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Background: High sugar and fat intakes are known to increase intrahepatocellular lipids (IHCLs) and to cause insulin resistance. High protein intake may facilitate weight loss and improve glucose homeostasis in insulin-resistant patients, but its effects on IHCLs remain unknown. Objective: The aim was to assess the effect of high protein intake on high-fat diet--induced IHCL accumulation and insulin sensitivity in healthy young men. Design: Ten volunteers were studied in a crossover design after 4 d of either a hypercaloric high-fat (HF) diet; a hypercaloric high-fat, high-protein (HFHP) diet; or a control, isocaloric (control) diet. IHCLs were measured by [sup.1]H-magnetic resonance spectroscopy, fasting metabolism was measured by indirect calorimetry, insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp, and plasma concentrations were measured by enzyme-linked immunosorbent assay and gas chromatography--mass spectrometry; expression of key lipogenic genes was assessed in subcutaneous adipose tissue biopsy specimens. Results: The HF diet increased IHCLs by 90 [+ or -] 26% and plasma tissue-type plasminogen activator inhibitor-1 (tPAI-1) by 54 [+ or -] 11% (P < 0.02 for both) and inhibited plasma free fatty acids by 26 [+ or -] 11% and [beta]-hydroxybutyrate by 61 [+ or -] 27% (P < 0.05 for both). The HFHP diet blunted the increase in IHCLs and normalized plasma [beta]-hydroxybutyrate and tPAI-I concentrations. Insulin sensitivity was not altered, whereas the expression of sterol regulatory element-binding protein-1c and key lipogenic genes increased with the HF and HFHP diets (P < 0.02). Bile acid concentrations remained unchanged after the HF diet but increased by 50 [+ or -] 24% after the HFHP diet (P = 0.14). Conclusions: Protein intake significantly blunts the effects of an HF diet on IHCLs and tPAI-1 through effects presumably exerted at the level of the liver. Protein-induced increases in bile acid concentrations may be involved. This trial was registered at www.clinicaltrials.gov as NCT00523562.

Background: Plant sterol (PS)-enriched foods have been shown to reduce plasma LDL-cholesterol concentrations. In most studies, however, PSs were incorporated into food products of high fat content. Objective: We examined the effect of daily consumption of PS-supplemented low-fat fermented milk (FM) on the plasma lipid profile and on systemic oxidative stress in hypercholesterolemic subjects. Design: Hypercholesterolemic subjects (LDL-cholesterol concentrations [greater than or equal to] 130 and [less than or equal to] 190 mg/dL; n = 194) consumed 2 low-fat portions of FM in the same meal daily for 6 wk. Subjects were randomly assigned to 2 groups: low-fat FM enriched with 0.8 g PS ester per portion or control FM. Plasma concentrations of lipids, oxidized LDL, [beta]-carotene, [beta]-sitosterol, campesterol, and high-sensitivity C-reactive protein were measured during the trial. Results: Plasma LDL-cholesterol concentrations were reduced by 9.5% and 7.8% after 3 and 6 wk, respectively, in the 1.6-g/d PS group compared with the control group, whereas plasma triacylglycerol and HDL-cholesterol concentrations were not significantly affected. In addition, there were no significant changes in serum/3-carotene on normalization to LDL cholesterol during the study period in both groups, whereas plasma concentrations of oxidized LDL were reduced significantly in the PS group compared with the control group (- 1.73 compared with 1.40 U/L, respectively; P < 0.05). Plasma sitosterol concentrations were increased by 35% (P < 0.001 compared with control); however, campesterol concentrations did not change during the study period. Conclusion: Daily consumption of 1.6 g PS in low-fat FM efficiently lowers LDL cholesterol in subjects with moderate hypercholesterolemia without deleterious effects on biomarkers of oxidative stress. KEY WORDS Plant sterol, hypercholesterolemia, oxidative stress, oxidized LDL, [beta]-carotene

The aim of the present study was to investigate how guar gum viscosity acts on starch digestion and glucose absorption in humans. Six healthy subjects received a mixed diet composed of 60.4% carbohydrate in the form of maize glucose or pregelatinized starch, to which was added 5.6% low- or high-viscosity guar gums. Meals were ingested or instilled in the duodenum and postprandial insulin and glucose responses were monitored for 3 h. Infusion of meals containing glucose showed that the delay in the diffusion rate to the duodenal mucosa due to bolus viscosity was not significant. Infusion of meals containing starch showed that a decrease in the digestion rate of starch in the upper small intestine accounted for part of the effect of viscosity on glycemic response, whereas the main effect of guar gum was apparently to slow gastric emptying.

The effect of ingestion of the same amount (30g) of a resistant starch (lintner) and cellulose on energy expenditure (EE), colonic fermentation (breath-hydrogen test), and blood glucose, insulin, and free fatty acid (FFA) concentrations were compared in seven healthy volunteers in a first experiment. In a second experiment the same indexes were measured in six healthy volunteers after the ingestion of diets composed of 50 g glucose alone or mixed with 30 g lintner, or cellulose, or pectin. In the first experiment no differences between lintner and cellulose were observed on the measured indexes. The notable difference was the increased apparent colonic fermentation with lintner after 6 h. In experiment 2, although insulin response was significantly lower in the pectin-added diet, the results obtained with the four different diets were not significantly different. The metabolic characteristics of lintner were closer to cellulose than to pectin. In conclusion, the acute effect of the ingestion of a resistant starch (lintner) on the measured metabolic indexes is similar to that of a known insoluble fiber--cellulose.

The fate of dietary leucine and phenylalanine was studied in five healthy, young adult men, by using a dual, stable isotope-tracer infusion approach to estimate amino acid fluxes, splanchnic (Sp) uptake, and delivery of absorbed amino acid to the peripheral circulation. Subject received two, 4-h tracer infusions of [[1-[sup.13]C]leucine and [sup.15]N]phenylalanine infused through a feeding tube placed in the duodenum, and [5,5,5-[sup.2][H.sub.3]]leucine, [ring-[sup.2][H.sub.5]phenylalanine, and [[6,6[sup.2][H.sub.2]]glucose infused simultaneously by vein. In one experiment subjects received an amino acid mixture (83 mg amino acid . [kg.sup.-1] . [h.sup.-1]) via the feeding tube and in the other experiment amino acids were supplied with carbohydrate (CHO) (167 mg . [kg.sup.-1] . [h.sup.-1]). Sp uptake of dietary leucine decreased with added dietary CHO (29% of ingested leucine for amino acids alone vs 20% with CHO; P < 0.05) but was not different for phenylalanine (P > 0.05). Addition of CHO decreased both release of leucine via protein breakdown and leucine oxidation and increased body leucine balance (P < 0.05). Am J Clin Nutr 1993;57:161-9