Insulin and Oleate Promote Translocation of Inosine-5' Monophosphate Dehydrogenase to Lipid Bodies

In the present study we identify inosine-5' monophosphate dehydrogenase (IMPDH), a key enzyme in de novo guanine nucleotide biosynthesis, as a novel lipid body-associated protein. To identify new targets of insulin we performed a comprehensive 2-DE analysis of P-32-labelled proteins isolated from 3T3-L1 adipocytes (Hill et al. J Biol Chem 2000; 275: 24313-24320). IMPDH was identified by liquid chromatography/tandem mass spectrometry as a protein which was phosphorylated in a phosphatidylinositol (PI) 3-kinase-dependent manner upon insulin treatment. Although insulin had no significant effect on IMPDH activity, we observed translocation of IMPDH to lipid bodies following insulin treatment. Induction of lipid body formation with oleic acid promoted dramatic redistribution of IMPDH to lipid bodies, which appeared to be in contact with the endoplasmic reticulum, the site of lipid body synthesis and recycling. Inhibition of PI 3-kinase blocked insulin- and oleate-induced translocation of IMPDH and reduced oleate-induced lipid accumulation. However, we found no evidence of oleate-induced IMPDH phosphorylation, suggesting phosphorylation and translocation may not be coupled events. These data support a role for IMPDH in the dynamic regulation of lipid bodies and fatty acid metabolism and regulation of its activity by subcellular redistribution in response to extracellular factors that modify lipid metabolism.

Effect of a tumour-derived lipid-mobilising factor on glucose and lipid metabolism in vivo

Treatment of ex-breeder male NMRI mice with lipid mobilising factor isolated from the urine of cachectic cancer patients, caused a significant increase in glucose oxidation to CO2, compared with control mice receiving phosphate buffered saline. Glucose utilisation by various tissues was determined by the 2-deoxyglucose tracer technique and shown to be elevated in brain, heart, brown adipose tissue and gastrocnemius muscle. The tissue glucose metabolic rate was increased almost three-fold in brain, accounting for the ability of lipid mobilising factor to decrease blood glucose levels. Lipid mobilising factor also increased overall lipid oxidation, as determined by the production of 14CO2 from [14C carboxy] triolein, being 67% greater than phosphate buffered saline controls over a 24 h period. There was a significant increase in [14C] lipid accumulation in plasma, liver and white and brown adipose tissue after administration of lipid mobilising factor. These results suggest that changes in carbohydrate metabolism and loss of adipose tissue, together with an increased whole body fatty acid oxidation in cachectic cancer patients, may arise from tumour production of lipid mobilising factor. © 2002 Cancer Research UK.

Lipid Metabolism of Monosodium Glutamate Obese Rats after Partial Removal of Adipose Tissue

We analyzed the effects of partial fat pad removal on retroperitoneal and epididymal fat depots and carcass metabolism of control (C) and MSG-obese (M) rats. Three-month-old C and M male Wistar rats were submitted to either partial surgical excision of epididymal and retroperitoneal fat tissue (lipectomy, L) or sham surgery (S) and studied after 7 or 30 days. Retroperitoneal and epididymal tissue re-growth after lipectomy was not observed, as indicated by the low pads weight of the L groups. The lipolysis rate was stimulated in LC7 and LM7, probably due to surgical stress and low insulin levels. In LM7, but not in LC7, in vivo lipogenesis rate increased in retroperitoneal and epididymal fat tissue, as did the diet-derived lipid accumulation in epididymal fat tissue. Although these local increases were no longer present in LM30, this group showed a large increase in the percentage of small area adipocytes in both pads as well as increased carcass lipogenesis rate. The present data showed that the partial removal of fat depots affected the metabolism of control and MSG-obese rats differently. In the obese animals only, it stimulated both local and carcass lipogenesis rate as well as adipocyte differentiation, i.e. responses likely to favor excised tissue re-growth and/or compensatory growth of non-excised depots.

Association between common lipid metabolism genes polymorphisms and sporadic colorectal adenocarcinoma risk

Lipids can modulate the risk of developing sporadic colorectal adenocarcinoma (SCA), since alterations into lipid metabolism and transport pathways influence directly cholesterol and lipids absorption by colonic cells and indirectly reactive oxygen species (ROS) synthesis in rectum cells due to lipid accumulation. Lipid metabolism is regulated by several proteins APOA1, APOB, APOC3, APOE, CETP, NPY, PON1 and PPARG that could influence both metabolism and transport processes. Is been reported that several common single-nucleotide polymorphisms (SNPs) in these genes could influence their function and/or expression, changing lipid metabolism balance. Thus, genetic changes in those genes can influence SCA development, once the majority of them were never studied in this disease. Furthermore, there are contradictory results between some studied polymorphisms and SCA risk. Thus, the aim of this study was to explore and describe lipid metabolism-associated genes common polymorphisms (APOA1 -75 G>A; APOB R3500Q; APOC3 C3175G, APOC3 T3206G; APOE Cys112/158Arg; CETP G279A, CETP R451Q; NPY Leu7Pro; PON1 Q192R; PPARG Pro12Ala) status among SCA, and their relationship with SCA risk. Genotyping of common lipid metabolism genes polymorphisms (APOA1 75 G>A; APOB R3500Q; APOC3 C3175G, APOC3 T3206G; APOE Cys112/158Arg; CETP G279A, CETP R451Q; NPY Leu7Pro; PON1 Q192R; PPARG Pro12Ala) were done by PCR-SSP techniques, from formalin-fixed and paraffin-embedded biopsies of 100 healthy individuals and 68 SCA subjects. Mutant genotypes of APOA1 -75AA (32% vs 12%; p=0.001; OR=3.51; 95% CI 1.59-7.72); APOB 3500AA (7% vs 0%; p=0.01); APOC3 3175GG (19% vs 2%; p=0.0002; OR=11.58; 95% CI 2.52-53.22), APOC3 3206GG (19% vs 0%; p<0.0001); CETP 279AA (12% vs 1%; p=0.003; OR=13.20; 95% CI 1.61-108.17), CETP 451AA (16% vs 0%; p<0.0001); NPY 7CC (15% vs 0%; p<0.0001); PPARG 12GG (10% vs 0%; p=0.001); and heterozygote genotype PON1 192AG (56% vs 22%; p<0.0001; OR=4.49; 95% CI 2.298.80) were found associated with SCA prevalence. While, APOE E4/E4 (0% vs 8%; p=0.02) mutant haplotype seemed to have a protective effect on SCA. Moreover, it also been founded differences between APOB 3500GA, APOC3 3206TG, CETP 279AA genotypes and PPARG 12Ala allele prevalence and tissue localization (colon vs rectum). These findings suggest a positive association between most of common lipid metabolism genes polymorphisms studied and SCA prevalence. Dysregulation of APOA1, APOB, APOC3, CETP, NPY, PON1 and PPARG genes could be associated with lower cholesterol plasma levels and increase ROS among colon and rectum mucosa. Furthermore, these results also support the hypothesis that CRC is related with intestinal lipid absorption decrease and secondary bile acids production increase. Moreover, the polymorphisms studied may play an important role as biomarkers to SCA susceptibility.

Association between common lipid metabolism genes polymorphisms and sporadic colorectal adenocarcinoma risk

Lipids can modulate the risk of developing sporadic colorectal adenocarcinoma (SCA), since alterations into lipid metabolism and transport pathways influence directly cholesterol and lipids absorption by colonic cells and indirectly reactive oxygen species (ROS) synthesis in rectum cells due to lipid accumulation. Lipid metabolism is regulated by several proteins APOA1, APOB, APOC3, APOE, CETP, NPY, PON1 and PPARG that could influence both metabolism and transport processes. Is been reported that several common single-nucleotide polymorphisms (SNPs) in these genes could influence their function and/or expression, changing lipid metabolism balance. Thus, genetic changes in those genes can influence SCA development, once the majority of them were never studied in this disease. Furthermore, there are contradictory results between some studied polymorphisms and SCA risk. Thus, the aim of this study was to explore and describe lipid metabolism-associated genes common polymorphisms (APOA1 -75 G>A; APOB R3500Q; APOC3 C3175G, APOC3 T3206G; APOE Cys112/158Arg; CETP G279A, CETP R451Q; NPY Leu7Pro; PON1 Q192R; PPARG Pro12Ala) status among SCA, and their relationship with SCA risk. Genotyping of common lipid metabolism genes polymorphisms (APOA1 75 G>A; APOB R3500Q; APOC3 C3175G, APOC3 T3206G; APOE Cys112/158Arg; CETP G279A, CETP R451Q; NPY Leu7Pro; PON1 Q192R; PPARG Pro12Ala) were done by PCR-SSP techniques, from formalin-fixed and paraffin-embedded biopsies of 100 healthy individuals and 68 SCA subjects. Mutant genotypes of APOA1 -75AA (32% vs 12%; p=0.001; OR=3.51; 95% CI 1.59-7.72); APOB 3500AA (7% vs 0%; p=0.01); APOC3 3175GG (19% vs 2%; p=0.0002; OR=11.58; 95% CI 2.52-53.22), APOC3 3206GG (19% vs 0%; p<0.0001); CETP 279AA (12% vs 1%; p=0.003; OR=13.20; 95% CI 1.61-108.17), CETP 451AA (16% vs 0%; p<0.0001); NPY 7CC (15% vs 0%; p<0.0001); PPARG 12GG (10% vs 0%; p=0.001); and heterozygote genotype PON1 192AG (56% vs 22%; p<0.0001; OR=4.49; 95% CI 2.298.80) were found associated with SCA prevalence. While, APOE E4/E4 (0% vs 8%; p=0.02) mutant haplotype seemed to have a protective effect on SCA. Moreover, it also been founded differences between APOB 3500GA, APOC3 3206TG, CETP 279AA genotypes and PPARG 12Ala allele prevalence and tissue localization (colon vs rectum). These findings suggest a positive association between most of common lipid metabolism genes polymorphisms studied and SCA prevalence. Dysregulation of APOA1, APOB, APOC3, CETP, NPY, PON1 and PPARG genes could be associated with lower cholesterol plasma levels and increase ROS among colon and rectum mucosa. Furthermore, these results also support the hypothesis that CRC is related with intestinal lipid absorption decrease and secondary bile acids production increase. Moreover, the polymorphisms studied may play an important role as biomarkers to SCA susceptibility.

Human leukemia inhibitory factor upregulates LDL receptors on liver cells and decreases serum cholesterol in the cholesterol-fed rabbit

In a previous study, we found that the cytokine (human) leukemia inhibitory factor (hLIF) significantly reduced plasma cholesterol levels and the accumulation of lipid in aortic tissues of cholesterol-fed rabbits after 4 weeks of treatment. The mechanisms by which this occurs were investigated in the present study. This involved examining the effect of hLIF on (1) the level of plasma cholesterol at different times throughout the 4-week treatment and diet period; (2) smooth muscle cell (SMC) and macrophage-derived foam cell formation in vitro; and (3) LDL receptor expression and uptake in the human hepatoma cell line HepG2. At time zero, an osmotic minipump (2-mL capacity; infusion rate, 2.5 mu L/h; 28 days) containing either hLIF (30 mu g.kg(-1).d(-1)) or saline was inserted into the peritoneal cavity of New Zealand White rabbits (N=24). Rabbits were divided into four groups of six animals each. Group 1 received a normal diet/saline; group 2, a normal diet/hLIF; group 3, a 1% cholesterol diet/saline; and group 4, a 1% cholesterol diet/hLIF. hLIF had no effect on the plasma lipids or artery wall of group 2 rabbits (normal diet). However, in group 4 rabbits, plasma cholesterol levels and the percent surface area of thoracic aorta covered by fatty streaks was decreased by approximate to 30% and 80%, respectively, throughout all stages of the 4-week treatment period. In vitro, hLIF failed to prevent lipoprotein uptake by either SMCs or macrophages (foam cell formation) when the cells were exposed to P-VLDL for 24 hours. In contrast, hLIF (100 ng/mL) added to cultured human hepatoma HepG2 cells induced a twofold or threefold increase in intracellular lipid accumulation in the medium containing 10% lipoprotein-deficient serum or 10% fetal calf serum, respectively. This was accompanied by a significant non-dose-dependent increase in LDL receptor expression in hLIF-treated HepG2 cells incubated with LDL (20 mu g/mL) when compared with controls (P

The cell biology of atherosclerosis - new developments

In the development of atherosclerotic lesions, three basic processes occur: 1) invasion of the artery wall by leucocytes, particularly monocytes and T-lymphocytes; 2) smooth muscle phenotypic modulation, proliferation, and synthesis of extracellular matrix; and 3) intracellular (macrophage and smooth muscle) lipoprotein uptake and lipid accumulation. Invasion of the vessel wall by leucocytes is mediated through the expression of adhesion molecules on both leucocytes and the endothelium making them 'sticky'. The adhesion molecules are induced by high serum cholesterol levels or complement fragments. Leucocytes which have adhered to the endothelium are chemo-attracted into the vessel wall by cytokines produced by early arriving leucocytes or by low density lipoprotein which has passively passed into the wall, in the process being trapped and oxidised. The oxidised low density lipoprotein is taken up by scavenger receptors (which are not subject to down-regulation) on both macrophages and smooth muscle cells. The overaccumulation of lipid is toxic to the cells and they die contributing to the central necrotic core. The macrophages and T-lymphocytes produce substances which induce smooth muscle cells of the artery wall to change from a 'contractile' (high volume fraction of myofilaments [V(v)myo]) to a 'synthetic' (low V(v)myo) phenotype. In this altered state they respond to growth factors released from macrophages, platelets, regenerating endothelial cells and smooth muscle cells; produce large amounts of matrix; express lipoprotein scavenger receptors; express adhesion molecules for leucocytes; and express HLA-DR following exposure to the T-lymphocyte product, IFN-delta, suggesting that they can become involved in a generalised immune reaction.

Low protein diet changes the energetic balance and sympathetic activity in brown adipose tissue of growing rats

Objective: The aim of this study was to assess the effects of protein restriction in growing rats. Methods: Rats (approximate weight, 100 g) were maintained with low-protein (LP; 6%) or normo-proteic (control; 17%) diets, and at the end of the 15th day, hormonal and biochemistry parameters and energetic balance were evaluated. Data were analyzed using Student`s t test (with statistical significance set at P <= .05). Results: LP animals were hyperphagic and showed increased energetic gain (24%) and energy expenditure (EE) compared with controls. The increase in EE was followed by increased sympathetic activity in brown adipose tissue, evidenced by increased norepinephrine turnover, suggesting increased thermogenesis. In spite of hyperphagia, protein ingestion in LP animals was lower than that of controls (P < 0.01). The LP diet impaired body growth and caused deep alterations in body chemical composition, with an increase in carcass lipid content (64%) and reductions of protein and water. In LP animals, postprandial glycemia was unchanged, and insulinemia was lower than in controls (P <= .01). Reduction in fasting glycemia without changes in insulinemia also was detected (P < .01), suggesting increased insulin sensitivity. The LP diet caused a 100% increase in serum leptin (P < .01). Conclusions: Protein restriction led to an increase in EE, with probable activation of thermogenesis in brown adipose tissue, evidenced by an increase in catecholamines levels. Despite the higher EE, energetic gain and lipids increased. The high level of leptin associated with hyperphagia led to the supposition that these animals are leptin resistant, and the increase in insulin sensitivity, suggested by the relation between insulin and glycemia in fasting and fed animals, might contribute to lipid accumulation. (C) 2009 Elsevier Inc. All rights reserved.

Molecular basis by which garlic suppresses atherosclerosis

The aim of this study was to determine the mechanism by which the aged garlic extract Kyolic has a protective effect against atherosclerosis. Plasma cholesterol of rabbits fed a 1% cholesterol-enriched diet for 6 wk was not reduced by supplementation with 800 muL Kyolic/(kg body . d). In spite of this, Kyolic reduced by 64% (P < 0.05) the surface area of the thoracic aorta covered by fatty streaks and significantly reduced aortic arch cholesterol. Kyolic also significantly inhibited by 50% the development of thickened, lipid-filled lesions in preformed neointimas produced by Fogarty 2F balloon catheter injury of the right carotid artery in cholesterol-fed rabbits. In vitro studies found that Kyolic completely prevented vascular smooth muscle phenotypic change from the contractile. high volume fraction of filament (V(v)myo) state, and inhibited proliferation of smooth muscle cells in the synthetic state with a 50% effective dose (ED50) of 0.2%. Kyolic also slightly inhibited the accumulation of lipid in cultured macrophages but not smooth muscle, and had no effect an the expression of adhesion molecules on the surface of the endothelium or the adherence of leukocytes. It is concluded that Kyolic exerts antiatherogenic effects through inhibition of smooth muscle phenotypic change and proliferation, and by another (unclarified) effect on lipid accumulation in the artery wall.

Effects of rosiglitazone and linoleic acid on human preadipocyte differentiation

Background Peroxisome proliferator activated receptor gamma (PPARgamma) is a ligand-activated transcription factor known to be central to both adipose tissue development and insulin action. Growth of adipose tissue requires differentiation of preadipocytes with acquisition of specific cellular functions including insulin sensitivity, leptin secretion and the capacity to store triglyceride. Dietary fatty acids and members of the thiazolidinedione class of compounds have been reported to influence adipogenesis at the transcriptional level. Here, we compare the effects of a dietary fatty acid, linoleic acid, and a thiazolidinedione, rosiglitazone, on biochemical and functional aspects of human preadipocyte differentiation in vitro . Materials and methods Human omental and subcutaneous preadipocytes were subcultured 2-3 times and subsequently differentiated for 21 days in the presence of either linoleic acid or rosiglitazone. Differentiation was assessed using a number of biochemical and functional parameters. Results Omental and subcutaneous preadipocytes differentiated in the presence of linoleic acid showed marked cytoplasmic triacylglycerol accumulation however, no biochemical markers of differentiation (LPL expression, G3PDH gene expression and enzyme activity and leptin expression or secretion) were detected. In contrast, treatment of these cells with rosiglitazone induced full biochemical differentiation as judged by all markers assessed, despite comparatively little lipid accumulation. The rosiglitazone effects were subcutaneous depot-specific. Cells treated with linoleic acid showed decreased glucose uptake cf rosiglitazone-treated cells. A luciferase reporter assay demonstrated that rosiglitazone potently activates h-peroxisome proliferator activated receptor gamma while linoleic acid had no effect. Conclusions These studies demonstrate that (a) human preadipocytes have the potential to accumulate triacylglycerol irrespective of their stage of biochemical differentiation; (b) while omental preadipocytes are refractory to biochemical differentiation in vitro , they are able to accumulate triacylglycerol; and (c) rosiglitazone and linoleic acid may exert their effects via different biochemical pathways.

Efeitos da depleção de nitrogênio sobre a biomassa e produção lipídica lipídica de três espécies de microalgas fitoplânticas

O uso de lipídios obtidos a partir da biomassa de microalgas tem sido descrito como uma alternativa promissora para a indústria petro-diesel e envolve etapas como o cultivo de microalgas, separação da biomassa e extração de lipídios. Para viabilizar a produção em larga escala, é necessário selecionar as espécies mais produtivas, diminuir os custos de produção e determinar as condições ideais de cultivo. Os gêneros Chlorella, Desmodesmus e Ankistrodesmus apresentam características favoráveis à produção comercial, tendo sido então selecionada uma espécie de cada no presente trabalho. O objetivo do estudo foi avaliar diferentes condições de cultivo de Ankistrodesmus fusiformis, Chlorella vulgaris e Desmodesmus spinosus visando o aumento da produtividade em biomassa e lipídios totais. As algas foram identificadas e cultivadas em laboratório, em condições controladas de temperatura a 26ºC (±1), aeração por borbulhamento à pressão ambiente e luminosidade fornecida por lâmpadas fluorescentes, com intensidade de 47,25 μmol de fótons m-2.s-1 (3500 lux), fotoperiodo de 12h e pH 7, sob duas concentrações estressantes de nitrato de sódio (0,10 g/L e 0,05g/L). Os cultivos duraram em média 16 dias, sendo as curvas de crescimento construídas com dados de espectrofotometria óptica coletados a cada 48h, e a biomassa obtida ao final do cultivo por centrifugação e liofilização de cada unidade experimental. Para extração dos lipídios totais, foi utilizada a mistura de clorofórmio: metanol (1:2), segundo a metodologia de Bligh & Dyer (1959). Os tratamentos de estresse em D.spinosus resultaram em maior acúmulo lipídico, com aumento de até 149,7%, porém com drástica diminuição do crescimento e biomassa. Em C. vulgaris, nos tratamentos de estresse, verificou-se apenas ligeiro aumento do peso seco e teor de lipídios, não havendo diferença significativa entre os tratamentos e o controle. Da mesma forma, A.fusiformis não mostrou respostas significativas ao estresse pela redução de nitrato de sódio do meio, havendo ligeira diminuição do conteúdo lipídico e aumento do crescimento e biomassa. Com respostas diferentes para cada espécie estudada, evidencia-se a necessidade do conhecimento da fisiologia e autoecologia da cepa a ser cultivada em escala comercial visando à produção de ácidos graxos para fins de biodiesel.

Evaluating the potential of yeast strains to produce added value products for the food and/or pharmaceutical industries

This study focus in the valorization of the apple pomace with the main goal of obtaining added value products. For that, hot compressed water technology was used for the extraction of phenolic compounds and hydrolysis of polysaccharides presents in the lignocellulosic structure of apple pomace to obtain simple sugars. The sugars have been utilized as alternative carbon source for growth, lipid accumulation and carotenoids production by five different yeast Yarrowia lipolytica, Rhodotorula mucilaginosa, Rhodotorula glutinis, Rhodosporidium babjevae and Rhodosporidium toruloides. Hydrolysis experiments were carried out with constant pressure of 100 bar, flow rate of 2mL/min and temperatures between 50°C and 250°C. The amount of total sugars present in apple pomace hydrolysates showed maximum values for the hydrolysis temperatures of 110°C and 190°C. In fact, these temperatures revealed the best results regarding the monosaccharides quantities. The amount of 5-HMF and furfural in each hydrolysate varied through the different temperatures. Maximum values for 5-HMF were obtained with 170°C, while furfural showed to be maximum at 210°C. Extraction of phenolic compounds were performed in simultaneously with hydrolysis reactions. Total phenolic compounds (TPC) increased along the temperature, however with small variations between 170°C and 250°C. Hydrolysates were then used as alternative carbon source to yeast growth. R. mucilaginosa shows the highest optical density, with the hydrolysate obtained at 130°C. Carotenoids produced by these yeast scored a total of 7.02μg carotenoids/g cell dry weight, while for the control assay, the same yeast scored 9.31μg caratonoides/g cell dry weight. β-carotene was quantified by HPLC, were 33% of the carotenoid production by R. mucilaginosa with hydrolysate as carbon source, corresponded to β-caroteno.

Ontogenetic changes in digestive enzymatic capacities of the spider crab, Maja brachydactyla (Decapoda: Majidae)

Ontogenetic changes in digestive capabilities were analyzed in larvae and first juveniles of the spider crab Maja brachydactyla. Activities of five proteinases (total proteases, trypsin, chymotrypsin, pepsin-like and aminopeptidase), three carbohydrases (amylase, maltase and chitinase), an esterase and an alkaline phosphatase were studied to evaluate digestive enzyme profiles of the species. Both quantitative (spectrophotometry and fluorometry) and qualitative (SDS-PAGE) approaches were used. All assayed enzymes were active from hatching (zoea I-ZI) throughout larval development and in first juveniles. Significant variations during ontogeny were found only in total activities likely as a consequence of digestive system development. Specific activity varied little over ontogeny, being significant only for chitinase. Total proteases, trypsin and pepsin-like activities showed a similar pattern of increase as larval ontogeny advanced, decreasing significantly in juveniles. Chymotrypsin continued to increase, showing maximum activity after metamorphosis. Proteinase zymograms confirmed strong proteolytic activity in first zoeas, with increasing bands over the course of ontogeny, decreasing after metamorphosis. A group of bands with high molecular mass was specific to larval stages. Amylase and maltase showed a parallel pattern of continuous increase of total activity as development advanced. Gel-SDS-PAGE showed unchanged patterns of amylase activity in first zoeas of different ages and the most complex set of bands during larval ontogeny in second zoea. Esterase total activity increased significantly as ZI's aged likely reflecting introduction of a lipid-enriched diet. The importance of lipid accumulation at the beginning of ontogeny was also confirmed by the protease/esterase and amylase/esterase activity ratios, which decreased from hatch to late ZI and might be explained as an adaptation, ensuring the next molt. The results suggest that larvae of M. brachydactyla are capable of digesting a variety of dietary substrates as soon as they hatch.

Smad3 deficiency in mice protects against insulin resistance and obesity induced by a high-fat diet.

OBJECTIVE-Obesity and associated pathologies are major global health problems. Transforming growth factor-beta/Smad3 signaling has been implicated in various metabolic processes, including adipogenesis, insulin expression, and pancreatic beta-cell function. However, the systemic effects of Smad3 deficiency on adiposity and insulin resistance in vivo remain elusive. This study investigated the effects of Smad3 deficiency on whole-body glucose and lipid homeostasis and its contribution to the development of obesity and type 2 diabetes.RESEARCH DESIGN AND METHODS-We compared various metabolic profiles of Smad3-knockout and wild-type mice. We also determined the mechanism by which Smad3 deficiency affects the expression of genes involved in adipogenesis and metabolism. Mice were then challenged with a high-fat diet to study the impact of Smad3 deficiency on the development of obesity and insulin resistance.RESULTS-Smad3-knockout mice exhibited diminished adiposity with improved glucose tolerance and insulin sensitivity. Chromatin immunoprecipitation assay revealed that Smad3 deficiency increased CCAAT/enhancer-binding protein beta-C/EBP homologous protein 10 interaction and exerted a differential regulation on proliferator-activated receptor beta/delta and proliferator-activated receptor gamma expression in adipocytes. Focused gene expression profiling revealed an altered expression of genes involved in adipogenesis, lipid accumulation, and fatty acid beta-oxidation, indicative of altered adipose physiology. Despite reduced physical activity with no modification in food intake, these mutant mice were resistant to obesity and insulin resistance induced by a high-fat diet.CONCLUSIONS-Smad3 is a multifaceted regulator in adipose physiology and the pathogenesis of obesity and type 2 diabetes, suggesting that Smad3 may be a potential target for the treatment of obesity and its associated disorders.

Severe hyperlipidemia causes impaired renin-angiotensin system function in apolipoprotein E deficient mice.

Dyslipidemia is a known risk factor for cardiovascular diseases and may associate with renal injury. Using mouse models with various degrees of hypercholesterolemia and hypertryliceridemia, we investigated the effects of lipids on the renin-angiotensin system (RAS). ApoE-/- mice were fed either a high fat diet (HF-ApoE-/-; mice developed hypertriglyceridemia and severe hypercholesterolemia) or regular chow (R-ApoE(-/-); mice developed less severe hypercholesterolemia only). Renal histopathology in the HF-ApoE-/- revealed massive lipid accumulation especially at the glomerular vascular pole. In these mice plasma renin concentration was significantly reduced (489+/-111 ng/(ml h) versus 1023+/-90 ng/(ml h) in R-ApoE-/- mice) and blood pressure was consequently significantly lower than in R-ApoE-/- (104+/-2 mmHg versus 115+/-2 mmHg, respectively). A model of renin-dependent renovascular hypertension (two-kidney, one clip) was generated and HF-ApoE-/- mice proved unable to increase renin secretion, and blood pressure, in response to diminished renal perfusion as compared to regular chow fed mice (665+/-90 ng/(ml h) versus 2393+/-372 ng/(ml h), respectively and 106+/-3 mmHg versus 140+/-2 mmHg, respectively). Hypertriglyceridemia and severe hypercholesterolemia are associated with renal lipid deposition and impaired renin secretion in ApoE-/- mice exposed to high fat diet. These observations further characterize the phenotype of this widely used mouse model and provide a rationale for the use of these mice to study lipid induced organ damage.