The adipocyte as an active participant in energy balance and metabolism

Nonprescribed physical activity energy expenditure is maintained with structured exercise and implicates a compensatory increase in energy intake

BACKGROUND

Exercise interventions elicit only modest weight loss, which might reflect a compensatory reduction in nonprescribed physical activity energy expenditure (PAEE).

OBJECTIVE

The objective was to investigate whether there is a reduction in nonprescribed PAEE as a result of participation in a 6-mo structured exercise intervention in middle-aged men.

DESIGN

Sedentary male participants [age: 54 ± 5 y; body mass index (in kg/m²): 28 ± 3] were randomly assigned to a 6-mo progressive exercise (EX) or control (CON) group. Energy expenditure during structured exercise (prescribed PAEE) and nonprescribed PAEE were determined with the use of synchronized accelerometry and heart rate before the intervention, during the intervention (2, 9, and 18 wk), and within a 2-wk period of detraining after the intervention.

RESULTS

Structured prescribed exercise increased total PAEE and had no detrimental effect on nonprescribed PAEE. Indeed, there was a trend for greater nonprescribed PAEE in the EX group (P = 0.09). Weight loss in the EX group (-1.8 ± 2.2 kg compared with +0.2 ± 2.2 kg in the CON group, P < 0.02) reflected only ≈40% of the 300-373 kcal/kg body mass potential energy deficit from prescribed exercise. Serum leptin concentration decreased by 24% in the EX group (compared with 3% in the CON group, P < 0.03), and we estimate that this was accompanied by a compensatory increase in energy intake of ≈100 kcal/d.

CONCLUSIONS

The adoption of regular structured exercise in previously sedentary, middle-aged, and overweight men does not result in a negative compensatory reduction in nonprescribed physical activity. The less-than-predicted weight loss is likely to reflect a compensatory increase in energy intake in response to a perceived state of relative energy insufficiency.

The role of leptin in the respiratory system: an overview

Since its cloning in 1994, leptin has emerged in the literature as a pleiotropic hormone whose actions extend from immune system homeostasis to reproduction and angiogenesis. Recent investigations have identified the lung as a leptin responsive and producing organ, while extensive research has been published concerning the role of leptin in the respiratory system. Animal studies have provided evidence indicating that leptin is a stimulant of ventilation, whereas researchers have proposed an important role for leptin in lung maturation and development. Studies further suggest a significant impact of leptin on specific respiratory diseases, including obstructive sleep apnoea-hypopnoea syndrome, asthma, COPD and lung cancer. However, as new investigations are under way, the picture is becoming more complex. The scope of this review is to decode the existing data concerning the actions of leptin in the lung and provide a detailed description of leptin's involvement in the most common disorders of the respiratory system.

Circulating retinol binding protein 4 in critically ill patients before specific treatment: prognostic impact and correlation with organ function, metabolism and inflammation

INTRODUCTION

Hyperglycemia and insulin resistance are well-known features of critical illness and impact the mortality rate, especially in sepsis. Retinol binding protein 4 (RBP4) promotes insulin resistance in mice and is systemically elevated in patients with obesity and type 2 diabetes. We investigated the potential role of RBP4 in critically ill patients.

METHODS

We conducted a prospective single-center study of serum RBP4 concentrations in critically ill patients. One hundred twenty-three patients (85 with sepsis, 38 without sepsis) were studied at admission to a medical intensive care unit (ICU) before initiation of specific intensive care treatment measures and compared to 42 healthy nondiabetic controls. Clinical data, various laboratory parameters and metabolic and endocrine functions were assessed. Patients were followed for approximately 3 years.

RESULTS

Serum RBP4 was significantly reduced in ICU patients, independently of sepsis, as compared to healthy controls (P < 0.001). Patients with liver cirrhosis as the primary underlying diagnosis for ICU admission had significantly lower RBP4 levels as compared with other ICU patients. Accordingly, in all ICU patients, serum RBP4 closely correlated with liver function and increased with renal failure. No significant differences of serum RBP4 concentrations in septic patients with pulmonary or other origins of sepsis or nonseptic patients could be revealed. Acute phase proteins were inversely correlated with RBP4 in sepsis patients. RBP4 did not differ between patients with or without obesity or preexisting diabetes. However, serum RBP4 levels correlated with endogenous insulin secretion (C-peptide) and insulin resistance (HOMA index). Low serum RBP4 upon admission was an adverse predictor of short-term survival in the ICU, but was not associated with overall survival during long-term follow-up.

CONCLUSIONS

Serum RBP4 concentrations are significantly reduced in critically ill patients. The strong associations with hepatic and renal function, insulin resistance and acute mortality collectively suggest a role of RBP4 in the pathogenesis of critical illness, possibly as a negative acute phase reactant, and allow a proposition as a potential novel biomarker for ICU patients.

Relevance of serum leptin and leptin-receptor concentrations in critically ill patients

The adipocyte-derived cytokine leptin was implicated to link inflammation and metabolic alterations. We investigated the potential role of leptin components in critically ill patients, because systemic inflammation, insulin resistance, and hyperglycemia are common features of critical illness. Upon admission to Medical Intensive Care Unit (ICU), free leptin and soluble leptin-receptor serum concentrations were determined in 137 critically ill patients (95 with sepsis, 42 without sepsis) and 26 healthy controls. Serum leptin or leptin-receptor did not differ between patients or controls and were independent of sepsis. However, serum leptin was closely associated with obesity and diabetes and clearly correlated with markers of metabolism and liver function. Leptin-receptor was an unfavourable prognostic indicator, associated with mortality during three years follow-up. Our study indicates a functional role of leptin in the pathogenesis of severe illness and emphasizes the impact of complex metabolic alterations on the clinical outcome of critically ill patients.

To eat or not to eat: the effect of AICAR on food intake regulation in yellow-bellied marmots (Marmota flaviventris)

Mammals that hibernate (hibernators) exhibit a circannual rhythm of food intake and body mass. In the laboratory during the winter hibernation period, many hibernators enter a series of multi-day torpor bouts, dropping their body temperature to near ambient, and cease to feed even if food is present in their cage. The mechanism(s) that regulates food intake in hibernators is unclear. Recently, AMP-activated protein kinase (AMPK) has been shown to play a key role in the central regulation of food intake in mammals. We hypothesized that infusing an AMPK activator, 5-aminoimidazole-4-carboxamide 1 B-D-ribofuranoside (AICAR), intracerebroventricularly (ICV) into the third ventricle of the hypothalamus would stimulate yellow-bellied marmots (Marmota flaviventris) to feed during their hibernation season. Infusion of AICAR ICV into marmots at an ambient temperature of 22 degrees C caused a significant (P<0.05) increase in food intake. In addition, animals stimulated to feed did not enter torpor during the infusion period. Marmots ICV infused with saline did not increase food intake and these animals continued to undergo torpor at an ambient temperature of 22 degrees C. Our results suggest that AICAR stimulated the food intake pathway, presumably by activating AMPK. These results support the hypothesis that AMPK may be involved in regulating food intake in hibernators and that there may be common neural pathways involved in regulating feeding and eliciting torpor.

The neuroendocrine basis of lactation-induced suppression of GnRH: role of kisspeptin and leptin

Lactation is an important physiological model of the integration of energy balance and reproduction, as it involves activation of potent appetitive neuropeptide systems coupled to a profound inhibition of pulsatile GnRH/LH secretion. There are multiple systems that contribute to the chronic hyperphagia of lactation: 1) suppression of the metabolic hormones, leptin and insulin, 2) activation of hypothalamic orexigenic neuropeptide systems NPY, AGRP, orexin (OX) and melanin concentrating hormone (MCH), 3) special induction of NPY expression in the dorsomedial hypothalamus, and 4) suppression of anorexigenic systems POMC and CART. These changes ensure adequate energy intake to meet the metabolic needs of milk production. There is significant overlap in all of the systems that regulate food intake with the regulation of GnRH, suggesting there could be several redundant factors acting to suppress GnRH/LH during lactation. In addition to an overall increase in inhibitory tone acting directly on GnRH cell bodies that is brought about by increases in orexigenic systems, there are also effects at the ARH to disrupt Kiss1/neurokinin B/dynorphin neuronal function through inhibition of Kiss1 and NKB. These changes could lead to an increase in inhibitory auto-regulation of the Kiss1 neurons and a possible disruption of pulsatile GnRH release. While the low levels of leptin and insulin contribute to the changes in ARH appetitive systems, they do not appear to contribute to the suppression of ARH Kiss1 or NKB. The inhibition of Kiss1 may be the key factor in the suppression of GnRH during lactation, although the mechanisms responsible for its inhibition are unknown.

Inflammation, a link between obesity and cardiovascular disease

Obesity, the most common nutritional disorder in industrialized countries, is associated with an increased mortality and morbidity of cardiovascular disease (CVD). Obesity is primarily considered to be a disorder of energy balance, and it has recently been suggested that some forms of obesity are associated with chronic low-grade inflammation. The present paper focuses on the current status of our knowledge regarding chronic inflammation, a link between obesity and CVDs, including heart diseases, vascular disease and atherosclerosis. The paper discusses the methods of body fat evaluation in humans, the endocrinology and distribution of adipose tissue in the genders, the pathophysiology of obesity, the relationship among obesity, inflammation, and CVD, and the adipose tissue-derived cytokines known to affect inflammation. Due to space limitations, this paper focuses on C-reactive protein, serum amyloid A, leptin, adiponectin, resistin, visfatin, chemerin, omentin, vaspin, apelin, and retinol binding protein 4 as adipokines.

Insights into amylin-leptin synergy

Although the adipokine leptin is regarded as the prototypical long-term signal of energy balance, obese individuals are largely nonresponsive to exogenous leptin administration. Restoration of leptin responsiveness in obesity has been elusive despite a detailed understanding of the molecular mechanisms of leptin signaling. Recent translational research findings point to a potential therapeutic approach that incorporates amylin (a beta-cell hormone) and leptin agonism, with amylin restoring or enhancing leptin sensitivity. Here we hypothesize various physiological, neurobiological and molecular mechanisms that could mediate the interaction of these two neurohormonal signals and discuss several methodological challenges. Understanding how amylin agonism improves leptin function could point to general therapeutic strategies for combating leptin resistance and associated obesity.

Carcinoembryonic antigen-related cell adhesion molecule 2 controls energy balance and peripheral insulin action in mice

BACKGROUND & AIMS

The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a transmembrane glycoprotein with pleotropic functions, including clearance of hepatic insulin. We investigated the functions of the related protein CEACAM2, which has tissue-specific distribution (kidney, uterus, and crypt epithelia of intestinal tissues), in genetically modified mice.

METHODS

Ceacam2-null mice (Cc2-/-) were generated from a 129/SvxC57BL/6J background. Female mice were assessed by hyperinsulinemic-euglycemic clamp analysis and indirect calorimetry and body fat composition was measured. Cc2-/- mice and controls were fed as pairs, given insulin tolerance tests, and phenotypically characterized.

RESULTS

Female, but not male Cc2-/- mice exhibited obesity that resulted from hyperphagia and reduced energy expenditure. Pair feeding experiments showed that hyperphagia led to peripheral insulin resistance. Insulin action was normal in liver but compromised in skeletal muscle of female Cc2-/- mice; the mice had incomplete fatty acid oxidation and impaired glucose uptake and disposal. The mechanism of hyperphagia in Cc2-/- mice is not clear, but appears to result partly from increased hyperinsulinemia-induced hypothalamic fatty acid synthase levels and activity. Hyperinsulinemia was caused by increased insulin secretion.

CONCLUSIONS

In mice, CEACAM2 is expressed by the hypothalamus. Cc2-/- mice develop obesity from hyperphagia and reduced energy expenditure, indicating its role in regulating energy balance and insulin sensitivity.

Obesity in dogs and cats: a metabolic and endocrine disorder

Obesity is defined as an accumulation of excessive amounts of adipose tissue in the body, and has been called the most common nutritional disease of dogs in Western countries. Most investigators agree that at least 33% of the dogs presented to veterinary clinics are obese, and that the incidence is increasing as human obesity increases in the overall population. Obesity is not just the accumulation of large amounts of adipose tissue, but is associated with important metabolic and hormonal changes in the body, which are the focus of this review. Obesity is associated with a variety of conditions, including osteoarthritis, respiratory distress, glucose intolerance and diabetes mellitus, hypertension, dystocia, decreased heat tolerance, some forms of cancer, and increased risk of anesthetic and surgical complications. Prevention and early recognition of obesity, as well as correcting obesity when it is present, are essential to appropriate health care, and increases both the quality and quantity of life for pets.

Lipocalin-2 deficiency impairs thermogenesis and potentiates diet-induced insulin resistance in mice

OBJECTIVE

Lipocalin (LCN) 2 belongs to the lipocalin subfamily of low-molecular mass-secreted proteins that bind small hydrophobic molecules. LCN2 has been recently characterized as an adipose-derived cytokine, and its expression is upregulated in adipose tissue in genetically obese rodents. The objective of this study was to investigate the role of LCN2 in diet-induced insulin resistance and metabolic homeostasis in vivo.

RESEARCH DESIGN AND METHODS

Systemic insulin sensitivity, adaptive thermogenesis, and serum metabolic and lipid profile were assessed in LCN2-deficient mice fed a high-fat diet (HFD) or regular chow diet.

RESULTS

The molecular disruption of LCN2 in mice resulted in significantly potentiated diet-induced obesity, dyslipidemia, fatty liver disease, and insulin resistance. LCN2(-/-) mice exhibit impaired adaptive thermogenesis and cold intolerance. Gene expression patterns in white and brown adipose tissue, liver, and muscle indicate that LCN2(-/-) mice have increased hepatic gluconeogenesis, decreased mitochondrial oxidative capacity, impaired lipid metabolism, and increased inflammatory state under the HFD condition.

CONCLUSIONS

LCN2 has a novel role in adaptive thermoregulation and diet-induced insulin resistance.

White adipose tissue genome wide-expression profiling and adipocyte metabolic functions after soy protein consumption in rats

Obesity is associated with an increase in adipose tissue mass due to an imbalance between high dietary energy intake and low physical activity; however, the type of dietary protein may contribute to its development. The aim of the present work was to study the effect of soy protein versus casein on white adipose tissue genome profiling, and the metabolic functions of adipocytes in rats with diet-induced obesity. The results showed that rats fed a Soy Protein High-Fat (Soy HF) diet gained less weight and had lower serum leptin concentration than rats fed a Casein High-Fat (Cas HF) diet, despite similar energy intake. Histological studies indicated that rats fed the Soy HF diet had significantly smaller adipocytes than those fed the Cas HF diet, and this was associated with a lower triglyceride/DNA content. Fatty acid synthesis in isolated adipocytes was reduced by the amount of fat consumed but not by the type of protein ingested. Expression of genes of fatty acid oxidation increased in adipose tissue of rats fed Soy diets; microarray analysis revealed that Soy protein consumption modified the expression of 90 genes involved in metabolic functions and inflammatory response in adipose tissue. Network analysis showed that the expression of leptin was regulated by the type of dietary protein and it was identified as a central regulator of the expression of lipid metabolism genes in adipose tissue. Thus, soy maintains the size and metabolic functions of adipose tissue through biochemical adaptations, adipokine secretion, and global changes in gene expression.

Menopause impacts the relation of plasma adiponectin levels with the metabolic syndrome

OBJECTIVE

Plasma adiponectin is negatively correlated with metabolic syndrome (MetS) components obesity and insulin sensitivity. Here, we set out to evaluate the effect of menopause on the association of plasma adiponectin with MetS.

DESIGN

Data on plasma adiponectin and MetS were available from 2256 individuals participating in the Erasmus Rucphen Family study. Odds ratios for MetS were calculated by logistic regression analysis using plasma adiponectin quartiles. The discriminative accuracy of plasma adiponectin for MetS was determined by calculating the area under the curve (AUC) of receiver operator. Analyses were performed in women and men, pre- and postmenopausal women and younger and older men.

RESULTS

Virtually all determinants of MetS differed significantly between groups. Low plasma adiponectin showed the highest risk for MetS in postmenopausal women (odds ratio = 18.6, 95% CI = 7.9-44.0). We observed a high discriminative accuracy of age and plasma adiponectin for MetS not only in postmenopausal women (AUC = 0.76) but also in other subgroups (AUC from 0.67 to 0.87). However, in all groups, the discriminative accuracy of age and body mass index (BMI) for MetS was similar to the discriminative accuracy of age and plasma adiponectin.

CONCLUSIONS

Low plasma levels of adiponectin are associated with increased prevalence of MetS, especially in postmenopausal women. Age and BMI have similar discriminatory accuracies for presence of MetS when compared with age and plasma adiponectin. Thus, we conclude that the association of plasma adiponectin with MetS is significantly affected by menopause but challenge the additional value of adiponectin for the discriminatory accuracy for presence of MetS.

Comparative effects of oleoyl-estrone and a specific beta3-adrenergic agonist (CL316, 243) on the expression of genes involved in energy metabolism of rat white adipose tissue

Background

The combination of oleoyl-estrone (OE) and a selective β₃-adrenergic agonist (B3A; CL316,243) treatment in rats results in a profound and rapid wasting of body reserves (lipid).

Methods

In the present study we investigated the effect of OE (oral gavage) and/or B3A (subcutaneous constant infusion) administration for 10 days to overweight male rats, compared with controls, on three distinct white adipose tissue (WAT) sites: subcutaneous inguinal, retroperitoneal and epididymal. Tissue weight, DNA (and, from these values cellularity), cAMP content and the expression of several key energy handling metabolism and control genes were analyzed and computed in relation to the whole site mass.

Results

Both OE and B3A significantly decreased WAT mass, with no loss of DNA (cell numbers). OE decreased and B3A increased cAMP. Gene expression patterns were markedly different for OE and B3A. OE tended to decrease expression of most genes studied, with no changes (versus controls) of lipolytic but decrease of lipogenic enzyme genes. The effects of B3A were widely different, with a generalized increase in the expression of most genes, including the adrenergic receptors, and, especially the uncoupling protein UCP1.

Discussion

OE and B3A, elicit widely different responses in WAT gene expression, end producing similar effects, such as shrinking of WAT, loss of fat, maintenance of cell numbers. OE acted essentially on the balance of lipolysis-lipogenesis and the blocking of the uptake of substrates; its decrease of synthesis favouring lipolysis. B3A induced a shotgun increase in the expression of most regulatory systems in the adipocyte, an effect that in the end favoured again the loss of lipid; this barely selective increase probably produces inefficiency, which coupled with the increase in UCP1 expression may help WAT to waste energy through thermogenesis.

Conclusions

There were considerable differences in the responses of the three WAT sites. OE in general lowered gene expression and stealthily induced a substrate imbalance. B3A increasing the expression of most genes enhanced energy waste through inefficiency rather than through specific pathway activation. There was not a synergistic effect between OE and B3A in WAT, but their combined action increased WAT energy waste.

Gastrointestinal regulatory peptides and their effects on fat tissue

PURPOSE OF REVIEW

Regulation of body weight, food intake and appetite is complex and the gastrointestinal tract represents a central organ participating in the regulation of energy homeostasis by signaling to other tissues relevant in this context. This update will provide information regarding recent advances in the understanding of the interaction of gastrointestinal peptides with adipocytes in fat tissue and which biological effects they may exert.

RECENT FINDINGS

Several gastrointestinal peptides signal to their functional cognate receptors on adipocytes in white adipose tissue (WAT) thereby regulating glucose homeostasis, lipogenesis, lipolysis, free fatty acid release and may also participate in adipocyte differentiation.

SUMMARY

Gastrointestinal peptides emanate from enteroendocrine cells in the luminal digestive tract and are critical regulators of energy homeostasis, food intake and appetite. Recent studies have identified that gastrointestinal peptides communicate with WAT and exert their biological effects on fat cells. Fundamental understanding of gastrointestinal peptides and their interaction with adipocytes will provide future insights for the development of pharmacological targets in the treatment of obesity and insulin resistant states.

Diabetes and apoptosis: liver

The liver is a central regulator of glucose homeostasis and stores or releases glucose according to metabolic demands. In insulin resistant states or diabetes the dysregulation of hepatic glucose release contributes significantly to the pathophysiology of these conditions. Acute or chronic liver disease can aggravate insulin resistance and the physiological effects of insulin on hepatocytes are disturbed. Insulin resistance has also been recognized as an independent risk factor for the development of liver injury. In the healthy liver tissue homeostasis is achieved through cell turnover by apoptosis and dysregulation of the physiological process resulting in too much or too little cell death can have potentially devastating effects on liver tissue. The delineation of the signaling pathways that mediate apoptosis changed the paradigms of understanding of many liver diseases. These signaling events include cell surface based receptor-ligand systems and intracellular signaling pathways that are regulated through kinases on multiple levels. The dissection of these signaling pathways has shown that the regulators of apoptosis signaling events in hepatocytes can also modulate insulin signaling pathways and that mediators of insulin resistance in turn influence liver cell apoptosis. This review will summarize the potential crosstalk between apoptosis and insulin resistance signaling events and discuss the involved mediators.

Brain-endocrine interactions: a microvascular route in the mediobasal hypothalamus

Blood-borne hormones acting in the mediobasal hypothalamus, like those controlling food intake, require relatively direct access to target chemosensory neurons of the arcuate nucleus (ARC). An anatomical substrate for this is a permeable microvasculature with fenestrated endothelial cells in the ARC, a system that has awaited comprehensive documentation. Here, the immunofluorescent detection of endothelial fenestral diaphragms in the rat ARC allowed us to quantitate permeable microvessels throughout its rostrocaudal extent. We have determined that permeable microvessels are part of the subependymal plexus irrigating exclusively the ventromedial (vm) ARC from the subadjacent neuroendocrine median eminence. Unexpectedly, permeable microvessels were concentrated proximal to the pituitary stalk. This marked topography strongly supports the functional importance of retrograde blood flow from the pituitary to the vmARC, therefore making a functional relationship between peripheral long-loop, pituitary short-loop, and neuroendocrine ultra-short loop feedback, altogether converging for integration in the vmARC (formerly known as the hypophysiotrophic area), thereby so pivotal as a multicompetent brain endocrinostat.

Functional analysis of FSP27 protein regions for lipid droplet localization, caspase-dependent apoptosis, and dimerization with CIDEA

The adipocyte-specific protein FSP27, also known as CIDEC, is one of three cell death-inducing DFF45-like effector (CIDE) proteins. The first known function for CIDEs was promotion of apoptosis upon ectopic expression in mammalian cells. Recent studies in endogenous settings demonstrated key roles for CIDEs in energy metabolism. FSP27 is a lipid droplet-associated protein whose heterologous expression enhances formation of enlarged lipid droplets and is required for unilocular lipid droplets typical of white adipocytes in vivo. Here, we delineate relationships between apoptotic function and lipid droplet localization of FSP27. We demonstrate that ectopic expression of FSP27 induces enlarged lipid droplets in multiple human cell lines, which is indicative that its mechanism involves ubiquitously present, rather than adipocyte-specific, cellular machinery. Furthermore, promotion of lipid droplet formation in HeLa cells via culture in exogenous oleic acid offsets FSP27-mediated apoptosis. Using transient cotransfections and analysis of lipid droplets in HeLa cells stably expressing FSP27, we show that FSP27 does not protect lipid droplets from action of ATGL lipase. Domain mapping with eGFP-FSP27 deletion constructs indicates that lipid droplet localization of FSP27 requires amino acids 174-192 of its CIDE C domain. The apoptotic mechanism of FSP27, which we show involves caspase-9 and mitochondrial cytochrome c, also requires this 19-amino acid region. Interaction assays determine the FSP27 CIDE C domain complexes with CIDEA, and Western blot reveals that FSP27 protein levels are reduced by coexpression of CIDEA. Overall, our findings demonstrate the function of the FSP27 CIDE C domain and/or regions thereof for apoptosis, lipid droplet localization, and CIDEA interaction.

Disruption of inducible 6-phosphofructo-2-kinase ameliorates diet-induced adiposity but exacerbates systemic insulin resistance and adipose tissue inflammatory response

Adiposity is commonly associated with adipose tissue dysfunction and many overnutrition-related metabolic diseases including type 2 diabetes. Much attention has been paid to reducing adiposity as a way to improve adipose tissue function and systemic insulin sensitivity. PFKFB3/iPFK2 is a master regulator of adipocyte nutrient metabolism. Using PFKFB3(+/-) mice, the present study investigated the role of PFKFB3/iPFK2 in regulating diet-induced adiposity and systemic insulin resistance. On a high-fat diet (HFD), PFKFB3(+/-) mice gained much less body weight than did wild-type littermates. This was attributed to a smaller increase in adiposity in PFKFB3(+/-) mice than in wild-type controls. However, HFD-induced systemic insulin resistance was more severe in PFKFB3(+/-) mice than in wild-type littermates. Compared with wild-type littermates, PFKFB3(+/-) mice exhibited increased severity of HFD-induced adipose tissue dysfunction, as evidenced by increased adipose tissue lipolysis, inappropriate adipokine expression, and decreased insulin signaling, as well as increased levels of proinflammatory cytokines in both isolated adipose tissue macrophages and adipocytes. In an in vitro system, knockdown of PFKFB3/iPFK2 in 3T3-L1 adipocytes caused a decrease in the rate of glucose incorporation into lipid but an increase in the production of reactive oxygen species. Furthermore, knockdown of PFKFB3/iPFK2 in 3T3-L1 adipocytes inappropriately altered the expression of adipokines, decreased insulin signaling, increased the phosphorylation states of JNK and NFkappaB p65, and enhanced the production of proinflammatory cytokines. Together, these data suggest that PFKFB3/iPFK2, although contributing to adiposity, protects against diet-induced insulin resistance and adipose tissue inflammatory response.

Adult consequences of post-weaning high fat feeding on the limbic-HPA axis of female rats

The peripubertal period is critical for the final maturation of circuits controlling energy homeostasis and stress response. However, the consequence of juvenile fat consumption on adult physiology is not clear. This study analyzed the adult consequences of post-weaning fat feeding on limbic-hypothalamic-pituitary-adrenal (HPA) axis components and on metabolic regulators of female rats. Wistar rats were fed either a high fat (HF) diet or the normal chow from weaning to puberty or to 3 months of age. Additional groups crossed their diets at puberty onset. Plasma leptin, insulin, and corticosterone levels were determined by radioimmunoassay and their brain receptors by western blot analysis. Adult HF-fed animals though not overweight, had higher corticosterone and reduced glucocorticoid receptor levels in the hypothalamus and hippocampus, compared to the controls. The alterations in HPA axis emerged already at puberty onset. Leptin receptor levels in the hypothalamus were reduced only by continuous fat feeding from weaning to adulthood. The pre-pubertal period appeared more vulnerable to diet-induced alterations in adulthood than the post-pubertal one. Switching from fat diet to normal chow at puberty onset restored most of the diet-induced alterations in the HPA axis. The corticosteroid circuit rather than the leptin or insulin system appears as the principal target for the peripubertal fat diet-induced effects in adult female rats.

Correlation of the leptin:adiponectin ratio with measures of insulin resistance in non-diabetic individuals

AIMS/HYPOTHESIS

Obesity is the dominant cause of insulin resistance. In adult humans it is characterised by a combination of adipocyte hypertrophy and, to a lesser extent, adipocyte hyperplasia. As hypertrophic adipocytes secrete more leptin and less adiponectin, the plasma leptin:adiponectin ratio (LAR) has been proposed as a potentially useful measure of insulin resistance and vascular risk. We sought to assess the usefulness of the LAR as a measure of insulin resistance in non-diabetic white adults.

METHODS

Leptin and adiponectin levels were measured in 2,097 non-diabetic individuals from the Ely and European Group for the Study of Insulin Resistance (EGIR) Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study cohorts. LAR was compared with fasting insulin and HOMA-derived insulin sensitivity (HOMA-S) in all individuals and with the insulin sensitivity index (M/I) from hyperinsulinaemic-euglycaemic clamp studies in 1,226 EGIR RISC participants.

RESULTS

The LAR was highly correlated with HOMA-S in men (r = -0.58, p = 4.5 x 10(-33) and r = -0.65, p = 1.1 x 10(-66) within the Ely and EGIR RISC study cohorts, respectively) and in women (r = -0.51, p = 2.8 x 10(-36) and r = -0.61, p = 2.5 x 10(-73)). The LAR was also strongly correlated with the clamp M/I value (r = -0.52, p = 4.5 x 10(-38) and r = -0.47, p = 6.6 x 10(-40) in men and women, respectively), similar to correlations between HOMA-S and the M/I value.

CONCLUSIONS/INTERPRETATION

The leptin:adiponectin ratio is a useful measure of insulin resistance in non-diabetic white adults. These data highlight the central role of adipocyte dysfunction in the pathogenesis of insulin resistance. Given that variations between fasting and postprandial leptin and adiponectin levels tend to be small, the leptin to adiponectin ratio might also have potential value in assessing insulin sensitivity in the non-fasted state.

Pathogenesis of adolescent idiopathic scoliosis in girls - a double neuro-osseous theory involving disharmony between two nervous systems, somatic and autonomic expressed in the spine and trunk: possible dependency on sympathetic nervous system and hormones with implications for medical therapy

Anthropometric data from three groups of adolescent girls - preoperative adolescent idiopathic scoliosis (AIS), screened for scoliosis and normals were analysed by comparing skeletal data between higher and lower body mass index subsets. Unexpected findings for each of skeletal maturation, asymmetries and overgrowth are not explained by prevailing theories of AIS pathogenesis. A speculative pathogenetic theory for girls is formulated after surveying evidence including: (1) the thoracospinal concept for right thoracic AIS in girls; (2) the new neuroskeletal biology relating the sympathetic nervous system to bone formation/resorption and bone growth; (3) white adipose tissue storing triglycerides and the adiposity hormone leptin which functions as satiety hormone and sentinel of energy balance to the hypothalamus for long-term adiposity; and (4) central leptin resistance in obesity and possibly in healthy females. The new theory states that AIS in girls results from developmental disharmony expressed in spine and trunk between autonomic and somatic nervous systems. The autonomic component of this double neuro-osseous theory for AIS pathogenesis in girls involves selectively increased sensitivity of the hypothalamus to circulating leptin (genetically-determined up-regulation possibly involving inhibitory or sensitizing intracellular molecules, such as SOC3, PTP-1B and SH2B1 respectively), with asymmetry as an adverse response (hormesis); this asymmetry is routed bilaterally via the sympathetic nervous system to the growing axial skeleton where it may initiate the scoliosis deformity (leptin-hypothalamic-sympathetic nervous system concept = LHS concept). In some younger preoperative AIS girls, the hypothalamic up-regulation to circulating leptin also involves the somatotropic (growth hormone/IGF) axis which exaggerates the sympathetically-induced asymmetric skeletal effects and contributes to curve progression, a concept with therapeutic implications. In the somatic nervous system, dysfunction of a postural mechanism involving the CNS body schema fails to control, or may induce, the spinal deformity of AIS in girls (escalator concept). Biomechanical factors affecting ribs and/or vertebrae and spinal cord during growth may localize AIS to the thoracic spine and contribute to sagittal spinal shape alterations. The developmental disharmony in spine and trunk is compounded by any osteopenia, biomechanical spinal growth modulation, disc degeneration and platelet calmodulin dysfunction. Methods for testing the theory are outlined. Implications are discussed for neuroendocrine dysfunctions, osteopontin, sympathoactivation, medical therapy, Rett and Prader-Willi syndromes, infantile idiopathic scoliosis, and human evolution. AIS pathogenesis in girls is predicated on two putative normal mechanisms involved in trunk growth, each acquired in evolution and unique to humans.

Stress and obesity: the role of the hypothalamic-pituitary-adrenal axis in metabolic disease

PURPOSE OF REVIEW

Chronic stress, combined with positive energy balance, may be a contributor to the increased risk for obesity, especially upper body obesity, and other metabolic diseases. This association may be mediated by alterations in the hypothalamic-pituitary-adrenal (HPA) axis. In this review, we summarize the major research that has been conducted on the role of the HPA axis in obesity and metabolic disease.

RECENT FINDINGS

Dysregulation in the HPA axis has been associated with upper body obesity, but data are inconsistent, possibly due to methodological differences across studies. In addition to systemic effects, changes in local cortisol metabolism in adipose tissue may also influence the risk for obesity. HPA axis dysregulation may be the causal link between conditions such as maternal malnutrition and sleep deprivation with metabolic disease.

SUMMARY

The present review provides evidence for the relationship between chronic stress, alterations in HPA activity, and obesity. Understanding these associations and its interactions with other factors will be important in developing effective treatments for obesity and related metabolic diseases.

Altered phenotype of NK cells from obese rats can be normalized by transfer into lean animals

In diet-induced obese rats, leptin-mediated natural killer (NK) cell activation has been demonstrated to be impaired by abrogated intracellular JAK2-STAT3 signaling. The contribution of the obese microenvironment to this NK cell dysfunction and its reversibility remains elusive. In this study, the functions of NK cells from diet-induced obese rats after adoptive transfer into lean littermates were investigated using in vivo and in vitro approaches. Endogenous NK cells of normal-weight and diet-induced obese F344 rats were depleted in vivo. Then, NK cells from either normal-weight or obese donors were transferred. The numbers of peripheral blood NK cells were analyzed by fluorescence-activated cell sorting (FACS) and the distribution pattern of NK cells in lung and spleen by immunohistochemistry. Ob-R expression was evaluated by immunohistology and activation of intracellular target proteins of Ob-R by immunoblotting. The numbers of NK cells in blood and lung were significantly higher in obese animals compared to lean ones after transfer of NK cells from obese F344 rats. This was correlated with increased postreceptor signaling (JAK-2p, PKBpT308, ERK-2p) without altered Ob-R expression in those NK cells transferred to lean (ob-->nw) vs. obese (ob-->ob) animals. These results show for the first time that the altered phenotype of NK cells from obese rats can be normalized by generation of a physiological (metabolic) environment of lean rats.

Leptin deficiency: clinical implications and opportunities for therapeutic interventions

The discovery of leptin has significantly advanced our understanding of the metabolic importance of adipose tissue and has revealed that both leptin deficiency and leptin excess are associated with severe metabolic, endocrine, and immunological consequences. We and others have shown that a prominent role of leptin in humans is to mediate the neuroendocrine adaptation to energy deprivation. Humans with genetic mutations in the leptin and leptin receptor genes have deregulated food intake and energy expenditure leading to a morbidly obese phenotype and a disrupted regulation in neuroendocrine and immune function and in glucose and fat metabolism. Observational and interventional studies in humans with (complete) congenital leptin deficiency caused by mutations in the leptin gene or with relative leptin deficiency as seen in states of negative energy balance such as lipoatrophy, anorexia nervosa, or exercise-induced hypothalamic and neuroendocrine dysfunction have contributed to the elucidation of the pathophysiological role of leptin in these conditions and of the clinical significance of leptin administration in these subjects. More specifically, interventional studies have demonstrated that several neuroendocrine, metabolic, or immune disturbances in these states could be restored by leptin administration. Leptin replacement therapy is currently available through a compassionate use program for congenital complete leptin deficiency and under an expanded access program to subjects with leptin deficiency associated with congenital or acquired lipoatrophy. In addition, leptin remains a potentially forthcoming treatment for several other states of energy deprivation including anorexia nervosa or milder forms of hypothalamic amenorrhea pending appropriate clinical trials.

Leptin prevents the metabolic effects of adiponectin in L6 myotubes

AIMS/HYPOTHESIS

Adiponectin and leptin are negatively and positively correlated with human obesity respectively, and have both been shown to regulate energy metabolism in skeletal muscle. However, little is known about their signalling and functional crosstalk. Here we investigated the effects of leptin on metabolic actions of (1) globular adiponectin (gAd) and (2) full-length adiponectin (fAd) in L6 cells.

METHODS

Glucose uptake was measured upon gAd and fAd treatment after incubation with different doses (0.3, 0.6, 3, 6, 60 nmol/l) of leptin for 6, 12 and 24 h. We also measured adiponectin receptor (ADIPOR) expression and stimulation of downstream signalling by gAd and fAd using co-immunoprecipitation and western blotting following leptin pretreatment, as well as analysis of fatty acid uptake and oxidation using radiolabelled tracers.

RESULTS

Leptin attenuated the stimulation of glucose uptake by gAd and fAd in a dose- and time-dependent manner, a finding correlated with decreased levels of ADIPOR1 and ADIPOR2. gAd and fAd increased palmitate uptake via activation of AMP protein kinase (T172), enhanced expression of the fatty acid transporter CD36, phosphorylated acetyl-CoA carboxylase (S79) and enhanced palmitate oxidation, all of which were attenuated by leptin pretreatment. Adiponectin can also enhance insulin sensitivity via direct signalling crosstalk; here we show that enhanced insulin-stimulated IRS-1 (Y612) and Akt (T308) phosphorylation in response to fAd was attenuated by leptin. APPL1 was recently identified as a critical mediator of adiponectin action in skeletal muscle. We demonstrated that leptin attenuated binding of APPL1 to LKB1, a downstream target leading to AMPK phosphorylation.

CONCLUSIONS/INTERPRETATION

The direct metabolic and insulin-sensitising effects of adiponectin were attenuated in the presence of leptin.

Lipid body formation plays a central role in cell fate determination during developmental differentiation of Myxococcus xanthus

Cell differentiation is widespread during the development of multicellular organisms, but rarely observed in prokaryotes. One example of prokaryotic differentiation is the gram-negative bacterium Myxococcus xanthus. In response to starvation, this gliding bacterium initiates a complex developmental programme that results in the formation of spore-filled fruiting bodies. How the cells metabolically support the necessary complex cellular differentiation from rod-shaped vegetative cells into spherical spores is unknown. Here, we present evidence that intracellular lipid bodies provide the necessary metabolic fuel for the development of spores. Formed at the onset of starvation, these lipid bodies gradually disappear until they are completely used up by the time the cells have become mature spores. Moreover, it appears that lipid body formation in M. xanthus is an important initial step indicating cell fate during differentiation. Upon starvation, two subpopulations of cells occur: cells that form lipid bodies invariably develop into spores, while cells that do not form lipid bodies end up becoming peripheral rods, which are cells that lack signs of morphological differentiation and stay in a vegetative-like state. These data indicate that lipid bodies not only fuel cellular differentiation but that their formation represents the first known morphological sign indicating cell fate during differentiation.

aP2-Cre-mediated inactivation of acetyl-CoA carboxylase 1 causes growth retardation and reduced lipid accumulation in adipose tissues

Adipose tissue is one of the major sites for fatty acid synthesis and lipid storage. We generated adipose (fat)-specific ACC1 knockout (FACC1KO) mice using the aP2-Cre/loxP system. FACC1KO mice showed prenatal growth retardation; after weaning, however, their weight gain was comparable to that of wild-type (WT) mice on a normal diet. Under lipogenic conditions of fasting/re-feeding a fat-free diet, lipid accumulation in adipose tissues of FACC1KO mice was significantly decreased; this is consistent with a 50-66% reduction in the ACC activity in these tissues compared with that of WT mice. Surprisingly, FACC1KO mice manifested skeletal growth retardation phenotype accompanied by decreased chondrocyte proliferation in the growth plate and lower trabecular bone density. In addition, there was about a 30% decrease in serum insulin-like growth factor I (IGF1), and while the serum leptin level was decreased by about 50%, it did not counteract the osteopenic effects of IGF1 on the bone. Fatty acid analyses of mutant bone lipids revealed relatively higher levels of C18:2n-6 and C18:3n-3 and lower levels of their elongation C20 homologs than that of WT cohorts, leading to lower levels of C20 homologs and bone development. Moreover, aP2-Cre-mediated ACC1 inactivation in bone tissue led to a decreased number of osteoblasts but not of osteoclasts. The downregulation of ACC1 on osteoblastogenesis may be the cause for the osteopenia phenotype of FACC1KO bone homeostasis.

Obesity, abdominal obesity, and insulin resistance

The correlation of body mass index (BMI) with both adiposity and risk for type 2 diabetes mellitus (DM) is positive. An elevated BMI is also associated with increased mortality from cardiovascular disease (CVD). However, for any given BMI measurement, some persons are at risk for type 2 DM and CVD, while others are not. This disparity of risk may relate to differences in age, fitness, and body composition, including body fat. Obesity- excess body fat- is associated with insulin resistance. Abdominal obesity, in particular, places people at higher risk for developing insulin resistance and, consequently, is associated with an increased risk for type 2 DM and CVD. The association between obesity and insulin resistance is largely due to changes in the function of adipose tissue, specifically, increased release of free fatty acids and abnormalities in adipokine secretion. The properties of visceral adipose tissue may cause these dysfunctions to become magnified. Weight loss has the potential to improve insulin sensitivity through alterations in adipose tissue function.

Low serum adiponectin levels are predictive of advanced hepatic fibrosis in patients with NAFLD

BACKGROUND

Adiponectin, an adipocytokine-mediating insulin action, has recently been found to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to assess possible associations between serum adiponectin levels and factors of the metabolic syndrome or histologic parameters in biopsy-proven NAFLD.

METHODS

Patients with persistently abnormal liver function tests satisfying inclusion criteria were subjected to liver biopsy. Fibrosis stage and the NAFLD activity score were recorded for each patient. Body mass index, waist-to-hip ratio, factors of the metabolic syndrome (central obesity, hyperglycemia, hypertriglyceridemia, low high-density lipoprotein, and hypertension), and biochemical tests were also recorded. Insulin resistance was calculated by the homeostasis model assessment method. Serum adiponectin concentration was measured by an enzyme-linked immunosorbent assay.

RESULTS

Forty-two NAFLD patients, including 9 with compensated cirrhosis, were included in the study. The presence of each factor of the metabolic syndrome was associated with hypoadiponectinemia. Adiponectin negatively correlated with homeostasis model assessment (r=-0.551, P=0.001). Adiponectin concentration was negatively associated with higher stages of fibrosis (one-wayanalysis of variance, P=0.007), and was not associated with NAFLD activity score. Using multivariate logistic regression, adiponectin concentration, aspartate aminotransferase/alanine aminotransferase ratio, and the presence of waist-to-hip ratio >1 were independent predictors of advanced fibrosis. The receiver operating characteristic curve for detecting advanced fibrosis using a combination of the independent variables had an area under the curve of 0.902+/-0.054, P<0.0001.

CONCLUSIONS

Low serum adiponectin levels in NAFLD patients are suggestive of advanced fibrosis. Therefore, assessment of serum adiponectin levels may be useful in clinical follow-up.

Identification and treatment of metabolic complications in pediatric obesity

Metabolic consequences of obesity including insulin resistance, type 2 diabetes mellitus, hyperlipidemia, hypertension, polycystic ovarian syndrome, and non-alcoholic fatty liver infiltration are rapidly emerging in the pediatric population. Identifying effective strategies for identifying and treating these obesity related comorbidities in children are crucial to the prevention of future cardiovascular disease and poor health outcomes.This review discusses the pathophysiologic connections between obesity, metabolic disease and cardiovascular risk. Current evidence and recommendations for screening and treatment for the metabolic consequences of pediatric obesity are reviewed.

Dietary sucrose intake is related to serum leptin concentration in overweight pregnant women

BACKGROUND

Overweight, characterized by low-degree systemic inflammation, predisposes women to impaired glucose metabolism during pregnancy. Adipokine leptin participates in the regulation of energy balance and immune action.

AIMS OF THE STUDY

Objective of the study was to evaluate if aberrations in glucose metabolism during pregnancy are related to leptin concentration and whether serum leptin concentration is affected by diet composition.

SUBJECTS AND METHODS

Normal-weight (n = 61) and overweight or obese (BMI > 25, n = 42) pregnant women visited study clinic at third trimester of pregnancy and one month postpartum. Serum fasting leptin and insulin as well as plasma glucose concentrations were measured, insulin resistance (HOMA) and sensitivity (QUICKI) calculated, and dietary intake from food records determined.

RESULTS

In overweight women leptin concentration was significantly higher both in pregnancy, 45.27 (95% CI 39.40-51.14) ng/ml, and postpartum, 31.84 (27.38-36.30) ng/ml, than in normal-weight women, 31.09 (95% CI 27.80-34.37) ng/ml and 16.23 (13.93-18.53) ng/ml, respectively. Equally, blood glucose concentration during pregnancy was higher, 4.82 (4.67-4.97)mmol/l, and insulin concentration, 15.34 (12.00-18.68) mU/l, more pronounced in overweight compared to normal-weight women, 4.51 (4.42-4.61) mmol/l and 8.28 (7.21-9.36) mU/l, respectively. Significantly higher HOMA and lower QUICKI were also detected in overweight compared to normal-weight women. At third trimester of pregnancy, leptin concentration correlated positively with insulin concentration in normal-weight (r = 0.561, P = 0.002) and overweight women (r = 0.736, P < 0.001), as well as with HOMA (r = 0.568, P = 0.002 and r = 0.731, P < 0.001, respectively) whereas negative association was found with QUICKI in normal-weight (r = -0.484, P = 0.011) and overweight women (r = -0.711, P < 0.001). Importantly, serum leptin concentration was affected by dietary sucrose intake both as quantitatively (r = 0.424, P = 0.009) and relative to energy intake (r = 0.408, P = 0.012) in overweight but not in normal-weight pregnant women.

CONCLUSIONS

Overweight-related elevation in serum leptin is associated with impaired regulation of glucose metabolism during pregnancy. The novel finding that dietary sucrose intake is related to serum leptin concentration is in line with the current dietary recommendations to overweight pregnant women with impaired glucose metabolism advising the lower intake of sucrose during pregnancy.

Proteomic characterization of thiazolidinedione regulation of obese adipose secretome in Zucker obese rats

Signaling molecules released by adipose tissue have been implicated in inflammation, adipocyte dysfunction and systemic insulin resistance. In this study, we used 2-D LC-MS/MS and quantitative proteomics approaches to characterize the obese adipose secretory proteins that are responsive to the thiazolidinediones class of PPAR-γ agonizts. We first showed the differential secretion profiling between obese and lean adipose tissue; 87 proteins were detected from the conditioned medium of adipose tissue of Zucker obese rats compared with 31 from lean rats. A total of 57 proteins comprising immune factors, inflammatory molecules, collagens, proteases, and extracellular matrix proteins were detected from obese, but not lean adipose tissue. More importantly, a quantitative proteomics approach using (18) O proteolytic labeling allowed quantification of the difference in the secretion levels of 77 proteins, and thiazolidinediones treatment suppressed the secretion of most of the obese adipose tissue secretome, thus resembling a lean tissue. We have demonstrated an application of identifying the obese adipose secretome and characterizing the regulation of adipose secretion in obesity and insulin resistance. Our data provide the first evidence of changes in adipose secretion in obesity at a global level and show that such changes are correlated with systemic insulin resistance.

Different modulation by dietary restriction of adipokine expression in white adipose tissue sites in the rat

Background

White adipose tissue (WAT) is a disperse organ acting as energy storage depot and endocrine/paracrine controlling factor in the management of energy availability and inflammation. WAT sites response under energy-related stress is not uniform. In the present study we have analyzed how different WAT sites respond to limited food restriction as a way to better understand the role of WAT in the pathogenesis of the metabolic syndrome.

Methods

Overweight male rats had their food intake reduced a 40% compared with free-feeding controls. On day ten, the rats were killed; circulating glucose, insulin, leptin, adiponectin, triacylglycerols and other parameters were measured. The main WAT sites were dissected: mesenteric, retroperitoneal, epididymal and subcutaneous inguinal, which were weighed and frozen. Later all subcutaneous WAT was also dissected and weighed. Samples were used for DNA (cellularity) analysis and mRNA extraction and semiquantitarive RT-PCR analysis of specific cytokine gene expressions.

Results

There was a good correlation between serum leptin and cumulative WAT leptin gene mRNA, but not for adiponectin. Food restriction reduced WAT size, but not its DNA content (except for epididymal WAT). Most cytokines were correlated to WAT site weight, but not to DNA. There was WAT site specialization in the differential expression (and probably secretion) of adipokines: subcutaneous WAT showed the highest concentration for leptin, CD68 and MCP-1, mesenteric WAT for TNFα (and both tissues for the interleukins 1β and 6); resistin was highly expressed in subcutaneous and retroperitoneal WAT.

Conclusion

Food restriction induced different patterns for mesenteric and the other WAT sites, which may be directly related to both the response to intestine-derived energy availability, and an inflammatory-related response. However, retroperitoneal WAT, and to a lower extent, subcutaneous and epididymal, reacted decreasing the expression of inflammatory markers and the signaling of decreased energy availability in their stores. The varying cytokine expression patterns highlight the fact that WAT sites show different inflammatory and signaling responses to energy availability; they are too much different to simply extend to the whole-body WAT the findings of one or even a couple of sites.

Plasma proteome analysis for anti-obesity and anti-diabetic potentials of chitosan oligosaccharides in ob/ob mice

Altered levels of adipokines, derived as a result of distorted adipocytes, are the major factors responsible for changing biochemical parameters in obesity that leads to the development of metabolic disorders such as insulin resistance and atherosclerosis. In our previous reports, chitosan oligosaccharides (CO) were proved to inhibit the differentiation of 3T3-L1 adipocytes. In the present study, an attempt was made to investigate the anti-obesity and anti-diabetic effect of CO on ob/ob mice, by means of differential proteomic analysis of plasma. This was followed by immunoblotting, and gene expression in adipose tissue to clarify the molecular mechanism. CO treatment showed reduced diet intake (13%), body weight gain (12%), lipid (29%) and glucose levels (35%). 2-DE results showed differential levels of five proteins namely RBP4, apoE, and apoA-IV by >2-fold down-regulation and by >2-fold of apoA-I and glutathione peroxidase (GPx) up-regulation after CO treatment. Immunoblotting studies of adiponectin and resistin showed amelioration in their levels in plasma. Furthermore, the results of gene expressions for adipose tissue specific TNF-alpha, and IL-6 secretary molecules were also down-regulated by CO treatment. Gene expressions of PPAR gamma in adipose tissue were in good agreement with the ameliorated levels of adipokines, thereby improving the pathological state. Taken together, CO might act as a potent down-regulator of obesity-related gene expression in ob/ob mice that may normalize altered plasma proteins to overcome metabolic disorders of obesity.

Obesity, serious mental illness and antipsychotic drugs

The prevalence of overweight and obesity is higher in people with mental illness than in the general population. Body weight is tightly regulated by a complex system involving the cortex and limbic system, the hypothalamus and the gastrointestinal tract. While there are justifiable concerns about the weight gain associated with antipsychotic medication, it is too simplistic to ascribe all obesity in people with serious mental illness (SMI) to their drug treatment. The development of obesity in SMI results from the complex interaction of the genotype and environment of the person with mental illness, the mental illness itself and antipsychotic medication. There are dysfunctional reward mechanisms in SMI that may contribute to poor food choices and overeating. While it is clear that antipsychotics have profound effects to stimulate appetite, no one receptor interaction provides an adequate explanation for this effect, and many mechanisms are likely to be involved. The complexity of the system regulating body weight allows us to start to understand why some individuals appear much more prone to weight gain and obesity than others.

Relatively lower body mass index is associated with an excess of severe truncal asymmetry in healthy adolescents: Do white adipose tissue, leptin, hypothalamus and sympathetic nervous system influence truncal growth asymmetry?

BACKGROUND

In healthy adolescents normal back shape asymmetry, here termed truncal asymmetry (TA), is evaluated by higher and lower subsets of BMI. The study was initiated after research on girls with adolescent idiopathic scoliosis (AIS) showed that higher and lower BMI subsets discriminated patterns of skeletal maturation and asymmetry unexplained by existing theories of pathogenesis leading to a new interpretation which has therapeutic implications (double neuro-osseous theory).

METHODS

5953 adolescents age 11-17 years (boys 2939, girls 3014) were examined in a school screening program in two standard positions, standing forward bending (FB) and sitting FB. The sitting FB position is thought to reveal intrinsic TA free from back humps induced by any leg-length inequality. TA was measured in both positions using a Pruijs scoliometer as angle of trunk inclinations (ATIs) across the back at each of three spinal regions, thoracic, thoracolumbar and lumbar. Abnormality of ATIs was defined as being outside 2 standard deviations for each age group, gender, position and spinal region, and termed severe TA.

RESULTS

In the sitting FB position after correcting for age,relatively lower BMIs are statistically associated with a greater number of severe TAs than with relatively higher BMIs in both girls (thoracolumbar region) and boys (thoracolumbar and lumbar regions).The relative frequency of severe TAs is significantly higher in girls than boys for each of the right thoracic (56.76%) and thoracolumbar (58.82%) regions (p = 0.006, 0.006, respectively). After correcting for age, smaller BMIs are associated with more severe TAs in boys and girls.

DISCUSSION

BMI is a surrogate measure for body fat and circulating leptin levels. The finding that girls with relatively lower BMI have significantly later menarche, and a significant excess of TAs, suggests a relation to energy homeostasis through the hypothalamus. The hypothesis we suggest for the pathogenesis of severe TA in girls and boys has the same mechanism as that proposed recently for AIS girls, namely: severe TAs are initiated by a genetically-determined selectively increased hypothalamic sensitivity (up-regulation, i.e. increased sensitivity) to leptin with asymmetry as an adverse response to stress (hormesis), mediated bilaterally mainly to the growing trunk via the sympathetic nervous system (leptin-hypothalamic-sympathetic nervous system (LHS) concept). The putative autonomic dysfunction is thought to be increased by any lower circulating leptin levels associated with relatively lower BMIs. Sympathetic nervous system activation with asymmetry leads to asymmetries in ribs and/or vertebrae producing severe TA when beyond the capacity of postural mechanisms of the somatic nervous system to control the shape distortion of the trunk. A test of this hypothesis testing skin sympathetic responses, as in the Rett syndrome, is suggested.

Serum resistin levels in critically ill patients are associated with inflammation, organ dysfunction and metabolism and may predict survival of non-septic patients

Introduction

Blood glucose levels and insulin resistance in critically ill patients on admission to intensive care units (ICUs) have been identified as factors influencing mortality. The pathogenesis of insulin resistance (IR) in critically ill patients is complex and not fully understood. Resistin is a hormone mainly derived from macrophages in humans and from adipose tissue in rodents, which regulates glucose metabolism and insulin sensitivity. In non-critically ill patients, resistin was found to be related to impaired glucose tolerance, insulin resistance, metabolic syndrome, obesity and type 2 diabetes. Therefore, resistin might represent a link between inflammation, acute phase response and insulin resistance in critically ill patients. We aimed to examine the correlation of serum resistin concentrations to parameters of inflammation, organ function, metabolism, disease severity and survival in critically ill patients.

Methods

On admission to the Medical ICU, 170 patients (122 with sepsis, 48 without sepsis) were studied prospectively and compared with 60 healthy non-diabetic controls. Clinical data, various laboratory parameters, metabolic and endocrine functions as well as investigational inflammatory cytokine profiles were assessed. Patients were followed for approximately three years.

Results

Resistin serum concentrations were significantly elevated in all critical care patients compared with healthy controls, and significantly higher in sepsis than in non-sepsis patients. Serum resistin concentrations were not associated with pre-existing type 2 diabetes or obesity. For all critically ill patients, a correlation to the homeostasis model assessment index of insulin resistance (HOMA-IR) was shown. Serum resistin concentrations were closely correlated to inflammatory parameters such as C-reactive protein, leukocytes, procalcitonin, and cytokines such as IL6 and TNF-α, as well as associated with renal failure and liver synthesis capacity. High resistin levels (> 10 ng/ml) were associated with an unfavourable outcome in non-sepsis patients on ICU and the overall survival.

Conclusions

Serum resistin concentrations are elevated in acute inflammation due to sepsis or systemic inflammatory response syndrome (SIRS). The close correlation with other acute phase proteins suggests a predominant, clinically relevant resistin release from macrophages in ICU patients. Moreover, resistin could potentially serve as a prognostic biomarker in non-sepsis critically ill patients.

Increased adipose tissue expression of lipocalin-2 in obesity is related to inflammation and matrix metalloproteinase-2 and metalloproteinase-9 activities in humans

Lipocalin-2 (LCN2) is a novel adipokine with potential roles in obesity, insulin resistance, and inflammation. The aim of the present work was to evaluate the effect of obesity on circulating concentrations and gene and protein expression levels of LCN2 in human visceral adipose tissue (VAT) as well as its involvement in inflammation. VAT biopsies from 47 subjects were used in the study. Real-time PCR and Western-blot analyses were performed to quantify levels of LCN2 in VAT as well as the association with other genes implicated in inflammatory pathways. Forty-four serum samples were used to analyze the circulating concentrations of LCN2. Zymography analysis was used to determine the activity of matrix metalloproteinase (MMP) in VAT. Obese patients exhibited increased mRNA (p < 0.0001) and protein (p = 0.017) expression levels of LCN2 compared to lean subjects. Although no differences in plasma LCN2 concentrations were observed, increased circulating LCN2/MMP-9 complex levels were found (p = 0.038) in the obese group. Moreover, obese individuals showed increased (p < 0.01) activity of MMP-2 and MMP-9/LCN2 complex, while a positive correlation (p < 0.01) between MMP-2 and MMP-9 activities and BMI was observed. Gene and protein expression levels of LCN2 in VAT were positively associated with inflammatory markers (p < 0.01). These findings represent the first observation that mRNA and protein levels of LCN2 are increased in human VAT of obese subjects. Furthermore, LCN2 is associated with MMP-2 and MMP-9 activities as well as with pro-inflammatory markers suggesting its potential involvement in the low-grade chronic inflammation accompanying obesity.

RIP140 gene and protein expression levels are downregulated in visceral adipose tissue in human morbid obesity

BACKGROUND

Receptor-interacting protein 140 (RIP140) is a corepressor for nuclear receptors with an important role in the inhibition of energy expenditure. Rip140-knockout mice are lean and resistant to diet-induced obesity due to an increase in mitochondrial biogenesis, fatty acid oxidation, and oxidative phosphorylation. The aim of the present work was to evaluate the effect of morbid obesity on gene and protein expression levels of RIP140 in visceral adipose tissue (VAT).

METHODS

VAT biopsies obtained from 17 subjects were used in the study. Patients were classified as lean (body mass index [BMI]=21.8+/-1.3 kg/m2) or obese (BMI=48.2+/-2.6 kg/m2). Reverse transcription polymerase chain reaction and Western blot analyses were performed to quantify the expression levels of RIP140 in VAT. We also analyzed glucose and lipid profile as well as some inflammatory factors.

RESULTS

Obese patients exhibited significantly lower RIP140 mRNA expression levels compared to lean subjects (lean=1.00+/-0.17 arbitrary units, obese=0.65+/-0.18 arbitrary units; P<0.05). Protein expression of RIP140 followed the same trend, being significantly higher in lean volunteers (lean=1.00+/-0.18 arbitrary units, obese=0.45+/-0.11 arbitrary units; P<0.05). Furthermore, a significant negative correlation was found between RIP140 protein levels and both BMI (rho=-0.85; P<0.001) and body fat percentage (rho=-0.88; P<0.001).

CONCLUSIONS

The lower gene and protein expression levels of RIP140 in obese subjects may suggest a compensatory mechanism in order to favor energy expenditure and reduce fat accumulation in obesity states.

CXC ligand 5 is an adipose-tissue derived factor that links obesity to insulin resistance

We show here high levels of expression and secretion of the chemokine CXC ligand 5 (CXCL5) in the macrophage fraction of white adipose tissue (WAT). Moreover, we find that CXCL5 is dramatically increased in serum of human obese compared to lean subjects. Conversely, CXCL5 concentration is decreased in obese subjects after a weight reduction program, or in obese non-insulin-resistant, compared to insulin-resistant, subjects. Most importantly we demonstrate that treatment with recombinant CXCL5 blocks insulin-stimulated glucose uptake in muscle in mice. CXCL5 blocks insulin signaling by activating the Jak2/STAT5/SOCS2 pathway. Finally, by treating obese, insulin-resistant mice with either anti-CXCL5 neutralizing antibodies or antagonists of CXCR2, which is the CXCL5 receptor, we demonstrate that CXCL5 mediates insulin resistance. Furthermore CXCR2-/- mice are protected against obesity-induced insulin resistance. Taken together, these results show that secretion of CXCL5 by WAT resident macrophages represents a link between obesity, inflammation, and insulin resistance.

Reduced intestinal absorption of dipeptides via PepT1 in mice with diet-induced obesity is associated with leptin receptor down-regulation

Leptin is a major determinant of energy homeostasis, acting both centrally and in the gastrointestinal tract. We previously reported that acute leptin treatment enhances the absorption of di- and tripeptides via the proton-dependent PepT1 transporter. In this study, we investigated the long term effect of leptin on PepT1 levels and activity in Caco2 cell monolayers in vitro. We then assessed the significance of the regulation of PepT1 in vivo in a model of diet-induced obesity. We demonstrated that 1) leptin regulated PepT1 at the transcriptional level, via the MAPK pathway, and at the translational level, via ribosomal protein S6 activation, in Caco2 cells and 2) this activation was systematically followed by a time- and concentration-dependent loss of leptin action reflecting desensitization. Deciphering this desensitization, we demonstrated that leptin induced a down-regulation of its own receptor protein and mRNA expression. More importantly, we showed, in mice with diet-induced obesity, that a 4-week hypercaloric diet resulted in a 46% decrease in PepT1-specific transport, because of a 30% decrease in PepT1 protein and a 50% decrease in PepT1 mRNA levels. As shown in Caco2 cells, these changes in PepT1 were supported by a parallel 2-fold decrease in leptin receptor expression in mice. Taken together, these results indicate that during induction of obesity, leptin resistance may also occur peripherally in the gastrointestinal tract, disrupting the absorption of oligopeptides and peptidomimetic drugs.