Abstract-Evidence is emerging that systemic metabolic disturbances contribute to cardiac myocyte dysfunction and clinically apparent heart failure, independent of associated coronary artery disease. To test the hypothesis that perturbation of lipid homeostasis in cardiomyocytes contributes to cardiac dysfunction, we engineered transgenic mice with cardiac-specific overexpression of fatty acid transport protein 1 (FATP1) using the ␣-myosin heavy chain gene promoter. Two independent transgenic lines demonstrate 4-fold increased myocardial free fatty acid (FFA) uptake that is consistent with the known function of FATP1. Increased FFA uptake in this model likely contributes to early cardiomyocyte FFA accumulation (2-fold increased) and subsequent increased cardiac FFA metabolism (2-fold). By 3 months of age, transgenic mice have echocardiographic evidence of impaired left ventricular filling and biatrial enlargement, but preserved systolic function. Doppler tissue imaging and hemodynamic studies confirm that these mice have predominantly diastolic dysfunction. Furthermore, ambulatory ECG monitoring reveals prolonged QT c intervals, reflecting reductions in the densities of repolarizing, voltage-gated K ϩ currents in ventricular myocytes. Our results show that in the absence of systemic metabolic disturbances, such as diabetes or hyperlipidemia, perturbation of cardiomyocyte lipid homeostasis leads to cardiac dysfunction with pathophysiological findings similar to those in diabetic cardiomyopathy. Moreover, the MHC-FATP model supports a role for FATPs in FFA import into the heart in vivo. Key Words: lipids Ⅲ metabolism Ⅲ cardiomyopathy C ardiomyopathy has been observed in a variety of metabolic disorders. In inherited disorders of ␤-oxidation, accumulation of unmetabolized lipid in cardiac myocytes is associated with ventricular systolic dysfunction. 1 In obesity, increased myocardial oxygen consumption and decreased efficiency may contribute to diastolic and systolic dysfunction. 2,3 In diabetes mellitus, heart failure in the absence of valvular or congenital heart disease, alcoholism, hypertension, or significant epicardial coronary atherosclerosis is defined as diabetic cardiomyopathy and accounts for significant morbidity and mortality in people with type 1 and type 2 diabetes. 4 Echocardiographic and hemodynamic studies suggest left ventricular (LV) diastolic impairment represents an early preclinical manifestation of diabetic cardiomyopathy that may progress over an extended period of time to both diastolic and systolic dysfunction. 5,6 In these metabolic disorders, systemic metabolic perturbations lead to myocyte dysfunction and/or loss. Glucotoxicity, 7 ATP depletion, 8 and maladaptive changes in metabolic substrate utilization 9 are mechanisms proposed to contribute to cardiac dysfunction. It has also been hypothesized that mismatch between tissue free fatty acid (FFA) import and utilization leads to lipid accumulation and results in lipotoxicity. In diabetes, this imbalance results from high-serum F...

No abstract

RATIONALE AND OBJECTIVES Non-invasive longitudinal imaging of tumor vasculature could provide new insights into the development of solid tumors, facilitating efficient delivery of therapeutics. In this study, we report three-dimensional imaging and characterization of tumor vascular architecture using a nanoparticle contrast agent and high-resolution computed tomography (CT) imaging. MATERIALS AND METHODS Five Balb/c mice implanted with 4T1/Luc syngeneic breast tumors cells were used for the study. The nanoparticle contrast agent was systemically administered and longitudinal CT imaging was performed pre-contrast and at serial time-points post-contrast, for up to 7 days for studying the characteristics of tumor-associated blood vessels. Gene-expression of tumor angiogenic biomarkers was measured using quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS Early-phase imaging demonstrated the presence of co-opted and newly developed tumor vessels. The co-opted vessels demonstrated wall-permeability and ‘leakiness’ characteristics evident by an increase in extra-vascular nanoparticle-based signal enhancement visible well beyond the margins of tumor. Diameters of tumor-associated vessels were larger than the contra-lateral normal vessels. Delayed-phase imaging also demonstrated significant accumulation of nanoparticle contrast agent both within and in areas surrounding the tumor. A heterogeneous pattern of signal enhancement was observed both within and among individual tumors. Gene-expression profiling demonstrated significant variability in several angiogenic biomarkers both within and among individual tumors. CONCLUSIONS The nanoparticle contrast agent and high-resolution CT imaging facilitated visualization of co-opted and newly developed tumors vessels as well as imaging of nanoparticle accumulation within tumors. The use of this agent could provide novel insights into tumor vascular biology and could have implications on the monitoring of tumor status.

Estrogen receptor-α (ERα) and progesterone receptor (PR) are expressed in most human breast cancers and are important predictive factors for directing therapy. Because of de novo and acquired resistance to endocrine therapy, there remains a need to identify which ERα-positive (ERα+)/PR-positive (PR+) tumors are most likely to respond. The purpose of this study was to use estrogen- and progestin-based radiopharmaceuticals to image ERα and PR in mouse mammary tumors at baseline and after hormonal therapy and to determine whether changes in these imaging biomarkers can serve as an early predictive indicator of therapeutic response. Methods Mammary adenocarcinomas that spontaneously develop in aged female mice deficient in signal transducer and activator of transcription-1 (STAT1) were used. Imaging of ERα and PR in primary tumor–bearing mice and mice implanted with mammary cell lines (SSM1, SSM2, and SSM3) derived from primary STAT1-deficient (STAT1−/−) tumors was performed. Hormonal treatments consisted of estradiol, an ER agonist; letrozole, an aromatase inhibitor; and fulvestrant, a pure ER antagonist. Small-animal PET/CT was performed using 18F-fluoroestradiol (18F-FES) for ER, 18F-fluoro furanyl norprogesterone (18F-FFNP) for PR, and 18F-FDG for glucose uptake. Tracer uptake in the tumor was quantified and compared with receptor concentration determined by in vitro assays of resected tumors. Results Primary STAT1−/− mammary tumors and implanted SSM2 and SSM3 tumors showed high 18F-FES and 18F-FFNP uptake and were confirmed to be ERα+/PR+. Classic estrogen-induced regulation of the progesterone receptor gene was demonstrated by increased 18F-FFNP uptake of estradiol-treated SSM3 tumors. Treatment with fulvestrant decreased 18F-FFNP, 18F-FES, and 18F-FDG uptake and inhibited growth of SSM3 tumors but decreased only 18F-FES uptake in SSM2 tumors, with no effect on growth, despite both tumors being ERα+/PR+. Decreased 18F-FFNP uptake by SSM3 tumors occurred early after initiation of treatment, before measurable tumor growth inhibition. Conclusion Using small-animal PET, a profile was identified that distinguished fulvestrant-sensitive from fulvestrant-resistant ERα+/PR+ tumors before changes in tumor size. This work demonstrates that imaging baseline tumoral 18F-FES uptake and initial changes in 18F-FFNP uptake in a non-invasive manner is a potentially useful strategy to identify responders and nonresponders to endocrine therapy at an early stage.

Diabetic cardiomyopathy is associated with abnormalities in glucose metabolism. We evaluated myocardial glucose metabolism in a rodent model of type 2 diabetes, namely the Zucker diabetic fatty (ZDF) rat, and validated PET measurements of glucose uptake against gene and protein expression of glucose transporters (GLUTs). Methods: Six lean and ZDF rats underwent small-animal PET at the age of 14 wk and at the age of 19 wk. The imaging protocol consisted of a 60-min dynamic acquisition with 18 F-FDG (18.5-29.6 MBq). Dynamic images were reconstructed using filtered backprojection with a 2.5 zoom on the heart and 40 frames per imaging session. PET measurements of myocardial glucose uptake (MGUp) rate and utilization were determined with an input function derived by the hybrid image-blood-sampling algorithm on recovery-corrected anterolateral myocardial regions of interest. After the PET session at week 19 (W19), hearts were extracted for gene and protein expression analysis of GLUT-1 and GLUT-4. The dependence of MGUp on gene expression of GLUT-1 and GLUT-4 was characterized by multiple-regression analysis. Results: MGUp in ZDF rats at both week 14 (W14) and W19 (P , 0.006) was significantly lower than MGUp in lean littermate control rats. Moreover, lean rats at W19 displayed significantly higher MGUp than they did at W14 (P 5 0.007). Consistent with a diminished MGUp result, gene expression of GLUT-4 was significantly (P 5 0.004) lower in ZDF rats. Finally, MGUp significantly (P 5 0.0003) correlated with gene expression of GLUT-4. Conclusion: Using small-animal PET, we confirmed alterations in myocardial glucose utilization and validated PET measurement of MGUp against gene and protein expression of GLUTs in the diabetic heart of an animal model of type 2 diabetes.