Gut microbiota intervention attenuates thermogenesis in broilers exposed to high temperature through modulation of the hypothalamic 5‑HT pathway

Background Broilers have a robust metabolism and high body temperature,which make them less tolerant to hightemperature(HT)environments and more susceptible to challenges from elevated temperatures.Gut microbes,functioning as symbionts within the host,possess the capacity to significantly regulate the physiological functions and environmental adaptability of the host.This study aims to investigate the effects of gut microbial intervention on the body temperature and thermogenesis of broilers at different ambient temperatures,as well as the underlying mechanism involving the"gut-brain"axis.Methods Broilers were subjected to gut microbiota interference with or without antibiotics(control or ABX)starting at 1 day of age.At 21 day of age,they were divided into 4 groups and exposed to different environments for 7 d:The control and ABX groups at room temperature(RT,24±1℃,60%relative humidity(RH),24 h/d)and the control-HT and ABX-HT groups at high temperature(HT,32±1℃,60%RH,24 h/d).Results The results demonstrated that the antibiotic-induced gut microbiota intervention increased body weight and improved feed conversion in broiler chickens(P<0.05).Under HT conditions,the microbiota intervention reduced the rectal temperature of broiler chickens(P<0.05),inhibited the expression of avUCP and thermogenesisrelated genes in breast muscle and liver(P<0.05),and thus decreased thermogenesis capacity.Furthermore,the gut microbiota intervention blunted the hypothalamic‒pituitary‒adrenal axis and hypothalamic–pituitary–thyroid axis activation induced by HT conditions.By analyzing the cecal microbiota composition of control and ABX chickens maintained under HT conditions,we found that Alistipes was enriched in control chickens.In contrast,antibioticinduced gut microbiota intervention resulted in a decrease in the relative abundance of Alistipes(P<0.05).Moreover,this difference was accompanied by increased hypothalamic 5-hydroxytryptamine(5-HT)content and TPH2 expression(P<0.05).Conclusions These findings underscore the critical role of the gut microbiota in regulating broiler thermogenesis via the gut-brain axis and suggest that the hypothalamic 5-HT pathway may be a potential mechanism by which the gut microbiota affects thermoregulation in broilers.

Relationship between Nonexercise Activity Thermogenesis and Calf Circumference in Older Women

Purpose: Frailty is a state of declined vitality of the body and mind with age in which life functions are impaired. In addition, there is a difference in the susceptibility of older women to frailty compared with that of older men. Therefore, assessing and encouraging physical activity in older adults before they become frail is essential. We aimed to clarify the relationship between calf circumference and body composition and assess the potential association between calf circumference and physical activity indices in older women. Methods: This cross-sectional study included 18 healthy older adults (age 69.0 ± 5.7 years). The physical characteristics, calf circumference, body composition, calf muscle thickness, and physical activity questionnaire that included items on exercise-related activity thermogenesis (EAT) and nonexercise activity thermogenesis (NEAT) were assessed. The association between calf circumference and these additional measures was examined. Results: Positive and significant correlations were found between the calf circumference and body weight, body mass index (BMI), skeletal muscle mass, skeletal muscle mass index, calf muscle thickness, total questionnaire score, and NEAT score (r = 0.66 - 0.87). However, no significant correlations were observed between the calf circumference and EAT scores. Conclusion: Calf circumference in older women may reflect NEAT activity. Improving NEAT activity is an important health-promoting factor in older women.

ATF4 regulates lipid metabolism and thermogenesis

Activating transcription factor 4 （ATF4） has been shown to play key roles in many physiological processes. There are no reports, however, demonstrating a direct link between ATF4 and lipid metabolism. We noticed that Atf4- deficient mice are lean, suggesting a possible role for ATF4 in regulating lipid metabolism. The goal of our current study is to investigate the involvement of ATF4 in lipid metabolism and elucidate the underlying mechanisms. Studies using Atf4-deficient mice revealed increased energy expenditure, as measured by oxygen consumption. These mice also showed increases in lipolysis, expression of uncoupling protein 2 （UCP2） and p-oxidation genes and decreases in expression of lipogenic genes in white adipose tissue （WAT）, suggesting increased utilization and decreased synthesis of fatty acids, respectively. Expression of UCP1, 2 and 3 was also increased in brown adipose tissue （BAT）, suggesting increased thermogenesis. The effect of ATF4 deletion on expression of UCPs in BAT suggests that increased thermogenesis may underlie increased energy expenditure. Thus, our study identifies a possible new function for ATF4 in regulating lipid metabolism and thermogenesis.

Diet-Induced Thermogenesis

An immense amount of information has now accrued about the factors that influence the increment of heat and the efficiency with which the energy of food is used by different animal species. Heat increment is one of the major factors that decrease the efficiency of energy utilization. In growing animals, the free energy content of the basal ATP requirement is typically about one-third of dietary basal heat production （thermogenesis）. Thermogenesis is an evolutionary and biologically significant mechanism for adaptive, homeostatic heat production in animals, including shivering thermogenesis （ST）, nonshivering thermogenesis （NST）, diet-induced thermogenesis （DIT）, febrile response （fever）, and so on. The main focus of this review is on the effect of DIT on energy metabolism.

Orexin receptor type 2 agonism inhibits thermogenesis in brown adipose tissue by attenuating afferent innervation

Orexin signaling has been associated with energy expenditure and brown adipose tissue(BAT)function.However,conflicting data exist in the field about how orexin signaling regulates BAT thermogenesis.In this study,we show that a specific orexin receptor type 2(OX2R)agonist[Ala11,D-Leu15]-OxB(OB-Ala)inhibited intrascapular brown adipose tissue(iBAT)thermogenesis by reducing sympathetic output to iBAT.This effect is mediated by OX2Rs located on afferent nerve endings innervating iBAT instead of brown adipocyte itself.Microinjection of OB-Ala into iBAT inhibited iBAT thermogenesis in mice upon cold exposure and neuronal activity in the paraventricular nucleus.Findings suggest that OB-Ala could inhibit iBAT thermogenesis by attenuating sensory input thereby inhibiting the sympathetic-sensory iBAT feedback loop.Our study uncovers a novel primary action site of orexin in the regulation of energy balance.

Is Non-exercise Activity Thermogenesis-a Target for Reversing Obesity?

Non-exercise activity thermogenesis (NEAT) is the energy expenditure of all physical activities other than volitional sporting-like exercise. NEAT includes all the activities that render us vibrant, unique and independent beings such as working, playing, and dancing. Because people of the same weight have markedly variable activity levels, it is not surprising that NEAT varies substantially between people by 2000 kcal/day. Evidence suggests that low NEAT may occur in obesity but in a very specific fashion. Obese individuals appear to exhibit an innate tendency to be seated for 2.5 hours per day more than sedentary lean counterparts. If obese individuals were to adopt the lean ‘NEAT-o-type’, they could potentially expend an additional 350 kcal/day. Obesity was rare a century ago and the human genotype has not changed over that time. Thus, the obesity epidemic may reflect the emergence of a chair-enticing environment to which those with an innate tendency to sit, did so and became obese. To reverse obesity therefore, we need to develop individual strategies to promote standing & ambulating time by 2.5 hours per day but also re-engineer our work, school and home environments to render active living the option of choice.

CMKLR1 senses chemerin/resolvin E1 to control adipose thermogenesis and modulate metabolic homeostasis

Induction of beige fat for thermogenesis is a potential therapy to improve homeostasis against obesity.β3-adrenoceptor(β3-AR),a type of G protein-coupled receptor(GPCR),is believed to mediate the thermogenesis of brown fat in mice.However,β3-AR has low expression in human adipose tissue,precluding its activation as a standalone clinical modality.This study aimed at identifying a potential GPCR target to induce beige fat.We found that chemerin chemokine-like receptor 1(CMKLR1),one of the novel GPCRs,mediated the development of beige fat via its two ligands,chemerin and resolvin E1(RvE1).The RvE1 levels were decreased in the obese mice,and RvE1 treatment led to a substantial improvement in obese features and augmented beige fat markers.Inversely,despite sharing the same receptor as RvE1,the chemerin levels were increased in obesogenic conditions,and chemerin treatment led to an augmented obese phenotype and a decline of beige fat markers.Moreover,RvE1 and chemerin induced or restrained the development of beige fat,respectively,via the mechanistic target of rapamycin complex 1(mTORC1)signaling pathway.We further showed that RvE1 and chemerin regulated mTORC1 signaling differentially by forming hydrogen bonds with different binding sites of CMKLR1.In conclusion,our study showed that RvE1 and chemerin affected metabolic homeostasis differentially,suggesting that selectively modulating CMKLR1 may be a potential therapeutic target for restoring metabolic homeostasis.

Opioid growth factor receptor promotes adipose tissue thermogenesis via enhancing lipid oxidation

The thermogenic brown and beige adipocytes consume fatty acids and generate heat to maintain core body temperature in the faceof cold challenges.Since their validated presence in humans,the activation of thermogenic fat has been an attractive target fortreating obesity and related metabolic diseases.Here,we reported that the opioid growth factor receptor(Ogfr)was highly expressedin adipocytes and promoted thermogenesis.The mice with genetic deletion of Ogfr in adipocytes displayed an impaired capacity tocounter environmental cold challenges.Meanwhile,Ogfr ablation in adipocytes led to reduced fatty acid oxidation,enhanced lipidaccumulation,impaired glucose tolerance,and exacerbated tissue inflammation under chronic high-fat diet(HFD)-fed conditions.At the cellular level,OGFr enhanced the production of mitochondrial trifunctional protein subunitα(MTPα)and also interacted withMTPα,thus promoting fatty acid oxidation.Together,our study demonstrated the important role of OGFr in fatty acid metabolismand adipose thermogenesis.

Carbonic anhydrase 2 mediates anti-obesity effects of black tea as thermogenic activator

Obesity is a metabolic disorder due to over-accumulation of adipose tissue and ultimately becomes a“disease”.Brown adipose tissue(BAT)thermogenesis and white adipose tissue(WAT)browning emerge as a potential strategy of anti-obesity by dissipating energy as heat.However,drugs based on adipose tissue thermogenesis have not been successfully approved yet.In current study,we found that black tea extract(BTE)obtained by patentauthorized manufacturing process prevented body weight gain as novel thermogenic activator with reduction of adiposity,improvement of adipose distribution,and glucose metabolism improvement in diet-induced obesity mice.Mechanismly,anti-obesity effect of BTE depends on promoting BAT thermogenesis and WAT browning with upregulation of uncoupling protein 1(UCP1),especially visceral adipose tissue(VAT)with browning resistance.Specifically,utilizing in silico approach of network pharmacology and molecular docking,we identified carbonic anhydrase 2(CA2)in nitrogen metabolism as anti-obesity target of BTE and further elucidated that protein kinase B(AKT)signaling pathway linked CA2 and UCP1.Meanwhile gut microbiota regulation may prompt the CA2-dependent thermogenesis activation.Our findings demonstrated anti-obesity effect of BTE as thermogenic activator through CA2-mediated BAT thermogenesis and WAT browning via CA2-AKT-UCP1 signaling pathway,which could be developed as promising anti-obesity agent with good safety and efficacy.

Berberine enhances Ucp1 expression via modulating the NFE2 response element in cold environments: new perspectives on the thermogenesis in brown adipose tissue

Berberine （BBR） has a variety of pharmacological activities. Studies have reported that BBR not only reduces heat stress-induced fever but also inhibits lower body temperatures due to cold stress. Heat stress can be reduced via BBR treatment, which antagonizes HSP70-TNFa to regulate the body temperature alteration. In cold stress, however, the molecular mechanism of BBR-induced inhibition of hypothermia remains unclear. Therefore, we studied whether BBR promoted uncoupling protein 1 （UCP1, a crucial protein of thermogenesis） expression and its mechanism under cold stress. Wild type mice and Ucpl-/- mice were used for the in vivo experiments, and primary brown adipocytes and brown adipocytes HIB-1B were used for the in vitro studies. The cold stress was set at 4℃. The results showed that at 4℃, the body temperature of mice was decreased. BBR effectively inhibited this hypothermia. Simultaneously, Ucpl expression in brown adipose tissue （BAT） cells was significantly increased, and BBR promoted Ucpl expression. However, in Ucpl-knockout mice, the effect of BBR on hypothermia disappeared during cold stress, indicating that the main target for BBR regulation of body temperature was Ucpl. Further studies showed that the transcriptional response element NFE2 （nuclear factor erythroid-derived 2） in the upstream of the Ucpl promoter region contributed to the positive regulatory role on Ucpl expression at lower temperature. BBR could bind to the sequence of NFE2 response element in a temperature-dependent manner. Increased affinity of BBR binding to NFE2 response element in cold stress significantly strengthened and enhanced the expression of Ucpl. This work was important for understanding the role of BBR on thermogenesis in BAT, body temperature regulation and temperature tolerance under cold conditions.

PITPNC1 promotes the thermogenesis of brown adipose tissue under acute cold exposure

Brown adipose tissue (BAT) plays an essential role in non-shivering thermogenesis. The phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) is identified as a lipid transporter that reciprocally transfers phospholipids between intracellular membrane structures. However, the physiological significance of PITPNC1 and its regulatory mechanism remain unclear. Here, we demonstrate that PITPNC1 is a key player in thermogenesis of BAT. While Pitpnc1^(−/−) mice do not differ with wildtype mice in body weight and insulin sensitivity on either chow or high-fat diet, they develop hypothermia when subjected to acute cold exposure at 4℃. The Pitpnc1^(−/−) brown adipocytes exhibit defective β-oxidation and abnormal thermogenesis-related metabolism pathways in mitochondria. The deficiency of lipid mobilization in Pitpnc1^(−/−) brown adipocytes might be the result of excessive accumulation of phosphatidylcholine and a reduction of phosphatidic acid. Our findings have uncovered significant roles of PITPNC1 in mitochondrial phospholipid homeostasis and BAT thermogenesis.

Activation of the cold-sensing TRPM8 channel triggers UCP1-dependent thermogenesis and prevents obesity

Brown adipose tissue(BAT)is an energy-expending organ that produces heat.Expansion or activation of BAT prevents obesity and diabetes.Chronic cold exposure enhances thermogenesis in BAT through uncoupling protein 1(UCP1)activation triggered via a b-adrenergic pathway.Here,we report that the cold-sensing transient receptor potential melastatin 8(TRPM8)is functionally present in mouse BAT.Challenging brown adipocytes with menthol,a TRPM8 agonist,up-regulates UCP1 expression and requires protein kinase A activation.Upon mimicking long-term cold exposure with chronic dietary menthol application,menthol significantly increased the core temperatures and locomotor activity in wild-type mice;these effects were absent in both TRPM82/2 and UCP12/2 mice.Dietary obesity and glucose abnormalities were also prevented by menthol treatment.Our results reveal a previously unrecognized role for TRPM8,suggesting that stimulation of this channel mediates BAT thermogenesis,which could constitute a promising way to treat obesity.

Rheb promotes brown fat thermogenesis by Notch-dependent activation of the PKA signaling pathway

Increasing brown and beige fat thermogenesis have an anti-obesity effect and thus great metabolic benefits.However,the molecular mechanisms regulating brown and beige fat thermogenesis remain to be further elucidated.We recently found that fat-specific knockout of Rheb promoted beige fat thermogenesis.In the current study,we show that Rheb has distinct effects on thermogenic gene expression in brown and beige fat.Fat-specific knockout of Rheb decreased protein kinase A(PKA)activity and thermogenic gene expression in brown adipose tissue of high-fat diet-fed mice.On the other hand,overexpression of Rheb activated PKA and increased uncoupling protein 1 expression in brown adipocytes.Mechanistically,Rheb overexpression in brown adipocytes increased Notch expression,leading to disassociation of the regulatory subunit from the catalytic subunit of PKA and subsequent PKA activation.Our study demonstrates that Rheb,by selectively modulating thermogenic gene expression in brown and beige adipose tissues,plays an important role in regulating energy homeostasis.

Rnf20 deficiency in adipocyte impairs adipose tissue development and thermogenesis

RNF20,an E3 ligase critical for monoubiquitination of histone H2B at lysine 120(H2Bub),has been implicated in the regulation of various cellar processes;however,its physiological roles in adipocytes remain poorly characterized.Here,we report that the adipocyte-specific knockout of Rnf20(ASKO)in mice led to progressive fat toss,organomegaly and hyperinsulinemia.Despite signs of hyperinsulinemia,normal insulin sensitivity and improved glucose tolerance were observed in the young and aged CD-fed ASKO mice.In addition,high-fat diet-fed ASKO mice developed severe liver steatosis.Moreover,we observed that the ASKO mice were extremely sensitive to a cold environment due to decreased expression levels of brown adipose tissue(BAT)selective genes,including uncoupling protein 1(l/cpf),and impaired mitochondrial functions.Significantly decreased levels of peroxisome proliterator-activated receptor gamma(Ppary)were observed in the gonadal white adipose tissues(gWAT)from the ASKO mice,suggesting that Rnf20 regulates adipogenesis,at least in part,through Ppary.Rosiglitazone-treated ASKO mice exhibited increased fat mass compared to that of the non-treated ASKO mice.Collectively,our results illustrate the critical role of RNF20 in control of white and brown adipose tissue development and physiological function.

Lysyl oxidase inhibition enhances browning of white adipose tissue and adaptive thermogenesis

Accumulating evidence from both animal and human studies suggests that activation of beige fat increases cellular energy expenditure,ultimately reducing adiposity.Here,we report the central role of adipocyte-derived lysyl oxidase(Lox)in the formation of thermogenic beige fat.Mice exposed to cold or aβ3 agonist showed drastically lower Lox expression in thermogenically activated beige fat.Importantly,inhibition of Lox activity with BAPN stimulated biogenesis of beige fat in inguinal white adipose tissue(iWAT)under housing conditions and potentiated cold-induced adaptive thermogenesis and beiging in both iWAT and epididymal white adipose tissue(eWAT).Notably,white adipocytes with Lox repression undergo transdifferentiation into beige adipocytes which can be suppressed by tumor necrosis factor-α(TNFα)via ERK activation.This work provides new insight into the molecular control to expand beige fat by Lox inhibition and suggest the potential for utilizing inhibitor of Lox to treat the emerging epidemics of obesity and diabetes.

DDB1 prepares brown adipocytes for cold-induced thermogenesis

Brown adipose tissue(BAT)plays a key role in thermogenesis during acute cold exposure.However,it remains unclear how BAT is prepared to rapidly turn on thermogenic genes.Here,we show that damage-specific DNA binding protein 1(DDB1)mediates the rapid transcription of thermogenic genes upon acute cold exposure.Adipose-or BAT-specific Ddb1 knockout mice show severely whitened BAT and significantly decreased expression of thermogenic genes.These mice develop hypothermia when subjected to acute cold exposure at 4℃ and partial lipodystrophy on a high-fat diet due to deficiency in fatty acid oxidation.Mechanistically,DDB1 binds the promoters of Ucp1 and Ppargc1a and recruits positive transcriptional elongation factor b(P-TEFb)to release promoter-proximally paused RNA polymerase II(Pol II),thereby enabling rapid and synchronized transcription of thermogenic genes upon acute cold exposure.Our findings have thus provided a regulatory mechanism of how BAT is prepared to respond to acute cold challenge.

Distinction of white,beige and brown adipocytes derived from mesenchymal stem cells

Adipose tissue is a major metabolic organ, and it has been traditionally classified as either white adipose tissue(WAT) or brown adipose tissue(BAT). WAT and BAT are characterized by different anatomical locations, morphological structures, functions, and regulations. WAT and BAT are both involved in energy balance. WAT is mainly involved in the storage and mobilization of energy in the form of triglycerides, whereas BAT specializes in dissipating energy as heat during cold- or diet-induced thermogenesis. Recently, brownlike adipocytes were discovered in WAT. These brownlike adipocytes that appear in WAT are called beige or brite adipocytes. Interestingly, these beige/brite cells resemble white fat cells in the basal state, but they respond to thermogenic stimuli with increased levels of thermogenic genes and increased respiration rates. In addition, beige/brite cells have a gene expressionpattern distinct from that of either white or brown fat cells. The current epidemic of obesity has increased the interest in studying adipocyte formation(adipogenesis), especially in beige/brite cells. This review summarizes the developmental process of adipose tissues that originate from the mesenchymal stem cells and the features of these three different types of adipocytes.

Thermogenic protein UCP1 and UCP3 expression in non- small cell lung cancer： relation with glycolysis and anaerobic metabolism

Uncoupling protein 1(UCP1)is a proton transporter/channel residing on the inner mitochondrial membrane and is involved in cellular heat production.Using immunohistochemistry,we investigated the expression of UCP1 and UCP3 in a series of 98 patients with non-small cell lung cancer(NSCLC)treated with surgery.Expression patterns were correlated with histopathological variables,prognosis,and the expression of enzymes/proteins related to cell metabolism.Bronchial epithelium did not express UCP1 or UCP3,while alveolar cells strongly expressed UCP1.In tumors,strong expression of UCP1 and UCP3 was recorded in43/98(43.8%)and 27/98(27.6%)cases,respectively.UCP1 was significantly associated with squamous cell histology(P=0.05),whilst UCP3 was more frequently overexpressed in large cell carcinomas(P=0.08),and was inversely related to necrosis(P=0.009).In linear regression analysis,UCP1 was directly related to markers of glycolysis[hexokinase(HXKII)and phosphofructokinase(PFK1)]and anaerobic glucose metabolism[pyruvate dehydrogenase kinase(PDK1)and lactate dehydrogenase(LDH5)].UCP3 was directly linked with a glucose transporter(GLUT2),monocarboxylate transporter(MCT2),glycolysis markers(PFK1 and aldolase),and with the phosphorylation of pyruvate dehydrogenase(p PDH).Kaplan-Meier survival analysis showed that UCP3 was significantly related to poor prognosis in squamous cell carcinomas(P=0.04).UCP1 and UCP3 are overexpressed in a large subgroup of non-small cell lung tumors and their expression coincides with increased glucose absorption,intensified glycolysis,and anaerobic glucose usage.Whether UCPs are targets for therapeutic interventions in lung cancer is a hypothesis that demands further investigation.

Daily physical activity and type 2 diabetes: A review

Physical activity improves glycemic control and reduces the risk of cardiovascular disease(CVD) and mortality in patients with type 2 diabetes(T2D). Moderate to vigorous physical activity is recommended to manage T2D; however, patients with T2D can be physically weak, making it difficult to engage in the recommended levels of physical activity. Daily physical activity includes various activities performed during both occupational and leisure time such as walking, gardening, and housework that type 2 diabetic patients should be able to perform without considerable physical burden. This review focuses on the association between daily physical activity and T2D. Walking was the most common form of daily physical activity, with numerous studies demonstrating its beneficial effects on reducing the risk of T2D, CVD, and mortality. Walking for at least 30 min per day was shown to reduce the risk of T2D by approximately 50%. Additionally, walking was associated with a reduction in mortality. In contrast, evidence was extremely limited regarding other daily physical activities such as gardening and housework in patients with T2D. Recent studies have suggested daily physical activity, including non-exercise activity thermogenesis, to be favorably associated with metabolic risks and mortality. However, well-designed longitudinal studies are warranted to elucidate its effects on overall health.

Fat deposition deficiency is critical for the high mortality of pre-weanling newborn piglets

Background: The high mortality of pre-weanling piglets is a dominant challenge which severely restricts the development of pig industry. A number of factors including nutrients imbalance and temperature variation during postnatal period of piglets have been reported to closely associated with the high mortality of postnatal piglets.This study aims to find out the relationship between fat deposition and survival of newborn piglets.Results: There were no differences in organ coefficient and bone density between the surviving and dead piglets(P > 0.05). The body weight and the fat deposition in the dead piglets were lower than the live individuals(P < 0.05).Consistently, the average sizes of white adipocytes in back and abdominal adipose tissues of dead piglets were smaller than the survivals(P < 0.05). The protein expression levels of adipocyte differentiation markers PPARγ and C/EBPα in the back and abdominal adipose tissues were lower in dead piglets compared to live piglets. The mRNA expressions of thermogenic markers PGC1α and PRDM16 in adipose tissues were decreased in the dead piglets(P < 0.05). The microarray of back fat samples from the surviving and dead piglets were conducted; two down-regulated genes namely AAMDC and CASTOR1 were identified from the dead piglets. According to quantitative real-time PCR(RT-PCR) analysis, the mRNA expression of AAMDC decreased, whereas CASTOR1 expression elevated in the dead piglets compared to the surviving piglets(P < 0.05).Conclusions: The fat deposition and adipocyte differentiation in the dead piglets are insufficient compared to the surviving piglets, which may attenuate the thermogenic ability of white adipose tissue(WAT). Our data indicate that fat deposition in newborn piglets is vital to their survival.