Patient perspective on exercise practices, preferences, and barriers in pediatric nonalcoholic fatty liver disease: A multicenter survey.

Background/Aims: Nonalcoholic fatty liver disease (NAFLD) is prevalent among children, and lifestyle modification is the primary treatment approach. However, the optimal exercise duration, frequency, and intensity for managing NAFLD remain undefined. This study aimed to gain insights from the patient perspective by examining exercise behaviors, preferences, and barriers in children with NAFLD. Methods: A multicenter survey was conducted among children 8-18 years with NAFLD in pediatric gastroenterology clinics. Participants completed a questionnaire on exercise practices, preferences, and barriers, while parents completed a questionnaire on their willingness and ability to support their child's exercise. Data were analyzed using χ 2 test with Yates' correction and two-sample t test. Results: The study included 408 children with NAFLD, with a mean age of 13.8 years. Approximately 52.5% of participants had physical education classes at school, while 59.5% engaged in extracurricular exercise, averaging 3.7 days per week. However, 11.5% reported no physical activity. A significant majority (81.1%) expressed interest in increasing their exercise levels, primarily driven by health-related factors. Time-related constraints were the most cited barriers to exercise (53.7%). Approximately 80% of parents demonstrated willingness and ability to support their child's exercise regimen. Conclusion: This study provides insights into exercise behaviors, preferences, and barriers among children with NAFLD. Half of the children lacked exercise opportunities at school but expressed interest in increasing their physical activity. Time limitation was the major obstacle cited. Parents are motivated to support increased physical activity. Exercise intervention programs for NAFLD should consider the perspective of the children and their families.

Predicting patients with dementia most at risk of needing psychiatric in-patient or enhanced community care using routinely collected clinical data: retrospective multi-site cohort study.

BACKGROUND: Dementia is a common and progressive condition whose prevalence is growing worldwide. It is challenging for healthcare systems to provide continuity in clinical services for all patients from diagnosis to death. AIMS: To test whether individuals who are most likely to need enhanced care later in the disease course can be identified at the point of diagnosis, thus allowing the targeted intervention. METHOD: We used clinical information collected routinely in de-identified electronic patient records from two UK National Health Service (NHS) trusts to identify at diagnosis which individuals were at increased risk of needing enhanced care (psychiatric in-patient or intensive (crisis) community care). RESULTS: We examined the records of a total of 25 326 patients with dementia. A minority (16% in the Cambridgeshire trust and 2.4% in the London trust) needed enhanced care. Patients who needed enhanced care differed from those who did not in age, cognitive test scores and Health of the Nation Outcome Scale scores. Logistic regression discriminated risk, with an area under the receiver operating characteristic curve (AUROC) of up to 0.78 after 1 year and 0.74 after 4 years. We were able to confirm the validity of the approach in two trusts that differed widely in the populations they serve. CONCLUSIONS: It is possible to identify, at the time of diagnosis of dementia, individuals most likely to need enhanced care later in the disease course. This permits the development of targeted clinical interventions for this high-risk group.

Prevalence of Adolescents Meeting Criteria for Metabolic and Bariatric Surgery.

BACKGROUND AND OBJECTIVES: The American Academy of Pediatrics endorses metabolic and bariatric surgery (MBS) as a safe and effective treatment of severe obesity in children with class 3 obesity or with class 2 obesity and qualifying comorbidities. The study objective was to determine eligibility and characteristics of adolescents who qualify for MBS based on American Academy of Pediatrics guidelines. METHODS: This retrospective cohort study analyzed electronic health record data of 603 051 adolescents aged 13 to 17 years between January 1, 2018, and December 31, 2021. Centers for Disease Control and Prevention criteria were used to define obesity classes 2 and 3. Multivariable logistic regression was used to evaluate the factors associated with meeting MBS eligibility criteria. RESULTS: Of the 603 041 adolescents evaluated, 22.2% had obesity (12.9% class 1, 5.4% class 2, and 3.9% class 3). The most frequently diagnosed comorbid conditions were gastroesophageal reflux disease (3.2%), hypertension (0.5%), and nonalcoholic fatty liver disease (0.5%). Among adolescents with class 2 obesity, 9.1% had 1 or more comorbidities qualifying for MBS, and 4.4% of all adolescents met the eligibility criteria for MBS. In multivariable modeling, males, Black and Hispanic adolescents, and those living in more deprived neighborhoods were more likely to meet MBS eligibility criteria. CONCLUSIONS: Overall, 1 in 23 adolescents met the eligibility criteria for MBS. Demographic and social determinants were associated with a higher risk for meeting these criteria. The study suggests that the health care system may face challenges in accommodating the demand for MBS among eligible adolescents.

Social-Emotional Learning for Whom? Implications of a Universal SEL Program and Teacher Well-being for Teachers' Interactions with Students.

Social-emotional learning interventions are intended to improve classroom dynamics and have the potential to enhance the well-being of students and their teachers. Using data drawn from an effectiveness trial of the Social Skills Improvement System SEL Edition Classwide Intervention Program (SSIS SEL CIP; Elliott and Gresham in SSIS SEL Edition Classwide Intervention Program manual, Pearson, Inc., 2017), the present quantitative study explored associations between classroom implementation of a universal SEL program, teachers' emotional well-being, and teacher-student interactions. The results from a sample of 80 first- and second-grade teachers located in three socioeconomically and geographically diverse regions of the USA indicated that implementation of the SSIS SEL CIP curriculum was positively associated with teachers' classroom organization skills at the end of the year. Findings also revealed an interaction between treatment condition and teacher emotional well-being such that control teachers with lower well-being also had lower quality classroom organization but this association did not exist for teachers in the intervention condition. Findings suggest that implementation of the SSIS SEL CIP may help to preserve positive teacher-student interactions even when teachers are reporting lower levels of emotional well-being.

Knowledge Hiding in Emergency Ambulance Healthcare Settings: Its Mediating Role in the Relationship between Organizational Support and Affective Commitment and Organizational Citizenship Behaviours.

Knowledge hiding-an intentional attempt to withhold or conceal knowledge from others-has been reported by recent studies to be a negative phenomenon in the workplace. Considering the importance of knowledge for organizational performance, this study intends to advance understanding by investigating the mediating role of knowledge hiding on the relationship between perceived organizational support and affective commitment as predictors and organizational citizenship behaviors and turnover intentions as outcomes. Using a cross-sectional design, the study was conducted in emergency ambulance healthcare settings on 305 medical or paramedical professionals. As indicated by structural equation modeling results, perceived organizational support and affective commitment positively predicted organizational citizenship behaviors but negatively predicted turnover intentions. Also, knowledge hiding was negatively associated with perceived organizational support, affective commitment, and organizational citizenship behaviors and positively with turnover intentions. Moreover, knowledge hiding mediated the relationship between perceived organizational support and affective commitment as predictors and organizational citizenship behaviors, respectively turnover intentions, as dependent variables.

The ß-NGF/TrkA Signalling Pathway Is Associated With the Production of Anti-Nucleoprotein IgG in Convalescent COVID-19.

Background: The presentation of SARS-CoV-2 infection varies from asymptomatic to severe COVID-19. Similarly, high variability in the presence, titre and duration of specific antibodies has been reported. While some host factors determining these differences, such as age and ethnicity have been identified, the underlying molecular mechanisms underpinning these differences remain poorly defined. Methods: We analysed serum and PBMC from 17 subjects with a previous PCR-confirmed SARS-CoV-2 infection and 10 unexposed volunteers following the first wave of the pandemic, in the UK. Anti-NP IgG and neutralising antibodies were measured, as well as a panel of infection and inflammation related cytokines. The virus-specific T cell response was determined by IFN-γ ELISPOT and flow cytometry after overnight incubation of PBMCs with pools of selected SARS-CoV-2 specific peptides. Results: Seven of 17 convalescent subjects had undetectable levels of anti-NP IgG, and a positive correlation was shown between anti-NP IgG levels and the titre of neutralising antibodies (IC50). In contrast, a discrepancy was noted between antibody levels and T cell IFN-γ production by ELISpot following stimulation with specific peptides. Among the analysed cytokines, ß-NGF and IL-1α levels were significantly different between anti-NP positive and negative subjects, and only ß-NGF significantly correlated with anti-NP positivity. Interestingly, CD4+ T cells of anti-NP negative subjects expressed lower amounts of the ß-NGF-specific receptor TrkA. Conclusions: Our results suggest that the ß-NGF/TrkA signalling pathway is associated with the production of anti-NP specific antibody in mild SARS-CoV-2 infection and the mechanistic regulation of this pathway in COVID-19 requires further investigation.

A General Bayesian Multidimensional Item Response Theory Model for Small and Large Samples.

Although item response theory (IRT) models such as the bifactor, two-tier, and between-item-dimensionality IRT models have been devised to confirm complex dimensional structures in educational and psychological data, they can be challenging to use in practice. The reason is that these models are multidimensional IRT (MIRT) models and thus are highly parameterized, making them only suitable for data provided by large samples. Unfortunately, many educational and psychological studies are conducted on a small scale, leaving the researchers without the necessary MIRT models to confirm the hypothesized structures in their data. To address the lack of modeling options for these researchers, we present a general Bayesian MIRT model based on adaptive informative priors. Simulations demonstrated that our MIRT model could be used to confirm a two-tier structure (with two general and six specific dimensions), a bifactor structure (with one general and six specific dimensions), and a between-item six-dimensional structure in rating scale data representing sample sizes as small as 100. Although our goal was to provide a general MIRT model suitable for smaller samples, the simulations further revealed that our model was applicable to larger samples. We also analyzed real data from 121 individuals to illustrate that the findings of our simulations are relevant to real situations.

Circulating TNF-like protein 1A (TL1A) is elevated early in rheumatoid arthritis and depends on TNF.

BACKGROUND: The tumor necrosis factor (TNF) superfamily cytokine TNF-like protein 1A (TL1A) and its receptor DR3 are essential for diverse animal models of autoimmune disease and may be pathogenic in rheumatoid arthritis (RA). However, the relationship of TL1A to disease duration, activity, and response to anti-TNF and other therapies in RA is not clear. METHODS: We measured soluble TL1A in synovial fluid (SF), serum, or plasma from RA first-degree relatives (FDRs) and in early RA and established disease. We measured the effects of anti-TNF and methotrexate (MTX) therapy on circulating TL1A from multiple independent RA treatment trials. We also determined the ability of a blocking anti-TL1A antibody to inhibit clinical disease and articular bone destruction in the murine collagen-induced arthritis (CIA) model of human RA. RESULTS: Soluble TL1A was specifically elevated in the blood and SF of patients with RA compared to patients with other diseases and was elevated early in disease and in at-risk anti-cyclic citrullinated peptide (CCP) (+) first-degree relatives (FDRs). Therapeutic TNF inhibition reduced serum TL1A in both responders and non-responders, whereas TL1A declined following MTX treatment only in responders. In murine CIA, TL1A blockade was clinically efficacious and reduced bone erosions. CONCLUSIONS: TL1A is specifically elevated in RA from early in the disease course and in at-risk FDRs. The decline in TL1A after TNF blockade suggests that TL1A levels may be a useful biomarker for TNF activity in RA. These results support the further investigation of the relationship between TL1A and TNF and TL1A blockade as a potential therapeutic strategy in RA.

Preoperative prealbumin and transferring: Relation to 30-day risk of complication in elective spine surgical patients.

OF BACKGROUND DATA: There is growing interest in identifying nutritional biomarkers associated with poor outcomes of elective spine surgery. Prealbumin and transferrin are both biomarkers of nutritional status that can be obtained from clinical laboratories. However, associations of preoperative measures of these nutritional biomarkers across their range with risk of complications from spine surgery have not been fully investigated. OBJECTIVE: Determine associations of preoperative prealbumin and transferrin levels with 30-day risk of complication among elective spine surgery patients. STUDY DESIGN: Cohort study with preoperative prealbumin and transferrin collected as standard of care. OUTCOME MEASURES: 30-day risk of medical complication. METHODS: Data were obtained from medical records of 274 consecutive adult patients ages ≥50 years who underwent elective spine surgery from June 2013 to June 2014. Prealbumin (mg/dL), serum transferrin (mg/dL), and preoperative factors were abstracted from medical records. Prealbumin and transferrin levels were categorized into quartiles and as below versus median or higher. The primary outcome measure was 30-day risk of medical complication, such as renal failure or infections. Associations of the biomarkers with outcome risk were assessed with chi-square tests and with risk ratios (RR) and 95% confidence intervals (CI) estimated with multivariable log-binomial regression. RESULTS: The 274 adults studied had a median prealbumin level of 27.4 mg/dL and a median transferrin level of 265.0 mg/dL. The 30-day risk of complication was 12.8% (95% CI: 8.8%-16.7%). Risk of complication did not vary by quartile for either prealbumin (P = .26) or transferrin (P = .49) and was not associated either with prealbumin (below median, RR = 1.1, 95% CI: 0.8, 1.5) or transferrin (below median, RR = 1.1, 95% CI: 0.8, 1.6). CONCLUSIONS: Among adults undergoing elective spine surgery, the 30-day risk of complication was not associated with prealbumin or transferrin. Nutrition status, as measured by prealbumin and transferrin, does not appear to be associated with complication risk. LEVEL OF EVIDENCE: Level III.

Toxicity Patterns of Clinically Relevant Metal Oxide Nanoparticles.

Nanostructured drugs are being approved for clinical use, although there is a serious deficit of systematic studies of these materials. Data on toxicity of nanoparticles (NPs) can vary due to different methods of preparation, size, and shape. We investigated the toxicity against cultured human cells, the acute toxicity in mice, and the influence on conjugative transfer of antibiotic resistance genes of clinically relevant NPs such as TiO2, ZrO2, HfO2, Ta2O5, Fe3O4, and AlOOH. NPs were synthesized as aqueous sols by the same method in aqueous solution, with almost identical size 2-10 nm. None of these NPs was cytotoxic at concentrations compatible with water solubility. Furthermore, TiO2, HfO2, Ta2O5, Fe3O4, and AlOOH were not toxic to mice after oral administration. However, ZrO2 showed rather high toxicity, with LD50 2277.8 mg/kg. Experiments with plasmid transfer between bacteria demonstrated that AlOOH NPs were the most hazardous since this material promoted the emergence of resistance to antibiotics. Thus, although our metal oxide NPs are largely non-toxic, their properties may differ in specific biological situations.

The magnitude of angular and translational displacement of dens fractures is dependent on the sagittal alignment of the cervical spine rather than the force of injury.

BACKGROUND CONTEXT: Although it is generally believed that the magnitude of dens fracture displacement is proportional to the amount of force applied to the cervical spine during injury, the factors responsible for displacement have not been studied. PURPOSE: Our aim was to determine factors that contribute to horizontal and angular displacement of dens fractures. STUDY DESIGN/SETTING: We conducted a retrospective review of adult patients who were admitted to our level 1 trauma center between January 1, 2008 and December 31, 2013. PATIENT SAMPLE: Angular and horizontal displacements of the fractured dens in 57 patients were measured. Subjects were grouped based on mechanism of fracture: motor vehicle accident, ground level fall, and higher falls. OUTCOME MEASURES: Cervical lordosis was measured between C2 and T1. C3-C4, C4-C5, C5-C6, and C6-C7 disc inclination angles were measured. Anteroposterior sagittal balance was assessed by comparing the sagittal position of the C2 body with the C7 body. METHODS: Data were analyzed using Pearson correlations, independent t tests, and support vector regression to construct predictive models that determine factors contributing to the angular and horizontal displacements. RESULTS: The mean horizontal displacement of the fractured dens was not significantly different among groups. However, the dens in those with ground level falls had a significantly greater mean fracture angle compared with the higher energy trauma groups (p=.01). There were positive correlations between angular displacement and C5-C6 disc space inclination angle (r=0.67, p<.01) and C6-C7 disc space inclination angle (r=0.61, p<.01). There were positive correlations between horizontal displacement and C6-C7 inclination angle (r=0.40, p<.01) and sagittal alignment (r=0.32, p<.01). The predictive model using all variables demonstrated that angular fracture displacement was only dependent on C5-C6 disc space inclination angle. Horizontal displacement was only dependent on C6-C7 inclination angle and anteroposterior sagittal balance. CONCLUSIONS: Disc space inclination angles of the lower cervical spine and the cervical sagittal balance most contribute to the magnitude of angular and horizontal displacement of the dens after fracture.

Development and Validation of an HPLC-UV Assay to Quantify Plasma Levels of Sulfametrol: A Preferential Antibiotic in Children.

BACKGROUND: Sulfonamides in combination with trimethoprim are frequently used antibiotics. They work synergistic. In infections with Pneumocystis jiroveci or Stenotrophomonas maltophilia, higher dosages are indicated than in other infections. Therapeutic drug monitoring (TDM) is warranted to assure the efficacy while limiting toxicity. Although trimethoprim in combination with sulfamethoxazole is the most common combination with established TDM target concentrations, the intravenous formulation is not suited for children because of its additives ethanol and propylene glycol to increase solubility. An alternative can be sulfametrol in combination with trimethoprim. When sulfametrol was introduced in the hospital, there was a need for a TDM method for sulfametrol. METHODS: A High Pressure Liquid Chromatography-Ultraviolet (HPLC-UV) detection method for sulfametrol determination in plasma was developed and validated according to the International Conference on Harmonization guidelines. Linearity, limit of detection, lower limit of quantification, recovery, process efficiency, selectivity, within-run precision, between-run precision, and sample stability were tested. RESULTS: All tested parameters met the required criteria. For linearity, r was 0.9948, lower limit of quantification was 10 mg/L, and limit of detection was 6 mg/L. Recovery was 100.4% and process efficiency 94.4%. Selectivity was met with no interfering peaks at the retention time of 4.2 minutes. Between-run precision and within-run precision were evaluated by replicating quality control levels, resulting in a within-run relative average standard deviation of 0.8% and a between-run relative standard deviation of 2.3%. Recovery of the samples after storing 8 days was 101.9% and recovery of already tested vials was 98.8% after 48 hours. CONCLUSIONS: In conclusion, an HPLC-UV method for sulfametrol determination in human plasma was developed and validated. The method is fast, accurate, reproducible, and has a short analysis time. It is now being used in routine TDM in our clinic.

Prevalence of degenerative changes of the atlanto-axial joints.

BACKGROUND CONTEXT: Degeneration of the atlantodens and atlanto-axial joints is associated with cervical spine pain and may also be associated with an increased risk of dens fracture. However, there is paucity of literature describing the prevalence of specific degenerative changes in the atlantodens and atlanto-axial facet joints. PURPOSE: To document age-related degenerative changes of the cervical spine in a large cohort of patients. STUDY DESIGN/SETTING: This is a retrospective cohort study. PATIENT SAMPLE: Adult trauma patients were admitted to our Level 1 trauma center. OUTCOME MEASURES: Osteoarthritis of the atlantodens and atlanto-axial facet joints of the cervical spine and the presence of intraosseous cyst and calcific synovitis, as determined by computed tomography (CT) scans. METHODS: We conducted a retrospective study of 1,543 adult trauma patients who received a cervical spine CT scan. The anterior atlantodens joint interval was measured. The presence or absence of intraosseous cysts and calcific synovitis was recorded. Degeneration of the atlantodens and atlanto-axial facet joints at age intervals was quantified. RESULTS: The atlantodens interval narrowed linearly with age (R(2)=0.992, p<.001). The prevalence of intraosseous cysts increased exponentially with age from 4.2% to 37.4%, and calcific synovitis increased from 0% to 11.1%. Intraosseous cyst formation generally began in the second and third decades of life and synovitis in the fifth and sixth decades of life. Facet joints also demonstrated age-related changes; however, the rate of degenerative changes was lower than in the atlantodens joint. CONCLUSIONS: To our knowledge, this is the first study that documents specific changes of both atlantodens and atlanto-axial facet joints as a function of age in a large cohort of 1,543 patients. These changes increased exponentially with age and may contribute to pain and limitation in motion. In light of our findings and recent studies demonstrating the association between degeneration and dens fracture in elderly, cervical spine radiographs of elderly patients should be carefully assessed for these changes.

The surgical management of early-stage cervical cancer.

PURPOSE OF REVIEW: The main objective is to update the literature data in the last year which may support a surgical approach to early cervical cancer [ECC; Stage International Federation of Gynecology and Obstetrics (FIGO) IA-IB1-IIA1]. Radical hysterectomy remains the gold standard by most international guidelines because surgical treatment has hardly changed in recent decades, except for stage IA1. RECENT FINDINGS: Trends in clinical research in the past 12-18 months involve minimal invasive surgery (with laparoscopic surgery or robotic-assisted surgery), fertility preservation (in the initial stages and in the absence of bad prognostic factors), nerve-sparing and sentinel node techniques. Some institutions have published studies in specific groups such as older, obese or pregnant women. SUMMARY: There is a growing trend to practice less aggressive surgery in order to preserve fertility in young women and avoid an excess of treatment in some selected patients. Therefore, nerve-sparing techniques can help to improve the quality of life. More studies are needed to demonstrate oncologic results of the sentinel node technique. Laparoscopic and robotic-assisted surgery can substitute open surgical treatment.

Adult leukemic synovitis is associated with leukemia of monocytic differentiation.

BACKGROUND: Leukemic synovitis is a rare complication of adult myeloid leukemias characterized by joint pain and swelling. It is important to recognize this diagnostic challenge as it may be the initial manifestation of leukemia or of relapse. METHODS: A retrospective search of patient files from 2 teaching hospitals identified 4 adult patients who presented with large joint arthritis and concurrent or subsequent leukemic synovitis. All patients presented with inflammatory arthritis of large joints, and leukemic synovitis was identified by the presence of leukemic cells in the synovial fluid or infiltrating the synovial membrane seen at biopsy. RESULTS: A leukemia of monocytic origin-acute myelomonocytic leukemia or chronic myelomonocytic leukemia-was diagnosed in all 4 patients. In 2 cases, leukemic synovitis was the initial manifestation of leukemia. In the third case, it was the first sign of relapse, and in the remaining case, it developed shortly after diagnosis of leukemia. All patients had either osteoarthritis or rheumatoid arthritis. One patient was diagnosed simultaneously with osteoarthritis and leukemia. The remaining patients had a prior history of arthritis. CONCLUSIONS: Adult leukemic synovitis occurs in association with leukemias of monocytic differentiation. Data presented here, and review of isolated case reports, support this association. The finding of large joint arthritis as a comorbidity in these 4 cases raises questions about the role of antecedent arthritis as a predisposing factor in the pathophysiology of leukemic synovitis.

A G468-T AMPD1 mutant allele contributes to the high incidence of myoadenylate deaminase deficiency in the Caucasian population.

Myoadenylate deaminase deficiency is the most common metabolic disorder of skeletal muscle in the Caucasian population, affecting approximately 2% of all individuals. Although most deficient subjects are asymptomatic, some suffer from exercise-induced myalgia suggesting a causal relationship between a lack of enzyme activity and muscle function. In addition, carriers of this derangement in purine nucleotide catabolism may have an adaptive advantage related to clinical outcome in heart disease. The molecular basis of myoadenylate deaminase deficiency in Caucasians has been attributed to a single mutant allele characterized by double C to T transitions at nucleotides +34 and +143 in mRNA encoded by the AMPD1 gene. Polymerase chain reaction-based strategies have been developed to specifically identify this common mutant allele and are considered highly sensitive. Consequently, some laboratories preferentially use this technique over other available diagnostic tests for myoadenylate deaminase deficiency. We previously identified a G468-T mutation in one symptomatic patient who was only heterozygous for the common AMPD1 mutant allele. In this report, nine additional individuals with this compound heterozygous genotype are revealed in a survey of 48 patients with documented deficiency of skeletal muscle adenosine monophosphate deaminase and exercise-induced myalgia. Western blot analysis of leftover biopsy material from one of these individuals does not detect any immunoreactive myoadenylate deaminase polypeptide. Baculoviral expression of the G468-T mutant allele produces a Q156H substitution enzyme exhibiting labile catalytic activity. These combined results demonstrate that the G468-T transversion is dysfunctional and further indicate that AMPD1 alleles harboring this mutation contribute to the high incidence of partial and complete myoadenylate deaminase deficiency in the Caucasian population. Consequently, genetic tests for abnormal AMPD1 expression designed to diagnose patients with metabolic myopathy, and to evaluate genetic markers for clinical outcome in heart disease should not be based solely on the detection of a single mutant allele.

Localization of N-terminal sequences in human AMP deaminase isoforms that influence contractile protein binding.

The reversible association of AMP deaminase (AMPD, EC 3.5.4.6) with elements of the contractile apparatus is an identified mechanism of enzyme regulation in mammalian skeletal muscle. All three members of the human AMPD multigene family contain coding information for polypeptides with divergent N-terminal and conserved C-terminal domains. In this study, serial N-terminal deletion mutants of up to 111 (AMPD1), 214 (AMPD2), and 126 (AMPD3) residues have been constructed without significant alteration of catalytic function or protein solubility. The entire sets of active enzymes are used to extend our understanding of the contractile protein binding of AMPD. Analysis of the most truncated active enzymes demonstrates that all three isoforms can associate with skeletal muscle actomyosin and suggests that a primary binding domain is located within the C-terminal 635-640 residues of each polypeptide. However, discrete stretches of N-terminal sequence alter this behavior. Residues 54-83 in the AMPD1 polypeptide contribute to a high actomyosin binding capacity of both isoform M spliceoforms, although the exon 2- enzyme exhibits significantly greater association compared to its exon 2+ counterpart. Conversely, residues 129-183 in the AMPD2 polypeptide reduce actomyosin binding of isoform L. In addition, residues 1-48 in the AMPD3 polypeptide dramatically suppress contractile protein binding of isoform E, thus allowing this enzyme to participate in other intracellular interactions.

Regulation of skeletal muscle ATP catabolism by AMPD1 genotype during sprint exercise in asymptomatic subjects.

Deficiency of myoadenylate deaminase, the muscle isoform of AMP deaminase encoded by the AMPD1 gene, is a common myopathic condition associated with alterations in skeletal muscle energy metabolism. However, recent studies have demonstrated that most individuals harboring this genetic abnormality are asymptomatic. Therefore, 18 healthy subjects with different AMPD1 genotypes were studied during a 30-s Wingate test in order to evaluate the influence of this inherited defect in AMPD1 expression on skeletal muscle energy metabolism and exercise performance in the asymptomatic population. Exercise performances were similar across the AMPD1 genotypes, whereas significant differences in several descriptors of energy metabolism were observed. Normal homozygotes (NN) exhibited the highest levels of AMP deaminase activities, net ATP catabolism, and IMP accumulation, whereas intermediate values were observed in heterozygotes (MN). Conversely, mutant homozygotes (MM) had very low AMP deaminase activities and showed no significant net catabolism of ATP or IMP accumulation. Accordingly, MM also did not show any postexercise increase in plasma ammonia. Unexpectedly, MN consistently exhibited greater increases in plasma ammonia compared with NN despite the relatively lower accumulation of IMP in skeletal muscle. Moreover, time course profiles of postexercise plasma ammonia and blood lactate accumulation also differed across AMPD1 genotypes. Finally, analysis of adenosine in leftover biopsy material revealed a modest twofold increase in MN and a dramatic 25-fold increase in MM.

Towards an understanding of the functional significance of N-terminal domain divergence in human AMP deaminase isoforms.

Human AMP deaminase (AMPD; EC 3.5.4.6) isoforms are encoded by a multigene family and have conserved C-terminal domains that contain catalytic residues and an ATP-binding site. N-terminal domains diverge dramatically, yet are conserved when compared across mammalian species. Cross-species conservation of entire gene-specific polypeptides (e.g., rat versus human AMPD1) suggests that divergent N-terminal domains may play a role in isoform-specific properties of the enzyme. It now has become evident that the majority of published data used to characterize purified AMPD isoforms were likely derived from preparations lacking significant portions of their N-terminal domains (up to nearly 100 residues). Accumulating evidence indicates that divergent N-terminal sequences do influence catalytic behavior, protein-protein interactions, and intracellular distributions of this enzyme.

Myoadenylate deaminase deficiency. A common inherited defect with heterogeneous clinical presentation.

Myoadenylate deaminase deficiency is a clinically heterogeneous metabolic disorder that is commonly diagnosed in a variety of neurologic settings. Although the molecular basis for this purine nucleotide catabolic derangement may typically be attributed to the inheritance of a single prevalent mutant allele, the clinical spectrum in the absence of other definable abnormalities can range from asymptomatic to mild exercise-induced myalgia. Moreover, myoadenylate deaminase deficiency is also found associated with other definable neuromuscular disorders. The myoadenylate deaminase deficiency in these latter cases may, in part, be precipitated by pathologic change or act synergistically in combination with another metabolic disease.