Systemic Administration of the Long-Acting GLP-1 Derivative NN2211 Induces Lasting and Reversible Weight Loss in Both Normal and Obese Rats

Philip J. Larsen 1 2 Christian Fledelius 0 Lotte Bjerre Knudsen 3 Mads Tang-Christensen 2 0 Pharma- cological Research 2 1 Neuroendocrine Pharmacology 2 Laboratory of Obesity Research, Center for Clinical and Basic Research , Ballerup , Denmark 3 Molecular Pharmacology, Novo Nordisk A/S, Copenhagen, Denmark. Laboratory of Obesity Research, Centre for Clinical and Basic Research , Ballerup Byvej 222, 2750 Ballerup , Denmark Postprandial release of the incretin glucagon-like peptide-1 (GLP-1) has been suggested to act as an endogenous satiety factor in humans. In rats, however, the evidence for this is equivocal probably because of very high endogenous activity of the GLP-1 degrading enzyme dipeptidyl peptidase-IV. In the present study, we show that intravenously administered GLP-1 (100 and 500 g/kg) decreases food intake for 60 min in hungry rats. This effect is pharmacologically specific as it is inhibited by previous administration of 100 g/kg exendin(9-39), and biologically inactive GLP-1(1-37) had no effect on food intake when administered alone (500 g/kg). Acute intravenous administration of GLP-1 also caused dose-dependent inhibition of water intake, and this effect was equally well abolished by previous administration of exendin(9-39). A profound increase in diuresis was observed after intravenous administration of both 100 and 500 g/kg GLP-1. Using a novel longacting injectable GLP-1 derivative, NN2211, the acute and subchronic anorectic potentials of GLP-1 and derivatives were studied in both normal rats and rats made obese by neonatal monosodium glutamate treatment (MSG). We showed previously that MSG-treated animals are insensitive to the anorectic effects of centrally administered GLP-1(7-37). Both normal and MSGlesioned rats were randomly assigned to groups to receive NN2211 or vehicle. A single bolus injection of NN2211 caused profound dose-dependent inhibition of overnight food and water intake and increased diuresis in both normal and MSG-treated rats. Subchronic multiple dosing of NN2211 (200 g/kg) twice daily for 10 days to normal and MSG-treated rats caused profound inhibition of food intake. The marked decrease in food intake was accompanied by reduced body weight in both groups, which at its lowest stabilized at 85% of initial body weight. Initial excursions in water intake and diuresis were transient as they were normalized within a few days of treatment. Lowered plasma levels of triglycerides and leptin were observed during NN2211 treatment in both normal and MSG-treated obese rats. - In a subsequent study, a 7-day NN2211 treatment period of normal rats ended with measurement of energy expenditure (EE) and body composition determined by indirect calorimetry and dual energy X-ray absorptiometry, respectively. Compared with vehicle-treated rats, NN2211 and pair-fed rats decreased their total EE corresponding to the observed weight loss, such that EE per weight unit of lean body mass was unaffected. Despite its initial impact on body fluid balance, NN2211 had no debilitating effects on body water homeostasis as confirmed by analysis of body composition, plasma electrolytes, and hematocrit. This is in contrast to pair-fed animals, which displayed hemoconcentration and tendency toward increased percentage of fat mass. The present series of experiments show that GLP-1 is fully capable of inhibiting food intake in rats via a peripherally accessible site. The loss in body weight is accompanied by decreased levels of circulating leptin indicative of loss of body fat. The profound weight loss caused by NN2211 treatment was without detrimental effects on body water homeostasis. Thus, long-acting GLP-1 derivatives may prove efficient as weight-reducing therapeutic agents for overweight patients with type 2 diabetes. Diabetes 50:2530 2539, 2001 Pmans, but the underlying mechanisms that eripheral administration of glucagon-like peptide-1 (GLP-1) acutely affects food intake in hudecrease food intake concomitant with earlier onset of subjective sensation of fullness are not fully understood (1 4). The anorectic effects of continuous intravenous administration of GLP-1 are present in individuals who are lean or obese or have type 2 diabetes (1,3,4), suggesting that the observed effects are part of a physiologically relevant meal-terminating system. Results from similar experiments in rats have been ambiguous, probably because of high activity of GLP-1 degrading enzyme dipeptidyl peptidase-IV (DPP-IV) (5,6). Thus, early experiments were unable to demonstrate peripheral effects of intraperitoneal GLP-1 injections on feeding behavior (7,8), whereas later experiments have shown significant but short-lasting anorectic effects of subcutaneous administration of GLP-1 (9). Anorexia induced by peripheral administration of GLP-1 involves vagal control of gastric motility (10,11). Central administration of 13 g of GLP-1 specifically inhibits food intake in rats via a hypothalamic site that is sensitive to neonatal monosodium glutamate (MSG) lesioning (12). However, central administration of slightly higher doses of GLP-1 leads to taste aversion, but because this latter effect is unaffected by MSG treatment, it further stresses the specificity of the central GLP-1induced anorexia (12). In addition, it is possible to elicit anorexia without concomitant taste aversion if GLP-1 is injected directly into the hypothalamic paraventricular nucleus (13). Acute injections of both GLP-1 and NN2211 exerts profound adipsia and diuresis. These effects on body water homeostasis could potentially hamper long-term treatment of patients with type 2 diabetes with GLP-1 agonists, and the potential anorectic effects of these agonists may be accompanied with debilitating affects on body water homeostasis. Given that peripheral administration of GLP-1 affects food intake in humans, we decided to study further the anorectic potential of this peptide in the laboratory rat. Dose-response studies investigating the effect of intravenously administered GLP-1(7-37) or a novel long-acting acylated GLP-1 derivative NN2211 (14) on food intake were performed. In continuation of acute pharmacological studies, we examined the effect on food intake and body weight of twice daily subcutaneous administration of NN2211 for 10 days followed by a 5-day recovery period. To study the impact of 7 days of NN2211 treatment on energy expenditure (EE) and body composition, we studied normal rats by indirect calorimetry and subsequently subjected them to dual energy X-ray absorptiometry (DEXA) scanning. Before, during, and after treatment, blood biochemical markers of energy and fluid homeostasis metabolic state were monitored. RESEARCH DESIGN AND METHODS Animals. All experiments were carried out on male Wistar rats. Normal male rats arrived at the animal facilities 2 weeks before experimentation, and until use, animals were housed three to four per cage under standard laboratory conditions (12:12 light:dark cycle, l (...truncated)