Metabonomic investigations in mice infected with Schistosoma mansoni: an approach for biomarker identification

Abstract

Schistosomiasis, a chronic and debilitating parasitic disease, affects approximately 200 million people in the developing world and imposes a substantial public health and economic impact. Accurately diagnosing at the individual level, monitoring disease progression, and assessing the impact of pharmacological interventions at the population level are of prime importance for controlling schistosomiasis. Using a Schistosoma mansoni-mouse model, we present a characterization of a parasitic infection by metabolic profiling, employing (1)H NMR spectroscopy and multivariate pattern recognition techniques. We infected 10 mice with 80 S. mansoni cercariae each and collected urine samples 49 and 56 days postinfection. Urine samples were also obtained from 10 uninfected control mice at the same time. The metabolic signature of an S. mansoni infection consists of reduced levels of the tricarboxylic acid cycle intermediates, including citrate, succinate, and 2-oxoglutarate, and increased levels of pyruvate, suggesting stimulated glycolysis. A disturbance of amino acid metabolism was also associated with an S. mansoni infection, as indicated by depletion of taurine, 2-oxoisocaproate, and 2-oxoisovalerate and elevation of tryptophan in the urine. A range of microbial-related metabolites, i.e., trimethylamine, phenylacetylglycine, acetate, p-cresol glucuronide, butyrate, propionate, and hippurate, were also coupled with an S. mansoni infection, indicating disturbances in the gut microbiota. Our work highlights the potential of metabolic profiling to enhance our understanding of biological responses to parasitic infections. It also holds promise as a basis for novel diagnostic tests with high sensitivity and specificity and for improved disease surveillance and control.

Fig. 1.

Typical 600 MHz ¹H NMR spectra of urine obtained from an uninfected control mouse (A) and a mouse with a 49-day-old S. mansoni infection (B). The spectra in the aromatic region (δ 6.5-8.5) were magnified 4 times compared with the region δ 2.8-4.3, whereas the region δ 0.7-2.8 was magnified 2 times. Keys to Figs. 1 and 2: 1, butyrate; 2, propionate; 3, d-3-hydroxybutyrate; 4, lactate; 5, 2-oxoisocaproate; 6, 2-oxoisovalerate; 7, alanine; 8, acetate; 9, pyruvate; 10, succinate; 11, citrate; 12, trimethylamine; 13, dimethylamine; 14, 2-oxoglutarate; 15, creatine; 16, creatinine; 17, trimethylamine N-oxide; 18, taurine; 19, phenylacetylglycine; 20, guanodinoacetic acid; 21, hippurate; 22, tryptophan; 23, formate; 24, malonate; 25, β-alanine; 26, isobutyramide; 27, 2-oxoisovaleramide; 28, p-cresol glucuronide.

Fig. 2.

COSY spectrum of an S. mansoni-infected mouse urine acquired at 600 MHz in an ¹H NMR spectrometer. The cross peaks indicate adjacent protons. For keys, see Fig. 1 legend.

Fig. 3.

PCA (A) and PLS-DA (B) scores plots derived from PCA of ¹H NMR spectra of urines collected from mice with 49-day-old S. mansoni infections (▪) or from uninfected control mice (•).

Fig. 4.

PC1 vs. PC2 scores plot from ¹H NMR spectra of urine from S. mansoni-infected (▪) and uninfected control (•) mice after resonance from trimethylamine (δ 2.88), phenylacetylglycine (δ 7.36, δ 3.76, δ 3.68), citrate (δ 2.54, δ 2.70), acetate (δ 1.92), lactate (δ 1.32, δ 4.12), and taurine (δ 3.24, δ 3.28, δ 3.40, δ 3.44) was removed.

Fig. 5.

Cooman plot of 600-MHz ¹H NMR spectra of urine from S. mansoni-infected mice from the training set (▪), uninfected control mice from the training set (•), infected mice from the test set (□), and control mice from the test set (○).