The role of various risk factors in the prevalence of cardiac autonomic neuropathy and associated diseases

The objectives of this thesis were three-fold: The first aim was to investigate the roles of various markers in the prevalence and complications of CAN and associated diseases with emphasis on diabetes mellitus. Specifically, this study investigated the role of heart rate variability (HRV) markers as well as the roles of genetic and family history risk factors. The second aim of this study was to develop mechanisms to predict CAN disease occurrence. The third aim of this current study was to develop a model for predicting diabetes mellitus (DM) and cardiovascular disease (CVD) simultaneously using common risk factors

The role of vitamin D and osteocalcin on diabetic macrovascular and microvascular events in the field study

Objective People with diabetes frequently develop vascular disease, and accumulating evidence suggests a coupled interaction between bone turnover and glycaemic control. We investigated the relationship between blood 25-hydroxy vitamin D (25OH-D) and osteocalcin (OCN) concentration on vascular disease risk in type 2 diabetes. Research design and methods The relationships between blood 25OH-D and OCN concentration at baseline and the incidence of macrovascular (including myocardial infarction, stroke) and microvascular (retinopathy, nephropathy, neuropathy, and amputation) disease were analysed with Cox proportional-hazards models and logistic regression in an observational study of patients in the 5-year Fenofibrate Intervention and Event Lowering in Diabetes trial. Results 50% of the patients low 25OH-D concentrations, as indicated by median blood 25OH-D concentration of 49nmol/L. These patients with a blood 25OH-D concentration < 50nmol/L had a higher cumulative incidence of macrovascular and microvascular events than those with levels ≥ 50nmol/L. Patients with OCN levels below the population mean of 9.1 ng/mL show a significantly higher cumulative incidence of microvascular events than those with ≥ 9.1 ng/mL. Higher baseline serum OCN was associated with a reduction in risk of microvascular events of 8% per 5ng/mL. Undercarboxylated OCN was not a significant predictor of micro- or macrovascular events. Multivariate analysis, stratified by treatment and adjusted for relevant confounders, identified blood 25OH-D and OCN concentration as an independent predictor of macrovascular and microvascular events

Exercise and peripheral vascular function in health and disease

“Chronic disease will never reach its clinical horizon to compromise health if it is attacked at its origin” [1]. Knowledge that one’s risk for cardiovascular events is related to the severity of endothelial dysfunction, and evidence that exercise training can improve endothelial function, has prompted speculation that measures of vascular function may serve as a “barometer” for cardiovascular health. This dissertation consists of three experiments intended to study vascular function and the manner in which it may influence or may be influenced by physical function. Project one examined the influence of high and low volume circuit weight training on forearm vascular function. Thirty-five individuals participated in a program consisting of 3 sessions/week for 5 weeks. Results indicated significant but similar strength gains in both groups (Hand Grip: Ä15.55%, Knee Extension: Ä21.00%, Bench Press: Ä35.31%; p\u3c0.05). Reactive hyperemic responses, a measure of vascular function, only changed in those individuals with the lowest pre-training vascular measures, independent of group assignment. Project two examined the link between vascular and physical function in peripheral neuropathy patients. Reactive hyperemic responses were significantly related to the time up and go test (r=-0.31, p=0.02) and the 6-minute walk distance (r=0.37, p=0.007). These data suggest a link between measures of vascular and physical function in these patients, indicating that those with better vascular function have greater physical function. Project three examined the effects of an acute bout of exercise on nitric oxide, oxidative stress and anti-oxidants, and brachial vasoreactivity, before, at peak exercise, and in recovery, in trained individuals. The results indicated a significant increase in reactive oxygen species and peroxynitrite, and a decrease in the anti-oxidant glutathione peroxidase at peak exercise. Brachial vasoreactivity was significantly lower immediately after exercise, but returned to pre-exercise levels at 20 minutes into recovery. These findings suggest an acute bout of exercise contributes to a significant rise in oxidative stress, which can in part be buffered by anti-oxidants systems, but may cause temporary blunting of arterial reactivity. Collectively, these findings indicate the importance of examining vascular function, and its controllers, and may extend the current understanding of preserving and/or maintaining vascular health

Genetic analysis of the microvascular complications of diabetes mellitus

There is increasing evidence to suggest that genetic factors are involved in the pathogenesis of microvascular complications in diabetes mellitus. Recent studies have suggested that genetic variations in the aldose reductase (ALR2) gene may contribute to the genetic susceptibility to microvascular complications. Aldose reductase is the first and rate-limiting enzyme of the polyol pathway and is implicated in the pathogenesis of diabetic microvascular disease (nephropathy, retinopathy and neuropathy). It has recently been shown that the three polymorphisms of the ALR2 gene are associated with susceptibility to microvascular complications in both TIDM and T2DM. The aim of this study was to investigate the CA dinucleotide repeat polymorphism (5'ALR2) that is located -2100bp and the C-106T substitution in the promoter region of the ALR2 gene, and also the A+ 11842C within intron 8 of the ALR2 gene itself. DNA from 285 Caucasoid patients with TIDM and well-defined microvascular disease and 120 normal healthy controls, as well as 60 Southern Indian patients with T2DM and 43 non diabetic controls were typed. The 5'ALR2 Z-2/X genotype was significantly increased in patients with nephropathy (n=92), retinopathy (n=160) and neuropathy (n=104) compared to those with no microvascular disease after 19 years duration of diabetes (uncomplicated, n=66) (46%, 41%, 42% vs. 24%, respectively). In contrast, the frequency of the Z+2/Y genotype (where Y is not Z-2) was significantly reduced in the patients with nephropathy, retinopathy and neuropathy compared to the uncomplicated (17%, 23%, 23% vs. 52%, respectively). Similar observations were made in the Southern Indian T2DM patients, however no significant differences were found. In the patients with TIDM the C-106 allele was associated with the Z-2 5'ALR2 allele. The C/Z-2 haplotype was present in 32% of the nephropaths, 32% of the retinopaths and 35% of the neuropaths compared to 11.5% of the uncomplicated. The A+ 11842 allele was also associated with the C-1 06 allele in TIDM patients with microvascular disease. The reported mitochondrial polymorphism (mt5178A/C) was not found in this. TIDM population, possibly due to differences in the background frequencies between ethnic groups. Family studies investigating the transmission of the 5'ALR2 and C-106T alleles from parents to offspring with diabetic nephropathy found preferential transmission of the Z-2 allele although this was not statistically significant. Functional studies of the activity of the ORE in TIDM patients with and without microvascular disease showed differences in the mean OREBP binding activity. OREB and OREC were found to have increased activity in response to hyperglycaemia in the complicated patients compared to the uncomplicated and normal controls. In conclusion, these results confirm the role of the aldose reductase gene in the genetic susceptibility to diabetic microvascular complications, and a possible role of the DI7S934 polymorphism in T2DM. These results also provide a novel insight into the role of the ORE of the ALR2 gene in the pathogenesis of diabetic microvascular complications. Further studies are now required to determine the molecular basis of these observations. Hopefully, in the future it will be possible to offer 'high risk' patients therapeutic intervention that will prevent the ravages of the long term complications of diabetes mellitus

Heart failure – risk factors and the validity of diagnoses

Heart failure (HF) is a global health problem. HF risk factors remain understudied. The roles that diabetes and sodium consumption play in HF remain unknown. Furthermore, the validity of HF diagnoses in the Finnish Hospital Discharge Register (FHDR) has not been thoroughly evaluated. This thesis aims to discover sodiumand diabetes-related HF risk factors, validate FHDR-based HF diagnoses, and investigate if the subtyping of register-based HF diagnoses could be improved through electronic health record (EHR) data mining. A 24-hour urinary sodium excretion (mean 183 mmol/d) was measured from 4,630 individuals to assess the relationship between salt intake and incident HF (Study I). We used data from 3,834 diabetic and 90,177 nondiabetic individuals to evaluate the diabetes status-related differences in risk factors and mediators of HF (Study II). Medical records of 120 HF cases and 120 controls were examined to study the validity of HF diagnoses (Study III). We drew data from 33,983 patients to assess if HF diagnoses could be subtyped more accurately through EHR data mining (Study IV) and validated the mining-based versus clinical subtyping in 100 randomly selected patients. In Study I, we observed that high sodium intake was associated with incident coronary artery disease (CAD) and diabetes, but not HF. In Study II, the risk of HF was 2.7-fold in individuals with diabetes compared to nondiabetic participants. Conventional cardiovascular disease risk factors and biomarkers for cardiac strain, myocardial injury, and inflammation were associated with incident HF in both groups. The strongest mediators of HF in diabetes were the direct effect of diabetes and the indirect effects mediated by obesity, cardiac strain/volume overload, and hyperglycemia. In studies III and IV, HF diagnoses of the FHDR had good predictive values (NPV 0.83, PPV 0.85), even when patients with preexisting heart conditions were used as controls. With additional EHR-mined data, the accuracy of our algorithm to correctly classify individuals into HF subtypes versus clinical assessment was 86 %. The findings in this thesis show that register-based HF is an accurate endpoint and that EHR data mining can improve this accuracy. Our results also elucidate the role of sodium and diabetes as HF risk factors.Sydämen vajaatoiminta: riskitekijät ja diagnoosien validiteetti Sydämen vajaatoiminta on maailmanlaajuinen terveysongelma, jonka riskitekijät ovat osin epäselviä. Suolan käytön yhteyttä ja diabeteksen aiheuttamaa korkeaa riskiä vajaatoimintaan ei ole riittävästi tutkittu. Vajaatoimintadiagnoosien validiteettia Hoitoilmoitusjärjestelmä (HILMO)-sairaalarekisterissä ei tiedetä. Tässä väitöskirjatyössä tutkittiin suolaan ja diabetekseen liittyviä sydämen vajaatoiminnan riskitekijöitä, validoitiin HILMO-pohjaiset vajaatoimintadiagnoosit ja selvitettiin, voidaanko vajaatoimintaa alatyypittää tekstinlouhintaa käyttämällä. Suolan saannin ja vajaatoiminnan välisen suhteen arvioimiseksi (tutkimus I) tutkittiin 4 630 henkilön vuorokausivirtsan natrium (keskimäärin 183 mmol/d). Diabetekseen liittyvien sydämen vajaatoiminnan riskitekijöiden selvittämiseksi (tutkimus II) käytiin läpi 3 834 diabeetikon ja 90 177 verrokin tiedot. Vajaatoimintadiagnoosien validiteettia (tutkimus III) varten tutkimme 120 vajaatoimintatapauksen ja 120 verrokin (joilla oli muu sydänsairaus) potilastiedot ja tarkempaa alatyypitystä (tutkimus IV) varten keräsimme tietoja 33 983 potilaasta ja validoimme tiedonlouhintaan perustuvan alatyypityksen 100 satunnaisella potilaalla. Tutkimuksessa I suolan saanti oli yhteydessä sepelvaltimotaudin ja diabeteksen kehittymiseen, mutta tulokset eivät olleet merkitseviä vajaatoiminnan osalta. Tutkimuksessa II diabeetikoiden vajaatoimintariski oli 2,7-kertainen verrokkeihin verrattuna. Molemmilla tavanomaiset riskitekijät ja sydämen venyvyyden, sydänvaurion ja tulehduksen merkkiaineet olivat yhteydessä vajaatoimintaan. Merkittävimmät diabeteksen vajaatoimintaa välittävät muuttujat olivat diabeteksen suora vaikutus sekä epäsuorat ylipainon, sydämen venymisen ja hyperglykemian vaikutukset. Tutkimuksissa III ja IV HILMO-rekisterin vajaatoimintadiagnoosin prediktiiviset arvot olivat hyviä (NPV 0,83, PPV 0,85) verrattuna muihin sydänsairaisiin potilaihin ja tiedonlouhinnan alatyypityksen tarkkuus verrattuna kliiniseen oli 86 %. Tämä väitöskirja osoittaa, että HILMO-pohjaiset vajaatoimintadiagnoosit toimivat tieteellisenä päätetapahtumana ja että vajaatoiminnan alatyyppiä voidaan tarkentaa tekstilouhinnalla, sekä tuo uutta tietoa suolasta ja diabeteksesta vajaatoiminnan riskitekijöinä

Characterising the Clinical Heterogeneity of Type 1 Diabetes

There is growing evidence that type 1 diabetes is not a single disease with a predictable course, but rather comprises a number of disease phenotypes characterised by distinct immunologic, genetic and metabolic features. Indeed, a recent shift towards onset in patients at lower genetic risk highlights the increasing importance of environmental and metabolic factors in disease pathogenesis. These factors may contribute to the development of microvascular complications and alter mortality risk. This thesis aims to characterise the heterogeneity of type 1 diabetes and its complications by describing four cohorts diagnosed between 1973 and 2014. Findings from this thesis contribute to understanding the heterogeneity of T1D and its disease course, identification of novel risk factors for microvascular complications and early risk factors for increased mortality. These findings may allow appropriate risk stratification and targeted intervention to prevent type 1 diabetes onset, the development of microvascular complications and to reduce mortalit

A Pharmacological Approach towards Myocardial Protection: New Perspectives in Acute and Chronic Cardiac Disease

Several cardiac diseases include myocardial ischaemia (acute or chronic), heart failure (systolic or diastolic) and left ventricular hypertrophy (either as a “primary” cause or developed secondary to other diseases) share the commonality of myocardial energetic deficiency or suboptimal myocardial metabolism. Therefore, approaches to modify myocardial metabolism in order to improve energetics present as an attractive therapeutic option. This is particularly useful when other options are limited: for example, lack of optimal symptom control with “maximal” treatment, or contraindications to other pharmacological treatment (by virtue of impairment of left ventricular systolic function and/or hypotension). The objective of this thesis is to examine the biochemical effects of various pharmacological agents towards modulation of myocardial metabolism, both in the acute (e.g. acute coronary syndrome) and chronic cardiac disease settings (e.g. diabetic heart). In particular, the effects of perhexiline, an interesting drug known to possess not only metabolic effects (by virtue of inhibiting carnitine palmitoyl transferase-1 [CPT-1], thereby shifting myocardial fatty acid oxidation towards glycolysis) but also anti-inflammatory effects, will be further explored. First, the pharmacokinetics and myocardial uptake profile of the individual perhexiline enantiomers were examined. This study showed that the myocardial uptake of both perhexiline enantiomers in patients were slow; and that in multivariate backward stepwise analysis, (-)-perhexiline was inversely correlated with on-treatment heart rate. This finding suggested that the weak calcium antagonist effect of perhexiline may potentially lie predominantly within the (-)- enantiomer. Additionally, other aspects of myocardial metabolism, including the nexus between inflammatory activation and metabolic effect, were investigated. In a study involving 12 patients presenting with acute coronary syndrome and hyperglycaemia, rapid reversal of hyperglycaemia with insulin infusion in 12 hours improved the anti-aggregatory effect of platelets, independent of the platelet content of the pro-inflammatory marker thioredoxin-interacting protein (TXNIP). Furthermore, this thesis also investigated the potential insulin sensitization effect of perhexiline in diabetic patients. This is a corollary of increased glucose utilization, which appears to be relevant even against the background of concomitant therapy with other insulin-sensitizing agents such as AMPK activators or ACE-inhibitors. Furthermore, platelet content of TXNIP tended to fall slightly (but not significantly) after perhexiline treatment, implying its lack of significant critical role in the improvement of both nitric oxide responsiveness and insulin sensitization. However, its overall contribution still cannot be completely ruled out. Lastly, in an in vitro experiment, the potency of inhibition of CPT-1 by both perhexiline enantiomers was investigated. It was found that the 50% inhibitory concentrations of both enantiomers were not significantly different. This provided evidence that the (differential) toxicity seen with the individual enantiomers (in previous studies) might be independent of CPT-1 inhibition. The CPT-1 inhibitory potency of several other cardiac drugs, including fluorinated perhexiline (developed by collaborators in Aberdeen, UK) and dronedarone (a benzofluranyl compound, structurally similar to amiodarone) was also determined in this thesis, and it was shown in particular that dronedarone was a potent CPT-1 inhibitor. The overall thrust of this work reinforces the concept that CPT-1 inhibition is seen with a large number of cardiovascular drugs, and is retained by enantiomers and structural analogues of perhexiline. The myocardial uptake of perhexiline and its enantiomers indicates a relatively slow process of equilibration with its primary sites of action.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 201

Diabetic cardiomyopathy

Diabetic cardiomyopathy is a distinct primary disease process, independent of coronary artery disease, which leads to heart failure in diabetic patients. Epidemiological and clinical trial data have confirmed the greater incidence and prevalence of heart failure in diabetes. Novel echocardiographic and MR (magnetic resonance) techniques have enabled a more accurate means of phenotyping diabetic cardiomyopathy. Experimental models of diabetes have provided a range of novel molecular targets for this condition, but none have been substantiated in humans. Similarly, although ultrastructural pathology of the microvessels and cardiomyocytes is well described in animal models, studies in humans are small and limited to light microscopy. With regard to treatment, recent data with thiazoledinediones has generated much controversy in terms of the cardiac safety of both these and other drugs currently in use and under development. Clinical trials are urgently required to establish the efficacy of currently available agents for heart failure, as well as novel therapies in patients specifically with diabetic cardiomyopathy

Fabry disease

Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A activity. FD is pan-ethnic and the reported annual incidence of 1 in 100,000 may underestimate the true prevalence of the disease. Classically affected hemizygous males, with no residual α-galactosidase A activity may display all the characteristic neurological (pain), cutaneous (angiokeratoma), renal (proteinuria, kidney failure), cardiovascular (cardiomyopathy, arrhythmia), cochleo-vestibular and cerebrovascular (transient ischemic attacks, strokes) signs of the disease while heterozygous females have symptoms ranging from very mild to severe. Deficient activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide within lysosomes, believed to trigger a cascade of cellular events. Demonstration of marked α-galactosidase A deficiency is the definitive method for the diagnosis of hemizygous males. Enzyme analysis may occasionnally help to detect heterozygotes but is often inconclusive due to random X-chromosomal inactivation so that molecular testing (genotyping) of females is mandatory. In childhood, other possible causes of pain such as rheumatoid arthritis and 'growing pains' must be ruled out. In adulthood, multiple sclerosis is sometimes considered. Prenatal diagnosis, available by determination of enzyme activity or DNA testing in chorionic villi or cultured amniotic cells is, for ethical reasons, only considered in male fetuses. Pre-implantation diagnosis is possible. The existence of atypical variants and the availability of a specific therapy singularly complicate genetic counseling. A disease-specific therapeutic option - enzyme replacement therapy using recombinant human α-galactosidase A - has been recently introduced and its long term outcome is currently still being investigated. Conventional management consists of pain relief with analgesic drugs, nephroprotection (angiotensin converting enzyme inhibitors and angiotensin receptors blockers) and antiarrhythmic agents, whereas dialysis or renal transplantation are available for patients experiencing end-stage renal failure. With age, progressive damage to vital organ systems develops and at some point, organs may start to fail in functioning. End-stage renal disease and life-threatening cardiovascular or cerebrovascular complications limit life-expectancy of untreated males and females with reductions of 20 and 10 years, respectively, as compared to the general population. While there is increasing evidence that long-term enzyme therapy can halt disease progression, the importance of adjunctive therapies should be emphasized and the possibility of developing an oral therapy drives research forward into active site specific chaperones