Chlorogenic acid (CGA) is one of the most abundant hydroxy cinnamic acid (phenolic acids) compounds in the human diet, such as coffee and tea. Accumulating evidence shows that CGA exhibits many biological effects, including anti-bacterial, anti-oxidant, anti-inflammation, anti-cancer, anti-diabetes, anti-hypertension and anti-obesity actions. There are also reports that CGA modulates glucose and lipid metabolism both in healthy and genetically metabolic disordered conditions. Furthermore, CGA confers hepato-protective benefits on protecting animals from LPS-induced or chemical injury. Therefore, researchers, led by YIN Yulong, at the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) chose CGA as research object.

Previous studies of the biological effects of CGA have been confined only to measurements of a single or several biochemical markers in tissues. This approach does not adequately reflect the overall metabolism of nutrients in animals or humans. Therefore, the traditional methods cannot be used to perform global screening of physiological perturbations, such that unexpected or novel responses or biomarkers are often not detected. Hence, it is necessary to employ a robust technique to simultaneously quantify and identify a large number (hundreds to thousands) of molecules in blood and other tissues.

Metabolomics has emerged as a biomarker discovery tool for metabolic profiling in nutritional research. Nuclear magnetic resonance (NMR) spectroscopy is one of the major techniques used in metabolomic studies as the spectra of biofluids or tissues contain a wealth of metabolic information and provide comprehensive biochemical profiles of low-molecular-weight metabolites whose concentrations are precisely regulated in response to various stimuli. Thus, NMR analysis aids in enhanced understanding of molecular mechanisms and in providing novel insight into the intervention effect or perturbation of diets with regard to nutrient metabolism and health. To capitalize on this advanced technique, the present study was conducted with ¹H NMR to screen the global metabolic profile of the serum and liver of CGA-supplemented rats.

In the current study, they found that CGA did not affect rat growth performance, serum biochemical profiles, or hepatic morphology. However, supplementation with CGA decreased serum concentrations of lactate, pyruvate, succinate, citrate, β-hydroxybutyrate and acetoacetate, while increasing serum concentrations of glycine and hepatic concentrations. In conclusion, the results support the hypothesis that supplementation of CGA to a normal diet will regulate energy metabolism and enhance anti-oxidant function of rats. Dietary supplementation with CGA increased the concentrations of glycine in the serum and the concentrations of glutathione in the liver, thus promoting the antioxidant activity in the whole body. CGA also beneficially modulates energy metabolism in rats. So it is suggested that glycine and glutathione in the blood circulation are useful biomarkers for the biological effects of CGA in vivo.

This research was supported by funding from National Natural Science Foundation of China (Grant No. 31001014), the Research Foundation (SKLF-TS-201108 and SKLF-TS-200817) and the Open Project Program (SKLF-KF-201005 and SKLF-KF-201216) of State Key Laboratory of Food Science and Technology at Nanchang University, and Texas A&M AgriLife Research H82000.H. Assaad was supported by a postdoctoral training grant (R25T-CA090301) from the National Cancer Institute.

The study entitled “Metabolomic analysis of amino acid and energy metabolism in rats supplemented with chlorogenic acid” has been published in Amino Acids, details could be found at http://link.springer.com/article/10.1007/s00726-014-1762-7.