The concentrations of the inflammatory proteins MCP-1 and IL-8 were positively correlated at the follow-up visit (Table 3.5). At baseline they were also correlated, although this did not reach statistical significance. The absolute change and percent change in MCP-1 and IL-8 concentrations from baseline to follow up were also significantly correlated.
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Table 3-4 Correlation between MCP-1 and IL-8 concentrations in patients at baseline and follow-up and the relationship between change in these variables (n=116)
Baseline Follow
up Absolute change Percent change Pearson Correlation Coefficie
nt: p value: 0.15 0.10 0.24 0.01 0.24 0.009 0.28 0.003
Both MCP-1 and IL-8 concentrations were ranked by their measurements at baseline and grouped into tertiles. PGA at baseline and at follow-up was examined in the context of these tertiles. PGA improved for all individuals, regardless of MCP-1 or IL-8 baseline tertile.
Individuals who were in the upper tertile of IL-8 concentration had the highest PGA score at baseline (54.34 compared to 44.21 for the lowest tertile and 40.18 for the middle tertile). This difference was statistically significant (p=0.008). At follow up, the upper, lower and middle tertiles had similar PGA scores, with values of 28.69, 25.69 and 26.94, respectively (p=0.73).
At baseline, the mean PGA score for the lower, middle and upper MCP-1 tertiles were 52.88, 44.57, and 39.95, respectively (p=0.01). At the follow up visit, the mean PGA scores had decreased to 31.89 for the lowest tertile, 26.89 for the middle tertile, and 22.22 for the upper tertile (p=0.03).
When MCP-1 concentration was stratified by IL-8 tertile, the concentration at baseline was 299.59 pg/mL for lowest tertile, 393.36 pg/mL for the middle tertile and 419.55
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pg/mL for the upper tertile (p=0.38). At follow up, the lowest tertile had a mean MCP-1 concentration of 377.74 pg/mL, the middle tertile was 439.10 pg/mL and the upper tertile was 440.08 pg/mL (p=0.58).
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Figure 3-2 Change in variables by MCP-1 and IL-8 tertiles. MCP-1 and IL-8 concentrations were ranked and divided into tertiles. A. PGA score by MCP-1 tertile. B. PGA score by IL-8 tertile. C. MCP-1 concentration by IL-8 tertile. 0 10 20 30 40 50 60 Baseline Follow up PGA sco re
Lower Middle Upper
0 10 20 30 40 50 60 Baseline Follow up PGA sco re
Lower Middle Upper
0 100 200 300 400 500 Baseline Follow up MC P -1 (pg /mL)
Lower Middle Upper
B
C A
50 3.5 Discussion
The individuals in this observational study had been prescribed MTX for treatment of an inflammatory condition. At the baseline visit, patients were MTX-naïve, and after at least 18 weeks on treatment returned for a follow-up. One hundred and nineteen Caucasians attended both the baseline and follow up visits and were analyzed in this study.
Treatment with the antifolate drug MTX caused decreases in plasma 5-MTHF, RBC total folate, and RBC 5-MTHF from the baseline visit to the follow up visit in this study population as a whole. Conversely, RBC THF increased from the baseline visit to the follow up visit. In turn, the ratio of 5-MTHF:THF decreased. Interestingly, despite the decrease in total folate and 5-MTHF, there was not a measurable change in tHcy
concentration between the baseline and the follow-up visits. Due to the fact that this was an observational study and not designed as an intervention, subjects were not asked to fast which is likely why no change in tHcy concentration was detected.
Both PGA and ARA class, measures of disease state, decreased significantly for between the two time points for the subjects in this study, demonstrating that this drug was
effective in improving clinical status for these subjects.
The concentration of MCP-1, an inflammatory protein that is involved in leukocyte recruitment, increased. This increase in MCP-1 from baseline to follow-up suggests a potentially pro-atherosclerotic effect from MTX treatment.
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Polymorphisms of several folate pathway enzymes were analyzed in this study. The most interesting genetic results were related to MTHFR 677C>T. The TT genotype seemed to affect several of the biochemical variables in a different manner than the CC and CT genotypes. MTHFR CC and CT subjects had decreased total RBC folate and RBC 5- MTHF between baseline and follow up visits, with an increase in RBC THF
concentration, while TT homozygotes had an increase in total RBC folate and RBC 5- MTHF, accompanied by a decrease in RBC THF. While MCP-1 concentration increased in CC and CT subjects, it decreased in TT homozygotes. PGA score did decrease for all of the genotype classes, although this decrease was slight and not significant in TT subjects, unlike the CC and CT groups which had quantitatively large and statistically significant decreases in PGA. These data suggest that MTHFR 677C>T genotype has distinct effects on biochemical and clinical variables associated with MTX treatment.
There were three toxicities reported prior to starting MTX therapy, and 31 were reported at the follow-up visit. Prior to analysis, toxicities that could be considered attributable to MTX were identified. Of the 31 toxicities reported while on MTX, six of the toxicities reported at follow-up were considered to be attributable to the drug. TYMS 1494del6 was the only polymorphism of those examined in this study that had an association with toxicities. It was not associated with the overall toxicities reported at follow-up, but did show a statistically significant association with the toxicities attributable to MTX. Due to the low numbers of toxicities in this study population, specifically the attributable
toxicities, it is possible that some of the polymorphisms might show an association with toxicity if there were more subjects and greater statistical power.
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Perhaps the most interesting finding of this study is that MCP-1 and IL-8 concentrations are positively correlated at baseline and at follow up, and the change in these variables is positively and significantly correlated as well. This indicates that these two potent biological molecules are at least partly coordinately regulated in patients being treated with MTX.
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