Functional coupling analysis suggests link between the obesity gene FTO and the BDNF-NTRK2 signaling pathway

Birth weight concerning obesity and diabetes gene expression in healthy infants; a case-control study

Background

Since obesity and diabetes are prevalent worldwide, identifying the factors affecting these two conditions can effectively alter them. We decided to investigate the expression of obesity and diabetes genes in infants with birth weights lower than 2500 g in comparison with infants with normal birth weights.

Methods

215 healthy infants between the ages of 5–6 months were used in the current case-control research, which was conducted at health and treatment facilities in Kermanshah. Infants who were healthy were chosen for the research after their weight and height were measured and compared to the WHO diagram to ensure that they were well-grown and in good health. There were 137 infants in the control group and 78 infants in the case group. All newborns had 5 cc of blood drawn intravenously. To assess the expression of the genes MC4R, MTNR1B, PTEN, ACACB, PPAR-γ, PPAR-α, NRXN3, NTRK2, PCSK1, A2BP1, TMEM18, LXR, BDNF, TCF7L2, FTO and CPT1A, blood samples were gathered in EDTA-coated vials. Chi-square, Mann-Whitney U, and Spearman analyses were used to examine the data.

Results

A significant inverse correlation between birth weight and obesity and diabetes genes, including MTNR1B, NTRK2, PCSK1, and PTEN genes (r= -0.221, -0.235, -0.246, and − 0.418, respectively). In addition, the LBW infant’s expression level was significantly up-regulated than the normal-weight infants (P = 0.001, 0.007, 0.001, and < 0.001, respectively). The expression level of the PPAR-a gene had a significantly positive correlation with birth weight (r = 0.19, P = 0.005). The expression level of the PPAR-a gene in the normal-weight infants was significantly up-regulated than the LBW infants (P = 0.049).

Conclusion

The expression levels of MTNR1B, NTRK2, PCSK1, and PTEN genes were up-regulated in the LBW infants; however, the expression level of PPAR-a gene was significantly down-regulated in the LBW infants compared to the infants with normal birth weight.

Fat mass and obesity-associated protein alleviates Aβ1-40 induced retinal pigment epithelial cells degeneration via PKA/CREB signaling pathway

Amyloid-β (Aβ) is thought to be a critical pathologic factor of retinal pigment epithelium (RPE) degeneration in age-related macular degeneration (AMD). Aβ induces inflammatory responses in RPE cells and recent studies demonstrate the N6-methyladenosine (m6A) regulatory role in RPE cell inflammation. m6A is a reversible epigenetic posttranslational modification, but its relationship with Aβ-induced RPE degeneration is yet to be thoroughly investigated. The present study explored the role and mechanism of m6A in Aβ-induced RPE degeneration model. This model was induced via intravitreally injecting oligomeric Aβ and the morphology of its retina was analyzed. One of m6A demethylases, the fat mass and obesity-associated (FTO) gene expression, was assessed. An m6A-messenger RNA (mRNA) epitranscriptomic microarray was employed for further bioinformatic analyses. It was confirmed that Aβ induced FTO upregulation within the RPE. Hypopigmentation alterations and structural disorganization were observed in Aβ-treated eyes, and inhibition of FTO exacerbated retinal degeneration and RPE impairment. Moreover, the m6A-mRNA epitranscriptomic microarray suggested that protein kinase A (PKA) was a target of FTO, and the PKA/cyclic AMP-responsive element binding (CREB) signaling pathway was involved in Aβ-induced RPE degeneration. m6A-RNA binding protein immunoprecipitation confirmed that FTO demethylated PKA within the RPE cells of Aβ-treated eyes. Altered expression of PKA and its downstream targets (CREB and brain-derived neurotrophic factor) was confirmed by quantitative reverse-transcription polymerase chain reaction and Western blot analyses. Hence, this study's findings shed light on FTO-mediated m6A modification in Aβ-induced RPE degeneration and indicate potential therapeutic targets for AMD.

Different lipid metabolic profiles and their associated genes in sessile serrated adenoma or polyps compared to hyperplastic polyps

The serrated pathway is important in the development of colorectal cancer; currently, knowledge about the lipid metabolism profiles of serrated lesions is limited. Clinical characteristics were compared via Pearson's chi-squared test, nonparametric Kruskal-Wallis test and ANOVA. For some missing values, the MCAR test and multiple imputations were performed. Compared to patients with HP, the rates of younger patients (<50) and male patients with SSA or SSP were increased (P<0.05). Additionally, the BMI index and triglyceride levels were increased in patients with SSA or SSP. Inversely, patients with SSA/P had lower levels of HDL (P<0.05). Interestingly, the value of uric acid and tumor size in SSA/P patients tended to be greater than those in HP patients, and the ratio of patients who smoked was also increased. Other characteristics, such as LDL, ALB, γ-GT, and the N/L ratio, were similar among the subtypes of serrated lesions. Analysis of GEO data (GSE43841) showed that 9 genes were associated with lipid metabolism, including ADRB3, DEGS2, PRKACB, SLC44A1, and CA4. PRKACB was downregulated in SSA/P tissue compared to HP tissue samples from the GSE76987 dataset and our hospital. In conclusion, compared to benign HP, lower HDL levels and higher triglyceride levels tended to occur in CRC precursor SSA/P lesions, and these factors may be associated with metabolic genomic markers, such as PRKACB.

Association of ADIPOQ-rs2241766 and FTO-rs9939609 genetic variants with body mass index trajectory in women of reproductive age over 6 years of follow-up: the PREDI study

BACKGROUND

Interindividual variations in body mass index (BMI) can be partially explained by genetic differences. We aimed to examine the association of the ADIPOQ-rs2241766, LEP-rs7799039 and FTO-rs9939609 genetic variants with BMI trajectory in women of reproductive age over 6 years of follow-up.

METHODS

This was a prospective study that used data from 435 women of the PREDI Study conducted in Brazil. Socioeconomic, biological and anthropometric data were collected at four time points: 2012 (baseline) in the maternity hospital, and 2013-14, 2016-17 and 2018 (1^st, 2^nd and 3^rd follow-ups) at the participant's home. Genotyping was performed by PCR-RFLP. Linear mixed-effect and Poisson regression models were used to address the association of ADIPOQ, LEP and FTO genotypes with BMI and overweight/obesity status.

RESULTS

Women carrying the risk allele (TA or AA) of the FTO-rs9939609 genetic variant had a 1.16 kg/m² higher BMI over the follow-up period than those carrying the wild-type genotype (TT), even when adjusted for potential confounders (95% CI: 0.23-2.10, p = 0.015). The risk of obesity associated with the FTO-TA or AA genotype decreased over the years, demonstrating an influence of time on its trajectory (IRR = 0.99, 95% CI: 0.98-0.99, p = 0.016). There was no variation in BMI trajectories for the ADIPOQ-rs2241766, LEP-rs7799039 or FTO-rs9939609 genetic variant.

CONCLUSIONS

The results of this study suggest that monitoring women of reproductive age with ADIPOQ-rs2241766 TG/GG or FTO-rs9939609 TA/AA genotypes may be an important strategy to reduce maternal excess body weight and, consequently, the long-term public health burden of obesity.

Sex differences in gene expression with galactosylceramide treatment in Cln3Δex7/8 mice

BACKGROUND

CLN3 disease is caused by mutations in the CLN3 gene. The purpose of this study is to discern global expression patterns reflecting therapeutic targets in CLN3 disease.

METHODS

Differential gene expression in vehicle-exposed mouse brain was determined after intraperitoneal vehicle/Galactosylceramide (GalCer) injections for 40 weeks with GeneChip Mouse Genome 430 2.0 arrays.

RESULTS

Analysis identified 66 genes in male and 30 in female brains differentially expressed in GalCer-treated versus vehicle-exposed Cln3Δex7/8 mice. Gene ontology revealed aberrations of biological function including developmental, cellular, and behavioral processes. GalCer treatment altered pathways of long-term potentiation/depression, estrogen signaling, synaptic vesicle cycle, ErbB signaling, and prion diseases in males, but prolactin signaling, selenium compound metabolism and steroid biosynthesis in females. Gene-gene network analysis highlighted networks functionally pertinent to GalCer treatment encompassing motor dysfunction, neurodegeneration, memory disorder, inflammation and astrogliosis in males, and, cataracts, inflammation, astrogliosis, and anxiety in females.

CONCLUSIONS

This study sheds light on global expression patterns following GalCer treatment of Cln3Δex7/8 mice. Understanding molecular effects of GalCer on mouse brain gene expression, paves the way for personalized strategies for treating this debilitating disease in humans.

Rs9939609 polymorphism of the fat mass and obesity-associated (FTO) gene and metabolic syndrome susceptibility in the Chinese population: a meta-analysis

PURPOSE

The relationship between the rs9939609 allele of fat mass and obesity-associated (FTO) gene and metabolic syndrome (MS) susceptibility has been evaluated by many studies, however, the results still remained controversial in the Chinese population. In order to provide more accurate results, we performed this meta-analysis.

METHODS

We searched PubMed, and Wanfang Med Online in both English and Chinese, and eight eligible studies comprising of 5345 cases and 9523 controls were eventually selected into our meta-analysis. The meta-analysis was performed using the STATA 12.0 software.

RESULTS

In pooled analysis, the FTO gene rs9939609 polymorphism significantly increased MS susceptibility under per-allele comparisons (A vs. T) (OR 1.21, 95% CI 1.10-1.35, P < 0.001) and in dominant model (OR 1.35, 95% CI 1.13-1.62, P < 0.001). Subgroup analyses under per-allele comparisons (A vs. T) indicated that the elevated risk was observed in adults (OR 1.26, 95% CI 1.08-1.47, P = 0.003) but not in children and adolescents (OR 1.14, 95% CI 0.95-1.36, P = 0.17), and that the risk for increasing MS was only identified in IDF groups (OR 1.22, 95% CI 1.03-1.43, P = 0.018) but not in NCEP ATP III groups (OR 1.14, 95% CI 0.95-1.36, P = 0.17); in both population-based (PB) and hospital-based (HB) groups, A alleles of rs9939609 appeared to be linked to increased MS susceptibilities (HB group: OR 1.51, 95% CI 1.10-2.08, P = 0.01; PB group: OR 1.19, 95% CI 1.09-1.30, P < 0.001). No significant association was established in dominant model subgroup analyses except PB group (OR 1.29, 95% CI 1.05-1.53, P < 0.001).

CONCLUSION

Our results suggested that the FTO gene rs9939609 polymorphism significantly increased MS susceptibility in Chinese. Our results should be verified by well-designed studies with larger sample size.

Maternal Obesity Alters Neurotrophin-Associated MAPK Signaling in the Hypothalamus of Male Mouse Offspring

Purpose

Maternal obesity has emerged as an important risk factor for the development of metabolic disorders in the offspring. The hypothalamus as the center of energy homeostasis regulation is known to function based on complex neuronal networks that evolve during fetal and early postnatal development and maintain their plasticity into adulthood. Development of hypothalamic feeding networks and their functional plasticity can be modulated by various metabolic cues, especially in early stages of development. Here, we aimed at determining the underlying molecular mechanisms that contribute to disturbed hypothalamic network formation in offspring of obese mouse dams.

Methods

Female mice were fed either a control diet (CO) or a high-fat diet (HFD) after weaning until mating and during pregnancy and gestation. Male offspring was sacrificed at postnatal day (P) 21. The hypothalamus was subjected to gene array analysis, quantitative PCR and western blot analysis.

Results

P21 HFD offspring displayed increased body weight, circulating insulin levels, and strongly increased activation of the hypothalamic insulin signaling cascade with a concomitant increase in ionized calcium binding adapter molecule 1 (IBA1) expression. At the same time, the global gene expression profile in CO and HFD offspring differed significantly. More specifically, manifest influences on several key pathways of hypothalamic neurogenesis, axogenesis, and regulation of synaptic transmission and plasticity were detectable. Target gene expression analysis revealed significantly decreased mRNA expression of several neurotrophic factors and co-factors and their receptors, accompanied by decreased activation of their respective intracellular signal transduction.

Conclusion

Taken together, these results suggest a potential role for disturbed neurotrophin signaling and thus impaired neurogenesis, axogenesis, and synaptic plasticity in the pathogenesis of the offspring’s hypothalamic feeding network dysfunction due to maternal obesity.

The 'Fat Mass and Obesity Related' (FTO) gene: Mechanisms of Impact on Obesity and Energy Balance

A cluster of single nucleotide polymorphisms (SNPs) in the first intron of the fat mass and obesity related (FTO) gene were the first common variants discovered to be associated with body mass index and body fatness. This review summarises what has been later discovered about the biology of FTO drawing together information from both human and animal studies. Subsequent work showed that the 'at risk' alleles of these SNPs are associated with greater food intake and increased hunger/lowered satiety, but are not associated with altered resting energy expenditure or low physical activity in humans. FTO is an FE (II) and 2-oxoglutarate dependent DNA/RNA methylase. Contrasting the impact of the SNPs on energy balance in humans, knocking out or reducing activity of the Fto gene in the mouse resulted in lowered adiposity, elevated energy expenditure with no impact on food intake (but the impact on expenditure is disputed). In contrast, overexpression of the gene in mice led to elevated food intake and adiposity, with no impact on expenditure. In rodents, the Fto gene is widely expressed in the brain including hypothalamic nuclei linked to food intake regulation. Since its activity is 2-oxoglutarate dependent it could potentially act as a sensor of citrate acid cycle flux, but this function has been dismissed, and instead it has been suggested to be much more likely to act as an amino acid sensor, linking circulating AAs to the mammalian target of rapamycin complex 1. This may be fundamental to its role in development but the link to obesity is less clear. It has been recently suggested that although the obesity related SNPs reside in the first intron of FTO, they may not only impact FTO but mediate their obesity effects via nearby genes (notably RPGRIP1L and IRX3).

Fat mass- and obesity-associated (FTO) gene and antipsychotic-induced weight gain: an association study

OBJECTIVES

Genetic variation in the fat mass- and obesity-associated gene (FTO) has been associated with obesity in the general population. In this study we have investigated these variants for association with antipsychotic-induced weight gain (AIWG).

METHODS

A total of 218 patients with chronic schizophrenia or schizoaffective disorder treated mostly with clozapine or olanzapine for up to 14 weeks were included in the study. We analyzed 4 polymorphisms in intron 1 of the FTO gene (rs1421085, rs8050136, rs9939609, rs9930506) for association with AIWG using ANCOVA.

RESULTS

No statistically significant associations were observed between the single nucleotide polymorphisms and AIWG. However, patients homozygous for the A-allele of rs9939609 gained numerically higher weight than the other genotypic groups (AA: 5.26 ± 6.7%; TA: 4.66 ± 5.6%; TT: 4.21 ± 5.3%).

CONCLUSION

Our current observations suggest that the FTO gene variants investigated may not play a major role in AIWG.

FTO and obesity: mechanisms of association

The Fat mass and obesity associated (FTO) gene is a newly identified genetic factor for obesity. However, the exact molecular mechanisms responsible for the effect of FTO on obesity remain largely unknown. Recent studies from genome-wide associated studies reveal that genetic variants in the FTO gene are associated not only with human adiposity and metabolic disorders, but also with cancer, a highly obesity-associated disease as well. Data from animal and cellular models further demonstrate that the perturbation of FTO enzymatic activity dysregulates genes related to energy metabolism, causing the malfunction of energy and adipose tissue homeostasis in mice. The most significant advance about FTO research is the recent discovery of FTO as the first N6-methyl-adenosine (m(6)A) RNA demethylase that catalyzes the m(6)A demethylation in α-ketoglutarate - and Fe(2+)-dependent manners. This finding provides the strong evidence that the dynamic and reversible chemical m(6)A modification on RNA may act as a novel epitranscriptomic marker. Furthermore, the FTO protein was observed to be partially localized onto nuclear speckles enriching mRNA processing factors, implying a potential role of FTO in regulating RNA processing. This review summarizes the recent progress about biological functions of FTO through disease-association studies as well as the data from in vitro and in vivo models, and highlights the biochemical features of FTO that might be linked to obesity.

FTO, RNA epigenetics and epilepsy

Several recent landmark papers describing N⁶-methyladenosine (m⁶A) RNA modifications have provided valuable new insights as to the importance of m⁶A in the RNA transcriptome and in furthering the understanding of RNA epigenetics. One endogenous enzyme responsible for demethylating RNA m⁶A, FTO, is highly expressed in the CNS and is likely involved in mRNA metabolism, splicing or other nuclear RNA processing events. microRNAs (miRNAs), a family of small, non-coding transcripts that bind to target mRNAs and inhibit subsequent translation, are highly expressed in the CNS and are associated with several neurological disorders, including epilepsy. miRNAs frequently bind to recognition sequences in the 3′UTR, a region that is also enriched for m⁶A. Certain specific miRNAs are upregulated by neuronal activity and are coupled to epileptogenesis; these miRNAs contain a consensus m⁶A site that if methylated could possibly regulate miRNA processing or function. This commentary highlights aspects from recent papers to propose a functional association between FTO, RNA epigenetics and epilepsy.