Proceedings of the annual meeting of the European Consortium of Lipodystrophies (ECLip), Pisa, Italy, 28-29 September 2023

Lipodystrophy syndromes are rare diseases primarily affecting the development or maintenance of the adipose tissue but are also distressing indirectly multiple organs and tissues, often leading to reduced life expectancy and quality of life. Lipodystrophy syndromes are multifaceted disorders caused by genetic mutations or autoimmunity in the vast majority of cases. While many subtypes are now recognized and classified, the disease remains remarkably underdiagnosed. The European Consortium of Lipodystrophies (ECLip) was founded in 2014 as a non-profit network of European centers of excellence working in the field of lipodystrophies aiming at promoting international collaborations to increase basic scientific understanding and clinical management of these syndromes. The network has developed a European Patient Registry as a collaborative research platform for consortium members. ECLip and ECLip registry activities involve patient advocacy groups to increase public awareness and to seek advice on research activities relevant from the patients perspective. The annual ECLip congress provides updates on the research results of various network groups members.

Metabolic and other morbid complications in congenital generalized lipodystrophy type 4

Morbidity and mortality rates in patients with autosomal recessive, congenital generalized lipodystrophy type 4 (CGL4), an ultra-rare disorder, remain unclear. We report on 30 females and 16 males from 10 countries with biallelic null variants in CAVIN1 gene (mean age, 12 years; range, 2 months to 41 years). Hypertriglyceridemia was seen in 79% (34/43), hepatic steatosis in 82% (27/33) but diabetes mellitus in only 21% (8/44). Myopathy with elevated serum creatine kinase levels (346-3325 IU/L) affected all of them (38/38). 39% had scoliosis (10/26) and 57% had atlantoaxial instability (8/14). Cardiac arrhythmias were detected in 57% (20/35) and 46% had ventricular tachycardia (16/35). Congenital pyloric stenosis was diagnosed in 39% (18/46), 9 had esophageal dysmotility and 19 had intestinal dysmotility. Four patients suffered from intestinal perforations. Seven patients died at mean age of 17 years (range: 2 months to 39 years). The cause of death in four patients was cardiac arrhythmia and sudden death, while others died of prematurity, gastrointestinal perforation, and infected foot ulcers leading to sepsis. Our study highlights high prevalence of myopathy, metabolic abnormalities, cardiac, and gastrointestinal problems in patients with CGL4. CGL4 patients are at high risk of early death mainly caused by cardiac arrhythmias.

Leptin increases hepatic triglyceride export via a vagal mechanism in humans

Recombinant human leptin (metreleptin) reduces hepatic lipid content in patients with lipodystrophy and overweight patients with non-alcoholic fatty liver disease and relative hypoleptinemia independent of its anorexic action. In rodents, leptin signaling in the brain increases very-low-density lipoprotein triglyceride (VLDL-TG) secretion and reduces hepatic lipid content via the vagus nerve. In this randomized, placebo-controlled crossover trial (EudraCT Nr. 2017-003014-22), we tested whether a comparable mechanism regulates hepatic lipid metabolism in humans. A single metreleptin injection stimulated hepatic VLDL-TG secretion (primary outcome) and reduced hepatic lipid content in fasted, lean men (n = 13, age range 20-38 years) but failed to do so in metabolically healthy liver transplant recipients (n = 9, age range 26-62 years) who represent a model for hepatic denervation. In an independent cohort of lean men (n = 10, age range 23-31 years), vagal stimulation by modified sham feeding replicated the effects of metreleptin on VLDL-TG secretion. Therefore, we propose that leptin has anti-steatotic properties that are independent of food intake by stimulating hepatic VLDL-TG export via a brain-vagus-liver axis.

Deciphering metformin action in obese mice: A critical re-evaluation of established protocols

BACKGROUND AND PURPOSE

Despite extensive efforts and a plethora of suggested targets and pathways, the mechanism via which metformin lowers blood glucose remains obscure. Obstacles that hamper progress in understanding metformin action include unexplained discrepancies between preclinical models and patients.

PROCEDURES

We treated obese male C57BL/6J mice fed high fat diet with metformin provided in the form of a single dose, daily intraperitoneal injections, admixture to drinking water, or continuous infusion via intraperitoneal minipumps.

RESULTS

The results suggest several superimposed components, via which metformin acts on blood glucose. These include (i) marked glucose lowering shortly after dosing, which fades rapidly with the decrease in metformin concentrations in plasma and liver, but could, at least to a major extent, rely on the mechanism also accounting for metformin's therapeutic action in humans; (ii) indirect action via reduced weight gain, which might be responsible for glucose lowering observed in many previous rodent studies; and (iii) deterioration of glucose homeostasis by prolonged treatment that can be unmasked by avoidance of dosing shortly before measuring blood glucose in combination with exclusion of weight-related actions via restricted feeding of the control mice.

CONCLUSIONS

Our work raises the question whether elucidation of metformin's anti-diabetic mechanism(s) in rodent experiments may in the past have been hampered by failure to mimic clinical circumstances, as caused by insufficient consideration of pharmacokinetics and multiplicity of involved actions.

Adipocyte STAT5 deficiency does not affect blood glucose homeostasis in obese mice

The aim of this study was to investigate whether the lack of signal transducer and activator of transcription 5 (STAT5) in mature adipocytes of obese mice (Stat5Adipoq mice) improves glucose and lipid metabolism as previously observed in lean mice. Male Stat5Adipoq mice and their wild type (WT) littermates were fed high-fat diet (HFD). Effects of adipocyte STAT5 deficiency on adiposity as well as on glucose and lipid metabolism were determined under ad libitum feeding and after weight loss induced by calorie restriction. Compared to WT mice, obese Stat5Adipoq mice showed modestly accelerated weight gain and blunted depletion of fat stores under calorie restriction (reduction in % body fat after 3 weeks: WT, -9.3±1.1, vs Stat5Adipoq, -5.9±0.8, p = 0.04). No differences were observed between Stat5Adipoq and WT mice with regard to parameters of glucose and lipid metabolism including basal glycaemia, glucose tolerance, and plasma triglycerides. In conclusion, STAT5 deficiency in the adipocyte of HFD-fed obese mice was associated with increased fat accumulation. In contrast to previous findings in lean mice, however, lipid accumulation was not associated with any improvement in glucose and lipid metabolism. Our results do not support adipocyte STAT5 as a promising target for the treatment of obesity-associated metabolic derangements.

Project "Backtoclinic I": An overview on the state of care of adult PKU patients in Austria

BACKGROUND

High rates of lost to follow-up (LTFU) adult patients are a major concern in the long-term management of phenylketonuria (PKU). To address this issue, we designed the project "Backtoclinic" with the purpose of identifying LTFU adult PKU patients in Austria as a first step to reestablish appropriate treatment.

SUBJECTS AND METHODS

Individuals born between 1966 and 1999 and diagnosed with PKU through the National Austrian Newborn Screening Program (NANSP) were identified using the NANSP's database. Follow-up data were collected in the Austrian metabolic centers (Medical University of Vienna, Graz, Innsbruck and Salzburg). Patients with no contact to any of these centers within the previous two years were classified as LTFU. Epidemiological characteristics of the whole study population as well as of LTFU- and currently in follow-up patients were analyzed.

RESULTS

Between 1966 and 1999, 281 individuals were diagnosed with PKU through the NANSP. Two patients died in their first year of life and were excluded from the analysis. Of the remaining 279 patients (mean age ± SD: 36.7 ± 9.1 y, 42.7% females), 177 (63.4%) are currently LTFU. The rate of LTFU patients is higher in men than in women (68.1% vs 57.5%), and markedly increases with age in both sexes. The gender gap is greatest in young adults (52.6% vs. 25.0% in the age range 20.0-24.9 y) and declines with age (94.4% vs. 80.0% in the age range > 45.0 y).

CONCLUSIONS

We found an alarming rate of 63.4% of LTFU adult PKU patients in Austria, and observed a gender gap in the PKU state of care. Our findings illustrate the urgent need for the metabolic community to identify LTFU adult PKU patients and to develop strategies to reestablish appropriate treatment for men and women with PKU.

Potential Impact of BMI on the Aggressiveness of Presentation and Clinical Outcome of Differentiated Thyroid Cancer

BACKGROUND

Obesity is a risk factor for several cancers, including differentiated thyroid cancer (DTC). Moreover, it has also been investigated as a potential risk factor for aggressiveness of DTC, but the data gathered so far are conflicting. The aim of our study was to evaluate the relationship between body mass index (BMI), aggressiveness of DTC at diagnosis, and clinical outcome.

METHODS

We evaluated 1058 consecutive DTC patients treated with total thyroidectomy and enrolled at the time of first radioactive iodine (131I) treatment. Patients were divided into 4 groups based on their BMI: underweight (< 18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), and obese (≥ 30 kg/m2). Histological aggressiveness of DTC at the time of diagnosis and clinical outcome according to 2015 American Thyroid Association (ATA) guidelines were evaluated.

RESULTS

No differences in histological features, ATA risk of recurrence, activity of 131I administered and prevalence of 131I avid metastatic disease after first131I treatment, have been demonstrated among the groups. Furthermore, at the end of follow up (median = 5.7 years), no differences were evident in the number of further treatments performed as well as in the clinical response.

CONCLUSIONS

In our study group of Caucasian subjects, we could not demonstrate any association between BMI and aggressiveness of DTC, neither at the time of diagnosis nor during follow-up. These data indicate that postsurgical assessment and therapeutic attitude for treatment and follow-up of DTC should be based on the class of risk applied to the general population, with no concern for BMI.