Investigations of the Effects of Gender, Diurnal Variation, and Age in Human Urinary Metabolomic Profiles

Abstract

Metabolomics may have the capacity to revolutionize disease diagnosis through the identification of scores of metabolites that vary during environmental, pathogenic, or toxicological insult. NMR spectroscopy has become one of the main tools for measuring these changes since an NMR spectrum can accurately identify metabolites and their concentrations. The predominant approach in analyzing NMR data has been through the technique of spectral binning. However, identification of spectral areas in an NMR spectrum is insufficient for diagnostic evaluation, since it is unknown whether areas of interest are strictly caused by metabolic changes or are simply artifacts. In this paper, we explore differences in gender, diurnal variation, and age in a human population. We use the example of gender differences to compare traditional spectral binning techniques (NMR spectral areas) to novel targeted profiling techniques (metabolites and their concentrations). We show that targeted profiling produces robust models, generates accurate metabolite concentration data, and provides data that can be used to help understand metabolic differences in a healthy population. Metabolites relating to mitochondrial energy metabolism were found to differentiate gender and age. Dietary components and some metabolites related to circadian rhythms were found to differentiate time of day urine collection. The mechanisms by which these differences arise will be key to the discovery of new diagnostic tests and new understandings of the mechanism of disease.

Age, Sexual Dimorphism, and Disease Associations in the Developing Human Fetal Lung Transcriptome

“…Sex-based differential expression of human corneal epithelial cells has also demonstrated that one of the enriched pathways is the DNA replication pathway (25). Similarly, sex differences in the expression of TCA cycle enzymes in skeletal muscle (26), and the excretion of citrate in urine (27), have been demonstrated. Together, the sex-specific pathways enriched in our analysis have previously been shown to differ between sexes, albeit in different tissues.…”

Urine Metabolite Analysis Offers Potential Early Diagnosis of Ovarian and Breast Cancers

“…Sample (600 mL) was subsequently transferred into 5 mm 535 pp NMR tubes (Wilmad LabGlass), and samples were stored at 4 C until NMR acquisition (within 24 hours of sample preparation). NMR spectra were acquired as previously described (7).…”

“…We have shown that NMR spectroscopy coupled with targeted profiling techniques offers a powerful approach to generate high-density metabolic data on biofluids (3)(4)(5)(6)(7)(8). Multivariate statistical analysis, including principal component analysis (PCA), partial least-squares-discriminant analysis (PLS-DA), or orthogonal partial least-squares-discriminant analysis (OPLS-DA) can be applied to these data or complex spectral data to aid in the characterization of changes related to a biological perturbation or disease.…”

The Emerging Field of Quantitative Blood Metabolomics for Biomarker Discovery in Critical Illnesses

“…Inherent variability can be minimized by collecting samples in the morning (08:30-09:30) preferably before food intake (33,34). For biofluids, the optimal sample volume is 0.1 to 0.5 ml.…”