Serum neurofilament light chain: a novel biomarker for early diabetic sensorimotor polyneuropathy

AIMS/HYPOTHESIS

No established blood-based biomarker exists to monitor diabetic sensorimotor polyneuropathy (DSPN) and evaluate treatment response. The neurofilament light chain (NFL), a blood biomarker of neuroaxonal damage in several neurodegenerative diseases, represents a potential biomarker for DSPN. We hypothesised that higher serum NFL levels are associated with prevalent DSPN and nerve dysfunction in individuals recently diagnosed with diabetes.

METHODS

This cross-sectional study included 423 adults with type 1 and type 2 diabetes and known diabetes duration of less than 1 year from the prospective observational German Diabetes Study cohort. NFL was measured in serum samples of fasting participants in a multiplex approach using proximity extension assay technology. DSPN was assessed by neurological examination, nerve conduction studies and quantitative sensory testing. Associations of serum NFL with DSPN (defined according to the Toronto Consensus criteria) were estimated using Poisson regression, while multivariable linear and quantile regression models were used to assess associations with nerve function measures. In exploratory analyses, other biomarkers in the multiplex panel were also analysed similarly to NFL.

RESULTS

DSPN was found in 16% of the study sample. Serum NFL levels increased with age. After adjustment for age, sex, waist circumference, height, HbA_1c, known diabetes duration, diabetes type, cholesterol, eGFR, hypertension, CVD, use of lipid-lowering drugs and use of non-steroidal anti-inflammatory drugs, higher serum NFL levels were associated with DSPN (RR [95% CI] per 1-normalised protein expression increase, 1.92 [1.50, 2.45], p<0.0001), slower motor (all p<0.0001) and sensory (all p≤0.03) nerve conduction velocities, lower sural sensory nerve action potential (p=0.0004) and higher thermal detection threshold to warm stimuli (p=0.023 and p=0.004 for hand and foot, respectively). There was no evidence for associations between other neurological biomarkers and DSPN or nerve function measures.

CONCLUSIONS/INTERPRETATION

Our findings in individuals recently diagnosed with diabetes provide new evidence associating higher serum NFL levels with DSPN and peripheral nerve dysfunction. The present study advocates NFL as a potential biomarker for DSPN.

A clinical screening score for diabetic polyneuropathy: KORA F4 and AusDiab studies

AIMS

Since screening for distal sensorimotor polyneuropathy (DSPN) in individuals with diabetes is being underused, our aim was to develop a clinical screening score for identifying individuals with DSPN.

METHODS

All participants with type 2 diabetes and aged 61-82 years from the German population-based KORA F4 Study (n=177) and the Australian population-based AusDiab Study (n=244) were combined into one study sample. Risk indicators of DSPN were identified and entered into a stepwise model-selection procedure, constructing two consecutive scores with increasing complexity (a base and clinical model).

RESULTS

The prevalence of DSPN was 18.2% (95% confidence interval (CI): 14.7-22.3). The base model comprised age (years), height (cm), weight (kg), pain or discomfort in the feet and/or legs (yes/no), and duration of diabetes (years), yielding an area under the receiver operating characteristics curve (AUC) of 0.80 (95% CI: 0.76-0.85). The clinical model additionally included diastolic blood pressure (mmHg) and serum creatinine levels (mmol/l). The AUC increased only marginally to 0.82 (0.77-0.87) (p for AUC comparison=0.188). The internal validation of the scores produced similar AUCs.

CONCLUSIONS

The screening scores developed in this study are a simple tool to differentiate between a high and low likelihood of having DSPN among individuals with type 2 diabetes.