Dietary methionine restriction increases fat oxidation in obese adults with metabolic syndrome.

[paymanz]

http://www.ncbi.nlm.nih.gov/pubmed/21346062

OBJECTIVE:

In preclinical reports, restriction of dietary methionine intake was shown to enhance metabolic flexibility, improve lipid profiles, and reduce fat deposition. The present report is the outcome of a "proof of concept" study to evaluate the efficacy of dietary methionine restriction (MR) in humans with metabolic syndrome.
METHODS:

Twenty-six obese subjects (six male and 20 female) meeting criteria for metabolic syndrome were randomized to a diet restricted to 2 mg methionine/kg body weight per day and were provided capsules containing either placebo (n = 12) or 33 mg methionine/kg body weight per day (n = 14). Energy expenditure, body composition, insulin sensitivity, and biomarkers of metabolic syndrome were measured before and after 16 wk on the respective diets.
RESULTS:

Insulin sensitivity and biomarkers of metabolic syndrome improved comparably in both dietary groups. Rates of energy expenditure were unaffected by the diets, but dietary MR produced a significant increase in fat oxidation (MR, 12.1 ± 6.0% increase; control, 8.1 ± 3.3% decrease) and reduction in intrahepatic lipid content (MR liver/spleen attenuation ratio, 8.1 ± 3.3% increase; control ratio, 2.2 ± 2.1% increase) that was independent of the comparable reduction in weight and adiposity that occurred in both groups.
CONCLUSIONS:

Sixteen weeks of dietary MR in subjects with metabolic syndrome produced a shift in fuel oxidation that was independent of the weight loss, decreased adiposity, and improved insulin sensitivity that was common to both diets.

 

[goodandevil]

Is methionine a methylator?

 

[Giraffe]

I wondered what the diet looked like. Diet restriction to 2 mg methionine/kg bodyweight seems impossible with proteins from real food. This is from the full text:

"The goal was to examine metabolic responses to limiting dietary methionine from approximately 35 mg/kg BW/d (control group) to approximately 2 mg/kg BW/d in the MR group (12). This required elimination of dietary meat, poultry, dairy, and grains, and was achieved using Hominex-2 medical food (Abbott Nutrition, Columbus, OH). This semisynthetic diet is a mixture of l-amino acids lacking methionine, but it provides 0.9 g of methionine sparing cystine/100 g of diet. Based on a target protein intake of 0.8 g/kg BW/d, methionine requirements of 12.6 mg/kg BW/d (13), and the methionine-sparing cystine content of Hominex-2, the diet would limit methionine to target levels of 2 mg/kg BW/d (12)."

Methionine and cystine are sulphur-containing amino acids. I found a couple of studies on cysteine's methionine sparing effect, none on taurine, but this: "To observe a sparing effect of cysteine on methionine requirements, it is essential that subjects receive an adequate supply of total SAAs." - Source: Dietary cysteine reduces the methionine requirement in men

They discuss the results of the study (original post) in more detail in the full text:

"Comprehensive preclinical data show that dietary MR increases EE, reduces plasma lipids, limits fat accretion, enhances insulin sensitivity, and increases longevity in rodents and flies (4–10, 15–19), but its efficacy in obese individuals with metabolic disease is unknown. In the present report, dietary MR produced a significant increase in fat oxidation and decrease in hepatic lipid, but failed to decrease adiposity, increase EE, or enhance insulin sensitivity."