•Maternal omega-3 deficiency has deleterious effects on pups’ brain development.•Maternal omega-3 deficiency alters fatty acid composition of the fetal and adult offspring brain.•Maternal omega-3 ...deficiency exacerbates maternal and fetal inflammation.•Maternal omega-3 deficiency induces spatial memory deficits in the adult offspring.•There is a strong negative correlation between brain content in omega-3 and cytokines production.
Maternal immune activation (MIA) is a common environmental insult on the developing brain and represents a risk factor for neurodevelopmental disorders. Animal models of in utero inflammation further revealed a causal link between maternal inflammatory activation during pregnancy and behavioural impairment relevant to neurodevelopmental disorders in the offspring. Accumulating evidence point out that proinflammatory cytokines produced both in the maternal and fetal compartments are responsible for social, cognitive and emotional behavioral deficits in the offspring.
Polyunsaturated fatty acids (PUFAs) are essential fatty acids with potent immunomodulatory activities. PUFAs and their bioactive derivatives can promote or inhibit many aspects of the immune and inflammatory response. PUFAs of the n-3 series (‘n-3 PUFAs’, also known as omega-3) exhibit anti-inflammatory/pro-resolution properties and promote immune functions, while PUFAs of the n-6 series (‘n-6 PUFAs’ or omega-6) favor pro-inflammatory responses. The present study aimed at providing insight into the effects of n-3 PUFAs on the consequences of MIA on brain development. We hypothesized that a reduction in n-3 PUFAs exacerbates both maternal and fetal inflammatory responses to MIA and later-life defects in memory in the offspring.
Based on a lipopolysaccharide (LPS) model of MIA (LPS injection at embryonic day 17), we showed that n-3 PUFA deficiency 1) alters fatty acid composition of the fetal and adult offspring brain; 2) exacerbates maternal and fetal inflammatory processes with no significant alteration of microglia phenotype, and 3) induces spatial memory deficits in the adult offspring. We also showed a strong negative correlation between brain content in n-3 PUFA and cytokine production in MIA-exposed fetuses. Overall, our study is the first to address the deleterious effects of n-3 PUFA deficiency on brain lipid composition, inflammation and memory performances in MIA-exposed animals and indicates that it should be considered as a potent environmental risk factor for the apparition of neurodevelopmental disorders.
The host response to peripheral inflammation induces fever and behavioural depression that are supposed to be centrally mediated by cytokines. Several proinflammatory cytokines activate ‘signal ...transducer and activator of transcription’ 3 (STAT3) via gp130-like receptor signaling. In order to determine which cells in the rat brain and pituitary are activated during bacterial inflammation, we investigated in a spatiotemporal manner the activation of STAT3 in these organs following peripheral lipopolysaccharide (LPS) challenge. Under basal conditions, STAT3 immunoreactivity was observed in neurones and some glial cells throughout the brain. Two hours after the administration of LPS, nuclear localisation of STAT3 (hallmark of activation) was observed in zones at the interface between brain and blood or cerebrospinal fluid such as pituitary, ependymal layer, meninges, glia limitans, circumventricular organs and surrounding nervous parenchyma. Four hours after LPS, the nuclear activation of STAT3 propagated to cells located inside the parenchyma (cortex, hypothalamus, corpus callosum and hippocampus among others) and declined 8 h after treatment. Double labelling of STAT3 and glial fibrillary acidic protein identified activated cells in the parenchyma as astrocytes.
These data show that STAT3 is activated in the pituitary and in brain astrocytes after a peripheral LPS challenge as demonstrated by immunohistochemistry. Astrocytes may therefore play a key role in the brain response to peripheral inflammation.
•Fish hydrolysate contains n-3 LC-PUFAs and low molecular weight peptides.•Fish hydrolysate prevents age-related short-term memory deficits.•Fish hydrolysate affects navigation strategies during ...spatial learning.•Fish hydrolysate possesses immunomodulatory and anxiolytic properties.•Fish hydrolysate is promising for the prevention of age-related cognitive decline.
Brain aging is characterized by a decline in cognitive functions, which can lead to the development of neurodegenerative pathologies. Age-related spatial learning and memory deficits are associated with a chronic low-grade inflammation. Anxiety disorders and stress response alterations, occurring for a part of the elderly, have also been linked to an increased neuroinflammation and thus, an accelerated cognitive decline. Nutrition is an innovative strategy to prevent age-related cognitive impairments. Among the nutrients, n-3 long chain polyunsaturated fatty acids (LC-PUFAs) and low molecular weight peptides from proteins, especially those from marine resources, are good candidates for their immunomodulatory, anxiolytic and neuroprotective properties. The aim of this study is to determine the combined effect of n-3 LC-PUFAs and low molecular weight peptides on cognitive functions, and their mechanism of action. We are the first to show that a dietary supplementation with a fish hydrolysate containing n-3 LC-PUFAs and low molecular weight peptides prevented the age-related spatial short-term memory deficits and modulated navigation strategies adopted during spatial learning. In addition, the fish hydrolysate displayed anxiolytic activities with the reduction of anxiety-like behaviour in aged mice, restored the plasmatic corticosterone levels similar to adult animals following an acute stress and modulated the hypothalamic stress response. These effects on behaviour can be explained by the immunomodulatory and neuroprotective properties of the fish hydrolysate that limited microgliosis in vivo, decreased LPS-induced expression of pro-inflammatory cytokines and increased the expression of growth factors such as BDNF and NGF in vitro. Thus, n-3 LC-PUFAs and low molecular weight peptides contained in the fish hydrolysate can play an important role in the limitation of neuroinflammation and stress response alterations during aging and represent a potential strategy for the prevention of age-related cognitive decline.
•Effect of lifelong omega-3 deficiency on sleep in physiology and under inflammation.•Omega-3 deficiency affects the architecture of sleep-wake activity.•Omega-3 deficiency decreases the amplitude of ...delta oscillations during NREM sleep.•Omega-3 deficiency affects the REM sleep response to an acute inflammatory challenge.
Essential polyunsaturated fatty acids (PUFA) from the n-3 and n-6 series constitute the building blocks of brain cell membranes where they regulate most aspects of cell physiology. They are either biosynthesized from their dietary precursors or can be directly sourced from the diet. An overall increase in the dietary n-6/n-3 PUFA ratio, as observed in the Western diet, leads to reduced n-3 PUFAs in tissues that include the brain. Some clinical studies have shown a positive correlation between dietary n-3 PUFA intake and sleep quantity, yet evidence is still sparse. We here used a preclinical model of dietary n-3 PUFA deficiency to assess the precise relationship between dietary PUFA intake and sleep/wake activity. Using electroencephalography (EEG)/electromyography (EMG) recordings on n-3 PUFA deficient or sufficient mice, we showed that dietary PUFA deficiency affects the architecture of sleep-wake activity and the oscillatory activity of cortical neurons during sleep. In a second part of the study, and since PUFAs are a potent modulator of inflammation, we assessed the effect of dietary n-3 PUFA deficiency on the sleep response to an inflammatory stimulus known to modulate sleep/wake activity. We injected mice with the endotoxin lipopolysaccharide (LPS) and quantified the sleep response across the following 12 h. Our results revealed that n-3 PUFA deficiency affects the sleep response in basal condition and after a peripheral immune challenge. More studies are now required aimed at deciphering the molecular mechanisms underlying the intimate relationship between n-3 PUFAs and sleep/wake activity.
Obesity is characterized by chronic low-grade inflammation that may lead to emotional distress and behavioural symptoms. This study assessed the relationship between adiposity, low-grade ...inflammation, eating behaviour and emotional status in obese women awaiting gastric surgery and investigated the effects of surgery-induced weight loss on this relationship.
A total of 101 women with severe or morbid obesity awaiting gastric surgery were recruited. Assessments were performed before and at 1 year post-surgery and included the measurement of neuroticism and extraversion using the revised Neuroticism-Extraversion-Openness personality inventory (NEO-PI-R) and eating behaviour using the Three-Factor Eating Questionnaire (TFEQ). Blood samples were collected for the measurement of serum inflammatory markers interleukin-6 (IL-6), high-sensitive C-reactive protein (hsCRP) and adipokines (leptin, adiponectin).
At baseline, body mass index (BMI) was positively correlated with inflammatory markers and adipokines. Regression analyses adjusting for age and diabetes revealed that baseline concentrations of IL-6 and hsCRP were associated with the depression and anxiety facets of neuroticism, with higher inflammation predicting higher anxiety and depression. This association remained significant after adjusting for BMI. Gastric surgery induced significant weight loss, which correlated with reduced inflammation. After controlling for BMI variations, decreases in inflammatory markers, notably hsCRP, were associated with reduced anxiety and TFEQ-cognitive restraint scores.
These findings indicate strong associations between adiposity, inflammation and affectivity in obese subjects and show that surgery-induced weight loss is associated concomitantly with reduced inflammation and adipokines and with significant improvement in emotional status and eating behaviour. Inflammatory status appears to represent an important mediator of emotional distress and psychological characteristics of obese individuals.
The inflammatory state of the adipose tissue, in particular visceral adipose tissue, is believed to contribute to systemic chronic low-grade inflammation associated with obesity. Nevertheless, the ...precise characterization of the inflammatory profile of obese subjects, associating adipose and systemic inflammatory markers, is still needed. In addition, the question whether inflammatory specificities in obesity influence the outcomes of bariatric surgery, such as weight reduction, remains to be elucidated. To address these questions, thirty-seven obese patients were included in the present study and about 70% of them were followed up to fourteen months after bariatric surgery. Systemic concentrations of inflammatory markers were assessed using ELISA before bariatric surgery. Samples of visceral adipose tissue were extracted during bariatric surgery and gene expression of cytokines and immune cells markers were evaluated using qRT-PCR. Our results indicate that cytokines were strongly inter-correlated in the adipose tissue. In addition, we have found significant associations of adipose expression of macrophage and T cells markers with adipose expression and with systemic levels of cytokines, including TNF-α and IL-6. Importantly, a higher inflammatory state of the visceral adipose tissue before bariatric surgery predicted a lower weight reduction after surgery, notably at early stages post-surgery. Taking together, these findings highlight the importance of the inflammatory state of the visceral adipose tissue in obesity-related inflammation, and its relevance regarding its impact on outcomes of obesity treatments.
Energy-dense food exposure and stress during development have been suggested to contribute to obesity and metabolic disorders later in life. Although these factors are frequently associated, the ...effects of their combination have not yet been investigated. In this study, using an animal model, we examined the long-term impact of maternal high-fat diet (HFD) and early-life stress (ELS) on energy homoeostasis control and food motivation.
Body weight growth under HFD, adipose tissue, body weight control in response to fasting and refeeding, food-motivated behaviour and mesolimbic dopamine function were examined in adult male offspring exposed to maternal HFD (during gestation and lactation) and/or ELS (maternal separation 3 h per day from postnatal day 2 to 14).
Maternal HFD or ELS alone had no significant effect on offspring body weight; however, the combination of these factors exacerbated body weight gain when animals were exposed to HFD after weaning. There are no other significant combinatory effects of these perinatal events. In contrast, independently of the maternal diet, ELS disrupted body weight control during a fasting-refeeding procedure, increased adipose tissue mass and altered lipid metabolism. Finally, maternal HFD and ELS both resulted in exacerbated food-motivated behaviour and blunted dopamine release in the nucleus accumbens during palatable food consumption.
We report a synergistic effect of perinatal HFD exposure and stress on the susceptibility to gain weight under HFD. However, ELS has a stronger impact than maternal HFD exposure on energy homoeostasis and food motivation in adult offspring. Altogether, our results suggest a programming effect of stress and nutrition supporting the hypothesis of the developmental origin of health and disease.
Understanding how malnutrition contributes to depression is building momentum. In the present study we unravel molecular and cellular mechanisms by which nutritional disturbances lead to impaired ...emotional behaviour in mice. Here we report that nutritional n-3 polyunsaturated fatty acids (PUFA) deficiency induces a chronic stress state reflected by disrupted glucocorticoid receptor (GR)-mediated signalling pathway along with hypothalamic-pituitary-adrenal (HPA) axis hyperactivity. This hyperactivity in turn resulted in neuronal atrophy in the dorsolateral (dl)- and dorsomedial (dm)- prefrontal cortex (PFC) and subsequent mood-related behaviour alterations, similarly to chronic social defeat stress. Supplementation of n-3 PUFA prevented detrimental chronic social defeat stress-induced emotional and neuronal impairments by impeding HPA axis hyperactivity. These results indicate a role for dietary n-3 PUFA in the prevention of HPA axis dysfunction associated with the development of some neuropsychiatric disorders including depression.
Maternal immune activation (MIA) and poor maternal nutritional habits are risk factors for the occurrence of neurodevelopmental disorders (NDD). Human studies show the deleterious impact of prenatal ...inflammation and low n-3 polyunsaturated fatty acid (PUFA) intake on neurodevelopment with long-lasting consequences on behavior. However, the mechanisms linking maternal nutritional status to MIA are still unclear, despite their relevance to the etiology of NDD. We demonstrate here that low maternal n-3 PUFA intake worsens MIA-induced early gut dysfunction, including modification of gut microbiota composition and higher local inflammatory reactivity. These deficits correlate with alterations of microglia-neuron crosstalk pathways and have long-lasting effects, both at transcriptional and behavioral levels. This work highlights the perinatal period as a critical time window, especially regarding the role of the gut-brain axis in neurodevelopment, elucidating the link between MIA, poor nutritional habits, and NDD.
Anxiety disorders and depression are well-documented in subjects exposed to adverse childhood events. Recently, maternal obesity and/or maternal consumption of high-fat diets (HFD) have been also ...proposed as risk factors for offspring mental health. Here using an animal model in rats, we explored the combinatorial effects of a maternal HFD (40% of energy from fat without impact on maternal weight; during gestation and lactation) and maternal separation (MS) in offspring. In the prefrontal cortex (PFC) of pups, MS led to changes in the expression of several genes such as Bdnf (brain derived neurotrophic factor), 5HT-r1a (serotonin receptor 1a) and Rest4 (neuron-restrictive silencer element, repressor element 1, silencing transcription factor (Rest), splicing variant 4). Surprisingly, perinatal HFD strongly attenuated the developmental alterations induced by MS. Furthermore, maternal HFD totally prevented the endophenotypes (anxiety, spatial memory, social behavior, hypothalamic-pituitary-adrenal (HPA) axis response to stress, hippocampal neurogenesis and visceral pain) associated with MS at adulthood. Finally, we also demonstrated that HFD intake reduced anxiety and enhanced maternal care in stressed dams. Overall, our data suggest that a HFD restricted to gestation and lactation, which did not lead to overweight in dams, had limited effects in unstressed offspring, highlighting the role of maternal obesity, rather than fat exposure per se, on brain vulnerability during development.
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