Abstract 41: Cardiomyocyte-specific Conditional Deletion of GSK-3β Leads to Cardiac Dysfunction in a High Fat Diet Induced Obesity Model

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Manisha Gupte ◽  
Samvruta Tumuluru ◽  
Anand P Singh ◽  
Prachi Umbarkar ◽  
Qinkun Zhang ◽  
...  

Introduction: Previous studies from our group have demonstrated that cardiac myocyte glycogen synthase kinase-3’s (GSK-3) are required to maintain normal cardiac physiology. Adult mice lacking both isoforms of GSK-3 (α and β) in cardiac myocytes exhibit excessive dilatative remodeling and ventricular dysfunction ultimately leading to death. While high fat diet (HFD) induced obesity is associated with increased risk of cardiovascular disease, the specific role of cardiac GSK-3α or GSK-3β in obesity-associated cardiac dysfunction is unknown. Objective: The primary goal of the present study was to investigate the role of cardiomyocyte GSK-3β in cardiac homeostasis in HFD-induced chronic obesity model. Method: Cardiomyocyte specific-GSK-3β knock out (CM-GSK-3βKO) and wild type (WT) mice were fed either a chow (11.5% calories from fat) or high-fat (60% calories from fat) for 24 weeks. Cardiac function was accessed by non-invasive transthoracic echocardiography. Results: HFD significantly increased body weight, lean and fat mass in the WT and CM-GSK-3βKO compared to chow. However, there was no difference in body weights, lean and fat mass between the two genotypes fed either a chow or HFD. Furthermore, ventricular chamber dimensions and cardiac function were comparable between the WT and CM-GSK-3βKO mice fed a chow diet. In contrast, high fat fed CM-GSK-3βKO hearts exhibit significant cardiac hypertrophy (heart weight/tibia length ratio) and ventricular dysfunction (reduced ejection fraction (EF) and fractional shortening (FS)) compared to the WT. Interestingly cardiomyocytes from HF fed CM-GSK-3βKO exhibit structural abnormalities and increased expression of pro-apoptotic protein Bax and reduced expression of Bcl-2, an anti-apoptotic protein. Conclusion: In summary, these data suggests that cardiac GSK-3β is important in the setting of HFD-induced chronic obesity to maintain cardiac function. In the absence of GSK-3β, cardiomyocytes undergo morphometric abnormalities, excessive fat infiltration and apoptosis leading to cardiac dysfunction.

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Maria Pini

Introduction: Sedentary lifestyle and excessive calorie intake are risk factors for CVD. We have demonstrated the cardioprotective effect of exercise in aged mice and the critical role of visceral adiposity and its profibrotic secretome in increasing cardiovascular risks in obesity and aging. The association between exercise, lowered plasma leptin and reduced inflammatory leukocytes has been recently shown in patients with atherosclerosis. It remains unclear whether elevated plasma leptin can preserve or alter cardiovascular function in obesity. Methods: We analyzed the effect of high fat diet (HFD) in C57BL/6J male mice on the heart in terms of function, structure, histology and key molecular markers. Two interventions were used: 1) active fat mass loss via exercise (daily swimming) during HFD; 2) passive fat mass loss via surgical removal of the visceral adipose tissue (VAT lipectomy) followed by HFD. Results: HFD increased body weight and adiposity, leading to higher plasma leptin, glucose and insulin levels, compared to control diet (CD) mice. HFD impaired left ventricle (LV) structure (hypertrophy, interstitial fibrosis) and cardiac function (echocardiography, in vivo hemodynamics). Atria of HFD mice had enhanced pro-inflammatory protein production. Exercise reduced circulating leptin levels in HFD mice by 50%, in line with fat mass loss. In contrast, lipectomy reduced visceral fat mass, but body weight, adiposity and plasma leptin did not change. Both exercise and VAT lipectomy improved cardiac contractility, reversed collagen deposition and oxidative stress in HFD mice. Both interventions downregulated LV pro-inflammatory markers. We proved the role of leptin in cardiac remodeling in vitro by incubating primary cardiac fibroblasts with hyperleptinemic plasma from HFD mice. Remarkably, plasma from HFD-EX (exercise) suppressed the fibro-proliferative and pro-inflammatory responses of cardiac fibroblasts. Conclusions: Leptin directly contribute to cardiac fibrosis in obesity via activation and proliferation of cardiac fibroblasts. Understanding how leptin signals to the heart might have implications in a wide range of CVD, potentially helping early stratification and personalized care.


2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Dan Shao ◽  
Nathan Roe ◽  
Loreta D Tomasi ◽  
Alyssa N Braun ◽  
Ana Mattos ◽  
...  

In the obese and diabetic heart, an imbalance between fatty acid uptake and fatty acid oxidation (FAO) promotes the development of cardiac lipotoxicity. We previously showed that cardiac specific deletion of acetyl CoA carboxylase 2 (ACC2) was effective in increasing myocardial FAO while maintaining normal cardiac function and energetics. In this study, we tested the hypothesis that ACC2 deletion in an adult heart would prevent the cardiac lipotoxic phenotype in a mouse model of diet-induced obesity. ACC2 flox/flox (CON) and ACC2 flox/flox-MerCreMer+ (iKO) after tamoxifen injection were subjected to a high fat diet (HFD) for 24 weeks. HFD induced similar body weight gain and glucose intolerance in CON and iKO. In isolated Langendorff-perfused heart experiments, HFD feeding increased FAO 1.6-fold in CON mice which was increased to 2.5-fold in iKO mice compared with CON on chow diet. Fractional shortening was significantly decreased in CON-HFD (32.8±2.8% vs. 39.2±3.2%, p< 0.05, n=5-6), but preserved in iKO-HFD mice (42.8±2.3%, vs. 38.5±1.4%, n=6), compared to respective chow fed controls. Diastolic function, assessed by E’/A’ ratio using tissue Doppler imaging, was significantly decreased in CON-HFD mice (1.11±0.08 vs. 0.91±0.09, p<0.05 n=5-6), while no difference was observed in iKO-HFD compared to iKO-chow (1.10±0.03 vs. 1.09±0.04, n=6). Heart weight /Tibia length ratio was significantly higher in CON than iKO mice after HFD feeding (7.19±0.22 vs. 6.47±0.28, p<0.05, n=6). Furthermore, HFD induced mitochondria super complex II, III and V instability, which was attenuated in iKO-HFD mice. These data indicate that elevated myocardial FAO per se does not cause the development of cardiac dysfunction in obese animals. In fact, enhancing FAO via ACC2 deletion prevents HFD induced cardiac dysfunction and attenuates pathological hypertrophy. These effects may be mediated, in part, by maintenance of mitochondrial integrity. Taken together, our findings suggest that promoting cardiac FAO is an effective strategy to resist the development of cardiac lipotoxicity during diet-induced obesity.


Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1120 ◽  
Author(s):  
Manisha Gupte ◽  
Prachi Umbarkar ◽  
Anand Prakash Singh ◽  
Qinkun Zhang ◽  
Sultan Tousif ◽  
...  

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-3β) in cardiac dysfunction associated with a developing obesity model (deletion of CM-GSK-3β prior to obesity). In the present study, we investigated the role of CM-GSK-3β in a clinically more relevant model of established obesity (deletion of CM-GSK-3β after established obesity). CM-GSK-3β knockout (GSK-3βfl/flCre+/−) and controls (GSK-3βfl/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-3β specifically in CMs and continued on the HFD for a total period of 55 weeks. To our complete surprise, CM-GSK-3β 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-3β in obese animals did not adversely affect the GSK-3αS21 phosphorylation (activity) and maintained canonical β-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.


2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Yu T Zhao ◽  
Jianfeng Du ◽  
Thomas J Zhao ◽  
Hao Wang ◽  
Marshall Kadin ◽  
...  

Background: p38 regulated/activated protein kinase (PRAK) plays a crucial role in modulating cell death and survival. However, the role of PRAK in mediating cardiac dysfunction and metabolic disorders remains unclear. We examined the effects of deletion of PRAK on modulating cardiac function and insulin resistance in mice exposed to a high fat diet (HFD). Methods: Wild type and PRAK -/- mice at 8 weeks old were exposed to either chow food or HFD for a consecutive 16 weeks. Glucose tolerance test and insulin tolerance test were employed to assess insulin resistance. Echocardiography was employed to assess myocardial function. Western blot was used to determine the molecular signaling involved in phosphorylation of IRS-1, AMPKα, ERK-44/42, and irisin. Real time-PCR was used to assess the hypertrophic genes of the myocardium. Histological analysis was employed to assess the hypertrophic response, interstitial myocardial fibrosis, and apoptosis in the heart. Results: HFD induced metabolic stress is indicated by glucose intolerance and insulin intolerance. PRAK knockout aggravated insulin resistance, as indicated by glucose intolerance and insulin intolerance testing as compared to wild type littermates. As compared to wild type, hyperglycemia and hypercholesterolemia were manifested in PRAK-knockout mice following high fat diet intervention. High fat diet intervention displayed a decline in fractional shortening (FS) and ejection fraction (EF). However, deletion of PRAK exacerbated the decline in EF and FS as compared to wild type mice following HFD treatment. In addition, PRAK knockout mice enhanced the expression of myocardial hypertrophic genes including ANP, BNP, and βMHC in HFD treatment, which was also associated with an increase in cardiomyocyte size and interstitial fibrosis. Western blot indicated that deletion of PRAK induces decreases in phosphorylation of IRS-1, AMPKα, and ERK44/42 as compared to wild type controls. Conclusion: Our finding indicates that deletion of PRAK promoted myocardial dysfunction, cardiac remodeling, and metabolic disorders in response to HFD.


2021 ◽  
Vol 22 (15) ◽  
pp. 7995
Author(s):  
Jianfeng Du ◽  
Yu Tina Zhao ◽  
Hao Wang ◽  
Ling X. Zhang ◽  
Gangjian Qin ◽  
...  

Regulated/activated protein kinase (PRAK) plays a crucial role in modulating biological function. However, the role of PRAK in mediating cardiac dysfunction and metabolic disorders remains unclear. We examined the effects of deletion of PRAK on modulating cardiac function and insulin resistance in mice exposed to a high-fat diet (HFD). Wild-type and PRAK−/− mice at 8 weeks old were exposed to either chow food or HFD for a consecutive 16 weeks. Glucose tolerance tests and insulin tolerance tests were employed to assess insulin resistance. Echocardiography was employed to assess myocardial function. Western blot was used to determine the molecular signaling involved in phosphorylation of IRS-1, AMPKα, ERK-44/42, and irisin. Real time-PCR was used to assess the hypertrophic genes of the myocardium. Histological analysis was employed to assess the hypertrophic response, interstitial myocardial fibrosis, and apoptosis in the heart. Western blot was employed to determine cellular signaling pathway. HFD-induced metabolic stress is indicated by glucose intolerance and insulin intolerance. PRAK knockout aggravated insulin resistance, as indicated by glucose intolerance and insulin intolerance testing as compared with wild-type littermates. As compared with wild-type mice, hyperglycemia and hypercholesterolemia were manifested in PRAK-knockout mice following high-fat diet intervention. High-fat diet intervention displayed a decline in fractional shortening and ejection fraction. However, deletion of PRAK exacerbated the decline in cardiac function as compared with wild-type mice following HFD treatment. In addition, PRAK knockout mice enhanced the expression of myocardial hypertrophic genes including ANP, BNP, and βMHC in HFD treatment, which was also associated with an increase in cardiomyocyte size and interstitial fibrosis. Western blot indicated that deletion of PRAK induces decreases in phosphorylation of IRS-1, AMPKα, and ERK44/42 as compared with wild-type controls. Our finding indicates that deletion of PRAK promoted myocardial dysfunction, cardiac remodeling, and metabolic disorders in response to HFD.


Author(s):  
Satya Murthy Tadinada ◽  
Eric T. Weatherford ◽  
Greg V. Collins ◽  
Gourav Bhardwaj ◽  
Jesse Cochran ◽  
...  

Molecular mechanisms underlying cardiac dysfunction and subsequent heart failure in diabetic cardiomyopathy are incompletely understood. Initially we intended to test the role of GRK2, a potential mediator of cardiac dysfunction in diabetic cardiomyopathy, but found that control animals on HFD did not develop cardiomyopathy. Cardiac function was preserved in both wildtype and GRK2 knockout animals fed high fat diet as indicated by preserved left ventricular ejection fraction (LVEF) although heart mass was increased. The absence of cardiac dysfunction led us to rigorously evaluate the utility of diet-induced obesity to model diabetic cardiomyopathy in mice. Using pure C57BL/6J animals and various diets formulated with different sources of fat- lard (32% saturated fat, 68% unsaturated fat) or hydrogenated coconut oil (95% saturated fat), we consistently observed left ventricular hypertrophy, preserved LVEF and preserved contractility measured by invasive hemodynamics in animals fed high fat diet. Gene expression patterns that characterize pathological hypertrophy were not induced but a modest induction of various collagen isoforms and matrix metalloproteinases were observed in heart with high fat diet feeding. PPARa-target genes that enhance lipid utilization such as Pdk4, CD36, AcadL and Cpt1b were induced, but mitochondrial energetics were not impaired. These results suggest while long-term fat feeding in mice induces cardiac hypertrophy and increases cardiac fatty acid metabolism, it may not be sufficient to activate pathological hypertrophic mechanisms that impair cardiac function or induce cardiac fibrosis. Thus, additional factors that are currently not understood may contribute to the cardiac abnormalities previously reported by many groups.


2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Dan Shao ◽  
Stephen C Kolwicz ◽  
Nathan Roe ◽  
Outi Villet ◽  
Loreta D Tomasi ◽  
...  

In the obese and diabetic heart, an imbalance between fatty acid uptake and fatty acid oxidation (FAO) promotes the development of cardiac lipotoxicity. We previously demonstrated that cardiac-specific deletion of ACC2 in adult mice was effective in increasing myocardial FAO while maintaining normal cardiac function and energetics. In this study, we tested the hypothesis that ACC2 deletion in an adult heart would prevent the cardiac lipotoxic phenotype in a mouse model of diet-induced obesity. ACC2 flox/flox (CON) and ACC2 flox/flox-MerCreMer+ (iKO) were injected with tamoxifen and subjected to a high fat diet (HFD) for 24 weeks. HFD induced similar body weight gain and glucose intolerance in CON and iKO. In isolated Langendorff-perfused heart experiments, HFD feeding increased FAO 1.6-fold in CON mice which was further increased to 1.9-fold in iKO mice compared with CON on chow diet. HFD induced systolic and diastolic dysfunction was abolished in iKO mice compared with CON mice (Fractional shortening 32.8±2.8% (CON) vs. 39.2±3.2% (iKO), E’/A’ ratio 0.91±0.09 (CON) vs. 1.11±0.08 (iKO), p< 0.05, n=5-6). Heart weight /Tibia length ratio was significantly higher in CON than iKO mice after HFD feeding (7.19±0.22 vs. 6.47±0.28, p<0.05, n=6). These data indicate that elevated myocardial FAO per se does not cause the development of cardiac dysfunction in obese animals. In fact, enhancing FAO via ACC2 deletion prevents HFD induced cardiac dysfunction and attenuates pathological hypertrophy. Molecular markers for ER stress such as p-PERK (1.5 fold) and p-JNK (2 fold) was elevated in CON-HFD hearts, which was completely attenuated in iKO-HFD hearts. Impairment of autophagy was also observed in CON-HFD hearts evidenced by decreases in LC3 II (60%) and increases in P62 (75%) level, while no difference in autophagy were observed in iKO-HFD hearts compared to iKO-chow. Therefore, the beneficial effect for enhancing cardiac fatty oxidation in HFD induced obesity model may be mediated, in part, by maintenance of cellular homeostasis and survival through regulating ER stress and autophagy. Taken together, our findings suggest that promoting cardiac FAO is an effective strategy to resist the development of cardiac lipotoxicity during diet-induced obesity.


2012 ◽  
Vol 302 (7) ◽  
pp. E807-E816 ◽  
Author(s):  
Zhiyou Zhang ◽  
Wenyi Zhang ◽  
Dae Young Jung ◽  
Hwi Jin Ko ◽  
Yongjin Lee ◽  
...  

TRPM2 Ca2+-permeable cation channel is widely expressed and activated by markers of cellular stress. Since inflammation and stress play a major role in insulin resistance, we examined the role of TRPM2 Ca2+ channel in glucose metabolism. A 2-h hyperinsulinemic euglycemic clamp was performed in TRPM2-deficient (KO) and wild-type mice to assess insulin sensitivity. To examine the effects of diet-induced obesity, mice were fed a high-fat diet for 4–10 mo, and metabolic cage and clamp studies were conducted in conscious mice. TRPM2-KO mice were more insulin sensitive partly because of increased glucose metabolism in peripheral organs. After 4 mo of high-fat feeding, TRPM2-KO mice were resistant to diet-induced obesity, and this was associated with increased energy expenditure and elevated expressions of PGC-1α, PGC-1β, PPARα, ERRα, TFAM, and MCAD in white adipose tissue. Hyperinsulinemic euglycemic clamps showed that TRPM2-KO mice were more insulin sensitive, with increased Akt and GSK-3β phosphorylation in heart. Obesity-mediated inflammation in adipose tissue and liver was attenuated in TRPM2-KO mice. Overall, TRPM2 deletion protected mice from developing diet-induced obesity and insulin resistance. Our findings identify a novel role of TRPM2 Ca2+ channel in the regulation of energy expenditure, inflammation, and insulin resistance.


2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Andre Leopoldo ◽  
Felipe de Sá ◽  
Wagner Estevam ◽  
Bruno Jacobsen ◽  
Artur Ferron ◽  
...  

Experimental studies have demonstrated that obesity induced by different types of high-fat and/or high-energy diets also lead to myocardial dysfunction. Nevertheless, few studies have evaluated the myocardial function in obesity-resistant rats. Moreover, the mechanisms underlying the participation of calcium (Ca 2+ ) handling on cardiac function in this model remain unknown. The aim of this study was to investigate in rodent model of obesity-resistant. In addition, as obesity-resistant group is fed a high-fat diet but did not become obese, this study tested whether obesity-resistant model develops cardiac abnormalities and impairment of calcium handling as obesity-prone. Male 30-day-old Wistar rats were fed standard (C) and alternately four palatable unsaturated high-fat diets (Ob) for 15 weeks. After experimental protocol, Ob rats consuming the unsaturated high-fat diets were ranked based on adiposity index. Rats on the unsaturated high-fat diets exhibiting the greatest adiposity index were referred to as OP, whereas those exhibiting the lowest adiposity index were referred to as OR. Obesity was determined by adiposity index and comorbidities were evaluated. Myocardial function was evaluated in isolated left ventricle papillary muscles under basal conditions and after inotropic and lusitropic maneuvers. After 15 weeks, final body weight, total body fat, adiposity index, triglycerides levels and heart weight were significantly greater in OP rats than C and OR rats, however, there was no change in systolic blood pressure between groups. The C, OP and OR muscles developed similar baseline data, but myocardial responsiveness to post-rest contraction stimulus was compromised in OP rats. In conclusion, obesity-resistant model by unsaturated high-fat diet, after 15 weeks, does not display nutritional and metabolic characteristics of obesity-prone. Furthermore, obesity-resistant does not promote cardiac abnormalities and impairment of calcium handling visualized in obesity-prone.


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