Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). While the etiology of MS is still largely unknown, scientists believe that the interaction of several endogenous and exogenous factors may be involved in this disease. Epidemiologists have seen an increased prevalence of MS in countries at high latitudes, where the sunlight is limited and where the populations have vitamin D deficiency and high melatonin levels. Although the functions and synthesis of vitamin D and melatonin are contrary to each other, both are involved in the immune system. While melatonin synthesis is affected by light, vitamin D deficiency may be involved in melatonin secretion. On the other hand, vitamin D deficiency reduces intestinal calcium absorption leading to gut stasis and subsequently increasing gut permeability. The latter allows gut microbiota to transfer more endotoxins such as lipopolysaccharides (LPS) into the blood. LPS stimulates the production of inflammatory cytokines within the CNS, especially the pineal gland. This review summarizes the current findings on the correlation between latitude, sunlight and vitamin D, and details their effects on intestinal calcium absorption, gut microbiota and neuroinflammatory mediators in MS. We also propose a new mechanistic pathway for the initiation of MS.

Metabolic disturbances have been implicated in demyelinating diseases including multiple sclerosis (MS). Melatonin, a naturally occurring hormone, has emerged as a potent neuroprotective candidate to reduce myelin loss and improve MS outcomes. In this study, we evaluated the effect of melatonin, at both physiological and pharmacological doses, on oligodendrocytes metabolism in an experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Results showed that melatonin decreased neurological disability scores and enhanced remyelination, significantly increasing myelin protein levels including MBP, MOG, and MOBP. In addition, melatonin attenuated inflammation by reducing pro-inflammatory cytokines (IL-1β and TNF-α) and increasing anti-inflammatory cytokines (IL-4 and IL-10). Moreover, melatonin significantly increased brain concentrations of lactate, N-acetylaspartate (NAA), and 3-hydroxy-3-methylglutaryl-coenzyme-A reductase (HMGCR). Pyruvate dehydrogenase kinase-4 (PDK-4) mRNA and protein expression levels were also increased in melatonin-treated, compared to untreated EAE mice. However, melatonin significantly inhibited active and total pyruvate dehydrogenase complex (PDC), an enzyme under the control of PDK4. In summary, although PDC activity was reduced by melatonin, it caused a reduction in inflammatory mediators while stimulating oligodendrogenesis, suggesting that oligodendrocytes are forced to use an alternative pathway to synthesize fatty acids for remyelination. We propose that combining melatonin and PDK inhibitors may provide greater benefits for MS patients than the use of melatonin therapy alone.

In recent years, the use of medicinal plants increased considerably; so that today, the use of traditional medicine, as well as medicinal plants is necessary for the aim of producing more effective drugs with fewer side effects and determining the effective doses. With the scientific name of Juglans regia, walnut plant is a medicinal plant with different properties that is considered less, despite having great therapeutic potential in the traditional medicine. The aim of this study was to review the dispersal of walnut plants, the chemical compounds, and therapeutic effects of walnuts on antioxidant activity, antidiabetic, hypolipidemic, antimicrobial, and antihypertensive activities, as well as liver protection. Data of this review study have been collected from the books and scientific articles published in databases such as Science Direct, Web of Science, Scopus, PubMed, and Scientific Information Database. While this plant having high antioxidant capabilities, walnuts are composed of many chemical compounds such as ascorbic acid, flavonoids, quercetin, and caffeic acid. Experimental studies have shown that walnuts reduced blood glucose and lipids and also decreased blood pressure. They have antioxidant, antidiabetic, antimicrobial, and liver-protective properties. The use of walnuts in traditional medicine and review of experimental studies demonstrated the presence of multiple, effective, and useful compounds which may provide the opportunity for the production of lipid-lowering, antidiabetes, and liver protective drugs. Due to the effects of walnuts on improving the complications of various diseases, the need for doing comprehensive clinical trials for the use of walnuts in the treatment of diseases is necessary.

Melatonin has a beneficial role in adult rat models of multiple sclerosis (MS). In this study, melatonin treatment (10 mg/kg/d) was investigated in young age (5-6 weeks old) Lewis rat model of acute experimental autoimmune encephalomyelitis (EAE) followed by assessing serum levels of lactate and melatonin. Results showed that clinical outcomes were exacerbated in melatonin- (neurological score = 6) vs PBS-treated EAE rats (score = 5). Melatonin caused a significant increase in serum IFN-γ, in comparison to PBS-treated EAE rats whereas no considerable change in IL-4 levels were found, although they were significantly lower than those of controls. The ratio of IFN-γ/IL-4, an indicator of Th-1/Th-2, was significantly higher in PBS- and melatonin- treated EAE rats, in comparison to controls. Moreover, results showed increased lymphocyte infiltration, activated astrocytes (GFAP+ cells) but also higher demyelinated plaques (MBP-deficient areas) in the lumbar spinal cord of melatonin-treated EAE rats. Finally, serum levels of lactate, but not melatonin, significantly increased in the melatonin group, compared to untreated EAE and normal rats. In conclusion, our results indicated a relationship between age and the development of EAE since a negative impact was found for melatonin on EAE recovery of young rats by enhancing IFN-γ, the ratio of Th1/Th2 cells, and astrocyte activation, which seems to delay the remyelination process. While melatonin levels decline in MS patients, lactate might be a potential diagnostic biomarker for prediction of disease progression. Early administration of melatonin in the acute phase of MS might be harmful and needs further investigations.

Cytokines are important factors of the immune system in autoimmune diseases such as multiple sclerosis (MS) in which damage caused by oxidants plays a major role in the pathology. Melatonin secreted by the pineal gland has recently been considered as an antioxidant. The purpose of this study was to determine the relationship between melatonin and cytokines in patients with MS. Thirty patients with MS and 30 healthy controls were selected. Serum levels of melatonin and cytokines, including interleukin-4, interferon-γ, and tumor necrosis factor alpha (TNF-α), were detected in all participants by the enzyme-linked immunosorbent assay (ELISA) method. There was a significant difference between patient and control groups in the levels of melatonin and TNF-α. Also, no significant correlation between the serum levels of melatonin and cytokines in both patient and control groups was seen. We concluded that decrease of melatonin and subsequent increase of pro-inflammatory cytokine, TNF-α, could be a factor in the inflammatory reactions in the pathologic process of MS.