Epac2a-null mice exhibit obesity-prone nature more susceptible to leptin resistance

BACKGROUND

The exchange protein directly activated by cAMP (Epac), which is primarily involved in cAMP signaling, has been known to be essential for controlling body energy metabolism. Epac has two isoforms: Epac1 and Epac2. The function of Epac1 on obesity was unveiled using Epac1 knockout (KO) mice. However, the role of Epac2 in obesity remains unclear.

METHODS

To evaluate the role of Epac2 in obesity, we used Epac2a KO mice, which is dominantly expressed in neurons and endocrine tissues. Physiological factors related to obesity were analyzed: body weight, fat mass, food intake, plasma leptin and adiponectin levels, energy expenditure, glucose tolerance, and insulin and leptin resistance. To determine the mechanism of Epac2a, mice received exogenous leptin and then hypothalamic leptin signaling was analyzed.

RESULTS

Epac2a KO mice appeared to have normal glucose tolerance and insulin sensitivity until 12 weeks of age, but an early onset increase of plasma leptin levels and decrease of plasma adiponectin levels compared with wild-type mice. Acute leptin injection revealed impaired hypothalamic leptin signaling in KO mice. Consistently, KO mice fed a high-fat diet (HFD) were significantly obese, presenting greater food intake and lower energy expenditure. HFD-fed KO mice were also characterized by greater impairment of hypothalamic leptin signaling and by weaker leptin-induced decrease in food consumption compared with HFD-fed wild-type mice. In wild-type mice, acute exogenous leptin injection or chronic HFD feeding tended to induce hypothalamic Epac2a expression.

CONCLUSIONS

Considering that HFD is an inducer of hypothalamic leptin resistance and that Epac2a functions in pancreatic beta cells during demands of greater work load, hypothalamic Epac2a may have a role in facilitating leptin signaling, at least in response to higher metabolic demands. Thus, our data indicate that Epac2a is critical for preventing obesity and thus Epac2a activators may be used to manage obesity and obesity-mediated metabolic disorders.

Acute necrotic stomatitis (noma) associated with methicillin-resistant Staphylococcus aureus infection in a newly acquired rhesus macaque (Macaca mulatta)

BACKGROUND

A newly acquired rhesus macaque was suffering from rapid destruction of the left cheek caused by necrotizing stomatitis.

METHODS

To restore reconstructive surgery and intensive care with antibiotics, wound protection, wound healing agents, and debridement were applied.

RESULTS

Staphylococcus aureus and Enterococcus faecalis were isolated from the culture of the lesion, and the antibiotic susceptibility test revealed methicillin-resistant Staphylococcus aureus infection. Vancomycin and ampicillin-sulbactam effectively treated the bacterial infections, and reconstructive surgery was performed once the infection was cleared. Topical application of recombinant human epidermal growth factor (rhEGF) was useful to treat exposed wound of the noma lesion.

CONCLUSIONS

Simian noma associated with methicillin-resistant Staphylococcus aureus (MRSA) had not previously been reported in non-human primates. Although noma associated with MRSA is hard to cure because of its rapid and destructive progress, the aggressive therapy used in this study led to the successful resolution of an acute necrotic stomatitis lesion in a rhesus macaque.

Effect of immature dendritic cell injection before heterotropic cardiac allograft

Although dendritic cells (DCs) are unrivaled for initiation of immune responses, the immunomodulatory capacity of chemically fixed DC has not been thoroughly evaluated. We monitored the tolerogenic capacity of chemically fixed DCs using allogeneic heart transplantations. Bone marrow progenitors were differentiated into immature DCs which were then chemically fixed and injected intravenously into recipient mice at 14 days before allogeneic heart transplantation. Chemically fixed DCs markedly prolonged graft survival in the major histocompatibility complex (MHC) I/II mismatch cardiac transplantation (B6 --> B10.A; median survival time [MST] 12.5 days vs >70 days). T cells that encountered chemically fixed DCs showed attenuated apoptotic cell death and inactivated phenotypes after allogeneic heterotropic heart transplantation. Furthermore, when DCs from interleukin (IL)-10-/- mice were treated, the in vitro T-cell response was greater than that from IL-12-/- mice. We have suggested that the chemically fixed DCs may mediate peripheral T-cell tolerance, with therapeutic potential for allogeneic transplantation.

Biochemical properties and substrate specificities of alkaline and histidine acid phytases

Phytases are a special class of phosphatase that catalyze the sequential hydrolysis of phytate to less-phosphorylated myo-inositol derivatives and inorganic phosphate. Phytases are added to animal feedstuff to reduce phosphate pollution in the environment, since monogastric animals such as pigs, poultry, and fish are unable to metabolize phytate. Based on biochemical properties and amino acid sequence alignment, phytases can be categorized into two major classes, the histidine acid phytases and the alkaline phytases. The histidine acid phosphatase class shows broad substrate specificity and hydrolyzes metal-free phytate at the acidic pH range and produces myo-inositol monophosphate as the final product. In contrast, the alkaline phytase class exhibits strict substrate specificity for the calcium-phytate complex and produces myo-inositol trisphosphate as the final product. This review describes recent findings that present novel viewpoints concerning the molecular basis of phytase classification.

Enzyme mechanism and catalytic property of beta propeller phytase

BACKGROUND

Phytases hydrolyze phytic acid (myo-inositol-hexakisphosphate) to less-phosphorylated myo-inositol derivatives and inorganic phosphate. Phytases are used in animal feed to reduce phosphate pollution in the environment. Recently, a thermostable, calcium-dependent Bacillus phytase was identified that represents the first example of the beta propeller fold exhibiting phosphatase activity. We sought to delineate the catalytic mechanism and property of this enzyme.

RESULTS

The crystal structure of the enzyme in complex with inorganic phosphate reveals that two phosphates and four calcium ions are tightly bound at the active site. Mutation of the residues involved in the calcium chelation results in severe defects in the enzyme's activity. One phosphate ion, chelating all of the four calcium ions, is close to a water molecule bridging two of the bound calcium ions. Fluoride ion, which is expected to replace this water molecule, is an uncompetitive inhibitor of the enzyme. The enzyme is able to hydrolyze any of the six phosphate groups of phytate.

CONCLUSIONS

The enzyme reaction is likely to proceed through a direct attack of the metal-bridging water molecule on the phosphorous atom of a substrate and the subsequent stabilization of the pentavalent transition state by the bound calcium ions. The enzyme has two phosphate binding sites, the "cleavage site", which is responsible for the hydrolysis of a substrate, and the "affinity site", which increases the binding affinity for substrates containing adjacent phosphate groups. The existence of the two nonequivalent phosphate binding sites explains the puzzling formation of the alternately dephosphorylated myo-inositol triphosphates from phytate and the hydrolysis of myo-inositol monophosphates.

Calcium-dependent catalytic activity of a novel phytase from Bacillus amyloliquefaciens DS11

The thermostable phytase from Bacillus amyloliquefaciens DS11 hydrolyzes phytate (myo-inositol hexakisphosphate, IP6) to less phosphorylated myo-inositol phosphates in the presence of Ca2+. In this report, we discuss the unique Ca2+-dependent catalytic properties of the phytase and its specific substrate requirement. Initial rate kinetic studies of the phytase indicate that the enzyme activity follows a rapid equilibrium ordered mechanism in which binding of Ca2+ to the active site is necessary for the essential activation of the enzyme. Ca2+ turned out to be also required for the substrate because the phytase is only able to hydrolyze the calcium-phytate complex. In fact, both an excess amount of free Ca2+ and an excess of free phytate, which is not complexed with each other, can act as competitive inhibitors. The Ca2+-dependent catalytic activity of the enzyme was further confirmed, and the critical amino acid residues for the binding of Ca2+ and substrate were identified by site-specific mutagenesis studies. Isothermal titration calorimetry (ITC) was used to understand if the decreased enzymatic activity was related to poor Ca2+ binding. The pH dependence of the Vmax and Vmax/Km consistently supported these observations by demonstrating that the enzyme activity is dependent on the ionization of amino acid residues that are important for the binding of Ca2+ and the substrate. The Ca2+-dependent activation of enzyme and substrate was found to be different from other histidine acid phytases that hydrolyze metal-free phytate.

Study of somatosensory evoked potentials (SSEPs) by stimulating vagina before and after hysterectomy

OBJECTIVE

To assess the changing status of women after hysterectomy using the electrodiagnostic method.

STUDY DESIGN

We compared pre- and postoperative somatosensory evoked potentials (SSEPs) through vaginal stimulation in twenty patients undergoing hysterectomy.

RESULTS

1) The latencies (Mean +/- SD) of the first positive peak (P1) and first negative peak (N1) in preoperative vaginal SSEP were 32.89 +/- 3.02 ms and 40.41 +/- 3.43 ms in the left side, 33.25 +/- 4.28 ms and 41.39 +/- 5.46 ms in the right side respectively. 2) The postoperative P1 and N1 latencies were 33.68 +/- 4.50 ms and 42.00 +/- 4.30 ms in the left side, 33.78 +/- 3.10 ms and 42.00 +/- 3.62 in the right side respectively.

CONCLUSION

There were no significant differences between the pre- and the postoperative vaginal SSEP by stimulating vagina in patients of hysterectomy.

Hemostatic ligature for operative laparoscopy

BACKGROUND

We introduce a safe and convenient method for ligature of vascular pedicles at laparoscopic surgery in which one laparoscopic and two auxillary ports are used.

TECHNIQUE

The first two-turn wrap around the loop is made extracorporeally with the hand and is locked by an intracorporeal tie with manipulation of the target tissue. Knot typing is finished with the second and third nontension tie of one-turn throws.

EXPERIENCE

We have used this method for laparoscopic surgery for more than 2.5 years and have not observed a failure or late hemorrhage.

CONCLUSION

Two-turn throw incomplete loop ligature is a useful and convenient technique for hemostasis in three-port pelviscopic operations.

Crystal structures of a novel, thermostable phytase in partially and fully calcium-loaded states

Phytases hydrolyze phytic acid to less phosphorylated myo-inositol derivatives and inorganic phosphate. A thermostable phytase is of great value in applications for improving phosphate and metal ion availability in animal feed, and thereby reducing phosphate pollution to the environment. Here, we report a new folding architecture of a six-bladed propeller for phosphatase activity revealed by the 2.1 A crystal structures of a novel, thermostable phytase determined in both the partially and fully Ca2+-loaded states. Binding of two calcium ions to high-affinity calcium binding sites results in a dramatic increase in thermostability (by as much as approximately 30 degrees C in melting temperature) by joining loop segments remote in the amino acid sequence. Binding of three additional calcium ions to low-affinity calcium binding sites at the top of the molecule turns on the catalytic activity of the enzyme by converting the highly negatively charged cleft into a favorable environment for the binding of phytate.

Increase of NAD glycohydrolase activity in uterine cervix cancers is caused by infiltration of lymphocytes

CD38 is a type II transmembrane glycoprotein which is expressed by hematopoietic and nonhematopoietic cells in human. It has two functions of ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities and the sum of these two enzyme activities is identical with NAD glycohydrolase (NADase) activity. The levels of NADase activity in human cervical carcinoma and normal cancer tissue were measured. With a total of 12 patients with cervical cancer and 11 women with normal cervix, cancer tissues were found to have significantly higher NADase and ADP-ribosyl cyclase activities than the control group. Moreover, immunoblot analysis showed an increase of immunoreactivity against CD38 in cervical cancer tissues compared with normal tissues. Immunohistochemical data indicated that the increase of CD38 expression was due to increased infiltration of lymphocytes.

Cloning and localization of two multigene receptor families in goldfish olfactory epithelium

Goldfish reproduction is coordinated by pheromones that are released by ovulating females and detected by males. Two highly potent pheromones, a dihydroxyprogesterone and a prostaglandin, previously have been identified, and their effects on goldfish behavior have been studied in depth. We have cloned goldfish olfactory epithelium cDNAs belonging to two multigene G-protein coupled receptor families as a step toward elucidating the molecular basis of pheromone recognition. One gene family (GFA) consists of homologs of putative odorant receptors (approximately 320 residues) found in the olfactory epithelium of other fish and mammals. The other family (GFB) consists of homologs of putative pheromone receptors found in the vomeronasal organ (VNO) of mammals and also in the nose of pufferfish. GFB receptors (approximately 840 residues) are akin to the V2R family of VNO receptors, which possess a large extracellular N-terminal domain and are homologs of calcium-sensing and metabotropic glutamate receptors. In situ hybridization showed that the two families of goldfish receptors are differentially expressed in the olfactory epithelium. GFB mRNA is abundant in rather compact cells whose nuclei are near the apical surface. In contrast, GFA mRNA is found in elongated cells whose nuclei are positioned deeper in the epithelium. Our findings support the hypothesis that the separate olfactory organ and VNO of terrestrial vertebrates arose in evolution by the segregation of distinct classes of neurons that were differentially positioned in the olfactory epithelium of a precursor aquatic vertebrate.