Search

Purpose It has been reported that the consumption of fruit granola (FG), mulberry leaves, and barley cookies as an afternoon snack suppresses the postprandial increase in glucose levels at dinner. However, there have been no reports on the second-meal effect of snacking on popular snacks, such as potato chips (PC), roasted sweet potato (SP), and black beans (BB), or on the interval between snacking and dinner. Method The present study was an open-label randomized crossover trial of five study groups (PC, SP, BB, FG, and no snack) regarding the second-meal effects with different intervals between snacks and dinner. The subjects consumed prescribed meals for lunch and dinner at 12:00 and 19:00, and a snack fixed at 838 kJ (= 200 kcal) at 15:00 or 17:00. Results When the participants snacked at 15:00, the postprandial glucose elevation at dinner was suppressed in the FG and SP groups, and the area under the curve (AUC) was also low. When they snacked at 17:00, the postprandial glucose elevation was suppressed in all the groups. The AUCs for PC, FG, and SP were lower than those for no snacking. On the other hand, carbohydrate intake increased with snacking, but the total AUC of snacks and dinner did not differ in any of the groups. The duration of hyperglycemia decreased with snack intake, as did the glucose amplitude. Conclusion We believe that the intake of carbohydrates and soluble fiber in snacks is an important factor in the second-meal effect at dinner. These results will contribute to the development of snacking and research into the second-meal effect.

The ability of dermal fibroblasts to synthesize collagen decreases with ages. The integrity of collagen fibers severely decreases in aged skin, causing its characteristic morphological changes such as wrinkles and sagging. To prevent and improve skin aging, the stimulation of collagen synthesis in dermal fibroblasts is important. Potato peels contain many biofunctional compounds, but not much is known about their effects on human skin physiology. To characterize the potential effects of a potato peel extract (PPE) against skin aging, we examined its effects on the synthesis of type I collagen by normal human dermal fibroblasts (NHDFs). Treatment with the PPE significantly increased the expression of type I collagen mRNA in NHDFs and their secretion of type I collagen. To elucidate the mechanism involved, we examined the signaling pathway controlled by transforming growth factor-β (TGF-β), which regulates the synthesis of type I collagen. Treatment of NHDFs with the PPE significantly increased the expression of TGF-β receptor mRNA. TGF-β signaling involves Smad-dependent and Smad-independent pathways, like phosphatidylinositol-3 kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK). The PPE did not activate Smad, but significantly activated Akt and ERK. These results demonstrate that the PPE activates PI3K/Akt and MAPK/ERK signals via TGF-β receptors, which stimulate the synthesis of type I collagen in NHDFs. These results suggest that the PPE could be a novel and effective antiaging material.

Digalactosyldiacylglycerol- (DGDG-) monoestolide is a characteristic glycolipid in oats. DGDG-monoestolides possess a unique structure whereby a fatty acid of DGDG is replaced by a fatty acid ester of hydroxy fatty acid (FAHFA). While the physiological effects of DGDG and FAHFA have been reported previously, the effects of DGDG-monoestolides are unknown. Hence, we isolated a major DGDG-monoestolide molecular species from oats, analyzed its structure, and evaluated its anti-inflammatory effect. Based on GC-MS, MS/MS, and NMR analyses, the isolated compound was identified as a DGDG-monoestolide that contains the linoleic acid ester of 15-hydroxy linoleic acid (LAHLA) and linoleic acid (i.e., DGDG-LAHLA). The isolated DGDG-LAHLA was evaluated for its anti-inflammatory effect on LPS-stimulated RAW264 cells. The production of nitric oxide and cytokines (IL-6, TNF-α, and IL-10) were significantly decreased by DGDG-LAHLA, suggesting the anti-inflammatory effect of DGDG-LAHLA for the first time. In addition, our data showed a pronounced uptake of DGDG-LAHLA by cells. Some compounds corresponding to the predicted DGDG-LAHLA metabolites were also detected, suggesting that both intact DGDG-LAHLA and its metabolites may contribute to the above anti-inflammatory activities. These results are expected to expand the availability of oats as a functional food.

The ability of dermal fibroblasts to synthesize collagen decreases with ages. The integrity of collagen fibers severely decreases in aged skin, causing its characteristic morphological changes such as wrinkles and sagging. To prevent and improve skin aging, the stimulation of collagen synthesis in dermal fibroblasts is important. Potato peels contain many biofunctional compounds, but not much is known about their effects on human skin physiology. To characterize the potential effects of a potato peel extract (PPE) against skin aging, we examined its effects on the synthesis of type I collagen by normal human dermal fibroblasts (NHDFs). Treatment with the PPE significantly increased the expression of type I collagen mRNA in NHDFs and their secretion of type I collagen. To elucidate the mechanism involved, we examined the signaling pathway controlled by transforming growth factor-β (TGF-β), which regulates the synthesis of type I collagen. Treatment of NHDFs with the PPE significantly increased the expression of TGF-β receptor mRNA. TGF-β signaling involves Smad-dependent and Smad-independent pathways, like phosphatidylinositol-3 kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK). The PPE did not activate Smad, but significantly activated Akt and ERK. These results demonstrate that the PPE activates PI3K/Akt and MAPK/ERK signals via TGF-β receptors, which stimulate the synthesis of type I collagen in NHDFs. These results suggest that the PPE could be a novel and effective antiaging material.

A potato fraction library was constructed to investigate functional secondary metabolites from 8 cultivars: Kitahime, Pilka, Sakurafubuki, Atlantic, Toyoshiro, Snowden, Kitamurasaki, and Northern Ruby, which were divided into flower, leaf, stem, roots, tuber peel, and tuber. Each fraction was a semi-purified extract and about 800 fractions were prepared for the library. They were analyzed by DAD-LC/MS to obtain structural information and were evaluated for various biological activities. LC/MS data showed that each part had a specific characteristic for their constituents supported by principal component analysis (PCA). Approximately 40% of fractions showed significant biological activities at 30 μg/mL, especially the flower fractions showed strong cytotoxicity. PCAs based on the activity and LC/MS data suggested that the strong cytotoxicity of flowers was derived from a complex mixture of potato glycoalkaloids. In addition, tuber peel fractions showed strong antimalarial activity, which had not been reported before. Also, some fractions showed significant antibacterial activities. Potato fraction library was constructed to search for functional secondary metabolites. Flower and tuber-peel fractions showed potent cytotoxicity and antimalarial activity, respectively.

Potato chips (PC) contain abundant amounts of the free radical scavenger ascorbic acid (AA) due to the rapid dehydration of potato tubers (Solanum tuberosum) that occurs during frying. To evaluate the antioxidant activity of PC, this study examined reactive oxygen species (ROS) levels in tissues from SMP30/GNL knockout (KO) mice that cannot synthesize AA and determined AA and ROS levels after the animals were fed 20 and 10% PC diets for 7 weeks. Compared with AA-sufficient mice, AA-depleted SMP30/GNL KO mice showed high ROS levels in tissues. SMP30/GNL KO mice fed a PC diet showed high AA and low ROS levels in the brain, heart, lung, testis, soleus muscle, plantaris muscle, stomach, small intestine, large intestine, eyeball, and epididymal fat compared with AA-depleted mice. The data suggest that PC intake increases AA levels and enhances ROS scavenging activity in tissues of SMP30/GNL KO mice, which are a promising model for evaluating the antioxidant activity of foods.

A filamentous fungus producing significant levels of arachidonic acid (AA, C20∶4n−6) was isolated from a freshwater pond sample and assigned to the species Mortierella alliacea. This strain, YN-15, accumulated AA mainly in the form of triglyceride in its mycelia. An optimized culture in 25 L of medium containing 12% glucose and 3% yeast extract yielded 46.1 g/L dry cell weight, 19.5 g/L total fatty acid, and 7.1 g/L AA by 7-d cultivation in a 50-L jar fermenter. Assimilation of soluble starch by YN-15 was notably enhanced by the addition of oleic acid, soybean oil, ammonium sulfate, or potassium phosphate to a starch-based medium. Using starch as a main carbon source in the pre-pilot scale cultivation improved the production of AA by up to 5.0 g/L. Mortierella alliacea strain YN-15 is therefore a promising fungal isolate for industrial production of AA and other polyunsaturated fatty acids.

Potato (Solanum tuberosum) tubers contain vitamin C (VC) and commercial potato chips have more VC content per wet weight by dehydration during frying. However, intestinal absorption of VC from orally ingested potatoes and its transfer to the blood remains questionable. The present study was designed to determine whether the dietary consumption of potatoes affects VC concentration in plasma and urinary excretion of VC in human subjects. After overnight fasting, five healthy Japanese men between 22 and 27 years of age consumed 87 g mashed potatoes and 282 g potato chips. Each portion contained 50 mg of VC, 50 mg VC in mineral water and mineral water. Before and after a single episode of ingestion, blood and urine samples were collected every 30 min or 1 h for 8 h. When measured by subtraction of the initial baseline value before administration of potatoes from the values measured throughout the 8 h test period, plasma VC concentrations increased almost linearly up to 3 h. Subsequently, the values of potato-fed subjects were higher than those of water, but did not differ significantly from those of VC in water (P = 0·14 andP = 0·5). Less VC tended to be excreted in urine during the 8 h test than VC in water alone (17·0 (sem7·5) and 25·9 (sem8·8)v.47·9 (sem17·9) μmol/mmol creatinine). Upon human consumption, mashed potatoes and potato chips provide VC content that is effectively absorbed in the intestine and transferred to the blood. Clearly, potatoes are a readily available source of dietary VC.

Acrylamide (AAm) is produced in food through the reaction of asparagine and reducing sugar. We examined several methods of reducing the level of AAm using potato tubers. The fried model system that we employed consisted of thin slices that were first treated in water under different conditions before frying. A sufficient amount of water present in the fry material acts as an inhibitor against the formation of AAm and allows only a negligible amount of AAm to form. It was found that given the low content of water, the fry material temperature was sufficiently high to allow a relatively large level of AAm to form. Examination of water treatment prior to frying revealed that higher-temperature treatment water and longer treatment time resulted in the formation of lower levels of AAm. Moreover, removing some of the residual heat had an inhibiting effect on the formation of AAm.

Acrylamide (AAm) is formed from asparagine (Asn) and reducing sugar during cooking of foods at high temperature. We examined the formation of AAm in a model system using a glass fiber filter paper, and looked for suitable conditions for inhibiting AAm formation. In frying, the formation rate was about 10 times that in a moistureless oven. Increase of frying temperature and frying time increased AAm formation when the residual moisture was 5% or less. AAm increased with increasing amount of glucose (Glc) addition up to 1 : 1 with respect to Asn, but then decreased. On the other hand, in the case of fructose, as the amount added was increased, AAm increased accordingly. The AAm formation rate with respect to Asn increased when valine (Val) was co-present in a Glc and Asn reaction system. Cysteine and lysine inhibited the AAm formation rate. Pathways for the formation of AAm are proposed.