Metabolic Response to Oral Microcystin-LR Exposure in the Rat by NMR-Based Metabonomic Study

Abstract

Microcystin-LR (MCLR), a potent hepatotoxin, is causing increased risks to public health. Although the liver is the main target organ of MCLR, the metabolic profiling of liver in response to MCLR in vivo remains unknown. Here, we comprehensively analyzed the metabolic change of liver and ileal flushes in rat orally gavaged with MCLR by 1 H nuclear magnetic resonance (NMR). Quantification of hepatic MCLR and its glutathione and cysteine conjugates by liquid chromatography−electrospray ionization−mass spectrometry (LC-ESI-MS) was conducted. Metabonomics results revealed significant associations of MCLR-induced disruption of hepatic metabolisms with inhibition of nutrient absorption, as evidenced by a severe decrease of 12 amino acids in the liver and their corresponding elevation in ileal flushes. The hepatic metabolism signature of MCLR was characterized by significant inhibition of tyrosine anabolism and catabolism, three disrupted pathways of choline metabolism, glutathione exhaustion, and disturbed nucleotide synthesis. Notably, substantial alterations of hepatic metabolism were observable even at the low MCLR-treated group (0.04 mg/kg MCLR), although no apparent histological changes in liver were observed in the low-and medium-dosed groups. These observations offered novel insights into the microcystin hepatotoxic mechanism at a functional level, thereby facilitating further assessment and clarification of human health risk from MCs exposure.

Effects of microcystin-LR on bacterial and fungal functional genes profile in rat gut

“…The significant variation of functional genes in fecal samples, together with our previous describing that nutrients such as amino acids and lipids were elevated in gut but deficient in liver (He et al, 2012), suggested that gut dysfunction happened when three doses of 1 mg MC-LR/kg bodyweight (48 h intervals) were given over one week. Generation of ROS including hydrogen peroxide (H 2 O 2 ) induced by MC-LR as described previously (Amado and Monserrat, 2010;Ding et al, 2001) was confirmed by the significantly enriched gene cat_bac (P < 0.05) ( Fig.…”

“…The total supernatant was evaporated to one-tenth of its initial volume and then isolated by HPLC with Waters C18 column. The purity of MC-LR was above 95% (the remainder was primarily comprised of pigment) and its identity was confirmed and determined by liquid chromatographyeelectrospray ionizationemass spectrometry (LC-ESI-MS, Thermo Electron, Waltham, MA) method described previously (He et al, 2012). MC-LR standard was obtained from SigmaeAldrich Ltd (St. Louis, MO, USA, purity >95%).…”

“…Animal experiments were performed as He et al described (He et al, 2012). Briefly, six male SpragueeDawley rat (140e150 g) aged 6 weeks were obtained from National Resource Center for Rodent Laboratory Animal (Beijing, China), and then fed ad libitum at the animal facilities of Wuhan Institute of Virology, Chinese Academy of science under controlled conditions (temperature, 20e22 C; relative humidity, 40e60%; dayenight light cycle, 12e12 h).…”

“…Moreover, MC-LR has been shown to cause severe erosion of villi in the small intestine (Ito et al, 2000), generation of reactive oxygen species (ROS) (Amado and Monserrat, 2010;Ding et al, 2001), alteration of cellular membrane organization, membrane fluidity and modification in the activity of intestinal membrane enzymes (Moreno et al, 2003). These damages of intestinal physiology and function might lead to nutrient absorption deficiency of digestive system with elevated lipids and amino acids in ileum of rat, whereas decreased amino acids, lipids and choline in liver, which thereby disrupted some metabolic pathways in liver including choline metabolism, nucleotide de novo synthesis, glutathione synthesis and glutathione depletion (He et al, 2012).…”

A review of reproductive toxicity of microcystins

“…For MCs, a number of studies have reported 'omics' analyses with multiple organisms, such as toxicogenomics (genomics applied to toxicology) [166][167][168][169][170][171], proteomics [32,36,144,145,[171][172][173][174] and metabolomics [139,[175][176][177]. These studies revealed that numerous genes and metabolic pathways involved in cytoskeleton assembly, oxidative stress, cell cycle regulation, and energetic metabolism were differentially regulated.…”