Search

Abstract Background Pathogenesis in non-alcoholic steatohepatitis (NASH) involves abnormal cholesterol metabolism and hepatic accumulation of toxic free cholesterol. Apical sodium-dependent bile acid transporter (ASBT) inhibition in the terminal ileum may facilitate removal of free cholesterol from the liver by reducing recirculation of bile acids (BAs) to the liver, thereby stimulating new BA synthesis from cholesterol. The aim of this phase 1 study in adult healthy volunteers (HVs) and patients with type 2 diabetes mellitus (T2DM) was to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of ASBT inhibition with volixibat (SHP626; formerly LUM002). Methods Participants were randomised 3:1 to receive once-daily oral volixibat (0.5 mg, 1 mg, 5 mg or 10 mg) or placebo for 28 days in two cohorts (HV and T2DM). Assessments included safety, faecal BA and serum 7α-hydroxy-4-cholesten-3-one (C4; BA synthesis biomarker). Results Sixty-one individuals were randomised (HVs: placebo, n = 12; volixibat, n = 38; T2DM: placebo, n = 3; volixibat, n = 8). No deaths or treatment-related serious adverse events were reported. Mild or moderate gastrointestinal adverse events were those most frequently reported with volixibat. With volixibat, mean total faecal BA excretion on day 28 was ~1.6–3.2 times higher in HVs (643.73–1239.3 μmol/24 h) and ~8 times higher in T2DM (1786.0 μmol/24 h) than with placebo (HVs: 386.93 μmol/24 h; T2DM: 220.00 μmol/24 h). With volixibat, mean C4 concentrations increased by ~1.3–5.3-fold from baseline to day 28 in HVs and by twofold in T2DM. Conclusions Volixibat was generally well tolerated. Increased faecal BA excretion and serum C4 levels support the mechanistic rationale for exploring ASBT inhibition in NASH. The study was registered with the Dutch clinical trial authority (Centrale Commissie Mensgebonden Onderzoek; trial registration number NL44732.056.13; registered 24 May 2013).

The results on time integrated and time-resolved two-pulse photon echo (2PE) measurements in solubilized light-harvesting complex II (LHC II) from spinach is described. The results obtained are discussed in comparison with data in the literature that were gathered from hole burning, transient absorption measurements, and spectra simulations.

This article describes the design and construction of an experimental setup for simultaneously monitoring kinetics of the fluorescence yield and delayed light emission. Data show that the equipment is useful to study photosystem II reaction kinetics involving pigment 680 and the accompanying redox states in photosynthesis.

Fourier transform infrared difference spectra because of light-induced Q(sub A)(super -*) formation were obtained in control photosystem II membrane fragments and in samples where the magnetic interaction with the non-heme iron center in its high-spin Fe2+ state is eliminated by three different techniques. Findings showed that the hydrogen bonding interaction of Q(sub A)(super -*) is practically unaltered upon non-heme iron depletion.

A study was conducted to analyze low-temperature absorption, fluorescence and persistent hole-burned spectra of aggregates of the trimeric light-harvesting antenna complex of photosystem II (LHC II). LHC II preparations were carried out by solubilization of salt washed PS II membrane fragments. Results led to the development of a framework that qualitatively accounts for the strong temperature dependence of aggregation-induced fluorescence quenching between 4.2 and 80 K.

The impact of the 90% reduction in galactolipid digalactosyldiacylglycerol (DGDG) in the dgd1 mutant of Arabidopsis thaliana on photosystem II was investigated. Results indicated that the kinetics of Q(sub A)(super *-) reoxidation by endogenous plastoquinone and the equilibrium constants between the states Q(sub A)(super -)Q(sub B) and Q(sub A)Q(sub B)(super *-) are very identical in the wild-type and the dgd1 mutant. Also, the dgd1 mutant has a small increase in the susceptibility to high-temperature stress.

Evidence for the existence of a discrete and relatively stable S-3 of the water oxidase in photosystem in spinach thylakoids was established through analytic studies of flash-induced oxygen oscillation patterns. Results have shown that in the S1 state, the average oxidation state of the four manganese ions in the water oxidase is at least Mn(III). Furthermore, the inhibition of the oxygen evolution is independent of the redox state of the water oxidase.

Experimental approaches and theoretical modeling were employed to analyzed the pH-induced structural changes of the isolated extrinsic 33 kilodalton protein of photosystem II. Results reveal that 33kDa protein is the only extrinsic protein which exhibits acid-alkaline hysterisis within the 7.0 and 3.8 pH range. Results also show that 33kDa protein consists of two highly conserved secondary structure domains, namely, an alpha-helix and an extended beta-sheet core.

The reductive relaxation of S2 and S3 by endogeneous redox groups was investigated using plastoquinone reconstituted photosystem II (PS II) membrane fragments derived from spinach. The results confirmed that the reaction coordinates of feeding electrons by endogeneous electron donors into the water oxidizing complex which achieve the S2 and S3 redox states are essentially unaffected by Triton X-100 treatment that is used in the isolation of PS II membrane fragments from thylakoids.

A special reconstitution procedure increases the size and functionally competent quinone pool in the photosystem (PS) II membrane fragments, the inside-out-vesicles and the PS II core complexes from spinach. The method uses a sonification step and the native plastoquinone-9 (PQ-9) as the quinone component. The nature of the quinone-type molecule affects pool reconstitution. PS II has many specific binding sites for PQs. The binding appears to be dependent on the structure of the quinone head group.

A study was conducted on hydrogen-ion concentration (pH)-induced structural changes in the water oxidizing complex (WOC) in redox state S1 using an independent assay. Structural factors of functional significance were identified through the reactivity of the WOC in redox state S1 toward the exogeneous hydrophilic reductants NH2NH2 and NH2OH. Data indicated the presence of static pH effects and the occurrence of three structural transitions in the WOC at pH values of approximately 5.3-5.6, 6.2-6.5 and beyond 7.4.