Neurofilament Light Chain [NfL]
Image: BestPractice
Wikipedia describes Neurofilaments this
way: NF are intermediate filaments found in the cytoplasm of neurons. They are
protein polymers measuring approximately 10 nm in diameter and many micrometers
in length. Together with microtubules
and microfilaments, they form the neuronal cytoskeleton. They are believed
to function primarily to provide structural support for axons and to regulate
axon diameter, which influences nerve
conduction velocity. Neurofilaments are found in vertebrate neurons in especially high concentrations in
axons, where they are all aligned in parallel along the long axis of the axon
forming a continuously overlapping array. In addition to their structural role
in axons, neurofilaments are also cargoes of axonal transport. Most of the
neurofilament proteins in axons are synthesized
in the nerve cell body, where they rapidly assemble into neurofilament polymers
within about 30 minutes. These assembled neurofilament polymers are transported
along the axon on microtubule tracks powered by microtubule motor proteins.
Muscle and not neuronal biomarkers correlate with severity in spinal and bulbar muscular atrophy
Objective: To determine whether blood biomarkers of neuronal damage (neurofilament light chain [NfL]), muscle damage (creatine kinase [CK]), and muscle mass (creatinine) are altered in spinal bulbar muscular atrophy (SBMA aka Kennedy's Disease) and can be used as biomarkers for disease severity.Methods: In this multicenter longitudinal prospective study, plasma and serum were collected from 2 cohorts of patients with SBMA in London, United Kingdom (n = 50), and Padova, Italy (n = 43), along with disease (amyotrophic lateral sclerosis [ALS]) and healthy controls, and levels of plasma and serum NfL, CK, and creatinine were measured. Disease severity was assessed by the SBMA Functional Rating Scale and the Adult Myopathy Assessment Tool at baseline and 12 and 24 months.
Results: Blood NfL concentrations were increased in ALS samples, but were unchanged in both SBMA cohorts, were stable after 12 and 24 months, and were not correlated with clinical severity. Normal NfL levels were also found in a well-established mouse model of SBMA. Conversely, CK concentrations were significantly raised in SBMA compared with ALS samples, and were not correlated to the clinical measures. Creatinine concentrations were significantly reduced in SBMA, and strongly and significantly correlated with disease severity.
Conclusions: While muscle damage and muscle mass biomarkers are abnormal in SBMA, axonal damage markers are unchanged, highlighting the relevant primary role of skeletal muscle in disease pathogenesis. Creatinine, but not CK, correlated with disease severity, confirming its role as a valuable biomarker in SBMA.
Note: The KDA just posted the research on their website. There was also a note from Pietro Fratta, who spoke about his biomarker research at last year's conference:
This
work uses blood samples from 93 Kennedy’s patients, alongside controls
and samples from models of disease, to look for traces of neuron and
muscle damage in Kennedy’s disease. It finds that muscle damage is
prominent, whilst neuron damage is below detection levels. This work
highlights the role of muscle damage in Kennedy’s disease, which is
extremely important for how therapies are designed. Further, this study
supports the use of a specific biomarker, creatinine, for Kennedy’s
disease clinical trials.
This
study was possible only thanks to the incredibly strong participation
to research of patients attending the Kennedy’s Clinic at the National
Hospital in London and the University of Padova.
