Estrogen levels are the core factor influencing postmenopausal osteoporosis (PMOP). Estrogen can affect the progression of PMOP by regulating bone metabolism, influencing major signaling pathways related to bone metabolism, and modulating immune responses. When estrogen levels decline, the activity of Sirtuins (SIRTs) is reduced. SIRTs are enzymes that function as NAD+-dependent deacetylases. SIRTs can modulate osteocyte function, sustain mitochondrial homeostasis, and modulate relevant signaling pathways, thereby improving bone metabolic imbalances, reducing bone resorption, and promoting bone formation. In PMOP, SIRT1, SIRT3, and SIRT6 are primarily affected. Oxidative stress (OS) is a crucial factor in PMOP, as it generates excessive reactive oxygen species (ROS) that exacerbate PMOP. There is a certain interplay between SIRTs and OS. The reduced activity of SIRTs leads to intensified OS and the excessive accumulation of ROS. In return, ROS suppresses the AMPK signaling pathway and the synthesis of NAD+, which consequently diminishes the function of SIRTs. Natural SIRT activators and natural antioxidants, which are characterized by high safety, convenience, and minimal side effects, represent a potential therapeutic strategy for PMOP. This study aims to investigate the mechanisms of SIRTs and OS in PMOP and summarize potential therapeutic strategies to assist in the improvement of PMOP.

Heart failure represents the terminal stage in the development of many cardiovascular diseases, and its pathological mechanisms are closely related to disturbances in energy metabolism and mitochondrial dysfunction in cardiomyocytes. In recent years, nicotinamide adenine dinucleotide (NAD⁺), a core coenzyme involved in cellular energy metabolism and redox homeostasis, has been shown to potentially ameliorate heart failure through the regulation of mitochondrial function. This review systematically investigates four core mechanisms of mitochondrial dysfunction in heart failure: imbalance of mitochondrial dynamics, excessive accumulation of reactive oxygen species (ROS) leading to oxidative stress injury, dysfunction of mitochondrial autophagy, and disturbance of Ca²⁺ homeostasis. These abnormalities collectively exacerbate the progression of heart failure by disrupting ATP production and inducing apoptosis and myocardial fibrosis. NAD⁺ has been shown to regulate mitochondrial biosynthesis and antioxidant defences through the activation of the deacetylase family (e.g., silent information regulator 2 homolog 1 (SIRT1) and SIRT3) and to increase mitochondrial autophagy to remove damaged mitochondria, thus restoring energy metabolism and redox balance in cardiomyocytes. In addition, the inhibition of NAD⁺-degrading enzymes (e.g., poly ADP-ribose polymerase (PARP), cluster of differentiation 38 (CD38), and selective androgen receptor modulators (SARMs)) increases the tissue intracellular NAD⁺ content, and supplementation with NAD⁺ precursors (e.g., β-nicotinamide mononucleotide (NMN), nicotinamide riboside, etc.) also significantly elevates myocardial NAD⁺ levels to ameliorate heart failure. This study provides a theoretical basis for understanding the central role of NAD⁺ in mitochondrial homeostasis and for the development of targeted therapies for heart failure.

Perimenopausal women have fluctuating estrogen levels, which often trigger a range of symptoms of perimenopausal syndromes as estrogen levels decrease. Changes in perimenopausal estrogen levels are closely related to pain in knee osteoarthritis (KOA), which has long been a research area of great interest in perimenopausal women. In recent years, it has been found that perimenopausal estrogen levels have an important role in KOA pain, namely, that estrogen can affect KOA pain through the regulation of inflammatory responses, inhibition of cellular senescence and apoptosis, and modulation of neurotransmitters, which may provide new ideas for KOA treatment. This study aims to describe the mechanism of estrogen level on knee osteoarthritis pain in perimenopause and related non-pharmacological measures, such as physical therapy, physical factor therapy, traditional Chinese medicine, and diet, which can provide a reference for the study and treatment of pain in perimenopausal women with KOA.

Osteoarthritis (OA) is one of the most common joint diseases worldwide, which is characterized by degenerative changes in articular cartilage and secondary osteophyte formation. Numerous factors influence OA, including aging, obesity, joint injury and chronic overloading. Among them, the senescence of chondrocytes is one of the key factors leading to OA. Chondrocyte senescence can trigger inflammatory responses, extracellular matrix (ECM) degradation, mitochondrial dysfunction and oxidative stress (OS), and autophagy. Sirtuin 6 (SIRT6), as a deacetylase related to aging, can regulate chondrocyte senescence and plays a certain part in OA. SIRT6 regulates the number and membrane integrity of mitochondria, alleviates excessive Reactive Oxygen Species (ROS) in mitochondria and reduces inflammation-mediated mitochondrial damage. In addition, SIRT6 can also regulate the activity of antioxidant enzymes, inhibit excessive ROS induced by inflammatory factors, and alleviate OS. However, as aging progresses, the activity of SIRT6 will decrease. Activating the activity of SIRT6 becomes a potential therapeutic target and has a certain alleviating effect on the development of OA. The supplementation of nicotinamide adenine dinucleotide (NAD+) precursors and SIRT6-specific activators can increase SIRT6, alleviate chondrocyte senescence, and reduce OA. This paper aims to focus on mitochondrial dysfunction and OS to explore SIRT6’s effects on OA chondrocytes’ senescence under aging and summarize the potential therapeutic targets for activating SIRT6 to provide assistance for the improvement of OA.

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder characterized by progressive loss of cognitive function. Its main pathological features include accumulation of Amyloid-beta (Aβ) plaques, excessive phosphorylation of microtubule-associated protein tau (tau protein), and neuroinflammation. In recent years, studies have confirmed intestinal flora is closely connected to AD. Gut–brain axis has an important part in AD. Intestinal flora can achieve signal communication between gut and brain through metabolic, immune, neural, and endocrine pathways, thereby slowing down AD. It has been discovered that exercise is not only beneficial to physical health but also has a positive impact on the brain function. In recent years, more and more studies have found exercise can alleviate AD through the following four major pathways: regulating the diversity of intestinal flora, strengthening the blood–brain barrier (BBB), regulating immune homeostasis, and upregulating the brain-derived neurotrophic factor (BDNF). In this review, we have summarized intestinal flora in AD and systematically expounded potential regulatory pathways of exercise in modulating intestinal flora for AD. This provides a more theoretical basis for subsequent research targeting “gut–brain axis” to regulate AD. At the same time, this review also summarizes differences in different exercise types on improving intestinal flora for alleviating AD, providing new ideas and strategies for AD.

This narrative review examines perimenopause as a critical transitional phase in women’s lives, often accompanied by elevated vulnerability to anxiety and depression. Dysfunction of the gut–brain axis is one of the key factors contributing to perimenopausal mood disorders and is currently receiving extensive attention. GBA dysfunction can trigger neurotransmitter metabolic imbalance, intestinal barrier impairment, and neuroinflammatory responses. Tryptophan (Trp) and γ-aminobutyric acid (GABA) serve as essential precursors and direct modulators of key neurotransmitters, and the dysregulation of their metabolic pathways has been implicated in perimenopausal anxiety and depression in animal models and limited clinical observations. Trp influences 5-hydroxytryptamine (5-HT) by affecting emotional states. GABA is the primary inhibitory neurotransmitter in the central nervous system and is closely associated with anxiety and depression. Fluctuations in estrogen levels during perimenopause significantly alter the composition and metabolic activity of the gut microbiota, which in turn affects Trp metabolism and GABA synthesis through increased intestinal permeability, activation of immune-inflammatory responses, and disruption of hypothalamic–pituitary–adrenal (HPA) axis function. Although traditional hormone replacement therapy and pharmacological treatments are effective, they are associated with some side effects. Preliminary evidence from in vitro and animal studies suggests that nutritional interventions targeting Trp and GABA metabolism within the gut–brain axis may offer a novel research direction, though their efficacy in perimenopausal women remains to be established. Potential nutritional strategies, including supplementation with Trp and its precursors, inhibition of the kynurenine pathway (KP), and supplementation with probiotics and prebiotics, can modulate Trp and GABA metabolism. This review focuses on Trp and GABA metabolic regulation via the gut–brain axis to explore pathogenesis of perimenopausal anxiety and depression and summarize potential nutritional intervention targets, thereby providing a scientific basis for emotional management in perimenopausal women.