Conjugated linoleic acid (CLA) has gained much attention recently due to its beneficial health and biological effects on animals and humans. However, the CLA-forming enzyme system has not been studied in details. Six strains of Lactobacillus acidophilus L11, L12, L14, L15, Lactobacillus fermentum and Lactobacillus reuteri were used to study the growth conditions and the production of CLA-forming enzyme in MRS media containing linoleic acid concentrations at 37°C. The purification and characterization of a CLA-forming enzyme were reported for the first time. The results showed that this enzyme has a molecular mass of 72 kDa, and is composed of two subunits. The optimal pH and temperature were 7.0 and 37°C, respectively. Kinetic study indicated that the enzyme has a high affinity for linoleic acid having a Km value of 1.49 x 10 -5 M and the Vmax was 17.1 muM/mg/min. The enzyme activity was inhibited by the metal chelators. (Abstract shortened by UMI.)

Thesis (M.Sc.). / Written for the School of Dietetics and Human Nutrition. Title from title page of PDF (viewed 2007/08/30). Includes bibliographical references.

No description available.

No description available.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 193-206).

Structured phospholipids with functional ingredients like conjugated linoleic acid (CLA) and plant sterols to deliver their physiological effects in different food formulations were synthesized. The lipase and phospholipase A2 catalyzed enzymatic acidolysis reaction between phospholipids (PLs) and CLA was used for fatty acid modification, while the phospholipase D catalyzed transphosphatidylation reaction between PLs and sterol was used for head group modification. Enzymatic processes were an effective way to produce structured phospholipids. Screening of four lipases and immobilized phospholipase A2 and combination of lipase and phospholipase showed that only Lipozyme RM IM and Lipozyme TL IM were effective in incorporation of CLA into PLs. The maximum incorporation achieved by the latter enzyme was 16% with soy PLs in 72 h. The class of phospholipids had a significant effect on the rate of incorporation of CLA compare to source of PLs. A method capable of predicting the rate of incorporation of CLA into phospholipids was developed using response surface methodology. A three-level four-factor Central Composite Rotatable Design (CCRD) was used. The four factors selected were lipase dosage (Ed, wt.% of substrate), substrate ratio (Sr,mol%), reaction time (ti, h) and reaction temperature (Te,oC). The enzyme load and substrate ratio had a greater effect on the rate of incorporation than did reaction time and temperature. A polynomial regression equation was developed to predict the reaction rate. The new phosphatidyl derivative, phosphatidyl-sitosterol, was found to be synthesized by the transfer reaction of phosphatidyl residue from phosphatidylcholine to β-sitosterol by phospholipase D from Streptomyces sp. in biphasic medium. The novel phosphatidyl .sitosterol derivative was identified by MALDI-TOF mass spectrometry. Plant sterols were modified to a more polar lipid class by synthesizing phospholipid derivatives of them. When these structured phospholipids were added to a whey protein based oil-in-water emulsion, the CLA incorporated structured phospholipids (CLA-PL) had higher heat stability and oxidative stability compared to the controls.

Research conducted for this dissertation had three goals; 1) determine if CLA can induce milk fat depression immediately postpartum, 2) determine if CLA can alter energy availability, 3) determine the mechanism behind the mammary gland's decreased sensitivity to CLA immediately postpartum. The first study provides strong evidence indicating CLA can decrease milk fat synthesis immediately postpartum, but the dose required is approximately 3x greater than in established lactation. This trial also provided evidence that CLA can alter energy status, as CLA decreased days to EBAL nadir by nearly 5 days. This is relevant as recovery of EBAL from its lowest point provides an important signal for initiating ovarian activity and days to nadir is highly correlated with days to first ovulation. Study two was designed to determine if CLA induced milk fat depression could improve energy status during heat stress. Rumen-inert CLA reduced milk fat synthesis, and was able to improve energy availability, but did not increase milk yield or yield of other milk components. Although production was unchanged in this study, the study did provide further evidence that rumen-inert CLA can alter energy availability. Study three utilized intravenous infusion of CLA in cows in mid and early lactation to determine the mechanism for the mammary gland's decreased sensitivity in early lactation. It is postulated that increased fatty acid oxidation and subsequent enhanced levels of circulating NEFA present during the transition period competitively prevent adequate CLA uptake by the mammary gland. In the current study, trans-10, cis-12 CLA concentration in milk was not different between early and established lactation, while milk fat yield was drastically reduced on d 4 and 5 of trans-10, cis-12 CLA infusion in mid lactation cows, but unaltered in early lactation. Further, NEFA levels were nearly 3 fold higher in early lactation than in mid lactation, providing further evidence that increased circulating NEFAs in early lactation are unlikely to be the source of the mammary gland's decreased sensitivity during this time. Do to the variation in gene expression observed in this trial, we were unable to make any definitive conclusions as to the sensitivity of the expression of genes involved in milk lipid synthesis to CLA in early vs. mid lactation.

Diabetic cardiomyopathy is defined as changes in the structure and function of the myocardium that occur in diabetic patients in the absence of other cardiovascular risk factors. Our laboratory has shown that conjugated linoleic acid (CLA - a naturally-occurring polyunsaturated fatty acid with multiple health benefits) prevents endothelin-1-induced myocyte hypertrophy in vitro, as well as cardiac hypertrophy in vivo using a rodent model of spontaneously hypertensive heart failure. These cardioprotective effects of CLA were mediated through activation of peroxisome proliferator activated receptors (PPAR isomers α and γ) and stimulation of diacylglycerol kinase ζ (DGKζ). Thus, the aims of this study were to (i) determine the effect of CLA on hyperglycemia-induced structural and functional abnormalities of cardiomyocytes, and (ii) assess the role of PPAR-γ and DGK. High glucose treatment induced hypertrophy of primary adult cardiomyocytes, as indicated by augmented cell size and protein synthesis compared to untreated cardiomyocytes. The hyperglycemia-induced hypertrophy was attenuated by pretreatment with CLA (30 µM). The ability of CLA to prevent hyperglycemia-induced hypertrophy was suppressed by GW9662 (1 µM) and R59022 (10 μM), pharmacological inhibitors of PPAR-γ and DGK, respectively. In addition to structural abnormalities, high glucose impaired contractile function of adult cardiomyocytes as measured by maximal velocity of shortening, maximal velocity of relengthening, and peak shortening. Hyperglycemia-induced contractile dysfunction was likewise prevented by pretreatment with CLA (30 µM). Collectively, these findings support the idea that hyperglycemia is an independent risk factor for the development of diabetic cardiomyopathy. Hypertrophy and contractile dysfunction elicited by high glucose were prevented by CLA. The antihypertrophic actions of CLA are mediated, at least in part, by activation of PPAR-γ and DGK.

Enlargement of adipocytes in obesity leads to alteration in adipokine production and these changes are linked to the development of obesity-related cardiovascular diseases. Adipokines specifically associated with obesity-related hypertension include angiotensinogen and adiponectin. Conjugated linoleic acid (CLA) has been reported to reduce blood pressure in obese insulin-resistant rats, but its mechanism of action has not been identified. The objective of this study was to determine whether CLA’s ability to improve obesity-related hypertension involves reducing adipocyte size and altering adipokine production. Fa/fa Zucker rats (6 or 16 week old) were fed diets containing CLA isomers for 8 weeks. The trans(t)10,cis(c)12-CLA isomer reduced adipocyte size in both younger and older rats. Despite beneficial changes in cell size of rats fed the t10,c12-CLA isomer, there were no changes in the renin-angiotensin system or pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 or the anti-inflammatory cytokine IL-10. In contrast, the t10,c12-CLA isomer increased adiponectin levels both in the circulation and in adipose tissue. This was associated with increased phosphorylation of endothelial nitric oxide synthase (eNOS) in adipose tissue and aorta. Direct treatment of CLA isomers in cultured endothelial cells did not increase eNOS phosphorylation but increases were observed with adiponectin treatment. In vivo, infusion with adiponectin increased eNOS phosphorylation in adipose of fa/fa Zucker rats in parallel with improvements in blood pressure. Similarly, when circulating levels of adiponectin increased in rats fed the t10,c12-CLA isomer diet, blood pressure was also attenuated. In younger rats, both the t10-c12 and c9,t11-CLA isomers were significantly different from the control group at week 8, however, only the t10,c12-CLA isomer was comparable to the commonly used anti-hypertensive medication captopril. In conclusion, the beneficial effects of the t10,c12-CLA isomer on blood pressure may in part be due to its ability to reduce the number of large adipocytes in vivo, thus increasing the production of adiponectin which subsequently activates vascular eNOS.

Diabetic cardiomyopathy is defined as changes in the structure and function of the myocardium that occur in diabetic patients in the absence of other cardiovascular risk factors. Our laboratory has shown that conjugated linoleic acid (CLA - a naturally-occurring polyunsaturated fatty acid with multiple health benefits) prevents endothelin-1-induced myocyte hypertrophy in vitro, as well as cardiac hypertrophy in vivo using a rodent model of spontaneously hypertensive heart failure. These cardioprotective effects of CLA were mediated through activation of peroxisome proliferator activated receptors (PPAR isomers α and γ) and stimulation of diacylglycerol kinase ζ (DGKζ). Thus, the aims of this study were to (i) determine the effect of CLA on hyperglycemia-induced structural and functional abnormalities of cardiomyocytes, and (ii) assess the role of PPAR-γ and DGK. High glucose treatment induced hypertrophy of primary adult cardiomyocytes, as indicated by augmented cell size and protein synthesis compared to untreated cardiomyocytes. The hyperglycemia-induced hypertrophy was attenuated by pretreatment with CLA (30 µM). The ability of CLA to prevent hyperglycemia-induced hypertrophy was suppressed by GW9662 (1 µM) and R59022 (10 μM), pharmacological inhibitors of PPAR-γ and DGK, respectively. In addition to structural abnormalities, high glucose impaired contractile function of adult cardiomyocytes as measured by maximal velocity of shortening, maximal velocity of relengthening, and peak shortening. Hyperglycemia-induced contractile dysfunction was likewise prevented by pretreatment with CLA (30 µM). Collectively, these findings support the idea that hyperglycemia is an independent risk factor for the development of diabetic cardiomyopathy. Hypertrophy and contractile dysfunction elicited by high glucose were prevented by CLA. The antihypertrophic actions of CLA are mediated, at least in part, by activation of PPAR-γ and DGK.