Date Published: February 20, 2019
Publisher: Public Library of Science
Author(s): Rafael Marins Rezende, Maria do Carmo Gouveia Pelúzio, Franciany de Jesus Silva, Emanuel Mattos Della Lucia, Lukiya Silva Campos Favarato, Hercia Stampini Duarte Martino, Antônio José Natali, Michael Bader.
The objective of this study was to verify the effects of aerobic exercise associated with tryptophan (TRP) supplementation on hyperalgesia, as well as on cortisol, IL-6 and TNF concentrations in female rats with experimental fibromyalgia (FM). Female Wistar rats (initial body weight: ~ 350 g; age: 12 months) were randomly divided into 5 groups: CON (Control); F (Fibromyalgia induced); FE (Fibromyalgia induced plus exercise); FES (Fibromyalgia induced plus exercise and TRP supplementation) and FS (Fibromyalgia induced plus TRP supplementation). Fibromyalgia was induced with two injections (20 μL) of acidic saline (pH 4.0) into the right gastrocnemius muscle with a 3-day interval. Control animals received the same doses of neutral saline (pH 7.4). The exercised animals underwent progressive low-intensity aerobic exercise (LIAE) on a treadmill (10–12 m/min, 30–45 min/day, 5 days/week) for three weeks. During this period, the supplemented animals received a TRP supplemented diet (210 g/week), while the others received a control diet. Mechanical hyperalgesia was evaluated weekly and serum cortisol and muscle IL-6 and TNF concentrations were assessed after three weeks of interventions. Experimental FM caused bilateral hind paw hyperalgesia and augmented serum cortisol and muscle IL-6 concentrations. After 3 weeks of interventions, LIAE alone reduced hyperalgesia (151%) and reduced serum cortisol concentrations (72%). Tryptophan supplementation itself diminished hyperalgesia (57%) and reduced serum cortisol concentrations (67%). Adding TRP supplementation to LIAE did not further reduce hyperalgesia significantly (11%), which was followed by an important decrease in muscle IL-6 concentrations (68%), though reduction in serum cortisol pulled back to 45%. Muscle TNF concentrations were not affected. In conclusion, the association of TRP supplementation to LIAE does not potentiate significantly the reduction of bilateral mechanical hyperalgesia promoted by LIAE in female rats with experimental FM, however an important decrease in IL-6 is evident.
Fibromyalgia (FM) is a syndrome characterized by chronic widespread pain, fatigue, anxiety and sleep, cognitive and mood disorders . It is present in 2 to 5% of the general population, particularly in women between 50 and 80 years of age [2,3]. Fibromyalgia has been linked to neuroendocrine abnormalities, involving the main stress modulator system, the hypothalamic-pituitary-adrenal (HPA) axis, and “deficits” in endogenous pain modulation systems [4–6].
The aim of this study was to verify the effects of aerobic exercise associated with TRP supplementation on hyperalgesia, as well as on cortisol, IL-6 and TNF concentrations in 12-month-old female rats with experimental FM. It was found that by the end of 3 weeks of intervention LIAE alone reduced bilateral hyperalgesia (~ 151%) and serum cortisol concentrations (72%), while TRP supplementation itself diminished bilateral hyperalgesia (~ 57%) and cortisol concentrations (67%). Although, muscle TNF concentrations were not affected, the association of LIAE with TRP supplementation further reduced bilateral hyperalgesia (~ 162%), being an important decrease (68%) in muscle IL-6 concentrations observed, though the serum cortisol concentrations backed off to 45%.