Free fatty acid and triglyceride content of Mycobacterium avium cultured under different growth conditions

Previous investigations demonstrated that Mycobacterium avium has a requirement for fatty acid, which can be fulfilled by palmitic (C16:0) or oleic (C18:1) acids, and that it incorporates the fatty acid into triglycerides that are later utilized. Mycobacterium avium was grown in continuous culture or batch-cultured in medium that contained palmitic acid as the fatty acid source, but lacked albumin. Cells were extracted and free fatty acids and triglycerides were obtained by preparative thin-layer chromatography. The triglycerides were further purified by column chromatography. The free fatty acids were methylated and analyzed by gas chromatography. Oleic acid represented 40 to 64% of the total free fatty acids, except for cells batch-cultured and limited for nitrogen. The latter cells contained about 27% oleic acid, and 24% of the free fatty acids were of sizes greater than C24:0. The amount of palmitic acid varied considerably, but it and oleic acid together usually accounted for 70% of the total free fatty acids. The overall fatty acid content of the triglycerides was similar to that of the free fatty acids. However, two size classes of triglycerides were found that approximated the sizes of tristearin (C54) and tricaprylin (C24), molecular weights of 892 and 471 daltons, respectively. It is concluded that these types of studies may eventually lead to more accurate identification of pathogenic mycobacteria by means of gas chromatographic analyses.     

Metabolic effects of dietary stearic acid in mice: changes in the fatty acid composition of triglycerides and phospholipids in various tissues.

The fatty acid patterns of triglycerides and phospholipids extracted from adipose tissue, liver, heart, kidney, spleen, and lung of 3 groups of C57BL/6 mice were determined after feeding diets rich in palmitic acid (16:0) (high palmitic: 16:0 = 45.1% of total fatty acids), stearic acid (18:0) (high stearic: 18:0 = 42.9% of total fatty acids) and oleic acid (18:1) (high oleic: 18:1 = 79.7% of total fatty acids) for 9 months. Triglyceride content of adipose, liver, heart, kidney, lung and spleen tissues was significantly enriched in palmitic acid in mice fed the high palmitic diet (range among all tissues: 19.9% +/- 0.2% to 29.0% +/- 1.9% of total fatty acids) and in oleic acid in mice fed the high oleic diet (range 56.0% +/- 1.9% to 71.6% +/- 1.2%). The stearic acid content of organ triglycerides in mice fed the high stearic diet ranged from 3.7% +/- 0.3% to 10.8% +/- 1.2%; however, the content of oleic acid on this diet (range: 57.0% +/- 1.8% to 71.4% +/- 1.7%) was similar to the one observed in mice fed the high oleic diet. In all organs, phospholipids had a significantly higher percentage of stearic acid (range: 23.5% +/- 0.9% to 51.5% +/- 6.6%) than triglycerides, regardless of diet. To evaluate the production of oleate from stearate and palmitate, 2 groups of mice were fed the high palmitic and the high stearic diets for 1 week and then injected intravenously with [1-14C]palmitate and [1-14C]stearate and the amount of labelled oleate in liver triglycerides was measured.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequential changes in lipid metabolism and the fatty acid profile in liver lipids during fasting and sepsis

The sequential changes in lipid metabolism and in the fatty acid profile of liver lipids during fasting and sepsis were studied. Liver and blood specimens were taken from normally fed rats and from nonseptically and septically fasted rats at 5, 24, and 48 hr. Sepsis was induced by injecting live Escherichia coli bacteria intraperitoneally. Sepsis attenuated the fasting-induced increase in beta-hydroxybutyrate and reduced liver and serum triglycerides at 5 hr. There was a percentage decline in the most abundant fatty acids in neutral lipids, namely oleic (18:1w9) and linoleic (18:2w6) acids. This was seen throughout fasting and septic fasting. These results indicate that 18:1w9 and 18:2w6 are used as energy substrates and are oxidized to beta-hydroxybutyrate during fasting and mainly to carbon dioxide during septic fasting. On the contrary, the most abundant fatty acids in phospholipids, stearic (18:0), arachidonic (20:4w6), and docosahexaenoic (22:6w3) acids, accumulated in neutral lipids and in phospholipids throughout fasting. However, during sepsis this accumulation was reduced in neutral lipids and reversed to a level below that in the fed and fasted state in phospholipids. These results indicate that a disturbance in membrane integrity and function induced by septic fasting may have pathophysiological consequences for lipid metabolism and liver function during sepsis.     

Effect of dietary elaidic versus vaccenic acid on blood and liver lipids in the hamster.

Male hamsters (30 per group) were fed five different semi-purified diets ad libitum. The diets, containing 30% of energy (en%) as fat, differed in their dietary fat composition (specified fatty acids exchanged at 10 en%) and were fed for 4 weeks. The five fatty acids compared in mixed triglycerides were elaidic acid (C18:1 9t), vaccenic acid (C18:1 11t), their cis-counterpart oleic acid (C18:1 9c), medium-chain fatty acids (MCFA; C8:0 and C10:0), and palmitic acid (C16:0). Compared with oleic acid, dietary MCFA and palmitic acid tended to increase blood cholesterol levels in the hamsters. The effect of elaidic and vaccenic acid on blood cholesterol did not differ from that of oleic acid. When elaidic acid and vaccenic acids were compared directly, the ratio of LDL/HDL-cholesterol in plasma was significantly higher in hamsters fed vaccenic acid than in those fed elaidic acid, and elaidic acid was incorporated at low levels, but more efficiently than vaccenic acid at the sn-2 position of platelet phospholipids. Biological consequences of this low incorporation are considered unlikely as levels of arachidonic acid (C20:4 n-6) and docosohexaenoic acid (C22:6 n-3) in the platelet phospholipids of all dietary groups did not differ. With respect to the effect on the LDL/HDL-cholesterol ratio, elaidic acid may be preferable to vaccenic acid. We conclude that this animal study does not provide evidence for the suggestion, based on epidemiological observations, that elaidic acid would be more detrimental to cardiovascular risk than vaccenic acid.     

Rapid changes in serum, plasma and erythrocyte lipid compositions, and serum transaminase levels during continuous enteral hyperalimentation by carbohydrates alone

Twelve normal men received twice their estimated basal energy requirement by a carbohydrate solution via a nasogastric catheter during 48 hours, followed by a seven-hour fast. Subsequently, in nine of them 0.5 mg epinephrine was given subcutaneously under ongoing fasting. During hyperalimentation, serum triglycerides, phospholipids, total and free cholesterol, phospholipids/free cholesterol ratio, and plasma free fatty acids decreased, whereas the percentage of free cholesterol increased. During fasting and subsequent epinephrine administration triglycerides and free fatty acids rose without reaching basal levels. Plasma and red blood cell (RBC) fatty acid composition already changed from two hours after the start of the feeding. Most markedly, a steady decrease in RBC 18:2c, omega 6, amounting to more than 17% of the basal value at the end of the observation period was found. Neither in plasma, nor in RBC a concomitant appearance of 20:3c, omega 9 was seen. In RBC, the relative amounts of the saturated fatty acids increased, whereas those of monounsaturated and polyunsaturated fatty acids decreased. RBC content of total fatty acids decreased and that of cholesterol increased. The ratios 16:1c, omega 7/16:0 and 18:3c, omega 6/18:2c, omega 6 in plasma, and 20:3c, omega 6/18:2c, omega 6 in plasma and RBC increased, whereas those of 18:1c, omega 7/16:1c, omega 7 and 20:3c, omega 6/18:3c, omega 6 in plasma decreased. After 48 hours feeding serum glutamic pyruvic transaminase and glutamic oxaloacetic transaminase levels were moderately increased and rose further during fasting. Thus, continuous enteral hyperalimentation by carbohydrates alone rapidly induces profound changes in serum-, plasma-, and RBC lipid compositions and serum parameters of hepatic function.(ABSTRACT TRUNCATED AT 250 WORDS)     

Association of fatty acid profile in plasma lipid fractions with HbA1c in type 2 diabetic patients

The aim of this pilot study has been the comparison of fatty acid profiles of diabetic and healthy subjects in order to evaluate the relationship between fatty acid profiles in plasma lipid fractions and glycated haemoglobin (HbA1c) in type 2 diabetes (T2D) patients. The fatty acid composition of fasting plasma lipid subfractions has been analyzed in patients (n?=?26) diagnosed with T2D and in corresponding control group (n?=?26) of healthy voluntary blood donors. Five subfractions containing phospholipids (PLs), diglycerides (DGs), free fatty acids (FFAs), triglycerides (TGs), and cholesterol esters (CEs) were isolated from plasma samples and separated by thin-layer chromatography. Fatty acid composition of these subfractions was analyzed by GC/FID. Significant changes in fatty acid profiles were found in all lipid fractions from T2D patients in comparison with the control group. HbA1c correlated negatively with delta 9 desaturation (9D) index. Significantly positive correlation of palmitic acid levels and negative correlation of oleic acid levels with HbA1c concentration were found in PL and TG fractions with higher significance in TGs. This pilot study has shown possible associations of HbA1c, common parameter measured in routine laboratories, with lipid metabolism. The strongest correlation was found in plasma TGs, especially in case of palmitic and oleic acids. This is the first report showing that metabolic control assessed by HbA1c is negatively associated with delta 9D index.     

Fatty acid composition of adipose tissue in patients with chronic liver disease

In this study plasma free fatty acids and adipose tissue fatty acid composition in 10 cirrhotic patients, 5 patients with non-cirrhotic chronic liver disease and in 5 controls have been investigated. Fatty acid composition of adipose tissue in cirrhotic patients demonstrated a significant increase of 16:1 and a decrease of 18:2. Monounsaturated fatty acids represented the major fraction both in cirrhotic patients (57.5%) and in controls (55.2%). Polyunsaturated fatty acids were significantly lower in cirrhotic patients (9.1%) than in controls (14.3%). In plasma, total free fatty acids were higher in cirrhotics (732 +/- 111 microM) than in controls (319 +/- 38 microM; mean +/- SE) and the individual fatty acid profile showed a prevalence of monounsaturated fatty acid (increase of 16:1 and 18:1 and decrease of 16:0 and 18:0). The decrease in polyunsaturated fatty acids in the composition of adipose tissue triglycerides could represent a marker of long-term reduction in lipid absorption, intake and/or enhanced lipid consumption. The resemblance between plasma and adipose tissue pattern in cirrhotic patients supports the hypothesis that increased lipolysis in such patients plays the most important role in influencing plasma free fatty acid composition.     

Selective mobilisation of fatty acids from human adipose tissue

Background: Adipose tissue is a storage organ for dietary fat. During fasting, fatty acids are released into serum as free fatty acids (FFA). Experimental studies indicate that fatty acids are selectively mobilised from adipose tissue into serum. The aim of this study was to investigate whether the composition of the serum FFA fraction reflects selective mobilisation in the fasting state in humans. Methods: The fatty acid composition of fasting serum FFA and adipose tissue were analysed from 112 patients with myocardial infarction and 107 healthy control subjects using gas-liquid chromatography. The subjects' habitual diet was analysed using a food-frequency questionnaire. Results: Significant correlations were found between serum FFA and adipose tissue, particularly for the percentage content of linoleic acid (r=0.73), eicosapentaenoic acid (r=0.68), alpha-linolenic acid (r=0.67) and palmitoleic acid (r=0.60). Percentage contents of palmitic, stearic, linoleic, alpha-linolenic, eicosapentaenoic and docosahexaenoic acid were higher in serum FFA than in adipose tissue, whereas oleic and palmitoleic acid were relatively more abundant in adipose tissue. This may indicate that the former group of fatty acids is preferentially mobilised from adipose tissue into serum. High correlations for polyunsaturated fatty acids were observed between percentage contents of dietary and adipose tissue fatty acids. The correlation of fatty acids between diet and serum FFA was weak, but a tendency towards higher correlations for polyunsaturated fatty acids was observed. Conclusions: Our findings are compatible with the hypothesis that, in the fasting state, fatty acids are selectively mobilised from adipose tissue into serum FFA.     

Changes in plasma free fatty acid concentrations in rheumatoid arthritis patients during fasting and their effects upon T-lymphocyte proliferation.

OBJECTIVE: To measure whether changes in the concentrations of circulating free fatty acids (FFAs) after a 7 day fast in rheumatoid arthritis (RA) patients would inhibit in vitro T-lymphocyte proliferation. METHODS: The concentration and composition of plasma FFAs were measured in nine RA patients at the conclusion of a 7 day fast. A FFA mixture was made up based on these findings (20% linoleic, 43% oleic, 10% stearic, 27% palmitic acid). Mitogen-induced lymphocyte proliferative responses were measured after co-culture of peripheral blood mononuclear cells (PBMC) from healthy individuals in the presence of increasing concentrations of this FFA mixture (from 0 to 2000 microM) and in the presence of FFA mixtures where the relative proportions of fatty acids varied. RESULTS: Both the concentration of the FFA mixture and the ratio between the unsaturated and saturated fatty acids significantly influenced in vitro lymphocyte proliferation (P<0.0001). Unexpectedly, the highest concentrations of the FFA mixture increased lymphocyte proliferation. At equimolar concentrations (600 microM), manipulating the amounts of oleic and linoleic fatty acids relative to stearic and palmitic fatty acids had a potent inhibitory effect upon lymphocyte proliferation. CONCLUSION: Fasting-associated increases in total plasma FFA concentrations do not inhibit, but rather enhance, in vitro lymphocyte proliferation. An inhibitory effect could only be achieved by manipulating the balance between the unsaturated and saturated fatty acids.     

Endogenous red blood cell membrane fatty acids and sudden cardiac arrest

Little is known of the associations of endogenous fatty acids with sudden cardiac arrest (SCA). We investigated the associations of SCA with red blood cell membrane fatty acids that are end products of de novo fatty acid synthesis: myristic acid (14:0), palmitic acid (16:0), palmitoleic acid (16:1 n7), vaccenic acid (18:1 n7), stearic acid (18:0), oleic acid (18:1 n9), and a related fatty acid, cis-7 hexadecenoic acid (16:1 n9). We used data from a population-based case-control study where cases, aged 25 to 74 years, were out-of-hospital SCA patients attended by paramedics in Seattle, WA (n = 265). Controls, matched to cases by age, sex, and calendar year, were randomly identified from the community (n = 415). All participants were free of prior clinically diagnosed heart disease. We observed associations of higher red blood cell membrane levels of 16:0, 16:1n-7, 18:1n-7, and 16:1n-9 with higher risk of SCA. In analyses adjusted for traditional SCA risk factors and trans- and n-3 fatty acids, a 1-SD-higher level of 16:0 was associated with 38% higher risk of SCA (odds ratio, 1.38; 95% confidence interval, 1.12-1.70) and a 1-SD-higher level of 16:1n-9 with 88% higher risk (odds ratio, 1.88; 95% confidence interval, 1.27-2.78). Several fatty acids that are end products of fatty acid synthesis are associated with SCA risk. Further work is needed to investigate if conditions that favor de novo fatty acid synthesis, such as high-carbohydrate/low-fat diets, might also increase the risk of SCA.     

Contrasting effects of low or high copper intake on rat tissue lipid essential fatty acid composition

The effects of low copper intake or copper supplementation on the metabolism of stearic acid have been studied previously, but their effects on essential fatty acids have not been reported. Male Sprague-Dawley rats were fed for 12 weeks on pelleted semi-synthetic diets containing less than 1 mg/kg copper (low copper), 6 mg/kg (copper control), or 250 mg/kg copper (copper supplemented). The fatty acid composition of the total phopholipids and triglycerides of plasma, liver, heart and adipose tissue was analyzed by gas liquid chromatography. In low copper rats compared to controls, palmitic and oleic acids were decreased but stearic acid and docosahexaenoic acid were increased in plasma, liver and heart phopholipids. Arachidonic acid was also increased in plasma and liver phospholipids in low copper rats. In liver triglycerides, linoleic and arachidonic acids were increased but palmitic and oleic acid were decreased in low copper rats. Copper supplementation had the opposite effect; palmitic and oleic acids were increased in phospholipids and triglycerides whereas essential fatty acids were generally decreased. Hence, copper not only has a direct effect on the desaturation of stearic acid but also has significant effects on the tissue lipid composition of essential fatty acids.     

Interaction of glucose and long chain fatty acids (C18) on antioxidant defences and free radical damage in porcine vascular smooth muscle cells in vitro

AIMS/HYPOTHESIS: Abnormalities of glucose and fatty acid metabolism in diabetes are believed to contribute to the development of oxidative stress and the long term vascular complications of the disease; therefore the interactions of glucose and long chain fatty acids on free radical damage and endogenous antioxidant defences were investigated in vascular smooth muscle cells. METHODS: Porcine vascular smooth muscle cells were cultured in 5 mmol/l or 25 mmol/l glucose for 10 days. Fatty acids, stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and alpha-linolenic acid (18:3) were added with defatted bovine serum albumin as a carrier for the final three days. RESULTS: Glucose (25 mmol/l) alone caused oxidative stress in the cells as evidenced by free radical-mediated damage to DNA, lipids, and proteins. The addition of fatty acids (0.2 mmol/l) altered the profile of free radical damage; the response was J-shaped with respect to the degree of unsaturation of each acid, and oleic acid was associated with least damage. At a lower concentration alpha-linolenic acid (0.01 mmol/l) was markedly different in that, when added to 25 mmol/l glucose it resulted in a decrease in free radical damage to DNA, lipids and proteins. This was accompanied by a marked increase in antioxidant and glutathione concentrations as well as by increased gene expression is of gamma-glutamylcysteine synthetase, the rate-limiting enzyme in glutathione synthesis. CONCLUSIONS/INTERPRETATION: The results clearly show that glucose and fatty acids interact in the production of oxidative stress in vascular smooth muscle cells.     

Long-chain fatty acids activate calcium channels in ventricular myocytes.

Nonesterified fatty acids accumulate at sites of tissue injury and necrosis. In cardiac tissue the concentrations of oleic acid, arachidonic acid, leukotrienes, and other fatty acids increase greatly during ischemia due to receptor or nonreceptor-mediated activation of phospholipases and/or diminished reacylation. In ischemic myocardium, the time course of increase in fatty acids and tissue calcium closely parallels irreversible cardiac damage. We postulated that fatty acids released from membrane phospholipids may be involved in the increase of intracellular calcium. We report here that low concentrations (3-30 microM) of each long-chain unsaturated (oleic, linoleic, linolenic, and arachidonic) and saturated (palmitic, stearic, and arachidic) fatty acid tested induced multifold increases in voltage-dependent calcium currents (ICa) in cardiac myocytes. In contrast, neither short-chain fatty acids (less than 12 carbons) or fatty acid esters (oleic and palmitic methyl esters) had any effect on ICa, indicating that activation of calcium channels depended on chain length and required a free carboxyl group. Inhibition of protein kinases C and A, G proteins, eicosanoid production, or nonenzymatic oxidation did not block the fatty acid-induced increase in ICa. Thus, long-chain fatty acids appear to directly activate ICa, possibly by acting at some lipid sites near the channels or directly on the channel protein itself. We suggest that the combined effects of fatty acids released during ischemia on ICa may contribute to ischemia-induced pathogenic events on the heart that involve calcium, such as arrhythmias, conduction disturbances, and myocardial damage due to cytotoxic calcium overload.     

Differential effect of oleic and palmitic acid on lipid accumulation and apoptosis in cultured hepatocytes

Background and Aim:  Studies have shown monounsaturated oleic acid to be less toxic than palmitic acid and to prevent/attenuate palmitic acid hepatocites toxicity in steatosis models in vitro . However, to what degree these effects are mediated by steatosis extent is unknown.
Methods:  We evaluated whether steatosis per se is associated with hepatocytes apoptosis and determined the role of oleic and palmitic acid, the most abundant fatty acids in western diets, on triglyceride accumulation and apoptosis in an in vitro model of steatosis induced in three hepatocytic cell lines (HepG2, HuH7, WRL68). The impact of incubation for 24 h with oleic (0.66 and 1.32 mM) and palmitic acid (0.33 and 0.66 mM), alone or combined (molar ratio 2 : 1) on steatosis, apoptosis, and insulin signalling, was evaluated.
Results:  Concurrent with PPARγ and SREBP-1 gene activation, steatosis extent was larger when cells were treated with oleic than with palmitic acid; the latter fatty acid was associated with increased PPARα expression. Cell apoptosis was inversely proportional to steatosis deposition. Moreover, palmitic, but not oleic acid, impaired insulin signalling. Despite the higher amount of fat resulting from incubation of the two fatty acids combined, the apoptosis rate and impaired insulin signalling were lower than in cells treated with palmitic acid alone, indicating a protective effect of oleic acid.
Conclusions:  Oleic acid is more steatogenic but less apoptotic than palmitic acid in hepatocityc cell cultures. These data may provide a biological basis for clinical findings on dietary patterns and pathogenetic models of nonalcoholic fatty liver disease.     

Effect of fatty acids on rat liver nuclear T3-receptor binding.

The effects of selected fatty acids (linoleic, oleic, and palmitic) on triiodothyronine (T3)-receptor binding were compared in isolated rat hepatocytes, rat liver nuclei, and receptor protein. Scatchard analysis indicated that the inhibition of T3-receptor binding by fatty acids was characterized by an increase in Kd and no change in maximum binding capacity (MBC). In isolated receptors, the rank order of potency for inhibition was linoleic acid greater than oleic acid greater than palmitic acid. The Ki for oleic acid in isolated receptors was the same as that for whole nuclei (15.4 +/- 1.3 v 16.3 +/- 1.9 mumol/L, respectively), indicating that the inhibition of nuclear T3 binding is probably at the level of the receptor protein itself. In isolated hepatocytes, linoleic acid was more potent than oleic acid in inhibiting T3 binding to nuclear receptors. Cell-associated T3 was not affected by the presence of fatty acids, implying that cellular uptake of T3 was not inhibited. High concentrations of fatty acids were necessary for inhibition of T3-receptor binding in isolated hepatocytes, with linoleic acid being one to two orders of magnitude less potent in isolated hepatocytes compared with isolated receptors (Ki, 179 +/- 12 v 4.4 +/- 0.5 mumol/L, respectively). It is concluded that the inhibitory effect of fatty acids on T3-receptor binding in isolated rat hepatocytes probably occurs at the level of the nuclear receptor, and does not involve an inhibition of the access of T3 to the receptor. However, in vivo it seems unlikely that fatty acids will have access to the nuclear receptors in sufficiently high concentrations to affect T3-receptor binding in liver cells.     

Fatty acid composition of erythrocyte membrane lipid obtained from children suffering from kwashiorkor and marasmus

The fatty acid composition of erythrocyte membrane (EM) lipids obtained from normal, kwashiorkor, and marasmic children was analyzed by gas chromatography. The proportion of palmitic acid (16:0) was lower and of oleic acid (18:1) higher in the kwashiorkor group than in the control group. The marasmic group showed lower proportions of eicosatrienoic acid (20:3) and arachidonic acid (20:4) and a higher proportion of oleic acid (18:1) than the control group. A significant difference was found between the marasmic and kwashiorkor groups with respect to arachidonic acid (20:4), which showed a lower proportion in the former group than the latter. The ratio of arachidonic acid to linoleic acid (20:4/18:2) was markedly lower in the marasmic group than the control group, suggesting a possible impairment in the conversion of linoleic acid to arachidonic acid in marasmic children. The ratio of unsaturated fatty acids to saturated fatty acids was markedly elevated in the kwashiorkor group over that of control group, indicating increased fluidity of EM in kwashiorkor. It is suggested that the altered membrane fatty acid composition reflects deranged lipid metabolism and affects the physical and physiological properties of EM and could contribute to changes in the activities of several red blood cell membrane-bound enzymes reported earlier in kwashiorkor children.     

Changes in the Fatty Acid Profile of Plasma and Adipose Tissue in Rats after Long-Term Ethanol Feeding

The effect of chronic ethanol feeding on the fatty acid composition of plasma and abdominal adipose tissue in rats was studied. Animals were maintained on a 30% ethanol solution in drinking water for 3 and 5 months. Control rats were given water. Caloric intake was similar in control and ethanol-fed rats at the end of the experimental period. However, a decrease in body weight was observed in rats that had consumed ethanol. Palmitoleic (16:1n7) and oleic (18:1n9) acids increased markedly, and linoleic acid (18:2n6) decreased in the plasma and in the adipose tissue of ethanol-fed rats with respect to control rats. After 3 months of ethanol ingestion, long-chain polyunsaturated fatty acids were reduced both in plasma and adipose tissue. When ethanol was administered for 5 months, only plasma long-chain polyunsaturated fatty acids of the n-3 series were decreased. This suggest that changes induced by ethanol ingestion in essential fatty acid metabolism is less pronounced when ethanol feeding is maintained for a long period of time.     

Glucose and insulin suppression of plasma free fatty acids in obese subjects with normal glucose tolerance or mild, newly diagnosed type 2 (non-insulin-dependent) diabetes

The in vivo suppressive effect of glucose and insulin on plasma free fatty acid concentrations was investigated in obese subjects with (n = 6) and without (n = 6) Type 2 (non-insulin-dependent) diabetes mellitus during a 4h-hyperglycemic glucose clamp (about 11.2 mmol/l). Somatostatin was infused (250 micrograms/h) during the third h of glucose clamp to inhibit glucose-stimulated insulin secretion. Plasma insulin values were similar in the two groups at fasting and all throughout the study (F = 0.04; p = NS, two way analysis of variance), while the amount of glucose metabolized during the clamp was lower in diabetic subjects. Plasma free fatty acid concentrations, which were similar in the two groups at fasting, decreased during hyperglycemia and glucose-induced hyperinsulinemia (0-120 min; 180-240 min), and rose during hyperglycemia and somatostatin-inhibited insulin secretion (120-180 min). However, plasma free fatty acid concentrations were significantly higher in diabetic subjects all along the study period both in absolute terms (F = 11.4; p less than 0.0001) and when individual data were recalculated as percent of fasting value (F = 13.3; p less than 0.0001). Our data suggest that suppressibility of fasting plasma free fatty acids is lower in obese Type 2 diabetes in comparison with obese non-diabetic subjects.     

Myocardial utilization of carbohydrate and lipids

Fatty acids represent a very important, if not the most important, substrate for myocardial energy metabolism. The heart derives fatty acids from circulating FFA bound to albumin and from plasma triglycerides. The rate of extraction of albumin bound FFA depends upon the albumin: FFA molar ratio and the metabolic state of the tissue. Since the albumin concentration in vivo is fairly constant, the albumin: fatty acid ratio is determined by the concentration of fatty acids in the serum. The fatty acid concentration is in turn regulated by dietary intake, de novo synthesis in the liver and adipose tissue, and the rate of fatty acid mobilization from adipose tissue. Mobilization from adipose tissue is increased during states of substrate deficiency such as fasting, diabetes or during the postabsorptive state and is decreased during periods of substrate excess. The rate of myocardial utilization of circulating triglycerides depends on the concentration of triglycerides and on the activity of lipoprotein lipases. The activity of these enzymes is under hormonal control and is increased by fasting or diabetes and is decreased by refeeding.     

The biomechanical integrity of bone in experimental diabetes

The effects of long-term exposure of a pancreatic beta cell line, INS-1, to major free fatty acids (FFA; palmitic acid, oleic acid and linoleic acid) and leptin on insulin secretion and cell viability by C,N-diphenyl-N'-4,5 dimethylthiazol 2-yl tetrazolium bromide (MTT) assay were examined. The cells were incubated with 1 mmol/l of each FFA and 25 or 100 ng/ml leptin, alone or in combination, for 4, 24 or 48 h before the insulin secretion experiments. Palmitic acid (C 16:0) significantly suppressed cell viability, and suppressed insulin secretion at 24 h. Treatment with oleic acid (C 18:1) or linoleic acid (C 18:2) enhanced basal insulin secretion and diminished glucose-stimulated insulin secretion (GSIS) at 48 h. In these groups, there were no differences in cell viability as compared to cells treated without FFA. Leptin did not affect insulin secretion at 4, 24 and 48 h, and in the cells co-treated with FFA and leptin, leptin did not ameliorate lipotoxicity. These results suggest that, in INS-1 cells, different FFA have different patterns of lipotoxicity with chronic exposure, and leptin has little direct effect on insulin secretion.