Improvement of diabetes, obesity and hypertension in type 2 diabetic KKAy mice by bis(allixinato)oxovanadium(IV) complex

Previously, we found that bis(allixinato)oxovanadium(IV) (VO(alx)(2)) exhibits a potent hypoglycemic activity in type 1-like diabetic mice. Since the enhancement of insulin sensitivity is involved in one of the mechanisms by which vanadium exerts its anti-diabetic effects, VO(alx)(2) was further tested in type 2 diabetes with low insulin sensitivity. The effect of oral administration of VO(alx)(2) was examined in obesity-linked type 2 diabetic KKA(y) mice. Treatment of VO(alx)(2) for 4 weeks normalized hyperglycemia, glucose intolerance, hyperinsulinemia, hypercholesterolemia and hypertension in KKA(y) mice; however, it had no effect on hypoadiponectinemia. VO(alx)(2) also improved hyperleptinemia, following attenuation of obesity in KKA(y) mice. This is the first example in which a vanadium compound improved leptin resistance in type 2 diabetes by oral administration. On the basis of these results, VO(alx)(2) is proposed to enhance not only insulin sensitivity but also leptin sensitivity, which in turn improves diabetes, obesity and hypertension in an obesity-linked type 2 diabetic animal.     

Role of tyrosine-57 and -65 in membrane-damaging and sphingomyelinase activities of Clostridium perfringens alpha-toxin

Clostridium perfringens alpha-toxin (370 residues) is a major virulence factor in the pathogenesis of gas gangrene. The toxin is composed of an N-terminal domain (1-250 residues) where lies the catalytic site and a C-terminal domain (251-370 residues), the Ca(2+)-binding domain, responsible for binding to membranes. The role of Tyr-57 and Tyr-65 close to the catalytic pocket (site) in the N-domain was investigated. Replacement of Tyr-57 and -65 with alanine, leucine, or phenylalanine did not affect the sphingomyelinase activity of the toxin for sodium deoxycholate-solubilized shingomyelin. However, the substitution of Tyr-57 and -65 with alanine or leucine resulted in a radical reduction in the hemolysis of sheep erythrocytes, the release of carboxyfluorescein from shingomyelin-cholesterol (1:1) liposomes, and a significant decrease in binding to the liposomes. The binding of variant toxins, Y57C/C169L and Y65C/C169L, labeled with the environmentally sensitive fluorophore, acrylodan, to the liposomes suggested insertion of the variants in a hydrophobic environment in the bilayer. These observations suggested that Tyr-57 and -65 play a role in the penetration of the toxin into the bilayer of membranes and access of the catalytic site to sphingomyelin in membranes, but do not participate in the enzymatic activity.     

Endogenous alphaCGRP protects against concanavalin A-induced hepatitis in mice

To evaluate hepatoprotective effect of alpha-calcitonin gene-related peptide (alphaCGRP), we compared the susceptibilities of alphaCGRP-/- and wild-type mice to concanavalin A (Con A)-induced hepatitis. Twelve hours after Con A administration, serum transaminases were markedly higher in alphaCGRP-/- than wild-type mice, and much more extensive TUNEL-positive lesions and DNA fragmentation were detected in the livers of alphaCGRP-/- mice. Notably, expression of IL-6 was selectively diminished in alphaCGRP-/- mice, suggesting that induction of IL-6 during acute inflammatory responses is blunted in alphaCGRP-/- mice. In addition, primary cultured alphaCGRP-/- hepatocytes were more susceptible to IFN-gamma-induced cell death than hepatocytes from wild-type mice. Administration of exogenous alphaCGRP reduced the incidence of apoptosis among hepatocytes and endothelial cells. It thus appears that alphaCGRP exerts a hepatoprotective effect by modulating cytokine expression and preventing apoptosis.     

Oral administration of a zinc complex improves type 2 diabetes and metabolic syndromes

Previously, we reported that intraperitoneal injections of the Zn(II) complex (Zn(alx)(2)) with allixin, which is isolated from dry garlic, with a Zn(O(4)) coordination environment, exhibited high anti-diabetic effects in obesity-linked type 2 diabetic KKA(y) mice. However, this complex exhibited low activity when administered orally. To improve the effect of Zn(alx)(2), we prepared a novel Zn(II) complex with the allixin-derivative bis(1,6-dimethyl-3-hydroxy-5-methoxy-2-pentyl-1,4-dihydropyridine-4- thionato)Zn(II), abbreviated as Zn(II)-thioallixin-N-methyl (Zn(tanm)(2)), having a Zn(S(2)O(2)) coordination environment; this complex has extremely high in vitro insulin-like activity. Because Zn was extensively absorbed from the gastrointestinal tract when Zn(tanm)(2) was orally administered, its anti-diabetic effects were examined in KKA(y) mice. Daily oral administrations of Zn(tanm)(2) for 4 weeks in KKA(y) mice significantly improved hyperglycemia, glucose intolerance, insulin resistance, hyperleptinemia, obesity, and hypertension. Interestingly, Zn(tanm)(2) increased depressed plasma adiponectin levels in the mice. Here, we propose that Zn(tanm)(2) will be an orally active therapeutic for obesity-linked type 2 diabetes and metabolic syndromes.     

Effect of exposure to high isoflavone-containing diets on prenatal and postnatal offspring mice

Isoflavone (IF), a type of phytoestrogen, has multiple beneficial effects, but too much phytoestrogen can have adverse effects on offspring. To examine whether chronic exposure to high IF has adverse effects on reproductive development, mice offspring were exposed to IF through dietary administration to dams during pregnancy and lactation and to the offspring directly after weaning until sacrifice. In male offspring, there was no difference between the IF group and controls; however, in female offspring in the IF group, remarkably earlier puberty and induction of multioocyte follicles on postnatal day (PND) 21 were observed. Gene expression levels of estrogen receptor beta decreased in the ovary and vagina on PND 21. These results suggest that chronic exposure to higher than normal levels of IF induces alterations in the reproductive development of female mice through an estrogenic effect.     

Formation of oriented polypeptides on Au(111) surface depends on the secondary structure controlled by peptide length.

We synthesized three different lengths of poly(L-lysine) containing an -SH group at the terminal (PLL(n)-SH, n (polymerization degree) = 4, 10, 30) and adsorbed them on an Au(111) surface. To analyze the formation process and the structure of self-assembled monolayers (SAMs), we used atomic force microscopy (AFM) and Fourier transform infrared reflection absorption spectra (FT-IR RAS). At the initial stage of SAM growth, formation of nanosize domains was confirmed by AFM imaging. The alpha-helical PLL(30)-SH exhibited a well-defined SAM structure after adsorption reached equilibrium. The alpha-helical PLL(30)-SH was almost perpendicular to the gold surface and exhibited interesting molecular packing due to the secondary structure of PLL(30)-SH and the underlying Au(111) array. The tilt angle of the helix axis from the substrate normal was estimated to be about 50 degrees (AFM) and 44 degrees (FT-IR RAS) respectively. On the other hand, PLL(4)-SH and PLL(10)-SH formed beta-sheet-type SAMs on the Au(111) surface based on the structure determined by FT-IR RAS spectrum.