Anti-obesity effects of the combined administration of CB1 receptor antagonist rimonabant and melanin-concentrating hormone antagonist SNAP-94847 in diet-induced obese mice.

OBJECTIVE: Current anti-obesity monotherapies have proven only marginally effective and are often accompanied by adverse side effects. The cannabinoid 1 (CB1) receptor antagonist rimonabant, while effective at producing weight loss, has been discontinued from clinical use owing to increased incidence of depression. This study investigates the interaction between the cannabinoid and melanin-concentrating hormone (MCH) systems in food intake, body weight control, and mood. DESIGN: Lean male C57BL/6 mice were injected i.p. with rimonabant (0.0, 0.03, 0.3 and 3.0 mg kg(-1)) or the MCH1-R antagonist SNAP-94847 (0.0, 1.0, 5.0 and 10.0 mg kg(-1)) to establish dose response parameters for each drug. Diet-induced obese (DIO) mice were given either vehicle, sub-threshold dose of rimonabant and SNAP-94847 alone or in combination. Impact on behavioral outcomes, food intake, body weight, plasma metabolites and expression of key metabolic proteins in the brown adipose tissue (BAT) and white adipose tissue (WAT) were measured. RESULTS: The high doses of rimonabant and SNAP-94847 produced a reduction in food intake after 2 and 24 h. Combining sub-threshold doses of rimonabant and SNAP-94847 produced a significantly greater loss of body weight in DIO mice compared with vehicle and monotherapies. In addition, combining sub effective doses of these drugs led to a shift in markers of thermogenesis in BAT and lipid metabolism in WAT consistent with increased energy expenditure and lipolysis. Furthermore, co-administration of rimonabant and SNAP-94847 produced a transient reduction in food intake, and significantly reduced fat mass and adipocyte size. Importantly, SNAP-94847 significantly attenuated the ability of rimonabant to reduced immobility time in the forced swim test. CONCLUSION: These results provide proof of principle that combination of rimonabant and a MCH1 receptor antagonist is highly effective in reducing body weight below that achieved by rimonabant and SNAP-94847 monotherapies. In addition, the combination therapy normalizes the rimonabant-induced behavioral changes seen in the forced swim test.

Neural and humoral changes associated with the adjustable gastric band: insights from a rodent model.

BACKGROUND: Bariatric surgical procedures, including the laparoscopic adjustable gastric band (LAGB), are currently the only effective treatments for morbid obesity, however, there is no clear understanding of the mechanisms underpinning the efficacy of LAGB. The aim of this study is to examine changes in activation of the sensory neuronal pathways and levels of circulating gut hormones associated with inflation of an AGB. DESIGN AND RESULTS: The trajectory within the central nervous system of polysynaptic projections of sensory neurons innervating the stomach was determined using the transsynaptically transported herpes simplex virus (HSV). Populations of HSV-infected neurons were present in the brainstem, hypothalamus and cortical regions associated with energy balance. An elevation of Fos protein was present within the nucleus of the solitary tract, a region of the brainstem involved in the control of food intake, following acute and chronic band inflation. Two approaches were used to test (1) the impact of inflation of the band alone (on a standard caloric background) or (2) the impact of a standard caloric meal (on the background of the inflated band) on circulating gut hormones. Importantly, there was a significant elevation of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) following oral gavage of a liquid meal in animals with pre-inflated bands. There was no impact of inflation of the band alone on circulating GLP-1, PYY or ghrelin in animals on a standard caloric background. CONCLUSION: These data are consistent with the notion that the LAGB exerts its effects on satiety, reduced food intake and reduced body weight by the modulation of both neural and hormonal responses with the latter involving an elevation of meal-related levels of GLP-1 and PYY. These data are contrary to the view that the surgery is purely 'restrictive'.

Glucagon-like peptide-1 receptor in the brain: role in neuroendocrine control of energy metabolism and treatment target for obesity.

The central glucagon-like peptide (GLP)-1 receptor mediates a number of metabolic processes, including feeding, body weight and glucose homeostasis. More recently, roles in energy expenditure and reward pathway modulation have been described. GLP-1 receptor agonism promotes insulin release and is currently used to treat type 2 diabetes humans, with a common side effect being weight loss. It is likely that many of these metabolic effects are mediated by GLP-1Rs located in the central nervous system, throughout areas known to be important in control of energy homeostasis. The physiological role of the GLP-1 receptor signalling in each of these brain nuclei is becoming clearer and the GLP-1 system appears to act as an integrator of peripheral energy availability and effector of metabolic regulation. This makes it an attractive target for obesity therapies, with excellent pre-clinical efficacy seen in molecules combining GLP-1 receptor agonism with glucagon receptor agonism. This review discusses what is known about the functions of the GLP-1 receptor in the central nervous system, and highlights the ways that this system may be targeted for development of new obesity therapeutics.