Multivariable analysis of host amino acids in plasma and liver during infection of malaria parasite Plasmodium yoelii

Abstract

Background: Malaria is the most significant human parasitic disease, and yet understanding of the energy metabolism of the principle pathogen, Plasmodium falciparum, remains to be fully elucidated. Amino acids were shown to be essential nutritional requirements since early times and much of the current knowledge of Plasmodium energy metabolism is based on early biochemical work, performed using basic analytical techniques, carried out almost exclusively on human plasma with considerable inter-individual variability.

Methods: In order to further characterize the fate of amino acid metabolism in malaria parasite, multivariate analysis using statistical modelling of amino acid concentrations (aminogram) of plasma and liver were determined in host infected with rodent malaria parasite, Plasmodium yoelii.

Results and conclusion: Comprehensive and statistical aminogram analysis revealed that P. yoelii infection caused drastic change of plasma and liver aminogram, and altered intra- and inter-correlation of amino acid concentration in plasma and liver. These findings of the interactions between amino acids and Plasmodium infection may provide insight to reveal the interaction between nutrients and parasites.

Figure 1

Plasma and liver amino acid concentrations vary in host infected with Plasmodium yoelii. Amino acid concentrations in plasma (A) and liver (B) were analysed on five days post-infection with Plasmodium yoelii. Shown are amino acids concentrations of uninfected mice (blue bars), infected mice (orange bars). Each bar represents mean ± SD of six mice. Asterisks denote: *p<0.05; **p<0.01; ***p<0.001. BALB/c mice were infected with 1×10⁶ RBCs parasitized with P. yoelii.

Figure 2

Aminogram in plasma and liver changes with Plasmodium infection. Alterations of aminogram in plasma (A) and liver (B) during Plasmodium infection are shown. The blue- and yellow-coloured cells represent z scores calculated for each amino acid [(observed mean - normal control mean)/normal control SD] in plasma and liver, respectively. Cluster analyses are applied to amino acids as described in the Methods. The z scores are as follows: yellow, positive changed; blue, negative changed; black, low variation. Coloured bars represent the mice condition and category of amino acids as follows; grey, uninfected mice; orange, P. yoelii-infected mice; light blue, essential amino acid for P. falciparum; pink, essential amino acid for mouse; green, non-essential amino acid for mouse; red, amino acid derivatives, urea, and ammonia.

Figure 3

Intracorrelation of aminogram variation in each tissue. (A) A schematic diagram of the experiment to investigate intracorrelation of aminogram variation in plasma and liver. (B) Heat map of the correlation matrix among amino acids in plasma and liver. The plot summarizes the Spearman’s rank correlation coefficients between 20 amino acids, 11 their derivative, urea, and ammonia in plasma and liver of mice. Coloured panel represents significant and strong correlation (|ρ|≧0.7, p<0.05) between amino acid concentrations in plasma or liver of uninfected (upper) and infected (lower) mice. Each colour indicates as follows; green, positively correlated in plasma; magenta, positively correlated in liver; light blue, negatively correlated in liver; white, not correlated.

Figure 4

Intercorrelation of aminogram variation between plasma and liver. (A) A schematic diagram of the experiment to investigate intercorrelation of aminogram variation between plasma and liver. (B) Heat map of the correlation matrix among amino acids between plasma and liver. The plot summarizes the Spearman’s rank correlation coefficients among amino acids and their derivatives between plasma and liver. Coloured panel represents significant and strong correlation (|ρ|≧0.7, p<0.05) between plasma and liver amino acid concentrations in uninfected (upper) and infected (lower) mice. Each colour indicates as follows; yellow, positively correlated; blue, negatively correlated; white, not correlated.