Fermentation of Resistant Starch Is Not a Predictor of Very High or Low Serum TMAO in Rats, but Results in Greater Serum TMAO than Controls

Abstract

Abstract Objectives Consumption of resistant starch (RS) has positive gut health benefits, but RS has been associated with increased serum trimethylamine oxide (TMAO). Increased serum TMAO has been linked to enhanced risk of cardiovascular death. A human study found that RS and a high fat (41% of energy) diet resulted in higher TMAO levels compared to a low RS diet, but this was not seen in a high carbohydrate diet (27% energy as fat). We wanted to ascertain serum TMAO in rats fed a high-RS diet with moderate (MF) or high fat (HF) diets compared to controls. Methods Twenty-four male, Sprague-Dawley rats (n = 6) were fed either 23% RS type 2, high-amylose diet or a control diet using 100% amylopectin with either MF (30% energy) or HF (42% energy) levels. A 2X choline amount had been used in the AIN-93M diets as substrate for ultimate production of TMAO. After six weeks, serum TMAO was measured using stable isotope dilution liquid chromatography tandem mass spectrometry. Data were analyzed as a 2 × 2 factorial followed by Tukey test (P < 0.05). Serum TMAO is assessed for risk of death over a seven-year period into quadrants. Quadrants 3 (4.28–7.89 µM) and 4 (7.91-186.1 µM) have greater risk. Quadrants 1 (0.12–2.55 µM) and 2 (2.56–4.27 µM) had much lower risk. Results Average TMAO level for rats fed RS HF was 2.94 ± 0.4, and RS MF was 2.42 ± 0.4. The control HF was 1.53 ± 0.17, and control MF was 1.06 ± 0.17. Rats fed RS had significantly greater TMAO levels of 2.68 ± 0.28, quadrant 2, while the control rats had an average of 1.3 ± 0.12, quadrant 1. There was no significant increased effect for MF vs. HF. However, the variability was similar for the two RS groups with values in quadrants 1–3. Amount of fermentation was not associated with TMAO amounts. For example, the RS rat with the lowest serum TMAO (0.87 µM) had an empty cecum weight (ECW) of 2.40 g, while the highest (4.41 µM) had an ECW of 2.29 g. Conclusions Sprague-Dawley rats fed either MF or HF had increased TMAO with consumption of RS. Data indicate amount of fermentation is not the reason for increased TMAO. Possible differences in gut bacteria that produce trimethylamine from choline may be cause of TMAO production in the rats. Funding Sources LSU AgCenter and Lerner Research Institute (Dr Stan Hazen) of Cleveland Clinic for analysis of serum TMAO, and starches were gifted from Ingredion Incorporated.