Introduction to the DISRUPT postprandial database: subjects, studies and methodologies.

Dysregulation of lipid and glucose metabolism in the postprandial state are recognised as important risk factors for the development of cardiovascular disease and type 2 diabetes. Our objective was to create a comprehensive, standardised database of postprandial studies to provide insights into the physiological factors that influence postprandial lipid and glucose responses. Data were collated from subjects (n = 467) taking part in single and sequential meal postprandial studies conducted by researchers at the University of Reading, to form the DISRUPT (DIetary Studies: Reading Unilever Postprandial Trials) database. Subject attributes including age, gender, genotype, menopausal status, body mass index, blood pressure and a fasting biochemical profile, together with postprandial measurements of triacylglycerol (TAG), non-esterified fatty acids, glucose, insulin and TAG-rich lipoprotein composition are recorded. A particular strength of the studies is the frequency of blood sampling, with on average 10-13 blood samples taken during each postprandial assessment, and the fact that identical test meal protocols were used in a number of studies, allowing pooling of data to increase statistical power. The DISRUPT database is the most comprehensive postprandial metabolism database that exists worldwide and preliminary analysis of the pooled sequential meal postprandial dataset has revealed both confirmatory and novel observations with respect to the impact of gender and age on the postprandial TAG response. Further analysis of the dataset using conventional statistical techniques along with integrated mathematical models and clustering analysis will provide a unique opportunity to greatly expand current knowledge of the aetiology of inter-individual variability in postprandial lipid and glucose responses.

Impact of age and menopausal status on the postprandial triacylglycerol response in healthy women.

OBJECTIVE: To examine the impact of age and the natural menopause on the postprandial triacylglycerol (TAG) response in healthy women. METHODS AND RESULTS: Thirty-seven premenopausal and sixty-one postmenopausal women underwent a sequential meal postprandial investigation, in which blood samples were taken at regular intervals after a test breakfast and lunch given at 0 and 330 min respectively. Lipids and glucose were measured in the fasting sample, with TAG analysed in the postprandial samples. Postmenopausal women were shown to have higher fasting total cholesterol, low density lipoprotein cholesterol (LDL-C) and glucose (P<0.02). Marked differences in the postprandial TAG response were evident between the groups, with a greater incremental area under the curve (IAUC) and maximum TAG concentration in the postmenopausal women (P<0.04). Multivariate regression analysis revealed both age and fasting TAG to be independently associated with the summary measures of the postprandial TAG response in the premenopausal women only. Interestingly, sub-division of the women into both younger and older pre- and postmenopausal subgroups, showed the most marked difference in TAG-IAUC to be between the younger and the older premenopausal women, whereas differences in fasting LDL-C were most evident between the older premenopausal and the younger postmenopausal women. CONCLUSIONS: Our results suggest a divergence in the relationship of age and menopausal status with fasting LDL-C and postprandial TAG which may reflect differences in the metabolic effects of age and the menopause on these lipid risk markers or a greater impact of early oestrogen decline on pathways of TAG rather than LDL metabolism.

Trajectories of entering the metabolic syndrome: the framingham heart study.

BACKGROUND: We evaluated the progression of the metabolic syndrome (MetS) and its components, the trajectories followed by individuals entering MetS, and the manner in which different trajectories predict cardiovascular disease and mortality. METHODS AND RESULTS: Using data from 3078 participants from the Framingham Offspring Study (a cohort study) who attended examinations 4 (1987), 5 (1991), and 6 (1995), we evaluated the progression of MetS and its components. MetS was defined according to the Adult Treatment Panel III criteria. Using logistic regression, we evaluated the predictive ability of the presence of each component of the MetS on the subsequent development of MetS. Additionally, we examined the probability of developing cardiovascular disease or mortality (until 2007) by having specific combinations of 3 that diagnose MetS. The prevalence of MetS almost doubled in 10 years of follow-up. Hyperglycemia and central obesity experienced the highest increase. High blood pressure was most frequently present when a diagnosis of MetS occurred (77.3%), and the presence of central obesity conferred the highest risk of developing MetS (odds ratio, 4.75; 95% confidence interval, 3.78 to 5.98). Participants who entered the MetS having a combination of central obesity, high blood pressure, and hyperglycemia had a 2.36-fold (hazard ratio, 2.36; 95% confidence interval, 1.54 to 3.61) increase of incident cardiovascular events and a 3-fold (hazard ratio, 3.09, 95% confidence interval, 1.93 to 4.94) increased risk of mortality. CONCLUSIONS: Particular trajectories and combinations of factors on entering the MetS confer higher risks of incident cardiovascular disease and mortality in the general population and among those with MetS. Intense efforts are required to identify populations with these particular combinations and to provide them with adequate treatment at early stages of disease.

Molecular basis for dimethylsulfoxide (DMSO) action on lipid membranes.

Dimethylsulfoxide (DMSO) is an aprotic solvent that has the ability to induce cell fusion and cell differentiation and enhance the permeability of lipid membranes. It is also an effective cryoprotectant. Insights into how this molecule modulates membrane structure and function would be invaluable toward regulating the above processes and for developing chemical means for enhancing or hindering the absorption of biologically active molecules, in particular into or via the skin. We show here by means of molecular simulations that DMSO can induce water pores in dipalmitoyl-phosphatidylcholine bilayers and propose this to be a possible pathway for the enhancement of penetration of actives through lipid membranes. DMSO also causes the membrane to become floppier, which would enhance permeability, facilitate membrane fusion, and enable the cell membrane to accommodate osmotic and mechanical stresses during cryopreservation.

Structure of hard-sphere fluid and precursor structures to crystallization.

The structural origin of the commonly observed split second peak of the radial distribution function of a supercooled or glassy liquid is examined in this work using the hard-sphere fluid as an example. A novel approach to the analysis of the microscopic structure of a fluid is described, which permits the decomposition of both the radial distribution function and bond-angle distribution function of a system of particles into contributions from a small number of ring structures. The method uses a modified shortest-path definition of rings appropriate to the analysis of the medium-range structure of dense systems. It is shown that the split peak is an indicator of the emergence of precursor structures to crystal formation. The origin of the split peak provides a structural link between fluid and crystalline phases and our results suggest that it is neither a structural feature peculiar to glassy phases nor a smooth structural continuation of the stable-fluid phase. This structural feature of simple glassy systems is more appropriately described as a signifier of the frustration of emerging crystalline order in a fluid.

Roles of carboxyl-terminal and farnesylated residues in the functions of the large hepatitis delta antigen.

The large hepatitis delta antigen (HDAg-L) mediates hepatitis delta virus (HDV) assembly and inhibits HDV RNA replication. Farnesylation of the cysteine residue within the HDAg-L carboxyl terminus is required for both functions. Here, HDAg-L proteins from different HDV genotypes and genotype chimeric proteins were analyzed for their ability to incorporate into virus-like particles (VLPs). Observed differences in efficiency of VLP incorporation could be attributed to genotype-specific differences within the HDAg-L carboxyl terminus. Using a novel assay to quantify the extent of HDAg-L farnesylation, we found that genotype 3 HDAg-L was inefficiently farnesylated when expressed in the absence of the small hepatitis delta antigen (HDAg-S). However, as the intracellular ratio of HDAg-S to HDAg-L was increased, so too was the extent of HDAg-L farnesylation for all three genotypes. Single point mutations within the carboxyl terminus of HDAg-L were screened, and three mutants that severely inhibited assembly without affecting farnesylation were identified. The observed assembly defects persisted under conditions where the mutants were known to have access to the site of VLP assembly. Therefore, the corresponding residues within the wild-type protein are likely required for direct interaction with viral envelope proteins. Finally, it was observed that when HDAg-S was artificially myristoylated, it could efficiently inhibit HDV RNA replication. Hence, a general association with membranes enables HDAg to inhibit replication. In contrast, although myristoylated HDAg-S was incorporated into VLPs far more efficiently than HDAg-S or nonfarnesylated HDAg-L, it was incorporated far less efficiently than wild-type HDAg-L; thus, farnesylation was required for efficient assembly.

Crystal nucleation in the hard sphere system.

The structure and growth of crystal nuclei that spontaneously form during computer simulations of the simplest nontrivial model of a liquid, the hard sphere system, is described in this work. Compact crystal nuclei are observed to form at densities within the coexistence region of the phase diagram. The nuclei possess a range of morphologies with a predominance of multiply twinned particles possessing in some cases a significant decahedral character. However the multiply twinned particles do not form from an initial decahedral core but appear to nucleate as blocks of a face-centered cubic crystal partially bounded by stacking faults.

A hepatitis B surface antigen mutant that lacks the antigenic loop region can self-assemble and interact with the large hepatitis delta antigen.

A novel hepatitis B virus surface antigen mutant harboring a deletion of most of the major antigenic loop region was competent for self-assembly and secretion. Although the mutant protein was competent for interaction with and incorporation of free large hepatitis delta antigen, it was partially defective in hepatitis delta virus RNP incorporation.