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1.
Christian von Loeffelholz Jürgen Kratzsch Gerhard Jahreis 《European Journal of Lipid Science and Technology》2003,105(6):251-259
Conjugated linoleic acids (CLA) are believed to influence body composition, blood lipids and certain endocrine parameters in animals and humans. The aim of this study was to investigate the effects of a six months dietary supplementation of 7 g CLA‐oil (containing 54% CLA) daily in two groups of male and female resistance‐trained athletes who were at a different training stage. The volunteers were matched according to their previous training: 7 beginners (3♀/4♂) and 7 advanced athletes (2♀/5♂). During the intervention period they performed a standardized training routine three times per week. Blood samples were taken and body mass index, body composition (bioelectrical impedance assessment) and nutrient intake (7‐day food record) were recorded at baseline as well as during and following dietary supplementation Results: Serum lipid concentrations, serum leptin, soluble leptin receptor and IGF‐I levels or body composition were similar in the two categories of athletes after CLA supplementation. However, despite a higher energy intake, a significant reduction of body fat (P <0.05) was observed and both groups tended to increase their body cell mass (not significant). Total body water increased in the novice athletes (P <0.05). Furthermore, total cholesterol (P = 0.049) increased over baseline levels in the novice athletes. These levels remained within the physiological range. In all athletes there was a significant correlation between percentage body fat and leptin (baseline: r2 = 0.46, P = 0.01, CLA: r2 = 0.49, P = 0.011), as well as between fat mass and serum leptin levels (baseline: r2 = 0.35, P = 0.033, CLA: r2 = 0.60, P = 0.002). Conclusions: Over a period of six months no differences were observed in the effects of a commercial CLA‐triacylglyceride (54% CLA, 7g/d) on selected endocrine parameters, blood lipids, food intake and body composition between advanced and novice resistance‐trained athletes who take part in a regular training program. 相似文献
2.
Supplementation with conjugated linoleic acid (CLA) induces a number of physiological effects in experimental animals, including
reduced body fat content, decreased aortic lipid deposition, and improved serum lipid profile. Controlled trials on the effects
of CLA in humans have hitherto been scarce. The aim of this study was to evaluate the effects of supplementation with CLA
in healthy humans on anthropometric and metabolic variables and on the fatty acid composition of serum lipids and thrombocytes.
Fifty-three healthy men and women, aged 23–63 yr, were randomly assigned to supplementation with CLA (4.2 g/d) or the same
amount of olive oil during 12 wk in a double-blind fashion. The proportion of body fat decreased (−3.8%, P<0.001) in the CLA-treated group, with a significant difference from the control group (P=0.050). Body weight, body mass index, and sagittal abdominal diameter were unchanged. There were no major differences between
the groups in serum lipoproteins, nonesterified fatty acids, plasma insulin, blood glucose, or plasminogen activator inhibitor
1 (PAI-1). In the CLA group the proportions of stearic, docosatetraenoic, and docosapentaenoic acids increased in serum lipids
and thrombocytes, while proportions of palmitic, oleic, and dihomoγ-linolenic acids decreased, causing a decrease of the estimated
Δ-6 and Δ-9 and an increase in the Δ-5 desaturase activities. These results suggest that supplementation with CLA may reduce
the proportion of body fat in humans and that CLA affects fatty acid metabolism. No effects on body weight, serum lipids,
glucose metabolism, or PAI-1 were seen. 相似文献
3.
Conjugated linoleic acid supplementation in humans: Effects on circulating leptin concentrations and appetite 总被引:3,自引:0,他引:3
Medina EA Horn WF Keim NL Havel PJ Benito P Kelley DS Nelson GJ Erickson KL 《Lipids》2000,35(7):783-788
Conjugated linoleic acid (CLA) has been demonstrated to reduce body fat in animals. However, the mechanism by which this reduction
occurs is unknown. Leptin may mediate the effect of CLA to decrease body fat. We assessed the effects of 64 d of CLA supplementation
(3 g/d) on circulating leptin, insulin, glucose, and lactate concentrations in healthy women. Appetite was assessed as a physiological
correlate of changes in circulating leptin levels. Analysis of plasma leptin concentrations adjusted for adiposity by using
fat mass as a covariate showed that CLA supplementation significantly decreased circulating leptin concentrations in the absence
of any changes of fat mass. Mean leptin levels decreased over the first 7 wk and then returned to baseline levels over the
last 2 wk of the study in the CLA-treated group. Appetite parameters measured at around the time when the greatest decreases
in leptin levels were observed showed no significant differences between supplementation and baseline determinations in the
CLA-supplemented group or between the CLA and placebo-supplemented groups. There was a nonsignificant trend for mean insulin
levels to increase toward the end of the supplementation period in CLA-treated subjects. CLA did not affect plasma glucose
and lactate over the treatment period. Thus, 64 d of CLA supplementation in women produced a transient decrease in leptin
levels but did not alter appetite. CLA did not affect these parameters in a manner that promoted decreases of adiposity. 相似文献
4.
Recent animal studies have demonstrated that dietary conjugated linoleic acid (CLA) reduces body fat and that this decrease
may be due to a change in energy expenditure. The present study examined the effect of CLA supplementation on body composition
and energy expenditure in healthy, adult women. Seventeen women were fed either a CLA capsule (3 g/d) or a sunflower oil placebo
for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94 d study where
diet and activity were controlled and held constant. Change in fat-free mass, fat mass, and percentage body fat were unaffected
by CLA supplementation (0.18±0.43 vs. 0.09±0.35 kg; 0.01±0.64 vs. −0.19±0.53 kg; 0.05±0.62 vs. −0.67±0.51%, placebo vs. CLA,
respectively). Likewise, body weight was not significantly different in the placebo vs. the CLA group (0.48±0.55 vs. −0.24±0.46
kg change). Energy expenditure (kcal/min), fat oxidation, and respiratory exchange ratio were measured once during the baseline
period and during weeks 4 and 8 of the intervention period. At all three times, measurements were taken while resting and
walking. CLA had no significant effect on energy expenditure, fat oxidation, or respiratory exchange ratio at rest or during
exercise. When dietary intake was controlled, 64 d of CLA supplementation at 3 g/d had no significant effect on body composition
or energy expenditure in adult women, which contrasts with previous findings in animals. 相似文献
5.
Kelley DS Simon VA Taylor PC Rudolph IL Benito P Nelson GJ Mackey BE Erickson KL 《Lipids》2001,36(7):669-674
The purpose of this study was to examine if conjugated linoleic acid (CLA) supplementation of diets would alter fatty acid
(FA) composition and function of peripheral blood mononuclear cells (PBMC). Seventeen women, 20–41 yr, participated in a 93-d
study conducted at the Metabolic Research Unit. The same diet (19, 30, and 51% energy from protein, fat, and carbohydrate,
respectively) was fed to all subjects throughout the study. Seven subjects (control group) supplemented their diet with six
daily capsules (1 g each) of placebo oil (sunflower) for 93 d. For the other 10 subjects (CLA group), the supplement was changed
to an equivalent amount of Tonalin capsules for the last 63 d of the study. Tonalin provided 3.9 g/d of a mixture of CLA isomers
(trans-10,cis-12, 22.6%; cis-11,trans-13, 23.6%; cis-9,trans-11, 17.6%; trans-8,cis-10, 16.6%; other isomers 19.6%), and 2.1 g/d of other FA. PBMC isolated on study days 30 and 90 were used to assess intracellular
cytokines by flow cytometry, secreted cytokines, and eicosanoid by enzyme-linked immonosorbent assay, and FA composition by
gas-liquid chromatography. After supplementation, total CLA concentration increased from 0.012 to 0.97% (P<0.0001) in PBMC lipids, but it did not significantly alter the concentration of other FA. CLA supplementation did not alter
the in vitro secretion of prostaglandin E2, leukotriene B4, interleukin-1β (IL-1β), or tumor necrosis factor α (TNFα) by PBMC simulated with lipopolysaccharide, and the secretion of
IL-2 by PBMC stimulated with phytohemagglutinin. Nor did it alter the percentage T cells producing IL-2, interferon γ, and
percentage of monocytes producing TNFα. The intracellular concentration of these cytokines was also not altered. None of the
variables tested changed in the control group. Our results show that CLA supplementation increased its concentration in PBMC
lipids, but did not alte their functions.
Parts of data included here were published as abstracts for the Experimental Biology and AOCS 2001 meetings. 相似文献
6.
We have reviewed the published literature regarding the effects of CLA on body composition and immune cell functions in humans
and in animal models. Results from studies in mice, hamsters, rats, and pigs generally support the notion that CLA reduced
depot fat in the normal or lean strains. However, in obese rats, it increased body fat or decreased it less than in the corresponding
lean controls. These studies also indicate that t10,c12-CLA was the isomer that reduced adipose fat; however, it also increased the fat content of several other tissues and increased
circulating insulin and the saturated FA content of adipose tissue and muscle. Four of the eight published human studies found
small but significant reductions in body fat with CLA supplementation; however, the reductions were smaller than the prediction
errors for the methods used. The other four human studies found no change in body fat with CLA supplementation. These studies
also report that CLA supplementation increased the risk factors for diabetes and cardiovascular disease including increased
blood glucose, insulin, insulin resistance, VLDL, C-reactive protein, lipid peroxidation, and decreased HDL. Most studies
regarding the effects of CLA on immune cell functions have been conducted with a mixture of isomers, and the results have
been variable. One study conducted in mice with the purified c9,t11-CLA and t10,c12-CLA isomers indicated that the two isomers have similar effects on immune cell functions. Some of the reasons for the discrepancies
between the effects of CLA in published reports are discussed. Although significant benefit to humans from CLA supplementation
is questionable, it may create several health risks in both humans and animals. On the basis of the published data, CLA supplementation
of adult human diets to improve body composition or enhance immune functions cannot be recommended at this time. 相似文献
7.
CLA intake in exclusively breast-fed infants is close to levels found to have physiological effects in animals. However, in
the majority of studies mixtures of CLA isomers have been used and the independent effects of the major CLA isomer in human
milk, cis-9, trans-11 CLA, at the intake level in exclusively breast-fed infants have hardly been studied. We therefore studied the effects
of cis-9, trans-11 CLA on plasma lipids and glucose, immune function, and bone metabolism in growing rats. Thirty male Sprague-Dawley rats
(n=10/group) were fed either 20 mg/kg/d cis-9, trans-11 CLA and 20 mg/kg/d sunflower oil (CLA20), 40 mg/kg/d cis-9, trans-11 CLA (CLA40), or 40 mg/kg/d sunflower oil (placebo) for 8 wk. No significant differences between groups were found in plasma
lipids, glucose, insulin, C-reactive protein, or lipid peroxidation. Liver fat content was lowest in the CLA20 group. In vitro interleukin 2 (IL-2) production increased, and tumor necrosis factor alpha, IL-1β, prostaglandin E2, and leukotriene B4 production decreased in the CLA20 group. No differences between groups were detected in IL-4, IL-6, or interferon gamma production,
plasma osteocalcin, insulin-like growth factor, or urinary deoxypyridino line crosslinks. Plasma tartrate-resistant acid phosphatase
5b activity was significantly increased in the CLA40 group. The results indicate anti-inflammatory effects and enhanced T-cell
function for the CLA20 group. No adverse effects were seen in the CLA20 group, whereas indications of increased bone resorption
rate were observed in the CLA40 group. 相似文献
8.
Prais Botelho A Santos-Zago LF Costa de Oliveira A 《Archivos latinoamericanos de nutrición》2008,58(2):156-163
Dietary supplementation with conjugated linoleic acid (CLA) may reduce body fat mass and increase lean body mass in various species. The objective of this study was to study the effects of conjugated linoleic acid (CLA) supplementation on body composition, serum leptin and triacylglycerol levels in Wistar rats. Rats received linoleic acid (group C) or conjugated linoleic acid (group AE, supplemented with AdvantEdge CLA, and group CO, supplemented with CLA One) in the concentrations of 2% of daily feed consumption. Serum leptin and triacylglycerol levels of rats were measured by means of commercial kits. After 42 days of supplementation, rats in the control group exhibited body fat contents of 53.94 +/- 6.80 g, and those in groups AE and CO had 45.43 +/- 4.86 g and 43.75 +/- 1.93 g, respectively, corresponding to a mean body fat reduction of 18%. Water, whole body protein and ash contents of rats supplemented with CLA were statistically higher relative to control group content (corresponding to a mean increasing of 7.65%; 6.5% and 12.35%, respectively). Experimental groups AE and CO, which received CLA supplementation, had statistically lower serum leptin levels (3.45 +/- 0.46 ng/mL and 3.08 +/- 0.19 ng/mL, respectively) relative to the control group (4.21 +/- 0.22 ng/mL) which received linoleic acid. Triacylglycerol levels did not change after CLA supplementation (p > 0.05). Supplementation with conjugated linoleic acid in the concentration of 2% of mean daily feed consumption was able to change body composition of rats after 42 days of experimentation. 相似文献
9.
Trans FA (TFA) have at least one trans double bond and comprise several isomers and types, including many of the CLA (e.g., c9, t11–18∶2 CLA). Some TFA may have adverse effects (e.g., cardiovascular disease), whereas some are though to have beneficial
effects (e.g., anticarcinogenicity). The presence of TFA in human tissues and fluids is related to dietary intake, although
this relationship is not completely understood—especially in regard to serum lipid fractions. This study was conducted as
part of an investigation designed to test the influence of butter (B), “low TFA” margarine (LT), and regular margarine (RM)
on milk fat content. Here we tested the secondary hypothesis that consumption of B, LT, and RM by lactating women would result
in differential distribution of TFA and CLA in major serum lipid classes. Breastfeeding women (n=11) participated in this randomized Latinsquare study consisting of five periods: intervention I (5 d), washout I (7 d),
intervention II (5 d), washout II (7 d), and intervention III (5 d). Extracted serum lipid was separated into cholesterol
ester (CE), TAG, and phospholipid (PL) fractions and analyzed for total and isomeric TFA and CLA concentrations. Data indicate
that TAG consistently contained the highest concentration of total t-18∶1. No interaction between treatment and fraction was found for any of the t-18∶1 isomers identified. Absolute concentration of each t-18∶1 isomer was greatest during the RM period, regardless of fraction. On a relative basis, concentrations of t10–18∶1 and t12–18∶1 were most responsive to treatment in the CE fraction. The concentration of c9, t11–18∶2 CLA was highest in the TAG fraction and lowest in the PL fraction, regardless of treatment. In summary, these results
indicate (i) that there is a differential distribution of some isomeric TFA and CLA among human serum lipid fractions and
(ii) that dietary TFA intake influences absolute and relative concentrations of some of the isomers in selected fractions. 相似文献
10.
CLA is a generic term describing different isomers of linoleic acid with two conjugated double bonds. Various metabolic effects
have been demonstrated following administration of CLA, including a change in body composition in animals. However, the effects
of pure CLA isomers are not fully understood. In addition, conjugated octadecatrienoic acids such as calendic acid have not
been extensively investigated. In this study, male and female ICR mice were fed pure CLA isomers (cis9,trans11 or trans10,cis12) or calendic acid (trans8,trans10,cis12) as their ethyl esters for 6 wk. Body protein content was significantly increased after feeding CLA isomers, either as
pure isomers or as a mixture. Calendic acid significantly decreased body fat content in males. CLA (pure isomers or a mixture)
significantly decreased body fat in both males and females, with the trans10,cis12 isomer being the most effective. The effect of the cis9,trans11 isomer was more pronounced in females than in males. It was concluded that the trans10,cis12 CLA isomer was mainly responsible for the decrease in fat content in mice, without a significant modification of feed efficiency,
and that it was more effective than calendic acid. 相似文献
11.
Gaofeng Yuan Haiyan Sun Andrew J. Sinclair Duo Li 《European Journal of Lipid Science and Technology》2009,111(6):537-545
The effects of two isomers of conjugated linolenic acid (CLnA), α‐eleostearic acid (α‐ESA) and punicic acid (PA), on body fat and lipid metabolism were investigated, compared with a conjugated linoleic acid (CLA) mixture (primarily cis9,trans11‐ and trans10,cis12‐18:2) and α‐linolenic acid (ALA), a non‐conjugated octadecatrienoic acid, in the present study. ICR mice were fed either a control diet or one of four experimental diets supplemented with 1% α‐ESA, 1% PA, 1% CLA mixture and 1% ALA in the form of triacylglycerols (TAG) for 6 weeks. The weights of perirenal and epididymal adipose tissues were significantly decreased while the liver weight was significantly increased in mice fed CLA, compared with the control. In contrast to CLA, the tissue weights in α—ESA‐, PA‐ and ALA‐fed mice were not affected. No significant differences were observed in TAG, total cholesterol, high‐density lipoprotein and low‐density lipoprotein cholesterol levels among the five groups. The liver TAG level was significantly decreased in mice fed α‐ESA and PA while it was significantly increased in mice fed the CLA mixture. These results indicate that CLnA and CLA have differential effects on body fat mass and liver TAG levels in mice. 相似文献
12.
The yeast Saccharomyces cerevisiae was cultivated in the presence of free CLA that was either a pure trans-10, cis-12 isomer, a pure cis-9, trans-11 isomer, or a 1∶1 mixture of the two, and the influence of these supplementations on the content and FA composition of
the lipids in the yeast was determined. Neither the pure isomers nor their 1∶1 mixture influenced the growth of the yeast,
but the trans-10, cis-12 isomer reduced the amount of cellular lipids by 40%. The reduction in total cellular lipids by the trans-10, cis-12 CLA was due to a reduction in TAG. Both of the isomers were incorporated into the yeast lipids, reaching a proportion
of about 33% in TAG. With the incorporation of CLA, the yeast reduced the amount and desaturation of endogenously synthesized
FA. These clear and pronounced isomer-specific effects of CLA on the yeast suggest that yeast might be a useful model to obtain
a more comprehensive view of the mechanisms of the action of CLA on lipid metabolism. 相似文献
13.
Dietary conjugated linolenic acid in relation to CLA differently modifies body fat mass and serum and liver lipid levels in rats 总被引:6,自引:0,他引:6
Koba K Akahoshi A Yamasaki M Tanaka K Yamada K Iwata T Kamegai T Tsutsumi K Sugano M 《Lipids》2002,37(4):343-350
The present study compared the effect of dietary conjugated linolenic acid (CLNA) on body fat and serum and liver lipid levels
with that of CLA in rats. FFA rich in linoleic acid, α-linolenic acid, CLA, or CLNA were used as experimental fats. Male Sprague-Dawley
rats (4 wk old) were fed purified diets containing 1% of one of these experimental fats. After 4 wk of feeding, adipose tissue
weights, serum and liver lipid concentrations, serum tumor necrosis factor (TNF)-α and leptin levels, and hepatic β-oxidation
activities were measured. Compared with linoleic acid, CLA and, more potently, CLNA were found to reduce perirenal adipose
tissue weight. The same trend was observed in the weight of epididymal adipose tissue. CLNA, but not CLA, was found to significantly
increase serum and liver IG concentrations. Serum FFA concentration was also increased in the CLNA group more than in the
other groups. The activity of β-oxidation in liver mitochondria and peroxisomes was significantly higher in the CLNA group
than in the other groups. Thus, the amount of liver TG exceeded the ability of hepatic β-oxidation. Significant positive correlation
was found between the adipose tissue weights and serum leptin levels in all animals (vs. perirenal: r=0.557, P<0.001; vs. epididymal: r=0.405, P<0.05). A less significant correlation was found between adipose tissue weights and serum TNF-α level (vs. perirenal: r=0.069, P<0.1; vs. epididymal: r=0.382, P<0.05). Although the mechanism for the specific effect of CLNA is not clear at present, these findings indicate that in rats
CLNA modulated the body fat and TG metabolism differently from CLA. 相似文献
14.
Ortwin Simon Klaus Mnner Klaus Schfer Angelos Sagredos Klaus Eder 《European Journal of Lipid Science and Technology》2000,102(6):402-410
In a performance trial, broiler chickens received 29 g per kg feed of a preparation containing 70% linoleic acid (LA) in the control treatment and another preparation containing approximately the same amount of conjugated linoleic acids (CLA) in the experimental treatment. Diets of CLA treatment contained 18 g CLA per kg feed. The CLA preparation contained the isomers cis‐9,trans‐11 and trans‐10,cis‐12 at a proportion 1:1, other CLA isomers were quantitively negligible. Performance parameters (weight gain and feed conversion ratio over a 42 day period) were not significantly influenced by CLA intake. However, fat content of liver, breast, and leg muscles was reduced and protein contents in liver and leg muscles were elevated significantly. Fat to protein ratios in the main edible parts were shifted in favour of protein in CLA treated animals. In all analysed tissue lipids the content of saturated fatty acids was increased and that of monounsaturated fatty acids was decreased significantly. At the same time CLA was incorporated in tissue lipids effectively reaching more than 10 g per 100 g of total fatty acids. With regard to isomers the cis‐9,trans‐11 isomer was found in higher concentrations in tissue lipid fractions compared to the trans‐10,cis‐12 isomer. It was concluded that nutrient repartitioning due to CLA intake described for other species is also valid for broilers. Using appropriate feeding strategies it is possible to produce CLA enriched food from broilers. 相似文献
15.
The content and positional distribution of CLA in TAG fractions of lamb tissues was examined with either preformed CLA or
the linoleic acid precursor of CLA in the diet as experimental treatments. The CLA content of phospholipid (PL) from these
tissues was also examined. Thirteen lambs were randomized to the following dietary treatments: (i) control diet (no supplement);
(ii) CLA supplementation (0.33 g d−1 for 21 d prior to weaning) to milk-replacer of pre-ruminating lambs, or (iii) feeding linoleic acid-rich oil (6% safflower
oil on a dry matter basis) to weaned ruminating lambs. At slaughter, tissue samples were procured from diaphragm, rib muscle,
and subcutaneous (SC) adipose tissue. Safflower oil supplementation in the diet resulted in an increase in CLA content of
the TAG from diaphragm, rib muscle, and SC adipose tissue by about threefold (P<0.05) on a mol% basis. CLA was localized to the sn-1/3 positions of TAG. Animals that received pre-formed CLA, however, had increased proportions of CLA at the sn-2 position of TAG from SC adipose tissue, suggesting that there were tissue-specific dietary effects and possible age-related
effects on the mode of FA incorporation into TAG. Safflower oil supplementation in the diet had no effect on the CLA content
of PL from diaphragm, rib muscle, and SC adipose tissue, suggesting that CLA was preferentially incorporated into the TAG
of these tissues. 相似文献
16.
CLA has a range of biological properties, including effects on lipid metabolism and body composition in experimental animals.
The prevalent isomer of CLA found in the human diet is 9c, 11t-CLA, and it is predominantly found in products containing fat from ruminant animals. This study investigated the effect of
dietary CLA on energy balance in mice. Synthetic CLA reduced body fat in growing male BAI B/c mice in a dose-dependent manner
over the range 0.25–1.0% w/w CLA in the diet. Weight gain was also reduced at the highest levels of dietary CLA, being only
5.88±2.68 g/4 mice (mean±1 SD) after 4 wk of 2.0% CLA in the diet, compared with weight groups. There was no significant effect
on weight gain if diets contained 0.5% synthetic CLA or less. These results suggest that high levels of a synthetic mixture
of CLA isomers modify energy metabolism and body composition and that high levels of synthetic CLA impair weight gain and
reduce body fat pad mass in growing mice. 相似文献
17.
CLA refers to isomers of octadecadienoic acid with conjugated double bonds. The most abundant form of CLA (rumenic acid (RA):
c9,t11-18∶2) is found in milk and beef fat. Further, CLA supplements containing RA and t10,c12−18∶2 are now available. Consumption of commercially produced CLA has been shown to decrease adipose accretion in growing
laboratory and production animals and cause milk fat depression in cows. We tested the hypothesis that CLA supplementation
would increase milk CLA concentration and decrease milk fat content in humans. Breastfeeding women (n=9) participated in this double-blind, placebo-controlled, crossover study divided into three periods: intervention l (5 d),
washout (7 d), and intervention II (5 d). Women were randomized to treatment order. During each intervention period, women
consumed 1.5 g of CLA supplement or placebo (olive oil) daily; during the washout period, no supplements were consumed. Milk
was collected by complete breast expression on the final day of each period; milk output was estimated by 24-h weighing on
the penultimate day of each intervention period. Milk RA and t10,c12−18∶2 concentrations were greater (P<0.05) during the CLA treatment period as compared to the placebo period. Milk fat content was significantly lower during
the CLA treatment, as compared to the placebo treatment (P<0.05). Data indicate no effect of treatment on milk output. Therefore, it would be prudent that lactating women not consume
commercially available CLA supplements at this time.
This paper was published in part in Masters, N., McGuire, M.A., and McGuire, M.K. (1999) Conjugated Linoleic Acid Supplementation
and Milk Fat Content in Humans, FASEB J. 13, A697. 相似文献
18.
CLA and body weight regulation in humans 总被引:3,自引:0,他引:3
CLA comprises a group of unsaturated FA isomers with a variety of biological effects in experimental animals. CLA reduces
body fat accumulation in animal models and has been suggested to have significant effects on lipid and glucose metabolism,
e.g., antidiabetic effects in obese Zucker rats. It has been proposed that the trans10-cis12 isomer is the active isomer associated with the antiobesity and insulin-sensitizing properties of CLA. The metabolic effects
in humans in general, and isomer-specific effects specifically, are not well characterized. In a series of controlled studies
in humans, we investigated the effects of CLA (given as the commercially available mixture of isomers and as the purified
trans10-cis12 CLA isomer) on anthropometry, lipid and glucose metabolism, and markers of lipid peroxidation. Preliminary results indicate
that CLA may slightly decrease body fat in humans also, particularly abdominal fat, but there is no effect on body weight
or body mass index. There is no simultaneous improvement in lipid or glucose metabolism. Rather, the trans10-cis12 CLA isomer unexpectedly caused significant impairment of the peripheral insulin sensitivity as well as of blood glucose
and serum lipid levels. In addition, CLA markedly elevated lipid peroxidation. Thus, the metabolic effects of CLA in human
seem complex; further studies, especially of isomer-specific effects and for longer time periods, are warranted. 相似文献
19.
CLA has been shown to induce or suppress excess liver lipid accumulation in various animal models. Interestingly, the state
of insulin resistance may be an important modulator of this effect. The objective of the current study was to determine how
feeding a dietary CLA mixture would affect liver lipid accumulation in insulin-resistant/obese and lean rats in relation to
liver function, lipidemia, liver TAG and phospholipid FA composition, and expression of hepatic markers of FA transport, oxidation,
and synthesis. Six-week-old fa/fa and lean Zucker rats (n=20/genotype) were fed either a 1.5% CLA mixture or a control diet for 8 wk. CLA supplementation reduced liver lipid concentration
of fa/fa rats by 62% in concurrence with improved liver function (lower serum alanine aminotransferase and alkaline phosphatase) and
favorable modification of the serum lipoprotein profile (reduced VLDL and LDL and elevated HDL) compared with control-fed
fa/fa rats. The fa/fa genotype had two-thirds the amount of CLA (as % total FA) incorporated into liver TAG and phospholipids compared with the
lean genotype. In both genotypes, CLA altered the hepatic FA profile (TAG greater than phospholipids) and these changes were
explained by a desaturase enzyme index. Liver-FA-binding protein and acyl CoA oxidase, markers of FA transport and oxidation,
respectively, were expressed at higher levels in CLA-fed fa/fa rats. In summary, these results illustrate a strong relationship between the state of insulin resistance and liver lipid
metabolism and suggest that CLA acts to favorably modify lipid metabolism in fa/fa Zucker rats. 相似文献
20.
Roger E Adams Andie Hsueh Betty Alford Clay King Huanbiao Mo Robert Wildman 《Journal of the International Society of Sports Nutrition》2006,3(2):28-9
Conjugated linoleic acid (CLA) supplementation has shown convincing effects at reducing body fat in animals; yet human study
results have been somewhat inconclusive. The purpose of this study is to determine whether four weeks of CLA supplementation,
the approximate length of a commercial package, can result in a positive change in visceral adipose tissue in resistance-trained
middle-aged men. Thirty overweight and moderately obese, but otherwise healthy male subjects (aged 35 to 55 years) currently
involved in resistance training, were randomly assigned into CLA and placebo groups in a double-blind, placebo controlled
approach. The study lasted for 12 weeks and consisted of three four-week periods. During the first four weeks (run-in period)
each subject received placebo (4 g safflower oil). Throughout the next four weeks (supplementation period), the placebo group
continued receiving placebo, while the CLA group received 3.2 g/d of CLA. During the final four weeks (run-out period) all
subjects received the placebo. Computed tomography (CT) scans were used to measure visceral adipose tissue (VAT) at weeks
4, 8 and 12. No significant reduction in VAT cross-sectional area was determined in the CLA group during the study. On the
contrary, a significant reduction in cross-sectional area of VAT of 23.12 cm2 during the supplementation period was measured in the placebo group, which was abated during the run-out period. Our results
suggest that CLA supplementation of 3.2 g/d for four weeks does not promote decreases in VAT in middle-aged men currently
participating in a resistance-training program. 相似文献