What the genetics of lipodystrophy can teach us about insulin resistance and diabetes

The Impact of Exercise Training Plus Dietary Interventions on Ectopic Fat in Population with Overweight/Obesity with and without Chronic Disease: A Systematic Review, Meta-analysis, and Metaregression of Randomized Clinical Trials

Background

The growing prevalence of obesity and related chronic diseases has led to increased interest in interventions targeting ectopic fat reduction to which its accumulation is linked to metabolic dysfunction.

Objectives

This study aimed to evaluate the effects of combined exercise training combined with dietary interventions compared with dietary interventions alone on ectopic fat [visceral fat area (VFA), liver fat, intramuscular fat (IMF), pancreatic fat, renal sinus fat, and pericardial and epicardial fats] in adults with overweight and obesity, both with and without chronic diseases.

Methods

Web of Science, Scopus, and PubMed were searched for original articles up to 1 March, 2024, that included exercise compared with control interventions on body weight and ectopic fat in adults with overweight or obesity. Weighted mean differences (WMD) for body weight, liver fat, pancreatic fat, and renal sinus fat and standardized mean differences (SMD) for VFA, IMF, pericardial and epicardial fats, and 95% confidence intervals were determined using random-effects models.

Results

Thirty-two studies, including 1488 participants and 38 intervention groups, met the inclusion criteria. The combined intervention of exercise and diet did not reduce body weight (WMD = -0.23 kg, P = 0.180), liver fat (WMD = 0.05%, P = 0.730), IMF (SMD = -0.08, P = 0.640), pericardial and epicardial fats (SMD = -0.12, P = 0.280), pancreatic fat (WMD = -0.24%, P = 0.370), and renal sinus fat (WMD = 0.01 cm2, P = 0.170) when compared with a diet-only group. Interestingly, exercise combined with diet significantly reduced VFA in participants with obesity (SMD = -0.12, P = 0.040) and healthy males (SMD = -0.33, P = 0.001) when compared with a diet-only group.

Conclusions

The findings suggest that combined exercise and dietary interventions did not lead to significant reductions in most ectopic fat depots when compared with diet alone. However, a modest reduction in VFA was observed in participants with obesity and healthy males. These results highlight the nuanced impact of exercise in combination with dietary interventions and the need to consider specific fat depots and participant characteristics in obesity management strategies.The trial was registered at PROSPERO as CRD42024546770.

Exploring lipodystrophy gene expression in adipocytes: unveiling insights into the pathogenesis of insulin resistance, type 2 diabetes, and clustering diseases (metabolic syndrome) in Asian Indians

Background

Studying the molecular mechanisms of lipodystrophy can provide valuable insights into the pathophysiology of insulin resistance (IR), type 2 diabetes (T2D), and other clustering diseases [metabolic syndrome (MetS)] and its underlying adipocentric disease (MetS disease).

Methods

A high-confidence lipodystrophy gene panel comprising 50 genes was created, and their expressions were measured in the visceral and subcutaneous (both peripheral and abdominal) adipose depots of MetS and non-MetS individuals at a tertiary care medical facility.

Results

Most lipodystrophy genes showed significant downregulation in MetS individuals compared to non-MetS individuals in both subcutaneous and visceral depots. In the abdominal compartment, all the genes showed relatively higher expression in visceral depot as compared to their subcutaneous counterpart, and this difference narrowed with increasing severity of MetS. Their expression level shows an inverse correlation with T2D, MetS, and HOMA-IR and with other T2D-related intermediate traits. Results also demonstrated that individualization of MetS patients could be done based on adipose tissue expression of just 12 genes.

Conclusion

Adipose tissue expression of lipodystrophy genes shows an association with MetS and its intermediate phenotypic traits. Mutations of these genes are known to cause congenital lipodystrophy syndromes, whereas their altered expression in adipose tissue contributes to the pathogenesis of IR, T2D, and MetS.

Ectopic lipid deposition in muscle and liver, quantified by proton magnetic resonance spectroscopy

Advances in the development of noninvasive imaging techniques have spurred investigations into ectopic lipid deposition in the liver and muscle and its implications in the development of metabolic diseases such as type 2 diabetes. Computed tomography and ultrasound have been applied in the past, though magnetic resonance-based methods are currently considered the gold standard as they allow more accurate quantitative detection of ectopic lipid stores. This review focuses on methodological considerations of magnetic resonance-based methods to image hepatic and muscle fat fractions, and it emphasizes anatomical and morphological aspects and how these may influence data acquisition, analysis, and interpretation.

Subcutaneous Transplantation of White Adipose Tissue

In the research setting, white adipose tissue (WAT) transplantation, also known as fat transplantation, is often used to understand the physiological function of adipocytes or associated stromal vascular cells such as macrophages in the context of local and systemic metabolism. The mouse is the most common animal model used where WAT from a donor is transferred either to a subcutaneous site of the same organism or to a subcutaneous region of a recipient. Here, we describe in detail the procedure for heterologous fat transplantation, and, given the need for survival surgery, peri- and postoperative care and subsequent histological confirmation of fat grafts will also be discussed.

Current Diagnosis, Treatment and Clinical Challenges in the Management of Lipodystrophy Syndromes in Children and Young People

Lipodystrophy is a heterogeneous group of disorders characterized by lack of body fat in characteristic patterns, which can be genetic or acquired. Lipodystrophy is associated with insulin resistance that can develop in childhood and adolescence, and usually leads to severe metabolic complications. Diabetes mellitus, hypertriglyceridemia, and hepatic steatosis ordinarily develop in these patients, and most girls suffer from menstrual abnormalities. Severe complications develop at a relatively young age, which include episodes of acute pancreatitis, renal failure, cirrhosis, and complex cardiovascular diseases, and all of these are associated with serious morbidity. Treatment of lipodystrophy consists of medical nutritional therapy, exercise, and the use of anti-hyperglycemic and lipid-lowering agents. New treatment modalities, such as metreleptin replacement, promise much in the treatment of metabolic abnormalities secondary to lipodystrophy. Current challenges in the management of lipodystrophy in children and adolescents include, but are not limited to: (1) establishing specialized centers with experience in providing care for lipodystrophy presenting in childhood and adolescence; (2) optimizing algorithms that can provide some guidance for the use of standard and novel therapies to ensure adequate metabolic control and to prevent complications; (3) educating patients and their parents about lipodystrophy management; (4) improving patient adherence to chronic therapies; (5) reducing barriers to access to novel treatments; and (5) improving the quality of life of these patients and their families.

Acromegaly with congenital generalized lipodystrophy - two rare insulin resistance conditions in one patient: a case report

BACKGROUND

Lipodystrophies are a group of diseases which are characterized by abnormal adipose tissue deposition and are frequently associated with metabolic changes. Congenital generalized lipodystrophy is an autosomal recessive syndrome, with a prevalence < 1:10 million. Acromegaly is a rare disease, secondary to the chronic hypersecretion of growth hormone and insulin-like growth factor-1, with characteristic metabolic and somatic effects. "Acromegaloidism" is a term used for patients who manifest clinical features of acromegaly, but do not present a demonstrable hormone growth hypersecretion. The extreme shortage of subcutaneous adipose tissues and muscle hypertrophy confer an acromegaloid-like appearance in these patients.

CASE PRESENTATION

We describe a case of a patient with the rare combination of Berardinelli-Seip congenital lipodystrophy and acromegaly; our patient is a 63-year-old white man, who was referred to an endocrinology consultation for suspected lipodystrophy. He had lipoatrophy of upper and lower limbs, trunk, and buttocks, with muscular prominence, acromegaloid facial appearance, large extremities, and soft tissue tumescence. In addition, he had dyslipidemia and prediabetes. His fat mass ratio (% trunk fat mass/% lower limbs fat mass) was 1.02 by densitometry and he also had hepatomegaly, with mild steatosis (from an abdominal ultrasound), and left ventricular hypertrophy (from an electrocardiogram). His first oral glucose tolerance test had growth hormone nadir of 0.92 ng/mL, and the second test, 10 months afterwards, registered growth hormone nadir of 0.64 ng/mL (growth hormone nadir < 0.3 ng/mL excludes acromegaly). Pituitary magnetic resonance imaging identified an area of hypocaptation of contrast product in relation to a pituitary adenoma and he was subsequently submitted to transsphenoidal surgical resection of the mass. A pathological evaluation showed pituitary adenoma with extensive expression of growth hormone and adrenocorticotropic hormone, as well as a rare expression of follicle-stimulating hormone and prolactin. A genetic study revealed an exon 3/exon 4 deletion of the AGPAT2 gene in homozygosity.

CONCLUSIONS

Congenital generalized lipodystrophy is a rare disease which occurs with acromegaloid features. As far as we know, we have described the first case of genetic lipodystrophy associated with true acromegaly. Although this is a rare association, the presence of congenital generalized lipodystrophy should not exclude the possibility of simultaneous acromegaly.

Unraveling LMNA Mutations in Metabolic Syndrome: Cellular Phenotype and Clinical Pitfalls

This study details the clinical and cellular phenotypes associated with two missense heterozygous mutations in LMNA, c.1745G>T p.(Arg582Leu), and c.1892G>A p.(Gly631Asp), in two patients with early onset of diabetes mellitus, hypertriglyceridemia and non-alcoholic fatty liver disease. In these two patients, subcutaneous adipose tissue was persistent, at least on the abdomen, and the serum leptin level remained in the normal range. Cellular studies showed elevated nuclear anomalies, an accelerated senescence rate and a decrease of replication capacity in patient cells. In cellular models, the overexpression of mutated prelamin A phenocopied misshapen nuclei, while the partial reduction of lamin A expression in patient cells significantly improved nuclear morphology. Altogether, these results suggest a link between lamin A mutant expression and senescence associated phenotypes. Transcriptome analysis of the whole subcutaneous adipose tissue from the two patients and three controls, paired for age and sex using RNA sequencing, showed the up regulation of genes implicated in immunity and the down regulation of genes involved in development and cell differentiation in patient adipose tissue. Therefore, our results suggest that some mutations in LMNA are associated with severe metabolic phenotypes without subcutaneous lipoatrophy, and are associated with nuclear misshaping.

Monogenic forms of lipodystrophic syndromes: diagnosis, detection, and practical management considerations from clinical cases

BACKGROUND

Lipodystrophic syndromes are rare diseases of genetic or acquired origin characterized by partial or generalized lack of body fat. Early detection and diagnosis are crucial to prevent and manage associated metabolic dysfunctions, i.e. insulin resistance, dyslipidemia, fatty liver, and diabetes, and to provide appropriate genetic counseling. By means of several representative case studies, this article illustrates the diagnostic and management challenges of lipodystrophic syndromes.

REVIEW

Berardinelli-Seip congenital lipodystrophy (BSCL) is typically diagnosed at birth, or soon thereafter, with generalized lipoatrophy and hepatomegaly secondary to hepatic steatosis. Physicians must also consider this diagnosis in adults with atypical non-autoimmune diabetes, hypertriglyceridemia, and a lean and muscular phenotype. The BSCL1 subtype due to mutations in the AGPAT2 gene can have an unusual presentation, especially in neonates and infants. Particular attention should be paid to infants presenting failure to thrive who also have hepatomegaly and metabolic derangements. The BSCL2 sub-type due to mutations in the BSCL gene tends to be more severe than BSCL1, and is characterized by greater fat loss, mild intellectual disability, earlier onset of diabetes, and higher incidence of premature death. Effective management from an earlier age may moderate the natural disease course. Partial lipodystrophies may easily be confused with common central obesity and/or metabolic syndrome. In patients with unexplained pancreatitis and hypertriglyceridemia, lipodystrophies such as familial partial lipodystrophy type 2 (FPLD2; Dunnigan type, due to LMNA mutations) should be considered. Oral combined contraceptives, which can reveal the disease by inducing severe hypertriglyceridemia, are contraindicated. Endogenous estrogens may also lead to "unmasking" of the FPLD2 phenotype, which often appears at puberty, and is more severe in females than males.

CONCLUSIONS

Diet and exercise, adapted to age and potential comorbidities, are essential prerequisites for therapeutic management of lipodystrophic syndromes. Metreleptin therapy can be useful to manage lipodystrophy-related metabolic complications.

Risk of diabetes in HIV-infected patients is associated with cirrhosis but not with chronic HCV coinfection in a French nationwide HIV cohort

BACKGROUND

Both human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infections have been reportedly associated with a higher risk of diabetes mellitus (DM) but results are conflicting.

AIMS

To determine whether there is an association between chronic HCV and the incidence of DM, and to study the role of factors such as cirrhosis, IFN-based HCV therapy, sustained virologic response (SVR) and chronic HBV infection among patients living with HIV (PLHIV) followed in a large French multicentre cohort in the combination antiretroviral therapy (cART) era.

METHODS

All PLHIV followed up in the Dat'AIDS cohort were eligible. Cox models for survival analysis were used to study the time to occurrence of DM.

RESULTS

Among 28 699 PLHIV, 4004 patients had chronic HCV infection. The mean duration of HCV follow-up was 12.5 ± 8.1 years. The rate ratio of DM was 2.74 per 1000 person-years. By multivariate analysis, increasing age, body mass index>25, AIDS status, nadir CD4 cell count ≤200/mm³ , detectable HIV viral load and cirrhosis (HR 2.26 95% CI 1.14-1.18; P < 0.0001) were predictors of DM, whereas longer cART duration was associated with a lower risk of DM. Chronic HCV and HBV infection and IFN-based HCV therapy were not associated with DM. In a subanalysis among HCV-infected patients, SVR was not related to DM.

CONCLUSIONS

Our study shows that in the HIV population, cirrhosis is associated with an increased occurrence of DM, but not chronic HCV infection or duration of HCV infection.

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.

Glucagon-like peptide-1 analogues - an efficient therapeutic option for the severe insulin resistance of lipodystrophic syndromes: two case reports

Background

Lipodystrophic syndromes are uncommon medical conditions which are normally associated with metabolic disorders, such as diabetes mellitus, dyslipidemia, and fatty liver disease. These complications are generally difficult to treat, particularly diabetes, due to severe insulin resistance. We present two case reports of successful treatment of diabetes with glucagon-like peptide-1 analogues in patients with clinical features of lipodystrophic syndromes.

Case presentation

Two white women aged 49 and 60 years manifested marked central body fat deposition with severe lipoatrophy of their limbs and buttocks and pronounced acanthosis nigricans. They had hypertension, dyslipidemia, fatty liver disease, and poorly controlled diabetes (glycated hemoglobin 8.3% and 10.2%, respectively) despite the use of three classes of oral antidiabetic drugs taken in combination in the first case, and high doses of insulin in the second case. Four months after the addition of glucagon-like peptide-1 analogue to their previous treatment they both showed a pronounced improvement in metabolic control (glycated hemoglobin 5.6% and 6.2%, respectively). In the first case, a weight loss of nearly 30 kg was recorded.

Conclusions

We intend to demonstrate that glucagon-like peptide-1 analogues could be a valuable tool for patients with lipodystrophic disorders, probably by improving body fat distribution, with favorable results in insulin-sensitivity and glycemic control.

Bone imaging findings in genetic and acquired lipodystrophic syndromes: an imaging study of 24 cases

OBJECTIVE

To describe the bone imaging features of lipodystrophies in the largest cohort ever published.

MATERIALS AND METHODS

We retrospectively examined bone imaging data in 24 patients with lipodystrophic syndromes. Twenty-two had genetic lipodystrophy: 12/22 familial partial lipodystrophy (FPLD) and 10/22 congenital generalized lipodystrophy (CGL), 8 with AGPAT2-linked CGL1 and 2 with seipin-linked CGL2. Two patients had acquired generalized lipodystrophy (AGL) in a context of non-specific autoimmune disorders. Skeletal radiographs were available for all patients, with radiographic follow-up for two. Four patients with CGL1 underwent MRI, and two of them also underwent CT.

RESULTS

Patients with FPLD showed non-specific degenerative radiographic abnormalities. Conversely, CGL patients showed three types of specific radiographic alterations: diffuse osteosclerosis (in 7 patients, 6 with CGL1 and 1 with CGL2), well-defined osteolytic lesions sparing the axial skeleton (7 CGL1 and 1 CGL2), and pseudo-osteopoikilosis (4 CGL1). Pseudo-osteopoikilosis was the sole bone abnormality observed in one of the two patients with AGL. Osteolytic lesions showed homogeneous low signal intensity (SI) on T1-weighted and high SI on T2-weighted MR images. Most of them were asymptomatic, although one osteolytic lesion resulted in a spontaneous knee fracture and secondary osteoarthritis in a patient with CGL1. MRI also showed diffuse fatty bone marrow alterations in patients with CGL1, with intermediate T1 and high T2 SI, notably in radiographically normal areas.

CONCLUSIONS

The three types of peculiar imaging bone abnormalities observed in generalized lipodystrophic syndromes (diffuse osteosclerosis, lytic lesions and/or pseudo-osteopoikilosis) may help clinicians with an early diagnosis in pauci-symptomatic patients.

One-year metreleptin improves insulin secretion in patients with diabetes linked to genetic lipodystrophic syndromes

Recombinant methionyl human leptin (metreleptin) therapy was shown to improve hyperglycaemia, dyslipidaemia and insulin sensitivity in patients with lipodystrophic syndromes, but its effects on insulin secretion remain controversial. We used dynamic intravenous (i.v.) clamp procedures to measure insulin secretion, adjusted to insulin sensitivity, at baseline and after 1 year of metreleptin therapy, in 16 consecutive patients with lipodystrophy, diabetes and leptin deficiency. Patients, with a mean [± standard error of the mean (s.e.m.)] age of 39.2 (±4) years, presented with familial partial lipodystrophy (n = 11, 10 women) or congenital generalized lipodystrophy (n = 5, four women). Their mean (± s.e.m.) BMI (23.9 ± 0.7 kg/m(2) ), glycated haemoglobin levels (8.5 ± 0.4%) and serum triglycerides levels (4.6 ± 0.9 mmol/l) significantly decreased within 1 month of metreleptin therapy, then remained stable. Insulin sensitivity (from hyperglycaemic or euglycaemic-hyperinsulinaemic clamps, n = 4 and n = 12, respectively), insulin secretion during graded glucose infusion (n = 12), and acute insulin response to i.v. glucose adjusted to insulin sensitivity (disposition index, n = 12), significantly increased after 1 year of metreleptin therapy. The increase in disposition index was related to a decrease in percentage of total and trunk body fat. Metreleptin therapy improves not only insulin sensitivity, but also insulin secretion in patients with diabetes attributable to genetic lipodystrophies.

POLD1: Central mediator of DNA replication and repair, and implication in cancer and other pathologies

The evolutionarily conserved human polymerase delta (POLD1) gene encodes the large p125 subunit which provides the essential catalytic activities of polymerase δ (Polδ), mediated by 5′–3′ DNA polymerase and 3′–5′ exonuclease moieties. POLD1 associates with three smaller subunits (POLD2, POLD3, POLD4), which together with Replication Factor C and Proliferating Nuclear Cell Antigen constitute the polymerase holoenzyme. Polδ function is essential for replication, with a primary role as the replicase for the lagging strand. Polδ also has an important proofreading ability conferred by the exonuclease activity, which is critical for ensuring replicative fidelity, but also serves to repair DNA lesions arising as a result of exposure to mutagens. Polδ has been shown to be important for multiple forms of DNA repair, including nucleotide excision repair, double strand break repair, base excision repair, and mismatch repair. A growing number of studies in the past decade have linked germline and sporadic mutations in POLD1 and the other subunits of Polδ with human pathologies. Mutations in Polδ in mice and humans lead to genomic instability, mutator phenotype and tumorigenesis. The advent of genome sequencing techniques has identified damaging mutations in the proofreading domain of POLD1 as the underlying cause of some inherited cancers, and suggested that mutations in POLD1 may influence therapeutic management. In addition, mutations in POLD1 have been identified in the developmental disorders of mandibular hypoplasia, deafness, progeroid features and lipodystrophy and atypical Werner syndrome, while changes in expression or activity of POLD1 have been linked to senescence and aging. Intriguingly, some recent evidence suggests that POLD1 function may also be altered in diabetes. We provide an overview of critical Polδ activities in the context of these pathologic conditions.

A Heterozygous ZMPSTE24 Mutation Associated with Severe Metabolic Syndrome, Ectopic Fat Accumulation, and Dilated Cardiomyopathy

ZMPSTE24 encodes the only metalloprotease, which transforms prelamin into mature lamin A. Up to now, mutations in ZMPSTE24 have been linked to Restrictive Dermopathy (RD), Progeria or Mandibulo-Acral Dysplasia (MAD). We report here the phenotype of a patient referred for severe metabolic syndrome and cardiomyopathy, carrying a mutation in ZMPSTE24. The patient presented with a partial lipodystrophic syndrome associating hypertriglyceridemia, early onset type 2 diabetes, and android obesity with truncal and abdominal fat accumulation but without subcutaneous lipoatrophy. Other clinical features included acanthosis nigricans, liver steatosis, dilated cardiomyopathy, and high myocardial and hepatic triglycerides content. Mutated fibroblasts from the patient showed increased nuclear shape abnormalities and premature senescence as demonstrated by a decreased Population Doubling Level, an increased beta-galactosidase activity and a decreased BrdU incorporation rate. Reduced prelamin A expression by siRNA targeted toward LMNA transcripts resulted in decreased nuclear anomalies. We show here that a central obesity without subcutaneous lipoatrophy is associated with a laminopathy due to a heterozygous missense mutation in ZMPSTE24. Given the high prevalence of metabolic syndrome and android obesity in the general population, and in the absence of familial study, the causative link between mutation and phenotype cannot be formally established. Nevertheless, altered lamina architecture observed in mutated fibroblasts are responsible for premature cellular senescence and could contribute to the phenotype observed in this patient.

Mandibular hypoplasia, deafness, progeroid features and lipodystrophy (MDPL) syndrome in the context of inherited lipodystrophies

BACKGROUND

Lipodystrophies are a large heterogeneous group of genetic or acquired disorders characterized by generalized or partial fat loss, usually associated with metabolic complications such as diabetes mellitus, hypertriglyceridemia and hepatic steatosis. Many efforts have been made in the last years in identifying the genetic etiologies of several lipodystrophy forms, although some remain to be elucidated.

METHODS

We report here the clinical description of a woman with a rare severe lipodystrophic and progeroid syndrome associated with hypertriglyceridemia and diabetes whose genetic bases have been clarified through whole-exome sequencing (WES) analysis.

RESULTS

This article reports the 5th MDPL (Mandibular hypoplasia, deafness, progeroid features, and lipodystrophy syndrome) patient with the same de novo p.S605del mutation in POLD1. We provided further genetic evidence that this is a disease-causing mutation along with a plausible molecular mechanism responsible for this recurring event. Moreover we overviewed the current classification of the inherited forms of lipodystrophy, along with their underlying molecular basis.

CONCLUSIONS

Progress in the identification of lipodystrophy genes will help in better understanding the role of the pathways involved in the complex physiology of fat. This will lead to new targets towards develop innovative therapeutic strategies for treating the disorder and its metabolic complications, as well as more common forms of adipose tissue redistribution as observed in the metabolic syndrome and type 2 diabetes.

iTRAQ-based analysis of progerin expression reveals mitochondrial dysfunction, reactive oxygen species accumulation and altered proteostasis

INTRODUCTION

Nuclear accumulation of a mutant form of the nuclear protein Lamin-A, called Progerin (PG) or Lamin AΔ50, occurs in Hutchinson-Gilford Progeria Syndrome (HGPS) or Progeria, an accelerated aging disease. One of the main symptoms of this genetic disorder is a loss of sub-cutaneous fat due to a dramatic lipodystrophy.

METHODS

We stably induced the expression of human PG and GFP -Green Fluorescent Protein- as control in 3T3L1 cells using a lentiviral system to study the effect of PG expression in the differentiation capacity of this cell line, one of the most used adipogenic models. Quantitative proteomics (iTRAQ) was done to study the effect of the PG accumulation. Several of the modulated proteins were validated by immunoblotting and real-time PCR. Mitochondrial function was analyzed by measurement of a) the mitochondrial basal activity, b) the superoxide anion production and c) the individual efficiency of the different complex of the respiratory chain.

RESULTS

We found that over-expression PG by lentiviral gene delivery leads to a decrease in the proliferation rate and to defects in adipogenic capacity when compared to the control. Quantitative proteomics analysis showed 181 proteins significantly (p<0.05) modulated in PG-expressing preadipocytes. Mitochondrial function is impaired in PG-expressing cells. Specifically, we have detected an increase in the activity of the complex I and an overproduction of Superoxide anion. Incubation with Reactive Oxygen Species (ROS) scavenger agents drives to a decrease in autophagic proteolysis as revealed by LC3-II/LC3-I ratio.

CONCLUSION

PG expression in 3T3L1 cells promotes changes in several Biological Processes, including structure of cytoskeleton, lipid metabolism, calcium regulation, translation, protein folding and energy generation by the mitochondria. Our data strengthen the contribution of ROS accumulation to the premature aging phenotype and establish a link between mitochondrial dysfunction and loss of proteostasis in HGPS.

Congenital lipodystrophies and dyslipidemias

Lipodystrophies are rare acquired and genetic disorders characterized by the selective loss of adipose tissue. One key metabolic feature of patients with congenital inherited lipodystrophy is hypertriglyceridemia. The precise mechanisms by which the lack of adipose tissue causes dyslipidemia remain largely unknown. In recent years, new insights have arisen from data obtained in vitro in adipocytes, yeast, drosophila, and very recently in several genetically modified mouse models of generalized lipodystrophy. A common metabolic pathway involving accelerated lipolysis and defective energy storage seems to contribute to the dyslipidemia associated with congenital generalized lipodystrophy syndromes, although the pathophysiological changes may vary with the nature of the mutation involved. Therapeutic management of dyslipidemia in patients with lipodystrophy is primarily based on specific approaches using recombinant leptin therapy. Preclinical studies suggest a potential efficacy of thiazolidinediones that remains to be assessed in dedicated clinical trials.

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

Lipodystrophies are a genetically heterogeneous group of disorders characterized by loss of subcutaneous adipose tissue and metabolic dysfunction, including insulin resistance, increased levels of free fatty acids, abnormal adipocytokine secretion, and ectopic fat deposition, which are also observed in patients with visceral obesity and/or type 2 diabetes mellitus. Pathophysiological, biochemical, and genetic studies suggest that impairment in multiple adipose tissue functions, including adipocyte maturation, lipid storage, formation and/or maintenance of the lipid droplet, membrane composition, DNA repair efficiency, and insulin signaling, results in severe metabolic and endocrine consequences, ultimately leading to specific lipodystrophic phenotypes. In this review, recent evidences on the causes and metabolic processes of lipodystrophies will be presented, proposing a disease model that could be potentially informative for better understanding of common metabolic diseases in humans, including obesity, metabolic syndrome, and type 2 diabetes.

On the formation of lipid droplets in human adipocytes: the organization of the perilipin-vimentin cortex

We report on the heterogeneity and diversity of lipid droplets (LDs) in early stages of adipogenesis by elucidating the cell and molecular biology of amphiphilic and cytoskeletal proteins regulating and stabilizing the generation of LDs in human adipose cells. A plethora of distinct and differently sized LDs was detected by a brief application of adipocyte differentiation medium and additional short treatment with oleic acid. Using these cells and highly specific antibodies for LD-binding proteins of the perilipin (PLIN) family, we could distinguish between endogenously derived LDs (endogenous LDs) positive for perilipin from exogenously induced LDs (exogenous LDs) positive for adipophilin, TIP47 and S3-12. Having optimized these stimulation conditions, we used early adipogenic differentiation stages to investigate small-sized LDs and concentrated on LD-protein associations with the intermediate-sized filament (IF) vimentin. This IF protein was described earlier to surround lipid globules, showing spherical, cage-like structures. Consequently - by biochemical methods, by immunofluorescence microscopy and by electron- and immunoelectron microscopy - various stages of emerging lipid globules were revealed with perilipin as linking protein between LDs and vimentin. For this LD-PLIN-Vimentin connection, a model is now proposed, suggesting an interaction of proteins via opposed charged amino acid domains respectively. In addition, multiple sheaths of smooth endoplasmic reticulum cisternae surrounding concentrically nascent LDs are shown. Based on our comprehensive localization studies we present and discuss a novel pathway for the LD formation.