Comparison of hormonal effects on glucose metabolism in Tenebrio molitor larval fat body, muscle and brain tissues

Abstract

Pathways of glucose metabolism in mealworm Tenebrio molitor larval fat body, mandibular muscle and brain tissues were studied, in vitro, by means of a micro-radiorespirometric method. The respiratory gaseous mixture supplied to tissues was composed of 30% O 2 and 70% N 2. Glucose and trehalose were used as energy substrates. The effects of the addition of different metabolic hormones were evaluated. Variations in the relative utilization of the two main glucose metabolic pathways were evaluated by using either [1- 14]Glucose or [6- 14]Glucose as substrates. The total expired CO 2 from the different tissues was measured in the presence of hormones. No significant variations were observed, except for the brain where total CO 2 significantly increased following addition of corpora cardiaca (CC) extracts. The insect insulin-like peptide (ILP) stimulated pentose cycle utilization for glucose degradation in both fat body and muscle, but not in brain tissue. The Tenebrio CC hormonal extracts rapidly diverted glucose from the pentose cycle in fat body which exhibits a highly active pentose pathway in controls; this effect lasted for a long time. Muscle and brain tissue, which did not spontaneously exhibit activity of the pentose cycle, were insensitive to CC extracts. Cumulative yields of 14CO 2 derived from [1- 14]glucose and [6- 14]glucose were recorded. In brain tissue, neither of the hormones used had any effect. In contrast, in muscle and particularly in the fat body, cumulative yields of 14CO 2 derived from [6- 14]glucose were modified significantly by both hormones.