Long-chain Non-esterified Fatty Acids Research Articles

Oral/taste sensitivity to non-esterified long-chain fatty acids with varying degrees of unsaturation.

Understanding human oral/taste sensitivity to long-chain non-esterified fatty acids (NEFA) with varying physicochemical properties is essential to reducing the intake of fats and altering the intake composition. This study investigated the differences in human taste sensitivity to two NEFA: oleic acid and linoleic acid. Twenty-four female subjects were divided into two equal sensitivity groups, and they performed discrimination tests for both fatty acids against bottled water using either the triangle or the DR A-Not A test. To achieve an accurate measurement of NEFA sensitivity, the stimulus was carefully prepared, avoiding additives that could interfere with the binding of fatty acids to receptors. Stimuli concentrations were selected to be within the lowest range (9.9 to 177.3μM) evaluated in previous research. Through a systematic stimulus control process, this study confirmed that greater sensitivity was exhibited to linoleic acid than oleic acid, resulting in better discrimination than previous studies.

Variability of oral/taste sensitivity to fat: An investigation of attribution from detection threshold methods with repeated measurements

Accumulating psychophysical evidence suggests substantial individual variability in oral/taste sensitivity to non-esterified, long-chain fatty acids (NEFA), which is commonly referred to as fat taste or oleogustus. Recent studies have sought to determine its associations with human factors such as body mass index (BMI) and food preferences, as it has been claimed that excessive fat consumption is related to several health conditions, including obesity. Yet, the findings are controversial. On the other hand, it has been noted that considerable variability also occurs based on the methodology used to measure the fatty acid taste. Specifically, learning effects have been observed over repeated measurements of the detection threshold of NEFA, yet there has been no methodology available to take into account these learning effects. Accordingly, in the present study, a novel methodology using a descending-block dual reminder A-Not A (DR A-Not A) method with a warm-up has been proposed to measure the NEFA detection threshold based on the signal detection theory and considering NEFA taste learning effects over repeated sessions. Homogeneous subjects (young adult Korean females within the normal BMI range, non-vegetarians) were randomized to either the novel descending-block DR A-Not A method or ascending triangle method that is commonly used for fat perception studies. Pure oleic acid emulsions were used as fat taste stimuli to be discriminated from pure mineral water. Each subject completed 14 repeated visits. For the ascending triangle method, 14 thresholds were determined using a stopping rule, while for the novel method, 7 thresholds were determined each per two consecutive days, using a criterion of a lower limit of 50% confidence interval of d' = 0.5, considering the practical aspects of taste studies in food sensory science. Based on the group median results of the last two visits, the variability of the detection thresholds was reduced using the novel descending-block DR A-Not A method due to better learning effects over repeated sessions. This shows the potential of the descending-block DR A-Not A threshold method for further studies on oral/taste sensitivity to fat.

The Interplay between Non-Esterified Fatty Acids and Plasma Zinc and Its Influence on Thrombotic Risk in Obesity and Type 2 Diabetes.

Thrombosis is a major comorbidity of obesity and type-2 diabetes mellitus (T2DM). Despite the development of numerous effective treatments and preventative strategies to address thrombotic disease in such individuals, the incidence of thrombotic complications remains high. This suggests that not all the pathophysiological mechanisms underlying these events have been identified or targeted. Non-esterified fatty acids (NEFAs) are increasingly regarded as a nexus between obesity, insulin resistance, and vascular disease. Notably, plasma NEFA levels are consistently elevated in obesity and T2DM and may impact hemostasis in several ways. A potentially unrecognized route of NEFA-mediated thrombotic activity is their ability to disturb Zn2+ speciation in the plasma. Zn2+ is a potent regulator of coagulation and its availability in the plasma is monitored carefully through buffering by human serum albumin (HSA). The binding of long-chain NEFAs such as palmitate and stearate, however, trigger a conformational change in HSA that reduces its ability to bind Zn2+, thus increasing the ion’s availability to bind and activate coagulation proteins. NEFA-mediated perturbation of HSA-Zn2+ binding is thus predicted to contribute to the prothrombotic milieu in obesity and T2DM, representing a novel targetable disease mechanism in these disorders.

Albumin-mediated alteration of plasma zinc speciation by fatty acids modulates blood clotting in type-2 diabetes.

Zn2+ is an essential regulator of coagulation and is released from activated platelets. In plasma, the free Zn2+ concentration is fine-tuned through buffering by human serum albumin (HSA). Importantly, the ability of HSA to bind/buffer Zn2+ is compromised by co-transported non-esterified fatty acids (NEFAs). Given the role of Zn2+ in blood clot formation, we hypothesise that Zn2+ displacement from HSA by NEFAs in certain conditions (such as type 2 diabetes mellitus, T2DM) impacts on the cellular and protein arms of coagulation. To test this hypothesis, we assessed the extent to which increasing concentrations of a range of medium- and long-chain NEFAs reduced Zn2+-binding ability of HSA. Amongst the NEFAs tested, palmitate (16 : 0) and stearate (18 : 0) were the most effective at suppressing zinc-binding, whilst the mono-unsaturated palmitoleate (16 : 1c9) was markedly less effective. Assessment of platelet aggregation and fibrin clotting parameters in purified systems and in pooled plasma suggested that the HSA-mediated impact of the model NEFA myristate on zinc speciation intensified the effects of Zn2+ alone. The effects of elevated Zn2+ alone on fibrin clot density and fibre thickness in a purified protein system were mirrored in samples from T2DM patients, who have derranged NEFA metabolism. Crucially, T2DM individuals had increased total plasma NEFAs compared to controls, with the concentrations of key saturated (myristate, palmitate, stearate) and mono-unsaturated (oleate, cis-vaccenate) NEFAs positively correlating with clot density. Collectively, these data strongly support the concept that elevated NEFA levels contribute to altered coagulation in T2DM through dysregulation of plasma zinc speciation.

Impact of maternal BMI and gestational diabetes mellitus on maternal and cord blood metabolome: results from the PREOBE cohort study.

Maternal obesity and gestational diabetes mellitus (GDM) were frequently reported to be risk factors for obesity and diabetes in offspring. Our goal was to study the impact of maternal prepregnancy BMI (pBMI) and GDM on both maternal and cord blood metabolic profiles. We used LC-MS/MS to measure 201 metabolites comprising phospholipids (PL), amino acids, non-esterified fatty acids (NEFA), organic acids, acyl carnitines (AC), and Krebs cycle metabolites in maternal plasma at delivery and cord plasma obtained from 325 PREOBE study participants. Several metabolites were associated with pBMI/GDM in both maternal and cord blood (p < 0.05), while others were specific to either blood sources. BMI was positively associated with leucine, isoleucine, and inflammation markers in both mother and offspring, while β-hydroxybutyric acid was positively associated only in cord blood. GDM showed elevated levels of sum of hexoses, a characteristic finding in both maternal and cord blood. Uniquely in cord blood of offspring born to GDM mothers, free carnitine was significantly lower with the same tendency observed for AC, long-chain NEFA, PL, specific Krebs cycle metabolites, and β-oxidation markers. Maternal BMI and GDM are associated with maternal and cord blood metabolites supporting the hypothesis of transgenerational cycle of obesity and diabetes.

Elevated Nonesterified Fatty Acids (NEFA) Are Associated with Blunted Hyperglycemia-Induced Increments in Brain Glucose Levels

Recently, we have demonstrated that obesity and T2DM are associated with blunted brain glucose transport capacity during acute hyperglycemia in humans, which was also associated with higher total NEFA levels. Palmitic acid has been shown in vitro to suppress brain glucose uptake by downregulating GLUT1 expression in brain endothelial cells. Thus, this current study was undertaken to determine whether specific NEFA composition is associated with blunted human brain glucose transport capacity. Plasma NEFA composition was assessed using Gas-Chromatography Mass-Spectroscopy in 8 healthy lean (HC) (4F/4M, age 33±11 years, BMI 23±2 kg/m2, HbA1C 5.0±0.2), 10 obese (OB) (6F/4M, age 34±11 years, BMI 39±6 kg/m2, HbA1C 5.3±0.3), and 6 T2DM individuals (5F/1M, age 52±5 years, BMI 33±2 kg/m2, HbA1C 9.5±1.3) at the end of a 2-hour hyperglycemic clamp (220mg/dl) and correlated with previously measured changes in intracerebral glucose levels. Blunted rise in brain glucose levels was observed in OB and T2DM vs. HC individuals (p&amp;lt;0.05). Plasma long-chain non-esterified fatty acids (LCFA) including saturated (myristic acid, palmitic acid, stearic acid), monounsaturated (palmitoleic acid, oleic acid) and polyunsaturated (linoleic acid, an essential fatty acid) were different across all 3 groups (p&amp;lt;0.05). Moreover, these LCFAs negatively correlated with hyperglycemia-induced change in brain glucose levels (myristic r=-0.45; p=0.03, palmitic: r=-0.49, p=0.02; stearic r=-0.44, p=0.04; palmitoleic r=-0.49, p=0.02; oleic r=-0.49, p=0.02; linoleic r=-0.41, p=0.05). Our results demonstrate an inverse relationship between elevated LCFA levels and blunted brain glucose uptake in humans, which appears to be non-specific for NEFA composition. As the ability to transport glucose into the brain is crucial for energy homeostasis, these findings highlight a potential role for NEFAs to modulate brain glucose transport and metabolism and in turn cognitive function. Disclosure W. Lam: None. L. Jiang: None. G. Butrico: None. G. Cline: None. E. Sanchez Rangel: None. M. Hamza: None. L. Parikh: None. R. Belfort-DeAguiar: Research Support; Self; GlaxoSmithKline plc.. D.L. Rothman: None. G.F. Mason: Consultant; Self; UCB, Inc., Sumitomo Dainippon Pharma Co., Ltd. R. Sherwin: Other Relationship; Self; QuintilesIMS, MannKind Corporation. Research Support; Self; Regeneron Pharmaceuticals, Inc.. Other Relationship; Self; ICON plc.. J. Hwang: None.

Albumin binding-site alteration in melancholic depression under pharmacotherapy: Recording with the use of subnanosecond fluorescence spectroscopy

It is known that the conformation of human serum albumin binding sites is sensitive to pathological processes. In this work, changes in the physical–chemical properties of albumin binding sites in melancholic depression were studied. The K-35 fluorescent probe (dimethylaminonaphthalic acid N-carboxyphenylimide, CAPIDAN) was used as a reporter of these changes. It is shown that the fluorescence decay of K-35 depends on the state of the drug-binding sites of albumin. The kinetics of fluorescence decay were measured with a time resolution of approximately 30–50 ps. The parameters that characterize the fluorescence decay of K-35 in serum were reliably responsive to melancholic depression and the dynamics of its treatment. With melancholic depression, a decrease in the concentration of nonesterified long-chain fatty acids that are capable of affecting binding sites of serum albumin was observed. However, variations in the concentration of NEFA cannot be considered as a cause of the alterations of albumin binding sites. In addition to NEFA, other factors are likely to affect structural and physical-chemical properties of albumin in depression patients.

What Is Lipotoxicity?

Enlarged fat cells in obese adipose tissue diminish capacity to store fat and are resistant to the anti-lipolytic effect of insulin. Insulin resistance (IR)-associated S-nitrosylation of insulin-signaling proteins increases in obesity. In accordance with the inhibition of insulin-mediated anti-lipolytic action, plasma free fatty acid (FFA) levels increase. Additionally, endoplasmic reticulum stress stimuli induce lipolysis by activating cyclic adenosine monophosphate/Protein kinase A (cAMP/PKA) and extracellular signal-regulated kinase ½ (ERK1/2) signaling in adipocytes. Failure of packaging of excess lipid into lipid droplets causes chronic elevation of circulating fatty acids, which can reach to toxic levels within non-adipose tissues. Deleterious effects of lipid accumulation in non-adipose tissues are known as lipotoxicity. In fact, triglycerides may also serve a storage function for long-chain non-esterified fatty acids and their products such as ceramides and diacylglycerols (DAGs). Thus, excess DAG, ceramide and saturated fatty acids in obesity can induce chronic inflammation and have harmful effect on multiple organs and systems. In this context, chronic adipose tissue inflammation, mitochondrial dysfunction and IR have been discussed within the scope of lipotoxicity.

High Fat Diets Induce Colonic Epithelial Cell Stress and Inflammation that is Reversed by IL-22.

Prolonged high fat diets (HFD) induce low-grade chronic intestinal inflammation in mice, and diets high in saturated fat are a risk factor for the development of human inflammatory bowel diseases. We hypothesized that HFD-induced endoplasmic reticulum (ER)/oxidative stress occur in intestinal secretory goblet cells, triggering inflammatory signaling and reducing synthesis/secretion of proteins that form the protective mucus barrier. In cultured intestinal cells non-esterified long-chain saturated fatty acids directly increased oxidative/ER stress leading to protein misfolding. A prolonged HFD elevated the intestinal inflammatory cytokine signature, alongside compromised mucosal barrier integrity with a decrease in goblet cell differentiation and Muc2, a loss in the tight junction protein, claudin-1 and increased serum endotoxin levels. In Winnie mice, that develop spontaneous colitis, HFD-feeding increased ER stress, further compromised the mucosal barrier and increased the severity of colitis. In obese mice IL-22 reduced ER/oxidative stress and improved the integrity of the mucosal barrier, and reversed microbial changes associated with obesity with an increase in Akkermansia muciniphila. Consistent with epidemiological studies, our experiments suggest that HFDs are likely to impair intestinal barrier function, particularly in early life, which partially involves direct effects of free-fatty acids on intestinal cells, and this can be reversed by IL-22 therapy.

Long-chain fatty acid analogues suppress breast tumorigenesis and progression.

Obesity and type 2 diabetes (T2D) are associated with increased breast cancer incidence and mortality, whereas carbohydrate-restricted ketogenic diets ameliorate T2D and suppress breast cancer. These observations suggest an inherent efficacy of nonesterified long-chain fatty acids (LCFA) in suppressing T2D and breast tumorigenesis. In this study, we investigated novel antidiabetic MEDICA analogues consisting of methyl-substituted LCFA that are neither β-oxidized nor esterified to generate lipids, prompting interest in their potential efficacy as antitumor agents in the context of breast cancer. In the MMTV-PyMT oncomouse model of breast cancer, in which we confirmed that tumor growth could be suppressed by a carbohydrate-restricted ketogenic diet, MEDICA treatment suppressed tumor growth, and lung metastasis, promoting a differentiated phenotype while suppressing mesenchymal markers. In human breast cancer cells, MEDICA treatment attenuated signaling through the STAT3 and c-Src transduction pathways. Mechanistic investigations suggested that MEDICA suppressed c-Src-transforming activity by elevating reactive oxygen species production, resulting in c-Src oxidation and oligomerization. Our findings suggest that MEDICA analogues may offer therapeutic potential in breast cancer and overcome the poor compliance of patients to dietary carbohydrate restriction.

Acute regulation of 5′-AMP-activated protein kinase by long-chain fatty acid, glucose and insulin in rat primary adipocytes

Palmitate increased AMPK (5′-AMP-activated protein kinase) activity, glucose utilization and 2-DOG (2-deoxyglucose) transport in rat adipocytes. All three effects were blocked by the AMPK inhibitor Compound C, leading to the conclusion that in response to an increase in long-chain NEFA (non-esterified fatty acid) concentration AMPK mediated an enhancement of adipocyte glucose transport, thereby providing increased glycerol 3-phosphate for FA (fatty acid) esterification to TAG (triacylglycerol). Activation of AMPK in response to palmitate was not due to an increase in the adipocyte AMP:ATP ratio. Glucose decreased AMPK activity and effects of palmitate and glucose on AMPK activity were antagonistic. While insulin had no effect on basal AMPK activity insulin did decrease AMPK activity in the presence of palmitate and also decreased the percentage effectiveness of palmitate to increase the transport of 2-DOG. It is suggested that activation of adipocyte AMPK by NEFA, as well as decreasing the activity of hormone-sensitive lipase, could modulate adipose tissue dynamics by increasing FA esterification and, under certain circumstances, FA synthesis.

Effects of Fatty Acids on Human Serum Albumin Binding Centers

Albumin is a carrier of nonesterified long-chain fatty acids and many other ligands. The status of its binding centers was studied for various proportions of nonesterified long-chain fatty acids and albumin as exemplified by palmitic acid. The status of the binding center was tested by recording K-35 probe fluorescence decay in the subnanosecond band. This method showed the work of three types of centers. Palmitic acid enhanced binding activity of all centers, though to a different degree: if the palmitic acid/albumin proportion increased to 2-3, the probe binding to type 1 centers (located in the drug center I region) increased 1.5 times, while binding to type 3 centers increased more than 3-fold. Modification of these centers by nonesterified long-chain fatty acids was similar in the isolated human albumin preparation and in diluted blood serum. Hence, K-35 probe showed the actual status of various albumin centers, their binding capacity depending to a different measure on the fatty acid charge of albumin.

Role of metabolically generated reactive oxygen species for lipotoxicity in pancreatic β‐cells

Chronically elevated concentrations of non-esterified fatty acids (NEFAs) in type 2 diabetes may be involved in β-cell dysfunction and apoptosis. It has been shown that long-chain saturated NEFAs exhibit a strong cytotoxic effect upon insulin-producing cells, while short-chain as well as unsaturated NEFAs are well tolerated. Moreover, long-chain unsaturated NEFAs counteract the toxicity of palmitic acid. Reactive oxygen species (ROS) formation and gene expression analyses together with viability assays in different β-cell lines showed that the G-protein-coupled receptors 40 and 120 do not mediate lipotoxicity. This is independent from the role, which these receptors, specifically GPR40, play in the potentiation of glucose-induced insulin secretion by saturated and unsaturated long-chain NEFAs. Long-chain NEFAs are not only metabolized in the mitochondria but also in peroxisomes. In contrast to mitochondrial β-oxidation, the acyl-coenzyme A (CoA) oxidases in the peroxisomes form hydrogen peroxide and not reducing equivalents. As β-cells almost completely lack catalase, they are exceptionally vulnerable to hydrogen peroxide generated in peroxisomes. ROS generation in the respiratory chain is less important because overexpression of catalase and superoxide dismutase in the mitochondria do not provide protection. Thus, peroxisomally generated hydrogen peroxide is the likely ROS that causes pancreatic β-cell dysfunction and ultimately β-cell death.

Triglyceride Deposit Cardiomyovasculopathy

Triglyceride deposit cardiomyovasculopathy (TGCV) is a novel disease concept we found in Japanese cardiac transplant candidates in 2008. Probands carried mutations in the PNPLA2 gene encoding adipose triglyceride lipase (ATGL). ATGL is the major enzyme that catalyzes the initial rate-limiting step of intracellular triglyceride hydrolysis to release free nonesterified long-chain fatty acids (LCFAs), which is an essential energy source for the normal heart. Patients with TGCV show ectopic accumulation of triglycerides in cardiomyocytes and smooth muscle cells resulting from abnormal intracellular metabolism of triglycerides and LCFA. TGCV is classified into primary and idiopathic TGCV with and without genetic ATGL deficiency, respectively. Both types of TGCV patients suffer from severe heart failure, arrhythmia, and coronary artery disease caused by lipotoxicity and energy failure at cellular levels. The Japan TGCV study group provided the diagnostic guideline and has been trying to develop a nutritional therapeutics with medium-chain fatty acids in order to overcome this intractable disease one day earlier. In this chapter, we describe clinical signs and symptoms, laboratory findings, diagnosis, and possible therapies of TGCV.

Fatty acids decrease mitochondrial generation of reactive oxygen species at the reverse electron transport but increase it at the forward transport

Long-chain nonesterified (“free”) fatty acids (FFA) can affect the mitochondrial generation of reactive oxygen species (ROS) in two ways: (i) by depolarisation of the inner membrane due to the uncoupling effect and (ii) by partly blocking the respiratory chain. In the present work this dual effect was investigated in rat heart and liver mitochondria under conditions of forward and reverse electron transport. Under conditions of the forward electron transport, i.e. with pyruvate plus malate and with succinate (plus rotenone) as respiratory substrates, polyunsaturated fatty acid, arachidonic, and branched-chain saturated fatty acid, phytanic, increased ROS production in parallel with a partial inhibition of the electron transport in the respiratory chain, most likely at the level of complexes I and III. A linear correlation between stimulation of ROS production and inhibition of complex III was found for rat heart mitochondria. This effect on ROS production was further increased in glutathione-depleted mitochondria. Under conditions of the reverse electron transport, i.e. with succinate (without rotenone), unsaturated fatty acids, arachidonic and oleic, straight-chain saturated palmitic acid and branched-chain saturated phytanic acid strongly inhibited ROS production. This inhibition was partly abolished by the blocker of ATP/ADP transfer, carboxyatractyloside, thus indicating that this effect was related to uncoupling (protonophoric) action of fatty acids. It is concluded that in isolated rat heart and liver mitochondria functioning in the forward electron transport mode, unsaturated fatty acids and phytanic acid increase ROS generation by partly inhibiting the electron transport and, most likely, by changing membrane fluidity. Only under conditions of reverse electron transport, fatty acids decrease ROS generation due to their uncoupling action.

Alleviation of fatty acid and hypoxia-reoxygenation-induced proximal tubule deenergization by ADP/ATP carrier inhibition and glutamate

Kidney proximal tubules develop a severe but highly reversible energetic deficit due to nonesterified fatty acid (NEFA)-induced dissipation of mitochondrial membrane potential (DeltaPsi(m)) during reoxygenation after severe hypoxia. To assess the mechanism for this behavior, we have compared the efficacies of different NEFA for inducing mitochondrial deenergization in permeabilized tubules measured using safranin O uptake and studied the modification of NEFA-induced deenergization by inhibitors of the ADP/ATP carrier and glutamate using both normoxic tubules treated with exogenous NEFA and tubules deenergized during hypoxia-reoxygenation (H/R). Among the long-chain NEFA that accumulate during H/R of isolated tubules and ischemia-reperfusion of the kidney in vivo, oleate, linoleate, and arachidonate had strong effects to dissipate DeltaPsi(m) that were slightly greater than palmitate, while stearate was inactive at concentrations reached in the cells. This behavior correlates well with the protonophoric effects of each NEFA. Inhibition of the ADP/ATP carrier with either carboxyatractyloside or bongkrekic acid or addition of glutamate to compete for the aspartate/glutamate carrier improved DeltaPsi(m) in the presence of exogenous oleate and after H/R. Effects on the two carriers were additive and restored safranin O uptake to as much as 80% of normal under both conditions. The data strongly support NEFA cycling across the inner mitochondrial membrane using anion carriers as the main mechanism for NEFA-induced deenergization in this system and provide the first evidence for a contribution of this process to pathophysiological events that impact importantly on energetics of intact cells.

Real-time quantification of fatty acid uptake using a novel fluorescence assay

Uptake of nonesterified long-chain fatty acids (LCFAs) into many cell types and organs such as liver, heart, intestine, and skeletal muscle occurs primarily through a saturable, protein-mediated mechanism. Membrane proteins that increase the uptake of LCFAs, such as FAT/CD36 and fatty acid transport proteins, represent significant therapeutic targets for the treatment of metabolic disorders, including type 2 diabetes. However, currently available methods for the quantification of LCFA uptake neither allow for real-time measurements of uptake kinetics nor are ideally suited for the development of LCFA uptake inhibitors in high-throughput screens. To address both problems, we developed a LCFA uptake assay using a fluorescently labeled fatty acid and a nontoxic cell-impermeable quenching agent that allows fatty acid transport to be measured in real time using fluorescence plate readers or standard fluorescence microscopy. With this assay, we faithfully reproduced known differentiation- and hormone-induced changes in LCFA uptake by 3T3-L1 cells and determined LCFA uptake kinetics with previously unobtainable temporal resolution. Applications of this novel assay should facilitate new insights into the biology of fatty acid uptake and provide new means for obesity-related drug discovery.

Uncoupling Effect of Fatty Acids in Halo- and Alkalotolerant Bacterium Bacillus pseudofirmus FTU

Natural uncouplers of oxidative phosphorylation, long-chain non-esterified fatty acids, cause uncoupling in the alkalo- and halotolerant bacterium Bacillus pseudofirmus FTU. The uncoupling effect in the bacterial cells was manifested as decrease of membrane potential and increase of respiratory activity. The membrane potential decrease was detected only in bacterial cells exhausted by their endogenous substrates. In proteoliposomes containing reconstituted bacterial cytochrome c oxidase, fatty acids caused a "mild" uncoupling effect by reducing membrane potential only at low rate of membrane potential generation. "Free respiration" induced by the "mild" uncouplers, the fatty acids, can be considered as possible mechanism responsible for adaptation of the bacteria to a constantly changed environment.

Direct effects of long-chain non-esterified fatty acids on vascular cells and their relevance to macrovascular complications of diabetes.

Diabetes leads to a marked increase in cardiovascular disease caused by atherosclerosis. Cardiovascular complications of diabetes are associated with lipid abnormalities, mainly manifested as elevated levels of triglycerides. Hydrolysis of triglycerides by lipases in the arterial wall is believed to cause increased levels of non-esterified fatty acids (NEFAs) in lesions of atherosclerosis. Recent research has shown that long-chain NEFAs have a multitude of direct effects on cell types involved in atherogenesis. Thus, some of the most common long-chained fatty acids present in triglycerides, oleic acid and linoleic acid, have been shown to induce adhesion molecule expression, cytokine expression and apoptosis in endothelial cells, to increase cholesterol uptake and reduce cholesterol efflux in macrophages, and to increase arterial smooth muscle cell proliferation and migration. Certain NEFAs liberated from triglycerides may therefore play an important role in accelerating atherosclerosis caused by diabetes by directly affecting the key cell types involved in atherogenesis.

Phytanic Acid Toxicity: Implications for the Permeability of the Inner Mitochondrial Membrane to Ions

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid), a degradation product of chlorophyll formed in the intestinal tracts of ruminants, is a constituent of milk products and meat. Because it is a branched-chain fatty acid, degradation of phytanic acid is initiated in mammalian peroxisomes. In certain peroxisomal disorders such as in Refsum disease, phytanic acid accumulates dramatically throughout the body to levels that are believed to be associated with neurological and cardiac abnormalities. Here it is shown that nonesterified phytanic acid alters the permeability of the inner mitochondrial membrane by (1) increasing the conductance to hydrogen H+; (2) promoting opening of the permeability transition pore; and (3) initiating the release of endogenous Mg++. But contrary to nonesterified long-chain fatty acids, phytanic acid only slightly stimulates the conductance of the inner membrane to K+ and Cl−. These results suggest that pathologically high tissue levels of nonesterified phytanic acid increase the permeability of the inner membrane by ions through activities that are harmful for the synthesis of mitochondrial adenosine 5′-triphosphate as well as for mitochondrial integrity.