Adiponectin suppresses colorectal carcinogenesis under the high-fat diet condition

BACKGROUND AND AIMS

The effect of adiponectin on colorectal carcinogenesis has been proposed but not fully investigated. We investigated the effect of adiponectin deficiency on the development of colorectal cancer.

METHODS

We generated three types of gene-deficient mice (adiponectin-deficient, adiponectin receptor 1-deficient, and adiponectin receptor 2-deficient) and investigated chemical-induced colon polyp formation and cell proliferation in colon epithelium. Western blot analysis was performed to elucidate the mechanism which affected colorectal carcinogenesis by adiponectin deficiency.

RESULTS

The numbers of colon polyps were significantly increased in adiponectin-deficient mice compared with wild-type mice fed a high-fat diet. However, no difference was observed between wild-type and adiponectin-deficient mice fed a basal diet. A significant increase in cell proliferative activity was also observed in the colonic epithelium of the adiponectin-deficient mice when compared with wild-type mice fed a high-fat diet; however, no difference was observed between wild-type and adiponectin-deficient mice fed a basal diet. Similarly, an increase in epithelial cell proliferation was observed in adiponectin receptor 1-deficient mice, but not in adiponectin receptor 2-deficient mice. Western blot analysis revealed activation of mammalian target of rapamycin, p70 S6 kinase, S6 protein and inactivation of AMP-activated protein kinase in the colon epithelium of adiponectin-deficient mice fed with high-fat diet.

CONCLUSIONS

Adiponectin suppresses colonic epithelial proliferation via inhibition of the mammalian target of the rapamycin pathway under a high-fat diet, but not under a basal diet. These studies indicate a novel mechanism of suppression of colorectal carcinogenesis induced by a Western-style high-fat diet.

Immunosuppressive effect of ER-38925, a retinoic acid receptor subtype α-selective agonist, in mouse models of human graft-vs-host disease

Graft-vs-host disease (GVHD) is a devastating disorder that determines the prognosis of patients who receive a bone marrow transplant. GVHD is caused by donor cells responding to host disparate MHC alleles. In this report, we demonstrate that ER-38925, a newly discovered retinoid agonist with selectivity to retinoic acid receptor subtype α (RAR-α), is a potent immunosuppressive agent in mouse models of human GVHD. In a mouse model of lethal acute GVHD (aGVHD), ER-38925 prolonged the lifespan of the recipient mice in a dose-dependent manner. Its effect at 1 mg/kg was almost comparable to that of cyclosporin A at 30 mg/kg. ER-38925 profoundly prevented the development of antiallogeneic cytotoxic T lymphocyte (CTL) response in the mouse model of aGVHD at 0.1 and 0.3 mg/kg. It strongly inhibited in vitro proliferation of alloantigenstimulated donor T lymphocytes, and RAR-α seemed to play an exclusive role in this effect since inhibition by all-trans retinoic acid, which can activate all subtypes of RAR, was completely reversed by an RAR-α selective antagonist. Moreover, it significantly inhibited the elevation of serum IL-12 and IFN-γ and LPS-induced serum TNF-α elevation, all of which are known to be crucial disease-exacerbating factors in this model and human GVHD, in the mouse model of aGVHD. These results suggest that ER-38925 prevents the development of aGVHD through substantial inhibition of anti-allogeneic responses of donor T lymphocytes. In addition, in vivo administration of ER-38925 also blocked serum anti-DNA autoantibody production in a mouse model of human chronic GVHD. This is the first report to clearly show the remarkable immunosuppressive effects of an RAR-α selective agonist in mouse models of human GVHD. These findings may allow an RAR-αselective agonist like ER-38925 to serve as a novel therapy to prevent both acute and chronic types of human GVHD.

A novel role for Fyn: Change in sphere formation ability in murine embryonic stem cells

Fyn, a member of the Src-family protein tyrosine kinase (PTK), is an essential factor in myelination in the CNS and is involved in murine embryonic stem (ES) cell growth and differentiation. Although dysfunctions of Fyn have been comparatively studied, the gain of function by ectopic expression, especially using ES cells, has seldom been investigated. In this article, we give the first report of the involvement of Fyn alteration in the sphere formation ability of murine ES cells. First, transient transfection of Fyn hardly affected multiplication and specialization. Then, we investigated Fyn overexpression using ES cells, which stably express Fyn. As a result, altered sphere formation capability was observed in all clones stably expressing Fyn. These results may provide important information for reproduction medical treatment using ES cells.

L3/Lhx8 is a pivotal factor for cholinergic differentiation of murine embryonic stem cells

L3/Lhx8 is a member of the LIM-homeobox gene family. Previously, we demonstrated that L3/Lhx8-null mice specifically lacked cholinergic neurons in the basal forebrain. In the present study, we conditionally suppressed L3/Lhx8 function during retinoic acid-induced neural differentiation of a murine embryonic stem (ES) cell line using an L3/Lhx8-targeted small interfering RNA (siRNA) produced by an H1.2 promoter-driven vector. Our culture conditions induced efficient differentiation of the ES cells into neurons and astrocytes, but far less efficient differentiation into oligodendrocytes. Suppression of L3/Lhx8 expression by siRNA led to a dramatic decrease in the number of cells positive for the cholinergic marker ChAT, and overexpression of L3/Lhx8 recovered this effect. However, no significant changes were observed in the number of Tuj1+ neurons and GABA+ cells. These results strongly suggest that L3/Lhx8 is a key factor in the cholinergic differentiation of murine ES cells and is involved in basal forebrain development.

Pharmacological evidence of cholinergic involvement in adult hippocampal neurogenesis in rats

In adult hippocampus, neural progenitor cells give rise to neurons throughout life, and the neurogenesis is modulated by various intrinsic and extrinsic factors. Recent reports showed that lesion of septal cholinergic nuclei projecting to hippocampus suppressed the survival of newborn cells in the dentate gyrus (DG) of hippocampus. Here, we studied whether pharmacological treatment to activate or inhibit the cholinergic system could modulate adult hippocampal neurogenesis. 5'-Bromo-2'-deoxyuridine (BrdU) was injected to label dividing cells before the drug treatment. Immunohistochemical analysis was performed in normal rats chronically treated with an acetylcholinesterase inhibitor donepezil or a muscarinic acetylcholine receptor blocker scopolamine for four weeks. Donepezil increased, but scopolamine decreased, the number of BrdU-positive cells in the DG as compared with the control. Neither drug altered the percentage of BrdU-positive cells that were also positive for a neuronal marker neuronal nuclei, nor net population of proliferative cells labeled with proliferating cell nuclear antigen. We also found that donepezil enhanced, and scopolamine suppressed, the expression level of phosphorylated cAMP response element binding protein (CREB), which is related to cell survival, in the DG. These results indicate that donepezil enhances and scopolamine suppresses the survival of newborn cells in the DG via CREB signaling without affecting neural progenitor cell proliferation and the neuronal differentiation. This is the first evidence that pharmacological manipulation of the cholinergic system can modulate adult hippocampal neurogenesis.

Absence of an association between the polymorphisms in the genes encoding adiponectin receptors and type 2 diabetes

AIMS/HYPOTHESIS

Secreted by adipocytes, adiponectin is a hormone that acts as an antidiabetic and anti-atherogenic adipokine. We recently cloned the genes encoding two adiponectin receptors (ADIPOR1 and ADIPOR2). The aim of this study was to examine whether ADIPOR1 and/or ADIPOR2 play a major role in genetic susceptibility to insulin resistance or type 2 diabetes in the Japanese population.

METHODS

By direct sequencing and a search of public databases, we identified single nucleotide polymorphisms (SNPs) in ADIPOR1 and ADIPOR2, and investigated whether these SNPs are associated with insulin resistance and type 2 diabetes in the Japanese population.

RESULTS

The linkage disequilibrium (LD) in the chromosomal region of ADIPOR1 was almost completely preserved, whereas the LD in ADIPOR2 was less well preserved. None of the SNPs in ADIPOR1 or ADIPOR2 were significantly associated with insulin resistance or type 2 diabetes. No differences in ADIPOR1 or ADIPOR2 haplotype frequencies were observed between type 2 diabetic and non-diabetic subjects.

CONCLUSIONS/INTERPRETATION

Genetic variations in ADIPOR1 or ADIPOR2 are unlikely to lead to a common genetic predisposition to insulin resistance or type 2 diabetes in the Japanese population.

New and reliable MRI diagnosis for progressive supranuclear palsy

OBJECTIVE

To evaluate the area of the midbrain and pons on mid-sagittal MRI in patients with progressive supranuclear palsy (PSP), Parkinson disease (PD), and multiple-system atrophy of the Parkinson type (MSA-P), compare these appearances and values with those of normal control subjects, and establish diagnostic MRI criteria for the diagnosis of PSP.

METHODS

The authors prospectively studied MRI of 21 patients with PSP, 23 patients with PD, 25 patients with MSA-P, and 31 age-matched normal control subjects. The areas of the midbrain tegmentum and the pons were measured on mid-sagittal MRI using the display tools of a workstation. The ratio of the area of the midbrain to the area of the pons was also evaluated in all subjects.

RESULTS

The average midbrain area of the patients with PSP (56.0 mm2) was significantly smaller than that of the patients with PD (103.0 mm2) and MSA-P (97.2 mm2) and that of the age-matched control group (117.7 mm2). The values of the area of the midbrain showed no overlap between patients with PSP and patients with PD or normal control subjects. However, patients with MSA-P showed some overlap of the values of individual areas with values from patients with PSP. The ratio of the area of the midbrain to the area of pons in the patients with PSP (0.124) was significantly smaller than that in those with PD (0.208) and MSA-P (0.266) and in normal control subjects (0.237). Use of the ratio allowed differentiation between the PSP group and the MSA-P group.

CONCLUSION

The area of the midbrain on mid-sagittal MRI can differentiate PSP from PD, MSA-P, and normal aging.

Lack of G protein-coupled sigma receptors in rat brain membranes: receptor-mediated high-affinity GTPase activity and [35S]GTPgammaS binding studies

Although sigma (sigma) receptors have been identified as an independent receptor family distinct from opioid and phencyclidine receptors, the physiological roles of these receptors are largely unknown. It is controversial whether there exist metabotropic sigma receptors that are coupled with heterotrimeric G proteins. In the present study, the stimulatory effects of sigma ligands on high-affinity GTPase activity and [35S]GTPgammaS binding were determined in the membranes prepared from rat cerebral cortex, hippocampus, and striatum. In either G protein activation assay, none of the sigma ligands examined had stimulatory effect in any brain regions, except for unambiguous concentration-dependent increase in [35S]GTPgammaS binding by (+)-3-(3-hydroxyphenyl)-N-(1-propyl) piperidine [(+)-3-PPP] in striatal membranes. However, the competition study clearly showed this response was mediated through dopamine D2-like receptors, but not sigma receptors. It is concluded that sigma receptors are not coupled to heterotrimeric G proteins, at least those of Gi/o type.

Direct phosphorylation of histamine H1 receptor by various protein kinases in vitro

Phosphorylation of G protein-coupled receptors (GPCRs) by various kinases is suggested to be an important step in initiating receptor desensitization. Some reports have indirectly demonstrated the involvement of protein kinase C (PKC)-mediated receptor phosphorylation in the desensitization of the histamine H1 receptor (H1R). In this study, human c-myc-epitope-tagged H1R (hm mcH1R) was expressed in Sf9 cells, and an in vitro approach was taken to obtain direct evidence that H1R could be phosphorylated by various kinases. When hm mcH1R, which had been immunoprecipitated with anti-c-myc antibody from Sf9 cell membranes, was incubated with PKC, cAMP-dependent protein kinase (PKA), calcium/calmodulin-dependent protein kinase II (CaMKII) or cGMP-dependent protein kinase (PKG), the immunoprecipitated receptor was phosphorylated by these kinases. Membrane-bound hm mcH1R, whose conformation is closer to its physiological state than that of the immunoprecipitated receptor, was also phosphorylated by PKC, PKA, CaMKII and PKG. Phosphorylation of immunoprecipitated and membrane-bound hm mcH1R was inhibited by kinase inhibitors. These data are the first demonstration of the phosphorylation of H1R by four protein kinases, i.e., PKC, PKA, CaMKII and PKG, and provide fundamental information to help us further understand the relationship between H1R phosphorylation and desensitization of this receptor.

Quantification of telomerase activity of regions unstained with iodine solution that surround oral squamous cell carcinoma

The aim of this study was to analyze the iodine-unstained region expanding around oral squamous cell carcinoma (SCC) by quantification of telomerase activity. The epithelial dysplasia often observed around SCC is considered to cause local recurrence or a second primary cancer. However these areas are hard to distinguish from normal mucosa. To clear the border of the expanding epithelial dysplasia around SCC, we stained with 3% iodine solution, and then decided the surgical margin. We measured quantification of telomerase activity in tumor, in epithelial dysplasia, and also in normal epithelium. Thirty-three primary cases of oral SCC which have iodine-unstained region around lesions were investigated. Fluorescense-based TRAP was applied to obtain quantification of telomerase activity. We obtained the following results: histological examination confirmed that every patient's unstained region consisted of various degrees of epithelial dysplasia. The quantified telomerase activities for squamous cell carcinoma, epithelial dysplasia and normal epithelium were 53.9, 39.6 and 2.7 U/microgP, respectively, and there was a significant difference between carcinoma and normal areas, and between dysplasia and normal epithelium. Therefore, these findings suggest that the areas of epithelial dysplasia unstained by iodine consist of cells that are nearly cancerous and excessively proliferative, and that epithelial dysplasia around SCC should be resected together with the tumor. Vital staining with iodine is useful for identifying epithelial dysplasia around SCC.