Insulin pulsatile release

Before we can start to develop a model we also have to decide how to interpret the behavior observed in Fig. 2.1. The variations in insulin and glucose concentrations could be generated by a damped oscillatory system that was continuously excited by external perturbations (e.g. through interaction with the pulsatile release of other hormones). However, the variations could also represent a disturbed self-sustained oscillation, or they could be an example of deterministic chaos. Here, it is important to realize that, with a sampling period of 10 min over the considered periods of 20-24 h, the number of data points are insufficient for any statistical analysis to distinguish between the possible modes. We need to make a choice and, in the present case, our choice is to consider the insulin-glucose regulation to operate... 

As a final comment to this section, let us note that experiments have also been performed to examine the possible physiological function of the oscillatory insulin secretion. An obvious question of interest was whether pulsatile release of insulin... 

Fig. 4.2-12 Use of the reverse dimerization system to control protein secretion in mammalian cells, (a) Scheme for inducible secretion, (b) Chemical structure of monomeric ligand AP21998. (c) Pulsatile release of insulin from engineered cells. 

Glucagon Gonadotropic hormones Gonadotropin-releasing hormone Growth hormone (GH) Insulin oscillations Insulin pulsatile secretion Luteinizing hormone (LH) Hypothalamus, and circadian rhythms, 461, 521... 

Second oscillator in cell cycle, 413,448-51 in Dictyostelium, 218 in glycolysis, 85,160 Secretion, of hormones, see Glucagon Gonadotropin-releasing hormone Growth hormone Insulin pulsatile secretion... 

Nolan, C. M., Serpe,M. J.,Lyon,L. A. Pulsatile release of insulin from layer-by-layer assembled microgel thin films. Macromol. Symp. 2005, 227, 285-294. 

The anterior pituitary releases GH in 6 to 8 pulsatile bursts over a 24 h period the major portion is released just prior to deep sleep. Its secretion is controlled by hypothalamic peptides GH-releasing hormone stimulates GH secretion, while somatostatin inhibits it. GH stimulates the synthesis of insulin-like growth factor-1 (IGF-1 somatomedin C) mainly, but not solely, in the liver. GH and IGF-1 receptors are widely scattered throughout the body, and both hormones exert important metabolic actions in various tissues, especially muscle and bone. 

Asplin, C.M., A.C. Faria, E.C. Carlsen, VA. Vaccaro, R.E. Barr, A. Iranmanesh et al. (1989). Alterations in the pulsatile mode of growth hormone release in men and women with insulin-dependent... 

Leffebvre, P.J., G. Paolisso, A.J. Scheen J.C. Henquin. 1987. Pulsatility of insulin and glucagon release Physiological significance and pharmacological implications. Diabetologia 30 443-52. 

HoUingdal M, Sturis 1, Gall MA, Damsbo P, Pincus S, Veldhuis ID, Porksen N, Schmitz O, Juhl CB. Repaglinide treatment amplifies first-phase insulin secretion and high-frequency pulsatile insulin release in Type 2 diabetes. Diabet Med 2005 22(10) 1408-1413. 

Kwok et al. have reported on the development of ULS-sensitive barrier membranes able to give a pulsatile drug release. A co-polymer of 2-hydroxyl methacrylate (HEMA) and PEG dimethacrylate was loaded with particulate insulin and PEG, after which the surface of the polymer was coated with methylene chains. Upon exposure to ultrasound the methylene chains became disordered, permitting the insulin to diffuse out of the matrix [100,101]. 

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