Metabolomic response to acute resistance exercise in healthy older adults by 1H-NMR

BACKGROUND

The favorable health-promoting adaptations to exercise result from cumulative responses to individual bouts of physical activity. Older adults often exhibit anabolic resistance; a phenomenon whereby the anabolic responses to exercise and nutrition are attenuated in skeletal muscle. The mechanisms contributing to age-related anabolic resistance are emerging, but our understanding of how chronological age influences responsiveness to exercise is incomplete. The objective was to determine the effects of healthy aging on peripheral blood metabolomic response to a single bout of resistance exercise and whether any metabolites in circulation are predictive of anabolic response in skeletal muscle.

METHODS

Thirty young (20-35 years) and 49 older (65-85 years) men and women were studied in a cross-sectional manner. Participants completed a single bout of resistance exercise consisting of eight sets of 10 repetitions of unilateral knee extension at 70% of one-repetition maximum. Blood samples were collected before exercise, immediately post exercise, and 30-, 90-, and 180-minutes into recovery. Proton nuclear magnetic resonance spectroscopy was used to profile circulating metabolites at all timepoints. Serial muscle biopsies were collected for measuring muscle protein synthesis rates.

RESULTS

Our analysis revealed that one bout of resistance exercise elicits significant changes in 26 of 33 measured plasma metabolites, reflecting alterations in several biological processes. Furthermore, 12 metabolites demonstrated significant interactions between exercise and age, including organic acids, amino acids, ketones, and keto-acids, which exhibited distinct responses to exercise in young and older adults. Pre-exercise histidine and sarcosine were negatively associated with muscle protein synthesis, as was the pre/post-exercise fold change in plasma histidine.

CONCLUSIONS

This study demonstrates that while many exercise-responsive metabolites change similarly in young and older adults, several demonstrate age-dependent changes even in the absence of evidence of sarcopenia or frailty.

TRIAL REGISTRATION

Clinical trial registry: ClinicalTrials.gov NCT03350906.

Pyruvate dehydrogenase kinase regulates vascular inflammation in atherosclerosis and increases cardiovascular risk

AIMS

Recent studies have revealed a close connection between cellular metabolism and the chronic inflammatory process of atherosclerosis. While the link between systemic metabolism and atherosclerosis is well established, the implications of altered metabolism in the artery wall are less understood. Pyruvate dehydrogenase kinase (PDK)-dependent inhibition of pyruvate dehydrogenase (PDH) has been identified as a major metabolic step regulating inflammation. Whether the PDK/PDH axis plays a role in vascular inflammation and atherosclerotic cardiovascular disease remains unclear.

METHODS AND RESULTS

Gene profiling of human atherosclerotic plaques revealed a strong correlation between PDK1 and PDK4 transcript levels and the expression of pro-inflammatory and destabilizing genes. Remarkably, the PDK1 and PDK4 expression correlated with a more vulnerable plaque phenotype, and PDK1 expression was found to predict future major adverse cardiovascular events. Using the small-molecule PDK inhibitor dichloroacetate (DCA) that restores arterial PDH activity, we demonstrated that the PDK/PDH axis is a major immunometabolic pathway, regulating immune cell polarization, plaque development, and fibrous cap formation in Apoe-/- mice. Surprisingly, we discovered that DCA regulates succinate release and mitigates its GPR91-dependent signals promoting NLRP3 inflammasome activation and IL-1β secretion by macrophages in the plaque.

CONCLUSIONS

We have demonstrated for the first time that the PDK/PDH axis is associated with vascular inflammation in humans and particularly that the PDK1 isozyme is associated with more severe disease and could predict secondary cardiovascular events. Moreover, we demonstrate that targeting the PDK/PDH axis with DCA skews the immune system, inhibits vascular inflammation and atherogenesis, and promotes plaque stability features in Apoe-/- mice. These results point toward a promising treatment to combat atherosclerosis.

Nuclear Magnetic Resonance Metabolomic Profiling and Urine Chemistries in Incident Kidney Stone Formers Compared with Controls

BACKGROUND

The urine metabolites and chemistries that contribute to kidney stone formation are not fully understood. This study examined differences between the urine metabolic and chemistries profiles of first-time stone formers and controls.

METHODS

High-resolution 1H-nuclear magnetic resonance (NMR) spectroscopy-based metabolomic analysis was performed in 24-hour urine samples from a prospective cohort of 418 first-time symptomatic kidney stone formers and 440 controls. In total, 48 NMR-quantified metabolites in addition to 12 standard urine chemistries were assayed. Analysis of covariance was used to determine the association of stone former status with urine metabolites or chemistries after adjusting for age and sex and correcting for the false discovery rate. Gradient-boosted machine methods with nested cross-validation were applied to predict stone former status.

RESULTS

Among the standard urine chemistries, stone formers had lower urine oxalate and potassium and higher urine calcium, phosphate, and creatinine. Among NMR urine metabolites, stone formers had lower hippuric acid, trigonelline, 2-furoylglycine, imidazole, and citrate and higher creatine and alanine. A cross-validated model using urine chemistries, age, and sex yielded a mean AUC of 0.76 (95% CI, 0.73 to 0.79). A cross-validated model using urine chemistries, NMR-quantified metabolites, age, and sex did not meaningfully improve the discrimination (mean AUC, 0.78; 95% CI, 0.75 to 0.81). In this combined model, among the top ten discriminating features, four were urine chemistries and six NMR-quantified metabolites.

CONCLUSIONS

Although NMR-quantified metabolites did not improve discrimination, several urine metabolic profiles were identified that may improve understanding of kidney stone pathogenesis.

NMRpQuant: an automated software for large scale urinary total protein quantification by one-dimensional 1H NMR profiles

SUMMARY

1H nuclear magnetic resonance (NMR) spectroscopy is an established bioanalytical technology for metabolic profiling of biofluids in both clinical and large-scale population screening applications. Recently, urinary protein quantification has been demonstrated using the same 1D 1H NMR experimental data captured for metabolic profiling. Here, we introduce NMRpQuant, a freely available platform that builds on these findings with both novel and further optimized computational NMR approaches for rigorous, automated protein urine quantification. The results are validated by interlaboratory comparisons, demonstrating agreement with clinical/biochemical methodologies, pointing at a ready-to-use tool for routine protein urinalyses.

AVAILABILITY AND IMPLEMENTATION

NMRpQuant was developed on MATLAB programming environment. Source code and Windows/macOS compiled applications are available at https://github.com/pantakis/NMRpQuant, and working examples are available at https://doi.org/10.6084/m9.figshare.18737189.v1.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

KATP channel dependent heart multiome atlas

Plasmalemmal ATP sensitive potassium (K_ATP) channels are recognized metabolic sensors, yet their cellular reach is less well understood. Here, transgenic Kir6.2 null hearts devoid of the K_ATP channel pore underwent multiomics surveillance and systems interrogation versus wildtype counterparts. Despite maintained organ performance, the knockout proteome deviated beyond a discrete loss of constitutive K_ATP channel subunits. Multidimensional nano-flow liquid chromatography tandem mass spectrometry resolved 111 differentially expressed proteins and their expanded network neighborhood, dominated by metabolic process engagement. Independent multimodal chemometric gas and liquid chromatography mass spectrometry unveiled differential expression of over one quarter of measured metabolites discriminating the Kir6.2 deficient heart metabolome. Supervised class analogy ranking and unsupervised enrichment analysis prioritized nicotinamide adenine dinucleotide (NAD⁺), affirmed by extensive overrepresentation of NAD⁺ associated circuitry. The remodeled metabolome and proteome revealed functional convergence and an integrated signature of disease susceptibility. Deciphered cardiac patterns were traceable in the corresponding plasma metabolome, with tissue concordant plasma changes offering surrogate metabolite markers of myocardial latent vulnerability. Thus, Kir6.2 deficit precipitates multiome reorganization, mapping a comprehensive atlas of the K_ATP channel dependent landscape.

A Randomized Trial of ω-3 Fatty Acid Supplementation and Circulating Lipoprotein Subclasses in Healthy Older Adults

BACKGROUND

Omega-3 (n-3) PUFAs are recognized for triglyceride-lowering effects in people with dyslipidemia, but it remains unclear if n-3-PUFA intake influences lipoprotein profiles in older adults without hypertriglyceridemia.

OBJECTIVES

The objective was to determine the effect of n-3-PUFA supplementation on plasma lipoprotein subfractions in healthy older men and women in the absence of cardiovascular disease (CVD) or hypertriglyceridemia. This was a secondary analysis and considered exploratory.

METHODS

Thirty young (20-35 y old) and 54 older (65-85 y old) men and women were enrolled in the study. Fasting plasma samples were collected. After baseline sample collection, 44 older adults were randomly assigned to receive either n-3-PUFA ethyl esters (3.9 g/d) or placebo (corn oil) for 6 mo. Pre- and postintervention plasma samples were used for quantitative lipoprotein subclass analysis using high-resolution proton NMR spectroscopy.

RESULTS

The number of large, least-dense LDL particles decreased 17%-18% with n-3 PUFAs compared with placebo (<1% change; P < 0.01). The number of small, dense LDL particles increased 26%-44% with n-3 PUFAs compared with placebo (∼11% decrease; P < 0.01). The cholesterol content of large HDL particles increased by 32% with n-3 PUFAs and by 2% in placebo (P < 0.01). The cholesterol content of small HDL particles decreased by 23% with n-3 PUFAs and by 2% in placebo (P < 0.01).

CONCLUSIONS

Despite increasing abundance of small, dense LDL particles that are associated with CVD risk, n-3 PUFAs reduced total triglycerides, maintained HDL, reduced systolic blood pressure, and shifted the HDL particle distribution toward a favorable cardioprotective profile in healthy older adults without dyslipidemia. This study suggests potential benefits of n-3-PUFA supplementation to lipoprotein profiles in healthy older adults without dyslipidemia, which should be considered when weighing the potential health benefits against the cost and ecological impact of widespread use of n-3-PUFA supplements.This trial was registered at clinicaltrials.gov as NCT03350906.

Impaired Muscle Mitochondrial Function in Familial Partial Lipodystrophy

CONTEXT

Familial partial lipodystrophy (FPL), Dunnigan variety is characterized by skeletal muscle hypertrophy and insulin resistance besides fat loss from the extremities. The cause for the muscle hypertrophy and its functional consequences is not known.

OBJECTIVE

To compare muscle strength and endurance, besides muscle protein synthesis rate between subjects with FPL and matched controls (n = 6 in each group). In addition, we studied skeletal muscle mitochondrial function and gene expression pattern to help understand the mechanisms for the observed differences.

METHODS

Body composition by dual-energy X-ray absorptiometry, insulin sensitivity by minimal modelling, assessment of peak muscle strength and fatigue, skeletal muscle biopsy and calculation of muscle protein synthesis rate, mitochondrial respirometry, skeletal muscle transcriptome, proteome, and gene set enrichment analysis.

RESULTS

Despite increased muscularity, FPL subjects did not demonstrate increased muscle strength but had earlier fatigue on chest press exercise. Decreased mitochondrial state 3 respiration in the presence of fatty acid substrate was noted, concurrent to elevated muscle lactate and decreased long-chain acylcarnitine. Based on gene transcriptome, there was significant downregulation of many critical metabolic pathways involved in mitochondrial biogenesis and function. Moreover, the overall pattern of gene expression was indicative of accelerated aging in FPL subjects. A lower muscle protein synthesis and downregulation of gene transcripts involved in muscle protein catabolism was observed.

CONCLUSION

Increased muscularity in FPL is not due to increased muscle protein synthesis and is likely due to reduced muscle protein degradation. Impaired mitochondrial function and altered gene expression likely explain the metabolic abnormalities and skeletal muscle dysfunction in FPL subjects.

1H Nuclear Magnetic Resonance Spectroscopy-Based Methods for the Quantification of Proteins in Urine

We described several postprocessing methods to measure protein concentrations in human urine from existing ¹H nuclear magnetic resonance (NMR) metabolomic spectra: (1) direct spectral integration, (2) integration of NCD spectra (NCD = 1D NOESY-CPMG), (3) integration of SMolESY-filtered 1D NOESY spectra (SMolESY = Small Molecule Enhancement SpectroscopY), (4) matching protein patterns, and (5) TSP line integral and TSP linewidth. Postprocessing consists of (a) removal of the metabolite signals (demetabolization) and (b) extraction of the protein integral from the demetabolized spectra. For demetabolization, we tested subtraction of the spin-echo 1D spectrum (CPMG) from the regular 1D spectrum and low-pass filtering of 1D NOESY by its derivatives (c-SMolESY). Because of imperfections in the demetabolization, in addition to direct integration, we extracted protein integrals by the piecewise comparison of demetabolized spectra with the reference spectrum of albumin. We analyzed 42 urine samples with protein content known from the bicinchoninic acid (BCA) assay. We found excellent correlation between the BCA assay and the demetabolized NMR integrals. We have provided conversion factors for calculating protein concentrations in mg/mL from spectral integrals in mM. Additionally, we found the trimethylsilyl propionate (TSP, NMR standard) spectral linewidth and the TSP integral to be good indicators of protein concentration. The described methods increase the information content of urine NMR metabolomics spectra by informing clinical studies of protein concentration.

Radiation Induced Metabolic Alterations Associate With Tumor Aggressiveness and Poor Outcome in Glioblastoma

Glioblastoma (GBM) is uniformly fatal with a 1-year median survival, despite best available treatment, including radiotherapy (RT). Impacts of prior RT on tumor recurrence are poorly understood but may increase tumor aggressiveness. Metabolic changes have been investigated in radiation-induced brain injury; however, the tumor-promoting effect following prior radiation is lacking. Since RT is vital to GBM management, we quantified tumor-promoting effects of prior RT on patient-derived intracranial GBM xenografts and characterized metabolic alterations associated with the protumorigenic microenvironment. Human xenografts (GBM143) were implanted into nude mice 24 hrs following 20 Gy cranial radiation vs. sham animals. Tumors in pre-radiated mice were more proliferative and more infiltrative, yielding faster mortality (p < 0.0001). Histologic evaluation of tumor associated macrophage/microglia (TAMs) revealed cells with a more fully activated ameboid morphology in pre-radiated animals. Microdialyzates from radiated brain at the margin of tumor infiltration contralateral to the site of implantation were analyzed by unsupervised liquid chromatography-mass spectrometry (LC-MS). In pre-radiated animals, metabolites known to be associated with tumor progression (i.e., modified nucleotides and polyols) were identified. Whole-tissue metabolomic analysis of pre-radiated brain microenvironment for metabolic alterations in a separate cohort of nude mice using ¹H-NMR revealed a significant decrease in levels of antioxidants (glutathione (GSH) and ascorbate (ASC)), NAD⁺, Tricarboxylic acid cycle (TCA) intermediates, and rise in energy carriers (ATP, GTP). GSH and ASC showed highest Variable Importance on Projection prediction (VIPpred) (1.65) in Orthogonal Partial least square Discriminant Analysis (OPLS-DA); Ascorbate catabolism was identified by GC-MS. To assess longevity of radiation effects, we compared survival with implantation occurring 2 months vs. 24 hrs following radiation, finding worse survival in animals implanted at 2 months. These radiation-induced alterations are consistent with a chronic disease-like microenvironment characterized by reduced levels of antioxidants and NAD⁺, and elevated extracellular ATP and GTP serving as chemoattractants, promoting cell motility and vesicular secretion with decreased levels of GSH and ASC exacerbating oxidative stress. Taken together, these data suggest IR induces tumor-permissive changes in the microenvironment with metabolomic alterations that may facilitate tumor aggressiveness with important implications for recurrent glioblastoma. Harnessing these metabolomic insights may provide opportunities to attenuate RT-associated aggressiveness of recurrent GBM.

Distinct Influence of Omega-3 Fatty Acids on the Plasma Metabolome of Healthy Older Adults

Omega-3 polyunsaturated fatty acids (n3-PUFA) are well recognized for their potent triglyceride-lowering effects, but the potential influence of these bioactive lipids on other biological processes, particularly in the context of healthy aging, remains unknown. With the goal of gaining new insight into some less well-characterized biological effects of n3-PUFAs in healthy older adults, we performed metabolomics of fasting peripheral blood plasma collected from 12 young adults and 12 older adults before and after an open-label intervention of n3-PUFA (3.9 g/day, 2.7 g eicosapentaenoic [EPA], 1.2 g docosahexaenoic [DHA]). Proton nuclear magnetic resonance (1H-NMR) based lipoprotein subclass analysis revealed the expected reduction in total triglyceride (TG), but also demonstrated that n3-PUFA supplementation reduced very low-density lipoprotein (VLDL) particle number, modestly increased high-density lipoprotein (HDL) cholesterol, and shifted the composition of HDL subclasses. Further metabolite profiling by 1H-NMR and mass spectrometry revealed pronounced changes in phospholipids, cholesterol esters, diglycerides, and triglycerides following n3-PUFA supplementation. Furthermore, significant changes in hydroxyproline, kynurenine, and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF) following n3-PUFA supplementation provide further insight into some less well-recognized biological effects of n3-PUFA supplementation, including possible effects on protein metabolism, the kynurenine pathway, and glucose metabolism.

TFAM Enhances Fat Oxidation and Attenuates High-Fat Diet-Induced Insulin Resistance in Skeletal Muscle

Diet-induced insulin resistance (IR) adversely affects human health and life span. We show that muscle-specific overexpression of human mitochondrial transcription factor A (TFAM) attenuates high-fat diet (HFD)-induced fat gain and IR in mice in conjunction with increased energy expenditure and reduced oxidative stress. These TFAM effects on muscle are shown to be exerted by molecular changes that are beyond its direct effect on mitochondrial DNA replication and transcription. TFAM augmented the muscle tricarboxylic acid cycle and citrate synthase facilitating energy expenditure. TFAM enhanced muscle glucose uptake despite increased fatty acid (FA) oxidation in concert with higher β-oxidation capacity to reduce the accumulation of IR-related carnitines and ceramides. TFAM also increased pAMPK expression, explaining enhanced PGC1α and PPARβ, and reversing HFD-induced GLUT4 and pAKT reductions. TFAM-induced mild uncoupling is shown to protect mitochondrial membrane potential against FA-induced uncontrolled depolarization. These coordinated changes conferred protection to TFAM mice against HFD-induced obesity and IR while reducing oxidative stress with potential translational opportunities.

Kidney harvesting and metabolite extraction for metabolomics studies in rodents

Elucidating the metabolic changes that accompany disease states via metabolomics analysis of tissues has become an important avenue of exploration in biomarker and therapeutic target discovery. Conventional harvesting techniques rely on post-euthanasia tissue harvest which introduces ischemic conditions and subsequent metabolome changes that may ultimately introduce artifacts into final analyses. In this chapter, we present protocols for low-ischemia time rapid kidney tissue harvest followed by metabolite extraction for metabolomics studies in rodents.

New aurone epoxide and auronolignan from the heartwood of Cotinus coggygria Scop

New aurone epoxide, 2,10-oxy-10-methoxysulfuretin (14), and new auronolignan (15), named cotinignan A, were isolated by silica gel column and semipreparative HPLC chromatography from the methylene chloride/methanol extract of Cotinus coggygria Scop. heartwood. In addition, thirteen known secondary metabolites namely sulfuretin, 2,3-trans-fustin, fisetin, butin, butein, taxifolin, eriodictyol, 3',5,5',7-tetrahydroxyflavanone, 3',4',7-trihydroxyflavone, 3-O-methyl-2,3-trans-fustin, 3-O-galloyl-2,3-trans-fustin, β-resorcylic acid and 3-O-β-sitosterol glucoside were isolated as well. Their structures were elucidated by 1D and 2D NMR, HR-ESI-MS, IR and UV. Ten out of eleven isolated flavonoids possess 7, 3' and 4' hydroxy groups. These structural features could be considered as chemotaxonomic characteristic of flavonoids from C. coggygria. Cotinignan A (15) represents new subclass of secondary metabolites - auronolignans.

Glycolytic Stimulation Is Not a Requirement for M2 Macrophage Differentiation

Enhanced glucose uptake and a switch to glycolysis are key traits of M1 macrophages, whereas enhanced fatty acid oxidation and oxidative phosphorylation are the main metabolic characteristics of M2 macrophages. Recent studies challenge this traditional view, indicating that glycolysis may also be critically important for M2 macrophage differentiation, based on experiments with 2-DG. Here we confirm the inhibitory effect of 2-DG on glycolysis, but also demonstrate that 2-DG impairs oxidative phosphorylation and significantly reduces ¹³C-labeled Krebs cycle metabolites and intracellular ATP levels. These metabolic derangements were associated with reduced JAK-STAT6 pathway activity and M2 differentiation marker expression. While glucose deprivation and glucose substitution with galactose effectively suppressed glycolytic activity, there was no effective suppression of oxidative phosphorylation, intracellular ATP levels, STAT6 phosphorylation, and M2 differentiation marker expression. These data indicate that glycolytic stimulation is not required for M2 macrophage differentiation as long as oxidative phosphorylation remains active.

Interferon Gamma Induces Reversible Metabolic Reprogramming of M1 Macrophages to Sustain Cell Viability and Pro-Inflammatory Activity

Classical activation of M1 macrophages with lipopolysaccharide (LPS) is associated with a metabolic switch from oxidative phosphorylation to glycolysis. However, the generalizability of such metabolic remodeling to other modes of M1 macrophage stimulation, e.g. type II interferons (IFNs) such as IFNγ, has remained unknown as has the functional significance of aerobic glycolysis during macrophage activation. Here we demonstrate that IFNγ induces a rapid activation of aerobic glycolysis followed by a reduction in oxidative phosphorylation in M1 macrophages. Elevated glycolytic flux sustains cell viability and inflammatory activity, while limiting reliance on mitochondrial oxidative metabolism. Adenosine triphosphate (ATP) distributed by aerobic glycolysis is critical for sustaining IFN-γ triggered JAK (Janus tyrosine kinase)-STAT-1 (Signal Transducer and Activator of Transcription 1) signaling with phosphorylation of the transcription factor STAT-1 as its signature trait. Inhibition of aerobic glycolysis not only blocks the M1 phenotype and pro-inflammatory cytokine/chemokine production in murine macrophages and also human monocytes/macrophages. These findings extend on the potential functional role of immuno-metabolism from LPS- to IFNγ-linked diseases such as atherosclerosis and autoimmune disease.

First and second trimester urinary metabolic profiles and fetal growth restriction: an exploratory nested case-control study within the infant development and environment study

BACKGROUND

Routine prenatal care fails to identify a large proportion of women at risk of fetal growth restriction (FGR). Metabolomics, the comprehensive analysis of low molecular weight molecules (metabolites) in biological samples, can provide new and earlier biomarkers of prenatal health. Recent research has suggested possible predictive first trimester urine metabolites correlating to fetal growth restriction in the third trimester. Our objective in this current study was to examine urinary metabolic profiles in the first and second trimester of pregnancy in relation to third trimester FGR in a US population from a large, multi-center cohort study of healthy pregnant women.

METHODS

We conducted a nested case-control study within The Infant Development and the Environment Study (TIDES), a population-based multi-center pregnancy cohort study. We identified 53 cases of FGR based on the AUDIPOG [Neonatal growth - AUDIPOG [Internet]. [cited 29 Nov 2016]. Available from: http://www.audipog.net/courbes_morpho.php?langue=en ] formula for birthweight percentile considering maternal height, age, and prenatal weight, as well as infant sex, gestational age, and birth rank. Cases were matched to 106 controls based on study site, maternal age (± 2 years), parity, and infant sex. NMR spectroscopy was used to assess concentrations of four urinary metabolites that have been previously associated with FGR (tyrosine, acetate, formate, and trimethylamine) in first and second trimester urine samples. We fit multivariate conditional logistic regression models to estimate the odds of FGR in relation to urinary concentrations of these individual metabolites in the first and second trimesters. Exploratory analyses of custom binned spectroscopy results were run to consider other potentially related metabolites.

RESULTS

We found no significant association between the relative concentrations of each of the four metabolites and odds of FGR. Exploratory analyses did not reveal any significant differences in urinary metabolic profiles. Compared with controls, cases delivered earlier (38.6 vs 39.8, p < 0.001), and had lower birthweights (2527 g vs 3471 g, p < 0.001). Maternal BMI was similar between cases and controls.

CONCLUSIONS

First and second trimester concentrations of urinary metabolites (acetate, formate, trimethylamine and tyrosine) did not predict FGR. This inconsistency with previous studies highlights the need for more rigorous investigation and data collection in this area before metabolomics can be clinically applied to obstetrics.

Genetic Depletion of Adipocyte Creatine Metabolism Inhibits Diet-Induced Thermogenesis and Drives Obesity

Diet-induced thermogenesis is an important homeostatic mechanism that limits weight gain in response to caloric excess and contributes to the relative stability of body weight in most individuals. We previously demonstrated that creatine enhances energy expenditure through stimulation of mitochondrial ATP turnover, but the physiological role and importance of creatine energetics in adipose tissue have not been explored. Here, we have inactivated the first and rate-limiting enzyme of creatine biosynthesis, glycine amidinotransferase (GATM), selectively in fat (Adipo-Gatm KO). Adipo-Gatm KO mice are prone to diet-induced obesity due to the suppression of elevated energy expenditure that occurs in response to high-calorie feeding. This is paralleled by a blunted capacity for β3-adrenergic activation of metabolic rate, which is rescued by dietary creatine supplementation. These results provide strong in vivo genetic support for a role of GATM and creatine metabolism in energy expenditure, diet-induced thermogenesis, and defense against diet-induced obesity.

Streptomyces sp. JS520 produces exceptionally high quantities of undecylprodigiosin with antibacterial, antioxidative, and UV-protective properties

A Gram-positive, red-pigment-producing bacterial strain, designated JS520 was isolated from the pristine sediment from the cave on mountain Miroc in Serbia. Strain was confirmed to belong to Streptomyces genus based on phenotypic and genetic analysis. Streptomyces sp. JS520 has the ability to produce exceptionally high amounts of deep red pigment into both solid and liquid media. Liquid chromatography and mass spectroscopy of the purified pigments revealed the major component to be undecylprodigiosin (93 %) with minor component being oxidatively cyclized derivative. The pigment production was affected by medium composition, temperature, pH, and the aeration rate. By medium optimization, yields of undecylprodigiosin of 138 mg l(-1) were achieved, what is the highest level of undecylprodigiosin production reported for the members of Gram-positive Streptomyces genus. Purified pigment had antimicrobial properties against bacterial Bacillus and Micrococcus species (50 μg ml(-1)) and against Candida albicans species (100-200 μg ml(-1) range). The ability to affect auto-oxidation of the linoleic acid was demonstrated for the purified undecylprodigiosin, suggesting antioxidative properties of this pigment. Multiple ecophysiological roles of the pigment were revealed by comparing cultures grown under pigment-producing and pigment-nonproducing conditions. Cells grown under undecylprodigiosin-producing conditions could tolerate presence of hydrogen peroxide exhibiting three times smaller zones of inhibition at 100 mM H(2)O(2). Undecylprodigiosin-producing cells were also less susceptible to tetracycline, kanamycin, chloramphenicol, and 8-hydroxyquinoline. While the growth of the cells not producing pigment was completely inhibited by 15 min of exposure to ultraviolet light (254 nm), cells producing undecylprodigiosin and cells supplied with purified pigment in vitro showed survival rates at 22 and 8 %, respectively.

Characterization of volatile compounds of 'Drenja', an alcoholic beverage obtained from the fruits of Cornelian cherry

In this study, volatile compounds were analyzed in five samples of home-made spirit beverage made by the distillation of fermented fruits of cornelian cherry (Cornus mas L.). The major volatile compounds, besides ethanol, identified and quantified were: methanol, acetaldehyde, 1-propanol, ethyl acetate, 2-methyl-1-propanol, 1-butanol, amyl alcohols, 1-hexanol and 2-phenylethanol. The minor volatiles were submitted to liquid-liquid extraction with dichloromethane and analyzed by gas chromatography and gas chromatography/ /mass spectrometry (GC/MS). A total of 84 compounds were identified. The most abundant compounds were straight-chain free fatty acids, ethyl esters of C6-C18 acids, limonene, 2-phenylethanol and 4-ethylphenol. Most of the compounds found in the 'Drenja' spirits investigated in this study are similar to those present in other alcoholic beverages.

Neurologic and histologic outcome after intraneural injections of lidocaine in canine sciatic nerves

BACKGROUND

Inadvertent intraneural injection of local anesthetics may result in neurologic injury. We hypothesized that an intraneural injection may be associated with higher injection pressures and an increase in the risk of neurologic injury.

METHODS

The study was conducted in accordance with the principles of laboratory animal care, and was approved by the Laboratory Animal Care and Use Committee. Fifteen dogs of mixed breed (16-21 kg) were studied. After general endotracheal anesthesia, the sciatic nerves (n= 30) were exposed bilaterally. Under direct vision, a 25-gauge, long-beveled needle (30 degrees) was placed either epineurally (n= 10) or intraneurally (n= 20), and 4 ml of preservative-free lidocaine 20 mg/ml was injected using an automated infusion pump (4 ml/min). Injection pressure data were acquired using an in-line manometer coupled to a computer via an analog-to-digital conversion board. After injection, the animals were awakened and subjected to serial neurologic examinations. One week later, the dogs were killed, the sciatic nerves excised and histologic examination was performed by pathologists blind to the purpose of the study.

RESULTS

All perineural injections resulted in low pressures (< or = 5 psi). In contrast, eight of 20 intraneural injections resulted in high pressures (20-38 psi) at the beginning of the injection. Twelve intraneural injections, however, resulted in pressures of less than 12 psi. Neurologic function returned to baseline within 3 h after perineural injections and within 24 h after intraneural injections, when the measured injection pressures were less than 12 psi. Neurologic deficits persisted throughout the study period after all eight intraneural injections that resulted in high injection pressures. Histologic examination of the affected nerves revealed fascicular axonolysis and cellular infiltration.

CONCLUSIONS

The data in our canine model of intraneural injection suggest that intraneural injections do not always lead to nerve injury. High injection pressures during intraneural injection may be indicative of intrafascicular injection and may predict the development of neurologic injury.