Muscle carnosine in experimental autoimmune encephalomyelitis and multiple sclerosis

Identification of brain-enriched proteins in CSF as biomarkers of relapsing remitting multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a clinically and biologically heterogenous disease with currently unpredictable progression and relapse. After the development and success of neurofilament as a cerebrospinal fluid (CSF) biomarker, there is reinvigorated interest in identifying other markers of or contributors to disease. The objective of this study is to probe the predictive potential of a panel of brain-enriched proteins on MS disease progression and subtype.

METHODS

This study includes 40 individuals with MS and 14 headache controls. The MS cohort consists of 20 relapsing remitting (RR) and 20 primary progressive (PP) patients. The CSF of all individuals was analyzed for 63 brain enriched proteins using a method of liquid-chromatography tandem mass spectrometry. Wilcoxon rank sum test, Kruskal-Wallis one-way ANOVA, logistic regression, and Pearson correlation were used to refine the list of candidates by comparing relative protein concentrations as well as relation to known imaging and molecular biomarkers.

RESULTS

We report 30 proteins with some relevance to disease, clinical subtype, or severity. Strikingly, we observed widespread protein depletion in the disease CSF as compared to control. We identified numerous markers of relapsing disease, including KLK6 (kallikrein 6, OR = 0.367, p < 0.05), which may be driven by active disease as defined by MRI enhancing lesions. Other oligodendrocyte-enriched proteins also appeared at reduced levels in relapsing disease, namely CNDP1 (carnosine dipeptidase 1), LINGO1 (leucine rich repeat and Immunoglobin-like domain-containing protein 1), MAG (myelin associated glycoprotein), and MOG (myelin oligodendrocyte glycoprotein). Finally, we identified three proteins-CNDP1, APLP1 (amyloid beta precursor like protein 1), and OLFM1 (olfactomedin 1)-that were statistically different in relapsing vs. progressive disease raising the potential for use as an early biomarker to discriminate clinical subtype.

CONCLUSIONS

We illustrate the utility of targeted mass spectrometry in generating potential targets for future biomarker studies and highlight reductions in brain-enriched proteins as markers of the relapsing remitting disease stage.

The potential roles of amino acids and their major derivatives in the management of multiple sclerosis

Recently, we reviewed the important role of carbohydrates and lipids metabolism in different clinical aspects of multiple sclerosis (MS) disease. In the current paper, we aimed to review the contribution of amino acids and their major derivatives to different clinical outcomes of the disease, including etiology, pathogenesis, diagnosis, prognosis, and treatment. In this line, Thr (threonine), Phe (phenylalanine), Glu (glutamate), Trp (tryptophan), and Sero (serotonin) are the main examples of biomolecules that have been suggested for MS therapy. It has been concluded that different amino acids and their derivatives might be considered prominent tools for the clinical management of MS disease.

Carnosine quenches the reactive carbonyl acrolein in the central nervous system and attenuates autoimmune neuroinflammation

Background

Multiple sclerosis (MS) is a chronic autoimmune disease driven by sustained inflammation in the central nervous system. One of the pathological hallmarks of MS is extensive free radical production. However, the subsequent generation, potential pathological role, and detoxification of different lipid peroxidation-derived reactive carbonyl species during neuroinflammation are unclear, as are the therapeutic benefits of carbonyl quenchers. Here, we investigated the reactive carbonyl acrolein and (the therapeutic effect of) acrolein quenching by carnosine during neuroinflammation.

Methods

The abundance and localization of acrolein was investigated in inflammatory lesions of MS patients and experimental autoimmune encephalomyelitis (EAE) mice. In addition, we analysed carnosine levels and acrolein quenching by endogenous and exogenous carnosine in EAE. Finally, the therapeutic effect of exogenous carnosine was assessed in vivo (EAE) and in vitro (primary mouse microglia, macrophages, astrocytes).

Results

Acrolein was substantially increased in inflammatory lesions of MS patients and EAE mice. Levels of the dipeptide carnosine (β-alanyl-l-histidine), an endogenous carbonyl quencher particularly reactive towards acrolein, and the carnosine-acrolein adduct (carnosine-propanal) were ~ twofold lower within EAE spinal cord tissue. Oral carnosine treatment augmented spinal cord carnosine levels (up to > tenfold), increased carnosine-acrolein quenching, reduced acrolein-protein adduct formation, suppressed inflammatory activity, and alleviated clinical disease severity in EAE. In vivo and in vitro studies indicate that pro-inflammatory microglia/macrophages generate acrolein, which can be efficiently quenched by increasing carnosine availability, resulting in suppressed inflammatory activity. Other properties of carnosine (antioxidant, nitric oxide scavenging) may also contribute to the therapeutic effects.

Conclusions

Our results identify carbonyl (particularly acrolein) quenching by carnosine as a therapeutic strategy to counter inflammation and macromolecular damage in MS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02306-9.

Carnosine and skeletal muscle dysfunction in a rodent multiple sclerosis model

Muscle weakness and fatigue are primary manifestations of multiple sclerosis (MS), a chronic disease of the central nervous system. Interventions that enhance muscle function may improve overall physical well-being of MS patients. Recently, we described that levels of carnosine, an endogenous muscle dipeptide involved in contractile function and fatigue-resistance, are reduced in muscle tissue from MS patients and a monophasic rodent MS model (experimental autoimmune encephalomyelitis, EAE). In the present study, we aimed to (1) confirm this finding in a chronic EAE model, along with the characterization of structural and functional muscle alterations, and (2) investigate the effect of carnosine supplementation to increase/restore muscle carnosine levels and improve muscle function in EAE. We performed muscle immunohistochemistry and ex vivo contractility measurements to examine muscle structure and function at different stages of EAE, and following nutritional intervention (oral carnosine: 3, 15 or 30 g/L in drinking water). Immunohistochemistry revealed progressively worsening muscle fiber atrophy and a switch towards a fast-twitch muscle phenotype during EAE. Using ex vivo muscle contractility experiments, we observed reductions in muscle strength and contraction speed, but no changes in muscle fatigability of EAE mice. However, carnosine levels were unaltered during all stages of EAE, and even though oral carnosine supplementation dose-dependently increased muscle carnosine levels up to + 94% after 56 days EAE, this did not improve muscle function of EAE mice. In conclusion, EAE mice display significant, yet time-dependent, muscular alterations, and carnosine intervention does not improve muscle function in EAE.

Carnosine, oxidative and carbonyl stress, antioxidants and muscle fiber characteristics of quadriceps muscle of patients with COPD

BACKGROUND

Oxidative/carbonyl stress is elevated in lower-limb muscles of patients with Chronic Obstructive Pulmonary Disease (COPD). Carnosine is a skeletal muscle antioxidant particularly present in fast-twitch fibers.

AIMS

To compare muscle carnosine, oxidative/carbonyl stress, antioxidants and fiber characteristics between patients with COPD and healthy controls (HCs), and between patients after stratification for airflow limitation (mild/moderate vs. severe/very-severe). To investigate correlates of carnosine in patients with COPD.

METHODS

A vastus lateralis muscle biopsy was obtained from 40 patients with stable COPD and 20 age/sex matched HCs. Carnosine, oxidative/carbonyl stress, antioxidants, fiber characteristics, quadriceps strength and endurance (QE), VO₂peak (incremental cycle test) and physical activity (PA) were determined.

RESULTS

Patients with COPD had a similar carnosine concentration (4.16 mmol/kg wet weight (WW) (SD 1.93)) to HCs (4.64 mmol/kgWW (SD 1.71)) and significantly higher percentage of fast-twitch fibers and lower QE, VO₂peak and PA vs. HCs. Patients with severe/very-severe COPD had a 30% lower carnosine concentration (3.24 mmol/kgWW (SD 1.79); n=15) vs. patients with mild/moderate COPD (4.71 mmol/kgWW (SD 1.83); n=25; P=0.02) and significantly lower VO₂peak and PA vs. patients with mild/moderate COPD. Carnosine correlated significantly with QE (r_s=0.427), VO₂peak (r_s=0.334), PA (r_s=0.379) and lung function parameters in patients with COPD.

CONCLUSION

Despite having the highest proportion of fast-twitch fibers, patients with severe/very-severe COPD displayed a 30% lower muscle carnosine concentration compared to patients with mild/moderate COPD. As no oxidative/carbonyl stress markers, nor antioxidants were affected, the observed carnosine deficiency is thought to be a possible first sign of muscle redox balance abnormalities.

Carnosine, Small but Mighty-Prospect of Use as Functional Ingredient for Functional Food Formulation

Carnosine is a dipeptide synthesized in the body from β-alanine and L-histidine. It is found in high concentrations in the brain, muscle, and gastrointestinal tissues of humans and is present in all vertebrates. Carnosine has a number of beneficial antioxidant properties. For example, carnosine scavenges reactive oxygen species (ROS) as well as alpha-beta unsaturated aldehydes created by peroxidation of fatty acid cell membranes during oxidative stress. Carnosine can oppose glycation, and it can chelate divalent metal ions. Carnosine alleviates diabetic nephropathy by protecting podocyte and mesangial cells, and can slow down aging. Its component, the amino acid beta-alanine, is particularly interesting as a dietary supplement for athletes because it increases muscle carnosine, and improves effectiveness of exercise and stimulation and contraction in muscles. Carnosine is widely used among athletes in the form of supplements, but rarely in the population of cardiovascular or diabetic patients. Much less is known, if any, about its potential use in enriched food. In the present review, we aimed to provide recent knowledge on carnosine properties and distribution, its metabolism (synthesis and degradation), and analytical methods for carnosine determination, since one of the difficulties is the measurement of carnosine concentration in human samples. Furthermore, the potential mechanisms of carnosine's biological effects in musculature, metabolism and on immunomodulation are discussed. Finally, this review provides a section on carnosine supplementation in the form of functional food and potential health benefits and up to the present, neglected clinical use of carnosine.

Dietary supplementation with L-carnosine improves patient-reported outcomes, autonomic nervous system performance, and brain metabolism in 3 adult patients with multiple sclerosis

This pilot trial reports the effects of L-carnosine administration on autonomic nervous system performance, brain metabolism, and various patient- and clinician-reported outcomes in a case series of patients with multiple sclerosis (MS). We hypothesized that medium-term L-carnosine supplementation would improve selected patient- and clinician-reported outcomes in MS patients, with no negative effects on self-reported side effects. L-carnosine (2 g/day) was administered orally for 8 weeks in 2 women and one man suffering from MS. The intensity of symptoms and signs of MS after L-carnosine administration diminished in 5 out of 7 domains in CASE 1, in 3 out of 7 domains in CASE 2, and one domain in CASE 3; general fatigue was reduced in all 3 cases at the follow-up. This was accompanied by an improved walking distance to exhaustion in all patients, with values improved for 51.1% in CASE 1, 19.5% in CASE 2, and 2.1% in CASE 3 at 8-week follow-up. Tests of autonomic cardiovascular reflexes demonstrate normalized parasympathetic modulation and balanced sympathetic function after L-carnosine intervention in all MS cases. An increase in serum total antioxidant capacity (TAC) was found at 8-week follow-up in all patients (from 4.6 to 49.6%); this was accompanied by lower blood lactate at post-administration in all cases (23.5% on average). Single-voxel 1.5 T MR spectroscopy revealed increased brain choline-contained compounds (18.9% on average), total creatine (21.2%), and myo-inositol levels (12.3%) in girus cinguli at 8-week follow-up in all MS cases. This case study demonstrates that an 8-week intervention with L-carnosine appears to be a safe and beneficial therapeutic strategy with regard to the reduction of presence and severity of symptoms of MS.

Immunomodulatory Effects of Exercise in Experimental Multiple Sclerosis

Multiple Sclerosis (MS) is a demyelinating and neurodegenerative disease. Though a specific antigen has not been identified, it is widely accepted that MS is an autoimmune disorder characterized by myelin-directed immune attack. Pharmacological treatments for MS are based on immunomodulatory or immunosuppressant drugs, designed to attenuate or dampen the immune reaction, to improve neurological functions. Recently, rehabilitation has gained increasing attention in the scientific community dealing with MS. Engagement of people with MS in exercise programs has been associated with a number of functional improvements in mobility, balance, and motor coordination. Moreover, several studies indicate the effectiveness of exercise against fatigue and mood disorders that are frequently associated with the disease. However, whether exercise acts like an immunomodulatory therapy is still an unresolved question. A good tool to address this issue is provided by the study of the immunomodulatory effects of exercise in an animal model of MS, including the experimental autoimmune encephalomyelitis (EAE), the Theiler's virus induced-demyelinating disease (TMEV-IDD) and toxic-demyelinating models, cuprizone (CPZ), and lysolecithin (LPC). So far, despite the availability of different animal models, most of the pre-clinical data have been gained in EAE and to a lesser extent in CPZ and LPC. These studies have highlighted beneficial effects of exercise, suggesting the modulation of both the innate and the adaptive immune response in the peripheral blood as well as in the brain. In the present paper, starting from the biological differences among MS animal models in terms of immune system involvement, we revise the literature regarding the effects of exercise in EAE, CPZ, and LPC, and critically highlight the advantages of either model, including the so-far unexplored TMEV-IDD, to address the immune effects of exercise in MS.

Exercise intensity-dependent immunomodulatory effects on encephalomyelitis

Background

Exercise training (ET) has beneficial effects on multiple sclerosis and its animal model experimental autoimmune encephalomyelitis (EAE). However, the intensity‐dependent effects of ET on the systemic immune system in EAE remain undefined.

Objective

(1) To compare the systemic immune modulatory effects of moderate versus high‐intensity ET protocols in protecting against development of EAE; (2) To investigate whether ET affects autoimmunity selectively, or causes general immunosuppression.

Methods

Healthy mice performed moderate or high‐intensity treadmill running programs. Proteolipid protein (PLP)‐induced transfer EAE was utilized to examine ET effects specifically on the systemic immune system. Lymph node (LN)‐T cells from trained versus sedentary donor mice were transferred to naïve recipients and EAE severity was assessed, by clinical assessment and histopathological analysis. LN‐T cells derived from donor trained versus sedentary PLP‐immunized mice were analyzed in vitro for proliferation assays by flow cytometry analysis and cytokine and chemokine receptor gene expression using real‐time PCR. T cell‐dependent immune responses of trained versus sedentary mice to the nonautoantigen ovalbumin and susceptibility to Escherichia coli‐induced acute peritonitis were examined.

Results

High‐intensity training in healthy donor mice induced significantly greater inhibition than moderate‐intensity training on proliferation and generation of encephalitogenic T cells in response to PLP‐immunization, and on EAE severity upon their transfer into recipient mice. High‐intensity training also inhibited LN‐T cell proliferation in response to ovalbumin immunization. E. coli bacterial counts and dissemination were not affected by training.

Interpretation

High‐intensity training induces superior effects in preventing autoimmunity in EAE, but does not alter immune responses to E. coli infection.

The Potential of Carnosine in Brain-Related Disorders: A Comprehensive Review of Current Evidence

Neurological, neurodegenerative, and psychiatric disorders represent a serious burden because of their increasing prevalence, risk of disability, and the lack of effective causal/disease-modifying treatments. There is a growing body of evidence indicating potentially favourable effects of carnosine, which is an over-the-counter food supplement, in peripheral tissues. Although most studies to date have focused on the role of carnosine in metabolic and cardiovascular disorders, the physiological presence of this di-peptide and its analogues in the brain together with their ability to cross the blood-brain barrier as well as evidence from in vitro, animal, and human studies suggest carnosine as a promising therapeutic target in brain disorders. In this review, we aim to provide a comprehensive overview of the role of carnosine in neurological, neurodevelopmental, neurodegenerative, and psychiatric disorders, summarizing current evidence from cell, animal, and human cross-sectional, longitudinal studies, and randomized controlled trials.

Pivotal role of carnosine in the modulation of brain cells activity: Multimodal mechanism of action and therapeutic potential in neurodegenerative disorders

Carnosine (β-alanyl-l-histidine), a dipeptide, is an endogenous antioxidant widely distributed in excitable tissues like muscles and the brain. Although discovered more than a hundred years ago and having been extensively studied in the periphery, the role of carnosine in the brain remains mysterious. Carnosinemia, a rare metabolic disorder with increased levels of carnosine in urine and low levels or absence of carnosinase in the blood, is associated with severe neurological symptoms in humans. This review deals with the role of carnosine in the brain in both physiological and pathological conditions, with a focus on preclinical evidence suggesting a high therapeutic potential of carnosine in neurodegenerative disorders. We review carnosine and carnosinemia's discoveries and the extensive research on the role and benefits of carnosine in the periphery. We then turn to carnosine's biochemistry and distribution in the brain. Using an array of recent observations as a foundation, we draw a parallel with the role of carnosine in muscles and speculate on the role of carnosine in promoting the metabolic support of neurons by glial cells. Finally, carnosine has been shown to exert a multimodal activity including inhibition of protein cross-linking and aggregation of amyloid-β and related proteins, free radical generation, nitric oxide detoxification, and an anti-inflammatory activity. It could thus play an important role in the prevention and treatment of neurodegenerative diseases such as Alzheimer's disease. We discuss the potential of carnosine in this context and speculate on new preclinical research directions.

Regular Exercise Modifies Histopathological Outcomes of Pharmacological Treatment in Experimental Autoimmune Encephalomyelitis

Background: Although it has been suggested that healthier lifestyle may optimize effects of the immunomodulation drugs for treating multiple sclerosis (MS), the knowledge regarding this kind of interactions is limited.

Objective: The aim of the present study was to investigate the effects of treadmill exercise in combination with pharmacological treatment in an animal model for MS.

Methods: C57BL/6J female mice were subjected to daily treadmill exercise for 4 weeks before immunization and 6 weeks before clinical presentation of disease. Dimethyl fumarate (DMF) or glatiramer acetate (GA) were administered after the first clinical relapse. Histopathological analyses were carried out in the lumbar spinal cord at peak disease and at 1 or 14 days post-treatment (dpt).

Results: Exercised-GA treated animals demonstrated decreased astrocytic response in the spinal dorsal horn with an improvement in the paw print pressure. Exercised-DMF treated animals showed an increased microglial/macrophage response on both ventral and dorsal horn that were associated with clinical improvement and synaptic motoneuron inputs density.

Conclusion: The present data suggest that prior regular exercise can modify the effects of pharmacological treatment administered after the first relapse in a murine model for MS.