Changes In Mitochondrial Activity Research Articles

The Adsorption of Chlorpromazine on the Surface of Gold Nanoparticles and Its Effect on the Toxicity to Selected Mammalian Cells

Chlorpromazine (CPZ) is a first-generation neuroleptic with well-established antitumor and antiviral properties. Currently, numerous studies are focused on developing new methods for CPZ delivery; however, the knowledge regarding its conjugates with metal nanoparticles remains limited. The aim of this study was to prepare CPZ conjugates with gold nanoparticles (AuNPs) and evaluate their biological activity on human lymphocytes (HUT-78 and COLO 720L), as well as human (COLO 679) and murine (B16-F0) melanoma cells, in comparison to the effects induced by unconjugated CPZ molecules and AuNPs with well-defined properties. During the treatment of cells with CPZ, AuNPs, and CPZ-AuNP conjugates, changes in mitochondrial activity, membrane integrity, and the secretion of lipid peroxidation mediators were studied using standard biological assays such as MTT, LDH, and MDA assays. It was found that positively charged CPZ-AuNP conjugates more effectively reduced cell viability compared to AuNPs alone. The dose-dependent membrane damage was correlated with oxidative stress resulting from exposure to CPZ-AuNP conjugates. The activity of the conjugates depended on their composition and the size of the AuNPs. It was concluded that conjugating CPZ to AuNPs reduced its biological activity, while the cellular response to the treatment varied depending on the specific cell type.

Changes in mitochondrial activity under the influence of 5-ALA

Changes in mitochondrial activity under the influence of 5-ALA

Metaplastic regeneration in the mouse stomach requires a reactive oxygen species pathway

In pyloric metaplasia, mature gastric chief cells reprogram via an evolutionarily conserved process termed paligenosis to re-enter the cell cycle and become spasmolytic polypeptide-expressing metaplasia (SPEM) cells. Here, we use single-cell RNA sequencing (scRNA-seq) following injury to the murine stomach to analyze mechanisms governing paligenosis at high resolution. Injury causes induced reactive oxygen species (ROS) with coordinated changes in mitochondrial activity and cellular metabolism, requiring the transcriptional mitochondrial regulator Ppargc1a (Pgc1α) and ROS regulator Nf2el2 (Nrf2). Loss of the ROS and mitochondrial control in Ppargc1a-/- mice causes the death of paligenotic cells through ferroptosis. Blocking the cystine transporter SLC7A11(xCT), which is critical in lipid radical detoxification through glutathione peroxidase 4 (GPX4), also increases ferroptosis. Finally, we show that PGC1α-mediated ROS and mitochondrial changes also underlie the paligenosis of pancreatic acinar cells. Altogether, the results detail how metabolic and mitochondrial changes are necessary for injury response, regeneration, and metaplasia in the stomach.

Cytochrome c levels affect the TOR pathway to regulate growth and metabolism under energy-deficient conditions.

Mitochondrial function is essential for plant growth, but the mechanisms involved in adjusting growth and metabolism to changes in mitochondrial energy production are not fully understood. We studied plants with reduced expression of CYTC-1, one of two genes encoding the respiratory chain component cytochrome c (CYTc) in Arabidopsis, to understand how mitochondria communicate their status to coordinate metabolism and growth. Plants with CYTc deficiency show decreased mitochondrial membrane potential and lower ATP content, even when carbon sources are present. They also exhibit higher free amino acid content, induced autophagy, and increased resistance to nutritional stress caused by prolonged darkness, similar to plants with triggered starvation signals. CYTc deficiency affects target of rapamycin (TOR)-pathway activation, reducing S6 kinase (S6K) and RPS6A phosphorylation, as well as total S6K protein levels due to increased protein degradation via proteasome and autophagy. TOR overexpression restores growth and other parameters affected in cytc-1 mutants, even if mitochondrial membrane potential and ATP levels remain low. We propose that CYTc-deficient plants coordinate their metabolism and energy availability by reducing TOR-pathway activation as a preventive signal to adjust growth in anticipation of energy exhaustion, thus providing a mechanism by which changes in mitochondrial activity are transduced to the rest of the cell.

Human Hematopoietic Stem Cells Have Altered Mitochondrial Activity after Stem Cell Transplantation

Hematopoietic stem cells (HSCs) give rise to the entire blood system. With their high regenerative potential, they are sometimes the only curative option for many malignancies. The success of HSCT depends on both the quantity of HSCs and on their ability to produce life-long blood. However, their regenerative potential is not unlimited. Transplanted HSCs sustain injury that alters their subsequent ability to generate blood cells. This leads to ineffective hematopoiesis and can ultimately lead to graft failure. Injury to HSCs is also a risk factor for secondary neoplasms, including leukemia. Our goal is to elucidate the mechanisms behind post-transplant HSC decline. Mitochondria are critically important for HSC function (Filippi Exp Hematol 2021). During regeneration of the bone marrow, HSCs become activated and undergo mitochondrial reprogramming, including reorganization of the mitochondrial network and enhanced mitochondrial activity (Filippi et al Blood 2019, Ito et al Nat Rev Mol Cell Biol 2014). However, after transplantation, HSCs accumulate mitochondria that are abnormal in organization and activity. These abnormal mitochondria lead to decline of HSC function and ineffective hematopoiesis (Hinge et al Cell Stem Cell 2020). While these findings have been replicated in murine models, it has not been studied within the human system. Our hypothesis is that after transplantation, human HSCs have altered mitochondria leading to ineffective hematopoiesis. We examined changes in HSC function using post-transplant samples of patient's bone marrow and a xenotransplant system (human CD34+ peripheral blood stem cells transplanted into sublethally irradiated immunodeficient NOD/SCID/IL-2 receptor-γ null mice). We first measured mitochondrial membrane potential using tetramethyl rhodamine ethyl ester (TMRE) dye and analyzed via flow cytometry. Three to six months after transplant in the xenotransplant model, we found that the mitochondrial membrane potential of huCD34+CD38-CD90+ HSCs was similar to the non-transplanted HSCs. However, huCD34+CD38+ progenitors exhibited a drastic 3-fold increase in mitochondrial membrane potential in comparison to the non-transplanted, huCD34+CD38+ progenitor cells. The mitochondrial membrane potential of CD34+CD38+ progenitors from transplanted bone marrow patient samples was also higher than non-transplanted CD34+CD38+bone marrow control cells. To understand if alterations in mitochondrial activity affect HSC differentiation, we placed xenotransplanted HSCs into in vitro culture. Post-transplanted huCD34+ cells failed to expand within 6 days of in vitro culture (serum-free culture with self-renewing cytokines, SCF+TPO+FLT3) compared to huCD34+ control. In subsequent differentiation assays, post-transplanted huCD34+ cultures gave rise to myeloid cells only. This contrasts with control huCD34+ cultures that produced myeloid, erythroid, and megakaryocytic cells. Interestingly, if the post-transplanted HSCs were given serum and cytokines for differentiation after only 3 days in self-renewing conditions, the cultured cells expanded similarly to non-transplanted HSCs and generated myeloid, erythroid, and megakaryocytic cells. This suggests that transplanted HSCs have decreased proliferation and differentiation ability in comparison to non-transplanted HSCs and respond differently to cytokines in vitro. This could account for ineffective hematopoiesis observed in some post-transplant patients. In conclusion, this study indicates that both mitochondrial activity and in-vitro growth change in HSCs after transplantation, despite re-establishing quiescence. This indicates that human hematopoietic stem and progenitor cells incur injury after transplantation. These findings are clinically important as the changes in mitochondrial activity in HSCs may play a role in post-transplant hematopoietic stem cell decline. Future single cell RNA sequencing analyses will provide mechanistic information regarding post-transplant changes in metabolism and potential targets for improving HSC function in transplant patients.

Long-Term Photobiomodulation of Cellular and Mitochondrial Activities in IMR-32 Cells Using an 810 nm Light-Emitting Diode

In photobiomodulation (PBM), biological tissues are stimulated using low-energy light. Mitochondria are thought to be integral to the process, and PBM effects vary with light parameters. Biphasic curves are commonly used to describe the dose response of PBM but do not fit in some cases. Dose-dependent PBM effects, especially mitochondrial responses, must be understood to optimize clinical therapies. However, most previous studies have reported short-term mitochondrial activity changes, neglecting long-term effects or dose-dependent changes in whole transcriptomes. We studied the effects of 3-day PBM with an 810 nm circular LED beam on human neuroblastoma IMR-32 cells. Two light doses with opposite effects on mitochondrial DNA copy number were chosen to analyze total RNA, protein content and function of mitochondrial respiratory complexes, and mitochondrial morphology. Daily 15-minute 810 nm light treatment enhanced drug resistance to the mitochondrial inhibitors and uncoupling agent via two distinct mechanisms: 1.40 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> light increased cell proliferation and the proportion of cells in the cell cycle S phase; 1.95 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> light enhanced oxidative phosphorylation at the RNA, protein, and functional levels and the proportion of network-like mitochondria. Our findings reveal the complexity of PBM dose responses and provide insights into light-cell interactions.

Evidence for Sex-dependent Bmal1 Control of Mitochondrial Dynamics in Rat Kidney

The circadian clock regulates Na+ transport with a necessary diurnal variation for optimal health. The clock gene, Bmal1, is known to regulate mitochondrial O 2 consumption, but whether or how this occurs in the kidney has not been established. An estimated 95% of O 2 consumption in the kidney is linked to sodium transport. We developed and used a novel Bmal1 knockout rat on a Sprague Dawley background. Male Bmal1 -/- rats do not have the typical night-day difference in Na + excretion, while female rats maintain this pattern. We recently observed that ADP-dependent O 2 consumption in permeabilized kidney tissue was significantly higher in both sexes of Bmal1 -/- rats but only during the active/dark period. We also observed a significant increase in cytochrome c oxidase activity in Bmal1 -/- rats during the dark vs. light period (164 ± 40 vs. 306 ± 40 pmol/s·mg; p=0.0031, t-test). Since these effects were observed in both male and female rats, these changes in mitochondrial activity cannot explain the difference in diurnal sodium excretion. Since mitochondrial morphology can impact oxidative phosphorylation and energy availability, we hypothesized that Bmal1 regulates mitochondrial morphology in the kidney. Male and female global Bmal1 +/+ and Bmal1 -/- rats at 12-14 weeks of age were maintained in regular 12:12 LD cycles. Outer renal medullary tissue was dissected and prepared for mRNA expression and transmission electron microscopy (EM). For EM, tissues were obtained at light (ZT2-4) or dark (ZT14-16) periods to correspond with the minimum and maximum whole-body energy consumption and peak and trough Bmal1 protein expression. Digital droplet PCR mRNA expression was conducted from tissue collected at 4hr intervals over 24hrs. EM images appear to show an elongation of mitochondrial morphology in females but not male Bmal1 -/- during the active time of day. Mitofusion1 (Mfn1) and fission 1 (Fis1) are genes that regulate mitochondrial structural dynamics. Mfn1 and Fis1 mRNA expression over 24hrs showed a significant interaction between genotype and time of day in male rats (p=0.004 and p=0.020, respectively, 2way ANOVA). In contrast, there were no significant differences in overall Mfn1 or Fis1 expression between female Bmal1 +/+ and Bmal1 -/- rats. Our findings demonstrate that Bmal1 is crucial in maintaining mitochondrial respiration coupling and ATP generation in the kidney. Furthermore, we suggest that female Bmal1 -/- rats can better compensate for impaired respiration by mitochondrial morphological changes when the molecular clock is dysfunctional. We further propose that the rhythmicity of Na + excretion in females, but not male, Bmal1 -/- rats is due to adjustments in mitochondrial morphology. T32 HL007457, P01HL136267, AHA 908953 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Therapeutic Efficacy of Malachite Green-Based Photodynamic Therapy in Acute Myeloid Leukemia

Aim: Acute myeloid leukemia (AML) is a disease characterized by relapse and treatment resistance in most patients. Therefore, there is a need for targeted therapies in AML. Photodynamic therapy (PDT) is a promising alternative for the treatment of malignant tumors. Also, PDT has the potential to be used individually or complementally in the treatment of leukemia. In this study, it was aimed to investigate possible the effect of malachite green (MG)-based PDT on acute myeloid leukemia cells. &#x0D; Materials and Methods: Cells were incubated with 0.19, 0.39, 0.78,1.56, 3.125, and 6.25 µM MG for one hour and irradiated with 46.4 J/cm2 of light. The trypan blue test was used to assess the viability of cells, and the change in mitochondrial activity was determined by MTT. Morphological features were determined by Giemsa staining and scanning electron microscopy. Cell cycle and Annexin V/PI assays (measuring fluorescence emitted by staining reagents) were measured by flow cytometry.&#x0D; Results: With the combination of MG and light, HL60 cell viability was found to be significantly reduced compared to the control group. Giemsa staining and SEM results showed that 3.125 μM MG-based PDT induced various morphological changes in cells typical for apoptosis. Late apoptosis was observed in cells treated with 3.125 μM MG combined PDT according to Annexin/PI staining, further showing that it caused an arrest in the subG1 phase of the cell cycle. &#x0D; Conclusion: MG-based PDT has the potential to inactivate HL60 cells. Thus, MG-based PDT may ensure a promising approach for treating acute myeloid leukemia cells.

Analysis of mitochondrial respiration and ATP synthase in frozen brain tissues

Studying mitochondrial respiration capacity is essential for gaining insights into mitochondrial functions. In frozen tissue samples, however, our ability to study mitochondrial respiration is restricted by damage elicited to the inner mitochondrial membranes by freeze-thaw cycles. We developed an approach that combines multiple assays and is tailored towards assessing mitochondrial electron transport chain and ATP synthase in frozen tissues. Using small amounts of frozen tissue, we systematically analyzed the quantity as well as activity of both the electron transport chain complexes and ATP synthase in rat brains during postnatal development. We reveal a previously little-known pattern of increasing mitochondrial respiration capacity with brain development. In addition to providing proof-of-principle evidence that mitochondrial activity changes during brain development, our study details an approach that can be applicable to many other types of frozen cell or tissue samples.

N6-Isopentenyladenosine Impairs Mitochondrial Metabolism through Inhibition of EGFR Translocation on Mitochondria in Glioblastoma Cells.

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor and is poorly susceptible to cytotoxic therapies. Amplification of the epidermal growth factor receptor (EGFR) and deletion of exons 2 to 7, which generates EGFR variant III (vIII), are the most common molecular alterations of GBMs that contribute to the aggressiveness of the disease. Recently, it has been shown that EGFR/EGFRvIII-targeted inhibitors enhance mitochondrial translocation by causing mitochondrial accumulation of these receptors, promoting the tumor drug resistance; moreover, they negatively modulate intrinsic mitochondria-mediated apoptosis by sequestering PUMA, leading to impaired apoptotic response in GBM cells. N6-isopentenyladenosine (i6A or iPA), a cytokinin consisting of an adenosine linked to an isopentenyl group deriving from the mevalonate pathway, has antiproliferative effects on numerous tumor cells, including GBM cells, by inducing cell death in vitro and in vivo. Here, we observed that iPA inhibits the mitochondrial respiration in GBM cells by preventing the translocation of EGFR/EGFRvIII to the mitochondria and allowing PUMA to interact with them by promoting changes in mitochondrial activity, thus playing a critical role in cell death. Our findings clearly demonstrate that iPA interferes with mitochondrial bioenergetic capacity, providing a rationale for an effective strategy for treating GBM.

Deciphering the Role of Klf10 in the Cerebellum.

Recent studies have demonstrated a new role for Klf10, a Krüppel-like transcription factor, in skeletal muscle, specifically relating to mitochondrial function. Thus, it was of interest to analyze additional tissues that are highly reliant on optimal mitochondrial function such as the cerebellum and to decipher the role of Klf10 in the functional and structural properties of this brain region. In vivo (magnetic resonance imaging and localized spectroscopy, behavior analysis) and in vitro (histology, spectroscopy analysis, enzymatic activity) techniques were applied to comprehensively assess the cerebellum of wild type (WT) and Klf10 knockout (KO) mice. Histology analysis and assessment of locomotion revealed no significant difference in Klf10 KO mice. Diffusion and texture results obtained using MRI revealed structural changes in KO mice characterized as defects in the organization of axons. These modifications may be explained by differences in the levels of specific metabolites (myo-inositol, lactate) within the KO cerebellum. Loss of Klf10 expression also led to changes in mitochondrial activity as reflected by a significant increase in the activity of citrate synthase, complexes I and IV. In summary, this study has provided evidence that Klf10 plays an important role in energy production and mitochondrial function in the cerebellum.

In vivo alterations of mitochondrial activity and amyloidosis in early-stage senescence-accelerated mice: a positron emission tomography study

PurposeWhile marked reductions in neural activity and mitochondrial function have been reported in Alzheimer’s disease (AD), the degree of mitochondrial activity in mild cognitive impairment (MCI) or early-stage AD remains unexplored. Here, we used positron emission tomography (PET) to examine the direct relationship between mitochondrial activity (18F-BCPP-EF) and β-amyloid (Aβ) deposition (11C-PiB) in the same brains of senescence-accelerated mouse prone 10 (SAMP10) mice, an Aβ-developing neuroinflammatory animal model showing accelerated senescence with deterioration in cognitive functioning similar to that in MCI.MethodsFive- to 25-week-old SAMP10 and control SAMR1 mice, were used in the experiments. PET was used to measure the binding levels (standard uptake value ratios; SUVRs) of [18F]2-tert-butyl-4-chloro-5-2H-pyridazin-3-one (18F-BCPP-EF) for mitochondrial complex 1 availability, and 11C-PiB for Aβ deposition, in the same animals, and immunohistochemistry for ATPB (an ATP synthase on the mitochondrial inner membrane) was also performed, to determine changes in mitochondrial activity in relation to amyloid burden during the early stage of cognitive impairment.ResultsThe SUVR of 18F-BCPP-EF was significantly lower and that of 11C-PiB was higher in the 15-week-old SAMP10 mice than in the control and 5-week-old SAMP10 mice. The two parameters were found to negatively correlate with each other. The immunohistochemical analysis demonstrated temporal upregulation of ATPB levels at 15-week-old, but decreased at 25 week-old SAMP10 mice.ConclusionThe present results provide in vivo evidence of a decrease in mitochondrial energy production and elevated amyloidosis at an early stage in SAMP10 mice. The inverse correlation between these two phenomena suggests a concurrent change in neuronal energy failure by Aβ-induced elevation of neuroinflammatory responses. Comparison of PET data with histological findings suggests that temporal increase of ATPB level may not be neurofunctionally implicated during neuropathological processes, including Aβ pathology, in an animal model of early-phase AD spectrum disorder.

Elucidating the Eradication Mechanism of Perillyl Alcohol against Candida glabrata Biofilms: Insights into the Synergistic Effect with Azole Drugs.

Increased incidences of fungal infections and associated mortality have accelerated the need for effective and alternative therapeutics. Perillyl alcohol (PA) is a terpene produced by the hydroxylation of limonene via the mevalonate pathway. In pursuit of an alternative antifungal agent, we studied the effect of PA on the biofilm community of Candida glabrata and on different cellular pathways to decipher its mode of action. PA efficiently inhibited growth and eradicated biofilms by reducing carbohydrate and eDNA content in the extracellular matrix. PA reduced the activity of hydrolytic enzymes in the ECM of C. glabrata biofilm. The chemical profiling study has given insights into the overall mode of action of PA in C. glabrata and the marked involvement of the cell wall and membrane, ergosterol biosynthesis, oxidative stress, and DNA replication. The spectroscopic and RT-PCR studies suggested a strong interaction of PA with chitin, β-glucan, ergosterol, and efflux pump, thus indicating increased membrane fluidity in C. glabrata. Furthermore, the microscopic and flow cytometry analysis emphasized that PA facilitated the change in mitochondrial activity, increased Ca2+ influx via overexpression of voltage-gated Ca2+ channels, and enhanced cytochrome C release from mitochondria. In addition, PA interferes with DNA replication and thus hinders the cell cycle progression at the S-phase. All these studies together established that PA mitigates the C. glabrata biofilms by targeting multiple cellular pathways. Interestingly, PA also potentiated the efficacy of azole drugs, particularly miconazole, against C. glabrata and its clinical isolates. Conclusively, the study demonstrated the use of PA as an effective antifungal agent alone or in combination with FDA-approved conventional drugs for fungal biofilm eradication.

The mitochondrial activity of leukocytes from Artibeus jamaicensis bats remains unaltered after several weeks of flying restriction

Bats are the only flying mammals known. They have longer lifespan than other mammals of similar size and weight and can resist high loads of many pathogens, mostly viruses, with no signs of disease. These distinctive characteristics have been attributed to their metabolic rate that is thought to be the result of their flying lifestyle. Compared with non-flying mammals, bats have lower production of reactive oxygen species (ROS), and high levels of antioxidant enzymes such as superoxide dismutase. This anti-oxidative vs. oxidative profile may help to explain bat's longer than expected lifespans.The aim of this study was to assess the effect that a significant reduction in flying has on bats leukocytes mitochondrial activity. This was assessed using samples of lymphoid and myeloid cells from peripheral blood from Artibeus jamaicensis bats shortly after capture and up to six weeks after flying deprivation. Mitochondrial membrane potential (Δψm), mitochondrial calcium (mCa2+), and mitochondrial ROS (mROS) were used as key indicators of mitochondrial activity, while total ROS and glucose uptake were used as additional indicators of cell metabolism.Results showed that total ROS and glucose uptake were statistically significantly lower at six weeks of flying deprivation (p < 0.05), in both lymphoid and myeloid cells, however no significant changes in mitochondrial activity associated with flying deprivation was observed (p > 0.05).These results suggest that bat mitochondria are stable to sudden changes in physical activity, at least up to six weeks of flying deprivation. However, decrease in total ROS and glucose uptake in myeloid cells after six weeks of captivity suggest a compensatory mechanism due to the lack of the highly metabolic demands associated with flying.

Mitochondrial phenotypes in purified human immune cell subtypes and cell mixtures.

Using a high-throughput mitochondrial phenotyping platform to quantify multiple mitochondrial features among molecularly defined immune cell subtypes, we quantify the natural variation in mitochondrial DNA copy number (mtDNAcn), citrate synthase, and respiratory chain enzymatic activities in human neutrophils, monocytes, B cells, and naïve and memory T lymphocyte subtypes. In mixed peripheral blood mononuclear cells (PBMCs) from the same individuals, we show to what extent mitochondrial measures are confounded by both cell type distributions and contaminating platelets. Cell subtype-specific measures among women and men spanning four decades of life indicate potential age- and sex-related differences, including an age-related elevation in mtDNAcn, which are masked or blunted in mixed PBMCs. Finally, a proof-of-concept, repeated-measures study in a single individual validates cell type differences and also reveals week-to-week changes in mitochondrial activities. Larger studies are required to validate and mechanistically extend these findings. These mitochondrial phenotyping data build upon established immunometabolic differences among leukocyte subpopulations, and provide foundational quantitative knowledge to develop interpretable blood-based assays of mitochondrial health.

Skeletal muscle type-specific mitochondrial adaptation to high-fat diet relies on differential autophagy modulation.

In obesity, skeletal muscle mitochondrial activity changes to cope with increased nutrient availability. Autophagy has been proposed as an essential mechanism involved in the regulation of mitochondrial metabolism. Still, the contribution of autophagy to mitochondrial adaptations in skeletal muscle during obesity is unknown. Here, we show that in response to high-fat diet (HFD) feeding, distinct skeletal muscles in mice exhibit differentially regulated autophagy that may modulate mitochondrial activity. We observed that after 4 and 40weeks of high-fat diet feeding, OXPHOS subunits and mitochondrial DNA content increased in the oxidative soleus muscle. However, in gastrocnemius muscle, which has a mixed fiber-type composition, the mitochondrial mass increased only after 40weeks of HFD feeding. Interestingly, fatty acid-supported mitochondrial respiration was enhanced in gastrocnemius, but not in soleus muscle after a 4-week HFD feeding. This increased metabolic profile in gastrocnemius was paralleled by preserving autophagy flux, while autophagy flux in soleus was reduced. To determine the role of autophagy in this differential response, we used an autophagy-deficient mouse model with partial deletion of Atg7 specifically in skeletal muscle (SkM-Atg7+/- mice). We observed that Atg7 reduction resulted in diminished autophagic flux in skeletal muscle, alongside blunting the HFD-induced increase in fatty acid-supported mitochondrial respiration observed in gastrocnemius. Remarkably, SkM-Atg7+/- mice did not present increased mitochondria accumulation. Altogether, our results show that HFD triggers specific mitochondrial adaptations in skeletal muscles with different fiber type compositions, and that Atg7-mediated autophagy modulates mitochondrial respiratory capacity but not its content in response to an obesogenic diet.

Metabolic reprogramming in chondrocytes to promote mitochondrial respiration reduces downstream features of osteoarthritis

Metabolic dysfunction in chondrocytes drives the pro-catabolic phenotype associated with osteoarthritic cartilage. In this study, substitution of galactose for glucose in culture media was used to promote a renewed dependence on mitochondrial respiration and oxidative phosphorylation. Galactose replacement alone blocked enhanced usage of the glycolysis pathway by IL1β-activated chondrocytes as detected by real-time changes in the rates of proton acidification of the medium and changes in oxygen consumption. The change in mitochondrial activity due to galactose was visualized as a rescue of mitochondrial membrane potential but not an alteration in the number of mitochondria. Galactose-replacement reversed other markers of dysfunctional mitochondrial metabolism, including blocking the production of reactive oxygen species, nitric oxide, and the synthesis of inducible nitric oxide synthase. Of more clinical relevance, galactose-substitution blocked downstream functional features associated with osteoarthritis, including enhanced levels of MMP13 mRNA, MMP13 protein, and the degradative loss of proteoglycan from intact cartilage explants. Blocking baseline and IL1β-enhanced MMP13 by galactose-replacement in human osteoarthritic chondrocyte cultures inversely paralleled increases in markers associated with mitochondrial recovery, phospho-AMPK, and PGC1α. Comparisons were made between galactose replacement and the glycolysis inhibitor 2-deoxyglucose. Targeting intermediary metabolism may provide a novel approach to osteoarthritis care.

Sex Differences in Neurophysiological Changes Following Voluntary Exercise in Adolescent Rats.

Background: Adolescence is a period of time characterized by the onset of puberty and is marked by cognitive and social developments and gross physical changes that can play a role in athletic performance. Sex differences are present with differences in body size, height, physiology and behavior which contribute to differences in athletic performance as well. Pre-clinical studies representing this active group are lacking.Methods: Acute and chronic effects of exercise were evaluated. Male and female adolescent rats were given voluntary access to a running wheel for 10 consecutive days. Running behavior (males and females) and estrous cycling (females only) were analyzed daily. A second group was given 10 days of voluntary access to a running wheel, then rested for 10 days to determine the long-term effects of exercise on the adolescent brain. Brain and muscle tissue were harvested at 10 and 20 day time points to understand exercise-dependent changes in mitochondrial activity and neuroplasticity. Animal cohorts were carried out at two different sites: University of California Los Angeles and Pepperdine University.Results: On average, running distance, intensity of run, and length of running bout increased for both male and female rats across the 10 days measured. Females ran significantly further and for longer intervals compared to males. Cortical and muscle expression of PGC1α showed similar levels at 10 days regardless of sex and exercise. There was a significant increase in expression at 20 days in all groups correlating with body size (p's < 0.05). Cortical and hippocampal levels of BDNF were similar across all groups, however, BDNF was significantly higher in exercised females at the acute compared to long-term time point.Discussion: Adolescent rats allowed 10 days of exercise show changes in physiologic function. There are sex differences in running behavior not impacted by sex hormones. These results are important to further our understanding of how exercise impacts the adolescent brain.

Nanoparticles for Targeted Drug Delivery to Cancer Stem Cells: A Review of Recent Advances.

Cancer stem cells (CSCs) are a subpopulation of cells that can initiate, self-renew, and sustain tumor growth. CSCs are responsible for tumor metastasis, recurrence, and drug resistance in cancer therapy. CSCs reside within a niche maintained by multiple unique factors in the microenvironment. These factors include hypoxia, excessive levels of angiogenesis, a change of mitochondrial activity from aerobic aspiration to aerobic glycolysis, an upregulated expression of CSC biomarkers and stem cell signaling, and an elevated synthesis of the cytochromes P450 family of enzymes responsible for drug clearance. Antibodies and ligands targeting the unique factors that maintain the niche are utilized for the delivery of anticancer therapeutics to CSCs. In this regard, nanomaterials, specifically nanoparticles (NPs), are extremely useful as carriers for the delivery of anticancer agents to CSCs. This review covers the biology of CSCs and advances in the design and synthesis of NPs as a carrier in targeting cancer drugs to the CSC subpopulation of cancer cells. This review includes the development of synthetic and natural polymeric NPs, lipid NPs, inorganic NPs, self-assembling protein NPs, antibody-drug conjugates, and extracellular nanovesicles for CSC targeting.

What Is the Metabolic Amplification of Insulin Secretion and Is It (Still) Relevant?

The pancreatic beta-cell transduces the availability of nutrients into the secretion of insulin. While this process is extensively modified by hormones and neurotransmitters, it is the availability of nutrients, above all glucose, which sets the process of insulin synthesis and secretion in motion. The central role of the mitochondria in this process was identified decades ago, but how changes in mitochondrial activity are coupled to the exocytosis of insulin granules is still incompletely understood. The identification of ATP-sensitive K+-channels provided the link between the level of adenine nucleotides and the electrical activity of the beta cell, but the depolarization-induced Ca2+-influx into the beta cells, although necessary for stimulated secretion, is not sufficient to generate the secretion pattern as produced by glucose and other nutrient secretagogues. The metabolic amplification of insulin secretion is thus the sequence of events that enables the secretory response to a nutrient secretagogue to exceed the secretory response to a purely depolarizing stimulus and is thus of prime importance. Since the cataplerotic export of mitochondrial metabolites is involved in this signaling, an orienting overview on the topic of nutrient secretagogues beyond glucose is included. Their judicious use may help to define better the nature of the signals and their mechanism of action.