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OBJECTIVE--Transgenic expression of diacylglycerol acyltransferase-1 (DGAT1) in skeletal muscle leads to protection against fat-induced insulin resistance despite accumulation of intramuscular triglyceride, a phenomenon similar to what is known as the 'athlete paradox.' The primary objective of this study is to determine how DGAT1 affects muscle fatty acid oxidation in relation to whole-body energy metabolism and insulin sensitivity. RESEARCH DESIGN AND METHODS--We first quantified insulin sensitivity and the relative tissue contributions to the improved whole-body insulin sensitivity in muscle creatine kisase (MCK)-DGAT1 transgenic mice by hyperinsulinemic-euglycemic clamps. Metabolic consequences of DGAT1 overexpression in skeletal muscles were determined by quantifying triglyceride synthesis/storage (anabolic) and fatty acid oxidation (catabolic), in conjunction with gene expression levels of representative marker genes in fatty acid metabolism. Whole-body energy metabolism including food consumption, body weights, oxygen consumption, locomotor activity, and respiration exchange ratios were determined at steady states. RESULTS--MCK-DGAT1 mice were protected against muscle lipoptoxicity, although they remain susceptible to hepatic lipotoxicity. While augmenting triglyceride synthesis, DGAT1 overexpression also led to increased muscle mitochondrial fatty acid oxidation efficiency, as compared with wild-type muscles. On a high-fat diet, MCK-DGAT1 mice displayed higher basal metabolic rates and 5-10% lower body weights compared with wild-type littermates, whereas food consumption was not different. CONCLUSIONS--DGAT1 overexpression in skeletal muscle led to parallel increases in triglyceride synthesis and fatty acid oxidation. Seemingly paradoxical, this phenomenon is characteristic of insulin-sensitive myofibers and suggests that DGAT1 plays an active role in metabolic 'remodeling' of skeletal muscle coupled with insulin sensitization., Despite the observation that higher fat content in skeletal muscle is associated with insulin resistance as commonly seen in obesity and type 2 diabetes, increased muscle fat content is also [...]

OBJECTIVE--Mitochondrial uncoupling proteins (UCPs) are involved in body weight regulation and glucose homeostasis. Genetic variants in the UCP2-UCP3 gene cluster, located on chromosome 11q13, may play a significant role in the development of type 2 diabetes. RESEARCH DESIGN AND METHODS--We conducted a comprehensive assessment of common single nucleotide polymorphisms (SNPs) at the 70-kb UCP2-UCP3 gene cluster in relation to type 2 diabetes risk in a prospective, case-control study nested in the Women's Health Initiative Observational Study, an ethnically diverse cohort of postmenopausal women including Caucasian, African, Hispanic, and Asian American subjects. We genotyped 14 tag SNPs in 1,584 incident type 2 diabetes case and 2,198 control subjects matched by age, ethnicity, clinical center, time of blood draw, and length of follow-up. RESULTS--We identified a haplotype set (rs591758-rs668514-rs647126-rs1800006, spanning the UCP2-UCP3 intergenic and UCP3 regions) as significantly associated with greater type 2 diabetes risk (nominal P = 0.0011, permutation P = 0.046) in Caucasian women, especially among overweight Caucasians (BMI >25 kg/[m.sup.2]) (nominal P = 0.0006, permutation P = 0.032). Compared with the most common haplotype (h1010 as the referent), haplotype h0001 (19.5% in control subjects) had odds ratios of 2.0 (95% CI 1.13-3.37) in Caucasians and 3.8 (1.44-9.93) in Caucasian overweight women. Similar haplotype-type 2 diabetes association was also observed among Hispanic women who were overweight. CONCLUSIONS--These findings suggest a role of UCP2-UCP3 gene cluster haplotypes in diabetes; in particular, the effects of the high-risk haplotypes were more apparent in overweight Caucasian women. These data warrant further confirmation in future prospective and experimental studies., Uncoupling proteins (UCPs) are members of the super family of anion carrier proteins located in the inner membrane of mitochondria (1). Among the five UCP homologues, UCP1-UCP5 (2), UCP2 and [...]

The CCAAT/enhancer-binding protein β (C/EBPβ) is required for adipocyte differentiation and maturation. We have studied the role of the transcription factor, C/EBPβ, in the development of diet-induced obesity. Mice with a deletion in the gene for C/EBPβ (C/EBP[β.sup.-/-]) and wild-type mice were fed a high-fat diet (60% fat) for 12 weeks. The C/EBP[β.sup.-/-] mice lost body fat, whereas the wild-type mice increased their total body fat on a high-fat diet. The C/EBP[β.sup.-/-] mice had lower levels of blood triglycerides, free fatty acids, cholesterol, and hepatic triglyceride accumulation compared with the wild-type mice, thus protecting them from diet-induced obesity and fatty liver on a high-fat diet. Deletion of C/EBPβ gene resulted in greatly reducing hepatic lipogenic genes, acetyl CoA carboxylase, and fatty acid synthase and increasing the expression of β-oxidation genes in the brown adipose tissue. C[O.sub.2] production was significantly higher in the C/EBP[β.sup.-/-] mice as was the level of uncoupling protein (UCP)-1 and UCP-3 in the muscle. In conclusion, the transcription factor C/EBPβ is an important regulator in controlling lipid metabolism and in the development of diet-induced obesity., In the last 20 years, the prevalence of obesity has greatly increased by ~10-15% (1). With the increase of obesity, there is an increased risk of certain diseases such as [...]

The cardioprotective effect of opioids or glycogen synthase kinase (GSK) inhibitors given at reperfusion has not been investigated in diabetes models. Therefore, nondiabetic (NDBR) or streptozotocin-induced diabetic (DBR) rat hearts were subjected to 30 min of ischemia and 2 h of reperfusion. Groups of NDBR or DBR were administered either vehicle, morphine (0.3 mg/kg), or the GSK inhibitor SB216763 (0.6 mg/kg) 5 min before reperfusion. SB216763 (but not morphine) reduced infarct size in DBRs (44 ± 1* and 55 ± 2%, respectively), while both agents reduced infarct size in NDBRs versus untreated NDBRs or DBRs (44 ± 3*, 42 ± 3*, 60 ± 2, and 56 ± 2%, respectively, *P < 0.001). Morphine-induced phospho- (P-)GSK3β was reduced 5 min after reperfusion in DBRs compared with NDBRs (0.83 ± 0.29 and 1.94 ± 0.12 [P < 0.05] pg/µg tissue, respectively). The GSK3β mediators, P-Akt, P-extracellular signal--related kinase (ERK)1, and P-signal transducer and activator of transcription (STAT)3, were also significantly reduced in untreated DBR compared with NDBR rats. Morphine-induced elevations of P-Akt, P-ERK1, P-p70s6, P--janus-activated kinase-2, and P-STAT3 in NDBRs were also blunted in DBRs. H9C2 cells raised in 25 mmol/l compared with 5.56 mmol/l glucose media also demonstrated reduced morphine-induced P-GSK3β, P-Akt, P-STAT3, and P-ERK1 after 15 min. Hence, acute GSK inhibition may provide a novel therapeutic strategy for diabetic patients during an acute myocardial infarction, whereas morphine is less effective due to signaling events that adversely affect GSK3β., Two of three diabetic patients experience a stroke or a heart attack. The relative risk of myocardial infarction also correlates with the level of hyperglycemia, even in nondiabetic patients (1,2). [...]

Casitas b-lineage lymphoma (c-Cbl) is a multiadaptor protein with E3-ubiquitin ligase activity residing within its RING finger domain. We have previously reported that c-Cbl-deficient mice exhibit elevated energy expenditure, reduced adiposity, and improved insulin action. In this study, we examined mice expressing c-Cbl protein with a loss-of-function mutation within the RING finger domain (c-[Cbl.sup.A/-] mice). Compared with control animals, c-[Cbl.sup.A/-] mice display a phenotype that includes reduced adiposity, despite greater food intake; reduced circulating insulin, leptin, and triglyceride levels; and improved glucose tolerance. c-[Cbl.sup.A/-] mice also display elevated oxygen consumption (13%) and are protected against high-fat diet-induced obesity and insulin resistance. Unlike c-[Cbl.sup.A/-] mice, mice expressing a mutant c-Cbl with the phosphatidylinositol (PI) 3-kinase binding domain ablated (c-[Cbl.sup.F/F] mice) exhibited an insulin sensitivity, body composition, and energy expenditure similar to that of wild-type animals. These results indicate that c-Cbl ubiquitin ligase activity, but not c-Cbl-dependent activation of PI 3-kinase, plays a key role in the regulation of whole-body energy metabolism., The increased incidence of obesity and its consequences (type 2 diabetes and cardiovascular disease) has led to increased efforts to understand the molecular control of energy balance and fat mass. [...]

OBJECTIVE--The purpose of this study was to investigate the association between coffee intake and incident diabetes based on an oral glucose tolerance test (OGTT) and examine coffee habits in those [...]

OBJECTIVE--We studied the association between polymorphisms in the UCP genes and diabetes complications in patients with type i diabetes. RESEARCH DESIGN AND METHODS--We analyzed 227 patients with type 1 diabetes [...]

We examined the effects of activation of peroxisome proliferator-activated receptor (PPAR)α, PPARγ, and both of them in combination in obese diabetic KKAy mice and investigated the mechanisms by which they improve insulin sensitivity. PPARα activation by its agonist, Wy-14,643, as well as PPARγ activation by its agonist, rosiglitazone, markedly improved insulin sensitivity. Interestingly, dual activation of PPARα and -γ by a combination of Wy-14,643 and rosiglitazone showed increased efficacy. Adipocyte size in Wy-14,643-treated KKAy mice was much smaller than that of vehicle- or rosiglitazone-treated mice, suggesting that activation of PPARα prevents adipocyte hypertrophy. Moreover, Wy-14,643 treatment reduced inflammation and the expression of macrophage-specific genes in white adipose tissue (WAT). Importantly, Wy-14,643 treatment upregulated expression of the adiponectin receptor (AdipoR)-1 and AdipoR2 in WAT, which was decreased in WAT of KKAy mice compared with that in nondiabetic control mice. Furthermore, Wy-14,643 directly increased expression of AdipoRs and decreased monocyte chemoattractant protein-1 expression in adipocytes and macrophages. Rosiglitazone increased serum adiponectin concentrations and the ratio of high molecular weight multimers of adiponectin to total adiponectin. A combination of rosiglitazone and Wy-14,643 increased both serum adiponectin concentrations and AdipoR expression in WAT. These data suggest that PPARα activation prevents inflammation in WAT and that dual activation of PPARα and -γ enhances the action of adiponectin by increasing both adiponectin and AdipoRs, which can result in the amelioration of obesity-induced insulin resistance., Peroxisome proliferator-activated receptor (PPAR)α and -γ are ligand-activated transcription factors and members of the nuclear hormone receptor superfamily that regulate the metabolism of glucose and lipids (1-6). PPARγ is one [...]

Decreased uncoupling protein (UCP)3 is associated with insulin resistance in muscle of pre-diabetic and diabetic individuals, but the function of UCP3 remains unclear. Our goal was to elucidate mechanisms underlying the negative correlation between UCP3 and insulin resistance in muscle. We determined effects of physiologic UCP3 overexpression on glucose and fatty acid oxidation and on mitochondrial uncoupling and reactive oxygen species (ROS) production in L6 muscle cells. An adenoviral construct caused a 2.2- to 2.5-fold increase in UCP3 protein. Palmitate oxidation was increased in muscle cells incubated under normoglycemic or hyperglycemic conditions, whereas adenoviral green fluorescent protein infection or chronic low doses of the uncoupler dinitrophenol had no effect. Increased UCP3 did not affect glucose oxidation, whereas dinitrophenol and insulin treatments caused increases. Basal oxygen consumption, assessed in situ using self-referencing microelectrodes, was not significantly affected, whereas dinitrophenol caused increases. Mitochondrial membrane potential was decreased by dinitrophenol but was not affected by increased UCP3 expression. Finally, mitochondrial ROS production decreased significantly with increased UCP3 expression. Results are consistent with UCP3 functioning to facilitate fatty acid oxidation and minimize ROS production. As impaired fatty acid metabolism and ROS handling are important precursors in muscular insulin resistance, UCP3 is an important therapeutic target in type 2 diabetes., Insulin resistance in muscle is a primary component of type 2 diabetes, a disease with a prevalence that is increasing at an alarming rate in modern society. The importance of [...]

For examining whether dissipating excess energy in the liver is a possible therapeutic approach to high-fat diet-induced metabolic disorders, uncoupling protein-1 (UCP1) was expressed in murine liver using adenoviral vectors in mice with high-fat diet-induced diabetes and obesity, and in standard diet-fed lean mice. Once diabetes with obesity developed, hepatic UCP1 expression increased energy expenditure, decreased body weight, and reduced fat in the liver and adipose tissues, resulting in markedly improved insulin resistance and, thus, diabetes and dyslipidemia. Decreased expressions of enzymes for lipid synthesis and glucose production and activation of AMP-activated kinase in the liver seem to contribute to these improvements. Hepatic UCP1 expression also reversed high-fat diet-induced hyperphagia and hypothalamic leptin resistance, as well as insulin resistance in muscle. In contrast, intriguingly, in standard diet-fed lean mice, hepatic UCP1 expression did not significantly affect energy expenditure or hepatic ATP contents. Furthermore, no alterations in blood glucose levels, body weight, or adiposity were observed. These findings suggest that ectopic UCP1 in the liver dissipates surplus energy without affecting required energy and exerts minimal metabolic effects in lean mice. Thus, enhanced UCP expression in the liver is a new potential therapeutic target for the metabolic syndrome., An explosive increase in the number of diabetic patients, which has become a major public health concern in most industrialized countries in recent decades (1), is mainly the result of [...]

The metabolic syndrome (visceral obesity, insulin resistance, type 2 diabetes, and dyslipidemia) resembles Cushing's Syndrome, but without elevated circulating glucocorticoid levels. An emerging concept suggests that the aberrantly elevated levels of the intracellular glucocorticoid reamplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) found in adipose tissue of obese humans and rodents underlies the phenotypic similarities between idiopathic and 'Cushing-oid' obesity. Transgenic overexpression of 11β-HSD-1 in adipose tissue reproduces a metabolic syndrome in mice, whereas 11β-HSD-1 deficiency or inhibition has beneficial metabolic effects, at least on liver metabolism. Here we report novel protective effects of 11β-HSD-1 deficiency on adipose function, distribution, and gene expression in five in 11β-HSD-1 nullizygous (11β-HSD-[1.sup.-/-]) mice. 11β-HSD-[1.sup.-/-] mice expressed lower resistin and tumor necrosis factor-α, but higher peroxisome proliferator-activated receptor-γ, adiponectin, and uncoupling protein-2 mRNA levels in adipose, indicating insulin sensitization. Isolated 11β-HSD-[1.sup.-/-] adipocytes exhibited higher basal and insulin-stimulated glucose uptake, 11β-HSD-[1.sup.-/-] mice also exhibited reduced visceral fat accumulation upon high-fat feeding. High-fat-fed 11β-HSD-[1.sup.-/-] mice rederived onto the C57BL/6J strain resisted diabetes and weight gain despite consuming more calories. These data provide the first in vivo evidence that adipose 11β-HSD-1 deficiency beneficially alters adipose tissue distribution and function, complementing the reported effects of hepatic 11β-HSD-1 deficiency or inhibition., Chronic exposure to high circulating glucocorticoid levels (Cushing's syndrome) causes visceral obesity and the associated metabolic abnormalities of insulin resistance, type 2 diabetes, dyslipidemia, and hypertension. Similar metabolic abnormalities occur [...]

This work identifies retinoic acid (RA), the acid form of vitamin A, as a signal that inhibits the expression of resistin, an adipocyte-secreted protein previously proposed to act as an inhibitor of adipocyte differentiation and as a systemic insulin resistance factor. Both 9-cis and all-trans RA reduced resistin mRNA levels in white and brown adipocyte cell model systems; the effect was time- and dose-dependent, was followed by a reduced secretion of resistin, and was reproduced by selective agonists of both RA receptors and retinoid receptors. Association of CCAAT/enhancer-binding protein α (a positive regulator of the resistin gene) and its coactivators p300, cAMP response element-binding protein binding protein, and retinoblastoma protein with the resistin gene promoter was reduced in RA-treated adipocytes. RA administration to normal mice resulted in reduced resistin mRNA levels in brown and white adipose tissues, reduced circulating resistin levels, reduced body weight, and improved glucose tolerance. Resistin expression was also downregulated after dietary vitamin A supplementation in mice. The results raise the possibility that vitamin A status may contribute to modulate systemic functions through effects on the production of adipocyte-derived protein signals., A dipose tissue an important secretory organ, and genes encoding adipocyte secreted proteins (adipokines) potentially involved in the regulation of energy homeostasis, adipose tissue development, and insulin sensitivity may be [...]

The central role of mitochondria in most pathways leading to programmed cell death (PCD) has focused our investigations into the mechanisms of glucose-induced neuronal degeneration. It has been postulated that hyperglycemic neuronal injury results from mitochondria membrane hyperpolarization and reactive oxygen species formation. The present study not only provides further evidence to support our model of glucose-induced PCD but also demonstrates a potent ability for uncoupling proteins (UCPs) to prevent this process. Dorsal root ganglion (DRG) neurons were screened for UCP expression by Western blotting and immunocytochemistry. The abilities of individual UCPs to prevent hyperglycemic PCD were assessed by adenovirus-mediated overexpression of UCP1 and UCP3. Interestingly, UCP3 is expressed not only in muscle, but also in DRG neurons under control conditions. UCP3 expression is rapidly downregulated by hyperglycemia in diabetic rats and by high glucose in cultured neurons. Overexpression of UCPs prevents glucose-induced transient mitochondrial membrane hyperpolarization, reactive oxygen species formation, and induction of PCD. The loss of UCP3 in DRG neurons may represent a significant contributing factor in glucose-induced injury. Furthermore, the ability to prevent UCP3 downregulation or to reproduce the uncoupling response in DRG neurons constitutes promising novel approaches to avert diabetic complications such as neuropathy., Diabetic neuropathy is the most common neuropathy in the western world. Although several etiologies have been proposed for this disease, an association has been found between hyperglycemia and dorsal root [...]

Uncoupling proteins (UCPs) are mitochondrial transporters present in the inner membrane of mitochondria. They are found in all mammals and in plants. They belong to the family of anion mitochondrial carriers including adenine nucleotide transporters. The term 'uncoupling protein' was originally used for UCP1, which is uniquely present in mitochondria of brown adipocytes, the thermogenic cells that maintain body temperature in small rodents. In these cells, UCP1 acts as a proton carrier activated by free fatty acids and creates a shunt between complexes of the respiratory chain and ATP synthase. Activation of UCP1 enhances respiration, and the uncoupling process results in a futile cycle and dissipation of oxidation energy as heat. UCP2 is ubiquitous and highly expressed in the lymphoid system, macrophages, and pancreatic islets. UCP3 is mainly expressed in skeletal muscles. In comparison to the established uncoupling and thermogenic activities of UCP1, UCP2 and UCP3 appear to be involved in the limitation of free radical levels in cells rather than in physiological uncoupling and thermogenesis. Moreover, UCP2 is a regulator of insulin secretion and UCP3 is involved in fatty acid metabolism. Diabetes 53 (Suppl. 1):S130-S135, 2004, Mitochondria are the cellular organelles where respiration occurs. They contain two compartments bounded by inner and outer membranes. The outer membrane is permeable to small metabolites, whereas the permeability of [...]

Increased plasminogen activator inhibitor 1 (PAI-1) has been linked to not only thrombosis and fibrosis but also to obesity and insulin resistance. Increased PAI-1 levels have been presumed to be consequent to obesity. We investigated the interrelationships of PAI-1, obesity, and insulin resistance in a high-fat/high-carbohydrate (HF) diet-induced obesity model in wild-type (WT) and PAI-1-deficient mice (PAI-[1.sup.-/-]). Obesity and insulin resistance developing in WT mice on an HF diet were completely prevented in mice lacking PAI-1. PAI-[1.sup.-/-] mice on an HF diet had increased resting metabolic rates and total energy expenditure compared with WT mice, along with a marked increase in uncoupling protein 3 mRNA expression in skeletal muscle, likely mechanisms contributing to the prevention of obesity. In addition, insulin sensitivity was enhanced significantly in PAI-[1.sup.-/-] mice on an HF diet, as shown by euglycemic-hyperinsulinemic clamp studies. Peroxisome proliferator-activated receptor (PPAR)-γ and adiponectin mRNA, key control molecules in lipid metabolism and insulin sensitivity, were maintained in response to an HF diet in white adipose tissue in PAI-[1.sup.-/-] mice, contrasting with downregulation in WT mice. This maintenance of PPAR-γ and adiponectin may also contribute to the observed maintenance of body weight and insulin sensitivity in PAI-[1.sup.-/-] mice. Treatment in WT mice on an HF diet with the angiotensin type 1 receptor antagonist to downregulate PAI-1 indeed inhibited PAI-1 increases and ameliorated diet-induced obesity, hyperglycemia, and hyperinsulinemia. PAI-1 deficiency also enhanced basal and insulin-stimulated glucose uptake in adipose cells in vitro. Our data suggest that PAI-1 may not merely increase in response to obesity and insulin resistance, but may have a direct causal role in obesity and insulin resistance. Inhibition of PAI-1 might provide a novel anti-obesity and anti-insulin resistance treatment., Obesity is reaching epidemic proportions worldwide. More than half of the adults in the U.S. are overweight or obese (1). Obesity is a strong risk factor for the development of [...]

We investigated whether decreased responsiveness of the heart to physiological increases in fatty acid availability results in lipid accumulation and lipotoxic heart disease. Lean and obese Zucker rats were either fed ad libitum or fasted overnight. Fasting increased plasma nonesterified fatty acid levels in both lean and obese rats, although levels were greatest in obese rats regardless of nutritional status. Despite increased fatty acid availability, the mRNA transcript levels of peroxisome proliferator-activated receptor (PPAR)-α-regulated genes were similar in fed lean and fed obese rat hearts. Fasting increased expression of all PPAR-α-regulated genes in lean Zucker rat hearts, whereas, in obese Zucker rat hearts, muscle carnitine palmitoyltransferase and medium-chain acyl-CoA dehydrogenase were unaltered with fasting. Rates of oleate oxidation were similar for hearts from fed rats. However, fasting increased rates of oleate oxidation only in hearts from lean rats. Dramatic lipid deposition occurred within cardiomyocytes of obese, but not lean, Zucker rats upon fasting. Cardiac output was significantly depressed in hearts isolated from obese rats compared with lean rats, regardless of nutritional status. Fasting increased cardiac output in hearts of lean rats only. Thus, the heart's inability to increase fatty acid oxidation in proportion to increased fatty acid availability is associated with lipid accumulation and contractile dysfunction of the obese Zucker rat., Obesity, insulin resistance, and diabetes are now major worldwide epidemics (1-3). Although much evidence exists suggesting a genetic component to these disorders, the dramatic surge in their incidence during recent [...]

Weight loss in response to caloric restriction is variable. Because skeletal muscle mitochondrial proton leak may account for a large proportion of resting metabolic rate, we compared proton leak in diet-resistant and diet-responsive overweight women and compared the expression and gene characteristics of uncoupling protein (UCP)2 and UCP3. Of 1,129 overweight women who completed the University of Ottawa Weight Management Clinic program, 353 met compliance criteria and were free of medical conditions that could affect weight loss. Subjects were ranked according to percent body weight loss during the first 6 weeks of a 900-kcal meal replacement protocol. The highest and lowest quintiles of weight loss were defined as diet responsive and diet resistant, respectively. After body weight had been stable for at least 10 weeks, 12 of 70 subjects from each group consented to muscle biopsy and blood sampling for determinations of proton leak, UCP mRNA expression, and genetic studies. Despite similar baseline weight and age, weight loss was 43% greater, mitochondrial proton leak-dependent (state 4) respiration was 51% higher (P = 0.0062), and expression of UCP3 mRNA abundance was 25% greater (P < 0.001) in diet-responsive than in diet-resistant subjects. There were no differences in UCP2 mRNA abundance. None of the known polymorphisms in UCP3 or its 5' flanking sequence were associated with weight loss or UCP3 mRNA abundance. Thus, proton leak and the expression of UCP3 correlate with weight loss success and may be candidates for pharmacological regulation of fat oxidation in obese diet-resistant subjects., At the Weight Management Program at the University of Ottawa, we have documented a 10-fold variation in the rate of weight loss in 353 highly compliant women on a standard [...]

Conjugated linoleic acid (CLA) is a heterogeneous group of positional and geometric isomers of linoleic acid. This study demonstrates the divergent effects of the cis-9 trans-11 (c9,t11-CLA) and trans-10 cis-12 (t10,c12-CLA) isomers of CLA on lipid metabolism and nutrient regulation of gene expression in ob/ob mice. The c9,t11-CLA diet decreased serum triacyl-glycerol (P = 0.01) and nonesterified fatty acid (NEFA) (P = 0.05) concentrations, and this was associated with reduced hepatic sterol regulatory element-binding protein-1c (SREBP-1c; P = 0.0045) mRNA expression, coupled with reduced levels of both the membrane-bound precursor and the nuclear forms of the SREBP-1 protein. C9,t11-CLA significantly reduced hepatic LXRα (P = 0.019) mRNA expression, a novel regulator of SREBP-1c. In contrast, c9,t11-CLA increased adipose tissue SREBP-1c mRNA expression (P = 0.0162) proportionally to the degree of reduction of tumor necrosis factor α (TNF-α) mRNA (P = 0.012). Recombinant TNF-α almost completely abolished adipose tissue SREBP-1α mRNA expression in vivo. The t10,c12-CLA diet promoted insulin resistance and increased serum glucose (P = 0.025) and insulin (P = 0.01) concentrations. T10,c12-CLA induced profound weight loss (P = 0.0001) and increased brown and white adipose tissue UCP-2 (P = 0.001) and skeletal muscle UCP-3 (P = 0.008) mRNA expression. This study highlights the contrasting molecular and metabolic effect of two isomers of the same fatty acids. The ameliorative effect of c9,t11-CLA on lipid metabolism may be ascribed to reduced synthesis and cleavage of hepatic SREBP-1, which in turn may be regulated by hepatic LXRα expression., The novel fatty acid conjugated linoleic acid (CLA) may have potential as a therapeutic nutrient with respect to dyslipidemia and insulin resistance that is characteristic of the metabolic syndrome. CLA [...]

Diabetes and obesity have long been known to be related. The recently characterized adipocyte hormone resistin (also called FIZZ3/ADSF) has been implicated as a molecular link between impaired glucose tolerance [...]

Recently, a role for uncoupling protein-3 (UCP3) in carbohydrate metabolism and in type 2 diabetes has been suggested. Mice overexpressing UCP3 in skeletal muscle showed reduced fasting plasma glucose levels, improved glucose tolerance after an oral glucose load, and reduced fasting plasma insulin levels. However, data regarding the expression of UCP3 in patients with type 2 diabetes is inconsistent, and so far, there have been no reports of UCP3 protein content. Here we compared, for the first time, the protein levels of UCP3 in vastus lateralis muscle in 14 male type 2 diabetic patients (age 49.8 ± 2.1 years; BMI 27.2 ± 1.2 kg/[m.sup.2]; mean ± SE) with 16 male control subjects (age 48.0 ± 1.9 years; BMI 23.4 ± 0.6 kg/[m.sup.2]). We found that UCP3 protein levels were twice as low in patients with type 2 diabetes compared with control subjects (117 ± 16 vs. 58 ± 12 AU; P = 0.007). There was no correlation between UCP3 content and BMI. In conclusion, UCP3 content is lower in type 2 diabetic patients compared with healthy control subjects. These results are consistent with a role for UCP3 in glucose homeostasis and suggest a role for UCP3 in type 2 diabetes., The human uncoupling protein UCP3 uncouples oxidative phosphorylation from ATP production and is therefore thought to play a role in human energy metabolism and obesity (1). Recently, a role for [...]

Whether insulin acutely regulates plasma leptin in humans is controversial. We examined the dosage-response and time-course characteristics of the effect of insulin on leptin in 10 men (age 42 ± [...]