Humanin attenuates palmitate-induced hepatic lipid accumulation and insulin resistance via AMPK-mediated suppression of the mTOR pathway

Humanin activates integrin αV-TGFβ axis and leads to glioblastoma progression

The role of mitochondria peptides in the spreading of glioblastoma remains poorly understood. In this study, we investigated the mechanism underlying intracranial glioblastoma progression. Our findings demonstrate that the mitochondria-derived peptide, humanin, plays a significant role in enhancing glioblastoma progression through the intratumoral activation of the integrin alpha V (ITGAV)-TGF beta (TGFβ) signaling axis. In glioblastoma tissues, humanin showed a significant upregulation in the tumor area compared to the corresponding normal region. Utilizing multiple in vitro pharmacological and genetic approaches, we observed that humanin activates the ITGAV pathway, leading to cellular attachment and filopodia formation. This process aids the subsequent migration and invasion of attached glioblastoma cells through intracellular TGFβR signaling activation. In addition, our in vivo orthotopic glioblastoma model provides further support for the pro-tumoral function of humanin. We observed a correlation between poor survival and aggressive invasiveness in the humanin-treated group, with noticeable tumor protrusions and induced angiogenesis compared to the control. Intriguingly, the in vivo effect of humanin on glioblastoma was significantly reduced by the treatment of TGFBR1 inhibitor. To strengthen these findings, public database analysis revealed a significant association between genes in the ITGAV-TGFβR axis and poor prognosis in glioblastoma patients. These results collectively highlight humanin as a pro-tumoral factor, making it a promising biological target for treating glioblastoma.

Small peptides: could they have a big role in metabolism and the response to exercise?

Exercise is a powerful non-pharmacological intervention for the treatment and prevention of numerous chronic diseases. Contracting skeletal muscles provoke widespread perturbations in numerous cells, tissues and organs, which stimulate multiple integrated adaptations that ultimately contribute to the many health benefits associated with regular exercise. Despite much research, the molecular mechanisms driving such changes are not completely resolved. Technological advancements beginning in the early 1960s have opened new avenues to explore the mechanisms responsible for the many beneficial adaptations to exercise. This has led to increased research into the role of small peptides (<100 amino acids) and mitochondrially derived peptides in metabolism and disease, including those coded within small open reading frames (sORFs; coding sequences that encode small peptides). Recently, it has been hypothesized that sORF-encoded mitochondrially derived peptides and other small peptides play significant roles as exercise-sensitive peptides in exercise-induced physiological adaptation. In this review, we highlight the discovery of mitochondrially derived peptides and newly discovered small peptides involved in metabolism, with a specific emphasis on their functions in exercise-induced adaptations and the prevention of metabolic diseases. In light of the few studies available, we also present data on how both single exercise sessions and exercise training affect expression of sORF-encoded mitochondrially derived peptides. Finally, we outline numerous research questions that await investigation regarding the roles of mitochondrially derived peptides in metabolism and prevention of various diseases, in addition to their roles in exercise-induced physiological adaptations, for future studies.

Mitochondrial-derived peptides: Antidiabetic functions and evolutionary perspectives

Mitochondrial-derived peptides (MDPs) are a novel class of bioactive microproteins encoded by short open-reading frames (sORF) in mitochondrial DNA (mtDNA). Currently, three types of MDPs have been identified: Humanin (HN), MOTS-c (Mitochondrial ORF within Twelve S rRNA type-c), and SHLP1-6 (small Humanin-like peptide, 1 to 6). The 12 S ribosomal RNA (MT-RNR1) gene harbors the sequence for MOTS-c, whereas HN and SHLP1-6 are encoded by the 16 S ribosomal RNA (MT-RNR2) gene. Special genetic codes are used in mtDNA as compared to nuclear DNA: (i) ATA and ATT are used as start codons in addition to the standard start codon ATG; (ii) AGA and AGG are used as stop codons instead of coding for arginine; (iii) the standard stop codon UGA is used to code for tryptophan. While HN, SHLP6, and MOTS-c are encoded by the H (heavy owing to high guanine + thymine base composition)-strand of the mtDNA, SHLP1-5 are encoded by the L (light owing to less guanine + thymine base composition)-strand. MDPs attenuate disease pathology including Type 1 diabetes (T1D), Type 2 diabetes (T2D), gestational diabetes, Alzheimer's disease (AD), cardiovascular diseases, prostate cancer, and macular degeneration. The current review will focus on the MDP regulation of T2D, T1D, and gestational diabetes along with an emphasis on the evolutionary pressures for conservation of the amino acid sequences of MDPs.

A novel link between chronic inflammation and humanin regulation in children

Objective

Children with inflammatory bowel disease (IBD) often suffer from poor bone growth and impaired bone health. Humanin is a cytoprotective factor expressed in bone and other tissues and we hypothesized that humanin levels are suppressed in conditions of chronic inflammation. To address this, humanin levels were analyzed in serum samples from IBD patients and in ex vivo cultured human growth plate tissue specimens exposed to IBD serum or TNF alone.

Methods

Humanin levels were measured by ELISA in serum from 40 children with IBD and 40 age-matched healthy controls. Growth plate specimens obtained from children undergoing epiphysiodesis surgery were cultured ex vivo for 48 hours while being exposed to IBD serum or TNF alone. The growth plate samples were then processed for immunohistochemistry staining for humanin, PCNA, SOX9 and TRAF2 expression. Dose-response effect of TNF was studied in the human chondrocytic cell line HCS-2/8. Ex vivo cultured fetal rat metatarsal bones were used to investigate the therapeutic effect of humanin.

Results

Serum humanin levels were significantly decreased in children with IBD compared to healthy controls. When human growth plate specimens were cultured with IBD serum, humanin expression was significantly suppressed in the growth plate cartilage. When cultured with TNF alone, the expression of humanin, PCNA, SOX9, and TRAF2 were all significantly decreased in the growth plate cartilage. Interestingly, treatment with the humanin analog HNG prevented TNF-induced bone growth impairment in cultured metatarsal bones.

Conclusion

Our data showing suppressed serum humanin levels in IBD children with poor bone health provides the first evidence for a potential link between chronic inflammation and humanin regulation. Such a link is further supported by the novel finding that serum from IBD patients suppressed humanin expression in ex vivo cultured human growth plates.

Emerging therapeutic options in the management of diabetes: recent trends, challenges and future directions

Diabetes is a serious health issue that causes a progressive dysregulation of carbohydrate metabolism due to insufficient insulin hormone, leading to consistently high blood glucose levels. According to the epidemiological data, the prevalence of diabetes has been increasing globally, affecting millions of individuals. It is a long-term condition that increases the risk of various diseases caused by damage to small and large blood vessels. There are two main subtypes of diabetes: type 1 and type 2, with type 2 being the most prevalent. Genetic and molecular studies have identified several genetic variants and metabolic pathways that contribute to the development and progression of diabetes. Current treatments include gene therapy, stem cell therapy, statin therapy, and other drugs. Moreover, recent advancements in therapeutics have also focused on developing novel drugs targeting these pathways, including incretin mimetics, SGLT2 inhibitors, and GLP-1 receptor agonists, which have shown promising results in improving glycemic control and reducing the risk of complications. However, these treatments are often expensive, inaccessible to patients in underdeveloped countries, and can have severe side effects. Peptides, such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), are being explored as a potential therapy for diabetes. These peptides are postprandial glucose-dependent pancreatic beta-cell insulin secretagogues and have received much attention as a possible treatment option. Despite these advances, diabetes remains a major health challenge, and further research is needed to develop effective treatments and prevent its complications. This review covers various aspects of diabetes, including epidemiology, genetic and molecular basis, and recent advancements in therapeutics including herbal and synthetic peptides.

Mitochondrial-derived peptides in cardiovascular disease: Novel insights and therapeutic opportunities

BACKGROUND

Mitochondria-derived peptides (MDPs) represent a recently discovered family of peptides encoded by short open reading frames (ORFs) found within mitochondrial genes. This group includes notable members including humanin (HN), mitochondrial ORF of the 12S rDNA type-c (MOTS-c), and small humanin-like peptides 1-6 (SHLP1-6). MDPs assume pivotal roles in the regulation of diverse cellular processes, encompassing apoptosis, inflammation, and oxidative stress, which are all essential for sustaining cellular viability and normal physiological functions. Their emerging significance extends beyond this, prompting a deeper exploration into their multifaceted roles and potential applications.

AIM OF REVIEW

This review aims to comprehensively explore the biogenesis, various types, and diverse functions of MDPs. It seeks to elucidate the central roles and underlying mechanisms by which MDPs participate in the onset and development of cardiovascular diseases (CVDs), bridging the connections between cell apoptosis, inflammation, and oxidative stress. Furthermore, the review highlights recent advancements in clinical research related to the utilization of MDPs in CVD diagnosis and treatment.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MDPs levels are diminished with aging and in the presence of CVDs, rendering them potential new indicators for the diagnosis of CVDs. Also, MDPs may represent a novel and promising strategy for CVD therapy. In this review, we delve into the biogenesis, various types, and diverse functions of MDPs. We aim to shed light on the pivotal roles and the underlying mechanisms through which MDPs contribute to the onset and advancement of CVDs connecting cell apoptosis, inflammation, and oxidative stress. We also provide insights into the current advancements in clinical research related to the utilization of MDPs in the treatment of CVDs. This review may provide valuable information with MDPs for CVD diagnosis and treatment.

Nonalcoholic fatty liver disease: Current therapies and future perspectives in drug delivery

Nonalcoholic fatty liver disease (NAFLD) affects approximately 25% of the adult population worldwide. This pathology can progress into end-stage liver disease with life-threatening complications, and yet no pharmacologic therapy has been approved. NAFLD is commonly characterized by excessive fat accumulation in the liver and is in closely associated with insulin resistance and metabolic disorders, which suggests that NAFLD is the hepatic manifestation of metabolic syndrome. Regarding treatment options, the current validated strategy relies on lifestyle modifications (exercise and diet restrictions). Although there are no approved drug-based treatments, several clinical trials are ongoing. Novel targets are being discovered, and the repurposing of drugs that show promising effects in NAFLD is starting to gain more interest. The field of nanotechnology has been growing at an increasing rate, with new and more efficient drug delivery strategies being developed for NAFLD treatment. Nanocarriers can easily encapsulate drugs that need to be better protected from the organism to exert their effect or that need help at reaching their target, thereby helping achieve a better bioavailability. Drug delivery systems can also be designed to target the site of the disease, in this case, the liver. In this review, we focus on the current knowledge of NAFLD pathology, the targets being considered for clinical trials, and the current guidelines and ongoing clinical trials, with a specific focus on potential oral treatments for NAFLD using promising drug delivery strategies.

Oroxylin-A alleviates hepatic lipid accumulation and apoptosis under hyperlipidemic conditions via AMPK/FGF21 signaling

Oroxylin-A (OA) is an O-methylated flavone that has been demonstrated to have anti-inflammatory properties in various disease models. However, the roles of OA in hepatic lipid metabolism and the specific molecular mechanisms by which it exerts these effects are not yet fully understood. In the current study, we aimed to investigate the effects of OA on hepatic lipid deposition and apoptosis, which play a pivotal role in the development of nonalcoholic fatty liver disease (NAFLD) in obesity in vitro models. We found that treatment with OA attenuated lipid accumulation, the expression of lipogenesis-associated proteins and apoptosis in palmitate-treated primary mouse hepatocytes. OA treatment suppressed phosphorylated NFκB and IκB expression in as well as TNFα and MCP-1 release from hepatocytes treated with palmitate. Treatment of hepatocytes with OA augmented AMPK phosphorylation and FGF21 expression. siRNA of AMPK or FGF21 abolished the effects of OA on inflammation as well as lipid accumulation and apoptosis in hepatocytes under palmitate treatment conditions. In conclusion, OA improves inflammation through the AMPK/FGF21 pathway, thereby attenuating lipid accumulation and apoptosis in hepatocytes. This study may help identify new targets for developing treatments for NAFLD.

Youth versus adult-onset type 2 diabetic kidney disease: Insights into currently known structural differences and the potential underlying mechanisms

Type 2 diabetes (T2D) is a global health pandemic with significant humanitarian, economic, and societal implications, particularly for youth and young adults who are experiencing an exponential rise in incident disease. Youth-onset T2D has a more aggressive phenotype than adult-onset T2D, and this translates to important differences in rates of progression of diabetic kidney disease (DKD). We hypothesize that youth-onset DKD due to T2D may exhibit morphometric, metabolic, and molecular characteristics that are distinct from adult-onset T2D and develop secondary to inherent differences in renal energy expenditure and substrate metabolism, resulting in a central metabolic imbalance. Kidney structural changes that are evident at the onset of puberty also serve to exacerbate the organ’s baseline high rates of energy expenditure. Additionally, the physiologic state of insulin resistance seen during puberty increases the risk for kidney disease and is exacerbated by both concurrent diabetes and obesity. A metabolic mismatch in renal energetics may represent a novel target for pharmacologic intervention, both for prevention and treatment of DKD. Further investigation into the underlying molecular mechanisms resulting in DKD in youth-onset T2D using metabolomics and RNA sequencing of kidney tissue obtained at biopsy is necessary to expand our understanding of early DKD and potential targets for therapeutic intervention. Furthermore, large-scale clinical trials evaluating the duration of kidney protective effects of pharmacologic interventions that target a metabolic mismatch in kidney energy expenditure are needed to help mitigate the risk of DKD in youth-onset T2D.

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

BACKGROUND

Autophagy, a highly conserved homeostatic mechanism, is essential for cell survival. The decline of autophagy function has been implicated in various diseases as well as aging. Although mitochondria play a key role in the autophagy process, whether mitochondrial-derived peptides are involved in this process has not been explored.

METHODS

We developed a high through put screening method to identify potential autophagy inducers among mitochondrial-derived peptides. We used three different cell lines, mice, c.elegans, and a human cohort to validate the observation.

RESULTS

Humanin, a mitochondrial-derived peptide, increases autophagy and maintains autophagy flux in several cell types. Humanin administration increases the expression of autophagy-related genes and lowers accumulation of harmful misfolded proteins in mice skeletal muscle, suggesting that humanin-induced autophagy potentially contributes to the improved skeletal function. Moreover, autophagy is a critical role in humanin-induced lifespan extension in C. elegans.

CONCLUSIONS

Humanin is an autophagy inducer.

GENERAL SIGNIFICANCE

This paper presents a significant, novel discovery regarding the role of the mitochondrial derived peptide humanin in autophagy regulation and as a possible therapeutic target for autophagy in various age-related diseases.

Colivelin, a synthetic derivative of humanin, ameliorates endothelial injury and glycocalyx shedding after sepsis in mice

Endothelial dysfunction plays a central role in the pathogenesis of sepsis-mediated multiple organ failure. Several clinical and experimental studies have suggested that the glycocalyx is an early target of endothelial injury during an infection. Colivelin, a synthetic derivative of the mitochondrial peptide humanin, has displayed cytoprotective effects in oxidative conditions. In the current study, we aimed to determine the potential therapeutic effects of colivelin in endothelial dysfunction and outcomes of sepsis in vivo. Male C57BL/6 mice were subjected to a clinically relevant model of polymicrobial sepsis by cecal ligation and puncture (CLP) and were treated with vehicle or colivelin (100-200 µg/kg) intraperitoneally at 1 h after CLP. We observed that vehicle-treated mice had early elevation of plasma levels of the adhesion molecules ICAM-1 and P-selectin, the angiogenetic factor endoglin and the glycocalyx syndecan-1 at 6 h after CLP when compared to control mice, while levels of angiopoietin-2, a mediator of microvascular disintegration, and the proprotein convertase subtilisin/kexin type 9, an enzyme implicated in clearance of endotoxins, raised at 18 h after CLP. The early elevation of these endothelial and glycocalyx damage biomarkers coincided with lung histological injury and neutrophil inflammation in lung, liver, and kidneys. At transmission electron microscopy analysis, thoracic aortas of septic mice showed increased glycocalyx breakdown and shedding, and damaged mitochondria in endothelial and smooth muscle cells. Treatment with colivelin ameliorated lung architecture, reduced organ neutrophil infiltration, and attenuated plasma levels of syndecan-1, tumor necrosis factor-α, macrophage inflammatory protein-1α and interleukin-10. These therapeutic effects of colivelin were associated with amelioration of glycocalyx density and mitochondrial structure in the aorta. At molecular analysis, colivelin treatment was associated with inhibition of the signal transducer and activator of transcription 3 and activation of the AMP-activated protein kinase in the aorta and lung. In long-term outcomes studies up to 7 days, co-treatment of colivelin with antimicrobial agents significantly reduced the disease severity score when compared to treatment with antibiotics alone. In conclusion, our data support that damage of the glycocalyx is an early pathogenetic event during sepsis and that colivelin may have therapeutic potential for the treatment of sepsis-associated endothelial dysfunction.

Patchouli alcohol ameliorates skeletal muscle insulin resistance and NAFLD via AMPK/SIRT1-mediated suppression of inflammation

Obesity-induced chronic low-grade inflammation and thus causes various metabolic diseases, such as insulin resistance and non-alcoholic fatty liver disease (NAFLD). Patchouli alcohol (PA), an active component extracted from patchouli, displayed anti-inflammatory effects on different cell types. However, the impact of PA on skeletal muscle insulin signaling and hepatic lipid metabolism remains unclear. This study aimed to investigate whether PA would affect insulin signaling impairment in myocytes and lipid metabolism in hepatocytes. Treatment with PA ameliorated palmitate-induced inflammation and aggravation of insulin signaling in C2C12 myocytes and lipid accumulation in HepG2 hepatocytes. Treatment of C2C12 myocytes and HepG2 cells with PA augmented AMP-activated protein kinase (AMPK) phosphorylation and Sirtuin 1 (SIRT1) expression in a dose-dependent manner. siRNA-mediated suppression of AMPK or SIRT1 mitigated the effects of PA on palmitate-induced inflammation and insulin resistance in C2C12 myocytes and lipid accumulation in HepG2 cells. Animal experiments demonstrated that PA administration increased AMPK phosphorylation and SIRT1 expression, and ameliorated inflammation, thereby attenuating skeletal muscle insulin resistance and hepatic steatosis in high-fat diet-fed mice. These results denote that PA alleviates skeletal muscle insulin resistance and hepatic steatosis through AMPK/SIRT1-dependent signaling. This study might provide a novel therapeutic approach for treating obesity-related insulin resistance and NAFLD.

The Role of Mitochondria-Derived Peptides in Cardiovascular Diseases and Their Potential as Therapeutic Targets

Mitochondria-derived peptides (MDPs) are small peptides hidden in the mitochondrial DNA, maintaining mitochondrial function and protecting cells under different stresses. Currently, three types of MDPs have been identified: Humanin, MOTS-c and SHLP1-6. MDPs have demonstrated anti-apoptotic and anti-inflammatory activities, reactive oxygen species and oxidative stress-protecting properties both in vitro and in vivo. Recent research suggests that MDPs have a significant cardioprotective role, affecting CVDs (cardiovascular diseases) development and progression. CVDs are the leading cause of death globally; this term combines disorders of the blood vessels and heart. In this review, we focus on the recent progress in understanding the relationships between MDPs and the main cardiovascular risk factors (atherosclerosis, insulin resistance, hyperlipidaemia and ageing). We also will discuss the therapeutic application of MDPs, modified and synthetic MDPs, and their potential as novel biomarkers and therapeutic targets.

Humanin Alleviates Insulin Resistance in Polycystic Ovary Syndrome: A Human and Rat Model-Based Study

Polycystic ovary syndrome (PCOS), the most common endocrine disorder in women of reproductive age, is characterized by hyperandrogenism and insulin resistance (IR); however, the pathogenesis of local ovarian IR in PCOS remains largely unclear. Humanin, a mitochondria-derived peptide, has been reported to be associated with IR. Our previous study confirmed that humanin is expressed in multiple cell types in the ovary and is present in follicular fluid. However, it remains unknown whether humanin participates in the pathogenesis of local ovarian IR or whether humanin supplementation can improve IR in PCOS patients. In this study, we compared humanin concentrations in follicular fluid from PCOS patients with and without IR. We further investigated the effect of humanin analogue (HNG) supplementation on IR in a rat model of dehydroepiandrosterone-induced PCOS. Humanin concentrations in the follicular fluid were found to be significantly lower in PCOS patients with IR than in those without IR. HNG supplementation attenuated both the increases in the levels of fasting plasma glucose and fasting insulin in rats with PCOS and the decreases in phosphorylation of IRS1, PI3K, AKT, and GLUT4 proteins in the granulosa cells of these rats. Combined supplementation with HNG and insulin significantly improved glucose consumption in normal and humanin-siRNA-transfected COV434 cells. In conclusion, downregulated humanin in the ovaries may be involved in the pathogenesis of IR in PCOS, and exogenous supplementation with HNG improved local ovarian IR through modulation of the IRS1/PI3K/Akt signaling pathway in a rat model. This finding supports the potential future use of HNG as a therapeutic drug for PCOS.

Transcriptional Profiles Reveal Deregulation of Lipid Metabolism and Inflammatory Pathways in Neurons Exposed to Palmitic Acid

The effects of the consumption of high-fat diets (HFD) have been studied to unravel the molecular pathways they are altering in order to understand the link between increased caloric intake, metabolic diseases, and the risk of cognitive dysfunction. The saturated fatty acid, palmitic acid (PA), is the main component of HFD and it has been found increased in the circulation of obese and diabetic people. In the central nervous system, PA has been associated with inflammatory responses in astrocytes, but the effects on neurons exposed to it have not been largely investigated. Given that PA affects a variety of metabolic pathways, we aimed to analyze the transcriptomic profile activated by this fatty acid to shed light on the mechanisms of neuronal dysfunction. In the current study, we profiled the transcriptome response after PA exposition at non-toxic doses in primary hippocampal neurons. Gene ontology and Reactome pathway analysis revealed a pattern of gene expression which is associated with inflammatory pathways, and importantly, with the activation of lipid metabolism that is considered not very active in neurons. Validation by quantitative RT-PCR (qRT-PCR) of Hmgcs2, Angptl4, Ugt8, and Rnf145 support the results obtained by RNAseq. Overall, these findings suggest that neurons are able to respond to saturated fatty acids changing the expression pattern of genes associated with inflammatory response and lipid utilization that may be involved in the neuronal damage associated with metabolic diseases.

Capmatinib attenuates lipogenesis in 3T3-L1 adipocytes through an adenosine monophosphate-activated protein kinase-dependent pathway

Recently, there is a rapid increase in the incidence of obesity, a condition for which there are no effective therapeutic agents. Capmatinib (CAP), a novel mesenchymal-to-epithelial transition inhibitor, is reported to attenuate pro-inflammatory mediators and oxidative stress. In this study, the effects of CAP on lipogenesis in the adipocytes were examined. Treatment with CAP dose-dependently suppressed lipid accumulation in, and differentiation of, and increased lipolysis in, 3T3-L1 adipocytes. Additionally, CAP treatment augmented adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and FNDC5 expression in the adipocytes. Transfection with si-AMPK or si-FNDC5 mitigated the CAP-induced suppression of lipogenesis and enhanced lipolysis. Furthermore, transfection with si-FNDC5 mitigated the CAP-induced phosphorylation of AMPK. These results suggest that the anti-obesity effect of CAP is mediated through the irisin/AMPK pathway and that CAP is a novel therapeutic agent for obesity.

Expression Profile of Mouse Gm20594, Nuclear-Encoded Humanin-Like Gene

Background

Mitochondrial-derived peptides (MDPs) such as MOTS-c and humanin have been studied for their cytoprotective functions. In mice, humanin-encoding Mtrnr2 is a mitochondrial pseudogene, and the humanin-like peptide is encoded by the nuclear Gm20594 gene. However, endogenous tissue-specific expression profiles of Gm20594 have not yet been identified.

Methods

Mtrnr1 and Gm20594 expression was profiled via reverse transcription using only oligo(dT) primers from tissues of C57BL6/J mice. To analyze altered expression upon mitochondrial biogenesis, C2C12 myocytes and brown adipocytes were differentiated. Mitochondrial DNA copy numbers were quantified for normalization.

Results

Both Mtrnr1 and Gm20594 were highly expressed in brown adipose tissue. When normalized against mitochondrial content, Mtrnr1 was identified as being highly expressed in the duodenum, followed by the jejunum. In models of mitochondrial biogenesis, both Mtrnr1 and Gm20594 were upregulated during myocyte and brown adipocyte differentiation. Increased Mtrnr1 expression during brown adipocyte differentiation remained significant after normalization against mitochondrial DNA copy number, whereas myocyte differentiation exhibited biphasic upregulation and downregulation in early and late phases, respectively.

Conclusion

Nuclear-encoded Gm20594 showed similar expression patterns of mitochondrial-encoded Mtrnr1. Brown adipose tissue presented the highest basal expression levels of Gm20594 and Mtrnr1. When normalized against mitochondrial DNA copy number, gut tissues exhibited the highest expression of Mtrnr1. Upregulation of Mtrnr1 during mitochondrial biogenesis is independent of mitochondrial content.

Mitochondrial-Derived Peptides in Diabetes and Its Complications

The changes of mitochondrial function are closely related to diabetes and its complications. Here we describe the effects of mitochondrial-derived peptides (MDPs), short peptides formed by transcription and translation of the open reading frame site in human mitochondrial DNA (mtDNA), on diabetes and its complications. We mainly focus on MDPs that have been discovered so far, such as Humanin (HN), mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) and Small humanin-like peptides (SHLP 1-6), and elucidated the role of MDPs in diabetes and its major complications stroke and myocardial infarction by improving insulin resistance, inhibiting inflammatory response and anti-apoptosis. It provides more possibilities for the clinical application of mitochondrial derived peptides.

Protective Mechanism of Humanin Against Oxidative Stress in Aging-Related Cardiovascular Diseases

Physiological reactive oxygen species (ROS) are important regulators of intercellular signal transduction. Oxidative and antioxidation systems maintain a dynamic balance under physiological conditions. Increases in ROS levels destroy the dynamic balance, leading to oxidative stress damage. Oxidative stress is involved in the pathogenesis of aging-related cardiovascular diseases (ACVD), such as atherosclerosis, myocardial infarction, and heart failure, by contributing to apoptosis, hypertrophy, and fibrosis. Oxidative phosphorylation in mitochondria is the main source of ROS. Increasing evidence demonstrates the relationship between ACVD and humanin (HN), an endogenous peptide encoded by mitochondrial DNA. HN protects cardiomyocytes, endothelial cells, and fibroblasts from oxidative stress, highlighting its protective role in atherosclerosis, ischemia-reperfusion injury, and heart failure. Herein, we reviewed the signaling pathways associated with the HN effects on redox signals, including Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2), chaperone-mediated autophagy (CMA), c-jun NH2 terminal kinase (JNK)/p38 mitogen-activated protein kinase (p38 MAPK), adenosine monophosphate-activated protein kinase (AMPK), and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)-Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3). Furthermore, we discussed the relationship among HN, redox signaling pathways, and ACVD. Finally, we propose that HN may be a candidate drug for ACVD.

Humanin: A mitochondrial-derived peptide in the treatment of apoptosis-related diseases

Humanin (HN) is a small mitochondrial-derived cytoprotective polypeptide encoded by mtDNA. HN exhibits protective effects in several cell types, including leukocytes, germ cells, neurons, tissues against cellular stress conditions and apoptosis through regulating various signaling mechanisms, such as JAK/STAT pathway and interaction of BCL-2 family of protein. HN is an essential cytoprotective peptide in the human body that regulates mitochondrial functions under stress conditions. The present review aims to evaluate HN peptide's antiapoptotic activities as a potential therapeutic target in the treatment of cancer, diabetes mellitus, male infertility, bone-related diseases, cardiac diseases, and brain diseases. Based on in vitro and in vivo studies, HN significantly suppressed the apoptosis during the treatment of bone osteoporosis, cardiovascular diseases, diabetes mellitus, and neurodegenerative diseases. According to accumulated data, it is concluded that HN exerts the proapoptotic activity of TNF-α in cancer, which makes HN as a novel therapeutic agent in the treatment of cancer and suggested that along with HN, the development of another mitochondrial-derived peptide could be a viable therapeutic option against different oxidative stress and apoptosis-related diseases.

Effects of Bitter Melon Saponin on the Glucose and Lipid Metabolism in HepG2 Cell and C. elegans

This study tried to explore how saponins from bitter melon (BMS) affect the glucose and lipid metabolism in palmitic acid-treated HepG2 cell and glucose-treated Caenorhabditis elegans (C. elegans). Results showed that BMS could effectively accelerate glucose consumption and elevate the levels of glycogen and ATP in palmitic acid-treated HepG2 cell, while significantly decreasing the triglyceride (TG) content. qRT-PCR data indicated that BMS might promote fatty acid β-oxidation by AMPK-ACC2-CPT1 pathway and glucose uptake by upregulating GLUT4 expression. In the model of glucose-treated C. elegans, we observed that BMS obviously inhibited fat accumulation, along with no toxicity towards some physical activities. The potential mechanism of BMS in the metabolism involved the suppression of synthesis of polyunsaturated fatty acids and enhancement of fatty acid β-oxidation. Taken together, BMS exhibited ability of regulating energy metabolism in HepG2 cell line and C. elegans.