Quercetin Modulates IGF-I and IGF-II Levels After Eccentric Exercise-Induced Muscle-Damage: A Placebo-Controlled Study

Abstract

Background: Prolonged or unaccustomed eccentric exercise may cause muscle damage and depending from its extent, this event negatively affects physical performance.

Objectives: The aim of the present investigation was to evaluate, in humans, the effect of the flavonoid quercetin on circulating levels of the anabolic insulin-like growth factor 1 (IGF-I) and insulin-like growth factor 2 (IGF-II), produced during the recovery period after an eccentric-induced muscle damage (EIMD).

Methods: A randomized, double-blind, crossover study has been performed; twelve young men ingested quercetin (1 g/day) or placebo for 14 days and then underwent an eccentric-induced muscle damaging protocol. Blood samples were collected, and cell damage markers [creatine kinase (CK), lactate dehydrogenase (LDH) and myoglobin (Mb)], the inflammatory responsive interleukin 6 (IL-6), IGF-I and IGF-II levels were evaluated before the exercise and at different recovery times from 24 hours to 7 days after EIMD.

Results: We found that, in placebo treatment the increase in IGF-I (72 h) preceded IGF-II increase (7 d). After Q supplementation there was a more marked increase in IGF-I levels and notably, the IGF-II peak was found earlier, compared to placebo, at the same time of IGF-I (72 h). Quercetin significantly reduced plasma markers of cell damage [CK (p<0.005), LDH (p<0.001) and Mb (p<0.05)] and the interleukin 6 level [IL-6 (p<0.05)] during recovery period following EIMD compared to placebo.

Conclusions: Our data are encouraging about the use of quercetin as dietary supplementation strategy to adopt in order to mitigate and promote a faster recovery after eccentric exercise as suggested by the increase in plasma levels of the anabolic factors IGF-I and IGF-II.

Keywords: anabolic factors; anti-inflammatory; antioxidant; eccentric exercise; skeletal muscle mass recovery.

Figure 1

Flow diagram of the study. Twelve subjects were randomly assigned to quercetin group (n = 6) or to placebo group (n = 6) and then crossed over to the opposite condition. Subjects were given two caps of quercetin (1 g/d) or placebo for 2 weeks. On day 15, subjects were submitted to eccentric exercise (EE). Blood collections were performed before the EE (Pre EE), 24, 48, 72 and 96 hours (24 h – 96 h), and 7 days after EE (7 d).

Figure 2

Effect of quercetin supplementation on creatine kinase (CK), lactate dehydrogenase (LDH), myoglobin (Mb) and Interleukin-6 (IL-6) plasma levels. The levels of creatine kinase (CK), lactate dehydrogenase (LDH), myoglobin (Mb) and Interleukin-6 (IL-6), were measured in plasma of quercetin/placebo supplemented subjects before the eccentric exercise (Pre EE) and after 24, 48, 72 and 96 hours (24 h – 96 h) and after 7 days (7 d) recovery time. Values are expressed as means ± pooled SEM. n =12 for each group. *P < 0.05 vs Pre EE and ^#P < 0.05 vs placebo.

Figure 3

Effect of quercetin supplementation on insulin-like growth factor 1 (IGF-I) and insulin-like growth factor 2 (IGF-II) plasma levels. The levels of insulin-like growth factor 1 (IGF-I) and insulin-like growth factor 2 (IGF-II) were measured in plasma of quercetin/placebo supplemented subjects before the eccentric exercise (Pre EE) and after 24, 48, 72 and 96 hours (24 h – 96 h) and after 7 days (7 d) recovery time. Values are expressed as means ± pooled SEM. n =12 for each group. *P < 0.05 vs Pre EE and ^#P < 0.05 vs placebo.