Omega‐3 fatty acids regulate plasticity in distinct hippocampal glutamatergic synapses

Dietary omega‐3 fatty acids accumulate and are actively retained in central nervous system membranes, mainly in synapses, dendrites and photoreceptors. Despite this selective enrichment, their impact on synaptic function and plasticity has not been fully determined at the molecular level. In this study, we explored the impact of omega‐3 fatty acid deficiency on synaptic function in the hippocampus. Dietary omega‐3 fatty acid deficiency for 5 months after weaning led to a 65% reduction in the concentration of docosahexaenoic acid in whole brain synaptosomal phospholipids with no impact on global dopaminergic or serotonergic turnover. We observed reduced concentrations of glutamate receptor subunits, including GluA1, GluA2 and NR2B, and synaptic vesicle proteins synaptophysin and synaptotagmin 1 in hippocampal synaptosomes of omega‐3 fatty acid‐deficient mice as compared to the omega‐3 fatty acid rich group. In contrast, an increased concentration of neuronal inositol 1,4,5‐trisphosphate‐receptor (IP₃‐R) was observed in the deficient group. Furthermore, omega‐3 fatty acid deficiency reduced the long‐term potentiation (LTP) in stratum oriens of the hippocampal CA1 area, but not in stratum radiatum. Thus, omega‐3 fatty acids seem to have specific effects in distinct subsets of glutamatergic synapses, suggesting specific molecular interactions in addition to altering plasma membrane properties on a more global scale.     

Pharmacokinetics of venlafaxine and its major metabolite o-desmethylvenlafaxine in freely moving mice using automated dosing/sampling system

Objective:

To assess the pharmacokinetics of venlafaxine (VEN) and its major metabolite o-desmethylvenlafaxine (ODV) in freely moving mice using automated dosing/infusion (ADI) and automated blood sampling (ABS) systems. In addition, concentration of VEN and its metabolite ODV were also measured in brain by microdialysis.

Materials and Methods:

Venlafaxine was administered directly via jugular vein or gastric catheterization and blood samples were collected through carotid artery. A series of samples with 10 μl of blood was collected from the mouse using ADI/ABS and analyzed with a validated LC-MS/MS system. Extracellular concentrations of VEN and ODV in brain were investigated by using microdialysis procedure.

Results:

The bioavailability of VEN was 11.6%. The percent AUC ratios of ODV to VEN were 18% and 39% following intravenous and intragastric administration, respectively. The terminal half-life of venlafaxine was about two hours. Extracellular concentration of VEN contributed 3.4% of the blood amount, while ODV was not detected in dialysate.

Conclusion:

This study suggests that besides rapid absorption of VEN, the first-pass metabolism is likely to contribute for its lower bioavailability in the mouse. The proposed automated technique can be used easily to conduct pharmacokinetic studies and is applicable to high-throughput manner in mouse model.KEY WORDS: Pharmacokinetics, microdialysis, O-desmethylvenlafaxine, venlafaxine     

Occupational silica exposure as a risk factor for scleroderma: a meta-analysis

Objectives  

Among potential environmental risk factors for systemic sclerosis (SSc), occupational exposures have received some attention. In this meta-analysis, we examined the association between SSc and occupational exposure to silica.     

Heart stopping tick

Although Lyme carditis is relatively rare within 4-6 wk of exposure, it can uncommonly present as the first sign of disseminated Lyme disease. Here we present 17 year old boy who presented to the emergency department with chest discomfort and was later found to have complete atrioventricular block due to lyme carditis. He had uneventful recovery after empiric treatment with ceftriaxone. Our case highlights the importance of considering reversible causes of complete AV block since appropriate therapy can avoid the need for permanent pacemaker insertion.     

Maculosin,a non-toxic antioxidant compound isolated from Streptomyces sp. KTM18

ContextStreptomyces species are prolific sources of bioactive secondary metabolites known especially for their antimicrobial and anticancer activities.ObjectiveThis study sought to isolate and characterize antioxidant molecules biosynthesized by Streptomyces sp. KTM18. The antioxidant potential of an isolated compound and its toxicity were accessed.Materials and methodsThe compound was purified using bioassay-guided chromatography techniques. Nuclear magnetic resonance (NMR) experiments were carried out for structure elucidation. The antioxidant potential of the isolated compound was determined using DPPH free radical scavenging assay. The toxicity of the isolated compound was measured using a brine shrimp lethality (BSL) assay.ResultsEthyl acetate extract of Streptomyces sp. KTM18 showed more than 90% inhibition of DPPH free radical at 50 µg/mL of the test concentration. These data were the strongest among 13 Streptomyces isolates (KTM12–KTM24). The active molecule was isolated and characterized as maculosin (molecular formula, C₁₄H₁₆N₂O₃ as determined by the [M + H]⁺ peak at 261.1259). The DPPH free radical scavenging activity of pure maculosin was higher (IC₅₀, 2.16 ± 0.05 µg/mL) than that of commercial butylated hydroxyanisole (BHA) (IC₅₀, 4.8 ± 0.05 µg/mL). No toxicity was observed for maculosin (LD₅₀, <128 µg/mL) in brine shrimp lethality assay (BSLA) up to the compound’s antioxidant activity (IC₅₀) concentration range. The commercial standard, berberine chloride, showed toxicity in BSLA with an LD₅₀ value of 8.63 ± 0.15 µg/mL.ConclusionsMaculosin may be a leading drug candidate in various cosmetic and therapeutic applications owing to its strong antioxidant and non-toxic properties.     

Pure Sertoli cell tumor of the ovary: A case report

Pure Sertoli cell tumors are an uncommon variant of rare ovarian Sertoli‐Leydig cell tumors. Due to nonspecific clinical and imaging features, diagnosis is often made after histopathological examination. The prognosis is excellent as most are detected in the early stages and surgical resection is often curative in most cases.     

Dyke-Davidoff-Masson syndrome: A rare case of hemiatrophy of brain—Case report from Nepal

Dyke-Davidoff-Masson syndrome (DDMS) is a rare neurological disorder that results from brain injury during intrauterine or early years of life. Prominent cortical sulci, dilated lateral ventricles, cerebral hemiatrophy, hyperpneumatization of the sinus, and compensatory hypertrophy of the skull are the characteristic findings. We describe a female patient who presented with a history of seizure, right-sided body weakness, and neuroimaging features of left cerebral hemiatrophy, dilatation of left lateral ventricle, left frontal sinus hyperpneumatization, asymmetric calvarial thickening, and elevation of the petrous ridge.     

Retinol binding protein 4 primes the NLRP3 inflammasome by signaling through Toll-like receptors 2 and 4

Adipose tissue (AT) inflammation contributes to systemic insulin resistance. In obesity and type 2 diabetes (T2D), retinol binding protein 4 (RBP4), the major retinol carrier in serum, is elevated in AT and has proinflammatory effects which are mediated partially through Toll-like receptor 4 (TLR4). We now show that RBP4 primes the NLRP3 inflammasome for interleukin-1β (IL1β) release, in a glucose-dependent manner, through the TLR4/MD2 receptor complex and TLR2. This impairs insulin signaling in adipocytes. IL1β is elevated in perigonadal white AT (PGWAT) of chow-fed RBP4-overexpressing mice and in serum and PGWAT of high-fat diet-fed RBP4-overexpressing mice vs. wild-type mice. Holo- or apo-RBP4 injection in wild-type mice causes insulin resistance and elevates PGWAT inflammatory markers, including IL1β. TLR4 inhibition in RBP4-overexpressing mice reduces PGWAT inflammation, including IL1β levels and improves insulin sensitivity. Thus, the proinflammatory effects of RBP4 require NLRP3-inflammasome priming. These studies may provide approaches to reduce AT inflammation and insulin resistance in obesity and diabetes.

The incidence of type 2 diabetes (T2D) continues to increase worldwide and constitutes a major global health threat (1). Insulin resistance in muscle, adipose tissue (AT), and liver is a hallmark of T2D, which is associated with low-grade chronic inflammation, characterized by increased serum cytokine levels and a proinflammatory immune profile in AT (2–4). Pattern recognition receptors including Toll-like receptors (TLRs) sense pathogenic microbial components (pathogen-associated molecular patterns, PAMPs) and also host-derived damage-associated molecular patterns (DAMPs), which results in nonpathogen-initiated inflammation often referred to as “sterile inflammation” (5). In obesity, TLR2 and TLR4 are implicated in inflammation-induced insulin resistance in AT, and genetic deletion of TLR2 or TLR4 in mice results in improved insulin sensitivity (6, 7). In obese, insulin-resistant humans, TLR2 and TLR4 expression and activation are increased in AT compared to healthy controls (8) and some evidence suggests that people taking an antiinflammatory agent (abatacept, also known as CTLA4-Ig) which blocks antigen presentation, may have improved insulin sensitivity (9, 10). TLR2 and TLR4 signal through the adaptor proteins myeloid differentiation primary response gene 88 (MyD88) and TIR-domain-containing adaptor-inducing IFN (TRIF) to activate proinflammatory signaling cascades including nuclear factor kappa B (NFκB) and c-Jun N-terminal kinase (JNK) (5, 11). This results in AT immune cell migration, activation, and cytokine secretion which augments insulin resistance in adipocytes (12). Thus, TLR2 and TLR4 contribute to AT inflammation and insulin resistance and their targeting may provide treatment strategies for T2D.Retinol binding protein 4 (RBP4), the major serum retinol transporter, is secreted by the liver and AT (13, 14). Serum RBP4 levels are elevated in obese, insulin-resistant mice and humans (15, 16). Genetic and pharmacological elevation of RBP4 induces insulin resistance in wild-type (WT) mice (16, 17) and reducing RBP4 levels improves insulin sensitivity (16, 18). In humans, RBP4 levels are elevated with prediabetes and correlate positively with many metabolic syndrome-related components, including increased waist/hip ratio, intraabdominal fat mass, dyslipidemia, hypertension, and cardiovascular disease in large epidemiological studies (15, 19–21). A gain-of-function polymorphism in the RBP4 promoter which increases adipose RBP4 expression is associated with an 80% increased risk of T2D in humans (19, 22).Inflammation is critical for RBP4-induced insulin resistance which is partially mediated through TLR4 (17, 18, 23). RBP4 induces insulin resistance in adipocytes indirectly by increasing proinflammatory cytokine secretion from macrophages (23). Insulin resistance and AT inflammation have been observed in two mouse models of RBP4 overexpression. Mice overexpressing RBP4 driven by a muscle-specific promoter (RBP4-Ox) have elevated serum and perigonadal white adipose tissue (PGWAT) RBP4 protein levels and PGWAT inflammation (17). Elevated AT RBP4 in these mice activates antigen presentation through the JNK pathway which results in proinflammatory CD4 T cell proliferation and Th1 polarization (17). Mice overexpressing RBP4 selectively in adipocytes also have AT inflammation and glucose intolerance even on a chow diet (14). Transfer of RBP4-activated dendritic cells into normal mice is sufficient to cause AT inflammation and insulin resistance (17). Interestingly, overexpression of RBP4 selectively in hepatocytes has been reported not to cause elevated circulating RBP4 levels and is not associated with insulin resistance (24) even though hepatocytes are thought to be the major site for RBP4 secretion (25). Adipocytes can contribute to circulating RBP4 levels especially in obesity (14). Taken together, these data suggest that RBP4 in AT may be an obesity and insulin-resistance-related damage-associated molecule pattern.Activation of PAMP and DAMP receptors in immune cells leads to the assembly of inflammasomes, which are multiprotein complexes that cleave and activate interleukin-1 beta (IL1β) and interleukin-18 (IL18) (26). The nucleotide-binding domain and leucine-rich repeat containing protein 3 (NLRP3) inflammasome plays a role in the pathogenesis of obesity, type 1 diabetes, type 2 diabetes, and metabolic syndrome (26–28). NLRP3 knockout (KO) protects against insulin resistance in mice (27). NLRP3 activation requires a two-step process. The first “priming” occurs in response to TLR-mediated activation of the NFκB pathway resulting in expression of pro-IL1β (26). The second “activating” step directly induces inflammasome assembly which recruits and cleaves procaspase-1 to its active form caspase-1 (26). Caspase-1 mediates the cleavage of pro-IL1β resulting in IL1β release (26). The NLRP3 inflammasome can be activated by metabolites which are elevated in obesity and insulin resistance, such as palmitate (29). While an ever-expanding list of several metabolites is known to provide the second signal in inflammasome activation, there is a paucity of data on the endogenous proteins and metabolites that provide the first priming signal in obesity and T2D. Here we show that RBP4 is an endogenous NLRP3-inflammasome priming agent and we investigate its upstream signaling pathways.Our data show that elevating RBP4 levels by RBP4 injection in WT mice or genetically induced RBP4 overexpression markedly elevates adipose IL1β expression, which leads to PGWAT inflammation and insulin resistance. IL1β is elevated in PGWAT of chow-fed RBP4-Ox mice and in serum and PGWAT of HFD-fed RBP4-Ox mice compared to WT mice. The RBP4-mediated proinflammatory effects are mediated specifically through TLR2 and a TLR4/MD2 receptor complex, which does not require the other adaptor proteins LPS-binding protein and CD14. The activation of macrophages by RBP4 through TLR2 and TLR4/MD2 requires signaling through the downstream pathways MyD88 and TRIF. TLR4 inhibition in RBP4-Ox reduces IL1β levels in PGWAT and improves insulin sensitivity. The RBP4-mediated increase in IL1β release from macrophages is glucose dependent. Thus, targeting the NLRP3 inflammasome or the upstream activating receptors or pathways may provide therapeutic avenues to ameliorate RBP4-mediated insulin resistance and T2D.