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Original Investigation
May 2018

Association of Serum Retinol-Binding Protein 4 Concentration With Risk for and Prognosis of Amyotrophic Lateral Sclerosis

Author Affiliations
  • 1Department of Neurology, University of Ulm, Ulm, Germany
  • 2Institute for Epidemiology and Medical Biometry, University of Ulm, Ulm, Germany
  • 3Department of Internal Medicine II–Cardiology, University of Ulm Medical Center, Ulm, Germany
  • 4Deutsches Herzzentrum München, Technische Universität München, Munich, Germany
  • 5German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich
  • 6Institut National de la Santé et de la Récherche Médicale Unité 1118, Université de Strasbourg, Strasbourg, France
JAMA Neurol. 2018;75(5):600-607. doi:10.1001/jamaneurol.2017.5129
Key Points

Question  Is retinol-binding protein 4 (a specific carrier for retinol but also expressed in adipose tissue and found to be causally associated with insulin resistance) associated with risk for and prognosis of amyotrophic lateral sclerosis?

Finding  Among 289 cases and 504 controls in this case-control cohort study, serum retinol-binding protein 4 concentration was inversely associated with risk for and prognosis of amyotrophic lateral sclerosis. Age, sex, and biomarkers for renal damage and fat mass (ie, leptin and adiponectin) did not substantially alter the association.

Meaning  If corroborated in prospective studies, interventions resulting in high retinol-binding protein 4 concentration may point to a relevant pathogenetic pathway and indicate a potential target for therapeutic intervention.

Abstract

Importance  Knowledge about the metabolic states of patients with amyotrophic lateral sclerosis (ALS) may provide a therapeutic approach.

Objective  To investigate the association between the onset and prognosis of ALS and serum retinol-binding protein 4 (RBP4) concentration as a biomarker for insulin resistance and vitamin A metabolism.

Design, Setting, and Participants  Case-control design for risk factors of ALS; cohort design for prognostic factors within ALS cases. Between October 1, 2010, and June 30, 2014, a population-based case-control study with randomly selected controls was established based on the ALS Registry Swabia in southern Germany, with a target population of 8.4 million inhabitants. Response rates were 64.8% among the cases and 18.7% among the controls. The dates of analysis were April 2016 to May 2017.

Main Outcomes and Measures  Serum samples were measured for RBP4. Information on covariates was assessed by an interview-based standardized questionnaire. Main outcomes and measures were adjusted odds ratios for risk of ALS associated with serum RBP4 concentration, as well as time to death associated with RBP4 concentration at baseline in ALS cases only. Conditional logistic regression was applied to calculate multivariable odds ratios for risk of ALS. Survival models were used in cases only to appraise their prognostic value.

Results  Data from 289 patients with ALS (mean [SD] age, 65.7 [10.5] years; 172 [59.5%] male) and 504 controls (mean [SD] age, 66.3 [9.8] years; 299 [59.3%] male) were included in the case-control study. Compared with controls, ALS cases were characterized by lower body mass index, less educational attainment, smoking, light occupational work intensity, and self-reported diabetes. The median serum RBP4 concentration was lower in ALS cases than in controls (54.0 vs 59.5 mg/L). In the multivariable model, increasing RBP4 concentration was associated with reduced odds for ALS (top vs bottom quartile odds ratio, 0.36; 95% CI, 0.22-0.59; P for trend <.001), which persisted after further adjustment for renal function and for leptin and adiponectin. Among 279 ALS cases during a median follow-up of 14.5 months, 104 died (mean [SD] age, 68.9 [10.3] years; 56 [53.9%] male). In this ALS cohort, an inverse association was found between serum RBP4 concentration as a continuous measure and survival.

Conclusions and Relevance  RBP4 was inversely related to risk for and prognosis of ALS, suggesting that vitamin A metabolism or impaired insulin signaling could be involved. Further research, including a prospective design and other biological markers, is necessary to clarify the role of insulin resistance in the pathogenesis of ALS.

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