Robust anti-obesity and metabolic effects of a dual GLP-1/glucagon receptor peptide agonist in rodents and non-human primates.

AIMS: To characterize the pharmacology of MEDI0382, a peptide dual agonist of glucagon-like peptide-1 (GLP-1) and glucagon receptors. MATERIALS AND METHODS: MEDI0382 was evaluated in vitro for its ability to stimulate cAMP accumulation in cell lines expressing transfected recombinant or endogenous GLP-1 or glucagon receptors, to potentiate glucose-stimulated insulin secretion (GSIS) in pancreatic ß-cell lines and stimulate hepatic glucose output (HGO) by primary hepatocytes. The ability of MEDI0382 to reduce body weight and improve energy balance (i.e. food intake and energy expenditure), as well as control blood glucose, was evaluated in mouse models of obesity and healthy cynomolgus monkeys following single and repeated daily subcutaneous administration for up to 2 months. RESULTS: MEDI0382 potently activated rodent, cynomolgus and human GLP-1 and glucagon receptors and exhibited a fivefold bias for activation of GLP-1 receptor versus the glucagon receptor. MEDI0382 produced superior weight loss and comparable glucose lowering to the GLP-1 peptide analogue liraglutide when administered daily at comparable doses in DIO mice. The additional fat mass reduction elicited by MEDI0382 probably results from a glucagon receptor-mediated increase in energy expenditure, whereas food intake suppression results from activation of the GLP-1 receptor. Notably, the significant weight loss elicited by MEDI0382 in DIO mice was recapitulated in cynomolgus monkeys. CONCLUSIONS: Repeated administration of MEDI0382 elicits profound weight loss in DIO mice and non-human primates, produces robust glucose control and reduces hepatic fat content and fasting insulin and glucose levels. The balance of activities at the GLP-1 and glucagon receptors is considered to be optimal for achieving weight and glucose control in overweight or obese Type 2 diabetic patients.

Dexamethasone counteracts the effect of prolactin on islet function: implications for islet regulation in late pregnancy.

Islets undergo a number of up-regulatory changes to meet the increased demand for insulin during pregnancy, including increased insulin secretion and beta-cell proliferation. It has been shown that elevated lactogenic hormone is directly responsible for these changes, which occur in a phasic pattern, peaking on day 15 of pregnancy and returning to control levels by day 20 (term). As placental lactogen levels remain elevated through late gestation, it was of interest to determine whether glucocorticoids (which increase during late gestation) could counteract the effects of lactogens on insulin secretion, beta-cell proliferation, and apoptosis. We found that insulin secretion measured over 24 h in culture and acute secretion measured over 1 h in response to high glucose were increased at least 2-fold by PRL treatment after 6 days in culture. Dexamethasone (DEX) treatment had a significant inhibitory effect on secretion in a dose-dependent manner at concentrations greater than 1 nM. At 100 nM, a concentration equivalent to the plasma corticosteroid level during late pregnancy, DEX inhibited secretion to below control levels. The addition of DEX (>1 nM) inhibited secretion from PRL-treated islets to levels similar to those produced by DEX treatment alone. Bromodeoxyuridine (10 microM) staining for the final 24 h of a 6-day culture showed that PRL treatment increased cell proliferation 6-fold over the control level. DEX treatment alone (1-1000 nM) did not reduce cell division below the control level, but significantly inhibited the rate of division in PRL-treated islets. YoYo-1, an ultrasensitive fluorescent nucleic acid stain, was added (1 microM; 8 h) to the medium after 1-3 days of culture to examine cell death. Islets examined under confocal microscopy showed that DEX treatment (100 nM) increased the number of cells with apoptotic nuclear morphologies. This was quantified by counting the number of YoYo-labeled nuclei per islet under conventional epifluorescence microscopy. The numbers of YoYo-1-positive nuclei per islet in control and PRL-treated islets were not different after 3 days of culture. However, DEX treatment increased YoYo-1 labeling 7-fold over that in controls. DEX also increased YoYo-1 labeling in PRL-treated islets 3-fold over the control level. These data show that the increased plasma glucocorticoid levels found during the late stages of pregnancy could effectively reverse PRL-induced up-regulation of islet function by inhibiting insulin secretion and cell proliferation while increasing apoptosis.

Role of cAMP in upregulation of insulin secretion during the adaptation of islets of Langerhans to pregnancy.

Islets undergo a number of upregulatory changes to meet the increased demand for insulin during pregnancy, including an increase in glucose-stimulated insulin secretion with a reduction in the stimulation threshold. Treatment with the lactogenic hormone prolactin (PRL) in vitro has been shown to induce changes in islets similar to those observed during pregnancy. We examined cAMP production in islets treated with PRL to determine if changes in cAMP are involved in the upregulation of insulin secretion. Insulin secretion and cAMP concentrations were measured from islets in response to a suprathreshold (6.8 mmol/l) or high (16.8 mmol/l) glucose concentration in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine. Insulin secretion increased by 2.1-, 5.0-, and 5.9-fold at the suprathreshold glucose concentration and by 1.6-, 2.3-, and 2.9-fold at the higher glucose concentration after 1, 3, and 5 days of PRL treatment, respectively. After a similar pattern, cAMP metabolism increased by 1.2-, 1.6-, and 2.1-fold at the suprathreshold glucose concentration and by 1.2-, 1.7-, and 2.2-fold at the high glucose concentration after 1, 3, and 5 days of PRL treatment, respectively. The similar increases in insulin secretion and cAMP concentration suggest that changes in cAMP metabolism are involved in lactogen-induced upregulation of insulin secretion. To gain additional insight into the role of cAMP in the upregulation of islet function after lactogen treatment, we examined the relationship between changes in cAMP concentration and insulin secretion. Under all conditions (differing glucose concentrations and time periods), the increase in insulin release was directly proportional to the increase in cAMP. Thus increased glucose-stimulated insulin secretion from lactogen-treated islets could be accounted for by increased generation of cAMP and did not appear to require any further specific changes in intracellular processes mediated by cAMP. Because the PRL receptor is not directly involved in cAMP metabolism, the lactogen-induced increase in cAMP was most likely due to the increase in glucose metabolism that we have previously demonstrated in PRL-treated islets and in islets during pregnancy.