Search

The impact of two dietary organic acids (OAs) on nutrient digestibility and intestinal morphology was determined in Nile tilapia under conditions of dissolved oxygen in the water: normoxia and hypoxia. Four diets designated as control (0 g/kg organic acid salt), KDF (2 g/kg potassium diformate), CAB (2 g/kg calcium butyrate) and their combination (4 g/kg of a mixture of KDF and CAB, ration 1:1) were formulated with 520 g/kg of soybean meal in order to produce soybean meal enteritis-like symptoms. The four diets were tested first under normoxic conditions (6 mg/L) for a period of 5 weeks, followed by a test period under hypoxic conditions (3 mg/L). The results showed that OAs were unable to significantly improve growth and nutrient digestibility under normoxic conditions but under hypoxic conditions, there was a significant enhancement of the growth and nutrient digestibility. Fish fed OA-supplemented diets showed improvements in the intestinal morphology under the normoxic conditions, and these effects were more pronounced under the hypoxic conditions. Experimental findings suggest that OAs can improve the nutrient digestibility and intestinal morphology under hypoxic conditions. A synergistic effect by the combination of formic and butyric acid on growth, digestibility and intestinal morphology was not found.

Targeting the protein–protein interaction (PPI) between nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associated protein 1 (Keap1) is a potential therapeutic strategy to control diseases involving oxidative stress. Here, six classes of known small-molecule Keap1–Nrf2 PPI inhibitors were dissected into 77 fragments in a fragment-based deconstruction reconstruction (FBDR) study and tested in four orthogonal assays. This gave 17 fragment hits of which six were shown by X-ray crystallography to bind in the Keap1 Kelch binding pocket. Two hits were merged into compound 8 with a 220–380-fold stronger affinity (Ki = 16 μM) relative to the parent fragments. Systematic optimization resulted in several novel analogues with Ki values of 0.04–0.5 μM, binding modes determined by X-ray crystallography, and enhanced microsomal stability. This demonstrates how FBDR can be used to find new fragment hits, elucidate important ligand–protein interactions, and identify new potent inhibitors of the Keap1–Nrf2 PPI. Targeting the protein-protein interaction (PPI) between nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associated protein 1 (Keap1) is a potential therapeutic strategy to control diseases involving oxidative stress. Here, six classes of known small-molecule Keap1-Nrf2 PPI inhibitors were dissected into 77 fragments in a fragment-based deconstruction reconstruction (FBDR) study and tested in four orthogonal assays. This gave 17 fragment hits of which six were shown by X-ray crystallography to bind in the Keap1 Kelch binding pocket. Two hits were merged into compound 8 with a 220-380-fold stronger affinity (Ki = 16 μM) relative to the parent fragments. Systematic optimization resulted in several novel analogues with Ki values of 0.04-0.5 μM, binding modes determined by X-ray crystallography, and enhanced microsomal stability. This demonstrates how FBDR can be used to find new fragment hits, elucidate important ligand-protein interactions, and identify new potent inhibitors of the Keap1-Nrf2 PPI.

The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) has a protective effect against oxidative stress and plays a major role in inflammation and central nervous system (CNS) diseases. Inhibition of the protein-protein interaction (PPI) between Nrf2 and its repressor protein, Kelch-like ECH-associated protein 1 (Keap1), leads to translocation of Nrf2 from the cytosol to the nucleus and expression of detoxifying antioxidant enzymes. To date, several non-covalent small-molecule Keap1-Nrf2 inhibitors have been identified; however, many of them contain carboxylic acids and are rather large in size, which likely prevents or decreases CNS permeability. This Perspective describes current small-molecule Keap1-Nrf2 inhibitors with experimental evidence for the ability to inhibit the Keap1-Nrf2 interaction by binding to Keap1 in a non-covalent manner. Binding data, biostructural studies, and biological activity are summarized for the inhibitors, and their potential as CNS tool compounds is discussed by analyzing physicochemical properties, including CNS multiparameter optimization (MPO) scoring algorithms. Finally, several strategies for identifying CNS-targeting Keap1 inhibitors are described.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Gentamicin pharmacokinetics show wide inter-individual variability across all age groups and impaired gentamicin clearance is associated with impaired creatinine clearance in older people. • Changes in body composition and renal function with old age and frailty are likely to affect the pharmacokinetics of gentamicin. • There is current debate on whether the Modification of Diet in Renal Disease (MDRD) equation estimate of glomerular filtration rate (GFR) should replace the Cockcroft Gault equation estimate of creatinine clearance for calculation of doses of renally excreted drugs. WHAT THIS STUDY ADDS • The volume of distribution of gentamicin is not significantly lower in frail than in non frail older people. • The correlation between volume of distribution of gentamicin and actual bodyweight is poor in frail and moderate in non frail older people. • Gentamicin clearance is significantly lower in frail than in non frail older people. • The Cockcroft Gault calculation of creatinine clearance, calculated using ideal bodyweight, gave the best estimate of gentamicin clearance in this population of frail and non frail older people. • The MDRD estimate of GFR and Cockcroft Gault estimate of creatinine clearance, calculated using actual bodyweight, overestimate gentamicin clearance in frail and non frail older people. AIMS Frailty, a syndrome of decreased physiological reserve that is prevalent in old age, impacts on clinical pharmacology. The aims of the study were to (1) determine whether frailty affects the pharmacokinetics of gentamicin and (2) assess the accuracy of different estimates of body size and renal clearance as estimates of gentamicin pharmacokinetics in older inpatients. METHODS This was an observational study of gentamicin pharmacokinetics in a cohort of Australian hospital inpatients aged ≥65 years, who were administered prophylactic intravenous gentamicin. RESULTS Of the 31 participants, 14 were frail and 17 non frail on the Reported Edmonton Frail Scale. The mean volume of distribution of gentamicin was 14.8 ± 1.4 l in frail participants and 15.3 ± 2.2 l in non frail (NS). Volume of distribution correlated best with lean bodyweight. Gentamicin clearance was significantly lower in frail participants (46.6 ± 10.7 ml min−1) than in non frail (58.2 ± 12.4 ml min−1, P= 0.01). The Cockcroft Gault estimate of creatinine clearance calculated using ideal bodyweight gave the best estimate of gentamicin clearance (mean error – 0.15 ml min−1, 95% CI −2.67, 2.39). The Cockcroft Gault creatinine clearance calculated using actual bodyweight and the estimated glomerular filtration rate from the modified diet in renal disease equation overestimated gentamicin clearance, with mean errors of −10.15 ml min−1 (95%CI −13.60, −6.71) and −18.86 ml min−1 (95% CI −22.45, −15.27), respectively. The Cockcroft Gault creatinine clearance calculated using lean bodyweight underestimated gentamicin clearance (mean error 6.54 ml min−1, 95% CI 4.18, 8.90). CONCLUSIONS Frail older people have significantly lower gentamicin clearance than non frail. The best estimate of gentamicin clearance is obtained from the Cockcroft Gault creatinine clearance calculated using ideal bodyweight.

Cellular signal transduction pathways are usually studied following administration of an external stimulus. However, disease-associated aberrant activity of the pathway is often due to misregulation of the equilibrium state. The transcription factor NF-jB is typically described as being held inactive in the cytoplasm by binding its inhibitor, IjB, until an external stimulus triggers IjB degradation through an IjB kinase-dependent degradation pathway. Combining genetic, biochemical, and computational tools, we investigate steady-state regulation of the NF-jB signaling module and its impact on stimulus responsiveness. We present newly measured in vivo degradation rate constants for NF-jB-bound and -unbound IjB proteins that are critical for accurate computational predictions of steady-state IjB protein levels and basal NF-jB activity. Simulations reveal a homeostatic NF-jB signaling module in which differential degradation rates of free and bound pools of IjB represent a novel cross-regulation mechanism that imparts functional robustness to the signaling module. Molecular Systems Biology 8 May 2007; doi:10.1038/msb4100148