Calorie restriction induces mitochondrial biogenesis and bioenergetic efficiency

Calorie restriction increases insulin sensitivity to promote beta cell homeostasis and longevity in mice

Caloric restriction (CR) can extend the organism life- and health-span by improving glucose homeostasis. How CR affects the structure-function of pancreatic beta cells remains unknown. We used single nucleus transcriptomics to show that CR increases the expression of genes for beta cell identity, protein processing, and organelle homeostasis. Gene regulatory network analysis reveal that CR activates transcription factors important for beta cell identity and homeostasis, while imaging metabolomics demonstrates that beta cells upon CR are more energetically competent. In fact, high-resolution microscopy show that CR reduces beta cell mitophagy to increase mitochondria mass and the potential for ATP generation. However, CR beta cells have impaired adaptive proliferation in response to high fat diet feeding. Finally, we show that long-term CR delays the onset of beta cell aging hallmarks and promotes cell longevity by reducing beta cell turnover. Therefore, CR could be a feasible approach to preserve compromised beta cell structure-function during aging and diabetes.

CYB5R3 overexpression exhibits sexual dimorphism: Mitochondrial and metabolic adaptations in transgenic female mice during calorie restriction

There is a pressing need to develop new strategies for enhancing health in the elderly and preventing the rise in age-related diseases. Calorie restriction without malnutrition (CR) stands among the different antiaging interventions. Lifelong CR leads to increased expression and activity of plasma membrane CYB5R3, and male mice overexpressing CYB5R3 exhibit some beneficial adaptations that are also seen with CR. However, the mechanisms involved in both interventions could be independent since key aspects of energy metabolism and tissue lipid profile do not coincide, and many of the changes induced by CR in mitochondrial abundance and dynamics in the liver and skeletal muscle could be counteracted by CYB5R3 overexpression. In this study, we sought to elucidate the impact of CR on key markers of metabolic status, mitochondrial function, and pro-oxidant/antioxidant balance in transgenic (TG) female mice overexpressing CYB5R3 compared to their WT littermates. In females fed ad libitum, CYB5R3 overexpression decreased fat mass, led to a preferred utilization of fatty acids as an energy source, upregulated key antioxidant enzymes, and boosted respiration both in skeletal muscle and liver mitochondria, supporting that CYB5R3 overexpression is phenotypic closer to CR in females than in males. Whereas some markers of mitochondrial biogenesis and dynamics were found decreased in TG females on CR, as also found for the levels of Estrogen Receptor α, mitochondrial abundance and activity were maintained both in skeletal muscle and in liver. Our results reveal overlapping metabolic adaptations resulting from the overexpression of CYB5R3 and CR in females, but a specific crosstalk occurs when both interventions are combined, differing from the adaptations observed in TG males.

Targeting organ-specific mitochondrial dysfunction to improve biological aging

In an aging society, unveiling new anti-aging strategies to prevent and combat aging-related diseases is of utmost importance. Mitochondria are the primary ATP production sites and key regulators of programmed cell death. Consequently, these highly dynamic organelles play a central role in maintaining tissue function, and mitochondrial dysfunction is a pivotal factor in the progressive age-related decline in cellular homeostasis and organ function. The current review examines recent advances in understanding the interplay between mitochondrial dysfunction and organ-specific aging. Thereby, we dissect molecular mechanisms underlying mitochondrial impairment associated with the deterioration of organ function, exploring the role of mitochondrial DNA, reactive oxygen species homeostasis, metabolic activity, damage-associated molecular patterns, biogenesis, turnover, and dynamics. We also highlight emerging therapeutic strategies in preclinical and clinical tests that are supposed to rejuvenate mitochondrial function, such as antioxidants, mitochondrial biogenesis stimulators, and modulators of mitochondrial turnover and dynamics. Furthermore, we discuss potential benefits and challenges associated with the use of these interventions, emphasizing the need for organ-specific approaches given the unique mitochondrial characteristics of different tissues. In conclusion, this review highlights the therapeutic potential of addressing mitochondrial dysfunction to mitigate organ-specific aging, focusing on the skin, liver, lung, brain, skeletal muscle, and lung, as well as on the reproductive, immune, and cardiovascular systems. Based on a comprehensive understanding of the multifaceted roles of mitochondria, innovative therapeutic strategies may be developed and optimized to combat biological aging and promote healthy aging across diverse organ systems.

Mitigating the effects of time in the heart and liver: the variable effects of short- and long-term caloric restriction

Caloric restriction (CR) is known for its anti-aging benefits, partly due to reduced oxidative stress and enhanced antioxidant defense. However, CR outcomes vary based on its intensity, timing, and duration. This study explored CR's effects on antioxidant activity in the heart and liver of male Wistar rats during aging. We investigated two CR paradigms: long-term CR (LTCR), started early in life, and short-term CR (STCR), initiated in middle or old age for 3 months. Contrary to previous findings of short-term CR deleterious effects of on the nervous system, our results revealed increased levels of key antioxidants after STCR. More specifically, we found an increase in GSH-Px and GSH under STCR that was particularly pronounced in the liver, while an increase in CAT and GR activities was observed in the heart of the STCR groups. Catalase was characterized as an enzyme particularly responsive to CR, as its activity was also increased in both the liver and heart after long-term caloric restriction. Our results highlight a significant tissue-specific response to CR and contribute to our understanding of the dynamic effects of CR, which in turn has implications for refining its therapeutic potential in combating age-related decline.

Alginate oligosaccharides exert protective effects on hydrogen peroxide-induced senescence in H9C2 cardiomyocytes by regulating the redox state of cells

Aging is a known independent risk factor for several cardiovascular diseases. Here, we evaluated potential effects and possible mechanisms through which alginate oligosaccharides (AOS) affect hydrogen peroxide (H2O2)-induced senescence in H9C2 cardiomyocytes. A series of AOS molecules, including oligoM, oligoG, M-5, and G-5, were investigated. AOS significantly decreased SA-β-gal and DAPI-stained positive cells, downregulated p53 and p21 (aging-related markers) expression, and eventually protected H9C2 cells from H2O2-induced senescence. AOS decreased reactive oxygen species and malondialdehyde production, recovered mitochondrial function, and alleviated the oxidative stress state by regulating PGC-1α and NADPH oxidase subunit expression. Furthermore, AOS treatment restored the expression of antioxidant enzymes in senescent H9C2 cells. Thus, our results show in vitro evidence that AOS alleviate senescence in H9C2 cells by regulating the redox state; thus, AOS may be an effective therapeutic agent that could protect against cardiomyocyte senescence.

Molecular Mechanisms of Healthy Aging: The Role of Caloric Restriction, Intermittent Fasting, Mediterranean Diet, and Ketogenic Diet-A Scoping Review

As the population ages, promoting healthy aging through targeted interventions becomes increasingly crucial. Growing evidence suggests that dietary interventions can significantly impact this process by modulating fundamental molecular pathways. This review focuses on the potential of targeted dietary strategies in promoting healthy aging and the mechanisms by which specific nutrients and dietary patterns influence key pathways involved in cellular repair, inflammation, and metabolic regulation. Caloric restriction, intermittent fasting, the Mediterranean diet, as well as the ketogenic diet showed promising effects on promoting healthy aging, possibly by modulating mTORC1 AMPK, an insulin signaling pathway. By understanding the intricate interplay between diet and molecular pathways, we can develop personalized dietary strategies that not only prevent age-related diseases, but also promote overall health and well-being throughout the aging process.

Mitochondrial redox state, bioenergetics, and calcium transport in caloric restriction: A metabolic nexus

Mitochondria congregate central reactions in energy metabolism, many of which involve electron transfer. As such, they are expected to both respond to changes in nutrient supply and demand and also provide signals that integrate energy metabolism intracellularly. In this review, we discuss how mitochondrial bioenergetics and reactive oxygen species production is impacted by dietary interventions that change nutrient availability and impact on aging, such as calorie restriction. We also discuss how dietary interventions alter mitochondrial Ca2+ transport, regulating both mitochondrial and cytosolic processes modulated by this ion. Overall, a plethora of literature data support the idea that mitochondrial oxidants and calcium transport act as integrating signals coordinating the response to changes in nutritional supply and demand in cells, tissues, and animals.

Effects of endurance training under calorie restriction on energy substrate metabolism in mouse skeletal muscle and liver

We investigated whether calorie restriction (CR) enhances metabolic adaptations to endurance training (ET). Ten-week-old male Institute of Cancer Research (ICR) mice were fed ad libitum or subjected to 30% CR. The mice were subdivided into sedentary and ET groups. The ET group performed treadmill running (20-25 m/min, 30 min, 5 days/week) for 5 weeks. We found that CR decreased glycolytic enzyme activity and monocarboxylate transporter (MCT) 4 protein content, while enhancing glucose transporter 4 protein content in the plantaris and soleus muscles. Although ET and CR individually increased citrate synthase activity in the plantaris muscle, the ET-induced increase in respiratory chain complex I protein content was counteracted by CR. In the soleus muscle, mitochondrial enzyme activity and protein levels were increased by ET, but decreased by CR. It has been suggested that CR partially interferes with skeletal muscle adaptation to ET.

The mitochondrial quality control system: a new target for exercise therapeutic intervention in the treatment of brain insulin resistance-induced neurodegeneration in obesity

Obesity is a major global health concern because of its strong association with metabolic and neurodegenerative diseases such as diabetes, dementia, and Alzheimer's disease. Unfortunately, brain insulin resistance in obesity is likely to lead to neuroplasticity deficits. Since the evidence shows that insulin resistance in brain regions abundant in insulin receptors significantly alters mitochondrial efficiency and function, strategies targeting the mitochondrial quality control system may be of therapeutic and practical value in obesity-induced cognitive decline. Exercise is considered as a powerful stimulant of mitochondria that improves insulin sensitivity and enhances neuroplasticity. It has great potential as a non-pharmacological intervention against the onset and progression of obesity associated neurodegeneration. Here, we integrate the current knowledge of the mechanisms of neurodegenration in obesity and focus on brain insulin resistance to explain the relationship between the impairment of neuronal plasticity and mitochondrial dysfunction. This knowledge was synthesised to explore the exercise paradigm as a feasible intervention for obese neurodegenration in terms of improving brain insulin signals and regulating the mitochondrial quality control system.

Nutritional approaches targeting mitochondria for the prevention of sarcopenia

A decline in function and loss of mass, a condition known as sarcopenia, is observed in the skeletal muscles with aging. Sarcopenia has a negative effect on the quality of life of elderly. Individuals with sarcopenia are at particular risk for adverse outcomes, such as reduced mobility, fall-related injuries, and type 2 diabetes mellitus. Although the pathogenesis of sarcopenia is multifaceted, mitochondrial dysfunction is regarded as a major contributor for muscle aging. Hence, the development of preventive and therapeutic strategies to improve mitochondrial function during aging is imperative for sarcopenia treatment. However, effective and specific drugs that can be used for the treatment are not yet approved. Instead studies on the relationship between food intake and muscle aging have suggested that nutritional intake or dietary control could be an alternative approach for the amelioration of muscle aging. This narrative review approaches various nutritional components and diets as a treatment for sarcopenia by modulating mitochondrial homeostasis and improving mitochondria. Age-related changes in mitochondrial function and the molecular mechanisms that help improve mitochondrial homeostasis are discussed, and the nutritional components and diet that modulate these molecular mechanisms are addressed.

Oxidative stress and the role of redox signalling in chronic kidney disease

Chronic kidney disease (CKD) is a major public health concern, underscoring a need to identify pathogenic mechanisms and potential therapeutic targets. Reactive oxygen species (ROS) are derivatives of oxygen molecules that are generated during aerobic metabolism and are involved in a variety of cellular functions that are governed by redox conditions. Low levels of ROS are required for diverse processes, including intracellular signal transduction, metabolism, immune and hypoxic responses, and transcriptional regulation. However, excess ROS can be pathological, and contribute to the development and progression of chronic diseases. Despite evidence linking elevated levels of ROS to CKD development and progression, the use of low-molecular-weight antioxidants to remove ROS has not been successful in preventing or slowing disease progression. More recent advances have enabled evaluation of the molecular interactions between specific ROS and their targets in redox signalling pathways. Such studies may pave the way for the development of sophisticated treatments that allow the selective control of specific ROS-mediated signalling pathways.

Rate of body weight gain during early gestation in F0 beef heifers has effects that extend multigenerationally to the F2 fetuses

Our aim was to investigate the effects of maternal (F0) body weight (BW) gain during the first 84 d of gestation on body composition, ovarian reserve, and hormonal and metabolic parameters of breeding-age F1 heifers, as well as the BW and morphometry of F2 fetuses. The study also evaluated the effect of maternal BW gain (F0) on the mRNA relative abundance of the small intestine of both F1 heifers and F2 fetuses. Crossbred Angus heifers (F0; n = 100) were managed to gain 0.20 kg/d (low gain [LG], n = 50) or 0.75 kg/d (moderate gain [MG], n = 50) for the first 84 d of gestation. Subsequently, F0 dams were managed on a common forage-based diet for the rest of gestation until the weaning of the F1 offspring. At 15 mo of age, a subset of F1 heifers was randomly selected for the current experiment (n = 8 LG and n = 8 MG). Heifers were bred via artificial insemination (AI; day 0), then harvested on day 84 of gestation. On days -10, 42, and 84, BW was recorded, and blood was collected and analyzed for concentrations of glucose, non-esterified fatty acids, progesterone, insulin, and insulin-like growth factor-1. The weight of F1 carcasses, organs, gravid uteri, and F2 fetuses and organs were recorded at harvest. Visible follicles were counted on F1 ovaries at harvest, and histology was used to count microscopic follicles. Liver and jejunal samples from F1 heifers were collected to measure tissue oxygen consumption and jejunal samples from F1 heifers and F2 fetuses were collected for mRNA relative abundance analysis. BW of F1 heifers from MG dams tended to be 12 kg greater (P = 0.06) than for F1 heifers from LG dams. Concentrations of glucose were greater (P = 0.03) in F1 heifers from the MG group, with no differences in other blood metabolites or follicular populations (P ≥ 0.16). Interestingly, mammary glands were heavier (P = 0.05), and placentas and body depth tended to be heavier and greater, respectively (P ≤ 0.10), for F2 fetuses from F0 LG heifers. Oxygen consumption in the liver and jejunum, as well as mRNA relative abundance in the jejunum of F1 heifers, were not affected by F0 rate of gain (P ≥ 0.16). However, the NDUFC1, SDHA, UQCR1, and PPARG genes were upregulated (P ≤ 0.05) in the jejunum of F2 fetuses from the LG group. In conclusion, BW gain of F0 heifers during early gestation exerts subtle effects on pre-breeding BW and blood metabolites in F1 offspring, with impacts present in F2 placenta, mammary gland, and intestine.

Significance of quantitative analyses of the impact of heterogeneity in mitochondrial content and shape on cell differentiation

Mitochondria, classically known as the powerhouse of cells, are unique double membrane-bound multifaceted organelles carrying a genome. Mitochondrial content varies between cell types and precisely doubles within cells during each proliferating cycle. Mitochondrial content also increases to a variable degree during cell differentiation triggered after exit from the proliferating cycle. The mitochondrial content is primarily maintained by the regulation of mitochondrial biogenesis, while damaged mitochondria are eliminated from the cells by mitophagy. In any cell with a given mitochondrial content, the steady-state mitochondrial number and shape are determined by a balance between mitochondrial fission and fusion processes. The increase in mitochondrial content and alteration in mitochondrial fission and fusion are causatively linked with the process of differentiation. Here, we critically review the quantitative aspects in the detection methods of mitochondrial content and shape. Thereafter, we quantitatively link these mitochondrial properties in differentiating cells and highlight the implications of such quantitative link on stem cell functionality. Finally, we discuss an example of cell size regulation predicted from quantitative analysis of mitochondrial shape and content. To highlight the significance of quantitative analyses of these mitochondrial properties, we propose three independent rationale based hypotheses and the relevant experimental designs to test them.

Late-life shift in caloric intake affects fly metabolism and longevity

The prevalence of obesity is increasing in older adults and contributes to age-related decline. Caloric restriction (CR) alleviates obesity phenotypes and delays the onset of age-related changes. However, how late in life organisms benefit from switching from a high-(H) to a low-calorie (L) diet is unclear. We transferred male flies from a H to a L (HL) diet or vice versa (LH) at different times during life. Both shifts immediately change fly rate of aging even when applied late in life. HL shift rapidly reduces fly mortality rate to briefly lower rate than in flies on a constant L diet, and extends lifespan. Transcriptomic analysis uncovers that flies aged on H diet have acquired increased stress response, which may have temporal advantage over flies aged on L diet and leads to rapid decrease in mortality rate after HL switch. Conversely, a LH shift increases mortality rate, which is temporarily higher than in flies aged on a H diet, and shortens lifespan. Unexpectedly, more abundant transcriptomic changes accompanied LH shift, including increase in ribosome biogenesis, stress response and growth. These changes reflect protection from sudden release of ROS, energy storage, and use of energy to growth, which all likely contribute to higher mortality rate. As the beneficial effects of CR on physiology and lifespan are conserved across many organisms, our study provides framework to study underlying mechanisms of CR interventions that counteract the detrimental effects of H diets and reduce rate of aging even when initiated later in life.

Mechanisms underlying retardation of aging by dietary energy restriction

Moderate restriction of dietary energy intake, referred to here as dietary restriction (DR), delays aging and extends lifespan in experimental animals compared with a diet of ad libitum feeding (AL) control animals. Basic knowledge of the mechanisms underlying the effects of DR could be applicable to extending the healthspan in humans. This review highlights the importance of forkhead box O (FoxO) transcription factors downstream of the growth hormone-insulin-like growth factor 1 signaling in the effects of DR. Our lifespan studies in mice with heterozygous Foxo1 or Foxo3 gene knockout indicated differential roles of FoxO1 and FoxO3 in the tumor-inhibiting and life-extending effects of DR. Subsequent studies suggested a critical role of FoxO3 in metabolic and mitochondrial bioenergetic adaptation to DR. Our studies also verified hypothalamic neuropeptide Y (Npy) as a vital neuropeptide showing pleiotropic and sexually dimorphic effects for extending the healthspan in the context of nutritional availability. Npy was necessary for DR to exert its effects in male and female mice; meanwhile, under AL conditions, the loss of Npy prevented obesity and insulin resistance only in female mice. Overnutrition disrupts FoxO- and Npy-associated metabolic and mitochondrial bioenergetic adaptive processes, causing the acceleration of aging and related diseases.

Calorie restriction modulates the transcription of genes related to stress response and longevity in human muscle: The CALERIE study

The lifespan extension induced by 40% caloric restriction (CR) in rodents is accompanied by postponement of disease, preservation of function, and increased stress resistance. Whether CR elicits the same physiological and molecular responses in humans remains mostly unexplored. In the CALERIE study, 12% CR for 2 years in healthy humans induced minor losses of muscle mass (leg lean mass) without changes of muscle strength, but mechanisms for muscle quality preservation remained unclear. We performed high-depth RNA-Seq (387-618 million paired reads) on human vastus lateralis muscle biopsies collected from the CALERIE participants at baseline, 12- and 24-month follow-up from the 90 CALERIE participants randomized to CR and "ad libitum" control. Using linear mixed effect model, we identified protein-coding genes and splicing variants whose expression was significantly changed in the CR group compared to controls, including genes related to proteostasis, circadian rhythm regulation, DNA repair, mitochondrial biogenesis, mRNA processing/splicing, FOXO3 metabolism, apoptosis, and inflammation. Changes in some of these biological pathways mediated part of the positive effect of CR on muscle quality. Differentially expressed splicing variants were associated with change in pathways shown to be affected by CR in model organisms. Two years of sustained CR in humans positively affected skeletal muscle quality, and impacted gene expression and splicing profiles of biological pathways affected by CR in model organisms, suggesting that attainable levels of CR in a lifestyle intervention can benefit muscle health in humans.

Effect of mitochondrial quantity and quality controls in white adipose tissue on healthy lifespan: Essential roles of GH/IGF-1-independent pathways in caloric restriction-mediated metabolic remodeling

Long-term caloric restriction is a conventional and reproducible dietary intervention to improve whole body metabolism, suppress age-related pathophysiology, and extend lifespan. The beneficial actions of caloric restriction are widely accepted to be regulated in both growth hormone/insulin-like growth factor 1-dependent and -independent manners. Although growth hormone/insulin-like growth factor 1-dependent regulatory mechanisms are well described, those occurring independent of growth hormone/insulin-like growth factor 1 are poorly understood. In this review, we focus on molecular mechanisms of caloric restriction regulated in a growth hormone/insulin-like growth factor 1-independent manner. Caloric restriction increases mitochondrial quantity and improves mitochondrial quality by activating an axis involving sterol regulatory element binding protein-c/peroxisome proliferator-activated receptor γ coactivator-1α/mitochondrial intermediate peptidase in a growth hormone/insulin-like growth factor 1-independent manner, particularly in white adipose tissue. Fibroblast growth factor 21 is also involved in this axis. Moreover, the axis may be regulated by lower leptin signaling. Thus, caloric restriction appears to induce beneficial actions partially by regulating mitochondrial quantity and quality in white adipose tissue in a growth hormone/insulin-like growth factor 1-independent manner.

Caloric restriction promotes beta cell longevity and delays aging and senescence by enhancing cell identity and homeostasis mechanisms

Caloric restriction (CR) extends organismal lifespan and health span by improving glucose homeostasis mechanisms. How CR affects organellar structure and function of pancreatic beta cells over the lifetime of the animal remains unknown. Here, we used single nucleus transcriptomics to show that CR increases the expression of genes for beta cell identity, protein processing, and organelle homeostasis. Gene regulatory network analysis link this transcriptional phenotype to transcription factors involved in beta cell identity (Mafa) and homeostasis (Atf6). Imaging metabolomics further demonstrates that CR beta cells are more energetically competent. In fact, high-resolution light and electron microscopy indicates that CR reduces beta cell mitophagy and increases mitochondria mass, increasing mitochondrial ATP generation. Finally, we show that long-term CR delays the onset of beta cell aging and senescence to promote longevity by reducing beta cell turnover. Therefore, CR could be a feasible approach to preserve compromised beta cells during aging and diabetes.

Caloric restriction promotes beta cell longevity and delays aging and senescence by enhancing cell identity and homeostasis mechanisms

Caloric restriction (CR) extends organismal lifespan and health span by improving glucose homeostasis mechanisms. How CR affects organellar structure and function of pancreatic beta cells over the lifetime of the animal remains unknown. Here, we used single nucleus transcriptomics to show that CR increases the expression of genes for beta cell identity, protein processing, and organelle homeostasis. Gene regulatory network analysis link this transcriptional phenotype to transcription factors involved in beta cell identity (Mafa) and homeostasis (Atf6). Imaging metabolomics further demonstrates that CR beta cells are more energetically competent. In fact, high-resolution light and electron microscopy indicates that CR reduces beta cell mitophagy and increases mitochondria mass, increasing mitochondrial ATP generation. Finally, we show that long-term CR delays the onset of beta cell aging and senescence to promote longevity by reducing beta cell turnover. Therefore, CR could be a feasible approach to preserve compromised beta cells during aging and diabetes.

Epigenetic activation of secretory phenotypes in senescence by the FOXQ1-SIRT4-GDH signaling

Although metabolic reprogramming is characterized as a hallmark of aging, implications of the crucial glutamate dehydrogenase (GDH) in human senescence remain poorly understood. Here, we report that GDH activity is significantly increased in aged mice and senescent human diploid fibroblasts. This enzymatic potentiation is associated with de-repression of GDH from its functionally suppressive ADP-ribosylation modification catalyzed by NAD-dependent ADP-ribosyltransferase/deacetylase SIRT4. A series of transcription analyses led to the identification of FOXQ1, a forkhead family transcription factor (TF), responsible for the maintenance of SIRT4 expression levels in juvenile cells. However, this metabolically balanced FOXQ1-SIRT4-GDH axis, is shifted in senescence with gradually decreasing expressions of FOXQ1 and SIRT4 and elevated GDH activity. Importantly, pharmaceutical inhibition of GDH suppresses the aberrantly activated transcription of IL-6 and IL-8, two major players in senescence-associated secretory phenotype (SASP), and this action is mechanistically associated with erasure of the repressive H3K9me3 (trimethylation of lysine 9 on histone H3) marks at IL-6 and IL-8 promoters, owing to the requirement of α-ketoglutaric acid (α-KG) from GDH-mediated glutamate dehydrogenase reaction as a cofactor for histone demethylation. In supplement with the phenotypic evidence from FOXQ1/SIRT4/GDH manipulations, these data support the integration of metabolism alterations and epigenetic regulation in driving senescence progression and highlight the FOXQ1-SIRT4-GDH axis as a novel druggable target for improving human longevity.

5-Hydroxymethylfurfural reduces skeletal muscle superoxide production and modifies force production in rats exposed to hypobaric hypoxia

Decreased blood-tissue oxygenation at high altitude (HA) increases mitochondrial oxidant production and reduces exercise capacity. 5-Hydroxymethylfurfural (5-HMF) is an antioxidant that increases hemoglobin's binding affinity for oxygen. For these reasons, we hypothesized that 5-HMF would improve muscle performance in rats exposed to a simulated HA of ~5500 m. A secondary objective was to measure mitochondrial activity and dynamic regulation of fission and fusion because they are linked processes impacted by HA. Fisher 344 rats received 5-HMF (40 mg/kg/day) or vehicle during exposure to sea level or HA for 72 h. Right ankle plantarflexor muscle function was measured pre- and post-exposure. Post-exposure measurements included arterial blood gas and complete blood count, flexor digitorum brevis myofiber superoxide production and mitochondrial membrane potential (ΔΨm), and mitochondrial dynamic regulation in the soleus muscle. HA reduced blood oxygenation, increased superoxide levels and lowered ΔΨm, responses that were accompanied by decreased peak isometric torque and force production at frequencies >75 Hz. 5-HMF increased isometric force production and lowered oxidant production at sea level. In HA exposed animals, 5-HMF prevented a decline in isometric force production at 75-125 Hz, prevented an increase in superoxide levels, further decreased ΔΨm, and increased mitochondrial fusion 2 protein expression. These results suggest that 5-HMF may prevent a decrease in hypoxic force production during submaximal isometric contractions by an antioxidant mechanism.

Coenzyme Q-related compounds to maintain healthy mitochondria during aging

Mitochondrial dysfunction is one of the main factors that affects aging progression and many age-related diseases. Accumulation of dysfunctional mitochondria can be driven by unbalanced mito/autophagy or by decrease in mitochondrial biosynthesis and turnover. Coenzyme Q is an essential component of the mitochondrial electron transport chain and a key factor in the protection of membrane and mitochondrial DNA against oxidation. Coenzyme Q levels decay during aging and this can be considered an accelerating factor in mitochondrial dysfunction and aging progression. Supplementation with coenzyme Q is successful for some tissues and organs but not for others. For this reason, the role of coenzyme Q in systemic aging is a complex picture that needs different strategies depending on the organ considered the main objective to be addressed. In this chapter we focus on the different effects of coenzyme Q and related compounds and the probable strategies to induce endogenous synthesis to maintain healthy aging.

Intermittent Fasting Sustainably Improves Glucose Tolerance in Normal Weight Male Mice Through Histone Hyperacetylation

To explore the mechanism by which intermittent fasting (IF) exerts prolonged effects after discontinuation, we examined mice that had been subjected to 4 cycles of fasting for 72 hours and ad libitum feeding for 96 hours per week (72hIF), followed by 4 weeks of ad libitum feeding, focusing on expression of genes for lipid metabolism in the skeletal muscle and histone acetylation in the promoter region. The 72hIF regimen resulted in metabolic remodeling, characterized by enhanced lipid utilization and mitochondrial activation in the muscle. This long-term IF (72hIF) caused stronger metabolic effects than alternate day fasting (24hIF) wherein fasting and refeeding are repeated every 24 hours. Upregulation of lipid oxidation genes and an increase in oxygen utilization were sustained even at 4 weeks after discontinuation of 72hIF, associated with histone hyperacetylation of the promoter region of uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) genes. An increase in leucine owing to fasting-induced muscle degradation was suggested to lead to the histone acetylation. These findings support the previously unappreciated notion that sustainable promotion of histone acetylation in lipid oxidation genes of the muscle and adipose tissues during and after IF may contribute to sustained metabolic effects of IF.

Diet Restriction Impact on High-Fat-Diet-Induced Obesity by Regulating Mitochondrial Cardiolipin Biosynthesis and Remodeling

Diet restriction (DR) ameliorates obesity by regulating mitochondrial function. Cardiolipin (CL), a mitochondrial phospholipid, is closely associated with mitochondrial function. This study aimed to evaluate the anti-obesity effects of graded levels of DR based on mitochondrial CL levels in the liver. Obese mice were treated with 0%, 20%, 40%, and 60% reductions in the normal diet compared to normal animals (0 DR, 20 DR, 40 DR, and 60 DR groups, respectively). Biochemical and histopathological analyses were performed to evaluate the ameliorative effects of DR on obese mice. The altered profile of mitochondrial CL in the liver was explored using a targeted metabolomics strategy by ultra-high-pressure liquid chromatography MS/MS coupled with quadrupole time-of-flight mass spectrometry. Finally, gene expression associated with CL biosynthesis and remodeling was quantified. Tissue histopathology and biochemical index evaluations revealed significant improvements in the liver after DR, except for the 60 DR group. The variation in mitochondrial CL distribution and DR levels showed an inverted U-shape, and the CL content in the 40 DR group was the most upregulated. This result is consistent with the results of the target metabolomic analysis, which showed that 40 DR presented more variation. Furthermore, DR led to increased gene expression associated with CL biosynthesis and remodeling. This study provides new insights into the mitochondrial mechanisms underlying DR intervention in obesity.

Mitochondria in cell senescence: A Friend or Foe?

Cell senescence denotes cell growth arrest in response to continuous replication or stresses damaging DNA or mitochondria. Mounting research suggests that cell senescence attributes to aging-associated failing organ function and diseases. Conversely, it participates in embryonic tissue maturation, wound healing, tissue regeneration, and tumor suppression. The acute or chronic properties and microenvironment may explain the double faces of senescence. Senescent cells display unique characteristics. In particular, its mitochondria become elongated with altered metabolomes and dynamics. Accordingly, mitochondria reform their function to produce more reactive oxygen species at the cost of low ATP production. Meanwhile, destructed mitochondrial unfolded protein responses further break the delicate proteostasis fostering mitochondrial dysfunction. Additionally, the release of mitochondrial damage-associated molecular patterns, mitochondrial Ca²⁺ overload, and altered NAD⁺ level intertwine other cellular organelle strengthening senescence. These findings further intrigue researchers to develop anti-senescence interventions. Applying mitochondrial-targeted antioxidants reduces cell senescence and mitigates aging by restoring mitochondrial function and attenuating oxidative stress. Metformin and caloric restriction also manifest senescent rescuing effects by increasing mitochondria efficiency and alleviating oxidative damage. On the other hand, Bcl2 family protein inhibitors eradicate senescent cells by inducing apoptosis to facilitate cancer chemotherapy. This review describes the different aspects of mitochondrial changes in senescence and highlights the recent progress of some anti-senescence strategies.

Food Polyphenols and Type II Diabetes Mellitus: Pharmacology and Mechanisms

Type II diabetes mellitus and its related complications are growing public health problems. Many natural products present in our diet, including polyphenols, can be used in treating and managing type II diabetes mellitus and different diseases, owing to their numerous biological properties. Anthocyanins, flavonols, stilbenes, curcuminoids, hesperidin, hesperetin, naringenin, and phenolic acids are common polyphenols found in blueberries, chokeberries, sea-buckthorn, mulberries, turmeric, citrus fruits, and cereals. These compounds exhibit antidiabetic effects through different pathways. Accordingly, this review presents an overview of the most recent developments in using food polyphenols for managing and treating type II diabetes mellitus, along with various mechanisms. In addition, the present work summarizes the literature about the anti-diabetic effect of food polyphenols and evaluates their potential as complementary or alternative medicines to treat type II diabetes mellitus. Results obtained from this survey show that anthocyanins, flavonols, stilbenes, curcuminoids, and phenolic acids can manage diabetes mellitus by protecting pancreatic β-cells against glucose toxicity, promoting β-cell proliferation, reducing β-cell apoptosis, and inhibiting α-glucosidases or α-amylase. In addition, these phenolic compounds exhibit antioxidant anti-inflammatory activities, modulate carbohydrate and lipid metabolism, optimize oxidative stress, reduce insulin resistance, and stimulate the pancreas to secrete insulin. They also activate insulin signaling and inhibit digestive enzymes, regulate intestinal microbiota, improve adipose tissue metabolism, inhibit glucose absorption, and inhibit the formation of advanced glycation end products. However, insufficient data are available on the effective mechanisms necessary to manage diabetes.

Conditioned place avoidance is associated with a distinct hippocampal phenotype, partly preserved pattern separation, and reduced reactive oxygen species production after stress

Stress is associated with contextual memory deficits, which may mediate avoidance of trauma-associated contexts in posttraumatic stress disorder. These deficits may emerge from impaired pattern separation, the independent representation of similar experiences by the dentate gyrus-Cornu Ammonis 3 (DG-CA3) circuit of the dorsal hippocampus, which allows for appropriate behavioral responses to specific environmental stimuli. Neurogenesis in the DG is controlled by mitochondrial reactive oxygen species (ROS) production, and may contribute to pattern separation. In Experiment 1, we performed RNA sequencing of the dorsal hippocampus 16 days after stress in rats that either develop conditioned place avoidance to a predator urine-associated context (Avoiders), or do not (Non-Avoiders). Weighted genome correlational network analysis showed that increased expression of oxidative phosphorylation-associated gene transcripts and decreased expression of gene transcripts for axon guidance and insulin signaling were associated with avoidance behavior. Based on these data, in Experiment 2, we hypothesized that Avoiders would exhibit elevated hippocampal (HPC) ROS production and degraded object pattern separation (OPS) compared with Nonavoiders. Stress impaired pattern separation performance in Non-Avoider and Avoider rats compared with nonstressed Controls, but surprisingly, Avoiders exhibited partly preserved pattern separation performance and significantly lower ROS production compared with Non-Avoiders. Lower ROS production was associated with better OPS performance in Stressed rats, but ROS production was not associated with OPS performance in Controls. These results suggest a strong negative association between HPC ROS production and pattern separation after stress, and that stress effects on these outcome variables may be associated with avoidance of a stress-paired context.

Phytotherapeutic targeting of the mitochondria in neurodegenerative disorders

Neurodegenerative diseases are characterized by degeneration or cellular atrophy within specific structures of the brain. Neurons are the major target of neurodegeneration. Neurons utilize 75-80% of the energy produced in the brain. This energy is either formed by utilizing the glucose provided by the cerebrovascular blood flow or by the in-house energy producers, mitochondria. Mitochondrial dysfunction has been associated with neurodegenerative diseases. But recently it has been noticed that neurodegenerative diseases are often associated with cerebrovascular diseases. Cerebral blood flow requires vasodilation which to an extent regulated by mitochondria. We hypothesize that when mitochondrial functioning is disrupted, it is not able to supply energy to the neurons. This disruption also affects cerebral blood flow, further reducing the possibilities of energy supply. Loss of sufficient energy leads to neuronal dysfunction, atrophy, and degeneration. In this chapter, we will discuss the metabolic modifications of mitochondria in aging-related neurological disorders and the potential of phytocompounds targeting them.

Resveratrol-Mediated Regulation of Mitochondria Biogenesis-associated Pathways in Neurodegenerative Diseases: Molecular Insights and Potential Therapeutic Applications

Neurodegenerative disorders include different neurological conditions that affect nerve cells, causing the progressive loss of their functions and ultimately leading to loss of mobility, coordination, and mental functioning. The molecular mechanisms underpinning neurodegenerative disease pathogenesis are still unclear. Nonetheless, there is experimental evidence to demonstrate that the perturbation of mitochondrial function and dynamics play an essential role. In this context, mitochondrial biogenesis, the growth, and division of preexisting mitochondria, by controlling mitochondria number, plays a vital role in maintaining proper mitochondrial mass and function, thus ensuring efficient synaptic activity and brain function. Mitochondrial biogenesis is tightly associated with the control of cell division and variations in energy demand in response to extracellular stimuli; therefore, it may represent a promising therapeutic target for developing new curative approaches to prevent or counteract neurodegenerative disorders. Accordingly, several inducers of mitochondrial biogenesis have been proposed as pharmacological targets for treating diverse central nervous system conditions. The naturally occurring polyphenol resveratrol has been shown to promote mitochondrial biogenesis in various tissues, including the nervous tissue, and an ever-growing number of studies highlight its neurotherapeutic potential. Besides preventing cognitive impairment and neurodegeneration through its antioxidant and anti-inflammatory properties, resveratrol has been shown to be able to enhance mitochondria biogenesis by acting on its main effectors, including PGC-1α, SIRT1, AMPK, ERRs, TERT, TFAM, NRF-1 and NRF-2. This review aims to present and discuss the current findings concerning the impact of resveratrol on the machinery and main effectors modulating mitochondrial biogenesis in the context of neurodegenerative diseases.

Twelve Weeks of Intermittent Caloric Restriction Diet Mitigates Neuroinflammation in Midlife Individuals with Multiple Sclerosis: A Pilot Study with Implications for Prevention of Alzheimer's Disease

BACKGROUND

Multiple sclerosis (MS) is a prototype neuroinflammatory disorder with increasingly recognized role for neurodegeneration. Most first-line treatments cannot prevent the progression of neurodegeneration and the resultant disability. Interventions can improve symptoms of MS and might provide insights into the underlying pathology.

OBJECTIVE

To investigate the effect of intermittent caloric restriction on neuroimaging markers of MS.

METHODS

We randomized ten participants with relapsing remitting MS to either a 12-week intermittent calorie restriction (iCR) diet (n = 5) or control (n = 5). Cortical thickness and volumes were measured through FreeSurfer, cortical perfusion was measured by arterial spin labeling and neuroinflammation through diffusion basis spectrum imaging.

RESULTS

After 12 weeks of iCR, brain volume increased in the left superior and inferior parietal gyri (p: 0.050 and 0.049, respectively) and the banks of the superior temporal sulcus (p: 0.01). Similarly in the iCR group, cortical thickness improved in the bilateral medial orbitofrontal gyri (p: 0.04 and 0.05 in right and left, respectively), the left superior temporal gyrus (p: 0.03), and the frontal pole (p: 0.008) among others. Cerebral perfusion decreased in the bilateral fusiform gyri (p: 0.047 and 0.02 in right and left, respectively) and increased in the bilateral deep anterior white matter (p: 0.03 and 0.013 in right and left, respectively). Neuroinflammation, demonstrated through hindered and restricted water fractions (HF and RF), decreased in the left optic tract (HF p: 0.02), and the right extreme capsule (RF p: 0.007 and HF p: 0.003).

CONCLUSION

These pilot data suggest therapeutic effects of iCR in improving cortical volume and thickness and mitigating neuroinflammation in midlife adults with MS.

Mitochondrial Aging and Senolytic Natural Products with Protective Potential

Living organisms do not disregard the laws of thermodynamics and must therefore consume energy for their survival. In this way, cellular energy exchanges, which aim above all at the production of ATP, a fundamental molecule used by the cell for its metabolisms, favor the formation of waste products that, if not properly disposed of, can contribute to cellular aging and damage. Numerous genes have been linked to aging, with some favoring it (gerontogenes) and others blocking it (longevity pathways). Animal model studies have shown that calorie restriction (CR) may promote longevity pathways, but given the difficult application of CR in humans, research is investigating the use of CR-mimetic substances capable of producing the same effect. These include some phytonutrients such as oleuropein, hydroxytyrosol, epigallo-catechin-gallate, fisetin, quercetin, and curcumin and minerals such as magnesium and selenium. Some of them also have senolytic effects, which promote the apoptosis of defective cells that accumulate over the years (senescent cells) and disrupt normal metabolism. In this article, we review the properties of these natural elements that can promote a longer and healthier life.

Transcriptome and Methylome Profiling in Rat Skeletal Muscle: Impact of Post-Weaning Protein Restriction

Skeletal muscle is programmable, and early-life nutritional stimuli may form epigenetic memory in the skeletal muscle, thus impacting adult muscle function, aging, and longevity. In the present study, we designed a one-month protein restriction model using post-weaning rats, followed by a two-month rebound feeding, to investigate how early-life protein restriction affects overall body growth and muscle development and whether these influences could be corrected by rebound feeding. We observed comprehensive alterations immediately after protein restriction, including retarded growth, altered biochemical indices, and disturbed hormone secretion. Transcriptome profiling of the gastrocnemius muscle followed by gene ontology analyses revealed that "myogenic differentiation functions" were upregulated, while "protein catabolism" was downregulated as a compensatory mechanism, with enhanced endoplasmic reticulum stress and undesired apoptosis. Furthermore, methylome profiling of the gastrocnemius muscle showed that protein restriction altered the methylation of apoptotic and hormone secretion-related genes. Although most of the alterations were reversed after rebound feeding, 17 genes, most of which play roles during muscle development, remained altered at the transcriptional level. In summary, early-life protein restriction may undermine muscle function in the long term and affect skeletal muscle development at the both transcriptional and methylation levels, which may hazard future muscle health.

Dietary restriction in senolysis and prevention and treatment of disease

Aging represents a key risk factor for a plethora of diseases. Targeting detrimental processes which occur during aging, especially before onset of age-related disease, could provide drastic improvements in healthspan. There is increasing evidence that dietary restriction (DR), including caloric restriction, fasting, or fasting-mimicking diets, extend both lifespan and healthspan. This has sparked interest in the use of dietary regimens as a non-pharmacological means to slow aging and prevent disease. Here, we review the current evidence on the molecular mechanisms underlying DR-induced health improvements, including removal of senescent cells, metabolic reprogramming, and epigenetic rejuvenation.

Stochastic survival of the densest and mitochondrial DNA clonal expansion in aging

The expansion of mitochondrial DNA molecules with deletions has been associated with aging, particularly in skeletal muscle fibers; its mechanism has remained unclear for three decades. Previous accounts have assigned a replicative advantage (RA) to mitochondrial DNA containing deletion mutations, but there is also evidence that cells can selectively remove defective mitochondrial DNA. Here we present a spatial model that, without an RA, but instead through a combination of enhanced density for mutants and noise, produces a wave of expanding mutations with speeds consistent with experimental data. A standard model based on RA yields waves that are too fast. We provide a formula that predicts that wave speed drops with copy number, consonant with experimental data. Crucially, our model yields traveling waves of mutants even if mutants are preferentially eliminated. Additionally, we predict that mutant loads observed in single-cell experiments can be produced by de novo mutation rates that are drastically lower than previously thought for neutral models. Given this exemplar of how spatial structure (multiple linked mtDNA populations), noise, and density affect muscle cell aging, we introduce the mechanism of stochastic survival of the densest (SSD), an alternative to RA, that may underpin other evolutionary phenomena.

Calorie Restriction Provides Kidney Ischemic Tolerance in Senescence-Accelerated OXYS Rats

Kidney diseases belong to a group of pathologies, which are most common among elderly people. With age, even outwardly healthy organisms start to exhibit some age-related changes in the renal tissue, which reduce the filtration function of kidneys and increase the susceptibility to injury. The therapy of acute kidney injury (AKI) is aggravated by the absence of targeted pharmacotherapies thus yielding high mortality of patients with AKI. In this study, we analyzed the protective effects of calorie restriction (CR) against ischemic AKI in senescence-accelerated OXYS rats. We observed that CR afforded OXYS rats with significant nephroprotection. To uncover molecular mechanisms of CR beneficial effects, we assessed the levels of anti- and proapoptotic proteins of the Bcl-2 family, COX IV, GAPDH, and mitochondrial deacetylase SIRT-3, as well as alterations in total protein acetylation and carbonylation, mitochondrial dynamics (OPA1, Fis1, Drp1) and kidney regeneration pathways (PCNA, GDF11). The activation of autophagy and mitophagy was analyzed by LC3 II/LC3 I ratio, beclin-1, PINK-1, and total mitochondrial protein ubiquitination. Among all considered protective pathways, the improvement of mitochondrial functioning may be suggested as one of the possible mechanisms for beneficial effects of CR.

Dietary interventions and molecular mechanisms for healthy musculoskeletal aging

Over the past decade, extensive efforts have focused on understanding age-associated diseases and how to prolong a healthy lifespan. The induction of dietary protocols such as caloric restriction (CR) and protein restriction (PR) has positively affected a healthy lifespan. These intervention ideas (nutritional protocols) have been the subject of human cohort studies and clinical trials to evaluate their effectiveness in alleviating age-related diseases (such as type II diabetes, cardiovascular disease, obesity, and musculoskeletal fragility) and promoting human longevity. This study summarizes the literature on the nutritional protocols, emphasizing their impacts on bone and muscle biology. In addition, we analyzed several CR studies using Gene Expression Omnibus (GEO) database and identified common transcriptome changes to understand the signaling pathway involved in musculoskeletal tissue. We identified nine novel common genes, out of which five were upregulated (Emc3, Fam134b, Fbxo30, Pip5k1a, and Retsat), and four were downregulated (Gstm2, Per2, Fam78a, and Sel1l3) with CR in muscles. Gene Ontology enrichment analysis revealed that CR regulates several signaling pathways (e.g., circadian gene regulation and rhythm, energy reserve metabolic process, thermogenesis) involved in energy metabolism. In conclusion, this study summarizes the beneficiary role of CR and identifies novel genes and signaling pathways involved in musculoskeletal biology.

Keeping the beat against time: Mitochondrial fitness in the aging heart

The process of aging strongly correlates with maladaptive architectural, mechanical, and biochemical alterations that contribute to the decline in cardiac function. Consequently, aging is a major risk factor for the development of heart disease, the leading cause of death in the developed world. In this review, we will summarize the classic and recently uncovered pathological changes within the aged heart with an emphasis on the mitochondria. Specifically, we describe the metabolic changes that occur in the aging heart as well as the loss of mitochondrial fitness and function and how these factors contribute to the decline in cardiomyocyte number. In addition, we highlight recent pharmacological, genetic, or behavioral therapeutic intervention advancements that may alleviate age-related cardiac decline.

Dietary regulation in health and disease

Nutriments have been deemed to impact all physiopathologic processes. Recent evidences in molecular medicine and clinical trials have demonstrated that adequate nutrition treatments are the golden criterion for extending healthspan and delaying ageing in various species such as yeast, drosophila, rodent, primate and human. It emerges to develop the precision-nutrition therapeutics to slow age-related biological processes and treat diverse diseases. However, the nutritive advantages frequently diversify among individuals as well as organs and tissues, which brings challenges in this field. In this review, we summarize the different forms of dietary interventions extensively prescribed for healthspan improvement and disease treatment in pre-clinical or clinical. We discuss the nutrient-mediated mechanisms including metabolic regulators, nutritive metabolism pathways, epigenetic mechanisms and circadian clocks. Comparably, we describe diet-responsive effectors by which dietary interventions influence the endocrinic, immunological, microbial and neural states responsible for improving health and preventing multiple diseases in humans. Furthermore, we expatiate diverse patterns of dietotheroapies, including different fasting, calorie-restricted diet, ketogenic diet, high-fibre diet, plants-based diet, protein restriction diet or diet with specific reduction in amino acids or microelements, potentially affecting the health and morbid states. Altogether, we emphasize the profound nutritional therapy, and highlight the crosstalk among explored mechanisms and critical factors to develop individualized therapeutic approaches and predictors.

Calorie Restriction Rescues Mitochondrial Dysfunction in Adck2-Deficient Skeletal Muscle

ADCK2 haploinsufficiency-mediated mitochondrial coenzyme Q deficiency in skeletal muscle causes mitochondrial myopathy associated with defects in beta-oxidation of fatty acids, aged-matched metabolic reprogramming, and defective physical performance. Calorie restriction has proven to increase lifespan and delay the onset of chronic diseases associated to aging. To study the possible treatment by food deprivation, heterozygous Adck2 knockout mice were fed under 40% calorie restriction (CR) and the phenotype was followed for 7 months. The overall glucose and fatty acids metabolism in muscle was restored in mutant mice to WT levels after CR. CR modulated the skeletal muscle metabolic profile of mutant mice, partially rescuing the profile of WT animals. The analysis of mitochondria isolated from skeletal muscle demonstrated that CR increased both CoQ levels and oxygen consumption rate (OCR) based on both glucose and fatty acids substrates, along with mitochondrial mass. The elevated aerobic metabolism fits with an increase of type IIa fibers, and a reduction of type IIx in mutant muscles, reaching WT levels. To further explore the effect of CR over muscle stem cells, satellite cells were isolated and induced to differentiate in culture media containing serum from animals in either ad libitum or CR diets for 72 h. Mutant cells showed slower differentiation alongside with decreased oxygen consumption. In vitro differentiation of mutant cells was increased under CR serum reaching levels of WT isolated cells, recovering respiration measured by OCR and partially beta-oxidation of fatty acids. The overall increase of skeletal muscle bioenergetics following CR intervention is paralleled with a physical activity improvement, with some increases in two and four limbs strength tests, and weights strength test. Running wheel activity was also partially improved in mutant mice under CR. These results demonstrate that CR intervention, which has been shown to improve age-associated physical and metabolic decline in WT mice, also recovers the defective aerobic metabolism and differentiation of skeletal muscle in mice caused by ADCK2 haploinsufficiency.

Regulation of the urea cycle by CPS1 O-GlcNAcylation in response to dietary restriction and aging

O-linked N-acetyl-glucosamine glycosylation (O-GlcNAcylation) of intracellular proteins is a dynamic process broadly implicated in age-related disease, yet it remains uncharacterized whether and how O-GlcNAcylation contributes to the natural aging process. O-GlcNAc transferase (OGT) and the opposing enzyme O-GlcNAcase (OGA) control this nutrient-sensing protein modification in cells. Here, we show that global O-GlcNAc levels are increased in multiple tissues of aged mice. In aged liver, carbamoyl phosphate synthetase 1 (CPS1) is among the most heavily O-GlcNAcylated proteins. CPS1 O-GlcNAcylation is reversed by calorie restriction and is sensitive to genetic and pharmacological manipulations of the O-GlcNAc pathway. High glucose stimulates CPS1 O-GlcNAcylation and inhibits CPS1 activity. Liver-specific deletion of OGT potentiates CPS1 activity and renders CPS1 irresponsive to further stimulation by a prolonged fasting. Our results identify CPS1 O-GlcNAcylation as a key nutrient-sensing regulatory step in the urea cycle during aging and dietary restriction, implying a role for mitochondrial O-GlcNAcylation in nutritional regulation of longevity.

Molecular mechanisms of exceptional lifespan increase of Drosophila melanogaster with different genotypes after combinations of pro-longevity interventions

Aging is one of the global challenges of our time. The search for new anti-aging interventions is also an issue of great actuality. We report on the success of Drosophila melanogaster lifespan extension under the combined influence of dietary restriction, co-administration of berberine, fucoxanthin, and rapamycin, photodeprivation, and low-temperature conditions up to 185 days in w¹¹¹⁸ strain and up to 213 days in long-lived E(z)/w mutants. The trade-off was found between longevity and locomotion. The transcriptome analysis showed an impact of epigenetic alterations, lipid metabolism, cellular respiration, nutrient sensing, immune response, and autophagy in the registered effect.

The lifespan of fruit flies can be extended up to 213 days under specialized conditions.

Regulation of Kidney Mitochondrial Function by Caloric Restriction

Caloric restriction (CR) prevents obesity and increases resilience against pathological stimuli in laboratory rodents. At the mitochondrial level, protection promoted by CR in the brain and liver is related to higher calcium uptake rates and capacities, avoiding Ca²⁺-induced mitochondrial permeability transition. Dietary restriction has also been shown to increase kidney resistance against damaging stimuli, but if these effects are related to similar mitochondrial adaptations has not been uncovered. Here, we characterized changes in mitochondrial function in response to six months CR in rats, measuring bioenergetic parameters, redox balance and calcium homeostasis. CR promoted an increase in succinate-supported mitochondrial oxygen consumption rates. While CR prevents mitochondrial reactive oxygen species production in many tissues, in kidney we found that mitochondrial H₂O₂ release was enhanced in a succinate-dependent manner. Surprisingly, and opposite to the effects observed in brain and liver, mitochondria from CR animals are more prone to Ca²⁺-induced mitochondrial permeability transition, in a manner reversed by antioxidant dithiothreitol. CR mitochondria also displayed higher calcium uptake rates, which were not accompanied by changes in calcium efflux rates, nor related to altered inner mitochondrial membrane potentials or amounts of the mitochondrial calcium uniporter (MCU). Instead, increased mitochondrial calcium uptake rates in CR kidneys correlate with a loss of MICU2, an MCU modulator. Interestingly, MICU2 is also modulated by CR in liver, suggesting it has a broader diet-sensitive regulatory role controlling mitochondrial calcium homeostasis. Together, our results highlight the organ-specific bioenergetic, redox, and ionic transport effects of CR, with some unexpected deleterious effects in kidney.

Telomeres and Mitochondrial Metabolism: Implications for Cellular Senescence and Age-related Diseases

Cellular senescence is an irreversible cell arrest process, which is determined by a variety of complicated mechanisms, including telomere attrition, mitochondrial dysfunction, metabolic disorders, loss of protein homeostasis, epigenetic changes, etc. Cellular senescence is causally related to the occurrence and development of age-related disease. The elderly is liable to suffer from disorders such as neurodegenerative diseases, cancer, and diabetes. Therefore, it is increasingly imperative to explore specific countermeasures for the treatment of age-related diseases. Numerous studies on humans and mice emphasize the significance of metabolic imbalance caused by short telomeres and mitochondrial damages in the onset of age-related diseases. Although the experimental data are relatively independent, more and more evidences have shown that there is mutual crosstalk between telomeres and mitochondrial metabolism in the process of cellular senescence. This review systematically discusses the relationship between telomere length, mitochondrial metabolic disorder, as well as their underlying mechanisms for cellular senescence and age-related diseases. Future studies on telomere and mitochondrial metabolism may shed light on potential therapeutic strategies for age-related diseases. Graphical Abstract The characteristics of cellular senescence mainly include mitochondrial dysfunction and telomere attrition. Mitochondrial dysfunction will cause mitochondrial metabolic disorders, including decreased ATP production, increased ROS production, as well as enhanced cellular apoptosis. While oxidative stress reaction to produce ROS, leads to DNA damage, and eventually influences telomere length. Under the stimulation of oxidative stress, telomerase catalytic subunit TERT mainly plays an inhibitory role on oxidative stress, reduces the production of ROS and protects telomere function. Concurrently, mitochondrial dysfunction and telomere attrition eventually induce a range of age-related diseases, such as T2DM, osteoporosis, AD, etc. :increase; :reduce;⟝:inhibition.

Positive Aspects of Oxidative Stress at Different Levels of the Human Body: A Review

Oxidative stress is the subject of numerous studies, most of them focusing on the negative effects exerted at both molecular and cellular levels, ignoring the possible benefits of free radicals. More and more people admit to having heard of the term "oxidative stress", but few of them understand the meaning of it. We summarized and analyzed the published literature data in order to emphasize the importance and adaptation mechanisms of basal oxidative stress. This review aims to provide an overview of the mechanisms underlying the positive effects of oxidative stress, highlighting these effects, as well as the risks for the population consuming higher doses than the recommended daily intake of antioxidants. The biological dose-response curve in oxidative stress is unpredictable as reactive species are clearly responsible for cellular degradation, whereas antioxidant therapies can alleviate senescence by maintaining redox balance; nevertheless, excessive doses of the latter can modify the redox balance of the cell, leading to a negative outcome. It can be stated that the presence of oxidative status or oxidative stress is a physiological condition with well-defined roles, yet these have been insufficiently researched and explored. The involvement of reactive oxygen species in the pathophysiology of some associated diseases is well-known and the involvement of antioxidant therapies in the processes of senescence, apoptosis, autophagy, and the maintenance of cellular homeostasis cannot be denied. All data in this review support the idea that oxidative stress is an undesirable phenomenon in high and long-term concentrations, but regular exposure is consistent with the hormetic theory.

Decline in Liver Mitochondria Metabolic Function Is Restored by Hochuekkito Through Sirtuin 1 in Aged Mice With Malnutrition

Malnutrition impairs basic daily activities and leads to physical frailty, which is aggravated in the elderly compared with young adults. It is also well-known that the elderly are more vulnerable to metabolic stress. Therefore, in this study, using a food restricted (FR) mouse, we aimed to evaluate the effect of aging on locomotor activity and liver metabolic function. Further, we also investigated the involvement of hepatic mitochondria in liver metabolic function during aging, as well as the therapeutic benefit of the traditional Japanese medicine, hochuekkito (HET). Our findings indicated that following food restriction provided as 30% of ad libitum intake for 5 days, the locomotor activity was lower in 23–26-month-old (aged) mice than in 9-week-old (young) mice. Further, compared with young mice, aged mice exhibited significant decreases in the levels of metabolites related to the urea cycle, mitochondrial function, and anti-oxidative stress. The livers of the aged mice also showed a greater decrease in mitochondrial DNA copy number than young mice. Furthermore, the gene expression levels of sirtuin 1 (SIRT1) and mitochondrial biogenesis-related regulators were attenuated in aged mice. However, these changes were partially restored by HET treatment, which also improved locomotor activity, and combined treatment with alanine resulted in more significant effects in this regard. Therefore, our findings suggested that the decrease in locomotor activity in aged FR mice was associated with a decline in the metabolic function of hepatic mitochondria via decreased SIRT1 expression, which was restored by HET treatment. This implies that enhancing the metabolic function of liver mitochondria can contribute to alleviating energy deficiency in the elderly.

Effects of Thiamin Restriction on Exercise-Associated Glycogen Metabolism and AMPK Activation Level in Skeletal Muscle

This study aimed to investigate the direct influence of a decrease in the cellular thiamin level, before the onset of anorexia (one of the symptoms of thiamin deficiency) on glycogen metabolism and the AMP-activated protein kinase (AMPK) activation levels in skeletal muscle at rest and in response to exercise. Male Wistar rats were classified as the control diet (CON) group or the thiamin-deficient diet (TD) group and consumed the assigned diets for 1 week. Skeletal muscles were taken from the rats at rest, those that underwent low-intensity swimming (LIS), or high-intensity intermittent swimming (HIS) conducted immediately before dissection. There were no significant differences in food intake, locomotive activity, or body weight between groups, but thiamin pyrophosphate in the skeletal muscles of the TD group was significantly lower than that of the CON group. Muscle glycogen and lactate levels in the blood and muscle were equivalent between groups at rest and in response to exercise. The mitochondrial content was equal between groups, and AMPK in the skeletal muscles of TD rats was normally activated by LIS and HIS. In conclusion, with a lowered cellular thiamin level, the exercise-associated glycogen metabolism and AMPK activation level in skeletal muscle were normally regulated.

Effects of dietary restriction on gut microbiota and CNS autoimmunity

Multiple sclerosis (MS) is the most common central nervous system (CNS) autoimmune disease. It is due to the interplay of genetic and environmental factors. Current opinion is that diet could play a pathogenic role in disease onset and development. Dietary restriction (DR) without malnutrition markedly improves health and increases lifespan in multiple model organisms. DR regimens that utilize continuous or intermittent food restriction can induce anti-inflammatory, immuno-modulatory and neuroendocrine adaptations promoting health. These adaptations exert neuroprotective effects in the main MS animal model, experimental autoimmune encephalomyelitis (EAE). This review summarizes the current knowledge on DR-induced changes in gut microbial composition and metabolite production and its impact on underlying functional mechanisms. Studies demonstrating the protective effects of DR regimens on EAE and people with MS are also presented. This is a rapidly developing research field with important clinical implications for personalized dietary interventions in MS prevention and treatment.

Recent Neurotherapeutic Strategies to Promote Healthy Brain Aging: Are we there yet?

Owing to the global exponential increase in population ageing, there is an urgent unmet need to develop reliable strategies to slow down and delay the ageing process. Age-related neurodegenerative diseases are among the main causes of morbidity and mortality in our contemporary society and represent a major socio-economic burden. There are several controversial factors that are thought to play a causal role in brain ageing which are continuously being examined in experimental models. Among them are oxidative stress and brain inflammation which are empirical to brain ageing. Although some candidate drugs have been developed which reduce the ageing phenotype, their clinical translation is limited. There are several strategies currently in development to improve brain ageing. These include strategies such as caloric restriction, ketogenic diet, promotion of cellular nicotinamide adenine dinucleotide (NAD+) levels, removal of senescent cells, 'young blood' transfusions, enhancement of adult neurogenesis, stem cell therapy, vascular risk reduction, and non-pharmacological lifestyle strategies. Several studies have shown that these strategies can not only improve brain ageing by attenuating age-related neurodegenerative disease mechanisms, but also maintain cognitive function in a variety of pre-clinical experimental murine models. However, clinical evidence is limited and many of these strategies are awaiting findings from large-scale clinical trials which are nascent in the current literature. Further studies are needed to determine their long-term efficacy and lack of adverse effects in various tissues and organs to gain a greater understanding of their potential beneficial effects on brain ageing and health span in humans.

Ghrelin mediated hippocampal neurogenesis

The stomach hormone, ghrelin, which is released during food restriction, provides a link between circulating energy state and adaptive brain function. The maintenance of such homeostatic systems is essential for an organism to survive and thrive, and accumulating evidence points to ghrelin being a key regulator of adult hippocampal neurogenesis and memory function. Aberrant neurogenesis is linked to cognitive decline in aging and neurodegeneration. Therefore, identifying endogenous metabolic factors that regulate new adult-born neuron formation is an important objective in understanding the link between nutritional status and CNS function. Here, we review current developments in our understanding of ghrelin's role in regulating neurogenesis and memory function.