Hyperketonemia decreases mitochondrial membrane potential and its normalization with chromium (III) supplementation in monocytes

Circular RNA Foxo3 in cardiac ischemia-reperfusion injury in heart transplantation: A new regulator and target

Ischemia-reperfusion (I/R) injury occurring in heart transplantation (HT) remains as a leading cause of transplant heart graft failure. Circular RNAs (circRNAs) play important roles in gene regulation and diseases. However, the impact of circRNAs on I/R injury during HT remains unknown. This study aims to investigate the role of circular RNA Foxo3 (circFoxo3) in I/R injury in HT. Using an in vivo mouse HT model and an in vitro cardiomyocyte culture model, we demonstrated that circFoxo3 is significantly upregulated in I/R-injured hearts and hypoxia/reoxygenation (H/R)-damaged cardiomyocytes. Knockdown of circFoxo3 using siRNA not only reduces cell apoptosis and death, mitochondrial damage, and expression of apoptosis/death-related genes in vitro, but also protects heart grafts from prolonged cold I/R injury in HT. We also show that circFoxo3 interacts with Foxo3 proteins and inhibits the phosphorylation of Foxo3 and that it indirectly affects the expression of miR-433 and miR-136. In conclusion, circRNA is involved in I/R injury in HT and knockdown of circFoxo3 with siRNA can reduce I/R injury and improve heart graft function through interaction with Foxo3. This study highlights that circRNA is a new type of molecular regulator and a potential target for preventing I/R injury in HT.

Melanoma-Time to fast or time to feast? An interplay between PPARs, metabolism and immunity

Development and progression of melanoma can be accelerated by intensification of particular metabolic pathways, such as aerobic glycolysis and avid amino acid catabolism, and is accompanied by aberrant immune responses within the tumor microenvironment. Contrary to other cancer types, melanoma reveals some unique tissue-specific features, such as melanogenesis, which is intertwined with metabolism. Nuclear peroxisome proliferator-activated receptors (PPARs) take part in regulation of systemic and cellular metabolism, inflammation and melanogenesis. They appear as a focal regulatory point for these three distinct processes by occupying the intersection among AMP-dependent protein kinase (AMPK), mammalian target of rapamycin (mTOR) and PPAR gamma coactivator 1-alpha (PGC-1α) signalling pathways. When deregulated, they may accelerate melanoma malignant growth. Presenting the contribution of PPARα and PPARγ in melanoma biology, we attempt to ask how two contrasting metabolic states: obesity and fasting, can change progression of the disease and possible outcome of the treatment. This short essay is aimed to provoke a discussion about some practical implications for melanoma prevention and treatment, especially: how metabolic manipulation may be exploited to overcome immunosuppression and support immune checkpoint blockade efficacy.

High Concentration of Ketone Body β-Hydroxybutyrate Modifies Synaptic Vesicle Cycle and Depolarizes Plasma Membrane of Rat Brain Synaptosomes

Ketoacidosis is a dangerous complication of diabetes mellitus in which plasma levels of ketone bodies can reach 20-25 mM. This condition is life-threatening. In contrast, a ketogenic diet, achieving plasma levels of ketone bodies of about 4-5 mM, can be used for treating different brain diseases. However, the factors leading to the conversion of the neuroprotective ketone bodies' action to the neurotoxic action during ketoacidosis are still unknown. We investigated the influence of high concentration (25 mM) of the main ketone body, β-hydroxybutyrate (BHB), on intrasynaptosomal pH (pHi), synaptic vesicle cycle, plasma membrane, and mitochondrial potentials. Using the fluorescent dye BCECF-AM, it was shown that BHB at concentrations of 8 and 25 mM did not influence pHi in synaptosomes. By means of the fluorescent dye acridine orange, it was demonstrated that 25 mM of BHB had no effect on exocytosis but inhibited compensatory endocytosis by 5-fold. Increasing buffer capacity with 25 mM HEPES did not affect endocytosis. Glucose abolished BHB-induced endocytosis inhibition. Using the fluorescent dye DiSC3(5), it was shown that 25 mM of BHB induced a significant plasma membrane depolarization. This effect was not impacted by glucose. Using the fluorescent dye rhodamine-123, it was shown that BHB alone (25 mМ) did not alter the potential of intrasynaptosomal mitochondria.Importantly, the high concentration of BHB (25 mМ) causes the depolarization of the plasma membrane and stronger inhibition of endocytosis compared with the intermediate concentration (8 mM).

2,3-Pyridine dicarboxylic acid functionalized gold nanoparticles: Insight into experimental conditions for Cr3+ sensing

Selectivity of gold nanoparticles (AuNPs) depends upon surface functionality; small changes in structure or concentration bring significant changes in the behavior of AuNPs. In this study, citrate-capped AuNPs were functionalized with ortho-dicarboxylate substituted pyridine (2,3-PDCA) and detailed studies on experimental conditions were carried out to check the stability of AuNPs and response for Cr³⁺. Stability of PDCA-AuNPs was found sensitive to the pH, ionic strength of buffer and its type. Capping behavior of PDCA on C-AuNPs was examined by FTIR spectroscopy. Surface morphology and size of synthesized AuNPs were confirmed by AFM, XRD, and DLS techniques where particles were found 11nm in size, monodisperse and spherical in shape. Interaction of stabilized AuNPs was tested with various metal ions; where Cr³⁺ induced the changes in localized surface plasmon band (LSPR) of PDCA-AuNPs which leads to a color change from wine red to violet blue. The phenomenon is explained as cooperative effect of citrate and pyridine nitrogen on surface of AuNPs in contrary to meta-dicarboxylate substituted pyridine derivatives. Further, under optimized and controlled conditions Cr³⁺ shows linear response with decrease in absorbance at LSPR intensity of AuNPs (518nm). Moreover, to demonstrate the applicability of method, Cr³⁺ was determined in the presence of Cr (VI) which shows 96% recovery.

Metabolic abnormalities induced by mitochondrial dysfunction in skeletal muscle of the renal carcinoma Eker (TSC2+/-) rat model

Tuberous sclerosis complex 2 (TSC2) is a mediator of insulin signal transduction, and a loss of function in TSC2 induces hyperactivation of mTORC1 pathway, which leads to tumorigenesis. We have previously demonstrated that Eker rat model, which is heterozygous for a TSC2 mutation, exhibits hyperglycemia and hyperketonemia. The present study was to investigate whether these changes also can affect metabolism in skeletal muscle of the Eker rat. Wild-type (TSC2+/+) and Eker (TSC2+/-) rats underwent an oral glucose tolerance test, and the latter showed decrease in whole-body glucose utilization. Additionally, reductions in the expression of glycolysis-, lipolysis-, and ketone body-related genes in skeletal muscle were observed in Eker rats. Furthermore, ATP content and mitochondrial DNA copy number were lower in skeletal muscle of Eker rats. These data demonstrate that heterozygous to mutation TSC2 not only affects the liver metabolism, but also skeletal muscle metabolism, via mitochondrial dysfunction.

Suppression of tumor growth by Pleurotus ferulae ethanol extract through induction of cell apoptosis, and inhibition of cell proliferation and migration

Cancer is the second leading cause of death worldwide. Edible medicinal mushrooms have been used in traditional medicine as regimes for cancer patients. Recently anti-cancer bioactive components from some mushrooms have been isolated and their anti-cancer effects have been tested. Pleurotus ferulae, a typical edible medicinal mushroom in Xinjiang China, has also been used to treat cancer patients in folk medicine. However, little studies have been reported on the anti-cancer components of Pleurotus ferulae. This study aims to extract bioactive components from Pleurotus ferulae and to investigate the anti-cancer effects of the extracts. We used ethanol to extract anti-cancer bioactive components enriched with terpenoids from Pleurotus ferulae. We tested the anti-tumour effects of ethanol extracts on the melanoma cell line B16F10, the human gastric cancer cell line BGC 823 and the immortalized human gastric epithelial mucosa cell line GES-1 in vitro and a murine melanoma model in vivo. Cell toxicity and cell proliferation were measured by MTT assays. Cell cycle progression, apoptosis, caspase 3 activity, mitochondrial membrane potential (MMP), migration and gene expression were studied in vitro. PFEC suppressed tumor cell growth, inhibited cell proliferation, arrested cells at G0/G1 phases and was not toxic to non-cancer cells. PFEC also induced cell apoptosis and necrosis, increased caspase 3 activity, reduced the MMP, prevented cell invasion and changed the expression of genes associated with apoptosis and the cell cycle. PFEC delayed tumor formation and reduced tumor growth in vivo. In conclusion, ethanol extracted components from Pleurotus ferulae exert anti-cancer effects through direct suppression of tumor cell growth and invasion, demonstrating its therapeutic potential in cancer treatment.

Increased susceptibility of natural killer T-cell-deficient mice to acetaminophen-induced liver injury

Acetaminophen (APAP) overdose causes severe, fulminant liver injury. The underlying mechanism of APAP-induced liver injury (AILI), studied by a murine model, displays similar characteristics of injury as those observed in patients. Previous studies suggest that aside from APAP-induced direct damage to hepatocytes, the hepatic innate immune system is activated and may contribute to the overall pathogenesis of AILI. The current study employed the use of two murine natural killer (NK) cells with T-cell receptor (NKT) cell knockout models (CD1d(-/-) and Jα18(-/-) ) to elucidate the specific role of NKT cells in AILI. Compared to wild-type (WT) mice, NKT cell-deficient mice were more susceptible to AILI, as indicated by higher serum alanine transaminase levels and mortality. Increased levels of cytochrome P450 2E1 (CYP2E1) protein expression and activities, which resulted in increased APAP protein adduct formation, were observed in livers of APAP-treated NKT cell-deficient mice, compared to WT mice. Compared to WT mice, starvation of NKT cell-deficient mice induced a higher increase of ketone bodies, which up-regulate CYP2E1 through protein stabilization.

CONCLUSION

Our data revealed a novel role of NKT cells in regulating responses to starvation-induced metabolic stress. Elevated ketone body production in NKT cell-deficient mice resulted in increased CYP2E1-mediated APAP biotransformation and susceptibility to AILI.

Hyperketonemia induces upregulation of LFA-1 in monocytes, which is mediated by ROS and P38 MAPK activation

Type 1 diabetic patients have hyperketonemia, elevated levels of pro-inflammatory and oxidative stress markers, and a higher incidence of vascular disease. This study examines the hypothesis that hyperketonemia increases reactive oxygen species (ROS) and is in part responsible for increased expression of adhesion molecules in monocytes. THP-1 monocytes were treated with acetoacetate (AA) or β-hydroxybutyrate (BHB) (0–10 mmol/L) for 24 h. Results show that AA, but not BHB, increases ROS production in monocytes. Pretreatment of monocytes with N-acetylcysteine (NAC) inhibited AA-induced ROS production. AA treatment induced upregulation of LFA-1 and pretreatment of monocytes with NAC or an inhibitor to p38 MAPK inhibited this upregulation in monocytes. This suggests that physiological concentrations of AA can contribute to increased ROS and activation of p38 MAPK, which may be responsible for AA-induced upregulation of LFA-1 in monocytes. Thus, hyperketonemia contributes to the risk for cardiovascular disease in type 1 diabetes.

Molecular mechanisms of chromium in alleviating insulin resistance

Type 2 diabetes is often associated with obesity, dyslipidemia and cardiovascular anomalies and is a major health problem approaching global epidemic proportions. Insulin resistance, a prediabetic condition, precedes the onset of frank type 2 diabetes and offers potential avenues for early intervention to treat the disease. Although lifestyle modifications and exercise can reduce the incidence of diabetes, compliance has proved to be difficult, warranting pharmacological interventions. However, most of the currently available drugs that improve insulin sensitivity have adverse effects. Therefore, attractive strategies to alleviate insulin resistance include dietary supplements. One such supplement is chromium, which has been shown to reduce insulin resistance in some, but not all, studies. Furthermore, the molecular mechanisms of chromium in alleviating insulin resistance remain elusive. This review examines emerging reports on the effect of chromium, as well as molecular and cellular mechanisms by which chromium may provide beneficial effects in alleviating insulin resistance.