Regulation of mealworm fat body glucose metabolism in vitro: Effects of natural and synthetic catabolic neurohormones

Abstract

Glucose metabolism by Tenebrio molitor larval fat body tissue was studied in vitro by means of a microradiorespirometric method and the effects of either natural or synthetic catabolic hormones were evaluated. The use of this microradiorespirometric method allowed us to measure glucose catabolism in small pieces of tissue with good sensitivity.The metabolic modifications (relative and absolute) induced in the activities of the pentose cycle and glycolysis-Krebs cycle, by larval mealworm Corpora cardiaca (CC) purified extracts, were compared with those produced by synthetic locust AKH I and mammalian glucagon. These metabolic variations were evaluated by measuring total C02 and by using either [l-14Clglucose or [6-'4Clglucose molecules as substrates. The kinetics of 14C02 production and the dose-response curves of hormones were determined. The total expired COz increases significantly (17-26%) during treatment with all of the hormones studied.Modifications to the kinetics of the specific radioactivity and the cumulative yields of 14C02 derived from [l-14C]glucose and [6-'4Clglucose under the influence of each of the hormones were recorded. CC extracts and AKH I rapidly (15 min) diverted glucose from pentose cycle ( -45%); glucose oxidation was increased ( + 26%), this effect appearing later (75 m i d . Mammalian glucagon rapidly and durably increased glucose catabolism both via the pentose cycle ( + 35%) and by the glycolytic pathway ( + 200%). o