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Open access

Dorte Glintborg, Hanne Mumm, Jens Juul Holst and Marianne Andersen

Context

Insulin resistance in polycystic ovary syndrome (PCOS) may increase the risk of reactive hypoglycaemia (RH) and decrease glucagon-like peptide-1 (GLP-1) secretion. The possible effects of treatment with oral contraceptives (OCP) and/or metformin on GLP-1 secretion and risk of RH in PCOS is undetermined.

Setting

Outpatient clinic.

Patients and interventions

Randomized, controlled clinical trial. Ninety women with PCOS were randomized to 12-month treatment with OCP (150 mg desogestrel + 30 mg ethinylestradiol), metformin (2 g/day) or metformin + OCP. Five-hour oral glucose tolerance tests (5-h OGTT) measuring fasting and area under the curve (AUC) for GLP-1, glucose, insulin and C-peptide were performed before and after the intervention period. Sixty-five women completed the study and 34 weight-matched healthy women were included as controls.

Main outcome measures

Changes in GLP-1, glucose, insulin and C-peptide during 5-h OGTT.

Results

Fasting GLP-1 levels increased during metformin + OCP vs OCP treatment, whereas AUC GLP-1 levels were unchanged during medical treatment. The prevalence of reactive hypoglycemia increased from 9/65 to 14/65 after intervention (P < 0.01) and was more common after treatment with metformin + OCP (increase from 3/23 to 6/23, P = 0.01). Reactive hypoglycaemia was associated with higher insulin and C-peptide levels during 5-h OGTT, but was unassociated with BMI and AUC GLP-1. GLP-1 levels were comparable in PCOS vs controls. AUC GLP-1 levels were significantly lower in obese vs lean patients and were inversely associated with BMI.

Conclusions

AUC GLP-1 levels were unchanged during treatment. Increased risk of hypoglycemia during metformin + OCP could be associated with increased insulin secretion.

Open access

Jeppe Skov, Jens Juul Holst, Jens Peter Gøtze, Jørgen Frøkiær and Jens Sandahl Christiansen

The antihypertensive actions of glucagon-like peptide-1 (GLP1) receptor agonists have been linked to the release of atrial natriuretic peptide (ANP) in mice. Whether a GLP1–ANP axis exists in humans is unknown. In this study, we examined 12 healthy young males in a randomized, controlled, double-blinded, single-day, cross-over study to evaluate the effects of a 2-h native GLP1 infusion. Plasma proANP concentrations were measured by an automated mid-region-directed proANP immunoassay and N-terminal pro B-type natriuretic peptide (BNP) on Roche Modular E170. Urine was collected for measurements of sodium excretion. Although GLP1 infusion increased the urinary sodium excretion markedly, there were no significant changes in either proANP or proBNP concentrations. When GLP1 infusion was stopped, sodium excretion declined rapidly. As proANP concentration reflects ANP secretion, our data could not confirm the existence of a GLP1–ANP axis in humans. Especially, the natriuretic effects of GLP1 seem unlikely to be mediated exclusively via ANP.

Open access

Meena Asmar, Ali Asmar, Lene Simonsen, Flemming Dela, Jens Juul Holst and Jens Bülow

Glucose-dependent insulinotropic polypeptide (GIP) in combination with hyperinsulinemia increase blood flow and triglyceride clearance in subcutaneous abdominal adipose tissue in lean humans. The present experiments were performed to determine whether the increase involves capillary recruitment. Eight lean healthy volunteers were studied before and after 1-h infusion of GIP or saline during a hyperglycemic-hyperinsulinemic clamp, raising plasma glucose and insulin to postprandial levels. Subcutaneous abdominal adipose tissue blood flow (ATBF) was measured by the 133Xenon clearance technique, and microvascular blood volume was determined by contrast-enhanced ultrasound imaging. During infusion of saline and the clamp, both ATBF (2.7 ± 0.5 ml/min, 100 g/tissue) and microvascular blood volume remained unchanged throughout the experiments. During GIP infusion and the clamp, ATBF increased ~fourfold to 11.4 ± 1.9 ml/min 100 g/tissue, P<0.001. Likewise, the contrast-enhanced ultrasound signal intensity, a measure of the microvascular blood volume, increased significantly one hour after infusion of GIP and the clamp (P=0.003), but not in the control experiments. In conclusion, the increase in ATBF during GIP infusion involves recruitment of capillaries in healthy lean subjects, which probably increases the interaction of circulating lipoproteins with lipoprotein lipase, thus promoting adipose tissue lipid uptake.