Uncovering Novel Extracellular Matrix Transcriptome Alterations in Lesions of Multiple Sclerosis.

The extracellular matrix (ECM) of the central nervous system (CNS) is an interconnected network of proteins and sugars with critical roles in both homeostasis and disease. In neurological diseases, excessive ECM deposition and remodeling impact both injury and repair. CNS lesions of multiple sclerosis (MS), a chronic inflammatory and degenerative disease, cause prominent alterations of the ECM. However, there are a lack of data investigating how the multitude of ECM members change in relation to each other and how this affects the MS disease course. Here, we evaluated ECM changes in MS lesions compared to a control brain using databases generated in-house through spatial mRNA-sequencing and through a public resource of single-nucleus RNA sequencing previously published by Absinta and colleagues. These results underline the importance of publicly available datasets to find new targets of interest, such as the ECM. Both spatial and public datasets demonstrated widespread changes in ECM molecules and their interacting proteins, including alterations to proteoglycans and glycoproteins within MS lesions. Some of the altered ECM members have been described in MS, but other highly upregulated members, including the SPARC family of proteins, have not previously been highlighted. SPARC family members are upregulated in other conditions by reactive astrocytes and may influence immune cell activation and MS disease course. The profound changes to the ECM in MS lesions deserve more scrutiny as they impact neuroinflammation, injury, and repair.

Prominent elevation of extracellular matrix molecules in intracerebral hemorrhage.

Background: Intracerebral hemorrhage (ICH) is the predominant type of hemorrhagic stroke with high mortality and disability. In other neurological conditions, the deposition of extracellular matrix (ECM) molecules is a prominent obstacle for regenerative processes and an enhancer of neuroinflammation. Whether ECM molecules alter in composition after ICH, and which ECM members may inhibit repair, remain largely unknown in hemorrhagic stroke. Methods: The collagenase-induced ICH mouse model and an autopsied human ICH specimen were investigated for expression of ECM members by immunofluorescence microscopy. Confocal image z-stacks were analyzed with Imaris 3D to assess the association of immune cells and ECM molecules. Sections from a mouse model of multiple sclerosis were used as disease and staining controls. Tissue culture was employed to examine the roles of ECM members on oligodendrocyte precursor cells (OPCs). Results: Among the lectican chondroitin sulfate proteoglycan (CSPG) members, neurocan but not aggrecan, versican-V1 and versican-V2 was prominently expressed in perihematomal tissue and lesion core compared to the contralateral area in murine ICH. Fibrinogen, fibronectin and heparan sulfate proteoglycan (HSPG) were also elevated after murine ICH while thrombospondin and tenascin-C was not. Confocal microscopy with Imaris 3D rendering co-localized neurocan, fibrinogen, fibronectin and HSPG molecules to Iba1+ microglia/macrophages or GFAP+ astrocytes. Marked differentiation from the multiple sclerosis model was observed, the latter with high versican-V1 and negligible neurocan. In culture, purified neurocan inhibited adhesion and process outgrowth of OPCs, which are early steps in myelination in vivo. The prominent expression of neurocan in murine ICH was corroborated in human ICH sections. Conclusion: ICH caused distinct alterations in ECM molecules. Among CSPG members, neurocan was selectively upregulated in both murine and human ICH. In tissue culture, neurocan impeded the properties of oligodendrocyte lineage cells. Alterations to the ECM in ICH may adversely affect reparative outcomes after stroke.

Energy expenditure deficits drive obesity in a mouse model of Alström syndrome.

OBJECTIVE: Alström syndrome (AS) is a rare multisystem disorder of which early onset childhood obesity is a cardinal feature. Like humans with AS, animal models with Alms1 loss-of-function mutations develop obesity, supporting the notion that ALMS1 is required for the regulatory control of energy balance across species. This study aimed to determine which component(s) of energy balance are reliant on ALMS1. METHODS: Comprehensive energy balance phenotyping was performed on Alms1tvrm102 mice at both 8 and 18 weeks of age. RESULTS: It was found that adiposity gains occurred early and rapidly in Alms1tvrm102 male mice but much later in females. Rapid increases in body fat in males were due to a marked reduction in energy expenditure (EE) during early life and not due to any genotype-specific increases in energy intake under chow conditions. Energy intake did increase in a genotype-specific manner when mice were provided a high-fat diet, exacerbating the effects of reduced EE on obesity progression. The EE deficit observed in male Alms1tvrm102 mice did not persist as mice aged. CONCLUSIONS: Either loss of ALMS1 causes a developmental delay in the mechanisms controlling early life EE or activation of compensatory mechanisms occurs after obesity is established in AS. Future studies will determine how ALMS1 modulates EE and how sex moderates this process.

Exogenous mitochondrial transfer increases energy expenditure and attenuates adiposity gains in mice with diet-induced obesity.

Obesity is associated with chronic multi-system bioenergetic stress that may be improved by increasing the number of healthy mitochondria available across organ systems. However, treatments capable of increasing mitochondrial content are generally limited to endurance exercise training paradigms, which are not always sustainable long-term, let alone feasible for many patients with obesity. Recent studies have shown that local transfer of exogenous mitochondria from healthy donor tissues can improve bioenergetic outcomes and alleviate the effects of tissue injury in recipients with organ specific disease. Thus, the aim of this project was to determine the feasibility of systemic mitochondrial transfer for improving energy balance regulation in the setting of diet-induced obesity. We found that transplantation of mitochondria from lean mice into mice with diet-induced obesity attenuated adiposity gains by increasing energy expenditure and promoting the mobilization and oxidation of lipids. Additionally, mice that received exogenous mitochondria demonstrated improved glucose uptake, greater insulin responsiveness, and complete reversal of hepatic steatosis. These changes were, in part, driven by adaptations occurring in white adipose tissue. Together, these findings are proof-of-principle that mitochondrial transplantation is an effective therapeutic strategy for limiting the deleterious metabolic effects of diet-induced obesity in mice.

Voicing the need to consider sex-specific differences in research.

Researchers are exploring sex differences in experimental models of both development and disease-but are we doing enough? In this collection of Voices, we celebrate researchers who are asking this question and starting to offer mechanistic clues on sexually dimorphic differences seen in interorgan communication, metabolic disease, neurological disorders, and more.

Chronic intake of high dietary sucrose induces sexually dimorphic metabolic adaptations in mouse liver and adipose tissue.

Almost all effective treatments for non-alcoholic fatty liver disease (NAFLD) involve reduction of adiposity, which suggests the metabolic axis between liver and adipose tissue is essential to NAFLD development. Since excessive dietary sugar intake may be an initiating factor for NAFLD, we have characterized the metabolic effects of liquid sucrose intake at concentrations relevant to typical human consumption in mice. We report that sucrose intake induces sexually dimorphic effects in liver, adipose tissue, and the microbiome; differences concordant with steatosis severity. We show that when steatosis is decoupled from impairments in insulin responsiveness, sex is a moderating factor that influences sucrose-driven lipid storage and the contribution of de novo fatty acid synthesis to the overall hepatic triglyceride pool. Our findings provide physiologic insight into how sex influences the regulation of adipose-liver crosstalk and highlight the importance of extrahepatic metabolism in the pathogenesis of diet-induced steatosis and NAFLD.

Adipocyte-Specific Modulation of KLF14 Expression in Mice Leads to Sex-Dependent Impacts on Adiposity and Lipid Metabolism.

Genome-wide association studies identified single nucleotide polymorphisms on chromosome 7 upstream of KLF14 to be associated with metabolic syndrome traits and increased risk for type 2 diabetes (T2D). The associations were more significant in women than in men. The risk allele carriers expressed lower levels of the transcription factor KLF14 in adipose tissues than nonrisk allele carriers. To investigate how adipocyte KLF14 regulates metabolic traits in a sex-dependent manner, we characterized high-fat diet-fed male and female mice with adipocyte-specific Klf14 deletion or overexpression. Klf14 deletion resulted in increased fat mass in female mice and decreased fat mass in male mice. Female Klf14-deficient mice had overall smaller adipocytes in subcutaneous fat depots but larger adipocytes in parametrial depots, indicating a shift in lipid storage from subcutaneous to visceral fat depots. They had reduced metabolic rates and increased respiratory exchange ratios consistent with increased use of carbohydrates as an energy source. Fasting- and isoproterenol-induced adipocyte lipolysis was defective in female Klf14-deficient mice, and concomitantly, adipocyte triglycerides lipase mRNA levels were downregulated. Female Klf14-deficient mice cleared blood triglyceride and nonesterified fatty acid less efficiently than wild-type. Finally, adipocyte-specific overexpression of Klf14 resulted in lower total body fat in female but not male mice. Taken together, consistent with human studies, adipocyte KLF14 deficiency in female but not in male mice causes increased adiposity and redistribution of lipid storage from subcutaneous to visceral adipose tissues. Increasing KLF14 abundance in adipocytes of females with obesity and T2D may provide a novel treatment option to alleviate metabolic abnormalities.

Group IIA secreted phospholipase A2 (PLA2G2A) augments adipose tissue thermogenesis.

Group IIA secreted phospholipase A2 (PLA2G2A) hydrolyzes glycerophospholipids at the sn-2 position resulting in the release of fatty acids and lysophospholipids. C57BL/6 mice do not express Pla2g2a due to a frameshift mutation (wild-type [WT] mice). We previously reported that transgenic expression of human PLA2G2A in C57BL/6 mice (IIA+ mice) protects against weight gain and insulin resistance, in part by increasing total energy expenditure. Additionally, we found that brown and white adipocytes from IIA+ mice have increased expression of mitochondrial uncoupling markers, such as uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor-gamma coactivator, and PR domain containing 16, suggesting that the energy expenditure phenotype might be due to an increased thermogenic capacity in adipose tissue. Here, we further characterize the impact of PLA2G2A on thermogenic mechanisms in adipose tissue. Metabolic analysis of WT and IIA+ mice revealed that even when housed within their thermoneutral zone, IIA+ mice have elevated energy expenditure compared to WT littermates. Increased energy expenditure in IIA+ mice is associated with increased citrate synthase activity in brown adipose tissue (BAT) and increased mitochondrial respiration in both brown and white adipocytes. We also observed that direct addition of recombinant PLA2G2A enzyme to in vitro cultured adipocytes results in the marked induction of UCP1 protein expression. Finally, we report that PLA2G2A induces the expression of numerous transcripts related to energy substrate transport and metabolism in BAT, suggestive of an increase in substrate flux to fuel BAT activity. These data demonstrate that PLA2G2A enhances adipose tissue thermogenesis, in part, through elevated substrate delivery and increased mitochondrial content in BAT.

The glycosyltransferase EXTL2 promotes proteoglycan deposition and injurious neuroinflammation following demyelination.

BACKGROUND: Chondroitin sulfate proteoglycans (CSPGs) are potent inhibitors of axonal regrowth and remyelination. More recently, they have also been highlighted as a modulator of macrophage infiltration into the central nervous system in experimental autoimmune encephalomyelitis, an inflammatory model of multiple sclerosis. METHODS: We interrogated results from single nucleotide polymorphisms (SNPs) lying in or close to genes regulating CSPG metabolism in the summary results from two publicly available systematic studies of multiple sclerosis (MS) genetics. A demyelinating injury model in the spinal cord of exostosin-like 2 deficient  (EXTL2-/-) mice was used to investigate the effects of dysregulation of EXTL2 on remyelination. Cell cultures of bone marrow-derived macrophages and primary oligodendrocyte precursor cells and neurons were supplemented with purified CSPGs or conditioned media to assess potential mechanisms of action. RESULTS: The strongest evidence for genetic association was seen for SNPs mapping to the region containing the glycosyltransferase exostosin-like 2 (EXTL2), an enzyme that normally suppresses CSPG biosynthesis. Six of these SNPs showed genome-wide significant evidence for association in one of the studies with concordant and nominally significant effects in the second study. We then went on to show that a demyelinating injury to the spinal cord of EXTL2-/- mice resulted in excessive deposition of CSPGs in the lesion area. EXTL2-/- mice had exacerbated axonal damage and myelin disruption relative to wild-type mice, and increased representation of microglia/macrophages within lesions. In tissue culture, activated bone marrow-derived macrophages from EXTL2-/- mice overproduce tumor necrosis factor α (TNFα) and matrix metalloproteinases (MMPs). CONCLUSIONS: These results emphasize CSPGs as a prominent modulator of neuroinflammation and they highlight CSPGs accumulating in lesions in promoting axonal injury.

TGR5 signaling mitigates parenteral nutrition-associated liver disease.

Bile acid receptors regulate the metabolic and immune functions of circulating enterohepatic bile acids. This process is disrupted by administration of parenteral nutrition (PN), which may induce progressive hepatic injury for unclear reasons, especially in the newborn, leading to PN-associated liver disease. To explore the role of bile acid signaling on neonatal hepatic function, we initially observed that Takeda G protein receptor 5 (TGR5)-specific bile acids were negatively correlated with worsening clinical disease markers in the plasma of human newborns with prolonged PN exposure. To test our resulting hypothesis that TGR5 regulates critical liver functions to PN exposure, we used TGR5 receptor deficient mice (TGR5-/-). We observed PN significantly increased liver weight, cholestasis, and serum hepatic stress enzymes in TGR5-/- mice compared with controls. Mechanistically, PN reduced bile acid synthesis genes in TGR5-/-. Serum bile acid composition revealed that PN increased unconjugated primary bile acids and secondary bile acids in TGR5-/- mice, while increasing conjugated primary bile acid levels in TGR5-competent mice. Simultaneously, PN elevated hepatic IL-6 expression and infiltrating macrophages in TGR5-/- mice. However, the gut microbiota of TGR5-/- mice compared with WT mice following PN administration displayed highly elevated levels of Bacteroides and Parabacteroides, and possibly responsible for the elevated levels of secondary bile acids in TGR5-/- animals. Intestinal bile acid transporters expression was unchanged. Collectively, this suggests TGR5 signaling specifically regulates fundamental aspects of liver bile acid homeostasis during exposure to PN. Loss of TGR5 is associated with biochemical evidence of cholestasis in both humans and mice on PN.NEW & NOTEWORTHY Parenteral nutrition is associated with deleterious metabolic outcomes in patients with prolonged exposure. Here, we demonstrate that accelerated cholestasis and parental nutrition-associated liver disease (PNALD) may be associated with deficiency of Takeda G protein receptor 5 (TGR5) signaling. The microbiome is responsible for production of secondary bile acids that signal through TGR5. Therefore, collectively, these data support the hypothesis that a lack of established microbiome in early life or under prolonged parenteral nutrition may underpin disease development and PNALD.

African American and Latinx Adolescents' Perspectives of Nursing as a Career Choice.

BACKGROUND: Ensuring a diverse nursing workforce that closely represents the diversity of the population is imperative for culturally competent and equitable care. To accomplish this, purposeful and strategic programs need to be integrated into secondary education. The purpose of this qualitative descriptive study was to explore the perceptions and attitudes about the nursing profession among African American and Latinx adolescents. METHOD: Four focus group sessions were conducted, and content analysis of the focus group narratives was completed. RESULTS: The majority of the 33 participants were female and 57% were Latinx. The three themes are Nursing Is a Caring Profession But…; Formation of Ideas About Nursing Often Come From Family, Friends, and the Media; and Deterrents to Pursuing Nursing. CONCLUSION: To decrease health disparities, nursing must address its lack of diversity. Based on these findings, our school of nursing has implemented a summer program for adolescents. [J Nurs Educ. 2019;58(9):519-524.].

Targeting the Chondroitin Sulfate Proteoglycans: Evaluating Fluorinated Glucosamines and Xylosides in Screens Pertinent to Multiple Sclerosis.

Chondroitin sulfate proteoglycans (CSPGs) are upregulated in insults to the central nervous system, including multiple sclerosis (MS), an inflammatory demyelinating condition of the central nervous system. CSPGs appear to be detrimental in MS, as they enhance immune responses and act as barriers to oligodendrocyte differentiation and thus remyelination. Despite their deleterious roles, strategies to selectively reduce CSPG production are lacking. The purpose of this study was to develop, screen, and describe a series of glucosamine derivatives and xylosides for their capacity to overcome detrimental CSPGs and inflammatory processes. Specifically, we assess the ability of analogues to interfere with CSPG biosynthesis, promote the outgrowth of oligodendrocyte precursor cells in an inhibitory environment, and lower inflammation by attenuating the proliferation of T lymphocytes. We highlight the beneficial activities of a novel compound, per-O-acetylated 4,4-difluoro-N-acetylglucosamine (Ac-4,4-diF-GlcNAc) in vitro, and report that it reduced inflammation and clinical severity in a mouse model of MS. Thus, this study represents an important advance, as we uncover that targeting CSPG biosynthesis with a potent inhibitor is an effective avenue to ameliorate inflammatory cascades and promote repair processes in MS and other neurological conditions.

Secretory phospholipase A2 group IIA enhances the metabolic rate and increases glucose utilization in response to thyroid hormone.

Secretory phospholipase A2 group IIA (PLA2G2A) is a phospholipase which has a role in inflammation, atherogenesis, and host defense. Previously, we found that PLA2G2A protects mice on high-fat diets from weight gain and insulin resistance. Here, we examined the regulation of PLA2G2A and the metabolic changes that occur in response to variations in thyroid status. In particular, the impact of PLA2G2A on the brown adipose tissue (BAT) thermogenic gene expression was explored. We induced hypothyroidism in C57BL/6 and PLA2G2A-overexpressing (IIA+) mice over a 10 wk period or treated them with thyroid hormone (T3) for 5 wk. There were no significant changes in PLA2G2A abundance in response to thyroid status. The energy expenditure of hypothyroid IIA+ mice did not increase; however, the energy expenditure, substrate utilization, insulin sensitivity, and glucose tolerance were all elevated in the IIA+ mice given T3. Moreover, white adipocytes from IIA+ mice were much more prone to "beiging," including increased expression of brown adipose thermogenic markers such as uncoupling protein 1 (UCP1), PR domain containing 16, and early B cell factor 2. Finally, the BAT of IIA+ mice had increased UCP1 and other proteins indicative of mitochondrial uncoupling and nonshivering adaptive thermogenesis. These data reveal a novel role for PLA2G2A on adipose tissue thermogenesis depending on thyroid status.-Kuefner, M. S., Deng, X., Stephenson, E. J., Pham, K., Park, E. A. Secretory phospholipase A2 group IIA enhances the metabolic rate and increases glucose utilization in response to thyroid hormone.

Disruption of brain-derived neurotrophic factor production from individual promoters generates distinct body composition phenotypes in mice.

Brain-derived neurotrophic factor (BDNF) is a key neuropeptide in the central regulation of energy balance. The Bdnf gene contains nine promoters, each producing specific mRNA transcripts that encode a common protein. We sought to assess the phenotypic outcomes of disrupting BDNF production from individual Bdnf promoters. Mice with an intact coding region but selective disruption of BDNF production from Bdnf promoters I, II, IV, or VI (Bdnf-e1-/-, -e2-/-, -e4-/-, and -e6-/-) were created by inserting an enhanced green fluorescent protein-STOP cassette upstream of the targeted promoter splice donor site. Body composition was measured by MRI weekly from age 4 to 22 wk. Energy expenditure was measured by indirect calorimetry at 18 wk. Food intake was measured in Bdnf-e1-/- and Bdnf-e2-/- mice, and pair feeding was conducted. Weight gain, lean mass, fat mass, and percent fat of Bdnf-e1-/- and Bdnf-e2-/- mice (both sexes) were significantly increased compared with wild-type littermates. For Bdnf-e4-/- and Bdnf-e6-/- mice, obesity was not observed with either chow or high-fat diet. Food intake was increased in Bdnf-e1-/- and Bdnf-e2-/- mice, and pair feeding prevented obesity. Mutant and wild-type littermates for each strain (both sexes) had similar total energy expenditure after adjustment for body composition. These findings suggest that the obesity phenotype observed in Bdnf-e1-/- and Bdnf-e2-/- mice is attributable to hyperphagia and not altered energy expenditure. Our findings show that disruption of BDNF from specific promoters leads to distinct body composition effects, with disruption from promoters I or II, but not IV or VI, inducing obesity.

The extracellular matrix: Focus on oligodendrocyte biology and targeting CSPGs for remyelination therapies.

The repair of myelin, termed remyelination, is a regenerative process that occurs within the central nervous system in conditions such as multiple sclerosis. Remyelination is enabled by oligodendrocytes that mature from oligodendrocyte precursor cells. Many factors influence the biology of oligodendrocytes and their capacity to reform myelin, and considerable evidence now implicates the extracellular matrix within the injured central nervous system as a major modifier of remyelination. Herein, we review current knowledge of components of the brain extracellular matrix that are beneficial or inhibitory for oligodendrocyte recruitment and maturation, and for their capacity to remyelinate where evidence exists. We highlight the detrimental roles of the chondroitin sulfate proteoglycans in remyelination and discuss approaches to alter the brain extracellular matrix for the wellbeing of oligodendrocytes and their capacity for myelin regeneration.

Pro-inflammatory roles of chondroitin sulfate proteoglycans in disorders of the central nervous system.

The extracellular matrix of the central nervous system is an interconnected network of proteins and sugars. It is crucial for homeostasis, but its remodeling in neurological diseases impacts both injury and repair. Here we introduce an extracellular matrix family member that participates in immune-matrix interactions, the chondroitin sulfate proteoglycans. Chondroitin sulfate proteoglycans integrate signals from the microenvironment to activate immune cells, and they boost inflammatory responses by binding immunological receptors including toll-like receptors, selectins, CD44, and ß1 integrin. Chondroitin sulfate proteoglycans also bind signaling molecules for immune cells such as cytokines and chemokines, and they activate matrix-degrading enzymes. Chondroitin sulfate proteoglycans accumulate in the damaged CNS, including during traumatic brain/spinal cord injury and multiple sclerosis, and they help drive pathogenesis. This Review aims to give new insights into the remodeling of chondroitin sulfate proteoglycans during inflammation, and how these matrix glycoproteins are able to drive neuroinflammation.

Glucocorticoid-Induced Metabolic Disturbances Are Exacerbated in Obese Male Mice.

The purpose of this study was to determine the effects of glucocorticoid-induced metabolic dysfunction in the presence of diet-induced obesity. C57BL/6J adult male lean and diet-induced obese mice were given dexamethasone, and levels of hepatic steatosis, insulin resistance, and lipolysis were determined. Obese mice given dexamethasone had significant, synergistic effects on fasting glucose, insulin resistance, and markers of lipolysis, as well as hepatic steatosis. This was associated with synergistic transactivation of the lipolytic enzyme adipose triglyceride lipase. The combination of chronically elevated glucocorticoids and obesity leads to exacerbations in metabolic dysfunction. Our findings suggest lipolysis may be a key player in glucocorticoid-induced insulin resistance and fatty liver in individuals with obesity.

Chondroitin sulfate proteoglycans as novel drivers of leucocyte infiltration in multiple sclerosis.

Multiple sclerosis presents with profound changes in the network of molecules involved in maintaining central nervous system architecture, the extracellular matrix. The extracellular matrix components, particularly the chondroitin sulfate proteoglycans, have functions beyond structural support including their potential interaction with, and regulation of, inflammatory molecules. To investigate the roles of chondroitin sulfate proteoglycans in multiple sclerosis, we used the experimental autoimmune encephalomyelitis model in a time course study. We found that the 4-sulfated glycosaminoglycan side chains of chondroitin sulfate proteoglycans, and the core protein of a particular family member, versican V1, were upregulated in the spinal cord of mice at peak clinical severity, correspondent with areas of inflammation. Versican V1 expression in the spinal cord rose progressively over the course of experimental autoimmune encephalomyelitis. A particular structure in the spinal cord and cerebellum that presented with intense upregulation of chondroitin sulfate proteoglycans is the leucocyte-containing perivascular cuff, an important portal of entry of immune cells into the central nervous system parenchyma. In these inflammatory perivascular cuffs, versican V1 and the glycosaminoglycan side chains of chondroitin sulfate proteoglycans were observed by immunohistochemistry within and in proximity to lymphocytes and macrophages as they migrated across the basement membrane into the central nervous system. Expression of versican V1 transcript was also documented in infiltrating CD45+ leucocytes and F4/80+ macrophages by in situ hybridization. To test the hypothesis that the chondroitin sulfate proteoglycans regulate leucocyte mobility, we used macrophages in tissue culture studies. Chondroitin sulfate proteoglycans significantly upregulated pro-inflammatory cytokines and chemokines in macrophages. Strikingly, and more potently than the toll-like receptor-4 ligand lipopolysaccharide, chondroitin sulfate proteoglycans increased the levels of several members of the matrix metalloproteinase family, which are implicated in the capacity of leucocytes to cross barriers. In support, the migratory capacity of macrophages in vitro in a Boyden chamber transwell assay was enhanced by chondroitin sulfate proteoglycans. Finally, using brain specimens from four subjects with multiple sclerosis with active lesions, we found chondroitin sulfate proteoglycans to be associated with leucocytes in inflammatory perivascular cuffs in all four patients. We conclude that the accumulation of chondroitin sulfate proteoglycans in the perivascular cuff in multiple sclerosis and experimental autoimmune encephalomyelitis boosts the activity and migration of leucocytes across the glia limitans into the central nervous system parenchyma. Thus, chondroitin sulfate proteoglycans represent a new class of molecules to overcome in order to reduce the inflammatory cascades and clinical severity of multiple sclerosis.

Secretory phospholipase A2 group IIA modulates insulin sensitivity and metabolism.

Secretory phospholipase A2 group IIA (PLA2G2A) is a member of a family of secretory phospholipases that have been implicated in inflammation, atherogenesis, and antibacterial actions. Here, we evaluated the role of PLA2G2A in the metabolic response to a high fat diet. C57BL/6 (BL/6) mice do not express PLA2g2a due to a frameshift mutation. We fed BL/6 mice expressing the human PLA2G2A gene (IIA+ mice) a fat diet and assessed the physiologic response. After 10 weeks on the high fat diet, the BL/6 mice were obese, but the IIA+ mice did not gain weight or accumulate lipid. The lean mass in chow- and high fat-fed IIA+ mice was constant and similar to the BL/6 mice on a chow diet. Surprisingly, the IIA+ mice had an elevated metabolic rate, which was not due to differences in physical activity. The IIA+ mice were more insulin sensitive and glucose tolerant than the BL/6 mice, even when the IIA+ mice were provided the high fat diet. The IIA+ mice had increased expression of uncoupling protein 1 (UCP1), sirtuin 1 (SIRT1), and PPARγ coactivator 1α (PGC-1α) in brown adipose tissue (BAT), suggesting that PLA2G2A activates mitochondrial uncoupling in BAT. Our data indicate that PLA2G2A has a previously undiscovered impact on insulin sensitivity and metabolism.

Expression of microRNAs and target proteins in skeletal muscle of rats selectively bred for high and low running capacity.

Impairments in mitochondrial function and substrate metabolism are implicated in the etiology of obesity and Type 2 diabetes. MicroRNAs (miRNAs) can degrade mRNA or repress protein translation and have been implicated in the development of such disorders. We used a contrasting rat model system of selectively bred high- (HCR) or low- (LCR) intrinsic running capacity with established differences in metabolic health to investigate the molecular mechanisms through which miRNAs regulate target proteins mediating mitochondrial function and substrate oxidation processes. Quantification of select miRNAs using the rat miFinder miRNA PCR array revealed differential expression of 15 skeletal muscles (musculus tibialis anterior) miRNAs between HCR and LCR rats (14 with higher expression in LCR; P < 0.05). Ingenuity Pathway Analysis predicted these altered miRNAs to collectively target multiple proteins implicated in mitochondrial dysfunction and energy substrate metabolism. Total protein abundance of citrate synthase (CS; miR-19 target) and voltage-dependent anion channel 1 (miR-7a target) were higher in HCR compared with LCR cohorts (~57 and ~26%, respectively; P < 0.05). A negative correlation was observed for miR-19a-3p and CS (r = 0.32, P = 0.015) protein expression. To determine whether miR-19a-3p can regulate CS in vitro, we performed luciferase reporter and transfection assays in C2C12 myotubes. MiR-19a-3p binding to the CS untranslated region did not change luciferase reporter activity; however, miR-19a-3p transfection decreased CS protein expression (∼70%; P < 0.05). The differential miRNA expression targeting proteins implicated in mitochondrial dysfunction and energy substrate metabolism may contribute to the molecular basis, mediating the divergent metabolic health profiles of LCR and HCR rats.