Dietary fatty acid composition and the hibernation patterns in free-ranging arctic ground squirrels

Laboratory experiments have demonstrated that the amount of polyunsaturated fatty acids (PUFAs) in the diet before hibernation influences patterns of mammalian torpor. The hibernation ability of ground squirrels is greatest (longest torpor bouts, greatest number of animals entering torpor) when the PUFA content of their fall diets is 33-74 mg/g, under laboratory conditions. The extent to which natural fall diets both (a) vary in PUFA content and (b) influence the torpor patterns of free-ranging populations of hibernating mammals is unknown, however. We conducted a 3-yr study on the diet PUFA contents and subsequent hibernation patterns of free-ranging arctic ground squirrels (Spermophilus parryii) in the Brooks Range of Alaska. We found that the PUFA contents of fall diets varied more than threefold among individuals. Our study also revealed that arctic ground squirrels that consumed a moderate-PUFA (33-74 mg/g) diet had (a) longer torpor bouts, (b) fewer arousals from torpor, (c) shorter arousal periods, (d) more days in torpor, and (e) greater probability of persisting in the population than those that consumed a high-PUFA (>74 mg/g) diet during the fall. No animals were demonstrated to have consumed a diet representing low-PUFA (<33 mg/g) values. Our study is therefore the first to demonstrate that estimated dietary PUFA levels of a free-ranging hibernator influence subsequent torpor patterns.     

The degree of dietary fatty acid unsaturation affects torpor patterns and lipid composition of a hibernator

Diets rich in unsaturated and polyunsaturated fatty acids have a positive effect on mammalian torpor, whereas diets rich in saturated fatty acids have a negative effect. To determine whether the number of double bonds in dietary fatty acids are responsible for these alterations in torpor patterns, we investigated the effect of adding to the normal diet 5% pure fatty acids of identical chain length (C18) but a different number of double bonds (0, 1, or 2) on the pattern of hibernation of the yellow-pine chipmunk, Eutamias amoenus. The response of torpor bouts to a lowering of air temperature and the mean duration of torpor bouts at an air temperature of 0.5°C (stearic acid C18:0, 4.5±0.8 days, oleic acid C18:1, 8.6±0.5 days; linoleic acid C18:2, 8.5±0.7 days) differed among animals that were maintained on the three experimental diets. The mean minimum body temperatures (C18:0, +2.3±0.3°C; C18:1, +0.3±0.2°C; C18:2,-0.2±0.2°C), which torpid individuals defended by an increase in metabolic rate, and the metabolic rate of torpid animals also differed among diet groups. Moreover, diet-induced differences were observed in the composition of total lipid fatty acids from depot fat and the phospholipid fatty acids of cardiac mitochondria. For depot fat 7 of 13 and for heart mitochondria 7 of 14 of the identified fatty acids differed significantly among the three diet groups. Significant differences among diet groups were also observed for the sum of saturated, unsaturated and polyunsaturated fatty acids. These diet-induced alterations of body fatty acids were correlated with some of the diet-induced differences in variables of torpor. The results suggest that the degree of unsaturation of dietary fatty acids influences the composition of tissues and membranes which in turn may influence torpor patterns and thus survival of hibernation.Abbreviations bm body mass - T _a air temperature - T _b body temperature - FA fatty acid - MR metabolic rate - MUFA monounsaturated fatty acids - PUFA polyunsaturated fatty acids - VO₂ rate of oxygen consumption - SFA saturated fatty acids - UFA unsaturated fatty acids - UI unsaturation index - SNK Student-Newman-Keuls test     

The impact of dietary fats,photoperiod, temperature and season on morphological variables,torpor patterns,and brown adipose tissue fatty acid composition of hamsters,Phodopus sungorus

We investigated how dietary fats and oils of different fatty acid composition influence the seasonal change of body mass, fur colour, testes size and torpor in Djungarian hamsters, Phodopus sungorus, maintained from autumn to winter under different photoperiods and temperature regimes. Dietary fatty acids influenced the occurrence of spontaneous torpor (food and water ad libitum) in P. sungorus maintained at 18°C under natural and artificial short photoperiods. Torpor was most pronounced in individuals on a diet containing 10% safflower oil (rich in polyunsaturated fatty acids), intermediate in individuals on a diet containing 10% olive oil (rich in monounsaturated fatty acids) and least pronounced in individuals on a diet containing 10% coconut fat (rich in saturated fatty acids). Torpor in P. sungorus on chow containing no added fat or oil was intermediate between those on coconut fat and olive oil. Dietary fatty acids had little effect on torpor in animals maintained at 23°C. Body mass, fur colour and testes size were also little affected by dietary fatty acids. The fatty acid composition of brown fat from hamsters maintained at 18°C and under natural photoperiod strongly reflected that of the dietary fatty acids. Our study suggests that the seasonal change of body mass, fur colour and testes size are not significantly affected by dietary fatty acids. However, dietary fats influence the occurrence of torpor in individuals maintained at low temperatures and that have been photoperiodically primed for the display of torpor.Abbreviations BAT brown adipose tissue - bm body mass - FA fatty acid(s) - MR metabolic rate - MUFA monounsaturated fatty acid(s) - PUFA polyunsaturated fatty acid(s) - SFA saturated fatty acid(s) - T _a air temperature - T _b body temperature - T_s body surface temperature(s) - TNZ thermoneutral zone - UFA unsaturated fatty acid(s)     

The Relationship Between Lipid Peroxidation, Hibernation, and Food Selection in Mammals

SYNOPSIS. A diet that has high levels of polyunsaturated fattyacids enhances mammalian torpor. Polyunsaturated fatty acidsare not synthesized by mammals, but are incorporated into bothmembrane and storage lipids when they occur in the diet. Polyunsaturatedfatty acids also undergo autoxidation more readily than otherfatty acids, thereby producing highly toxic lipid peroxides.Lipid peroxidation increases during torpor. Natural selectionin mammalian hibernators should thus have favored the evolutionof dietary preferences that maximize hibernation ability whilesimultaneously minimizing the degree of lipid peroxidation duringtorpor. This hypothesis was tested in laboratory experimentsand field studies involving golden-mantled ground squirrels(Spermophilus lateralis). We found that the intake of polyunsaturatedfatty acids isrestricted during the fall and autoxidation intissues occurs mostly during the later phases of hibernation.     

Seasonal changes in critical enzymes of lipogenesis and triacylglycerol synthesis in the marmot (Marmota flaviventris)

Fatty acid metabolism and triacylglycerol synthesis are critical processes for the survival of hibernating mammals that undergo a prolonged fasting period. Fatty acid synthase, fatty-acid-CoA ligase, diacylglycerol acyltransferase, and monoacylglycerol acyltransferase activities were measured in liver and in white and brown adipose tissue, in order to determine whether enzymes of lipogenesis and triacylglycerol synthesis vary seasonally during hibernation in the yellow-bellied marmot (Marmota flaviventris). Compared with mid-winter hibernation, fatty acid synthase activity was higher in all three tissues during early spring when marmots emerged from hibernation and in mid-summer when they were feeding, consistent with the synthesis of fatty acids from the carbohydrate-rich summer diet. Fatty-acid-CoA ligase and diacylglycerol acyltransferase activities were highest in summer in white adipose tissue when triacylglycerol synthesis would be expected to be high; diacylglycerol acyltransferase activity was also high in brown adipose tissue during spring and summer. In liver, however, diacylglycerol acyltransferase specific activity was highest during hibernation, suggesting that triacylglycerol synthesis may be prominent in liver in winter. Monoacylglycerol acyltransferase activity, which may aid in the retention of essential fatty-acids, was 80-fold higher in liver than in white or brown adipose tissue, but did not vary seasonally. Its dependence on palmitoyl-CoA suggests that a divalent cation might play a role in enzyme activation. The high hepatic diacylglycerol acyltransferase activity during hibernation suggests that the metabolism of very low density lipoprotein may be important in the movement of adipose fatty acids to brown adipose tissue and muscle during the rewarming that occurs periodically during hibernation. These studies suggest that enzymes of lipid metabolism vary seasonally in the marmot, consistent with requirements of this hibernator for triacylglycerol synthesis and metabolism.Abbreviations BAT brown adipose tissue - DGAT diacylglycerol acyltransferase - FAS fatty acid synthase - K _m Michaelis constant - MGAT monoacylglycerol acyltransferase - RQ respiratory quotiant - VLDL very low density lipoprotein - WAT white adipose tissue     

Dietary gamma-linolenic acid in the form of borage oil causes less body fat accumulation accompanying an increase in uncoupling protein 1 mRNA level in brown adipose tissue

Rats were fed a low-fat diet containing 2% safflower oil or 20% fat diets containing either safflower oil rich in linoleic acid, borage oil containing 25% gamma (gamma)-linolenic acid or enzymatically prepared gamma-linolenic acid enriched borage oil containing 47% gamma-linolenic acid for 14 days. Energy intake and growth of animals were the same among groups. A high safflower oil diet compared with a low-fat diet caused significant increases in both epididymal and perirenal white adipose tissue weights. However, high-fat diets rich in gamma-linolenic acid failed to do so. Compared with a low-fat diet, all the high-fat diets increased mRNA levels of uncoupling protein 1 and lipoprotein lipase in brown adipose tissue. The extents of the increase were greater with high-fat diets rich in gamma-linolenic acid. Various high-fat diets, compared with a low-fat diet, decreased glucose transporter 4 mRNA in white adipose tissue to the same levels. The amount and types of dietary fat did not affect the leptin mRNA level in epididymal white adipose tissue. However, a high safflower oil diet, but not high-fat diets rich in gamma-linolenic acid relative to a low-fat diet, increased perirenal white adipose tissue leptin mRNA levels. All high-fat diets, relative to a low-fat diet, increased the hepatic mitochondrial fatty acid oxidation rate and fatty acid oxidation enzyme mRNA abundances to the same levels. High-fat diets also increased these parameters in the peroxisomal pathway, and the increases were greater with high-fat diets rich in gamma-linolenic acid. The physiological activity in increasing brown adipose tissue gene expression and peroxisomal fatty acid oxidation was similar between the two types of borage oil differing in gamma-linolenic acid content. It was suggested that dietary gamma-linolenic acid attenuates body fat accumulation through the increase in gene expressions of uncoupling protein 1 in brown adipose tissue. An increase in hepatic peroxisomal fatty acid oxidation may also contribute to the physiological activity of gamma-linolenic acid in decreasing body fat mass.     

Dissociation of Large and Small Bovine Casein Micelles by Dialysis

The effects of dietary fat types on the thermogenic activity of brown adipocytes isolated from rat were examined. When beef tallow (saturated fatty acids + oleic) and safflower oil (linoleic) were the dietary fats, the respiration rates of brown adipocytes activated either by norepinephrine or an uncoupler of mitochondrial respiration (carbonylcyanide-m-chlorophenylhydrazone) were both slightly higher in rats fed the polyunsaturated fat. When the effects of safflower oil and evening primrose oil (linoleīc + γ-linolenic) were compared, the activated respiration rate tended to be higher in the latter. The respiratory responses to varying concentrations of norepinephrine were apparently dependent on the dietary fat types. Triglyceride stored in interscapular brown adipose tissue appeared to be modified by dietary fat types. Dietary fat also characteristically modified the fatty acid compositions of interscapular brown and epididymal white adipose tissues. Thus, the type of dietary fat caused an alteration to the thermogenesis of brown adipose tissue at the cellular level.     

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     

Influence of Dietary Conjugated Linoleic Acid and Fat Source on Body Fat and Apoptosis in Mice*

Objective: To determine whether altered dietary essential fatty acid (linoleic and arachidonic acid) concentrations alter sensitivity to conjugated linoleic acid (CLA)‐induced body fat loss or DNA fragmentation. Research Methods and Procedures: Mice were fed diets containing soy oil (control), coconut oil [essential fatty acid deficient (EFAD)], or fish oil (FO) for 42 days, and then diets were supplemented with a mixture of CLA isomers (0.5% of the diet) for 14 days. Body fat index, fat pad and liver weights, DNA fragmentation in adipose tissue, and fatty acid profiles of adipose tissue were determined. Results: The EFAD diet decreased (p < 0.05) linoleic and arachidonic acid in mouse adipose tissue but did not affect body fat. Dietary CLA caused a reduction (p < 0.05) in body fat. Mice fed the EFAD diet and then supplemented with CLA exhibited a greater reduction (p < 0.001) in body fat (20.21% vs. 6.94% in EFAD and EFAD + CLA‐fed mice, respectively) compared with mice fed soy oil. Dietary FO decreased linoleic acid and increased arachidonic acid in mouse adipose tissue. Mice fed FO or CLA were leaner (p < 0.05) than control mice. FO + CLA‐fed mice did not differ in body fat compared with FO‐fed mice. Adipose tissue apoptosis was increased (p < 0.001) in CLA‐supplemented mice and was not affected by fat source. Discussion: Reductions in linoleic acid concentration made mice more sensitive to CLA‐induced body fat loss only when arachidonic acid concentrations were also reduced. Dietary essential fatty acids did not affect CLA‐induced DNA fragmentation.     

Effect of dietary fatty acids on lipoprotein lipase gene expression in the liver and visceral adipose tissue of fed and starved red sea bream Pagrus major

Juvenile red sea bream Pagrus major were fed either a commercial diet (diet 1) or diets supplemented with 10% oleate (diet 2), 5% oleate+5% linoleate (diet 3) or 5% oleate+5% n-3 polyunsaturated fatty acid mixture (diet 4) for 4 weeks. Following the conditioning period, the effects of dietary fatty acids on lipoprotein lipase (LPL) gene expression in the liver and visceral adipose tissue of fed (5 h post-feeding) and starved (48 h post-feeding) fish were investigated by competitive polymerase chain reaction. Fish liver showed substantial LPL mRNA expression that is not found in adult rat liver. When compared with diet 1, diets 2-4 tended to increase the LPL mRNA level in the liver, but tended to decrease it in the visceral adipose tissue under the fed condition. The reciprocal regulation of the liver and visceral adipose LPL mRNA abundance by dietary fatty acids was comparable to that of rat brown and white adipose tissue, respectively. The change in the LPL mRNA level by fatty acids was not completely consistent with the degree of fatty acid unsaturation. Our results indicate that the regulatory effect of dietary fatty acids on LPL gene expression was tissue-specific and related to feeding conditions, but was not solely dependent on the degree of unsaturation of fatty acids.     

Effects of high fat diets on hibernation and adipose tissue in Turkish hamsters

Summary The effects of dietary fat saturation and fat content on hibernation and several properties of white and brown adipose tissue (WAT and BAT, respectively) were investigated in Turkish hamsters (Mesocricetus brandti). Male hamsters were housed in a long photoperiod (LD 16:8) at 23°C and fed one of three diets: (1) chow (6.5% fat per weight), (2) chow+13.5% vegetable oil (OIL, 20% fat per weight [largely unsaturated fat]) and (3) chow+13.5% vegetable shortening [SHORTENING, 20% fat per weight (largely saturated fat)]. Five weeks later body weights had stabilized and the animals were transferred to a short photoperiod (LD 8:16) at 3°C. At the peak of the hibernation season (17 weeks) the animals were sacrificed within 24 h of arousal. Chow-fed hamsters had the greatest percentage of animals hibernating and days found torpid compared with the two fat-fed groups, with no differences found between the latter two groups for these measures. There were no differences between hibernating (HIB) and nonhibernating (NON-HIB) hamsters across or within the diet groups for any of the BAT measures [uncoupling protein content, mitochondrial mass, lipoprotein lipase (LPL) activity, and in vivo lipogenesis], nor were there significant effects of the diet on these measures. CHOW-and OIL-fed HIB hamsters showed decreases in body weight. All HIB groups had decreases in each carcass component, several fat pad weights, testes weight, and food intake. No consistent differences in WAT LPL activity or in vivo lipogenesis were found between HIB and NON-HIB hamsters. Feeding saturated high fat diets inhibits hibernation in some species; however, in the present experiment, feeding of both saturated and unsaturated fat-laden diets inhibited hibernation to a similar degree.Abbreviations BAT brown adipose tissue - COA cytochrome-c oxidase - DS dorsal subcutaneus - DSWAT dorsal subcutaneous white adipose tissue - E epididymal - EWAT epididymal white adipose tissue - FFDM fat-free dry mass - HIB hibernating - I interscapular - IBAT intercapsular brown adipose tissue - IS inguinal subeutaneus - ISWAT inguinal subcutaneous white adipose tissue - LPL lipoprotein lipase - NON-HIB non-hibernating - R retroperitoneal - RWAT retroperitoneal white adipose tissue - SDS sodium dodecyl sul - UCP uncoupling protein - WAT white adipose tissue     

Activity and mRNA levels of enzymes involved in hepatic fatty acid synthesis and oxidation in mice fed conjugated linoleic acid

The effects of dietary conjugated linoleic acid (CLA) on the activity and mRNA levels of hepatic enzymes involved in fatty acid synthesis and oxidation were examined in mice. In the first experiment, male ICR and C57BL/6J mice were fed diets containing either a 1.5% fatty acid preparation rich in CLA or a preparation rich in linoleic acid. In the second experiment, male ICR mice were fed diets containing either 1.5% linoleic acid, palmitic acid or the CLA preparation. After 21 days, CLA relative to linoleic acid greatly decreased white adipose tissue mass but caused hepatomegaly accompanying an approximate 10-fold increase in the tissue triacylglycerol content irrespective of mouse strain. CLA compared to linoleic acid greatly increased the activity and mRNA levels of various lipogenic enzymes in both experiments. Moreover, CLA increased the mRNA expression of Delta6- and Delta5-desaturases, and sterol regulatory element binding protein-1 (SREBP-1). The mitochondrial and peroxisomal palmitoyl-CoA oxidation rate was about 2.5-fold higher in mice fed CLA than in those fed linoleic acid in both experiments. The increase was associated with the up-regulation of the activity and mRNA expression of various fatty acid oxidation enzymes. The palmitic acid diet compared to the linoleic acid diet was rather ineffective in modulating the hepatic lipid levels or activity and mRNA levels of enzymes in fatty acid metabolism. It is apparent that dietary CLA concomitantly increases the activity and mRNA levels of enzymes involved in fatty acid synthesis and oxidation, and desaturation of polyunsaturated fatty acid in the mouse liver. Both the activation of peroxisomal proliferator alpha and up-regulation of SREBP-1 may be responsible for this.     

Dose-dependent effects of dietary gamma-linolenic acid on rat spleen lymphocyte functions.

Feeding rodents a diet rich in evening primrose oil (EPO), which contains 5-10 g gamma-linolenic acid (GLA)/100 g total fatty acids, has been shown to decrease lymphocyte proliferation and natural killer cell activity. However, EPO contains a very high level of linoleic acid which itself can affect lymphocyte functions and it is not clear to what extent the effects of EPO can be attributed to GLA. The current study investigated the effect of two levels of GLA in the rat diet upon immune cell functions; the level of linoleic acid was maintained below 30 g/100 g total fatty acids. Weanling rats were fed on high fat (178 g/kg) diets which contained 4.4 g or 10 g GLA/100 g total fatty acids in place of a proportion of linoleic acid. The total polyunsaturated fatty acid content and the n-6 to n-3 polyunsaturated fatty acid ratio of the diet were maintained at 35 g/100 g total fatty acids and 7, respectively. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet, with an increase in the proportions of GLA and dihomo-gamma-linolenic acid when the diets containing GLA were fed; these diets also increased the proportion of arachidonic acid in spleen leukocytes. Spleen lymphocyte proliferation in response to concanavalin A was significantly reduced (by 60%) by feeding the diet containing the higher level of GLA, but not by the diet containing the lower level of GLA. Spleen natural killer cell activity and prostaglandin E (PGE) production by spleen leukocytes were not significantly affected by inclusion of GLA in the diet, although there was a tendency towards decreased natural killer cell activity by cells from rats fed the high GLA diet. Thus, this study shows that dietary GLA is capable of altering the fatty acid composition of cells of the immune system and of exerting some immunomodulatory effects, but that the level of GLA in the diet must exceed 4.4 g/100 g total fatty acids for these effects to become apparent.     

Effect of diet on fatty acid compositions in Sciaenops ocellatus

The role of dietary polyunsaturated fatty acids (PUFAs) on the fatty acid composition of juvenile red drum Sciaenops ocellatus was investigated. Individuals (n = 435) were fed three natural diets (Gulf menhaden Brevoortia patronus, brown shrimp Farfantapenaeus aztecus and Atlantic brief squid Lolliguncula brevis) that had significantly different proximate composition, energy density and PUFA compositions for 40 days. Diets were characterized as containing: high lipid, high protein, high energy and low PUFA (fish‐based), low lipid, low protein, low energy, moderate PUFA (shrimp‐based), and low lipid, high protein, moderate energy and high PUFA levels (squid‐based), respectively. Specimens were collected at days 0, 5, 10, 20 and 40 to evaluate rate of dietary fatty acid composition in tissues. Two‐source mixing models were used to calculate dietary fatty acid accumulation in consumer tissues. Results indicated that juvenile red drum incorporated an average of 35% dietary PUFAs after 5 days. Although relative biomass and dietary proximate composition had an effect upon the dietary fatty acid contribution, red drum averaged 91% incorporation of the five most prevalent PUFAs [18 : 2 (n ? 6), 20 : 4 (n ? 6), 20 : 5 (n ? 3), 22 : 5 (n ? 3) and 22 : 6 (n ? 3)] across all diets after 40 days. Growth varied as a function of diet and rates were higher for individuals fed the squid diet than those fed shrimp or fish diets primarily due to increased levels of protein and PUFAs [including 22 : 6 (n ? 3); 25·8%] in the diet. Red drum fed squid exhibited the greatest increase in average dietary fatty acid contribution by day 5, a trend that continued for the duration of the experiment. Since PUFA composition in red drum was significantly influenced by diet in as few as 5 days and almost completely incorporated into body tissues after 40 days, results from this study support the premise that fatty acids (especially PUFAs) are promising dietary indicators and may be useful for future studies examining trophic relationships of estuarine and marine fishes.     

Activities of liver microsomal fatty acid desaturases in zinc-deficient rats force-fed diets with a coconut oil/safflower oil mixture of linseed oil

The present study was conducted to investigate the effect of zinc deficiency on fatty acid desaturation in rats fed two different types of dietary fat, a mixture of coconut oil and safflower oil (7∶1, w/w, “coconut oil diet”) or linseed oil (“linseed oil diet”). In order to ensure an adequate food intake, all rats were force-fed by gastric tube. Zinc deficiency caused statistical significant reducion of Δ9-desaturase activity in liver microsomes of rats fed coconut oil diet and tendencial reduction (p<0.15) in rats fed linseed oil diet compared with control rats fed diets with the same type of fat. In agreement with this effect, zinc deficiency in the rats fed both types of dietary fat increased the ratio between total saturated and total monounsaturated fatty in liver phospholipids and liver microsomes. Zinc deficient rats on the coconut oil diet had unchanged Δ6-desaturase activity with linoleic acid as substrate and lowered activity with α-linolenic acid as substrate. In contrast, zinc deficient rats on the linseed oil diet had increased Δ6-desaturase activity with linoleic acid as substrate and unchanged activity with α-linolenic acid. Because linoleic acid is the main substrate for Δ6-desaturase in the rats fed coconut oil diet, and α-linolenic acid is the main substrate in the rats fed linseed oil diet, it is concluded that in vivo Δ6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Δ5-desaturase was also not changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Δ4-, Δ5-, and Δ6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, the enzyme studies and also fatty acid composition data of liver phospholipids and microsomes indicate that zinc deficiency does not considerably disturb desaturation of linoleic and α-linolenic acid. Therefore, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in literature are not due to disturbed desaturation of linoleic acid in zinc deficiency. The present study also indicates that zinc deficiency enhances incorporation of eicosapentaenoic acid into phosphatidylcholine of rats fed diets with large amounts ofn-3 polyunsaturated fatty acids.     

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     

Novel Plant Growth Inhibitors and an Insect Antifeedant from Chrysanthemum coronarium (Japanese Name: Shungiku)

The effect of overnight fasting on the dietary protein-dependent change in the fatty acid composition of tissue lipids was studied in rats fed with casein or soybean protein (20%) diets containing 5 or 2% corn oil. The activity of the Δ6-desaturase of liver microsomes, a key enzyme of linoleate metabolism to arachidonate, was depressed significantly by overnight fasting, and the protein effect disappeared, irrespective of the level of dietary fat. The proportion of linoleate in liver phosphatidylcholine was decreased, whereas that of arachidonate was increased after overnight fasting in rats fed with a low fat diet, resulting in an elevation of the linoleate desaturation index. Although the effect of fasting became obscure on a high fat diet, the protein effects were maintained even after fasting. A similar trend was also observed in various lipid fractions. Thus, the effect of dietary protein on the polyunsaturated fatty acid profile was not modulated by overnight fasting, particularly when a minimal amount of linoleic acid was supplied.     

Growth and fatty acid composition of freshwater prawn, Macrobrachium rosenbergii, larvae fed diets containing various ratios of cod liver oil–corn oil mixture

A feeding trial was conducted to determine the effect of replacing costly cod liver oil with corn oil as a source of dietary lipid on the growth and fatty acid composition of the larval freshwater prawn, Macrobrachium rosenbergii de Man. Prawn larvae were weaned to artificial diets containing cod liver oil and corn oil either singly or in various combinations (2 : 1, 1 : 1, 1 : 2, w/w). Weaning to artificial diets from Artemia nauplii commenced at larval stage III with complete substitution by stage X. The reference group was reared solely on Artemia nauplii during the entire experiment. Incorporation of corn oil at 33–67% of dietary supplemental oil did not have significant effects on the post‐larval production. However, larvae fed with corn oil alone revealed a significantly lower post‐larval production compared to other experimental diets as well as to the reference group. No significant differences (P > 0.05) were observed in dry weight, protein and lipid concentration among larvae fed on various dietary treatments. Palmitic (16 : 0) and oleic/vaccenic (18 : 1) acids were the dominant saturated and monounsaturated fatty acids in larval tissues, respectively, whereas the polyunsaturated fraction was dominated by eicosapentaenoic (20 : 5n‐3) acid. The polyunsaturated fatty acid composition was dominated by n‐3 acids rather than n‐6 fatty acids. The fatty acid composition of the prawn in general reflected that of the diet. Larvae on diets containing higher concentrations of corn oil rich in linoleic (18 : 2n‐6) acid showed a higher concentration of this acid in their tissues. No evidence of de novo synthesis of linoleic (18 : 2n‐6) acid was found. Higher levels of stearic (18 : 0), arachidonic (20 : 4n‐6) and eicosapentaenoic (20 : 5n‐3) acids found in larvae as compared with those fed Artemia and artificial diets strongly indicated the larval ability in chain elongation and desaturation of palmitic (16 : 0), linoleic (18 : 2n‐6) or linolenic (18 : 3n‐3) acids, respectively. Despite a large variation of n‐3 to n‐6 ratios of the live and artificial diets, larval n‐3 to n‐6 ratios were relatively stable among different dietary treatments, possibly indicative of the importance of such a ratio in the larval fatty acid metabolism.     

Polyunsaturated dietary lipids lower the selected body temperature of a lizard

Summary Cold acclimation lowers the selected body temperature (T _b) in many ectothermic vertebrates. This change in behavioural thermoregulation is accompanied by an increase in the proportion of polyunsaturated fatty acids in tissues and cellular membranes. We investigated how diets containing different fatty acids, known to significantly alter the fatty acid composition of animal tissues and membranes, affect the selected T _b of the lizard Tiliqua rugosa. Lizards on a diet containing many polyunsaturated fatty acids (10% sunflower oil) showed a 3–5°C decrease in T _b, whereas T _b in animals on a diet containing mainly saturated fatty acids (10% sheep fat) did not change. Our study suggests that the composition of dietary lipids influences thermoregulation in ectothermic vertebrates and may thus play a role in the seasonal adjustment of their physiology.Abbreviations CST central standard time - T _a air temperature - T _b Body temperature     

Dietary conjugated linoleic acid reduces body fat mass and affects gene expression of proteins regulating energy metabolism in mice

ICR and C57BL/6J mice were fed experimental diets containing either a 2% fatty acid preparation rich in conjugated linoleic acid (CLA) or a preparation rich in linoleic acid and free of CLA for 21 days. CLA greatly decreased weights of white adipose tissue and interscapular brown adipose tissue in the two strains. CLA reduced mRNA levels of glucose transporter 4 (Glut 4) in white and brown adipose tissue of both strains. A CLA-dependent decrease in mRNA levels of peroxisome proliferator activated receptor (PPAR) gamma was seen in interscapular brown adipose tissue of both strains and in white adipose tissue of C57BL/6J but not ICR mice. Dietary CLA was found to cause a decrease in the mRNA levels of uncoupling protein (UCP) 1 in brown adipose tissue when the value was corrected for the expression of a house-keeping gene (beta-actin) in the two strains. Uncorrected values were, however, indistinguishable between the animals fed the CLA diet and CLA-free diet. UCP 3 expression in brown adipose tissue was much lower in mice fed the CLA diet than in those fed the control diet in both strains. In contrast, CLA greatly up-regulated the gene expression of UCP 2 in brown adipose tissue. Dietary CLA also increased UCP 2 mRNA level in skeletal muscle. It is apparent that dietary CLA decreases white and brown adipose tissue mass, accompanying changes in the gene expression of proteins regulating energy metabolism in white and brown adipose tissues, and skeletal muscle of mice.