Glucose-6-phosphate dehydrogenase deficiency accelerates arterial aging in diabetes

AIMS

High glucose levels and Glucose-6-Phosphate Dehydrogenase deficiency (G6PDd) have both tissue inflammatory effects. Here we determined whether G6PDd accelerates arterial aging (information linked stiffening) in diabetes.

METHODS

Plasma glucose, interleukin 6 (IL6), and arterial stiffness (indexed as carotid-femoral Pulse Wave Velocity, PWV) and red blood cell G6PD activity were assessed in a large (4448) Sardinian population.

RESULTS

Although high plasma glucose in diabetics, did not differ by G6DP status (178.2 ± 55.1 vs 169.0 ± 50.1 mg/dl) in G6DPd versus non-G6PDd subjects, respectively, IL6, and PWV (adjusted for age and glucose) were significantly increased in G6PDd vs non-G6PDd subjects (PWV, 8.0 ± 0.4 vs 7.2 ± 0.2 m/sec) and (IL6, 6.9 ± 5.0 vs 4.2 ± 3.0 pg/ml). In non-diabetics, neither fasting plasma glucose, nor IL6, nor PWV were impacted by G6PDd.

CONCLUSION

G6PDd in diabetics is associated with increased inflammatory markers and accelerated arterial aging.

Age-dependent contribution of intrinsic mechanisms to sinoatrial node function in humans

Average beat interval (BI) and beat interval variability (BIV) are primarily determined by mutual entrainment between the autonomic-nervous system (ANS) and intrinsic mechanisms that govern sinoatrial node (SAN) cell function. While basal heart rate is not affected by age in humans, age-dependent reductions in intrinsic heart rate have been documented even in so-called healthy individuals. The relative contributions of the ANS and intrinsic mechanisms to age-dependent deterioration of SAN function in humans are not clear. We recorded ECG on patients (n = 16 < 21 years and n = 23 41-78 years) in the basal state and after ANS blockade (propranolol and atropine) in the presence of propofol and dexmedetomidine anesthesia. Average BI and BIV were analyzed. A set of BIV features were tested to designated the "signatures" of the ANS and intrinsic mechanisms and also the anesthesia "signature". In young patients, the intrinsic mechanisms and ANS mainly contributed to long- and short-term BIV, respectively. In adults, both ANS and intrinsic mechanisms contributed to short-term BIV, while the latter also contributed to long-term BIV. Furthermore, anesthesia affected ANS function in young patients and both mechanisms in adult. The work also showed that intrinsic mechanism features can be calculated from BIs, without intervention.

Prolonged fasting times reap greater geroprotective effects when combined with caloric restriction in adult female mice

Emerging new evidence highlights the importance of prolonged daily fasting periods for the health and survival benefits of calorie restriction (CR) and time-restricted feeding (TRF) in male mice; however, little is known about the impact of these feeding regimens in females. We placed 14-month-old female mice on five different dietary regimens, either CR or TRF with different feeding windows, and determined the effects of these regimens on physiological responses, progression of neoplasms and inflammatory diseases, serum metabolite levels, and lifespan. Compared with TRF feeding, CR elicited a robust systemic response, as it relates to energetics and healthspan metrics, a unique serum metabolomics signature in overnight fasted animals, and was associated with an increase in lifespan. These results indicate that daytime (rest-phase) feeding with prolonged fasting periods initiated late in life confer greater benefits when combined with imposed lower energy intake.

Photobiomodulation therapy mitigates cardiovascular aging and improves survival

BACKGROUND

Photobiomodulation (PBM) therapy, a form of low-dose light therapy, has been noted to be effective in several age-associated chronic diseases such as hypertension and atherosclerosis. Here, we examined the effects of PBM therapy on age-associated cardiovascular changes in a mouse model of accelerated cardiac aging.

METHODS

Fourteen months old Adenylyl cyclase type VIII (AC8) overexpressing transgenic mice (n = 8) and their wild-type (WT) littermates (n = 8) were treated with daily exposure to Near-Infrared Light (850 nm) at 25 mW/cm2 for 2 min each weekday for a total dose of 1 Einstein (4.5 p.J/cm2 or fluence 3 J/cm2 ) and compared to untreated controls over an 8-month period. PBM therapy was administered for 3.5 months (Early Treatment period), paused, due to Covid-19 restrictions for the following 3 months, and restarted again for 1.5 months. Serial echocardiography and gait analyses were performed at monthly intervals, and serum TGF-β1 levels were assessed following sacrifice.

RESULTS

During the Early Treatment period PBM treatments: reduced the age-associated increases in left ventricular (LV) mass in both genotypes (p = 0.0003), reduced the LV end-diastolic volume (EDV) in AC8 (p = 0.04); and reduced the left atrial dimension in both genotypes (p = 0.02). PBM treatments substantially increased the LV ejection fraction (p = 0.03), reduced the aortic wall stiffness (p = 0.001), and improved gait symmetry, an index of neuro-muscular coordination (p = 0.005). The effects of PBM treatments, measured following the pause, persisted. Total TGF-β1 levels were significantly increased in circulation (serum) in AC8 following PBM treatments (p = 0.01). We observed a striking increase in cumulative survival in PBM-treated AC8 mice (100%; p = 0.01) compared to untreated AC8 mice (43%).

CONCLUSION

PBM treatment mitigated age-associated cardiovascular remodeling and reduced cardiac function, improved neuromuscular coordination, and increased longevity in an experimental animal model. These responses correlate with increased TGF-β1 in circulation. Future mechanistic and dose optimization studies are necessary to assess these anti-aging effects of PBM, and validation in future controlled human studies is required for effective clinical translation.

A small erythropoietin derived non-hematopoietic peptide reduces cardiac inflammation, attenuates age associated declines in heart function and prolongs healthspan

Background

Aging is associated with increased levels of reactive oxygen species and inflammation that disrupt proteostasis and mitochondrial function and leads to organism-wide frailty later in life. ARA290 (cibinetide), an 11-aa non-hematopoietic peptide sequence within the cardioprotective domain of erythropoietin, mediates tissue protection by reducing inflammation and fibrosis. Age-associated cardiac inflammation is linked to structural and functional changes in the heart, including mitochondrial dysfunction, impaired proteostasis, hypertrophic cardiac remodeling, and contractile dysfunction. Can ARA290 ameliorate these age-associated cardiac changes and the severity of frailty in advanced age?

Methods

We conducted an integrated longitudinal (n = 48) and cross-sectional (n = 144) 15 months randomized controlled trial in which 18-month-old Fischer 344 x Brown Norway rats were randomly assigned to either receive chronic ARA290 treatment or saline. Serial echocardiography, tail blood pressure and body weight were evaluated repeatedly at 4-month intervals. A frailty index was calculated at the final timepoint (33 months of age). Tissues were harvested at 4-month intervals to define inflammatory markers and left ventricular tissue remodeling. Mitochondrial and myocardial cell health was assessed in isolated left ventricular myocytes. Kaplan-Meier survival curves were established. Mixed ANOVA tests and linear mixed regression analysis were employed to determine the effects of age, treatment, and age-treatment interactions.

Results

Chronic ARA290 treatment mitigated age-related increases in the cardiac non-myocyte to myocyte ratio, infiltrating leukocytes and monocytes, pro-inflammatory cytokines, total NF-κB, and p-NF-κB. Additionally, ARA290 treatment enhanced cardiomyocyte autophagy flux and reduced cellular accumulation of lipofuscin. The cardiomyocyte mitochondrial permeability transition pore response to oxidant stress was desensitized following chronic ARA290 treatment. Concurrently, ARA290 significantly blunted the age-associated elevation in blood pressure and preserved the LV ejection fraction. Finally, ARA290 preserved body weight and significantly reduced other markers of organism-wide frailty at the end of life.

Conclusion

Administration of ARA290 reduces cell and tissue inflammation, mitigates structural and functional changes within the cardiovascular system leading to amelioration of frailty and preserved healthspan.

Dilated hypertrophic phenotype of the carotid artery is associated with accelerated age-associated central arterial stiffening

Hypertrophic carotid geometric phenotypes (h-CGP) are predictors of incident cardiovascular disease (CVD). While arterial aging is hypothesized as a contributor to this associated risk, the association of CGPs with chronological age is not clear. In this manuscript we examine whether hypertrophic CGPs represent accelerated biological, rather than chronological, aging by examining their association with carotid-femoral pulse wave velocity (PWV), the hallmark of arterial aging. We analyzed data from 5516 participants of the SardiNIA study with a wide range of age at baseline (20-101 years), and a median follow-up time of 13 years (mean 11.5 years; maximum 17.9 years). Baseline CGPs were defined based on the common carotid lumen diameter, wall thickness, and their ratio. Subject-specific rates of change of PWV, blood pressure parameters, body mass index, glucose, and lipids were estimated using linear mixed effects models. Compared to those with typical(t-) CGP, those with dilated hypertrophy (dh-) CGP had a greater longitudinal increase in PWV; this increase was significantly greater among older individuals and men. The greater PWV longitudinal increase in dh-CGP remained significant after adjusting for baseline values and rates of change of covariates. Dilated hypertrophic CGP is independently associated with accelerated increase in age-associated arterial stiffening over time, with a strong association in men than in women. Future studies are needed to examine if this association mediates the increased risk for CVD observed in individuals with hypertrophic cardiac remodelling and the role of retarding it to reduce this risk. HIGHLIGHTS: • Individuals with dilated hypertrophic geometric phenotypes of the common carotid artery (increased age- and sex-specific wall thickness and lumen diameter) have greater future central arterial stiffening, independently of other determinants of arterial stiffening. • The dilated hypertrophic phenotype group has a greater age-specific arterial dilation, wall thickening, and stiffness (the arterial aging triad). This suggests that this phenotype is a form of accelerated aging that might explain the worse clinic outcomes observed in this group. • Understanding the natural history of the carotid geometric phenotype across the lifespan and the determinants of the deleterious progression towards the dilated hypertrophic phenotype are needed to develop interventions that reduce the adverse clinical outcomes associated with it.

Emergence of heartbeat frailty in advanced age I: perspectives from life-long EKG recordings in adult mice

The combined influences of sinoatrial nodal (SAN) pacemaker cell automaticity and its response to autonomic input determine the heart's beating interval variability and mean beating rate. To determine the intrinsic SAN and autonomic signatures buried within EKG RR interval time series change in advanced age, we measured RR interval variability before and during double autonomic blockade at 3-month intervals from 6 months of age until the end of life in long-lived (those that achieved the total cohort median life span of 24 months and beyond) C57/BL6 mice. Prior to 21 months of age, time-dependent changes in intrinsic RR interval variability and mean RR interval were relatively minor. Between 21 and 30 months of age, however, marked changes emerged in intrinsic SAN RR interval variability signatures, pointing to a reduction in the kinetics of pacemaker clock mechanisms, leading to reduced synchronization of molecular functions within and among SAN cells. This loss of high-frequency signal processing within intrinsic SAN signatures resulted in a marked increase in the mean intrinsic RR interval. The impact of autonomic signatures on RR interval variability were net sympathetic and partially compensated for the reduced kinetics of the intrinsic SAN RR interval variability signatures, and partially, but not completely, shifted the EKG RR time series intervals to a more youthful pattern. Cross-sectional analyses of other subsets of C57/BL6 ages indicated that at or beyond the median life span of our longitudinal cohort, noncardiac, constitutional, whole-body frailty was increased, energetic efficiency was reduced, and the respiratory exchange ratio increased. We interpret the progressive reduction in kinetics in intrinsic SAN RR interval variability signatures in this context of whole-body frailty beyond 21 months of age to be a manifestation of "heartbeat frailty."

Inflammatory Role of Milk Fat Globule-Epidermal Growth Factor VIII in Age-Associated Arterial Remodeling

Background

Age‐associated aortic remodeling includes a marked increase in intimal medial thickness (IMT), associated with signs of inflammation. Although aortic wall milk fat globule–epidermal growth factor VIII (MFG‐E8) increases with age, and is associated with aortic inflammation, it is not known whether MFG‐E8 is required for the age‐associated increase in aortic IMT. Here, we tested whether MFG‐E8 is required for the age‐associated increase in aortic IMT.

Methods and Results

To determine the role of MFG‐E8 in the age‐associated increase of IMT, we compared aortic remodeling in adult (20‐week) and aged (96‐week) MFG‐E8 (−/−) knockout and age matched wild‐type (WT) littermate mice. The average aortic IMT increased with age in the WT from 50±10 to 70±20 μm (P<0.0001) but did not significantly increase with age in MFG‐E8 knockout mice. Because angiotensin II signaling is implicated as a driver of age‐associated increase in IMT, we infused 30‐week‐old MFG‐E8 knockout and age‐matched littermate WT mice with angiotensin II or saline via osmotic mini‐pumps to determine whether MFG‐E8 is required for angiotensin II–induced aortic remodeling. (1) In WT mice, angiotensin II infusion substantially increased IMT, elastic lamina degradation, collagen deposition, and the proliferation of vascular smooth muscle cells; in contrast, these effects were significantly reduced in MFG‐E8 KO mice; (2) On a molecular level, angiotensin II treatment significantly increased the activation and expression of matrix metalloproteinase type 2, transforming growth factor beta 1, and its downstream signaling molecule phosphorylated mother against decapentaplegic homolog 2, and collagen type I production in WT mice; however, in the MFG‐E8 knockout mice, these molecular effects were significantly reduced; and (3) in WT mice, angiotensin II increased levels of aortic inflammatory markers phosphorylated nuclear factor‐kappa beta p65, monocyte chemoattractant protein 1, tumor necrosis factor alpha, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 molecular expression, while in contrast, these inflammatory markers did not change in knockout mice.

Conclusions

Thus, MFG‐E8 is required for both age‐associated proinflammatory aortic remodeling and also for the angiotensin II–dependent induction in younger mice of an aortic inflammatory phenotype observed in advanced age. Targeting MFG‐E8 would be a novel molecular approach to curb adverse arterial remodeling.

Effect of Cardiotonic Steroid Marinobufagenin on Vascular Remodeling and Cognitive Impairment in Young Dahl-S Rats

The hypertensive response in Dahl salt-sensitive (DSS) rats on a high-salt (HS) diet is accompanied by central arterial stiffening (CAS), a risk factor for dementia, and heightened levels of a prohypertensive and profibrotic factor, the endogenous Na/K-ATPase inhibitor marinobufagenin (MBG). We studied the effect of the in vivo administration of MBG or HS diet on blood pressure (BP), CAS, and behavioral function in young DSS rats and normotensive Sprague-Dawley rats (SD), the genetic background for DSS rats. Eight-week-old male SD and DSS rats were given an HS diet (8% NaCl, n = 18/group) or a low-salt diet (LS; 0.1% NaCl, n = 14-18/group) for 8 weeks or MBG (50 µg/kg/day, n = 15-18/group) administered via osmotic minipumps for 4 weeks in the presence of the LS diet. The MBG-treated groups received the LS diet. The systolic BP (SBP); the aortic pulse wave velocity (aPWV), a marker of CAS; MBG levels; spatial memory, measured by a water maze task; and tissue collection for the histochemical analysis were assessed at the end of the experiment. DSS-LS rats had higher SBP, higher aPWV, and poorer spatial memory than SD-LS rats. The administration of stressors HS and MBG increased aPWV, SBP, and aortic wall collagen abundance in both strains vs. their LS controls. In SD rats, HS or MBG administration did not affect heart parameters, as assessed by ECHO vs. the SD-LS control. In DSS rats, impaired whole-heart structure and function were observed after HS diet administration in DSS-HS vs. DSS-LS rats. MBG treatment did not affect the ECHO parameters in DSS-MBG vs. DSS-LS rats. The HS diet led to an increase in endogenous plasma and urine MBG levels in both SD and DSS groups. Thus, the prohypertensive and profibrotic effect of HS diet might be partially attributed to an increase in MBG. The prohypertensive and profibrotic functions of MBG were pronounced in both DSS and SD rats, although quantitative PCR revealed that different profiles of profibrotic genes in DSS and SD rats was activated after MBG or HS administration. Spatial memory was not affected by HS diet or MBG treatment in either SD or DSS rats. Impaired cognitive function was associated with higher BP, CAS, and cardiovascular remodeling in young DSS-LS rats, as compared to young SD-LS rats. MBG and HS had similar effects on the cardiovascular system and its function in DSS and SD rats, although the rate of change in SD rats was lower than in DSS rats. The absence of a cumulative effect of increased aPWV and BP on spatial memory can be explained by the cerebrovascular and brain plasticity in young rats, which help the animals to tolerate CAS elevated by HS and MBG and to counterbalance the profibrotic effect of heightened MBG.

Ankle-Brachial Index and Energy Production in People Without Peripheral Artery Disease: The BLSA

Background Lower ankle-brachial index (ABI) values within the 0.90 to 1.40 range are associated with poorer mitochondrial oxidative capacity of thigh muscles in cross-sectional analyses. Whether ABI decline is associated with greater declines in thigh muscle oxidative capacity with aging is unknown. Method and Results We analyzed data from 228 participants (100 men) of the BLSA (Baltimore Longitudinal Study of Aging), aged 39 to 97 years, with an ABI between 0.9 and 1.40 at baseline and at follow-up (mean follow-up period of 2.8 years). We examined mitochondrial oxidative capacity of the left thigh muscle, by measuring the postexercise phosphocreatine recovery rate constant (kPCr) from phosphorus-31 magnetic resonance spectroscopy. Greater kPCr indicated higher mitochondrial oxidative capacity. Although kPCr was available on the left leg only, ABI was measured in both legs. Longitudinal rates of change (Change) of left and right ABI and kPCr of the left thigh muscle were estimated using linear mixed effects models, and their association was analyzed by standardized multiple linear regressions. In multivariate analysis including sex, age, baseline kPCr, both left and right baseline ABI, and ABI change in both legs, (kPCr)Change was directly associated with ipsilateral (left) (ABI)Change (standardized [STD]-β=0.14; P=0.0168) but not with contralateral (right) (ABI)Change (P=0.22). Adjusting for traditional cardiovascular risk factors, this association remained significant (STD-β=0.18; P=0.0051). (kPCr)Change was steeper in White race participants (STD-β=0.16; P=0.0122) and body mass index (STD-β=0.13; P=0.0479). There was no significant association with current smoking status (P=0.63), fasting glucose (P=0.28), heart rate (P=0.67), mean blood pressure (P=0.78), and low-density lipoprotein (P=0.75), high-density lipoprotein (P=0.82), or triglycerides (P=0.15). Conclusions In people without peripheral arterial disease, greater decline in ABI over time, but not baseline ABI, was associated with faster decline in thigh mitochondrial oxidative capacity in the ipsilateral leg. Further studies are needed to examine whether early interventions that improve lower extremity muscle perfusion can improve and prevent the decline of muscle energetics.

A remarkable adaptive paradigm of heart performance and protection emerges in response to marked cardiac-specific overexpression of ADCY8

Adult (3 month) mice with cardiac-specific overexpression of adenylyl cyclase (AC) type VIII (TG^AC8) adapt to an increased cAMP-induced cardiac workload (~30% increases in heart rate, ejection fraction and cardiac output) for up to a year without signs of heart failure or excessive mortality. Here, we show classical cardiac hypertrophy markers were absent in TG^AC8, and that total left ventricular (LV) mass was not increased: a reduced LV cavity volume in TG^AC8 was encased by thicker LV walls harboring an increased number of small cardiac myocytes, and a network of small interstitial proliferative non-cardiac myocytes compared to wild type (WT) littermates; Protein synthesis, proteosome activity, and autophagy were enhanced in TG^AC8 vs WT, and Nrf-2, Hsp90α, and ACC2 protein levels were increased. Despite increased energy demands in vivo LV ATP and phosphocreatine levels in TG^AC8 did not differ from WT. Unbiased omics analyses identified more than 2,000 transcripts and proteins, comprising a broad array of biological processes across multiple cellular compartments, which differed by genotype; compared to WT, in TG^AC8 there was a shift from fatty acid oxidation to aerobic glycolysis in the context of increased utilization of the pentose phosphate shunt and nucleotide synthesis. Thus, marked overexpression of AC8 engages complex, coordinate adaptation "circuity" that has evolved in mammalian cells to defend against stress that threatens health or life (elements of which have already been shown to be central to cardiac ischemic pre-conditioning and exercise endurance cardiac conditioning) that may be of biological significance to allow for proper healing in disease states such as infarction or failure of the heart.

Ca2+ and Membrane Potential Transitions During Action Potentials Are Self-Similar to Each Other and to Variability of AP Firing Intervals Across the Broad Physiologic Range of AP Intervals During Autonomic Receptor Stimulation

Ca2+ and V m transitions occurring throughout action potential (AP) cycles in sinoatrial nodal (SAN) cells are cues that (1) not only regulate activation states of molecules operating within criticality (Ca2+ domain) and limit-cycle (V m domain) mechanisms of a coupled-clock system that underlies SAN cell automaticity, (2) but are also regulated by the activation states of the clock molecules they regulate. In other terms, these cues are both causes and effects of clock molecular activation (recursion). Recently, we demonstrated that Ca2+ and V m transitions during AP cycles in single SAN cells isolated from mice, guinea pigs, rabbits, and humans are self-similar (obey a power law) and are also self-similar to trans-species AP firing intervals (APFIs) of these cells in vitro, to heart rate in vivo, and to body mass. Neurotransmitter stimulation of β-adrenergic receptor or cholinergic receptor-initiated signaling in SAN cells modulates their AP firing rate and rhythm by impacting on the degree to which SAN clocks couple to each other, creating the broad physiologic range of SAN cell mean APFIs and firing interval variabilities. Here we show that Ca2+ and V m domain kinetic transitions (time to AP ignition in diastole and 90% AP recovery) occurring within given AP, the mean APFIs, and APFI variabilities within the time series of APs in 230 individual SAN cells are self-similar (obey power laws). In other terms, these long-range correlations inform on self-similar distributions of order among SAN cells across the entire broad physiologic range of SAN APFIs, regardless of whether autonomic receptors of these cells are stimulated or not and regardless of the type (adrenergic or cholinergic) of autonomic receptor stimulation. These long-range correlations among distributions of Ca2+ and V m kinetic functions that regulate SAN cell clock coupling during each AP cycle in different individual, isolated SAN cells not in contact with each other. Our numerical model simulations further extended our perspectives to the molecular scale and demonstrated that many ion currents also behave self-similar across autonomic states. Thus, to ensure rapid flexibility of AP firing rates in response to different types and degrees of autonomic input, nature "did not reinvent molecular wheels within the coupled-clock system of pacemaker cells," but differentially engaged or scaled the kinetics of gears that regulate the rate and rhythm at which the "wheels spin" in a given autonomic input context.

A cross-sectional study of functional and metabolic changes during aging through the lifespan in male mice

Aging is associated with distinct phenotypical, physiological, and functional changes, leading to disease and death. The progression of aging-related traits varies widely among individuals, influenced by their environment, lifestyle, and genetics. In this study, we conducted physiologic and functional tests cross-sectionally throughout the entire lifespan of male C57BL/6N mice. In parallel, metabolomics analyses in serum, brain, liver, heart, and skeletal muscle were also performed to identify signatures associated with frailty and age-dependent functional decline. Our findings indicate that declines in gait speed as a function of age and frailty are associated with a dramatic increase in the energetic cost of physical activity and decreases in working capacity. Aging and functional decline prompt organs to rewire their metabolism and substrate selection and toward redox-related pathways, mainly in liver and heart. Collectively, the data provide a framework to further understand and characterize processes of aging at the individual organism and organ levels.

Impact of Stiffer Arteries on the Response to Antihypertensive Treatment: A Longitudinal Study of the SardiNIA Cohort

OBJECTIVES

Carotid-femoral pulse wave velocity (PWV), an index of arterial stiffness and a proxy of arterial aging, has been reported to be an independent determinant of cardiovascular health. Whether the effects of antihypertensive treatment vary in the presence of accelerated arterial aging (stiffer artery, ie, PWV >10 m/s) has not been established. We tested this hypothesis in a longitudinal study in a large community-dwelling population.

DESIGN

Longitudinal population study with repeated measures.

SETTING AND PARTICIPANTS

Study population consisted of a cohort of 6011 volunteers (2546 men and 3465 women, age range 14-101 years; 15,011 observations over a median follow-up of 6.8 years) participating in the SardiNIA Study.

MEASURES

Repeated measures of PWV, blood pressure (BP), and metabolic risk factors and the antihypertensive medication trajectories of BP and PWV over time were assessed via mixed effects models.

RESULTS

Antihypertensive treatment significantly affected the trajectory of BP in both participants with (-0.47 ± 0.20 mmHg/y, P = .02) and participants without stiffer arteries (-0.47 ± 0.07 mmHg/y, P = .001). They also affected the trajectory of PWV in participants with stiffer artery, independent of the BP values.

CONCLUSIONS AND IMPLICATIONS

Antihypertensive treatment is effective in reducing both BP and PWV in older individuals with stiffer arteries.

Subclinical Longitudinal Change in Ankle-Brachial Index With Aging in a Community-Dwelling Population Is Associated With Central Arterial Stiffening

Background Aging is associated with a modest decline in ankle-brachial index (ABI); however, the underpinnings of this decline are not fully understood. The greater systolic ankle than brachial blood pressure, a normal ABI implies, is partially attributed to lower central than peripheral arterial stiffness. Hence, we examined the hypothesis that the age-associated decline in ABI is associated with central arterial stiffening with aging, assessed by pulse wave velocity. Methods and Results We analyzed longitudinal data from 974 participants aged 27 to 95 years from the Baltimore Longitudinal Study of Aging who were free of clinically significant cardiovascular disease. Participants had an average of 4 visits with a 6.8-year average follow-up time. Linear mixed-effects models showed that the average ABI decline beyond the age of 70 years was 0.03 per decade. In multiple regression analysis, the ABI rate of change was inversely associated with initial age (standardized β=-0.0711, P=0.0282), independent of peripheral disease factors and baseline ABI. After adjustment, the pulse wave velocity rate of change was inversely associated with ABI rate of change (standardized β=-0.0993, P=0.0040), rendering the association of the latter with initial age nonsignificant (standardized β=-0.0265, P=0.5418). Conclusions A modest longitudinal decline in ABI beyond the age of 70 years was shown to be independent of traditional risk factors for peripheral arterial disease but was accounted for by an increase in pulse wave velocity. A modest decline in ABI with aging might be a manifestation of changes in central hemodynamics and not necessarily attributable to peripheral flow-limiting factors.

Overexpression of a Neuronal Type Adenylyl Cyclase (Type 8) in Sinoatrial Node Markedly Impacts Heart Rate and Rhythm

Heart rate (HR) and HR variability (HRV), predictors of over-all organism health, are widely believed to be driven by autonomic input to the sinoatrial node (SAN), with sympathetic input increasing HR and reducing HRV. However, variability in spontaneous beating intervals in isolated SAN tissue and single SAN cells, devoid of autonomic neural input, suggests that clocks intrinsic to SAN cells may also contribute to HR and HRV in vivo. We assessed contributions of both intrinsic and autonomic neuronal input mechanisms of SAN cell function on HR and HRV via in vivo, telemetric EKG recordings. This was done in both wild type (WT) mice, and those in which adenylyl cyclase type 8 (ADCY8), a main driver of intrinsic cAMP-PKA-Ca²⁺ mediated pacemaker function, was overexpressed exclusively in the heart (TG^AC8). We hypothesized that TG^AC8 mice would: (1) manifest a more coherent pattern of HRV in vivo, i.e., a reduced HRV driven by mechanisms intrinsic to SAN cells, and less so to modulation by autonomic input and (2) utilize unique adaptations to limit sympathetic input to a heart with high levels of intrinsic cAMP-Ca²⁺ signaling. Increased adenylyl cyclase (AC) activity in TG^AC8 SAN tissue was accompanied by a marked increase in HR and a concurrent marked reduction in HRV, both in the absence or presence of dual autonomic blockade. The marked increase in intrinsic HR and coherence of HRV in TG^AC8 mice occurred in the context of: (1) reduced HR and HRV responses to β-adrenergic receptor (β-AR) stimulation; (2) increased transcription of genes and expression of proteins [β-Arrestin, G Protein-Coupled Receptor Kinase 5 (GRK5) and Clathrin Adaptor Protein (Dab2)] that desensitize β-AR signaling within SAN tissue, (3) reduced transcripts or protein levels of enzymes [dopamine beta-hydorxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT)] required for catecholamine production in intrinsic cardiac adrenergic cells, and (4) substantially reduced plasma catecholamine levels. Thus, mechanisms driven by cAMP-PKA-Ca²⁺ signaling intrinsic to SAN cells underlie the marked coherence of TG^AC8 mice HRV. Adaptations to limit additional activation of AC signaling, via decreased neuronal sympathetic input, are utilized to ensure the hearts survival and prevent Ca²⁺ overload.

Prostate-Specific Antigen Trends Predict the Probability of Prostate Cancer in a Very Large U.S. Veterans Affairs Cohort

If prostate-specific antigen (PSA) trends help identify elevated prostate cancer (PCa) risk, they might provide early warning of progressing cancer for further evaluation and justify annual testing. Our objective was to determine whether PSA trends predict PCa likelihood. A biopsy cohort of 361,657 men was obtained from a Veterans Affairs database (1999–2012). PSA trends were estimated for the 310,458 men with at least 2 PSA tests prior to biopsy. Cancer tumors may grow exponentially with cells doubling periodically. We hypothesized that PSA from prostate cancer grows exponentially above a no cancer baseline. We estimated PSA trends on that basis along with five descriptive variables: last PSA before biopsy, growth rate in PSA from cancer above a baseline, PSA variability around the trend, number of PSA tests, and time span of tests. PSA variability is a new variable that measures percentage deviations of PSA tests from estimated trends with 0% variability for a smoothly increasing trend. Logistic regression models were used to estimate relationships between the probability of PCa at biopsy and the trend variables and age. All five PSA trend variables and age were significant predictors of prostate cancer at biopsy (p < 0.0001). An overall logistic regression model achieved an AUC of 0.67 for men with at least 4 tests over at least 3 years, which was a substantial improvement over a single PSA (AUC 0.58). High probability of PCa was associated with low PSA variability (smooth trends), high PSA, high growth rate, many tests over a long time-span and older age. For example, at 4.0 PSA the probability of cancer is 32% for 1 PSA test and increases to 68% for 8 tests over 7 years with smooth, fast growth (0% variability and 50% exponential growth). Our results show that smooth, fast exponential growth in PSA above a baseline predicts an increased probability of PCa. The probability increases as smooth (low variability) trends are observed for more tests over a longer time span, which makes annual testing worth considering. Worrisome PSA trends might be used to trigger further evaluation and continued monitoring of the trends—even at low PSA levels.

Age and Prostate-Specific Antigen Level Prior to Diagnosis Predict Risk of Death from Prostate Cancer

A single early prostate-specific antigen (PSA) level has been correlated with a higher likelihood of prostate cancer diagnosis and death in younger men. PSA testing in older men has been considered of limited utility. We evaluated prostate cancer death in relation to age and PSA level immediately prior to prostate cancer diagnosis. Using the Veterans Affairs database, we identified 230,081 men aged 50-89 years diagnosed with prostate cancer and at least one prior PSA test between 1999 and 2009. Prostate cancer-specific death over time was calculated for patients stratified by age group (e.g., 50-59 years, through 80-89 years) and PSA range at diagnosis (10 ranges) using Kaplan-Meier methods. Risk of 10-year prostate cancer mortality across age and PSA was compared using log-rank tests with a Bonferroni adjustment for multiple testing. 10.5% of men diagnosed with prostate cancer died of cancer during the 10-year study period (mean follow-up = 3.7 years). Higher PSA values prior to diagnosis predict a higher risk of death in all age groups (p < 0.0001). Within the same PSA range, older age groups are at increased risk for death from prostate cancer (p < 0.0001). For PSA of 7-10 ng/mL, cancer-specific death, 10 years after diagnosis, increased from 7% for age 50-59 years to 51% for age 80-89 years. Men older than 70 years are more likely to die of prostate cancer at any PSA level than younger men, suggesting prostate cancer remains a significant problem among older men (even those aged 80+) and deserves additional study.

Stochasticity intrinsic to coupled-clock mechanisms underlies beat-to-beat variability of spontaneous action potential firing in sinoatrial node pacemaker cells

Recent evidence indicates that the spontaneous action potential (AP) of isolated sinoatrial node cells (SANCs) is regulated by a system of stochastic mechanisms embodied within two clocks: ryanodine receptors of the "Ca(2+) clock" within the sarcoplasmic reticulum, spontaneously activate during diastole and discharge local Ca(2+) releases (LCRs) beneath the cell surface membrane; clock crosstalk occurs as LCRs activate an inward Na(+)/Ca(2+) exchanger current (INCX), which together with If and decay of K(+) channels prompts the "M clock," the ensemble of sarcolemmal-electrogenic molecules, to generate APs. Prolongation of the average LCR period accompanies prolongation of the average AP beating interval (BI). Moreover, the prolongation of the average AP BI accompanies increased AP BI variability. We hypothesized that both the average AP BI and AP BI variability are dependent upon stochasticity of clock mechanisms reported by the variability of LCR period. We perturbed the coupled-clock system by directly inhibiting the M clock by ivabradine (IVA) or the Ca(2+) clock by cyclopiazonic acid (CPA). When either clock is perturbed by IVA (3, 10 and 30 μM), which has no direct effect on Ca(2+) cycling, or CPA (0.5 and 5 μM), which has no direct effect on the M clock ion channels, the clock system failed to achieve the basal AP BI and both AP BI and AP BI variability increased. The changes in average LCR period and its variability in response to perturbations of the coupled-clock system were correlated with changes in AP beating interval and AP beating interval variability. We conclude that the stochasticity within the coupled-clock system affects and is affected by the AP BI firing rate and rhythm via modulation of the effectiveness of clock coupling.

Longitudinal perspective on the conundrum of central arterial stiffness, blood pressure, and aging

The age-associated increase in arterial stiffness has long been considered to parallel or to cause the age-associated increase in blood pressure (BP). Yet, the rates at which pulse wave velocity (PWV), a measure of arterial stiffness, and BP trajectories change over time within individuals who differ by age and sex have not been assessed and compared. This study determined the evolution of BP and aortic PWV trajectories during a 9.4-year follow-up in >4000 community-dwelling men and women of 20 to 100 years of age at entry into the SardiNIA Study. Linear mixed effects model analyses revealed that PWV accelerates with time during the observation period, at about the same rate over the entire age range in both men and women. In men, the longitudinal rate at which BP changed over time, however, did not generally parallel that of PWV acceleration: at ages>40 years the rates of change in systolic BP (SBP) and pulse pressure (PP) increase plateaued and then declined so that SBP, itself, also declined at older ages, whereas PP plateaued. In women, SBP, diastolic BP, and mean BP increased at constant rates across all ages, producing an increasing rate of increase in PP. Therefore, increased aortic stiffness is implicated in the age-associated increase in SBP and PP. These findings indicate that PWV is not a surrogate for BP and that arterial properties other than arterial wall stiffness that vary by age and sex also modulate the BP trajectories during aging and lead to the dissociation of PWV, PP, and SBP trajectories in men.

The N-glycoform of sRAGE is the key determinant for its therapeutic efficacy to attenuate injury-elicited arterial inflammation and neointimal growth

Signaling of the receptor for advanced glycation end products (RAGE) has been implicated in the development of injury-elicited vascular complications. Soluble RAGE (sRAGE) acts as a decoy of RAGE and has been used to treat pathological vascular conditions in animal models. However, previous studies used a high dose of sRAGE produced in insect Sf9 cells (sRAGE(Sf9))and multiple injections to achieve the therapeutic outcome. Here, we explore whether modulation of sRAGE N-glycoform impacts its bioactivity and augments its therapeutic efficacy. We first profiled carbohydrate components of sRAGE produced in Chinese hamster Ovary cells (sRAGE(CHO)) to show that a majority of its N-glycans belong to sialylated complex types that are not shared by sRAGE(Sf9). In cell-based NF-κB activation and vascular smooth muscle cell (VSMC) migration assays, sRAGE(CHO) exhibited a significantly higher bioactivity relative to sRAGE(Sf9) to inhibit RAGE alarmin ligand-induced NF-κB activation and VSMC migration. We next studied whether this N-glycoform-associated bioactivity of sRAGE(CHO) is translated to higher in vivo therapeutic efficacy in a rat carotid artery balloon injury model. Consistent with the observed higher bioactivity in cell assays, sRAGE(CHO) significantly reduced injury-induced neointimal growth and the expression of inflammatory markers in injured vasculature. Specifically, a single dose of 3 ng/g of sRAGE(CHO) reduced neointimal hyperplasia by over 70%, whereas the same dose of sRAGE(Sf9) showed no effect. The administered sRAGE(CHO) is rapidly and specifically recruited to the injured arterial locus, suggesting that early intervention of arterial injury with sRAGE(CHO) may offset an inflammatory circuit and reduce the ensuing tissue remodeling. Our findings showed that the N-glycoform of sRAGE is the key determinant underlying its bioactivity and thus is an important glycobioengineering target to develop a highly potent therapeutic sRAGE for future clinical applications.

KEY MESSAGE

The specific N-glycoform modification is the key underlying sRAGE bioactivity Markedly reduced sRAGE dose to attenuate neointimal hyperplasia and inflammation Provide a molecular target for glycobioengineering of sRAGE as a therapeutic protein Blocking RAGE alarmin ligands during acute injury phase offsets neointimal growth.

Resveratrol improves adipose insulin signaling and reduces the inflammatory response in adipose tissue of rhesus monkeys on high-fat, high-sugar diet

Obesity is associated with a chronic, low-grade, systemic inflammation that may contribute to the development of insulin resistance and type 2 diabetes. Resveratrol, a natural compound with anti-inflammatory properties, is shown to improve glucose tolerance and insulin sensitivity in obese mice and humans. Here, we tested the effect of a 2-year resveratrol administration on proinflammatory profile and insulin resistance caused by a high-fat, high-sugar (HFS) diet in white adipose tissue (WAT) from rhesus monkeys. Resveratrol supplementation (80 and 480 mg/day for the first and second year, respectively) decreased adipocyte size, increased sirtuin 1 expression, decreased NF-κB activation, and improved insulin sensitivity in visceral, but not subcutaneous, WAT from HFS-fed animals. These effects were reproduced in 3T3-L1 adipocytes cultured in media supplemented with serum from monkeys fed HFS ± resveratrol diets. In conclusion, chronic administration of resveratrol exerts beneficial metabolic and inflammatory adaptations in visceral WAT from diet-induced obese monkeys.

Testing the product of slopes in related regressions

A study was conducted of the relationships among neuroprotective factors and cytokines in brain tissue of mice at different ages that were examined on the effect of dietary restriction on protection after experimentally induced brain stroke. It was of interest to assess whether the cross-product of the slopes of pairs of variables vs. age was positive or negative. To accomplish this, the product of the slopes was estimated and tested to determine if it is significantly different from zero. Since the measurements are taken on the same animals, the models used must account for the non-independence of the measurements within animals. A number of approaches are illustrated. First a multivariate multiple regression model is employed. Since we are interested in a nonlinear function of the parameters (the product) the delta method is used to obtain the standard error of the estimate of the product. Second, a linear mixed-effects model is fit that allows for the specification of an appropriate correlation structure among repeated measurements. The delta method is again used to obtain the standard error. Finally, a non-linear mixed-effects approach is taken to fit the linear-mixed-effects model and conduct the test. A simulation study investigates the properties of the procedure.

Design Issues in Longitudinal Studies

In designing a longitudinal study one needs to decide on two critical components: duration of study and frequency of visits. In addition, other issues involving sample size, power, number of observations per subject must be addressed. If the study is meant to be completed within a certain time frame, would it better to have a fixed time between observations (which might allow the study to terminate early if its objectives are met) or to spread out the observations over the entire study period? At some point during the study, it may be of interest to see if additional data points would contribute substantially. Assume that the longitudinal data will be analyzed using a linear mixed-effects model. In this investigation we use the standard errors of estimates of model parameters as the criterion. We seek to address the issues using three approaches. First, subsets of a data set are constructed in a number of ways and the standard errors are examined. Second, using a variety of designs, the covariance matrix of the fixed-effects is computed and the standard errors are examined. Finally, a simulation study is conducted.

Abstract 167: Predictors of Anxiety Disorder Episodes and Device Related Distress in the First Five Years following Implantable Cardioverter Defibrillator Placement

Trait anxiety is a dispositional factor that predisposes individuals to respond to perceived threats with more frequent and intense elevations in emotional states associated with arousal of the autonomic nervous system, which is thought to lead to the development of anxiety disorders. Trait anxiety has demonstrated promise in the empirical literature as a potential predictor of long term outcomes in ICD recipients. The present study adds novel information to this body of literature by studying the relation of trait anxiety to clinical diagnoses of anxiety disorders based on the Structured Clinical Interview for DSM-IV-TR Axis I Disorders (SCID).

Two hundred and seven recipients of ICDs within the past five years were evaluated using the SCID to establish past and current anxiety disorder diagnoses. Self-report questionnaires were administered to assess device-related appraisals and functional impairment. Participants were 70% (n=144/207) male, 63% (n=130/207) married and 29% currently working (60/207) with a mean age of 63.0 (±12.3) years. Ninety-seven (47%) shocked and 110 (53%) non-shocked ICD recipients were interviewed.

ICD recipients high in trait anxiety (n = 59/207, 29%) had significantly higher rates of current episodes of obsessive compulsive disorder (χ 2 = 9.05; p<.01), and anxiety disorder due to a general medical condition (GMC; χ 2 = 6.38; p<.05) during the first five years post ICD implant in comparison to those low in trait anxiety (n=147/207, 71%). Additionally, ICD recipients high in trait anxiety had significantly higher rates of a history of episodes of anxiety disorder due to GMC (χ 2 = 9.05; p<.001).

ICD recipients high in trait anxiety (n = 59, 29%) reported greater device-related distress ( t = 5.65;p<.001), greater body image concerns ( t =2.39;p<.01), and greater fear of shock ( t = -3.98;p<.001), as well as fewer positive perceptions of their ICD ( t = 2.39; p<.05). Moreover, ICD recipients high in trait anxiety reported greater functional limitations ( t = 5.69; p<.001), and greater perceptions of disability in work, social, and family life ( t = -4.09; p<.001).

Women (n=63/207; 30%) reported greater mean levels of trait anxiety ( t = -2.10; p<.05) and fear of shock ( t = -2.41; p<.05) in comparison to men. Individuals who met criteria for current panic disorder ( t = 2.86; p<.01), agoraphobia ( t = 4.78; p<.001), social phobia ( t = 3.04; p<.05), posttraumatic stress disorder ( t = 3.82; p<.01), and anxiety due to GMC ( t = 3.94; p<.001) were significantly younger than those without these diagnoses.

The results from the current study suggest that assessment of trait anxiety may help clinicians identify individuals at risk for poor adjustment following ICD placement, even before implantation. Early identification of risk for maladjustment via pre-implant predictors might allow ICD recipients to enjoy the full benefits associated with these devices - longer and better quality of life.

Screening for prostate cancer using multivariate mixed-effects models

Using several variables known to be related to prostate cancer, a multivariate classification method is developed to predict the onset of clinical prostate cancer. A multivariate mixed-effects model is used to describe longitudinal changes in prostate specific antigen (PSA), a free testosterone index (FTI), and body mass index (BMI) before any clinical evidence of prostate cancer. The patterns of change in these three variables are allowed to vary depending on whether the subject develops prostate cancer or not and the severity of the prostate cancer at diagnosis. An application of Bayes' theorem provides posterior probabilities that we use to predict whether an individual will develop prostate cancer and, if so, whether it is a high-risk or a low-risk cancer. The classification rule is applied sequentially one multivariate observation at a time until the subject is classified as a cancer case or until the last observation has been used. We perform the analyses using each of the three variables individually, combined together in pairs, and all three variables together in one analysis. We compare the classification results among the various analyses and a simulation study demonstrates how the sensitivity of prediction changes with respect to the number and type of variables used in the prediction process.

Associations of large artery structure and function with adiposity: effects of age, gender, and hypertension. The SardiNIA Study

In the context of obesity epidemic, no large population study has extensively investigated the relationships between total and abdominal adiposity and large artery structure and function nor have such relationships been examined by gender, by age, by hypertensive status. We investigated these potential relationships in a large cohort of community dwelling volunteers participating the SardiNIA Study.

METHODS AND RESULTS

Total and visceral adiposity and arterial properties were assessed in 6148 subjects, aged 14-102 in a cluster of 4 towns in Sardinia, Italy. Arterial stiffness was measured as aortic pulse wave velocity (PWV), arterial thickness and lumen as common carotid artery (CCA) intima-media thickness (IMT) and diameter, respectively. We reported a nonlinear relationship between total and visceral adiposity and arterial stiffness, thickness, and diameter. The association between adiposity and arterial properties was steeper in women than in men, in younger than in older subjects. Waist correlated with arterial properties better than BMI. Within each BMI quartile, increasing waist circumference was associated with further significant changes in arterial structure and function.

CONCLUSION

The relationship between total or abdominal adiposity and arterial aging (PWV and CCA IMT) is not linear as described in the current study. Therefore, BMI- and/or waist-specific reference values for arterial measurements might need to be defined.

A pedometer-based intervention to improve physical activity, fitness, and coronary heart disease risk in National Guard personnel

To compare the effects of a pedometer-based behavioral intervention (Fitness for Life [FFL] program) and a traditional high-intensity fitness (TRAD) program on physical activity (PA), Army Physical Fitness Test (APFT), and coronary heart disease risk factors in Army National Guard members who failed the APFT 2-mile run. From a pool of 261 Army National Guard, a total of 156 were randomized to TRAD or FFL for 24 weeks consisting of a 12-week progressive conditioning program followed by 12 weeks of maintenance. For both groups, the total APFT score and 2-mile run time/score improved from baseline to 12 weeks (FFL: down 7.4%, p = 0.03; TRAD: down 5%, p = 0.08) but at 24 weeks they had regressed toward baseline. PA improved modestly and coronary risk profile changed minimally in both groups. A pedometer-based exercise intervention had results similar to a high-intensity program for improving PA, APFT, and 2-mile run times/score. Neither group sustained the improved run times over the 12 weeks of maintenance.

Age and energy intake interact to modify cell stress pathways and stroke outcome

OBJECTIVE

Age and excessive energy intake/obesity are risk factors for cerebrovascular disease, but it is not known if and how these factors affect the extent of brain damage and outcome in ischemic stroke. We therefore determined the interactions of age and energy intake on the outcome of ischemic brain injury, and elucidated the underlying mechanisms.

METHODS

We utilized a novel microchip-based immunoaffinity capillary electrophoresis technology to measure a panel of neurotrophic factors, cytokines, and cellular stress resistance proteins in brain tissue samples from young, middle-aged, and old mice that had been maintained on control or energy-restricted diets prior to middle cerebral artery occlusion and reperfusion.

RESULTS

Mortality from focal ischemic stroke was increased with advancing age and reduced by an intermittent fasting (IF) diet. Brain damage and functional impairment were reduced by IF in young and middle-aged mice, but not in old mice. The basal and poststroke levels of neurotrophic factors (brain-derived neurotrophic factor and basic fibroblast growth factor), protein chaperones (heat shock protein 70 and glucose regulated protein 78), and the antioxidant enzyme heme oxygenase-1 were decreased, whereas levels of inflammatory cytokines were increased in the cerebral cortex and striatum of old mice compared with younger mice. IF coordinately increased levels of protective proteins and decreased inflammatory cytokines in young, but not in old mice.

INTERPRETATION

Reduction in dietary energy intake differentially modulates neurotrophic and inflammatory pathways to protect neurons against ischemic injury, and these beneficial effects of IF are compromised during aging, resulting in increased brain damage and poorer functional outcome.

Modeling a Cross-Sectional Response Variable with Longitudinal Predictors: An Example of Pulse Pressure and Pulse Wave Velocity

We wish to model pulse wave velocity (PWV) as a function of longitudinal measurements of pulse pressure (PP) at the same and prior visits at which the PWV is measured. A number of approaches are compared. First, we use the PP at the same visit as the PWV in a linear regression model. In addition, we also use the average of all available PP's as the explanatory variable in a linear regression model. Next, a two-stage process is applied. The longitudinal PP is modeled using a linear mixed-effects model. This modeled PP is used in the regression model to describe PWV. An approach for using the longitudinal PP data is to obtain a measure of cumulative burden, the area under the PP curve (AUC). This AUC is used as an explanatory variable to model PWV. Finally, a joint Bayesian model is constructed similar to the two-stage model.

Longitudinal paths to the metabolic syndrome: can the incidence of the metabolic syndrome be predicted? The Baltimore Longitudinal Study of Aging

OBJECTIVE

To determine the predictors of incidence of metabolic syndrome (MetS) (Adult Treatment Panel III criteria) and to determine if longitudinal changes in specific MetS components differ by age or gender in participants who developed versus those who did not develop MetS.

METHODS

A total of 506 men and 461 women (baseline age 52.4 +/- 17.5 years) from the Baltimore Longitudinal Study on Aging (BLSA) were followed longitudinally (at least two study visits), and censored when they developed the MetS or reported use of antihypertensive or lipid-lowering medications.

RESULTS

After a follow-up period of 6 years, the incidence of the MetS was 25.5% in men and 14.8% in women. As many as 66% of men and 73% of women with one or two altered MetS components at baseline did not develop the MetS. Predictors of developing MetS were higher baseline abdominal obesity or triglycerides and lower high-density lipoprotein cholesterol (area under receiver-operated curve [AUC] = 0.84 in men, 0.88 in women). Addition of the rate of changes in MetS components over time slightly improved predictive accuracy (AUC = 0.94 in men, 0.92 in women). Men were more likely than women to have the MetS without obesity, whereas women were more likely than men to have the MetS without an altered glucose metabolism.

CONCLUSIONS

The patterns of MetS components and the longitudinal changes that lead to the MetS are different in men and women. Interestingly, components with the highest prevalence prior to MetS development, such as elevated blood pressure, are not necessarily the stronger risk factors.

Model choice can obscure results in longitudinal studies

BACKGROUND

This article examines how different parameterizations of age and time in modeling observational longitudinal data can affect results.

METHODS

When individuals of different ages at study entry are considered, it becomes necessary to distinguish between longitudinal and cross-sectional differences to overcome possible selection biases.

RESULTS

Various models were fitted using data from longitudinal studies with participants with different ages and different follow-up lengths. Decomposing age into two components-age at entry into the study (first age) and the longitudinal follow-up (time) compared with considering age alone-leads to different conclusions.

CONCLUSIONS

In general, models using both first age and time terms performed better, and these terms are usually necessary to correctly analyze longitudinal data.

Endogenous sodium pump inhibitors and age-associated increases in salt sensitivity of blood pressure in normotensives

Factors that mediate increases in salt sensitivity of blood pressure with age remain to be clarified. The present study investigated 1) the effects of high-NaCl intake on two Na pump inhibitors, endogenous ouabain (EO) and marinobufagenin (MBG), in middle-aged and older normotensive Caucasian women; and 2) whether individual differences in EO and MBG are linked to variations in sodium excretion or salt sensitivity. A change from 6 days of a lower (0.7 mmol.kg(-1).day(-1))- to 6 days of a higher (4 mmol.kg(-1).day(-1))-NaCl diet elicited a sustained increase in MBG excretion that directly correlated with an increase in the fractional Na excretion and was inversely related to age and to an age-dependent increase in salt sensitivity. In contrast, EO excretion increased only transiently in response to NaCl loading and did not vary with age or correlate with fractional Na excretion or salt sensitivity. A positive correlation of both plasma and urine levels of EO and MBG during salt loading may indicate a casual link between two Na pump inhibitors in response to NaCl loading, as observed in animal models. A linear mixed-effects model demonstrated that age, dietary NaCl, renal MBG excretion, and body mass index were each independently associated with systolic blood pressure. Thus, a sustained increase in MBG in response to acutely elevated dietary NaCl is inversely linked to salt sensitivity in normotensive middle-aged and older women, and a relative failure of MBG elaboration by these older persons may be involved in the increased salt sensitivity with advancing age.

Changes in leisure time physical activity and risk of all-cause mortality in men and women: the Baltimore Longitudinal Study of Aging

BACKGROUND

Higher levels of leisure time physical activity (LTPA) are associated with reduced mortality. However it is unclear how changes in LTPA over time impact all-cause mortality in men and women.

METHODS

From 1958 to 1996 for men (n=1316) and 1978 to 1996 for women (n=776), participants aged 19-90+ years from the Baltimore Longitudinal Study of Aging (Baltimore, MD) were assessed for LTPA at baseline and at approximately 2-year intervals over a mean follow-up of 21.2+/-9.4 years for men and 10.2+/-5.6 years for women. Death occurred in 538 men and 90 women. LTPA was derived from self-reports of time spent in 97 activities converted into MET-min per 24 h and was further grouped into high-, moderate- and low-intensity LTPA. The longitudinal data was analyzed using mixed effects models to determine the rate of change in LTPA at each assessment. Proportional hazard models were used to assess the associations between LTPA at baseline and rate of change in LTPA with all-cause mortality.

RESULTS

In younger (<70 years) men, those who reported increases or negligible declines in total and high-intensity LTPA had lower all-cause mortality compared to those with greater declines in LTPA. In older (>or=70 years) men, the association between rate of change in high-intensity LTPA and mortality was similar to that seen in younger men. For women, longitudinal analyses showed neither rates of change in total, high-, moderate- nor low-intensity LTPA were predictive of mortality.

CONCLUSIONS

In this health-conscious population, greater longitudinal declines in total and high-intensity LTPA are independent predictors of all-cause mortality in men.

ANP differentially modulates marinobufagenin-induced sodium pump inhibition in kidney and aorta

NaCl loading and plasma volume expansion stimulate 2 natriuretic systems, vasoconstrictor, digitalis-like Na/K-ATPase inhibitors and vasorelaxant ANP peptides. Several hormones, including ANP, regulate activity of the Na/K-ATPase by modulation of its phosphorylation state. We studied effects of ANP on Na/K-ATPase phosphorylation and inhibition by an endogenous sodium pump ligand, marinobufagenin, in the aorta and renal medulla from male Sprague-Dawley rats. Marinobufagenin dose-dependently inhibited the Na/K-ATPase in renal and vascular membranes at the level of higher (nanomolar) and lower affinity (micromolar) binding sites. Marinobufagenin (1 nmol/L) inhibited Na/K-ATPase in aortic sarcolemma (18%) and in renal medulla (19%). prepro-ANP 104 to 123 (ppANP) and alpha-human ANP ([alpha-hANP] both 1 nmol/L) potentiated marinobufagenin-induced Na/K-ATPase inhibition in the kidney, but reversed the effect of marinobufagenin in the aorta. Similarly, ppANP and alpha-hANP modulated the sodium pump (ouabain-sensitive (86)Rb uptake) inhibitory effects of marinobufagenin in the aorta and renal medulla. In renal medulla, ppANP and alpha-hANP induced alpha-1 Na/K-ATPase phosphorylation, whereas in aorta, both peptides dephosphorylated Na/K-ATPase. The effect of ppANP on Na/K-ATPase phosphorylation and inhibition was mimicked by a protein kinase G activator, 8-Br-PET-cGMP (10 micromol/L), and prevented by a protein kinase G inhibitor, KT5823 (60 nmol/L). Our results suggest that alpha-1 Na/K-ATPase inhibition by marinobufagenin in the kidney is enhanced via Na/K-ATPase phosphorylation by ANP, whereas in the aorta, ANP exerts an opposite effect. The concurrent production of a vasorelaxant, ANP, and a vasoconstrictor, marinobufagenin, potentiate each other's natriuretic effects, but ANP peptides may offset the deleterious vasoconstrictor effect of marinobufagenin.

apoE4 allele and the natural history of cardiovascular risk factors

The aims of the present study were to compare the longitudinal changes in traditional cardiovascular (CV) risk factors (blood pressure, BMI, total and HDL-cholesterol, triglycerides, and blood glucose) in men with and without the apolipoprotein (apo)E4 allele. Three hundred six men from the Baltimore Longitudinal Study of Aging, ranging in age from 20 to 92 yr, were studied. Repeated measurements of CV risk factors were performed over a median follow-up time of 7 yr (maximum 14.3 yr) for men. Longitudinal changes in these CV risk factors were analyzed by linear mixed-effects models. The prevalence of the apoE4 allele was 25.5%. apoE4 was independently associated with accelerated changes over time in fasting plasma glucose (+9.5% vs. no change in those without apoE4 in the 6th age-decade over 10 yr). No significant effect of apoE4 on longitudinal changes in total or HDL-cholesterol, triglycerides, or blood pressures was observed. In conclusion, apoE4 influences fasting plasma glucose and its changes over time. This could explain, in part, the increased CV risk associated with the apoE4 genotype observed in men.

Accelerated longitudinal decline of aerobic capacity in healthy older adults

BACKGROUND

The ability of older persons to function independently is dependent largely on the maintenance of sufficient aerobic capacity and strength to perform daily activities. Although peak aerobic capacity is widely recognized to decline with age, its rate of decline has been estimated primarily from cross-sectional studies that may provide misleading, overly optimistic estimates of aging changes.

METHODS AND RESULTS

To determine longitudinal rate of change in aerobic capacity and the influence of age, gender, and physical activity on these changes, we performed serial measurements of peak treadmill oxygen consumption (peak VO2) in 375 women and 435 men ages 21 to 87 years from the Baltimore Longitudinal Study of Aging, a community-dwelling cohort free of clinical heart disease, over a median follow-up period of 7.9 years. A linear mixed-effects regression model was used to calculate the predicted longitudinal 10-year rate of change in peak VO2, expressed in milliliters per minute, for each age decade from the 20s through the 70s after adjustment for self-reported leisure-time physical activity. A longitudinal decline in peak VO2 was observed in each of the 6 age decades in both sexes; however, the rate of decline accelerated from 3% to 6% per 10 years in the 20s and 30s to >20% per 10 years in the 70s and beyond. The rate of decline for each decade was larger in men than in women from the 40s onward. Similar longitudinal rates of decline prevailed when peak VO2 was indexed per kilogram of body weight or per kilogram of fat-free mass and in all quartiles of self-reported leisure-time physical activity. When the components of peak VO2 were examined, the rate of longitudinal decline of the oxygen pulse (ie, the O2 utilization per heart beat) mirrored that of peak VO2, whereas the longitudinal rate of heart rate decline averaged only 4% to 6% per 10 years, and accelerated only minimally with age.

CONCLUSIONS

The longitudinal rate of decline in peak VO2 in healthy adults is not constant across the age span in healthy persons, as assumed by cross-sectional studies, but accelerates markedly with each successive age decade, especially in men, regardless of physical activity habits. The accelerated rate of decline of peak aerobic capacity has substantial implications with regard to functional independence and quality of life, not only in healthy older persons, but particularly when disease-related deficits are superimposed.

Data from a longitudinal study provided measurements of cognition to screen for Alzheimer's disease

BACKGROUND

This article presents a computerized method to help predict individuals at risk for developing Alzheimer's disease (AD). This would be a valuable tool for clinicians in developing treatment plans for potential AD patients. Using the initial level and rates of change in visual memory performance, such a method could predict potential AD patients in a fast and inexpensive manner. A longitudinal case-control study of 52 female and 145 male participants was performed in a gerontology research center using premorbid tests of visual memory and neurologic examinations to identify individuals with and without dementia and AD.

METHODS

The classification method for each individual starts on the second examination and proceeds to compute that person's risk of AD one examination at a time based on all the follow-up information of the remaining individuals.

RESULTS

By performing a crossvalidation study, the optimal combination of sensitivity and specificity derived from a receiver operating characteristic (ROC) curve showed 65% of the Alzheimer cases and 75% of the noncases were correctly classified for females, while 65 and 60% of cases and noncases, respectively, were correctly classified for males.

CONCLUSION

Longitudinal measurements of cognition can be useful in detecting the presence of AD.

The metabolic syndrome in older individuals: prevalence and prediction of cardiovascular events: the Cardiovascular Health Study

OBJECTIVE

The prevalence of the metabolic syndrome, a potent risk factor for cardiovascular diseases (CVDs), has not been adequately explored in older individuals. Moreover, two sets of criteria have been proposed for the definition of metabolic syndrome, one by the World Health Organization (WHO) and one by the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATPIII). We therefore investigated the prevalence of this syndrome in a subgroup of older participants from the Cardiovascular Health Study (CHS) who were free of CVD at baseline. We also compared the prognostic significance of the two definitions of the metabolic syndrome.

RESEARCH DESIGN AND METHODS

A total of 2,175 subjects from the CHS who were free of CVD at baseline and not taking antihypertensive or lipid-lowering medications were studied. Prevalence of the metabolic syndrome was assessed with both the WHO and ATPIII criteria. The incidence of coronary or cerebrovascular disease was ascertained during a median follow-up time of 4.1 years.

RESULTS

Prevalence of the metabolic syndrome was 28.1% by ATPIII criteria and 21.0% by WHO criteria. The two sets of criteria provided concordant classification for 80.6% of participants. Multivariate Cox propotional hazard models showed that the metabolic syndrome defined with the ATPIII criteria, but not with the WHO criteria, was an independent predictor of coronary or cerebrovascular events and was associated with a 38% increased risk (hazard ratio 1.38 [95% CI 1.06-1.79], P < 0.01).

CONCLUSIONS

Prevalence of the metabolic syndrome in older individuals is approximately 21-28% (depending on the definition used). The two sets of criteria have 80% concordance in classifying subjects. As defined by the ATPIII criteria, the metabolic syndrome yields independent prognostic information, even after adjusting for traditional cardiovascular risk factors and the individual domains of the metabolic syndrome.

Comparison of cardiorespiratory fitness versus leisure time physical activity as predictors of coronary events in men aged < or = 65 years and > 65 years

Both high peak oxygen consumption (VO(2)) and high levels of leisure time physical activity (LTPA) are associated with a reduced risk of cardiovascular morbidity and mortality. We examined the contributions of LTPA and peak VO(2) to the risk of coronary events (CEs) in healthy younger (< or = 65 years, n = 522) and older (>65 years, n = 167) men from the Baltimore Longitudinal Study of Aging. LTPA derived from self reports of time spent in 97 activities were converted into METs-minutes/24 hours and grouped into high (> or = 6 METs), moderate- (4 to 5.9 METs), and low-intensity LTPA (<4 METs). Cardiorespiratory fitness was determined by measuring peak VO(2) during a maximal treadmill exercise test. Over a mean follow-up of 13.4 +/- 6.3 years, CEs occurred in 63 men. After accounting for coronary risk factors, proportional-hazards analyses showed a relative CE risk of 0.53 (p <0.0001) for a SD increase in peak VO(2) in younger men and 0.61 (p = 0.024) in older men, whereas total LTPA was unrelated to coronary risk in either age group. When the 3 LTPA intensity levels were substituted for total LTPA in the model, peak VO(2) remained the only predictor of events in younger men, whereas high-intensity LTPA (RR = 0.39 for tertile 3 vs tertiles 1 and 2, p = 0.016) and peak VO(2) (RR = 0.61/SD increase, p = 0.024) were of similar importance in older men. Thus, in healthy younger men, higher cardiorespiratory fitness but not LTPA predicts a reduced risk of coronary heart disease, independent of conventional risk factors. For older men, high-intensity LTPA and fitness appear to be of similar importance in reducing coronary risk.

Low levels of prostate-specific antigen predict long-term risk of prostate cancer: results from the Baltimore Longitudinal Study of Aging

OBJECTIVES

To evaluate the relationship between low prostate-specific antigen (PSA) levels that are considered normal and the long-term risk of prostate cancer.

METHODS

The relative risk of, and cumulative probability of freedom from, prostate cancer by PSA level and age decade was evaluated in male participants of a longitudinal aging study, the Baltimore Longitudinal Study of Aging (National Institute on Aging). The relative risk was estimated from a Cox proportional hazards regression model for men aged 40 to 49.9 (n = 351) and 50 to 59.9 (n = 445). The disease-free probability was determined by Kaplan-Meier survival analysis.

RESULTS

The relative risk of prostate cancer for men aged 40 to 49.9 was 3.75 (range 1.6 to 8.6) when the PSA level was at or greater than the median (0.60 ng/mL) compared with men with PSA levels less than the median. This risk was similar for men aged 50 to 59.9 when comparing those with PSA levels greater than and less than the median (0.71 ng/mL). At 25 years, the cumulative probability of freedom from prostate cancer for men aged 40 to 49.9 was 89.6% (range 81% to 97%) and 71.6% (range 60% to 83%) when the PSA level was less than and greater than the median, respectively. The 25-year disease-free probability for men aged 50 to 59.9 was 83.6% (range 76% to 91%) and 58.9% (range 48% to 70%) when the PSA level was less than and greater than the median, respectively.

CONCLUSIONS

The association between the baseline serum PSA level and the subsequent risk of prostate cancer suggests that the biologic events that predispose to prostate cancer begin early in middle age. Men who have baseline PSA levels that are "normal" but reflect a higher risk of prostate cancer may be the most appropriate candidates for future prevention trials. Those men with the lowest risk of prostate cancer on the basis of the baseline PSA measurements are unlikely to benefit from frequent PSA surveillance in an effort to detect prostate cancer early.

Impact of donor/recipient traits independent of rejection on long-term renal function

This study describes renal function at multiple points in time after transplantation and the influence of donor and recipient factors independent of rejection on this function. Donor and recipient records for 83 consecutive cadaveric renal transplants performed between 1992 and 1994 at Johns Hopkins Bayview Medical Center were reviewed retrospectively. Donor age, gender, weight, terminal serum creatinine (Cr), intensive care unit days, blood pressure, presence of cardiac arrest, kidney only versus multiple organ donation, and cold ischemia time and recipient age, gender, weight, pretransplant pregnancy status, and rejection episodes were recorded. The influences of each of these parameters on changes in recipient Cr clearance over time (derived using the Cockcroft-Gault formula from recipient serum Cr at 3 months and annually up to 5 years) were analyzed first individually, then together in an analysis with multiple explanatory variables. Parameters indicative of donor ischemia (ie, donor blood pressure, pressor administration, and occurrence of cardiac arrest) were not predictive of the course of recipient Cr clearance. With the inclusion of rejection, this analysis shows the magnitude of the independent effects that donor age, donor Cr clearance, and recipient gender have on the subsequent time course of recipient Cr clearance (P < 0.05). Recipient gender and the presence of rejection appear to have a fixed effect on the level of Cr clearance, whereas donor age and donor Cr clearance appear to influence the level and the time course of recipient Cr clearance. Of all these factors, donor age appears to have the greatest impact on recipient Cr clearance at all times. Analyzing renal function in this way may prove to be a more sensitive indicator than actuarial survival analysis for evaluating the early effects of changes in transplantation protocols and pharmacologic interventions.

Today men with prostate cancer have larger prostates

OBJECTIVES

To examine the relationship between prostate size and the method of cancer detection in men with organ-confined prostate cancer, and compare prostate size in men with and without cancer.

METHODS

Prostate volume was evaluated in 720 men who had undergone radical prostatectomy for Stage T1c or Stage T2 cancer. Men with Stage T2 cancer were divided into those treated before 1989 (when widespread prostate-specific antigen [PSA] testing began), or not. Gland volume was also examined in 265 men participating in the Baltimore Longitudinal Study of Aging who had no clinical evidence of cancer. Volumes were compared using linear regression to allow for age.

RESULTS

Prostate volume in men with Stage T1c cancer was statistically significantly larger than in men with Stage T2 cancer diagnosed in the pre-PSA era after adjusting for age (P = 0.0001), and statistically significantly larger than in men without cancer above age 47 years based on 95% confidence intervals. Prostate volumes in men with Stage T2 cancer diagnosed in the pre-PSA era and in men without cancer were not statistically significantly different.

CONCLUSIONS

Prostate volume in men with PSA-detected, organ-confined cancer is larger than in men with palpable organ-confined cancer diagnosed in either the pre-PSA era or PSA era. These discrepancies may reflect a diagnostic bias due to the effect of benign prostatic hyperplasia on serum PSA that results in the selection of men with larger prostates for biopsy.