Postprandial lipaemia induces an acute decrease of insulin sensitivity in healthy men independently of plasma NEFA levels

Associations of dietary pattern, insulin resistance and risk of developing metabolic syndrome among Chinese population

Evidence regarding the role of dietary patterns in metabolic syndrome (MetS) is limited. The mechanistic links between dietary patterns, insulin resistance, and MetS are not fully understood. This study aimed to evaluate the associations between dietary patterns and the risk of MetS in a Chinese population using a longitudinal design. Data from the China Health and Nutrition Survey, a nationally representative survey, were analyzed. MetS cases were identified based on biomarker data collected in 2009. Factor analysis was employed to identify dietary patterns, while logistic regression models were utilized to examine the association between dietary patterns and MetS. Mediation models were applied to assess multiple mediation effects. Two dietary patterns were revealed by factor analysis. Participants in the higher quartiles of the traditional Chinese dietary pattern had lower odds of MetS than those in the lowest quartile (Q1) (OR = 0.58, 95%CI: 0.48, 0.69 for Q4; OR = 0.75, 95%CI: 0.63, 0.89 for Q3). Conversely, participants in the higher quartiles of the modern Chinese dietary pattern had higher odds of MetS compared to those in the lowest quartile (Q1) (OR = 1.40, 95%CI: 1.17, 1.68 for Q4; OR = 1.27, 95%CI: 1.06, 1.52 for Q3). Significant associations between dietary patterns and MetS were mediated by insulin resistance. Therefore, dietary patterns in Chinese adults are associated with MetS, and these associations appear to be mediated through insulin resistance. These findings underscore the critical role of dietary patterns in the development of MetS and establish a foundation for culturally tailored dietary interventions aimed at reducing rates the prevalence of MetS among Chinese adults.

Effects of the timing of acute mulberry leaf extract intake on postprandial glucose metabolism in healthy adults: a randomised, placebo-controlled, double-blind study

BACKGROUND/OBJECTIVES

Glucose tolerance is controlled by the internal clock and is worse in the evening. From a chrononutrition perspective, diabetes prevention requires evaluating the antidiabetic effects of the timing of functional ingredients and nutrient intake. The purpose of this study was to investigate the timing effects of acute mulberry leaf extract (MLE) intake on postprandial glucose levels in young adults.

SUBJECTS/METHODS

Twelve young adults underwent four trials. Blood samples were collected in a fasting state and at 30, 60, 120, and 180 min after eating a mixed meal. The study had a randomised, placebo-controlled, double-blind trial design involving: (1) morning placebo trial (08:00 h; MP trial), (2) evening placebo trial (18:00 h; EP trial), (3) morning MLE trial (08:00 h; MM trial), and (4) evening MLE trial (18:00 h; EM trial).

RESULTS

The incremental area under the blood glucose curve (iAUC) in the EM trials was significantly lower than that in the EP trials (P = 0.010). The postprandial glucose concentrations 120 min after the meal were significantly lower in the EM trials than those in the EP trials (P = 0.006). The postprandial insulin concentrations at 120 min were significantly lower in the MM trials than those in the MP trials (P = 0.034). Moreover, the postprandial insulin concentrations 180 min after the meal were significantly lower in the EM trials than those in the EP trials (P = 0.034).

CONCLUSIONS

MLE intake in the evening, but not in the morning, was effective in improving glucose tolerance.

TRIAL REGISTRATION

Clinical trial reference: UMIN 000045301; website of trial registry: https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000051340 .

Oral fat tolerance testing identifies abnormal pancreatic β-cell function and insulin resistance in individuals with normal glucose tolerance

AIMS/INTRODUCTION

Insulin sensitivity and β-cell function are affected by lipid metabolism disorders, even before the onset of type 2 diabetes. People are in the postprandial state most of the time. Therefore, identifying postprandial hyperlipemia is important. This study aimed to assess patients with abnormalities in lipid metabolism, but with normal glucose tolerance, using oral fat tolerance testing (OFTT) to identify defects in insulin sensitivity and β-cell function.

MATERIALS AND METHODS

We included 248 volunteers with normal glucose tolerance who underwent OFTT. They were divided into three groups in accordance with their fasting and 4-h postprandial triglyceride (TG) concentrations. Their lipid concentrations during OFTT were compared. The disposition index (DI) was applied to estimate β-cell function, and the Matsuda insulin sensitivity index (ISI_M ) was used to assess insulin sensitivity. We used multiple linear regression analysis to estimate the relationships of fasting and postprandial TG concentrations with β-cell function and insulin sensitivity .

RESULTS

The changes in TG concentrations during OFTT were more marked than those in low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol or total cholesterol concentrations. As lipid metabolism deteriorated, the ISI_M and the DI gradually decreased. Multiple linear regression analysis showed that fasting and 4-h postprandial TG concentrations affected LnISI_M and LnDI.

CONCLUSIONS

In individuals with normal glucose tolerance, β-cell function and insulin sensitivity gradually decrease with a deterioration in the lipid profile. Not only fasting TG, but also postprandial TG concentrations are independent risk factors for impaired β-cell function and insulin resistance.

Identification of the Chinese Population That Can Benefit Most From Postprandial Lipid Testing: Validation of the Use of Oral Fat Tolerance Testing in Clinical Practice

BACKGROUND

Dyslipidemia has become increasingly prevalent in recent decades. Blood lipid concentrations are significantly influenced by diet; however, postprandial triglyceride concentration (PTG) is not often measured. PTG can reflect the risks of diabetes and cardiovascular disease, but not all individuals would benefit from PTG testing.

OBJECTIVE

The aim of the present study was to determine the PTG response in a Chinese cohort and identify who would benefit from diagnostic PTG measurement.

METHODS

A total of 400 Chinese adults were enrolled and underwent oral fat tolerance test (OFTT), which was well tolerated. The participants were assigned to groups according to their fasting triglyceride concentration to evaluate the usefulness of PTG testing. A PTG concentration > 2.5 mmol/L was defined as high (HPTG).

RESULTS

Of the 400 participants, 78.9% showed an undesirable PTG response. Those with FTG ≥1.0 mmol/L had a delayed PTG peak and higher peak values. Seventy-five percent of those with 1.0 mmol/L ≤FTG <1.7 mmol/L had HPTG, of whom 18.6% had impaired glucose tolerance.

CONCLUSIONS

The present data confirm the previously reported predictive value of PTG testing. Moreover, the findings indicate that Chinese people with FTGs of 1.0 -1.7 mmol/L may benefit most from the identification of postprandial hyperlipidemia through OFTT because more than half of them have occult HPTG, which may require treatment. Thus, the detection of HPTG using an OFTT represents a useful means of identifying dyslipidemia and abnormal glucose metabolism early.

CLINICAL TRIAL REGISTRATION

[http://www.chictr.org.cn/index.aspx], identifier ChiCTR1800019514.

High prevalence of nonalcoholic steatohepatitis and abnormal liver stiffness in a young and obese Mexican population

OBJECTIVE

To identify nonalcoholic steatohepatitis (NASH) and liver stiffness in Mexican subjects with different body mass index (BMI).

METHODS

A cross-sectional study was conducted in 505 adults. Risk for NASH was defined as the presence of one or more of the following biochemical and metabolic parameters (BMPs): fasting glucose ≥100 mg/dl, triglycerides (TG) ≥150 mg/dl, homeostatic model assessment of insulin resistance (HOMA-IR) ≥2.5, aspartate aminotransferase (AST) >54 IU/L and alanine aminotransferase (ALT) >42 IU/L. Body mass index measurement and nutritional assessment were performed by standard procedures. Liver fibrosis stage was determined by liver stiffness measurement using transitional elastography (TE) or by liver biopsy (LB).

RESULTS

Risk for NASH was 57% (290/505). Most BMPs values incremented by BMI category. Among 171 at-risk patients, 106 subjects were evaluated by TE and 65 subjects by LB. Abnormal liver stiffness (≥6.0 kPa) was prevalent in 54% (57/106) of the cases, whereas by LB, 91% (59/65) of patients with obesity had NASH and liver fibrosis. Furthermore, liver fibrosis was prevalent in 46% (6/13) in normal weight individuals, whereas 4.6% (3/65) of patients with a BMI ≥ 35 kg/m2 showed no histopathological abnormalities. Overall, 67.8% (116/171) of the patients had abnormal liver stiffness or NASH. The normal weight patients with liver damage consumed relatively a higher fat-rich diet compared to the other groups whereas the remaining subgroups shared a similar dietary pattern.

CONCLUSION

Young patients with overweight and obesity showed a high prevalence of altered BMPs related to abnormal liver stiffness assessed by TE and NASH by LB. Early diagnostic strategies are required to detect the risk for NASH and avoid further liver damage in populations with a rising prevalence of obesity by defining the risk factors involved in the onset and progression of NASH.

Effects of immediate-release niacin and dietary fatty acids on acute insulin and lipid status in individuals with metabolic syndrome

BACKGROUND

The nature of dietary fats profoundly affects postprandial hypertriglyceridemia and glucose homeostasis. Niacin is a potent lipid-lowering agent. However, limited data exist on postprandial triglycerides and glycemic control following co-administration of high-fat meals with a single dose of niacin in subjects with metabolic syndrome (MetS). The aim of the study was to explore whether a fat challenge containing predominantly saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) or MUFAs plus omega-3 long-chain polyunsaturated (LCPUFAs) fatty acids together with a single dose of immediate-release niacin have a relevant role in postprandial insulin and lipid status in subjects with MetS.

RESULTS

In a randomized crossover within-subject design, 16 men with MetS were given a single dose of immediate-release niacin (2 g) and ∼15 cal kg^-1 body weight meals containing either SFAs, MUFAs, MUFAs plus omega-3 LCPUFAs or no fat. At baseline and hourly over 6 h, plasma glucose, insulin, C-peptide, triglycerides, free fatty acids (FFAs), total cholesterol, and both high- and low-density lipoprotein cholesterol were assessed. Co-administered with niacin, high-fat meals significantly increased the postprandial concentrations of glucose, insulin, C-peptide, triglycerides, FFAs and postprandial indices of β-cell function. However, postprandial indices of insulin sensitivity were significantly decreased. These effects were significantly attenuated with MUFAs or MUFAs plus omega-3 LCPUFAs when compared with SFAs.

CONCLUSION

In the setting of niacin co-administration and compared to dietary SFAs, MUFAs limit the postprandial insulin, triglyceride and FFA excursions, and improve postprandial glucose homeostasis in MetS. © 2017 Society of Chemical Industry.

Impact of nonfasting triglycerides/high-density lipoprotein cholesterol ratio on secondary prevention in patients treated with statins

BACKGROUND

Some studies have demonstrated that low-density lipoprotein cholesterol (LDL-C) lowering therapy is one of the most important strategies to prevent coronary artery disease. Also, serum triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C) are recognized as independent risk factors of cardiovascular diseases. The aim of this study was to investigate whether the nonfasting TG/HDL-C ratio could affect the incidence of cardiovascular events after percutaneous coronary intervention (PCI) even in patients treated with statins.

METHODS AND RESULTS

One thousand one hundred seventy consecutive patients were enrolled, all of whom underwent successful PCI for acute coronary syndrome or stable angina and continued statin treatments after PCI. They were equally divided into three groups on the basis of a nonfasting TG/HDL-C ratio 3 months after PCI. Among these groups, the incidence of major adverse cardiac events (MACE) was measured during a maximum of 5 years after PCI. MACE was defined as cardiac death, nonfatal myocardial infarction, revascularization due to new stenosis or restenosis. Kaplan-Meier analysis demonstrated that patients with higher TG/HDL-C ratio had a significantly higher incidence of MACE than other groups (p<0.001). In addition, Cox proportional hazards regression analysis indicated that the nonfasting TG/HDL-C ratio was significantly correlated with the incidence of MACE.

CONCLUSION

The nonfasting TG/HDL-C ratio was a valuable predictor of cardiovascular events after PCI in patients treated with statins.

The impact of triglycerides on glucose tolerance: Lipotoxicity revisited

Elevated plasma triglycerides (TGs) are early key features of conditions associated with a dysregulation in glucose metabolism and may predict the development of type 2 diabetes (T2D) over time. Although the acute ingestion of lipid, either mixed with or shortly before the meal, is neutral or slightly beneficial on glucose tolerance, a short-term increase in plasma TGs induced by either an i.v. lipid infusion or a high-fat diet produces a deterioration of glucose control. Accordingly, chronic lowering of plasma TGs by fibrates improves glucose homeostasis and may also prevent T2D. The chronic effects of the elevation of dietary lipid intake are less clear, particularly in humans, being the quality of fat probably more important than total fat intake. Although on the bases of the available experimental and clinical evidence it cannot be easily disentangled, with respect to elevated non-esterified fatty acids (NEFA) the relative contribution of elevated TGs to glucose homeostasis disregulation seems to be greater and also more plausible. In conclusion, although the association between elevated plasma TGs and impaired glucose tolerance is commonly considered not causative or merely a consequence of NEFA-mediated lipotoxicity, the available data suggest that TGs per se may directly contribute to disorders of glucose metabolism.

Association between dietary fat intake and insulin resistance in Chinese child twins

Dietary fat intake is correlated with increased insulin resistance (IR). However, it is unknown whether gene-diet interaction modulates the association. This study estimated heritability of IR measures and the related genetic correlations with fat intake, and tested whether dietary fat intake modifies the genetic influence on type 2 diabetes (T2D)-related traits in Chinese child twins. We included 622 twins aged 7-15 years (n 311 pairs, 162 monozygotic (MZ), 149 dizygotic (DZ)) from south-eastern China. Dietary factors were measured using FFQ. Structural equation models were fit using Mx statistical package. The intra-class correlation coefficients for all traits related to T2D were higher for MZ twins than for DZ twins. Dietary fat and fasting serum insulin (additive genetic correlation (r A) 0·20; 95 % CI 0·08, 0·43), glucose (r A 0·12; 95 % CI 0·01, 0·40), homoeostasis model of assessment-insulin resistance (Homa-IR) (r A 0·22; 95 % CI 0·10, 0·50) and the quantitative insulin sensitivity check index (Quicki) (r A -0·22; 95 % CI -0·40, 0·04) showed strong genetic correlations. Heritabilities of dietary fat intake, fasting glucose and insulin were estimated to be 52, 70 and 70 %, respectively. More than 70 % of the phenotypic correlations between dietary fat and insulin, glucose, Homa-IR and the Quicki index appeared to be mediated by shared genetic influence. Dietary fat significantly modified additive genetic effects on these quantitative traits associated with T2D. Analysis of Chinese twins yielded high estimates of heritability of dietary fat intake and IR. Genetic factors appear to contribute to a high proportion of the variance for both insulin sensitivity and IR. Dietary fat intake modifies the genetic influence on blood levels of insulin and glucose, Homa-IR and the Quicki index.

Antisense-Mediated Lowering of Plasma Apolipoprotein C-III by Volanesorsen Improves Dyslipidemia and Insulin Sensitivity in Type 2 Diabetes

OBJECTIVE

To determine the effects of volanesorsen (ISIS 304801), a second-generation 2'-O-methoxyethyl chimeric antisense inhibitor of apolipoprotein (apo)C-III, on triglyceride (TG) levels and insulin resistance in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A randomized, double-blind, placebo-controlled trial was performed in 15 adult patients with type 2 diabetes (HbA1c >7.5% [58 mmol/mol]) and hypertriglyceridemia (TG >200 and <500 mg/dL). Patients were randomized 2:1 to receive volanesorsen 300 mg or placebo for a total of 15 subcutaneous weekly doses. Glucose handling and insulin sensitivity were measured before and after treatment using a two-step hyperinsulinemic-euglycemic clamp procedure.

RESULTS

Treatment with volanesorsen significantly reduced plasma apoC-III (-88%, P = 0.02) and TG (-69%, P = 0.02) levels and raised HDL cholesterol (HDL-C) (42%, P = 0.03) compared with placebo. These changes were accompanied by a 57% improvement in whole-body insulin sensitivity (P < 0.001). Importantly, we found a strong relationship between enhanced insulin sensitivity and both plasma apoC-III (r = -0.61, P = 0.03) and TG (r = -0.68, P = 0.01) suppression. Improved insulin sensitivity was sufficient to significantly lower glycated albumin (-1.7%, P = 0.034) and fructosamine (-38.7 μmol/L, P = 0.045) at the end of dosing and HbA1c (-0.44% [-4.9 mmol/mol], P = 0.025) 3 months postdosing.

CONCLUSIONS

Volanesorsen reduced plasma apoC-III and TG while raising HDL-C levels. Importantly, glucose disposal, insulin sensitivity, and integrative markers of diabetes also improved in these patients after short-term treatment.

Postprandial Hypertriglyceridemia Predicts Development of Insulin Resistance Glucose Intolerance and Type 2 Diabetes

Insulin resistance (IR) and type 2 diabetes mellitus (T2DM) have been found to be associated with postprandial hypertriglyceridemia (PPHTg). However, whether PPHTg can cause IR and diabetes is not clear. We therefore investigated the role of PPHTg in development of T2DM in rat model of T2DM. 96 male Wistar rats were randomized into four groups (24 rats each). Control Group A, high sucrose diet (HSD) Group B, HSD+Pioglitazone (10mg/kg/day) Group C and HSD+Atorvastatin (20mg/kg/day) Group D. Fat and glucose tolerance tests were done at regular intervals in all groups besides insulin and body weight measurement. At 26 weeks, low dose streptozotocin (15mg/kg,i.p.) was given to half of the rats. All rats were followed up till 48 weeks. PPHTg developed as early as week 2 in Group B and stabilized by week 14. Group B displayed highest PPHTg compared to other groups. Atorvastatin treatment (Group D) abolished PPHTg which became comparable to controls, pioglitazone treatment partially blunted PPHTg resulting in intermediate PPHTg. Group B with highest PPHTg showed highest subsequent IR, glucose intolerance (GI) and highest incidence of prediabetes at week 26 and diabetes at week 34 and 46 compared to other groups. Group D rats displayed lower IR, GI, low incidence of prediabetes and diabetes at these time points compared to Groups B and C. ROC analysis showed that triglyceride area under the curve of each time point significantly predicts the risk of diabetes. Present study provides the evidence that PPHTg predicts the development of IR, GI and T2DM in rat model of diet induced T2DM.

Postprandial lipemia induces pancreatic α cell dysfunction characteristic of type 2 diabetes: studies in healthy subjects, mouse pancreatic islets, and cultured pancreatic α cells

BACKGROUND

Type 2 diabetes is associated with pancreatic α cell dysfunction, characterized by elevated fasting plasma glucagon concentrations and inadequate postprandial glucose- and insulin-induced suppression of glucagon secretion. The cause and the underlying mechanisms of α cell dysfunction are unknown.

OBJECTIVE

Because Western dietary habits cause postprandial lipemia for a major part of a day and, moreover, increase the risk of developing type 2 diabetes, we tested the hypothesis that postprandial lipemia with its characteristic elevation of triglyceride-rich lipoproteins (TGRLs) might cause pancreatic α cell dysfunction.

DESIGN

In a crossover study with 7 healthy volunteers, 2 experiments using 2 fat-enriched meals were performed on each volunteer; meal 1 was designed to increase plasma concentrations of both TGRLs and nonesterified fatty acids and meal 2 to increase TGRLs only. Intravenous glucose boli were injected at 0800 after an overnight fast and postprandially at 1300, 3 h after ingestion of a fat-enriched meal. Glucagon concentrations were measured throughout the days of the experiments. In addition to the study in humans, in vitro experiments were performed with mouse pancreatic islets and cultured pancreatic alpha TC 1 clone 9 (αTC1c9) cells, which were incubated with highly purified TGRLs.

RESULTS

In humans, postprandial lipemia increased plasma glucagon concentrations and led to an inadequate glucose- and insulin-induced suppression of glucagon. There was no difference between the 2 meal types. In mouse pancreatic islets and cultured pancreatic αTC1c9 cells, purified postprandial TGRLs induced abnormalities in glucagon kinetics comparable with those observed in humans. The TGRL-induced α cell dysfunction was due to reduced γ-aminobutyric acid A receptor activation in pancreatic α cells.

CONCLUSION

We concluded that postprandial lipemia induces pancreatic α cell dysfunction characteristic of type 2 diabetes and, therefore, propose that pancreatic α cell dysfunction could be viewed, at least partly, as a postprandial phenomenon.

The effects of sex, metabolic syndrome and exercise on postprandial lipemia

OBJECTIVE

Exercise has been suggested to have cardioprotective benefits due to a lowering of postprandial triglycerides (PPTG). We hypothesized that a morning exercise bout would significantly lower PPTG measured over a full day, in response to moderate fat meals (35% energy) in men more so than women, and in metabolic syndrome (MetS) relative to normal weight (NW) individuals.

MATERIALS/METHODS

Participants completed two randomized study days; one control and one exercise day (60 min of morning exercise, 60% VO(2peak)). Meals were consumed at breakfast, lunch and dinner with the energy expended during exercise replaced on the active day. The areas (AUC) and incremental areas (IAUC) under the curve were calculated for total triglycerides, total cholesterol and other metabolites.

RESULTS

Exercise did not significantly change the PPTG AUC & IAUC overall, or within, or between, each sex or group (NW and MetS). Exercise induced a 30% decrease in total cholesterol IAUC (p=0.003) in NW subjects. Overall, women had a lower IAUC for PPTG compared to men (p=0.037), with the greatest difference between MetS women and MetS men, due to a sustained drop in TG after lunch in the women. This suggests that PP, rather than fasting, lipid analyses may be particularly important when evaluating sex differences in metabolic risk.

CONCLUSIONS

With energy replacement, moderate morning exercise did not result in a significant decrease in PPTG excursions. Exercise did elicit a significant decrease in PP cholesterol levels in NW subjects, suggesting a potential mechanism for the cardioprotective effects of exercise.

Within-person variation in the postprandial lipemic response of healthy adults

BACKGROUND

The response to dietary fat plays a key role in metabolic health. Although this can vary widely between individuals, variation within an individual and the associated contribution of phenotypic and genotypic factors to this variation are less defined.

OBJECTIVES

The objectives were to quantify within-person variation in triacylglycerol response by means of a novel variation score (S(v)) and to explore the phenotypic and genotypic factors associated with this score.

DESIGN

Two consecutive 5-h oral-lipid-tolerance tests (OLTTs) were conducted in 51 healthy adults aged 18-60 y with a BMI (in kg/m²) of 18.5 to 49.8. Detailed body composition, physical function, biochemistry, and genotype data were gathered.

RESULTS

The postprandial triacylglycerol response profile did not differ (P = 0.64) across OLTTs for the group; nor did average concentrations of functional markers apolipoprotein C2 (P = 0.73) and apolipoprotein C3 (P = 0.74). S(v) was low in most (82%) of the adults and was significantly (P < 0.05) associated with age, fasting triacylglycerol, triacylglycerol AUC, and fasting nonessential fatty acids. Significant associations were also observed between S(v) and single nucleotide polymorphisms in 7 genes (APOA1, IL1α, IL1β, TLR4, TCF7L2, CCK1Rec, and STAT3) after correction for phenotypic differences.

CONCLUSIONS

This work showed that the within-person variability in postprandial lipemic response is low in most healthy adults. It also showed that variability in this response is associated with a defined set of phenotypic and genotypic characteristics.

Impact of postprandial glycaemia on health and prevention of disease

Postprandial glucose, together with related hyperinsulinemia and lipidaemia, has been implicated in the development of chronic metabolic diseases like obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). In this review, available evidence is discussed on postprandial glucose in relation to body weight control, the development of oxidative stress, T2DM, and CVD and in maintaining optimal exercise and cognitive performance. There is mechanistic evidence linking postprandial glycaemia or glycaemic variability to the development of these conditions or in the impairment in cognitive and exercise performance. Nevertheless, postprandial glycaemia is interrelated with many other (risk) factors as well as to fasting glucose. In many studies, meal-related glycaemic response is not sufficiently characterized, or the methodology with respect to the description of food or meal composition, or the duration of the measurement of postprandial glycaemia is limited. It is evident that more randomized controlled dietary intervention trials using effective low vs. high glucose response diets are necessary in order to draw more definite conclusions on the role of postprandial glycaemia in relation to health and disease. Also of importance is the evaluation of the potential role of the time course of postprandial glycaemia.

Effects of a meal rich in 1,3-diacylglycerol on postprandial cardiovascular risk factors and the glucose-dependent insulinotropic polypeptide in subjects with high fasting triacylglycerol concentrations

It was previously reported that compared to triacylglycerol (TAG) oil, diacylglycerol (DAG) oil improves postprandial lipid response. However, the effects of DAG oil on postprandial hyperglycemia and incretin response have not yet been determined. In this study, the effects of DAG oil on both postprandial hyperlipidemia and hyperglycemia and the response to the glucose-dependent insulinotropic polypeptide (GIP) were studied. This randomized, double-blind, crossover study analyzed data for 41 individuals with high fasting triacylglycerol concentrations. The subjects ingested test meals (30.3 g of protein, 18.6 g of fat, and 50.1 g of carbohydrate) containing 10 g of DAG oil (DAG meal) or TAG oil (TAG meal) after fasting for at least 12 h. Blood samples were collected prior to and 0.5, 2, 3, 4, and 6 h after ingestion of the test meal. Postprandial TAG concentrations were significantly lower after the DAG meal compared with the TAG meal. Postprandial TAG, insulin, and GIP concentrations were significantly lower after the DAG meal compared with the TAG meal in 26 subjects with fasting serum TAG levels between 1.36 and 2.83 mmol/L. DAG-oil-based meals, as a replacement for TAG oil, may provide cardiovascular benefits in high-risk individuals by limiting lipid and insulin excursions.

Dietary fatty acids linking postprandial metabolic response and chronic diseases

Chronic diseases are by far one of the main causes of mortality in the world. One of the current global recommendations to counteract disability and premature death resulting from chronic diseases is to decrease the consumption of energy-dense high-fat diets, particularly those rich in saturated fatty acids (SFA). The most effective replacement for SFA in terms of risk factor outcomes for chronic disease are polyunsaturated fatty acids (PUFA) and monounsaturated fatty acids (MUFA). The biochemical basis for healthy benefits of such a dietary pattern has been widely evaluated under fasting conditions. However, the increasing amount of data available from multiple studies suggest that the postprandial state, i.e., "the period that comprises and follows a meal", plays an important, yet underappreciated, role in the genesis of numerous pathological conditions. In this review, the potential of MUFA, PUFA, and SFA to postprandially affect selected metabolic abnormalities related to chronic diseases is discussed.

Postprandial hypertriglyceridemia predicts improvement in insulin resistance in obese patients after bariatric surgery

BACKGROUND

Morbidly obese patients have associated diseases, such as diabetes, hypertension, hyperlipidemia, and cardiovascular disease. Bariatric surgery improves these obesity-related co-morbidities, including insulin resistance. Evidence has shown that patients with morbid obesity have postprandial hypertriglyceridemia (HTG) and that this type of HTG is related to the degree of insulin resistance. Also, bariatric surgery produces a dramatic reduction in triglyceride levels. However, it is unknown whether patients with postprandial HTG have a different clinical evolution after bariatric surgery. The setting of our study was a university hospital.

METHODS

We studied 57 morbidly obese patients who had mild or severe postprandial HTG after fat overload (<30 mg/dL or >90 mg/dL increase in triglycerides, respectively). All the patients underwent bariatric surgery. After surgery, the anthropometric and biochemical variables and the Homeostasis Model Assessment of Insulin Resistance were measured for 1 year at 0, 15, 30, 45, 90, 180, and 365 days after surgery.

RESULTS

The patients with more severe postprandial HTG had a greater percentage of change in the Homeostasis Model Assessment of Insulin Resistance at 30, 90, and 180 days after surgery than the patients with less severe postprandial HTG. Multiple regression analysis showed that the postprandial triglyceride levels predict the variation in the Homeostasis Model Assessment of Insulin Resistance index, more so than did traditional variables, such as anthropometric, inflammatory, or hormonal data.

CONCLUSION

The postprandial HTG level might be the best predictor of improved insulin resistance in morbidly obese patients after bariatric surgery.

Postprandial triglyceride-rich lipoproteins induce hepatic insulin resistance in HepG2 cells independently of their receptor-mediated cellular uptake

Non-alcoholic fatty liver disease (NAFLD) is associated with hepatic insulin resistance with the molecular basis of this association being not well understood. Here we studied the effect of hepatic triglyceride accumulation induced by postprandial triglyceride-rich lipoproteins (TGRL) on hepatic insulin sensitivity in HepG2 cells. Incubation of HepG2 cells with purified TGRL particles induced hepatocellular triglyceride accumulation paralleled by diminished insulin-stimulated glycogen content and glycogen synthase activity. Accordingly, insulin-induced inhibition of glycogen synthase phosphorylation as well as insulin-induced GSK-3 and AKT phosphorylation were reduced by TGRL. The effects of TGRL were dependent on the presence of apolipoproteins and more pronounced for denser TGRL. Moreover, TGRL effects required the presence of heparan sulfate-proteoglycans on the cell membrane and lipase activity but were independent of the cellular uptake of TGRL particles by receptors of the LDL receptor family. We suggest postprandial lipemia to be an important factor in the pathogenesis of NAFLD.

Effects of meals rich in either monounsaturated or saturated fat on lipid concentrations and on insulin secretion and action in subjects with high fasting triglyceride concentrations

BACKGROUND

The nature of dietary fats and fasting concentrations of triglycerides affect postprandial hypertriglyceridemia and glucose homeostasis.

OBJECTIVES

The objectives were to examine the effects of meals enriched in monounsaturated fatty acids (MUFAs) or saturated fatty acids (SFAs) on postprandial lipid, glucose, and insulin concentrations and to examine the extent of β cell function and insulin sensitivity in subjects with high fasting triglyceride concentrations.

DESIGN

Fourteen men with fasting hypertriglyceridemia and normal glucose tolerance were given meals (≈10 kcal/kg body weight) containing MUFAs, SFAs, or no fat. Blood samples were collected at baseline and hourly over 8 h for analysis.

RESULTS

The high-fat meals significantly increased postprandial concentrations of triglycerides, nonesterified fatty acids, and insulin and postprandial indexes of β cell function. However, postprandial indexes of insulin sensitivity decreased significantly. These effects were significantly attenuated with MUFAs relative to SFAs.

CONCLUSIONS

MUFAs postprandially buffered β cell hyperactivity and insulin intolerance relative to SFAs in subjects with high fasting triglyceride concentrations. These data suggest that, in contrast with SFAs, MUFA-based strategies may provide cardiovascular benefits to persons at risk by limiting lipid and insulin excursions and may contribute to optimal glycemic control after meal challenges.

Is the effect of prior exercise on postprandial lipaemia the same for a moderate-fat meal as it is for a high-fat meal?

Moderate-intensity exercise can lower the TAG response to a high-fat meal; however, the British diet is moderate in fat, and no study to date has compared the effect of such exercise on responses to high-fat and moderate-fat meals. The present work investigated the effect of brisk walking performed 13 h before intake of both high-fat and moderate-fat meals on postprandial plasma TAG concentrations. Eight inactive, overweight men completed four separate 2 d trials, i.e. rest (Con) or a 90-min treadmill walk (Ex) on the evening of day 1, followed by the ingestion of a moderate-fat (Mod) or high-fat (High) meal on the morning of day 2. High-fat meals contained 66 % of total energy as fat, while the percentage was 35 % for moderate-fat meals; both the meals were, however, isoenergetic. On day 2, venous blood was sampled in the fasted state, 30 and 60 min after ingesting the test meal and then hourly until 6 h post-meal. Exercise reduced plasma TAG concentrations significantly (P < 0·001), with no exercise × meal interaction (P = 0·459). Walking reduced the total TAG response to a high-fat meal by 29 % (relative to High Con); the same bout of exercise performed before ingesting a moderate-fat meal lowered total TAG by 26 % (compared with Mod Con). The ability of a single moderate-intensity aerobic exercise bout to lower postprandial TAG concentrations is just as great, in percentage terms, when the test meal ingested is of a moderate rather than a high fat content.

Effect of postprandial lipemia on plasma concentrations of A-FABP, RBP-4 and visfatin

BACKGROUND AND AIMS

Several studies indicate that changes in the plasma concentrations of adipocyte-fatty acid binding protein (A-FABP), retinol binding protein-4 (RBP-4) and visfatin are associated with chronic states of insulin resistance. Recent studies have shown that postprandial lipemia induces an acute state of insulin resistance. The aim of this study was to investigate the effect of postprandial lipemia on the plasma concentrations of A-FABP, RBP-4 and visfatin.

METHODS AND RESULTS

In a within-subject crossover study, we administered a standardized high-fat meal to 24 healthy subjects (12 males and 12 females). Plasma concentrations of adipocytokines were measured in the morning after an overnight fast and during postprandial lipemia, i.e. 2, 4 and 6 hours after meal ingestion (postprandial experiment). To exclude potential confounding factors affecting the adipocytokine plasma concentrations, a control experiment without meal ingestion was performed over the same time period (postabsorptive control experiment). Comparing plasma concentrations of A-FABP, RBP-4 and visfatin between the postprandial and the postabsorptive control experiments, we found no significant differences. Within either of the two experiments, a decrease of A-FABP was noted reaching, however, statistical significance only in the postprandial experiment, i.e. 2 and 4 hours after meal ingestion.

CONCLUSION

Postprandial lipemia has no significant effect on the plasma concentrations of visfatin, A-FABP or RBP-4 in relation to their postabsorptive plasma profiles. We conclude that prolonged states of insulin resistance are required to affect plasma concentrations of these adipocytokines.

Insulin pump use in adults with type 1 diabetes--practical issues

In recent years continuous subcutaneous insulin infusion pumps have become widely adopted in many parts of the world in the treatment of type 1 diabetes in adults. A comprehensive summary of all aspects of pump therapy is beyond the scope of this article, and in this review we will focus on several practical issues that in our experience are of clinical importance in the care of patients using insulin pumps. These include: benefits and risks of pump therapy, including the use of pumps to limit hypoglycemia; individual patient considerations in choosing between pump therapy and multiple daily injections; common pump-specific etiologies of erratic glucose control, including routine clinical practices that can assist with the detection of these problems; and the use of different pump bolus types for prandial insulin coverage.

Consumption of fructose-sweetened beverages for 10 weeks increases postprandial triacylglycerol and apolipoprotein-B concentrations in overweight and obese women

Fructose consumption in the USA has increased over the past three decades. During this time, obesity, insulin resistance and the metabolic syndrome have also increased in prevalence. While diets high in fructose have been shown to promote insulin resistance and increase TAG concentrations in animals, there are insufficient data available regarding the long-term metabolic effects of fructose consumption in humans. The objective of the present study was to investigate the metabolic effects of 10-week consumption of fructose-sweetened beverages in human subjects under energy-balanced conditions in a controlled research setting. Following a 4-week weight-maintaining complex carbohydrate diet, seven overweight or obese (BMI 26.8-33.3 kg/m2) postmenopausal women were fed an isoenergetic intervention diet, which included a fructose-sweetened beverage with each meal, for 10 weeks. The intervention diet provided 15 % of energy from protein, 30 % from fat and 55 % from carbohydrate (30 % complex carbohydrate, 25 % fructose). Fasting and postprandial glucose, insulin, TAG and apoB concentrations were measured. Fructose consumption increased fasting glucose concentrations and decreased meal-associated glucose and insulin responses (P = 0.0002, P = 0.007 and P = 0.013, respectively). Moreover, after 10 weeks of fructose consumption, 14 h postprandial TAG profiles were significantly increased, with the area under the curve at 10 weeks being 141 % higher than at baseline (P = 0.04). Fructose also increased fasting apoB concentrations by 19 % (P = 0.043 v. baseline). In summary, consumption of fructose-sweetened beverages increased postprandial TAG and fasting apoB concentrations, and the present results suggest that long-term consumption of diets high in fructose could lead to an increased risk of CVD.

Consumption of fructose-sweetened beverages for 10 weeks increases postprandial triacylglycerol and apolipoprotein-B concentrations in overweight and obese women

Fructose consumption in the USA has increased over the past three decades. During this time, obesity, insulin resistance and the metabolic syndrome have also increased in prevalence. While diets high in fructose have been shown to promote insulin resistance and increase TAG concentrations in animals, there are insufficient data available regarding the long-term metabolic effects of fructose consumption in humans. The objective of the present study was to investigate the metabolic effects of 10-week consumption of fructose-sweetened beverages in human subjects under energy-balanced conditions in a controlled research setting. Following a 4-week weight-maintaining complex carbohydrate diet, seven overweight or obese (BMI 26.8-33.3 kg/m2) postmenopausal women were fed an isoenergetic intervention diet, which included a fructose-sweetened beverage with each meal, for 10 weeks. The intervention diet provided 15 % of energy from protein, 30 % from fat and 55 % from carbohydrate (30 % complex carbohydrate, 25 % fructose). Fasting and postprandial glucose, insulin, TAG and apoB concentrations were measured. Fructose consumption increased fasting glucose concentrations and decreased meal-associated glucose and insulin responses (P = 0.0002, P = 0.007 and P = 0.013, respectively). Moreover, after 10 weeks of fructose consumption, 14 h postprandial TAG profiles were significantly increased, with the area under the curve at 10 weeks being 141 % higher than at baseline (P = 0.04). Fructose also increased fasting apoB concentrations by 19 % (P = 0.043 v. baseline). In summary, consumption of fructose-sweetened beverages increased postprandial TAG and fasting apoB concentrations, and the present results suggest that long-term consumption of diets high in fructose could lead to an increased risk of CVD.

Distinctive postprandial modulation of beta cell function and insulin sensitivity by dietary fats: monounsaturated compared with saturated fatty acids

BACKGROUND

Exaggerated and prolonged postprandial triglyceride concentrations are associated with numerous conditions related to insulin resistance, including obesity, type 2 diabetes, and the metabolic syndrome. Although dietary fats profoundly affect postprandial hypertriglyceridemia, limited data exist regarding their effects on postprandial glucose homeostasis.

OBJECTIVE

We sought to determine whether postprandial glucose homeostasis is modulated distinctly by high-fat meals enriched in saturated fatty acids (SFAs) or monounsaturated fatty acids (MUFAs).

DESIGN

Normotriglyceridemic subjects with normal fasting glucose and normal glucose tolerance were studied. Blood samples were collected over the 8 h after ingestion of a glucose and triglyceride tolerance test meal (GTTTM) in which a panel of dietary fats with a gradual change in the ratio of MUFAs to SFAs was included. On 5 separate occasions, basal and postprandial concentrations of glucose, insulin, triglyceride, and free fatty acids (FFAs) were measured.

RESULTS

High-fat meals increased the postprandial concentrations of insulin, triglycerides, and FFAs, and they enhanced postprandial beta cell function while decreasing insulin sensitivity (as assessed with different model-based and empirical indexes: insulinogenic index, insulinogenic index/homeostasis model assessment of insulin resistance, area under the curve for insulin/area under the curve for glucose, homeostasis model assessment for beta cell function, and GTTTM-determined insulin sensitivity, oral glucose insulin sensitivity, and the postprandial Belfiore indexes for glycemia and blood FFAs. These effects were significantly ameliorated, in a direct linear relation, when MUFAs were substituted for SFAs.

CONCLUSIONS

The data presented here suggest that beta cell function and insulin sensitivity progressively improve in the postprandial state as the proportion of MUFAs with respect to SFAs in dietary fats increases.

Postprandial cytokine concentrations and meal composition in obese and lean women

The aim of this study was to compare the acute effect of (i) meals rich in saturated fat, oleic acid, and alpha-linolenic acid and (ii) meals rich in starch and fiber on markers of inflammation and oxidative stress in obese and lean women. In a crossover study, 15 abdominally obese women (age, 54 +/- 9 years; BMI, 37.3 +/- 5.5 kg/m2) and 14 lean women (age, 53 +/- 10 years; BMI, 22.9 +/- 1.9 kg/m2) consumed meals rich in cream (CR), olive oil (OL), canola oil (CAN), potato (POT), and All-Bran (BRAN) in random order. Blood samples were collected before and up to 6 h after the meals and plasma interleukin-6 (IL-6), IL-8, tumor necrosis factor-alpha (TNF-alpha), lipid peroxides (LPOs), free-fatty acids (FFAs), insulin, glucose, and cortisol were measured. Plasma IL-6 decreased significantly 1 h after the meals then increased significantly above baseline at 4h and 6h in obese women and at 6h in lean women. The incremental area under the curve (iAUC) for IL-6 was significantly (P = 0.02) higher in obese compared with lean women and was significantly lower following the high fiber BRAN meal compared with a POT meal (P = 0.003). Waist circumference (R = 0.491, P = 0.007) and cortisol AUC (R = -0.415, P = 0.03) were significant determinants of the magnitude of 6h changes in plasma IL-6 after the meals. These findings suggest that the postprandial response of plasma IL-6 concentrations may be influenced by the type of carbohydrate in the meal, central adiposity, and circulating cortisol concentrations in women.

Mechanism of action of exenatide to reduce postprandial hyperglycemia in type 2 diabetes

We examined the contributions of insulin secretion, glucagon suppression, splanchnic and peripheral glucose metabolism, and delayed gastric emptying to the attenuation of postprandial hyperglycemia during intravenous exenatide administration. Twelve subjects with type 2 diabetes (3 F/9 M, 44 +/- 2 yr, BMI 34 +/- 4 kg/m2, Hb A(1c) 7.5 +/- 1.5%) participated in three meal-tolerance tests performed with double tracer technique (iv [3-3H]glucose and oral [1-14C]glucose): 1) iv saline (CON), 2) iv exenatide (EXE), and 3) iv exenatide plus glucagon (E+G). Acetaminophen was given with the mixed meal (75 g glucose, 25 g fat, 20 g protein) to monitor gastric emptying. Plasma glucose, insulin, glucagon, acetaminophen concentrations and glucose specific activities were measured for 6 h post meal. Post-meal hyperglycemia was markedly reduced (P < 0.01) in EXE (138 +/- 16 mg/dl) and in E+G (165 +/- 12) compared with CON (206 +/- 15). Baseline plasma glucagon ( approximately 90 pg/ml) decreased by approximately 20% to 73 +/- 4 pg/ml in EXE (P < 0.01) and was not different from CON in E+G (81 +/- 2). EGP was suppressed by exenatide [231 +/- 9 to 108 +/- 8 mg/min (54%) vs. 254 +/- 29 to189 +/- 27 mg/min (26%, P < 0.001, EXE vs. CON] and partially reversed by glucagon replacement [247 +/- 15 to 173 +/- 18 mg/min (31%)]. Oral glucose appearance was 39 +/- 4 g in CON vs. 23 +/- 6 g in EXE (P < 0.001) and 15 +/- 5 g in E+G, (P < 0.01 vs. CON). The glucose retained within the splanchnic bed increased from approximately 36g in CON to approximately 52g in EXE and to approximately 60g in E+G (P < 0.001 vs. CON). Acetaminophen((AUC)) was reduced by approximately 80% in EXE vs. CON (P < 0.01). We conclude that exenatide infusion attenuates postprandial hyperglycemia by decreasing EGP (by approximately 50%) and by slowing gastric emptying.

Association of liver disease with postprandial large intestinal triglyceride-rich lipoprotein accumulation and pro/antioxidant imbalance in normolipidemic non-alcoholic steatohepatitis

BACKGROUND

Dietary fat excess and antioxidant deficiency, altered lipid metabolism, and increased lipoperoxidation have been associated with non-alcoholic steatohepatitis (NASH), but the relative importance of each of these factors is unclear.

AIMS

To assess acute intestinal and hepatic very-low-density lipoprotein (VLDL) subfraction metabolism, lipid peroxidation, and pro/antioxidant imbalance after a fat load in NASH.

METHODS

Dietary habits, circulating adipokines, fasting and postprandial lipids, intestinal and hepatic VLDL, oxidized low-density lipoproteins (oxLDL), and total antioxidant status (TAS) were correlated to postprandial liver enzymes and to liver histology in 28 non-obese non-diabetic normolipidemic patients with NASH and 28 healthy controls.

RESULTS

Despite similar fasting profiles, NASH had more pronounced intestinal and hepatic VLDL1 accumulation, LDL lipid peroxidation and TAS fall postprandially. Postprandial intestinal VLDL1 independently predicted oxLDL and TAS responses in NASH. In NASH, hepatic steatosis was independently associated with postprandial intestinal VLDL1 and TAS; necroinflammation with postprandial serum gamma-glutamyltransferase, oxLDL and TAS responses; and fibrosis with adiponectin and postprandial TAS and oxLDL responses.

CONCLUSIONS

Postprandial intestinal VLDL1 accumulation is associated with a pro-oxidant imbalance in normolipidemic non-diabetic NASH, and both correlate with the severity of liver disease. Modulating postprandial lipoprotein metabolism may be beneficial in NASH, even if normolipidemic.

Effects of diacylglycerol on glucose, lipid metabolism, and plasma serotonin levels in lean Japanese

OBJECTIVE

Diacylglycerol (DAG)-rich oil has been suggested to suppress postprandial hyperlipidemia and promote negative caloric balance by increasing energy expenditure (EE), due to small intestine physiochemical dynamics that differ from triacylglycerol (TAG). We studied the effect of DAG on postprandial glucose/insulin metabolism by loading of carbohydrate with oil. Further, to reveal the mechanism for increased EE by DAG, we measured plasma serotonin, which is mostly present in the small intestine and mediates peripheral sympathetic thermogenesis.

METHODS AND PROCEDURES

Randomized crossover study with 2-week wash-out interval between differing fat ingestion. Seven male, lean, Japanese students ingested DAG or TAG oil with 40 g of carbohydrate. Measurements of metabolic parameters were performed before and at 2, 4, and 6 h after fat ingestion. Plasma serotonin levels and cholesterol concentration in each lipoprotein were measured using high-performance liquid chromatography (HPLC).

RESULTS

The substitution of DAG for TAG decreased very-low-density lipoprotein-cholesterol (VLDL-C) by 45.6% at 2 h, and decreased serum insulin by 41.3% at 4 h after ingestion. The incremental area under the curve (IAUC) for VLDL-C was positively correlated with the IAUC for insulin. Concurrently, DAG elevated plasma serotonin levels by 47.3% at 2 h, while TAG did not influence.

DISCUSSION

This study indicates that the substitution of DAG for TAG suppresses the postprandial increase in serum VLDL-C and insulin. This study also demonstrates that DAG ingestion increases plasma serotonin, proposing a possible mechanism for a postprandial increase in EE by DAG.

A discrete Single Delay Model for the Intra-Venous Glucose Tolerance Test

Background

Due to the increasing importance of identifying insulin resistance, a need exists to have a reliable mathematical model representing the glucose/insulin control system. Such a model should be simple enough to allow precise estimation of insulin sensitivity on a single patient, yet exhibit stable dynamics and reproduce accepted physiological behavior.

Results

A new, discrete Single Delay Model (SDM) of the glucose/insulin system is proposed, applicable to Intra-Venous Glucose Tolerance Tests (IVGTTs) as well as to multiple injection and infusion schemes, which is fitted to both glucose and insulin observations simultaneously. The SDM is stable around baseline equilibrium values and has positive bounded solutions at all times. Applying a similar definition as for the Minimal Model (MM) S_I index, insulin sensitivity is directly represented by the free parameter K_xgI of the SDM.

In order to assess the reliability of Insulin Sensitivity determinations, both SDM and MM have been fitted to 40 IVGTTs from healthy volunteers. Precision of all parameter estimates is better with the SDM: 40 out of 40 subjects showed identifiable (CV < 52%) K_xgI from the SDM, 20 out of 40 having identifiable S_I from the MM. K_xgI correlates well with the inverse of the HOMA-IR index, while S_I correlates only when excluding five subjects with extreme S_I values. With the exception of these five subjects, the SDM and MM derived indices correlate very well (r = 0.93).

Conclusion

The SDM is theoretically sound and practically robust, and can routinely be considered for the determination of insulin sensitivity from the IVGTT. Free software for estimating the SDM parameters is available.