Differential toxicity profile of secreted and processed α-Klotho expression over mineral metabolism and bone microstructure

Distinct role of Klotho in long bone and craniofacial bone: skeletal development, repair and regeneration

Bone defects are highly prevalent diseases caused by trauma, tumors, inflammation, congenital malformations and endocrine abnormalities. Ideally effective and side effect free approach to dealing with bone defects remains a clinical conundrum. Klotho is an important protein, which plays an essential role in regulating aging and mineral ion homeostasis. More recently, research revealed the function of Klotho in regulating skeleton development and regeneration. Klotho has been identified in mesenchymal stem cells, osteoblasts, osteocytes and osteoclasts in different skeleton regions. The specific function and regulatory mechanisms of Klotho in long bone and craniofacial bone vary due to their different embryonic development, ossification and cell types, which remain unclear and without conclusion. Moreover, studies have confirmed that Klotho is a multifunctional protein that can inhibit inflammation, resist cancer and regulate the endocrine system, which may further accentuate the potential of Klotho to be the ideal molecule in inducing bone restoration clinically. Besides, as an endogenous protein, Klotho has a promising potential for clinical therapy without side effects. In the current review, we summarized the specific function of Klotho in long bone and craniofacial skeleton from phenotype to cellular alternation and signaling pathway. Moreover, we illustrated the possible future clinical application for Klotho. Further research on Klotho might help to solve the existing clinical difficulties in bone healing and increase the life quality of patients with bone injury and the elderly.

Eternal Youth: A Comprehensive Exploration of Gene, Cellular, and Pharmacological Anti-Aging Strategies

The improvement of human living conditions has led to an increase in average life expectancy, creating a new social and medical problem-aging, which diminishes the overall quality of human life. The aging process of the body begins with the activation of effector signaling pathways of aging in cells, resulting in the loss of their normal functions and deleterious effects on the microenvironment. This, in turn, leads to chronic inflammation and similar transformations in neighboring cells. The cumulative retention of these senescent cells over a prolonged period results in the deterioration of tissues and organs, ultimately leading to a reduced quality of life and an elevated risk of mortality. Among the most promising methods for addressing aging and age-related illnesses are pharmacological, genetic, and cellular therapies. Elevating the activity of aging-suppressing genes, employing specific groups of native and genetically modified cells, and utilizing senolytic medications may offer the potential to delay aging and age-related ailments over the long term. This review explores strategies and advancements in the field of anti-aging therapies currently under investigation, with a particular emphasis on gene therapy involving adeno-associated vectors and cell-based therapeutic approaches.

FGF23 and klotho at the intersection of kidney and cardiovascular disease

Cardiovascular disease is the leading cause of death in patients with chronic kidney disease (CKD). As CKD progresses, CKD-specific risk factors, such as disordered mineral homeostasis, amplify traditional cardiovascular risk factors. Fibroblast growth factor 23 (FGF23) regulates mineral homeostasis by activating complexes of FGF receptors and transmembrane klotho co-receptors. A soluble form of klotho also acts as a 'portable' FGF23 co-receptor in tissues that do not express klotho. In progressive CKD, rising circulating FGF23 levels in combination with decreasing kidney expression of klotho results in klotho-independent effects of FGF23 on the heart that promote left ventricular hypertrophy, heart failure, atrial fibrillation and death. Emerging data suggest that soluble klotho might mitigate some of these effects via several candidate mechanisms. More research is needed to investigate FGF23 excess and klotho deficiency in specific cardiovascular complications of CKD, but the pathophysiological primacy of FGF23 excess versus klotho deficiency might never be precisely resolved, given the entangled feedback loops that they share. Therefore, randomized trials should prioritize clinical practicality over scientific certainty by targeting disordered mineral homeostasis holistically in an effort to improve cardiovascular outcomes in patients with CKD.

The possible anti-seizure properties of Klotho

Recurrent seizures in epilepsy may lead to progressive neuronal damage, which can diminish health-related quality of life. Evaluation and control of pathological processes in the brain is valuable. It seems imperative that new markers and approaches for seizure alleviation be discovered. Klotho (Kl), an antiaging protein, has protective effects in the brain against neurological disorders. It may also have antiseizure effects by improving creatine transfer to the brain, upregulating excitatory amino acid transporters, and inhibiting insulin/insulin-like growth factor-1 (IGF-1), Wingless (Wnt), transforming growth factor-beta (TGF-β), and retinoic-acid-inducible gene-I (RIG-I)/nuclear translocation of nuclear factor-κB (NF-κB) pathways. Stimulation and activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and apoptosis signal-regulating kinase 1 (ASK1)/p38 mitogen‑activated protein kinase (MAPK) signaling pathways could also be considered other possible antiseizure mechanisms of Kl. In the present review, the roles of Kl in the central nervous system as well as its possible anti-seizure properties are discussed for the first time.

Fibroblast growth factor 23, klotho and heparin

PURPOSE OF REVIEW

Fibroblast growth factor (FGF) 23 is a bone-derived hormone that regulates phosphate and vitamin D metabolism by targeting the kidney. When highly elevated, such as in chronic kidney disease (CKD), FGF23 can also target the heart and induce pathologic remodeling. Here we discuss the mechanisms that underlie the physiologic and pathologic actions of FGF23, with focus on its FGF receptors (FGFR) and co-receptors.

RECENT FINDINGS

Klotho is a transmembrane protein that acts as an FGFR co-receptor for FGF23 on physiologic target cells. Klotho also exists as a circulating variant, and recent studies suggested that soluble klotho (sKL) can mediate FGF23 effects in cells that do not express klotho. Furthermore, it has been assumed that the actions of FGF23 do not require heparan sulfate (HS), a proteoglycan that acts as a co-receptor for other FGF isoforms. However, recent studies revealed that HS can be part of the FGF23:FGFR signaling complex and modulate FGF23-induced effects.

SUMMARY

sKL and HS have appeared as circulating FGFR co-receptors that modulate the actions of FGF23. Experimental studies suggest that sKL protects from and HS accelerates CKD-associated heart injury. However, the in vivo relevance of these findings is still speculative.

Alterations in the microenvironment and the effects produced of TRPV5 in osteoporosis

The pathogenesis of osteoporosis involves multiple factors, among which alterations in the bone microenvironment play a crucial role in disrupting normal bone metabolic balance. Transient receptor potential vanilloid 5 (TRPV5), a member of the TRPV family, is an essential determinant of the bone microenvironment, acting at multiple levels to influence its properties. TRPV5 exerts a pivotal influence on bone through the regulation of calcium reabsorption and transportation while also responding to steroid hormones and agonists. Although the metabolic consequences of osteoporosis, such as loss of bone calcium, reduced mineralization capacity, and active osteoclasts, have received significant attention, this review focuses on the changes in the osteoporotic microenvironment and the specific effects of TRPV5 at various levels.