Genetic Studies of Metabolomics Change After a Liquid Meal Illuminate Novel Pathways for Glucose and Lipid Metabolism

Humans spend the greater part of the day in a postprandial state. However, the genetic basis of postprandial blood measures is relatively uncharted territory. We examined the genetics of variation in concentrations of postprandial metabolites (t = 150 min) in response to a liquid mixed meal through genome-wide association studies (GWAS) performed in the Netherlands Epidemiology of Obesity (NEO) study (n = 5,705). The metabolite response GWAS identified an association between glucose change and rs10830963:G in the melatonin receptor 1B (β [SE] -0.23 [0.03], P = 2.15 × 10^-19). In addition, the ANKRD55 locus led by rs458741:C showed strong associations with extremely large VLDL (XXLVLDL) particle response (XXLVLDL total cholesterol: β [SE] 0.17 [0.03], P = 5.76 × 10^-10; XXLVLDL cholesterol ester: β [SE] 0.17 [0.03], P = 9.74 × 10^-10), which also revealed strong associations with body composition and diabetes in the UK Biobank (P < 5 × 10^-8). Furthermore, the associations between XXLVLDL response and insulinogenic index, HOMA-β, Matsuda insulin sensitivity index, and HbA_1c in the NEO study implied the role of chylomicron synthesis in diabetes (with false discovery rate-corrected q <0.05). To conclude, genetic studies of metabolomics change after a liquid meal illuminate novel pathways for glucose and lipid metabolism. Further studies are warranted to corroborate biological pathways of the ANKRD55 locus underlying diabetes.

Genomics of Postprandial Lipidomics in the Genetics of Lipid-Lowering Drugs and Diet Network Study

Postprandial lipemia (PPL) is an important risk factor for cardiovascular disease. Inter-individual variation in the dietary response to a meal is known to be influenced by genetic factors, yet genes that dictate variation in postprandial lipids are not completely characterized. Genetic studies of the plasma lipidome can help to better understand postprandial metabolism by isolating lipid molecular species which are more closely related to the genome. We measured the plasma lipidome at fasting and 6 h after a standardized high-fat meal in 668 participants from the Genetics of Lipid-Lowering Drugs and Diet Network study (GOLDN) using ultra-performance liquid chromatography coupled to (quadrupole) time-of-flight mass spectrometry. A total of 413 unique lipids were identified. Heritable and responsive lipid species were examined for association with single-nucleotide polymorphisms (SNPs) genotyped on the Affymetrix 6.0 array. The most statistically significant SNP findings were replicated in the Amish Heredity and Phenotype Intervention (HAPI) Heart Study. We further followed up findings from GOLDN with a regional analysis of cytosine-phosphate-guanine (CpGs) sites measured on the Illumina HumanMethylation450 array. A total of 132 lipids were both responsive to the meal challenge and heritable in the GOLDN study. After correction for multiple testing of 132 lipids (α = 5 × 10-8/132 = 4 × 10-10), no SNP was statistically significantly associated with any lipid response. Four SNPs in the region of a known lipid locus (fatty acid desaturase 1 and 2/FADS1 and FADS2) on chromosome 11 had p < 8.0 × 10-7 for arachidonic acid FA(20:4). Those SNPs replicated in HAPI Heart with p < 3.3 × 10-3. CpGs around the FADS1/2 region were associated with arachidonic acid and the relationship of one SNP was partially mediated by a CpG (p = 0.005). Both SNPs and CpGs from the fatty acid desaturase region on chromosome 11 contribute jointly and independently to the diet response to a high-fat meal.

Changes in corticotropin releasing factor system transcript levels in relation to feeding condition in Acipenser dabryanus

CRF system, structural conservation, has an association with feeding regulation in mammals. However, mammals and fish have different physiological mechanisms, the potential role of CRF system for feeding regulation in teleost fish are most unknown. To better explore possible feeding mechanisms of CRF system in Acipenser dabryanus, the gene expression patterns of CRF system have been investigated after different energy status. CRF and two receptors have been studied in Acipenser dabryanus in previous study, thus, four components of CRF system (UI, UCN2, UCN3 and CRF-BP) have been studied in this study. Results showed post-prandial increased UCNs mRNA expressions, and 10 days fasting decreased UCNs mRNA expressions, and the mRNA abundance of CRF-BP has no significant differences. Above, this study confirmed the CRF system has potential role for feeding regulation in Acipenser dabryanus.

Postprandial remodeling of high-density lipoprotein following high saturated fat and high carbohydrate meals

BACKGROUND

Humans spend most of the time in the postprandial state, yet most knowledge about high-density lipoproteins (HDL) derives from the fasted state. HDL protein and lipid cargo mediate HDL's antiatherogenic effects, but whether these HDL constituents change in the postprandial state and are affected by dietary macronutrients remains unknown.

OBJECTIVES

This study aimed to assess changes in HDL protein and lipid composition after the consumption of a high-carbohydrate or high saturated fat (HSF) meal.

METHODS

We isolated HDL from plasma collected during a randomized, cross-over study of metabolically healthy subjects. Subjects consumed isocaloric meals consisting predominantly of either carbohydrate or fat. At baseline and at 3 and 6 hours postprandial, we quantified HDL protein and lipid composition by liquid chromatography-mass spectrometry.

RESULTS

A total of 15 subjects were included (60% female, aged 34 ± 15 years, body mass index: 24.1 ± 2.7 kg/m2). Consumption of the HSF meal led to HDL enrichment in total lipid (P = .006), triglyceride (P = .02), and phospholipid (P = .008) content and a corresponding depletion in protein content. After the HSF meal, 16 of the 25 measured phosphatidylcholine species significantly increased in abundance (P values range from .027 to <.001), along with several sphingolipids including ceramides (P < .004), lactosylceramide (P = .023), and sphingomyelin-14 (P = .013). Enrichment in apolipoprotein A-I (P = .001) was the only significant change in HDL protein composition after the HSF meal. The high-carbohydrate meal conferred only minimal changes in HDL composition.

CONCLUSION

Meal macronutrient content acutely affects HDL composition in the postprandial state, with the HSF meal resulting in enrichment of HDL phospholipid content with possible consequences for HDL function.

Insulin signaling and reduced glucocorticoid receptor activity attenuate postprandial gene expression in liver

Hepatic circadian gene transcription is tightly coupled to feeding behavior, which has a profound impact on metabolic disorders associated with diet-induced obesity. Here, we describe a genomics approach to uncover mechanisms controlling hepatic postprandial gene expression. Combined transcriptomic and cistromic analysis identified hundreds of circadian-regulated genes and enhancers controlled by feeding. Postprandial suppression of enhancer activity was associated with reduced glucocorticoid receptor (GR) and Forkhead box O1 (FOXO1) occupancy of chromatin correlating with reduced serum corticosterone levels and increased serum insulin levels. Despite substantial co-occupancy of feeding-regulated enhancers by GR and FOXO1, selective disruption of corticosteroid and/or insulin signaling resulted in dysregulation of specific postprandial regulated gene programs. In combination, these signaling pathways operate a major part of the genes suppressed by feeding. Importantly, the feeding response was disrupted in diet-induced obese animals, which was associated with dysregulation of several corticosteroid- and insulin-regulated genes, providing mechanistic insights to dysregulated circadian gene transcription associated with obesity.

The liver is an essential organ regulating metabolic homeostasis in response to fluctuations of metabolites induced by daily rhythms of food intake. Homeostasis is maintained by precise dynamic regulation of signaling pathways controlling a wealth of enzymatic reactions involving lipid, bile acid, amino acid and glucose synthesis, storage, and redistribution in hepatocytes. Precise temporal expression of hepatic enzymes is crucial for metabolic homeostasis; a major part of circadian hepatic protein expression is regulated by precisely timed gene transcription. Here, we use a genomics approach to identify genes and regulatory regions of the genome involved in feeding-regulated gene expression. We find that transcription factors acting downstream of glucocorticoid and insulin signaling are enriched at regulatory regions repressed by feeding. Importantly, insulin and glucocorticoid signaling operate to cooperatively control the majority of feeding-mediated gene repression, and these signaling pathways are dysregulated in diet-induced obesity impacting dynamic hepatic gene expression.

Circulating miRNA measurements are reflective of cholesterol-based changes in rainbow trout (Oncorhynchus mykiss)

MicroRNAs (miRNAs) are a class of small non-coding RNAs which are known to posttranscriptionally regulate the expression of most genes in both animals and plants. Meanwhile, studies have shown that numbers of miRNAs are present in body fluids including the plasma. Despite the mode of action of these circulating miRNAs still remains unknown, they have been found to be promising biomarkers for disease diagnosis, prognosis and response to treatment. In order to evaluate the potential of miRNAs as non-invasive biomarkers in aquaculture, a time-course experiment was implemented to investigate the postprandial regulation of miRNAs levels in liver and plasma as well as the hepatic expression of genes involved in cholesterol metabolism. We showed that miR-1, miR-33a, miR-122, miR-128 and miR-223 were expressed in the liver of rainbow trout and present at detectable level in the plasma. We also demonstrated that hepatic expression of miR-1, miR-122 and miR-128 were regulated by feed intake and reached their highest levels 12 hours after the meal. Interestingly, we observed that circulating levels of miR-128 and miR-223 are subjected to postprandial regulations similar to that observed in their hepatic counterparts. Statistical correlations were observed between liver and plasma for miR-128 and miR-223 and between hepatic and circulating miR-122, miR-128 and miR-223 and expression of genes related to cholesterol synthesis and efflux or glucose phosphorylation. These results demonstrated that circulating miR-122, miR-128 and miR-223 are potential biomarkers of cholesterol metabolism in rainbow trout.

Modulation of Drosophila post-feeding physiology and behavior by the neuropeptide leucokinin

Behavior and physiology are orchestrated by neuropeptides acting as central neuromodulators and circulating hormones. An outstanding question is how these neuropeptides function to coordinate complex and competing behaviors. In Drosophila, the neuropeptide leucokinin (LK) modulates diverse functions, but mechanisms underlying these complex interactions remain poorly understood. As a first step towards understanding these mechanisms, we delineated LK circuitry that governs various aspects of post-feeding physiology and behavior. We found that impaired LK signaling in Lk and Lk receptor (Lkr) mutants affects diverse but coordinated processes, including regulation of stress, water homeostasis, feeding, locomotor activity, and metabolic rate. Next, we sought to define the populations of LK neurons that contribute to the different aspects of this physiology. We find that the calcium activity in abdominal ganglia LK neurons (ABLKs), but not in the two sets of brain neurons, increases specifically following water consumption, suggesting that ABLKs regulate water homeostasis and its associated physiology. To identify targets of LK peptide, we mapped the distribution of Lkr expression, mined a brain single-cell transcriptome dataset for genes coexpressed with Lkr, and identified synaptic partners of LK neurons. Lkr expression in the brain insulin-producing cells (IPCs), gut, renal tubules and chemosensory cells, correlates well with regulatory roles detected in the Lk and Lkr mutants. Furthermore, these mutants and flies with targeted knockdown of Lkr in IPCs displayed altered expression of insulin-like peptides (DILPs) and transcripts in IPCs and increased starvation resistance. Thus, some effects of LK signaling appear to occur via DILP action. Collectively, our data suggest that the three sets of LK neurons have different targets, but modulate the establishment of post-prandial homeostasis by regulating distinct physiological processes and behaviors such as diuresis, metabolism, organismal activity and insulin signaling. These findings provide a platform for investigating feeding-related neuroendocrine regulation of vital behavior and physiology.

Modulation of the peripheral blood transcriptome by the ingestion of probiotic yoghurt and acidified milk in healthy, young men

The metabolic health benefits of fermented milks have already been investigated using clinical biomarkers but the development of transcriptomic analytics in blood offers an alternative approach that may help to sensitively characterise such effects. We aimed to assess the effects of probiotic yoghurt intake, compared to non-fermented, acidified milk intake, on clinical biomarkers and gene expression in peripheral blood. To this end, a randomised, crossover study was conducted in fourteen healthy, young men to test the two dairy products. For a subset of seven subjects, RNA sequencing was used to measure gene expression in blood collected during postprandial tests and after two weeks daily intake. We found that the postprandial response in insulin was different for probiotic yoghurt as compared to that of acidified milk. Moreover changes in several clinical biomarkers were associated with changes in the expression of genes representing six metabolic genesets. Assessment of the postprandial effects of each dairy product on gene expression by geneset enrichment analysis revealed significant, similar modulation of inflammatory and glycolytic genes after both probiotic yoghurt and acidified milk intake, although distinct kinetic characteristics of the modulation differentiated the dairy products. The aryl hydrocarbon receptor was a major contributor to the down-regulation of the inflammatory genesets and was also positively associated with changes in circulating insulin at 2h after yoghurt intake (p = 0.05). Daily intake of the dairy products showed little effect on the fasting blood transcriptome. Probiotic yoghurt and acidified milk appear to affect similar gene pathways during the postprandial phase but differences in the timing and the extent of this modulation may lead to different physiological consequences. The functional relevance of these differences in gene expression is supported by their associations with circulating biomarkers.

Influences of Breakfast on Clock Gene Expression and Postprandial Glycemia in Healthy Individuals and Individuals With Diabetes: A Randomized Clinical Trial

OBJECTIVE

The circadian clock regulates glucose metabolism by mediating the activity of metabolic enzymes, hormones, and transport systems. Breakfast skipping and night eating have been associated with high HbA1c and postprandial hyperglycemia after lunch and dinner. Our aim was to explore the acute effect of breakfast consumption or omission on glucose homeostasis and clock gene expression in healthy individuals and individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a crossover design, 18 healthy volunteers and 18 volunteers with 14.5 ± 1.5 years diabetes, BMI 30.7 ± 1.1 kg/m2, and HbA1c 7.6 ± 0.1% (59.6 ± 0.8 mmol/mol) were randomly assigned to a test day with breakfast and lunch (YesB) and a test day with only lunch (NoB). Postprandial clock and clock-controlled gene expression, plasma glucose, insulin, intact glucagon-like peptide 1 (iGLP-1), and dipeptidyl peptidase IV (DPP-IV) plasma activity were assessed after breakfast and lunch.

RESULTS

In healthy individuals, the expression level of Per1, Cry1, Rorα, and Sirt1 was lower (P < 0.05) but Clock was higher (P < 0.05) after breakfast. In contrast, in individuals with type 2 diabetes, Per1, Per2, and Sirt1 only slightly, but significantly, decreased and Rorα increased (P < 0.05) after breakfast. In healthy individuals, the expression level of Bmal1, Rorα, and Sirt1 was higher (P < 0.05) after lunch on YesB day, whereas the other clock genes remained unchanged. In individuals with type 2 diabetes, Bmal1, Per1, Per2, Rev-erbα, and Ampk increased (P < 0.05) after lunch on the YesB day. Omission of breakfast altered clock and metabolic gene expression in both healthy and individuals with type 2 diabetes.

CONCLUSIONS

Breakfast consumption acutely affects clock and clock-controlled gene expression leading to normal oscillation. Breakfast skipping adversely affects clock and clock-controlled gene expression and is correlated with increased postprandial glycemic response in both healthy individuals and individuals with diabetes.

The Effect of PCSK9 Loss-of-Function Variants on the Postprandial Lipid and ApoB-Lipoprotein Response

CONTEXT

Proprotein convertase subtilisin kexin 9 (PCSK9) mediates degradation of the low-density lipoprotein receptor (LDLR), thereby increasing plasma low-density lipoprotein cholesterol (LDL-C). Variations in the PCSK9 gene associated with loss of function (LOF) of PCSK9 result in greater expression of hepatic LDLR, lower concentrations of LDL-C, and protection from cardiovascular disease (CVD). Apolipoprotein-B (apoB) remnants also contribute to CVD risk and are similarly cleared by the LDLR. We hypothesized that PCSK9-LOF carriers would have lower fasting and postprandial remnant lipoproteins on top of lower LDL-C.

OBJECTIVE

To compare fasting and postprandial concentrations of triglycerides (TGs), total apoB, and apoB48 as indicators of remnant lipoprotein metabolism in PCSK9-LOF carriers with those with no PCSK9 variants.

DESIGN

Case-control, metabolic study.

SETTING

Clinical Research Center of The Ottawa Hospital.

PARTICIPANTS

Persons with one or more copies of the L10ins/A53V and/or I474V and/or R46L PCSK9 variant and persons with no PCSK9 variants.

INTERVENTION

Oral fat tolerance test.

MAIN OUTCOMES MEASURES

Fasting and postprandial plasma TG, apoB48, total apoB, total cholesterol, and PCSK9 were measured at 0, 2, 4, and 6 hours after an oral fat load.

RESULTS

Participants with PCSK9-LOF variants (n = 22) had reduced fasting LDL-C (-14%) as well as lower fasting TG (-21%) compared with noncarrier controls (n = 23). LOF variants also had reduced postprandial total apoB (-17%), apoB48 (-23%), and TG (-18%). Postprandial PCSK9 declined in both groups (-24% vs -16%, respectively).

CONCLUSIONS

Participants carrying PCSK9-LOF variants had attenuated levels of fasting and postprandial TG, apoB48, and total apoB. This may confer protection from CVD and further validate the use of PCSK9 inhibitors to lower CVD risk.

Evidence that ghrelin may be associated with the food intake of gibel carp (Carassius auratus gibelio)

Ghrelin, a non-amidated peptide hormone, is a potent anorectic neuropeptide implicated in feeding regulation in mammals and non-mammalian vertebrates. However, the involvement of ghrelin in the feeding behavior of teleosts has not been well understood. To better understand the role of ghrelin in the regulation of appetite in fish, in this study, we cloned the cDNAs encoding ghrelin and investigated their mRNA distributions in gibel carp tissues. We also assessed the effects of different nutritional status on ghrelin mRNA abundance. Ghrelin mRNAs were ubiquitously expressed in ten tissues (intestine, liver, brain, mesonephron, head kidney, spleen, skin, heart, muscle, gill and pituitary gland), and relatively high expression levels were detected in the gut. Postprandial studies analysis revealed a significant postprandial decrease in ghrelin mRNA expression in the gut (1 and 3 h after the regular feeding time). In addition, ghrelin mRNA expression in the gut significantly increased at day 7 after fasting and declined sharply after refeeding, which suggested that ghrelin might be involved in the regulation of appetite in gibel carp. Overall, our result provides basis for further investigation into the regulation of feeding in gibel carp.

The anti-adipogenic effect of peripheral blood mononuclear cells is absent with PCSK9 loss-of-function variants

OBJECTIVE

To determine the effect of (1) an oral fat load and (2) pro-protein convertase subtilisin/kexin type (PCSK) 9 loss-of-function (LOF) variant status on the ability of peripheral blood mononuclear cells (PBMC) to inhibit human adipogenesis.

METHODS

PBMC from subjects with one or more PCSK9 LOF variants versus non-variant controls were compared in the fasting state and after an oral fat load.

RESULTS

Fasting triglyceride (TG) levels were lower in the LOF variant versus non-variant group but rose to the same level after the oral fat load. Conditioned medium from PBMC was obtained in fasting (PBMC-CM-F) and 4-h postprandial (PBMC-CM-PP) states. PBMC-CM-PP from non-variant controls inhibited adipogenesis of human preadipocytes more than did PBMC-CM-F. In contrast, PBMC-CM-F or -PP from PCSK9 LOF variant subjects had no effect on adipogenesis. After the oral fat load, PBMC from PCSK9 LOF variant subjects showed significant increases in mRNA levels of interleukin-1β, tumor necrosis factor-α, sterol regulatory element binding protein-1c, CD36, and monocyte chemoattractant protein-1 (MCP-1), only MCP-1 mRNA levels increased in PBMC from non-variant controls.

CONCLUSIONS

The absence of anti-adipogenic action of PBMC from PCSK9 LOF variant subjects points to a novel role for PCSK9 in PBMC-adipose cell interactions.

Postprandial kinetics of gene expression of proteins involved in the digestive process in rainbow trout (O. mykiss) and impact of diet composition

The impact of increased incorporation of plant ingredients on diets for rainbow trout was evaluated in terms of gene expression of gastric (gastric lipase, pepsinogen) and intestinal (prolidase, maltase, phospholipase A2) digestive enzymes and nutrient transporters (peptide and glucose transporters), as well as of postprandial levels of plasma glucose, triglycerides and total free amino acids. For that purpose, trout alevins were fed from the start of exogenous feeding one of three different experimental diets: a diet rich in fish meal and fish oil (FM-FO), a plant-based diet (noFM-noFO) totally free from fish meal and fish oil, but containing plant ingredients and a Mixed diet (Mixed) intermediate between the FM-FO and noFM-noFO diets. After 16 months of rearing, all fish were left unfed for 72 h and then given a single meal to satiation. Blood, stomach and anterior intestine were sampled before the meal and at 2, 6 and 12 h after this meal. The postprandial kinetics of gene expression of gastric and intestinal digestive enzymes and nutrient transporters were then followed in trout fed the FM-FO diet. The postprandial profiles showed that the expression of almost all genes studied was stimulated by the presence of nutrients in the digestive tract of trout, but the timing (appearance of peaks) varied between genes. Based on these data, we have focused on the molecular response to dietary factors in the stomach and the intestine at 6 and 12 h after feeding, respectively. The reduction in FM and FO levels of dietary incorporation induced a significant decrease in the gene expression of gastric lipase, GLUT2 and PEPT1. The plasma glucose and triglycerides levels were also reduced in trout fed the noFM-noFO diet. Consequently, the present study suggests a decrease in digestive capacities in trout fed a diet rich in plant ingredients.

Genome-wide association study of triglyceride response to a high-fat meal among participants of the NHLBI Genetics of Lipid Lowering Drugs and Diet Network (GOLDN)

OBJECTIVE

The triglyceride (TG) response to a high-fat meal (postprandial lipemia, PPL) affects cardiovascular disease risk and is influenced by genes and environment. Genes involved in lipid metabolism have dominated genetic studies of PPL TG response. We sought to elucidate common genetic variants through a genome-wide association (GWA) study in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN).

METHODS

The GOLDN GWAS discovery sample consisted of 872 participants within families of European ancestry. Genotypes for 2,543,887 variants were measured or imputed from HapMap. Replication of our top results was performed in the Heredity and Phenotype Intervention (HAPI) Heart Study (n = 843). PPL TG response phenotypes were constructed from plasma TG measured at baseline (fasting, 0 hour), 3.5 and 6 hours after a high-fat meal, using a random coefficient regression model. Association analyses were adjusted for covariates and principal components, as necessary, in a linear mixed model using the kinship matrix; additional models further adjusted for fasting TG were also performed. Meta-analysis of the discovery and replication studies (n = 1715) was performed on the top SNPs from GOLDN.

RESULTS

GOLDN revealed 111 suggestive (p < 1E-05) associations, with two SNPs meeting GWA significance level (p < 5E-08). Of the two significant SNPs, rs964184 demonstrated evidence of replication (p = 1.20E-03) in the HAPI Heart Study and in a joint analysis, was GWA significant (p = 1.26E-09). Rs964184 has been associated with fasting lipids (TG and HDL) and is near ZPR1 (formerly ZNF259), close to the APOA1/C3/A4/A5 cluster. This association was attenuated upon additional adjustment for fasting TG.

CONCLUSION

This is the first report of a genome-wide significant association with replication for a novel phenotype, namely PPL TG response. Future investigation into response phenotypes is warranted using pathway analyses, or newer genetic technologies such as metabolomics.

Postprandial molecular responses in the liver of the barramundi, Lates calcarifer

The regulation of gene expression by nutrients is an important mechanism governing energy storage and growth in most animals, including fish. At present, very few genes that regulate intermediary metabolism have been identified in barramundi, nor is there any understanding of their nutritional regulation. In this study, a partial barramundi liver transcriptome was assembled from next-generation sequencing data and published barramundi EST sequences. A large number of putative metabolism genes were identified in barramundi, and the changes in the expression of 24 key metabolic regulators of nutritional pathways were investigated in barramundi liver over a time series immediately after a meal of a nutritionally optimised diet for this species. Plasma glucose and free amino acid levels showed a mild postprandial elevation which peaked 2 h after feeding, and had returned to basal levels within 4 or 8 h, respectively. Significant activation or repression of metabolic nuclear receptor regulator genes were observed, in combination with activation of glycolytic and lipogenic pathways, repression of the final step of gluconeogenesis and activation of the Akt-mTOR pathway. Strong correlations were identified between a number of different metabolic genes, and the coordinated co-regulation of these genes may underlie the ability of this fish to utilise dietary nutrients. Overall, these data clearly demonstrate a number of unique postprandial responses in barramundi compared with other fish species and provide a critical step in defining the response to different dietary nutrient sources.

Genetic variation in SULF2 is associated with postprandial clearance of triglyceride-rich remnant particles and triglyceride levels in healthy subjects

Context

Nonfasting (postprandial) triglyceride concentrations have emerged as a clinically significant cardiovascular disease risk factor that results from accumulation of remnant triglyceride-rich lipoproteins (TRLs) in the circulation. The remnant TRLs are cleared from the circulation by hepatic uptake, but the specific mechanisms involved are unclear. The syndecan-1 heparan sulfate proteoglycan (HSPG) pathway is important for the hepatic clearance of remnant TRLs in mice, but its relevance in humans is unclear.

Objective

We sought to determine whether polymorphisms of the genes responsible for HSPG assembly and disassembly contribute to atherogenic dyslipoproteinemias in humans.

Patients And Design

We performed an oral fat load in 68 healthy subjects. Lipoproteins (chylomicrons and very low density lipoproteins 1 and 2) were isolated from blood, and the area under curve and incremental area under curve for postprandial variables were calculated. Single nucleotide polymorphisms in genes encoding syndecan-1 and enzymes involved in the synthesis or degradation of HSPG were genotyped in the study subjects.

Results

Our results indicate that the genetic variation rs2281279 in SULF2 associates with postprandial clearance of remnant TRLs and triglyceride levels in healthy subjects. Furthermore, the SNP rs2281279 in SULF2 associates with hepatic SULF2 mRNA levels.

Conclusions

In humans, mild but clinically relevant postprandial hyperlipidemia due to reduced hepatic clearance of remnant TRLs may result from genetic polymorphisms that affect hepatic HSPG.

Molecular cloning, expression analysis, and potential food intake attenuation effect of peptide YY in grass carp (Ctenopharyngodon idellus)

The peptide YY (PYY) is a 36 amino acid peptide involved in the food intake control in vertebrates. We have cloned and characterized a PYY gene from grass carp Ctenopharyngodon idellus. The full-length cDNA encodes a precursor protein of grass carp PYY (gcPYY) that consists of a putative 28-amino acid signal peptide, a 36-amino acid mature peptide, an amidation-proteolytic site, and a 30-amino acid carboxy-terminal extension. The gcPYY gene is comprised of 4 exons interspaced by 3 introns as seen in PYYs from other species. Amino acid alignment and gene structure comparison indicate that the structure of PYY is well preserved throughout vertebrate phylogeny. The tissue distribution and postprandial changes in gcPYY mRNA expression were evaluated by real-time PCR, which showed that the gcPYY is expressed abundantly in the central nervous system, with significantly increased expression following a single meal. During embryogenesis, the presence of gcPYY mRNA was detected in early developing embryos, and high expression levels were observed when most larvae completed their switch from endogenous nourishment to exogenous feeding. Reduced food intake by juveniles during a single meal after giving perpheral injection of gcPYY1-36 suggests a potentially important role of PYY in the food intake attenuation in grass carp.

Sterol regulatory element-binding factor 2 (SREBF-2) predicts 7-year NAFLD incidence and severity of liver disease and lipoprotein and glucose dysmetabolism

We prospectively assessed the impact of a sterol regulatory element-binding factor-2 (SREBF-2) polymorphism on the risk of developing nonalcoholic fatty liver disease (NAFLD) and on liver histology and lipoprotein and glucose metabolism in biopsy-proven NAFLD. In a population-based study, we followed 175 nonobese, nondiabetic participants without NAFLD or metabolic syndrome at baseline, characterized for the SREBF-2 rs133291 C/T polymorphism, dietary habits, physical activity, adipokines, C-reactive protein (CRP), and endothelial adhesion molecules. A comparable cohort of NAFLD patients underwent liver biopsy, an oral glucose tolerance test with minimal model analysis to yield glucose homeostasis parameters, and an oral fat tolerance test with measurement of plasma lipoproteins, adipokines, and cytokeratin-18 fragments. After 7 years, 27% of subjects developed NAFLD and 5% developed diabetes. SREBF-2 predicted incident NAFLD and diabetes and CRP and endothelial adhesion molecule changes. In biopsy-proven NAFLD patients, SREBF-2 predicted nonalcoholic steatohepatitis (odds ratio 2.92 [95% CI 2.08-4.18], P = 0.002) and the severity of tissue insulin resistance, β-cell dysfunction, and oral fat intolerance (characterized by higher postprandial lipemia, cholesterol enrichment of triglyceride-rich lipoproteins and oxidized LDLs, HDL cholesterol fall, adipokine imbalance, and postprandial apoptosis activation). An SREBF-2 polymorphism predisposes individuals to NAFLD and associated cardiometabolic abnormalities and affects liver histology and glucose and lipid metabolism in biopsy-proven NAFLD.

Sterol regulatory element-binding protein-1c mediates increase of postprandial stearic acid, a potential target for improving insulin resistance, in hyperlipidemia

Elevated serum free fatty acids (FFAs) levels play an important role in the development of insulin resistance (IR) and diabetes. We investigated the dynamic changes and the underlying regulatory mechanism of postprandial FFA profile in hyperlipidemia (HLP) and their relation with insulin sensitivity in both humans and mice. We found that serum stearic acid (SA) is the only fatty acid that is increased dramatically in the postprandial state. The elevation of SA is due to increased insulin-stimulated de novo synthesis mediated by sterol regulatory element-binding protein-1c (SREBP-1c)/acetyl-CoA carboxylase/fatty acid synthase/elongation of long-chain fatty acid family member 6 (ELOVL6) and the elongation of palmitic acid (PA) catalyzed by ELOVL6. Downregulation of SREBP-1c or ELOVL6 by small interfering RNA can reduce SA synthesis in liver and serum SA level, followed by amelioration of IR in HLP mice. However, inhibition of SREBP-1c is more effective in improving IR than suppression of ELOVL6, which resulted in accumulation of PA. In summary, increased postprandial SA is caused by the insulin-stimulated SREBP-1c pathway and elongation of PA in HLP. Reduction of postprandial SA is a good candidate for improving IR, and SREBP-1c is potentially a better target to prevent IR and diabetes by decreasing SA.

Postprandial regulation of hepatic microRNAs predicted to target the insulin pathway in rainbow trout

Rainbow trout are carnivorous fish and poor metabolizers of carbohydrates, which established this species as a model organism to study the comparative physiology of insulin. Following the recent characterisation of key roles of several miRNAs in the insulin action on hepatic intermediary metabolism in mammalian models, we investigated the hypothesis that hepatic miRNA expression is postprandially regulated in the rainbow trout and temporally coordinated in the context of insulin-mediated regulation of metabolic gene expression in the liver. To address this hypothesis, we used a time-course experiment in which rainbow trout were fed a commercial diet after short-term fasting. We investigated hepatic miRNA expression, activation of the insulin pathway, and insulin regulated metabolic target genes at several time points. Several miRNAs which negatively regulate hepatic insulin signaling in mammalian model organisms were transiently increased 4 h after the meal, consistent with a potential role in acute postprandial negative feed-back regulation of the insulin pathway and attenuation of gluconeogenic gene expression. We equally observed a transient increase in omy- miRNA-33 and omy-miRNA-122b 4 h after feeding, whose homologues have potent lipogenic roles in the liver of mammalian model systems. A concurrent increase in the activity of the hepatic insulin signaling pathway and the expression of lipogenic genes (srebp1c, fas, acly) was equally observed, while lipolytic gene expression (cpt1a and cpt1b) decreased significantly 4 h after the meal. This suggests lipogenic roles of omy-miRNA-33 and omy-miRNA-122b may be conserved between rainbow trout and mammals and that these miRNAs may furthermore contribute to acute postprandial regulation of de novo hepatic lipid synthesis in rainbow trout. These findings provide a framework for future research of miRNA regulation of hepatic metabolism in trout and will help to further elucidate the metabolic phenotype of rainbow trout.

Interleukin 1B variant -1473G/C (rs1143623) influences triglyceride and interleukin 6 metabolism

CONTEXT

IL1b (IL1B or IL1β), a key modulator of the immune response, exerts its functions mainly via IL6 regulation. Fatty meals cause transient hypertriglyceridemia and are considered to be proinflammatory, but the extent of these responses shows high interindividual susceptibility.

OBJECTIVE

We evaluated the influence of a genetic variant located in the promoter region of IL1B (-1473G/C) on fasting and postprandial lipids and IL6.

DESIGN, SETTING, AND PARTICIPANTS

A total of 477 people over age 65 yr were genotyped for IL1B -1473G/C, and we evaluated fasting lipids depending on genotype. Then, 88 healthy young men were also genotyped and were fed a saturated fatty acid-rich meal. Serial blood samples were drawn for 11 h after the meal, and lipid fractions and IL6 were assayed. MAIN OUTCOME AND INTERVENTIONS: Fasting lipids were studied in the aged persons. Fasting and postprandial measurements of lipids and IL6 were performed in the healthy young men.

RESULTS

In the aged persons, CC subjects (minor allele homozygotes) showed higher triglyceride (P = 0.002) and cholesterol (P = 0.011) levels. Healthy young male carriers of the minor C allele showed higher postprandial triglycerides (P = 0.037), and those carried into large triglyceride-rich lipoproteins (P = 0.004). In addition, they showed higher postprandial IL6 concentrations (P = 0.008).

CONCLUSIONS

Our work shows that inflammatory genes may regulate fasting and postprandial lipids because the carriers of the minor allele of an IL gene variant have altered lipid metabolism. To reinforce these gene-phenotype findings, IL6 (the natural effector of IL1B) was increased in these persons.

Postprandial effects on appetite-related neuropeptide expression in the brain of Atlantic salmon, Salmo salar

Following feeding of a single meal to Atlantic salmon, the temporal changes in the brain mRNA expression of neuropeptide y (npy), cocaine-amphetamine regulated transcript (cart), peptide yy (pyy), two isoforms of agouti-related protein (agrp), two isoforms of cholecystokinin (cck), and four isoforms of proopiomelanocortin (pomc) were assessed by q-PCR. In the course of 24h post-feeding (hpf), several of the brain neuropeptides displayed changes in mRNA expression compared to an unfed control group, indicating that food intake and processing affect the regulation of expression of these genes in Atlantic salmon. Expression of cart, cck-l, pomc-a1 and pomc-b all increased within 3h of feeding, while most of the feed was still in the stomach, suggesting that these neuropeptides play central anorexigenic roles similar to those described in higher vertebrates, including determining meal intervals. On the other hand, the npy and agrp isoforms which have been described as playing orexigenic roles in mammals, showed an opposite response in salmon and both were elevated in the first 3h after feeding. The different isoforms of cck, agrp and pomc had different mRNA expression patterns, which indicate specific roles related to feeding regulation. The minimal effect of feeding and digestion on pyy expression in the brain indicates that PYY plays a minor role in the central control of short-term food intake in Atlantic salmon.

Role of heparanase on hepatic uptake of intestinal derived lipoprotein and fatty streak formation in mice

Background

Heparanase modulates the level of heparan sulfate proteoglycans (HSPGs) which have an important role in multiple cellular processes. Recent studies indicate that HSPGs have an important function in hepatic lipoprotein handling and processes involving removal of lipoprotein particles.

Principal Findings

To determine the effects of decreased HSPGs chain length on lipoprotein metabolism and atherosclerosis, transgenic mice over-expressing the human heparanase gene were studied.

Hepatic lipid uptake in hpa-Tg mice were evaluated by giving transgenic mice oral fat loads and labeled retinol. Sections of aorta from mice over-expressing heparanase (hpa-Tg) and controls (C57/BL6) fed an atherogenic diet were examined for evidence of atherosclerosis. Heparanase over-expression results in reduced hepatic clearance of postprandial lipoproteins and higher levels of fasting and postprandial serum triglycerides. Heparanase over-expression also induces formation of fatty streaks in the aorta. The mean lesion cross-sectional area in heparanase over-expressing mice was almost 6 times higher when compared to control mice (23,984 µm²±5,922 vs. 4,189 µm²±1,130, p<0.001).

Conclusions

Over-expression of heparanase demonstrates the importance of HSPGs for the uptake of intestinal derived lipoproteins and its role in the formation of fatty streaks.

The Ala54Thr polymorphism of the FABP2 gene influences the postprandial fatty acids in patients with type 2 diabetes

CONTEXT

The Ala54Thr polymorphism of FABP2 gene increases affinity of intestinal fatty acid-binding protein 2 for long-chain dietary fatty acids (FA) in subjects without diabetes.

OBJECTIVE

Our objective was to evaluate whether the Ala54Thr polymorphism of the FABP2 gene influences the FA composition in chylomicrons after a standard meal in patients with type 2 diabetes.

METHODS

This clinical trial studied 11 patients with TT and 15 patients with AA genotypes for Ala54Thr polymorphism of FABP2 gene selected from a Brazilian type 2 diabetic cohort. FA in chylomicrons (gas chromatography), plasma glucose, and serum triglycerides were measured after an overnight fast at baseline and, after a standard test meal, at 2-h intervals during 8 h.

RESULTS

During the test meal, the curves response of unsaturated FA of patients with TT genotype were different from patients with AA genotype: only patients with TT genotype exhibited an increase, with a postprandial peak at 6 h in monounsaturated FA [0.479 (0.248-0.709) to 1.674 (0.698-2.650) g/liter], polyunsaturated FA [0.338 (0.154-0.522) to 1.827 (0.389-3.265) g/liter], and trans-unsaturated FA [0.025 (0.013-0.037) to 0.122 (0.040-0.205) g/liter] (generalized estimating equations for repeated measurements: P<0.05 for all). The increase of saturated FA did not reach statistical significance. Diabetes treatment, previous diet, FA at baseline, and the increase of plasma glucose and triglycerides during the test meal were not different between TT and AA genotypes.

CONCLUSIONS

The TT genotype in Ala54Thr polymorphism of FABP2 gene in patients with type 2 diabetes increased dietary FA absorption, and this might increase the susceptibility to the effects of dietary lipids.

Genetic effects on postprandial variations of inflammatory markers in healthy individuals

Circulating levels of inflammatory markers predict the risk of cardiovascular disease (CVD), mediated perhaps in part by dietary fat intake, through mechanisms only partially understood. To evaluate post-fat load changes in inflammatory markers and genetic influences on these changes, we administered a standardized high-fat meal to 838 related Amish subjects as part of the Heredity and Phenotype Intervention (HAPI) Heart Study and measured a panel of inflammatory markers, including C-reactive protein (CRP), interleukin-1beta (IL-1beta), matrix metalloproteinase-1 and -9 (MMP-1 and MMP-9), and white blood cell (WBC) count, before and 4 h after fat challenge (CRP prechallenge only). Heritabilities (h(2) +/- s.d.) of basal inflammatory levels ranged from 16 +/- 8% for MMP-9 (P = 0.02) to 90 +/- 7% for MMP-1 (P < 0.0001). Post-fat load, circulating levels of WBC, MMP-1, and MMP-9 increased by 16, 32, and 43% (all P < 0.0001), with no significant changes in IL-1beta. Postprandial changes over the 4-h period were modestly heritable for WBC (age- and sex-adjusted h(2) = 14 +/- 9%, P = 0.04), but the larger MMP-1 and MMP-9 changes appeared to be independent of additive genetic effects. These results reveal that a high-fat meal induces a considerable inflammatory response. Genetic factors appear to play a significant role influencing basal inflammatory levels but to have minimal influence on post-fat intake inflammatory changes.

779 TC of CCK-1 intron 1 is associated with postprandial syndrome (PDS) in Japanese male subjects

BACKGROUND/AIMS

The role of genetics in the susceptibility to functional dyspepsia (FD) is not well established. Cholecystokinin (CCK) is released from enteroendocrine cells in the duodenal mucosa after food ingestion and signals satiation through peripheral or central actions. A common polymorphisms of CCK and it's receptor gene has been shown to be associated with panic disorder and schizophrenia. It was investigated the prevalence of CCK polymorphism in dyspeptic patients in a Japanese population.

METHODOLOGY

A total of 124 dyspeptic patients, 119 non-symptomatic healthy controls participated in this study. Dyspeptic patients were also classified by Rome III criteria. T779C of Cholecystokinin (CCK)-1 intron 1, by polymerase chain reaction-restriction fragment length polymorphism. H. pylori infection status was examined by histology or antibody against H. pylori.

RESULTS

Although frequency of CCK-1 polymorphisms in overall dyspeptic patients, subgroups by Roma III criteria and non-symptomatic healthy controls did not show any significant differences, 779 T carriers significantly increased the risk of postprandial syndrome (PDS) in male subjects (53.5% vs, 84.2; OR = 4.63, 95% CI = 1.24-17.31, p = 0.018). This significant association was also remained after logistic regression analysis with adjustment for age and H. pylori infection status (OR = 4.99, 95% CI = 1.31-18.95, p = 0.018). In female and different H. pylori infection status, no significant association was observed between CCK-1 polymorphisms and dyspepsia.

CONCLUSION

Our data suggest that the 779 T carriers of CCK-1 intron 1 is associated with an increased risk of PDS in Japanese male subjects.

Glucokinase regulatory protein gene polymorphism affects postprandial lipemic response in a dietary intervention study

Postprandial triglyceridemia is an emerging risk factor for cardiovascular disease. However, most of the genes that influence postprandial triglyceridemia are not known. We evaluated whether a common nonsynonymous SNP rs1260326/P446L in the glucokinase regulatory protein (GCKR) gene influenced variation in the postprandial lipid response after a high-fat challenge in seven hundred and seventy participants in the Amish HAPI Heart Study who underwent an oral high-fat challenge and had blood samples taken in the fasting state and during the postprandial phase at 1, 2, 3, 4, and 6 h. We found that the minor T allele at rs1260326 was associated with significantly higher fasting TG levels after adjusting for age, sex, and family structure (P (a) = 0.06 for additive model, and P (r) = 0.0003 for recessive model). During the fat challenge, the T allele was associated with significantly higher maximum TG level (P (a) = 0.006), incremental maximum TG level (P (a) = 0.006), TG area under the curve (P (a) = 0.02) and incremental TG area under the curve (P (a) = 0.03). Our data indicate that the rs1260326 T allele of GCKR is associated with both higher fasting levels of TG as well as the postprandial TG response, which may result in higher atherogenic risk.

Characterization of human gene expression changes after olive oil ingestion: an exploratory approach

Olive oil consumption is protective against risk factors for cardiovascular and cancer diseases. A nutrigenomic approach was performed to assess whether changes in gene expression could occur in human peripheral blood mononuclear cells after oli ve oil ingestion at postprandial state. Six healthy male volunteers ingested, at fasting state, 50 ml of olive oil. Prior to intervention a 1-week washout period with a controlled diet and sunflower oil as the only source of fat was followed. During the 3 days before and on the intervention day, a very low-phenolic compound diet was followed. At baseline (0 h) and at post-ingestion (6 h), total RNA was isolated and gene expression (29,082 genes) was evaluated by microarray. From microarray data, nutrient-gene interactions were observed in genes related to metabolism, cellular processes, cancer, and atherosclerosis (e.g. USP48 by 2.16; OGT by 1.68-fold change) and associated processes such as inflammation (e.g. AKAP13 by 2.30; IL-10 by 1.66-fold change) and DNA damage (e.g. DCLRE1C by 1.47; POLK by 1.44- fold change). When results obtained by microarray were verified by qRT-PCR in nine genes, full concordance was achieved only in the case of up-regulated genes. Changes were observed at a real-life dose of olive oil, as it is daily consumed in some Mediterranean areas. Our results support the hypothesis that postprandial protective changes related to olive oil consumption could be mediated through gene expression changes.

High-fat meal-induced changes in the duodenum mucosa transcriptome

In order to identify the potential peripheral signals of appetite and satiety from duodenum, we have performed a transcriptomic study in the mucosa after high-fat (HF) and low-fat (LF) meal ingestion. After fasting, one group of mice was killed and the others were fed ad libitum with HF or LF diet, and killed 30 min, 1 h, and 3 h after the beginning of the meal. The duodenum mucosa was sampled, and the serial analysis of gene expression (SAGE) method was performed. The mRNA regulations were confirmed by real-time PCR. Energy, protein, and fat intakes were higher in the HF than in the LF group. Gene expression profile revealed 118 characterized or partially characterized differentially expressed transcripts. The HF meal delayed the expressions of peptidases compared to the LF groups. Most of mRNAs related to fat absorption, including apolipoprotein A-IV (Apoa4), were decreased in HF1h group, whereas plasma triglyceride (TG) levels were comparable between HF and LF groups. Noteworthy, these downregulations were concomitant to a break in fat intake 1 h after HF meal. At the same time, the HF meal induced transcripts related to cell growth and organization, whereas transcripts involved in cell defense were repressed. Moreover, we have identified fat-responsive transcripts. This study has characterized the molecular responses of duodenum mucosa after HF or LF meal ingestion. Characterization of novel fat-specific candidates whose relations with feeding behavior have never been reported may contribute to the development of new therapeutic targets for appetite and satiety controls.

Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, A-V, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.

Exploring the midgut transcriptome of Phlebotomus papatasi: comparative analysis of expression profiles of sugar-fed, blood-fed and Leishmania-major-infected sandflies

Background

In sandflies, the blood meal is responsible for the induction of several physiologic processes that culminate in egg development and maturation. During blood feeding, infected sandflies are also able to transmit the parasite Leishmania to a suitable host. Many blood-induced molecules play significant roles during Leishmania development in the sandfly midgut, including parasite killing within the endoperitrophic space. In this work, we randomly sequenced transcripts from three distinct high quality full-length female Phlebotomus papatasi midgut-specific cDNA libraries from sugar-fed, blood-fed and Leishmania major-infected sandflies. Furthermore, we compared the transcript expression profiles from the three different cDNA libraries by customized bioinformatics analysis and validated these findings by semi-quantitative PCR and real-time PCR.

Results

Transcriptome analysis of 4010 cDNA clones resulted in the identification of the most abundant P. papatasi midgut-specific transcripts. The identified molecules included those with putative roles in digestion and peritrophic matrix formation, among others. Moreover, we identified sandfly midgut transcripts that are expressed only after a blood meal, such as microvilli associated-like protein (PpMVP1, PpMVP2 and PpMVP3), a peritrophin (PpPer1), trypsin 4 (PpTryp4), chymotrypsin PpChym2, and two unknown proteins. Of interest, many of these overabundant transcripts such as PpChym2, PpMVP1, PpMVP2, PpPer1 and PpPer2 were of lower abundance when the sandfly was given a blood meal in the presence of L. major.

Conclusion

This tissue-specific transcriptome analysis provides a comprehensive look at the repertoire of transcripts present in the midgut of the sandfly P. papatasi. Furthermore, the customized bioinformatic analysis allowed us to compare and identify the overall transcript abundance from sugar-fed, blood-fed and Leishmania-infected sandflies. The suggested upregulation of specific transcripts in a blood-fed cDNA library were validated by real-time PCR, suggesting that this customized bioinformatic analysis is a powerful and accurate tool useful in analysing expression profiles from different cDNA libraries. Additionally, the findings presented in this work suggest that the Leishmania parasite is modulating key enzymes or proteins in the gut of the sandfly that may be beneficial for its establishment and survival.

Heterozygote men with familial hypercholesterolaemia may have an abnormal triglyceride response post-prandially. Evidence for another predictor of vascular risk in familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is associated with premature coronary heart disease (CHD). Post-prandial hypertriglyceridaemia has also been associated with cardiovascular disease. Thus, an abnormal post-prandial triglyceride (TG) clearance may contribute to the heterogeneity in the risk of CHD in heterozygous (h) FH. Therefore, we investigated the response of TG levels to a fatty meal in men with hFH. We studied 26 Greek men divided into two groups: the hFH group of 14 men, mean age 39 (SD = 11) years and the control group of 12 healthy men, mean age 43 (50:5) years. An increased TG response to the fatty meal was defined as a post-prandial TG concentration (at 4, 6 or 8 h) greater than the highest TG concentration in any hour in any control individual. All hFH patients had normal baseline fasting TG levels. However, seven hFH men showed an abnormal TG response after the fatty meal; these patients had higher baseline fasting TG levels than others [1.5 (0.2) vs. 1.0 (0.4) mmol/l, p = 0.005]. The hFH men constituted a heterogeneous group regarding their TG response to the fatty meal compared with healthy men because 50% with higher, but nevertheless 'normal' basal TG levels, had an abnormal post-prandial TG response. The reduced activity of low-density lipoprotein receptors in hFH together with other defects in TG handling may explain the abnormal rise of TG levels post-prandially.

Small dense LDL phenotype is associated with postprandial increases of large VLDL and remnant-like particles in patients with acute myocardial infarction

BACKGROUND

The small dense low-density lipoprotein (LDL) phenotype (pattern B), high concentrations of remnant-like particles (RLPs), and postprandial lipemia are newly recognized risk factors for coronary heart disease (CHD). However, the associations of these lipoprotein abnormalities remain unclear. The aim of this study was to investigate the relationships among LDL phenotype, very-low-density lipoprotein (VLDL) subclasses, and postprandial lipoprotein metabolism in CHD patients.

METHOD

We performed an oral fat tolerance test in 32 patients with acute myocardial infarction and compared the following parameters between patients characterized by either large buoyant LDL (pattern A) versus pattern B: lipids and apolipoproteins (apo) in the plasma and Svedberg flotation rates (Sf) >400 (chylomicron), Sf 60-400 (large VLDL), and Sf 20-60 (small VLDL) fractions.

RESULT

Fasting levels of triglyceride, RLP-cholesterol and RLP-triglyceride were slightly higher in the pattern B patients. Postprandial increases of RLP-cholesterol and the cholesterol and triglyceride of large VLDL fractions were significantly greater in the pattern B patients. The areas under the curves of cholesterol, triglyceride, and apo-B in large VLDL fractions were significantly higher in pattern B, while those in small VLDL were not. RLP-cholesterol and RLP-triglyceride in fasting and fed states correlated very highly with the corresponding cholesterol and triglyceride concentrations in large VLDL fractions.

CONCLUSION

These results suggest that postprandial increase of large VLDL fractions and RLPs contribute to the formation of small dense LDL in CHD patients.

Postprandial hyperglycemia and insulin sensitivity differ among lean young adults of different ethnicities

Both postprandial hyperglycemia and insulin resistance (IR) have implications for the development of cardiovascular disease. The present study was designed to examine differences in postprandial glycemia and insulin sensitivity among young adults of different ethnic origins. Lean, healthy subjects (n = 60) from five ethnic groups [20 European Caucasians, 10 Chinese, 10 South East (SE) Asians, 10 Asian Indians and 10 Arabic Caucasians] were matched for age, body mass index, waist circumference, birth weight and current diet. A 75-g white bread carbohydrate challenge was fed to assess postprandial glycemia and insulinemia. Insulin sensitivity was assessed in three groups by the euglycemic-hyperinsulinemic clamp and in all subjects by homeostasis model assessment (HOMA) modeling. Postprandial hyperglycemia (incremental area under the curve) and insulin sensitivity (M-value) both showed a twofold variation among the groups (P < 0.001) and were significantly related to each other (R(2) = 56%, P < 0.001). Young SE Asians had the highest postprandial glycemia and lowest insulin sensitivity, whereas European and Arabic Caucasian subjects were the most insulin sensitive and carbohydrate tolerant. These findings suggest that IR is evident even in lean, young adults of some ethnic groups and is associated with significant increases in postprandial glycemia and insulinemia in response to a realistic carbohydrate load.

Insulin resistance affects the regulation of lipoprotein lipase in the postprandial period and in an adipose tissue-specific manner

AIMS

Insulin is a potent stimulator of adipose tissue lipoprotein lipase (LPL). Logically, the postprandial period is therefore a privileged time of the day for the regulation of LPL by insulin in this tissue. It is not clear to what extent a defect such as insulin resistance could affect this regulation and contribute to postprandial, as well as fasting, hypertriglyceridaemia. The aim of the present protocol was to study the relationship between insulin resistance and LPL in adipose tissue and in plasma, in the particular context of the postprandial period.

METHODS

For this study, 26 adult nondiabetic individuals (12 women and 14 men) with a wide range of whole-body insulin-mediated glucose uptake (as assessed with an insulin suppression test) were studied. An abdominal subcutaneous fat biopsy on one occasion, and post-heparin plasma on another occasion, were obtained 4 h into a standardized meal profile administered in the fasting state.

RESULTS

Postprandial triglyceride excursions (evaluated by the incremental area under the curve during the metabolic meal profile) were inversely correlated to adipose tissue LPL mRNA levels (rho = -0.43, P < 0.03) as well as to adipose tissue LPL heparin-releasable activity (rho = -0.58, P < 0.01). Steady-state plasma glucose (SSPG) concentrations during the insulin suppression test, a reflection of the degree of insulin resistance, were also negatively correlated to adipose tissue LPL mRNA (rho = -0.50, P < 0.02) and activity (rho = -0.56, P < 0.01). There was no correlation between plasma post-heparin LPL activity/mass and postprandial triglycerides nor with insulin resistance.

CONCLUSION

Regulation of adipose tissue LPL is significantly affected in insulin-resistant individuals in the postprandial period. This presumed impaired effect of insulin on LPL postprandially could be an important contributor to the atherogenic dyslipidaemia described in insulin resistance syndrome.

Metabolic heterogeneity underlying postprandial lipemia among men with low fasting high density lipoprotein cholesterol concentrations

The high triglyceride (TG) and low high density lipoprotein (HDL) cholesterol dyslipidemia has been associated with increased postprandial lipemia. Although fasting TG is a powerful predictor of postprandial hyperlipidemia, the role of hypoalphalipoproteinemia in postprandial TG metabolism is uncertain. We have studied postprandial lipemia among 63 men with low fasting plasma HDL cholesterol concentrations (<0.9 mmol/L), but with either low (<2.0 mmol/L) or high (>2.0 mmol/L) fasting plasma TG levels. A significant relationship was noted between postprandial TG response and fasting HDL cholesterol concentration (r = -0.43; P: < 0.0005). We also found that men with high TG/low HDL dyslipidemia (high TG and low HDL cholesterol; n = 16) were characterized by abdominal obesity as well as increased visceral adipose tissue accumulation, whereas normolipidemic controls (low TG and high HDL cholesterol; n = 26) and men with isolated low HDL cholesterol concentrations (low TG and low HDL cholesterol; n = 17) were not characterized by features of the insulin resistance syndrome (visceral obesity, hyperinsulinemia, and hypertriglyceridemia). Although controls and men with isolated low HDL cholesterol levels had similar postprandial lipemic responses, men with the high TG/low HDL dyslipidemia had a marked increase in their postprandial TG responses to the fat load compared with the other subgroups (P: < 0. 001). Men with the high TG/low HDL dyslipidemia were also characterized by higher concentrations of apolipoprotein (apo) B-48 and B-100 particles (chylomicron remnants and very low density lipoproteins, respectively) before and during the postprandial period compared with the other subjects. These results suggest that low HDL cholesterol concentration is a heterogeneous metabolic phenotype that it is not associated with postprandial hyperlipidemia unless accompanied by other features of the insulin resistance syndrome.