Participants
Twenty-nine patients with chronic neuropathic pain were enrolled and completed the study. The participants investigated here presented mean (standard deviation) age of 51.4 (6.5) years, body weight of 86.8 (19.9) kg, with a mean height of 164.9 (9.2) cm and a mean BMI of 31.8. (6.2) kg/m2. All patients had eGFR > 30 mL/min/1.73m2. In terms of the cause of neuropathic pain, 19 participants had diabetic neuropathy and 10 participants had neuropathic pain related to causes other than diabetes. Within the non-diabetic participants (n=10), 2 participants were diagnosed with cervical disc herniation and 8 with lumbar disc herniation. Patients with diabetes presented either well-controlled diabetes with HbA1c < 8% (n=9) or poorly controlled diabetes with HbA1c ≥ 8% (n=10). The reported mean basal pain on VAS was 7.9 (1.5) (Table 1). Individual demographic and biochemical characteristics were shown in Tables S1 and S2 (Supporting Information).
For the polymorphism 808G>T (SLC22A2 gene), 22 participants were genotyped as wild-type homozygous (GG) and 7 were genotyped as heterozygous (GT), with a minor allele frequency (MAF) of 12%, which is consistent with the MAF of 11.9% found for the Brazilian population [52]. Eleven participants were genotyped as wild-type homozygous (CC) for the polymorphism 1507C>T (SLC22A4 gene), 13 participants were genotyped as heterozygous (CT) and 5 were genotyped as mutant homozygous (TT), with a MAF of 39%, similar to the MAF of 32.9% found in the Brazilian population [52]. The genotype distributions of both polymorphisms were in Hardy-Weinberg equilibrium (Table S3 – Supporting Information).