Insulinoma induces a hyperinsulinemia-mediated decrease of GLUT2 and GLP1 receptor in normal pancreatic ß-cells.

There have been several clinical reports of transient postoperative hyperglycemia in patients with insulinoma, but the effect of insulinoma on normal ß-cells has not been investigated. We examined the glucose transporter 2 (GLUT2) and glucagon-like peptide 1 receptor (GLP1R) expression in normal pancreatic ß-cells of five patients with insulinoma and five patients with normal glucose tolerance (NGT) as controls. The positive rate of GLUT2-or GLP1R-positive islets in the nontumor area was calculated by the ratio with the analyzed islets. For functional in vitro analyses, q-PCR and Western blotting were performed after insulin loading on MIN6 cells. The expression rates of both GLUT2 and GLP1R were significantly lower in nontumor area islets of insulinoma patients than in patients with NGT (GLUT2: 31.6 ± 15.3% vs 95.9 ± 6.7%, p < 0.01, GLP1R: 66.8 ± 15.0% vs 96.7 ± 5.0%, p < 0.01). Exposure of MIN6 cells to high concentrations of insulin resulted in a significant decrease in GLUT2 protein for 12 h and GLP1R protein for 24 h (GLUT2; 1.00 ± 0.079 vs 0.81 ± 0.04. p = 0.02, GLP1R; 1.00 ± 0.10 vs 0.50 ± 0.24, p = 0.03) but not in those mRNAs. Our findings show that insulinoma is associated with the downregulation of GLUT2 and GLP1R expression in nontumor area islets. These phenomena may be caused by high levels of insulin.

History and characteristics of Okinawan longevity food.

Okinawan food culture in the Ryukyu island is one of the world's most interesting culture because its consumers have the longest life expectancies and low disability rates. It is a product of cultural synthesis, with a core of Chinese food culture, inputs through food trade with South-East Asia and the Pacific and strong Japanese influences in eating style and presentation. The Satsamu sweet potato provides the largest part of the energy intake (and contributes to self-sufficiency), there is a wide array of plant foods including seaweed (especially konbu) and soy, and of herbaceous plants, accompanied by fish and pork, and by green tea and kohencha tea. Infusing multiple foodstuff and drinking the broth is characteristic. Raw sugar is eaten. The concept that 'food is medicine' and a high regard accorded medical practice are also intrinsic of Okinawan culture. Again, food-centered and ancestral festivities keeep the health dimensions well-developed. Pork, konbu and tofu (soy bean-curd) are indispensable ingredients in festival menus, and the combination of tofu and seaweed are used everyday. Okinawan food culture is intimately linked with an enduring belief of the system and highly developed social structure and network.

Reciprocal responses to exercise in hepatic ketogenesis and lipid secretion in the rat.

The effects of 4 weeks of voluntary exercise (rotating wheel) on serum and liver lipid levels were studied in 6-week-old male Wistar rats. The hypotriglyceridemic effect of exercise was not influenced by the dietary fat levels (4.5 and 14.5%), whereas the hypocholesterolemic effect was higher in a low-fat diet than in a high-fat diet. Although the serum cholesterol-lowering effect of exercise was marginal, the beneficial effect on hepatic lipids was observed only in rats fed a high-cholesterol diet. The hepatic contribution to the serum lipid-lowering action of exercise was examined in the isolated perfused livers of rats fed a low fat diet. The reduction (34%) of serum triglyceride by exercise corresponded to the decrease (32%) in the hepatic triglyceride secretion rate, indicating a significant role of the liver in the hypotriglyceridemic effect of exercise. In contrast, the decrease (31%) in serum total cholesterol was considerably greater than that (23%) in the hepatic secretion, suggesting an extra-hepatic contribution. On the other hand, the hepatic production of ketone body was increased by exercise. These results indicate that the altered hepatic partition of long-chain free fatty acids between esterification and oxidation is one of the causative factors for the serum lipid-lowering effect of exercise.

Characteristics of the distribution of lectin receptors in intrahepatic cholangiocellular carcinoma.

The receptors of peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA) and Ulex europaeus agglutinin I (UEA-I) were localized in intrahepatic cholangiocellular carcinoma, hepatocellular carcinoma, intrahepatic bile ducts and normal, cirrhotic and pericarcinomatous liver using the avidin-biotin-peroxidase complex method. It was found that epithelial cells of normal bile ducts had many UEA-I receptors, fewer DBA receptors and no PNA receptors. The positive rates of PNA, UEA-I and DBA receptors in 18 cases of intrahepatic cholangiocellular carcinoma were 88.9%, 61.1% and 33.3% respectively, which were significantly higher than those in hepatocellular carcinoma (16.0%, 4.0% and 4.0% respectively). Hepatocytes in normal, cirrhotic and pericarcinomatous liver had no receptors for these three lectins. It is suggested that lectin receptor distribution in intrahepatic cholangiocellular carcinoma is obviously different from that in normal bile duct cells and in hepatocellular carcinoma, and might be used as an auxiliary index in its clinical diagnosis.

Effects of Okinawan sugar cane wax and fatty alcohol on serum and liver lipids in the rat.

Partially purified Okinawan sugar cane wax and fatty alcohol were fed to Wistar strain rats to examine the effects on serum and liver cholesterol (Chol), triglyceride (TG) and phospholipid (PL). The fecal excretion of neutral sterols in the rats was also determined. There were no significant differences found in the body weight gain, food intake and liver weight among the animals of experimental diet groups. An addition of 0.5% sugar cane wax to the diet significantly lowered the concentrations of serum and liver Chol in the rats. There were no significant differences observed in PL and TG levels either in serum or liver among the experimental groups. These results indicate that cane wax, one of the elements contained in sugar cane rind as well as in black sugar, may have a cholesterol-lowering effect on the serum and liver of the rats. The amount of feces excreted by the three experimental diet groups of rats were exactly the same and also no significant differences were found in the excretion of Chol.

Separation and partial purification of wax and fatty alcohol from Okinawan sugar cane rind lipids.

A composition analysis of Okinawan sugar cane rind materials was conducted, and it was found that the main components were lipids, crude fiber and water indicating about 27%, 19.6% and 14.6%, respectively. The lipids were effectively extracted from rind materials by benzene. Wax (18%) and fatty alcohol (8%) were found to be the main components, totaling up to 96% of the lipids. Separation and partial purification of wax and fatty alcohol were attempted by means of silica gel column chromatography, thin-layer chromatography (TLC), infrared (IR) absorption spectra and gas-liquid chromatography-mass spectrometry (GC-MS). The major components of the wax were considered to be two compounds with the molecular weights of 408 (C-26) and 436 (C-28), and those of fatty alcohol were di-ol with molecular weights of 440 (C-29) and 468 (C-31). Both wax and fatty alcohol were purified by rechromatography on a silica gel column and the samples obtained seemed to be satisfactory for use in experimental rats' diets.

Effects of Okinawan sugar cane rind on serum and liver cholesterol and triglyceride levels in the rat.

Okinawan sugar cane rind was fed to Wistar strain rats to examine its effects on the serum and liver cholesterol (Chol) and triglyceride (TG). At the same time, the effects of sugar cane rind on the fecal excretion of neutral sterols of the rats were examined. There were no significant differences found in the food intakes and the liver weight between the rats fed with sugar cane rind and other groups. The addition of 1% Chol to the diet caused a significant increase in body weight gain but the supplementation of sugar cane rind (2%) showed an effect on weight control of rats. The serum Chol and TG levels of the rats given sugar cane rind were lowered significantly. However, the lipid levels in the liver were almost the same when compared with the control groups. The amount of feces excreted by the rats fed with sugar cane rind was about 37% more than that of the control group, and the fecal excretion of neutral sterols was significantly higher.