Whole Exome Sequencing in Multi-Incident Families Identifies Novel Candidate Genes for Multiple Sclerosis.

Multiple sclerosis (MS) is a degenerative disease of the central nervous system in which auto-immunity-induced demyelination occurs. MS is thought to be caused by a complex interplay of environmental and genetic risk factors. While most genetic studies have focused on identifying common genetic variants for MS through genome-wide association studies, the objective of the present study was to identify rare genetic variants contributing to MS susceptibility. We used whole exome sequencing (WES) followed by co-segregation analyses in nine multi-incident families with two to four affected individuals. WES was performed in 31 family members with and without MS. After applying a suite of selection criteria, co-segregation analyses for a number of rare variants selected from the WES results were performed, adding 24 family members. This approach resulted in 12 exonic rare variants that showed acceptable co-segregation with MS within the nine families, implicating the genes MBP, PLK1, MECP2, MTMR7, TOX3, CPT1A, SORCS1, TRIM66, ITPR3, TTC28, CACNA1F, and PRAM1. Of these, three genes (MBP, MECP2, and CPT1A) have been previously reported as carrying MS-related rare variants. Six additional genes (MTMR7, TOX3, SORCS1, ITPR3, TTC28, and PRAM1) have also been implicated in MS through common genetic variants. The proteins encoded by all twelve genes containing rare variants interact in a molecular framework that points to biological processes involved in (de-/re-)myelination and auto-immunity. Our approach provides clues to possible molecular mechanisms underlying MS that should be studied further in cellular and/or animal models.

Reduced Voluntary Activation During Brief and Sustained Contractions of a Hand Muscle in Secondary-Progressive Multiple Sclerosis Patients.

BACKGROUND: Secondary-progressive multiple sclerosis (SPMS) patients have structural cortical damage resulting in increased compensatory cortical activity during (submaximal) performance. However, functional effects of changed cortical output are difficult to measure. The interpolated-twitch technique allows for measurement of voluntary activation (VA) necessary for force production. This study aimed to determine VA, force, and muscle fatigue during brief and sustained contractions in SPMS patients. Because fatigue effects are not confined to the motor system, we additionally examined fatiguing effects on cognitive performance. METHODS: Twenty-five SPMS and 25 sex-, age-, and education-matched participants performed brief (5 seconds) and sustained (2 minutes) maximal index finger abductions. To evaluate VA, double-pulse twitches were evoked before, during, and after contractions. Additionally, data were compared with data obtained in relapsing-remitting multiple sclerosis (RRMS) patients. Subjects also performed choice-reaction time tasks before and after the sustained contraction. RESULTS: During brief contractions, VA (85% vs 94%,P= .004) and force (25 N vs 32 N,P= .011) were lower for SPMS patients than controls. During sustained contractions, VA (P= .001) was also lower, resulting in greater force decline (73% vs 63%,P< .001) and reduced peripheral fatigue (19% vs 50%,P< .001). Comparisons with RRMS resulted in lower VA, greater force decline, and greater estimated central fatigue in SPMS. SPMS patients were slower (P< .001) and made more errors (P< .001) than controls, but neither group reduced their performance after the sustained contraction. CONCLUSION: SPMS patients had lower VA than RRMS patients and controls. The importance of voluntary activation for muscle force and fatigability warrants targeted rehabilitation strategies.

Muscle Fatigability During a Sustained Index Finger Abduction and Depression Scores Are Associated With Perceived Fatigue in Patients With Relapsing-Remitting Multiple Sclerosis.

INTRODUCTION: Fatigue is a common and debilitating symptom in patients with multiple sclerosis (MS). Self-reported levels of perceived fatigue are associated with both patient characteristics and clinical measures. Pilot analysis indicated that muscle fatigability combined with depression scores was highly associated with perceived fatigue in patients with MS. Studies that combine physiological and psychological constructs to explain MS-related fatigue are scarce. Therefore, the present study aimed to evaluate the robustness of the association between perceived fatigue, muscle fatigability, and depression scores in MS. METHODS: Eighty-six patients with relapsing-remitting MS completed 2 fatigue questionnaires (Fatigue Severity Scale [FSS] and Modified Fatigue Impact Scale [MFIS]) and a depression questionnaire (Hospital Anxiety and Depression Scale [HADS]). Maximal index finger abduction force (maximum voluntary contraction [MVC]) was measured, as well as muscle fatigability during a 2-minutes sustained maximal contraction. Multivariable regression analyses were used to analyze the association between perceived fatigue, and muscle fatigability and depression scores. RESULTS: Perceived fatigue was associated with depression, muscle fatigability, and, depending on the questionnaire, to sex or to MVC. The model explained 40% and 48% of the variation in perception of fatigue as indexed with FSS questionnaire (r(partial): HADS 0.45, muscle fatigability 0.45, MVC -0.14, sex 0.32), and MFIS physical questionnaire (r(partial): HADS 0.59, muscle fatigability 0.49, MVC -0.38), respectively. CONCLUSIONS: The found association accentuates the importance of including both physiological fatigability-related and psychological mood-related constructs in models to explain perceived fatigue in patients with MS. The model also directs future research toward applying effortful conditions and emphasizes the importance of assessing different constructs when evaluating rehabilitation strategies to reduce MS-related fatigue.

Reduced Dual-Task Performance in MS Patients Is Further Decreased by Muscle Fatigue.

BACKGROUND: Multiple sclerosis (MS) can be accompanied by motor, cognitive, and sensory impairments. Additionally, MS patients often report fatigue as one of their most debilitating symptoms. It is, therefore, expected that MS patients will have difficulties in performing cognitive-motor dual tasks (DTs), especially in a fatiguing condition. OBJECTIVE: To determine whether MS patients are more challenged by a DT than controls in a fatiguing and less-fatiguing condition and whether DT performance is associated with perceived fatigue. METHODS: A group of 19 MS patients and 19 age-, sex-, and education-matched controls performed a cognitive task (2-choice reaction time task) separately or concurrent with a low-force or a high-force motor task (index finger abduction at 10% or 30% maximal voluntary contraction). RESULTS: MS patients performed less well on a cognitive task than controls. Cognitive task performance under DT conditions decreased more for MS patients. Moreover, under high-force DT conditions, cognitive performance declined in both groups but to a larger degree for MS patients. Besides a decline in cognitive task performance, MS patients also showed a stronger decrease in motor performance under high-force DT conditions. DT costs were positively related to perceived fatigue as measured by questionnaires. CONCLUSIONS: Compared with controls, MS patients performed less well on DTs as demonstrated by a reduction in both cognitive and motor performances. This performance decrease was stronger under fatiguing conditions and was related to the sense of fatigue of MS patients. These data illustrate problems that MS patients may encounter in daily life because of their fatigue.

Cerebral white matter blood flow and energy metabolism in multiple sclerosis.

BACKGROUND: Cerebral blood flow (CBF) is reduced in normal-appearing white matter (NAWM) of subjects with multiple sclerosis (MS), but the underlying mechanism is unknown. OBJECTIVE: The objective of this article is to assess the relationship between reduced NAWM CBF and both axonal mitochondrial metabolism and astrocytic phosphocreatine (PCr) metabolism. METHODS: Ten healthy controls and 25 MS subjects were studied with 3 Tesla magnetic resonance imaging. CBF was measured using pseudo-continuous arterial spin labeling. N-acetylaspartate/creatine (NAA/Cr) ratios (axonal mitochondrial metabolism) were obtained using (1)H-MR spectroscopy and PCr/ß-ATP ratios using (31)P-MR spectroscopy. In centrum semiovale NAWM, we assessed correlations between CBF and both NAA/Cr and PCr/ß-ATP ratios. RESULTS: Subjects with MS had a widespread reduction in CBF of NAWM (centrum semiovale, periventricular, frontal and occipital), and gray matter (frontoparietal cortex and thalamus). Compared to controls, NAA/Cr in NAWM of the centrum semiovale of MS subjects was decreased, whereas PCr/ß-ATP was increased. We found no correlations between CBF and PCr/ß-ATP. CBF and NAA/Cr correlated in controls (p = 0.02), but not in MS subjects (p = 0.68). CONCLUSIONS: Our results suggest that in MS patients there is no relationship between reduced CBF in NAWM and impaired axonal mitochondrial metabolism or astrocytic PCr metabolism.

Therapeutic potential of fluoxetine in neurological disorders.

The selective serotonin reuptake inhibitor (SSRI) fluoxetine, which is registered for a variety of psychiatric disorders, has been found to stimulate the cAMP-responsive element binding protein (CREB), increase the production of brain-derived neurotrophic factor (BNDF) and the neurotrophic peptide S100beta, enhance glycogenolysis in astrocytes, block voltage-gated calcium and sodium channels, and decrease the conductance of mitochondrial voltage-dependent anion channels (VDACs). These mechanisms of actions suggest that fluoxetine may also have potential for the treatment of a number of neurological disorders. We performed a Pubmed search to review what is known about possible therapeutic effects of fluoxetine in animal models and patients with neurological disorders. Beneficial effects of fluoxetine have been noted in animal models of stroke, multiple sclerosis, and epilepsy. Fluoxetine was reported to improve neurological manifestations in patients with Alzheimer's disease, stroke, Huntington's disease, multiple sclerosis, traumatic brain injury, and epilepsy. Clinical studies so far were small and often poorly designed. Results were inconclusive and contradictory. However, the available preclinical data justify further clinical trials to determine the therapeutic potential of fluoxetine in neurological disorders.

Erythrocyte membrane fatty acids in benign and progressive forms of multiple sclerosis.

BACKGROUND: There is no good explanation why a proportion of patients with multiple sclerosis (MS) have a relatively benign form of the disease. An imbalance between saturated and unsaturated fatty acids (FA) might influence the disease course of MS. AIM: To assess whether the erythrocyte membrane fatty acid composition, which is a biological marker of long term dietary FA consumption, is different between patients with benign and progressive MS. METHODS: The erythrocyte membrane FA composition was measured by gas chromatography in 23 healthy controls, 27 patients with benign MS, 32 patients with secondary progressive MS and 23 patients with primary progressive MS. None of the patients was following a special diet. RESULTS: No significant differences in levels of saturated and unsaturated FA or in omega-3- and omega-6-polyunsaturated FA were found between controls and patients with the different subtypes of MS. CONCLUSION: Our data suggest that factors other than dietary fatty acid consumption are responsible for the different disease courses of MS.

Oxidative stress in serum and peripheral blood leukocytes in patients with different disease courses of multiple sclerosis.

BACKGROUND: The role of oxidative stress in patients with multiple sclerosis (MS) is poorly understood. OBJECTIVE: To investigate oxidative stress in serum and peripheral blood leukocytes in patients with different disease courses of MS. METHODS: Diene conjugate (DC) levels (a measure of lipid peroxidation), total antioxidative activity (AOA) and total antiradical activity (ARA) were measured in serum and peripheral blood leukocytes from 30 patients with benign relapsing remitting MS (BMS), 27 with secondary progressive MS (SPMS), 29 with primary progressive MS (PPMS), and 30 healthy controls. All MS patients were in a clinically stable phase. RESULTS: Serum DC levels were elevated in patients with BMS (p <0.05), SPMS (p <0.01) and PPMS (p <0.001). Serum total AOA and ARA were not different between MS patients and controls. Compared to controls, leukocyte DC levels were not different in each MS subgroup, but total ARA was elevated. There was a strong correlation, both in controls and MS patients, between leukocyte DC levels and leukocyte total ARA (p <0.0001) and leukocyte total AOA (p <0.0001). CONCLUSION: Oxidative stress occurs in progressive as well as benign MS. The finding that cells withstand oxidative stress, due to upregulated cellular antioxidant defence mechanisms, suggests that reactive oxygen species (ROS) formation in MS is not necessarily deleterious.

Serum uric acid levels and leukocyte nitric oxide production in multiple sclerosis patients outside relapses.

BACKGROUND: A number of studies found that patients with multiple sclerosis (MS) have low serum levels of uric acid. It is unclear whether this represents a primary deficit or secondary effect. Uric acid is a scavenger of peroxynitrite, which is the product of nitric oxide (NO) and superoxide. Because peripheral blood leukocyte NO production and NO metabolites in serum are raised in MS patients, associations might be expected between serum uric acid levels and peripheral NO production. METHODS: Serum levels of uric acid and NO production by peripheral blood leukocytes were measured in 60 patients with MS without a relapse in the past 3 months, and 30 age- and sex-matched healthy controls. Uric acid was determined with the uricase PAP method, and NO production was assayed by measuring nitrite concentration in supernatants of lysed leukocytes. RESULTS: Serum uric acid levels were not different between MS patients and controls. Compared to controls, patients with MS had significantly higher peripheral blood leukocytes nitrite concentrations (p<0.001). There was no correlation between leukocyte nitrite concentration and serum uric acid levels. CONCLUSIONS: Our findings suggest that in MS patients there is no primary deficit in serum uric acid. NO production by peripheral blood leukocytes is increased, but there is no association with serum uric acid levels.