Metformin Scavenges Methylglyoxal To Form a Novel Imidazolinone Metabolite in Humans.

Methylglyoxal (MG) is a highly reactive dicarbonyl compound involved in the formation of advanced glycation endproducts (AGE). Levels of MG are elevated in patients with type-2 diabetes mellitus (T2DM), and AGE have been implicated in the progression of diabetic complications. The antihyperglycemic drug metformin (MF) has been suggested to be a scavenger of MG. The present work examined and characterized unequivocally the resulting scavenged product from the metformin-MG reaction. The primary product was characterized by (1)H, (13)C, 2D-HSQC, and HMBC NMR and tandem mass spectrometry. X-ray diffraction analysis determined the structure of the metformin and MG-derived imidazolinone compound as (E)-1,1-dimethyl-2-(5-methyl-4-oxo-4,5-dihydro-1H-imidazol-2-yl)guanidine (IMZ). A LC-MS/MS multiple reaction monitoring method was developed to detect and quantify the presence of IMZ in metformin-treated T2DM patients. Urine from >90 MF-treated T2DM patients was analyzed, with increased levels of MF directly correlating with elevations in IMZ. Urinary MF was detected in the range of 0.17 µM to 23.0 mM, and simultaneous measurement of IMZ concentrations were in the range of 18.8 nM to 4.3 µM. Since plasma concentrations of MG range from 40 nM to 4.5 µM, the level of IMZ production may be of therapeutic significance. Thus, in addition to lowering hepatic gluconeogenesis, metformin also scavenges the highly reactive MG in vivo, thereby reducing potentially detrimental MG protein adducts, with subsequent reductions in diabetic complications.

Mechanistic basis of altered morphine disposition in nonalcoholic steatohepatitis.

Morphine is metabolized in humans to morphine-3-glucuronide (M3G) and the pharmacologically active morphine-6-glucuronide (M6G). The hepatobiliary disposition of both metabolites relies upon multidrug resistance-associated proteins Mrp3 and Mrp2, located on the sinusoidal and canalicular membrane, respectively. Nonalcoholic steatohepatitis (NASH), the severe stage of nonalcoholic fatty liver disease, alters xenobiotic metabolizing enzyme and transporter function. The purpose of this study was to determine whether NASH contributes to the large interindividual variability and postoperative adverse events associated with morphine therapy. Male Sprague-Dawley rats were fed a control diet or a methionine- and choline-deficient diet to induce NASH. Radiolabeled morphine (2.5 mg/kg, 30 µCi/kg) was administered intravenously, and plasma and bile (0-150 or 0-240 minutes), liver and kidney, and cumulative urine were analyzed for morphine and M3G. The antinociceptive response to M6G (5 mg/kg) was assessed (0-12 hours) after direct intraperitoneal administration since rats do not produce M6G. NASH caused a net decrease in morphine concentrations in the bile and plasma and a net increase in the M3G/morphine plasma area under the concentration-time curve ratio, consistent with upregulation of UDP-glucuronosyltransferase Ugt2b1. Despite increased systemic exposure to M3G, NASH resulted in decreased biliary excretion and hepatic accumulation of M3G. This shift toward systemic retention is consistent with the mislocalization of canalicular Mrp2 and increased expression of sinusoidal Mrp3 in NASH and may correlate to increased antinociception by M6G. Increased metabolism and altered transporter regulation in NASH provide a mechanistic basis for interindividual variability in morphine disposition that may lead to opioid-related toxicity.

Transmission mode desorption electrospray ionization (TM-DESI) for simultaneous analysis of potential inorganic and organic components of radiological dispersion devices (RDDs).

Transmission mode desorption electrospray ionization (TM-DESI) coupled to an ion trap mass spectrometer capable of source collision-induced dissociation (CID) was used to completely analyze radiological dispersion device components. Source CID significantly enhanced the signal for metal ions by reducing adducts while eliminating chemical noise from background molecules through extensive fragmentation. Source CID spectra yielded reasonably accurate isotopic ratios for the metals studied. By switching the source CID on and off between scans, all major constituents in mixtures of simulated radionuclides and explosives were simultaneously observed. These results indicate that TM-DESI/ion trap technology could be a powerful on-site tool for nuclear forensics.

Three fatal intoxications due to methylone.

We present three fatal intoxications of methylone, a cathinone derivative. Blood was analyzed with a routine alkaline liquid-liquid extraction and analyzed by gas chromatography coupled with a mass spectrometer (GC-MS). Methylone was identified by a full scan mass spectral comparison to an analytical standard of methylone. For a definitive and conclusive confirmation and quantitation, methylone was also derivatized with heptafluorobutyric anhydride and analyzed by GC-MS. In all three fatalities, the deceased exhibited seizure-like activity and elevated body temperatures (103.9, 105.9 and 107°F) before death. Two of the three cases also exhibited metabolic acidosis. One of the three cases had prolonged treatment and hospitalization before death with symptoms similar to sympathomimetic toxicity, including metabolic acidosis, rhabdomyolysis, acute renal failure and disseminated intravascular coagulation. The laboratory results for this patient over the 24 h period of hospitalization were significant for increased lactate, liver transaminases, creatinine, myoglobin, creatine kinase and clotting times, and decreased pH, glucose and calcium. Peripheral blood methylone concentrations in the three fatal cases were 0.84, 3.3 and 0.56 mg/L. In conlusion, peripheral blood methylone concentrations in excess of 0.5 mg/L may result in death due to its toxic properties, which can include elevated body temperature and other sympathomimetic-like symptoms.