Maternal nutrient restriction in sheep: hypertension and decreased nephron number in offspring at 9 months of age

Abstract

Pregnant ewes were fed either a 50% nutrient-restricted (NR; n= 8) or a control 100% (C; n= 8) diet from day 28 to day 78 of gestation (dGA; term = 150 dGA). Lambs were born naturally, and fed to appetite throughout the study period. At 245 +/- 1 days postnatal age (DPNA), offspring were instrumented for blood pressure measurements, with tissue collection at 270 DPNA. Protein expression was assessed using Western blot, glomerulus number determined via acid maceration and hormone changes by radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA). NR lambs had higher mean arterial pressure (MAP; 89.0 +/- 6.6 versus 73.4 +/- 1.6 mmHg; P < 0.05), fewer renal glomeruli (57.8 +/- 23.8 versus 64.6 +/- 19.3 x 10(4); P < 0.05), increased expression of angiotensin converting enzyme (ACE) in the renal cortex (942 +/- 130 versus 464 +/- 60 arbitrary pixel units (apu); P < 0.03), and increased angiotensin II receptor AT2 expression in the renal medulla (63.3 +/- 12.1 versus 19.5 +/- 44.2 x 10(4) apu; P < 0.03). All data are presented as mean +/-S.E.M. The present data indicate that global maternal nutrient restriction (50%) during early to mid-gestation impairs renal nephrogenesis, increases MAP, and alters expression of AT2 and ACE without an associated change in birth weight. These data demonstrate the existence of a critical window of fetal susceptibility during early to mid-gestation that alters kidney development and blood pressure regulation in later life.

Figure 1. Mean arterial pressure (MAP) versus glomerulus number (GN) of control (C, n = 8, open symbols) and nutrient-restricted (NR, n = 8, filled symbols) lambs at 9 months of age

NR lambs show a strong negative relationship between MAP and GN (r=–0.85; P < 0.01; y=–5.82x+ 416.3). This negative relationship between MAP and GN was not observed in the C lambs (r= 0.38; P= 0.35; y=–3.23x+ 95.0). Singles and twins are shown as circles and triangles, respectively.

Figure 2. ACE expression was increased (P < 0.01) in the renal cortex of the nutrient-restricted lambs (NR, n = 8, filled symbols) in contrast to the controls (C, n = 8, open symbols) and lambs at 9 months of age

Singles and twins are shown with circles and triangles, respectively. Box plots represent the 75th and 25th percentiles and the median.

Figure 3. AT2 expression was increased (P < 0.05) in the renal medulla of the nutrient-restricted lambs (NR, n = 8, filled symbols) in contrast to the controls (C, n = 8, open symbols) and lambs at 9 months of age

Singles and twins are shown with circles and triangles, respectively. Box plots represent the 75th and 25th percentiles and the median.