Short-term caloric restriction exerts neuroprotective effects following mild traumatic brain injury by promoting autophagy and inhibiting astrocyte activation

Non-pharmacological interventions for traumatic brain injury

Heterogeneity and variability of symptoms due to the type, site, age, sex, and severity of injury make each case of traumatic brain injury (TBI) unique. Considering this, a universal treatment strategy may not be fruitful in managing outcomes after TBI. Most of the pharmacological therapies for TBI aim at modifying a particular pathway or molecular process in the sequelae of secondary injury rather than a holistic approach. On the other hand, non-pharmacological interventions such as hypothermia, hyperbaric oxygen, preconditioning with dietary adaptations, exercise, environmental enrichment, deep brain stimulation, decompressive craniectomy, probiotic use, gene therapy, music therapy, and stem cell therapy can promote healing by modulating multiple neuroprotective mechanisms. In this review, we discussed the major non-pharmacological interventions that are being tested in animal models of TBI as well as in clinical trials. We evaluated the functional outcomes of various interventions with an emphasis on the links between molecular mechanisms and outcomes after TBI.

p17/C18-ceramide-mediated mitophagy is an endogenous neuroprotective response in preclinical and clinical brain injury

Repeat concussions (or repetitive mild traumatic brain injury [rmTBI]) are complex pathological processes consisting of a primary insult and long-term secondary complications and are also a prerequisite for chronic traumatic encephalopathy (CTE). Recent evidence implies a significant role of autophagy-mediated dysfunctional mitochondrial clearance, mitophagy, in the cascade of secondary deleterious events resulting from TBI. C18-ceramide, a bioactive sphingolipid produced in response to cell stress and damage, and its synthesizing enzyme (CerS1) are precursors to selective stress-mediated mitophagy. A transporter, p17, mediates the trafficking of CerS1, induces C18-ceramide synthesis in the mitochondrial membrane, and acts as an elimination signal in cell survival. Whether p17-mediated mitophagy occurs in the brain and plays a causal role in mitochondrial quality control in secondary disease development after rmTBI are unknown. Using a novel repetitive less-than-mild TBI (rlmTBI) injury paradigm, ablation of mitochondrial p17/C18-ceramide trafficking in p17 knockout (KO) mice results in a loss of C18-ceramide-induced mitophagy, which contributes to susceptibility and recovery from long-term secondary complications associated with rlmTBI. Using a ceramide analog with lipid-selenium conjugate drug, LCL768 restored mitophagy and reduced long-term secondary complications, improving cognitive deficits in rlmTBI-induced p17KO mice. We obtained a significant reduction of p17 expression and a considerable decrease of CerS1 and C18-ceramide levels in cortical mitochondria of CTE human brains compared with age-matched control brains. These data demonstrated that p17/C18-ceramide trafficking is an endogenous neuroprotective mitochondrial stress response following rlmTBI, thus suggesting a novel prospective strategy to interrupt the CTE consequences of concussive TBI.

Progress in research on the role of clinical nutrition in treating traumatic brain injury affecting the neurovascular unit

The neurovascular unit (NVU) is composed of neurons, glial cells, and blood vessels. NVU dysfunction involves the processes of neuroinflammation, and microcirculatory disturbances, as well as neuronal injury after traumatic brain injury (TBI). Traditional anti-inflammatory drugs have limited efficacy in improving the prognosis of TBI. Thus, treatments that target NVU dysfunction may provide a breakthrough. A large number of clinical studies have shown that the nutritional status of patients with TBI was closely related to their conditions and prognoses. Nutrient complexes and complementary therapies for the treatment of TBI are therefore being implemented in many preclinical studies. Importantly, the mechanism of action for this treatment may be related to repair of NVU dysfunction by ensuring adequate omega-3 fatty acids, curcumin, resveratrol, apigenin, vitamins, and minerals. These nutritional supplements hold promise for translation to clinical therapy. In addition, dietary habits also play an important role in the rehabilitation of TBI. Poor dietary habits may worsen the pathology and prognosis of TBI. Adjusting dietary habits, especially with a ketogenic diet, may improve outcomes in patients with TBI. This article discusses the impact of clinical nutrition on NVU dysfunction after TBI, focusing on nutritional complexes and dietary habits.

Epidrugs in the Therapy of Central Nervous System Disorders: A Way to Drive on?

The polygenic nature of neurological and psychiatric syndromes and the significant impact of environmental factors on the underlying developmental, homeostatic, and neuroplastic mechanisms suggest that an efficient therapy for these disorders should be a complex one. Pharmacological interventions with drugs selectively influencing the epigenetic landscape (epidrugs) allow one to hit multiple targets, therefore, assumably addressing a wide spectrum of genetic and environmental mechanisms of central nervous system (CNS) disorders. The aim of this review is to understand what fundamental pathological mechanisms would be optimal to target with epidrugs in the treatment of neurological or psychiatric complications. To date, the use of histone deacetylases and DNA methyltransferase inhibitors (HDACis and DNMTis) in the clinic is focused on the treatment of neoplasms (mainly of a glial origin) and is based on the cytostatic and cytotoxic actions of these compounds. Preclinical data show that besides this activity, inhibitors of histone deacetylases, DNA methyltransferases, bromodomains, and ten-eleven translocation (TET) proteins impact the expression of neuroimmune inflammation mediators (cytokines and pro-apoptotic factors), neurotrophins (brain-derived neurotropic factor (BDNF) and nerve growth factor (NGF)), ion channels, ionotropic receptors, as well as pathoproteins (β-amyloid, tau protein, and α-synuclein). Based on this profile of activities, epidrugs may be favorable as a treatment for neurodegenerative diseases. For the treatment of neurodevelopmental disorders, drug addiction, as well as anxiety disorders, depression, schizophrenia, and epilepsy, contemporary epidrugs still require further development concerning a tuning of pharmacological effects, reduction in toxicity, and development of efficient treatment protocols. A promising strategy to further clarify the potential targets of epidrugs as therapeutic means to cure neurological and psychiatric syndromes is the profiling of the epigenetic mechanisms, which have evolved upon actions of complex physiological lifestyle factors, such as diet and physical exercise, and which are effective in the management of neurodegenerative diseases and dementia.

A comparative study of acetyl-l-carnitine and caloric restriction impact on hippocampal autophagy, apoptosis, neurogenesis, and astroglial function in AlCl3-induced Alzheimer's in rats

Alzheimer's disease (AD) is a worldwide chronic progressive neurodegenerative disease. We aimed to investigate and compare the neuroprotective impact of acetyl-l-carnitine and caloric restriction (CR) on AlCl₃-induced AD to explore the pathogenesis and therapeutic strategies of AD. Sixty-seven adult male Wistar rats were allocated into Control, AlCl₃, AlCl₃-acetyl-l-carnitine, and AlCl₃-CR groups. Each of AlCl₃ and acetyl-l-carnitine were given by gavage in a daily dose of 100 mg/kg and CR was conducted by giving 70% of the daily average caloric intake of the control group. Rats were subjected to behavioral assessment using open field test, Y maze, novel object recognition test and passive avoidance test, biochemical assay of serum phosphorylated tau (pTau), hippocampal homogenate phosphorylated adenosine monophosphate-activated protein kinase, Beclin-1, Bcl-2-associated X protein, and B cell lymphoma 2 (Bcl2) as well as hippocampal Ki-67 and glial fibrillary acidic protein immunohistochemistry. AlCl₃-induced cognitive and behavioral deficits coincident with impaired autophagy and enhanced apoptosis associated with defective neurogenesis and defective astrocyte activation. Acetyl-l-carnitine and CR partially protect against AlCl₃-induced behavioral, cognitive, biochemical, and histological changes, with more ameliorative effect of acetyl-l-carnitine on hippocampal apoptotic markers, and more obvious behavioral and histological improvement with CR.

Dietary energy restriction in neurological diseases: what's new?

Energy-restricted diet is a specific dietary regimen, including the continuous energy-restricted diet and the intermittent energy-restricted diet. It has been proven effective not only to reduce weight and extend the lifespan in animal models, but also to regulate the development and progression of various neurological diseases such as epilepsy, cerebrovascular diseases (stroke), neurodegenerative disorders (Alzheimer's disease and Parkinson's disease) and autoimmune diseases (multiple sclerosis). However, the mechanism in this field is still not clear and a systematic neurological summary is still missing. In this review, we first give a brief summary of the definition and mainstream strategies of energy restrictions. We then review evidence about the effects of energy-restricted diet from both animal models and human trials, and update the current understanding of mechanisms underlying the biological role of energy-restricted diet in the fight against neurological diseases. Our review thus contributes to the modification of dietary regimen and the search for special diet mimics.

Nutrition and adult neurogenesis in the hippocampus: Does what you eat help you remember?

Neurogenesis is a complex process by which neural progenitor cells (NPCs)/neural stem cells (NSCs) proliferate and differentiate into new neurons and other brain cells. In adulthood, the hippocampus is one of the areas with more neurogenesis activity, which is involved in the modulation of both emotional and cognitive hippocampal functions. This complex process is affected by many intrinsic and extrinsic factors, including nutrition. In this regard, preclinical studies performed in rats and mice demonstrate that high fats and/or sugars diets have a negative effect on adult hippocampal neurogenesis (AHN). In contrast, diets enriched with bioactive compounds, such as polyunsaturated fatty acids and polyphenols, as well as intermittent fasting or caloric restriction, can induce AHN. Interestingly, there is also growing evidence demonstrating that offspring AHN can be affected by maternal nutrition in the perinatal period. Therefore, nutritional interventions from early stages and throughout life are a promising perspective to alleviate neurodegenerative diseases by stimulating neurogenesis. The underlying mechanisms by which nutrients and dietary factors affect AHN are still being studied. Interestingly, recent evidence suggests that additional peripheral mediators may be involved. In this sense, the microbiota-gut-brain axis mediates bidirectional communication between the gut and the brain and could act as a link between nutritional factors and AHN. The aim of this mini-review is to summarize, the most recent findings related to the influence of nutrition and diet in the modulation of AHN. The importance of maternal nutrition in the AHN of the offspring and the role of the microbiota-gut-brain axis in the nutrition-neurogenesis relationship have also been included.

Dietary Restriction against Parkinson's Disease: What We Know So Far

Dietary restriction (DR) is defined as a moderate reduction in food intake while avoiding malnutrition. The beneficial effects of DR are being increasingly acknowledged in aging and in a series of age-related neurodegenerative disorders, for example, Parkinson's disease (PD). To date, the pathogenesis of PD remains elusive and there is no cure for it in spite of intensive research over decades. In this review, we summarize the current knowledge on the efficacy of DR on PD, focusing on the underlying mechanisms involving general metabolism, neuroendocrinolgy, neuroinflammation, gut microbiome, and so on. We anticipate that this review will provide future perspectives for PD prevention and treatment.

Scientific Evidences of Calorie Restriction and Intermittent Fasting for Neuroprotection in Traumatic Brain Injury Animal Models: A Review of the Literature

It has widely been accepted that food restriction (FR) without malnutrition has multiple health benefits. Various calorie restriction (CR) and intermittent fasting (IF) regimens have recently been reported to exert neuroprotective effects in traumatic brain injury (TBI) through variable mechanisms. However, the evidence connecting CR or IF to neuroprotection in TBI as well as current issues remaining in this research field have yet to be reviewed in literature. The objective of our review was therefore to weigh the evidence that suggests the connection between CR/IF with recovery promotion following TBI. Medline, Google Scholar and Web of Science were searched from inception to 25 February 2022. An overwhelming number of results generated suggest that several types of CR/IF play a promising role in promoting post-TBI recovery. This recovery is believed to be achieved by alleviating mitochondrial dysfunction, promoting hippocampal neurogenesis, inhibiting glial cell responses, shaping neural cell plasticity, as well as targeting apoptosis and autophagy. Further, we represent our views on the current issues and provide thoughts on the future direction of this research field.

Mammalian target of rapamycin (mTOR) signaling pathway and traumatic brain injury: A novel insight into targeted therapy

Traumatic brain injury (TBI) is one of the most concerning health issues in which the normal brain function may be disrupted as a result of a blow, bump, or jolt to the head. Loss of consciousness, amnesia, focal neurological defects, alteration in mental state, and destructive diseases of the nervous system such as cognitive impairment, Parkinson's, and Alzheimer's disease. Parkinson's disease is a chronic progressive neurodegenerative disorder, characterized by the early loss of striatal dopaminergic neurons. TBI is a major risk factor for Parkinson's disease. Existing therapeutic approaches have not been often effective, indicating the necessity of discovering more efficient therapeutic targets. The mammalian target of rapamycin (mTOR) signaling pathway responds to different environmental cues to modulate a large number of cellular processes such as cell proliferation, survival, protein synthesis, autophagy, and cell metabolism. Moreover, mTOR has been reported to affect the regeneration of the injured nerves throughout the central nervous system (CNS). In this context, recent evaluations have revealed that mTOR inhibitors could be potential targets to defeat a group of neurological disorders, and thus, a number of clinical trials are investigating their efficacy in treating dementia, autism, epilepsy, stroke, and brain injury, as irritating neurological defects. The current review describes the interplay between mTOR signaling and major CNS-related disorders (esp. neurodegenerative diseases), as well as the mTOR signaling-TBI relationship. It also aims to discuss the promising therapeutic capacities of mTOR inhibitors during the TBI.

Innate immune remodeling by short-term intensive fasting

Previous studies have shown that long-term light or moderate fasting such as intermittent fasting can improve health and prolong lifespan. However, in humans short-term intensive fasting, a complete water-only fasting has little been studied. Here, we used multi-omics tools to evaluate the impact of short-term intensive fasting on immune function by comparison of the CD45+ leukocytes from the fasting subjects before and after 72-h fasting. Transcriptomic and proteomic profiling of CD45+ leukocytes revealed extensive expression changes, marked by higher gene upregulation than downregulation after fasting. Functional enrichment of differentially expressed genes and proteins exposed several pathways critical to metabolic and immune cell functions. Specifically, short-term intensive fasting enhanced autophagy levels through upregulation of key members involved in the upstream signals and within the autophagy machinery, whereas apoptosis was reduced by down-turning of apoptotic gene expression, thereby increasing the leukocyte viability. When focusing on specific leukocyte populations, peripheral neutrophils are noticeably increased by short-term intensive fasting. Finally, proteomic analysis of leukocytes showed that short-term intensive fasting not only increased neutrophil degranulation, but also increased cytokine secretion. Our results suggest that short-term intensive fasting boost immune function, in particular innate immune function, at least in part by remodeling leukocytes expression profile.

Overnight Caloric Restriction Prior to Cardiac Arrest and Resuscitation Leads to Improved Survival and Neurological Outcome in a Rodent Model

While interest toward caloric restriction (CR) in various models of brain injury has increased in recent decades, studies have predominantly focused on the benefits of chronic or intermittent CR. The effects of ultra-short, including overnight, CR on acute ischemic brain injury are not well studied. Here, we show that overnight caloric restriction (75% over 14 h) prior to asphyxial cardiac arrest and resuscitation (CA) improves survival and neurological recovery as measured by, behavioral testing on neurological deficit scores, faster recovery of quantitative electroencephalography (EEG) burst suppression ratio, and complete prevention of neurodegeneration in multiple regions of the brain. We also show that overnight CR normalizes stress-induced hyperglycemia, while significantly decreasing insulin and glucagon production and increasing corticosterone and ketone body production. The benefits seen with ultra-short CR appear independent of Sirtuin 1 (SIRT-1) and brain-derived neurotrophic factor (BDNF) expression, which have been strongly linked to neuroprotective benefits seen in chronic CR. Mechanisms underlying neuroprotective effects remain to be defined, and may reveal targets for providing protection pre-CA or therapeutic interventions post-CA. These findings are also of high importance to basic sciences research as we demonstrate that minor, often-overlooked alterations to pre-experimental dietary procedures can significantly affect results, and by extension, research homogeneity and reproducibility, especially in acute ischemic brain injury models.

Impact of supervised beego, a traditional Chinese water-only fasting, on thrombosis and haemostasis

Beego is a traditional Chinese complete water-only fasting practice initially developed for spiritual purposes, later extending to physical fitness purposes. Beego notably includes a psychological induction component that includes meditation and abdominal breathing, light body exercise and ends with a specific gradual refeeding program before returning to a normal diet. Beego has regained its popularity in recent decades in China as a strategy for helping people in subhealthy conditions or with metabolic syndrome, but we are unaware of any studies examining the biological effects of this practice. To address this, we here performed a longitudinal study of beego comprising fasting (7 and 14 day cohorts) and a 7-day programmed refeeding phase. In addition to detecting improvements in cardiovascular physiology and selective reduction of blood pressure in hypertensive subjects, we observed that beego decreased blood triacylglycerol (TG) selectively in TG-high subjects and increased cholesterol in all subjects during fasting; however, the cholesterol levels were normalised after completion of the refeeding program. Strikingly, beego reduced platelet formation, activation, aggregation and degranulation, resulting in an alleviated thrombosis risk, yet maintained haemostasis by sustaining levels of coagulation factors and other haemostatic proteins. Mechanistically, we speculate that downregulation of G6B and MYL9 may influence the observed beego-mediated reduction in platelets. Fundamentally, our study supports that supervised beego reduces thrombosis risk without compromising haemostasis capacity. Moreover, our results support that beego under medical supervision can be implemented as non-invasive intervention for reducing thrombosis risk, and suggest several lines of intriguing inquiry for future studies about this fasting practice (http://www.chictr.org.cn/index.aspx, number, ChiCTR1900027451).

Nutritional interventions to improve neurophysiological impairments following traumatic brain injury: A systematic review

Traumatic brain injury (TBI) accounts for significant global health burden. Effects of TBI can become chronic even following mild injury. There is a need to develop effective therapies to attenuate the damaging effects of TBI and improve recovery outcomes. This literature review using a priori criteria (PROSPERO; CRD42018100623) summarized 43 studies between January 1998 and July 2019 that investigated nutritional interventions (NUT) delivered with the objective of altering neurophysiological (NP) outcomes following TBI. Risk of bias was assessed for included studies, and NP outcomes recorded. The systematic search resulted in 43 of 3,748 identified studies met inclusion criteria. No studies evaluated the effect of a NUT on NP outcomes of TBI in humans. Biomarkers of morphological changes and apoptosis, oxidative stress, and plasticity, neurogenesis, and neurotransmission were the most evaluated NP outcomes across the 43 studies that used 2,897 animals. The risk of bias was unclear in all reviewed studies due to poorly detailed methodology sections. Taking these limitations into account, anti-oxidants, branched chain amino acids, and ω-3 polyunsaturated fatty acids have shown the most promising pre-clinical results for altering NP outcomes following TBI. Refinement of pre-clinical methodologies used to evaluate effects of interventions on secondary damage of TBI would improve the likelihood of translation to clinical populations.

Western diet aggravates neuronal insult in post-traumatic brain injury: Proposed pathways for interplay

Traumatic brain injury (TBI) is a global health burden and a major cause of disability and mortality. An early cascade of physical and structural damaging events starts immediately post-TBI. This primary injury event initiates a series of neuropathological molecular and biochemical secondary injury sequelae, that last much longer and involve disruption of cerebral metabolism, mitochondrial dysfunction, oxidative stress, neuroinflammation, and can lead to neuronal damage and death. Coupled to these events, recent studies have shown that lifestyle factors, including diet, constitute additional risk affecting TBI consequences and neuropathophysiological outcomes. There exists molecular cross-talk among the pathways involved in neuronal survival, neuroinflammation, and behavioral outcomes, that are shared among western diet (WD) intake and TBI pathophysiology. As such, poor dietary intake would be expected to exacerbate the secondary damage in TBI. Hence, the aim of this review is to discuss the pathophysiological consequences of WD that can lead to the exacerbation of TBI outcomes. We dissect the role of mitochondrial dysfunction, oxidative stress, neuroinflammation, and neuronal injury in this context. We show that currently available data conclude that intake of a diet saturated in fats, pre- or post-TBI, aggravates TBI, precludes recovery from brain trauma, and reduces the response to treatment.

Does calorie restriction improve cognition?

Calorie restriction (CR) has been considered the most effective non-pharmacological intervention to counteract aging-related diseases and improve longevity. This intervention has shown beneficial effects in the prevention and treatment of several chronic diseases and functional declines related to aging, such as Parkinson's, Alzheimer's, and neuroendocrine disorders. However, the effects of CR on cognition show controversial results since its effects vary according to intensity, duration, and the period of CR. This review focuses on the main studies published in the last ten years regarding the consequences of CR on cognition in different neurological diseases and conditions of experimental animals. Also, possible CR mimetics are discussed. These findings highlight the potential beneficial effects of CR of up to 40 % on cognition when started early in life in non human animals.

Efficacy of a Short-Term Low-Calorie Diet in Overweight and Obese Patients with Chronic Sciatica: A Randomized Controlled Trial

Objectives: Chronic sciatica is a common condition. According to Traditional Persian Medicine and recent studies, calorie reduction is thought to be helpful for this condition. The purpose of this work is to evaluate a short-term low-calorie diet (LCD) for ameliorating chronic sciatica in the context of pain relief and reduced disability for patients. Design: In this randomized controlled trial, 96 candidates for the nonsurgical treatment of chronic sciatica were randomly assigned to two groups to receive a 1-month LCD (intervention) or ordinary diet (control), both in combination with nonsteroidal anti-inflammatory drugs (NSAIDs). Afterward, patients were visited at baseline and on days 15, 30, and 60 after treatment. Pain and disability were evaluated using the short-form McGill pain questionnaire (SFMPQ) and the Roland-Morris disability questionnaire (RMDQ), respectively. Results: Both mean RMDQ scores and SFMPQ scores decreased significantly in the LCD group compared to the control group. SFMPQ descriptor scale scores at baseline and on days 15, 30, and 60 in the LCD group were 7.71 ± 1.69, 6.63 ± 1.61, 5.54 ± 1.87, and 4.96 ± 2.02, respectively, and in the control group were 6.63 ± 1.44, 6.69 ± 1.32, 6.64 ± 1.98, and 6.62 ± 2.53, respectively (p = 0.001). RMDQ scores at baseline and on days 15, 30, and 60 in LCD group were 11.17 ± 3.90, 8.60 ± 1.97, 7.50 ± 2.71, and 6.77 ± 3.06, respectively, and in the control group, 10.00 ± 2.20, 9.98 ± 2.29, 9.94 ± 2.94, and 9.85 ± 3.32, respectively (p < 0.001). Conclusion: A short-term (1-month) LCD is effective in decreasing pain and disability in candidates for nonsurgical treatment of chronic sciatica.

Modulation of autophagy in traumatic brain injury

Traumatic brain injury (TBI) is defined as a traumatically induced structural injury or physiological disruption of brain function as a result of external forces, leading to adult disability and death. A growing body of evidence reveals that alterations in autophagy-related proteins exist extensively in both experimentally and clinically after TBI. Of note, the autophagy pathway plays an essential role in pathophysiological processes, such as oxidative stress, inflammatory response, and apoptosis, thus contributing to neurological properties of TBI. With this in mind, this review summarizes a comprehensive overview on the beneficial and detrimental effects of autophagy in pathophysiological conditions and how these activities are linked to the pathogenesis of TBI. Moreover, the relationship between oxidative stress, inflammation, apoptosis, and autophagy occur TBI. Ultimately, multiple compounds and various drugs targeting the autophagy pathway are well described in TBI. Therefore, autophagy flux represents a potential clinical therapeutic value for the treatment of TBI and its complications.

Periodic dietary restriction ameliorates amyloid pathology and cognitive impairment in PDAPP-J20 mice: Potential implication of glial autophagy

Dietary restriction promotes cell regeneration and stress resistance in multiple models of human diseases. One of the conditions that could potentially benefit from this strategy is Alzheimer's disease, a chronic, progressive and prevalent neurodegenerative disease. Although there are no effective pharmacological treatments for this pathology, lifestyle interventions could play therapeutic roles. Our objectives were 1) to evaluate the effects of dietary restriction on cognition, hippocampal amyloid deposition, adult neurogenesis and glial reactivity and autophagy in a mouse model of familial Alzheimer's disease, and 2) to analyze the role of glial cells mediating the effects of nutrient restriction in an in vitro model. Therefore, we established a periodic dietary restriction protocol in adult female PDAPP-J20 transgenic mice for 6 weeks. We found that dietary restriction, not involving overall caloric restriction, attenuated cognitive deficits, amyloid pathology and microglial reactivity in transgenic mice when compared with ad libitum-fed transgenic animals. Also, transgenic mice showed an increase in the astroglial positive signal for LC3, an autophagy-associated protein. In parallel, hippocampal adult neurogenesis was decreased in transgenic mice whereas dietary-restricted transgenic mice showed a neurogenic status similar to controls. In vitro experiments showed that nutrient restriction decreased astroglial and, indirectly, microglial NFκB activation in response to amyloid β peptides. Furthermore, nutrient restriction was able to preserve astroglial autophagic flux and to decrease intracellular amyloid after exposure to amyloid β peptides. Our results suggest neuroprotective effects of nutrient restriction in Alzheimer's disease, with modulation of glial activation and autophagy being potentially involved pathways.

Aging, lifestyle and dementia

Aging is the greatest risk factor for most diseases including cancer, cardiovascular disorders, and neurodegenerative disease. There is emerging evidence that interventions that improve metabolic health with aging may also be effective for brain health. The most robust interventions are non-pharmacological and include limiting calorie or protein intake, increasing aerobic exercise, or environmental enrichment. In humans, dietary patterns including the Mediterranean, Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) and Okinawan diets are associated with improved age-related health and may reduce neurodegenerative disease including dementia. Rapamycin, metformin and resveratrol act on nutrient sensing pathways that improve cardiometabolic health and decrease the risk for age-associated disease. There is some evidence that they may reduce the risk for dementia in rodents. There is a growing recognition that improving metabolic function may be an effective way to optimize brain health during aging.

Cardiolipin-Dependent Mitophagy Guides Outcome after Traumatic Brain Injury

Mitochondrial energy production is essential for normal brain function. Traumatic brain injury (TBI) increases brain energy demands, results in the activation of mitochondrial respiration, associated with enhanced generation of reactive oxygen species. This chain of events triggers neuronal apoptosis via oxidation of a mitochondria-specific phospholipid, cardiolipin (CL). One pathway through which cells can avoid apoptosis is via elimination of damaged mitochondria by mitophagy. Previously, we showed that externalization of CL to the mitochondrial surface acts as an elimination signal in cells. Whether CL-mediated mitophagy occurs in vivo or its significance in the disease processes are not known. In this study, we showed that TBI leads to increased mitophagy in the human brain, which was also detected using TBI models in male rats. Knockdown of CL synthase, responsible for de novo synthesis of CL, or phospholipid scramblase-3, responsible for CL translocation to the outer mitochondrial membrane, significantly decreased TBI-induced mitophagy. Inhibition of mitochondrial clearance by 3-methyladenine, mdivi-1, or phospholipid scramblase-3 knockdown after TBI led to a worse outcome, suggesting that mitophagy is beneficial. Together, our findings indicate that TBI-induced mitophagy is an endogenous neuroprotective process that is directed by CL, which marks damaged mitochondria for elimination, thereby limiting neuronal death and behavioral deficits.SIGNIFICANCE STATEMENT Traumatic brain injury (TBI) increases energy demands leading to activation of mitochondrial respiration associated with enhanced generation of reactive oxygen species and resultant damage to mitochondria. We demonstrate that the complete elimination of irreparably damaged organelles via mitophagy is activated as an early response to TBI. This response includes translocation of mitochondria phospholipid cardiolipin from the inner membrane to the outer membrane where externalized cardiolipin mediates targeted protein light chain 3-mediated autophagy of damaged mitochondria. Our data on targeting phospholipid scramblase and cardiolipin synthase in genetically manipulated cells and animals strongly support the essential role of cardiolipin externalization mechanisms in the endogenous reparative plasticity of injured brain cells. Furthermore, successful execution and completion of mitophagy is beneficial in the context of preservation of cognitive functions after TBI.

The role of autophagy in acute brain injury: A state of flux?

It is established that increased autophagy is readily detectable after various types of acute brain injury, including trauma, focal and global cerebral ischemia. What remains controversial, however, is whether this heightened detection of autophagy in brain represents a homeostatic or pathologic process, or an epiphenomenon. The ultimate role of autophagy after acute brain injury likely depends upon: 1) the degree of brain injury and the overall autophagic burden; 2) the capacity of individual cell types to ramp up autophagic flux; 3) the local redox state and signaling of parallel cell death pathways; 4) the capacity to eliminate damage associated molecular patterns and toxic proteins and metabolites both intra- and extracellularly; and 5) the timing of the pro- or anti-autophagic intervention. In this review, we attempt to reconcile conflicting studies that support both a beneficial and detrimental role for autophagy in models of acute brain injury.

Autophagy-mediated neuroprotection induced by octreotide in an ex vivo model of early diabetic retinopathy

Neuronal injury plays a major role in diabetic retinopathy (DR). Our hypothesis was that the balance between neuronal death and survival may depend on a similar equilibrium between apoptosis and autophagy and that a neuroprotectant may act by influencing this equilibrium. Ex vivo mouse retinal explants were treated with high glucose (HG) for 10days and the somatostatin analog octreotide (OCT) was used as a neuroprotectant. Chloroquine (CQ) was used as an autophagy inhibitor. Apoptotic and autophagic markers were evaluated using western blot and immunohistochemistry. HG-treated explants displayed a significant increase of apoptosis paralleled by a significant decrease of the autophagic flux, which was likely to be due to increased activity of the autophagy regulator mTOR (mammalian target of rapamycin). Treatment with OCT rescued HG-treated retinal explants from apoptosis and determined an increase of autophagic activity with concomitant mTOR inhibition. Blocking the autophagic flux with CQ completely abolished the anti-apoptotic effect of OCT. Immunohistochemical observations showed that OCT-induced autophagy is localized to populations of bipolar and amacrine cells and to ganglion cells. These observations revealed the antithetic role of apoptosis and autophagy, highlighting their equilibrium from which neuronal survival is likely to depend. These data suggest the crucial role covered by autophagy, which could be considered as a molecular target for DR neuroprotective treatment strategies.