High-fat diets impede the lowering effect of cyclosporine A on rat brain lipids and interact with the expression of apolipoproteins E and J.

Cyclosporine A (CsA), a common immunosuppressive agent, produces hyperlipidemia and apolipoprotein profile alterations in plasma as well as neurological and psychiatric complications. In rats, 10 mg CsA/kg/d treatments for 3 wk induce alterations of the electroencephalogram, and of the blood and brain lipids. Using this model, we evaluated whether triacylglycerol (TG)- and lecithin (PC)-enriched diets, reported to decrease epileptic episodes (TG) and to improve memory, could modify the effects of CsA treatment on brain lipids and possibly change apolipoprotein (apo) E and apoJ gene expression. To evaluate this hypothesis, three groups of rats were treated for 3 wk with CsA and received a low-fat, PC, or TG diet. Three other groups were fed the above-mentioned diets and were treated with the CsA solvent. As a control, one group was fed only the low-fat diet. The CsA-mediated decreases in brain cholesterol and PC contents, under a low-fat diet, were eliminated by the TG and PC diets. These high-fat diets induced a global increase in hippocampal transcriptional activity, as revealed by elevated polyadenylated RNA levels. The apoE and apoJ mRNA levels in the cortex and hippocampus of rats receiving the solvent were not statistically different between the TG- and PC-enriched diets but showed important variations compared with the low-fat diet solvent-treated group. A differential effect between the two high-fat diets was observed in the hippocampus, resulting in a significant increase of the apoE to apoJ ratio with the PC diet. The balance between apoE and apoJ is presumed to be important in encephalopathic mechanisms, by its involvement through low levels of brain cholesterol and PC, that might be associated with mental disorders. Our results therefore suggest that diet enrichment with polyunsaturated fat might be beneficial during CsA therapy. However, if the high levels in PC used here are more beneficial on CsA peripheral side effects than similar enrichment in TG, this does not seem to be the case in the brain. Thus, lower levels in PC should be tested.

Glycemic and insulinemic meal responses modulate postprandial hepatic and intestinal lipoprotein accumulation in obese, insulin-resistant subjects.

BACKGROUND: Exacerbated postprandial lipemia is a risk factor for cardiovascular disease and is linked to insulin status. Limited data on the effect of dietary carbohydrate on postprandial lipoprotein accumulation are available. OBJECTIVE: We tested the hypothesis that dietary carbohydrates with different glucose availability alter postprandial lipoprotein metabolism differently in obese, insulin-resistant subjects. DESIGN: After an overnight fast, 9 subjects with central obesity and insulin resistance but normal triacylglycerolemia randomly ingested 2 test meals with comparable amounts of fat (28-29 g) and digestible carbohydrate (91-94 g) but with different quantities of slowly available glucose (SAG) in cereal products (17 or 2 g SAG/100 g for biscuits and wheat flakes, respectively). Blood samples were collected before and for 6 h after meal intakes. RESULTS: The postmeal 0-2-h areas under the curve (AUCs) for glycemia and insulinemia were significantly lower (P < 0.05) after the biscuit meal than after the flakes meal. Plasma triacylglycerol concentrations increased significantly after the flakes meal but not after the biscuit meal (1.5-fold higher 0-6-h AUC for the flakes meal). Apolipoprotein B-100 concentrations in the triacylglycerol-rich lipoprotein fraction increased significantly 2 h after the flakes meal but not after the biscuit meal (3-fold higher 0-6-h AUC for the flakes meal). Apolipoprotein B-48 concentrations increased (P < 0.05) 4 h after the flakes meal but not after the biscuit meal (2.3-fold higher 0-6-h AUC for the flakes meal). CONCLUSION: Mixed meals containing slowly digestible carbohydrate that induces low glycemic and insulinemic responses reduce the postprandial accumulation of both hepatically and intestinally derived triacylglycerol-rich lipoproteins in obese subjects with insulin resistance.