Associations between serum leptin, iron status, and dietary iron intake in young adults

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Leptin,a hormone secreted by adipose tissue, is a regulator of energy intake and expenditure. Iron, an essential micronutrient, functions as a cofactor for proteins and enzymes involved inoxygen transport and energy metabolism. Dietary iron intake and adipocyte iron levels have been recently demonstrated to suppress leptin expression in animals. Additionally, recent studies indicate aninverse association between serum leptin and serum ferritin (SF) in humans, independent of body mass. However, associations between iron status and serum leptin have not been examined in healthy young adults. As such, the objective of this study was to explore relationships between serum leptin, iron status indicators (SF, soluble transferrin receptor[sTfR], transferrin saturation [TS], hemoglobin, and hepcidin), and dietaryiron intake in young adults (n = 513, males = 306, females = 207, age[mean ± SE] = 20.6 ± 0.1 yrs, body fat = 17.4 ± 0.5 %). Biomarkers were assessed in blood from fasted volunteers; dietary iron intake was assessed using food frequency questionnaires. Univariate line arregression indicated negative correlations (P < 0.05) between serum leptin and SF (r = −0.26), TS (r = −0.21), hemoglobin (r = −0.36), and hepcidin (r =−0.09), and a positive association (P < 0.05) between serum leptin and sTfR(r = 0.10). In fully adjusted (age, body fat percentage, inflammation, and race) linear regression models, serum leptin and hemoglobin were positively associated (P < 0.05) in men (β ± SE = 0.07 ±0.02), but not women (β = 0.01 ± 0.02), whereas serum leptin and dietary iron intake were negatively associated (P < 0.05) in men (β = −0.53 ± 0.24), but not women (β = 0.25 ± 0.21). Associations between serum leptin and other iron status indicators were not statistically significant in either sex in fully adjusted models. Taken together, these data suggest that associations between serum leptin, iron status, and dietary iron intake are not independent of body fatness in young adults. Future studies conducted in large cohorts with individuals with varying body composition are required to elucidate the potential link between iron status and appetite regulation.Support or Funding InformationResearch supported by USAMRMC.