Association of insulin resistance with serum ferritin and aminotransferases-iron hypothesis

Table 3 Estimated beta cell function and insulin sensitivity indices by quintile of serum ferritin concentrations

	Quintile 1	Quintile 2	Quintile 3	Quintile 4	Quintile 5	P1	P2	P3
Beta cell function by the homeostasis model assessment (%B)4
Non-Hispanic white males	103 (96, 110)	98 (92, 105)	97 (90, 104)	106 (94, 118)	113 (102, 124)	NS	NS	NS
Non-Hispanic white females	117 (110, 124)	115 (108, 122)	109 (103, 114)	111 (104, 119)	110 (102, 118)	NS	NS	NS
Non-Hispanic black males	113 (104, 122)	118 (107, 130)	112 (103, 120)	144 (107, 181)	117 (106, 129)	NS	NS	NS
Non-Hispanic black females	177 (156, 197)	178 (161, 196)	151 (137, 164)	135 (121, 150)	135 (123, 147)	0.000001	NS	NS
Hispanic males	104 (91, 118)	112 (101, 124)	106 (97, 114)	123 (106, 141)	128 (116, 140)	0.004	NS	NS
Hispanic females	152 (140, 165)	150 (135, 164)	140 (129, 150)	136 (124, 147)	130 (119, 141)	0.003	NS	NS
Insulin sensitivity by the homeostasis model assessment (%S)5
Non-Hispanic white males	0.503 (0.472, 0.535)	0.549 (0.513, 0.585)	0.518 (0.484, 0.553)	0.494 (0.463, 0.525)	0.421 (0.388, 0.455)	0.00005	NS	0.05
Non-Hispanic white females	0.643 (0.610, 0.677)	0.603 (0.570, 0.637)	0.574 (0.539, 0.609)	0.555 (0.519, 0.591)	0.455 (0.420, 0.491)	< 0.000001	0.04	0.02
Non-Hispanic black males	0.562 (0.516, 0.608)	0.553 (0.504, 0.601)	0.559 (0.512, 0.605)	0.555 (0.498, 0.611)	0.48 (0.426, 0.535)	0.04	NS	0.05
Non-Hispanic black females	0.510 (0.476, 0.545)	0.479 (0.437, 0.522)	0.453 (0.421, 0.485)	0.458 (0.422, 0.495)	0.379 (0.343, 0.414)	0.000001	0.02	0.007
Hispanic males	0.538 (0.495, 0.580)	0.533 (0.489, 0.578)	0.527 (0.472, 0.583)	0.524 (0.460, 0.588)	0.338 (0.307, 0.370)	< 0.000001	0.01	0.007
Hispanic females	0.523 (0.482, 0.563)	0.535 (0.484, 0.587)	0.464 (0.426, 0.502)	0.444 (0.403, 0.485)	0.321 (0.289, 0.352)	< 0.000001	0.005	0.003
Insulin sensitivity by the simple QUICKI6
Non-Hispanic white males	0.339 (0.336, 0.342)	0.343 (0.340, 0.346)	0.340 (0.336, 0.343)	0.337 (0.334, 0.341)	0.327 (0.323, 0.331)	< 0.000001	0.008	0.002
Non-Hispanic white females	0.352 (0.349, 0.355)	0.348 (0.345, 0.351)	0.345 (0.342, 0.348)	0.343 (0.340, 0.346)	0.33 (0.327, 0.334)	< 0.000001	0.00005	0.00001
Non-Hispanic black males	0.344 (0.339, 0.348)	0.342 (0.338, 0.347)	0.343 (0.339, 0.348)	0.341 (0.335, 0.346)	0.333 (0.328, 0.338)	0.003	0.03	0.01
Non-Hispanic black females	0.340 (0.336, 0.343)	0.335 (0.331, 0.339)	0.333 (0.329, 0.337)	0.333 (0.329, 0.337)	0.322 (0.317, 0.326)	< 0.000001	0.0006	0.0001
Hispanic males	0.341 (0.336, 0.345)	0.34 (0.336, 0.345)	0.339 (0.335, 0.344)	0.337 (0.332, 0.342)	0.318 (0.314, 0.322)	< 0.000001	0.0001	0.00001
Hispanic females	0.340 (0.336, 0.344)	0.340 (0.336, 0.345)	0.334 (0.330, 0.338)	0.330 (0.326, 0.335)	0.315 (0.310, 0.319)	< 0.000001	0.00003	0.00002

Data presented mean with 95%CI. ¹P values for trend, unadjusted; ²P values for trend, after adjustment for age and body mass index; ³P values for trend, after adjustment for age, body mass index, alcohol consumption, and mineral/iron supplement;

⁴%B = (20 × fasting insulin concentration in mU/L) / (fasting glucose concentration in mmol/L - 3.5). Those with negative %B were excluded from analysis;

⁵%S = 22.5/(fasting insulin concentration in mU/L × fasting glucose concentration in mmol/L);

⁶Quicki = 1/[log(fasting glucose concentration in mg/dL) + log(fasting insulin concentration in mU/L)]. NS: Not significant; QUICKI: Quantitative insulin sensitivity check index.