Chemical and thermal characteristics of milk-fat fractions isolated by a melt crystallization

Anhydrous milk fat (AMF) was fractionated by a two-stage dry fractionation process to produce three fractions: high melting (HMF), middle melting (MMF), and low melting (LMF). The HMF (m.p. 42°C) exhibited a broad melting range similar to a plastic fat. The MMF (m.p. 33°C) resembled the original AMF (m.p. 31°C), but with slightly higher solid fat content. The LMF (m.p. 16°C) was liquid at ambient temperature. Differences in the thermal properties of these fractions were attributed to the triacylglycerols (TAG) and their fatty acid composition. Saturated TAG with carbon numbers of 36–54 were concentrated in the HMF; whereas unsaturated TAG of carbon number 36–54 predominated in the LMF. Likewise, the long-chain saturated fatty acids were significantly higher and the long-chain unsaturated fatty acids were significantly lower in the HMF fraction. Binary blends of milk-fat fractions with a range of melting profiles were produced by mixing HMF with AMF, MMF, or LMF. Laboratory-prepared fractions were similar to commercially available fractions.     

Dietary Cocoa Butter or Refined Olive Oil Does Not Alter Postprandial hsCRP and IL-6 Concentrations in Healthy Women

Contrary to other long chain saturated fatty acids (SFA), fats high in stearic acid do not raise plasma cholesterol concentrations, however, a slight elevation in inflammatory markers, plasma fibrinogen and interleukin-6 (IL-6), has been observed in the fasting state. The effect of stearic acid on inflammation in the postprandial state has not yet been reported. We conducted a single blind crossover, randomized, postprandial study to compare the effects of a fat load of cocoa butter high in stearic acid and olive oil in ten healthy women. The test meals contained 1 g of fat per kg body weight (mean 62 g). Blood samples were collected at 0 (fasting), 4 and 6 h. Both diets resulted in a significant increase in serum triacylglycerol (TAG) concentration over time (P = 0.003) and a decrease in serum IL-6 concentration after 4 h followed by an increase to post absorptive values after 6 h (P < 0.001); whereas serum high sensitivity C-reactive protein (hsCRP) concentration was not affected. There was no difference between diets in effects on serum TAG, hsCRP and IL-6 concentrations and no association between postprandial lipemia and inflammatory markers. High intake of dietary fats increase postprandial serum TAG, however, may not affect inflammatory markers postprandially. Thus, fat rich in stearic acid does not seem to increase postprandial inflammation.     

Tempering method for chocolate containing milk-fat fractions

Anhydrous milk fat (AMF) was fractionated by a two-stage dry fractionation process to produce three fractions—high-(HMF), middle-(MMF), and low-melting (LMF). The effect of replacing 12.2–40% by weight of cocoa butter with these fractions on the tempering profile of milk chocolate was studied. Degree of temper was evaluated by differential scanning calorimetry, and expressed as the ratio of enthalpies of melting for higher-stability polymorphs to those of lesser stability. The degree of temper was dependent on the crystallization time and temperature, and the type and quantity of milk-fat fraction in the formulation. Chocolates containing AMF or its fractions in concentrations of up to 20 wt% (total fat basis) were tempered after a conventional thermocycling tempering process (50°C/30 min, 27.7°C/4 min, 31°C/2 min) to obtain products with good contraction and mold release properties. For those milk chocolate formulations that did not temper by the conventional method and resulted in poor contraction and mold release, a new tempering protocol was developed. Lower crystallization temperatures and/or longer holding times were required at concentrations of AMF, MMF, or LMF above 20%. Chocolate containing HMF required slightly higher crystallization temperatures because of high viscosity. Chocolates containing up to 35% HMF and up to 40% of the total weight of fat in the chocolate of AMF, MMF, and LMF were successfully tempered by adjusting crystallization time and temperature.     

Soluble fiber and soybean protein reduce atherosclerotic lesions in guinea pigs. Sex and hormonal status determine lesion extension

These studies were undertaken to assess guinea pigs as potential models for early atherosclerosis development. For that purpose, male, female, and ovariectomized (to mimic menopause) guinea pigs were fed a control or a TEST diet for 12 wk. Differences between diets were the type of protein (60% casein/40% soybean vs. 100% soybean) and the type of fiber (12.5% cellulose vs. 2.5% cellulose/5% pectin/5% psyllium) for control and TEST diets, respectively. Diet had no effect on plasma cholesterol or triacylglycerol (TAG) concentrations; however, there were significant effects related to sex/hormonal status. Ovariectomized guinea pigs had higher plasma cholesterol and TAG concentrations than males or females (P<0.01). In contrast to effects on plasma lipids, hepatic cholesterol and TAG were 50% lower in the TEST groups (P<0.01) compared to controls. Low density lipoproteins (LDL) from guinea pigs fed the TEST diet had a lower number of cholesteryl ester (CE) molecules and a smaller diameter than LDL from controls. Atherosclerotic lesions were modulated by both diet (P<0.0001) and sex (P<0.0001). Guinea pigs fed the TEST diet had 25% less lesion extension whereas males had 20% larger occlusion of the arteries compared to both female and ovariectomized guinea pigs. Significant positive correlations were found between LDL CE and atherosclerotic lesions (r=0.495, P<0.05) and LDL size and fatty streak area (r=0.56, P<0.01). In addition, females fed the TEST diet had the lowest plasma and hepatic cholesterol concentrations, the smallest LDL particles, and the least atherosclerosis involvement compared to the other groups. These data indicate that dietary factors and sex/hormonal status play a role in determining plasma lipids and atherosclerosis in guinea pigs.     

Variations of <Emphasis Type="Italic">trans</Emphasis> octadecenoic acid in milk fat induced by feeding different starch-based diets to cows

The impact of starch sources differing in their velocities of ruminal degradation on the milk fat of dairy cows was studied. The animals received diets containing a slowly degradable (potatoes) or rapidly degradable (wheat) starch concentrate (40% of the dry matter) in a total mixed diet. Milk fat was the only animal performance factor affected: Cows produced significantly less milk fat when fed the wheat diet than the potato diet (−3.3 g/kg, −122 g/d; P<0.05). With the wheat diet, milk fat was poorer in short-chain FA and richer in unsaturated longchain FA, especially in trans octadecenoic acid (4.4 vs. 2.7% of the total FA, P<0.05). A very large increase in the isomer trans-10 18∶1 (+1.46% of the total FA) was observed. Because no difference in volatile FA concentrations in the rumen was revealed, the increase in trans octadecenoic acids, and particularly the isomer trans-10 18∶1, was associated with the larger postprandial drop in ruminal pH with wheat. Similar concentrate levels and FA profiles in both diets indicated that the decrease in milk fat was due to changes in the ruminal environment. Quicker degradation of wheat starch, and hence a greater drop in pH with this diet associated with the absence of any effect on volatile FA, strengthen the hypothesis developed in the literature of enzyme inhibition via increased levels of trans octadecenoic acids, especially the trans-10 isomer. Hence, milk fat can be decreased with rapidly degradable starch sources and not only with high levels of concentrates in the diet or added fat. More detailed work is necessary to elucidate the microorganisms involved and to determine whether metabolic pathways similar to those reported for high-concentrate diets are involved.     

Effect of modified dairy fat on postprandial and fasting plasma lipids and lipoproteins in healthy young men

Fatty acid profile of milk fat can be modified by cow feeding strategies. Our aim was postprandially and after 4 wk to compare the effect of a modified milk fat (M diet) [with 16% of the cholesterolemic saturated fatty acid (C12–16) replaced by mainly oleic and stearic acids] with the effect of D diet, including a conventional Danish milk fat on plasma lipids and lipoproteins. A side effect of the cow feeding regime was a 5% (w/w) increase in trans fatty acid in M diet. Eighteen subjects were fed for two periods of 4 wk strictly controlled isoenergetic test diets with 40% of energy from total fat and the same content of dietary cholesterol in a randomized study with cross-over design. Contrary to expectations, fasting low density lipoprotein (LDL) cholesterol concentration did not differ after the experimental periods. However, M diet resulted in a higher fasting total triacylglycerol concentration compared to D diet (P=0.009). Postprandial samples were taken at two different occasions (i) at day 21, after breakfast and lunch and (ii) on the last day of the study 2, 4, 6, and 8 h after a fat load. Postprandial plasma triacylglycerol and chylomicron triacylglycerol showed higher peak values after D diet than M diet (interaction effect, diet × times P<0.05). In conclusion, M diet did not lower LDL cholesterol compared to D diet. Thus any cholesterol-lowering effect of oleic and stearic acids may have been obscured by the high content of cholesterol-raising saturated fatty acids in milk fat. A higher content of the trans fatty acids in M diet might have counteracted the cholesterol neutral/decreasing effect and increased plasma triacylglycerol.     

Dietary fats and energy levels differently affect tissue lipogenic enzyme activity in finishing pigs

The aim of the present study was to determine the relationship between high and low digestible energy levels (9.5 vs. 15.4 MJ ME/kg) and either tallow or soy oil supplementation (5%rpar; on lipogenic activities and fatty acid profile of the backfat tissue outer layer and liver tissue in finishing pigs. Twenty Large White pigs averaging 30 (initial) to 106 kg (final) live weight were allocated into four dietary groups and fed the diets ad libitum. The lipid content and fatty acid composition of the tissues were determined and glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME), and fatty acid synthase (FAS) activity were measured. Growth performance and carcass measurements were affected by the dietary energy levels but not by the fat sources. Lipid deposition rate of animals fed the low energy diets was lowered regardless whether tallow or soy oil was supplemented. Unlike lipid deposition, fatty acid profile was influenced by both dietary factors. Pigs fed the low energy diet supplemented with soy oil exhibited the lowest level of saturated (P<0.001), monounsaturated (P<0.001), and the highest level of polyenic fatty acids in the backfat, the opposite was the case for the pigs fed the high energy diet supplemented with beef tallow. The fatty acid profile of the adipose tissue of animals fed the other two diets were intermediate, but clear distinction of the profile due to diets was visible. Independent of dietary treatments, lipogenic activities were up to 10 times higher in the backfat than in the liver. G6PDH activity was higher (P<0.05) due to high energy diet, whereas the activities of ME and FAS were not affected. Animals fed the high energy diet either supplemented with tallow or soy oil exhibited higher ME activity lpar;P<0.05) in the backfat, without any effects on G6PDH activity. In contrast, dietary fat sources affected the FAS activity, with lower activity lpar;P<0.05) exhibited in the backfat of animals fed the soy oil diets. The present results indicate that dietary manipulation, which change the flux through the pathway of lipogenesis and pentose-phosphate must affect differently the activities of the involved enzymes. The effect of the dietary energy level was stronger and overwhelmed the inducing effect of the PUFA on the activities of the collateral enzymes. In contrast the immediately involved lipogenic enzyme FAS responded more to dietary PUFA stimulation than to the energy supply.     

Regulation of very low density lipoprotein apo B metabolism by dietary fat saturation and chain length in the guinea pig

Studies investigated the effects of dietary fatty acid composition and saturation on the regulation of very low density lipoprotein (VLDL) apo B flux, clearance, and conversion to low density lipoprotein (LDL) in guinea pigs fed semipurified diets containing 15% (w/w) corn oil (CO), lard (LA), or palm kernel oil (PK). Plasma cholesterol levels were highest with dietary PK (3.1±1.0 mmol/L) followed by LA (2.4±0.4 mmol/L) and CO (1.6±0.4 mmol/L) intake. VLDL particles were larger (P<0.05) in the LA (78±7 nm) and PK (69±10 nm) groups compared to animals fed CO (49±5 nm). VLDL-apo B fractional catabolic rates (FCR) were highest in guinea pigs fed the LA diet (P<0.05) and VLDL apo B flux, estimated from VLDL ¹²⁵I-apo B turnover kinetics, were higher in LA compared to PK or CO fed guinea pigs. In the case of PK consumption, the kinetic estimates of VLDL apo B flux significantly underestimated rates compared to direct VLDL apo B secretion measurements and LDL turnover analyses. These data demonstrate that differences in the composition and amount of saturated fatty acids have differential effects on VLDL apo B flux, catabolism, and conversion to LDL which, together with changes in LDL receptor-mediated catabolism, determine plasma LDL cholesterol levels in guinea pigs. The data also indicate that kinetic analysis of VLDL metabolism in PK fed animals is inaccurate possibly due to the presence of a small, nonequilibrating pool of newly synthesized VLDL which is rapidly converted to LDL.     

Sparing effects of selenium and ascorbic acid on vitamin C and E in guinea pig tissues

Background

Selenium (Se), vitamin C and vitamin E function as antioxidants within the body. In this study, we investigated the effects of reduced dietary Se and L-ascorbic acid (AA) on vitamin C and α-tocopherol (AT) status in guinea pig tissues.

Methods

Male Hartley guinea pigs were orally dosed with a marginal amount of AA and fed a diet deficient (Se-D/MC), marginal (Se-M/MC) or normal (Se-N/MC) in Se. An additional diet group (Se-N/NC) was fed normal Se and dosed with a normal amount of AA. Guinea pigs were killed after 5 or 12 weeks on the experimental diets at 24 and 48 hours post AA dosing.

Results

Liver Se-dependent glutathione peroxidase activity was decreased (P < 0.05) in guinea pigs fed Se or AA restricted diets. Plasma total glutathione concentrations were unaffected (P > 0.05) by reduction in dietary Se or AA. All tissues examined showed a decrease (P < 0.05) in AA content in Se-N/MC compared to Se-N/NC guinea pigs. Kidney, testis, muscle and spleen showed a decreasing trend (P < 0.05) in AA content with decreasing Se in the diet. Dehydroascorbic acid concentrations were decreased (P < 0.05) in several tissues with reduction in dietary Se (heart and spleen) or AA (liver, heart, kidney, muscle and spleen). At week 12, combined dietary restriction of Se and AA decreased AT concentrations in most tissues. In addition, restriction of Se (liver, heart and spleen) and AA (liver, kidney and spleen) separately also reduced AT in tissues.

Conclusion

Together, these data demonstrate sparing effects of Se and AA on vitamin C and AT in guinea pig tissues.     

Dietary Conjugated Linoleic Acid Induces Lipolysis in Adipose Tissue of Coconut Oil-Fed Mice but not Soy Oil-Fed Mice

Mice fed diets containing conjugated linoleic acid (CLA) are leaner than mice not fed CLA. This anti-obesity effect is amplified in mice fed coconut oil-containing or fat free diets, compared to soy oil diets. The present objective was to determine if CLA alters lipolysis in mice fed different base oils. Mice were fed diets containing soy oil (SO), coconut oil (CO), or fat free (FF) for 6 weeks, followed by 10 or 12 days of CLA or no CLA supplementation. Body fat, tissue weights, and ex vivo lipolysis were determined. Relative protein abundance and activation of perilipin, hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL), and adipose differentiation related protein (ADRP) were determined by western blotting. CLA feeding caused mice to have less (P < 0.05) body fat than non-CLA fed mice. This was enhanced in CO and FF-fed mice (CLA × oil source, P < 0.05). There was also a CLA × oil source interaction on lipolysis as CO + CLA and FF + CLA-fed mice had increased (P < 0.05) rates of lipolysis but SO + CLA-fed mice did not. However, after 12 days of CLA consumption, activated perilipin was increased (P < 0.05) only in SO + CLA-fed mice and total HSL and ATGL were decreased (P < 0.05) in CO + CLA-fed mice. Therefore, the enhanced CLA-induced body fat loss in CO and FF-fed mice appears to involve increased lipolysis but this effect may be decreasing by 12 days of CLA consumption.     

Carbohydrate type and amount alter intravascular processing and catabolism of plasma lipoproteins in guinea pigs

To test the effects of exchanging dietary complex and simple carbohydrate for fat calories on lipoprotein metabolism, guinea pigs were fed two different fat/carbohydrate ratios: 2.5∶58% (w/w) or 25∶29% (w/w) with either sucrose or starch as the carbohydrate source. Animals fed high-fat had higher plasma low-density lipoprotein (LDL) and hepatic cholesterol concentrations than animals fed low-fat diets (P<0.01). The cholesteryl ester content per particle was higher, and the number of triacylglycerol (TAG) molecules was lower in very low density lipoprotein (VLDL) and LDL from animals fed high-fat diets. Intake of high-fat/sucrose resulted in higher plasma LDL concentrations than intake of high-fat/starch, and animals fed low-fat/starch had the highest plasma TAG concentrations associated with VLDL particles containing more TAG molecules, as well as a TAG-enriched LDL. The activity of plasma lecithin cholesteryl:acyl transferase (LCAT) was highest in animals fed high-fat/sucrose, and heart lipoprotein lipase (LPL) activity was higher in animals fed high-fat diets. Hepatic apoprotein B/E (apo B/E) receptor number (B_max) was increased 21% with low-fat diets (P<0.01). These results suggest that the hypercholesterolemia induced by high-fat and by sucrose intake are associated with a higher plasma LCAT activity which results in a cholesteryl ester-enriched VLDL which, by the action of LPL, might be more readily converted to LDL through the delipidation cascade leading to downregulation of hepatic apo B/E receptors. The hypertriglyceridemia associated with low-fat intake may result from increased production of VLDL TAG, which would explain the increased TAG content and the higher TAG/CE ratio of VLDL from animals fed the low-fat/starch diet.     

Effect of a modified milk fat and calcium in purified diets on cholesterol metabolism in hamsters

Modification of milk fat both by partially replacing saturated FA with oleic acid (18∶1) and by increasing calcium intake independently reduces plasma cholesterol. Whether modification of both factors together would synergistically reduce plasma cholesterol is unknown. Seventy-two male golden Syrian hamsters were separated into four diet treatment groups (n=18/group) and fed ad libitum for 7 wk. Diets contained either modified milk fat (MMF) or regular milk fat (RMF) with either 0.5% (MMF and RMF) or 1.3% calcium (w/w) (MMFC and RMFC). All diets contained 11% test fat, 4% soybean oil, and 0.15% cholesterol (w/w). During the last week, feces were collected for three consecutive days for analysis of fecal FA, cholesterol, and calcium excretion. Overnight-fasted animals were sacrificed, and plasma and livers were collected for lipid analysis. Neither MMF nor additional calcium significantly affected plasma lipids. However, significant interactions existed between MMF and additional calcium for the ratio of LDL cholesterol to HDL cholesterol (LDL/HDL), indicating that increased calcium intake reduced this ratio only in RMF animals. In addition, MMF reduced LDL/HDL relative to RMF. MMF significantly increased hepatic total and esterified cholesterol. Additional calcium significantly increased fecal calcium and saturated FA (SFA) excretion, whereas MMF significantly reduced SFA excretion. RMFC induced the highest excretion of 16∶0 among all groups. Replacement of SFA with 18∶1 in the MMF reduced the impact of high calcium on LDL/HDL. Additional calcium reduced LDL/HDL only in the presence of RMF, which may be achieved through an increased excretion of 16∶0.     

Dietary fatty acid profile affects endurance in rats

Typically, athletes are advised to increase their consumption of carbohydrates for energy and, along with the general population, to reduce consumption of saturated fats. It is now recognized that fats are not identical in their influence on metabolism, and we argue that the composition of the polyunsaturated fat component should not be ignored. The aim of this study was to manipulate the dietary fatty acid profile in a high-carbohydrate diet in order to investigate the effect of dietary polyunsaturates on submaximal endurance performance in rats. Rats were fed one of three isoenergetic diets containing 22 energy percentage (E%) fat for 9 wk. The diets comprised an essential fatty acid-deficient diet (containing mainly saturated fatty acids); a diet high in n-6 fatty acids, High n-6; and a diet enriched with n-3 fatty acids, High n-3. Submaximal endurance in rats fed the High n-3 diet was 44% less than in rats fed the High n-6 diet (P<0.02). All rats were then fed a standard commercial laboratory diet for a 6-wk recovery period, and their performances were reevaluated. Although endurance in all groups was lower than at 9 wk, it was again significantly 50% lower in the High n-3 group than the High n-6 group (P<0.005). Although n-3 fats are considered beneficial for cardiovascular health, they appear to reduce endurance times, and their side effects need to be further investigated.     

Influence of triacylglycerol structure and fatty acid profile of dietary fats on milk triacylglycerols in the rat. A two-generation study

We investigated the influence of dietary fatty acid profile and triacylglycerol structure on the fatty acid profile and triacylglycerol structure of milk lipids in two generations of rats. Three groups of rats received diets containing 20% fat of which approximately 20% was n-3 fatty acids located in different positions of the triacylglycerol: a fish oil-based diet [docosahexaenoic acid (22:6n-3) predominantly in thesn-2 position], a seal oil-based diet (22:6n-3) predominantly in thesn-1/sn-3 position or a plant oil-based diet [α-linolenic acid (18:3n-3) distributed evenly between the three positions]. This design allowed us to investigate (i) the effect of the triacylglycerol structure of the dietary fat; (ii) the effect of receiving the n-3 fatty acids as long-chain derivatives or as the precursor, 18:3n-3; and (iii) the long-term effects over two generations. The fatty acid profiles of the milk lipids largely reflected the diets, but in the second generation, the level of medium-chain fatty acids was higher (P<0.05) in the milk from rats fed the fish oil diet (24%) compared with the other dietary groups (15 and 18%). This suggests an increased endogenous synthesis of fatty acids in the mammary glands of the fish oil-fed rats. The levels of long-chain n-3 fatty acids in milk were higher (P<0.05) in rats fed maire n-3 fatty acids in milk were higher (P<0.05) in rats fed marie oils (8–12%) compared with rats fed vegetable oil (1%) in both generations. The level of long-chain n-3 fatty acids was significantly higher in the milk from the fish oil-fed rats (12.3%) compared to the seal-oil fed rats (8.0%) in the first generation, but not in the second generation (8.9 vs. 9.1%). The general structure of milk triacylglycerols was maintained in the three experimental groups with 16:0 acylated in thesn-2 position and 18:1 in thesn-1/sn-3 positions. The triacylglycerol structure of mammalian milk appears to be conserved even during extreme dietary manipulation over two generations and an extensive enrichment with long-chain n-3 polyunsaturated fatty acids requires their presence in the diet.     

Influence of stearic acid on hemostatic risk factors in humans

Stearic acid has been claimed to be prothrombotic. Elevated plasma factor VII coagulant activity (FVIIc) may raise the risk of coronary thrombosis in the event of plaque rupture. Fibrinogen, an acute-phase protein, is necessary for normal blood clotting; however, elevated levels of fibrinogen increase the risk of coronary heart disease (CHD). Here I report the results of three controlled, human dietary intervention studies, which used a randomized crossover design to investigate the hemostatic effects of stearic acid-rich test diets in healthy young men. A diet high in stearic acid (shea butter) resulted in a 13% lower fasting plasma FVIIc than a high palmitic acid diet, and was 18% lower than a diet high in myristic and lauric acids (P=0.001) after 3 wk of intervention. The stearic acid-rich test fat increased plasma fibrinogen concentrations slightly compared with the myristic-lauric acid diet (P<0.01). When investigating the acute effects of fatty meals, those high in stearic acid (synthesized test fat) resulted in a smaller postprandial increase in FVII than those high in trans and oleic FA, indicating a smaller increase in activated FVII after ingesting stearic acid compared with fats high in monounsaturated FA, probably caused by lower postprandial lipemia. Thus, the present investigations did not find dietary stearic acid to be more thrombogenic, in either fasting effects compared with other longchain FA, or in acute effects compared with dietary unsaturated FA, including trans monounsaturated FA. The slightly increased effect on fasting plasma fibrinogen may be biologically insignificant, but it should be investigated further.     

Atorvastatin and simvastatin have distinct effects on hydroxy methylglutaryl-CoA reductase activity and mRNA abundance in the guinea pig

The effects of atorvastatin and simvastatin on hydroxy methylglutary (HMG)-CoA reductase activity and mRNA abundance were studied in guinea pigs randomized to three groups: untreated animals and those treated with 20 mg/kg of atorvastatin or simvastatin. Guinea pigs were fasted for 0, 6, 12, or 18 h in an attempt to remove the drug from their systems. Reductase activity and mRNA levels were analyzed after each time point. Reductase inhibitor treatment resulted in 50–60% lower cholesterol concentrations compared to untreated guinea pigs (P<0.0001), while plasma triacylglycerol (TAG) concentrations did not differ among groups. Plasma cholesterol and TAG were 50–70% lower after 18 h fasting in the three groups (P<0.001). In the nonfasting state, simvastatin and atorvastatin treatment did not affect HMG-CoA reductase activity compared with untreated animals. However, after 6 h of fasting, simvastatin-treated guinea pigs had higher HMG-CoA reductase activity than untreated animals (P<0.01), suggesting that the drug had been removed from the enzyme. In contrast, atorvastatin-treated guinea pigs maintained low enzyme activity even after 18 h of fasting. Further, HMG-CoA reductase mRNA abundance was increased by sevenfold after atorvastatin treatment and by twofold after simvastatin treatment (P<0.01). These results suggest that sinvastatin and atorvastatin have different half-lives, which may affect HMG-CoA reductase mRNA levels. The increase in reductase activity by simvastatin during fasting could be related to an effect of this statin in stabilizing the enzyme. In contrast, atorvastatin, possibly due to its longer half-life, prolonged inhibition of HMG-CoA reductase activity and resulted in a greater increase in mRNA synthesis.     

Fish Oil and Olive Oil Supplementation in Late Pregnancy and Lactation Differentially Affect Oxidative Stress and Inflammation in Sows and Piglets

This study was conducted to compare the effects of fish oil and olive oil supplementation in late pregnancy and during lactation on oxidative stress and inflammation in sows and their piglets. A total of 24 sows were fed a basal diet supplemented with additional corn starch (CON), fish oil (FO) or olive oil (OO). Sows fed an OO diet during late gestation had a higher piglet birth weight compared with CON‐fed and FO‐fed sows (P < 0.05). Furthermore, sows from the OO group had a higher milk fat content than sows from CON and FO groups, and a lower pre‐weaning mortality of piglets was observed in the OO group (P < 0.05). Maternal FO supplementation resulted in increased malondialdehyde concentration in sow plasma, colostrum, milk and piglet plasma than in CON and OO groups (P < 0.05). However, an increased total antioxidant capacity (T‐ACC) and activities of glutathione peroxidase (GSH‐Px) and total superoxide dismutase (T‐SOD) were also observed in the FO group (P < 0.05). Sows fed an OO diet had significantly decreased interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6) and tumor necrosis factor‐α (TNF‐α) concentrations in milk compared with CON and FO fed sows (P < 0.05). Moreover, lower plasma IL‐1β and TNF‐α levels were observed in piglets from the OO group compared with the CON group (P < 0.05). Collectively, these results suggest that an OO diet is most beneficial in late gestation and during lactation in sows. However, FO increases the susceptibility to oxidative stress in sows and piglets.     

Positional distribution of decanoic acid: Effect on chylomicron and VLDL TAG structures and postprandial lipemia

Although medium-chain FA (MCFA) are mainly absorbed via the portal venous system, they are also incorporated into chylomicron TAG; therefore, the positional distribution of MCFA in TAG is likely to affect their metabolic fate. We studied chylomicron and VLDL TAG structures, as well as the magnitude of postprandial lipemia, after two oral fat loads containing decanoic acid (10∶0) predominantly at the sn-1(3),2 (MML) or at the sn-1,3 positions (MLM) of TAG in a randomized, double-blind, crossover clinical trial with 10 healthy, normal-weight volunteers. An MS-MS method was used to analyze TAG regioisomers. The position of decanoic acid in chylomicron TAG reflected its position in the TAG ingested, and TAG with none, one, two, or three decanoic acid residues were detected after ingestion of both fats. More (P<0.05) 30∶0 and 38∶1 TAG (acyl carbons:double bonds) and fewer 46∶5, 54∶5 and 54∶4 TAG were found in chylomicrons after ingestion of MML than after MLM. The VLDL TAG composition did not differ between the fat loads but did change (P<0.05) 2 to 6 h after ingestion of both fats. No statistical differences were seen between the fat loads in areas under the plasma, chylomicron, or VLDL TAG response curves or in FFA concentrations. Thus, the positional distribution of MCFA in TAG affects their metabolic, fate, but the magnitude of postprandial lipemia does not seem to be dependent on the positional distribution of MCFA in the ingested fat.     

Hepatic lipid characteristics and histopathology of laying hens fed CLA or n−3 fatty acids

The effect of dietary CLA and n−3 PUFA on hepatic TAG accumulation, histopathology, and FA incorporation in lipid classes by laying chickens was investigated. One hundred twenty 30-wk-old single-comb white leghorn laying hens were distributed randomly to four treatments (3 replications of 10 birds) and were fed diets containing CLA and animal fat (Diet I), 18∶3n−3 (Diet II), or long-chain n−3 FA (Diet III). A sunflower oil (n−6 FA)-based diet was the control. Feeding Diet I resulted in an increase in hepatic total lipids (P<0.05). The liver TAG content was 32.2, 18.9, 29.4, and 18.7 mg/g for hens fed Diet I, Diet II, Diet III, and the control diet, respectively (P<0.05). The serum TAG was lowest in bilds fed Diet II (P<0.05). Diet I resulted in an increase in the total number of fat vacuoles and lipid infiltration in hepatocytes (P<0.05). The number of cells with 75% or higher lipid vacuolation was observed only in birds fed Diet I. Feeding diets containing CLA resulted in an increase in the content of the c9,t11 CLA isomer in liver TAG and PC (P<0.05). No difference was observed in the CLA concentration of hepatic PE fractions. The content of DHA (22∶6n−3) was higher in the TAG, PC, and PE of hens fed Diet II and Diet III than Diet I and the control (P<0.05). Feeding CLA resulted in an increase in total saturated FA in the TAG and PC fractions (P<0.05). Long-term feeding of CLA in laying birds leads to an increase in liver TAG and may predispose birds to fatty liver hemorrhagic syndrome.     

Lactation curves and effect of pup removal on milk fat of C57BI/6J mice fed different diet fats

Groups of C57BI/6J mice, fed either acis (C-Diet) ortrans diet (T-Diet) were milked without preconditioning at 6, 8, 10 and 12 dayspostpartum. On day 10, groups of mice were also milked 4, 6 and 18 h after separation of the pups. Except for the 18-h separation, all T-Diet fed animals produced milk of lower fat content than did the C-Diet animals (P<0.001) throughout the lactation period measured. In the C-Diet mice, the 6-h separation period resulted in a decrease (P<0.03) in fat, but the diet-depressed milk fat of T-Diet animals was not decreased further until the 18-h separation period. Milk volume increased as lactation progressed and was greatly increased as a result, of preconditioning (P<-0.001), even at 4 h of separation when fat was not reduced, and was always greater for T-Diet animals. Within diet groups, fatty acid composition was similar throughout the lactation period studied and was not affected by preconditioning, except in the 18-h separation period, whende novo fatty acids were significantly reduced (P≤0.05). The data are consistent with the hypothesis that preconditioning results in lowered milk fat values and that preconditioning techniques can explain discrepancies in literature values for murine milk fat. Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April, 1990.