Mitochondrial Uncoupling Proteins (UCPs) as Key Modulators of ROS Homeostasis: A Crosstalk between Diabesity and Male Infertility?

Mini-encyclopedia of mitochondria-relevant nutraceuticals protecting health in primary and secondary care-clinically relevant 3PM innovation

Despite their subordination in humans, to a great extent, mitochondria maintain their independent status but tightly cooperate with the "host" on protecting the joint life quality and minimizing health risks. Under oxidative stress conditions, healthy mitochondria promptly increase mitophagy level to remove damaged "fellows" rejuvenating the mitochondrial population and sending fragments of mtDNA as SOS signals to all systems in the human body. As long as metabolic pathways are under systemic control and well-concerted together, adaptive mechanisms become triggered increasing systemic protection, activating antioxidant defense and repair machinery. Contextually, all attributes of mitochondrial patho-/physiology are instrumental for predictive medical approach and cost-effective treatments tailored to individualized patient profiles in primary (to protect vulnerable individuals again the health-to-disease transition) and secondary (to protect affected individuals again disease progression) care. Nutraceuticals are naturally occurring bioactive compounds demonstrating health-promoting, illness-preventing, and other health-related benefits. Keeping in mind health-promoting properties of nutraceuticals along with their great therapeutic potential and safety profile, there is a permanently growing demand on the application of mitochondria-relevant nutraceuticals. Application of nutraceuticals is beneficial only if meeting needs at individual level. Therefore, health risk assessment and creation of individualized patient profiles are of pivotal importance followed by adapted nutraceutical sets meeting individual needs. Based on the scientific evidence available for mitochondria-relevant nutraceuticals, this article presents examples of frequent medical conditions, which require protective measures targeted on mitochondria as a holistic approach following advanced concepts of predictive, preventive, and personalized medicine (PPPM/3PM) in primary and secondary care.

Signatures of metabolic diseases on spermatogenesis and testicular metabolism

Diets leading to caloric overload are linked to metabolic disorders and reproductive function impairment. Metabolic and hormonal abnormalities stand out as defining features of metabolic disorders, and substantially affect the functionality of the testis. Metabolic disorders induce testicular metabolic dysfunction, chronic inflammation and oxidative stress. The disruption of gastrointestinal, pancreatic, adipose tissue and testicular hormonal regulation induced by metabolic disorders can also contribute to a state of compromised fertility. In this Review, we will delve into the effects of high-fat diets and metabolic disorders on testicular metabolism and spermatogenesis, which are crucial elements for male reproductive function. Moreover, metabolic disorders have been shown to influence the epigenome of male gametes and might have a potential role in transmitting phenotype traits across generations. However, the existing evidence strongly underscores the unmet need to understand the mechanisms responsible for transgenerational paternal inheritance of male reproductive function impairment related to metabolic disorders. This knowledge could be useful for developing targeted interventions to prevent, counteract, and most of all break the perpetuation chain of male reproductive dysfunction associated with metabolic disorders across generations.

Causal relationship between genetically predicted type 2 diabetes mellitus and male infertility

Background

Diabetes mellitus (DM) stands as the most prevalent endocrine abnormality affecting the physiological systems and organs and impairing the male reproductive functions. Type 2 Diabetes Mellitus (T2DM), accounting for about 90-95% of DM, is closely associated with male infertility. However, the magnitude of the causal relationships between T2DM and male infertility remains unclear. The current investigation was to explore the causal relationship between T2DM and male infertility utilizing the Mendelian Randomization (MR) analysis.

Methods

A two-sample MR (2SMR) analysis was conducted to investigate the causal relationship between T2DM and male infertility in the European population from the genome-wide association study (GWAS) summary data that was publicly accessible. GWAS for T2DM and male infertility were extracted from the IEU Open GWAS Project database, with the resulting data encompassing 680 cases and 72,799 controls as the outcome data. Five MR methods were employed for the 2SMR analyses, namely the MR-Egger, weighted median estimation (WME), weighted mode (WM), inverse-variance weighted (IVW), and simple mode. The primary analytical technique utilized in this study was the IVW method, and a multivariate MR analysis was executed to examine the potential mediating influences of T2DM on male infertility.

Results

Following were the odds ratios (ORs) and associated 95% CIs derived from IVW (fixed effects), MR-Egger, WM, WME, and simple mode approaches: 0.824 (95% CI 0.703-0.966), 0.726 (95% CI 0.527-1.001), 0.827 (95% CI 0.596-1.150), 0.841 (95% CI 0.654-1.082), and 0.875 (95% CI 0.544-1.405), respectively. The outcomes of the heterogeneity tests were P=0.378 and P=0.384, respectively, implying no heterogeneity. Egger-intercept outcomes were P=0.374, highlighting the absence of pleiotropy. The stability of the results was affirmed through the leave-one-out analysis. Notably, all F-values surpassed 10, indicating the absence of weak bias attributed to instrument variables(IVs).

Conclusions

This research furnishes evidence supporting a causal association between T2DM and male infertility. These insights offer a foundation for future investigations aiming to establish the association between genetically predicted T2DM and male infertility. These outcomes suggest the significance of active monitoring and proactive measures for preventing infertility in male individuals with T2DM. Furthermore, careful consideration is required for individuals of reproductive age to prevent and treat T2DM.

Unraveling the impact of melatonin treatment: Oxidative stress, metabolic responses, and morphological changes in HuH7.5 hepatocellular carcinoma cells

In addition to its highly aggressive nature and late diagnosis, hepatocellular carcinoma (HCC) does not respond effectively to available chemotherapeutic agents. The search is on for an ideal and effective compound with low cost and minimal side effects that can be used as an adjunct to chemotherapeutic regimens. One of the mechanisms involved in the pathology of HCC is the oxidative stress, which plays a critical role in tumor survival and dissemination. Our group has already demonstrated the antitumor potential of melatonin against HuH 7.5 cells. In the present study, we focused on the effects of melatonin on oxidative stress parameters and their consequences on cell metabolism. HuH 7.5 cells were treated with 2 and 4 mM of melatonin for 24 and 48 h. Oxidative stress biomarkers, antioxidant enzyme, mitochondrial membrane potential, formation of lipid bodies and autophagic vacuoles, cell cycle progression, cell death rate and ultrastructural cell alterations were evaluated. The treatment with melatonin increased oxidative stress biomarkers and reduced antioxidant enzyme activities of HuH 7.5 cells. Additionally, melatonin treatment damaged the mitochondrial membrane and increased lipid bodies and autophagic vacuole formation. Melatonin triggered cell cycle arrest and induced cell death by apoptosis. Our results indicate that the treatment of HuH 7.5 cells with melatonin impaired antioxidant defense systems, inhibited cell cycle progression, and caused metabolic stress, culminating in tumor cell death.

Age-associated sex difference in the expression of mitochondria-based redox sensitive proteins and effect of pioglitazone in nonhuman primate brain

BACKGROUND

Paraoxonase 2 (PON2) and neuronal uncoupling proteins (UCP4 and UCP5) possess antioxidant, anti-apoptotic activities and minimize accumulation of reactive oxygen species in mitochondria. While age and sex are risk factors for several disorders that are linked with oxidative stress, no study has explored the age- and sex-dependent expression of PON2 isoforms, UCP4 and UCP5 in primate brain or identified a drug to activate UCP4 and UCP5 in vivo. Preclinical studies suggest that the peroxisome proliferator-activated receptor gamma agonist, pioglitazone (PIO), can be neuroprotective, although the mechanism responsible is unclear. Our previous studies demonstrated that pioglitazone activates PON2 in primate brain and we hypothesized that pioglitazone also induces UCP4/5. This study was designed to elucidate the age- and sex-dependent expression of PON2 isoforms, UCP4 and UCP5, in addition to examining the impact of systemic PIO treatment on UCP4 and UCP5 expression in primate brain.

METHODS

Western blot technique was used to determine the age- and sex-dependent expression of UCP4 and UCP5 in substantia nigra and striatum of African green monkeys. In addition, we tested the impact of daily oral pioglitazone (5 mg/kg/day) or vehicle for 1 or 3 weeks on expression of UCP4 and UCP5 in substantia nigra and striatum in adult male monkeys. PIO levels in plasma and cerebrospinal fluid (CSF) were determined using LC-MS.

RESULTS

We found no sex-based difference in the expression of PON2 isoforms, UCP4 and UCP5 in striatum and substantia nigra of young monkeys. However, we discovered that adult female monkeys exhibit greater expression of PON2 isoforms than males in substantia nigra and striatum. Our data also revealed that adult male monkeys exhibit greater expression of UCP4 and UCP5 than females in substantia nigra but not in striatum. PIO increased UCP4 and UCP5 expression in substantia nigra and striatum at 1 week, but after 3 weeks of treatment this activation had subsided.

CONCLUSIONS

Our findings demonstrate a sex-, age- and region-dependent profile to the expression of PON2, UCP4 and UCP5. These data establish a biochemical link between PPARγ, PON2, UCP4 and UCP5 in primate brain and demonstrate that PON2, UCP4 and UCP5 can be pharmacologically stimulated in vivo, revealing a novel mechanism for observed pioglitazone-induced neuroprotection. We anticipate that these outcomes will contribute to the development of novel neuroprotective treatments for Parkinson's disease and other CNS disorders.

Metabolite Profile Characterization of Cyanobacterial Strains with Bioactivity on Lipid Metabolism Using In Vivo and In Vitro Approaches

Cyanobacteria have demonstrated their therapeutic potential for many human diseases. In this work, cyanobacterial extracts were screened for lipid reducing activity in zebrafish larvae and in fatty-acid-overloaded human hepatocytes, as well as for glucose uptake in human hepatocytes and ucp1 mRNA induction in murine brown adipocytes. A total of 39 cyanobacteria strains were grown and their biomass fractionated, resulting in 117 chemical fractions. Reduction of neutral lipids in zebrafish larvae was observed for 12 fractions and in the human hepatocyte steatosis cell model for five fractions. The induction of ucp1 expression in murine brown adipocytes was observed in six fractions, resulting in a total of 23 bioactive non-toxic fractions. All extracts were analyzed by untargeted UPLC-Q-TOF-MS mass spectrometry followed by multivariate statistical analysis to prioritize bioactive strains. The metabolite profiling led to the identification of two markers with lipid reducing activity in zebrafish larvae. Putative compound identification using mass spectrometry databases identified them as phosphatidic acid and aromatic polyketides derivatives-two compound classes, which were previously associated with effects on metabolic disorders. In summary, we have identified cyanobacterial strains with promising lipid reducing activity, whose bioactive compounds needs to be identified in the future.

Mitochondrial Damage-Associated Molecular Patterns and Metabolism in the Regulation of Innate Immunity

The innate immune system, as the host's first line of defense against intruders, plays a critical role in recognizing, identifying, and reacting to a wide range of microbial intruders. There is increasing evidence that mitochondrial stress is a major initiator of innate immune responses. When mitochondria's integrity is disrupted or dysfunction occurs, the mitochondria's contents are released into the cytosol. These contents, like reactive oxygen species, mitochondrial DNA, and double-stranded RNA, among others, act as damage-related molecular patterns (DAMPs) that can bind to multiple innate immune sensors, particularly pattern recognition receptors, thereby leading to inflammation. To avoid the production of DAMPs, in addition to safeguarding organelles integrity and functionality, mitochondria may activate mitophagy or apoptosis. Moreover, mitochondrial components and specific metabolic regulations modify properties of innate immune cells. These include macrophages, dendritic cells, innate lymphoid cells, and so on, in steady state or in stimulation that are involved in processes ranging from the tricarboxylic acid cycle to oxidative phosphorylation and fatty acid metabolism. Here we provide a brief summary of mitochondrial DAMPs' initiated and potentiated inflammatory response in the innate immune system. We also provide insights into how the state of activation, differentiation, and functional polarization of innate immune cells can be influenced by alteration to the metabolic pathways in mitochondria.

Post-translational modifications and protein quality control of mitochondrial channels and transporters

Mitochondria play a critical role in energy metabolism and signal transduction, which is tightly regulated by proteins, metabolites, and ion fluxes. Metabolites and ion homeostasis are mainly mediated by channels and transporters present on mitochondrial membranes. Mitochondria comprise two distinct compartments, the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM), which have differing permeabilities to ions and metabolites. The OMM is semipermeable due to the presence of non-selective molecular pores, while the IMM is highly selective and impermeable due to the presence of specialized channels and transporters which regulate ion and metabolite fluxes. These channels and transporters are modulated by various post-translational modifications (PTMs), including phosphorylation, oxidative modifications, ions, and metabolites binding, glycosylation, acetylation, and others. Additionally, the mitochondrial protein quality control (MPQC) system plays a crucial role in ensuring efficient molecular flux through the mitochondrial membranes by selectively removing mistargeted or defective proteins. Inefficient functioning of the transporters and channels in mitochondria can disrupt cellular homeostasis, leading to the onset of various pathological conditions. In this review, we provide a comprehensive overview of the current understanding of mitochondrial channels and transporters in terms of their functions, PTMs, and quality control mechanisms.

Developmental Stage-Dependent Changes in Mitochondrial Function in the Brain of Offspring Following Prenatal Maternal Immune Activation

Maternal immune activation (MIA) is an important risk factor for neurodevelopmental disorders such as autism. The aim of the current study was to investigate the development-dependent changes in the mitochondrial function of MIA-exposed offspring, which may contribute to autism-like deficits. MIA was evoked by the single intraperitoneal administration of lipopolysaccharide to pregnant rats at gestation day 9.5, and several aspects of mitochondrial function in fetuses and in the brains of seven-day-old pups and adolescent offspring were analyzed along with oxidative stress parameters measurement. It was found that MIA significantly increased the activity of NADPH oxidase (NOX), an enzyme generating reactive oxygen species (ROS) in the fetuses and in the brain of seven-day-old pups, but not in the adolescent offspring. Although a lower mitochondrial membrane potential accompanied by a decreased ATP level was already observed in the fetuses and in the brain of seven-day-old pups, persistent alterations of ROS, mitochondrial membrane depolarization, and lower ATP generation with concomitant electron transport chain complexes downregulation were observed only in the adolescent offspring. We suggest that ROS observed in infancy are most likely of a NOX activity origin, whereas in adolescence, ROS are produced by damaged mitochondria. The accumulation of dysfunctional mitochondria leads to the intense release of free radicals that trigger oxidative stress and neuroinflammation, resulting in an interlinked vicious cascade.

Inhibition of Mitochondrial Uncoupling Proteins Arrests Human Spermatozoa Motility without Compromising Viability

Mitochondrial uncoupling proteins (UCPs) are central in the regulation of mitochondrial activity and reactive oxygen species (ROS) production. High oxidative stress is a major cause of male infertility; however, UCPs expression and function in human spermatozoa are still unknown. Herein, we aimed to assess the expression and function of the different homologs (UCP1-6) in human spermatozoa. For this purpose, we screened for the mRNA expression of all UCP homologs. Protein expression and immunolocalization of UCP1, UCP2, and UCP3 were also assessed. Highly motile spermatozoa were isolated from human normozoospermic seminal samples (n = 16) and incubated with genipin, an inhibitor of UCPs (0, 0.5, 5, and 50 µM) for 3 h at 37 °C. Viability and total motility were assessed. Mitochondrial membrane potential and ROS production were evaluated. Media were collected and the metabolic profile and antioxidant potential were analyzed by ¹H-NMR and FRAP, respectively. The expression of all UCP homologs (UCP1-6) mRNA by human spermatozoa is herein reported for the first time. UCP1-3 are predominant at the head equatorial segment, whereas UCP1 and UCP2 are also expressed at the spermatozoa midpiece, where mitochondria are located. The inhibition of UCPs by 50 µM genipin, resulting in the UCP3 inhibition, did not compromise sperm cell viability but resulted in irreversible total motility loss that persisted despite washing or incubation with theophylline, a cAMP activator. These effects were associated with decreased mitochondrial membrane potential and lactate production. No differences concerning UCP3 expression, however, were observed in spermatozoa from normozoospermic versus asthenozoospermic men (n = 6). The inhibition of UCPs did not increase ROS production, possibly due to the decreased mitochondrial activity and genipin antioxidant properties. In sum, UCPs are major regulators of human spermatozoa motility and metabolism. The discovery and characterization of UCPs' role in human spermatozoa can shed new light on spermatozoa ROS-related pathways and bioenergetics physiology.

The interaction of TRPV1 and lipids: Insights into lipid metabolism

Transient receptor potential vanilloid 1 (TRPV1), a non-selective ligand-gated cation channel with high permeability for Ca²⁺, has received considerable attention as potential therapeutic target for the treatment of several disorders including pain, inflammation, and hyperlipidemia. In particular, TRPV1 regulates lipid metabolism by mechanisms that are not completely understood. Interestingly, TRPV1 and lipids regulate each other in a reciprocal and complex manner. This review surveyed the recent literature dealing with the role of TRPV1 in the hyperlipidemia-associated metabolic syndrome. Besides TRPV1 structure, molecular mechanisms underlying the regulatory effect of TRPV1 on lipid metabolism such as the involvement of uncoupling proteins (UCPs), ATP-binding cassette (ABC) transporters, peroxisome proliferation-activated receptors (PPAR), sterol responsive element binding protein (SREBP), and hypoxia have been discussed. Additionally, this review extends our understanding of the lipid-dependent modulation of TRPV1 activity through affecting both the gating and the expression of TRPV1. The regulatory role of different classes of lipids such as phosphatidylinositol (PI), cholesterol, estrogen, and oleoylethanolamide (OEA), on TRPV1 has also been addressed.

UCP2 as a Cancer Target through Energy Metabolism and Oxidative Stress Control

Despite numerous therapies, cancer remains one of the leading causes of death worldwide due to the lack of markers for early detection and response to treatment in many patients. Technological advances in tumor screening and renewed interest in energy metabolism have allowed us to identify new cellular players in order to develop personalized treatments. Among the metabolic actors, the mitochondrial transporter uncoupling protein 2 (UCP2), whose expression is increased in many cancers, has been identified as an interesting target in tumor metabolic reprogramming. Over the past decade, a better understanding of its biochemical and physiological functions has established a role for UCP2 in (1) protecting cells from oxidative stress, (2) regulating tumor progression through changes in glycolytic, oxidative and calcium metabolism, and (3) increasing antitumor immunity in the tumor microenvironment to limit cancer development. With these pleiotropic roles, UCP2 can be considered as a potential tumor biomarker that may be interesting to target positively or negatively, depending on the type, metabolic status and stage of tumors, in combination with conventional chemotherapy or immunotherapy to control tumor development and increase response to treatment. This review provides an overview of the latest published science linking mitochondrial UCP2 activity to the tumor context.

Evaluation of Human Spermatozoa Mitochondrial Membrane Potential Using the JC-1 Dye

Mitochondria are fundamental for human spermatozoa motility and fertilizing ability. Mitochondria participate not only in ATP production, but also in reactive oxygen species production, redox equilibrium, and calcium regulation, all of which are central for human spermatozoa motility, capacitation, acrosome reaction, and ultimately, oocyte fertilization. Mitochondrial membrane potential is a key indicator of mitochondrial health and activity. Most commonly used methods for the study of mitochondrial membrane potential, however, cannot be applied to human spermatozoa due to their unique characteristics, including high motility and time-dependent decay of quality, limiting the study of this important parameter in these cells. Here, we describe an easy, fast, and cheap protocol for the quantitative evaluation of human spermatozoa mitochondrial membrane potential, using the fluorescent cationic dye 5,5,6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimi-dazoylcarbocyanine iodide (JC-1). JC-1 is a sensitive marker for mitochondrial membrane potential, exhibiting a potential-dependent accumulation in the mitochondria. At high mitochondrial membrane potential, JC-1 forms J-aggregates, which emit red fluorescence, whereas at low mitochondrial membrane potential, JC-1 remains at its monomer state, which emits green fluorescence. We first describe how to evaluate human spermatozoa mitochondrial membrane potential using JC-1 and a fluorescence plate reader, for high-throughput studies. The calculation of the JC-1 ratio (indicative of the J-aggregates/monomers ratio) is then used to quantitatively evaluate mitochondrial health and activity. In addition, we describe an imaging protocol for the qualitative evaluation of human spermatozoa mitochondrial membrane potential using a fluorescence microscope. This allows for a visual analysis of the results that can complement the quantitative data. These protocols can be used to study the effects of spermatozoa exposure to compounds of interest, and alterations due to diseases or different conditions. While these protocols are illustrated with human spermatozoa, they can be adapted and used on spermatozoa of different species. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Quantitative evaluation of human spermatozoa mitochondrial membrane potential using the JC-1 dye and a fluorescence plate reader Basic Protocol 2: Qualitative evaluation of human spermatozoa mitochondrial membrane potential using the JC-1 dye and fluorescence microscopy Support Protocol: Preparation of the JC-1 working solution.

Recent Advances in Molecular Research on Hydrogen Sulfide (H2S) Role in Diabetes Mellitus (DM)-A Systematic Review

Abundant experimental data suggest that hydrogen sulfide (H₂S) is related to the pathophysiology of Diabetes Mellitus (DM). Multiple molecular mechanisms, including receptors, membrane ion channels, signalingmolecules, enzymes, and transcription factors, are known to be responsible for the H₂S biological actions; however, H₂S is not fully documented as a gaseous signaling molecule interfering with DM and vascular-linked pathology. In recent decades, multiple approaches regarding therapeutic exploitation of H₂S have been identified, either based on H₂S exogenous apport or on its modulated endogenous biosynthesis. This paper aims to synthesize and systematize, as comprehensively as possible, the recent literature-related data regarding the therapeutic/rehabilitative role of H₂S in DM. This review was conducted following the “Preferred reporting items for systematic reviews and meta-analyses” (PRISMA) methodology, interrogating five international medically renowned databases by specific keyword combinations/“syntaxes” used contextually, over the last five years (2017–2021). The respective search/filtered and selection methodology we applied has identified, in the first step, 212 articles. After deploying the next specific quest steps, 51 unique published papers qualified for minute analysis resulted. To these bibliographic resources obtained through the PRISMA methodology, in order to have the best available information coverage, we added 86 papers that were freely found by a direct internet search. Finally, we selected for a connected meta-analysis eight relevant reports that included 1237 human subjects elicited from clinical trial registration platforms. Numerous H₂S releasing/stimulating compounds have been produced, some being used in experimental models. However, very few of them were further advanced in clinical studies, indicating that the development of H₂S as a therapeutic agent is still at the beginning.

Palmitate Induces Mitochondrial Energy Metabolism Disorder and Cellular Damage via the PPAR Signaling Pathway in Diabetic Cardiomyopathy

PURPOSE

To establish an in vitro lipotoxicity model with mouse cardiomyocytes (MCMs) and investigate the molecular mechanism of the peroxisome proliferator-activated receptors (PPAR) signaling on mitochondrial energy metabolism disorder and cellular injury in diabetic cardiomyopathy (DCM).

METHODS

Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed on the differentially expressed genes (DEGs) of DCM. CCK-8 method was used to detect the proliferation inhibition effect of palmitate (PA) on MCMs. Oil red O staining and mRNA levels of CD36 were used to verify intracellular lipid accumulation. DCFH-DA method was used to determine the content of intracellular reactive oxygen species (ROS), and ATP levels were detected by the ATP Detection Kit. Transmission electron microscope (TEM) was used to observe the mitochondrial structure. Western blot was used to detect the expression levels of PPARα, PPARγ, P-mTOR, mTOR, PGC-1α, UCP2, and BNP. In addition, the expression of PPARγ was also detected by cellular immunofluorescence staining. BNP levels were detected by qRT-PCR and the ELISA Kit.

RESULTS

KEGG pathway analysis combined with GO analysis has shown that PPAR signaling played a significant regulatory role in mitochondrial biogenesis and fatty acid metabolism in DCM. Then, MCMs stimulated with PA for 24 h were selected as an in vitro lipotoxicity model. PA decreased cell viability, cell membrane shrinkage, and lipid accumulation. Meanwhile, PA-induced increase in cellular ROS led to ATP generation reduction and mitochondrial damage. Furthermore, the expression levels of p-mTOR- PPARα/γ were decreased, and the expressions of PGC-1α and UCP2 were increased. The levels of BNP were elevated, demonstrating PA impaired cardiomyocytes.

CONCLUSION

Mitochondrial energy metabolism obstacle and cell injury appeared in cardiac lipotoxicity of DCM, associated with lipid accumulation and increased ROS, indicating a crosstalk with the PPAR pathway mediated mechanism.