Obesity isemerging as the leading cause for morbidity and mortality around world, and itis defined as a disproportionate body weight for height with an excessiveaccumulation of adipose tissue that is usually accompanied by mild, chronic,systemic inflammation.
Obesity is associated with many diet-related chronicdiseases including diabetes mellitus, cardiovascular disease, stroke,hypertension and certain type of cancers. (Williams et al. 2015). The convenient supply of high calorie food and decreased physicalactivity have contributed to a rapid increase of obesity in developingcountries, such as Sri Lanka. This will be a double sword attack on developingcountries as the developing country has to deal with over and under nutrition. Lifestylemodification through behavioral counselling by an interventionist is consideredas the first step in the management of obesity, as the cost and complicationsare low. However 5-8% weight reduction is observed and patients tend to regainthe weight after cessation of behavioral counselling (Anon 2014). Pharmacotherapy is advised as adjunct to a reduced-calorie dietand increased activity for long-term weight management.
Number of anti-obesitydrugs were brought to the market, but withdrawn later due to adversecomplications. This cause unpleasant situation among patients and prescribedfor short term. The seriousness of the situation and failing to find a solutionurge for new therapeutic strategies. Recent advancesin genetics have showed that the body mass index (BMI) is heritable. Twin andadoption studies estimating the heritability of fat mass to be between 40 and 60%(Raman 2002).
The Genome Wide Association Studies (GWAS); a study that comparesDNA markers across the genome in people with a disease or trait to people hasidentified that the Fat mas and obesity – related transcript (FTO) is associatedwith Type 2 Diabetes, but further analysis confirmed that the FTO is associatedwith BMI. Thirteen independent cohort studies have confirmed the association ofFTO with BMI (Frayling et al. 2007). Further analysis of GWAS revealedthat Single nucleotide polymorphisms (including rs9939609, rs17817449,rs3751812, rs1421085 and rs9930506) in the intron 1 of FTO are associated withobesity (Scuteri et al. 2007). Homozygous of above alleles weigh 3kg more than the baseline andit is estimated that 1 billion of us share the homozygous allele (Leibel 2008). Mechanistic information of the FTO proteinIn 2007, Schofield’sgroup has done a bioinformatic sequence analysis studies and predicted that FTOprotein contains a double-stranded beta-helix (DSBH) fold that is homologous tothose of Fe(II) and 2-Oxoglutarate (2OG) oxygenases (Gerken et al.
2007). 2OG oxygenases regulate wide range of functions including: DNArepair, posttranslational modifications, the regulation of the hypoxicresponse, and fatty-acid metabolism (Trewick et al. 2002). In 2007, Schofield’s group demonstrated that using recombinantmurine Fto catalyses the Fe(II)-and 2OG-dependent demethylation of3-methylthymine in single-stranded DNA, with concomitant production ofsuccinate, formaldehyde, and carbon dioxide.
Studies on the wild type indicatedthe Fto mRNA is abundantly expressed in arcuate nucleus, which regulate thefeeding and fasting (Gerken et al. 2007). Recent studies have showed that FTO gene might represent animportant regulatory site for both FTO, as well as RPGRIP1L (retinitispigmentosa GTPase regulator-interacting protein-1 like), whose transcriptionalstart is located in the opposite direction of and close to the first exon ofFTO (Stratigopoulos et al. 2008). Structure of FTO proteinThe proteinstructure of the FTO is important to develop inhibitors using the strategy ofStructure-based drug design.
Crystallo- graphic analyses reveal inhibition by2OG cosubstrate or primary substrate competitors as well as compounds that bindacross both cosubstrate and primary substrate binding sites (Aik et al. 2013). Further studies have showed that FTO protein has preference fornumber of substrates (Han et al. 2010). Schofield’s group possess large number of small molecules thoseare related 2OG oxygenases, which can be used to evaluate the structure of FTOprotein. Small molecule inhibitionSmall moleculeinhibition is vital for unrevealing, either invitro or in vivo biologicalmechanisms, as obtaining crystallographic structures are difficult.
Simpleinhibition studies such as differential scanning flurometry can be performed toidentify inhibitors. As the Schofield group possess large number of potentialsmall molecules, it would be interesting to evaluate the inhibition potentialof those. (McMurray et al. 2015) Experimental Plan:· Molecular biology studies will be conducted tounravel the linkage between FTO gene and obesity by incorporating knockoutmouse or small interfering RNAs (siRNA).
· Comprehensive studies on FTO regulation in foodintake and energy expenditure using animal models – in vivo models. · Inhibition studies: Use the differentialscanning flurometry based assay to screen 2OG analogues and metal chelators toidentify the most potent inhibitors for the FTO protein. · Efforts will be made to obtain crystals ofFTO-small molecule complex and solve them.