Metabolic profiling detects early effects of environmental and lifestyle exposure to cadmium in a human population

Table 2 Correlation coefficients (standardized beta values) derived from multiple linear regression of key metabolite to lifestyle factors.

Metabolite	Chemical shift	Sample number	Correlation to Y variable
	(ppm)	number	(U-Cd)	age	sex	smoking status^a
3-HV	1.276 to 1.269	160	-0.056	-0.326***	-0.233**	-0.023
DMG	2.936 to 2.920	176	-0.127	-0.122	-0.168	-0.052
citrate (1)	2.515 to 2.590	175	0.194*	-0.078	0.126	-0.298***
citrate (2)	2.515 to 2.590	143	0.228*	-0.060	0.157	-0.203*
citrate (3)	2.515 to 2.590	108	0.251*	-0.046	0.121	n/a
Creatinine	4.073 to 4.040	178	-0.010	-0.427***	-0.395***	0.015
Creatine	3.940 to 3.930	178	-0.006	0.088	0.321***	0.150
4-DEA	1.118 to 1.108	152	-0.042	-0.370***	-0.076	0.039

^aSmoking status was classified into three classes. 1 = never smoked, 2 = past smoker and 3 = current smoker. Specific exclusions were made for each metabolite identified where coinciding interferences made the relevant resonance unsuitable for integration. All six metabolites were correlated to at least one of the epidemiological factors in either the PLS/PLS-DA regression analysis or the covariance/correlation models. Asterisks denote statistical significance (ANOVA with Bonferroni post-hoc correction): * P < 0.05, ** P < 0.01, *** P < 0.001. U-Cd was log normally distributed.
citrate (1) all three classes included (never smoked, past- and current-smoker). Note, three samples excluded. citrate (2) current-smokers additionally excluded. citrate (3) past- and current-smokers additionally excluded. ANOVA, analysis of variance; 3-HV, 3-hydroxyisovalerate; DMG, dimethylglycine; 4-DEA, 4-deoxyerythronic acid; PLS, partial least squares; PLS-DA, partial least squares - discriminant analysis; U-Cd, urinary cadmium.

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