Role of circulating molecules in age-related cardiovascular and metabolic disorders

Socioeconomic status as a potential mediator of arterial aging in marginalized ethnic and racial groups: current understandings and future directions

Cardiovascular diseases (CVDs) are the leading cause of death in the United States. However, disparities in CVD-related morbidity and mortality exist as marginalized racial and ethnic groups are generally at higher risk for CVDs (Black Americans, Indigenous People, South and Southeast Asians, Native Hawaiians, and Pacific Islanders) and/or development of traditional CVD risk factors (groups above plus Hispanics/Latinos) relative to non-Hispanic Whites (NHW). In this comprehensive review, we outline emerging evidence suggesting these groups experience accelerated arterial dysfunction, including vascular endothelial dysfunction and large elastic artery stiffening, a nontraditional CVD risk factor that may predict risk of CVDs in these groups with advancing age. Adverse exposures to social determinants of health (SDOH), specifically lower socioeconomic status (SES), are exacerbated in most of these groups (except South Asians-higher SES) and may be a potential mediator of accelerated arterial aging. SES negatively influences the ability of marginalized racial and ethnic groups to meet aerobic exercise guidelines, the first-line strategy to improve arterial function, due to increased barriers, such as time and financial constraints, lack of motivation, facility access, and health education, to performing conventional aerobic exercise. Thus, identifying alternative interventions to conventional aerobic exercise that 1) overcome these common barriers and 2) target the biological mechanisms of aging to improve arterial function may be an effective, alternative method to aerobic exercise to ameliorate accelerated arterial aging and reduce CVD risk. Importantly, dedicated efforts are needed to assess these strategies in randomized-controlled clinical trials in these marginalized racial and ethnic groups.

Exploration of New Therapies for Heart Failure Targeting Age-Related Mechanisms

Evidence indicates a role of cellular senescence and systemic insulin resistance (hyperinsulinemia) in the pathogenesis of age-related cardiovascular-metabolic disorders, including heart failure, atherosclerotic diseases, obesity, and diabetes. "Metabolic remodeling" is one of the keywords for aging research, and studies with brown adipose tissue have shown that maintaining the homeostasis of this organ is crucial to suppressing the progression of pathologies in obesity and heart failure. The mechanisms contributing to the synchronization of aging (sync-aging) are mysterious and interesting. "Senometabolite" or "senoprotein" are defined as circulating molecules that have causal roles in sync-aging, which requires the establishment of new concepts: age-related fibrotic disorders (A-FiDs), and senometabolite-related disorders (SRDs). Globally, researchers are active in comprehensive and conclusive studies targeting age-related circulating molecules. Recently, the senolytic approach opened a new avenue for aging research. Senolysis, mediated through a genetic/pharmacologic/vaccination approach, reversed aging and pathologies in age-related diseases. Suppression of prosenescent molecules (senocules) and senolysis, the specific depletion of senescent cells, will become next-generation therapies for cardiovascular diseases.

GDF11 and aging biology - controversies resolved and pending

Since the exogenous administration of GDF11, a TGF-ß superfamily member, was reported to have beneficial effects in some models of human disease, there have been many research studies in GDF11 biology. However, many studies have now confirmed that exogenous administration of GDF11 can improve physiology in disease models, including cardiac fibrosis, experimental stroke, and disordered metabolism. GDF11 is similar to GDF8 (also called Myostatin), differing only by 11 amino acids in their mature signaling domains. These two proteins are now known to be biochemically different both in vitro and in vivo. GDF11 is much more potent than GDF8 and induces more strongly SMAD2 phosphorylation in the myocardium compared to GDF8. GDF8 and GDF11 prodomain are only 52% identical and are cleaved by different Tolloid proteases to liberate the mature signaling domain from inhibition of the prodomain. Here, we review the state of GDF11 biology, highlighting both resolved and remaining controversies.

Immunotherapy targeting plasma ASM is protective in a mouse model of Alzheimer's disease

Acid sphingomyelinase (ASM) has been implicated in neurodegenerative disease pathology, including Alzheimer's disease (AD). However, the specific role of plasma ASM in promoting these pathologies is poorly understood. Herein, we explore plasma ASM as a circulating factor that accelerates neuropathological features in AD by exposing young APP/PS1 mice to the blood of mice overexpressing ASM, through parabiotic surgery. Elevated plasma ASM was found to enhance several neuropathological features in the young APP/PS1 mice by mediating the differentiation of blood-derived, pathogenic Th17 cells. Antibody-based immunotherapy targeting plasma ASM showed efficient inhibition of ASM activity in the blood of APP/PS1 mice and, interestingly, led to prophylactic effects on neuropathological features by suppressing pathogenic Th17 cells. Our data reveals insights into the potential pathogenic mechanisms underlying AD and highlights ASM-targeting immunotherapy as a potential strategy for further investigation.

Capillaries as a Therapeutic Target for Heart Failure

Prognosis of heart failure remains poor, and it is urgent to find new therapies for this critical condition. Oxygen and metabolites are delivered through capillaries; therefore, they have critical roles in the maintenance of cardiac function. With aging or age-related disorders, capillary density is reduced in the heart, and the mechanisms involved in these processes were reported to suppress capillarization in this organ. Studies with rodents showed capillary rarefaction has causal roles for promoting pathologies in failing hearts. Drugs used as first-line therapies for heart failure were also shown to enhance the capillary network in the heart. Recently, the approach with senolysis is attracting enthusiasm in aging research. Genetic or pharmacological approaches concluded that the specific depletion of senescent cells, senolysis, led to reverse aging phenotype. Reagents mediating senolysis are described to be senolytics, and these compounds were shown to ameliorate cardiac dysfunction together with enhancement of capillarization in heart failure models. Studies indicate maintenance of the capillary network as critical for inhibition of pathologies in heart failure.

Reciprocal blood exchange in heterochronic parabionts has a deleterious effect on the lifespan of young animals without a positive effect for old animals

Our previous study showed that the exchange of blood between heterochronic parabionts for 3 months did not rejuvenate the immune system of the old partners. Moreover, the young immune system became more aged and began to function according to the "old" principle. Does this "forced aging" affect all organism's systems in this model? We checked the levels of corticosterone, testosterone, IGF-1, insulin, thyroxine in the blood of heterochronic parabionts but did not find significant changes compared to the age-related controls. Since numerous data support the possibility of rejuvenation of the brain, muscles, and other tissues using the model of heterochronic parabiosis, as well as opposite data, we planned to assess the overall effect of this long-term blood exchange on the rate of organism aging. We measured the lifespan of animals that exchanged with blood for 3 months and then were disconnected. Median and maximum life expectancy decreased in young heterochronic parabionts compared with the isochronic control. Old heterochronic parabionts showed only a small trend towards an increase in the median lifespan but it was not statistically significant, and the maximum lifespan did not change compared to the isochronic parabionts. These data support our assumption that old blood contains factors capable of inducing aging in young animals. Finding and selective suppression of aging factor production in the organism could be the key research field for life extension.

Serum Pigment Epithelium-Derived Factor Levels are Associated with Estradiol and Decrease After Adjusting for Alanine Aminotransferase in Chinese Women Based on Multiple Linear Regression Analysis

PURPOSE

To assess changes in pigment epithelium-derived factor (PEDF) levels in patients with metabolic syndrome (MetS) and to investigate sexual dimorphism in serum PEDF levels and their relationships with estradiol.

METHODS

A total of 318 individuals (145 men, 173 women) who underwent health examinations in our department were selected. Serum PEDF, estradiol and other metabolic parameters were determined. Homeostasis model assessment of insulin resistance (HOMA- IR) and homeostasis model assessment of β-cell function (HOMA-β) were calculated to evaluate insulin resistance and β-cell function, respectively. Multiple linear regression analysis was used to analyse the factors influencing serum PEDF.

RESULTS

Serum PEDF levels were significantly higher in subjects with MetS in both men and women (12.09±2.75 vs 8.97±3.19 μg/mL in men and 11.31±2.79 vs 8.40±2.32 μg/mL in women, MetS vs non-MetS, P<0.001). Correlation analysis showed that serum PEDF levels were significantly correlated with body mass index (BMI), waist circumference, waist-to-hip ratio, diastolic blood pressure (DBP), fasting and 2-h postprandial glucose, fasting and 2-h postprandial insulin, HOMA-β, HOMA-IR, hemoglobin A1c (HbA1c), alanine aminotransferase (ALT), aspartate aminotransferase (AST), uric acid (UA), triacylglycerol (TG) and high-density lipoprotein cholesterol (HDL-C). Elevated ALT, HOMA-IR and TG were significant predictors of increased PEDF concentrations. In women, estradiol was inversely correlated with PEDF levels (r=-0.25, P=0.011), and the association was no longer significant after adjustment for ALT.

CONCLUSION

PEDF could be used as a biomarker of MetS in both men and women. This study reported for the first time that circulating PEDF displays sexual dimorphism, which could be related to estrogen. The association between estrogen and circulating PEDF levels was attenuated after adjusting for ALT.