Mitochondrial DNA methylation drift and postoperative delirium in mice

Swimming Exercise Pretreatment Attenuates Postoperative Delirium-Like Behavior in Type 2 Diabetic Rats by Enhancing Mitochondrial Biogenesis Through Activation of SIRT2 Deacetylation

Postoperative delirium (POD) is a common postsurgical complication that seriously affects patients' prognosis and imposes a heavy burden on families and society. Type 2 diabetes mellitus (T2DM) is a major risk factor for POD. The susceptibility mechanisms of POD in T2DM individuals and the role of exercise preconditioning remain unclear. Adult rats with and without T2DM were used to assess the promotive effect of diabetes on postoperative delirium-like behavior. The diabetic rats were also subjected to a swimming exercise program before surgery. The potential beneficial effect of exercise preconditioning on postoperative cognition was evaluated by examining neurobehavior, hippocampal neuroinflammation, mitochondrial morphology, and function in diabetic rats. Finally, underlying mechanisms were further analyzed by exploring the role of the sirtuin family in vivo and in vitro. We found that performing tibial fracture surgery resulted in delirium-like behavior and inhibited hippocampal mitochondrial biogenesis in diabetic rats but not in healthy rats. Preoperative swimming exercise was beneficial in attenuating delirium-like behavior, inhibiting neuroinflammation, and improving mitochondrial biogenesis and function. Preoperative swimming exercise achieved these positive effects by upregulating SIRT2-mediated peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) deacetylation and activating mitochondrial biogenesis in T2DM rats.

Effect of combination of multiple anti-inflammatory drugs strategy on postoperative delirium among older patients undergoing hip fracture surgery: a pilot randomized controlled trial

BACKGROUND

Postoperative delirium is the most common complication in older patients and is associated with surgery-induced inflammation. Although inflammation plays a key role in delirium, the potential benefits of a comprehensive anti-inflammatory approach to managing perioperative systemic inflammation remain underexplored. This study evaluated whether a perioperative anti-inflammatory bundle strategy, combining dexmedetomidine, glucocorticoids, ulinastatin, and nonsteroidal anti-inflammatory drugs, reduces the risk of postoperative delirium in older patients undergoing hip fracture surgery.

METHODS

This dual-center, double-blind, placebo-controlled, parallel-group, pilot study was conducted from August 2023 to January 2024 at two tertiary university hospitals. A total of 132 patients aged ≥ 65 years with an American Society of Anesthesiologists physical status of 2 or 3 scheduled for elective hip fracture surgery were screened and randomized to receive either an anti-inflammatory drug bundle or a placebo. The primary outcome was postoperative delirium, identified within the first three postoperative days. Postoperative blood inflammatory markers and acute pain were measured for mediation analysis.

RESULTS

Of the 132 patients randomized, 123 (93%) completed the trial (mean age, 82 years; 75% women). The prevalence of postoperative delirium was significantly lower in the anti-inflammatory bundle group (15%, 9/62) compared to the placebo group (44%, 27/61) (risk difference, - 30 percentage points [95% CI, - 45 to - 15]; relative risk [RR], 0.33 [95% CI, 0.17 to 0.64]; P = 0.001). No major adverse events were reported in either group. The postoperative CRP level in the anti-inflammatory bundle group was significantly lower (predicted mean difference: - 29.4 [95% CI: - 46.5, - 12.2] mg·L-1; adjusted P < 0.001). Mediation analysis showed a significant indirect association between the anti-inflammatory bundle and postoperative delirium through reduced systemic inflammation (odds ratio [OR], 0.61 [95% CI, 0.26 to 0.87]).

CONCLUSIONS

This study demonstrates that a perioperative anti-inflammatory bundle significantly reduces the prevalence of postoperative delirium in older patients undergoing hip fracture surgery, without major side effects. Systemic inflammation mediates the protective effect of the intervention. These findings provide preliminary evidence supporting the anti-inflammatory bundle strategy, paving the way for large-scale multicenter trials to optimize postoperative delirium prevention strategies.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Trial Registry (ChiCTR2300074303) by Ayixia Nawan on August 3, 2023, prior to patient enrollment.

Recent developments in delirium after oral and maxillofacial free-flap reconstruction

Postoperative delirium (POD), a common complication following surgery and anesthesia, is particularly prone to occur after reconstruction surgery in the oral and maxillofacial region. The occurrence of POD seriously affects the incidence of postoperative complications, the survival of free flaps, the length of hospital stays, and brings great pain to patients and their families, and even increases perioperative mortality. Currently, a large number of studies have reported on the risk factors for POD after oral and maxillofacial free-flap reconstruction. Multiple independent risk factors have been identified, including age, history of excessive alcohol consumption, and perioperative nutritional status. This review summarizes the relevant literature and hopes to provide insights for the prevention of POD in high-risk patients.

Post-operative cognitive dysfunction is exacerbated by high-fat diet via TLR4 and prevented by dietary DHA supplementation

Post-operative cognitive dysfunction (POCD) is an abrupt decline in neurocognitive function arising shortly after surgery and persisting for weeks to months, increasing the risk of dementia diagnosis. Advanced age, obesity, and comorbidities linked to high-fat diet (HFD) consumption such as diabetes and hypertension have been identified as risk factors for POCD, although underlying mechanisms remain unclear. We have previously shown that surgery alone, or 3-days of HFD can each evoke sufficient neuroinflammation to cause memory deficits in aged, but not young rats. The aim of the present study was to determine if HFD consumption before surgery would potentiate and prolong the subsequent neuroinflammatory response and memory deficits, and if so, to determine the extent to which these effects depend on activation of the innate immune receptor TLR4, which both insults are known to stimulate. Young-adult (3mo) & aged (24mo) male F344xBN F1 rats were fed standard chow or HFD for 3-days immediately before sham surgery or laparotomy. In aged rats, the combination of HFD and surgery caused persistent deficits in contextual memory and cued-fear memory, though it was determined that HFD alone was sufficient to cause the long-lasting cued-fear memory deficits. In young adult rats, HFD + surgery caused only cued-fear memory deficits. Elevated proinflammatory gene expression in the hippocampus of both young and aged rats that received HFD + surgery persisted for at least 3-weeks after surgery. In a separate experiment, rats were administered the TLR4-specific antagonist, LPS-RS, immediately before HFD onset, which ameliorated the HFD + surgery-associated neuroinflammation and memory deficits. Similarly, dietary DHA supplementation for 4 weeks prior to HFD onset blunted the neuroinflammatory response to surgery and prevented development of persistent memory deficits. These results suggest that HFD 1) increases risk of persistent POCD-associated memory impairments following surgery in male rats in 2) a TLR4-dependent manner, which 3) can be targeted by DHA supplementation to mitigate development of persistent POCD.

The possible role of gut microbiota dysbiosis in the pathophysiology of delirium in older persons

Delirium is a clinical syndrome characterized by an acute change in attention, awareness and cognition with fluctuating course, frequently observed in older patients during hospitalization for acute medical illness or after surgery. Its pathogenesis is multifactorial and still not completely understood, but there is general consensus on the fact that it results from the interaction between an underlying predisposition, such as neurodegenerative diseases, and an acute stressor acting as a trigger, such as infection or anesthesia. Alterations in brain insulin sensitivity and metabolic function, increased blood-brain barrier permeability, neurotransmitter imbalances, abnormal microglial activation and neuroinflammation have all been involved in the pathophysiology of delirium. Interestingly, all these mechanisms can be regulated by the gut microbiota, as demonstrated in experimental studies investigating the microbiota-gut-brain axis in dementia. Aging is also associated with profound changes in gut microbiota composition and functions, which can influence several aspects of disease pathophysiology in the host. This review provides an overview of the emerging evidence linking age-related gut microbiota dysbiosis with delirium, opening new perspectives for the microbiota as a possible target of interventions aimed at delirium prevention and treatment.

Roles of Mitochondrial DNA Damage in Kidney Diseases: A New Biomarker

The kidney is a mitochondria-rich organ, and kidney diseases are recognized as mitochondria-related pathologies. Intact mitochondrial DNA (mtDNA) maintains normal mitochondrial function. Mitochondrial dysfunction caused by mtDNA damage, including impaired mtDNA replication, mtDNA mutation, mtDNA leakage, and mtDNA methylation, is involved in the progression of kidney diseases. Herein, we review the roles of mtDNA damage in different setting of kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD). In a variety of kidney diseases, mtDNA damage is closely associated with loss of kidney function. The level of mtDNA in peripheral serum and urine also reflects the status of kidney injury. Alleviating mtDNA damage can promote the recovery of mitochondrial function by exogenous drug treatment and thus reduce kidney injury. In short, we conclude that mtDNA damage may serve as a novel biomarker for assessing kidney injury in different causes of renal dysfunction, which provides a new theoretical basis for mtDNA-targeted intervention as a therapeutic option for kidney diseases.

Reactive oxygen species contribute to delirium-like behavior by activating CypA/MMP9 signaling and inducing blood-brain barrier impairment in aged mice following anesthesia and surgery

Postoperative delirium (POD) is common in the elderly and is associated with poor clinical outcomes. Reactive oxygen species (ROS) and blood-brain barrier (BBB) damage have been implicated in the development of POD, but the association between these two factors and the potential mechanism is not clear. Cyclophilin A (CypA) is a specifically chemotactic leukocyte factor that can be secreted in response to ROS, which activates matrix metalloproteinase 9 (MMP9) and mediates BBB breakdown. We, therefore, hypothesized that ROS may contribute to anesthesia/surgery-induced BBB damage and delirium-like behavior via the CypA/MMP9 pathway. To test these hypotheses, 16-month-old mice were subjected to laparotomy under 3% sevoflurane anesthesia (anesthesia/surgery) for 3 h. ROS scavenger (N-acetyl-cysteine) and CypA inhibitor (Cyclosporin A) were used 0.5 h before anesthesia/surgery. A battery of behavior tests (buried food test, open field test, and Y maze test) was employed to evaluate behavioral changes at 24 h before and after surgery in the mice. Levels of tight junction proteins, CypA, MMP9, postsynaptic density protein (PSD)-95, and synaptophysin in the prefrontal cortex were assessed by western blotting. The amounts of ROS and IgG in the cortex of mice were observed by fluorescent staining. The concentration of S100β in the serum was detected by ELISA. ROS scavenger prevented the reduction in TJ proteins and restored the permeability of BBB as well as reduced the levels of CypA/MMP9, and further alleviated delirium-like behavior induced by anesthesia/surgery. Furthermore, the CypA inhibitor abolished the increased levels of CypA/MMP, which reversed BBB damage and ameliorated delirium-like behavior caused by ROS accumulation. Our findings demonstrated that ROS may participate in regulating BBB permeability in aged mice with POD via the CypA/MMP9 pathway, suggesting that CypA may be a potential molecular target for preventing POD.

Epigenetic Mechanisms of Postoperative Cognitive Impairment Induced by Anesthesia and Neuroinflammation

Cognitive impairment after surgery is a common problem, affects mainly the elderly, and can be divided into postoperative delirium and postoperative cognitive dysfunction. Both phenomena are accompanied by neuroinflammation; however, the precise molecular mechanisms underlying cognitive impairment after anesthesia are not yet fully understood. Anesthesiological drugs can have a longer-term influence on protein transcription, thus, epigenetics is a possible mechanism that impacts on cognitive function. Epigenetic mechanisms may be responsible for long-lasting effects and may implicate novel therapeutic approaches. Hence, we here summarize the existing literature connecting postoperative cognitive impairment to anesthesia. It becomes clear that anesthetics alter the expression of DNA and histone modifying enzymes, which, in turn, affect epigenetic markers, such as methylation, histone acetylation and histone methylation on inflammatory genes (e.g., TNF-alpha, IL-6 or IL1 beta) and genes which are responsible for neuronal development (such as brain-derived neurotrophic factor). Neuroinflammation is generally increased after anesthesia and neuronal growth decreased. All these changes can induce cognitive impairment. The inhibition of histone deacetylase especially alleviates cognitive impairment after surgery and might be a novel therapeutic option for treatment. However, further research with human subjects is necessary because most findings are from animal models.