We compared a kinetic method (KM) and a colorimetric method (CM) for measuring erythrocyte aspartate aminotransferase (EAST) activity. Twenty-three healthy college students including 7 men and 16 women, aged from 22 to 40 years, participated in this study. Vitamin B-6 status was assessed by EAST activity coefficient (EAST-AC), the ratio of EAST stimulated activity by adding PLP in vitro (EAST-SA) to basal activity (EAST-BA). These subjects' EAST indices (EAST-BA, EAST-SA and EAST-AC) were compared to their plasma PLP concentration and their dietary intake of vitamin B-6 as determined by the food frequency questionnaire (FFQ) and 3-day dietary record. There was a significant correlation (r=0.59, p<0.01) in EAST-BA obtained by the two methods, while the correlation of EAST-SA values between the two methods was not significant (r=0.40, p=0.06). EAST-AC obtained with KM was linearly associated (r=0.57, p<0.01) to EAST-AC obtained with CM, but was 1.26 times higher (p<0.01) than that with CM. Thus, the method used for the determination of the normal EAST-AC value needs to be noted. None of EAST indices measured were significantly correlated with plasma PLP concentration. There was a high correlation for vitamin B-6 intake (r=0.65, p<0.01) and the ratio of vitamin B-6 to dietary protein (r=0.58, p<0.01) estimated between the FFQ and the 3-day dietary record. The results suggested the high validity of the FFQ for determining vitamin B-6 intake. Neither of these dietary methods was, however, correlated with any EAST activity indices or the plasma PLP concentration. / Graduation date: 1995

Previous studies have found that smoking may have a negative effect on vitamin B-6 indices and have demonstrated a possible association between smoking and depressed plasma pyridoxal-5'-phosphate (PLP) concentration. Individuals with plasma PLP values below the adequate level of 30 nmoles/L might benefit from consumption of vitamin B-6 supplements, but no data are available on vitamin B-6 status in smokers consuming a controlled vitamin B-6 intake and receiving a vitamin B-6 supplement. The objectives of this research were to assess vitamin B-6 status in smokers as compared to non-smokers receiving a controlled diet and to evaluate the effect of an oral vitamin B-6 supplementation in these subjects. The vitamin B-6 (B-6) status of 5 (four males / one female) smokers (S) and 4 (three males / one female) non-smokers (NS) was assessed. A constant diet was fed for 20 days and provided 1.95 mg of B-6 or 1.65 mg of B-6 for males and females, respectively. For the last 10 days, an additional 2-mg of pyridoxine (PN) was given daily. Blood samples were collected on days 1.7, 11.14 and 21; and 24 hour urine samples were collected daily. Urinary 4-pyridoxic acid (4-PA) and total B-6 (UB6) excretion, plasma B-6 vitamers (PLP, PN, pyridoxal and 4-PA) and red blood cell PLP (RBC PLP) concentrations, as well as plasma alkaline phosphatase activity (APA) were determined. Mean plasma PLP, 4-PA, and RBC PLP concentrations were significantly lower (P [less than or equal to] 0.05) at all time points in S compared to NS. With a daily supplement of 2-mg vitamin B-6, the mean plasma PLP concentration of S increased 85.8% but was 48.5% lower than that of NS consuming 1.65-1.95 mg/d of B-6. Mean plasma pyridoxal concentrations were not different between S and NS before and after supplementation. Excretion of 4-PA was not significantly different between S and NS, but the mean values of 4-PA excretion were consistently greater in NS compared to that of S throughout the 20-day study. The percent of ingested B-6 excreted as 4-PA for the S and NS was 38 and 49 in the non-supplemented period, and 47 and 53 in the supplemented period, respectively, indicating that non-smokers excreted more 4-PA than smokers. However, the difference in 4-PA excretion between S and NS was not significantly different both before and after supplementation (P>0.05). In addition, there was no significant difference between S and NS for plasma PN concentration, AP, and UB6 excretion for both periods. Results suggested an adverse effect of smoking on B-6 metabolism, thus an increased requirement of vitamin B-6 in smokers. A 2-mg PN supplement was sufficient to bring the concentration of plasma PLP in smokers to the level suggested as adequate, but it didn't bring it to the level of non-smokers. / Graduation date: 1999

Trained male cyclists (6 in study 1, 5 in study 2) cycled to exhaustion (EXH) at 75% of VO₂ max twice; once in the non-supplemented (NS) state and once in the vitamin B-6 (B-6)(20 mg PN) supplemented (S) state. The diet contained 2.3 mg B-6 in study 1 and 1.9 mg B-6 in study 2. Urine was collected during each dietary period. During each exercise (EX) test, blood was drawn prior to (PRE), one hour during (DX), immediately after (POST) and one hour after (POST 60) EX and sweat was collected. Compared to baseline (PRE) levels, plasma pyridoxal 5'-phosphate (PLP) and vitamin B-6 (PB-6) concentrations increased at DX, decreased at POST, and decreased below PRE at POST 60 in the NS and S states. EX to EXH in the S state resulted in a greater increase in PLP DX in study 1 (31% increase vs. 16%) and PB-6 in study 2 (25% increase vs. 11%) as compared to the NS state. Red blood cell (RBC) PLP significantly increased from POST to POST 60 in the S state in study 2. The excretion of urinary 4-pyridoxic acid (4-PA) and urinary B-6 (UB-6) was not significantly altered by EX to EXH. The mean excretion of 4-PA was significantly greater in the NS state in study 2 (7.98 ±1.83 mmol/d) as compared to the excretion in study 1 (6.20 ±0.93 mmol/d), whereas the excretion was significantly greater in the S state in study 1 (92.2 ±8.69 mmol/d) compared to the excretion in study 2 (82.7 ±6.16 mmol/d). The percent of B-6 intake excreted as UB-6 (6% in study 1 and 10% in study 2) was significantly different between the studies in the NS state. Vitamin B-6 supplementation did not significantly alter the rise in growth hormone (hGH) concentration seen with EX to EXH. The loss of B-6 in sweat with EX to EXH was not altered by B-6 supplementation. The loss of B-6 in sweat ranged from 0.0011 mmol to 0.0039 mmol. Therefore, EX to EXH in the B-6 S state resulted in a greater increase in plasma PLP and PB-6 DX as compared to the NS state. The decrease in PB-6 and PLP at POST 60 in the S state coincided with a significant increase in RBC PLP, suggesting the movement of B-6 from the plasma into the RBC at POST 60. EX to EXH and B-6 supplementation did not alter the excretion of 4-PA or UB-6 suggesting that B-6 metabolism was unchanged. The loss of B-6 in sweat was comparable to previously reported values and was not altered by B-6 supplementation. B-6 supplementation did not alter the changes in hGH resulting from EX to EXH alone. / Graduation date: 1995

Graduation date: 1993