Exposure to the Amino Acids Histidine, Lysine, and Threonine Reduces mTOR Activity and Affects Neurodevelopment in a Human Cerebral Organoid Model

Evidence of the impact of nutrition on human brain development is compelling. Previous in vitro and in vivo results show that three specific amino acids, histidine, lysine, and threonine, synergistically inhibit mTOR activity and behavior. Therefore, the prenatal availability of these amino acids could be important for human neurodevelopment. However, methods to study the underlying mechanisms in a human model of neurodevelopment are limited. Here, we pioneer the use of human cerebral organoids to investigate the impact of amino acid supplementation on neurodevelopment. In this study, cerebral organoids were exposed to 10 mM and 50 mM of the amino acids threonine, histidine, and lysine. The impact was determined by measuring mTOR activity using Western blots, general cerebral organoid size, and gene expression by RNA sequencing. Exposure to threonine, histidine, and lysine led to decreased mTOR activity and markedly reduced organoid size, supporting findings in rodent studies. RNA sequencing identified comprehensive changes in gene expression, with enrichment in genes related to specific biological processes (among which are mTOR signaling and immune function) and to specific cell types, including proliferative precursor cells, microglia, and astrocytes. Altogether, cerebral organoids are responsive to nutritional exposure by increasing specific amino acid concentrations and reflect findings from previous rodent studies. Threonine, histidine, and lysine exposure impacts the early development of human cerebral organoids, illustrated by the inhibition of mTOR activity, reduced size, and altered gene expression.

Fetal malnutrition is associated with impairment of endogenous melatonin synthesis in pineal via hypermethylation of promoters of protein kinase C alpha and cAMP response element-binding

This study investigated whether and how fetal malnutrition would influence endogenous melatonin synthesis, and whether such effect of fetal malnutrition would transmit to the next generation. We enrolled 2466 participants and 1313 of their offspring. The urine 6-hydroxymelatonin sulfate and serum melatonin rhythm were measured. Methylation microarray detection and bioinformatics analysis were performed to identify hub methylated sites. Additionally, rat experiment was performed to elucidate mechanisms. The participants with fetal malnutrition had lower 6-hydroxymelatonin sulfate (16.59 ± 10.12 μg/24 hours vs 24.29 ± 11.99 μg/24 hours, P < .001) and arear under curve of melatonin rhythm (67.11 ± 8.16 pg/mL vs 77.11 ± 8.04 pg/mL, P < .001). We identified 961 differentially methylated sites, in which the hub methylated sites were locating on protein kinase C alpha (PRKCA) and cAMP response element-binding protein (CREB1) promoters, mediating the association of fetal malnutrition with impaired melatonin secretion. However, such effects were not observed in the offspring (all P > .05). Impaired histomorphology of pineal, decreased melatonin in serum, pineal, and pinealocyte were also found in the in vivo and in vitro experiments (P < .05 for the differences of the indicators). Hypermethylation of 10 CpG sites on the PRKCA promoter and 8 CpG sites on the CREB1 promoter were identified (all P < .05), which down-regulated PRKCA and CREB1 expressions, leading to decreased expression of AANAT, and then resulting in the impaired melatonin synthesis. Collectively, fetal malnutrition can impair melatonin synthesis through hypermethylation of PRKCA and CREB1 promoters, and such effects cannot be transmitted to the next generation.

Effects of perinatal undernutrition on social transmission of food preference in adult male Wistar rats

Nutrition plays a fundamental role in learning and memory, and early experimental undernutrition interferes with brain memory processes. Social transmission of food preference (STFP) is a natural olfactory paired-associate learning test that has not been used to assess the effects of early undernutrition on memory consolidation. Male Wistar rats were randomly divided into two groups: control and early undernourished. The underfed rats received different percentages of a balanced diet during gestation. After birth, pups were underfed by alternating every 12 h between two lactating dams, one with ligated nipples. Weaning occurred on PD 25 followed by an ad lib diet until PD 90. Demonstrator rats were given powdered food mixed with cinnamon, followed by a 30-min interaction with an underfed observer. Thereafter, the observer had two choices of food: cinnamon or cocoa. During the food preference test, control and underfed OBS rats preferred the food containing cinnamon. Through social interaction, the UG OBS rats showed latency for head contacts and oral-nasal investigation was higher in the underfed rats; only head contacts and oral-nasal investigation frequency was lower; with the duration lower, but oral-nasal investigation duration was higher (p < 0.05). In the preference phase, the OBS underfed rat latencies for both stimuli were prolonged, the frequency lower only for cocoa, and the duration lower for cinnamon but higher for cocoa (p < 0.05). Findings suggested that early undernutrition interfered with the attentive social transmission to take a decision during the preference phase, but not with the short-term memory consolidation of social food preference.

Transcriptomic regulations in oligodendroglial and microglial cells related to brain damage following fetal growth restriction

Fetal growth restriction (FGR) is a major complication of human pregnancy, frequently resulting from placental vascular diseases and prenatal malnutrition, and is associated with adverse neurocognitive outcomes throughout life. However, the mechanisms linking poor fetal growth and neurocognitive impairment are unclear. Here, we aimed to correlate changes in gene expression induced by FGR in rats and abnormal cerebral white matter maturation, brain microstructure, and cortical connectivity in vivo. We investigated a model of FGR induced by low-protein-diet malnutrition between embryonic day 0 and birth using an interdisciplinary approach combining advanced brain imaging, in vivo connectivity, microarray analysis of sorted oligodendroglial and microglial cells and histology. We show that myelination and brain function are both significantly altered in our model of FGR. These alterations, detected first in the white matter on magnetic resonance imaging significantly reduced cortical connectivity as assessed by ultrafast ultrasound imaging. Fetal growth retardation was found associated with white matter dysmaturation as shown by the immunohistochemical profiles and microarrays analyses. Strikingly, transcriptomic and gene network analyses reveal not only a myelination deficit in growth-restricted pups, but also the extensive deregulation of genes controlling neuroinflammation and the cell cycle in both oligodendrocytes and microglia. Our findings shed new light on the cellular and gene regulatory mechanisms mediating brain structural and functional defects in malnutrition-induced FGR, and suggest, for the first time, a neuroinflammatory basis for the poor neurocognitive outcome observed in growth-restricted human infants. GLIA 2016;64:2306-2320.

Low protein diet during gestation and lactation increases food reward seeking but does not modify sucrose taste reactivity in adult female rats

INTRODUCTION

Nutritional deficiencies during neural development may lead to irreversible changes, even after nutritional rehabilitation, promoting morphological and functional adaptations of structures involved with various behaviours including feeding behaviour. However, the ability of the exposure low protein diet during gestation and lactation to affect the hedonic component of food intake is still poorly understood, especially in females.

METHODS

Wistar rats were divided into two groups according to the diet offered to the dams during pregnancy and lactation: control female (CF; diet with 17% protein, n=7) and low protein female (LPF; diet with 8% protein, n=7). The following parameters were evaluated: (a) body weight during weaning, 30, 45, 60, 75, 90 days of life; (b) standard diet intake from 110 to 132 days of life; (c) fat diet and consumption of simple carbohydrates (HFHS) for 1h at 145 days of life; (d) incentive runway task 60 days after 82 days of life; (e) taste reactivity at 90 days of life; and (f) neuronal activation in the caudate putamen, amygdala, paraventricular nucleus of the hypothalamus under stimulus HFHS at 145 days of life.

RESULTS

The exposure, a low protein diet during gestation and lactation, decreased the body weight throughout the study period from weaning to 90 days of life. However, there was no significant change in the body weight of low protein females from 110 to 132 days of life compared with the control females. There was an increase in the rate of the search for reward and reduced the latency of the perception of bitter taste. The exposure, a low protein diet during gestation and lactation, also promoted hypophagy in adult females compared with control animals. The low protein female had increased HFHS diet consumption compared with the control. Undernutrition increased neuronal activation in response to HFHS diet consumption compared with female controls in the amygdala and in the caudate putamen.

CONCLUSION

Females subjected to the exposure, a low protein diet during gestation and lactation, exhibit hypophagy on a standard diet but a higher consumption of a diet rich in lipids and simple carbohydrates. And also were more motivated by the pursuit of reward and reduced latency of the bitter taste reactivity, and increased the number of immunoreactive cells c-fos protein activated in the caudate putamen, amygdala and paraventricular nucleus.