Diabetes is known to result in a large number of alterations which affect various systems and organs. One of the more prominent disorders associated with diabetes is that of cardiac disease. Clinically, diabetics suffer from morbidity and mortality of cardiac origin to a greater extent than the nondiabetic population. Various functional studies have also revealed that the efficiency of diabetic hearts to function as pumps is lower than that of normal hearts. Experimentally, myocardial function of either rats or dogs made diabetic with either streptozotocin (STZ) or alloxan has been studied and a depression clearly demonstrated in both the species. The abnormalities of cardiac function in experimental diabetes are accompanied by depression of various enzyme systems in the heart. These include the ability of the sarcoplasmic reticulum (SR) to take up calcium; the myosin and actomyosin ATPase activities; and the Na⁺, K⁺ ATPase activity. All these changes can be prevented and reversed by insulin treatment suggesting that the myocardial problems seen in STZ or alloxan diabetic animals are due to diabetes and not direct toxicities of the drugs. It is not known whether the beneficial effects of in vivo insulin treatment are due to its direct myocardial effects or whether they are secondary to its effects mediated via normalisation of metabolism in diabetic animals. Thus, in the first part of the present investigation, we examined the direct effects of insulin on hearts from either control or diabetic rats using the isolated working heart preparation. Rats made diabetic with STZ (55 mg/kg) were sacrificed either 3 days or 6 weeks after induction of the disease and their hearts isolated and perfused in the working heart mode. Glucose concentrations varying from 5mM to 20mM were used in the perfusion medium, either in the presence or absence of insulin (5mU/mL). Left ventricular function was expressed as left ventricular developed pressure (LVDP) and the rates of contraction and relaxation (positive and negative dP/dt respectively) at various left atrial filling pressures. Three days after injecting STZ into rats, the animals exhibited hypoinsulinemia, hyperglycemia and their body weights although not significantly different from those of control animals, tended to be lower than the body weights of controls. Animals treated in this manner did not exhibit depression of cardiac function when compared with the myocardial function of control rats. Hearts from control rats exposed to regular insulin in the presence of 5mM glucose exhibited values of contractility which were significantly greater as compared with those obtained from control rat hearts not exposed to the hormone. When insulin was perfused along with a higher concentration of glucose (10mM), function of control rat hearts was affected to a significant extent. As opposed to the effects on control rat hearts, insulin failed to increase contractility in hearts from 3 day diabetic rats when either 5 or 10mM glucose was used in the perfusion medium. The study was then repeated using animals which had been diabetic for six weeks. At the time of sacrifice, these animals were hypoinsulinemic, hyperglycemic and weighed significantly less than their age-matched controls. Analysis of cardiac function revealed a significant depression in diabetic rats as compared with controls. Increasing glucose concentrations from 5 to 20mM in the perfusion medium did not affect the function of either control or diabetic rat hearts. Perfusion with regular insulin increased contractility in control rat hearts; the increase in contractility was not affected by increasing the glucose concentration from 5 to 10mM. However, contractility of diabetic rat hearts was not affected by insulin perfusion when either 5 or 10mM glucose was used in the perfusion medium. In order to eliminate the possibility of involvement of glucagon (which may contaminate commercial insulin preparations) in the effects of insulin on control rat hearts, part of the study was repeated using glucagon - free insulin. While the glucagon - free insulin increased contractility in control rat hearts, diabetic rat hearts were not affected. These results are identical to those obtained with regular insulin, suggesting that the effects of insulin observed were due to insulin itself. Although insulin treatment prevents and reverses diabetes - induced myocardial alterations in the rats, due to its widespread metabolic effects, it is not a good tool for investigating the specific factors which cause the cardiac abnormalities. In addition, a major problem with insulin treatment clinically is the fact that hypoglycemia can be associated with it, inadequate control occurs in some diabetics and secondary complications, such as myocardial problems, occur despite insulin treatment. It is thus desirable to have treatments which selectively affect certain aspects of diabetes so that the suspected underlying causes can be corrected specifically and their significance in causing the myocardial problems assessed. It would also be useful to have drug treatments which could either substitute for insulin or could be used in addition to the peptide. We have thus studied the effectiveness of certain treatments in preventing diabetes - induced myocardial alterations. The first one used was methyl palmoxirate, a fatty acid analog which is reported to reduce blood glucose levels in diabetic rats and dogs. The glucose - lowering effect is mediated via inhibition of fatty acid metabolism due to inhibition of carnitine acyl transferase resulting in inhibition of acyl carnitine formation and eventually inhibition of fatty acid transport across the mitochondrial membrane. Rats were treated with the drug (25mg/kg/day p.o.) three days after they were injected with either STZ or buffer. The treatment was carried out for 6 weeks and cardiac performance was then assesed. Untreated and treated diabetic rats were hypoinsulinemic, hyperglycemic and hyperlipedemic at the time of sacrifice. Cardiac function, which was depressed in diabetic animals, was still depressed despite the methyl palmoxirate treatment. However, the ability of the myocardial sarcoplasmic reticulum (SR) to take up calcium, which was depressed in diabetic rats, was normal in treated diabetic rats. Also, the levels of long chain acyl carnitines (LCAC) in the myocardial SR were normalised by methyl palmoxirate treatment in diabetic rats. In an effort to normalise diabetes - induced myocardial alterations in rats, we then attempted a combination of either methyl palmoxirate or carnitine (as both can prevent the depression of SR calcium uptake) with thyroid hormone treatment (as it can normalise myosin ATPase depression in diabetic rat hearts). The treatment protocol was identical to that described above (30µg/kg/day s.c. T₃ was used). Although the general features of both control and diabetic animals were not affected by either of the combination treatments, cardiac dysfunction in diabetic rats was prevented by methyl palmoxirate and T₃ treatment. Carnitine and T₃ treatment, on the other hand, affected the function of diabetic rat hearts only at the lower left atrial filling pressures. These results suggest that the combination treatment of methyl palmoxirate and T₃ affect parameters besides SR calcium uptake and myosin ATPase. This is because the combination of carnitine and T₃, which also supposedly affects same parameters as the other combination, could not prevent the myocardial alterations. One of the possible reasons for the effectiveness of the combination of methyl palmoxirate and T₃ could be that animals treated with methyl palmoxirate derived at least part of their metabolic energy (especially at higher left atrial filling pressures) from glucose and thus reduced the oxygen demand at higher filling pressures as opposed to the untreated diabetic rat hearts which depended completely on fatty acids for their metabolic energy demands. / Pharmaceutical Sciences, Faculty of / Graduate

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

INTRODUÇÃO: Em pacientes com infarto do miocárdio (IM) e disfunção cardíaca, a evidência de viabilidade miocárdica é primordial, e o exame tomográfico por emissão de pósitrons com 18F-fluoro-desoxi-glicose (18FDG-PET) é o padrão-ouro para essa identificação. Existe preferência, na literatura, pela realização do clamp hiperínsulínico euglicêmico (CLAMP) antes da injeção de 18FDG para estimular todo o miocárdio a consumir glicose (GLI), garantindo assim a sua captação pelas áreas de miocárdio hibernado (MH). No entanto, essa técnica é trabalhosa, além do risco de hipoglicemia durante a realização. Desenvolvemos uma nova técnica na qual o paciente é submetido a uma dieta restrita em carboidratos (DIETA) por 24 horas antes do exame, sem a necessidade de CLAMP, com o objetivo de diminuir os níveis de insulina e aumentar ácidos graxos livres (AGL), estimulando o miocárdio normal a consumir AGL, e não GLI. A área de MH, porém, não consegue realizar o metabolismo oxidativo de AGL, mantendo o consumo de GLI. OBJETIVOS: comparar o PET após DIETA (PET-DIETA) com o PET após CLAMP (PET-CLAMP), para a pesquisa de viabilidade miocárdica. MÉTODOS: Trinta pacientes com IM prévio e hipocinesia na área infartada foram submetidos à cintilografia de perfusão miocárdica com 99mTc-sestamibi (MIBI), PET-CLAMP e PET-DIETA. A DIETA limitava-se a 15-20g de carboidratos por dia. Os exames foram submetidos à análise visual e classificados por escores (0 a 4). Foram consideras áreas de mismatch (MH) aquelas com hipoperfusão ao MIBI e captação presente no PET-CLAMP ou no PET-DIETA, em um modelo de 17 segmentos, além da análise por parede, território arterial e por paciente. A análise por segmentos foi realizada ainda dividindo-se os pacientes em diabéticos (DM) e não diabéticos (NDM). O PET-DIETA também foi submetido à análise automática (por percentual de captação) RESULTADOS: Durante o CLAMP, seis (20%) pacientes apresentaram hipoglicemia. Nenhum paciente apresentou hipoglicemia após a DIETA. Houve concordância na análise visual do PET-CLAMP e PET-DIETA para detecção de áreas de mismatch em 94,5% dos segmentos analisados, com um índice kappa de 0,78 (concordância substancial). Essa concordância se manteve na análise por parede (0,80), território arterial (k=0,79) e por paciente (0,79). Quando dividimos os pacientes em NDM (22) e DM (8), encontramos k=0,78 para o subgrupo NDM e 0,70 para o subgrupo DM. A análise automática para o PET-DIETA evidenciou, quando comparada com a análise visual do PET-CLAMP, uma concordância moderada, com índice kappa de 0,50 para análise por segmento, 0,54 por parede, 0,60 por território arterial e 0,48 por paciente. CONCLUSÕES: Concluímos assim que o exame de PET-DIETA apresenta uma excelente concordância para detecção de áreas de mismatch com o PET-CLAMP, ambos em conjunto com a análise do MIBI, possivelmente com mais segurança para o paciente. Essa concordância se mantém quando avaliamos os subgrupos de DM e NDM / BACKGROUND: In patients with myocardial infarction and left ventricular dysfunction, the evidence of myocardial viability has important clinical implications. Positron emission tomography (PET) using 18F-fluoro-desoxi-glucose (18FDG) is considered the gold standard for viability detection. The euglycemic hyperinsulinemic clamping (CLAMP) before 18FDG injection stimulates uptake of both glucose and 18FDG in the myocardium, including areas of hibernating myocardium (MH), and it is the most used protocol. However, this imaging protocol has an increased risk for hypoglycemia and is relatively time-consuming. We developed a new protocol using a 24 hours low-carbohydrate diet (DIET), aiming to reduce insulin levels and increase free fatty acids (FFA). This protocol stimulates the normal myocardium to use FFA, not glucose, but the area of hibernating myocardium (viable area) may not use oxidative metabolism with FFA, keeping glucose uptake and becoming a hot spot at PET images. The aim of this study was to compare both techniques by segments, regions, vascular territories and patients. METHODS: Thirty patients with previous myocardial infarction and left ventricular dysfunction were studied. All of them underwent into a SPECT perfusion scan with 99mTc-sestamibi and two 18FDG PET studies to asses myocardial viability, one with CLAMP (PET-CLAMP) and another using a 24 hours low-carbohydrate diet (PET-DIET). For the analysis, the myocardium was divided into 17 segments, 5 regions and 3 vascular territories. A visual and an automatic semi-quantitative analysis (only for PET-DIET) were carried out according to the following score indicating radiotracer uptake: 0 = normal to 4 = absent. Myocardial viability was defined as the presence of normal or mildly reduced FDG uptake in an area with reduced perfusion (99mTc-sestamibi uptake). We also performed subgroup analyses in diabetes (DM) and non-diabetic patients (NDM). RESULTS: While using CLAMP protocol, six (20%) patients had hypoglycemia. None of the patients had hypoglycemia after using DIET. High agreement rates were observed with visual analysis in comparing mismatch areas (kappa=0,78 substancial concordance). Similar rates were find in regions (0,80), vascular territories (0,79) and patient (0,79) analysis. In subgroup analysis, DM (8) presented with kappa=0,70 and NDM (22) with kappa=0,78. Upon analysis, the automatic method for PET-DIET showed moderate agreement when compared with PET-CLAMP visual analysis by segments (Kappa=0,50), regions (0,54), vascular territories (0,60) and patient (0,48). CONCLUSIONS: This has led to the suggestion that PET-DIET study proved an excellent agreement in detects mismatch areas assessed by PET-CLAMP, with probably more safety. The same results occurs in the in diabetes and non-diabetic patients subgroups

INTRODUÇÃO: Em pacientes com infarto do miocárdio (IM) e disfunção cardíaca, a evidência de viabilidade miocárdica é primordial, e o exame tomográfico por emissão de pósitrons com 18F-fluoro-desoxi-glicose (18FDG-PET) é o padrão-ouro para essa identificação. Existe preferência, na literatura, pela realização do clamp hiperínsulínico euglicêmico (CLAMP) antes da injeção de 18FDG para estimular todo o miocárdio a consumir glicose (GLI), garantindo assim a sua captação pelas áreas de miocárdio hibernado (MH). No entanto, essa técnica é trabalhosa, além do risco de hipoglicemia durante a realização. Desenvolvemos uma nova técnica na qual o paciente é submetido a uma dieta restrita em carboidratos (DIETA) por 24 horas antes do exame, sem a necessidade de CLAMP, com o objetivo de diminuir os níveis de insulina e aumentar ácidos graxos livres (AGL), estimulando o miocárdio normal a consumir AGL, e não GLI. A área de MH, porém, não consegue realizar o metabolismo oxidativo de AGL, mantendo o consumo de GLI. OBJETIVOS: comparar o PET após DIETA (PET-DIETA) com o PET após CLAMP (PET-CLAMP), para a pesquisa de viabilidade miocárdica. MÉTODOS: Trinta pacientes com IM prévio e hipocinesia na área infartada foram submetidos à cintilografia de perfusão miocárdica com 99mTc-sestamibi (MIBI), PET-CLAMP e PET-DIETA. A DIETA limitava-se a 15-20g de carboidratos por dia. Os exames foram submetidos à análise visual e classificados por escores (0 a 4). Foram consideras áreas de mismatch (MH) aquelas com hipoperfusão ao MIBI e captação presente no PET-CLAMP ou no PET-DIETA, em um modelo de 17 segmentos, além da análise por parede, território arterial e por paciente. A análise por segmentos foi realizada ainda dividindo-se os pacientes em diabéticos (DM) e não diabéticos (NDM). O PET-DIETA também foi submetido à análise automática (por percentual de captação) RESULTADOS: Durante o CLAMP, seis (20%) pacientes apresentaram hipoglicemia. Nenhum paciente apresentou hipoglicemia após a DIETA. Houve concordância na análise visual do PET-CLAMP e PET-DIETA para detecção de áreas de mismatch em 94,5% dos segmentos analisados, com um índice kappa de 0,78 (concordância substancial). Essa concordância se manteve na análise por parede (0,80), território arterial (k=0,79) e por paciente (0,79). Quando dividimos os pacientes em NDM (22) e DM (8), encontramos k=0,78 para o subgrupo NDM e 0,70 para o subgrupo DM. A análise automática para o PET-DIETA evidenciou, quando comparada com a análise visual do PET-CLAMP, uma concordância moderada, com índice kappa de 0,50 para análise por segmento, 0,54 por parede, 0,60 por território arterial e 0,48 por paciente. CONCLUSÕES: Concluímos assim que o exame de PET-DIETA apresenta uma excelente concordância para detecção de áreas de mismatch com o PET-CLAMP, ambos em conjunto com a análise do MIBI, possivelmente com mais segurança para o paciente. Essa concordância se mantém quando avaliamos os subgrupos de DM e NDM / BACKGROUND: In patients with myocardial infarction and left ventricular dysfunction, the evidence of myocardial viability has important clinical implications. Positron emission tomography (PET) using 18F-fluoro-desoxi-glucose (18FDG) is considered the gold standard for viability detection. The euglycemic hyperinsulinemic clamping (CLAMP) before 18FDG injection stimulates uptake of both glucose and 18FDG in the myocardium, including areas of hibernating myocardium (MH), and it is the most used protocol. However, this imaging protocol has an increased risk for hypoglycemia and is relatively time-consuming. We developed a new protocol using a 24 hours low-carbohydrate diet (DIET), aiming to reduce insulin levels and increase free fatty acids (FFA). This protocol stimulates the normal myocardium to use FFA, not glucose, but the area of hibernating myocardium (viable area) may not use oxidative metabolism with FFA, keeping glucose uptake and becoming a hot spot at PET images. The aim of this study was to compare both techniques by segments, regions, vascular territories and patients. METHODS: Thirty patients with previous myocardial infarction and left ventricular dysfunction were studied. All of them underwent into a SPECT perfusion scan with 99mTc-sestamibi and two 18FDG PET studies to asses myocardial viability, one with CLAMP (PET-CLAMP) and another using a 24 hours low-carbohydrate diet (PET-DIET). For the analysis, the myocardium was divided into 17 segments, 5 regions and 3 vascular territories. A visual and an automatic semi-quantitative analysis (only for PET-DIET) were carried out according to the following score indicating radiotracer uptake: 0 = normal to 4 = absent. Myocardial viability was defined as the presence of normal or mildly reduced FDG uptake in an area with reduced perfusion (99mTc-sestamibi uptake). We also performed subgroup analyses in diabetes (DM) and non-diabetic patients (NDM). RESULTS: While using CLAMP protocol, six (20%) patients had hypoglycemia. None of the patients had hypoglycemia after using DIET. High agreement rates were observed with visual analysis in comparing mismatch areas (kappa=0,78 substancial concordance). Similar rates were find in regions (0,80), vascular territories (0,79) and patient (0,79) analysis. In subgroup analysis, DM (8) presented with kappa=0,70 and NDM (22) with kappa=0,78. Upon analysis, the automatic method for PET-DIET showed moderate agreement when compared with PET-CLAMP visual analysis by segments (Kappa=0,50), regions (0,54), vascular territories (0,60) and patient (0,48). CONCLUSIONS: This has led to the suggestion that PET-DIET study proved an excellent agreement in detects mismatch areas assessed by PET-CLAMP, with probably more safety. The same results occurs in the in diabetes and non-diabetic patients subgroups