Chloroquine attenuates diet-induced obesity and glucose intolerance through a mechanism that might involve FGF-21, but not UCP-1-mediated thermogenesis and inhibition of adipocyte autophagy

Chloroquine diphosphate (CQ), a weak base used to inhibit autophagic flux and treat malaria and rheumatoid diseases, has been shown, through unknown mechanisms, to improve glucose and lipid homeostasis in patients and rodents. We investigate herein the molecular mechanisms underlying these CQ beneficial metabolic actions in diet-induced obese mice. For this, C57BL6/J mice fed with either a chow or a high-fat diet (HFD) and uncoupling protein 1 (UCP-1) KO and adipocyte Atg7-deficient mice fed with a HFD were treated or not with CQ (60 mg/kg of body weight/day) during 8 weeks and evaluated for body weight, adiposity, glucose homeostasis and brown and white adipose tissues (BAT and WAT) UCP-1 content. CQ reduced body weight gain and adipose tissue and liver masses in mice fed with a HFD, without altering food intake, oxygen consumption, respiratory exchange ratio, spontaneous motor activity and feces caloric content. CQ attenuated the insulin intolerance, hyperglycemia, hyperinsulinemia, hypertriglyceridemia and hypercholesterolemia induced by HFD intake, such effects that were associated with increases in serum and liver fibroblast growth factor 21 (FGF-21) and BAT and WAT UCP-1 content. Interestingly, CQ beneficial metabolic actions of reducing body weight and adiposity and improving glucose homeostasis were preserved in HFD-fed UCP-1 KO and adipocyte Atg7 deficient mice. CQ reduces body weight gain and adiposity and improves glucose homeostasis in diet-induced obese mice through mechanisms that might involve FGF-21, but not UCP1-mediated nonshivering thermogenesis or inhibition of adipocyte autophagy.

Use of Active Learning During Emergency Remote Teaching in COVID-19 Pandemic

The mandatory isolation caused by COVID-19 required the adoption of emergency remote teaching, which caused difficulties for instructors, especially for those who use active learning that depends on student participation in class. This study aimed to investigate the ability of instructors to apply active learning effectively given the pandemic context. This was a cross-sectional observational study carried out in an undergraduate medical school. The sample was composed from one to three classes of 28 instructors that were observed synchronously. Each class was analyzed using a form created from an adaptation of the PORTAAL tool, aiming to evaluate quantitatively essential elements for active learning. We observed that the mean times devoted to activities and active participation of students were 54.8% and 33.1% of the total class time, respectively. Among the time spent in student interactions, the intra-group demanded the highest percentage of the class time. Additionally, 22.0% of the activities presented a high level in Bloom's taxonomy and there was a positive correlation between the percentage of activities at higher Bloom levels and the percentage of class time with student participation, intra-group or between-group interactions, supporting the use of higher-order cognitive skills in a collaborative and student-centered context. In conclusion, our findings indicate that some instructors were able to apply essential elements for an active and collaborative learning even during the emergency remote teaching.

The involvement of the adrenergic nervous system in activating human brown adipose tissue and browning

Obesity is a chronic condition of multifactorial etiology characterized by excessive body fat due to a calorie intake higher than energy expenditure. Given the intrinsic limitations of surgical interventions and the difficulties associated with lifestyle changes, pharmacological manipulation is currently one of the main therapies for metabolic diseases. Approaches aiming to promote energy expenditure through induction of thermogenesis have been explored and, in this context, brown adipose tissue (BAT) activation and browning have been shown to be promising strategies. Although such processes are physiologically stimulated by the sympathetic nervous system, not all situations that are known to increase adrenergic signaling promote a concomitant increase in BAT activation or browning in humans. Thus, a better understanding of factors involved in the thermogenesis attributed to these tissues is needed to enable the development of future therapies against obesity. Herein we carry out a critical review of original articles in humans under conditions previously known to trigger adrenergic responses-namely, cold, catecholamine-secreting tumor (pheochromocytoma and paraganglioma), burn injury, and adrenergic agonists-and discuss which of them are associated with increased BAT activation and browning. BAT is clearly stimulated in individuals exposed to cold or treated with high doses of the β3-adrenergic agonist mirabegron, whereas browning is certainly induced in patients after burn injury or with pheochromocytoma, as well as in individuals treated with β3-adrenergic agonist mirabegron for at least 10 weeks. Given the potential effect of increasing energy expenditure, adrenergic stimuli are promising strategies in the treatment of metabolic diseases.

PPARγ-induced upregulation of subcutaneous fat adiponectin secretion, glyceroneogenesis and BCAA oxidation requires mTORC1 activity

The nutrient sensors peroxisome proliferator-activated receptor γ (PPARγ) and mechanistic target of rapamycin complex 1 (mTORC1) closely interact in the regulation of adipocyte lipid storage. The precise mechanisms underlying this interaction and whether this extends to other metabolic processes and the endocrine function of adipocytes are still unknown. We investigated herein the involvement of mTORC1 as a mediator of the actions of the PPARγ ligand rosiglitazone in subcutaneous inguinal white adipose tissue (iWAT) mass, endocrine function, lipidome, transcriptome and branched-chain amino acid (BCAA) metabolism. Mice bearing regulatory associated protein of mTOR (Raptor) deletion and therefore mTORC1 deficiency exclusively in adipocytes and littermate controls were fed a high-fat diet supplemented or not with the PPARγ agonist rosiglitazone (30 mg/kg/day) for 8 weeks and evaluated for iWAT mass, lipidome, transcriptome (Rnaseq), respiration and BCAA metabolism. Adipocyte mTORC1 deficiency not only impaired iWAT adiponectin transcription, synthesis and secretion, PEPCK mRNA levels, triacylglycerol synthesis and BCAA oxidation and mRNA levels of related proteins but also completely blocked the upregulation in these processes induced by pharmacological PPARγ activation with rosiglitazone. Mechanistically, adipocyte mTORC1 deficiency impairs PPARγ transcriptional activity by reducing PPARγ protein content, as well as by downregulating C/EBPα, a co-partner and facilitator of PPARγ. In conclusion, mTORC1 and PPARγ are essential partners involved in the regulation of subcutaneous adipose tissue adiponectin production and secretion and BCAA oxidative metabolism.

Complement System in Brain Architecture and Neurodevelopmental Disorders

Current evidence indicates that certain immune molecules such as components of the complement system are directly involved in neurobiological processes related to brain development, including neurogenesis, neuronal migration, synaptic remodeling, and response to prenatal or early postnatal brain insults. Consequently, complement system dysfunction has been increasingly implicated in disorders of neurodevelopmental origin, such as schizophrenia, autism spectrum disorder (ASD) and Rett syndrome. However, the mechanistic evidence for a causal relationship between impaired complement regulation and these disorders varies depending on the disease involved. Also, it is still unclear to what extent altered complement expression plays a role in these disorders through inflammation-independent or -dependent mechanisms. Furthermore, pathogenic mutations in specific complement components have been implicated in the etiology of 3MC syndrome, a rare autosomal recessive developmental disorder. The aims of this review are to discuss the current knowledge on the roles of the complement system in sculpting brain architecture and function during normal development as well as after specific inflammatory insults, such as maternal immune activation (MIA) during pregnancy, and to evaluate the existing evidence associating aberrant complement with developmental brain disorders.

Rare RELN variants affect Reelin-DAB1 signal transduction in autism spectrum disorder

The Reelin-DAB1 signaling pathway plays a crucial role in regulating neuronal migration and synapse function. Although many rare heterozygous variants in the Reelin gene (RELN) have been identified in patients with autism spectrum disorder (ASD), most variants are still of unknown clinical significance. Also, genetic data suggest that heterozygous variants in RELN alone appear to be insufficient to cause ASD. Here, we describe the identification and functional characterization of rare compound heterozygous missense variants in RELN in a patient with ASD in whom we have previously reported hyperfunctional mTORC1 signaling of yet unknown etiology. Using iPSC-derived neural progenitor cells (NPCs) from this patient, we provide experimental evidence that the identified variants are deleterious and lead to diminished Reelin secretion and impaired Reelin-DAB1 signal transduction. Also, our results suggest that mTORC1 pathway overactivation may function as a second hit event contributing to downregulation of the Reelin-DAB1 cascade in patient-derived NPCs, and that inhibition of mTORC1 by rapamycin attenuates Reelin-DAB1 signaling impairment. Taken together, our findings point to an abnormal interplay between Reelin-DAB1 and mTORC1 networks in nonsyndromic ASD.

Regulation of adiposity by mTORC1

Obesity is characterized by an excessive increase in the adipose tissue mass, and is associated with higher incidence of several chronic metabolic diseases, such as type 2 diabetes. Therefore, its increasing prevalence is a public health concern, and it is important to better understand its etiology to develop new therapeutic strategies. Evidence accumulated over the years indicates that obesity is associated with a marked activation in adipose tissue of the mechanistic target of rapamycin complex 1 (mTORC1), a signaling pathway that controls lipid metabolism, and adipocyte formation and maintenance. Curiously, mTORC1 is also involved in the control of nonshivering thermogenesis and recruitment as well as browning of white adipose tissue. In this review, we explored mTORC1 functions in adipocytes and presented evidence, suggesting that mTORC1 may either increase or reduce adiposity, depending on the conditions and activation levels.

Adipocyte mTORC1 deficiency promotes adipose tissue inflammation and NLRP3 inflammasome activation via oxidative stress and de novo ceramide synthesis

Mechanistic target of rapamycin complex (mTORC)1 activity is increased in adipose tissue of obese insulin-resistant mice, but its role in the regulation of tissue inflammation is unknown. Herein, we investigated the effects of adipocyte mTORC1 deficiency on adipose tissue inflammation and glucose homeostasis. For this, mice with adipocyte raptor deletion and controls fed a chow or a high-fat diet were evaluated for body mass, adiposity, glucose homeostasis, and adipose tissue inflammation. Despite reducing adiposity, adipocyte mTORC1 deficiency promoted hepatic steatosis, insulin resistance, and adipose tissue inflammation (increased infiltration of macrophages, neutrophils, and B lymphocytes; crown-like structure density; TNF-α, interleukin (IL)-6, and monocyte chemoattractant protein 1 expression; IL-1β protein content; lipid peroxidation; and de novo ceramide synthesis). The anti-oxidant, N-acetylcysteine, partially attenuated, whereas treatment with de novo ceramide synthesis inhibitor, myriocin, completely blocked adipose tissue inflammation and nucleotide oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3)-inflammasome activation, but not hepatic steatosis and insulin resistance induced by adipocyte raptor deletion. Rosiglitazone treatment, however, completely abrogated insulin resistance induced by adipocyte raptor deletion. In conclusion, adipocyte mTORC1 deficiency induces adipose tissue inflammation and NLRP3-inflammasome activation by promoting oxidative stress and de novo ceramide synthesis. Such adipose tissue inflammation, however, is not an underlying cause of the insulin resistance displayed by these mice.

Dysfunctional mTORC1 Signaling: A Convergent Mechanism between Syndromic and Nonsyndromic Forms of Autism Spectrum Disorder?

Whereas autism spectrum disorder (ASD) exhibits striking heterogeneity in genetics and clinical presentation, dysfunction of mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway has been identified as a molecular feature common to several well-characterized syndromes with high prevalence of ASD. Additionally, recent findings have also implicated mTORC1 signaling abnormalities in a subset of nonsyndromic ASD, suggesting that defective mTORC1 pathway may be a potential converging mechanism in ASD pathology across different etiologies. However, the mechanistic evidence for a causal link between aberrant mTORC1 pathway activity and ASD neurobehavioral features varies depending on the ASD form involved. In this review, we first discuss six monogenic ASD-related syndromes, including both classical and potentially novel mTORopathies, highlighting their contribution to our understanding of the neurobiological mechanisms underlying ASD, and then we discuss existing evidence suggesting that aberrant mTORC1 signaling may also play a role in nonsyndromic ASD.

Oral Administration of Linoleic Acid Induces New Vessel Formation and Improves Skin Wound Healing in Diabetic Rats

Introduction

Impaired wound healing has been widely reported in diabetes. Linoleic acid (LA) accelerates the skin wound healing process in non-diabetic rats. However, LA has not been tested in diabetic animals.

Objectives

We investigated whether oral administration of pure LA improves wound healing in streptozotocin-induced diabetic rats.

Methods

Dorsal wounds were induced in streptozotocin-induced type-1 diabetic rats treated or not with LA (0.22 g/kg b.w.) for 10 days. Wound closure was daily assessed for two weeks. Wound tissues were collected at specific time-points and used to measure fatty acid composition, and contents of cytokines, growth factors and eicosanoids. Histological and qPCR analyses were employed to examine the dynamics of cell migration during the healing process.

Results

LA reduced the wound area 14 days after wound induction. LA also increased the concentrations of cytokine-induced neutrophil chemotaxis (CINC-2αβ), tumor necrosis factor-α (TNF-α) and leukotriene B₄ (LTB₄), and reduced the expression of macrophage chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1 (MIP-1). These results together with the histological analysis, which showed accumulation of leukocytes in the wound early in the healing process, indicate that LA brought forward the inflammatory phase and improved wound healing in diabetic rats. Angiogenesis was induced by LA through elevation in tissue content of key mediators of this process: vascular-endothelial growth factor (VEGF) and angiopoietin-2 (ANGPT-2).

Conclusions

Oral administration of LA hastened wound closure in diabetic rats by improving the inflammatory phase and angiogenesis.

mTORC1 inhibition with rapamycin exacerbates adipose tissue inflammation in obese mice and dissociates macrophage phenotype from function

Genetic- and diet-induced obesity and insulin resistance are associated with an increase in mechanistic target of rapamycin complex (mTORC) 1 activity in adipose tissue. We investigated herein the effects of pharmacological mTORC1 inhibition in the development of adipose tissue inflammation induced by high-fat diet (HFD) feeding, as well as in the polarization, metabolism and function of bone marrow-derived macrophages (BMDM). For this, C57BL/6J mice fed with a standard chow diet or a HFD (60% of calories from fat) and treated with either vehicle (0.1% Me₂SO, 0.2% methylcellulose) or rapamycin (2mg/kg/ day, gavage) during 30days were evaluated for body weight, adiposity, glucose tolerance and adipose tissue inflammation. Although rapamycin did not affect the increase in body weight and adiposity, it exacerbated the glucose intolerance and adipose tissue inflammation induced by HFD feeding, as evidenced by the increased adipose tissue percentage of M1 macrophages, naive and activated cytotoxic T lymphocytes, and mRNA levels of proinflammatory molecules, such as TNF-α, IL-6 and MCP-1. In BMDM in vitro, pharmacological mTORC1 inhibition induced phosphorylation of NFκB p65 and spontaneous polarization of macrophages to a proinflammatory M1 profile, while it impaired M2 polarization induced by IL-4+IL-13, glycolysis and phagocytosis. Altogether, these findings indicate that mTORC1 activity is an important determinant of adipose tissue inflammatory profile and macrophage plasticity, metabolism and function.

Constitutive adipocyte mTORC1 activation enhances mitochondrial activity and reduces visceral adiposity in mice

Mechanistic target of rapamycin complex 1 (mTORC1) loss of function reduces adiposity whereas partial mTORC1 inhibition enhances fat deposition. Herein we evaluated how constitutive mTORC1 activation in adipocytes modulates adiposity in vivo. Mice with constitutive mTORC1 activation in adipocytes induced by tuberous sclerosis complex (Tsc)1 deletion and littermate controls were evaluated for body mass, energy expenditure, glucose and fatty acid metabolism, mitochondrial function, mRNA and protein contents. Adipocyte-specific Tsc1 deletion reduced visceral, but not subcutaneous, fat mass, as well as adipocyte number and diameter, phenotypes that were associated with increased lipolysis, UCP-1 content (browning) and mRNA levels of pro-browning transcriptional factors C/EBPβ and ERRα. Adipocyte Tsc1 deletion enhanced mitochondrial oxidative activity, fatty acid oxidation and the expression of PGC-1α and PPARα in both visceral and subcutaneous fat. In brown adipocytes, however, Tsc1 deletion did not affect UCP-1 content and basal respiration. Adipocyte Tsc1 deletion also reduced visceral adiposity and enhanced glucose tolerance, liver and muscle insulin signaling and adiponectin secretion in mice fed with purified low- or high-fat diet. In conclusion, adipocyte-specific Tsc1 deletion enhances mitochondrial activity, induces browning and reduces visceral adiposity in mice.

PPARγ activation attenuates glucose intolerance induced by mTOR inhibition with rapamycin in rats

mTOR inhibition with rapamycin induces a diabetes-like syndrome characterized by severe glucose intolerance, hyperinsulinemia, and hypertriglyceridemia, which is due to increased hepatic glucose production as well as reduced skeletal muscle glucose uptake and adipose tissue PPARγ activity. Herein, we tested the hypothesis that pharmacological PPARγ activation attenuates the diabetes-like syndrome associated with chronic mTOR inhibition. Rats treated with the mTOR inhibitor rapamycin (2 mg·kg(-1)·day(-1)) in combination or not with the PPARγ ligand rosiglitazone (15 mg·kg(-1)·day(-1)) for 15 days were evaluated for insulin secretion, glucose, insulin, and pyruvate tolerance, skeletal muscle and adipose tissue glucose uptake, and insulin signaling. Rosiglitazone corrected fasting hyperglycemia, attenuated the glucose and insulin intolerances, and abolished the increase in fasting plasma insulin and C-peptide levels induced by rapamycin. Surprisingly, rosiglitazone markedly increased the plasma insulin and C-peptide responses to refeeding in rapamycin-treated rats. Furthermore, rosiglitazone partially attenuated rapamycin-induced gluconeogenesis, as evidenced by the improved pyruvate tolerance and reduced mRNA levels of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. Rosiglitazone also restored insulin's ability to stimulate glucose uptake and its incorporation into glycogen in skeletal muscle of rapamycin-treated rats, which was associated with normalization of Akt Ser(473) phosphorylation. However, the rapamycin-mediated impairments of adipose tissue glucose uptake and incorporation into triacylglycerol were unaffected by rosiglitazone. Our findings indicate that PPARγ activation ameliorates some of the disturbances in glucose homeostasis and insulin action associated with chronic rapamycin treatment by reducing gluconeogenesis and insulin secretion and restoring muscle insulin signaling and glucose uptake.

PPARγ activation attenuates cold-induced upregulation of thyroid status and brown adipose tissue PGC-1α and D2

Here, we investigated whether pharmacological PPARγ activation modulates key early events in brown adipose tissue (BAT) recruitment induced by acute cold exposure with the aim of unraveling the interrelationships between sympathetic and PPARγ signaling. Sprague-Dawley rats treated or not with the PPARγ ligand rosiglitazone (15 mg·kg(-1)·day(-1), 7 days) were kept at 23°C or exposed to cold (5°C) for 24 h and evaluated for BAT gene expression, sympathetic activity, thyroid status, and adrenergic signaling. Rosiglitazone did not affect the reduction in body weight gain and the increase in feed efficiency, Vo(2), and BAT sympathetic activity induced by 24-h cold exposure. Rosiglitazone strongly attenuated the increase in serum total and free T4 and T3 levels and BAT iodothyronine deiodinase type 2 (D2) and PGC-1α mRNA levels and potentiated the reduction in BAT thyroid hormone receptor (THR) β mRNA levels induced by cold. Administration of T3 to rosiglitazone-treated rats exacerbated the cold-induced increase in energy expenditure but did not restore a proper activation of D2 and PGC-1α, nor further increased uncoupling protein 1 expression. Regarding adrenergic signaling, rosiglitazone did not affect the changes in BAT cAMP content and PKA activity induced by cold. Rosiglitazone alone or in combination with cold increased CREB binding to DNA, but it markedly reduced the expression of one of its major coactivators, CREB binding protein. In conclusion, pharmacological PPARγ activation impairs short-term cold elicitation of BAT adrenergic and thyroid signaling, which may result in abnormal tissue recruitment and thermogenic activity.

A proteomic analysis of the functional effects of fatty acids in NIH 3T3 fibroblasts

Previous studies have demonstrated that long chain fatty acids influence fibroblast function at sub-lethal concentrations. This study is the first to assess the effects of oleic, linoleic or palmitic acids on protein expression of fibroblasts, as determined by standard proteomic techniques. The fatty acids were not cytotoxic at the concentration used in this work as assessed by membrane integrity, DNA fragmentation and the MTT assay but significantly increased cell proliferation. Subsequently, a proteomic analysis was performed using two dimensional difference gel electrophoresis (2D-DIGE) and MS based identification. Cells treated with 50 μM oleic, linoleic or palmitic acid for 24 h were associated with 24, 22, 16 spots differentially expressed, respectively. Among the identified proteins, α-enolase and far upstream element binding protein 1 (FBP-1) are of importance due to their function in fibroblast-associated diseases. However, modulation of α-enolase and FBP-1 expression by fatty acids was not validated by the Western blot technique.

Moderate exercise improves leucocyte function and decreases inflammation in diabetes

The genesis and progression of diabetes occur due in part to an uncontrolled inflammation profile with insulin resistance, increased serum levels of free fatty acids (FFA), proinflammatory cytokines and leucocyte dysfunction. In this study, an investigation was made of the effect of a 3-week moderate exercise regimen on a treadmill (60% of VO₂(max) , 30 min/day, 6 days a week) on inflammatory markers and leucocyte functions in diabetic rats. The exercise decreased serum levels of tumour necrosis factor (TNF)-α (6%), cytokine-induced neutrophil chemotactic factor 2 alpha/beta (CINC-2α/β) (9%), interleukin (IL)-1β (34%), IL-6 (86%), C-reactive protein (CRP) (41%) and FFA (40%) in diabetic rats when compared with sedentary diabetic animals. Exercise also attenuated the increased responsiveness of leucocytes from diabetics when compared to controls, diminishing the reactive oxygen species (ROS) release by neutrophils (21%) and macrophages (28%). Exercise did not change neutrophil migration and the proportion of neutrophils and macrophages in necrosis (loss of plasma membrane integrity) and apoptosis (DNA fragmentation). Serum activities of creatine kinase (CK) and lactate dehydrogenase (LDH) were not modified in the conditions studied. Therefore, physical training did not alter the integrity of muscle cells. We conclude that moderate physical exercise has marked anti-inflammatory effects on diabetic rats. This may be an efficient strategy to protect diabetics against microorganism infection, insulin resistance and vascular complications.

Dietary free oleic and linoleic acid enhances neutrophil function and modulates the inflammatory response in rats

The high ingestion of oleic (OLA) and linoleic (LNA) acids by Western populations, the presence of inflammatory diseases in these populations, and the importance of neutrophils in the inflammatory process led us to investigate the effects of oral ingestion of unesterified OLA and LNA on rat neutrophil function. Pure OLA and LNA were administered by gavage over 10 days. The doses used (0.11, 0.22 and 0.44 g/kg of body weight) were based on the Western consumption of OLA and LNA. Neither fatty acid affected food, calorie or water intake. The fatty acids were not toxic to neutrophils as evaluated by cytometry using propidium iodide (membrane integrity and DNA fragmentation). Neutrophil migration in response to intraperitoneal injection of glycogen and in the air pouch assay, was elevated after administration of either OLA or LNA. This effect was associated with enhancement of rolling and increased release of the chemokine CINC-2alphabeta. Both fatty acids elevated L-selectin expression, whereas no effect on beta(2)-integrin expression was observed, as evaluated by flow cytometry. LNA increased the production of proinflammatory cytokines (IL-1beta and CINC-2alphabeta) by neutrophils after 4 h in culture and both fatty acids decreased the release of the same cytokines after 18 h. In conclusion, OLA and LNA modulate several functions of neutrophils and can influence the inflammatory process.