Programming of growth, insulin resistance and vascular dysfunction in offspring of late gestation diabetic rats.

ODM (offspring of diabetic mothers) have an increased risk of developing metabolic and cardiovascular dysfunction; however, few studies have focused on the susceptibility to disease in offspring of mothers developing diabetes during pregnancy. We developed an animal model of late gestation diabetic pregnancy and characterized metabolic and vascular function in the offspring. Diabetes was induced by streptozotocin (50 mg/kg of body weight, intraperitoneally) in pregnant rats on gestational day 13 and was partially controlled by twice-daily injections of insulin. At 2 months of age, ODM had slightly better glucose tolerance than controls (P<0.05); however, by 6 months of age this trend had reversed. A euglycaemic-hyperinsulinamic clamp revealed insulin resistance in male ODM (P<0.05). In 6-8-month-old female ODM, aortas had significantly enhanced contractility in response to KCl, ET-1 (endothelin-1) and NA (noradrenaline). No differences in responses to ET-1 and NA were apparent with co-administration of L-NNA (NG-nitro-L-arginine). Relaxation in response to ACh (acetylcholine), but not SNP (sodium nitroprusside), was significantly impaired in female ODM. In contrast, males had no between-group differences in response to vasoconstrictors, whereas relaxation to SNP and ACh was greater in ODM compared with control animals. Thus the development of diabetes during pregnancy programmes gender-specific insulin resistance and vascular dysfunction in adult offspring.

Murine aortic reactivity is programmed equally by maternal low protein diet or late gestation dexamethasone.

OBJECTIVE: In rats, maternal low protein diet induces growth restriction, increases fetal glucocorticoid exposure and programs cardiovascular and endocrine dysfunction in adult offspring. We hypothesized that both maternal low protein diet and late gestation dexamethasone program murine offspring to develop hypertension, vascular dysfunction, and glucose intolerance. METHODS: An iso-caloric low protein diet (LP) was provided to dams from E0 to E19. Additional dams received a normal protein diet without (NP) or with either dexamethasone (NP-Dex, 0.1 mg/kg/d sc) or normal saline (NP-NS) from E10 to E18. RESULTS: Offspring of dams given LP weighed less at 10 days than NP offspring, while Dex administration did not alter pup weight. At 4 months, all four groups had similar systolic blood pressures and no detectable differences were evoked by oral L-NAME. Offspring of LP mice had impaired glucose clearance that was directly correlated with their weight at 10 days. Aortic rings from offspring of both LP and NP-Dex exposed dams had impaired vasodilatation to acetylcholine. CONCLUSIONS: These findings demonstrate that both maternal low protein diet and late gestation dexamethasone program murine offspring to develop endothelial dysfunction in the absence of hypertension, while only maternal LP impaired perinatal growth and glucose clearance in adult offspring. KEYWORDS: Acetylcholine; blood pressure; developmental biology; fetal programming

Early gestation dexamethasone alters baroreflex and vascular responses in newborn lambs before hypertension.

Exposure of the early gestation ovine fetus to exogenous glucocorticoids induces alterations in postnatal cardiovascular physiology, including hypertension. To determine whether autonomic function and systemic vascular reactivity are altered by in utero programming before the development of systemic hypertension, we examined arterial baroreflex function and in vivo hemodynamic and in vitro vascular responses to vasoactive agents in 10- to 14-day-old newborn lambs exposed to early gestation glucocorticoids. Dexamethasone (Dex, 0.28 mg.kg-1.day-1) or saline was administered to pregnant ewes by intravenous infusion over 48 h beginning at 27 days gestation (term 145 days), and lambs were allowed to deliver (n=6 in each group). Resting mean arterial blood pressure (MABP; 77+/-1 vs. 74+/-3 mmHg) and heart rate (HR; 249+/-9 vs. 226+/-21 beats/min) were similar in Dex-exposed and control animals, respectively. The arterial baroreflex curve, relating changes in HR to MABP, was significantly shifted toward higher pressure in the Dex-exposed lambs although no change in the sensitivity (gain) of the response was seen. In vivo changes in blood pressure in response to bolus doses of ANG II (20, 50, and 100 ng/kg) and phenylephrine (2, 5, and 10 microg/kg) were similar in the two groups. However, Dex lambs displayed greater decreases in MABP in response to ganglionic blockade with tetraethylammonium bromide (10 mg/kg; -30+/-3 vs. -20+/-3 mmHg, P<0.05) and greater increases in MABP after nitric oxide synthase blockade with NG-nitro-L-arginine (25 mg/kg; 23+/-3 vs. 13+/-2 mmHg, P<0.05) compared with control lambs. By in vitro wire myography, mesenteric and femoral artery microvessel contractile responses to KCl were similar, whereas responses to endothelin (in mesenteric) and norepinephrine (in femoral) were significantly attenuated in Dex lambs compared with controls. Femoral vasodilatory responses to forskolin and sodium nitroprusside were similar in the two groups (n=4). These findings suggest that resetting of the baroreflex, accompanied by increased sympathetic activity and altered nitric oxide-mediated compensatory vasodilatory function, may be important contributors to programming of hypertension.

Newborn lamb coronary artery reactivity is programmed by early gestation dexamethasone before the onset of systemic hypertension.

Exposure of the early gestation ovine fetus to exogenous glucocorticoids induces organ-specific alterations in postnatal cardiovascular physiology. To determine whether early gestation corticosteroid exposure alters coronary reactivity before the development of systemic hypertension, dexamethasone (0.28 mg x kg(-1) x day(-1)) was administered to pregnant ewes by intravenous infusion over 48 h beginning at 27 days gestation (term, 145 days). Vascular responsiveness was assessed in endothelium-intact coronary arteries isolated from 1-wk-old steroid-exposed and age-matched control lambs (N = 6). Calcium imaging was performed in fura 2-loaded primary cultures of vascular smooth muscle cells (VSMC) from the harvested coronary arteries. Early gestation steroid exposure did not significantly alter mean arterial blood pressure or coronary reactivity to KCl, thromboxane A(2) mimetic U-46619, or ANG II. Steroid exposure significantly increased coronary artery vasoconstriction to acetylcholine and endothelin-1. Vasodilatation to adenosine, but not nitroprusside or forskolin, was significantly attenuated following early gestation steroid exposure. Endothelin-1 or U-46619 stimulation resulted in a comparable increase in intracellular calcium concentration ([Ca(2+)](i)) in coronary VSMC isolated from either dexamethasone-treated or control animals. However, the ANG II- or KCl-mediated increase in [Ca(2+)](i) in control VSMC was significantly attenuated in VSMC harvested from dexamethasone-treated lambs. Coronary expression of muscle voltage-gated l-type calcium channel alpha-1 subunit protein was not significantly altered by steroid exposure, whereas endothelial nitric oxide synthase expression was attenuated. These findings demonstrate that early gestation glucocorticoid exposure elicits primary alterations in coronary responsiveness before the development of systemic hypertension. Glucocorticoid-induced alterations in coronary physiology may provide a mechanistic link between an adverse intrauterine environment and later cardiovascular disease.