Please validate my answers to the attached quiz and respond to Question 2 as I dont know the answer: Case Study 1 Riboflavin is required to generate the active form of vitamin B6 (pyridoxal 5-phosphate; PLP) in tissues, but the relevance of this metabolic interaction for nutritional status of vitamin B6 is unclear because riboflavin biomarkers are rarely measured in human studies. To address this issue, a study was recently conducted at Ulster University (Jungert et al J Nutr, 2020). The aim of the study was to examine the interrelationship between riboflavin and vitamin B6 in 407 healthy adults aged 18–92 y who did not use B-vitamin supplements, and to investigate whether plasma PLP concentration differed by riboflavin status groups in the total sample and in both age groups (<60 compared with ≥60 y). Vitamin B6 status was assessed by plasma PLP concentrations and erythrocyte glutathione reductase activation coefficient (EGRac) was used as a functional indicator of riboflavin status. Table: Plasma PLP concentrations according to riboflavin status categories EGRac Optimal (≤ 1.26) (n = 100) Low (1.27–1.39) (n = 157) Deficient (≥ 1.40) (n = 150) P EGRac 1.21 (1.18, 1.24)a 1.32 (1.29, 1.35)b 1.51 (1.44, 1.61)c <0.001 Dietary riboflavin intake 2, mg/d 1.8 (1.5, 2.3)a 1.6 (1.3, 2.1)b 1.4 (1.1, 1.9)c <0.001 Dietary vitamin B-6 intake 2, mg/d 2.0 (1.7, 2.4)a 1.9 (1.5, 2.3)a,b 1.8 (1.5, 2.1)b 0.012 BMI 2, kg/m² 26.6 (24.1, 29.8) 26.5 (24.1, 29.4) 25.7 (23.0, 29.0) 0.331 Plasma PLP2, nmol/L Total sample (n = 407) 63.0 (42.7, 80.6)a 56.2 (38.9, 71.9)a,b 54.9 (37.8, 67.6)b 0.001 Age < 60 y (n = 172) 74.7 (58.2, 104.7)a 57.9 (41.5, 73.7)b 59.7 (43.2, 75.5)b 0.002 Age ≥ 60 y (n = 235) 60.7 (38.7, 74.3)a 55.2 (38.4, 70.9)a 46.6 (33.1, 61.4)a 0.049 Data are presented as median (interquartile range). 1 Differences in EGRac, dietary riboflavin and vitamin B-6 intakes and BMI values across EGRac groups were tested using Kruskal Wallis test, and post hoc tests with Bonferroni adjustment were performed (if overall test was significant). Different superscript letters for values within the same row indicate significant differences between the groups. 2Analysis of covariance (ANCOVA) with Bonferroni post hoc test was conducted to investigate differences in PLP concentrations across EGRac groups after adjusting for age, sex and dietary vitamin B-6 Abbreviations: PLP, pyridoxal 5´-phosphate concentration; EGRac, erythrocyte glutathione reductase activation coefficient; BMI, body mass index. (a) In this sample of healthy adults, what proportion (%) were determined to have (i) optimal and (ii) deficient riboflavin status (4 marks) Answer – • (100/407)x100= 24.57% had optimal status. • i(150/407)x100= 36.85% had deficient status (b) Is biomarker status of riboflavin reflecting dietary riboflavin intake in this sample? Explain your answer by referring to the data provided. (2 marks) (c) Explain what is meant by a functional indicator of status and describe the principle underpinning the EGRac assay, as used to measure riboflavin status in the current study (4 marks) Answer – Functional indices are measurements of the metabolic effects that a given vitamin or mineral etc. will have on the body compared to direct indices that measures the concentration of a vitamin or mineral in circulation. Erythrocyte glutathione reductase activation coefficient (EGRAC) is an index of riboflavin deficiency or, more exactly, of flavin adenine dinucleotide (FAD) deficiency in man. EGRAC is considered the gold standard of measuring riboflavin status, EGRAC works by measuring the activity of glutathione reductase both before and after in vitro reactivation with the FAD, therefore EGRAC is the ratio of FAD stimulated-unstimulated enzyme activity and therefore measures the tissue saturation levels of riboflavin, thus making it a functional indicator. (d) (i) (ii) (iii) (iv) Describe in detail the metabolic relationship between riboflavin and vitamin B6 (4 marks) Answer: Riboflavin is a key requirement for the generation of the active form of Vit B6 known as pyridoxal-5-phosphate (PLP) this occurs due to the coenzymes of riboflavin FMN aiding in the conversion of pyridoxine Phosphate to PLP with the enzyme pyridoxine Phosphate oxidase. How did riboflavin status influence vitamin B6 status in this population? Explain your answer (2 marks) Answer: Riboflavin directly influences this vitamin B6 status in the population, This is because of the coenzyme FMN is not at a sufficient level, the amount of pyridoxine phosphate being converted to PLP will drop and there for effect the levels of B6 within the body, this can be observed in the study when looking at the optimal levels EGRAC having higher levels of riboflavin and then go onto have greater levels of PLP as well compared to deficient and low levels, however it must be noted that those with low level status of riboflavin using EGRAC still had higher levels of PLP than subjects who were considered deficient when using the EGRAC method. How did age influence the association between riboflavin and B6 in this population?
