The data was divided into deciles of plasma betaine concentration to find underlying functional relationships between plasma betaine and lipid fractions. The median plasma betaine concentrations of the deciles were compared with the median BMI and plasma lipid concentrations of the same groups, using polynomial regression since not all relationships appeared to be linear. Plasma betaine concentrations appeared to be positively associated with HDL-cholesterol in all 6 best subset models but ceased to be significant when BMI was included in an explicit multiple regression model rather than waist. The model for HDL-cholesterol shown in T863 Figure 1 can be slightly improved by using the ratio of plasma dimethylglycine to betaine instead of plasma dimethylglycine concentrations; this ratio term is more significant than the concentration. Variables that did not enter any of the best subset models as significant factors include plasma homocysteine, creatinine and urea. Age was not a significant factor in any of the models for plasma betaine. The urinary excretions of betaine and dimethylglycine were not significant in any of the models for predicting plasma lipids or BMI that were calculated that included these urinary measures. In none of the models in Figure 1 was the explained variance more than 20% of the total variance. Blood pressure was not recorded in this study. Clinicallydiagnosed hypertension was recorded as a variable but given that the majority of subjects were receiving medication that would modify blood pressure this was regarded as a compromised measure; it did not enter into any of the best subset models for blood lipid fractions, though it was a significant 2-Methylserotonin maleate predictor of BMI. BMI and plasma non-HDL cholesterol concentrations decreased approximately linearly with increasing plasma betaine concentrations, but the relationship with plasma triglyceride concentrations was not linear, the binomial term being significant. Above a plasma betaine concentration of about 45 mmol/L no association was detected between plasma betaine and triglyceride concentrations, whereas low plasma betaine concentrations were strongly associated with elevated plasma triglycerides.