Treatment with a DC-SIGN ligand reduces macrophage polarization and diastolic dysfunction in the aging female but not male mouse hearts

Development of Anti-Inflammatory Agents Utilizing DC-SIGN Mediated IL-10 Secretion in Autoimmune and Immune-Mediated Disorders: Bridging Veterinary and Human Health

DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin) is a C-type lectin receptor expressed on dendritic cells and M2 macrophages, playing a key role in immune regulation and pathogen recognition. Its ability to mediate anti-inflammatory effects by interacting with specific ligands triggers pathways that suppress pro-inflammatory responses and promote tissue repair, making it a potential therapeutic target for inflammatory and autoimmune diseases. DC-SIGN homologs in various animal species share structural similarities and perform comparable immune functions, offering valuable insights into its broader application across species. By recognizing carbohydrate ligands on pathogens, DC-SIGN facilitates immune modulation, which can be harnessed for developing therapies aimed at controlling inflammation. In veterinary medicine, autoimmune and inflammatory diseases, such as rheumatoid arthritis and inflammatory bowel disease, represent significant challenges, and the anti-inflammatory properties of DC-SIGN could provide new therapeutic options to improve disease management and enhance animal health. Future investigations should focus on the structural and functional analysis of DC-SIGN homologs in various species, as well as the development of preclinical models to translate these findings into clinical interventions bridging veterinary and human health.

Sex Differences in Response to Diet Enriched With Glutathione Precursors in the Aging Heart

Common features of the aging heart are dysregulated metabolism, inflammation, and fibrosis. Elevated oxidative stress is another hallmark of cardiac aging that can exacerbate each of these conditions. We hypothesize that by increasing natural antioxidant levels (glutathione), we will improve cardiac function. Twenty-one-month-old mice were fed glycine and N-acetyl cysteine (GlyNAC; glutathione precursors)-supplemented or control diets for 12 weeks. Heart function was monitored longitudinally, and the exercise performance was determined at the end of the study. We found that the GlyNAC diet was beneficial for old male but not old female mice, leading to an increase of Ndufb8 expression (a subunit of the mitochondrial respiratory chain complex), and higher enzymatic activity for CPT1b and CrAT, 2 carnitine acyltransferases that are critical to cardiomyocyte metabolism. Although no quantifiable change of collagen turnover was detected, hearts from GlyNAC-fed old males exhibited a slight but significant enrichment in Fmod, a protein that can inhibit collagen fibril formation, possibly reducing extracellular matrix stiffness and thus improving diastolic function. Cardiac diastolic function was modestly improved in males but not females, and surprisingly GlyNAC-fed female mice showed a decline in exercise performance. In summary, our work supports the concept that aged male and female hearts are phenotypically different. These basic differences may affect the response to pharmacological and diet interventions, including antioxidants.

Immunosenescence: A new direction in anti-aging research

The immune system is a major regulatory system of the body, that is composed of immune cells, immune organs, and related signaling factors. As an organism ages, observable age-related changes in the function of the immune system accumulate in a process described as 'immune aging. Research has shown that the impact of aging on immunity is detrimental, with various dysregulated responses that affect the function of immune cells at the cellular level. For example, increased aging has been shown to result in the abnormal chemotaxis of neutrophils and decreased phagocytosis of macrophages. Age-related diminished functionality of immune cell types has direct effects on host fitness, leading to poorer responses to vaccination, more inflammation and tissue damage, as well as autoimmune disorders and the inability to control infections. Similarly, age impacts the function of the immune system at the organ level, resulting in decreased hematopoietic function in the bone marrow, a gradual deficiency of catalase in the thymus, and thymic atrophy, resulting in reduced production of related immune cells such as B cells and T cells, further increasing the risk of autoimmune disorders in the elderly. As the immune function of the body weakens, aging cells and inflammatory factors cannot be cleared, resulting in a cycle of increased inflammation that accumulates over time. Cumulatively, the consequences of immune aging increase the likelihood of developing age-related diseases, such as Alzheimer's disease, atherosclerosis, and osteoporosis, among others. Therefore, targeting the age-related changes that occur within cells of the immune system might be an effective anti-aging strategy. In this article, we summarize the relevant literature on immune aging research, focusing on its impact on aging, in hopes of providing new directions for anti-aging research.

Klotho enhances diastolic function in aged hearts through Sirt1-mediated pathways

Aging leads to a progressive decline in cardiac function, increasing the risk of heart failure with preserved ejection fraction (HFpEF). This study elucidates the impact of α-Klotho, an anti-aging hormone, on cardiac diastolic dysfunction and explore its downstream mechanisms. Aged wild-type and heterozygous Klotho-deficient mice received daily injection of soluble α-Klotho (sKL) for 10 weeks, followed by a comprehensive assessment of heart function by echocardiography, intracardiac pressure catheter, exercise tolerance, and cardiac pathology. Our findings show that klotho deficiency accentuated cardiac hypertrophy, diastolic dysfunction, and exercise intolerance, while sKL treatment ameliorates these abnormalities and improves cardiac capillary densities. Downstream of klotho, we focused on the Sirtuin1 (Sirt1) signaling pathway to elucidate the potential underlying mechanism by which Klotho improves diastolic function. We found that decreased Klotho levels were linked with Sirt1 deficiency, whereas sKL treatment restored Sirt1 expression in aged hearts and mitigated the DNA damage response pathway activation. Through tandem mass tag proteomics and unbiased acetylomics analysis, we identified 220 significantly hyperacetylated lysine sites in critical cardiac proteins of aged hearts. We found that sKL supplementation attenuated age-dependent DNA damage and cardiac diastolic dysfunction. In contrast, Klotho deficiency significantly increased hyperacetylation of several crucial cardiac contractile proteins, potentially impairing ventricular relaxation and diastolic function, thus predisposing to HFpEF. These results suggest the potential benefit of sKL supplementation as a promising therapeutic strategy for combating HFpEF in aging.

Innate immunity in peripheral tissues is differentially impaired under normal and endotoxic conditions in aging

Chronic low-grade inflammation is a hallmark of aging, aka "inflammaging", which is linked to a wide range of age-associated diseases. Immune dysfunction increases disease susceptibility, and increases morbidity and mortality of aging. Innate immune cells, including monocytes, macrophages and neutrophils, are the first responders of host defense and the key mediators of various metabolic and inflammatory insults. Currently, the understanding of innate immune programming in aging is largely fragmented. Here we investigated the phenotypic and functional properties of innate immune cells in various peripheral tissues of young and aged mice under normal and endotoxic conditions. Under the steady state, aged mice showed elevated pro-inflammatory monocytes/macrophages in peripheral blood, adipose tissue, liver, and colon. Under lipopolysaccharide (LPS)-induced inflammatory state, the innate immune cells of aged mice showed a different response to LPS stimulus than that of young mice. LPS-induced immune responses displayed differential profiles in different tissues and cell types. In the peripheral blood, when responding to LPS, the aged mice showed higher neutrophils, but lower pro-inflammatory monocytes than that in young mice. In the peritoneal fluid, while young mice exhibited significantly elevated pro-inflammatory neutrophils and macrophages in response to LPS, aged mice exhibited decreased pro-inflammatory neutrophils and variable cytokine responses in macrophages. In the adipose tissue, LPS induced less infiltrated neutrophils but more infiltrated macrophages in old mice than young mice. In the liver, aged mice showed a more robust increase of pro-inflammatory macrophages compared to that in young mice under LPS stimulation. In colon, macrophages showed relatively mild response to LPS in both young and old mice. We have further tested bone-marrow derived macrophages (BMDM) from young and aged mice, we found that BMDM from aged mice have impaired polarization, displaying higher expression of pro-inflammatory markers than those from young mice. These data collectively suggest that innate immunity in peripheral tissues is impaired in aging, and the dysregulation of immunity is tissue- and cell-dependent. Our findings in the rodent model underscore the complexity of aging immunity. Further investigation is needed to determine whether the immune profile observed in aged mice is applicable in age-associated diseases in humans.

The Role of Methionine-Rich Diet in Unhealthy Cerebrovascular and Brain Aging: Mechanisms and Implications for Cognitive Impairment

As aging societies in the western world face a growing prevalence of vascular cognitive impairment and Alzheimer's disease (AD), understanding their underlying causes and associated risk factors becomes increasingly critical. A salient concern in the western dietary context is the high consumption of methionine-rich foods such as red meat. The present review delves into the impact of this methionine-heavy diet and the resultant hyperhomocysteinemia on accelerated cerebrovascular and brain aging, emphasizing their potential roles in cognitive impairment. Through a comprehensive exploration of existing evidence, a link between high methionine intake and hyperhomocysteinemia and oxidative stress, mitochondrial dysfunction, inflammation, and accelerated epigenetic aging is drawn. Moreover, the microvascular determinants of cognitive deterioration, including endothelial dysfunction, reduced cerebral blood flow, microvascular rarefaction, impaired neurovascular coupling, and blood-brain barrier (BBB) disruption, are explored. The mechanisms by which excessive methionine consumption and hyperhomocysteinemia might drive cerebromicrovascular and brain aging processes are elucidated. By presenting an intricate understanding of the relationships among methionine-rich diets, hyperhomocysteinemia, cerebrovascular and brain aging, and cognitive impairment, avenues for future research and potential therapeutic interventions are suggested.

A defective mechanosensing pathway affects fibroblast-to-myofibroblast transition in the old male mouse heart

The cardiac fibroblast interacts with an extracellular matrix (ECM), enabling myofibroblast maturation via a process called mechanosensing. Although in the aging male heart, ECM is stiffer than in the young mouse, myofibroblast development is impaired, as demonstrated in 2-D and 3-D experiments. In old male cardiac fibroblasts, we found a decrease in actin polymerization, α-smooth muscle actin (α-SMA), and Kindlin-2 expressions, the latter an effector of the mechanosensing. When Kindlin-2 levels were manipulated via siRNA interference, young fibroblasts developed an old-like fibroblast phenotype, whereas Kindlin-2 overexpression in old fibroblasts reversed the defective phenotype. Finally, inhibition of overactivated extracellular regulated kinases 1 and 2 (ERK1/2) in the old male fibroblasts rescued actin polymerization and α-SMA expression. Pathological ERK1/2 overactivation was also attenuated by Kindlin-2 overexpression. In contrast, old female cardiac fibroblasts retained an operant mechanosensing pathway. In conclusion, we identified defective components of the Kindlin/ERK/actin/α-SMA mechanosensing axis in aged male fibroblasts.

Sex-specific phenotypes in the aging mouse heart and consequences for chronic fibrosis

The incidence of diastolic dysfunction increases with age in both humans and mice. This is characterized by increased passive stiffness and slower relaxation of the left ventricle. The stiffness arises at least partially from progressively increased interstitial collagen deposition because of highly secretory fibroblasts. In the past, we demonstrated that AMPK activation via the drug 5-aminoimidazole-4-carboxamide riboside (AICAR) in middle-aged mice reduced adverse remodeling after myocardial infarction. Therefore, as an attempt to normalize the fibroblast phenotype, we used 21-mo-old male and female mice and treated them with AICAR (0.166 mg/g body wt) where each mouse was followed in a functional study over a 3-mo period. We found sex-related differences in extracellular matrix (ECM) composition as well as heart function indices at baseline, which were further accentuated by AICAR treatment. AICAR attenuated the age-related increase in left atrial volume (LAV, an indicator of diastolic dysfunction) in female but not in male hearts, which was associated with reduced collagen deposition in the old female heart, and reduced the transcription factor Gli1 expression in cardiac fibroblasts. We further demonstrated that collagen synthesis was dependent on Gli1, which is a target of AMPK-mediated degradation. By contrast, AICAR had a minor impact on cardiac fibroblasts in the old male heart because of blunted AMPK phosphorylation. Hence, it did not significantly improve old male heart function indices. In conclusion, we demonstrated that male and female hearts are phenotypically different, and sex-specific differences need to be considered when analyzing the response to pharmacological intervention.NEW & NOTEWORTHY The aging heart develops diastolic dysfunction because of increased collagen deposition. We attempted to reduce collagen expression in the old heart by activating AMPK using AICAR. An improvement of diastolic function and reduction of cardiac fibrosis was found only in the female heart and correlated with decreased procollagen expression and increased degradation of the transcription factor Gli1. Male hearts display blunted AICAR-dependent AMPK activation and therefore this treatment had no benefits for the male mice.

Targeting the Metabolic-Inflammatory Circuit in Heart Failure With Preserved Ejection Fraction

PURPOSE OF REVIEW

Heart failure with preserved ejection fraction (HFpEF) is a leading cause of morbidity and mortality. The current mechanistic paradigm supports a comorbidity-driven systemic proinflammatory state that evokes microvascular and myocardial dysfunction. Crucially, diabetes and obesity are frequently prevalent in HFpEF patients; as such, we review the involvement of a metabolic-inflammatory circuit in disease pathogenesis.

RECENT FINDINGS

Experimental models of diastolic dysfunction and genuine models of HFpEF have facilitated discovery of underlying drivers of HFpEF, where metabolic derangement and systemic inflammation appear to be central components of disease pathophysiology. Despite a shared phenotype among these models, molecular signatures differ depending on type and combination of comorbidities present. Inflammation, oxidative stress, hypertension, and metabolic derangements have been positioned as therapeutic targets to suppress the metabolic-inflammatory circuit in HFpEF. However, the stratification of unique patient phenogroups within the collective HFpEF subgroup argues for specific interventions for distinct phenogroups.

Alginate oligosaccharide alleviates D-galactose-induced cardiac ageing via regulating myocardial mitochondria function and integrity in mice

Ageing is a crucial risk factor for the development of age‐related cardiovascular diseases. Therefore, the molecular mechanisms of ageing and novel anti‐ageing interventions need to be deeply studied. Alginate oligosaccharide (AOS) possesses high pharmacological activities and beneficial effects. Our study was undertaken to investigate whether AOS could be used as an anti‐ageing drug to alleviate cardiac ageing. D‐galactose (D‐gal)‐induced C57BL/6J ageing mice were established by subcutaneous injection of D‐gal (200 mg·kg^‐1·d^‐1) for 8 weeks. AOS (50, 100 and 150 mg·kg^‐1·d^‐1) were administrated intragastrically for the last 4 weeks. As a result, AOS prevented cardiac dysfunction in D‐gal‐induced ageing mice, including partially preserved ejection fraction (EF%) and fractional shortening (FS%). AOS inhibited D‐gal‐induced up‐regulation of natriuretic peptides A (ANP), brain natriuretic peptide (BNP) and ageing markers p53 and p21 in a dose‐dependent manner. To further explore the potential mechanisms contributing to the anti‐ageing protective effect of AOS, the age‐related mitochondrial compromise was analysed. Our data indicated that AOS alleviated D‐gal‐induced cardiac ageing by improving mitochondrial biogenesis, maintaining the mitochondrial integrity and enhancing the efficient removal of impaired mitochondria. AOS also decreased the ROS production and oxidative stress status, which, in turn, further inhibiting cardiac mitochondria from being destroyed. Together, these results demonstrate that AOS may be an effective therapeutic agent to alleviate cardiac ageing.