Loss of Insulin Receptor in Osteoprogenitor Cells Impairs Structural Strength of Bone

Table 1

Selected properties of bone, as determined by μCT and three-point bending, for males (top) and females (bottom), comparing control (IR flox) and OIRKO mice.

Property (male)	Units	IR flox (𝑛=6)	OIRKO (𝑛=9)	𝑃-value
Metaphysis (trabecular bone)
BV/TV	%	11.71±0.94	8.95±2.04	0.009
Tb.N	mm^−1	5.15±0.33	4.95±0.61	0.47
Tb.Th	mm	0.0392±0.002	0.0344±0.002	<0.001
Tb.Sp	mm	0.195±0.013	0.206±0.028	0.38
SMI^a	—	2.33±0.08	2.61±0.20	0.006
Tb.TMD	mgHA/cm^3	901±8	888±17	0.10
Diaphysis (cortical bone)
Ma.V	mm^3	1.22±0.12	1.03±0.11	0.005
Ct.Th	mm	0.148±0.011	0.124±0.011	0.001
Imin	mm^4	0.102±0.007	0.066±0.009	<0.001
Ct.Ar	mm^2	0.640±0.033	0.4892±0.044	<0.001
Length	mm	13.70±0.35	12.59±0.36	<0.001
Slenderness^b	mm/mm^2	20.8±0.7	25.1±2.2	<0.001
Ct.TMD	mgHA/cm^3	1185±27	1176±25	0.49
Stiffness	N/mm	40.7±8.5	36.9±12.6	0.57
Modulus	GPa	4.2±0.8	6.1±2.6	0.137
Bending strength	MPa	147±17	172±36	0.177
Property (female)	Units	IR flox (𝑛=6)	OIRKO (𝑛=9)	𝑃-value
Metaphysis (trabecular bone)
BV/TV	%	4.38±0.92	4.84±1.52	0.52
Tb.N	mm^−1	3.37±0.33	3.35±0.59	0.95
Tb.Th	mm	0.037±0.002	0.036±0.004	0.53
Tb.Sp	mm	0.302±0.032	0.316±0.084	0.69
SMI^a	—	3.19±0.17	2.80±0.18	0.001
Tb.TMD	mgHA/cm^3	916±13	901±30	0.28
Diaphysis (cortical bone)
Ma.V	mm^3	1.07±0.07	1.01±0.08	0.16
Ct.Th	mm	0.162±0.005	0.138±0.011	<0.001
Imin	mm^4	0.093±0.010	0.072±0.007	<0.001
Ct.Ar	mm^2	0.651±0.028	0.538±0.048	<0.001
Length	mm	14.41±0.39	13.22±0.45	<0.001
Slenderness^b	mm/mm^2	21.3±0.687	23.5±1.236	0.002
Ct.TMD	mgHA/cm^3	1251±15	1209±13	<0.001
Stiffness	N/mm	80.6±11.5	57.3±6.7	<0.001
Modulus	GPa	9.4±1.5	8.5±1.2	0.26
Bending strength	MPa	166±10	161±13	0.50

aStructural model index characterizes the shape of trabecular bone (1: platelike; 3: rodlike). ^bSlenderness is the ratio of the length to the total cross-sectional area of the femur midshaft. Abbreviations: BV/TV: bone volume/tissue volume; Tb.N: trabecular number; Tb.Th: trabecular thickness; Tb.Sp: trabecular separation; SMI: structural model index; Tb.TMD: trabecular tissue mineral density; Ma.V: marrow volume; Ct.Th.: cortical thickness; Imin: moment of inertia; Ct.Ar: cortical area; Ct.TMD: cortical tissue mineral density. Significant differences are highlighted in bold font.