SCD1 mRNA Research Articles

CAMP Response Element Binding Protein1 Is Essential for Activation of Steroyl Co-Enzyme A Desaturase 1 (Scd1) in Mouse Lung Type II Epithelial Cells

Cyclic AMP Response Element-Binding Protein 1 (Creb1) is a transcription factor that mediates cyclic adenosine 3′, 5′-monophosphate (cAMP) signalling in many tissues. Creb1−/− mice die at birth due to respiratory failure and previous genome-wide microarray analysis of E17.5 Creb1−/− fetal mouse lung identified important Creb1-regulated gene targets during lung development. The lipogenic enzymes stearoyl-CoA desaturase 1 (Scd1) and fatty acid synthase (Fasn) showed highly reduced gene expression in Creb1−/− lungs. We therefore hypothesized that Creb1 plays a crucial role in the transcriptional regulation of genes involved in pulmonary lipid biosynthetic pathways during lung development. In this study we confirmed that Scd1 and Fasn mRNA levels were down regulated in the E17.5 Creb1−/− mouse lung while the lipogenic-associated transcription factors SrebpF1, C/ebpα and Pparγ were increased. In vivo studies using germline (Creb1−/−) and lung epithelial-specific (Creb1EpiΔ/Δ) Creb1 knockout mice showed strongly reduced Scd1, but not Fasn gene expression and protein levels in lung epithelial cells. In vitro studies using mouse MLE-15 epithelial cells showed that forskolin-mediated activation of Creb1 increased both Scd1 gene expression and protein synthesis. Additionally, MLE15 cells transfected with a dominant-negative ACreb vector blocked forskolin-mediated stimulation of Scd1 gene expression. Lipid profiling in MLE15 cells showed that dominant-negative ACreb suppressed forskolin-induced desaturation of ether linked lipids to produce plasmalogens, as well as levels of phosphatidylethanolamine, ceramide and lysophosphatidylcholine. Taken together these results demonstrate that Creb1 is essential for the induction and maintenance of Scd1 in developing fetal mouse lung epithelial cells.

Dual probiotic strains suppress high fructose-induced metabolic syndrome

To investigate the effect of novel probiotics on the clinical characteristics of high-fructose induced metabolic syndrome. Male Wistar rats aged 4 wk were fed a 70% w/w high-fructose diet (n = 27) or chow diet (n = 9) for 3 wk to induce metabolic syndrome, the rats were then randomized into groups and administered probiotic [Lactobacillus curvatus (L. curvatus) HY7601 and Lactobacillus plantarum (L. plantarum) KY1032] at 10(9) cfu/d or 10(10) cfu/d or placebo by oral gavage for 3 wk. Food intake and body weight were measured once a week. After 6 wk, the rats were fasted for 12 h, then anesthetized with diethyl ether and sacrificed. Blood samples were taken from the inferior vena cava for plasma analysis of glucose, insulin, C-peptide, total-cholesterol, triglycerides and thiobarbituric acid-reacting substances. Real-time polymerase chain reaction was performed using mouse-specific Taqman probe sets to assess genes related to fatty acid β-oxidation, lipogenesis and cholesterol metabolism in the liver. Target gene expression was normalized to the housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase. Rodents fed a high-fructose diet developed clinical characteristics of the metabolic syndrome including increased plasma glucose, insulin, triglycerides, total cholesterol and oxidative stress levels, as well as increased liver mass and liver lipids compared to chow fed controls. Probiotic treatment (L. curvatus HY7601 and L. plantarum KY1032) at high (10(10) cfu/d) or low dosage (10(9) cfu/d) lowered plasma glucose, insulin, triglycerides and oxidative stress levels. Only high-dose probiotic treatment reduced liver mass and liver cholesterol. Probiotic treatment reduced lipogenesis via down-regulation of SREBP1, FAS and SCD1 mRNA levels and increased β-oxidation via up-regulation of PPARα and CPT2 mRNA levels. Probiotic L. curvatus HY7601 and L. plantarum KY1032 combined suppressed the clinical characteristics of high-fructose-induced metabolic syndrome, therefore, may provide a natural alternative for the treatment of diet-induced metabolic syndrome.

Short communication: In vivo deposition of [1-13C]vaccenic acid and the product of its Δ9-desaturation, [1-13C]rumenic acid, in the body tissues of lactating goats fed oils

This study was conducted in lactating goats with the aim of measuring the deposition of trans-11 18:1 (vaccenic acid, VA) and the product of its Δ9-desaturation, cis-9, trans-11 18:2 (rumenic acid, RA), in the major tissues that are involved in lipid metabolism in the lactating ruminant (i.e., mammary secretory tissue, liver, and omental and perirenal adipose tissues) and examining its potential link with variations in the expression of genes encoding Δ9-desaturase [stearoyl-CoA desaturases 1 and 5 (SCD1 and SCD5)]. Eight lactating goats were fed a diet supplemented with sunflower oil (n=4) or sunflower oil plus fish oil and additional starch (n=4), based on the hypothesis that these dietary treatments could affect Δ9-desaturase gene expression in specific tissues. A chemical tracer, 1.5g of [1-13C]VA as nonesterified fatty acid, was delivered by jugular injection. Goats were slaughtered 4 d later, and tissue samples were collected for the measurement of [13C]VA and [13C]RA enrichment and SCD1 and SCD5 expression. The addition of fish oil and additional starch to a diet containing sunflower oil was associated with several changes in [13C]VA and [13C]RA enrichment. These results support previous studies suggesting that mammary secretory tissue is the primary site of Δ9-desaturation in lactating goats. In adipose tissues, the [13C]VA + [13C]RA enrichment was consistent with a net uptake of circulating fatty acids to reconstitute body reserves at the end of the lactation cycle. The putative uptake of [13C]RA synthesized by other tissues precludes any conclusion from being drawn regarding potential Δ9-desaturation in the liver of goats, despite the detection of SCD1 and SCD5 mRNA in this tissue. Finally, no significant effect of dietary treatment was observed for SCD1 or SCD5 mRNA abundance in the mammary secretory tissue or other body tissues.

Adiponectin and leptin secretion are differentially modulated in subcutaneous and visceral adipose tissue by endoplasmic reticulum stress

Obesity is associated with altered adipokine secretion but the underlying mechanisms responsible for this phenomenon remains unknown. Endoplasmic reticulum stress (ERS) is common alteration in several cell types during obesity.ObjectiveTo evaluate whether ERS alters adiponectin and leptin production in subcutaneus (SAT) and viceral (VAT) adipose tissue in mice and in cultured adipocytes.MethodsMice were fed chow diet supplemented with pioglitazone (120mg/kg) for 2 w, in order to stimulate adipokine production and injected with tunicamicyn (2μg/g body weight) for 8 or 24h before euthanasia. For in vitro analysis, primary SAT and VAT adipocytes were cultured with pioglitazone with or without tunicamicyn for 8 or 24h.ResultsATF6 and BiP mRNA increased in SAT and VAT of mice injected with tunicamicyn and in cultured adipocytes but at higher magnitude in VAT. Pioglitazone augmented perilipin, SREBP1 and SCD1 mRNA content as expected but interestingly, tunicamicyn reduced this induction. Adiponectin content in adipose tissue and serum was dramatically reduced in mice injected with tunicamicyn and leptin increased.ConclusionsTunicamicyn induces ERS in both adipose depots but at higher magnitude in VAT. ERS impairs the pioglitazone effect on adipose tissue gene expression. ERS reduces adiponectin secretion but increases leptin production in adipose tissue. This work is supported by CONACyT (84757).

Unusual increase of Scd1 and Elovl6 expression in rat inguinal adipose tissue

Abstract It is generally accepted that the location of body fat deposits may play an important role in the risk of developing some endocrine and metabolic diseases. We have studied the effect of food restriction and food restriction/refeeding, often practiced by individuals trying to lose body weight, on the expression of genes which are associated with obesity and certain metabolic disorders in inguinal, epididymal, and perirenal rat white adipose tissues. Gene expression was analyzed by real time semi-quantitative polymerase chain reaction and by Western blot. We found that prolonged food restriction caused a significant decrease of body and adipose tissue mass as well as the increase of Scd1 and Elovl6 gene expressions in all main rat adipose tissue deposits. Food restriction/refeeding caused increases of: a) Scd1 and Elovl6 mRNA levels in adipose tissue, b) Scd1 protein level and c) desaturation index in adipose tissue. The increased expression of both genes was unusually high in inguinal adipose tissue. The results suggest that the increase of Scd1 and Elovl6 gene expressions in white adipose tissue by prolonged food restriction and prolonged food restriction/refeeding may contribute to accelerated fat recovery that often occurs in individuals after food restriction/refeeding.

Differential Induction of Stearoyl-CoA Desaturase 1 and 2 Genes by Fibrates in the Liver of Rats

The administration of fibrates (fenofibrate, bezafibrate and clofibric acid) to rats induced stearoyl-CoA desaturase (SCD) in the liver, and increased relative expression of mRNAs encoding SCD1 and SCD2 in dose- and time-dependent manners. The magnitudes of the increases in SCD2 mRNA level caused by fenofibrate and clofibric acid were much higher than those of SCD1 at relatively higher doses of the fibrates, and a relatively long time (7 or 14 d) was required for significant induction of SCD2 mRNA expression compared with that of SCD1. Although the absolute number of transcripts for SCD2 was 1,800 times lower than that of SCD1 in the control liver, it was strikingly increased by fibrates. These results suggest that differential regulations operate for the gene expression between SCD1 and SCD2, and that the physiological significance of SCD2 is distinct from that of SCD1 in the liver.

Effects of polyunsaturated fatty acids from plant oils and algae on milk fat yield and composition are associated with mammary lipogenic and SREBF1 gene expression

The main aim of the present study was to examine the effects of long-term supplementing diets with saturated or unprotected polyunsaturated fatty acids from two different plant oils rich in either n-3 or n-6 fatty acids (FAs) plus docosahexaenoic acid (DHA)-rich algae on mammary gene expression and milk fat composition in lactating dairy cows. Gene expression was determined from mammary tissue and milk epithelial cells. Eighteen primiparous German Holstein dairy cows in mid-lactation were randomly assigned into three dietary treatments that consist of silage-based diets supplemented with rumen-stable fractionated palm fat (SAT; 3.1% of the basal diet dry matter, DM), or a mixture of linseed oil (2.7% of the basal diet DM) plus DHA-rich algae (LINA; 0.4% of the basal diet DM) or a mixture of sunflower oil (2.7% of the basal diet DM) plus DHA-rich algae (SUNA; 0.4% of the basal diet DM), for a period of 10 weeks. At the end of the experimental period, the cows were slaughtered and mammary tissues were collected to study the gene expression of lipogenic enzymes. During the last week, the milk yield and composition were determined, and milk was collected for FA measurements and the isolation of milk purified mammary epithelial cells (MECs). Supplementation with plant oils and DHA-rich algae resulted in milk fat depression (MFD; yield and percentage). The secretion of de novo FAs in the milk was reduced, whereas the secretion of trans-10,cis-12-CLA and DHA were increased. These changes in FA secretions were associated in mammary tissue with a joint down-regulation of mammary lipogenic enzyme gene expression (stearoyl-CoA desaturase, SCD1; FA synthase, FASN) and expression of the regulatory element binding transcription factor (SREBF1), whereas no effect was observed on lipoprotein lipase (LPL) and glycerol-3-phosphate acyltransferase 1, mitochondrial (GPAM). A positive relationship between mammary SCD1 and SREBF1 mRNA abundances was observed, suggesting a similar regulation for these genes. Such data on mammary gene expression in lactating cows presenting MFD contribute to strengthen the molecular mechanisms that govern milk fat synthesis in the mammary glands. In purified MEC, the dietary treatments had no effect on gene expressions. Differences between mammary tissue and milk purified MEC gene expression were attributed to the effect of lipid supplements on the number of milk purified MEC and its RNA quality, which are determinant factors for the analysis of gene expression using milk cells.

Jacaric Acid, a Linolenic Acid Isomer with a Conjugated Triene System, Reduces Stearoyl-CoA Desaturase Expression in Liver of Mice

Conjugated fatty acid is a collective term used for fatty acids with conjugated double bond systems. Seed oils from certain plants include conjugated linolenic acids, which have a conjugated triene system and are geometrical and positional isomers of α-linolenic acid. One of these isomers, jacaric acid (JA, 8c, 10t, 12c-18:3), has not been examined widely. Therefore, we investigated the absorption and metabolism of JA in normal animals (ICR mice). An oral dose of JA of 5 mg/day for 1 week had no effects on body weight, food intake and tissue weight of mice. JA was detected in the serum, kidney, liver, lung and epididymal white adipose tissue. Analysis of the fatty acid composition in liver and white adipose tissue showed a tendency to increase levels of saturated fatty acids (SFAs) such as palmitic acid (16:0) and stearic acid (18:0) and to decrease levels of monounsaturated fatty acids (MUFAs) such as palmitoleic acid (16:1) and oleic acid (18:1). Thus, JA treatment decreased the desaturation index (16:1/16:0, 18:1/18:0) in liver and white adipose tissue. This index is used as an indicator of the activity of stearoyl coenzyme A desaturase (SCD), an endoplasmic reticulum enzyme that catalyzes the biosynthesis of MUFAs from SFAs. The change in this index indicates that JA inhibited SCD activity in ICR mice, and further experiments showed that JA also decreased the expression level of SCD-1 mRNA. Inhibition of SCD activity may have anti-obesity and anti-diabetes effects, and therefore the findings in this study suggest that JA may be effective for preventing obesity and diabetes.

Distinct regulation of stearoyl-CoA desaturase 1 gene expression by cis and trans C18:1 fatty acids in human aortic smooth muscle cells

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 48h at 100μM. 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.

Omega-3 fatty acid deficiency increases stearoyl-CoA desaturase expression and activity indices in rat liver: Positive association with non-fasting plasma triglyceride levels

Although omega-3 ( n−3) fatty acids negatively regulate triglyceride biosynthesis, the mechanisms mediating this effect are poorly understood, and emerging evidence suggests that stearoyl-CoA desaturase (Scd1) is required for de novo triglyceride biosynthesis. To investigate this mechanism, we determined the effects of perinatal n−3 deficiency and postnatal repletion on rat liver Scd1 mRNA expression and activity indices (liver 16:1/16:0 and 18:1/18:0 ratios), and determined relationships with postprandial (non-fasting) plasma triglyceride levels. Rats were fed conventional diets with or without the n−3 fatty acid precursor α-linolenic acid (ALA, 18:3 n−3) during perinatal development (E0-P100), and a subset of rats fed the ALA− diet were switched to the ALA+ diet post-weaning (P21-P100, repletion). Compared with controls, rats fed the ALA− diet exhibited significantly lower liver long-chain n−3 fatty acid compositions and elevations in monounsaturated fatty acid composition, both of which were normalized in repleted rats. Liver Scd1 mRNA expression and activity indices (16:1/16:0 and 18:1/18:0 ratios) were significantly greater in n−3 deficient rats compared with controls and repleted rats. Among all rats, liver Scd1 mRNA expression was positively correlated with liver 18:1/18:0 and 16:1/16:0 ratios. Plasma triglyceride levels, but not glucose or insulin levels, were significantly greater in n−3 deficient rats compared with controls and repleted rats. Liver Scd1 mRNA expression and activity indices were positively correlated with plasma triglyceride levels. These preclinical findings demonstrate that n−3 fatty acid status is an important determinant of liver Scd1 mRNA expression and activity, and suggest that down-regulation of Scd1 is a mechanism by which n−3 fatty acids repress constitutive triglyceride biosynthesis.

Cloning of comparative gene identification-58 gene in avian species and investigation of its developmental and nutritional regulation in chicken adipose tissue1

Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme of lipolysis in chicken adipose tissue. Its regulation is not fully understood. Recent studies suggest ATGL may be regulated by physical protein-protein interactions. Comparative gene identification 58 (CGI-58) has been identified as an activator of ATGL in mice. The purpose of the current study was to clone and sequence the CGI-58 gene in avian species and to investigate its regulation during development, fasting, and refeeding. Here, we report the cloning and sequencing of the complete coding sequence of CGI-58 and the deduced AA sequences for the domestic chicken, turkey, and Coturnix quail. The CGI-58 protein is a 343-AA protein in the chicken and quail, and a 344-AA protein in the turkey. Sequence comparisons with the human and mouse show that the CGI-58 gene is highly conserved among avian and mammalian species, with complete identities at the predicted lipid-binding site. Cell fractionation of chicken fat cells and stromal-vascular cells revealed that CGI-58 is expressed primarily in mature adipocytes (P < 0.01). When compared in multiple organs and tissues, avian CGI-58 is expressed predominantly in the adipose tissue (P < 0.001), similar to ATGL. To understand CGI-58 expression during adipose tissue development, its mRNA expression was measured along with ATGL and stearoyl CoA desaturase (SCD-1) mRNA, an adipogenic marker, in embryos and adults. Messenger RNA expression of CGI-58 increased (P < 0.05) immediately after hatching, concurrent with peak ATGL expression. It is interesting that CGI-58 remained somewhat increased at posthatch d 11 and 33 as SCD-1 mRNA expression increased (P < 0.05). To evaluate the response of CGI-58 to nutritional status, chickens and quail were fasted for 24 h and subsequently refed. After the fasting period, CGI-58 mRNA was induced (P < 0.05) for both chickens and quail and was returned to control levels upon refeeding. The ATGL mRNA responded similarly, increasing dramatically after fasting and quickly decreasing with refeeding. The direct relationship between CGI-58 and ATGL mRNA expression indicates a role for CGI-58 in activating ATGL-mediated lipolysis in avian species.

Non-receptor-mediated actions are responsible for the lipid-lowering effects of iodothyronines in FaO rat hepatoma cells

Iodothyronines influence lipid metabolism and energy homeostasis. Previous studies demonstrated that 3,5-l-diiodothyronine (T(2)), as well as 3,3',5-L-triiodothyronine (T(3)), was able to both prevent and reverse hepatic steatosis in rats fed a high-fat diet, and this effect depends on a direct action of iodothyronines on the hepatocyte. However, the involvement of thyroid hormone receptors (TRs) in mediating the lipid-lowering effect of iodothyronines was not elucidated. In this study, we investigated the ability of T(2) and T(3) to reduce the lipid overloading using the rat hepatoma FaO cells defective for functional TRs. The absence of constitutive mRNA expression of both TRα1 and TRβ1 in FaO cells was verified by RT-qPCR. To mimic the fatty liver condition, FaO cells were treated with a fatty acid mixture and then exposed to pharmacological doses of T(2) or T(3) for 24 h. Lipid accumulation, mRNA expression of the peroxisome proliferator-activated receptors (PPAR-α, -γ, -δ) the acyl-CoA oxidase (AOX), and the stearoyl CoA desaturase (SCD1), as well as fuel-stimulated O(2) consumption in intact cells, were evaluated. Lipid accumulation was associated with an increase in triacylglycerol content, PPARγ mRNA expression, and a decrease in PPARδ and SCD1 mRNA expression. The addition of T(2) or T(3) to lipid-overloaded cells resulted in i) reduction in lipid content; ii) downregulation of PPARα, PPARγ, and AOX expression; iii) increase in PPARδ expression; and iv) stimulation of mitochondrial uncoupling. These data demonstrate, for the first time, that in the hepatocyte, the lipid-lowering actions of both T(2) and T(3) are not mediated by TRs.

Atypical antipsychotic medications increase postprandial triglyceride and glucose levels in male rats: Relationship with stearoyl-CoA desaturase activity

Recent preclinical and clinical evidence suggests that the stearoyl-CoA desaturase-1 ( Scd1) enzyme plays a key role in the regulation of triglyceride (TG) biosynthesis and insulin sensitivity, and in vitro studies have found that antipsychotic medications up-regulate Scd1 mRNA expression. To investigate these effects in vivo, rats were treated with risperidone (1.5, 3, and 6 mg/kg/d), paliperidone (1.5, 3, and 6 mg/kg/d), olanzapine (2.5, 5, and 10 mg/kg/d), quetiapine (5, 10, and 20 mg/kg/d), haloperidol (1, and 3 mg/kg/d) or vehicle through their drinking water for 40 days. Effects on liver Scd1 mRNA expression and an index of Scd1 activity (the plasma 18:1/18:0 ratio, ‘desaturation index’) were determined, as were postprandial plasma triglyceride (TG), glucose, insulin, and polyunsaturated fatty acid (PUFA) levels. All atypical antipsychotics increased the plasma 18:1/18:0 ratio, but not liver Scd1 mRNA expression, at doses found to also increase plasma TG levels. Among all rats (n = 122), the plasma 18:1/18:0 ratio accounted for 56% of the variance in TG concentrations. The plasma 18:1/18:0 ratio was also positively associated with erythrocyte and heart membrane phospholipid 18:1 n-9 composition. All antipsychotics except risperidone increased glucose levels at specific doses, and none of the antipsychotics significantly altered insulin levels. The plasma 18:1/18:0 ratio accounted for 20% of the variance in glucose levels. Plasma omega-3 and omega-6 PUFA levels were inversely correlated with the plasma 18:1/18:0 ratio and TG and glucose levels. These in vivo data demonstrate that different atypical antipsychotic medications increase the plasma 18:1/18:0 ratio in association with elevations in postprandial TG and glucose levels, and that concomitant elevations in PUFA biosynthesis oppose these effects.

Ncb5or Deficiency Increases Fatty Acid Catabolism and Oxidative Stress

The endoplasmic reticulum-associated NADH cytochrome b(5) oxidoreductase (Ncb5or) is widely distributed in animal tissues. Ncb5or(-/-) mice develop diabetes at age 7 weeks and have increased susceptibility to the diabetogenic oxidant streptozotocin. Ncb5or deficiency also results in lipoatrophy and increased hepatocyte sensitivity to cytotoxic effects of saturated fatty acids. Here we investigate the mechanisms of these phenomena in prediabetic Ncb5or(-/-) mice and find that, despite increased rates of fatty acid uptake and synthesis and higher stearoyl-CoA desaturase (SCD) expression, Ncb5or(-/-) liver accumulates less triacylglycerol (TAG) than wild type (WT). Increased fatty acid catabolism and oxidative stress are evident in Ncb5or(-/-) hepatocytes and reflect increased mitochondrial content, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) expression, fatty acid oxidation rates, oxidative stress response gene expression, and oxidized glutathione content. Ncb5or(-/-) hepatocytes readily incorporate exogenous fatty acids into TAG but accumulate more free fatty acids (FFA) and have greater palmitate-induced oxidative stress responses and cell death than WT, all of which are alleviated by co-incubation with oleate via TAG channeling. A high fat diet rich in palmitate and oleate stimulates both lipogenesis and fatty acid catabolism in Ncb5or(-/-) liver, resulting in TAG levels similar to WT but increased intracellular FFA accumulation. Hepatic SCD-specific activity is lower in Ncb5or(-/-) than in WT mice, although Ncb5or(-/-) liver has a greater increase in Scd1 mRNA and protein levels. Together, these findings suggest that increased FFA accumulation and catabolism and oxidative stress are major consequences of Ncb5or deficiency in liver.

Growth hormone enhances arachidonic acid metabolites in a growth hormone transgenic mouse.

In a transgenic growth hormone (GH) mouse model, highly elevated GH increases overall growth and decreases adipose depots while low or moderate circulating GH enhances adipose deposition with differential effects on body growth. Using this model, the effects of low, moderate, and high chronic GH on fatty acid composition were determined for adipose and hepatic tissue and the metabolites of 20:4n-6 (arachidonic acid) were characterized to identify metabolic targets of action of elevated GH. The products of Δ-9 desaturase in hepatic, but not adipose, tissue were reduced in response to elevated GH. Proportional to the level of circulating GH, the products of Δ-5 and Δ-6 were increased in both adipose and hepatic tissue for the omega-6 lipids (e.g., 20:4n-6), while only the hepatic tissues showed an increase for omega-3 lipids (e.g., 22:6n-3). The eicosanoids, PGE₂ and 12-HETE, were elevated with high GH but circulating thromboxane was not. Hepatic PTGS1 and 2 (COX1 and COX 2), SOD1, and FADS2 (Δ-6 desaturase) mRNAs were increased with elevated GH while FAS mRNA was reduced; SCD1 (stearoyl-coenzyme A desaturase) and SCD2 mRNA did not significantly differ. The present study showed that GH influences the net flux through various aspects of lipid metabolism and especially the desaturase metabolic processes. The combination of altered metabolism and tissue specificity suggest that the regulation of membrane composition and its effects on signaling pathways, including the production and actions of eicosanoids, can be mediated by the GH regulatory axis.

Modulation of palmitate-induced endoplasmic reticulum stress and apoptosis in pancreatic β-cells by stearoyl-CoA desaturase and Elovl6

Induction of endoplasmic reticulum (ER) stress and apoptosis by elevated exogenous saturated fatty acids (FAs) plays a role in the pathogenesis of β-cell dysfunction and loss of islet mass in type 2 diabetes. Regulation of monounsaturated FA (MUFA) synthesis through FA desaturases and elongases may alter the susceptibility of β-cells to saturated FA-induced ER stress and apoptosis. Herein, stearoyl-CoA desaturase (SCD)1 and SCD2 mRNA expression were shown to be induced in islets from prediabetic hyperinsulinemic Zucker diabetic fatty (ZDF) rats, whereas SCD1, SCD2, and fatty acid elongase 6 (Elovl6) mRNA levels were markedly reduced in diabetic ZDF rat islets. Knockdown of SCD in INS-1 β-cells decreased desaturation of palmitate to MUFA, lowered FA partitioning into complex neutral lipids, and increased palmitate-induced ER stress and apoptosis. Overexpression of SCD2 increased desaturation of palmitate to MUFA and attenuated palmitate-induced ER stress and apoptosis. Knockdown of Elovl6 limited palmitate elongation to stearate, increasing palmitoleate production and attenuating palmitate-induced ER stress and apoptosis, whereas overexpression of Elovl6 increased palmitate elongation to stearate and palmitate-induced ER stress and apoptosis. Overall, these data support the hypothesis that enhanced MUFA synthesis via upregulation of SCD2 activity can protect β-cells from elevated saturated FAs, as occurs in prediabetic states. Overt type 2 diabetes is associated with diminished islet expression of SCD and Elovl6, and this can disrupt desaturation of saturated FAs to MUFAs, rendering β-cells more susceptible to saturated FA-induced ER stress and apoptosis.

Skeletal Muscle Gene Expression Profile Is Modified by Dietary Protein Source and Calcium during Energy Restriction

Background/Aims: The potential of whey protein and calcium to modify skeletal muscle gene expression during energy restriction (ER) was investigated in a model of diet-induced obesity. Methods: Obese C57BL/6J mice received casein (calcium 0.4%) and two different high-calcium (1.8%) whey protein-based [whey protein isolate (WPI) + Ca and α-lactalbumin + Ca] diets for ER. Results: Compared to casein, WPI and α-lactalbumin-based diets altered 208 and 287 genes, respectively, of which 186 genes were common to WPI and α-lactalbumin diets. These genes represented 31 KEGG pathways. The Wnt signaling was the most enriched pathway among the 101 genes regulated by α-lactalbumin only, whereas the 22 genes regulated by WPI only were not associated with KEGG pathways. Unlike casein, WPI and α-lactalbumin diets decreased Aldh1a7, Fasn, leptin, Nr4a3 and Scd1 mRNA expression, indicating dietary protein source-dependent alterations in muscle lipid and fatty acid metabolism. Muscle weight or lean body mass maintenance did not differ between groups although modest changes in hypertrophy/atrophy signaling were found. Conclusion: The skeletal muscle gene expression profile is modified by the dietary protein source and calcium during ER which may explain, at least in part, the greater anti-obesity effect of whey proteins and calcium compared to casein.

Endurance training-induced accumulation of muscle triglycerides is coupled to upregulation of stearoyl-CoA desaturase 1

Stearoyl-CoA desaturase (SCD), a rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids, has recently been shown to be a critical control point in regulation of liver and skeletal muscle metabolism. Herein, we demonstrate that endurance training significantly increases both SCD1 mRNA and protein levels in the soleus muscle, whereas it does not affect SCD1 expression in the EDL muscle and liver. Desaturation index (18:1Δ9/18:0 ratio), an indirect indicator of SCD1 activity, was also significantly higher (3.6-fold) in soleus of trained rats compared with untrained animals. Consistent with greater SCD1 expression/activity, the contents of free fatty acids, diacylglycerol, and triglyceride were elevated in soleus of trained rats. However, training did not affect lipid concentration in EDL and liver. Additionally, endurance training activated the AMP-activated protein kinase pathway as well as increased peroxisome proliferator-activated receptor (PPAR)-δ and PPARα gene expression and activity in soleus and liver. Increased lipid accumulation in soleus was coupled with elevated protein levels of fatty acid synthase, mRNA levels of diacylglycerol acyltransferase and glycerol-3-phosphate transferase, as well as increased levels of proteins involved in fatty acid transport (fatty acid translocase/CD36, fatty acid transport protein 1). Interestingly, sterol regulatory element-binding protein (SREBP)-1c expression and SREBP-1 protein levels were not affected by exercise training. Together, the obtained data suggest that SCD1 upregulation plays an important role in adaptation of oxidative muscle to endurance training.

Maternal undernutrition alters fat cell size distribution, but not lipogenic gene expression, in the visceral fat of the late gestation guinea pig fetus

This study investigated the development of adipose tissue in the guinea pig and the impact of maternal undernutrition on the structural and functional characteristics of perirenal adipose tissue in the dam and fetus. Date-mated guinea pigs were provided with either ad libitum feed (Control, C) or 85% of food intake per body weight of the Controls (Undernutrition, UN). Maternal (C, n = 6; UN, n = 7) perirenal adipose tissue (PAT) was collected at 60 d gestation and fetal PAT was collected at 50 d (C, n = 4) and 60 d (C, n = 8 and UN, n = 7) gestation (term, 69 d). The expression of stearoyl-CoA desaturase (SCD-1), fatty acid synthase (FAS), lipoprotein lipase (LPL), leptin and glycerol 3 phosphate dehydrogenase (G3PDH) mRNA and glucose transporters 1 and 4 (GLUT1 and GLUT4) was determined by Real Time PCR. There was no effect of maternal UN on total or relative PAT mass in the pregnant dam. There was an increase in G3PDH, but not LPL, leptin, FAS or GLUT4 mRNA expression, in UN dams compared to Controls ( P < 0.05). In the fetal guinea pig there was no effect of maternal UN on total or relative PAT mass, however, the UN fetuses had a higher percentage of larger lipid locules in their PAT compared to Controls ( P < 0.05). The expression of FAS, LPL, SCD-1, leptin, G3PDH and GLUT4 mRNA in PAT was not different between the Control and UN fetuses. These results support previous studies which have demonstrated that maternal undernutrition is associated with an increased accumulation of visceral adipose tissue in utero, and extend them by showing that maternal undernutrition results in early changes in the size distribution of lipid locules in visceral fat depots that precede changes in lipogenic gene expression.

Elevated Delta-6 desaturase ( FADS2) gene expression in the prefrontal cortex of patients with bipolar disorder

Although evidence suggests that a dysregulation in polyunsaturated fatty acid (PUFA) homeostasis may contribute to the pathoetiology of bipolar disorder (BD), there is currently nothing known about the expression of genes that mediate long-chain PUFA biosynthesis in BD patients. In the present study we determined FADS1 (Δ5 desaturase), FADS2 (Δ6 desaturase), HELO1 [ ELOVL5] (elongase), PEX19 (peroxisome), and SCD (stearoyl-CoA desaturase [Δ9 desaturase]) mRNA expression in the postmortem prefrontal cortex of non-psychiatric controls ( n = 12) and BD patients ( n = 12) by real-time reverse transcriptase polymerase chain reaction (RT-PCR). Changes in the activities of corresponding enzyme products were estimated from fatty acid product: precursor ratios. After correcting for multiple comparisons, FADS2 mRNA expression was significantly greater in BD patients relative to controls (+27%, p = 0.004). Indices of Δ6 desaturase activity, including 20:4/18:2 (+18%, p = 0.15) and 20:3/18:2 (+12%, p = 0.25) ratios, were numerically, but not significantly, greater in BD patients relative to controls. There were no significant group differences in FADS1 (+17%, p = 0.32), HELO1 (+4%, p = 0.81), PEX19 (−2%, p = 0.91), and SCD (+4%, p = 0.85) mRNA expression, or indices of Δ5 desaturase (+5%, 0.59), elongase (+3%, p = 0.62), and stearoyl-CoA desaturase (−11%, p = 0.10) activities. These preliminary findings demonstrate that FADS2 mRNA expression is significantly and selectively elevated in the prefrontal cortex of BD patients, and may contribute to dysregulated central PUFA biosynthesis and pro-inflammatory signaling implicated in the pathophysiology of BD.