| Chronic kidney disease (CKD) is a serious and prevalent health problem. Metabolomics, as a novel approach, is an important part of systems biology and has been used for CKD therapy. Diuretics have been widely applied to treat CKD in clinic. However, a long-term usage of chemical diuretics can result in various side-effects such as hyperglycemia, ototoxicity and arrhythmia. Traditional Chinese medicine is an important source for new prodrug and new drug discovery. P. cocos and its epidermis are common traditional Chinese medicine that applied to exert diuretic effects and treat kidney disease. Modern investigations show that triterpenes and polysaccharides are the main chemical components of P. cocos with diuretic, nephroprotective and anti-tumor bioactivities. Triterpenes are the major constituents of P. cocos epidermis, which are mainly used for diuresis to alleviate edema.ObjectiveFirstly, this study was to investigate diuretic activity of P. cocos and its epidermis as well as their action mechanisms. Secondly, we explored therapeutic effect of the active fraction of P. cocos epidermis on CKD. Thirdly, the current study uncovers biochemical action mechanism of P. cocos epidermis for treating CKD by using UPLC-HDMS-based metabolomics approach.Methods1. Diuretic activity of P. cocos and its epidermis. Saline-loading SD rats were used to evaluate diuretic activity of P. cocos and its epidermis. After oral administration with the extracts of P. cocos and its epidermis, urine volumes within 6 h were recorded and the urinary electrolyte ion including Na+, K+and Cl" as well as pH value were analyzed.2. CKD model and therapeutic effect of P. cocos epidermis. SD rats were randomly divided into control, CKD and ethnol extract of P. cocos epidermis treatment groups. The rats in CKD and P. cocos epidermis treatment groups were orally administrated with adenine (200 mg/kg body weight) once a day continuously for two weeks. The rats in P. cocos epidermis treatment group were orally administrated with ethanol extract of P. cocos epidermis (60 mg/kg) while control group and CKD group were given water for two weeks. Two weeks later, individual rats were placed in metabolic cages (1 rat/cage) to obtain 24 h urine collections. Serum, urine and kidney tissue were collected for the determination of serum biochemistry, blood parameter, histopathology and metabolomics.3. UPLC-HDMS-based metabolomics was employed to study the therapeutic effect of ethanol extract of P. cocos epidermis on CKD and elucidate its biochemical action mechanism. The metabolic profiles of serum, urine and kidney tissue were analyzed using multivariate statistical analysis. Combined with blood biochemistry and tissue histopathology, biomarkers were identified, their changes were analyzed before and after treatment with P. cocos epidermis on CKD and the biochemical action mechanism were uncovered.Results1. No obvious diuretic activity was observed after oral administration of aqueous extracts of P. cocos and P. cocos epidermis. However, the ethanol extract of P. cocos epidermis and its ethyl acetate fraction presented a remarkable diuretic activity with K+retention and Na+excretion.2. Serum urea, creatinine, uric acid levels as well as white blood cells level were markedly increased in the adenine-induced CKD rats. Red blood cells and hemoglobin levels were significantly decreased. The above-mentioned kidney function and blood parameters were restored by treatment of ethnol extract of P. cocos epidermis.3. UPLC-HDMS-metabolomics indicated that ethanol extract of P. cocos epidermis could prevent adenine-induced chronic renal injury. LysoPC(18:1), lysoPC(17:0), lysoPC(16:0), phytosphingosine, tryptophan and creatinine were serum biomarkers of CKD rats. The metabolic pathways of lipids and amino acids were interfered by adenine. Creatinine, dopamine, uremic toxins and amino acids were urinary biomarkers of CKD rats. Polyunsaturated fatty acid, creatinine, uremic toxins and allantoin were identified in kidney tissue. Polyunsaturated fatty acid and uremic toxins were main biomarkers in kidney tissue of CKD rats. These results demonstrated that pathological alternations were closely associated with changed biomarkers. This paper firstly systematically revealed that adenine caused the disturbance of fatty acid metabolism, amino acid metabolism and energy metabolism in adenine-induced CKD rats. Treatment with ethanol extract of P. cocos epidermis restored abnormal levels of the biomarkers as well as their metabolic pathways, improved amino acid and lipid metabolisms induced by adenine in CKD. The study indicated P. cocos epidermis had a preferable therapeutic effect on chronic kidney injury.ConclusionThe ethanol extract of P. cocos epidermis and its ethyl acetate fraction presented a remarkable diuretic activity. UPLC-HDMS-based metabolomics showed that rats with adenine-induced CKD were obviously alleviated by the ethanol extract of P. cocos epidermis and the biochemical action mechanism was closely associated with lipid metabolism and amino acid metabolism. |
