Decreased energy levels can cause and sustain obesity

Changes in the urinary metabolome accompanied alterations in body mass and composition in women with overweight - impact of high versus low protein breakfast

INTRODUCTION

Understanding why subjects with overweight and with obesity vary in their response to dietary interventions is of major interest for developing personalized strategies for body mass regulation.

OBJECTIVES

The aim of this study was to investigate the relationship between changes in the urine metabolome and body mass during a breakfast meal intervention. Furthermore, we aimed to elucidate if the baseline urine metabolome could predict the response to the two types of breakfast meals (high versus low protein) during the intervention.

METHODS

A total of 75 young, women with overweight were randomly allocated to one of two intervention groups: (1) High-protein (HP) or (2) low-protein (LP) breakfast as part of their habitual diet during a 12-week intervention. Beside the breakfast meal, participants were instructed to eat their habitual diet and maintain their habitual physical activity level. Nuclear magnetic resonance-based metabolomics was conducted on urine samples collected at baseline (wk 0), mid-intervention (wk 6), and at endpoint (wk 12). At baseline and endpoint, body mass was measured and DXA was used to measure lean body mass and fat mass.

RESULTS

The baseline urine metabolite profile showed a slightly higher correlation (R2 = 0.56) to body mass in comparison with lean body mass (R2 = 0.51) and fat mass (R2 = 0.53). Baseline 24-h urinary excretion of trigonelline (p = 0.04), N, N-dimethylglycine (p = 0.02), and trimethylamine (p = 0.03) were significantly higher in individuals who responded with a reduction in body mass to the HP breakfast.

CONCLUSIONS

Differences in the urine metabolome were seen for women that obtained a body weight loss in the response to the HP breakfast intervention and women who did not obtain a body weight loss, indicating that the urine metabolome contains information about the metabolic phenotype that influences the responsiveness to dietary interventions.

A U-shaped association between dietary phosphorus intake and new-onset diabetes: A nationwide cohort study in China

BACKGROUND AND AIMS

The association between dietary phosphorus intake and the risk of diabetes remains uncertain. We aimed to investigate the relation of dietary phosphorus intake with new-onset diabetes among Chinese adults.

METHODS AND RESULTS

A total of 16,272 participants who were free of diabetes at baseline from the China Health and Nutrition Survey were included. Dietary intake was measured by 3 consecutive 24-h dietary recalls combined with a household food inventory. Participants with self-reported physician-diagnosed diabetes, or fasting glucose ≥7.0 mmol/L or glycated hemoglobin ≥6.5% during the follow-up were defined as having new-onset diabetes. During a median follow-up of 9.0years, 1101 participants developed new-onset diabetes. Overall, the association between dietary phosphorus intake with new-onset diabetes followed a U-shape (P for nonlinearity<0.001). The risk of new-onset diabetes significantly decreased with the increment of dietary phosphorus intake (per SD increment: HR, 0.64; 95%CI, 0.48-0.84) in participants with phosphorus intake <921.6 mg/day, and increased with the increment of dietary phosphorus intake (per SD increment: HR, 1.33; 95%CI, 1.16-1.53) in participants with phosphorus intake ≥921.6 mg/day. Consistently, when dietary phosphorus intake was assessed as quintiles, compared with those in the 3rd quintile (905.0-<975.4 mg/day), significantly higher risks of new-onset diabetes were found in participants in the 1st-2nd quintiles (<905.0 mg/day: HR, 1.59; 95%CI, 1.30-1.94), and 4th-5th quintiles (≥975.4 mg/day: HR, 1.46; 95%CI, 1.19-1.78).

CONCLUSIONS

There was a U-shaped association between dietary phosphorus intake and new-onset diabetes in general Chinese adults, with an inflection point at 921.6 mg/day and a minimal risk at 905.0-975.4 mg/day of dietary phosphorus intake.

Altered motivation states for physical activity and 'appetite' for movement as compensatory mechanisms limiting the efficacy of exercise training for weight loss

Weight loss is a major motive for engaging in exercise, despite substantial evidence that exercise training results in compensatory responses that inhibit significant weight loss. According to the Laws of Thermodynamics and the CICO (Calories in, Calories out) model, increased exercise-induced energy expenditure (EE), in the absence of any compensatory increase in energy intake, should result in an energy deficit leading to reductions of body mass. However, the expected negative energy balance is met with both volitional and non-volitional (metabolic and behavioral) compensatory responses. A commonly reported compensatory response to exercise is increased food intake (i.e., Calories in) due to increased hunger, increased desire for certain foods, and/or changes in health beliefs. On the other side of the CICO model, exercise training can instigate compensatory reductions in EE that resist the maintenance of an energy deficit. This may be due to decreases in non-exercise activity thermogenesis (NEAT), increases in sedentary behavior, or alterations in sleep. Related to this EE compensation, the motivational states associated with the desire to be active tend to be overlooked when considering compensatory changes in non-exercise activity. For example, exercise-induced alterations in the wanting of physical activity could be a mechanism promoting compensatory reductions in EE. Thus, one's desires, urges or cravings for movement-also known as "motivation states" or "appetence for activity"-are thought to be proximal instigators of movement. Motivation states for activity may be influenced by genetic, metabolic, and psychological drives for activity (and inactivity), and such states are susceptible to fatigue-or reward-induced responses, which may account for reductions in NEAT in response to exercise training. Further, although the current data are limited, recent investigations have demonstrated that motivation states for physical activity are dampened by exercise and increase after periods of sedentarism. Collectively, this evidence points to additional compensatory mechanisms, associated with motivational states, by which impositions in exercise-induced changes in energy balance may be met with resistance, thus resulting in attenuated weight loss.

Development of a Physical Therapy-Based Exercise Program for Adults with Down Syndrome

In adults with Down syndrome, the combination of low physical activity and fitness levels and the high prevalence of musculoskeletal co-morbidities stresses the need for specialized exercise programs. The goal of this research study was to develop a specialized exercise program for individuals with Down syndrome using the physical therapy approach of a systems review as the foundation. We first conducted an overview of the literature on co-morbidities in adults with Down syndrome using the systems review method to categorize these findings. We extracted recommendations for content and delivery of an exercise program based on the literature review, and finally composed a specialized exercise program for individuals with Down syndrome adhering to these recommendations.

Identification of Metabolic Syndrome-Related miRNA-mRNA Regulatory Networks and Key Genes Based on Bioinformatics Analysis

Metabolic syndrome, which affects approximately one-quarter of the world's population, is a combination of multiple traits and is associated with high all-cause mortality, increased cancer risk, and other hazards. It has been shown that the epigenetic functions of miRNAs are closely related to metabolic syndrome, but epigenetic studies have not yet fully elucidated the regulatory network and key genes associated with metabolic syndrome. To perform data analysis and screening of potential differentially expressed target miRNAs, mRNAs and genes based on a bioinformatics approach using a metabolic syndrome mRNA and miRNA gene microarray, leading to further analysis and identification of metabolic syndrome-related miRNA-mRNA regulatory networks and key genes. The miRNA gene set (GSE98896) and mRNA gene set (GSE98895) of peripheral blood samples from patients with metabolic syndrome from the GEO database were screened, and set|logFC|> 1 and adjusted P < 0.05 were used to identify the differentially expressed miRNAs and mRNAs. Differentially expressed miRNA transcription factors were predicted using FunRich software and subjected to GO and KEGG enrichment analysis. Next, biological process enrichment analysis of differentially expressed mRNAs was performed with Metascape. Differentially expressed miRNAs and mRNAs were identified and visualized as miRNA-mRNA regulatory networks based on the complementary pairing principle. Data analysis of genome-wide metabolic syndrome-related mRNAs was performed using the gene set enrichment analysis (GSEA) database. Finally, further WGCNA of the set of genes most closely associated with metabolic syndrome was performed to validate the findings. A total of 217 differentially expressed mRNAs and 158 differentially expressed miRNAs were identified by screening the metabolic syndrome miRNA and mRNA gene sets, and these molecules mainly included transcription factors, such as SP1, SP4, and EGR1, that function in the IL-17 signalling pathway; cytokine-cytokine receptor interaction; proteoglycan syndecan-mediated signalling events; and the glypican pathway, which is involved in the inflammatory response and glucose and lipid metabolism. miR-34C-5P, which was identified by constructing a miRNA-mRNA regulatory network, could regulate DPYSL4 expression to influence insulin β-cells, the inflammatory response and glucose oxidative catabolism. Based on GSEA, metabolic syndrome is known to be closely related to oxidative phosphorylation, DNA repair, neuronal damage, and glycolysis. Finally, RStudio and DAVID were used to perform WGCNA of the gene sets most closely associated with metabolic syndrome, and the results further validated the conclusions. Metabolic syndrome is a common metabolic disease worldwide, and its mechanism of action is closely related to the inflammatory response, glycolipid metabolism, and impaired mitochondrial function. miR-34C-5P can regulate DPYSL4 expression and can be a potential research target. In addition, UQCRQ and NDUFA8 are core genes of oxidative phosphorylation and have also been identified as potential targets for the future treatment of metabolic syndrome.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Associations of body mass index, fasting insulin, and inflammation with mortality: a prospective cohort study

BACKGROUND/OBJECTIVES

Obesity is often considered to increase the risk for premature mortality. Higher fasting insulin and c-reactive protein are associated with higher body mass index (BMI) and all-cause mortality, so may confound the association between obesity and mortality. Our objective was to determine the independent associations between BMI, fasting insulin, c-reactive protein, and all-cause mortality in a general population sample.

METHODS

This prospective cohort study included non-institutionalized US adults (≥20 years) from the National Health and Nutrition Examination Surveys 1999-2000 to 2013-2014. The main exposures of interest were BMI, fasting insulin, c-reactive protein. Mortality data were obtained through linking participants to the National Death Index (ending December 31, 2015).

RESULTS

There were 12,563 participants with a median age of 45 years (range 20-85) and 47.9% were male. The median BMI was 27 kg/m² (IQR 24-32), median fasting insulin was 54 pmol/L (IQR 35-87), and median c-reactive protein was 1.9 mg/L (IQR 0.8-4.4). In a Cox model adjusted for age, biological sex, cigarette smoking, and ten chronic conditions, higher BMI parameterized with quadratic and linear terms was not associated with mortality. When fasting insulin and the natural logarithm of c-reactive protein were included in the model, an inverse association between BMI and mortality was present (compared to the referent category of 5th percentile: 1st percentile, HR 1.10, 95% CI 1.06-1.13; 99th percentile, HR 0.48, 95% CI 0.34-0.69). In contrast, higher levels of fasting insulin and c-reactive protein were associated with an increased risk of mortality (for fasting insulin: 1st percentile, HR 0.98, 95% CI 0.97-0.99; 99th percentile, HR 1.83, 95% CI 1.48-2.26; for c-reactive protein, 1st percentile, HR 0.87, 95% CI 0.84-0.90; 99th percentile, HR 2.77, 95% CI 2.12-3.62).

CONCLUSIONS

Higher fasting insulin and higher c-reactive protein confound the association between BMI and the risk of all-cause mortality. The increase in mortality that has been attributed to higher BMI is more likely due to hyperinsulinemia and inflammation rather than obesity.

An original amino acid formula favours in vitro corneal epithelial wound healing by promoting Fn1, ITGB1, and PGC-1α expression

Corneal disorders are frequent, involving most diabetic patients; among its manifestations, they include delayed wound healing. Since maintenance of mitochondrial homeostasis is fundamental for the cell, stimulation of mitochondrial biogenesis represents a unique therapeutic tool for preventing and treating disorders with a deficit in energy metabolism. We have recently demonstrated that a branched-chain amino acid (BCAA)-enriched mixture (BCAAem) supported mitochondrial biogenesis in cardiac and skeletal muscle, reduced liver damage caused by alcohol, and prevented the doxorubicin-dependent mitochondrial damage in cardiomyocytes. The present study aimed to investigate a new amino acid mixture, named six amino acids (6AA), to promote corneal epithelial wound healing by regulating mitochondrial biogenesis. A murine epithelium cell line (TKE2) exposed to this mixture showed increased mitochondrial biogenesis markers, fibronectin 1 (Fn1) and integrin beta 1 (ITGB1) involved in extracellular matrix synthesis and cell migration. Most importantly, the 6AA mixture completely restored the wound in scratch assays, confirming the potential of this new formula in eye disorders like keratopathy. Moreover, our results demonstrate for the first time that peroxisome proliferator-receptor γ coactivator 1 α (PGC-1α) is expressed in TKE2 cells, which controls mitochondrial function and corneal repair process. These results could be relevant for the treatment mainly focused on corneal re-epithelialisation.

Trait Energy and Fatigue May Be Connected to Gut Bacteria among Young Physically Active Adults: An Exploratory Study

Recent scientific evidence suggests that traits energy and fatigue are two unique unipolar moods with distinct mental and physical components. This exploratory study investigated the correlation between mental energy (ME), mental fatigue (MF), physical energy (PE), physical fatigue (PF), and the gut microbiome. The four moods were assessed by survey, and the gut microbiome and metabolome were determined from 16 S rRNA analysis and untargeted metabolomics analysis, respectively. Twenty subjects who were 31 ± 5 y, physically active, and not obese (26.4 ± 4.4 kg/m2) participated. Bacteroidetes (45%), the most prominent phyla, was only negatively correlated with PF. The second most predominant and butyrate-producing phyla, Firmicutes (43%), had members that correlated with each trait. However, the bacteria Anaerostipes was positively correlated with ME (0.048, p = 0.032) and negatively with MF (−0.532, p = 0.016) and PF (−0.448, p = 0.048), respectively. Diet influences the gut microbiota composition, and only one food group, processed meat, was correlated with the four moods—positively with MF (0.538, p = 0.014) and PF (0.513, p = 0.021) and negatively with ME (−0.790, p < 0.001) and PE (−0.478, p = 0.021). Only the Firmicutes genus Holdemania was correlated with processed meat (r = 0.488, p = 0.029). Distinct metabolic profiles were observed, yet these profiles were not significantly correlated with the traits. Study findings suggest that energy and fatigue are unique traits that could be defined by distinct bacterial communities not driven by diet. Larger studies are needed to confirm these exploratory findings.

Associations of Chronic Inflammation, Insulin Resistance, and Severe Obesity With Mortality, Myocardial Infarction, Cancer, and Chronic Pulmonary Disease

IMPORTANCE

Chronic inflammation and insulin resistance often accompany severe obesity, and all are associated with disease risk.

OBJECTIVE

To examine how the association of severe obesity with adverse outcomes may be modified by the presence of systemic inflammation and/or insulin resistance.

DESIGN, SETTING, AND PARTICIPANTS

This population-based, retrospective cohort study included all residents of Alberta, Canada, aged 18 years and older with at least 1 procedure to ascertain severe obesity and measures of C-reactive protein, fasting glucose, triglyceride, and high-density lipoprotein cholesterol levels. Participants were observed from April 2003 to March 2017, and data analysis was conducted from June 2018 to December 2018.

EXPOSURES

Severe obesity (body mass index ≥35 or ≥40 after January 1, 2017, as indicated with a procedure-fee modifier), chronic inflammation (all measures of C-reactive protein >10 mg/L), and a surrogate measure of insulin resistance.

MAIN OUTCOMES AND MEASURES

All-cause death, first acute myocardial infarction during follow-up, first cancer diagnosis during follow-up, and new chronic pulmonary disease.

RESULTS

Among 420 636 participants, the median age was 45 years (interquartile range, 34-56 years; range, 18-97 years), 157 799 (37.5%) were male, 185 782 (44.2%) had insulin resistance, 71 987 (17.1%) had severe obesity, and 10 770 (2.6%) had inflammation. In women with chronic inflammation, the presence of severe obesity was associated with a lower mortality risk (hazard ratio [HR], 0.75; 95% CI, 0.65-0.86), but there was no difference in risk in men with inflammation (HR, 0.89; 95% CI, 0.78-1.02). In contrast, the presence of severe obesity was associated with a higher mortality risk in men without inflammation (HR, 1.20; 95% CI, 1.13-1.26), but there was no difference in risk in women without inflammation (HR, 1.00; 95% CI, 0.95-1.06). For myocardial infarction, severe obesity was associated with increased risk in both women and men without inflammation (women: HR, 1.26; 95% CI, 1.17-1.36; men: HR, 1.35; 95% CI, 1.27-1.43) but not in women and men with inflammation (women: HR, 0.85; 95% CI, 0.67-1.07; men: HR, 0.90; 95% CI, 0.71-1.14). Severe obesity was associated with increased risk in women and men, irrespective of chronic inflammation, for new chronic pulmonary disease (women with inflammation: HR, 1.34; 95% CI, 1.23-1.46; women without inflammation: HR, 1.58; 95% CI, 1.54-1.62; men with inflammation: HR, 1.41; 95% CI, 1.29-1.54; men without inflammation: HR, 1.65; 95%, CI, 1.60-1.71) and cancer (women with inflammation: HR, 1.16; 95% CI, 1.03-1.30; women without inflammation, HR, 1.32; 95% CI, 1.28-1.36; men with inflammation: HR, 1.17; 95% CI, 1.04-1.32; men without inflammation: HR, 1.33; 95% CI, 1.28-1.39). Similar to chronic inflammation, severe obesity was not always associated with higher risk in participants with insulin resistance.

CONCLUSIONS AND RELEVANCE

The findings suggest that severe obesity with systemic inflammation is associated with a different prognosis than severe obesity without inflammation.

Perspective: A Historical and Scientific Perspective of Sugar and Its Relation with Obesity and Diabetes

Fructose-containing added sugars, such as sucrose and high-fructose corn syrup, have been experimentally, epidemiologically, and clinically shown to be involved in the current epidemics of obesity and diabetes. Here we track this history of intake of sugar as it relates to these epidemics. Key experimental studies that have identified mechanisms by which fructose causes obesity and diabetes are reviewed, as well as the evidence that the uricase mutation that occurred in the mid-Miocene in ancestral humans acted as a "thrifty gene" that increases our susceptibility for fructose-associated obesity today. We briefly review recent evidence that obesity can also be induced by nondietary sources of fructose, such as from the metabolism of glucose (from high-glycemic carbohydrates) through the polyol pathway. These studies suggest that fructose-induced obesity is driven by engagement of a "fat switch" and provide novel insights into new approaches for the prevention and treatment of these important diseases.

Mitochondrial dysfunction and oxidative stress in metabolic disorders - A step towards mitochondria based therapeutic strategies

Mitochondria are the powerhouses of the cell and are involved in essential functions of the cell, including ATP production, intracellular Ca2+ regulation, reactive oxygen species production & scavenging, regulation of apoptotic cell death and activation of the caspase family of proteases. Mitochondrial dysfunction and oxidative stress are largely involved in aging, cancer, age-related neurodegenerative and metabolic syndrome. In the last decade, tremendous progress has been made in understanding mitochondrial structure, function and their physiology in metabolic syndromes such as diabetes, obesity, stroke and hypertension, and heart disease. Further, progress has also been made in developing therapeutic strategies, including lifestyle interventions (healthy diet and regular exercise), pharmacological strategies and mitochondria-targeted approaches. These strategies were mainly focused to reduce mitochondrial dysfunction and oxidative stress and to maintain mitochondrial quality in metabolic syndromes. The purpose of our article is to highlight the recent progress on the mitochondrial role in metabolic syndromes and also summarize the progress of mitochondria-targeted molecules as therapeutic targets to treat metabolic syndromes. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.

Therapeutic Strategies for Mitochondrial Dysfunction and Oxidative Stress in Age-Related Metabolic Disorders

Mitochondria are complex, intercellular organelles present in the cells and are involved in multiple roles including ATP formation, free radicals generation and scavenging, calcium homeostasis, cellular differentiation, and cell death. Many studies depicted the involvement of mitochondrial dysfunction and oxidative damage in aging and pathogenesis of age-related metabolic disorders and neurodegenerative diseases. Remarkable advancements have been made in understanding the structure, function, and physiology of mitochondria in metabolic disorders such as diabetes, obesity, cardiovascular diseases, and stroke. Further, much progress has been done in the improvement of therapeutic strategies, including lifestyle interventions, pharmacological, and mitochondria-targeted therapeutic approaches. These strategies were mainly focused to reduce the mitochondrial dysfunction caused by oxidative stress and to retain the mitochondrial health in various diseases. In this chapter, we have highlighted the involvement of mitochondrial dysfunction in the pathophysiology of various disorders and recent progress in the development of mitochondria-targeted molecules as therapeutic measures for metabolic disorders.

Phosphorus Supplementation Recovers the Blunted Diet-Induced Thermogenesis of Overweight and Obese Adults: A Pilot Study

Diet-induced thermogenesis (DIT) is believed to be largely related to ATP production, which is dependent on phosphorus (P) availability. We aimed to test the effect of P addition on DIT of lean and overweight/obese healthy subjects. DIT was measured with or without P in 10 lean and 13 overweight/obese adults in a double-blind randomized cross-over pilot study with one week washout period. After 10 h overnight fast, resting metabolic rate, respiratory quotient, and substrate utilization were measured at fasting and every 30 min for 3 h after subjects drank a standardized glucose solution, with P (500 mg) or placebo pills. Subjective ratings of hunger and satiety were assessed before and after the end of each experiment using validated visual analogue scale (VAS) questionnaires. Overweight/obese subjects had a blunted DIT with placebo, while P supplementation induced a 23% increase in their DIT area under the curve (p < 0.05), which was associated with a significant increase in carbohydrate oxidation. Subjects had lower appetite following P supplementation, which was expressed as a significantly (p = 0.02) lower desire to eat a meal (4.0 ± 0.7 cm) compared with placebo (5.8 ± 0.9 cm). P supplementation recovers the blunted diet-induced thermogenesis in overweight and obese subjects and enhances their postprandial satiety.

Comparison of the Effects of Amitriptyline and Flunarizine on Weight Gain and Serum Leptin, C Peptide and Insulin Levels when used as Migraine Preventive Treatment

The tricyclic antidepressant amitriptyline (AMT) and the calcium channel blocker flunarizine are frequently used in the preventive treatment of migraine, but the side-effect of prominent weight gain that frequently emerges during preventive treatment of migraine with these agents often leads to the discontinuation of therapy. In this study, we aimed to investigate the possible relationship between the weight gain associated with the use of these agents and serum levels of leptin, C-peptide and insulin in patient with migraine. Forty-nine migraine patients with a body mass index (BMI) < 25 and without any endocrinological, immunological or chronic diseases were randomly divided into two groups, receiving AMT or flunarizine. There was a statistically significant increase in serum levels of leptin, C-peptide, insulin and measures of BMI in both groups when measured at the 12th week of therapy compared to their respective basal levels. To our knowledge this is the first study investigating the effects of AMT and flunarizine on serum leptin levels in preventive use of migraine treatment. A result from this study indicates that AMT and flunarizine may cause leptin resistance possibly by different mechanisms and thereby result in increase in serum leptin levels and BMI.

Effect of phosphorus supplementation on weight gain and waist circumference of overweight/obese adults: a randomized clinical trial

Background:

Phosphorus status is inversely correlated with body weight; however, the effect of phosphorus supplementation on body weight in a controlled design has not been studied.

Methods:

This is a double-blind, randomized, placebo-controlled trial of 63 adults aged 18–45 years with a body mass index (BMI) of ⩾25 kg m⁻² and normal kidney function at the American University of Beirut. Participants were randomly assigned to the placebo or phosphorus group where daily placebo or phosphorus supplements were ingested with three main meals (breakfast, lunch and dinner) for a period of 12 weeks. Primary outcomes were changes in anthropometric measures, blood metabolites (including lipid profile, glucose and insulin) and subjective appetite scores. The trial is registered with Clinical Trial.gov, NCT02329990.

Results:

Body weight was significantly lower in the phosphorus group when compared with the placebo group (−0.65 kg (95% confidence interval (CI) −1.69 to 0.40) vs 1.13 kg (95% CI 0.19 to 2.06), P=0.01). Similarly, BMI and waist circumference were significantly lower in the phosphorus group when compared with the placebo group (−0.24 kg m⁻² (95% CI −0.59 to 0.12) vs 0.42 kg m⁻² (95% CI 0.05 to 0.78), P=0.01; −3.62 cm (95% CI−4.90 to −2.33) vs 0.38 cm ( 95% CI−0.44 to 1.20), P<0.001; respectively). Several parameters of subjective appetite scores were decreased in the phosphorus-supplemented group.

Conclusions:

Phosphorus supplementation for 12 weeks significantly decreases body weight, BMI, waist circumference and subjective appetite scores. These findings support a promising role of the mineral phosphorus in the prevention and management of obesity, especially abdominal adiposity. The exact mechanisms of action and longer-term effects still need to be elucidated.

The odd-carbon medium-chain fatty triglyceride triheptanoin does not reduce hepatic steatosis

BACKGROUND & AIMS

Non-alcoholic fatty-liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. Previously, we showed that a high-protein diet minimized diet-induced development of fatty liver and even reversed pre-existing steatosis. A high-protein diet leads to amino-acid catabolism, which in turn causes anaplerosis of the tricarboxylic-acid (TCA) cycle. Therefore, we hypothesized that anaplerosis of the TCA cycle could be responsible for the high-protein diet-induced improvement of NAFLD by channeling amino acids into the TCA cycle. Next we considered that an efficient anaplerotic agent, the odd-carbon medium-chain triglyceride triheptanoin (TH), might have similar beneficial effects.

METHODS

C57BL/6J mice were fed low-fat (8en%) or high-fat (42en%) oleate-containing diets with or without 15en% TH for 3 weeks.

RESULTS

TH treatment enhanced the hepatic capacity for fatty-acid oxidation by a selective increase in hepatic Ppara, Acox, and Cd36 expression, and a decline in plasma acetyl-carnitines. It also induced pyruvate cycling through an increased hepatic PCK1 protein concentration and it increased thermogenesis reflected by an increased Ucp2 mRNA content. TH, however, did not reduce hepatic lipid content.

CONCLUSION

The comparison of the present effects of dietary triheptanoin with a previous study by our group on protein supplementation shows that the beneficial effects of the high-protein diet are not mimicked by TH. This argues against anaplerosis as the sole explanatory mechanism for the anti-steatotic effect of a high-protein diet.

The childhood obesity epidemic as a result of nongenetic evolution: the maternal resources hypothesis

Over the past century, socioenvironmental evolution (eg, reduced pathogenic load, decreased physical activity, and improved nutrition) led to cumulative increments in maternal energy resources (ie, body mass and adiposity) and decrements in energy expenditure and metabolic control. These decrements reduced the competition between maternal and fetal energy demands and increased the availability of energy substrates to the intrauterine milieu. This perturbation of mother-conceptus energy partitioning stimulated fetal pancreatic β-cell and adipocyte hyperplasia, thereby inducing an enduring competitive dominance of adipocytes over other tissues in the acquisition and sequestering of nutrient energy via intensified insulin secretion and hyperplastic adiposity. At menarche, the competitive dominance of adipocytes was further amplified via hormone-induced adipocyte hyperplasia and weight-induced decrements in physical activity. These metabolic and behavioral effects were propagated progressively when obese, inactive, metabolically compromised women produced progressively larger, more inactive, metabolically compromised children. Consequently, the evolution of human energy metabolism was markedly altered. This phenotypic evolution was exacerbated by increments in the use of cesarean sections, which allowed both the larger fetuses and the metabolically compromised mothers who produced them to survive and reproduce. Thus, natural selection was iatrogenically rendered artificial selection, and the frequency of obese, inactive, metabolically compromised phenotypes increased in the global population. By the late 20th century, a metabolic tipping point was reached at which the postprandial insulin response was so intense, the relative number of adipocytes so large, and inactivity so pervasive that the competitive dominance of adipocytes in the sequestering of nutrient energy was inevitable and obesity was unavoidable.

S-glutathionylation reactions in mitochondrial function and disease

Mitochondria are highly efficient energy-transforming organelles that convert energy stored in nutrients into ATP. The production of ATP by mitochondria is dependent on oxidation of nutrients and coupling of exergonic electron transfer reactions to the genesis of transmembrane electrochemical potential of protons. Electrons can also prematurely “spin-off” from prosthetic groups in Krebs cycle enzymes and respiratory complexes and univalently reduce di-oxygen to generate reactive oxygen species (ROS) superoxide (O₂•⁻) and hydrogen peroxide (H₂O₂), important signaling molecules that can be toxic at high concentrations. Production of ATP and ROS are intimately linked by the respiratory chain and the genesis of one or the other inherently depends on the metabolic state of mitochondria. Various control mechanisms converge on mitochondria to adjust ATP and ROS output in response to changing cellular demands. One control mechanism that has gained a high amount of attention recently is S-glutathionylation, a redox sensitive covalent modification that involves formation of a disulfide bridge between glutathione and an available protein cysteine thiol. A number of S-glutathionylation targets have been identified in mitochondria. It has also been established that S-glutathionylation reactions in mitochondria are mediated by the thiol oxidoreductase glutaredoxin-2 (Grx2). In the following review, emerging knowledge on S-glutathionylation reactions and its importance in modulating mitochondrial ATP and ROS production will be discussed. Major focus will be placed on Complex I of the respiratory chain since (1) it is a target for reversible S-glutathionylation by Grx2 and (2) deregulation of Complex I S-glutathionylation is associated with development of various disease states particularly heart disease. Other mitochondrial enzymes and how their S-glutathionylation profile is affected in different disease states will also be discussed.

The threshold shift paradigm of obesity: evidence from surgically induced weight loss

BACKGROUND

The high prevalence of obesity has called attention to the near-intractable problem of sustained weight reduction and its underlying mechanisms. With diet-induced weight loss, achieved body weight is closely related to initial body weight.

OBJECTIVE

The objective was to compare the relation between initial and achieved body mass index (BMI) in patients treated with diet-induced weight loss or bariatric surgery.

DESIGN

We analyzed data from a cohort of 223 healthy individuals who lost a mean (±SD) of 5 ± 3 kg body weight over 3 y by diet (diet group) and data from 182 obese individuals [BMI (in kg/m(2)) ≥35] who had lost an average of 47 ± 17 kg 1 y after Roux-en-Y gastric bypass (a restrictive procedure; n = 71) or biliopancreatic diversion (a malabsorptive procedure; n = 111) (surgery group).

RESULTS

In the diet group, final BMI was strongly related to initial BMI (r = 0.96, P < 0.0001). By multivariate analysis, the decrease in BMI at 3 y was age independent and was predicted only by initial BMI and sex (both P < 0.0001). Strikingly, final BMI was also strongly related to initial BMI (r = 0.67, P < 0.0001) in the surgery group, irrespective of the type of operation. The surgically induced decrease in BMI was predicted by age (P = 0.0002) and initial BMI (P < 0.0001). In 110 surgery patients, serum leptin concentrations decreased from 39 ± 16 to 10 ± 5 ng/mL after surgery (P < 0.0001) and were correlated with BMI both before and after surgery, but the slope of the relation was significantly (P < 0.01) flatter after surgery.

CONCLUSION

The strong predictivity of initial BMI for achieved BMI observed even when voluntary control of energy intake is interfered with through diverse anatomical rearrangements of the gastrointestinal tract supports the concept of a weight "threshold" paradigm: in the obese, anabolic responses are triggered by adiposity-related signals at a higher threshold, which leads to defense of a higher body weight.

Dietary factors evoke thermogenesis in adipose tissues

In dietary factors, energetic food constituents and the "non-energetic food constituents" such as smell and taste through sensory nerve stimulation have been found to be linked intrinsically with the accelerated expression of diet-induced thermogenesis that accompanies the burning of fat within brown adipose tissues (BAT). The compounds are responsible for BAT and uncoupling protein-1 (UCP1) activation or induction caused by food components. Many of these activate and strengthen BAT activation through the following pathway: sensory stimulations induce sympathetic nerve activation through central phase. In the fight against obesity, the development of food compounds and pharmaceuticals that activate or induce BAT and UCP1 is expected. In this review, we discuss that how dietary compounds effect thermogenesis through BAT and UCP1.

Mitochondrial DNA copy number in peripheral blood is independently associated with visceral fat accumulation in healthy young adults

Aims. Visceral obesity is associated with an increased risk of cardiometabolic diseases and it is important to identify the underlying mechanisms. There is growing evidence that mitochondrial dysfunction is associated with metabolic disturbances related to visceral obesity. In addition, maintaining mitochondrial DNA (mtDNA) copy number is important for preserving mitochondrial function. Therefore, we investigated the relationship between mtDNA copy number and visceral fat in healthy young adults. Methods. A total of 94 healthy young subjects were studied. Biomarkers of metabolic risk factors were assessed along with body composition by computed tomography. mtDNA copy number was measured in peripheral leukocytes using real-time polymerase chain reaction (PCR) methods. Results. The mtDNA copy number correlated with BMI (r = -0.22, P = 0.04), waist circumference (r = -0.23, P = 0.03), visceral fat area (r = -0.28, P = -0.01), HDL-cholesterol levels (r = 0.25, P = 0.02), and hs-CRP (r = 0.32, P = 0.02) after adjusting for age and sex. Both stepwise and nonstepwise multiple regression analyses confirmed that visceral fat area was independently associated with mtDNA copy number (β = -0.33, P < 0.01, β = 0.32, and P = 0.03, resp.). Conclusions. An independent association between mtDNA content and visceral adiposity was identified. These data suggest that mtDNA copy number is a potential predictive marker for metabolic disturbances. Further studies are required to understand the causality and clinical significance of our findings.

Low phosphorus status might contribute to the onset of obesity

Overweight and obesity are becoming global health problems. Although genetics certainly plays a role, weight gain is ultimately the result of a failure in the balance between energy expenditure and energy intake. Obesity during the past few decades was paralleled with several changes in dietary habits favouring low phosphorus consumption. This is believed to compromise adenosine triphosphate (ATP) production that is involved in the regulation of energy metabolism. Ingestion of high-carbohydrate-low phosphorus food is known to increase insulin release, to simultaneously stimulate peripheral uptake of phosphorus and the phosphorylation of many compounds. This creates a competition for phosphorus that compromises its availability for ATP production, possibly translated into low diet-induced thermogenesis. Moreover, reduced hepatic ATP production is believed to be transmitted through neural afferents to the central nervous system, resulting in an increase in food intake. On the other hand, the positive relation between phosphorus and red blood cell 2,3-diphosphoglycerate, which reduces oxygen affinity to haemoglobin, would be expected to reduce the capacity for physical activity. In line with that, plasma phosphorus status was reported to be inversely related to body weight. Adequate intakes of phosphorus are thus potentially protective against rising obesity epidemic across the globe.

Inflammation induced by RAW macrophages suppresses UCP1 mRNA induction via ERK activation in 10T1/2 adipocytes

Recently, it has been demonstrated that uncoupling protein-1 (UCP1)-expressing white adipocytes (brown-like adipocytes) are important for energy expenditure in white adipose tissue (WAT), in which energy expenditure decreases under obese conditions. However, the relationship between the induction of brown-like adipocytes and the decrease in energy expenditure in obese WAT remains to be elucidated. Here, we show that proinflammatory cytokines derived from activated macrophages suppress the induction of UCP1 promoter activity and mRNA expression via an extracellular signal-related kinase (ERK) in white adipocytes. The coculture with RAW264.7 (RAW) macrophages suppressed the induction of UCP1 mRNA expression by isoproterenol (ISO), a typical β-adrenergic receptor agonist, in C3H10T1/2 (10T1/2) adipocytes. A conditioned medium derived from lipopolysaccharide (LPS)-activated macrophages and tumor necrosis factor-α (TNF-α) also suppressed the induction of UCP1 mRNA but did not affect its mRNA stability. By using a luciferase reporter assay system, the conditioned medium and TNF-α also suppressed the activity of the UCP1 promoter and transcriptional factors binding to the cAMP response element (CRE). Importantly, PD98059, an ERK inhibitor, partially abrogated the suppression of UCP1 promoter activation and mRNA induction. These results indicate that ERK is an important factor in the suppression of UCP1 transcriptional activation in the interaction between white adipocytes and activated macrophages. This report suggests a possible mechanism of the UCP1 transcriptional suppression in white adipocytes associated with obese and diabetic conditions.

Mild mitochondrial uncoupling does not affect mitochondrial biogenesis but downregulates pyruvate carboxylase in adipocytes: role for triglyceride content reduction

In adipocytes, mitochondrial uncoupling is known to trigger a triglyceride loss comparable with the one induced by TNFα, a proinflammatory cytokine. However, the impact of a mitochondrial uncoupling on the abundance/composition of mitochondria and its connection with triglyceride content in adipocytes is largely unknown. In this work, the effects of a mild mitochondrial uncoupling triggered by FCCP were investigated on the mitochondrial population of 3T3-L1 adipocytes by both quantitative and qualitative approaches. We found that mild mitochondrial uncoupling does not stimulate mitochondrial biogenesis in adipocytes but induces an adaptive cell response characterized by quantitative modifications of mitochondrial protein content. Superoxide anion radical level was increased in mitochondria of both TNFα- and FCCP-treated adipocytes, whereas mitochondrial DNA copy number was significantly higher only in TNFα-treated cells. Subproteomic analysis revealed that the abundance of pyruvate carboxylase was reduced significantly in mitochondria of TNFα- and FCCP-treated adipocytes. Functional study showed that overexpression of this major enzyme of lipid metabolism is able to prevent the triglyceride content reduction in adipocytes exposed to mitochondrial uncoupling or TNFα. These results suggest a new mechanism by which the effects of mitochondrial uncoupling might limit triglyceride accumulation in adipocytes.

Hepatic response to aluminum toxicity: dyslipidemia and liver diseases

Aluminum (Al) is a metal toxin that has been implicated in the etiology of a number of diseases including Alzheimer's, Parkinson's, dialysis encephalopathy, and osteomalacia. Al has been shown to exert its effects by disrupting lipid membrane fluidity, perturbing iron (Fe), magnesium, and calcium homeostasis, and causing oxidative stress. However, the exact molecular targets of aluminum's toxicity have remained elusive. In the present review, we describe how the use of a systems biology approach in cultured hepatoblastoma cells (HepG2) allowed the identification of the molecular targets of Al toxicity. Mitochondrial metabolism is the main site of the toxicological action of Al. Fe-dependent and redox sensitive enzymes in the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) are dramatically decreased by Al exposure. In an effort to compensate for diminished mitochondrial function, Al-treated cells stabilize hypoxia inducible factor-1α (HIF-1α) to increase ATP production by glycolysis. Additionally, Al toxicity leads to an increase in intracellular lipid accumulation due to enhanced lipogenesis and a decrease in the β-oxidation of fatty acids. Central to these effects is the alteration of α-ketoglutarate (KG) homeostasis. In Al-exposed cells, KG is preferentially used to quench ROS leading to succinate accumulation and HIF-1α stabilization. Moreover, the channeling of KG to combat oxidative stress leads to a reduction of l-carnitine biosynthesis and a concomitant decrease in fatty acid oxidation. The fluidity and interaction of these metabolic modules and the implications of these findings in liver-related disorders are discussed herein.

Effect of a mitochondria-targeted vitamin E derivative on mitochondrial alteration and systemic oxidative stress in mice

The objective of the present study was to determine whether a mitochondria-targeted vitamin E derivative (MitoVit E) would affect certain mitochondrial parameters, as well as systemic oxidative stress. A total of sixty-four mice were fed a high-fat (HF) diet for 5 weeks. They were then switched to either a low-fat (LF) or a medium-fat (MF) diet, and administered orally with MitoVit E (40 mg MitoVit E/kg body weight) or drug vehicle (10 % (v/v) ethanol in 0·9 % (w/v) NaCl solution), every other day for 5 weeks. Mitochondrial ATP and H(2)O(2) production rates in both the liver and the gastrocnemius were not affected by MitoVit E administration in either LF or MF diet-fed mice. However, the number and average size of the subsarcolemmal mitochondria, but not the intermyofibrillar mitochondria, from the soleus muscle were significantly higher in the MF group receiving MitoVit E (MF-E) than in the MF group receiving vehicle only (MF-C). After the mice were switched from the HF diet to the four dietary treatments (LF-C, LF-E, MF-C and MF-E), the decrease in urinary isoprostane concentration was significantly greater in the LF-E group than in the other three groups during the whole study (weeks 6-10). In addition, MitoVit E significantly increased plasma superoxide dismutase (SOD) activity in the MF diet-fed group without affecting plasma glutathione peroxidase activity or H(2)O(2) levels. Overall, these data suggest that MitoVit E affects subsarcolemmal mitochondrial density and systemic oxidative stress parameters such as plasma SOD activity and urinary isoprostane concentration.

A mitochondria-targeted vitamin E derivative decreases hepatic oxidative stress and inhibits fat deposition in mice

Our objective in this study was to determine whether a mitochondria-targeted vitamin E derivative (MitoVit E) would decrease oxidative stress and associated obesity by preventing a previously proposed aconitase inhibition cascade. Sixty-four mice were fed a high-fat (HF) diet for 5 wk. They were then switched to either a low-fat (LF) or a medium-fat (MF) diet and gavaged with MitoVit E (40 mg MitoVit E x kg body weight(-1)) or drug vehicle (10% ethanol in 0.9% NaCl solution) every other day for 5 wk. Epididymal fat weight, as well as liver lipid and remaining carcass lipid, were significantly lower in the MF group receiving MitoVit E (MF-E) than in the MF group receiving vehicle only (MF-C). Liver mitochondrial H(2)O(2) production and the protein carbonyl level were also significantly lower in MF-E than in MF-C mice. In contrast, none of the biochemical variables (aconitase activity, ATP and H(2)O(2) production, and protein carbonyl level) in the muscle mitochondria were modified by MitoVit E in either MF or LF groups. Expression of acetyl-CoA carboxylase and fatty acid synthase in both liver and adipose tissue of MF groups was not affected by MitoVit E. However, expression of carnitine palmitoyltransferase 1a in the liver and uncoupling protein 2 in adipose tissue were significantly enhanced by MitoVit E in both LF and MF groups. In conclusion, MitoVit E attenuates hepatic oxidative stress and inhibits fat deposition in mice but not through alleviation of the aconitase inhibition cascade.

Increased phosphorus content of preload suppresses ad libitum energy intake at subsequent meal

Food intake is believed to be partially controlled by hepatic signals related to adenosine triphosphate (ATP) status. We hypothesized that increased phosphorus content of one meal can stimulate hepatic ATP synthesis of the next meal, which in turn contributes to satiation. This hypothesis was tested by measuring the energy intake after phosphorus addition to several preloads. The phosphorus content of the different preloads was found to be inversely related to the energy intake at a subsequent meal, although the exact mechanism behind such effects was not studied. Such findings point to a potential role for phosphorus in the control of food intake.

Experimental rat models to study the metabolic syndrome

Being the metabolic syndrome a multifactorial condition, it is difficult to find adequate experimental models to study this pathology. The obese Zucker rats, which are homozygous for the fa allele, present abnormalities similar to those seen in human metabolic syndrome and are a widely extended model of insulin resistance. The usefulness of these rats as a model of non-insulin-dependent diabetes mellitus is nevertheless questionable, and they neither can be considered a clear experimental model of hypertension. Some experimental models different from the obese Zucker rats have also been used to study the metabolic syndrome. Some derive from the spontaneously hypertensive rats (SHR). In this context, the most important are the obese SHR, usually named Koletsky rats. Hyperinsulinism, associated with either normal or slightly elevated levels of blood glucose, is present in these animals, but SHR/N-corpulent rats are a more appropriated model of non-insulin-dependent diabetes mellitus. The SHR/NDmc corpulent rats, a subline of SHR/N-corpulent rats, also exhibit metabolic and histopathologic characteristics associated with human metabolic disorders. A new animal model of the metabolic syndrome, stroke-prone-SHR (SHRSP) fatty rats, was obtained by introducing a segment of the mutant leptin receptor gene from the Zucker line heterozygous for the fa gene mutation into the genetic background of the SHRSP. Very recently, it has been developed as a non-obese rat model with hypertension, fatty liver and characteristics of the metabolic syndrome by transgenic overexpression of a sterol-regulatory element-binding protein in the SHR rats. The Wistar Ottawa Karlsburg W rats are also a new strain that develops a nearly complete metabolic syndrome. Moreover, a new experimental model of low-capacity runner rats has also been developed with elevated blood pressure levels together with the other hallmarks of the metabolic syndrome.

A novel role for fatty acid transport protein 1 in the regulation of tricarboxylic acid cycle and mitochondrial function in 3T3-L1 adipocytes

Fatty acid transport proteins (FATPs) are integral membrane acyl-CoA synthetases implicated in adipocyte fatty acid influx and esterification. Whereas some FATP1 translocates to the plasma membrane in response to insulin, the majority of FATP1 remains within intracellular structures and bioinformatic and immunofluorescence analysis of FATP1 suggests the protein primarily resides in the mitochondrion. To evaluate potential roles for FATP1 in mitochondrial metabolism, we used a proteomic approach following immunoprecipitation of endogenous FATP1 from 3T3-L1 adipocytes and identified mitochondrial 2-oxoglutarate dehydrogenase. To assess the functional consequence of the interaction, purified FATP1 was reconstituted into phospholipid-containing vesicles and its effect on 2-oxoglutarate dehydrogenase activity evaluated. FATP1 enhanced the activity of 2-oxoglutarate dehydrogenase independently of its acyl-CoA synthetase activity whereas silencing of FATP1 in 3T3-L1 adipocytes resulted in decreased activity of 2-oxoglutarate dehydrogenase. FATP1 silenced 3T3-L1 adipocytes exhibited decreased tricarboxylic acid cycle activity, increased cellular NAD(+)/NADH, increased fatty acid oxidation, and increased lactate production indicative of altered mitochondrial energy metabolism. These results reveal a novel role for FATP1 as a regulator of tricarboxylic acid cycle activity and mitochondrial function.

Low-fat oxidation may be a factor in obesity among men with schizophrenia

OBJECTIVE

Obesity associated with atypical antipsychotic medications is an important clinical issue for people with schizophrenia. The purpose of this project was to determine whether there were any differences in resting energy expenditure (REE) and respiratory quotient (RQ) between men with schizophrenia and controls.

METHOD

Thirty-one men with schizophrenia were individually matched for age and relative body weight with healthy, sedentary controls. Deuterium dilution was used to determine total body water and subsequently fat-free mass (FFM). Indirect calorimetry using a Deltatrac metabolic cart was used to determine REE and RQ.

RESULTS

When corrected for FFM, there was no significant difference in REE between the groups. However, fasting RQ was significantly higher in the men with schizophrenia than the controls.

CONCLUSION

Men with schizophrenia oxidised proportionally less fat and more carbohydrate under resting conditions than healthy controls. These differences in substrate utilisation at rest may be an important consideration in obesity in this clinical group.

Proteomic analysis of mitochondrial proteins of basal and lipolytically (isoproterenol and TNF-alpha)-stimulated adipocytes

The regulation of adipocyte lipolysis is increasingly believed to influence insulin resistance, in a process that may be associated with mitochondrial dysfunction. However, the molecular basis of the relationship between mitochondrial protein expression, lipolytic responsiveness, and insulin resistance remains unknown. A set of proteins that shows altered abundances in the mitochondria of untreated and treated 3T3-L1 adipocytes with TNF-alpha or isoproterenol was identified. These include the proteins associated with energy production, including fatty acid oxidation, TCA cycle, and oxidative phosphorylation. Proteins associated with oxidative stress dissipation were down-regulated in lipolytically stimulated adipocytes. Lipolytic stimulation with isoproterenol and TNF-alpha, which is also a potent proinflammatory cytokine, showed some noticeable differences in mitochondrial protein expression. For example, isoproterenol markedly enhanced the expression of prohibitin which is involved in the integrity of mitochondria but TNF-alpha did not. These results provide valuable information on mitochondrial dysfunction associated with oxidative stress induced by lipolytic stimulation.

The role of impaired mitochondrial lipid oxidation in obesity

Obesity represents a disruption in balancing fuel intake with energy expenditure in favor of energy conservation. Adiposity is known to be carefully regulated and, over time, highly resistant to major changes, raising questions about how energy homeostasis can become dysregulated in favor of fat accumulation. In obesity, the excess lipid accumulation represents a surfeit of energy, but those who are obese often experience rapid fatigue and decreased physical endurance, reflecting an energy deficiency. To develop an explanation for this apparent contradiction in energy homeostasis and the chronic overeating relative to energy used in obesity, a review of the literature was conducted. The resulting model of obesity is based on a growing body of research demonstrating that altered mitochondrial energy production, particularly in skeletal muscles, is a major anomaly capable of setting off a chain of metabolic events leading to obesity. Alterations in skeletal muscle mitochondria distribution and their oxidative and glycolytic energy capacities in obesity are described. The metabolic responses of obese and normal individuals to exercise are contrasted, and the effects of weight loss on energy production are presented. The effect of altered fat oxidation is considered in relation to energy regulation by the central nervous system and the development of major obesity comorbidities, including systemic inflammation, insulin resistance and diabetes, and cardiovascular disease. Recommendations for clinical intervention and additional research are proposed based on the model presented of impaired mitochondrial function in obesity.

Aconitate hydratase of mammals under oxidative stress

Data on the structure, functions, regulation of activity, and expression of cytosolic and mitochondrial aconitate hydratase isoenzymes of mammals are reviewed. The role of aconitate hydratase and structurally similar iron-regulatory protein in maintenance of homeostasis of cell iron is described. Information on modifications of the aconitate hydratase molecule and changes in expression under oxidative stress is generalized. The role of aconitate hydratase in the pathogenesis of some diseases is considered.

High-throughput electronic biology: mining information for drug discovery

The vast range of in silico resources that are available in life sciences research hold much promise towards aiding the drug discovery process. To fully realize this opportunity, computational scientists must consider the practical issues of data integration and identify how best to apply these resources scientifically. In this article we describe in silico approaches that are driven towards the identification of testable laboratory hypotheses; we also address common challenges in the field. We focus on flexible, high-throughput techniques, which may be initiated independently of 'wet-lab' experimentation, and which may be applied to multiple disease areas. The utility of these approaches in drug discovery highlights the contribution that in silico techniques can make and emphasizes the need for collaboration between the areas of disease research and computational science.

Defective mitochondrial biogenesis: a hallmark of the high cardiovascular risk in the metabolic syndrome?

The metabolic syndrome is a group of risk factors of metabolic origin that are accompanied by increased risk for type 2 diabetes mellitus and cardiovascular disease. These risk factors include atherogenic dyslipidemia, elevated blood pressure and plasma glucose, and a prothrombotic and proinflammatory state. The condition is progressive and is exacerbated by physical inactivity, advancing age, hormonal imbalance, and genetic predisposition. The metabolic syndrome is a particularly challenging clinical condition because its complex molecular basis is still largely undefined. Impaired cell metabolism has, however, been suggested as a relevant pathophysiological process underlying several clinical features of the syndrome. In particular, defective oxidative metabolism seems to be involved in visceral fat gain and in the development of insulin resistance in skeletal muscle. This suggests that mitochondrial function may be impaired in the metabolic syndrome and, thus, in the consequent cardiovascular disease. We have recently found that mitochondrial biogenesis and function are enhanced by nitric oxide in various cell types and tissues, including cardiac muscle. Increasing evidence suggests that this mediator acts as a metabolic sensor in cardiomyocytes. This implies that a defective production of nitric oxide might be linked to dysfunction of the cardiomyocyte metabolism. Here we summarize some recent findings and propose a hypothesis for the high cardiovascular risk linked to the metabolic syndrome.

TNF-alpha downregulates eNOS expression and mitochondrial biogenesis in fat and muscle of obese rodents

Obesity is associated with chronic low-grade inflammation. Thus, at metabolically relevant sites, including adipose tissue and muscle, there is abnormal production of proinflammatory cytokines such as TNF-alpha. Here we demonstrate that eNOS expression was reduced, with a concomitant reduction of mitochondrial biogenesis and function, in white and brown adipose tissue and in the soleus muscle of 3 different animal models of obesity. The genetic deletion of TNF receptor 1 in obese mice restored eNOS expression and mitochondrial biogenesis in fat and muscle; this was associated with less body weight gain than in obese wild-type controls. Furthermore, TNF-alpha downregulated eNOS expression and mitochondrial biogenesis in cultured white and brown adipocytes and muscle satellite cells of mice. The NO donors DETA-NO and SNAP prevented the reduction of mitochondrial biogenesis observed with TNF-alpha. Our findings demonstrate that TNF-alpha impairs mitochondrial biogenesis and function in different tissues of obese rodents by downregulating eNOS expression and suggest a novel pathophysiological process that sustains obesity.

New insights in the pathogenesis of non-alcoholic fatty liver disease

PURPOSE OF REVIEW

The hallmark of non-alcoholic fatty liver disease is hepatic steatosis. This is mostly a benign condition, but for largely unknown reasons it progresses to liver fibrosis, cirrhosis, and ultimately hepatocellular carcinoma in about 10% of patients. In this review we discuss recent progress in the understanding of the etiology of non-alcoholic fatty liver disease.

RECENT FINDINGS

In the last few years many connections between carbohydrate and triglyceride homeostasis, as well as inflammation, have surfaced. These seemingly unrelated metabolic pathways are linked by the action of diverse nuclear receptors. Many intermediates in lipid metabolism were shown to be activating ligands of these receptors, explaining the dysregulation of intermediary metabolism and induction of insulin resistance by a lipid overload. In addition to invoking a derangement in nuclear receptor regulation, excessive hepatic lipid influx may have direct metabolic consequences, particularly on mitochondrial function.

SUMMARY

Non-alcoholic fatty liver disease is a multifactorial disease. Many aspects of the disease and the links to inflammation can be understood when the multiple functions of the regulating nuclear receptors are taken into account. Many of these nuclear receptors seem attractive targets to develop therapy for non-alcoholic fatty liver disease and the closely related metabolic syndrome.

The evolution of human fatness and susceptibility to obesity: an ethological approach

Human susceptibility to obesity is an unusual phenomenon amongst animals. An evolutionary analysis, identifying factors favouring the capacity for fat deposition, may aid in the development of preventive public health strategies. This article considers the proximate causes, ontogeny, fitness value and evolutionary history of human fat deposition. Proximate causes include diet composition, physical activity level, feeding behaviour, endocrine and genetic factors, psychological traits, and exposure to broader environmental factors. Fat deposition peaks during late gestation and early infancy, and again during adolescence in females. As in other species, human fat stores not only buffer malnutrition, but also regulate reproduction and immune function, and are subject to sexual selection. Nevertheless, our characteristic ontogenetic pattern of fat deposition, along with relatively high fatness in adulthood, contrasts with the phenotype of other mammals occupying the tropical savannah environment in which hominids evolved. The increased value of energy stores in our species can be attributed to factors increasing either uncertainty in energy availability, or vulnerability to that uncertainty. Early hominid evolution was characterised by adaptation to a more seasonal environment, when selection would have favoured general thriftiness. The evolution of the large expensive brain in the genus Homo then favoured increased energy stores in the reproducing female, and in the offspring in early life. More recently, the introduction of agriculture has had three significant effects: exposure to regular famine; adaptation to a variety of local niches favouring population-specific adaptations; and the development of social hierarchies which predispose to differential exposure to environmental pressures. Thus, humans have persistently encountered greater energy stress than that experienced by their closest living relatives during recent evolution. The capacity to accumulate fat has therefore been a major adaptive feature of our species, but is now increasingly maladaptive in the modern environment where fluctuations in energy supply have been minimised, and productivity is dependent on mechanisation rather than physical effort. Alterations to the obesogenic environment are predicted to play a key role in reducing the prevalence of obesity.

Weight gain in relation to plasma levels of complement factor 3: results from a population-based cohort study

AIMS/HYPOTHESIS

Mice that are deficient for complement factor 3 (C3) have shown resistance to weight gain, despite increased food intake. Cross-sectional studies of humans have reported correlations between C3 and obesity. This longitudinal study explored whether C3 predicts a large weight gain in middle-aged men.

METHODS

Plasma concentrations of C3 and complement factor 4 (C4) were measured in 2,706 non-diabetic healthy men aged between 38 and 50 years, who were re-examined after a mean period of 6.1 years.

RESULTS

After adjustments for initial weight, age, height and follow-up time, the odds of incurring large weight gain (75th percentile, > or =3.8 kg) were 1.00 (reference), 0.96 (95% CI:0.7-1.2), 1.1 (CI:0.9-1.5) and 1.4 (CI:1.1-1.8), respectively, among men with C3 levels in the first, second, third and fourth quartiles (p for trend=0.01) respectively. This relationship remained significant after further adjustments for lifestyle factors (physical inactivity, alcohol, smoking), metabolic factors (glucose or homeostasis model assessment values, cholesterol, triglycerides), inflammatory markers (fibrinogen, haptoglobin, ceruloplasmin, orosomucoid, alpha1-antitrypsin) and for C4. C4 was associated with weight gain after adjustments for initial weight, height, follow-up time and lifestyle factors, but not after adjustments for C3.

CONCLUSIONS/INTERPRETATION

C3 is a risk factor for incurring large weight gain in middle-aged men.

Developmental and metabolic implications of the hypoxic ventilatory response

This review explores the evidence to support the leading hypothesis that the metabolic response to hypoxia early in life provides the pathophysiological basis for the metabolic syndrome. Hypoxia is a frequent occurrence during early development and induces a state of energy depletion that triggers a wide range of 'metabolic' responses to preserve homeostasis. Recent interest in the sequelae of energy depletion through hypoxic mechanisms has grown, particularly because of demonstrated links with ensuing metabolic abnormalities and increased risk for future cardiovascular disease. The 'metabolic syndrome' refers to the combination of obesity, hyperinsulinaemia, dyslipidaemia and hypertension in adults. The metabolic responses to energy depletion during early development provide explanations for some of the mechanisms that ultimately lead to serological features of metabolic dysfunction in children with sleep-disordered breathing. Thus, the acute compensatory response of energy conservation to hypoxia during early development at the cellular, serological and whole organism levels suggests that the metabolic abnormalities that develop later in life may in fact originate very early in life; in other words, constitute early life antecedents of adult disease. Evidence regarding the circumstances under which responses to hypoxia become maladaptive will be discussed, with a focus on chronic conditions and those associated with intermittent respiratory dysfunction such as sleep-disordered breathing.