Endocrine Abstracts

Introduction

Glucagon-like peptide-1 (GLP-1) plays an important role in the pathophysiology of type 2 diabetes mellitus (T2DM). However, results from previous studies on the GLP-1 secretory responses in individuals with different glucose tolerance states remain controversial. This may be contributed by the heterogeneous characteristics of the patients recruited.

Aim

To examine whether GLP-1 secretion is affected by any of the demographic or metabolic parameters in 3 ethnic groups of Malaysian cohort.

Methods

In this cross sectional study, 171 subjects consisting of Malays, Chinese and Indians, were divided into normal glucose tolerance (NGT) (n = 57), prediabetes (n = 54) and T2DM (n = 60) after undergoing a 75 g oral glucose tolerance test (OGTT). Plasma total GLP-1 concentrations were measured at 0, 30 and 120 min during OGTT. As an index of GLP-1 secretory response, area under the curve (AUC) of GLP-1 (AUC_GLP-1) was calculated by trapezoidal rule. Relationships between parameters were examined by using stepwise multiple linear regression analyses.

Results

Using AUC_GLP-1 as a depedent parameter, age, gender, ethnicity, systolic blood pressure (SBP), fasting total cholesterol and fasting triglyceride explained 27% (adjusted r²) of the variation of GLP-1 response following OGTT. There was a strong positive association between increasing age and AUC_GLP-1 (B = 44.81, P <0.001). Male had higher GLP-1 response to OGTT than female (B = -881.49, P = 0.043). Ethnicity was a significant determinant of AUC_GLP-1 with the Indians exhibiting higher GLP-1 secretion than the Malays (B = 932.23, P = 0.005). AUC_GLP-1 was negatively correlated with triglyceride (B = -676.38, P = 0.02). In contrast to our expectation, AUC_GLP-1 was positively associated with increased SBP (B = 16.08, P = 0.039) and total cholesterol (B = 571.57, P = 0.031). No association was detected between AUC_GLP-1 and body mass index, waist circumference, HbA1c, fasting insulin and fasting glucose.

Conclusions

In Malaysian cohort, older age, male and Indians had higher GLP-1 responses following OGTT. These demographic factors need to be taken into account when studying GLP-1 secretory responses between T2DM patients and healthy controls. Subjects with increased fasting triglyceride level had lower GLP-1 responses. The positive relationship between GLP-1 response and risk factors which increase insulin resistance such as high total cholesterol and increased SBP might involve an adaptive response and require further study.