Altered GDF15 and FGF21 Levels in Response to Strenuous Exercise: A Study in Marathon Runners

Background: Recreational marathon runners face strong physiological challenges. Assessment of potential biomarkers for the biological responses of runners will help to discriminate individual race responsiveness and their physiological consequences. This study sought to analyze the changes in the plasma levels of GDF15 and FGF21, novel endocrine factors related to metabolic stress, in runners following the strenuous exercise of a marathon race. Methods: Blood samples were obtained from eighteen male runners (mean ±SD, age: 41.7 ±5.0 years, BMI: 23.6 ± 1.8) 48 h before, immediately after, and 48 h after a marathon race, and from age-matched sedentary individuals. The level of GDF15, FGF21, and 38 additional biochemical and hematological parameters were determined. Results: The basal levels of GDF15 and FGF21 did not differ between runners before the race and sedentary individuals. Significant increases in the mean levels of GDF15 (4.2-fold) and FGF21 (20-fold) were found in runners immediately after the race. The magnitudes of these increases differed markedly among individuals and did not correlate with each other. The GDF15 and FGF21 levels had returned to the basal level 48 h post-race. The post-race value of GDF15 (but not FGF21) correlated positively with increased total white cell count (r = 0.50, P = 0.01) and neutrophilia (r = 0.10, P = 0.01). Conclusion: GDF15 and FGF21 are transiently increased in runners following a marathon race. The induction of GDF15 levels is associated with alterations in circulating immune cells levels

Bone Morphogenetic Protein-8B levels at birth and in the first year of life: relation to metabolic-endocrine variables and brown adipose tissue activity

Objective: Bone morphogenetic protein-8B (BMP8B) is an adipokine produced by brown adipose tissue (BAT) contributing to thermoregulation and metabolic homeostasis in rodent models. In humans, BAT activity is particularly relevant in newborns and young infants. We assessed BMP8B levels and their relationship with BAT activity and endocrine-metabolic parameters in young infants to ascertain its potentiality as biomarker in early life. Methods and Materials: BMP8B concentrations were assessed longitudinally by ELISA in a cohort of 27 girls and 23 boys at birth, and at age 4 and 12 months, together with adiposity parameters (DXA), and circulating endocrine-metabolic variables. BAT activity was measured by infrared thermography. BMP8B gene expression (qRT-PCR) was determined in BAT, white fat, and liver samples from neonatal necropsies, and in placenta and cord blood. Results: BMP8B levels were high at birth, particularly in boys (P=0.04 vs girls), declined progressively, and remained well above those in healthy adults and pregnant women at age one year (P<0.05 and P<0.001, respectively). Neonatal BMP8B transcript levels were higher in BAT than in white fat, liver and cord blood. Circulating BMP8B levels during the first year of life marginally correlated with bone mineral density and gains in lean mass. Conclusion: BMP8B levels are high at birth and decline progressively over the first year of life remaining above adult levels. Although changes in BMP8B concentrations overall reflect those in BAT activity during development, BMP8B levels are unlikely to be useful to predict individual variations in endocrine-metabolic status and BAT activity in healthy young infants

The kallikrein-kinin pathway as a mechanism for auto-control of brown adipose tissue activity

Brown adipose tissue (BAT) is known to secrete regulatory factors in response to thermogenic stimuli. Components of the BAT secretome may exert local effects that contribute to BAT recruitment and activation. Here, we found that a thermogenic stimulus leads to enhanced secretion of kininogen (Kng) by BAT, owing to induction of kininogen 2 (Kng2) gene expression. Noradrenergic, cAMP-mediated signals induce KNG2 expression and release in brown adipocytes. Conversely, the expression of kinin receptors, that are activated by the Kng products bradykinin and [Des-Arg9]-bradykinin, are repressed by thermogenic activation of BAT in vivo and of brown adipocytes in vitro. Loss-of-function models for Kng (the circulating-Kng-deficient BN/Ka rat) and bradykinin (pharmacological inhibition of kinin receptors, kinin receptor-null mice) signaling were coincident in showing abnormal overactivation of BAT. Studies in vitro indicated that Kng and bradykinin exert repressive effects on brown adipocyte thermogenic activity by interfering the PKA/p38 MAPK pathway of control of Ucp1 gene transcription, whereas impaired kinin receptor expression enhances it. Our findings identify the kallikrein-kinin system as a relevant component of BAT thermogenic regulation that provides auto-regulatory inhibitory signaling to BAT

A role for Oncostatin M in the impairment of glucose homeostasis in obesity

CONTEXT: Oncostatin M (OSM) plays a key role in inflammation, but its regulation and function during obesity is not fully understood. OBJECTIVE: The aim of this study was to evaluate the relationship of OSM with the inflammatory state that leads to impaired glucose homeostasis in obesity. We also assessed whether OSM immunoneutralization could revert metabolic disturbances caused by a high-fat diet (HFD) in mice. DESIGN: 28 patients with severe obesity were included and stratified into two groups: (1) glucose levels 100 mg/dL. White adipose tissue was obtained to examine OSM gene expression. Human adipocytes were used to evaluate the effect of OSM in the inflammatory response, and HFD-fed C57BL/6J mice were injected with anti-OSM antibody to evaluate its effects. RESULTS: OSM expression was elevated in subcutaneous and visceral fat from patients with obesity and hyperglycemia, and correlated with Glut4 mRNA levels, serum insulin, homeostatic model assessment of insulin resistance, and inflammatory markers. OSM inhibited adipogenesis and induced inflammation in human adipocytes. Finally, OSM receptor knockout mice had increased Glut4 mRNA levels in adipose tissue, and OSM immunoneutralization resulted in a reduction of glucose levels and Ccl2 expression in adipose tissue from HFD-fed mice. CONCLUSIONS: OSM contributes to the inflammatory state during obesity and may be involved in the development of insulin resistance

The molecular signature of HIV-1-associated Lipomatosis reveals differential involvement of Brown and Beige/Brite Adipocyte cell lineages

Highly active antiretroviral therapy has remarkably improved quality of life of HIV-1-infected patients. However, this treatment has been associated with the so-called lipodystrophic syndrome, which conveys a number of adverse metabolic effects and morphological alterations. Among them, lipoatrophy of subcutaneous fat in certain anatomical areas and hypertrophy of visceral depots are the most common. Less frequently, lipomatous enlargements of subcutaneous fat at distinct anatomic areas occur. Lipomatous adipose tissue in the dorso-cervical area ('buffalo hump') has been associated with a partial white-to-brown phenotype transition and with increased cell proliferation, but, to date, lipomatous enlargements arising in other parts of the body have not been characterized. In order to establish the main molecular events associated with the appearance of lipomatosis in HIV-1 patients, we analyzed biopsies of lipomatous tissue from 'buffalo hump' and from other anatomical areas in patients, in comparison with healthy subcutaneous adipose tissue, using a marker gene expression approach. Both buffalo-hump and non-buffalo-hump lipomatous adipose tissues exhibited similar patterns of non-compromised adipogenesis, unaltered inflammation, non-fibrotic phenotype and proliferative activity. Shorter telomere length, prelamin A accumulation and SA-β-Gal induction, reminiscent of adipocyte senescence, were also common to both types of lipomatous tissues. Buffalo hump biopsies showed expression of marker genes of brown adipose tissue (e.g. UCP1) and, specifically, of 'classical' brown adipocytes (e.g. ZIC1) but not of beige/brite adipocytes. No such brown fat-related gene expression occurred in lipomatous tissues at other anatomical sites. In conclusion, buffalo hump and other subcutaneous adipose tissue enlargements from HIV-1-infected patients share a similar lipomatous character. However, a distorted induction of white-to-'classical brown adipocyte' phenotype appears unique of dorso-cervical lipomatosis. Thus, the insults caused by HIV-1 viral infection and/or antiretroviral therapy leading to lipomatosis are acting in a location- and adipocyte lineage-dependent manner

Nous actors moleculars en la fisiologia del teixit adipós i patologies associades

[cat] El teixit adipós ha passat d’ésser considerat un mer reservori d’energia a un òrgan complex, implicat de forma activa en l’homeòstasi energètica i amb funcions endocrines de rellevància. Les malalties en què hi està involucrat per excés (obesitat) o manca (lipodistròfies) provoquen, coherentment, alteracions metabòliques greus que suposen un risc per a la salut. A nivell de balanç energètic, dos tipus de teixit adipós disposen de funcions diametralment oposades dins l’organisme: El teixit adipós blanc (TAB) té com a objectiu emmagatzemar reserves lipídiques en condicions d’excés de nutrients i mobilitzar-les per a garantir el funcionament dels diversos òrgans, mentre que el teixit adipós marró (TAM) pot dissipar energia en forma de calor per tal de regular la temperatura corporal. Tot i que se n’hi creia absent, el recent descobriment de la presència de TAM i de la capacitat d’inducció del mateix (“browning”) en individus humans adults ha despertat un creixent interès en aquest teixit, donada la potencial aplicació del seu reclutament com a teràpia contra l’obesitat. Les cèl·lules majoritàries del teixit adipós i que realitzen les seves funcions principals són els adipòcits, blancs en el cas del TAB o marrons clàssics i beix/brite en el del TAM. No obstant, aquests estan en estreta comunicació amb altres tipus cel·lulars, especialment amb les cèl·lules del sistema immunitari, les quals produeixen diversos factors bioactius. La producció de mediadors inflamatoris en situacions patològiques i d’estrès altera la biologia dels adipòcits i la secreció de llurs hormones (adipocines), afectant l’organisme a nivell global, mentre que en condicions de salut mediadors antiinflamatoris milloren la funció adipocitària. A la present tesi doctoral s’analitzà el patró d’expressió gènica als fenòmens de lipomatosi associats a una lipodistròfia d’origen genètic (FPLD2) i a l’associada a la infecció pel virus de la immunodeficiència humana i a la teràpia antiretroviral d’alta activitat (HALS). També s’identifiquen noves proteïnes secretables produïdes preferentment pel TAM respecte al TAB a partir d’aproximacions in silico amb la seva posterior validació funcional in vitro i in vivo. Els lipomes són insults patofisiològics ocasionals en les lipodistròfies, però estan menys caracteritzats que d’altres de concomitants. En general, presentaren alteracions heterogènies, especialment a nivell de cicle cel·lular i senescència, tant en el cas de l’FPLD2 com en la HALS. En aquesta darrera, la comparació entre els lipomes pertanyents a ubicacions anatòmiques diverses i a la zona dorsocervical va permetre detectar diferències entre tots dos tipus d’insults quant a l’existència d’un fenotip de TAM clàssic aberrant, ZIC1+, als segons, tot posant de manifest la complexitat de les alteracions en la biologia del teixit adipós en aquestes malalties. Emprant aproximacions bioinformàtiques s’identificaren diverses proteïnes secretades sobreexpressades al TAM, de les quals es procedí a la caracterització d’una en concret. CXCL14 és una quimiocina pleiotròpica amb funcions metabòliques descrites a nivell de TAB, si bé el seu paper al TAM era, fins el moment, desconegut. Com es demostrà, CXCL14 és produïda pels adipòcits marrons i la seva expressió i secreció són induïdes per estímuls simpàtics. Els animals deficients per a aquest gen mostraven alteracions en transcrits de termogènesi, de metabolisme lipídic i d’infiltració immunitària, les quals es traduïen en una disminució de la funció termogènica del TAM. Anàlisis de quimiotaxi i d’expressió gènica revelaren que la CXCL14 produïda pels adipòcits marrons realitza accions de tipus paracrí, actuant sobre macròfags activats alternativament. D’altra banda, l’administració continuada de CXCL14 exògena activà el browning als dipòsits de TAB, quelcom que suggereix accions també endocrines. En conjunt, aquests resultats destaquen el paper de l’adipocina marró CXCL14 en les interaccions teixit adipós-sistema immunitari i en la comunicació intra i intertissular que requereix la coordinació de tota maquinària termogènica.[eng] Adipose tissue was hitherto considered just an energy storage site, but it is currently widely recognized as a dynamic homeostatic organ with relevant endocrine properties. The main function of white adipose tissue (WAT) is to store and release lipids on demand, whereas brown adipose tissue (BAT) dissipates energy as heat. The discovery of thermally-inducible BAT in human adult subjects has revamped research on it since this ability could be harnessed to improve obesity. Adipocytes, white in BAT and classic brown or beige/brite in BAT, are the main functional actors in adipose tissue, but a close cross-talk with other cell types, especially those of the immune system, is present. Accordingly, stress and production of inflammatory cytokines in pathological conditions alters the biology of adipocytes and the secretion of adipose-derived hormones (adipokines), while in healthy adipose tissue immune cell-derived anti-inflammatory cytokines improve adipose functions. The current doctoral thesis aims to assess alterations in the transcriptional signature of lipomas in lipodystrophies and to identify novel secretable proteins preferentially produced by BAT. Lipomas are a recurring symptom in lipodystrophies, but they have been poorly characterized to date. In general, lipomas exhibited heterogenic alterations in respect to healthy and lipoatrophic adipose tissue, mostly related to cell cycle control. In the case of HIV-1- and HAART-associated lipodystrophy, a differential expression pattern between dorso-cervical lipomas and those arising at different anatomical sites revealed the existence of a brown-like molecular signature in the former. Several proteins were identified in silico as potential brown adipokines. Among them, chemokine CXCL14 was considered to be a promising candidate, since validation studies revealed differential expression between WAT and BAT, transcriptional induction in the presence of thermogenic stimuli and release by brown adipocytes. Brown adipocyte-derived CXCL14 was able to blunt proinflammatory, classical macrophage activation and to recruit alternatively activated macrophages, which are known to be involved in BAT activation. Coherently, continuous external administration of CXCL14 increased browning and alternatively activated macrophage abundance of WAT depots, whereas CXCL14 knock-out mice exhibited compromised expression of transcripts related to BAT function and immune infiltration. These results indicate an instrumental role for CXCL14 in coordinating adaptive thermogenesis

Secretory proteome of brown adipocytes in response to cAMP-mediated thermogenic activation

Background: The secretory properties of brown adipose tissue are thought to contribute to the association between active brown fat and a healthy metabolic status. Although a few brown adipokines have been identified, a comprehensive knowledge of the brown adipose tissue secretome is lacking. Methods: Here, to examine the effects of thermogenic activation of brown adipocytes on protein secretion, we used isobaric tags for relative and absolute quantification (iTRAQ) analysis to determine how the secreted proteome of brown adipocytes (that detected in cell culture medium) differed in response to cAMP. Results: Our results indicated that 56 secreted proteins were up-regulated in response to cAMP. Of them, nearly half (29) corresponded to extracellular matrix components and regulators. Several previously known adipokines, were also detected. Unexpectedly, we also found five components of the complement system. Only 15 secreted proteins were down-regulated by cAMP; of them three were ECM-related and none was related to the complement system. We observed a partial concordance between the cAMP-regulated release of proteins (both from proteomics and from antibody-based quantification of specific proteins) and the cAMP-mediated regulation of their encoding transcript for the up-regulated secreted proteins. However, a stronger concordance was seen for the down-regulated secreted proteins. Conclusions: The present results highlight the need to investigate previously unrecognized processes such as the role of extracellular matrix in thermogenic activation-triggered brown fat remodeling, as well as the intriguing question of how brown adipocyte-secreted complement factors contribute to the signaling properties of active brown adipose tissue

Reduced circulating levels of chemokine CXCL14 in adolescent girls with polycystic ovary syndrome: normalization after insulin sensitization

Objective: CXCL14 (C-X-C motif chemokine ligand-14) is a chemokine released by active brown fat, showing protective effects against insulin resistance in experimental models. Polycystic ovary syndrome (PCOS) in adolescent girls is usually related to hepato-visceral fat excess and insulin resistance, and associates with comorbidities such as type 2 diabetes. Treatment with a low-dose combination of one antiandrogen and antimineralocorticoid drug (spironolactone) and two insulin sensitizers (pioglitazone/metformin) (SPIOMET) is particularly effective in improving these metabolic derangements. Adipose tissue may be involved in the metabolic alterations of PCOS, and it is a likely target of therapeutic action. We investigated the alterations in CXCL14 levels and the effects of drugs composing SPIOMET treatment on CXCL14 in human adipocytes. Research design and methods: We studied 51 adolescent patients with PCOS and 21 age-matched healthy controls. Thirty-one adolescent patients with PCOS under SPIOMET or oral contraception-based treatment were also studied. For studies in vitro, Simpson Golabi Behmel Syndrome (SGBS) adipose cells were used. Gene expression for CXCL14 and other genes was quantified using quantitative real-time PCR. The levels of CXCL14 and adipokines in serum and cell culture media were determined by ELISA. Results: Serum CXCL14 levels are reduced in patients with PCOS. One-year SPIOMET treatment normalized CXCL14 concentrations and improved the metabolic status of patients with PCOS. Pioglitazone induced CXCL14 expression in differentiating human SGBS adipocytes, in parallel with the induction of marker genes of brown adipogenesis. Spironolactone induced CXCL14 expression and release in differentiated human adipocytes. Conclusion: Insulin sensitization with SPIOMET normalizes the abnormally low levels of CXCL14 in girls with PCOS. This is consistent with the effects of pioglitazone and spironolactone inducing CXCL14 expression and promoting a brown-like phenotype in adipocytes. CXCL14 may be a novel biomarker for PCOS as well as a potential mediator of the beneficial effects of the SPIOMET combination and may hold promise as a therapeutic modulator of the disorder

Use of infrared thermography to estimate brown fat activation after a cooling protocol in patients with severe obesity that underwent bariatric surgery

Background: In contrast to the energy-storing role of white adipose tissue (WAT), brown adipose tissue (BAT) acts as the main site of non-shivering thermogenesis in mammals and has been reported to play a role in protection against obesity and associated metabolic alterations in rodents. Infrared thermography (IRT) has been proposed as a novel non-invasive, safe, and quick method to estimate BAT thermogenic activation in humans. The aim of this study is to determine whether the IRT could be a potential new tool to estimate BAT thermogenic activation in patients with severe obesity in response to bariatric surgery. Methods: Supraclavicular BAT thermogenic activation was evaluated using IRT in a cohort of 31 patients (50 ± 10 years old, BMI = 44.5 ± 7.8; 15 undergoing laparoscopy sleeve gastrectomy and 16 Roux-en-Y gastric bypass) at baseline and 6 months after a bariatric surgery. Clinical parameters were determined at these same time points. Results: Supraclavicular BAT-related activity was detected in our patients by IRT after a cooling stimulus. The BAT thermogenic activation was higher at 6 months after laparoscopy sleeve gastrectomy (0.06 ± 0.1 vs 0.32 ± 0.1), while patients undergoing to a roux-en-Y gastric bypass did not change their thermogenic response using the same cooling stimulus (0.09 ± 0.1 vs 0.08 ± 0.1). Conclusions: Our study postulates the IRT as a potential tool to evaluate BAT thermogenic activation in patients with obesity before and after a bariatric surgery. Further studies are needed to evaluate differences between LSG technique and RYGB on BAT activation. Keywords: Brown adipose tissue; Infrared thermography; Metabolic surgery; Obesity