Effects of high monounsaturated and polyunsaturated fat diets on plasma lipoproteins and lipid peroxidation in type 2 diabetes mellitus

Cardiovascular complications in a diabetes prediction model using machine learning: a systematic review

Prediction model has been the focus of studies since the last century in the diagnosis and prognosis of various diseases. With the advancement in computational technology, machine learning (ML) has become the widely used tool to develop a prediction model. This review is to investigate the current development of prediction model for the risk of cardiovascular disease (CVD) among type 2 diabetes (T2DM) patients using machine learning. A systematic search on Scopus and Web of Science (WoS) was conducted to look for relevant articles based on the research question. The risk of bias (ROB) for all articles were assessed based on the Prediction model Risk of Bias Assessment Tool (PROBAST) statement. Neural network with 76.6% precision, 88.06% sensitivity, and area under the curve (AUC) of 0.91 was found to be the most reliable algorithm in developing prediction model for cardiovascular disease among type 2 diabetes patients. The overall concern of applicability of all included studies is low. While two out of 10 studies were shown to have high ROB, another studies ROB are unknown due to the lack of information. The adherence to reporting standards was conducted based on the Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis (TRIPOD) standard where the overall score is 53.75%. It is highly recommended that future model development should adhere to the PROBAST and TRIPOD assessment to reduce the risk of bias and ensure its applicability in clinical settings. Potential lipid peroxidation marker is also recommended in future cardiovascular disease prediction model to improve overall model applicability.

Metabolic Effects of Monounsaturated Fatty Acid-Enriched Diets Compared With Carbohydrate or Polyunsaturated Fatty Acid-Enriched Diets in Patients With Type 2 Diabetes: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

Dietary interventions in patients with type 2 diabetes (T2D) are important for preventing long-term complications. Although a healthy diet is crucial, there is still uncertainty about the optimal macronutrient composition. We performed a meta-analysis comparing diets high in cis-monounsaturated fatty acids (MUFA) to diets high in carbohydrates (CHO) or in polyunsaturated fatty acids (PUFA) on metabolic risk factors in patients with T2D.

RESEARCH DESIGN AND METHODS

We systematically reviewed PubMed, MEDLINE, and Cochrane databases and prior systematic reviews and meta-analyses to identify interventions assessing HbA1c, fasting plasma glucose and insulin, LDL and HDL cholesterol, triglycerides, body weight, or systolic/diastolic blood pressure. Meta-analyses were conducted using both fixed- and random-effects models to calculate the weighted mean difference (WMD) and 95% CI.

RESULTS

We identified 24 studies totaling 1,460 participants comparing high-MUFA to high-CHO diets and 4 studies totaling 44 participants comparing high-MUFA to high-PUFA diets. When comparing high-MUFA to high-CHO diets, there were significant reductions in fasting plasma glucose (WMD -0.57 mmol/L [95% CI -0.76, -0.39]), triglycerides (-0.31 mmol/L [-0.44, -0.18]), body weight (-1.56 kg [-2.89, -0.23]), and systolic blood pressure (-2.31 mmHg [-4.13, -0.49]) along with significant increases in HDL cholesterol (0.06 mmol/L [0.02, 0.10]). When high-MUFA diets were compared with high-PUFA diets, there was a significant reduction in fasting plasma glucose (-0.87 mmol/L [-1.67, -0.07]). All of the outcomes had low to medium levels of heterogeneity, ranging from 0.0 to 69.5% for diastolic blood pressure (Phet = 0.011).

CONCLUSIONS

Our meta-analysis provides evidence that consuming diets high in MUFA can improve metabolic risk factors among patients with T2D.

Fatty fish in the diet of patients with type 2 diabetes: comparison of the metabolic effects of foods rich in n-3 and n-6 fatty acids

BACKGROUND

Dietary advice, including modification of dietary fat quality, is the basis of treatment of diabetes, but there is some uncertainty about the optimal amount of polyunsaturated fatty acids of the n-6 (omega-6) and n-3 (omega-3) series.

OBJECTIVE

The objective was to compare the effects of diets rich in n-3 or n-6 fatty acids on glucose and lipoprotein metabolism in type 2 diabetes.

DESIGN

In a crossover study during 2 consecutive 3.5-wk periods, the participants were provided diets with identical nutrient compositions containing either a high proportion of n-3 (n-3 diet) or n-6 (n-6 diet) fatty acids through the inclusion of fatty fish or lean fish and fat containing linoleic acid, respectively.

RESULTS

Blood glucose concentrations at fasting and during the day were lower with the n-6 than with the n-3 diet (P = 0.009 and P = 0.029, respectively), and the area under the insulin curve during the day was significantly higher (P = 0.03) with the n-6 diet. Both diets showed similar effects on insulin sensitivity and plasminogen activator inhibitor 1 concentrations. The reductions in VLDLs and serum apolipoprotein B concentrations were more pronounced after the n-3 diet.

CONCLUSIONS

The risk related to the moderately higher blood glucose concentrations with the n-3-enriched diet may be counteracted by positive effects with regard to lipoprotein concentrations. An increase in long-chain n-3 fatty acids from fatty fish, and of n-6 fatty acids from linoleic acid, may be recommended for patients with type 2 diabetes.

Dietary advice for treatment of type 2 diabetes mellitus in adults

BACKGROUND

While initial dietary management immediately after formal diagnosis is an 'accepted' cornerstone of treatment of type 2 diabetes mellitus, a formal and systematic overview of its efficacy and method of delivery is not currently available.

OBJECTIVES

To assess the effects of type and frequency of different types of dietary advice for adults with type 2 diabetes.

SEARCH STRATEGY

We carried out a comprehensive search of The Cochrane Library, MEDLINE, EMBASE, CINAHL, AMED, bibliographies and contacted relevant experts.

SELECTION CRITERIA

All randomised controlled trials, of six months or longer, in which dietary advice was the main intervention.

DATA COLLECTION AND ANALYSIS

The lead investigator performed all data extraction and quality scoring with duplication being carried out by one of the other six investigators independently with discrepancies resolved by discussion and consensus. Authors were contacted for missing data.

MAIN RESULTS

Thirty-six articles reporting a total of eighteen trials following 1467 participants were included. Dietary approaches assessed in this review were low-fat/high-carbohydrate diets, high-fat/low-carbohydrate diets, low-calorie (1000 kcal per day) and very-low-calorie (500 kcal per day) diets and modified fat diets. Two trials compared the American Diabetes Association exchange diet with a standard reduced fat diet and five studies assessed low-fat diets versus moderate fat or low-carbohydrate diets. Two studies assessed the effect of a very-low-calorie diet versus a low-calorie diet. Six studies compared dietary advice with dietary advice plus exercise and three other studies assessed dietary advice versus dietary advice plus behavioural approaches. The studies all measured weight and measures of glycaemic control although not all studies reported these in the articles published. Other outcomes which were measured in these studies included mortality, blood pressure, serum cholesterol (including LDL and HDL cholesterol), serum triglycerides, maximal exercise capacity and compliance. The results suggest that adoption of regular exercise is a good way to promote better glycaemic control in type 2 diabetic patients, however all of these studies were at high risk of bias.

AUTHORS' CONCLUSIONS

There are no high quality data on the efficacy of the dietary treatment of type 2 diabetes, however the data available indicate that the adoption of exercise appears to improve glycated haemoglobin at six and twelve months in people with type 2 diabetes. There is an urgent need for well-designed studies which examine a range of interventions, at various points during follow-up, although there is a promising study currently underway.

Effects of a high polyunsaturated fat diet and vitamin E supplementation on high-density lipoprotein oxidation in humans

Oxidative modification of high-density lipoproteins (HDL) impairs several biologic functions critical to its role in reverse cholesterol transport. We therefore investigated the effect of dietary polyunsaturated fat and vitamin E on the kinetics of HDL oxidation. Ten subjects were fed sequentially: a baseline diet in which the major fat source was olive oil; a high polyunsaturated fat diet in which the major fat source was safflower oil; and the safflower oil diet plus 800 I.U. vitamin E per day. Plasma lipoprotein levels, vitamin E content, fatty acid composition, and oxidation lag time and rate were determined after 3 weeks on each diet. The polyunsaturated fat diet increased the mean HDL(2) lag time from 45.8+/-12.5 to 83.3+/-11.6 min with no change in oxidation rate. Addition of vitamin E further increased the HDL(2) lag time to 115.6+/-4.4 min and decreased the HDL(2) oxidation rate 10-fold. Neither the polyunsaturated diet alone nor the diet with vitamin E supplementation had any effect on HDL(3) oxidation. We conclude that under conditions of controlled dietary fat intake, a high polyunsaturated fat intake does not increase the oxidation susceptibility of HDL subfractions, and that in this setting, vitamin E supplementation reduces the oxidation susceptibility of HDL(2). These data suggest that antioxidants could influence HDL function in vivo.

Increased Ability of LDL from Normolipidemic Type 2 Diabetic Women to Generate Peroxides

Background: We assessed the ability of LDL from 30 type 1 diabetic patients (18 men, 12 women), 65 type 2 diabetic patients (35 men, 30 women), and 35 controls (19 men, 16 women) to generate peroxides. The men and women in the diabetic groups were studied separately and matched for age, body mass index, duration of diabetes, glycohemoglobin, and conventional lipid characteristics according to the presence or absence of hyperlipidemia.

Methods: The ability of LDL to form peroxides was assessed by measuring the thiobarbituric acid-reactive substances corrected for LDL-cholesterol [ratio of malondialdehyde (MDA) to LDL-cholesterol]. LDL particle size was expressed as the ratio of LDL-cholesterol to apolipoprotein B (LDL-cholesterol/apoB).

Results: The MDA/LDL-cholesterol ratio was higher in type 1 and type 2 diabetic patients with hyperlipidemia than in controls. The MDA/LDL-cholesterol ratio was also higher in type 2 normolipidemic women than in controls (P <0.01). The LDL-cholesterol/apoB ratio was lower in type 2 diabetic women than in type 2 diabetic men (P <0.05). The MDA/LDL-cholesterol ratio was negatively correlated with the LDL-cholesterol/apoB ratio (r = −0.78, P <0.001) in hyperlipidemic type 1 (not type 2) diabetic patients. In normolipidemic type 2 diabetic patients, the MDA/LDL-cholesterol ratio was also negatively correlated with the LDL-cholesterol/apoB ratio (r = −0.75, P <0.001) because of the highly significant negative correlation in type 2 diabetic women (r = −0.89, P <0.01).

Conclusions: LDL from well-controlled type 2 diabetic women is smaller and more prone to form peroxides. This could explain why diabetic women are at greater risk of cardiovascular disease.

Polyenylphosphatidylcholine decreases alcohol-induced oxidative stress in the baboon

Diets supplemented with polyunsaturated fatty acids or triglycerides exacerbate alcohol-induced liver injury in rats, whereas, in baboons, polyenylphosphatidylcholine (PPC) protects against alcohol-induced fibrosis and cirrhosis. Because the aggravation in rats was attributed to enhanced lipid peroxidation, the present study was undertaken to assess parameters of oxidative stress in percutaneous liver biopsies of baboons fed alcohol, with or without PPC (2.8 g per 1000 calories). F2-isoprostanes and 4-hydroxynonenal, breakdown products of lipid peroxidation, were determined by gas chromatography/mass spectrometry, and alpha-tocopherol was measured by HPLC with electrochemical detection. Hepatic 4-hydroxynonenal was significantly increased in animals fed alcohol, but this was fully prevented by PPC. F2-isoprostanes were also significantly lower after PPC and ethanol than after ethanol alone, and the alcohol-induced glutathione decrease was attenuated. All of these parameters were normal in the animals withdrawn from alcohol, even with persistence of significant liver disease. Because peroxidation products are fibrogenic, their decrease could contribute to the antifibrogenic property of the phospholipids. In conclusion, PPC significantly attenuates ethanol-induced oxidative stress, which may explain, at least in part, its protective effect against alcoholic liver injury.

Lipoprotein composition in NIDDM: effects of dietary oleic acid on the composition, oxidisability and function of low and high density lipoproteins

Oxidation of low density lipoprotein (LDL) plays an important role in the pathogenesis of atherosclerosis and is related to the fatty acid composition which is altered in diabetes mellitus. This study examines the relationship between the fatty acid composition of LDL and high density lipoprotein (HDL) and lipoprotein oxidation. A group of nine non-insulin-dependent diabetic (NIDDM) patients were compared to seven healthy control subjects before and after a high monounsaturated diet. Lipoproteins were isolated and oxidisability was measured by conjugated diene formation and lipid peroxide analysis. Serum HDL cholesterol was significantly lower in the diabetic patients. LDL cholesteryl ester linoleic acid in the diabetic patients was significantly higher at baseline and decreased after diet (p < 0.05) while oleic acid increased in both diabetic and non-diabetic subjects (p < 0.05). HDL cholesteryl ester oleic acid was lower in the diabetic patients compared with control subjects (p < 0.05) before diet and it increased significantly after diet (p < 0.05). LDL lipid peroxides and conjugated diene formation were related to LDL glycation (r = 0.46, p < 0.05 and r = 0.49, p < 0.05, respectively). Both decreased following diet (lipid peroxides for diabetic patients from 476 +/- 30 to 390 +/- 20 nmol/mg protein p < 0.05 and for control subjects from 350 +/- 36 to 198 +/- 30 nmol/mg protein p < 0.05). HDL conjugated diene formation decreased in both groups after diet but only significantly in the control group (55.4 +/- 7.5 to 53.2 +/- 6.7 nmol/mg protein for diabetic patients and 45.8 +/- 6.4 to 31.6 +/- 4.8 nmol/mg protein p < 0.05 for control subjects). There was a positive correlation between LDL lipid peroxide formation and percentage of cholesteryl ester linoleic acid in LDL from diabetic patients (r = 0.61, p < 0.05) and control subjects (r = 0.91, p < 0.01). Fatty acid composition of LDL was reflected in the composition of HDL. In the presence of HDL lipoprotein peroxidation decreased. This decrease in lipoprotein peroxidation was positively related to the percentage of linoleic acid in LDL (r = 0.71, p < 0.05). This study confirms the close relationship between the fatty acid composition of LDL and HDL and demonstrates the importance of the fatty acid composition of the cholesteryl ester fraction in relation to LDL oxidation in diabetes. Linoleic acid in HDL appears to be a protecting factor against oxidation.

Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases

The main pathway for the hepatic oxidation of ethanol to acetaldehyde proceeds via ADH and is associated with the reduction of NAD to NADH; the latter produces a striking redox change with various associated metabolic disorders. NADH also inhibits xanthine dehydrogenase activity, resulting in a shift of purine oxidation to xanthine oxidase, thereby promoting the generation of oxygen-free radical species. NADH also supports microsomal oxidations, including that of ethanol, in part via transhydrogenation to NADPH. In addition to the classic alcohol dehydrogenase pathway, ethanol can also be reduced by an accessory but inducible microsomal ethanoloxidizing system. This induction is associated with proliferation of the endoplasmic reticulum, both in experimental animals and in humans, and is accompanied by increased oxidation of NADPH with resulting H2O2 generation. There is also a concomitant 4- to 10-fold induction of cytochrome P4502E1 (2E1) both in rats and in humans, with hepatic perivenular preponderance. This 2E1 induction contributes to the well-known lipid peroxidation associated with alcoholic liver injury, as demonstrated by increased rates of superoxide radical production and lipid peroxidation correlating with the amount of 2E1 in liver microsomal preparations and the inhibition of lipid peroxidation in liver microsomes by antibodies against 2E1 in control and ethanol-fed rats. Indeed, 2E1 is rather "leaky" and its operation results in a significant release of free radicals. In addition, induction of this microsomal system results in enhanced acetaldehyde production, which in turn impairs defense systems against oxidative stress. For instance, it decreases GSH by various mechanisms, including binding to cysteine or by provoking its leakage out of the mitochondria and of the cell. Hepatic GSH depletion after chronic alcohol consumption was shown both in experimental animals and in humans. Alcohol-induced increased GSH turnover was demonstrated indirectly by a rise in alpha-amino-n-butyric acid in rats and baboons and in volunteers given alcohol. The ultimate precursor of cysteine (one of the three amino acids of GSH) is methionine. Methionine, however, must be first activated to S-adenosylmethionine by an enzyme which is depressed by alcoholic liver disease. This block can be bypassed by SAMe administration which restores hepatic SAMe levels and attenuates parameters of ethanol-induced liver injury significantly such as the increase in circulating transaminases, mitochondrial lesions, and leakage of mitochondrial enzymes (e.g., glutamic dehydrogenase) into the bloodstream. SAMe also contributes to the methylation of phosphatidylethanolamine to phosphatidylcholine. The methyltransferase involved is strikingly depressed by alcohol consumption, but this can be corrected, and hepatic phosphatidylcholine levels restored, by the administration of a mixture of polyunsaturated phospholipids (polyenylphosphatidylcholine). In addition, PPC provided total protection against alcohol-induced septal fibrosis and cirrhosis in the baboon and it abolished an associated twofold rise in hepatic F2-isoprostanes, a product of lipid peroxidation. A similar effect was observed in rats given CCl4. Thus, PPC prevented CCl4- and alcohol-induced lipid peroxidation in rats and baboons, respectively, while it attenuated the associated liver injury. Similar studies are ongoing in humans.

Oxidation of low-density lipoprotein in NIDDM: its relationship to fatty acid composition

The increased risk of atherosclerotic disease in diabetic subjects may be due to enhanced foam cell formation following an increased susceptibility of low density lipoprotein to oxidative modification. This study has compared fatty acid content and lipoprotein oxidisability in 10 non-insulin-dependent diabetic subjects with that in 10 control subjects. Both groups were normocholesterolaemic and the diabetic subjects had higher triglyceride levels (2.2 +/- 0.4 vs 1.2 +/- 0.2 mmol/l, p < 0.05). The fatty acid composition was compared in low density lipoprotein following Folch extraction, separation by thin layer chromatography (for the lipid classes) and analysis by gas liquid chromatography. Low density lipoprotein oxidisability was assessed by conjugated diene and thiobarbituric acid reacting substance formation in the presence of copper ions. The esterified/free cholesterol ratio was higher in the low density lipoprotein from patients compared to control subjects (2.9 +/- 0.1 vs 1.9 +/- 0.3, p < 0.05). Linoleic acid in the cholesteryl ester fraction of the lipoprotein was higher in the patients than in the control subjects (48.2 +/- 2.2% vs 42.4 +/- 3.4%, p < 0.05) as was the total quantity of linoleic acid in the cholesteryl ester fraction (317.8 +/- 68.0 vs 213.2 +/- 28.0 micrograms/mg protein, p < 0.05) and in the low-density lipoprotein as a whole (443.2 +/- 70.0 vs 340.2 +/- 28.2 micrograms/mg protein, p < 0.05). Lipoprotein oxidisability was also increased in the diabetic group with increased formation of thiobarbituric acid reacting substances (35.6 +/- 7.2 vs 22.3 +/- 3.5 nmol/mg protein, p < 0.05, increased total diene formation (502 +/- 60 vs 400 +/- 30 nmol/mg protein, p < 0.05) and increased rate of diene formation (7.2 +/- 0.6 vs 5.1 +/- 0.9 nmol diene.mg protein-1.min-1, p < 0.05). This study indicates that low-density lipoprotein from diabetic subjects is more susceptible to oxidation. This could, in vivo, accelerate foam-cell formation thereby increasing atherosclerotic risk in diabetic subjects.