Metabolomics reveals the metabolic shifts following an intervention with rye bread in postmenopausal women--a randomized control trial

Abstract

Background: Epidemiological studies have consistently shown that whole grain (WG) cereals can protect against the development of chronic diseases, but the underlying mechanism is not fully understood. Among WG products, WG rye is considered even more potent because of its unique discrepancy in postprandial insulin and glucose responses known as the rye factor. In this study, an NMR-based metabolomics approach was applied to study the metabolic effects of WG rye as a tool to determine the beneficial effects of WG rye on human health.

Methods: Thirty-three postmenopausal Finnish women with elevated serum total cholesterol (5.0-8.5 mmol/L) and BMI of 20-33 kg/m² consumed a minimum of 20% of their daily energy intake as high fiber WG rye bread (RB) or refined wheat bread (WB) in a randomized, controlled, crossover design with two 8-wk intervention periods separated by an 8-wk washout period. At the end of each intervention period, fasting serum was collected for NMR-based metabolomics and the analysis of cholesterol fractions. Multilevel partial least squares discriminant analysis was used for paired comparisons of multivariate data.

Results: The metabolomics analysis of serum showed lower leucine and isoleucine and higher betaine and N,N-dimethylglycine levels after RB than WB intake. To further investigate the metabolic effects of RB, the serum cholesterol fractions were measured. Total- and LDL-cholesterol levels were higher after RB intake than after WB (p<0.05).

Conclusions: This study revealed favorable shifts in branched amino acid and single carbon metabolism and an unfavorable shift in serum cholesterol levels after RB intake in postmenopausal women, which should be considered for evaluating health beneficial effects of rye products.

Figure 1

Rank product (RP^1/20) from multilevel partial least-squares discriminant analysis models of the comparsion between the NMR spectra of serum after the intake of refined wheat bread vs the intake of whole grain rye bread in postmeopuasal women (n=33). 1: Isoleusine; 2: Leusine; 3: N,N-dimethylglycine; 4: Betaine; 5: an overlapping signal with glucose at 3.875 ppm; 6: small signal in an overlapping area at 3.965 ppm. Chemical shift indicates the chemical shift of the spectral buckets used for multivariate analysis.