Association of the fatty acid profile of serum lipids with glucose and insulin metabolism during 2 fat-modified diets in subjects with impaired glucose tolerance

The Benefits of Including Hummus and Hummus Ingredients into the American Diet to Promote Diet Quality and Health: A Comprehensive Review

Over the last decade, hummus has become an increasingly popular food. Given the ingredients (i.e., primarily chickpeas and tahini), nutrient composition, versatility, and acceptability, hummus can play a unique role when included in the American diet, to promote diet quality and improve health. The purpose of this paper is to provide a comprehensive review of the scientific evidence examining the effects of acute and long-term consumption of hummus and hummus ingredients on diet quality and risk factors related to type 2 diabetes, cardiovascular disease, and obesity. In addition, food pattern/menu modeling is included to illustrate the potential nutritional impact of consuming hummus to meet dietary guidelines. In general, the consumption of hummus and/or its respective ingredients has been shown to improve postprandial glycemic control, fasting lipids, appetite control, and daily food intake compared to other commonly consumed foods. The incorporation of hummus into the American diet can also improve diet quality by replacing foods higher in saturated fats, sodium, or added sugars. Collectively, these findings support the addition of hummus and/or hummus ingredients as an important component of a healthy dietary pattern.

Serum phospholipid monounsaturated fatty acid composition and Δ-9-desaturase activity are associated with early alteration of fasting glycemic status

Because alterations in blood fatty acid (FA) composition by dietary lipids are associated with insulin resistance and related metabolic disorders, we hypothesized that serum phospholipid FA composition would reflect the early alteration of fasting glycemic status, even in people without metabolic syndrome (MetS). To examine this hypothesis, serum phospholipid FA, desaturase activities, fasting glycemic status, and cardiometabolic parameters were measured in study participants (n = 1022; 30-69 years; male, n = 527; female, n = 495; nondiabetics without disease) who were stratified into normal fasting glucose (NFG) and impaired fasting glucose (IFG) groups. Total monounsaturated FA (MUFA), oleic acid (OA; 18:1n-9), dihomo-γ-linolenic acid (DGLA; 20:3n-6), Δ-9-desaturase activity (D9D; 18:1n-9/18:0), and DGLA/linoleic acid (20:3n-6/18:2n-6) in serum phospholipids were significantly higher in IFG subjects than NFG controls. Study subjects were subdivided into 4 groups, based on fasting glucose levels and MetS status. Palmitoleic acid (16:1n-7) was highest in IFG-MetS and lowest in NFG-non-MetS subjects. Oleic acid and D9D were higher in IFG-MetS than in the other 3 groups. Dihomo-γ-linolenic acid and DGLA/linoleic acid were higher in MetS than in non-MetS, regardless of fasting glucose levels. The high-sensitivity C-reactive proteins (hs-CRPs) and 8-epi-prostaglandin-F2α were higher in IFG than in NFG, regardless of MetS status. Oxidized low-density lipoproteins were higher in IFG-MetS than in the other 3 groups. Total MUFAs, OA, and D9D were positively correlated with homeostasis model assessment of insulin resistance, fasting glucose, triglyceride, hs-CRP, and 8-epi-prostaglandin-F2α. Palmitoleic acid was positively correlated with triglyceride and hs-CRP. Lastly, total MUFA, OA, palmitoleic acid, and D9D were associated with early alteration of fasting glycemic status, therefore suggesting that these may be useful markers for predicting the risk of type 2 diabetes and cardiometabolic diseases.

Effect of saturated fatty acid-rich dietary vegetable oils on lipid profile, antioxidant enzymes and glucose tolerance in diabetic rats

OBJECTIVE

To study the effect of saturated fatty acid (SFA)-rich dietary vegetable oils on the lipid profile, endogenous antioxidant enzymes and glucose tolerance in type 2 diabetic rats.

MATERIALS AND METHODS

Type 2 diabetes was induced by administering streptozotocin (90 mg/kg, i.p.) in neonatal rats. Twenty-eight-day-old normal (N) and diabetic (D) male Wistar rats were fed for 45 days with a fat-enriched special diet (10%) prepared with coconut oil (CO) - lauric acid-rich SFA, palm oil (PO) - palmitic acid-rich SFA and groundnut oil (GNO) - control (N and D). Lipid profile, endogenous antioxidant enzymes and oral glucose tolerance tests were monitored.

RESULTS

D rats fed with CO (D + CO) exhibited a significant decrease in the total cholesterol and non-high-density lipoprotein cholesterol. Besides, they also showed a trend toward improving antioxidant enzymes and glucose tolerance as compared to the D + GNO group, whereas D + PO treatment aggravated the dyslipidemic condition while causing a significant decrease in the superoxide dismutase levels when compared to N rats fed with GNO (N + GNO). D + PO treatment also impaired the glucose tolerance when compared to N + GNO and D + GNO.

CONCLUSION

The type of FA in the dietary oil determines its deleterious or beneficial effects. Lauric acid present in CO may protect against diabetes-induced dyslipidemia.

Dietary fats and prevention of type 2 diabetes

Although type 2 diabetes is determined primarily by lifestyle and genes, dietary composition may affect both its development and complications. Dietary fat is of particular interest because fatty acids influence glucose metabolism by altering cell membrane function, enzyme activity, insulin signaling, and gene expression. This paper focuses on the prevention of type 2 diabetes and summarizes the epidemiologic literature on associations between types of dietary fat and diabetes risk. It also summarizes controlled feeding studies on the effects of dietary fats on metabolic mediators, such as insulin resistance. Taken together, the evidence suggests that replacing saturated fats and trans fatty acids with unsaturated (polyunsaturated and/or monounsaturated) fats has beneficial effects on insulin sensitivity and is likely to reduce risk of type 2 diabetes. Among polyunsaturated fats, linoleic acid from the n-6 series improves insulin sensitivity. On the other hand, long-chain n-3 fatty acids do not appear to improve insulin sensitivity or glucose metabolism. In dietary practice, foods rich in vegetable oils, including non-hydrogenated margarines, nuts, and seeds, should replace foods rich in saturated fats from meats and fat-rich dairy products. Consumption of partially hydrogenated fats should be minimized. Additional controlled, long-term studies are needed to improve our knowledge on the optimal proportion of different types of fats to prevent diabetes.

Fatty acids and insulin sensitivity

PURPOSE OF REVIEW

Given the pathophysiological importance of insulin resistance, the potential impact of dietary fatty acids is highly relevant. The effects of different types of dietary fatty acids on insulin sensitivity in humans are discussed, with focus on recent controlled studies.

RECENT FINDINGS

Observational studies assessing fatty acid composition in serum or tissues suggest that insulin resistance is associated with relatively high intakes of saturated fat (e.g. palmitic acid) and low intakes of polyunsaturated fat (e.g. linoleic acid), findings that are supported by recent clinical data. Most controlled studies have hitherto examined the effect of monounsaturated fat on insulin sensitivity, several indicating that it has beneficial effects when substituted for saturated fat. More clinical data comparing n-6 polyunsaturated, monounsaturated and saturated fat are needed to identify the optimal dietary fat composition, especially in patients with insulin resistance/obesity and diabetes. The total fat content of the background diet should also be considered in future studies. Finally, we and others hypothesize that dietary fatty acids may partly mediate their effects on insulin action by regulating the activity of lipogenic enzymes and desaturases.

SUMMARY

Substituting saturated fat with unsaturated fat seems to have beneficial effects on insulin sensitivity, although the clinical significance of modifying fat quality alone is still unclear.

Differential effects of n-3 polyunsaturated fatty acids on metabolic control and vascular reactivity in the type 2 diabetic ob/ob mouse

Diets rich in monounsaturated fatty acids (MUFA) are recommended for individuals with type 2 diabetes mellitus (T2DM). The American Heart Association recommends increasing intakes of n-3 polyunsaturated fatty acids (PUFA) to reduce the risk of vascular disease in high-risk individuals; however, the long-term effects of these bioactive fatty acids on glucose metabolism in insulin resistance are controversial. The present studies were conducted to evaluate the effects of diets rich in both MUFA and alpha linolenic acid (C18:3n-3, ALA), eicosapentaenoic acid (C20:5n-3, EPA), or docosahexaenoic acid (C22:6n-3, DHA), on glycemic control and other parameters related to vascular health in a mouse model of T2DM and insulin resistance. Male ob/ob mice (n = 15 per treatment) were fed 1 of 4 lipid-modified formula diets (LFDs) for 4 weeks: (1) MUFA control, (2) ALA blend, (3) EPA blend, and (4) DHA blend. A portion of a MUFA-rich lipid blend in the control LFD was replaced with 11% to 14% energy as n-3 PUFA. After 4 weeks, plasma glucose response to a standard meal (1.5 g carbohydrate/kg body weight) and insulin challenge (2 U/kg body weight, IP) was assessed, and samples were collected for analysis of glucose, insulin, and lipids. Vascular reactivity of isolated aortic rings was assessed in an identical follow-up study. The results showed that insulin-resistant mice fed an LFD with EPA and/or DHA blends had significantly (P < .05) lower triglycerides and free fatty acids, but insulin sensitivity and fasting plasma glucose were not improved. However, mice fed with the ALA blend had significantly improved insulin sensitivity when compared to those fed with other LFD (P < .05). Animals fed an LFD with n-3 PUFA from marine or plant sources showed significantly improved vascular responses as compared with the MUFA-rich LFD (E(max), P < .05) and ob/ob reference mice consuming chow (E(max) and pEC(50), P < .05). In summary, long-term consumption of LFD with n-3 PUFAs improved blood lipids and vascular function in an animal model of insulin resistance and T2DM; however, only MUFA-rich LFD with ALA also improved both insulin sensitivity and glycemic responses. Further studies of MUFA-rich LFD with ALA with individuals who have T2DM are warranted.

Effects of milk enriched with omega-3 fatty acid, oleic acid and folic acid in patients with metabolic syndrome

BACKGROUND & AIMS

Patients with metabolic syndrome (MS) have increased cardiovascular risk factors. Dietary modifications mainly polyunsatturated fatty acids intake, can improve them. The present study was performed to assess the effects of enriched milk with omega-3 and oleic fatty acids, folic acid and vitamin E, in these patients.

METHODS

We performed a randomized, placebo-controlled and open clinical trial, among 72 patients with MS for 3 months. Thirty-six of them consumed 500 cm(3) per day of semi-skimmed milk (control group), and the others consumed 500 cm(3) per day of enriched milk (test group). Daily supplements in this group were 5.7 g of oleic acid, 0.2g of omega-3 fatty acid, 150 microg of folic acid and 7.5mg of vitamin E. Serum for total and HDL cholesterol, triglycerol, Apo B, glucose, insulin, hs-CRP, homocysteine and fatty acids contents in serum phospholipids, was obtained at the beginning and at the end of the study. LDL cholesterol was calculated by Friedewald formula.

RESULTS

Four patients in the test group, and two in the control group dropped out. In the test group a decrease in serum total cholesterol (-6.2%, P=0.006), LDL cholesterol (-7.5%, P=0.032), triglycerol (-13.3%, P=0.016), Apo B (-5.7%, P=0.036), glucose (-5.3%, P=0.013), and homocysteine (-9.5%, P=0.00) was observed. Any of these parameters changed in the control group.

CONCLUSIONS

Dietary supplementation with 500 cm(3) of enriched milk with omega-3 fatty acid, oleic acid and folic acid, reduces serum tryglicerides, total and LDL cholesterol, Apo B, glucose and homocysteine in patients with MS. This milk is well tolerated and accepted by the patients.

Influence of diet on atherogenic risk in children with renal transplants

Cardiovascular disease is one of the main causes of morbidity and mortality in recipients of renal transplants. Although the risk for cardiovascular disease is in part genetically determined, it may also be influenced by diet. The aim of the present study was to analyze the cross-sectional association of dietary intake of nutrients with biochemical markers of atherogenic risk. The influence of diet on the plasma profile of fatty acids was specifically investigated. Twenty-nine children and adolescents (mean age 14 years, range 6-18 years) with stable renal transplants and on a normal diet recorded their food intake for a period of 3 days. The mean calorie intake was 40.6 kcal/kg per day (protein provided 16% of total calories, carbohydrates 45%, and fat 39%). Plasma levels of total cholesterol and low-density lipoprotein-cholesterol were significantly and positively related to intake of monounsaturated fatty acids ( r=0.66, P =0.007 and r =0.62, P =0.02, respectively) and to plasma levels of elaidic acid, a trans fatty acid ( r=0.43, P =0.02 and r =0.54, P =0.01, respectively). Insulin resistance, estimated from values of plasma glucose ( r=0.70, P =0.03), plasma insulin ( r=0.59, P =0.02), and HOMA index ( r=0.62, P =0.01), was also directly related to the intake of monounsaturated fatty acids. Plasma plasminogen activator inhibitor-1 activity correlated positively with total fat intake ( r=0.59, P =0.04). Plasma levels of homocysteine were negatively related to the intake of carbohydrates ( r=-0.62, P =0.02). We conclude that reasonable dietary recommendations to minimize the atherogenic risk in children with stable renal transplants should include a protein intake adjusted to the requirements for age, a large intake of carbohydrates leading to a low glycemic load, and a fat intake of less than 30% of the total calorie intake. The amount of monounsaturated and trans fatty acids in the diet should be especially limited. A sufficient intake of polyunsaturated fatty acids, with an adequate ratio between omega 6 and omega 3 components, should also be provided.

Nutrition therapy for dyslipidemia

National guidelines indicate patients with elevated low- density lipoprotein cholesterol should consume less than 7% of calories from saturated fat and less than 200 mg of cholesterol. Trans fatty acids should also be limited. Incorporation of functional foods, such as stanol-containing margarine, soy products, and soluble fiber-rich cereals and vegetables can provide further benefit. In addition to weight loss and physical activity, individuals with hypertriglyceridemia benefit from a diet moderate in fat and carbohydrate rather than a low-fat diet. Including monounsaturated or omega-3 fatty acids lowers serum triglycerides. Many of the dietary strategies to optimize serum lipids also contribute to glycemic control in patients with diabetes mellitus.