Impaired development of fetal serotonergic neurons in intrauterine growth restricted baboons

Strength of nonhuman primate studies of developmental programming: review of sample sizes, challenges, and steps for future work

Nonhuman primate (NHP) studies are crucial to biomedical research. NHPs are the species most similar to humans in lifespan, body size, and hormonal profiles. Planning research requires statistical power evaluation, which is difficult to perform when lacking directly relevant preliminary data. This is especially true for NHP developmental programming studies, which are scarce. We review the sample sizes reported, challenges, areas needing further work, and goals of NHP maternal nutritional programming studies. The literature search included 27 keywords, for example, maternal obesity, intrauterine growth restriction, maternal high-fat diet, and maternal nutrient reduction. Only fetal and postnatal offspring studies involving tissue collection or imaging were included. Twenty-eight studies investigated maternal over-nutrition and 33 under-nutrition; 23 involved macaques and 38 baboons. Analysis by sex was performed in 19; minimum group size ranged from 1 to 8 (mean 4.7 ± 0.52, median 4, mode 3) and maximum group size from 3 to 16 (8.3 ± 0.93, 8, 8). Sexes were pooled in 42 studies; minimum group size ranged from 2 to 16 (mean 5.3 ± 0.35, median 6, mode 6) and maximum group size from 4 to 26 (10.2 ± 0.92, 8, 8). A typical study with sex-based analyses had group size minimum 4 and maximum 8 per sex. Among studies with sexes pooled, minimum group size averaged 6 and maximum 8. All studies reported some significant differences between groups. Therefore, studies with group sizes 3-8 can detect significance between groups. To address deficiencies in the literature, goals include increasing age range, more frequently considering sex as a biological variable, expanding topics, replicating studies, exploring intergenerational effects, and examining interventions.

The long-term effect of maternal dietary protein restriction on 5-HT1A receptor function and behavioral responses to stress in adulthood

Maternal nutrition impacts fetal development, and may play a role in determining resilience to stress and vulnerability to stress-precipitated psychiatric disorders, such as anxiety and depression. In this study, we examined the effect of a reduction in maternal dietary protein during pregnancy on the brain neurochemistry and behavior of offspring. We focused specifically on the serotonin system, the 5-HT_1A receptor and the responsivity of offspring as adults to stress. Dams were fed either a low protein diet (10% protein by weight) or isocaloric control diet (20% protein by weight). The low protein diet did not alter maternal food intake and body weight, or litter size and the average birth weight of male or female littermates. 5-HT_1A receptor function, as measured by quantitative autoradiography of 8-OH-DPAT (1 μM)-stimulated [³⁵S]GTPγS binding, was markedly reduced in hippocampus of weanling female, but not male offspring (postnatal day, PND 21) of dams fed the low protein diet. The number of serotonergic cell bodies in the rostral raphe, and 5-HT metabolism in the limbic system of weanling offspring was not altered by maternal low protein diet. The deficit in hippocampal 5-HT_1A receptor function observed in weanling female offspring persisted into adulthood (PND 112), and was accompanied by an increased sensitivity to stress, specifically increased immobility during a 15-minute forced swim challenge and increased anorexia following 30-minute restraint (PND 97-100). The present work begins to uncover important future directions for understanding the early developmental origins of resilience to stress, and factors that may put individuals at greater risk for stress-related psychiatric disorders.

Increased aggressive and affiliative display behavior in intrauterine growth restricted baboons

BACKGROUND

We hypothesized intrauterine growth restricted offspring (IUGR) demonstrate higher rates of aggression and higher dominance ranks than control (CTR) offspring with normal weight at term; if aggressive behavior is advantageous during resource scarcity, developmental programming may lead to an association between aggression and IUGR.

METHODS

We studied 22 group-housed baboons (ages 3-5 years). CTR (male n = 8, female n = 5) mothers ate ad libitum. IUGR (male n = 4, female n = 5) mothers were fed 70% feed eaten by CTR mothers during pregnancy and lactation.

RESULTS

IUGR showed higher rates of aggressive displays (P < 0.01) and friendly displays (P < 0.02). Dominance ranks and physical aggression rates did not differ between groups.

CONCLUSIONS

High rates of IUGR aggressive display might reflect developmental programming of behavioral phenotypes enhancing fitness. Friendly displays may reflect reconciliation. Potential mechanisms include neurodevelopment and learning. Exploration of IUGR as a risk factor for behavioral patterns is important for developing diagnostic and therapeutic strategies.