The renin-angiotensin system and cardiovascular autonomic control in aging

Sex-associated differences in cardiac ageing: Clinical aspects and molecular mechanisms

Despite the extensive clinical and scientific advances in prevention, diagnostics and treatment, cardiovascular diseases (CVD) remain the leading cause of morbidity and mortality worldwide for people aged 65 and over. Of all ageing-related diseases, CVD are responsible for almost one-third of deaths in the elderly, being above all cancers combined. Age is an independent and unavoidable risk factor contributing to the impairment of heart and blood vessels. As the average age of the population in industrialized countries has doubled in the last century, and almost a fifth of the world's population is predicted to be over 65 in the next decade, we can assume that the burden of CVD will fall primarily on the elderly. Evidence from basic and clinical science has shown that sex significantly influences the onset and severity of CVD. In women, CVD usually develop later than in men and with atypical symptomatology. After menopause, however, the incidence and severity of CVD increase in women, reaching equality in both sexes. Although intrinsic sexual dimorphism in cardiovascular ageing may contribute to the sex differences in CVD progression, the molecular mechanisms associated with cardiovascular ageing and their clinical value are not known in detail. In this review, we discuss the scientific knowledge available, focusing on structural, hormonal, genetic/epigenetic and inflammatory pathways, seeking to transfer these findings to the cardiovascular clinic in terms of prevention, diagnosis, prognosis and management of these pathologies and proposing possible validation of target specifics.

Enhanced vasorin signaling mitigates adverse cardiovascular remodeling

Arterial stiffening is a critical risk factor contributing to the exponential rise in age-associated cardiovascular disease incidence. This process involves age-induced arterial proinflammation, collagen deposition, and calcification, which collectively contribute to arterial stiffening. The primary driver of proinflammatory processes leading to collagen deposition in the arterial wall is the transforming growth factor-beta1 (TGF-β1) signaling. Activation of this signaling is pivotal in driving vascular extracellular remodeling, eventually leading to arterial fibrosis and calcification. Interestingly, the glycosylated protein vasorin (VASN) physically interacts with TGF-β1, and functionally restraining its proinflammatory fibrotic signaling in arterial walls and vascular smooth muscle cells (VSMCs). Notably, as age advances, matrix metalloproteinase type II (MMP-2) is activated, which effectively cleaves VASN protein in both arterial walls and VSMCs. This age-associated/MMP-2-mediated decrease in VASN levels exacerbates TGF-β1 activation, amplifying arterial fibrosis and calcification in the arterial wall. Importantly, TGF-β1 is a downstream molecule of the angiotensin II (Ang II) signaling pathway in the arterial wall and VSMCs, which is modulated by VASN. Indeed, chronic administration of Ang II to young rats significantly activates MMP-2 and diminishes the VASN expression to levels comparable to untreated older control rats. This review highlights and discusses the role played by VASN in mitigating fibrosis and calcification by alleviating TGF-β1 activation and signaling in arterial walls and VSMCs. Understanding these molecular physical and functional interactions may pave the way for establishing VASN-based therapeutic strategies to counteract adverse age-associated cardiovascular remodeling, eventually reducing the risk of cardiovascular diseases.

The Senescent Heart-"Age Doth Wither Its Infinite Variety"

Cardiovascular diseases are a leading cause of morbidity and mortality world-wide. While many factors like smoking, hypertension, diabetes, dyslipidaemia, a sedentary lifestyle, and genetic factors can predispose to cardiovascular diseases, the natural process of aging is by itself a major determinant of the risk. Cardiac aging is marked by a conglomerate of cellular and molecular changes, exacerbated by age-driven decline in cardiac regeneration capacity. Although the phenotypes of cardiac aging are well characterised, the underlying molecular mechanisms are far less explored. Recent advances unequivocally link cardiovascular aging to the dysregulation of critical signalling pathways in cardiac fibroblasts, which compromises the critical role of these cells in maintaining the structural and functional integrity of the myocardium. Clearly, the identification of cardiac fibroblast-specific factors and mechanisms that regulate cardiac fibroblast function in the senescent myocardium is of immense importance. In this regard, recent studies show that Discoidin domain receptor 2 (DDR2), a collagen-activated receptor tyrosine kinase predominantly located in cardiac fibroblasts, has an obligate role in cardiac fibroblast function and cardiovascular fibrosis. Incisive studies on the molecular basis of cardiovascular aging and dysregulated fibroblast function in the senescent heart would pave the way for effective strategies to mitigate cardiovascular diseases in a rapidly growing elderly population.

Changes in time structure of periodic leg movements during sleep in restless legs syndrome: Effects of sex and age

BACKGROUND

The objective of this study was to check the hypothesis that in women with restless legs syndrome (RLS) different changes occur in periodic leg movements during sleep (PLMS) during the post-menopausal period (using >50 years as a proxy) than in men of the same age.

METHODS

We recruited 36 untreated patients aged 18-50 years (19 men, median age 40 years, and 17 women, median age 37 years) while the remaining 67 were >50 years old (24 men, median age 66.6 years, and 43 women, median age 60.0 years). Leg movement activity during sleep was analyzed by means of an approach utilizing indexes especially suitable to assess leg movement periodicity.

RESULTS

No significant difference was seen between men in the two age groups; conversely, in women, a clear and significant increase in Periodicity Index was observed in the older group, along with a decrease in isolated leg movements. In women, a clear age-related enhancement of PLMS was found in the intermovement interval graphs, especially in the 16-22 s range, which was more evident than that observed in men. The results remained unchanged also when they were replicated by selecting only subjects aged 18-45 years vs. those aged >55 years.

CONCLUSIONS

Our findings indicate that assessing PLMS in women after menopause is clinically relevant because they are probably connected with the hormonal fluctuations of this period of life. Translationally, identifying and addressing PLMS in post-menopausal women is crucial for optimizing their sleep health and addressing potential health risks associated with sleep disturbances.

Role of the autonomic nervous system in young, middle-aged, and older individuals with essential hypertension and sleep-related changes in neurocardiac regulation

Essential hypertension involves complex cardiovascular regulation. The autonomic nervous system function fluctuates throughout the sleep-wake cycle and changes with advancing age. However, the precise role of the autonomic nervous system in the development of hypertension during aging remains unclear. In this study, we characterized autonomic function during the sleep-wake cycle in different age groups with essential hypertension. This study included 97 men (53 with and 44 without hypertension) aged 30-79 years. They were stratified by age into young (< 40 years), middle-aged (40-59 years), and older (60-79 years) groups. Polysomnography and blood pressure data were recorded for 2 min before and during an hour-long nap. Autonomic function was assessed by measuring heart rate variability and blood pressure variability. Data were analyzed using t tests, correlation analyses, and two-way analysis of variance. During nonrapid eye movement (nREM), a main effect of age was observed on cardiac parasympathetic measures and baroreflex sensitivity (BRS), with the highest and lowest levels noted in the younger and older groups, respectively. The coefficients of the correlations between these measures and age were lower in patients with hypertension than in normotensive controls. The BRS of young patients with hypertension was similar to that of their middle-aged and older counterparts. However, cardiac sympathetic activity was significantly higher (p = 0.023) and BRS was significantly lower (p = 0.022) in the hypertension group than in the control group. During wakefulness, the results were similar although some of the above findings were absent. Autonomic imbalance, particularly impaired baroreflex, plays a more significant role in younger patients with hypertension. The nREM stage may be suitable for gaining insights into the relevant mechanisms.

Mechanisms of sex and gender differences in hypertension

The mechanisms that control blood pressure are multifaceted including the sympathetic nervous system and the renin-angiotensin system leading to vasoconstriction and sodium reabsorption that causes a shift in the pressure-natriuesis relationship to higher blood pressures. Sex steroids can affect these mechanisms either directly or indirectly, and the effects may be different depending on the sex of the individual. This review will discuss some of the major blood pressure-controlling mechanisms and how sex steroids may affect them and the need for future studies to better clarify the mechanisms responsible for sex and gender differences in blood pressure control. New mechanisms that are identified, along with what is already known, will provide better tools for treatment of hypertension in men and women of all ethnicities and decrease the risk of cardiovascular disease in the future.

Hydrogen Sulfide Inhibited Sympathetic Activation in D-Galactose-Induced Aging Rats by Upregulating Klotho and Inhibiting Inflammation in the Paraventricular Nucleus

The present study aimed to explore the central relationship between cardiovascular conditions and aging. D-galactose (D-gal) was utilized to induce an accelerated aging model and to evaluate the effects of hydrogen sulfide (H₂S) on aging-related cardiovascular risk factors and mechanisms. Eight-week-old Sprague Dawley rats were given an intraperitoneal injection of 250 mg/kg D-gal every day with or without H₂S (56 μmol/kg) for 12 weeks. We found that D-gal treatment induced a noticeably aging-related increase in p16, p53 and p21 protein levels and senescence-associated beta-galactosidase staining. In addition, the level of noradrenalin was increased, accompanied by enhanced blood pressure and renal sympathetic nerve activity in aged rats. The greater sympathetic responses were related with the increased level of inflammation. The decreased level of klotho in the paraventricular nucleus neuron also contributed to sympathetic activation in D-gal-induced aged rats. However, the exogenous administration of H₂S attenuated the sympathetic activity in aged rats, as evidenced by the decreased blood pressure, renal sympathetic nerve activity and noradrenalin level. The ameliorated cellular senescence, inflammation and heightened klotho in the paraventricular nucleus were attributed to the protective effects of H₂S. The present study provides further evidence for the drug development of H₂S for the prevention or treatment of the aging-associated cardiovascular diseases.

Control of aging by the renin–angiotensin system: a review of C. elegans, Drosophila, and mammals

The free-living, non-parasitic nematode Caenorhabditis elegans is a premier model organism for the study of aging and longevity due to its short lifespan, powerful genetic tools, and conservation of fundamental mechanisms with mammals. Approximately 70 percent of human genes have homologs in C. elegans, including many that encode proteins in pathways that influence aging. Numerous genetic pathways have been identified in C. elegans that affect lifespan, including the dietary restriction pathway, the insulin/insulin-like growth factor (IGF) signaling pathway, and the disruption of components of the mitochondrial electron transport chain. C. elegans is also a powerful system for performing drug screens, and many lifespan-extending compounds have been reported; notably, several FDA-approved medications extend the lifespan in C. elegans, raising the possibility that they can also extend the lifespan in humans. The renin–angiotensin system (RAS) in mammals is an endocrine system that regulates blood pressure and a paracrine system that acts in a wide range of tissues to control physiological processes; it is a popular target for drugs that reduce blood pressure, including angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs). Emerging evidence indicates that this system influences aging. In C. elegans, decreasing the activity of the ACE homolog acn-1 or treatment with the ACE-inhibitor Captopril significantly extends the lifespan. In Drosophila, treatment with ACE inhibitors extends the lifespan. In rodents, manipulating the RAS with genetic or pharmacological interventions can extend the lifespan. In humans, polymorphisms in the ACE gene are associated with extreme longevity. These results suggest the RAS plays a conserved role in controlling longevity. Here, we review studies of the RAS and aging, emphasizing the potential of C. elegans as a model for understanding the mechanism of lifespan control.