The effects of postprandial glucose and insulin levels on postprandial endothelial function in subjects with normal glucose tolerance

Background

Type 2 diabetes mellitus (T2DM) patients are at increased risk of developing cardiovascular events. Unfortunately traditional risk assessment scores, including the Framingham Risk Score (FRS), have only modest accuracy in cardiovascular risk prediction in these patients.

Methods

We sought to determine the prognostic values of different non-invasive markers of atherosclerosis, including brachial artery endothelial function, carotid artery atheroma burden, ankle-brachial index, arterial stiffness and computed tomography coronary artery calcium score (CACS) in 151 T2DM Chinese patients that were identified low-intermediate risk from the FRS recalibrated for Chinese (<20% risk in 10?years). Patients were prospectively followed-up and presence of atherosclerotic events documented for a mean duration of 61?±?16?months.

Results

A total of 17 atherosclerotic events in 16 patients (11%) occurred during the follow-up period. The mean FRS of the study population was 5.0?±?4.6% and area under curve (AUC) from receiver operating characteristic curve analysis for prediction of atherosclerotic events was 0.59?±?0.07 (P?=?0.21). Among different vascular assessments, CACS?>?40 had the best prognostic value (AUC 0.81?±?0.06, P?<?0.01) and offered significantly better accuracy in prediction compared with FRS (P?=?0.038 for AUC comparisons). Combination of FRS with CACS or other surrogate vascular markers did not further improve the prognostic values over CACS alone. Multivariate Cox regression analysis identified CACS?>?40 as an independent predictor of atherosclerotic events in T2DM patients (Hazards Ratio 27.11, 95% Confidence Interval 3.36-218.81, P?=?0.002).

Conclusions

In T2DM patients identified as low-intermediate risk by the FRS, a raised CACS?>?40 was an independent predictor for atherosclerotic events.     

Alteration of intracellular secretory acute phase response proteins expressed in human hepatocyte induced by exposure with interleukin-6

Interleukin-6 (IL-6) is a principal proinflammatory cytokine inducing the acute phase response in various tissues, including liver. Here, we adopt the FD-LC-MS/MS method, consisting of fluorogenic derivatization (FD), separation by liquid chromatography (LC), and identification of proteins by LC-tandem mass spectrometry (MS/MS), to reveal how exposure to IL-6 alters temporally the intracellular secretory acute phase response (sAPR) proteins expressed in human hepatocytes as compared to non-exposure. Nine altered sAPR proteins were identified in cultures in response to IL-6. Seven of them (serum amyloid A protein, haptoglobin, fibrinogen α chain, fibrinogen β chain, fibrinogen γ chain, α(1)-acid glycoprotein and α(1)-antitrypsin) were significantly increased and two (β(2)-glycoprotein 1 and transferrin) were significantly decreased in response to IL-6. In addition, the transmission speed of transferrin might be much faster than the other sAPR proteins. These results suggest a different molecular mechanism for protein synthesis and the secretory pathway among the sAPR proteins. In this study, we observed the simultaneously and temporally altered expression of sAPR proteins which had been induced by exposure to IL-6 in human hepatocytes, in contrast to previous reports, in all of which the proteins were tested from the time they were secreted into the medium from the cells.     

Fear is readily associated with an out-group face in a minimal group context

Research on prepared learning demonstrates that fear-conditioning biases may exist to natural hazards (e.g., snakes) compared to nonnatural hazards (e.g., electrical cords) and that fear is more readily learned toward exemplars of a racial out-group than toward exemplars of one's own race. Here we push the limits of the generalizability of the mechanisms underlying race biases in a fear-conditioning paradigm by using arbitrary group categories not distinguished by race. Groups were distinguishable solely by t-shirt color, with assignment based on performance in a perceptual task. In this “minimal group paradigm,” we found that out-group exemplars were more readily associated with an aversive stimulus than exemplars of one's in-group. Our findings suggest that prepared learning in an intergroup context is not limited to contexts involving racial categories involving histories rife with cultural stereotypes and that previous findings of learning biases along racial lines may be interpreted as a by-product of a broader psychological system for prepared fear learning toward categories of agents that may have posed persistent threats over human evolutionary history.     

Diabetes Medication Use and Blood Lactate Level among Participants with Type 2 Diabetes: The Atherosclerosis Risk in Communities Carotid MRI Study

Background

The objective of this study is to compare lactate levels between users and non-users of diabetes medications under the hypothesis that the level of lactate is a marker of oxidative capacity.

Methods

The cross-sectional data of 493 participants aged 61–84 with type 2 diabetes who participated in the Atherosclerosis Risk in Communities Carotid MRI study were analyzed using survey weighted linear regression.

Results

Median plasma lactate level was 8.58 (95% CI: 8.23, 8.87) mg/dl. Comparing users of diabetic medications with non-users, thiazolidinedione use was significantly associated with lower lactate level (7.57 (6.95–8.25) mg/dL vs. 8.78 (8.43–9.14) mg/dL), metformin use with a slightly higher lactate level (9.02 (8.51–9.58) mg/dL vs. 8.36 (7.96–8.77) mg/dL), and sulfonylurea and insulin use were not associated with lactate level. After adjustment for demographic and lifestyle factors, the plasma lactate level for thiazolidinedione users was 15.78% lower than that for non-users (p<0.001). Considering use of each medication separately and in combination did not change the results.

Conclusion

In conclusion, thiazolidinedione use was associated with lower plasma lactate level compared to non-use and metformin use was only marginally associated with a slightly higher lactate level. These results are consistent with the previously demonstrated effects of diabetes medications on oxidative metabolism. Further investigation of the role that diabetes medications play in improvement of oxidative metabolism is warranted.     

Fibril formation of hsp10 homologue proteins and determination of fibril core regions: differences in fibril core regions dependent on subtle differences in amino acid sequence

Heat shock protein 10 (hsp10) is a member of the molecular chaperones and works with hsp60 in mediating various protein folding reactions. GroES is a representative protein of hsp10 from Escherichia coli. Recently, we found that GroES formed a typical amyloid fibril from a guanidine hydrochloride (Gdn-HCl) unfolded state at neutral pH. Here, we report that other hsp10 homologues, such as human hsp10 (Hhsp10), rat mitochondrial hsp10 (Rhsp10), Gp31 from T4 phage, and hsp10 from the hyperthermophilic bacteria Thermotoga maritima, also form amyloid fibrils from an unfolded state. Interestingly, whereas GroES formed fibrils from either the Gdn-HCl unfolded state (at neutral pH) or the acidic unfolded state (at pH 2.0-3.0), Hhsp10, Rhsp10, and Gp31 formed fibrils from only the acidic unfolded state. Core peptide regions of these protein fibrils were determined by proteolysis treatment followed by a combination of Edman degradation and mass spectroscopy analyses of the protease-resistant peptides. The core peptides of GroES fibrils were identical for fibrils formed from the Gdn-HCl unfolded state and those formed from the acidic unfolded state. However, a peptide with a different sequence was isolated from fibrils of Hhsp10 and Rhsp10. With the use of synthesized peptides of the determined core regions, it was also confirmed that the identified regions were capable of fibril formation. These findings suggested that GroES homologues formed typical amyloid fibrils under acidic unfolding conditions but that the fibril core structures were different, perhaps owing to differences in local amino acid sequences.     

Sequential action of ATP-dependent subunit conformational change and interaction between helical protrusions in the closure of the built-in lid of group II chaperonins

ATP drives the conformational change of the group II chaperonin from the open lid substrate-binding conformation to the closed lid conformation to encapsulate an unfolded protein in the central cavity. The detailed mechanism of this conformational change remains unknown. To elucidate the intra-ring cooperative action of subunits for the conformational change, we constructed Thermococcus chaperonin complexes containing mutant subunits in an ordered manner and examined their folding and conformational change abilities. Chaperonin complexes containing wild-type subunits and mutant subunits with impaired ATP-dependent conformational change ability or ATP hydrolysis activity, one by one, exhibited high protein refolding ability. The effects of the mutant subunits correlate with the number and order in the ring. In contrast, the use of a mutant lacking helical protrusion severely affected the function. Interestingly, these mutant chaperonin complexes also exhibited ATP-dependent conformational changes as demonstrated by small angle x-ray scattering, protease digestion, and changes in fluorescence of the fluorophore attached to the tip of the helical protrusion. However, their conformational change is likely to be transient. They captured denatured proteins even in the presence of ATP, whereas addition of ATP impaired the ability of the wild-type chaperonin to protect citrate synthase from thermal aggregation. These results suggest that ATP binding/hydrolysis causes the independent conformational change of the subunit, and further conformational change for the complete closure of the lid is induced and stabilized by the interaction between helical protrusions.     

Effect of the interaction between lipoxygenase pathway and progesterone on the regulation of hydroxysteroid 11-Beta dehydrogenase 2 in cultured human term placental trophoblasts

Placental hydroxysteroid 11-beta dehydrogenase 2 (HSD11B2) plays an important role in pregnancy maintenance and fetal maturation. In the event of intrauterine infection, lipoxygenase (LOX) metabolites are produced in the placenta and contribute to preterm labor and adverse fetal outcomes. On the other hand, LOX metabolites are involved in production of progesterone, which is required for pregnancy maintenance. In this study, we evaluated the interaction between the LOX pathway, progesterone, and HSD11B2. Specifically, we hypothesized that LOX metabolites would alter HSD11B2 and this effect would be mediated by progesterone. We cultured human term placental trophoblasts in the presence and absence of the LOX inhibitors Nordihydroguaiaretic acid (NDGA), AA861, and Baicalein; the LOX metabolites Leukotriene B(4) and 12(S)-Hydroxyeicosatetraenoate (12-HETE); and progesterone and progesterone receptor antagonist RU486. By radiometric conversion assay, real-time quantitative PCR, Western blot analysis, and ELISA, we examined HSD11B2 enzyme activity, HSD11B2 mRNA and HSD11B2 protein expression, and progesterone output. LOX metabolites down-regulated HSD11B2 activity and HSD11B2 expression. LOX inhibitors up-regulated HSD11B2 activity and HSD11B2 and HSD11B2 expression, and these effects were attenuated by addition of LOX metabolites. Net progesterone output was increased by LOX metabolites and decreased by LOX inhibitors. Progesterone down-regulated HSD11B2 activity and HSD11B2 and HSD11B2 expression, and these effects were blocked by RU486. Furthermore, the suppressive effect of 12-HETE on HSD11B2 activity was also reversed by RU486. We conclude that HSD11B2 in human placental trophoblasts is decreased by progesterone and increased by inhibition of endogenous LOX metabolites, and that a component of the effect of LOX metabolites on HSD11B2 is mediated by their stimulation of endogenous progesterone output.     

Cellular redox state protects acetaldehyde-induced alteration in cardiomyocyte function by modifying Ca2+ release from sarcoplasmic reticulum

Recent studies indicate that low concentrations of acetaldehyde may function as the primary factor in alcoholic cardiomyopathy by disrupting Ca(2+) handling or disturbing cardiac excitation-contraction coupling. By producing reactive oxygen species, acetaldehyde shifts the intracellular redox potential from a reduced state to an oxidized state. We examined whether the redox state modulates acetaldehyde-induced Ca(2+) handling by measuring Ca(2+) transient using a confocal imaging system and single ryanodine receptor type 2 (RyR2) channel activity using the planar lipid bilayer method. Ca(2+) transient was recorded in isolated rat ventricular myocytes with incorporated fluo 3. Intracellular reduced glutathione level was estimated using the monochlorobimane fluorometric method. Acetaldehyde at 1 and 10 microM increased Ca(2+) transient amplitude and its relative area in intact myocytes, but acetaldehyde at 100 microM decreased Ca(2+) transient area significantly. Acetaldehyde showed a minor effect on Ca(2+) transient in myocytes in which intracellular reduced glutathione content had been decreased against challenge of diethylmaleate to a level comparable to that induced by exposure to approximately 50 microM acetaldehyde. Channel activity of the RyR2 with slightly reduced cytoplasmic redox potential from near resting state (-213 mV) or without redox fixation was augmented by all concentrations of acetaldehyde (1-100 microM) used here. However, acetaldehyde failed to activate the RyR2 channel, when the cytoplasmic redox potential was kept with a reduced (-230 mV) or markedly oxidized (-180 mV) state. This result was similar to effects of acetaldehyde on Ca(2+) transient in diethylmaleate-treated myocytes, probably being in oxidized redox potential. The present results suggest that acetaldehyde acts as an RyR2 activator to disturb cardiac muscle function, and redox potential protects the heart from acetaldehyde-induced alterations in myocytes.