Social stress alters sleep in FGF21-deficient mice.

Although several previous studies have suggested a relationship between sleep and the stress response, the mechanism underlying this relationship remains largely unknown. Here, we show that fibroblast growth factor 21 (FGF21), a lipid metabolism-related hormone, may play a role in this relationship. In this study, we examined differences in the stress response between FGF21 knockout (KO) mice and wild-type (WT) mice after social defeat stress (SDS). When the amount of non-rapid eye movement (NREM) sleep, rapid eye movement (REM) sleep and wakefulness were averaged over the dark period after SDS, only KO mice showed significant differences in NREM sleep and wakefulness. In the social interaction test, KO mice seemed to be more prone to social avoidance. Our real-time (RT) -PCR results revealed that the mRNA expression of the stress- and sleep-related gene gamma-aminobutyric acid A receptor subunit alpha 2 was significantly lower in WT mice than in KO mice. Moreover, KO mice showed lower plasma levels of ketone bodies, which also affect sleep/wake regulation, than WT mice. These results suggested that FGF21 might influence sleep/wake regulation by inducing production of an anti-stress agent and/or ketone bodies, which may result in resilience to social stress.

Effect of Oral Paprika Xanthophyll Intake on Abdominal Fat in Healthy Overweight Humans: A Randomized, Double-blind, Placebo-controlled Study.

PURPOSE: Xanthophylls that exist in various vegetables and fruits have beneficial actions, such as antioxidant activity and an anti-metabolic syndrome effect, and daily intake of xanthophylls could play an important role in preventing lifestyle-related diseases. We investigated whether intake of xanthophylls from red paprika could decrease the abdominal fat area in the healthy overweight volunteers with a body mass index (BMI) ranging from 25 to < 30 kg/m2. METHODS: In a randomized, double-blind, placebo-controlled, parallel-group study, 100 healthy volunteers were assigned to oral administration of paprika xanthophyll capsules (containing 9.0 mg of paprika xanthophylls) or placebo capsules for 12 weeks. The primary endpoint was the effect of paprika xanthophyll intake on the abdominal visceral fat area (VFA) as determined by computed tomography. The secondary endpoints were as follows: 1) changes of the abdominal subcutaneous fat area (SFA), total fat area (TFA), and BMI; 2) changes of lipid metabolism parameters, glucose metabolism parameters, and other blood parameters. RESULTS: After 12 weeks, VFA was smaller in the paprika xanthophyll group than in the placebo group. In the paprika xanthophyll group, there was a significant decrease of SFA, TFA, and BMI after 12 weeks compared with baseline, and the reduction of SFA, TFA, and BMI was significantly greater in the paprika xanthophyll group than in the placebo group. Moreover, total cholesterol and low-density lipoprotein cholesterol decreased significantly in the paprika xanthophyll group, but not in the placebo group. No adverse effects were caused by intake of paprika xanthophyll capsules. CONCLUSIONS: Intake of paprika xanthophylls for 12 weeks significantly reduced the abdominal fat area and BMI in healthy overweight volunteers without causing any adverse effects. These findings suggest that paprika xanthophyll is a safe food ingredient that improves lipid metabolism and reduces abdominal fat. TRIAL REGISTRATION: UMIN-CTR UMIN000021529.