Lifestyle in many parts of the world today is characterized by an enormous meal and “between-meal” intake of calories from solid food and snacks as well as drinkable calories. This lifestyle is often referred to as “western world lifestyle”, and it is generally regarded as unhealthy. Our food earlier consisted of an average of 10% protein, 30% fat and 60% carbohydrates; the carbohydrates mostly in the form of slowly absorbed carbohydrates. The food and especially the between-meal snack consumed today often has a much higher amount of quickly absorbed carbohydrates and fat. The amount of quickly absorbed carbohydrates may be measured as the glycemic index or as the fraction of mono- and di-saccharide of the total amount of carbohydrates. The excess intake of quickly absorbed carbohydrates and/or high fat leads to reduced feelings of hunger, and to increased stress (W F Horn, N Keim. Effects of glycemic index on hunger, stress and aroursal. FASEB Journal 2003:17(4-5):A7097). Also, some human beings have cravings for sweet and/or fat food, sometimes enhanced by stress or premenstrual tension, or they may have psychological problems manifested as binge eating or compulsive eating habits. As a consequence of this western world lifestyle and the psychological disorders described above there is a general excessive intake of food like sodas, juice, chocolate milk, sweetened coffee, candy, chocolate, cake, biscuits, crackers, french fries, burgers, white bread with jam or jelly or honey, chips, sweet and fat cereals.
GLP-1 has been described as an incretin hormone with a large array of effects. GLP-1 was discovered in 1984 and found to be an important incretin [Nauck, M. A.; Kleine, N.; Orskov, C.; Hoist, J. J.; Willms, B.; Creutzfeldt, W., Diabetologia 1993, 36, 741-744]. It is released from the L-cells in the intestine upon a meal and potently releases insulin from the beta-cells in the pancreas. Numerous effects other than just stimulation of insulin release have been ascribed to GLP-1. In the pancreas, GLP-1 not only releases insulin, it does so in a glucose-dependent manner, and it has a number of other functionally important effects: stimulation of insulin biosynthesis, restoration of glucose sensitivity to the islets, stimulation of increased expression of the glucose transporter GLUT-2 and glucokinase. 4,5,6GLP-1 also has a number of effects on regulation of beta-cell mass, stimulation of replication and growth of existing beta-cells, inhibition of apoptosis and neogenesis of new b-cells from duct precursor cells, which leads to reduced hepatic glucose output. In the gut, GLP-1 is a potent inhibitor of motility and gastric emptying and has also been shown to inhibit gastric acid secretion. The inhibition of gastric emptying leads to decreased food intake and reduced body weight [Flint, A.; Raben, A.; Astrup, A.; Hoist, J. J., J Clin Inv 1998, 101, 515-520; Zander, M.; Madsbad, S.; Madsen, J. L.; Hoist, J. J., Lancet 2002, 359, 824-830]11,12. Thus, the current belief is that the GLP-1 agonists may be able to control the progression of the type 2 diabetes disease by not only controlling blood glucose, but also by a number of other effects. GLP-1 has also been proposed to have direct effects on glucose uptake in liver, muscle and adipose tissue but the quantitative significance of these effects has been questioned [Kieffer, T. J.; Habener, J. F., Endocrine Reviews 1999, 20, 876-913]. New publications even suggest that it does not stop here, there may be specific receptors in the heart which along with the benefits of reducing blood glucose may prevent cardiovascular complications, and that GLP-1 stimulates memory and learning capabilities. A comprehensive review exists on the glucagon-like peptides [Kieffer, T. J.; Habener, J. F., Endocrine Reviews 1999, 20, 876-9139.
A large number of articles have been published on the effects of GLP-1 on food intake. GLP-1 reduces food intake, both after central administration and after peripheral administration (Turton, Nature 196:379; 69-72, Flint J Clin Inv 1998, 101, 515-520). Also, central administration of high doses of GLP-1 induces taste aversion (Tang-Christensen, Diabetes 1998:47:530-537). However, site directed micro injections of GLP-1 into the PVN induces pharmacologically specific inhibition of feeding without induction of taste aversive behaviour (McMahon, Wellman, Am. J. Phys 1998:274, R23-R29). In animals having their arcuate nucleus lesioned by neonatal monosodium glutamate treatment, central administration of GLP-1 has lost its anorectic potential but is still inducing taste aversion (Tang-Christensen, Diabetes 1998:47:530-537). Further support of dissociated specific satiety inducing central targets of GLP-1 and non-specific taste aversion inducing central targets come from lesion studies showing that PVN constitute a target where GLP-1 elicits satiety whereas the central amygdala and the parabrachial nuclei constitute areas involved in mediating GLP-1 induced taste aversion (van Dijk and Thiele, Neuropeptides 1999: 33, 406-414). Other studies have confirmed that there are diverse roles of GLP-1 receptors in the control of food intake and taste aversion (Kinzig, J Neuroscience 2002:22(23): 10470-10476). Also, chronic repetitive central administration of the GLP-1 antagonist, exendin-9-39, enhances food intake suggesting that an endogenous tone of satiety mediating GLP-1 exists in central pathways mediating body weight homeostasis (Meeran, Endocrinology 199:140:244-250). In a human study, continuous infusion of GLP-1 to type 2 diabetic patients gave rise to marked improvement of glycaemic control and caused moderate yet non-significant weight loss (Zander, Lancet 2002: 359, 824-830). The site of the anorectic action of peripherally administered GLP-1 is unknown but participation of both central and peripheral sites in GLP-1 are likely, because a recent study has shown that radiolabelled GLP-1 readily gains access to the central nervous system (Hassan, Nucl Med Biol 1999:26:413-420). The nucleus of the solitary tract is situated adjacent to the blood brain barrier free area postrema, and other studies using radio-labelled neuropeptides have shown that peripheral administration of neuropeptides gain access both to the area postrema as well as the adjacent subpostreme regions including the dorsal vagal complex (Whitcomb Am J Phys 1990: 259:G687-G691). Thus, it is likely that peripherally administered GLP-1 enters the nucleus of the solitary tract with resulting impact on ascending neurones involved in regulation of food intake. Interaction of GLP-1 with vagal afferents from the gastrointestional tract should also be considered as mediator of its anorectic actions because transection of the vagus nerve renders the stomach of anaesthetised pigs insensitive to the akinetic actions of intravenously administered GLP-1 (Wettergren, Am J Phys 1998:275:984-992). Probably both vagal afferents and GLP-1 receptors accessible from the periphery are responsible for the anorexia induced by GLP-1, because we have seen that bilateral subdiaphragmatic vagotomy on rats carrying the anorectic GLP-1 producing tumour has no impact on the development of anorexia (Jensen, JCI 1998: 101:503-510). Last, GLP-1 has been shown to inhibit intake of different kinds of food, both rich in fat and in carbohydrate (Bjenning, Diabetes Res and Clin Prac 2000:50(1):S386).
Despite this in-dept knowledge it as never been described that a GLP-1 agonist has the effect of specifically modifying the intake of food associated with an unhealthy western world lifestyle. This effect could be useful in the treatment of all kinds of disorders linked to an increased intake of sweet or fat food.
Earlier studies suggest that seretoninergic drugs effect a selective reduction in the intake of carbohydrate rich food [Wurthman, Neurophsycopharmacology, 1993, 9, 201-210].