Molecular mechanisms associated with leptin resistance: n-3 polyunsaturated fatty acids induce alterations in the tight junction of the brain

High-fat diets cause peripheral leptin resistance, and dietary lipid composition affects sensitivity to leptin. We examined the role of n-3 polyunsaturated fatty acid (PUFA) in peripheral leptin resistance. Dietary PUFAs (0.4% wt/wt) caused insensitivity to peripherally but not intracerebroventricularly administered leptin. n-3 PUFA increased body weight, associated with a significant reduction of leptin concentration in the cerebrospinal fluid. Dietary n-3 PUFA reduced transport of endogenous or exogenously administered leptin into the brain, associated with increased expression of hypothalamic occludin, but caused no change in expression of leptin receptors, proteins associated with leptin signaling or other tight junction proteins. Continuous intracerebroventricular infusion of an antisense morpholino oligonucleotide targeted to occludin mRNA reversed n-3 PUFA-induced insensitivity to peripherally administered leptin. We conclude that n-3 PUFA induces peripheral leptin resistance via an increase in the expression of hypothalamic occludin, reducing paracellular transport of leptin into the brain.     

Role of 14-3-3gamma in FE65-dependent gene transactivation mediated by the amyloid beta-protein precursor cytoplasmic fragment

The amyloid beta-protein precursor intracellular domain fragment (AICD) is generated from amyloid beta-protein precursor by consecutive cleavages. AICD is thought to activate FE65-dependent gene expression, but the molecular mechanism remains under consideration. We found that dimeric 14-3-3gamma bound both AICD and FE65 simultaneously, and this binding facilitated FE65-dependent gene transactivation by enhancing the association of AICD with FE65. 14-3-3gamma bound to the 667VTPEER672 motif of AICD and, most interestingly, the phosphorylation of AICD at Thr-668 in this motif inhibited the interaction with 14-3-3gamma and blocked gene transactivation. 14-3-3gamma required a sequence between the WW domain and the first phosphotyrosine interaction domain of FE65 for association with FE65. Deletion of this region blocked 14-3-3gamma binding to FE65 and suppressed AICD-mediated FE65-dependent gene transactivation, although the deletion mutant FE65 was still able to bind Tip60, a histone acetyltransferase that forms a complex with FE65 in the nucleus. Taken together, these data demonstrate that 14-3-3gamma facilitates FE65-dependent gene transactivation by forming a complex containing AICD and FE65, and phosphorylation of AICD down-regulates FE65-dependent gene transactivation through the dissociation of 14-3-3gamma and/or FE65 from AICD. Our findings suggest that multiple interactions of AICD with FE65 and 14-3-3gamma modulate FE65-dependent gene transactivation.     

Evidence for Cd101 but not Fcgr1 as candidate for type 1 diabetes locus, Idd10

Among polygenes conferring susceptibility to type 1 diabetes in the NOD mouse, Idd10 on distal chromosome 3 has been shown to be important for disease susceptibility. In this study, we investigated the candidacy of Fcgr1 and Cd101 for Idd10, by congenic mapping and candidate gene sequencing. Among seven NOD-related strains studied, the IIS mouse was found to possess a recombinant Idd10 interval with the same sequence at Fcgr1 as the NOD mouse, but a different sequence at Cd101 from that in the NOD mouse with 10 amino acid substitutions. The frequency of type 1 diabetes in NOD mice congenic for IIS Idd10 (NOD.IISIdd10) was significantly reduced as compared to that in the NOD mouse, despite the presence of the identical Fcgr1 sequence. These data indicate that IIS mice possess a resistant allele at Idd10, and suggest that Cd101, but not Fcgr1, is responsible for the Idd10 effect.     

Enzymatic and structural characterization of type II isopentenyl diphosphate isomerase from hyperthermophilic archaeon Thermococcus kodakaraensis

Enzymatic and thermodynamic characteristics of type II isopentenyl diphosphate (IPP):dimethylallyl diphosphate (DMAPP) isomerase (Tk-IDI) from Thermococcus kodakaraensis, which catalyzes the interconversion of IPP and DMAPP, were examined. FMN was tightly bound to Tk-IDI, and the enzyme required NADPH and Mg2+ for the isomerization in both directions. The melting temperature (Tm), the change of enthalpy (deltaH(m)), and the heat capacity change (deltaC(p)) of Tk-IDI were 88.0 degrees C, 444 kJ mol(-1), and 13.2 kJ mol(-1) K(-1), respectively, indicating that Tk-IDI is fairly thermostable. Kinetic parameters dramatically changed when the temperature crossed 80 degrees C even though its native overall structure was stably maintained up to 90 degrees C, suggesting that local conformational change would occur around 80 degrees C. This speculation was supported by the result of the circular dichroism analysis that showed the shift of the alpha-helical content occurred at 80 degrees C.     

Activation of big MAP kinase 1 (BMK1/ERK5) inhibits cardiac injury after myocardial ischemia and reperfusion

Big MAP kinase 1 (BMK1/ERK5) plays a critical role in pre-natal development of the cardiovascular system and post-natal eccentric hypertrophy of the heart. Of the two isoforms upstream of MAPK-kinase 5 (MEK5) known to exist, only the longer MEK5alpha isoform potently activates BMK1. We generated cardiac-specific constitutively active form of the MEK5alpha (CA-MEK5alpha transgenic (Tg) mice), and observed a 3 to 4-fold increase in endogenous BMK1 activation and hyperphosphorylation of connexin 43 in the ventricles of the Tg compared to wild-type mice. The CA-MEK5alpha-Tg-mice demonstrated a profoundly accelerated recovery of left ventricular developed pressure after ischemia/reperfusion. We propose a novel role for BMK1 in protecting the heart from ischemia/reperfusion-induced cardiac injury.     

Human projected area factors for detailed direct and diffuse solar radiation analysis

Projected area factors for individual segments of the standing and sedentary human body were modelled for both direct and diffuse solar radiation using detailed 3D geometry and radiation models. The local projected area factors with respect to direct short-wave radiation are a function of the solar azimuth angle () between 0°<<360° and the solar altitude () angles between –90°<<+90°. In case of diffuse solar radiation from the isotropic sky the local human projected area factors were modelled as a function of the ground albedo () ranging between 0<<1. The model was validated against available experimental data and showed good general agreement with projected area factors measured for both the human body as a whole and for local quantities. Scientists can use the equations to predict the inhomogeneous irradiation and absorption of direct and diffuse solar radiation and UV-radiation at surfaces of the human body. In conjunction with detailed multi-node models of human thermoregulation the equations can be used to predict the physiological implications of solar radiation and outdoor weather conditions on humans.     

A role of activated Sonic hedgehog signaling for the cellular proliferation of oral squamous cell carcinoma cell line

Sonic hedgehog (Shh) is a secreted morphogen crucial for appropriate cellular proliferation during mammalian development. The activated Shh signaling is known to predispose to human tumors such as medulloblastoma and basal cell carcinoma, while a role of Shh signaling in the other common tumors is still controversial. Here we showed the overexpression of Shh in five cell lines among 14 human oral squamous cell carcinoma (OSCC) cell lines. One of the Shh-expressing OSCC cell lines HSQ-89 showed the inhibition of G1/S transition and apoptotic cell death by treatment with Cyclopamine, a steroidal alkaloid that blocks the intracellular Shh signaling. Furthermore, we found that treatment with Y-27632, a specific inhibitor of Rho-associated kinase, mimicked the effect of Cyclopamine on the cell cycle progression of HSQ-89. Our study revealed the involvement of activated Shh signaling in the cellular proliferation of OSCC cells, indicating Shh signaling might be a good therapeutic target for OSCC.     

Alteration of the timing of implantation by in vivo gene transfer: delay of implantation by suppression of nuclear factor kappaB activity and partial rescue by leukemia inhibitory factor

Nuclear factor kappaB (NF-kappaB) is activated in the murine endometrium during implantation period [Am. J. Reprod. Immunol. 51 (2004) 16]. Transient transfection of IkappaBalpha mutant (IkappaBalphaM) cDNA into the mouse uterine cavity using hemagglutinating virus of Japan envelope vector suppressed uterine NF-kappaB activity less than half of that observed in control on days 3.5 and 4.5 p.c. IkappaBalphaM cDNA transfection led to significant delay of implantation. After IkappaBalphaM cDNA transfection, LIF mRNA expression in the uterus was significantly suppressed on days 3.5 and 4.5 p.c. Co-transfection of LIF cDNA with IkappaBalphaM cDNA in the uterus partially rescued the delay of implantation induced by suppression of NF-kappaB activity. Taken together, these findings indicate that NF-kappaB activation determines the timing of the implantation, at least in part, via control of LIF expression.