Characterization of the use of liraglutide for glycemic control in healthy and Type 1 diabetes mellitus suffering dogs

Glucagon-like peptide 1 (GLP-1) is a glucose-lowering, intestinal-derived factor with multiple physiological effects, making it attractive for diabetes therapy. However, the therapeutic potential of endogenous GLP-1 is limited, because of rapid inactivation by dipeptidyl peptidase-4. Recently, enhanced incretin preparations, such as liraglutide, have emerged, which are more resistant to degradation and longer lasting. Liraglutide is a long-acting acylated human GLP-1 receptor agonist, with a 97% amino acid sequence identity to endogenous human GLP-1, and 100% amino acid sequence homology with canine GLP-1. Since liraglutide has yet to be examined for use in dogs, and the incretin effect has been reported to exist in dogs, we sought to initially characterize liraglutide's ability for glycemic control in healthy dogs, under an oral glucose tolerance test (OGTT) environment initially. This was followed up a more realistic scenario involving food with insulin injection +/- liraglutide injection resulting in a glucose curve based study involving dogs suffering from Type 1 diabetes mellitus (T1DM). Overall, liraglutide had a stabilizing effect on glucose levels, maintaining circulating levels between 77.0 and 137.0mg/ml throughout the OGTT test period, resulting in a significant reduction of 13.8% in glucose AUC0-120 min (total area under the curve for 0-120 min) as compared to baseline control in healthy dogs (n=5). Interestingly, the liraglutide associated reduction in circulating glucose was not accompanied by any significant increase in insulin. Moreover, T1DM dogs (n=4) responded favorably to liraglutide treatment, which lead to a significant reduction of 46.0% in glucose AUC0-12h (total area under the curve for 0-12h), and a significant reduction of 66.5% in serum glucose as compared to baseline controls (insulin treatment only). Therefore, liraglutide's prandial glucagon suppressive ability appears to play a key role in its glucose-lowering capability, and offers great potential for use with dogs suffering from T1DM.

Travelling and splitting of a wave of hedgehog expression involved in spider-head segmentation

During development segmentation is a process that generates a spatial periodic pattern. Peak splitting of waves of gene expression is a mathematically predicted, simple strategy accounting for this type of process, but it has not been well characterized biologically. Here we show temporally repeated splitting of gene expression into stripes that is associated with head axis growth in the spider Achaearanea embryo. Preceding segmentation, a wave of hedgehog homologue gene expression is observed to travel posteriorly during development stage 6. This stripe, co-expressing an orthodenticle homologue, undergoes two cycles of splitting and shifting accompanied by convergent extension, serving as a generative zone for the head segments. The two orthodenticle and odd-paired homologues are identified as targets of Hedgehog signalling, and evidence suggests that their activities mediate feedback to maintain the head generative zone and to promote stripe splitting in this zone. We propose that the 'stripe-splitting' strategy employs genetic components shared with Drosophila blastoderm subdivision, which are required for participation in an autoregulatory signalling network.

Evolution: structural and functional diversity of cadherin at the adherens junction

Adhesion between cells is essential to the evolution of multicellularity. Indeed, morphogenesis in animals requires firm but flexible intercellular adhesions that are mediated by subcellular structures like the adherens junction (AJ). A key component of AJs is classical cadherins, a group of transmembrane proteins that maintain dynamic cell-cell associations in many animal species. An evolutionary reconstruction of cadherin structure and function provides a comprehensive framework with which to appreciate the diversity of morphogenetic mechanisms in animals.

Chromatin in the nuclear landscape

Chromatin affects many, if not all aspects, of nuclear organization and function. For this reason, we have focused our attention on elucidating some of the basic mechanisms regulating the formation and maintenance of chromatin, specifically concerning Polycomb repressive complex 2 (PRC2) and PR-Set7. PRC2 is responsible for catalyzing trimethylation of lysine 27 of histone H3 and thus has a critical role in the formation of facultative heterochromatin. PR-Set7 is responsible for catalyzing monomethylation of lysine 20 of histone H4 and is required for proper cell cycle progression and DNA damage response. We have also expanded our work to establish novel techniques and approaches to determine how chromatin is spatially regulated within the nuclear landscape.

Early embryonic development in the spider Achaearanea tepidariorum: Microinjection verifies that cellularization is complete before the blastoderm stage

The spider Achaearanea tepidariorum is emerging as a non-insect model for studying developmental biology. However, the availability of microinjection into early embryos of this spider has not been reported. We defined the early embryonic stages in A. tepidariorum and applied microinjection to its embryos. During the preblastoderm 16- and 32-nucleus stages, the energids were moving toward the egg periphery. When fluorochrome-conjugated dextran was microinjected into the peripheral region of 16-nucleus stage embryos, it was often incorporated into a single energid and inherited in the progeny without leaking out to surrounding energids. This suggested that 16-nucleus stage embryos consisted of compartments, each containing a single energid. These compartments were considered to be separate cells. Fluorochrome-conjugated dextran could be introduced into single cells of 16- to 128-nucleus stage embryos, allowing us to track cell fate and movement. Injection with mRNA encoding a nuclear localization signal/green fluorescent protein fusion construct demonstrated exogenous expression of the protein in live spider embryos. We propose that use of microinjection will facilitate studies of spider development. Furthermore, these data imply that in contrast to the Drosophila syncytial blastoderm embryo, the cell-based structure of the Achaearanea blastoderm embryo restricts diffusion of cytoplasmic gene products.

Disruption of endothelial tight junctions in a patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS)

An electron microscopic study revealed disruption of capillary endothelial tight junctions (TJs) in both biopsied muscle, taken at 5 years and 1 month of age, and the autopsied brain, taken at 13 years and 6 months of age, in a patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) and mitochondrial DNA (mtDNA) point mutation A3243G. This endothelial barrier disruption might result in vasogenic edema and systemic lactic acidosis, possibly the critical pathology of MELAS.

Cell migration that orients the dorsoventral axis is coordinated with anteroposterior patterning mediated by Hedgehog signaling in the early spider embryo

The early embryo of the spider Achaearanea tepidariorum is emerging as a model for the simultaneous study of cell migration and pattern formation. A cell cluster internalized at the center of the radially symmetric germ disc expresses the evolutionarily conserved dorsal signal Decapentaplegic. This cell cluster migrates away from the germ disc center along the basal side of the epithelium to the germ disc rim. This cell migration is thought to be the symmetry-breaking event that establishes the orientation of the dorsoventral axis. In this study, knockdown of a patched homolog, At-ptc, that encodes a putative negative regulator of Hedgehog (Hh) signaling, prevented initiation of the symmetry-breaking cell migration. Knockdown of a smoothened homolog, At-smo, showed that Hh signaling inactivation also arrested the cells at the germ disc center, whereas moderate inactivation resulted in sporadic failure of cell migration termination at the germ disc rim. hh transcript expression patterns indicated that the rim and outside of the germ disc were the source of the Hh ligand. Analyses of patterning events suggested that in the germ disc, short-range Hh signal promotes anterior specification and long-range Hh signal represses caudal specification. Moreover, negative regulation of Hh signaling by At-ptc appears to be required for progressive derepression of caudal specification from the germ disc center. Cell migration defects caused by At-ptc and At-smo knockdown correlated with patterning defects in the germ disc epithelium. We propose that the cell migration crucial for dorsoventral axis orientation in Achaearanea is coordinated with anteroposterior patterning mediated by Hh signaling.

The proximal half of the Drosophila E-cadherin extracellular region is dispensable for many cadherin-dependent events but required for ventral furrow formation

The formation of the ventral furrow during Drosophila gastrulation is driven by coordinated apical constriction. Cell-cell adhesion is thought to regulate apical constriction, but the mechanisms are poorly understood. DE-cadherin, an epithelial classic cadherin, has in its membrane-proximal extracellular region a suite of domains absent from vertebrate/urochordate classic cadherins. We constructed DEΔP, a DE-cadherin derivative that lacks the membrane-proximal half of the extracellular region but retains the entire cytoplasmic domain and still exhibits strong cell-cell binding ability. The extracellular region of DEΔP consists of only cadherin repeats, mimicking vertebrate/urochordate classic cadherins. In animals lacking DE-cadherin, DEΔP organized adherens junction assembly and functioned fully in many cadherin-dependent processes, including oogenesis. Embryos in which DE-cadherin was entirely replaced by DEΔP established the blastoderm epithelium but failed to form a ventral furrow. Apical constrictions were initiated relatively normally but subsequently decelerated. These were then followed by catastrophic disruption of the junctional network. Our results suggest that although the membrane-proximal half of the DE-cadherin extracellular region is dispensable for many developmental events, it is essential for efficient and robust apical constriction during ventral furrow formation.

Assessing the immune state of dogs suffering from pituitary gland dependent hyperadrenocorticism by determining changes in peripheral lymphocyte subsets

In order to evaluate the immune state of dogs suffering from pituitary-dependent hyperadrenocorticism (PDH), peripheral lymphocyte subsets were examined. Twenty seven PDH dogs and eight healthy control dogs were used in the current study. Eight healthy dogs served as the control group. Twenty seven PDH dogs were categorized into 4 groups based on their post serum cortisol concentrations by ACTH stimulation test: 2-5, excellent control (n = 8); 5-20, fair control (n = 7); >20, poor control (n = 4); and untreated (n = 8). Cell counts were executed with white blood cells (WBC), lymphocytes, CD3(+) (T lymphocytes), CD4(+) (Helper T lymphocytes), CD8(+) (Cytotoxic T lymphocytes), CD21(+) (B lymphocytes) cells in addition to calculating CD4(+)/CD8(+) ratio. Results indicated a significant difference in lymphocyte numbers and lymphocyte subset populations (CD3(+), CD4(+), CD8(+), and CD21(+) cells) between PDH and control dogs. Moreover, comparison of the PDH groups (excellent control; fair control; poor control; untreated) demonstrated that all groups had a significant decrease in lymphocytes numbers (CD3(+), CD4(+) and CD21(+) cell counts) as compared to control group. Meanwhile, no significant differences were observed in WBC counts and CD4(+)/CD8(+) ratio between groups. Furthermore, lymphocyte subset distribution in excellent control PDH dogs without concurrent disease (n = 4) better resembled that of control dogs as compared to PDH dogs with concurrent disease (n = 4). PDH dogs may be suffering from an immuno-depressed state as evidenced by significant differences in lymphocyte subset populations. Furthermore, treatment of both PDH and concurrent disease might improve lymphocyte subset distribution.

Participation of the secreted dipeptidyl and tripeptidyl aminopeptidases in asaccharolytic growth of Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis secretes gingipains, endopeptidases essential for the asaccharolytic growth of this bacterium. P. gingivalis also secretes dipeptidyl aminopeptidases (DPPIV and DPP-7) and a tripeptidyl aminopeptidase (PTP-A), although their role in asaccharolytic growth is unclear. The present study was carried out to elucidate the role of these dipeptidyl/tripeptidyl aminopeptidases on the asaccharolytic growth of P. gingivalis.

MATERIAL AND METHODS

Knockout mutants for the DPPIV (dpp), dpp7 and/or PTP-A genes were constructed. Brain-heart infusion medium supplemented with sterile hemin and menadione (BHIHM) was used as a complex medium, and the minimal medium used was GA, in which the sole energy source was a mixture of immunoglobulin G and bovine serum albumin. Growth of P. gingivalis was monitored by measuring the optical density of the culture.

RESULTS

All knockout mutants for DPPIV, dpp7 and PTP-A grew as well as strain W83 in BHIHM. In GA, growth of single-knockout and double-knockout mutants was similar to that of W83, whereas growth of a triple-knockout mutant (83-47A) was reduced. We purified recombinant DPPIV and recombinant PTP-A from recombinant Escherichia coli overproducers, and purified DPP-7 from the triple-knockout mutant 83-4A. GA supplemented with the three purified dipeptidyl/tripeptidyl aminopeptidases supported the growth of 83-47A.

CONCLUSION

DPPIV, DPP-7 and PTP-A contribute to the normal growth of P. gingivalis by cleaving substrate peptides into short-chain polypeptides that are efficient energy sources for P. gingivalis.

Overexpression/enhanced kinase activity of BCR/ABL and altered expression of Notch1 induced acute leukemia in p210BCR/ABL transgenic mice

Chronic myelogenous leukemia (CML) is a hematopoietic disorder, which begins as indolent chronic phase but inevitably progresses to fatal blast crisis. p210BCR/ABL, a constitutively active tyrosine kinase, is responsible for disease initiation but molecular mechanism(s) underlying disease evolution remains largely unknown. To explore this process, we employed retroviral insertional mutagenesis to CML-exhibiting p210BCR/ABL transgenic mice (Tg). Virus infection induced acute lymphoblastic leukemia (ALL) in p210BCR/ABL Tg with a higher frequency and in a shorter latency than wild-type littermates, and inverse PCR detected two retrovirus common integration sites (CISs) in p210BCR/ABL Tg tumors. Interestingly, one CIS was the transgene itself, where retrovirus integrations induced upregulation of p210BCR/ABL and production of truncated BCR/ABL with an enhanced kinase activity. Another CIS was Notch1 gene, where retrovirus integrations resulted in overexpression of Notch1 and generation of Notch1 lacking the C-terminal region (Notch1DeltaC) associated with stable expression of its activated product, C-terminal-truncated Notch intracellular domain (NICD Delta C). In addition, generation of Tg for both p210BCR/ABL and Notch1DeltaC developed ALL in a shortened period with Stat5 activation, demonstrating the cooperative oncogenicity of Notch1DeltaC/NICD Delta C with p210BCR/ABL involving Stat5-mediated pathway. These results demonstrated that overexpression/enhanced kinase activity of BCR/ABL and altered expression of Notch1 induces acute leukemia in a transgenic model for CML.