**Author details**

humans and animals on producing genomic effects that alter calcium, phosphate, and the metabolism of phospholipids [103]. These changes are important for the normal, functional development of the skeletal musculature. There is evidence that the ingestion of vitamin D improves muscle strength and functional capacity. It should be considered that vitamin D decreases in elderly populations, and supplementation is necessary [104]. Recent studies have centered on the potential therapeutic implications of vitamin D and its deficiency, in the regulation of chronic pain processing in FM, through the interactions of central and peripheral complexes. The primary functional scenario of the interaction is based on the presence of the vitamin D receptor and the 1α-hydroxylase (enzyme that converts the 25-hydroxyvitamin D by hydroxylation to the active 1,25 di-hydroxyl-vitamin D (1,25 (OH) 2D3) in many areas of the human central nervous system, among which are: the prefrontal cortex, the amygdala, the raphe, the gelatinous substance, the cerebellum, the hippocampus, the cingulate cortex, the substance *nigra*, the thalamus, and the hypothalamus [105]. Both the receptor and the enzyme have been found in neuronal and glial cells [106]. The general characteristics of hypovitaminosis D are body pain, especially in the shoulder, the thoracic cavity, and lumbar and pelvic regions. The biological relationship between generalized chronic pain and vitamin D deficiency continues to be an interesting investigative topic. Patients with FM could have vitamin D deficiencies due to the characteristics of their pain, poor mobility, or the associated depression that decreases free time exposed to sunlight, or by the increase in adiposity that favors the decrease in vitamin D synthesis. Therefore, the participation of the 1,25-OHD in the regulation of the immune system could be involved in vitamin D deficiency and muscular pain [107]. A systematic review that sought evidence of an association between FM and vitamin D deficiency was inconclusive, without finding improvement in muscular pain after supplementation. However, patients with concurrent risk factors between FM and other pathologies like osteoporosis should be tested in case a vitamin D deficiency is found that would favor muscle strength [108]. The search between vitamin D deficiency and the pres-

In conclusion, oxidative stress, mitochondrial dysfunction, autophagy, multivitamin deficiencies, and the imbalance between oxidants and antioxidants are an intriguing and clinically attractive topic to elucidate the state and progression of FM. Pharmacological treatment alone is insufficient for the majority of patients who suffer from FM syndrome. It is recommended to approach treatment in a multidisciplinary way in clinical practice. Moderate physical activity and the supplementation/ingestion of antioxidants could be beneficial in regulating the

ence of FM remains an inconclusive matter.

24 Discussions of Unusual Topics in Fibromyalgia

**8. Conclusion**

oxidative state.

**Conflicts of interest**

There are no conflicts of interest to report.

This study did not receive any funding.

Alejandra Guillermina Miranda-Díaz\* and Simón Quetzalcóatl Rodríguez-Lara

\*Address all correspondence to: kindalex1@outlook.com

Department of Physiology, Institute of Clinical and Experimental Therapeutics, University Health Sciences Centre, University of Guadalajara, Guadalajara, Jalisco, México
