Dietary Tryptophan and the Risk of Metabolic Syndrome: Total Effect and Mediation Effect of Sleep Duration

Abstract

Purpose Tryptophan affects energy homeostasis, glucose metabolism, blood pressure, and sleep. However, studies investigating the association between tryptophan and metabolic syndrome (MetSyn) are rare. We aimed to investigate the associations of dietary tryptophan with MetSyn incidence and potential mediation via sleep duration. Methods Data of 7890 participants were obtained from the China Health and Nutrition Survey (1997–2011) (male: 49.9%; mean age=43.43 years;median follow-up=129.76 months; MetSyn incidence: 16.3%). A combination of individual 24-hour recall and household survey was used to assess dietary intake. In total, 6720 and 4474 participants who reported sleep duration and had blood samples taken, respectively, were incorporated into subgroup analyses. MetSyn was defined according to National Cholesterol Education Program Adult Treatment Panel (NCEP ATP) III criteria (2004), and tryptophan consumption and sleep duration were assessed by self-report in each survey. Multivariate Cox regression models were used to assess the associations between tertiles of tryptophan intake and MetSyn. Generalized linear regression models were used to evaluate the effect of tryptophan on sleep duration and plasma biomarkers. Results Dietary tryptophan showed a protective effect on the risk of MetSyn. The hazard ratio (95% CI) of MetSyn was 0.77 (0.65–0.90) for individuals with a high tertile of tryptophan. Sleep duration was significantly higher, and HbA 1c , total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and apolipoprotein B (APO-B) were lower in the high tertile of tryptophan compared to the low tertile ( P <0.05). In addition, mediation effects on the association between tryptophan intake and MetSyn risk were observed for sleep duration (estimated mediation percentage: 26.5%). Conclusion Our study demonstrated a negative association between dietary tryptophan and MetSyn incidence, and the mediation effect of sleep duration on this association, after adjusting for numerous confounders such as nutrients and food patterns. These findings may have important public health implications for the improvement of cardiometabolic health.

The Complex Effects of Light on Metabolism in Humans

“…A study examining the combined effects of tryptophan supplementation during breakfast and daytime light exposure (5000 lux) in 33 healthy men (22 ± 3.1 yrs) showed it promoted melatonin secretion in the evening compared to a tryptophan-lacking breakfast under dim light conditions (<50 lux) [ 175 ]. Similar findings were reported in an epidemiological study on college students [ 176 ], along with a study on the dietary intake of tryptophan on metabolic syndrome [ 177 ].…”

Tryptophan Prevents the Development of Non-Alcoholic Fatty Liver Disease

“…L-tryptophan reduced visceral fat accumulation by 43% and decreased total liver lipids and triglycerides by 38% and 27%, respectively, compared to HCD rats but did not affect cholesterol levels ( Figure 1A–D ), although it was previously reported to reduce total blood cholesterol levels in patients. 42 The livers of rats that received L-tryptophan in combination with HCD had a predominantly red-brown color with alternating single yellow-white areas. The number of large lipid droplets in the liver parenchyma was 25% less compared to obese rats (group II) ( Table 1 ).…”

Extracts of tropical green seaweed Caulerpa lentillifera reduce hepatic lipid accumulation by modulating lipid metabolism molecules in HepG2 cells

“…A supplement of tryptophan in rats promoted fatty acid oxidation and resulted in decreased serum lipid, LDL and VLDL [ 22 ]. Dietary tryptophan in humans reduced serum total cholesterol, LDL and apolipoprotein B, and it increased sleep duration, suggesting a protective role against metabolic syndrome [ 23 ]. This study has some potential limitations.…”