Soluble CD163 levels are elevated in cerebrospinal fluid and serum in people with Type 2 diabetes mellitus and are associated with impaired peripheral nerve function.

Aims To measure soluble CD163 levels in the cerebrospinal fluid and serum of people with Type 2 diabetes, with and without polyneuropathy, and to relate the findings to peripheral nerve function. Methods A total of 22 people with Type 2 diabetes and 12 control subjects without diabetes were included in this case–control study. Participants with diabetes were divided into those with neuropathy (n = 8) and those without neuropathy (n = 14) based on clinical examination, vibratory perception thresholds and nerve conduction studies. Serum and cerebrospinal fluid soluble CD163 levels were analysed using an enzyme-linked immunosorbent assay. Results Soluble CD163 levels were significantly higher in the cerebrospinal fluid and serum of the participants with Type 2 diabetes compared with the control participants [cerebrospinal fluid: median (range) 107 (70–190) vs 84 (54–115) μg/l, P < 0.01 and serum: 2305 (920–7060) vs 1420 (780–2740) μg/l, P < 0.01). Cerebrospinal fluid soluble CD163 was positively related to impaired peripheral nerve conduction (nerve conduction study rank score: r = 0.42; P = 0.0497) and there was a trend for higher levels of soluble CD163 in the cerebrospinal fluid and serum in participants with neuropathy than in those without neuropathy [cerebrospinal fluid: median (range) 131 (86–173) vs 101 (70–190) μg/l, P = 0.08 and serum: 3725 (920–7060) vs 2220 (1130–4780), P = 0.06). Conclusions Cerebrospinal fluid soluble CD163 level is associated with impaired peripheral nerve function. Higher levels of soluble CD163 in people with diabetic polyneuropathy suggest that inflammation plays a role in the development of neural impairment. The relationship between cerebrospinal fluid soluble CD163 level and peripheral nerve conduction indicates that soluble CD163 may be a potential biomarker for the severity of diabetic polyneuropathy.