Alström syndrome: an ultra-rare monogenic disorder as a model for insulin resistance, type 2 diabetes mellitus and obesity

Effect of SPTLC1 on type 2 diabetes mellitus

BACKGROUND

Although numerous single nucleotide polymorphism in multiple genes involve in the risk of type 2 diabetes mellitus (T2D), the single gene defects of T2D with strong family history is not clear yet. SPTLC1 are causative for hereditary sensory and autonomic neuropathy, which is clinical overlapping with diabetic peripheral neuropathy. Mice with adipocyte-specific deletion of SPTLC1 had impaired glucose tolerances and insulin sensitivity. Thus, it is necessary to investigate the SPTLC1 mutations in adult-onset T2D with strong family history.

AIM

To analyze the role of SPTLC1 mutation on adult-onset T2D with strong family history.

METHODS

By whole-exome sequence analysis of a patient with T2D and his family members, an uncertain variant in SPTLC1 was identified. Bioinformation analysis was used to evaluate the influence of mutation, rare variant gene-level associations for SPTLC1 in T2D, and the relationship between SPTLC1 mRNA and T2D in human islets from GSE25724. The effect of G371R of SPTLC1 on the characteristics of inflammatory cytokines and apoptosis was also tested on human embryonic kidney (HEK) 293 cells.

RESULTS

A single nucleotide variation in SPTLC1 (c.1111G>A: p.G371R) was identified in a family with T2D. The deleterious variant was predicted by functional analysis through hidden Markov models and mendelian clinically applicable pathogenicity software. This pathogenicity might be derived from the different amino acid properties. In HEK 293T cells, p.G371R of SPTLC1 induced the expression of tumor necrosis factor-α and the percent of apoptosis. Meanwhile, rare variant gene-level associations for SPTLC1 also refer to the high risk of T2D (the overall odds ratio = 2.4968, P = 0.0164). Data from GSE25724 showed that SPTLC1 mRNA was lower in pancreatic islets from T2D human islets (P = 0.046), and was associated with the decreased level of insulin mRNA expression (Spearman r = 0.615, P = 0.025).

CONCLUSION

The study classified SPTLC1 p.G371R mutation as the likely pathogenic mutation from an adult-onset T2D patients with strong family history T2D.

Stapled peptides as potential therapeutics for diabetes and other metabolic diseases

The field of peptide drug research has experienced notable progress, with stapled peptides featuring stabilized α-helical conformation, emerging as a promising field. These peptides offer enhanced stability, cellular permeability, and binding affinity and exhibit potential in the treatment of diabetes and metabolic disorders. Stapled peptides, through the disruption of protein-protein interactions, present varied functionalities encompassing agonism, antagonism, and dual-agonism. This comprehensive review offers insight into the technology of peptide stapling and targeting of crucial molecular pathways associated with glucose metabolism, insulin secretion, and food intake. Additionally, we address the challenges in developing stapled peptides, including concerns pertaining to structural stability, peptide helicity, isomer mixture, and potential side effects.

Characterisation of infantile cardiomyopathy in Alström syndrome using ALMS1 knockout induced pluripotent stem cell derived cardiomyocyte model

Alström syndrome (AS) is an inherited rare ciliopathy characterised by multi-organ dysfunction and premature cardiovascular disease. This may manifest as an infantile-onset dilated cardiomyopathy with significant associated mortality. An adult-onset restrictive cardiomyopathy may also feature later in life. Loss of function pathogenic variants in ALMS1 have been identified in AS patients, leading to a lack of ALMS1 protein. The biological role of ALMS1 is unknown, particularly in a cardiovascular context. To understand the role of ALMS1 in infantile cardiomyopathy, the reduction of ALMS1 protein seen in AS patients was modelled using human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), in which ALMS1 was knocked out. MuscleMotion analysis and calcium optical mapping experiments suggest that ALMS1 knockout (KO) cells have increased contractility, with altered calcium extrusion and impaired calcium handling dynamics compared to wildtype (WT) counterparts. Seahorse metabolic assays showed ALMS1 knockout iPSC-CMs had increased glycolytic and mitochondrial respiration rates, with ALMS1 knockout cells portraying increased energetic demand and respiratory capacity than WT counterparts. Using senescence associated β-galactosidase (SA-β gal) staining assay, we identified increased senescence of ALMS1 knockout iPSC-CMs. Overall, this study provides insights into the molecular mechanisms in AS, particularly the role of ALMS1 in infantile cardiomyopathy in AS, using iPSC-CMs as a 'disease in a dish' model to provide insights into multiple aspects of this complex disease.

Discriminating insulin resistance in middle-aged nondiabetic women using machine learning approaches

Objective

We employed machine learning algorithms to discriminate insulin resistance (IR) in middle-aged nondiabetic women.

Methods

The data was from the National Health and Nutrition Examination Survey (2007-2018). The study subjects were 2084 nondiabetic women aged 45-64. The analysis included 48 predictors. We randomly divided the data into training (n = 1667) and testing (n = 417) datasets. Four machine learning techniques were employed to discriminate IR: extreme gradient boosting (XGBoosting), random forest (RF), gradient boosting machine (GBM), and decision tree (DT). The area under the curve (AUC) of receiver operating characteristic (ROC), accuracy, sensitivity, specificity, positive predictive value, negative predictive value, and F1 score were compared as performance metrics to select the optimal technique.

Results

The XGBoosting algorithm achieved a relatively high AUC of 0.93 in the training dataset and 0.86 in the testing dataset to discriminate IR using 48 predictors and was followed by the RF, GBM, and DT models. After selecting the top five predictors to build models, the XGBoost algorithm with the AUC of 0.90 (training dataset) and 0.86 (testing dataset) remained the optimal prediction model. The SHapley Additive exPlanations (SHAP) values revealed the associations between the five predictors and IR, namely BMI (strongly positive impact on IR), fasting glucose (strongly positive), HDL-C (medium negative), triglycerides (medium positive), and glycohemoglobin (medium positive). The threshold values for identifying IR were 29 kg/m2, 100 mg/dL, 54.5 mg/dL, 89 mg/dL, and 5.6% for BMI, glucose, HDL-C, triglycerides, and glycohemoglobin, respectively.

Conclusion

The XGBoosting algorithm demonstrated superior performance metrics for discriminating IR in middle-aged nondiabetic women, with BMI, glucose, HDL-C, glycohemoglobin, and triglycerides as the top five predictors.

Phenoage and longitudinal changes on transthoracic echocardiography in Alström syndrome: a disease of accelerated ageing?

Alström syndrome (AS) is an ultra-rare disorder characterised by early-onset multi-organ dysfunction, such as insulin resistance, obesity, dyslipidaemia, and renal and cardiovascular disease. The objective is to explore whether AS is a disease of accelerated ageing and whether changes over time on echocardiography could reflect accelerated cardiac ageing. Cross-sectional measurement of Phenoage and retrospective analysis of serial echocardiography were performed between March 2012 and November 2022. The setting is a single national tertiary service jointly run by health service and patient charity. Forty-five adult patients aged over 16 years were included, 64% were male and 67% of White ethnicity. The median Phenoage was 48 years (interquartile range [IQR]: 35-72) in the 34 patients for whom this was calculable, which was significantly higher than the median chronological age of 29 years (IQR: 22-39, p<0.001). Phenoage was higher than chronological age in 85% (N=29) of patients, with a median difference of +18 years (IQR: +4, +34). On echocardiography, significant decreases were observed over time in left ventricular (LV) size at end-diastole (average of 0.046 cm per year, p<0.001) and end-systole (1.1% per year, p=0.025), with significant increase in posterior wall thickness at end-diastole (0.009 cm per year, p=0.008). LV systolic function measured by global longitudinal strain reduced (0.34 percentage points per year, p=0.020) and E/e'lat increased (2.5% per year, p=0.019). Most AS patients display a higher Phenoage compared to chronological age. Cardiac changes in AS patients were also reflective of accelerated ageing, with a reduction in LV size and increased wall thickening. AS may be a paradigm disease for premature ageing.

Whole-exome sequencing reveals novel variants of monogenic diabetes in Tunisia: impact on diagnosis and healthcare management

Introduction: Monogenic diabetes (MD) accounts for 3%-6% of all cases of diabetes. This prevalence is underestimated due to its overlapping clinical features with type 1 and type 2 diabetes. Hence, genetic testing is the most appropriate tool for obtaining an accurate diagnosis. In Tunisia, few cohorts of MD have been investigated until now. The aim of this study is to search for pathogenic variants among 11 patients suspected of having MD in Tunisia using whole-exome sequencing (WES). Materials and methods: WES was performed in 11 diabetic patients recruited from a collaborating medical center. The pathogenicity of genetic variation was assessed using combined filtering and bioinformatics prediction tools. The online ORVAL tool was used to predict the likelihood of combinations of pathogenic variations. Then, Sanger sequencing was carried out to confirm likely pathogenic predicted variants among patients and to check for familial segregation. Finally, for some variants, we performed structural modeling to study their impact on protein function. Results: We identified novel variants related to MD in Tunisia. Pathogenic variants are located in several MODY and non-MODY genes. We highlighted the presence of syndromic forms of diabetes, including the Bardet-Biedl syndrome, Alström syndrome, and severe insulin resistance, as well as the presence of isolated diabetes with significantly reduced penetrance for Wolfram syndrome-related features. Idiopathic type 1 diabetes was also identified in one patient. Conclusion: In this study, we emphasized the importance of genetic screening for MD in patients with a familial history of diabetes, mainly among admixed and under-represented populations living in low- and middle-income countries. An accurate diagnosis with molecular investigation of MD may improve the therapeutic choice for better management of patients and their families. Additional research and rigorous investigations are required to better understand the physiopathological mechanisms of MD and implement efficient therapies that take into account genomic context and other related factors.

Alström's Syndrome, Leber's Hereditary Optic Neuropathy, or Retinitis Pigmentosa? A Case of Misdiagnosis

A case of a patient with the Alström syndrome (AS) that was misdiagnosed as Leber's hereditary optic neuropathy or retinitis pigmentosa for 13 years is presented. AS is a rare genetic disorder caused by mutations in the ALMS1 gene. AS may lead to abnormal ciliary formation and function. AS affects metabolism, and symptomatology includes type 2 diabetes mellitus (T2DM), obesity, hypogonadism and gynecomastia in males, progressive bilateral sensorineural hearing loss, cardiomyopathy, nonalcoholic fatty liver disease (NAFLD), cirrhosis, and chronic progressive kidney disease. The onset of the above symptoms may vary significantly. The ophthalmic manifestation is early onset cone-rod dystrophy that starts as progressive vision loss, photophobia, and nystagmus in the first months of life. An accurate diagnosis may enable specialists to facilitate a significantly positive effect in the everyday life of a patient. Genetic counseling may also be recommended for these patients. Diagnosis was confirmed by DNA testing, thus highlighting its necessity in everyday practice.

Ciliopathies in pediatric endocrinology

Ciliopathies are a group of disorders that involve many organs and systems. In this review, we consider the role of the cilium in multiorgan pathology with a focus on endocrinological aspects. Identification of new genes and mutations is the major challenge in development of a tailored and appropriate therapy. It is expected that new mutations will be identified to characterize ciliopathies and promote new therapies.

Hematopoietic Stem Cells and Metabolic Deterioration in Alström Syndrome, a Rare Genetic Model of the Metabolic Syndrome

Alström syndrome (AS) is a rare genetic disease caused by ALMS1 mutations, characterized by short stature, and vision and hearing loss. Patients with AS develop the metabolic syndrome, long-term organ complications, and die prematurely. We explored the association between AS and a shortage of hematopoietic stem/progenitor cells (HSPCs), which is linked to metabolic diseases and predicts diabetic complications. We included patients with AS at a national referral center. We measured HSPCs with flow cytometry at baseline and follow-up. We followed patients up to January 2022 for metabolic worsening and end-organ damage. We evaluated HSPC levels and mobilization as well as bone marrow histology in a murine model of AS. In 23 patients with AS, we found significantly lower circulating HSPCs than in healthy blood donors (-40%; P = .002) and age/sex-matched patients (-25%; P = .022). Longitudinally, HSPCs significantly declined by a further 20% in patients with AS over a median of 36 months (interquartile range 30-44). Patients with AS who displayed metabolic deterioration over 5.3 years had lower levels of HSPCs, both at baseline and at last observation, than those who did not deteriorate. Alms1-mutated mice were obese and insulin resistant and displayed significantly reduced circulating HSPCs, despite no overt hematological abnormality. Contrary to what was observed in diabetic mice, HSPC mobilization and bone marrow structure were unaffected. We found depletion of HSPCs in patients with AS, which was recapitulated in Alms1-mutated mice. Larger and longer studies will be needed to establish HSPCs shortage as a driver of metabolic deterioration leading to end-organ damage in AS.

Identification of a novel mutation in ALMS1 in a Chinese patient with monogenic diabetic syndrome by whole-exome sequencing

Alstrom syndrome (AS) is one type of monogenic diabetic syndromes caused by mutation in the ALMS1. Due to rare prevalence and overlaps of clinical symptoms, monogenic diabetes is often misdiagnosed. Here, we report a Chinese diabetes patient with poor blood glucose control and insulin resistance. With whole-exome sequencing (WES), this patient was classified into monogenic diabetes and diagnosed as AS with one novel gene mutation identified. This study highlights the clinical application of WES in the diagnosis of monogenic diabetes.

Achievements, prospects and challenges in precision care for monogenic insulin-deficient and insulin-resistant diabetes

Integration of genomic and other data has begun to stratify type 2 diabetes in prognostically meaningful ways, but this has yet to impact on mainstream diabetes practice. The subgroup of diabetes caused by single gene defects thus provides the best example to date of the vision of 'precision diabetes'. Monogenic diabetes may be divided into primary pancreatic beta cell failure, and primary insulin resistance. In both groups, clear examples of genotype-selective responses to therapy have been advanced. The benign trajectory of diabetes due to pathogenic GCK mutations, and the sulfonylurea-hyperresponsiveness conferred by activating KCNJ11 or ABCC8 mutations, or loss-of-function HNF1A or HNF4A mutations, often decisively guide clinical management. In monogenic insulin-resistant diabetes, subcutaneous leptin therapy is beneficial in some severe lipodystrophy. Increasing evidence also supports use of 'obesity therapies' in lipodystrophic people even without obesity. In beta cell diabetes the main challenge is now implementation of the precision diabetes vision at scale. In monogenic insulin-resistant diabetes genotype-specific benefits are proven in far fewer patients to date, although further genotype-targeted therapies are being evaluated. The conceptual paradigm established by the insulin-resistant subgroup with 'adipose failure' may have a wider influence on precision therapy for common type 2 diabetes, however. For all forms of monogenic diabetes, population-wide genome sequencing is currently forcing reappraisal of the importance assigned to pathogenic mutations when gene sequencing is uncoupled from prior suspicion of monogenic diabetes.

Case Report:Pregnancy and birth in a mild phenotype of Alström syndrome

Background: Alström syndrome (AS) is an ultrarare multisystemic progressive disease caused by autosomal recessive variations of the ALMS1 gene (2p13). AS is characterized by double sensory impairment, cardiomyopathy, childhood obesity, extreme insulin resistance, early nonalcoholic fatty liver disease, renal dysfunction, respiratory disease, endocrine and urologic disorders. In female AS patients, hyperandrogenism has been described but fertility issues and conception have not been investigated so far.

Case: This case report describes the spontaneous conception, pregnancy, and birth in a 27-year-old woman with AS, characterized by a mild phenotype with late onset of visual impairment, residual perception of light, and hypertension. Before pregnancy, menses were regular with increased levels of dihydrotestosterone and androstanediol glucuronide in the follicular phase, and the ovaries and endometrium were normal during vaginal ultrasound. A thorough clinical follow-up of the maternal and fetal conditions was carried out. A weight gain of 10 kg during pregnancy was recorded, and serial blood and urine tests were all within the normal range, except for mild anemia. The course of pregnancy was uneventful up to 34 weeks of gestation when preeclampsia developed with an abnormally high level of blood pressure and edema in the lower limbs. At 35 weeks + 3 days of gestation, an urgent cesarean section was performed, and a healthy male weighing 1,950 g was born. Histological examination of the placenta showed partial signs of flow obstruction, limited abruption areas, congested fetal vessels and villi, and a small single infarcted area.

Conclusion: The present case demonstrates for the first time that conceiving is possible for patients with ALMS. Particular attention should be given to the management of AS systemic comorbidities through the course of pregnancy.

Palmitic acid control of ciliogenesis modulates insulin signaling in hypothalamic neurons through an autophagy-dependent mechanism

Palmitic acid (PA) is significantly increased in the hypothalamus of mice, when fed chronically with a high-fat diet (HFD). PA impairs insulin signaling in hypothalamic neurons, by a mechanism dependent on autophagy, a process of lysosomal-mediated degradation of cytoplasmic material. In addition, previous work shows a crosstalk between autophagy and the primary cilium (hereafter cilium), an antenna-like structure on the cell surface that acts as a signaling platform for the cell. Ciliopathies, human diseases characterized by cilia dysfunction, manifest, type 2 diabetes, among other features, suggesting a role of the cilium in insulin signaling. Cilium depletion in hypothalamic pro-opiomelanocortin (POMC) neurons triggers obesity and insulin resistance in mice, the same phenotype as mice deficient in autophagy in POMC neurons. Here we investigated the effect of chronic consumption of HFD on cilia; and our results indicate that chronic feeding with HFD reduces the percentage of cilia in hypothalamic POMC neurons. This effect may be due to an increased amount of PA, as treatment with this saturated fatty acid in vitro reduces the percentage of ciliated cells and cilia length in hypothalamic neurons. Importantly, the same effect of cilia depletion was obtained following chemical and genetic inhibition of autophagy, indicating autophagy is required for ciliogenesis. We further demonstrate a role for the cilium in insulin sensitivity, as cilium loss in hypothalamic neuronal cells disrupts insulin signaling and insulin-dependent glucose uptake, an effect that correlates with the ciliary localization of the insulin receptor (IR). Consistently, increased percentage of ciliated hypothalamic neuronal cells promotes insulin signaling, even when cells are exposed to PA. Altogether, our results indicate that, in hypothalamic neurons, impairment of autophagy, either by PA exposure, chemical or genetic manipulation, cause cilia loss that impairs insulin sensitivity.

Allelic overload and its clinical modifier effect in Bardet-Biedl syndrome

Bardet–Biedl syndrome (BBS) is an autosomal recessive ciliopathy characterized by extensive inter- and intra-familial variability, in which oligogenic interactions have been also reported. Our main goal is to elucidate the role of mutational load in the clinical variability of BBS. A cohort of 99 patients from 77 different families with biallelic pathogenic variants in a BBS-associated gene was retrospectively recruited. Human Phenotype Ontology terms were used in the annotation of clinical symptoms. The mutational load in 39 BBS-related genes was studied in index cases using different molecular and next-generation sequencing (NGS) approaches. Candidate allele combinations were analysed using the in silico tools ORVAL and DiGePred. After clinical annotation, 76 out of the 99 cases a priori fulfilled established criteria for diagnosis of BBS or BBS-like. BBS1 alleles, found in 42% of families, were the most represented in our cohort. An increased mutational load was excluded in 41% of the index cases (22/54). Oligogenic inheritance was suspected in 52% of the screened families (23/45), being 40 tested by means of NGS data and 5 only by traditional methods. Together, ORVAL and DiGePred platforms predicted an oligogenic effect in 44% of the triallelic families (10/23). Intrafamilial variable severity could be clinically confirmed in six of the families. Our findings show that the presence of more than two alleles in BBS-associated genes correlated in six families with a more severe phenotype and associated with specific findings, highlighting the role of the mutational load in the management of BBS cases.

Alström Syndrome with Early Vision and Hearing Impairement

Alström syndrome (ALMS) is an autosomal recessive disorder characterized by multiple organ involvement, including progressive cone-rod dystrophy, sensorineural hearing loss, childhood obesity, and type 2 diabetes mellitus. Pathogenic variants in the ALMS1 gene are the known cause for the occurrence of this devastating condition. Here we report on a 12 year old boy referred to the University Clinic with early signs of impaired hearing and vision, obesity, and scoliosis. Central vision was first affected, followed by peripheral vision. In addition, his weight began increasing after the age of two years, reaching 78 kg at a height of 157 cm (BMI 31.64). No polydactyly was present. His mental development was normal in spite of his hearing and vision impairments. There was acanthosis nigricans on the neck. ECG and the cardiac ultrasound were normal. At the age of 12 years, his testicles are 12 ml and his pubertal status is P2 A2. OGTT revealed impaired glucose tolerance with elevated insulin concentrations 121ulU/mL (reference range 2,00-29,1 ulU/mL). Renal function was unaffected, liver functions were normal. Uric acid and lipids were within normal plasma concentrations. A Whole Exome Sequencing was performed and a homozygous ALMS1 pathogenic, frameshift gene variant (LRG_741t1(ALMS1):c.4156dup; p.Thr1386AsnfsTer15) was determined as the cause of the disease. Both parents were carriers for the variant. The absence of mental retardation and polydactyly differentiates Alström and Bardet-Biedle syndrome.

The Interaction of Obesity and Reproductive Function in Adolescents

Obesity is increasing worldwide, including in pediatrics. Adequate nutrition is required for initiation of menses, and there is a clear secular trend toward earlier pubertal onset and menarche in females in countries around the globe. Similar findings of earlier pubertal start are suggested in males. However, as individuals and populations have crossed into over-nutritional states including overweight and obesity, the effect of excess weight on disrupting reproductive function has become apparent. Hypothalamic hypogonadism and polycystic ovary syndrome are two conditions where reproductive function appears to directly relate to excess weight. Clinical findings in individuals with certain polygenic and monogenic obesity syndromes, which also have reproductive disruptions, have helped elucidate neurologic pathways that are common to both. Clinical endocrinopathies such as hypothyroidism or panhypopituitarism also aide in the understanding of the role of the endocrine system in weight gain. Understanding the intersection of obesity and reproductive function may lead to future therapies which can treat both conditions.

A novel variant site of Alstrom syndrome in a Chinese child: a case report

BACKGROUND

Alstrom syndrome (ALMS) is an ultra-rare multisystem genetic disorder caused by autosomal recessive inheritance of the ALMS1 gene. It manifests as multisystem dysfunction, displaying unique clinical signs and symptoms and various severity, which may lead to delayed prognosis or misdiagnosis in medical practice. Although almost 300 pathogenic variants have been reported, there are some variant sites that have not been recognized yet.

CASE DESCRIPTION

We report a case of a 14-year-old boy with manifestations, including binocular vision loss, acanthosis nigricans, type 2 diabetes, insulin resistance, elevated transaminase, hepatic fibrosis, and proteinuria. Compound heterozygous variants in the ALMS1 gene have been discovered by whole exon sequencing. One of his variant sites was C. 8158C>T, which was from his father. And the other variant site was C. 3575C>A, which was from his mother. To the great of our knowledge, this site has not been reported before. Both of the variants make the synthesis of the peptide chain terminated in advance and an incomplete polypeptide chain is formed.

CONCLUSIONS

The clinical presentations of ALMS are complicated and varied. Although early diagnosis can be made according to typical clinical symptoms, whole exon sequencing is necessary for the diagnosis of ALMS, as indicated by our study.

Novel mutations of the Alström syndrome 1 gene in an infant with dilated cardiomyopathy: A case report

BACKGROUND

Alström syndrome (AS) is a rare autosomal recessive disease that is generally induced by mutations of the Alström syndrome 1 (ALMS1) gene. We report a case of AS, extend the spectrum of ALMS1 mutations and highlight the biological role of ALMS1 to explore the relationship between dilated cardiomyopathy (DCM) and mutations in ALMS1.

CASE SUMMARY

We present the case of an infant with AS mainly manifesting with DCM that was caused by a novel mutation of the ALMS1 gene. Whole-exome sequencing revealed a simultaneous large deletion and point mutation in ALMS1, leading to frameshift and missense mutations, respectively, rather than nonsense or frameshift mutations, which have been reported previously. Upon optimized anti-remodeling therapy, biohumoral exams and arrhythmic burden of the infant were alleviated at follow-up after 6 mo.

CONCLUSION

We identified novel mutations of ALMS1 and extended the spectrum of ALMS1 mutations in an infant with AS.

Retinal ciliopathies through the lens of Bardet-Biedl Syndrome: Past, present and future

The primary cilium is a highly specialized and evolutionary conserved organelle in eukaryotes that plays a significant role in cell signaling and trafficking. Over the past few decades tremendous progress has been made in understanding the physiology of cilia and the underlying pathomechanisms of various ciliopathies. Syndromic ciliopathies consist of a group of disorders caused by ciliary dysfunction or abnormal ciliogenesis. These disorders have multiorgan involvement in addition to retinal degeneration underscoring the ubiquitous distribution of primary cilia in different cell types. Genotype-phenotype correlation is often challenging due to the allelic heterogeneity and pleiotropy of these disorders. In this review, we discuss the clinical and genetic features of syndromic ciliopathies with a focus on Bardet-Biedl syndrome (BBS) as a representative disorder. We discuss the structure and function of primary cilia and their role in retinal photoreceptors. We describe the progress made thus far in understanding the functional and genetic characterization including expression quantitative trait locus (eQTL) analysis of BBS genes. In the future directions section, we discuss the emerging technologies, such as gene therapy, as well as anticipated challenges and their implications in therapeutic development for ciliopathies.

A review of Alström syndrome: a rare monogenic ciliopathy

Alström syndrome is a rare monogenic ciliopathy caused by a mutation to the Alström syndrome 1 (ALMS1) gene. Alström syndrome has an autosomal recessive nature of inheritance. Approximately 1,200 cases of Alström syndrome have been identified worldwide. Complications of the disease are likely caused by dysfunctional cilia with complications arising early in life. The known complications of Alström syndrome have been reported to impact multiple major organ systems, including the endocrine system, cardiac system, renal system, sensory system, and hepatic system. The symptoms of Alström syndrome have great variability in presentation and intensity but often lead to organ damage. This has resulted in a shortened lifespan for individuals affected by Alström syndrome. Individuals with the disease rare exceed the age of 50. Currently, there are no specific treatments for Alström syndrome that can cure the disease, prevent the complications, or reverse the complications. Current management involves management of symptoms with the goal of improving quality of life and lifespan. This review aims to summarize the current knowledge on the epidemiology, diagnosis, pathophysiology, complications, management, and prognosis of Alström syndrome. In addition to that, this review also aims to raise awareness and encourage research on Alström syndrome as the condition has a huge impact on affected individuals.

Liver Fibrosis and Steatosis in Alström Syndrome: A Genetic Model for Metabolic Syndrome

Alström syndrome (ALMS) is an ultra-rare monogenic disease characterized by insulin resistance, multi-organ fibrosis, obesity, type 2 diabetes mellitus (T2DM), and hypertriglyceridemia with high and early incidence of non-alcoholic fatty liver disease (NAFLD). We evaluated liver fibrosis quantifying liver stiffness (LS) by shear wave elastography (SWE) and steatosis using ultrasound sonographic (US) liver/kidney ratios (L/K) in 18 patients with ALMS and 25 controls, and analyzed the contribution of metabolic and genetic alterations in NAFLD progression. We also genetically characterized patients. LS and L/K values were significantly higher in patients compared with in controls (p < 0.001 versus p = 0.013). In patients, LS correlated with the Fibrosis-4 Index and age, while L/K was associated with triglyceride levels. LS showed an increasing trend in patients with metabolic comorbidities and displayed a significant correlation with waist circumference, the homeostasis model assessment, and glycated hemoglobin A1c. SWE and US represent promising tools to accurately evaluate early liver fibrosis and steatosis in adults and children with ALMS during follow-up. We described a new pathogenic variant of exon 8 in ALMS1. Patients with ALMS displayed enhanced steatosis, an early increased age-dependent LS that is associated with obesity and T2DM but also linked to genetic alterations, suggesting that ALMS1 could be involved in liver fibrogenesis.