The effect of Katsura-uri (Japanese pickling melon, Cucumis melo var. conomon) and its derived ingredient methylthioacetic acid on energy metabolism during aerobic exercise

[Purpose] We investigated the effect of Katsura-uri (Japanese pickling melon; Cucumis melo var. conomon) on energy metabolism during exercise in human and animal studies. Methods Eight healthy men (mean age, 21.4 ± 0.7 years) participated in a single-blind, crossover study. Thirty minutes after ingesting the Katsura-uri drink or placebo drink, they exercised on a cycle ergometer at 40% maximal heart rate for 30 min. Respiratory gas analysis was performed during exercise to examine oxygen consumption and substrate utilization. Blood biochemical parameters were evaluated during exercise. In the animal study, the effect of methylthioacetic acid (MTA), a Katsura-uri derived component was examined in mice. Immediately after running at 25 m/min for 30 min, biochemical parameters in the hind limb muscle and blood of mice were measured. [Results] Oxygen consumption during exercise was higher in the Katsura-uri condition (19.8 ± 3.5 mL/kg/min) than the placebo condition (18.6 ± 3.0 mL/kg/min) (P < 0.05). The elevation of blood lactate was lower in the Katsura-uri condition (1.7 ± 0.4 mM) than the placebo condition (2.2 ± 0.6 mM) 15 min after beginning exercise (P < 0.05). There was a higher positive correlation between lactate concentration and carbohydrate oxidation during exercise in the Katsura-uri condition (R2 = 0.86) compared to the placebo condition (R2 = 0.47). The decrease in intermuscular pH and the increase in blood lactate following exercise were prevented by MTA supplementation (250 ppm) with significant differences in the MTA-supplemented group compared to the control group. [Conclusions] These results suggest that the ingestion of Katsura-uri and/or MTA improves glucose metabolism and acidification in skeletal muscles during exercise in human and animal studies

A new strategy to protect Katsura-uri (Japan's heirloom pickling melon, Cucumis melo var. conomon) from extinction

Background: Katsura-uri (Cucumis melo var. conomon), an heirloom vegetable cultivated in Kyoto, Japan is at the risk of extinction. Japanese food culture has traditionally used immature and midripened fruit in the preparation of pickles, the consumer demand of which has markedly decreased. A new strategy was adopted for Katsura-uri, aimed at increasing its inclusion in the present diet habit (e.g., Katsura-uri juice as a functional drink to prevent obesity and diabetes). Methods: Chemical analysis was performed to determine sugar profiles of fully ripened Katsura-uri fruits that uniquely possess muskmelon-like fragrance. In the questionnaire-based sensory evaluation, palatability was compared among the fruit juices without sweeteners and those with sugar or zero-calorie sweetener. Results: Chemical analysis results showed that the fully ripened Katsura-uri fruit had significantly lower levels of fructose, glucose, and sucrose (low-calories and lack of sweetness) than muskmelon fruits. In the questionnaire-based sensory evaluation, zero-calorie sweetener dramatically improved the palatability of the unprocessed fruit juice without altering its low-calorie properties and muskmelon-like fragrance. Conclusion: This demonstrated a new strategy to protect this heirloom vegetable from extinction by adding a new function that could increase its demand as a low-calorie fruit in the present diet habit for human health

Preparation of contemporary dishes and a functional drink using Japan's heirloom vegetable, Katsura-uri

Background: The fruit of Katsura-uri, traditionally used in the preparation of pickles in Japan, is facing an extinction crisis. In addition to the traditional dishes prepared from Katsura-uri, alternative dishes using the fruit should be devised to increase consumer demands for the protection of the heirloom vegetable. We attempted designing new Katsura-uri contemporary dishes and assessed the application of Katsura-uri juice as a functional drink without raising blood glucose levels. Methods: Cooking experiments were conducted with Katsura-uri in its ripening stages, based on the advice from a licensed chef and a registered dietitian in Japan. In the questionnaire-based sensory evaluation, consumer acceptability of Katsura-uri juice was assessed. The blood glucose levels were measured after healthy volunteers consumed the juice. Results: We demonstrated six new Katsura-uri dishes. In the questionnaire-based sensory evaluation of Katsura-uri juice, the assessment values for taste and fragrance were high. In human trials, the levels of incremental area under the curve and glucose spike were significantly lower after consumption of Katsura-uri juice, as compared to those after consumption of muskmelon juice. Conclusion: Katsura-uri-containing contemporary dishes and juice would help continue the consumption of the vegetable. Based on the results of the questionnaire, we also concluded that the use of Katsura-uri as a functional drink without raising blood glucose levels is superior to its use as contemporary dishes. These findings provide useful strategies to protect Katsura-uri from extinction