Assays for insulin and insulin-like activity based on adipocytes.

Data from the metabolic assays (and signaling assays; see below) are calculated as stimulation factor above basal activity (absence of insulin/compound/drug candidate) for processes stimulated (e.g., lipogenesis, glucose transport, and GLUT4 translocation) or as difference between the basal and insulin/compound/drug candidate-induced values for processes downregulated (e.g., lipolysis). In each case, these data, which reflect the responsiveness of the metabolic effector system studied toward the respective stimulus (insulin/compound/drug candidate), are normalized to the basal (set at 0 %) and maximal insulin action (set at 100 %; elicited by maximally effective concentration of insulin). For characterization of the sensitivity of the metabolic effector system toward the respective stimulus, effective concentrations for the induction of 150 % (or higher) of the basal activity (set at 100 %) can be given. These so-called EC150-values facilitate the insulin-independent comparison of the relative potency of the insulin-like activity between compounds/drug candidates, in general, and in particular for those frequently observed stimuli, which do not elicit the same maximal response in % stimulation or inhibition and/or fail to approach the maximal insulin response