Circulating soluble transferrin receptor concentration decreases after exercise-induced improvement of insulin sensitivity in obese individuals

Abstract

Background: Circulating soluble transferrin receptor (sTfR) has been recently found to be associated negatively with insulin sensitivity. Objective: To evaluate circulating sTfR concentration after changing insulin sensitivity in obese individuals. Design: Circulating sTfR concentration was evaluated after diet-induced weight loss in obese women (diet (D) group, n ¼ 8); after diet-induced weight loss plus resistance training (D þ RT group, n ¼ 11); and after follow-up without weight loss (control (C) group, n ¼ 7). Results: After 16 weeks, insulin sensitivity (HOMA (Homeostasis Model Assessment) value) significantly improved in parallel to weight loss (À7.3%) and reduced total fat mass (evaluated using magnetic resonance imaging) in the D group. Thigh muscle mass decreased significantly (P ¼ 0.03). Serum sTfR concentration did not change significantly. In the D þ RT group, weight loss (À8.7%) and improvement of insulin sensitivity were of similar magnitude. Thigh muscle mass was preserved (P ¼ 0.8). Serum sTfR concentration decreased significantly (P ¼ 0.001). Interestingly, higher the thigh muscle volume after weight loss, higher the decrease in circulating sTfR concentration. We also found that higher the increases in leg force at week 16, higher the decrease in circulating sTfR concentration in all individuals as a whole. No significant changes were observed in insulin sensitivity, sTfR concentration or thigh muscle mass in the C group. Conclusion: These findings suggest a long-term regulation of serum sTfR concentration by exercise-induced improvement of insulin sensitivity in obese individuals.

Biomarkers of iron metabolism are independently associated with impaired glucose metabolism and type 2 diabetes: the KORA F4 study

“…The finding of strong sTfR association with fasting insulin and HOMA-IR without finding consistent associations with hyperglycemia suggests a reverse causation scenario, with high sTfR levels being caused by high insulin levels in an insulin-resistant state. This would be in line with the observation of Fernandez-Real et al (38), who observed a decrease in sTfR concentration after exercise-induced improvement of insulin sensitivity in 26 obese women.…”

Mechanisms Linking Glucose Homeostasis and Iron Metabolism Toward the Onset and Progression of Type 2 Diabetes

“…When obese subjects were submitted to a diet and exercise program resulting in weight loss, circulating sTfR significantly decreased, and this decrease was proportional to changes in muscle volume and leg and arm force. Weight loss induced by diet alone did not affect circulating sTfR (37).…”

Osteocalcin Effect on Human β-Cells Mass and Function

“…Clinical studies have reported positive association of serum osteocalcin level with insulin sensitivity and secretion in normal subjects (24) and in patients with type 2 diabetes (49,50). Clinical studies have reported positive association of serum osteocalcin level with insulin sensitivity and secretion in normal subjects (24) and in patients with type 2 diabetes (49,50).…”

“…Kanazawal and colleagues (21) demonstrated that osteocalcin levels nega-tively correlated with fasting plasma glucose, hemoglobin A1c, percent fat, pulse wave velocity, and intima to media thickness. A Spanish study (24), performed in a cross sectional study of adult men and women who experienced weight loss with or without exercise, found that circulating osteocalcin was associated with insulin sensitivity and insulin secretion. Similar observations were reported in groups of postmenopausal women (23).…”