There was still a dearth of information on the link between obesity and serum neurofilament light protein (sNfL), particularly when it came to the interplay of sNfL, WWI, and ABSI. Initially, we established a positive association of WWI, ABSI, and sNfL levels in our research. Additionally, this positive correlation showed no significant dependence on gender, age, race, stroke, smoking, or congestive heart failure. Furthermore, we illustrated that WWI and ABSI, as novel obesity-related indices, offer improved explanation of this positive association. To our understanding, this work represents the first to investigate the connection of WWI, ABSI, and sNfL, offering preliminary evidence on the influence of obesity on neurodegenerative conditions.
What is already known on this subject?
Reviewing previous studies, various cross-sectional studies have explained the associations between neural and non-neural factors with sNfL. Neurodegenerative diseases or traumatic impacts can cause neuronal damage, leading to increased sNfL levels [20]. Among non-neural factors, models predicting sNfL concentrations showed significantly increased explanatory power when considering aging, cardiovascular factors, and kidney function [21]. Recent research indicates that increases in sNfL are associated with environmental exposure to glyphosate (a herbicide), phthalates (plastic additives), and smoke[17, 22, 23].
What this study adds?
To determine the connection of new obesity indices and sNfL in this study, we considered non-neural body factors and environmental influences, using a multivariable linear regression technique to adjust for pertinent hazards such as hypertension, heart failure, hypercholesterolemia, and smoke, to mitigate potential biases related to neurological, cardiovascular diseases and environmental exposure. Therefore, the association between new obesity indices and sNfL levels further enhances the understanding of the complexity of interactions between physiological, pathological, and toxicological factors with sNfL levels. Given recent research on sNfL, more comprehensive and extensive exploration of this advanced biomarker for neurodegenerative changes may aid clinical decision-making and treatment.
Moderate and chronic inflammation is often linked to obesity[24, 25]. The body's production of inflammatory mediators[26] has verified a positive correlation in NfL and inflammatory cytokines (IL-1β and IL-6) [27]. This finding aligns with prior animal studies indicating elevated a great quantity of inflammatory mediators (IL-2, IL-4, IL-6, and TNF-α) and cultivated CSF NfL levels link to chronic neuroinflammation and immune responses[28]. This cross-section study demonstrated a positive correlation of WWI, ABSI, and sNfL levels, this further corroborates the potential mechanisms linking obesity with sNfL levels. In summary, WWI and ABSI, as effective tools for more accurately reflecting body composition, are closely associated with sNfL levels.
sNfL has been proposed as a valuable indicator for various neurological disorders, especially predicting cognitive decline and the severity of brain lesions [29]. sNfL has a clear role in providing reliable measurements of neuroaxonal damage caused by demyelination processes and the neuroprotective effects of drugs[30]. Numerous neurodegenerative illnesses, including Alzheimer's and Parkinson's, are at threat due to obesity and obesity-related glucose homeostasis problems[31]. Large-scale, long-term, prospective studies have shown that BMI and plasma NfL increase rapidly over time[32], and that middle-aged obesity is significantly link to the risk of dementia and structural brain changes [33, 34]. Its potential role in guiding clinical innovations for neurodegenerative diseases warrants further exploration. Recent studies suggest that reduced NO production and related insulin resistance in obesity might contribute to cognitive impairment and neurodegeneration [35]. And the role of miRNA in obese phenotypes [36] and neurodegenerative diseases[37, 38] has been confirmed. Additionally, recent progress in elucidating the molecular mechanisms of obesity and neurodegenerative diseases have identified astrocytes and endoplasmic reticulum stress as crucial links bridging obesity and neurodegenerative pathologies[39]. Current advancements suggest that neuroinflammation serves as an alterable route connecting obesity and Alzheimer's disease[40]. This increased the possibility of using innovative clinical approaches to treat and prevent neurodegenerative illnesses. Therefore, this research suggests that the correlation between obesity and sNfL provides guidance for clinical interventions in high-risk populations for neurodegenerative diseases. Although the specific mechanisms linking obesity and neurodegenerative diseases require further investigation, effective weight management, maintaining physical health, and regular health check-ups provide valuable insights for clinical guidelines.
Strength and limits
NHANES, a broadly representative cross-sectional survey, is our study's primary strength. Sampling weights facilitate the evaluation of WWI, ABSI, and sNfL relationships. To ensure study accuracy, the authors controlled for confounding factors. Subgroup analyses additionally occurred to determine the reliability of WWI, ABSI, and sNfL correlations across populations. Furthermore, our study examines how obesity indices affect neuro-related biomarkers. This extensive study sheds light on how neuro-related indicators affect obesity's negative impacts.
However, we acknowledge the limitations of our investigation. First, our cross-section study restricts our causal inferences despite a strong correlation of WWI, ABSI, and sNfL levels. Therefore, further validation is needed in prospective cohort studies. Secondly, the sNfL data utilized in this study were confined to the NHANES 2013–2014 cycle, where sNfL measurements were available. Given the absence of sNfL data in other NHANES cycles, our findings may not fully represent the cross-section profiles of these patients. Consequently, further large-scale longitudinal cohort studies are warranted to validate our initial observations. Moreover, although we accounted for numerous covariates, we recognize the potential for biases stemming from unmeasured confounding variables. These may involve drug usage, the existence of long-term illness including diabetes, renal disease, and hepatic disorders, among others. Finally, despite rigorous methodological approaches, our study is hampered by the relative population size for subgroup estimation. In order to yield more dependable and definitive outcomes in future experimental subgroups, it is imperative to expand the sample size significantly. This method will help to clarify the examined events in more whole sense.