Sulphonylureas and pregnancy

Safety considerations with pharmacological treatment of gestational diabetes mellitus

The number of women with gestational diabetes mellitus (GDM: diabetes first diagnosed in pregnancy) continues to grow, as do the associated risks of antenatal and postnatal complications and the chance of future diabetes and obesity in both mother and offspring. Recent randomised controlled trials have demonstrated clear benefits for intensive management of GDM using lifestyle modification, self blood glucose monitoring, close clinical supervision and, where glycaemia remains inadequately controlled, insulin therapy. More recently, metformin and glibenclamide have been shown to adequately reduce hyperglycaemia as part of a stepped approach to GDM management, with a switch to insulin therapy where necessary. Other oral medications have not been shown to be safe in pregnancy. Human insulin therapy is safe within the limits of hypoglycaemia and weight gain. Most insulin analogues are also now considered safe for use in pregnancy (insulin lispro, aspart and detemir). Metformin therapy is oral, and therefore preferred to insulin, but is associated with more gastrointestinal adverse effects, although not hypoglycaemia or weight gain. Conversely, glibenclamide is also an oral therapy but is associated with hypoglycaemia and weight gain. However, metformin crosses the placenta and it remains unclear whether glibenclamide crosses the placenta or not: long-term risks have not been shown, and are thought to be minimal, but further studies are needed. Metformin is seen by some as the treatment of choice where weight gain is an issue, providing that the unanswered questions over the long-term safety of oral agents have been discussed.

Role of ATP-sensitive potassium channels in normal and hypertension-associated pregnancy in rats

1. Activation of vascular ATP-sensitive K(+) (K(ATP)) channels has been implicated in vasodilator responses to pregnancy. 2. The effect of glibenclamide, a K(ATP) channel inhibitor, on systolic blood pressure (SBP) and renal function was evaluated in pregnant and non-pregnant spontaneously hypertensive rats, as well as in normotensive and hypertensive Wistar rats that had been made hypertensive by simultaneous treatment with N(G)-nitro-l-arginine methyl ester (0.4 mg/mL) and indomethacin (2 mg/kg, i.p.) from Day 1 of gestation. Pregnant animals received 10 mg/kg glibenclamide for 12 days starting at Day 7. In addition, the mRNA levels of the vascular K(ATP) channel (Kir6.2) were estimated in aorta and kidney using real-time reverse transcription-polymerase chain reaction on Day 19 of pregnancy. 3. The decreased SBP observed in pregnant Wistar rats was paralleled by an increase in Kir6.2 mRNA levels. Glibenclamide blunted systemic vasodilation and reduced the mRNA expression of Kir6.2. There was no pregnancy induced vasodilation and no change in Kir6.2 mRNA expression in SHR. Glibenclamide had no effect on pregnant SHR. Hypertensive Wistar rats exhibited high SBP, followed by increased Kir6.2 mRNA levels. The effects of glibenclamide were not evaluated in this group because glibenclamide induced intense vaginal bleeding. 4. The results of the present study suggest that K(ATP) channels may be involved in pregnancy induced vasodilation during normotensive pregnancy, but not in pregnant SHR. Glibenclamide may have an abortive effect if administered during the early phases of gestation or in association with nitric oxide and prostaglandin inhibitors.

Recent advances in the treatment of gestational diabetes

Despite four decades of research there is a lack of international consensus on the screening, diagnosis, treatment and follow up of gestational diabetes mellitus (GDM). Currently, GDM is managed by diet modification, exercise and exogenous human insulin. During the last decade, several insulin analogues and oral antihyperglycaemic drugs have revolutionised the management of diabetes mellitus in non-pregnant women. Most of these recent drugs still remain investigational in GDM due to concerns about their safety in pregnancy. This review will focus primarily on the pharmacological treatment of GDM. It will objectively assess the value of these exciting new drugs in pregnancy as they could potentially benefit every woman with GDM.

Tolbutamide alters glucose transport and metabolism in the embryonic mouse heart

BACKGROUND

Tolbutamide is a sulfonylurea oral hypoglycemic agent widely used for the treatment of non insulin-dependent diabetes mellitus. Tolbutamide produces dysmorphogenesis in rodent embryos and becomes concentrated in the embryonic heart after maternal oral dosing. Tolbutamide increases glucose metabolism in extra-pancreatic adult tissues, but this has not previously been examined in embryonic heart.

METHODS

CD-1 mouse embryos were exposed on GD 9.5 to tolbutamide (0, 100, 250, or 500 microg/ml) for 6, 12, or 24 hr in whole-embryo culture. Isolated hearts were evaluated for (3)H-2DG uptake and conversion of (14)C-glucose to (14)C-lactate. Glut-1, HKI, and GRP78 protein levels were determined by Western analysis, and Glut-1 mRNA was measured by RT-PCR.

RESULTS

Cardiac (3)H-2DG uptake increased after exposure to 500 microg/ml tolbutamide for 6 hr, and 100, 250, or 500 microg/ml tolbutamide for 24 hr, compared to controls. Glycolysis increased after exposure to 500 microg/ml tolbutamide for 6 or 24 hr compared to controls. Glut-1 protein levels increased in hearts exposed to 500 microg/ml tolbutamide for 12 or 24 hr, and Glut-1 mRNA increased in hearts exposed to 500 microg/ml tolbutamide for 24 hr compared to controls. HKI protein levels increased in hearts exposed to 500 microg/ml tolbutamide for 6 hr, but not 12 or 24 hr. There was no effect on GRP78 protein levels in hearts exposed to tolbutamide for 6, 12, or 24 hr.

CONCLUSIONS

Tolbutamide stimulates glucose uptake and metabolism in the embryonic heart, as occurs in adult extra-pancreatic tissues. Glut-1 and HKI, but not GRP78, are likely involved in tolbutamide-induced cardiac dysmorphogenesis.