The impact of triglycerides on glucose tolerance: Lipotoxicity revisited

Effects of Weight Loss and Weight Maintenance on Lipoprotein Insulin Resistance Scores in Adults with Overweight and Obesity

Background: An elevated lipoprotein insulin resistance (LP-IR) score corresponds to insulin resistance in adults with overweight and obesity, yet data are lacking regarding the impact of exercise interventions on LP-IR. The purpose of this secondary analysis was to evaluate the effects of a weight loss and weight maintenance intervention on LP-IR score in adults with overweight and obesity. Methods: Thirty sedentary adults with overweight and obesity completed a 10-week OPTIFAST® weight loss program with supervised aerobic exercise to achieve clinical weight loss (CWL) (≥7% from baseline). Aerobic exercise volume increased weekly until 700 MET min/week was reached. Participants who reached CWL were randomized to groups at volumes at either physical activity (PA-REC) or weight maintenance (WM-REC) recommendations (weeks 11-28). Plasma blood samples were analyzed via nuclear magnetic resonance spectroscopy at baseline, after weight loss (week 10), and following weight maintenance (week 28). Results: Following the weight loss phase, on average, participants significantly (p < 0.001) reduced LP-IR score (-12.1 ± 13.5), body weight (-8.9 ± 2.7%), and waist circumference (-7.7 ± 4.1 cm). During the weight maintenance phase, there were no changes in LP-IR score between exercise groups (PA-REC: 4.1 ± 13.6; WM-REC: -2.0 ± 11.2; P = 0.7). The PA-REC group had improvements in LP-IR score from baseline (49.8 ± 24.6 to 36.6 ± 27.6, P < 0.001), yet there were no within-group changes during the weight maintenance phase (P > 0.05). Conclusion: LP-IR score improved during weight loss in adults with overweight and obesity and were sustained during the weight maintenance phase in the PA-REC group. Aerobic exercise at least at minimum guidelines following CWL can preserve LP-IR score improvements and may indicate a reduced T2DM risk in adults with overweight and obesity.

An antireductant approach ameliorates misfolded proinsulin-induced hyperglycemia and glucose intolerance in male Akita mice

Protein folding in the endoplasmic reticulum (ER) requires a high ratio of oxidized to reduced glutathione (GSSG/rGSH). Since the GSSG/rGSH depends on total glutathione (tGSH = GSSG + rGSH) levels, we hypothesized that limiting GSH biosynthesis will ameliorate protein misfolding by enhancing the ER oxidative milieu. As a proof-of-concept, we used DL-buthionine-(S,R)-sulfoximine (BSO) to inhibit GSH biosynthesis in Akita mice, which are prone to proinsulin misfolding. We conducted a 2-week intervention to investigate if BSO was safe and a 6-week intervention to find its effect on glucose intolerance. In both cohorts, male heterozygous Akita (AK) and wild-type (WT) mice were continuously administered 15 mM BSO. No adverse effects were observed on body weight, food intake, and water intake in either cohort. Unaltered levels of plasma aspartate and alanine aminotransferases, and cystatin-C, indicate that BSO was safe. BSO-induced decreases in tGSH were tissue-dependent with maximal effects in the kidneys, where it altered the expression of genes associated with GSH biosynthesis, redox status, and proteostasis. BSO treatment decreased random blood glucose levels to 80% and 67% of levels in untreated mice in short-term and long-term cohorts, respectively, and 6-h fasting blood glucose to 82% and 74% of levels in untreated mice, respectively. BSO also improved glucose tolerance by 37% in AK mice in the long-term cohort, without affecting insulin tolerance. Neither glucose tolerance nor insulin tolerance were affected in WT. Data indicate that BSO might treat misfolded proinsulin-induced glucose intolerance. Future studies should investigate the effect of BSO on proinsulin misfolding and if it improves glucose intolerance in individuals with Mutant Insulin Diabetes of Youth.

Relationship between Marriage and Prediabetes among Healthcare Workers: Mediating Effect of Triglycerides

Background and Objectives: In the literature, relationships between being married and having prediabetes or diabetes are inconsistent. We aimed to investigate whether marriage is a protective or risk factor for prediabetes and to uncover new insights into its impact on prediabetes. Materials and Methods: In this cross-sectional observational study, questionnaires were distributed by email to 1039 staff members who participated in an employee health check from a hospital affiliated with a medical university in Taiwan. Fasting blood glucose and triglyceride (TG) levels were checked and the questionnaires elicited basic demographic characteristics and included the Copenhagen Burnout Inventory and Nordic Musculoskeletal Questionnaire. The chi-square test or Fisher's exact test, logistic regression, and mediation analysis were conducted for statistical analysis. Results: Among the group aged 20-37 years, married (OR = 1.89, 95%CI: 1.08, 3.33), obesity (OR = 2.95, 95%CI: 1.49, 5.83), neck and shoulder pain (OR = 1.31, 95%CI: 1.01, 1.69), and elevated TG levels (OR = 1.01, 95%CI: 1.00, 1.01) were independent risk factors for prediabetes (impaired fasting glucose). For those >38 years old, overweight (OR = 2.08, 95%CI: 1.27, 3.43), obesity (OR = 4.30, 95%CI: 2.38, 7.79), and elevated triglyceride (TG) (OR = 1.003, 95%CI: 1.00, 1.01) were the independent risk factors for impaired fasting glucose. Increased TG levels serve as a mediating factor (Zm = 2.64, p < 0.01) linking marriage to an increased risk of prediabetes for the group aged 20-37 years. Conclusions: TGs play a significant role in the association between marriage and prediabetes among the group aged 20-37 years. Therefore, dietary habits, especially those of young adult couples should be considered. Our findings connect marital status to prediabetes, facilitating advances in diabetes prevention.

Ultrarapid-Acting Microneedles for Immediate Delivery of Biotherapeutics

Subcutaneous (SC) injection is a common administration route for rapid and efficient delivery of biotherapeutics. However, syringe-based injections usually require professional assistance and are associated with pain and potential risks of infections, thus leading to undesired patient compliance and poor life quality. Herein, this work presents an ultrarapid-acting microneedle (URA-MN) patch for immediate transdermal delivery of therapeutics in a minimally invasive manner. Effervescent agents are incorporated into the tip of URA-MN for rapid generation of CO2 bubbles upon insertion into the skin, immediately powering the biotherapeutics release within a few minutes. The release kinetics of diverse agents including liraglutide (LRT), insulin, and heparin from the URA-MN patches are evaluated in three different mouse models, and the rapid release of biotherapeutics and potent therapeutic effects are achieved with only 5 min administration. Noteworthily, attributed to the short application duration and negligible residuals of MN matrix remaining in the skin, the URA-MN patch shows desirable biocompatibility after six-week administration.

Lipid-induced glucose intolerance is driven by impaired glucose kinetics and insulin metabolism in healthy individuals

AIMS

Hypertriglyceridemia is associated with an increased risk of type 2 diabetes. We aimed to comprehensively examine the effects of hypertriglyceridemia on major glucose homeostatic mechanisms involved in diabetes progression.

METHODS

In this randomized, cross-over, single-blinded study, two dual-labeled, 3-hour oral glucose tolerance tests were performed during 5-hour intravenous infusions of either 20 % Intralipid or saline in 12 healthy subjects (age 27.9 ± 2.6 years, 11 men, BMI 22.6 ± 1.4 kg/m²) to evaluate lipid-induced changes in insulin metabolism and glucose kinetics. Insulin sensitivity, β cell secretory function, and insulin clearance were assessed by modeling glucose, insulin and C-peptide data. Intestinal glucose absorption, endogenous glucose production, and glucose clearance were assessed from glucose tracers. The effect of triglycerides on β-cell secretory function was examined in perifusion experiments in murine pseudoislets and human pancreatic islets.

RESULTS

Mild acute hypertriglyceridemia impaired oral glucose tolerance (mean glucose: +0.9 [0.3, 1.5] mmol/L, p = 0.008) and whole-body insulin sensitivity (Matsuda index: -1.67 [-0.50, -2.84], p = 0.009). Post-glucose hyperinsulinemia (mean insulin: +99 [17, 182] pmol/L, p = 0.009) resulted from reduced insulin clearance (-0.16 [-0.32, -0.01] L min^-1 m^-2, p = 0.04) and enhanced hyperglycemia-induced total insulin secretion (+11.9 [1.1, 22.8] nmol/m², p = 0.02), which occurred despite a decline in model-derived β cell glucose sensitivity (-41 [-74, -7] pmol min^-1 m^-2 mmol^-1 L, p = 0.04). The analysis of tracer-derived glucose metabolic fluxes during lipid infusion revealed lower glucose clearance (-96 [-152, -41] mL/kg_FFM, p = 0.005), increased 2-hour oral glucose absorption (+380 [42, 718] μmol/kg_FFM, p = 0.04) and suppressed endogenous glucose production (-448 [-573, -123] μmol/kg_FFM, p = 0.005). High-physiologic triglyceride levels increased acute basal insulin secretion in murine pseudoislets (+11 [3, 19] pg/aliquot, p = 0.02) and human pancreatic islets (+286 [59, 512] pg/islet, p = 0.02).

CONCLUSION

Our findings support a critical role for hypertriglyceridemia in the pathogenesis of type 2 diabetes in otherwise healthy individuals and dissect the glucose homeostatic mechanisms involved, encompassing insulin sensitivity, β cell function and oral glucose absorption.

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.

Impact of COVID-19 Lockdown on the Metabolic Control Parameters in Patients with Diabetes Mellitus: A Systematic Review and Meta-Analysis

BACKGROUND

Abrupt implementation of lockdowns during the coronavirus disease 2019 (COVID-19) pandemic affected the management of diabetes mellitus in patients worldwide. Limited access to health facilities and lifestyle changes potentially affected metabolic parameters in patients at risk. We conducted a meta-analysis to determine any differences in the control of metabolic parameters in patients with diabetes, before and during lockdown.

METHODS

We performed searches of five databases. Meta-analyses were carried out using random- or fixed-effect approaches to glycaemic control parameters as the primary outcome: glycosylated hemoglobin (HbA1c), random blood glucose (RBG), fasting blood glucose (FBG), time-in-range (TIR), time-above-range (TAR), time-below-range (TBR). Mean difference (MD), confidence interval (CI), and P value were calculated. Lipid profile was a secondary outcome and is presented as a descriptive analysis.

RESULTS

Twenty-one studies enrolling a total of 3,992 patients with type 1 or type 2 diabetes mellitus (T1DM or T2DM) were included in the study. Patients with T1DM showed a significant improvement of TIR and TAR (MD=3.52% [95% CI, 0.29 to 6.74], I2=76%, P=0.03; MD=-3.36% [95% CI, -6.48 to -0.25], I2=75%, P=0.03), while FBG among patients with T2DM significantly worsened (MD=3.47 mg/dL [95% CI, 1.22 to 5.73], I2=0%, P<0.01). No significant difference was found in HbA1c, RBG, and TBR. Use of continuous glucose monitoring in T1DM facilitated good glycaemic control. Significant deterioration of lipid parameters during lockdown, particularly triglyceride, was observed.

CONCLUSION

Implementation of lockdowns during the COVID-19 pandemic did not worsen glycaemic control in patients with diabetes. Other metabolic parameters improved during lockdown, though lipid parameters, particularly triglyceride, worsened.

The triglyceride-glucose index is a more powerful surrogate marker for predicting the prevalence and incidence of type 2 diabetes mellitus than the homeostatic model assessment of insulin resistance

AIMS

Insulin resistance is an independent risk factor for developing type 2 diabetes. Therefore, this study compared the predictability of the triglyceride-glucose (TyG) index and the homeostatic model assessment of insulin resistance (HOMA-IR) for the prevalence and incidence of type 2 diabetes.

METHODS

We analyzed data from 9730 adults aged 40-69 years at baseline and 7783 participants without diabetes who were followed up in the Korean Genome and Epidemiology Study survey. From 2001 to 2002 (baseline survey) to 2013-2014, this survey was conducted biennially (six follow-ups). The average follow-up period was 9.0 years.

RESULTS

The TyG index showed better predictability for the prevalence of type 2 diabetes than HOMA-IR (TyG index: 0.784, HOMA-IR: 0.728, p < 0.001). The area under the time-dependent receiver operating characteristic curve of the TyG index for incident type 2 diabetes was 0.640 (0.628-0.652), which was significantly higher than that of HOMA-IR [0.531 (0.521-0.541)] (p < 0.001).

CONCLUSIONS

The TyG index is superior to HOMA-IR for predicting type 2 diabetes. The TyG index could, therefore, be more useful for the early detection and prevention of type 2 diabetes.

Familial hypercholesterolemia in Gran Canaria: Founder mutation effect and high frequency of diabetes

INTRODUCTION

Gran Canaria is a region of genetic isolation of familial hypercholesterolemia due to a founder mutation, p. [Tyr400_Phe402del], in the LDL receptor (LDLR) gene. Initial data suggest that its carriers could have a high prevalence of diabetes.

MATERIAL AND METHODS

Patients over 30 years of age with familial hypercholesterolemia and a confirmed mutation in LDLR were recruited from a tertiary hospital in Gran Canaria. The prevalence of diabetes and other clinical data were compared among carriers of p. [Tyr400_Phe402del] and those with other LDLR mutations.

RESULTS

76.4% of the 89 participants were carriers of p.[Tyr400_Phe402del]. The prevalence of diabetes in this group was significantly higher (25 vs. 4%, P=.045). These cases also had a higher prevalence of cardiovascular disease and higher levels of LDL cholesterol and triglycerides. There were no differences in age, weight, body mass index, waist, age of onset, and time of statin treatment. However, they required PCSK9 inhibitors more often (51.5 vs 24%, P=.027).

CONCLUSIONS

The mutation p.[Tyr400_Phe402del] is associated with a high prevalence of diabetes, not explained by classic risk factors, such as age, obesity, or long-term use of statins.

Short-term impact of COVID-19 lockdown on metabolic control of patients with well-controlled type 2 diabetes: a single-centre observational study

AIMS/HYPOTHESIS

The strict rules applied in Italy during the recent COVID-19 pandemic, with the prohibition to attend any regular outdoor activity, are likely to influence the degree of metabolic control in patients with type 2 diabetes. We explored such putative effect immediately after the resolution of lockdown rules, in the absence of any variation of pharmacologic treatment.

METHODS

One-hundred and fourteen patients with adequate metabolic control took part in this single-centre, prospective, observational study. The metabolic profile tested 1 week after the end of the lockdown was compared with the last value and the mean of the last three determinations performed before the pandemic emergency (from 6 months to 2 years before).

RESULTS

After 8 weeks of lockdown, an increase of HbA1c > 0.3% (mean +0.7%) was observed in 26% of the participants; these were also characterized by a persistent elevation in serum triglycerides able to predict the worsening of glucose control.

CONCLUSIONS

Lockdown determined a relevant short-term metabolic worsening in approximately one-fourth of previously well-controlled type 2 diabetic individuals; pre-lockdown triglycerides were the only parameter able to predict such derangement of glucose control.

Functional Status of Pancreatic α and β Cells in Type 2 Diabetes Mellitus Patients with Different Plasma Triglyceride Levels: A Retrospective Analysis

OBJECTIVE

To investigate the functional status of pancreatic α and β cells in Type 2 diabetes mellitus (T2DM) patients with different plasma triglyceride (TG) levels. TG levels can be prognostic markers for T2DM.

METHODS

A total of 328 patients with T2DM were divided into three groups according to different TG levels: the TGL group: TG < 1.7 mmol/L; TGM group: 1.7 mmol/L ≤ TG < 2.3 mmol/L; and TGH group: TG ≥ 2.3 mmol/L. An oral glucose tolerance test (OGTT), insulin release test, and glucagon release test were performed in each patient. The changes of glucagon, glucagon/insulin ratio, early insulin secretion index (ΔI ₃₀/ΔG ₃₀), and area under the insulin curve (AUC_I) were compared among each group. Also, the correlations between glucagon and pancreatic β-cell function, glycosylated hemoglobin (HbA1c), and other indices were analyzed.

RESULTS

With the increase of TG, the fasting and postprandial glucagon levels, the glucagon/insulin ratio, and the area under the glucagon curve (AUC_G) presented an increasing trend. The homeostasis model assessment of insulin resistance (HOMA-IR) of the TGH group was significantly increased compared to the TGL and TGM groups. In addition to the increase in TG levels, the insulin sensitivity index (ISI), homeostasis model assessment for β-cell function index (HOMA-β), ΔI ₃₀/ΔG ₃₀, and AUC_I displayed a reducing trend. Glucagon was negatively correlated with ΔI ₃₀/ΔG ₃₀, high-density lipoprotein (HDL), HOMA-β, body mass index (BMI), ISI, and AUC_I (P < 0.05) and positively correlated with fasting blood glucose (FPG), AUC_G, HOMA-IR, HbA1c, duration, TG, low-density lipoprotein (LDL), and total cholesterol (TC) (P < 0.05).

CONCLUSION

Hypertriglyceridemia aggravated the dysfunction of pancreatic α and β cells. A reasonable control of the TG level makes it easier for blood glucose to reach the standard.

Benzyl Isothiocyanate Ameliorates High-Fat Diet-Induced Hyperglycemia by Enhancing Nrf2-Dependent Antioxidant Defense-Mediated IRS-1/AKT/TBC1D1 Signaling and GLUT4 Expression in Skeletal Muscle

Obesity caused lipotoxicity, which results in insulin resistance. We studied whether benzyl isothiocyanate (BITC) improved insulin resistance in muscle. BITC was studied in vivo in mice fed a high-fat diet (HFD) and in vitro in C2C12 myotubes treated with palmitic acid (PA). In C2C12 cells, BITC mitigated PA inhibition of glucose uptake and phosphorylation of IRS-1, AKT, and TBC1D1 in response to insulin. BITC upregulated the expression of HO-1, GSTP, and GCLM mRNA and protein as well as GSH contents, which suppressed oxidative damage. Knockdown of Nrf2 abrogated BITC enhancement of antioxidant defense and subsequently reversed BITC protection against PA-induced insulin resistance. Moreover, BITC upregulated the expression of GLUT4, PPARγ, and C/EBPα. In HFD-fed mice, plasma total cholesterol, nonesterified fatty acid, and glucose levels and HOMA-IR were dose-dependently decreased with 0.05 or 0.1% BITC administration. In gastrocnemius muscle, compared with the HFD group, BITC increased the phosphorylation of AKT and TBC1D1, GSH contents, and the expression of antioxidant enzymes as well as GLUT4. These results indicate that BITC ameliorates obesity-induced hyperglycemia by enhancing insulin sensitivity in muscle. This is partly attributed to its inhibition of lipotoxicity-induced oxidative insult and upregulation of GLUT4 expression.

The metabolic changes in the hippocampus of an atherosclerotic rat model and the regulation of aerobic training

Atherosclerosis has been associated with the progression of cognitive impairment and the effect of metabolic changes in the brain on cognitive function may be pronounced. The aim is to reveal the metabolic changes during atherosclerosis and clarify the possible role of exercise in regulating hippocampal metabolism. Hence, A rat model of atherosclerosis was established by high-fat diet feeding in combination with vitamin D3 intraperitoneal injection, then 4 weeks of aerobic exercise was conducted. Metabolomics based on GC-MS was applied to detect small molecules metabolites and western blot was used to detect the concentration of enzymes involved in metabolic changes in rat hippocampus. Compared to the control group, metabolites including xylulose 5-phosphate, threonine, succinate, and nonanoic acid were markedly elevated, whereas methyl arachidonic acid and methyl stearate decreased in the AS group, accompanied by a raised concentration of aldose reductase and glucose 6-phosphate dehydrogenase as well as a declined concentration of acetyl-CoA carboxylase and fatty acid synthase. After 4 weeks' aerobic exercise, the levels of succinic acid, branched chain amino acids, nonanoic acid, desmosterol, and aldose reductase decreased, whereas methyl arachidonic acid, methyl stearate, and glyceraldehyde-3-phosphate elevated in the hippocampus of the TAS group in comparison with the AS group. These results suggest that atherosclerosis could cause a severe metabolic disturbance, and aerobic exercise plays an important role in regulating atherosclerosis-induced disorder of glucose metabolism in the hippocampus.

Disruption of fasting and post-load glucose homeostasis are largely independent and sustained by distinct and early major beta-cell function defects: a cross-sectional and longitudinal analysis of the Relationship between Insulin Sensitivity and Cardiovascular risk (RISC) study cohort

BACKGROUND/AIMS

Uncertainty still exists on the earliest beta-cell defects at the bases of the type 2 diabetes. We assume that this depends on the inaccurate distinction between fasting and post-load glucose homeostasis and aim at providing a description of major beta-cell functions across the full physiologic spectrum of each condition.

METHODS

In 1320 non-diabetic individuals we performed an OGTT with insulin secretion modeling and a euglycemic insulin clamp, coupled in subgroups to glucose tracers and IVGTT; 1038 subjects underwent another OGTT after 3.5 years. Post-load glucose homeostasis was defined as mean plasma glucose above fasting levels (δOGTT). The analysis was performed by two-way ANCOVA.

RESULTS

Fasting plasma glucose (FPG) and δOGTT were weakly related variables (stβ = 0.12) as were their changes over time (r = -0.08). Disruption of FPG control was associated with an isolated and progressive decline (approaching 60%) of the sensitivity of the beta-cell to glucose values within the normal fasting range. Disruption of post-load glucose control was characterized by a progressive decline (approaching 60%) of the slope of the full beta-cell vs glucose dose-response curve and an early minor (30%) decline of potentiation. The acute dynamic beta-cell responses, neither per se nor in relation to the degree of insulin resistance appeared to play a relevant role in disruption of fasting or post-load homeostasis. Follow-up data qualitatively and quantitatively confirmed the results of the cross-sectional analysis.

CONCLUSION

In normal subjects fasting and post-load glucose homeostasis are largely independent, and their disruption is sustained by different and specific beta-cell defects.

A nomogram for predicting 5-year incidence of type 2 diabetes in a Chinese population

PURPOSE

To develop a nomogram for predicting 5-year incidence of type 2 diabetes (T2D) in Chinese adults.

METHODS

This is a retrospective cohort study from a prospectively collected database. We included a total 32,766 adults free of T2D at baseline with a median follow-up of 3 years. Univariate and multivariate Cox regression analyses were applied to identify independent predictors. A nomogram was constructed to predict 5-year incident rate of T2D based on the multivariate analysis results. Harrell's C-indexes and calibration plots were used to evaluate the accuracy of the nomogram in both internal and external validations.

RESULTS

The overall prevalence of T2D was 2.1%. Participants were randomly divided into a training set (n = 21,844) and a validation set (n = 10,922). After multivariate analysis in the training set, age, sex, BMI, hypertension, dyslipidemia, smoking status, and family history were found as risk predictors and integrated into the nomogram. Harrell's C-indexes were 0.815 (95% CI: 0.797-0.834) and 0.779 (95% CI: 0.747-0.811) in the training and validation sets, respectively. The calibration plots demonstrated good agreement between the estimated probability and the actual observation.

CONCLUSION

Our nomogram could be a simple and reliable tool for predicting 5-year risk of developing T2D in high-risk Chinese. Through the model, early identifying high-risk individuals is helpful for timely intervention to reduce the incidence of T2D.

Postprandial Lipemia Modulates Pancreatic Alpha-Cell Function in the Prediction of Type 2 Diabetes Development: The CORDIOPREV Study

Diabetes (T2DM) is a major global health issue, and developing new approaches to its prevention is of paramount importance. We hypothesized that abnormalities in lipid metabolism are involved in alpha-cell deregulation. We therefore studied the metabolic factors underlying alpha-cell dysfunction in T2DM progression after a dietary intervention (Mediterranean and low-fat). Additionally, we evaluated whether postprandial glucagon levels may be considered as a predictive factor of T2DM in cardiovascular patients. Non-T2DM participants from the CORDIOPREV study were categorized by tertiles of the area under the curve (AUC) for triacylglycerols and also by tertiles of AUC for glucagon. Our results showed that patients with higher triacylglycerols levels presented elevated postprandial glucagon (P = 0.009). Moreover, we observed higher risk of T2DM (hazard ratio: 2.65; 95% confidence interval: 1.56-4.53) in subjects with elevated glucagon. In conclusion, high postprandial lipemia may induce alpha-cell dysfunction in cardiovascular patients. Our results also showed that postprandial glucagon levels could be used to predict T2DM development.

Causal relationships between lipid and glycemic levels in an Indian population: A bidirectional Mendelian randomization approach

BACKGROUND

Dyslipidemia and abnormal glycemic traits are leading causes of morbidity and mortality. Although the association between the two traits is well established, there still exists a gap in the evidence for the direction of causality.

OBJECTIVE

This study aimed to examine the direction of the causal relationship between lipids and glycemic traits in an Indian population using bidirectional Mendelian randomization (BMR).

METHODS

The BMR analysis was conducted on 4900 individuals (2450 sib-pairs) from the Indian Migration Study. Instrument variables were generated for each lipid and glycemic trait (fasting insulin, fasting glucose, HOMA-IR, HOMA-β, LDL-cholesterol, HDL-cholesterol, total cholesterol and triglycerides) to examine the causal relationship by applying two-stage least squares (2SLS) regression in both directions.

RESULTS

Lipid and glycemic traits were found to be associated observationally, however, results from 2SLS showed that only triglycerides, defined by weighted genetic risk score (wGRS) of 3 SNPs (rs662799 at APOAV, rs780094 at GCKR and rs4420638 at APOE/C1/C4), were observed to be causally effecting 1.15% variation in HOMA-IR (SE = 0.22, P = 0.010), 1.53% in HOMA- β (SE = 0.21, P = 0.001) and 1.18% in fasting insulin (SE = 0.23, P = 0.009). No evidence for a causal effect was observed in the reverse direction or between any other lipid and glycemic traits.

CONCLUSION

The study findings suggest that triglycerides may causally impact various glycemic traits. However, the findings need to be replicated in larger studies.

Circulating palmitoleic acid is an independent determinant of insulin sensitivity, beta cell function and glucose tolerance in non-diabetic individuals: a longitudinal analysis

AIMS/HYPOTHESIS

Experimental studies suggest that the fatty acid palmitoleate may act as an adipocyte-derived lipid hormone (or 'lipokine') to regulate systemic metabolism. We investigated the relationship of circulating palmitoleate with insulin sensitivity, beta cell function and glucose tolerance in humans.

METHODS

Plasma NEFA concentration and composition were determined in non-diabetic individuals from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study cohort at baseline (n = 1234) and after a 3 year follow-up (n = 924). Glucose tolerance, insulin secretion and beta cell function were assessed during an OGTT. Whole-body insulin sensitivity was measured by a hyperinsulinaemic-euglycaemic clamp (M/I) and OGTT (oral glucose insulin sensitivity index [OGIS]). The liver insulin resistance index was calculated using clinical and biochemical data. Body composition including fat mass was determined by bioelectrical impedance.

RESULTS

Circulating palmitoleate was proportional to fat mass (r = 0.21, p < 0.0001) and total NEFA levels (r = 0.19, p < 0.0001). It correlated with whole-body insulin sensitivity (M/I: standardised regression coefficient [std. β] = 0.16, p < 0.0001), liver insulin resistance (std. β = -0.14, p < 0.0001), beta cell function (potentiation: std. β = 0.08, p = 0.045) and glucose tolerance (2 h glucose: std. β = -0.24, p < 0.0001) after adjustment for age, sex, BMI, adiposity and other NEFA. High palmitoleate concentrations prevented the decrease in insulin sensitivity associated with excess palmitate (p = 0.0001). In a longitudinal analysis, a positive independent relationship was observed between changes in palmitoleate and insulin sensitivity over time (std. β = 0.07, p = 0.04).

CONCLUSIONS/INTERPRETATION

We demonstrated that plasma palmitoleate is an independent determinant of insulin sensitivity, beta cell function and glucose tolerance in non-diabetic individuals. These results support the role of palmitoleate as a beneficial lipokine released by adipose tissue to prevent the negative effects of adiposity and excess NEFA on systemic glucose metabolism.

Angiotensin-converting enzyme 2 regulates endoplasmic reticulum stress and mitochondrial function to preserve skeletal muscle lipid metabolism

Objective

Endoplasmic reticulum (ER) stress and mitochondrial function affected intramuscular fat accumulation. However, there is no clear evident on the effect of the regulation of ER stress and mitochondrial function by Angiotensin-converting enzyme 2 (ACE2) on the prevention of intramuscular fat metabolism. We investigated the effects of ACE2 on ER stress and mitochondrial function in skeletal muscle lipid metabolism.

Methods

The triglyceride (TG) content in skeletal muscle of ACE2 knockout mice and Ad-ACE2-treated db/db mice were detected by assay kits. Meanwhile, the expression of lipogenic genes (ACCα, SREBP-1c, LXRα, CPT-1α, PGC-1α and PPARα), ER stress and mitochondrial function related genes (GRP78, eIF2α, ATF4, BCL-2, and SDH6) were analyzed by RT-PCR. Lipid metabolism, ER stress and mitochondrial function related genes were analyzed by RT-PCR in ACE2-overexpression C2C12 cell. Moreover, the IKKβ/NFκB/IRS-1 pathway was determined using lysate sample from skeletal muscle of ACE2 knockout mice.

Results

ACE2 deficiency in vivo is associated with increased lipid accumulation in skeletal muscle. The ACE2 knockout mice displayed an elevated level of ER stress and mitochondrial dysfunctions in skeletal muscle. In contrast, activation of ACE2 can ameliorate ER stress and mitochondrial function, which slightly accompanied by reduced TG content and down-regulated the expression of skeletal muscle lipogenic proteins in the db/db mice. Additionally, ACE2 improved skeletal muscle lipid metabolism and ER stress genes in the C2C12 cells. Mechanistically, endogenous ACE2 improved lipid metabolism through the IKKβ/NFκB/IRS-1 pathway in skeletal muscle.

Conclusions

ACE2 was first reported to play a notable role on intramuscular fat regulation by improving endoplasmic reticulum and mitochondrial function. This study may provide a strategy for treating insulin resistance in skeletal muscle.

High fat meals increases postprandial fat oxidation rate but not postprandial lipemia

BACKGROUND

This study investigated the effects of ingesting meals with the same calorie intake but distinct nutritional contents after exercise on postprandial lipemia the next day.

METHODS

Eight healthy male participants completed two 2-day trials in a random order. On day 1, the participants underwent five 12 min bouts of cycling exercise with a bout of higher intensity exercise (4 min) after each and then a bout of lower intensity cycling (2 min). The total exercise time was 90 min. After the exercise, the participants ingested three high-fat or low-fat meals. On Day 2, the participants were asked to rest in the laboratory and ingest a high-fat meal. Their postprandial reaction after a high-fat meal was observed.

RESULTS

Postprandial triglyceride concentrations in the high-fat diet trial and low-fat diet trial exhibited nonsignificant differences. Total TG AUC were no significantly different on HF trial and LF trial (HF: 6.63 ± 3.2; LF: 7.20 ± 3.4 mmol/L*4 h. p = 0.586). However, the postprandial fat oxidation rate total AUC (HF: 0.58 ± 0.1; LF: 0.39 ± 0.2 g/min*4 h. p = 0.045), plasma glucose, and insulin concentration of the high-fat trial were significantly higher than those of the low-fat trial.

CONCLUSIONS

This study revealed that meals with distinct nutritional contents after a 90-min exercise increased the postprandial fat oxidation rate but did not influence the postprandial lipemia after a high-fat meal the next day.

Panax notoginseng saponins alleviate skeletal muscle insulin resistance by regulating the IRS1-PI3K-AKT signaling pathway and GLUT4 expression

Panax notoginseng saponins (PNS) are a commonly used traditional medicine to treat diabetes in China. Recent studies have confirmed their anti-diabetic effects, but the underlying mechanisms have remained unclear. The present study was designed to explore whether PNS decrease hyperglycemia by improving insulin sensitivity in skeletal muscle and to elucidate the molecular mechanisms. The anti-diabetic effects of PNS were analyzed in a skeletal myoblast cell line, C2C12, and in high fat diet-induced diabetic KKAy mice. C2C12 cells were treated with PNS (50, 100, and 200 μg·L^-1 ) and examined for glucose uptake, cell viability and expression of components of the phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway. KKAy mice were intraperitoneally injected with PNS (200 mg·kg^-1 ) for 6 weeks. Body weight, blood glucose, serum insulin, serum lipid, glucose and insulin tolerance were measured to evaluate the anti-diabetic effects of PNS. Pathological changes, apoptosis and the PI3K-AKT signaling pathway were analyzed in KKAy skeletal muscle. PNS significantly increased insulin-induced glucose uptake, but did not affect the cell viability of C2C12 cells. In addition, PNS reduced blood glucose and serum insulin levels and improved glucose tolerance and insulin tolerance of KKAy mice. Pathological changes and apoptosis of skeletal muscle were relieved by PNS treatment. Moreover, PNS treatment enhanced expression of mRNA encoding IRS1 and GLUT4, as well as the protein expression of phosphorylated (p) -insulin receptor substrate 1 (IRS1), p-PI3K, p-AKT and glucose transporter type 4 (GLUT4) in C2C12 and KKAy mouse muscle. Collectively, these data indicate that PNS reduces hyperglycemia and insulin resistance through up-regulating GLUT4 expression and the IRS1-PI3K-AKT signaling pathway. Furthermore, PNS alleviated diabetes skeletal muscle pathological damage. Thus, our data suggest that PNS may be promising anti-diabetic compounds.

Effect of biotin supplementation on fatty acid metabolic pathways in 3T3-L1 adipocytes

Several studies have shown that pharmacological concentrations of biotin decrease serum lipid concentrations and the expression of lipogenic genes. Previous studies on epididymal adipose tissue in mice revealed that 8 weeks of dietary biotin supplementation increased the protein abundance of the active form of AMPK and the inactive forms acetyl CoA carboxylase (ACC)-1 and - 2, and decreased serum free fatty acid concentrations but did not affect lipolysis. These data suggest that pharmacological concentrations of the vitamin might affect fatty acid metabolism. In this work, we investigated the effects of pharmacological biotin concentrations on fatty acid synthesis, oxidation, and uptake in 3T3-L1 adipocytes. Similar to observations in mice, biotin-supplemented 3T3-L1 adipose cells increased the protein abundance of active ^T172 -AMPK and inactive ACC-1 and -2 forms. No changes were observed in the expression of the transcriptional factor PPARα and carnitine-palmitoyltransferase-1 (CPT-1). Radiolabeled assays indicated a decrease in fatty acid synthesis; an increase in fatty acid oxidation and fatty acid incorporation rate into the lipid fraction between control cells and biotin-supplemented cells. The data revealed an increase in the mRNA abundance of the fatty acid transport proteins Fatp1 and Acsl1 but not Cd36 or Fatp4 mRNA. Furthermore, the abundance of glycerol phosphate acyl transferase-3 protein was increased. Triglyceride content was not affected. Lipid droplet numbers showed an increase and their areas were smaller in the biotin-supplemented group. In conclusion, these data indicate that biotin supplementation causes a decrease in fatty acid synthesis and an increase in its oxidation and uptake. © 2018 BioFactors, 45(2):259-270, 2019.

Different Contributions of Dyslipidemia and Obesity to the Natural History of Type 2 Diabetes: 3-Year Cohort Study in China

AIM

It is known that different stages of type 2 diabetes represent distinct pathophysiological changes, but how the spectrum of risk factors varies at different stages is not yet clarified. Hence, the aim of this study was to compare the effect of different metabolic variables on the natural history of type 2 diabetes.

METHODS

A total of 5,213 nondiabetic (normal glucose tolerance (NGT) and prediabetes) Chinese older than 40 years participated this prospective cohort study, and 4,577 completed the 3-year follow-up. Glycemic status was determined by standard oral glucose tolerance test both at enrollment and follow-up visit. Predictors for conversion in glycemic status were studied in a corresponding subcohort using the multiple logistic regression analysis.

RESULTS

The incidence of prediabetes and diabetes of the cohort was 93.6 and 42.2 per 1,000 person-years, respectively. After a 3-year follow-up, 33.1% of prediabetes patients regressed to NGT. The predictive weight of body mass index (BMI), serum triglyceride, total cholesterol, and systolic blood pressure in different paths of conversions among diabetes, prediabetes, and NGT differed. Specifically, BMI was the strongest predictor for regression from prediabetes to NGT, while triglyceride was most prominent for onset of diabetes. One SD increase in serum triglyceride was associated with a 1.29- (95% CI 1.10-1.52; P = 0.002) or 1.12- (95% CI 1.01-1.27; P = 0.039) fold higher risk of diabetes for individuals with NGT or prediabetes, respectively.

CONCLUSION

Risk factors for different stages of diabetes differed, suggesting personalized preventive strategies for individuals with different basal glycemic statuses.

Impact of Nutrient Type and Sequence on Glucose Tolerance: Physiological Insights and Therapeutic Implications

Pharmacological and dietary interventions targeting postprandial glycemia have proved effective in reducing the risk for type 2 diabetes and its cardiovascular complications. Besides meal composition and size, the timing of macronutrient consumption during a meal has been recently recognized as a key regulator of postprandial glycemia. Emerging evidence suggests that premeal consumption of non-carbohydrate macronutrients (i.e., protein and fat "preloads") can markedly reduce postprandial glycemia by delaying gastric emptying, enhancing glucose-stimulated insulin release, and decreasing insulin clearance. The same improvement in glucose tolerance is achievable by optimal timing of carbohydrate ingestion during a meal (i.e., carbohydrate-last meal patterns), which minimizes the risk of body weight gain when compared with nutrient preloads. The magnitude of the glucose-lowering effect of preload-based nutritional strategies is greater in type 2 diabetes than healthy subjects, being comparable and additive to current glucose-lowering drugs, and appears sustained over time. This dietary approach has also shown promising results in pathological conditions characterized by postprandial hyperglycemia in which available pharmacological options are limited or not cost-effective, such as type 1 diabetes, gestational diabetes, and impaired glucose tolerance. Therefore, preload-based nutritional strategies, either alone or in combination with pharmacological treatments, may offer a simple, effective, safe, and inexpensive tool for the prevention and management of postprandial hyperglycemia. Here, we survey these novel physiological insights and their therapeutic implications for patients with diabetes mellitus and altered glucose tolerance.

Triglyceride-rich very low-density lipoproteins (VLDL) are independently associated with insulin secretion in a multiethnic cohort of adolescents

Excess insulin secretion and hyperinsulinaemia contribute to the progression of type 2 diabetes. However, the mechanisms leading to insulin hypersecretion remain largely unknown. Based on our preliminary data, we examined whether triglycerides and very low-density lipoprotein (VLDL) are independently associated with insulin secretion, and whether ethnicity/race modulates these associations. Fasting triglycerides and VLDL were measured in a multiethnic cohort of 630 non-diabetic adolescents. Insulin secretion, β-cell function parameters, insulin sensitivity and insulin clearance were estimated through a 3-h oral glucose tolerance test. Metabolic assessments were repeated after 2 years in 239 subjects. Triglycerides and triglyceride-rich VLDL (large and medium size fractions) were associated with both basal and glucose-stimulated insulin secretion, after adjustment for age, sex, ethnicity, BMI z-score, plasma glucose, and insulin sensitivity. Ethnicity per se had an impact on lipid profile and β-cell function, but did not modulate the effect of triglycerides/VLDL on insulin secretion. At follow-up, changes in triglyceride levels were proportional to changes in insulin secretion. These findings support the hypothesis that hypertriglyceridaemia is an important stimulus for β-cell insulin release in young people under both fasting and fed conditions.

Reappraisal of attenuated insulin sensitivity in the evolution of non-alcoholic fatty liver disease

BACKGROUND/OBJECTIVES

It has been unknown if attenuated insulin sensitivity (Si) in non-alcoholic fatty liver disease (NAFLD) is a cause or a result. We examined the impact of attenuated Si on NAFLD evolution.

SUBJECTS/METHODS

We observed 4856 NAFLD- and diabetes-free participants for a mean 2.9 years. Si was indexed by single point insulin sensitivity estimator (SPISE = [600 × HDL-c^0.185]/[TG^0.2 × BMI^1.338]), correlating with 1/HOMA-IR in an independent cohort (n = 1537, Spearman rho = 0.519, P < 0.01). Fatty liver (FL) was diagnosed by ultrasonography and diabetes by fasting plasma glucose (FPG) ≥ 7 mmol/L and/or glycohemoglobin A1c ≥ 6.5%. Multinominal comparison was performed with incident FL (FL_w/oDM, n = 486), diabetes (DM_w/oFL, n = 171), and FL plus diabetes (FL/diabetes, n = 58) as targets; none of the above (n = 4,138) was the control. SPISE was taken as a predictor with adjustment for covariates. Trajectory of SPISE during the 5 years before development of each condition was also assessed.

RESULTS

With SPISE tertile 3 (>10.06) as the reference, tertile 1 (<8.07) was related to incident FL_w/oDM and FL/diabetes with OR (95% CI) 3.47 (2.60-4.63) and 1.78 (1.10-2.87), respectively, and tertile 2 (8.07-10.06) related to FL_w/oDM with OR (95% CI) 1.38 (1.03-1.85). Low SPISE was not significantly related to incident diabetes. At -5 years, SPISE was 12% (P < 0.05) and 13% (P < 0.01) lower in those developed FL_w/oDM and FL/diabetes, respectively, than the control. At year 0, SPISE in the two groups was 18% and 21% lower than the control, respectively (P < 0.01).

CONCLUSIONS

Attenuation of Si indexed by SPISE was a risk factor for NAFLD.

The insulinotropic effect of a high-protein nutrient preload is mediated by the increase of plasma amino acids in type 2 diabetes

AIMS

Eating protein before carbohydrate reduces postprandial glucose excursions by enhancing insulin and glucagon-like peptide-1 (GLP-1) secretion in type 2 diabetes (T2D). We tested the hypothesis that this insulinotropic effect depends on the elevation of plasma amino acids (AA) after the digestion of food protein.

METHODS

In 16 T2D patients, we measured plasma AA levels through the course of two 75-g oral glucose tolerance tests (OGTT) preceded by either 500-ml water or a high-protein nutrient preload (50-g Parmesan cheese, one boiled egg, and 300-ml water). Changes in beta cell function were evaluated by measuring and modelling plasma glucose, insulin, and C-peptide through the OGTT. Changes in incretin hormone secretion were assessed by measuring plasma GLP-1.

RESULTS

Plasma AA levels were 24% higher after the nutrient preload (p < 0.0001). This increment was directly proportional to both the enhancement of beta cell function (r = 0.58, p = 0.02) and the plasma GLP-1 gradients (r = 0.57, p = 0.02) produced by the nutrient preload. Among single AA, glutamine showed the strongest correlation with changes in beta cell function (r = 0.61, p = 0.01), while leucine showed the strongest correlation with GLP-1 responses (r = 0.74, p = 0.001).

CONCLUSIONS

The elevation of circulating AA that occurs after a high-protein nutrient preload is associated with an enhancement of beta cell function and GLP-1 secretion in T2D. Manipulating the meal sequence of nutrient ingestion may reduce postprandial hyperglycaemia through a direct and GLP-1-mediated stimulation of insulin secretion by plasma AA.

TRIAL REGISTRATION NUMBER

NCT02342834.

The manifold role of the mitochondria in skeletal muscle insulin resistance

PURPOSE OF REVIEW

The role of mitochondria in the development of skeletal muscle insulin resistance has been an area of intense investigation and debate for over 20 years. The mitochondria is a multifaceted organelle that plays an integral part in substrate metabolism and cellular signalling. This article aims to summarize the current findings and thought regarding the relationship between mitochondria and insulin resistance in skeletal muscle.

RECENT FINDINGS

Skeletal muscle insulin resistance was earlier thought to result from deficiency in mitochondrial oxidative capacity and ectopic lipid accumulation. Recent evidence suggests that skeletal muscle insulin resistance in high-energy intake models (i.e. obesity) results primarily from disrupted mitochondrial bioenergetics and alterations in mitochondrial-associated cell signalling. These signalling pathways include reactive oxygen species and redox balance, fatty acid β-oxidation intermediates, mitochondrial derived peptides, sirtuins, microRNAs and novel nuclear-encoded, mitochondria-acting peptides.

SUMMARY

The pathophysiology of skeletal muscle insulin resistance is likely multifactorial involving many coordinated physiological processes. However, it is apparent that the mitochondria play an essential role in skeletal muscle insulin sensitivity in health, ageing and in numerous metabolic diseases. Deciphering the manifold functions of the mitochondria will allow us to understand the complex relationship between mitochondria and skeletal muscle insulin resistance.

A short-term increase in dietary cholesterol and fat intake affects high-density lipoprotein composition in healthy subjects

BACKGROUND AND AIMS

High-cholesterol and high-fat diets alter biochemical composition and anti-oxidant properties of high-density lipoproteins (HDL) in animals. Whether this occurs in humans is unknown. Therefore, we examined the effect of a short-term elevation in dietary cholesterol and fat intake on HDL composition in healthy subjects.

METHODS AND RESULTS

In a randomized, crossover clinical trial, 14 healthy young volunteers followed a 14-day low-cholesterol/low-fat diet (LChF) and a 14-day isocaloric high-cholesterol/high-fat diet (HChF) in a random order. After each diet, we measured HDL concentrations of hydroxyeicosatetraenoic acids (HETE), hydroxyoctadecadienoic acids (HODE), and haptoglobin, as well as serum amyloid A (SAA) and paroxonase-1 activity (PON-1). HDL concentrations of 15-HETE (+254%, p = 0.002), 5-HETE (+116%, p = 0.004), 13-HODE (+102%, p = 0.049), and SAA levels (+75%, p = 0.007) were significantly higher after the HChF than after the LChF. Furthermore, haptoglobin was marginally increased (+32%, p = 0.091) while PON-1 activity was unaffected (-16%, p = 0.366) by the HChF.

CONCLUSION

In healthy subjects, a short-term elevation in dietary cholesterol and fat intake increases HDL lipid hydroperoxide content (15-HETE, 5-HETE, 13-HODE) and SAA levels, which are key features of dysfunctional HDL. This is the first study showing that a physiologic manipulation of dietary cholesterol and fat intake affects HDL lipidome and proteome in healthy subjects independently of weight changes.

CLINICAL TRIAL REGISTRATION

NCT02549144.

Plant sterols lower LDL-cholesterol and triglycerides in dyslipidemic individuals with or at risk of developing type 2 diabetes; a randomized, double-blind, placebo-controlled study

Background

Managing cardiovascular disease (CVD) risk factors, e.g., dyslipidemia in type-2 diabetes mellitus (T2DM) is critically important as CVD is the most common cause of death in T2DM patients. This study aimed to investigate the effect of plant sterols (PS) on lowering both elevated low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG).

Methods

In a double-blind, randomized, placebo-controlled, parallel study, 161 individuals at increased risk of and with established T2DM, consumed low-fat spreads without or with added PS (2 g/d) for 6 weeks after a 2-week run-in period. Increased risk of developing T2DM was defined by the Australian T2DM Risk Assessment Tool (AUSDRISK). Fasting serum/plasma total cholesterol (TC), LDL-C, TG, high-density lipoprotein cholesterol (HDL-C), glucose and insulin were measured at baseline and after 6 weeks. Effects on acute and chronic postprandial blood lipids, glucose and insulin were measured over 4-h in 39 individuals with T2DM following a mixed meal challenge without and with added 2 g/d PS at week 6. The study was registered at clinicaltrials.gov (NCT02288585).

Results

Hundred fifty-one individuals completed the study and 138 (57% men, 43% women; 44 with and 94 at risk of T2DM) were included in per protocol analysis. Baseline LDL-C and TG were 3.8 ± 1.0 and 2.5 ± 0.8 mmol/l, respectively. PS intake significantly lowered fasting LDL-C (−4.6%, 95%CI −1.2; −8.0; p = 0.009), TC (−4.2%, 95%CI −1.2; −7.1; p = 0.006) and TG (−8.3%, 95% −1.1, −15.0; p = 0.024) with no significant changes in HDL-C, glucose or insulin. Postprandial lipid (TG, TC, LDL-C, HDL-C, remnant cholesterol), glucose and insulin responses did not differ.

Conclusions

In individuals at risk of and with established T2DM and with elevated TG and LDL-C, 2 g/d of PS results in dual LDL-C plus TG lowering. Postprandial lipid or glycemic responses did not differ between PS and control treatment.

Effects of an Intermittent Grape-Seed Proanthocyanidin (GSPE) Treatment on a Cafeteria Diet Obesogenic Challenge in Rats

Obesity is highly associated with the pathologies included in the concept of the Metabolic Syndrome. Grape-seed proanthocyanins (GSPE) have showed very positive effects against all these metabolic disruptions; however, there is, as yet, no consensus about their effectiveness against an obesogenic challenge, such as a cafeteria diet. We determined the effectiveness of a dose of 500 mg GSPE/kg b.w. (body weight) against the obesogenic effects of a 17-week cafeteria diet, administered as a sub-chronic treatment, 10–15 days before, intermittently and at the end of the diet, in Wistar rats. Body weight, adiposity, indirect calorimetry and plasma parameters were analyzed. GSPE pre-treatment showed a long-lasting effect on body weight and adiposity that was maintained for seven weeks after the last dose. A corrective treatment was administered for the last two weeks of the cafeteria diet intervention; however, it did not effectively correct any of the parameters assessed. The most effective treatment was an intermittent GSPE dosage, administered every second week during the cafeteria diet. This limited body weight gain, adiposity and most lipotoxic effects. Our results support the administration of this GSPE dose, keeping an intermittent interval between dosages longer than every second week, to improve obesogenic disruptions produced by a cafeteria diet.

Effects of evolving lipid-lowering drugs on carbohydrate metabolism

The understanding that statins reduce but not eliminate the cardiovascular risk associated with disturbed lipid metabolism and the existence of forms of dyslipidemia that are unresponsive or only partially responsive to statins have led to the development of many novel lipid-lowering drugs. Accumulating evidence suggests that the interplay between carbohydrate and lipid metabolism is bidirectional. Thus, any intervention that affects lipid metabolism has the potential to influence the homeostasis of glucose. In this review we summarize the available data on the effects of the evolving lipid-lowering drugs on carbohydrate metabolism.

Reducing Cholesterol and Fat Intake Improves Glucose Tolerance by Enhancing β Cell Function in Nondiabetic Subjects

CONTEXT

A diet low in cholesterol and fat is commonly recommended to prevent metabolic and cardiovascular diseases; however, its effect on glucose tolerance is largely unknown.

OBJECTIVE

We examined whether and by which mechanisms a chronic reduction of cholesterol and fat intake affects glucose tolerance in nondiabetic individuals, independently of weight changes.

DESIGN AND PARTICIPANTS

In this crossover, randomized clinical trial, 30 healthy subjects, including 15 with family history of type 2 diabetes (T2D) (T2D offspring), underwent a 75-g oral glucose tolerance test (OGTT) after two 14-day isocaloric high-cholesterol, high-fat (HChF) or low-cholesterol, and low-fat (LChF) diets.

MAIN OUTCOME MEASURES

We evaluated changes in glucose tolerance, β cell function, insulin clearance, and insulin sensitivity by modeling plasma glucose, insulin, and C-peptide levels during the OGTT.

RESULTS

The shift from the HChF to the LChF diet was neutral on body weight but increased glucose tolerance (mean glucose -5%, P = 0.01) and three components of β cell function: glucose sensitivity (+17%, P = 0.01), insulin secretion at fasting glucose (+20%, P = 0.02), and potentiation (+19%, P = 0.03). The LChF diet improved insulin sensitivity (+7%, P = 0.048) only in T2D offspring, who tended to be more susceptible to the positive effect of the diet on glucose tolerance.

CONCLUSIONS

A chronic and isocaloric decrease in dietary cholesterol and fat intake improves glucose tolerance by diffusely ameliorating β cell function in nondiabetic subjects. Individuals genetically predisposed to develop T2D tend to be more susceptible to the positive effect of this dietary intervention on glucose tolerance and insulin sensitivity.

Different Dietary Patterns and New-Onset Diabetes Mellitus After Kidney Transplantation: A Cross-Sectional Study

OBJECTIVE

To verify the association of dietary patterns and dietary components with new-onset diabetes mellitus after transplantation (NODAT).

DESIGN

Cross-sectional study.

SUBJECTS

Adult kidney transplant recipients, without history of diabetes before transplantation, who received a kidney transplant and were followed up for at least 1 year. One hundred and sixteen subjects recruited between January 2013 and August 2014. Diagnosis of NODAT was established according to the American Diabetes Association criteria for type 2 diabetes.

METHODS

Demographic, clinical, and anthropometric data were collected. Dietary intake was assessed by food frequency questionnaire, administered by a registered dietitian. Dietary patterns were identified by cluster analysis. Chi-square test was used to verify the association between dietary patterns and NODAT. Total energy, fiber, and cholesterol intake were calculated. Consumption of macronutrients, carbohydrates, proteins, and fats (total fats and saturated, monounsaturated, polyunsaturated and trans fatty acids), were expressed in percentage of total energy intake.

RESULTS

Twenty-eight patients developed NODAT in the follow-up period. They presented higher body mass index and body fat percentage, as well as higher levels of triglycerides and urinary protein/creatinine ratio than the non-NODAT group. Two dietary patterns, I and II, were identified. Pattern II was characterized by higher intake of total, saturated, monounsaturated, and trans fats than pattern I. No association between the dietary patterns and NODAT was identified (P = .905), and there was no difference in the distribution of macronutrients, dietary fiber, and dietary cholesterol between the groups with and without NODAT.

CONCLUSION

Posttransplant dietary patterns were not different between patients with and without NODAT. Further larger and prospective studies are needed to evaluate a possible relationship between dietary components and NODAT incidence in kidney transplant recipients.