Iodomethylated fatty acid metabolism in mice and dogs

The myocardial uptake of fatty acids labeled with radioactive iodine and injected i.v. can only be evaluated with SPECT if their oxidation kinetics is slow enough. For this reason, we evaluated different iodomethylated fatty acids in mice and dogs to determine which of them shows the highest myocardial uptake and the slowest oxidation. The most suitable was found to be 16-iodo-3-methyl hexadecanoic acid (mono beta) since its myocardial fixation was the same as that of the reference, i.e. 16-iodo-9-hexadecenoic acid (IHA), whereas it was degraded more slowly. Thirty min after injection of mono beta into dogs, the decrease in myocardial activity with respect to the maximum was two fold less than after IHA injection. The myocardial uptake of the two dimethylated fatty acids studied, i.e. 16-iodo-2,2-methyl hexadecanoic acid and 16-iodo-3,3-methyl hexadecanoic acid, was less than that of IHA in mice and dogs. In the latter, the myocardial uptake was so small that we were unable to study the time course of its activity. Consequently, these dimethylated fatty acids are not suitable for the study of the myocardial uptake of fatty acids in man.     

Demonstration of disturbed free fatty acid metabolism of myocardium in patients with non-insulin-dependent diabetes mellitus as measured with iodine-123-heptadecanoic acid

Myocardial free fatty acid metabolism and left ventricular function were evaluated in 15 middle-aged patients with non-insulin-dependent diabetes mellitus (NIDDM) and in 8 healthy control subjects. The study subjects had no evidence of coronary heart disease on the basis of clinical history, exercise ECG or myocardial perfusion scintigraphy. During peak exercise, iodine-123 hepatadecanoic acid (HDA) was intravenously injected. Myocardial activity distribution of ¹²³I-HDA was measured 10, 30, and 50 min after exercise using single-photon emission tomography (SPET); and then further corrected by free ¹²³I-iodine. Venous blood samples were drawn for detecting the plasma activity of ¹²³I. The net extraction of ¹²³I-HDA into the myocardium was obtained by dividing the corrected tissue ¹²³I concentration by the integral of the plasma time activity curve. The net extraction was 0.40 ± 0.06 min^–1 (mean ± SD) patients with NIDDM and 0.38 ± 0.06 min^–1 in control subjects (P>0.1), respectively. The faster elimination rate of ¹²³I-HDA was found in patients with NIDDM (0.029±0.008 min^–1) than in control subjects (0.022±0.004 min^–1; P<0.01). There was no statistically significant difference in left ventricular ejection fraction (LVEF) at rest between patients with NIDDM (53±9%) and control subjects (56±2%), whereas the increase of LVEF during exercise remained lower in patients with NIDDM (3.4±8.2%) than in control subjects (11.8±5.8%; P<0.025). A significant correlation (r=0.64; P < 0.01) was found between the net extraction of ¹²³I-HDA and the change of LVEF, as well as with exercise load (r=0.68; P<0.01). In conclusion, evidence of an increased fatty acid utilization and triglyceride synthesis rate was observed in the diabetic myocardium. Offprint requests to: J.T. Kuikka     

Efficacy of 15-(123I)-p-iodophenyl pentadecanoic acid (IPPA) in assessing myocardial metabolism in a model of reversible global ischemia

In a canine model of reversible global ischemia, the residual quantity of ¹²³I was assessed following a bolus injection of 15-p-(¹²³I)-iodophenyl pentadecanoic acid (¹²³I-IPPA). This technique was used to assess changes in free fatty acid metabolism following the utilization of three cardioplegic formulations. Cardioplegic arrest was initiated with Tyers' iso-osmolar (IO) solution (Group A); IO+superoxide dismutase (SOD) (Group B) and IO+allopurinol (Group C). Pre and post operative scanning were completed with 2–5 mCi ¹²³I-IPPA. Clearance was assessed by IPPA time activity curve analysis generating t _1/2 (half lives in min) for the early and late phases of the curve. The assessment between groups demonstrated that the elimination of ¹²³I-IPPA products (early phase) was faster from the lateral wall in groups B and C versus group A (14±12 min, 13±9 min and 24±10 min, respectively). The elimination of IPPA (late phase) was also faster from the lateral wall in groups B and C when compared to group A (240±270 min, 132±85 min and 416±238 min). Examining the changes between control and postoperative values for each area of the left ventricle within each group demonstrated no significant, changes for groups B and C. Group A, however, demonstrated significantly increased t _1/2 values for the lateral wall (early and late phases) and the apical wall (late phase). From this study it can be concluded that following 2 h of reversible global ischemia and reperfusion, the assessment of turnover of ¹²³I-IPPA can be used to differentiate the effectiveness of various cardioplegic formulations. It appears that cardioplegic solutions supplemented with allopurinol and SOD (groups B and C) may be better able to protect myocardial fatty acid metabolism compared to Tyers' iso-osmolar solution (group A).Supported by the British Columbia Heart Foundation     

Mathematical model of the metabolism of 123I-16-iodo-9-hexadecenoic acid in an isolated rat heart. Validation by comparison with experimental measurements

The aim of the present study was to demonstrate that it is possible to estimate the intracellular metabolism of a fatty acid labelled with iodine using external radioactivity measurements. ¹²³I-16-iodo-9-hexadecenoic acid (IHA) was injected close to the coronary arteries of isolated rat hearts perfused according to the Langendorff technique. The time course of the cardiac radioactivity was measured using an INa crystal coupled to an analyser. The obtained curves were analysed using a four-compartment mathematical model, with the compartments corresponding to the vascular-IHA (O), intramyocardial free-IHA (1), esterified-IHA (2) and iodide (3) pools. Curve analysis using this model demonstrated that, as compared to substrate-free perfusion, the presence of glucose (11 mM) increased IHA storage and decreased its oxidation. These changes were enhanced by the presence of insulin. A comparison of these results with measurements of the radioactivity levels within the various cellular fractions validated our proposed mathematical model. Thus, using only a mathematical analysis of a cardiac time-activity curve, it is possible to obtain quantitative information about IHA distribution in the different intracellular metabolic pathways. This technique is potentially useful for the study of metabolic effects of ischaemia or anoxia, as well as for the study of the influence of various substrates or drugs on IHA metabolism in isolated rat hearts.     

Angiotensin-converting enzyme inhibitor therapy affects myocardial fatty acid metabolism after acute myocardial infarction

BACKGROUND: Angiotensin-converting enzyme (ACE) inhibitor therapy has an early mortality benefit in unselected patients with acute myocardial infarction (AMI). However, the effects of ACE inhibition on myocardial fatty acid metabolism in this patient population have not been studied. We tested the hypothesis that ACE inhibitor therapy improves myocardial fatty acid metabolism and decreases mortality rate in patients after AMI. METHODS: Forty-two patients after first anterior AMI and primary angioplasty were randomly assigned to titrated oral enalapril (n = 24) or placebo therapy (n = 18). Iodine 123-labeled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) single photon emission computed tomography imaging was performed an average of 4.8 days after AMI and 1 month after AMI. BMIPP abnormalities were quantified as a severity index by a polar map. RESULTS: There were no significant changes in baseline characteristics, cardiac function, and angiographic findings between patients in the enalapril group and patients in the placebo group. However, BMIPP severity index from acute phase to chronic phase was significantly decreased in the enalapril-treated group (118+/-48 to 82+/-36, P<.05), but not in the placebo group (123+/-65 to 115+/-58, P not significant). CONCLUSION: ACE inhibition therapy improved myocardial fatty acid metabolism and regional left ventricular function in patients after anterior AMI. BMIPP single photon emission computed tomography findings imply that this better outcome may be attributable to an improvement of cellular function with ACE inhibitors.     

Dynamic changes in cardiac fatty acid metabolism in the stunned human myocardium

BACKGROUND: The chronological changes or mechanisms in cardiac fatty acid metabolism under clinical conditions of hypoxia and ischemia have not been fully elucidated. 123-15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) can be used with single photon emission computed tomography (SPECT) to evaluate myocardial fatty acid metabolism. We investigated chronological changes in energy metabolism in the stunned human myocardium by means of 123I-BMIPP myocardial SPECT. METHODS AND RESULTS: We conducted 123I-BMIPP myocardial SPECT in 10 patients with stunned myocardium during the acute, subacute and chronic phases after onset. The left ventricle was divided into 9 regions on SPECT, and the degree of abnormalities in each region was scored in four grades from normal (0) to defect (4). We also examined wash-out rates on BMIPP images. The scores on early BMIPP images in the acute, subacute and chronic phases were 5.6 +/- 1.8, 13.4 +/- 3.5 and 2.5 +/- 1.1, respectively, and the score was highest in the subacute phase (p < 0.001). Similarly, scores on the late images were 2.3 +/- 1.7, 18.3 +/- 4.5 and 4.7 +/- 2.6, respectively, and highest in the subacute phase (p < 0.001). The wash-out rates (normal: 18.2 +/- 2.1%) in the acute, subacute and chronic phases were 12.1 +/- 4.8%, 44.9 +/- 10.0% and 23.1 +/- 4.6%, respectively, with the value being lowest during the acute phase (p < 0.05), and highest during the subacute phase (p < 0.001). CONCLUSION: These results suggested that fatty acid metabolism in the stunned human myocardium changes dynamically over time.     

Single photon emission tomography imaging of myocardial oxidative metabolism with 15-(p-[123I]iodophenyl) pentadecanoic acid in patients with coronary artery disease and aorto-coronary bypass graft surgery

A total of 29 patients with coronary artery disease (CAD) were investigated with 15-(p-[¹²³I] iodophenyl)pentadecanoic acid (¹²³I-IPPA) and sequential single photon emission tomography (SPET). Of these, 19 were studied after aorto-coronary bypass graft surgery. Some 13 patients without evidence of CAD served as a control group. Two SPET studies (early and late) were carried out within 45 min after intravenous administration of 200 MBq ¹²³I-IPPA at peak sub-maximal exercise. Semi-quantification of uptake (related to perfusion) and turnover (linked to metabolism) was obtained by segmental comparison of oblique slices. Taking coronary arteriography as the gold standard, ¹²³I-IPPA scintigraphy had the following figures of merit for sensitivity and specificity in the diagnosis of CAD: for the left anterior descending artery territory 93% and 95%, for the left circumflex artery region 96% and 92%, and for the right coronary artery territory 77% and 92%, respectively. In all, 90% of the reperfused myocardial segments showed an improvement of uptake. Of these, 61% exhibited increased turnover after revascularization and 39% had pathologic turnover and thus a dissociation of improvement of perfusion and oxidative metabolism after surgery. Offprint requests to: J. Kropp     

Effect of 3-methyl-branching on the metabolism in rat hearts of radioiodinated iodovinyl long chain fatty acids

The metabolism of two new 3-methyl-branched iodovinyl fatty acids in rat hearts was evaluated by determining the subcellular and lipid pool distribution of these radiolabeled analogues after intravenous injection. Methyl branching had been introduced into the straight chain analogue, 19-iodo-18-nonadecenoic acid (IVN), to produce the monomethyl analogue, 19-iodo-3-(R,S)-methyl-18-nonadecenoic acid (BMIVN) and the dimethyl derivative, 19-iodo-3,3-dimethyl-18-nonadecenoic acid (DMIVN) in the hope of inhibiting oxidation. Since the presence of 3-methyl branching results in delayed myocardial clearance in rats, differences were sought in the lipid and subcellular distribution of these branched analogues that might correlate with the prolonged retention and reflect differences in metabolism. Hearts of rats injected intravenously with the radiolabeled fatty acids were removed and homogenized and the homogenates partitioned between the chloroform-methanol (organic) fraction and the aqueous fraction. Comparison of the distribution of radioactivity between the organic and aqueous fractions showed that most of the DMIVN and BMIVN activity was in the organic fraction with IVN activity initially divided equally between the two fractions. Identification of the lipid components of these organic fractions showed that there was slow incorporation of DMIVN into the triglyceride and polar lipid fractions with a slow loss from the free fatty acid fraction. With the straight chain IVN analogue which shows rapid washout from rat hearts, there was loss of activity from all 3 lipid components during the 60 min. The monomethyl branched BMIVN analogue demonstrated predominant storage in the polar lipid fraction with some incorporation into triglycerides. Subcellular distribution studies of the three analogues also showed differences that correlated with the observed differences in heart retention properties. With the unbranched IVN analogue, radioactivity was found primarily in the cytoplasmic fraction 30 min after injection, whereas the branched analogues demonstrated a much higher association with the microsomal and mitochondrial fractions of the heart. In rats fed prior to injection, these differences in the subcellular distribution profiles were minimized. The lipid and subcellular distribution patterns reported here for the methyl branched analogues as compared to those of the straight chain iodovinyl fatty acid may provide some understanding as to the mechanisms of retention in rat myocardium.Research supported by the Office of Health and Environmental Research, U.S. Department of Energy, under contract DE-AC0 5-840 R21400 with Martin Marietta Energy Systems, Inc.     

Hypertensive left ventricular hypertrophy is associated with abnormal myocardial fatty acid metabolism and myocardial efficiency

BACKGROUND: Hypertension-induced left ventricular hypertrophy (LVH) is associated with an increased risk of cardiovascular morbidity and death by mechanisms not well characterized. METHODS AND RESULTS: Myocardial fatty acid (FA) metabolism and left ventricular (LV) mass were evaluated in 13 patients with hypertensive LVH with normal LV ejection fraction and 42 normal control subjects (primary cohort). Contractile performance was also evaluated in 5 hypertensive LVH patients and 5 matched normal control subjects (magnetic resonance [MR] substudy). Myocardial FA utilization (MFAU) and myocardial FA oxidation (MFAO) were assessed by positron emission tomography by use of 1-carbon-11 palmitate. Myocardial contractile function (strain and stress) was determined by cardiac MR imaging with tissue tagging and calibrated arterial pressure traces; myocardial external minute work and efficiency were derived. In the primary cohort decreased MFAO was predictive of increased LV mass (model r(2) = 0.61, P = .03). In the MR substudy decreased MFAO (corrected for myocardial oxygen consumption [MVO(2)]) in the hypertensive LVH group compared with the normal group (MFAU/MVO(2), 26 +/- 5 vs 37 +/- 8; MFAO/MVO(2), 24 +/- 6 vs 35 +/- 7; both P = .03) was paralleled by decreased myocardial external minute work (0.13 +/- 0.03 J x g(-1) x min(-1) vs 0.17 +/- 0.04 J x g(-1) x min(-1), P = .07) and decreased myocardial efficiency (5.2% +/- 1.4% vs 7.1% +/- 1.0%, P = .03). CONCLUSIONS: Abnormalities in myocardial FA metabolism are apparent in hypertensive LVH, and these abnormalities may be responsible, at least in part, for a reduction in myocardial efficiency.     

Serial evaluation of fatty acid metabolism in rats with myocardial infarction by pinhole SPECT

BACKGROUND: Iodine 123-labeled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) is mainly trapped in the myocardium as triglyceride, depending on the adenosine triphosphate level. Ten percent to 20% of it is metabolized through alpha-oxidation after beta-oxidation; however, the precise mechanism of the regulatory pathways of BMIPP is yet to be clarified. METHODS AND RESULTS: A brief left coronary artery occlusion (10-30 minutes) was performed in 28 male Wistar-Kyoto rats. Dual single photon emission computed tomography images of BMIPP and thallium 201 were obtained 3 days and 24 days after the operation. The activities of 3-hydroxyacyl-coenzyme A dehydrogenase (HAD), citrate synthase (CS), and alpha-glycerol-phosphate dehydrogenase (GPD) were then measured in both ischemic and nonischemic regions. BMIPP and Tl-201 chloride severity scores were also evaluated conventionally. CS and HAD levels were significantly lower in the ischemic region than in the nonischemic region in the chronic group (CS, 102.9 +/- 28.1 vs 138.7 +/- 33.7 micromol/g/min, respectively, P =.0051; HAD, 54.7 +/- 20.1 vs 78.6 +/- 18.7 micromol/g/min, respectively, P =.0031). There was no difference in GPD between the ischemic and nonischemic regions. The BMIPP severity score had closer inverse relations with HAD (acute, r = -0.82; chronic, r = -0.80) and CS (acute, r = -0.87; chronic, r = -0.81), but not with GPD, than did Tl-201 chloride severity score. CONCLUSIONS: BMIPP imaging correlates well with the activities of HAD and CS, suggesting that a decrease in BMIPP uptake reflects deterioration of both fatty acid metabolism and citrate cycle and shows information other than regional myocardial perfusion.     

Assessment of myocardial fatty acid metabolism in atrioventricular synchronous pacing: Analysis of iodine 123-labeled beta-methyl iodophenyl pentadecanoic acid SPECT

Background  We used beta-methyl iodophenyl pentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT) to evaluate fatty acid metabolism in patients who were candidates for permanent pacemaker implantation and in patients with atrioventricular (AV) synchronous pacing. Methods and Results  We performed BMIPP SPECT studies in 66 patients with bradyarrhythmia, of whom 11 patients were candidates for permanent pacemaker implantation, 27 patients had atrial pacing (atrial sensing, inhibited mode, simple programmable [AAI]), and 28 patients had atrial synchronous ventricular inhibited pacing (ventricular pacing, 2-chamber sensing, atrial-triggered and ventricular-inhibited, multiprogrammable [VDD]) or atrial and ventricular pacing in sequence (atrial and ventricular sensing, atrial-inhibited and atrial-triggered, ventricular-inhibited, multiprogrammable [DDD]). A qualitative assessment revealed that the BMIPP uptake at the septal, inferior, and apical regions was significantly decreased in the patients with VDD/DDD compared with both the candidates for permanent pacemaker implantation and the patients with AAI. The total extent score (ES) and severity score (SS) were significantly higher in the patients with VDD/DDD than in the other 2 groups. Significant regional differences of both ES and SS values were observed at the septal and inferior regions in the patients with VDD/DDD compared with the other groups. No differences were found between the qualitative and quantitative measures of BMIPP uptake in the candidates for permanent pacemaker implantation and those in the patients with AAI. Conclusion  Our study suggests that AV synchronous right ventricular pacing resulting in the delayed conduction and depolarization of myocardial cells may directly interfere with regional cellular free fatty acid uptake and metabolism.     

Metabolism of 15 (p123I iodophenyl-)pentadecanoic acid in heart muscle and noncardiac tissues

The uptake and turnover of (p¹²³I iodophenyl-) pentadecanoic acid (I-PPA), a radioiodinated free-fatty-acid analog, was examined in the heart, lung, liver, kidneys, spleen, and skeletal muscle of rats. At 2 min post injection, a high cardiac uptake of 4.4% dose per gram had already been achieved; this was followed by a rapid, two-component, tracer clearance. The kinetics of tissue concentrations of labeled hydrophilic catabolites indicated a rapid oxidation of I-PPA and the subsequent washout of I-PPA catabolites from heart-muscle tissue. The fractional distribution of the labeled cardiac lipids compared favorably with previously reported values for ³H-oleic-or ¹⁴C-palmitic-acid-labeled myocardial lipids. Typical patterns of I-PPA metabolism were observed in tissues depending on primary fatty-acid oxidation, lipid metabolism regulation, or I-PPA-catabolite excretion. The tissue concentrations and kinetics of I-PPA and its metabolites in the heart muscle indicated that general pathways of cardiac-lipid metabolism are traced by this new -emitting isotope-labeled radiopharmaceutical.     

Assessment of contractile response to dobutamine stress by means of ECG-gated myocardial SPECT: Comparison with myocardial perfusion and fatty acid metabolism

The present study assessed left ventricular performance during dobutamine stress measured using gated SPECT, and compared the results to myocardial perfusion and fatty acid metabolism. METHODS: Thirty-six patients with myocardial infarction given (99m)Tc-sestamibi or (99m)Tc-tetrofosmin were examined by gated SPECT at rest and during dobutamine stress (4-20 microg x kg(-1) x min(-1)). After acquiring data at the highest dose, 201TlCl was injected and dual-isotope SPECT was performed to assess myocardial ischemia. Thirty of 36 patients also underwent myocardial SPECT with 123I-BMIPP. Regional wall motion changes during dobutamine infusion were determined from the gated SPECT data and classified as: (1) Improvement, (2) Worsening, (3) No change, and (4) Biphasic response. For myocardial segments of each infarct area, stress 201Tl, rest (99m)Tc and (123)I-BMIPP uptakes were graded on a five-point scoring system of defects from 0 (normal) to 4 (grossly defective). RESULTS: Rest 99mTc defect score index (DSI) in No change area was significantly higher than that in Biphasic area. The ADSI (stress 201Tl - rest (99m)Tc) in Biphasic area was significantly higher than those in Improvement and No change areas. The deltaDSI (BMIPP - (99m)Tc) in Worsening area tended to be higher than that in No Change area. Conclusions: Regional contractile response to dobutamine stress analyzed by gated SPECT showed that the response in-myocardial infarct areas could be classified by rest and stress myocardial perfusion and BMIPP accumulation.     

31P NMR measurements of the effects of unsaturated fatty acids on cellular phospholipid metabolism

³¹P NMR measurements on extracts prepared from a variety of cultured mammalian cell lines and primary rat hepatocytes have shown changes in the levels of several phospholipid metabolites after incubation of cells with unsaturated fatty acids. These data suggest a possible link between the accumulation of neutral lipid and the changes in phospholipid metabolite concentrations that have been observed in some tumor cells and other rapidly growing tissues such as the regenerating liver and mitogen-stimulated lymphocytes.     

左旋卡尼汀对肾性高血压大鼠糖脂代谢和心肌重构的影响

目的观察左旋卡尼汀（L—camitine，L—CN）对肾性高血压大鼠心肌代谢和心肌重构的保护作用。方法实验分为3组：正常对照组、高血压模型组、高血压治疗组。采用两肾一夹手术方法，制备高血压大鼠模型。10周后行心脏超声、血流动力学检查，测定血脂、血糖、血游离脂肪酸（FFA）浓度，计算心脉指数（CI），取心肌组织行常规石蜡切片和超薄切片，分别观察心肌显微结构和超微结构的改变。结果经10周治疗，高血压治疗组与模型组相比，血FFA浓度明显下降（P〈0．05），高密度脂蛋白胆固醇（HDL—C）明显升高（P〈0．05），CI明显下降（P〈0．05）；心肌未见明显坏死、溶解和心肌细胞肥大，心肌超微结构大致正常。结论L—CN可平衡高血压肥厚心肌的糖、脂代谢紊乱，降低血FFA浓度，减轻高血压大鼠的心肌重构。     

Myocardial fatty acid metabolism in diabetic mice with125I-BMIPP

In patients with diabetes mellitus, the existence of diabetic cardiomyopathy was substantiated. This study was undertaken to evaluate the myocardiac fatty acid metabolism of diabetic mice (n = 21) and controls (n = 21) in¹²⁵I-BMIPP in fasted and unfasted states.¹²⁵I-BMIPP of 370 kBq was given and thirty minutes later, animals from both groups were killed. Samples of hearts, liver and other organs were removed, weighed and then counted in a scintillation counter. The percent injected dose/g of hearts of diabetic mice was significantly reduced compared to controls in unfasted (p < 0.05) and fasted (p < 0.01) groups. These findings may reflect impaired fatty acid utilization of the hearts in diabetic mice compared to controls.     

Comparison of 16-iodohexadecanoic acid (IHDA) and 15-p-iodophenylpentadecanoic acid (IPPA) metabolism and kinetics in the isolated rat heart

Time courses of radioactivity (residue curves) were obtained following bolus injection into working rat hearts of two ¹²⁵I-labeled long chain fatty acids: 16-iodohexadecanoic acid (IHDA) and 15-p-iodophenylpentadecanoic acid (IPPA). Residue curves were analyzed in terms of a rapid vascular washout component, an early tissue clearance component, and a very slow late component. For IHDA and IPPA in control hearts, early myocardial clearance kinetics were rate limited by the diffusion of catabolites. Sensitivity of the kinetics to impaired fatty acid oxidation was examination by pretreatment of animals with 2[5(4-chlorophenyl)pentyl]oxirane-2-carboxylate (POCA). Decreased fatty acid oxidation was indicated in IHDA and IPPA residue curves by a decrease in the relative size of the early clearance component. Analysis of radiolabeled species in coronary effluent and heart homogenates showed that back diffusion of IPPA was slower than that of IHDA; this discrepancy was most apparent in POCA hearts. In vitro binding assays suggested higher tissue: albumin relative affinity for IPPA than for IHDA. Thus, IPPA early clearance kinetics were more closely related to the clearance of labeled catabolite(s) and were therefore more sensitive to the oxidation rate of long chain fatty acids.     

游离指肪酸对大鼠瘦素体基因表达及蛋白酷氨酸磷酸化的影响

目的：观察游离脂肪酸是否会对大鼠肝脏,骨骼肌及胰腺组织瘦素（leptin) 受体的蛋白及基因表达以及酪氨酸磷酸化产生一定的影响,方法：用静脉注射法制备高游离脂肪酸大鼠模型,处死后取肝脏,骨骼2肌及胰腺组织,提取蛋白后用Western印迹法检测瘦素受体的蛋白水平,用RTPCR法检测瘦素受体RNA含量的变化,应用免疫沉淀法检测瘦素受体的酪氨酸磷酸化程度,结果：高游离脂肪酸组大鼠肝脏,骨骼肌和胰腺组织瘦素受体的蛋白水平与对照组大鼠相比无明显差异（P＞0．05）,经RT－PCR结果分析表发现,高游离脂肪酸组大鼠肝脏,骨骼肌和胰腺组织瘦素受体的RNA水平与对照组大鼠相比无明显差异（P＞0．05）,高游离脂肪酸组大鼠肝脏,骨骼肌和胰腺组织瘦素受体的酷氨酸磷酸化程度与对照组大鼠相比有显著差异（P＜0．05）,瘦素受体的酷氨酸磷酸化程度显著降低,提示游离脂肪酸抑制了大鼠肝脏,骨骼肌组织的瘦素受体的酷氨酸残基的磷酸化,崦高游离脂肪酸组大鼠胰腺组织的瘦素受体的酷氨酸磷酸化程度与对照组大鼠相比没有显著差异（P＞0．05）,结论：游离脂肪酸可显著降低大鼠肝脏及骨骼肌组织瘦素受体的酪氨酸磷酸化程度,提示游离脂肪酸的抑制了大鼠肝脏,骨骼肌组织纱受体的酷氨酸残基的磷酸化,游离脂肪酸可通过对大鼠肝脏及骨骼肌瘦素受体的磷酸化程度产生一定的抑制作用,从而进一步引起胰岛素抵抗。