Genetic obesity alters recruitment of TANK-binding kinase 1 and AKT into hypothalamic lipid rafts domains

Intermittent Fasting Improves Social Interaction and Decreases Inflammatory Markers in Cortex and Hippocampus

Autism spectrum disorder (ASD) is a psychiatric condition characterized by reduced social interaction, anxiety, and stereotypic behaviors related to neuroinflammation and microglia activation. We demonstrated that maternal exposure to Western diet (cafeteria diet or CAF) induced microglia activation, systemic proinflammatory profile, and ASD-like behavior in the offspring. Here, we aimed to identify the effect of alternate day fasting (ADF) as a non-pharmacologic strategy to modulate neuroinflammation and ASD-like behavior in the offspring prenatally exposed to CAF diet. We found that ADF increased plasma beta-hydroxybutyrate (BHB) levels in the offspring exposed to control and CAF diets but not in the cortex (Cx) and hippocampus (Hpp). We observed that ADF increased the CD45 + cells in Cx of both groups; In control individuals, ADF promoted accumulation of CD206 + microglia cells in choroid plexus (CP) and increased in CD45 + macrophages cells and lymphocytes in the Cx. Gestational exposure to CAF diet promoted defective sociability in the offspring; ADF improved social interaction and increased microglia CD206 + in the Hpp and microglia complexity in the dentate gyrus. Additionally, ADF led to attenuation of the ER stress markers (Bip/ATF6/p-JNK) in the Cx and Hpp. Finally, biological modeling showed that fasting promotes higher microglia complexity in Cx, which is related to improvement in social interaction, whereas in dentate gyrus sociability is correlated with less microglia complexity. These data suggest a contribution of intermittent fasting as a physiological stimulus capable of modulating microglia phenotype and complexity in the brain, and social interaction in male mice.

Prenatal Programming of Monocyte Chemotactic Protein-1 Signaling in Autism Susceptibility

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that involves functional and structural defects in selective central nervous system (CNS) regions, harming the individual capability to process and respond to external stimuli, including impaired verbal and non-verbal communications. Etiological causes of ASD have not been fully clarified; however, prenatal activation of the innate immune system by external stimuli might infiltrate peripheral immune cells into the fetal CNS and activate cytokine secretion by microglia and astrocytes. For instance, genomic and postmortem histological analysis has identified proinflammatory gene signatures, microglia-related expressed genes, and neuroinflammatory markers in the brain during ASD diagnosis. Active neuroinflammation might also occur during the developmental stage, promoting the establishment of a defective brain connectome and increasing susceptibility to ASD after birth. While still under investigation, we tested the hypothesis whether the monocyte chemoattractant protein-1 (MCP-1) signaling is prenatally programmed to favor peripheral immune cell infiltration and activate microglia into the fetal CNS, setting susceptibility to autism-like behavior. In this review, we will comprehensively provide the current understanding of the prenatal activation of MCP-1 signaling by external stimuli during the developmental stage as a new selective node to promote neuroinflammation, brain structural alterations, and behavioral defects associated to ASD diagnosis.

Prenatal programing of motivated behaviors: can innate immunity prime behavior?

Prenatal programming during pregnancy sets physiological outcomes in the offspring by integrating external or internal stimuli. Accordingly, pregnancy is an important stage of physiological adaptations to the environment where the fetus becomes exposed and adapted to the maternal milieu. Maternal exposure to high-energy dense diets can affect motivated behavior in the offspring leading to addiction and impaired sociability. A high-energy dense exposure also increases the pro-inflammatory cytokines profile in plasma and brain and favors microglia activation in the offspring. While still under investigation, prenatal exposure to high-energy dense diets promotes structural abnormalities in selective brain regions regulating motivation and social behavior in the offspring. The current review addresses the role of energy-dense foods programming central and peripheral inflammatory profiles during embryonic development and its effect on motivated behavior in the offspring. We provide preclinical and clinical evidence that supports the contribution of prenatal programming in shaping immune profiles that favor structural and brain circuit disruption leading to aberrant motivated behaviors after birth. We hope this minireview encourages future research on novel insights into the mechanisms underlying maternal programming of motivated behavior by central immune networks.

Maternal high-dense diet programs interferon type I signaling and microglia complexity in the nucleus accumbens shell of rats showing food addiction-like behavior

OBJECTIVE

This study aimed to characterize the molecular immune networks and microglia reactivity in the nucleus accumbens (NAc) shell affected by fetal nutritional programming leading to addiction-like behavior in the offspring of Wistar rats. Fetal nutritional programming by energy-dense foods leads to addiction-like behavior in the offspring. Exposure to energy-dense foods also activates systemic and central inflammation in the offspring.

METHODS

Females Wistar rats were exposed to cafeteria (CAF) diet or control diet for 9 weeks (prepregnancy, pregnancy and lactation), and male offspring at 2 months of age were diagnosed with food addiction-like behavior using operant conditioning. Global microarray analysis, RTqPCR, proinflammatory plasma profile and microglia immunostaining were performed in the NAc shell of male rats. SIM-A9 microglia cells were stimulated with IFN-α and palmitic acid, and microglia activation and phagocytosis were determined by RTqPCR and incubation of green-fluorescent latex beads, respectively.

RESULTS

Microarray analysis in the NAc shell of the male offspring exposed to CAF during development and diagnosed with addiction-like behavior showed increasing in the type I interferon-inducible gene, Ift1 , gene network. Genomic and cellular characterization also confirmed microglia hyperreactivity and upregulation of the Ifit1 in the NAc shell of animals with addiction-like behavior. In-vitro models demonstrated that microglia do respond to IFN-α promoting a time-dependent genomic expression of Ift1, IL-1β and IL-6 followed by increased phagocytosis.

CONCLUSION

Prenatal exposure to energy-dense foods primes the IFN type I signaling and microglia complexity in the NAc shell of rats diagnosed with food addiction-like behavior.

Role of hypothalamic de novo ceramides synthesis in obesity and associated metabolic disorders

Background

Sphingolipid-mediated signalling pathways are described as important players in the normal functioning of neurons and nonneuronal cells in the central nervous system (CNS).

Scope of review

This review aims to show role of de novo ceramide synthesis in the CNS in controling key physiological processes, including food intake, energy expenditure, and thermogenesis. The corollary is a condition that leads to a dysfunction in ceramide metabolism in these central regions that can have major consequences on the physiological regulation of energy balance.

Major conclusions

Excessive hypothalamic de novo ceramide synthesis has been shown to result in the establishment of central insulin resistance, endoplasmic reticulum stress, and inflammation. Additionally, excessive hypothalamic de novo ceramide synthesis has also been associated with changes in the activity of the autonomic nervous system. Such dysregulation of hypothalamic de novo ceramide synthesis forms the key starting point for the initiation of pathophysiological conditions such as obesity – which may or may not be associated with type 2 diabetes.

Clusterin overexpression as a potential neuroprotective response to the pathological effects of high fat dieting on the brain reward system

High-fat diets (HFDs) can lead to pathological changes in the brain underlying several behavioral disturbances (e.g., reward deficiency). To further increase our knowledge of these associations, we studied the sucrose reward and the brain expression of clusterin, a protein that is overexpressed after several kind of brain damaging conditions. C57BL/6J male mice were differentially fed on an HFD or standard chow for 41 days and underwent 11 sucrose place conditioning sessions followed by 4 extinction sessions to monitor the effects of HFD on sucrose reward by means of free choice tests. We quantified clusterin expression by immunochemistry in the nucleus accumbens, dorsal striatum and cingulate cortex. HFD tended to provoke a transient potentiation in the acquisition of sucrose-conditioned place preference, but this effect was followed by a much more consistent reduction in sucrose preference, which spontaneously disappeared after 31 days of an HFD with no need for extinction learning. The HFD mice showed higher clusterin expression in the nucleus accumbens but not in the other brain areas studied. The results confirm that HFDs strongly influence the rewarding properties of palatable foods and suggest a direct connection with neurotoxic alterations in the brain reward system tagged by clusterin overexpression.

Metabolic Flexibility Assists Reprograming of Central and Peripheral Innate Immunity During Neurodevelopment

Central innate immunity assists time-dependent neurodevelopment by recruiting and interacting with peripheral immune cells. Microglia are the major player of central innate immunity integrating peripheral signals arising from the circumventricular regions lacking the blood-brain barrier (BBB), via neural afferent pathways such as the vagal nerve and also by choroid plexus into the brain ventricles. Defective and/or unrestrained activation of central and peripheral immunity during embryonic development might set an aberrant connectome establishment and brain function, leading to major psychiatric disorders in postnatal stages. Molecular candidates leading to central and peripheral innate immune overactivation identified metabolic substrates and lipid species as major contributors of immunological priming, supporting the role of a metabolic flexibility node during trained immunity. Mechanistically, trained immunity is established by an epigenetic program including DNA methylation and histone acetylation, as the major molecular epigenetic signatures to set immune phenotypes. By definition, immunological training sets reprogramming of innate immune cells, enhancing or repressing immune responses towards a second challenge which potentially might contribute to neurodevelopment disorders. Notably, the innate immune training might be set during pregnancy by maternal immune activation stimuli. In this review, we integrate the most valuable scientific evidence supporting the role of metabolic cues assisting metabolic flexibility, leading to innate immune training during development and its effects on aberrant neurological phenotypes in the offspring. We also add reports supporting the role of methylation and histone acetylation signatures as a major epigenetic mechanism regulating immune training.

Maternal cafeteria diet exposure primes depression-like behavior in the offspring evoking lower brain volume related to changes in synaptic terminals and gliosis

Maternal nutritional programming by caloric exposure during pregnancy and lactation results in long-term behavioral modification in the offspring. Here, we characterized the effect of maternal caloric exposure on synaptic and brain morphological organization and its effects on depression-like behavior susceptibility in rats' offspring. Female Wistar rats were exposed to chow or cafeteria (CAF) diet for 9 weeks (pre-pregnancy, pregnancy, and lactation) and then switched to chow diet after weaning. By postnatal day 60, the male Wistar rat offspring were tested for depressive-like behavior using operational conditioning, novelty suppressed feeding, sucrose preference, and open-field test. Brain macro and microstructural morphology were analyzed using magnetic resonance imaging deformation-based morphometry (DBM) and western blot, immunohistochemistry for NMDA and AMPA receptor, synaptophysin and myelin, respectively. We found that the offspring of mothers exposed to CAF diet displayed deficient motivation showing decrease in the operant conditioning, sucrose preference, and suppressed feeding test. Macrostructural DBM analysis showed reduction in the frontomesocorticolimbic circuit volume including the nucleus accumbens (NAc), hippocampus, and prefrontal cortex. Microstructural analysis revealed reduced synaptic terminals in hippocampus and NAc, whereas increased glial fibrillary acidic protein in hippocampus and lateral hypothalamus, as well as a decrease in the hippocampal cell number and myelin reduction in the dentate gyrus and hilus, respectively. Also, offspring exhibited increase of the GluR1 and GLUR2 subunits of AMPA receptor, whereas a decrease in the mGluR2 expression in hippocampus. Our findings reveal that maternal programming might prime depression-like behavior in the offspring by modulating macro and micro brain organization of the frontomesocorticolimbic circuit.

Potential role of primed microglia during obesity on the mesocorticolimbic circuit in autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disease which involves functional and structural defects in selective central nervous system (CNS) regions that harm function and individual ability to process and respond to external stimuli. Individuals with ASD spend less time engaging in social interaction compared to non-affected subjects. Studies employing structural and functional magnetic resonance imaging reported morphological and functional abnormalities in the connectivity of the mesocorticolimbic reward pathway between the nucleus accumbens and the ventral tegmental area (VTA) in response to social stimuli, as well as diminished medial prefrontal cortex in response to visual cues, whereas stronger reward system responses for the non-social realm (e.g., video games) than social rewards (e.g., approval), associated with caudate nucleus responsiveness in ASD children. Defects in the mesocorticolimbic reward pathway have been modulated in transgenic murine models using D2 dopamine receptor heterozygous (D2+/-) or dopamine transporter knockout mice, which exhibit sociability deficits and repetitive behaviors observed in ASD phenotypes. Notably, the mesocorticolimbic reward pathway is modulated by systemic and central inflammation, such as primed microglia, which occurs during obesity or maternal overnutrition. Therefore, we propose that a positive energy balance during obesity/maternal overnutrition coordinates a systemic and central inflammatory crosstalk that modulates the dopaminergic neurotransmission in selective brain areas of the mesocorticolimbic reward pathway. Here, we will describe how obesity/maternal overnutrition may prime microglia, causing abnormalities in dopamine neurotransmission of the mesocorticolimbic reward pathway, postulating a possible immune role in the development of ASD.

Age-dependent membrane release and degradation of full-length glycosylphosphatidylinositol-anchored proteins in rats

Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are associated with the surface of eucaryotic cells only through a covalently coupled carboxy-terminal GPI glycolipid structure which is anchored at the outer leaflet of plasma membranes. This mode of membrane association may be responsible for the recent observations that full-length GPI-APs harbouring the complete GPI anchor are (i) released from isolated rat adipocytes in vitro and (ii) expressed in rat and human serum. The upregulation of the adipocyte release in response to increased cell size and blood glucose/insulin levels of the donor rats and downregulation of the expression in serum of insulin resistant and diabetic rats have been reconciled with enhanced degradation of the full-length GPI-APs released into micelle-like complexes together with (lyso) phospholipids and cholesterol by serum GPI-specific phospholipase D (GPI-PLD). Here by using a sensitive and reliable sensing method for full-length GPI-APs, which relies on surface acoustic waves propagating over microfluidic chips, the upregulation of (i) the release of the full-length GPI-APs CD73, alkaline phosphatase and CD55 from isolated adipocyte plasma membranes monitored in a "lab-on-the-chip" configuration, (ii) their release from isolated rat adipocytes into the incubation medium and (iii) the lipolytic cleavage of their GPI anchors in serum was demonstrated to increase with age (3-16 weeks) and body weight (87-477 g) of (healthy) donor rats. In contrast, the amount of full-length GPI-APs in rat serum, as determined by chip-based sensing, turned out to decline with age/body weight. These correlations suggest that age-/weight-induced alterations (in certain biophysical/biochemical characteristics) of plasma membranes are responsible for the release of full-length GPI-APs which becomes counteracted by elevated GPI-PLD activity in serum. Thus, sensitive and specific measurement of these GPI-AP-relevant parameters may be useful for monitoring of age-related cell surface changes, in general, and diseases, in particular.

LRP1-Mediated AggLDL Endocytosis Promotes Cholesteryl Ester Accumulation and Impairs Insulin Response in HL-1 Cells

The cardiovascular disease (CVD) frequently developed during metabolic syndrome and type-2 diabetes mellitus is associated with increased levels of aggregation-prone small LDL particles. Aggregated LDL (aggLDL) internalization is mediated by low-density lipoprotein receptor-related protein-1 (LRP1) promoting intracellular cholesteryl ester (CE) accumulation. Additionally, LRP1 plays a key function in the regulation of insulin receptor (IR) and glucose transporter type 4 (GLUT4) activities. Nevertheless, the link between LRP1, CE accumulation, and insulin response has not been previously studied in cardiomyocytes. We aimed to identify mechanisms through which aggLDL, by its interaction with LRP1, produce CE accumulation and affects the insulin-induced intracellular signaling and GLUT4 trafficking in HL-1 cells. We demonstrated that LRP1 mediates the endocytosis of aggLDL and promotes CE accumulation in these cells. Moreover, aggLDL reduced the molecular association between IR and LRP1 and impaired insulin-induced intracellular signaling activation. Finally, aggLDL affected GLUT4 translocation to the plasma membrane and the 2-NBDG uptake in insulin-stimulated cells. We conclude that LRP1 is a key regulator of the insulin response, which can be altered by CE accumulation through LRP1-mediated aggLDL endocytosis.

Priming of Hypothalamic Ghrelin Signaling and Microglia Activation Exacerbate Feeding in Rats' Offspring Following Maternal Overnutrition

Maternal overnutrition during pregnancy leads to metabolic alterations, including obesity, hyperphagia, and inflammation in the offspring. Nutritional priming of central inflammation and its role in ghrelin sensitivity during fed and fasted states have not been analyzed. The current study aims to identify the effect of maternal programming on microglia activation and ghrelin-induced activation of hypothalamic neurons leading to food intake response. We employed a nutritional programming model exposing female Wistar rats to a cafeteria diet (CAF) from pre-pregnancy to weaning. Food intake in male offspring was determined daily after fasting and subcutaneous injection of ghrelin. Hypothalamic ghrelin sensitivity and microglia activation was evaluated using immunodetection for Iba-1 and c-Fos markers, and Western blot for TBK1 signaling. Release of TNF-alpha, IL-6, and IL-1β after stimulation with palmitic, oleic, linoleic acid, or C6 ceramide in primary microglia culture were quantified using ELISA. We found that programmed offspring by CAF diet exhibits overfeeding after fasting and peripheral ghrelin administration, which correlates with an increase in the hypothalamic Iba-1 microglia marker and c-Fos cell activation. Additionally, in contrast to oleic, linoleic, or C6 ceramide stimulation in primary microglia culture, stimulation with palmitic acid for 24 h promotes TNF-alpha, IL-6, and IL-1β release and TBK1 activation. Notably, intracerebroventricular (i.c.v.) palmitic acid or LPS inoculation for five days promotes daily increase in food intake and food consumption after ghrelin administration. Finally, we found that i.c.v. palmitic acid substantially activates hypothalamic Iba-1 microglia marker and c-Fos. Together, our results suggest that maternal nutritional programing primes ghrelin sensitivity and microglia activation, which potentially might mirror hypothalamic administration of the saturated palmitic acid.

Insulin and Autophagy in Neurodegeneration

Crosstalk in the pathophysiological processes underpinning metabolic diseases and neurodegenerative disorders have been the subject of extensive investigation, in which insulin signaling and autophagy impairment demonstrate to be a common factor in both conditions. Although it is still somewhat conflicting, pharmacological and genetic strategies that regulate these pathways may be a promising approach for aggregate protein clearancing and consequently the delaying of onset or progression of the disease. However, as the response due to this modulation seems to be time-dependent, finding the right regulation of autophagy may be a potential target for drug development for neurodegenerative diseases. In this way, this review focuses on the role of insulin signaling/resistance and autophagy in some neurodegenerative diseases, discussing pharmacological and non-pharmacological interventions in these diseases.

Maternal Flavonoids Intake Reverts Depression-Like Behaviour in Rat Female Offspring

Maternal hypercaloric exposure during pregnancy and lactation is a risk factor for developing diseases associated with inflammation such as obesity, diabetes and, neurological diseases in the offspring. Neuroinflammation might modulate neuronal activation and flavonoids are dietary compounds that have been proven to exert anti-inflammatory properties. Thus, the aim of the present study is to evaluate the effect of maternal supplementation with flavonoids (kaempferol-3-O-glucoside and narirutin) on the prevention of depression-like behaviour in the female offspring of dams fed with an obesogenic diet during the perinatal period. Maternal programming was induced by high fat (HFD), high sugar (HSD), or cafeteria diets exposure and depressive like-behaviour, referred to as swimming, climbing, and immobility events, was evaluated around postnatal day 56–60 before and after 30 mg/kg i.p. imipramine administration in the female offspring groups. Central inflammation was analyzed by measuring the TANK binding kinase 1 (TBK1) expression. We found that the offspring of mothers exposed to HSD programming failed to show the expected antidepressant effect of imipramine. Also, imipramine injection, to the offspring of mothers exposed to cafeteria diet, displayed a pro-depressive like-behaviour phenotype. However, dietary supplementation with flavonoids reverted the depression-like behaviour in the female offspring. Finally, we found that HSD programming increases the TBK1 inflammatory protein marker in the hippocampus. Our data suggest that maternal HSD programming disrupts the antidepressant effect of imipramine whereas cafeteria diet exposure leads to depressive-like behaviour in female offspring, which is reverted by maternal flavonoid supplementation.

Eating as a motivated behavior: modulatory effect of high fat diets on energy homeostasis, reward processing and neuroinflammation

Eating is a basic motivated behavior that provides fuel for the body and supports brain function. To ensure survival, the brain's feeding circuits are tuned to monitor peripheral energy balance and promote food-seeking behavior when energy stores are low. The brain's bias toward a positive energy state, which is necessary to ensure adequate nutrition during times of food scarcity, is evolutionarily conserved across mammalian species and is likely to drive overeating in the presence of a palatable, energy-dense diet. Animal models of diet-induced overeating have played a vital role in investigating how the drive to consume palatable food may override the homeostatic processes that serve to maintain energy balance. These animal models have provided valuable insights into the neurobiological mechanisms underlying homeostatic and non-homeostatic eating, motivation and food reward, and the development of obesity and related comorbidities. Here, we provide a brief review of this literature and discuss how diet-induced inflammation in the central nervous system impacts the neural control of food intake and regulation of body weight. The connection between diet and the immune system provides an exciting new direction for the study of ingestive behavior and the pathophysiology of obesity.

Mechanism for Decreased Gene Expression of β4-Galactosyltransferase 5 upon Differentiation of 3T3-L1 Mouse Preadipocytes to Adipocytes

Upon differentiation of cells, remarkable changes in the structures of glycans linked to lipids on cell surface have been observed. Lactosylceramide (Lac-Cer) serves as a common precursor for a series of glycosphingolipids with diverse structures. In the present study, we examined the underlying mechanism for the biosynthesis of Lac-Cer upon differentiation of 3T3-L1 mouse preadipocytes to adipocytes. TLC analysis showed that the amounts of Lac-Cer decrease in 3T3-L1 adipocytes compared to 3T3-L1 preadipocytes. In accordance with this change, the gene expression level of β4-galactosyltransferase (β4GalT) 5, which was identified as Lac-Cer synthase, decreased drastically upon differentiation of 3T3-L1 preadipocytes. The analysis of the transcriptional mechanism of the β4GalT5 gene demonstrated that the core promoter region is identified between nucleotides -299 and -1 relative to the translational start site. During adipocyte differentiation, the expression levels and promoter activities of the β4GalT5 gene decreased dramatically. Since the Specificity protein 1 (Sp1)-binding sites in the promoter region were critical for the promoter activity, it is suggested that Sp1 plays an important role for the expression of the β4GalT5 gene in 3T3-L1 cells. The gene and protein expression of Sp1 decreased significantly upon differentiation of 3T3-L1 preadipocytes. Taken together, the present study suggest that the expression of the β4GalT5 gene decreases through reduced expression of the Sp1 gene and protein upon differentiation of 3T3-L1 peradipocytes to adipocytes, which may lead to the decreased amounts of Lac-Cer in 3T3-L1 adipocytes.

Tyrphostin AG17 inhibits adipocyte differentiation in vivo and in vitro

Background

Excessive subcutaneous adiposity in obesity is associated to positive white adipocyte tissue (WAT) differentiation (adipogenesis) and WAT expandability. Here, we hypothesized that supplementation with the insulin inhibitor and mitochondrial uncoupler, Tyrphostin (T-AG17), in vitro and in vivo inhibits adipogenesis and adipocyte hypertrophy.

Methods

We used a 3T3-L1 proadipocyte cell line to identify the potential effect of T-AG17 on adipocyte differentiation and fat accumulation in vitro. We evaluated the safety of T-AG17 and its effects on physiological and molecular metabolic parameters including hormonal profile, glucose levels, adipogenesis and adipocyte hypertrophy in a diet-induced obesity model using C57BL/6 mice.

Results

We found that T-AG17 is effective in preventing adipogenesis and lipid synthesis in the 3T3-L1 cell line, as evidenced by a significant decrease in oil red staining (p < 0.05). In obese C57BL/6 mice, oral administration of T-AG17 (0.175 mg/kg for 2 weeks) lead to decreased fat accumulation and WAT hypertrophy. Further, T-AG17 induced adipocyte apoptosis by activating caspase-3. In the hepatocytes of obese mice, T-AG17 promoted an increase in the size of lipid inclusions, which was accompanied by glycogen accumulation. T-AG17 did not alter serum biochemistry, including glucose, insulin, leptin, free fatty acids, creatinine, and aspartate aminotransferase.

Conclusion

T-AG17 promotes adipocyte apoptosis in vivo and is an effective modulator of adipocyte differentiation and WAT hypertrophy in vitro and in vivo. Therefore, T-AG17 may be useful as a pharmacological obesity treatment.

Central Modulation of Neuroinflammation by Neuropeptides and Energy-Sensing Hormones during Obesity

Central nervous system (CNS) senses energy homeostasis by integrating both peripheral and autonomic signals and responding to them by neurotransmitters and neuropeptides release. Although it is previously considered an immunologically privileged organ, we now know that this is not so. Cells belonging to the immune system, such as B and T lymphocytes, can be recruited into the CNS to face damage or infection, in addition to possessing resident immunological cells, called microglia. In this way, positive energy balance during obesity promotes an inflammatory state in the CNS. Saturated fatty acids from the diet have been pointed out as powerful candidates to trigger immune response in peripheral system and in the CNS. However, how central immunity communicates to peripheral immune response remains to be clarified. Recently there has been a great interest in the neuropeptides, POMC derived peptides, ghrelin, and leptin, due to their capacity to suppress or induce inflammatory responses in the brain, respectively. These may be potential candidates to treat different pathologies associated with autoimmunity and inflammation. In this review, we will discuss the role of lipotoxicity associated with positive energy balance during obesity in proinflammatory response in microglia, B and T lymphocytes, and its modulation by neuropeptides.

Microglia activation due to obesity programs metabolic failure leading to type two diabetes

Obesity is an energy metabolism disorder that increases susceptibility to the development of metabolic diseases. Recently, it has been described that obese subjects have a phenotype of chronic inflammation in organs that are metabolically relevant for glucose homeostasis and energy. Altered expression of immune system molecules such as interleukins IL-1, IL-6, IL-18, tumor necrosis factor alpha (TNF-α), serum amyloid A (SAA), and plasminogen activator inhibitor-1 (PAI-1), among others, has been associated with the development of chronic inflammation in obesity. Chronic inflammation modulates the development of metabolic-related comorbidities like metabolic syndrome (insulin resistance, glucose tolerance, hypertension and hyperlipidemia). Recent evidence suggests that microglia activation in the central nervous system (CNS) is a priority in the deregulation of energy homeostasis and promotes increased glucose levels. This review will cover the most significant advances that explore the molecular signals during microglia activation and inflammatory stage in the brain in the context of obesity, and its influence on the development of metabolic syndrome and type two diabetes.