Impaired pancreatic beta‐cell function after a single dose of oral iron: A before‐and‐after (pre–post) study

• Published in: Journal of human nutrition and dietetics Vol. 36; no. 3; pp. 1111 - 1120
• Main Authors: Venkatesan, Padmanaban, Ramasamy, Jagadish, Vanitha, S., Jacob, Molly, Varghese, Joe
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-06-2023
• Subjects: Acute effects; Beta cells; Blood Glucose; Clearances; diabetes mellitus; Diabetes Mellitus, Type 2; Glucose; Glucose tolerance; Humans; Insulin; Insulin Resistance; Insulin secretion; Insulin-Secreting Cells - physiology; insulin‐secreting cells; Iron; Iron sulfates; Kinetics; Male; Males; oral iron; Pancreas; Secretion; Sulfates; Transferrin; insulin-secreting cells; diabetes mellitus; insulin secretion; oral iron
• ISSN: 0952-3871; 1365-277X
• DOI: 10.1111/jhn.13074

Background
Although in vitro and animal studies have shown that iron loading in pancreatic beta cells impairs insulin secretion, no human studies have documented the acute effects of oral iron on beta‐cell insulin secretory capacity. In the present study, we determined beta‐cell insulin secretory capacity at baseline and after a single oral dose of iron (ferrous sulphate, 120 mg elemental iron) in healthy male individuals.
Methods
Fifteen healthy male volunteers underwent an oral glucose tolerance test (OGTT) to document baseline glucose tolerance and insulin secretion kinetics (baseline OGTT). One week later, the same subjects underwent a second OGTT, 2 h after an oral dose of ferrous sulphate (120 mg of elemental iron) (post‐iron OGTT). Changes in disposition index, insulin secretion kinetics, glucose tolerance, insulin resistance, insulin clearance and iron‐related parameters in serum were determined.
Results
Compared to baseline OGTT, the areas under the curve (AUC) for serum iron and transferrin saturation increased by 125% and 118%, respectively, in the post‐iron OGTT. The disposition index decreased by 20% (p = 0.009) and the AUC for glucose concentrations increased by 5.7% (p < 0.001) during the post‐iron OGTT. The insulin secretion rate was marginally lower during the first hour (−3.5%, p = 0.63), but became significantly higher during the second hour (22%, p = 0.005) of the post‐iron OGTT. Insulin resistance and insulin clearance rate were not affected by iron intake.
Conclusions
The decrease in disposition index and glucose tolerance observed after the oral dose of iron points to an acute iron‐induced impairment in pancreatic beta‐cell insulin secretory capacity.
Key points
Fifteen healthy males underwent an oral glucose tolerance test (OGTT) before and after oral intake of a single dose of iron (120 mg).
Iron intake increased the areas under the curve of glucose and decreased the disposition index.
Insulin resistance and insulin clearance rates were unaffected.
We conclude that iron intake resulted in an acute decrease in beta‐cell function.