Associations of Fecal Microbiota with Ectopic Fat in African Caribbean Men

OBJECTIVE

The gut microbiome has been associated with visceral fat (VAT) in European and Asian populations; however, associations with VAT and with ectopic fats among African-ancestry individuals are not known. Our objective was to investigate cross-sectional associations of fecal microbiota diversity and composition with VAT and ectopic fat, as well as body mass index (BMI), among middle-aged and older African Caribbean men.

METHODS

We included in our analysis n = 193 men (mean age = 62.2 ± 7.6 years; mean BMI = 28.3 ± 4.9 kg/m2) from the Tobago Health Study. We assessed fecal microbiota using V4 16s rRNA gene sequencing. We evaluated multivariable-adjusted associations of microbiota features (alpha diversity, beta diversity, microbiota differential abundance) with BMI and with computed tomography-measured VAT and ectopic fats (pericardial and intermuscular fat; muscle and liver attenuation).

RESULTS

Lower alpha diversity was associated with higher VAT and BMI, and somewhat with higher pericardial and liver fat. VAT, BMI, and pericardial fat each explained similar levels of variance in beta diversity. Gram-negative Prevotellaceae and Negativicutes microbiota showed positive associations, while gram-positive Ruminococcaceae microbiota showed inverse associations, with ectopic fats.

CONCLUSIONS

Fecal microbiota features associated with measures of general adiposity also extend to metabolically pernicious VAT and ectopic fat accumulation in older African-ancestry men.

Discovery of genomic and transcriptomic pleiotropy between kidney function and soluble receptor for advanced glycation end-products using correlated meta-analyses: The Long Life Family Study (LLFS)

Patients with chronic kidney disease (CKD) have increased oxidative stress and chronic inflammation, which may escalate the production of advanced glycation end-products (AGE). High soluble receptor for AGE (sRAGE) and low estimated glomerular filtration rate (eGFR) levels are associated with CKD and aging. We evaluated whether eGFR calculated from creatinine and cystatin C share pleiotropic genetic factors with sRAGE. We employed whole-genome sequencing and correlated meta-analyses on combined genomewide association study (GWAS) p -values in 4,182 individuals (age range: 24-110) from the Long Life Family Study (LLFS). We also conducted transcriptome-wide association studies (TWAS) on whole blood in a subset of 1,209 individuals. We identified 59 pleiotropic GWAS loci ( p <5×10 -8 ) and 17 TWAS genes (Bonferroni- p <2.73×10 -6 ) for eGFR traits and sRAGE. TWAS genes, LSP1 and MIR23AHG , were associated with eGFR and sRAGE located within GWAS loci, lncRNA- KCNQ1OT1 and CACNA1A/CCDC130 , respectively. GWAS variants were eQTLs in the kidney glomeruli and tubules, and GWAS genes predicted kidney carcinoma. TWAS genes harbored eQTLs in the kidney, predicted kidney carcinoma, and connected enhancer-promoter variants with kidney function-related phenotypes at p <5×10 -8 . Additionally, higher allele frequencies of protective variants for eGFR traits were detected in LLFS than in ALFA-Europeans and TOPMed, suggesting better kidney function in healthy-aging LLFS than in general populations. Integrating genomic annotation and transcriptional gene activity revealed the enrichment of genetic elements in kidney function and kidney diseases. The identified pleiotropic loci and gene expressions for eGFR and sRAGE suggest their underlying shared genetic effects and highlight their roles in kidney- and aging-related signaling pathways.

Skeletal muscle adiposity is a novel risk factor for poor cognition in African Caribbean women

OBJECTIVE

Skeletal muscle adiposity (myosteatosis) is recognized as a major risk factor for cardiometabolic diseases, and it increases with aging. The relationship of myosteatosis with cognitive impairment is unknown.

METHODS

The association of calf myosteatosis (measured by computed tomography-derived skeletal muscle density; higher values indicate less myosteatosis) with cognitive function was examined among 626 African Caribbean women who were aged 40 to 84 years, a population highly vulnerable to increased myosteatosis. Cognition was assessed by the Digit Symbol Substitution Test (DSST), a test of information processing speed (higher scores indicate better performance). Linear regression was used to assess the association of muscle density with DSST.

RESULTS

Adjusting for age, education, muscle area, BMI, hypertension, diabetes, cardiovascular event history, lifestyle factors, lipid-lowering medication use, and menopausal status, a one-SD lower muscle density was associated with a 1.69-point lower DSST score (p = 0.002). BMI, diabetes, and hypertension interactions were not statistically significant, suggesting that the main association was not moderated by overall obesity or cardiometabolic diseases.

CONCLUSIONS

These findings suggest that greater myosteatosis is associated with slower information processing speed, an early indicator of cognitive impairment. Further studies are needed to establish this association in this and other populations using an expanded battery of cognitive tests with longitudinal follow-up and to identify the biological mechanisms underlying this relationship.

Exogenous exposures shape genetic predisposition to lipids, Alzheimer's, and coronary heart disease in the MLXIPL gene locus

Associations of single nucleotide polymorphisms (SNPs) of the MLXIPL lipid gene with Alzheimer's (AD) and coronary heart disease (CHD) and potentially causal mediation effects of their risk factors, high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG), were examined in two samples of European ancestry from the US (22,712 individuals 587/2,608 AD/CHD cases) and the UK Biobank (UKB) (232,341 individuals; 809/15,269 AD/CHD cases). Our results suggest that these associations can be regulated by several biological mechanisms and shaped by exogenous exposures. Two patterns of associations (represented by rs17145750 and rs6967028) were identified. Minor alleles of rs17145750 and rs6967028 demonstrated primary (secondary) association with high TG (lower HDL-C) and high HDL-C (lower TG) levels, respectively. The primary association explained ~50% of the secondary one suggesting partly independent mechanisms of TG and HDL-C regulation. The magnitude of the association of rs17145750 with HDL-C was significantly higher in the US vs. UKB sample and likely related to differences in exogenous exposures in the two countries. rs17145750 demonstrated a significant detrimental indirect effect through TG on AD risk in the UKB only (βIE = 0.015, pIE = 1.9 × 10-3), which suggests protective effects of high TG levels against AD, likely shaped by exogenous exposures. Also, rs17145750 demonstrated significant protective indirect effects through TG and HDL-C in the associations with CHD in both samples. In contrast, rs6967028 demonstrated an adverse mediation effect through HDL-C on CHD risk in the US sample only (βIE = 0.019, pIE = 8.6 × 10-4). This trade-off suggests different roles of triglyceride mediated mechanisms in the pathogenesis of AD and CHD.

Abstract 3015: Soluble CD137 and risk of hepatocellular carcinoma: nested case-control studies in cohorts in Shanghai and Singapore

Background: Chronic inflammation plays a significant role in hepatocellular carcinoma (HCC). With rising incidence and poor prognosis of HCC, identifying relatively less invasive biomarkers, especially inflammatory ones, may improve the assessment and stratification of HCC risk. The objective of our studies was to assess if CD8+ T cell cytokines in pre-diagnostic serum are associated with risk of HCC development.

Methods: We conducted two parallel case-control studies of HCC nested within the Shanghai Cohort Study (SCS) and the Singapore Chinese Health Study (SCHS), two prospective cohorts of 81,000 individuals with 25+ years of follow-up. The serum concentrations of five CD8+ T cell cytokines ─ soluble CD137 (sCD137), soluble Fas (sFas), perforin, macrophage inflammatory protein 1-beta (MIP-1β), and tumor necrosis factor alpha (TNF-α) ─ were determined using Luminex bead-based immunoassay on 315 HCC cases and 315 individually matched controls in the SCS, and on 197 HCC case-control pairs in the SCHS. Conditional logistic regression was used to estimate odds ratio (OR) and 95% confidence interval (CI) for HCC with elevated levels of cytokines with adjustment for body mass index, alcohol drinking, cigarette smoking, seropositivity of hepatitis surface antigen (HBsAg), and history of diabetes.

Results: sCD137 levels were statistically significantly higher in HCC cases than controls in both cohorts. Compared with the 1st quartile (Q1) of sCD137, multivariable-adjusted ORs (95% CI) of HCC for the 4th quartile (Q4) were 3.8 (1.7-8.3) in the SCS and 3.5 (1.4 -8.5) in the SCHS (both Ptrend’s &lt; 0.001). Among HBsAg-negative individuals, ORs (95% CIs) for Q2, Q3, & Q4 of sCD137 were 2.7 (1.5-4.9), 2.7 (1.4-5.0), and 4.5 (2.4-8.5), respectively, compared with Q1 (Ptrend &lt; 0.001) in both SCS and SCHS combined. The corresponding ORs (95% CIs) among HBsAg- positive individuals were 21.0 (9.3-47.6), 34.1 (13.8-84.2), and 56.7 (23.3-137.9), respectively, with a P=0.095 for multiplicative interaction. The sCD137-HCC risk association remained constant over different time periods from blood draw to HCC diagnosis: ORs (95% CIs) for Q4 vs. Q1 were 4.7 (1.2-17.5) for &lt;5 years, 3.7 (1.3-10.6) for 5-10 years, and 3.94 (1.6-9.5) for more than 10 years between blood collection and cancer diagnosis. sFas was positively associated with HCC risk in the SCHS but not in the SCS. There was no statistically significant association for perforin, MIP-1β, or TNF-α with HCC risk in either cohort.

Conclusion: These novel and validated findings demonstrated that serum sCD137 levels were significantly elevated many years prior to HCC diagnosis, and had a potential synergistic effect with chronic viral infection on the HCC risk. sCD137 may be developed as a immune monitoring biomarker for risk stratification and assessment, which can lead to early diagnosis and improve prognosis of HCC patients.

Citation Format: Claire E. Thomas, Jennifer J. Adibi, Allison L. Kuipers, Brenda Diergaarde, Hung N. Luu, Aizhen Jin, Woon-Puay Koh, Yu-Tang Gao, Jennifer Adams-Haduch, Renwei Wang, Anna Lokshin, Jaideep Behari, Jian-Min Yuan. Soluble CD137 and risk of hepatocellular carcinoma: nested case-control studies in cohorts in Shanghai and Singapore [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3015.

Soluble CD137 and risk of hepatocellular carcinoma: nested case-control studies in cohorts in Shanghai and Singapore

BACKGROUND

The majority of hepatocellular carcinoma (HCC) cases occur in the presence of cirrhosis. Biomarkers of cirrhosis-associated immune dysfunction such as CD8+ T cell cytokines could aid HCC risk assessment.

METHODS

CD8+ T cell cytokines were determined in pre-diagnostic serum in two studies including 315 HCC case-control pairs in the Shanghai Cohort Study (SCS) and 197 pairs in the Singapore Chinese Health Study (SCHS). Conditional logistic regression was used to estimate odds ratio (OR) and 95% confidence interval (CI) for HCC with levels of five cytokines-soluble CD137 (sCD137), soluble Fas (sFas), perforin, macrophage inflammatory protein 1-beta (MIP-1β), and tumour necrosis factor alpha (TNF-α).

RESULTS

sCD137 levels were significantly higher in HCC cases than controls in both cohorts (Ps < 0.001). Compared with the lowest quartile, multivariable-adjusted ORs (95% CI) of HCC for the highest sCD137 quartile were 3.79 (1.73, 8.30) in the SCS and 3.49 (1.44, 8.48) in the SCHS. The sCD137-HCC association was independent of hepatitis B seropositivity and follow-up time. No other cytokine was consistently associated with HCC risk.

CONCLUSION

sCD137 was associated with higher risk of HCC in two studies nested in general population cohorts. sCD137 may be a long-term risk marker of HCC development.

Abstract P561: Reallocation of Sedentary Time With Light Physical Activity is Associated With Higher Sleep Efficiency in African Caribbeans

Introduction: Sleep efficiency (or sleep continuity, i.e., a ratio of time spent sleeping to time spent in bed), is inversely associated with hypertension, impaired glucose metabolism, CVD risk, and mortality risk. Prolonged sedentary behavior and physical activity are independently associated with sleep efficiency. However, it is not well documented how substituting time in sedentary behavior with physical activity affects sleep efficiency, especially among African-ancestry populations, who are at high risk for CVD.

Aim: To determine if displacement of sedentary time with activity was cross-sectionally associated with higher sleep efficiency among African Caribbean men (n=231) and women (n=668) from the Tobago Health Study.

Methods: Sleep efficiency, sedentary behavior (SB), light physical activity (LPA), and moderate to vigorous physical activity (MVPA) were collected using a SenseWear Pro Armband. Participants wore the armband at all times, except in water, for 4-7 days. We used the Isotemporal Substitution Framework paired with linear regression to examine associations of SB, LPA and MVPA with sleep efficiency adjusting for age, education, BMI, hypertension, diabetes, smoking, alcohol consumption, caffeine intake, and sleep medication.

Results: Men (mean age ± Standard deviation: 63.2 ± 8.2 years; mean BMI 28.2 ± 4.8 kg/m 2 ) spent on average less time in SB (12.4 ± 2.9 hours/day) and more time in LPA (4.7 ± 2.1 hours /day) and MVPA (0.92 ± 0.88 hours/day) than women (mean age 55.6 ± 8.7 years; mean BMI 31.8 ± 6.4 kg/m 2 ) (all p-vales <0.001). Men had lower sleep efficiency (74.6% ± 10.4) than women (81.2% ± 0.96; p-value <0.001). Cross-sectionally reallocating 1 hour of SB with LPA was associated with a 1% higher sleep efficiency (p-value=0.016) in men and with a 0.37% higher sleep efficiency in women (p-value=0.074). In men, reallocating 1 hour of SB with MVPA and 1 hour of LPA with MVPA were significantly associated with lower sleep efficiency [-1.9% (p-value=0.014) and -2.8% (p-value=0.017), respectively]; in women these associations were not statistically significant. Interaction term for sex and sleep efficiency was statistically significant (p-value <0.0001).

Conclusions: In this population with short sleep duration, reallocating 1 hour of SB with LPA was associated with higher sleep efficiency in both genders. In contrast, among men only, reallocating 1 hour of SB to MVPA and 1 hour of LPA to MVPA were unexpectedly associated with lower sleep efficiency. Further research is warranted to understand these relationships longitudinally to determine how truly replacing SB for activities of different intensities impacts sleep health, which could then potentially inform lifestyle guidelines in older Caribbeans. In this highly sedentary population, interventions aimed at increasing LPA may be easier to implement and maintain and provide greater sleep and overall health benefit.

Abstract P664: Proteomic Profiling of African-Ancestry Adults Identifies Potential Novel Biomarkers of Vascular Aging

During the aging process, the vasculature undergoes pathologic changes which are strongly associated with hypertension and future cardiovascular disease (CVD) risk. Previous work to identify protein biomarkers of these subclinical vascular changes, which have largely focused on single proteins, has observed many associations in different populations. However, research in African-ancestry populations, who are at high risk for hypertensive CVD, is limited and may be biased by the existing research in Whites. Therefore, we used a proteomic approach to identify biomarkers of vascular aging as assessed by pulse-wave velocity (PWV) and abdominal aortic calcification (AAC). We included 346 African-ancestry men from the Tobago Health Study, a prospective cohort study of community-dwelling men aged ≥40 years residing on the Caribbean island of Tobago. These men were aged from 53-89 years old (mean ± SD = 63.4 ± 8.1 years) and were overweight on average (mean ± SD BMI = 27.7 ± 4.3kg/m2). 79.2% of men had hypertension, 24.6% had diabetes, and 5.9% were current smokers. We quantified protein expression using the Olink® Target 96 Cardiovascular III proteomics panel which includes 92 proteins with known association to human cardiovascular processes (CVDIII; Olink®, Waltham, MA). Brachial-ankle PWV (cm/s) was measured using an automated waveform analyzer. AAC was measured in the aorta at the iliac bifurcation via CT and scored using the Agatston method. Partial Spearman correlations were calculated to assess the relationship between each protein biomarker and both vascular aging outcomes adjusting for age, Olink® assay batch, height, weight, diabetes status, hypertension status, and current smoking. There were 13 and 5 proteins correlated with PWV and AAC, respectively (at P<0.05). All correlations were in the direct direction of effect. Only one protein, cystatin B, was correlated with both PWV and AAC (r= 0.17 and 0.12, P=0.002 and 0.03; respectively). After applying false discovery rate adjustment for multiple comparisons, only fatty acid binding protein 4 (FABP4) and PWV remained significant (r=0.18, P=0.046). In general, proteins categorized by Olink® as belonging to the inflammatory pathway were most likely to be correlated with PWV; whereas, those in the hormone response pathway were most frequently correlated with AAC. Our results highlight that FABP4, a protein related to atherosclerosis via inflammation, may also be an important marker of arterial stiffening in these African-ancestry men. Additionally, we identified cystatin B, a member of the cathepsin protease pathway, as a strong correlate of both PWV and AAC, which may warrant further research into it as a novel biomarker of vascular aging and CVD in this high-risk population. In conclusion, proteomics may be an effective tool for evaluating and identifying novel markers of vascular aging and CVD in underrepresented populations.

Association of leukocyte telomere length with perceived physical fatigability

BACKGROUND

Leukocyte telomere length (LTL) is a potential genomic marker of biological aging, but its relation to fatigability, a prognostic indicator of phenotypic aging (e.g., functional decline) is unknown. We hypothesized shorter LTL would predict greater perceived physical fatigability, but that this association would be attenuated by adjusting for chronological age.

METHODS

Two generations of participants (N = 1997; 309 probands, 1688 offspring) were from the Long Life Family Study (age = 73.7 ± 10.4, range 60-108, 54.4 % women), a longitudinal cohort study of aging. LTL was assayed at baseline. Perceived physical fatigability was measured 8.0 ± 1.1 years later using the validated, self-administered 10-item Pittsburgh Fatigability Scale (PFS, 0-50, higher scores = greater fatigability). Generalized estimating equations were generated to model the association between LTL and PFS Physical scores.

RESULTS

Prevalence of greater physical fatigability (PFS scores≥15) was 41.9 %. Using generalized estimating equations, a one kilobase pair shorter LTL was associated with higher PFS Physical scores (β = 1.8, p < .0001), accounting for family structure, and adjusting for field center, follow-up time, sex, and follow-up body mass index, physical activity, and chronic health conditions. When age was included as a covariate, the association was fully attenuated (β = 0.1, p = .78).

CONCLUSION

LTL may provide an alternative method for estimating an individual's lifetime exposure to chronic stressors, but does not appear to provide additional information not captured by chronological age. Further research is needed to characterize the interaction between age, LTL, and perceived fatigability, and develop a method of identifying individuals at risk for deleterious aging.

Replacing sedentary time with light activity was associated with less adiposity across several depots in African ancestry men

OBJECTIVE

The aim of this study was to determine whether displacement of sedentary time with activity was cross-sectionally associated with less adiposity among Black Caribbean men in the Tobago Health Study.

METHODS

Objectively assessed activity was categorized as sedentary (< 1.5 metabolic equivalents; METs), light (≥ 1.5 to < 3.0 METs), or moderate-to-vigorous (≥ 3.0 METs) using the SenseWear Pro armband. Computed tomography scans of the chest, abdomen, liver, and thigh were used to assess subcutaneous and ectopic adipose tissue. The isotemporal substitution framework paired with linear regression was used to examine associations between activity and adiposity adjusting for age, height, total awake time, and multiple comparisons.

RESULTS

On average, participants (n = 271) were 63 years old with 11.2 h/d of sedentary behavior, 4.5 h/d of light activity, and 54 min/d of moderate-to-vigorous activity. Replacing sedentary time with light activity was cross-sectionally associated with lower volume and higher density of abdominal and thigh subcutaneous adiposity, visceral adiposity, abdominal and thigh intermuscular adiposity, and pericardial adiposity and higher liver attenuation (p values ≤ 0.0001).

CONCLUSIONS

Displacement of sedentary time with light activity was associated with less adiposity among this Black Caribbean cohort. Interventions focused on increasing light activity may be easier to maintain than higher intensity interventions and thus may be more successful at reducing adiposity.

Physical resilience after a diagnosis of cardiovascular disease among offspring of long-lived siblings

Health benefits of longevity-enriched families transmit across generations and a lower incidence of cardiovascular diseases (CVD) have been shown to contribute to this phenomenon. In the current study, we investigated whether the offspring of long-lived siblings also have better survival after a CVD diagnosis compared to matched controls, i.e., are they both robust and resilient? Offspring of long-lived siblings were identified from three nationwide Danish studies and linked to national registers. Offspring with first diagnosis of acute myocardial infarction, chronic ischemic heart disease, heart failure or cerebrovascular disease between 1996 and 2011 were included and matched with two controls from the Danish population on sex, year of birth and diagnosis, and type of CVD. Stratified Cox proportional-hazards models on the matching data were performed to study 10-year overall survival. A total of 402 offspring and 804 controls were included: 64.2% male with a median age at diagnosis of 63.0. For offspring and controls, overall survival was 73% and 65% at 10 years from diagnosis, respectively. Offspring of long-lived siblings had a significantly better survival than controls, and this association was slightly attenuated after controlling for marital status, medication and Charlson Comorbidity Index score simultaneously. This study suggested that offspring of long-lived siblings not only show lower CVD incidence but also a better survival following CVD diagnosis compared to matched population controls. The higher biological resilience appears to be a universal hallmark of longevity-enriched families, which makes them uniquely positioned for studying healthy aging and longevity mechanisms.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10433-021-00641-7.

Abstract 2260: Non-alcoholic fatty liver disease polygenic risk score and risk of hepatocellular carcinoma in an East Asian population

Purpose: It is difficult to identify people with non-alcoholic fatty liver disease (NAFLD) who are at high risk for the development of hepatocellular carcinoma (HCC). A polygenic risk score (PRS) for hepatic fat derived from non-Asians has been reported to be associated with HCC risk in European populations. However, population level data of this risk in non-European populations are lacking.

Methods: Utilizing resources from the Singapore Chinese Health Study (SCHS), we examined the relationship between the previously published hepatic fat PRS (HFC-PRS) and HCC risk. We also constructed and evaluated a NAFLD-related PRS (NAFLD-PRS); the final version included SNPs in similar gene regions as the HFC-PRS but weighted by effect estimates for NAFLD among those with East Asian ancestry. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) of HCC incidence with both HFC-PRS and NAFLD-PRS.

Results: The HFC-PRS and NAFLD-PRS were highly correlated (Spearman r = 0.79, P &lt; 0.001). The highest quartiles of both the HFC-PRS and the NAFLD-PRS were associated with significantly increased risk of HCC with HR of 2.39 (95% CI 1.51, 3.78) and 1.77 (95% CI 1.15, 2.73), respectively, compared to their respective lowest quartile.

Conclusion: The HFC-PRS and the NAFLD-PRS may both be useful in stratifying Asian populations according to their risk of HCC. In addition, the association between the NAFLD-PRS, derived from East Asians, and HCC risk suggests a potential causal role for NAFLD in the development of HCC in this population.

Citation Format: Claire E. Thomas, Brenda Diergaarde, Allison L. Kuipers, Jennifer J. Adibi, Hung N. Luu, Xuling Chang, Rajkumar Dorajoo, Chew-Kiat Heng, Chiea-Chuen Khor, Renwei Wang, Aizhen Jin, Woon-Puay Koh, Jian-Min Yuan. Non-alcoholic fatty liver disease polygenic risk score and risk of hepatocellular carcinoma in an East Asian population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2260.

NAFLD polygenic risk score and risk of hepatocellular carcinoma in an East Asian population

It is difficult to identify people with nonalcoholic fatty liver disease (NAFLD) who are at high risk for developing hepatocellular carcinoma (HCC). A polygenic risk score (PRS) for hepatic fat (HFC-PRS) derived from non-Asians has been reported to be associated with HCC risk in European populations. However, population-level data of this risk in Asian populations are lacking. Utilizing resources from 24,333 participants of the Singapore Chinese Health Study (SCHS), we examined the relationship between the HFC-PRS and HCC risk. In addition, we constructed and evaluated a NAFLD-related PRS (NAFLD-PRS) with HCC risk in the SCHS. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of HCC incidence with both HFC-PRS and NAFLD-PRS. The HFC-PRS and NAFLD-PRS were highly correlated (Spearman r = 0.79, p < 0.001). The highest quartiles of both the HFC-PRS and the NAFLD-PRS were associated with significantly increased risk of HCC with HR of 2.39 (95% CI 1.51, 3.78) and 1.77 (95% CI 1.15, 2.73), respectively, compared with their respective lowest quartile. Conclusion: The PRS for hepatic fat content or NAFLD may be useful for assessing HCC risk in both Asian and European populations. The findings of this and prior studies support a potential causal role of genetically determined NAFLD in HCC development.

Aortic Area as an Indicator of Subclinical Cardiovascular Disease

Aim:

Outward arterial remodeling occurs early in cardiovascular disease (CVD) and, as such, measuring arterial dimension may be an early indicator of subclinical disease.

Objective:

The objective of our study was to measure area at three aortic locations: The ascending thoracic (ASC), the descending thoracic (DSC), and the abdominal (ABD), and to test for association with traditional CVD risk factors and subclinical CVD throughout the body.

Methods:

We measured ASC, DSC, and ABD using computed tomography (CT) in 408 African ancestry men aged 50-89 years. We assessed prevalent CVD risk factors via participant interview and clinical exam, and subclinical CVD, including carotid atherosclerosis through B-mode carotid ultrasound, vascular calcification via chest and abdominal CT, and arterial stiffness via pulse-wave velocity (PWV).

Results:

As expected, all aortic areas were in correlation with each other (r=0.39-0.63, all p<0.0001) and associated with greater age, greater body size, and hypertension (p≤0.01 for all). After adjustment for traditional CVD risk factors, ASC was positively associated with carotid atherosclerosis (p<0.01). A greater area at each location was associated with greater PWV (p<0.03 for all), with the DSC region showing the most significant association.

Conclusion:

This is the first study to test the association of aortic area measured at multiple points with subclinical CVD. We found that combined CT assessment of ascending and descending aortic area may indicate a high risk of prevalent subclinical CVD elsewhere in the body independent of age, body size, and blood pressure.

Relative associations of abdominal and thigh compositions with cardiometabolic diseases in African Caribbean men

BACKGROUND

Regional body compositions are differentially associated with cardiometabolic risk factors. Simultaneous inclusion of both upper and lower body composition predictors in models is not often done, and studies which do include both measures (1) tend to exclude some tissue(s) of potential metabolic relevance, and (2) have used study populations with underrepresentation of individuals with African ancestries. Further, most body composition analyses do not employ compositional data analytic approaches, which may result in spurious associations.

OBJECTIVE

The objective of this analysis was to assess associations of abdominal and thigh adipose (AT) and muscle tissues with hypertension and type 2 diabetes using compositional data analytic methods.

RESEARCH DESIGN AND METHODS

This cross-sectional analysis included 610 African Caribbean men (median age: 62 years; mean BMI: 27.8 kg/m2). Abdominal (three components: subcutaneous [ASAT] and visceral [VAT] AT, 'other' abdominal tissue) and mid-thigh (four components: subcutaneous and intermuscular AT, muscle, bone) compositions were measured by computed tomography; additive log ratio transformations were applied to each composition. Regression models were used to simultaneously assess associations of abdominal and thigh component ratios with continuous risk factors (blood pressures, fasting glucose and insulin, HOMA-IR) and disease categories.

RESULTS

A two-fold increase in ASAT:'Other' ratio was associated with higher continuous risk factors and with odds of being in a higher hypertension (OR: 1.77, 95%CI: 1.10-2.84) or diabetes (OR: 1.81, 95%CI: 1.06-3.10) category. A two-fold increased VAT ratio was only associated with higher log-insulin and log-HOMA-IR (β = 0.10, p < 0.05 for both), while a two-fold increased thigh muscle:bone ratio was associated with a lower diabetes category (OR: 0.37, 95%CI: 0.14-1.01).

CONCLUSIONS

These findings support ASAT as a significant driver of cardiometabolic disease in African Ancestry populations, independent of other abdominal and thigh tissues.

Pleiotropic effects between cardiovascular disease risk factors and measures of cognitive and physical function in long-lived adults

Cardiovacular disease (CVD) is the leading cause of death among older adults and is often accompanied by functional decline. It is unclear what is driving this co-occurrence, but it may be behavioral, environmental and/or genetic. We used a family-based study to estimate the phenotypic and shared genetic correlation between CVD risk factors and physical and cognitive functional measures. Participants (n = 1,881) were from the Long Life Family Study, which enrolled families based on their exceptional longevity (sample mean age = 69.4 years, 44% female). Cardiovascular disease risk factors included carotid vessel measures [intima-media thickness and inter-adventitial diameter], obesity [body mass index (BMI) and waist circumference], and hypertension [systolic and diastolic blood pressures]. Function was measured in the physical [gait speed, grip strength, chair stand] and cognitive [digital symbol substitution test, retained and working memory, semantic fluency, and trail making tests] domains. We used SOLAR to estimate the genetic, environmental, and phenotypic correlation between each pair adjusting for age, age², sex, field center, smoking, height, and weight. There were significant phenotypic correlations (range |0.05–0.22|) between CVD risk factors and physical and cognitive function (all P < 0.05). Most significant genetic correlations (range |0.21–0.62|) were between CVD risk factorsand cognitive function, although BMI and waist circumference had significant genetic correlation with gait speed and chair stand time (range |0.29–0.53|; all P < 0.05). These results suggest that CVD risk factors may share a common genetic-and thus, biologic-basis with both cognitive and physical function. This is particularly informative for research into the genetic determinants of chronic disease.

Association of physical activity with blood pressure in African ancestry men

This study tested the association of objectively measured physical activity with blood pressure and hypertension in African Caribbean men, an understudied population segment known to be at high-risk for cardiovascular disease (CVD) which has low levels of high-exertion physical activity. Men (N = 310) were from the Tobago Health Study and aged 50–89 years. Systolic (SBP) and diastolic (DBP) blood pressures were measured using an automated device, and hypertension was defined as SBP ≥ 140 mmHg, DBP ≥ 90 mmHg, or current use of antihypertensive medication. Physical activity was measured using the SenseWear Pro armband (SWA) and consisted of daily time engaged in sedentary behavior (SB), light physical activity (LPA), and moderate to vigorous activity (MVPA), as well as daily step count. Multiple regression analyses using the isotemporal substitution framework were used to test for associations between activity and blood pressures. Models were adjusted in stages for SWA wear time, age, antihypertensive medication use, alcohol consumption, smoking, diabetes, CVD, family history of hypertension, salt intake, and adiposity.

Replacement of SB with LPA was associated with lower SBP adjusted for wear time (β = -0.84, p < 0.05), but attenuated after adjustment for age. Replacement of SB with LPA was associated with lower DBP (β = -0.50) and lower odds of hypertension (OR = 0.88), adjusted for wear time and age (both p < 0.05). All model associations of replacement of SB with LPA were stronger when restricted to men not taking antihypertensive medications, regardless of their hypertension status.

These results support the strategy of increasing light physical activity for blood pressure management in high-risk Afro-Caribbean men.

Heterogeneity of the Predictive Polygenic Risk Scores for Coronary Heart Disease Age-at-Onset in Three Different Coronary Heart Disease Family-Based Ascertainments

BACKGROUND

Polygenic risk scores (PRS) for coronary heart disease (CHD) may contribute to assess the overall risk of CHD. We evaluated how PRS may influence CHD risk when the distribution of age-at-onset, sex, and family health history differ significantly.

METHODS

Our study included 3 family-based ascertainments: LLFS (Long Life Family Study, N_Individuals=4572), which represents a low CHD risk, and Family Heart Study, which consists of randomly selected families (FamHS-random, N_Individuals=1806), and high CHD risk families (FamHS-high risk, N_Individuals=2301). We examined the effects of PRS, sex, family ascertainment, PRS interaction with sex (PRS*sex) and with family ascertainment (PRS*LLFS and PRS*FamHS-high risk) on CHD, corrected for traditional cardiovascular risk factors using Cox proportional hazard regression models.

RESULTS

Healthy-aging LLFS presented ≈17 years delayed for CHD age-at-onset compared with FamHS-high risk (P<1.0×10^-4). Sex-specific association (P<1.0×10^-17) and PRS*sex (P=2.7×10^-3) predicted prevalent CHD. CHD age-at-onset was associated with PRS (hazard ratio [HR], 1.57; P=1.3×10^-5), LLFS (HR, 0.54; P=2.6×10^-5), and FamHS-high risk (HR, 2.86; P=6.70x10^-15) in men, and with PRS (HR, 1.76; P=7.70×10^-3), FamHS-high risk (HR, 4.88; P=8.70×10^-10), and PRS×FamHS-high risk (HR, 0.61; P=3.60×10^-2) in women. In the PRS extreme quartile distributions, CHD age-at-onset was associated (P<0.05) with PRS, FamHS-high risk, and PRS interactions with both low and high CHD risk families for women. For men, the PRS quartile results remained similar to the whole distribution.

CONCLUSIONS

Differences in CHD family-based ascertainments show evidence of PRS interacting with sex to predict CHD risk. In women, CHD age-at-onset was associated with PRS, CHD family history, and interactions of PRS with family history. In men, PRS and CHD family history were the major effects on the CHD age-at-onset. Understanding the heterogeneity of risks associated with CHD end points at both the personal and familial levels may shed light on the underlying genetic effects influencing CHD and lead to more personalized risk prediction.

Genetic association analysis of the cardiovascular biomarker: N-terminal fragment of pro-B-type natriuretic peptide (NT-proBNP)

BACKGROUND

NT-proBNP is a biomarker of cardiovascular disease (CVD). Little is known about the heritability and genetic variants associated with NT-proBNP. Therefore, we estimated the heritability of and examined genetic associations of SNPs in the BNP gene region with circulating NT-proBNP and prevalent CVD in 4,331 participants from the Long Life Family Study (LLFS).

METHODS AND RESULTS

Genotypes of 10 SNPs from the NPPB and NPPA regions that encode BNP and A-type natriuretic peptide, respectively, were tested for association with NT-proBNP and prevalent cardiovascular disease and risk factors. We performed analyses using the Sequential Oligogenic Linkage Analysis (SOLAR) program to account for family relatedness, and adjusted all models for age, sex, and field center. The mean age of the LLFS was 69.8 years (range 24-110) with 55.4% females. NT-proBNP was significantly heritable (h2 = 0.21; P = 4x10-14), and the minor alleles of rs632793 (p<0.001) and rs41300100 (p = 0.05) were independently associated with higher serum NT-proBNP levels. Additionally, the minor allele of rs632793 was significantly and consistently associated with lower prevalent CVD, including blood pressures, independent of NT-proBNP level (all P<0.05). Results for prevalent CVD, but not NT-proBNP levels, showed significant interaction by familial generation.

CONCLUSION

In this family-based study of subjects with exceptional longevity, we identified several allelic variants in the BNP gene region associated with NT-pro-BNP levels and prevalent CVD.

A Meta-Analysis of the Transferability of Bone Mineral Density Genetic Loci Associations From European to African Ancestry Populations

Genetic studies of bone mineral density (BMD) largely have been conducted in European populations. We therefore conducted a meta-analysis of six independent African ancestry cohorts to determine whether previously reported BMD loci identified in European populations were transferable to African ancestry populations. We included nearly 5000 individuals with both genetic data and assessments of BMD. Genotype imputation was conducted using the 1000G reference panel. We assessed single-nucleotide polymorphism (SNP) associations with femoral neck and lumbar spine BMD in each cohort separately, then combined results in fixed effects (or random effects if study heterogeneity was high, I2 index >60) inverse variance weighted meta-analyses. In secondary analyses, we conducted locus-based analyses of rare variants using SKAT-O. Mean age ranged from 12 to 68 years. One cohort included only men and another cohort included only women; the proportion of women in the other four cohorts ranged from 52% to 63%. Of 56 BMD loci tested, one locus, 6q25 (C6orf97, p = 8.87 × 10-4 ), was associated with lumbar spine BMD and two loci, 7q21 (SLC25A13, p = 2.84 × 10-4 ) and 7q31 (WNT16, p = 2.96 × 10-5 ), were associated with femoral neck BMD. Effects were in the same direction as previously reported in European ancestry studies and met a Bonferroni-adjusted p value threshold, the criteria for transferability to African ancestry populations. We also found associations that met locus-specific Bonferroni-adjusted p value thresholds in 11q13 (LRP5, p < 2.23 × 10-4 ), 11q14 (DCDC5, p < 5.35 × 10-5 ), and 17p13 (SMG6, p < 6.78 × 10-5 ) that were not tagged by European ancestry index SNPs. Rare single-nucleotide variants in AKAP11 (p = 2.32 × 10-2 ), MBL2 (p = 4.09 × 10-2 ), MEPE (p = 3.15 × 10-2 ), SLC25A13 (p = 3.03 × 10-2 ), STARD3NL (p = 3.35 × 10-2 ), and TNFRSF11A (p = 3.18 × 10-3 ) were also associated with BMD. The majority of known BMD loci were not transferable. Larger genetic studies of BMD in African ancestry populations will be needed to overcome limitations in statistical power and to identify both other loci that are transferable across populations and novel population-specific variants. © 2020 American Society for Bone and Mineral Research (ASBMR).

Relationship Between Serum IGF-1 and BMI Differs by Age

BACKGROUND

Serum levels of insulin-like growth factor 1 (IGF-1) and body mass index (BMI) are both associated with susceptibility to age-related diseases. Reports on the correlation between them have been conflicting, with both positive to negative correlations reported. However, the age ranges of the participants varied widely among these studies.

METHODS

Using data on 4241 participants (aged 24-110) from the Long Life Family Study, we investigated the relationship between IGF-1 and BMI by age groups using regression analysis.

RESULTS

When stratified by age quartile, the relationship between IGF-1 and BMI varied: in the first quartile (Q1, 20-58 years) the relationship was negative (β = -0.2, p = .002); in Q2 (58-66 years) and Q3 (67-86 years) the relationship was negative (β = -0.07, β = -0.01, respectively) but nonsignificant; and in Q4 (87-110 years) the relationship was positive (β = 0.31, p = .0002). This pattern did not differ by sex. We observed a similar age-related pattern between IGF-1 and BMI among participants in the third National Health and Nutritional Examination Survey.

CONCLUSIONS

Our results that the relationship between IGF-1 and BMI differs by age may explain some of the inconsistency in reports about their relationship and encourage additional studies to understand the mechanisms underlying it.

Epidemiology of Perceived Physical Fatigability in Older Adults: The Long Life Family Study

BACKGROUND

Fatigability is a construct that measures whole-body tiredness anchored to activities of a fixed intensity and duration; little is known about its epidemiology and heritability.

METHODS

Two generations of family members enriched for exceptional longevity and their spouses were enrolled (2006-2009) in the Long Life Family Study (LLFS). At Visit 2 (2014-2017, N = 2,355) perceived physical fatigability was measured using the 10-item self-administered Pittsburgh Fatigability Scale (PFS), along with demographic, medical, behavioral, physical, and cognitive risk factors.

RESULTS

Residual genetic heritability of fatigability was 0.263 (p = 6.6 × 10-9) after adjustment for age, sex, and field center. PFS physical scores (mean ± SD) and higher physical fatigability prevalence (% PFS ≥ 15) were greater with each age strata: 60-69 (n = 1,009, 11.0 ± 7.6, 28%), 70-79 (n = 847, 12.5 ± 8.1, 37%), 80-89 (n = 253, 19.3 ± 9.9, 65.2%), and 90-108 (n = 266, 28.6 ± 9.8, 89.5%), p < .0001, adjusted for sex, field center, and family relatedness. Women had a higher prevalence of perceived physical fatigability compared to men, with the largest difference in the 80-89 age strata, 74.8% versus 53.5%, p < .0001. Those with greater body mass index, worse physical and cognitive function, and lower physical activity had significantly higher perceived physical fatigability.

CONCLUSIONS

Perceived physical fatigability is highly prevalent in older adults and strongly associated with age. The family design of LLFS allowed us to estimate the genetic heritability of perceived physical fatigability. Identifying risk factors associated with higher perceived physical fatigability can inform the development of targeted interventions for those most at risk, including older women, older adults with depression, and those who are less physically active.

Hepatic and Skeletal Muscle Adiposity Are Associated with Diabetes Independent of Visceral Adiposity in Nonobese African-Caribbean Men

Background: Adipose tissue (AT) around and within non-AT organs (i.e., ectopic adiposity) is emerging as a strong risk factor for type 2 diabetes (T2D). Not known is whether major ectopic adiposity depots, such as hepatic, skeletal muscle, and pericardial adiposity (PAT), are associated with T2D independent of visceral adiposity (VAT). More data are particularly needed among high-risk nonobese minority populations, as the race/ethnic gap in T2D risk is greatest among nonobese. Methods: Thus, we measured several ectopic adiposity depots by computed tomography in 718 (mean age = 64 years) African-Caribbean men on the Island of Tobago overall, and stratified by obesity (obese N = 187 and nonobese N = 532). Results: In age, lifestyle risk factors, health status, lipid-lowering medication intake, body mass index and all other adiposity-adjusted regression analyses, and hepatic and skeletal muscle adiposity were associated with T2D among nonobese men only (all P < 0.05), despite no association between VAT and PAT and T2D. Conclusions: Our results support the "ectopic fat syndrome" theory in the pathogenesis of T2D among nonobese African-Caribbean men. Longitudinal studies are needed to clarify the independent role of ectopic adiposity in T2D, and to identify possible biological mechanisms underlying this relationship, particularly in high-risk African ancestry and other nonwhite populations.

Associations of Thigh and Abdominal Adipose Tissue Radiodensity with Glucose and Insulin in Nondiabetic African-Ancestry Men

OBJECTIVE

Decreased radiodensity of adipose tissue (AT) located in the visceral AT (VAT), subcutaneous AT (SAT), and intermuscular AT (IMAT) abdominal depots is associated with hyperglycemia, hyperinsulinemia, and insulin resistance independent of AT volumes. These associations were sought in African-ancestry men, who have higher risk for type 2 diabetes and have been underrepresented in previous studies.

METHODS

This cross-sectional analysis included 505 nondiabetic men of African-Caribbean ancestry (median age: 61 years; median BMI: 26.8 kg/m² ) from the Tobago Health Study. AT volumes and radiodensities were assessed using computed tomography, including abdominal (VAT and SAT) and thigh (IMAT) depots. Associations between AT radiodensities were assessed with fasting serum glucose and insulin and with insulin resistance (updated homeostatic model assessment of insulin resistance, HOMA2-IR).

RESULTS

Higher radiodensity in any AT depot was associated with lower log-insulin and log-HOMA2-IR (β range: -0.16 to -0.18 for each; all P < 0.0001). No AT radiodensity was associated with glucose. Thigh IMAT radiodensity associations were independent of, and similar in magnitude to, VAT radiodensities. Model fit statistics suggested that AT radiodensities were a better predictor for insulin and insulin resistance compared with AT volumes in individuals with overweight and obesity.

CONCLUSIONS

AT radiodensities at multiple depots are significantly associated with insulin and insulin resistance in African-ancestry men.

Wnt Pathway Gene Expression Is Associated With Arterial Stiffness

Background

Animal and in vitro experiments implicate the Wnt pathway in cardiac development, fibrosis, vascular calcification, and atherosclerosis, but research in humans is lacking. We examined peripheral blood Wnt pathway gene expression and arterial stiffness in 369 healthy African ancestry men (mean age, 64 years).

Methods and Results

Gene expression was assessed using a custom Nanostring nCounter gene expression panel (N=43 genes) and normalized to housekeeping genes and background signal. Arterial stiffness was assessed via brachial‐ankle pulse‐wave velocity. Fourteen Wnt genes showed detectable expression and were tested individually as predictors of pulse‐wave velocity using linear regression, adjusting for age, height, weight, blood pressure, medication use, resting heart rate, current smoking, alcohol intake, and sedentary lifestyle. Adenomatous polyposis coli regulator of Wnt signaling pathway (APC), glycogen synthase kinase 3β (GSK3B), and transcription factor 4 (TCF4) were significantly associated with arterial stiffness (P<0.05 for all). When entered into a single model, APC and TCF4 expression remained independently associated with arterial stiffness (P=0.04 and 0.003, respectively), and each explained ≈3% of the variance in pulse‐wave velocity.

Conclusions

The current study establishes a novel association between in vivo expression of the Wnt pathway genes, APC and TCF4, with arterial stiffness in African ancestry men, a population at high risk of hypertensive vascular disease.

BODY COMPOSITION ACROSS THE LIFESPAN IN AFRICAN CARIBBEAN MEN: FINDINGS FROM THE TOBAGO LONGITUDINAL STUDY OF AGING

Body composition changes vary by age and ethnicity and have a major impact on health and physical function. However, little is known about the magnitude, tempo and patterns of these changes in African-ancestry populations, particularly outside the U.S. Thus, we examined age-specific rates-of-change in lean and fat mass in a unique population-based, longitudinal cohort study of 2621 African-ancestry men on the Caribbean island of Tobago (age: 62.0±11.8 years, range: 32-99 years). Body composition was measured with DXA at study entry and after an average of 4 and 9 years. Annualized rates of change and 95% confidence intervals were calculated using all 3 time-points with Generalized Estimating Equations stratified by 5-year baseline age-groups. Lean mass declined at a fairly constant rate in age-strata up through age ≤64 years (-0.72; -0.76, -0.67%/yr), but accelerated to -0.92 %/yr (-1.02, -0.82 %/yr) among those aged 65-69, and to -1.16 %/yr (-1.30, -1.03 %/yr) among those aged 70-74 years – plateauing in those aged 75+. This pattern of age acceleration was observed in arm but not leg lean mass. The age-specific rates of decline in lean mass in this cohort of African Caribbean men appear to be lower than those reported in older African American men. In contrast to lean mas, fat mass increased by 2.93 %/yr (2.72, 3.15 %/yr) and this rate of increase was fairly uniform across the lifespan. Additional research is needed to better define the lifestyle, medical and biological factors contributing to body composition changes across the lifespan in African-ancestry populations.

PREVALENCE AND HERITABILITY OF PERCEIVED MENTAL FATIGABILITY IN THE LONG LIFE FAMILY STUDY

We examined the prevalence and heritability of perceived mental fatigability among older adults enrolled in the Long Life Family Study. Participants (N=2342; 55% female) self-administered the Pittsburgh Fatigability Scale (PFS; scores range 0-50; higher score=greater fatigability). Using the PFS mental subscale, we evaluated differences across age strata (adjusted for family structure and field center) and estimated genetic heritability using the variance covariance methods implemented in SOLAR to determine genetic heritability (adjusted for age, sex, and field center). PFS mental score (mean±SD) and prevalence of higher mental fatigability (PFS ≥13) was greater across age strata: 60-69 (N=996, 5.9± 6.5, 14.5%), 70-79 (N=830, 6.8 ±7.6, 18.7%), 80-89 (N=251, 11.7±10.8, 41.8%), and ≥90 (N=265, 20.2±13.6, 67.2%), p<0.0001. Only among those ≥90, females (21.7±13.5) had greater mental fatigability than males (18.0±13.5), p=0.03. Residual heritability of mental fatigability was 0.17, p<0.0001. Future analyses will evaluate correlates of mental fatigability to identify potential avenues for intervention.

ASSESSING THE RELATIONSHIP BETWEEN SERUM IGF-1 AND ADIPOSITY BY AGE IN THE LONG LIFE FAMILY STUDY

Serum levels of insulin-like growth factor 1 (IGF-1) and measures of adiposity, such as body mass index (BMI), are associated with susceptibility to age-related diseases. Previous reports of the relationship between IGF-1 and BMI ranged from positive to negative to no relationship, perhaps because previous reports studied different age cohorts. Using data on 4270 participants (aged 24-110 years) from the Long Life Family Study, we investigated the relationship between IGF-1 and BMI overall and by age groups. IGF-1 and BMI were positively correlated in the total sample (β=0.161, r2= 0.0038, p=1.8-05). However, further analyses revealed that the relationship between IGF-1 and BMI varied by age quartile: in the 1st quartile (24-58yo) the relationship was negative (β=−0.204, r2= 0.011, p=0.0008); in the 2nd quartile (59-66yo) the relationship was negative but non-significant (β=−0.069, r2= 0.0012, p=0.28); in the 3rd quartile (67-86yo) the relationship was positive but non-significant (β=0.106, r2= 0.002, p=0.13); and in the 4th quartile (87-110yo) the relationship was positive (β=0.388, r2= 0.019, p=1.2−05). This pattern did not differ by sex. We also detected a similar age-related pattern between IGF-1 and BMI using an independent dataset (NHANES III), comprising 2550 men and women aged 20-90 years. Our results may clarify some of the inconsistency in previous literature about the relationship between IGF-1 and BMI. Additional studies of IGF-1 and adiposity measures are needed to better understand the underlying mechanisms involved.

Genome-wide linkage analysis of carotid artery traits in exceptionally long-lived families

BACKGROUND AND AIMS

Atherosclerosis develops with age and is partially controlled by genetics. Research to date has identified common variants with small effects on atherosclerosis related traits. We aimed to use family-based genome-wide linkage analysis to identify chromosomal regions potentially harboring rare variants with larger effects for atherosclerosis related traits.

METHODS

Participants included 2205 individuals from the Long Life Family Study (LLFS), which recruited families with exceptional longevity from Boston, New York, Pittsburgh, and Denmark. Participants underwent B-mode ultrasonography of the carotid arteries to measure intima-media thickness (IMT), inter-adventitial diameter (IAD), and plaque presence and severity. We conducted residual heritability and genome-wide linkage analyses adjusted for age, age², sex, and field center using pedigree-based maximum-likelihood methods in SOLAR.

RESULTS

All carotid traits were significantly heritable with a range of 0.68 for IAD to 0.38 for IMT. We identified three chromosomal regions with linkage to IAD (3q13; max LOD 5.3), plaque severity (17q22-q23, max LOD 3.2), and plaque presence (17q24, max LOD 3.1). No common allelic variants within these linkage peaks were associated with the carotid artery traits.

CONCLUSIONS

We identified three chromosomal regions with evidence of linkage to carotid artery diameter and atherosclerotic plaque in exceptionally long-lived families. Since common allelic variants within our linkage peaks did not account for our findings, future follow-up resequencing of these regions in LLFS families should help advance our understanding of atherosclerosis, CVD, and healthy vascular aging.

Aortic Stiffness is Associated with Increased Risk of Incident Dementia in Older Adults

Cardiovascular disease risk factors, including age, hypertension, and diabetes, contribute to aortic stiffness and subclinical cardiovascular and brain disease, increasing dementia risk. Aortic stiffness, measured by carotid-femoral pulse wave velocity (cfPWV), reduces the buffering of pulsatile blood flow, exposing cerebral small arteries to microvascular damage. High cfPWV is related to white matter hyperintensities and brain amyloid deposition, and to cognitive decline, but it is unclear whether cfPWV independently predicts incident dementia. Therefore, we tested the hypothesis that cfPWV predicts incident dementia in older adults, independent of potential confounders. The Cardiovascular Health Study Cognition Study followed 532 non-demented older adults with annual cognitive exams from 1998-99 through 2013. CfPWV was measured on 356 (mean age = 78, 59% women) between 1996-2000. Over 15 years, 212 (59.6%) developed dementia (median time from cfPWV measurement = 4 years). In age and sex-adjusted Cox models, cfPWV was significantly associated with increased risk of dementia, but systolic blood pressure, mean arterial pressure and pulse pressure were not. CfPWV (transformed as - 1/cfPWV) remained significantly associated with dementia risk when further adjusted for education, race, APOEɛ4, diabetes, body mass index, mean arterial pressure, and anti-hypertensive medication (hazard ratio = 1.60, 95% CI = 1.02, 2.51). Results were similar when further adjusted for baseline global cognition, subclinical brain measures, and coronary artery calcification. Finally, higher cfPWV was related to lower physical activity intensity and higher systolic blood pressure, heart rate, and waist circumference measured 5 years prior. An important unanswered question is whether interventions to slow arterial stiffening can reduce the risk of dementia.

Serum Vitamin D and Age-Related Muscle Loss in Afro-Caribbean Men: The Importance of Age and Diabetic Status

BACKGROUND

Prospective studies examining the potential association of vitamin D with age-related muscle loss have shown inconsistent results.

OBJECTIVE

To examine the association between baseline serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), and prospective change in lean mass with aging in African ancestry population. We also determined if associations were modulated by age and diabetes mellitus (DM).

DESIGN

Prospective observational cohort study.

SETTING

Data were collected from a random sub-sample of 574 men, participants of the Tobago Bone Health Study (TBHS).

PARTICIPANTS

574 Afro-Caribbean men, aged 43+ years (mean age: 59.1 ± 10.5), who were randomly selected as the participants in both the baseline and the follow-up visits.

MEASUREMENTS

Baseline fasting serum 25(OH)D was measured using liquid chromatography mass spectrometry (LC-MS/MS), and and 1,25(OH)2D was measured using radioimmunosassay (RIA). Changes in dual-energy X-ray absorptiometry (DXA)-measured appendicular lean mass (ALM), and total body lean mass (TBLM) were measured over an average of 6.0 ± 0.5 years. The associations of 25(OH)D and 1,25(OH)2D with ALM and TBLM were assessed by multiple linear regression model after adjusting for potential confounders.

RESULTS

When stratifying all men into two groups by age, greater baseline 25(OH)D and 1,25(OH)2D levels were associated with smaller losses of ALM and TBLM in older (age 60+ years) but not in younger (age 43 - 59 years) men. When stratifying by DM status, the associations of 25(OH)D and 1,25(OH)2D with declines in ALM and TBLM were statistically significant only in prediabetic, but not among normal glycemic or diabetic men.

CONCLUSION

Higher endogenous vitamin D concentrations are associated with less lean mass loss with aging among older and prediabetic Afro-Caribbean men independent of potential confounders. Our findings raise a possibility that maintaining high serum vitamin D level might be important for musculoskeletal health in elderly and prediabetic African ancestry men.

Wnt Pathway Inhibitor DKK1: A Potential Novel Biomarker for Adiposity

Emerging evidence indicates that ectopic skeletal muscle adiposity may be a risk factor for type 2 diabetes (T2D), especially in persons of African ancestry. In vitro studies suggest that a Wnt pathway inhibitor, Dickkopf-related protein 1 (DKK1), plays a role in adiposity regulation and could be a biomarker for adiposity in humans. The objective of this study was to test whether serum DKK1 levels relate to adiposity measures in a cohort from an African ancestry population at high risk for T2D. Fasting serum DKK1 was measured in a sample of 159 men of African ancestry aged ≥40 years (mean age ± SD, 63.5 ± 8.2 years; mean body mass index, 27.8 ± 4.5 kg/m²). Anthropometrics included total-body and trunk adiposity measured by dual-energy x-ray absorptiometry and lower-leg skeletal muscle density measured by CT [which reflects the intramuscular adiposity content (mg/cm³)]. Serum DKK1 was positively correlated with BMI (r = 0.20; P = 0.01), waist circumference (r = 0.15; P = 0.046), DXA total-body adiposity (r = 0.24; P = 0.003), and DXA trunk adiposity (r = 0.21; P = 0.009), independent of age and height. In addition, serum DKK1 was inversely correlated with skeletal muscle density (r = −0.25; P = 0.002), independent of age, BMI, and calf muscle area. No significant correlation was found between serum DKK1 and fasting serum glucose or insulin levels or insulin resistance estimated by homeostasis model assessment. These findings suggest that higher levels of serum DKK1 may be associated with greater overall, central, and ectopic skeletal muscle adiposity. Further studies are needed to unravel the potential role of DKK1 in the regulation of adiposity in humans.

Muscle Attenuation Is Associated With Newly Developed Hypertension in Men of African Ancestry

Increased ectopic adipose tissue infiltration in skeletal muscle is associated with insulin resistance and diabetes mellitus. We evaluated whether change in skeletal muscle adiposity predicts subsequent development of hypertension in men of African ancestry, a population sample understudied in previous studies. In the Tobago Health Study, a prospective longitudinal study among men of African ancestry (age range 40-91 years), calf intermuscular adipose tissue, and skeletal muscle attenuation were measured with computed tomography. Hypertension was defined as a systolic blood pressure ≥140 mm Hg, or a diastolic blood pressure ≥90 mm Hg, or receiving antihypertensive medications. Logistic regression was performed with adjustment for age, insulin resistance, baseline and 6-year change in body mass index, baseline and 6-year change in waist circumference, and other potential confounding factors. Among 746 normotensive men at baseline, 321 (43%) developed hypertension during the mean 6.2 years of follow-up. Decreased skeletal muscle attenuation was associated with newly developed hypertension after adjustment for baseline and 6-year change of body mass index (odds ratio [95% confidence interval] per SD, 1.3 [1.0-1.6]) or baseline and 6-year change of waist circumference (odds ratio [95% confidence interval] per SD, 1.3 [1.0-1.6]). No association was observed between increased intermuscular adipose tissue and hypertension. Our novel findings show that decreased muscle attenuation is associated with newly developed hypertension among men of African ancestry, independent of general and central adiposity and insulin resistance. Further studies are needed to adjust for inflammation, visceral and other ectopic adipose tissue depots, and to confirm our findings in other population samples.

Greater skeletal muscle fat infiltration is associated with higher all-cause mortality among men of African ancestry

BACKGROUND

fat infiltration within and around skeletal muscle (i.e. myosteatosis) increases with ageing, is greater in African versus European ancestry men and is associated with poor health. Myosteatosis studies of mortality are lacking, particularly among African ancestry populations.

METHODS

in the Tobago Health study, a prospective longitudinal study, we evaluated the association of all-cause mortality with quantitative computed tomography (QCT) measured lower leg myosteatosis (intermuscular fat (IM fat) and muscle density) in 1,652 African ancestry men using Cox proportional hazards models. Date of death was abstracted from death certificates and/or proxy.

RESULTS

one hundred and twelve deaths occurred during follow-up (mean 5.9 years). In all men (age range 40-91 years), higher all-cause mortality was associated with greater IM fat (HR (95% CI) per SD: 1.29 (1.06-1.57)) and lower muscle density (HR (95% CI) per SD lower: 1.37 (1.08-1.75)) in fully adjusted models. Similar mortality hazard rates were seen in the subset of elderly men (aged ≥65 years) with greater IM fat (1.40 (1.11-1.78) or lower muscle density (1.66 (1.24-2.21)) in fully adjusted models.

CONCLUSIONS

our study identified a novel, independent association between myosteatosis and all-cause mortality in African ancestry men. Further studies are needed to establish whether this association is independent of other ectopic fat depots and to identify possible biological mechanisms underlying this relationship.

Optimal serum cholesterol concentrations are associated with accelerated bone loss in African ancestry men

We tested if serum lipid and lipoprotein cholesterol levels are associated with longitudinal measures of bone mineral density (BMD) in 1289 African ancestry men. After 6 years of mean follow-up, men with clinically optimal levels of low-density lipoprotein (LDL), high-density lipoprotein (HDL), or triglycerides at baseline experienced the greatest BMD loss, independent of potential confounding factors (all p < 0.05).

INTRODUCTION

Studies of lipid and lipoprotein cholesterol associations with bone mineral density (BMD) and bone loss have been inconclusive, and longitudinal data are sparse. Therefore, the aim of this study was to test if fasting serum lipid and lipoprotein cholesterol levels are associated with areal and volumetric BMD and BMD change.

METHODS

We determined the association of serum triglycerides, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) cholesterol concentrations with cross-sectional and longitudinal (mean follow-up, 6.1 years) measures of BMD in a cohort of 1289 in African ancestry men (mean age, 56.4 years). Fasting serum triglycerides, HDL, and LDL were measured at baseline concurrent with BMD assessments. Dual-energy X-ray absorptiometry was used to quantify integral hip BMD, and peripheral quantitative computed tomography at the radius and tibia was used to quantify volumetric BMD. Men were categorized as optimal, borderline, or high risk for triglyceride, HDL, and LDL concentrations based on Adult Treatment Panel III guidelines.

RESULTS

Lower serum triglyceride or LDL and higher HDL concentrations were associated with lower trabecular BMD at baseline (all p < 0.05). Similarly, men classified as having optimal levels of LDL, HDL, or triglycerides at baseline experienced the greatest integral BMD loss at the hip and trabecular BMD loss at the tibia (all p < 0.05), independent of potential confounding factors.

CONCLUSIONS

We found that clinically optimal serum lipid and lipoprotein cholesterol concentrations were associated with accelerated bone loss among Afro-Caribbean men. Further studies are needed to better understand the mechanisms involved and potential clinical significance of these findings.

Association of Circulating Renin and Aldosterone With Osteocalcin and Bone Mineral Density in African Ancestry Families

Hypertension is associated with accelerated bone loss, and the renin-angiotensin-aldosterone system is a key regulator of blood pressure. Although components of this system are expressed in human bone cells, studies in humans are sparse. Thus, we studied the association of circulating renin and aldosterone with osteocalcin and bone mineral density. We recruited 373 African ancestry family members without regard to health status from 6 probands (mean family size: 62 and relative pairs: 1687). Participants underwent a clinical examination, dual-energy x-ray absorptiometry, and quantitative computed tomographic scans. Renin activity, aldosterone concentration, and osteocalcin were measured in fasting blood samples. Aldosterone/renin ratio was calculated as aldosterone concentration/renin activity. All models were analyzed using pedigree-based variance components methods. Full models included adjustment for age, sex, body composition, comorbidities, lifestyle factors, blood pressure, and antihypertensive medication. Higher renin activity was significantly associated with lower total osteocalcin and with higher trabecular bone mineral density (both P<0.01). There were also significant genetic correlations between renin activity and whole-body bone mineral density. There were no associations with aldosterone concentration in any model and results for aldosterone/renin ratio were similar to those for renin activity. This is the first study to report a significant association between renin activity and a marker of bone turnover and bone mineral density in generally healthy individuals. Also, there is evidence for significant genetic pleiotropy and, thus, there may be a shared biological mechanism underlying both the renin-angiotensin-aldosterone system and bone metabolism that is independent of hypertension.

Association of Lipopolysaccharide-Binding Protein With Aging-Related Adiposity Change and Prediabetes Among African Ancestry Men

OBJECTIVE

Cross-sectional studies suggest that lipopolysaccharide-binding protein (LBP) may be associated with obesity and metabolic disorders. However, prospective studies examining LBP are lacking. This prospective study investigated the association between LBP and metabolic abnormalities in 580 African ancestry men (mean age, 59.1 ± 10.5 years).

RESEARCH DESIGN AND METHODS

We measured fasting serum LBP at baseline. Changes in adiposity and glucose homeostasis as well as case subjects with new type 2 diabetes and impaired fasting glucose (IFG) were assessed at a follow-up visit ~6 years later. Baseline LBP values were tested across quartiles for linear trend with metabolic measures. Multivariable logistic regression was used to determine the odds of new cases of IFG or diabetes per 1-SD greater baseline LBP.

RESULTS

LBP was significantly associated with baseline BMI, waist circumference, whole-body and trunk fat, skeletal muscle density, fasting serum insulin, and HOMA-insulin resistance (IR) (all P < 0.01). Greater baseline LBP was significantly associated with longitudinal increases in the percentage of trunk fat (P = 0.025) and HOMA-IR (P = 0.034), but only borderline so with a decrease in skeletal muscle density (P = 0.057). In men with normal glucose, baseline LBP was associated with increased odds of having IFG at follow-up after adjustment for age, baseline trunk fat, and lifestyle factors (odds ratio per 1-SD LBP: 1.51; 95% CI 1.02-2.21). This association was attenuated after additional adjustment for change in trunk fat (P = 0.067).

CONCLUSIONS

LBP may be a marker of prediabetes. Some of this association appears to be mediated through increased central and ectopic skeletal muscle adiposity.

Myosteatosis increases with aging and is associated with incident diabetes in African ancestry men

OBJECTIVE

Skeletal muscle fat infiltration (known as myosteatosis) is greater in African compared with European ancestry men and may play an important role in the development of type 2 diabetes (T2D). However, prospective studies examining the magnitude of changes in myosteatosis with aging and their metabolic consequences are sparse.

METHODS

Longitudinal changes in peripheral quantitative computed tomography measured calf myosteatosis [intermuscular fat (mm(2) ) and skeletal muscle density as a measure of intramuscular fat (mg/cm(3) )] were examined in 1515 Afro-Caribbean men aged 40+ years recruited without regard to their health status.

RESULTS

During an average of 6.2 years of follow-up, an age-related increase in intermuscular fat and a decrease in skeletal muscle density were observed (all P < 0.0001), which remained significant in those who lost weight, gained weight, or remained weight stable (all P < 0.0001). In addition, muscle density loss accelerated with increasing age (P < 0.0001). Increased intermuscular fat during follow-up was associated with an increased incident risk of T2D independent of factors known to be associated with T2D (odds ratios per 1-SD increase in intermuscular fat = 1.29; 95% CI = 1.08-1.53).

CONCLUSIONS

Our findings suggest that both inter- and intramuscular fat increase with advancing age and that intermuscular fat contributes to development of T2D among African ancestry men.

Renal Function and Bone Loss in a Cohort of Afro-Caribbean Men

Poor renal function is associated with increased rates of bone loss and osteoporotic fractures in Caucasian men. The importance of kidney function for skeletal health in African ancestry men, who are a population segment with a high prevalence of chronic kidney disease as well as high peak bone mass, is not well known. We examined the relationship between estimated glomerular filtration rate (eGFR) and rates of bone loss in a large population cohort of otherwise healthy Afro-Caribbean men aged 40 years and older. Dual X-ray absorptiometry of the proximal femur and quantitative computed tomography of the proximal radius and tibia were obtained approximately 6 years apart. We calculated eGFR from serum creatinine that was measured in fasting samples in 1451 men. Impaired kidney function (IKF, eGFR<60 ml/min/1.7 m(2)) was observed in 8.6% of the cohort. The relationship between IKF and baseline BMD and annualized rate of change in BMD was analyzed controlling for potentially important confounders. IKF was not associated with baseline BMD. In contrast, men with IKF experienced a rate of decline in areal BMD at the total hip, femoral neck and trochanter and cortical volumetric BMD compared to those with normal kidney function (p<0.05 for all). Impaired kidney function was not associated with changes in trabecular volumetric BMD. In conclusion, poorer kidney function is associated with accelerated bone loss among otherwise healthy Afro-Caribbean men even after controlling for age and other important medical and lifestyle related variables.

Greater Skeletal Muscle Fat Infiltration Is Associated With Higher All-Cause and Cardiovascular Mortality in Older Men

BACKGROUND

Skeletal muscle fat infiltration (myosteatosis) increases with aging, and has been associated with poor metabolic and musculoskeletal health, independent of overall adiposity. Studies examining the relationship of myosteatosis and mortality among older individuals recruited without regard to their health status are sparse.

METHODS

We evaluated the association of peripheral computed tomography measured calf myosteatosis (intermuscular fat and muscle density as a measure of intramuscular fat) with mortality in 1,063 community-dwelling older men. Cox proportional hazards models were used to estimate the risk of mortality independent of potential confounders.

RESULTS

During a mean follow-up of 7.2 years, 317 participants died. After adjustment for potential covariates and additional adjustment for whole body fat, lower skeletal muscle density was associated with increased all-cause mortality and cardiovascular disease mortality (hazard ratio [95% confidence interval] per standard deviation lower skeletal muscle density: 1.24 [1.09-1.41] and 1.46 [1.15-1.86], respectively), and to some extent with noncardiovascular disease mortality (1.18 [1.0-1.38], p = .053). After adjusting for trunk fat in a separate multivariable model, the association between skeletal muscle density and all-cause and cardiovascular disease mortality remained significant (both p < .01), while its association with noncardiovascular disease mortality became of borderline significance (p = .085). No other measures of adiposity, including calf intermuscular fat, were associated with mortality.

CONCLUSION

Our study reveals an independent association between skeletal muscle density and mortality in a community-based sample of older, predominantly Caucasian men. Further studies are needed to establish if this association is independent of other ectopic fat depots, and to identify the biological mechanisms underlying this relationship.

Heritability and genetics of serum dickkopf 1 levels in African ancestry families

The aim of the study was to determine the heritability of serum dickkopf-1 (DKK1) and its association with DKK1 polymorphisms in African ancestry subjects. Serum DKK1 was measured in 422 Afro-Caribbean men and women aged 18+ from 7 large, multi-generational families (mean family size: 60; 3,215 relative pairs). Twenty-four common single nucleotide polymorphisms (SNPs) were genotyped within an 80 kilobase-pair region encompassing the DKK1 gene. Heritability was estimated and SNPs were tested for association with serum DKK1 using variance components analysis. DKK1 mRNA expression was tested in peripheral blood of 16 individuals from each of the rs7069912 genotypes. Mean serum DKK1 was 1724.1 pg/mL and was significantly lower in women than men (P = 0.043). Residual genetic heritability of serum DKK1 was 0.4460 (P < 0.0001). Six SNPs reached nominal significance with DKK1, with rs7069912 being significant after adjustment for multiple comparisons. Two of these six SNPs represented independent association signals (rs7069912 and rs16928725), which accounted for 4.6% of the phenotypic variation in DKK1. Additionally, carriers of the rs7069912 variant had significantly greater DKK1 expression than non-carriers (P = 0.036). Serum DKK1 levels are highly heritable in the African ancestry families. Two SNPs within the DKK1 region accounted for nearly 5% of the variation in serum DKK1.

Association of circulating sclerostin with vascular calcification in Afro-Caribbean men

OBJECTIVE

Sclerostin, a Wingless (Wnt) pathway antagonist, is an established regulator of bone mineralization in humans but its potential importance in the regulation of vascular calcification is less clear. Therefore, our objective was to assess the relationship of serum sclerostin levels with coronary and aortic artery calcification (CAC and AAC, respectively) in Afro-Caribbean men on the island of Tobago.

METHODS

Serum sclerostin levels and computed tomography of CAC and AAC were measured in 191 men (age mean(SD): 62.9(8.0)years) recruited without regard to health status. Multivariable logistic regression models were used to assess the cross-sectional association of sclerostin with prevalent arterial calcification.

RESULTS

Mean(SD) sclerostin was 45.2 pmol/L (15.6 pmol/L). After adjusting for risk factors including age, physical and lifestyle characteristics, comorbidities, lipoproteins and kidney function, 1 SD greater sclerostin level was associated with a 1.61-times (95%CI 1.02-2.53) greater odds of having CAC. Sclerostin was not associated with AAC in any model.

CONCLUSIONS

This is the first study to show that, among Afro-Caribbean men, greater serum sclerostin concentrations were associated with prevalence and extent of CAC. Further studies are needed to better define the role of the Wnt signaling pathway in arterial calcification in humans.

Association of volumetric bone mineral density with abdominal aortic calcification in African ancestry men

SUMMARY

We tested for association between cortical and trabecular volumetric bone mineral density (vBMD) with abdominal aortic calcification (AAC) prevalence in 278 Afro-Caribbean men. AAC was present in 68.3 % of the men. Greater cortical, but not trabecular, vBMD was associated with significantly decreased odds of AAC independent of traditional risk factors.

INTRODUCTION

The aim of this study is to assess the prevalence and correlates of AAC in a sample of 278 Afro-Caribbean men (mean age 56) and to test for a largely unexplored association between cortical and trabecular vBMD with AAC prevalence.

METHODS

Men were recruited consecutively as part of an ongoing prospective cohort study of body composition in men aged 40+. For this analysis, AAC was assessed by computed tomography of the abdomen from L3 to S1. Aortic calcium was scored using the Agatston method, and prevalence was defined as a score ≥10 to rule out false positives. Men also had BMD assessed using peripheral quantitative computed tomography at 4 % (trabecular vBMD) and 33 % (cortical vBMD) of the radius and tibia.

RESULTS

Abdominal aortic calcification was present in 68.3 % of the men. Significant independent predictors of AAC prevalence were increased age, increased BMI, hypertension, and current smoking. Age was the strongest predictor, with each SD (7.8 year) increase in age conferring 2.7 times increased odds of having AAC (P < 0.0001). A one SD greater cortical, but not trabecular, vBMD was associated with a significant decreased odds of AAC prevalence independent of other traditional risk factors (OR 0.65; 95 % CI 0.45-0.92).

CONCLUSIONS

Cortical vBMD is inversely associated with AAC presence. This finding suggests that there may be shared physiology between cortical bone compartment remodeling and vascular calcification.

Relative influence of heritability, environment and genetics on serum sclerostin

SUMMARY

We determined factors associated with serum sclerostin in 446 Afro-Caribbean family members. Age, weight, sex, diabetes and kidney function were associated with sclerostin. Sclerostin was heritable, and nine SNPs in the SOST gene region were associated with sclerostin. Variation in serum sclerostin is a heritable factor that is determined by both genetic and environmental factors.

INTRODUCTION

Sclerostin, encoded by the SOST gene, is a Wnt inhibitor that regulates bone mineralization and is a candidate gene locus for osteoporosis. However, little is known about the genetic and non-genetic sources of inter-individual variation in serum sclerostin levels.

METHODS

Serum sclerostin was measured in 446 Afro-Caribbean men and women aged 18+ from seven large, multigenerational families (mean family size, 64; 3,840 relative pairs). Thirty-six common single nucleotide polymorphisms (SNP) were genotyped within a 100 kb region encompassing the gene encoding sclerostin (SOST). Genetic and non-genetic factors were tested for association with serum sclerostin.

RESULTS

Mean serum sclerostin was 41.3 pmol/l and was greater in men than in women (P < 0.05). Factors associated with higher serum sclerostin were increased age and body weight, male sex, diabetes and decreased glomerular filtration rate, which collectively accounted for 25.4 % of its variation. Residual genetic heritability of serum sclerostin was 0.393 (P < 0.0001). Nine SNPs reached nominal significance with sclerostin. Three of those nine SNPs represented independent association signals (rs851056, rs41455049 and rs9909172), which accounted for 7.8 % of the phenotypic variation in sclerostin, although none of these SNPs surpassed a Bonferroni correction for multiple comparisons.

CONCLUSIONS

Serum sclerostin is a heritable trait that is also determined by environmental factors including age, sex, adiposity, diabetes and kidney function. Three independent common SNPs within the SOST region may collectively account for a significant proportion of the variation in serum sclerostin.

Skeletal muscle adiposity is associated with serum lipid and lipoprotein levels in Afro-Caribbean men

OBJECTIVE

When compared with other ethnic groups, African ancestry individuals have lower triglycerides and higher High-density lipoprotein cholesterol (HDL-C) levels, although the mechanisms for these differences remain unclear. A comprehensive array of factors potentially related to fasting serum lipid and lipoprotein levels in African ancestry men was evaluated.

DESIGN AND METHODS

Men (1,821) underwent dual-energy X-ray absorptiometry measures of total body fat and quantitative computed tomography assessments of calf skeletal muscle adiposity [subcutaneous and intermuscular adipose tissue (AT), and muscle density as a measure of intra-muscular AT].

RESULTS

Multivariable linear regression analysis identified age (-), total body fat (+), subcutaneous AT (-), fasting glucose (+), fasting insulin (+), diastolic blood pressure (+), and non-African ancestry (+) as independent correlates of triglycerides (all P < 0.05). Total body fat (+), intra-muscular AT (-), and diastolic blood pressure (+) were independent correlates of Low-density lipoprotein cholesterol (LDL-C) (all P < 0.001). Age (+), waist circumference (-), fasting insulin (-), physical activity (+), and alcohol intake (+) were independent correlates of HDL-C (all P < 0.05).

CONCLUSIONS

A novel relationship between skeletal muscle adiposity and serum lipid and lipoprotein levels in African ancestry men, independent of total and central adiposity was illuminated. In African ancestry populations, genetic factors are likely a significant determinant of triglycerides levels.

Evidence for a genetic link between bone and vascular measures in African ancestry families

Bone mineral density (BMD) has been inversely associated with subclinical and clinical cardiovascular disease (CVD) in population studies, but the potential mechanisms underlying this relationship are unclear. To test if there is a genetic basis underlying this association, we determined the phenotypic and genetic correlations between BMD and carotid artery ultrasound measures in families. Dual-energy X-ray absorptiometry and peripheral quantitative computed tomography were used to measure BMD in 461 individuals with African ancestry belonging to seven large, multigenerational families (mean family size 66; 3414 total relative pairs). Carotid artery ultrasound was used to measure adventitial diameter (AD) and intima-media thickness (IMT). Phenotypic and genetic correlations between BMD and carotid measures were determined using pedigree-based maximum likelihood methods. We adjusted for potential confounding factors, including age, sex, body weight, height, menopausal status, smoking, alcohol intake, walking for exercise, diabetes, hypertension, serum lipid and lipoprotein levels, inflammation markers, and kidney function. We found statistically significant phenotypic (ρ = -0.19) and genetic (ρG  = -0.70) correlations (p < 0.05 for both) between lumbar spine BMD and AD in fully adjusted models. There was also a significant genetic correlation between trabecular BMD at the radius and IMT in fully adjusted models (ρG  = -0.398; p < 0.05). Our findings indicate that the previously observed association between osteoporosis and CVD in population-based studies may be partly mediated by genetic factors and that the pleiotropic effects of these genes may operate independently of traditional risk pathways.

Effects of weight loss and insulin reduction on arterial stiffness in the SAVE trial

Background

Chronic arterial stiffness contributes to the negative health effects of obesity and insulin resistance, which include hypertension, stroke, and increased cardiovascular and all-cause mortality. Weight loss and improved insulin sensitivity are individually associated with improved central arterial stiffness; however, their combined effects on arterial stiffness are poorly understood. The purpose of this study was to determine how insulin levels modify the improvements in arterial stiffness seen with weight loss in overweight and obese young adults.

Methods

To assess the effects of weight loss and decreased fasting insulin on vascular stiffness, we studied 339 participants in the Slow the Adverse Effects of Vascular Aging (SAVE) trial. At study entry, the participants were aged 20–45, normotensive, non-diabetic, and had a body-mass index of 25–39.9 kg/m². Measures of pulse wave velocity (PWV) in the central (carotid-femoral (cfPWV)), peripheral (femoral-ankle (faPWV)), and mixed (brachial-ankle (baPWV)) vascular beds were collected at baseline and 6 months. The effects of 6-month change in weight and insulin on measures of PWV were estimated using multivariate regression.

Results

After adjustment for baseline risk factors and change in systolic blood pressure, 6-month weight loss and 6-month change in fasting insulin independently predicted improvement in baPWV but not faPWV or cfPWV. There was a significant interaction between 6-month weight change and change in fasting insulin when predicting changes in baPWV (p < 0.001). Individuals experiencing both weight loss and insulin reductions showed the greatest improvement in baPWV.

Conclusions

Young adults with excess weight who both lower their insulin levels and lose weight see the greatest improvement in vascular stiffness. This improvement in vascular stiffness with weight loss and insulin declines may occur throughout the vasculature and may not be limited to individual vascular beds.

Trial registration

NCT00366990

Genetic analysis of serum osteocalcin and bone mineral in multigenerational Afro-Caribbean families

Osteocalcin is a major component of bone matrix. Concentrations of total, carboxylated, and uncarboxylated osteocalcin, are highly heritable and genetically correlated with bone mineral content (BMC) within African ancestry families.

INTRODUCTION

Osteocalcin (OC) is a protein constituent of bone matrix and a marker of bone formation. We characterized the heritability of serum OC measures and identified genomic regions potentially involved in the regulation of OC via high-density genome-wide linkage analysis in African ancestry individuals.

METHODS

African ancestry individuals (n = 459) were recruited, without regard to health status, from seven probands (mean family size = 66; 4,373 relative pairs). Residual heritability of serum OC measures was estimated and multipoint quantitative trait linkage analysis was performed using pedigree-based maximum likelihood methods.

RESULTS

Residual heritabilities of total OC, uncarboxylated OC, carboxylated OC and percent uncarboxylated OC were 0.74 ± 0.10, 0.89 ± 0.08, 0.46 ± 0.10 and 0.41 ± 0.09, respectively. All OC measures were genetically correlated with whole body BMC. We obtained strong evidence of bivariate linkage for percent uncarboxylated OC and whole body BMC on chromosome 17 (logarithm of the odds [LOD] = 3.15, 99 cM).

CONCLUSIONS

All forms of OC were highly heritable and genetically correlated with total body BMC in these African ancestry families. The identified linkage region contains several candidate genes for bone and energy metabolism including COL1A1 and TNFRSF11A. Further studies of this genomic region may reveal novel insight into the genetic regulation of OC and bone mineralization.

Markers of inflammation are heritable and associated with subcutaneous and ectopic skeletal muscle adiposity in African ancestry families

Abstract Background: Skeletal muscle adipose tissue (AT) infiltration, or myosteatosis, appears to be greater in African compared with European ancestry individuals and may play a role in type 2 diabetes mellitus (T2DM), a disease that disproportionally affects African ancestry populations. Inflammation is one mechanism that may link myosteatosis with increased T2DM risk, but studies examining the relationship between inflammation and myosteatosis are lacking.

METHODS

To examine these associations, we measured skeletal muscle subcutaneous AT, intermuscular AT, and skeletal muscle density using quantitative computed tomography and serum markers of inflammation in 471 individuals from 8 Afro-Caribbean multigenerational families [mean family size 67; mean age 43 years; mean body mass index (BMI) 28 kg/m(2)].

RESULTS

After removing the variation attributable to significant covariates, heritabilities of inflammation markers [C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α)] ranged from 33% (TNFα) to 40% (CRP); all P<0.01. Higher CRP, IL-6, and TNF-α were associated with lower subcutaneous AT around skeletal muscle (r=-0.13 to -0.19, P<0.05). Higher CRP was additionally associated with lower skeletal muscle density, indicative of greater intramuscular AT (r=-0.10, P<0.05), hyperinsulinemia (r=0.12, P<0.05), and increased homeostasis model assessment of insulin resistance (HOMA-IR) (r=0.17, P<0.01).

CONCLUSIONS

Our findings suggest that heredity may play a significant role in the determination of several markers of inflammation in African ancestry individuals. Higher concentrations of CRP appear to be associated with greater skeletal muscle AT infiltration, lower subcutaneous AT, hyperinsulinemia, and insulin resistance. Longitudinal studies are needed to further evaluate the relationship between inflammation with changes in skeletal muscle AT distribution with aging and the incidence of T2DM.