Abstract
Background and AimsGlucagon-like peptide-1 (GLP-1) may provide beneficial cardiovascular effects, possibly due to enhanced myocardial energetic efficiency by increasing myocardial glucose uptake (MGU). We assessed the effects of GLP-1 on MGU in healthy subjects during normo- and hypoglycemia.Materials and MethodsWe included eighteen healthy men in two randomized, double-blinded, placebo-controlled cross-over studies. MGU was assessed with GLP-1 or saline infusion during pituitary-pancreatic normo- (plasma glucose (PG): 4.5 mM, n = 10) and hypoglycemic clamps (PG: 3.0 mM, n = 8) by positron emission tomography with 18fluoro-deoxy-glucose (18F-FDG) as tracer.ResultsIn the normoglycemia study mean (± SD) age was 25±3 years, and BMI was 22.6±0.6 kg/m2 and in the hypoglycemia study the mean age was 23±2 years with a mean body mass index of 23±2 kg/m2. GLP-1 did not change MGU during normoglycemia (mean (+/− SD) 0.15+/−0.04 and 0.16+/−0.03 µmol/g/min, P = 0.46) or during hypoglycemia (0.16+/−0.03 and 0.13+/−0.04 µmol/g/min, P = 0.14). However, the effect of GLP-1 on MGU was negatively correlated to baseline MGU both during normo- and hypoglycemia, (P = 0.006, r2 = 0.64 and P = 0.018, r2 = 0.64, respectively) and changes in MGU correlated positively with the level of insulin resistance (HOMA 2IR) during hypoglycemia, P = 0.04, r2 = 0.54. GLP-1 mediated an increase in circulating glucagon levels at PG levels below 3.5 mM and increased glucose infusion rates during the hypoglycemia study. No differences in other circulating hormones or metabolites were found.ConclusionsWhile GLP-1 does not affect overall MGU, GLP-1 induces changes in MGU dependent on baseline MGU such that GLP-1 increases MGU in subjects with low baseline MGU and decreases MGU in subjects with high baseline MGU. GLP-1 preserves MGU during hypoglycemia in insulin resistant subjects.ClinicalTrials.gov registration numbers: NCT00418288: (hypoglycemia) and NCT00256256: (normoglycemia).
Highlights
Type 2 diabetes (T2D) is estimated to affect approximately 400 million people before 2030 [1]
The effect of glucagon-like peptide-1 (GLP-1) on myocardial glucose uptake (MGU) was negatively correlated to baseline MGU both during normo- and hypoglycemia, (P = 0.006, r2 = 0.64 and P = 0.018, r2 = 0.64, respectively) and changes in MGU correlated positively with the level of insulin resistance (HOMA 2IR) during hypoglycemia, P = 0.04, r2 = 0.54
GLP-1 mediated an increase in circulating glucagon levels at plasma glucose (PG) levels below 3.5 mM and increased glucose infusion rates during the hypoglycemia study
Summary
Type 2 diabetes (T2D) is estimated to affect approximately 400 million people before 2030 [1]. Because patients with T2D have elevated circulating free fatty acids (FFA) they have increased beta oxidation of FFAs at the expense of reduced glucose oxidation. The glucagon-like peptide-1 (GLP-1) receptor agonists are validated anti-diabetic medications. They mimic a range of physiological actions of native GLP-1 on glucose metabolism including stimulation of insulin secretion, inhibition of glucagon secretion, inhibition of gastric emptying and reduction of appetite and food intake [7]. Native GLP-1 and GLP-1 analogues are reported to have several significant cardiovascular effects providing the opportunity to address the multifactorial issues involved in increased mortality and morbidity associated with T2D as well as in patients with cardiac disease and no diabetes [8]. Glucagon-like peptide-1 (GLP-1) may provide beneficial cardiovascular effects, possibly due to enhanced myocardial energetic efficiency by increasing myocardial glucose uptake (MGU). We assessed the effects of GLP-1 on MGU in healthy subjects during normo- and hypoglycemia
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