Serum Asprosin Concentrations in Children with Prader-Willi Syndrome: Correlations with Metabolic Parameters

Lack of correlation between asprosin serum levels and hyperphagic behavior in subjects with prader-Willi Syndrome

PURPOSE

Individuals with Prader-Willi syndrome (PWS) exhibit hyperphagic behavior, the severity of which varies throughout life. The mechanisms underlying this behavior are still unknown. Asprosin is a new discovered adipokine involved in the regulation of food intake, glucose homeostasis and energy balance. In this study we assessed asprosin serum levels in a cohort of children, adolescents and adults with PWS with the aim to correlate them with hyperphagic behavior, body mass index (BMI) and metabolic parameters, and to evaluate age-related changes.

METHODS

This cross-sectional study included 87 children and adolescents and 31 adults with PWS. Auxological data, fasting levels of glucose, insulin, total cholesterol, high-density lipoprotein-cholesterol (HDL-C), triglycerides (TG) and asprosin were collected, and the homeostasis model assessment for insulin resistance (HOMA-IR) was determined. The 11-item Italian version of the Hyperphagia Questionnaire (HQ) was administered to the parents/caregivers of the patients to assess hyperphagia.

RESULTS

Patients were analysed according to age (children < 10 years, adolescents between 10 and 17.9 years, adults ≥ 18 years) or BMI categories [normal weight (NW), overweight (OW), and obesity (OB)]. No significant correlations were found between asprosin levels and cardiometabolic risk factors in the whole cohort. Higher values of asprosin were found in adults compared with adolescents, as well as in the OB group compared to the NW group (p = 0.014). Hyperphagia total score and hyperphagic subdimensions were significantly lower in children compared to adults (p < 0.05). Similarly, hyperphagia total score and hyperphagic subdimensions were significantly lower in the NW group compared to the OB group. Asprosin levels were significantly higher in patients with deletion versus patients with uniparental disomy (p = 0.037). By logistic regression analysis, HQ total score and hyperphagic subdimensions were significantly associated with BMI-SDS independently of age, sex, and asprosin levels.

CONCLUSION

In conclusion, our data demonstrated higher asprosin levels in PWS individuals with OB compared to NW, while differences by age and sex were inconsistent. The lower levels of hyperphagia, BMI-SDS, and metabolic variables in children with PWS compared to adults underline that prevention of obesity should start very early in life and should be maintained over time.

The Effects of Growth Hormone Treatment Beyond Growth Promotion in Patients with Genetic Syndromes: A Systematic Review of the Literature

Recombinant human growth hormone therapy (rhGH) has been widely accepted as the safe treatment for short stature in children with such genetic syndromes as Prader-Willi syndrome and Turner or Noonan syndrome. Some patients with short stature and rare genetic syndromes are treated with rhGH as growth hormone-deficient individuals or as children born small for their gestational age. After years of experience with this therapy in syndromic short stature, it has been proved that there are some aspects of long-term rhGH treatment beyond growth promotion, which can justify rhGH use in these individuals. This paper summarizes the data of a literature review of the effects of rhGH treatment beyond growth promotion in selected genetic syndromes. We chose three of the most common syndromes, Prader-Willi, Turner, and Noonan, in which rhGH treatment is indicated, and three rarer syndromes, Silver-Russel, Kabuki, and Duchenne muscular dystrophy, in which rhGH treatment is not widely indicated. Many studies have shown a significant impact of rhGH therapy on body composition, resting energy expenditure, insulin sensitivity, muscle tonus, motor function, and mental and behavioral development. Growth promotion is undoubtedly the primary benefit of rhGH therapy; nevertheless, especially with genetic syndromes, the additional effects should also be considered as important indications for this treatment.

Asprosin in health and disease, a new glucose sensor with central and peripheral metabolic effects

Adipose tissue malfunction leads to altered adipokine secretion which might consequently contribute to an array of metabolic diseases spectrum including obesity, diabetes mellitus, and cardiovascular disorders. Asprosin is a novel diabetogenic adipokine classified as a caudamin hormone protein. This adipokine is released from white adipose tissue during fasting and elicits glucogenic and orexigenic effects. Although white adipose tissue is the dominant source for this multitask adipokine, other tissues also may produce asprosin such as salivary glands, pancreatic B-cells, and cartilage. Significantly, plasma asprosin levels link to glucose metabolism, lipid profile, insulin resistance (IR), and β-cell function. Indeed, asprosin exhibits a potent role in the metabolic process, induces hepatic glucose production, and influences appetite behavior. Clinical and preclinical research showed dysregulated levels of circulating asprosin in several metabolic diseases including obesity, type 2 diabetes mellitus (T2DM), polycystic ovarian syndrome (PCOS), non-alcoholic fatty liver (NAFLD), and several types of cancer. This review provides a comprehensive overview of the asprosin role in the etiology and pathophysiological manifestations of these conditions. Asprosin could be a promising candidate for both novel pharmacological treatment strategies and diagnostic tools, although developing a better understanding of its function and signaling pathways is still needed.

Fibrillin-1 and asprosin, novel players in metabolic syndrome

Fibrillin-1 is a major component of the extracellular microfibrils, where it interacts with other extracellular matrix proteins to provide elasticity to connective tissues, and regulates the bioavailability of TGFβ family members. A peptide consisting of the C-terminal 140 amino acids of fibrillin-1 has recently been identified as a glucogenic hormone, secreted from adipose tissue during fasting and targeting the liver to release glucose. This fragment, called asprosin, also signals in the hypothalamus to stimulate appetite. Asprosin levels are correlated with many of the pathologies indicative of metabolic syndrome, including insulin resistance and obesity. Previous studies and reviews have addressed the therapeutic potential of asprosin as a target in obesity, diabetes and related conditions without considering mechanisms underlying the relationship between generation of asprosin and expression of the much larger fibrillin-1 protein. Profibrillin-1 undergoes obligatory cleavage at the cell surface as part of its assembly into microfibrils, producing the asprosin peptide as well as mature fibrillin-1. Patterns of FBN1 mRNA expression are inconsistent with the necessity for regulated release of asprosin. The asprosin peptide may be protected from degradation in adipose tissue. We present evidence for an alternative possibility, that asprosin mRNA is generated independently from an internal promoter within the 3' end of the FBN1 gene, which would allow for regulation independent of fibrillin-synthesis and is more economical of cellular resources. The discovery of asprosin opened exciting possibilities for treatment of metabolic syndrome related conditions, but there is much to be understood before such therapies could be introduced into the clinic.