Body fat distribution, serum glucose, lipid and insulin response to meals in Alström syndrome

Alström Syndrome: A Review Focusing on Its Diverse Clinical Manifestations and Their Etiology as a Ciliopathy

Alström syndrome is a form of inherited obesity caused by a single gene abnormality and is inherited as an autosomal recessive trait. It is characterised by a variety of clinical manifestations, including progressive visual and hearing impairment, type 2 diabetes mellitus, dilated cardiomyopathy, and hepatic and renal dysfunction, in addition to obesity. Recent insights underline the pivotal involvement of the disease-associated gene (ALMS1) in cilia formation and function, leading to the classification of its clinical manifestations as a ciliopathy. This review delineates the diverse clinical indicators defining the syndrome and elucidates its pathological underpinnings.

Alström Syndrome: A Challenging Case Study of a Female Saudi Patient With Type 2 Diabetes Mellitus and Complete Vision Loss

Alström syndrome is a genetic disease that impacts numerous systems in the human body. The symptoms can vary and appear gradually. Childhood obesity, heart disease (cardiomyopathy), abnormalities in vision, and hearing issues are the main symptoms of this disorder in children. Diabetes mellitus, hepatic issues, and renal dysfunction can all occur over time. Genetic alterations in the ALMS1 gene are the cause of Alström syndrome. It has an autosomal recessive inheritance pattern. We address the case of a Saudi woman in her 20s. She had been initially referred for type 2 diabetes, intellectual disability since early childhood, metabolic acidosis, and micrognathia; however, she also exhibited blindness, chronic kidney disease (CKD), and hearing loss, all of which are indicative of Alström syndrome. DNA testing showed that she has a homozygous pathogenic variant in the ALMS gene. Autosomal recessive Alström syndrome has been confirmed as a genetic diagnosis. No other clinically significant variations were found that are associated with the mentioned phenotype. By reporting this mutation, we hope to learn more about the genotypic range of the disease, particularly in the Saudi population. As each member of the family underwent genetic testing, we established a stringent follow-up schedule for our patient and her family.

Body Fat Distribution Contributes to Defining the Relationship between Insulin Resistance and Obesity in Human Diseases

The risk for metabolic and cardiovascular complications of obesity is defined by body fat distribution rather than global adiposity. Unlike subcutaneous fat, visceral fat (including hepatic steatosis) reflects insulin resistance and predicts type 2 diabetes and cardiovascular disease. In humans, available evidence indicates that the ability to store triglycerides in the subcutaneous adipose tissue reflects enhanced insulin sensitivity. Prospective studies document an association between larger subcutaneous fat mass at baseline and reduced incidence of impaired glucose tolerance. Case-control studies reveal an association between genetic predisposition to insulin resistance and a lower amount of subcutaneous adipose tissue. Human peroxisome proliferator-activated receptorgamma (PPAR-γ) promotes subcutaneous adipocyte differentiation and subcutaneous fat deposition, improving insulin resistance and reducing visceral fat. Thiazolidinediones reproduce the effects of PPAR-γ activation and therefore increase the amount of subcutaneous fat while enhancing insulin sensitivity and reducing visceral fat. Partial or virtually complete lack of adipose tissue (lipodystrophy) is associated with insulin resistance and its clinical manifestations, including essential hypertension, hypertriglyceridemia, reduced HDL-c, type 2 diabetes, cardiovascular disease, and kidney disease. Patients with Prader Willi syndrome manifest severe subcutaneous obesity without insulin resistance. The impaired ability to accumulate fat in the subcutaneous adipose tissue may be due to deficient triglyceride synthesis, inadequate formation of lipid droplets, or defective adipocyte differentiation. Lean and obese humans develop insulin resistance when the capacity to store fat in the subcutaneous adipose tissue is exhausted and deposition of triglycerides is no longer attainable at that location. Existing adipocytes become large and reflect the presence of insulin resistance.

Whole-exome sequencing establishes a diagnosis of Alstrom syndrome: a case report

BACKGROUND

Alstrom syndrome (ALMS) is a rare genetic disorder. ALMS is characterized by progressive bilateral sensorineural hearing impairment, cone-rod dystrophy, infantile-onset cardiomyopathy, hypertriglyceridemia, accelerated non-alcoholic fatty liver disease, renal dysfunction and insulin-resistant diabetes mellitus (DM). DM typically develop in childhood or adolescence. Dilated cardiomyopathy may arise in infancy. Clinical symptoms appear with great variability and severity. Several cases have been reported worldwide; however, diagnosis remains challenging.

CASE DESCRIPTION

We report an 8-year-and-11-month-old female diagnosed with ALMS who had a long history of obesity and amblyopia from infancy. We found high levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in this patient. She showed no hearing disfunction. Recently, she presented with sudden-onset insulin-resistant DM. Genetic analysis revealed the heterozygous mutations c.8366delT, p.L2789* and c.6829C>T, p.R2277*. c.8366delT, which results in premature protein termination, has not been reported previously in ALMS1. Although the patient's two sisters died of acute heart failure following infection at 4 and 14 months respectively, she showed no signs of cardiomyopathy until now.

CONCLUSIONS

This case provides an unusual cause of genetic syndrome associated with diabetes. A detailed medical history, physical examination and appropriate gene analysis are critical for diagnosis. Our case identifies a novel ALMS1 mutation and reaffirms the great clinical variation of this disease even within families.

Alstrom's Syndrome: An Experience of Tertiary Care Center

Alstrom's syndrome (AS) is an autosomal recessively inherited multisystemic disorder that falls under the umbrella of ciliopathy. It is characterized by poor vision, hearing impairment, cardiomyopathy, childhood obesity, diabetes mellitus type 2, dyslipidemia, pulmonary, hepatic, and renal failure besides systemic fibrosis. Biallelic pathogenic variants in ALMS1 gene cause AS. Retrospective study (1990–2017) included 12 Saudi patients with AS based on their phenotype, biochemical markers, and genotype. The study was approved by Fisal Specialist Hospital and Research Centre, Riyadh (RAC number 2131129) on October 2, 2012. This study showed clinical and genetic heterogeneity; six patients showed a founder mutation (IVS18–2A > T in exon 19), whereas six others showed private mutations. AS in Saudi Arabia is underdiagnosed probably because of its variable clinical manifestations. We report 12 Saudi patients with AS to enhance the awareness about this syndrome.

Consensus clinical management guidelines for Alström syndrome

Alström Syndrome (ALMS) is an ultra-rare multisystem genetic disorder caused by autosomal recessive variants in the ALMS1 gene, which is located on chromosome 2p13. ALMS is a multisystem, progressive disease characterised by visual disturbance, hearing impairment, cardiomyopathy, childhood obesity, extreme insulin resistance, accelerated non-alcoholic fatty liver disease (NAFLD), renal dysfunction, respiratory disease, endocrine and urologic disorders. Clinical symptoms first appear in infancy with great variability in age of onset and severity. ALMS has an estimated incidence of 1 case per 1,000,000 live births and ethnically or geographically isolated populations have a higher-than-average frequency. The rarity and complexity of the syndrome and the lack of expertise can lead to delayed diagnosis, misdiagnosis and inadequate care. Multidisciplinary and multiprofessional teams of experts are essential for the management of patients with ALMS, as early diagnosis and intervention can slow the progression of multi-organ dysfunctions and improve patient quality of life.These guidelines are intended to define standard of care for patients suspected or diagnosed with ALMS of any age. All information contained in this document has originated from a systematic review of the literature and the experiences of the authors in their care of patients with ALMS. The Appraisal of Guidelines for Research & Evaluation (AGREE II) system was adopted for the development of the guidelines and for defining the related levels of evidence and strengths of recommendations.These guidelines are addressed to: a) specialist centres, other hospital-based medical teams and staffs involved with the care of ALMS patients, b) family physicians and other primary caregivers and c) patients and their families.

Diffuse left ventricular interstitial fibrosis is associated with sub-clinical myocardial dysfunction in Alström Syndrome: an observational study

Background

Alström syndrome is a rare inherited ciliopathy with progressive multisystem involvement. Dilated cardiomyopathy is common in infancy and recurs or presents de novo in adults with high rates of premature cardiovascular death. Although Alström syndrome is characterised by fibrosis in solid organs such as the liver, the pathogenesis of related cardiomyopathy are not clear. To date it is not known whether diffuse interstitial myocardial fibrosis is present before the onset of heart failure symptoms or changes in conventional parameters of left ventricular function.

Methods

In this observational study, 26 patients with Alström syndrome (mean age 27 ± 9 years, 65 % male, 24 h ABPM 130 ± 14 / 77 ± 9 mmHg) without symptomatic cardiovascular disease were recruited from a single centre and compared to matched healthy controls. All subjects underwent cardiac MRI (1.5 T) to assess ventricular function, diffuse interstitial myocardial fibrosis by measurement of extracellular volume on T1-mapping (MOLLI) and coarse replacement fibrosis using standard late gadolinium enhancement imaging.

Results

Global extracellular volume was increased in Alström syndrome with wider variation compared to controls (0.30 ± 0.05 vs. 0.25 ± 0.01, p < 0.05). Left ventricular long axis function and global longitudinal strain were impaired in Alström syndrome without change in ejection fraction, ventricular size or atrial stress (NT-proBNP) (p < 0.05). Global extracellular volume was associated with reduced peak systolic longitudinal strain (r = −0.73, p < 0.01) and strain rate (r = −0.57, p < 0.01), increased QTc interval (r = 0.49, p < 0.05) and serum triglycerides (r = 0.66, p < 0.01). Nine (35 %) patients had diffuse mid-wall late gadolinium enhancement in a non-coronary artery distribution.

Conclusion

Diffuse interstitial myocardial fibrosis is common in Alström syndrome and is associated with impaired left ventricular systolic function. Serial studies are required to determine whether global extracellular volume may be an independent imaging biomarker of vulnerability to dilated cardiomyopathy and heart failure.

Modification of severe insulin resistant diabetes in response to lifestyle changes in Alström syndrome

BACKGROUND

Alström syndrome is a recessively inherited condition characterised by severe insulin resistance and metabolic syndrome with progression to type 2 diabetes, hepatic dysfunction and coronary artery disease. The metabolic responses to lifestyle changes in the syndrome have not been reported.

CASE REPORTS

We describe the effects on glycaemia of intense cycling in two insulin treated Alström patients with diabetes, and the effects of opposite lifestyle changes over one year in two others.

METHODS

After practise and clinical assessment two patients aged 21 and 39 years undertook a 380 km cycle ride over 4 days by tandem. The effects of planned reductions in insulin therapies and increased regular carbohydrate ingestion were monitored by frequent capillary blood glucose measurements. Two siblings aged 22 and 25 years underwent assessment of glycaemia, C-peptide/glucose ratio serum lipids, hepatic function and ultrasound, Enhanced Liver Fibrosis test and measures of insulin resistance. Measurements were repeated one year later after profound lifestyle changes.

RESULTS

Aerobic exercise strikingly improved blood glucose control despite reduction in insulin dose and increased carbohydrate intake. Increase in exercise and exclusion of fast foods improved all aspects of the metabolic syndrome and induced remission of diabetes in one sibling. Reduction in exercise and consumption of high energy foods in the other resulted in development of type 2 diabetes, severe metabolic syndrome and fatty liver in the other.

CONCLUSIONS

Despite dual sensory loss and genetic basis for insulin resistance, Alström patients can successfully ameliorate the metabolic syndrome with lifestyle changes.

The progression from obesity to type 2 diabetes in Alström syndrome

BACKGROUND

Alström syndrome (ALMS) is a rare autosomal recessive monogenic disease associated with obesity, hyperinsulinemia, and alterations of glucose metabolism that often lead to the development of type 2 diabetes at a young age.

OBJECTIVE

To study the relationship between weight and metabolism in a group of ALMS patients and matched controls.

RESEARCH DESIGN AND METHODS

Fifteen ALMS patients (eight males, seven females; aged 3-51) were compared in a cross-sectional study with an age- and weight-matched control population. Anthropometric parameters, fat mass, glucose and insulin secretion in basal and dynamic oral glucose tolerance test (OGTT) conditions were measured. Furthermore, anthropometric and body composition data were obtained from an international group of 27 ALMS patients (13 males, 14 females, age range: 4-29 yr).

RESULTS

In ALMS we observed an inverse correlation between age and standard deviation scores for height, weight, and body mass index. The OGTT glycemic curves of ALMS subjects were similar to those of age-matched controls, whereas insulin response was clearly greater. In ALMS individuals the insulin response showed a reduction with age. We documented pathologic values of the derived indices homeostasis model assessment of insulin resistance (HOMA-IR), insulin sensitivity index, HOMA%β-cell and insulinogenic index in ALMS, but unlike the insulin-resistance indices, the β-cell function indices showed a significant reduction with age.

CONCLUSIONS

In ALMS the progression from the early onset obesity toward the impaired fasting glucose or impaired glucose tolerance and overt diabetes is mostly because of a progressive failure of β-cell insulin secretion without any further worsening of insulin resistance with age, even in the presence of weight reduction.

Alström syndrome: genetics and clinical overview

Alström syndrome is a rare autosomal recessive genetic disorder characterized by cone-rod dystrophy, hearing loss, childhood truncal obesity, insulin resistance and hyperinsulinemia, type 2 diabetes, hypertriglyceridemia, short stature in adulthood, cardiomyopathy, and progressive pulmonary, hepatic, and renal dysfunction. Symptoms first appear in infancy and progressive development of multi-organ pathology leads to a reduced life expectancy. Variability in age of onset and severity of clinical symptoms, even within families, is likely due to genetic background.Alström syndrome is caused by mutations in ALMS1, a large gene comprised of 23 exons and coding for a protein of 4,169 amino acids. In general, ALMS1 gene defects include insertions, deletions, and nonsense mutations leading to protein truncations and found primarily in exons 8, 10 and 16. Multiple alternate splice forms exist. ALMS1 protein is found in centrosomes, basal bodies, and cytosol of all tissues affected by the disease. The identification of ALMS1 as a ciliary protein explains the range of observed phenotypes and their similarity to those of other ciliopathies such as Bardet-Biedl syndrome.Studies involving murine and cellular models of Alström syndrome have provided insight into the pathogenic mechanisms underlying obesity and type 2 diabetes, and other clinical problems. Ultimately, research into the pathogenesis of Alström syndrome should lead to better management and treatments for individuals, and have potentially important ramifications for other rare ciliopathies, as well as more common causes of obesity and diabetes, and other conditions common in the general population.

Alström syndrome: insights into the pathogenesis of metabolic disorders

Genetic causes of obesity include the ciliopathies Alström syndrome and Bardet-Biedl syndrome. In these disorders, mutations cause dysfunction of the primary cilium, an organelle involved in intracellular and intercellular sensing and signaling. Alström syndrome is an autosomal-recessive disorder caused solely by mutations in ALMS1. By contrast, Bardet-Biedl syndrome is caused by mutations in at least 14 genes involved in primary cilium function. Despite equivalent levels of obesity, patients with Alström syndrome are more likely than those with Bardet-Biedl syndrome to develop childhood type 2 diabetes mellitus (T2DM), suggesting that ALMS1 might have a specific role in β-cell function and/or peripheral insulin signaling pathways. How mutations in genes that encode proteins involved in primary cilium function lead to the clinical phenotypes of these syndromes is being revealed by work in mutant mouse models. With the aid of these models, insights are being obtained into the pathogenic mechanisms that underlie obesity, insulin resistance and T2DM. Research into ciliopathies, including Alström syndrome and Bardet-Biedl syndrome, should lead not only to improved treatments for individuals with these genetic disorders, but also to improved understanding of the cellular pathways involved in other common causes of obesity and T2DM.

Combined occurrence of diabetes mellitus and retinitis pigmentosa

The combined occurrence of diabetes mellitus (DM) and retinitis pigmentosa (RP) is rare. It has been reported in the form of four different syndromes that are inherited in an autosomal recessive fashion. We describe two cases of DM and RP occurring together. The first case was a 35-year-old male who presented with insulin-treated diabetes, obesity, hypertension, polydactyly, normal cognitive functions, an ataxic gait, blindness secondary to RP, dyslipidemia, impaired renal function, and multiple renal cysts. He was diagnosed clinically as having Bardet-Biedl syndrome. The second case was a 34-year-old male who presented with insulin-resistant diabetes, hypertension, blindness secondary to RP, deafness, normal cognitive functions, primary infertility, renal, and liver impairment. He was diagnosed clinically as having Alström syndrome. Because of overlapping clinical manifestations and the cost and time involved in genetic studies, clinical criteria can be used for diagnosis and as a guide for genetic mapping in these patients.

New insights and therapies for the metabolic consequences of Alström syndrome

PURPOSE OF REVIEW

Recent studies have begun to evaluate the heterogeneity of insulin resistance in syndromes associated with type 2 diabetes, dyslipidaemia and associated cardiac, renal and hepatic consequences. These insights are of particular importance in Alström syndrome in which all of these conditions coexist from a young age with considerable morbidity and reduction in life expectancy. Clear definition of the phenotype in the syndrome may clarify biochemical pathways of crucial importance in propensity to diabetic complications and heart disease in the general population. This review will focus on ways in which more effective treatments can be put in place for Alström families from childhood and adolescence.

RECENT FINDINGS

Studies of body fat distribution, insulin resistance, glucose metabolism and dyslipidaemia in Alström syndrome will be discussed as well as genotypic and phenotypic variation in the syndrome in the context of recent metabolic studies in insulin resistance. Potential therapies including low-carbohydrate diet, niaspan and incretins will be considered.

SUMMARY

These new insights will encourage early introduction of protective nutrition, exercise and drug therapies in Alström syndrome and suggest novel approaches to understanding diabetes mellitus, hyperlipidaemias and heart disease in the general population.

Cardiac magnetic resonance imaging in Alström syndrome

Background

A case series of the cardiac magnetic resonance imaging findings in seven adult Alström patients.

Methods

Seven patients from the National Specialist Commissioning Group Centre for Alström Disease, Torbay, England, UK, completed the cardiac magnetic resonance imaging protocol to assess cardiac structure and function in Alström cardiomyopathy.

Results

All patients had some degree of left and right ventricular dysfunction. Patchy mid wall gadolinium delayed enhancement was demonstrated, suggesting an underlying fibrotic process. Some degree of cardiomyopathy was universal. No evidence of myocardial infarction or fatty infiltration was demonstrated, but coronary artery disease cannot be completely excluded. Repeat scanning after 18 months in one subject showed progression of fibrosis and decreased left ventricular function.

Conclusion

Adult Alström cardiomyopathy appears to be a fibrotic process causing impairment of both ventricles. Serial cardiac magnetic resonance scanning has helped clarify the underlying disease progression and responses to treatment. Confirmation of significant mutations in the ALMS1 gene should lead to advice to screen the subject for cardiomyopathy, and metabolic disorders.