Humanin

Abstract

The sperm quality, freezability, and fertility of crossbred bulls exhibit significant unpredictability, which consequently impacts the breeding program. The present study documents the supplementation of humanin, a mitochondria-derived peptide, on crossbred bull's sperm quality, freezability, antioxidant status and in-vitro fertility. For this objective a total of 24 ejaculates, 8 from each of the three Vrindavani crossbred bulls, were selected based on sperm progressive motility (≥ 70%) and concentration (≥ 500 million). The selected fresh semen samples were divided into four aliquots and diluted with Tris-Fructose-Egg-Yolk-Glycerol (TFEGY) extender supplemented with various concentrations of humanin peptide; control (Group-1) without supplementation; Group II with 2.5 µM; Group III supplemented with 5 µM and Group IV supplemented with 7.5 µM. Semen quality parameters, sperm kinematics, sperm plasma membrane integrity, mitochondrial membrane potential, sperm cryo-capacitation status, ejaculate freezability rate, antioxidant status and in-vitro fertility assays were done. At the pre-freeze stage, there was no significant effect on the percentage of individual progressive motility in any group. Supplementation with 5 µM humanin resulted in an 87.5% ejaculate recovery rate after cryopreservation. At the post-thaw stage, sperm quality parameters, sperm kinematics, sperm plasma membrane integrity, mitochondrial membrane potential, sperm cryo-capacitation status, antioxidant status and in-vitro fertility were significantly improved in Group III (5 µM humanin supplementation). In conclusion, our results demonstrate that humanin supplementation in crossbred bull semen enhances semen freezability and post-thaw ejaculate recovery rate.

Abstract

Duchenne muscular dystrophy (DMD) is a progressive muscle disease for which glucocorticoid (GC) treatment is standard therapy. Patients typically suffer from short stature and osteoporosis, caused by the underlying disease and adverse effects of GCs. We investigated whether the mitochondrial peptide humanin (HNG) could prevent GC-induced growth retardation and osteoporosis in mouse models of DMD. Male mdx mice (B10.mdx and D2.mdx) were treated with GCs, with/without HNG, from 5 to 9 weeks of age using two different treatment regimens. Tibial growth was monitored by weekly X-ray imaging; growth plates analyzed with immunohistochemistry and histomorphometry; and bone structure examined using peripheral quantitative computed tomography. Effects on skeletal muscle were evaluated by immunohistochemistry, qPCR, and ex vivo force measurements. D2.mdx, but not B10.mdx, showed decreased bone growth and impaired bone structure compared with wild type (WT). D2.mdx also displayed increased growth plate height with lower endogenous humanin expression than D2.WT. GC treatment caused growth retardation and reductions in cortical bone area, thickness, and mineral content. Co-administration with HNG prevented bone growth impairment at one week of treatment and mitigated GC adverse effects on cortical bone in B10.mdx mice. Adding HNG to GCs did not exacerbate skeletal muscle pathology; in fact, HNG had a mild enlarging effect on muscle fibers. These data suggest that HNG is a potential candidate for improving bone health in DMD during GC therapy. Further in vivo studies are needed to determine optimal HNG dosing and to assess the effects of long-term treatment on skeletal muscle function.

Abstract

Mitochondria-derived peptides (MDPs) are bioactive molecules encoded by small open reading frames within mitochondrial DNA (mtDNA). Humanin, the first MDP to be discovered, functions as a cytoprotective factor, protecting cells from stress-induced apoptosis. Subsequent discoveries expanded this family to include Mitochondrial Open-reading-frame of the Twelve S rRNA-c (MOTS-c), a key regulator of metabolic homeostasis and stress adaptation, and the Small Humanin-Like Peptides (SHLP1-6), which modulate mitochondrial bioenergetics and insulin sensitivity. MDPs play critical roles in liver homeostasis by maintaining mitochondrial function and metabolic balance. Intracellularly, they modulate mitochondrial activity, oxidative stress, and apoptosis, promoting hepatocyte survival. Extracellularly, they act in autocrine, paracrine, or endocrine manners, engaging receptors or signaling pathways to regulate nuclear gene expression and metabolic adaptation. Emerging evidence highlights their relevance in metabolic dysfunction-associated steatotic liver disease (MASLD). Humanin exerts hepatoprotective effects by inhibiting apoptosis and modulating lipid metabolism. MOTS-c activates AMPK, regulates nuclear gene expression, suppresses fibrotic and inflammatory signaling, and restores mitochondrial function in MASLD and fibrosis models. SHLPs, particularly SHLP2, enhance mitochondrial function and insulin sensitivity, supporting glucose homeostasis and mitigating oxidative stress. Collectively, MDPs establish a novel paradigm in mitochondrial signaling, extending mtDNA function beyond energy production. This review summarizes current insights into MDP biology and highlights its emerging therapeutic potential in chronic liver disease.

Abstract

Globally, breast cancer is the most frequently diagnosed malignancy and the second leading cause of cancer-related mortality among women. The ongoing pursuit of early detection has driven interest in identifying and validating novel diagnostic biomarkers that could enhance prognosis and therapeutic outcomes. Humanin, a mitochondrial-derived peptide (MDP) with reported cytoprotective properties, has been implicated in cancer biology and may play a role in breast cancer pathogenesis.

Abstract

Colorectal cancer (CRC) is a widely occurring malignancy with significant mortality on a global scale, making up close to 10% of all diagnosed cancers in 2020. While traditional CRC diagnostics and research have focused on nuclear genomic alterations, emerging evidence has highlighted the multifaceted roles of mitochondrial DNA (mtDNA) in the pathogenesis and clinical management of CRC. In this review, we examine three interlaced aspects of mtDNA in CRC: (1) Liquid biopsy biomarkers: Cell-free mtDNA circulating in the blood serving as a minimally invasive diagnostic and monitoring tool; (2) Nuclear mtDNA (NUMT)-driven genomic instability: The somatic nuclear incorporation of mtDNA (NUMT segments, or NUMT), contributing to mutational burden and chromosomal disruption in tumours; and (3) Mitochondria-encoded micropeptide signaling - small peptides encoded by the mtDNA that modulate cellular pathways and tumour behaviour. Recent high-impact studies have demonstrated that tumour-derived mtDNA in biofluids can augment cancer detection sensitivity, although technical challenges remain due to mtDNA fragmentation and background noise. Meanwhile, genomic analyses have uncovered a significant increase in NUMT insertion events in CRC cells, linking mitochondrial genome escape to nuclear genome instability and identifying potential numtogenesis suppressor genes. A novel dimension of mito-nuclear interactions in cancer was discovered in mitochondrial microproteins, such as humanin and mitochondrial open reading frame of the 12S rRNA type-c. Humanin exhibits both tumour-promoting and cytoprotective properties under specific conditions, while mitochondrial open reading frame of the 12S rRNA type-c possesses tumour-suppressive activities under other conditions. The outcomes of clinical, mechanistic, and translational research, revealing how mtDNA-based biomarkers and involvement contribute towards early detection, prognostication, and treatment of CRC, are presented.

Abstract

This study aimed to evaluate the cytoprotective effects of the mitochondrial-derived peptide, Small Humanin-Like Peptide-2 (SHLP2), on pre-osteoblastic cells exposed to sub-toxic oxidative stress, with the aim of preserving bone homeostasis under conditions of inflammaging. Pre-osteoblastic MC3T3-E1 cells were cultured under sub-toxic oxidative stress induced by 600 µM H2O2. The study evaluated the effects of SHLP2 (at 10 µM concentration) through assays for mitochondrial activity, reactive oxygen species (ROS) generation, apoptosis markers, and osteogenic differentiation. Quantitative polymerase chain reaction, alkaline phosphatase (ALP) staining, and Alizarin Red S biomineralization assays were performed to assess gene expression, osteogenic activity, and biomineralization. Oxidatively stressed but untreated cells served as the positive control (PC), while oxidative stress-free cells were used as the mock control. Statistical analyses were performed using one-way ANOVA and t-tests. SHLP2 treatment significantly (p < 0.001) improved cell viability and reduced ROS activity in oxidatively stressed cells. A significant (p < 0.001) decrease in apoptotic markers, including p53 and BAX, and an increase in anti-apoptotic BCL-2 levels, were observed. Additionally, SHLP2 treatment upregulated key osteogenic markers, including RUNX2, OSX, and ALP, compared to PC. When compared to the mock group, SHLP2 restored ALP activity to 95.6% by day 14. By day 21, the biomineralization assay demonstrated 94.92% activity following SHLP2 treatment. SHLP2 treatment effectively mitigates oxidative stress in pre-osteoblastic cells, providing apoptosis protection and preserving osteogenic activity. These findings underscore the potential of SHLP2 as an adjuvant therapeutic agent for enhancing the tissue microenvironment in conditions such as periodontitis and inflammaging.

Abstract

Humanin (HN) and MOTS-c are mitochondrial-derived peptides (MDPs) known for their neuroprotective and metabolic functions. Their circulating and tissue levels decline with age and in neurodegenerative diseases such as Alzheimer's disease (AD). This study aimed to evaluate whether blood and plasma gene expression and plasma protein levels of HN and MOTS-c are associated with AD markers, their role in the conversion from mild cognitive impairment (MCI) to AD, and their overall association with the disease. A case-control study was conducted, including patients with AD and MCI, and individuals with subjective cognitive decline (SCD) as controls. Gene expression levels were quantified from total RNA isolated from blood and plasma, normalised to mitochondrial DNA copy number (mtDNA-CN). ELISA was used to measure plasma HN and MOTS-c protein concentrations. HN and MOTS-c transcript levels differed significantly among study groups, whereas plasma protein concentrations did not discriminate between AD and MCI. In silico and RNA decay assays revealed faster degradation of HN mRNA and delayed but stable recovery of MOTS-c mRNA. Overall, blood and plasma transcript levels-but not circulating protein levels-of these MDPs were significantly reduced in AD compared to SCD, suggesting their potential as early biomarkers of Alzheimer's disease.

Abstract

Hypoxic/ischemic brain injury remains a major clinical challenge, yet the cellular mechanisms linking oxygen-glucose deprivation/reperfusion (OGD/R) to opioid receptor regulation in human neurons are still not fully understood. The trafficking of μ-opioid receptors (MOR) and κ-opioid receptors (KOR) is a key regulator of neuronal survival under stress. Most studies to date in this field have employed rodent models. However, given the molecular and physiological differences between rodents and humans, this study employed human induced pluripotent stem cell (iPSC)-derived neurons to investigate opioid receptor trafficking during OGD/R, as well as the neuroprotective effects of Herkinorin.

Abstract

To investigate the possible contribution of nitrosative stress, mitochondrial peptide levels (humanin and mitochondrial open-reading frame of the 12S rRNA-c), and ferroptosis parameters in corneal epithelial cells obtained from patients with keratoconus.

Abstract

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease that increases the risk of cardiovascular complications. The atherogenic index of plasma (AIP) is a risk marker for T2DM and cardiovascular disease on the basis of lipid profiles. T2DM and CVD risk are also associated with nonlipid biomarkers, including oxidative stress, inflammation, and mitochondrial dysfunction, and are linked to diabetes progression. This study applies hierarchical random forest (HRF) machine learning to identify stage-specific predictors of AIP in normoglycemic, prediabetic, and diabetic individuals. Participants were divided into normal (< 5.7%), prediabetic (5.7-6.4%), and diabetic (≥ 6.5%) groups based on their HbA1c values. Clinical, oxidative, inflammatory, and mitochondrial biomarkers were included in the study. Lipid measures directly contributing to the AIP calculation were excluded to minimize collinearity. Predictive models were developed via random forest (RF) and hierarchical random forest (HRF) approaches. HRF incorporates repeated threefold cross-validation to improve stability and feature importance across subgroups. Model performance was evaluated via the coefficient of determination (R²) and mean squared error (MSE). HRF models revealed distinct biomarker profiles associated with AIP and diabetes progression associated with inflammation, oxidative stress, and mitochondrial function variables. Waist-to-height ratio was the main contributing variable in the stratified dataset. For the stratified data, mitochondrial redox markers (p66Shc, humanin) were among the top predictors in the normoglycemia group. In individuals with prediabetes, the importance of these cytokines decreased, whereas oxidative stress-associated biomarkers (GSH, 8-OHdG) provided more accurate classifications. In the diabetes group, 8-OHdG remained moderately predictive, whereas the mitochondrial peptide MOTSc and inflammatory markers (IL-1β) were key features. These results indicate that the progression from mitochondrial-associated changes in the early stages of diabetes to immunometabolic dysfunction in individuals with established diabetes is correlated with AIP. Hierarchical random forest machine learning combined with glycemic stratification reveals evolving biomarker associations with the atherogenic index of plasma linked with diabetes progression. Mitochondrial and immune markers contribute differently across disease stages, supporting their potential use in stage-specific risk stratification and targeted intervention in T2DM management.

Abstract

Introduction: Humanin, a mitochondrial-derived peptide, decreases in the elderly. This study evaluated the effects of concurrent moderate-intensity endurance training (MIET) or high-intensity interval training (HIIT) with D-galactose injection on cardiac function, and the serum and heart levels of humanin and IGF-1 in Wistar male rats. Methods: Left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), ±maxdp/dt, contractility index (CI) and, Tau were monitored by PowerLab system in CTL, CTL + MIET, CTL + HIIT, D-gal, D-gal + MIET, and D-gal + HIIT groups. The histopathological score, fibrosis, and humanin and IGF-1 levels were measured with hematoxylin & eosin, Masson's trichrome, and enzyme-linked immunosorbent assay, respectively. Results: Histopathological score and heart fibrosis were reduced by HIIT and MIET in the D-gal group. LVSP, ±maxdp/dt, and CI were lower, while LVEDP and Tau were higher in the D-gal group than in the CTL group. MIET and HIIT alleviated the changes in LVSP, ±maxdp/dt, CI, LVEDP, and Tau. HIIT and MIET increased humanin levels in heart and serum of the D-gal group by modifying IGF-1 levels. Conclusion: The study suggests HIIT and MIET may improve cardiac function by regulating the IGF-1-humanin signaling pathway.

Abstract

Small humanin-like peptide-6 (SHLP6), is derived from the mitochondrial genome. The 3D structure of SHLP6 was evaluated using PEPstr, with homology modeling predicting a Cyt-C structure with a DOPE score of -645.717 and a GA341 score of 0.2832. The analysis showed that 96.5 % of residues were in favored regions in the Ramachandran plot, indicating a stable protein conformation. Molecular docking studies revealed that SHLP6 has binding affinities with apoptotic proteins such as Caspase 8 (-77.6 ± 2.9 kcal/mol), Bcl-2 (39.2 ± 15.3 kcal/mol), Bax (43.6 ± 7.7 kcal/mol), Cyt-C (-53.2 ± 8.7 kcal/mol), and CAT (-62.5 ± 1.3 kcal/mol). The interaction of SHLP6 with DRP1 (-47.7 ± 1.9 kcal/mol) was found to promote apoptosis, while interactions with SIRT1 (-49.1 ± 4.7 kcal/mol), IGF-1 (-58.7 ± 3.6 kcal/mol), and INSR (-66.4 ± 3.4 kcal/mol) suggest a potential role in controlling neurodegeneration. Molecular dynamics simulations confirmed the compact conformation of Caspase-8, high structural stability of SIRT1, and flexibility of DRP1. Treatment with SHLP6 (40 μg/ml) reduced developmental toxicity and improved antioxidant enzyme levels (SOD and CAT) in stress-induced zebrafish larvae. SHLP6 treatment also improved AChE levels in H2O2-exposed zebrafish larvae. SHLP6 treatment upregulated SOD, CAT, PRKN, p62, LCIII, SIRT1 and NDUFS4 genes, while modulating inflammation by downregulating TNF-α through IL-10 upregulation. SHLP6 efficiently restored locomotory activity in stress-induced zebrafish larvae. FTIR analysis indicated alterations in the secondary structure of proteins, and Congo red staining showed a 10 % decrease in BSA aggregation with SHLP6 treatment. These findings suggest that SHLP6 can be a promising therapeutic agent in enhancing antioxidant defenses, restoring mitochondrial health, and modulating inflammatory responses to mitigate oxidative stress-induced cellular dysfunction.

Abstract

Elimination of apoptotic neutrophils by macrophages, a process called efferocytosis, is a critical step in the resolution of inflammation. Efferocytosis induces the reprogramming of macrophages towards a pro-resolving phenotype and triggers the secretion of pro-resolving factors. While mouse efferocytic macrophages are well-described, less is known about human efferocytic macrophages. Here, using RNA sequencing analysis of three different types of in vitro-derived human efferocytic macrophages, we observed a common modulation of mitochondrial metabolism-related genes in human M0, M1, and M2a-like macrophages, thus correlating with some previous results obtained in other non-human models. These results led us to identify for the first time some particular genes regulated in humans like PLIN5 and MTLN. We also shed light on a mitochondrial gene (MT-RNR2) coding a secreted factor called HUMANIN. Mainly known for its antioxidant and neuroprotective effects, we found that HUMANIN was also associated with pro-resolving properties in human and mouse models. Indeed, HUMANIN was produced early during the resolution of inflammation in an acute peritonitis mouse model. Preventive HUMANIN administration in this model reduced leukocyte infiltration and pro-inflammatory cytokine secretion. These anti-inflammatory properties were accompanied by the early acquisition of a CD11blow non-efferocytic phenotype by mouse macrophages and by an enhanced expression of pro-resolving genes including Alox15 and Retnla. The ability of HUMANIN to dampen pro-inflammatory cytokine secretion was also confirmed in primary human neutrophils. Finally, HUMANIN was also detected in gingival crevicular fluids of patients suffering from periodontitis after the onset of inflammation, suggesting a role of HUMANIN in the control of inflammation. Overall, our data shed light on new aspects of efferocytosis in humans and identify the pro-resolving potential of HUMANIN. This illustrates its prospective therapeutic interest in inflammatory disorders.

Abstract

Humanin is the first short peptide in a speculated group of peptides produced by mitochondria that possess potent cytoprotective properties against various forms of stress. Despite being a prevalent peptide in testes and spermatozoa, there has been no report on the identification or quantification of humanin in buck sperm cells or the reproductive tract. This study aimed to establish the presence of humanin in the epididymis, testes and semen of Sirohi and Barbari bucks, whereas also assessing its seasonal expression, as goats are reported to be seasonal breeders in India. A total of 12 bucks were selected, and an indirect immunofluorescence test was conducted to detect humanin using a commercially available anti-humanin antibody. Immunofluorescence examination of the male reproductive tract revealed the presence of green fluorescence, indicating humanin, in the elongated spermatids of the caput epididymis and the interstitial space of the testicles. In ejaculated spermatozoa, humanin was localised in the neck and acrosomal regions. Humanin was also observed in the upper middle region of ejaculated spermatozoa. However, during the rainy season, humanin expression was stronger or brighter, and throughout the summer and winter, there was little fluorescence. The rainy season was also markedly associated with increased levels of sperm concentration, progressive motility and mitochondrial membrane potential in semen. However, superoxide dismutase activity and lipid peroxidation levels also exhibited substantial seasonal variation.

Abstract

This study aimed to evaluate the diagnostic significance of circulating mitochondrial-derived peptides, Humanin and MOTS-c, the long non-coding RNA GAS5, and exosomal microRNAs miR-21 and miR-103 in stratifying prostate diseases, including benign prostatic hyperplasia (BPH), precancerous lesions (PL), and prostate cancer (PCa). These biomarkers were selected based on their established roles in cellular stress responses, apoptosis regulation, inflammation, and tumor progression. A cohort of 375 male patients suspected of prostate cancer were enrolled. Plasma and exosomal levels of Humanin, MOTS-c, GAS5, miR-21, and miR-103 were measured. Diagnostic performance was assessed using receiver operating characteristic (ROC) curve analysis, principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and decision tree models. Results showed significant downregulation of Humanin and GAS5 in both PL and PCa compared to BPH, supporting their role in early disease transition. Exosomal miR-21 and miR-103 were significantly upregulated in PCa, with miR-21 exhibiting outstanding discriminative power between BPH and PL (AUC = 1.000) and between PL and PCa (AUC = 0.9932). MOTS-c, a mitochondrial-derived peptide, displayed elevated levels in PL compared to BPH, suggesting its involvement in early malignant transformation. A plasma-only diagnostic model combining Humanin, GAS5, and MOTS-c reached 95% cross-validated classification accuracy across clinical groups. Combination of circulating Humanin, MOTS-c, GAS5, and exosomal miRNAs provides a promising non-invasive biomarker panel for risk stratification in prostate diseases. This integrated molecular approach may enhance diagnostic precision and guide personalized clinical decision-making in prostate cancer management.

Abstract

Mitochondrial-derived peptides (MDPs), including humanin, MOTS-c, and small humanin-like peptides (SHLPs), have emerged as promising therapeutic candidates for neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). This review systematically evaluates current literature retrieved from databases including PubMed, Scopus, and Web of Science using keywords such as "mitochondrial-derived peptides," "neurodegeneration," "humanin," "MOTS-c," and "SHLPs." Studies were included based on their relevance to mitochondrial function, oxidative stress, neuroprotection, and anti-inflammatory mechanisms in AD, PD, and HD models. Despite growing interest, current research remains limited in understanding the precise molecular pathways. Our review highlights their role in mitigating disease-specific pathologies such as Amyloid-beta (Aβ) toxicity in AD, dopaminergic neuron loss in PD, and mutant huntingtin aggregation in HD while also emphasizing their potential to attenuate oxidative stress and neuroinflammation. By identifying critical knowledge gaps, particularly in the areas of molecular mechanisms of MDPs in neuroprotection, targeted delivery, and clinical translation, this review provides a comprehensive framework to guide future investigations.

Abstract

Parkinson's disease (PD) is the second most common neurodegenerative disorder and mainly occurs in people above the age of 60 years. It is defined by the progressive degeneration of dopaminergic neurons of the substantia nigra pars compacta, which results in the classic motor symptoms. Though aggregation of alpha-synuclein and Lewy body formation are still the core of the disease pathogenesis, PD pathogenesis is complex with mitochondrial dysfunction, oxidative stress, neuroinflammation, impaired autophagy, and endoplasmic reticulum (ER)-Golgi stress. Of these, mitochondrial dysfunction has been the focus of special interest because of its key function in energy metabolism and generation of reactive oxygen species (ROS), which can hasten the neuronal damage. Over the past few years, mitochondrial-derived peptides (MDPs), also k/a mitochondrial microproteins such as Humanin, Small Humanin-Like Peptides (SHLPs), and Mitochondrial Open Reading Frame of the 12S rRNA type-c (MOTS-c) have been identified as new hope for modulating cellular stress responses. Their therapeutic opportunities to impact major pathogenic processes in PD, including inflammation, oxidative stress, and metabolic dysfunction, make them new targets for disease-modifying therapies. With the escalating load of PD and the limitation of existing symptomatic therapies, novel molecular targets need to be explored urgently. Research into the mechanisms involving MDPs in PD not only enhances the insight into disease mechanisms but could potentially lead the way toward next-generation therapies. This article is intended to thoroughly review the role of MDPs in PD pathogenesis and highlight their importance as novel therapeutic agents. With the growing burden of PD and the absence of disease-modifying therapies, exploring novel mitochondrial signaling pathways offers an urgently needed therapeutic direction.

Abstract

Can Gly[14]-humanin (HNG) improve cyclophosphamide-induced premature ovarian insufficiency (POI)?

Abstract

Vascular aging profoundly affects the onset of cardiovascular diseases in the elderly, mostly as a result of mitochondrial dysfunction. This review examines the protective roles of mitochondrial-derived peptides such as humanin, MOTS-c, and small humanin-like peptides in mitigating vascular aging. These peptides, encoded by mitochondrial DNA, are crucial for regulating apoptosis, inflammation, and oxidative stress, which have a major role in vascular health. MDPs have significant prospects as therapeutic and biomarker possibilities for the early diagnosis and intervention of vascular aging. MDPs influence the functions of endothelial and vascular smooth muscle cells by modulating critical signaling pathways, including AMPK, mTOR, and sirtuins. These pathways are essential for facilitating cellular metabolism, enhancing stress resilience, and prolonging longevity. Moreover, MDPs are essential in mitochondrial bioenergetics and dynamics, vital for mitigating endothelial dysfunction and enhancing vascular resilience. Furthermore, MDPs contribute to immunological modulation and the regulation of inflammatory responses, underscoring their potential therapeutic applications in the treatment of age-related vascular disorders. This review analyzes the various functions of MDPs in vascular health and their therapeutic importance, advocating for more studies to optimize their clinical benefits. By understanding the comprehensive roles and mechanisms of these multifunctional peptides, we can better appreciate their capacity to prevent and treat vascular aging and associated cardiovascular disorders. Future research should aim to further elucidate their therapeutic effects and optimize their clinical applications.

Abstract

Humanin is an endogenous human peptide with cytoprotective effects, including inhibition of apoptosis via interaction with BCL-2 proteins such as BAX. The therapeutic benefits of HN have been well-documented, and administering humanin and related endogenous human peptides for treatment of disease, aging, and enhancement of athletic performance is becoming more widespread. However, very little is known about the actual molecular structure of humanin and how it interacts with its protein partners. Here we present the amyloid-like β-sheet fibrillization of HN along with characterization of its secondary structure properties via transmission electron microscopy and other biophysical techniques. We identified several important HN mutants and documented their effects on the fibrillization process. Mutants that display inhibited β-sheet fibrillization were associated with those previously identified to be secretion deficient in vitro, highlighting the importance of β-sheet structure for membrane interactions. Successful β-sheet structural transitions are also required for productive interactions with BCL-2 family proteins resulting in apoptosis inhibition. Implications of fibrillization on the administration of HN is discussed.

Abstract

Copper sulfate exposure induces oxidative stress by triggering excessive reactive oxygen species (ROS) production, leading to inflammatory responses, neuroinflammation, and cellular dysfunction. Small humanin-like peptide-6 (SHLP-6), a mitochondria-derived peptide with anti-aging and anti-cancer properties, has not been explored for its protective effects against copper sulfate toxicity. This study investigates the antioxidant, anti-inflammatory, and neuroprotective potential of SHLP-6 in zebrafish larvae exposed to copper sulfate.

Abstract

Humanin (HN) is an endogenous micropeptide also known as a mitochondria-derived peptide. It has a neuroprotective effect against Alzheimer's disease (AD) and other neurodegenerative diseases by improving hippocampal acetylcholine and attenuating the development of oxidative stress and associated neurotoxicity. HN protects the neuron from the toxic effects of amyloid beta (Aβ). HN is regarded as a biomarker of mitochondrial stress. Interestingly, aging reduces brain expression of HN, leading to cognitive impairment and elevating the risk of neurodegeneration, including AD. However, in old subjects and AD patients, circulating HN levels increase as a compensatory mechanism to reduce neurodegeneration and mitochondrial dysfunction in AD. Conversely, other studies demonstrated a reduction in circulating HN levels in AD. These findings indicated controversial points regarding the precise mechanistic role of HN in AD. Therefore, the aim of this review was to discuss the exact role of HN in AD neuropathology and also to discuss the molecular mechanisms of HN in AD.

Abstract

Mitochondria‑derived peptides (MDPs) are a unique class of peptides encoded by short open reading frames in mitochondrial DNA, including the mitochondrial open reading frame of the 12S ribosomal RNA type‑c (MOTS‑c). Recent studies suggest that MDPs offer therapeutic benefits in various diseases, including neurodegenerative disorders and types of cancer, due to their ability to increase cellular resilience. Mitochondrial dysfunction is a key factor in the onset and progression of cardiovascular diseases (CVDs), such as atherosclerosis and heart failure, as it disrupts energy metabolism, increases oxidative stress and promotes inflammation. MDPs such as humanin and MOTS‑c have emerged as important regulators of mitochondrial health, as they show protective effects against these processes. Recent studies have shown that MDPs can restore mitochondrial function, reduce oxidative damage and alleviate inflammation, thus counteracting the pathological mechanisms that drive CVDs. Therefore, MDPs hold promise as therapeutic agents that are capable of slowing, stopping, or even reversing CVD progression and their use presents a promising strategy for future treatments. However, the clinical application of MDPs remains challenging due to their low bioavailability, poor stability and high synthesis costs. Thus, it is necessary to improve drug delivery systems to enhance the bioavailability of MDPs. Moreover, integrating basic research with clinical trials is essential to bridge the gap between experimental findings and clinical applications.

Abstract

Age-related macular degeneration (AMD), the leading cause of irreversible vision loss in the US, is on the rise among the elderly. Uncontrolled mitochondria-derived peptide production from mtDNA disruption and 16S or 12S rRNA damage could worsen AMD. Our previous work has shown that Humanin G possesses cytoprotective effects in retinal pigment epithelial (RPE) cells. However, MOTS-c, a highly efficient mitochondrial peptide, has yet to be evaluated on retinal cell survival. In this study, we show that there are differences in effects between wild-type (wt-) and differentiated ARPE19 cells (diff-ARPE19), implying that the cellular differentiation status may influence how cells respond to MOTS-c. MOTS-c has dose-dependent effects on apoptosis, inflammation, and mitochondrial biogenesis in diff-ARPE19 cells. Lower doses (500 nM) have more significant impacts than 5 µM concentrations. In diff-ARPE19 cells, a lower dose of MOTS-c can reduce the negative impact of hypoxia on cellular survival and gene expression, including apoptosis (CASP3, CASP9), mitochondrial biogenesis (TFAM, PGC-1α), and metabolic sensor (AMPK). However, it had no significant effect on ROS levels or NRF1 expression, regardless of MOTS-c dose. Exposing diff-ARPE19 cells to varied MOTS-c dosages before and after therapy in a chemically induced hypoxic environment yields no extra benefits as compared to MOTS-c treatment alone. MOTS-c had different effects on the expression of genes linked with apoptosis, mitochondrial biogenesis, and antioxidant activity in AMD patients versus age-matched control cybrids. The MOTS-c peptide appears to enhance cellular metabolism and regulate gene expression, which could potentially provide therapeutic benefits in AMD.

Abstract

Autophagy is a self-eating cellular process in which the cell breaks down worn-out organelles, damaged/defective proteins, and toxins. Impaired autophagy is a significant factor in the development of various metabolic disorders, along with oxidative stress, inflammation, mitochondrial and endoplasmic reticulum dysfunction. These disorders pose a significant health and economic burden on the global human population, owing to their steadily rising prevalence. Therefore, modulating the expression of proteins involved in the autophagy-related pathways can be a promising avenue for curbing the development and progression of these disorders. Humanin (HN) is a 24-amino acid mitochondrial-derived peptide. It possesses anti-oxidant, anti-inflammatory, and pro-apoptotic properties. The analogs of HN can be generated by replacing specific amino acids in the polypeptide chain, thereby functionally modifying the peptide. Among these, humanin- glycine (HNG) is the most widely studied analog in both in vivo and in vitro disease models. It is far more potent than HN, with a potency that is 1000 times greater. To the best of our knowledge, this review is the first to discuss and examine the available evidence regarding the potential involvement of HN or its analogs in regulating autophagy pathways. The review primarily highlights that HN is an autophagy inducer, which can promote cell survival in the presence of metabolic and oxidative stress, particularly the HNG analog. Future research is imperative to comprehensively evaluate the effects of HN and its analogs on autophagy. Further investigations are needed to correlate its levels with various autophagic markers in different metabolic diseases, offering the potential for groundbreaking discoveries in understanding disease mechanisms and developing novel therapeutic strategies.