Page 12 - Demo

Themetabolismof tagatoseisidentical to thatof fructosebutittakesplaceataslowerspeedTagatoseisalsotransformedinto tagatose-1-phosphateanditiscleavedbyaldolaseBintoglyceraldehydeanddihydroxyacetonephosphateThisisthepointatwhichglucosetagatoseandfructosemetabolismsareconnectedTagatose-1-phosphateisanactivatorofglucokinasesoglucoseistransformedintoglucose-6-phosphateatahigherrate Thehigherconcentrationofglucose-6-phosphatepromotestheactionofthehepaticglycogensynthaseandglycogenesis takesplaceMoreover,tagatose-1-phosphateisaninhibitorofglycogenphosphorylase soglucoseremainsstoredasglycogenTheseeffectsleadtoalowerpost-prandialglycaemia(2238)15CholesterolmetabolismCholesterolandlipidestersliketriacylglycerolsarehydrophobicmoleculesbut theyneed tobe transportedinblood tothe tissues where they willbe storedorconsumedFor thatpurposethereare someparticlescalledlipoproteins thatactaslipidcarriersThey formcomplexes through thenon-covalentassociationoflipidstoapoproteinsLipoproteinsarewatersolubleparticleswithahydrophobiccoreandapolarsurface Thereareseveral typesoflipoproteinsdependingontheirdensitiesandfunctions(3940)–Chylomicrons theycarrymainly triacylglycerols from thedietandtransportthemfromtheintestinetoothertissuesTheselipoproteinsare thelargestin sizeand theones with thelowestdensity.–Very-low-densitylipoprotein(VLDL)theytransportallthelipidsthathavebeensynthesisedintheliver(mainlytriglycerides)totheothertissues(iemuscleandadiposetissue)260ANALESRANFwwwanalesranfcomLaingestamaternade fructosamodulaelmetabolismodelcolesterolenrespuestaaunadietaoccidentalenladescendenciaPalomaLópezLaizElenaFausteetalAnRealAcadFarmVol88Nº3(2022)·pp257-275VLDLishigherindensitythanchylomicronsThemicrosomaltriglyceridetransferprotein(MTTP)playsacentralroleintheassemblyofVLDL–Low-densitylipoproteins(LDL)theycontainprimarilycholesterolandcholesterylesters Thesemoleculesare transportedtoextrahepatictissuesLDLuptakebythetissuesismediatedthrough the specificinteractionofitsapoBprotein with theLDLreceptor(LDLR)presentin thecellmembrane After thisinteractionLDLreachesthecytosolofthecellsthroughanendocytosismediatedmechanism–High-densitylipoproteins(HDL)theyareresponsibleforthereversecholesterol transport(RCT)as theycarrycholesterolandcholesterylesters fromextrahepatic tissues to theliver.HDLuptakebytheliveroccursviatheScavengerreceptorclassBtype1(SR-B1)receptor.Theselipoproteinsworktogethertotransportthelipidsthroughoutthebody,ascanbeseeninFigure316FoetalprogrammingFoetalprogrammingpostulates that thereisprogrammingduringtheembryogenicandfoetalstagethatinducespermanentchangesin theadult Thesemodificationscanbestructuralphysiologicalandmetabolicandtheywillincreasetheriskofindividualstodevelopvariousdiseases(41)Theprogrammingcanbeperformed throughepigeneticsthenutritionalconditionsand theenvironmentof themotherduringthegestationcan vary theexpressionof somegenes Alsoimprintedgenesaredifferentiallyexpresseddependingonthesexoftheindividual(42)Figure3LipoproteinsandlipidtransportCreatedwithBioRender.com