Mechanism for the increase in plasma triacylglycerol concentrations after consumption of short-term, high-carbohydrate diets

Dietary Regulation of Hepatic Triacylglycerol Content-the Role of Eucaloric Carbohydrate Restriction with Fat or Protein Replacement

Accumulation of hepatic triacylglycerol (TG) is highly associated with impaired whole-body insulin-glucose homeostasis and dyslipidemia. The summarized findings from human intervention studies investigating the effect of reduced dietary carbohydrate and increased fat intake (and in studies also increased protein) while maintaining energy intake at eucaloric requirements reveal a beneficial effect of carbohydrate reduction on hepatic TG content in obese individuals with steatosis and indices of insulin resistance. Evidence suggests that the reduction of hepatic TG content after reduced intake of carbohydrates and increased fat/protein intake in humans, results from regulation of fatty acid (FA) metabolism within the liver, with an increase in hepatic FA oxidation and ketogenesis, together with a concomitant downregulation of FA synthesis from de novo lipogenesis. The adaptations in hepatic metabolism may result from reduced intrahepatic monosaccharide and insulin availability, reduced glycolysis and increased FA availability when carbohydrate intake is reduced.

A very high-carbohydrate diet differentially affects whole-body glucose tolerance and hepatic insulin resistance in rats

OBJECTIVES

This study was performed to assess the effects of long-term intake of a very high carbohydrate (VHCHO) diet (76% of total energy from carbohydrate [CHO]) on whole-body glucose tolerance and hepatic insulin resistance.

METHODS AND MATERIALS

Male Sprague Dawley rats were fed either a control high-CHO diet (59% total energy from CHO; n = 8) or a VHCHO diet (76% total energy from CHO; n = 8) for 17 wk. At 4, 8, 12, and 16 wk of the dietary intervention, oral glucose tolerance test and homeostasis model assessment of insulin resistance (HOMA-IR) measurements were taken to assess whole-body glucose tolerance and hepatic insulin resistance, respectively. The triacylglycerol concentration in the liver was measured at the end of the 17-wk intervention period.

RESULTS

The VHCHO diet group showed significantly higher muscle glucose transporter 4 content and a smaller area under the curve for plasma glucose, but not insulin, in the oral glucose tolerance test compared with the control group. On the other hand, the VHCHO diet group had a significantly higher hepatic triacylglycerol concentration and HOMA-IR measurement compared with the control group. The hepatic triacylglycerol concentration was significantly and positively correlated with HOMA-IR.

CONCLUSIONS

The results of the present study suggest that long-term intake of a VHCHO diet exerts differential effects on whole-body glucose tolerance and hepatic insulin resistance.

Association of dietary patterns with general and central obesity among Chinese adults: a longitudinal population-based study

BACKGROUND

Limited evidence exists for the association between dietary patterns and later obesity phenotypes among Chinese adults. This longitudinal study aimed to evaluate associations of dietary patterns with general and central obesity in Chinese adults.

METHODS

Based on the China Health and Nutrition Survey (CHNS) waves 2004 and 2015, the study was conducted on 4207 adult men and women (age range: 18-65 years). Dietary intakes were assessed by three consecutive 24-h dietary recalls, and dietary patterns were identified using exploratory factor analysis. Longitudinal associations of dietary patterns with general and central obesity were evaluated using logistic regression analyses.

RESULTS

The prevalence rates of general and central obesity were 14.2% and 42.1%, respectively. Factor analysis extracted three major dietary patterns: "traditional southern," "modern," and "traditional northern." After adjustment for potential confounders, adults in the highest quartile of the traditional southern dietary group were less likely to develop over 10 years general (odds ratio [OR] = 0.50, 95% confidence interval [95%CI]: 0.39, 0.65) and central (OR = 0.52, 95%CI: 0.43, 0.63) obesity compared to those in the lowest quartile group. The modern dietary pattern was not significantly associated with general and central obesity. Adherence to the traditional northern dietary pattern increased the chance of both general and central obesity (OR = 1.61, 95%CI: 1.23, 2.10; OR = 1.64, 95%CI: 1.36, 1.98) after 10 years.

CONCLUSIONS

Our study provides longitudinal evidence for associations between dietary patterns and later obesity phenotypes among Chinese adults. Our findings may guide the development of evidence-based preventive nutrition interventions to control the obesity epidemic.

Relationship Analysis of Inorganic Arsenic Exposure and Metabolic Syndrome Based on Propensity Score Matching in Xinjiang, China

PURPOSE

The role of inorganic arsenic (iAs) in the risk of metabolic syndrome (MetS) remains unclear. This investigation focused on the effect of iAs exposure on MetS and whether the results are consistent in different subgroups.

PATIENTS AND METHODS

The present study was conducted on 629 men and 616 women aged 35-70 years and living in Xinjiang Uygur Autonomous Region, China. The 1:1 propensity score matching (PSM) was adopted to regulate the confounding factors, and the multivariate logistic regression was performed to assess the relationship between urinary iAs and MetS.

RESULTS

The median content of urinary iAs was examined as 2.20 μg/dL (interquartile range: 1.30-3.20 μg/dL), and the MetS prevalence reached 23.69% (295 cases/950 participants). After the confounding factors were adjusted, the ORs (95% CIs) for MetS from the minimal to the maximum urinary iAs quartiles reached 1.171 (0.736,1.863), 1.568 (1.008, 2.440) and 2.011 (1.296, 3.120), respectively (referencing 1.00) (P for trend=0.001). After the PSM, the urinary iAs content still plays a potential prediction role in MetS (P for trend=0.011). In addition, as revealed from the subgroup analysis, the urinary iAs content was a predictor of MetS in the female patients, whereas it did not serve as a significant predictor of MetS in the male patients (P for interaction<0.05).

CONCLUSION

The increased urinary iAs content was associated with the increased prevalence of MetS in Chinese population. More attention should be paid to female urinary iAs content to avoid the high prevalence of MetS.

Shared genetic etiology between Parkinson's disease and blood levels of specific lipids

Parkinson’s disease (PD) is characterized by the degeneration of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies. The mechanisms underlying these molecular and cellular effects are largely unknown. Previously, based on genetic and other data, we built a molecular landscape of PD that highlighted a central role for lipids. To explore which lipid species may be involved in PD pathology, we used published genome-wide association study (GWAS) data to conduct polygenic risk score-based analyses to examine putative genetic sharing between PD and blood levels of 370 lipid species and lipid-related molecules. We found a shared genetic etiology between PD and blood levels of 25 lipids. We then used data from a much-extended GWAS of PD to try and corroborate our findings. Across both analyses, we found genetic overlap between PD and blood levels of eight lipid species, namely two polyunsaturated fatty acids (PUFA 20:3n3-n6 and 20:4n6), four triacylglycerols (TAG 44:1, 46:1, 46:2, and 48:0), phosphatidylcholine aa 32:3 (PC aa 32:3) and sphingomyelin 26:0 (SM 26:0). Analysis of the concordance—the agreement in genetic variant effect directions across two traits—revealed a significant negative concordance between PD and blood levels of the four triacylglycerols and PC aa 32:3 and a positive concordance between PD and blood levels of both PUFA and SM 26:0. Taken together, our analyses imply that genetic variants associated with PD modulate blood levels of a specific set of lipid species supporting a key role of these lipids in PD etiology.

Honey does not adversely impact blood lipids of adult men and women: a randomized cross-over trial

Consumption of added sugars in the US is estimated to be approximately 1.5 times recommended levels and has been linked to increased risk for developing chronic diseases. We hypothesized that relative to sugar, honey would reduce energy intake and improve serum lipid profiles. To test this, we assessed the short-term (1-week) and relatively long-term (1-month) effects of honey versus sucrose on changes in dietary intake and serum lipid concentrations. Thirty-seven apparently healthy subjects (21 males; 16 females) aged 24-57 years (BMI = 17.6-37.2 kg/m²) completed two 4-week trials in a randomized, cross-over design separated by ≥4-week washout. During each trial, subjects consumed either clover honey or sucrose providing 1.2 g/kg/day of carbohydrate under free-living conditions with instructions to avoid changing their habitual food intake. Serum triglyceride (TG) concentrations were elevated (P < .05) after 1 week for both trials but only remained elevated (P < .05) at the 4-week time-point during sucrose consumption. The elevation after 1 week during the honey trial was concurrent with a transient increase (P < .05) in body weight. No effects on serum concentrations of insulin, total cholesterol, low density lipoprotein-cholesterol, or high density lipoprotein-cholesterol were detected for either trial. Subjects consumed significantly less energy (P < .05), carbohydrate (P < .005), sugars (P < .05), and saturated fat (P < .05) during the honey trial. These data suggest that honey may serve as a favorable substitute for sucrose with regard to reduced energy intake, carbohydrate and sugars, without negatively influencing serum lipid concentrations.

Dietary Impact on Postprandial Lipemia

Abnormalities in postprandial lipemia (PPL), particularly those related to triglyceride-rich lipoproteins, are considered an independent cardiovascular risk factor. As diet is known to be one of the main modulators of PPL, the aim of this review was to summarize and discuss current knowledge on the impact of diet and its components on PPL in humans; specifically, the impact of weight loss, different nutrients (quantity and quality of dietary fats, carbohydrates, and proteins), alcohol and other bioactive dietary components (i.e., polyphenols), as well as the effect of different dietary patterns. The possible mechanisms behind the metabolic effects of each dietary component were also discussed.

Anti-TNF-α Agent Tamarind Kunitz Trypsin Inhibitor Improves Lipid Profile of Wistar Rats Presenting Dyslipidemia and Diet-induced Obesity Regardless of PPAR-γ Induction

The increasing prevalence of obesity and, consequently, chronic inflammation and its complications has increased the search for new treatment methods. The effect of the purified tamarind seed trypsin inhibitor (TTIp) on metabolic alterations in Wistar rats with obesity and dyslipidemia was evaluated. Three groups of animals with obesity and dyslipidemia were formed, consuming a high glycemic index and glycemic load (HGLI) diet, for 10 days: Obese/HGLI diet; Obese/standard diet; Obese/HGLI diet + TTIp (730 μg/kg); and one eutrophic group of animals was fed a standard diet. Rats were evaluated daily for food intake and weight gain. On the 11th day, animals were anesthetized and sacrificed for blood and visceral adipose tissue collection. TTIp treated animals presented significantly lower food intake than the untreated group (p = 0.0065), TG (76.20 ± 18.73 mg/dL) and VLDL-C (15.24 ± 3.75 mg/dL). Plasma concentrations and TNF-α mRNA expression in visceral adipose tissue also decreased in obese animals treated with TTIp (p < 0.05 and p = 0.025, respectively) with a negative immunostaining. We conclude that TTIp presented anti-TNF-α activity and an improved lipid profile of Wistar rats with dyslipidemia and obesity induced by a high glycemic index and load diet regardless of PPAR-γ induction.

Mechanisms Preserving Insulin Action during High Dietary Fat Intake

Prolonged intervention studies investigating molecular metabolism are necessary for a deeper understanding of dietary effects on health. Here we provide mechanistic information about metabolic adaptation to fat-rich diets. Healthy, slightly overweight men ingested saturated or polyunsaturated fat-rich diets for 6 weeks during weight maintenance. Hyperinsulinemic clamps combined with leg balance technique revealed unchanged peripheral insulin sensitivity, independent of fatty acid type. Both diets increased fat oxidation potential in muscle. Hepatic insulin clearance increased, while glucose production, de novo lipogenesis, and plasma triacylglycerol decreased. High fat intake changed the plasma proteome in the immune-supporting direction and the gut microbiome displayed changes at taxonomical and functional level with polyunsaturated fatty acid (PUFA). In mice, eucaloric feeding of human PUFA and saturated fatty acid diets lowered hepatic triacylglycerol content compared with low-fat-fed control mice, and induced adaptations in the liver supportive of decreased gluconeogenesis and lipogenesis. Intake of fat-rich diets thus induces extensive metabolic adaptations enabling disposition of dietary fat without metabolic complications.

Nutritional Ketosis and Mitohormesis: Potential Implications for Mitochondrial Function and Human Health

Impaired mitochondrial function often results in excessive production of reactive oxygen species (ROS) and is involved in the etiology of many chronic diseases, including cardiovascular disease, diabetes, neurodegenerative disorders, and cancer. Moderate levels of mitochondrial ROS, however, can protect against chronic disease by inducing upregulation of mitochondrial capacity and endogenous antioxidant defense. This phenomenon, referred to as mitohormesis, is induced through increased reliance on mitochondrial respiration, which can occur through diet or exercise. Nutritional ketosis is a safe and physiological metabolic state induced through a ketogenic diet low in carbohydrate and moderate in protein. Such a diet increases reliance on mitochondrial respiration and may, therefore, induce mitohormesis. Furthermore, the ketone β-hydroxybutyrate (BHB), which is elevated during nutritional ketosis to levels no greater than those resulting from fasting, acts as a signaling molecule in addition to its traditionally known role as an energy substrate. BHB signaling induces adaptations similar to mitohormesis, thereby expanding the potential benefit of nutritional ketosis beyond carbohydrate restriction. This review describes the evidence supporting enhancement of mitochondrial function and endogenous antioxidant defense in response to nutritional ketosis, as well as the potential mechanisms leading to these adaptations.

Impact of liver fat on the differential partitioning of hepatic triacylglycerol into VLDL subclasses on high and low sugar diets

Dietary sugars are linked to the development of non-alcoholic fatty liver disease (NAFLD) and dyslipidaemia, but it is unknown if NAFLD itself influences the effects of sugars on plasma lipoproteins. To study this further, men with NAFLD (n = 11) and low liver fat ‘controls’ (n = 14) were fed two iso-energetic diets, high or low in sugars (26% or 6% total energy) for 12 weeks, in a randomised, cross-over design. Fasting plasma lipid and lipoprotein kinetics were measured after each diet by stable isotope trace-labelling.

There were significant differences in the production and catabolic rates of VLDL subclasses between men with NAFLD and controls, in response to the high and low sugar diets. Men with NAFLD had higher plasma concentrations of VLDL₁-triacylglycerol (TAG) after the high (P<0.02) and low sugar (P<0.0002) diets, a lower VLDL₁-TAG fractional catabolic rate after the high sugar diet (P<0.01), and a higher VLDL₁-TAG production rate after the low sugar diet (P<0.01), relative to controls. An effect of the high sugar diet, was to channel hepatic TAG into a higher production of VLDL₁-TAG (P<0.02) in the controls, but in contrast, a higher production of VLDL₂-TAG (P<0.05) in NAFLD. These dietary effects on VLDL subclass kinetics could be explained, in part, by differences in the contribution of fatty acids from intra-hepatic stores, and de novo lipogenesis. The present study provides new evidence that liver fat accumulation leads to a differential partitioning of hepatic TAG into large and small VLDL subclasses, in response to high and low intakes of sugars.

Opposite Regulation of Insulin Sensitivity by Dietary Lipid Versus Carbohydrate Excess

To understand the mechanisms in lipid-induced insulin resistance, a more physiological approach is to enhance fatty acid (FA) availability through the diet. Nine healthy men ingested two hypercaloric diets (in 75% excess of habitual caloric intake) for 3 days, enriched in unsaturated FA (78 energy % [E%] fat) (UNSAT) or carbohydrates (80 E% carbohydrate) (CHO) as well as a eucaloric control diet (CON). Compared with CON, the UNSAT diet reduced whole-body and leg glucose disposal during a hyperinsulinemic-euglycemic clamp, while decreasing hepatic glucose production. In muscle, diacylglycerol (DAG) and intramyocellular triacylglycerol were increased. The accumulated DAG was sn-1,3 DAG, which is known not to activate PKC, and insulin signaling was intact. UNSAT decreased PDH-E1α protein content and increased inhibitory PDH-E1α Ser³⁰⁰ phosphorylation and FA oxidation. CHO increased whole-body and leg insulin sensitivity, while increasing hepatic glucose production. After CHO, muscle PDH-E1α Ser³⁰⁰ phosphorylation was decreased, and glucose oxidation increased. After UNSAT, but not CHO, muscle glucose-6-phosphate content was 103% higher compared with CON during the clamp. Thus, PDH-E1α expression and covalent regulation, and hence the tricarboxylic acid cycle influx of pyruvate-derived acetyl-CoA relative to β-oxidation-derived acetyl-CoA, are suggested to impact on insulin-stimulated glucose uptake. Taken together, the oxidative metabolic fluxes of glucose and FA are powerful and opposite regulators of insulin action in muscle.

Insights into the Hexose Liver Metabolism-Glucose versus Fructose

High-fructose intake in healthy men is associated with characteristics of metabolic syndrome. Extensive knowledge exists about the differences between hepatic fructose and glucose metabolism and fructose-specific mechanisms favoring the development of metabolic disturbances. Nevertheless, the causal relationship between fructose consumption and metabolic alterations is still debated. Multiple effects of fructose on hepatic metabolism are attributed to the fact that the liver represents the major sink of fructose. Fructose, as a lipogenic substrate and potent inducer of lipogenic enzyme expression, enhances fatty acid synthesis. Consequently, increased hepatic diacylglycerols (DAG) are thought to directly interfere with insulin signaling. However, independently of this effect, fructose may also counteract insulin-mediated effects on liver metabolism by a range of mechanisms. It may drive gluconeogenesis not only as a gluconeogenic substrate, but also as a potent inducer of carbohydrate responsive element binding protein (ChREBP), which induces the expression of lipogenic enzymes as well as gluconeogenic enzymes. It remains a challenge to determine the relative contributions of the impact of fructose on hepatic transcriptome, proteome and allosterome changes and consequently on the regulation of plasma glucose metabolism/homeostasis. Mathematical models exist modeling hepatic glucose metabolism. Future models should not only consider the hepatic adjustments of enzyme abundances and activities in response to changing plasma glucose and insulin/glucagon concentrations, but also to varying fructose concentrations for defining the role of fructose in the hepatic control of plasma glucose homeostasis.

Gender Difference on the Association between Dietary Patterns and Obesity in Chinese Middle-Aged and Elderly Populations

Dietary patterns are linked to obesity, but the gender difference in the association between dietary patterns and obesity remains unclear. We explored this gender difference in a middle-aged and elderly populations in Shanghai. Residents (n = 2046; aged ≥45 years; 968 men and 1078 women) who participated in the Shanghai Food Consumption Survey were studied. Factor analysis of data from four periods of 24-h dietary recalls (across 2012-2014) identified dietary patterns. Height, body weight, and waist circumference were measured to calculate the body mass index. A log binominal model examined the association between dietary patterns and obesity, stratified by gender. Four dietary patterns were identified for both genders: rice staple, wheat staple, snacks, and prudent patterns. The rice staple pattern was associated positively with abdominal obesity in men (prevalence ratio (PR) = 1.358; 95% confidence interval (CI) 1.132-1.639; p = 0.001), but was associated negatively with general obesity in women (PR = 0.745; 95% CI: 0.673-0.807; p = 0.031). Men in the highest quartile of the wheat staple pattern had significantly greater risk of central obesity (PR = 1.331; 95% CI: 1.094-1.627; p = 0.005). There may be gender differences in the association between dietary patterns and obesity in middle-aged and elderly populations in Shanghai, China.

Sweet Taste Receptor TAS1R2 Polymorphism (Val191Val) Is Associated with a Higher Carbohydrate Intake and Hypertriglyceridemia among the Population of West Mexico

Some high-carbohydrate diets may lead to obesity and multiple metabolic disorders, including hypertriglyceridemia (HTG). This lipid abnormality is considered an important risk factor for cardiovascular disease and type 2 diabetes. The sweet taste receptor TAS1R2 polymorphism (Ile191Val) has been reported to be associated with carbohydrate intake. The aim of this study was to analyze the association of the TAS1R2 gene polymorphism with carbohydrate intake and HTG among the population of West Mexico. In a cross-sectional study, 441 unrelated subjects were analyzed for TAS1R2 genotypes (Ile/Ile, Ile/Val and Val/Val) by an allelic discrimination assay. Biochemical tests and a three-day food record were assessed. The Val/Val genotype carriers had a higher intake of total carbohydrates, fiber and servings of cereals and vegetables than the other genotype carriers. The Val/Val genotype conferred a higher risk for HTG than the Ile/Val and Ile/Ile genotypes (OR = 3.26, 95%CI 1.35–7.86, p = 0.006 and OR = 2.61, 95%CI 1.12–6.07, p = 0.02, respectively). Furthermore, the Val/Val genotype was associated with approximately 30% higher triglycerides compared with Ile/Val and Ile/Ile genotypes (β = 44.09, 95%CI 9.94–78.25, p = 0.01 and β = 45.7, 95%CI 10.85–80.54, p = 0.01, respectively). In conclusion, the Val/Val genotype of TAS1R2 was associated with a higher carbohydrate intake and HTG.

Atkins diet program rapidly decreases atherogenic index of plasma in trained adapted overweight men

BACKGROUND

The Atkins diet program is a great example of the application of low carbohydrate diets for obesity, with the intention of weight loss and improvement in cardiovascular risk (CV risk). A good CV risk predictor is the atherogenic index of plasma (AIP) calculated as log (TG/HDL [mmol]), which is strongly affected by serum triglycerides, which in turn is associated with the carbohydrate intake. This study determined the effect of the initial phase of Atkins diet program, consisting in 20 g/day of carbohydrate intake with positive urinary ketones measure, in AIP of 12 adult overweight trained adapted men. The AIP was calculated before and after intervention.

RESULTS

After 14 days, BMI and triglycerides decreased significantly, while HDL-C increased. No alterations were described in LDL plasmatic concentration. Prior to the diet, 58.3% of subjects presented high CV risk and after 14 days of the diet program only 33.3% of subjects were classified as high CV risk, while more than 66% were low CV risk. The intervention was effective in 11 of 12 participants. However, in one person the dietary intervention increased AIP index.

CONCLUSION

The initial phase of Atkins diet program could significantly decrease the AIP in 11 of 12 adult overweight trained adapted men. Dietary individual responses need to be more studied.

Major Dietary Patterns in Relation to General and Central Obesity among Chinese Adults

Limited evidence exists for the association between diet pattern and obesity phenotypes among Chinese adults. In the present study, we analyzed the cross-sectional data from 474,192 adults aged 30-79 years from the China Kadoorie Biobank baseline survey. Food consumption was collected by an interviewer-administered questionnaire. Three dietary patterns were extracted by factor analysis combined with cluster analysis. After being adjusted for potential confounders, individuals following a traditional southern dietary pattern had the lowest body mass index (BMI) and waist circumference (WC); the Western/new affluence dietary pattern had the highest BMI; and the traditional northern dietary pattern had the highest WC. Compared to the traditional southern dietary pattern in multivariable adjusted logistic models, individuals following a Western/new affluence dietary pattern had a significantly increased risk of general obesity (prevalence ratio (PR): 1.06, 95% confidence interval (CI): 1.03-1.08) and central obesity (PR: 1.07, 95% CI: 1.06-1.08). The corresponding risks for the traditional northern dietary pattern were 1.05 (1.02-1.09) and 1.17 (1.25-1.18), respectively. In addition, the associations were modified by lifestyle behaviors, and the combined effects with alcohol drinking, tobacco smoking, and physical activity were analyzed. Further prospective studies are needed to elucidate the diet-obesity relationships.

Dietary patterns and their associations with childhood obesity in China

Dietary patterns represent the combined effects of foods, and illustrate efficaciously the impact of diet on health outcomes. Some findings of previous studies have limited applicability to Chinese children due to cultural factors. The present study was designed to identify dietary patterns and determine their relationships with obesity among Chinese children and adolescents. Data collected from 1282 children and adolescents aged 7-17 years from the 2011 China Health and Nutrition Survey (CHNS) were used. Dietary patterns were identified using factor analysis of data from three consecutive 24-h dietary recalls. Weight and height were measured following standard methods, and BMI was calculated. Three dietary patterns were identified: modern (high intakes of milk, fast foods and eggs), traditional north (high intakes of wheat, tubers and other cereals) and traditional south (high intakes of vegetables, rice and pork). After adjusting for some confounders and total energy intake, subjects in the highest quartiles of the modern and traditional north patterns were found to have significantly greater risk of obesity (OR 3·10, 95 % CI 1·52, 6·32, and OR 2·42, 95 % CI 1·34, 4·39, respectively). In conclusion, the modern dietary pattern and the traditional north dietary pattern were associated with higher risk of obesity. Promoting healthier eating patterns could help prevent obesity in Chinese children.

Differential effects of low-fat and high-fat diets on fed-state hepatic triacylglycerol secretion, hepatic fatty acid profiles, and DGAT-1 protein expression in obese-prone Sprague-Dawley rats

The purpose of this study was to compare the effects of short-term low-fat (LF) and high-fat (HF) diets on fed-state hepatic triacylglycerol (TAG) secretion, the content of proteins involved in TAG assembly and secretion, fatty acid oxidation (FAO), and the fatty acid profile of stored TAG. Using selectively bred obese-prone Sprague-Dawley rats, we directly measured fed-state hepatic TAG secretion, using Tyloxapol (a lipoprotein lipase inhibitor) and a standardized oral mixed meal (45% carbohydrate, 40% fat, 15% protein) bolus in animals fed a HF or LF diet for 2 weeks, after which the rats were maintained on their respective diet for 1 week (washout) prior to the liver being excised to measure protein content, FAO, and TAG fatty acid profiles. Hepatic DGAT-1 protein expression was ∼27% lower in HF- than in LF-fed animals (p < 0.05); the protein expression of all other molecules was similar in the 2 diets. The fed-state hepatic TAG secretion rate was ∼39% lower (p < 0.05) in HF- (4.62 ± 0.18 mmol·h(-1)) than in LF- (7.60 ± 0.57 mmol·h(-1)) fed animals. Hepatic TAG content was ∼2-fold higher (p < 0.05) in HF- (1.07 ± 0.15 nmol·g(-1) tissue) than in LF- (0.50 ± 0.16 nmol·g(-1) tissue) fed animals. In addition, the fatty acid profile of liver TAG in HF-fed animals closely resembled the diet, whereas in LF-fed animals, the fatty acid profile consisted of mostly de novo synthesized fatty acids. FAO was not altered by diet. LF and HF diets differentially alter fed-state hepatic TAG secretion, hepatic fatty acid profiles, and DGAT-1 protein expression.

One day of mixed meal overfeeding reduces hepatic insulin sensitivity and increases VLDL particle but not VLDL-triglyceride secretion in overweight and obese men

CONTEXT

The exact mechanisms responsible for increased plasma triglyceride (TG) concentration in obese people are unclear, and it is not known whether excess energy intake per se is involved in the pathophysiology of this abnormality.

OBJECTIVE

The purpose of our study was to examine how excess energy intake from a balanced diet for 1 day affects very-low-density lipoprotein (VLDL)-TG kinetics and its putative regulators hepatic insulin sensitivity and plasma free fatty acid availability.

SUBJECTS AND DESIGN

We used stable isotope-labeled tracer methods to evaluate glucose and lipid kinetics in 8 overweight and obese men (age, 38 ± 3 years; body mass index, 33.7 ± 1.7 kg/m(2); means ± SEM) on 2 occasions (randomized crossover design): once, the day after they consumed a balanced diet that provided an amount of energy that matched their energy expenditure, and another time, the day after they consumed a balanced diet that provided 30% excess calories. Eight healthy, lean men (34 ± 1 years; 22.5 ± 0.6 kg/m(2)) were studied under isocaloric conditions only to provide a reference for normal lipid kinetics.

RESULTS

VLDL-TG and VLDL-apolipoprotein B-100 (apoB-100) concentrations and secretion rates were significantly greater (P < .01) in overweight/obese compared with lean men. Hypercaloric, compared with isocaloric, feeding in overweight/obese men increased glucose rate of appearance in plasma (904 ± 21 vs 873 ± 26 μmol/min), the hepatic insulin resistance index (10.9 ± 2.2 vs 8.3 ± 1.8), and VLDL-apoB-100 concentration and secretion rate (1.91 ± 0.24 vs. 1.53 ± 0.13 nmol/min), whereas VLDL-apoB-100 plasma clearance rate, VLDL-TG secretion and plasma clearance rates, and free fatty acid rate of appearance in plasma were not affected by overfeeding.

CONCLUSION

One day of moderate overfeeding (30% excess energy intake) stimulates hepatic glucose and VLDL-apo B-100 secretion rates but has no effect on hepatic and adipose tissue fatty acid metabolism in overweight/obese men.

Effect of fish oil supplementation on serum triglycerides, LDL cholesterol and LDL subfractions in hypertriglyceridemic adults

BACKGROUND AND AIMS

The well-established triglyceride (TG) lowering effect of fish oil is accompanied by an increase in LDL-cholesterol (LDL-C) concentration. Less is known about the differential impact on LDL particle distribution - the smaller particles being associated with a greater risk for atherosclerosis. We aimed to examine the changes in serum concentrations of four subclasses of LDL particles as well as shifts in LDL phenotype patterns (A, B, AB) among hypertriglyceridemic adults.

METHODS AND RESULTS

This was a secondary analysis from a double-blind, parallel design, placebo controlled trial with 42 adults that experienced significant TG lowering and modest increases in total LDL-C concentrations after 12 weeks of 4 g/d EPA + DHA. Reduction in serum TG concentrations (mean ± SEM) was -26 ± 4% (-0.81 ± 10.12 mmol/L), p < 0.0001. Total LDL-C concentration increased by 13 ± 3% (+0.31 ± 0.08 mmol/L), p < 0.0001. The 12-week changes in concentrations of LDL1, LDL2, LDL3 and LDL4 were +0.06 ± 0.02 mmol/L [+2.2 ± 0.7 mg/dL], +0.07 ± 0.03 mmol/L [+2.6 ± 1.0 mg/dL], +0.16 ± 0.05 mmol/L [+6.3 ± 1.8 mg/dL], and +0.04 ± 0.04 mmol/L [+1.4 ± 1.7 mg/dL], respectively (+20 ± 5%, +64 ± 13%, +26 ± 6%, and +17 ± 9%), p < 0.05 for all but LDL4. Changes in LDL phenotype patterns A, B and A/B were negligible and not statistically significant.

CONCLUSION

In this population of hypertriglyceridemic adults, dietary supplementation with fish oil resulted in an increase in total LDL-C concentration which was distributed relatively evenly across the range of smaller and more atherogenic as well as larger and less atherogenic LDL particles.

Effect of acute negative and positive energy balance on basal very-low density lipoprotein triglyceride metabolism in women

Background

Acute reduction in dietary energy intake reduces very low-density lipoprotein triglyceride (VLDL-TG) concentration. Although chronic dietary energy surplus and obesity are associated with hypertriglyceridemia, the effect of acute overfeeding on VLDL-TG metabolism is not known.

Objective

The aim of the present study was to investigate the effects of acute negative and positive energy balance on VLDL-TG metabolism in healthy women.

Design

Ten healthy women (age: 22.0±2.9 years, BMI: 21.2±1.3 kg/m²) underwent a stable isotopically labeled tracer infusion study to determine basal VLDL-TG kinetics after performing, in random order, three experimental trials on the previous day: i) isocaloric feeding (control) ii) hypocaloric feeding with a dietary energy restriction of 2.89±0.42 MJ and iii) hypercaloric feeding with a dietary energy surplus of 2.91±0.32 MJ. The three diets had the same macronutrient composition.

Results

Fasting plasma VLDL-TG concentrations decreased by ∼26% after hypocaloric feeding relative to the control trial (P = 0.037), owing to decreased hepatic VLDL-TG secretion rate (by 21%, P = 0.023) and increased VLDL-TG plasma clearance rate (by ∼12%, P = 0.016). Hypercaloric feeding increased plasma glucose concentration (P = 0.042) but had no effect on VLDL-TG concentration and kinetics compared to the control trial.

Conclusion

Acute dietary energy deficit (∼3MJ) leads to hypotriglyceridemia via a combination of decreased hepatic VLDL-TG secretion and increased VLDL-TG clearance. On the other hand, acute dietary energy surplus (∼3MJ) does not affect basal VLDL-TG metabolism but disrupts glucose homeostasis in healthy women.

Acute high-intensity endurance exercise is more effective than moderate-intensity exercise for attenuation of postprandial triglyceride elevation

Acute exercise has been shown to attenuate postprandial plasma triglyceride elevation (PPTG). However, the direct contribution of exercise intensity is less well understood. The purpose of this study was to examine the effects of exercise intensity on PPTG and postprandial fat oxidation. One of three experimental treatments was performed in healthy young men ( n = 6): nonexercise control (CON), moderate-intensity exercise (MIE; 50% V̇o2peak for 60 min), or isoenergetic high-intensity exercise (HIE; alternating 2 min at 25% and 2 min at 90% V̇o2peak). The morning after the exercise, a standardized meal was provided (16 kcal/kg BM, 1.02 g fat/kg, 1.36 g CHO/kg, 0.31 g PRO/kg), and measurements of plasma concentrations of triglyceride (TG), glucose, insulin, and β-hydroxybutyrate were made in the fasted condition and hourly for 6 h postprandial. Indirect calorimetry was used to determine fat oxidation in the fasted condition and 2, 4, and 6 h postprandial. Compared with CON, both MIE and HIE significantly attenuated PPTG [incremental AUC; 75.2 (15.5%), P = 0.033, and 54.9 (13.5%), P = 0.001], with HIE also significantly lower than MIE ( P = 0.03). Postprandial fat oxidation was significantly higher in MIE [83.3 (10.6%) of total energy expenditure] and HIE [89.1 (9.8) %total] compared with CON [69.0 (16.1) %total, P = 0.039, and P = 0.018, respectively], with HIE significantly greater than MIE ( P = 0.012). We conclude that, despite similar energy expenditure, HIE was more effective than MIE for lowering PPTG and increasing postprandial fat oxidation.

Suppression in growth hormone during overeating ameliorates the increase in insulin resistance and cardiovascular disease risk

Previously, we reported that overeating for only a few days markedly suppressed the secretion of growth hormone (GH). The purpose of the present study was to determine the role of this reduction in GH concentration on key metabolic adaptations that occur during 2 wk of overeating. Nine nonobese, healthy adults were admitted to the hospital for 2 wk, during which time they ate ∼4,000 kcal/day (70 kcal·kg fat-free mass(-1)·day(-1); 50% carbohydrate, 35% fat, and 15% protein), and their plasma GH concentration was allowed to decline naturally (control). An additional eight subjects underwent the same overeating intervention and received exogenous GH treatment (GHT) administered in four daily injections to mimic physiological GH secretion throughout the 2-wk overeating period. We measured plasma insulin and glucose concentrations in the fasting and postprandial state as well as fasting lipolytic rate, proteolytic rate, and fractional synthetic rate (FSR) using stable-isotope tracer methods. GHT prevented the fall in plasma GH concentration, maintaining plasma GH concentration at baseline levels (1.2 ± 0.2 ng/ml), which increased fasting and postprandial assessments of insulin resistance (P < 0.05) and increased fasting lipidemia (all P < 0.05 vs. control). In addition, preventing the suppression in GH with overeating also blunted the increase in systemic proteolysis (P < 0.05 GHT vs. control). However, GHT did not alter lipolysis or FSR in response to overeating. In conclusion, our main findings suggest that the suppression in GH secretion that naturally occurs during the early stages of overeating may help attenuate the insulin resistance and hyperlipidemia that typically accompany overeating.

The opposite effects of high-sucrose and high-fat diet on Fatty Acid oxidation and very low density lipoprotein secretion in rat model of metabolic syndrome

Aims. To determine the effect of two different diets (high-sucrose (HS) and high-fat (HF)) on the main metabolic pathways potentially contributing to the development of steatosis: (1) activity of the liver lysosomal and heparin-releasable lipases; (2) fatty acid (FFA) oxidation; (3) FFA synthesis de novo; (4) VLDL output in vivo in a rat model of metabolic syndrome (MetS), hereditary hypertriglyceridemic (HHTg) rats fed HS or HF diets. Results. Both diets resulted in triacylglycerol (TAG) accumulation in the liver (HF > HS). The intracellular TAG lipolysis by lysosomal lipase was increased in both groups and positively correlated with the liver TAG content. Diet type significantly affected partitioning of intracellular TAG-derived fatty acids among FFA-utilizing metabolic pathways as HS feeding accentuated VLDL secretion and downregulated FFA oxidation while the HF diet had an entirely opposite effect. FFA de novo synthesis from glucose was significantly enhanced in the HS group (fed ≫ fasted) while being completely eradicated in the HF group. Conclusions. We found that in rats prone to the development of MetS associated diseases dietary-induced steatosis is not simply a result of impaired TAG degradation but that it depends on other mechanisms (elevated FFA synthesis or attenuated VLDL secretion) that are specific according to diet composition.

Clinical use of a carbohydrate-restricted diet to treat the dyslipidemia of the metabolic syndrome

BACKGROUND

The metabolic syndrome is characterized by an atherogenic dyslipidemia identifiable using lipoprotein subclass analysis. This study assesses the effect of a carbohydrate-restricted diet on the dyslipidemia of the metabolic syndrome in a clinical setting.

METHODS

This is a retrospective chart review of patients attending a preventive medicine clinic using lipoprotein subclass analysis (by NMR spectroscopy) to identify the atherogenic dyslipidemia. If present, patients were counseled to begin a carbohydrate-restricted diet (< 20 g/day). Patients already on statin therapy were included only if the medication dose was not changed. The outcomes were changes in body weight, fasting serum lipid profiles and serum lipoprotein subclasses.

RESULTS

Of 122 patients identified, 80 patients had complete pre- and post-treatment data. The mean (+/-SD) age was 66 +/- 9 years, baseline weight was 85 +/- 12 kg, BMI was 28.1 +/- 3.6, 73% were male, 99% were Caucasian. Sixty-five percent were taking statin medication. Carbohydrate-restriction led to a 13% reduction in total cholesterol, 16% reduction in LDL cholesterol, 38% reduction in triglycerides, and a 13% increase in HDL cholesterol (all p values < 0.001). Carbohydrate-restriction also led to a reduction in LDL particle concentration of 28%, a reduction in small LDL of 82%, a reduction of large VLDL of 62%, and an increase in large HDL of 30% (all p values < 0.001).

CONCLUSIONS

A carbohydrate-restricted diet recommendation led to improvements in lipid profiles and lipoprotein subclass traits of the metabolic syndrome in a clinical outpatient setting, and should be considered as a treatment for the metabolic syndrome.

Dietary intake is not associated to the metabolic syndrome in elderly women

Background:

The metabolic syndrome is a complex metabolic disturbance due to an interaction between genetic factors, poor dietary habits and physical inactivity.

Aims:

To investigate the role of dietary intake on the prevalence of the metabolic syndrome in a population of elderly, socially active women in Brazil.

Patients and Methods:

A total of 284 women with mean age 69.3 ± 6.3 years were evaluated in a cross-sectional retrospective study. The metabolic syndrome was diagnosed according to criteria of the International Diabetes Federation. The dietary intake was evaluated through a questionnaire for 24-hour dietary recall. The groups with or without the metabolic syndrome were compared for dietary intake and risk factors for metabolic syndrome by the multiple regression model adjusted for age, smoking, physical activity, educational level, total energy intake and fiber contents of the diet. The odds ratio for the presence of the metabolic syndrome was calculated for each nutrient by quartile for total energy intake adjusted by the residue method.

Results:

The prevalence of metabolic syndrome was 32% in the sample. There was not found any association between dietary intake, including all macronutrients and several micronutrients, and the presence of metabolic syndrome.

Conclusion:

No associations were observed between nutritional factors and the prevalence of the metabolic syndrome in elderly women, a result possibly due to the fact that these factors have an influence in earlier phases of life, or to a recent modification of dietary habits, which however was not able to prevent the establishment of the syndrome.

Long-term high fructose and saturated fat diet affects plasma fatty acid profile in rats

As the consumption of fructose and saturated fatty acids (FAs) has greatly increased in western diets and is linked with an increased risk of metabolic syndrome, the aim of this study was to investigate the effects of a moderate (10 weeks) and a prolonged (30 weeks) high fructose and saturated fatty acid (HFS) diet on plasma FA composition in rats. The effects of a few weeks of HFS diet had already been described, but in this paper we tried to establish whether these effects persist or if they are modified after 10 or 30 weeks. We hypothesized that the plasma FA profile would be altered between 10 and 30 weeks of the HFS diet. Rats fed with either the HFS or a standard diet were tested after 10 weeks and again after 30 weeks. After 10 weeks of feeding, HFS-fed rats developed the metabolic syndrome, as manifested by an increase in fasting insulinemia, total cholesterol and triglyceride levels, as well as by impaired glucose tolerance. Furthermore, the plasma FA profile of the HFS group showed higher proportions of monounsaturated FAs like palmitoleic acid [16:1(n-7)] and oleic acid [18:1(n-9)], whereas the proportions of some polyunsaturated n-6 FAs, such as linoleic acid [18:2(n-6)] and arachidonic acid [20:4(n-6)], were lower than those in the control group. After 30 weeks of the HFS diet, we observed changes mainly in the levels of 16:1(n-7) (decreased) and 20:4(n-6) (increased). Together, our results suggest that an HFS diet could lead to an adaptive response of the plasma FA profile over time, in association with the development of the metabolic syndrome.

A rice-based traditional dietary pattern is associated with obesity in Korean adults

BACKGROUND

Dietary patterns are critical in the prevention of chronic disease. The relationship between specific dietary patterns and obesity has not been evaluated in a Korean adult population.

OBJECTIVE

This study examined whether specific dietary patterns are associated with obesity using survey data of the largest, nationally representative, general Korean population.

DESIGN

The cross-sectional study was comprised of 10,089 Korean adults (19 years or older) who participated in the second and third Korean National Health and Nutrition Examination Surveys conducted in 2001 and 2005, respectively. Dietary data were assessed by 24-hour recall method. Obesity was defined as body mass index (calculated as kg/m(2)) ≥25, which is the cutoff point for adults in the Asian and Pacific regions.

RESULTS

Four dietary patterns were derived using factor analysis (white rice and kimchi pattern; high-fat, sweets, and coffee pattern; meat and alcohol pattern; and grains, vegetables, and fish pattern). Each dietary pattern explained 8.6%, 6.7%, 5.7%, and 5.7% of the variation in food intake, respectively. The white rice and kimchi pattern (P for trend=0.0039) and the high-fat, sweets, and coffee pattern (P for trend=0.0054) were positively associated with obesity after adjustments for age, sex, energy intake, alcohol intake, smoking status, physical activity, and chronic diseases. No significant association was found among the meat and alcohol pattern; the grains, vegetables, and fish pattern; and obesity.

CONCLUSIONS

Specific dietary patterns, which include the white rice and kimchi and high-fat, sweets, and coffee patterns, may be independently associated with obesity in Korean adults.

Effect of the protein:carbohydrate ratio in hypoenergetic diets on metabolic syndrome risk factors in exercising overweight and obese women

Overweight and obesity are growing problems both in Canada and around the world. Obesity is associated with a number of chronic diseases including type 2 diabetes and CVD, which puts a tremendous burden on the health care systems in place. The present study sought to investigate whether there were differences in the effectiveness of three low-fat, hypo- and isoenergetic diets differing in protein:carbohydrate ratio, low protein (LP, 1 g protein:4 g carbohydrate), normal protein (NP, 1 g protein:2 g carbohydrate) or high protein (HP, 1 g protein:1 g carbohydrate), on weight loss and markers of the metabolic syndrome (MetS) in overweight women. Subjects were randomly assigned to receive one of three intervention diets, all of which included a 60 min exercise programme three times/week for 12 weeks. Of the total subjects, fifty-four overweight and obese local women with MetS risk factors completed the study. All groups had similar improvements in body weight, insulin sensitivity, lipid profile, blood pressure and fitness. Subjects reported that the NP diet was easier to comply with and achieved better improvements in body fat, waist circumference and waist:hip ratio, and preservation of lean mass compared with the other two diets. In conclusion, energy restriction and exercise both facilitate weight loss in overweight and obese subjects and reduce symptoms of the MetS. A diet with a 1:2 protein:carbohydrate ratio promoted better improvements than either the LP or HP diets, and may be superior in reducing long-term chronic disease risk in this population.

A high-fat diet and the threonine-encoding allele (Thr54) polymorphism of fatty acid-binding protein 2 reduce plasma triglyceride-rich lipoproteins

The threonine-encoding allele (Thr54) of the fatty acid-binding protein 2 (FABP2) DNA polymorphism is associated with increased triglyceride (TG)-rich lipoproteins (TRL). We hypothesized that the TRL response to diets of varied fat content is affected by the FABP2 A54T polymorphism, specifically that a high-fat diet would reduce TRL and that the Thr54 allele would have an enhanced response. Sixteen healthy, postmenopausal women completed a crossover dietary intervention that included three 8-week, isoenergetic diet treatments. The treatments consisted of high fat (40% of energy as fat), low fat (20% of energy), and low fat + n-3 fatty acids (20% of energy plus 3% as n-3 fatty acids). Eight subjects were homozygous for the wild type (Ala54/Ala54) of the FABP2 polymorphism, whereas 8 subjects had at least 1 Thr54 allele (7, Ala54/Thr54; 1, Thr54/Thr54). High-fat diet showed significantly reduced plasma TGs, chylomicron TG, and very low-density lipoprotein TG from baseline in all participants. Although carriers of the Thr54 allele of the FABP2 polymorphism had significantly reduced TRL, there is no evidence of an interaction, which does not support our hypothesis. The alanine-encoding allele did not influence the dietary effects on the plasma lipids.

A diet lower in digestible carbohydrate results in lower postprandial glucose concentrations compared with a traditional canine diabetes diet and an adult maintenance diet in healthy dogs

The aim of this study was to compare the effects of three diets with varying macronutrient and fibre contents on postprandial plasma glucose, triglyceride, free fatty acid, and insulin concentrations over a 12 h period in 12 healthy neutered lean dogs. Each diet was fed to each dog for 3 weeks in a three-period cross-over study. Plasma analyte concentrations were measured prior to and after a meal at the end of the third week of each period. Postprandial glucose concentrations for the moderate carbohydrate and fibre diet were 0.4-0.7 mmol/L (8-12 mg/dL) lower than for both higher carbohydrate diets (p≤0.02). Postprandial glucose, insulin, and triglyceride concentrations in some dogs did not return to baseline by 12 h after feeding of each of the three diets. These results indicate that the moderate carbohydrate and fibre diet warrants evaluation in diabetic dogs. Variables should be measured over at least 12 h after feeding to fully evaluate postprandial dietary effects on these analytes.

Associations of the SREBP-1c gene polymorphism with gender-specific changes in serum lipids induced by a high-carbohydrate diet in healthy Chinese youth

We investigated the possible association between the sterol regulatory element-binding protein-1c gene (SREBP-1c) rs2297508 polymorphism and the changes in lipid profiles in a high-carbohydrate and low-fat (high-CHO/LF) diet in a Chinese population well characterized by a lower incidence of coronary heart disease and a diet featuring higher carbohydrate and lower fat. Fifty-six healthy youth (aged 22.89 ± 1.80 years) were given wash-out diets of 31% fat and 54% carbohydrate for 7 days, followed by the high-CHO/LF diet of 15% fat and 70% carbohydrate for 6 days, without total energy restriction. Fasting blood samples were collected. Serum variables of lipid and glucose metabolism after the wash-out and high-CHO/LF diets, as well as the rs2297508 polymorphism, were analyzed. Compared with the male subjects on the wash-out diet, significantly elevated levels of high-density lipoprotein cholesterol (HDL-C) and decreased levels of apolipoprotein B-100 were observed in the male carriers of the C allele after the high-CHO/LF diet. In the female subjects, significantly increased triacylglycerol levels, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) were found in the GG genotype after the high-CHO/LF diet. These results suggest that the C allele of the rs2297508 polymorphism is associated with a retardation of the increases in serum triacylglycerol, serum insulin, and HOMA-IR in females and with the elevated serum HDL-C in males after the high-CHO/LF diet.

Lifestyle intervention leading to moderate weight loss normalizes postprandial triacylglycerolemia despite persisting obesity

Obesity is associated with impaired postprandial triacylglycerolemia, an independent risk factor for cardiovascular disease. Given that obesity is hard to treat, efforts should focus on treating its comorbidities. We aimed to investigate whether moderate weight loss normalizes postprandial triacylglycerol (TAG) concentrations, in the absence of the acute effects of negative energy balance. For this purpose, postprandial lipemia was investigated in eight obese but otherwise healthy, sedentary men (age: 41.3 ± 4.1 years, BMI: 36.5 ± 1.6 kg·m(-2)), once before and again after a 10% weight loss followed by ≥4 weeks of weight maintenance, and was compared with that of eight age-matched healthy lean men (BMI: 24.7 ± 0.6 kg·m(-2)). Dietary intervention consisted of reduced carbohydrate and saturated fat intake and increased monounsaturated fat intake. Obese volunteers were advised to increase physical activity using pedometers to record daily activity. Postprandial triacylglycerolemia after weight loss was reduced by 27-46% (P < 0.05), and became similar to that of lean men despite persisting obesity (BMI after weight loss: 32.9 ± 1.5 kg·m(-2)). Reduction in postprandial TAG responses was inversely correlated with the decrease in postprandial insulin sensitivity index (ISI) after weight loss (r = -0.714, P = 0.047). We conclude that moderate weight loss induced by a low-carbohydrate and saturated fat diet and a slight increase in daily physical activity normalizes postprandial triacylglycerolemia in obese men, independently of acute diet-induced negative energy balance, and possibly through enhancement of insulin action.

A comparison of normal versus low dietary carbohydrate intake on substrate oxidation during and after moderate intensity exercise in women

We compared the effects of consuming a 2-day low-carbohydrate (CHO) diet (low-CHO; 20% CHO, 40% protein, 40% fat) versus an isocaloric 2-day moderate-CHO diet (mod-CHO; 55% CHO, 15% protein, 30% fat) on substrate oxidation during and after exercise in ten active, young women. Subjects were 24.9 ± 6.2% body fat with a VO(2max) of 68.8 ± 13.8 ml/kg FFM/min. For 2 days prior to exercise, subjects consumed either the mod-CHO or the low-CHO diet and then completed treadmill exercise at 55% of VO(2max) until 350 kcal of energy was expended. During exercise and for 2 h post-exercise, expired gases were analyzed to determine oxidation rates for CHO (CHO-OX) and fat (FAT-OX). Significant differences (p < 0.05) were found between diets for CHO-OX and FAT-OX (mg/kg FFM/min) during exercise, 1 h post-ex, and 2 h post-ex. During exercise, FAT-OX was higher (low-CHO 8.7 ± 2.2 vs. mod-CHO 6.2 ± 2.2) and CHO-OX was lower (low-CHO 25.1 ± 5.6 vs. mod-CHO 31.1 ± 6.2) following the low-CHO diet. A similar trend was observed during 1 h post-ex for FAT-OX (low-CHO 2.2 ± 0.5 vs. mod-CHO 1.6 ± 0.5) and CHO-OX (low-CHO 2.5 ± 1.2 vs. mod-CHO 4.1 ± 1.9), as well as 2 h post-ex for FAT-OX (low-CHO vs. 1.9 ± 0.5 mod-CHO 1.7 ± 0.4) and CHO-OX (low-CHO 2.5 ± 0.9 vs. mod-CHO 3.1 ± 1.1). Significant positive correlations were observed between VO(2max) and CHO-OX during exercise and post-exercise, as well as significant negative correlations between VO(2max) and FAT-OX post-exercise in the low-CHO condition. Waist circumference and FAT-OX exhibited a significant negative correlation during exercise in the low-CHO condition. Dietary macronutrient intake influenced substrate oxidation in active young women during and after moderate intensity exercise.

Effects of energy balance on postprandial triacylglycerol metabolism

PURPOSE OF REVIEW

To present the effect of negative energy balance on postprandial triacylglycerol concentrations (pTAG), an independent risk factor for the development of cardiovascular disease.

RECENT FINDINGS

Aerobic exercise reduces pTAG; however, recent findings confirm that this effect is only evident with an accompanying energy deficit. Moreover, a recent study showed that acute diet-induced energy deficit also reduces pTAG. The extent of energy deficit required to significantly attenuate pTAG depends on the type of given meal, the type of deficit (aerobic/resistance exercise, diet, or combination of diet and exercise), and patients' health status. Apart from the acute effects, prolonged energy deficit leading to moderate weight loss attenuates pTAG, when it is combined with other known hypotriacylglycerolemic agents, such as carbohydrate restriction.

SUMMARY

For healthy population, it seems that it is up to patient's preference and ability which type of energy deficit will follow to attenuate pTAG; an energy deficit of approximately 30 kJ/kg of body mass is required; for resistance exercise a smaller deficit is probably sufficient. More studies are needed to investigate dose-response/plateau effects, the effects of energy deficit-energy surplus every other day, and the threshold of energy deficit-weight loss in diabetics and other high-risk populations. Finally, investigation of the underlying mechanisms may be clinicall helpful in individualizing the appropriate intervention.

Current concepts in triglyceride metabolism, pathophysiology, and treatment

It is becoming more evident that age, gender, and race play a significant role in the metabolic profiles that are seen among individuals in a clinical setting. It is important to understand these variances in metabolic profiles; and with these variances in mind it is now possible to understand why a single diet might not decrease cardiovascular disease risk profiles uniformly for everyone. Much is now understood about triglyceride metabolism and its contribution to energy storage. In this review we will focus on triglycerides; their production, metabolism and influence on daily life, as well as the various methods for the treatment of hypertryglyceridemia and prevention of its sequelae.

Dietary meat fats and burden of cardiovascular disease risk factors, in the elderly: a report from the MEDIS study

Dietary fats have long been associated with human health, and especially cardiovascular disease (CVD). Some observational studies have shown that reduction in dietary fats, and particularly cholesterol is associated with lower cardiovascular risk; however, other prospective studies or randomized controlled trials of dietary fat reduction or modification have shown varying results on CVD morbidity and mortality. In this work we evaluated the relationships between dietary fats and a cluster of CVD risk factors (i.e., diabetes, obesity, hypercholesterolemia, hypertension), among elderly individuals without known CVD. In particular, dietary and clinical data from 1486 elderly (aged 65 to 100 years) men and women living in Cyprus, Mitilini, Samothraki, Cephalonia, Crete, Lemnos, Syros, Naxos, Corfu and Zakynthos islands, and participated in the MEDIS study, were analysed. Data analysis revealed that 18.5% of males and 33.3% of females had three or four cardiovascular disease risk factors; the major source of fat was olive oil (mean intake for men and women 50.0 +/- 19.3 g/day and 46.0 +/- 16.8 g/day, p < 0.001). In addition it was observed that a 5% increase in energy adjusted fat intake from meat was associated with a 21% increase in the likelihood of having one additional CVD risk factor (95%CI 6%-39%); no significant associations were observed regarding the other types of fat consumed by the elderly participants. These findings may state a hypothesis that the consumption of fat only from meat or its products seems to increase the burden of CVD risk factors among CVD-free, elderly people.

Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity

The content of meals consumed after exercise can impact metabolic responses for hours and even days after the exercise session. The purpose of this study was to compare the effect of low dietary carbohydrate (CHO) vs. low energy intake in meals after exercise on insulin sensitivity and lipid metabolism the next day. Nine healthy men participated in four randomized trials. During the control trial (CON) subjects remained sedentary. During the other three trials, subjects exercised [65% peak oxygen consumption (Vo(2 peak)); cycle ergometer and treadmill exercise] until they expended approximately 800 kcal. Dietary intake during CON and one exercise trial (BAL) was designed to provide sufficient energy and carbohydrate to maintain nutrient balance. In contrast, the diets after the other two exercise trials were low in either CHO (LOW-CHO) or energy (LOW-EN). The morning after exercise we obtained a muscle biopsy, assessed insulin sensitivity (S(i); intravenous glucose tolerance test) and measured lipid kinetics (isotope tracers). Although subjects were in energy balance during both LOW-CHO and CON, the lower muscle glycogen concentration during LOW-CHO vs. CON (402 +/- 29 vs. 540 +/- 33 mmol/kg dry wt, P < 0.01) coincided with a significant increase in S(i) [5.2 +/- 0.7 vs. 3.8 +/- 0.7 (mU/l)(-1) x min(-1); P < 0.05]. Conversely, despite ingesting several hundred fewer kilocalories after exercise during LOW-EN compared with BAL, this energy deficit did not affect S(i) the next day [4.9 +/- 0.9, and 5.0 +/- 0.8 (mU/l)(-1) x min(-1)]. Maintaining an energy deficit after exercise had the most potent effect on lipid metabolism, as measured by a higher plasma triacylglycerol concentration, and increased plasma fatty acid mobilization and oxidation compared with when in nutrient balance. Carbohydrate deficit after exercise, but not energy deficit, contributed to the insulin-sensitizing effects of acute aerobic exercise, whereas maintaining an energy deficit after exercise augmented lipid mobilization.

The role of Mediterranean type of diet on the development of cancer and cardiovascular disease, in the elderly: a systematic review

BACKGROUND

The proportion of elderly worldwide is increasing. This increase in life expectancy, is staggering posing tremendous challenges in disease burden, especially, in chronic diseases such as obesity, diabetes, hypertension, hypercholesterolemia, cancer and cardiovascular disease (CVD). Limited studies investigate the effect of Mediterranean diet on cardiovascular risk and cancer in older populations. In this review, findings from observational studies are summarized to evaluate the effect of Mediterranean diet on cancer and cardiovascular disease risk in elderly people.

METHODS

Published results from observational studies that assessed food habits on cancer and cardiovascular disease risk in elderly were retrieved and summarized.

RESULTS

In all studies diet had an effect on cardiovascular disease risk. The Mediterranean diet, a high-quality diet and increased fruit and vegetable consumption were all found to be cardioprotective.

CONCLUSION

The systematically reviewed studies reveal that a high adherence to a Mediterranean type of diet or "prudent diet" is associated with reduced risk of CVD and some types of cancer, even in the elderly. Also dietary intervention strategies can prevent morbidity, premature mortality and improve quality of life in older persons worldwide.

Effects of dietary coconut oil on the biochemical and anthropometric profiles of women presenting abdominal obesity

The effects of dietary supplementation with coconut oil on the biochemical and anthropometric profiles of women presenting waist circumferences (WC) >88 cm (abdominal obesity) were investigated. The randomised, double-blind, clinical trial involved 40 women aged 20-40 years. Groups received daily dietary supplements comprising 30 mL of either soy bean oil (group S; n = 20) or coconut oil (group C; n = 20) over a 12-week period, during which all subjects were instructed to follow a balanced hypocaloric diet and to walk for 50 min per day. Data were collected 1 week before (T1) and 1 week after (T2) dietary intervention. Energy intake and amount of carbohydrate ingested by both groups diminished over the trial, whereas the consumption of protein and fibre increased and lipid ingestion remained unchanged. At T1 there were no differences in biochemical or anthropometric characteristics between the groups, whereas at T2 group C presented a higher level of HDL (48.7 +/- 2.4 vs. 45.00 +/- 5.6; P = 0.01) and a lower LDL:HDL ratio (2.41 +/- 0.8 vs. 3.1 +/- 0.8; P = 0.04). Reductions in BMI were observed in both groups at T2 (P < 0.05), but only group C exhibited a reduction in WC (P = 0.005). Group S presented an increase (P < 0.05) in total cholesterol, LDL and LDL:HDL ratio, whilst HDL diminished (P = 0.03). Such alterations were not observed in group C. It appears that dietetic supplementation with coconut oil does not cause dyslipidemia and seems to promote a reduction in abdominal obesity.

Factors Associated with the Prevalence of Diabetes Mellitus Among Elderly Men and Women Living in Mediterranean Islands: The MEDIS Study

BACKGROUND

The aim of the present work was to evaluate the relationships between socio-demographic, clinical, lifestyle and psychological characteristics and the presence of diabetes mellitus, among elderly individuals without known cardiovascular disease.

METHODS

During 2005-2007, 1190 elderly (aged 65 to 100 years) men and women (from Cyprus, Mitilini, Samothraki, Cephalonia, Crete, Lemnos, Corfu and Zakynthos) were enrolled. Socio-demographic, clinical and lifestyle factors were assessed using standard procedures. Diabetes mellitus was defined as fasting blood glucose >125 mg/dl or use of special medication.

RESULTS

21% of males and 23% of females had diabetes. Only 70% of diabetic participants were on a special diet and 76% were receiving pharmaceutical treatment. Diabetic individuals had higher prevalence of hypertension (80% vs. 64%, p < 0.001) and hypercholesterolemia (63% vs. 51%, p < 0.001) and reported lower physical activity status (p < 0.001), compared with non-diabetic participants. After adjusting for various confounders, hypertension and hypercholesterolemia were associated with a 144% (95% CI, 1.37-4.35) and 83% (95% CI, 1.13-2.94) higher likelihood of having diabetes, while moderate and vigorous exercise correlated with a 82% (95% CI, 0.09-0.81) and 67% (95% CI, 0.11-0.97) lower likelihood of diabetes.

CONCLUSIONS

A considerable proportion of our elderly sample had diabetes and other metabolic disorders, almost 25% of which were untreated. Promotion of physical activities, even in the elderly, may contribute to reducing their burden of diabetes and provide them with a better quality of living.

Increased body mass and depressive symptomatology are associated with hypercholesterolemia, among elderly individuals; results from the MEDIS study

BACKGROUND

Hypercholesterolemia is one of the most important factors causing cardiovascular disease (CVD). The aim of the present work was to evaluate the relationships between socio-demographic, clinical, lifestyle and depression status and the presence of hypercholesterolemia, among elderly individuals without known CVD.

METHODS

During 2005-2007, 1190 elderly (aged 65 to 100 years) men and women (from Cyprus, Mitilini, Samothraki, Cephalonia, Crete, Lemnos, Corfu and Zakynthos) were enrolled. Socio-demographic, clinical and lifestyle factors were assessed through standard procedures. Symptoms of depression were evaluated using the short-form of the Geriatric Depression Scale (GDS, range 0-15). Dietary habits were assessed through a semi-quantitative food frequency questionnaire. Hypercholesterolemia was defined as total serum cholesterol > 200 mg/dL or use of lipids lowering medication.

RESULTS

44.6% of males and 61.9% of females had hypercholesterolemia (p < 0.001). Only, 63% of hypercholesterolemic participants were under special diet or pharmaceutical treatment. Hypercholisterolemic individuals had higher prevalence of obesity (43% vs. 25%), hypertension (76% vs. 57%) and diabetes (25% vs. 17%) compared with normal participants (p < 0.001). Furthermore, hypercholisterolemic participants showed higher depression levels (p = 0.002). After adjusting for various confounders, GDS score and BMI correlated with 13% (95%CI 0.98-1.30) and 14% (95%CI 0.99-1.31) higher likelihood of having hypercholesterolemia.

CONCLUSION

A considerable proportion of our elderly sample had hypercholesterolemia, while 1/3 of them were untreated. Furthermore, presence of hypercholesterolemia was correlated with depressive symptomatology and increased BMI.

Perfil lipídico tecidual de ratos alimentados com diferentes fontes lipídicas

OBJETIVO:Determinar se fontes lipídicas com diferentes razões de ácidos graxos insaturados e saturados (PUFA+MUFA)/SFA na dieta altera o perfil lipídico tecidual, a concentração de lipídios (mg/g) dos tecidos hepáticos e mesentérico e a digestibilidade lipídica. MÉTODOS: Foi realizada cromatografia gasosa para determinar o perfil de ácidos graxos nos tecidos hepático e adiposo de ratos alimentados com diferentes fontes lipídicas. O coeficiente de digestibilidade foi determinado a partir da relação entre a quantidade de lipídios consumidos e a quantidade fecal excretada. RESULTADOS:Diferentes fontes lipídicas (óleo de soja, manteiga, margarina e gorduras de porco e de peixe) não alteraram o coeficiente de digestibilidade e o peso hepático, mas alteraram a deposição de lipídios em todos os tecidos adiposos estudados. Não foi possível fazer a correlação direta entre o perfil dietário dos ácidos graxos não essenciais e sua deposição nos tecidos estudados, visto que a lipogênese de novo impede a identificação dos ácidos graxos dietários. CONCLUSÃO:Não foi constatada uma relação direta entre o perfil dietário dos ácidos graxos e sua deposição nos tecidos estudados, exceto para os ácidos graxos trans e linoléico (C18:2) que não são sintetizados no rato. Esses ácidos graxos apresentaram uma concentração tecidual diretamente proporcional àquela das fontes dietárias. Quanto à razão (PUFA+MUFA)/SFA, encontrada no tecido hepático dos diferentes grupos, observa-se que esta foi diretamente proporcional aos valores apresentados pelas fontes lipídicas dietárias. Entretanto, essa associação não foi observada nos tecidos adiposos analisados.