Mitochondrial DNA copy number in peripheral blood of IgA nephropathy: a cross-sectional study

Figures & data

Figure 1. The protocol for selection of IgAN patients.

Table 1. Characteristics of patients with IgAN stratified by mtDNA-CN.

Characteristics	mtDNA-CN (low)	mtDNA-CN (high)	p Value
mtDNA-CN (SD)	–0.4828 ± 0.4646	0.4673 ± 0.3000	.0001*
Sex (male), n (%)	176 (52.85%)	168 (50.76%)	.6418
Age, years	36.14 ± 10.64	36.24 ± 10.34	.8971
Estimated GFR (mL/min/1.73 m^2)	60.01 ± 35.43	66.52 ± 34.40	.0167*
Serum creatinine (μmol/L)	195.4 ± 190.6	161.9 ± 153.9	.0129*
Proteinuria (g/24 h)	2.262 ± 2.408	2.002 ± 2.177	.1439
Blood urea nitrogen (mmol/L)	8.697 ± 5.655	7.591 ± 4.553	.0057*
Uric acid (μmol/L)	444.3 ± 120.6	430.6 ± 108.8	.1232
Oxford classification^a
Mesangial hypercellularity (M1), n (%)	218 (71.01%)	197 (63.96%)	.0622
Endocapillary hypercellularity (E1), n (%)	59 (19.22%)	69 (22.40%)	.3316
Segmental glomerulosclerosis (S1), n (%)	184 (59.93%)	187 (60.71%)	.7800
Tubular atrophy/interstitial fibrosis (T1,T2), n (%)	135 (43.97%)	122 (39.61%)	.4414
Crescents (C1,C2), n (%)	188 (61.24%)	187 (60.71%)	.5070

eGFR: estimated glomerular filtration rate; SCr: serum creatinine; BUN: blood urea nitrogen; UA: uric acid; mtDNA: mitochondrial DNA; CN: copy number.

Data are shown as mean ± standard deviation for continuous variables or n (%) for categorical variables. SD (with a mean of 0) as the unit of standardized determination for mtDNA-CN.

^a Forty-nine patients without complete Oxford classification are excluded.

* p-value < 0.05.

Figure 2. Correlations of mtDNA-CN in peripheral blood with renal function. Association between mtDNA-CN in peripheral blood and eGFR (A), SCr (B), BUN (C), UA (D), and proteinuria (E) were analyzed by Spearman’s rank correlation analysis. N = 664. eGFR: estimated glomerular filtration rate; mtDNA: mitochondrial DNA; CN: copy number. SD (with a mean of 0) as the unit of standardized determination for mtDNA-CN.

Figure 3. mtDNA-CN in patients with IgAN stratified by eGFR. Data were analyzed by Student’s t-test. mtDNA: mitochondrial DNA; CN: copy number. SD (with a mean of 0) as the unit of standardized determination for mtDNA-CN.

Table 2. mtDNA-CN characteristics of patients with IgAN stratified by eGFR.

Characteristics	EGFR ≥60 (mL/min/1.73 m^2) (n = 352)	EGFR <60 (mL/min/1.73 m^2) (n = 312)	p Value
Sex (male), n (%)	84 (50.00%)	221 (53.25%)	.1153
Age, years	34.19 ± 9.361	38.45 ± 11.22	.0001*
Serum creatinine (μmol/L)	84.80 ± 19.88	284.6 ± 206.9	.0001*
Proteinuria (g/24 h)	1.477 ± 1.818	2.871 ± 2.547	.0001*
Blood urea nitrogen (mmol/L)	5.107 ± 1.375	11.57 ± 5.691	.0001*
Uric acid (μmol/L)	390.2 ± 89.42	490.8 ± 117.3	.0001*
Oxford classification^a
Mesangial hypercellularity (M1), n (%)	109 (32.83%)	91 (32.15%)	.8588
Endocapillary hypercellularity (E1), n (%)	276 (83.13%)	211 (74.55%)	.0091*
Segmental glomerulosclerosis (S1), n (%)	142 (42.77%)	104 (36.74%)	.1078
Tubular atrophy/interstitial fibrosis (T1,T2), n (%)	300 (90.36%)	237 (83.74%)	.0006*
Crescents (C1,C2), n (%)	311 (93.67%)	266 (93.99%)	.2258

eGFR: estimated glomerular filtration rate; SCr: serum creatinine; BUN: blood urea nitrogen; UA: uric acid; mtDNA: mitochondrial DNA; CN: copy number.

Data are shown as mean ± standard deviation for continuous variables or n (%) for categorical variables. SD (with a mean of 0) as the unit of standardized determination for mtDNA-CN.

^a Forty-nine patients without complete Oxford classification are excluded.

* p-value < 0.05.

Table 3. Multivariable logistic regression analyses of associations between mtDNA-CN and renal impairment.

Variables	p	OR	95% CI
mtDNA-CN (SD)	.042	0.757	(0.580, 0.983)
Proteinuria (g/24 h)	<.001	1.436	(1.287, 1.571)
Sex	.042	0.709	(0.510, 0.987)
Age	<.001	1.045	(1.027, 1.062)

Variables were identified by using exploratory univariable analyses with explanatory variables entered into the multivariable stepwise logistic regression model. N = 664. SD (with a mean of 0) as the unit of standardized determination for mtDNA-CN.

Figure 4. Relationships between mtDNA-CN and renal pathological changes in IgAN patients. Data were analyzed by Student’s t-test. SD (with a mean of 0) as the unit of standardized determination for mtDNA-CN. N = 615. Forty-nine individuals were excluded due to incomplete pathological Oxford classification information. Renal pathological changes were scored by professional pathologists referring to Oxford MEST-C Classification. Patients were scored M0 or M1 in terms of mesangial hypercellularity: when >50% of glomeruli showing four or more cells in one or more mesangial area, not including central core and region of the vascular pole were scored M1. E score or S score were defined as absent (0) or present (1) of endocapillary hypercellularity (E) or segmental glomerulosclerosis (S). T score was defined in terms of estimated percentage of interstitial fibrosis and tubular atrophy: T0 (≤25%), T1 (26–50%), and T2 (>50%). C score referred to crescents: C0 (0%), C1 (0% to <25%), and C2 (>25%).