Carl-Erik Høy

The digestion of dietary triacylglycerols

Dietary triacylglycerols (TAGs) are the major lipid components in the human diet and they are carriers of energy as well as important fatty acids. Many factors affect the digestion and absorption of TAGs. Evidence is accumulating that, in addition to the overall fatty acid profile, the TAG structure and the species composition are of importance when considering the nutritional effects of a dietary fat. There is good evidence that in addition to its short-term effects in the intestine on absorption of fatty acids the TAG structure also has long-term effects resulting from differences in the profile of absorbed fatty acids. Observations on the different atherogenic potential of dietary fats have given us a clear indication of the importance of the TAG structure for absorption of saturated fatty acids. In this context, one may focus on the effects of the structure of dietary fats as such, or one may speculate additionally on the possibilities of modifying the structure of fats to affect their absorption and the distribution of the fatty acids in the body after digestion and uptake. In this review we will summarize diverse aspects of TAG digestion and absorption, as well as the influences of the fatty acid composition and the intramolecular structure of dietary TAGs on their digestion and absorption.

Production of specific-structured lipids by enzymatic interesterification: Elucidation of Acyl migration by response surface design

Production of specific-structured lipids (SSL) by lipase-catalyzed interesterification has been attracting more and more attention recently. However, it was found that acyl migration occurs during the reaction and causes the production of byproducts. In this paper, the elucidation of acyl migration by response surface design was carried out in the Lipozyme IM (Rhizomucor miehei)-catalyzed interesterification between rapeseed oil and capric acid in solvent-free media. A five-factor response surface design was used to evaluate the influence of five major factors and their relationships. The five factors, water content, reaction temperature, enzyme load, reaction time and substrate ratio, were varied at three levels together with two star points. All parameters besides substrate ratio had strong positive influences on acyl migration, and reaction temperature was most significant. The contour plots clearly show the interactions between the parameters. The migration rates of different fatty acids were also compared from three different sets of experiments during the lipase-catalyzed reaction. The best-fitting quadratic response surface model was determined by regression and backward elimination. The coefficients of determination (R2) of the model were 0.996 and 0.981 for Q2 value. The results show that the fitted quadratic model satisfactorily expresses acyl migration for the enzymatic interesterification in the batch reactor used.

Maternal fish oil supplementation in lactation: Effect on visual acuity and n−3 fatty acid content of infant erythrocytes

Studies on formula-fed infants indicate a beneficial effect of dietary DHA on visual acuity. Cross-sectional studies have shown an association between breast-milk DHA levels and visual acuity in breast-fed infants. The objective in this study was to evaluate the biochemical and functional effects of fish oil (FO) supplements in lactating mothers. In this double-blinded randomized trial, Danish mothers with habitual fish intake below the 50th percentile of the Danish National Birth Cohort were randomized to microencapsulated FO [1.3 g/d long-chain n−3 FA (n−3 LCPUFA)] or olive oil (OO). The intervention started within a week after delivery and lasted 4 mon. Mothers with habitual high fish intake and their infants were included as a reference group. Ninety-seven infants completed the trial (44 OO-group, 53 FO-group) and 47 reference infants were followed up. The primary outcome measures were: DHA content of milk samples (0, 2, and 4 mon postnatal) and of infant red blood cell (RBC) membranes (4 mon postnatal), and infant visual acuity (measured by swept visual evoked potential at 2 and 4 mon of age). FO supplementation gave rise to a threefold increase in the DHA content of the 4-mon milk samples (P<0.001). DHA in infant RBC reflected milk contents (r=0.564, P<0.001) and was increased by almost 50% (P<0.001). Infant visual acuity was not significantly different in the randomized groups but was positively associated at 4 mon with infant RBC-DHA (P=0.004, multiple regression). We concluded that maternal FO supplementation during lactation did not enhance visual acuity of the infants who completed the intervention. However, the results showed that infants with higher RBC levels of n−3 LCPUFA had a better visual acuity at 4 mon of age, suggesting that n−3 LCPUFA may influence visual maturation.

Does Fat in Milk, Butter and Cheese Affect Blood Lipids and Cholesterol Differently?

Objective: To compare the effects of isoenergetic amounts of milk, cheese and butter (adjusted to the same content of lactose and casein) on fasting and postprandial blood lipids and lipoproteins, and on postprandial glucose and insulin response. Design: The experiments were designed to provide 20% of total energy from dairy fat, as either whole milk, mean (±SD) 2164 (±97) g, butter 93 (±4) g, and hard cheese 305 (±45) g, which were served to 14 healthy young men for three periods of three weeks each, separated by washout periods, in a randomized, cross-over study with strictly controlled dietary intake. Fasting blood samples were taken at the end of the study periods. Measurements of the postprandial effect of the three different dairy test products (0.7 g of milk fat/kg body weight) were carried out on day 4 of each intervention period. Blood samples were taken before and at 2, 4, 6 and 8 hours following intake of the meals. Results: Fasting LDL cholesterol concentration was significantly higher after butter than cheese diet (p = 0.037), with a borderline significant difference in total cholesterol (p = 0.054) after the experimental periods of three weeks. Postprandial glucose showed a higher response after cheese diet than after milk diet (p = 0.010, diet × time interaction). Conclusions: A different effect of fat in milk and butter could not be confirmed in this study. The moderately lower LDL cholesterol after cheese diet compared to butter diet should be investigated further.

Effects of dietary linseed oil and marine oil on lipid peroxidation in monkey liver in vivo and in vitro

Diets rich in linoleic acid (CO) from corn oil, or in linoleic acid and either α-linolenic acid (LO) based on linseed oil or n−3 fatty acids (MO) from menhaden oil were fed to male and female Cynomolgus monkeys for 15 wk. In the liver a 40% reduction of α-tocopherol occurred in the MO group relative to the CO and LO groups followed by increased formation of lipofuscinin vivo. A four-fold increase of α-tocopherol in the MO diet (MO+E) brought the level in the liver to that found with CO and LO. The increased peroxidation in the MO group in the liver phospholipids was associated with the replacement of 60% of the n−6 fatty acids by n−3 fatty acids from menhaden oil. Similar fatty acid profiles were found in groups fed MO and MO+E, respectively. Compared to the CO fed group, feeding α-linolenic acid only resulted in a slight incorporation of n−3 fatty acids in the liver membranes mainly due to a direct incorporation of α-linolenic acid. However, in monkeys fed menhaden oil more than 30% of the total fatty acids in the liver phospholipids were n−3 fatty acids. The various diets did not influence the activity of liver catalase (EC 1.11.1.6) nor superoxide dismutase (EC 1.15.1.1), but glutathione-peroxidase activity (EC 1.11.1.9) was higher in monkeys fed the MO diet. The catalase activity in females was 20% higher than in males. In anin vitro assay, liver microsomes from monkeys fed the MO diet or the MO diet supplemented with tocopherol produced similar amounts of thiobarbituric acid reactive substances and at a much higher rate than microsomes from the CO and LO groups. It appeared that α-tocopherol did not protect long-chain n−3 C20 and C22 fatty acids as well as n−6 fattya acids against peroxidation. The present data showed that monkeys were not fully able to compensate for increased peroxidative stress but a four-fold supplement of vitamin E to the diets reduced the oxidation.

Intestinal Absorption of Octanoic, Decanoic, and Linoleic Acids: Effect of Triglyceride Structure

The influence of triglyceride structure on the intestinal absorption of specific triglycerides was investigated. A bolus of either a structured or a randomized oil was given to lymph-cannulated rats. The structured oil contained medium-chain fatty acids (MCFA) in the sn-1 and sn-3 position of the triglyceride, and linoleic acid (C18:2 n-6) in the sn-2 position, whereas in the randomized oil the same fatty acids were distributed randomly between the three positions. The absorption of MCFA was highest from the randomized oil, where approximately 33% of the MCFA were located in the sn-2 position. The absorption of C18:2 n-6 was highest from the structured oil, where C18:2 n-6 is located in the sn-2 position, indicating that the intestinal absorption is influenced by triglyceride structure, and that the absorption is enhanced for fatty acids located in the sn-2 position. Prior to lymph collection, the rats were fed either a fish oil or a vegetable oil diet. The absorption of C18:2 n-6 was highest in the rats previously fed the fish oil diet. The incorporation of the highly unsaturated fatty acids from the fish oil into the membrane phospholipids may thus influence the absorption of fat.

The stereospecific triacylglycerol structures and fatty acid profiles of human milk and infant formulas

Background: The stereospecific structures of the triacylglycerol molecules in human milk differ from that of cows milk and vegetable oils, which are the fat sources used in infant formula. In human milk, palmitic acid (16:0) is predominantly esterified in the sn2 position, whereas vegetable oils or cows milk fat contain most of their 16:0 in the outer positions of the triacylglycerol molecules. Furthermore, human milk contains long-chain polyunsaturated fatty acids, which are not present in either cows milk or vegetable oils. Methods: By standard lipid analysis procedures, we examined the triacylglycerol structures and fatty acid profiles of fats from 28 infant formulas or formulas for special indications available in the Danish market from 1999 to 2003. Results: The total fatty acid compositions of the formulas showed a 16:0 content almost similar to human milk, whereas the content in the sn2 position was considerably lower. The content of oleic acid was found to be equal to or higher than in human milk in 21 of 28 formulas, whereas the content in the sn2 position was higher in all but one formula. Most formulas had linoleic acid levels considerably above that of human milk. Long-chain polyunsaturated fatty acids (arachidonic acid and docosahexaenoic acid) were present in all preterm formulas, but only in 3 of the term formulas. Conclusion: We found that most of the examined infant formulas, both preterm and term as well as special formulas, had stereospecific structures and fatty acid profiles that differed considerably from that of human milk.

Correlation between level of (n − 3) polyunsaturated fatty acids in brain phospholipids and learning ability in rats. A multiple generation study

The effects of dietary n - 3 polyunsaturated fatty acids (PUFAs) on major brain phospholipids were examined in the rat throughout four generations. Dietary fats were: a seal oil (22:6(n - 3) located mainly in the sn-1/3-position of the TG); a fish oil (22:6(n - 3) located mainly in the sn-2 position of the TG); or a vegetable oil containing 18:3(n - 3). The effect of the TG structure of the dietary fat and chain length of n - 3 PUFA on assimilation in the brain was compared with chow fed rats. The rats fed marine fats had significantly higher levels of long-chain n - 3 PUFAs in brain PE and PS, compared to the vegetable oil and chow fed rats, but no effects of TG structure of dietary fat were observed. Dietary 18:3(n - 3) raised the amount of 22:6(n - 3) compared to the control group, but not to the levels of the marine groups that received preformed 22:6(n - 3). Fish oil fed rats had higher levels of 20:5(n - 3) and 22:5(n - 3) compared with the seal oil fed rats, whereas 22:6(n - 3) were similar. Only minor changes in PI, PIP, and PIP2 were found. The fourth generation was tested for spatial learning ability in a Morris water maze. The experimental groups had similar learning abilities, which were increased compared to the control group.

Dietary intervention increases n-3 long-chain polyunsaturated fatty acids in skeletal muscle membrane phospholipids of obese subjects. Implications for insulin sensitivity

Objective  Cross‐sectional studies suggest that the fatty acid (FA) composition of phospholipids in skeletal muscle cell membrane may modulate insulin sensitivity in humans. We examined the impact of a hypocaloric low‐fat dietary intervention on membrane FA composition and insulin sensitivity.

Effect of high-dose growth hormone and glutamine on body composition, urine creatinine excretion, fatty acid absorption, and essential fatty acids status in short bowel patients : A randomized, double-blind, crossover, placebo-controlled study

BACKGROUND Positive effects of high dose growth hormone and glutamine (GH + GLN) on body composition in short bowel patients have been described. Lack of effects on intestinal absorption found in some studies has been ascribed to concomitant essential fatty acid (EFA) deficiency. This study describes changes in body weight (BW) and composition, 24-h urine creatinine excretion, intestinal fatty acid absorption (total, saturated, unsaturated and EFA), and EFA status in relation to treatment with GH + GLN in 8 short bowel patients. METHODS A double-blind, crossover study between placebo and growth hormone (mean, 0.12 mg/kg/day) plus oral (mean, 28 g/day) and parenteral glutamine (mean, 5.2 g/day) for 28 days. Body composition was measured by dual-energy absorptiometry (DEXA) scans. Intestinal fatty acid absorption was evaluated in balance studies, and EFAs were measured in plasma phospholipids by gas liquid chromatography. RESULTS Active treatment did not increase BW, lean body mass (LBM), fat mass (FM) and bone mass significantly compared with placebo treatment, but BW increased 1.03 kg (1.7%, P < 0.05), LBM 2.93 kg (8.7%, P < 0.001) and FM decreased 2.41 kg (10.6%, P < 0.001) in comparison with baseline. Twenty-four-hour urine creatinine excretion did not differ between study periods. No changes in intestinal absorption of fatty acids were seen, and no changes in EFAs measured in plasma phospholipids were observed. Only 1 of 8 patients, who did not receive parenteral lipids, had a Holman index above 0.2, indicative of EFA deficiency. All developed peripheral oedema. CONCLUSIONS Combined high dose growth hormone and glutamine administered for 4 weeks, did not improve absorption of fatty acids or EFA status in short bowel patients. No changes in BW or composition were seen when comparing treatment to placebo periods. The increase in LBM measured by DEXA scan, comparing treatment and baseline periods, was not accompanied by an increase in the 24-h urinary creatinine excretion and is suspected to be associated with an accumulation in extracellular fluids.Background: Positive effects of high dose growth hormone and glutamine (GH + GLN) on body composition in short bowel patients have been described. Lack of effects on intestinal absorption found in some studies has been ascribed to concomitant essential fatty acid (EFA) deficiency. This study describes changes in body weight (BW) and composition, 24-h urine creatinine excretion, intestinal fatty acid absorption (total, saturated, unsaturated and EFA), and EFA status in relation to treatment with GH + GLN in 8 short bowel patients. Methods: A double-blind, crossover study between placebo and growth hormone (mean, 0.12 mg/kg/day) plus oral (mean, 28 g/day) and parenteral glutamine (mean, 5.2 g/day) for 28 days. Body composition was measured by dual-energy absorptiometry (DEXA) scans. Intestinal fatty acid absorption was evaluated in balance studies, and EFAs were measured in plasma phospholipids by gas liquid chromatography. Results: Active treatment did not increase BW, lean body mass (LBM), fat mass (FM) and bone mass significantly compared with placebo treatment, but BW increased 1.03 kg (1.7%, P < 0.05), LBM 2.93 kg (8.7%, P < 0.001) and FM decreased 2.41 kg (10.6%, P < 0.001) in comparison with baseline. Twenty-four-hour urine creatinine excretion did not differ between study periods. No changes in intestinal absorption of fatty acids were seen, and no changes in EFAs measured in plasma phospholipids were observed. Only 1 of 8 patients, who did not receive parenteral lipids, had a Holman index above 0.2, indicative of EFA deficiency. All developed peripheral oedema. Conclusions: Combined high dose growth hormone and glutamine administered for 4 weeks, did not improve absorption of fatty acids or EFA status in short bowel patients. No changes in BW or composition were seen when comparing treatment to placebo periods. The increase in LBM measured by DEXA scan, comparing treatment and baseline periods, was not accompanied by an increase in the 24-h urinary creatinine excretion and is suspected to be associated with an accumulation in extracellular fluids.