In vitro 1H-NMR spectroscopic analysis of metabolites in fast- and slow-twitch muscles of young rats

Metabolome in Tibialis and Soleus Muscles in Wild-Type and Pin1 Knockout Mice through High-Resolution Magic Angle Spinning 1H Nuclear Magnetic Resonance Spectroscopy

Skeletal muscles are heterogenous tissues composed of different myofiber types that can be classified as slow oxidative, fast oxidative, and fast glycolytic which are distinguished on the basis of their contractile and metabolic properties. Improving oxidative metabolism in skeletal muscles can prevent metabolic diseases and plays a protective role against muscle wasting in a number of neuromuscular diseases. Therefore, achieving a detailed understanding of the factors that regulate myofiber metabolic properties might provide new therapeutic opportunities for these diseases. Here, we investigated whether peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) is involved in the control of myofiber metabolic behaviors. Indeed, PIN1 controls glucose and lipid metabolism in a number of tissues, and it is also abundant in adult skeletal muscles; however, its role in the control of energy homeostasis in this tissue is still to be defined. To start clarifying this topic, we compared the metabolome of the tibialis anterior muscle (mainly glycolytic) and soleus muscle (oxidative) in wild-type and Pin1 knockout mice with High-Resolution Magic Angle Spinning (HR-MAS) NMR on intact tissues. Our analysis reveals a clear demarcation between the metabolomes in the two types of muscles and allows us to decode a signature able to discriminate the glycolytic versus oxidative muscle phenotype. We also detected some changes in Pin1-depleted muscles that suggest a role for PIN1 in regulating the metabolic phenotype of skeletal muscles.

Isolated murine skeletal muscles utilize pyruvate over glucose for oxidation

INTRODUCTION

Fuel sources for skeletal muscle tissue include carbohydrates and fatty acids, and utilization depends upon fiber type, workload, and substrate availability. The use of isotopically labeled substrate tracers combined with nuclear magnetic resonance (NMR) enables a deeper examination of not only utilization of substrates by a given tissue, but also their contribution to tricarboxylic acid (TCA) cycle intermediates.

OBJECTIVES

The goal of this study was to determine the differential utilization of substrates in isolated murine skeletal muscle, and to evaluate how isopotomer anlaysis provided insight into skeletal muscle metabolism.

METHODS

Isolated C57BL/6 mouse hind limb muscles were incubated in oxygenated solution containing uniformly labeled 13C6 glucose, 13C3 pyruvate, or 13C2 acetate at room temperature. Isotopomer analysis of 13C labeled glutamate was performed on pooled extracts of isolated soleus and extensor digitorum longus (EDL) muscles.

RESULTS

Pyruvate and acetate were more avidly consumed than glucose with resultant increases in glutamate labeling in both muscle groups. Glucose incubation resulted in glutamate labeling, but with high anaplerotic flux in contrast to the labeling by pyruvate. Muscle fiber type distinctions were evident by differences in lactate enrichment and extent of substrate oxidation.

CONCLUSION

Isotope tracing experiments in isolated muscles reveal that pyruvate and acetate are avidly oxidized by isolated soleus and EDL muscles, whereas glucose labeling of glutamate is accompanied by high anaplerotic flux. We believe our results may set the stage for future examination of metabolic signatures of skeletal muscles from pre-clinical models of aging, type-2 diabetes and neuromuscular disease.

The effect of acute taurine ingestion on 4-km time trial performance in trained cyclists

Taurine (TAU) has been shown to improve exercise time to exhaustion and 3-km running performance; however, no studies have considered the effect of acute TAU ingestion on short duration cycling time trial (TT) performance. The aim of this study was to determine the effects of a single oral acute dose of 1000 mg of TAU on a laboratory simulated 4-km cycling TT. Eleven trained male cyclists performed three, 4-km TTs. The first of the trials was a familiarisation, followed by two subsequent trials which were performed two hours after the consumption of either 1000 mg of TAU or placebo (P), using a double-blind randomised crossover design. Capillary blood samples were obtained prior to the start and immediately after each TT for the measurement of lactate, pH and HCO3-. There was no effect of TAU (p = 0.731, d = 0.151) on performance (390 ± 27 and 388 ± 21 s for TAU and P, respectively), nor were there any condition main effects for VO2, lactate, pH, or HCO3- (p > 0.05) despite post TT changes in lactate (7.3 ± 2.5 mmol l-1, p < 0.001, d = 2.86, 7.6 ± 2.0 mmol l-1 p < 0.001, d = 3.75); pH (-0.255 ± 0.1, p < 0.001, d = 2.62, -0.258 ± 0.09, p < 0.001, d = 2.87); HCO3- (-13.58 ± 2.7 mmol l-1, p < 0.001, d = 5.04 vs. -13.36 ± 2.3, p < 0.001, d = 5.72 for TAU and P, respectively). The findings of this study suggest that a pre-exercise dose of 1000 mg TAU offers no performance advantage during 4-km TT nor does it alter the blood buffering responses in trained cyclists.

Taurine: the appeal of a safe amino acid for skeletal muscle disorders

Taurine is a natural amino acid present as free form in many mammalian tissues and in particular in skeletal muscle. Taurine exerts many physiological functions, including membrane stabilization, osmoregulation and cytoprotective effects, antioxidant and anti-inflammatory actions as well as modulation of intracellular calcium concentration and ion channel function. In addition taurine may control muscle metabolism and gene expression, through yet unclear mechanisms. This review summarizes the effects of taurine on specific muscle targets and pathways as well as its therapeutic potential to restore skeletal muscle function and performance in various pathological conditions. Evidences support the link between alteration of intracellular taurine level in skeletal muscle and different pathophysiological conditions, such as disuse-induced muscle atrophy, muscular dystrophy and/or senescence, reinforcing the interest towards its exogenous supplementation. In addition, taurine treatment can be beneficial to reduce sarcolemmal hyper-excitability in myotonia-related syndromes. Although further studies are necessary to fill the gaps between animals and humans, the benefit of the amino acid appears to be due to its multiple actions on cellular functions while toxicity seems relatively low. Human clinical trials using taurine in various pathologies such as diabetes, cardiovascular and neurological disorders have been performed and may represent a guide-line for designing specific studies in patients of neuromuscular diseases.

Pattern recognition analysis of proton nuclear magnetic resonance spectra of extracts of intestinal epithelial cells under oxidative stress

BACKGROUND

Mesenteric ischemia-reperfusion induces gut mucosal damage. Intestinal mucosal wounds are repaired by epithelial restitution. Although many different molecular mechanisms have been shown to affect cell metabolism under oxidative conditions, these molecular mechanisms and metabolic phenotypes are not well understood. Nuclear magnetic resonance (NMR) spectroscopic data can be used to study metabolic phenotypes in biological systems. Pattern recognition with multivariate analysis is one chemometric technique. The purpose of this study was to visualize, using a chemometric technique to interpret NMR data, different degrees of oxidant injury in rat small intestine (IEC-6) cells exposed to H2O2.

METHODS

Oxidant stress was induced by H2O2 in IEC-6 cells. Cell restitution and viability were assessed at different H2O2 concentrations and time points. Cells were harvested for pattern recognition analysis of (1)H-NMR data.

RESULTS

Cell viability and restitution were significantly suppressed by H2O2 in a dose-dependent manner compared with control. Each class was clearly separated into clusters by partial least squares discriminant analysis, and class variance was greater than 90% from 2 factors.

CONCLUSION

Pattern recognition of NMR spectral data using a chemometric technique clearly visualized the differences of oxidant injury in IEC-6 cells under oxidant stress.

Symmorphosis through dietary regulation: a combinatorial role for proteolysis, autophagy and protein synthesis in normalising muscle metabolism and function of hypertrophic mice after acute starvation

Animals are imbued with adaptive mechanisms spanning from the tissue/organ to the cellular scale which insure that processes of homeostasis are preserved in the landscape of size change. However we and others have postulated that the degree of adaptation is limited and that once outside the normal levels of size fluctuations, cells and tissues function in an aberant manner. In this study we examine the function of muscle in the myostatin null mouse which is an excellent model for hypertrophy beyond levels of normal growth and consequeces of acute starvation to restore mass. We show that muscle growth is sustained through protein synthesis driven by Serum/Glucocorticoid Kinase 1 (SGK1) rather than Akt1. Furthermore our metabonomic profiling of hypertrophic muscle shows that carbon from nutrient sources is being channelled for the production of biomass rather than ATP production. However the muscle displays elevated levels of autophagy and decreased levels of muscle tension. We demonstrate the myostatin null muscle is acutely sensitive to changes in diet and activates both the proteolytic and autophagy programmes and shutting down protein synthesis more extensively than is the case for wild-types. Poignantly we show that acute starvation which is detrimental to wild-type animals is beneficial in terms of metabolism and muscle function in the myostatin null mice by normalising tension production.

Proton nuclear magnetic resonance and pattern recognition analysis of liver extracts from rats under different anesthetics

Background

Although general anesthesia is widely used in the surgical arena, the mechanisms by which general anesthetics act remain unclear. We previously described alterations in gene expression ratios in hepatic tissue taken from rats treated with anesthetics. Consequently, it is considered that anesthetics influence liver metabolism. Thus, the goal of this study was to use pattern recognition analysis of proton nuclear magnetic resonance spectra to visualize changes in liver metabolic phenotypes in response to widely used intravenous anesthetics (propofol and dexmedetomidine) and inhalational anesthetics (sevoflurane and isoflurane).

Methods

Rats were randomized into 13 groups (n = 6 in each group), and each group received one of following agents: propofol, dexmedetomidine, sevoflurane, isoflurane, or no anesthetic (control group). The liver was directly removed from rats immediately after or 24 h or 48 h after a 6-h period of anesthesia. Hydrophilic compounds were extracted from the liver and were analyzed with proton nuclear magnetic resonance spectroscopy. All spectral data were processed and analyzed by principal component analysis for comparison of metabolite profiles.

Results

Data were visualized by plotting principal component (PC) scores. In the plots, each point represents an individual sample. Each group was clustered separately on the plots, and the PC scores of the propofol group were clearly distinct from those of the control group and other anesthetic groups. The difference in PC scores was more pronounced immediately after completion of anesthesia when compared with 24 or 48 h after completion of anesthesia. Although the effect of intravenous anesthetics on the liver dissipated over time, the effect of inhalational anesthetics persisted.

Conclusions

Propofol, dexmedetomidine, sevoflurane and isoflurane exert different effects on liver metabolism. In particular, liver metabolism was markedly altered after exposure to propofol. The effect of anesthesia on the liver under propofol or dexmedetomidine resolved rapidly when compared with the effect under sevoflurane or isoflurane.

A NMR-based metabolomic approach for differentiation of hagfish dental and somatic skeletal muscles

The hagfish dental muscle is a large and specialized element of the feeding apparatus that helps ingest food. This muscle has enzymatic activities and contractile properties different from the hagfish somatic skeletal muscle. To verify the functional relevance of protein alterations, we examined the metabolomic differentiation of hagfish dental and somatic skeletal muscles using ¹H-nuclear magnetic resonance (NMR)-based metabolomics and multivariate analysis that separated hagfish dental and somatic muscles by principal component analysis and partial least squares for discriminant analysis. Our analysis of assigned metabolites showed that anserine and taurine levels were higher in dental muscle, but creatine, fructose, glucose, glycerate, pyruvate, and succinate levels were higher in somatic muscle. We concluded that the primary energy sources of dental and somatic muscles are related to the citric acid cycle and the anaerobic glycolysis and metabolism of creatine. Thus, ¹H-NMR-based metabolomics can be integrated with the previous proteomic approach to derive biochemical and physiological information about hagfish muscles.

Pattern recognition analysis of proton nuclear magnetic resonance spectra of brain tissue extracts from rats anesthetized with propofol or isoflurane

BACKGROUND

General anesthesia is routinely used as a surgical procedure and its safety has been endorsed by clinical outcomes; however, its effects at the molecular level have not been elucidated. General anesthetics influence glucose metabolism in the brain. However, the effects of anesthetics on brain metabolites other than those related to glucose have not been well characterized. We used a pattern recognition analysis of proton nuclear magnetic resonance spectra to visualize the changes in holistic brain metabolic phenotypes in response to the widely used intravenous anesthetic propofol and the volatile anesthetic isoflurane.

METHODOLOGY/PRINCIPAL FINDINGS

Rats were randomized into five groups (n = 7 each group). Propofol and isoflurane were administered to two groups each, for 2 or 6 h. The control group received no anesthesia. Brains were removed directly after anesthesia. Hydrophilic compounds were extracted from excised whole brains and measured by proton nuclear magnetic resonance spectroscopy. All spectral data were processed and analyzed by principal component analysis for comparison of the metabolite profiles. Data were visualized by plotting principal component (PC) scores. In the plots, each point represents an individual sample. The propofol and isoflurane groups were clustered separately on the plots, and this separation was especially pronounced when comparing the 6-h groups. The PC scores of the propofol group were clearly distinct from those of the control group, particularly in the 6-h group, whereas the difference in PC scores was more subtle in the isoflurane group and control groups.

CONCLUSIONS/SIGNIFICANCE

The results of the present study showed that propofol and isoflurane exerted differential effects on holistic brain metabolism under anesthesia.

Noninvasive measurement of temperature and fractional dissociation of imidazole in human lower leg muscles using 1H-nuclear magnetic resonance spectroscopy

The temperature change of the fractional dissociation of imidazole (α-imidazole) in resting human lower leg muscles was measured noninvasively using 1H-nuclear magnetic resonance spectroscopy at 3.0 and 1.5 T on five normal male volunteers aged 30.6 ± 10.4 yr (mean ± SD). Using 1H-nuclear magnetic resonance spectroscopy, water, carnosine, and creatine in the muscles could be simultaneously analyzed. Carnosine contains imidazole protons. The chemical shifts of water and carnosine imidazole protons relative to creatine could be used for estimating temperatures and α-imidazole, respectively. Using the chemical shift, the values of temperature in gastrocnemius (Gast) and soleus muscles at ambient temperature (21–25°C) were estimated to be 35.5 ± 0.5 and 37.4 ± 0.6°C (means ± SE), respectively (significantly different; P < 0.01). The estimated values of α-imidazole in these muscles were 0.620 ± 0.007 and 0.630 ± 0.013 (means ± SE), respectively (not significant). Alternation of the surface temperature of the lower leg from 40 to 10°C significantly changed the temperature in Gast ( P < 0.0001) from 38.1 ± 0.5 to 28.0 ± 1.2°C, and the α-imidazole in Gast decreased from 0.631 ± 0.003 to 0.580 ± 0.011 ( P < 0.05). However, the values of α-imidazole and the temperature in soleus muscles were not significantly affected by this maneuver. These results indicate that the α-imidazole in Gast changed significantly with alternation in muscle temperature ( r = 0.877, P < 0.00001), and its change was estimated to be 0.0058/°C.