According to a study, levels of the hormone irisin in people with Prader-Willi syndrome (PWS) may be related to their genetic background and vitamin D supplement intake.
The results support Irisin as a biomarker of cognitive function in adults with the disorder.
The study, “Genetic background and vitamin D supplementation can affect irisin levels in Prader-Willi syndromeWas published in the Journal of Endocrinological Investigation.
PWS is caused by the loss of paternal genes on chromosome 15 that control metabolism, appetite, growth, intellectual skills, and social behavior.
The most common cause is deletion of these genes (called DEL15), while other genetic mechanisms underlying PWS are inheritance of two copies of chromosome 15 from the mother instead of one from each biological parent – called maternal uniparental disomy (UPD) – and embossing include defects that make changes to the DNA in sperm and egg cells.
In terms of bone health, adolescents and adults with PWS have lower bone mineral density and bone mineral content, which increases the risk of osteoporosis (weak and brittle bones) and other complications.
Irisin is a hormone released by muscles in response to exercise and is known to affect metabolic parameters in muscle and fat cells. Its levels have been linked to increases in bone mass, and more recent data have reported the hormone’s effect on certain brain functions and its role in cognitive impairment.
However, the role of irisin in PWS has not been fully explored. Therefore, a team from Italy tried to understand the relationship between blood irisin levels in PWS patients and their genetic background, metabolic profile, cognitive function and bone health.
The study included 26 children (mean age 9.48 years) and 52 adults (mean age 30.6 years) with PWS. To serve as age-adjusted controls, the study also included 26 children who attended the hospital for minor surgery or electrocardiographic exams of heart function, and 54 adults of normal weight.
The genetic background of all patients was examined: DEL15 was found in 32 adults and 16 children, while UPD was found in 20 adults and 10 children.
Children were treated with growth hormone (GH) for at least a year with a daily dose between 0.025 and 0.035 mg / kg. Six adult patients received GH at a mean dose of 0.23 mg / day.
Vitamin D supplements were taken by four children (15%) and half of adults with PWS. The daily doses were 12.5 micrograms in children and 20 micrograms in adults.
Height, weight, body mass index (a measure of body fat), fat mass, lean mass, bone mineral density, and bone mineral content were also determined.
Parameters measured included blood levels of irisine, glucose, insulin, total cholesterol, HDL and LDL cholesterol (known as “good” and “bad” cholesterol) and triglycerides (a type of fat).
Intelligence quotient (IQ) was used to assess cognitive function with specific scales for children and adults.
The results showed that the irisin blood concentration was not significantly different between patients and controls. However, hormone levels were lower in children and adults with DEL15 than in controls.
In children with PWS, the only two parameters that differed between the DEL15 and UPD groups were total cholesterol and LDL, as they were lower in children with genetic deletion.
Adult patients taking vitamin D supplementation had irisin levels similar to controls but higher levels than patients not taking such supplements.
The results also showed that low irisin levels in adults with DEL15 or UPD are not related to vitamin D supplementation.
These results could indicate that “vitamin D supplementation plays an important role in regulating irisin levels in adult PWS patients,” the researchers wrote.
Both genetics and vitamin D levels predicted irisin levels in patients with PWS, the researchers concluded. In children in particular, hormone levels were mainly predicted by weight, genetic background, vitamin D levels in the blood, and bone mineral density.
In adult patients, genetics, IQ, vitamin D levels, bone mineral density, sex steroid replacement therapy, and treatment with growth hormones (and their duration and age at the start of treatment) were the best predictors of irisin levels. The association with growth hormone and sex steroid replacement therapy suggests that “the key role in starting therapy is to normalize levels of [irisin] in these subjects, ”wrote the researchers.
The association with IQ also supports irisin’s role as a biomarker of cognitive impairment in adults with PWS.
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José received his PhD in Neuroscience from the Universidade of Porto in Portugal. He also studied biochemistry at Universidade do Porto and was a postdoctoral fellow with Weill Cornell Medicine in New York and the University of Western Ontario in London, Ontario, Canada. His work ranged from the association of central cardiovascular and pain control to the neurobiological basis of hypertension and the molecular pathways that drive Alzheimer’s disease.
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