BMAL1 Proteostasis, Circadian Dysfunction, and Ferroptotic Vulnerability in Osteoporosis: Current Evidence and Experimental Priorities

Jun 9, 2026Calcified tissue international

Disrupted Daily Protein Control and Cell Death Risk Linked to Bone Loss: Current Findings and Research Needs

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Abstract

Current evidence supports that ferroptosis is directly established in osteoblasts and osteocytes across several contexts related to osteoporosis.

Circadian regulation in bone involves more than just the abundance of BMAL1 and should be understood within a larger biological clock network.
Ferroptosis, a type of cell death, is implicated in osteoblasts and osteocytes in various osteoporosis-related conditions, including postmenopausal and diabetic scenarios.
BMAL1 plays a crucial role in the differentiation of skeletal cells and their ability to adapt to stress, although its degradation and related processes in bone cells have not been shown yet.
Although clockophagy is not an established pathway in skeletal cells, the existing literature provides a framework for exploring the potential pathogenic role of BMAL1 proteostasis in osteoporosis.

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Osteoporosis is increasingly recognized as a disorder of impaired skeletal adaptation in which endocrine stress, metabolic injury, altered mechanotransduction, remodeling imbalance, and redox vulnerability converge. Bone is also a circadian tissue, and ferroptosis is now directly implicated in skeletal cell dysfunction across several osteoporosis-related settings. This review examines whether proteostatic instability of brain and muscle ARNT-like 1 (BMAL1) could represent a mechanistically relevant link between these processes. To keep interpretation proportionate to the available data, bone-established evidence is distinguished from extra-skeletal bridge mechanisms and disease-contextual extrapolations that remain unproven in bone. Current evidence supports three conclusions. First, circadian regulation in bone extends beyond BMAL1 transcript abundance and must be interpreted within the broader clock network. Second, ferroptosis is directly established in osteoblasts and osteocytes across postmenopausal, glucocorticoid-related, diabetic, iron-overload, and unloading-related contexts. Third, BMAL1 is functionally important for skeletal differentiation and stress adaptation, but selective BMAL1 degradation and clockophagy have not yet been demonstrated in skeletal cells. Taken together, the literature does not justify describing clockophagy as an established skeletal pathway, but it does support a testable framework for defining when BMAL1 proteostasis may become pathogenic in osteoporosis and which experiments could most decisively validate or refute that possibility.

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BMAL1 Proteostasis, Circadian Dysfunction, and Ferroptotic Vulnerability in Osteoporosis: Current Evidence and Experimental Priorities

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