Résumé
Clinical data of a child with SIM1 gene mutation-related obesity who visited Beijing Children′s Hospital, Capital Medical University in February 2022 was retrospectively analyzed.This 5-year-and-4-month-old girl was admitted for early onset obesity.She showed obesity at 29 months old, accompanied by severe obstructive sleep apnea syndrome.The patient and her mother had heterozygous variations in the SIM1 gene.Literature has reported a total of 42 patients with obesity caused by SIM1 gene mutations from different families in the world, and nearly 1/3 of patients had clinical manifestations beyond obesity, such as developmental delay, cognitive and behavioral problems, mild dysmorphic appearance, and neuroendocrine abnormalities.The patient in this study was mainly characterized by early onset obesity.At present, 58 SIM1 gene mutations are found to be related to obesity, which are mostly concentrated in the C-terminal domain.The allele frequency of p. T46R and p. D707H has reached 9.5%; therefore, p.T46R and p. D707H are considered hot spot variations, suggesting that SIM1 gene analysis should be improved for patients with early onset obesity.
Résumé
This study reported two women with extreme obesity who underwent metabolic surgery due to their mutations in leptin receptor (LEPR).Genomic DNA was extracted from the anticoagulant blood samples of the two patients and their parents.A panel of genes related to metabolic diseases or whole exon sequencing was screened and the results were confirmed by Sanger sequencing.This is the first time that these three mutations in LEPR were reported.Two patients complained insatiety and early-onset obesity since childhood at clinics.Patient 1 was a 39-year-old woman with height 150 cm,weight 130 kg,and BMI 57.8 kg/m2.Serum leptin level was 156.4 μg/L.A homozygous mutation of c.2317G＞T was found in exon 15 of LEPR gene in patient 1,which was descended from her father and mother respectively.Patient 2 was a 37-year-old woman with height 158 cm,weight 167 kg,and BMI 67 kg/m2.Serum leptin level was 193.4 μg/L.Genetic analysis showed compound heterozygous mutations of c.1482delT and c.1892C ＞ A.Her father showed heterozygous c.1482delT mutation,and her mother carried heterozygous c.1892C ＞ A mutation.Two patients all underwent metabolic surgery with body weight reduction of about 22 kg and 40 kg respectively after first six months.However,the follow-up studies showed that the body weight of patient 1 rebounded to pre-surgery level in two years and patient 2 did not further lose weight in the following six months.
Résumé
Elucidation of obesity susceptibility genes through genome wide approaches as well as candidate gene approaches provides great promise in ultimately determining the genetic underpinnings of obesity. The complex nature of human obesity stems from the multiple interaction of several genes that control the physiology of food intake, energy expenditure, development of the body, and behavioural patterns towards food intake, and the environment. According to twin, adoptees and family studies, genetic factors account for 40-70% of the variability observed in human adiposity. Twin studies supported that the heritability of adiposity is higher than other quantitative traits. The heritability of obesity traits has been further evidenced by identification of quantitative trait loci (QTL) and genes through methods such as genome-wide scans (studies conducted on unrelated obese individuals), linkage analyses (conducted in families), and association studies (investigating the correlation between obesity and polymorphisms). The number of contributing genes, however, is still unknown. Although research on the genetic basis of obesity has advanced, the mechanisms underlying the condition are still complex due to its heterogeneity even within families.