The morphology and metabolism of intraabdominal adipose tissue in men

Interactions between inflammation, sex steroids, and Alzheimer's disease risk factors

Alzheimer's disease (AD) is an age-related neurodegenerative disorder for which there are no effective strategies to prevent or slow its progression. Because AD is multifactorial, recent research has focused on understanding interactions among the numerous risk factors and mechanisms underlying the disease. One mechanism through which several risk factors may be acting is inflammation. AD is characterized by chronic inflammation that is observed before clinical onset of dementia. Several genetic and environmental risk factors for AD increase inflammation, including apolipoprotein E4, obesity, and air pollution. Additionally, sex steroid hormones appear to contribute to AD risk, with age-related losses of estrogens in women and androgens in men associated with increased risk. Importantly, sex steroid hormones have anti-inflammatory actions and can interact with several other AD risk factors. This review examines the individual and interactive roles of inflammation and sex steroid hormones in AD, as well as their relationships with the AD risk factors apolipoprotein E4, obesity, and air pollution.

Differential Role of Adipose Tissues in Obesity and Related Metabolic and Vascular Complications

This review focuses on the contribution of white, brown, and perivascular adipose tissues to the pathophysiology of obesity and its associated metabolic and vascular complications. Weight gain in obesity generates excess of fat, usually visceral fat, and activates the inflammatory response in the adipocytes and then in other tissues such as liver. Therefore, low systemic inflammation responsible for insulin resistance contributes to atherosclerotic process. Furthermore, an inverse relationship between body mass index and brown adipose tissue activity has been described. For these reasons, in recent years, in order to combat obesity and its related complications, as a complement to conventional treatments, a new insight is focusing on the role of the thermogenic function of brown and perivascular adipose tissues as a promising therapy in humans. These lines of knowledge are focused on the design of new drugs, or other approaches, in order to increase the mass and/or activity of brown adipose tissue or the browning process of beige cells from white adipose tissue. These new treatments may contribute not only to reduce obesity but also to prevent highly prevalent complications such as type 2 diabetes and other vascular alterations, such as hypertension or atherosclerosis.

Preclinical In vivo Imaging for Fat Tissue Identification, Quantification, and Functional Characterization

Localization, differentiation, and quantitative assessment of fat tissues have always collected the interest of researchers. Nowadays, these topics are even more relevant as obesity (the excess of fat tissue) is considered a real pathology requiring in some cases pharmacological and surgical approaches. Several weight loss medications, acting either on the metabolism or on the central nervous system, are currently under preclinical or clinical investigation. Animal models of obesity have been developed and are widely used in pharmaceutical research. The assessment of candidate drugs in animal models requires non-invasive methods for longitudinal assessment of efficacy, the main outcome being the amount of body fat. Fat tissues can be either quantified in the entire animal or localized and measured in selected organs/regions of the body. Fat tissues are characterized by peculiar contrast in several imaging modalities as for example Magnetic Resonance Imaging (MRI) that can distinguish between fat and water protons thank to their different magnetic resonance properties. Since fat tissues have higher carbon/hydrogen content than other soft tissues and bones, they can be easily assessed by Computed Tomography (CT) as well. Interestingly, MRI also discriminates between white and brown adipose tissue (BAT); the latter has long been regarded as a potential target for anti-obesity drugs because of its ability to enhance energy consumption through increased thermogenesis. Positron Emission Tomography (PET) performed with 18F-FDG as glucose analog radiotracer reflects well the metabolic rate in body tissues and consequently is the technique of choice for studies of BAT metabolism. This review will focus on the main, non-invasive imaging techniques (MRI, CT, and PET) that are fundamental for the assessment, quantification and functional characterization of fat deposits in small laboratory animals. The contribution of optical techniques, which are currently regarded with increasing interest, will be also briefly described. For each technique the physical principles of signal detection will be overviewed and some relevant studies will be summarized. Far from being exhaustive, this review has the purpose to highlight some strategies that can be adopted for the in vivo identification, quantification, and functional characterization of adipose tissues mainly from the point of view of biophysics and physiology.

Long-Term Impacts of Foetal Malnutrition Followed by Early Postnatal Obesity on Fat Distribution Pattern and Metabolic Adaptability in Adult Sheep

We aimed to investigate whether over- versus undernutrition in late foetal life combined with obesity development in early postnatal life have differential implications for fat distribution and metabolic adaptability in adulthood. Twin-pregnant ewes were fed NORM (100% of daily energy and protein requirements), LOW (50% of NORM) or HIGH (150%/110% of energy/protein requirements) diets during the last trimester. Postnatally, twin-lambs received obesogenic (HCHF) or moderate (CONV) diets until 6 months of age, and a moderate (obesity correcting) diet thereafter. At 2½ years of age (adulthood), plasma metabolite profiles during fasting, glucose, insulin and propionate (in fed and fasted states) tolerance tests were examined. Organ weights were determined at autopsy. Early obesity development was associated with lack of expansion of perirenal, but not other adipose tissues from adolescence to adulthood, resulting in 10% unit increased proportion of mesenteric of intra-abdominal fat. Prenatal undernutrition had a similar but much less pronounced effect. Across tolerance tests, LOW-HCHF sheep had highest plasma levels of cholesterol, urea-nitrogen, creatinine, and lactate. Sex specific differences were observed, particularly with respect to fat deposition, but direction of responses to early nutrition impacts were similar. However, prenatal undernutrition induced greater metabolic alterations in adult females than males. Foetal undernutrition, but not overnutrition, predisposed for adult hypercholesterolaemia, hyperureaemia, hypercreatinaemia and hyperlactataemia, which became manifested only in combination with early obesity development. Perirenal expandability may play a special role in this context. Differential nutrition recommendations may be advisable for individuals with low versus high birth weights.

The relationship between adipocyte size and the transcript levels of SNAP23, BSCL2 and COPA genes in pigs

Breed-specific differences in fat tissue accumulation in the pig provide an opportunity to study the genetic background of this process. In the present study three pig breeds, differing in fatness, were analyzed in terms of the size of adipocytes derived from three tissues (subcutaneous, visceral and longissimus dorsi muscle) in relation to transcript levels of genes (SNAP23, BSCL2 and COPA), which encode proteins involved in lipid droplet formation. The analysis of adipocyte size revealed significant effects of breed and tissue and confirmed earlier reports that an elevated backfat thickness in some pig breeds is correlated with a larger adipocyte size. Variability in the transcript abundance of the studied genes among breeds and tissues was observed. We found a positive correlation between the abundance of the SNAP23 transcript and adipocyte diameter. The obtained results indicate that SNAP23 may be considered as an interesting candidate gene involved in adipose tissue growth in the pig.

Physiological and Psychological Changes Following Liposuction of Large Volumes of Fat in Overweight and Obese Women

BACKGROUND

Liposuction can remove a substantial amount of body fat. We investigated the effects of liposuction of large volumes of fat on anthropometrics, body composition (BIA), metabolic hormones, and psychological measures in overweight/obese women. To our knowledge, this is the first study to examine both physiological and psychological changes following liposuction of large volumes of fat in humans.

METHOD

Nine premenopausal healthy overweight/obese women (age = 35.9 ± 7.1 SD, weight = 84.4 kg ± 13.6, BMI = 29.9 kg/m² ± 2.9) underwent liposuction, removing 3.92 kg ± 1.04 SD of fat. Following an overnight fast, height, weight, waist, and hip circumferences were measured at baseline (one week pre-surgery) and post-surgery (wk 1,4,12). Blood samples were drawn for fasting concentrations of glucose, insulin, leptin, and ghrelin. The Body Shape Questionnaire (BSQ), Body Dysmorphic Disorder (BDD) Examination Self-Report (BDDE-SR), and Zung Self-Rating Depression Scale (ZDS) were administered.

RESULTS

Body weight, BMI, waist circumference, and body fat consistently decreased over time (p < .05). Glucose did not change significantly, but insulin decreased from wk 1 to wk 12 (p < .05). Leptin decreased from baseline to wk 1 (p = .01); ghrelin increased but not significantly. Changes in body fat and waist circumference (baseline to wk 1) correlated positively with changes in insulin during that period, and correlated inversely with changes in ghrelin (p < .05). BSQ scores decreased significantly over time (p = .004), but scores for BDDE-SR (p = .10) and ZDS (p = .24) did not change significantly.

CONCLUSION

Liposuction led to significant decreases in body weight and fat, waist circumference, and leptin levels. Changes in body fat and waist circumference correlated with concurrent changes in the adipose-related hormones, insulin and ghrelin (baseline to wk 1), and body shape perception improved. Thus, besides the obvious cosmetic effects, liposuction led to several positive body composition, hormonal, and psychological changes.

Adipose tissue mitochondrial respiration and lipolysis before and after a weight loss by diet and RYGB

OBJECTIVE

To study adipose tissue mitochondrial respiration and lipolysis following a massive weight loss.

METHODS

High resolution respirometry of adipose tissue biopsies and tracer determined whole body lipolysis. Sixteen obese patients with type 2 diabetes (T2DM) and 27 without (OB) were studied following a massive weight loss by diet and Roux-en-Y gastric bypass (RYGB).

RESULTS

The mitochondrial respiratory rates were similar in OB and T2DM, and the mass-specific oxygen flux increased significantly 4 and 18 months post-surgery (P < 0.05). With normalization to mitochondrial content, no differences in oxidative capacity after RYGB were seen. The ratio between the oxidative phosphorylation system capacity (P) and the capacity of the electron transfer system (E) increased 18 months after RYGB in both groups (P < 0.05). Lipolysis per fat mass was similar in the two groups and was increased (P < 0.05) and lipid oxidation during hyperinsulinemia decreased 4 months post-surgery. In T2DM, visceral fat mass was always higher relative to the body fat mass (%) compared to OB.

CONCLUSIONS

Adipose tissue mitochondrial respiratory capacity increases with RYGB. Adipocytes adapt to massive weight loss by increasing the phosphorylation system ratio (P/E), suggesting an increased ability to oxidize substrates after RYGB. Lipolysis increases in the short term post-surgery, and insulin sensitivity for suppression of lipolysis increases with RYGB.

Lipids generated during acute pancreatitis increase inflammatory status of macrophages by interfering with their M2 polarization

BACKGROUND

Necrosis of adipose tissue is a common complication of acute pancreatitis. The areas of steatonecrosis become a source of inflammatory mediators, including chemically modified fatty acids which could influence the progression of the systemic inflammation. In an experimental model of acute pancreatitis we analyzed the effects of lipids generated by two representative areas of adipose tissue on the switch to the M1 phenotype in macrophages.

METHODS

Pancreatitis was induced in rats by intraductal administration of 5% taurocholate and after 6 h, lipids from retroperitoneal, mesenteric or epididymal adipose tissues were collected. Lipid uptake, phenotype polarization and the activation of PPARγ and NFκB were evaluated in macrophages treated with these lipids.

RESULTS

After induction of pancreatitis, lipids from visceral adipose tissue promote the switch to an increased pro-inflammatory phenotype in macrophages. This effect is not related with a higher activation of NFκB but with an interfering effect on the activation of M2 phenotype.

CONCLUSIONS

During acute pancreatitis, lipids generated by some areas of adipose tissue interfere on the M2 polarization of macrophages, thus resulting in a more intense pro-inflammatory M1 response.

Should we wait for metabolic complications before operating on obese patients? Gastric bypass outcomes in metabolically healthy obese individuals

BACKGROUND

A subgroup of obese patients without metabolic disorders has been identified and defined as metabolically healthy but morbidly obese (MHMO).

OBJECTIVES

To compare Roux-en-Y gastric bypass (RYGB) outcomes between MHMO and metabolically unhealthy morbidly obese (MUMO) patients to assess whether the obesity phenotype could affect the results.

SETTING

A university-affiliated tertiary care center.

METHODS

One hundred nineteen consecutive patients underwent RYGB; 102 completed the 2-year follow-up and were divided into 2 groups (MHMO and MUMO) according to Wildman criteria, including blood pressure, triglycerides, high-density lipoprotein cholesterol (HDL-C), fasting blood sugar, C-reactive protein (CRP), and homeostasis model assessment of insulin resistance (HOMA-IR). Weight loss and metabolic parameter changes were analyzed.

RESULTS

Twenty-one of 102 (20.6%) patients were identified as MHMO; they were mostly women (90.5%) and were significantly younger than MUMO patients (39.4 ± 9.1 yr versus 47.2 ± 10, P = .001); 12.6% were lost to follow-up. MHMO phenotype was significantly associated with a greater percentage of excess body mass index loss (P = .03), independent of gender, age, and redo procedures. All metabolic parameters were significantly improved 2 years after surgery in the MUMO group. HOMA-IR, CRP, and triglycerides were significantly lower 2 years after surgery in the MHMO group, whereas fasting blood sugar and HDL-C were unchanged. At 2 years of follow-up, 92.3% of the population was metabolically healthy.

CONCLUSIONS

RYGB is an effective procedure to achieve weight loss and had a strong positive metabolic effect in both MHMO and MUMO phenotypes. RYGB led to an increase of the metabolically healthy status and may prevent or delay the onset of metabolic disorders.

Adipose tissue signaling by nuclear receptors in metabolic complications of obesity

In recent years white adipose tissue inflammation has been recognized to be associated with obesity. Adipocytes and adipose tissue associated macrophages (ATMs) secrete bioactive molecules, including adipokines, chemokines/cytokines and free fatty acids that modulate the development of low-grade inflammation and insulin resistance responsible for obesity-related metabolic and cardiovascular diseases. Nuclear receptors, notably peroxisome-proliferator-activated receptors, are sensors of dietary lipids and control transcriptional programs of key metabolic and inflammatory pathways in adipocytes and macrophages. This review focuses on mechanisms by which nuclear receptors maintain white adipose tissue homeostasis. The identification of ATMs as active players in the initiation of chronic inflammation and the links between inflammatory signaling and metabolic dysfunction will be presented, followed by discussion of recent evidence for nuclear receptors in ATM function, with an emphasis on the paracrine interaction between adipocytes and ATMs.

Increased peroxisome proliferator-activated receptor γ expression levels in visceral adipose tissue, and serum CCL2 and interleukin-6 levels during visceral adipose tissue accumulation

This study was conducted to determine the mRNA and protein expression levels of peroxisome proliferator-activated receptors (PPARs) in visceral adipose tissue, as well as serum adipokine levels, in Sprague Dawley rats. The rats were fed either a normal (control rats) or excessive (experimental rats) intake of food for 8 or 16 weeks, then sacrificed, at which time visceral and subcutaneous adipose tissues, as well as blood samples, were collected. The mRNA and protein expression levels of PPARs in the visceral adipose tissues were determined using reverse transcription-polymerase chain reaction and Western blotting, respectively. In addition, the levels of adipokines in the serum samples were determined using commercial ELISA kits. The results revealed that at 8 weeks, the mass of subcutaneous adipose tissue was higher than that of the visceral adipose tissue in the experimental rats, but the reverse occurred at 16 weeks. Furthermore, at 16 weeks the experimental rats exhibited an upregulation of PPARγ mRNA and protein expression levels in the visceral adipose tissues, and significant increases in the serum levels of CCL2 and interleukin (IL)-6 were observed, compared with those measured at 8 weeks. In conclusion, this study demonstrated that the PPARγ expression level was likely correlated with serum levels of CCL2 and IL-6, molecules that may facilitate visceral adipose tissue accumulation. In addition, the levels of the two adipokines in the serum may be useful as surrogate biomarkers for the expression levels of PPARγ in accumulated visceral adipose tissues.

Non-alcoholic fatty liver disease and obesity: Biochemical, metabolic and clinical presentations

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. Presentation of the disease ranges from simple steatosis to non-alcoholic steatohepatitis (NASH). NAFLD is a hepatic manifestation of metabolic syndrome that includes central abdominal obesity along with other components. Up to 80% of patients with NAFLD are obese, defined as a body mass index (BMI) > 30 kg/m². However, the distribution of fat tissue plays a greater role in insulin resistance than the BMI. The large amount of visceral adipose tissue (VAT) in morbidly obese (BMI > 40 kg/m²) individuals contributes to a high prevalence of NAFLD. Free fatty acids derived from VAT tissue, as well as from dietary sources and de novo lipogenesis, are released to the portal venous system. Excess free fatty acids and chronic low-grade inflammation from VAT are considered to be two of the most important factors contributing to liver injury progression in NAFLD. In addition, secretion of adipokines from VAT as well as lipid accumulation in the liver further promotes inflammation through nuclear factor kappa B signaling pathways, which are also activated by free fatty acids, and contribute to insulin resistance. Most NAFLD patients are asymptomatic on clinical presentation, even though some may present with fatigue, dyspepsia, dull pain in the liver and hepatosplenomegaly. Treatment for NAFLD and NASH involves weight reduction through lifestyle modifications, anti-obesity medication and bariatric surgery. This article reviews the available information on the biochemical and metabolic phenotypes associated with obesity and fatty liver disease. The relative contribution of visceral and liver fat to insulin resistance is discussed, and recommendations for clinical evaluation of affected individuals is provided.

Grading scale of visceral adipose tissue thickness and their relation to the nonalcoholic fatty liver disease

CONTEXT

The mesenteric fat is drained by the portal system, being related to the metabolic syndrome which is an impor-tant risk factor for non-alcoholic fatty liver disease (NAFLD).

OBJECTIVES

Graduate of visceral fat thickness and correlate with the NAFLD degree through ultrasonography method.

METHODS

We studied 352 subjects for age, gender, measures of subcutaneous fat thickness and visceral fat thickness as well as the presence and degree of liver fatty. Was analyzed the independent relationship between visceral fat thickness and NAFLD, and linear regression analysis was used in order to predict the visceral fat thickness from subcutaneous fat thickness.

RESULTS

The mean age of 225 women (63.9%) and 127 men (36.1%) was 47.5 ± 14.0 (18-77) years, 255 subjects had normal examinations, 97 had NAFLD thus distributed, 37 grade 1, 32 grade 2, and 28 grade 3. The subcutaneous fat thickness ranged from 0.26 to 3.50 cm with a mean of 1.3 ± 0.6 cm and visceral fat thickness ranged from 0.83 to 8.86 cm with a mean of 3.6 ± 1.7 cm. Linear regression showed that for every increase of 1 cm in subcutaneous fat thickness the visceral fat thickness will increase 0.9 cm.

CONCLUSIONS

The visceral fat thickness measured by ultrasonography is a useful and seems to be able to help estimate the risk of NAFLD.

Eating behavior and stress: a pathway to obesity

Stress causes or contributes to a huge variety of diseases and disorders. Recent evidence suggests obesity and other eating-related disorders may be among these. Immediately after a stressful event is experienced, there is a corticotropin-releasing-hormone (CRH)-mediated suppression of food intake. This diverts the body’s resources away from the less pressing need to find and consume food, prioritizing fight, flight, or withdrawal behaviors so the stressful event can be dealt with. In the hours following this, however, there is a glucocorticoid-mediated stimulation of hunger and eating behavior. In the case of an acute stress that requires a physical response, such as a predator-prey interaction, this hypothalamic-pituitary-adrenal (HPA) axis modulation of food intake allows the stressful event to be dealt with and the energy used to be replaced afterward. In the case of ongoing psychological stress, however, chronically elevated glucocorticoids can lead to chronically stimulated eating behavior and excessive weight gain. In particular, stress can enhance the propensity to eat high calorie “palatable” food via its interaction with central reward pathways. Activation of this circuitry can also interact with the HPA axis to suppress its further activation, meaning not only can stress encourage eating behavior, but eating can suppress the HPA axis and the feeling of stress. In this review we will explore the theme of eating behavior and stress and how these can modulate one another. We will address the interactions between the HPA axis and eating, introducing a potential integrative role for the orexigenic hormone, ghrelin. We will also examine early life and epigenetic modulation of the HPA axis and how this can influence eating behavior. Finally, we will investigate the clinical implications of changes to HPA axis function and how this may be contributing to obesity in our society.

The relationship between regional abdominal fat distribution and both insulin resistance and subclinical chronic inflammation in non-diabetic adults

OBJECTIVE

Obesity is associated with a high risk of insulin resistance (IR) and its metabolic complications. It is still debated that distributions of adipose tissue relate to an excess risk of IR and chronic inflammation in different race. This study was designed to examine the relation between insulin sensitivity, chronic inflammation and central fat distribution in non-diabetic volunteers in Taiwanese.

METHODS

There were 328 volunteers without family history of diabetes mellitus and with normal oral glucose tolerance test enrolled. Total body fat and abdominal fat were measured. Abdominal fat was categorized into intraperitoneal (IP), retroperitoneal (RP) and subcutaneous (SC) fat. The IR index was estimated by homeostatic model assessment. Five inflammatory markers: adiponectin, leptin, tumor necrosing factor-α (TNF-α), resistin and high sensitive CRP (hs-CRP) were measured.

RESULTS

IR was related to IP fat (r = 0.23, p < 0.001), but not RP fat, SC fat or total body fat. After correcting for age and sex, IP fat was the only significant predictor of IR (r2 = 58%, p = 0.001). Leptin showed the strongest relationship with all fat compartments (IP fat: r = 0.44, p = 0.001; RP fat: r = 0.36, p = 0.005, SC fat: r = 0.54, p < 0.001; total body fat: r = 0.61, p < 0.001). The hs-CRP and adiponectin were closely related both to IP (r = 0.29, p = 0.004; r = -0.20, p = 0.046, respectively) and total body fat (r = 0.29, p = 0.004; r = -0.29, p = 0.005, respectively), but not RP, or SC fat. TNF-α and resistin were not correlated to any fat compartment. After correcting for age and sex, leptin variance was mostly explained by SC fat (41.3%), followed by IP fat (33.6%) and RP fat (25.3%). The hs-CRP and adiponectin variance were mostly explained by IP fat (40% and 49% respectively).

CONCLUSIONS

IP fat is better predictors of IR and subclinical chronic inflammation in Taiwanese adults. A disproportionate accumulation of abdominal fat is associated with increased risk of cardiovascular diseases.

Adiposity measurements in association with metabolic syndrome in older men have different clinical implications

Obesity is a major public health problem, and measuring adiposity accurately and predicting its future comorbidities are important issues. Therefore, we hypothesized that 4 adiposity measurements, body mass index (BMI), waist circumference (WC), waist-to-height ratio, and body fat percentage, have different physiological meanings and distinct associations with adverse health consequences. This study aimed to investigate the relationship of these 4 measurements with metabolic syndrome (MetS) components and identify the most associated factor for MetS occurrence in older, non-medicated men. Cross-sectional data from 3004 men, all 65 years of age and older, were analyzed. The correlation and association between adiposity measurements and MetS components were evaluated by Pearson correlation and multiple linear regression. Based on multivariate logistic regression, BMI and WC were significantly associated with MetS and were selected to build a combined model of receiver operating characteristic curves to increase the diagnosis accuracy for MetS. The results show that BMI is independently associated with systolic and diastolic blood pressure; WC and body fat percentage are associated with fasting plasma glucose and log transformation of triglyceride; BMI and WC are negatively associated with high-density lipoprotein cholesterol (HDL-C); and WC is a better discriminate for MetS than BMI, although the combined model (WC + BMI) is not significantly better than WC alone. Based on these results, we conclude that the 4 adiposity measurements have different clinical implications. Thus, in older men, BMI is an important determinant for blood pressure and HDL-C. Waist circumference is associated with the risk of fasting plasma glucose, HDL-C, triglyceride, and MetS occurrence. The combined model did not increase the diagnosis accuracy.

Study of serum insulin levels in patients of euglycemic essential hypertension: a cross sectional study in North Indian population

OBJECTIVE

Essential hypertension is associated with multiple metabolic abnormalities, among them one of the most important is hyperinsulinemia. Hyperinsulinemia has been suggested as being responsible for the increased arterial pressure in patients with essential hypertension. But this is contradicted by the finding that all patients of essential hypertension are not hyperinsulinemic. The present study was conducted to explore the hypothesis that hyperinsulinemia plays a pathogenic role in hypertension in euglycemic North Indian population.

METHODS AND MATERIALS

120 subjects were studied (60 hypertensive and 60 normotensive). Blood pressure, fasting insulin levels, lipid profile and BMI were calculated for both the groups. Statistical analysis was done using online statistical software freely at www.openepi.com.

RESULTS

Hypertensive subjects were characterized by increased fasting insulin levels (16.77±7.62 vs. 8.84±2.04μIU/ml, p<0.01), increased BMI (p<0.01) and dyslipidemia, i.e. increased total cholesterol, high serum triglycerides, high LDL-C and low HDL-C with p<0.01. There was a positive correlation of fasting insulin levels with BMI, total cholesterol and LDL-C (p<0.01) and a negative correlation with HDL-C (p<0.05). However, serum insulin levels showed a non significant correlation with mean systolic and mean diastolic blood pressure (p>0.05).

CONCLUSIONS

Our study showed a significant increase in serum insulin levels in hypertensive patients thereby supporting a possible pathogenic role of insulin resistance in onset of hypertension even when the fasting blood sugar is within normal limits.

Sex differences in metabolic and adipose tissue responses to juvenile-onset obesity in sheep

Sex is a major factor determining adipose tissue distribution and the subsequent adverse effects of obesity-related disease including type 2 diabetes. The role of gender on juvenile obesity and the accompanying metabolic and inflammatory responses is not well established. Using an ovine model of juvenile onset obesity induced by reduced physical activity, we examined the effect of gender on metabolic, circulatory, and related inflammatory and energy-sensing profiles of the major adipose tissue depots. Despite a similar increase in fat mass with obesity between genders, males demonstrated a higher storage capacity of lipids within perirenal-abdominal adipocytes and exhibited raised insulin. In contrast, obese females became hypercortisolemic, a response that was positively correlated with central fat mass. Analysis of gene expression in perirenal-abdominal adipose tissue demonstrated the stimulation of inflammatory markers in males, but not females, with obesity. Obese females displayed increased expression of genes involved in the glucocorticoid axis and energy sensing in perirenal-abdominal, but not omental, adipose tissue, indicating a depot-specific mechanism that may be protective from the adverse effects of metabolic dysfunction and inflammation. In conclusion, young males are at a greater risk than females to the onset of comorbidities associated with juvenile-onset obesity. These sex-specific differences in cortisol and adipose tissue could explain the earlier onset of the metabolic-related diseases in males compared with females after obesity.

Expression studies of six human obesity-related genes in seven tissues from divergent pig breeds

Obesity has reached epidemic proportions globally and has become the cause of several major health risks worldwide. Presently, more than 100 loci have been related to obesity and metabolic traits in humans by genome-wide association studies. The complex genetic architecture behind obesity has triggered a need for the development of better animal models than rodents. The pig has emerged as a very promising biomedical model to study human obesity traits. In this study, we have characterized the expression patterns of six obesity-related genes, leptin (LEP), leptin receptor (LEPR), melanocortin 4 receptor (MC4R), fat mass and obesity associated (FTO), neuronal growth regulator 1 (NEGR)1 and adiponectin (ADIPOQ), in seven obesity-relevant tissues (liver; muscle; pancreas; hypothalamus; and retroperitoneal, subcutaneous and mesenteric adipose tissues) in two pig breeds (production pigs and Göttingen minipigs) that deviate phenotypically and genetically from each other with respect to obesity traits. We observe significant differential expression for LEP, LEPR and ADIPOQ in muscle and in all three adipose tissues. Interestingly, in pancreas, LEP expression is only detected in the fat minipigs. FTO shows significant differential expression in all tissues analyzed, and NEGR1 shows significant differential expression in muscle, pancreas, hypothalamus and subcutaneous adipose tissue. The MC4R transcript can be detected only in hypothalamus. In general, the expression profiles of the investigated genes are in accordance with those observed in human studies. Our study shows that both the differences between the investigated breeds and the phenotypic state with respect to obesity/leanness play a large role for differential expression of the obesity-related genes.

Exercise training enhances white adipose tissue metabolism in rats selectively bred for low- or high-endurance running capacity

Impaired visceral white adipose tissue (WAT) metabolism has been implicated in the pathogenesis of several lifestyle-related disease states, with diminished expression of several WAT mitochondrial genes reported in both insulin-resistant humans and rodents. We have used rat models selectively bred for low- (LCR) or high-intrinsic running capacity (HCR) that present simultaneously with divergent metabolic phenotypes to test the hypothesis that oxidative enzyme expression is reduced in epididymal WAT from LCR animals. Based on this assumption, we further hypothesized that short-term exercise training (6 wk of treadmill running) would ameliorate this deficit. Approximately 22-wk-old rats (generation 22) were studied. In untrained rats, the abundance of mitochondrial respiratory complexes I-V, citrate synthase (CS), and PGC-1 was similar for both phenotypes, although CS activity was greater than 50% in HCR (P = 0.09). Exercise training increased CS activity in both phenotypes but did not alter mitochondrial protein content. Training increased the expression and phosphorylation of proteins with roles in β-adrenergic signaling, including β3-adrenergic receptor (16% increase in LCR; P < 0.05), NOR1 (24% decrease in LCR, 21% decrease in HCR; P < 0.05), phospho-ATGL (25% increase in HCR; P < 0.05), perilipin (25% increase in HCR; P < 0.05), CGI-58 (15% increase in LCR; P < 0.05), and GLUT4 (16% increase in HCR; P < 0.0001). A training effect was also observed for phospho-p38 MAPK (12% decrease in LCR, 20% decrease in HCR; P < 0.05) and phospho-JNK (29% increase in LCR, 20% increase in HCR; P < 0.05). We conclude that in the LCR-HCR model system, mitochondrial protein expression in WAT is not affected by intrinsic running capacity or exercise training. However, training does induce alterations in the activity and expression of several proteins that are essential to the intracellular regulation of WAT metabolism.

Using a novel coculture model to dissect the role of intramuscular lipid load on skeletal muscle insulin responsiveness under reduced estrogen conditions

Reductions in estrogen function lead to adiposity and peripheral insulin resistance. Significant metabolic changes have been found in adipocytes and skeletal muscle with disruptions in the estrogen-signaling axis; however, it is unclear if intercellular communication exists between these tissues. The purpose of this study was to examine the impact of isolated adipocytes cocultured with single adult skeletal muscle fibers (SMF) collected from control female (SHAM) and ovariectomized female (OVX) mice. In addition, a second purpose was to compare differential effects of primary adipocytes from omental and inguinal adipose depots on SMF from these same groups. OVX SMF displayed greater lipid content, impaired insulin signaling, and lower insulin-induced glucose uptake compared with SHAM SMF without coculture. In the SHAM group, regardless of the adipose depot of origin, coculture induced greater intracellular lipid content compared with control SHAM SMF. The increased lipid in the SMF was associated with impaired insulin-induced glucose uptake when adipocytes were of omental, but not inguinal, origin. Coculture of OVX SMF with omental or inguinal adipocytes resulted in higher lipid content but no further reduction in insulin-induced glucose uptake compared with control OVX SMF. The data indicate that, in the OVX condition, there is a threshold for lipid accumulation in skeletal muscle beyond which there is no further impairment in insulin responsiveness. These results also demonstrate depot-specific effects of adipocyte exposure on skeletal muscle glucose uptake and further implicate a role for increased intracellular lipid storage in the pathogenesis of insulin resistance when estrogen levels are reduced.

Celastrol, an NF-κB inhibitor, improves insulin resistance and attenuates renal injury in db/db mice

The NF-κB pathway plays an important role in chronic inflammatory and autoimmune diseases. Recently, NF-κB has also been suggested as an important mechanism linking obesity, inflammation, and metabolic disorders. However, there is no current evidence regarding the mechanism of action of NF-κB inhibition in insulin resistance and diabetic nephropathy in type 2 diabetic animal models. We investigated the effects of the NF-κB inhibitor celastrol in db/db mice. The treatment with celastrol for 2 months significantly lowered fasting plasma glucose (FPG), HbA1C and homeostasis model assessment index (HOMA-IR) levels. Celastrol also exhibited significant decreases in body weight, kidney/body weight and adiposity. Celastrol reduced insulin resistance and lipid abnormalities and led to higher plasma adiponectin levels. Celastrol treatment also significantly mitigated lipid accumulation and oxidative stress in organs including the kidney, liver and adipose tissue. The treated group also exhibited significantly lower creatinine levels and urinary albumin excretion was markedly reduced. Celastrol treatment significantly lowered mesangial expansion and suppressed type IV collagen, PAI-1 and TGFβ1 expressions in renal tissues. Celastrol also improved abnormal lipid metabolism, oxidative stress and proinflammatory cytokine activity in the kidney. In cultured podocytes, celastrol treatment abolished saturated fatty acid-induced proinflammatory cytokine synthesis. Taken together, celastrol treatment not only improved insulin resistance, glycemic control and oxidative stress, but also improved renal functional and structural changes through both metabolic and anti-inflammatory effects in the kidney. These results suggest that targeted therapy for NF-κB may be a useful new therapeutic approach for the management of type II diabetes and diabetic nephropathy.

Pathophysiology of human visceral obesity: an update

Excess intra-abdominal adipose tissue accumulation, often termed visceral obesity, is part of a phenotype including dysfunctional subcutaneous adipose tissue expansion and ectopic triglyceride storage closely related to clustering cardiometabolic risk factors. Hypertriglyceridemia; increased free fatty acid availability; adipose tissue release of proinflammatory cytokines; liver insulin resistance and inflammation; increased liver VLDL synthesis and secretion; reduced clearance of triglyceride-rich lipoproteins; presence of small, dense LDL particles; and reduced HDL cholesterol levels are among the many metabolic alterations closely related to this condition. Age, gender, genetics, and ethnicity are broad etiological factors contributing to variation in visceral adipose tissue accumulation. Specific mechanisms responsible for proportionally increased visceral fat storage when facing positive energy balance and weight gain may involve sex hormones, local cortisol production in abdominal adipose tissues, endocannabinoids, growth hormone, and dietary fructose. Physiological characteristics of abdominal adipose tissues such as adipocyte size and number, lipolytic responsiveness, lipid storage capacity, and inflammatory cytokine production are significant correlates and even possible determinants of the increased cardiometabolic risk associated with visceral obesity. Thiazolidinediones, estrogen replacement in postmenopausal women, and testosterone replacement in androgen-deficient men have been shown to favorably modulate body fat distribution and cardiometabolic risk to various degrees. However, some of these therapies must now be considered in the context of their serious side effects. Lifestyle interventions leading to weight loss generally induce preferential mobilization of visceral fat. In clinical practice, measuring waist circumference in addition to the body mass index could be helpful for the identification and management of a subgroup of overweight or obese patients at high cardiometabolic risk.

[Role of white adipose tissue in vascular complications due to obesity]

The contribution of white adipose tissue to the vascular complications associated with obesity is analysed in this review. White adipose tissue is an active metabolic organ and secretor of several molecules with endocrine, paracrine and autocrine actions. Weight gain produced in the obesity, induces an excess of fat, mainly in the visceral depot, which is responsible for the activation of different signalling pathways, leading to a higher production of proinflammatory cytokines. As adipocytes as infiltrated macrophages and lymphocytes and endothelial cells contribute to a chronic low grade inflammatory situation present in obesity. Moreover, the increase in adiposity activates the inflammatory response in the adipocyte themselves, as well as in the hepatocyte. Finally, proinflammatory and proatherogenic mediators produced by white adipose tissue and liver associated to immune cells generate insulin resistance in peripheral tissues and contribute to the beginning of atherogenic process.

Effects of Dexamethasone on Primarily Cultured Newly Differentiated Rat Adipocytes from Different Adipose Tissue Regions

The effects of dexamethasone (dex) on newly differentiated adipocytes in primary culture derived from mesenteric, retroperitoneal, epididymal, and inguinal subcutaneous adipose tissues of male rats were studied. The degree of differentiation was similar in these adipose precursor cells derived from different regions as assessed by lipoprotein lipase (LPL) activity, an early marker of adipocyte differentiation. LPL activity was increased by addition of dex, and no differences in degree of activation were observed in cells from different adipose tissue regions. Development of both basal and isoproterenol-stimulated lipolysis was also similar in adipose precursor cells from different adipose tissue regions. Dex addition enhanced the isoproterenol-stimulated lipolysis with no regional differences. Studies of binding of [3H]-dex showed no regional differences in either binding affinity or maximal binding capacity. It is concluded that dex stimulates both LPL activity and lipolytic activity in newly differentiated rat adipocytes in primary culture. This seems, however, not to vary in magnitude in cells obtained from different adipose tissue regions. This might be due to the apparent similarity of number and affinity of glucocorticoid binding sites. Regional variations in glucocorticoid regulated LPL and lipolytic activity in adipose tissue might therefore not be due to inherent differences between adipocytes.

Growth Hormone Secretion after Testosterone Administration to Men with Visceral Obesity

Visceral obesity in men has been reported to be characterized by low testosterone (T) and insulin-like growth factor I (IGF-I) concentrations, the latter suggesting a relative growth hormone (GH) deficiency. Since T and GH-secretions are interrelated, men with visceral obesity were substituted with T for 14 days, and diurnal secretion pattern of GH as well as IGF-I concentrations, and metabolic variables were followed. Visceral obese men were characterized by a decreased total GH secretion and diminished peak amplitude, size, and number. T-substitution was followed by elevation of IGF-I levels. The IGF-I increase correlated with the elevation of T-concentration, and was most pronounced in men with the lowest concentrations of free T from the outset. There were no detectable changes in total quantity, amplitude, size or number of peaks of GH secretion. Glucose, chlolesterol and triglycerides as well as diastolic blood pressure decreased. There were no changes in thyroid or hematology variables. T-substitution of visceral obese men is followed by an elevation of IGF-I concentrations. It is suggested that this might be due either to minor, non-detectable increases in GH secretion, or to direct effects of T on IGF-I concentrations. The regulatory mechanisms by which T-administration are leading to metabolic and anthropometric improvements, might be direct effects of T, with or without mediation via GH secretion.

Levels of free fatty acids (FFA) are associated with insulin resistance but do not explain the relationship between adiposity and insulin resistance in Hispanic Americans: the IRAS Family Study

CONTEXT AND OBJECTIVE

We investigated whether free fatty acids (FFA) mediate the association between adiposity and insulin resistance in the Hispanic-American families of the Insulin Resistance Atherosclerosis Family Study.

DESIGN

In 815 Hispanic individuals in the Insulin Resistance Atherosclerosis Family Study, we tested for association between the following: 1) levels of adiposity [body mass index (BMI), visceral and sc adipose tissue area (VAT and SAT)] and circulating levels of FFA; 2) levels of circulating FFA and insulin sensitivity (S(I)); and 3) levels of adiposity and S(I), additionally testing to see whether levels of FFA mediated or modified the relationship between adiposity and S(I.)

RESULTS

After adjusting for age, sex, clinic site, and admixture, increasing levels of BMI, VAT, and SAT were weakly associated with increasing levels of circulating FFA (BMI: P = 0.024; VAT: P = 2.33 × 10(-3); SAT: P = 0.018; percent variation explained: ∼1.00%). Increasing levels of circulating FFA were associated with decreasing S(I) (P = 8.10 × 10(-11)). Increasing BMI, VAT, and SAT were also associated with decreasing S(I) (BMI: P = 4.98 × 10(-71); VAT: P = 1.48 × 10(-64); SAT: P = 4.21 × 10(-62)), but this relationship was not significantly mediated by FFA. VAT, but not BMI or SAT, interacts with levels of FFA to influence S(I) (P = 0.021).

CONCLUSIONS

Although levels of circulating FFA are associated both with increasing adiposity and decreasing S(I), they do not appear to mediate the association between levels of adiposity and S(I) in this large cohort of Hispanic-Americans. These results may indicate that FFA contribute to insulin resistance independent of adiposity.

Short-term regional meal fat storage in nonobese humans is not a predictor of long-term regional fat gain

Although body fat distribution strongly predicts metabolic health outcomes related to excess weight, little is known about the factors an individual might exhibit that predict a particular fat distribution pattern. We utilized the meal fatty acid tracer-adipose biopsy technique to assess upper and lower body subcutaneous (UBSQ and LBSQ, respectively) meal fat storage in lean volunteers who then were overfed to gain weight. Meal fatty acid storage in UBSQ and LBSQ adipose tissue, as well as daytime substrate oxidation (indirect calorimetry), was measured in 28 nonobese volunteers [n = 15 men, body mass index = 22.1 ± 2.5 (SD)] before and after an ∼8-wk period of supervised overfeeding (weight gain = 4.6 ± 2.2 kg, fat gain = 3.8 ± 1.7 kg). Meal fat storage (mg/g adipose tissue lipid) in UBSQ (visit 1: 0.78 ± 0.34 and 1.04 ± 0.71 for women and men, respectively, P = 0.22; visit 2: 0.71 ± 0.24 and 0.90 ± 0.37 for women and men, respectively, P = 0.08) and LBSQ (visit 1: 0.60 ± 0.23 and 0.48 ± 0.29 for women and men, respectively, P = 0.25; visit 2: 0.62 ± 0.24 and 0.65 ± 0.23 for women and men, respectively, P = 0.67) adipose tissue did not differ between men and women at either visit. Fractional meal fatty acid storage in UBSQ (0.31 ± 0.15) or LBSQ (0.19 ± 0.13) adipose tissue at visit 1 did not predict the percent change in regional body fat in response to overfeeding. These data indicate that meal fat uptake trafficking in the short term (24 h) is not predictive of body fat distribution patterns. In general, UBSQ adipose tissue appears to be a favored depot for meal fat deposition in both sexes, and redistribution of meal fatty acids likely takes place at later time periods.

Physical activity and exercise in the regulation of human adipose tissue physiology

Physical activity and exercise are key components of energy expenditure and therefore of energy balance. Changes in energy balance alter fat mass. It is therefore reasonable to ask: What are the links between physical activity and adipose tissue function? There are many complexities. Physical activity is a multifaceted behavior of which exercise is just one component. Physical activity influences adipose tissue both acutely and in the longer term. A single bout of exercise stimulates adipose tissue blood flow and fat mobilization, resulting in delivery of fatty acids to skeletal muscles at a rate well-matched to metabolic requirements, except perhaps in vigorous intensity exercise. The stimuli include adrenergic and other circulating factors. There is a period following an exercise bout when fatty acids are directed away from adipose tissue to other tissues such as skeletal muscle, reducing dietary fat storage in adipose. With chronic exercise (training), there are changes in adipose tissue physiology, particularly an enhanced fat mobilization during acute exercise. It is difficult, however, to distinguish chronic "structural" changes from those associated with the last exercise bout. In addition, it is difficult to distinguish between the effects of training per se and negative energy balance. Epidemiological observations support the idea that physically active people have relatively low fat mass, and intervention studies tend to show that exercise training reduces fat mass. A much-discussed effect of exercise versus calorie restriction in preferentially reducing visceral fat is not borne out by meta-analyses. We conclude that, in addition to the regulation of fat mass, physical activity may contribute to metabolic health through beneficial dynamic changes within adipose tissue in response to each activity bout.

Blockade of cannabinoid receptor 1 improves insulin resistance, lipid metabolism, and diabetic nephropathy in db/db mice

The endocannabinoid system is important in the pathogenesis of obesity-related metabolic disorders. However, the effect of inhibiting the endocannabinoid system in type 2 diabetic nephropathy is unclear. Therefore, we examined the effect of the cannabinoid (CB)1 receptor antagonist, SR141716, on insulin resistance and diabetic nephropathy in db/db mice. Six-week-old db/db mice were treated with the CB1-specific antagonist SR141716 (10 mg/kg · d) for 3 months. Treatment with SR141716 significantly improved insulin resistance and lipid abnormalities. Concomitantly, CB1 antagonism improved cardiac functional and morphological abnormality, hepatic steatosis, and phenotypic changes of adipocytes into small differentiated forms, associated with increased adiponectin expression and decreased lipid hydroperoxide levels. CB1 receptor was overexpressed in diabetic kidneys, especially in podocytes. Treatment with the SR141716 markedly decreased urinary albumin excretion and mesangial expansion and suppressed profibrotic and proinflammatory cytokine synthesis. Furthermore, SR141716 improved renal lipid metabolism and decreased urinary 8-isoprostane levels, renal lipid hydroperoxide content, and renal lipid content. In cultured podocytes, high-glucose stimulation increased CB1 receptor expression, and SR141716 treatment abolished high-glucose-induced up-regulation of collagen and plasminogen activator inhibitor-1 synthesis. Additionally, knockdown of CB1 receptor expression by stealth small interfering RNA abolished high-glucose-induced sterol-regulatory element-binding protein-1 expression in podocytes. These findings suggest that CB1 blockade improves insulin resistance and protect against renal injury through both metabolic and antifibrotic effects in type 2 diabetic nephropathy. Targeting CB1 blockade could therefore provide a new therapeutic target to prevent type 2 diabetic nephropathy.

Effect of green tea (Camellia sinensis) consumption on the components of metabolic syndrome in elderly

OBJECTIVE

To evaluate the effect of the consumption of green tea on components of MS in the elderly.

DESIGN

Intervention study.

SETTING

The sample was selected from the Geriatric Service of Hospital São Lucas of Pontifical Catholic University of Rio Grande do Sul.

PARTICIPANTS

45 elderly with MS were enrolled and allocated into two groups: green tea group (GTG, n= 24), who drank green tea and control group (CG, n= 21) without intervention.

INTERVENTION

The GTG received sachets of 1.0 g of green tea, and should drink three cups per day for 60 days and the CG was instructed not to make changes in their lifestyle.

MEASUREMENTS

The diagnostic criteria for MS used were the International Diabetes Federation. The lipidic and glycemic profile, and anthropometric measurements were evaluated before and after intervention.

RESULTS

There was a statistically significant weight loss only in GTG [71.5±12.6 kg to 70.3±12.6 kg (p<0.001)]. A statistically significant decrease in BMI [-0.5±0.4 kg/m2 in GTG and -0.2±0.6 kg/m2 in CG (P=0.032)] and waist circumference [-2.2±2.0 cm in GTG and - 0.3±1.8 cm in CG (P=0.002)] were observed. The intake of green tea did not change the biochemical parameters.

CONCLUSION

The consumption of green tea was effective in inducing weight loss, reducing BMI and waist circumference in the elderly with MS.

Heterogeneity among white adipose tissue depots in male C57BL/6J mice

The widespread prevalence of obesity has lead to extensive research on white adipose tissue (WAT), which frequently uses the C57BL/6J mouse strain as a model. In many studies, results obtained in one WAT depot are often extrapolated to all WAT. However, functional differences among WAT depots are now becoming apparent. Thus, to identify the molecular mechanisms responsible for WAT depot-specific differences under "normal" conditions, four C57BL/6J mouse WAT depots (inguinal, mesenteric, epididymal, and retroperitoneal) were analyzed. Depot proteomic profiles, along with weights, protein contents, adipocyte sizes and oxidative stress were determined. Mesenteric WAT had almost twice the protein content of the other depots analyzed. Mean adipocyte size was highest in epididymal and lowest in mesenteric and inguinal depots. The proteome of inguinal WAT displayed low levels of enzymes involved in ATP generation, glucose and lipid metabolism, and antioxidant proteins. Higher levels of these proteins were observed in mesenteric and epididymal WAT, with variable levels in the retroperitoneal depot. Some of these proteins showed depot-specific correlations with plasma levels of insulin, leptin, and adiponectin. In agreement with the proteomic data, levels of the antioxidant protein heat shock protein β1 (HSPβ1) also were lower in inguinal WAT when analyzed by western blotting and immunohistochemistry. Also, lipid peroxidation products showed similar trends. Our results are consistent with lower triglyceride turnover and lower oxidative stress in inguinal than mesenteric and epididymal WAT. The observed WAT depot-specific differences provide clues as to the mechanisms leading to these depots' respective diverse functions.

Inverse regulation of basal lipolysis in perigonadal and mesenteric fat depots in mice

Given the strong link between visceral adiposity and (hepatic) insulin resistance as well as liver steatosis, it is crucial to characterize obesity-associated alterations in adipocyte function, particularly in fat depots drained to the liver. Yet these adipose tissues are not easily accessible in humans, and the most frequently studied depot in rodents is the perigonadal, which is drained systemically. In the present study, we aimed to study alterations in lipolysis between mesenteric and perigonadal adipocytes in mice. Basal free fatty acid and glycerol release was significantly lower in perigonadal compared with mesenteric adipocytes isolated from chow-fed C57BL/6J mice. However, this difference completely vanished in high-fat diet-fed mice. Consistently, protein levels of the G(0)/G(1) switch gene 2 (G0S2), which were previously found to be inversely related to basal lipolysis, were significantly lower in mesenteric compared with perigonadal fat of chow-fed mice. Similarly, perilipin was differently expressed between the two depots. In addition, adipocyte-specific overexpression of G0S2 led to significantly decreased basal lipolysis in mesenteric adipose tissue of chow-fed mice. In conclusion, lipolysis is differently regulated between perigonadal and mesenteric adipocytes, and these depot-specific differences might be explained by altered regulation of G0S2 and/or perilipin.

The metabolically healthy but obese phenotype in African Americans

Obesity has become one of the leading public health concerns in the United States and worldwide. While obesity is associated with the metabolic syndrome, some obese individuals do not possess the constellation of the metabolic abnormalities and are referred to as metabolically healthy but obese (MHO) persons. Limited data exist on the prevalence and characteristics of the MHO in African Americans. The authors studied 126 obese African Americans and defined the MHO phenotype as an individual with a body mass index ≥30 kg/m(2) , high-density lipoprotein cholesterol ≥40 mg/dL, absence of type 2 diabetes mellitus, and absence of arterial hypertension. The correlates of the MHO phenotype with anthropometrical and metabolic indices were examined, as well as the effect of age on these correlates. Results showed that 36 (28.5%) of the individuals were identified with the MHO phenotype. Waist circumference (WC) and waist-to-hip ratio (WHR) were significantly lower (P<.05) in MHO than in non-MHO patients. While there were significant lower levels of low-density lipoprotein and triglycerides in MHO among patients younger than 40 years, the significance was lost among patients 40 years or older. This study indicates that increased WC and WHR may be early premetabolic syndrome markers in obese individuals and should warrant aggressive risk factor reduction therapy to prevent future development of related cardiovascular conditions.

Decrease of total subcutaneous adipose tissue from infancy to childhood

OBJECTIVES

The observation and research of body composition is a topic of present interest. For the assessment of health and variables influencing growth and nutrition, it is of utmost interest to focus on the population of young children.

SUBJECTS AND METHODS

The measurements of subcutaneous body fat distribution in a sample of clinically healthy children ages 0 to 7 years were examined. The optical device LIPOMETER was applied to measure the thickness of subcutaneous adipose tissue layers (in millimeters) at 15 well-defined body sites. This set of measurement points defines the subcutaneous adipose tissue topography. In the present study, subcutaneous adipose tissue topography was determined in 275 healthy children (128 girls and 147 boys) divided into 3 age groups.

RESULTS

The results of the measurements are presented in 3 levels: total subcutaneous adipose tissue, 4 body regions, and 15 body sites. Our results show a clear physiological decrease in subcutaneous body fat in boys (-43.8%) and girls (-39.8%). One interesting finding was that the decrease occurs mainly in the trunk, abdomen, and lower extremities, whereas the body fat distribution of the upper extremities did not differ. Furthermore, slight subcutaneous adipose tissue topography differences between both sexes were found.

CONCLUSIONS

The present study provides basic documentation of subcutaneous adipose tissue topography in healthy children ages 0 to 7 years. An accurate description of subcutaneous adipose tissue topography in healthy subjects could help to characterize various diseases in relation to overnutrition and malnutrition throughout childhood.

Similar VLDL-TG storage in visceral and subcutaneous fat in obese and lean women

OBJECTIVE

Excess visceral fat accumulation is associated with the metabolic disturbances of obesity. Differential lipid redistribution through lipoproteins may affect body fat distribution. This is the first study to investigate VLDL-triglyceride (VLDL-TG) storage in visceral fat.

RESEARCH DESIGN AND METHODS

Nine upper-body obese (UBO; waist circumference >88 cm) and six lean (waist circumference <80 cm) women scheduled for elective tubal ligation surgery were studied. VLDL-TG storage in visceral, upper-body subcutaneous (UBSQ), and lower-body subcutaneous (LBSQ) fat were measured with [9,10-(3)H]-triolein-labeled VLDL.

RESULTS

VLDL-TG storage in visceral fat accounted for only ~0.8% of VLDL-TG turnover in UBO and lean women, respectively. A significantly larger proportion of VLDL-TG turnover was stored in UBSQ (~5%) and LBSQ (~4%) fat. The VLDL-TG fractional storage was similar in UBO and lean women for all regional depots. VLDL-TG fractional storage and VLDL-TG concentration were correlated in UBO women in UBSQ fat (r = 0.68, P = 0.04), whereas an inverse association was observed for lean women in visceral (r = -0.89, P = 0.02) and LBSQ (r = -0.87, P = 0.02) fat.

CONCLUSIONS

VLDL-TG storage efficiency is similar in all regional fat depots, and trafficking of VLDL-TG into different adipose tissue depots is similar in UBO and lean women. Postabsorptive VLDL-TG storage is unlikely to be of major importance in the development of preferential upper-body fat distribution in obese women.

Utilization of dietary glucose in the metabolic syndrome

This review is focused on the fate of dietary glucose under conditions of chronically high energy (largely fat) intake, evolving into the metabolic syndrome. We are adapted to carbohydrate-rich diets similar to those of our ancestors. Glucose is the main energy staple, but fats are our main energy reserves. Starvation drastically reduces glucose availability, forcing the body to shift to fatty acids as main energy substrate, sparing glucose and amino acids. We are not prepared for excess dietary energy, our main defenses being decreased food intake and increased energy expenditure, largely enhanced metabolic activity and thermogenesis. High lipid availability is a powerful factor decreasing glucose and amino acid oxidation. Present-day diets are often hyperenergetic, high on lipids, with abundant protein and limited amounts of starchy carbohydrates. Dietary lipids favor their metabolic processing, saving glucose, which additionally spares amino acids. The glucose excess elicits hyperinsulinemia, which may derive, in the end, into insulin resistance. The available systems of energy disposal could not cope with the excess of substrates, since they are geared for saving not for spendthrift, which results in an unbearable overload of the storage mechanisms. Adipose tissue is the last energy sink, it has to store the energy that cannot be used otherwise. However, adipose tissue growth also has limits, and the excess of energy induces inflammation, helped by the ineffective intervention of the immune system. However, even under this acute situation, the excess of glucose remains, favoring its final conversion to fat. The sum of inflammatory signals and deranged substrate handling induce most of the metabolic syndrome traits: insulin resistance, obesity, diabetes, liver steatosis, hyperlipidemia and their compounded combined effects. Thus, a maintained excess of energy in the diet may result in difficulties in the disposal of glucose, eliciting inflammation and the development of the metabolic syndrome.

Wheel running prevents the accumulation of monounsaturated fatty acids in the liver of ovariectomized mice by attenuating changes in SCD-1 content

Decreases in female sex steroids enhance the accumulation of visceral fat mass, leading to a predisposition to developing metabolic diseases. The purpose of this study was to determine whether loss of ovarian function alters the amount and (or) the fatty acid (FA) composition of triacylglycerol (TAG) levels in the liver of ovary-intact (SHAM) or ovariectomized (OVX) mice. We also sought to determine whether voluntary wheel running could attenuate the associated changes in the liver. Twenty-two C57/BL6 female mice were divided into 2 groups (SHAM, OVX) and were then subdivided into sedentary and exercising groups (SHAM-Sed, SHAM-Ex, OVX-Sed, OVX-Ex). Visceral fat mass significantly increased in the OVX-Sed animals; however, the effect was attenuated in the OVX-Ex animals. Total hepatic TAG content did not significantly increase in the OVX-Sed animals; however, SHAM-Ex and OVX-Ex animals demonstrated significant decreases in TAG levels. A significant increase in the FA desaturase index (18:1/18:0 and 16:1/16:0) was detected in the OVX-Sed animals compared with all other groups, which corresponded to increases in stearoyl-CoA desaturase (SCD-1) content. These results indicate that loss of ovarian function alters FA composition of hepatic TAG mediated by increases in SCD-1. These data indicate that female sex steroids influence lipid metabolism in the liver and provide important insight concerning the influence of exercise on hepatic function.

The relationship between indices of iron status and selected anthropometric cardiovascular disease risk markers in an African population: the THUSA study

There is evidence that certain indices of iron status are associated with anthropometric measures, which are used independently as markers of cardiovascular disease (CVD) risk. This study examined whether this association exists in an African population. The study was a cross-sectional comparative study that examined a total of 1 854 African participants. Ferritin was positively associated with body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), percentage body fat and subscapular skinfold thickness. Serum ferritin concentration was higher in the high-WHR category than the normal-WHR category for both genders. Additionally, WC and WHR increased with increasing ferritin concentrations in both genders. Serum iron was lower in the obese than the normal-weight and pre-obese women only. In this population-based study, increased serum ferritin concentrations associated positively with increased WHR and WC, indicating that individuals or populations at risk of iron overload as defined by high serum ferritin concentrations may be at a greater risk of developing CVD.

Obesity, Visceral Fat, and NAFLD: Querying the Role of Adipokines in the Progression of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of clinicopathologic conditions ranging from steatosis alone to nonalcoholic steatohepatitis (NASH), with varying risks for progression to cirrhosis and hepatocellular carcinoma. There is mounting evidence that NAFLD not only complicates obesity, but also perpetuates its metabolic consequences. Critical event that leads to progressive liver injury in NAFLD is unknown. Obesity reflects a generalized proinflammatory state with its increased inflammatory markers like C reactive protein, IL-6, IL-8, IL-10, PAI-1, TNF-α, and hepatocyte growth factor. The elevated production of these adipokines is increasingly considered to be important in the development of diseases linked to obesity and the metabolic syndrome. Disordered cytokine production is likely to play a role in the pathogenesis of NAFLD. There is no effective treatment for NAFLD, though weight loss may halt disease progression and revert histological changes, the underlying mechanism remaining elusive. All stages of the disease pathway from prevention, early identification/diagnosis, and treatment require an understanding of the pathogenesis of liver injury in NAFLD.

The glucocorticoid contribution to obesity

Obesity is fast becoming the scourge of our time. It is one of the biggest causes of death and disease in the industrialized world, and affects as many as 32% of adults and 17% of children in the USA, considered one of the world's fattest nations. It can also cost countries billions of dollars per annum in direct and indirect care, latest estimates putting the USA bill for obesity-related costs at $147 billion in 2008. It is becoming clear that the pathophysiology of obesity is vastly more complicated than the simple equation of energy in minus energy out. A combination of genetics, sex, perinatal environment and life-style factors can influence diet and energy metabolism. In this regard, psychological stress can have significant long-term impact upon the propensity to gain and maintain weight. In this review, we will discuss the ability of psychological stress and ultimately glucocorticoids (GCs) to alter appetite regulation and metabolism. We will specifically focus on (i) GC regulation of appetite and adiposity, (ii) the apparent sexual dimorphism in stress effects on obesity and (iii) the ability of early life stress to programme obesity in the long term.

Distinct stem cells subpopulations isolated from human adipose tissue exhibit different chondrogenic and osteogenic differentiation potential

Recently adipose tissue has become a research topic also for the searching for an alternative stem cells source to use in cell based therapies such as tissue engineer. In fact Adipose Stem Cells (ASCs) exhibit an important differentiation potential for several cell lineages such as chondrogenic, osteogenic, myogenic, adipogenic and endothelial cells. ASCs populations isolated using standard methodologies (i.e., based on their adherence ability) are very heterogeneous but very few studies have analysed this aspect. Consequently, several questions are still pending, as for example, on what regard the existence/ or not of distinct ASCs subpopulations. The present study is originally aimed at isolating selected ASCs subpopulations, and to analyse their behaviour towards the heterogeneous population regarding the expression of stem cell markers and also regarding their osteogenic and chondrogenic differentiation potential. Human Adipose derived Stem Cells (hASCs) subpopulations were isolated using immunomagnetic beads coated with several different antibodies (CD29, CD44, CD49d, CD73, CD90, CD 105, Stro-1 and p75) and were characterized by Real Time RT-PCR in order to assess the expression of mesenchymal stem cells markers (CD44, CD73, Stro-1, CD105 and CD90) as well as known markers of the chondrogenic (Sox 9, Collagen II) and osteogenic lineage (Osteopontin, Osteocalcin). The obtained results underline the complexity of the ASCs population demonstrating that it is composed of several subpopulations, which express different levels of ASCs markers and exhibit distinctive differentiation potentials. Furthermore, the results obtained clearly evidence of the advantages of using selected populations in cell-based therapies, such as bone and cartilage regenerative medicine approaches.

A novel method for the isolation of subpopulations of rat adipose stem cells with different proliferation and osteogenic differentiation potentials

Bone marrow has been the elected cell source of studies published so far concerning bone and cartilage tissue-engineering approaches. Recent studies indicate that adipose tissue presents significant advantages over bone marrow as a cell source for tissue engineering. Most of these studies report the use of adipose stem cells (ASCs) isolated by a method based on the enzymatic digestion of the adipose tissue and on the ability of stem cells to adhere to a cell culture plastic surface. Using this method, a heterogeneous population was obtained containing different cell types that have been shown to compromise the proliferation and differentiation potential of the stem cells. This paper reports the development and optimization of a new isolation method that enables purified cell populations to be obtained that exhibit higher osteogenic differentiation and/or proliferation potential. This method is based on the use of immunomagnetic beads coated with specific antibodies and it is compared with other methods described in the literature for the selection of stem cell populations, e.g. methods based on a gradient solution and enzymatic digestion. The results showed that the isolation method based on immunomagnetic beads allows distinct subpopulations of rat ASCs to be isolated, showing different stem cells marker expressions and different osteogenic differentiation potentials. Therefore, this method can be used to study niches in ASC populations and/or also allow adipose tissue to be used as a stem cell source in a more efficient manner, increasing the potential of this cell source in future clinical applications.

Depot-specific differences in the insulin response of adipose-derived stromal cells

Visceral adiposity is more strongly linked to insulin resistance than subcutaneous adiposity. High insulin levels can be mitogenic or adipogenic to adipocytes, but little is known regarding these effects of insulin on stromal cells from visceral and subcutaneous fat depots. Consequently, we measured adipogenesis and mitosis in response to elevated insulin levels in rat adipose-derived stromal cells (ADSCs) from visceral (perirenal) and subcutaneous depots. Insulin alone, at 10 microM, did not stimulate adipogenesis in naïve perirenal visceral (pvADSCs) or subcutaneous ADSCs (scADSCs), although a significant increase in proliferation occurred in both. Adipogenesis, induced using adipocyte differentiation medium (AM), resulted in greater lipid accumulation in pvADSCs, but the associated decrease in proliferation was less than in scADSCs. Omission of insulin from AM significantly reduced lipid accumulation in pvADSCs, but had little effect in scADSC, whilst proliferation was inhibited more in scADSCs than pvADSCs. Consequently, insulin is more lipogenic and less mitogenic in differentiating pvADSCs compared to scADSCs.