APOE - a genetic marker of comorbidity in subjects with morbid obesity

Insights into the roles of Apolipoprotein E in adipocyte biology and obesity

Apolipoprotein E (APOE) is a multifunctional protein expressed by various cell types, including hepatocytes, adipocytes, immune cells of the myeloid lineage, vascular smooth muscle cells, astrocytes, etc. Initially, APOE was discovered as an arginine-rich peptide within very-low-density lipoprotein, but it was subsequently found in triglyceride-rich lipoproteins in humans and other animals, where its presence facilitates the clearance of these lipoproteins from circulation. Recent epidemiolocal studies and experimental research in mice suggest a link between ApoE and obesity. The latest findings highlight the role of endogenous adipocyte ApoE in regulating browning of white adipose tissue, beige adipocyte differentiation, thermogenesis and energy homeostasis. This review focuses on the emerging evidence showing the involvement of ApoE in the regulation of obesity and its associated metabolic diseases.

Next-Generation Sequencing of a Large Gene Panel for Outcome Prediction of Bariatric Surgery in Patients with Severe Obesity

Obesity is a chronic disease in which abnormal deposition of fat threatens health, leading to diabetes, cardiovascular diseases, cancer, and other chronic illnesses. According to the WHO, 19.8% of the adult population in Italy is obese, and the prevalence is higher among men. It is important to know the predisposition of an individual to become obese and to respond to bariatric surgery, the most up-to-date treatment for severe obesity. To this purpose, we developed an NGS gene panel, comprising 72 diagnostic genes and 244 candidate genes, and we sequenced 247 adult obese Italian patients. Eleven deleterious variants in 9 diagnostic genes and 17 deleterious variants in 11 candidate genes were identified. Interestingly, mutations were found in several genes correlated to the Bardet-Biedl syndrome. Then, 25 patients were clinically followed to evaluate their response to bariatric surgery. After a 12-month follow-up, the patients that carried deleterious variants in diagnostic or candidate genes had a reduced weight loss, as compared to the other patients. The NGS-based panel, including diagnostic and candidate genes used in this study, could play a role in evaluating, diagnosing, and managing obese individuals, and may help in predicting the outcome of bariatric surgery.

Bioinformatics analysis to obtain critical genes regulated in subcutaneous adipose tissue after bariatric surgery

Bariatric surgery (BS) is a dependable method for managing obesity and metabolic diseases, however, the regulatory processes of lipid metabolism are still not well elucidated. Differentially expressed genes (DEGs) were analysed through three transcriptomic datasets of GSE29409, GSE59034 and GSE72158 from the GEO database regarding subcutaneous adipose tissue (SAT) after BS, and 37 DEGs were identified. The weighted gene co-expression network analysis (WGCNA), last absolute shrinkage and selection operator (LASSO) logistic regression and support vector machine-recursive feature elimination (SVM-RFE) algorithms further screened four key genes involved in the regulation of STMN2, SFRP4, APOE and MXRA5. The GSE53376 dataset was used to further confirm the differential expression of SFRP4, APOE and MXRA5 in the postoperative period. GSEA analysis reveals activation of immune-related regulatory pathways after surgery. Finally, the silencing of MXRA5 was found by experimental methods to affect the expression of PPARγ and CEBPα during the differentiation of preadipocytes, as well as to affect the formation of lipid droplets. In conclusion, SAT immunoregulation was mobilized after BS, while MXRA5 was involved in the regulation of lipid metabolism.

The Peripheral Kynurenine Pathway and Psychosomatic Comorbidity in Subjects with Morbid Obesity Undergoing Bariatric Surgery

Background: The Kynurenine pathway (KP) is involved in various disorders, but little is known about the KP and psychosomatic complaints. The aim was to study the peripheral KP and psychosomatic comorbidity in subjects with morbid obesity. Methods: Psychosomatic comorbidity (perceived general health, muscle-skeletal pain, well-being, mood disorders, fatigue, self-esteem, sleepiness, and sense of humour) was registered, and serum samples were collected six months before and after bariatric surgery. Results: A total of 141 subjects (men/women, 116/25) with a mean age of 43.0 (SD 8.7) years and BMI of 42.1 (SD 3.8) kg/m2 were included. No significant associations were seen between the psychosomatic disorders and the KP. There was a significant downregulation of all KP metabolites after surgery, a reduction in CRP, and strong associations between CRP and the KP, particularly with the ratios of Kynurenine/Tryptophan and Quinolinic acid (QA)/Xanthurenic acid (XA). The QA/XA ratio was negatively associated with diabetes. Conclusions: The peripheral KP seemed to be of minor importance for the psychosomatic comorbidity in subjects with morbid obesity. The downregulation of all KP metabolites after bariatric surgery indicated reduced inflammation. The QA/XA ratio seemed to be a marker of insulin sensitivity and favourable glucose control.

APOE Polymorphism and Endocrine Functions in Subjects with Morbid Obesity Undergoing Bariatric Surgery

BACKGROUND

Obesity is an interplay between genes and the environment, including lifestyle. The genetics of obesity is insufficiently understood. Apolipoprotein E (APOE) genetic polymorphism has been associated with a wide range of disorders. Knowing that some APOE alleles are associated with obesity and endocrine disorders that are common in obesity, the present study aimed at exploring associations between APOE polymorphisms and endocrine functions in subjects with obesity undergoing bariatric surgery.

METHODS

Analyses of hormones in blood collected before and one year after bariatric surgery were examined. The APOE alleles were grouped as follows: E2 = ε2ε2 + ε2ε3; E3 = ε3ε3 + ε2ε4; E4 = ε3ε4 + ε4ε4. The APOE groups were analysed as nominal and ordered groups (E2-E3-E4) with a linear mixed model to predict the hormonal effects of the groups.

RESULTS

Forty-nine women (79%) and thirteen (21%) men with a mean age of 47.7 (SD 8.5) years were included in the study. The adiponectin level was significantly lower (p < 0.05) in the E2 group compared with the E4 group. Adiponectin and cortisol were positively and negatively associated, respectively, with the ordered APOE groups.

CONCLUSIONS

The ordered APOE groups E2-E3-E4 were significantly associated with high and low levels of adiponectin and cortisol, respectively. The findings indicate APOE-mediated effects on body weight and metabolic functions in subjects with morbid obesity.

Quantile-dependent expressivity of serum C-reactive protein concentrations in family sets

Background

“Quantile-dependent expressivity” occurs when the effect size of a genetic variant depends upon whether the phenotype (e.g., C-reactive protein, CRP) is high or low relative to its distribution. We have previously shown that the heritabilities (h²) of coffee and alcohol consumption, postprandial lipemia, lipoproteins, leptin, adiponectin, adiposity, and pulmonary function are quantile-specific. Whether CRP heritability is quantile-specific is currently unknown.

Methods

Serum CRP concentrations from 2,036 sibships and 6,144 offspring-parent pairs were analyzed from the Framingham Heart Study. Quantile-specific heritability from full-sib (β_FS, h² ={(1 + 8r_spouseβ_FS)^0.5 − 1}/(2r_spouse)) and offspring-parent regression slopes (β_OP, h² = 2β_OP/(1 + r_spouse)) were estimated robustly by quantile regression with nonparametric significance determined from 1,000 bootstrap samples.

Results

Quantile-specific h² (±SE) increased with increasing percentiles of the offspring’s age- and sex-adjusted CRP distribution when estimated from β_OP (P_trend = 0.0004): 0.02 ± 0.01 at the 10th, 0.04 ± 0.01 at the 25th, 0.10 ± 0.02 at the 50th, 0.20 ± 0.05 at the 75th, and 0.33 ± 0.10 at the 90th percentile, and when estimated from β_FS (P_trend = 0.0008): 0.03±0.01 at the 10th, 0.06 ± 0.02 at the 25th, 0.14 ± 0.03 at the 50th, 0.24 ± 0.05 at the 75th, and 0.53 ± 0.21 at the 90th percentile.

Conclusion

Heritability of serum CRP concentration is quantile-specific, which may explain or contribute to the inflated CRP differences between CRP (rs1130864, rs1205, rs1800947, rs2794521, rs3091244), FGB (rs1800787), IL-6 (rs1800795, rs1800796), IL6R (rs8192284), TNF-α (rs1800629) and APOE genotypes following CABG surgery, stroke, TIA, curative esophagectomy, intensive periodontal therapy, or acute exercise; during acute coronary syndrome or Staphylococcus aureus bacteremia; or in patients with chronic rheumatoid arthritis, diabetes, peripheral arterial disease, ankylosing spondylitis, obesity or inflammatory bowel disease or who smoke.

Increased ApoE Expression in Follicular Fluid and the ApoE Genotype Are Associated With Endometriosis in Chinese Women

More than 10% of women suffer from endometriosis (EMT) during their reproductive years. EMT can cause pain and infertility and requires further study from multiple perspectives. Previous reports have indicated that an increase inapolipoprotein E (ApoE) may be associated with a lower number of retrieved mature oocytes in older women, and an association between ApoE and spontaneous pregnancy loss may exist in patients with EMT. The purpose of this study was to investigate the existence of an increase in ApoE in follicular fluid (FF) and the possible relationship between ApoE and EMT in Chinese women. In the current study, 217 Chinese women (111 control subjects and 106 EMT patients) were included. The ApoE genotypes were identified by Sanger sequencing. We found that ApoE expression in FF was higher in patients with EMT than in the control group. In addition, a significant difference in ApoE4 carriers (ϵ3/ϵ4, ϵ4/ϵ4) was found between the control subjects and the patients with EMT. Furthermore, a nonparametric test revealed significant differences in the numbers of blastocysts and high-quality blastocysts, but not the hormone levels of FSH, LH, and E2, between the two groups. We also established a multifactor (BMI, high-quality blastocysts, and ϵ4) prediction model with good sensitivity for identifying patients who may suffer from EMT. Our results demonstrate that ApoE expression in FF is increased in EMT, the ApoE-ϵ4 allele is significantly linked to EMT, and a combined analysis of three factors (BMI, high-quality blastocysts, and ϵ4) could be used as a predictor of EMT.