Control of Brown Adipose Tissue Glucose and Lipid Metabolism by PPARγ

Brown adipose tissue (BAT) non-shivering thermogenesis impacts energy homeostasis in rodents and humans. Mitochondrial uncoupling protein 1 in brown fat cells produces heat by dissipating the energy generated by fatty acid and glucose oxidation. In addition to thermogenesis and despite its small relative size, sympathetically activated BAT constitutes an important glucose, fatty acid, and triacylglycerol-clearing organ, and such function could potentially be used to alleviate dyslipidemias, hyperglycemia, and insulin resistance. To date, chronic sympathetic innervation and peroxisome proliferator-activated receptor (PPAR) γ activation are the only recognized inducers of BAT recruitment. Here, we review the major differences between these two BAT inducers in the regulation of lipolysis, fatty acid oxidation, lipid uptake and triacylglycerol synthesis, glucose uptake, and de novo lipogenesis. Whereas BAT recruitment through sympathetic drive translates into functional thermogenic activity, PPARγ-mediated recruitment is associated with a reduction in sympathetic activity leading to increased lipid storage in brown adipocytes. The promising therapeutic role of BAT in the treatment of hypertriglyceridemic and hyperglycemic conditions is also discussed

Myeloid-Specific Rictor Deletion Induces M1 Macrophage Polarization and Potentiates In Vivo Pro-Inflammatory Response to Lipopolysaccharide

The phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) axis plays a central role in attenuating inflammation upon macrophage stimulation with toll-like receptor (TLR) ligands. The mechanistic target of rapamycin complex 2 (mTORC2) relays signal from PI3K to Akt but its role in modulating inflammation in vivo has never been investigated. To evaluate the role of mTORC2 in the regulation of inflammation in vivo, we have generated a mouse model lacking Rictor, an essential mTORC2 component, in myeloid cells. Primary macrophages isolated from myeloid-specific Rictor null mice exhibited an exaggerated response to TLRs ligands, and expressed high levels of M1 genes and lower levels of M2 markers. To determine whether the loss of Rictor similarly affected inflammation in vivo, mice were either fed a high fat diet, a situation promoting chronic but low-grade inflammation, or were injected with lipopolysaccharide (LPS), which mimics an acute, severe septic inflammatory condition. Although high fat feeding contributed to promote obesity, inflammation, macrophage infiltration in adipose tissue and systemic insulin resistance, we did not observe a significant impact of Rictor loss on these parameters. However, mice lacking Rictor exhibited a higher sensitivity to sceptic shock when injected with LPS. Altogether, these results indicate that mTORC2 is a key negative regulator of macrophages TLR signalling and that its role in modulating inflammation is particularly important in the context of severe inflammatory challenges. These observations suggest that approaches aimed at modulating mTORC2 activity may represent a possible therapeutic approach for diseases linked to excessive inflammation.Howard Hughes Medical Institute (Investigator)National Institutes of Health (U.S.) (NIH grant CA103866)National Institutes of Health (U.S.) (NIH grant CA129105)National Institutes of Health (U.S.) (NIH grant AI47389)Canadian Institutes of Health ResearchNatural Sciences and Engineering Research Council of CanadaFonds de la recherche en santé du Québe

Immunometabolism: Molecular mechanisms, diseases, and therapies 2018

Immunometabolism: Molecular mechanisms, diseases, and therapies 201

Mechanisms underlying skeletal muscle insulin resistance induced by fatty acids: importance of the mitochondrial function

Insulin resistance condition is associated to the development of several syndromes, such as obesity, type 2 diabetes mellitus and metabolic syndrome. Although the factors linking insulin resistance to these syndromes are not precisely defined yet, evidence suggests that the elevated plasma free fatty acid (FFA) level plays an important role in the development of skeletal muscle insulin resistance. Accordantly, in vivo and in vitro exposure of skeletal muscle and myocytes to physiological concentrations of saturated fatty acids is associated with insulin resistance condition. Several mechanisms have been postulated to account for fatty acids-induced muscle insulin resistance, including Randle cycle, oxidative stress, inflammation and mitochondrial dysfunction. Here we reviewed experimental evidence supporting the involvement of each of these propositions in the development of skeletal muscle insulin resistance induced by saturated fatty acids and propose an integrative model placing mitochondrial dysfunction as an important and common factor to the other mechanisms

Dietary sulfur amino acid restriction upregulates DICER to confer beneficial effects

Dietary restriction (DR) improves health and prolongs lifespan in part by upregulating type III endoribonuclease DICER in adipose tissue. In this study, we aimed to specifically test which missing dietary component was responsible for DICER upregulation. Methods: We performed a nutrient screen in mouse preadipocytes and validated the results in vivo using different kinds of dietary interventions in wild type or genetically modified mice and worms, also testing the requirement of DICER on the effects of the diets. Results: We found that sulfur amino acid restriction (i.e., methionine or cysteine) is sufficient to increase Dicer mRNA expression in preadipocytes. Consistently, while DR increases DICER expression in adipose tissue of mice, this effect is blunted by supplementation of the diet with methionine, cysteine, or casein, but not with a lipid or carbohydrate source. Accordingly, dietary methionine or protein restriction mirrors the effects of DR. These changes are associated with alterations in serum adiponectin. We also found that DICER controls and is controlled by adiponectin. In mice, DICER plays a role in methionine restriction-induced upregulation of Ucpl in adipose tissue. In C. elegans, DR and a model of methionine restriction also promote DICER expression in the intestine (an analog of the adipose tissue) and prolong lifespan in a DICER-dependent manner. Conclusions: We propose an evolutionary conserved mechanism in which dietary sulfur amino acid restriction upregulates DICER levels in adipose tissue leading to beneficial health effects29124135CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP305069/2015-2; 304995/2014-288887.143923/2017-002017/01184-9; 2017/07975-8; 2017/22057-5; 2015/03292-8; 2012/07259-7; 2016/02207-0; 2010/52557-0; 2015/01316-7; 2012/50558-5; 2015/19530-5We thank Elzira Elisabeth Saviani and Emanoel Cabral for valuable technical support. We thank the National Institute of Science and Technology on Photonics Applied to Cell Biology (INFABIC) at the Universidade Estadual de Campinas to provide access to microscopes, the Caenorhabditis Genetics Center (CGC) for worms and Dr. Amy Pasquinelli for the dcr-1 RNAi clone. CGC is funded by NIH Office of Research Infrastructure Programs ( P40 OD010440 ). We thank Carmen Perrone for sharing the composition of the methionine restriction diet, for valuable discussion and for sharing samples of rats exposed to methionine restriction. This study was funded by grants of the Fundação de Amparo à Pesquisa do Estado de São Paulo ( 2017/01184-9 , 2017/07975-8 , 2017/22057-5 , 2015/03292-8 , 2012/07259-7 , 2016/02207-0 , 2010/52557-0 , 2015/01316-7 , 2012/50558-5 and 2015/19530-5 ), Conselho Nacional de Desenvolvimento Científico e Tecnológico ( 305069/2015-2 and 304995/2014-2 ) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - German Academic Exchange Service ( PROBRAL - 88887.143923/2017-00 )

The Hepatokine TSK does not affect brown fat thermogenic capacity, body weight gain, and glucose homeostasis

Objectives Hepatokines are proteins secreted by the liver that impact the functions of the liver and various tissues through autocrine, paracrine, and endocrine signaling. Recently, Tsukushi (TSK) was identified as a new hepatokine that is induced by obesity and cold exposure. It was proposed that TSK controls sympathetic innervation and thermogenesis in brown adipose tissue (BAT) and that loss of TSK protects against diet-induced obesity and improves glucose homeostasis. Here we report the impact of deleting and/or overexpressing TSK on BAT thermogenic capacity, body weight regulation, and glucose homeostasis. Methods We measured the expression of thermogenic genes and markers of BAT innervation and activation in TSK-null and TSK-overexpressing mice. Body weight, body temperature, and parameters of glucose homeostasis were also assessed in the context of TSK loss and overexpression. Results The loss of TSK did not affect the thermogenic activation of BAT. We found that TSK-null mice were not protected against the development of obesity and did not show improvement in glucose tolerance. The overexpression of TSK also failed to modulate thermogenesis, body weight gain, and glucose homeostasis in mice

Palmitoleic acid (n-7) increases white adipocytes GLUT4 content and glucose uptake in association with AMPK activation

Background: Palmitoleic acid was previously shown to improve glucose homeostasis by reducing hepatic glucose production and by enhancing insulin-stimulated glucose uptake in skeletal muscle. Herein we tested the hypothesis that palmitoleic acid positively modulates glucose uptake and metabolism in adipocytes.Methods: for this, both differentiated 3 T3-L1 cells treated with either palmitoleic acid (16: 1n7, 200 mu M) or palmitic acid (16: 0, 200 mu M) for 24 h and primary adipocytes from mice treated with 16: 1n7 (300 mg/kg/day) or oleic acid (18: 1n9, 300 mg/kg/day) by gavage for 10 days were evaluated for glucose uptake, oxidation, conversion to lactate and incorporation into fatty acids and glycerol components of TAG along with the activity and expression of lipogenic enzymes.Results: Treatment of adipocytes with palmitoleic, but not oleic (in vivo) or palmitic (in vitro) acids, increased basal and insulin-stimulated glucose uptake and GLUT4 mRNA levels and protein content. Along with uptake, palmitoleic acid enhanced glucose oxidation (aerobic glycolysis), conversion to lactate (anaerobic glycolysis) and incorporation into glycerol-TAG, but reduced de novo fatty acid synthesis from glucose and acetate and the activity of lipogenic enzymes glucose 6-phosphate dehydrogenase and ATP-citrate lyase. Importantly, palmitoleic acid induction of adipocyte glucose uptake and metabolism were associated with AMPK activation as evidenced by the increased protein content of phospho(p) Thr172AMPKa, but no changes in pSer473Akt and pThr308Akt. Importantly, such increase in GLUT4 content induced by 16: 1n7, was prevented by pharmacological inhibition of AMPK with compound C.Conclusions: in conclusion, palmitoleic acid increases glucose uptake and the GLUT4 content in association with AMPK activation

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Myeloid-specific Rictor deletion induces M1 macrophage polarization and potentiates in vivo pro-inflammatory response to lipopolysaccharide.

The phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) axis plays a central role in attenuating inflammation upon macrophage stimulation with toll-like receptor (TLR) ligands. The mechanistic target of rapamycin complex 2 (mTORC2) relays signal from PI3K to Akt but its role in modulating inflammation in vivo has never been investigated. To evaluate the role of mTORC2 in the regulation of inflammation in vivo, we have generated a mouse model lacking Rictor, an essential mTORC2 component, in myeloid cells. Primary macrophages isolated from myeloid-specific Rictor null mice exhibited an exaggerated response to TLRs ligands, and expressed high levels of M1 genes and lower levels of M2 markers. To determine whether the loss of Rictor similarly affected inflammation in vivo, mice were either fed a high fat diet, a situation promoting chronic but low-grade inflammation, or were injected with lipopolysaccharide (LPS), which mimics an acute, severe septic inflammatory condition. Although high fat feeding contributed to promote obesity, inflammation, macrophage infiltration in adipose tissue and systemic insulin resistance, we did not observe a significant impact of Rictor loss on these parameters. However, mice lacking Rictor exhibited a higher sensitivity to septic shock when injected with LPS. Altogether, these results indicate that mTORC2 is a key negative regulator of macrophages TLR signalling and that its role in modulating inflammation is particularly important in the context of severe inflammatory challenges. These observations suggest that approaches aimed at modulating mTORC2 activity may represent a possible therapeutic approach for diseases linked to excessive inflammation