An investigation of obesity as an etiology of male infertility in a rat model
| dc.contributor.advisor | Du Plessis, Stefan S. | en_ZA |
| dc.contributor.advisor | Aboua, Yapo Guillaume | en_ZA |
| dc.contributor.advisor | Van der Horst, Gerhard | en_ZA |
| dc.contributor.advisor | Marais, Erna | en_ZA |
| dc.contributor.author | Skosana, Bongekile Trisha | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Medicine and Health Science. Dept. of Biomedical Sciences: Medical Physiology. | en_ZA |
| dc.date.accessioned | 2021-03-08T13:47:41Z | |
| dc.date.accessioned | 2021-04-21T14:36:16Z | |
| dc.date.available | 2021-03-08T13:47:41Z | |
| dc.date.available | 2021-04-21T14:36:16Z | |
| dc.date.issued | 2021-03 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Until recent decades, the inability to produce offspring has been seen as a female-related issue, but better understanding has made it evident that male fertility is l ikewise an essential determinant of couple fertility. Infertility in males has numerous causative factors, including lifestyle factors and obesity. Obesity has been shown to compromise fertility through changes in several aspects of reproductive function, including dysregulation ofhormones (the HPG axis) and changes in the structure of the reproductive organs. There is, however, a great deal that is still unknown about how obesity and infertility interchangeably affect each other. New molecular techniques such as proteomics have been shown to provide insights into disease-causing mechanisms. These techniques may provide an avenue to discover more intrinsic changes that obesity may give rise to; it can also aid in the discovery of mechanisms through which obesity can act to bring about changes in male fertility. The overall aims of this study were: (1) To examine the effects of obesity on male fertility by observing specific macroscopic (anthropometric), microscopic (sperm parameters, histology of the testis and epididymis) and molecular (antioxidant enzyme, reproductive hormones) changes in a diet-induced obesity animal model; (2) To examine changes in protein expression within the reproductive tissues of obese animals, quantify these changes, and identify the affected molecular pathways. This study made use of an animal model of diet-induced obesity (DIO) to assess the effects of obesity on male reproductive organs and sperm parameters. Male Wistar rats (n=40) were randomly and equally divided into control (age-matched) and DIO groups and received standard rat chow or a high caloric diet ad libitum for 54 weeks, respectively. A long-term diet was chosen to mimic the gradual and chronic onset of obesity. At 60 weeks of age, rats were sacrificed by euthanasia. Each animal had their body weight measured and immediately examined post-mortem to determine visceral fat weight, testis weight and non-fasting blood glucose. Blood was collected from the thoracic cavity and used for plasma extraction and haematocrit analysis. Testis and epididymides were excised, weighed and preserved appropriately for subsequent sperm parameter evaluations (morphology and viability), histological analysis (H & E staining), protein determination, antioxidant evaluation (catalase, superoxide dismutase, glutathione, lipid peroxidation), and proteomics analysis (Liquid Chromatography Mass Spectrometry (LC-MS/MS)). The chronic diet elevated body and visceral fat weights significantly in the DIO group compared to controls. Sperm morphology and viability, as well as estradiol production were negatively altered in the DIO group. These changes were associated with alterations in several macroscopic, microscopic and molecular changes including changes in relative testicular weight, histological aberrations, and a reduction in antioxidant enzymes within the testis and epididymis respectively. Interestingly, testosterone was not significantly reduced, as seen in experiments with a shorter DIO feeding duration. This points towards a compensatory mechanism to counteract chronically increased testosterone concentrations. Protein expression profiles of the DIO and control groups suggest that the predominant molecular pathways affected by th treatment were related to metabolism. These seem to be the possible driver of changes in other proteins including those involved in the production of reactive oxygen species (ROS). Some lesser researched antioxidant proteins were increased in expression to counteract ROS. The negative histological changes observed in the DIO group were linked to the underexpression of structural proteins involved in cell-to-cell adhesion. Reproductive proteins including those involved in sperm production, fertilization and the early stages of embryonic development were reduced in expression in the DIO group. These negative changes were possibly instigated by the observed increases in stress proteins, redox and inflammatory proteins. It is therefore evident that long-term obesity can impair male reproductive parameters and could be a contributing factor to the decline in male fertility by affecting sperm and reproductive parameters. Proteomic analysis of the epididymis and sperm showed that proteins essential in metabolism, ROS production, stress, inflammation and in the regulation of reproductive function as well as sperm and epididymis structure were negatively affected. In addition, long-term obesity can mask detrimental changes in physiology due to compensatory mechanisms, making changes in reproductive parameters difficult to explain. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Tot ‘n paar dekades gelede was die onvermoë om 'n nageslag te produseer, gesien as 'n vroulike probleem, maar beter begrip het dit duidelik gemaak dat manlike vrugbaarheid ook 'n noodsaaklike bepalende faktor vir egpaarvrugbaarheid is. Onvrugbaarheid by mans het talle oorsaaklike faktore, insluitend lewenstylfaktore en vetsug. Daar is getoon dat vetsug vrugbaarheid in gevaar stel deur veranderinge in verskeie aspekte van voortplantingsfunksie, insluitend wanregulering van hormones (die HPG-as) en veranderinge in die struktuur van die voortplantingsorgane. Daar is egter nog baie onbekend oor hoe vetsug en onvrugbaarheid mekaar onderling beïnvloed. Nuwe molekulêre tegnieke, soos proteomika, het getoon dat dit insigte kan bied in meganismes wat siektes veroorsaak. Hierdie tegnieke kan 'n manier wees om meer intrinsieke veranderinge te ontdek waartoe vetsug kan lei; dit kan ook help met die ontdekking van meganismes waardeur vetsug kan optree om veranderinge in manlike vrugbaarheid teweeg te bring. Die algemene doelstellings van hierdie studie was: (1) Om die effekte van vetsug op manlike vrugbaarheid te ondersoek deur spesifieke makroskopiese (antropometriese), mikroskopiese (spermparameters, histologie van die testis en epididymis) en molekulêre (antioksidant ensieme, voortplantingshormone) se veranderinge waar te neem in 'n dieet-geïnduseerde vetsugtige dieremodel; (2) Om veranderinge in proteïenuitdrukking binne die voortplantingsweefsel van vetsugtige diere te ondersoek, hierdie veranderinge te kwantifiseer en die aangetaste molekulêre paaie te identifiseer. In hierdie studie is 'n diermodel van dieet-geïnduseerde vetsug (DIO) gebruik om die gevolge van vetsug op manlike geslagsorgane en spermparameters te bepaal. Manlike Wistar-rotte (n = 40) is ewekansig en gelykop verdeel in kontrole- (ouderdom-ooreenstemmende) en DIO-groepe en het onderskeidelik standard rotkos of 'n hoë kalorie-dieet ad libitum vir 54 weke lank ontvang. 'n Langtermyndieet is gekies om die geleidelike en chroniese aanvang van vetsug na te boots. Op 60 weke ouderdom is rotte deur genadedood geoffer. Elke dier se liggaamsmassa is gemeet en onmiddellik nadoods ondersoek om die viserale vetmassa, die testisgewig en die nie-vaste bloedglukose te bepaal. Bloed is uit die borsholte versamel en vir plasma-ekstraksie gebruik en hematokritanalise. Testis en epididimis is uitgesny, geweeg en toepaslik bewaar vir daaropvolgende spermparameter-evaluasies (morfologie en lewensvatbaarheid), histologiese analise (H & E-kleuring), proteïenbepaling, anti-oksidant-evaluering (katalase, superoksied-dismutase, glutathion, lipiedperoksidasie) en proteomika-analise (Vloeistofchromatografie massaspektrometrie (LC-MS / MS)). Die chroniese dieet het liggaams- en viserale vet-massa aansienlik verhoog in die DIO-groep vergeleke die kontroles. Verskeie voortplantingsparameters was in die DIO-diere geaffekteer. v Spermmorfologie en lewensvatbaarheid, sowel as oestradiolproduksie, was negatief verander. Dit was geassosieer met veranderinge in verskeie makroskopiese, mikroskopiese en molekulêre veranderinge, insluitend 'n verandering in die relatiewe testikulêre gewig, histologiese afwykings en 'n vermindering in antioksidant ensieme binne die testis en epididimis. Interessant genoeg was testosteroon nie betekenisvol verminder, soos gesien in eksperimente met 'n korter DIO-voedingstydperk, nie. Dit dui op 'n kompenserende meganisme om chroniese verhoogde testosteroonkonsentrasies teë te werk. In hierdie geval kan dit toegeskryf word aan moontlike aanpassings aan die setpunt van die HPG-as om tekorte in die testikelfunksie of defekte in die testosteroon terugvoermeganisme teë te werk. Proteïen-uitdrukkingsprofiele van die DIO en kontrolegroepe dui op talle onderliggende veranderinge. Die oorwegende paaie wat geraak was, hou verband met metabolisme. Dit blyk die moontlike oorsaak van veranderinge in ander proteïene te wees, insluitend proteïene wat betrokke is by die produksie van reaktiewe suurstofspesies (ROS). Sommige anti-oksidant proteïene, wat minder ondersoek is, was egter verhoog in uitdrukking in 'n poging om ROS teë te werk. Die negatiewe histologiese veranderinge wat in die DIO-groep waargeneem is, kan gekoppel word aan die onderuitdrukking van strukturele proteïene wat betrokke is by sel-tot-sel-adhesie. Proteïene wat betrokke is by selmotiliteit, sel siklus, DNA herstel en replikasie was negatief beïnvloed; dit is noodsaaklik vir lewensvatbaarheid en die produksie van funksionele proteïene. Reproduksieproteïene, insluitend proteïene wat betrokke is by spermproduksie, bevrugting en die vroeë stadiums van embrionale ontwikkeling, was verminder in die DIO-groep. Die negatiewe veranderinge wat gelys is, is moontlik aangewakker deur die waargenome toename in stresproteïene, redoks en inflammatoriese proteïene. Dit is dus duidelik dat vetsug op die lang termyn manlike reproduksieparameters kan benadeel en 'n bydraende faktor kan wees tot die afname in manlike vrugbaarheid deur sperm- en reproduksieparameters te beïnvloed. Proteomiese analise van die epididimis en sperm het getoon dat proteïene wat noodsaaklik is vir metabolisme, ROS-produksie, stres, inflammasie en die regulering van die voortplantingsfunksie en die sperm- en epididimis-struktuur negatief beïnvloed was. Daarbenewens kan vetsug op die lang termyn skadelike veranderinge in fisiologie as gevolg van kompenserende meganismes verberg, wat veranderinge in reproduktiewe parameters moeilik verklaarbaar kan maak. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | 360 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110011 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Obesity | en_ZA |
| dc.subject | Male infertility | en_ZA |
| dc.subject | Reproductive health | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | An investigation of obesity as an etiology of male infertility in a rat model | en_ZA |
| dc.type | Thesis | en_ZA |