Vitamin D supplementation affects the IGF system in men after acute exercise

Objective Contradictory data between the Insulin-Like Growth Factor System (IGF) system and exercise may be due to alteration in IGF binding proteins. Vitamin D (D) deficiency has been related to muscle weakness and Insulin Like Growth Factor Binding Protein 3 (IGFBP3). A Vit. D and acute exercise merge is proposed to modify the IGF system. Design D insufficient and deficient men (39.0 ± 8.6 yo with serum D (25OH D) 20.0 ± 7.7 ng/mL) did 1 h of stretching (ST), aerobic (AB), and resistance (RT) exercises, before and after 28 d of 4000 IU/d Vit. D3 (D, n = 6) or Placebo (P, n = 7). ST, a time/attention control visit, interchanged unreceptive movements. AB was moderate intensity treadmill walking. RT rotated moderate strength 50% 1-RM repetitions (15, 10) of squat, bench press, leg press, and lat pull down. Serum Total IGF1 (TIGF1), Insulin Like Growth Factor Binding Protein 1 (IGFBP1), and IGFBP3 were measured before (T1, fasting), immediately after (T2), and 2 h post (T3) exercise. Results After ST, IGFBP3 was greater in the D group at T2 (2948, 2130 ng/mL; p \u3c 0.03) and T3 (3087, 2212; p \u3c 0.02). During RT, TIGF1 decreased in the Placebo (P) group from T1 to T3 (151.4, 107.3 ng/mL; p \u3c 0.05), while IGFBP1 increased in the D group from T1 to T3 (26.5, 96.2 ng/mL; p \u3c 0.05). RT IGFBP3 was greater at T1, T2, and T3 in the D group (2932.5, 2110.7; p \u3c 0.03), (3163.9, 2392.5; p \u3c 0.04), and (3355.3, 2353.1; p \u3c 0.01). In AB, IGFBP3 was greater in the D group at T2 (3128.6, 2226.3.0; p \u3c 0.04) and T3 (2949.7, 2135.1; p \u3c 0.05). Conclusion D supplementation amplified IGFBP3 after low or moderate activity which may increase the delivery of IGF1 to tissues. Resistance exercise with D not only increased IGFBP3 and IGFBP1 levels but also conserved TIGF1 levels, possibly shifting the IGF system for enriched muscle well-being