Organ reserve, excess metabolic capacity, and aging

Cumulative effects of mutation accumulation on mitochondrial function and fitness

The impact of mutations on the mitochondria deserves specific interest due to the crucial role played by these organelles on numerous cellular functions. This study examines the effects of repeated bottlenecks on mitochondrial function and fitness. Daphnia pulex mutation accumulation lines (MA) lines were maintained for over 120 generations under copper and no copper conditions. Following the MA propagation, Daphnia from MA lines were raised under optimal and high temperatures for two generations before assessing mitochondrial and phenotypic traits. Spontaneous mutation accumulation under copper led to a later age at maturity and lowered fecundity in the MA lines. Mitochondrial respiration was found to be 10% lower in all mutation accumulation (MA) lines as compared to the non-MA control. MtDNA copy number was elevated in MA lines compared to the control under optimal temperature suggesting a compensatory mechanism. Three MA lines propagated under low copper had very low mtDNA copy number and fitness, suggesting mutations might have affected genes involved in mtDNA replication or mitochondrial biogenesis. Overall, our study suggests that mutation accumulation had an impact on life history traits, mtDNA copy number, and mitochondrial respiration. Some phenotypic effects were magnified under high temperatures. MtDNA copy number appears to be an important mitigation factor to allow mitochondria to cope with mutation accumulation up to a certain level beyond which it can no longer compensate.

A novel clinical prediction model for in-hospital mortality in sepsis patients complicated by ARDS: A MIMIC IV database and external validation study

Background

Sepsis complicated by ARDS significantly increases morbidity and mortality, underscoring the need for robust predictive models to enhance patient management.

Methods

We collected data on 6390 patients with ARDS-complicated sepsis from the MIMIC IV database. Following rigorous data cleaning, including outlier management, handling missing values, and transforming variables, we conducted univariate analysis and logistic multivariate regression. We employed the LASSO machine learning algorithm to identify risk factors closely associated with patient outcomes. These factors were then used to develop a new clinical prediction model. The model underwent preliminary assessment and internal validation, and its performance was further tested through external validation using data from 225 patients at a major tertiary hospital in China. This validation assessed the model's discrimination, calibration, and net clinical benefits.

Results

The model, illustrated by a concise nomogram, demonstrated significant discrimination with an area under the curve (AUC) of 0.711 in the internal validation set and 0.771 in the external validation set, outperforming conventional severity scores such as the SOFA and SAPS II. It also showed good calibration and net clinical benefits.

Conclusions

Our model serves as a valuable tool for identifying sepsis patients with ARDS at high risk of in-hospital mortality. This could enable the implementation of personalized treatment strategies, potentially improving patient outcomes.

The elderly in the post-anesthesia care unit

It is increasingly conceivable that elderly patients will be treated in perioperative settings as the world's population shifts toward an older age distribution. They are more prone to a variety of unfavorable outcomes as a consequence of the physiological changes that accompany aging and the coexistence of multiple medical conditions. Postoperative complications in elderly patients are linked to a large increase in morbidity and mortality and the burden placed on the healthcare system. Our goal is to determine how elderly patients' recovery after anesthesia differs from that of younger patients. In addition, we will discuss the main postoperative complications experienced by elderly patients and the measures that are utilized to limit the risk of these complications developing.

Selecting patients for early interdisciplinary rehabilitation during neurointensive care after moderate to severe traumatic brain injury

BACKGROUND

Early interdisciplinary rehabilitation (EIR) in neurointensive care is a limited resource reserved for patients with moderate to severe traumatic brain injury (TBI) believed to profit from treatment. We evaluated how key parameters related to injury severity and patient characteristics were predictive of receiving EIR, and whether these parameters changed over time.

METHODS

Among 1003 adult patients with moderate to severe TBI admitted over 72 h to neurointensive care unit during four time periods between 2005 and 2020, EIR was given to 578 and standard care to 425 patients. Ten selection criteria thought to best represent injury severity and patient benefit were evaluated (Glasgow Coma Scale, Head Abbreviated Injury Scale, New-Injury-Severity-Scale, intracranial pressure monitoring, neurosurgery, age, employment, Charlson Comorbidity Index, severe psychiatric disease, and chronic substance abuse).

RESULTS

In multivariate regression analysis, patients who were employed (adjOR 1.99 [95% CI 1.41, 2.80]), had no/mild comorbidity (adjOR 3.15 [95% CI 1.72, 5.79]), needed neurosurgery, had increasing injury severity and were admitted by increasing time period were more likely to receive EIR, whereas receiving EIR was less likely with increasing age (adjOR 0.97 [95% CI 0.96, 0.98]) and chronic substance abuse. Overall predictive ability of the model was 71%. Median age and comorbidity increased while employment decreased from 2005 to 2020, indicating patient selection became less restrictive with time.

CONCLUSION

Injury severity and need for neurosurgery remain important predictors for receiving EIR, but the importance of age, employment, and comorbidity have changed over time. Moderate prediction accuracy using current clinical criteria suggest unrecognized factors are important for patient selection.

NHANES 2011-2014 Reveals Decreased Cognitive Performance in U.S. Older Adults with Metabolic Syndrome Combinations

A relationship between metabolic syndrome and cognitive impairment has been evidenced across research; however, conflicting results have been observed. A cross-sectional study was conducted on 3179 adults older than 60 from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) to analyze the relationship between metabolic syndrome and cognitive impairment. In our results, we found that adults with abdominal obesity, high triglycerides, and low HDL cholesterol had 4.39 fewer points in the CERAD immediate recall test than adults without any metabolic syndrome factors [Beta = -4.39, SE = 1.32, 17.75 (1.36) vs. 22.14 (0.76)]. In addition, people with this metabolic syndrome combination exhibited 2.39 fewer points in the CERAD delayed recall test than those without metabolic syndrome criteria [Beta = -2.39, SE = 0.46, 4.32 (0.49) vs. 6.71 (0.30)]. It was also found that persons with high blood pressure, hyperglycemia, and low HDL-cholesterol levels reached 4.11 points less in the animal fluency test than people with no factors [Beta = -4.11, SE = 1.55, 12.67 (2.12) vs. 16.79 (1.35)]. These findings suggest that specific metabolic syndrome combinations are essential predictors of cognitive impairment. In this study, metabolic syndrome combinations that included obesity, fasting hyperglycemia, high triglycerides, and low HDL-cholesterol were among the most frequent criteria observed.

Towards early detection of neurodegenerative diseases: A gut feeling

The gastrointestinal tract communicates with the nervous system through a bidirectional network of signaling pathways called the gut-brain axis, which consists of multiple connections, including the enteric nervous system, the vagus nerve, the immune system, endocrine signals, the microbiota, and its metabolites. Alteration of communications in the gut-brain axis is emerging as an overlooked cause of neuroinflammation. Neuroinflammation is a common feature of the pathogenic mechanisms involved in various neurodegenerative diseases (NDs) that are incurable and debilitating conditions resulting in progressive degeneration and death of neurons, such as in Alzheimer and Parkinson diseases. NDs are a leading cause of global death and disability, and the incidences are expected to increase in the following decades if prevention strategies and successful treatment remain elusive. To date, the etiology of NDs is unclear due to the complexity of the mechanisms of diseases involving genetic and environmental factors, including diet and microbiota. Emerging evidence suggests that changes in diet, alteration of the microbiota, and deregulation of metabolism in the intestinal epithelium influence the inflammatory status of the neurons linked to disease insurgence and progression. This review will describe the leading players of the so-called diet-microbiota-gut-brain (DMGB) axis in the context of NDs. We will report recent findings from studies in model organisms such as rodents and fruit flies that support the role of diets, commensals, and intestinal epithelial functions as an overlooked primary regulator of brain health. We will finish discussing the pivotal role of metabolisms of cellular organelles such as mitochondria and peroxisomes in maintaining the DMGB axis and how alteration of the latter can be used as early disease makers and novel therapeutic targets.

New horizons in understanding oral health and swallowing function within the context of frailty

Frailty is a complex and multidimensional condition wherein declines in physiologic reserve and function place individuals in a state of heightened vulnerability and decreased resiliency. There has been growing interest in both research and clinical settings to understand how to best define, assess and characterise frailty in older adults. To this end, various models and clinical assessment tools have been used to define and measure frailty. While differences exist among these models and tools, a common unifying theme is a focus on physical function and activity. Notably absent across many available conceptual models and clinical tools are items directly related to oral and swallowing function. This is an important oversight as widespread changes to both oral and swallowing function are evident in older adults. Indeed, emerging evidence suggests many of the functional domains affected in frail older adults, such as nutrition and sarcopenia, have cyclical relationships with impairments in oral (oral hypofunction) and swallowing function (dysphagia) as well. The increasing appreciation for the interrelationships among oral hypofunction, dysphagia and frailty provides an opportunity for refinement of frailty assessment and characterisation in older adults to incorporate metrics specific to oral and swallowing function.

Vulnerability to chronic stress and the phenotypic heterogeneity of presbycusis with subjective tinnitus

Age-related functional reserve decline and vulnerability of multiple physiological systems and organs, as well as at the cellular and molecular levels, result in different frailty phenotypes, such as physical, cognitive, and psychosocial frailty, and multiple comorbidities, including age-related hearing loss (ARHL) and/or tinnitus due to the decline in auditory reserve. However, the contributions of chronic non-audiogenic cumulative exposure, and chronic audiogenic stress to phenotypic heterogeneity of presbycusis and/or tinnitus remain elusive. Because of the cumulative environmental stressors throughout life, allostasis systems, the hypothalamus-pituitary-adrenal (HPA) and the sympathetic adrenal-medullary (SAM) axes become dysregulated and less able to maintain homeostasis, which leads to allostatic load and maladaptation. Brain-body communication via the neuroendocrine system promotes systemic chronic inflammation, overmobilization of energetic substances (glucose and lipids), and neuroplastic changes via the non-genomic and genomic actions of glucocorticoids, catecholamines, and their receptors. These systemic maladaptive alterations might lead to different frailty phenotypes and physical, cognitive, and psychological comorbidities, which, in turn, cause and exacerbate ARHL and/or tinnitus with phenotypic heterogeneity. Chronic audiogenic stressors, including aging accompanying ontological diseases, cumulative noise exposure, and ototoxic drugs as well as tinnitus, activate the HPA axis and SAM directly and indirectly by the amygdala, promoting allostatic load and maladaptive neuroplasticity in the auditory system and other vulnerable brain regions, such as the hippocampus, amygdala, and medial prefrontal cortex (mPFC). In the auditory system, peripheral deafferentation, central disinhibition, and tonotopic map reorganization may trigger tinnitus. Cross-modal maladaptive neuroplasticity between the auditory and other sensory systems is involved in tinnitus modulation. Persistent dendritic growth and formation, reduction in GABAergic inhibitory synaptic inputs induced by chronic audiogenic stresses in the amygdala, and increased dendritic atrophy in the hippocampus and mPFC, might involve the enhancement of attentional processing and long-term memory storage of chronic subjective tinnitus, accompanied by cognitive impairments and emotional comorbidities. Therefore, presbycusis and tinnitus are multisystem disorders with phenotypic heterogeneity. Stressors play a critical role in the phenotypic heterogeneity of presbycusis. Differential diagnosis based on biomarkers of metabonomics study, and interventions tailored to different ARHL phenotypes and/or tinnitus will contribute to healthy aging and improvement in the quality of life.

Cardiometabolic Risk after SARS-CoV-2 Virus Infection: A Retrospective Exploratory Analysis

OBJECTIVE

The aim of this study is to characterize the cardiometabolic risk of individuals who were infected with the SARS-CoV-2 virus and subsequently admitted to a hospital in a major city in mainland Portugal.

METHODS

This is a retrospective exploratory study using a sample of 102 patients, with data analysis including descriptive statistics, nonparametric measures of association between variables based on Spearman's rank-order correlation, a logistic regression model for predicting the likelihood that an individual might eventually pass away, and a multiple linear regression model to predict a likely increase in the number of days an infected patient remained in the hospital.

RESULTS

About 62.7% of the individuals required intensive care on the second day of hospitalization, remaining 14.2 days in the intensive care unit (ICU) on average. The likelihood that an individual might eventually pass away due to SARS-CoV-2 virus infection increases for the older than younger ones and increases even more if he/she suffers from cardiometabolic disorders such as obesity, especially cardiovascular disease. Older individuals and those with obesity and hypertension remained more days in the ICU.

CONCLUSIONS

A later age and the prevalence of cardiometabolic disorders severely affect the care pathway of individuals infected with the SARS-CoV-2 virus.

Homeostatic medicine: a strategy for exploring health and disease

Homeostasis is a process of dynamic balance regulated by organisms, through which they maintain an internal stability and adapt to the external environment for survival. In this paper, we propose the concept of utilizing homeostatic medicine (HM) as a strategy to explore health and disease. HM is a science that studies the maintenance of the body’s homeostasis. It is also a discipline that investigates the role of homeostasis in building health, studies the change of homeostasis in disease progression, and explores ways to restore homeostasis for the prevention, diagnosis and treatment of disease at all levels of biological organization. A new dimension in the medical system with a promising future HM focuses on how homeostasis functions in the regulation of health and disease and provides strategic directions in disease prevention and control. Nitric oxide (NO) plays an important role in the control of homeostasis in multiple systems. Nitrate is an important substance that regulates NO homeostasis through the nitrate-nitrite-NO pathway. Sialin interacts with nitrate and participates in the regulation of NO production and cell biological functions for body homeostasis. The interactions between nitrate and NO or sialin is an important mechanism by which homeostasis is regulated.

Assessing the Role of Operative Intervention in Elderly Patients With Nonfunctional Pancreatic Neuroendocrine Neoplasms

OBJECTIVES

Resection of locoregional pancreatic neuroendocrine neoplasms (PanNENs) is typically recommended, but there is a paucity of data on the management of elderly patients.

METHODS

The National Cancer Database (2004-2016) was queried for patients 80 years or older with localized PanNENs. Patients were grouped as nonoperative or operative management. Postoperative outcomes and survival were compared.

RESULTS

In total, 591 patients were included: 202 underwent resection, and 389 did not. Increasing age and pancreatic head tumors were associated with lower likelihood of resection. The overall 90-day mortality rate was 6.4%, which was higher for pancreatoduodenectomy than distal pancreatectomy (13.6% vs 5.1%, respectively). Operatively managed patients had longer median survival (80.8 vs 45.0 months, P < 0.001), and this association was independent of tumor location. On multivariable Cox regression, resection remained associated with longer survival (hazard ratio, 0.69; 95% confidence interval, 0.50-0.95). Among operatively managed patients, age and tumor location were not associated with survival; however, greater comorbidity and high-risk tumor-specific features were associated with worse survival.

CONCLUSIONS

Resection of nonfunctional PanNENs in elderly patients is associated with improved survival compared with nonoperative management. Resection could be considered in appropriate operative candidates, regardless of tumor location, but the perioperative mortality rate must be considered.

Biological ageing with HIV infection: evaluating the geroscience hypothesis

Although people with HIV are living longer, as they age they remain disproportionately burdened with multimorbidity that is exacerbated in resource-poor settings. The geroscience hypothesis postulates that a discrete set of between five and ten hallmarks of biological ageing drive multimorbidity, but these processes have not been systematically examined in the context of people with HIV. We examine four major hallmarks of ageing (macromolecular damage, senescence, inflammation, and stem-cell dysfunction) as gerodrivers in the context of people with HIV. As a counterbalance, we introduce healthy ageing, physiological reserve, intrinsic capacity, and resilience as promoters of geroprotection that counteract gerodrivers. We discuss emerging geroscience-based diagnostic biomarkers and therapeutic strategies, and provide examples based on recent advances in cellular senescence, and other, non-pharmacological approaches. Finally, we present a conceptual model of biological ageing in the general population and in people with HIV that integrates gerodrivers and geroprotectors as modulators of homoeostatic reserves and organ function over the lifecourse.

Prehabilitation, enhanced recovery after surgery, or both? A narrative review

This narrative review presents a biological rationale and evidence to describe how the preoperative condition of the patient contributes to postoperative morbidity. Any preoperative condition that prevents a patient from tolerating the physiological stress of surgery (e.g. poor cardiopulmonary reserve, sarcopaenia), impairs the stress response (e.g. malnutrition, frailty), and/or augments the catabolic response to stress (e.g. insulin resistance) is a risk factor for poor surgical outcomes. Prehabilitation interventions that include exercise, nutrition, and psychosocial components can be applied before surgery to strengthen physiological reserve and enhance functional capacity, which, in turn, supports recovery through attaining surgical resilience. Prehabilitation complements Enhanced Recovery After Surgery (ERAS) care to achieve optimal patient outcomes because recovery is not a passive process and it begins preoperatively.

Methodological Proposal for Strength and Power Training in Older Athletes: A Narrative Review

INTRODUCTION

Within the adult population, it is not uncommon to meet older athletes who challenge the negative stereotypes associated with aging. Although their physical performance is superior to their sedentary counterparts, they are not immune to impaired neuromuscular function, leading to a decreased physical capacity and an increased risk of injuries. Despite the abundant information about the benefits of strength/power training in advanced ages, there are no methodological proposals that guide physical activity professionals to program this type of training.

OBJECTIVE

This study aimed to review the factors related to the decrease in sports performance within older athletes and the benefits of a strength/power program in order to provide a methodological proposal to organize training in this population.

METHODS

This is a review article. First, databases from PubMed, Science Direct, and SPORTSDiscus and search engines, namely Google Scholar and Scielo, were reviewed, using standard keywords such as strength and power training, evaluation of physical performance, neuromuscular function, and risk of injury in the elderly athlete. All related articles published during the period 1963 to 2020 were considered. A total of 1837 documents were found. By removing 1715 unrelated documents, 122 articles were included in the study after revision control.

RESULTS

Strength/power training is key to alleviating the loss of performance in older athletes and the benefits in neuromuscular function, which helps reduce the rate of serious injuries, maintaining sports practice for a longer period of time. In order to design an appropriate program, a prior evaluation of the individual's physical-technical level must be carried out, respecting the biologicalpedagogical principles and safety regulations.

CONCLUSION

The methodological proposal delivered in this review can serve as a technical guide for physical activity professionals, which will be able to structure the strength/power training and thus preserve the sports practice in older athletes for a longer time.

SARS-CoV-2 and mitochondrial health: implications of lifestyle and ageing

Infection with SARs-COV-2 displays increasing fatality with age and underlying co-morbidity, in particular, with markers of the metabolic syndrome and diabetes, which seems to be associated with a "cytokine storm" and an altered immune response. This suggests that a key contributory factor could be immunosenescence that is both age-related and lifestyle-induced. As the immune system itself is heavily reliant on mitochondrial function, then maintaining a healthy mitochondrial system may play a key role in resisting the virus, both directly, and indirectly by ensuring a good vaccine response. Furthermore, as viruses in general, and quite possibly this new virus, have also evolved to modulate immunometabolism and thus mitochondrial function to ensure their replication, this could further stress cellular bioenergetics. Unlike most sedentary modern humans, one of the natural hosts for the virus, the bat, has to "exercise" regularly to find food, which continually provides a powerful adaptive stimulus to maintain functional muscle and mitochondria. In effect the bat is exposed to regular hormetic stimuli, which could provide clues on how to resist this virus. In this paper we review the data that might support the idea that mitochondrial health, induced by a healthy lifestyle, could be a key factor in resisting the virus, and for those people who are perhaps not in optimal health, treatments that could support mitochondrial function might be pivotal to their long-term recovery.

Management of odontogenic infections and sepsis: an update

The management of odontogenic infections has improved over recent decades, but further improvements are still required. The ongoing education of GDPs and their dental teams on this issue continues to be important, especially during the current COVID-19 pandemic, where remote triage poses additional difficulties and challenges.Odontogenic infections can lead to sepsis, a potentially life-threatening condition caused by the body's immune system responding in an abnormal way. This can lead to tissue damage, organ failure and death. A patient with non-odontogenic-related infection could also present with sepsis at a dental practice. Early recognition and prompt management of sepsis improves outcomes. GDPs and their dental teams should be trained in the recognition and management of sepsis. Age-specific sepsis decision support tools have been developed by the UK Sepsis Trust to help dental staff recognise and manage patients with suspected sepsis.The aim of this article is to provide an update on the management of odontogenic infections and sepsis.

The Relationship of COVID-19 Severity with Cardiovascular Disease and Its Traditional Risk Factors: A Systematic Review and Meta-Analysis

BACKGROUND

Whether cardiovascular disease (CVD) and its traditional risk factors predict severe coronavirus disease 2019 (COVID-19) is uncertain, in part, because of potential confounding by age and sex.

METHODS

We performed a systematic review of studies that explored pre-existing CVD and its traditional risk factors as risk factors of severe COVID-19 (defined as death, acute respiratory distress syndrome, mechanical ventilation, or intensive care unit admission). We searched PubMed and Embase for papers in English with original data (≥10 cases of severe COVID-19). Using random-effects models, we pooled relative risk (RR) estimates and conducted meta-regression analyses.

RESULTS

Of the 661 publications identified in our search, 25 papers met our inclusion criteria, with 76,638 COVID-19 patients including 11,766 severe cases. Older age was consistently associated with severe COVID-19 in all eight eligible studies, with RR >~5 in >60-65 versus <50 years. Three studies showed no change in the RR of age after adjusting for covariate(s). In univariate analyses, factors robustly associated with severe COVID-19 were male sex (10 studies; pooled RR = 1.73, [95% CI 1.50-2.01]), hypertension (8 studies; 2.87 [2.09-3.93]), diabetes (9 studies; 3.20 [2.26-4.53]), and CVD (10 studies; 4.97 [3.76-6.58]). RR for male sex was likely to be independent of age. For the other three factors, meta-regression analyses suggested confounding by age. Only four studies reported multivariable analysis, but most of them showed adjusted RR ~2 for hypertension, diabetes, and CVD. No study explored renin-angiotensin system inhibitors as a risk factor for severe COVID-19.

CONCLUSIONS

Despite the potential for confounding, these results suggest that hypertension, diabetes, and CVD are independently associated with severe COVID-19 and, together with age and male sex, can be informative for predicting the risk of severe COVID-19.

OPA1 deficiency accelerates hippocampal synaptic remodelling and age-related deficits in learning and memory

A healthy mitochondrial network is essential for the maintenance of neuronal synaptic integrity. Mitochondrial and metabolic dysfunction contributes to the pathogenesis of many neurodegenerative diseases including dementia. OPA1 is the master regulator of mitochondrial fusion and fission and is likely to play an important role during neurodegenerative events. To explore this, we quantified hippocampal dendritic and synaptic integrity and the learning and memory performance of aged Opa1 haploinsufficient mice carrying the Opa1Q285X mutation (B6; C3-Opa1Q285STOP ; Opa1+/- ). We demonstrate that heterozygous loss of Opa1 results in premature age-related loss of spines in hippocampal pyramidal CA1 neurons and a reduction in synaptic density in the hippocampus. This loss is associated with subtle memory deficits in both spatial novelty and object recognition. We hypothesize that metabolic failure to maintain normal neuronal activity at the level of a single spine leads to premature age-related memory deficits. These results highlight the importance of mitochondrial homeostasis for maintenance of neuronal function during ageing.

Integrating functional ageing into daily clinical practice

The analysis of the ageing trajectory clearly demonstrates the constant involvement of functional ability in daily life, from its development in youth, to its preservation through midlife into very old age. While maintaining function appears to be largely related to persistent regular exercise, the risk factors for functional decline are extremely diverse, ranging from a decrease or discontinuation of physical activity, to nutritional/metabolic disturbances, chronic diseases and unfavourable socio-demographic and socio-economic contexts. Prevention of functional decline is a major public health challenge, both for individuals and for society as a whole, and needs to be urgently addressed. Engaging citizens to be conscious of their responsibility for, and role in their own ageing process is equally as important as reinforcing the involvement of society in promoting healthy ageing through enhanced basic and health education, promotion of a healthy diet, long term practice of moderate physical activity, and the continual battle against deleterious life habits and behaviours. The success of these combined actions would be quite simply demonstrated by a change from the current pandemics of morbidity, to the compression of disability, which is expected by all.

Moderation of mitochondrial respiration mitigates metabolic syndrome of aging

Deregulation of mitochondrial dynamics leads to the accumulation of oxidative stress and unhealthy mitochondria; consequently, this accumulation contributes to premature aging and alterations in mitochondria linked to metabolic complications. We postulate that restrained mitochondrial ATP synthesis might alleviate age-associated disorders and extend healthspan in mammals. Herein, we prepared a previously discovered mitochondrial complex IV moderate inhibitor in drinking water and orally administered to standard-diet-fed, wild-type C57BL/6J mice every day for up to 16 mo. No manifestation of any apparent toxicity or deleterious effect on studied mouse models was observed. The impacts of an added inhibitor on a variety of mitochondrial functions were analyzed, such as respiratory activity, mitochondrial bioenergetics, and biogenesis, and a few age-associated comorbidities, including reactive oxygen species (ROS) production, glucose abnormalities, and obesity in mice. It was found that mitochondrial quality, dynamics, and oxidative metabolism were greatly improved, resulting in lean mice with a specific reduction in visceral fat plus superb energy and glucose homeostasis during their aging period compared to the control group. These results strongly suggest that a mild interference in ATP synthesis through moderation of mitochondrial activity could effectively up-regulate mitogenesis, reduce ROS production, and preserve mitochondrial integrity, thereby impeding the onset of metabolic syndrome. We conclude that this inhibitory intervention in mitochondrial respiration rectified the age-related physiological breakdown in mice by protecting mitochondrial function and markedly mitigated certain undesired primary outcomes of metabolic syndrome, such as obesity and type 2 diabetes. This intervention warrants further research on the treatment of metabolic syndrome of aging in humans.

Differential Susceptibility and Vulnerability of Brain Cells in C57BL/6 Mouse to Mitochondrial Dysfunction Induced by Short-Term Cuprizone Exposure

Cuprizone (CPZ) is a chemical chelator toxic to mitochondria of cells. While inducing oligodendrocyte (OL) loss and demyelination, CPZ caused no fatal damage to the other brain cells (neurons, astrocytes, and microglia) in previous studies, suggesting differential susceptibility and vulnerability of brain cells to the CPZ intoxication. To demonstrate this interpretation, C57BL/6 mice were fed rodent chow without or with CPZ (0.2%, w/w) for 7 days. One day later, mitochondrial function of brain cells was assessed by proton magnetic resonance spectroscopy (¹H-MRS) and biochemical analysis. Another batch of mice were processed to localize the CPZ-induced damage to mitochondrial DNA, label brain cells, and identify apoptotic cells. Compared to controls, CPZ-exposed mice showed significantly lower levels of N-acetyl-L-aspartate, phosphocreatine, and ATP detected by ¹H-MRS, indicating mitochondrial dysfunction in brain cells. Susceptibility analysis showed an order of OLs, microglia, and astrocytes from high to low, in terms of the proportion of 8-OHdG labeled cells in each type of these cells in corpus callosum. Vulnerability analysis showed the highest proportion of caspase-3 positive cells in labeled OLs in cerebral cortex and hippocampus, where neurons showed no caspase-3 labeling, but the highest proportion of 8-OHdG labeling, indicating a lowest vulnerability but highest susceptibility to CPZ-induced mitochondrial dysfunction. Immature OLs, microglia, and astrocytes showed adaptive changes in proliferation and activation in response to CPZ-exposure. These data for the first time demonstrated the CPZ-induced mitochondria dysfunction in brain cells of living mouse and specified the differential susceptibility and vulnerability of brain cells to the CPZ intoxication.

Incomplete Healing as a Cause of Aging: The Role of Mitochondria and the Cell Danger Response

The rate of biological aging varies cyclically and episodically in response to changing environmental conditions and the developmentally-controlled biological systems that sense and respond to those changes. Mitochondria and metabolism are fundamental regulators, and the cell is the fundamental unit of aging. However, aging occurs at all anatomical levels. At levels above the cell, aging in different tissues is qualitatively, quantitatively, and chronologically distinct. For example, the heart can age faster and differently than the kidney and vice versa. Two multicellular features of aging that are universal are: (1) a decrease in physiologic reserve capacity, and (2) a decline in the functional communication between cells and organ systems, leading to death. Decreases in reserve capacity and communication impose kinetic limits on the rate of healing after new injuries, resulting in dyssynchronous and incomplete healing. Exercise mitigates against these losses, but recovery times continue to increase with age. Reinjury before complete healing results in the stacking of incomplete cycles of healing. Developmentally delayed and arrested cells accumulate in the three stages of the cell danger response (CDR1, 2, and 3) that make up the healing cycle. Cells stuck in the CDR create physical and metabolic separation—buffer zones of reduced communication—between previously adjoining, synergistic, and metabolically interdependent cells. Mis-repairs and senescent cells accumulate, and repeated iterations of incomplete cycles of healing lead to progressively dysfunctional cellular mosaics in aging tissues. Metabolic cross-talk between mitochondria and the nucleus, and between neighboring and distant cells via signaling molecules called metabokines regulates the completeness of healing. Purinergic signaling and sphingolipids play key roles in this process. When viewed against the backdrop of the molecular features of the healing cycle, the incomplete healing model provides a new framework for understanding the hallmarks of aging and generates a number of testable hypotheses for new treatments.

Metabolic features and regulation of the healing cycle-A new model for chronic disease pathogenesis and treatment

Without healing, multicellular life on Earth would not exist. Without healing, one injury predisposes to another, leading to disability, chronic disease, accelerated aging, and death. Over 60% of adults and 30% of children and teens in the United States now live with a chronic illness. Advances in mass spectrometry and metabolomics have given scientists a new lens for studying health and disease. This study defines the healing cycle in metabolic terms and reframes the pathophysiology of chronic illness as the result of metabolic signaling abnormalities that block healing and cause the normal stages of the cell danger response (CDR) to persist abnormally. Once an injury occurs, active progress through the stages of healing is driven by sequential changes in cellular bioenergetics and the disposition of oxygen and carbon skeletons used for fuel, signaling, defense, repair, and recovery. >100 chronic illnesses can be organized into three persistent stages of the CDR. One hundred and two targetable chemosensory G-protein coupled and ionotropic receptors are presented that regulate the CDR and healing. Metabokines are signaling molecules derived from metabolism that regulate these receptors. Reframing the pathogenesis of chronic illness in this way, as a systems problem that maintains disease, rather than focusing on remote trigger(s) that caused the initial injury, permits new research to focus on novel signaling therapies to unblock the healing cycle, and restore health when other approaches have failed.