Adiponectin Knockout Research Articles

Adiponectin deficiency is a critical factor contributing to cognitive dysfunction in obese mice after sevoflurane exposure

BackgroundThe number of major operations performed in obese patients is expected to increase given the growing prevalence of obesity. Obesity is a risk factor for a range of postoperative complications including perioperative neurocognitive disorders. However, the mechanisms underlying this vulnerability are not well defined. We hypothesize that obese subjects are more vulnerable to general anaesthesia induced neurotoxicity due to reduced levels of adiponectin. This hypothesis was tested using a murine surgical model in obese and adiponectin knockout mice exposed to the volatile anaesthetic agent sevoflurane.MethodsObese mice were bred by subjecting C57BL/6 mice to a high fat diet. Cognitive function, neuroinflammatory responses and neuronal degeneration were assessed in both obese and lean mice following exposure to 2 h of sevoflurane to confirm sevoflurane-induced neurotoxicity. Thereafter, to confirm the role of adiponectin deficiency in, adiponectin knockout mice were established and exposed to the sevoflurane. Finally, the neuroprotective effects of adiponectin receptor agonist (AdipoRon) were examined.ResultsSevoflurane triggered significant cognitive dysfunction, neuroinflammatory responses and neuronal degeneration in the obese mice while no significant impact was observed in the lean mice. Similar cognitive dysfunction and neuronal degeneration were also observed in the adiponectin knockout mice after sevoflurane exposure. Administration of AdipoRon partially prevented the deleterious effects of sevoflurane in both obese and adiponectin knockout mice.ConclusionsOur findings demonstrate that obese mice are more susceptible to sevoflurane-induced neurotoxicity and cognitive impairment in which adiponectin deficiency is one of the underlying mechanisms. Treatment with adiponectin receptor agonist ameliorates this vulnerability. These findings may have therapeutic implications in reducing the incidence of anaesthesia related neurotoxicity in obese subjects.

Inhibition of angiogenesis and regenerative lung growth in Lepob/ob mice through adiponectin-VEGF/VEGFR2 signaling.

Obesity is associated with impairment of wound healing and tissue regeneration. Angiogenesis, the formation of new blood capillaries, plays a key role in regenerative lung growth after unilateral pneumonectomy (PNX). We have reported that obesity inhibits angiogenesis. The effects of obesity on post-PNX lung vascular and alveolar regeneration remain unclear. Unilateral PNX is performed on Lep o b / o b obese mice to examine vascular and alveolar regeneration. Regenerative lung growth and expression of vascular endothelial growth factor (VEGF) and its receptor VEGFR2 induced after PNX are inhibited in Lep o b / o b obese mice. The levels of adiponectin that exhibits pro-angiogenic and vascular protective properties increase after unilateral PNX, while the effects are attenuated in Lep o b / o b obese mice. Post-PNX regenerative lung growth and increases in the levels of VEGF and VEGFR2 are inhibited in adiponectin knockout mice. Adiponectin stimulates angiogenic activities in human lung endothelial cells (ECs), which is inhibited by decreasing the levels of transcription factor Twist1. Adiponectin agonist, AdipoRon restores post-PNX lung growth and vascular and alveolar regeneration in Lep o b / o b obese mice. These findings suggest that obesity impairs lung vascular and alveolar regeneration and adiponectin is one of the key factors to improve lung regeneration in obese people.

Aerobic exercise training-induced bone and vascular adaptations in mice lacking adiponectin

Adiponectin regulates lipid and glucose metabolism, and insulin sensitivity in various target organs; however, the effects of adiponectin on bone health remain controversial. Exercise training can enhance bone density, bone microarchitecture, and blood flow. This study aimed to elucidate the role of adiponectin in adaptations of bone microarchitecture and bone vasculature in response to aerobic exercise training.Adult male C57BL/6 wild-type (WT) and homozygous adiponectin knockout (AdipoKO) mice were either treadmill exercise trained or remained sedentary for 8–10 weeks. The trabecular structures of the distal femoral metaphysis, a weight-bearing bone, and the mandible, a non-weight-bearing bone, were examined using microcomputed tomography. The femoral principal nutrient arteries were isolated to assess vasoreactivity (vasodilation and vasoconstriction) and structural remodeling.At the femoral metaphysis, impaired trabecular bone structures, including reduced connectivity density and increased trabecular spacing, were observed in AdipoKO mice compared to WT mice. In addition, nitric oxide-mediated, endothelium-dependent vasodilation was substantially reduced, and wall-to-lumen ratio was significantly increased in the femoral principal nutrient artery of AdipoKO mice. Interestingly, although exercise training-induced enhancements in trabecular connectivity density were observed at the femoral metaphysis of both WT and AdipoKO, increased vasoconstrictor responses were only observed in the femoral principal nutrient artery of WT mice, not in the AdipoKO mice. In mandibular trabecular bone, exercise training increased trabecular bone volume fraction (BV/TV, %) and intersection surface in the mandible of both WT and AdipoKO mice.These findings indicate that adiponectin is crucial for maintaining normal bone microarchitecture and vasculature. Although the absence of adiponectin compromises bone vascular adaptation to exercise training in mice, some exercise training-induced alterations in bone microarchitecture occurred in the absence of adiponectin, suggesting contribution of compensatory mechanisms during exercise training.

High-fat diet impact on prostate gland from adiponectin knockout mice: Morphometric, metabolic and inflammatory cytokines analyses

AimsObesity is a global public health issue, and some studies have linked it to an increased risk of prostatic diseases. This study aimed to evaluate the effects of a high-fat diet on metabolic parameters and prostate morphology in wild-type (WT) and adiponectin knockout (KO) mice. Main methodsMale WT and KO mice were fed a control diet (CD) or high-fat diet (HFD) for 6 months. Serum metabolic parameters, inflammatory cytokines in epididymal fat tissue, dorsal prostatic lobe morphometry and histopathology were analyzed. Key findingsCD WT and CD KO mice did not exhibit altered metabolic or prostatic parameters. However, HFD WT mice showed altered glucose and insulin tolerance even without excessive weight gain. On the other hand, HFD KO mice developed obesity, with an increase in low-density lipoprotein (11.8 ± 5.1 vs. 31.4 ± 3.6 mg/dL), high-density lipoprotein (73.4 ± 7.4 vs. 103.4 ± 2.5 mg/dL), and total cholesterol levels (126.2 ± 16.1 vs. 294.6 ± 23.2 mg/dL), a decrease in insulin levels (28.7 ± 12.2 vs. 4.6 ± 2.3 μIU/mL), and glucose and insulin resistance. We also observed that HFD KO animals display an increase in inflammatory cytokines, such as IL6, IL1β, and IL1RA. The dorsal prostate from HFD KO animals also presented significant increases in the mast cells (1.9 ± 0,7 vs. 5,3 ± 1.5 cells/field) and Ki67 index (2.91 ± 0.6 vs. 4.7 ± 0.4 %). SignificanceThe above findings highlight the complex interactions between adiponectin, metabolism, malnutrition, and prostate health. Metabolic deregulation combined with adipose inflammation potentially induces a proliferative and inflammatory microenvironment in the prostate gland under conditions of low adiponectin production, potentially impairing prostate morphophysiology in the context of obesity and aging.

Ischemia-induced cardiac dysfunction is exacerbated in adiponectin-knockout mice due to impaired autophagy flux.

Strategies to enhance autophagy flux have been suggested to improve outcomes in cardiac ischemic models. We explored the role of adiponectin in mediating cardiac autophagy under ischemic conditions induced by permanent coronary artery ligation. We studied the molecular mechanisms underlying adiponectin's cardio-protective effects in adiponectin knockout (Ad-KO) compared with wild-type (WT) mice subjected to ischemia by coronary artery ligation and H9c2 cardiomyocyte cell line exposed to hypoxia. Systemic infusion of a cathepsin-B activatable near-infrared probe as a biomarker for autophagy and detection via noninvasive three-dimensional fluorescence molecular tomography combined with computerized tomography to quantitate temporal changes, indicated increased activity in the myocardium of WT mice after myocardial infarction which was attenuated in Ad-KO. Seven days of ischemia increased myocardial adiponectin accumulation and elevated ULK1/AMPK phosphorylation and autophagy assessed by Western blotting for LC3 and p62, an outcome not observed in Ad-KO mice. Cell death, assessed by TUNEL analysis and the ratio of Bcl-2:Bax, plus cardiac dysfunction, measured using echocardiography with strain analysis, were exacerbated in Ad-KO mice. Using cellular models, we observed that adiponectin stimulated autophagy flux in isolated primary adult cardiomyocytes and increased basal and hypoxia-induced autophagy in H9c2 cells. Real-time temporal analysis of caspase-3/7 activation and caspase-3 Western blot indicated that adiponectin suppressed activation by hypoxia. Hypoxia-induced mitochondrial reactive oxygen species production and cell death were also attenuated by adiponectin. Importantly, the ability of adiponectin to reduce caspase-3/7 activation and cell death was not observed in autophagy-deficient cells generated by CRISPR-mediated deletion of Atg7. Collectively, our data indicate that adiponectin acts in an autophagy-dependent manner to attenuate cardiomyocyte caspase-3/7 activation and cell death in response to hypoxia invitro and ischemia in mice.

Depleting inositol pyrophosphate 5-InsP7 protected the heart against ischaemia-reperfusion injury by elevating plasma adiponectin.

Adiponectin is an adipocyte-derived circulating protein that exerts cardiovascular and metabolic protection. Due to the futile degradation of endogenous adiponectin and the challenges of exogenous administration, regulatory mechanisms of adiponectin biosynthesis are of significant pharmacological interest. Here, we report that 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) generated by inositol hexakisphosphate kinase 1 (IP6K1) governed circulating adiponectin levels via thiol-mediated protein quality control in the secretory pathway. IP6K1 bound to adiponectin and DsbA-L and generated 5-InsP7 to stabilize adiponectin/ERp44 and DsbA-L/Ero1-Lα interactions, driving adiponectin intracellular degradation. Depleting 5-InsP7 by either IP6K1 deletion or pharmacological inhibition blocked intracellular adiponectin degradation. Whole-body and adipocyte-specific deletion of IP6K1 boosted plasma adiponectin levels, especially its high molecular weight forms, and activated AMPK-mediated protection against myocardial ischaemia-reperfusion injury. Pharmacological inhibition of 5-InsP7 biosynthesis in wild-type but not adiponectin knockout mice attenuated myocardial ischaemia-reperfusion injury. Our findings revealed that 5-InsP7 is a physiological regulator of adiponectin biosynthesis that is amenable to pharmacological intervention for cardioprotection.

Endogenous renal adiponectin drives gluconeogenesis through enhancing pyruvate and fatty acid utilization

Adiponectin is a secretory protein, primarily produced in adipocytes. However, low but detectable expression of adiponectin can be observed in cell types beyond adipocytes, particularly in kidney tubular cells, but its local renal role is unknown. We assessed the impact of renal adiponectin by utilizing male inducible kidney tubular cell-specific adiponectin overexpression or knockout mice. Kidney-specific adiponectin overexpression induces a doubling of phosphoenolpyruvate carboxylase expression and enhanced pyruvate-mediated glucose production, tricarboxylic acid cycle intermediates and an upregulation of fatty acid oxidation (FAO). Inhibition of FAO reduces the adiponectin-induced enhancement of glucose production, highlighting the role of FAO in the induction of renal gluconeogenesis. In contrast, mice lacking adiponectin in the kidney exhibit enhanced glucose tolerance, lower utilization and greater accumulation of lipid species. Hence, renal adiponectin is an inducer of gluconeogenesis by driving enhanced local FAO and further underlines the important systemic contribution of renal gluconeogenesis.

Abstract P2117: Hypoadiponectinemia-induced Epigenetic Downregulation Of Endogenous Antioxidants Exacerbates Cardiac Ischemia-reperfusion Injury In Diabetic Mice

Diabetes worsen myocardial ischemic/reperfusion (MI/R) injury, but the underlying mechanism is still not fully understood. Epigenetics regulation is markedly involved in the process. Adiponectin (APN), a cardioprotective adipokine, is suppressed by diabetes, and dysregulated miRNAs are implicated in disease development. However, it is unclear whether hypoadiponectinemia alters cardiac miRNA profile, contributing to diabetic heart injury. Wild-type (WT) and APN knockout (APN-KO) mice were subjected to MI/R and cardiac microRNA profile were determined. Comparing those miRNAs that increased in APN-KO mice following MI/R, miR-449b was most significantly upregulated (3.98-fold over WT mice). Administering miR-449b mimic increased apoptosis, enlarged infarct size, and impaired cardiac function in WT mice. In contrast, anti-miR-449b decreased apoptosis, reduced infarct size, and improved cardiac function in APN-KO mice. In depth Bioinformatic analysis revealed oxidative stress as the top pathway regulated by miR449b. Venn analysis followed by luciferase assay identified Nrf-1 and Ucp3 as the two most important miR-449b targets. Administrating anti-miR-449b to APN-KO mice attenuated MI/R-stimulated superoxide overproduction. High glucose/high lipid in vitro treatment simulated ischemia/reperfusion upregulated miR-449b, leading to inhibition of Nrf-1 and Ucp3. These pathological effects were attenuated by anti-miR-449b or Nrf-1 overexpression. Clinically relevant cohorh study in high-fat diet (HFD)-induced diabetic mice followed with MI/R identified the copied pheonotype. Administration of anti-miR-449b or APN preserved cardiac Nrf-1 expression, reduced cardiac oxidative stress, decreased apoptosis and infarct size, and improved cardiac function. In conclusion, the study shows that hypoadiponectinemia upregulates miR-449b, suppressing Nrf-1/Ucp3 expression, which leads to oxidative stress and worsens MI/R injury. The APN/miR-449b/oxidative stress pathway could potentially be a therapeutic target for diabetic MI/R injury.

Hypoadiponectinemia-induced upregulation of microRNA449b downregulating Nrf-1 aggravates cardiac ischemia-reperfusion injury in diabetic mice

Diabetes enhances myocardial ischemic/reperfusion (MI/R) injury via an incompletely understood mechanism. Adiponectin (APN) is a cardioprotective adipokine suppressed by diabetes. However, how hypoadiponectinemia exacerbates cardiac injury remains incompletely understood. Dysregulation of miRNAs plays a significant role in disease development. However, whether hypoadiponectinemia alters cardiac miRNA profile, contributing to diabetic heart injury, remains unclear. Methods and Results: Wild-type (WT) and APN knockout (APN-KO) mice were subjected to MI/R. A cardiac microRNA profile was determined. Among 23 miRNAs increased in APN-KO mice following MI/R, miR-449b was most significantly upregulated (3.98-fold over WT mice). Administrating miR-449b mimic increased apoptosis, enlarged infarct size, and impaired cardiac function in WT mice. In contrast, anti-miR-449b decreased apoptosis, reduced infarct size, and improved cardiac function in APN-KO mice. Bioinformatic analysis predicted 73 miR-449b targeting genes, and GO analysis revealed oxidative stress as the top pathway regulated by these genes. Venn analysis followed by luciferase assay identified Nrf-1 and Ucp3 as the two most important miR-449b targets. In vivo administration of anti-miR-449b in APN-KO mice attenuated MI/R-stimulated superoxide overproduction. In vitro experiments demonstrated that high glucose/high lipid and simulated ischemia/reperfusion upregulated miR-449b and inhibited Nrf-1 and Ucp3 expression. These pathological effects were attenuated by anti-miR-449b or Nrf-1 overexpression. In a final attempt to validate our finding in a clinically relevant model, high-fat diet (HFD)-induced diabetic mice were subjected to MI/R and treated with anti-miR-449b or APN. Diabetes significantly increased miR-449b expression and downregulated Nrf-1 and Ucp3 expression. Administration of anti-miR-449b or APN preserved cardiac Nrf-1 expression, reduced cardiac oxidative stress, decreased apoptosis and infarct size, and improved cardiac function. Conclusion: We demonstrated for the first time that hypoadiponectinemia upregulates miR-449b and suppresses Nrf-1/Ucp3 expression, promoting oxidative stress and exacerbating MI/R injury in this population. Dysregulated APN/miR-449b/oxidative stress pathway is a potential therapeutic target against diabetic MI/R injury.

Microvascular Function in Skeletal Muscle of Acute Adiponectin Knockout Mice

Adiponectin contributes to the regulation of vascular and metabolic functions in skeletal muscle. Although circulating adiponectin is known to increase with aerobic exercise training, a direct role for adiponectin in adaptation of microvasculature of skeletal muscle to aerobic exercise training has not been documented. We exercise trained young adult mice with normal circulating adiponectin (wild type, WT) and mice in which adiponectin was acutely deleted (Cre-Lox conditional knockout system induced with Tamoxifen chow, AdipoKO) before undergoing 8 weeks of exercise training. Sedentary WT and AdipoKO mice were housed under similar cage conditions for 8 weeks. We determined skeletal muscle oxidative capacity, exercise tolerance, lean and fat mass, and we assessed reactivity of 1A arterioles from the gastrocnemius muscle. Exercise training increased exercise tolerance in both WT and AdipoKO mice. Exercise training increased lean mass and reduced fat mass in both WT and AdipoKO mice. Myogenic constriction to intraluminal pressure changes was increased by exercise training in gastrocnemius muscle 1A arterioles from both WT and AdipoKO mice. In contrast, phenylephrine-induced contractile responses were increased by exercise training in WT, but not AdipoKO mice. These data suggest that adiponectin is an important contributor to adaptations of contractile function that occur in skeletal muscle in response to exercise training; however, the training-induced increase in exercise tolerance and muscle mass that occurred in both WT and AdipoKO mice suggests that loss of adiponectin impacts smooth muscle function independently of metabolic adaptations in skeletal muscle. NIH R56AG068156 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Adiponectin reverses β-Cell damage and impaired insulin secretion induced by obesity.

Obesity significantly decreases life expectancy and increases the incidence of age-related dysfunctions, including β-cell dysregulation leading to inadequate insulin secretion. Here, we show that diluted plasma from obese human donors acutely impairs β-cell integrity and insulin secretion relative to plasma from lean subjects. Similar results were observed with diluted sera from obese rats fed ad libitum, when compared to sera from lean, calorically restricted, animals. The damaging effects of obese circulating factors on β-cells occurs in the absence of nutrient overload, and mechanistically involves mitochondrial dysfunction, limiting glucose-supported oxidative phosphorylation and ATP production. We demonstrate that increased levels of adiponectin, as found in lean plasma, are the protective characteristic preserving β-cell function; indeed, sera from adiponectin knockout mice limits β-cell metabolic fluxes relative to controls. Furthermore, oxidative phosphorylation and glucose-sensitive insulin secretion, which are completely abrogated in the absence of this hormone, are restored by the presence of adiponectin alone, surprisingly even in the absence of other serological components, for both the insulin-secreting INS1 cell line and primary islets. The addition of adiponectin to cells treated with plasma from obese donors completely restored β-cell functional integrity, indicating the lack of this hormone was causative of the dysfunction. Overall, our results demonstrate that low circulating adiponectin is a key damaging element for β-cells, and suggest strong therapeutic potential for the modulation of the adiponectin signaling pathway in the prevention of age-related β-cell dysfunction.

AdipoRon accelerates bone repair of calvarial defect in diet-induced obesity mice

ObjectivesTo investigate the role of AdipoRon in bone wound healing of calvaria critical-sized defects (CSD) in diet-induced obesity (DIO) mice. Materials and methodsAfter establishing the calvaria CSD in normal-chow (NC), DIO and Adiponectin knockout (APNKO) mice, AdipoRon or vehicle was orally gavaged for 3 weeks. The bone defects were analyzed by micro-CT and H&E staining. The expression of osteogenesis-related factor in the defect area, and the chemotactic gradient of SDF-1 between bone marrow and bone defect area were further analyzed. ResultsAdipoRon downregulated body weight and alleviated fasting blood glucose level of DIO mice after treatment with AdipoRon in 14 and 21 days. Newly formed bone was significantly increased in the defect area of DIO and APNKO mice after treatment with AdipoRon compared with vehicle treatment. No significant difference was shown in NC mice. Furthermore, compared with NC mice, a significant decrease of BV/TV%, Tb.N value and formed bone percentage were shown in DIO and APNKO mice. The treatment with AdipoRon could reverse of decreased value and increase the newly formed bone in those mice. AdipoRon promoted col-1α expression in wound sites in DIO and APNKO mice. AdipoRon nearly quadrupled the chemotactic gradient of SDF-1 by decreasing SDF-1 expression in bone marrow and increasing it in the bone defect area in APNKO and DIO treated mice. ConclusionAdipoRon alleviates the obesity status in DIO mice with calvarial defect and increase new bone formation in calvarial defects in DIO and APNKO mice by modulating chemotactic gradient of SDF-1.

Globular adiponectin-mediated vascular remodeling by affecting the secretion of adventitial-derived tumor necrosis factor-α induced by urotensin II.

In this study, we explored how adiponectin mediated urotensin II (UII)‍-induced tumor necrosis factor-‍α (TNF-‍α) and α‍-smooth muscle actin (α‍-SMA) expression and ensuing intracellular signaling pathways in adventitial fibroblasts (AFs). Growth-arrested AFs and rat tunica adventitia of vessels were incubated with UII and inhibitors of signal transduction pathways for 1‍‒‍24 h. The cells were then harvested for TNF-α receptor (TNF-‍α-R) messenger RNA (mRNA) and TNF-‍α protein expression determination by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Adiponectin and adiponectin receptor (adipoR) expression was measured by RT-PCR, quantitative real-time PCR (qPCR), immunohistochemical analysis, and cell counting kit-8 (CCK-8) cell proliferation experiments. We then quantified TNF-α and α-SMA mRNA and protein expression levels by qPCR and immunofluorescence (IF) staining. RNA interference (RNAi) was used to explore the function of the adipoR genes. To investigate the signaling pathway, we applied western blotting (WB) to examine phosphorylation of adenosine 5'-monophosphate (AMP)‍-activated protein kinase (AMPK). In vivo, an adiponectin (APN)‍-knockout (APN-KO) mouse model mimicking adventitial inflammation was generated to measure TNF-α and α‍-SMA expression by application of qPCR and IF, with the goal of gaining a comprehensive atlas of adiponectin in vascular remodeling. In both cells and tissues, UII promoted TNF-α protein and TNF-α-R secretion in a dose- and time-dependent manner via Rho/protein kinase C (PKC) pathway. We detected marked expression of adipoR1, T-cadherin, and calreticulin as well as a moderate presence of adipoR2 in AFs, while no adiponectin was observed. Globular adiponectin (gAd) fostered the growth of AFs, and acted in concert with UII to induce α-SMA and TNF-α through the adipoR1/T-cadherin/calreticulin/AMPK pathway. In AFs, gAd and UII synergistically induced AMPK phosphorylation. In the adventitial inflammation model, APN deficiency up-regulated the expression of α-SMA, UII receptor (UT), and UII while inhibiting TNF-‍α expression. From the results of our study, we can speculate that UII induces TNF‍-‍α protein and TNF-‍α‍-R secretion in AFs and rat tunica adventitia of vessels via the Rho and PKC signal transduction pathways. Thus, it is plausible that adiponectin is a major player in adventitial progression and could serve as a novel therapeutic target for cardiovascular disease administration.

Bone marrow adipose tissue

Bone marrow adipose tissue (BMAT) represents > 10% total fat mass in healthy humans and further increases in diverse clinical conditions. Like white adipose tissue (WAT), BMAT can produce hormones such as adiponectin, suggesting that it may exert systemic metabolic effects. Unlike WAT, BMAT increases in conditions of caloric restriction (CR), in which it is a key source of increased circulating adiponectin. Thus, BMAT appears developmentally and functionally distinct from WAT. However, the impact of BMAT on health and disease remains poorly understood. Thus, the objective of my research is to determine the fundamental functions and clinical significance of BMAT. My lab's research combines preclinical animal models, human clinical studies and data science approaches using the UK Biobank. Mouse models include CR studies in adiponectin knockout mice, to test if BMAT acts via adiponectin to influence the metabolic, skeletal and immunological effects of CR. Clinical studies include the use of positron emission tomography and computed tomography (PET-CT) to assess BMAT's metabolic functions in vivo. Finally, we are using deep learning to analyse BMAT in magnetic resonance imaging data from the UK Biobank, thereby allowing us to identify the physiological, pathological and genetic factors associated with altered BMAT. (1) Adiponectin KO mice: We have found, unexpectedly, that lack of adiponectin enhances, rather than impairs, CR-induced improvements in glucose tolerance. Compared to wild-type counterparts, KO mice have lower fasting glucose during CR. Adiponectin KO also alters the immunological effects of CR. (2) PET-CT studies: in mice we find that BMAT glucose uptake is not insulin or cold-responsive, demonstrating that BMAT is metabolically distinct from WAT and brown adipose tissue. In humans, we have found that BMAT has high basal glucose uptake under fasting conditions, greater even than that of skeletal muscle. Thus, BMAT may influence systemic metabolic homeostasis as a site of high glucose disposal. (3) UK Biobank studies: our deep learning segmentations have yielded expected inverse associations between BMFF and bone mineral density (BMD) and identified new site- and sex-dependent relationships between BMFF, BMD and peripheral adiposity. Our preclinical and clinical studies have identified new fundamental functions of BMAT and adiponectin, including metabolic and immunological effects. In our UK Biobank studies, we have developed and validated a new deep learning method for high-throughput BMFF analysis in the UKBB. Our initial results already provide new insights for the role of BMAT in skeletal and metabolic health. We have since analysed BMFF in ∼ 37,000 subjects and are pursuing Genome- and Phenome-Wide Association Studies to identify genetic and pathophysiological factors associated with altered BMAT. Together, our research establishes the utility of machine learning for population-level BMFF analysis and promises to elucidate the full impact of BMAT on human health and disease. William Cawthorn is an Associate Professor at the Centre for Cardiovascular Science, University of Edinburgh. His PhD research (Institute of Metabolic Science, University of Cambridge) investigated the regulation of adipogenesis while his postdoctoral studies (University of Michigan) focussed on mesenchymal cell fate and the function bone marrow adipose tissue (BMAT). In 2015, he established his laboratory at The University of Edinburgh with the overarching research goal of determining the function of BMAT. To do so his lab combines preclinical animal models, human clinical studies and data science approaches using the UK Biobank. Methods include in-depth metabolic phenotyping, immunological analyses, the development of novel biomedical imaging techniques, and artificial intelligence to open new avenues for population-level studies. Together, his research addresses the interplay between metabolism, immunological function and skeletal health, both in the context of fundamental biology and chronic diseases. He is a founding member and current Interim President of the International Bone Marrow Adiposity Society and is also the University of Edinburgh's Open Science Ambassador for the League of European Research Institutions (LERU).

Adiponectin Intervention to Regulate Betatrophin Expression, Attenuate Insulin Resistance and Enhance Glucose Metabolism in Mice and Its Response to Exercise.

Aims: Adiponectin stimulates mitochondrial biogenesis through peroxisome proliferator-activated receptor-coactivator1α (PGC-1α), a major regulator of mitochondrial biogenesis, and its effect on the genesis of insulin resistance is organ-specific. Expressed predominantly in fat and liver tissues, betatrophin is primarily involved in lipid metabolism, and could be a putative therapeutic target in metabolic syndrome and T2D. We hypothesized that the adiponectin pathway may regulate the production and/or secretion of betatrophin in liver. We aimed to determine whether exercise and adiponectin affect betatrophin to improve insulin resistance in mice. Methods: To investigate this hypothesis, we used wild-type C57BL/6 mice subjected to a high-fat diet, an exercise regimen, and i.p. injection of recombinant mouse adiponectin (Acrp30), and adiponectin knockout (Adipoq−/−) mice (C57BL/6 background) subjected to i.p. injection of Acrp30. Results: In Adipoq–/– mice, betatrophin levels in the plasma and liver were upregulated. In mice, plasma and liver betatrophin levels were significantly upregulated following a high-fat diet. Exercise and i.p. Acrp30 downregulated betatrophin levels and increased adiponectin mRNA and protein expression in the plasma and liver. The trend of change in PGC-1α and betatrophin levels in the liver was consistent. Conclusions/interpretation: Exercise reverses pathogenic changes in adiponectin and betatrophin levels in insulin-resistant mice. Exercise increased adiponectin levels and reduced betatrophin levels. Furthermore, exercise reduced betatrophin levels via adiponectin, which modulated the LKB1/AMPK/PGC-1α signaling axis but was not solely dependent on it for exerting its effects.

Adiponectin/AdiopR1 signaling prevents mitochondrial dysfunction and oxidative injury after traumatic brain injury in a SIRT3 dependent manner

Mitochondrial dysfunction and oxidative injury, which contribute to worsening of neurological deficits and poor clinical outcomes, are hallmarks of secondary brain injury after TBI. Adiponectin (APN), beyond its well-established regulatory effects on metabolism, is also essential for maintaining normal brain functions by binding APN receptors that are ubiquitously expressed in the brain. Currently, the significance of the APN/APN receptor (AdipoR) signaling pathway in secondary injury after TBI and the specific mechanisms have not been conclusively determined. In this study, we found that APN knockout aggravated brain functional deficits, increased brain edema and lesion volume, and exacerbated oxidative stress as well as apoptosis after TBI. These effects were significantly alleviated after APN receptor agonist (AdipoRon) treatment. Moreover, we found that AdipoR1, rather than AdipoR2, mediated the protective effects of APN/AdipoR signaling against oxidative stress and brain injury after TBI. In neuron-specific AdipoR1 knockout mice, mitochondrial damage was more severe after TBI, indicating a potential association between APN/AdipoR1 signaling inactivation and mitochondrial damage. Mechanistically, neuron-specific knockout of SIRT3, the most important deacetylase in the mitochondria, reversed the neuroprotective effects of AdipoRon after TBI. Then, PRDX3, a critical antioxidant enzyme in the mitochondria, was identified as a vital downstream target of the APN/SIRT3 axis to alleviate oxidative injury after TBI. Finally, we revealed that APN/AdipoR1 signaling promotes SIRT3 transcription by activating the AMPK-PGC pathway. In conclusion, APN/AdipoR1 signaling plays a protective role in post-TBI oxidative damage by restoring the SIRT3-mediated mitochondrial homeostasis and antioxidant system.

Adiponectin regulates the circadian rhythm of glucose and lipid metabolism.

Adiponectin is a cytokine secreted from adipocytes and regulates metabolism. Although serum adiponectin levels show diurnal variations, it is not clear if the effects of adiponectin are time-dependent. Therefore, this study conducted locomotor activity analyses and various metabolic studies using the adiponectin knockout (APN (−/−)) and the APN (+/+) mice to understand whether adiponectin regulates the circadian rhythm of glucose and lipid metabolism. We observed that the adiponectin gene deficiency does not affect the rhythmicity of core circadian clock genes expression in several peripheral tissues. In contrast, the adiponectin gene deficiency alters the circadian rhythms of liver and serum lipid levels and results in the loss of the time dependency of very-low-density lipoprotein-triglyceride secretion from the liver. In addition, the whole-body glucose tolerance of the APN (−/−) mice was normal at CT10 but reduced at CT22, compared to the APN (+/+) mice. The decreased glucose tolerance at CT22 was associated with insulin hyposecretion in vivo. In contrast, the gluconeogenesis activity was higher in the APN (−/−) mice than in the APN (+/+) mice throughout the day. These results indicate that adiponectin regulates part of the circadian rhythm of metabolism in the liver.

Sevoflurane preconditioning protects against acute MI/R injury via enhancing AdipoR1-Cav3 interaction and alleviating endoplasmic reticulum stress

Whether and how sevoflurane preconditioning (SevoPre) exerts protection against acute myocardial ischemia/reperfusion (MI/R) injury remains elusive. We observed significant myocardial injury, as evidenced by infarct size, cardiomyocyte apoptosis, and circulating troponin-I, at 3 h of MI/R in both wildtype and adiponectin knockout mice. The injury was significantly ameliorated by SevoPre in wildtype mice, but not in adiponectin knockout mice. In wildtype mice, we found that MI/R could increase endoplasmic reticulum stress of cardiomyocytes, and impair association of adiponectin receptor 1 and ceveolin-3, both of which processes were largely restored by SevoPre. In summary, we demonstrated that significant injury had already took place at 3 h of MI/R, which could be ameliorated by SevoPre via promoting affinity of adiponectin receptor 1 and ceveolin-3, and then attenuating endoplasmic reticulum stress of cardiomyocytes.

Microvascular Function in Skeletal Muscle of Adiponectin Knockout Mice

Adiponectin is known to be an important regulator of both metabolic and vascular function in skeletal muscle; however, a direct role for adiponectin in exercise training‐induced microvascular adaptation of skeletal muscle has not been documented. We assessed oxidative metabolism, capillarity, and endothelium‐dependent vasodilation in soleus and gastrocnemius muscles of sedentary and exercise trained, wild type (WT) and adiponectin knockout (AdipoKO) mice. WT and AdipoKO mice were obtained at 10‐12 wks of age and underwent treadmill exercise training (1 hr/day, 5 days/wk for 8 wks) or remained sedentary in cages. In sedentary mice, citrate synthase activity and capillarity were increased in soleus muscle of AdiopKO mice as compared to WT mice. In soleus muscle feed arteries from sedentary mice, endothelium‐dependent vasodilation to acetylcholine was reduced in AdipoKO mice as compared to WT mice. Exercise training increased capillarity and citrate synthase activity in soleus muscle of WT mice, but not AdipoKO mice. Exercise training did not alter endothelium‐dependent dilation in soleus feed arteries from either AdipoKO or WT mice. In 1A arterioles from the gastrocnemius muscle of sedentary mice, endothelium‐dependent vasodilation to acetylcholine was not altered in AdipoKO compared to WT mice; however, exercise training increased endothelium‐dependent vasodilation to acetylcholine in WT, but not AdipoKO mice. These data suggest that deletion of adiponectin and a reduction of endothelial vasodilatory function stimulates a compensatory increase in oxidative capacity and capillarity in soleus muscle; however, no further increase in these parameters occurs in soleus muscle of AdipoKO mice in response to exercise training. In contrast, in gastrocnemius muscle, endothelial vasodilatory function was not affected by deletion of adiponectin in sedentary mice, but endothelium‐dependent vasodilation of 1A arterioles increased in response to exercise training in WT, but not in AdipoKO mice. Taken together, these data suggest that the role of adiponectin in adaptation of metabolic and microvascular function in response to exercise training is muscle‐specific.

Obesity in Angiogenesis and Lung Regeneration

Obesity is associated with impairment of wound healing and tissue regeneration. Angiogenesis, the formation of new blood capillaries, plays a key role in organ regeneration and repair. We and other groups have reported that inhibition of angiogenesis attenuates lung growth after unilateral pneumonectomy (PNX) and that obesity is accompanied by endothelial cell dysfunction. The aim of this project is to investigate the effects of obesity on post‐PNX lung vascular and alveolar morphogenesis. We have found that post‐PNX regenerative lung growth is inhibited in Lepob/ob obese mice compared to Lepob/+ mice. The levels of the major angiogenic factor, vascular endothelial growth factor (VEGF) are higher in the serum and the lung tissue collected from post‐PNX mice compared to those from sham‐operated control mice, while these effects are attenuated in post‐PNX Lepob/ob mice. The levels of adiponectin, one of the adipokines that exhibits pro‐angiogenic and vascular protective properties, increase in the remaining mouse lungs after unilateral PNX, while these effects are attenuated in Lepob/ob obese mice. Regenerative lung growth, vascular and alveolar morphogenesis, and VEGF levels in the post‐PNX mouse lungs are inhibited in adiponectin knockout mice. These results suggest that obesity inhibits post‐PNX regenerative lung growth through adiponectin‐VEGF signaling. Modulation of adiponectin‐VEGF signaling may be the efficient strategy to restore lung regeneration and repair in obese people.