Humanin-induced autophagy plays important roles in skeletal muscle function and lifespan extension

Icariin Ameliorates D-galactose-induced Cell Injury in Neuron-like PC12 Cells by Inhibiting MPTP Opening

OBJECTIVE

Icariin (ICA) has a good neuroprotective effect and can upregulate neuronal basal autophagy in naturally aging rats. Mitochondrial dysfunction is associated with brain aging-related neurodegenerative diseases. Abnormal opening of the mitochondrial permeability transition pore (mPTP) is a crucial factor in mitochondrial dysfunction and is associated with excessive autophagy. This study aimed to explore that ICA protects against neuronal injury by blocking the mPTP opening and down-regulating autophagy levels in a D-galactose (D-gal)-induced cell injury model.

METHODS

A cell model of neuronal injury was established in rat pheochromocytoma cells (PC12 cells) treated with 200 mmol/L D-gal for 48 h. In this cell model, PC12 cells were pre-treated with different concentrations of ICA for 24 h. MTT was used to detect cell viability. Senescence associated β-galactosidase (SA-β-Gal) staining was used to observe cell senescence. Western blot analysis was performed to detect the expression levels of a senescence-related protein (p21), autophagy markers (LC3B, p62, Atg7, Atg5 and Beclin 1), mitochondrial fission and fusion-related proteins (Drp1, Mfn2 and Opa1), and mitophagy markers (Pink1 and Parkin). The changes of autophagic flow were detected by using mRFP-GFP-LC3 adenovirus. The intracellular ultrastructure was observed by transmission electron microscopy. Immunofluorescence was used to detect mPTP, mitochondrial membrane potential (MMP), mitochondrial reactive oxygen species (mtROS) and ROS levels. ROS and apoptosis levels were detected by flow cytometry.

RESULTS

D-gal treatment significantly decreased the viability of PC12 cells, and markedly increased the SA-β-Gal positive cells as compared to the control group. With the D-gal stimulation, the expression of p21 was significantly up-regulated. Furthermore, D-gal stimulation resulted in an elevated LC3B II/I ratio and decreased p62 expression. Meanwhile, autophagosomes and autolysosomes were significantly increased, indicating abnormal activation of autophagy levels. In addition, in this D-gal-induced model of cell injury, the mPTP was abnormally open, the ROS generation was continuously increased, the MMP was gradually decreased, and the apoptosis was increased. ICA effectively improved mitochondrial dysfunction to protect against D-gal-induced cell injury and apoptosis. It strongly inhibited excessive autophagy by blocking the opening of the mPTP. Cotreatment with ICA and an mPTP inhibitor (cyclosporin A) did not ameliorate mitochondrial dysfunction. However, the protective effects were attenuated by cotreatment with ICA and an mPTP activator (lonidamine).

CONCLUSION

ICA inhibits the activation of excessive autophagy and thus improves mitochondrial dysfunction by blocking the mPTP opening.

Mitochondrial Targeted Interventions for Aging

Changes in mitochondrial function play a critical role in the basic biology of aging and age-related disease. Mitochondria are typically thought of in the context of ATP production and oxidant production. However, it is clear that the mitochondria sit at a nexus of cell signaling where they affect metabolite, redox, and energy status, which influence many factors that contribute to the biology of aging, including stress responses, proteostasis, epigenetics, and inflammation. This has led to growing interest in identifying mitochondrial targeted interventions to delay or reverse age-related decline in function and promote healthy aging. In this review, we discuss the diverse roles of mitochondria in the cell. We then highlight some of the most promising strategies and compounds to target aging mitochondria in preclinical testing. Finally, we review the strategies and compounds that have advanced to clinical trials to test their ability to improve health in older adults.

[Gly14]-humanin exerts a protective effect against D-galactose-induced primary ovarian insufficiency in mice

RESEARCH QUESTION

Is there a protective effect of the humanin derivative [Gly14]-humanin (HNG) on a D-gal-induced mouse model of primary ovarian insufficiency (POI), and what is the underlying mechanism?

DESIGN

D-gal (200 mg/kg/day) was injected subcutaneously for 6 weeks to induce the mouse POI model. Mice treated with HNG were injected intraperitoneally with different concentrations for 6 weeks. Ovarian morphology, function, levels of sex hormones and states of oxidative stress in the ovary and body were evaluated.

RESULTS

Compared with the D-gal group, 10 mg/kg HNG improved the abnormal ovarian morphology and oestrous cycle (P = 0.0036), increased the number of ovarian follicles (P = 0.0016) and litters (P = 0.0127), and increased the levels of oestrogen (P = 0.0043) and AMH (P = 0.0147). Antioxidant indicators in the ovaries and serum of mice, including total antioxidant capacity (P = 0.0004 and P = 0.0032, respectively), catalase (P = 0.0173 and P = 0.0103, respectively) and glutathione (both P < 0.0001) were significantly increased. The oxidation indicator malondialdehyde decreased significantly (all P < 0.01). Apoptosis of ovarian granulosa cells was significantly reduced (P = 0.0140) as was the expression of senescence-related proteins p53, p21 and p16 (all P < 0.01). The level of autophagy in ovarian tissue of mice treated with high increased (significantly increased LC3 protein [P < 0.0001] and significantly reduced p62 protein [P = 0.0007]).

CONCLUSIONS

HNG inhibited D-gal-induced oxidative stress, apoptosis and ovarian damage, promoting ovarian autophagy. HNG may be a potential prophylactic agent against POI.

Synthetic Activators of Autophagy

Autophagy is a central process for degradation of intracellular components that do not operate correctly. Molecular mechanisms underlying this process are extremely difficult to study, since they involve a large number of participants. The main task of autophagy is redistribution of cellular resources in response to environmental changes, such as starvation. Recent studies show that autophagy regulation could be the key to achieve healthy longevity, as well as to create therapeutic agents for treatment of neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. Thus, development of autophagy activators with established detailed mechanism of action is a really important area of research. Several commercial companies are at various stages of development of such molecules, and some of them have already begun to introduce autophagy activators to the market.

Neuroprotective Action of Humanin and Humanin Analogues: Research Findings and Perspectives

Humanin is a 24-mer peptide first reported in the early 2000s as a new neuroprotective/cytoprotective factor rescuing neuronal cells from death induced by various Alzheimer's disease-associated insults. Nowadays it is known that humanin belongs to the novel class of the so-called mitochondrial-derived peptides (which are encoded by mitochondrial DNA) and has been shown to exert beneficial cytoprotective effects in a series of in vitro and/or in vivo experimental models of human diseases, including not only neurodegenerative disorders but other human diseases as well (e.g., age-related macular degeneration, cardiovascular diseases, or diabetes mellitus). This review article is focused on the presentation of recent in vitro and in vivo research results associated with the neuroprotective action of humanin as well as of various, mainly synthetic, analogues of the peptide; moreover, the main mode(s)/mechanism(s) through which humanin and humanin analogues may exert in vitro and in vivo regarding neuroprotection have been reported. The prospects of humanin and humanin analogues to be further investigated in the frame of future research endeavors against neurodegenerative/neural diseases have also been briefly discussed.

Autophagy in sarcopenia: Possible mechanisms and novel therapies

With global population aging, age-related diseases, especially sarcopenia, have attracted much attention in recent years. Characterized by low muscle strength, low muscle quantity or quality and low physical performance, sarcopenia is one of the major factors associated with an increased risk of falls and disability. Much effort has been made to understand the cellular biological and physiological mechanisms underlying sarcopenia. Autophagy is an important cellular self-protection mechanism that relies on lysosomes to degrade misfolded proteins and damaged organelles. Research designed to obtain new insight into human diseases from the autophagic aspect has been carried out and has made new progress, which encourages relevant studies on the relationship between autophagy and sarcopenia. Autophagy plays a protective role in sarcopenia by modulating the regenerative capability of satellite cells, relieving oxidative stress and suppressing the inflammatory response. This review aims to reveal the specific interaction between sarcopenia and autophagy and explore possible therapies in hopes of encouraging more specific research in need and unlocking novel promising therapies to ameliorate sarcopenia.

The role of cannabidiol in aging

Aging is usually considered a key risk factor associated with multiple diseases, such as neurodegenerative diseases, cardiovascular diseases and cancer. Furthermore, the burden of age-related diseases has become a global challenge. It is of great significance to search for drugs to extend lifespan and healthspan. Cannabidiol (CBD), a natural nontoxic phytocannabinoid, has been regarded as a potential candidate drug for antiaging. An increasing number of studies have suggested that CBD could benefit healthy longevity. Herein, we summarized the effect of CBD on aging and analyzed the possible mechanism. All these conclusions may provide a perspective for further study of CBD on aging.

Mitochondria-derived peptides in healthy ageing and therapy of age-related diseases

Mitochondrial-derived peptides (MDPs) are small bioactive peptides encoded by mitochondrial DNA and involved in various stress-protecting mechanisms. To date, eight mitochondrial-derived peptides have been identified: MOTS-c sequence is hidden in the 12 S rRNA gene (MT-RNR1), and the other 7 (humanin and small humanin-like peptides 1-6) are encoded by the 16 S rRNA (MT-RNR2) gene. While the anti-apoptotic, anti-inflammatory and cardioprotective activities of MDPs are well described, recent research suggests that MDPs are sensitive metabolic sensors, closely connected with mtDNA mutation-associated diseases and age-associated metabolic disorders. In this chapter, we focus on the recent progress in understanding the metabolo-protective properties of MDPs, their role in maintenance of the cellular and mitochondrial homeostasis associated with age-related diseases: Alzheimer's disease, cognitive decline, macular degeneration and cataracts. Also, we will discuss MDPs-based and MDPs-targeted interventions to treat age-related diseases and extend a healthy lifespan.

Humanin and Its Pathophysiological Roles in Aging: A Systematic Review

BACKGROUND

Senescence is a cellular aging process in all multicellular organisms. It is characterized by a decline in cellular functions and proliferation, resulting in increased cellular damage and death. These conditions play an essential role in aging and significantly contribute to the development of age-related complications. Humanin is a mitochondrial-derived peptide (MDP), encoded by mitochondrial DNA, playing a cytoprotective role to preserve mitochondrial function and cell viability under stressful and senescence conditions. For these reasons, humanin can be exploited in strategies aiming to counteract several processes involved in aging, including cardiovascular disease, neurodegeneration, and cancer. Relevance of these conditions to aging and disease: Senescence appears to be involved in the decay in organ and tissue function, it has also been related to the development of age-related diseases, such as cardiovascular conditions, cancer, and diabetes. In particular, senescent cells produce inflammatory cytokines and other pro-inflammatory molecules that can participate to the development of such diseases. Humanin, on the other hand, seems to contrast the development of such conditions, and it is also known to play a role in these diseases by promoting the death of damaged or malfunctioning cells and contributing to the inflammation often associated with them. Both senescence and humanin-related mechanisms are complex processes that have not been fully clarified yet. Further research is needed to thoroughly understand the role of such processes in aging and disease and identify potential interventions to target them in order to prevent or treat age-related conditions.

OBJECTIVES

This systematic review aims to assess the potential mechanisms underlying the link connecting senescence, humanin, aging, and disease.

Identification of AGXT2, SHMT1, and ACO2 as important biomarkers of acute kidney injury by WGCNA

Acute kidney injury (AKI) is a serious and frequently observed disease associated with high morbidity and mortality. Weighted gene co-expression network analysis (WGCNA) is a research method that converts the relationship between tens of thousands of genes and phenotypes into the association between several gene sets and phenotypes. We screened potential target genes related to AKI through WGCNA to provide a reference for the diagnosis and treatment of AKI. Key biomolecules of AKI were investigated based on transcriptome analysis. RNA sequencing data from 39 kidney biopsy specimens of AKI patients and 9 normal subjects were downloaded from the GEO database. By WGCNA, the top 20% of mRNAs with the largest variance in the data matrix were used to construct a gene co-expression network with a p-value < 0.01 as a screening condition, showing that the blue module was most closely associated with AKI. Thirty-two candidate biomarker genes were screened according to the threshold values of |MM|≥0.86 and |GS|≥0.4, and PPI and enrichment analyses were performed. The top three genes with the most connected nodes, alanine-glyoxylate aminotransferase 2(AGXT2), serine hydroxymethyltransferase 1(SHMT1) and aconitase 2(ACO2), were selected as the central genes based on the PPI network. A rat AKI model was constructed, and the mRNA and protein expression levels of the central genes in the model and control groups were verified by PCR and immunohistochemistry experiments. The results showed that the relative mRNA expression and protein levels of AGXT2, SHMT1 and ACO2 showed a decrease in the model group. In conclusion, we inferred that there is a close association between AGXT2, SHMT1 and ACO2 genes and the development of AKI, and the down-regulation of their expression levels may induce AKI.

Novel Insights into Mitochondrial DNA: Mitochondrial Microproteins and mtDNA Variants Modulate Athletic Performance and Age-Related Diseases

Sports genetics research began in the late 1990s and over 200 variants have been reported as athletic performance- and sports injuries-related genetic polymorphisms. Genetic polymorphisms in the α-actinin-3 (ACTN3) and angiotensin-converting enzyme (ACE) genes are well-established for athletic performance, while collagen-, inflammation-, and estrogen-related genetic polymorphisms are reported as genetic markers for sports injuries. Although the Human Genome Project was completed in the early 2000s, recent studies have discovered previously unannotated microproteins encoded in small open reading frames. Mitochondrial microproteins (also called mitochondrial-derived peptides) are encoded in the mtDNA, and ten mitochondrial microproteins, such as humanin, MOTS-c (mitochondrial ORF of the 12S rRNA type-c), SHLPs 1-6 (small humanin-like peptides 1 to 6), SHMOOSE (Small Human Mitochondrial ORF Over SErine tRNA), and Gau (gene antisense ubiquitous in mtDNAs) have been identified to date. Some of those microproteins have crucial roles in human biology by regulating mitochondrial function, and those, including those to be discovered in the future, could contribute to a better understanding of human biology. This review describes a basic concept of mitochondrial microproteins and discusses recent findings about the potential roles of mitochondrial microproteins in athletic performance as well as age-related diseases.

Acrolein Promotes Aging and Oxidative Stress via the Stress Response Factor DAF-16/FOXO in Caenorhabditis elegans

For this investigation, Caenorhabditis elegans (C. elegans) served, for the first time, as a model organism to evaluate the toxic effect and possible underlying mechanisms under acrolein (ACR) exposure. The results showed that ACR exposure (12.5–100 μM) shortened the lifespan of C. elegans. The reproductive capacity, body length, body width, and locomotive behavior (head thrash) of C. elegans were diminished by ACR, especially the doses of 50 and 100 μM. Furthermore, ACR significantly enhanced the endogenous ROS levels of C. elegans, inhibited the antioxidant-related enzyme activities, and affected the expression of antioxidant related genes. The increasing oxidative stress level promoted the migration of DAF-16 into the nucleus that was related to the DAF-16/FOXO pathway. It was also confirmed by the significant decrease of the lifespan-shortening trend in the daf-16 knockout mutant. In conclusion, ACR exposure induced aging and oxidative stress in C.elegans, resulting in aging-related decline and defense-related DAF-16/FOXO pathways’ activation.

Mitochondria-derived peptides in aging and healthspan

The mechanisms that explain mitochondrial dysfunction in aging and healthspan continue to be studied, but one element has been unexplored: microproteins. Small open reading frames in circular mitochondria DNA can encode multiple microproteins, called mitochondria-derived peptides (MDPs). Currently, eight MDPs have been published: humanin, MOTS-c, and SHLPs 1–6. This Review describes recent advances in microprotein discovery with a focus on MDPs. It discusses what is currently known about MDPs in aging and how this new understanding could add to the way we understand age-related diseases including type 2 diabetes, cancer, and neurodegenerative diseases at the genomic, proteomic, and drug-development levels.

The Molecular Structure and Role of Humanin in Neural and Skeletal Diseases, and in Tissue Regeneration

Humanin (HN) belongs to a member of mitochondrial-derived peptides (MDPs) which are encoded by mitochondrial genes. HN shares sequence homology with thirteen HN-like proteins, named MTRNR2L1 to MTRNR2L13, which encompass 24–28 amino acid residues in length. HN mediates mitochondrial status and cell survival by acting via an intracellular mechanism, or as a secreted factor via extracellular signals. Intracellularly, it binds Bcl2-associated X protein (BAX), Bim and tBid, and IGFBP3 to inhibit caspase activity and cell apoptosis. When released from cells as a secreted peptide, HN interacts with G protein-coupled formyl peptide receptor-like 1 (FPRL1/2) to mediate apoptosis signal-regulating kinase (ASK) and c-Jun N-terminal kinase (JNK) signalling pathways. Additionally, it interacts with CNTFR-α/gp130/WSX-1 trimeric receptors to induce JAK2/STA3 signalling cascades. HN also binds soluble extracellular proteins such as VSTM2L and IGFBP3 to modulate cytoprotection. It is reported that HN plays a role in neuronal disorders such as Alzheimer’s disease, as well as in diabetes mellitus, infertility, and cardiac diseases. Its roles in the skeletal system are emerging, where it appears to be involved with the regulation of osteoclasts, osteoblasts, and chondrocytes. Understanding the molecular structure and role of HN in neural and skeletal diseases is vital to the application of HN in tissue regeneration.

Humanin ameliorates late-onset hypogonadism in aged male rats

BACKGROUND

The reproductive potential declines with age. Late-onset hypogonadism is characterized by reduced serum testosterone. Humanin is a mitochondrial-derived signaling peptide encoded by short open reading frames within the mitochondrial genome. It may protect against some age-related diseases such as atherosclerosis by its cytoprotective effects.

OBJECTIVE

it aimed to investigate the potential anti-aging effects of humanin on the testicular architecture, oxidative stress, some apoptotic and inflammatory markers in the hypogonadal aged male rats.

METHODS

Forty male albino rats were divided into 4 groups: normal adult controls, aged vehicle-treated group, aged testosterone-treated group, and aged humanin-treated group. Twenty-month-old male rats with declined serum testosterone were selected to be the animal models of late-onset hypogonadism. Testicular weights, serum testosterone, and some sperm parameters were measured. Testicular tissue IL-6 and TNF-α, superoxide dismutase activity, glutathione peroxidase, and malondialdehyde were assessed. The activity of caspase-3, BCL2, PCNA, and the nuclear factor erythroid 2-related factor 2-antioxidant response element pathway were evaluated. Testes were subjected to histopathological and immunohistochemical examination. Statistical analysis was executed using One Way Analysis of variance (ANOVA) followed by Post hoc (LSD) test to compare means among all studied groups.

RESULTS

humanin treatment significantly improved serum testosterone, some sperm characteristics, and antioxidant defenses. It decreased active caspase-3, pro-apoptotic BAX expression, and increased antiapoptotic BCL2 and proliferating cell nuclear antigen (PCNA) possibly via activating the (Nrf2-ARE) pathway.

CONCLUSION

humanin might be a promising therapeutic modality in late-onset hypogonadism as it ameliorated some age-related testicular and hormonal adverse effects.

Mitochondrial-derived peptides: New markers for cardiometabolic dysfunction

Great attention is being paid to the evaluation of new markers in blood circulation for the estimation of tissue metabolism disturbance. This endogenous disturbance may contribute to the onset and progression of cardiometabolic disease. In addition to their role in energy production and metabolism, mitochondria play a main function in cellular mechanisms, including apoptosis, oxidative stress and calcium homeostasis. Mitochondria produce mitochondrial-derived peptides that mediate the transcriptional stress response by translocating into the nucleus and interacting with deoxyribonucleic acid. This class of peptides includes humanin, mitochondrial open reading frame of the 12S ribosomal ribonucleic acid type c (MOTS-c) and small humanin-like peptides. Mitochondrial-derived peptides are regulators of metabolism, exerting cytoprotective effects through antioxidative stress, anti-inflammatory responses and antiapoptosis; they are emerging biomarkers reflecting mitochondrial function, and the circulating concentration of these proteins can be used to diagnose cardiometabolic dysfunction. The aims of this review are: (1) to describe the emerging role for mitochondrial-derived peptides as biomarkers; and (2) to discuss the therapeutic application of these peptides.