Alkylresorcinols as a biomarker for whole grain rye and wheat intake in the finnish diabetes prevention trial

Abstract: Type 2 diabetes (T2D) is a public health problem of great concern. Globally it is increasing and it generates a huge economic burden to society and problems for the individuals. Whole grain has shown to have a protective role against T2D in epide-miological studies and underlying mechanisms are poorly understood, but de-creased energy intake, higher insulin sensitivity and improved glucose tolerance have been suggested and partly confirmed in studies. Alkylresorcinols (AR) are phenolic lipids found in different homologs only in the outer parts of wheat and rye among commonly consumed foods. It is used as a biomarker of whole grain for rye and wheat intake. The Finnish Diabetes Prevention Study (DPS) started in 1993 with the purpose to evaluate if an intensive diet- and exercise program could pre-vent or delay T2D in persons with impaired glucose tolerance (IGT). The aim of this study was to investigate if there was a difference in whole grain cereal intake among non-diabetics and people who developed diabetes under a period of 8 years. A fraction of the subjects in the (DPS) was studied. The aim was also to investigate differences in whole grain intake between participants who got lifestyle intervention and those who did not. Plasma AR was measured and used as a proxy of whole grain rye and wheat intake. Quality control samples were included in each batch to ensure adequate precision. AR were extracted with diethyl ether and further cleaned up with solid phase extraction (SPE). AR were made more volatile through derivat-isation with trifluoroacetic anhydride (TFAA) and analyzed with gas chromatog-raphy-mass spectrometry (GC-MS). The coefficient of variation (CV) within batch-es were ≤ 9% and between batches ≤ 15% except of one homolog, C25. No signifi-cant difference was found in total AR concentration between the lifestyle interven-tion and control groups or between subjects who developed diabetes during follow up and non-diabetic controls. Even if there was no difference in plasma AR be-tween the lifestyle intervention- and control groups there was a significant differ-ence in fiber intake (p=0.001). The Finnish population consumes large amounts of whole grain in the form of rye bread. When the subjects were advised to raise their consumption of dietary fiber during the lifestyle intervention, it is likely they did this with other foods than rye and wheat sources. The main findings of this study were a positive correlation between the AR C17/C21 ratio and time to T2D diagno-sis (p=0.027) and the fact that the AR C17/C21 ratio was higher within non-diabetics than diabetics (p=0.025). This indicates that individuals with a high intake of whole grain rye develop T2D later than those with a low intake, or does not de-velop it at all, i.e. that whole grain rye is protective. This should be confirmed with more sophisticated analysis of data in the present study but that is out of scope for this study.