Increased Adipose Tissue Mass Research Articles

Obesity and endocrine therapy: Host factors and breast cancer outcome

Obesity is becoming increasingly prevalent and it has been linked to poor breast cancer outcomes. Because obesity is associated with increased adipose tissue mass and aromatase activity [the target of aromatase inhibitors (AIs)], there is concern that these agents may be less effective in women who are overweight or obese. Four of the randomized trials of AIs vs. tamoxifen conducted in the adjuvant breast cancer setting (ATAC, BIG 1-98 and TEAM in the postmenopausal setting and ABCSG-12 in the premenopausal setting) have reported effects of body mass index (BMI) on the relative effectiveness of an AI vs. tamoxifen. Obesity was confirmed as an adverse prognostic factor in ATAC and BIG 1-98 but not the TEAM study; in ABSCG-12, obesity was associated with poor outcomes in the anastrozole arm only. In the three postmenopausal trials, the use of an AI vs. tamoxifen was associated with better outcomes at all levels of BMI [all hazard ratios for recurrence <1, although 95% confidence intervals often included 1 due to lower power and smaller reductions in risk]. Of note, there was no significant interaction of BMI with letrozole (vs. tamoxifen) in the BIG 1-98 trial; while ATAC investigators concluded that the relative benefit of anastrozole (vs. tamoxifen) might be better in thinner (vs. heavier) women. In ABCSG-12, the use of anastrozole (vs. tamoxifen) was associated with significantly worse outcomes in women with BMI ≥25 kg/m2 (similar to the detrimental effect of anastrozole on overall survival seen in the parent trial). These findings do not support the use of BMI as a predictor of AI (vs. tamoxifen) benefit in the adjuvant setting in postmenopausal breast cancer.

Betaine supplementation causes increase in carnitine metabolites in the muscle and liver of mice fed a high-fat diet as studied by nontargeted LC-MS metabolomics approach

Betaine (BET) reduces diet-induced liver lipid accumulation, and may relieve obesity-related metabolic disturbances. The aim of our study was to analyze metabolite alterations after supplementation of BET, polydextrose (PDX, a soluble dietary fiber), or their combination (BET PDX) via drinking water to C57BL/6J mice fed a high-fat (HF) diet. BET supplementation increased BET levels in plasma, muscle, and liver (p < 0.05), and the nontargeted LC-MS metabolite profiling revealed an increase in several metabolites in the carnitine biosynthesis pathway after BET supplementation both in liver and muscle. These included carnitine and acetylcarnitine (1.4-fold, p < 0.05), propionylcarnitine and γ-butyrobetaine (1.5-fold, p < 0.05), and several other short-chain acylcarnitines (p < 0.05) in muscle. These changes were slightly higher in the BET PDX group. Furthermore, BET reduced the HF diet induced accumulation of triglycerides in liver (p < 0.05). The supplementations did not attenuate the HF diet induced increase in body weight gain or the increase in adipose tissue mass. Instead, the combination of BET and PDX tended to increase adiposity. Our results suggest that increased availability of BET in different tissues, especially in muscle, after BET supplementation has an impact on carnitine metabolism, and this could further explain the link between BET and lipid metabolism.

Function of seipin: New insights from Bscl2/seipin knockout mouse models

Mutations in BSCL2/seipin cause Berardinelli-Seip congenital lipodystrophy (BSCL), a rare recessive disorder characterized by near absence of adipose tissue and severe insulin resistance. Since the discovery of the gene in 2001, several cellular studies intended to unravel the biological function of seipin and revealed that seipin-deficiency alters adipocyte differentiation and lipid droplet morphology. However, the exact function of the protein remains unclear and the pathophysiology of BSCL in patients carrying BSCL2/seipin mutations is poorly understood. A major breakthrough in the field of seipin came recently, with the demonstration by three independent groups that Bscl2-deficient mice (Bscl2(-/-)) developed severe lipodystrophy with only residual white and brown fat pads, validating a critical role for seipin in adipose tissue homeostasis. Using in vivo, ex vivo and in vitro methods, these studies demonstrate that seipin plays a key role in adipogenesis, lipid droplet homeostasis and cellular triglyceride lipolysis. In addition to adipose tissue impairment, Bscl2(-/-) mice are diabetic and display severe hepatic steatosis. Treatment with thiazolidinediones (TZD) in Bscl2(-/-) mice increases adipose tissue mass and partially rescues the metabolic complications associated with BSCL, highlighting that lipoatrophy is the major cause of the BSCL phenotype. Except an unexpected hypotriglyceridemia, Bscl2(-/-) mice phenotype represents an almost perfect picture of the human disease. This review analyses how these studies using Bscl2(-/-) mice brought new insights into seipin function and the mechanisms involved in the pathophysiology of BSCL. We also analyse some of the human data in the light of the mouse phenotyping and discuss the validity of Bscl2(-/-) mice model to test pharmaceutical approaches for treating BSCL and its associated metabolic complications.

Vascular endothelial growth factor-B as a therapeutic target to prevent ectopic fat deposition.

Vascular endothelial growth factor-B as a therapeutic target to prevent ectopic fat deposition.

Decorin expression is regulated by LPS and sodium salicylate in 3T3‐L1 Adipocytes

Obesity is caused by an increase in adipose tissue mass. Extracellular matrix (ECM) within adipose tissue can impact adipose tissue function. Obesity is characterized as a state of low‐grade, chronic inflammation. Small leucine‐rich‐proteoglycans (SLRPs) are ECM proteins that are play important roles in regulation of inflammation. We determined whether inflammation regulates the expression of SLRPs in adipocytes and preadipocytes. 3T3‐L1 preadipocytes and adipocytes were treated with varying concentrations of lipopolysaccharide (LPS). We show a dose‐dependent increase in decorin transcript expression with LPS treatment in both preadipocytes and adipocytes. Additionally, LPS treatment at 100ng/ml increased protein levels of decorin in differentiated 3T3‐L1 adipocytes. Sodium salicylate is an anti‐inflammatory compound that inhibits NFêB activation. Sodium salicylate (10mM) treatment led to a suppression of decorin transcript abundance compared to untreated cells (p&lt;0.05). Sodium salicylate also partially suppressed LPS‐induced decorin expression. This data suggests that the expression of decorin is influenced by inflammation and decorin may be a potential target of obesity‐related inflammation.

Modulation of Cardiovascular Function by Adipokines

Cardiovascular disease (CVD) and associated risk factors such as obesity remain at the forefront of health concerns. Adipose tissue has been well established as an endocrine organ that becomes dysfunctional with increased adipose tissue mass. The secretion of several adipokines is altered in subjects with abdominal adiposity and these changes to the endocrine balance may contribute to increased CVD risk. The identification and characterization of disease-specific proteins within the adipose tissue offers a novel therapeutic target for prevention or treatment of cardiovascular complications. This review will discuss the latest developments on therapeutic targets within the context of adipokines, such as adiponectin, C1q/ tumor necrosis factor (TNF) related proteins (CTRPs), visfatin, vaspin, chemerin and omentin, and their involvement in obesity-related cardiovascular complications.

Effects of Weight Loss and Exercise on Apelin Serum Concentrations and Adipose Tissue Expression in Human Obesity

Objective: Apelin is an adipokine which plays a role in the regulation of glucose homeostasis and may contribute to the link between increased adipose tissue mass and obesity related metabolic diseases. Here we investigate the role of omental and subcutaneous (SC) adipose tissue apelin and its receptor APJ mRNA expression in human obesity and test the hypothesis that changes in circulating apelin are associated with reduced fat mass in three weight loss intervention studies. Methods: Apelin serum concentration was measured in 740 individuals in a cross-sectional (n = 629) study including a subgroup (n = 161) for which omental and SC apelin mRNA expression has been analyzed and in three interventions: 12 weeks exercise (n = 60), 6 months calorie-restricted diet (n = 19), 12 months after bariatric surgery (n = 32). Results: Apelin mRNA is significantly higher expressed in adipose tissue of patients with type 2 diabetes and correlates with circulating apelin, BMI, body fat, C-reactive protein, and insulin sensitivity. Obesity surgery-induced weight loss causes a significant reduction in omental and SC apelin expression. All interventions led to significantly reduced apelin serum concentrations which significantly correlate with improved insulin sensitivity, independently of changes in BMI. Conclusions: Reduced apelin expression and serum concentration may contribute to improved insulin sensitivity beyond significant weight loss.

Does leptin signal adiposity in the egg-laying mammal, Tachyglossus aculeatus?

Leptin is a peptide hormone best known for its role in feedback regulation of adiposity in eutherian mammals. Normally an increase in adipose tissue mass leads to an increase in circulating leptin which increases energy expenditure and limits food intake, but in hibernating eutherian mammals this relationship may change to allow prehibernatory fattening. The echidna (Tachyglossus aculeatus) is a monotreme mammal which accumulates significant fat reserves before entering hibernation, and mates immediately at the end of hibernation. We hypothesised that echidnas would show a strong relationship between body mass and plasma leptin for most of the year which would change during the pre-hibernatory period. We measured plasma leptin and body mass in free-ranging echidnas over several reproductive and hibernation cycles. There were significant seasonal variations in plasma leptin in both sexes, with the highest levels occurring in hibernation and in mating females. The lowest levels were found in males when they were foraging maximally after the reproductive period. We used mass%, body mass at the time of sampling as a percentage of long term mean mass, as a proxy for adiposity. There was a weak negative relationship between mass% and plasma leptin, from which we infer a weak negative relationship between adiposity and plasma leptin as has been found in reptiles and birds, rather than the strong positive relationship found in other mammals.

Abstract 142: Effects of Omega-3 Fatty Acids on 3T3-L1 Preadipocyte Differentiation and Inflammatory Response

Objective: Adipose tissue (AT)-specific inflammation in obesity is associated with several metabolic disorders such as insulin resistance, and hepatic steatosis. We and others have shown that fish oil containing the omega-3 fatty acids increases AT mass in animal models which is associated with reduced AT-inflammation, hepatic steatosis, and dyslipidemia. Therefore, the objective of this study is to determine whether the omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) induce the differentiation process in 3T3-L1 preadipocytes. Methods: 3T3-L1 cells were pretreated and differentiated in the presence of different long chain fatty acids such as oleic acid (OA), stearic acid (SA), EPA, DHA, or a mixture of EPA and DHA (E+D) at a concentration of 50 μM. Results: Oil red O staining revealed that the differentiation process was remarkably increased in cells treated with DHA and, to a lesser extent with SA, compared to control cells differentiated in the absence of fatty acids. Real time PCR analysis showed that the expression of aP2, a marker of preadipocyte differentiation, was increased significantly in cells treated with DHA (4.1-fold, P &lt;0.001) or SA (2.8-fold, p&lt;0.05), compared to undifferentiated control cells. DHA and E+D but not SA increased the expression of cEBP alpha, another marker of differentiation (8.0-fold and 6.2-fold in DHA and E+D, respectively, P &lt;0.001). EPA and OA did not increase the expression of these differentiation markers. SA but not DHA-mediated increase in preadipocyte differentiation was associated with an increase in the expression of MCP-1, an inflammatory marker (1.9-fold, P &lt;0.05). Analysis of MAPK pathways that modulate cell differentiation and inflammation showed that treatment with DHA but not other fatty acids, led to a significant decrease in the phosphorylation of ERK1/2 and p38 MAPK compared to differentiated control cells. Conclusions: Our data demonstrate that EPA and DHA have differential effects with regard to the differentiation of preadipocytes. Our data also show that unlike SA, the differentiation induced by DHA is not associated with an activation of inflammatory pathways suggesting that this effect of DHA is beneficial in improving the lipid storage function of AT.

Maternal low protein diet and postnatal high fat diet increases adipose imprinted gene expression

Maternal and postnatal diet can alter Igf2 gene expression and DNA methylation. To test whether maternal low protein and postnatal high fat (HF) diet result in alteration in Igf2 expression and obesity, we fed obese‐prone Sprague‐Dawley rats 8% (LP) or 20% (NP) protein for 3 wk prior to breeding and through pregnancy and lactation. At weaning, male offspring were placed on 10% (NE) or 45% (HE) fat, thus, giving 4 groups (LP‐NE, NP‐NE, LP‐HE, NP‐HE). At 12 wk, LP‐HE rats had the greatest increase in body wt (14‐fold) and adipose tissue mass (27‐fold). LP‐HE rats also had the greatest increase in Igf2 expression (~7.5‐ fold increase) in subcutaneous adipose tissue (ScAT) while no difference was found in the visceral adipose tissue (VisAT). To determine whether DNA methylation may be involved, we measured the methylation status of the Igf2 imprinting control region but found no differences. Because mitochondria play a central role in regulating energy metabolism, we tested whether mitochondrial (mt) copy number is altered with increased calories from HF diet. Results showed that LP‐HE rats had the lowest mt copy number in ScAT (1.4 fold‐change relative NP‐NE) while no difference was found in VisAT. These data demonstrate that maternal low protein and postnatal HF diet results in greater propensity to develop obesity by increased adipose tissue mass, increased ScAT Igf2 expression, and reduced ScAT mt copy numbers.

High fat diet increases adipose tissue mass, but not lean tissue mass in age‐relevant postmenopausal mice in association with induction of VEGF expression and angiogenesis in adipose tissue

The role of angiogenesis in obesity has not been clearly characterized. In the present study, ovariectomy (OVX) was performed in 8 eighty week‐old C57BL/6 mice, then followed by a low‐fat (4%, LF, n=4) or a high‐fat (60%, HF, n=4) diet for 4 wks. The lean mass (LM) or fat mass (FM) composition was monitored by EchoMRI weekly. At the end of the experiment, blood samples, visceral fat, and the heart and limb muscles were collected for measuring VEGF expression using ELISA and vascular density (VD) using CD31 immunochemistry. Increased body weight (47.6±3.5 vs. 34.6±2.8 g; P&lt;0.01) was due to increased FM (23.3±2.7 vs. 11.6±2.1 g; P&lt;0.01) in OVX/HF vs. OVX/LF mice. But, a high fat diet didn't change LM (22.8±2.1 vs. 21.5±1.9 g) in OVX/HF mice, compared to OVX/LF mice. There was a two‐fold increase in the ratio of visceral fat/BW in OVX/HF mice, compared to those in OVX/LF group (0.084±0.005 vs. 0.043±0.003; P&lt;0.01). Plasma VEGF levels (70±7 vs. 49±3 pg/ml) and visceral fat VEGF levels (431±39 vs. 210±22 pg/mg protein) were significantly increased in OVX/HF mice, compared to OVX/LF group, respectively (4=6; P&lt;0.01). There was an increased VD in visceral fat but not in the heart and limb muscles in OVX/HF mice, compared to OVX/LF group. The results support the hypothesis that adipose tissue responds more sensitively to a high fat diet due to increased VEGF expression and angiogenesis.

Metabolic comparison of weight matched obese male and female mice

Estrogen is a known regulator of body composition and insulin sensitivity. However, a reduction in body weight (BW) is commonly associated with the reported benefits of estrogen. The purpose of this study was to compare the metabolic health of obese male and female mice matched for BW. Male and female mice were fed a high fat diet until they achieved a BW where insulin resistance is typically observed (45 g). BW gain was much more rapid in male mice as it took 3.5 months to achieve this target BW (44 g) while it took 6 months for females to achieve a similar BW (46 g). Plasma estrogen concentrations were not different between obese (92.7 pg/mL) and age matched lean (92.5 pg/mL) female mice. Despite a similar final BW, obese females had significantly larger gonadal (3.7 vs 2.2 g) and subcutaneous (3.3 vs 2.3 g) fat pads as compared to obese males. Glucose area under the curve following a glucose tolerance test was significantly improved in obese female mice as compared to obese male mice. Improved glucose tolerance was associated with reduced gonadal fat gene expression of CD11c, MCP‐1 and IL‐6 with a trend for decreased IL‐1β. Overall, our data demonstrate that circulating concentrations of estrogen were not altered in obese female mice and when matched for BW, female mice displayed increased adipose tissue mass, reduced adipose tissue inflammation and improved glucose tolerance as compared to obese male mice.

Neurobeachin, a Regulator of Synaptic Protein Targeting, Is Associated with Body Fat Mass and Feeding Behavior in Mice and Body-Mass Index in Humans

Neurobeachin (Nbea) regulates neuronal membrane protein trafficking and is required for the development and functioning of central and neuromuscular synapses. In homozygous knockout (KO) mice, Nbea deficiency causes perinatal death. Here, we report that heterozygous KO mice haploinsufficient for Nbea have higher body weight due to increased adipose tissue mass. In several feeding paradigms, heterozygous KO mice consumed more food than wild-type (WT) controls, and this consumption was primarily driven by calories rather than palatability. Expression analysis of feeding-related genes in the hypothalamus and brainstem with real-time PCR showed differential expression of a subset of neuropeptide or neuropeptide receptor mRNAs between WT and Nbea+/− mice in the sated state and in response to food deprivation, but not to feeding reward. In humans, we identified two intronic NBEA single-nucleotide polymorphisms (SNPs) that are significantly associated with body-mass index (BMI) in adult and juvenile cohorts. Overall, data obtained in mice and humans suggest that variation of Nbea abundance or activity critically affects body weight, presumably by influencing the activity of feeding-related neural circuits. Our study emphasizes the importance of neural mechanisms in body weight control and points out NBEA as a potential risk gene in human obesity.

Gene expression of adipose tissue, endothelial cells and platelets in subjects with metabolic syndrome (Review)

Metabolic syndrome is a combination of medical disorders including hypertension, dyslipidemia, hyperglycemia, insulin resistance and increased waist circumference, and is associated with a higher risk of cardiovascular disease. An increase in adipose tissue mass is associated with the augmented secretion of certain adipokines, such as interleukin-6, tumor necrosis factor-α and resistin, which cause endothelial dysfunction (an increase in vasoconstrictor molecules and in the expression of adhesion molecules as well as a decrease of vasodilator molecules, amongst other features) and hemostasis alterations that also favor a prothrombotic state (increased fibrinogen and plasminogen activator inhibitor-1 concentrations and platelet activation/aggregation). This interaction between adipose tissue, endothelial cells and platelets is associated with an increase or decrease in the expression of several transcription factors (peroxisome proliferator-activated receptors, CCAAT-enhancer-binding proteins, carbohydrate responsive element-binding proteins and sterol regulatory element-binding proteins) that play a crucial role in the regulation of distinct metabolic pathways related to the metabolic syndrome. In the present review, we present the primary changes in adipose tissue, endothelial cells and platelets in subjects with metabolic syndrome and their possible target sites at the gene expression level.

P4-03-02: High Fat Diet-Induced Postmenopausal Obesity Promotes Tumor Angiogenesis and Breast Cancer Progression in Age-Relevant Ovariectomized Mice.

Abstract Background: Obese postmenopausal women have 50% higher risk of breast cancer than non-obese women. The mechanisms of postmenopausal obesity-induced breast cancer are poorly understood due to lack of the established animal model that mimics postmenopausal obesity related to breast cancer progression. Material and Methods: Using age-relevant C57BL/6 mice, this study determined whether postmenopausal obesity increases VEGF expression, tumor angiogenesis, and breast tumor growth. Ovariectomy (OVX) was performed in 12 sixty week-old female mice (life span is about 140 weeks), then followed by a low-fat (5%, LF, n=6) or a high-fat (60%, HF, n=6) diet for 12 weeks. In the 8th wk of the dietary program, 10^6 E0771 (mouse breast cancer) cells were injected in the left fourth mammary gland. Tumor size was monitored using dial calipers for 4 wk. Body weights were monitored weekly. At the end of the experiment, blood samples, visceral fat, and tumors were collected for measuring VEGF expression using ELISA and intratumoral microvessel density (IMD) using CD31 immunochemistry. Results: Body weight was significantly increased in OVX/HF mice, compared to OVX/LF group (55.3±1.7 vs. 41.5±1.5 g; P&amp;lt;0.01). There was a two-fold increase in the ratio of visceral fat/BW in OVX/HF mice, compared to those in OVX/LF group (0.062±0.005 vs. 0.032±0.003; P&amp;lt;0.01). Postmenopausal obesity significantly increased breast tumor weight over the control (4.62±0.63 vs. 1.98±0.27 g; P&amp;lt;0.01) and IMD (173±3.7 vs. 139±4.3 IM#/mm^2; P&amp;lt;0.01). Tumor VEGF levels were higher in OVX/HF mice, compared to OVX/LF group (73.3±3.8 vs. 49.5±4.3 pg/mg protein; P&amp;lt;0.01). Plasma VEGF levels (69±7.1 vs. 48±3.5 pg/ml) and visceral fat VEGF levels (424.4±39.5 vs. 208.5±22.4 pg/mg protein) were significantly increased in OVX/HF mice, compared to OVX/LF group, respectively (n=6; P&amp;lt;0.01). Interestingly, adipose tissue primary culture showed that subcutaneous fat released more VEGF, compared to visceral fat (6.77±1.14 vs. 0.94±0.16 pg/mg tissue; n=6; P&amp;lt;0.01). The abdominal subcutaneous fat expressed more VEGF proteins than visceral fat in OVX/HF mice (692±72 vs. 431±44 pg/mg protein; n=6; P&amp;lt;0.01). There was a strong positive linear correlation between increased breast tumor weight and visceral fat weight in OVX mice (R2=0.7379; N=12; P&amp;lt;0.01). However, there was no significant difference in heart, or kidney weight/body weight ratio between postmenopausal obesity (OVX/HF) mice and the control mice (OVX/LF). Discussion: Our observations indicate that ovariectomy plus a high fat diet with the inoculation of E0771 (mouse ER+ breast cancer) cells in female wild type &amp;gt;60 week old mice can mimic human obesity-induced postmenopausal breast cancer. The increased tumor angiogenesis in postmenopausal obese mice was correlated with increased breast tumor growth, adipose tissue mass, and adipokines such as VEGF. These findings support the hypothesis that postmenopausal obesity promotes tumor angiogenesis and breast cancer progression, possibly through increased adipose tissue mass and adipokines such as VEGF that could systemically and locally affect breast cancer progression. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-03-02.

Impact of murine intestinal apolipoprotein A-IV expression on regional lipid absorption, gene expression, and growth

Apolipoprotein A-IV (apoA-IV) is synthesized by intestinal enterocytes during lipid absorption and secreted into lymph on the surface of nascent chylomicrons. A compelling body of evidence supports a central role of apoA-IV in facilitating intestinal lipid absorption and in regulating satiety, yet a longstanding conundrum is that no abnormalities in fat absorption, feeding behavior, or weight gain were observed in chow-fed apoA-IV knockout (A4KO) mice. Herein we reevaluated the impact of apoA-IV expression in C57BL6 and A4KO mice fed a high-fat diet. Fat balance and lymph cannulation studies found no effect of intestinal apoA-IV gene expression on the efficiency of fatty acid absorption, but gut sac transport studies revealed that apoA-IV differentially modulates lipid transport and the number and size of secreted triglyceride-rich lipoproteins in different anatomic regions of the small bowel. ApoA-IV gene deletion increased expression of other genes involved in chylomicron assembly, impaired the ability of A4KO mice to gain weight and increase adipose tissue mass, and increased the distal gut hormone response to a high-fat diet. Together these findings suggest that apoA-IV may play a unique role in integrating feeding behavior, intestinal lipid absorption, and energy storage.

Fatty Acids, Obesity, and Insulin Resistance: Time for a Reevaluation

There is a widespread acceptance in the literature that plasma nonesterified fatty acids (NEFA), also called free fatty acids (FFA), can mediate many adverse metabolic effects, most notably insulin resistance. Elevated NEFA concentrations in obesity are thought to arise from an increased adipose tissue mass. It is also argued that the process of fatty acid mobilization from adipose tissue, normally suppressed by insulin, itself becomes insulin resistant—thus, lipolysis is further increased, potentially leading to a vicious cycle. Although we have also accepted this model for many years (1,2), recently there has been a steady accumulation of data, both in the literature and from our own research, that has forced us to realize that this simple story is not always true. Here we review the background to the idea of “fatty acids as metabolic villains,” together with data from the literature and from our own studies, which tend to show another side to the fatty acids/insulin resistance story. We will first examine the relationship between systemic concentrations of NEFA and obesity/insulin resistance and then study adipose tissue in the obese state with regard to its adaptation for NEFA release. NEFA circulate in the plasma bound to plasma albumin. Their function was largely elucidated in the 1950s through the work of Vincent Dole (3) at the Rockefeller Institute in New York and Robert Gordon (4,5) at the National Institutes of Health. Gordon demonstrated the origin of plasma NEFA from adipose tissue and their use by tissues such as the liver and myocardium, but not the brain. We now recognize that NEFA are the vehicle by which triacylglycerol (TG) stored in adipose tissue is transported to its sites of utilization. NEFA turnover is rapid, with a plasma half-life around 2–4 min (6). The only significant site of NEFA liberation …

Proteomic analysis of 3T3-L1 adipocyte mitochondria during differentiation and enlargement.

The increase in adipose tissue mass arises in part from progressive lipid loading and triglyceride accumulation in adipocytes. Enlarged adipocytes produce the highest levels of pro-inflammatory molecules and reactive oxygen species (ROS). Since mitochondria are the site for major metabolic processes (e.g., TCA cycle) that govern the extent of triglyceride accumulation as well as the primary site of ROS generation, we quantitatively investigated changes in the adipocyte mitochondrial proteome during different stages of differentiation and enlargement. Mitochondrial proteins from 3T3-L1 adipocytes at different stages of lipid accumulation (days 0-18) were digested and labeled using the iTRAQ 8-plex kit. The labeled peptides were fractionated using a liquid phase isoelectric fractionation system (MSWIFT) to increase the depth of proteome coverage and analyzed using LC-MS/MS. A total of 631 proteins in the mitochondrial fraction, including endoplasmic reticulum-associated and golgi-related mitochondrial proteins, were identified and classified into 12 functional categories. A total of 123 proteins demonstrated a statistically significant change in expression in at least one of the time points over the course of the experiment. The identified proteins included enzymes and transporters involved in the TCA cycle, fatty acid oxidation, and ATP synthesis. Our results indicate that cultured adipocytes enter a state of metabolic-overdrive where increased flux through the TCA cycle and increased fatty acid oxidation occur simultaneously. The proteomic data also suggest that accumulation of reduced electron carriers and the resultant oxidative stress may be attractive targets for modulating adipocyte function in metabolic disorders.

Myeloid-specific estrogen receptor α deficiency impairs metabolic homeostasis and accelerates atherosclerotic lesion development

ERα is expressed in macrophages and other immune cells known to exert dramatic effects on glucose homeostasis. We investigated the impact of ERα expression on macrophage function to determine whether hematopoietic or myeloid-specific ERα deletion manifests obesity-induced insulin resistance in mice. Indeed, altered plasma adipokine and cytokine levels, glucose intolerance, insulin resistance, and increased adipose tissue mass were observed in animals harboring a hematopoietic or myeloid-specific deletion of ERα. A similar obese phenotype and increased atherosclerotic lesion area was displayed in LDL receptor-KO mice transplanted with ERα(-/-) bone marrow. In isolated macrophages, ERα was necessary for repression of inflammation, maintenance of oxidative metabolism, IL-4-mediated induction of alternative activation, full phagocytic capacity in response to LPS, and oxidized LDL-induced expression of ApoE and Abca1. Furthermore, we identified ERα as a direct regulator of macrophage transglutaminase 2 expression, a multifunctional atheroprotective enzyme. Our findings suggest that diminished ERα expression in hematopoietic/myeloid cells promotes aspects of the metabolic syndrome and accelerates atherosclerosis in female mice.

Energy status, measured by computer tomography (CT)-scanning, and milk quality of dairy goats fed rations with various energy concentrations

The milk produced by Norwegian goats varies in quality with regard to level of free fatty acids (FFA) and sensory quality. The aim of this study was to relate the milk quality to the changes in the energy status of dairy goats during early and mid lactation when fed rations with various energy concentrations. Twelve goats of the Norwegian Dairy Breed were from lactation weeks 3 to 18 fed grass silages prepared from the primary growth at a very early or normal stage of maturity (harvesting times (HT) 1 and 3, respectively), supplemented with a low (LC; 0.6kg daily) or normal (NC; 1.2kg daily) level of concentrate. Energy status was estimated by changes in body composition measured by computer tomography (CT), calculated energy balance and blood parameters.Calculated increase in adipose tissue mass of the goats was highest for HT 1. During the first 18weeks of lactation only the goats fed the lowest energy diet (HT 3 with LC) mobilized from the adipose tissue (in average 3.26kg). The other goats deposited body fat throughout this period, and had low (<0.3mmol/l) blood concentration of non-esterified fatty acids (NEFA). Calculated energy balance was positive throughout the indoor experiment for goats fed HT 1. Both net energy lactation (NEL) intake and milk yield increased with earlier stage of grass maturity and was positively correlated to daily gain in adipose tissue mass. Milk FFA tended to be higher (P=0.09) for goats offered HT 1 (1.48mEq/l) than HT 3 (0.99mEq/l), but was not significantly affected by concentrate level. A high milk FFA concentration was correlated to a high NEL intake. The level of milk FFA increased when the goats were let out on mountain pasture in lactation weeks 26–30. This study documents that it is possible to avoid fat mobilization in early lactation by feeding the goats high energy diets, based on high quality grass silage. However, a high plane of nutrition during early and mid lactation seemed to increase milk lipolysis. A high-energy diet offered indoors during the first 18weeks of lactation did neither improve milk quality during the same period nor in the following mountain pasture period.