Mitochondrial Bioenergetics Disorders

Mitochondrial Clinic

The mitochondrial clinic at CHCO is a recognized Mitochondrial Care Network site. We see patients with known mitochondrial diagnoses for ongoing management and conduct diagnostic evaluations for patients with symptoms that are likely to be due to mitochondrial disease. While not a multidisciplinary clinic, we do provide coordinated care with other specialists throughout CHCO for our pediatric patients. We do see adult patients, but our scope is limited to consultation and does not include coordination of care. We have established relationships with colleagues in audiology, ophthalmology, neurology, hepatology, gastroenterology, cardiology, endocrinology and other subspecialties to ensure that our patients with mitochondrial disease are able to see providers that are experienced in the care of patients with mitochondrial diseases. We are affiliated with the CHCO Research Institute and conduct clinical trials for patients with mitochondrial diseases that recruit from our clinic. Our clinic is closely integrated with the CHCO precision diagnostic laboratory and we can provide access to specialized functional testing of the mitochondria locally.  

Directed by Dr. Austin Larson, we have a mitochondrial clinic that is recognized as a Mitochondrial Care Network Certified Center as supported by the Mitochondrial Medicine Society (www.mitonetowrk.org/about).

Clinical Trials

We participated in a clinical trial of Elamipretide SPIMM-300 and SPIMM-301 (NCT03323749) (publication under review).

 

We are currently in start-up of several new clinical trials. Once clinical trials will begin, they will be listed here.  

 

Clinical Studies

 

Respiratory Chain Disorders

Our group is participating in the NIH-funded North American Mitochondrial Disease Consortium (NAMDC) (www.rarediseasesnetwork.org/cms/namdc) and contribute to the natural history database (study 7401 ON www.rarediseasesnetwork.org/cms/namdc/Get-Involved/Studies).  

 

We have done several clinical studies. These include:

 

Published studies:

• Liver transplantation in MNGIE syndrome
• Impact of ketogenic diet on pyruvate dehydrogenase deficiency
• A recognition method for complex V defects on newborn screening allowing rapid diagnosis
• Treatment of coenzyme Q in COQ2

 

Current studies:

• A study of the clinical features of the m.8363G>A mutation in several large families

 

Fatty Acid Oxidation Disorders

The disorders of fatty acid oxidation (FAODs) represent another group of bioenergetic disorders. My long history of involvement in these disorders included the first use of D,L-3-hydroxybutyrate (ketones) for use in multiple acyl-CoA dehydrogenase deficiency (MADD) and similar FAODs. Together with professor Terry Derks of Groningen, The Netherlands, we supported the work of the graduate student Willemijn Van Rijt for studies of the clinical presentation of MADD patients, the response through a world-wide survey to D,L-3-hydroxybutyrate treatment, and the pharmacokinetics of the two isomers D-3-hydroxybutyrate and L-3-hydroxybutyrate, which differ substantially.

 

Current Studies:

• Treatment with bezafibrate in our MADD patient is a new development with Dr. Aaina Kochhar (Principal Investigator).

The mitochondrial diagnostic laboratory is integrated into the Pathology service of Children’s Hospital Colorado. The laboratory provides functional mitochondrial testing for suspected bioenergetics disorders. These assays are available in multiple tissues: skeletal muscle, liver, heart muscle, and fibroblasts.

 

The lab actively adapts assays developed in the research laboratory into validated clinical assays and makes them widely available for clinical use.

 

Specific clinical tests include:

• Respiratory chain enzyme assays for complexes I, II, III, II-III combined, IV and citrate synthase
• in-gel activity staining after separation on a blue native PAGE gel for complexes I, II, IV and V (and for III in select tissues)
• Pyruvate dehydrogenase enzyme activity
• Complex I assembly assay in fibroblasts, tracing the pathological presence of intermediates
  

Link to Laboratory Requisition & Ordering Information: www.childrenscolorado.org/docters-and-departments/departments/pathology-laboratory-medicine/lab-requisition-order

 

Contact Person:

 

Dr. Marisa Friederich

 

Telephone: (720) 777-0528

 

Email

 

Our primary research involves diagnostic studies of primary mitochondrial disorders. Mitochondrial disorders are oxidative phosphorylation disorders that affect the function of the respiratory chain and the main substrates through the Krebs cycle. The complex dual genomic origin (both mitochondrial DNA and nuclear DNA) results in extreme phenotypic and genetic heterogeneity with already nearly 300 genetic causes identified. The past decade has seen a shift to diagnosis using next-gen sequencing (whole exome or whole genome sequencing as well as mitochondrial DNA next-gen sequencing). This has greatly improved diagnostic identification including the identification of multiple new potential genetic causes. However, it frequently results in identification of variants of unknown significance (VOUS). To resolve these VOUS, our research laboratory develops and explores functional assays and uses them to identify and confirm new genetic causes of mitochondrial dysfunction.

 

Diagnostic Assay Studies

 

We have been developing several techniques that could assist in the diagnostic evaluation of genetic causes using minimally invasive tissue of fibroblasts. Fibroblasts were rarely used in the past due to its reported low sensitivity of only about 50% in known cases of mitochondrial disorders using respiratory chain enzyme assays, although a systematic study was never done. By expanding the functional assays with several new assays, we have been able to greatly increase the diagnostic yield in fibroblasts (to the high 80%).

 

In addition to respiratory chain enzyme assays, we have added in fibroblasts: blue native PAGE with in-gel activity staining, western blot of mitochondrial proteins, complex I assembly assay, complex V ATPase enzyme assay, mitochondrial translation assay, lipoate western blot assay, aconitase mitochondrial and cytosolic, and respirometry. We are in the process of adding additional assays including complex V dependent ATP synthesis (Complex V forward reaction, supported by a Mitochondrial Gateway grant. Testing for ARS2 defects is planned.

 

We validate our assays in > 40 control fibroblast cell lines providing a good grasp of the range of normal. We are in the process of analyzing > 100 fibroblast cell lines from patients with genetically proven primary mitochondrial disorders which will allow us to derive the data on sensitivity. We have also collected more than 30 cell lines of patients with either clinical similarities to mitochondrial diseases or of disorders with known, presumed or potential secondary mitochondrial dysfunction to analyze the specificity of the functional tests. This has already shown surprising results such as finding of abnormal complex I and complex V assembly in EIF2AK3 mutant cell line, a cause of Wolcott-Ralison syndrome, in which thus far mitochondrial dysfunction had not yet been suspected, let alone documented. Overall, this comprehensive study of the diagnostic utility will evaluate over 100 patient cell lines, over 30 normal controls and 40 disease controls evaluated with at least five groups of tests to derive sensitivity and specificity (involving a total of >2300 data sets), providing a first comprehensive and systematic study of clinical utility of mitochondrial functional testing.

 

This study is funded by the NAMDC U54 grant with added support from CHCO Foundation Summits for Samantha, CU Foundation Mitochondrial Fund, and Miracles for Mito.

 

New Genetic Causes of Mitochondrial Dysfunction

 

Through our diagnostic work and our clinic we have come into contact with patients with new tentative genetic causes of mitochondrial dysfunction. We have provided functional assays to support this finding and to begin to explore the biochemical mechanisms for the pathological dysfunction. We have thus far already evaluated 7 new nuclear genes that had not yet been identified or 7 genes for whom only a single or very few prior publications existed (for instance new genes: CARS2, TMEM126B, NDUFB10, ATP5FD1, PMPCB, Gat^CAB complex, SQOR, with a new complex V defect in writing. Other genes with functional characterization include: MRPL44, HSD10, GFM1, FARS2, NUBPL, and a few newly recognized mitochondrial DNA mutations.

 

Mitochondrial Hepatopathies

 

We have been a diagnostic center for the mitochondrial hepatopathies (mitochondrial liver diseases) as part of the ChiLDREN consortium directed by Dr. Ron Sokol. We are currently evaluating the mitochondrial protein biomarkers FGF21 and GDF15 for their use in mitochondrial liver diseases, whereas past studies have exclusively focused on myopathies.

 

Other Aspects of Mitochondrial Diseases

 

We are also studying the one-carbon metabolism aspect of the universal mitochondrial stress response in muscle from patients with single mtDNA deletion syndromes (supported by a pilot grant of the NAMDC consortium awarded to Dr. Mike Swanson).

Our research is funded in part by grants from the NIH through the North American Mitochondrial Disease Consortium (NAMDC), and through the NIDDK.

 

Our mitochondrial center is funded in part through the efforts of the non-profit charitable organization Miracles for Mito (https://www.miraclesformito.org). Philanthropic contributions have been made through the Children’s Hospital Colorado Foundation Summits for Samantha Fund, and through the University of Colorado Foundation Mitochondrial Research Fund. Miracles for Mito have raised nearly one million dollars that supports our mitochondrial center. They also are a resource for patients and their families affected by mitochondrial disease.

How Can I Help Support this Work?

To give to the CU Foundation Mitochondrial Research Fund, please contact Jerry Sinning at 303-724-7825 or email.

Online donations accepted at https://giving.cu.edu/fund/write-fund  (enter “Mitochondrial Research Fund #02-22648” in the Comments box when making your contribution).