ABSTRACT
Despite decades of use of low protein diets (LPD) in the management of chronic kidney disease (CKD), their mechanisms of action are unclear. A reduced production of uremic toxins could contribute to the benefits of LPDs. Aromatic amino-acids (AA) are precursors of major uremic toxins such as p-cresyl sulfate (PCS) and indoxyl sulfate (IS). We hypothesize that a low aromatic amino acid diet (LA-AAD, namely a low intake of tyrosine, tryptophan and phenylalanine) while being normoproteic, could be as effective as a LPD, through the decreased production of uremic toxins. Kidney failure was chemically induced in mice with a diet containing 0.25% (w/w) of adenine. Mice received three different diets for six weeks: normoproteic diet (NPD: 14.7% proteins, aromatic AAs 0.019%), LPD (5% proteins, aromatic AAs 0.007%) and LA-AAD (14% proteins, aromatic AAs 0.007%). Both LPD and LA-AAD significantly reduced proteinuria, kidney fibrosis and inflammation. While LPD only slightly decreased plasma free PCS and free IS compared to NPD; free fractions of both compounds were significantly decreased by LA-AAD. These results suggest that a LA-AAD confers similar benefits of a LPD in delaying the progression of CKD through a reduction in some key uremic toxins production (such as PCS and IS), with a lower risk of malnutrition.
Subject(s)
Amino Acids, Aromatic/adverse effects , Diet, Protein-Restricted/methods , Kidney/pathology , Malnutrition/prevention & control , Renal Insufficiency, Chronic/diet therapy , Animals , Diet, Protein-Restricted/adverse effects , Disease Models, Animal , Fibrosis , Humans , Male , Malnutrition/etiology , Mice , Renal Insufficiency, Chronic/pathology , Uremic Toxins/metabolismABSTRACT
Roughly one-half of bladder cancer incidence in the United States can be attributed to known causes, mainly cigarette smoking, and it has been hypothesized that the aromatic amines in tobacco smoke are important etiological agents. Nonsmokers are also exposed, through unknown sources, to many of the same carcinogenic aromatic amines that are present in cigarette smoke. Previous epidemiological studies have not tested whether either of these aromatic amine exposures are associated with cancer risk. We conducted a population-based case-control study in Los Angeles County, California, involving 761 case patients with bladder cancer and 770 individually matched control subjects. In-person interviews provided information on tobacco smoking and other potential risk factors. Quantitative analysis of hemoglobin adducts of 4- and 3-aminobiphenyl (ABP) was used to assess aromatic amine exposure. Adducts of both aminobiphenyls were significantly higher in cases than in controls, independent of cigarette smoking at the time of blood collection and lifetime smoking history. Adjustment for other risk factors as well as for metabolic differences did not materially alter the associations. Our findings strengthen the connection between exposure to aromatic amines in tobacco smoke and cigarette smoking-related bladder cancer and suggest that environmental exposure to arylamines may account for a significant proportion of nonsmoking-related bladder cancer in the general population.
Subject(s)
Amino Acids, Aromatic/adverse effects , Smoking/adverse effects , Urinary Bladder Neoplasms/epidemiology , Urinary Bladder Neoplasms/etiology , Adult , Amino Acids, Aromatic/metabolism , Aminobiphenyl Compounds/metabolism , Biomarkers/blood , Carcinogens, Environmental/adverse effects , Carcinogens, Environmental/metabolism , Case-Control Studies , Environmental Exposure/adverse effects , Female , Hemoglobins/metabolism , Humans , Los Angeles/epidemiology , Male , Middle Aged , Risk Factors , Smoking/metabolism , Statistics as Topic , Tobacco Smoke Pollution/adverse effects , Urinary Bladder Neoplasms/metabolismABSTRACT
Genomic injury induced by environmental carcinogens, such as polycyclic aromatic hydrocarbons and aromatic amines, is the initial step that can trigger mutagenesis and carcinogenesis. In addition to the physico-chemical property of DNA damaging agents, several important factors such as primary sequence, chromatin structure, methylation, protein association, and transcriptional activity can affect not only the initial level and distribution of DNA damage but also the efficiency of repair. Therefore, mapping the DNA damage induced by environmental agents in cancer-related genes such as p53 and ras at the sequence level provides essential information for assessing their carcinogenic potential. Recently, using the E. coli nucleotide excision enzyme complex, UvrABC nucleases in combination with ligation-mediated polymerase chain reaction, we developed a method to map DNA damage in the p53 and ras genes. These studies led us to conclude that targeted DNA damage, in combination with growth selection, contributes greatly in shaping the mutation spectrum in these genes in human cancer. Here we present the rationale and details of this approach, typical experimental results and necessary precautions.
