The mitochondrial fission protein Drp1 in liver is required to mitigate NASH and prevents the activation of the mitochondrial ISR

Mitochondrial structure and function: A new direction for the targeted treatment of chronic liver disease with Chinese herbal medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive fat accumulation, biological clock dysregulation, viral infections, and sustained inflammatory responses can lead to liver inflammation, fibrosis, and cancer, thus promoting the development of chronic liver disease. A comprehensive understanding of the etiological factors leading to chronic liver disease and the intrinsic mechanisms influencing its onset and progression can aid in identifying potential targets for targeted therapy. Mitochondria, as key organelles that maintain the metabolic homeostasis of the liver, provide an important foundation for exploring therapeutic targets for chronic liver disease. Recent studies have shown that active ingredients in herbal medicines and their natural products can modulate chronic liver disease by influencing the structure and function of mitochondria. Therefore, studying how Chinese herbs target mitochondrial structure and function to treat chronic liver diseases is of great significance.

AIM OF THE STUDY

Investigating the prospects of herbal medicine the Lens of chronic liver disease based on mitochondrial structure and function.

MATERIALS AND METHODS

A computerized search of PubMed was conducted using the keywords "mitochondrial structure", "mitochondrial function", "mitochondria and chronic liver disease", "botanicals, mitochondria and chronic liver disease".Data from the Web of Science and Science Direct databases were also included. The research findings regarding herbal medicines targeting mitochondrial structure and function for the treatment of chronic liver disease are summarized.

RESULTS

A computerized search of PubMed using the keywords "mitochondrial structure", "mitochondrial function", "mitochondria and chronic liver disease", "phytopharmaceuticals, mitochondria, and chronic liver disease", as well as the Web of Science and Science Direct databases was conducted to summarize information on studies of mitochondrial structure- and function-based Chinese herbal medicines for the treatment of chronic liver disease and to suggest that the effects of herbal medicines on mitochondrial division and fusion.The study suggested that there is much room for research on the influence of Chinese herbs on mitochondrial division and fusion.

CONCLUSIONS

Targeting mitochondrial structure and function is crucial for herbal medicine to combat chronic liver disease.

Mitochondrial dynamics and psychiatric disorders: The missing link

Elucidating the molecular mechanisms of psychopathology is crucial for optimized diagnosis and treatment. Accumulating data have underlined how mitochondrial bioenergetics affect major psychiatric disorders. However, how mitochondrial dynamics, a term addressing mitochondria quality control, including mitochondrial fission, fusion, biogenesis and mitophagy, is implicated in psychopathologies remains elusive. In this review, we summarize the existing literature on mitochondrial dynamics perturbations in psychiatric disorders/neuropsychiatric phenotypes. We include preclinical/clinical literature on mitochondrial dynamics recalibrations in anxiety, depression, post-traumatic stress disorder (PTSD), bipolar disorder and schizophrenia. We discuss alterations in mitochondrial network, morphology and shape, molecular markers of the mitochondrial dynamics machinery and mitochondrial DNA copy number (mtDNAcn) in animal models and human cohorts in brain and peripheral material. By looking for common altered mitochondrial dynamics patterns across diagnoses/phenotypes, we highlight mitophagy and biogenesis as regulators of anxiety and depression pathophysiology, respectively, as well as the fusion mediator dynamin-like 120 kDa protein (Opa1) as a molecular hub contributing to psychopathology. Finally, we comment on limitations and future directions in this novel neuropsychiatry field.

Mechanistic Insights into Metabolic Function of Dynamin-Related Protein 1 (DRP1)

DRP1 plays crucial roles in mitochondrial and peroxisome fission. However, the mechanisms underlying the functional regulation of DRP1 in adipose tissue during obesity remain unclear. To elucidate the metabolic and pathological significance of diminished DRP1 in obese adipose tissue, we utilized adipose tissue-specific DRP1 KO mice challenged with an HFD. We observed significant metabolic dysregulations in the KO mice. Mechanistically, DRP1 exerts multifaceted functions in mitochondrial dynamics and ER-lipid droplet cross-talk in normal mice. Loss-of-function of DRP1 resulted in abnormally giant mitochondrial shapes, distorted mitochondrial membrane structure, and disrupted cristae architecture. Meanwhile, DRP1 deficiency induced the retention of nascent lipid droplets in ER, leading to perturbed overall lipid dynamics in the KO mice. Collectively, dysregulation of the dynamics of mitochondria, ER, and lipid droplets contributes to whole-body metabolic disorders, as evidenced by perturbations in energy metabolites. Our findings demonstrate that DRP1 plays a pivotal role in energy homeostasis in adipose tissue during obesity.

GSDME promotes MASLD by regulating pyroptosis, Drp1 citrullination-dependent mitochondrial dynamic, and energy balance in intestine and liver

Dysregulated metabolism, cell death, and inflammation contribute to the development of metabolic dysfunction-associated steatohepatitis (MASH). Pyroptosis, a recently identified form of programmed cell death, is closely linked to inflammation. However, the precise role of pyroptosis, particularly gasdermin-E (GSDME), in MASH development remains unknown. In this study, we observed GSDME cleavage and GSDME-associated interleukin-1β (IL-1β)/IL-18 induction in liver tissues of MASH patients and MASH mouse models induced by a choline-deficient high-fat diet (CDHFD) or a high-fat/high-cholesterol diet (HFHC). Compared with wild-type mice, global GSDME knockout mice exhibited reduced liver steatosis, steatohepatitis, fibrosis, endoplasmic reticulum stress, lipotoxicity and mitochondrial dysfunction in CDHFD- or HFHC-induced MASH models. Moreover, GSDME knockout resulted in increased energy expenditure, inhibited intestinal nutrient absorption, and reduced body weight. In the mice with GSDME deficiency, reintroduction of GSDME in myeloid cells-rather than hepatocytes-mimicked the MASH pathologies and metabolic dysfunctions, as well as the changes in the formation of neutrophil extracellular traps and hepatic macrophage/monocyte subclusters. These subclusters included shifts in Tim4+ or CD163+ resident Kupffer cells, Ly6Chi pro-inflammatory monocytes, and Ly6CloCCR2loCX3CR1hi patrolling monocytes. Integrated analyses of RNA sequencing and quantitative proteomics revealed a significant GSDME-dependent reduction in citrullination at the arginine-114 (R114) site of dynamin-related protein 1 (Drp1) during MASH. Mutation of Drp1 at R114 reduced its stability, impaired its ability to redistribute to mitochondria and regulate mitophagy, and ultimately promoted its degradation under MASH stress. GSDME deficiency reversed the de-citrullination of Drp1R114, preserved Drp1 stability, and enhanced mitochondrial function. Our study highlights the role of GSDME in promoting MASH through regulating pyroptosis, Drp1 citrullination-dependent mitochondrial function, and energy balance in the intestine and liver, and suggests that GSDME may be a potential therapeutic target for managing MASH.

Is mitochondrial morphology important for cellular physiology?

Mitochondria are double membrane-bound organelles the network morphology of which in cells is shaped by opposing events of fusion and fission executed by dynamin-like GTPases. Mutations in these genes can perturb the form and functions of mitochondria in cell and animal models of mitochondrial diseases. An expanding array of chemical, mechanical, and genetic stressors can converge on mitochondrial-shaping proteins and disrupt mitochondrial morphology. In recent years, studies aimed at disentangling the multiple roles of mitochondrial-shaping proteins beyond fission or fusion have provided insights into the homeostatic relevance of mitochondrial morphology. Here, I review the pleiotropy of mitochondrial fusion and fission proteins with the aim of understanding whether mitochondrial morphology is important for cell and tissue physiology.

Mitochondrial dysfunction: A promising therapeutic target for liver diseases

The liver is an important metabolic and detoxification organ and hence demands a large amount of energy, which is mainly produced by the mitochondria. Liver tissues of patients with alcohol-related or non-alcohol-related liver diseases contain ultrastructural mitochondrial lesions, mitochondrial DNA damage, disturbed mitochondrial dynamics, and compromised ATP production. Overproduction of mitochondrial reactive oxygen species induces oxidative damage to mitochondrial proteins and mitochondrial DNA, decreases mitochondrial membrane potential, triggers hepatocyte inflammation, and promotes programmed cell death, all of which impair liver function. Mitochondrial DNA may be a potential novel non-invasive biomarker of the risk of progression to liver cirrhosis and hepatocellular carcinoma in patients infected with the hepatitis B virus. We herein present a review of the mechanisms of mitochondrial dysfunction in the development of acute liver injury and chronic liver diseases, such as hepatocellular carcinoma, viral hepatitis, drug-induced liver injury, alcoholic liver disease, and non-alcoholic fatty liver disease. This review also discusses mitochondrion-centric therapies for treating liver diseases.

Ginseng-derived nanoparticles alleviate alcohol-induced liver injury by activating the Nrf2/HO-1 signalling pathway and inhibiting the NF-κB signalling pathway in vitro and in vivo

BACKGROUND

Previous studies have confirmed the antioxidant and anti-inflammatory effects of active ginseng components that protect against liver injury. However, ginseng-derived nanoparticles (GDNPs), low-immunogenicity nanovesicles derived from ginseng, have not been reported to be hepatoprotective.

PURPOSE

In this study, we investigated whether GDNPs could attenuate alcohol-induced liver injury in LO2 cells and mice by modulating oxidative stress and inflammatory pathways, thereby advancing the theoretical basis for the development of novel pharmacological treatments.

STUDY DESIGN

Alcohol was used to construct in vitro and in vivo models of alcoholic liver injury. To explore the mechanisms by which GDNPs exert their protective effects against alcoholic liver injury, we examined the expression of oxidative stress-related genes and analysed inflammatory responses in vitro and in vivo. The experimental findings were verified using network pharmacology.

METHODS

The composition of the GDNPs was analysed using liquid chromatography-mass spectrometry. GDNPs were extracted and purified using differential ultracentrifugation and sucrose density gradient centrifugation. In vitro models of alcoholic liver injury were established using LO2 cells, whereas C57BL/6 J mice were used as in vivo models. Oxidative stress, inflammation, and liver injury indicators were measured using appropriate kits. Levels of proteins associated with oxidative stress and inflammation were measured via western blot, while nuclear factor erythroid2-related factor 2 (Nrf2) and NF-κB protein expression was tested using immunofluorescence, immunohistochemistry, and flow cytometry. The levels of relevant transcription factors were determined using qPCR. Experimental haematoxylin and eosin staining was used to characterise the liver histological appearance and damage in mice. Network pharmacological analysis of GDNP mRNA sequencing of GDNPs was used to predict drug targets and disease associations using TCMSP.

RESULTS

GDNPs primarily included 77 compounds, including organic acids and their derivatives, amino acids and their derivatives, sugars, terpenoids, and flavonoids. GDNPs have features that allow them to be taken up by LO2 cells and promote their proliferation. In vitro data indicated that GDNPs reduced the levels of alcohol-induced reactive oxygen species by activating the Nrf2/HO-1 signalling pathway, whilst inhibiting the NF-κB pathway and thereby reducing NO, tumour necrosis factor-α, and interleukin-1β levels to alleviate inflammation. An in vivo model showed that GDNPs improved the liver parameters and pathology in mice with alcoholic liver injury. GDNPs activate the Nrf2/HO-1/Keap1 signalling pathway in a p62-dependent manner to exert antioxidant effects. Furthermore, the TLR4/NF-κB signalling pathway was involved in the in vivo anti-inflammatory effect. Network pharmacology also confirmed that the effects of GDNPs on liver disease were associated with oxidative stress and inflammation-related targets and pathways.

CONCLUSION

This study showed for the first time that GDNPs can alleviate alcohol-induced liver damage by activating the Nrf2/HO1 signalling pathway and blocking the NF-κB signalling pathway, thus lowering oxidative stress and inflammatory responses. Hereby, we present the Nrf2/HO1 and NF-κB signalling pathways as potential targets and GDNPs as a novel therapeutic approach for the management of alcohol-induced liver damage.

Mitochondrial dynamics, quality control, and mtDNA in alcohol-associated liver disease and liver cancer

Mitochondria are intracellular organelles responsible for energy production, glucose and lipid metabolism, cell death, cell proliferation, and innate immune response. Mitochondria are highly dynamic organelles that constantly undergo fission, fusion, and intracellular trafficking, as well as degradation and biogenesis. Mitochondrial dysfunction has been implicated in a variety of chronic liver diseases including alcohol-associated liver disease, metabolic dysfunction-associated steatohepatitis, and HCC. In this review, we provide a detailed overview of mitochondrial dynamics, mitophagy, and mitochondrial DNA-mediated innate immune response, and how dysregulation of these mitochondrial processes affects the pathogenesis of alcohol-associated liver disease and HCC. Mitochondrial dynamics and mitochondrial DNA-mediated innate immune response may thereby represent an attractive therapeutic target for ameliorating alcohol-associated liver disease and alcohol-associated HCC.

Drp1 controls complex II assembly and skeletal muscle metabolism by Sdhaf2 action on mitochondria

The dynamin-related guanosine triphosphatase, Drp1 (encoded by Dnm1l), plays a central role in mitochondrial fission and is requisite for numerous cellular processes; however, its role in muscle metabolism remains unclear. Here, we show that, among human tissues, the highest number of gene correlations with DNM1L is in skeletal muscle. Knockdown of Drp1 (Drp1-KD) promoted mitochondrial hyperfusion in the muscle of male mice. Reduced fatty acid oxidation and impaired insulin action along with increased muscle succinate was observed in Drp1-KD muscle. Muscle Drp1-KD reduced complex II assembly and activity as a consequence of diminished mitochondrial translocation of succinate dehydrogenase assembly factor 2 (Sdhaf2). Restoration of Sdhaf2 normalized complex II activity, lipid oxidation, and insulin action in Drp1-KD myocytes. Drp1 is critical in maintaining mitochondrial complex II assembly, lipid oxidation, and insulin sensitivity, suggesting a mechanistic link between mitochondrial morphology and skeletal muscle metabolism, which is clinically relevant in combatting metabolic-related diseases.

A two-way street - cellular metabolism and myofibroblast contraction

Tissue fibrosis is characterised by the high-energy consumption associated with myofibroblast contraction. Although myofibroblast contraction relies on ATP production, the role of cellular metabolism in myofibroblast contraction has not yet been elucidated. Studies have so far only focused on myofibroblast contraction regulators, such as integrin receptors, TGF-β and their shared transcription factor YAP/TAZ, in a fibroblast-myofibroblast transition setting. Additionally, the influence of the regulators on metabolism and vice versa have been described in this context. However, this has so far not yet been connected to myofibroblast contraction. This review focuses on the known and unknown of how cellular metabolism influences the processes leading to myofibroblast contraction and vice versa. We elucidate the signalling cascades responsible for myofibroblast contraction by looking at FMT regulators, mechanical cues, biochemical signalling, ECM properties and how they can influence and be influenced by cellular metabolism. By reviewing the existing knowledge on the link between cellular metabolism and the regulation of myofibroblast contraction, we aim to pinpoint gaps of knowledge and eventually help identify potential research targets to identify strategies that would allow switching tissue fibrosis towards tissue regeneration.

VCD-induced menopause mouse model reveals reprogramming of hepatic metabolism

OBJECTIVE

Menopause adversely impacts systemic energy metabolism and increases the risk of metabolic disease(s) including hepatic steatosis, but the mechanisms are largely unknown. Dosing female mice with vinyl cyclohexene dioxide (VCD) selectively causes follicular atresia in ovaries, leading to a murine menopause-like phenotype.

METHODS

In this study, we treated female C57BL6/J mice with VCD (160 mg/kg i.p. for 20 consecutive days followed by verification of the lack of estrous cycling) to investigate changes in body composition, energy expenditure (EE), hepatic mitochondrial function, and hepatic steatosis across different dietary conditions.

RESULTS

VCD treatment induced ovarian follicular loss and increased follicle-stimulating hormone (FSH) levels in female mice, mimicking a menopause-like phenotype. VCD treatment did not affect body composition, or EE in mice on a low-fat diet (LFD) or in response to a short-term (1-week) high-fat, high sucrose diet (HFHS). However, the transition to a HFHS lowered cage activity in VCD mice. A chronic HFHS diet (16 weeks) significantly increased weight gain, fat mass, and hepatic steatosis in VCD-treated mice compared to HFHS-fed controls. In the liver, VCD mice showed suppressed hepatic mitochondrial respiration on LFD, while chronic HFHS resulted in compensatory increases in hepatic mitochondrial respiration. Also, liver RNA sequencing revealed that VCD promoted global upregulation of hepatic lipid/cholesterol synthesis pathways.

CONCLUSION

Our findings suggest that the VCD-induced menopause model compromises hepatic mitochondrial function and lipid/cholesterol homeostasis that sets the stage for HFHS diet-induced steatosis while also increasing susceptibility to obesity.

ATF4 Signaling in HIV-1 Infection: Viral Subversion of a Stress Response Transcription Factor

Cellular integrated stress response (ISR), the mitochondrial unfolded protein response (UPRmt), and IFN signaling are associated with viral infections. Activating transcription factor 4 (ATF4) plays a pivotal role in these pathways and controls the expression of many genes involved in redox processes, amino acid metabolism, protein misfolding, autophagy, and apoptosis. The precise role of ATF4 during viral infection is unclear and depends on cell hosts, viral agents, and models. Furthermore, ATF4 signaling can be hijacked by pathogens to favor viral infection and replication. In this review, we summarize the ATF4-mediated signaling pathways in response to viral infections, focusing on human immunodeficiency virus 1 (HIV-1). We examine the consequences of ATF4 activation for HIV-1 replication and reactivation. The role of ATF4 in autophagy and apoptosis is explored as in the context of HIV-1 infection programmed cell deaths contribute to the depletion of CD4 T cells. Furthermore, ATF4 can also participate in the establishment of innate and adaptive immunity that is essential for the host to control viral infections. We finally discuss the putative role of the ATF4 paralogue, named ATF5, in HIV-1 infection. This review underlines the role of ATF4 at the crossroads of multiple processes reflecting host-pathogen interactions.

LAMC2 mitigates ER stress by enhancing ER-mitochondria interaction via binding to MYH9 and MYH10

Highly proliferative and metastatic tumors are constantly exposed to both intrinsic and extrinsic factors that induce adaptation to stressful conditions. Chronic adaptation to endoplasmic reticulum (ER) ER stress is common to many different types of cancers, and poses a major challenge for acquired drug resistance. Here we report that LAMC2, an extracellular matrix protein upregulated in many types of cancers, is localized in the ER of lung, breast, and liver cancer cells. Under tunicamycin-induced ER stress, protein level of LAMC2 is upregulated. Transfection of cancer cells with LAMC2 resulted in the attenuation of ER stress phenotype, accompanied by elevation in mitochondrial membrane potential as well as reduction in reactive oxygen species (ROS) levels and apoptosis. In addition, LAMC2 forms protein complexes with MYH9 and MYH10 to promote mitochondrial aggregation and increased ER-mitochondria interaction at the perinuclear region. Moreover, overexpression of LAMC2 counteracts the effects of ER stress and promotes tumor growth in vivo. Taken together, our results revealed that in complex with MYH9 and MYH10, LAMC2 is essential for promoting ER-mitochondria interaction to alleviate ER stress and allow cancer cells to adapt and proliferate under stressful conditions. This study provides new insights and highlights the promising potential of LAMC2 as a therapeutic target for cancer treatment.

An update on the therapeutic role of RNAi in NAFLD/NASH

Unhealthy lifestyles have given rise to a growing epidemic of metabolic liver diseases, including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). NAFLD often occurs as a consequence of obesity, and currently, there is no FDA-approved drug for its treatment. However, therapeutic oligonucleotides, such as RNA interference (RNAi), represent a promising class of pharmacotherapy that can target previously untreatable conditions. The potential significance of RNAi in maintaining physiological homeostasis, understanding pathogenesis, and improving metabolic liver diseases, including NAFLD, is discussed in this article. We explore why NAFLD/NASH is an ideal target for therapeutic oligonucleotides and provide insights into the delivery platforms of RNAi and its therapeutic role in addressing NAFLD/NASH.

Mitochondrial Dysfunction in Metabolic Dysfunction Fatty Liver Disease (MAFLD)

Nonalcoholic fatty liver disease (NAFLD) has become an increasingly common disease in Western countries and has become the major cause of liver cirrhosis or hepatocellular carcinoma (HCC) in addition to viral hepatitis in recent decades. Furthermore, studies have shown that NAFLD is inextricably linked to the development of extrahepatic diseases. However, there is currently no effective treatment to cure NAFLD. In addition, in 2020, NAFLD was renamed metabolic dysfunction fatty liver disease (MAFLD) to show that its pathogenesis is closely related to metabolic disorders. Recent studies have reported that the development of MAFLD is inextricably associated with mitochondrial dysfunction in hepatocytes and hepatic stellate cells (HSCs). Simultaneously, mitochondrial stress caused by structural and functional disorders stimulates the occurrence and accumulation of fat and lipo-toxicity in hepatocytes and HSCs. In addition, the interaction between mitochondrial dysfunction and the liver-gut axis has also become a new point during the development of MAFLD. In this review, we summarize the effects of several potential treatment strategies for MAFLD, including antioxidants, reagents, and intestinal microorganisms and metabolites.

VCD-induced menopause mouse model reveals reprogramming of hepatic metabolism

Menopause adversely impacts systemic energy metabolism and increases the risk of metabolic disease(s) including hepatic steatosis, but the mechanisms are largely unknown. Dosing female mice with vinyl cyclohexene dioxide (VCD) selectively causes follicular atresia in ovaries, leading to a murine menopause-like phenotype. In this study, we treated female C57BL6/J mice with VCD (160mg/kg i.p. for 20 consecutive days followed by verification of the lack of estrous cycling) to investigate changes in body composition, energy expenditure (EE), hepatic mitochondrial function, and hepatic steatosis across different dietary conditions. VCD treatment induced ovarian follicular loss and increased follicle-stimulating hormone (FSH) levels in female mice, mimicking a menopause-like phenotype. VCD treatment did not affect body composition, or EE in mice on a low-fat diet or in response to a short-term (1-week) high-fat, high sucrose diet (HFHS). However, the transition to a HFHS lowered cage activity in VCD mice. A chronic HFHS diet (16 weeks) significantly increased weight gain, fat mass, and hepatic steatosis in VCD-treated mice compared to HFHS-fed controls. In the liver, VCD mice showed suppressed hepatic mitochondrial respiration on LFD, while chronic HFHS diet resulted in compensatory increases in hepatic mitochondrial respiration. Also, liver RNA sequencing revealed that VCD promoted global upregulation of hepatic lipid/cholesterol synthesis pathways. Our findings suggest that the VCD- induced menopause model compromises hepatic mitochondrial function and lipid/cholesterol homeostasis that sets the stage for HFHS diet-induced steatosis while also increasing susceptibility to obesity.

Evaluation of the efficacy of mitochondrial fission inhibitor (Mdivi-1) using non-alcoholic steatohepatitis (NASH) liver organoids

Non-alcoholic steatohepatitis (NASH) is known to progress to cirrhosis and hepatocellular carcinoma in some patients. Although NASH is associated with abnormal mitochondrial function related to lipid metabolism, mechanisms for the development and effective treatments are still unclear. Therefore, new approaches to elucidate the pathophysiology are needed. In the previous study, we generated liver organoids from different stages of NASH model mice that could recapitulate the part of NASH pathology. In the present study, we investigated the relationship between mitochondrial function and NASH disease by comparing NASH liver organoids (NLO) and control liver organoids (CLO). Compared with CLO, mitochondrial and organoid morphology was abnormal in NLO, with increased expression of mitochondrial mitogen protein, DRP1, and mitochondria-derived reactive oxygen species (ROS) production. Treatment of NLO with a DPR1 inhibitor, Mdivi-1 resulted in the improvement of morphology and the decreased expression of fibrosis-related markers, Col1a1 and Acta2. In addition, treatment of NASH model mice with Mdivi-1 showed a decrease in fatty liver. Mdivi-1 treatment also prevented fibrosis and ROS production in the liver. These results indicate that NLO undergoes enhanced metabolism and abnormal mitochondrial morphology compared with CLO. It was also suggested that Mdivi-1 may be useful as a therapeutic agent to ameliorate NASH pathology.

Natural Drugs: A New Direction for the Prevention and Treatment of Diabetes

Insulin resistance, as a common pathological process of many metabolic diseases, including diabetes and obesity, has attracted much attention due to its relevant influencing factors. To date, studies have mainly focused on the shared mechanisms between mitochondrial stress and insulin resistance, and they are now being pursued as a very attractive therapeutic target due to their extensive involvement in many human clinical settings. In view of the complex pathogenesis of diabetes, natural drugs have become new players in diabetes prevention and treatment because of their wide targets and few side effects. In particular, plant phenolics have received attention because of their close relationship with oxidative stress. In this review, we briefly review the mechanisms by which mitochondrial stress leads to insulin resistance. Moreover, we list some cytokines and genes that have recently been found to play roles in mitochondrial stress and insulin resistance. Furthermore, we describe several natural drugs that are currently widely used and give a brief overview of their therapeutic mechanisms. Finally, we suggest possible ideas for future research related to the unique role that natural drugs play in the treatment of insulin resistance through the above targets.

The pre-conception maternal exposure to Sofosbuvir affects the mitochondrial biogenesis in prenatal fetal tissues: Experimental study on rats

BACKGROUND

Hepatitis C virus (HCV) infection is a global public health problem and Egypt has the highest HCV prevalence worldwide. Hence, global efforts target to eliminate HCV by 2030. Sofosbuvir is a nucleotide analogue inhibitor of HCV polymerase essential for viral replication. Animal studies prove that Sofosbuvir metabolites cross the placenta and are excreted in the milk of nursing animals. We aimed to investigate the possible effects of preconception maternal exposure to Sofosbuvir on mitochondrial biogenesis in prenatal fetal liver, skeletal muscle, and placental tissues.

METHODS

The study was conducted on 20 female albino rats divided into a control group receiving a placebo and an exposed group receiving 4 mg/kg orally/day for 3 months of Sofosbuvir. At the end of the treatment period, pregnancy was induced in both groups by mating with healthy male rats overnight. At gestational day 17, all pregnant female rats were sacrificed. Each fetus was dissected to obtain the fetal liver, skeletal muscle, and placental tissues.

RESULTS

The results of our study indicated that the exposure of young female rats to Sofosbuvir affects pregnancy outcomes. Fetal liver and muscle showed lower mitochondrial DNA-copy number (mtDNA-CN) by about 24% and 29% respectively, peroxisome proliferator-activated receptor-gamma coactivator-1 alpha and its downstream targets; nuclear respiratory factor-1 and mitochondrial transcription factor A. While the placental tissues showed different patterns, particularly elevated in mtDNA-CN by about 43%.

CONCLUSIONS

The study provides preliminary evidence of the detrimental effects of Sofosbuvir on the pregnancy outcomes of the exposed females and may impair the placental and fetal organs' development. These effects may be mediated through modulating mitochondrial homeostasis and functions.

Mitochondrial morphology controls fatty acid utilization by changing CPT1 sensitivity to malonyl-CoA

Changes in mitochondrial morphology are associated with nutrient utilization, but the precise causalities and the underlying mechanisms remain unknown. Here, using cellular models representing a wide variety of mitochondrial shapes, we show a strong linear correlation between mitochondrial fragmentation and increased fatty acid oxidation (FAO) rates. Forced mitochondrial elongation following MFN2 over-expression or DRP1 depletion diminishes FAO, while forced fragmentation upon knockdown or knockout of MFN2 augments FAO as evident from respirometry and metabolic tracing. Remarkably, the genetic induction of fragmentation phenocopies distinct cell type-specific biological functions of enhanced FAO. These include stimulation of gluconeogenesis in hepatocytes, induction of insulin secretion in islet β-cells exposed to fatty acids, and survival of FAO-dependent lymphoma subtypes. We find that fragmentation increases long-chain but not short-chain FAO, identifying carnitine O-palmitoyltransferase 1 (CPT1) as the downstream effector of mitochondrial morphology in regulation of FAO. Mechanistically, we determined that fragmentation reduces malonyl-CoA inhibition of CPT1, while elongation increases CPT1 sensitivity to malonyl-CoA inhibition. Overall, these findings underscore a physiologic role for fragmentation as a mechanism whereby cellular fuel preference and FAO capacity are determined.

Sexually dimorphic hepatic mitochondrial adaptations to exercise: a mini-review

Exercise is a physiological stress that disrupts tissue and cellular homeostasis while enhancing systemic metabolic energy demand mainly through the increased workload of skeletal muscle. Although the extensive focus has been on skeletal muscle adaptations to exercise, the liver senses these disruptions in metabolic energy homeostasis and responds to provide the required substrates to sustain increased demand. Hepatic metabolic flexibility is an energetically costly process that requires continuous mitochondrial production of the cellular currency ATP. To do so, the liver must maintain a healthy functioning mitochondrial pool, attained through well-regulated and dynamic processes. Intriguingly, some of these responses are sex-dependent. This mini-review examines the hepatic mitochondrial adaptations to exercise with a focus on sexual dimorphism.