The Effects of Age and Fasting Models on Blood Pressure, Insulin/Glucose Profile, and Expression of Longevity Proteins in Male Rats

The role of Klotho and sirtuins in sleep-related cardiovascular diseases: a review study

The prevalence of sleep disorders has been reported from 1.6% to 56.0%, worldwide. Sleep deprivation causes cardiovascular diseases (CVDs) including atherosclerosis, vascular aging, hypertension, heart dysfunction, reduced heart rate variability, and cardiac arrhythmia. Reduced tissue oxygen causes various CVDs by activating pro-inflammatory factors and increasing oxidative stress. Sleep disorders are more important and prevalent in older people and cause more severe cardiovascular complications. On the other hand, the reduction of Klotho level, an age-dependent protein whose expression decreases with age, is associated with age-related diseases. Sirtuins, class III histone deacetylases, also are among the essential factors in postponing cellular aging and increasing the lifespan of organisms, and they do this by regulating different pathways in the cell. Sirtuins and Klotho play an important role in the pathophysiology of CVDS and both have anti-oxidative stress and anti-inflammatory activity. Studies have shown that the levels of Klotho and sirtuins are altered in sleep disorders. In this article, alterations of Klotho and sirtuins in sleep disorders and in the development of sleep-related CVDs were reviewed and the possible signaling pathways were discussed. The inclusion criteria were studies with keywords of different types of sleep disorders and CVDs, klotho, SIRT1-7, and sirtuins in PubMed, Scopus, Embase، Science Direct، Web of Sciences and Google Scholar by the end of 2023. The studies revealed there is a bidirectional relationship between sleep disorders and the serum and tissue levels of Klotho and sirtuins and sleep related-CVDs.

Intermittent Metabolic Switching and Vascular Cognitive Impairment

Intermittent fasting (IF), a dietary pattern alternating between eating and fasting periods within a 24-hour cycle, has garnered recognition for its potential to enhance both healthspan and lifespan in animal models and humans. It also shows promise in alleviating age-related diseases, including neurodegeneration. Vascular cognitive impairment (VCI) spans a severity range from mild cognitive deficits to severe cognitive deficits and loss of function in vascular dementia. Chronic cerebral hypoperfusion has emerged as a significant contributor to VCI, instigating vascular pathologies such as microbleeds, blood-brain barrier dysfunction, neuronal loss, and white matter lesions. Preclinical studies in rodents strongly suggest that IF has the potential to attenuate pathological mechanisms, including excitotoxicity, oxidative stress, inflammation, and cell death pathways in VCI models. Hence, this supports evaluating IF in clinical trials for both existing and at-risk VCI patients. This review compiles existing data supporting IF's potential in treating VCI-related vascular and neuronal pathologies, emphasizing the mechanisms by which IF may mitigate these issues. Hence providing a comprehensive overview of the available data supporting IF's potential in treating VCI by emphasizing the underlying mechanisms that make IF a promising intervention for VCI.

Effects of alternate-day fasting and time-restricted feeding in obese middle-aged female rats

OBJECTIVES

Obesity is a multifactorial condition associated with metabolic alterations that can be aggravated during female aging. Calorie restriction via intermittent fasting (IF) diets may reduce body weight and therefore have the potential to decrease obesity and associated comorbidities, such as insulin resistance. This study investigated the effects of two IF protocols, alternate-day fasting (ADF) and time-restricted feeding (TRF) in middle-aged obese female rats.

METHODS

Wistar rats (age 15 mo) were fed with standard chow or high-fat diet for 8 wk and then separated into the following groups (n = 5-8 each) for another 8 wk: control (received standard chow), obese (received high-fat diet), obese + ADF (24-h fasting protocol), and obese + TRF (14 h daily).

RESULTS

At the end of the study, both IF protocols were able to reduce body weight and body mass index compared with the obese group. However, no changes were observed in adiposity and glucose homeostasis. We also found an increase in total leukocytes, lymphocytes, and monocytes in the TRF group and a higher number of platelets in the ADF group. Blood lipid profiles, including triglycerides and high-density lipoprotein, as well as liver stress responses, such as heat shock protein 70 and malondialdehyde, were not changed by IF.

CONCLUSIONS

Although ADF and TRF protocols resulted in a reduction of body weight and body mass index, these dietary interventions did not promote health benefits, such as reducing blood lipid profile, adiposity, and insulin resistance. In addition, ADF and TRF increased inflammatory biomarkers, which may increase the risk of obesity-associated comorbidities.

The contradictory role of branched-chain amino acids in lifespan and insulin resistance

Branched-chain amino acids (BCAAs; a mixture of leucine, valine and isoleucine) have important regulatory effects on glucose and lipid metabolism, protein synthesis and longevity. Many studies have reported that circulating BCAA levels or dietary intake of BCAAs is associated with longevity, sarcopenia, obesity, and diabetes. Among them, the influence of BCAAs on aging and insulin resistance often present different benefits or harmful effects in the elderly and in animals. Considering the nonobvious correlation between circulating BCAA levels and BCAA uptake, as well as the influence of diseases, diet and aging on the body, some of the contradictory conclusions have been drawn. The regulatory mechanism of the remaining contradictory role may be related to endogenous branched-chain amino acid levels, branched-chain amino acid metabolism and mTOR-related autophagy. Furthermore, the recent discovery that insulin resistance may be independent of longevity has expanded the research thinking related to the regulatory mechanism among the three. However, the negative effects of BCAAs on longevity and insulin resistance were mostly observed in high-fat diet-fed subjects or obese individuals, while the effects in other diseases still need to be studied further. In conclusion, there is still no definite conclusion on the specific conditions under which BCAAs and insulin resistance extend life, shorten life, or do not change lifespan, and there is still no credible and comprehensive explanation for the different effects of BCAAs and insulin resistance on lifespan.

The Role of SIRT3 in Exercise and Aging

The health benefits of regular exercise are well established. Nonetheless, the molecular mechanism(s) responsible for exercise-induced health benefits remain a topic of debate. One of the key cell-signaling candidates proposed to provide exercise-induced benefits is sirtuin 3 (SIRT3). SIRT3, an NAD+ dependent mitochondrial deacetylase, positively modulates many cellular processes, including energy metabolism, mitochondrial biogenesis, and protection against oxidative stress. Although the exercise-induced change in SIRT3 signaling is a potential mechanism contributing to the health advantages of exercise on aging, studies investigating the impact of exercise on SIRT3 abundance in cells provide conflicting results. To resolve this conundrum, this narrative review provides a detailed analysis of the role that exercise-induced changes in SIRT3 play in providing the health and aging benefits associated with regular physical activity. We begin with an overview of SIRT3 function in cells followed by a comprehensive review of the impact of exercise on SIRT3 expression in humans and other mammalians. We then discuss the impact of SIRT3 on aging, followed by a thorough analysis of the cell-signaling links between SIRT3 and exercise-induced adaptation. Notably, to stimulate future research, we conclude with a discussion of key unanswered questions related to exercise, aging, and SIRT3 expression.

Exercise Training Attenuates Cardiac Vulnerability and Promotes Cardiac Resistance to Isoproterenol-Induced Injury Following Hookah Smoke Inhalation in Male Rats: Role of Klotho and Sirtuins

Hookah smoking is on the rise around the world. Present study investigated the heart resistance to harmful stress following long-term waterpipe tobacco smoking (WTS) and moderate-intensity exercise training intervention in male Wistar rats. Animals were randomly divided into a non-ischemic heart control group and four ischemic heart groups including ISO (isoproterenol-treated), Ex + ISO (subjected to exercise plus ISO), S + ISO (exposed to hookah smoke plus ISO), and Ex + S + ISO (subjected to exercise along with hookah smoke plus ISO). After eight weeks of training and WTS, heart ischemia induced by isoproterenol injections. Then, cardiac functional indices and some biochemical and histopathological parameters were assessed. WTS + ISO reduced systolic pressure, ± dP/dt max, and contractility indices (P < 0.001 vs. ISO group) and increased end diastolic pressure and Tau index (P < 0.001 vs. ISO) of the left ventricle. Also, WTS + ISO was associated with an increase in Bax protein level and Bax/Bcl-2 ratio (P < 0.05 and P < 001, respectively, vs. ISO group) as apoptotic markers of heart tissue. Hookah smoke significantly decreased SIRT1 (P < 0.05 and P < 0.001, respectively, vs. ISO) and klotho (P < 0.01 and P < 0.001, respectively, vs. ISO) in serum and heart, and SIRT3 and pS9-GSK-3β (P < 001 and P < 0.05, respectively, vs. ISO) in heart tissue. Combination of exercise with WTS prevented the hookah smoke-induced alterations in apoptotic markers, cardiac functional indices, and SIRT1, SIRT3, klotho, and pS9-GSK-3β proteins. The findings demonstrated that hookah smoke inhalation intensifies ventricular dysfunction and decreases heart resistance to harmful stresses. Moderate-intensity exercise training attenuated these complications partly through recovering the klotho and sirtuins levels and apoptosis-survival balancing.

Manipulating Cellular Energetics to Slow Aging of Tissues and Organs

Up to now numerous studies in the field of gerontology have been published. Nevertheless, a well-known food restriction remains the most reliable and efficient way of lifespan extension. Physical activity is also a well-documented anti-aging intervention being especially efficient in slowing down the age-associated decline of skeletal muscle mass. In this review we focus on the molecular mechanisms of the effect of physical exercise on muscle tissues. We also discuss the possibilities of pharmacological extension of this effect to the rest of the tissues. During the exercise, the level of ATP decreases triggering activation of AMP-dependent protein kinase (AMPK). This kinase stimulates antioxidant potential of the cells and their mitochondrial respiratory capacity. The exercise also induces mild oxidative stress, which, in turn, mediates the stimulation via hormetic response. Furthermore, during the exercise cells generate activators of mammalian target of rapamycin (mTOR). The intracellular ATP level increases during the rest periods between exercises thus promoting mTOR activation. Therefore, regular exercise intermittently activates anti-oxidant defenses and mitochondrial biogenesis (via AMPK and the hormetic response) of the muscle tissue, as well as its proliferative potential (via mTOR), which, in turn, impedes the age-dependent muscle atrophy. Thus, the intermittent treatment with activators of (i) AMPK combined with the inducers of hormetic response and of (ii) mTOR might partly mimic the effects of physical exercise. Importantly, pharmacological activation of AMPK takes place in the absence of ATP level decrease. The use of uncouplers of respiration and oxidative phosphorylation at the phase of AMPK activation could also prevent negative consequences of the cellular hyper-energization. It is believed that the decline of both antioxidant and proliferative potentials of the cells causes the age-dependent decline of multiple tissues, rather than only the muscular one. We argue that the approach above is applicable for the majority of tissues in an organism.

Aging alters acetylation status in skeletal and cardiac muscles

During aging, organs such as skeletal muscle and heart require sufficient NAD+ both as a coenzyme for oxidative-reductive electron transfer and as a substrate for multiple signaling pathways. Sirtuins (SIRTs), a family of NAD+-dependent deacetylase, play an important role in regulating mitochondrial homeostasis and antioxidant defense by deacetylating transcription factors and enzymes such as PGC-1α, p65, GCN5, and SOD2. However, age-related DNA damage and increased SASP activate PARP-1 and CD38, the enzymes competing with SIRTs for NAD+. Thus, it is important to know how aging alters intracellular NAD+ status and NAD+-depending enzyme expression in muscles. In this study, we report that the acetylation level of muscle protein pool, as well as major SIRTs target proteins (PGC-1α, GCN5, p65, and SOD2), was significantly increased in hindlimb and cardiac muscles of 24-month old mice compared with their 6-month old counterparts, despite the fact that most members of the SIRT family were upregulated with aging. Aging increased the protein content of PARP-1 and CD38, whereas decreased NAD+ levels in both skeletal and heart muscles. Aged muscles demonstrated clear signs of mitochondrial dysfunction, oxidative stress, and inflammation. Taken together, our data suggest that despite the upregulation of SIRTs, aged muscles suffered from NAD+ deficit partly due to the competition of elevated CD38 and PARP-1. The enhanced acetylation of several key proteins involved in broad cellular functions may contribute to the age-related muscle deterioration.

Restoration of the Renin-Angiotensin System Balance Is a Part of the Effect of Fasting on Cardiovascular Rejuvenation: Role of Age and Fasting Models

Intermittent fasting (IF) is an intervention that can be beneficial for health span and mitigate the risk of developing age-related cardiovascular diseases; however, the involved mechanisms are not well understood. The present study investigated the effects of IF regimens on the plasma level of angiotensin II (Ang II), and the expression of Ang II receptors (AT1aR and AT2R) and angiotensin-converting enzyme 2 (ACE2) in the heart and aorta of male, 3-, 12-, and 24-month-old Wistar rats fed ad libitum (AL), fed ad libitum and fasted 1 day per week (FW), or fasted every other day (EOD) for 3 months. Aging was associated with high circulating levels of Ang II, high level of AT1aR protein expression in the heart and aorta, and low level of AT2R protein expression in the heart and aorta. Both FW and EOD decreased Ang II levels (p < 0.01, p < 0.001) and AT1aR protein expression in the heart (p < 0.01, p < 0.001) and aorta (p < 0.001) of old rats. Both FW and EOD increased the expression of AT2R protein in the heart (p < 0.05 and p < 0.001, respectively). However, only EOD increased the expression of AT2R protein (p < 0.05) in the aorta. In the old group, both the FW and EOD regimens induced a significant increase in the expression of ACE2 protein in the heart (p < 0.01, p < 0.001 vs. age-matched AL group, respectively). The results suggest that a part of the recovery effect of fasting on cardiovascular system in old rats is mediated through restoration of the balance of renin-angiotensin system.