Quantitative ultrastructural evidence of myelin malformation in optic nerves of rats submitted to a multideficient diet

A hydrolyzed lipid blend diet promotes myelination in neonatal piglets in a region and concentration-dependent manner

The impact of early life nutrition on myelin development is of interest given that cognitive and behavioral function depends on proper myelination. Evidence shows that myelination can be altered by dietary lipid, but most of these studies have been performed in the context of disease or impairment. Here, we assessed the effects of lipid blends containing various levels of a hydrolyzed fat (HF) system on myelination in healthy piglets. Piglets were sow-reared, fed a control diet, or a diet containing 12%, 25%, or 53% HF consisting of cholesterol, fatty acids, monoglycerides, and phospholipid from lecithin. At postnatal day 28/29, magnetic resonance imaging (MRI) was performed to assess changes to brain development, followed by brain collection for microscopic analyses of myelin in targeted regions using CLARITY tissue clearing, immunohistochemistry, and electron microscopy techniques. Sow-reared piglets exhibited the highest overall brain white matter volume by MRI. However, a 25% HF diet resulted in the greatest total myelin density in the prefrontal cortex based on 3D modeling analysis of myelinated filaments. Nodal gap length and g-ratio were inversely correlated with percentage of HF in the corpus callosum, as well as in the PFC and internal capsule for g-ratio, indicating that a 53% HF diet resulted in the thickest myelin per axon and a 0% HF control diet the thinnest in specific brain regions. These findings indicate that HF promoted myelination in the neonatal piglet in a region- and concentration-dependent manner.

Undernutrition - thirty years of the Regional Basic Diet: the legacy of Naíde Teodósio in different fields of knowledge

Undernutrition is characterized by an imbalance of essential nutrients with an insufficient nutritional intake, a disorder in which the clinical manifestations in most cases are the result of the economic and social context in which the individual lives. In 1990, the study by the medical and humanitarian Naíde Teodósio (1915-2005) and coworkers, which formulated the Regional Basic Diet (RBD) model for inducing undernutrition, was published. This diet model took its origin from the observation of the dietary habits of families that inhabited impoverished areas from the Pernambuco State. RBD mimics an undernutrition framework that extends not only to the Brazilian population, but to populations in different regions worldwide. The studies based on RBD-induced deficiencies provide a better understanding of the impact of undernutrition on the pathophysiological mechanisms underlying the most diverse prevalent diseases. Indexed papers that are analyzed in this review focus on the importance of using RBD in different areas of knowledge. These papers reflect a new paradigm in translational medicine: they show how the study of pathology using the RBD model in animals over the past 30 years has and still can help scientists today, shedding light on the mechanisms of prevalent diseases that affect impoverished populations.

Evaluation Using Spectral-Domain Optical Coherence Tomography of the Effects of Malnutrition on Ocular Parameters in Pediatric Patients

SIGNIFICANCE

We determined decreases in choroidal thickness and retinal nerve fiber layer (RNFL) thickness in all quadrants. Our findings show that the choroid and RNFL are affected before the emergence of ocular symptoms in malnourished children.

PURPOSE

We aimed to determine whether the RNFL, a component of the neuronal structure, and the choroid, supplying the retina, are affected in children with malnutrition using spectral-domain optical coherence tomography.

METHODS

One hundred twenty-six malnourished patients without ocular symptoms, aged between 5 and 10 years, and 116 healthy children were included in the study. Age, sex, weight-for-age (WFA) z score, height-for-age z score, body mass index-for-age z score, and spectral-domain optical coherence tomography data were recorded.

RESULTS

Average RNFL thickness was 96.5 μm (82.0 to 128.0 μm) in the malnutrition group and 111.0 μm (95.0 to 128.0 μm) in the control group (P < .001). Retinal nerve fiber layer thickness was statistically significantly lower in all quadrants in malnourished patients compared with the control group. Median choroidal thickness in the foveal center was 304.0 μm (250.0 to 375.0 μm) in the malnutrition group and 345.0 μm (280.0 to 403.0 μm) in the control group (P < .001). Choroidal thickness in all quadrants was also statistically significantly lower in malnourished patients. Positive correlation was determined between average RNFL thicknesses and WFA z score. Average RNFL thickness decreased as WFA z score decreased (r = 0.730 and P < .001). Positive correlation was also observed between choroidal thickness in the foveal center and WFA z score. Foveal center choroidal thickness decreased in line with WFA z score (r = 0.786 and P < .001).

CONCLUSIONS

Our results show that the retinal nerve fiber layer and choroidal thickness decreased in malnourished children without clinically reported ocular symptoms. A decreased retinal nerve fiber layer and choroidal thickness may be an important clue to the prevention of retinal pathologies that may develop at later ages if the malnutrition is not addressed.

Developmental Changes in Oligodendrocyte Genesis, Myelination, and Associated Behavioral Dysfunction in a Rat Model of Intra-generational Protein Malnutrition

Impairments in oligodendrocyte development and resultant myelination deficits appear as a common denominator to all neurological diseases. An optimal in utero environment is obligatory for normal fetal brain development and later life brain functioning. Late embryonic and early postnatal brains from F1 rat born to protein malnourished mothers were studied through a combination of immunocytochemical and quantitative PCR assay for analyzing the relative expression of platelet-derived growth factor receptor-α (PDGFRα), myelin-associated glycoprotein (MAG), proteolipid protein (PLP), and myelin oligodendrocyte glycoprotein (MOG) to determine oligodendrocyte genesis, differentiation, maturation, and myelination. Myelin integrity and corpus callosum caliber was assessed by Luxol fast blue (LFB) staining, whereas grip strength test and open field activity monitoring for behavioral evaluation in F1 rats. We demonstrate that intra-generational protein deprivation results in drastically low PDGFRα+ oligodendrocyte precursor (OPC) population and significantly reduced expression of myelin protein genes resulting in poor pre-myelinating and mature myelinating oligodendrocyte number, hypo-myelination, and misaligned myelinated fibers. LFB staining and MOG immunolabeling precisely revealed long-term changes in corpus callosum (CC) caliber and demyelination lesions in LP brain supporting the behavioral and cognitive changes at early adolescence and adulthood following maternal protein malnutrition (PMN). Thus, intra-generational PMN negatively affects the oligodendrocyte development and maturation resulting in myelination impairments and associated with behavioral deficits typically mimicking clinical hallmarks of neuropsychiatric disorders. Our results further strengthen and augment the hypothesis "Impaired gliogenesis is a big hit for neuropsychiatric phenotype."

Low omega-6/omega-3 ratio in a maternal protein-deficient diet promotes histone-3 changes in progeny neural cells and favors leukemia inhibitory factor genetranscription

Omega-3 (n-3) fatty acids modulate epigenetic changes critical to genesis and differentiation of neural cells. Conversely, maternal protein-malnutrition can negatively modify these changes. This study investigated whether a low n-6/n-3 ratio in a maternal diet could favor histone-3 (H3) modifications, gene transcription and differentiation in the offspring neural cells even under protein-deficiency. Female rats fed a control (Ct), or 3 types of multideficient diets differing in protein levels or linoleic/alpha-linolenic fatty acid ratios (RBD, RBD-C, RBD-SO) from 30 days prior to mating and during pregnancy. Cerebral cortex tissue and cortical cultures of progeny embryonic neurons and postnatal astrocytes were analyzed. H3K9 acetylation and H3K27 or H3K4 di-methylation levels were assessed by flow cytometry and/or immunocytochemistry. In astrocyte cultures and cortical tissue, the GFAP protein levels were assessed. Glial derived neurotrophic factor (GDNF) and leukemia inhibitory factor (LIF) gene expression were evaluated in the cortical tissue. GFAP levels were similar in astrocytes of Ct, RBD and RBD-C, but 65% lower in RBD-SO group. Higher levels of H3K9Ac were found in the neurons and H3K4Me2 in the astrocytes of the RBD group. No intergroup difference in the cortical GDNF mRNA expression or the H3K27Me2 levels in astrocytes was detected. LIF mRNA levels were higher in the RDB (P=.002) or RBD-C (P=.004) groups than in the control. The findings indicate the importance of dietary n-3 availability for the brain, even under a protein-deficient condition, inducing Histone modifications and increasing LIF gene transcription, involved in neural cell differentiation and reactivity.

Alterations of neocortico-limbic association fibers and correlation with diet in prediabetes diagnosed by impaired fasting glucose

PURPOSE

To assess the existence of alterations in the micro-integrity of the fasciculus in prediabetic subjects. The issue of micro-integrity in white matter tracts has not been adequately addressed in prediabetes.

MATERIALS AND METHODS

Sixty-four prediabetic subjects and 54 controls were enrolled. All participants completed 24-hour diet records and 3-day diet records and received diffusion tensor imaging at 3T. The data for white matter micro-integrity were analyzed and compared between prediabetic subjects and controls with age and gender as covariates. In addition, voxel-wise regression between white matter micro-integrity, diet, and preprandial glucose levels were used to explore the relationship between white matter micro-integrity and diet or serum glucose levels.

RESULTS

We found that prediabetic subjects had significant reductions in the micro-integrity of bilateral anterior thalamic radiation, left inferior longitudinal fasciculus, and left superior longitudinal fasciculus (corrected P < 0.05). In addition, total carbohydrate intake amount and preprandial serum glucose levels were negatively correlated with the micro-integrity in the left inferior longitudinal fasciculus and left anterior thalamic radiation (r: -0.47, corrected P < 0.05).

CONCLUSION

Restrictive alterations in the white matter micro-integrity of the anterior thalamic radiation and inferior and superior longitudinal fasciculi might represent the initial "hot spots" for white matter tract alterations, which might play a role in the development of prediabetes. J. Magn. Reson. Imaging 2016;43:1500-1506.

Behavioral experiences as drivers of oligodendrocyte lineage dynamics and myelin plasticity

Many behavioral experiences are known to promote hippocampal neurogenesis. In contrast, the ability of behavioral experiences to influence the production of oligodendrocytes and myelin sheath formation remains relatively unknown. However, several recent studies indicate that voluntary exercise and environmental enrichment can positively influence both oligodendrogenesis and myelination, and that, in contrast, social isolation can negatively influence myelination. In this review we summarize studies addressing the influence of behavioral experiences on oligodendrocyte lineage cells and myelin, and highlight potential mechanisms including experience-dependent neuronal activity, metabolites, and stress effectors, as well as both local and systemic secreted factors. Although more study is required to better understand the underlying mechanisms by which behavioral experiences regulate oligodendrocyte lineage cells, this exciting and newly emerging field has already revealed that oligodendrocytes and their progenitors are highly responsive to behavioral experiences and suggest the existence of a complex network of reciprocal interactions among oligodendrocyte lineage development, behavioral experiences, and brain function. Achieving a better understanding of these relationships may have profound implications for human health, and in particular, for our understanding of changes in brain function that occur in response to experiences. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.

Spreading depression features and Iba1 immunoreactivity in the cerebral cortex of developing rats submitted to treadmill exercise after treatment with monosodium glutamate

Physical exercise and excessive consumption of monosodium glutamate (MSG) can affect the morphological and electrophysiological organization of the brain during development. However, the interaction of both factors remains unclear. We analyzed the effect of this interaction on the excitability-related phenomenon known as cortical spreading depression (CSD) and the microglial reaction expressed as Iba1-immunolabeled cells in the rat motor cortex. MSG (2g/kg or 4g/kg) was administered every other day during the first 14 postnatal days. Treadmill exercise started at 21-23 days of life and lasted 3 weeks, 5 days/week, for 30min/day. At 45-60 days, CSD was recorded for 4h at two cortical points and the CSD parameters (velocity, amplitude, and duration of the negative potential change) calculated. Confirming previous observations, exercised rats presented with lower CSD velocities (3.29±0.18mm/min) than the sedentary group (3.80±0.18mm/min; P<0.05). MSG increased CSD velocities in the exercised rats compared to saline-treated and exercised animals in a dose-dependent manner (3.49±0.19, 4.05±0.18, and 3.27±0.26 for 2g/kg MSG, 4g/kg MSG, and saline, respectively; P<0.05). The amplitude (ranging from 14.3±5.9 to 18.7±6.2mV) and duration (46.7±11.1 to 60.5±11.6s) of the negative slow potential shift of the CSD were similar in all groups. Both exercise and MSG treatment increased Iba1 immunolabeling. The results confirm that physical exercise decelerates CSD propagation. However, it does not impede the CSD-accelerating action of MSG. These effects were accompanied by a cortical microglia reaction. Therefore, the data suggest that treadmill exercise early in life can influence the development of cortical electrical activity.

Propagation of spreading depression inversely correlates with cortical myelin content

OBJECTIVE

Cortical myelin can be severely affected in patients with demyelinating disorders of the central nervous system. However, the functional implication of cortical demyelination remains elusive. In this study, we investigated whether cortical myelin influences cortical spreading depression (CSD).

METHODS

CSD measurements were performed in rodent models of toxic and autoimmune induced cortical demyelination, in neuregulin-1 type I transgenic mice displaying cortical hypermyelination, and in glial fibrillary acidic protein-transgenic mice exhibiting pronounced astrogliosis.

RESULTS

Cortical demyelination, but not astrogliosis or inflammation per se, was associated with accelerated CSD. In contrast, hypermyelinated neuregulin-1 type I transgenic mice displayed a decelerated CSD propagation.

INTERPRETATION

Cortical myelin may be crucially involved in the stabilization and buffering of extracellular ion content that is decisive for CSD propagation velocity and cortical excitability, respectively. Our data thus indicate that cortical involvement in human demyelinating diseases may lead to relevant alterations of cortical function.