Conjugated linoleic acid reduces hepatic steatosis, improves liver function, and favorably modifies lipid metabolism in obese insulin-resistant rats

Disruption of the peripheral biological clock may play a role in sleep deprivation-induced dysregulation of lipid metabolism in both the daytime and nighttime phases

STUDY OBJECTIVES

This study aimed to examine the effect of sleep deprivation (SD) on lipid metabolism or lipid metabolism regulation in the liver and white adipose tissue (WAT) during the light and dark phases and explored the possible mechanisms underlying the diurnal effect of SD on lipid metabolism associated with clock genes.

METHODS

Male C57BL/6J mice aged 2 months were deprived of sleep daily for 20 h for ten consecutive days with weakly forced locomotion. The body weights and food consumption levels of the SD and control mice were recorded, and the mice were then sacrificed at ZT (zeitgeber time) 2 and ZT 14. The peripheral clock genes, enzymes involved in fat synthesis and catabolism in the WAT, and melatonin signalling pathway-mediated lipid metabolism in the liver were assessed. Untargeted metabolomics and tandem mass tag (TMT) proteomics were used to identify differential lipid metabolism pathways in the liver.

RESULTS

Bodyweight gain and daily food consumption were dramatically elevated after SD. Profound disruptions in the diurnal regulation of the hepatic peripheral clock and enzymes involved in fat synthesis and catabolism in the WAT were observed, with a strong emphasis on hepatic lipid metabolic pathways, while melatonin signalling pathway-mediated lipid metabolism exhibited moderate changes.

CONCLUSIONS

In mice, ten consecutive days of SD increased body weight gain and daily food consumption. In addition, SD profoundly disrupted lipid metabolism in the WAT and liver during the light and dark periods. These diurnal changes may be related to disorders of the peripheral biological clock.

Conjugated linoleic acid isomers induced dyslipidemia and lipoatrophy are exacerbated by rosiglitazone in ApoE null mice fed a Western diet

BACKGROUND: Insulin sensitizers have been used to treat Type 2 diabetes. However, their non-negligible side effects have led to cardiovascular concerns and the withdrawal of a member, rosiglitazone. OBJECTIVE: We combined conjugated linoleic acid (CLA) with rosiglitazone to test for amelioration of side effects posed by rosiglitazone in vivo. METHODS: We utilized ApoE null mice fed with Western diet (WD) to test our hypothesis. Mice were fed WD, with or without CLA administration, for 12 weeks. CLA utilized in our study consisted of a 1:1 ratio of 95% pure c9,t11, and t10,c12 isomers at a concentration of 0.1% w/v in fat-free milk. Starting from Week 12, select mice received rosiglitazone. RESULTS: It was found that mice receiving CLA from Week 0 and rosiglitazone from Week 12 had the lowest body weight and exacerbated hepatomegaly. Although these mice had attenuated insulin resistance compared to mice receiving only Western diet, they display a marked increase in total plasma cholesterol and low-density lipoprotein (LDL) cholesterol. Mice receiving early CLA administration developed hyperleptinemia, which was not restored by rosiglitazone. CONCLUSION: Taken together, against the background of ApoE null genotype and WD feeding, simultaneous administration of 1:1 CLA and rosiglitazone led to dyslipidemic lipoatrophy.

Effects of resistance training and nigella sativa on type 2 diabetes: implications for metabolic markers, low-grade inflammation and liver enzyme production

CONTEXT

Proper nutrition and exercise are effective strategies to improve overall metabolic health in diabetic patients.

OBJECTIVE

This study evaluated the effects of Nigella sativa (NS) supplementation during resistance training (RT) on some biochemical variables in type 2 diabetes patients.

METHODS

Forty patients were assigned to groups: RT + NS (RN), NS, RT + placebo (RP), and control (CO). RT was performed and NS was consumed for 8 weeks. Blood samples were collected at rest immediately before and after the 8 week intervention.

RESULTS

RT or NS by themselves reduced HOMA-IR, insulin, glucose, TG, TC, LDL, ESR, CRP, AST, ALT and ALP, and increased HDL and HOMA-S. The combination of RT and NS, rather than each intervention alone, had significant effects on reduction of HOMA-IR, insulin, ESR and CRP as well as increases in HDL, HOMA-β/S.

CONCLUSION

RT combined with NS is sometimes a better strategy compared to single interventions for improving diabetes related biomarkers in type 2 diabetic patients.

Evaluating the effect of a mixture of two main conjugated linoleic acid isomers on hepatic steatosis in HepG2 cellular model

Hepatic steatosis is an early form of non-alcoholic fatty liver disease (NAFLD), caused by abnormal fat deposition in the hepatocytes. Conjugated linoleic acid (CLA) is a group of positional and geometric dienoic isomers of linoleic acid that attract significant attention because of its beneficial effects on chronic diseases such as cancer, obesity, and metabolic syndrome. This study examined the influence of a mixture of two main CLA isomers (CLA-mix) on lipid accumulation and lipid metabolism-related genes using HepG2 cells treated with palmitic acid (PA) as an in vitro model for hepatic steatosis. Methods and Results: HepG2 cells were treated for 24 h: control (BSA), model (BSA + PA), and treated groups (BSA-PA + non-toxic concentrations of CLA-mix). Intracellular lipid deposition, triglyceride (TG), total cholesterol (TC) and gene expression were measured by Oil-Red O staining, colorimetric assay kits and real-time PCR, respectively. CLA-mix at high concentrations had significantly decreased intracellular total lipid and TG deposition compared to the model group. However, none of the CLA-mix concentrations had a significant effect on the intracellular TC level. CLA-mix significantly increased the expression of some genes mainly regulated by PPARα but did not alter the expression of lipogenesis-related genes. Conclusions: These results demonstrate that high concentrations of CLA-mix protect against hepatic steatosis and play a role in regulating fatty acid oxidation and bile excretion through the PPARα pathway. It is suggested that the effect of different ratios of two main CLA isomers on the amount and ratio of bile compounds be investigated in future studies.

Cis-9, Trans-11 Conjugated Linoleic Acid Reduces Phosphoenolpyruvate Carboxykinase Expression and Hepatic Glucose Production in HepG2 Cells

Dysregulated hepatic gluconeogenesis is a hallmark of insulin resistance and type 2 diabetes mellitus (T2DM). Although existing drugs have been proven to improve gluconeogenesis, achieving this objective with functional food is of interest, especially using conjugated linoleic acid (CLA) found in dairy products. Both cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12) isomers of CLA were tested in human (HepG2) and rat (H4IIE) hepatocytes for their potential effects on gluconeogenesis. The hepatocytes exposed for 24 h with 20 μM of c9,t11-CLA had attenuated the gluconeogenesis in both HepG2 and H4IIE by 62.5% and 80.1%, respectively. In contrast, t10,c12-CLA had no effect. Of note, in HepG2 cells, the exposure of c9,t11-CLA decreased the transcription of gluconeogenic enzymes, cytosolic phosphoenolpyruvate carboxykinase (PCK1) by 87.7%, and glucose-6-phosphatase catalytic subunit (G6PC) by 38.0%, while t10,c12-CLA increased the expression of G6PC, suggesting the isomer-specific effects of CLA on hepatic glucose production. In HepG2, the peroxisome proliferator-activated receptor (PPAR) agonist, rosiglitazone, reduced the glucose production by 72.9%. However, co-administration of c9,t11-CLA and rosiglitazone neither exacerbated nor attenuated the efficacy of rosiglitazone to inhibit glucose production; meanwhile, t10,c12-CLA abrogated the efficacy of rosiglitazone. Paradoxically, PPARγ antagonist GW 9662 also led to 70.2% reduction of glucose production and near undetectable PCK1 expression by abrogating CLA actions. Together, while the precise mechanisms by which CLA isomers modulate hepatic gluconeogenesis directly or via PPAR warrant further investigation, our findings establish that c9,t11-CLA suppresses gluconeogenesis by decreasing PEPCK on hepatocytes.

Dietary Docosahexaenoic Acid (DHA) and Eicosapentaenoic Acid (EPA) Operate by Different Mechanisms to Modulate Hepatic Steatosis and Hyperinsulemia in fa/fa Zucker Rats

Hepatic steatosis, an early stage of non-alcoholic fatty liver disease, is commonly present in obesity and type 2 diabetes, and is associated with reduced hepatic omega-3 polyunsaturated fatty acid (n3-PUFA) status that impacts on the anti-inflammatory and insulin sensitizing functions of n3-PUFA. Our objective was to directly compare plant- and marine-based n3-PUFA (α-linoleic acid (ALA)), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)) for their effects on hepatic steatosis, markers of hepatic inflammation and fibrosis, and insulinemia in obese rats. Fa/fa Zucker rats were provided diets containing ALA, EPA, DHA, or linoleic acid (LA, n6-PUFA) for eight weeks and compared to baseline fa/fa rats and lean Zucker rats fed LA-rich diet for eight weeks. Both DHA and EPA groups had liver lipid similar to baseline, however, DHA was more effective than EPA for reducing hepatic fatty acid synthase (FAS), increasing the proportion of smaller lipid droplets, reversing early fibrotic damage, and reducing fasting hyperinsulinemia. EPA was more effective for reducing FoxO1. Dietary ALA did not attenuate hepatic steatosis, most inflammatory markers or FAS. In summary, amongst the n3-PUFA, DHA was the most effective for elevating hepatic DHA levels, and preventing progression of hepatic steatosis via reductions in FAS and a marker of fibrosis.

Co-administration of conjugated linoleic acid and rosiglitazone increases atherogenic co-efficient and alters isoprenaline-induced vasodilatation in rats fed high fat diet

The cis(c)-9, trans(t)-11 (c9,t11) and t10,c12 isomers of conjugated linoleic acid (CLA) have been reported as agonists of peroxisome proliferator-activated receptor (PPAR) and beneficial in lipidemia and glycemia. However, it is unclear whether CLA isomers enhance or antagonize effects of conventional drugs targeting PPAR. Male Sprague-Dawley rats were fed high fat diet (HFD) for 8 weeks and treated without or with CLA, rosiglitazone or both for 4 weeks. Oral glucose tolerance and surrogate markers of insulin resistance were not significantly different for all treatments compared to untreated normal diet (ND) or HFD group, except lipoprotein levels. The combination of CLA and rosiglitazone had suppressed levels of low and high density lipoproteins (46 % and 25 %, respectively), compared to HFD-alone. Conversely, the atherogenic co-efficient of the animals received HFD or HFD+rosiglitazone+CLA was 2-folds higher than ND, HFD+rosiglitazone or HFD+CLA. Isolated aortic rings from the combined CLA and rosiglitazone treated animals were less sensitive to isoprenaline-induced relaxation among endothelium-denuded aortas with a decreased efficacy and potency (R(max)=53+/-4.7 %; pEC50=6+/-0.2) compared to endothelium-intact aortas (R(max)=100+/-9.9 %; pEC50=7+/-0.2). Our findings illustrate that the combination of CLA and rosiglitazone precede the atherogenic state with impaired endothelium-independent vasodilatation before the onset of HFD-induced insulin resistance.

Conjugated linoleic acid improves glycemic response, lipid profile, and oxidative stress in obese patients with non-alcoholic fatty liver disease: a randomized controlled clinical trial

Aim

To investigate if conjugated linoleic acid supplementation (CLA) affects metabolic factors and oxidative stress in non-alcoholic fatty liver disease (NAFLD).

Methods

The study was a randomized, controlled clinical trial conducted in specialized and subspecialized clinics of Tabriz University of Medical Sciences from January 2014 to March 2015. 38 obese NAFLD patients were randomly allocated into either the intervention group, receiving three 1000 mg softgel of CLA with a weight loss diet and 400 IU vitamin E, or into the control group, receiving only weight loss diet and 400 IU vitamin E for eight weeks. Dietary data and physical activity, as well as anthropometric, body composition, metabolic factors, and oxidative stress were assessed at baseline and at the end of the study.

Results

Weight, body composition, and serum oxidative stress, insulin, and lipid profile significantly improved in both groups, while hemoglobin A1c (HbA1c) levels (P = 0.004), total cholesterol to high density lipoprotein ratio (P = 0.008), low density lipoprotein to high density lipoprotein ratio (LDL/HDL) (P = 0.002), and alanine aminotransferase to aspartate aminotransferase (ALT/AST) ratio (P = 0.025) significantly decreased in the intervention group. At the end of the study, fat mass (P = 0.001), muscle mass (P = 0.023), total body water (P = 0.004), HbA1c (P < 0.001), triglycerides (P = 0.006), LDL/HDL ratio (P = 0.027), and ALT/AST ratio (P = 0.046) were significantly better in the CLA group than in the control group.

Conclusion

CLA improved insulin resistance, lipid disturbances, oxidative stress, and liver function in NAFLD. Therefore, it could be considered as an effective complementary treatment in NAFLD.

Registration number: IRCT2014020516491N1.

Pathway-based approach using hierarchical components of collapsed rare variants

MOTIVATION

To address 'missing heritability' issue, many statistical methods for pathway-based analyses using rare variants have been proposed to analyze pathways individually. However, neglecting correlations between multiple pathways can result in misleading solutions, and pathway-based analyses of large-scale genetic datasets require massive computational burden. We propose a Pathway-based approach using HierArchical components of collapsed RAre variants Of High-throughput sequencing data (PHARAOH) for the analysis of rare variants by constructing a single hierarchical model that consists of collapsed gene-level summaries and pathways and analyzes entire pathways simultaneously by imposing ridge-type penalties on both gene and pathway coefficient estimates; hence our method considers the correlation of pathways without constraint by a multiple testing problem.

RESULTS

Through simulation studies, the proposed method was shown to have higher statistical power than the existing pathway-based methods. In addition, our method was applied to the large-scale whole-exome sequencing data with levels of a liver enzyme using two well-known pathway databases Biocarta and KEGG. This application demonstrated that our method not only identified associated pathways but also successfully detected biologically plausible pathways for a phenotype of interest. These findings were successfully replicated by an independent large-scale exome chip study.

AVAILABILITY AND IMPLEMENTATION

An implementation of PHARAOH is available at http://statgen.snu.ac.kr/software/pharaoh/

CONTACT

tspark@stats.snu.ac.kr

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Individual CLA Isomers, c9t11 and t10c12, Prevent Excess Liver Glycogen Storage and Inhibit Lipogenic Genes Expression Induced by High-Fructose Diet in Rats

This study assessed the effects of individual conjugated linoleic acid isomers, c9t11-CLA and t10c12-CLA, on nonalcoholic fatty liver disease (NAFLD) and systemic endothelial dysfunction in rats fed for four weeks with control or high-fructose diet. The high-fructose diet hampered body weight gain (without influencing food intake), increased liver weight and glycogen storage in hepatocytes, upregulated expression of fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD-1), and increased saturated fatty acid (SFA) content in the liver. Both CLA isomers prevented excessive accumulation of glycogen in the liver. Specifically, t10c12-CLA decreased concentration of serum triacylglycerols and LDL + VLDL cholesterol, increased HDL cholesterol, and affected liver lipid content and fatty acid composition by downregulation of liver SCD-1 and FAS expression. In turn, the c9t11-CLA decreased LDL+VLDL cholesterol in the control group and downregulated liver expression of FAS without significant effects on liver weight, lipid content, and fatty acid composition. In summary, feeding rats with a high-fructose diet resulted in increased liver glycogen storage, indicating the induction of gluconeogenesis despite simultaneous upregulation of genes involved in de novo lipogenesis. Although both CLA isomers (c9t11 and t10c12) display hepatoprotective activity, the hypolipemic action of the t10c12-CLA isomer proved to be more pronounced than that of c9t11-CLA.

A diet high in α-linolenic acid and monounsaturated fatty acids attenuates hepatic steatosis and alters hepatic phospholipid fatty acid profile in diet-induced obese rats

This study investigated the efficacy of the plant-based n-3 fatty acid, α-linolenic acid (ALA), a dietary precursor of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), for modulating hepatic steatosis. Rats were fed high fat (55% energy) diets containing high oleic canola oil, canola oil, a canola/flax oil blend (C/F, 3:1), safflower oil, soybean oil, or lard. After 12 weeks, C/F and weight-matched (WM) groups had 20% less liver lipid. Body mass, liver weight, glucose and lipid metabolism, inflammation and molecular markers of fatty acid oxidation, synthesis, desaturation and elongation did not account for this effect. The C/F group had the highest total n-3 and EPA in hepatic phospholipids (PL), as well as one of the highest DHA and lowest arachidonic acid (n-6) concentrations. In conclusion, the C/F diet with the highest content of the plant-based n-3 ALA attenuated hepatic steatosis and altered the hepatic PL fatty acid profile.

Inhibition of smooth muscle cell proliferation by adiponectin requires proteolytic conversion to its globular form

Accelerated atherosclerosis is the primary cardiovascular manifestation of diabetes and correlates inversely with levels of circulating adiponectin, an anti-atherosclerotic adipokine that declines in diabetes. We therefore initiated a study to examine the mechanisms by which adiponectin, a hormone released from adipose tissue, influences the proliferation of vascular smooth muscle cells (SMCs). Addition of adiponectin to quiescent porcine coronary artery SMCs increased both protein and DNA synthesis and concurrently activated ERK1/2 and Akt. By contrast, globular adiponectin, a truncated form of this protein, exhibited anti-mitogenic properties as indicated by the inhibition of protein and DNA synthesis in SMCs stimulated with platelet-derived growth factor (PDGF). Whereas globular adiponectin did not stimulate growth-related signal transduction pathways, it was able to block the PDGF-dependent phosphorylation of eukaryotic elongation factor 2 kinase, a regulator of protein synthesis. Proteolysis of adiponectin with trypsin, which produces globular adiponectin, reversed the growth-stimulating actions of the undigested protein. As the existence of globular adiponectin remains controversial, western blotting was used to establish its presence in rat serum. We found that globular adiponectin was detectable in rat serum, but this result was not obtained with all antibodies. The contrasting properties of adiponectin and its globular form with respect to SMC proliferation suggest that protection against atherosclerosis may therefore be mediated, in part, by the level of globular adiponectin.

Dietary supplementation oftrans-11-vaccenic acid reduces adipocyte size but neither aggravates nor attenuates obesity-mediated metabolic abnormalities infa/faZucker rats

Conjugated linoleic acid (CLA) present in dairy and ruminant fat has beneficial effects on metabolic syndrome characteristics in humans and some rodent models. Production practices to increase the milk content of CLA are also substantially elevatingtrans-11-vaccenic acid (VA). Questions are being raised whether VA has the same beneficial actions as CLA or has adverse biological effects similar to industrially producedtrans-fatty acids. The present study examined the effects of dietary supplementation of either 0 or 1·5 % (w/w) VA for 8 weeks on lipidaemia, glycaemia, blood pressure, hepatic steatosis, adipocyte size and molecular markers of inflammation and insulin signalling infa/faZucker rats. Dietary supplementation of VA did not alter feed intake, weight gain, blood pressure or organ:body weight (BW) ratios, except the epididymal fat:BW ratio which was lower in the VA group compared with the control group. The total liver lipid concentration as an indicator of hepatic steatosis was not different between the groups. Likewise, there were no changes in fasting lipidaemia, glycaemia or oral glucose tolerance. Although there were no physiological differences observed between the groups, animals supplemented with VA had smaller adipocytes (approximately 7 % smaller than the controls). The VA group also had higher adipophilin and IL-10 protein levels in epididymal adipose tissue (1·7- and 1·4-fold higher than the controls, respectively); however, there were no changes observed in critical nodes of insulin signalling. The present study provides evidence that supplementation with VA, a naturally producedtrans-fat, has some positive effects on adipose tissue and did not exacerbate obesity-mediated metabolic abnormalities.

Contrasting apoptotic responses of conjugated linoleic acid in the liver of obese Zucker rats fed palm oil or ovine fat

We hypothesized that reducing weight properties of conjugated linoleic acid (CLA) are due to adipocyte apoptosis and that CLA differentially modulates the apoptotic responses in hepatic lipotoxicity from rats fed saturated fat diets. Obese Zucker rats were fed atherogenic diets (2%w/w of cholesterol) formulated with high (15%w/w) saturated fat, from vegetable or animal origin, supplemented or not with 1% of a mixture (1:1) of cis-9, trans-11 and trans-10, cis-12 CLA isomers for 14 weeks. CLA induced no changes on retroperitoneal fat depot weight, which was in line with similar levels of apoptosis. Interestingly, CLA had a contrasting effect on cell death in the liver according to the dietary fat. CLA increased hepatocyte apoptosis, associated with upregulation of Fas protein in rats fed palm oil, compared to rats receiving palm oil alone. However, rats fed ovine fat alone displayed the highest levels of hepatic cell death, which were decreased in rats fed ovine fat plus CLA. This reducing effect of CLA was related to positively restoring endoplasmic reticulum (ER) ATF-6α, BiP and CHOP protein levels and increasing phosphorylated c-Jun NH(2)-terminal kinase (JNK) and c-Jun, thus suggesting an adaptive response of cell survival. These findings reinforce the role of CLA as regulator of apoptosis in the liver. Moreover, the dietary fat composition is a key factor in activation of apoptosis.

trans-trans Conjugated linoleic acid enriched soybean oil reduces fatty liver and lowers serum cholesterol in obese zucker rats

Conjugated linoleic acid (CLA) is a collection of octadecadienoic fatty acids that have been shown to possess numerous health benefits. The CLA used in our study was produced by the photoisomerization of soybean oil and consists of about 20% CLA; this CLA consists of 75% trans-trans (a mixture of t8,t10; t9,t11; t10,t12) isomers. This method could be readily used to increase the CLA content of all soybean oil used as a food ingredient. The objective of this study was to determine the effects of trans-trans CLA-rich soy oil, fed as a dietary supplement, on body composition, dyslipidemia, hepatic steatosis, and markers of glucose control and liver function of obese fa/fa Zucker rats. The trans-trans CLA-rich soy oil lowered the serum cholesterol and low density lipoprotein-cholesterol levels by 41 and 50%, respectively, when compared to obese controls. Trans-trans CLA-rich soy oil supplementation also lowered the liver lipid content significantly (P < 0.05) with a concomitant decrease in the liver weight in the obese rats. In addition, glycated hemoglobin values were improved in the group receiving CLA-enriched soybean oil in comparison to the obese control. PPAR-γ expression in white adipose tissue was unchanged. In conclusion, trans-trans CLA-rich soy oil was effective in lowering total liver lipids and serum cholesterol.

Incorporation profiles of conjugated linoleic acid isomers in cell membranes and their positional distribution in phospholipids

Although the conjugated linoleic acids (CLA) have several isomer-specific biological effects including anti-carcinogenic and anti-adipogenic effects, their mechanisms of action remain unclear. To determine their potential effects on membrane structure and function, we studied the incorporation profiles of four CLA isomers (trans-10 cis-12 (A), trans-9 trans-11 (B), cis-9 trans-11 (C), and cis-9 cis-11 (D)) in CHO and HepG2 cells. All four isomers were incorporated into cellular lipids as efficiently as linoleic acid (LA), with the majority of the incorporated CLA present in membrane rafts. Of the four isomers, only CLA-A increased the cholesterol content of the raft fraction. Over 50% of the incorporated CLAs were recovered in phosphatidylcholine of CHO cells, but in HepG2 the neutral lipids contained the majority of CLA. The desaturation index (18:1/18:0 and 16:1/16:0) was reduced by CLA-A, but increased by CLA-B, the effects being apparent mostly in raft lipids. The Δ⁹ desaturase activity was inhibited by CLAs A and C. Unlike LA, which was mostly found in the sn-2 position of phospholipids, most CLAs were also incorporated significantly into the sn-1 position in both cell types. These studies show that the incorporation profiles of CLA isomers differ significantly from that of LA, and this could lead to alterations in membrane function, especially in the raft-associated proteins.

Combination of conjugated linoleic acid with fish oil prevents age-associated bone marrow adiposity in C57Bl/6J mice

The inverse relationship between fat in bone marrow and bone mass in the skeleton of aging subjects is well known. However, there is no precise therapy for the treatment of bone marrow adiposity. We investigated the ability of conjugated linoleic acid (CLA) and fish oil (FO), alone or in combination, to modulate bone loss using 12 months old C57Bl/6J mice fed 10% corn oil diet as control or supplemented with 0.5% CLA or 5% FO or 0.5% CLA+5% FO for 6 months. We found, CLA-fed mice exhibited reduced body weight, body fat mass (BFM) and enhanced hind leg lean mass (HLLM) and bone mineral density (BMD) in different regions measured by dual energy x-ray absorptiometry (DXA); however, associated with fatty liver and increased insulin resistance; whereas, FO fed mice exhibited enhanced BMD, improved insulin sensitivity, with no changes in BFM and HLLM. Interestingly, CLA+FO fed mice exhibited reduced body weight, BFM, peroxisome proliferator-activated receptor gamma and cathepsin K expression in bone marrow with enhanced BMD and HLLM. Moreover, CLA+FO supplementation reduced liver hypertrophy and improved insulin sensitivity with remarkable attenuation of bone marrow adiposity, inflammation and oxidative stress in aging mice. Therefore, CLA with FO combination might be a novel dietary supplement to reduce fat mass and improve BMD.

Serum adipokine profile and fatty acid composition of adipose tissues are affected by conjugated linoleic acid and saturated fat diets in obese Zucker rats

Conjugated linoleic acid (CLA) has been reported as having body fat lowering properties and the ability to modulate the inflammatory system in several models. In the present study, the effects of CLA added to saturated fat diets, from vegetable and animal origins, on the serum adipokine profile of obese Zucker rats were assessed. In addition, the fatty acid composition of epididymal and retroperitoneal adipose tissues was determined and a principal component analysis (PCA) was used to assess possible relationships between fatty acids and serum metabolites. Atherogenic diets (2 % cholesterol) were formulated with palm oil and ovine fat and supplemented or not with 1 % of a mixture (1:1) of cis-9, trans-11 and trans-10, cis-12-CLA isomers. CLA-fed animals exhibited lower daily feed intake, final body and liver weights, and hepatic lipids content. Total and LDL-cholesterol levels were increased in CLA-supplemented groups. CLA also promoted higher adiponectin and lower plasminogen activator inhibitor-1 (PAI-1) serum concentrations. In contrast to palm oil diets, ovine fat increased insulin resistance and serum levels of leptin, TNF-alpha and IL-1beta. Epididymal and retroperitoneal adipose tissues had similar deposition of individual fatty acids. The PCA analysis showed that the trans-10, cis-12-CLA isomer was highly associated with adiponectin and PAI-1 levels. Summing up, CLA added to vegetable saturated enriched diets, relative to those from animal origin, seems to improve the serum profile of adipokines and inflammatory markers in obese Zucker rats due to a more favourable fatty acid composition.

Influence of conjugated linoleic acid on the porcine immune response and morbidity: a randomized controlled trial

Background

Conjugated linoleic acid (CLA) has diverse influences on the immune response in different experimental models. In the present study we investigated the effect of CLA feeding on inflammatory and immune responses in a piglet model. We studied the duration of this effect and possible detrimental effects of CLA feeding. After 12 weeks of CLA and control supplementation and washout, animals were sacrificed and parenchymal organs were histologically examined.

Results

In activated peripheral mononuclear cells interferon-γ was significantly (p = 0.008) lower in the CLA group by the end of the feeding period. This effect disappeared as soon as supplementation was stopped. No differences were found in the tumour necrosis factor-α, interleukin-10 production, serum immunoglobulin-G levels and fat infiltration of the liver, except that fat storage cell infiltration was significantly (p < 0.04) higher in the CLA-fed group. The effect of time for interferon-γ, interleukin-10 and immunoglobulin-G levels was statistically significant.

Conclusion

At the end of the feeding period the interferon-γ response was depressed. However, the maturation of the piglet immune system in our young pig model probably outweighs the impact of CLA feeding on the immune response, even though liver fat storage cell infiltration, which plays an important role in liver regeneration, increased during CLA feeding of the piglets.

Altered plasma adipokines and markers of oxidative stress suggest increased risk of cardiovascular disease in First Nation youth with obesity or type 2 diabetes mellitus

OBJECTIVE

To evaluate cardiovascular disease risk in First Nation youth with and without type 2 diabetes mellitus (T2DM) or obesity by comparing pro- and anti-inflammatory adipokines, markers of oxidative stress and the plasma phospholipid fatty acid profile.

METHOD

Self-declared First Nation youth (12-15 yr) with T2DM (n = 24) as well as age-, gender-, and body mass index-matched controls (obese group; n = 19) and unmatched controls (control group; n = 34) were recruited from a pediatric diabetes clinic.

RESULTS

Plasma tumor necrosis factor-alpha, ultrasensitive C-reactive protein, resistin, and total antioxidant status were not different among the three groups. Plasma total leptin, soluble leptin receptor, and free leptin were significantly higher in the T2DM group than the control group (p < 0.001, p = 0.019, p < 0.001, respectively) but did not differ from the obese group. Similarly, oxidized low-density lipoprotein was higher in the T2DM group compared with controls (p = 0.002) but not in the obese group. However, interleukin-6 was significantly higher (p < 0.001) in the T2DM group compared with both the control and the obese groups, suggesting that T2DM, but not an increase in adiposity, was responsible for this elevation. Adiponectin was significantly lower in the T2DM group compared with the control group only (p = 0.035).

CONCLUSIONS

Changes in plasma adipokines and oxidative stress can already be detected in youth with T2DM; however, many of the changes are mirrored in obese youth, suggesting that both these populations are at an increased risk for future cardiovascular complications.

Trans-10, cis-12-conjugated linoleic acid reduces the hepatic triacylglycerol content and the leptin mRNA level in adipose tissue in obese Zucker fa/fa rats

Conjugated linoleic acid (CLA) isomers have been reported to reduce body weight and beneficially affect glucose metabolism in animals, but the results are inconsistent and seem to depend on animal model and type of CLA isomer. In the present study, feeding male Zucker fa/fa rats diets supplemented with 1% trans-10, cis-12-CLA for 10 d reduced the liver TAG content without improving the overall adiposity, and enhanced hepatic mitochondrial and peroxisomal beta-oxidation. The increased carnitine palmitoyltransferase (CPT)-I activity and mRNA level as well as the increased n-3:n-6 PUFA ratio in liver suggest that trans-10, cis-12-CLA increased the hepatic beta-oxidation by stimulation of PPARalpha. The reduced hepatic TAG content may be partly due to lower activity of stearoyl-CoA desaturase, as the ratios of 18 : 1n-9:18 : 0 and 16 : 1n-7:16 : 0 were reduced in liver. Trans-10, cis-12-CLA increased the CPT-I mRNA in retroperitoneal white adipose tissue (WAT), and increased uncoupling protein-2 mRNA in epididymal and inguinal WAT depots. Leptin mRNA level was decreased in all examined WAT depots, implying reduced insulin sensitivity. The resistin mRNA level was increased in all WAT depots, whereas adiponectin mRNA was reduced in inguinal and retroperitoneal WAT. The present results suggest that dietary supplementation with trans-10, cis-12-CLA may increase the catabolism of lipids in liver and adipose tissue. Moreover, we provide new data suggesting that trans-10, cis-12-CLA modulates the expression of resistin and adiponectin inversely in adipose tissue. Hence, the present results suggest that trans-10, cis-12-CLA may have some beneficial effects on lipid metabolism and adiposity but possibly reduces insulin sensitivity.

Dietary trans-10, cis-12 conjugated linoleic acid reduces early glomerular enlargement and elevated renal cyclooxygenase-2 levels in young obese fa/fa zucker rats

Conjugated linoleic acid (CLA) slows the progression of disease in models of chronic kidney disease. Because obesity is associated with nephropathy and increased renal cyclooxygenase (COX) levels, the effects of dietary CLA on kidney function, morphology, and COX protein levels in the kidneys of young obese (fa/fa) Zucker rats, a model of metabolic syndrome, were examined. In study 1, 6-wk-old fa/fa and lean Zucker rats were given a mixture of CLA isomers (1.5% CLA, wt:wt) or the control diet (CTL) with no CLA for 8 wk. To examine specific isomer effects, study 2 used the same model with the following diets: 0.4% (g/g) cis-9, trans-11 (c9,t11) CLA; 0.4% trans-10, cis-12 (t10,c12) CLA; a combination of these 2 isomers (0.4% each); or CTL diets with no CLA. In study 1, fa/fa rats given the CLA mixture had 11% smaller kidney weights and 28% smaller glomeruli, and feed intake and body weight did not differ from the CTL rats. In study 2, diet also did not affect body weights, but fa/fa rats given a diet containing t10,c12 CLA had 7% lower kidney weights, 20% smaller glomeruli, and 39% lower COX-2 protein levels than CTL rats. In conclusion, dietary t10,c12 CLA reduces the enlargement of glomeruli in young obesity-associated nephropathy and is associated with lower protein levels of renal COX-2. Long-term studies with CLA supplementation are required to determine whether these changes would lead to reduction in development of renal disease associated with obesity.

Anti-obesity effects of conjugated linoleic acid, docosahexaenoic acid, and eicosapentaenoic acid

Obesity has become a prevailing epidemic throughout the globe. Effective therapies for obesity become attracting. Food components with beneficial effects on "weight loss" have caught increasing attentions. Conjugated linoleic acid (CLA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) belong to different families of polyunsaturated fatty acids (PUFA). However, they have similar effects on alleviating obesity and/or preventing from obesity. They influence the balance between energy intake and expenditure; and reduce body weight and/or fat deposition in animal models, but show little effect in healthy human subjects. They inhibit key enzymes responsible for lipid synthesis, such as fatty acid synthase and stearoyl-CoA desaturase-1, enhance lipid oxidation and thermogenesis, and prevent free fatty acids from entering adipocytes for lipogenesis. PUFA also exert suppressive effects on several key factors involved in adipocyte differentiation and fat storage. Despite their similar effects and shared mechanisms, they display differences in the regulation of lipid metabolism. Moreover, DHA and EPA exhibit "anti-obesity" effect as well as improving insulin sensitivity, while CLA induces insulin resistance and fatty liver in most cases. A deeper and more detailed investigation into the complex network of anti-obesity regulatory pathways by different PUFA will improve our understanding of the mechanisms of body weight control and reduce the prevalence of obesity.

Abnormal immune responses in fa/fa Zucker rats and effects of feeding conjugated linoleic acid

OBJECTIVE

The objective of this study was to characterize immune function in the fa/fa Zucker rat, and to determine the effects of feeding conjugated linoleic acid (CLA) isomers on immune function.

METHODS AND PROCEDURES

Lean and fa/fa Zucker rats were fed for 8 weeks nutritionally complete diets with different CLA isomers (%wt/wt): control (0%), c9t11 (0.4%), t10c12 (0.4%), or MIX (0.4% c9t11 + 0.4% t10c12). Isolated splenocytes were used to determine phospholipid (PL) fatty acid composition and cell phenotypes, or stimulated with mitogen to determine their ability to produce cytokines, immunoglobulins (Ig), and nitric oxide (NO).

RESULTS

Splenocyte PL of fa/fa rats had a higher proportion of total monounsaturated fatty acids and n -3 polyunsaturated fatty acids (PUFA), and lower n -6 PUFA and n -6-to-n -3 PUFA ratio (P < 0.05). Feeding CLA increased the content of CLA isomers into PL, but there were lower proportions of each CLA isomer in fa/fa rats. Splenocytes of fa/fa rats produced more amounts of IgA, IgG, and IgM, NO, and interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) (P < 0.05). Obese rats fed the t10c12 diet produced less TNF-alpha and IL-1beta (lippopolysaccharide (LPS), P < 0.05). Splenocytes of fa/fa rats produced less concanavalin A (ConA)-stimulated IL-2 (P < 0.0001) than lean rats, except fa/fa rats fed the c9t11 diet (P < 0.05).

DISCUSSION

The c9t11 and t10c12 CLA isomers were incorporated into the membrane PL of the fa/fa Zucker rat, but to a lesser extent than lean rats. Splenocytes of obese rats responded in a proinflammatory manner and had reduced T-cell function and feeding the t10c12 and c9t11 CLA isomers may improve some of these abnormalities by distinct methods.

Dietary conjugated linoleic acid decreases adipocyte size and favorably modifies adipokine status and insulin sensitivity in obese, insulin-resistant rats

Conjugated linoleic acids (CLA) have been shown to alter adiposity in some species with varying effects on insulin resistance. The objective of this 8-week study was to investigate the effects of feeding a CLA mixture (1.5%, wt/wt) on adipocyte size, insulin sensitivity, adipokine status, and adipose lipid composition in fa/fa vs lean Zucker rats. The fa/fa CLA-fed rats had smaller adipocytes and improved insulin sensitivity compared with fa/fa rats fed the control diet. Conjugated linoleic acids did not affect select markers of adipose differentiation, lipid filling, lipid uptake, or oxidation. Dietary CLA, compared with the control diet, reduced circulating leptin and elevated fasting serum adiponectin concentrations in fa/fa rats. Adipose resistin messenger RNA levels were greater in fa/fa CLA-fed rats compared with fa/fa control rats. CLA did not markedly alter adipose phospholipid fatty acid composition, and the changes in the triacylglycerol fatty acid composition reflected a lower delta-9 desaturase index of CLA-fed vs control-fed rats. In conclusion, CLA reduced adipocyte size and favorably modified adipokine status and insulin sensitivity in fa/fa Zucker rats.

Dietary conjugated linoleic acid preserves pancreatic function and reduces inflammatory markers in obese, insulin-resistant rats

Pancreatic preservation is an important part of diabetes management that may occur with improved peripheral insulin sensitivity and attenuated low-grade adipose tissue inflammation. The objective of the current study was to determine the response of obese, insulin-resistant fa/fa Zucker rats vs lean controls to dietary conjugated linoleic acid (CLA) supplementation with respect to pancreatic islet size, insulin resistance, and markers of inflammation and adipose glucose uptake. Six-week-old fa/fa and lean Zucker rats (n = 20 per genotype) were fed either a 1.5% CLA mixture or control diet for 8 weeks. Oral glucose tolerance testing was conducted at 7.5 weeks. Fasting serum haptoglobin, insulin, and C-peptide were assayed, and select messenger RNA (mRNA) and protein markers of inflammation and glucose metabolism were measured in adipose and liver tissues. CLA-fed fa/fa Zucker rats had smaller islet cell size, improved oral glucose tolerance and insulinemia, and attenuated serum haptoglobin levels compared with control-fed fa/fa Zucker rats, despite no differences in body weight and a slightly higher visceral adipose mass. CLA did not alter insulin sensitivity or islet size in lean Zucker rats. The CLA-fed fa/fa rats also had greater adipose glucose transporter-4 mRNA and less adipose tumor necrosis factor alpha mRNA and protein compared with control-fed fa/fa rats. In contrast, other markers of inflammation and glucose metabolism including adipose macrophage inflammatory factor, macrophage inflammatory protein-2, and liver pyruvate carboxylase and pyruvate dehydrogenase kinase 4 were not significantly changed. These results suggest that CLA supplementation preserved pancreatic function in conjunction with improved peripheral glucose use and reduced inflammation in fa/fa Zucker rats.