Biochemical characterization of muscle tissue of limb girdle muscular dystrophy: an 1H and 13C NMR study

Interactions between gut microbiota and skeletal muscle

The gut microbiota is now recognized as a major contributor to the host’s nutrition, metabolism, immunity, and neurological functions. Imbalanced microbiota (ie, dysbiosis) is linked to undernutrition-induced stunting, inflammatory and metabolic diseases, and cancers. Skeletal muscle also takes part in the interorgan crosstalk regulating substrate metabolism, immunity, and health. Here, we review the reciprocal influence of gut microbiota and skeletal muscle in relation to juvenile growth, performance, aging, and chronic diseases. Several routes involving the vascular system and organs such as the liver and adipose tissue connect the gut microbiota and skeletal muscle, with effects on fitness and health. Therapeutic perspectives arise from the health benefits observed with changes in gut microbiota and muscle activity, further encouraging multimodal therapeutic strategies.

Advancements in magnetic resonance imaging-based biomarkers for muscular dystrophy

Recent years have seen steady progress in the identification of genetic muscle diseases as well as efforts to develop treatment for these diseases. Consequently, sensitive and objective new methods are required to identify and monitor muscle pathology. Magnetic resonance imaging offers multiple potential biomarkers of disease severity in the muscular dystrophies. This Review uses a pathology-based approach to examine the ways in which MRI and spectroscopy have been used to study muscular dystrophies. Methods that have been used to quantitate intramuscular fat, edema, fiber orientation, metabolism, fibrosis, and vascular perfusion are examined, and this Review describes how MRI can help diagnose these conditions and improve upon existing muscle biomarkers by detecting small increments of disease-related change. Important challenges in the implementation of imaging biomarkers, such as standardization of protocols and validating imaging measurements with respect to clinical outcomes, are also described.

Metabolic fingerprinting of joint tissue of collagen-induced arthritis (CIA) rat: In vitro, high resolution NMR (nuclear magnetic resonance) spectroscopy based analysis

Rheumatoid arthritis (RA) is a systemic autoimmune disease whose major characteristics persistent joint inflammation that results in joint destruction and failure of the function. Collagen-induced arthritis (CIA) rat is an autoimmune disease model and in many ways shares features with RA. The CIA is associated with systemic manifestations, including alterations in the metabolism. Nuclear magnetic resonance (NMR) spectroscopy-based metabolomics has been successfully applied to the perchloric acid extract of the joint tissue of CIA rat and control rat for the analysis of aqueous metabolites. GPC (Glycerophosphocholine), carnitine, acetate, and creatinine were important discriminators of CIA rats as compared to control rats. Level of lactate (significance; p = 0.004), alanine (p = 0.025), BCA (Branched-chain amino acids) (p = 0.006) and creatinine (p = 0.023) was significantly higher in CIA rats as compared to control rats. Choline (p = 0.038) and GPC (p = 0.009) were significantly reduced in CIA rats as compared to control rats. Choline to GPC correlation was good and negative (Pearson correlation = -0.63) for CIA rats as well as for control rats (Pearson correlation = -0.79). All these analyses collectively considered as metabolic fingerprinting of the joint tissue of CIA rat as compared to control rat. The metabolic fingerprinting of joint tissue of CIA rats was different as compared to control rats. The metabolic fingerprinting reflects inflammatory disease activity in CIA rats with synovitis, demonstrating that underlying inflammatory process drives significant changes in metabolism that can be measured in the joint tissue. Therefore, the outcome of this study may be helpful for understanding the mechanism of metabolic processes in RA. This may be also helpful for the development of advanced diagnostic methods and therapy for RA.

Perturbation of muscle metabolism in patients with muscular dystrophy in early or acute phase of disease: In vitro, high resolution NMR spectroscopy based analysis

BACKGROUND

Muscular dystrophy is an inherited muscle disease, characterized by progressive muscle wasting and weakness of variable distribution and severity.

METHODS

In vitro, high-resolution proton nuclear magnetic resonance (NMR) spectroscopy based analysis was performed on perchloric acid (PCA) extract of muscle specimens of patients suffering from various types of muscular dystrophies to identify alteration in hydrophilic low-molecular weight substances (aqueous metabolites) as compared to muscle of control subjects as well as in between the types of muscular dystrophy. Muscle tissue specimens were obtained from Duchenne muscular dystrophy (DMD) [n=11], Becker muscular dystrophy (BMD) [n=12], facioscapulohumeral dystrophy (FSHD) [n=9] and limb girdle muscular dystrophy (LGMD)-2B [n=22]. Control muscle specimens [n=40] were also taken.

RESULTS

Concentration of branched chain amino acids (BCA), glutamine/glutamate (Gln/Glu), acetate (Ace) and fumarate (Fum) was decreased and His was increased in muscle tissue of DMD, BMD, FSHD and LGMD-2B patients as compared to control subjects. Alanine (Ala) was significantly reduced in BMD, FSHD and LGMD-2B patients as compared to control subjects. Tyrosine (Tyr) was present only in the muscle tissue of control subjects. Propionate (Prop) was present in muscle tissue of DMD, BMD, FSHD and LGMD-2B patients and was absent in muscle tissue of control subjects. Concentration of BCA and Prop is significantly reduced in patients with DMD as compared to BMD, but Glucose is significantly higher in patients with DMD as compared to BMD. Quantity of Glucose, His and Gln/glu are significantly higher in patients with DMD as compared to FSHD, but Prop is significantly reduced in patients with DMD as compared to FSHD. Concentration of Ala and His is significantly higher in patients with DMD as compared to LGMD-2B, but BCA, Glucose and Prop are significantly reduced in patients with DMD as compared to LGMD-2B. Concentration of His is significantly higher in patients with BMD as compared to FSHD. Concentration of His is significantly reduced and Glucose is higher in patients with LGMD-2B as compared to BMD. Glucose concentration is significantly reduced in patients with FSHD as compared to LGMD-2B. ROC curves supported the noticeable discrimination in between the patients with DMD and FSHD for the quantity of Gln/Glu, and patients with LGMD-2B and DMD for the quantity of Ala. Collectively, these findings showed the perturbation of muscle metabolism in muscular dystrophy.

CONCLUSIONS

The data of presented study may be used as supporting information for existing methods of the diagnosis for patients with muscular dystrophy.

Metabolic status of patients with muscular dystrophy in early phase of the disease: In vitro, high resolution NMR spectroscopy based metabolomics analysis of serum

AIMS

Proton Nuclear Magnetic Resonance (NMR) based metabolomics analysis is extensively used to explore the metabolic profiling of biofluids. This approach was used for the analysis of metabolites in serum of patients with major types of muscular dystrophy in early phase of the disease.

MATERIAL AND METHODS

Proton NMR spectroscopy based qualitative (assignment of metabolites) and quantitative (quantification of metabolites) analysis of metabolites in native serum of patients with Duchenne muscular dystrophy (DMD) [n=88; n represent the number], Becker muscular dystrophy (BMD) [n=40], facioscapulohumeral dystrophy (FSHD) [n=22], limb girdle muscular dystrophy (LGMD)-2B [n=35] and myotonic dystrophy (DM) [n=21] as compared to normal subjects [n=50] were performed.

KEY FINDINGS

Quantity of branched chain amino acids was elevated in serum of patients with DMD, BMD, FSHD and DM-1 as compared to normal subjects. Acetate level was elevated in serum of patients with DMD, BMD, FSHD, LGMD-2B and DM-1 as compared to normal subjects. Level of glutamine was reduced in serum of patients with DMD, BMD, LGMD-2B, FSHD and elevated in DM-1 patients as compared to normal subjects. Quantity of tyrosine was increased in serum of BMD patients as compared to normal subjects. There was a reduction in the level of lysine in serum of FSHD, LGMD-2B and DM-1 patients as compared to normal subjects. Citrate level was reduced in serum of FSHD patients, but elevated in LGMD-2B patients. Lactate level was reduced in serum of LGMD-2B patients and histidine was reduced in serum of patients with FSHD as compared to normal subjects.

SIGNIFICANCE

Outcome of this study may be useful as supportive information for the existing diagnostic methods of the muscular dystrophy.

Separation of small metabolites and lipids in spectra from biopsies by diffusion-weighted HR-MAS NMR: a feasibility study

High Resolution Magic Angle Spinning (HR-MAS) NMR allows metabolic characterization of biopsies. HR-MAS spectra from tissues of most organs show strong lipid contributions that are overlapping metabolite regions, which hamper metabolite estimation. Metabolite quantification and analysis would benefit from a separation of lipids and small metabolites. Generally, a relaxation filter is used to reduce lipid contributions. However, the strong relaxation filter required to eliminate most of the lipids also reduces the signals for small metabolites. The aim of our study was therefore to investigate different diffusion editing techniques in order to employ diffusion differences for separating lipid and small metabolite contributions in the spectra from different organs for unbiased metabonomic analysis. Thus, 1D and 2D diffusion measurements were performed, and pure lipid spectra that were obtained at strong diffusion weighting (DW) were subtracted from those obtained at low DW, which include both small metabolites and lipids. This subtraction yielded almost lipid free small metabolite spectra from muscle tissue. Further improved separation was obtained by combining a 1D diffusion sequence with a T2-filter, with the subtraction method eliminating residual lipids from the spectra. Similar results obtained for biopsies of different organs suggest that this method is applicable in various tissue types. The elimination of lipids from HR-MAS spectra and the resulting less biased assessment of small metabolites have potential to remove ambiguities in the interpretation of metabonomic results. This is demonstrated in a reproducibility study on biopsies from human muscle.

Metabolic abnormalities of gastrointestinal mucosa in celiac disease: An in vitro proton nuclear magnetic resonance spectroscopy study

BACKGROUND AND AIM

Celiac disease (CeD) is a common autoimmune disorder in which ingestion of gluten and related proteins leads to inflammation in the small intestine. Although the histological findings in CeD are characteristic, they are not specific. In this study, proton nuclear magnetic resonance (NMR) spectroscopy was used to investigate the differences in metabolic profile of duodenal mucosal biopsies of patients with CeD and controls to find out the biomarker/s of villous atrophy.

METHODS

Duodenal mucosal biopsies were collected from 29 CeD patients (mean age 26.2 ± 10.8 years) and 17 controls (mean age 34.1 ± 11.1 years) and were subjected to proton NMR spectroscopy following perchloric acid extraction. Assignment of metabolite resonances was carried out and their concentrations were determined. For comparison between the groups unpaired t-test/Wilcoxon rank sum test was used. Partial least squares-discriminant analysis was performed to study the clustering behavior of the samples from CeD patients and controls using the Unscrambler 10.2 software.

RESULTS

Partial least squares-discriminant analysis clearly differentiated CeD patients from controls. Significantly higher concentrations of isoleucine, leucine, aspartate, succinate, and pyruvate, and lower concentration of glycerophosphocholine, were observed in the duodenal mucosa of CeD patients compared with controls. The results suggest abnormalities in glycolysis, Krebs cycle (energy deficiency), and amino acid metabolism, which may affect the biosynthetic pathways and consequently contribute to villous atrophy.

CONCLUSIONS

NMR spectroscopy with multivariate analysis of duodenal mucosal biopsies revealed a characteristic metabolic profile in CeD patients. The work provided an insight in determining biomarker/s for villous atrophy and diagnosis of CeD patients.

Only fat infiltrated muscles in resting lower leg of FSHD patients show disturbed energy metabolism

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by asymmetric dysfunctioning of individual muscles. Currently, it is unknown why specific muscles are affected before others and more particularly what pathophysiology is causing this differential progression. The aim of our study was to use a combination of (31)P magnetic resonance spectroscopic imaging (MRSI) and T1-weighted MRI to uncover metabolic differences in fat infiltrated and not fat infiltrated muscles in patients with FSHD. T1-weighted images and 3D (31)P MRSI were obtained from the calf muscles of nine patients with diagnosed FSHD and nine healthy age and sex matched volunteers. Muscles of patients were classified as fat infiltrated (PFM) and non fat-infiltrated (PNM) based on visual assessment of the MR images. Ratios of phosphocreatine (PCr), phosphodiesters (PDE) and inorganic phosphate (Pi) over ATP and tissue pH were compared between PFM and PNM and the same muscles in healthy volunteers. Of all patients, seven showed moderate to severe fatty infiltration in one or more muscles. In these muscles, decreases in PCr/ATP and increases in tissue pH were observed compared to the same muscles in healthy volunteers. Interestingly, these differences were absent in the PNM group. Our data show that differences in metabolite ratios and tissue pH in skeletal muscle between healthy volunteers and patients with FSHD appear to be specific for fat infiltrated muscles. Normal appearing muscles on T1 weighted images of patients showed normal phosphoryl metabolism, which suggests that in FSHD disease progression is truly muscle specific.

Novel corrective equations for complete estimation of human tissue lipids after their partial destruction by perchloric acid pre-treatment: high-resolution (1)H-NMR-based study

Owing to the small quantity of tissue available in human biopsy specimens, aqueous and lipid components often have to be determined in the same tissue sample. Perchloric acid (PCA) used for the extraction of aqueous metabolites has a deleterious effect on lipid components; the severity of the damage is not known. In this study, human muscle tissue was first treated with PCA to extract aqueous metabolites, and the residue was then used for lipid extraction by conventional methods, i.e. the methods of Folch and Bligh & Dyer and a standardised one using methanol/chloroform (1:3, v/v) used in our laboratory. A (1)H-NMR spectrum was obtained for each lipid extract. Lipid was quantified by measuring the integral area of N(+)-(CH(3))(3) signals of phospholipids (PLs). Triacylglycerol (TG) and cholesterol (CHOL) were quantified using the -CH(2)- signals of glycerol and the C18 methyl signal, respectively. This study shows that prior use of PCA caused marked attenuation of TG, PL, and CHOL. This was confirmed by recovery experiments and observation of the direct effect of PCA on the standard lipid components. On the basis of the quantity of lipid lost in each case, three novel equations (with respect to TG, PL, and CHOL) were derived. Application of these equations to lipid quantities estimated in different pathological tissues after PCA pre-treatment produced values equivalent to those estimated without PCA use. This study conclusively shows that PCA pre-treatment damages all three lipid moieties, TG, PL, and CHOL. When PCA is used in a fixed ratio to the tissue, the lipid damage is also proportional and correctable by statistically derived equations. These equations will be useful in human biopsy specimens where aqueous and lipid components have to be studied using the same tissue sample because of the small quantity available.

A Rostrocaudal Muscular Dystrophy Caused by a Defect in Choline Kinase Beta, the First Enzyme in Phosphatidylcholine Biosynthesis

Muscular dystrophies include a diverse group of genetically heterogeneous disorders that together affect 1 in 2000 births worldwide. The diseases are characterized by progressive muscle weakness and wasting that lead to severe disability and often premature death. Rostrocaudal muscular dystrophy (rmd) is a new recessive mouse mutation that causes a rapidly progressive muscular dystrophy and a neonatal forelimb bone deformity. The rmd mutation is a 1.6-kb intragenic deletion within the choline kinase beta (Chkb) gene, resulting in a complete loss of CHKB protein and enzymatic activity. CHKB is one of two mammalian choline kinase (CHK) enzymes (alpha and beta) that catalyze the phosphorylation of choline to phosphocholine in the biosynthesis of the major membrane phospholipid phosphatidylcholine. While mutant rmd mice show a dramatic decrease of CHK activity in all tissues, the dystrophy is only evident in skeletal muscle tissues in an unusual rostral-to-caudal gradient. Minor membrane disruption similar to dysferlinopathies suggest that membrane fusion defects may underlie this dystrophy, because severe membrane disruptions are not evident as determined by creatine kinase levels, Evans Blue infiltration, and unaltered levels of proteins in the dystrophin-glycoprotein complex. The rmd mutant mouse offers the first demonstration of a defect in a phospholipid biosynthetic enzyme causing muscular dystrophy, representing a unique model for understanding mechanisms of muscle degeneration.

In vivo 2D magnetic resonance spectroscopy of small animals

Localized in vivo NMR spectroscopy, chemical shift imaging or multi-voxel spectroscopy are potentially useful tools in small animals that are complementary to MRI, adding biochemical information to the mainly anatomical data provided by imaging of water protons. However the contribution of such methods remains hampered by the low spectral resolution of the in vivo 1D spectra. Two-dimensional methods widely developed for in vitro studies have been proposed as suitable approaches to overcome these limitations in resolution. The different homonuclear and heteronuclear sequences adapted to in vivo studies are reviewed. Their specific contributions to the spectral resolution of spectroscopic data and their limitations for in vivo investigations are discussed. The applications to experimental models of pathological processes or pharmacological treatment in mainly brain and muscle are presented. According to their combined sensitivity, acquisition duration and spatial resolution, the heteronuclear 2D experiments, which are mainly used for 1H detected-13C spectroscopy after administration of 13C-labeled compounds, appear to be less efficient than 1H detected-13C 1D methods at high field. However, the applications of 2D proton homonuclear methods show that they remain the best tools for in vivo studies when an improved resolution is required.