratios (HRs) were calculated using the Cox proportional hazard regression model stratified by sex and the presence of TCVRFs. Covariates were age, systolic blood pressure, anti-hypertensive medication use, and serum total cholesterol levels. A standard 12-lead electrocardiogram at rest was used to screen AF. Cause-specific mortality was classified according to the International Classification of Disease code.

Results: Compared with participants without AF, multivariable-adjusted hazard ratios (with 95% confidence intervals) for stroke mortality among participants without TCVRFs were 4.3 (1.1–17.8) and 15.0 (5.5–40.8) for men and women with AF, respectively. HRs for total cardiovascular disease mortality were 6.2 (2.8–14.2) for men and 10.7 (4.8–24.1) for women. For participants with TCVRFs, multivariable-adjusted HRs for stroke mortality were 3.1 (2.2–4.6) and 4.3 (2.6–7.3), whereas HRs for total cardiovascular disease mortality were 2.9 (2.2–3.8) and 3.5 (2.4–5.1) for men and women, respectively.

Conclusions: AF was found to be an independent risk factor for stroke and total cardiovascular mortality even in individuals without other TCVRFs.

Aim: Both oxidative stress and inflammation are involved in the pathogenesis of cardiovascular disease (CVD). The serum level of derivatives of reactive oxygen metabolites (d-ROMs) is a measure of the total amount of hydroperoxides serving as a marker of oxidative stress. We investigated whether d-ROMs could predict the clinical outcomes in hemodialysis patients and whether the associations of d-ROMs with the outcomes are independent of a marker of inflammation, C-reactive protein (CRP).

Methods: This was a prospective cohort study in hemodialysis patients. The key exposures were the serum levels of d-ROMs and CRP. The outcome measures were all-cause mortality and new CVD events.

Results: A total of 517 patients were analyzed. d-ROMs correlated positively with CRP. During follow-up for 5 years, 107 patients died, and 190 patients experienced new CVD events. In the Kaplan–Meier analyses, both higher d-ROMs and higher CRP levels predicted higher risks for mortality and CVD events. By Cox proportional-hazard regression analysis adjusted for potential confounders excluding CRP, d-ROMs exhibited a significant association with all-cause mortality, but this association was no longer significant after further adjustment for CRP. Using the same model, CRP exhibited a significant association with all-cause mortality, but this association was no longer significant after further adjustment for d-ROMs. When we analyzed new CVD events as the outcome, CRP was a significant predictor, whereas the level of d-ROMs was not.

Conclusions: Although d-ROMs predicted mortality and CVD events in unadjusted models, the associations of d-ROMs with these outcomes were not independent of CRP. Oxidative stress and inflammation appear to share common causal pathways.

Aim: We previously revealed that Ca^＋＋-activated calmodulin binds to ABCA1 by the region near the PEST sequence and retards its calpain-mediated degradation to increase HDL biogenesis. Calmodulin activity is reportedly modulated also by other nutritional divalent cations; thus, we attempted to determine whether Zn^＋＋ is involved in the regulation of ABCA1 stability through the modulation of calmodulin activity.

Methods: The effects of Zn^＋＋ on ABCA1 expression was investigated in J774 mouse macrophage cell-line cells and HepG2 human hepatoma cell-line cells.

Results: Zn^＋＋ increased ABCA1 expression, not by increasing the mRNA but by attenuating its decay rate, more prominently in the presence of cAMP. Accordingly, it enhanced cell cholesterol release with extracellular apolipoprotein A-I. Calmodulin binding to ABCA1 was increased by Zn^＋＋ and Ca^＋＋. Zn^＋＋ suppressed calpain-mediated hydrolysis of the peptide of ABCA1 cytosolic loop, including the PEST sequence and the calmodulin-binding site, in a calmodulin- dependent fashion, in the presence of the minimum amount of Ca^＋＋ to activate calpain, but not calmodulin. Calpain activity was not directly inhibited by Zn^＋＋ at the concentration for enhancing calmodulin binding to ABCA1.

Conclusion: Nutritional divalent cation Zn^＋＋ is involved in the regulation of ABCA1 activity and biogenesis of HDL through the modulation of calmodulin activity. The results were consistent with previous clinical findings that Zn^＋＋ increased plasma HDL in the conditions of sympathetic activation, such as type 2 diabetes and chronic hemodialysis.

Aim: We examined the effect of modulating the shear stress (SS) profile using forearm warming and cooling on subsequent endothelial function in the brachial artery (BA) during exercise.

Methods: Twelve healthy young subjects immersed their right forearm in water (15 ℃ or 42 ℃) during a leg cycling exercise at 120–130 bpm for 60 min. The same exercise without water immersion served as a control. The BA diameter and blood velocity were simultaneously recorded using Doppler ultrasonography to evaluate the antegrade, retrograde, and mean shear rates (SRs, an estimate of SS) before, during, and after exercise. The endothelial function in the right BA was evaluated using flow-mediated dilation (FMD) (%) using two-dimensional high-resolution ultrasonography before (baseline) and 15 and 60 min after exercise.

Results: During exercise, compared with the control trial, higher antegrade and mean SRs and lower retrograde SRs were observed in the warm trial; conversely, lower antegrade and mean SRs and higher retrograde SRs were observed in the cool trial. At 15 min postexercise, no significant change was observed in the FMD from baseline in the warm (Δ%FMD: +1.6%, tendency to increase; p = 0.08) and control trials (Δ%FMD: +1.1%). However, in the cool trial, the postexercise FMD at 60 min decreased from baseline (Δ%FMD: −2.7%) and was lower than that of the warm (Δ%FMD: +1.5%) and control (Δ%FMD: +1.2%) trials. Accumulated changes in each SR during and after exercise were significantly correlated with postexercise FMD changes.

Conclusion: Modulation of shear profiles in the BA during exercise appears to be associated with subsequent endothelial function.

Aims: The relationship between central arterial stiffness and aging-related intracranial arteriopathy is not well investigated in the general population. In a population-based study, we investigated arterial stiffness in relation to intracranial atherosclerotic stenosis and intracranial arterial dolichoectasia.

Methods: This study was a cross-sectional analysis on 1,123 subjects (aged 56.0±9.3 years, 37.9% men) of the population-based Shunyi study in China. Arterial stiffness was assessed by measuring brachial-ankle pulse wave velocity (baPWV). Intracranial atherosclerotic stenosis and intracranial arterial dolichoectasia were evaluated via brain magnetic resonance angiography. Multivariate regression models were constructed to investigate the association between baPWV and intracranial large artery diseases.

Results: Increased baPWV was significantly associated with higher prevalence of intracranial atherosclerotic stenosis (odds ratio for the highest quartile of baPWV compared with the lowest quartile, 3.66 [95% confidence interval, 1.57– 8.54]), after adjustment for cardiovascular risk factors in multivariate analysis. BaPWV was not associated with the presence of basilar artery dolichoectasia and dilation of basilar artery and internal carotid artery. When the diameters of intracranial arteries were regarded as continuous variables, increased baPWV was inversely related to the internal carotid artery diameter in fully adjusted models (β±SE, −0.083±0.042, p = 0.047).

Conclusions: This population-based study demonstrates that arterial stiffness was more likely associated with intracranial stenotic arteriopathy other than intracranial dilative arteriopathy.

Aim: Deep vein thrombosis (DVT) is a common complication of orthopedic surgery. Multiple lines of evidence indicate that genetic factors play an important role in the development of DVT following orthopedic surgery (DVTFOS). Recent evidence suggested that the solute carrier family 44 member 2 (SLC44A) gene may contribute to the risk of DVT. In this study, we aimed to investigate the associations of SLC44A2 and DVTFOS in Chinese Han individuals.

Methods: In the study, 2,655 subjects, including 689 DVTFOS patients and 1,966 controls, were recruited. Eighteen SNPs were genotyped in the study. Genetic association analyses were performed at both the single marker and haplotype levels. Bioinformatics analyses were conducted to predict the functional consequences of significant SNPs.

Results: SNP rs2288904 of SLC44A2 was identified as being significantly associated with DVTFOS (P = 0.0003, OR [95%CI] = 1.28[1.12–1.46]). Allelic analyses showed that the G allele of this SNP significantly elevated the risks of DVTFOS, which was replicated in the genotypic association analyses. Moreover, a two-SNP haplotype, including rs2288904, was found to be strongly correlated with the risk of DVTFOS (P = 4.15×10^－11). Widespread effects in the expression quantitative trait loci were identified for rs2288904 in multiple tissues.

Conclusion: In summary, our results provide further supportive evidence of the association of SLC44A2 with the risk of DVTFOS, which also provide clues for understanding the important roles of the SLC44A2 gene in the pathogenesis of DVTFOS and in the development of preventive strategies.