Association between GDF15, poverty and mortality in urban middle-aged African American and white adults.

Mortality disparities are influenced by race and poverty. There is limited information about whether poverty influences biologic markers of mortality risk. Emerging data suggests that growth differentiation factor 15 (GDF15) is associated with mortality; however, the interplay between GDF15, sociodemographic factors and mortality is not known. We sought to evaluate the interactions between GDF15 and sex, race and poverty status on mortality. Serum GDF15 was measured in 1036 African American and white middle-aged men and women above and below 125% of the Federal poverty status from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Multivariable adjusted Cox regression models were used to assess the association between log-transformed GDF15 (logGDF15) and 12-year mortality outcomes (all-cause, cardiovascular- and cancer-specific outcomes) and interactions with sex, race and poverty status. Likelihood ratio tests were used to assess significance of the interaction terms. Median GDF15 was 655.2 pg/mL (IQR = 575.1). During 12.2 years of follow-up, 331 died of which 94 cardiovascular- and 87 were cancer-specific deaths. One unit of increase in logGDF15 was associated with a hazard ratio for all-cause mortality, cardiovascular- and cancer-specific mortality of 2.26 (95% confidence interval [CI], 1.94-2.64), 2.74 (95%CI, 2.06-3.63) and 1.41 (95%CI, 1.00-2.00), respectively. There was an interaction between logGDF15 and poverty status on all-cause mortality (p<0.05). The GDF15×poverty status interaction term improved model calibration for all-cause mortality. Our study provides the first evidence that the effect of elevated GDF15 on all-cause mortality is modified by poverty status.

Novel age-associated DNA methylation changes and epigenetic age acceleration in middle-aged African Americans and whites.

BACKGROUND: African Americans (AAs) experience premature chronic health outcomes and longevity disparities consistent with an accelerated aging phenotype. DNA methylation (DNAm) levels at specific CpG positions are hallmarks of aging evidenced by the presence of age-associated differentially methylated CpG positions (aDMPs) that are the basis for the epigenetic clock for measuring biological age acceleration. Since DNAm has not been widely studied among non-European populations, we examined the association between DNAm and chronological age in AAs and whites, and the association between race, poverty, sex, and epigenetic age acceleration. RESULTS: We measured genome-wide DNA methylation (866,836 CpGs) using the Illumina MethylationEPIC BeadChip in blood DNA extracted from 487 middle-aged AA (N = 244) and white (N = 243), men (N = 248), and women (N = 239). The mean (sd) age was 48.4 (8.8) in AA and 49.0 (8.7) in whites (p = 0.48). We identified 4930 significantly associated aDMPs in AAs and 469 in whites. Of these, 75.6% and 53.1% were novel, largely driven by the increased number of measured CpGs in the EPIC array, in AA and whites, respectively. AAs had more age-associated DNAm changes than whites in genes implicated in age-related diseases and cellular pathways involved in growth and development. We assessed three epigenetic age acceleration measures (universal, intrinsic, and extrinsic). AAs had a significantly slower extrinsic aging compared to whites. Furthermore, compared to AA women, both AA and white men had faster aging in the universal age acceleration measure (+ 2.04 and + 1.24 years, respectively, p < 0.05). CONCLUSIONS: AAs have more wide-spread methylation changes than whites. Race and sex interact to underlie biological age acceleration suggesting altered DNA methylation patterns may be important in age-associated health disparities.

Frailty in middle age is associated with frailty status and race-specific changes to the transcriptome.

Frailty is an aging-associated syndrome resulting from diminished capacity to respond to stressors and is a significant risk factor for disability and mortality. Although frailty is usually studied in old age, it is present in mid-life. Given the increases in mortality statistics among middle-aged Americans, understanding molecular drivers of frailty in a younger, diverse cohort may facilitate identifying pathways for early intervention. We analyzed frailty-associated, genome-wide transcriptional changes in middle-aged blacks and whites. Next generation RNA sequencing was completed using total RNA from peripheral blood mononuclear cells (n = 16). We analyzed differential gene expression patterns and completed a parametric analysis of gene set enrichment (PAGE). Differential gene expression was validated using RT-qPCR (n = 52). We identified 5,082 genes differentially expressed with frailty. Frailty altered gene expression patterns and biological pathways differently in blacks and whites, including pathways related to inflammation and immunity. The validation study showed a significant two-way interaction between frailty, race, and expression of the cytokine IL1B and the transcription factor EGR1. The glucose transporter, SLC2A6, the neutrophil receptor, FCGR3B, and the accessory protein, C17orf56, were decreased with frailty. These results suggest that there may be demographic dependent, divergent biological pathways underlying frailty in middle-aged adults.

Altered Extracellular Vesicle Concentration, Cargo, and Function in Diabetes.

Type 2 diabetes is a chronic age-associated degenerative metabolic disease that reflects relative insulin deficiency and resistance. Extracellular vesicles (EVs) (exosomes, microvesicles, and apoptotic bodies) are small (30-400 nm) lipid-bound vesicles capable of shuttling functional proteins, nucleic acids, and lipids as part of intercellular communication systems. Recent studies in mouse models and in cell culture suggest that EVs may modulate insulin signaling. Here, we designed cross-sectional and longitudinal cohorts of euglycemic participants and participants with prediabetes or diabetes. Individuals with diabetes had significantly higher levels of EVs in their circulation than euglycemic control participants. Using a cell-specific EV assay, we identified that levels of erythrocyte-derived EVs are higher with diabetes. We found that insulin resistance increases EV secretion. Furthermore, the levels of insulin signaling proteins were altered in EVs from individuals with high levels of insulin resistance and ß-cell dysfunction. Moreover, EVs from individuals with diabetes were preferentially internalized by circulating leukocytes. Cytokine levels in the media and in EVs were higher from monocytes incubated with diabetic EVs. Microarray of these leukocytes revealed altered gene expression pathways related to cell survival, oxidative stress, and immune function. Collectively, these results suggest that insulin resistance increases the secretion of EVs, which are preferentially internalized by leukocytes, and alters leukocyte function.

Frailty in a racially and socioeconomically diverse sample of middle-aged Americans in Baltimore.

Frailty is a risk factor for disability and mortality, and is more prevalent among African American (AA) elderly than whites. We examine frailty in middle-aged racially and economically diverse adults, and investigate how race, poverty and frailty are associated with mortality. Data were from 2541 participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span study in Baltimore, Maryland; 35-64 years old at initial assessment (56% women; 58% AA). Frailty was assessed using a modified FRAIL scale of fatigue, resistance, ambulation, illness and weight loss, and compared with difficulties in physical functioning and daily activities. Frailty prevalence was calculated across race and age groups, and associations with survival were assessed by Cox Regression. 278 participants were frail (11%); 924 pre-frail (36%); 1339 not frail (53%). For those aged 45-54, a higher proportion of whites (13%) than AAs (8%) were frail; while the proportions were similar for those 55-64 (14%,16%). Frailty was associated with overall survival with an average follow-up of 6.6 years, independent of race, sex and poverty status (HR = 2.30; 95%CI 1.67-3.18). In this sample of economically and racially diverse older adults, the known association of frailty prevalence and age differed across race with whites having higher prevalence at younger ages. Frailty was associated with survival beyond the risk factors of race and poverty status in this middle-aged group. Early recognition of frailty at these younger ages may provide an effective method for preventing or delaying disabilities.

Protective Effects of BDNF against C-Reactive Protein-Induced Inflammation in Women.

BACKGROUND: Since high sensitivity C-reactive protein (hsCRP) is predictive of cardiovascular events, it is important to examine the relationship between hsCRP and other inflammatory and oxidative stress markers linked to cardiovascular disease (CVD) etiology. Previously, we reported that hsCRP induces the oxidative stress adduct 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG) and that these markers are significantly associated in women. Recent data indicates that brain-derived neurotrophic factor (BDNF) may have a role in CVD. METHODS AND RESULTS: We examined BDNF levels in 3 groups of women that were age- and race-matched with low (<3 mg/L), mid (>3-20 mg/L), and high (>20 mg/L) hsCRP (n = 39 per group) and found a significant association between hsCRP, BDNF, and 8-oxodG. In African American females with high hsCRP, increases in BDNF were associated with decreased serum 8-oxodG. This was not the case in white women where high hsCRP was associated with high levels of BDNF and high levels of 8-oxodG. BDNF treatment of cells reduced CRP levels and inhibited CRP-induced DNA damage. CONCLUSION: We discovered an important relationship between hsCRP, 8-oxodG, and BDNF in women at hsCRP levels >3 mg/L. These data suggest that BDNF may have a protective role in counteracting the inflammatory effects of hsCRP.

The influence of health disparities on targeting cancer prevention efforts.

Despite the advances in cancer medicine and the resultant 20% decline in cancer death rates for Americans since 1991, there remain distinct cancer health disparities among African Americans, Hispanics, Native Americans, and the those living in poverty. Minorities and the poor continue to bear the disproportionate burden of cancer, especially in terms of stage at diagnosis, incidence, and mortality. Cancer health disparities are persistent reminders that state-of-the-art cancer prevention, diagnosis, and treatment are not equally effective for and accessible to all Americans. The cancer prevention model must take into account the phenotype of accelerated aging associated with health disparities as well as the important interplay of biological and sociocultural factors that lead to disparate health outcomes. The building blocks of this prevention model will include interdisciplinary prevention modalities that encourage partnerships across medical and nonmedical entities, community-based participatory research, development of ethnically and racially diverse research cohorts, and full actualization of the prevention benefits outlined in the 2010 Patient Protection and Affordable Care Act. However, the most essential facet should be a thoughtful integration of cancer prevention and screening into prevention, screening, and disease management activities for hypertension and diabetes mellitus because these chronic medical illnesses have a substantial prevalence in populations at risk for cancer disparities and cause considerable comorbidity and likely complicate effective treatment and contribute to disproportionate cancer death rates.

Age-related changes in microRNA levels in serum.

MicroRNAs (miRNAs) are small noncoding RNAs that post-transcriptionally regulate gene expression by targeting specific mRNAs. Altered expression of circulating miRNAs have been associated with age-related diseases including cancer and cardiovascular disease. Although we and others have found an age-dependent decrease in miRNA expression in peripheral blood mononuclear cells (PBMCs), little is known about the role of circulating miRNAs in human aging. Here, we examined miRNA expression in human serum from young (mean age 30 years) and old (mean age 64 years) individuals using next generation sequencing technology and real-time quantitative PCR. Of the miRNAs that we found to be present in serum, three were significantly decreased in 20 older individuals compared to 20 younger individuals: miR-151a-5p, miR-181a-5p and miR-1248. Consistent with our data in humans, these miRNAs are also present at lower levels in the serum of elderly rhesus monkeys. In humans, miR-1248 was found to regulate the expression of mRNAs involved in inflammatory pathways and miR-181a was found to correlate negatively with the pro-inflammatory cytokines IL-6 and TNFα and to correlate positively with the anti-inflammatory cytokines TGFß and IL-10. These results suggest that circulating miRNAs may be a biological marker of aging and could also be important for regulating longevity. Identification of stable miRNA biomarkers in serum could have great potential as a noninvasive diagnostic tool as well as enhance our understanding of physiological changes that occur with age.

Association of oxidative DNA damage and C-reactive protein in women at risk for cardiovascular disease.

OBJECTIVE: The aim of the current study was to examine the relationship between clinical markers of inflammation and 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG), an oxidative stress marker, in middle-aged women drawn from the HANDLS study, a longitudinal epidemiological study. METHODS AND RESULTS: We examined commonly assayed markers of inflammation, the DNA base adduct 8-oxodG, a marker of oxidative stress, and cardiovascular risk factors in a cohort of women matched on age and race in 3 groups (n=39 per group) who had low (<3 mg/L) high-sensitivity C-reactive protein (hsCRP), mid (>3-20 mg/L), and high (>20 mg/L) hsCRP. We found a significant relationship between hsCRP level and the oxidative stress marker, 8-oxodG. 8-oxodG was positively correlated with systolic blood pressure, pulse pressure, and interleukin-23. hsCRP was associated with obesity variables, high-density lipoprotein, serum insulin levels, interleukin-12p70 and intracellular adhesion molecule-1. Incubation of primary human endothelial cells with hsCRP generated reactive oxygen species in vitro. Furthermore, hsCRP specifically induced DNA base lesions, but not other forms of DNA damage, including single and double strand breaks. CONCLUSIONS: These data suggest that in women 8-oxodG is associated with hsCRP and is independently related to select cardiovascular risk factors. Our data in women suggest that hsCRP may contribute to cardiovascular disease by increasing oxidative stress.

Oxidative damage to DNA and single strand break repair capacity: relationship to other measures of oxidative stress in a population cohort.

It is well accepted that oxidative DNA repair capacity, oxidative damage to DNA and oxidative stress play central roles in aging and disease development. However, the correlation between oxidative damage to DNA, markers of oxidant stress and DNA repair capacity is unclear. In addition, there is no universally accepted panel of markers to assess oxidative stress in humans. Our interest is oxidative damage to DNA and its correlation with DNA repair capacity and other markers of oxidative stress. We present preliminary data from a small comet study that attempts to correlate single strand break (SSB) level with single strand break repair capacity (SSB-RC) and markers of oxidant stress and inflammation. In this limited study of four very small age-matched 24-individual groups of male and female whites and African-Americans aged 30-64 years, we found that females have higher single strand break (SSB) levels than males (p=0.013). There was a significant negative correlation between SSB-RC and SSB level (p=0.041). There was a positive correlation between SSBs in African American males with both heme degradation products (p=0.008) and high-sensitivity C-reactive protein (hs-CRP) (p=0.022). We found a significant interaction between hs-CRP and sex in their effect on residual DNA damage (p=0.002). Red blood cell reduced glutathione concentration was positively correlated with the levels of oxidized bases detected by endonuclease III (p=0.047), heme degradation products (p=0.015) and hs-CRP (p=0.020). However, plasma carbonyl levels showed no significant correlation with other markers. The data from the literature and from our very limited study suggest a complex relationship between measures of oxidative stress and frequently used clinical parameters believed to reflect inflammation or oxidative stress.

Recruitment and retention strategies for minority or poor clinical research participants: lessons from the Healthy Aging in Neighborhoods of Diversity across the Life Span study.

PURPOSE OF THE STUDY: Investigating health disparities requires studies designed to recruit and retain racially and socioeconomically diverse cohorts. It is critical to address the barriers that disproportionately affect participation in clinical research by minorities and the socioeconomically disadvantaged. This study sought to identify and rectify these barriers to recruit and retain a biracial (African American and non-Hispanic White) and socioeconomically diverse cohort for a longitudinal study. DESIGN AND METHOD: The Healthy Aging in Neighborhoods of Diversity across the Life Span study is a 20-year longitudinal examination of how race and socioeconomic status influence the development of age-related health disparities. One goal was to create a multifactorial recruitment and retention strategy. The recruitment paradigm targeted known barriers and identified those unique to the study's urban environment. The retention paradigm mirrored the recruitment plan but was based on specifically developed approaches. RESULTS: This cohort recruitment required attention to developing community partnerships, designing the research study to meet the study hypotheses and to provide benefit to participants, providing a safe community-based site for the research and creating didactics to develop staff cultural proficiency. These efforts facilitated study implementation and enhanced recruitment resulting in accrual of a biracial and socioeconomically diverse cohort of 3,722 participants. IMPLICATIONS: Recruiting and retaining minority or poor research participants is challenging but possible. The essential facets include clear communication of the research hypothesis, focus on providing a direct benefit for participants, and selection of a hypothesis that is directly relevant to the community studied.

microRNA expression patterns reveal differential expression of target genes with age.

Recent evidence supports a role for microRNAs (miRNAs) in regulating the life span of model organisms. However, little is known about how these small RNAs contribute to human aging. Here, we profiled the expression of over 800 miRNAs in peripheral blood mononuclear cells from young and old individuals by real-time RT-PCR analysis. This genome-wide assessment of miRNA expression revealed that the majority of miRNAs studied decreased in abundance with age. We identified nine miRNAs (miR-103, miR-107, miR-128, miR-130a, miR-155, miR-24, miR-221, miR-496, miR-1538) that were significantly lower in older individuals. Among them, five have been implicated in cancer pathogenesis. Predicted targets of several of these miRNAs, including PI3 kinase (PI3K), c-Kit and H2AX, were found to be elevated with advancing age, supporting a possible role for them in the aging process. Furthermore, we found that decreasing the levels of miR-221 was sufficient to cause a corresponding increase in the expression of the predicted target, PI3K. Taken together, these findings demonstrate that changes in miRNA expression occur with human aging and suggest that miRNAs and their predicted targets have the potential to be diagnostic indicators of age or age-related diseases.

Age, sex, and race influence single-strand break repair capacity in a human population.

Recently, we developed an improved comet assay protocol for evaluating single-strand break repair capacity (SSB-RC) in unstimulated cryopreserved human peripheral blood mononuclear cells (PBMCs). This methodology facilitates control of interexperimental variability [A.R. Trzeciak, J. Barnes, M.K. Evans, A modified alkaline comet assay for measuring DNA repair capacity in human populations. Radiat. Res. 169 (2008) 110-121]. The fast component of SSB repair (F-SSB-RC) was assessed using a novel parameter, the initial rate of DNA repair, and the widely used half-time of DNA repair. The slow component of SSB repair (S-SSB-RC) was estimated using the residual DNA damage after 60 min. We have examined repair of gamma-radiation-induced DNA damage in PBMCs from four age-matched groups of male and female whites and African-Americans between ages 30 and 64. There is an increase in F-SSB-RC with age in white females (P<0.01) and nonsignificant decrease in F-SSB-RC in African-American females (P=0.061). F-SSB-RC is lower in white females than in white males (P<0.01). There is a decrease in F-SSB-RC with age in African-American females as compared to white females (P<0.002) and African-American males (nonsignificant, P=0.059). Age, sex, and race had a similar effect on intercellular variability of DNA damage in gamma-irradiated and repairing PBMCs. Our findings suggest that age, sex, and race influence SSB-RC as measured by the alkaline comet assay. SSB-RC may be a useful clinical biomarker.