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Research Article
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Lipotoxicity Observed at the Early Phase of Obesity in Cats Fed on High-fat Diet
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Nobuko Mori,
Gebin Li,
Megumi Fujiwara,
Shingo Ishikawa,
Koh Kawasumi,
Ichiro Yamamoto
and
Toshiro Arai
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ABSTRACT
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The prevalence of obese cats has increased because of over calorie diet and physical inactivity. Obesity has been found to be associated with oxidative stress and Reactive Oxygen Species (ROS). Unfortunately oxidative stress status at the early phase of obesity in high fat fed cats is not well understood. The objectives of this study were (1) To evaluate lipid and glucose metabolism using enzymatic, hormonal and oxidative stress biomarkers at the early obese phase of cats fed on a high-fat diet and (2) To identify rapidly changing variables to use as a diagnostic marker for lipid metabolic disorders in cats. Total 13 domestic female cats were divided into two groups which were fed on control and high-fat diet for eight weeks, respectively. After the feeding period, they were compared in metabolic variables and oxidative stress markers in plasma and tissues. As results, High-fat diet including much long chain fatty acids promoted rapid changes in lipid metabolism, particularly accelerated β-oxidation of fatty acids and oxidative stress in the liver of the cats. G6PD, GPx and SOD were increased in the liver. Insulin resistance was not apparent at the early phase of obesity in cats. Plasma activities of SOD also increased at the early phase of obesity in cats. Remarkable alternation for oxidative stress in liver was observed at the early phase of obesity in cats fed on high fat diet and SOD may be a potential marker of the early phase of obesity in cats.
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Received: November 08, 2013;
Accepted: February 17, 2014;
Published: April 10, 2014
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INTRODUCTION
Obesity has increased markedly in small domestic animals worldwide as in human.
Some evidence suggests that about 25% of cats brought to veterinary hospitals
are obese (Butterwick, 2000). Some evidence also indicates
that fat accumulation in tissues is closely related to occurrence of metabolic
syndrome, diabetes mellitus, hepatic disorders, cardiovascular disease and cancers
in increasingly obese human populations (Higdon and Frei,
2003; Keaney et al., 2003; Suzuki
et al., 2003). Furthermore, obesity has been found to be associated
with oxidative stress (DArchivio et al., 2012)
and Reactive Oxygen Species (ROS) which are the result of direct and indirect
inflammatory mediators and have significant associations with obesity in humans
(Dandona et al., 2001). The prevalence of obese
cats has increased because of over calorie diet and physical inactivity, as
in case of humans. In addition, oxidative stress status by high-fat feeding
at the early phase of obesity in cats is not well understood. The deleterious
effect of tissue fat accumulation on glucose metabolism was coined by Unger
(2003) as the term lipotoxicity. And lipotoxicity-mediated dysfunction
leads insulin resistance followed by diabetes mellitus (Gehrmann
et al., 2010). Thus, the objectives of this study were (1) To evaluate
lipid and glucose metabolism using enzymatic, hormonal and oxidative stress
biomarkers at the early phase of obesity in cats fed on high-fat diet (HFdiet)
and (2) To identify rapidly changing variables to use as diagnostic maker for
lipid metabolic diseases in cats.
MATERIALS AND METHODS
Animals: In this study, 13 cats (domestic female, aged from 10 to 30
months, not spayed) were used. Veterinarians diagnosed that they were healthy
and without any clinical manifestations. All cats were housed individually and
maintained for eight weeks at AQS Co. Ltd. (Narita, Japan). Cats were divided
into two groups. One was a control group with five cats: mean±SD body
weight (BW): 2.40±0.32 kg; age: 10±0 months. During the experimental
period, these cats were fed on a commercial diet (Zoo animal diet ZN for cats,
Oriental Yeast Co. LTD., Tokyo, Japan). The components of commercial diet were
moisture (5.5%); crude protein (33.6%); crude fat (16%); crude fiber (3.5%);
crude ash (5.8%) and nitrogen free extract (35.9%). The caloric content was
4210 kcal kg-1. The other eight cats (BW: 2.55±0.33 kg; Age:
14.9±6.7 months) were fed on a high-fat diet (HF diet), made to order
from Nippon Pet Food, Inc., (Tokyo, Japan). The composition of the HF diet was
moisture (7.0%); crude protein (32.7%); crude fat (23.9%); crude fiber (0.9%);
crude ash (5.5%) and nitrogen free extract (29.9%). The energy fat composition
was 46.2% and caloric content was 4660 kcal kg-1. The fatty acid
composition in the HF diet is shown in Table 1. Cats in the
two groups (control and HF diet) were fed on respective diets ad libitum for
their daily energy requirement (DER) from 9:00 AM to 8:30 AM of the next day.
On the day for blood sampling, any surplus diet was removed at 4:00 PM of the
previous day. DER was calculated as 1.4xRER (BW0.75x70). RER is the resting
energy requirement for each cat on the basis of its BW before the meal at 9:00
AM. Incidentally, before the experiment, all cats were maintained with the same
commercial diet (Zoo animal diet ZN for cats, Oriental Yeast Co., Ltd., Tokyo.
Japan).
Table 1: |
Components of fatty acids included in high-fat diet for cats |
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Cats were housed in individual cages and provided with water ad libitum. The
animal room was maintained at 24±2°C and at 55±10% relative
humidity on a 12:12 h light: dark cycle (light on 8:00 AM to 8:00 PM). This
study was approved by the Nippon Veterinary and Life Science University Animal
Research Committee.
Blood sampling and collection of tissue samples: Preprandial blood (5
mL) was withdrawn from the jugular vein of overnight fasted cats into heparinized
tubes before and after the control and HF diets feeding experiment. The blood
samples were immediately centrifuged at 1700 g for 10 min at 4°C to obtain
plasma and stored at -80°C until analyzed. And each two animals of two groups
were fasted for overnight and premeditated with 0.05 mg kg-1 of BW
acepromazine malate (Tech America, KS, US) and anesthetized with isoflurane.
Liver and adipose tissues samples (0.2-0.3 g) were taken from the anesthetized
animals by laparotomy and all procedure were performed under minimal stress
conditions to the animals. Cytosol fractions of liver and adipose tissues were
isolated by the previous described method (Washizu
et al., 1999). All fractions were prepared and stored at -80°C until
analyzed.
Plasma metabolic variables and oxidative stress markers: Plasma glucose,
triglyceride (TG) and total cholesterol concentrations, lactate dehydrogenase
(LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and
alkaline phosphatase (ALP) activities were determined using an auto analyzer
with the manufacturers reagents (Monolis, Inc., Tokyo, Japan). Non esterified
fatty acids (NEFA) concentrations were measured using a commercial kit (NEFA-C
test, Wako Pure Chemical Industries, Tokyo, Japan). Plasma adiponectin and insulin
concentrations were measured with a commercial kit, Mouse/Rat Adiponectin ELISA
Kit, (Otsuka, Tokyo, Japan) and Cat Insulin ELISA kit, (SHIBAYAGI Co., Gunma,
Japan) respectively. The insulin specific antibody contained in the Cat Insulin
ELISA kit was shown not to cross-react with pro-insulin. Plasma levels of glutathione
peroxidase (GPx) and superoxide dismutase (SOD) as antioxidant enzymes , malonaldehyde
(MDA) as the oxidative stress marker which are formed at the end of long oxidative
processes were measured using commercial kits (GPx: Colorimetric assay kit for
glutathione peroxidase activity, Northwest Life Science Specialties LLC, Vancouver,
WA, USA; SOD: Colorimetric Assay for Superoxide Scavenging Activity, Northwest
Life Science Specialties LLC, Vancouver, WA, USA; MDA: Malondialdehyde Assay
kit, Northwest Life Science Specialties LLC, Vancouver, WA, USA). Glucose-6-phosphate
dehydrogenase (G6PD) activities as an antioxidant enzyme in cytosol fraction
of liver and subcutaneous fat were determined by spectrophotometric methods
(Bergmeyer, 1984). Enzyme activities in cytosol fractions
are expressed as mU per mg of protein in the fractions. The enzyme unit (U)
was defined as 1 μmoL of substrate degraded min-1. Protein concentration
in the fractions was determined by the Bradford assay (Bradford,
1976) using bovine serum albumin as a standard.
Histopathological analysis of hepatic cells: Hepatic tissues in cats fed on control diet and HF diet were stained with Oil Red O. Each tissue preparation was assayed microscopically.
Statistical analysis: Results are given as means±standard deviations
(SD). One-way ANOVA with Holm-Sidak multiple comparisons and Kruskal-Wallis
with Dunns method on multiple comparisons were used to compare groups
for plasma analysis results. Statistical significance was set at p<0.05 for
One-way ANOVA. Statistical analysis was done using Sigmaplot software (Sigmaplot
11.0, Build 11.0.077; Systat Software, Inc., San Jose, CA, USA).
RESULTS
Body weight and plasma metabolic parameters: Results of plasma metabolic
parameters of all cats are shown in Table 2. Control and HF
diet cat showed significant body weight gains after feeding for eight weeks
(p = 0.003). Plasma AST and ALT activities of HF diet cats increased significantly
after HF diet feeding (AST: p = 0.003; ALT: p = 0.046). Insulin concentrations
in plasma of HF diet cats decreased significantly after HF diet feeding (p<0.001).
Triglyceride concentrations showed a downward trend and adiponectin and NEFA
levels showed an upward trend in HF diet cats after HF diet feeding.
Oxidative stress markers in plasma and lipid metabolizing tissues: Figure 1 shows GPx and SOD activities and MDA concentrations as oxidative stress markers in plasma of cats. Plasma SOD activities of HF diet cats was significantly higher than after control diet cats. GPx activities increased, but MDA concentration didnt change in plasma of HF diet cats after 8 weeks feeding periods. Table 3 shows activities of enzymes as oxidative stress marker in liver and subcutaneous fat of two cats from each group as in liver of HF diet cats, G6PD, GPx and SOD activities increased greatly compared to those of the control cats, whereas these three enzyme activities in adipose tissue didnt change in HF diet cats. Histopathological changes in liver of cats: Figure 2 shows the histopathological changes in liver of the control diet cat (Fig. 2a) and HF diet cat (Fig. 2b) after feeding. Figure 2b showed that numerous fat droplets were observed inside and outside cells. However, these hepatic cells had not yet become larger or undergone differentiation.
Table 2: |
Comparison of plasma metabolite and horomone concentrations
and enzyme activities in control and high-fat diet cats |
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Values are presented as means±SD, HF: High fat diet
feeding cats, *: Significantly different from control diet cats after feeding
(Holm-sidak one-way ANOVA p<0.05), **: Significantly different from HF
diet cats before feeding (Holm-sidak one-way ANOVA p<0.05) |
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Fig. 1(a-c): |
Oxidative stress marker activities in plasma.Oxidative stress
marker activities in cat plasma before and after feeding control diet and
high-fat diet, (a) Glutathione peroxidase (GPx), (b) Superoxide dismutase
(SOD), (c) Malonaldehyde (MDA), Control diet cats (n = 5). High-fat diet
cats (n = 8). Results are expressed as Means±SD. GPx and MDA were
used Holm-Sidak One-way ANOVA as normality test of them were passed. SOD
was used Kruskal-Wallis One-Way ANOVA and Dunns method on multiple
comparisons. *: Significantly different from after control diet cats (p<0.05) |
DISCUSSION
Plasma metabolite concentrations reflect changes in the physical conditions
of animals with metabolic disorders (Downs et al.,
1997; Pitkanen et al., 1999). Hormones and
enzymes in plasma are frequently used as diagnostic indicators of metabolic
disorders (Neumann et al., 2008). Increases in
plasma TG and ALT levels are clinical signs indicating fat accumulation in the
liver of animals (Hsiao et al., 2007; Iacobellis
et al., 2008).
Table 3: |
G6PD, GPx and SOD activities in tissue of cats fed on control
and HF diets |
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G6PD: Glucose-6-phosphate dehydrogenase, GPx: Glutathione
peroxidase, SOD: Superoxide dismutase HF: High fat diet, Enzyme activities
are presented as mU mg-1 protein |
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Fig. 2(a-b): |
Histopathological changes in liver of cats after 8 weeks feeding,
(a) Hepatic cells in control diet cat and (b) Hepatic cells in high-fat
diet cat, both tissue preparations were stained with Oil red O Magnification:
1000x |
Understanding the physiological changes induced by obesity could be used to
prevent excess body fat accumulation and manage obesity-induced diseases, such
as diabetes mellitus and hyperlipidemia.
In this study, we examined some of these markers in order to evaluate lipid and glucose metabolism and fatty acid oxidation status at the early phase of obesity in cats fed on HF diet for eight weeks. Our results showed that some metabolic variables such as plasma glucose, triglyceride, total cholesterol, adiponectin, NEFA, ALP and LDH did not change significantly despite significant gain in body weight after the HF diet feeding. In contrast, plasma ALT and AST activities in the after HF diet cats were significantly higher than those in the controls. Increased ALT and AST activities at the early phase of obesity in cats suggest that slight hepatic lesion was induced by excess lipids into the liver. Thus, β-oxidation of fatty acid in the liver may be activated by feeding cats with HF diet.
Previous reports indicated that HF diet containing much long chain fatty acids
promoted fatty acid β-oxidation and suppressed glycolysis in the liver.
As a consequence, long chain fatty acids accumulate to greater extent in body
fat compared to medium chain fatty acids (Papamandjaris
et al., 1998; Geliebter et al., 1983).
Long chain triacylglycerols fed rats have lower oxygen consumption and sympathetic
activation of brown adipose tissue than medium chain triacylglycerols fed rats
(Rothwell and Stock, 1987; Young
and Walgren, 1994). These long chain fatty acids in the HF diet might promote
β-oxidation in the cat liver. In hepatic cells, Radical Oxygen Species
(ROS) and lipoperoxide production are associated with acceleration of β-oxidation
of fatty acids in mitochondria which induces increased risk of hepatic inflammation
and cirrhosis. G6PD, GPx and SOD activities in the livers of HF diet cats were
higher than those in the control cats. This finding indicated that G6PD, GPx
and SOD activities in liver might be used highly sensitive oxidative stress
markers. G6PD activity was approximately 4 to 6-fold higher, GPx activity was
approximately 3 to 10-fold higher and SOD in hepatic tissue was 2 to 4-fold
higher in the HF diet cats compared to the control cats.
Some evidence for human type 2 diabetes mellitus patients have suggested a
decrease in anti-oxidant defense markers such as GPx and SOD and an increase
in oxidative damage markers such as MDA (Kasznicki et
al., 2012; Piwowar et al., 2007; Ziegler
et al., 2004). These findings didnt agree with our present
results. However, the above changes are reported in the type 2 diabetes mellitus
patients with obesity for over several years. In obesity related human type2
diabetes mellitus, SOD activities in erythrocytes and plasma MDA concentrations
increased markedly and these findings indicated elevations of lipid oxidation
in tissues (Moussa, 2008). Also, total SOD activity
and lipid peroxidation were higher in diabetics compared to non-diabetics (De
Bandeira et al., 2012). Increased plasma SOD activities in obese
cats with HF diet possibly indicate defensive reaction against elevation of
ROS production owing to accelerated β-oxidation of excess fatty acids.
Table 4 shows a summary of changes in plasma metabolic parameters
in obese cats referencing previous studies (Tanner et
al., 2007; Fettman et al., 1998). Some
similar metabolic changes are observed in obese cats. Changes in plasma lipid
concentrations as abnormality in lipid metabolism precede changes in plasma
glucose concentrations or occurrence of insulin resistance at the early phase
of obesity in cats. However, Fettman et al. (1998)
demonstrated that body weight gains were remarkably correlated with plasma insulin
concentrations. Plasma insulin concentrations may not be an adequate responding
marker for acute obesity but they may be a distinguishing marker for chronic
obesity for a long period. The obese cats in the study by Fettman
et al. (1998) exhibited insulin resistance after six months of be
obese.
Table 4: |
Changes in plasma metabolic parameters in obese cats |
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Fig. 3: |
Flow chart of changing metabolic conditions in obese cats
due to high-fat diet ROS: Reactive oxygen species |
Lipid metabolism is considered quickly to be responded alternatively at the
early phase of obesity in cats. Acceleration of β-oxidation of fatty acids
may promote ROS production in the liver which would trigger the onset of inflammation
in the obese cats. Oxidative stress induces insulin resistance, glucose intolerance
and diabetes mellitus in humans (Ceriello and Motz, 2004).
Severe oxidative stress and inflammation for a long period may result in damage
of pancreatic β-cell with low anti-oxidant activity (Valko
et al., 2007). ROS at high concentrations cause disturbances both
in cell signaling and gene expression associated with lesions in pancreatic
β-cells (Maechler et al., 1999). Consequently,
oxidative stress and low grade inflammation may lead insulin resistance in obese
animal with abnormality in lipid metabolism (Fig. 3). Series
of these changes in lipid metabolism is summarized as lipotoxicity (Loria
et al., 2013).
Unfortunately, we were unable to adequately determine oxidative stress marker activities in lipid metabolizing tissues because of an insufficient number of cats. However, it was proved that oxidative stress markers levels changed quickly in plasma of obese cats reflecting oxidative status in livers. CONCLUSION
In Conclusions, Feeding a HF diet including several long chain fatty acids
to cats promoted rapid changes in lipid metabolism, such as accelerated β-oxidation
of fatty acids leading oxidative stress in the liver. Increasing anti-oxidative
stress markers may be activated earlier in order to defend against augmented
ROS production in the liver. Similarly, SOD, an anti-oxidative stress marker
in plasma, increased significantly at the early phase of obesity in cats. At
the early phase of obesity in cats fed on HF diet, plasma adiponectin concentrations
were considerably high and plasma TG, cholesterol and NEFA concentrations were
maintained with the control ranges. Insulin resistance was not apparent at the
early phase of obesity in cats. Before Plasma metabolites and hormones as diagnostic
markers for hyperlipidemia and diabetes mellitus change remarkably, oxidative
stress is induced in liver in obese cats fed on HF diet. Our study indicated
that alternation for oxidative stress was observed at the early phase of obesity
in cats fed on HF diet and plasma SOD activity may be a potential marker at
the early phase of obesity in cats.
ACKNOWLEDGMENTS This study was supported in part by the Strategic Research Base Development Program for Private Universities from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), 2008-2012.
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REFERENCES |
1: De Bandeira, S., M., S.G. da Guedes, L.J. da Fonseca, A.S. Pires and D.P. Gelain et al., 2012. Characterization of blood oxidative stress in type 2 diabetes mellitus patients: Increase in lipid peroxidation and SOD activity. Oxidative Med. Cell. Longevity. 10.1155/2012/819310
2: Bergmeyer, H.U., 1984. Glucose 6-Phosphate Dehydrogenase. In: Methods of Enzymatic Analysis, Bergmeyer, H.U., J. Bergmeyer and M. Grassl (Eds.). 3rd Edn., Verlag Chemie, Weiheim, pp: 222-223.
3: Bradford, M.M., 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem., 72: 248-254. CrossRef | PubMed | Direct Link |
4: Butterwick, R.F., 2000. How fat is that cat? J. Feline Med. Surg., 2: 91-94. CrossRef |
5: Ceriello, A. and E. Motz, 2004. Is oxidative stress the pathogenic mechanism underlying insulin resistance, diabetes and cardiovascular disease? The common soil hypothesis revisited. Arteriosclerosis Thrombosis Vasc. Biol., 24: 816-823. CrossRef | Direct Link |
6: Dandona, P., P. Mohanty, H. Ghanim, A. Aljada and R. Browne et al., 2001. The suppressive effect of dietary restriction and weight loss in the obese on the generation of reactive oxygen species by leukocytes, lipid peroxidation and protein carbonylation. J. Clin. Endocrinol. Metab., 86: 355-362. CrossRef | PubMed | Direct Link |
7: D'Archivio, M., G. Annuzzi, R. Vari, C. Filesi and R. Giacco et al., 2012. Predominant role of obesity/insulin resistance in oxidative stress development. Eur. J. Clin. Invest., 42: 70-78. CrossRef | Direct Link |
8: Downs, L.G., S.M. Crispin, V. LeGrande-Defretin, G. Perez-Camargo, T. McCappin and C.H. Bolton, 1997. The influence of lifestyle and diet on the lipoprotein profile of Border Collies. Res. Vet. Sci., 63: 35-42. CrossRef |
9: Fettman, M.J., C.A. Stanton, L.L. Banks, D.E. Johnson, D.W. Hamar, R.L. Hegstad and S. Johnston, 1998. Effects of weight gain and loss on metabolic rate, glucose tolerance and serum lipids in domestic cats. Res. Vet. Sci., 64: 11-16. CrossRef | PubMed | Direct Link |
10: Gehrmann, W., M. Elsner and S. Lenzen, 2010. Role of metabolically generated reactive oxygen species for lipotoxicity in pancreatic β-cells. Diabetes Obes. Metab., 2: 149-158. CrossRef | PubMed |
11: Geliebter, A., N. Torbay, E.F. Bracco, S.A. Hashim and T.B. Van Itallie, 1983. Over feeding with medium-chain triglyceride diet results in diminished deposition off at. Am. J. Clin. Nutr., 37: l-4. PubMed | Direct Link |
12: Higdon, J.V. and B. Frei, 2003. Obesity and oxidative stress: A direct link to CVD? Arterioscler. Thromb. Vasc. Biol., 23: 365-367. CrossRef |
13: Hsiao, P.J., K.K. Kuo, S.J. Shin, Y.H. Yang and W.Y. Lin et al., 2007. Significant correlations between severe fatty liver and risk factors for metabolic syndrome. J. Gastroenterol. Hepatol., 22: 2118-2123. PubMed |
14: Iacobellis, G., A.M. Pellicelli, B. Grisorio, G. Barbarini, F. Leonetti, A.M. Sharma and G. Barbaro, 2008. Relation of epicardial fat and alanine aminotransferase in subjects with increased visceral fat. Obesity, 16: 179-183. CrossRef | PubMed |
15: Kasznicki, J., M. Kosmalski, A. Sliwinska, M. Mrowicka, M. Stanczyk, I. Majsterek and J. Drzewoski, 2012. Evaluation of oxidative stress markers in pathogenesis of diabetic neuropathy. Mol. Biol. Rep., 39: 8669-8678. CrossRef |
16: Keaney Jr., J.F., M.G. Larson, R.S. Vasan, P.W. Wilson and I. Lipinska et al., 2003. Obesity and systemic oxidative stress: Clinical correlates of oxidative stress in the framingham study. Arteriosclerosis Thrombosis Vasc. Biol., 23: 434-439. CrossRef | PubMed | Direct Link |
17: Loria, P., A. Lonardo and F. Anania, 2013. Liver and diabetes. A vicious circle. Hepatol. Res., 43: 51-64. CrossRef | PubMed |
18: Maechler, P., L. Jornot and C.B. Wollheim, 1999. Hydrogen peroxide alters mitochondrial activation and insulin secretion in pancreatic beta cells. J. Biol. Chem., 274: 27905-27913. PubMed |
19: Moussa, S.A., 2008. Oxidative stress in diabetes mellitus. Rom. J. Biophys., 18: 225-236. Direct Link |
20: Neumann, S., H. Welling, T. Bilzer and S. Thuere, 2008. Myopathy and alterations in serum 3-methylhistidine in dogs with liver disease. Res. Vet. Sci., 84: 178-184. CrossRef |
21: Papamandjaris, A.A., D.E. MacDougall and P.J. Jones, 1998. Medium chain fatty acid metabolism and energy expenditure: Obesity treatment implications. Life Sci., 62: 1203-1215. PubMed |
22: Pitkanen, O.M., H. Vanhanen and E. Ptkanen, 1999. Metabolic syndrome is associated with changes in D-mannose metabolism. Scand. J. Clin. Lab. Invest., 59: 607-612. PubMed |
23: Piwowar, A., M. Knapik-Kordecka and M. Warwas, 2007. AOPP and its relations with selected markers of oxidative/antioxidative system in type 2 diabetes mellitus. Diabetes Res. Clin. Pract., 77: 188-192. CrossRef | Direct Link |
24: Rothwell, N.J. and M.J. Stock, 1987. Stimulation of thermogenesis and brown fat activity in rats fed medium chain triglyceride. Metabolism, 36: 128-130. CrossRef | Direct Link |
25: Suzuki, K., Y. Ito, J. Ochiai, Y. Kusuhara and S. Hashimoto et al., 2003. Relationship between obesity and serum markers of oxidative stress and inflammation. Asian Pac. J. Cancer Prev., 4: 259-266. PubMed |
26: Tanner, A.E., J. Martin and K.E. Saker, 2007. Oxidative stress and inflammatory state induced by obesity in the healthy feline. J. Anim. Physiol. Anim. Nutr., 9: 163-166. CrossRef | Direct Link |
27: Unger, R.H., 2003. Lipid overload and overflow: Metabolic trauma and the metabolic syndrome. Trends Endocrinol. Metab., 14: 398-403. PubMed |
28: Valko, M., D. Leibfritz, J. Moncol, M.T.D. Cronin, M. Mazur and J. Telser, 2007. Free radicals and antioxidants in normal physiological functions and human disease. Int. J. Biochem. Cell Biol., 39: 44-84. CrossRef | PubMed | Direct Link |
29: Washizu, T., A. Tanaka, T. Sako, M. Washizu and T. Arai, 1999. Comparison of the activities of enzymes related to glycolysis and gluconeogenesis in the liver of dogs and cats. Res. Vet. Sci., 67: 205-206. PubMed | Direct Link |
30: Young, J.B. and M.C. Walgren, 1994. Differential effects of dietary fats on sympathetic nervous system activity in the rat. Metabolism, 43: 51-60. CrossRef | Direct Link |
31: Ziegler, D., C.G. Sohr and J. Nourooz-Zadeh, 2004. Oxidative stress and antioxidant defense in relation to the severity of diabetic polyneuropathy and cardiovascular autonomic neuropathy. Diabetes Care, 27: 2178-2183. Direct Link |
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