Decrease in beta-Cell Proliferation Precedes Apoptosis during Diabetes Development in Bio-Breeding/Worcester Rat: Beneficial Role of Exendin-4

In autoimmune type 1 diabetes mellitus, proinflammatory cytokine-mediated apoptosis of beta-cells has been considered to be the first event directly responsible for beta-cell mass reduction. In the Bio-Breeding (BB) rat, an in vivo model used in the study of autoimmune diabetes, beta-cell apoptosis is observed from 9 wk of age and takes place after an insulitis period that begins at an earlier age. Previous studies by our group have shown an antiproliferative effect of proinflammatory cytokines on cultured beta-cells in Wistar rats, an effect that was partially reversed by Exendin-4, an analogue of glucagon-like peptide-1. In the current study, the changes in beta-cell apoptosis and proliferation during insulitis stage were also determined in pancreatic tissue sections in normal and thymectomized BB rats, as well as in Wistar rats of 5, 7, 9, and 11 wk of age. Although stable beta-cell proliferation in Wistar and thymectomized BB rats was observed along the course of the study, a decrease in beta-cell proliferation and beta-cell mass from the age of 5 wk, and prior to the commencement of apoptosis, was noted in BB rats. Exendin-4, in combination with anti-interferon-gamma antibody, induced a near-total recovery of beta-cell proliferation during the initial stages of insulitis. This highlights the importance of early intervention and, as well, the possibilities of new therapeutic approaches in preventing autoimmune diabetes by acting, initially, in the insulitis stage and, subsequently, on beta-cell regeneration and on beta-cell apoptosis.

The Endocannabinoid System as Pharmacological Target Derived from Its CNS Role in Energy Homeostasis and Reward. Applications in Eating Disorders and Addiction

The endocannabinoid system (ECS) has been implicated in many physiological functions, including the regulation of appetite, food intake and energy balance, a crucial involvement in brain reward systems and a role in psychophysiological homeostasis (anxiety and stress responses). We first introduce this important regulatory system and chronicle what is known concerning the signal transduction pathways activated upon the binding of endogenous cannabinoid ligands to the Gi/0-coupled CB1 cannabinoid receptor, as well as its interactions with other hormones and neuromodulators which can modify endocannabinoid signaling in the brain. Anorexia nervosa (AN) and bulimia nervosa (BN) are severe and disabling psychiatric disorders, characterized by profound eating and weight alterations and body image disturbances. Since endocannabinoids modulate eating behavior, it is plausible that endocannabinoid genes may contribute to the biological vulnerability to these diseases. We present and discuss data suggesting an impaired endocannabinoid signaling in these eating disorders, including association of endocannabinoid components gene polymorphisms and altered CB1-receptor expression in AN and BN. Then we discuss recent findings that may provide new avenues for the identification of therapeutic strategies based on the endocannabinod system. In relation with its implications as a reward-related system, the endocannabinoid system is not only a target for cannabis but it also shows interactions with other drugs of abuse. On the other hand, there may be also a possibility to point to the ECS as a potential target for treatment of drug-abuse and addiction. Within this framework we will focus on enzymatic machinery involved in endocannabinoid inactivation (notably fatty acid amide hydrolase or FAAH) as a particularly interesting potential target. Since a deregulated endocannabinoid system may be also related to depression, anxiety and pain symptomatology accompanying drug-withdrawal states, this is an area of relevance to also explore adjuvant treatments for improving these adverse emotional reactions.