Isoform-Specific Role of GSK-3 in High Fat Diet Induced Obesity and Glucose Intolerance.

Obesity-associated metabolic disorders are rising to pandemic proportions; hence, there is an urgent need to identify underlying molecular mechanisms. Glycogen synthase kinase-3 (GSK-3) signaling is highly implicated in metabolic diseases. Furthermore, GSK-3 expression and activity are increased in Type 2 diabetes patients. However, the isoform-specific role of GSK-3 in obesity and glucose intolerance is unclear. Pharmacological GSK-3 inhibitors are not isoform-specific, and tissue-specific genetic models are of limited value to predict the clinical outcome of systemic inhibiion. To overcome these limitations, we created novel mouse models of ROSA26CreERT2-driven, tamoxifen-inducible conditional deletion of GSK-3 that allowed us to delete the gene globally in an isoform-specific and temporal manner. Isoform-specific GSK-3 KOs and littermate controls were subjected to a 16-week high-fat diet (HFD) protocol. On an HFD, GSK-3α KO mice had a significantly lower body weight and modest improvement in glucose tolerance compared to their littermate controls. In contrast, GSK-3ß-deletion-mediated improved glucose tolerance was evident much earlier in the timeline and extended up to 12 weeks post-HFD. However, this protective effect weakened after chronic HFD (16 weeks) when GSK-3ß KO mice had a significantly higher body weight compared to controls. Importantly, GSK-3ß KO mice on a control diet maintained significant improvement in glucose tolerance even after 16 weeks. In summary, our novel mouse models allowed us to delineate the isoform-specific role of GSK-3 in obesity and glucose tolerance. From a translational perspective, our findings underscore the importance of maintaining a healthy weight in patients receiving lithium therapy, which is thought to work by GSK-3 inhibition mechanisms.

Deletion of Cardiomyocyte Glycogen Synthase Kinase-3 Beta (GSK-3ß) Improves Systemic Glucose Tolerance with Maintained Heart Function in Established Obesity.

Obesity is an independent risk factor for cardiovascular diseases (CVD), including heart failure. Thus, there is an urgent need to understand the molecular mechanism of obesity-associated cardiac dysfunction. We recently reported the critical role of cardiomyocyte (CM) Glycogen Synthase Kinase-3 beta (GSK-3ß) in cardiac dysfunction associated with a developing obesity model (deletion of CM-GSK-3ß prior to obesity). In the present study, we investigated the role of CM-GSK-3ß in a clinically more relevant model of established obesity (deletion of CM-GSK-3ß after established obesity). CM-GSK-3ß knockout (GSK-3ßfl/flCre+/-) and controls (GSK-3ßfl/flCre-/-) mice were subjected to a high-fat diet (HFD) in order to establish obesity. After 12 weeks of HFD treatment, all mice received tamoxifen injections for five consecutive days to delete GSK-3ß specifically in CMs and continued on the HFD for a total period of 55 weeks. To our complete surprise, CM-GSK-3ß knockout (KO) animals exhibited a globally improved glucose tolerance and maintained normal cardiac function. Mechanistically, in stark contrast to the developing obesity model, deleting CM-GSK-3ß in obese animals did not adversely affect the GSK-3αS21 phosphorylation (activity) and maintained canonical ß-catenin degradation pathway and cardiac function. As several GSK-3 inhibitors are in the trial to treat various chronic conditions, including metabolic diseases, these findings have important clinical implications. Specifically, our results provide critical pre-clinical data regarding the safety of GSK-3 inhibition in obese patients.

Cardiomyocyte SMAD4-Dependent TGF-ß Signaling is Essential to Maintain Adult Heart Homeostasis.

The role of the transforming growth factor (TGF)-ß pathway in myocardial fibrosis is well recognized. However, the precise role of this signaling axis in cardiomyocyte (CM) biology is not defined. In TGF-ß signaling, SMAD4 acts as the central intracellular mediator. To investigate the role of TGF-ß signaling in CM biology, the authors deleted SMAD4 in adult mouse CMs. We demonstrate that CM-SMAD4-dependent TGF-ß signaling is critical for maintaining cardiac function, sarcomere kinetics, ion-channel gene expression, and cardiomyocyte survival. Thus, our findings raise a significant concern regarding the therapeutic approaches that rely on systemic inhibition of the TGF-ß pathway for the management of myocardial fibrosis.

Ponatinib-induced cardiotoxicity: delineating the signalling mechanisms and potential rescue strategies.

AIMS: Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myelogenous leukaemia (CML). However, cardiotoxicity of these agents remains a serious concern. The underlying mechanism of these adverse cardiac effects is largely unknown. Delineation of the underlying mechanisms of TKIs associated cardiac dysfunction could guide potential prevention strategies, rescue approaches, and future drug design. This study aimed to determine the cardiotoxic potential of approved CML TKIs, define the associated signalling mechanism and identify potential alternatives. METHODS AND RESULTS: In this study, we employed a zebrafish transgenic BNP reporter line that expresses luciferase under control of the nppb promoter (nppb:F-Luciferase) to assess the cardiotoxicity of all approved CML TKIs. Our in vivo screen identified ponatinib as the most cardiotoxic agent among the approved CML TKIs. Then using a combination of zebrafish and isolated neonatal rat cardiomyocytes, we delineated the signalling mechanism of ponatinib-induced cardiotoxicity by demonstrating that ponatinib inhibits cardiac prosurvival signalling pathways AKT and extra-cellular-signal-regulated kinase (ERK), and induces cardiomyocyte apoptosis. As a proof of concept, we augmented AKT and ERK signalling by administration of Neuregulin-1ß (NRG-1ß), and this prevented ponatinib-induced cardiomyocyte apoptosis. We also demonstrate that ponatinib-induced cardiotoxicity is not mediated by inhibition of fibroblast growth factor signalling, a well-known target of ponatinib. Finally, our comparative profiling for the cardiotoxic potential of CML approved TKIs, identified asciminib (ABL001) as a potentially much less cardiotoxic treatment option for CML patients with the T315I mutation. CONCLUSION: Herein, we used a combination of in vivo and in vitro methods to systematically screen CML TKIs for cardiotoxicity, identify novel molecular mechanisms for TKI cardiotoxicity, and identify less cardiotoxic alternatives.

Inhibition of GSK-3 to induce cardiomyocyte proliferation: a recipe for in situ cardiac regeneration.

With an estimated 38 million current patients, heart failure (HF) is a leading cause of morbidity and mortality worldwide. Although the aetiology differs, HF is largely a disease of cardiomyocyte (CM) death or dysfunction. Due to the famously limited amount of regenerative capacity of the myocardium, the only viable option for advanced HF patients is cardiac transplantation; however, donor's hearts are in very short supply. Thus, novel regenerative strategies are urgently needed to reconstitute the injured hearts. Emerging data from our lab and others have elucidated that CM-specific deletion of glycogen synthase kinase (GSK)-3 family of kinases induces CM proliferation, and the degree of proliferation is amplified in the setting of cardiac stress. If this proliferation is sufficiently robust, one could induce meaningful regeneration without the need for delivering exogenous cells to the injured myocardium (i.e. cardiac regeneration in situ). Herein, we will discuss the emerging role of the GSK-3s in CM proliferation and differentiation, including their potential implications in cardiac regeneration. The underlying molecular interactions and cross-talk among signalling pathways will be discussed. We will also review the specificity and limitations of the available small molecule inhibitors targeting GSK-3 and their potential applications to stimulate the endogenous cardiac regenerative responses to repair the injured heart.

Cardiomyocyte-specific deletion of GSK-3ß leads to cardiac dysfunction in a diet induced obesity model.

BACKGROUND AND RATIONALE: Obesity, an independent risk factor for the development of myocardial diseases is a growing healthcare problem worldwide. It's well established that GSK-3ß is critical to cardiac pathophysiology. However, the role cardiomyocyte (CM) GSK-3ß in diet-induced cardiac dysfunction is unknown. METHODS: CM-specific GSK-3ß knockout (CM-GSK-3ß-KO) and littermate controls (WT) mice were fed either a control diet (CD) or high-fat diet (HFD) for 55weeks. Cardiac function was assessed by transthoracic echocardiography. RESULTS: At baseline, body weights and cardiac function were comparable between the WT and CM-GSK-3ß-KOs. However, HFD-fed CM-GSK-3ß-KO mice developed severe cardiac dysfunction. Consistently, both heart weight/tibia length and lung weight/tibia length were significantly elevated in the HFD-fed CM-GSK-3ß-KO mice. The impaired cardiac function and adverse ventricular remodeling in the CM-GSK-3ß-KOs were independent of body weight or the lean/fat mass composition as HFD-fed CM-GSK-3ß-KO and controls demonstrated comparable body weight and body masses. At the molecular level, on a CD, CM-GSK-3α compensated for the loss of CM-GSK-3ß, as evident by significantly reduced GSK-3αs21 phosphorylation (activation) resulting in a preserved canonical ß-catenin ubiquitination pathway and cardiac function. However, this protective compensatory mechanism is lost with HFD, leading to excessive accumulation of ß-catenin in HFD-fed CM-GSK-3ß-KO hearts, resulting in adverse ventricular remodeling and cardiac dysfunction. CONCLUSION: In summary, these results suggest that cardiac GSK-3ß is crucial to protect against obesity-induced adverse ventricular remodeling and cardiac dysfunction.

Chronic Neuregulin-1ß Treatment Mitigates the Progression of Postmyocardial Infarction Heart Failure in the Setting of Type 1 Diabetes Mellitus by Suppressing Myocardial Apoptosis, Fibrosis, and Key Oxidant-Producing Enzymes.

BACKGROUND: Type 1 diabetes mellitus (DM) patients surviving myocardial infarction (MI) have substantially higher cardiovascular morbidity and mortality compared to their nondiabetic counterparts owing to the more frequent development of subsequent heart failure (HF). Neuregulin (NRG)-1ß is released from cardiac microvascular endothelial cells and acts as a paracrine factor via the ErbB family of tyrosine kinase receptors expressed in cardiac myocytes to regulate cardiac development and stress responses. Because myocardial NRG-1/ErbB signaling has been documented to be impaired during HF associated with type 1 DM, we examined whether enhancement of NRG-1ß signaling via exogenous administration of recombinant NRG-1ß could exert beneficial effects against post-MI HF in the type 1 diabetic heart. METHODS AND RESULTS: Type 1 DM was induced in male Sprague Dawley rats by a single injection of streptozotocin (STZ) (65 mg/kg). Two weeks after induction of type 1 DM, rats underwent left coronary artery ligation to induce MI. STZ-diabetic rats were treated with saline or NRG-1ß (100 µg/kg) twice per week for 7 weeks, starting 2 weeks before experimental MI. Residual left ventricular function was significantly greater in the NRG-1ß-treated STZ-diabetic MI group compared with the vehicle-treated STZ-diabetic MI group 5 weeks after MI as assessed by high-resolution echocardiography. NRG-1ß treatment of STZ-diabetic MI rats was associated with reduced myocardial fibrosis and apoptosis as well as decreased gene expression of key oxidant-producing enzymes. CONCLUSIONS: These results suggest that recombinant NRG-1ß may be a promising therapeutic for HF post-MI in the setting of type 1 DM.

Entanglement of GSK-3ß, ß-catenin and TGF-ß1 signaling network to regulate myocardial fibrosis.

Nearly every form of the heart disease is associated with myocardial fibrosis, which is characterized by the accumulation of activated cardiac fibroblasts (CFs) and excess deposition of extracellular matrix (ECM). Although, CFs are the primary mediators of myocardial fibrosis in a diseased heart, in the traditional view, activated CFs (myofibroblasts) and resulting fibrosis were simply considered the secondary consequence of the disease, not the cause. Recent studies from our lab and others have challenged this concept by demonstrating that fibroblast activation and fibrosis are not simply the secondary consequence of a diseased heart, but are crucial for mediating various myocardial disease processes. In regards to the mechanism, the vast majority of literature is focused on the direct role of canonical SMAD-2/3-mediated TGF-ß signaling to govern the fibrogenic process. Herein, we will discuss the emerging role of the GSK-3ß, ß-catenin and TGF-ß1-SMAD-3 signaling network as a critical regulator of myocardial fibrosis in the diseased heart. The underlying molecular interactions and cross-talk among signaling pathways will be discussed. We will primarily focus on recent in vivo reports demonstrating that CF-specific genetic manipulation can lead to aberrant myocardial fibrosis and sturdy cardiac phenotype. This will allow for a better understanding of the driving role of CFs in the myocardial disease process. We will also review the specificity and limitations of the currently available genetic tools used to study myocardial fibrosis and its associated mechanisms. A better understanding of the GSK-3ß, ß-catenin and SMAD-3 signaling network may provide a novel therapeutic target for the management of myocardial fibrosis in the diseased heart.

Defining a Novel Role for the Pdx1 Transcription Factor in Islet ß-Cell Maturation and Proliferation During Weaning.

The transcription factor encoded by the Pdx1 gene is a critical transcriptional regulator, as it has fundamental actions in the formation of all pancreatic cell types, islet ß-cell development, and adult islet ß-cell function. Transgenic- and cell line-based experiments have identified 5'-flanking conserved sequences that control pancreatic and ß-cell type-specific transcription, which are found within areas I (bp -2694 to -2561), II (bp -2139 to -1958), III (bp -1879 to -1799), and IV (bp -6200 to -5670). Because of the presence in area IV of binding sites for transcription factors associated with pancreas development and islet cell function, we analyzed how an endogenous deletion mutant affected Pdx1 expression embryonically and postnatally. The most striking result was observed in male Pdx1ΔIV mutant mice after 3 weeks of birth (i.e., the onset of weaning), with only a small effect on pancreas organogenesis and no deficiencies in their female counterparts. Compromised Pdx1 mRNA and protein levels in weaned male mutant ß-cells were tightly linked with hyperglycemia, decreased ß-cell proliferation, reduced ß-cell area, and altered expression of Pdx1-bound genes that are important in ß-cell replication, endoplasmic reticulum function, and mitochondrial activity. We discuss the impact of these novel findings to Pdx1 gene regulation and islet ß-cell maturation postnatally.

GRMD cardiac and skeletal muscle metabolism gene profiles are distinct.

BACKGROUND: Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene, which codes for the dystrophin protein. While progress has been made in defining the molecular basis and pathogenesis of DMD, major gaps remain in understanding mechanisms that contribute to the marked delay in cardiac compared to skeletal muscle dysfunction. METHODS: To address this question, we analyzed cardiac and skeletal muscle tissue microarrays from golden retriever muscular dystrophy (GRMD) dogs, a genetically and clinically homologous model for DMD. A total of 15 dogs, 3 each GRMD and controls at 6 and 12 months plus 3 older (47-93 months) GRMD dogs, were assessed. RESULTS: GRMD dogs exhibited tissue- and age-specific transcriptional profiles and enriched functions in skeletal but not cardiac muscle, consistent with a "metabolic crisis" seen with DMD microarray studies. Most notably, dozens of energy production-associated molecules, including all of the TCA cycle enzymes and multiple electron transport components, were down regulated. Glycolytic and glycolysis shunt pathway-associated enzymes, such as those of the anabolic pentose phosphate pathway, were also altered, in keeping with gene expression in other forms of muscle atrophy. On the other hand, GRMD cardiac muscle genes were enriched in nucleotide metabolism and pathways that are critical for neuromuscular junction maintenance, synaptic function and conduction. CONCLUSIONS: These findings suggest differential metabolic dysfunction may contribute to distinct pathological phenotypes in skeletal and cardiac muscle.

Neuregulin-1ß induces proliferation, survival and paracrine signaling in normal human cardiac ventricular fibroblasts.

Neuregulin-1ß (NRG-1ß) is critical for cardiac development and repair, and recombinant forms are currently being assessed as possible therapeutics for systolic heart failure. We previously demonstrated that recombinant NRG-1ß reduces cardiac fibrosis in an animal model of cardiac remodeling and heart failure, suggesting that there may be direct effects on cardiac fibroblasts. Here we show that NRG-1ß receptors (ErbB2, ErbB3, and ErbB4) are expressed in normal human cardiac ventricular (NHCV) fibroblast cell lines. Treatment of NHCV fibroblasts with recombinant NRG-1ß induced activation of the AKT pathway, which was phosphoinositide 3-kinase (PI3K)-dependent. Moreover, the NRG-1ß-induced PI3K/AKT signaling in these cells required phosphorylation of both ErbB2 and ErbB3 receptors at tyrosine (Tyr)1248 and Tyr1289 respectively. RNASeq analysis of NRG-1ß-treated cardiac fibroblasts obtained from three different individuals revealed a global gene expression signature consistent with cell growth and survival. We confirmed enhanced cellular proliferation and viability in NHCV fibroblasts in response to NRG-1ß, which was abrogated by PI3K, ErbB2, and ErbB3 inhibitors. NRG-1ß also induced production and secretion of cytokines (interleukin-1α and interferon-γ) and pro-reparative factors (angiopoietin-2, brain-derived neurotrophic factor, and crypto-1), suggesting a role in cardiac repair through the activation of paracrine signaling.

Translating golden retriever muscular dystrophy microarray findings to novel biomarkers for cardiac/skeletal muscle function in Duchenne muscular dystrophy.

BACKGROUND: In Duchenne muscular dystrophy (DMD), abnormal cardiac function is typically preceded by a decade of skeletal muscle disease. Molecular reasons for differences in onset and progression of these muscle groups are unknown. Human biomarkers are lacking. METHODS: We analyzed cardiac and skeletal muscle microarrays from normal and golden retriever muscular dystrophy (GRMD) dogs (ages 6, 12, or 47+ mo) to gain insight into muscle dysfunction and to identify putative DMD biomarkers. These biomarkers were then measured using human DMD blood samples. RESULTS: We identified GRMD candidate genes that might contribute to the disparity between cardiac and skeletal muscle disease, focusing on brain-derived neurotropic factor (BDNF) and osteopontin (OPN/SPP1, hereafter indicated as SPP1). BDNF was elevated in cardiac muscle of younger GRMD but was unaltered in skeletal muscle, while SPP1 was increased only in GRMD skeletal muscle. In human DMD, circulating levels of BDNF were inversely correlated with ventricular function and fibrosis, while SPP1 levels correlated with skeletal muscle function. CONCLUSION: These results highlight gene expression patterns that could account for differences in cardiac and skeletal disease in GRMD. Most notably, animal model-derived data were translated to DMD and support use of BDNF and SPP1 as biomarkers for cardiac and skeletal muscle involvement, respectively.

Interest in genetic testing in Ashkenazi Jewish Parkinson's disease patients and their unaffected relatives.

Our objective was to explore interest in genetic testing among Ashkenazi Jewish (AJ) Parkinson's Disease (PD) cases and first-degree relatives, as genetic testing for LRRK2 G2019S is widely available. Approximately 18 % of AJ PD cases carry G2019S mutations; penetrance estimations vary between 24 and 100 % by age 80. A Genetic Attitude Questionnaire (GAQ) was administered at two New York sites to PD families unaware of LRRK2 G2019S mutation status. The association of G2019S, age, education, gender and family history of PD with desire for genetic testing (outcome) was modeled using logistic regression. One-hundred eleven PD cases and 77 relatives completed the GAQ. Both PD cases and relatives had excellent PD-specific genetic knowledge. Among PD, 32.6 % "definitely" and 41.1 % "probably" wanted testing, if offered "now." Among relatives, 23.6 % "definitely" and 36.1 % "probably" wanted testing "now." Desire for testing in relatives increased incrementally based on hypothetical risk of PD. The most important reasons for testing in probands and relatives were: if it influenced medication response, identifying no mutation, and early prevention and treatment. In logistic regression, older age was associated with less desire for testing in probands OR = 0.921 95%CI 0.868-0.977, p = 0.009. Both probands and relatives express interest in genetic testing, despite no link to current treatment or prevention.

Troponin elevation in subarachnoid hemorrhage does not impact in-hospital mortality.

BACKGROUND: Cardiac dysfunction is a well-known complication of subarachnoid hemorrhage (SAH). Our objective was to determine the frequency of troponin abnormalities in SAH and determine its impact on in-hospital mortality. METHODS: With IRB approval, we retrospectively reviewed 225 consecutive SAH patients admitted to our institution from August 1, 2006 to June 1, 2009. Traumatic SAH patients were excluded. Data were collected on demographics, Hunt and Hess score (HH), in-hospital mortality, and peak troponin values on admission. CT images were independently reviewed and graded by the study neurologist for Fisher grade (FG) and the presence of intraventricular hemorrhage (IVH). RESULTS: Among the 225 SAH patients, the mean age was 57.3 years (range, 21-90). The majority of patients were female (67%), FG 3 (75%), and had IVH (62%). Among the 201 patients with troponin I values, the mean troponin level was 0.93 (range, 0.01-25.8 ng/mL) and 47 (23%) had elevated troponin I levels. In unadjusted analysis, elevated troponin I level was significantly associated with in-hospital mortality. With multivariable logistic regression adjusting for age, HH, FG, and IVH, elevated troponin I level was no longer associated with in-hospital mortality (p. 0.34). In multivariate analysis, the independent predictors of in-mortality were age and severe grade HH (4-5). CONCLUSIONS: Troponin I elevation after SAH is not an independent predictor of in-hospital mortality.

Adipocyte deficiency of angiotensinogen prevents obesity-induced hypertension in male mice.

Previous studies demonstrated that diet-induced obesity increased plasma angiotensin II concentrations and elevated systolic blood pressures in male mice. Adipocytes express angiotensinogen and secrete angiotensin peptides. We hypothesize that adipocyte-derived angiotensin II mediates obesity-induced increases in systolic blood pressure in male high fat-fed C57BL/6 mice. Systolic blood pressure was measured by radiotelemetry during week 16 of low-fat or high-fat feeding in Agt(fl/fl) and adipocyte angiotensinogen-deficient mice (Agt(aP2)). Adipocyte angiotensinogen deficiency had no effect on diet-induced obesity. Basal 24-hour systolic blood pressure was not different in low fat-fed Agt(fl/fl) compared with Agt(aP2) mice (124 ± 3 versus 128 ± 3 mm Hg, respectively). In Agt(fl/fl) mice, high-fat feeding significantly increased systolic blood pressure (24 hours; 134 ± 2 mm Hg; P<0.05). In contrast, high fat-fed Agt(aP2) mice did not exhibit an increase in systolic blood pressure (126 ± 2 mm Hg). Plasma angiotensin II concentrations were increased by high-fat feeding in Agt(fl/fl) mice (low fat, 32 ± 14; high fat, 219 ± 58 pg/mL; P<0.05). In contrast, high fat-fed Agt(aP2) mice did not exhibit elevated plasma angiotensin II concentrations (high fat, 18 ± 7 pg/mL). Similarly, adipose tissue concentrations of angiotensin II were significantly decreased in low fat- and high fat-fed Agt(aP2) mice compared with controls. In conclusion, adipocyte angiotensinogen deficiency prevented high fat-induced elevations in plasma angiotensin II concentrations and systolic blood pressure. These results suggest that adipose tissue serves as a major source of angiotensin II in the development of obesity hypertension.

Deficiency of ACE2 in Bone-Marrow-Derived Cells Increases Expression of TNF-α in Adipose Stromal Cells and Augments Glucose Intolerance in Obese C57BL/6 Mice.

Deficiency of ACE2 in macrophages has been suggested to promote the development of an inflammatory M1 macrophage phenotype. We evaluated effects of ACE2 deficiency in bone-marrow-derived stem cells on adipose inflammation and glucose tolerance in C57BL/6 mice fed a high fat (HF) diet. ACE2 activity was increased in the stromal vascular fraction (SVF) isolated from visceral, but not subcutaneous adipose tissue of HF-fed mice. Deficiency of ACE2 in bone marrow cells significantly increased mRNA abundance of F4/80 and TNF-α in the SVF isolated from visceral adipose tissue of HF-fed chimeric mice, supporting increased presence of inflammatory macrophages in adipose tissue. Moreover, deficiency of ACE2 in bone marrow cells modestly augmented glucose intolerance in HF-fed chimeric mice and increased blood levels of glycosylated hemoglobin. In summary, ACE2 deficiency in bone marrow cells promotes inflammation in adipose tissue and augments obesity-induced glucose intolerance.

Angiotensin converting enzyme 2 contributes to sex differences in the development of obesity hypertension in C57BL/6 mice.

OBJECTIVE: Obesity promotes hypertension, but it is unclear if sex differences exist in obesity-related hypertension. Angiotensin converting enzyme 2 (ACE2) converts angiotensin II (AngII) to angiotensin-(1-7) (Ang-[1-7]), controlling peptide balance. We hypothesized that tissue-specific regulation of ACE2 by high-fat (HF) feeding and sex hormones contributes to sex differences in obesity-hypertension. METHODS AND RESULTS: HF-fed females gained more body weight and fat mass than males. HF-fed males exhibiting reduced kidney ACE2 activity had increased plasma angiotensin II levels and decreased plasma Ang-(1-7) levels. In contrast, HF-fed females exhibiting elevated adipose ACE2 activity had increased plasma Ang-(1-7) levels. HF-fed males had elevated systolic and diastolic blood pressure that were abolished by losartan. In contrast, HF-fed females did not exhibit increased systolic blood pressure until females were administered the Ang-(1-7) receptor antagonist, D-Ala-Ang-(1-7). Deficiency of ACE2 increased systolic blood pressure in HF-fed males and females, which was abolished by losartan. Ovariectomy of HF-fed female mice reduced adipose ACE2 activity and plasma Ang-(1-7) levels, and promoted obesity-hypertension. Finally, estrogen, but not other sex hormones, increased adipocyte ACE2 mRNA abundance. CONCLUSIONS: These results demonstrate that tissue-specific regulation of ACE2 by diet and sex hormones contributes to sex differences in obesity-hypertension.