Background: Sphingomyelin (SM) diminishes the fluidity of the surface monolayer of high-density lipoproteins (HDL), affecting their intravascular metabolism and antiatherogenic properties. Since overweight is associated with an altered HDL structure, weight loss may result in changes in HDL subclasses, particularly in their SM content. Therefore, we determined the plasma SM concentrations associated to both total HDL and HDL subclasses after weight loss in obese patients.
Methods: Fifty overweight patients, 40 women and 10 men, aged 38.6±6.4 y, were given an energy-restricted diet according to their sex, age, and height. No physical activity was prescribed. Plasma SM concentrations of HDL subclasses were determined by a gel surface method developed for this study. Cholesterol of HDL subclasses was also determined by enzymatic methods performed on a gel surface.
Results: Mean weight lost was 3.5±0.4 kg after 6 weeks of dietary intervention. As expected, insulin resistance and blood pressure decreased whereas lipid profile improved, except for HDL-cholesterol. SM in plasma and in all HDL subclasses significantly decreased after intervention. The magnitude of HDL-SM reduction was statistically associated with the amelioration of the components of the metabolic syndrome; the reduction of BMI explained the decrement of HDL-SM in a multivariate analysis.
Conclusion: HDL-SM decreased after weight loss by an energy-restricted diet. Further, the association of this decrement with the improvement of blood pressure, lipid profile and the decrease of insulin resistance, was statistically significant; all HDL subclasses were similarly affected. Whether a reduction in HDL-SM contributes to the cardiovascular benefits of weight loss remains to be elucidated.
Keywords: HDL; Metabolic syndrome; Obesity; Sphingomyelin; Weight loss.
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