Leptin and the metabolic syndrome in patients with myotonic dystrophy type 1

Therapeutic potential of oleic acid supplementation in myotonic dystrophy muscle cell models

BACKGROUND

We recently reported that upregulation of Musashi 2 (MSI2) protein in the rare neuromuscular disease myotonic dystrophy type 1 contributes to the hyperactivation of the muscle catabolic processes autophagy and UPS through a reduction in miR-7 levels. Because oleic acid (OA) is a known allosteric regulator of MSI2 activity in the biogenesis of miR-7, here we sought to evaluate endogenous levels of this fatty acid and its therapeutic potential in rescuing cell differentiation phenotypes in vitro. In this work, four muscle cell lines derived from DM1 patients were treated with OA for 24 h, and autophagy and muscle differentiation parameters were analyzed.

RESULTS

We demonstrate a reduction of OA levels in different cell models of the disease. OA supplementation rescued disease-related phenotypes such as fusion index, myotube diameter, and repressed autophagy. This involved inhibiting MSI2 regulation of direct molecular target miR-7 since OA isoschizomer, elaidic acid (EA) could not cause the same rescues. Reduction of OA levels seems to stem from impaired biogenesis since levels of the enzyme stearoyl-CoA desaturase 1 (SCD1), responsible for converting stearic acid to oleic acid, are decreased in DM1 and correlate with OA amounts.

CONCLUSIONS

For the first time in DM1, we describe a fatty acid metabolism impairment that originated, at least in part, from a decrease in SCD1. Because OA allosterically inhibits MSI2 binding to molecular targets, reduced OA levels synergize with the overexpression of MSI2 and contribute to the MSI2 > miR-7 > autophagy axis that we proposed to explain the muscle atrophy phenotype.

Dyslipidemia in Muscular Dystrophy: A Systematic Review and Meta-Analysis

BACKGROUND

Muscular dystrophies (MDs) are characterized by chronic muscle wasting but also poorly understood metabolic co-morbidities. We have recently shown that Duchenne MD (DMD) patients, dogs and asymptomatic carriers are affected by a new form of dyslipidemia that may exacerbate muscle damage.

OBJECTIVE

We aimed to perform a systematic review and meta-analysis for evidence that other types of MDs are associated with dyslipidemia compared to healthy controls.

METHODS

Search was conducted using MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials for reports that compare plasma/serum lipids from MD patients and controls, and meta-analysis of cross-sectional studies quantifying total cholesterol, high-density lipoprotein, low density lipoprotein and triglycerides was performed.

RESULTS

Out of 749 studies, 17 met our inclusion criteria for meta-analysis. 14 of the 17 studies (82% ) included investigated myotonic dystrophy (DM); other studies were on pseudohypertrophic MD (PMD) or DMD. As a whole, MD individuals had significantly higher levels of circulating total cholesterol (Hedges' g with 95% confidence interval [CI], 0.80 [0.03 - 1.56]; p = 0.04) and triglycerides (Hedges' g with 95% confidence interval [CI], 2.28[0.63 - 3.92]; p = 0.01) compared to controls. Meta-regression analysis showed the percentage of male gender was significantly associated with the difference in total cholesterol (beta = 0.05; 95% CI, - 0.02 to 0.11; p = 0.043) and high-density lipoprotein (beta = - 9.38; 95% CI, - 16.26 to - 2.50; p = 0.028).

CONCLUSIONS

MD is associated with significantly higher circulating levels of total cholesterol and triglycerides. However, caution on the interpretation of these findings is warranted and future longitudinal research is required to better understand this relationship.

Assessment of body composition, metabolism, and pulmonary function in patients with myotonic dystrophy type 1

Abnormal body composition in myotonic dystrophy type 1 (DM1) are affected by energy intake above resting energy expenditure (REE). We aim to investigate the characteristics and relationship between body composition, REE, and pulmonary function in patients with DM1, and to examine their changes in 1 year. The study design was a single-center, cross-sectional, and longitudinal study of body composition, REE characteristics, and pulmonary function. Twenty-one male patients with DM1 and 16 healthy volunteers were registered in the study. Body composition was measured using dual-energy X-ray absorptiometry (DEXA). Fat mass (FM) index (kg/m2), fat-FM index (kg/m2), and skeletal mass index (kg/m2) were calculated. The measurements were taken breath by breath with a portable indirect calorimeter. The REE was calculated using the oxygen intake (VO2) and carbon dioxide output (VCO2) in the Weir equation. Basal energy expenditure (BEE) was calculated by substituting height, weight, and age into the Harris-Benedict equation. The study enrolled male patients with DM1 (n = 12) and healthy male volunteers (n = 16). Patients with DM1 (n = 7) and healthy volunteers (n = 14) could be followed in 1 year. The body composition of patients with DM1 was significantly higher in the FM index and significantly lower in the fat-FM index and skeletal mass index. The REE of patients with DM1 was significantly lower and was not associated with body composition. Patients with DM1 had poor metabolism that was not related to body composition. FM was high and lean body mass was low.

Endocrine Dysfunction in Patients With Myotonic Dystrophy

Myotonic dystrophy is a dominantly inherited multisystem disorder that results from increased CTG repeats in the 3' region of the myotonic dystrophy protein kinase gene (DMPK). The mutant DMPK mRNA remains in the nucleus and sequesters RNA-binding proteins, including regulators of mRNA splicing. Myotonic dystrophy is characterized by a highly variable phenotype that includes muscle weakness and myotonia, and the disorder may affect the function of many endocrine glands. DMPK mRNA is expressed in muscle, testis, liver, pituitary, thyroid, and bone; the mutated form leads to disruption of meiosis and an increase in fetal insulin receptor-A relative to adult insulin receptor-B, resulting in adult primary testicular failure and insulin resistance predisposing to diabetes, respectively. Patients with myotonic dystrophy are also at increased risk for hyperlipidemia, nonalcoholic fatty liver disease, erectile dysfunction, benign and malignant thyroid nodules, bone fractures, miscarriage, preterm delivery, and failed labor during delivery. Circulating parathyroid hormone and adrenocorticotropic hormone levels may be elevated, but the mechanisms for these associations are unclear. This review summarizes what is known about endocrine dysfunction in individuals with myotonic dystrophy.

Metabolic Alterations in Myotonic Dystrophy Type 1 and Their Correlation with Lipin

Myotonic dystrophy type 1 (DM1) is an autosomal dominant hereditary and multisystemic disease, characterized by progressive distal muscle weakness and myotonia. Despite huge efforts, the pathophysiological mechanisms underlying DM1 remain elusive. In this review, the metabolic alterations observed in patients with DM1 and their connection with lipin proteins are discussed. We start by briefly describing the epidemiology, the physiopathological and systemic features of DM1. The molecular mechanisms proposed for DM1 are explored and summarized. An overview of metabolic syndrome, dyslipidemia, and the summary of metabolic alterations observed in patients with DM1 are presented. Patients with DM1 present clinical evidence of metabolic alterations, namely increased levels of triacylglycerol and low-density lipoprotein, increased insulin and glucose levels, increased abdominal obesity, and low levels of high-density lipoprotein. These metabolic alterations may be associated with lipins, which are phosphatidate phosphatase enzymes that regulates the triacylglycerol levels, phospholipids, lipid signaling pathways, and are transcriptional co-activators. Furthermore, lipins are also important for autophagy, inflammasome activation and lipoproteins synthesis. We demonstrate the association of lipin with the metabolic alterations in patients with DM1, which supports further clinical studies and a proper exploration of lipin proteins as therapeutic targets for metabolic syndrome, which is important for controlling many diseases including DM1.

Clinical Care Recommendations for Cardiologists Treating Adults With Myotonic Dystrophy

Myotonic dystrophy is an inherited systemic disorder affecting skeletal muscle and the heart. Genetic testing for myotonic dystrophy is diagnostic and identifies those at risk for cardiac complications. The 2 major genetic forms of myotonic dystrophy, type 1 and type 2, differ in genetic etiology yet share clinical features. The cardiac management of myotonic dystrophy should include surveillance for arrhythmias and left ventricular dysfunction, both of which occur in progressive manner and contribute to morbidity and mortality. To promote the development of care guidelines for myotonic dystrophy, the Myotonic Foundation solicited the input of care experts and organized the drafting of these recommendations. As a rare disorder, large scale clinical trial data to guide the management of myotonic dystrophy are largely lacking. The following recommendations represent expert consensus opinion from those with experience in the management of myotonic dystrophy, in part supported by literature-based evidence where available.

Insulin Signaling as a Key Moderator in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant genetic disease characterized by multi-system involvement. Affected organ system includes skeletal muscle, heart, gastro-intestinal system and the brain. In this review, we evaluate the evidence for alterations in insulin signaling and their relation to clinical DM1 features. We start by summarizing the molecular pathophysiology of DM1. Next, an overview of normal insulin signaling physiology is given, and evidence for alterations herein in DM1 is presented. Clinically, evidence for involvement of insulin signaling pathways in DM1 is based on the increased incidence of insulin resistance seen in clinical practice and recent trial evidence of beneficial effects of metformin on muscle function. Indirectly, further support may be derived from certain CNS derived symptoms characteristic of DM1, such as obsessive-compulsive behavior features, for which links with altered insulin signaling has been demonstrated in other diseases. At the basic scientific level, several pathophysiological mechanisms that operate in DM1 may compromise normal insulin signaling physiology. The evidence presented here reflects the importance of insulin signaling in relation to clinical features of DM1 and justifies further basic scientific and clinical, therapeutically oriented research.

Body composition analysis in patients with myotonic dystrophy types 1 and 2

INTRODUCTION

To date, there are only several reports on body composition in myotonic dystrophy type 1 (DM1) and there are no data for myotonic dystrophy type 2 (DM2). The aim was to analyze body composition of patients with DM1 and DM2, and its association with socio-demographic and clinical features of the diseases.

METHODS

There were no statistical differences in sociodemographic features between 20 DM1 patients and 12 DM2 patients. Body composition was assessed by DEXA (dual-energy x-ray absorptiometry). A three-compartment model was used: bone mineral content (BMC), fat mass (FM), and lean tissue mass (LTM).

RESULTS

Patients with DM1 and DM2 had similar total body mass (TBM), BMC, FM, and LTM. Patients with DM1 had higher trunk-limb fat index (TLFI) in comparison to DM2 patients which indicates visceral fat deposition in DM1 (1.16 ± 0.32 for DM1 vs. 0.87 ± 0.23 for DM2, p < 0.05). Right ribs bone mineral density was lower in DM2 group (0.68 ± 0.07 g/cm² vs. 0.61 ± 0.09 g/cm², p < 0.05). Higher percentage of FM in legs showed correlation with lower strength of the upper leg muscles in DM1 (ρ = - 0.47, p < 0.05). Higher muscle strength in DM2 patients was in correlation with higher bone mineral density (ρ = + 0.62, p < 0.05 for upper arm muscles, ρ = + 0.87, p < 0.01 for lower arm muscles, ρ = + 0.72, p < 0.05 for lower leg muscles).

CONCLUSION

DM1 patients had visceral obesity, and percentage of FM correlated with a degree of muscle weakness in upper legs. In DM2 patients, degree of muscle weakness was in correlation with higher FM index and lower bone mineral density.

Hyperleptinemia in children with autosomal recessive spinal muscular atrophy type I-III

Background

Autosomal-recessive proximal spinal muscular atrophies (SMA) are disorders characterized by a ubiquitous deficiency of the survival of motor neuron protein that leads to a multisystemic disorder, which mostly affects alpha motor neurons. Disease progression is clinically associated with failure to thrive or weight loss, mainly caused by chewing and swallowing difficulties. Although pancreatic involvement has been described in animal models, systematic endocrinological evaluation of the energy metabolism in humans is lacking.

Methods

In 43 patients with SMA type I-III (8 type I; 22 type II; 13 type III), aged 0.6–21.8 years, auxological parameters, pubertal stage, motor function (Motor Function Measurement 32 –MFM32) as well as levels of leptin, insulin glucose, hemoglobin A1c, Homeostasis Model Assessment index and an urinary steroid profile were determined.

Results

Hyperleptinemia was found in 15/35 (43%) of our patients; 9/15 (60%) of the hyperleptinemic patients were underweight, whereas 1/15 (7%) was obese. Hyperleptinemia was associated with SMA type (p = 0.018). There was a significant association with decreased motor function (MFM32 total score in hyperleptinemia 28.5%, in normoleptinemia 54.7% p = 0.008, OR 0.969; 95%-CI: 0.946–0.992). In addition, a higher occurrence of hirsutism, premature pubarche and a higher variability of the urinary steroid pattern were found.

Conclusion

Hyperleptinemia is highly prevalent in underweight children with SMA and is associated with disease severity and decreased motor function. Neuronal degradation of hypothalamic cells or an increase in fat content by muscle remodeling could be the cause of hyperleptinemia.

Leptin and metabolic syndrome in patients with Duchenne/Becker muscular dystrophy

OBJECTIVES

To determine whether patients with Duchenne/Becker muscular dystrophy (DMD/BMD) have components of metabolic syndrome (MetSy) and to evaluate whether leptin is associated with components of MetSy.

METHODS

This study included 78 patients (nine, <6 years of age; 54, 6 to <16 years of age; and 15 patients, ≥16 years of age). Obesity and body fat mass were determined by waist circumference and dual-energy X-ray absorptiometry, respectively. A 12-h fasting blood sample was collected in the morning. Patients were categorized into four groups according to the number of criteria for MetSy: group 0: none; group 1: one; group 2: two and group 3: three or more criteria.

RESULTS

All age groups showed components of MetSy. The concentration of these components was significantly higher in patients ≥16 years old. The prevalence of hypertriglyceridemia was from ~37% to 46% in all age groups. The prevalence of MetSy was 7.1% for patients from 6 to <16 years of age and 24% for patients ≥16 years of age. Serum leptin levels increased significantly (P < 0.05) with age; the highest (13.43 ± 9.4 ng/ml) value was observed in patients >16 years of age. Total leptin was correlated with the number of patients with MetSy (r = 0.383; P = 0.001).

CONCLUSIONS

Components of MetSy are significant in patients with DMD/BMD. A high prevalence of hypertriglyceridemia was observed. Younger patients with DMD/BMD have risk factors for MetSy. Although leptin increased according to different degrees of MetSy, this relation disappeared when the body fat was corrected by leptin; therefore, the association could be caused by a common risk factor-fat.

Myotonic Dystrophy Type 1 Complicated With Peripheral Arterial Occlusive Disease: A Case Report

Myotonic dystrophy (MD) is the most common adult muscular dystrophy characterized by multi-systemic clinical manifestations involving the brain, smooth muscle, cardiovascular and endocrine systems. However, peripheral arterial occlusive disease (PAOD) is an uncommon presentation of MD type 1 (DM1), which has not been reported in recent literature. A 53-year-old female, previously confirmed as DM1, presented with vague claudication of both lower limbs. The diagnosis of PAOD based on results of ankle-brachial index, ultrasonography, and abdominal computed tomography angiography studies was followed by aortobifemoral artery bypass surgery. Although the arterial patency was restored after the operation, she did not recover from post-operative respiratory complications. Screening of PAOD is necessary for DM1 with general risk factors of occlusive arteriopathy. However, surgery should be reserved for the most severe cases.

Metabolic syndrome in patients with myotonic dystrophy type 1

INTRODUCTION

The aim of this study was to assess the frequency and features of metabolic syndrome (MetS) in myotonic dystrophy type 1 (DM1).

METHODS

We studied 66 DM1 patients (50% men, aged 41.9 ± 10.5 years, disease duration of 19.3 ± 8.6 years). New worldwide consensus criteria for MetS from 2009 were used.

RESULTS

Components of MetS were present at the following frequencies: hypertriglyceridemia 67%; low HDL cholesterol 35%; hypertension 18%; central obesity 14%; and hyperglycemia 9%. MetS was present in 11 (17%) patients. The presence of MetS was not associated with patients' gender, age, disease severity, disease duration, or CTG repeat length (P > 0.05). Patients with MetS had significantly lower total SF-36 scores as a measure of quality of life in comparison to patients without MetS (P < 0.05).

CONCLUSION

Although certain components of MetS were very frequent in patients with DM1, only 17% met the criteria for MetS.

Brain pathology in myotonic dystrophy: when tauopathy meets spliceopathy and RNAopathy

Myotonic dystrophy (DM) of type 1 and 2 (DM1 and DM2) are inherited autosomal dominant diseases caused by dynamic and unstable expanded microsatellite sequences (CTG and CCTG, respectively) in the non-coding regions of the genes DMPK and ZNF9, respectively. These mutations result in the intranuclear accumulation of mutated transcripts and the mis-splicing of numerous transcripts. This so-called RNA gain of toxic function is the main feature of an emerging group of pathologies known as RNAopathies. Interestingly, in addition to these RNA inclusions, called foci, the presence of neurofibrillary tangles (NFT) in patient brains also distinguishes DM as a tauopathy. Tauopathies are a group of nearly 30 neurodegenerative diseases that are characterized by intraneuronal protein aggregates of the microtubule-associated protein Tau (MAPT) in patient brains. Furthermore, a number of neurodegenerative diseases involve the dysregulation of splicing regulating factors and have been characterized as spliceopathies. Thus, myotonic dystrophies are pathologies resulting from the interplay among RNAopathy, spliceopathy, and tauopathy. This review will describe how these processes contribute to neurodegeneration. We will first focus on the tauopathy associated with DM1, including clinical symptoms, brain histology, and molecular mechanisms. We will also discuss the features of DM1 that are shared by other tauopathies and, consequently, might participate in the development of a tauopathy. Moreover, we will discuss the determinants common to both RNAopathies and spliceopathies that could interfere with tau-related neurodegeneration.

Decreased concentration of adiponectin together with a selective reduction of its high molecular weight oligomers is involved in metabolic complications of myotonic dystrophy type 1

OBJECTIVE

The hormone adiponectin exerts beneficial pleiotropic effects on biological and metabolic processes. Although a well-recognized insulin sensitizer, its characteristic has yet to be clearly defined. Myotonic dystrophy type 1 (DM1) is a rare genetic disorder that features muscle wasting and metabolic comorbidity, and patients have an increased risk of developing type 2 diabetes. We analyzed circulating levels of adiponectin and its oligomers to determine whether their expression correlates with metabolic alterations in DM1 patients.

DESIGN AND METHODS

We measured the anthropometric and biochemical features and three insulin resistance (IR) indices (homeostasis model assessment, quantitative insulin sensitivity check index, and McAuley) of 21 DM1 patients and of 82 age-, sex-, and weight-matched controls. In the blood samples of patients and controls, adiponectin levels were measured by ELISA, and its oligomers were characterized by using western blotting and gel filtration. The adiponectin gene was molecularly analyzed in patients.

RESULTS

DM1 patients had significantly higher body mass index, waist circumference, triglycerides (TGs), glucose, tumor necrosis factor α, and IR; conversely, they had significantly lower concentrations of total serum adiponectin with a selective, pronounced decrease of its high molecular weight (HMW) oligomers. There was a strong negative correlation between adiponectin and TGs in DM1 patients.

CONCLUSIONS

Our results endorse the hypothesis that decreased expression of adiponectin together with a selective reduction of its HMW oligomers contributes to the worsening of IR and its metabolic complications in DM1 patients. These findings suggest that adiponectin and HMW oligomers may serve as biomarkers and are promising therapeutic agents for IR and its consequences in DM1.