Effects of Freeze-Dried Grape Powder on High-Density Lipoprotein Function in Adults with Metabolic Syndrome: A Randomized Controlled Pilot Study.

High-density lipoprotein (HDL) particles are protective against atherosclerosis. However, HDL function is impaired in metabolic syndrome (MetS) due to low-grade inflammation and dyslipidemia. Foods containing polyphenols, such as grapes, may prevent HDL dysfunction via antioxidant or anti-inflammatory effects. We evaluated the effects of grape powder ingestion on measures of HDL function in adults with MetS. Twenty adults (age: 32-70 years; body mass index: 25.3-45.4 kg/m2) consumed either 60 grams/day of freeze-dried grape powder (GRAPE) or a placebo for 4 weeks, separated by a 3-week washout period, in a randomized, double-blind crossover study. The primary outcome was serum paraoxonase-1 (PON1) arylesterase activity, a measure of HDL antioxidant function. Secondary outcomes included PON1 lactonase activity, plasma lipids, metabolic markers, cholesterol efflux capacity, and other HDL functional markers. After 4 weeks, GRAPE did not alter the serum PON1 activity or other markers of HDL function compared with placebo. Measures of HDL function were positively correlated with each other and inversely with measures of insulin resistance and inflammation. GRAPE intake led to a significant reduction in fasting plasma triglycerides compared with placebo (P = 0.032). No other significant effects of GRAPE were observed for other plasma lipids, anthropometrics, or metabolic measures. Grape powder consumption did not impact HDL function in this cohort of adults with MetS. However, it was shown to improve fasting triglycerides, a risk factor for cardiovascular disease.