The Ratio of sTfR/Ferritin is Associated with the Expression Level of TfR in Rat Bone Marrow Cells After Endurance Exercise

Abstract

Currently, it is unclear which index of haematological parameters could be used to most easily monitor iron deficiency during endurance training. To address this question, 16 male Wistar rats were randomly assigned to two groups: a sedentary group (n = 8) and an exercised group (n = 8). Initially, animals in the exercise group started running on a treadmill at a rate of 30 m/min, on a 0% grade, for 1 min/session. Running time was gradually increased by 2 min/day. The training plan was one session per day during the initial 2 weeks and two sessions per day during the third to ninth week. At the end of the 9-week experiment, we analysed the blood of the experimental animals for haemoglobin levels, erythrocyte numbers, haematocrit, serum iron levels, total iron binding capacity, transferrin saturation, serum ferritin levels and soluble transferrin receptor (sTfR) levels, and we calculated the ratio of sTfR/ferritin. Erythrocyte numbers, haemoglobin levels and haematocrit values were decreased after 9 weeks of exercise, but sTfR and sTfR/ferritin values were increased (P < 0.01 or P < 0.05). The training regime significantly increased TfR mRNA levels in the bone marrow cells of the exercised rats compared with the sedentary group (1.8 ± 0.5 vs. 1.1 ± 0.2, P < 0.01). These results revealed a significant correlation between TfR levels in the bone marrow cells and the ratio of sTfR/ferritin (r = 0.517; P < 0.01) and sTfR levels (r = 0.206; P < 0.05) in sedentary and exercised rats. In conclusion, we show that sTfR indices and the ratio of sTfR/ferritin could be useful indicators for monitoring iron deficiency during endurance training.

Hepcidin and sports anemia

“…A significant increase of the rate of radioactive iron uptake by the erythroblasts of the exercised rats was also observed. The sTfR levels significantly increased as well in the exercised rats when compared with the sedentary group [26]. These results implied that intensive exercise could lead to an increase in erythropoietic activity of the marrow.…”

“…When the body iron demand increases, iron storage in organs and tissues decreases. Intensive exercise can lead to an increase in erythropoietic activity of the marrow [25,26], and the synthesis of hemoglobin requires a large amount of iron. Therefore, intensive exercise could induce a reduction of iron stores in liver.…”

“…Although exercise can increase erythropoietic activity in marrow [25], it was found that erythrocyte numbers, haemoglobin levels and haematocrit values were significantly decreased after intensive training [20,26]. This observation may be resulted from the reduced iron absorption in small intestine and the decreased iron export to the circulation from parenchymal cells and macrophages.…”

“…Studies by Qian et al [25] and Tian et al [26] both indicated that extensive exercise could lead to an increase in erythropoietic activity of bone marrow. It has also been demonstrated that increased erythropoiesis can suppress hepcidin expression significantly [51].…”

The effect of 8-week different-intensity walking exercises on serum hepcidin, IL-6, and iron metabolism in pre-menopausal women

“…Therefore, exercise-induced changes in iron metabolism should be analyzed in detail. Even though exercise can increase erythropoietic activity in bone marrow (38), intensive training was found to have negative effects on erythrocyte numbers, Hb levels, and hematocrit (Hct) values (19,47). The main reason for this may be the reduced iron absorption in small intestine and the decreased iron export to the circulation from parenchymal cells and macrophages.…”