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

Abstract

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.

Figure 1

Daily blood glucose values in pregnant dams with diabetes induced by injection of STZ () on day 13 of gestation and sham controls (). Glucose values represent average daily values. Values are means ± SE. (p < 0.05 between groups for all data points.) The mean values in the control groups ranged from 97.8 to 99.4 mg/dl with SE range of 2.73 - 4.08 mg/dl.

Figure 2

Weight distribution of 1 day old male (A) and female (B) rat pups of diabetic (STZ) (—) or control mothers (). The distribution is shown as a normalized frequency plot. Tick marks representing weights of each pup are shown below the x-axis. N, number of animals in each group.

Figure 3

Blood glucose levels during intraperitoneal glucose tolerance tests in female offspring of a diabetic (ODM, (), n = 17 at 2 and 5 months) and control (CON (), n = 19 at 2 and 5 months) and in male offspring of diabetic (n = 44 at 2 months, n = 42 at 5 months) and control (n = 39 at 2 months, n = 37 at 5 months) mothers. A, females at 2 months; B, males at months; C, females at 5 months; D, males at 5 months. Values are means ± SE. * p < 0.05 compared to control at same time point. Total area under the curve, as determined by the trapezoidal rule, was not significantly different between CON and ODM offspring for either gender at any age.

Figure 4

Blood glucose (left panel) and plasma insulin (right panel) levels during intravenous glucose tolerance tests in 6 mo old male offspring of diabetic (ODM (), n = 6) or control (CON, n = 6 ()) rats. Values are means ± SE. No differences in any time point or in total area under the curve, as determined by the trapezoidal rule, were detected.

Figure 5

Female aortic responsiveness to KCl (A), serotonin (5-HT) (B), noradrenaline (NA) (C), endothelin-1 (ET-1) (D), and angiotensin II (ANG II) (E) in the presence or absence (rubbed) of vascular endothelium and to noradrenaline (NA) (F) and endothelin-1 (ET-1) (G) in the presence or absence of L-NNA (n = 7 for each group). For figures A-E: endothelium intact ODM (), intact control (), rubbed ODM (), rubbed control (). For figures F,G: ODM (),control (),ODM + L-NNA (), control + L-NNA (). Values are means ± SE. ** p < 0.05 between endothelium intact ODM and intact control at specific concentrations. * p < 0.05 between rubbed and intact within same treatment groups (ANOVA). ¶ p < 0.05 between intact ODM and intact control (for all figures), or between rubbed ODM and rubbed control (figure B-E) or between L-NNA treated ODM and L-NNA treated controls (figures F,G) (treatment group effect, ANOVA).

Figure 6

Concentration-response curves for female aorta vasodilation produced by sodium nitroprusside (A) and acetylcholine (B) (n = 7 for each group). Endothelium intact ODM (), intact control (), rubbed ODM () and rubbed control (). Values are means ± SE. * p < 0.05 between intact and rubbed within same treatment group (ANOVA). ¶ p < 0.05 between intact ODM and intact control, or between rubbed ODM and rubbed control (treatment group effect, ANOVA).

Figure 7

Abdominal aorta lumen area and wall area and diameter in female (left column) and male (right column) offspring of control (black columns) and diabetic (white columns) mothers. Values are means ± SE. * p<0.05 compared to control.

Figure 8

Male aortic responsiveness to KCl (A), serotonin (5-HT) (B), angiotensin II (AII) (C), endothelin-1 (ET-1) (D), and noradrenaline (NA) (E) in the presence or absence (rubbed) of vascular endothelium and to ET-1 (F) and NA (G) in the presence or absence of LNNA (n = 7 for each group). For figures A-E: endothelium intact ODM (), intact control (), rubbed ODM (), rubbed control (). For figures F,G: ODM (),control (),ODM + L-NNA (), control + L-NNA (). Values are means ± SE. * p < 0.05 between rubbed and intact within same treatment groups (ANOVA). ¶ p < 0.05 between intact ODM and intact control (for all figures), or between rubbed ODM and rubbed control (figure B-E) (treatment group effect, ANOVA).

Figure 9

Concentration-response curves for male aorta vasodilation produced by sodium nitroprusside (A) and acetylcholine (B) (n = 7 for each group). Endothelium intact ODM (), intact control (), rubbed ODM () and rubbed control (). Values are means ± SE. * p < 0.05 between intact and rubbed within same treatment group (ANOVA). ¶ p < 0.05 between intact ODM and intact control (treatment group effect, ANOVA).