Hypoxic-ischemic encephalopathy (HIE) is a primary contributor to neonatal death and neurodevelopmental disorders, accounting for approximately 25 % of neonatal deaths globally [1]. While mild hypothermia therapy offers some neuroprotective and prognostic benefits for neonates with HIE, its effectiveness is limited by a narrow therapeutic window and diminished efficacy in severe cause of HIE [2]. Therefore, exploring additional treatment avenues for HIE is necessary.

Hypoxic-ischemic brain damage (HIBD) induces a spectrum of damage responses, with mitochondria being the primary targets [3], [4]. Hypoxia-ischemia (HI) deplete high-energy phosphates, leading to membrane transporter dysfunctions and intracellular calcium overload [5]. This excess calcium compromises mitochondrial integrity, triggering cell death through apoptosis and necrosis [5]. Moreover, HI disrupts mitochondrial dynamics, including fission, fusion, autophagy, and biogenesis [5]. Thus, safeguarding and enhancing mitochondrial function post-neonatal hypoxic-ischemic events is crucial for developing effective HIBD treatment strategies.

PGC-1α, a pivotal regulator of mitochondrial biogenesis is essential for maintaining mitochondrial function and antioxidant capacity [6], [7]. Sirt1, an NAD+ dependent deacetylase, activates PGC-1α through deacetylation, promoting mitochondrial fatty acid metabolism post-HI [8], [9]. Activation of Sirt1 has been shown to bolster mitochondrial function by elevating PGC-1α levels [10]. Cells rapidly adjust to HI through post-translational modifications, with the modulation of PGC-1α, Sirt1, and AMPK playing a crucial role in the energy balance between glycolysis and mitochondrial function [3], [11], [12]. Enhancing the Sirt1/PGC-1α pathway has demonstrated neuronal protection in HIE contexts [13]. Additionally, mitochondrial DNA (mtDNA) stability, crucial for mitochondrial function, is largely governed by the mitochondrial transcription factor A (TFAM), which is regulated by PGC-1α, further highlighting the significance of the Sirt1-PGC-1α-TFAM pathway in mitigating HIE neuronal damage [14], [15], [16].

Vitamin K (VK), a fat-soluble vitamin comprising VK1 and VK2 subtypes, presents a unique therapeutic potential [17]. Although VK1 administration may lead to toxic effects, MK-4, a subtype of VK2, is prevalent in the brain and lacks significant side effects [17], [18]. VK1 has good clinical effect in preventing the haemorrhagic disease of the newborn [19]. Beyond mirroring VK1′s benefits, MK-4 exhibits protective properties against various diseases and enhances mitochondrial function, including respiratory capacity and biogenesis, and improves insulin resistance and muscle fiber expression [20], [21], [22]. Furthermore, MK-4 also shows promise in mitigating cell damage and preserving organ function in ischemia–reperfusion injuries [23], [24]. Research has revealed that MK-4 can alleviate apoptosis via the Sirt1 pathway and confer protection against conditions such as jaw necrosis, subarachnoid hemorrhage, and chronic diabetes [25], [26], [27]. As a pivotal figure in the sirtuin family, Sirt1, though predominantly a nuclear protein, has been extensively documented to activate PGC-1α, contributing to the amelioration of mitochondrial dysfunction [28]. Specifically, MK-4′s role in alleviating insulin resistance in skeletal muscle is mediated through the enhancement of mitochondrial function via Sirt1 signaling [22]. In the nervous system, the Sirt1/PGC-1α signaling pathway is crucial in diminishing mitochondria-induced oxidative stress and apoptosis, especially following subarachnoid hemorrhage (SAH) [29]. Additionally, TFAM, vital for mtDNA replication and transcription, relies on PGC-1α [30]. A reduction in PGC-1α levels leads to decreased TFAM expression, thereby compromising mitochondrial stability [31].

Despite these insights, the exact mechanisms by which MK-4 offers protection in ischemia–reperfusion injuries remain partially understood. This gap in knowledge points towards an improvement in mitochondrial function as a potential pathway. Therefore, we hypothesized that MK-4 plays a neuroprotective role in neonatal hypoxic-ischemic encephalopathy triggered by hypoxia–ischemia, through the mediation of the Sirt1-PGC-1α-TFAM pathway, thereby enhancing mitochondrial function.