Differences in short-term metabolic responses to a lipid load in lean (resistant) vs obese (susceptible) young male subjects with habitual high-fat consumption

Pentacyclic triterpenoid acids in Styrax as potent and highly specific inhibitors against human carboxylesterase 1A

Human carboxylesterase 1A1 (hCES1A) is a promising target for the treatment of hyperlipidemia and obesity-associated metabolic diseases. To date, the highly specific and efficacious hCES1A inhibitors are rarely reported. This study aims to find potent and highly specific hCES1A inhibitors from herbs, and to investigate their inhibitory mechanisms. Following large-scale screening of herbal products, Styrax was found to have the most potent hCES1A inhibition activity. After that, a practical bioactivity-guided fractionation coupling with a chemical profiling strategy was used to identify the fractions from Styrax with strong hCES1A inhibition activity and the major constituents in these bioactive fractions were characterized by LC-TOF-MS/MS. The results demonstrated that seven pentacyclic triterpenoid acids (PTAs) in two bioactive fractions from Styrax potently inhibit hCES1A, with IC50 values ranging from 41 nM to 478 nM. Among all the identified PTAs, epibetulinic acid showed the most potent inhibition activity and excellent specificity towards hCES1A. Both inhibition kinetic analyses and in silico analysis suggested that epibetulinic acid potently inhibited hCES1A in a mixed inhibition manner. Collectively, our findings demonstrate that some PTAs in Styrax are potent and highly specific inhibitors of hCES1A and these constituents can be used as promising lead compounds for the development of more efficacious hCES1A inhibitors.

The Effect of Partly Replacing Vegetable Fat with Bovine Milk Fat in Infant Formula on Postprandial Lipid and Energy Metabolism: A Proof-of-principle Study in Healthy Young Male Adults

SCOPE

Infant formula (IF) uses besides vegetable fats also bovine milk fat, which differs in triacylglycerol (TAG) structure. Furthermore, it differs in fatty acid (FA) composition. Whether changing fat source in IF affects postprandial energy metabolism, lipemic response, and blood lipid profile is unknown.

METHODS AND RESULTS

A proof-of-principle study, with a randomized controlled double-blind cross-over design, is conducted. Twenty healthy male adults consumed drinks with either 100% vegetable fat (VEG) or 67% bovine milk fat and 33% vegetable fat (BOV), on 2 separate days. For a detailed insight in the postprandial responses, indirect calorimetry is performed continuously, and venous blood samples are taken every 30 min, until 5 h postprandially. No differences in postprandial energy metabolism, serum lipids, lipoprotein, or chylomicron concentrations are observed between drinks. After consumption of VEG-drink, C18:2n-6 in serum increased. Observed differences in chylomicron FA profile reflect differences in initial FA profile of test drinks. Serum ketone bodies concentrations increase following consumption of BOV-drink.

CONCLUSIONS

The use of bovine milk fat in IF does neither affect postprandial energy metabolism nor lipemic response in healthy adults, but alters postprandial FA profiles and ketone metabolism. Whether the exact same effects occur in infants requires experimental verification.

Leptin mediates postprandial increases in body temperature through hypothalamus-adrenal medulla-adipose tissue crosstalk

Meal ingestion increases body temperature in multiple species, an effect that is blunted by obesity. However, the mechanisms responsible for these phenomena remain incompletely understood. Here we show that refeeding increases plasma leptin concentrations approximately 8-fold in 48-hour-fasted lean rats, and this normalization of plasma leptin concentrations stimulates adrenomedullary catecholamine secretion. Increased adrenal medulla-derived plasma catecholamines were necessary and sufficient to increase body temperature postprandially, a process that required both fatty acids generated from adipose tissue lipolysis and β-adrenergic activation of brown adipose tissue (BAT). Diet-induced obese rats, which remained relatively hyperleptinemic while fasting, did not exhibit fasting-induced reductions in temperature. To examine the impact of feeding-induced increases in body temperature on energy balance, we compared rats fed chronically by either 2 carbohydrate-rich boluses daily or a continuous isocaloric intragastric infusion. Bolus feeding increased body temperature and reduced weight gain compared with continuous feeding, an effect abrogated by treatment with atenolol. In summary, these data demonstrate that leptin stimulates a hypothalamus-adrenal medulla-BAT axis, which is necessary and sufficient to induce lipolysis and, as a result, increase body temperature after refeeding.

Body composition, not dietary fatty acid composition, explains metabolic responses following a high-fat meal in premenopausal normal-weight women: a single-blind, randomised, crossover study

The aim of this study was to examine the effect of three different fatty acid (FA)-rich meals enriched in either SFA, MUFA or PUFA on postprandial metabolic responses in premenopausal, normal-weight women. For this randomised, single-blind, crossover study, three high-fat (HF) meals rich in either SFA, MUFA or PUFA (65 % energy from fat; 35 % of participants’ total daily energy needs) were tested. For each visit, anthropometrics and RMR were measured following a 12–15 h fast. Then, participants consumed one of the HF meals, and respiratory gases were collected using indirect calorimetry for 3 h postprandially. Energy expenditure (EE) following a SFA-rich meal was significantly higher than a MUFA-rich meal (P = 0·04; η2 = 0·19), but SFA was not significantly different from PUFA. There was a trend towards significance in EE between PUFA and MUFA (P = 0·06). After adjusting for fat-free mass (FFM), there were no longer condition or time effects for EE, although FFM remained a significant predictor (P = 0·005; η2 = 0·45). There were no significant differences between conditions for dietary-induced thermogenesis or substrate oxidation. The relationship between fat mass (FM) and both total fat oxidation (r 0·62; P = 0·025) and total change in RER following a MUFA-rich meal was observed (r −0·55; P = 0·05). In conclusion, weight loss through increases in EE may be best achieved by increasing FFM rather than selection of FA type. Further, a relationship exists between FM and fat oxidation following a MUFA-rich meal, most likely due to an unidentified mechanism.

Effect of macronutrient composition on meal-induced thermogenesis in adolescents with obesity

PURPOSE

Manipulation of meal macronutrient may be a useful way to modulate meal-induced thermogenesis (MIT) to induce increases in energy expenditure. The objective of this study was to examine in adolescents with obesity and of healthy weight and the effect of a high protein and high carbohydrate meal on MIT.

METHODS

An acute cross-over study with adolescents aged 11-19 years was undertaken. Participants consumed in random order, a high 79% carbohydrate (HCHO), and a high 55% protein (HP) meal (adjusted to 25% of energy requirements). MIT and subjective appetite were assessed for 4 h postprandial and an ad libitum lunch served. Data calculated as total AUC and expressed as mean ± SEM.

RESULTS

Thirteen adolescents with obesity (mean BMI z score 2.3 ± 0.1) and 13 healthy weight (BMI z score 0.0 ± 0.2) participated. Mean MIT (% of energy intake) was greater after the HP (8.19 ± 0.709%) compared with the HCHO meal (4.36 ± 0.480%) (p < 0.001). The HP compared with the HCHO meal promoted greater fullness (12,994 ± 1208 vs 11,186 ± 1220 mm/4 h) (p = 0.016) and decreased hunger (8868 ± 1315 vs 10984 mm ± 1438 mm/4 h) (p = 0.007). These effects observed were independent of body weight.

CONCLUSIONS

High protein meals can increase MIT and fullness and reduce hunger compared with high carbohydrate meals in adolescents with obesity. Future research is warranted to determine if MIT can be targeted through manipulation of dietary choices to support weight management strategies.

TRIAL REGISTRATION

This study is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR). Trial ID: ACTRN12612001066875.

Obesity, Metabolic Syndrome, and Musculoskeletal Disease: Common Inflammatory Pathways Suggest a Central Role for Loss of Muscle Integrity

Inflammation can arise in response to a variety of stimuli, including infectious agents, tissue injury, autoimmune diseases, and obesity. Some of these responses are acute and resolve, while others become chronic and exert a sustained impact on the host, systemically, or locally. Obesity is now recognized as a chronic low-grade, systemic inflammatory state that predisposes to other chronic conditions including metabolic syndrome (MetS). Although obesity has received considerable attention regarding its pathophysiological link to chronic cardiovascular conditions and type 2 diabetes, the musculoskeletal (MSK) complications (i.e., muscle, bone, tendon, and joints) that result from obesity-associated metabolic disturbances are less frequently interrogated. As musculoskeletal diseases can lead to the worsening of MetS, this underscores the imminent need to understand the cause and effect relations between the two, and the convergence between inflammatory pathways that contribute to MSK damage. Muscle mass is a key predictor of longevity in older adults, and obesity-induced sarcopenia is a significant risk factor for adverse health outcomes. Muscle is highly plastic, undergoes regular remodeling, and is responsible for the majority of total body glucose utilization, which when impaired leads to insulin resistance. Furthermore, impaired muscle integrity, defined as persistent muscle loss, intramuscular lipid accumulation, or connective tissue deposition, is a hallmark of metabolic dysfunction. In fact, many common inflammatory pathways have been implicated in the pathogenesis of the interrelated tissues of the musculoskeletal system (e.g., tendinopathy, osteoporosis, and osteoarthritis). Despite these similarities, these diseases are rarely evaluated in a comprehensive manner. The aim of this review is to summarize the common pathways that lead to musculoskeletal damage and disease that result from and contribute to MetS. We propose the overarching hypothesis that there is a central role for muscle damage with chronic exposure to an obesity-inducing diet. The inflammatory consequence of diet and muscle dysregulation can result in dysregulated tissue repair and an imbalance toward negative adaptation, resulting in regulatory failure and other musculoskeletal tissue damage. The commonalities support the conclusion that musculoskeletal pathology with MetS should be evaluated in a comprehensive and integrated manner to understand risk for other MSK-related conditions. Implications for conservative management strategies to regulate MetS are discussed, as are future research opportunities.

Prediction Equations Overestimate the Energy Requirements More for Obesity-Susceptible Individuals

Predictive equations to estimate resting metabolic rate (RMR) are often used in dietary counseling and by online apps to set energy intake goals for weight loss. It is critical to know whether such equations are appropriate for those susceptible to obesity. We measured RMR by indirect calorimetry after an overnight fast in 26 obesity susceptible (OSI) and 30 obesity resistant (ORI) individuals, identified using a simple 6-item screening tool. Predicted RMR was calculated using the FAO/WHO/UNU (Food and Agricultural Organisation/World Health Organisation/United Nations University), Oxford and Miflin-St Jeor equations. Absolute measured RMR did not differ significantly between OSI versus ORI (6339 vs. 5893 kJ·d⁻¹, p = 0.313). All three prediction equations over-estimated RMR for both OSI and ORI when measured RMR was ≤5000 kJ·d⁻¹. For measured RMR ≤7000 kJ·d⁻¹ there was statistically significant evidence that the equations overestimate RMR to a greater extent for those classified as obesity susceptible with biases ranging between around 10% to nearly 30% depending on the equation. The use of prediction equations may overestimate RMR and energy requirements particularly in those who self-identify as being susceptible to obesity, which has implications for effective weight management.

Lean and obese dietary phenotypes: differences in energy and substrate metabolism and appetite

This study aimed to characterise lean and obese phenotypes according to diet and body composition, and to compare fasting and postprandial appetite and metabolic profiles following a high-fat test meal. A total of ten lean (BMI<25 kg/m2) high-fat (LHF), ten lean low-fat (LLF; >40 and <30 % energy from fat) and ten obese (BMI>30 kg/m2) high-fat consumers (OHF; >40 % energy from fat) were recruited. Before and following the test meal (4727 kJ (1130 kcal), 77 % fat, 20 % carbohydrate (CHO) and 3 % protein), fasting plasma glucose, insulin, leptin, ghrelin, peptide YY (PYY), RER, RMR and subjective appetite ratings (AR) were measured for 6 h. Thereafter, subjects consumed a self-selected portion of a standardised post-test meal (40 % fat, 45 % CHO and 15 % protein) and reported AR. Fasting (P=0·01) and postprandial (P<0·001) fat oxidation was significantly higher in LHF than in LLF but was not different between LHF and OHF. Although similar between the lean groups, fasting and postprandial energy expenditures were significantly higher in OHF compared with LHF (P<0·01). Despite similar AR across groups, LLF consumed a relatively greater quantity of the post-test meal than did LHF (7·87 (sd 2·96) v. 7·23 (sd 2·67) g/kg, P=0·013). The lean groups showed appropriate changes in plasma ghrelin and PYY following the test meal, whereas the OHF group showed a blunted response. In conclusion, the LHF phenotype had a greater capacity for fat oxidation, which may be protective against weight gain. OHF individuals had a blunted appetite hormone response to the high-fat test meal, which may subsequently increase energy intake, driving further weight gain.

Higher visceral adiposity is associated with an enhanced early thermogenic response to carbohydrate-rich food

BACKGROUND

Studies examining the dynamics of the thermic effect of feeding (TEF) of specific food items and the relationship of TEF to visceral adiposity are limited.

METHODS

We measured resting energy expenditure (REE) and early-TEF (40-min postprandial, e-TEF) after 8-h fast by indirect calorimetry in 40 obese men, and imaged abdominal fat tissues by magnetic resonance imaging. Each participant was examined on two occasions, 3-weeks apart. At each examination we measured fasting REE and then postprandial REE following the isocaloric [∼380 kcal] consumption of either 56 gr walnuts [(8% carbohydrates; 84% fat, of which 72% polyunsaturated fat)], or 5-slices (150gr) of whole-grain bread (48% carbohydrates; 32% fat). e-TEF was calculated as the area under the curve between the fasting and postprandial tests.

RESULTS

Participants had a mean age of 45 ± 8 years, body-mass-index (BMI) = 31.1 ± 3.8 kg/m(2), total abdominal fat area = 901.4 ± 240 cm(2), visceral fat area (VAT) = 260 ± 102.9 cm(2), fasting REE = 1854 ± 205 kcal, REE/kg = 19.39 ± 1.73 kcal/kg, and respiratory quotient (RQ, CO2 eliminated/O2 consumed) = 0.82 ± 0.04. Individuals who exhibited increased e-TEF (top ΔAUC median) to bread had higher VAT (299 cm(2) vs. 223 cm(2); p = 0.024) and higher BMI (32.4 kg/m(2) vs. 30.0 kg/m(2); p = 0.013), compared to their peers with the lower e-TEF response (ΔAUC below median). As expected, postprandial e-TEF was higher after whole-grain bread consumption [ΔAUC = +14 kcal/40min] compared to walnuts [ΔAUC = -2 kcal/40 min; p < 0.001].

CONCLUSIONS

Higher early thermic effect of high-carbohydrate food, likely reflecting digestion, early absorption and/or sympathetic tone (rather than metabolic utilization (oxidation)), associates with visceral adiposity. Future studies are required to determine if this association represents an added causality between early carbohydrate processing and visceral fat accumulation.

Thermic effect of a meal and appetite in adults: an individual participant data meta-analysis of meal-test trials

Background

Thermic effect of a meal (TEF) has previously been suggested to influence appetite.

Objective

The aim of this study was to assess whether there is an association between appetite and TEF. Second, to examine whether protein intake is associated with TEF or appetite.

Design

Individual participant data (IPD) meta-analysis on studies were performed at the Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark. Five randomized meal-test studies, with 111 participants, were included. The included studies measured energy expenditure (EE) in respiration chambers and pre- and postprandial appetite sensations using Visual Analog Scales (VAS). The primary meta-analysis was based on a generic-inverse variance random-effects model, pooling individual study Spearman's correlation coefficients, resulting in a combined r-value with 95% confidence interval (95% CI). The I² value quantifies the proportion (%) of the variation in point estimates due to among-study differences.

Results

The IPD meta-analysis found no association between satiety and TEF expressed as the incremental area under the curve (TEF_iAUC) (r=0.06 [95% CI −0.16 to 0.28], P=0.58; I²=15.8%). Similarly, Composite Appetite Score (CAS) was not associated with TEF_iAUC (r=0.08 [95% CI −0.12 to 0.28], P=0.45; I²=0%). Posthoc analyses showed no association between satiety or CAS and TEF expressed as a percentage of energy intake (EI) (P>0.49) or TEF expressed as a percentage of baseline EE (P>0.17). When adjusting for covariates, TEF_iAUC was associated with protein intake (P=0.0085).

Conclusions

This IPD meta-analysis found no evidence supporting an association between satiety or CAS and TEF at protein intakes ∼15 E% (range 11–30 E%).

Differential proinflammatory and oxidative stress response and vulnerability to metabolic syndrome in habitual high-fat young male consumers putatively predisposed by their genetic background

The current nutritional habits and lifestyles of modern societies favor energy overloads and a diminished physical activity, which may produce serious clinical disturbances and excessive weight gain. In order to investigate the mechanisms by which the environmental factors interact with molecular mechanisms in obesity, a pathway analysis was performed to identify genes differentially expressed in subcutaneous abdominal adipose tissue (SCAAT) from obese compared to lean male (21–35 year-old) subjects living in similar obesogenic conditions: habitual high fat dietary intake and moderate physical activity. Genes involved in inflammation (ALCAM, CTSB, C1S, YKL-40, MIF, SAA2), extracellular matrix remodeling (MMP9, PALLD), angiogenesis (EGFL6, leptin) and oxidative stress (AKR1C3, UCHL1, HSPB7 and NQO1) were upregulated; whereas apoptosis, signal transcription (CITED 2 and NR3C1), cell control and cell cycle-related genes were downregulated. Interestingly, the expression of some of these genes (C1S, SAA2, ALCAM, CTSB, YKL-40 and tenomodulin) was found to be associated with some relevant metabolic syndrome features. The obese group showed a general upregulation in the expression of inflammatory, oxidative stress, extracellular remodeling and angiogenic genes compared to lean subjects, suggesting that a given genetic background in an obesogenic environment could underlie the resistance to gaining weight and obesity-associated manifestations.

Effect of high-oleic canola and flaxseed oils on energy expenditure and body composition in hypercholesterolemic subjects

OBJECTIVE

The fatty acid profile of dietary fats may contribute to its channelling toward oxidation versus storage, influencing energy and weight balance. Our objective was to compare the effects of diets enriched with high-oleic canola oil (HOCO), alone or blended with flaxseed oil (FXCO), on energy expenditure, substrate utilization, and body composition versus a typical Western diet (WD).

MATERIALS/METHODS

Using a randomized crossover design, 34 hypercholesterolemic subjects (n=22 females) consumed 3 controlled diets for 28 days containing ~49% energy from carbohydrate, 14% energy from protein, and 37% energy from fat, of which 70% of fat was provided by HOCO rich in oleic acid, FXCO rich in alpha-linolenic acid, or WD rich in saturated fat. Indirect calorimetry measured energy expenditure and substrate oxidation. Body composition was analyzed by dual-energy x-ray absorptiometry.

RESULT

After 28 days, resting and postprandial energy expenditure and substrate oxidation were not different after consumption of the HOCO or FXCO diets compared with a typical Western diet. No significant changes in body composition measures were observed between diets. However, the android-to-gynoid ratio tended to increase (P=.055) after the FXCO diet compared with the HOCO diet.

CONCLUSIONS

The data suggest that substituting a typical Western dietary fatty acid profile with HOCO or FXCO does not significantly modulate energy expenditure, substrate oxidation or body composition in hypercholesterolemic males and females.

High-fat diet-induced obesity in animal models

Epidemiological studies have shown a positive relationship between dietary fat intake and obesity. Since rats and mice show a similar relationship, they are considered an appropriate model for studying dietary obesity. The present paper describes the history of using high-fat diets to induce obesity in animals, aims to clarify the consequences of changing the amount and type of dietary fats on weight gain, body composition and adipose tissue cellularity, and explores the contribution of genetics and sex, as well as the biochemical basis and the roles of hormones such as leptin, insulin and ghrelin in animal models of dietary obesity. The major factors that contribute to dietary obesity - hyperphagia, energy density and post-ingestive effects of the dietary fat - are discussed. Other factors that affect dietary obesity including feeding rhythmicity, social factors and stress are highlighted. Finally, we comment on the reversibility of high-fat diet-induced obesity.

A dysregulation in CES1, APOE and other lipid metabolism-related genes is associated to cardiovascular risk factors linked to obesity

OBJECTIVE

The aim of the present study was to investigate the relationship between the differential expression of genes related to lipid metabolism in subcutaneous adipose tissue and metabolic syndrome features in lean and obese subjects with habitual high fat intake.

METHODS

Microarray and RT-PCR analysis were used to analyze and validate differential gene expression in subcutaneous abdominal adipose tissue samples from lean and obese phenotype subjects.

RESULTS

Several genes and transcripts involved in lipolysis were down-regulated, such as AKAP1, PRKAR2B, Gi and CIDEA, whereas NPY1R and CES1 were up-regulated, when comparing obese to lean subjects. Similarly, transcripts associated with cholesterol and lipoprotein metabolism showed a differential expression, with APOE and ABCA being decreased and VLDLR being increased in obese versus lean subjects. In addition, positive correlations were found between different markers of the metabolic syndrome and CES1 and NPY1R mRNA expressions, while APOE showed an inverse association with some of them.

CONCLUSION

Different expression patterns in transcripts encoding for proteins involved in lipolysis and lipoprotein metabolism were found between lean and obese subjects. Moreover, the dysregulation of genes such as CES1 and APOE seems to be associated with some physiopathological markers of insulin resistance and cardiovascular risk factors in obesity.

ZAG, a lipid mobilizing adipokine, is downregulated in human obesity

The main goal of this study was to compare the expression of Zinc-alpha2-glycoprotein (ZAG), a recently described adipokine, in obese and lean subjects. ZAG expression was determined by Real-time PCR analysis in subcutaneous abdominal adipose tissue of eighteen young men, 9 lean (BMI = 23.1 +/- 0.4 kg/m2) and 9 obese (34.7 +/- 1.2 kg/m2) with a similar habitual dietary intake of fat and physical activity, which were assessed by validated methods. Our data revealed that ZAG gene was downregulated (-70%; p < 0.05) in subcutaneous adipose tissue of obese compared to lean subjects. Moreover, statistically significant positive correlations between ZAG gene expression and serum adiponectin (r = 0.89; p < 0.01) and a negative correlation with the plasma levels of leptin (r = -0.82; p < 0.05) and waist circumference (r = -0.64; p < 0.05) were found in obese subjects. Our data suggest that this novel adipokine could play a role in human susceptibility to obesity related disorders and that upregulation of ZAG could be a promising therapeutic target for metabolic syndrome treatment.

Metabolic effects of oral versus transdermal estrogen in growth hormone-treated girls with turner syndrome

BACKGROUND

Transdermal (TD) estrogen is often preferred over the oral route in postmenopausal and GH-deficient women taking estrogen, but this has not been studied in detail in girls.

OBJECTIVE

Our objective was to study the metabolic effects of oral vs. TD estrogen in GH-treated girls with Turner syndrome.

DESIGN AND METHODS

Eleven girls with Turner syndrome, mean age 13.4 +/- 0.5 (se) yr, on GH for at least 6 months were recruited. Studies included [(13)C]leucine and d5-glycerol infusions, indirect calorimetry, dual-emission x-ray absorptiometry, and hormone and substrate measurements. They received, in random order, 17beta-estradiol orally (0.5, 1, and 2 mg for 2 wk each) and TD (0.025, 0.0375, and 0.05 mg for 2 wk each), and studies were repeated after each 6-wk course with 4 wk washout in between.

RESULTS

Rates of whole-body protein turnover, oxidation and synthesis, lipolysis, lipid and carbohydrate oxidation, and resting energy expenditure were unaffected by either form of estrogen; nor were lipids, insulin, and fibrinogen concentrations affected. Plasma IGF-I concentrations did not change clinically significantly with either form of estrogen, despite higher estrogen concentrations after oral estrogen. Estradiol concentrations did not correlate with any variables measured.

CONCLUSIONS

In GH-treated girls with Turner syndrome, neither oral nor TD estrogen adversely affected rates of protein turnover, lipolysis, and lipid oxidation rates or plasma lipids, fibrinogen, or fasting insulin concentrations. There was no clinically significant change in IGF-I concentrations after either form of estrogen. In aggregate, these data suggest that the route of delivery of estrogen does not adversely affect these metabolic effects of GH in young girls with Turner syndrome.