| Summary: | Background: Increased iron stores are associated with increased risk of type 2 diabetes, however, the mechanisms
underlying these associations are poorly understood. Because a reduction of circulating osteocalcin levels after iron
overload have been demonstrated in cell cultures, and osteocalcin is related to glucose and insulin metabolism, the ironinduced
osteocalcin reductions could contribute to explain the role of iron metabolism in the development of type 2
diabetes mellitus.
Objective: To analyzed the associations between serum total and uncarboxylated osteocalcin and adiponectin
concentrations with serum ferritin and soluble transferrin receptor (sTfR) in elderly subjects.
Design: We evaluated a total of 423 subjects from the PREDIMED cohort in a population-based cross-sectional analysis.
Extensive clinical, nutritional and laboratory measurements, including total and uncarboxylated osteocalcin, adiponectin,
ferritin and sTfR were recorded.
Results: Serum ferritin was positively correlated with increased glucose and insulin circulating levels but also with HOMA-IR,
and was inversely associated with total osteocalcin and adiponectin. A regression analysis revealed that serum ferritin and
transferrin receptor levels were significantly associated with a decrease in total and uncarboxylated osteocalcin. Serum sTfR
levels were associated with lower uncarboxylated osteocalcin levels in the whole-study subjects and remained significant
only in the IFG (impaired fasting glucose) individuals.
Conclusions: We described, for the first time, an inverse association between serum ferritin and sTfR with osteocalcin and
extend previous results on adiponectin, thus supporting that factors related to iron metabolism could contribute to the
insulin resistance and the development of type 2 diabetes mellitus.
Trial Registration: Controlled-Trials.com ISRCTN35739639 ,http://www.controlled-trials.com/ISRCTN35739639..
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