Impact of Plasma Xanthine Oxidoreductase Activity on the Mechanisms of Distal Symmetric Polyneuropathy Development in Patients with Type 2 Diabetes

Abstract

To unravel associations between plasma xanthine oxidoreductase (XOR) and diabetic vascular complications, especially distal symmetric polyneuropathy (DSP), we investigated plasma XOR activities using a novel assay. Patients with type 2 diabetes mellitus (T2DM) with available nerve conduction study (NCS) data were analyzed. None were currently taking XOR inhibitors. XOR activity of fasting blood samples was assayed using a stable isotope-labeled substrate and LC-TQMS. JMP Clinical version 5.0. was used for analysis. We analyzed 54 patients. Mean age was 64.7 years, mean body mass index was 26.0 kg/m², and mean glycated hemoglobin was 9.4%. The logarithmically transformed plasma XOR activity (ln-XOR) correlated positively with hypoxanthine, xanthine, visceral fatty area, and liver dysfunction but negatively with HDL cholesterol. ln-XOR correlated negatively with diabetes duration and maximum intima-media thickness. Stepwise multiple regression analysis revealed ln-XOR to be among selected explanatory factors for various NCS parameters. Receiver operating characteristic curves showed the discriminatory power of ln-XOR. Principal component analysis revealed a negative relationship of ln-XOR with F-waves as well as positive relationships of ln-XOR with hepatic steatosis and obesity-related disorders. Taken together, our results show plasma XOR activity to be among potential disease status predictors in T2DM patients. Plasma XOR activity measurements might reliably detect pre-symptomatic DSP.

Keywords: distal symmetric polyneuropathy; type 2 diabetes; xanthine oxidoreductase.

Figure 1

Distribution of plasma XOR activity (A) with logarithmically transformed data (B) displayed as a histogram.

Figure 2

Correlations of individual parameters with logarithmically transformed plasma XOR activity. Results of sex, hypoxanthine, xanthine, UA, age, BMI, waist circumference, VFA, height, SBP, DBP, duration of diabetes, Brinkman index, vibration, minimum ABI, maximum IMT, FBG, HbA1c, Cre, eGFR, ACR, Plt, AST, ALT, γGTP, AAR, APRI, FIB-4 index, Alb, HDL cholesterol, LDL cholesterol, TG, EPA/AA, CRP, BNP, anti-diabetic drugs, antihyperlipidemic agents, and antihypertensive agents are shown in (A), those of various NCS parameters in (B). Solid lines indicate regression lines, while each dotted line shows the threshold level of each of the NCS parameters in panel (B). The thresholds for peroneal/tibial amplitude potential, peroneal/tibial conduction velocity, and peroneal/tibial F-wave for prediction of incident DSP were 6.2/8.4 mV, 42.4/41.4 m/s, and 51.8/57.6 ms, respectively. SBP, systolic blood pressure; DBP, diastolic blood pressure; Cre, serum creatinine; eGFR, estimated glomerular filtration rate; ACR, albumin to creatinine ratio; Plt, platelet count; FIB-4 index, fibrosis-4 index; EPA/AA, eicosapentaenoic acid to arachidonic acid ratio; BNP, B-type natriuretic peptide; CRP, C-reactive protein; αGIs, α-glucosidase inhibitors; GLP-1RAs/DPP4is, GLP-1 agonists/dipeptidyl peptidase-4 inhibitors; SGLT2, sodium-glucose co-transporter 2 inhibitors; ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blockers; CCBs, calcium channel blockers; Amp, amplitude potential; CV, conduction velocity; F-wave, F-wave latency. r2: coefficient of determination, vibration: perception time for a fork vibration.

Figure 2

Correlations of individual parameters with logarithmically transformed plasma XOR activity. Results of sex, hypoxanthine, xanthine, UA, age, BMI, waist circumference, VFA, height, SBP, DBP, duration of diabetes, Brinkman index, vibration, minimum ABI, maximum IMT, FBG, HbA1c, Cre, eGFR, ACR, Plt, AST, ALT, γGTP, AAR, APRI, FIB-4 index, Alb, HDL cholesterol, LDL cholesterol, TG, EPA/AA, CRP, BNP, anti-diabetic drugs, antihyperlipidemic agents, and antihypertensive agents are shown in (A), those of various NCS parameters in (B). Solid lines indicate regression lines, while each dotted line shows the threshold level of each of the NCS parameters in panel (B). The thresholds for peroneal/tibial amplitude potential, peroneal/tibial conduction velocity, and peroneal/tibial F-wave for prediction of incident DSP were 6.2/8.4 mV, 42.4/41.4 m/s, and 51.8/57.6 ms, respectively. SBP, systolic blood pressure; DBP, diastolic blood pressure; Cre, serum creatinine; eGFR, estimated glomerular filtration rate; ACR, albumin to creatinine ratio; Plt, platelet count; FIB-4 index, fibrosis-4 index; EPA/AA, eicosapentaenoic acid to arachidonic acid ratio; BNP, B-type natriuretic peptide; CRP, C-reactive protein; αGIs, α-glucosidase inhibitors; GLP-1RAs/DPP4is, GLP-1 agonists/dipeptidyl peptidase-4 inhibitors; SGLT2, sodium-glucose co-transporter 2 inhibitors; ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blockers; CCBs, calcium channel blockers; Amp, amplitude potential; CV, conduction velocity; F-wave, F-wave latency. r2: coefficient of determination, vibration: perception time for a fork vibration.

Figure 2

Correlations of individual parameters with logarithmically transformed plasma XOR activity. Results of sex, hypoxanthine, xanthine, UA, age, BMI, waist circumference, VFA, height, SBP, DBP, duration of diabetes, Brinkman index, vibration, minimum ABI, maximum IMT, FBG, HbA1c, Cre, eGFR, ACR, Plt, AST, ALT, γGTP, AAR, APRI, FIB-4 index, Alb, HDL cholesterol, LDL cholesterol, TG, EPA/AA, CRP, BNP, anti-diabetic drugs, antihyperlipidemic agents, and antihypertensive agents are shown in (A), those of various NCS parameters in (B). Solid lines indicate regression lines, while each dotted line shows the threshold level of each of the NCS parameters in panel (B). The thresholds for peroneal/tibial amplitude potential, peroneal/tibial conduction velocity, and peroneal/tibial F-wave for prediction of incident DSP were 6.2/8.4 mV, 42.4/41.4 m/s, and 51.8/57.6 ms, respectively. SBP, systolic blood pressure; DBP, diastolic blood pressure; Cre, serum creatinine; eGFR, estimated glomerular filtration rate; ACR, albumin to creatinine ratio; Plt, platelet count; FIB-4 index, fibrosis-4 index; EPA/AA, eicosapentaenoic acid to arachidonic acid ratio; BNP, B-type natriuretic peptide; CRP, C-reactive protein; αGIs, α-glucosidase inhibitors; GLP-1RAs/DPP4is, GLP-1 agonists/dipeptidyl peptidase-4 inhibitors; SGLT2, sodium-glucose co-transporter 2 inhibitors; ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blockers; CCBs, calcium channel blockers; Amp, amplitude potential; CV, conduction velocity; F-wave, F-wave latency. r2: coefficient of determination, vibration: perception time for a fork vibration.

Figure 2

Correlations of individual parameters with logarithmically transformed plasma XOR activity. Results of sex, hypoxanthine, xanthine, UA, age, BMI, waist circumference, VFA, height, SBP, DBP, duration of diabetes, Brinkman index, vibration, minimum ABI, maximum IMT, FBG, HbA1c, Cre, eGFR, ACR, Plt, AST, ALT, γGTP, AAR, APRI, FIB-4 index, Alb, HDL cholesterol, LDL cholesterol, TG, EPA/AA, CRP, BNP, anti-diabetic drugs, antihyperlipidemic agents, and antihypertensive agents are shown in (A), those of various NCS parameters in (B). Solid lines indicate regression lines, while each dotted line shows the threshold level of each of the NCS parameters in panel (B). The thresholds for peroneal/tibial amplitude potential, peroneal/tibial conduction velocity, and peroneal/tibial F-wave for prediction of incident DSP were 6.2/8.4 mV, 42.4/41.4 m/s, and 51.8/57.6 ms, respectively. SBP, systolic blood pressure; DBP, diastolic blood pressure; Cre, serum creatinine; eGFR, estimated glomerular filtration rate; ACR, albumin to creatinine ratio; Plt, platelet count; FIB-4 index, fibrosis-4 index; EPA/AA, eicosapentaenoic acid to arachidonic acid ratio; BNP, B-type natriuretic peptide; CRP, C-reactive protein; αGIs, α-glucosidase inhibitors; GLP-1RAs/DPP4is, GLP-1 agonists/dipeptidyl peptidase-4 inhibitors; SGLT2, sodium-glucose co-transporter 2 inhibitors; ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blockers; CCBs, calcium channel blockers; Amp, amplitude potential; CV, conduction velocity; F-wave, F-wave latency. r2: coefficient of determination, vibration: perception time for a fork vibration.

Figure 2

Correlations of individual parameters with logarithmically transformed plasma XOR activity. Results of sex, hypoxanthine, xanthine, UA, age, BMI, waist circumference, VFA, height, SBP, DBP, duration of diabetes, Brinkman index, vibration, minimum ABI, maximum IMT, FBG, HbA1c, Cre, eGFR, ACR, Plt, AST, ALT, γGTP, AAR, APRI, FIB-4 index, Alb, HDL cholesterol, LDL cholesterol, TG, EPA/AA, CRP, BNP, anti-diabetic drugs, antihyperlipidemic agents, and antihypertensive agents are shown in (A), those of various NCS parameters in (B). Solid lines indicate regression lines, while each dotted line shows the threshold level of each of the NCS parameters in panel (B). The thresholds for peroneal/tibial amplitude potential, peroneal/tibial conduction velocity, and peroneal/tibial F-wave for prediction of incident DSP were 6.2/8.4 mV, 42.4/41.4 m/s, and 51.8/57.6 ms, respectively. SBP, systolic blood pressure; DBP, diastolic blood pressure; Cre, serum creatinine; eGFR, estimated glomerular filtration rate; ACR, albumin to creatinine ratio; Plt, platelet count; FIB-4 index, fibrosis-4 index; EPA/AA, eicosapentaenoic acid to arachidonic acid ratio; BNP, B-type natriuretic peptide; CRP, C-reactive protein; αGIs, α-glucosidase inhibitors; GLP-1RAs/DPP4is, GLP-1 agonists/dipeptidyl peptidase-4 inhibitors; SGLT2, sodium-glucose co-transporter 2 inhibitors; ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blockers; CCBs, calcium channel blockers; Amp, amplitude potential; CV, conduction velocity; F-wave, F-wave latency. r2: coefficient of determination, vibration: perception time for a fork vibration.

Figure 3

ROC curves for various NCS parameters stratified by the thresholds identified for prediction of incident DSP. (A) Peroneal CV, (B) peroneal F-wave, (C) tibial F-wave. ROC, receiver operating characteristic; AUC, area under the curve; F-wave, F-wave latency. NCV parameters were stratified by the thresholds identified for the prediction of incident DSP according to a previous report as described in the “Patients and Methods” section, that is, the thresholds for peroneal conduction velocity, peroneal F-wave, and tibial F-wave were 42.4 m/s, 51.8 ms, and 57.6 ms, respectively.

Figure 4

Visualization of correlations between variabilities in PCA biplots. PC, principal component; Amp, amplitude; CV, conduction velocity; WC, waist circumference.