Polar Bear (Ursus maritimus) Adipose Tissue Fatty Acid Composition Compared to Fatty Acid Constituents of a Common Milk Replacer

This study compared the fatty acid composition of polar bear (Ursus maritimus) adipose tissue (n=2) to the fatty acid (FA) composition in published literature for maternal milk (n=3 samples) and a primary milk formula (liquid Esbilac, Pet Ag Inc., Hampshire, IL) commonly used in hand rearing, to look at possible dietary influences on ultimate body fat constituency. All tissue and commercial milk fatty acids were analyzed on a percent relative (% of fat) basis for consistency in reporting results and to make easier comparisons between samples with varying fat contents. Thirty‐eight individual fatty acid profiles were measured and the results tabulated into saturated, monounsaturated and polyunsaturated fats. The tissue adipose results for the two cubs had similar patterns throughout the assay. Saturated FA totals were 30% of the total fat, monounsaturated FA represented 50% of the total fat, and polyunsaturated FA was 15%. Similar fatty acid proportions were reported when comparing adipose to published data for maternal milk of polar bears. The most striking differences were between the commercial milk replacer (liquid Esbilac) and the tissue samples and maternal milk values. Esbilac FA summaries for saturated FAs were 24%, monounsaturated were 26%, and polyunsaturated comprised 50% of the total fat. Polyunsaturated fat in Esbilac is substantially higher than the tissue and milk scores. Although lipid sources from whole cream or half‐and‐half are used to increase the fat concentration of milk replacers for the hand‐reared polar bear cub, alternative ingredients such as fish oil may prove more suitable for this species, as their FA profiles better duplicate natural diets and resulting lipid stores in milk and adipose tissues of free‐ranging polar bears. Zoo Biol 0:1–11, 2006. © 2006 Wiley‐Liss, Inc.     

Seasonal and sex differences in the structure and chemical composition of adipose tissue in wild polar bears (Ursus maritimus)

Biopsy samples of adipose tissue from the upper thigh were collected in spring and in late summer/autumn from 370 wild polar bears ( Ursus maritimus ), including adult females with and without cubs, adult males and juveniles. Mean adipocyte volume was measured from all samples and chemical assays of the lipid, total protein and collagen were also performed on samples from 53 bears. Mean adipocyte volume was smaller in all specimens in spring than in late summer/autumn, but the differences were greatest for solitary adult females. The range of adipocyte volumes was much greater for adult females than for adult males, and in females only, mean adipocyte volume correlated significantly with total body mass. Therefore, adipocyte volume measurements from biopsy samples provide some information about fatness in adult females, but are worthless as an indicator of body composition in males and juveniles. In juveniles and females, but not adult males, the lipid content of the adipose tissue was up to 18% lower in autumn than in spring. The collagen content was significantly higher in autumn than in spring in all bears except females with cubs. We suggest that these differences in chemical composition arise from accumulation of water within and between the adipocytes, which would minimize tissue shrinkage, and from changes in the vascularization of the adipose tissue. These properties may be adaptations to rapid fattening and prolonged fasting and the sex differences may reflect the contrasting reproductive strategy of female and male polar bears.     

The effect of immunocastration on adipose tissue deposition and composition in pigs

Immunocastrated pigs (IC) exhibit intensive fat deposition after immunisation, but the underlying mechanisms of intensified fat metabolism and deposition are not yet fully understood. Moreover, there is also a lack of comparative studies performed on IC, entire males (EM) and surgical castrates (SC). The main objective of our research was, therefore, to characterise the adipose tissue from the quantitative, histo-morphological and biochemical perspectives in IC 5 weeks after their immunisation in comparison to EM and SC. Immunocastrated pigs had an intermediate position in carcass fatness traits between EM (the leanest) and SC (the fattest). The histo-morphological traits of the subcutaneous adipose tissue of IC were similar to those of SC and differed from those of EM; i.e., they exhibited larger adipocytes in the outer backfat and a larger lobulus surface area in both backfat layers than EM. Intensive fat tissue development in IC was corroborated with higher activities of lipogenic enzymes (i.e., fatty acid synthase, malic enzyme, glucose 6-phosphate dehydrogenase, citrate cleavage enzyme), which was especially pronounced in the subcutaneous adipose tissue of IC (1.5- to 2.7-fold higher activity than in EM or SC). The fatty acid composition of the backfat in IC was similar to that in EM pigs. Both IC and EM exhibited less saturated and more polyunsaturated fatty acids than SC. In contrast, the fatty acid composition of the intramuscular fat of longissimus dorsi muscle in IC pigs was more similar to SC than to EM (higher monounsaturated and lower polyunsaturated fatty acid content in IC and SC than EM). In this study, it was demonstrated that immunocastration notably influenced lipid metabolism. This was shown by increased quantity of lipid depots and with changes in adipose tissue cellularity compared to EM, with changes in the fatty acid composition of the intramuscular fat and enhanced lipogenic activity compared to both EM and SC. These results provide new insights into the specificity of adipose tissue development and deposition in IC compared to EM and SC.     

Brown and white adipose tissue lipid composition in three successive progenies of rats: Effects of ethanol exposure

The effect of ethanol exposure on the fatty acid composition of brown and white adipose tissue in three successive rat progenies at the end of an experimental period (24 weeks) was studied. Ethanol‐treated rats received a standard rat chow diet and 5, 10 and 15% ethanol in the ad libitum drinking fluid over 3 successive weeks. Then a concentration of 20% ethanol was maintained for 5 additional weeks up to the end of the experimental period. The males and females in the ethanol treated group were mated to obtain the 1st generation of offspring. Then female and male rats from the 1st generation were mated to obtain the 2nd generation. Finally, males and females from the 2nd generation were mated to obtain the 3rd generation of ethanol treated rats. Another group served as control and received only water and a standard rat chow diet. The control group was handled in the same way as the other experimental groups. In the 1st and 2nd generations the percentage of stearic acid (18:0) decreased and palmitoleic (16:ln7) and oleic acid (18:ln9) increased in both adipose tissues of ethanol‐treated rats with respect to control. Additionally, n‐3 and n‐6 series were reduced both in brown and white adipose tissues. In the 3rd generation the fatty acid composition of the white adipose tissue was similar to that of control rats. Thus, no significant difference in essential fatty acids and oleic acid (18:ln9) were found. However, the fatty acid composition of the brown adipose tissue, in the 3rd generation, was similar to that observed in the 1st and 2nd generation. Thus, a decrease in essential fatty acids and an increase in oleic acid (18:ln9) was found. This suggests adaptation to ethanol consumption during successive progenies in white adipose tissue. However, in brown adipose tissue the values indicate a triglyceride storing during the thermogenesis, which is more important to newborns.     

Remote biopsy darting and marking of polar bears

Remote biopsy darting of polar bears (Ursus maritimus) is less invasive and time intensive than physical capture and is therefore useful when capture is challenging or unsafe. We worked with two manufacturers to develop a combination biopsy and marking dart for use on polar bears. We had an 80% success rate of collecting a tissue sample with a single biopsy dart and collected tissue samples from 143 polar bears on land, in water, and on sea ice. Dye marks ensured that 96% of the bears were not resampled during the same sampling period, and we recovered 96% of the darts fired. Biopsy heads with 5 mm diameters collected an average of 0.12 g of fur, tissue, and subcutaneous adipose tissue, while biopsy heads with 7 mm diameters collected an average of 0.32 g. Tissue samples were 99.3% successful (142 of 143 samples) in providing a genetic and sex identification of individuals. We had a 64% success rate collecting adipose tissue and we successfully examined fatty acid signatures in all adipose samples. Adipose lipid content values were lower compared to values from immobilized or harvested polar bears, indicating that our method was not suitable for quantifying adipose lipid content.     

Effects of deep-bedded finishing system on market pig performance, composition and pork quality

The purpose of this study was to compare effects of finishing environment on growth performance, pork quality and lipid composition of pork. Environments compared were standard confinement (CON) and deep-bedded semi-outdoor systems. The deep-bedded method employed in the current study was the use of hoop structures. Hoops are large, tent-like shelters with cornstalks or straw for bedding. Gilts ranging in weight from 59 to 71 kg were randomly assigned to treatments of Hoop (n = 50) and CON (n = 18) environments. Gilts were fed a two-phase dietary sequence, ad libitum for 45 days. Six gilts per treatment were selected for carcass composition and quality evaluation. The experiment was replicated a total of five times. Pigs raised in the Hoop environment gained significantly less and required significantly more feed for growth than pigs raised in the CON environment. Carcasses from CON-finished pigs were significantly fatter at the 10th rib, which lowered carcass percentage fat-free lean(FFL) and they also had greater loin marbling scores compared with carcasses from Hoop-finished pigs (P < 0.05). Significant replication effects were noted on beginning weight, live weight, carcass weight, percentage FFL, backfat, lipid content and adipose firmness. Carcasses from Hoop pigs had lower proportions of palmitic acid (P < 0.05), and higher proportions of oleic and linoleic acid (P < 0.05) in the inner layer of adipose tissue. The proportion of saturated fatty acid was lower, and that of mono- and poly-unsaturated fatty acid was higher in the inner layer of the adipose tissue of Hoop pigs. Variations in fatty acid composition and lipid deposition may have been caused by environmental temperature, since decreases in environmental temperature accompanied compositional variation of the adipose, leading to higher proportions of monounsaturated fatty acid and lower proportions of saturated and polyunsaturated fatty acid in adipose tissue, regardless of treatment. Volatile profile analysis revealed that adipose tissue of Hoop pigs had significantly higher amounts of 3-butanal and heptanal compared with CON pigs, which may be related to the amount of oleic and linoleic acids composing the adipose tissue. These data indicate finishing pigs in hoop structures allows for exposure to fluctuating temperatures, which may influence the growth of pigs, as well as fatty acid composition and firmness of pork products.     

Adipose tissue in the mammalian heart and pericardium: structure, foetal development and biochemical properties

1. The occurrence and relative abundance of adipose tissue around the heart and in the pericardium of wild and domesticated mammals are reviewed and some new data reported. 2. For macaque monkeys and a wide range of other adult mammals, the mean volume of epicardial adipocytes is constant at about half the average of that of other depots, although the relative mass of this depot is unrelated to the abundance of adipose tissue in the rest of the body. 3. In young adult guinea-pigs, the maximum rate of fatty acid synthesis is significantly higher in epicardial adipose tissue than that in the pericardial, perirenal and popliteal depots. 4. The rate of fatty acid release by epicardial adipose tissue is approximately twice that of the pericardial and perirenal depots. 5. The protein contents of guinea-pig epicardial and pericardial adipose tissue are similar, and are significantly higher than those of the perirenal and popliteal adipose tissue and there are no site-specific differences in the abundance of mitochondria. 6. In adult Macaca monkeys, the capacity of the epicardial adipose tissue for glucose utilization is about half that of the intra-abdominal depots. 7. The principal difference between epicardial adipose tissue and that elsewhere in the body is its greater capacity for fatty acid release. 8. It is suggested that cardiac adipose tissue may act as a local energy supply for adjacent myocardium and/or as a buffer against toxic levels of free fatty acids.     

Differences in tissue-specific lipid composition between embryos of wild and captive breeding alligators (Alligator mississippiensis)

Fertile eggs obtained from alligators reared in captivity typically exhibit high rates of embryonic mortality. Also, the fatty acid composition of the yolk lipid of the captive eggs is markedly different from that observed in eggs from wild alligators, possibly as a result of differences in maternal diet in the two situations. The fatty acid compositions of tissue lipids during the embryonic development of wild and captive alligators were compared. The lipids of liver, adipose tissue and heart of the two types of embryo displayed fatty acid profiles which generally reflected the acyl compositions of the respective yolks. Thus the lipids from these tissues of the captive embryos contained markedly higher proportionate levels of linoleic and linolenic acids, lower levels of palmitoleic acid, and, in general, lower levels of docosahexaenoic acid and other C20 and C22 polyunsaturates, in comparison to the values for the wild embryos. In contrast, the fatty acid composition of the brain phosphoglycerides was very similar in the two types of embryo. Thus, at least in those embryos which had survived during the developmental period studied, the brain was able to maintain a relatively constant fatty acid composition, in spite of major differences between the wild and captive eggs in the proportions of the various fatty acids supplied from the yolk. It is suggested that a major cause of embryonic mortality in the captive embryos could be a failure to maintain an adequate level of docosahexaenoic acid in the developing brain.     

Fatty acid composition of muscle and heart tissue of Nile perch,Lates niloticus,and Nile tilapia,Oreochromis niloticus,from various populations in Lakes Victoria and Kioga,Uganda

The fatty acid composition in the heart tissue and muscle tissue of the Nile perch, Lates niloticus, and Nile tilapia, Oreochromis niloticus populations from Lakes Kioga and Victoria was determined by methanolysis and gas chromatography of the resulting fatty acid methyl esters. The analytical data were treated by multivariate principal component analysis. The most abundant individual fatty acids were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1n9), vaccenic acid (18:1n7), arachidonic acid (20:4n6) and docosahexaenoic acid (22:6n3). Due to high levels of both n6 and n3 fatty acids, the ratios of n3 to n6 were between 1 and 2, typical for freshwater fish species. Two Lake Victoria and one Lake Kioga populations of Nile tilapia and Nile perch were distinguished by the fatty acid profiles in their heart and muscle tissue. The heart tissue showed better separation than muscle tissue, due to dominance of polar phospholipids. It is rationalised that genetics are more important than diet in determining the fatty acid composition of the tissues.     

Lipid synthesis and deposition by adult Richardson's ground squirrels in the natural environment

Summary Adult male Richardson's ground squirrels,Spermophilus richardsonii, were estimated to have emerged from hibernation in late February to early March, and adult females in mid to late March. Half of the females trapped in late March were not pregnant, as against 10% after that time. In late March males and all females had similar WAT (white adipose tissue) deposits. Between late March and early June, WAT deposits in males increased from 14 g to 64 g (a rate of 5.6 g per week). In non-parous females WAT deposits increased from 13 g to 48 g from late March to late May (4.2 g per week). Fat deposits decreased during lactation but thereafter increased from 8 g to 29 g (a rate of 6.0 g per week) between early May and early June. In males the rate of fatty acid synthesis in BAT (brown adipose tissue), liver and WAT did not change from late March to late May, and rates in the corresponding tissues of non-pregnant females were similar to those in males. Fatty acid synthesis decreased during late pregnancy and lactation. After lactation, the rate of fatty acid synthesis in all tissues increased to that in males and non-pregnant females. Males initiated fattening 5–7 weeks earlier than females. It is concluded that compared with adult males, the later immergence of adult female Richardson's ground squirrels into hibernation is due primarily to later initiation of fattening and less to differences in rate of lipid synthesis after the reproductive period. Rates of fatty acid synthesis in liver and BAT were several times greater than that in WAT. The former tissues may contribute fatty acids for prehibernatory fattening.Abbreviations BAT brown adipose tissue - WAT white adipose tissue     

Meal fatty acid uptake in adipose tissue: gender effects in nonobese humans

We tested for gender differences in dietary fatty acid metabolism in 12 nonobese men and 12 nonobese women using the meal fatty acid tracer/adipose tissue biopsy study design. In addition to determining body composition, measurements of regional adipose tissue lipoprotein lipase activity, blood flow, and fat cell size were performed to place the meal fatty acid kinetic studies in perspective. Twenty-four hours after ingesting the test meal, the concentration of meal fatty acids was greater (P < 0.05) in abdominal subcutaneous than in thigh adipose tissue in both men (0. 61 +/- 0.12 vs. 0.45 +/- 0.09 mg/g) and women (0.59 +/- 0.10 vs. 0. 43 +/- 0.05) but was not different between men and women. A greater percentage of dietary fat was stored in subcutaneous adipose tissue in women than in men (38 +/- 3 vs. 24 +/- 3%, respectively, P < 0. 05), and a greater portion of meal fatty acid disposal was unaccounted for in men. Significant gender differences in regional adipose tissue blood flow after meal ingestion were noted; the differences were in the direction that could support greater nutrient storage in lower body fat in women.     

Adaptive modification of membrane phospholipid fatty acid composition and metabolic thermosuppression of brown adipose tissue in heat-acclimated rats

Thermogenesis, especially facultative thermogenesis by brown adipose tissue (BAT), is less important in high ambient temperature and the heat-acclimated animals show a lower metabolic rate. Adaptive changes in the metabolic activity of BAT are generally found to be associated with a modification of membrane phospholipid fatty acid composition. However, the effect of heat acclimation on membrane phospholipid fatty acid composition is as yet unknown. In this study, we examined the thermogenic activity and phospholipid fatty acid composition of interscapular BAT from heat-acclimated rats (control: 25±1°C, 50% relative humidity and heat acclimation: 32±0.5°C, 50% relative humidity). Basal thermogenesis and the total thermogenic capacity after noradrenaline stimulation, as estimated by in vitro oxygen consumption of BAT (measured polarographically using about 1-mm³ tissue blocks), were smaller in the heat-acclimated group than in the control group. There was no difference in the tissue content of phospholipids between the groups when expressed per microgram of DNA. The phospholipid fatty acid composition was analyzed by a capillary gas chromatograph. The state of phospholipid unsaturation, as estimated by the number of double bonds per fatty acid molecule, was similar between the groups. The saturated fatty acid level was higher in the heat-acclimated group. Among the unsaturated fatty acids, heat acclimation decreased docosahexaenoic acid and oleic acid levels, and increased the arachidonic acid level. The tissue level of docosahexaenoic acid correlated with the basal oxygen consumption of BAT (r=0.6, P<0.01) and noradrenaline-stimulated maximum values of oxygen consumption (r=0.5, P<0.05). Our results show that heat acclimation modifies the BAT phospholipid fatty acids, especially the n-3 polyunsaturated fatty acid docosahexaenoic acid, which is possibly involved in the metabolic thermosuppression. Received: 9 August 1999 / Revised: 8 November 1999 / Accepted: 24 November 1999     

Tissue specific differences in the fatty acid composition of the marmoset monkey (Callithrix jacchus)

1. The possible relationship between the fatty acid composition of the adipose tissue of the marmoset monkey (Callithrix jacchus) and its dietary lipid intake was examined after a long-term feeding trial. 2. Only the proportions of stearic and linoleic acid in the adipose tissue were similar to those in the diet. The proportions of all other saturated and unsaturated fatty acid components were significantly different thus greatly reducing the potential value of this relationship in the marmoset. 3. The phospholipid fatty acid profiles of cardiac and skeletal muscle, aortae, kidney, liver, lung and brain were also compared to those of the plasma, platelets or red blood cells. 4. With the exception of the liver where the fatty acid profile is similar to that of the plasma, no clear relationships were found between the fatty acid profiles of these tissues and the components of the blood. 5. The fatty acid composition of skeletal muscle was very similar to that of the cardiac muscle of the marmoset, suggesting that muscle biopsy might be useful as an index of cardiac muscle composition.     

Use of structured triacylglycerols containing predominantly stearic and oleic acids to probe early events in metabolic processing of dietary fat.

Early events in the metabolic processing of dietary triacylglycerol may have an important impact on subsequent development of risk factors for coronary heart disease. We have used structured triacylglycerols containing predominantly stearic or oleic acids at the sn -2 position to probe aspects of the processing of dietary fatty acids presented to adipose tissue in chylomicron-triacylglycerol. Studies were conducted on 14 healthy women who were given meals containing 85 g carbohydrate and 60 g of either of the two structured triacylglycerols in random order. Systemic concentrations and arterio-venous differences across adipose tissue for plasma triacylglycerol and non-esterified fatty acids were measured, together with analysis of the fatty acid composition of the relevant fractions. The stereo-specific structure of the ingested triacylglycerol was largely preserved in chylomicron-triacylglycerol. Systemic concentrations of total and individual non-esterified fatty acids were not significantly different after ingestion of the two fats, nor were their rates of release across adipose tissue. The composition of non-esterified fatty acids released from adipose tissue changed after the meal to reflect more closely the composition of the triacylglycerol ingested, but again no significant differences were observed between the two test meals. There was no detectable release of monoacylglycerol from adipose tissue after either test meal.We conclude that the environment for lipoprotein lipase action in adipose tissue in vivo is likely to be highly organized, such that there is no release of monoacylglycerol, nor preferential uptake or release of fatty acids from chylomicron-triacylglycerol according to the nature or the position within triacylglycerol of the fatty acid.     

Fatty acid composition of cholesterol esters in brains of patients with Schilder's disease, G M1 -gangliosidosis and Tay-Sachs disease, and its possible relationship to the -position fatty acids of lecithin

Abstract— Cholesterol esters were isolated from cerebral cortex and white matter of patients with Schilder's disease, G_M1-gangliosidosis and Tay-Sachs disease, and the fatty acid composition was determined by gas-liquid chromatography. The fatty acid composition was similar among the three pathological conditions, but it was entirely different from that reported for cholesterol esters of normal brain. Lecithin and ethanolamine phospholipids were isolated from the same brain specimens, treated with snake venom phospholipase A, and the fatty acids at the a’and β-positions of the glycerol moiety were determined separately. The fatty acid composition of cholesterol esters was similar to that of the β-position fatty acids of lecithin of white matter in all samples, and was quite different from those of the a'-position of lecithin, or of the a’or β-position of ethanolamine phospholipids. The results indicate that the source of fatty acids for cholesterol esterification in nonspecific sudanophilic demyelination is different from that in normal brain, and that the most likely source is the β-linked fatty acids of lecithin. There are two possible enzymic mechanisms; activation of phospholipase A and subsequent esterification of the liberated β-position fatty acids to cholesterol, or direct transacylation by lecithin-cholesterol acyl transferase.     

Influence of low ambient temperature and dietary lipids on adipose tissue and plasma fatty acid composition of the Japanese quail.

Japanese quail were maintained on synthetic diets containing 15% corn oil, 15% tallow, and zero fat, and were later exposed at 3.5 degrees C for 21 days. A distinct influence of dietary fat composition upon the adipose tissue triglyceride fatty acid composition was detected, but no change in fatty acid composition was produced with cold exposure. The fatty acid composition of adipose tissue from quail acclimatized to winter temperatures showed no trend towards a greater degree of unsaturation. There was no evidence of a gross selective mobilization of certain fatty acids from the depot lipids. Regional variation in the fatty acid composition of avian fats is discussed with respect to the level of food intake and body temperature.     

Fatty acid composition of the depot fats of the Polynesian rat,Rattus exulans,Tokelau Islands

The fatty acid composition of the stomach contents, adipose tissue, and perinephric fat of Polynesian rats (Rattus exulans Peale), from the Tokelau Is indicated that the dietary fat consisted mainly, if not exclusively, of coconut oil. Lower ratios of lauric : myristic acids were found in the depot fats of the Polynesian rats than in the dietary coconut oil. These results were consistent with chain elongation of lauric to myristic acid after ingestion, as previously reported in rats and other mammals.     

High content of polyunsaturated fatty acids in muscle phospholipids of a fast runner,the European brown hare (Lepus europaeus)

To investigate both seasonal changes and possible intracorporal gradients of phospholipid fatty acid composition, skeletal muscles (n=124), hearts (n=27), and livers (n=34) from free-living brown hares (Lepus europaeus) were analyzed. Phospholipids from both skeletal muscles and heart had a high degree of unsaturation with 66.8±0.63% and 65.7±0.5% polyunsaturated fatty acids, respectively. This is the highest proportion of polyunsaturated fatty acids reported in any mammalian tissue. Polyunsaturated fatty acid content in skeletal muscles was 2.3% greater in winter compared to summer (F_1,106=17.7; P=0.0001), which may reflect thermoregulatory adjustments. Arachidonate (C20:4n-6) showed the greatest seasonal increase (+2.5%; F=7.95; P=0.0057). However, there were no pronounced differences in polyunsaturated fatty acid content between skeletal muscles from different locations in the body (m. iliopsoas, m. longissimus dorsi and m. vastus). Total muscle phospholipid polyunsaturated fatty acid content was correlated with polyunsaturated fatty acid content in triacyglycerols from perirenal white adipose tissue depots (r²=0.61; P=0.004). Polyunsaturated fatty acids were enriched in muscle phospholipids (56.8–73.6%), compared to white adipose tissue lipids (20.9–61.2%), and liver phospholipids (25.1–54.2%). We suggest that the high degree of muscle membrane unsaturation is related to hare-specific traits, such as a high maximum running speed.Abbreviations BMR basal metabolic rate - DPA docosapentaenoic acid - DHA docosahexaenoic acid - FA fatty acid - MUFA monounsaturated fatty acid - PC principal component - PUFA polyunsaturated fatty acid - SFA saturated fatty acid - UI unsaturation index - WAT white adipose tissueCommunicated by: G. Heldmaier     

Effects of dietary fat and zinc on adiposity,serum leptin and adipose fatty acid composition in C57BL/6J mice

Zinc (Zn) has been implicated in altered adipose metabolism, insulin resistance and obesity. The objective of this study was to investigate the effects dietary Zn deficiency and supplementation on adiposity, serum leptin and fatty acid composition of adipose triglycerides and phospholipid in C57BL/6J mice fed low-fat (LF) or high-fat (HF) diets for a 16 week period. Weanling C57BL/6J mice were fed LF (16% kcal from soybean oil) or HF (39% kcal from lard and 16% kcal from soybean oil) diets containing 3, 30 or 150 mg Zn/kg diet (ZD = Zn-deficient, ZC = Zn control and ZS = Zn-supplemented, respectively). HF-fed mice had higher fat pad weights and lower adipose Zn concentrations than the LF-fed mice. The ZD and ZS groups had a reduced content of fatty acids in adipose triglycerides compared to the ZC group, suggesting that zinc status may influence fatty acid accumulation in adipose tissue. Serum leptin concentration was positively correlated with body weight and body fat, and negatively correlated with adipose Zn concentration. Dietary fat, but not dietary Zn, altered the fatty acid composition of adipose tissue phospholipid and triglyceride despite differences in Zn status assessed by femur Zn concentrations. The fatty acid profile of adipose triglycerides generally reflected the diets. HF-fed mice had a higher percentage of C20:4 n-6, elevated ratio of n-6/n-3, lower ratio of PUFA/SAT and reduced percentage of total n-3 fatty acids in adipose phospholipid, a fatty acid profile associated with obesity-induced risks for insulin resistance and impaired glucose transport. In summary, the reduced adipose Zn concentrations in HF-fed mice and the negative correlation between serum leptin and adipose Zn concentrations support an interrelationship among obesity, leptin and Zn metabolism.     

White adipose tissue composition in the free-ranging fat-tailed dwarf lemur (Cheirogaleus medius; Primates), a tropical hibernator

In temperate species, hibernation is enhanced by high levels of essential fatty acids in white adipose tissue. Essential fatty acids cannot be synthesized by mammals, thus nutritional ecology should play a key role in physiological adaptations to hibernation. Tropical hibernators are exposed to different physiological demands than hibernators in temperate regions and are expected to be subject to different constraints. The aims of this study were to assess whether or not the tropical hibernator Cheirogaleus medius shows biochemical changes in its white adipose tissue before and during hibernation. A capture-recapture study was combined with feeding observations in western Madagascar. Before and after hibernation, 77 samples of white adipose tissue from 57 individuals of C. medius, as well as dietary items eaten during pre-hibernation fattening, were sampled and analyzed for their fatty acid composition. In contrast to temperate hibernators, C. medius exhibits extremely low essential fatty acid concentrations in its white adipose tissue (2.5%) prior to hibernation. The fatty acid pattern of the white adipose tissue did not change during pre-hibernation fattening and did not reflect dietary fatty acid composition. During hibernation, fat stores showed only minor but significant compositional changes. Because of its prevalence, the main fuel during hibernation was the monounsaturated oleic acid, which seemed to be preferentially synthesized from dietary carbohydrates. Results suggest that essential fatty acids do not represent an ecological limitation for hibernation in the tropics, at least not in the fat-tailed dwarf lemur.