Opportunities to optimize lifestyle interventions in combination with glucagon-like peptide-1-based therapy.

Obesity is a chronic multi-system disease and major driver of type 2 diabetes and cardiometabolic disease. Nutritional interventions form the cornerstone of obesity and type 2 diabetes management. Some interventions such as Mediterranean diet can reduce incident cardiovascular disease, probably independently of weight loss. Weight loss of 5% or greater can improve many adiposity-related comorbidities. Although this can be achieved with lifestyle intervention, it is often difficult to sustain in the longer term due to adaptive endocrine changes. In recent years glucagon-like-peptide-1 receptor agonists (GLP-1RAs) have emerged as effective treatments for both type 2 diabetes and obesity. Newer GLP-1RAs can achieve average weight loss of 15% or greater and improve cardiometabolic health. There is heterogeneity in the weight loss response to GLP-1RAs, with a substantial number of patients unable to achieve 5% or greater weight. Weight loss, on average, is lower in older adults, male patients and people with type 2 diabetes. Mechanistic studies are needed to understand the aetiology of this variable response. Gastrointestinal side effects leading to medication discontinuation are a concern with GLP-1RA treatment, based on real-world data. With weight loss of 20% or higher with newer GLP-1RAs, nutritional deficiency and sarcopenia are also potential concerns. Lifestyle interventions that may potentially mitigate the side effects of GLP-1RA treatment and enhance weight loss are discussed here. The efficacy of such interventions awaits confirmation with well-designed randomized controlled trials.

Analyses of potential causal contributors to increased waist/hip ratio-associated cardiometabolic disease: A combined and sex-stratified Mendelian randomization study.

BACKGROUND: Increased waist/hip ratio (WHR) contributes to type 2 diabetes, fatty liver, dyslipidaemia, hypertension and coronary artery disease, with potential sex-differential effects. Postulated mediators include increased lipid flux, branched-chain amino acids, glycine and glycoprotein acetyl, but their relative contributions and sex-specific impact on WHR-associated cardiometabolic disease (CMD) are not established. METHODS: We therefore undertook combined and sex-stratified Mendelian randomization (MR) to assess the relative causal contributions of these mediators to WHR-associated CMD using summary statistics from the largest genome-wide association studies in European ancestries. RESULTS: In sex-combined MR analyses, increased WHR significantly reduces high-density lipoprotein (beta = -0.416, SE = 0.029, p = 2.87E-47), increases triglyceride (beta = 0.431, SE = 0.029, p = 1.87E-50), type 2 diabetes (odds ratio = 2.747, SE = 0.09, p = 26E-23), coronary artery disease (odds ratio = 1.478, SE = 0.045, p = 6.96E-18), alanine transaminase (beta = 0.062, SE = 0.004, p = 6.88E-67), and systolic (beta = 0.134, SE = 0.022, p = 7.81E-10) and diastolic blood pressure (beta = 0.162, SE = 0.026, p = 5.38E-10). Adjustment for the mediators attenuated WHR's effects, but the associations remained significant with concordant results in females. In males, a similar pattern was seen, except after adjusting for the effect of the ratio of monounsaturated fatty acid to total free fatty acid, the potential causal effect of WHR was no longer significant: high-density lipoprotein (beta = -0.117, SE = 0.069, p = .09) and triglyceride (beta = 0.051, SE = 0.068, p = .459). CONCLUSIONS: MR suggests WHR increases the risk of CMD independent of these mediators, with the exception of dyslipidaemia in males, which is largely driven by the monounsaturated fatty acid to total free fatty acid ratio.

Glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter-2 inhibitors for the treatment of diabetes mellitus in liver transplant recipients.

AIM: To investigate the efficacy and safety of glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 (SGLT2) inhibitors in liver transplant (LT) recipients with diabetes. METHODS: A single-centre, retrospective analysis of prospectively collected data from an LT recipient database (1990-2023) was conducted. We included adults with pre-existing diabetes and post-transplant diabetes, newly started on GLP-1RAs and/or SGLT2 inhibitors after LT. Metabolic and biochemical parameters and outcomes were collected for up to 12 months after starting medications and were compared to those in patients receiving dipeptidyl peptidase-4 (DPP-4) inhibitors. Statistical analysis included descriptive statistics and linear mixed models. RESULTS: We included participants on GLP-1RAs (n = 46), SGLT2 inhibitors (n = 87), combination therapy (n = 12), and a DPP-4 inhibitor comparator (n = 217). Both GLP-1RAs and combination therapy decreased mean glycated haemoglobin (HbA1c) levels, and combination therapy remained significant when adjusted for DPP-4 inhibitor treatment (-3.5%, 95% CI [-6.1, -0.95]; p = 0.0089) at 12 months. All three groups had significant decreases in mean weight and body mass index, but these remained significant in the GLP-1RA (-5.2 kg, 95% CI [-8.7, -1.7], p = 0.0039 and 1.99 kg/m2, 95% CI [-3.4, -0.6], p = 0.0048) and combination therapy groups (-5.4 kg, 95% CI [-10.5, -0.36], p = 0.04 and -3.4 kg/m2, 95% CI [-5.5, -1.3], p = 0.0015) when adjusted for DPP-4 inhibitor treatment at 12 months. Alanine aminotransferase levels decreased with GLP-1RA and combination therapy. There were two (1.4%) cases of graft rejection. CONCLUSION: We found that GLP-1RAs, SGLT2 inhibitors, and their combination, led to significant weight loss in LT recipients with diabetes. Combination therapy, in particular, lowered HbA1c and alanine aminotransferase levels compared to DPP-4 inhibitors. Further studies are needed to assess long-term safety and efficacy.

Genetically determined lean mass and dietary response.

Weight loss attenuates many obesity-related co-morbidities, but is difficult to sustain with dietary change. Dietary adherence, not macronutrient composition, is a better predictor of weight loss. Weight loss-induced endocrine changes promote food intake and increase energy efficiency, contributing to the difficulty with dietary adherence and weight regain. Macronutrient preference is partly genetically determined, suggesting that personalized dietary interventions might be more successful. In this issue, Li et al. report that a genetic risk score comprising the cumulative weighted effects of variants previously associated with increased lean mass is associated with increased satiety and weight loss 6 months after initiating a low- but not a high-fat diet. The effects were attenuated by 2 years. These findings suggest that genetic variants may influence response to specific diet. Further studies are necessary to assess whether genetically determined lean mass is causally associated with dietary response. Significant progress has recently been made in identifying additional genetic determinants of lean mass, which will enable such investigations and potentially inform future nutritional studies.

Obesity as a multisystem disease: Trends in obesity rates and obesity-related complications.

Obesity is a chronic multisystem disease associated with increased morbidity and mortality. The increasing prevalence of obesity makes it a major healthcare challenge across both developed and developing countries. Traditional measures such as body mass index do not always identify individuals at increased risk of comorbidities, yet continue to be used in deciding who qualifies for weight loss treatment. A better understanding of how obesity is associated with comorbidities, in particular non-metabolic conditions, is needed to identify individuals at risk in order to prioritize treatment. For metabolic disorders such as type 2 diabetes (T2D), weight loss can prevent T2D in individuals with prediabetes. It can improve and reverse T2D if weight loss is achieved early in the course of the disease. However, access to effective weight loss treatments is a significant barrier to improved health for people with obesity. In the present paper, we review the rising prevalence of obesity and why it should be classed as a multisystem disease. We will discuss potential mechanisms underlying its association with various comorbidities and how these respond to treatment, with a particular focus on cardiometabolic disease, malignancy and mental health.

Epileptic seizure detection: a comparative study between deep and traditional machine learning techniques.

Electroencephalography is the recording of brain electrical activities that can be used to diagnose brain seizure disorders. By identifying brain activity patterns and their correspondence between symptoms and diseases, it is possible to give an accurate diagnosis and appropriate drug therapy to patients. This work aims to categorize electroencephalography signals on different channels' recordings for classifying and predicting epileptic seizures. The collection of the electroencephalography recordings contained in the dataset attributes 179 information and 11,500 instances. Instances are of five categories, where one is the symptoms of epilepsy seizure. We have used traditional, ensemble methods and deep machine learning techniques highlighting their performance for the epilepsy seizure detection task. One dimensional convolutional neural network, ensemble machine learning techniques like bagging, boosting (AdaBoost, gradient boosting, and XG boosting), and stacking is implemented. Traditional machine learning techniques such as decision tree, random forest, extra tree, ridge classifier, logistic regression, K-Nearest Neighbor, Naive Bayes (gaussian), and Kernel Support Vector Machine (polynomial, gaussian) are used for classifying and predicting epilepsy seizure. Before using ensemble and traditional techniques, we have preprocessed the data set using the Karl Pearson coefficient of correlation to eliminate irrelevant attributes. Further accuracy of classification and prediction of the classifiers are manipulated using k-fold cross-validation methods and represent the Receiver Operating Characteristic Area Under the Curve for each classifier. After sorting and comparing algorithms, we have found the convolutional neural network and extra tree bagging classifiers to have better performance than all other ensemble and traditional classifiers.

Phenotypic and genetic analysis of an adult cohort with extreme obesity.

CONTEXT: Adult extreme obesity (EO) is a growing health concern. The prevalence of known obesity associated co-morbidities namely cardio-metabolic and neuro-psychiatric disease in EO is not fully established. The contribution of pathogenic genetic variants, previously implicated in early childhood onset obesity, to adult EO is also not established. OBJECTIVE: We undertook phenotypic and genetic analysis of adult patients with extreme obesity (EO, BMI > 50). Specifically, we assessed the prevalence of eating disorders, cardio-metabolic, and neuro-psychiatric disease and the presence of pathogenic variants in known monogenic obesity genes. DESIGN: A total of 55 patients with EO from a single site bariatric surgery referral program were assessed for the presence of eating disorders, cardio-metabolic, and neuro-psychiatric disease. The 54 obese (O) patients with a BMI < 50 from the same program were identified for phenotypic comparison. The 45 EO patients underwent whole exome sequencing to identify deleterious variants in known monogenic obesity genes. OUTCOMES: (1) Presence of eating disorders, cardio-metabolic, and neuro-psychiatric disease in EO compared to O. (2) Onset of obesity in the EO group. (3) Presence of deleterious variants in genes previously implicated in monogenic obesity in the EO group. RESULTS: The EO group had higher prevalence of lifetime neuro-psychiatric disease (67.3% vs. 37%, p = 0.001) and sleep apnea (74.6% vs. 51.9%, p = 0.01) but lower prevalence of type 2 diabetes (30.1% vs. 50%, p = 0.045) compared to O. There were no significant differences in binge eating, dyslipidemia, hypertension, and cardiac disease. In the EO group, we found previously unreported singleton variants in NTRK2 (pS667W, bio-informatically predicted to be deleterious) and BDNF (pE23K). No previously confirmed loss of function variants in monogenic obesity genes were found. CONCLUSIONS: Adults with EO have significantly increased prevalence of neuro-psychiatric disease and a possibly lower burden of type 2 diabetes compared to less obese patients. Known monogenic causes of obesity were not highly prevalent in this cohort. Further studies are warranted to confirm these preliminary findings.

Residual cardiovascular risk among people with diabetes.

Type 2 diabetes (T2D) is a growing health concern across both developed and developing countries. Cardiovascular disease (CVD) remains the major cause of increased mortality in this patient population. In recent years, effective low density lipoprotein lowering treatments and other risk reduction strategies have substantially reduced the risk of atherosclerotic CVD, yet patients with T2D continue to remain at increased risk for atherosclerotic CVD. Here, we will briefly review various proposed underlying mechanisms for this residual risk with a more in-depth focus on the potential role of triglyceride-rich lipoproteins in residual risk and potential avenues to target this pharmacologically.

Intranasal glucagon acutely increases energy expenditure without inducing hyperglycaemia in overweight/obese adults.

AIM: To assess the acute effects of 0.7 mg intranasal glucagon (ING) vs intranasal placebo (INP) on food intake and resting energy expenditure (REE). METHODS: A single-blind, crossover study was conducted in 19 overweight/obese adults (15 men, 4 women). REE was assessed by indirect calorimetry over 90 minutes, after which appetite was assessed using a visual analogue scale, and ad libitum caloric intake was assessed. Plasma samples were obtained at baseline and at 15-minute intervals post-treatment up to 90 minutes. RESULTS: ING increased total REE (INP 61.5 ± 1.2 kcal vs ING 69.4 ± 1.2 kcal; P = 0.027). There were no between-treatment differences in blood glucose, food intake and appetite. There were no adverse effects. CONCLUSION: ING acutely increases REE without increasing plasma glucose. Longer term studies with multiple daily dosing will establish whether this affects body weight.

Glucagon-like peptide-2 mobilizes lipids from the intestine by a systemic nitric oxide-independent mechanism.

AIM: To test the hypothesis that gut hormone glucagon-like peptide-2 (GLP-2) mobilizes intestinal triglyceride (TG) stores and stimulates chylomicron secretion by a nitric oxide (NO)-dependent mechanism in humans. METHODS: In a randomized, single-blind, cross-over study, 10 healthy male volunteers ingested a high-fat formula followed, 7 hours later, by one of three treatments: NO synthase inhibitor L-NG -monomethyl arginine acetate (L-NMMA) + GLP-2 analogue teduglutide, normal saline + teduglutide, or L-NMMA + placebo. TG in plasma and lipoprotein fractions were measured, along with measurement of blood flow in superior mesenteric and coeliac arteries using Doppler ultrasound in six participants. RESULTS: Teduglutide rapidly increased mesenteric blood flow and TG concentrations in plasma, in TG-rich lipoproteins, and most robustly in chylomicrons. L-NMMA significantly attenuated teduglutide-induced enhancement of mesenteric blood flow but not TG mobilization and chylomicron secretion. CONCLUSIONS: GLP-2 mobilization of TG stores and stimulation of chylomicron secretion from the small intestine appears to be independent of systemic NO in humans.

Effects of intranasal insulin on endogenous glucose production in insulin-resistant men.

The effects of intranasal insulin on the regulation of endogenous glucose production (EGP) in individuals with insulin resistance were assessed in a single-blind, crossover study. Overweight or obese insulin-resistant men (n = 7; body mass index 35.4 ± 4.4 kg/m2 , homeostatic model assessment of insulin resistance 5.6 ± 1.6) received intranasal spray of either 40 IU insulin lispro or placebo in 2 randomized visits. Acute systemic spillover of intranasal insulin into the circulation was matched with a 30-minute intravenous infusion of insulin lispro in the nasal placebo arm. EGP was assessed under conditions of a pancreatic clamp with a primed, constant infusion of glucose tracer. Under these experimental conditions, compared with placebo, intranasal administration of insulin did not significantly affect plasma glucose concentrations, EGP or glucose disposal in overweight/obese, insulin-resistant men, in contrast to our previous study, in which an equivalent dose of intranasal insulin significantly suppressed EGP in lean, insulin-sensitive men. Insulin resistance is probably associated with impairment in centrally mediated insulin suppression of EGP.

Evaluation of the specific effects of intranasal glucagon on glucose production and lipid concentration in healthy men during a pancreatic clamp.

AIM: To investigate the specific effects of intranasal glucagon (ING) on plasma glucose, endogenous glucose production (EGP) and lipid concentration. METHODS: We conducted a single-blind, randomized, crossover study at our academic investigation unit. Under pancreatic clamp conditions with tracer infusion, 1 mg ING or intranasal placebo (INP) was administered to 10 healthy men. As pilot studies showed that ING transiently increased plasma glucagon, we infused intravenous glucagon for 30 minutes along with INP to ensure similar plasma glucagon concentrations between interventions. The main outcome measures were plasma glucose, EGP, free fatty acid (FFA) and triglyceride (TG) concentrations. RESULTS: In the presence of similar plasma glucagon concentrations, the increase in plasma glucose under these experimental conditions was attenuated with ING (mean plasma glucose analysis of variance P < .001) with reduction in EGP (P = .027). No significant differences were seen in plasma FFA and TG concentrations. CONCLUSION: ING raises plasma glucose but this route of administration attenuates the gluco-stimulatory effect of glucagon by reducing EGP. This observation invites speculation about a potential central nervous system effect of glucagon, which requires further investigation. If ING is developed as a treatment for hypoglycaemia, this attenuated effect on plasma glucose should be taken into account.

Effects of Intranasal Insulin on Triglyceride-Rich Lipoprotein Particle Production in Healthy Men.

OBJECTIVE: Insulin administered directly into the brain acutely suppresses hepatic glucose production and triglyceride-rich lipoprotein (TRL) secretion in rodents. In addition, intranasally administered insulin, which selectively raises cerebrospinal fluid insulin concentration, suppresses hepatic glucose production in humans; however, its effect on TRL secretion in humans has not previously been examined. In this study, we examined whether intranasal insulin, administered at a dose that has previously been shown to suppress hepatic glucose production, modulates TRL particle secretion by the liver and intestine in humans. APPROACH AND RESULTS: Nine healthy, normolipidemic, and normoglycemic men participated in a study consisting of 2 randomized study arms. Subjects received intranasal lispro insulin (40 IU) or placebo. Because intranasal insulin results in a rapid and transient increase in systemic insulin concentration after administration, we matched systemic insulin concentrations in the 2 study arms by infusing lispro insulin intravenously for 30 minutes together with intranasal placebo administration. Apo (apolipoprotein) B100-containing (hepatically derived) and apoB48-containing (intestinally derived) TRL lipoprotein particle turnover were measured for the ensuing 10 hours under pancreatic clamp conditions and constant fed state, using stable isotope enrichment techniques and multicompartmental modeling. Under these experimental conditions, no significant effects of intranasal insulin versus placebo on TRL apoB100 or B48 concentrations, fractional catabolic rates, or production rates were observed. CONCLUSIONS: Insulin delivered intranasally at a dose that has been shown to raise cerebrospinal fluid insulin concentration and suppress hepatic glucose production does not affect TRL particle production by the liver and intestine in healthy men. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT03141827.

Intravenous Glucose Acutely Stimulates Intestinal Lipoprotein Secretion in Healthy Humans.

OBJECTIVE: Increased production of intestinal triglyceride-rich lipoproteins (TRLs) contributes to dyslipidemia and increased risk of atherosclerotic cardiovascular disease in insulin resistance and type 2 diabetes. We have previously demonstrated that enteral glucose enhances lipid-stimulated intestinal lipoprotein particle secretion. Here, we assessed whether glucose delivered systemically by intravenous infusion also enhances intestinal lipoprotein particle secretion in humans. APPROACH AND RESULTS: On 2 occasions, 4 to 6 weeks apart and in random order, 10 healthy men received a constant 15-hour intravenous infusion of either 20% glucose to induce hyperglycemia or normal saline as control. Production of TRL-apolipoprotein B48 (apoB48, primary outcomes) and apoB100 (secondary outcomes) was assessed during hourly liquid-mixed macronutrient formula ingestion with stable isotope enrichment and multicompartmental modeling, under pancreatic clamp conditions to limit perturbations in pancreatic hormones (insulin and glucagon) and growth hormone. Compared with saline infusion, glucose infusion induced both hyperglycemia and hyperinsulinemia, increased plasma triglyceride levels, and increased TRL-apoB48 concentration and production rate (P<0.05), without affecting TRL-apoB48 fractional catabolic rate. No significant effect of hyperglycemia on TRL-apoB100 concentration and kinetic parameters was observed. CONCLUSIONS: Short-term intravenous infusion of glucose stimulates intestinal lipoprotein production. Hyperglycemia may contribute to intestinal lipoprotein overproduction in type 2 diabetes. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02607839.

Effects of bariatric surgery on hepatic and intestinal lipoprotein particle metabolism.

PURPOSE OF REVIEW: Insulin resistance and type 2 diabetes, driven largely by obesity, are characterized by an increase in triglyceride-rich lipoproteins (TRLs) due to both reduced TRL clearance from the circulation and increased production by the liver (apoB-100 containing VLDLs) and intestine (apoB-48 containing chylomicrons). Bariatric surgery is the only treatment currently that leads to marked, sustained weight loss. Here, we will review the effects of bariatric surgery on circulating triglyceride/TRL and TRL production and clearance. RECENT FINDINGS: Bariatric surgery leads to a marked reduction in fasting and postprandial plasma triglyceride. Only one study to date has assessed TRL kinetics after bariatric surgery and has reported a reduction in TRL apoB-100 concentration (i.e. the number of VLDL particles) due to reduced production and increased clearance and reduced TRL apoB-48 concentration (the number of chylomicron particles) due to reduced production. Some bariatric surgery studies have reported no/weak correlation between weight loss and improvements in triglyceride/TRL, suggesting that as yet unidentified factors beyond weight loss may contribute to the marked changes in TRL that occur postbariatric surgery. SUMMARY: Available data suggest that bariatric surgery reduces triglyceride and intestinal and hepatic TRL production with increased clearance of hepatic TRL particles. These effects of bariatric surgery on TRL kinetics need to be confirmed with additional studies. Further studies are also needed to compare the effects of various bariatric surgery procedures on TRL kinetics and to elucidate underlying mechanisms.

New Insights into the Regulation of Chylomicron Production.

Dietary lipids are efficiently absorbed by the small intestine, incorporated into triglyceride-rich lipoproteins (chylomicrons), and transported in the circulation to various tissues. Intestinal lipid absorption and mobilization and chylomicron synthesis and secretion are highly regulated processes. Elevated chylomicron production rate contributes to the dyslipidemia seen in common metabolic disorders such as insulin-resistant states and type 2 diabetes and likely increases the risk for atherosclerosis seen in these conditions. An in-depth understanding of the regulation of chylomicron production may provide leads for the development of drugs that could be of therapeutic utility in the prevention of dyslipidemia and atherosclerosis. Chylomicron secretion is subject to regulation by various factors, including diet, body weight, genetic variants, hormones, nutraceuticals, medications, and emerging interventions such as bariatric surgical procedures. In this review we discuss the regulation of chylomicron production, mechanisms that underlie chylomicron dysregulation, and potential avenues for future research.

Glucagon-like peptide-2 regulates release of chylomicrons from the intestine.

BACKGROUND & AIMS: The intestine efficiently incorporates and rapidly secretes dietary fat as chylomicrons (lipoprotein particles comprising triglycerides, phospholipids, cholesterol, and proteins) that contain the apolipoprotein isoform apoB-48. The gut can store lipids for many hours after their ingestion, and release them in chylomicrons in response to oral glucose, sham feeding, or unidentified stimuli. The gut hormone glucagon-like peptide-2 (GLP-2) facilitates intestinal absorption of lipids, but its role in chylomicron secretion in human beings is unknown. METHODS: We performed a randomized, single-blind, cross-over study, with 2 study visits 4 weeks apart, to assess the effects of GLP-2 administration on triglyceride-rich lipoprotein (TRL) apoB-48 in 6 healthy men compared with placebo. Subjects underwent constant intraduodenal feeding, with a pancreatic clamp and primed constant infusion of deuterated leucine. In a separate randomized, single-blind, cross-over validation study, 6 additional healthy men ingested a high-fat meal containing retinyl palmitate and were given either GLP-2 or placebo 7 hours later with measurement of TRL triglyceride, TRL retinyl palmitate, and TRL apoB-48 levels. RESULTS: GLP-2 administration resulted in a rapid (within 30 minutes) and transient increase in the concentration of TRL apoB-48, compared with placebo (P = .03). Mathematic modeling of stable isotope enrichment and the mass of the TRL apoB-48 suggested that the increase resulted from the release of stored, presynthesized apoB-48 from the gut. In the validation study, administration of GLP-2 at 7 hours after the meal, in the absence of additional food intake, robustly increased levels of TRL triglycerides (P = .007), TRL retinyl palmitate (P = .002), and TRL apoB-48 (P = .04) compared with placebo. CONCLUSIONS: Administration of GLP-2 to men causes the release of chylomicrons that comprise previously synthesized and stored apoB-48 and lipids. This transiently increases TRL apoB-48 levels compared with placebo. Clinical trials number at www.clinicaltrials.gov: NCT 01958775.

Dietary carbohydrates and intestinal lipoprotein production.

PURPOSE OF REVIEW: To review new evidence that dietary monosaccharides enhance intestinal chylomicron secretion. RECENT FINDINGS: There is abundant evidence linking diets that are high in carbohydrate content with hypertriglyceridemia. In addition, epidemiological studies reveal that the increase in dietary sugars and refined carbohydrates are associated with the rising prevalence of the metabolic syndrome and type 2 diabetes. Association studies, however, cannot prove causation. Mechanistic studies to date have focused on the link between carbohydrate ingestion and hepatic very low-density lipoprotein metabolism, with very little appreciation that dietary carbohydrates may also regulate intestinal lipid absorption and chylomicron secretion. We have recently studied this phenomenon in healthy humans and have shown that both glucose and fructose, infused concomitantly with a lipid emulsion directly into the duodenum and under conditions of a pancreatic clamp, stimulate chylomicron particle secretion. There are a paucity of data regarding the cellular and molecular mechanisms of this effect, which remains largely unknown and a matter of speculation. SUMMARY: Sugar in the diet enhances dietary fat absorption and chylomicron secretion. Whether this phenomenon contributes quantitatively to the well described hypertriglyceridemia that occurs with diets high in carbohydrate and low in fat requires further investigation, as does the underlying cellular mechanism. A thorough understanding of this phenomenon could provide useful information to optimize dietary guidelines.

Novel role of enteral monosaccharides in intestinal lipoprotein production in healthy humans.

OBJECTIVE: Overproduction of triglyceride-rich lipoproteins (TRLs) by liver and intestine contributes to hypertriglyceridemia and may increase cardiovascular risk. Dietary carbohydrates, especially fructose, have been shown to amplify postprandial lipemia but little is known about its effect on intestinal TRL particle production. Here, we examined intestinal and hepatic TRL particle production in response to enteral glucose or fructose in the presence of enteral lipid. APPROACH AND RESULTS: In 2 randomized studies, 4 to 6 weeks apart, 7 healthy male subjects received intraduodenal infusion of Intralipid plus saline or glucose. TRL-apolipoprotein (apo) B48 and apoB100 kinetics were assessed under pancreatic clamp conditions. In a separate study of another 7 subjects under similar conditions, glucose was replaced by fructose. When coinfused with Intralipid into the duodenum, glucose markedly stimulated TRL-apoB48 production (P<0.01), with a concomitant moderate increase in fractional clearance (P<0.05), resulting in net elevation of TRL-apoB48 concentration. TRL-apoB100 concentration, fractional clearance, and production were not significantly affected by glucose. When glucose was replaced by fructose, both TRL-apoB100 and apoB48 production (P<0.05), but not fractional clearance, were enhanced compared with Intralipid alone. CONCLUSIONS: These results reveal a novel role of monosaccharides in acutely enhancing intestinal lipoprotein particle production, thereby aggravating hyperlipidemia.

High-dose resveratrol treatment for 2 weeks inhibits intestinal and hepatic lipoprotein production in overweight/obese men.

OBJECTIVE: Overproduction of hepatic apolipoprotein B (apoB)-100 containing very low-density lipoprotein particles and intestinal apoB-48 containing chylomicrons contributes to hypertriglyceridemia seen in conditions such as obesity and insulin resistance. Some, but not all, preclinical and clinical studies have demonstrated that the polyphenol resveratrol ameliorates insulin resistance and hypertriglyceridemia. Here, we assessed intestinal and hepatic lipoprotein turnover, in humans, after 2 weeks of treatment with resveratrol (1000 mg daily for week 1 followed by 2000 mg daily for week 2) or placebo. APPROACH AND RESULTS: Eight overweight or obese individuals with mild hypertriglyceridemia were studied on 2 occasions, 4 to 6 weeks apart, after treatment with resveratrol or placebo in a randomized, double-blinded, crossover study. Steady-state lipoprotein kinetics was assessed in a constant fed state with a primed, constant infusion of deuterated leucine. Resveratrol treatment did not significantly affect insulin sensitivity (homeostasis model of assessment of insulin resistance), fasting or fed plasma triglyceride concentration. Resveratrol reduced apoB-48 production rate by 22% (P=0.007) with no significant effect on fractional catabolic rate. Resveratrol reduced apoB-100 production rate by 27% (P=0.02) and fractional catabolic rate by 26% (P=0.04). CONCLUSIONS: These results indicate that 2 weeks of high-dose resveratrol reduces intestinal and hepatic lipoprotein particle production. Long-term studies are needed to evaluate the potential clinical benefits of resveratrol in patients with hypertriglyceridemia, who have increased concentrations of triglyceride-rich lipoprotein apoB-100 and apoB-48. CLINICAL TRIAL REGISTRATION URL: www.clinicaltrials.gov. Unique identifier: NCT01451918.