Investigation of the relationship between hemoglobin and serum iron levels and early-phase insulin secretion in non-diabetic subjects.
OBJECTIVE
Recent biological and epidemiological studies have found that insulin resistance is linked to iron overload. However, little is known about the association between hemoglobin and/or serum iron levels and pancreatic β-cell function. In this gender-separated cross-sectional study, we aimed to investigate the association of hemoglobin and serum iron levels with early-phase insulin secretion in non-diabetic subjects.


METHODS
A total of 804 non-diabetic Japanese subjects (482 males and 322 females) aged over 30 years old were enrolled in the study. Early-phase insulin secretion was estimated using the insulinogenic index (IGI [ΔInsulin(30-0 min)/ΔGlucose(30-0 min)]) during a 75-g oral glucose tolerance test.


RESULTS
Simple linear regression analysis showed that IGI negatively correlated with hemoglobin levels in male but not in female subjects. However, IGI did not correlate with serum iron levels in either gender. Multivariate linear regression analysis in male subjects revealed that hemoglobin levels were predictors of IGI, responsible for 3.0 % of IGI variation (P = 0.008). The association was independent of age, BMI, fasting glucose and insulin levels, and lipid profiles. In non-diabetic Japanese males, hemoglobin levels significantly and negatively correlated with early-phase insulin secretion.


CONCLUSIONS
Our finding suggests that elevated hemoglobin levels may have a gender-specific impact on β-cell function and could be an independent predictor of β-cell dysfunction.
Department of Internal Medicine, Iida Municipal Hospital, 438 Yawata-machi, Iida, Nagano, 395-8502, Japan. masanori19810813@yahoo.co.jp.|Division of Companion Diagnostics, Department of Pathology of Microbiology, Nihon University School of Medicine, 30-1 Ooyaguchi-kamimachi, Itabashi-ku, Tokyo, 173-8610, Japan. masanori19810813@yahoo.co.jp.
Masanori
M
Shimodaira
Department of Internal Medicine, Iida Municipal Hospital, 438 Yawata-machi, Iida, Nagano, 395-8502, Japan.
Shinji
S
Okaniwa
Division of Companion Diagnostics, Department of Pathology of Microbiology, Nihon University School of Medicine, 30-1 Ooyaguchi-kamimachi, Itabashi-ku, Tokyo, 173-8610, Japan.
Tomohiro
T
Nakayama
D000328:Adult; D000368:Aged; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D007333:Insulin Resistance; D000078790:Insulin Secretion; D007501:Iron / Q000097:blood*; D008297:Male; D008875:Middle Aged
D006454:Hemoglobins; D007328:Insulin; D007501:Iron
Diabetes; Hemoglobin; Insulinogenic index; Iron; β-Cell function