Studies were performed to elucidate the mechanism responsible for the reduction in K m values of UDP-glucuronosyltransferase 2B7 (UGT2B7) substrates observed for incubations conducted in the presence of albumin. Addition of bovine serum albumin (BSA) and fatty acid-free human serum albumin (HSA-FAF), but not "crude" HSA, resulted in an approximate 90% reduction in the K m values for the glucuronidation of zidovudine (AZT) by human liver microsomes (HLM) and UGT2B7 and a 50 to 75% reduction in the S 50 for 4-methylumbelliferone (4MU) glucuronidation by UGT2B7, without affecting V max . Oleic, linoleic, and arachidonic acids were shown to be the most abundant unsaturated long-chain fatty acids present in crude HSA and in the membranes of HLM and human embryonic kidney (HEK)293 cells, and it was demonstrated that these and other unsaturated long-chain fatty acids were UGT2B7 substrates.Glucuronides with R f (retention factor) values corresponding to the glucuronides of linoleic and arachidonic acid were detected when HLM and HEK293 cell lysates were incubated with radiolabeled cofactor, and the intensity of the bands was modulated by the presence of crude HSA (increased) and BSA or HSA-FAF (decreased). Oleic, linoleic, and arachidonic acid inhibited AZT and 4MU glucuronidation by HLM and/or UGT2B7, due to an increase in K m /S 50 without a change in V max . Addition of BSA and HSA-FAF reversed the inhibition. Likewise, coexpression of UGT2B7 and HSA in HEK293 cells reduced the K m /S 50 values of these substrates. It is postulated that BSA and HSA-FAF sequester inhibitory fatty acids released during incubations, and the apparent high K m values observed for UGT2B7 substrates arise from the presence of these endogenous inhibitors.

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WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Current evidence suggests the use of non‐steroidal anti‐inflammatory drugs (NSAIDs) increases the risk of myocardial infarction and heart failure. However, some studies have failed to demonstrate a significant relationship. • Differences in patient demographics, study design, and the varying types and classes of NSAIDs studied might either confound or modify the association between NSAID use and risk of myocardial infarction and heart failure, and prevent accurate data interpretation. WHAT THIS STUDY ADDS • NSAID use is not associated with an increased risk of either incident myocardial infarction or heart failure in elderly patients. • NSAID use is associated with a reduction in all‐cause mortality in this cohort. AIMS We studied the association between either non‐selective NSAIDs (ns‐NSAIDs), selective COX‐2 inhibitors, or any NSAID and risk of incident myocardial infarction (MI) and heart failure (HF), and all‐cause mortality in elderly subjects. METHODS We conducted a retrospective nested case‐control study on Australian veterans using nationwide hospital admission and pharmacy dispensing data. We estimated adjusted odds ratios (OR) with 95% confidence intervals (CI) for the risk of events for three different measures of prescription supply exposure over the last 2 years: (i) supplied at least once, (ii) supply frequency: supplied more than twice within the last 30 days, once or twice within the last 30 days, and once or more 30 days to 2 years and (iii) total supplies. RESULTS We identified 83 623 cases and 1 662 099 matched controls (1:20) contributing 3 862 931 persons‐years of observation. NSAID use at least once within the last 2 years did not significantly affect the risk of MI (OR 1.00, 95% CI 0.96, 1.04) but was associated with a mildly reduced risk of HF (OR 0.95, 95% CI 0.92, 0.98). There was a reduced all‐cause mortality with at least one supply of either ns‐NSAIDs (OR 0.94, 95% CI 0.90, 0.97), selective COX‐2 inhibitors (OR 0.90, 95% CI 0.88, 0.93), or any NSAID (OR 0.87, 95% CI 0.85, 0.90). Risk of death was also inversely associated with the number of prescription supplies. CONCLUSIONS NSAID use is not associated with an increased risk of incident MI and HF but is associated with a reduction in all‐cause mortality in Australian veterans.

There is currently little information regarding the localization of UDP-glucuronosyltransferases (UGTs) in human renal cortex and medulla, and the functional contribution of renal UGTs to drug glucuronidation remains poorly defined. Using human kidney sections and human kidney cortical microsomes (HKCM) and human kidney medullary microsomes (HKMM), we combined immunohistochemistry to investigate UGT1A and UGT2B7 expression with in vitro microsomal studies to determine the kinetics of S-naproxen acyl glucuronidation. With the exception of the glomerulus, Bowman's capsule, and renal vasculature, UGT1A proteins and UGT2B7 were expressed throughout the proximal and distal convoluted tubules, the loops of Henle, and the collecting ducts. Additionally, UGT1A and UGT2B7 expression was demonstrated in the macula densa, supporting a potential role of UGTs in regulating aldosterone. Consistent with the immunohistochemical data, S-naproxen acyl glucuronidation was catalyzed by HKCM and HKMM. Kinetic data were well described by the two-enzyme Michaelis-Menten equation. K m values for the high-affinity components were 34 Ϯ 14 M (HKCM) and 45 Ϯ 14 M (HKMM). Fluconazole inhibited the high-affinity component establishing UGT2B7 as the enzyme responsible for S-naproxen glucuronidation in cortex and medulla. The low-affinity component was relatively unaffected by fluconazole (Ͻ15% inhibition), supporting the presence of other UGTs with S-naproxen glucuronidation capacity (e.g., UGT1A6 and UGT1A9) in cortex and medulla. We postulate that the ubiquitous distribution of UGTs in mammalian kidney may buffer physiological responses to endogenous mediators, but at the same time competitive xenobiotic-endobiotic interactions may provide an explanation for the adverse renal effects of drugs, including nonsteroidal anti-inflammatory drugs.