Metabolic Effectors Research Articles

Acylglycerol Kinase Maintains Metabolic State and Immune Responses of CD8+ T Cells

CD8+ Tcell expansions and functions rely on glycolysis, but the mechanisms underlying CD8+ Tcell glycolytic metabolism remain elusive. Here, we show that acylglycerol kinase (AGK) is required for the establishment and maintenance of CD8+ Tcell metabolic and functional fitness. AGK deficiency dampens CD8+ Tcell antitumor functions invivo and perturbs CD8+ Tcell proliferation invitro. Activation of phosphatidylinositol-3-OH kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling, which mediates elevated CD8+ Tcell glycolysis, is tightly dependent on AGK kinase activity. Mechanistically, Tcell antigen receptor (TCR)- and CD28-stimulated recruitment of PTEN to the plasma membrane facilitates AGK-PTEN interaction and AGK-triggered PTEN phosphorylation, thereby restricting PTEN phosphatase activity in CD8+ Tcells. Collectively, these results demonstrate that AGK maintains CD8+ Tcell metabolic and functional state by restraining PTEN activity and highlight a critical role for AGK in CD8+ Tcell metabolic programming and effector function.

The deubiquitinase Otub1 controls the activation of CD8+ T cells and NK cells by regulating IL-15-mediated priming

CD8 T cells and natural killer (NK) cells, central cellular components of immune responses against pathogens and cancer, rely on IL-15 for homeostasis. Here we show that IL-15 also mediates homeostatic priming of CD8 T cells for antigen-stimulated activation, which is controlled by a deubiquitinase, Otub1. IL-15 mediates membrane recruitment of Otub1, which inhibits ubiquitin-dependent activation of AKT, a pivotal kinase for T cell activation and metabolism. Otub1 deficiency in mice causes aberrant responses of CD8 T cells to IL-15, rendering naive CD8 T cells hyper-sensitive to antigen stimulation characterized by enhanced metabolic reprograming and effector functions. Otub1 also controls the maturation and activation of NK cells. Consistently, Otub1 deletion profoundly enhances anticancer immunity through unleashing the activity of CD8 T cells and NK cells. These findings suggest that Otub1 controls the activation of CD8 T cells and NK cells by functioning as a checkpoint of IL-15-mediated priming.

2015-P: 14-3-3zeta Is Required for PKA-Dependent Lipolysis

The molecular scaffold, 14-3-3?, was previously found to be essential for visceral adipogenesis, but its contributions to the function of mature adipocytes is not known. As it can regulate the activities of metabolic effectors, we hypothesized that 14-3-3? also has essential roles in adipocyte function. 3T3-L1 adipocytes and mouse models were used to study if 14-3-3? regulates lipolysis. Depletion of 14-3-3? by siRNA abrogated glycerol and free fatty acid (FFA) release from 3T3-L1 cells treated with Isoproterenol (ISO, 1 μM), Forskolin (FSK, 10 μM), and dibutyryl cAMP (1 mM). In contrast, over-expression of 14-3-3? potentiated ISO-mediated FFA release. Knockdown of 14-3-3? did not affect cAMP generation in ISO- and FSK-treated 3T3-L1 cells, but mRNA levels of lipases (Atgl, Hsl, and Magl) and Pparg were reduced, suggesting a loss of adipocyte identity. Decreased activation and total expression of PKA substrates, including Hsl and CREB, were detected in 14-3-3?-depleted 3T3-L1 cells. Taken together, these data suggest that 14-3-3? is necessary for lipolysis from 3T3-L1 adipocytes. To understand adipocyte-specific roles of 14-3-3?, tamoxifen (TMX)-inducible, adipocyte-specific 14-3-3? knockout (adi14-3-3?KO) mice were used. Four weeks after TMX exposure (5 days, 50 mg/kg), no effects on body weight were found. After an overnight fast, adi14-3-3?KO mice displayed impaired lipolysis following i.p CL-316,243 (1 mg/kg) injections. In contrast, transgenic over-expression of 14-3-3? did not affect lipolysis. Adi14-3-3?KO mice also displayed glucose intolerance following i.p. glucose (2 g/kg). Real-time PCR confirmed significant reductions in Atgl, Hsl, and Pparg mRNA levels in adi14-3-3?KO mice, suggesting impaired adipocyte function. Collectively, these results demonstrate essential functions of 14-3-3? in facilitating lipolysis and, potentially, adipocyte maturity. Future studies are aimed at understanding how 14-3-3? regulates other aspects of adipocyte function, including diet-induced expansion of fat mass. Disclosure A. Oppong: None. Y. Mugabo: None. G.E. Lim: None. Funding Canadian Institutes of Health Research

ERRα as a Bridge Between Transcription and Function: Role in Liver Metabolism and Disease.

As transcriptional factors, nuclear receptors (NRs) function as major regulators of gene expression. In particular, dysregulation of NR activity has been shown to significantly alter metabolic homeostasis in various contexts leading to metabolic disorders and cancers. The orphan estrogen-related receptor (ERR) subfamily of NRs, comprised of ERRα, ERRβ, and ERRγ, for which a natural ligand has yet to be identified, are known as central regulators of energy metabolism. If AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) can be viewed as sensors of the metabolic needs of a cell and responding acutely via post-translational control of proteins, then the ERRs can be regarded as downstream effectors of metabolism via transcriptional regulation of genes for a long-term and sustained adaptive response. In this review, we will focus on recent findings centered on the transcriptional roles played by ERRα in hepatocytes. Modulation of ERRα activity in both in vitro and in vivo models via genetic or pharmacological manipulation coupled with chromatin-immunoprecipitation (ChIP)-on-chip and ChIP-sequencing (ChIP-seq) studies have been fundamental in delineating the direct roles of ERRα in the control of hepatic gene expression. These studies have identified crucial roles for ERRα in lipid and carbohydrate metabolism as well as in mitochondrial function under both physiological and pathological conditions. The regulation of ERRα expression and activity via ligand-independent modes of action including coregulator binding, post-translational modifications (PTMs) and control of protein stability will be discussed in the context that may serve as valuable tools to modulate ERRα function as new therapeutic avenues for the treatment of hepatic metabolic dysfunction and related diseases.

Toll-like receptor 2 regulates metabolic reprogramming in gastric cancer via superoxide dismutase 2.

Toll‐like receptors (TLRs) play critical roles in host defense after recognition of conserved microbial‐ and host‐derived components, and their dysregulation is a common feature of various inflammation‐associated cancers, including gastric cancer (GC). Despite the recent recognition that metabolic reprogramming is a hallmark of cancer, the molecular effectors of altered metabolism during tumorigenesis remain unclear. Here, using bioenergetics function assays on human GC cells, we reveal that ligand‐induced activation of TLR2, predominantly through TLR1/2 heterodimer, augments both oxidative phosphorylation (OXPHOS) and glycolysis, with a bias toward glycolytic activity. Notably, DNA microarray‐based expression profiling of human cancer cells stimulated with TLR2 ligands demonstrated significant enrichment of gene‐sets for oncogenic pathways previously implicated in metabolic regulation, including reactive oxygen species (ROS), p53 and Myc. Moreover, the redox gene encoding the manganese‐dependent mitochondrial enzyme, superoxide dismutase (SOD)2, was strongly induced at the mRNA and protein levels by multiple signaling pathways downstream of TLR2, namely JAK‐STAT3, JNK MAPK and NF‐κB. Furthermore, siRNA‐mediated suppression of SOD2 ameliorated the TLR2‐induced metabolic shift in human GC cancer cells. Importantly, patient‐derived tissue microarrays and bioinformatics interrogation of clinical datasets indicated that upregulated expression of TLR2 and SOD2 were significantly correlated in human GC, and the TLR2‐SOD2 axis was associated with multiple clinical parameters of advanced stage disease, including distant metastasis, microvascular invasion and stage, as well as poor survival. Collectively, our findings reveal a novel TLR2‐SOD2 axis as a potential biomarker for therapy and prognosis in cancer.

Functional Proteomics of Breast Cancer Metabolism Identifies GLUL as Responder during Hypoxic Adaptation.

Hypoxia as well as metabolism are central hallmarks of cancer, and hypoxia-inducible factors (HIFs) and metabolic effectors are crucial elements in oxygen-compromised tumor environments. Knowledge of changes in the expression of metabolic proteins in response to HIF function could provide mechanistic insights into adaptation to hypoxic stress, tumorigenesis, and disease progression. We analyzed time-resolved alterations in metabolism-associated protein levels in response to different oxygen potentials across breast cancer cell lines. Effects on the cellular metabolism of both HIF-dependent and -independent processes were analyzed by reverse-phase protein array profiling and a custom statistical model. We revealed a strong induction of glucose transporter 1 (GLUT1) and lactate dehydrogenase A (LDHA) as well as reduced glutamate-ammonia ligase (GLUL) protein levels across all cell lines tested as consistent changes upon hypoxia induction. Low GLUL protein levels were correlated with aggressive molecular subtypes in breast cancer patient data sets and also with hypoxic tumor regions in a xenograft mouse tumor model. Moreover, low GLUL expression was associated with poor survival in breast cancer patients and with high HIF-1α-expressing patient subgroups. Our data reveal time-resolved changes in the regulation of metabolic proteins under oxygen-deprived conditions and elucidate GLUL as a strong responder to HIFs and the hypoxic environment.

Powdery Mildews Are Characterized by Contracted Carbohydrate Metabolism and Diverse Effectors to Adapt to Obligate Biotrophic Lifestyle.

Powdery mildew is a widespread plant disease caused by obligate biotrophic fungal pathogens involving species-specific interactions between host and parasite. To gain genomic insights into the underlying obligate biotrophic mechanisms, we analyzed 15 microbial genomes covering powdery and downy mildews and rusts. We observed a genome-wide, massive contraction of multiple gene families in powdery mildews, such as enzymes in the carbohydrate metabolism pathway, when compared with ascomycete phytopathogens, while the fatty acid metabolism pathway maintained its integrity. We also observed significant differences in candidate secreted effector protein (CSEP) families between monocot and dicot powdery mildews, perhaps due to different selection forces. While CSEPs in monocot mildews are likely subject to positive selection causing rapid expansion, CSEP families in dicot mildews are shrinking under strong purifying selection. Our results not only illustrate obligate biotrophic mechanisms of powdery mildews driven by gene family evolution in nutrient metabolism, but also demonstrate how the divergence of CSEPs between monocot and dicot lineages might contribute to species-specific adaption.

Highly efficient 5' capping of mitochondrial RNA with NAD+ and NADH by yeast and human mitochondrial RNA polymerase

Bacterial and eukaryotic nuclear RNA polymerases (RNAPs) cap RNA with the oxidized and reduced forms of the metabolic effector nicotinamide adenine dinucleotide, NAD+ and NADH, using NAD+ and NADH as non-canonical initiating nucleotides for transcription initiation. Here, we show that mitochondrial RNAPs (mtRNAPs) cap RNA with NAD+ and NADH, and do so more efficiently than nuclear RNAPs. Direct quantitation of NAD+- and NADH-capped RNA demonstrates remarkably high levels of capping in vivo: up to ~60% NAD+ and NADH capping of yeast mitochondrial transcripts, and up to ~15% NAD+ capping of human mitochondrial transcripts. The capping efficiency is determined by promoter sequence at, and upstream of, the transcription start site and, in yeast and human cells, by intracellular NAD+ and NADH levels. Our findings indicate mtRNAPs serve as both sensors and actuators in coupling cellular metabolism to mitochondrial transcriptional outputs, sensing NAD+ and NADH levels and adjusting transcriptional outputs accordingly.

Hindbrain dorsal vagal complex AMPK controls hypothalamic gluco-regulatory transmitter and counter-regulatory hormone responses to hypoglycemia

Pharmacologic activation of the hindbrain dorsal vagal complex energy sensor 5′-adenosine monophosphate-activated protein kinase (AMPK) causes site-specific adjustments in hypothalamic AMPK activity. DVC A2 noradrenergic neurons are a likely source of metabolo-sensory cues to downstream network components as they express substrate fuel-sensitive AMPK. This study investigated the hypothesis that DVC AMPK controls hypothalamic sensor, metabolic effector transmitter, and counter-regulatory hormone responses to insulin-induced hypoglycemia. Male rats were injected into the caudal fourth ventricle with the AMPK inhibitor compound C (Ccor vehicle before hypoglycemia. Arcuate (ARH), ventromedial (VMN), and dorsomedial (DMN) nuclei and lateral hypothalamic area (LHA) were micropunch-dissected for norepinephrine ELISA and Western blot analyses. Hypoglycemic stimulation of norepinephrine activity in each site was impeded by compound C. Hypoglycemia caused drug-revocable (ARH) or -refractory (VMN, DMN) reductions in AMPK, alongside hindbrain AMPK-dependent augmentation of phospho-AMPK expression in each location. Compound C prevented hypoglycemic augmentation of gluco-stimulatory ARH neuropeptide Y, VMN neuronal nitric oxide synthase, and LHA orexin-A expression, while hypoglycemic suppression of the catabolic neuron protein markers ARH pro-opiomelanocortin and VMN glutamate decarboxylase65/67 was respectively averted or unaffected by drug treatment. DMN RFamide-related peptide-1 and -3 profiles were correspondingly amplified or suppressed hindbrain AMPK-reliant mechanisms during hypoglycemia. Results show that DVC AMPK is required for hypoglycemic intensification of norepinephrine activity in characterized hypothalamic gluco-regulatory structures, and that this sensor regulates AMPK activation and metabolic effector transmission in those sites.

Impact of Lactobacillus casei BL23 on the Host Transcriptome, Growth and Disease Resistance in Larval Zebrafish.

In this study, zebrafish were treated with Lactobacillus strains as probiotics from hatching to puberty, and the effect of treatment with L. casei BL23 on the development and immunity response of the host was investigated. Genes that were differentially expressed (DEGs) in the overall body and intestine were detected at 14 days post fertilization (dpf) and 35 dpf, respectively, using whole transcriptome sequencing (mRNAseq). We showed that zebrafish raised by continuous immersion with L. casei BL23 showed a higher final body weight at 14 dpf (P < 0.05), and 35 dpf (P < 0.01). DEGs between L. casei BL23 treatment and control group at 14 dpf were involved in myogenesis, cell adhesion, transcription regulation and DNA-binding and activator. At 35 dpf, 369 genes were DEGs in the intestine after treatment with L. casei BL23, which were involved in such categories as signaling, secretion, motor proteins, oxidoreductase and iron, tight junctions, lipid metabolism, growth regulation, proteases, and humoral and cellular effectors. KEGG analysis showed DEGs to be involved in such pathways as those associated with tight junctions and the PPAR signal pathway. RT-qPCR analysis showed that expression of insulin-like growth factors-I (igf1), peroxisome proliferator activated receptors-α (ppar-α) and -β (ppar-β), Vitamin D receptor-α (vdr-α), and retinoic acid receptor-γ (rar-γ) was up-regulated in fish treated with L. casei BL23 at 35 dpf. After 35 days of treatment, the mortality rate in L. casei BL23 treated group was lower than the control after challenge with A. hydrophila (P < 0.05), and the pro-inflammatory cytokine il-1β, anti-inflammatory cytokine il-10 and complement component 3a (c3a) showed more expression in L. casei BL23 group at 8h after challenge, 24 h after challenge, or both.. Together, these data suggest that specific Lactobacillus probiotic strains can accelerate the development profile and enhance immunity in zebrafish, which supports the rationale of early administration of probiotics in aquaculture.

The imbroglio of the physiological Cra effector clarified at last.

Owing to its role in controlling carbon and energy metabolism, the catabolite repressor/activator protein Cra has been one of the most studied prokaryotic regulators of the last 30 years. Yet, a key mechanistic detail of its biological function - i.e. the nature of the metabolic effector that rules its DNA-binding ability - has remained controversial. Despite the high affinity of Cra for fructose-1-phosphate (F1P), the prevailing view claimed that fructose-1,6-biphosphate (FBP) was the key physiological effector. Building on such responsiveness to FBP, Cra was proposed to act as a glycolytic flux sensor and central regulator of critical metabolic transactions. At the same time, data raised on the Cra protein of Pseudomonas putida ruled out that FBP could be an effector - but instead suggested that it was the unintentional carrier of a small contamination by F1P, the actual signal molecule. While these data on the P. putida Cra were received with skepticism - if not dismissal - by the community of the time, the paper by (Bley-Folly et al, 2018) now demonstrates beyond any reasonable doubt that the one and only effector of E. coli Cra is F1P and that every action of FBP on this regulator can be traced to its systematic mix with the authentic binder.

"NAD-capQ" detection and quantitation of NAD caps.

RNA 5′ cap structures comprising the metabolic effector nicotinamide adenine dinucleotide (NAD) have been identified in diverse organisms. Here we report a simple, two-step procedure to detect and quantitate NAD-capped RNA, termed “NAD-capQ.” By use of NAD-capQ we quantitate NAD-capped RNA levels in Escherichia coli, Saccharomyces cerevisiae, and human cells, and we measure increases in NAD-capped RNA levels in cells from all three organisms harboring disruptions in their respective “deNADding” enzymes. We further show that NAD-capped RNA levels in human cells respond to changes in cellular NAD concentrations, indicating that NAD capping provides a mechanism for human cells to directly sense and respond to alterations in NAD metabolism. Our findings establish NAD-capQ as a versatile, rapid, and accessible methodology to detect and quantitate 5′-NAD caps on endogenous RNA in any organism.

The Phytophthora cactorum genome provides insights into the adaptation to host defense compounds and fungicides

Phytophthora cactorum is a homothallic oomycete pathogen, which has a wide host range and high capability to adapt to host defense compounds and fungicides. Here we report the 121.5 Mb genome assembly of the P. cactorum using the third-generation single-molecule real-time (SMRT) sequencing technology. It is the second largest genome sequenced so far in the Phytophthora genera, which contains 27,981 protein-coding genes. Comparison with other Phytophthora genomes showed that P. cactorum had a closer relationship with P. parasitica, P. infestans and P. capsici. P. cactorum has similar gene families in the secondary metabolism and pathogenicity-related effector proteins compared with other oomycete species, but specific gene families associated with detoxification enzymes and carbohydrate-active enzymes (CAZymes) underwent expansion in P. cactorum. P. cactorum had a higher utilization and detoxification ability against ginsenosides–a group of defense compounds from Panax notoginseng–compared with the narrow host pathogen P. sojae. The elevated expression levels of detoxification enzymes and hydrolase activity-associated genes after exposure to ginsenosides further supported that the high detoxification and utilization ability of P. cactorum play a crucial role in the rapid adaptability of the pathogen to host plant defense compounds and fungicides.

PRL Phosphatases Promote Tumor Progression by Regulating the Level of Intracellular Magnesium

The Phosphatase of Regenerative Liver (PRL) enzymes (PRL‐1,‐2,‐3; gene name PTP4A1, PTP4A2, PTP4A3) are members of the protein tyrosine phosphatase family. These enzymes have been identified as key contributors to tumor progression and metastasis in several human cancers, yet the molecular basis of their pro‐oncogenic property is unclear. Using mass spectrometry studies, we identified the CNNM magnesium transporters as key binding partners of PRLs in an evolutionarily conserved complex that regulates the intracellular magnesium concentration. Structural analysis of this complex indicates that the second cystathionine β‐synthase (CBS) domain of CNNM underlines a binding loop unique to the CNNM family that only exists in organisms having PRL orthologs. Mutation of an evolutionarily conserved aspartic acid located in this CBS domain of CNNM3 was able to completely abolish the interaction with PRL‐2 resulting in reduced tumor growth. Also, either the abolishment of complex formation or PRL‐2 knockdown resulted in reduced magnesium transport. Since magnesium is a critical metabolic effector, we confirmed that mitochondrial respiration is altered in cells isolated from PRL2‐null animals and is associated with a lower ATP turnover. This is also consistent with the observed decreased body weight of PRL‐2−/− mice, suggesting that their cellular metabolism is inherently less efficient. As cellular magnesium transport is regulated by intrinsic mechanisms controlling various magnesium transporters and magnesium uptake in cells, we also aimed to examine the involvement of PRLs in the adaptive response related to changes in magnesium availability. Using various cell lines cultured under low magnesium conditions, we observed a decrease in intracellular magnesium levels correlating with a marked increase of PRL‐1 and ‐2 (PRL‐1/2) expression. Although the expression levels of the magnesium transporter CNNM3 remained unchanged after magnesium depletion, we found that the interaction between endogenous PRL‐1/2 and CNNM3 was also markedly increased, indicating a pivotal regulatory role for PRL‐1/2 in the complex to compensate for decreased magnesium availability. On the contrary, upon increasing intracellular magnesium levels by overexpressing the TRPM7 magnesium transporter, we observed a reduction of PRL‐1/2 expression. Consistent with this, using an in vivo reporter mouse model, PRL‐2 tissue expression was upregulated when dietary magnesium was limited. Overall, our findings suggest that PRL phosphatases regulate cellular magnesium levels, essential for cell survival/proliferation, which may explain much of the clinical relationship between PRLs and cancer.Support or Funding InformationThis research is supported by an operating grant from Canadian Institutes of Health Research (CIHR); CIHR MOP 142497.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Removal of Feedback Inhibition of Corynebacterium glutamicum Phosphoenolpyruvate Carboxylase by Addition of a Short Terminal Peptide

Phosphoenolpyruvate carboxylase (PEPC) catalyzes the carboxylation of phosphoenolpyruvate (PEP) in the presence of bicarbonate to form oxaloacetate (OAA), and it plays an important role in high-efficient production of OAA-derived metabolites such as lysine, glutamate and succinate. However, PEPCs often suffered from serious feedback inhibition by various metabolic effectors like aspartate. Here, the feedback inhibition of PEPC from Corynebacterium glutamicum was removed by adding a short terminal peptide like His-tag. The effect of His-tag location on the structure and important properties such as activity, thermostability and feedback inhibition of PEPC has been investigated. The purified untagged PEPC, Nterminal His-tagged PEPC (PEPC-N-His) and C-terminal His-tagged PEPC (PEPC-C-His) were characterized. PEPCN- His (439.71/sec/mM) showed a 1.26 and 186-fold higher catalytic efficiency than untagged PEPC (348.59/sec/mM) and PEPC-C-His (2.36/sec/mM), respectively. Both PEPCN- His and untagged PEPC were significantly inhibited by aspartate at the concentrations above 4 mM (residual activities < 10%), while PEPC-C-His was almost desensitized to aspartate within 10 mM (around 90% of residual activity). Structural analysis showed that the extension of C-terminus may cause steric hindrance for aspartate binding with enzymes, leading to the deregulation of feedback inhibition of PEPC-C-His. This study provides a deeper understanding of the effect of terminal fragments on the structure and function of PEPCs, and helps to engineer the feedback inhibition of PEPCs and structurally similar enzymes.

Mitochondrial cyclophilin D ablation is associated with the activation of Akt/p70S6K pathway in the mouse kidney

The mitochondrial matrix protein cyclophilin D (CypD) is an essential component of the mitochondrial permeability transition pore (MPTP). Here we characterized the effects of CypD ablation on bioenergetics in the kidney. CypD loss triggers a metabolic shift in Ppif−/− male and female mouse kidneys towards glycolysis and Krebs cycle activity. The shift is accompanied by increased glucose consumption and a transcriptional upregulation of effectors of glucose metabolism in the kidney. These included activation of Akt, AMPK (only in males) and p70S6K kinases. Gender specific differences between the Ppif−/− male and female mouse kidneys were observed including activation of pro-surviving ERK1/2 kinase and inhibited expression of pro-apoptotic and pro-fibrotic JNK and TGFβ1 proteins in Ppif−/− females. They also showed the highest expression of phosphorylated-ERK1/2 and Akt S473 proteins of all four investigated animal groups. Furthermore, Ppif−/− females showed higher lactate concentrations and ATP/ADP-ratios in the kidney than males. These metabolic and transcriptional modifications could provide an additional level of protection to Ppif−/− females. In summary, loss of mitochondrial CypD results in a shift in bioenergetics and in activation of glucose-metabolism regulating Akt/AMPK/p70S6 kinase pathways that is expected to affect the capability of Ppif−/− mice kidneys to react to stimuli and injury.

AKT modulates the autophagy-lysosome pathway via TFEB

The serine and threonine kinase AKT (also known as protein kinase B, PKB) integrates inputs from growth factors and metabolic effectors to control key multifunctional signaling hubs via direct phos...

Cold-induced conversion of cholesterol to bile acids in mice shapes the gut microbiome and promotes adaptive thermogenesis

Adaptive thermogenesis is an energy-demanding process that is mediated by cold-activated beige and brown adipocytes, and it entails increased uptake of carbohydrates, as well as lipoprotein-derived triglycerides and cholesterol, into these thermogenic cells. Here we report that cold exposure in mice triggers a metabolic program that orchestrates lipoprotein processing in brown adipose tissue (BAT) and hepatic conversion of cholesterol to bile acids via the alternative synthesis pathway. This process is dependent on hepatic induction of cytochrome P450, family 7, subfamily b, polypeptide 1 (CYP7B1) and results in increased plasma levels, as well as fecal excretion, of bile acids that is accompanied by distinct changes in gut microbiota and increased heat production. Genetic and pharmacological interventions that targeted the synthesis and biliary excretion of bile acids prevented the rise in fecal bile acid excretion, changed the bacterial composition of the gut and modulated thermogenic responses. These results identify bile acids as important metabolic effectors under conditions of sustained BAT activation and highlight the relevance of cholesterol metabolism by the host for diet-induced changes of the gut microbiota and energy metabolism.

Dipeptidyl Peptidase-4 and Adolescent Idiopathic Scoliosis: Expression in Osteoblasts

It has been proposed that girls with adolescent idiopathic scoliosis (AIS) tend to have a taller stature and a lower body mass index. Energy homeostasis, that is known to affect bone growth, could contribute to these characteristics. In circulation, dipeptidyl peptidase-4 (DPP-4) inactivates glucagon-like peptide-1 (GLP-1), an incretin that promotes insulin secretion and sensitivity. Our objectives were to investigate DPP-4 status in plasma and in osteoblasts of AIS subjects and controls and to evaluate the regulatory role of metabolic effectors on DPP-4 expression. DPP-4 activity was assessed in plasma of 113 girls and 62 age-matched controls. Osteoblasts were isolated from bone specimens of AIS patients and controls. Human cells were incubated with glucose, insulin, GLP-1 and butyrate. Gene and protein expressions were evaluated by RT-qPCR and Western blot. Our results showed 14% inferior plasma DPP-4 activity in AIS patients when compared to healthy controls (P = 0.0357). Similarly, osteoblasts derived from AIS subjects had lower DPP-4 gene and protein expression than controls by 90.5% and 57.1% respectively (P < 0.009). DPP-4 expression was regulated in a different manner in osteoblasts isolated from AIS participants compared to controls. Our results suggest a role for incretins in AIS development and severity.

Metabolic network failures in Alzheimer's disease: A biochemical road map

IntroductionThe Alzheimer's Disease Research Summits of 2012 and 2015 incorporated experts from academia, industry, and nonprofit organizations to develop new research directions to transform our understanding of Alzheimer's disease (AD) and propel the development of critically needed therapies. In response to their recommendations, big data at multiple levels are being generated and integrated to study network failures in disease. We used metabolomics as a global biochemical approach to identify peripheral metabolic changes in AD patients and correlate them to cerebrospinal fluid pathology markers, imaging features, and cognitive performance. MethodsFasting serum samples from the Alzheimer's Disease Neuroimaging Initiative (199 control, 356 mild cognitive impairment, and 175 AD participants) were analyzed using the AbsoluteIDQ-p180 kit. Performance was validated in blinded replicates, and values were medication adjusted. ResultsMultivariable-adjusted analyses showed that sphingomyelins and ether-containing phosphatidylcholines were altered in preclinical biomarker-defined AD stages, whereas acylcarnitines and several amines, including the branched-chain amino acid valine and α-aminoadipic acid, changed in symptomatic stages. Several of the analytes showed consistent associations in the Rotterdam, Erasmus Rucphen Family, and Indiana Memory and Aging Studies. Partial correlation networks constructed for Aβ1–42, tau, imaging, and cognitive changes provided initial biochemical insights for disease-related processes. Coexpression networks interconnected key metabolic effectors of disease. DiscussionMetabolomics identified key disease-related metabolic changes and disease-progression-related changes. Defining metabolic changes during AD disease trajectory and its relationship to clinical phenotypes provides a powerful roadmap for drug and biomarker discovery.