Dietary fat quality impacts metabolic impairments of type 2 diabetes risk differently in male and female CD-1® mice.

Metabolic impairments associated with type 2 diabetes, including insulin resistance and loss of glycaemic control, disproportionately impact the elderly. Lifestyle interventions, such as manipulation of dietary fat quality (i.e. fatty acid (FA) composition), have been shown to favourably modulate metabolic health. Yet, whether or not chronic consumption of beneficial FAs can protect against metabolic derangements and disease risk during ageing is not well defined. We sought to evaluate whether long-term dietary supplementation of fish-, dairy- or echium-derived FAs to the average FA profile in a U.S. American diet may offset metabolic impairments in males and females during ageing. One-month-old CD-1® mice were fed isoenergetic, high-fat (40 %) diets with the fat content composed of either 100 % control fat blend (CO) or 70 % CO with 30 % fish oil, dairy fat or echium oil for 13 months. Every 3 months, parameters of glucose homoeostasis were evaluated via glucose and insulin tolerance tests. Glucose tolerance improved in males consuming a diet supplemented with fish oil or echium oil as ageing progressed, but not in females. Yet, females were more metabolically protected than males regardless of age. Additionally, Spearman correlations were performed between indices of glucose homoeostasis and previously reported measurements of diet-derived FA content in tissues and colonic bacterial composition, which also revealed sex-specific associations. This study provides evidence that long-term dietary fat quality influences risk factors of metabolic diseases during ageing in a sex-dependent manner; thus, sex is a critical factor to be considered in future dietary strategies to mitigate type 2 diabetes risk.

Tissue and Circulating Fatty Acids as Biomarkers to Evaluate Long-Term Fat Intake Are Tissue and Sex Dependent in CD-1 Mice.

BACKGROUND: There is currently no consensus on which tissues are optimal for assessing specific diet-derived fatty acids (FAs) as biomarkers for long-term dietary studies. OBJECTIVES: This study measured the content of unique diet-derived FAs from dairy, echium, and fish in tissues (adipose, muscle, liver, erythrocyte membranes, and plasma phospholipids, cholesterol esters, triglycerides, and free fatty acids) after long-term feeding in CD-1 mice. METHODS: Beginning at weaning, mice (n = 10-11/sex/diet) were fed 1 of 4 diets (40% kcal/total energy) that only differed in FA composition: control fat blend (CON), reflecting the FA profile of the average US American diet, or CON supplemented with 30% of fish oil (FO), dairy fat (DF), or echium oil (EO). After 13 mo, tissues were collected to determine FAs via gas-liquid chromatography. Tissue FAs were analyzed via 2-factor ANOVA, and relationships between FA intake and tissue content were assessed with Spearman correlations. RESULTS: As anticipated, 20:5n-3 (ω-3) tissue content was ≤32-fold greater in FO- compared with CON-fed mice (P < 0.05). In addition, 20:5n-3 intake strongly correlated with its content in all tissues (ρ = 0.67-0.76; P < 0.05). Echium oil intake also influenced tissue FA content in mice as expected. For example, 18:3n-6 was ≤25-fold greater in adipose, muscle, and liver tissues of EO-fed compared with CON-fed mice (P < 0.05). Tissue content of FAs typically considered biomarkers of dairy fat intake (15:0, 16:1 t9, and 17:0) was often not greater in mice fed DF than other diet groups, although 18:2 c9, t11 content was ≤6-fold greater in tissues from DF-fed compared with CON-fed mice (P < 0.05). The content of dairy-derived FAs in blood fractions of females was up to 2-fold greater compared with males, whereas docosapentaenoic acid content was up to 1-fold greater in all blood fractions and in liver tissue of males compared with females (P < 0.05). In adipose, muscle, and liver tissue, the content of γ-linolenic acid and stearidonic acid was less than 1-fold greater in females than in males (P < 0.05). CONCLUSIONS: Our study indicates that the distribution of dietary FAs is tissue and sex dependent in aged CD-1 mice. Research using FA biomarkers should assess a combination of FA biomarkers to accurately validate patterns of FA intake and source.

Physicochemical and microstructural properties and probiotic survivability of symbiotic almond yogurt alternative using polymerized whey protein as a gelation agent.

A plain symbiotic almond yogurt-like product was formulated and developed using a plant-based starter YF-L02 (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus supplemented with Lactobacillus acidophilus, Lactobacillus paracasei, and Bifidobacterium animalis) and inulin; 0.6% polymerized whey protein (PWP), 0.3% pectin, and 0.05% xanthan gum were optimized for the formula of the almond yogurt alternative. Two groups with/without calcium citrate and vitamin D2 were prepared and analyzed for chemical composition, changes in pH, viscosity, and probiotic survivability during storage at 4 °C for 10 weeks. The results showed that (1) over 10 weeks storage, the differences in the pH, viscosity, and probiotic survivability between the control and the fortified samples were not significant (P > 0.05); (2) the pH of both yogurt samples decreased 0.2 units while their viscosity slightly increased during storage; (3) the populations of L. paracasei and B. animalis remained above 106 cfu/g during the storage, whereas the population of L. acidophilus decreased dramatically during the first 4 weeks, especially the control group; (4) the microstructure was examined by scanning electron microscopy, revealing a compact and denser gel structure formed by 0.6% PWP with the presence of 0.3% pectin and 0.05% xanthan gum. In conclusion, PWP might be a proper gelation agent for the formulation of symbiotic almond yogurt alternative. PRACTICAL APPLICATION: In this study, polymerized whey protein was used as a gelation agent to formulate symbiotic almond yogurt alternatives with comparable physical texture and probiotic survivability to dairy yogurt during storage. This technology may be used for the development of plant-based fermented foods.

Fatty Acid Content of Retail Cow's Milk in the Northeastern United States-What's in It for the Consumer?

The fatty acid (FA) composition and content of whole milk (3.25% fat) from organic, omega-3 (n-3) FA fortified, and conventional retail brands available in the northeastern U.S. were assessed monthly via gas chromatography. Among the retail labels, organic milk stood out as it contained a distinct and more healthful FA profile, consistently comprising a higher content of unique bioactive FAs (short-chain FAs, odd- and branched-chain FAs, vaccenic acid, and conjugated linoleic acids) per serving, particularly during the warm season. The total content of saturated FAs did not differ by retail label. While organic and n-3 fortified milk contained a similar content of total n-3 FAs, the proportion of individual n-3 FAs differed significantly (organic milk: 18:3 n-3; n-3 fortified milk: 20:6 n-3) as a result of the production system and process, respectively. Overall, per serving, the FA profile of organic milk may provide added nutritional and health benefits.

Colonic bacterial composition is sex-specific in aged CD-1 mice fed diets varying in fat quality.

Evidence suggests that sex influences the effect of diet on the gut bacterial composition, yet, no studies have been performed assessing dietary fatty acid composition (i.e., fat quality) in this context. This study examined the effect of dietary fat quality on colonic bacterial composition in an aged, genetically-diverse mouse population. CD-1 mice were fed isoenergetic diets consisting of (1) control fat (CO; "Western-style" fat blend), (2) CO supplemented with 30% fish oil, (3) CO supplemented with 30% dairy fat, or (4) CO supplemented with 30% echium oil. Fecal samples were collected at mid-life and aged (reproductively senescent) time points. Overall, the abundance of Bacteroidetes was greater in mice fed echium oil compared to mice fed the control fat. Examination of colonic bacterial relative abundance also revealed sex differences, with 73 bacterial taxa being differentially expressed in males and females. Notably, results showed a strong interactive effect among the diet, sex, and age of mice which influenced colonic bacterial relative abundance and alpha diversity. In males, supplementation of the diet with dairy fat or echium oil caused the abundance of Bacteroidetes and Bacteroides to change with age. Additionally, supplementation of the diet with fish oil induced sex-dependent changes in the alpha diversity of aged mice compared to mid-life. This work supports that sex is a critical factor in colonic bacterial composition of an aged, genetically-heterogenous population. Moreover, this study establishes that the effectiveness of dietary interventions for health maintenance and disease prevention via direct or indirect manipulation of the gut microbiota is likely dependent on an individual's sex, age, and genetic background.

Fetal and neonatal exposure to trans-fatty acids impacts on susceptibility to atherosclerosis in apo E*3 Leiden mice.

Nutrition during pregnancy can impact on the susceptibility of the offspring to CVD. Postnatal consumption of trans-fatty acids (TFA), associated with partially hydrogenated vegetable oil (PHVO), increases the risk of atherosclerosis, whereas evidence for those TFA associated with ruminant-derived dairy products and meat remain equivocal. In this study, we investigate the impact of maternal consumption of dietary PHVO (P) and ruminant milk fat (R) on the development of atherosclerosis in their offspring, using the transgenic apoE*3 Leiden mouse. Dams were fed either chow (C) or one of three high-fat diets: a diet reflecting the SFA content of a 'Western' diet (W) or one enriched with either P or R. Diets were fed during either pregnancy alone or pregnancy and lactation. Weaned offspring were then transferred to an atherogenic diet for 12 weeks. Atherosclerosis was assessed as lipid staining in cross-sections of the aorta. There was a significant effect of maternal diet during pregnancy on development of atherosclerosis (P=0·013) in the offspring with those born of mothers fed R or P during pregnancy displaying smaller lesions that those fed C or W. This was not associated with changes in total or lipoprotein cholesterol. Continuing to feed P during lactation increased atherosclerosis compared with that seen in offspring of dams fed P only during pregnancy (P<0·001). No such effect was seen in those from mothers fed R (P=0·596) or W (P=901). We conclude that dietary TFA have differing effects on cardiovascular risk at different stages of the lifecycle.

Trans-Fatty Acid-Stimulated Mammary Gland Growth in Ovariectomized Mice is Fatty Acid Type and Isomer Specific.

We previously reported that the trans-18:2 fatty acid trans-10, cis-12 conjugated linoleic acid (t10,c12-CLA) stimulates mammary gland development independent of estrogen and its receptor. Given the negative consequences of dietary trans-fatty acids on various aspects of human health, we sought to establish whether other trans-fatty acids could similarly induce ovary-independent mammary gland growth in mice. Prepubertal BALB/cJ mice were ovariectomized at 21 days of age then were fed diets enriched with cis-9, trans-11 CLA (c9,t11-CLA), or mixtures of trans-18:1 fatty acids supplied by partially hydrogenated sunflower, safflower, or linseed oil. The resultant mammary phenotype was evaluated 3 weeks later and compared to the growth response elicited by t10,c12-CLA, or the defined control diet. Whereas partially hydrogenated safflower oil increased mammary gland weight, none of the partially hydrogenated vegetable oils promoted mammary ductal growth. Similarly, the c9,t11-CLA supplemented diet was without effect on mammary development. Taken together, our data emphasize a unique effect of t10,c12-CLA in stimulating estrogen-independent mammary gland growth manifest as increased mammary ductal area and elongation that was not recapitulated by c9,t11-CLA or the partially hydrogenated vegetable oil diets.

Lipid Encapsulation Provides Insufficient Total-Tract Digestibility to Achieve an Optimal Transfer Efficiency of Fatty Acids to Milk Fat.

Transfer efficiencies of rumen-protected n-3 fatty acids (FA) to milk are low, thus we hypothesized that rumen-protection technologies allow for biohydrogenation and excretion of n-3 FA. The objectives of this study were to i) investigate the ruminal protection and post-ruminal release of the FA derived from the lipid-encapsulated echium oil (EEO), and ii) assess the bioavailability and metabolism of the EEO-derived FA through measuring the FA content in plasma lipid fractions, feces, and milk. The EEO was tested for rumen stability using the in situ nylon bag technique, then the apparent total-tract digestibility was assessed in vivo using six Holstein dairy cattle. Diets consisted of a control (no EEO); 1.5% of dry matter (DM) as EEO and 1.5% DM as encapsulation matrix; and 3% DM as EEO. The EEO was rumen-stable and had no effect on animal production. EEO-derived FA were incorporated into all plasma lipid fractions, with the highest proportion of n-3 FA observed in cholesterol esters. Fecal excretion of EEO-derived FA ranged from 7-14%. Biohydrogenation products increased in milk, plasma, and feces with EEO supplementation. In conclusion, lipid-encapsulation provides inadequate digestibility to achieve an optimal transfer efficiency of n-3 FA to milk.

Lipid-Encapsulated Echium Oil (Echium plantagineum) Increases the Content of Stearidonic Acid in Plasma Lipid Fractions and Milk Fat of Dairy Cows.

The objective of this study was to evaluate the impact of feeding lipid-encapsulated echium oil (EEO) on animal performance and milk fatty acid profile. Twelve Holstein dairy cows were used in a 3 × 3 Latin Square design with 14 day periods. Treatments were a control diet (no supplemental fat), 1.5% dry matter (DM) as EEO and 3.0% DM as EEO. Treatments had no negative effect on animal performance (dry matter intake, milk yield, and fat yield). The milk fat content of total n-3 fatty acids and stearidonic acid (SDA) increased with EEO supplementation (P < 0.001). The proportion of SDA increased in all plasma lipid fractions with EEO supplementation (P < 0.001). Transfer of SDA from EEO into milk fat was 3.4 and 3.2% for the 1.5 and 3% EEO treatments, respectively. In conclusion, EEO increases the content of n-3 fatty acids in milk fat; however, the apparent transfer efficiency was low.

Diet-induced metabolic change induces estrogen-independent allometric mammary growth.

Lifetime breast cancer risk reflects an unresolved combination of early life factors including diet, body mass index, metabolic syndrome, obesity, and age at first menses. In parallel, the onset of allometric growth by the mammary glands around puberty is widely held to be estrogen (E)-dependent. Here we report that several physiological changes associated with metabolic syndrome in response to a diet supplemented with the trans-10, cis-12 isomer of conjugated linoleic acid lead to ovary-independent allometric growth of the mammary ducts. The E-independence of this diet-induced growth was highlighted by the fact that it occurred both in male mice and with pharmacological inhibition of either E receptor function or E biosynthesis. Reversal of the metabolic phenotype with the peroxisome proliferator-activated receptor-γ agonist rosiglitazone abrogated diet-induced mammary growth. A role for hyperinsulinemia and increased insulin-like growth factor-I receptor (IGF-IR) expression during mammary growth induced by the trans-10, cis-12 isomer of conjugated linoleic acid was confirmed by its reversal upon pharmacological inhibition of IGF-IR function. Diet-stimulated ductal growth also increased mammary tumorigenesis in ovariectomized polyomavirus middle T-antigen mice. Our data demonstrate that diet-induced metabolic dysregulation, independently of ovarian function, stimulates allometric growth within the mammary glands via an IGF-IR-dependent mechanism.

Ruminant-produced trans-fatty acids raise plasma HDL particle concentrations in intact and ovariectomized female Hartley guinea pigs.

Cardiovascular disease (CVD) is the leading cause of death among women worldwide, and risk for developing CVD increases postmenopause. Consumption of trans-fatty acids (tFA) has been positively associated with CVD incidence and mortality. The current study was designed to assess the effects of diets high in industrially produced (IP)-tFA, from partially hydrogenated vegetable oils (PHVO), and ruminant-produced (RP)-tFA, from butter oil (BO), on risk factors for CVD. Thirty-two female Hartley guinea pigs, one-half of which were ovariectomized (OVX) to mimic the postmenopausal condition, were fed hypercholesterolemic diets containing 9% by weight PHVO or BO (n = 8/diet and ovariectomy) for 8 wk. The plasma and hepatic lipids did not differ between IP- and RP-tFA groups or between intact and OVX guinea pigs. The BO diet resulted in higher concentrations of plasma total and small HDL particle subclass concentrations than the PHVO diet regardless of ovariectomy status. The intact BO group had higher concentrations of large HDL particles than the intact PHVO group. HDL mean particle size tended to be larger (P = 0.07) in the PHVO groups compared with the BO groups regardless of ovariectomy status. There was a trend toward an interaction between diet and ovariectomy status for LDL mean particle size, which tended to be larger in OVX guinea pigs fed PHVO (P = 0.07). In summary, consumption of IP- and RP-tFA resulted in differential effects on HDL particle subclass profiles in female guinea pigs. The effect of tFA consumption and hormonal status on HDL particle subclass metabolism and the subsequent impact on CVD in females warrants further investigation.

Differential effects of the trans-18:1 isomer profile of partially hydrogenated vegetable oils on cholesterol and lipoprotein metabolism in male F1B hamsters.

Trans-fatty acid consumption from partially hydrogenated vegetable oil (PHVO) has been positively associated with multiple cardiovascular disease risk factors and events. This study was designed to examine the effects of trans-fatty acid isomer profile of PHVO on plasma lipids and lipoproteins and hepatic expression of key genes involved in cholesterol and fatty acid metabolism. Thirty-three male F(1)B strain Syrian Golden Hamsters were allocated to 1 of 3 hypercholesterolemic diets containing (5% by weight): 1) tristearin [control fat (CON)]; 2) partially hydrogenated high-oleic acid sunflower oil (PH-SUN); or 3) partially hydrogenated high-linoleic acid safflower oil (PH-SAF). PH-SUN contained more trans-4 to trans-10 18:1 compared with PH-SAF, which contained more trans-11 to trans-16 18:1. The addition of both PHVO to the diet increased plasma total cholesterol concentrations relative to CON, but only PH-SUN increased the plasma ratio of non-HDL:HDL cholesterol compared with CON. PH-SUN increased VLDL (total, large, and medium) and IDL particle concentrations while decreasing total, medium, and small HDL particle concentrations relative to CON. Both PHVO diets increased the hepatic cholesterol ester concentration, whereas the hepatic TG concentration was lower in PH-SUN compared with PH-SAF and CON. Levels of hepatic LDL receptor, HMG-CoA reductase, and sterol response element binding protein 1 mRNA were specifically reduced in the PH-SUN group compared to the CON group. Expression of SREBP1c was upregulated in both PHVO groups compared to CON, whereas only the PH-SAF group had higher levels of the lipogenic enzymes acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase-1 compared to CON. These results indicate that differences in the trans-fatty acid profile of PHVO can differentially affect lipid and lipoprotein metabolism.

Ruminant-produced trans-fatty acids raise plasma total and small HDL particle concentrations in male Hartley guinea pigs.

Although trans-fatty acid (tFA) intake has been positively associated with coronary heart disease (CHD), the relative effect of consuming industrially produced (IP)- compared with ruminant-produced (RP)-tFA on CHD risk factors is unclear. This study was designed to examine the effects of feeding partially hydrogenated vegetable oil (PHVO), IP-tFA source, and butter oil (BO), RP-tFA source, on the development of atherosclerosis and risk factors associated with CHD. Forty-eight male Hartley guinea pigs were fed a hypercholesterolemic diet containing (9% by weight) PHVO, BO, coconut oil (CO; positive control), or soybean oil (SO; negative control) for 8 or 12 wk (n = 6/group). Morphological analysis revealed that none of the groups developed atherosclerosis. Plasma and hepatic lipids did not differ between the tFA groups, but total and small HDL particles were significantly higher in the BO group than in the PHVO group and mean HDL particle size was significantly smaller in the BO group than in the PHVO group. Compared with the other treatment groups, the SO treatment resulted in significantly lower total cholesterol (TC) and LDL cholesterol in plasma, whereas hepatic TC was significantly higher in the SO group than in the other treatment groups. Plasma and hepatic cholesterol concentrations did not differ between the tFA and CO treatments. These results demonstrate that when fed at a high dose, IP- and RP-tFA had the same effect on established CHD risk factors in male Hartley guinea pigs. The effects of RP-tFA on HDL particle sizes and concentrations warrant further investigation.

Extensive analysis of long-chain polyunsaturated fatty acids, CLA, trans-18:1 isomers, and plasmalogenic lipids in different retail beef types.

The objective of this investigation was to provide a comprehensive analysis of the total lipid composition of present-day retail beef meat available at the consumer level and to evaluate the total lipid composition with special emphasis on the nutritional value. For this purpose, 40 beef cuts were obtained from four cattle farms based on either a natural grazing system (NGS) or an intensive production system (IPS). The total lipid composition was analyzed using complementary chemical and chromatographic procedures. The content of n-3 LC-PUFA, CLA, total trans-18:1, and branched-chain fatty acids was significantly higher in NGS beef than in IPS beef. The trans-18:1 and CLA profiles were affected by the different production systems, whereby they can be utilized empirically to differentiate between feeding regimen and production management. Fatty acid ratios that have health implications ( n-6/ n-3, LA/alphaLNA, and AA/EPA) were remarkably beneficial for NGS beef compared with IPS beef. In conclusion, from the human health perspective, beef raised on NGS is clearly superior with regard to a more favorable fatty acid profile in comparison to IPS beef.

Dietary supplementation with trans-11- and trans-12-18 : 1 increases cis-9, trans-11-conjugated linoleic acid in human immune cells, but without effects on biomarkers of immune function and inflammation.

Trans-fatty acid intake is associated with an increased risk of CHD and diabetes. The effects of single trans-fatty acid isomers are largely unexplored. The present study examined the effects of a 6-week supplementation with two trans-18 : 1 isomers (trans-11 and trans-12) in human subjects on immune cells, several inflammatory and immunological biomarkers (for example, IL, TNFalpha, C-reactive protein, adiponectin, intercellular adhesion molecule-1, prostacyclin, phagocytic process). Following a 2-week adaptation period without supplements, the test group (n 12) received vaccenic acid (trans-11-18:1) and trans-12-18 : 1 in equal amounts (6.0 g/d) for 6 weeks. The control group (n 12) consumed an oil without trans-fatty acids and conjugated linoleic acids (CLA). Samples were collected at the end of both periods. Trans-11- and trans-12-18 : 1 were significantly increased in cellular lipids. The endogenous synthesis of cis-9, trans-11-CLA from trans-11-18 : 1 was demonstrated via increased CLA in cellular lipids of the test group. Generally, trans-isomer supplementation did not affect either inflammatory biomarkers (for example, IL-6, IL-8, TNFalpha) or immune function (for example, phagocytosis) during the present study. The dietary supplementation of trans-11- and trans-12-18 : 1 (6 g/d) and their accumulation in leucocytes had no effects on biomarkers of inflammation and immune function. However, because of the limited data on the safety of trans-fatty acid intake and effects of individual trans isomers on human health (for example, trans-9-18 : 1, trans-10-18 : 1) at present, it is prudent to reduce trans-fat intake in general.

Dietary supplementation with 11trans- and 12trans-18:1 and oxidative stress in humans.

BACKGROUND: High consumption of trans fat has been associated with high oxidative stress in humans, which could increase the risk of the development or acceleration of several diseases, such as atherosclerosis, cancer, and type 2 diabetes. OBJECTIVE: Several urinary and blood biomarkers of oxidative stress [8-iso-prostaglandin-F(2alpha) (PGF(2alpha)), 15-keto-dihydro-PGF(2alpha), and 7,8-dihydro-8-oxo-2'-deoxy-guanosine in urine and alpha-,beta-,gamma-,delta-tocopherol, and retinol in plasma] were monitored to evaluate the oxidative stress induced by dietary supplementation of 11trans- and 12trans-18:1 isomers in humans during a 6-wk intervention. DESIGN: After a 14-d adaptation period free of trans fatty acid supplementation (baseline), the test group (n = 12) received 3.0 g 11trans-18:1/d and 3.0 g 12trans-18:1/d (Sigma 6.0 g/d), and the control group (n = 12) consumed a control oil free of trans fatty acids and conjugated linoleic acids for 6 wk. RESULTS: The postintervention concentration of urinary 8-iso-PGF(2alpha) (free radical-induced lipid peroxidation) in the test group was significantly higher than baseline and significantly higher than that observed in the control group. The concentrations of 15-keto-dihydro-PGF(2alpha) (cyclooxygenase-mediated inflammatory response indicator) and 7,8-dihydro-8-oxo-2'-deoxy-guanosine (oxidative DNA damage) were not affected by the 11trans- and 12trans-18:1 supplementation. CONCLUSIONS: Although an increase in urinary 8-iso-PGF(2alpha) was observed and the effects of prolonged high (ie, >5.0 g/d) consumption of trans fat could be relevant to the development of disease, the mean intakes of 11trans- and 12trans-18:1 in Europeans are estimated to be significantly below the amounts administered in this study (ie, 6.0 g/d); such low intakes could minimize the possible risk of detrimental effects on human health.

The conversion efficiency of trans-11 and trans-12 18:1 by Delta9-desaturation differs in rats.

The present study evaluated and compared the efficiency of the conversion of t11 18:1 and t12 18:1 to their corresponding dienoic acids (c9,tn 18:2) and assessed whether differences due to gender existed in several tissues of rats. Three groups of 4-wk-old male and female rats were fed for 3 wk a diet supplemented with 0, 0.5, or 1% of a trans-octadecenoic acid isomer mixture (tOIM) containing t11 18:1 and t12 18:1 in equal proportion. t11 18:1 and t12 18:1 were incorporated in a tissue-specific manner, and the accrual was significant with increased dietary intake of these trans fatty acid (tFA) isomers. The t12 18:1 isomer was more readily incorporated into the rat tissues than the t11 18:1 isomer. From t11 and t12 18:1, the respective desaturase products, c9,t11 18:2 and c9,t12 18:2, were formed. The calculated conversion rates varied greatly among the tissues of the rats but they were consistently lower for t12 18:1 than for t11 18:1, suggesting that t12 18:1 is a poorer substrate than t11 18:1 for Delta9-desaturase. For both fatty acids investigated, the calculated conversion rates in decreasing order of conversion efficiency were: testes = kidneys > adipose tissue > ovaries > muscle > liver > heart. Overall, there were distinct differences in the conversion of t11 18:1 and t12 18:1, indicating that these 2 fatty acids are metabolized differently despite their structural similarities. Such metabolic differences in tFA accumulation and metabolism may have potential implication in assessing the safety of these tFA isomers because there is a positive correlation between the intake of tFA and the incidence of various diseases.

Trans-11-18 : 1 is effectively Delta9-desaturated compared with trans-12-18 : 1 in humans.

The aim of this human intervention study was to evaluate the Delta9-desaturation of trans-11-18 : 1 (trans-vaccenic acid; tVA) to cis-9,trans-11-18 : 2 (c9,t11 conjugated linoleic acid; CLA) and of trans-12-18 : 1 (t12) to cis-9,trans-12-18 : 2 after a short-term (7 d) and a long-term (42 d) supplementation period. The conversion rates of both trans-18 : 1 isomers were estimated by lipid analysis of serum and red blood cell membranes (RBCM). Subjects started with a 2-week adaptation period without supplements. During the 42 d intervention period, the diet of the test group was supplemented with 3 g/d of tVA and 3 g/d of t12. The diet of the control group was supplemented with a control oil. Serum tVA and t12 levels in the test group increased by fivefold and ninefold after 7 d, respectively, and by eight- and 12-fold after 42 d, respectively, when compared with the adaptation period (P< or =0.002). The serum c9,t11 CLA levels increased by 1.7- and 2.0-fold after 7 d and 42 d, respectively (P< or =0.001). After 42 d, the test group's RBCM c9,t11 CLA content was elevated by 20 % (P=0.021), whereas in the control group it was decreased by 50 % (P=0.002). The conversion rate of tVA was estimated at 24 % by serum and 19 % by RBCM. No increase in c9,t12-18 : 2 was observed in the serum and RBCM, and thus no conversion of t12 could be determined. In conclusion, the endogenous conversion of dietary tVA to c9,t11 CLA contributes approximately one quarter to the human CLA pool and should be considered when determining the CLA supply.