Lipodystrophic diabetes mellitus: a lesson for other forms of diabetes?

Identification of Interactive Genetic Loci Linked to Insulin Resistance in Metabolic Syndrome-An Update

Metabolic syndrome is a metabolic disorder characterized by hypertension, dyslipidemia, impaired glucose tolerance, and abdominal obesity. Impaired insulin action or insulin resistance initiates metabolic syndrome. The prevalence of insulin resistance is increasing all over the world. Insulin resistance results in the defective metabolism of carbohydrates and lipids, in addition to low-grade chronic inflammation. Insulin resistance is associated with metabolic syndrome, which is a risk factor for a number of pathological conditions, such as Type 2 diabetes (T2D), cardiovascular disease (CVD), nonalcoholic fatty liver disease (NAFLD), and polycystic ovarian syndrome (PCOS). Genome-wide association studies have increased our understanding of many loci linked to these diseases and others. In this review, we discuss insulin resistance and its contribution to metabolic syndrome and these diseases. We also discuss the genetic loci associated with them. Genetic testing is invaluable in the identification and stratification of susceptible populations and/or individuals. After susceptible individuals and/or populations have been identified via genetic testing or screening, lifestyle modifications such as regular exercise, weight loss, a healthy diet, and smoking cessation can reduce or prevent metabolic syndrome and its associated pathologies.

From adiposity to steatosis: metabolic dysfunction-associated steatotic liver disease, a hepatic expression of metabolic syndrome - current insights and future directions

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing health concern and the risk of its development is connected with the increasing prevalence of metabolic syndrome (MetS) which occurs as a result of some complex obesity-induced metabolic changes. It is a common chronic liver disease characterized by excessive fat accumulation in the liver, the tendency to progress to more severe forms, and a corresponding increase in morbidity and mortality. Thus, effectively addressing the rising burden of the disease requires a thorough understanding of its complex interrelationship with obesity and MetS.

MAIN BODY

MASLD results from complex interactions involving obesity, insulin resistance, and dyslipidaemia, leading to hepatic lipid accumulation, and is influenced by several genetic and environmental factors such as diet and gut microbiota dysbiosis. It has extensive metabolic and non-metabolic implications, including links to MetS components like hyperglycaemia, hypertension, and dyslipidaemia, and progresses to significant liver damage and other extra-hepatic risks like cardiovascular disease and certain cancers. Diagnosis often relies on imaging and histology, with non-invasive methods preferred over liver biopsies. Emerging biomarkers and OMIC technologies offer improved diagnostic capabilities but face practical challenges. Advancements in artificial intelligence (AI), lifestyle interventions, and pharmacological treatments show promise, with future efforts focusing on precision medicine and novel diagnostic tools to improve patient outcome.

CONCLUSION

Understanding the pathogenic mechanisms underlying the development of MASLD within the context of metabolic syndrome (MetS) is essential for identifying potential therapeutic targets. Advancements in non-invasive diagnostic tools and novel pharmacological treatments, hold promise for improving the management of MASLD. Future research should focus on precision medicine and innovative therapies to effectively address the disease and its consequences.

Lipoatrophic diabetes in familial partial lipodystrophy type 2: From insulin resistance to diabetes

AIM

Subjects with Familial Partial Lipodystrophy type 2 (FPLD2) are at high risk to develop diabetes. To better understand the natural history and variability of this disease, we studied glucose tolerance, insulin response to an oral glucose load, and metabolic markers in the largest cohort to date of subjects with FPLD2 due to the same LMNA variant.

METHODS

A total of 102 patients aged > 18 years, with FPLD2 due to the LMNA 'Reunionese' variant p.(Thr655Asnfs*49) and 22 unaffected adult relatives with normal glucose tolerance (NGT) were enrolled. Oral Glucose Tolerance Tests (OGTT) with calculation of derived insulin sensitivity and secretion markers, and measurements of HbA1c, C-reactive protein, leptin, adiponectin and lipid profile were performed.

RESULTS

In patients with FPLD2: 65% had either diabetes (41%) or prediabetes (24%) despite their young age (median: 39.5 years IQR 29.0-50.8) and close-to-normal BMI (median: 25.5 kg/m² IQR 23.1-29.4). Post-load OGTT values revealed insulin resistance and increased insulin secretion in patients with FPLD2 and NGT, whereas patients with diabetes were characterized by decreased insulin secretion. Impaired glucose tolerance with normal fasting glucose was present in 86% of patients with prediabetes. Adiponectin levels were decreased in all subjects with FPLD2 and correlated with insulin sensitivity markers.

CONCLUSIONS

OGTT reveals early alterations of glucose and insulin metabolism in patients with FPLD2, and should be systematically performed before excluding a diagnosis of prediabetes or diabetes to adapt medical care. Decreased adiponectin is an early marker of the disease. Adiponectin replacement therapy warrants further study in FPLD2.

Metabolic causes and consequences of nonalcoholic fatty liver disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is a multifactorial metabolic disorder that was first described in 1980. It has been prevalent and on the rise for many years and is associated with other metabolic disorders such as obesity and type 2 diabetes mellitus (T2DM). NAFLD can be best described as a metabolic dysfunction that stems from insulin resistance-induced hepatic lipogenesis. This lipogenesis increases oxidative stress and hepatic inflammation and is often potentiated by genetic and gut microbiome dysfunction. As NAFLD progresses from simple steatosis to non-alcoholic steatohepatitis (NASH) and to cirrhosis and hepatocellular carcinoma (HCC), the odds of complications including cardiovascular disease (CVD), chronic kidney disease (CKD), and overall mortality increase. The aim of this review is to describe the metabolic causes and consequences of NAFLD while examining the risks that each stage of NAFLD poses. In this review, the etiology of "lean" NAFLD, the impact of obesity, T2DM, genetics, and microbiome dysbiosis on NAFLD progression are all explored. This review will also discuss the core issue behind the progression of NAFLD: insulin resistance (IR). Upon describing the causes and consequences of NAFLD, the effectiveness of diet modification, lifestyle changes, and glucagon-like peptide 1 receptor (GLP-1) agonists to retard NAFLD progression and stem the rate of complications is examined.

Type 2 diabetes in pediatrics

Type 2 diabetes (T2D) in adolescents has become an increasing health concern throughout the world and its prevention and screening should be implemented in pediatric care. As clinical features at presentation, in some cases can be similar to type 1 diabetes and family history can be in favour of a monogenic form of diabetes, it is pivotal for physicians to be aware of youth-onset T2D specificities to ensure an accurate diagnosis. The global increase of overweight and obesity can complicate the diagnostic process and makes it essential to apply a systematic approach to each new diagnosis. Microvascular complications may be present at the time of diagnosis and chronic complications are frequent and need to be screened regularly. Regular screening of comorbidities should also be performed. Childhood T2D should be followed up by pediatric diabetes units to avoid diagnostic errors and delay in care. A multidisciplinary approach, by an experienced team, is pivotal to provide treatment options targeting the unique needs of pediatric patients. Treatment programs must include the whole family and address all the aspects of the care (lifestyle, pharmacological therapy, psychological aspects, complications and comorbidities). An organized process of transition to adult care is essential.

Insulin and Insulin Receptors in Adipose Tissue Development

Insulin is a major endocrine hormone also involved in the regulation of energy and lipid metabolism via the activation of an intracellular signaling cascade involving the insulin receptor (INSR), insulin receptor substrate (IRS) proteins, phosphoinositol 3-kinase (PI3K) and protein kinase B (AKT). Specifically, insulin regulates several aspects of the development and function of adipose tissue and stimulates the differentiation program of adipose cells. Insulin can activate its responses in adipose tissue through two INSR splicing variants: INSR-A, which is predominantly expressed in mesenchymal and less-differentiated cells and mainly linked to cell proliferation, and INSR-B, which is more expressed in terminally differentiated cells and coupled to metabolic effects. Recent findings have revealed that different distributions of INSR and an altered INSR-A:INSR-B ratio may contribute to metabolic abnormalities during the onset of insulin resistance and the progression to type 2 diabetes. In this review, we discuss the role of insulin and the INSR in the development and endocrine activity of adipose tissue and the pharmacological implications for the management of obesity and type 2 diabetes.

Not quite type 1 or type 2, what now? Review of monogenic, mitochondrial, and syndromic diabetes

Diabetes mellitus is a heterogeneous group of conditions defined by resultant chronic hyperglycemia. Given the increasing prevalence of diabetes mellitus and the increasing understanding of genetic etiologies, we present a broad review of rare genetic forms of diabetes that have differing diagnostic and/or treatment implications from type 1 and type 2 diabetes. Advances in understanding the genotype-phenotype associations in these rare forms of diabetes offer clinically available examples of evolving precision medicine where defining the correct genetic etiology can radically alter treatment approaches. In this review, we focus on forms of monogenic diabetes, mitochondrial diabetes, and syndromic diabetes.

Definitive diagnosis of mandibular hypoplasia, deafness, progeroid features and lipodystrophy (MDPL) syndrome caused by a recurrent de novo mutation in the POLD1 gene

Segmental progeroid syndromes with lipodystrophy are extremely rare, heterogeneous, and complex multi-system disorders that are characterized by phenotypic features of premature aging affecting various tissues and organs. In this study, we present a "sporadic/isolated" Japanese woman who was ultimately diagnosed with mandibular hypoplasia, deafness, progeroid features, and progressive lipodystrophy (MDPL) syndrome (MIM #615381) using whole exome sequencing analysis. She had been suspected as having atypical Werner syndrome and/or progeroid syndrome based on observations spanning a 30-year period; however, repeated genetic testing by Sanger sequencing did not identify any causative mutation related to various subtypes of congenital partial lipodystrophy (CPLD) and/or mandibular dysplasia with lipodystrophy (MAD). Recently, MDPL syndrome has been described as a new entity showing progressive lipodystrophy. Furthermore, polymerase delta 1 (POLD1) gene mutations on chromosome 19 have been identified in patients with MDPL syndrome. To date, 21 cases with POLD1-related MDPL syndrome have been reported worldwide, albeit almost entirely of European origin. Here, we identified a de novo mutation in exon 15 (p.Ser605del) of the POLD1 gene in a Japanese case by whole exome sequencing. To the best of our knowledge, this is the first identified case of MDPL syndrome in Japan. Our results provide further evidence that mutations in POLD1 are responsible for MDPL syndrome and serve as a common genetic determinant across different ethnicities.

Adipocyte Dynamics and Reversible Metabolic Syndrome in Mice with an Inducible Adipocyte-Specific Deletion of the Insulin Receptor

Insulin and IGF1 signaling are important for adipose tissue development and function; however, their role in mature adipocytes is unclear. Mice with a tamoxifen-inducible knockout of insulin and/or IGF1 receptors (IR/IGF1R) demonstrate a rapid loss of white and brown fat due to increased lipolysis and adipocyte apoptosis. This results in insulin resistance, glucose intolerance, hepatosteatosis, islet hyperplasia with hyperinsulinemia, and cold intolerance. This phenotype, however, resolves over 10-30 days due to a proliferation of preadipocytes and rapid regeneration of both brown and white adipocytes as identified by mTmG lineage tracing. This cycle can be repeated with a second round of receptor inactivation. Leptin administration prior to tamoxifen treatment blocks development of the metabolic syndrome without affecting adipocyte loss or regeneration. Thus, IR is critical in adipocyte maintenance, and this loss of adipose tissue stimulates regeneration of brown/white fat and reversal of metabolic syndrome associated with fat loss.