Across glucocorticoid, chemotherapeutic, and metabolic-drug models, exercise invariably protects skeletal muscle by re-establishing FoxO3a Ser²⁵³ phosphorylation, driving the transcription factor out of the nucleus and relieving the MuRF1/Atrogin-1 axis. What distinguishes one model from another is which upstream brake is recruited and whether parallel catabolic routes (autophagy, MSTN/Smad) are also restrained (Supplementary Table S1).

In rats treated with dexamethasone, running and resistance lifting decrease HDAC4-mediated deacetylation of FoxO3a, restoring its phosphorylation and suppressing MuRF1/Atrogin-1 expression (Liang et al., 2025). Resistance work goes a step further and upregulates Sestrin2, an AMPK–AKT facilitator that blocks FoxO3a nuclear import even when HDAC4 activity persists (Yang Y. et al., 2023). These observations imply that exercise modality selects distinct regulators (HDAC4 versus Sestrin2) while converging on the same FoxO3a endpoint.

In mice injected with cisplatin, treadmill or weighted-ladder protocols reinstate AKT/PGC-1α signaling, rebound FoxO3a phosphorylation, and limit MuRF1/Atrogin-1 induction (Bae et al., 2021; Sakai et al., 2017). Yet only one study reports concordant repression of autophagy genes such as Beclin-1, BNIP3, and LC3-II (Bae et al., 2021), highlighting a methodological controversy. Autophagy control appears sensitive to drug dose, exercise intensity, and sampling time, whereas FoxO inhibition is comparatively robust.

In rats subjected to chronic doxorubicin exposure, endurance exercise normalizes FoxO3a phosphorylation but leaves MuRF1 or autophagy markers unchanged, suggesting a FoxO-independent proteolytic drive (Kwon, 2020). By contrast, in an acute doxorubicin toxicity model, short-term running cuts FoxO1/FoxO3 mRNA and BNIP3 expression, a response attributed to a surge in PGC-1α, an established FoxO corepressor (Kavazis et al., 2014). Thus, time-course (acute vs. chronic) rather than exercise per se dictates whether downstream atrogenes track with FoxO modulation.

In mice receiving dapagliflozin, resistance training lowers the total abundance of FoxO1/3a proteins, not merely their phosphorylation, and rescues mTORC1-anabolic signaling. It preserves muscle despite persistent glycosuria (Yang X. et al., 2023). This finding broadens the catalogue of exercise-controlled nodes from post-translational phosphorylation to outright protein turnover.

In summary (Figure 2), pharmacologically driven muscle‐wasting states share a common vulnerability. They all hinge on unchecked FoxO3a activity to amplify ubiquitin-proteasome and, variably, autophagy catabolism. Exercise consistently exploits this vulnerability by restoring FoxO3a phosphorylation and nuclear exclusion. It does so through drug- and modality-specific routes (HDAC4, Sestrin2, PGC-1α/TFEB, or accelerated FoxO protein turnover). These nuances matter clinically. Selecting the proper exercise method could target the dominant upstream inhibition for a given therapy. Thereby, it maximizes muscle preservation without pharmacologic add-ons. Nevertheless, the field is still performed in young-rodent models, and autophagy read-outs remain inconsistent, warnings that FoxO3a may not always be the final arbiter of drug-induced atrophy, especially in chronic or multimorbid settings. Bridging these gaps will require integrative studies in aged or diseased humans, systematic tracking of parallel catabolic circuits, and trials that match exercise dose and modality to the specific pharmacologic insult. Only then can we translate the elegant convergence on FoxO3a into reliable, personalized countermeasures against therapy-related muscle loss.

This section examines muscle-specific studies focused on recovery and hypertrophy, particularly involving FOXO protein regulation under different exercise protocols and supplementation strategies. These findings emphasize the modulation of catabolic and anabolic pathways to enhance muscle growth and recovery (Supplementary Table S1).

In aged soleus (a predominantly oxidative muscle) high-intensity interval training (HIIT) only blunted FoxO3 when it was paired with branched-chain amino acids (BCAA) carried in nano-chitosan; upslope running further amplified this effect, implying that both a nutrient signal (leucine-sensitive mTORC1) and the higher mechanical load typical of incline work are necessary to override the catabolic FoxO program in senescent slow-twitch fibers (Sadri et al., 2020). By contrast, in the younger, mixed-fiber gastrocnemius, the same HIIT stimulus without supplements suppressed FoxO1 and simultaneously raised Akt phosphorylation, lowered myostatin/Smad2-3 signaling, and expanded cross-sectional area (Biglari et al., 2020). Taken together, these data suggest that the fast/slow fiber composition and nutritional state dictate whether FoxO1 or FoxO3 is the dominant brake on hypertrophy, as well as whether Akt/mTOR or the myostatin/Smad pathway provides the primary counter-signal.

Resistance training introduces a different regulatory layer. When ladder-climbing in rats was combined with pharmacological TGF-β1/Smad blockade, FoxO1/3 transcripts fell more sharply than with loading alone, and mTOR/S6K1 activation increased commensurately (Nikooie et al., 2020). This synergy suggests crosstalk: both FoxOs and Smads converge on the promoters of atrogenes, such as MuRF1/Atrogin-1, so simultaneous suppression of each pathway may be required for maximal protein synthesis under high mechanical tension.

Following myocardial infarction, systemic inflammation and circulating catabolic cytokines typically dephosphorylate (activate) FoxO3, accelerating soleus wasting. Progressive resistance exercise partially restored FoxO3 phosphorylation (the inactive, cytoplasmic form), reinstated redox enzymes, and attenuated glycolytic over-reliance, thereby limiting proteolysis and preserving contractile architecture (Souza et al., 2023). The finding underscores that, in disease, the beneficial FoxO shift arises less from increased Akt signaling and more from the dampening of stress kinases that otherwise drive FoxO nuclear import.

Mechanistically, the studies converge on a unifying theme. FoxO inhibition is necessary but not sufficient for muscle growth. A second signal is always present: nutrient-dependent mTORC1 in the HIIT + BCAA model, load-induced S6K1 in resistance training, or redox normalization after infarction. The relative contribution of FoxO1 versus FoxO3 also appears to be fiber-type dependent, with FoxO3 dominating in oxidative muscles and FoxO1 shaping responses in glycolytic or mixed fibers.

Collectively, these muscle-specific studies show that FoxO proteins act as an adaptable regulator rather than a simple on/off switch for hypertrophy. Exercise intensity, contraction mode, muscle phenotype, nutritional cues, and pathological stress each bias the regulatory role differently, explaining why identical changes in FoxO phosphorylation can lead to divergent outcomes. Integrating FoxO modulation with the parallel Akt/mTOR, myostatin/Smad, and redox axes, therefore, offers a more precise blueprint for designing exercise or adjuvant therapies that maximize recovery and growth while minimizing atrophy in both healthy and diseased states.

Recent research highlights the role of exercise in enhancing cardiac metabolic efficiency and promoting angiogenesis through the modulation of FoxO proteins (Table 1).

In healthy juvenile rats exposed to progressively heavier swim sessions, a sharp decline in miR-223-3p relieves post-transcriptional repression of FoxO1, allowing nuclear accumulation that drives GLUT4 transcription and accelerates cardiac glucose clearance (Carrillo et al., 2023). In fructose-fed Wistar rats performing low-intensity treadmill running, FoxO1 not only rises in abundance but is enzymatically reset. SIRT1 removes inhibitory acetyl groups, allowing FoxO1 to shift its focus toward genes that favor fatty acid oxidation over lipid storage (Kostić et al., 2023). Although both activate FoxO1, they rely on different molecular levers—microRNA suppression versus deacetylation—and their metabolic outcomes diverge in substrate preference (glucose versus fatty acids). This emphasizes that FoxO1 activity is finely graded rather than simply switched on or off.

A different picture emerges in the diabetic myocardium. Combining moderate treadmill training with the histone-deacetylase metabolite sodium butyrate lowers miR-34a, reduces FoxO1 protein, and permits a HIF-1α-driven angiogenic pathway to dominate (Sarlak et al., 2023). Suppressing FoxO1 is advantageous here because excessive FoxO1 can oppose HIF-1α-mediated vessel formation and exacerbate oxidative stress. Thus, when oxygen delivery is the critical constraint, dampening FoxO1 becomes cardioprotective.

Taken together, these rodent studies show that both the direction (up- or downregulation) and the qualitative nature (post-transcriptional versus post-translational) of FoxO1 control match the dominant stressor—substrate overload, lipotoxicity, or hypoxia.

Recent research demonstrates the beneficial modulation of cardiac function through various signaling pathways involving FoxO proteins (Table 1).

Two hypertensive rat studies illustrate the cardioprotective face of FoxO3 activation. In spontaneously hypertensive rats, treadmill exercise combined with the DIKTNKPVIF peptide enhanced AMPK and SIRT1 activity, leading to FoxO3 deacetylation, mitochondrial biogenesis, and a coordinated reduction in oxidative stress, apoptosis, and fibrosis (Ho et al., 2022). A parallel study substituting the soybean peptide VH-4 for DIKTNKPVIF produced a closely aligned AMPKα1/SIRT1/PGC-1α response, again lowering hypertensive damage, despite reporting FoxO3 phosphorylation rather than deacetylation (Baskaran et al., 2022). The mechanistic convergence—improved mitochondrial quality control—underscores that post-translational status (phosphorylated vs. deacetylated) can be less important than the broader signaling context in which FoxO3 operates.

In aged rat hearts, endurance swimming alone phosphorylated FoxO3 via the PI3K/Akt pathway, favoring its cytoplasmic retention. Adding the SIRT1 activator resveratrol tipped the balance back toward nuclear FoxO3 exclusion without abolishing AMPK signaling. The dual intervention minimized apoptosis and fibrosis while improving diastolic function (Lin et al., 2014). This experiment illustrates how FoxO3 “inactivation” can still be beneficial when it prevents the persistence of pro-apoptotic gene programs that dominate in senescence.

Progressive swim training in adult female mice induced canonical physiological hypertrophy; the response was blunted when FoxO1 was deleted. Although Akt-mediated FoxO1 phosphorylation nominally reduces its transcriptional activity, residual nuclear FoxO1 proved indispensable for upregulating autophagy genes and the chaperone Hsp70, both of which are critical for protein quality control during growth. Thus, phosphorylation is an oversimplification; low-level FoxO1 activity appears permissive for adaptive remodeling (Weeks et al., 2021).

Across these rodent models, aerobic exercise was the standard stimulus. Whether resistance training or mixed-modality exercises, more typical of human cardiac rehabilitation, evoke the same FoxO patterns remains untested. Species differences also matter: rodent hearts rely more heavily on glycolytic flux and manifest larger Akt responses than adult human hearts, potentially magnifying FoxO phosphorylation. Limited human data (endomyocardial biopsies from endurance athletes and explanted failing hearts before/after ventricular unloading) suggest exercise reduces nuclear FoxO3 abundance and increases PGC-1α expression, but sample sizes are small, and longitudinal evidence is lacking. Moreover, nutraceutical co-interventions (DIKTNKPVIF, VH-4, resveratrol) that accentuated FoxO signaling in rodents have not been evaluated clinically, highlighting a clear translational gap.

Regular physical exercise has been shown to influence various molecular pathways associated with cognitive impairment and neuroprotection. This section presents recent studies that explore the relationship between exercise and protein regulation in cognitive health (Table 3).

A three-month aerobic training in African Americans with mild cognitive impairment (MCI) elevated skeletal-muscle and circulating FoxO1 and FBXO32 in men but not in women (Bedada et al., 2021). That sex-specific divergence, observable in the clinic rather than in pre-clinical models, underlines both the translational promise of the pathway (FoxO1 is inducible without pharmaceuticals) and the persistent knowledge gap (we do not know whether the same stimulus would modulate FoxO3a, or whether resistance or mixed-mode exercise might eliminate the female “non-responder” phenotype).

Pre-clinical studies elaborate the mechanistic palette through which different exercise modalities converge on FoxO signalling while still producing context-specific outcomes. In a mouse model of cerebral ischemia, voluntary wheel running increased myokine irisin; irisin, in turn, upregulated the longevity protein Klotho, permitting nuclear FoxO3a accumulation and MnSOD transcription, thereby quenching reactive oxygen species and improving cognition (Jin et al., 2021). By contrast, high-intensity interval training (HIIT) in diabetic rats relied on a metabolic cue—lactate—to activate SIRT1, deacetylate FoxO3, drive PINK1/Parkin-dependent mitophagy, and limit Tau and Aβ deposition (Khosravi et al., 2024). In another metabolic milieu (streptozotocin-induced diabetes), moderate-intensity treadmill running favored PI3K/AKT-mediated phosphorylation of FoxO1, keeping it out of the nucleus, thereby damping NF-κB/NLRP3 inflammasome activity and restoring synaptic plasticity (Wang et al., 2019). Finally, in aging mice, aerobic exercise reduced the expression of the pro-apoptotic DAPK1/CDKN2A/REDD1 axis while simultaneously phosphorylating and excluding FoxO1 from the nucleus, thereby curbing FasL-driven cell death and preserving memory (Liu et al., 2023). Taken together, these experiments demonstrate that FoxO activation (via deacetylation or nuclear import) is desirable when enhanced proteostasis or antioxidant defense is rate-limiting. In contrast, FoxO inhibition (via phosphorylation-dependent export) is beneficial when excessive catabolic or inflammatory signaling predominates.

A comparison highlights species and mode-of-exercise differences that the literature often glosses over. Rodent data are almost exclusively derived from treadmill or swimming paradigms that mimic steady-state endurance work, whereas the lone human trial used mixed aerobic machines; resistance training, known to produce qualitatively different PI3K/AKT and mTOR dynamics, remains virtually unexplored. Moreover, the molecular “switch” that toggles FoxO between protective and maladaptive roles varies across tissues or disease models. SIRT1-driven deacetylation predominates in diabetic HIIT, irisin-Klotho signaling in cerebral ischemia, and canonical PI3K/AKT phosphorylation in systemic inflammation. Whether these discrepancies reflect species-specific regulation, fiber-type composition, or simply the metabolic context (hyperglycemia, hypoxia, senescence) is unresolved.

In Na Zhao’s study, the FoxO protein is regulated through the activation of the SIRT1/FoxO1/3 axis following 12 weeks of treadmill exercise in APP/PS1 mice. This exercise regimen effectively enhanced PINK1/Parkin-mediated mitophagy activity in the hippocampus, thereby improving mitochondrial function and reducing β-amyloid plaque accumulation. The study demonstrated that SIRT1 activation, which is triggered by an elevated NAD+/NADH ratio, promotes the deacetylation and activation of FoxO1 and FoxO3, stabilizing PINK1 and facilitating mitophagy. Moreover, inhibition of SIRT1 using the specific inhibitor EX527 confirmed that the SIRT1-FoxO1/3 pathway is essential for exercise-induced mitophagy. This mechanism ultimately leads to ameliorated learning and memory deficits in Alzheimer’s disease mouse models, suggesting a potential therapeutic strategy targeting mitophagy dysfunction via the SIRT1-FOXO1/3 axis (Zhao N. et al., 2023).

In Yea-Hyun Leem’s study, the FoxO protein, specifically FoxO3a, is regulated through the SIRT3/FoxO3a signaling axis which is activated by creatine supplementation and exercise. This activation promotes antioxidative effects by enhancing the expression of antioxidant enzymes, thereby mitigating oxidative stress and neuroinflammation. The study demonstrates that the activation of the AMPK/Nrf2 and SIRT3/FoxO3a pathways leads to reduced α-synuclein oligomerization and necroptotic cell death in the substantia nigra area of a Parkinson’s disease mouse model, ultimately contributing to neurobehavioral recovery and neuroprotection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity (Leem et al., 2024).

Research has demonstrated that exercise can modulate various signaling pathways to promote neuroprotection and recovery following stroke and ischemic injury. This section highlights recent studies exploring the regulatory mechanisms involving FOXO proteins in these contexts (Table 3).

A study investigated the role of the AMPK/FOXO3a/SKP2/CARM1 signaling pathway activated by exercise pretreatment before ischemic stroke in mice. This pathway enhances transcriptional activity of transcription factor EB (TFEB), improving autophagic flux in the peri-infarct cortex. Exercise-induced AMPK activation increases FOXO3a phosphorylation, stabilizing CARM1, which binds to TFEB to enhance its transcriptional activity. This process reduces neuroinflammation, oxidative stress, and apoptosis, resulting in improved neurological function and reduced brain injury. Blocking TFEB or inhibiting AMPK nullified these protective effects, underscoring the significance of the AMPK-FOXO3a-TFEB pathway in exercise-mediated stroke protection (Zhao Y. et al., 2023).

Another study examined the PI3K/AKT/FoxO1 signaling pathway activated by exercise post-conditioning following ischemic stroke in rats. Exercise post-conditioning increased phosphorylation of PI3K, AKT, and FoxO1, promoting cytoplasmic retention of phosphorylated FoxO1 and thereby reducing its nuclear activity. This reduction in FoxO1 nuclear translocation suppressed the expression of gluconeogenic enzymes PCK-1 and PCK-2, lowering oxidative stress, apoptosis, and glucose levels. The findings indicate that exercise post-conditioning improves neurological function and reduces infarct volume by inhibiting gluconeogenesis through the PI3K/AKT/FoxO1 pathway (Li et al., 2023).

In conclusion, these studies highlight the critical role of FOXO signaling pathways in mediating exercise-induced neuroprotection and recovery following ischemic injury. Targeting these pathways through exercise-based interventions may offer promising therapeutic strategies for enhancing post-stroke recovery.

In the study by Liu et al., the FoxO protein is regulated through the FoxO signaling pathway during resistance exercise, specifically mediated by the protein kinase Sgk1. The RNA sequencing analysis revealed that Sgk1 is consistently upregulated in the frontal cortex, hippocampus, and muscle, with significant association to pathways related to learning, memory, and cognition. Further analysis indicated that Sgk1 is particularly enriched in the FoxO signaling pathway, which is recognized as the most significantly altered pathway among the tissues examined. This regulation promotes synaptic plasticity, improved cognitive performance, and enhanced mental health. Additionally, Sgk1 was identified as a key myokine likely contributing to the muscle-brain crosstalk mechanism. The positive correlation between Sgk1 expression and cognitive performance suggests its potential role as a candidate myokine for improving cognition and mental health through resistance exercise (Liu et al., 2024).

In Khoramipour’s study, the FoxO1 protein is regulated through the leptin signaling pathway after 8 weeks of HIIT in male rats with T2DM. HIIT enhanced hypothalamic leptin receptor expression and activated the downstream JAK2/STAT3 pathway, leading to increased phosphorylation of STAT3. Phosphorylated STAT3 promotes the expression of anorexigenic neuropeptides such as POMC and CART, while simultaneously inhibiting orexigenic neuropeptides. Additionally, HIIT reduced the expression of suppressor of cytokine signaling (SOCS3) and FoxO1 in the hypothalamus, thereby relieving the inhibition of anorexigenic pathways. Reduced FOXO1 activity, achieved through its phosphorylation and exclusion from the nucleus, allowed increased POMC gene expression, contributing to improved appetite regulation. The study found that HIIT improved hypothalamic appetite regulation by enhancing leptin signaling and downregulating FOXO1, which is crucial for appetite control in T2D rats (Khoramipour et al., 2023).

Physical exercise has been shown to modulate insulin sensitivity and resistance through various molecular pathways involving the FOXO1 protein. This section highlights recent studies investigating the regulatory mechanisms by which exercise impacts insulin signaling and glucose metabolism (Table 4).

In mice, a single mesocycle of HIIT provokes a surge in muscle-derived exosomes enriched for miR-133a and miR-133b. Once taken up by hepatocytes, these microRNAs directly suppress FoxO1 mRNA, thereby lowering PEPCK and G6Pase expression and normalizing glucose tolerance—even when canonical insulin signalling remains defective (Castaño et al., 2020). This exosomal mechanism is notable because it operates upstream of AKT and may therefore compensate for insulin-resistant states in which AKT activation is blunted.

By contrast, moderate-intensity continuous training relies on the canonical insulin–AKT pathway. Eight weeks of treadmill running in pre-diabetic or overtly diabetic mice markedly increases hepatic AKT phosphorylation, promotes FoxO1 phosphorylation at Ser256, drives its nuclear export, and diminishes transcription of PEPCK (Kazeminasab et al., 2023). Interestingly, the same protocol in healthy mice raises IRS-1 and AKT activity without further altering FoxO1 localization, suggesting that a metabolic “ceiling effect” limits additional repression once FoxO1 is already maximally inhibited. Thus, aerobic training appears to restore, rather than simply augment, AKT-FoxO1 coupling when insulin resistance is present.

Resistance exercise adds a third layer. Short-term ladder climbing performed by obese mice enhances both AKT and GSK3β phosphorylation in the liver, thereby phosphorylating FoxO1 and reducing PEPCK and G6Pase expression. However, this process occurs without altering adiposity or circulating insulin levels (Pereira et al., 2022). These data imply that mechanical–load–derived cues can directly reprogram hepatic glucose output, separating the glycemic benefits of resistance training from weight loss per se—a clinically relevant distinction for individuals who struggle to reduce fat mass.

Taken together, the three modalities reveal a pattern of mechanistic divergence that nonetheless converges on the inhibition of FoxO1. HIIT delivers endocrine microRNAs that silence FoxO1 transcripts; endurance exercise restores AKT-mediated phosphorylation of FoxO1 in insulin-resistant livers; resistance exercise mobilizes mechano-sensitive pathways that also activate AKT and collateral regulators, such as GSK3β. Each route may dominate or fail depending on the patient’s metabolic phenotype, disease duration, or even age- and sex-related differences in exosome biogenesis, or insulin signalling fidelity. Collectively, current evidence suggests that HIIT, continuous aerobic training, and resistance exercise all enhance insulin sensitivity by suppressing hepatic FoxO1.

The regulation of FoxO proteins through various exercise regimes and nutritional interventions has been a topic of extensive research. This section summarizes key studies that investigate how FoxO proteins, particularly FoxO1 and FoxO3, respond to exercise, dietary supplements, and their combined effects on metabolic health (Table 4).

Rodent endurance work provides the evidence that acute aerobic bouts blunt FoxO-driven gluconeogenesis. In the classic swimming study by Ropelle et al., diet-induced obese rats underwent a single session of moderate-intensity swimming, resulting in the rapid re-phosphorylation of hepatic Akt. It forces FoxO1 into the cytoplasm and suppresses PEPCK/G6Pase transcription (Ropelle et al., 2009). The same stimulus downregulated PGC-1α, weakening its co-activator synergy with FoxO1. Mechanistically, this illustrates a tight Akt/FoxO/PGC-1α triad in which endurance exercise acutely shifts liver metabolism from glucose production to storage. Notably, the effect size (approximately a 50% rise in FoxO1 Ser²⁵⁶ phosphorylation) was achieved without changes in total FoxO1 protein, underscoring that post-translational modification, rather than abundance, is the primary control point in the obese liver.

By contrast, chronic swimming combined with a bioactive peptide in senescence-accelerated mice rewired FoxO3 rather than FoxO1 (Asokan et al., 2020). Twelve weeks of progressive aquatic training elevated pAMPK, SIRT1, and PGC-1α, culminating in FoxO3 phosphorylation and cytoplasmic retention. The switch from an Akt-to-AMPK-centered axis highlights that the upstream kinase controlling FoxO can diverge with training duration and energetic stress. Akt responds to insulin/glucose flux, whereas AMPK senses muscle ATP depletion. Notably, suppression of cardiac and hepatic apoptosis in this ageing model aligns with FoxO3’s canonical role in mitochondrial quality control, suggesting that endurance exercise curbs oxidative damage via AMPK/SIRT1/FoxO3 signalling rather than the Akt/FoxO1 route dominant in the obese but otherwise young rat.

Moving from muscle–liver cross-talk to adipose tissue, Lu et al. mined three transcriptomic datasets spanning intense cycling in humans and treadmill running in mice (Lu et al., 2023). Moderate-intensity bouts upregulated a FoxO-centered lipid-catabolic genes and improved adipose immune tone; in contrast, maximal efforts triggered a broad inflammatory transcriptome, including NF-κB and NLRP3 components, despite further FoxO activation. The observation that the FoxO pathway itself is not anti-inflammatory under high-load conditions emphasizes intensity-specific bifurcation. FoxO can sit upstream of both favorable (lipolytic) and adverse (inflammatory) outputs, depending on the surrounding signal milieu. The inter-species concordance—similar FoxO target enrichment in mouse and human adipose tissue, despite distinct exercise modes—supports translational relevance but also highlights the need for dose-finding studies in humans.

Human resistance data remain scarce. However, the 16-week treadmill-based strength protocol in postmenopausal women begins to close the gap (Yang et al., 2024). Training alone raised peripheral-blood-mononuclear-cell SIRT1 without altering FoxO1 mRNA, whereas DHA co-supplementation modestly increased FoxO1 expression but did not change hepatic FoxO1 activity. Clinically, the combined intervention improved MASLD biomarkers, indicating that metabolic benefit can accrue even when FoxO regulation is incomplete. The dissociation between circulating-cell expression and hepatic action echoes a recurrent translational barrier: tissue-specific FoxO status is rarely accessible in vivo, complicating the interpretation of human trials.

Across these studies, two mechanistic themes emerge. First, post-translational gating dominates FoxO control. Phosphorylation by Akt or AMPK (with SIRT1-mediated deacetylation as a parallel modifier) determines subcellular localization and transcriptional output, while changes in total FoxO protein are secondary. Second, exercise intensity and duration re-route the upstream kinase axes, shifting FoxO from an insulin-sensitive gluconeogenic repressor (Akt-FoxO1) toward an energy-sensing mitophagy regulator (AMPK-FoxO3). Diet augments this re-routing—either by providing antioxidant peptides that amplify AMPK signalling (Asokan et al., 2020) or by delivering n-3 PUFAs that selectively boost FoxO1 transcription (Yang et al., 2024). Notably, endurance paradigms in rodents converge on improvements in insulin sensitivity and organelle quality.

In contrast, early human studies suggest a broader metabolic benefit that is only partially dependent on FoxO. This divergence highlights a translational gap. Rodents permit tissue biopsies and kinase mapping, whereas human trials must rely on blood surrogates and imaging, thereby limiting mechanistic resolution.

Collectively, the data indicate that FoxO proteins function as context-dependent metabolic switches, whose activity is modulated by the type and dose of exercise, as well as concurrent nutritional cues. Endurance swimming and moderate cycling preferentially engage Akt- or AMPK-driven FoxO phosphorylation to suppress gluconeogenesis, stimulate lipolysis, and enhance mitochondrial defense, whereas resistance-oriented interventions in humans achieve metabolic benefits even with incomplete FoxO modulation. Going forward, integrating tissue-targeted biomarkers into human trials and systematically mapping kinase-specific FoxO signatures across various exercise intensities will be crucial to translating these mechanistic insights into precise, clinically actionable prescriptions for metabolic disease.