Changes in fatty-acid composition of body fat before and after birth in Tanzania: an international comparative study.

Changes in the fatty-acid composition of human adipose tissue before birth and during infancy and childhood were studied in Tanzania and compared with data for British and Dutch infants in relation to their diet. From the 32nd to the 37th week of gestation in Tanzania the proportion in the body fat of the unsaturated fatty acid linoleic acid tended to rise, suggesting an adequate supply of this essential fatty acid from the mother to the fetus. At term 2.5% of the total fatty acids of the body fat was linoleic acid, which corresponded with values in Dutch newborn infants but was significantly higher than those in British infants. During infancy in Tanzania the composition of the fat showed a dramatic increase in the proportions of the saturated fatty acids lauric acid and myristic acid, which did not occur in Dutch and British infants. The proportion of linoleic acid increased to 8%. These changes were a reflection of the fatty-acid composition of the fat in the human milk that the infants received. During weaning (1-2 years of age) the fatty-acid composition changed only slightly. The specific fatty-acid composition of the fat in Tanzanian breast milk may have a beneficial influence on the extent of intestinal absorption in the newborn child.     

Effects of postnatal age and diet on the fatty acid composition of plasma lipid fractions in preterm infants

Diet and postnatal age effect the fatty acid composition of plasma and tissue lipids. This work was designed as a transversal study to evaluate the changes in the fatty acid composition of plasma phospholipids, cholesteryl esters, triglycerides and free fatty acids in preterm infants (28-35 weeks gestational age), fed human milk (HM) and milk formula (MF) from birth to 1 month of life. Sixteen blood samples were obtained from cord, and 19 at 6-8 h after birth, 14 at 1 week and 9 at 4 weeks from HM-fed infants and 18 at 1 week and 14 at 4 weeks from MF-fed ones. Groups had similar mean birth weight, gestational age and sex ratio. The MF provided 69 kcal/dl and contained 16% of linoleic acid and 1.3% of alpha-linolenic acid on the total fat. Plasma lipid fractions were extracted and separated by thin-layer chromatography and fatty acid methyl esters were quantitated by gas liquid chromatography. In plasma phospholipids, linoleic acid (18:2 omega 6) continuously increased from birth to 1 month of age, but no changes were seen as related to type of diet; polyunsaturated fatty acids greater than 18 carbon atoms of both the omega 6 and omega 3 series (PUFA omega 6 greater than 18 C and omega 3 greater than 18 C) dropped from birth to 1 week and continued to decrease in MF-fed infants until 1 month; eicosatrienoic (20:3 omega 6), arachidonic (20:4 omega 6) and docosahexaenoic (22:6 omega 3) were the fatty acids implicated. In cholesteryl esters palmitoleic (16:1 omega 7) and oleic (18:1 omega 9) acids decreased from birth to 1 month and linoleic acid increased and arachidonic acid dropped, especially in MF fed infants. In triglycerides, palmitic, palmitoleic and stearic acid (18:0) decreased during the first month of life; oleic acid remained constant and linoleic acid increased in all infants, but arachidonic acid decreased only in those fed formula. Free fatty acids showed a similar behavior in fatty acids and in plasma triglycerides. Preterm neonates seem to have special requirements of long-chain PUFA and adapted MF should contain these fatty acids in similar amounts to those of HM to allow the maintenance of an adequate tissue structure and physiology.     

Lipid composition and vitamin E content in human colostrum and mature milk

Lipidic components, as well as fatty acid composition and vitamin E content were determined in colostrum (days 3-5 of postpartum) and mature milk (day 21) in 8 women from Murcia (Spain). Triglycerides concentration was higher and cholesterol and esterified cholesterol were lower in mature milk than in colostrum, whereas phospholipid content was similar. These differences indicate that the diameter of milk fat globules increases in mature milk. The percentage of medium-chain fatty acids (12:0 and 14:0) increased in mature milk as compared to colostrum, reflecting de novo synthesis of fatty acids. With the only exception of stearic acid which was lower in mature milk than in colostrum, the remaining long-chain fatty acids was similar. The proportion of both linoleic (18:2) and eicosapentaenoic (20:5) acids found in mature milk and colostrum is higher than in studies from other countries and may reflect the intake of high proportions of polyunsaturated fat from vegetable oils and fish in the studied women. Both vitamin E content and vitamin E/linoleic acid ratio in mature milk are lower than in colostrum, evidencing the efficient mechanism of mammary gland vitamin E uptake around parturition.     

Chronic undernutrition and traditional weaning foods are associated with fat stores in ariaal infants of Northern Kenya

The high proportion of human infant fat is hypothesized to protect infant brains by mobilizing against growth disturbances caused by acute nutritional and pathogen stress during weaning. However, individuals who experience chronic nutritional stress have been shown to store fat rather than mobilize fat stores, although this has not been demonstrated during infancy. This study investigated the relationship between fat development, diet, and nutritional status among 239 breastfeeding Ariaal infants, a group of settled pastoralists who experience both acute and chronic nutritional stress residing in Marsabit District, Kenya. This study had three goals: 1) To investigate the pattern of fat accumulation among Ariaal infants compared with a reference population; 2) to explore the relationship between chronic nutritional stress and fat deposits; and 3) to determine the relationship between traditional weaning foods, particularly cow's milk, and infant's fat. Infants, particularly infants experiencing chronic nutritional stress, were found to accumulate fat deposits in a manner that suggests reduced oxidation of fat stores. Infant upper arm fat area significantly increases with age over the weaning period compared with reference populations, who show a decline in body fat. Chronically undernourished infants were particularly likely to have increased levels of upper arm fat compared with normal infants or acutely undernourished infants. In addition, infants who consume cow's milk are significantly fatter than those that do not. These results suggest that Ariaal infants have both physiological and cultural mechanisms for fat storage in the face of their nutritionally stressed environment. Am J Phys Anthropol 153:286–296, 2014. © 2013 Wiley Periodicals, Inc.     

DGAT1 underlies large genetic variation in milk-fat composition of dairy cows

Dietary fat may play a role in the aetiology of many chronic diseases. Milk and milk-derived foods contribute substantially to dietary fat, but have a fat composition that is not optimal for human health. We measured the fat composition of milk samples in 1918 Dutch Holstein Friesian cows in their first lactation and estimated genetic parameters for fatty acids. Substantial genetic variation in milk-fat composition was found: heritabilities were high for short- and medium-chain fatty acids (C4:0-C16:0) and moderate for long-chain fatty acids (saturated and unsaturated C18). We genotyped 1762 cows for the DGAT1 K232A polymorphism, which is known to affect milk-fat percentage, to study the effect of the polymorphism on milk-fat composition. We found that the DGAT1 K232A polymorphism has a clear influence on milk-fat composition. The DGAT1 allele that encodes lysine (K) at position 232 (232K) is associated with more saturated fat; a larger fraction of C16:0; and smaller fractions of C14:0, unsaturated C18 and conjugated linoleic acid (P < 0.001). We conclude that selective breeding can make a significant contribution to change the fat composition of cow's milk.     

Long-chain polyunsaturated fatty acids in breast milk in La Plata, Argentina: relationship with maternal nutritional status

Milk fat is the major source of energy for breastfed infants; it also supplies polyunsaturated fatty acids (PUFAs) essential for the development of brain, retina, and other organs. Maternal nutritional status is critical for the newborn, and little information exists regarding the PUFA status of vulnerable populations living in Southern regions. We studied the relationship between maternal nourishment and milk fatty acid composition. Mother nutritional status (normal, overweight or obese) was estimated on the body mass index. Milk protein, total lipid, and fatty acid composition were determined. Milk protein was not affected by mother's nutritional status. In obese mothers an increase in lipid content, linoleic acid, total n-6 and total PUFAs was observed comparing to the other groups. Disregarding the nutritional status, the ratio n-6/n-3 fatty acids was very high and the 22:6n-3 content was very low, when compared with those of mothers from other countries. This finding led us to urge Public Health officers to promote changes in the dietary habits of nursing women.     

Selective retention of n-3 and n-6 fatty acids in human milk lipids in the face of increasing proportions of medium chain-length (C10-14) fatty acids

This paper reports the results of our analysis of the impact high levels of de novo fatty acids have on the proportions of essential and non-essential fatty acids in human milk lipids. The data for seven fatty acids (linoleic, alpha-linolenic, arachidonic (AA), docosahexaenoic (DHA), palmitic, stearic and oleic) were derived from several studies conducted in Nigeria. The proportion by weight of each of these fatty acids was plotted versus the proportion of C10-14 fatty acids. As the proportion of C10-14 fatty acids increased from 15 to 65%, there was not a proportional decrease in the percentages of all seven fatty acids, but, instead, preferential incorporation of the essential fatty acids, AA and DHA into the triacylglycerol component of the milk. At the same time, the proportions of stearic and oleic acid declined by 69% and 86%, respectively. However, the proportions of linoleic acid, palmitic acid, DHA, AA and alpha-linolenic acid, in milk lipids decreased by only 44%, 40%, 39%, 28% and 2.3%, respectively. These observations indicate that as the contribution of C10-14 fatty acids increases, essential fatty acids are preferentially incorporated into milk triacylglycerols at the expense of oleic acid and stearic acid.     

Changes in the fatty acid profiles of red blood cell membrane phospholipids in human neonates during the first month of life

We have studied the changes in the fatty acid profiles of red blood cell membrane phospholipids in 47 infants who were exclusively fed human milk from birth to 1 month of life. Twenty blood samples were obtained from cord, 15 at 7 days and 12 at 30 days after birth. Membrane phospholipids were obtained from erythrocyte ghosts by thin-layer chromatography and fatty acid composition was determined by gas liquid chromatography. Phosphatidylcholine showed the most important changes during early life; stearic, w6 eicosatrienoic and arachidonic acids decreased whereas oleic and linoleic acids increased. In phosphatidylethanolamine, palmitic and stearic acid declined and oleic, linoleic and docosahexenoic acids increased with advancing age. Small changes were noted for individual fatty acids in phosphatidylserine. In sphingomyelin stearic acid increased from birth to 1 month and linoleic, arachidonic and nervonic acids decreased. Total polyunsaturated fatty acids of the w6 series greater than 18 carbon atoms increased with advancing age in phosphatidylethanolamine and decreased in choline and serine phosphoglycerides and in sphingomyelin. Long chain fatty acids derived from linoleic acid decreased in phosphatidylcholine but increased in ethanolamine and serine phosphoglycerides. The different behavior in the changes observed in fatty acid patterns for each erythrocyte membrane phospholipid may be a consequence of its different location in the cell membrane bilayer and specific exchange with plasma lipid fractions.     

Prevalence of anemia among James Bay Cree infants of northern Quebec

BACKGROUND: Anemia is common among First Nation infants in Canada, often as a result of iron deficiency, which places them at risk for psychomotor impairment. Prevalence data are unavailable, and the risk factors are unknown. This study assessed the prevalence of anemia and associated risk factors among 9-month-old Cree infants in northern Quebec. METHODS: Between January 1995 and October 1998, 6 of 9 Cree villages in the James Bay region adopted a screening protocol for anemia in 9-month-old infants. Cross-sectional data were obtained from medical charts. The data for babies of very low birth weight and those with fever or infection were excluded. Among the 386 babies whose hemoglobin concentration was known, the type of milk consumed at the time of screening was known for 354. Associations between hemoglobin concentration and mean cell volume at 9 months, and milk type and weight gain since birth were analysed. RESULTS: The mean hemoglobin concentration of the 386 infants was 114.1 (standard deviation [SD] 10.6) g/L. The prevalence of anemia was 31.9% (95% confidence interval [CI] 27.2%-36.7%) with a hemoglobin cutoff value of 110 g/L, 17.6% 95% CI 13.9%-21.7%) with a cutoff value of 105 g/L, and 7.8% (95% CI 5.3%-10.9%) with a cutoff value of 100 g/L. Babies exclusively fed formula at 9 months had a higher mean hemoglobin concentration (118.5 [SD 9.9] g/L) than those exclusively fed breast milk (109.9 [SD 10.0] g/L), cow''s milk (112.5 [SD 10.1] g/L) or more than one type of milk (112.0 [SD 10.8] g/L) (p < 0.05). Compared with formula, the odds ratio (OR) for anemia was 7.9 (95% CI 3.4-18.2) for breast milk, 5.0 (95% CI 2.0-12.7) for cow''s milk and 5.2 (95% CI 1.9-14.6) for mixed milks. Infants fed formula and those fed cow''s milk had significantly greater weight gains since birth, by 724 g and 624 g respectively, than breast-fed infants (p < 0.05). When milk type was controlled for, weight gain since birth was significantly associated with the presence of microcytic erythrocytes (OR comparing highest tertile of weight gain to lowest tertile 2.9, 95% CI 1.2-6.6). INTERPRETATION: Iron-deficiency anemia is highly prevalent among James Bay Cree infants. Measures to increase iron intake are required.     

Fatty acid composition of human milk in Kuwaiti mothers

Kuwaiti diet is exceptionally rich in fat, carbohydrates and proteins. In addition, subjects in Kuwait are exposed to extreme heat and sun light. Fatty acid profiles of human milk obtained from 19 full breast feeding Kuwaiti mothers were analyzed. Dietary patterns for individual mothers were determined by 24 h dietary recall and food frequency questionnaire. The fatty acid content of human milk was affected by the diet consumed by the lactating mother. The content of long chain polyunsaturated fatty acids (LCP) in human milk lipids did not correlate with their parent fatty acids like linoleic and alpha-linolenic acids. However the human milk LCP were related to the of content of LCP in the maternal diet. Mothers reporting a high fish consumption showed significant amounts of C22:6, omega 3 and C20:5, omega 3 fatty acids. As a general conclusion, breast milk produced by a well nourished mother is better suited to meet the lipid requirements of infants.     

Essential fatty acid consideration at birth in the premature neonate and the specific requirement for preformed prostaglandin precursors in the infant

The essentiality of certain PUFA is probably related to their capability to be incorporated into lipids and to act as precursor in the formation of ecosanoids. Esterified to phospholipids, the EFA influence the physico-chemical characteristics of biomembranes. Normal growth of infants is dependent upon an adequate supply of EFA. The human fetus, like the adult, is unable to synthesize the EFA, which must therefore be derived from the maternal circulation and pass through the placenta. Increased concentration of the polyenoic fatty acids with advanced gestational age may result from increased synthetic activity of these fatty acids by the fetus or the placenta or by preferential transfer of these fatty acids across the placenta. Several clinical manifestations have been ascribed in the human infant to prolonged EFA deficiency; however, none of these findings were noted in a group of sick newborn infants with very rapid onset of deficiency. Platelet dysfunction, decreased prostaglandin biosynthesis and turnover and altered pulmonary surfactant are among the effects of EFA deficiency on infants. Supplementation of the diet with EFA, parenterally or by the inunction of oil rich in linoleic acid, were reported to alleviate the symptoms of EPA deficiency. The minimal estimated requirement of linoleic acid is 1% of calories and 4% is an optimal intake. Most diets, including human breast milk, infant formulas and parenteral fat emulsions, far exceed the optimal intake of linoleic acid. Relatively little is known about the possible effects of high levels of linoleate in the diet.     

Enrichment of soybean milk with calcium

Calcium in soymilk was increased to that of human milk by the addition of 0.2% calcium lactate. It was, however, impossible to raise the calcium content of soymilk to that of cow's milk. The maximum amount of calcium lactate that could be added to soymilk without coagulation of the milk protein was found to be 0.45% which resulted in about 75 mg of Ca/100 ml of soymilk. This amount was approximately 60% of the calcium in cow's milk. Sodium citrate had to be added in combination with calcium lactate to reinforce colloidal stability of the milk. The ratio of Ca to P in the milk containing added 0.45% calcium lactate was comparable to that of cow's milk and at the amount normally consumed daily by infants and children it seemed to meet the requirements of Ca and P.     

Plasma fatty acids and [13C]linoleic acid metabolism in preterm infants fed a formula with medium-chain triglycerides

Most preterm infant formulas contain medium-chain triacylglycerols (MCT), but the effects of MCT on polyunsaturated fatty acid status and metabolism are controversial. Thus, we studied the effects of MCT on linoleic acid metabolism using stable isotopes. Enterally fed preterm infants were randomized to receive for 7 days 40% of fat as MCT (n = 10) or a formula without MCT (n = 9). At study day 5, infants received orally 2 mg/kg body weight of (13)C-labeled linoleic acid. Fatty acids in plasma lipid classes and (13)C enrichment of phospholipid fatty acids were measured and tracer oxidation was monitored. Compared with the control group, the MCT group showed lower breath (13)CO(2) and higher plasma triacylglycerol contents of octanoic acid, of decanoic acid, and of total long-chain polyunsaturated fatty acids (57.1 +/- 4.4 micro mol/l vs. 37.9 +/- 4.8 micro mol/l, P < 0.01). Concentrations of several polyunsaturated fatty acids in plasma phospholipids and non esterified fatty acids were higher in the MCT group. (13)C concentrations in phospholipid n-6 fatty acids indicated no difference in the relative conversion of linoleic to arachidonic acid. We conclude that oral MCT effectively reduce polyunsaturated fatty acid and long chain polyunsaturated fatty acid oxidation in preterm infants without compromising endogenous n-6 long chain polyunsaturated fatty acid synthesis.     

Lipoprotein lipase activity and its relationship to high milk fat transfer during lactation in grey seals

Lipoprotein lipase regulates the hydrolysis of circulating triglyceride and the uptake of fatty acids by most tissues, including the mammary gland and adipose tissue. Thus, lipoprotein lipase is critical for the uptake and secretion of the long-chain fatty acids in milk and for the assimilation of a high-fat milk diet by suckling young. In the lactating female, lipoprotein lipase appears to be regulated such that levels in adipose tissue are almost completely depressed while those in the mammary gland are high. Thus, circulating fatty acids are directed to the mammary gland for milk fat production. Phocid seals serve as excellent models in the study of lipoprotein lipase and fat transfer during lactation because mothers may fast completely while secreting large quantities of high fat milks and pups deposit large amounts of fat as blubber. We measured pup body composition and milk fat intake by isotope (deuterium oxide) dilution and plasma post-heparin lipoprotein lipase activity in six grey seal (Halichoerus grypus) mother-pup pairs at birth and again late in the 16-day laction period. Maternal post-heparin lipoprotein lipase activity increased by an average of four-fold by late lactation (P=0.027), which paralleled an increase in milk fat concentration (from 38 to 56%; P=0.043). Increasing lipoprotein lipase activity was correlated with increasing milk fat output (1.3–2.1 kg fat per day) over lactation (P=0.019). Maternal plasma triglyceride (during fasting) was inversely correlated to lipoprotein lipase activity (P=0.027) and may be associated with the direct incorporation of longchain fatty acids from blubber into milk. In pups, post-heparin lipoprotein lipase activity was already high at birth and increased as total body fat content (P=0.028) and the ratio of body fat: protein incrased (P=0.036) during lactation. Although pup plasma triglyceride increased with increasing daily milk fat intake (P=0.023), pups effectively cleared lipid from the circulation and deposited 70% of milk fat consumed throughout lactation. Lipoprotein lipase may play an important role in the mechanisms involved with the extraordinary rates of fat transfer in phocid seals.Abbreviations FFA free fatty acid - HL hepatic lipase - LPL lipoprotein lipase - PH-HL post-heparin hepatic lipase - PH-LPL post-heparin lipoprotein lipase - VLDL very low density lipoprotein     

Supplementation of suckling rats with cow's milk induces hyperphagia and higher visceral adiposity in females at adulthood,but not in males

In humans, complementary feeding should be started after 6 months-old; the introduction of any food or water before this time is considered early weaning, which is associated with health problems in adulthood. Cow's milk is a common food introduced to children less than 6 months that has inadequate nutritional composition mainly due to a worse casein: whey protein ratio compared to human milk. We hypothesized that suckling rats fed with cow's milk, rich in bioactive peptides, develop further metabolic dysfunctions. From postnatal day (PN) 14 to 20, Wistar rat pups were divided into 3 groups: rat milk (RM) – pups received rat milk orally in a syringe; cow's milk (CM), pups received cow's milk; CM with high protein (CM-H), CM with twice protein amount of rat milk. Pups were killed on PN21 and PN180. At PN21, CM males had lower visceral fat mass compared with other groups. Serum corticosterone was higher in CM-H males, despite no change in glucocorticoid metabolism in liver and visceral fat. At PN180, CM and CM-H females had greater fat depots and hyperphagia, although no alteration in leptinemia and leptin signaling in hypothalamus. CM-H females had a trend of hypoinsulinemia and significant decrease in HOMA-β, suggesting lower insulin secretion. Males from CM-H group had only lower total body protein mass. CM males had hypercorticosteronemia associated with lower expression of 11βHDS1 in visceral fat. In conclusion, early introduction of cow's milk in neonate rats leads to gender-dependent differences in metabolic and endocrine parameters in the short- and long-term.     

Identification of the conjugated linoleic acid isomer that inhibits milk fat synthesis

Conjugated linoleic acids (CLA) are octadecadienoic fatty acids that have profound effects on lipid metabolism. Our previous work showed that CLA (mixture of isomers) markedly reduced milk fat synthesis. In this study, our objective was to evaluate the effects of specific CLA isomers. Multiparous Holstein cows were used in a 3x3 Latin square design, and treatments were 4-day abomasal infusions of 1) skim milk (control), 2) 9,11 CLA supplement, and 3) 10,12 CLA supplement. CLA supplements provided 10 g/day of the specific CLA isomer (cis-9,trans-11 or trans-10,cis-12). Treatments had no effect on intake, milk yield, or milk protein yield. Only the 10,12 CLA supplement affected milk fat, causing a 42 and 44% reduction in milk fat percentage and yield, respectively. Milk fat composition revealed that de novo synthesized fatty acids were extensively reduced. Increases in ratios of C(14:0) to C(14:1) and C(18:0) to C(18:1) indicated the 10,12 CLA supplement also altered Delta(9)-desaturase. Treatments had minimal effects on plasma concentrations of glucose, nonesterified fatty acids, insulin, or insulin-like growth factor-I. Overall, results demonstrate that trans-10,cis-12 CLA is the isomer responsible for inhibition of milk fat synthesis.     

Effects of intravenous infusions of acetate, β-hydroxybutyrate, triglyceride and other metabolites on the composition of the milk fat and blood in cows

1. The effects in the cow of intravenous infusions of sodium acetate, butyrate, propionate, β-hydroxybutyrate, malonate, citrate or succinate, of glucose or of an emulsion of cottonseed oil on the secretion of the component fatty acids of milk fat and on the composition of the blood plasma of the jugular vein have been studied. 2. Glucose and cottonseed oil were the only metabolities consistently to affect the yield of milk fat. Glucose decreased the yield of milk fat through a diminished secretion of the C₁₈ fatty acids and in two out of three cows also of the steam-volatile fatty acids (C₄–C₁₀). The cottonseed oil caused an increase in the yield of milk fat through an increased secretion of linoleic acid, the major component acid of the cottonseed oil. In three out of four cows, acetate caused an increase in the yield of milk fat through an increased secretion of mainly palmitic acid. 3. The effects of the infusions on milk-fat secretion are discussed in relation to existing knowledge on the origin of the fatty acids of milk fat.     

Significance of Milk pH in Newborn Infants

Bottle-fed infants do not gain weight as rapidly as breast-fed babies during the first week of life. This weight lag can be corrected by the addition of a small amount of alkali (sodium bicarbonate or trometamol) to the feeds. The alkali corrects the acidity of cow''s milk which now assumes some of the properties of human breast milk. It has a bacteriostatic effect on specific Escherichia coli in vitro, and in infants it produces a stool with a preponderance of lactobacilli over E. coli organisms. When alkali is removed from the milk there is a decrease in the weight of an infant and the stools contain excessive numbers of E. coli bacteria.A pH-corrected milk appears to be more physiological than unaltered cow''s milk and may provide some protection against gastroenteritis in early life. Its bacteriostatic effect on specific E. coli may be of practical significance in feed preparations where terminal sterilization and refrigeration are not available. The study was conducted during the week after birth, and no conclusions are derived for older infants. The long-term effects of trometamol are unknown. No recommendation can be given for the addition of sodium bicarbonate to milks containing a higher content of sodium.     

Excess body fat in men decreases plasma fatty acid availability and oxidation during endurance exercise

The effect of relative body fat mass on exercise-induced stimulation of lipolysis and fatty acid oxidation was evaluated in 15 untrained men (5 lean, 5 overweight, and 5 obese with body mass indexes of 21 +/- 1, 27 +/- 1, and 34 +/- 1 kg/m2, respectively, and %body fat ranging from 12 to 32%). Palmitate and glycerol kinetics and substrate oxidation were assessed during 90 min of cycling at 50% peak aerobic capacity (VO2 peak) by use of stable isotope-labeled tracer infusion and indirect calorimetry. An inverse relationship was found between %body fat and exercise-induced increase in glycerol appearance rate relative to fat mass (r2 = 0.74; P < 0.01). The increase in total fatty acid uptake during exercise [(micromol/kg fat-free mass) x 90 min] was approximately 50% smaller in obese (181 +/- 70; P < 0.05) and approximately 35% smaller in overweight (230 +/- 71; P < 0.05) than in lean (354 +/- 34) men. The percentage of total fatty acid oxidation derived from systemic plasma fatty acids decreased with increasing body fat, from 49 +/- 3% in lean to 39 +/- 4% in obese men (P < 0.05); conversely, the percentage of nonsystemic fatty acids, presumably derived from intramuscular and possibly plasma triglycerides, increased with increasing body fat (P < 0.05). We conclude that the lipolytic response to exercise decreases with increasing adiposity. The blunted increase in lipolytic rate in overweight and obese men compared with lean men limits the availability of plasma fatty acids as a fuel during exercise. However, the rate of total fat oxidation was similar in all groups because of a compensatory increase in the oxidation of nonsystemic fatty acids.     

Prenatal and postnatal transfer of fatty acids from mother to pup in the hooded seal

Unlike most mammals, hooded seal (Cystophora cristata) pups are born with a substantial layer of adipose tissue. Subsequently, during the brief lactation period of only 4 days, fasting mothers mobilize enormous amounts of lipid from blubber and secrete milk (60% fat) at rates of 10 kg·day^-1. Pups gain 7 kg·day^-1 due primarily to the deposition of fat in blubber. We measured blubber content and fatty acid composition of blubber and milk in hooded seal mother-pup pairs at birth and over the 4-day lactation period to examine the nature and source of fetal lipids, the incorporation of maternal blubber fatty acids into milk lipid, and patterns of fatty acid deposition in suckling young. The fatty acid composition of the blubber of the newborn was notably different from that of its mother. Fetal deposition was likely due to a combination of both fetal synthesis and direct placental transfer of maternal circulating fatty acids. The blubber of the newborn was characterized by high levels (>90% of total fatty acids) of saturated and monounsaturated fatty acids of primarily endogenous origin. In particular, the fetus appeared to have high Δ-9 desaturase activity as evidenced by the large amounts of 14:1n-5 (4.2%) and 16:1n-7 (37.0%) in newborn blubber compared to maternal blubber (0.2% and 14.1%, respectively). Nevertheless, essential and long-chain polyunsaturated fatty acids of the n-3 and n-6 families, which could only have originated by direct transfer from the mother, comprised>7% of pup blubber fatty acids and indicated greater rates of placental transfer than found in humans. In hooded seal mothers, rapid lipid transfer during the brief lactation period appeared to be facilitated by direct incorporation of mobilized fatty acids into milk. Although some differences in proportions of specific fatty acids were found between milk and maternal blubber, most of these differences declined over the course of lactation. However, selective mobilization of 20:5n-3 from maternal blubber into milk was apparent throughout lactation and resulted in elevated levels in pup blubber at weaning compared to maternal blubber. Ingested fatty acids were deposited directly and without modification into the blubber of pups, and by 4 days the fatty acid composition of pup blubber was virtually identical to that of the milk consumed.