The biosynthesis of hepatic cholesterol esters and triglycerides is impaired in mice with a disruption of the gene for stearoyl-CoA desaturase 1

Characterization of fatty acid profile in the liver of SHR/NDmcr-cp (cp/cp) rats, a model of the metabolic syndrome

The fatty acid profile of hepatic lipid in spontaneously hypertensive rats (SHR)/NDmcr-cp (cp/cp) rats (SHR/NDcp), which offer an animal model of the metabolic syndrome, was characterized by comparing those in Wistar Kyoto rats (WKY), SHR, stroke-prone spontaneously hypertensive rats (SHRSP) and SHR/NDmcr-cp (+/+) rats (SHR/ND+) . Hierarchical clustering analysis revealed that SHR/NDcp and the other four strains and/or substrains of rats were clearly disparate in fatty acid profile of hepatic lipid and that the disparity observed was due to the drastic increases in the mass of monounsaturated fatty acids, especially palmitoleic acid and oleic acid, in the liver of SHR/NDcp. Activities of stearoyl-CoA desaturase (SCD) and palmitoyl-CoA chain elongase in hepatic microsomes of SHR/NDcp were markedly higher than those of WKY, SHR, SHRSP and SHR/ND+. Activities of palmitoleoyl-CoA chain elongase in the liver of SHR/NDcp were also higher, but to a lesser extent. mRNA levels of SCD1 and elongation of very long-chain fatty acids (Elovl6), but not Elovl5, in the liver of SHR/NDcp were remarkably higher than those of the other four groups of rats. These results suggest that the enhanced expressions of SCD1 and Elovl6 induced abnormalities in fatty acid profile in the liver of SHR/NDcp.

Omega-3 fatty acid deficiency augments risperidone-induced hepatic steatosis in rats: positive association with stearoyl-CoA desaturase

Psychiatric patients frequently exhibit long-chain n-3 (LCn-3) fatty acid deficits and elevated triglyceride (TAG) production following chronic exposure to second generation antipsychotics (SGAs). Emerging evidence suggests that SGAs and LCn-3 fatty acids have opposing effects on stearoyl-CoA desaturase-1 (SCD1), which plays a pivotal role in TAG biosynthesis. Here we evaluated whether low LCn-3 fatty acid status would augment elevations in rat liver and plasma TAG concentrations following chronic treatment with the SGA risperidone (RSP), and evaluated relationships with hepatic SCD1 expression and activity indices. In rats maintained on the n-3 fatty acid-fortified (control) diet, chronic RSP treatment significantly increased liver SCD1 mRNA and activity indices (18:1/18:0 and 16:1/16:0 ratios), and significantly increased liver, but not plasma, TAG concentrations. Rats maintained on the n-3 deficient diet exhibited significantly lower liver and erythrocyte LCn-3 fatty acid levels, and associated elevations in LCn-6/LCn-3 ratio. In n-3 deficient rats, RSP-induced elevations in liver SCD1 mRNA and activity indices (18:1/18:0 and 16:1/16:0 ratios) and liver and plasma TAG concentrations were significantly greater than those observed in RSP-treated controls. Plasma glucose levels were not altered by diet or RSP, and body weight was lower in RSP- and VEH-treated n-3 deficient rats. These preclinical data support the hypothesis that low n-3 fatty acid status exacerbates RSP-induced hepatic steatosis by augmenting SCD1 expression and activity.

Dietary fat is a lipid source in 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD)-elicited hepatic steatosis in C57BL/6 mice

2,3,7,8-Tetrachlorodibenzo-ρ-dioxin (TCDD) increases fatty acid (FA) transport and FA levels resulting in hepatic steatosis in mice. Diet as a source of lipids was investigated using customized diets, stearoyl-CoA desaturase 1 (Scd1) null mice, and (14)C-oleate (18:1n9) uptake studies. C57BL/6 mice fed with 5, 10, or 15% fat or 50, 60 or 70% carbohydrate diets exhibited increased relative liver weight following gavage with 30 µg/kg TCDD for 168 h. Hepatic lipid extract analysis from mice fed with 5, 10, and 15% fat diets identified a dose-dependent increase in total FAs induced by TCDD. Mice fed with fat diet also exhibited a dose-dependent increase in the dietary essential linoleic (18:2n6) and α-linolenic (18:3n3) acids. No dose-dependent FA increase was detected on carbohydrate diets, suggesting dietary fat as a source of lipids in TCDD-induced steatosis as opposed to de novo lipogenesis. TCDD also induced oleate levels threefold in Scd1 null mice that are incapable of desaturating stearate (18:0). This is consistent with oleate representing > 90% of all monounsaturated FAs in rodent chow. Moreover, TCDD increased hepatic (14)C-oleate levels twofold in wild type and 2.4-fold in Scd1 null mice concurrent with the induction of intestinal and hepatic lipid transport genes (Slc27a, Fabp, Ldlr, Cd36, and Apob). In addition, computational scanning identified putative dioxin response elements and in vivo ChIP-chip analysis revealed regions of aryl hydrocarbon receptor (AhR) enrichment in lipid transport genes differentially regulated by TCDD. Collectively, these results suggest the AhR mediates increased uptake of dietary fats that contribute to TCDD-elicited hepatic steatosis.

Sleep, sleep-disordered breathing and lipid homeostasis: translational evidence from murine models and children

Impaired sleep, particularly in the context of sleep-disordered breathing (SDB), is associated with a vast array of comorbidities, including obesity. It is well known that the etiology of obesity is both complex and multifactorial. Recent trends have shown that obesity rates have risen at an alarming rate in children, and this has likely contributed to an increased prevalence of SDB in children. Like the 'chicken and the egg' hypothesis, the temporal relationship of obesity and SDB is unclear but it is speculated that these two conditions converge to promote a fundamental disruption to normal lipid homeostasis. In this review, the effect of sleep disruption and SDB on lipid homeostasis in both murine and human models will be critically examined, with the intent of demonstrating that disrupted sleep in children is itself a precursor to obesity via disordered lipid homeostasis.

Stearoyl-CoA desaturase-1 (SCD1) augments saturated fatty acid-induced lipid accumulation and inhibits apoptosis in cardiac myocytes

Mismatch between the uptake and utilization of long-chain fatty acids in the myocardium leads to abnormally high intracellular fatty acid concentration, which ultimately induces myocardial dysfunction. Stearoyl-Coenzyme A desaturase-1 (SCD1) is a rate-limiting enzyme that converts saturated fatty acids (SFAs) to monounsaturated fatty acids. Previous studies have shown that SCD1-deficinent mice are protected from insulin resistance and diet-induced obesity; however, the role of SCD1 in the heart remains to be determined. We examined the expression of SCD1 in obese rat hearts induced by a sucrose-rich diet for 3 months. We also examined the effect of SCD1 on myocardial energy metabolism and apoptotic cell death in neonatal rat cardiac myocytes in the presence of SFAs. Here we showed that the expression of SCD1 increases 3.6-fold without measurable change in the expression of lipogenic genes in the heart of rats fed a high-sucrose diet. Forced SCD1 expression augmented palmitic acid-induced lipid accumulation, but attenuated excess fatty acid oxidation and restored reduced glucose oxidation. Of importance, SCD1 substantially inhibited SFA-induced caspase 3 activation, ceramide synthesis, diacylglycerol synthesis, apoptotic cell death, and mitochondrial reactive oxygen species (ROS) generation. Experiments using SCD1 siRNA confirmed these observations. Furthermore, we showed that exposure of cardiac myocytes to glucose and insulin induced SCD1 expression. Our results indicate that SCD1 is highly regulated by a metabolic syndrome component in the heart, and such induction of SCD1 serves to alleviate SFA-induced adverse fatty acid catabolism, and eventually to prevent SFAs-induced apoptosis.

C57Bl/6 N mice on a western diet display reduced intestinal and hepatic cholesterol levels despite a plasma hypercholesterolemia

Background

Small intestine and liver greatly contribute to whole body lipid, cholesterol and phospholipid metabolism but to which extent cholesterol and phospholipid handling in these tissues is affected by high fat Western-style obesogenic diets remains to be determined.

Methods

We therefore measured cholesterol and phospholipid concentration in intestine and liver and quantified fecal neutral sterol and bile acid excretion in C57Bl/6 N mice fed for 12 weeks either a cholesterol-free high carbohydrate control diet or a high fat Western diet containing 0.03% (w/w) cholesterol. To identify the underlying mechanisms of dietary adaptations in intestine and liver, changes in gene expression were assessed by microarray and qPCR profiling, respectively.

Results

Mice on Western diet showed increased plasma cholesterol levels, associated with the higher dietary cholesterol supply, yet, significantly reduced cholesterol levels were found in intestine and liver. Transcript profiling revealed evidence that expression of numerous genes involved in cholesterol synthesis and uptake via LDL, but also in phospholipid metabolism, underwent compensatory regulations in both tissues. Alterations in glycerophospholipid metabolism were confirmed at the metabolite level by phospolipid profiling via mass spectrometry.

Conclusions

Our findings suggest that intestine and liver react to a high dietary fat intake by an activation of de novo cholesterol synthesis and other cholesterol-saving mechanisms, as well as with major changes in phospholipid metabolism, to accommodate to the fat load.

Stearoyl-CoA Desaturase 1 (SCD1) is a key factor mediating diabetes in MyD88-deficient mice

Saturated fatty acids, acting as ligands for toll-like receptor 4 (TLR4), induce inflammation and mediate the development of insulin resistance. Myeloid differentiation factor 88 (MyD88) is an adaptor protein for TLR4. Previously, we found MyD88-deficient mice fed a high-fat diet (HFD) exhibited a severe diabetic phenotype. Stearoyl-CoA Desaturase 1 (SCD1) is the rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids and known as a risk factor of diabetes. In the present study, we found SCD1 was dramatically increased in HFD-fed MyD88-deficient mice liver. This finding showed the novel linkage between MyD88 and SCD1 in the development of diabetes mellitus.

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, 18:3n-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.

Cholesterol and lipoprotein dynamics in a hibernating mammal

Hibernating mammals cease feeding during the winter and rely primarily on stored lipids to fuel alternating periods of torpor and arousal. How hibernators manage large fluxes of lipids and sterols over the annual hibernation cycle is poorly understood. The aim of this study was to investigate lipid and cholesterol transport and storage in ground squirrels studied in spring, summer, and several hibernation states. Cholesterol levels in total plasma, HDL and LDL particles were elevated in hibernators compared with spring or summer squirrels. Hibernation increased plasma apolipoprotein A-I expression and HDL particle size. Expression of cholesterol 7 alpha-hydroxylase was 13-fold lower in hibernators than in active season squirrels. Plasma triglycerides were reduced by fasting in spring but not summer squirrels. In hibernators plasma β-hydroxybutyrate was elevated during torpor whereas triglycerides were low relative to normothermic states. We conclude that the switch to a lipid-based metabolism during winter, coupled with reduced capacity to excrete cholesterol creates a closed system in which efficient use of lipoproteins is essential for survival.

Daily intake of cod or salmon for 2 weeks decreases the 18:1n-9/18:0 ratio and serum triacylglycerols in healthy subjects

Intake of fish and omega-3 (n-3) fatty acids is associated with a reduced concentration of plasma triacylglycerols (TAG) but the mechanisms are not fully clarified. Stearoyl-CoA desaturase-1 (SCD1) activity, governing TAG synthesis, is affected by n-3 fatty acids. Peripheral blood mononuclear cells (PBMC) display expression of genes involved in lipid metabolism. The aim of the present study was to estimate whether intake of lean and fatty fish would influence n-3 fatty acids composition in plasma phospholipids (PL), serum TAG, 18:1n-9/18:0 ratio in plasma PL, as well as PBMC gene expression of SCD1 and fatty acid synthase (FAS). Healthy males and females (n = 30), aged 20-40, consumed either 150 g of cod, salmon, or potato (control) daily for 15 days. During intervention docosahexaenoic acid (DHA, 22:6n-3) increased in the cod group (P < 0.05), while TAG concentration decreased (P < 0.05). In the salmon group both eicosapentaenoic acid (EPA, 20:5n-3) and DHA increased (P < 0.05) whereas TAG concentration and the 18:1n-9/18:0 ratio decreased (P < 0.05). Reduction of the 18:1n-9/18:0 ratio was associated with a corresponding lowering of TAG (P < 0.05) and an increase in EPA and DHA (P < 0.05). The mRNA levels of SCD1 and FAS in PBMC were not significantly altered after intake of cod or salmon when compared with the control group. In conclusion, both lean and fatty fish may lower TAG, possibly by reducing the 18:1n-9/18:0 ratio related to allosteric inhibition of SCD1 activity, rather than by influencing the synthesis of enzyme protein.

Plasma phospholipid fatty acid concentrations and risk of gastric adenocarcinomas in the European Prospective Investigation into Cancer and Nutrition (EPIC-EURGAST)

BACKGROUND

Epidemiologic data suggest that diet is a risk factor in the etiology of gastric cancer. However, the role of dietary fatty acids, a modifiable risk factor, remains relatively unexplored.

OBJECTIVE

The objective of this study was to determine the association of plasma phospholipid fatty acid concentrations, as biomarkers of exogenous and endogenously derived fatty acids, with the risk of gastric adenocarcinoma in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition-Europe Gastric Cancer (EPIC-EURGAST).

DESIGN

Fatty acids were measured by gas chromatography in prediagnostic plasma phospholipids from 238 cases matched to 626 controls by age, sex, study center, and date of blood donation. Conditional logistic regression models adjusted for Helicobacter pylori infection status, BMI, smoking, physical activity, education, and energy intake were used to estimate relative cancer risks.

RESULTS

Positive risk associations for gastric cancer were observed in the highest compared with the lowest quartiles of plasma oleic acid (OR: 1.72; 95% CI: 1.01, 2.94), di-homo-γ-linolenic acid (OR: 1.92; 95% CI: 1.10, 3.35), α-linolenic acid (OR: 3.20; 95% CI: 1.70, 6.06), and the ratio of MUFAs to saturated fatty acids, as an indicator of stearoyl-CoA desaturase-1 enzyme activity (OR: 1.40; 95% CI: 0.81, 2.43). An inverse risk association was observed with the ratio of linoleic to α-linolenic acid (OR: 0.37; 95% CI: 0.20, 0.66).

CONCLUSION

These data suggest that a specific prediagnostic plasma phospholipid fatty acid profile, characterized mainly by high concentrations of oleic acid, α-linolenic acid, and di-homo-γ-linolenic acid, which presumably reflect both a complex dietary pattern and altered fatty acid metabolism, may be related to increased gastric cancer risk.

Dietary phospholipids ameliorate fructose-induced hepatic lipid and metabolic abnormalities in rats

Overconsumption of fructose results in hepatic dyslipidemia, which has a documented correlation with metabolic syndrome. We examined whether the ingestion of phospholipids (PL) from soybeans prevents fructose-induced metabolic abnormalities. Rats were fed either a fructose-free diet (C), a 60% fructose diet (F), or a 60% fructose plus 3% PL diet (F-PL) for 10 wk. At wk 8, plasma glucose concentrations after glucose loading were significantly higher in rats fed the F diet than in rats fed the C and F-PL diets, which did not differ from one another. The concentrations of hepatic TG, diglycerides, ceramides, and oleates in rats fed the F diet for 10 wk was significantly higher than those in rats fed the C diet. The increases were prevented by concurrent PL ingestion; concentrations did not differ between the F-PL and C groups. Dietary fructose increased the mRNA expression of SREBP1, ChREBP, and genes related to lipogenesis. PL completely inhibited these increases. Furthermore, reflecting the difference at the mRNA level, lipogenic enzyme activities were greater in rats fed the F diet than in rats fed the C diet, and PL ingestion suppressed the increased activities by fructose feeding. Treatment of cultured Hep-G2 cells with fructose for 24 h increased the levels of SREBP1 and ChREBP nuclear proteins, which were suppressed by culture with purified PL components, especially phosphatidylethanolamine and phosphatidylinositol. These findings indicate that PL prevents fructose-induced metabolic abnormalities in association with alterations of the hepatic lipid profile by inhibiting de novo lipogenesis.

Aryl hydrocarbon receptor-mediated induction of Stearoyl-CoA desaturase 1 alters hepatic fatty acid composition in TCDD-elicited steatosis

2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD) induces hepatic dyslipidemia mediated by the aryl hydrocarbon receptor (AhR). Stearoyl-CoA desaturase 1 (Scd1) performs the rate-limiting step in monounsaturated fatty acid (MUFA) synthesis, desaturating 16:0 and 18:0 into 16:1n7 and 18:1n9, respectively. To further examine the role of Scd1 in TCDD-induced hepatotoxicity, comparative studies were performed in Scd1(+/+) and Scd1(-/-) mice treated with 30 μg/kg TCDD. TCDD induced Scd1 activity, protein, and messenger RNA (mRNA) levels approximately twofold. In Scd1(+/+) mice, hepatic effects were marked by increased vacuolization and inflammation and a 3.5-fold increase in serum alanine aminotransferase (ALT) levels. Hepatic triglycerides (TRGs) were induced 3.9-fold and lipid profiling by gas chromatography-mass spectroscopy measured a 1.9-fold increase in fatty acid (FA) levels, consistent with the induction of lipid transport genes. Induction of Scd1 altered FA composition by decreasing saturated fatty acid (SFA) molar ratios 8% and increasing MUFA molar ratios 9%. Furthermore, ChIP-chip analysis revealed AhR enrichment (up to 5.7-fold), and computational analysis identified 16 putative functional dioxin response elements (DREs) within Scd1 genomic loci. Band shift assays confirmed AhR binding with select DREs. In Scd1(-/-) mice, TCDD induced minimal hepatic vacuolization and inflammation, while serum ALT levels remained unchanged. Although Scd1 deficiency attenuated TCDD-induced TRG accumulation, overall FA levels remained unchanged compared with Scd1(+/+) mice. In Scd1(-/-) mice, TCDD induced SFA ratios 8%, reduced MUFA ratios 13%, and induced polyunsaturated fatty acid ratios 5% relative to treated Scd1(+/+) mice. Collectively, these results suggest that AhR regulation of Scd1 not only alters lipid composition but also contributes to the hepatotoxicity of TCDD.

Transcriptional profile of genes involved in oxidative stress and antioxidant defense in a dietary murine model of steatohepatitis

Oxidative stress is a core abnormality responsible for disease progression in nonalcoholic steatohepatitis (NASH). However, the relevant pathways that contribute to oxidative damage in vivo remain poorly understood. Here we explore the gene-expression patterns related to oxidative stress, antioxidant defense, and reactive oxygen metabolism in an established dietary murine model of NASH. C57BL/6 mice were placed on either a methionine- and choline-deficient (MCD) or a control (CTL) diet for 6 weeks. Hepatic oxidative damage and the development of NASH were monitored by biochemical and histologic indices. Analysis of 84 oxidative stress-related genes was performed by real-time reverse transcription polymerase chain reaction (PCR) in the livers of the two groups of mice. Mice on the MCD diet showed increased ALT, histologic features of NASH, and oxidative liver damage with increases in 4-hydroxynonenal and 3-nitrotyrosine. Of the genes analyzed, the GPx family were most significantly upregulated, whereas SCD1 was most significantly downregulated. Other genes that were significantly upregulated included Fmo2 and peroxiredoxins, whereas genes downregulated included Catalase and Serpinb1b. Our data demonstrate that oxidative stress-related genes are differentially expressed in the livers of mice with diet-induced NASH. These findings have important implications for NASH pathogenesis and the development of novel therapeutic strategies for patients with this condition.

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 6mg/kg/d), paliperidone (1.5, 3, and 6mg/kg/d), olanzapine (2.5, 5, and 10mg/kg/d), quetiapine (5, 10, and 20mg/kg/d), haloperidol (1, and 3mg/kg/d) or vehicle through their drinking water for 40days. 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 18:1n-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.

Consumption of high-oleic acid ground beef increases HDL-cholesterol concentration but both high- and low-oleic acid ground beef decrease HDL particle diameter in normocholesterolemic men

On the basis of previous results from this laboratory, this study tested the hypothesis that ground beef high in MUFA and low in SFA would increase the HDL-cholesterol (HDL-C) concentration and LDL particle diameter. In a crossover dietary intervention, 27 free-living normocholesterolemic men completed treatments in which five 114-g ground beef patties/wk were consumed for 5 wk with an intervening 4-wk washout period. Patties contained 24% total fat with a MUFA:SFA ratio of either 0.71 (low MUFA, from pasture-fed cattle) or 1.10 (high MUFA, from grain-fed cattle). High-MUFA ground beef provided 3.21 g more 18:1(n-9), 1.26 g less 18:0, 0.89 g less 16:0, and 0.36 g less 18:1(trans) fatty acids per patty than did the low-MUFA ground beef. Both ground beef interventions decreased plasma insulin and HDL(2) and HDL(3) particle diameters and increased plasma 18:0 and 20:4(n-6) (all P ≤ 0.05) relative to baseline values. Only the high-MUFA ground beef intervention increased the HDL-C concentration from baseline (P = 0.02). The plasma TG concentration was positively correlated with the plasma insulin concentration (r = 0.40; P < 0.001) and negatively correlated with HDL-C (r = -0.47; P < 0.001) and plasma 18:0 (r = -0.24; P < 0.01). Plasma insulin and HDL diameters were not correlated (r = 0.01; P > 0.50), indicating that reductions in these measures were not coordinately regulated. The data indicate that dietary beef interventions have effects on risk factors for cardiovascular disease that are independent (insulin, HDL diameters) and dependent (HDL-C) on beef fatty acid composition.

Metabolic changes in skin caused by Scd1 deficiency: a focus on retinol metabolism

We previously reported that mice with skin-specific deletion of stearoyl-CoA desaturase-1 (Scd1) recapitulated the skin phenotype and hypermetabolism observed in mice with a whole-body deletion of Scd1. In this study, we first performed a diet-induced obesity experiment at thermoneutral temperature (33°C) and found that skin-specific Scd1 knockout (SKO) mice still remain resistant to obesity. To elucidate the metabolic changes in the skin that contribute to the obesity resistance and skin phenotype, we performed microarray analysis of skin gene expression in male SKO and control mice fed a standard rodent diet. We identified an extraordinary number of differentially expressed genes that support the previously documented histological observations of sebaceous gland hypoplasia, inflammation and epidermal hyperplasia in SKO mice. Additionally, transcript levels were reduced in skin of SKO mice for genes involved in fatty acid synthesis, elongation and desaturation, which may be attributed to decreased abundance of key transcription factors including SREBP1c, ChREBP and LXRα. Conversely, genes involved in cholesterol synthesis were increased, suggesting an imbalance between skin fatty acid and cholesterol synthesis. Unexpectedly, we observed a robust elevation in skin retinol, retinoic acid and retinoic acid-induced genes in SKO mice. Furthermore, SEB-1 sebocytes treated with retinol and SCD inhibitor also display an elevation in retinoic acid-induced genes. These results highlight the importance of monounsaturated fatty acid synthesis for maintaining retinol homeostasis and point to disturbed retinol metabolism as a novel contributor to the Scd1 deficiency-induced skin phenotype.

Targeting thermogenesis and related pathways in anti-obesity drug discovery

The health consequences of the obesity epidemic are a huge burden on patients and society. Yet it remains an unmet therapeutic need. Lifestyle or behaviour modification, although desirable, seems to benefit only a few and bariatric surgery is not an option for all and not without risks. Nevertheless, bariatric surgery is currently the gold standard in terms of weight loss therapy and any weight loss agent will be in combination with management of lifestyle modification. Sadly, there is a poor history for the pharmacological treatment of obesity and repeated safety concerns have attracted intense regulatory scrutiny. Indeed, recent market withdrawals leave us with just one agent approved for the long term treatment of obesity and that is only mildly efficacious in terms of weight loss, although it is beneficial in terms of metabolic health. There are two broad pharmacological approaches that can be applied in obesity drug discovery: reduce intake (or absorption) or increase expenditure (thermogenesis) of calories. In this review we will look at the latter approach. We will cover regulatory requirements and the rationale for this approach. We believe that post-obese subjects display abnormal metabolic responses to weight loss that almost inevitably leads to weight regain. We will then explore a number of approaches that potentially increase thermogenesis in humans. The challenge we have is in accumulating enough human data to validate this approach using drugs.

Plasma omega 3 polyunsaturated fatty acid status and monounsaturated fatty acids are altered by chronic social stress and predict endocrine responses to acute stress in titi monkeys

Disturbances in fatty acid (FA) metabolism may link chronic psychological stress, endocrine responsiveness, and psychopathology. Therefore, lipid metabolome-wide responses and their relationships with endocrine (cortisol, insulin, and adiponectin) responsiveness to acute stress (AS) were assessed in a primate model of chronic social stress (CS). Compared to controls (not exposed to CS), CS increased (P≤0.05) circulating triacylglycerol (TG) and phosphatidylethanolamine (PE) n-6/n-3 and reduced (P≤0.05) cholesterol ester (CE) 16:1n7 and phosphatidylcholine (PC) 18:1n7, suggesting lower omega-3 FA status and stearoyl-CoA desaturase activity, respectively. Cortisol responses to AS positively correlated with TG n-6/n-3 (r=0.93; P=0.007), but only in CS monkeys. The adiponectin response to AS inversely correlated with CE n-6/n3 (r=-0.89; P=0.045) and positively with TG 16:1n7 (r=0.98; P=0.004), only in CS monkeys. Our results are consistent with previously reported FA profiles in stress-related psychopathology and suggest that compositional changes of specific lipid FAs may form new functional markers of chronic psychological stress.

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.

The fatty acid desaturation index of blood lipids, as a biomarker of hepatic stearoyl-CoA desaturase expression, is a predictive factor of breast cancer risk

PURPOSE OF REVIEW

This review summarizes epidemiological data linking the fatty acid desaturation index measured in blood lipids, as a biomarker of hepatic stearoyl-CoA desaturase activity, the key enzyme involved in the synthesis of monounsaturated fatty acids from saturated fatty acids, to breast cancer risk. The biological plausibility of this association is discussed.

RECENT FINDINGS

Epidemiological cohort studies reported an association between a high saturated to monounsaturated fatty acid ratio measured in blood lipids, indicating low stearoyl-CoA desaturase-1 activity, and decreased breast cancer risk. The suppression of stearoyl-CoA desaturase expression reduces cancer cell proliferation and in-vitro invasiveness, and dramatically impairs tumor formation and growth. These effects could not be overcome by supplying exogenous monounsaturated fatty acids.

SUMMARY

Epidemiological findings, in accordance with experimental data, suggested that decreased hepatic stearoyl-CoA desaturase expression/activity may be related to decreased risk of breast cancer.

Relationships between hepatic stearoyl-CoA desaturase-1 activity and mRNA expression with liver fat content in humans

Stearoyl-CoA desaturase-1 (SCD1) has gained much interest as a future drug target to treat fatty liver and its consequences. However, there are few and inconsistent human data about expression and activity of this important enzyme. We investigated activity and expression of SCD1 and their relationships with liver fat (LF) content in human liver samples. Fifty subjects undergoing liver surgery were studied. SCD1 activity was estimated from the ratio of oleate (C18:1) to stearate (C18:0) within lipid subfractions. Furthermore, SCD1 mRNA expression and LF content were measured. Similarly to previous studies, we observed a strong positive correlation between LF content and the C18:1/C18:0 ratio in the combined fatty acid (FA) fractions (r = 0.96, P < 0.0001), which could be interpreted as higher SCD1 activity with increasing LF. However, hepatic SCD1 mRNA expression did not correlate with LF (r = 0.16, P = 0.13). To solve these conflicting data, we analyzed the FA composition of hepatic lipid subfractions. With increasing LF content the amount of FAs from the triglyceride (TG) fraction increased (r = 0.96, P < 0.0001), whereas the FAs from the phospholipid (PL) fraction remained unchanged (r = -0.17, P = 0.19). Of these two major lipid fractions, the C18:1/C18:0 ratio in TG was 16-fold higher than in PL. Supporting the SCD1 mRNA expression data, the C18:1/C18:0 ratio of the TG or PL fraction did not correlate with LF (r = 0.26, P = 0.12 and r = 0.08, P = 0.29). We provide novel information that SCD1 activity and mRNA expression appear not to be elevated in subjects with high LF content. We suggest that the FA composition of lipid subclasses, rather than of mixed lipids, should be analyzed to estimate SCD1 activity.

Stearoyl CoA desaturase 1: role in cellular inflammation and stress

Stearoyl CoA desaturase 1 (SCD1) catalyzes the rate-limiting step in the production of MUFA that are major components of tissue lipids. Alteration in SCD1 expression changes the fatty acid profile of these lipids and produces diverse effects on cellular function. High SCD1 expression is correlated with metabolic diseases such as obesity and insulin resistance, whereas low levels are protective against these metabolic disturbances. However, SCD1 is also involved in the regulation of inflammation and stress in distinct cell types, including β-cells, adipocytes, macrophages, endothelial cells, and myocytes. Furthermore, complete loss of SCD1 expression has been implicated in liver dysfunction and several inflammatory diseases such as dermatitis, atherosclerosis, and intestinal colitis. Thus, normal cellular function requires the expression of SCD1 to be tightly controlled. This review summarizes the current understanding of the role of SCD1 in modulating inflammation and stress.

Efficacy of long-term ezetimibe therapy in patients with nonalcoholic fatty liver disease

BACKGROUND

Hyperlipidemia, insulin resistance, and oxidative stress can heavily contribute to the initiation and progression of nonalcoholic fatty liver disease (NAFLD). Currently, there is no established treatment for this disease. Recently, several studies have shown that ezetimibe (EZ), a lipid-lowering drug, attenuates liver steatosis in an experimental NAFLD model. This study was designed to assess the efficacy of long-term EZ monotherapy in patients with NAFLD.

METHODS

A total of 45 patients with newly diagnosed liver biopsy-proven NAFLD were treated with EZ (10 mg/day) for 24 months. NAFLD-related biochemical parameters, imaging by computerized tomography, and liver biopsy were studied before and after treatment.

RESULTS

Ezetimibe therapy significantly improved NAFLD-related metabolic parameters including visceral fat area, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-R), triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-Ch), oxidative-LDL, the net electronegative charge modified-LDL, profiles of lipoprotein particle size and fatty acids component, and estimated desaturase activity. EZ therapy also significantly lowered serum alanine aminotransferase and high-sensitivity C-reactive protein levels, whereas no significant changes were found in serum type IV collagen 7S, adiponectin, leptin, and resistin levels. Histological features of steatosis grade (P = 0.0003), necroinflammatory grade (P = 0.0456), ballooning score (P = 0.0253), and NAFLD activity score (NAS) (P = 0.0007) were significantly improved from baseline. However, the fibrosis stage was not significantly (P = 0.6547) changed.

CONCLUSION

The results in this study suggest that the long-term EZ therapy can lead to improvement in metabolic, biochemical, and histological abnormalities of NAFLD. Therefore, EZ may be a promising agent for treatment of NAFLD.

Soraphen A, an inhibitor of acetyl CoA carboxylase activity, interferes with fatty acid elongation

Acetyl CoA carboxylase (ACC1 and ACC2) generates malonyl CoA, a substrate for de novo lipogenesis (DNL) and an inhibitor of mitochondrial fatty acid β-oxidation (FAO). Malonyl CoA is also a substrate for microsomal fatty acid elongation, an important pathway for saturated (SFA), mono- (MUFA) and polyunsaturated fatty acid (PUFA) synthesis. Despite the interest in ACC as a target for obesity and cancer therapy, little attention has been given to the role ACC plays in long chain fatty acid synthesis. This report examines the effect of pharmacological inhibition of ACC on DNL and palmitate (16:0) and linoleate (18:2, n-6) metabolism in HepG2 and LnCap cells. The ACC inhibitor, soraphen A, lowers cellular malonyl CoA, attenuates DNL and the formation of fatty acid elongation products derived from exogenous fatty acids, i.e., 16:0 and 18:2, n-6; IC(50)∼5nM. Elevated expression of fatty acid elongases (Elovl5, Elovl6) or desaturases (FADS1, FADS2) failed to override the soraphen A effect on SFA, MUFA or PUFA synthesis. Inhibition of fatty acid elongation leads to the accumulation of 16- and 18-carbon unsaturated fatty acids derived from 16:0 and 18:2, n-6, respectively. Pharmacological inhibition of ACC activity will not only attenuate DNL and induce FAO, but will also attenuate the synthesis of very long chain saturated, mono- and polyunsaturated fatty acids.

Mechanisms and genes involved in enhancement of HIV infectivity by tobacco smoke

HIV infection is more common among smokers than nonsmokers, and, remarkably, HIV-infected individuals are about 3 times more likely to smoke than the uninfected general population. However, the relationship between tobacco smoking and HIV/AIDS disease progression remains controversial. In this study, we demonstrate a potent enhancing effect of aqueous tobacco smoke extract (TSE) on HIV infectivity that is nicotine-independent. This increased infectivity is neither NF-κB mediated nor a direct result of oxidative stress, as it cannot be blocked by antioxidants. On the contrary, TSE itself was found to possess significant antioxidant potential, enabling it to protect the viability of both infected cells and HIV virions in the presence of peroxide. Assessment of TSE-induced alterations in cellular gene expression that may be involved in increasing HIV infectivity in T cells showed that TSE up-regulates some genes known to be capable of enhancing HIV and HCV infection, or protecting HIV, but down-regulates several genes involved in cellular defense and antigen presentation. These results demonstrate that tobacco smoke can enhance HIV infectivity, possibly by a combination of direct (antioxidant) and indirect (gene-based) mechanisms. This raises the concern that smoking may thereby increase the risk of acquisition or progression of HIV infection.

Loss of stearoyl-CoA desaturase activity leads to free cholesterol synthesis through increased Xbp-1 splicing

Stearoyl-CoA desaturase-1 (SCD-1) is the rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids (MUFA), which are required for efficient neutral lipid esterification. In the present investigation, we demonstrate that loss of SCD-1 activity increases free cholesterol (FC) content and induces Xbp-1 splicing. We assessed the small molecule SCD-1 inhibitor A939572 on [(14)C]stearate incorporation into neutral lipids and found its incorporation into triglyceride was unaffected, whereas labeled cholesteryl ester (CE) content was notably diminished. Using either A939572 or liver knockout mice (LKO), we show that loss of SCD-1 activity increases FC levels and activates the liver X receptor (LXR) pathway. Using adenoviral delivery of an active form of X-box binding protein-1 (Xbp-1; Xbp-1s), we show increased sterol synthesis only when cells lack the ability to generate MUFA. The results of the cell-based model were confirmed in LKO mice where fasting-refeeding decreased CE, increased FC, and increased Xbp-1s. On the basis of the present data, we conclude that SCD-1 activity is required for efficient cholesterol esterification to MUFA and that loss of its activity increases Xbp-1s-mediated FC synthesis. It is likely that the accumulation of FC enhances Xbp-1 splicing, induces LXR transcriptional activity, and increases ABCA1 (ATP-binding cassette transporter A1) expression to maintain cholesterol homeostasis.

Metabolic consequences of intermittent hypoxia: relevance to obstructive sleep apnea

Obstructive sleep apnea (OSA) is recurrent obstruction of the upper airway leading to sleep fragmentation and intermittent hypoxia (IH) during sleep. There is growing evidence from animal models of OSA that IH is independently associated with metabolic dysfunction, including dyslipidemia and insulin resistance. The precise mechanisms by which IH induces metabolic disturbances are not fully understood. Over the last decade, several groups of investigators developed a rodent model of IH, which emulates the oxyhemoglobin profile in human OSA. In the mouse model, IH induces dyslipidemia, insulin resistance and pancreatic endocrine dysfunction, similar to those observed in human OSA. Recent reports provided new insights in possible mechanisms by which IH affects lipid and glucose metabolism. IH may induce dyslipidemia by up-regulating lipid biosynthesis in the liver, increasing adipose tissue lipolysis with subsequent free fatty acid flux to the liver, and inhibiting lipoprotein clearance. IH may affect glucose metabolism by inducing sympathetic activation, increasing systemic inflammation, increasing counter-regulatory hormones and fatty acids, and causing direct pancreatic beta-cell injury. IH models of OSA have improved our understanding of the metabolic impact of OSA, but further studies are needed before we can translate recent basic research findings to clinical practice.

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.

Stearoyl-coenzyme A desaturase 1 inhibition and the metabolic syndrome: considerations for future drug discovery

PURPOSE OF REVIEW

The metabolic syndrome has become a leading health concern in developed countries. In the search for strategies to combat this growing problem, stearoyl-CoA desaturase 1 (SCD1) inhibition has been proposed as an attractive therapeutic strategy. However, recent studies warn of potentially harmful consequences of SCD1 inhibition. The purpose of this review is to discuss recent insights into the potential for SCD1 inhibitors as viable metabolic syndrome therapeutics.

RECENT FINDINGS

SCD1 converts saturated fatty acids (SFAs) to monounsaturated fatty acids (MUFAs). Although SCD1 inhibition protects against diet-induced obesity, hepatic steatosis, and insulin resistance, recent studies have demonstrated that the accumulation of SCD1 substrates (SFA) can promote inflammation, atherosclerosis, steatohepatitis, and pancreatic beta cell dysfunction in preclinical rodent models. This suggests SCD1 may play a critical role in suppressing inflammatory diseases by shuttling proinflammatory SFAs into less biologically active MUFA-enriched neutral lipids. Given this, SCD1 inhibitors given in conjunction with anti-inflammatory agents may provide a useful strategy to prevent the metabolic syndrome without deleterious side-effects seen with SCD1 inhibition alone.

SUMMARY

SCD1 inhibitors continue to hold promise as metabolic syndrome therapeutics; yet consideration must be taken to avoid the proinflammatory side-effects secondary to accumulation SCD1 substrates (SFAs).

Decrease in membrane phospholipid unsaturation induces unfolded protein response

Various kinds of fatty acids are distributed in membrane phospholipids in mammalian cells and tissues. The degree of fatty acid unsaturation in membrane phospholipids affects many membrane-associated functions and can be influenced by diet and by altered activities of lipid-metabolizing enzymes such as fatty acid desaturases. However, little is known about how mammalian cells respond to changes in phospholipid fatty acid composition. In this study we showed that stearoyl-CoA desaturase 1 (SCD1) knockdown increased the amount of saturated fatty acids and decreased that of monounsaturated fatty acids in phospholipids without affecting the amount or the composition of free fatty acid and induced unfolded protein response (UPR), evidenced by increased expression of C/EBP homologous protein (CHOP) and glucose-regulated protein 78 (GRP78) mRNAs and splicing of Xbox-binding protein 1 (XBP1) mRNA. SCD1 knockdown-induced UPR was rescued by various unsaturated fatty acids and was enhanced by saturated fatty acid. Lysophosphatidylcholine acyltransferase 3 (LPCAT3), which incorporates preferentially polyunsaturated fatty acids into phosphatidylcholine, was up-regulated in SCD1 knockdown cells. Knockdown of LPCAT3 synergistically enhanced UPR with SCD1 knockdown. Finally we showed that palmitic acid-induced UPR was significantly enhanced by LPCAT3 knockdown as well as SCD1 knockdown. These results suggest that a decrease in membrane phospholipid unsaturation induces UPR.

Palmitoleate attenuates palmitate-induced Bim and PUMA up-regulation and hepatocyte lipoapoptosis

BACKGROUND & AIMS

Saturated free fatty acids induce hepatocyte lipoapoptosis. This lipotoxicity involves an endoplasmic reticulum stress response, activation of JNK, and altered expression and function of Bcl-2 proteins. The mono-unsaturated free fatty acid palmitoleate is an adipose-derived lipokine which suppresses free fatty acid-mediated lipotoxicity by unclear mechanisms. Herein we examined the mechanisms responsible for cytoprotection.

METHODS

We employed isolated human and mouse primary hepatocytes, and the Huh-7 and Hep 3B cell lines for these studies. Cells were incubated in presence and absence of palmitate (16:0), stearate (18:0), and or palmitoleate (16:1, n-7).

RESULTS

Palmitoleate significantly reduced lipoapoptosis by palmitate or stearate in both primary cells and cell lines. Palmitoleate accentuated palmitate-induced steatosis in Huh-7 cells excluding inhibition of steatosis as a mechanism for reduced apoptosis. Palmitoleate inhibited palmitate induction of the endoplasmic reticulum stress response as demonstrated by reductions in CHOP expression, eIF2-alpha phosphorylation, XBP-1 splicing, and JNK activation. Palmitate increased expression of the BH3-only proteins PUMA and Bim, which was attenuated by palmitoleate. Consistent with its inhibition of PUMA and Bim induction, palmitoleate prevented activation of the downstream death mediator Bax.

CONCLUSIONS

These data suggest palmitoleate inhibits lipoapoptosis by blocking endoplasmic reticulum stress-associated increases of the BH3-only proteins Bim and PUMA.

Plasma fatty acid composition, estimated desaturase activities, and intakes of energy and nutrient in Japanese men with abdominal obesity or metabolic syndrome

To examine predictive factors for abdominal obesity or metabolic syndrome, we investigated the association of plasma fatty acid composition, estimated desaturase activity, and nutrient intakes, with abdominal obesity or metabolic syndrome in Japanese males. Clinical characteristics, the fatty acid composition of plasma cholesteryl esters, and energy and nutrient intakes were analyzed in 3 groups: metabolic syndrome (MS, n=24), abdominal obesity (OB, n=43), and control (n=27). The estimated desaturase activities were calculated by the ratio of 16:1n-7/16:0, 18:3n-6/18:2n-6, and 20:4n-6/20:3n-6 in plasma cholesteryl esters as surrogates of the measure of the delta 9, delta 6, delta 5 desaturase (D9-16D, D6D and D5D) activities, respectively. Plasma fatty acid composition did not differ significantly between the OB group and the control group. The MS group had higher levels of palmitoleic, oleic, and gamma-linolenic acids, but a lower level of linoleic acid than the control. Stronger D6D activity and weaker D5D activity were observed in the OB group. A higher level of D9-16D activity as well as a higher level of D6D activity and a lower level of D5D activity was observed in the MS group. A logistic regression analysis showed that the low D5D activity and high D9-16D activity were predictive of the development of abdominal obesity from controls (odds ratio=0.39, p<0.05) and metabolic syndrome from abdominal obesity (odds ratio=2.44, p<0.05), respectively. In the multiple linear regression analysis, D5D activity positively correlated with the intake of eicosapentaenoic acid (EPA). In conclusion, the estimated D5D activity was a predictive factor for abdominal obesity and the estimated D9-16D activity was a predictive factor for developing metabolic syndrome from abdominal obesity in Japanese male subjects. Dietary intake of EPA would play an important role in preventing abdominal obesity and the development of metabolic syndrome.

Protective effect of Codonopsis lanceolata root extract against alcoholic fatty liver in the rat

Alcohol intake remains the most important cause of fatty liver throughout the world. The current study was undertaken to determine whether dietary supplementation with Codonopsis lanceolata root water extract attenuates the development of alcoholic fatty liver in rats and to elucidate the molecular mechanism for such an effect. Male Sprague-Dawley rats were fed normal diet (ND), ethanol diet (ED) (36% of total energy from ethanol), or 0.5% C. lanceolata root extract-supplemented ethanol diet (ED+C) for 8 weeks. C. lanceolata root water extract supplemented to rats with chronic alcohol consumption ameliorated the ethanol-induced accumulations of hepatic cholesterol and triglyceride. Chronic alcohol consumption up-regulated the hepatic expression of genes involved in inflammation, fatty acid synthesis, and cholesterol metabolism, including tumor necrosis factor alpha (TNFalpha), liver X receptor alpha (LXRalpha), sterol regulatory element-binding protein (SREBP)-1c, fatty acid synthase, acetyl-coenzyme A carboxylase alpha (ACC), stearoyl-coenzyme A desaturase 1, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), and low-density lipoprotein receptor (LDLR). The ethanol-induced up-regulations of TNFalpha, LXRalpha, SREBP-1c, HMGR, and LDLR genes in the liver were reversed by feeding C. lanceolata root water extract for 8 weeks. Moreover, ethanol-induced decreases in the ratio of phospho-5'-AMP-activated protein kinase (AMPK) alpha/AMPKalpha and phospho-ACC/ACC protein levels in the liver were significantly restored (135% and 35% increases, respectively, P < .05) by supplementing them with C. lanceolata root water extract. In conclusion, C. lanceolata root water extract appears to be protective against alcoholic fatty liver through the regulation of SREBP-1c, LXRalpha, HMGR, and LDLR genes and by the phosphorylation of AMPKalpha and ACC, which are implicated in lipid metabolism.

Effect of maternal undernutrition on vascular expression of micro and messenger RNA in newborn and aging offspring

The aim of this study was to test the hypothesis that maternal undernutrition (MUN) alters offspring vascular expression of micro-RNAs (miRNAs), which, in turn, could regulate the expression of a host of genes involved with angiogenesis and extracellular matrix remodeling. The expression of miRNA and mRNA in the same aortic specimens in 1-day-old (P1) and 12-mo-old offspring aortas of dams, which had 50% food restriction from gestation day 10 to term, was determined by specific rat miRNA and DNA arrays. MUN significantly downregulated the expression of miRNAs 29c, 183, and 422b in the P1 group and 200a, 129, 215, and 200b in the 12-mo group, and upregulated the expression of miRNA 189 in the P1 group and 337 in the 12-mo group. The predicted target genes of the miRNAs altered in the two age groups fell into the categories of: 1) structural genes, such as collagen, elastin, and enzymes involved in ECM remodeling; and 2) angiogenic factors. MUN primarily altered the expression of mRNAs in the functional category of cell cycle/mitosis in the P1 group and anatomic structure and apoptosis in the 12-mo age group. Several of the predicted target genes of miRNAs altered in response to MUN were identified by the DNA array including integrin-beta(1) in the P1 aortas and stearoyl-CoA desaturase-1 in the 12-mo age groups. These results are consistent with the hypothesis that MUN modulation of offspring gene expression may be mediated in part by a miRNA mechanism.

De novo lipogenesis and stearoyl-CoA desaturase are coordinately regulated in the human adipocyte and protect against palmitate-induced cell injury

De novo lipogenesis (DNL) is paradoxically up-regulated by its end product, saturated fatty acids (SAFAs). We tested the hypothesis that SAFA-induced up-regulation of DNL reflects coordinate up-regulation of elongation and desaturation pathways for disposal of SAFAs and production of monounsaturated fatty acids to protect cells from SAFA toxicity. Human preadipocytes were differentiated in vitro for 14 days with [U-(13)C]palmitate (0-200 microM) to distinguish exogenous fatty acids from those synthesized by DNL. Exogenous palmitate up-regulated DNL (p < 0.001) concomitantly with SCD and elongation (each p < 0.001). Adipocytes from some donors were intolerant to high palmitate concentrations (400 microM). Palmitate-intolerant cells showed lower TG accumulation. They had lower expression of SCD mRNA and less monounsaturated fatty acids in TG, emphasizing the importance of desaturation for dealing with exogenous SAFAs. There was greater [U-(13)C]palmitate incorporation in phospholipids. SCD knockdown with small interfering RNA caused down-regulation of DNL and of expression of DNL-related genes, with reduced membrane fluidity (p < 0.02) and insulin sensitivity (p < 0.01), compared with scrambled small interfering RNA controls. There was preferential channeling of DNL-derived versus exogenous palmitate into elongation and of DNL-derived versus exogenous stearate into desaturation. DNL may not act primarily to increase fat stores but may serve as a key regulator, in tandem with elongation and desaturation, to maintain cell membrane fluidity and insulin sensitivity within the human adipocyte.