Lipid, glycemic, and insulin responses to meals rich in saturated, cis-monounsaturated, and polyunsaturated (n-3 and n-6) fatty acids in subjects with type 2 diabetes

The Role of Fenugreek in the Management of Type 2 Diabetes

The number of people diagnosed with type 2 diabetes is on the increase worldwide. Of growing concern, the prevalence of type 2 diabetes in children and youths is increasing rapidly and mirrors the increasing burden of childhood obesity. There are many risk factors associated with the condition; some are due to lifestyle, but many are beyond our control, such as genetics. There is an urgent need to develop better therapeutics for the prevention and management of this complex condition since current medications often cause unwanted side effects, and poorly managed diabetes can result in the onset of related comorbidities. Naturally derived compounds have gained momentum for preventing and managing several complex conditions, including type 2 diabetes. Here, we provide an update on the benefits and limitations of fenugreek and its components as a therapeutic for type 2 diabetes, including its bioavailability and interaction with the microbiome.

Metabolic and Vascular Effect of the Mediterranean Diet

Several studies indicated how dietary patterns that were obtained from nutritional cluster analysis can predict disease risk or mortality. Low-grade chronic inflammation represents a background pathogenetic mechanism linking metabolic risk factors to increased risk of chronic degenerative diseases. A Mediterranean diet (MeDi) style has been reported as associated with a lower degree of inflammation biomarkers and with a protective role on cardiovascular and cerebrovascular events. There is heterogeneity in defining the MedDiet, and it can, owing to its complexity, be considered as an exposome with thousands of nutrients and phytochemicals. Recently, it has been reported a novel positive association between baseline plasma ceramide concentrations and cardiovascular events and how adherence to a Mediterranean Diet-style may influence the potential negative relationship between elevated plasma ceramide concentrations and cardiovascular diseases (CVD). Several randomized controlled trials (RCTs) showed the positive effects of the MeDi diet style on several cardiovascular risk factors, such as body mass index, waist circumference, blood lipids, blood pressure, inflammatory markers and adhesion molecules, and diabetes and how these advantages of the MeDi are maintained in comparison of a low-fat diet. Some studies reported a positive effect of adherence to a Mediterranean Diet and heart failure incidence, whereas some recent studies, such as the PREDIMED study, showed that the incidence of major cardiovascular events was lower among those assigned to MeDi supplemented with extra-virgin olive oil or nuts than among those assigned to a reduced-fat diet. New studies are needed to better understand the molecular mechanisms, whereby the MedDiet may exercise its effects. Here, we present recent advances in understanding the molecular basis of MedDiet effects, mainly focusing on cardiovascular diseases, but also discussing other related diseases. We review MedDiet composition and assessment as well as the latest advances in the genomic, epigenomic (DNA methylation, histone modifications, microRNAs, and other emerging regulators), transcriptomic (selected genes and whole transcriptome), and metabolomic and metagenomic aspects of the MedDiet effects (as a whole and for its most typical food components). We also present a review of the clinical effects of this dietary style underlying the biochemical and molecular effects of the Mediterranean diet. Our purpose is to review the main features of the Mediterranean diet in particular its benefits on human health, underling the anti-inflammatory, anti-oxidant and anti-atherosclerotic effects to which new knowledge about epigenetic and gut-microbiota relationship is recently added.

The Acute Effect of Oleic- or Linoleic Acid-Containing Meals on Appetite and Metabolic Markers; A Pilot Study in Overweight or Obese Individuals

Despite the abundance of plant-derived fats in our diet, their effects on appetite, and metabolic markers, remain unclear. This single-blinded 3-way cross-over pilot study aimed to investigate the ability of the two most abundant dietary plant-derived fats, oleic (OA) and linoleic (LA) acids, to modulate postprandial appetite and levels of circulating appetite and metabolic regulators in overweight/obese individuals. Meals were a high-carbohydrate control, a high-OA or a high-LA meal, and provided 30% of participants' estimated energy requirements. Meals were consumed after an overnight fast, with blood samples collected over 3¼ h. Appetite parameters were assessed via a validated visual analogue scale questionnaire. Hormones and other circulating factors were quantified using multiplex immunoassays. Eight participants (age 45.8 ± 3.6 (years), body mass index 32.0 ± 1.3 (kg/m²)) completed the study. All meals significantly increased fullness and reduced desire to eat. The control and high-OA meals significantly decreased prospective food intake. The high-LA meal increased ghrelin levels (p < 0.05), a hormone which encourages food intake. This was coupled with a significant acute increase in resistin levels, which impairs insulin signaling. Taken together, this study indicates that in overweight/obese individuals, high-LA meals may promote excess energy intake and alter glucose handling, though a larger cohort may be required to strengthen results.

Curcumin alleviates postprandial glycaemic response in healthy subjects: A cross-over, randomized controlled study

In the current study, we aimed to evaluate the effects of a single dose of curcumin and/or fish oil on postprandial glycaemic parameters in healthy individuals. This was a randomised, placebo-controlled and crossover study. Sixteen (n = 16) volunteers were randomised to receive placebo, curcumin (180 mg) tablets, fish oil (1.2 g long chain omega-3 polyunsaturated fatty acids) capsules and curcumin + fish oil prior to a standard meal on 4 test days separated by a week. Blood glucose, serum insulin and triglycerides were measured at intervals between 0–120 min. Difference between the treatments was measured using two-way repeated measures analysis of variance and pair-wise comparisons using Wilcoxon signed-rank or paired t-test as appropriate. Postprandial glucose concentrations were significantly lower in the curcumin (60.6%, P = 0.0007) and curcumin + fishoil group (51%, P = 0.002) groups at 60 min from baseline. Compared with placebo, area under the curve (AUC) for change in blood glucose concentration was reduced by curcumin (36%, P = 0.003) and curcumin + fishoil (30%, 0.004), but not fish oil alone (p = 0.105). Both curcumin (P = 0.01) and curcumin + fishoil (P = 0.03) treatments significantly lowered postprandial insulin (AUC) by 26% in comparison with placebo. Curcumin, but not fish oil, reduces postprandial glycaemic response and insulin demand for glucose control.

Evaluation of fish oil-rich in MUFAs for anti-diabetic and anti-inflammation potential in experimental type 2 diabetic rats

The advantages of monounsaturated fatty acids (MUFAs) on insulin resistance and type 2 diabetes mellitus (T2DM) have been well established. However, the molecular mechanisms of the anti-diabetic action of MUFAs remain unclear. This study examined the anti-hyperglycemic effect and explored the molecular mechanisms involved in the actions of fish oil- rich in MUFAs that had been acquired from hybrid catfish (Pangasius larnaudii×Pangasianodon hypophthalmus) among experimental type 2 diabetic rats. Diabetic rats that were fed with fish oil (500 and 1,000 mg/kg BW) for 12 weeks significantly reduced the fasting plasma glucose levels without increasing the plasma insulin levels. The diminishing levels of plasma lipids and the muscle triglyceride accumulation as well as the plasma leptin levels were identified in T2DM rats, which had been administrated with fish oil. Notably, the plasma adiponectin levels increased among these rats. The fish oil supplementation also improved glucose tolerance, insulin sensitivity and pancreatic histological changes. Moreover, the supplementation of fish oil improved insulin signaling (p-Akt^Ser473 and p-PKC-ζ/λ^Thr410/403), p-AMPK^Thr172 and membrane GLUT4 protein expressions, whereas the protein expressions of pro-inflammatory cytokines (TNF-α and nuclear NF-κB) as well as p-PKC-θ^Thr538 were down regulated in the skeletal muscle. These data indicate that the effects of fish oil-rich in MUFAs in these T2DM rats were partly due to the attenuation of insulin resistance and an improvement in the adipokine imbalance. The mechanisms of the anti-hyperglycemic effect are involved in the improvement of insulin signaling, AMPK activation, GLUT4 translocation and suppression of pro-inflammatory cytokine protein expressions.

Acute Changes in Non-esterified Fatty Acids in Patients with Type 2 Diabetes Receiving Bariatric Surgery

BACKGROUND

The purpose of this study was to compare acute changes of non-esterified fatty acids (NEFA) in relation to beta cell function (BCF) and insulin resistance in obese patients with type 2 diabetes (T2D) who underwent laparoscopic gastric bypass (GBP), laparoscopic sleeve gastrectomy (SG) or very low calorie diet (VLCD).

METHODS

In a non-randomised study, fasting plasma samples were collected from 38 obese patients with T2D, matched for age, body mass index (BMI) and glycaemic control, who underwent GBP (11) or SG (14) or VLCD (13). Samples were collected the day before and 3 days after the intervention, during a 75-g oral glucose tolerance test. Glucose, insulin, c-peptide, glucagon like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) were measured, and individual NEFAs were measured using a triple-quadrupole liquid chromatography-mass spectrometry (LC-MS/MS). BCF by mathematical modelling and insulin resistance were estimated.

RESULTS

Palmitic acid significantly decreased after each intervention. Monounsaturated/polyunsaturated ratio (MUFA/PUFA) and unsaturated/saturated fat ratios increased after each intervention. BCF was improved only after VLCD. Linoleic acid was positively correlated with total insulin secretion (p = 0.03). Glucose sensitivity correlated with palmitic acid (p = 0.01), unsaturated/saturated ratio (p = 0.0008) and MUFA/PUFA (p = 0.009). HOMA-IR correlated with stearic acid (p = 0.03), unsaturated/saturated ratio (p = 0.005) and MUFA/PUFA (p = 0.009). GIP AUC0-120 correlated with stearic acid (p = 0.04), but not GLP-1.

CONCLUSIONS

GBP, SG and VLCD have similar acute effects on decreasing palmitic acid. Several NEFAs correlated with BCF parameters and HOMA-IR.

Addition of a dairy fraction rich in milk fat globule membrane to a high-saturated fat meal reduces the postprandial insulinaemic and inflammatory response in overweight and obese adults

Meals high in SFA, particularly palmitate, are associated with postprandial inflammation and insulin resistance. Milk fat globule membrane (MFGM) has anti-inflammatory properties that may attenuate the negative effects of SFA-rich meals. Our objective was to examine the postprandial metabolic and inflammatory response to a high-fat meal composed of palm oil (PO) compared with PO with an added dairy fraction rich in MFGM (PO+MFGM) in overweight and obese men and women (n 36) in a randomised, double-blinded, cross-over trial. Participants consumed two isoenergetic high-fat meals composed of a smoothie enriched with PO with v. without a cream-derived complex milk lipid fraction ( dairy fraction rich in MFGM) separated by a washout of 1-2 weeks. Serum cytokines, adhesion molecules, cortisol and markers of inflammation were measured at fasting, and at 1, 3 and 6 h postprandially. Glucose, insulin and lipid profiles were analysed in plasma. Consumption of the PO + MFGM v. PO meal resulted in lower total cholesterol (P = 0·021), LDL-cholesterol (P = 0·046), soluble intracellular adhesion molecule (P = 0·005) and insulin (P = 0·005) incremental AUC, and increased IL-10 (P = 0·013). Individuals with high baseline C-reactive protein (CRP) concentrations (≥3 mg/l, n 17) had higher (P = 0·030) insulin at 1 h after the PO meal than individuals with CRP concentrations <3 mg/l (n 19). The addition of MFGM attenuated this difference between CRP groups. The addition of a dairy fraction rich in MFGM attenuated the negative effects of a high-SFA meal by reducing postprandial cholesterol, inflammatory markers and insulin response in overweight and obese individuals, particularly in those with elevated CRP.

Effect of 12 Weeks High Oleic Peanut Consumption on Cardio-Metabolic Risk Factors and Body Composition

Epidemiological evidence indicates an inverse association between nut consumption and obesity, inflammation, hyperlipidaemia and glucose intolerance. We investigated effects of high oleic peanut consumption vs. a nut free diet on adiposity and cardio-metabolic risk markers. In a randomised cross-over design, 61 healthy subjects (65 ± 7 years, body mass index (BMI) 31 ± 4 kg/m²) alternated either high oleic peanuts (15%-20% of energy) or a nut free diet for 12 weeks. Body composition and mass, waist circumference, C-reactive protein (CRP), lipids, glucose and insulin were assessed at baseline and after each phase. Repeated measures analysis of variance (ANOVA) compared the two diets. Consistent with other nut studies, there were no differences in lipids, CRP, glucose and insulin with peanut consumption. In contrast, some reports have demonstrated benefits, likely due to differences in the study cohort. Energy intake was 10% higher (853 kJ, p < 0.05), following peanut consumption vs. control, attributed to a 30% increase in fat intake (p < 0.001), predominantly monounsaturated (increase 22 g, p < 0.05). Despite greater energy intake during the peanut phase, there were no differences in body composition, and less than predicted increase (0.5 kg) in body weight for this additional energy intake, possibly due to incomplete nutrient absorption and energy utilisation.

Postprandial glycaemic response: how is it influenced by characteristics of cereal products?

Cereal products exhibit a wide range of glycaemic indexes (GI), but the interaction of their different nutrients and starch digestibility on blood glucose response is not well known. The objective of this analysis was to evaluate how cereal product characteristics can contribute to GI and insulinaemic index and to the parameters describing glycaemic or insulinaemic responses (incremental AUC, maximum concentration and Δ_peak). Moreover, interactions between the different cereal products characteristics and glycaemic response parameters were assessed for the first time. Relationships between the cereal products characteristics and the glycaemic response were analysed by partial least square regressions, followed by modelling. A database including 190 cereal products tested by the usual GI methodology was used. The model on glycaemic responses showed that slowly digestible starch (SDS), rapidly digestible starch (RDS) and fat and fibres, and several interactions involving them, significantly explain GI by 53 % and Δ_peak of glycaemia by 60 %. Fat and fibres had important contributions to glycaemic response at low and medium SDS contents in cereal products, but this effect disappears at high SDS levels. We showed also for the first time that glycaemic response parameters are dependent on interactions between starch digestibility (interaction between SDS and RDS) and nutritional composition (interaction between fat and fibres) of the cereal products. We also demonstrated the non-linear effect of fat and fibres (significant effect of their quadratic terms). Hence, optimising both the formula and the manufacturing process of cereal products can improve glucose metabolism, which is recognised as strongly influential on human health.

Postprandial Dysmetabolism and Oxidative Stress in Type 2 Diabetes: Pathogenetic Mechanisms and Therapeutic Strategies

Postprandial dysmetabolism in type 2 diabetes (T2D) is known to impact the progression and evolution of this complex disease process. However, the underlying pathogenetic mechanisms still require full elucidation to provide guidance for disease prevention and treatment. This review focuses on the marked redox changes and inflammatory stimuli provoked by the spike in blood glucose and lipids in T2D individuals after meals. All the causes of exacerbated postprandial oxidative stress in T2D were analyzed, also considering the consequence of enhanced inflammation on vascular damage. Based on this in-depth analysis, current strategies of prevention and pharmacologic management of T2D were critically reexamined with particular emphasis on their potential redox-related rationale.

Clustering effects on postprandial insulin secretion and sensitivity in response to meals with different fatty acid compositions

Dietary fatty acids play a role in glucose homeostasis. The aim of this study was to assess the individual relationship between dietary saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids with postprandial β-cell function and insulin sensitivity in subjects with normal and high fasting triglycerides. We assessed postprandial β-cell function (by the insulinogenic index and the ratio of the insulin to glucose areas under the time-concentration curve) and insulin sensitivity (by the oral glucose and the minimal model insulin sensitivity indices) over four nonconsecutive, randomly assigned, high-fat meals containing a panel of SFA (palmitic and stearic acids), MUFA (palmitoleic and oleic acids) and PUFA (linoleic and α-linolenic acids) in 14 subjects with normal and in 14 subjects with high fasting triglycerides. The proportions of each fatty acid in the meals and the values for surrogate measures of postprandial β-cell function and insulin sensitivity were subjected to a Pearson correlation and hierarchical cluster analysis, which revealed two classes of dietary fatty acids for regulating postprandial glucose homeostasis. We successfully discriminated the adverse effects of SFA palmitic acid from the beneficial effects of MUFA oleic acid on postprandial β-cell function (r ≥ 0.84 for SFA palmitic acid and r ≥ -0.71 for MUFA oleic acid; P < 0.05) and insulin sensitivity (r ≥ -0.92 for SFA palmitic acid and r ≥ 0.89 for MUFA oleic acid; P < 0.001) both in subjects with normal and high fasting triglycerides. In conclusion, dietary MUFA oleic acid, in contrast to SFA palmitic acid, favours the tuning towards better postprandial glycaemic control in subjects with normal and high fasting triglycerides.

Type 2 diabetes, PUFAs, and vitamin D: their relation to inflammation

Chronic diseases have become one of the most important public health problems, due to their high costs for treatment and prevention. Until now, researchers have considered that the etiology of Type 2 diabetes mellitus (T2DM) is multifactorial. Recently, the study of the innate immune system has offered an explanation model of the pathogenesis of T2DM. On the other hand, there is evidence about the beneficial effect of polyunsaturated fatty acids (PUFA) n-3 and n-6 in patients with chronic inflammatory diseases including diabetes. Furthermore, high vitamin D plasmatic concentrations have been associated with the best performance of pancreatic β cells and the improving of this disease. In conclusion, certain fatty acids in the adequate proportion as well as 25-hydroxivitamin D can modulate the inflammatory response in diabetic people, modifying the evolution of this disease.

Nutritional management of type 2 diabetes mellitus and obesity and pharmacologic therapies to facilitate weight loss

Diet plays an integral role in the treatment of type 2 diabetes mellitus (T2DM). Unfortunately, many patients with T2DM do not have access to a registered dietitian or certified diabetes educator, and rates of physician counseling about diet remain low. This article provides an overview of the current recommendations for the nutritional management of T2DM, which are endorsed by the American Diabetes Association (ADA). Medical nutrition therapy, which provides a flexible and individualized approach to diet, emphasizes the total number (rather than the type) of carbohydrate consumed. Because fat intake also affects glycemia and cardiovascular risk, a reduction in daily mono- and polyunsaturated fat intake is recommended for most patients with T2DM. Weight loss plays an important adjunct role in treating patients with T2DM, because the majority of individuals with T2DM are overweight or obese. Patient lifestyle modification, which encompasses diet, physical activity, and behavioral therapy, can be used to facilitate weight loss in conjunction with several different dietary approaches. These include low-carbohydrate, low-fat, low-glycemic index, and Mediterranean diets. Studies have demonstrated that modest weight loss (5%-10% of body weight) is associated with significant improvements in patient measures of glycemic control, lipids, blood pressure, and other cardiovascular risk factors. Furthermore, a modest weight loss of as little as 4.5 kg can result in reducing the glycated hemoglobin level by approximately 0.5%. Pharmacologic agents, when combined with these approaches, may further augment weight loss. Familiarity with these principles can help physicians provide dietary counseling to their patients with T2DM and obesity.

Effects of the n-6/n-3 polyunsaturated fatty acids ratio on postprandial metabolism in hypertriacylglycerolemia patients

Background

Atherosclerosis is a postprandial phenomenon. The balanced n-6/n-3 PUFA ratio contributing to the prevention of atherosclerosis has been well shown, but the effect of the ratio on postprandial metabolism has not been fully investigated. The aim of this study was to investigate the effects of the n-6/n-3 PUFAs ratio on postprandial metabolism in hypertriacylglycerolemia patients, comparing them to healthy controls.

Methods

Test meals with 0.97 (high n-3) and 8.80 (low n-3) n-6/n-3 PUFAs ratio were administered in a randomized crossover design to 8 healthy and 8 hypertriacylglycerolemia subjects. Blood samples were collected for 8 hours after meals to measure triglyceride (TG), total cholesterol (TC), HDL, ApoA, ApoB, glucose, insulin, inflammatory makers including tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), endothelial function including nitric oxide (NO) and endothelin-1 (ET-1).

Results

According to repeated–measures ANOVA, the postprandial response of lipid, glucose, insulin, inflammation and endothelial function were not significantly different between meals. The postprandial TG and NO response were significantly different between healthy control (HC) and hypertriglyceridemia group (HTG) after both meals (P < 0.01). After both meals maximal change and iAUC for TG was all higher in HTG group than HC group, the difference was significant after low n-3 meal but not after high n-3 meal. The concentration of glucose, insulin, IL-6, TNFα and ET-1 at each time point was higher and NO was lower in HTG group, but the maximal change and iAUC had no significant difference except for iAUC of insulin, IL-6 and diAUC of NO after low n-3 meal.

Conclusions

The ratio of n-6 and n-3 maybe do not acutely influence the postprandial metabolism, inflammatory response and endothelial function, but the low n-3 meal can strengthen the difference between HTG and HC group.

Responses to high-fat challenges varying in fat type in subjects with different metabolic risk phenotypes: a randomized trial

Background

The ability of subjects to respond to nutritional challenges can reflect the flexibility of their biological system. Nutritional challenge tests could be used as an indicator of health status but more knowledge on metabolic and immune responses of different subjects to nutritional challenges is needed. The aim of this study was to compare the responses to high-fat challenges varying in fat type in subjects with different metabolic risk phenotypes.

Methodology/Principal Findings

In a cross-over design 42 men (age 50–70 y) consumed three high-fat shakes containing saturated fat (SFA), monounsaturated fat (MUFA) or n-3 polyunsaturated (PUFA). Men were selected on BMI and health status (lean, obese or obese diabetic) and phenotyped with MRI for adipose tissue distribution. Before and 2 and 4 h after shake consumption blood was drawn for measurement of expression of metabolic and inflammation-related genes in peripheral blood mononuclear cells (PBMCs), plasma triglycerides (TAG), glucose, insulin, cytokines and ex vivo PBMC immune response capacity. The MUFA and n-3 PUFA challenge, compared to the SFA challenge, induced higher changes in expression of inflammation genes MCP1 and IL1β in PBMCs. Obese and obese diabetic subjects had different PBMC gene expression and metabolic responses to high-fat challenges compared to lean subjects. The MUFA challenge induced the most pronounced TAG response, mainly in obese and obese diabetic subjects.

Conclusion/Significance

The PBMC gene expression response and metabolic response to high-fat challenges were affected by fat type and metabolic risk phenotype. Based on our results we suggest using a MUFA challenge to reveal differences in response capacity of subjects.

Trial Registration

ClinicalTrials.gov NCT00977262

A bioactivity guided study on the antidiabetic activity of Juniperus oxycedrus subsp. oxycedrus L. leaves

ETHNOPHARMACOLOGICAL RELEVANCE

Juniperus (Cupressaceae) species are widely used as folk medicine in spreading countries. Decoction of Juniperus oxycedrus subsp. oxycedrus L. leaves is used internally to lower blood glucose levels in Turkey.

AIM OF THE STUDY

To determine hypoglycaemic and antidiabetic activities of Juniperus oxycedrus subsp. oxycedrus leaves and to identify active compounds through bioactivity guided isolation technique.

MATERIALS AND METHODS

Ethanol and water extracts of Juniperus oxycedrus subsp. oxycedrus (Joso), leaves on oral administration were studied using in vivo models in normal, glucose-hyperglycemic and streptozotocin-induced diabetic rats. Through in vivo bioactivity-guided fractionation processes, a nonpolar fraction was separated from the n-hexane subextract by silica gel column chromatography as the main active fraction. Subfractions of this fraction was found to possess antidiabetic activity and their chemical composition was investigated by GC-FID and GC-MS, simultaneously.

RESULTS

This is the first report on the antidiabetic constituents of Joso leaves. Fatty acids, such as palmitic, linoleic and linolenic acid were found as the major compounds in subfractions.

CONCLUSION

Results indicated that Joso leaf extract and its active constituents might be beneficial for diabetes mellitus.

Dietary monounsaturated fatty acids are protective against metabolic syndrome and cardiovascular disease risk factors

Over 50 years of research has sought to define the role dietary fat plays in cardiovascular disease (CVD) risk. Although optimal dietary fat quantity has been keenly pursued over past decades, attention has recently centered on the value of dietary fat quality. The purpose of the present review is to provide a critical assessment of the current body of evidence surrounding efficacy of dietary monounsaturated fatty acids (MUFA) for reduction of traditional risk factors defining metabolic syndrome (MetS) and CVD. Due to existing and emerging research on health attributes of MUFA rich diets, and to the low prevalence of chronic disease in populations consuming MUFA rich Mediterranean diets, national dietary guidelines are increasingly recommending dietary MUFA, primarily at the expense of saturated fatty acids (SFA). Consumption of dietary MUFA promotes healthy blood lipid profiles, mediates blood pressure, improves insulin sensitivity and regulates glucose levels. Moreover, provocative newer data suggest a role for preferential oxidation and metabolism of dietary MUFA, influencing body composition and ameliorating the risk of obesity. Mounting epidemiological and human clinical trial data continue to demonstrate the cardioprotective activity of the MUFA content of dietary fat. As the debate on the optimal fatty acid composition of the diet continues, the benefit of increasing MUFA intakes, particularly as a substitute for dietary SFA, deserves considerable attention.

The evidence for medical nutrition therapy for type 1 and type 2 diabetes in adults

This article reviews the evidence and nutrition practice recommendations from the American Dietetic Association's nutrition practice guidelines for type 1 and type 2 diabetes in adults. The research literature was reviewed to answer nutrition practice questions and resulted in 29 recommendations. Here, we present the recommendations and provide a comprehensive and systematic review of the evidence associated with their development. Major nutrition therapy factors reviewed are carbohydrate (intake, sucrose, non-nutritive sweeteners, glycemic index, and fiber), protein intake, cardiovascular disease, and weight management. Contributing factors to nutrition therapy reviewed are physical activity and glucose monitoring. Based on individualized nutrition therapy client/patient goals and lifestyle changes the client/patient is willing and able to make, registered dietitians can select appropriate interventions based on key recommendations that include consistency in day-to-day carbohydrate intake, adjusting insulin doses to match carbohydrate intake, substitution of sucrose-containing foods, usual protein intake, cardioprotective nutrition interventions, weight management strategies, regular physical activity, and use of self-monitored blood glucose data. The evidence is strong that medical nutrition therapy provided by registered dietitians is an effective and essential therapy in the management of diabetes.

(n-3) Fatty Acids: Clinical Trials in People with Type 2 Diabetes

Recent human clinical trials of the effects of (n-3) fatty acids on participants with type 2 diabetes (T2D) were reviewed, focusing on 11 clinical trials conducted within the past 4 y, and subsequent to a Cochrane Database meta-analysis of this topic. Doses of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in these studies were mostly in the range of ∼2 g/d provided for 6 wk to 6 mo. Summarizing across these studies, there were no changes in fasting glucose or insulin compared with baseline or placebo. (n-3) Fatty acids generally decreased serum triglycerides but had varying effects on serum cholesterol, LDL cholesterol, and HDL cholesterol. A few studies indicated beneficial effects of (n-3) fatty acids on arterial blood flow. The effects of EPA and/or DHA have not yet been studied in clinical trials in participants at risk for T2D; the prevention or exacerbation of T2D by fish oil or EPA and DHA supplements of amounts >0.5 g/d deserves study. The prevention of adverse vascular effects of T2D by (n-3) fatty acids may be a promising direction for further study.

Benefits versus risks associated with consumption of fish and other seafood

Fish provide nutrition for much of the world's population, and when not contaminated with chemicals, fish is a very good food. A major benefit of fish is that they are high in polyunsaturated fatty acids (PUFAs), low in saturated fat, and they contain other critical nutrients. Much of the benefit of fish consumption derives from their high levels of long chain omega-3 PUFAs, which are produced by aquatic microorganisms and bioconcentrate in the aquatic food supply. The PUFAs are essential, in that humans and other vertebrates are not able to synthesize them and therefore must obtain them from the diet. The PUFAs particularly concentrate in the nervous system, alter immune system function reduce serum triglyceride levels and have been reported to reduce the risk of sudden death after a myocardial infarction. But the problem is that most fish have at least some degree of chemical contamination with methylmercury, (which binds to muscle) and/or with persistent organic pollutants such as dioxins, polychlorinated biphenyls, polybrominated diphenyl ethers, chlorinated pesticides (which concentrate in fish fat). These chemicals have adverse effects on nervous system function, modulate the immune system, and are associated with elevations in risk of cardiovascular disease. Thus the question of benefits and risk from fish consumption is complex but very important.

Potential impact of omega-3 treatment on cardiovascular disease in type 2 diabetes

PURPOSE OF REVIEW

Hypothesis-generating systematic review of the impact of marine-derived omega-3 polyunsaturated fatty acids (PUFAs) on lipid, glycemic and hematological risk factors in type 2 diabetes using pooled data from randomized controlled trials searched up to 20 September 2008.

RECENT FINDINGS

Seven new trials in 2007 and 2008 were identified from 206 abstracts to give a total of 24 trials between 1966 and 2008 involving 1533 participants that could be pooled. The mean omega-3 PUFAs dose and duration of treatment in the new trials was 2.4 g/day and 24 weeks, respectively. Compared with placebo, omega-3 PUFAs supplementation decreased triglycerides by 7% (mean -0.17 mmol/l, 24 trials, 1530 participants), fibrinogen by 10% (mean -0.96 micromol/l, three trials, 159 participants), ADP platelet aggregation to ADP by 22% (mean -10.30%, two trials, 64 participants) and to collagen by 21% (mean -10.55%, two trials, 64 participants), with an LDL-cholesterol increase of 3% (mean 0.08 mmol/l, 21 trials, 1104 participants). None of the following risk factors appeared to be beneficially influenced: HDL-cholesterol, LDL particle size, glycemia, insulinemia, inflammatory biomarkers, blood pressure. However for some of these risk factors (such as inflammatory biomarkers) the number of trial patients was small Higher doses of omega-3 PUFAs (>or=2 g/day) may have greater triglyceride lowering effects.

SUMMARY

This systematic review and meta-analysis confirms the triglyceride lowering effects of omega-3 PUFAs, demonstrates potential dose-response effects and shows improvements in thrombogenesis. Omega-3 PUFAs raise LDL levels without concomitant changes in lipid particle size. Changes seen in conventional risk factors are insufficient to explain the cardiovascular disease risk reductions suggested to occur with omega-3 PUFAs.