Thiamine increases resident endoglin positive cardiac progenitor cells and atrial contractile force in humans: A randomised controlled trial

BACKGROUND

The heart has an intrinsic ability to regenerate, orchestrated by progenitor or stem cells. However, the relative complexity of non-resident cardiac progenitor cell (CPC) therapy makes modulation of resident CPCs a more attractive treatment target. Thiamine analogues improve resident CPC function in pre-clinical models. In this double blinded randomised controlled trial (identifier: ACTRN12614000755639), we examined whether thiamine would improve CPC function in humans.

METHODS AND RESULTS

High dose oral thiamine (one gram twice daily) or matching placebo was administered 3-5 days prior to coronary artery bypass surgery (CABG). Right atrial appendages were collected at the time of CABG, and CPCs isolated. There was no difference in the primary outcome (proliferation ability of CPCs) between treatment groups. Older age was not associated with decreased proliferation ability. In exploratory analyses, isolated CPCs in the thiamine group showed an increase in the proportion of CD34^-/CD105⁺ (endoglin) cells, but no difference in CD34^-/CD90⁺ or CD34⁺ cells. Thiamine increased maximum force developed by isolated trabeculae, with no difference in relaxation time or beta-adrenergic responsiveness.

CONCLUSION

Thiamine does not improve proliferation ability of CPC in patients undergoing CABG, but increases the proportion of CD34^-/CD105⁺ cells. Having not met its primary endpoint, this study provides the impetus to re-examine CPC biology prior to any clinical outcome-based trial examining potential beneficial cardiovascular effects of thiamine.

Early dysregulation of cardiac-specific microRNA-208a is linked to maladaptive cardiac remodelling in diabetic myocardium

Background

The diabetic heart undergoes remodelling contributing to an increased incidence of heart failure in individuals with diabetes at a later stage. The molecular regulators that drive this process in the diabetic heart are still unknown.

Methods

Real-time (RT) PCR analysis was performed to determine the expression of cardiac specific microRNA-208a in right atrial appendage (RAA) and left ventricular (LV) biopsy tissues collected from diabetic and non-diabetic patients undergoing coronary artery bypass graft surgery. To determine the time-dependent changes, cardiac tissue were collected from type 2 diabetic mice at different age groups. A western blotting analysis was conducted to determine the expression of contractile proteins α- and β-myosin heavy chain (MHC) and thyroid hormone receptor-α (TR-α), the negative regulator of β-MHC. To determine the beneficial effects of therapeutic modulation of miR-208a, high glucose treated adult mouse HL-1 cardiomyocytes were transfected with anti-miR-208a.

Results

RT-PCR analysis showed marked upregulation of miR-208a from early stages of diabetes in type 2 diabetic mouse heart, which was associated with a marked increase in the expression of pro-hypertrophic β-MHC and downregulation of TR-α. Interestingly, upregulation of miR-208a preceded the switch of α-/β-MHC isoforms and the development of diastolic and systolic dysfunction. We also observed significant upregulation of miR-208a and modulation of miR-208a associated proteins in the type 2 human diabetic heart. Therapeutic inhibition of miR-208a activity in high glucose treated HL-1 cardiomyocytes prevented the activation of β-MHC and hence the hypertrophic response.

Conclusion

Our results provide the first evidence that early modulation of miR-208a in the diabetic heart induces alterations in the downstream signaling pathway leading to cardiac remodelling and that therapeutic inhibition of miR-208a may be beneficial in preventing diabetes-induced adverse remodelling of the heart.

Data supporting the activation of autophagy genes in the diabetic heart

This data article contains full list of autophagy related genes that are altered in diabetic heart. This article also shows data from in vitro cultured cardiomyocytes that are exposed the high glucose treatment to simulate hyperglycemic state in vitro. The interpretation of these data and further extensive insights into the regulation of SG biogenesis by AMPK can be found in “Type-2 diabetes increases autophagy in the human heart through promotion of Beclin-1 mediated pathway” (Munasinghe et al., in press) [1].

Type-2 diabetes increases autophagy in the human heart through promotion of Beclin-1 mediated pathway

BACKGROUND

Diabetes promotes progressive loss of cardiac cells, which are replaced by a fibrotic matrix, resulting in the loss of cardiac function. In the current study we sought to identify if excessive autophagy plays a major role in inducing this progressive loss.

METHODS AND RESULTS

Immunofluorescence and western blotting analysis of the right atrial appendages collected from diabetic and non-diabetic patients undergoing coronary artery bypass graft surgery showed a marked increase in the level of autophagy in the diabetic heart, as evidenced by increased expression of autophagy marker LC3B-II and its mediator Beclin-1 and decreased expression of p62, which incorporates into autophagosomes to be efficiently degraded. Moreover, a marked activation of pro-apoptotic caspase-3 was observed. Electron microscopy showed increased autophagosomes in the diabetic heart. In vivo measurement of autophagic flux by choloroquine injection resulted in further enhancement of LC3B-II in the diabetic myocardium, confirming increased autophagic activity in the type-2 diabetic heart. Importantly, in-vitro genetic depletion of beclin-1 in high glucose treated adult rat cardiomyocytes markedly inhibited the level of autophagy and subsequent apoptotic cell death.

CONCLUSIONS

These findings demonstrate the pathological role of autophagy in the type-2 diabetic heart, opening up a potentially novel therapeutic avenue for the treatment of diabetic heart disease.

Impaired relaxation despite upregulated calcium-handling protein atrial myocardium from type 2 diabetic patients with preserved ejection fraction

BACKGROUND

Diastolic dysfunction is a key factor in the development and pathology of cardiac dysfunction in diabetes, however the exact underlying mechanism remains unknown, especially in humans. We aimed to measure contraction, relaxation, expression of calcium-handling proteins and fibrosis in myocardium of diabetic patients with preserved systolic function.

METHODS

Right atrial appendages from patients with type 2 diabetes mellitus (DM, n = 20) and non-diabetic patients (non-DM, n = 36), all with preserved ejection fraction and undergoing coronary artery bypass grafting (CABG), were collected. From appendages, small cardiac muscles, trabeculae, were isolated to measure basal and β-adrenergic stimulated myocardial function. Expression levels of calcium-handling proteins, sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) and phospholamban (PLB), and of β1-adrenoreceptors were determined in tissue samples by Western blot. Collagen deposition was determined by picro-sirius red staining.

RESULTS

In trabeculae from diabetic samples, contractile function was preserved, but relaxation was prolonged (Tau: 74 ± 13 ms vs. 93 ± 16 ms, non-DM vs. DM, p = 0.03). The expression of SERCA2a was increased in diabetic myocardial tissue (0.75 ± 0.09 vs. 1.23 ± 0.15, non-DM vs. DM, p = 0.007), whereas its endogenous inhibitor PLB was reduced (2.21 ± 0.45 vs. 0.42 ± 0.11, non-DM vs. DM, p = 0.01). Collagen deposition was increased in diabetic samples. Moreover, trabeculae from diabetic patients were unresponsive to β-adrenergic stimulation, despite no change in β1-adrenoreceptor expression levels.

CONCLUSIONS

Human type 2 diabetic atrial myocardium showed increased fibrosis without systolic dysfunction but with impaired relaxation, especially during β-adrenergic challenge. Interestingly, changes in calcium-handling protein expression suggests accelerated active calcium re-uptake, thus improved relaxation, indicating a compensatory calcium-handling mechanism in diabetes in an attempt to maintain diastolic function at rest despite impaired relaxation in the diabetic fibrotic atrial myocardium. Our study addresses important aspects of the underlying mechanisms of diabetes-associated diastolic dysfunction, which is crucial to developing new therapeutic treatments.

Rapid onset of cardiomyopathy in STZ-induced female diabetic mice involves the downregulation of pro-survival Pim-1

Background

Diabetic women are five times more likely to develop congestive heart failure compared with two fold for men. The underlying mechanism for this gender difference is not known. Here we investigate the molecular mechanisms responsible for this female disadvantage and attempt safeguarding cardiomyocytes viability and function through restoration of pro-survival Pim-1.

Methods and Results

Diabetes was induced by injection of streptozotocin in CD1 mice of both genders. Functional and dimensional parameters measurement using echocardiography revealed diastolic dysfunction in female diabetic mice within 8 weeks after STZ-induced diabetes. This was associated with significant downregulation of pro-survival Pim-1 and upregulation of pro-apoptotic Caspase-3, microRNA-1 and microRNA-208a. Male diabetic mice did not show any significant changes at this time point (P < 0.05 vs. female diabetic). Further, the onset of ventricular remodelling was quicker in female diabetic mice showing marked left ventricular dilation, reduced ejection fraction and poor contractility (P < 0.05 vs. male diabetic at 12 and 16 weeks of STZ-induced diabetes). Molecular analysis of samples from human diabetic hearts confirmed the results of pre-clinical studies, showing marked downregulation of Pim-1 in the female diabetic heart (P < 0.05 vs. male diabetic). Finally, in vitro restoration of Pim-1 reversed the female disadvantage in diabetic cardiomyocytes.

Conclusions

We provide novel insights into the molecular mechanisms behind the rapid onset of cardiomyopathy in female diabetics. These results suggest the requirement for the development of gender-specific treatments for diabetic cardiomyopathy.

Kinky circumflex grafts: the left appendage flip maneuver

The "too-long," or redundant, circumflex graft is notorious for its tendency to form a kink. The acute angle (the kink) typically occurs over the front of the pulmonary trunk. Described herein are (1) the left appendage flip maneuver, a simple solution to correct graft kink, and (2) analysis and explanation of vein graft kink.

Effects of age and coronary artery disease on cerebrovascular reactivity to carbon dioxide in humans

Alterations in cerebrovascular reactivity to CO2, an index of cerebrovascular function, have been associated with increased risk of stroke. We hypothesised that cerebrovascular reactivity is impaired with increasing age and in patients with symptomatic coronary artery disease (CAD). Cerebrovascular and cardiovascular reactivity to CO2 was assessed at rest and during hypercapnia (5% CO2) and hypocapnia (hyperventilation) in subjects with symptomatic CAD (n=13) and age-matched old (n=9) and young (n=20) controls without CAD. Independent of CAD, reductions in middle cerebral artery blood velocity (transcranial Doppler) and cerebral oxygenation (near-infrared spectroscopy) were correlated with increasing age (r = -0.68, r = -0.51, respectively, P < 0.01). In CAD patients, at rest and during hypercapnia, cerebral oxygenation was lower (P < 0.05 vs. young). Although middle cerebral artery blood velocity reactivity was unaltered in the hypercapnic range, middle cerebral artery blood velocity reactivity to hypocapnia was elevated in the CAD and age-matched controls (P < 0.01 vs. young), and was associated with age (r = 0.62, P < 0.01). Transient drops in arterial PCO2 occur in a range of physiological and pathophysiological situations, therefore, the elevated middle cerebral artery blood velocity reactivity to hypocapnia combined with reductions in middle cerebral artery blood velocity may be important mechanisms underlying neurological risk with aging. In CAD patients, additional reductions in cerebral oxygenation may place them at additional risk of cerebral ischaemia.

Top-end aortocoronary anastomosis made easy: the visor technique

The importance of the proximal aortocoronary anastomosis is overshadowed by its lack of literary attention. This aortic connection, sometimes difficult to perform, is simplified by the Visor technique.

Rupture of aortic pseudoaneursym arising from a transverse aortotomy line 12 years following mechanical aortic valve replacement

Pseudoaneurysm formation at the site of aortotomy is a rare complication following aortic valve replacement; it appears to be more common in those whose valve is replaced for endocarditis or in those who develop an early postoperative endocarditis or sepsis. We discuss the case of a 77-year-old male, who presented 12 years following mechanical aortic valve replacement, with rupture of an ascending aortic pseudoaneurysm arising from a transverse aortotomy line. 

New shapes and sizes: a T-tube coronary conduit

A novel type of coronary artery graft named a T-tube conduit is described. This reversed saphenous graft, coming in three different variations, is useful at long arteriotomies, at revision redo anastomoses, and when size mismatch exists between vein and artery.

Fractured rib with penetrating cardiopulmonary injury

Described is an unusual injury, arising from a motorized vehicle accident, in which a detached fractured rib from a flail chest caused lung perforation and hemopericardium. The full diagnosis was only appreciated on computed tomography. Therefore, thoracotomy averted potential disaster.

Long-term function in University of Cape Town prostheses in the tricuspid position

A 55-year-old woman undergoing triple-valve replacement was found at operation to have a well preserved and functioning University of Cape Town prosthesis that had been inserted 18 years earlier for tricuspid stenosis. Case reporting, valve reappraisal, and factual updating on another case, the world's first documented tricuspid valve replacement for Ebstein's anomaly, are presented. These two remarkable in vivo successes speak well for this historic collar stud valve.

Transesophageal echocardiography in acute aortic transection

Confirming the diagnosis of acute transection of the descending aorta can be problematic. Unnecessary patient movement and time delay are often associated with conventional investigations. We describe a patient in whom such an injury was clearly and quickly defined at the bedside by transesophageal echocardiography.

Placement of an apical chest tube by a posterior intercostal approach

Apical pneumothorax due to incomplete expansion of the lung is not uncommon following thoracotomy and also occurs in some patients with recurring spontaneous pneumothorax. Standard methods of intercostal drainage may be unsatisfactory because of difficulty in placing an intercostal tube safely and accurately within the apical air space.

Tracheal stenosis caused by congenital vascular ring anomaly misinterpreted as asthma for 45 years

Dyspnoeic conditions simulating asthma are not uncommon in adult and paediatric practice. Vascular ring anomalies in particular may be misdiagnosed, resulting in unnecessary delay before corrective surgery. We report a rare case of symptomatic double aortic arch in an adult which emphasises the above points.

Bronchopleural fistula. A novel type of window thoracostomy

Bronchopleural fistula usually associated with chronic empyema after lung operations continues to occur in modern surgical practice. Successful treatment depends to a large extent on adequate dependent drainage of the empyema space. Tube thoracostomy, although useful initially, is unacceptable as long-term treatment. Window thoracostomy as currently performed is effective but unnecessarily extensive. We describe a simpler procedure, triangular window thoracostomy, for use as a permanent pleurocutaneous stoma or as an interim measure before definitive surgical treatment.

Oesophago-pericardial fistula and cardiac tamponade after oesophagoscopy

A case of oesophago-pericardial fistula following oesophagoscopy and dilatation is reported. This is a rare and usually fatal complication of oesophageal instrumentation. This case is of further interest as cardiac tamponade following a Niopam swallow subsequently occurred, and the patient survived emergency surgery.

Pericardial hemangiopericytoma as a cause of dysphagia

A 68-year-old woman was seen with recent-onset dysphagia. Investigations suggested a large retrocardiac tumor. At thoracotomy, a highly vascular tumor was found, involving the posterior and left aspect of the pericardium with attachment to the heart. The lesion was partially removed, and histopathological analysis revealed a malignant hemangiopericytoma. To our knowledge, this tumor site and its presentation have not been reported before.