Adipose Tissue Thermogenesis Research Articles

Macrophages: key mediators of fat storage

Immunometabolism Recent work has suggested that macrophages may regulate adiposity, but the mechanisms underlying this process remain unresolved. Cox et al. report that a macrophage-derived growth factor, Pvf3, and its receptor on fat body cells are needed for lipid storage in fruit fly larvae (see the Perspective by O'Brien and Domingos). The mouse Pvf3 ortholog, PDGFcc, was similarly required to store fat in newborn and adult mice. When PDGFcc was blocked or deleted, food intake and absorption were normal, but mice increased their energy expenditure partly due to enhanced brown adipose tissue thermogenesis. PDGFcc was produced exclusively by fat-resident macrophages rather than by those mediating inflammation and insulin resistance. This work may inform future treatments for lipodystrophy, cachexia, and obesity. Science , abe9383, this issue p. [eabe9383][1]; see also abj5072, p. [24][2] [1]: /lookup/doi/10.1126/science.abe9383 [2]: /lookup/doi/10.1126/science.abj5072

Study on the experimental verification and regulatory mechanism of Rougui-Ganjiang herb-pair for the actions of thermogenesis in brown adipose tissue based on network pharmacology

Ethnopharmacological relevanceCinnamomum cassia Presl (Rougui) has character of xin、gan、wen, belongs to Jing of heart、lung、bladder, and has the effect of dispersing cold and relieving pain. It is widely used to resolve the exterior and dissipate cold in Treatise on Febrile Diseases (Shang Han Lun), such as Chaihu Guizhi Ganjiang Tang and Guizhi Renshen Tang. Both these two prescriptions contain Cinnamomum cassia Presl and Zingiber officinale Rosc (Ganjiang). Rougui-Ganjiang herb-pair (RGHP) can warm viscera and remove cold, which is widely used in Shang Han Lun. And in modern times, recent studies have showed that cinnamon and ginger also have the effect of thermogenesis and regulating the body temperature, respectively. Aim of the studyTo maintain the body thermal homeostasis and prevent cold invasion of main organs, in this study, we assessed the underlying physiological changes induced by RGHP in mice exposed to −20 °C and explored the mechanisms for the thermogenic actions of RGHP in brown adipose tissue (BAT) by network pharmacology and molecular docking. Materials and methodsMale Kunming (KM) mice were fed normal diet with orally administration of distilled water or ethanol RGHP extract (three doses: 375,750 and 1500 mg/kg) for 21 days, once per day and then exposed to −20 °C for 2 h. The core temperature, activity ability and the degree of frostbite in mice, morphological and ATP content of adipocytes were measured. In addition, the network pharmacology was employed to predict the targets of RGHP’ s thermogenesis effect on BAT. Pathway analysis and biological process with key genes was carried out through KEGG and GO analysis, respectively. Furthermore, the core ingredients and targets obtained by network pharmacology were verified by molecular docking and Western blot assays. ResultsRGHP can significantly increase the core body temperature, reduce the degree of frostbite and enhance the activity ability of mice after cold exposure. Meanwhile, it can also improve the lipid morphology and decrease ATP production in BAT. A network pharmacology-based analysis identified 246 ingredients from RGHP (two herbs), which related to 222 target genes. There were 8 common genes between 222 compounds target genes and 62 thermogenesis associated target genes, which linked to 49 potential compounds. There are 24 ingredients which degree are greater than the average. Among them, we found that oleic acid, EIC, 6-gingerol, eugenol, isohomogenol and sitogluside could be detected in mice plasma. The cAMP-PPAR signaling pathway was enriched for thermogenesis after KEGG analysis with 8 genes. Molecular docking analysis and Western blot assay further confirmed that oleic acid, 6-gingerol, eugenol and isohomogenol were potential active ingredients for RGHP's heat production effect. And UCP1, PGC-1α, PPARα and PPARγ are key thermogenesis proteins. ConclusionsRGHP treatment can significantly maintain the rectal temperature of mice by enhancing the BAT heat production. RGHP exhibited the heat production effect, which might be mainly attributed to increasing thermogenesis through the cAMP-PPAR signaling pathway in cold exposure mice. Oleic acid, 6-gingerol, eugenol and isohomogenol might be considered the potential therapeutic ingredients which affect the key targets of thermogenesis effect.

Involvement of TRP Channels in Adipocyte Thermogenesis: An Update.

Obesity prevalence became a severe global health problem and it is caused by an imbalance between energy intake and expenditure. Brown adipose tissue (BAT) is a major site of mammalian non-shivering thermogenesis or energy dissipation. Thus, modulation of BAT thermogenesis might be a promising application for body weight control and obesity prevention. TRP channels are non-selective calcium-permeable cation channels mainly located on the plasma membrane. As a research focus, TRP channels have been reported to be involved in the thermogenesis of adipose tissue, energy metabolism and body weight regulation. In this review, we will summarize and update the recent progress of the pathological/physiological involvement of TRP channels in adipocyte thermogenesis. Moreover, we will discuss the potential of TRP channels as future therapeutic targets for preventing and combating human obesity and related-metabolic disorders.

Free Thyroxine Levels are Associated with Cold Induced Thermogenesis in Healthy Euthyroid Individuals.

Thyroid hormone (TH) is an important regulator of mammalian metabolism and facilitates cold induced thermogenesis (CIT) in brown adipose tissue (BAT). Profound hypothyroidism or hyperthyroidism lead to alterations in BAT function and CIT. In euthyroid humans the inter-individual variation of thyroid hormones is relatively large. Therefore, we investigated whether levels of free thyroxine (T4) or free triiodothyronine (T3) are positively associated with CIT in euthyroid individuals. We performed an observational study in 79 healthy, euthyroid volunteers (mean age 25.6 years, mean BMI 23.0 kg · m-2). Resting energy expenditure (REE) was measured by indirect calorimetry during warm conditions (EEwarm) and after a mild cold stimulus of two hours (EEcold). CIT was calculated as the difference between EEcold and EEwarm. BAT activity was assessed by 18F-FDG-PET after a mild cold stimulus in a subset of 26 participants. EEcold and CIT were significantly related to levels of free T4 (R2 = 0.11, p=0.0025 and R2 = 0.13, p=0.0011, respectively) but not to free T3 and TSH. Cold induced BAT activity was also associated with levels of free T4 (R2 = 0.21, p=0.018). CIT was approximately fourfold higher in participants in the highest tertile of free T4 as compared to the lowest tertile. Additionally, free T4 was weakly, albeit significantly associated with outdoor temperature seven days prior to the respective study visit (R2 = 0.06, p=0.037). These finding suggests that variations in thyroid hormone levels within the euthyroid range are related to the capability to adapt to cool temperatures and affect energy balance.

β3-Adrenergic receptors regulate human brown/beige adipocyte lipolysis and thermogenesis.

β3-Adrenergic receptors (β3-ARs) are the predominant regulators of rodent brown adipose tissue (BAT) thermogenesis. However, in humans, the physiological relevance of BAT and β3-AR remains controversial. Herein, using primary human adipocytes from supraclavicular neck fat and immortalized brown/beige adipocytes from deep neck fat from 2 subjects, we demonstrate that the β3-AR plays a critical role in regulating lipolysis, glycolysis, and thermogenesis. Silencing of the β3-AR compromised genes essential for thermogenesis, fatty acid metabolism, and mitochondrial mass. Functionally, reduction of β3-AR lowered agonist-mediated increases in intracellular cAMP, lipolysis, and lipolysis-activated, uncoupling protein 1–mediated thermogenic capacity. Furthermore, mirabegron, a selective human β3-AR agonist, stimulated BAT lipolysis and thermogenesis, and both processes were lost after silencing β3-AR expression. This study highlights that β3-ARs in human brown/beige adipocytes are required to maintain multiple components of the lipolytic and thermogenic cellular machinery and that β3-AR agonists could be used to achieve metabolic benefit in humans.

Chemerin regulates formation and function of brown adipose tissue: Ablation results in increased insulin resistance with high fat challenge and aging.

Apart from its role in inflammation and immunity, chemerin is also involved in white adipocyte biology. To study the role of chemerin in adipocyte metabolism, we examined the function of chemerin in brown adipose tissue. Brown and white adipocyte precursors were differentiated into adipocytes in the presence of Chemerin siRNA. Chemerin-deficient (Chem-/- ) mice were compared to wild-type mice when fed a high-fat diet. Chemerin is expressed during brown adipocyte differentiation and knock down of chemerin mRNA results in decreased brown adipocyte differentiation with reduced fatty acid uptake in brown adipocytes. Chem-/- mice are leaner than wild-type mice but gain more weight when challenged with high-fat diet feeding, resulting in a larger increase in fat deposition. Chem-/- mice develop insulin resistance when on a high-fat diet or due to age. Brown adipose depots in Chem-/- mice weigh more than in wild-type mice, but with decreased mitochondrial content and function. Compared to wild-type mice, male Chem-/- mice have decreased oxygen consumption, CO2 production, energy expenditure, and a lower respiratory exchange ratio. Additionally, body temperature of Chem-/- mice is lower than that of wild-type mice. These results revealed that chemerin is expressed during brown adipocyte differentiation and has a pivotal role in energy metabolism through brown adipose tissue thermogenesis.

TRPM8 modulates temperature regulation in a sex-dependent manner without affecting cold-induced bone loss.

Trpm8 (transient receptor potential cation channel, subfamily M, member 8) is expressed by sensory neurons and is involved in the detection of environmental cold temperatures. TRPM8 activity triggers an increase in uncoupling protein 1 (Ucp1)-dependent brown adipose tissue (BAT) thermogenesis. Bone density and marrow adipose tissue are both influenced by rodent housing temperature and brown adipose tissue, but it is unknown if TRPM8 is involved in the co-regulation of thermogenesis and bone homeostasis. To address this, we examined the bone phenotypes of one-year-old Trpm8 knockout mice (Trpm8-KO) after a 4-week cold temperature challenge. Male Trpm8-KO mice had lower bone mineral density than WT, with smaller bone size (femur length and cross-sectional area) being the most striking finding, and exhibited a delayed cold acclimation with increased BAT expression of Dio2 and Cidea compared to WT. In contrast to males, female Trpm8-KO mice had low vertebral bone microarchitectural parameters, but no genotype-specific alterations in body temperature. Interestingly, Trpm8 was not required for cold-induced trabecular bone loss in either sex, but bone marrow adipose tissue in females was significantly suppressed by Trpm8 deletion. In summary, we identified sex differences in the role of TRPM8 in maintaining body temperature, bone microarchitecture and marrow adipose tissue. Identifying mechanisms through which cold temperature and BAT influence bone could help to ameliorate potential bone side effects of obesity treatments designed to stimulate thermogenesis.

1206-P: Effects of Short-Term Administration of Delta-9-tetrahydrocannabinol on Metabolic Parameters of C57bl/6 Mice

Cancer and HIV-related cachexias are among the qualifying conditions for medical cannabis use. Although effective to alleviate nausea and vomiting, clinical trials demonstrated little to no impact of cannabinoids on weight gain in patients. Consistent with this, cannabis users have a lower prevalence of obesity in epidemiological studies. Since cannabinoid-1 receptors (CB1R) regulate food intake and adipose tissue thermogenesis, we studied the metabolic effects of a low dose of delta-9-tetrahydrocannabinol (THC), a CB1R agonist and the main bioactive chemical in cannabis, in 8-week old male mice maintained on a 10%-fat-calorie diet. Mice received daily intraperitoneal injections of THC (3 mg/Kg, n = 15) or vehicle (n = 12) just before the dark cycle for 7 days. THC-treated mice gained an average of 1.6 grams compared to 2.6 grams gained by the vehicle-treated mice (p = 0.03). Despite the attenuated weight gain, automated home cage phenotyping revealed an increase in food intake in the 90 minutes after injections in the THC-treated mice (mean = 0.78 vs. 0.53 grams; p = 0.001). No differences, however, were detected in overall light (p = 0.39) or dark-cycle food intake (p = 0.07). THC-treated mice also showed reduced locomotor activity in the dark cycle compared to vehicle-treated mice (p <0.001). There were no robust differences in indirect calorimetry parameters between groups in the dark cycle, whereas the respiratory exchange rates were lower among THC-treated mice during the light cycle (p = 0.01). Gene expression studies revealed reduced CB1R mRNA levels in brown adipose (mean = 0.61; p = 0.02) and liver (mean = 0.30; p = 0.04) of THC-treated mice. In summary, administration of a low dose of THC was associated with attenuated weight gain in male C57BL/6 mice, possibly through downregulation of CB1R in metabolically active tissues. Future studies will elucidate the effects of chronic THC administration on CB1R expression and thermogenesis under high fat feeding and obesity. Disclosure E. Kurjan: n/a. L. K. Olson: None. O. Alshaarawy: None. Funding National Institutes of Health (R00AT009156)

1180-P: Short-Term Low-Protein Diet Ameliorates Metabolic Dysfunction in Diabetic Lipodystrophic Mice

Long-term ad libitum dietary restriction such as low-protein diet (LPD) improves metabolic health and extend the life spans of mice and possibly human. However, most studies conducted thus far have mainly focused on preventive rather than the treatment potential of LP diets. To determine whether dietary protein or caloric restriction could be used to treat preexisting metabolic symptoms, particularly in a more severely affected mouse model, we subjected hyperglycemic lipodystrophic IRFKO (adipose-specific insulin receptor knockout) mice to LPD (5.1% kcal from protein). Interestingly, postprandial blood glucose (BG) values of the IRFKO mice began to improve 10 days after the introduction of LPD. The IRFKO mice became normoglycemic 2 weeks after the onset of the LPD treatment. Activation of adaptive thermogenesis in brown (BAT) and beige adipose tissues promotes energy expenditure (EE) and utilization of BG and triglyceride (TG). A LPD has been previously shown to promote EE via the sympathetic nervous system (SNS). Consistent with previous study, we observed that a LPD acutely and sustainably upregulates EE in both the WT and IRFKO mice. This is likely due to LPD dramatically improves BAT functions by transforming the whitened unilocular lipid droplet BAT in the IRFKO mice into normal looking brown multi-locular lipid droplet BAT within 1 week of LPD treatment. This is further supported by significant increase in thermogenic markers expression in the BAT after LPD. Besides thermogenic markers, we also observed a time-dependent regulation of gene markers for fatty acid transport, oxidation and glucose metabolism in BAT after LPD. Together with changes in blood chemistry in the IRFKO mice, we think that glucose and lipid-lowering effects of LPD is the consequence of continuous activation of EE leading to utilization and depletion of systemic thermogenic fuels. Taken together, our data suggest that short-term LPD could be a potential strategy for the treatment of metabolic syndrome. Disclosure M. D. Munoz: None. M. A. Mccann: None. P. Kim: None. C. Liew: None.

Rottlerin, a Polyphenolic Compound, Alleviate Body Adiposity by Enhancing Lipolysis and Thermogenesis in Diet-Induced Obesity Mice

ObjectivesRottlerin (mallotoxin) is a polyphenolic compound in Mallotus philippensis. The anti-tumor, anti-inflammation, and mitochondrial uncoupling regulation effects of rottlerin have been known. However, the anti-obesity effect was not reported yet. Thus, we hypothesized that rottlerin would suppress body fat accumulation in obesity-induced mice. MethodsFive-week-old male C57BL/6 mice were fed a high-fat diet (HFD) (60% kcal from fat) ad libitum for 8 weeks. Mice were randomly assigned to five groups as follows: 1) normal diet (18% kcal from fat), 2) negative control (60% kcal from fat), 3) rottlerin 10 (HFD + rottlerin 10 mg/kg bw), 4) rottlerin 20 (HFD + 20 mg/kg bw), 5) positive control (HFD + metformin 150 mg/kg bw). Rottlerin was daily supplemented by oral gavage. Body weight and feed intake were measured each week. ResultsBody weight and weight gain were reduced in rottlerin 20 compared to the control (P < 0.001). Body fat mass was also significantly decreased by rottlerin (P < 0.05). Total feed intake and lean mass were similar among HFD groups. Furthermore, energy expenditure was dose-dependently facilitated by rottlerin. RNA-sequencing results supported these findings that rottlerin 20 up-regulated fatty acid beta-oxidation, heat generation, and brown cell differentiation in white-adipose tissues. Rottlerin promoted a catabolic pathway such as lipolysis, thermogenesis, and oxidation in white adipose tissues. Moreover, non-esterified fatty acid levels were decreased by rottlerin (P < 0.05), and hepatic triglyceride contents tended to decline in rottlerin 20 without hepatotoxicity. Non-shivering thermogenesis enzymes, PRDM16 (P = 0.06) and UCP1 (P < 0.01), were stimulated by rottlerin. ConclusionsRottlerin supplementation altered body adiposity accumulation via enhancing fat utilization, lipolysis, and thermogenesis in obese mice. We suggest that rottlerin is a potent nutraceutical for anti-obesity. Funding SourcesThis work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Science and ICT; MSIT).

Diet-Induced Non-anemic Iron Deficiency Attenuates Adaptive Thermogenesis via Defective Iron Metabolism of Adipose Tissue in C57BL/6 Mice

ObjectivesIron deficiency is one of the most common nutrient deficiencies worldwide. Adaptive thermogenesis plays a critical role for maintaining energy homeostasis. Currently, the role of dietary iron deficiency on adaptive thermogenesis is unknown. We hypothesized that dietary iron deficiency attenuates adaptive thermogenesis via dysfunctional iron metabolism in adipose tissue. MethodsC57BL/6 male mice were fed a diet containing either adequate-iron (Cont: 35ppm) or deficient-iron (ID: 3ppm) throughout for 14 weeks and the last 10 weeks were fed a high-fat diet to induce obesity. Systemic iron status was evaluated by measuring serum ferritin, hemoglobin (Hb), and hematocrit (HCt). The iron content of adipose tissue was determined by ICP-MS spectrometer. The protein and gene expressions related to iron-handling and thermogenesis were measured in adipose tissue by Western blot analysis and qPCR. To assess adaptive thermogenic function, mice were exposed to cold temperature acutely (3 hour) or administrated with β3-adrenoceptor agonist (CL) for 5 days. The core body temperature and thermogenesis were determined by a rectal thermometer and infrared camera, respectively. ResultsThe ID mice displayed a non-anemic iron deficiency with reduced serum ferritin (p < 0.01), increased weight gain (p < 0.05) and decreased insulin sensitivity (p < 0.05) compared to Cont. The iron content was significantly reduced in the inguinal (iWAT, p < 0.05) of the ID mice, which was linked with reduced thermogenic heat release upon acute cold treatment. In addition, ID mice markedly reduced the adipose tissue browning and thermogenic heat release upon CL stimulation compared with Cont. In terms of iron metabolism, CL-induced coordinated iron uptake for mitochondrial biogenesis in the iWAT was impaired in the ID mice, which was comparable to inflammation-mediated defective adipose tissue browning and thermogenesis. ConclusionsIron deficiency induced visceral obesity and compromised thermogenic function due to defective iron metabolism in C57BL6 mice. Funding SourcesNational Institutes of Health Grant 1R21HD094273.

Secretin activates brown fat and induces satiation.

Brown adipose tissue (BAT) thermogenesis is activated by feeding. Recently, we revealed a secretin-mediated gut-BAT-brain axis, which stimulates satiation in mice, but the purpose of meal-induced BAT activation in humans has been unclear. In this placebo-controlled, randomized crossover study, we investigated the effects of intravenous secretin on BAT metabolism (measured with [18F]FDG and [15O]H2O positron emission tomography) and appetite (measured with functional magnetic resonance imaging) in healthy, normal weight men (GUTBAT trial no. NCT03290846). Participants were blinded to the intervention. Secretin increased BAT glucose uptake (primary endpoint) compared to placebo by 57% (median (interquartile range, IQR), 0.82 (0.77) versus 0.59 (0.53) μmol per 100 g per min, 95% confidence interval (CI) (0.09, 0.89), P = 0.002, effect size r = 0.570), while BAT perfusion remained unchanged (mean (s.d.) 4.73 (1.82) versus 6.14 (3.05) ml per 100 g per min, 95%CI (-2.91, 0.07), P = 0.063, effect size d = -0.549) (n = 15). Whole body energy expenditure increased by 2% (P = 0.011) (n = 15). Secretin attenuated blood-oxygen level-dependent activity (primary endpoint) in brain reward circuits during food cue tasks (significance level false discovery rate corrected at P = 0.05) (n = 14). Caloric intake did not significantly change, but motivation to refeed after a meal was delayed by 39 min (P = 0.039) (n = 14). No adverse effects were detected. Here we show in humans that secretin activates BAT, reduces central responses to appetizing food and delays the motivation to refeed after a meal. This suggests that meal-induced, secretin-mediated BAT activation is relevant in the control of food intake in humans. As obesity is increasing worldwide, this appetite regulating axis offers new possibilities for clinical research in treating obesity.

Chrysin Stimulates Subcutaneous Fat Thermogenesis in Mice by Regulating PDGFRα and MicroRNA Expressions.

The activation of adipose tissue browning and thermogenesis provides a new strategy to counter obesity and associated metabolic diseases. Here, a natural flavonoid chrysin is used as the supplement of a high-fat diet (HFD). Dietary chrysin alleviates adiposity and insulin resistance in HFD-fed mice. Meanwhile, dietary chrysin elevates systemic energy expenditure and enhances the uncoupling protein-1 (UCP1) level in subcutaneous adipose tissue (SAT), which is accompanied by the increased thermogenic program, beige preadipocyte number, and angiogenesis in SAT. Dietary chrysin also induces the expression of SAT platelet-derived growth factor receptor α (PDGFRα), which commits adipose progenitor cells to differentiate into beige or white adipocytes in response to various environmental signals. Double immunofluorescent staining for UCP1 and PDGFRα reveals that chrysin elevates the number of UCP1+PDGFRα+ beige progenitors in SAT. Further, chrysin treatment reverses the effects of the specific PDGFRα inhibitor imatinib on browning differentiation of stromal vascular fraction cells from SAT. Finally, chrysin-induced adipocyte browning is correlated with the expressions of microRNAs as PDGFRα inhibitors or thermogenesis suppressors. In conclusion, dietary chrysin promotes subcutaneous adipocyte browning and systematic energy expenditure by regulating PDGFRα and microRNA expressions in HFD-fed mice.

Association of triple negative breast cancer (TNBC) with high thermogenesis with worse survival and unfavorable tumor microenvironment (TME).

e12546 Background: Norepinephrine released during cold stress by housing 4T1 TNBC mice at 22°C increases tumor growth with a pro-tumorigenic TME [lower CD8+ T-cells, higher myeloid derived suppressor cells (MDSC) and regulatory T-cells (Treg)] compared with mice housed at 30°C. Norepinephrine activates thermogenesis in adipose tissue. Worse survival has been reported among females with malignancies living in cold versus warm climate. These findings led us to hypothesize that TNBC with enhanced thermogenesis is associated with worse outcome and unfavorable TME. Methods: mRNA expression data for 298 and 143 TNBC patients was accessed from METABRIC and GSE96058 breast cancer cohorts, respectively. TNBC were classified into “high” (top tertile) and “low” thermogenesis (bottom two-third) using Gene Set Variation Analysis (GSVA) with KEGG thermogenesis pathway. Computer algorithms xCell and Gene Set Enrichment Analysis (GSEA) were used. Interferon (IFN)-γ signature was calculated using GSVA. Gene expression data was used to quantify adipocytes, angiogenesis, chemokines and cytolytic activity (CYT). R software was used for analysis. False discovery rate (FDR) &lt; 0.25 for GSEA and p &lt; 0.05 was considered statistically significant. Results: High-thermogenesis TNBC was associated with a worse median disease specific survival 14.7 years vs. not reached [HR 1.49 (95% CI 1.02-2.18)], p &lt; 0.05 in METABRIC and a trend towards worse overall survival in both METABRIC and GSE96058. Higher fraction of adipocytes (p &lt; 0.001) and angiogenesis markers including CD31, vWF, Vascular endothelial cadherin, claudin 5, JAM2 and sphingosine-1-phosphate related gene S1PR1 (p &lt; 0.01) were observed explaining the worse survival in high-thermogenesis TNBC. This group was significantly enriched in fatty acid metabolism and adipogenesis pathways (FDR &lt; 0.25) on GSEA. On the other hand, low-thermogenesis TNBC was enriched in mitotic spindle, E2F targets, G2M checkpoint, MYC targets consistent with higher Ki67 (p &lt; 0.05) in this group; and also in IFN-α and IFN-γ response (FDR &lt; 0.25). High-thermogenesis TNBC was associated with lower IFN-γ and granzyme B expression (p &lt; 0.05). Favorable cytotoxic-T cell attracting chemokines CCL5, CXCL9, CXCL10 and CXCL11 were lower; MDSC-, Treg-favoring chemokine CXCL12 was higher (p &lt; 0.05). There were lower M1 and more M2 macrophages (p &lt; 0.001) with lower CYT. There was higher expression of dual-specificity phosphatase-1 ( DUSP1)(p &lt; 0.05), which is upregulated following glucocorticoid receptor activation. Conclusions: We investigated the clinical relevance of preclinical findings and observed that high-thermogenesis TNBC is associated with worse survival and unfavorable TME. Further research is warranted to validate if high thermogenesis could reflect tumors under thermal stress and develop novel strategies to abrogate stress and improve outcomes.

NBR1 is a critical step in the repression of thermogenesis of p62-deficient adipocytes through PPAR\u03b3

Activation of non-shivering thermogenesis is considered a promising approach to lower body weight in obesity. p62 deficiency in adipocytes reduces systemic energy expenditure but its role in sustaining mitochondrial function and thermogenesis remains unresolved. NBR1 shares a remarkable structural similarity with p62 and can interact with p62 through their respective PB1 domains. However, the physiological relevance of NBR1 in metabolism, as compared to that of p62, was not clear. Here we show that whole-body and adipocyte-specific ablation of NBR1 reverts the obesity phenotype induced by p62 deficiency by restoring global energy expenditure and thermogenesis in brown adipose tissue. Impaired adrenergic-induced browning of p62-deficient adipocytes is rescued by NBR1 inactivation, unveiling a negative role of NBR1 in thermogenesis under conditions of p62 loss. We demonstrate that upon p62 inactivation, NBR1 represses the activity of PPARγ, establishing an unexplored p62/NBR1-mediated paradigm in adipocyte thermogenesis that is critical for the control of obesity.

Peripheral-specific Y1 receptor antagonism increases thermogenesis and protects against diet-induced obesity

Obesity is caused by an imbalance between food intake and energy expenditure (EE). Here we identify a conserved pathway that links signalling through peripheral Y1 receptors (Y1R) to the control of EE. Selective antagonism of peripheral Y1R, via the non-brain penetrable antagonist BIBO3304, leads to a significant reduction in body weight gain due to enhanced EE thereby reducing fat mass. Specifically thermogenesis in brown adipose tissue (BAT) due to elevated UCP1 is enhanced accompanied by extensive browning of white adipose tissue both in mice and humans. Importantly, selective ablation of Y1R from adipocytes protects against diet-induced obesity. Furthermore, peripheral specific Y1R antagonism also improves glucose homeostasis mainly driven by dynamic changes in Akt activity in BAT. Together, these data suggest that selective peripheral only Y1R antagonism via BIBO3304, or a functional analogue, could be developed as a safer and more effective treatment option to mitigate diet-induced obesity.

Cold-induction of afadin in brown fat supports its thermogenic capacity

The profound energy-expending nature of brown adipose tissue (BAT) thermogenesis makes it an attractive target tissue to combat obesity-associated metabolic disorders. While cold exposure is the strongest inducer of BAT activity, the temporal mechanisms tuning BAT adaptation during this activation process are incompletely understood. Here we show that the scaffold protein Afadin is dynamically regulated by cold in BAT, and participates in cold acclimation. Cold exposure acutely increases Afadin protein levels and its phosphorylation in BAT. Knockdown of Afadin in brown pre-adipocytes does not alter adipogenesis but restricts β3-adrenegic induction of thermogenic genes expression and HSL phosphorylation in mature brown adipocytes. Consistent with a defect in thermogenesis, an impaired cold tolerance was observed in fat-specific Afadin knockout mice. However, while Afadin depletion led to reduced Ucp1 mRNA induction by cold, stimulation of Ucp1 protein was conserved. Transcriptomic analysis revealed that fat-specific ablation of Afadin led to decreased functional enrichment of gene sets controlling essential metabolic functions at thermoneutrality in BAT, whereas it led to an altered reprogramming in response to cold, with enhanced enrichment of different pathways related to metabolism and remodeling. Collectively, we demonstrate a role for Afadin in supporting the adrenergic response in brown adipocytes and BAT function.

Does a high-fat diet-induced obesity model brown adipose tissue thermogenesis? A systematic review.

IntroductionIn this systematic review, we analysed studies that assessed the brown adipose tissue (BAT) activity in the high-fat/cafeteria diet model of obesity in rats.Material and methodsScopus, PubMed, Embase, and ScienceDirect databases were searched from January 2017 to November 2017. Using specific combinations of medical subject heading (MeSH) descriptors, seven papers remained after the inclusion and exclusion criteria.ResultsMost papers showed an increase in BAT thermogenesis in rodents fed high-fat/cafeteria diet. Some studies did not mention the diet composition or housing temperature, and the most of them investigated the thermogenesis superficially, being limited to the analysis of the UCP 1 expression.ConclusionsDespite the consolidated use of high-fat/cafeteria diets as a model to induce obesity, the identification of the energy expenditure arm has been slow, especially the direct quantitative assessment of the contribution of BAT to the increase in metabolic rate in rats fed a cafeteria/high-fat diet.

Identification of PACAP-Expressing Neurons in the Hypothalamic Origins of Sympathetic Outflow Tracts Terminating in Brown Adipose Tissue of Mice

Abstract Adaptive thermogenesis in brown adipose tissue is stimulated by the sympathetic nervous system (SNS) in response to cold stress. Using retrograde viral transneuronal tract tracers, previous studies have identified that the paraventricular nucleus (PVN), ventromedial hypothalamus (VMH), and median preoptic nucleus (MnPO) contain neurons that are part of sympathetic outflow tracts to brown adipose tissue, presumptively involved in SNS stimulation of interscapular brown adipose tissue (iBAT). Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is a peptide hormone known to regulate energy homeostasis, acting in both the central (CNS) and peripheral nervous system (PNS). Mice lacking PACAP have impaired adrenergic-induced thermogenesis and a cold-sensitive phenotype. In the CNS, PACAP is highly expressed in the VMH, MnPO, and PVN of the hypothalamus. Injection of PACAP into the VMN increased core body temperature and sympathetic nerve activity to brown adipose tissue. While these studies show exogenous PACAP can activate sympathetic outflow tracts to brown adipose tissue, they do not confirm that endogenously expressed PACAP induces sympathetic nerve activity as an adaptive mechanism to cold stress, or if sympathetic outflow tracts originating in the hypothalamus express PACAP. We hypothesize that PACAP is expressed in neurons of sympathetic outflow tracts originating in the hypothalamus. To test this hypothesis, PACAP-eGFP transgenic mice were injected with the retrograde neural tracer, pseudorabies virus tagged with β-galactosidase (β-gal, PRV-BaBlu), in iBAT where postganglionic nerves innervate the tissue. Five-days post-infection, animals were culled, brains removed and cryosectioned. Neurons positive for green fluorescent protein (eGFP) and/or β-gal immunoreactivity (ir) were identified by immunohistochemistry in serial coronal and sagittal brain cryo-sections. Co-occurrence of eGFP-ir and β-gal-ir, inferred PACAP expressing neurons present in sympathetic outflow tracts (ImageJ). Co-occurrence was identified in several structures in the hypothalamus and thalamus. In conclusion, this study presents neuroanatomical evidence for populations of PACAPinergic neurons in the hypothalamus that are part of sympathetic outflow tracts to brown adipose tissue, providing further evidence of a central role for PACAP in regulating energy homeostasis.

Spexin Friend or Foe? Novel Role of Spexin During Thermogenesis of White Adipose Tissue

Spexin (SPX) is a novel adipokine playing an emerging role in metabolic diseases due to its involvement in carbohydrate homeostasis, weight loss, appetite control, gastrointestinal movement, among others. Moreover, plasma levels are reduced in obese and type II diabetic patients. In vitro, SPX favors lipolysis in adipocytes and hepatocytes and inhibits white adipogenesis. Therefore, the aim of this study was to evaluate the role of SPX in white adipose tissue (AT) thermogenesis. C57BL/6J male mice were treated or not with SPX for ten days (ip. 29 µg/kg/day; CTR and SPX). At day 3 mice were randomly divided: a group was kept at room temperature (RT) and the other at 4°C to stimulate thermogenesis (CTR-C and SPX-C). Caloric intake and body weight was daily recorded. At the end of the protocol plasma, Brown AT (BAT), abdominal AT (Epidydimal, EAT) and subcutaneous AT (Inguinal, IAT) depots were collected for several measurements. We found that caloric intake was increased when animals were exposed to cold (P<0.001). Body weight change revealed a differential effect of SPX depending on temperature (interaction SPX x Cold, P<0.05): SPX animals weighted less than CTR at RT, but upon cold stimulation there was no difference. No changes were observed for plasma glucose levels, however plasma triglycerides (Tg) levels decreased after cold exposure regardless SPX treatment (Cold P<0.01). Liver Tg content showed a SPX x Cold interaction effect (P<0.0001), where, upon cold stimulation, CTR-C animals increased their levels, but on the contrary SPX-C mice decreased it. EAT, IAT and BAT relative mass showed an interaction effect of variables (SPX x Cold P<0.05). When compared upon cold, SPX-C mice had less AT mass compared to CTR-C mice. IAT and EAT mRNA expression of UCP1 and Cox8b showed SPX x Cold interaction (P<0.05), with a tendency of reduction or no difference in SPX at RT, but with a significant decrease in SPX-C compared to CTR-C mice upon cold exposure. PGC1a expression was increased in EAT from cold exposed-mice and in IAT only in CTR-C mice. UCP1 protein levels showed different results depending on the AT depot. For IAT SPX x Cold interaction (P<0.05) was observed, where SPX inhibited UCP1 stimulation only upon cold exposure. On the contrary, for EAT UCP1 levels decreased in SPX-treated mice, regardless cold exposure (SPX P<0.05). In conclusion, SPX treatment in vivo reduced the thermogenic process in subcutaneous and abdominal AT, being more evident upon cold stimulation. PICT2017-2038, PICT2017-2314.