Maternal low-protein diet or hypercholesterolemia reduces circulating essential amino acids and leads to intrauterine growth restriction

Abstract

Objective: We have examined maternal mechanisms for adult-onset glucose intolerance, increased adiposity, and atherosclerosis using two mouse models for intrauterine growth restriction (IUGR): maternal protein restriction and hypercholesterolemia.

Research design and methods: For these studies, we measured the amino acid levels in dams from two mouse models for IUGR: 1) feeding C57BL/6J dams a protein-restricted diet and 2) feeding C57BL/6J LDL receptor-null (LDLR(-/-)) dams a high-fat (Western) diet.

Results: Both protein-restricted and hypercholesterolemic dams exhibited significantly decreased concentrations of the essential amino acid phenylalanine and the essential branched chain amino acids leucine, isoleucine, and valine. The protein-restricted diet for pregnant dams resulted in litters with significant IUGR. Protein-restricted male offspring exhibited catch-up growth by 8 weeks of age and developed increased adiposity and glucose intolerance by 32 weeks of age. LDLR(-/-) pregnant dams on a Western diet also had litters with significant IUGR. Male and female LDLR(-/-) Western-diet offspring developed significantly larger atherosclerotic lesions by 90 days compared with chow-diet offspring.

Conclusions: In two mouse models of IUGR, we found reduced concentrations of essential amino acids in the experimental dams. This indicated that shared mechanisms may underlie the phenotypic effects of maternal hypercholesterolemia and maternal protein restriction on the offspring.

FIG. 1.

Characterization of offspring from control and protein-restricted litters. A: Mean litter birth weights of 9% low-protein diet litters compared with 19% control protein litters, P = 0.003. B: Growth curve of male offspring from 4 to 32 weeks of age. *Weights were significantly different at the P ≤ 0.05 level at 4 and 32 weeks. C: Persistent growth restriction in female protein-restricted offspring, from 4 to 32 weeks of age. *Values significantly different at the P ≤ 0.05 level. D: Increased adiposity in low-protein male offspring at 32 weeks of age, P = 0.025. E: Glucose intolerance in low-protein male offspring. Blood glucose concentrations of male protein-restricted offspring after administration of a standard intraperitoneal challenge of 2 mg/g body weight (wt) glucose. n = 12, 9, 9, 9, and 8 for control offspring; and n = 14, 13, 13, 10, and 9 for the protein-restricted offspring at time 0, 0.5, 1, 1.5, and 2 h, respectively. F: Area under the curve (AUC) for protein-restricted male offspring after administration of a standard intraperitoneal glucose load.

FIG. 2.

Characterization of LDLR^−/− control and Western-diet offspring at birth and at 90 days of age. A: Prepregnancy total plasma concentrations of LDLR^−/− females on chow and Western diets. B: Birth weight of offspring from LDLR^−/− dams on Western diet compared with controls, P = 0.02. C: Lower body weight of Western-diet offspring at 90 days of age compared with controls, P = 0.05. D: Nose-to-tail-tip length in Western offspring, P = 0.0004 for maternal cholesterol effect in both male and female offspring. E: Gonadal fat pad weight normalized by body weight, P = 0.04 for maternal cholesterol effect for male and female offspring. F: Atherosclerotic lesion size of the proximal aorta at 90 days of age, P = 0.02 for maternal cholesterol effect in both males and females. G: Representative lesions at 90 days of age in the LDLR^−/− offspring exposed to maternal hypercholesterolemia. 1, Whole proximal aortic section; 2, one lesion enlarged. (Please see http://dx.doi.org/10.2337/db07-1530 for a high-quality digital representation of this figure.)

FIG. 3.

Hypoaminoacidemia in protein-restricted and hypercholesterolemic dams. A: Plasma urea and amino acid concentrations in dams on a 23% protein control diet (n = 8; □) and 9% low-protein diet (n = 3; ▪) and in LDLR^−/− dams on a Western diet (n = 11; ▪) and control chow diet (n = 9; □). * P < 0.05. ** P < 0.005. *** P < 0.0005. B: Representative chromatogram of the high-performance liquid chromatography peaks for one plasma sample.