[Comparison of non-glucose versus glucose stimulation test in estimating islet β-cell function in individuals with differential glucose tolerance].

OBJECTIVE: To explore the values of arginine stimulation, oral glucose-insulin release and intravenous glucose tolerance tests to assess the function of islet β-cell in individuals with differential glucose tolerance.

METHODS: Healthy subjects (n = 38) and those with impaired glucose regulation (IGR) without a family history of diabetes (n = 31), 32 normal glucose tolerance (NGT, n = 32) and impaired glucose regulation as first-degree relatives of type 2 diabetes mellitus (DM) (IGR, n = 36) and 35 newly-diagnosed type 2 DM (n = 35) were recruited. All of them received arginine C-peptide releasing test (AST), oral glucose-insulin release test (OG-IRT) and intravenous glucose tolerance test (IVGTT). ACRARG was used to reflect non-glucose stimulated insulin secretion function, AIR0-10 for first-phase insulin secretion function and ΔI30/ΔG30 for early insulin secretion function. The changes of islet-β-cell function indicators were detected in individuals with different glucose tolerance.

RESULTS: (1) No significant differences existed in ACRARG among five groups (all P > 0.05). (2) In terms of AIR0-10, the patients of type 2 DM had lower levels than those with IGR and NGT with or without a family history of DM (all P < 0.01). No significant difference existed among the subjects of IGR regardless of a family history of DM (P > 0.05). However, the subjects of IGR with or without a family history of DM had lower levels than those with NGT regardless of a family history of DM (P < 0.01 or P < 0.05). The subjects of NGT with a family history of DM had lower levels than those with NGT without a family history of DM (50.0 (24.3 - 85.1) vs 69.4 (46.1 - 94.8), P < 0.05). (3) ΔI30/ΔG30: no significant difference existed between the patients of type 2 DM and IGT with a family history of DM (P > 0.05). However, the subjects of type 2 DM had lower levels than those of IGR without a family history of DM and NGT with or without a family history of DM (all P < 0.01). The subjects of IGR with or without a family history of DM had lower levels than those with NGT regardless of a family history of DM (all P < 0.01). No significant difference existed among the subjects of NGT with or without a family history of DM (P > 0.05). And it was the same with IGR group.

CONCLUSION: The acute C-peptide response to arginine stimulation test may not be used to evaluate the early phase insulin secretion among the subjects of early-stage DM, impaired glucose regulation and high diabetic risks.