Dietary fat, insulin sensitivity and the metabolic syndrome
Riccardi G1, Giacco R, Rivellese AA。
作者信息：临床和实验医学系，“联邦政府”大学，医学院，通过S Pansini 5, 80131，那不勒斯，意大利。firstname.lastname@example.org
胰岛素抵抗（Insulin Resistance) 是代谢综合征中各种代谢异常的发病机制。它可以由不同的环境因素引起，包括饮食习惯。高能量/高脂饮食的摄取与超重有强烈的正相关关系，反过来又会 降低胰岛素敏感性，尤其是当体内脂肪过多位于腹部区域时。然而，脂肪摄入与超重之间的联系并不局限于高脂肪食物的高能量含量; 一些人在遗传上倾向于肥胖，从而使 氧化膳食脂肪的能力受损。胰岛素敏感性也受饮食脂肪的质量影响，与体重无关。
Dietary fat, insulin sensitivity and the metabolic syndrome.
Riccardi G1, Giacco R, Rivellese AA.
Department of Clinical and Experimental Medicine, "FedericoII" University, Medical School, Via S Pansini 5, 80131, Napoli, Italy. email@example.com
Insulin resistance is the pathogenetic link underlying the different metabolic abnormalities clustering in the metabolic syndrome. It can be induced by different environmental factors, including dietary habits.
Consumption of energy-dense/high fat diets is strongly and positively associated with overweight that, in turn, deteriorates insulin sensitivity, particularly when the excess of body fat is located in abdominal region.
Nevertheless the link between fat intake and overweight is not limited to the high-energy content of fatty foods; the ability to oxidize dietary fat is impaired in some individuals genetically predisposed to obesity. Insulin sensitivity is also affected by the quality of dietary fat, independently of its effects on body weight. Epidemiological evidence and intervention studies clearly show that in humans saturated fat significantly worsen insulin-resistance, while monounsaturated and polyunsaturated fatty acids improve it through modifications in the composition of cell membranes which reflect at least in part dietary fat composition.
A recent multicenter study (KANWU) has shown that shifting from a diet rich in saturated fatty acids to one rich in monounsaturated fat improves insulin sensitivity in healthy people while a moderate alpha-3 fatty acids supplementation does not affect insulin sensitivity. There are also other features of the metabolic syndrome that are influenced by different types of fat, particularly blood pressure and plasma lipid levels. Most studies show that alpha-3 fatty acids reduce blood pressure in hypertensive but not in normotensive subjects while shifting from saturated to monounsaturated fat intake reduces diastolic blood pressure.
In relation to lipid abnormalities alpha-3 fatty acids reduce plasma triglyceride levels but in parallel, increase LDL cholesterol. Substitution of unsaturated fat for saturated fat not only reduces LDL cholesterol but contributes also to reduce plasma triglycerides in insulin resistant individuals.
In conclusion, there is evidence available in humans indicating that dietary fat quality influences insulin sensitivity and associated metabolic abnormalities. Therefore, prevention of the metabolic syndrome has to be targeted: (1) to correct overweight by reducing the energy density of the habitual diet (i.e., fat intake) and (2) to improve insulin sensitivity and associated metabolic abnormalities through a reduction of dietary saturated fat, partially replaced, when appropriate, by monounsaturated and polyunsaturated fats.