male syrian hamsters known to develop insulin resistance and glucose intolerance were purchased at 4 weeks of age and kept on rodent diet for 10 weeks at 72 degrees f . and a 14 hr : 10 hr daily light : dark cycle . when animals were 14 weeks of age on this daily photoperiod ( known to be insulin resistant and glucose intolerant under these conditions ), bromocriptine mesylate was administered intraperitoneally ( ip ) for 2 weeks at 4 mg / kg per hamster 13 hours after light onset to half of the animals , while the other half received vehicle injections for 2 weeks . after 2 weeks of treatment both bromocriptine and vehicle groups were divided into two groups for a total of 4 groups : 1 . vehicle for 2 weeks and vehicle at initiation of a glucose tolerance test ( gtt ); 2 . vehicle for 2 weeks and exendin - 4 at initiation of the gtt ; 3 . bromocriptine for 2 weeks and vehicle at gtt ; 4 . bromocriptine for 2 weeks and exendin - 4 at gtt . glucose tolerance test was performed among all 4 study groups on day 15 of the study by challenge with 3 g / kg body weight of glucose at 7 hours after light onset among each of the 4 treatment groups —( bromocriptine or vehicle treatment for 2 weeks and with ip injection of either vehicle or 4 μg / kg of exendin - 4 , a glp - 1 analog [ sigma chemical , st louis , mo .] dissolved in saline ) at the gtt . also , an additional group of hamsters treated with vehicle for 2 weeks received exendin - 4 on the day of gtt at 8 μg / kg . blood was drawn from the jugular vein and blood glucose level was measured every 30 minutes for 2 hours after the glucose load administration . in a similarly designed experiment among 4 groups of animals , insulin was injected ip at 240 ng / kg in place of exendin - 4 as the first phase insulin secretagogue ( fpis ). 494 obese type 2 diabetes subjects who were poorly controlled on a sulphonylurea dose that was stable for at least 60 days prior to study initiation were enrolled in a multicentre study , with 244 randomized to treatment with cycloset plus a stabilized dose of currently used sulphonylurea , and 250 randomized to treatment with placebo plus a stabilized dose of currently used sulphonylurea . subjects were admitted to a clinical research center one week prior and 24 weeks after the start of cycloset administration and administered standardized meals at breakfast lunch and dinner . one - hour postprandial plasma insulin and glycated hemoglobin a1c ( hba1c ) ( a measure of glycemic control ) were measured one week prior and 24 weeks after the start of cycloset administration . cycloset induced improvements in hba1c relative to placebo were analyzed as a function of the baseline 1 - hour postprandial insulin level in the study subjects . timed bromocriptine administration for 2 weeks did not statistically significantly reduced blood glucose area under curve ( auc ) during the gtt over two hours after glucose administration ( 21 % reduction , p & lt ; 0 . 09 ). likewise exendin - 4 immediately prior to glucose administration at either 4 ug / kg or 8 ug / kg did not statistically significantly reduced blood glucose area under curve ( auc ) during the gtt over two hours after glucose administration ( 19 % and 27 % reduction , p = 0 . 23 and p = 0 . 13 respectively ). however , in animals that were treated both with bromocriptine for 2 weeks and received exendin - 4 at 4 ug / kg prior to gtt initiation a statistically significant decrease of glucose auc of 60 % was observed ( p & lt ; 0 . 0002 ). thus no statistically significant effect of either the dopamine agonist treatment or of the first - phase insulin secretagogue on glucose intolerance was observed , yet the combination of the two produced a marked improvement in glucose intolerance , the numerical value of which was 50 % greater than the addition of the two drug effects separately and also more than double the effect of doubling the dose of exendin - 4 ( p = 0 . 05 ). even when viewed in these terms , a 50 % reduction in the gtt auc represents a robust improvement in relative glucose intolerance ( ceriello a et al nutr metab cardiovasc dis 16 : 453 - 6 , 2006 ; abdul - ghani m a et al , diabetes care 32 : 281 - 86 , 2009 ). this synergistic effect of these agents ( 0 + 0 = marked effect ) allows for the lowering of the first - phase insulin secretagogue ( fpis ) dose and yet to achieve better results when combined with a centrally acting dopamine agonist ( as evidenced by the result that 2 × the exendin - 4 dose did not produce any benefit to glucose intolerance and was not even half the numerical effect of the dopamine agonist / half fpis dose on glucose intolerance ). the lowering of the fpis allows for reducing its side effects and strain on the beta cell ( beta cell exhaustion ) which is beneficial to the treated subject . in a similarly designed experiment as above but replacing the fpis from exendin - 4 to exogenous insulin itself , glucose auc over two hours after such glucose administration was not significantly reduced by 2 weeks of treatment with bromocriptine ( 28 % reduction , p = 0 . 23 ) or by insulin administration immediately prior to glucose administration ( p = 0 . 64 ). however , animals that were both treated with bromocriptine for 2 weeks and received insulin prior to the gtt exhibited a decrease of glucose auc of 55 % ( p = 0 . 014 ). once again , the combination of a fpis ( insulin ) plus a central acting dopamine agonist produces an effect much greater than the sum of the individual treatments as each were ineffective in producing any beneficial result . once again , even when viewed in numerical terms irrespective of statistical significance , the combination produced a reduction in glucose intolerance of 50 % greater than the addition of each therapy alone which as stated above is a marked improvement in glucose intolerance with demonstrable health benefits . the observation that this synergism is achieved with 2 markedly different fpis molecules that share only the ability to increase plasma insulin level after a meal when administered prior to the meal indicates that this is a class phenomenon and not something particular to the fpis agents employed . previously it has been demonstrated that various agents that increase central dopaminergic activity all improve metabolic disorders , again indicating that the phenomenon , in a general sense , is not molecule specific , but rather a class effect . therefore , this synergism may be fully expected to be a class interaction synergism . inasmuch as meals for humans are typically 3 times per day , it is possible to reduce this combination synergistic therapeutic for metabolic disorders to a once - daily dosing by preparing long acting fpis with short acting agents that increase central dopaminergic activity at specific time of day only in unique dosage forms . such dosage forms provide the benefit of the synergism , allow for the maximal effect of the dopamine stimulation by timing it to the appropriate time of day , and provide for convenience of use ( only a single administration per day ). such dosage forms may take the form of non - oral or oral routes of administration . the average 1 - hour postprandial plasma insulin level was 50 μu / ml in both cycloset and placebo treated groups at the start of the study ; incoming hba1c was 9 . 4 % and 9 . 5 % respectively . in the cycloset treated group hba1c was reduced by 0 . 3 % over 24 weeks of treatment , while hba1c went up by 0 . 26 % in the placebo arm ( p & lt ; 0 . 0001 ). for subjects with incoming 1 - hour postprandial insulin & lt ; 30 uu / ml there was no effect of cycloset on hba1c , for subjects with incoming 1 - hour postprandial & gt ; 30 uu / ml and & lt ; 50 uu / ml the cycloset effect was − 0 . 57 ( p & lt ; 0004 ) and among subjects with incoming 1 - hour postprandial insulin & gt ; 50 μu / ml the cycloset effect on hba1c was − 0 . 79 ( p & lt ; 0 . 0001 ). these results indicate that the effect of the dopamine agonist to improve glycemic control in t2d subjects is positively correlated with 1 - hour postprandial insulin level in the subjects supporting the concept that the combination of an agent that increases central dopaminergic activity with a fpis will produce synergistic improvements in glucose metabolism . moreover the collective results of these animal and human studies indicate that pharmaceutical agents that preserve pancreatic beta cell function per se , i . e ., retard the loss of appropriate beta cell insulin responsiveness to meal glucose ( and as such improve postprandial insulin secretory response to glucose ) such as thiazolidinediones and glucagon like peptide 1 analogs , will also synergize with agents that increase central dopaminergic activity to improve metabolic disorders and produce long lasting benefit on glycemic control ( e . g ., for a year or more ). this combination of therapies for the treatment of metabolic disorders is also envisioned by this invention as well . exendin - 4 , a 39 amino acid peptide , originally isolated from heloderma suspectum ( gila monster lizard ) venom , activates glp - 1 ( glucagon - like peptide - 1 ) receptors to increase intracellular camp in pancreatic acinar cells . synthetic exendin - 4 is also known as exenatide , or byetta ; its molecular weight is : 4187 . glp - 1 is a gastrointestinal hormone , which regulates blood glucose primarily by stimulating glucose - dependent insulin release ( first phase insulin secretion ). exendin - 4 is a high affinity glucagon - like peptide 1 ( glp - 1 ) receptor agonist ( kd = 136 μm ). exendin - 4 is a long - acting agonist of the glp - 1 receptor . exenatide has comparable potency to glp - 1 and is resistant to degradation by dpp - iv . exenatide improves glycemic control primarily by reducing postprandial hyperglycemia . exendin - 4 dose used in this study is comparable to the dose used in the studies reported by strauss et al ., 2008 and nachnani et al ., 2010 . cervera et al ., ( 2008 ) mechanism of action of exenatide to reduce postprandial hyperglycemia in type 2 diabetes . am j physiol endocrinol metab 294 : e846 - e852 . eng , j . et al ., ( 1992 ) isolation and characterization of exendin - 4 an exendin - 3 analogue from heloderma suspectum venom . j . biol . chem . 267 , 7402 . goke et al ( 1993 ) exendin - 4 is a high potency agonist and truncated exendin -( 9 - 39 )- amide an antagonist at the glucagon - like peptide 1 -( 7 - 36 )- amide receptor of insulin - secreting b - cells . j . biol . chem . 268 19650 . nachnani j . et al ., ( 2010 ) biochemical and histological effects of exendin - 4 ( exenatide ) on the rat pancreas . diabetologia 53 : 153 - 159 . thorens et al ( 1993 ) cloning and functional expression of the human islet glp - 1 receptor . diabetes 42 1678 . strauss a . et al ., ( 2008 ) exendin - 4 improves the oral glucose tolerance in diabetic rats : pancreas regeneration , better function of pancreatic islets , or impaired glucose uptake ? transplantation proceedings , 40 , 533 - 535
the present invention is directed to a method of treating a metabolic disorder or key elements of a metabolic disorder such method comprising the use of an agent that increases central dopaminergic activity plus a first - phase insulin secretagouge .