Elevated levels of mercapturic acids of acrolein and crotonaldehyde in the urine of Chinese women in Singapore who regularly cook at home

10.1371/journal.pone.0120023PLoS ONE103e012002

Restructuring of the Gut Microbiome by Intermittent Fasting Prevents Retinopathy and Prolongs Survival in db/db Mice

Intermittent fasting (IF) protects against the development of metabolic diseases and cancer, but whether it can prevent diabetic microvascular complications is not known. In db/db mice, we examined the impact of long-term IF on diabetic retinopathy (DR). Despite no change in glycated hemoglobin, db/db mice on the IF regimen displayed significantly longer survival and a reduction in DR end points, including acellular capillaries and leukocyte infiltration. We hypothesized that IF-mediated changes in the gut microbiota would produce beneficial metabolites and prevent the development of DR. Microbiome analysis revealed increased levels of Firmicutes and decreased Bacteroidetes and Verrucomicrobia. Compared with db/db mice on ad libitum feeding, changes in the microbiome of the db/db mice on IF were associated with increases in gut mucin, goblet cell number, villi length, and reductions in plasma peptidoglycan. Consistent with the known modulatory effects of Firmicutes on bile acid (BA) metabolism, measurement of BAs demonstrated a significant increase of tauroursodeoxycholate (TUDCA), a neuroprotective BA, in db/db on IF but not in db/db on AL feeding. TGR5, the TUDCA receptor, was found in the retinal primary ganglion cells. Expression of TGR5 did not change with IF or diabetes. However, IF reduced retinal TNF-α mRNA, which is a downstream target of TGR5 activation. Pharmacological activation of TGR5 using INT-767 prevented DR in a second diabetic mouse model. These findings support the concept that IF prevents DR by restructuring the microbiota toward species producing TUDCA and subsequent retinal protection by TGR5 activation

Ethylation and methylation of hemoglobin in smokers and non-smokers

Two previous studies demonstrated elevated levels of 3-ethyladenine in smokers\u27 urine, suggesting that cigarette smoke may contain a DNA ethylating agent. We hypothesized that such an agent would also lead to elevated levels of N-terminal N-ethylvaline in hemoglobin. N-terminal N-alkylated valines in hemoglobin can be measured using a modified Edman degradation, which employs pentafluorophenyl isothiocyanate to produce a pentafluorophenylthiohydantoin. The latter is quantified by gas chromatography-negative ion chemical ionization-mass spectrometry (GC-NICI-MS). We modified the published method to increase its sensitivity and selectivity, thereby allowing quantification of N-terminal N-ethylvaline. Modifications included the use of a deuterated peptide as the internal standard, the introduction of an HPLC purification step, and the use of tandem mass spectrometry (MS/MS) for detection and quantification of the analyte, 1-ethyl-5-isopropyl-3-pentafluorophenyl-2-thiohydantoin. We also quantified N-terminal N-methylvaline in the same samples. The mean level of N-terminal N-ethylvaline in the hemoglobin of smokers was 3.76 ± 2.77 pmol/g globin (n = 39), significantly higher than in non-smokers, 2.50 ± 1.65 pmol/g globin (n = 28), P = 0.023. The difference remained significant after correction for gender and age. The mean level of N-terminal N-methylvaline in smokers was 997 ± 203 pmol/g globin (n = 45) compared with 904 ± 149 pmol/g globin in non-smokers (n = 29); these values were not significantly different when corrected for gender and age. As levels of hemoglobin and DNA adducts often correlate, the results of this study support the proposal that cigarette smoke contains an as yet unidentified ethylating agent, which might be involved in DNA damage and tumor initiation