OBJECTIVE:To study the effects of three weight-maintenance diets with different macronutrient composition on carbohydrate, lipid metabolism, insulin and incretin levels in insulin-resistant subjects.

METHODS:A prospective study was performed in eleven (7 W, 4 M) offspring of obese and type 2 diabetes patients. Subjects had a BMI>25 Kg/m2, waist circumference (men/women)>102/88, HBA1c<6.5% and were regarded as insulin-resistant after an OGTT (Matsuda ISIm<4). They were randomly divided into three groups and underwent three dietary periods each of 28 days in a crossover design: a) diet high in saturated fat (SAT), b) diet rich in monounsaturated fat (MUFA; Mediterranean diet) and c) diet rich in carbohydrate (CHO).

RESULTS:Body weight and resting energy expenditure did not changed during the three dietary periods. Fasting serum glucose concentrations fell during MUFA-rich and CHO-rich diets compared with high-SAT diets (5.02 +/- 0.1, 5.03 +/- 0.1, 5.50 +/- 0.2 mmol/L, respectively. Anova<0.05). The MUFA-rich diet improved insulin sensitivity, as indicated by lower homeostasis model analysis-insulin resistance (HOMA-ir), compared with CHO-rich and high-SAT diets (2.32 +/- 0.3, 2.52 +/- 0.4, 2.72 +/- 0.4, respectively, Anova<0.01). After a MUFA-rich and high-SAT breakfasts (443 kcal) the postprandial integrated area under curve (AUC) of glucose and insulin were lowered compared with isocaloric CHO-rich breakfast (7.8 +/- 1.3, 5.84 +/- 1.2, 11.9 +/- 2.7 mmol . 180 min/L, Anova<0.05; and 1004 +/- 147, 1253 +/- 140, 2667 +/- 329 pmol . 180 min/L, Anova<0.01, respectively); while the integrated glucagon-like peptide-1 response increased with MUFA and SAT breakfasts compared with isocaloric CHO-rich meals (4.22 +/- 0.7, 4.34 +/- 1.1, 1.85 +/- 1.1, respectively, Anova<0.05). Fasting and postprandial HDL cholesterol concentrations rose with MUFA-rich diets, and the AUCs of triacylglycerol fell with the CHO-rich diet. Similarly fasting proinsulin (PI) concentration fell, while stimulated ratio PI/I was not changed by MUFA-rich diet.

CONCLUSIONS:Weight maintenance with a MUFA-rich diet improves HOMA-ir and fasting proinsulin levels in insulin-resistant subjects. Ingestion of a virgin olive oil-based breakfast decreased postprandial glucose and insulin concentrations, and increased HDL-C and GLP-1 concentrations as compared with CHO-rich diet.

There is evidence from a population-based study of an inverse relationship between monounsaturated fatty acids (MUFA) energy intake and age-related cognitive decline (ARCD), while high polyunsaturated fatty acids (PUFA) intake was positively associated with cognitive impairment in elderly subjects. We investigated the possible role of MUFA and PUFA on age-related cognitive changes. A population-based, prospective study was carried out on 278, 186, and 95 nondemented elderly subjects (65-84 years) evaluated for global cognitive functions (Mini-Mental State Examination, MMSE) at the first (1992-1993), second (1995-1996), and third survey (2000-2001), respectively, from the randomized cohort of Casamassima, Bari, Italy (n=704), one of the eight centers of the Italian Longitudinal Study on Aging (ILSA). MUFA and PUFA intakes were assessed at baseline with a semi-quantitative food frequency questionnaire. High MUFA and PUFA energy intakes and total energy intake were significantly associated with a better cognitive performance in a 8.5-year follow-up. In this prospective population-based study on older nondemented subjects with a typical Mediterranean diet, high MUFA and PUFA intakes appeared to be protective against ARCD.

OBJECTIVES:This study evaluated the glycemic, insulinemic, and glucagon-like peptide-1 (GLP-1) responses of subjects with type 2 diabetes mellitus to consumption of two diabetes-specific tube-feeding formulas (slowly digested carbohydrate formula [SDC] and diabetes-specific formula [DSF]) and one formula intended for individuals without diabetes (standard formula [STND]).

METHODS:Forty-eight subjects controlled with diet and/or oral antihyperglycemic medications received the SDC, DSF, and STND. Postprandial glucose, insulin, and GLP-1 were measured on three occasions after an overnight fast in a double-blinded, randomized, three-treatment, crossover design.

RESULTS:The positive area under the curve for glucose and insulin with the STND was higher (P<0.001) compared with the SDC and DSF. The adjusted GLP-1 concentration at 60 min was higher for the SDC compared with the DSF and STND (P<0.05).

CONCLUSION:Both lower-carbohydrate diabetes-specific formulas resulted in a lower postprandial blood glucose response compared with the STND. The formula also rich in slowly digested carbohydrate and monounsaturated and omega-3 fatty acids (SDC) produced significantly lower blood glucose and insulin responses and higher levels of GLP-1 in the presence of significantly lower insulin concentrations. These results support the view that the quantity and quality of carbohydrate and fat may play important roles in the management of patients with type 2 diabetes mellitus and could result in improved beta-cell function over the long term.

Recent evidence suggested a protective role of dietary monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) intakes against several chronic diseases and, therefore, an increased human longevity. After a median follow-up of 8.5 years, we investigated the possible role of MUFA, PUFA, and other selected food groups in protecting against all-causes mortality in a population-based, prospective study, conducted in one of the eight centers of the Italian Longitudinal Study on Aging (ILSA), Casamassima, Bari, Italy. Out of 704 elderly subjects (65-84 years), 278 nondemented persons agreed to participate at the first survey (1992-1993). During the follow-up, there were 91 deaths. A semi-quantitative food frequency questionnaire evaluating macronutrient daily intakes were performed at the first survey. Higher MUFA intake was associated with an increase of survival (hazard ratio 0.81, 95% CI 0.66-0.99), a higher unsaturated fatty acids (UFA) to SFA ratio (hazard ratio 1.20, 95% CI 0.99-1.45) increased total mortality only marginally, while no effect about other selected food groups were found. In conclusion, in this prospective study on older nondemented subjects with a typical Mediterranean diet, a higher MUFA intake increased survival, while a higher UFA/SFA ratio increased total mortality, but only marginally.