Effect of dietary fatty acid composition on food intake, triglycerides, and hypothalamic peptides

Abstract

While a high-fat diet when compared to low-fat diet is known to produce overeating and health complications, less is known about the effects produced by fat-rich diets differing in their specific composition of fat. This study examined the effects of a high-fat diet containing relatively high levels of saturated compared to unsaturated fatty acids (HiSat) to a high-fat diet with higher levels of unsaturated fatty acids (USat). A HiSat compared to USat meal caused rats to consume more calories in a subsequent chow test meal. The HiSat meal also increased circulating levels of triglycerides (TG) and expression of the orexigenic peptides, galanin (GAL) in the hypothalamic paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH). A similar increase in TG levels and PVN GAL and PFLH OX was also seen in rats given chronic access to the HiSat compared to USat diet, while neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus showed decreased expression. The importance of TG in producing these changes was supported by the finding that the TG-lowering medication gemfibrozil as compared to vehicle, when peripherally administered before consumption of a HiSat meal, significantly decreased the expression of OX, while increasing the expression of NPY and AgRP. These findings substantiate the importance of the fat composition in a diet, indicating that those rich in saturated compared to unsaturated fatty acids may promote overeating by increasing circulating lipids and specific hypothalamic peptides, GAL and OX, known to preferentially stimulate the consumption of a fat-rich diet.

Published by Elsevier B.V.

Figures

Figure 1

A 10-kcal HiSat meal stimulates circulating triglyceride levels and subsequent chow intake more than a 10-kcal USat or chow meal. Data are mean ± S.E.M., *p < 0.05 vs. chow or USat meal.

Figure 2

Figure. 2A. A 10-kcal HiSat compared to USat meal stimulates circulating triglyceride levels and differentially affects peptide gene expression in various hypothalamic areas 60 min later. The HiSat diet stimulates galanin (GAL) mRNA expression in the paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH), while it does not significantly affect neuropeptide Y (NPY) or agouti-related protein (AgRP) in the arcuate nucleus (ARC). Data are mean ± S.E.M., *p < 0.05, **p < 0. 01 vs. USat meal. Figure. 2B. As in male rats, a 10-kcal HiSat compared to USat meal in females stimulates circulating triglyceride levels and differentially affects peptide gene expression in various hypothalamic areas 60 min later. The HiSat diet stimulates galanin (GAL) mRNA expression in the paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH), while it does not significantly affect neuropeptide Y (NPY) or agouti-related protein (AgRP) in the arcuate nucleus (ARC). Data are mean ± S.E.M., *p < 0.05, **p < 0.01 vs. USat meal.

Figure 2

Figure. 2A. A 10-kcal HiSat compared to USat meal stimulates circulating triglyceride levels and differentially affects peptide gene expression in various hypothalamic areas 60 min later. The HiSat diet stimulates galanin (GAL) mRNA expression in the paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH), while it does not significantly affect neuropeptide Y (NPY) or agouti-related protein (AgRP) in the arcuate nucleus (ARC). Data are mean ± S.E.M., *p < 0.05, **p < 0. 01 vs. USat meal. Figure. 2B. As in male rats, a 10-kcal HiSat compared to USat meal in females stimulates circulating triglyceride levels and differentially affects peptide gene expression in various hypothalamic areas 60 min later. The HiSat diet stimulates galanin (GAL) mRNA expression in the paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH), while it does not significantly affect neuropeptide Y (NPY) or agouti-related protein (AgRP) in the arcuate nucleus (ARC). Data are mean ± S.E.M., *p < 0.05, **p < 0.01 vs. USat meal.

Figure 3

A HiSat compared to USat diet presented over a 30-day period increases 24-h caloric intake in the first week of access but not in subsequent weeks. Data are mean ± S.E.M., **p < 0.01 vs. USat diet.

Figure 4

A HiSat compared to USat diet for 30 days increases circulating triglyceride levels and differentially affects peptide gene expression in various hypothalamic areas. The HiSat diet stimulates galanin (GAL) mRNA expression in the paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH), while it reduces neuropeptide Y (NPY) and agouti-related protein (AgRP) mRNA expression in the arcuate nucleus (ARC). Data are mean ± S.E.M., *p < 0.05, **p < 0.01 vs. USat diet.

Figure 5

Lowering triglyceride levels with gemfibrozil (50 mg/kg i.g.) after a 10-kcal HiSat meal affects hypothalamic gene expression. Gemfibrozil compared to vehicle decreases orexin (OX) mRNA in the perifornical lateral hypothalamus (PFLH), while having no effect on galanin (GAL) mRNA in the paraventricular nucleus (PVN), and it increases neuropeptide Y (NPY) and agouti-related protein (AgRP) mRNA expression in the arcuate nucleus (ARC). Data are mean ± S.E.M., **p < 0.05, **p < 0.01 vs. vehicle.