Myocardial flow regulation in people with mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes/myoclonic epilepsy and ragged red fibers and other mitochondrial syndromes

The application of brain organoid for drug discovery in mitochondrial diseases

Mitochondrial diseases are difficult to treat due to the complexity and multifaceted nature of mitochondrial dysfunction. Brain organoids are three-dimensional (3D) structures derived from human pluripotent stem cells designed to mimic brain-like development and function. Brain organoids have received a lot of attention in recent years as powerful tools for modeling human diseases, brain development, and drug screening. Screening compounds for mitochondrial diseases using brain organoids could provide a more physiologically relevant platform for drug discovery. Brain organoids offer the possibility of personalized medicine because they can be derived from patient-specific cells, allowing testing of drugs tailored to specific genetic mutations. In this article, we highlight how brain organoids offer a promising avenue for screening compounds for mitochondrial diseases and address the challenges and limitations associated with their use. We hope this review will provide new insights into the further progress of brain organoids for mitochondrial screening studies.

Plasma Lipidomic Patterns in Patients with Symptomatic Coronary Microvascular Dysfunction

Coronary microvascular dysfunction (MVD) is a syndrome of abnormal regulation of vascular tone, particularly during increased metabolic demand. While there are several risk factors for MVD, some of which are similar to those for coronary artery disease (CAD), the cause of MVD is not understood. We hypothesized that MVD in symptomatic non-elderly subjects would be characterized by specific lipidomic profiles. Subjects (n = 20) aged 35–60 years and referred for computed tomography coronary angiography (CTA) for chest pain but who lacked obstructive CAD (>50% stenosis), underwent quantitative regadenoson stress-rest myocardial contrast echocardiography (MCE) perfusion imaging for MVD assessment. The presence of MVD defined by kinetic analysis of MCE data was correlated with lipidomic profiles in plasma measured by liquid chromatography and high-resolution mass spectrometry. Nine of twenty subjects had evidence of MVD, defined by reduced hyperemic perfusion versus other subjects (beta-value 1.62 ± 0.44 vs. 2.63 ± 0.99 s⁻¹, p = 0.009). Neither the presence of high-risk but non-obstructive CAD on CTA, nor CAD risk factors were different for those with versus without MVD. Lipidomic analysis revealed that patients with MVD had lower concentrations of long-carbon chain triacylglycerols and diacylglycerols, and higher concentrations of short-chain triacylglycerols. The diacylglycerol containing stearic and linoleic acid classified all participants correctly. We conclude that specific lipidomic plasma profiles occur in MVD involving saturated long-chain fatty acid-containing acylglycerols that are distinctly different from those in non-obstructive CAD. These patterns could be used to better characterize the pathobiology and potential treatments for this condition.

Quantification of PET Myocardial Blood Flow

PURPOSE OF REVIEW

The aim of this review is to provide an update on quantification of myocardial blood flow (MBF) with positron emission tomography (PET) imaging. Technical and clinical aspects of flow quantification with PET are reviewed.

RECENT FINDINGS

The diagnostic and prognostic values of myocardial flow quantification have been established in numerous studies and in various populations. MBF quantification has also shown itself to be particularly useful in the assessment of coronary microvascular dysfunction and in evaluation of cardiac allograft vasculopathy. Overall, myocardial flow reserve (MFR) and hyperemic MBF can lead to improved risk stratification by providing information complementary to that of other markers of disease severity, such as fractional flow reserve. Flow quantification enhances MPI's ability to detect both significant epicardial disease and microvascular dysfunction. With recent technological and methodological advances, flow quantification with PET is no longer restricted to cyclotron-equipped academic centers.

Myocardial blood flow and oxygen consumption in patients with Friedreich's ataxia prior to the onset of cardiomyopathy

OBJECTIVES

We tested the hypothesis, in patients with Friedreich's ataxia and no overt structural heart disease, that impairment of cardiac oxidative metabolism may be compensated for either by increased rest myocardial blood flow or more efficient oxygen consumption in performance of external work.

BACKGROUND

Friedreich's ataxia is characterized by a mutant frataxin gene, which causes mitochondrial iron overload and impaired energy production. Further, it is frequently associated with cardiomyopathy. Studies using magnetic resonance spectroscopy, however, suggest impaired cardiac energetics even in the absence of structural heart disease.

METHODS

Positron emission tomography measured rest myocardial blood flow (N-13-ammonia method) and myocardial oxygen consumption (11-C-acetate, Kmono) in Friedreich's ataxia patients (n=8; 31+/-5 years, mean+/-SD, four women) and healthy controls (n=8; 30+/-7 years, five women) matched for stroke work index and age. Stroke work index and power were determined by electrocardiogram gated positron emission tomography N-13-ammonia using modified Simpson's rule to compute left ventricular volumes.

RESULTS

Neither stroke work index nor rest myocardial blood flow differed significantly between the groups. Although myocardial oxygen consumption was lower in Friedreich's ataxia (P<0.001), Kmono/rest myocardial blood flow, an index of myocardial oxygen extraction, did not differ between the groups. Power/Kmono, an index of the efficiency of myocardial oxygen consumption, was greater in Friedreich's ataxia (P<0.04). Rest myocardial blood flow normalized to rate pressure product was lower in Friedreich's ataxia (P<0.05).

CONCLUSIONS

Prior to the onset of cardiomyopathy, selected patients with Friedreich's ataxia may compensate for impaired cardiac energetics through more efficient oxygen consumption rather than increased rest myocardial blood flow. The data illustrate a more general mechanism pertaining to metabolic regulation of myocardial blood flow and myocardial oxygen consumption.