Biomedical subjects

M Enser

Publications and source records attributed to M Enser.

At least 19 recordsLinked to original sources

PubMed2004

Biohydrogenation of dietary n-3 PUFA and stability of ingested vitamin E in the rumen, and their effects on microbial activity in sheep.

The present study investigated the susceptibility of dietary n-3 PUFA to ruminal biohydrogenation, the stability of ingested vitamin E in the rumen and the subsequent uptake of PUFA and vitamin E into plasma. Six cannulated sheep were assigned to six diets over five 33 d periods, in an incomplete 6x5 Latin square. The diets, based on dried grass, were formulated to supply 50 g fatty acids/kg DM using three lipid sources: Megalac (calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK), linseed (formaldehyde-treated; Trouw Nutrition, Northwich, Ches., UK) and linseed-fish oil (formaldehyde-treated linseed+fish oil). The diets were supplemented with 100 or 500 mg alpha-tocopheryl acetate/kg DM. Fat source or level of vitamin E in the diet did not alter microbial activity in the rumen. Biohydrogenation of linoleic acid (18 : 3n-6; 85-90 %), linolenic acid (18 : 3n-3; 88-93 %), docosahexaenoic acid (22 : 6n-3; 91 %) and EPA (20 : 5n-3; 92 %) was extensive. Feeding formaldehyde-treated linseed elevated concentrations of 18 : 3n-3 in plasma, whilst 22 : 6n-3 and 20 : 5n-3 were only increased by feeding the linseed-fish oil blend. Duodenal recovery of ingested vitamin E was high (range 0.79-0.92 mg/mg fed). High dietary vitamin E was associated with increased plasma alpha-tocopherol (2.57 v. 1.46 microg/ml for 500 and 100 mg alpha-tocopheryl acetate/kg DM respectively), although all concentrations were low. Plasma vitamin E levels, however, tended to decrease as the type and quantity of PUFA in the diet increased. The present study illustrates that nutritionally beneficial PUFA in both fish and linseed oils are highly susceptible to biohydrogenation in the rumen. Although alpha-tocopheryl acetate resisted degradation in the rumen, plasma vitamin E status remained deficient to borderline, suggesting either that uptake may have been impaired or metabolism post-absorption increased.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Effects of dietary n-3 polyunsaturated fatty acids, breed and dietary vitamin E on the fatty acids of lamb muscle, liver and adipose tissue.

The effect of feeding n-3 PUFA on the fatty acid composition of muscle, adipose tissue and liver of lambs was investigated. Groups of eight ram lambs per breed, SuffolkxLleyn (24 kg live weight) and Scottish Blackface (18 kg live weight), were each fed one of six diets containing one of three fat sources (50 g fatty acids/kg DM; Megalac((R)) (calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK) and formaldehyde-treated whole linseed (Trouw Nutrition UK, Northwich, Ches., UK) either alone or with fish oil (1:1, w/w) and either 100 or 500 mg alpha-tocopheryl acetate/kg DM. Feed was offered ad libitum until slaughter at approximately half breed mature live weight. The type of dietary fat had no effect on intake, growth rate or feed conversion ratio. The 3.0-fold higher concentration of 18 : 3n-3 in the linseed compared with the Megalac((R)) diet approximately doubled (P<0.001) the concentration in the neutral and polar lipid fractions of musculus semimembranosus and liver, and in adipose tissue it increased 2.5-fold. Feeding protected linseed also increased (P<0.001) concentrations of 20 : 5n-3 and 22 : 5n-3 in muscle polar lipids and both lipid fractions of liver. The linseed-fish oil raised the 20 : 5n-3 concentrations above those for the linseed diet and also increased 22 : 6n-3. Scottish Blackface lambs had lower concentrations of 18 : 3n-3 in all lipids compared with Suffolk x Lleyn lambs, but more 20 : 5n-3 in the polar lipids of muscle and liver. High levels of dietary vitamin E were associated with small decreases in the concentration of monounsaturated fatty acids and increases in PUFA. Linseed raised the PUFA : saturated fatty acid ratios in liver and adipose tissue but not in muscle, and improved the n-6 : n-3 fatty acid ratio, as did the linseed-fish oil. Different combinations of dietary fatty acids and better protection against rumen biohydrogenation are required to improve muscle PUFA : saturated fatty acids ratios.

Adipose Tissue↗

PubMed2004

Manipulation of the n-3 polyunsaturated fatty acid content of muscle and adipose tissue in lambs.

Fifty Suffolk-crossbred wether lambs, with an initial live weight of 29 +/- 2.1 kg, were allocated to one of five concentrate-based diets formulated to have a similar fatty acid content (60 g/kg DM), but containing either linseed oil (high in 18:3n-3); fish oil (high in 20:5n-3 and 22:6n-3); protected linseed and soybean (PLS; high in 18:2n-6 and 18:3n-3); fish oil and marine algae (fish/algae; high in 20:5n-3 and 22:6n-3); or PLS and algae (PLS/algae; high in 18:3n-3 and 22:6n-3). Lambs were slaughtered when they reached 40 kg. Growth performance and intake were similar (P > 0.35) among treatments. By contrast, gain:feed was higher (P < 0.05) in lambs fed the fish oil compared with the linseed oil or PLS/algae diets. Total fatty acid concentration (mg/100 g) in the neutral lipid of the longissimus muscle was not affected by treatment (P > 0.87) but was least (P < 0.05) in the phospholipid fraction in lambs fed the linseed oil diet. Lambs fed either diet containing marine algae contained the highest (P < 0.05) percentage of 22:6n-3 in the phospholipid (mean of 5.2%), 2.8-fold higher than in sheep fed the fish oil diet. In lambs fed the fish/algae diet, the percentage of 20:5n-3 was highest (P < 0.05), contributing some 8.7, 0.8, and 0.5% of the total fatty acids in the muscle phospholipid, neutral lipids, and adipose tissue, respectively. The percentage of 18:3n-3 in the phospholipid fraction of the LM was highest (P < 0.05) in lambs fed the linseed oil diet (6.9%), a value double that of sheep fed the PLS diet. By contrast, lambs fed the PLS diet had twice the percentage of 18:3n-3 in the muscle neutral lipids (3.8%) than those offered the linseed oil diet, and 5.5-fold greater than lambs fed the fish/algae treatment (P < 0.05), an effect that was similar in the adipose tissue. The percentage of 18:2n-6 was highest (P < 0.05) in lambs fed the PLS diet, where it contributed 33.7, 10.1, and 11.2% in the muscle phospholipid, neutral lipids, and adipose tissue, respectively. The highest (P < 0.05) muscle PUFA-to-saturated fatty acid (P:S) ratio was obtained in lambs fed the PLS diet (0.57), followed by the PLS/algae diet (0.46), and those fed the fish oil or linseed oil diets had the lowest ratios (0.19 and 0.26, respectively). The favorable P:S ratio of lambs fed the PLS/algae diet, in conjunction with the increased levels of 20:5n-3 and 22:6n-3, enhanced the nutritional qualities of lamb to more closely resemble what is recommended for the human diet.

Adipose Tissue↗

PubMed2003

Effect of a high-linolenic acid diet on lipogenic enzyme activities, fatty acid composition, and meat quality in the growing pig.

Forty-eight Duroc-cross gilts (40 kg initial BW) were fed a control or a linseed diet containing 60 g of whole crushed linseed/kg. Both diets were supplemented with 150 mg of vitamin E/kg. Eight pigs from each dietary treatment were slaughtered at 20, 60, or 100 d after the start of the experiment. There was no effect (P > 0.05) of diet on growth, carcass characteristics, or foreloin tissue composition. Feeding the linseed diet increased (P < 0.05) the content of n-3 PUFA in plasma, muscle, and adipose tissue, but docosahexaenoic acid was not (P > 0.05) altered by diet. The proportions of n-3 PUFA were highest (P < 0.01) in pigs fed the linseed-diet for 60 d, regardless of tissue (plasma, muscle, or adipose tissue) or lipid (neutral lipids and phospholipids) class. The linseed diet produced a PUFA:saturated fatty acid ratio > or = 0.4 in all groups and tissues, which is close to the recommended value for the entire diet of humans, as well as a robust decrease in the n-6:n-3 ratio. The decrease (P < 0.01) in the percentage of oleic acid in adipose tissue of pigs fed the linseed diet for 60 d could be attributed to a 40% decrease (P < 0.001) in stearoyl-CoA-desaturase activity. Diet did not (P > 0.05) affect the activities of acetyl-CoA-carboxylase, malic enzyme, or glucose-6-phosphate-dehydrogenase in any tissues. Muscle vitamin E content was decreased (P < 0.001) 30% in pigs fed crushed linseed for 60 d, whereas lower (P < 0.001) concentrations of skatole in pork fat were observed in linseed-fed pigs at all slaughter times. Inclusion of linseed (flaxseed) in swine diets is a valid method of improving the nutritional value of pork without deleteriously affecting organoleptic characteristics, oxidation, or color stability.

Animal Feed↗

PubMed2002

Effects of dietary fat source and breed on the carcass composition, n-3 polyunsaturated fatty acid and conjugated linoleic acid content of sheep meat and adipose tissue.

Seventy-two 8-week-old ram lambs from three breeds, Suffolk, Soay and Friesland, were offered one of four diets based on dried grass and formulated to have a similar fatty acid content (60 g/kg DM) and containing: Megalac (high in 16 : 0, control; Volac Ltd, Royston, Herts., UK), whole linseed (18 : 3n-3), fish oil (20 : 5n-3 and 22 : 6n-3) or whole linseed plus fish oil. The lambs were slaughtered at approximately half of their mature live weight (43, 21 and 43 kg for Suffolk, Soay and Friesland lambs, respectively). Fish oil reduced DM intake and lamb live-weight gain (P<0.001), while DM intake, live-weight gain and subcutaneous fat content were highest in Suffolk and lowest in Soay lambs. Linseed feeding doubled the proportion (x100) of 18 : 3n-3 in the longissimus dorsi from 1.4 to 3.1 and in the subcutaneous adipose tissue from 1.2 to 2.6 (P<0.001). Suffolk and particularly Soay lambs contained higher proportions of 18 : 3n-3 than Friesland lambs in the longissimus dorsi, while in the adipose tissue, Suffolk lambs had the highest level. Feeding fish oil increased the muscle proportion (x100) of 20 : 5n-3 from 0.7 to 2.3 and 22 : 6n-3 from 0.3 to 0.8 (P<0.001). By contrast, the proportions of the longer-chain n-3 polyunsaturated fatty acids were similar across all three breeds. All three lipid supplements containing n-3 polyunsaturated fatty acids increased the content of muscle trans-18 : 1 relative to the control values, but conjugated linoleic acid (cis-9,trans-11-18 : 2) only increased in the muscle of lambs fed linseed. Feeding linseed or fish oil lowered the n-6 : n-3 ratio in sheep meat, but neither diet nor breed had much effect on the polyunsaturated fatty acid: saturated fatty acid ratio.

Adipose Tissue↗

PubMed2001

Manipulating the fatty acid composition of muscle and adipose tissue in beef cattle.

Enhancing the n-3 polyunsaturated fatty acid (PUFA) content of beef is important in view of the generally saturated nature of fatty acids in ruminant meats and the negative effect this can have on human health. This study examined the effects of different sources of dietary n-3 PUFA on the performance of steers and the fatty acid composition of m. longissimus thoracis muscle and associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of four concentrates (60:40 forage:concentrate on a DM basis) containing differing sources of lipid: Megalac (16:0), lightly bruised whole linseed (18:3n-3), fish oil (20:5n-3 and 22:6n-3) and a mixture of linseed and fish oil (1:1, on an oil basis). Diets were formulated so that total dietary oil intake was 6 %, approximately half of which was from the experimental test oil. Linseed feeding not only increased the levels of 18:3n-3 in muscle phospholipid from 9.5 to 19 mg/100 g muscle but also enhanced the synthesis of 20:5n-3, the level of which increased from 10 to 15 mg/100 g muscle. Linseed also increased the proportion of 18:3n-3 in muscle neutral lipid and in adipose tissue lipids by a factor of 1.64 and 1.75 respectively. Fish oil feeding doubled the proportion of 20:5n-3 and 22:6n-3 in muscle phospholipids. The proportion of 18:1 trans in muscle neutral lipid was higher on the n-3 PUFA diets than the control diet, 0.04 and 0.02 respectively. Despite the implied modification to rumen metabolism, lipid source did not affect feed intake, growth rate, cold carcass weight or carcass fatness, but carcass conformation score was higher on fish oil treatments (P < 0.05). However, total muscle fatty acid content was not different between treatments and ranged from 3.5-4.3 % of tissue weight. The increase in n-3 PUFA in the meat produced by feeding linseed or fish oil lowered the n-6:n-3 ratio but had little effect on the P:S ratio.

Adipose Tissue↗

PubMed1999

Manipulating meat quality and composition.

Meat quality describes the attractiveness of meat to consumers. The present paper focuses on two major aspects of meat quality, tenderness and flavour. Both aspects of quality can be influenced by nutrition, principally through its effects on the amount and type of fat in meat. In several countries, high levels of intramuscular fat (marbling fat), i.e. above 30 g/kg muscle weight in longissimus, are deemed necessary for optimum tenderness, although poor relationships between fat content and tenderness have generally been found in European studies, where fat levels are often very low, e.g. below 10 g/kg in UK pigs. Muscle lipid may be a marker for red oxidative (type 1) muscle fibres which are found at higher concentrations in tender muscles and carcasses. Nutritional treatment can be used to manipulate the fatty acid content of muscle to improve nutritional balance, i.e. increase the polyunsaturated (PUFA): saturated fatty acid value and reduce the n-6:n-3 PUFA value. Increasing PUFA levels may also change flavour because of their greater susceptibility to oxidative breakdown and the generation of abnormal volatile compounds during cooking. This situation particularly applies to the n-3 PUFA which are the most unsaturated meat lipids. In pigs, a concentration of 3 mg alpha-linolenic acid (18:3)/100 mg in muscle and fat tissue fatty acids can easily be achieved by including whole linseed in the diet. This level has led to abnormal odours and flavours in some studies, but not in others. In cattle and sheep, feeding whole linseed raised 18:3 concentrations in muscle fatty acids from about 0.7 mg/100 mg to > 1 mg/100 mg. As with pigs, this diet also increased levels of long-chain n-3 PUFA formed from 18:3, including eicosapentaenoic acid (20:5). Although this increase led to greater oxidative breakdown of lipids during storage and the generation of large quantities of lipid-derived volatile compounds during cooking, there were no deleterious effects on odour or flavour. When 18:3 levels are raised in lamb and beef because of grass feeding, the intensity of the flavours increases in comparison with grain-fed animals which consume and deposit relatively more linoleic acid (18:2). In ruminants, very high levels of 18:2 produced by feeding protected oil supplements cause the cooked beef to be described as oily, bland or pork-like.

Animal Nutritional Physiological Phenomena↗

PubMed1999

Effect of the polyunsaturated fatty acid composition of beef muscle on the profile of aroma volatiles.

The effect of n-3 polyunsaturated fatty acids (PUFAs) in beef muscle on the composition of the aroma volatiles produced during cooking was measured. The meat was obtained from groups of steers fed different supplementary fats: (i) a palm-oil-based control; (ii) bruised whole linseed, which increased muscle levels of alpha-linolenic (C18:3 n-3) and eicosapentaenoic acid (EPA, C20:5 n-3); (iii) fish oil, which increased EPA and docosahexaenoic acid (C22:6 n-3); (iv) equal quantities of linseed and fish oil. Higher levels of lipid oxidation products were found in the aroma extracts of all of the steaks with increased PUFA content, after cooking. In particular, n-alkanals, 2-alkenals, 1-alkanols, and alkylfurans were increased up to 4-fold. Most of these compounds were derived from the autoxidation of the more abundant mono- and di-unsaturated fatty acids during cooking, and such autoxidation appeared to be promoted by increased levels of PUFAs.

Animal Feed↗

PubMed1997

Factors influencing fatty acids in meat and the role of antioxidants in improving meat quality.

Meat has been identified, often wrongly, as a food having a high fat content and an undesirable balance of fatty acids. In fact lean meat is very low in fat (20-50 g/kg), pork and poultry have a favourable balance between polyunsaturated and saturated fatty acids (P:S) and grazing ruminants produce muscle with a desirable n-6:n-3 polyunsaturated fatty acid ratio. In all species, meat fatty acid composition can be changed via the diet, more easily in single-stomached pigs and poultry where the linoleic, alpha-linolenic and long-chain polyunsaturated fatty acid content responds quickly to raised dietary concentrations. Recent work in pigs has attempted to manipulate the n-6:n-3 ratio by feeding higher levels of alpha-linolenic acid (e.g. in rapeseed) or its products eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) present in fish oils. In ruminants the challenge is to increase the P:S ratio whilst retaining values for n-6:n-3 found in cattle and sheep fed on forage diets. The saturating effect of the rumen can be overcome by feeding polyunsaturated fatty acids which are protected either chemically, by processing, or naturally e.g. within the seed coat. Some protection occurs when grain-based or grass-based diets are fed normally, leading to relatively more n-6 or n-3 fatty acids respectively. These produce different flavours in cooked meat due to the different oxidative changes occurring during storage and cooking. In pigs and poultry, high n-3 fatty acid concentrations in meat are associated with fishy flavours whose development can be prevented with high dietary (supranutritional) levels of the antioxidant vitamin E. In ruminants, supranutritional vitamin E delays the oxidative change of oxymyoglobin to brown metmyoglobin and may also influence the characteristic flavours of beef and lamb.

Animal Feed↗

PubMed1990

De novo design and structure-activity relationships of peptide emulsifiers and foaming agents.

A series of eight amphipathic peptides (8, 11, 15, 2 x 18, 22, 26, 29 amino acids in length) were designed to investigate the effects of amino acid composition, peptide length and secondary structure on surface activity assessed as emulsification and foaming activity. The potential for alpha-helix formation at the hydrophobic/hydrophilic interface was maximized through the use of helix-forming amino acids, a relatively large hydrophobic surface of 200 degrees of arc and ion pairs between basic and acidic amino acids on the hydrophilic surface. Emulsification activity increased rapidly between 11 and 22 residues as alpha-helicity in aqueous solution increased. Despite their small size, the peptides produced exceptionally stable emulsions, compared with proteins. Foaming activity was enhanced by the presence of aromatic amino acids and the activity of the best peptide examined was superior to that of bovine serum albumin and beta-lactoglobulin.

Amino Acid Sequence↗

PubMed1989

Effects of adrenalectomy on muscle fibre growth and fibre-type composition in obese-hyperglycaemic (ob/ob) and lean mice.

Adrenalectomy of obese mice increases the weights of their skeletal muscles towards normal. We have investigated whether this increased growth was specific for the fast phasic muscles and white, glycolytic fibres most affected by obesity and whether the proportions of the different fibre types were restored to normal. Male obese hyperglycaemic mice (ob/ob) and lean mice were adrenalectomized at 6 weeks of age and examined 6 weeks later. In obese mice body weight gain and blood glucose were markedly decreased, although still higher than in lean mice. The weight of the heart was decreased to normal in obese mice and unaffected in lean mice. In lean mice the weights of the biceps brachii, gastrocnemius and soleus muscles increased by similar small amounts after adrenalectomy. In obese mice the fast gastrocnemius and biceps brachii recovered most in weight, the soleus somewhat less, but all remained smaller than in lean adrenalectomized mice. The increased growth of the biceps brachii in obese mice after adrenalectomy was non-specific with a similar increase in size of all fibre types, including the fast red fibres which were not affected by obesity. Fibre type proportions were not normalized by adrenalectomy of obese mice but were significantly changed in adrenalectomized lean mice. We conclude that it is possible only partially to normalize muscle weight and fibre type composition in obese mice by adrenalectomy. We suppose that its effects are manifest because of other defects such as insulin resistance and that these are not all reversed by adrenalectomy.

Adrenalectomy↗

PubMed1988

Effects of litter size and subsequent gold-thioglucose-induced obesity on adipose tissue weight, distribution and cellularity in male and female mice: an age study.

1. Over- or undernutrition of newborn mice was caused by suckling in litters consisting initially of four or eighteen pups. After weaning mice were fed ad lib. At 13 weeks of age some mice from large litters received gold thioglucose (GTG: 600 mg/kg intraperitoneally) to induce hyperphagia, and mice were killed at 13, 19.5, 26, 39 and 52 weeks. 2. Total carcass lipid and the size and number of adipocytes in the inguinal subcutaneous, genital, perirenal and mesenteric depots were determined. 3. Mice, both male and female, raised in small litters were heavier and had more carcass fat at all ages than mice raised in large litters. After GTG-treatment mice from large litters were heavier and fatter than mice raised in small litters. 4. Fat distribution between the depots was related to carcass lipid content and not to treatment. The order of depot development was subcutaneous, parametrial, perirenal and mesenteric in females and epididymal, subcutaneous, perirenal and mesenteric in males. At 13 weeks the depots in males were more developed than those in females. 5. Litter size had no effect on adipocyte volume in female mice at 13 weeks but by 52 weeks small-litter mice had larger cells in all depots and more cells in the parametrial and perirenal depots. 6. Male mice from small litters had bigger cells at 13 weeks in all depots compared with males from large litters but by 52 weeks no significant differences remained. Greater numbers of cells were present only in the perirenal and mesenteric depots of small-litter males at some ages. 7. Depots of GTG-treated large-litter female mice had larger cells than those of small-litter females, while a similar number of cells was found by 52 weeks in all but the perirenal depot, which had significantly more cells. 8. GTG treatment of male mice from large litters also caused bigger cells than in small-litter mice, and an increased depot cell number at earlier ages in all but the epididymal depot. By 52 weeks cell numbers were similar in depots from small-litter and GTG-treated large-litter mice, except for the epididymal depot from the latter which had fewer cells. 9. Increases in cell numbers with age in different depots occurred independently of existing cell mean volume and even of tissue growth, suggesting the presence of an in-built chronology, at least in older mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗

PubMed1988

Muscles of diabetic (db/db) mice: fibre size, fibre type and the effects of a thermogenic, beta-adrenoceptor agonist.

The size and morphological characteristics of muscles from diabetic obese (db/db) mice and their normal lean littermates were investigated. The soleus muscles were similar in size in diabetic and normal mice but the biceps brachii and gastrocnemius were significantly lighter in the diabetic animals. In the biceps brachii the small size resulted from an overall reduction in fibre diameter, which was most acute in the fast white fibres, and an increase in the proportion of smaller fast intermediate fibres. Treatment of diabetic mice with BRL 26830 a thermogenic, beta-adrenoceptor agonist, restored the weight, fibre diameter and fibre type composition of the biceps brachii to that of lean littermates. This treatment also increased the weight of the gastrocnemius, together with its protein content. Since BRL 26830 restored normoglycaemia in the diabetic mice, without decreasing their body weight, we suppose that it improved insulin action in their muscles and this, in turn, stimulated muscle growth.

Adrenergic beta-Agonists↗

PubMed1987

Effect of sodium 2-n-pentadecyl-benzimidazole-5-carboxylate (M & B 35347B), an inhibitor of acetyl-CoA carboxylase, on lipogenesis and fat deposition in obese hyperglycaemic (ob/ob) and lean mice.

A high rate of lipogenesis in obese mice plays a major role in their excessive deposition of body lipid. Inhibition of lipogenesis may decrease their obesity. Therefore, we have investigated the effects of sodium 2-n-pentadecyl-benzimidazole-5-carboxylate (M & B 35347B), an inhibitor of acetyl-CoA carboxylase, on in-vivo lipogenesis in obese and lean mice. It significantly inhibited hepatic cholesterol and fatty acid synthesis, measured using 3H2O, in both lean and obese mice, with or without a glucose load. Brown adipose tissue (scapular) lipogenesis was decreased by M & B 35347B in obese mice but not in lean mice. In white adipose tissue, M & B 35347B did not affect the rates of lipogenesis in either scapular white, inguinal or epididymal depots of obese mice, or the inguinal and scapular white depot of lean mice. However, it doubled lipogenesis in the epididymal fat pad of lean mice. After a glucose load, lipogenesis in the lean epididymal fat pad was not inhibited but that in the inguinal depot was. M & B 35347B inhibited acetyl CoA carboxylase of adipose tissue in vitro but only a small inhibition was detected after in-vivo treatment. These different responses according to type of mouse, treatment and tissue site appear to stem from differences in inhibitor concentration and the importance of acetyl CoA carboxylase as the rate-limiting enzyme of lipogenesis. The weight gain of obese mice dosed orally (200 mg M & B 35347B/kg daily) for 60 days was unaffected and they continued to deposit excess body fat. This presumably occurred because of the lack of inhibition of fatty acid synthesis in white adipose tissue.

Acetyl-CoA Carboxylase↗

PubMed1986

Brown adipose tissue triacylglycerol fatty acids of obese and lean mice: in situ and in transplants.

The triacylglycerols of white adipose tissue (WAT) from animals with high rates of lipogenesis, such as obese hyperglycemic mice or hypothalamically lesioned rats, contain high proportions of palmitoleic acid (16:1) and low proportions of linoleic acid (18:2). These differences appear to result from dilution of dietary 18:2 by synthesized fatty acids, particularly 16:1. To test this we have investigated the triacylglycerol fatty acid composition of brown and white adipose tissue of lean and obese mice, as brown adipose tissue (BAT) has a higher lipogenic rate than WAT and lipogenesis is faster in obese than in lean mice. Between three and eight weeks of age the proportions of fatty acids in the tissues changed, with a marked fall in milk-derived lauric and myristic acids. From 8 to 16 weeks they were more stable and the proportions of 16:1 and 18:2 in the different tissues were as expected, with the highest and lowest proportions, respectively, in BAT from obese mice. When BAT from obese mice was transplanted under the kidney capsule of lean mice, or vice versa, for one month, the fatty acid composition of the grafts changed toward that of the host BAT. The proportions of 18:2 and, to a lesser extent, 16:1 were slightly higher in the grafts than in the hosts but since this also occurred in lean-to-lean and obese-to-obese grafts it was probably a transplantation artifact. Overall, the results confirm that the physiological environment, rather than the source of the adipose tissue, is the major determinant of its fatty acid composition.

Adipose Tissue↗

PubMed1985

Effect of gold thioglucose-induced obesity on adipose tissue weight and cellularity in male and female mice suckled in large and small litters: investigations into sex differences and site differences.

1. Over- or undernutrition of newborn mice was caused by suckling in litters consisting initially of four or eighteen pups. After weaning, mice were fed ad lib. At 13 weeks some mice received gold thioglucose (GTG, 600 mg/kg, intraperitoneally) to induce hyperphagia, and all were killed at 39 weeks. 2. Mice suckled in small litters were heavier, with more body fat and protein. GTG treatment induced rapid weight gain and treated mice from large litters were heavier than untreated mice from small litters. However, the effect of litter size was not totally removed since GTG-treated small-litter mice were heavier than GTG-treated large-litter mice and had more fat, although body protein was not different. 3. Fat distribution between the depots was related to total body fatness and not to the treatment. 4. In male mice, preweaning undernutrition resulted in smaller fat depots containing smaller cells. GTG treatment of large-litter mice restored both to the levels found in small-litter mice: the depots of the latter mice were not significantly different after treatment. 5. In female mice, preweaning undernutrition resulted not only in smaller depots and cells but also fewer cells in all depots except mesenteric. GTG-treatment caused larger depots and cells in all mice with no difference in cell size whether mice were from large or small litters. The number of cells in the perirenal and mesenteric depots was greater in GTG-treated mice and was the same whether mice were from large or small litters. 6. We conclude that the level of preweaning nutrition does not affect the ability of adipose tissue to develop subsequently through hypertrophy or hyperplasia of the adipocytes or both, given a sufficient energy surplus consisting of normal pelleted feed, low in lipid.

Adipose Tissue↗

PubMed1984

Mechanical and chemical properties of the skin and its collagen from lean and obese-hyperglycaemic (ob/ob) mice.

We have compared the mechanical and chemical properties of the skin and its collagen from 24-week-old obese-hyperglycaemic (ob/ob) and lean mice. The skin from obese mice was mechanically weaker and generated a lower hydrothermal isometric force. However, there were no significant differences from lean mice in the type of reducible cross-links in the collagen or in its solubility, although it contained more reducible cross-links and glycosylated lysine. The total amount of skin collagen was similar in obese and lean mice from 3 to 24 weeks of age but the skin surface area was 60% greater in 24-week-old obese mice. When corrected for collagen content the tensile strength of skin from obese mice was greater than that from lean mice and we suppose that the weakness of obese mouse skin is caused by a failure of collagen deposition to match the increase in skin surface area as the animals become obese.

Aging↗

PubMed1984

A histochemical and morphological study of skeletal muscle from obese hyperglycaemic ob/ob mice.

The histochemical and morphological characteristics of muscles from lean and obese hyperglycaemic ob/ob mice were compared to determine the nature of the low skeletal muscle mass of the latter. Gastrocnemius and biceps brachii muscles from obese ob/ob mice were significantly lighter than those from lean mice, whereas the weights of soleus muscles were not significantly different. The small mass of the biceps brachii muscle resulted from a decrease in diameter of the large glycolytic fast white and fast intermediate fibres and a reduction in the proportion of fast white fibres. The size and frequency of the more oxidative fast red fibres was not different. The histochemical appearance of all fibre types studied from muscles in obese mice was identical to equivalent fibres in lean mice. The fat content of muscles from obese mice was three times greater than in lean mice whereas muscle DNA concentration was similar.

Adenosine Triphosphatases↗