Doctoral Degrees (Human Nutrition)

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Browsing Doctoral Degrees (Human Nutrition) by browse.metadata.advisor "Blaauw, Renée"

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    The effect of β-glucan prebiotic fibre (oats) on the gut microbiome of chronic kidney disease patients (Stage IV and V) and impact on kidney function
    (Stellenbosch : Stellenbosch University, 2022-04) Ebrahim, Zarina; Blaauw, Renée; Moosa, M. Rafique; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Global Health. Human Nutrition.
    ENGLISH SUMMARY: Background: Chronic kidney disease (CKD) is increasing in global prevalence and has many nutritional complications. Increasing evidence suggests that gut dysbiosis is involved in CKD progression through various mechanisms including intestinally derived uraemic toxins, dietary, and immune-mediated factors. Therefore, modulating the gut microbiome may improve outcomes in CKD. The aim of this research project was to investigate the effect of a ß-glucan prebiotic supplement on kidney outcomes, uraemic toxins and the gut microbiome in predialysis CKD participants. Methods: This study was a randomised controlled intervention study over 18 weeks, performed at Tygerberg Hospital predialysis clinic in Cape Town, South Africa. There was a pre-randomisation period of four weeks where participants were counselled on a CKD diet before being randomised. At randomisation, the intervention group received the ß-glucan supplement and continued the diet, while the control group continued with the diet only. There were follow-ups at weeks 4, 8 and 14 after randomisation. The objectives were to assess nutritional status, kidney function, plasma levels of uraemic toxins and gut microbiota using 16S rRNA sequencing at pre-randomisation. Additionally, differences in these outcomes were measured at randomisation baseline (week 0), week 8 and week 14 between the intervention and the control groups. Anthropometrical measurements were done which included weight, height, waist circumference, mid-upper arm circumference and triceps. Clinical investigations included investigating for oedema as well as gastrointestinal symptom measurement. Stool consistency was described using the Bristol Stool Score (BSS). Dietary intake was measured using a quantified food frequency questionnaire (QFFQ) and a dietary adherence score sheet. Although most of the investigations was done locally, the uraemic toxins analysis was performed at the nephrology laboratories at the University of Ghent in Belgium, while the gut microbiome analysis was performed at VIB laboratories (Leuven, Belgium). Statistical analysis was performed using IBM®SPSS®version 26/27 and R Statistical Software. Results: Seventy participants were enrolled in the study at the pre-randomisation visit. The mean age of the participants was 41.7 ± 11.8 years, with a slight predominance of females (53%). Most participants were unemployed, earning less than US$126 per month. Hypertension was the main cause of kidney failure and most participants were in stage 5 CKD. A very high prevalence of overweight (30%) and obesity (36%) was found at pre-randomisation, with a low prevalence of undernutrition (3%). Abdominal obesity was found in 60% of participants. Dietary assessment showed an unhealthy dietary pattern. After four weeks, 59 participants were randomised. The diet intervention resulted in significant nutritional changes in participants after four weeks, while uraemic toxins remained unchanged. There was a significant reduction in body mass index (P < 0.006) and waist circumference (P < 0.001). Almost all dietary intake variables were significantly reduced and there was a high dietary adherence. Serum total cholesterol (P < 0.045) and triglyceride levels (P < 0.017) were also reduced. After randomisation to either the ß-glucan prebiotic or the diet, kidney function did not significantly change. However, there was a significant reduction in uraemic toxins in free IxS at week 8 (P = 0.003) and week 14 (P < 0.001), total and free pCG (P < 0.001, P < 0.001, respectively) and free pCS (P = 0.006) at week 14. There were no significant changes in dietary intake, clinical symptoms or anthropometry during the trial. The gut microbiome revealed that two enterotypes were prevalent, namely the Bacteroides2 and Prevotella enterotypes. The inter-individual Bray–Curtis distance (ß-diversity) was significantly higher in the control group than the intervention group at baseline (P < 0.0001), week 8 (P < 0.0001) and week 14 (P = 0.02). There were no differences in relative abundance of genera between groups. The redundancy analysis showed a few factors significantly affected the gut microbiome: these included triglyceride levels (P < 0.001), cause of kidney failure (P < 0.001), gender (P < 0.001), body mass index (P = 0.002), high- density lipoprotein (P < 0.001) and the prebiotic intervention (P = 0.002). Conclusion:While four weeks of the diet resulted in some nutritional changes in participants before randomisation, it did not affect other outcomes of the study. Once randomised, the prebiotic did not significantly affect kidney function, while it significantly reduced uraemic toxins and the gut microbiome, according to the RDA analysis. The ß-glucan prebiotic therefore had some beneficial effects on outcomes in CKD participants.