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1.  MR Molecular Imaging of Aortic Angiogenesis 
JACC. Cardiovascular imaging  2010;3(8):824-832.
The objectives of this study were to use magnetic resonance (MR) molecular imaging to 1) characterize the aortic neovascular development in a rat model of atherosclerosis and 2) monitor the effects of an appetite suppressant on vascular angiogenesis progression.
The James C. Russell:LA corpulent rat strain (JCR:LA-cp) is a model of metabolic syndrome characterized by obesity, insulin resistance, hyperlipidemia, and vasculopathy, although plaque neovascularity has not been reported in this strain. MR molecular imaging with ανβ3-targeted nanoparticles can serially map angiogenesis in the aortic wall and monitor the progression of atherosclerosis.
Six-week old JCR:LA-cp (+/?; lean, n = 5) and JCR:LA-cp (cp/cp; obese, n = 5) rats received standard chow, and 6 obese rats were fed the appetite suppressant benfluorex over 16 weeks. Body weight and food consumption were recorded at baseline and weeks 4, 8, 12, and 16. MR molecular imaging with ανβ3-targeted paramagnetic nanoparticles was performed at weeks 0, 8, and 16. Fasted plasma triglyceride, cholesterol, and glucose were measured immediately before MR scans. Plasma insulin and leptin levels were assayed at weeks 8 and 16.
Benfluorex reduced food consumption (p < 0.05) to the same rate as lean animals, but had no effect on serum cholesterol or triglyceride levels. MR (3-T) aortic signal enhancement with ανβ3-targeted nanoparticles was initially equivalent between groups, but increased (p < 0.05) in the untreated obese animals over 16 weeks. No signal change (p > 0.05) was observed in the benfluorex-treated or lean rat groups. MR differences paralleled adventitial microvessel counts, which increased (p < 0.05) among the obese rats and were equivalently low in the lean and benfluorex-treated animals (p > 0.05). Body weight, insulin, and leptin were decreased (p < 0.05) from the untreated obese animals by benfluorex, but not to the lean control levels (p < 0.05).
Neovascular expansion is a prominent feature of the JCR:LA-cp model. MR imaging with ανβ3-targeted nanoparticles provided a noninvasive assessment of angiogenesis in untreated obese rats, which was suppressed by benfluorex.
PMCID: PMC3425389  PMID: 20705262
angiogenesis; atherosclerosis; metabolic syndrome; nanoparticle
2.  Increased hypolipidemic benefits of cis-9, trans-11 conjugated linoleic acid in combination with trans-11 vaccenic acid in a rodent model of the metabolic syndrome, the JCR:LA-cp rat 
Conjugated linoleic acid (cis-9, trans-11 CLA) and trans-11 vaccenic acid (VA) are found naturally in ruminant-derived foods. CLA has been shown to have numerous potential health related effects and has been extensively investigated. More recently, we have shown that VA has lipid-lowering properties associated with reduced hepatic lipidogenesis and chylomicron secretion in the JCR:LA-cp rat. The aim of this study was to evaluate potential additional hypolipidemic effects of purified forms of CLA and VA in an animal model of the metabolic syndrome (the JCR:LA-cp rat).
Twenty four obese JCR:LA-cp rats were randomized and assigned to one of three nutritionally adequate iso-caloric diets containing 1% w/w cholesterol and 15% w/w fat for 16 wk: 1) control diet (CD), 2) 1.0% w/w cis-9, trans-11 CLA (CLA), 3) 1.0% w/w VA and 1% w/w cis-9, trans-11 CLA (VA+CLA). Lean rats were fed the CD to represent normolipidemic conditions.
Fasting plasma triglyceride (TG), total cholesterol and LDL-cholesterol concentrations were reduced in obese rats fed either the CLA diet or the VA+CLA diet as compared to the obese control group (p < 0.05, p < 0.001; p < 0.001, p < 0.01; p < 0.01, p < 0.001, respectively). The VA+CLA diet reduced plasma TG and LDL-cholesterol to the level of the normolipidemic lean rats and further decreased nonesterified fatty acids compared to the CLA diet alone. Interestingly, rats fed the VA+CLA diet had a higher food intake but lower body weight than the CLA fed group (P < 0.05). Liver weight and TG content were lower in rats fed either CLA (p < 0.05) or VA+CLA diets (p < 0.001) compared to obese control, consistent with a decreased relative protein abundance of hepatic acetyl-CoA carboxylase in both treatment groups (P < 0.01). The activity of citrate synthase was increased in liver and adipose tissue of rats fed, CLA and VA+CLA diets (p < 0.001) compared to obese control, suggesting increased mitochondrial fatty acid oxidative capacity.
We demonstrate that the hypolipidemic effects of chronic cis-9, trans-11 CLA supplementation on circulating dyslipidemia and hepatic steatosis are enhanced by the addition of VA in the JCR:LA-cp rat.
PMCID: PMC3161353  PMID: 20633302
3.  Prebiotic fibres dose-dependently increase satiety hormones and alter Bacteroidetes and Firmicutes in lean and obese JCR:LA-cp rats 
The British journal of nutrition  2011;107(4):10.1017/S0007114511003163.
There is a growing interest in modulating gut microbiota with diet in the context of obesity. The purpose of the present study was to evaluate the dose-dependent effects of prebiotics (inulin and oligofructose) on gut satiety hormones, energy expenditure, gastric emptying and gut microbiota. Male lean and obese JCR:LA-cp rats were randomised to either of the following: lean 0 % fibre (LC), lean 10 % fibre (LF), lean 20 % fibre (LHF), obese 0 % fibre (OC), obese 10 % fibre (OF) or obese 20 % fibre (OHF). Body composition, gastric emptying, energy expenditure, plasma satiety hormone concentrations and gut microbiota (using quantitative PCR) were measured. Caecal proglucagon and peptide YY mRNA levels were up-regulated 2-fold in the LF, OF and OHF groups and 3-fold in the LHF group. Ghrelin O-acyltransferase mRNA levels were higher in obese v. lean rats and decreased in the OHF group. Plasma ghrelin response was attenuated in the LHF group. Microbial species measured in the Bacteroidetes division decreased, whereas those in the Firmicutes increased in obese v. lean rats and improved with prebiotic intake. Bifidobacterium and Lactobacillus increased in the OHF v. OC group. Bacteroides and total bacteria negatively correlated with percentage of body fat and body weight. Enterobacteriaceae increased in conjunction with glucose area under the curve (AUC) and glucagon-like peptide-1 AUC. Bacteroides and total bacteria correlated positively with ghrelin AUC yet negatively with insulin AUC and energy intake (P<0·05). Several of the mechanisms through which prebiotics act (food intake, satiety hormones and alterations in gut microbiota) are regulated in a dose-dependent manner. The combined effects of prebiotics may have therapeutic potential for obesity.
PMCID: PMC3827017  PMID: 21767445 CAMSID: cams3660
Inulin; Oligofructose; Satiety response; Gut microbiota
4.  Differential Secretion of Satiety Hormones With Progression of Obesity in JCR: LA-corpulent Rats 
Obesity (Silver Spring, Md.)  2008;16(4):10.1038/oby.2007.128.
To characterize the gastrointestinal tract at the onset and in well-established obesity.
Methods and Procedures
Lean (+/?) and obese (cp/cp) male JCR:LA-cp rats lacking a functional leptin receptor were killed at 3.5 weeks and 9 months of age and plasma concentrations of satiety hormones determined. The small intestine, colon, and stomach were measured, weighed, and mRNA levels of satiety genes quantified.
At the onset of obesity, obese rats had greater intestine, colon, and liver mass when adjusted for body weight compared to lean rats. Conversely, adult rats with established obesity had lower intestine and colon mass and length after adjustment for body weight. Early changes in gene expression included decreased ghrelin mRNA levels in stomach and increased peptide YY (PYY) mRNA levels in duodenum of young obese rats. After massive accumulation of adipose tissue had occurred, adult obese rats had increased proglucagon and ghrelin mRNA expression in the proximal intestine. In the distal small intestine, obese rats had lower proglucagon, ghrelin, and PYY mRNA levels. Finally, at the onset and in well-established obesity, obese rats had higher plasma insulin, amylin, glucagon like peptide-1 (GLP-1), and PYY, a finding, with the exception of insulin, unique to this model. Plasma total ghrelin levels were significantly lower at the onset of obesity and established obesity compared to the lean rats.
Several defects are manifested in the obese gut early on in the disease before the accumulation of large excesses of body fat and represent potential targets for early intervention in obesity.
PMCID: PMC3827016  PMID: 18239578 CAMSID: cams3665
5.  Effect of prebiotic fibre supplementation on hepatic gene expression and serum lipids: a dose–response study in JCR:LA-cp rats 
The British journal of nutrition  2009;103(11):10.1017/S0007114509993539.
Prebiotic fibres have been proposed to promote weight loss and lower serum cholesterol; however, the mechanisms are not fully understood. The aim of the present research was to identify possible mechanisms through which prebiotic fibres improve serum lipids. Lean and obese JCR:La-cp rats aged 8 weeks consumed one of three diets supplemented with 0, 10 or 20 % prebiotic fibre for 10 weeks. Rats were anaesthetised and a fasting blood sample was taken for lipid analysis. Real-time PCR was used to determine gene expression for cholesterol and fatty acid regulatory genes in liver tissue. Liver and caecal digesta cholesterol and TAG content were quantified. Both doses of prebiotic fibre lowered serum cholesterol levels by 24 % in the obese hyperlipidaemic rats (P<0·05). This change was associated with an increase in caecal digesta as well as an up-regulation of genes involved in cholesterol synthesis and bile production. Additionally, there was a 42 % reduction in TAG accumulation in the liver of the obese rats with 10 % prebiotic diet (P<0·05); however, no change in liver fatty acid synthase (FAS). Prebiotic fibres appear to lower cholesterol levels through increased cholesterol excretion in the form of bile and inhibit the accumulation of TAG in the liver through a mechanism unrelated to FAS. These effects appear to be limited to the obese model and particularly the 10 % dose. The present work is significant as it provides insight into the mechanisms of action for prebiotic fibres on lipid metabolism and furthers the development of dietary treatments for hypercholesterolaemia.
PMCID: PMC3827012  PMID: 20021705 CAMSID: cams3654
Inulin and oligofructose; Lipid metabolism; Liver TAG; Cholesterol content; Gene expression
6.  Glucose Tolerance, Lipids, and GLP-1 Secretion in JCR:LA-cp Rats Fed a High Protein Fiber Diet 
Obesity (Silver Spring, Md.)  2008;16(1):10.1038/oby.2007.16.
We have shown that individually, dietary fiber and protein increase secretion of the anorexigenic and insulinotropic hormone, glucagon-like peptide-1 (GLP-1).
Our objective was to combine, in one diet, high levels of fiber and protein to maximize GLP-1 secretion, improve glucose tolerance, and reduce weight gain.
Methods and Procedures
Lean (+/?) and obese (cp/cp) male James C Russell corpulent (JCR:LA-cp) rats lacking a functional leptin receptor were fed one of four experimental diets (control, high protein (HP), high fiber (HF, prebiotic fiber inulin), or combination (CB)) for 3 weeks. An oral glucose tolerance test (OGTT) was performed to evaluate plasma GLP-1, insulin and glucose. Plasma lipids and intestinal proglucagon mRNA expression were determined.
Energy intake was lower with the HF diet in lean and obese rats. Weight gain did not differ between diets. Higher colonic proglucagon mRNA in lean rats fed a CB diet was associated with higher GLP-1 secretion during OGTT. The HP diet significantly reduced plasma glucose area under the curve (AUC) during OGTT in obese rats, which reflected both an increased GLP-1 AUC and higher fasting insulin. Diets containing inulin resulted in the lowest plasma triglyceride and total cholesterol levels.
Overall, combining HP with HF in the diet increased GLP-1 secretion in response to oral glucose, but did not improve glucose tolerance or lipid profiles more than the HF diet alone did. We also suggest that glycemic and insulinemic response to prebiotics differ among rat models and future research work should examine their role in improving glucose tolerance in diet-induced vs. genetic obesity with overt hyperleptinemia.
PMCID: PMC3827014  PMID: 18223610 CAMSID: cams3664
7.  Arterial Retention of Remnant Lipoproteins Ex Vivo Is Increased in Insulin Resistance Because of Increased Arterial Biglycan and Production of Cholesterol-Rich Atherogenic Particles That Can Be Improved by Ezetimibe in the JCR:LA-cp Rat 
Literature supports the “response-to-retention” hypothesis—that during insulin resistance, impaired metabolism of remnant lipoproteins can contribute to accelerated cardiovascular disease progression. We used the JCR:LA-cp rat model of metabolic syndrome (MetS) to determine the extent of arterial accumulation of intestinal-derived remnants ex vivo and potential mechanisms that contribute to exacerbated cholesterol deposition in insulin resistance.
Methods and Results
Arteries from control and MetS (insulin-resistant) JCR:LA-cp rats were perfused ex vivo with Cy5-labeled remnant lipoproteins, and their arterial retention was quantified by confocal microscopy. Arterial proteoglycans were isolated from control and MetS rats at 6, 12, and 32 weeks of age. There was a significant increase in the arterial retention of remnants and in associated cholesterol accumulation in MetS rats as compared to control rats. Mechanistic studies reveal that increased cholesterol deposition is a result of greater arterial biglycan content; longer glycosaminoglycans and increased production of cholesterol-rich intestinal-derived remnants, as compared to controls. Additionally, perfusion of vessels treated with ezetimibe, alone or in combination with simvastatin, with remnants isolated from the respective treatment group reduced ex vivo arterial retention of remnant-derived cholesterol ex vivo as compared to untreated controls.
Increased progression of atherosclerotic cardiovascular disease in MetS and type 2 diabetes mellitus might be explained in part by an increase in the arterial retention of cholesterol-rich remnants. Furthermore, ezetimibe alone or in combination treatment with simvastatin could be beneficial in ameliorating atherosclerotic cardiovascular disease in insulin resistance and MetS.
PMCID: PMC3541624  PMID: 23316299
arterial remodeling; biglycan; metabolic syndrome; triglyceride-rich remnant lipoproteins
8.  Leptin Deficiency and Its Effects on Tibial and Vertebral Bone Mechanical Properties in Mature Genetically Lean and Obese JCR:LA-Corpulent Rats 
Journal of Obesity  2012;2012:650193.
Leptin signaling deficient rodents have emerged as models of obesity/insulin resistance syndrome. Altered leptin signaling, however, can affect axial and appendicular bone geometrical properties differently, and, thus, we hypothesized that leptin-deficiency would differentially influence mechanical properties of vertebrae and tibiae compared to lean rats. Mature (9 mo) leptin receptor deficient obese (cp/cp; n = 8) and lean (+/?; n = 7) male JCR:LA-corpulent rats were used to test that hypothesis. Tibiae and the sixth lumbar vertebrae (L6) were scanned with micro-CT and were broken in three point-bending (tibiae) or axial loading (L6). Supporting the hypothesis, vertebrae and tibiae were differentially affected by leptin signaling deficiency. Tibiae, but not vertebrae, were significantly shorter in obese rats and achieved a significantly greater load (>18%), displacement (>15%), and stress (>18%) at the proportional limit, relative to the lean rats. Conversely, L6 in obese rats had significantly reduced displacement (>25%) and strain (>32%) at proportional limit, relative to the lean rats. Those combined results suggest that the etiology and duration of obesity may be important determinants of bone mechanical properties, and axial and appendicular bones may be affected differently.
PMCID: PMC3409537  PMID: 22888408
9.  Acute-Phase Serum Amyloid A: An Inflammatory Adipokine and Potential Link between Obesity and Its Metabolic Complications 
PLoS Medicine  2006;3(6):e287.
Obesity is associated with low-grade chronic inflammation, and serum markers of inflammation are independent risk factors for cardiovascular disease (CVD). However, the molecular and cellular mechanisms that link obesity to chronic inflammation and CVD are poorly understood.
Methods and Findings
Acute-phase serum amyloid A (A-SAA) mRNA levels, and A-SAA adipose secretion and serum levels were measured in obese and nonobese individuals, obese participants who underwent weight-loss, and persons treated with the insulin sensitizer rosiglitazone. Inflammation-eliciting activity of A-SAA was investigated in human adipose stromal vascular cells, coronary vascular endothelial cells and a murine monocyte cell line. We demonstrate that A-SAA was highly and selectively expressed in human adipocytes. Moreover, A-SAA mRNA levels and A-SAA secretion from adipose tissue were significantly correlated with body mass index ( r = 0.47; p = 0.028 and r = 0.80; p = 0.0002, respectively). Serum A-SAA levels decreased significantly after weight loss in obese participants ( p = 0.006), as well as in those treated with rosiglitazone ( p = 0.033). The magnitude of the improvement in insulin sensitivity after weight loss was significantly correlated with decreases in serum A-SAA ( r = −0.74; p = 0.034). SAA treatment of vascular endothelial cells and monocytes markedly increased the production of inflammatory cytokines, e.g., interleukin (IL)-6, IL-8, tumor necrosis factor alpha, and monocyte chemoattractant protein-1. In addition, SAA increased basal lipolysis in adipose tissue culture by 47%.
A-SAA is a proinflammatory and lipolytic adipokine in humans. The increased expression of A-SAA by adipocytes in obesity suggests that it may play a critical role in local and systemic inflammation and free fatty acid production and could be a direct link between obesity and its comorbidities, such as insulin resistance and atherosclerosis. Accordingly, improvements in systemic inflammation and insulin resistance with weight loss and rosiglitazone therapy may in part be mediated by decreases in adipocyte A-SAA production.
Editors' Summary
Obesity often alters an individual's overall metabolism, which in turn leads to complications like diabetes, high blood pressure, and an increased risk of cardiovascular disease (disease of the heart and blood vessels, such as stroke or heart attacks). Having established a strong link between inflammation and cardiovascular disease, scientists now think that obesity might cause persistent low-level inflammation, and that this is the reason for the cardiovascular problems seen in many obese people. By better understanding the links between obesity, inflammation, and cardiovascular disease, the hope is that scientists may be able to find medications that can be given to obese people to reduce their risk of heart attacks and strokes.
Why Was This Study Done?
Previous research had suggested that a substance in the blood called A-SAA, which is raised by inflammation, might be a “missing link” between inflammation and cardiovascular disease, since an individual's baseline level of A-SAA is associated with the risk for cardiovascular disease (in other words, the higher the A-SAA, the higher the risk of cardiovascular disease). In the new study, researchers wanted to know whether the reason that obese people have a higher risk of cardiovascular disease is because they have higher blood levels of A-SAA.
What Did the Researchers Do and Find?
They found that obese people had higher levels of A-SAA in their blood. A-SAA appears to be produced in fat cells (or adipocytes) and then released into the blood. Obese people have higher numbers of fat cells, which could by itself account for the higher blood levels of A-SAA, but the researchers also found that the average fat cell from an obese individual produces and secretes higher levels of A-SAA than fat cells from lean individuals. When the researchers studied people who underwent weight loss, they found that A-SAA levels fell in response to weight loss, and this was associated with improvements in their metabolism. They then studied obese individuals who received the diabetes drug rosiglitazone (which is known to reduce inflammation). They found that even though these individuals did not lose weight, their A-SAA levels dropped as their metabolism improved. Trying to get at the mechanisms by which A-SAA might cause inflammation and diabetes, the researchers found that exposure to A-SAA can stimulate the activation of proinflammation molecules in a number of different cells, including blood vessel cells. It can also stimulate cells to break down fat stores and release fats, which could lead to metabolic complications and ultimately contribute to diabetes.
What Do These Findings Mean?
Together with similar results from other studies, the findings here suggest that A-SAA could promote inflammation, and that elevated levels of A-SAA in obese individuals could contribute to the chronic low-level inflammatory state that puts them at higher risk for cardiovascular complications. The authors speculate that drugs that reduce the blood levels of A-SAA might be useful as treatments for obese patients (to lower their risk of heart attacks and strokes). However, as they acknowledge, additional studies are needed to establish that A-SAA is indeed a causal link between obesity and inflammation and whether it plays a major role before it could be considered a promising drug target.
Additional Information.
Please access these Web sites via the online version of this summary at
• MedlinePlus pages on obesity and cardiovascular disease
• US Centers for Disease Control and Prevention pages on obesity and cardiovascular disease
• Wikipedia pages on obesity and cardiovascular disease (note: Wikipedia is a free Internet encyclopedia that anyone can edit)
Higher levels of Acute-phase serum amyloid A (A-SAA), a proinflammatory adipokine, in obese individuals may contribute to the chronic low-level inflammatory state that puts them at higher risk for cardiovascular complications.
PMCID: PMC1472697  PMID: 16737350
10.  Chronic Active Hepatitis Induced by Helicobacter hepaticus in the A/JCr Mouse Is Associated with a Th1 Cell-Mediated Immune Response 
Infection and Immunity  1998;66(7):3142-3148.
Helicobacter hepaticus infection in A/JCr mice results in chronic active hepatitis characterized by perivascular, periportal, and parenchymal infiltrates of mononuclear and polymorphonuclear cells. This study examined the development of hepatitis and the immune response of A/JCr mice to H. hepaticus infection. The humoral and cell-mediated T helper immune response was profiled by measuring the postinfection (p.i.) antibody response in serum, feces, and bile and by the production of cytokines and proliferative responses by splenic mononuclear cells to H. hepaticus antigens. Secretory immunoglobulin A (IgA) and systemic IgG2a antibody developed by 4 weeks p.i. and persisted through 12 months. Splenocytes from infected mice proliferated and produced more gamma interferon (IFN-γ) than interleukin-4 (IL-4) or IL-5 when cultured with H. hepaticus outer membrane proteins. The predominantly IgG2a antibody response in serum and the in vitro production of IFN-γ in excess of IL-4 or IL-5 are consistent with a Th1 immune response reported in humans and mice infected with Helicobacter pylori and Helicobacter felis, respectively. Mice infected with H. hepaticus developed progressively severe perivascular, periportal, and hepatic parenchymal lesions consisting of lymphohistiocytic and plasmacytic cellular infiltrates. In addition, transmural typhlitis was observed at 12 months p.i. The characterization of a cell-mediated Th1 immune response to H. hepaticus infection in the A/JCr mouse should prove valuable as a model for experimental regimens which manipulate the host response to Helicobacter.
PMCID: PMC108325  PMID: 9632578
11.  Differential effects of inhalation exposure to PM2.5 on hypothalamic monoamines and corticotrophin releasing hormone in lean and obese rats 
Neurotoxicology  2012;36:106-111.
Acute exposure to airborne pollutants, especially particulate matter (PM2.5) is known to increase hospital admissions for cardiovascular conditions, increase cardiovascular related mortality and predispose the elderly and obese individuals to cardiovascular conditions. The mechanisms by which PM2.5 exposure affects the cardiovascular system is not clear. Since the autonomic system plays an important role in cardiovascular regulation, we hypothesized that PM2.5 exposure most likely activates the paraventricular nucleus (PVN) of the hypothalamus to cause an increase in sympathetic nervous system and/or stress axis activity. We also hypothesized that these changes may be sustained in obese rats predisposing them to higher cardiovascular risk. To test this, adult male Brown Norway (BN) rats were subjected to one day or three days of inhalation exposures to filtered air (FA) of concentrated air particulate (CAP) derived from ambient PM2.5. Corpulent JCR-LA rats were exposed to FA or CAP for four days. Animals were sacrificed 24 hours after the last inhalation exposure. Their brains were removed, frozen and sectioned. The PVN and median eminence (ME) were microdissected. PVN was analyzed for norepinephrine (NE), dopamine (DA) and 5-hydroxyindole acetic acid (5–HIAA) levels using HPLC-EC. ME was analyzed for corticotrophin releasing hormone (CRH) levels by ELISA. One day exposure to CAP increased NE levels in the PVN and CRH levels in the ME of BN rats. Repeated exposures to CAP did not affect NE levels in the PVN of BN rats, but increased NE levels in JCR/LA rats. A similar pattern was observed with 5-HIAA levels. DA levels on the other hand, were unaffected in both BN and JCR/LA strains. These data suggest that repeated exposures to PM2.5 continue to stimulate the PVN in obese animals but not lean rats.
PMCID: PMC3402685  PMID: 22426024
Particulate matter; repeated exposure; sympathetic nervous system; stress axis; cardiovascular risk
12.  Effects of Elaidic Acid on Lipid Metabolism in HepG2 Cells, Investigated by an Integrated Approach of Lipidomics, Transcriptomics and Proteomics 
PLoS ONE  2013;8(9):e74283.
Trans fatty acid consumption in the human diet can cause adverse health effects, such as cardiovascular disease, which is associated with higher total cholesterol, a higher low density lipoprotein-cholesterol level and a decreased high density lipoprotein-cholesterol level. The aim of the study was to elucidate the hepatic response to the most abundant trans fatty acid in the human diet, elaidic acid, to help explain clinical findings on the relationship between trans fatty acids and cardiovascular disease. The human HepG2 cell line was used as a model to investigate the hepatic response to elaidic acid in a combined proteomic, transcriptomic and lipidomic approach. We found many of the proteins responsible for cholesterol synthesis up-regulated together with several proteins involved in the esterification and hepatic import/export of cholesterol. Furthermore, a profound remodeling of the cellular membrane occurred at the phospholipid level. Our findings contribute to the explanation on how trans fatty acids from the diet can cause modifications in plasma cholesterol levels by inducing abundance changes in several hepatic proteins and the hepatic membrane composition.
PMCID: PMC3772929  PMID: 24058537
13.  Adipose tissue stearoyl-CoA desaturase 1 index is increased and linoleic acid is decreased in obesity-prone rats fed a high-fat diet 
Fatty acid (FA) composition and desaturase indices are associated with obesity and related metabolic conditions. However, it is unclear to what extent desaturase activity in different lipid fractions contribute to obesity susceptibility. Our aim was to test whether desaturase activity and FA composition are linked to an obese phenotype in rats that are either obesity prone (OP) or resistant (OR) on a high-fat diet (HFD).
Two groups of Sprague–Dawley rats were given ad libitum (AL-HFD) or calorically restricted (HFD-paired; pair fed to calories consumed by chow-fed rats) access to a HFD. The AL-HFD group was categorized into OP and OR sub-groups based on weight gain over 5 weeks. Five different lipid fractions were examined in OP and OR rats with regard to proportions of essential and very long-chain polyunsaturated FAs: linoleic acid (LA), alpha-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid and the stearoyl-CoA desaturase 1 (SCD-1) product 16:1n-7. FA ratios were used to estimate activities of the delta-5-desaturase (20:4n-6/20:3n-6), delta-6-desaturase (18:3n-6/18:2n-6), stearoyl-CoA desaturase 1 (SCD-1; 16:1n-7/16:0, SCD-16 and 18:1n-9/18:0, SCD-18), de novo lipogenesis (16:0/18:2n-6) and FA elongation (18:0/16:0). Fasting insulin, glucose, adiponectin and leptin concentrations were measured in plasma.
After AL-HFD access, OP rats had a significantly higher SCD-16 index and 16:1n-7 proportion, but a significantly lower LA proportion, in subcutaneous adipose tissue (SAT) triacylglycerols, as well as significantly higher insulin and leptin concentrations, compared with OR rats. No differences were found between the two phenotypes in liver (phospholipids; triacylglycerols) or plasma (cholesterol esters; phospholipids) lipid fractions or for plasma glucose or adiponectin concentrations. For the desaturase indices of the HFD-paired rats, the only significant differences compared with the OP or OR rats were higher SCD-16 and SCD-18 indices in SAT triacylglycerols in OP compared with HFD-paired rats.
The higher SCD-16 may reflect higher SCD-1 activity in SAT, which in combination with lower LA proportions may reflect higher insulin resistance and changes in SAT independent of other lipid fractions. Whether a lower SCD-16 index protects against diet-induced obesity is an interesting possibility that warrants further investigation.
PMCID: PMC3558438  PMID: 23298201
Desaturase; Diet-induced obesity; Fatty acid composition; High-fat diet; Linoleic acid; Obesity prone; Obesity resistant; Subcutaneous adipose tissue; SCD-1; Stearoyl-CoA desaturase
14.  Palmitoleic acid reduces intramuscular lipid and restores insulin sensitivity in obese sheep 
Obese sheep were used to assess the effects of palmitoleic (C16:1 cis-9) acid infusion on lipogenesis and circulating insulin levels. Infusion of 10 mg/kg body weight (BW)/day C16:1 intravenously in obese sheep reduced (P<0.01) weight gain by 77%. Serum palmitoleic levels increased (P<0.05) in a linear manner with increasing levels of C16:1 infusion. Cis-11 vaccenic (C18:1 cis-11) acid, a known elongation product of palmitoleic acid, was also elevated (P<0.05) in serum after 14 days and 21 days of infusion. Plasma insulin levels were lower (P<0.05) (10 mg/kg BW/day C16:1) than controls (0 mg/kg BW/day C16:1) at 14 days and 28 days of infusion. Infusion of C16:1 resulted in linear increases in tissue concentrations of palmitoleic, cis-11 vaccenic, eicosapentaenoic, and docosapentaenoic acids in a dose-dependent manner. Total lipid content of the semitendinosus (ST) muscle and mesenteric adipose tissue was reduced (P<0.01) in both 5 mg/kg and 10 mg/kg BW C16:1 dose levels. Total lipid content and mean adipocyte size in the longissimus muscle was reduced (P<0.05) in the 10 mg/kg BW C16:1 dose level only, whereas total lipid content and adipocyte size of the subcutaneous adipose tissue was not altered. Total lipid content of the liver was also unchanged with C16:1 infusion. Palmitoleic acid infusion upregulated (P<0.05) acetyl-CoA carboxylase (ACC), fatty acid elongase-6 (ELOVL6), and Protein kinase, AMP-activated, alpha 1 catalytic subunit, transcript variant 1 (AMPK) mRNA expressions in liver, subcutaneous adipose, and ST muscle compared to the controls. However, mRNA expression of glucose transporter type 4 (GLUT4) and carnitine palmitoyltransferase 1b (CPT1B) differed between tissues. In the subcutaneous adipose and liver, C16:1 infusion upregulated (P<0.05) GLUT4 and CPT1B, whereas these genes were downregulated (P<0.05) in ST muscle with C16:1 infusion. These results show that C16:1 infusion for 28 days reduced weight gain, intramuscular adipocyte size and total lipid content, and circulating insulin levels. These changes appear to be mediated through alterations in expression of genes regulating glucose uptake and fatty acid oxidation specifically in the muscles.
PMCID: PMC4243576  PMID: 25429233
adipocytes; longissimus muscle; lipogenesis; insulin level; serum; fatty acid
15.  Effects of solvents and alcohols on the polar lipid composition of Clostridium butyricum under conditions of controlled lipid chain composition. 
Applied and Environmental Microbiology  1991;57(12):3517-3521.
Clostridium butyricum has been grown in media devoid of biotin, to which long-chain fatty acids have been added to promote growth. We have shown previously that, under these conditions, exogenous fatty acids are extensively incorporated into the cellular phospholipids. Cells grown with elaidic acid, trans-9-18:1, have normal ratios of the glycerol acetal of plasmenylethanolamine (GAPlaE) to phosphatidylethanolamine (PE) plus plasmenylethanolamine (PlaE) compared with cells grown with biotin. When ethanol, cyclohexane, or n-octanol was added to elaidate-containing media, the ratio of GAPlaE to PE plus PlaE was significantly increased. Addition of dodecane and n-butanol did not affect this ratio. When cells were grown with oleic acid in the absence of biotin, the GAPlaE to PE plus PlaE ratio was increased 5.4-fold compared with elaidate-grown cells. In oleate-supplemented media, the addition of solvents or n-alcohols produced no further increase in this ratio. We conclude that these changes in lipid composition represent cellular responses to perturbation of the equilibria between the lamellar and nonlamellar liquid crystalline phases in the cell membrane.
PMCID: PMC184005  PMID: 1785927
16.  Turnover of Phospholipids in an Unsaturated Fatty Acid Auxotroph of Escherichia coli 
Journal of Bacteriology  1972;112(3):1396-1407.
The membrane phospholipids of an unsaturated fatty acid auxotroph of Escherichia coli were found to undergo turnover. These phospholipids were excreted into the culture medium, and were replaced in the cell with newly synthesized phospholipids. Phospholipids of growing cells supplemented with elaidic acid underwent rapid turnover, while those of cells supplemented with oleate, or cis-vaccenate plus palmitoleate, underwent slow turnover. Starvation for required amino acids stimulated this turnover in the latter two cases. Protein was also lost from growing cells. However, after amino acid starvation this loss ceased while phospholipid turnover continued. Electron micrographs of growing cells indicated that large pieces of membrane-like material were separating from the cell surface.
PMCID: PMC251577  PMID: 4629658
17.  Leptin- and Leptin Receptor-Deficient Rodent Models: Relevance for Human Type 2 Diabetes 
Current Diabetes Reviews  2014;10(2):131-145.
Among the most widely used animal models in obesity-induced type 2 diabetes mellitus (T2DM) research are the congenital leptin- and leptin receptor-deficient rodent models. These include the leptin-deficient ob/ob mice and the leptin receptor-deficient db/db mice, Zucker fatty rats, Zucker diabetic fatty rats, SHR/N-cp rats, and JCR:LA-cp rats. After decades of mechanistic and therapeutic research schemes with these animal models, many species differences have been uncovered, but researchers continue to overlook these differences, leading to untranslatable research. The purpose of this review is to analyze and comprehensively recapitulate the most common leptin/leptin receptor-based animal models with respect to their relevance and translatability to human T2DM. Our analysis revealed that, although these rodents develop obesity due to hyperphagia caused by abnormal leptin/leptin receptor signaling with the subsequent appearance of T2DM-like manifestations, these are in fact secondary to genetic mutations that do not reflect disease etiology in humans, for whom leptin or leptin receptor deficiency is not an important contributor to T2DM. A detailed comparison of the roles of genetic susceptibility, obesity, hyperglycemia, hyperinsulinemia, insulin resistance, and diabetic complications as well as leptin expression, signaling, and other factors that confound translation are presented here. There are substantial differences between these animal models and human T2DM that limit reliable, reproducible, and translatable insight into human T2DM. Therefore, it is imperative that researchers recognize and acknowledge the limitations of the leptin/leptin receptor-based rodent models and invest in research methods that would be directly and reliably applicable to humans in order to advance T2DM management.
PMCID: PMC4082168  PMID: 24809394
Diabetes; leptin/leptin receptor mutations; obesity; rodent models; translational barrier.
18.  Loss of function mutation in toll-like receptor-4 does not offer protection against obesity and insulin resistance induced by a diet high in trans fat in mice 
Toll-like receptor-4 (TLR4) triggers inflammatory signaling in response to microbial lipoploysaccharide. It has been reported that loss of TLR4 protected against saturated fat-induced inflammation and insulin resistance. It is not known whether loss of TLR4 function offers protection against trans fat (TF) induced obesity, inflammation, and insulin resistance. We investigated whether mice with loss of function mutation in TLR4 were resistant to TF-induced pathologies such as obesity, inflammation, hyperglycemia, and hyperinsulinemia.
C57BL/6j and C57BL/10 mice were cross bred to generate TLR4 mutant and wild type (WT). TLR4 mutant (n = 12) and WT (n = 12) mice were fed either low fat (LF) (13.5% fat energy) or high TF diets (60% fat energy) for 12 weeks. In vitro experiments were conducted on mouse macrophage cells (RAW 264.7 and J774A.1) to investigate whether elaidic (trans 18:1) or oleic acid (cis 18:1) would upregulate inflammatory markers.
TLR4 mutant mice were ~26.4% heavier than WT mice. In both genotypes, mice that received TF diet were significantly heavier than those mice that received LF diet (P < 0.01). TLR4 mutant mice compared to WT mice had significantly higher fasting blood glucose, serum insulin, insulin resistance, serum leptin, and serum cholesterol when they received TF diet (P < 0.05). No upregulation of iNOS or COX2 in response to either elaidic or oleic acid in macrophage cells was observed.
Loss of function mutation in TLR4 not only did not protect mice from TF-induced obesity, hyperglycemia, hyperinsulinemia, and hypercholesterolemia but also exacerbated the above pathologies suggesting that functional TLR4 is necessary in attenuating TF-induced deleterious effects. It is likely that TF induces pathologies through pathways independent of TLR4.
PMCID: PMC3048481  PMID: 21314942
19.  Effects of Chronic Antagonism of Endocannabinoid-1 Receptors on Glucose Tolerance and Insulin Action in Skeletal Muscles of Lean and Obese Zucker Rats 
Cardiorenal Medicine  2011;1(1):31-44.
Antagonism of the endocannabinoid receptor-1 (CB1R) directly improves whole-body metabolic parameters of insulin resistance. The present investigation determined the effects of chronic CB1R antagonism on whole-body and skeletal-muscle insulin action in insulin-sensitive lean and insulin-resistant obese Zucker rats.
Animals were either fed ad libitum or in pairs, or treated with SR141716 (10 mg/kg i.p. for 14 days).
Food intake was significantly reduced (p < 0.05) after initial SR141716 treatment and remained decreased in both lean and obese animals until day 13. Fasting plasma glucose decreased (24%) and insulin increased (43%) in lean SR141716-treated (24%) rats compared to lean ad libitum-fed controls, but not in the corresponding obese groups. Fasting plasma free fatty acids were reduced by CB1R antagonism in lean (21%) and obese (42%) animals. Whole-body insulin sensitivity was increased (36%) in obese SR141716-treated rats compared to obese ad libitum-fed controls, which was associated with reduced insulin secretion during an oral glucose tolerance test. Insulin-stimulated glucose transport activity in the soleus was greatest in the respective SR141716-treated lean and obese groups compared to the corresponding ad libitum- and pair-fed controls. Chronic SR141716 treatment did not induce alterations in signaling factors associated with the regulation of glucose transport [protein kinase B (Akt), glycogen synthase kinase-3β, 5′-AMP-dependent protein kinase, or p38 mitogen-activated protein kinase] in the soleus.
These results indicate that, while the chronic treatment with CB1R antagonism markedly diminished food intake in lean and obese Zucker rats, there are also significant metabolic improvements in whole-body and skeletal-muscle insulin action mediated by CB1R antagonism through mechanisms independent of reduced caloric intake.
PMCID: PMC3101519  PMID: 22258464
CB1 receptor; Insulin resistance; Soleus muscle; SR141716; Zucker rat
20.  Global Transcript Profiles of Fat in Monozygotic Twins Discordant for BMI: Pathways behind Acquired Obesity  
PLoS Medicine  2008;5(3):e51.
The acquired component of complex traits is difficult to dissect in humans. Obesity represents such a trait, in which the metabolic and molecular consequences emerge from complex interactions of genes and environment. With the substantial morbidity associated with obesity, a deeper understanding of the concurrent metabolic changes is of considerable importance. The goal of this study was to investigate this important acquired component and expose obesity-induced changes in biological pathways in an identical genetic background.
Methods and Findings
We used a special study design of “clonal controls,” rare monozygotic twins discordant for obesity identified through a national registry of 2,453 young, healthy twin pairs. A total of 14 pairs were studied (eight male, six female; white), with a mean ± standard deviation (SD) age 25.8 ± 1.4 y and a body mass index (BMI) difference 5.2 ± 1.8 kg/m2. Sequence analyses of mitochondrial DNA (mtDNA) in subcutaneous fat and peripheral leukocytes revealed no aberrant heteroplasmy between the co-twins. However, mtDNA copy number was reduced by 47% in the obese co-twin's fat. In addition, novel pathway analyses of the adipose tissue transcription profiles exposed significant down-regulation of mitochondrial branched-chain amino acid (BCAA) catabolism (p < 0.0001). In line with this finding, serum levels of insulin secretion-enhancing BCAAs were increased in obese male co-twins (9% increase, p = 0.025). Lending clinical relevance to the findings, in both sexes the observed aberrations in mitochondrial amino acid metabolism pathways in fat correlated closely with liver fat accumulation, insulin resistance, and hyperinsulinemia, early aberrations of acquired obesity in these healthy young adults.
Our findings emphasize a substantial role of mitochondrial energy- and amino acid metabolism in obesity and development of insulin resistance.
Leena Peltonen and colleagues uncover the metabolic changes that result from obesity through an analysis of genetically identical twin pairs in which one was obese and the other was not.
Editors' Summary
Around the world, the proportion of people who are obese (people with an unhealthy amount of body fat) is increasing. In the US, for example, 1 adult in 7 was obese in the mid 1970s. That is, their body mass index (BMI)—their weight in kilograms divided by their height in meters squared—was more than 30. Nowadays, 1 US adult in 3 has a BMI this high and, by 2025, it is predicted that 1 in 2 will be obese. This obesity epidemic is being driven by lifestyle changes that encourage the over-consumption of energy-rich foods and discourage regular physical activity. The resultant energy imbalance leads to weight gain (the excess energy is stored as body fat or adipose tissue) and also triggers numerous metabolic changes, alterations in the chemical processes that convert food into the energy and various substances needed to support life. These obesity-related metabolic changes increase a person's risk of developing adverse health conditions such as diabetes, a condition in which dangerously high levels of sugar from food accumulate in the blood.
Why Was This Study Done?
The changes in human fat in obesity have not been completely understood, although the abnormal metabolism of adipose tissue is increasingly seen as playing a critical part in excessive weight gain. It has been very difficult to decipher which molecular and metabolic changes associated with obesity are the result of becoming obese, and which might contribute towards the acquisition of obesity in humans in the first place. To discover more about the influence of environment on obesity-induced metabolic changes, the researchers in this study have investigated these changes in pairs of genetically identical twins.
What Did the Researchers Do and Find?
The researchers recruited 14 pairs of genetically identical Finnish twins born between 1975 and 1979 who were “obesity discordant”—that is, one twin of each pair had a BMI of about 25 (not obese); the other had a BMI of about 30 (obese). The researchers took fat and blood samples from each twin, determined the insulin sensitivity of each, and measured the body composition and various fat stores of each. They found that the obese twins had more subcutaneous, intra-abdominal, and liver fat and were less insulin sensitive than the non-obese twins. Insulin sensitivity correlated with the amount of liver fat. Analysis of gene expression in the fat samples showed that 19 gene pathways (mainly inflammatory pathways) were expressed more strongly (up-regulated) in the obese twins than the non-obese twins, whereas seven pathways were down-regulated. The most highly down-regulated pathway was a mitochondrial pathway involved in amino acid breakdown, but mitochondrial energy metabolism pathways were also down-regulated. Finally, mitochondrial DNA copy number in fat was reduced in the obese twins by nearly half, a novel observation that could partly account for the obesity-induced metabolic defects of these individuals.
What Do These Findings Mean?
These and other findings identify several pathways that are involved in the development of obesity and insulin resistance. In particular, they suggest that changes in mitochondrial energy production pathways and in mitochondrial amino acid metabolism pathways could play important roles in the development of obesity and of insulin resistance and in the accumulation of liver fat even in young obese people. The study design involving identical twins has here produced some evidence for aberrations in molecules critical for acquired obesity. The results suggest that careful management of obesity by lifestyle changes has the potential to correct the obesity-related metabolic changes in fat that would otherwise lead to diabetes and other adverse health conditions in obese individuals. In addition, they suggest that the development of therapies designed to correct mitochondrial metabolism might help to reduce the illnesses associated with obesity.
Additional Information.
Please access these Web sites via the online version of this summary at
The MedlinePlus encyclopedia has pages on obesity and diabetes (in English and Spanish)
The US Centers for Disease Control and Prevention provides information on all aspects of obesity (in English and Spanish)
The UK National Health Service's health Web site (NHS Direct) provides information about obesity
The International Obesity Taskforce provides information about preventing obesity and on diabetes and obesity
The UK Foods Standards Agency and the United States Department of Agriculture provide online tools and useful advice about healthy eating for adults and children
Information is available for patients and carers from the US National Diabetes Information Clearinghouse on diabetes, including information on insulin resistance
PMCID: PMC2265758  PMID: 18336063
21.  Chronic unpredictable stress regulates visceral adipocyte‐mediated glucose metabolism and inflammatory circuits in male rats 
Physiological Reports  2014;2(5):e00284.
Chronic psychological stress is a prominent risk factor involved in the pathogenesis of many complex diseases, including major depression, obesity, and type II diabetes. Visceral adipose tissue is a key endocrine organ involved in the regulation of insulin action and an important component in the development of insulin resistance. Here, we examined for the first time the changes on visceral adipose tissue physiology and on adipocyte‐associated insulin sensitivity and function after chronic unpredictable stress in rats. Male rats were subjected to chronic unpredictable stress for 35 days. Total body and visceral fat was measured. Cytokines and activated intracellular kinase levels were determined using high‐throughput multiplex assays. Adipocyte function was assessed via tritiated glucose uptake assay. Stressed rats showed no weight gain, and their fat/lean mass ratio increased dramatically compared to control animals. Stressed rats had significantly higher mesenteric fat content and epididymal fat pad weight and demonstrated reduced serum glucose clearing capacity following glucose challenge. Alterations in fat depot size were mainly due to changes in adipocyte numbers and not size. High‐throughput molecular screening in adipocytes isolated from stressed rats revealed activation of intracellular inflammatory, glucose metabolism, and MAPK networks compared to controls, as well as significantly reduced glucose uptake capacity in response to insulin stimulation. Our study identifies the adipocyte as a key regulator of the effects of chronic stress on insulin resistance, and glucose metabolism, with important ramifications in the pathophysiology of several stress‐related disease states.
Our study identifies the adipocyte as a key regulator of the effects of chronic stress on insulin resistance, and glucose metabolism, with important ramifications in the pathophysiology of several stress‐related disease states.
PMCID: PMC4098730  PMID: 24819750
Adipocytes; adipokines; fat tissue; insulin resistance; stress
22.  Interleukin-6 Is Essential for Primary Resistance to Francisella tularensis Live Vaccine Strain Infection 
Infection and Immunity  2013;81(2):585-597.
We employed Francisella tularensis live vaccine strain (LVS) to study mechanisms of protective immunity against intracellular pathogens and, specifically, to understand protective correlates. One potential molecular correlate identified previously was interleukin-6 (IL-6), a cytokine with pleotropic roles in immunity, including influences on T and B cell functions. Given its role as an immune modulator and the correlation with successful anti-LVS vaccination, we examined the role IL-6 plays in the host response to LVS. IL-6-deficient (IL-6 knockout [KO]) mice infected with LVS intradermally or intranasally or anti-IL-6-treated mice, showed greatly reduced 50% lethal doses compared to wild-type (WT) mice. Increased susceptibility was not due to altered splenic immune cell populations during infection or decreased serum antibody production, as IL-6 KO mice had similar compositions of each compared to WT mice. Although LVS-infected IL-6 KO mice produced much less serum amyloid A and haptoglobin (two acute-phase proteins) than WT mice, there were no other obvious pathophysiological differences between LVS-infected WT and IL-6 KO mice. IL-6 KO or WT mice that survived primary LVS infection also survived a high-dose LVS secondary challenge. Using an in vitro overlay assay that measured T cell activation, cytokine production, and abilities of primed splenocytes to control intracellular LVS growth, we found that IL-6 KO total splenocytes or purified T cells were slightly defective in controlling intracellular LVS growth but were equivalent in cytokine production. Taken together, IL-6 is an integral part of a successful immune response to primary LVS infection, but its exact role in precipitating adaptive immunity remains elusive.
PMCID: PMC3553820  PMID: 23230288
23.  Reduced tyrosine kinase activity of the insulin receptor in obesity-diabetes. Central role of tumor necrosis factor-alpha. 
Journal of Clinical Investigation  1994;94(4):1543-1549.
Insulin resistance is an important metabolic abnormality often associated with infections, cancer, obesity, and especially non-insulin-dependent diabetes mellitus (NIDDM). We have previously demonstrated that tumor necrosis factor-alpha produced by adipose tissue is a key mediator of insulin resistance in animal models of obesity-diabetes. However, the mechanism by which TNF-alpha interferes with insulin action is not known. Since a defective insulin receptor (IR) tyrosine kinase activity has been observed in obesity and NIDDM, we measured the IR tyrosine kinase activity in the Zucker (fa/fa) rat model of obesity and insulin resistance after neutralizing TNF-alpha with a soluble TNF receptor (TNFR)-lgG fusion protein. This neutralization resulted in a marked increase in insulin-stimulated autophosphorylation of the IR, as well as phosphorylation of insulin receptor substrate 1 (IRS-1) in muscle and fat tissues of the fa/fa rats, restoring them to near control (lean) levels. In contrast, no significant changes were observed in insulin-stimulated tyrosine phosphorylations of IR and IRS-1 in liver. The physiological significance of the improvements in IR signaling was indicated by a concurrent reduction in plasma glucose, insulin, and free fatty acid levels. These results demonstrate that TNF-alpha participates in obesity-related systemic insulin resistance by inhibiting the IR tyrosine kinase in the two tissues mainly responsible for insulin-stimulated glucose uptake: muscle and fat.
PMCID: PMC295304  PMID: 7523453
24.  Insulin resistance in obese Zucker rat (fa/fa) skeletal muscle is associated with a failure of glucose transporter translocation. 
Journal of Clinical Investigation  1992;90(4):1568-1575.
The genetically obese Zucker rat (fa/fa) is characterized by a severe resistance to the action of insulin to stimulate skeletal muscle glucose transport. The goal of the present study was to identify whether the defect associated with this insulin resistance involves an alteration of transporter translocation and/or transporter activity. Various components of the muscle glucose transport system were investigated in plasma membranes isolated from basal or maximally insulin-treated skeletal muscle of lean and obese Zucker rats. Measurements of D- and L-glucose uptake by membrane vesicles under equilibrium exchange conditions indicated that insulin treatment resulted in a four-fold increase in the Vmax for carrier-mediated transport for lean animals [from 4.5 to 17.5 nmol/(mg.s)] but only a 2.5-fold increase for obese rats [from 3.6 to 9.1 nmol/(mg.s)]. In the lean animals, this increase in glucose transport function was associated with a 1.8-fold increase in the transporter number as indicated by cytochalasin B binding, a 1.4-fold increase in plasma membrane GLUT4 protein, and a doubling of the average carrier turnover number (intrinsic activity). In the obese animals, there was no change in plasma membrane transporter number measured by cytochalasin B binding, or in GLUT4 or GLUT1 protein. However, there was an increase in carrier turnover number similar to that seen in the lean litter mates. Measurements of GLUT4 mRNA in red gastrocnemius muscle showed no difference between lean and obese rats. We conclude that the insulin resistance of the obese rats involves the failure of translocation of transporters, while the action of insulin to increase the average carrier turnover number is normal.
PMCID: PMC443204  PMID: 1401086
25.  Distinct regulation of stearoyl-CoA desaturase 1 gene expression by cis and trans C18:1 fatty acids in human aortic smooth muscle cells 
Genes & Nutrition  2011;7(2):209-216.
Consumption of trans fatty acids is positively correlated with cardiovascular diseases and with atherogenic risk factors. Trans fatty acids might play their atherogenic effects through lipid metabolism alteration of vascular cells. Accumulation of lipids in vascular smooth muscle cells is a feature of atherosclerosis and a consequence of lipid metabolism alteration. Stearoyl-CoA desaturase 1 (scd1) catalyses the production of monounsaturated fatty acids (e.g. oleic acid) and its expression is associated with lipogenesis induction and with atherosclerosis development. We were interested in analysing the regulation of delta-9 desaturation rate and scd1 expression in human aortic smooth muscle cells (HASMC) exposed to cis and trans C18:1 fatty acid isomers (cis-9 oleic acid, trans-11 vaccenic acid or trans-9 elaidic acid) for 48 h at 100 μM. Treatment of HASMC with these C18:1 fatty acid isomers led to differential effects on delta-9 desaturation; oleic acid repressed the desaturation rate more potently than trans-11 vaccenic acid, whereas trans-9 elaidic acid increased the delta-9 desaturation rate. We then correlated the delta-9 desaturation rate with the expression of scd1 protein and mRNA. We showed that C18:1 fatty acids controlled the expression of scd1 at the transcriptional level in HASMC, leading to an increase in scd1 mRNA content by trans-9 elaidic acid treatment, whereas a decrease in scd1 mRNA content was observed with cis-9 oleic acid and trans-11 vaccenic acid treatments. Altogether, this work highlights a differential capability of C18:1 fatty acid isomers to control scd1 gene expression, which presumes of different consequent effects on cell functions.
PMCID: PMC3316751  PMID: 22057664
Stearoyl-CoA desaturase; trans fatty acids; Oleic acid; Vascular smooth muscle cells; Atherosclerosis

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