Hypolipidemic potential of squid homogenate irrespective of a relatively high content of cholesterol

BACKGROUND: Our previous study has shown that regardless of a relatively high amount of cholesterol, squid homogenate lowers serum and hepatic cholesterol in animals. Since this work, we have developed a new method to inhibit autolysis of squid proteins with sodium citrate. This study aims to investigate how squid homogenate prepared with sodium citrate affects lipid metabolism in Sprague–Dawley rats at the molecular level. METHODS: We prepared squid homogenate with sodium citrate to inhibit autolysis of squid protein. In Experiment 1 (Exp. 1), rats were given a cholesterol-free control diet or a squid diet, with squid homogenate added at the level of 5% as dietary protein for 4 weeks. Blood, the liver and adipose tissue were taken after 6 hours fasting. Serum and hepatic lipids and activities of enzymes related to lipid metabolism were measured. In Experiment 2 (Exp. 2), the above-mentioned diets had cholesterol added at the level of 0.1% and given to rats. Lipid parameters, enzyme activities, and gene expression of proteins involved in lipid metabolism in the liver and the small intestine were determined. In addition, feces were collected for two days at the end of Exp. 2 to measure fecal excretion of steroids. RESULTS: In Exp.1, serum triglyceride and cholesterol were ~50% and ~20% lower, respectively, in the squid diet-fed rats than in the control diet-fed animals while hepatic cholesterol was ~290% higher in the squid diet-fed rats. When cholesterol was included into the diets (Exp. 2), serum lipids were significantly lower in the squid group while no difference of hepatic lipid was seen between two groups. Activities of hepatic lipogenic enzymes were significantly lower in rats on the squid diet while the enzyme responsible for fatty acid oxidation was not modified (Expt. 1 and 2). Hepatic level of mRNA of microsomal triglyceride transfer protein was significantly lower in the squid group. In the small intestine, the squid diet exhibited significantly lower gene expression of proteins involved in fatty acid transport and cholesterol absorption. Fecal secretion of acidic steroids, but not neutral steroids, was higher in rats fed the squid diet than in those fed the control diet. CONCLUSION: These results imply that newly-developed squid homogenate has hypolipidemic potential primarily through decreased absorption of bile acids in the small intestine and suppressed lipogenesis in the liver

Effects of employment of distinct strategies to capture antibody on antibody delivery into cultured cells

The characteristics of antibody delivery into cultured HeLa cells were examined by using two delivery systems. Both systems used a cell-penetrating peptide as a tool for intrusion of an antibody into the cells, but either a “protein A derivative” or “hydrophobic motif” was employed to capture the antibody. When we examined the uptake of the Alexa Fluor-labeled antibody by use of these two systems, both systems were found to effectively deliver the antibody into the cultured cells. However, when we compared the amount of antibody delivered by these systems with the amount of transferrin uptake, the former was 10 times smaller than the latter. The lower efficiency of antibody delivery than transferrin uptake seemed to be attributable to the involvement of the antibody delivery reagent, which failed to catch the antibody molecule. This interpretation was validated by an experiment using a larger amount of antibody, and the amount of antibody delivered by the “protein A derivative” system under this condition was determined to be 13 ng proteins/105 cells. The antibody delivery achieved by the “protein A derivative” or “hydrophobic motif” showed two differences, i.e., a difference in intracellular distribution of the delivered antibody molecules and a difference in the fluorescence spectrum observed with cellular lysates. Possible reasons for these differences between the two delivery systems are discussed

Isolation of cDNA Encoding 7H6-Reactive Polypeptide Defines a New Class of Protein with alpha-Helical Coiled-Coil Structure and DA-Box Similar to Yeast Chromosomal Segregation Proteins

7H6 monoclonal antibody was recently developed in our laboratory by im-munizing mice with a bile canaliculus-rich fraction of the rat liver. The anti-body reacted with a novel 155 Kd polypeptide designated 7H6 antigen that specifically localizes at tight junctions of various epithelia. Correlations of the paracellular barrier function of the tight junction with expression of the 7H6 antigen at the cell border have suggested important roles of this polypeptide for the maintenance of tight junctional functions. As the first step for the analysis of the antigen at the molecular level, we isolated a series of cDNA clones encod-ing 7H6-reactive polypeptides. Five clones were isolated by immunoscreening. Among them a clone designated RL5.3 which carries the largest 5.3Kb insert was characterized in this study. Both plaque screening and immunoblotting of the fusion protein produced by the RL5.3 clone with lysogen confirmed that the pro-tein specifically reacts with the 7H6 monoclonal antibody. Using DNA fragmentsof the RL5.3 clone, 21 clones were further identified. Studies with restriction enzymes and probe hybridization revealed that all the cDNA clones were derived from a single class of transcripts. A partial sequence identified one open reading frame with an α-helical coiled-coil structure and highly conserved aspartate (D)- alanine (A) residues with a helix-loop-helix structure corresponding to DA- box. Since this domain has been specifically found in yeast chromosomal segregation proteins (SMC1, CUT3 and CUT14), the polypeptide encoded by the RL5.3 clone provides the first rodent counterpart of these protein family. Yeast is known to be lethal when SMC and CUT proteins are deleted, suggesting essential roles of these proteins for cell cycle progression as a regulator for chromosomal segregation. Identification of a mammalian counterpart of this pro-tein family may give us some clues for a better understanding of fundamental regulatory mechanisms in the function of tigh junctions

Ablation of the N-type calcium channel ameliorates diabetic nephropathy with improved glycemic control and reduced blood pressure

Pharmacological blockade of the N-and L-type calcium channel lessens renal injury in kidney disease patients. The significance of specific blockade of α1 subunit of N-type calcium channel, Ca[v]2.2, in diabetic nephropathy, however, remains to be clarified. To examine functional roles, we mated Ca[v]2.2-/- mice with db/db (diabetic) mice on the C57BLKS background. Ca[v]2.2 was localized in glomeruli including podocytes and in distal tubular cells. Diabetic Ca[v]2.2-/- mice significantly reduced urinary albumin excretion, glomerular hyperfiltration, blood glucose levels, histological deterioration and systolic blood pressure (SBP) with decreased urinary catecholamine compared to diabetic Ca[v]2.2+/+ mice. Interestingly, diabetic heterozygous Ca[v]2.2+/- mice also decreased albuminuria, although they exhibited comparable systolic blood pressure, sympathetic nerve activity and creatinine clearance to diabetic Ca[v]2.2+/+ mice. Consistently, diabetic mice with cilnidipine, an N-/L-type calcium channel blocker, showed a reduction in albuminuria and improvement of glomerular changes compared to diabetic mice with nitrendipine. In cultured podocytes, depolarization-dependent calcium responses were decreased by ω-conotoxin, a Ca[v]2.2-specific inhibitor. Furthermore, reduction of nephrin by transforming growth factor-β (TGF-β) in podocytes was abolished with ω-conotoxin, cilnidipine or mitogen-activated protein kinase kinase inhibitor. In conclusion, Ca[v]2.2 inhibition exerts renoprotective effects against the progression of diabetic nephropathy, partly by protecting podocytes

Rapid and sensitive XAFS using a tunable X-ray undulator at BL10XU of SPring-8

The design and performance of the high-brilliance XAFS facility at BL10XU of SPring-8, aimed at rapid and sensitive measurement of X-ray absorption fine structure (XAFS), is reported. Both undulator gap and double-crystal monochromator have been successfully controlled covering a wide energy range (5-30 keV). A versatile goniometer system, consisting of two independent high-precision goniometers. is capable of polarized XAFS in fluorescence mode and surface-sensitive experiments using a grazing-incidence geometry. By sharing major components, i.e. a monolithic Ge 100-pixel array detector and a closed-cycle He cryostat, both polarized XAFS and X-ray standing wave (XSW) experiments can be performed at low temperature (15-300 K). The performance of the spectrometer has been evaluated by recording XAFS spectra in transmission mode