KUS121, a VCP modulator, has an ameliorating effect on acute and chronic heart failure without calcium loading via maintenance of intracellular ATP levels.

AIMS: As heart failure (HF) progresses, ATP levels in myocardial cells decrease, and myocardial contractility also decreases. Inotropic drugs improve myocardial contractility but increase ATP consumption, leading to poor prognosis. Kyoto University Substance 121 (KUS121) is known to selectively inhibit the ATPase activity of valosin-containing protein, maintain cellular ATP levels, and manifest cytoprotective effects in several pathological conditions. The aim of this study is to determine the therapeutic effect of KUS121 on HF models. METHODS AND RESULTS: Cultured cell, mouse, and canine models of HF were used to examine the therapeutic effects of KUS121. The mechanism of action of KUS121 was also examined. Administration of KUS121 to a transverse aortic constriction (TAC)-induced mouse model of HF rapidly improved the left ventricular ejection fraction and improved the creatine phosphate/ATP ratio. In a canine model of high frequency-paced HF, administration of KUS121 also improved left ventricular contractility and decreased left ventricular end-diastolic pressure without increasing the heart rate. Long-term administration of KUS121 to a TAC-induced mouse model of HF suppressed cardiac hypertrophy and fibrosis. In H9C2 cells, KUS121 reduced ER stress. Finally, in experiments using primary cultured cardiomyocytes, KUS121 improved contractility and diastolic capacity without changing peak Ca2+ levels or contraction time. These effects were not accompanied by an increase in cyclic adenosine monophosphate or phosphorylation of phospholamban and ryanodine receptors. CONCLUSIONS: KUS121 ameliorated HF by a mechanism totally different from that of conventional catecholamines. We propose that KUS121 is a promising new option for the treatment of HF.

Survival and process outgrowth of human iPSC-derived cells expressing Purkinje cell markers in a mouse model for spinocerebellar degenerative disease.

Purkinje cells are the sole output neurons of the cerebellar cortex and play central roles in the integration of cerebellum-related motor coordination and memory. The loss or dysfunction of Purkinje cells due to cerebellar atrophy leads to severe ataxia. Here we used in vivo transplantation to examine the function of human iPS cell-derived cerebellar progenitors in adult transgenic mice in which Purkinje-specific cell death occurs due to cytotoxicity of polyglutamines. Transplantation using cerebellar organoids (42-48 days in culture), which are rich in neural progenitors, showed a viability of >50% 4 weeks after transplantation. STEM121+ grafted cells extended their processes toward the deep cerebellar nuclei, superior cerebellar peduncle, and vestibulocerebellar nuclei. The transplanted cells were mostly located in the white matter, and they were not found in the Purkinje cell layer. MAP2-positive fibers seen in the molecular layer of cerebellar cortex received VGluT2 inputs from climbing fibers. Transplanted neural progenitors overgrew in the host cerebellum but were suppressed by pretreatment with the γ-secretase inhibitor DAPT. Hyperproliferation was also suppressed by transplantation with more differentiated organoids (86 days in culture) or KIRREL2-positive cells purified by FACS sorting. Transplanted cells expressed Purkinje cell markers, GABA, CALB1 and L7, though they did not show fan-shaped morphology. We attempted to improve neuronal integration of stem cell-derived cerebellar progenitors by transplantation into the adult mouse, but this was not successfully achieved. Our findings in the present study contribute to regenerative medical application for cerebellar degeneration and provide new insights into cerebellar development in future.

A novel VCP modulator KUS121 exerts renoprotective effects in ischemia-reperfusion injury with retaining ATP and restoring ERAD-processing capacity.

Acute kidney injury (AKI) is a life-threatening condition and often progresses to chronic kidney disease or the development of other organ dysfunction even after recovery. Despite the increased recognition and high prevalence of AKI worldwide, there has been no established treatment so far. The aim of this study was to investigate the renoprotective effect of Kyoto University substance 121 (KUS121), a novel valosin-containing protein modulator, on AKI. In in vitro experiments, we evaluated cell viability and ATP levels of proximal tubular cells with or without KUS121 under endoplasmic reticulum (ER) stress conditions. In in vivo experiments, the effects of KUS121 were examined in mice with AKI caused by ischemia-reperfusion injury. ER-associated degradation (ERAD)-processing capacity was evaluated by quantification of the ERAD substrate CD3delta-YFP. KUS121 protected proximal tubular cells from cell death under ER stress. The apoptotic response was mitigated as indicated by the suppression of C/EBP homologous protein expression and caspase-3 cleavage, with maintained intracellular ATP levels by KUS121 administration. KUS121 treatment suppressed the elevation of serum creatinine and neutrophil gelatinase-associated lipocalin levels and attenuated renal tubular damage after ischemia-reperfusion. The expression of inflammatory cytokines in the kidney was also suppressed in the KUS121-treated group. Valosin-containing protein expression levels were not altered by KUS121 both in vitro and in vivo. KUS121 treatment restored ERAD-processing capacity associated with potentiation of its upstream pathway, phosphorylated inositol-requiring enzyme-1α, and spliced X box-binding protein-1. In conclusion, these findings indicate that KUS121 can protect renal tubular cells from ER stress-induced injury, suggesting that KUS121 could be a novel and promising therapeutic compound for ischemia-associated AKI.NEW & NOTEWORTHY Novel findings of this study are as follows: 1) Kyoto University substance 121 (KUS121), a novel valosin-containing protein (VCP) modulator, can reduce ATP consumption of VCP; 2) KUS121 reduced endoplasmic reticulum (ER) stress and improved cell viability in proximal tubular cells; 3) KUS121 exerted renoprotective effects against ischemia-reperfusion injury; and 4) KUS121 may prevent ischemic acute kidney injury with ATP retention and restoring ER-associated degradation capacity.

KUS121 attenuates the progression of monosodium iodoacetate-induced osteoarthritis in rats.

Currently there is no effective treatment available for osteoarthritis (OA). We have recently developed Kyoto University Substances (KUSs), ATPase inhibitors specific for valosin-containing protein (VCP), as a novel class of medicine for cellular protection. KUSs suppressed intracellular ATP depletion, endoplasmic reticulum (ER) stress, and cell death. In this study, we investigated the effects of KUS121 on chondrocyte cell death. In cultured chondrocytes differentiated from ATDC5 cells, KUS121 suppressed the decline in ATP levels and apoptotic cell death under stress conditions induced by TNFα. KUS121 ameliorated TNFα-induced reduction of gene expression in chondrocytes, such as Sox9 and Col2α. KUS121 also suppressed ER stress and cell death in chondrocytes under tunicamycin load. Furthermore, intraperitoneal administration of KUS121 in vivo suppressed chondrocyte loss and proteoglycan reduction in knee joints of a monosodium iodoacetate-induced OA rat model. Moreover, intra-articular administration of KUS121 more prominently reduced the apoptosis of the affected chondrocytes. These results demonstrate that KUS121 protects chondrocytes from stress-induced cell death in vitro and in vivo, and indicate that KUS121 is a promising novel therapeutic agent to prevent the progression of OA.

VCP relocalization limits mitochondrial activity, GSH depletion and ferroptosis during starvation in PC3 prostate cancer cells.

During periods of crisis, cells must compensate to survive. To this end, cells may need to alter the subcellular localization of crucial proteins. Here, we show that during starvation, VCP, the most abundant soluble ATPase, relocalizes and forms aggregate-like structures at perinuclear regions in PC3 prostate cancer cells. This movement is associated with a lowered metabolic state, in which mitochondrial activity and ROS production are reduced. VCP appears to explicitly sense glutamine levels, as removal of glutamine from complete medium triggered VCP relocalization and its addition to starvation media blunted VCP relocalization. Cells cultured in Gln(+) starvation media exhibited uniformly distributed VCP in the cytoplasm (free VCP) and underwent ferroptotic cell death, which was associated with a decrease in GSH levels. Moreover, the addition of a VCP inhibitor, CB-5083, in starvation media prevented VCP relocalization and triggered ferroptotic cell death. Likewise, expression of GFP-fused VCP proteins, irrespective of ATPase activities, displayed free VCP and triggered cell death during starvation. These results indicate that free VCP is essential for the maintenance of mitochondrial function and that PC3 cells employ a strategy of VCP self-aggregation to suppress mitochondrial activity in order to escape cell death during starvation, a novel VCP-mediated survival mechanism.

Hop flower extracts mitigate retinal ganglion cell degeneration in a glaucoma mouse model.

In glaucoma, retinal ganglion cells degenerate progressively, leading to visual field loss and blindness. Presently, the only treatment strategy for glaucoma is lowering the intraocular pressure. However, there are cases in which patients develop progressive visual field loss even though their intraocular pressures are within normal ranges. Therefore, the development of novel therapeutic strategies is an urgent endeavor. Besides high intraocular pressure, several other factors have been proposed to be associated with glaucoma progression, e.g., myopia, blood flow impairment, and amyloid ß accumulation. We have previously reported that hop flower extracts possess γ-secretase inhibitory activities and reduce amyloid ß deposition in the brains of Alzheimer's disease model mice. In the current study, we showed that administration of hop flower extracts to glutamate-aspartate transporter (GLAST) knockout mice, the glaucoma model mice, attenuated glaucomatous retinal ganglion cell degeneration. Preservation of retinal ganglion cells in hop flower extract-administered mice was confirmed using optical coherence tomography, confocal scanning laser ophthalmoscopy, and retinal flatmount and histological evaluations. Hop flower extracts are, therefore, deemed a possible candidate as a novel therapeutic agent to treat glaucoma.

A VCP modulator, KUS121, as a promising therapeutic agent for post-traumatic osteoarthritis.

Post-traumatic osteoarthritis (PTOA) is a major cause which hinders patients from the recovery after intra-articular injuries or surgeries. Currently, no effective treatment is available. In this study, we showed that inhibition of the acute stage chondrocyte death is a promising strategy to mitigate the development of PTOA. Namely, we examined efficacies of Kyoto University Substance (KUS) 121, a valosin-containing protein modulator, for PTOA as well as its therapeutic mechanisms. In vivo, in a rat PTOA model by cyclic compressive loading, intra-articular treatments of KUS121 significantly improved the modified Mankin scores and reduced damaged-cartilage volumes, as compared to vehicle treatment. Moreover, KUS121 markedly reduced the numbers of TUNEL-, CHOP-, MMP-13-, and ADAMTS-5-positive chondrocytes in the damaged knees. In vitro, KUS121 rescued human articular chondrocytes from tunicamycin-induced cell death, in both monolayer culture and cartilage explants. It also significantly downregulated the protein or gene expression of ER stress markers, proinflammatory cytokines, and extracellular-matrix-degrading enzymes induced by tunicamycin or IL-1ß. Collectively, these results demonstrated that KUS121 protected chondrocytes from cell death through the inhibition of excessive ER stress. Therefore, KUS121 would be a new, promising therapeutic agent with a protective effect on the progression of PTOA.

Single-cell dynamics of pannexin-1-facilitated programmed ATP loss during apoptosis.

ATP is essential for all living cells. However, how dead cells lose ATP has not been well investigated. In this study, we developed new FRET biosensors for dual imaging of intracellular ATP level and caspase-3 activity in single apoptotic cultured human cells. We show that the cytosolic ATP level starts to decrease immediately after the activation of caspase-3, and this process is completed typically within 2 hr. The ATP decrease was facilitated by caspase-dependent cleavage of the plasma membrane channel pannexin-1, indicating that the intracellular decrease of the apoptotic cell is a 'programmed' process. Apoptotic cells deficient of pannexin-1 sustained the ability to produce ATP through glycolysis and to consume ATP, and did not stop wasting glucose much longer period than normal apoptotic cells. Thus, the pannexin-1 plays a role in arresting the metabolic activity of dead apoptotic cells, most likely through facilitating the loss of intracellular ATP.

Effect of VCP modulators on gene expression profiles of retinal ganglion cells in an acute injury mouse model.

In glaucoma, retinal ganglion cells are damaged, leading to the progressive constriction of the visual field. We have previously shown that the valosin-containing protein (VCP) modulators, Kyoto University Substance (KUS)121 and KUS187, prevent the death of retinal ganglion cells in animal models of glaucoma, including the one generated by N-methyl-D-aspartate (NMDA)-induced neurotoxicity. KUSs appeared to avert endoplasmic reticulum (ER) stress by maintaining ATP levels, resulting in the protection of ganglion cells from cell death. To further elucidate the protective mechanisms of KUSs, we examined gene expression profiles in affected ganglion cells. We first injected KUS-treated mice with NMDA and then isolated the affected retinal ganglion cells using fluorescence-activated cell sorting. Gene expression in the cells was quantified using a next-generation sequencer. Resultantly, we found that KUS121 upregulated several genes involved in energy metabolism. In addition, we observed the upregulation of Zfp667, which has been reported to suppress apoptosis-related genes and prevent cell death. These results further support the suitability of KUS121 as a therapeutic drug in protecting retinal ganglion cells in ophthalmic disorders, such as glaucoma.

Safety and effectiveness of a novel neuroprotectant, KUS121, in patients with non-arteritic central retinal artery occlusion: An open-label, non-randomized, first-in-humans, phase 1/2 trial.

Kyoto University Substance (KUS) 121, an ATPase inhibitor of valosin-containing protein, is a novel neuroprotectant. We tested the safety and effectiveness of KUS121 in patients with acute central retinal artery occlusion (CRAO). We conducted an investigator-initiated, first-in-humans, phase 1/2 clinical trial. Nine patients with non-arteritic CRAO symptoms lasting for 4-48 h were enrolled. These patients received daily intravitreal injections of KUS121 for 3 days: 25 µg (low-dose) in the first three patients and 50 µg (high-dose) in the next six patients. The primary endpoint was the safety of the drug. As a secondary endpoint, pharmacokinetics was evaluated. Other key secondary endpoints were changes in best-corrected visual acuity (BCVA), measured using the Early Treatment Diabetic Retinopathy Study chart, visual field scores, and retinal sensitivities between baseline and week 12; and decimal BCVA at week 12. Administration of KUS121 did not result in serious adverse events. All nine patients (100%) showed significant improvement of BCVA. Average readable letter counts, visual field scores, and retinal sensitivities also improved. Decimal BCVA at week 12 was better than 0.1 in four patients (44%) and equal to or better than 0.05 in seven patients (78%). This first-in-humans clinical trial provides support for the safety and efficacy of intravitreal KUS121 injection. To substantiate the safety and effectiveness for patients with acute CRAO, further larger scale clinical studies will be needed.

Genetic screening for potassium channel mutations in Japanese autosomal dominant spinocerebellar ataxia.

Spinocerebellar ataxia (SCA) is a genetically heterogeneous disease characterized by cerebellar ataxia. Many causative genes have been identified to date, the most common etiology being the abnormal expansion of repeat sequences, and the mutation of ion channel genes also play an important role in the development of SCA. Some of them encode calcium and potassium channels. However, due to limited reports about potassium genes in SCA, we screened 192 Japanese individuals with dominantly inherited SCA who had no abnormal repeat expansions of causative genes for potassium channel mutations (KCNC3 for SCA13 and KCND3 for SCA19/SCA22) by target sequencing. As a result, two variants were identified from two patients: c.1973G>A, p.R658Q and c.1018G>A, p.V340M for KCNC3, and no pathogenic variant was identified for KCND3. The newly identified p.V340M exists in the extracellular domain, and p.R658Q exists in the intracellular domain on the C-terminal side, although most of the reported KCNC3 mutations are present at the transmembrane site. Adult-onset and slowly progressive cerebellar ataxia are the main clinical features of SCA13 and SCA19 caused by potassium channel mutations, which was similar in our cases. SCA13 caused by KCNC3 mutations may present with deep sensory loss and cognitive impairment in addition to cerebellar ataxia. In this study, mild deep sensory loss was observed in one case. SCA caused by potassium channel gene mutations is extremely rare, and more cases should be accumulated in the future to elucidate its pathogenesis due to channel dysfunction.

OLIVe: A Genetically Encoded Fluorescent Biosensor for Quantitative Imaging of Branched-Chain Amino Acid Levels inside Single Living Cells.

Branched-chain amino acids (BCAAs) are essential amino acids, controlling cellular metabolic processes as signaling molecules; therefore, utilization of intracellular BCAAs may be regulated by the availability of nutrients in the environment. However, spatial and temporal regulation of intracellular BCAA concentration in response to environmental conditions has been unclear due to the lack of suitable methods for measuring BCAA concentrations inside single living cells. Here, we developed a Förster resonance energy transfer (FRET)-based genetically encoded biosensor for BCAAs, termed optical biosensor for leucine-isoleucine-valine (OLIVe). The biosensor showed approximately 2-fold changes in FRET values corresponding to BCAA concentrations. Importantly, FRET signals from HeLa cells expressing OLIVe in the cytoplasm and nucleus correlated with bulk intracellular BCAA concentrations determined from populations of cells by a biochemical method, and were decreased by knockdown of L-type amino acid transporter 1 (LAT1), a transporter for BCAAs, indicating that OLIVe can reliably report intracellular BCAA concentrations inside single living cells. We also succeeded in imaging BCAA concentrations in the mitochondria using mitochondria-targeted OLIVe. Using the BCAA imaging technique, we found apparently correlated concentrations between the cytoplasm and the mitochondria. We also found that extracellular non-BCAA amino acids affected intracellular BCAA concentrations. Of these amino acids, extracellular glutamine markedly increased intracellular BCAA concentrations in a LAT1-dependent manner. Unexpectedly, extracellular pyruvate was also found to have significant positive effects on maintaining intracellular BCAA concentrations, suggesting that the cells have pyruvate-dependent systems to import BCAAs and/or to regulate BCAA metabolism.

Cardioprotective Effects of VCP Modulator KUS121 in Murine and Porcine Models of Myocardial Infarction.

No effective treatment is yet available to reduce infarct size and improve clinical outcomes after acute myocardial infarction by enhancing early reperfusion therapy using primary percutaneous coronary intervention. The study showed that Kyoto University Substance 121 (KUS121) reduced endoplasmic reticulum stress, maintained adenosine triphosphate levels, and ameliorated the infarct size in a murine cardiac ischemia and reperfusion injury model. The study confirmed the cardioprotective effect of KUS121 in a porcine ischemia and reperfusion injury model. These findings confirmed that KUS121 is a promising novel therapeutic agent for myocardial infarction in conjunction with primary percutaneous coronary intervention.

Roles of Toll-like receptor 2/4, monoacylglycerol lipase, and cyclooxygenase in social defeat stress-induced prostaglandin E2 synthesis in the brain and their behavioral relevance.

Inflammation in the brain and periphery has been associated with stress-related pathology of mental illness. We have shown that prostaglandin (PG) E2, an arachidonic acid-derived lipid mediator, and innate immune receptors Toll-like receptor (TLR) 2/4 are crucial for repeated stress-induced behavioral changes in rodents. However, how the stress induces PGE2 synthesis in the brain and whether TLR2/4 are involved in the PGE2 synthesis remain unknown. Using mice lacking TLR2 and TLR4 in combination, here we show that social defeat stress (SDS) induced the PGE2 synthesis in subcortical, but not cortical, tissues in a TLR2/4-dependent manner. It is known that PGE2 in the brain is mainly derived by monoacylglycerol lipase (MAGL)-mediated conversion of endocannabinoid 2-arachidonoylglycerol to free-arachidonic acid, a substrate for cyclooxygenase (COX) for PGE2 synthesis. We found that TLR2/4 deletion reduced the mRNA expression of MAGL and COX1 in subcortical tissues after repeated SDS. Perturbation of MAGL and COX1 as well as COX2 abolished SDS-induced PGE2 synthesis in subcortical tissues. Furthermore, systemic administration of JZL184, an MAGL inhibitor, abolished repeated SDS-induced social avoidance. These results suggest that SDS induces PGE2 synthesis in subcortical regions of the brain via the MAGL-COX pathway in a TLR2/4-dependent manner, thereby leading to social avoidance.

Ellagic acid, extracted from Sanguisorba officinalis, induces G1 arrest by modulating PTEN activity in B16F10 melanoma cells.

In Chinese medicine, herbal medicine is commonly used to treat individuals suffering from many types of diseases. We thus expected that some herbal medicines would contain promising compounds for cancer chemotherapy. Indeed, we found that Sanguisorba officinalis extracts strongly inhibit the growth of B16F10 melanoma cells, and we identified ellagic acid (EA) as the responsible ingredient. B16F10 cells treated with EA exhibited strong G1 arrest accompanied by accumulation of p53, followed by inactivation of AKT. Addition of a PTEN inhibitor, but not a p53 inhibitor, abrogated the EA-induced AKT inactivation and G1 arrest. The PTEN inhibitor also diminished EA-induced p53 accumulation. Furthermore, EA apparently increased the protein phosphatase activity of PTEN, as demonstrated by the reduced phosphorylation level of FAK, a protein substrate of PTEN. Furthermore, an in vitro PTEN phosphatase assay on PIP3 showed the direct modulation of PTEN activity by EA. These results suggest that EA functions as an allosteric modulator of PTEN, enhancing its protein phosphatase activity while inhibiting its lipid phosphatase activity. It is notable that a combination of EA and cisplatin, a widely used chemotherapy agent, dramatically enhanced cell death in B16F10 cells, suggesting a promising strategy in chemotherapy.

KUS121, a valosin-containing protein modulator, attenuates ischemic stroke via preventing ATP depletion.

Reduced adenosine triphosphate (ATP) levels in ischemic stroke constitute an upstream contributor to neuronal cell death. We have recently created a small chemical, named Kyoto University Substance 121 (KUS121), which can reduce cellular ATP consumption. In this study, we examined whether KUS121 has neuroprotective effects in rodent cerebral ischemia models. We evaluated cell viability and ATP levels in vitro after oxygen glucose deprivation (OGD) in rat cortical primary neuronal cultures incubated with or without KUS121. We found that KUS121 protected neurons from cell death under OGD by preventing ATP depletion. We also used in vivo ischemic stroke models of transient distal middle cerebral artery occlusion in C57BL/6 and B-17 mice. Administration of KUS121 in these models improved functional deficits and reduced brain infarction volume after transient focal cerebral ischemia in both C57BL/6 and B-17 mice. These results indicate that KUS121 could be a novel type of neuroprotective drug for ischemic stroke.

Emodin, as a mitochondrial uncoupler, induces strong decreases in adenosine triphosphate (ATP) levels and proliferation of B16F10 cells, owing to their poor glycolytic reserve.

Many types of cancer cells show a characteristic increase in glycolysis, which is called the "Warburg effect." By screening plant extracts, we identified one that decreases cellular adenosine triphosphate (ATP) levels and suppresses proliferation of malignant melanoma B16F10 cells, but not of noncancerous MEF cells. We showed that its active ingredient is emodin, which showed strong antiproliferative effects on B16F10 cells both in vitro and in vivo. Moreover, we also found that emodin can function as a mitochondrial uncoupler. Consistently, three known mitochondrial uncouplers also displayed potent antiproliferative effects and preferential cellular ATP reduction in B16F10 cells, but not in MEF cells. These uncouplers provoked comparable mitochondrial uncoupling in both cell types, but they manifested dramatically different cellular effects. Namely in MEF cells, these uncouplers induced three to fivefold increases in glycolysis from the basal state, and this compensatory activation appeared to be responsible for the maintenance of cellular ATP levels. In contrast, B16F10 cells treated with the uncouplers showed less than a twofold enhancement of glycolysis, which was not sufficient to compensate for the decrease of ATP production. Together, these results raise the possibility that uncouplers could be effective therapeutic agents specifically for cancer cells with prominent "Warburg effect."

PPARα-Mediated Positive-Feedback Loop Contributes to Cold Exposure Memory.

Fluctuations in food availability and shifts in temperature are typical environmental changes experienced by animals. These environmental shifts sometimes portend more severe changes; e.g., chilly north winds precede the onset of winter. Such telltale signs may be indicators for animals to prepare for such a shift. Here we show that HEK293A cells, cultured under starvation conditions, can "memorize" a short exposure to cold temperature (15 °C), which was evidenced by their higher survival rate compared to cells continuously grown at 37 °C. We refer to this phenomenon as "cold adaptation". The cold-exposed cells retained high ATP levels, and addition of etomoxir, a fatty acid oxidation inhibitor, abrogated the enhanced cell survival. In our standard protocol, cold adaptation required linoleic acid (LA) supplementation along with the activity of Δ-6-desaturase (D6D), a key enzyme in LA metabolism. Moreover, supplementation with the LA metabolite arachidonic acid (AA), which is a high-affinity agonist of peroxisome proliferator-activated receptor-alpha (PPARα), was able to underpin the cold adaptation, even in the presence of a D6D inhibitor. Cold exposure with added LA or AA prompted a surge in PPARα levels, followed by the induction of D6D expression; addition of a PPARα antagonist or a D6D inhibitor abrogated both their expression, and reduced cell survival to control levels. We also found that the brief cold exposure transiently prevents PPARα degradation by inhibiting the ubiquitin proteasome system, and starvation contributes to the enhancement of PPARα activity by inhibiting mTORC1. Our results reveal an innate adaptive positive-feedback mechanism with a PPARα-D6D-AA axis that is triggered by a brief cold exposure in cells. "Cold adaptation" could have evolved to increase strength and resilience against imminent extreme cold temperatures.

A Trace Amount of Galactose, a Major Component of Milk Sugar, Allows Maturation of Glycoproteins during Sugar Starvation.

Milk sugar is composed of glucose and galactose. Galactose is less suitable as an energy source than glucose. Thus, it has been a puzzle as to why mammals utilize galactose as a major component of milk sugar. Here we show that in hypoglycemic conditions, the presence of a trace amount of galactose, but not glucose, is able to maintain the production of mature glycoproteins and to abolish cell-death-inducing endoplasmic reticulum stress. In severely sugar-limited conditions, both glucose and galactose enter into the glycolytic pathway, but galactose is not able to raise the phosphofructokinase 1 activity, leading to the accumulation of fructose-6-phosphate, which in turn is utilized for the maturation of glycoproteins (e.g., growth factor receptors) and allows the activation of their intracellular signaling and prevents cell death from hypoglycemic conditions. Thus trace amounts of galactose may play unexpectedly important roles in the growth of infants and their protection during starvation.