Maternal nutrient restriction during early fetal kidney development attenuates the renal innate inflammatory response in obese young adult offspring

Abstract

Obesity is an independent risk factor for developing chronic kidney disease. Toll-like receptor 4 (TLR4), interleukin (IL)-18, and uncoupling protein 2 (UCP2) are important components of the innate immune system mediating inflammatory renal damage. Early to midgestation maternal nutrient restriction appears to protect the kidney from the deleterious effects of early onset obesity, although the mechanisms remain unclear. We examined the combined effects of gestational maternal nutrient restriction during early fetal kidney development and early onset obesity on the renal innate immune response in offspring. Pregnant sheep were randomly assigned to a normal (control, 100%) or nutrient-restricted (NR, 50%) diet from days 30 to 80 gestation and 100% thereafter. Offspring were killed humanely at 7 days or, following rearing in an obesogenic environment, at 1 yr of age, and renal tissues were collected. IL-18 and TLR4 expression were strongly correlated irrespective of intervention. Seven-day NR offspring had significantly lower relative renal mass and IL-18 mRNA expression. At 1 yr of age, obesity resulted in increased mRNA abundance of TLR4, IL-18, and UCP2, coupled with tubular atrophy and greater immunohistological staining of glomerular IL-6 and medullary tumor necrosis factor (TNF)-alpha. NR obese offspring had a marked reduction of TLR4 abundance and renal IL-6 staining. In conclusion, maternal nutrient restriction during early fetal kidney development attenuates the effects of early onset obesity-related nephropathy, in part, through the downregulation of the innate inflammatory response. A better understanding of maternal nutrition and the in utero nutritional environment may offer therapeutic strategies aimed at reducing the burden of later kidney disease.

Fig. 1.

Experimental protocol from conception through to adulthood. Lean animals were utilized from a parallel study to investigate the ontological expression of the genes of interest. See materials and methods for further details.

Fig. 2.

The ontological development of renal tissue gene expression for Toll-like receptor 4 (TLR4; A), interleukin (IL)-18 (B), and uncoupling protein (UCP) 2 mRNA (C) from neonatal to adult life. D: positive correlation between renal TLR4 and IL-18 mRNA in lean animals from all ages (r² = 0.87, P < 0.0001) (n = 26). mRNA abundance determined by real-time PCR and expressed as a degree of change to the 7-day-old animals (control); n = 5–8 control animals/time point, and values are expressed as means ± SE. *P < 0.05.

Fig. 3.

mRNA abundance of TLR4 (A), IL-18 (B), and UCP2 (C) in renal tissue of 7-day-old control and nutrient-restricted (NR) offspring as determined by quantitative real-time PCR (qPCR). Data are expressed relative to the housekeeping gene 18S and normalized to the control group to give the degree of change; n = 5–7 animals/group. Data represent means ± SE. *P < 0.05.

Fig. 4.

mRNA abundance of TLR4 (A), IL-18 (B), and UCP2 (C) in renal tissue of 1-yr-old Lean, Obese, and NR-Obese offspring as determined by qPCR. Data are expressed relative to the housekeeping gene 18S and normalized to the Lean group to give the degree of change; n = 7–10 animals/group. Data represent means ± SE. *P < 0.05 and **P < 0.01.

Fig. 5.

Quantitative immunohistochemistry of tumor necrosis factor (TNF)-α in renal tissue of young adult offspring. TNF-α stained with 3,3′-diaminobenzidine (DAB, red-brown color) as described in materials and methods. Renal cortex (A) and medulla (E) quantification and representative micrographs (×20) of Lean (B and F), Obese (C and G), and NR-Obese (D and H) offspring. Data represent means ± SE; n = 5–7 animals/group. *P < 0.05.

Fig. 6.

Quantitative immunohistochemistry of IL-6 in renal cortical tissue of young adult offspring. IL-6 stained with DAB (red-brown color) as described in materials and methods. A: cortical glomerular quantification. B: total cortical staining excluding glomeruli. Representative micrographs (×20) of Lean (C), Obese (D), and NR-Obese (E) offspring. Data represent means ± SE; n = 5–6 animals/group. *P < 0.05 and **P < 0.01.

Fig. 7.

Semiquantitative measurement of tubular atrophy (A) as described in materials and methods. Tubular atrophy was scored as: 0 (no tubular atrophy), 1 (<25% atrophic tubules), 2 (25–50% atrophic tubules), and 3 (>50% atrophic tubules). Representative micrographs (×40) of Lean (B), Obese (C), and NR-Obese (D) offspring demonstrating marked dilated and atrophic tubules in the renal cortex of Obese and NR-Obese animals. Data represent means ± SE; n = 7 animals/group. *P < 0.05.