The food matrix or the food processing, or both, could have adverse effects on the hypocholesterolemic properties of oat beta-glucan.

Skeletal muscle and adipose tissue lipolysis rates were quantitatively compared in 12 healthy nonobese and 14 insulin-resistant obese subjects for 3.5 h after an oral glucose load using microdialysis measurements of interstitial glycerol concentrations and determinations of local blood flow with 133 Xe clearance in the gastrocnemius muscle and in abdominal subcutaneous adipose tissue. Together with measurements of arterialized venous plasma glycerol, the absolute rates of glycerol mobilization were estimated. In the basal state, skeletal muscle and adipose tissue glycerol levels were 50% higher (P < 0.05-0.01) and adipose tissue blood flow (ATBF) and muscle blood flow (MBF) rates were 30-40% lower (P < 0.02-0.05) in obese versus nonobese subjects. After glucose ingestion, adipose tissue glycerol levels were rapidly and transiently reduced, whereas in muscle, a progressive and less pronounced fall in glycerol levels was evident. MBF remained unchanged in both study groups, whereas ATBF increased more markedly (P < 0.01) in the nonobese versus obese subjects after the oral glucose load. The fasting rates of glycerol release per unit of tissue weight from skeletal muscle were between 20 and 25% of that from adipose tissue in both groups. After glucose ingestion, the rates of glycerol release from skeletal muscle and from adipose tissue were almost identical in nonobese and obese subjects. However, the kinetic patterns differed markedly between tissues; in adipose tissue, the rate of glycerol mobilization was suppressed by 25-30% (P < 0.05) after glucose ingestion, whereas no significant reduction was registered in skeletal muscle. We conclude that significant amounts of glycerol are released from skeletal muscle, which suggests that muscle lipolysis provides an important endogenous energy source in humans. In response to glucose ingestion, the regulation of skeletal muscle glycerol release differs from that in adipose tissue; although the rate of glycerol release from adipose tissue is clearly suppressed, the rate of glycerol mobilization from skeletal muscle remains unaltered. In quantitative terms, the rate of glycerol release per unit of tissue weight in adipose tissue and in skeletal muscle is similar in nonobese and obese subjects in both the postabsorptive state and after glucose ingestion. Diabetes 49:797-802, 2000 S keletal muscle insulin resistance, as reflected by attenuated insulin-mediated glucose disposal, is a key finding of the various clinical components of the metabolic syndrome (e.g., obesity, dyslipidemia, hypertension, and type 2 diabetes) and thus is a predisposing factor in the pathogenesis of premature atherosclerotic cardiovascular disease (1). Among the putative mechanisms underlying insulin resistance, increased attention has been paid to elevated circulating concentrations of free fatty acids (FFAs). We have known for many years that an inverse relationship exists regarding the use of lipids and carbohydrates as metabolic fuels and that inappropriate elevation of FFA levels mediates an i...

The effects of beta-glucan, soy protein, isoflavones, plant sterols and stanols, garlic and tocotrienols on serum lipoproteins have been of great interest the last decade. From a critical review of the literature, it appeared that recent studies found positive as well as no effects of beta-glucan from oats on serum LDL cholesterol concentrations. These conflicting results may suggest that the cholesterol-lowering activity of products rich in oat beta-glucan depends on factors, such as its viscosity in the gastrointestinal tract, the food matrix and/or food processing. The effects of beta-glucan from barley or yeast on the lipoprotein profile are promising, but more human trials are needed to further substantiate these effects. It is still not clear whether the claimed hypocholesterolemic effects of soy can be attributed solely to the isoflavones. Several studies found no changes in serum LDL cholesterol concentrations after consumption of isolated soy isoflavones (without soy protein), indicating that a combination of soy protein and isoflavones may be needed for eliciting a cholesterol-lowering effect of soy. Therefore, the exact (combination of) active ingredients in soy products need to be identified. The daily consumption of 2-3 g of plant sterols or stanols reduces LDL cholesterol concentrations by 9-14%. It has been demonstrated that functional foods enriched with plant sterols and stanols are effective in various population groups, and in combination with cholesterol-lowering diets or drugs. Whether garlic or garlic preparations can be used as a lipid-lowering agent is still uncertain. It is important to characterize the active components in garlic and their bioavailability after ingestion. It is not very likely that tocotrienols from palm oil or rice bran oil have favorable effects on the human serum lipoprotein profile.

Products enriched with plant sterol and stanol esters selectively lower LDL cholesterol. Consumption appears to be safe, and these functional foods thus have great potential for cardiovascular risk management. Although values remain within the normal range, one possible concern is that they lower lipid-standardized concentrations of the plasma carotenoids. Whether this affects health in the longer-term or in selected patient groups is not known. Therefore, especially in view of the increasing number of functional foods that will be on the market in the very near future, there is a clear need to establish an effective post-marketing safety net.