The effects of alcohol abstinence on BDNF, ghrelin, and leptin secretions in alcohol-dependent patients with glucose intolerance.

BACKGROUND: Alcohol use affecting the risk of type 2 diabetes mellitus (T2DM) is poorly identified as well as the role of brain-derived neurotrophic factor (BDNF), ghrelin, and leptin in alcohol dependence with T2DM. We tested the hypothesis that alcohol abstinence affects diabetes-related factors and BDNF, ghrelin, and leptin secretions in alcohol-dependent patients with glucose intolerance. METHODS: A total of 64 male alcohol-dependent patients were classified into normal glucose tolerance (NGT), pre-diabetes mellitus (pre-DM), and diabetes mellitus (DM) groups according to a 75-g oral glucose tolerance test (OGTT). All participants got alcohol dependence rehabilitation treatment for 30 days, and then we compared changes in BDNF, ghrelin, and leptin between pre- and post-alcohol abstinence. RESULTS: After alcohol abstinence, both pre-DM and DM groups had significantly decreased levels of fasting glucose. All 3 groups exhibited elevated ghrelin levels and reduced leptin levels, but BDNF levels were significantly increased only in the pre-DM group. The pre-DM group had large increases in BDNF and ghrelin levels compared with those of the NGT group. Moreover, decreases in homeostasis model assessment of insulin resistance (HOMA-IR), fasting glucose, and leptin levels in the DM group were larger than those in the NGT group. CONCLUSIONS: Alcohol abstinence might influence diabetes-related factors of alcohol-dependent patients with glucose intolerance. Further, BDNF, ghrelin, and leptin differently affect this improvement, depending on the stage of DM. In the pre-DM group, elevated BDNF and ghrelin levels are likely to influence insulin sensitivity, insulin resistance, and fasting glucose levels. Further, reduced leptin levels after abstinence might be related to improved glucose kinetics in patients with diabetes.

Intracellular domains of amyloid precursor-like protein 2 interact with CP2 transcription factor in the nucleus and induce glycogen synthase kinase-3beta expression.

Amyloid precursor protein (APP) is a member of a gene family that includes two APP-like proteins, APLP1 and 2. Recently, it has been reported that APLP1 and 2 undergo presenilin-dependent gamma-secretase cleavage, as does APP, resulting in the release of an approximately 6 kDa intracellular C-terminal domain (ICD), which can translocate into the nucleus. In this study, we demonstrate that the APLP2-ICDs interact with CP2/LSF/LBP1 (CP2) transcription factor in the nucleus and induce the expression of glycogen synthase kinase 3beta (GSK-3beta), which has broad-ranged substrates such as tau- and beta-catenin. The significance of this finding is substantiated by the in vivo evidence of the increase in the immunoreactivities for the nuclear C-terminal fragments of APLP2, and for GSK-3beta in the AD patients' brain. Taken together, these results suggest that APLP2-ICDs contribute to the AD pathogenesis, by inducing GSK-3beta expression through the interaction with CP2 transcription factor in the nucleus.

Directed evolution of a novel N-carbamylase/D-hydantoinase fusion enzyme for functional expression with enhanced stability.

Bifunctional enzymes find a wide application as a monitoring facility and a potential biocatalyst in molecular biology and biotechnology. Recombination of natural enzymes to a bifunctional fusion offers valuable tools, but the functional and structural instability of artificial fusion enzymes remains to be solved. Based on structural traits of microbial D-hydantoinase, we attempted to construct a bifunctional N-carbamylase/D-hydantoinase fusion enzyme that would be useful for the synthesis of nonnatural D-amino acids in a concerted fashion. The bifunctional ability of D-hydantoinase, as a fusion partner, was noticeable, but the resulting fusion enzyme was subjected to serious proteolysis in vivo, as generally encountered in the expression of large the multidomain polypeptide in E. coli. In an effort to improve the structural instability imposed by artificial linear fusion, directed evolution of the fusion enzyme was performed using DNA shuffling with a consensus primer to maintain a crucial domain for the enzyme activity. The evolved fusion enzyme, F11, was selected after repeated rounds, and this enzyme was found to show sixfold increased performance in the production of D-amino acid compared with the parent fusion enzyme, which was mainly due to the enhanced structural stability of the evolved fusion enzyme. This result is an example showing that directed evolution of the linearly fused polypeptide may broaden the opportunity to generate a fusion enzyme with greater potential.

Generation of protein lineages with new sequence spaces by functional salvage screen.

A variety of different methods to generate diverse proteins, including random mutagenesis and recombination, are currently available and most of them accumulate the mutations on the target gene of a protein, whose sequence space remains unchanged. On the other hand, a pool of diverse genes, which is generated by random insertions, deletions and exchange of the homologous domains with different lengths in the target gene, would present the protein lineages resulting in new fitness landscapes. Here we report a method to generate a pool of protein variants with different sequence spaces by employing green fluorescent protein (GFP) as a model protein. This process, designated functional salvage screen (FSS), comprises the following procedures: a defective GFP template expressing no fluorescence is first constructed by genetically disrupting a predetermined region(s) of the protein and a library of GFP variants is generated from the defective template by incorporating the randomly fragmented genomic DNA from Escherichia coli into the defined region(s) of the target gene, followed by screening of the functionally salvaged, fluorescence-emitting GFPs. Two approaches, sequence-directed and PCR-coupled methods, were attempted to generate the library of GFP variants with new sequences derived from the genomic segments of E.coli. The functionally salvaged GFPs were selected and analyzed in terms of the sequence space and functional properties. The results demonstrate that the functional salvage process not only can be a simple and effective method to create protein lineages with new sequence spaces, but also can be useful in elucidating the involvement of a specific region(s) or domain(s) in the structure and function of protein.