Risk factors for developing osteoporosis in diabetic kidney disease and its correlation with calcium-phosphorus metabolism, FGF23, and Klotho

Table 1 Comparison of patient biographical information

	Normal (n = 55)	OP (n = 103)	t/χ2	P value
Gender, n (%)			5.313	0.021
Male	33 (60.0)	42 (40.8)
Female	22 (40.0)	61 (59.2)
Age (years)	51.39 ± 10.84	62.32 ± 10.34	6.224	< 0.0001
Body mass index (kg/m2)	24.93 ± 3.72	24.87 ± 3.44	0.102	0.919
Comorbidities, n (%)	17 (30.9)	37 (35.9)	0.401	0.527
Disease duration (years)	7.32 ± 3.22	13.42 ± 3.84	10.042	< 0.0001

OP: Osteoporosis.

Table 2 Comparison of biochemical indicators and calcium-phosphorus metabolic indexes

	Normal (n= 55)	OP (n = 103)	t/χ2	P value
FBG (mmol/L)	8.32 ± 2.83	8.39 ± 2.31	0.167	0.867
HbA1c (%)	7.44 ± 2.10	7.59 ± 2.09	0.429	0.668
Scr (µmol/L)	93.42 ± 20.13	94.32 ± 21.38	0.257	0.797
eGFR (mL/min × 1.73 m2)	89.42 ± 20.31	80.74 ± 24.23	2.265	0.025
Alb (g/L)	34.29 ± 8.39	32.83 ± 7.36	1.131	0.260
25-(OH)-D3 (ng/mL)	37.42 ± 17.32	25.33 ± 9.27	5.723	< 0.0001
iPTH (pg/mL)	39.72 ± 18.42	72.43 ± 18.48	10.610	< 0.0001
Blood Ca (mmol/L)	2.21 ± 0.19	1.98 ± 0.34	4.640	< 0.0001
Blood P (mmol/L)	1.13 ± 0.17	1.37 ± 0.34	4.912	< 0.0001
Calcium-phosphorus product (mmol2/L2)	2.64 ± 0.32	3.11 ± 0.78	4.276	< 0.0001
24-hour urinary phosphate excretion (mmol/24 hour)	20.42 ± 9.45	14.32 ± 5.97	4.961	< 0.0001
Fractional excretion of phosphate (%)	12.42 ± 1.74	40.28 ± 7.42	27.408	< 0.0001
FGF23 (ng/L)	267.32 ± 48.42	358.79 ± 53.72	10.544	< 0.0001
Klotho (ng/L)	253.79 ± 0.48	352.91 ± 0.57	1098.0	< 0.0001

OP: Osteoporosis; FBG: Fasting blood glucose; HbA1c: Hemoglobin A1c; Scr: Serum creatinine; eGFR: Estimated glomerular filtration rate; Alb: Albumin; iPTH: Intact parathyroid hormone; Ca: Calcium; P: Phosphorus.

Table 3 Correlation of calcium-phosphorus metabolic indexes with FGF23 and Klotho

	Normal (n = 55)				OP (n = 103)
	FGF23		Klotho		FGF23		Klotho
	r	P value	r	P value	r	P value	R	P value
25-(OH)-D3	−0.201	0.029	0.195	0.031	−0.342	< 0.001	0.356	< 0.001
iPTH	0.211	0.023	−0.205	0.028	0.352	< 0.001	−0.370	< 0.001
Blood Ca	−0.198	0.031	0.220	0.020	−0.364	< 0.001	0.377	< 0.001
Blood P	0.231	0.018	−0.221	0.020	0.337	< 0.001	−0.357	< 0.001
Calcium-phosphorus product	0.199	0.030	−0.035	0.774	0.384	< 0.001	−0.366	< 0.001
24-hour urinary phosphate excretion	−0.083	0.610	0.138	0.104	−0.379	< 0.001	0.401	< 0.001
Fractional excretion of phosphate	0.242	0.016	−0.244	0.015	0.338	< 0.001	−0.378	< 0.001

OP: Osteoporosis; iPTH: Intact parathyroid hormone; Ca: Calcium; P: Phosphorus.

Table 4 Logistic regression analysis of osteoporosis in diabetic kidney disease

Variable	B	Standard error	Standardization coefficient	t	P value
Lumbar bone mineral density
Constant	0.732	0.078		13.924	< 0.001
25-(OH)-D3	0.164	0.013	-0.372	8.942	< 0.001
iPTH	-0.329	0.030	0.201	7.995	< 0.001
blood Ca	0.228	0.017	0.101	10.424	< 0.001
Urinary phosphorus excretion fraction	-0.101	0.002	0.282	9.049	< 0.001
FGF23	-0.284	0.019	0.118	8.024	< 0.001
Klotho	0.118	0.005	-0.208	13.229	< 0.001
Age	-0.332	-0.032	-0.394	12.049	< 0.001
Gender	-0.492	0.074	-0.220	10.004	< 0.001
Bone mineral density of the left femoral neck
Constant	0.809	0.067		15.424	< 0.001
25-(OH)-D3	0.180	0.040	-0.394	8.492	< 0.001
iPTH	-0.364	0.038	0.233	6.824	< 0.001
Blood Ca	0.275	0.020	0.164	7.663	< 0.001
Urinary phosphorus excretion fraction	-0.128	0.008	0.840	5.312	0.003
FGF23	-0.295	0.042	0.175	4.990	0.007
Klotho	0.131	0.007	-0.232	9.402	< 0.001
Age	-0.347	-0.012	-0.384	8.448	< 0.001
Gender	-0.488	0.067	-0.214	7.940	< 0.001

iPTH: Intact parathyroid hormone; Ca: Calcium.