Metabolic effect of AOS-iron in rats with iron deficiency anemia using LC-MS/MS based metabolomics

Highlights

• Twenty-two metabolites were identified as potential biomarkers by LC-MS/MS metabolomics.

• The metabolic pathway of IDA in rats is clarified.

• AOS-iron restored the major metabolites in relevant pathway disrupted by IDA to normal.

Abstract

Iron deficiency anemia (IDA) is a worldwide nutritional problem. The metabolic mechanism of IDA is still unclear. So, the underlying metabolic mechanism of iron supplementation has not been reported even if various iron supplements to treat IDA have been studied. The present study aimed to investigate the metabolic mechanisms of IDA and agar oligosaccharide-iron complex (AOS-iron) supplementation in IDA rats by assessing the changes of endogenous metabolites in serum and liver using LC-MS/MS metabolomics approach. Orthogonal partial least-squares discriminant analysis (OPLS-DA) score plots showed significant separation of metabolites in serum and liver among the normal, anemia model and AOS-iron groups. Seventeen and eight metabolites were identified from serum and liver, respectively. Pathway enrichment analysis suggested that potential biomarkers were strongly involved in the biosynthesis of saturated and unsaturated fatty acids, sphingolipid metabolism, glycerophospholipid metabolism, linoleic acid metabolism, Fcγ receptor (FcγR)-mediated phagocytosis, pancreatic cancer metabolism, regulation of autophagy, gonadotropin releasing hormone (GnRH) signaling pathway, fatty acid metabolism, pantothenate and CoA biosynthesis, glutathione metabolism and primary bile acid biosynthesis. After supplementing 2 mg Fe/kg·bw AOS-iron for 4 weeks, the major metabolites in related pathways disrupted by IDA were restored to normal levels. Therefore, AOS-iron effectively treated IDA by regulating metabolic disorders.

Introduction

As a trace element in the human body, iron is essential for various metabolic and life activities, such as oxygen transport, myelination, DNA synthesis, and neurotransmitter synthesis and metabolism (Niu et al., 2018, Padmanabhan et al., 2015). Iron deficiency causes a decrease in the activity of various iron-containing enzymes, which in turn induces a decrease in metabolic level of oxygen and in immunity, and various metabolic disorders (Kanjaksha, 2006, Soppi, 2018). Long-term iron deficiency can seriously deplete iron stores in the body, leading to iron deficiency anemia (IDA) (Clark, 2008). IDA is currently one of the world's four major nutritional deficiency diseases, especially in underdeveloped and developing countries. It is an important goal for future health to reduce IDA worldwide.

Ferrous sulfate has been approved as an iron supplement by pharmacopoeias and food additive regulations in many countries. It has high iron content and is inexpensive, but its bioavailability is low because of the influence of other ingredients in the food (Tolkien, Stecher, Mander, Pereira, & Powell, 2015). In recent years, some new iron supplements (such as polysaccharide-iron complexes, peptide-iron complexes, iron nanocomposite and ferrous fumarate) have been studied (Cui et al., 2017, Cui et al., 2017, Kianpour et al., 2017, Li et al., 2018, Liang et al., 2018, Zhu et al., 2017). The research mainly involves the preparation process, physicochemical properties, structural characteristics, antioxidant activity and iron supplementation effect. However, at present, the metabolic pathways for IDA and the metabolic mechanism of IDA treatment with iron supplements have not been reported. We previously prepared agar oligosaccharide-iron complex (AOS-iron) as a novel chelated iron supplement, which was soluble and stable at physiological pH. AOS-iron was absorbed in a molecular form, and the ferric iron in AOS-iron was quickly reduced to ferrous iron (He, An, Teng, Huang, & Song, 2019). AOS-iron were more effectively restored the food intake, body weight, Hb, RBC, SI, SF and LI in IDA rats, compared to ferrous gluconate and ferrous sulfate (He et al., 2019). So, it is necessary to further study the mechanism of iron supplementation.

Metabolomics, an important part of systems biology, is a new omics that has emerged following genomics, transcriptomics and proteomics, which primarily explore biological pathways involved in disease pathogenesis and determine the biological effects of treatment by measuring the content of endogenous metabolites (Turi et al., 2018, Zhang et al., 2015). Metabolomics has been successfully used in the diagnosis and monitoring of disease or drug treatment progress, such as hemolytic anemia (Liu, Liu, Gu, Qin, & Tian, 2016), type 2 diabetes (Merino et al., 2018, Zhou et al., 2018), Parkinson’s disease (Babu et al., 2018), and hypertension (Zheng et al., 2019). This implies that metabolomics is currently the most promising technique for diagnosing the pathophysiological changes in diseases development and treatment. Serum and liver are important organs for studying the iron metabolic pathway. Serum iron content reflects iron transport in the body (Bergsland et al., 2017). Liver is an important organ in metabolism and the main iron storage organ in the body, playing a central regulatory role in iron metabolism (Siimes and Dallman, 2010, Sikorska et al., 2016). Therefore, the study of serum and liver metabolomics has great significance in the treatment of IDA.

In the present study, an IDA rat model was established by feeding the animals a low iron diet, and the IDA rats were treated with AOS-iron. The serum and liver metabolomics approach, based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with multivariate analyze (PCA and OPLS-DA), were applied to identify the potentially biomarkers for IDA and reveal the underlying mechanisms of AOS-iron treatment. The objectives of our study were to determine: (1) the metabolic pathways of IDA in rats, (2) whether AOS-iron can restore the major metabolites in relevant pathways disrupted by IDA to normal levels, thus achieving the effect of iron supplementation.