The level and species of plasma non-esterified fatty acids are not related to elevated plasma apolipoprotein B levels in familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL), the leading cause of familial hyperlipidemia with premature coronary artery disease, has been associated with insulin resistance and elevated plasma levels of apolipoproten B (apoB) and non-esterified fatty acids (NEFA). Becaus dietary fats affect plasma cholesterol levels, and specific saturated fatty acids (FA) are particularly potent stimulators in vitro of apoB secretio from hepatocytes, we hypothesized that FCHL patients would exhibit elevations in plasma levels of total FA or specific saturated species. Five families containing 12 FCHL subjects (5 adults, 7 children and 8 normals (5 adults, 3 children) were assessed by dietary, anthropometric, and plasma measurements (glucose, insulin, lipoproteins, total NEFA, and specific FA types). After adjustment of the data for age, gender, and family affiliation, multivariate ANOVA indicated that FCHL was significantly associated with elevated plasma levels of apoB (p = 0.001) and insulin (p< 0.001) and increased body weight (p=0.043). Nevertheless, dietary intakes of total and saturated fat were comparable in the two groups, as were plasma levels of total NEFA and the major saturated species. In a study population possessing the salient features of FCHL, circulating total NEFA were not elevated, nor were specific saturated NEFA that had been associated with apoB oversecretion in vitro. Despite the speculated link between plasma FA and apoB overproduction in FCHL, our data suggest that other metabolic factors underlie this disease.

Compared with saturated fatty acids, dietary monounsaturated fatty acids and carbohydrates increase atherosclerosis and VLDL cholesterol levels in LDL receptor-deficient, but not apolipoprotein E-deficient, mice

Heart-healthy dietary recommendations include decreasing the intake of saturated fatty acids (SFA). However, the relative benefit of replacing SFA with monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), or carbohydrates (CARB) is still being debated. We have used two mouse models of atherosclerosis, low density lipoprotein receptor-deficient (LDLRKO) and apolipoprotein E-deficient (apoEKO) mice to measure the effects of four isocaloric diets enriched with either SFA, MUFA, PUFA, or CARB on atherosclerotic lesion area and lipoprotein levels. In LDLRKO mice, compared with the SFA diet, the MUFA and CARB diets significantly increased atherosclerosis in both sexes, but the PUFA diet had no effect. The MUFA and CARB diets also increased very low density lipoprotein-cholesterol (VLDL-C) and LDL-cholesterol (LDL-C) in males and VLDL-C levels in females. Analysis of data from LDLRKO mice on all diets showed that atherosclerotic lesion area correlated positively with VLDL-C levels (males: r = 0.47, P < 0.005; females: r = 0.52, P < 0.001). In contrast, in apoEKO mice there were no significant dietary effects on atherosclerosis in either sex. Compared with the SFA diet, the CARB diet significantly decreased VLDL-C in males and the MUFA, PUFA, and CARB diets decreased VLDL-C and the CARB diet decreased LDL-C in females. In summary, in LDLRKO mice the replacement of dietary SFA by either MUFA or CARB causes a proportionate increase in both atherosclerotic lesion area and VLDL-C. There were no significant dietary effects on atherosclerotic lesion area in apoEKO mice. These results are surprising and suggest that, depending on the underlying genotype, dietary MUFA and CARB can actually increase atherosclerosis susceptibility, probably by raising VLDL-C levels through a non-LDL receptor, apoE-dependent pathway.

Fatty acid analysis of transplanted adipose tissue

OBJECTIVE

To determine whether autologously transferred human adipose tissue maintains viability in vivo for prolonged periods.

DESIGN

Six healthy female patients (mean age, 61.5 years; mean body mass index, 23.4 kg/m2) received autologous fat transplants from the gluteus to the nasolabial folds. Subcutaneous fat was sampled from facial and gluteal sites 4 times in 1 year.

SETTING

Private practice, basic science research center.

INTERVENTION

After local anesthesia, 10 g of subcutaneous adipose tissue was harvested from the right buttock of each patient. Ten milligrams of adipose tissue was aspirated from the right nasolabial fold. Five grams of gluteal fat was then injected into each nasolabial fold using a uniform monolayer threading technique with no overcorrection. As controls, 10 mg of adipose tissue was obtained from the opposite left buttock and left cheek. Adipose tissue from the transplanted and control facial and gluteal sites was sampled at 4, 6, and 12 months after transplantation.

MAIN OUTCOME MEASUREMENTS

Gluteal fat has more monounsaturated fatty acids and less saturated fatty acids than facial fat. This unique site-specific fatty acid pattern was used to assess the course of the survival of transplanted adipose tissue in the nasolabial region. In all fat samples, the percent area (weight percentage) was obtained for each fatty acid (C12:0 to C22:6 omega-3) using capillary gas chromatography. Clinical results were also analyzed by macrophotographs.

RESULTS

As expected, gluteal fat had significantly more monounsaturated fatty acids and less saturated fatty acids than facial fat. In 5 of 6 patients, at 4, 6, and 12 months after transplantation, the fatty acid pattern at the transplanted recipient site was similar to the pattern of the control facial site. However, at 4 months, 1 patient had a fatty acid pattern in the transplant recipient site that was similar to the pattern of her gluteal fat. This pattern persisted for 1 year. Fat retention at the transplant site was corroborated by photographic assessment.

CONCLUSIONS

Long-term adipocyte survival is an achievable goal following fat transfer. The importance of harvesting and injection techniques as well as adipose tissue characteristics require further study.

Effect of high-carbohydrate feeding on triglyceride and saturated fatty acid synthesis

It has been known for decades that low-fat, high-carbohydrate diets can increase plasma triglyceride levels, but the mechanism for this effect has been uncertain. Recently, new isotopic and nonisotopic methods have been used to determine in vivo whether low-fat, high-carbohydrate diets increase triglyceride levels by stimulating fatty acid synthesis. The results of a series of studies in lean and obese weight-stable volunteers showed that very-low-fat (10%), high-carbohydrate diets enriched in simple sugars increased the fraction of newly synthesized fatty acids, along with a proportionate increase in the concentration of plasma triglyceride. Furthermore, the concentration of the saturated fatty acid, palmitate, increased and the concentration of the essential polyunsaturated fatty acid, linoleate, decreased in triglyceride and VLDL triglyceride. The magnitude of the increase in triglyceride varied considerably among subjects, was unrelated to sex, body mass index, or insulin levels, and was higher when fatty acid synthesis was constantly elevated rather than having a diurnal variation. It was notable that minimal stimulation of fatty acid synthesis occurred with higher fat diets (>30%) or with 10% fat diets enriched in complex carbohydrate. Public health recommendations to reduce dietary fat must take into account the distinct effects of different types of carbohydrate that may increase plasma triglycerides and fatty acid synthesis in a highly variable manner. The mediators and health consequences of this dietary effect deserve further study.

Relationship between carbohydrate-induced hypertriglyceridemia and fatty acid synthesis in lean and obese subjects

We previously reported that a eucaloric, low fat, liquid formula diet enriched in simple carbohydrate markedly increased the synthesis of fatty acids in lean volunteers. To examine the diet sensitivity of obese subjects, 7 obese and 12 lean volunteers were given two eucaloric low fat solid food diets enriched in simple sugars for 2 weeks each in a random-order, cross-over design (10% fat, 75% carbohydrate vs. 30% fat, 55% carbohydrate, ratio of sugar to starch 60:40). The fatty acid compositions of both diets were matched to the composition of each subject's adipose tissue and fatty acid synthesis measured by the method of linoleate dilution in plasma VLDL triglyceride. In all subjects, the maximum % de novo synthesized fatty acids in VLDL triglyceride 3;-9 h after the last meal was higher on the 10% versus the 30% fat diet. There was no significant difference between the dietary effects on lean (43+/-13 vs. 12+/-13%) and obese (37+/-15 vs. 6+/-6%) subjects, despite 2-fold elevated levels of insulin and reduced glucagon levels in the obese. Similar results were obtained for de novo palmitate synthesis in VLDL triglyceride measured by mass isotopomer distribution analysis after infusion of [(13)C]acetate. On the 10% fat diet, plasma triglycerides (fasting and 24 h) were increased and correlated with fatty acid synthesis. Triglycerides were higher when fatty acid synthesis was constantly elevated rather than having diurnal variation.Thus, eucaloric, solid food diets which are very low in fat and high in simple sugars markedly stimulate fatty acid synthesis from carbohydrate, and plasma triglycerides increase in proportion to the amount of fatty acid synthesis. However, this dietary effect is not related to body mass index, insulin, or glucagon levels.

Analysis of the heel pad fat in rheumatoid arthritis

The heel fat pad is organized, both in structure and in composition, to bear the stresses and strains of normal activities and to permit pain-free weightbearing. The fatty acid composition of heel pads in 11 patients with rheumatoid arthritis, a disease process frequently associated with heel fat pad atrophy, was analyzed using gas-liquid chromatography and was compared with that of patients without systemic disease. The heels of patients with rheumatoid arthritis demonstrated a significant change in the composition of saturated fatty acids when compared with heels of nonrheumatoid patients. This composition reflects an increased fat viscosity, which decreases the ability of the heel to absorb and dissipate the energy generated during ambulation. This factor could cause degeneration of the heel septal system, with resulting fat pad atrophy.

Human fatty acid synthesis is reduced after the substitution of dietary starch for sugar

Using new nonisotopic and isotopic methods, we showed previously that fatty acid synthesis was markedly stimulated in weight-stable normal volunteers by a very-low-fat formula diet with 10% of energy as fat and 75% as short glucose polymers. In this study, we determined whether fatty acid synthesis was equally stimulated by a very-low-fat solid diet made with foods consumed typically. Four normal volunteers consumed the same very-low-fat formula diet for 25 d and then an isoenergetic solid food diet with 10% of energy as fat and 75% as starch, simple sugars, and fiber for 25 d. To measure fatty acid synthesis, the fatty acid compositions of the diets were matched to the composition of each subject's adipose tissue and compared with the composition of VLDL-triacylglycerol. In all subjects, the large increases in newly formed palmitate and decreases in linoleate in VLDL-triacylglycerol were quickly reversed by the solid food diet, and the fraction of de novo synthesized fatty acids in fasting VLDL-triacylglycerol decreased from 30-54% to 0-1%. In a second group of subjects, the stimulation of fatty acid synthesis by the formula diet with 75% glucose polymers was similarly reduced by a formula diet with amounts of fat, starch, and sugar chosen to mimic those of the solid food diet, but persisted after the addition of fiber or a diet with 75% sugar. In conclusion, an increase in fatty acid synthesis and palmitaterich, linoleate-poor VLDL-triacylglycerol induced by very-low-fat, high-sugar diets may be reduced by the substitution of dietary starch for sugar with potentially beneficial effects on cardiovascular health.

Diet composition and energy balance in humans

Inpatient metabolic studies of human subjects were performed to obtain data on important nutritional issues. It was shown that wide variations in the ratio of carbohydrate to fat do not alter total 24-h energy need. Studies of the fatty acid composition of plasma low-density lipoproteins during low-fat feeding indicated that there can be considerable lipogenesis from carbohydrate in humans during isoenergetic feeding. The energy cost of this conversion must be small or be counterbalanced by other changes in energy metabolism because measured energy need was unaltered by fat-to-carbohydrate ratios. Energy need was, however, markedly varied by changes in body weight. Subjects at their usual body weights who had experimentally induced increases in body weight became inefficient and required a higher energy intake for weight maintenance. The reverse occurred with a reduction in body weight. The set point at which energy storage is defended is clearly different in obese persons.

Lipoprotein lipase controls fatty acid entry into adipose tissue, but fat mass is preserved by endogenous synthesis in mice deficient in adipose tissue lipoprotein lipase

Lipoprotein lipase (LPL) is the rate-limiting enzyme for the import of triglyceride-derived fatty acids by muscle, for utilization, and adipose tissue (AT), for storage. Relative ratios of LPL expression in these two tissues have therefore been suggested to determine body mass composition as well as play a role in the initiation and/or development of obesity. To test this, LPL knockout mice were mated to transgenics expressing LPL under the control of a muscle-specific promoter (MCK) to generate induced mutants with either relative (L2-MCK) or absolute AT LPL deficiency (L0-MCK). L0-MCK mice had normal weight gain and body mass composition. However, AT chemical composition indicated that LPL deficiency was compensated for by large increases in endogenous AT fatty acid synthesis. Histological analysis confirmed that such up-regulation of de novo fatty acid synthesis in L0-MCK mice could produce normal amounts of AT as early as 20 h after birth. To assess the role of AT LPL during times of profound weight gain, L0-MCK and L2-MCK genotypes were compared on the obese ob/ob background. ob/ob mice rendered deficient in AT LPL (L0-MCK-ob/ob) also demonstrated increased endogenous fatty acid synthesis but had diminished weight and fat mass. These findings reveal marked alterations in AT metabolism that occur during LPL deficiency and provide strong evidence for a role of AT LPL in one type of genetic obesity.

Fatty acid composition of adipose tissue, an indication of dietary fatty acids, and breast cancer prognosis

PURPOSE

Fatty acid composition of adipose tissue is an indicator of the long-term ingestion pattern of several specific fatty acids. There is good correlation of antecedent diet with the essential fatty acids, and there is reflection of the diet with the fatty acids that can be synthesized. The relationship between the fatty acid levels and lymph node status and clinical outcome was examined.

METHODS

At the time of diagnostic surgery, 161 women with clinical stage T1NO breast cancer had subcutaneous adipose tissue (breast and abdominal) aspirated. The concentrations of 35 fatty acids, seven summed classes, and six fatty acid groups were measured by capillary gas chromatography. Lymph node status was determined with axillary dissection, and patients were followed-up (mean, 7.3 years) for clinical outcome.

RESULTS

There was no significant association of any adipose tissue fatty acids with overall survival, although few (16 of 161 women) died of breast cancer. However, the odds of having positive lymph nodes (57 of 161 women) were significantly higher for women with a greater adipose tissue proportion of oleic acid (odds ratio [OR], 7.56; 95% confidence interval [CI], 1.78 to 32.1) or total saturated acids (OR, 8.43; 95% CI, 1.48 to 40.0) and significantly lower with a higher proportion of trans fatty acids (OR, 0.24; 95% CI, 0.07 to 0.77), as assessed by multivariate logistic regression.

CONCLUSION

These data support previous research with dietary questionnaire methodology, suggesting that specific dietary fatty acids may be associated with breast cancer promotion. Further research with long-term clinical follow-up is necessary to investigate these observations in large, diverse populations before dietary recommendations can be envisioned.

Effects of shrimp consumption on plasma lipoproteins

Shrimp is very low in total fat, yet it has a high cholesterol content. Although shrimp is a popular food in the American diet, many people avoid it because of its high cholesterol content. The objective of this study was to test the effect of the addition of cholesterol from shrimp to a low-fat baseline diet as well as to compare the effect of an equal amount of dietary cholesterol derived from shrimp or egg on the plasma lipoprotein pattern of normolipidemic subjects. In a randomized crossover trial, a diet containing 300 g shrimp/d, which supplied 590 mg dietary cholesterol/d, significantly increased low-density-lipoprotein (LDL) cholesterol by 7.1% (P = 0.014) and high-density-lipoprotein (HDL) cholesterol by 12.1% (P = 0.0001) when compared with a baseline diet matched for fat content but containing only 107 mg cholesterol/d. However, because the percentage increase in LDL cholesterol was less than for HDL cholesterol, the shrimp diet did not worsen the ratio of total cholesterol to HDL cholesterol or the ratio of LDL to HDL cholesterol. Moreover, shrimp consumption decreased triacylglycerol (triglyceride) concentrations by 13% (P = 0.004). The diet containing two large eggs per day with 581 mg dietary cholesterol/d also raised LDL- and HDL-cholesterol concentrations compared with baseline, but the percentage increase in LDL cholesterol (10.2%, P = 0.0001) was more than for HDL cholesterol (7.6%, P = 0.004) and there was a trend toward worse lipoprotein ratios. In a comparison of the two high-cholesterol diets, the shrimp diet produced significantly lower ratios of total to HDL cholesterol and lower ratios of LDL to HDL cholesterol than the egg diet as well as lower triacylglycerol concentrations. We conclude that moderate shrimp consumption in normolipidemic subjects will not adversely affect the overall lipoprotein profile and can be included in "heart healthy" nutritional guidelines.

Human fatty acid synthesis is stimulated by a eucaloric low fat, high carbohydrate diet

A new experimental approach was used to determine whether a eucaloric, low fat, high carbohydrate diet increases fatty acid synthesis. Normally volunteers consumed low fat liquid formula diets (10% of calories as fat and 75% as glucose polymers, n = 7) or high fat diets (40% of calories as fat and 45% as glucose polymers, n = 3) for 25 d. The fatty acid composition of each diet was matched to the composition of each subject's adipose tissue and compared with the composition of VLDL triglyceride. By day 10, VLDL triglyceride was markedly enriched in palmitate and deficient in linoleate in all subjects on the low fat diet. Newly synthesized fatty acids accounted for 44 +/- 10% of the VLDL triglyceride. Mass isotopomer distribution analysis of palmitate labeled with intravenously infused 13C-acetate confirmed that increased palmitate synthesis was the likely cause for the accumulation of triglyceride palmitate and "dilution" of linoleate. In contrast, there was minimal fatty acid synthesis on the high diet. Thus, the dietary substitution of carbohydrate for fat stimulated fatty acid synthesis and the plasma accumulation of palmitate-enriched, linoleate-deficient triglyceride. Such changes could have adverse effects on the cardiovascular system.

Fatty acid composition of normal and atrophied heel fat pad

Capillary gas-liquid chromatography was used to analyze the fatty acid composition of normal heel fat pads from subjects without systemic disease (N = 8) and atrophied heels from patients with diabetic peripheral neuropathy (N = 4), rheumatoid arthritis (N = 1), peripheral vascular disease (N = 1), and hereditary sensory neuropathy (N = 1). In the normal subjects, the fatty acid composition of subcutaneous abdominal fat was also obtained for comparison. Three saturated fatty acids (myristate, palmitate, and stearate) and four unsaturated fatty acids (palmitoleate, oleate, vaccenate, and linoleate) comprised over 90% of the total fatty acid composition. Higher percentages of unsaturated fatty acids and lower percentages of saturated fatty acids were found in the normal heel fat pads when compared to subcutaneous abdominal fat. The increase in the ratio of unsaturated fatty acids to saturated fatty acids (4.4 versus 2.5, P < .01) may decrease triglyceride viscosity and enhance the biomechanical efficiency of the heel fat pad. Though the number of patients is small, no statistically significant compositional differences were noted between the heel fat from normal subjects and from subjects with peripheral neuropathies, rheumatoid arthritis, or peripheral vascular disease. However, the heel fatty acid composition of the one subject with a hereditary sensory neuropathy was less unsaturated and more saturated than normal with a ratio of unsaturates to saturates similar to that of the abdomen (2.8).

Changes in abdominal and gluteal adipose-tissue fatty acid compositions in obese subjects after weight gain and weight loss

The fatty acid compositions of abdominal and gluteal subcutaneous adipose tissues of eight obese subjects were measured after an initial 5-10-wk period of weight maintenance on a liquid-formula diet (40% of calories as corn oil, 45% as carbohydrate, and 15% as protein), after a 10% increase in weight (11-20 kg) on a solid-food diet of each subject's choice (n = 5) or after a 20% decrease in weight (26-37 kg) on 800 kcal/d of the same corn-oil-formula diet (n = 5). After weight gain or weight loss, all subjects maintained their new weights for 2-10 wk on the same corn-oil-formula diet. As hypothesized, there were minimal changes in the concentrations of 41 fatty acids identified in both abdominal and gluteal tissues after all dietary phases, and small site-specific differences in the levels of saturated and monounsaturated fatty acids were not altered. The largest change was a 15% decrease (P less than 0.05) in 18:3n-3 in both abdominal and gluteal tissues during weight loss, despite higher levels in the diet than in the baseline adipose tissue. This decrease occurred without coexisting decreases in 22:5n-3 and 22:6n-3, two elongase-desaturase products of 18:3n-3 that were not detectable in the diet.

Adipose-tissue fatty acid composition in recipients of long-term total parenteral nutrition (TPN)

Adipose-tissue fatty acid composition was studied in nine patients requiring long-term total parenteral nutrition (TPN). The patients received 17 +/- 8% of total energy as soybean-oil emulsion (Intralipid) and 66 +/- 8% as glucose. Despite low intake of 9c-16:1, 11c-18:1, and 13c-18:1, adipose-tissue concentrations of these monounsaturated fatty acids were higher in the TPN patients than in free-living control subjects (P less than 0.05) and inversely correlated with the percent energy from fat (r = -0.56, P = 0.11; r = -0.64, P = 0.06; r = -0.81, P = 0.008, respectively). This suggests that these fatty acids accumulated from endogenous synthesis from carbohydrate and thus may be markers of the percent fat in the diet. The essential fatty acids, 18:2 and 18:3n-3, positively correlated with the percent energy from fat (r = 0.79, P = 0.01; r = 0.80, P = 0.01, respectively). Linear-regression analysis suggests that normal adipose-tissue stores of 18:2 and 18:3n-3 are maintained when intravenous soybean-oil emulsion provides 11-20% and 4-12%, respectively, of total energy.

Correlation of isomeric fatty acids in human adipose tissue with clinical risk factors for cardiovascular disease

The relationships between the adipose tissue concentrations of 19 geometric and positional fatty acid isomers and 10 cardiovascular disease risk factors were determined in 76 free-living adult males. The percentages for trans isomers (total mean +/- SD 4.14 +/- 0.97%) and cis isomers (total mean +/- SD 2.91 +/- 0.34%) in adipose tissue generally agreed with dietary estimates based on the consumption of hydrogenated oils. A major exception was the percentage of 11c-18:1, which was twofold higher in adipose tissue. The total level of fatty acid isomers in adipose tissue or a factor (derived by factor analysis) that was representative of isomers of dietary origin was not significantly correlated with the cardiovascular risk factors. Only three trans isomers (11t-18:1, 12t-18:1, and 5t-14:1) and three cis isomers (11c-18:1, 13c-18:1, and 7c-16:1) were weakly correlated either positively or negatively with age, body mass index, plasma and lipoprotein cholesterol, and/or blood pressure (P less than 0.05, r greater than 0.231).

Leukotriene B4 generation in patients with established pulmonary failure

We investigated the cause of the reduced leukotriene B4 (LTB4) production seen in neutrophils from patients with established adult respiratory distress syndrome compared with control neutrophils. Lymphocytes/monocytes from controls were found to synergistically enhance the amount of LTB4 produced when incubated with neutrophils. This synergistic effect was not seen in cells from patients with adult respiratory distress syndrome. Fatty-acid analysis of neutrophils from patients with adult respiratory distress syndrome and controls showed remarkable similarity in all quantities of fatty acids measured except for arachidonic acid, where there was a 22% reduction in patients' cells compared with controls. Assay of the rate of generation of LTB4 and its degradation product, 20-hydroxy LTB4, revealed that reduced LTB4 generation in patients' neutrophils was not due to increased degradation of LTB4 by hydroxylase enzymes. When the amount of LTB4 being generated per milliliter of whole blood was analyzed in the patients with adult respiratory distress syndrome and compared with controls, it was determined that the potential to generate LTB4 in patients in the intensive care unit was three to five times greater than in controls.

Limits for the use of (18O)cholesterol and (18O)sitosterol in studies of cholesterol metabolism in humans

The present study was undertaken in order to determine whether 18O-labeled sterols could be used in place of 14C-sterols in clinical studies of cholesterol metabolism. (3 beta-18OH)Cholesterol and (3 beta-18OH)sitosterol were simply and inexpensively synthesized and precisely and accurately quantified by gas chromatography/mass spectrometry. 18O-Sterols added to fecal homogenate and saponified were completely recovered. However, in a series of validation studies in humans, the fecal recoveries of orally administered (18O)cholesterol and (18O)sitosterol were significantly lower than the recoveries of 14C-sterols given simultaneously. We found that the losses were largely limited to the coprostanol and ethylcoprostanol fecal metabolites. In vitro fecal incubations of 18O-sterols and unlabeled water or of unlabeled sterols with H2(18)O indicated that the losses occurred during fecal bacterial metabolism and were likely due to 3 beta-oxygen exchange with the oxygen of water, possibly via a 3-ketosteroid intermediate. These data indicate that (18O)cholesterol and (18O)sitosterol are invalid tracers for the measurement of human cholesterol metabolism by methods based on fecal sterol recovery.