Betaine Delayed Muscle Loss by Attenuating Samtor Complex Inhibition for mTORC1 Signaling Via Increasing SAM Level.

SCOPE: The muscle loss during aging results from the blunt of protein synthesis and poses threat to the elderly health. This study aims to investigate whether betaine affects muscle loss by improving protein synthesis. METHODS AND RESULTS: Male C57BL/6J mice are raised from age 12 or 15 months. Mice are fed with AIN-93M diet without or with 2% w/v betaine in distilled water as control group or betaine intervention group (Bet), respectively. Betaine supplementation to mice demonstrates better body composition, grip strength, and motor function. Muscle morphology upregulates expression of myogenic regulate factors, and elevates myosin heavy chain and also improves in Bet group. Betaine promotes muscle protein synthesis via tethering mammalian target of rapamycin complex1 protein kinase (mTORC1) on the lysosomal membrane thereby activating mTORC1 signaling. All these effects aforementioned are time-dependent (p < 0.05). Ultrahigh-performance liquid chromatography results show that betaine increases S-adenosyl-l-methionine (SAM) via methionine cycle. SAM sensor-Samtor-overexpression in C2C12 cells could displace mTORC1 from lysosome thereby inhibiting the mTORC1 signaling. Addition of betaine attenuates this inhibition by increasing SAM level and then disrupting interaction of Samtor complex. CONCLUSIONS: These observations indicate that betaine could promisingly promote protein synthesis to delay age-related muscle loss.

[Anti-atherosclerotic effect of betaine in apolipoprotein E-deficient mice].

OBJECTIVE: To study the effect of betaine on the formation of atherosclerotic plaque in apolipoprotein E (ApoE)-deficient mice and explore its anti-inflammatory mechanism. METHODS: Seven-week-old ApoE-deficient mice (C57BL/6J background) were divided into four groups randomly based on body weight: model group and three betaine groups. Wild-type mice with the same age and genetic background were used as control group. The control group and model group were fed AIN-93G diet. Three betaine groups were fed AIN-93G diet supplemented with 1, 2, 4 g betaine/100 g diet, respectively. Serum tumor necrosis factor-alpha (TNF-alpha), monocyte chemoattractant protein-1, lipid levels and methylation status of TNF-alpha promotor in aorta were determined at 0, 7 and 14 weeks. The percentage of aorta sinus plaque to lumen area was measured at 14-week. RESULTS: The percentage of aorta sinus plaque to lumen area of 1% and 2% betaine groups were (11.43+/-2.65)% and (12.09+/-3.07)%, respectively, which were 41% and 33% smaller than that of the model group (t=3.117, 3.010, respectively, and P<0.01). Serum TNF-alpha level of three betaine groups were (56.33+/-3.86), (63.04+/-4.67) and (65.52+/-3.97) pg/ml, respectively, which were lower than that of the model group (79.40+/-4.68) pg/ml (t=9.270, 6.571 and 5.576, respectively, P<0.001), but there was no significant difference in the methylation status of TNF-alpha promotor among all five groups. CONCLUSION: Betaine could inhibit the development of atherosclerosis via anti-inflammation.

Dietary fatty acids regulate cholesterol induction of liver CYP7alpha1 expression and bile acid production.

In the present study we investigated the effects of dietary fats containing predominantly PUFA, monounsaturated FA (MUFA), or saturated FA (SFA) on lipid profile and liver cholesterol 7alpha-hydroxylase (CYP7alpha1) mRNA expression and bile acid production in C57BL/6J mice. The animals (n = 75) were randomly divided into five groups and fed a basic chow diet (AIN-93G) (BC diet), a chow diet with 1 g/100 g of cholesterol (Chol diet), a chow diet with 1 g/100 g of cholesterol and 14 g/100 g of safflower oil (Chol + PUFA diet), a chow diet with 1 g/100 g of cholesterol and olive oil (Chol + MUFA diet), or a chow diet with 1 g/100 g of cholesterol and myristic acid (Chol + SFA diet) for 6 wk. The results showed that the Chol + SFA diet decreased CYP7alpha1 gene expression and bile acid pool size, resulting in increased blood and liver cholesterol levels. Addition of PUFA and MUFA to a 1% cholesterol diet increased the bile acid pool production or bile acid excretion and simultaneously decreased liver cholesterol accumulation despite decreased CYP7alpha1 mRNA expression. The results indicate that the decreased bile acid pool size induced by the SFA diet is related to inhibition of the liver CYP7alpha1 gene expression, but an increased bile acid pool size and improved cholesterol homeostasis are disassociated from the liver CYP7alpha1 gene expression.