A novel unstable mutation in mitochondrial DNA responsible for maternally inherited diabetes and deafness

OBJECTIVE

The m.3243A>G mutation in mitochondrial DNA (mtDNA) is responsible for maternally inherited diabetes and deafness (MIDD). Other mtDNA mutations are extremely rare.

RESEARCH DESIGN AND METHODS

We studied a patient presenting with diabetes and deafness who does not carry the m.3243A>G mutation.

RESULTS

We identified a deficiency of respiratory chain complex I in the patient’s fibroblasts. mtDNA sequencing revealed a novel mutation that corresponds to an insertion of one or two cytosine residues in the coding region of the MT-ND6 gene (m.14535_14536insC or CC), leading to premature stop codons. This heteroplasmic mutation is unstable in the patient’s somatic tissues.

CONCLUSIONS

We describe for the first time an unstable mutation in a mitochondrial gene coding for a complex I subunit, which is responsible for the MIDD phenotype. This mutation is likely favored by the m.14530T>C polymorphism, which is homoplasmic and leads to the formation of an 8-bp polyC tract responsible for genetic instability.The most common form of maternally inherited diabetes and deafness (MIDD) is associated with the m.3243A>G mutation in mitochondrial DNA (mtDNA), which is located in the tRNA^Leu gene (1). The mutation that affects up to 1% of diabetic patients leads to both impaired glucose-induced insulin secretion (2) and progressive β-cell loss (3). However, in some rare cases characterized by a highly suggestive phenotype but without m.3243A>G mutation, geneticists should look for other diabetes-prone variants (4). Here, we describe a patient presenting an MIDD phenotype who carries a novel unstable mutation in the mitochondrial MT-ND6 gene responsible for a deficiency in the respiratory chain complex I.     

Risk factors for post-traumatic stress disorder symptoms following critical illness requiring mechanical ventilation: a prospective cohort study

Introduction  

Post-traumatic stress disorder (PTSD) has been identified in a significant portion of intensive care unit (ICU) survivors. We sought to identify factors associated with PTSD symptoms in patients following critical illness requiring mechanical ventilation.     

Anatomical Congruence of Metabolic and Electromagnetic Activation Signals during a Self-Paced Motor Task: A Combined PET–MEG Study

We have investigated the degree of spatial correlation between the cerebral blood flow variations measured by positron emission tomography (PET) and the electromagnetic sources as measured by magnetoencephalography (MEG) in five subjects while performing a self-paced right index finger tapping task. Data were processed independently for each technique using both single-case and intersubject analysis. PET and MEG were coregistered with anatomical magnetic resonance images for each subject. Both extension and flexion motor-related fields were extracted from the MEG signal. Using the single dipole model we identified the motor evoked field 1 (MEF1) in all subjects and the motor field (MF) in three subjects. Individual and intersubject averaged PET data showed consistent contralateral primary sensorimotor (PSM) hand area and bilateral supplementary motor area activation. MEG individual and intersubject averaged results demonstrated that both MEF1 and MF dipoles were localized within the PSM PET activated area. Individual PSM mass center to dipole distance was 12 and 15.3 mm on average for the MEF1 and the MF component, respectively. For the same components, the intersubject averaged analysis shows distances between the PETZ-score maximum and the dipole locations of 6.3 and 15.0 mm, respectively. These results show that PET and MEG MEF1 activation signals spatially coincide within instrumental, registration, and modeling errors.     

Subject-specific cardiovascular system model-based identification and diagnosis of septic shock with a minimally invasive data set: animal experiments and proof of concept

A cardiovascular system (CVS) model and parameter identification method have previously been validated for identifying different cardiac and circulatory dysfunctions in simulation and using porcine models of pulmonary embolism, hypovolemia with PEEP titrations and induced endotoxic shock. However, these studies required both left and right heart catheters to collect the data required for subject-specific monitoring and diagnosis-a maximally invasive data set in a critical care setting although it does occur in practice. Hence, use of this model-based diagnostic would require significant additional invasive sensors for some subjects, which is unacceptable in some, if not all, cases. The main goal of this study is to prove the concept of using only measurements from one side of the heart (right) in a 'minimal' data set to identify an effective patient-specific model that can capture key clinical trends in endotoxic shock. This research extends existing methods to a reduced and minimal data set requiring only a single catheter and reducing the risk of infection and other complications-a very common, typical situation in critical care patients, particularly after cardiac surgery. The extended methods and assumptions that found it are developed and presented in a case study for the patient-specific parameter identification of pig-specific parameters in an animal model of induced endotoxic shock. This case study is used to define the impact of this minimal data set on the quality and accuracy of the model application for monitoring, detecting and diagnosing septic shock. Six anesthetized healthy pigs weighing 20-30 kg received a 0.5 mg kg(-1) endotoxin infusion over a period of 30 min from T0 to T30. For this research, only right heart measurements were obtained. Errors for the identified model are within 8% when the model is identified from data, re-simulated and then compared to the experimentally measured data, including measurements not used in the identification process for validation. Importantly, all identified parameter trends match physiologically and clinically and experimentally expected changes, indicating that no diagnostic power is lost. This work represents a further with human subjects validation for this model-based approach to cardiovascular diagnosis and therapy guidance in monitoring endotoxic disease states. The results and methods obtained can be readily extended from this case study to the other animal model results presented previously. Overall, these results provide further support for prospective, proof of concept clinical testing with humans.     

Treatment options for articular cartilage defects of the knee

The treatment of symptomatic articular cartilage defects of the knee has evolved tremendously in the past decade. Previously, there were limited treatment options available to patients who suffered from either partial-thickness or full-thickness cartilage lesions. Because articular cartilage has a limited capacity for healing, patients were often treated symptomatically until they became candidates for osteotomy or total joint replacement. Recently, both reparative and restorative procedures have been developed to address this significant source of morbidity in young active patients. Microfracture is a reparative technique that induces a healing response to occur in an area of articular cartilage damage. Osteochondral autografts and allografts in addition to autologous chondrocyte implantation are restorative techniques aimed at recreating a more normal articular surface. Both types of procedures have been developed to alleviate the symptoms associated with focal chondral defects, as well as limit their potential to progress to a diffuse degenerative arthritis. Treatment can vary depending on both cartilage defect and patient factors. This article summarizes the various treatment options that have recently become available.     

Usefulness of procalcitonin for the diagnosis of ventilator-associated pneumonia

OBJECTIVE: To assess the predictive capacity for the diagnosis of ventilator-associated pneumonia (VAP) of serum procalcitonin levels before and on the day it is suspected. DESIGN AND SETTING: Single-center observational study in the intensive care unit of a teaching hospital. PATIENTS AND PARTICIPANTS: Consecutive patients whose serum procalcitonin levels were available on the day that VAP was clinically suspected (day 1) and at some time within the preceding 5 days ("before"). MEASUREMENTS AND RESULTS: Serum procalcitonin levels were determined on day 1 and "before". Among the 73 suspected episodes VAP was confirmed by quantitative bronchoalveolar lavage cultures in 32 and refuted in 41. Respective median "before" procalcitonin levels were 1.89 ng/ml (interquartile range 0.18-6.01) and 2.14 (0.76-5.75) in patients with and without VAP, but their respective median day-1 procalcitonin levels did not differ: 1.07[Symbol: see text]ng/ml (0.39-6.57) vs. 1.40 (0.67-3.39). On day 1 a 0.5[Symbol: see text]ng/ml procalcitonin threshold had 72% sensitivity but only 24% specificity for diagnosing VAP. Between "before" and day 1, procalcitonin increased in 41% and 15% of patients with and without VAP, respectively. Thus a procalcitonin rise on day 1, compared to its "before" level, had 41% sensitivity and 85% specificity for diagnosing VAP, with respective positive and negative predictive values of 68% and 65%. CONCLUSIONS: Crude values and procalcitonin rise had poor diagnostic value for VAP in this particular setting and thus should not be used to initiate antibiotics when VAP is clinically suspected.     

Glycosylated flavones as selective inhibitors of topoisomerase IV.

Three flavonoids which promoted Escherichia coli topoisomerase IV-dependent DNA cleavage were isolated from cottonseed flour and identified as quercetin 3-O-beta-D-glucose-[1,6]-O-alpha-L-rhamnose (rutin), quercetin 3-O-beta-D-galactose-[1,6]-O-alpha-L-rhamnose, and quercetin 3-O-beta-D-glucose (isoquercitrin). The most active one (rutin) also inhibited topoisomerase IV-dependent decatenation activity (50% inhibitory concentration, 64 microg/ml) and induced the SOS response of a permeable E. coli strain. Derivatives of quercetin glycosylated at position C-3 were shown to induce two site-specific DNA cleavages of pBR322 DNA, which were mapped by DNA sequence analysis to the gene encoding resistance to tetracycline. Cleavage at these sites was hardly detectable in cleavage reactions with quercetin or fluoroquinolones. None of the three flavonoids isolated from cottonseeds had any stimulatory activity on E. coli DNA gyrase-dependent or calf thymus topoisomerase II-dependent DNA cleavage, and they were therefore specific to topoisomerase IV. These results show that selective inhibitors of topoisomerase IV can be derived from the flavone structure. This is the first report on a DNA topoisomerase inhibitor specific for topoisomerase IV.     

Effects of Four Different Meal Types on the Population Pharmacokinetics of Single-Dose Rifapentine in Healthy Male Volunteers

Rifapentine and its primary metabolite, 25-desacetyl rifapentine, are active against mycobacterium tuberculosis. The objectives of this study were to describe the population pharmacokinetics of rifapentine and 25-desacetyl rifapentine in fasting and fed states. Thirty-five male healthy volunteers were enrolled in an open-label, randomized, sequential, five-way crossover study. Participants received a single 900-mg dose of rifapentine after meals with high fat (meal A), bulk and low fat (meal B), bulk and high fat (meal C), high fluid and low fat (meal D), or 200 ml of water (meal E). Venous blood samples were collected over 72 h after each rifapentine dose, and plasma was analyzed for rifapentine and 25-desacetyl rifapentine using high-performance liquid chromatography. Pharmacokinetic data were analyzed by nonlinear mixed-effect modeling using NONMEM. Compared with the fasting state, meal A had the greatest effect on rifapentine oral bioavailability, increasing it by 86%. Meals B, C, and D resulted in 33%, 46%, and 49% increases in rifapentine oral bioavailability, respectively. Similar trends were observed for 25-desacetyl rifapentine. As meal behavior has a substantial impact on rifapentine exposure, it should be considered in the evaluation of optimal dosing approaches.Rifapentine (RFP), a cyclopentyl rifamycin, is an orally administered drug registered by the Food and Drug Administration (FDA) for the treatment of pulmonary tuberculosis (TB). It exerts its antibacterial activity through inhibition of DNA-dependent RNA polymerase in susceptible strains of Mycobacterium tuberculosis (32). RFP has a microbiologically active metabolite, 25-desacetyl rifapentine (25-DRFP) (10). RFP has a long half-life (5, 17) and superior in vitro potency against M. tuberculosis in comparison with rifampin and rifabutin (10), making it an attractive candidate for shortening and simplifying antitubercular therapy.Currently, RFP is dosed at 600 mg either once weekly or twice weekly in human immunodeficiency virus (HIV)-negative patients with noncavitary TB (2). There is concern that the development of acquired rifamycin monoresistance (ARR), treatment failure, and relapse may be associated with intermittent dosing (4, 20), insufficient companion drug exposure (33), or low rifamycin concentrations (9, 21). RFP''s sterilizing effect has been shown to be dose dependent in murine studies which suggest that daily doses of RFP may reduce treatment duration to just 3 months (25, 26, 37), and higher doses of RFP are associated with improved early bactericidal activity in humans (29). Clinical trials are currently evaluating new antituberculosis regimens containing higher doses of RFP used intermittently or daily doses of RFP. Concomitant food has a marked effect on RFP absorption (6). The effect of food on systemic RFP exposure may therefore impact treatment activity and safety. The aim of this study was to investigate the effect of meals differing in fat and bulk content on the rate and extent of RFP absorption and 25-DRFP disposition. The study was designed to include meals comprising largely maize, a staple cereal in many parts of Africa and South America, and a light meal (i.e., a reconstituted powdered chicken soup). The study was conducted in 1999 shortly after the release of results from studies evaluating intermittent 600-mg doses of rifapentine, which displayed unacceptably high relapse rates in patients with lung cavities or immune suppression. It was therefore anticipated that future studies would evaluate higher doses of the drug.     

Effects of multiple daily injection therapy with Humalog mixtures versus separately injected insulin lispro and NPH insulin in adults with type I diabetes mellitus

BACKGROUND: Injection of insulin lispro (LP) before meals provides a more physiologic insulin activity profile than regular human insulin, but the relatively short duration of action of LP may allow the blood glucose (BG) level to increase during the late postprandial period (4-7 hours after meals) unless basal insulin is optimally replaced. One approach to basal insulin optimization has been to combine small doses of NPH with LP before meals. When used in a similar fashion, premixed, fixed-ratio insulin preparations containing LP and NPL (an LP-based intermediate-acting insulin) may provide the basis for an optimized basal-bolus insulin regimen. OBJECTIVE: This study assessed mean late postprandial glycemic control during treatment with a premixed formulation consisting of a high proportion of LP (75% LP/25% NPL; H) and a premixed formulation consisting of a medium proportion of LP (50% LP/50% NPL; M). The H/M formulation was given before meals and was compared with treatment with preprandial LP + NPH (LP + N) in patients with type 1 diabetes mellitus (DM). METHODS: This multicenter, randomized, open-label, 2-period crossover study was conducted at 4 centers in Italy and 1 center in France. Patients eligible for the study had type 1 DM, were > or = 18 years of age, and had a glycosylated hemoglobin (HbA(1c)) <150% of the upper limit of normal. Patients were randomly assigned to 1 of 2 treatment sequences: LP self-mixed with NPH before meals plus NPH alone at bedtime for 8 weeks (LP + N) followed by preprandial H or M, plus NPH alone at bedtime for 8 weeks (H/M), or the opposite sequence. Assessments included 8-point self-monitored BG profiles, HbA(1c), and hypoglycemia (any sign or symptom of hypoglycemia or BG < 3.0 mmol/L [<54.0 mg/dL]). The primary outcome measure was the late postprandial BG value, calculated as the mean of the combined prelunch (late postbreakfast), predinner (late postlunch), and bedtime (late postdinner) values. RESULTS: A total of 89 patients with type 1 DM were enrolled (44 men, 45 women; mean [SD] age, 38.3 [12.8] years; mean [SD] body weight, 70.8 [11.6] kg; mean [SD] body mass index, 24.6 [3.0] kg/m(2); mean [SD] duration of diabetes, 17.8 [10.5] years; mean HbA(1c), 7.9% [0.88%]). The mean (SD) late postprandial BG values were similar between treatments (8.9 [2.1] mmol/L [160.3 (37.8) mg/dL] for H/M vs 9.0 [1.8] mmol/L [162.1 (32.4) mg/dL] for LP + N), as were the end point HbA(1c) values (7.8% [0.9%] for H/M vs 7.9% [0.8%] for LP + N). The rate of hypoglycemia was significantly higher during treatment with H/M, primarily because of episodes occurring between 12 PM and 6 PM, but was relatively low in both groups (mean/median rate per patient per 30 days: 2.87/2.14 for H/M and 2.11/1.07 for LP + N; P < 0.05). CONCLUSIONS: In this population of patients with type 1 DM, preprandial H/M provided an effective alternative regimen for prandial and basal insulin replacement. Late postprandial BG control, an indicator of basal insulin sufficiency, was similar to that achieved with an intensified regimen of LP + N injected separately before meals, and the end point HbA(1c) was similar between the 2 treatments.