PRIMARY:~In patients with type 2 diabetes with inadequate glycemic control on diet and exercise after 6 weeks of treatment:~Objective: To assess the effects of co-administration of sitagliptin and metformin compared to placebo on hepatic glucose production (HGP).~Hypothesis: After 6 weeks of treatment, the co-administration of sitagliptin and metformin provides greater reduction in hepatic glucose production (HGP) compared to placebo.~SECONDARY:~In patients with type 2 diabetes with inadequate glycemic control on diet and exercise after 6 weeks of treatment:~Objective: To assess the effects of co-administration of sitagliptin and metformin compared to placebo on post-meal glucose during meal tolerance test (MTT).~Hypothesis: After 6 weeks of treatment the co-administration of sitagliptin and metformin provides greater reduction in the total glucose AUC (0-6 hr) during MTT compared to placebo.~Objective: To assess the effects of co-administration of sitagliptin and metformin compared to placebo on fasting plasma glucose (FPG).~Hypothesis: After 6 weeks of treatment the co-administration of sitagliptin and metformin provides greater reduction in FPG compared to placebo.~Objective: To assess the effects sitagliptin alone compared to placebo on HGP. Hypothesis: After 6 weeks of treatment, sitagliptin alone provides greater reduction in HGP compared to placebo~EXPLORATORY OBJECTIVES:~(i) Objective: after 6 weeks of treatment, to assess the effects co-administration of sitagliptin and metformin compared to placebo on:~active and inactive incretin concentrations (fasting and post-meal GLP-1 and fasting and post-meal GIP).~glucagon concentration (fasting and post-meal).~parameters of insulin secretion and insulin sensitivity.~splanchnic glucose uptake.~(ii) Objective: after 6 weeks of treatment, to assess the effects co-administration of sitagliptin and metformin compared to treatment with sitagliptin alone and metformin alone on:~glucose concentration (fasting and total glucose AUC [0-6 hr]).~active and inactive incretin concentrations (fasting and post-meal GLP-1 and fasting and post-meal GIP).~glucagon concentration (fasting and post-meal).~parameters of insulin secretion and insulin sensitivity.~HGP.~splanchnic glucose uptake. (iii) Objective: after 6 weeks of treatment, to assess the effects of sitagliptin alone and metformin alone compared to placebo on:~glucose concentration (fasting and total glucose AUC [0-6 hr]).~active and inactive incretin concentrations (fasting and post-meal GLP-1 and fasting and post-meal GIP).~glucagon concentration (fasting and post-meal).~parameters of insulin secretion and insulin sensitivity.~HGP.~splanchnic glucose uptake.
In patients with type 2 diabetes with inadequate glycemic control on diet and exercise after 6 weeks of treatment:~Objective: To assess the effects of co-administration of sitagliptin and metformin compared to placebo on hepatic glucose production (HGP).~Hypothesis: After 6 weeks of treatment, the co-administration of sitagliptin and metformin provides greater reduction in hepatic glucose production (HGP) compared to placebo.