Diurnal Variation of Urinary Fabry Disease Biomarkers during Enzyme Replacement Therapy Cycles

Analysis of Globotriaosylceramide (Gb3) in Liquid Urine: A Straightforward Assay Using Tandem Mass Spectrometry

Fabry disease (FD) is a lysosomal storage disorder caused by variants in the GLA gene encoding α-galactosidase A, an enzyme required for catabolism of globotriaosylceramide (Gb3). Accumulation of Gb3 in patients' cells, tissues, and biological fluids causes clinical manifestations including ventricular hypertrophy, renal insufficiency, and strokes. This protocol describes a methodology to analyze urinary Gb3 and creatinine. Samples are diluted with an internal standard solution containing Gb3(C17:0) and creatinine-D3, centrifuged, and directly analyzed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) using an 8.7-min method. Eight Gb3 isoforms [C16:0, C18:0, C20:0, C22:1, C22:0, C24:1, C24:0, and (C24:0)OH] are analyzed and the total is normalized to creatinine. Confirmation ions are monitored to detect potential interferences. The Gb3 limit of quantification is 0.023 µg/ml. Its interday coefficients of variation (3 concentrations measured) are ≤15.4%. This method minimizes matrix effects (≤6.5%) and prevents adsorption or precipitation of Gb3. Urine samples are stable (bias <15%) for 2 days at 21°C, 7 days at 4°C, and 4 freeze/thaw cycles, whereas prepared samples are stable for 5 days at 21°C, and 14 days at 4°C. The Gb3/creatinine age-related upper reference limits (mean + 2 standard deviations) are 29 mg/mol creatinine (<7 years) and 14 mg/mol creatinine (≥7 years). This simple, robust protocol has been fully validated (ISO 15189) and provides a valuable tool for diagnosis and monitoring of FD patients. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Analysis of urinary globotriaosylceramide (Gb3) and creatinine by UHPLC-MS/MS Support Protocol 1: Preparation of the urinary quality controls Support Protocol 2: Preparation of the urine matrix used for the Gb3 calibration curve Support Protocol 3: Preparation of the Gb3 calibrators Support Protocol 4: Preparation of the working solution containing the internal standards Support Protocol 5: Preparation of the creatinine calibrators Support Protocol 6: Preparation of the UHPLC solutions and mobile phases.

Molecular biomarkers, network biomarkers, and dynamic network biomarkers for diagnosis and prediction of rare diseases

The difficulty of converting scientific research findings into novel pharmacological treatments for rare and life-threatening diseases is enormous. Biomarkers related to multiple biological processes involved in cell growth, proliferation, and disease occurrence have been identified in recent years with the development of immunology, molecular biology, and genomics technologies. Biomarkers are capable of reflecting normal physiological processes, pathological processes, and the response to therapeutic intervention; as such, they play vital roles in disease diagnosis, prevention, drug response, and other aspects of biomedicine. The discovery of valuable biomarkers has become a focal point of current research. Numerous studies have identified molecular biomarkers based on the differential expression/concentration of molecules (e.g., genes/proteins) for disease state diagnosis, characterization, and treatment. Although technological breakthroughs in molecular analysis platforms have enabled the identification of a large number of candidate biomarkers for rare diseases, only a small number of these candidates have been properly validated for use in patient treatment. The traditional molecular biomarkers may lose vital information by ignoring molecular associations/interactions, and thus the concept of network biomarkers based on differential associations/correlations of molecule pairs has been established. This approach promises to be more stable and reliable in diagnosing disease states. Furthermore, the newly-emerged dynamic network biomarkers (DNBs) based on differential fluctuations/correlations of molecular groups are able to recognize pre-disease states or critical states instead of disease states, thereby achieving rare disease prediction or predictive/preventative medicine and providing deep insight into the dynamic characteristics of disease initiation and progression.

Quantitation of a Urinary Profile of Biomarkers in Gaucher Disease Type 1 Patients Using Tandem Mass Spectrometry

Gaucher disease is a rare inherited disorder caused by a deficiency of the lysosomal acid beta-glucocerebrosidase enzyme. Metabolomic studies by our group targeted several new potential urinary biomarkers. Apart from lyso-Gb₁, these studies highlighted lyso-Gb₁ analogs −28, −26, −12 (A/B), +2, +14, +16 (A/B), +30, and +32 Da, and polycyclic lyso-Gb₁ analogs 362, 366, 390, and 394 Da. The main objective of the current study was to develop and validate a robust UPLC-MS/MS method to study the urine distribution of these biomarkers in patients. Method: Urine samples were purified using solid-phase extraction. A 12 min UPLC-MS/MS method was developed. Results: Validation assays revealed high precision and accuracy for creatinine and lyso-Gb₁. Most lyso-Gb₁ analogs had good recovery rates and high intra- and interday precision assays. Biomarker-estimated LOD and LOQ levels ranged from 56–109 pM to 186–354 pM, respectively. Comparison between GD patients and healthy controls showed significant differences in most biomarker levels. Typically, treated GD patients presented lower biomarker levels compared to untreated patients. Conclusions: These data suggest that the metabolites investigated might be interesting GD biomarkers. More studies with a larger cohort of patients will be needed to better understand the clinical significance of these GD biomarkers.

Biomarkers in Rare Diseases

There is no single global definition of a rare disease, and for different geographical areas the definition is based on the disease occurrence in that population [...].