Reduced neurogenesis in the rat hippocampus following high fructose consumption.

In this study, we investigated how prolonged consumption of sugar solution affects hippocampal neurogenesis. We gave rats sucrose or fructose solution for four weeks and observed a 40% reduction in BrdU/NeuN-immunoreactive cells in the hippocampal dentate gyrus. This reduction in hippocampal neurogenesis was accompanied by increased apoptosis in the hippocampus and increased circulating levels of TNF-α. Therefore, we hypothesize that the reduction in hippocampal neurogenesis may be due to the increased apoptosis induced by TNF-α. Our results suggest that chronic ingestion of fructose is detrimental to the survival of newborn hippocampal neurones. The results presented in the present study add to the list of harmful effects associated with prolonged and excessive consumption of sugary beverages and soft drinks.

A large scale method for preparation of plant thylakoids for use in body weight regulation.

A method for preparation of thylakoids from plant leaves on a large scale is described. The method involves: 1) disruption of the cells with a blender followed by filtration to remove large cell debris and non disrupted cells. 2) precipitation of the thylakoids by adjusting the pH to the isoelectric point, pH 4.7. 3) a washing step by dilution of the precipitate in water followed by precipitation at the same pH. 4) concentration of the precipitate by freeze- thawing or freeze -drying to get the final product. The product is characterized, with respect to protein composition, by SDS-PAGE and mass-spectroscopy, the content of carotenoids, particularly the xanthophylls violaxanthin, antheraxanthin, and zeaxanthin. The thylakoid preparation has about the same capacity to inhibit pancreatic lipase/colipase activity as thylakoids prepared by standard laboratory methods using sucrose in the medium and centrifugation. In a study with mice, it was found that, when the thylakoids were added to the food over 32 days, they significantly reduced the body weight gain and the percentage body fat. The large scale method described here allows studies on the effect of thylakoids in appetite regulation on experimental animals in a longer lasting time and also on humans.

Thylakoids suppress appetite by increasing cholecystokinin resulting in lower food intake and body weight in high-fat fed mice.

Thylakoids are membranes isolated from plant chloroplasts which have previously been shown to inhibit pancreatic lipase/colipase catalysed hydrolysis of fat in vitro and induce short-term satiety in vivo. The purpose of the present study was to examine if dietary supplementation of thylakoids could affect food intake and body weight during long-term feeding in mice. Female apolipoprotein E-deficient mice were fed a high-fat diet containing 41% of fat by energy with and without thylakoids for 100 days. Mice fed the thylakoid-enriched diet had suppressed food intake, body weight gain and body fat compared with the high-fat fed control mice. Reduced serum glucose, serum triglyceride and serum free fatty acid levels were found in the thylakoid-treated animals. The satiety hormone cholecystokinin was elevated, suggesting this hormone mediates satiety. Leptin levels were reduced, reflecting a decreased fat mass. There was no sign of desensitization in the animals treated with thylakoids. The results suggest that thylakoids are useful to suppress appetite and body weight gain when supplemented to a high-fat food during long-term feeding.

Thylakoids promote release of the satiety hormone cholecystokinin while reducing insulin in healthy humans.

OBJECTIVE: The effects of a promising new appetite suppressor named "thylakoids" (membrane proteins derived from spinach leaves) were examined in a single meal in man. Thylakoids inhibit the lipase/colipase hydrolysis of triacylglycerols in vitro and suppress food intake, decrease body-weight gain and raise the satiety hormone cholecystokinin (CCK) in rats, but their effects in man remain unclear. The aim of this study was to investigate whether thylakoids, when added to a test meal, affect appetite regulation and blood parameters in healthy individuals. MATERIAL AND METHODS: In an intervention crossover study, healthy individuals of normal weight (n=11) were offered a high-fat meal with and without the addition of thylakoids. Blood samples were taken 0 (prior to meal), 30, 60, 120, 180, 240, 300 and 360 min after the start of the meal. Blood samples were analysed for satiety and hunger hormones (CCK, leptin and ghrelin), insulin and blood metabolites (glucose and free fatty acids). RESULTS: The CCK level increased, in particular between the 120 min time-point and onwards, the ghrelin level was reduced at 120 min and leptin level increased at 360 min after intake of the thylakoid-enriched meal. The insulin level was reduced, whereas glucose concentrations were unchanged. Free fatty acids were reduced between time-point 120 min and onwards after the thylakoid meal. CONCLUSIONS: The addition of thylakoids to energy-dense food promotes satiety signals and reduces insulin response during a single meal in man.

Chloroplast membranes retard fat digestion and induce satiety: effect of biological membranes on pancreatic lipase/co-lipase.

Human obesity is a global epidemic, which causes a rapidly increased frequency of diabetes and cardiovascular disease. One reason for obesity is the ready availability of refined food products with high caloric density, an evolutionarily new event, which makes over-consumption of food inevitable. Fat is a food product with high caloric density. The mechanism for regulation of fat intake has therefore been studied to a great extent. Such studies have shown that, as long as fat stays in the intestine, satiety is promoted. This occurs through the fat-released peptide hormones, the best known being CCK (cholecystokinin), which is released by fatty acids. Hence, retarded fat digestion with prolonged time for delivery of fatty acids promotes satiety. Pancreatic lipase, together with its protein cofactor, co-lipase, is the main enzymatic system responsible for intestinal fat digestion. We found that biological membranes, isolated from plants, animals or bacteria, inhibit the lipase/co-lipase-catalysed hydrolysis of triacylglycerols even in the presence of bile salt. We propose that the inhibition is due to binding of lipase/co-lipase to the membranes and adsorption of the membranes to the aqueous/triacylglycerol interface, thereby hindering lipase/co-lipase from acting on its lipid substrate. We also found that chloroplast membranes (thylakoids), when added to refined food, suppressed food intake in rats, lowered blood lipids and raised the satiety hormones, CCK and enterostatin. Consequently, the mechanism for satiety seems to be retardation of fat digestion allowing the fat products to stay longer in the intestine.

Fatty acids and glucose in high concentration down-regulates ATP synthase beta-subunit protein expression in INS-1 cells.

Chronic hyperglycemia and hyperlipidemia exert deleterious effects on beta-cell function and impair glucose-induced insulin release, referred to as glucotoxicity and lipotoxticity. These abnormalities are associated with decreased glucose-induced ATP production; ATP serves as an important signal for insulin secretion. To investigate the mechanism of the impaired ATP formation, we examined the effects of elevated glucose and fatty acids levels on ATP synthase beta-subunit expression, ATP content and insulin secretion in INS-1 insulinoma beta-cells. ATP synthase beta-subunit expression was measured by western blot, ATP content was monitored by ATP luminescence and insulin secretion detected by radio immunoassay. Our result indicated that chronic exposure to high doses of fatty acids together with high levels glucose produced a marked decrease in ATP synthase beta-subunit protein expression. Reduction of ATP synthase beta-subunit protein expression occurred with a decreased intracellular ATP concentration and insulin secretion at high fatty acid concentrations. These results indicate that high glucose together with fatty acids impair the production of ATP in beta-cells through the suppression of mitochondrial ATP synthesis. We conclude that ATP synthase beta-subunit may have an important role in the glucolipotoxicity of islet cells and suggest that ATP synthase beta-subunit might be a target of lipotoxicity in beta-cells.

Maximal lengthening contractions increase p70 S6 kinase phosphorylation in human skeletal muscle in the absence of nutritional supply.

The aim of this study was to compare the training stimuli of eccentric (lengthening) and concentric (shortening) contractions regarding the effect on signaling enzymes involved in protein synthesis. Ten male subjects performed 4 x 6 maximal eccentric contractions on one leg followed by 4 x 6 maximal concentric contractions on the other. Six additional subjects performed the same protocol, but with maximal concentric and submaximal eccentric exercise of equal force to that of the maximal concentric contractions. Muscle biopsy samples were taken from the vastus lateralis before, immediately after, and 1 and 2 h after exercise in both legs. The average peak force produced during the maximal eccentric exercise was 31% higher than during the maximal concentric exercise, 2,490 (+/-100) vs. 1,894 (+/-108) N (P < 0.05). The maximal eccentric contractions led to two- to eightfold increases in the phosphorylation of p70 S6 kinase (p70(S6k)) and the ribosomal protein S6 that persisted for 2 h into recovery but no significant changes in phosphorylation of Akt or mammalian target of rapamycin (mTOR). Maximal concentric and submaximal eccentric contractions did not induce any significant changes in Akt, mTOR, p70(S6k), or S6 phosphorylation up to 2 h after the exercise. The results indicate that one session of maximal eccentric contractions activates p70(S6k) in human muscle via an Akt-independent pathway and suggest that maximal eccentric contractions are more effective than maximal concentric contractions in stimulating protein synthesis in the absence of a nutritional intake, an effect that may be mediated through a combination of greater tension and stretching of the muscle.

Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise.

BCAAs (leucine, isoleucine, and valine), particularly leucine, have anabolic effects on protein metabolism by increasing the rate of protein synthesis and decreasing the rate of protein degradation in resting human muscle. Also, during recovery from endurance exercise, BCAAs were found to have anabolic effects in human muscle. These effects are likely to be mediated through changes in signaling pathways controlling protein synthesis. This involves phosphorylation of the mammalian target of rapamycin (mTOR) and sequential activation of 70-kD S6 protein kinase (p70 S6 kinase) and the eukaryotic initiation factor 4E-binding protein 1. Activation of p70 S6 kinase, and subsequent phopsphorylation of the ribosomal protein S6, is associated with enhanced translation of specific mRNAs. When BCAAs were supplied to subjects during and after one session of quadriceps muscle resistance exercise, an increase in mTOR, p70 S6 kinase, and S6 phosphorylation was found in the recovery period after the exercise with no effect of BCAAs on Akt or glycogen synthase kinase 3 (GSK-3) phosphorylation. Exercise without BCAA intake led to a partial phosphorylation of p70 S6 kinase without activating the enzyme, a decrease in Akt phosphorylation, and no change in GSK-3. It has previously been shown that leucine infusion increases p70 S6 kinase phosphorylation in an Akt-independent manner in resting subjects; however, a relation between mTOR and p70 S6 kinase has not been reported previously. The results suggest that BCAAs activate mTOR and p70 S6 kinase in human muscle in the recovery period after exercise and that GSK-3 is not involved in the anabolic action of BCAAs on human muscle.