Effects of caloric restriction on lipid metabolism in man: changes of tissue lipoprotein lipase activities and of serum lipoproteins

Maternal High Fat Diet and its Expressions in the Heart and Liver in the Mice Embryogenesis

BACKGROUND

The developmental biology for the nonalcoholic fatty liver disease and coronary heart disease are known but elaborative ideas of triglycerides phenomenon in the embryo-genesis of the liver and the heart are still not clear.

OBJECTIVE

The aim of the study was to relate different triglycerides like LXRα, LPL, LDL R, PPARG-, SREBP-1C expression in the high fat fed mice with the normal fed diet mice in the process of developmental and embryo-genesis biology.

METHODS

Tissue preparation was done by ripalysis. Different protein content was obtained via western blot for the 6 samples namely a-17.5 days mice embryo heart; b- 0th day or the birthday mice infant heart; c-1 week mice infant heart; d-2 weeks mice infant heart; e-3 weeks mice infant heart; f-Adult mice heart. Protein lysates from the heart tissues of the mice was obtained via homegenization and centrifugation. Hematoxylin and Eosin (H and E) was done to see the fat droplets in the liver tissues at the different developmental stages.

RESULT

LXRα,SREBP-1C expression in 17.5 days mice embryo heart and 0th day or the birthday mice infant heart is highly expressed in the high fat diet. LDL-R in the high fat diet mice is increased in 2 weeks mice infant heart but in17.5 days mice embryo heart and in 0th day or the birthday mice infant heart it is low expression but from 1week mice infant heart to the adult mice heart the expression is in decreasing trend. Similarly LPL is highly expressed in17.5 days mice embryo heart and 1 week mice infant heart and thus low expression in decreasing order until adult mice heart.Thus, these results collectively shows that maternal HF diet increases expression of proteins such as LPL, LDLr in the embryo phase and thus getting normal expressions in the adult phase that facilitate Triglycerides (TAG) hydrolysis across the liver and the heart. Also,maternal high fat diet increases the SREBP1c expression, leading to stimulation of LPL Expression.

CONCLUSION

In summary, using a pregnant mice model, we found that maternal high fat diet increases the fetal fat accumulation. Elevated placental LPL activity and expression of genes that facilitate placental lipid transport suggest that enhanced placental lipid transport may play a key role in maternal nutrition and obesity-induced fetal fat accumulation.

The effects of chronic unpredicted mild stress on maternal negative emotions and gut microbiota and metabolites in pregnant rats

Background

Chronic long-term stress is associated with a range of disorders, including depression and a variety of other chronic illnesses. It is well known that maternal exposure to psychosocial stress during pregnancy significantly increases the likelihood of adverse pregnancy outcomes. The gut microbiota has been a popular topic, it is a key mediator of the gut-brain axis and plays an important role in human health; changes in the gut microbiota have been related to chronic stress-induced health impairment, however, the relationship between maternal negative emotions and abnormal gut microbiota and its metabolites during maternal exposure to chronic stress during pregnancy remains unclear.

Methods

Pregnant rats were subjected to chronic unpredicted mild stress (CUMS) to establish the rat model of chronic stress during pregnancy. The behavioral changes were recorded using sucrose preference test (SPT) and open-field test (OFT), plasma corticosterone levels were determined by radioimmunoassay, and a comprehensive method combining 16S rRNA gene sequencing and gas chromatography-mass spectrometry (GC-MS) metabolomics was used to study the effects of stress during pregnancy on the function of intestinal microbiota and its metabolites.

Results

Chronic stress during pregnancy not only increased maternal plasma corticosterone (P < 0.05), but also caused maternal depression-like behaviors (P < 0.05). Chronic stress during pregnancy changed the species composition at the family level of maternal gut microbiota, the species abundance of Ruminococcaceae in the stress group (23.45%) was lower than the control group (32.67%) and the species abundance of Prevotellaceae in the stress group (10.45%) was higher than the control group (0.03%) (P < 0.05). Vertical locomotion and 1% sucrose preference percentage in pregnant rats were negatively correlated with Prevotellaceae (r =  - 0.90, P < 0.05). Principal component analysis with partial least squares discriminant analysis showed that the integration points of metabolic components in the stress and control groups were completely separated, indicating that there were significant differences in the metabolic patterns of the two groups, and there were seven endogenous metabolites that differed (P < 0.05).

Conclusions

The negative emotional behaviors that occur in pregnant rats as a result of prenatal chronic stress may be associated with alterations in the gut microbiota and its metabolites. These findings provide a basis for future targeted metabolomics and gut flora studies on the effects of chronic stress during pregnancy on gut flora.

Comparing the responses of grain fed feedlot cattle under moderate heat load and during subsequent recovery with those of feed restricted thermoneutral counterparts: plasma biochemistry

Responses to heat stress in ruminants reflect the integration of local climatic conditions, environment/production system and the animal's homeostatic and homeorhetic capacities. Thus, the goal of ameliorating heat stress requires experimental settings that, within limits, closely resemble the target production system and cohort. We investigated the blood biochemical changes of two sequential cohorts of twelve 518 ± 23 kg grain fed Black Angus steers. Each cohort consisted of two treatments of 6 head/group: a thermally challenged (TC) treatment and a feed restricted thermoneutral (FRTN) treatment. Both groups were housed in climate controlled rooms for 19 days, with the TC group experiencing three distinct periods: PreChallenge, Challenge and Recovery. PreChallenge and Recovery delivered thermoneutral conditions, while Challenge consisted of 7 days of moderate diurnal heat load. The FRTN group was maintained in thermoneutral conditions at all times. Both groups were then relocated to outdoor pens for a further 40 days to detect any enduring change to metabolism as a consequence of the treatments. We compared blood biochemical responses of the treatments and inferred likely metabolic changes. Relative to the FRTN group, the TC animals experienced limited supply of triglycerides, cholesterol and glutamine during moderate heat load, suggesting constraints to energy metabolism. Lower blood urea during Recovery and in outdoor pens implied a requirement to capture N rather than allow its excretion. Altered liver enzyme profiles indicated a higher level of hepatic stress in the TC group. By the completion of feedlot finishing, the groups were not separable on most measures.

Effects of prenatal cold stress on maternal serum metabolomics in rats

Our previous studies have shown that prenatal cold stress leads to placental inflammatory response and induces anxiety-like behavior reduced in offspring rats. However, the role and mechanisms by which prenatal cold stress affects offspring remain unclear. The aim of this study was to determine the metabolic profiles from the maternal serum and helpful in understanding the role and mechanisms by which prenatal cold stress affects the offspring. In this study, liquid chromatography-mass spectrometry (LC/MS) was used to analyze serum metabolites, and PCA, PLS-DA, and OPLS-DA were performed to analyze changes in metabolites in the maternal serum after cold stress of 3 or 7 days. The results showed that 19 metabolites in the CS (cold stress 7 days)-NS (control) group and 23 metabolites in the CT (cold stress 3 days)-NT (control) group were significantly altered. These metabolites were mainly associated with unsaturated fatty acid synthesis, and arachidonic acid, linoleic acid, and glutamine and glutamate metabolism. The data indicated that prenatal cold stress not only affected the maternal neuroendocrine system, but also affected the immune system, and lipid and amino acid metabolism. These results further supported the findings of our previous studies on the effects of prenatal cold stress on the mother and offspring. A more comprehensive understanding of these data may lead to maternal intervention that can reverse the damage of prenatal stressors.

Integrative analysis of indirect calorimetry and metabolomics profiling reveals alterations in energy metabolism between fed and fasted pigs

Background

Fasting is a simple metabolic strategy that is used to estimate the maintenance energy requirement where the energy supply for basic physiological functions is provided by the mobilization of body reserves. However, the underlying metabolic components of maintenance energy expenditure are not clear. This study investigated the differences in heat production (HP), respiratory quotient (RQ) and plasma metabolites in pigs in the fed and fasted state, using the techniques of indirect calorimetry and metabolomics.

Methods

Nine barrows (45.2 ± 1.7 kg BW) were fed corn-soybean based meal diets and were kept in metabolism crates for a period of 14 d. After 7 d adaptation, pigs were transferred to respiratory chambers to determine HP and RQ based on indirect calorimetry. Pigs were fed the diet at 2,400 kJ ME/(kg BW^0.6·d) during d 8 to 12. The last 2 d were divided into 24 h fasting and 48 h fasting treatment, respectively. Plasma samples of each pig were collected from the anterior vena cava during the last 3 d (1 d while pigs were fed and 2 d during which they were fasted). The metabolites of plasma were determined by high-resolution mass spectrometry using a metabolomics approach.

Results

Indirect calorimetry analysis revealed that HP and RQ were no significant difference between 24 h fasting and 48 h fasting, which were lower than those of fed state (P <  0.01). The nitrogen concentration of urine tended to decrease with fasting (P = 0.054). Metabolomics analysis between the fed and fasted state revealed differences in 15 compounds, most of which were not significantly different between 24 h fasting and 48 h fasting. Identified compounds were enriched in metabolic pathways related to linoleic acid metabolism, amino acid metabolism, sphingolipid metabolism, and pantothenate and CoA biosynthesis.

Conclusion

These results suggest that the decreases in HP and RQ of growing pigs under fasting conditions were associated with the alterations of linoleic acid metabolism and amino acid metabolism. The integrative analysis also revealed that growing pigs under a 24-h fasting were more appropriate than a 48-h fasting to investigate the metabolic components of maintenance energy expenditure.

Maternal High-Fat Feeding Increases Placental Lipoprotein Lipase Activity by Reducing SIRT1 Expression in Mice

This study investigated how maternal overnutrition and obesity regulate expression and activation of proteins that facilitate lipid transport in the placenta. To create a maternal overnutrition and obesity model, primiparous C57BL/6 mice were fed a high-fat (HF) diet throughout gestation. Fetuses from HF-fed dams had significantly increased serum levels of free fatty acid and body fat. Despite no significant difference in placental weight, lipoprotein lipase (LPL) protein levels and activity were remarkably elevated in placentas from HF-fed dams. Increased triglyceride content and mRNA levels of CD36, VLDLr, FABP3, FABPpm, and GPAT2 and -3 were also found in placentas from HF-fed dams. Although both peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer binding protein-α protein levels were significantly increased in placentas of the HF group, only PPARγ exhibited a stimulative effect on LPL expression in cultured JEG-3 human trophoblasts. Maternal HF feeding remarkably decreased SIRT1 expression in placentas. Through use of an SIRT1 activator and inhibitor and cultured trophoblasts, an inhibitory effect of SIRT1 on LPL expression was demonstrated. We also found that SIRT1 suppresses PPARγ expression in trophoblasts. Most importantly, inhibition of PPARγ abolished the SIRT1-mediated regulatory effect on LPL expression. Together, these results indicate that maternal overnutrition induces LPL expression in trophoblasts by reducing the inhibitory effect of SIRT1 on PPARγ.

An increase in high-density lipoprotein cholesterol after weight loss intervention is associated with long-term maintenance of reduced visceral abdominal fat

OBJECTIVES

It is generally agreed that excess abdominal fat, in particular visceral abdominal fat (VAF), is related to an increased risk for obesity-related complications. We examined the association between metabolic risk factors and maintaining VAF after weight loss intervention.

METHODS

A total of 54 postmenopausal, obese women who achieved a VAF loss of at least 10% from their baseline values during a 14-week intervention were enrolled as subjects. Body weight, VAF assessed by CT scans, and metabolic risk factors (that is, blood pressure, lipids and glucose) were measured at baseline (week 0), post-intervention (week 15), and at a 2-year follow-up (week 105). The subjects were divided into two groups according to their changes in VAF between weeks 15 and 105 (follow-up period): (1) VAF gainers (VAF changes > 0 cm², n=28) or (2) VAF maintainers (VAF changes ≤ 0 cm², n=26).

RESULTS

The mean change in VAF of all subjects during the 14-week intervention was -34±16 cm² (-29.7±12.3%) (P<0.01). Along with this change, improvements (P<0.05) were observed in all metabolic risk factors except for high-density lipoprotein cholesterol (HDLC). During the follow-up period, there were interactions between the two VAF groups in HDLC, triglycerides (TG) and total cholesterol (TC)/HDLC ratio (all P<0.01). In particular, the HDLC of VAF maintainers improved, and the value at week 105 exceeded baseline level (P<0.01). However, systolic and diastolic blood pressure, TC and low-density lipoprotein cholesterol in the VAF maintainers increased (all P<0.05) back to their mean baseline level despite a further decrease in their VAF during the follow-up period (P<0.01).

CONCLUSIONS

This study shows that long-term maintenance of VAF after weight loss intervention is associated with improvements in HDLC and TG among obese, postmenopausal women.

Exercise of low energy expenditure along with mild energy intake restriction acutely reduces fasting and postprandial triacylglycerolaemia in young women

A single bout of prolonged, moderate-intensity endurance exercise lowers fasting and postprandial TAG concentrations the next day. However, the TAG-lowering effect of exercise is dose-dependent and does not manifest after light exercise of low energy cost ( < 2 MJ). We aimed to investigate whether superimposing mild energy intake restriction to such exercise, in order to augment total energy deficit, potentiates the hypotriacylglycerolaemic effect. Eight healthy, sedentary, premenopausal women (age 27.1 (sem 1.3) years; BMI 21.8 (sem 0.9) kg/m2) performed two oral fat tolerance tests in the morning on two different occasions: once after a single bout of light exercise (100 min at 30 % of peak oxygen consumption; net energy expenditure 1.04 (sem 0.01) MJ) coupled with mild energy intake restriction (1.39 (sem 0.22) MJ) on the preceding day, and once after resting coupled with isoenergetic feeding on the preceding day (control). Fasting plasma TAG, TAG in the TAG-rich lipoproteins (TRL-TAG) and serum insulin concentrations were 18, 34 and 30 % lower, respectively, after exercise plus diet compared with the control trial (P < 0.05). Postprandial concentrations of plasma TAG and TRL-TAG were 19 and 27 % lower after exercise plus diet compared with the control condition (P < 0.01), whereas postprandial insulin concentrations were not different. It is concluded that a combination of light exercise along with mild hypoenergetic diet may be a practical and feasible intervention to attenuate fasting and postprandial triacylglycerolaemia, especially for people who cannot exercise for prolonged periods of time at moderate-to-high intensities, such as many sedentary individuals.

An increase in plasma adiponectin multimeric complexes follows hypocaloric diet-induced weight loss in obese and overweight pre-menopausal women

Adiponectin is involved in the regulation of glucose and fatty acid metabolism, influences whole-body insulin sensitivity and protects arterial walls against the development of atherosclerosis. Plasma adiponectin is decreased in obese, insulin-resistant and Type 2 diabetic patients. Adiponectin circulates in plasma as high-, medium- and low-molecular-weight (‘mass’) forms (HMW, MMW and LMW respectively). The HMW form is believed to be closely associated with insulin sensitivity. The aim of the present study was to investigate whether diet-induced changes in body weight and insulin sensitivity were associated with changes in the quantity of adiponectin multimeric complexes. A total of 20 overweight or obese women (age, 39.4±9.5 years; body mass index, 32.2±6.4 kg/m2) underwent 12 weeks of low caloric diet (600 kcal/day less than energy requirements; where 1 kcal≈4.184 kJ). Plasma samples were drawn before and after the study for biochemical analysis and Western blot detection of adiponectin multimeric complexes. The hypocaloric diet resulted in a weight reduction (89.8±16.4 kg compared with 83.1±15.6 kg; P<0.001) and an improvement in whole-body insulin sensitivity, as measured by HOMA (homoeostasis model assessment index; 1.9±0.8 compared with 1.5±0.7; P=0.013). Increases in the quantities of the HMW, MMW and LMW forms by 5.5, 8.5 and 18.1% respectively, were observed (P<0.05 for all of the forms). Total plasma adiponectin was increased by 36% with borderline significance (P=0.08). No correlations between changes in adiponectin complexes and changes in indices of insulin sensitivity were observed. In conclusion, diet-induced weight loss improved insulin sensitivity as well as increased the amount of HMW, MMW and LMW adiponectin complexes in plasma.

Almonds vs complex carbohydrates in a weight reduction program

OBJECTIVE

To evaluate the effect of an almond-enriched (high monounsaturated fat, MUFA) or complex carbohydrate-enriched (high carbohydrate) formula-based low-calorie diet (LCD) on anthropometric, body composition and metabolic parameters in a weight reduction program.

DESIGN

A randomized, prospective 24-week trial in a free-living population evaluating two distinct macronutrient interventions on obesity and metabolic syndrome-related parameters during weight reduction.

SUBJECTS

In total, 65 overweight and obese adults (age: 27-79 y, body mass index (BMI): 27-55 kg/m(2)).

INTERVENTION

A formula-based LCD enriched with 84 g/day of almonds (almond-LCD; 39% total fat, 25% MUFA and 32% carbohydrate as percent of dietary energy) or self-selected complex carbohydrates (CHO-LCD; 18% total fat, 5% MUFA and 53% carbohydrate as percent of dietary energy) featuring equivalent calories and protein.

MAIN OUTCOME MEASUREMENTS

Various anthropometric, body composition and metabolic parameters at baseline, during and after 24 weeks of dietary intervention.

RESULTS

LCD supplementation with almonds, in contrast to complex carbohydrates, was associated with greater reductions in weight/BMI (-18 vs -11%), waist circumference (WC) (-14 vs -9%), fat mass (FM) (-30 vs -20%), total body water (-8 vs -1%) and systolic blood pressure (-11 vs 0%), P=0.0001-0.05. A 62% greater reduction in weight/BMI, 50% greater reduction in WC and 56% greater reduction in FM were observed in the almond-LCD as compared to the CHO-LCD intervention. Ketone levels increased only in the almond-LCD group (+260 vs 0%, P<0.02). High-density lipoprotein cholesterol (HDL-C) increased in the CHO-LCD group and decreased in the almond-LCD group (+15 vs -6%, P=0.05). Glucose, insulin, diastolic blood pressure, total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C) and LDL-C to HDL-C ratio decreased significantly to a similar extent in both dietary interventions. Homeostasis model analysis of insulin resistance (HOMA-IR) decreased in both study groups over time (almond-LCD: -66% and CHO-LCD: -35%, P<0.0001). Among subjects with type 2 diabetes, diabetes medication reductions were sustained or further reduced in a greater proportion of almond-LCD as compared to CHO-LCD subjects (96 vs 50%, respectively) [correction].

CONCLUSION

Our findings suggest that an almond-enriched LCD improves a preponderance of the abnormalities associated with the metabolic syndrome. Both dietary interventions were effective in decreasing body weight beyond the weight loss observed during long-term pharmacological interventions; however, the almond-LCD group experienced a sustained and greater weight reduction for the duration of the 24-week intervention. Almond supplementation of a formula-based LCD is a novel alternative to self-selected complex carbohydrates and has a potential role in reducing the public health implications of obesity.

Life-style and serum lipids and lipoproteins

In reviewing the trends and influences of life-style in this country on health and disease in the latter half of 20th century, we focused our attention on 4 major habits of smoking, drinking, exercise and diets, and collected data on the Japanese to conduct a meta-analysis of their relationship with serum lipids and lipoproteins, which are the metabolic risk factors most closely related to atherosclerosis. 1) The percentage of smokers was 54.0% in adult males and 14.5% in adult females in 1999. In the data of 7,256 subjects (mean age 47 years) in 16 papers, smoking increased triglycerides by 13 mg/dl (0.15 mmol/L) or in 559 non-drinkers with a mean age of 49 years in 3 papers by 18 mg/dl (0.20 mmol/L), and decreased HDL-cholesterol by 3.5 mg/dl (0.09 mmol/L) with every 20 cigarettes smoked according to the regression equation. 2) As for drinking, the annual ethanol consumption per adult was 8.5L in 1996. The effects of alcohol on serum lipids were analyzed in 27,035 males (mean age 47 years) in 24 studies. Drinking elevated triglycerides by a mean of 10 mg/dl (0.11 mmol/L), and also HDL-cholesterol by 2.5 mg/dl (0.06 mmol/L) per 23 g of alcohol intake (corresponding to 1 go of sake or 1 large bottle of beer). 3) Concerning exercise habit, 25% of males and 21% of females (mean age 47 years) regularly performed exercise such as jogging, swimming, aerobics, and tennis. However, walking was regarded as an easy exercise to be practiced by subjects of all ages. The effects of walking on serum lipids were studied in a total of 46,074 subjects (mean age 47 years) in 8 populations. Triglycerides were significantly lower by 10 mg/dl (0.11 mol/L), and HDL-cholesterol higher by 3 mg/dl (0.08 mmol/L) in those who walked 6,000 or more steps/day than in those who walked less than 2,000 steps/day. The effects of harder exercise like jogging or swimming were analyzed in 2,242 subjects in 14 papers (mean age 44 years). Triglycerides decreased by 10 mg/dl (0.11 mmol/L), and HDL-cholesterol elevated by 5 mg/dl (0.13 mmol/L) with an increase in the exercise intensity by one level of about 300 kcal. In exercise therapy, triglycerides were decreased by a mean of 20 mg/dl (0.23 mmol/L), and HDL cholesterol increased by a mean of 10 mg/dl (0.26 mmol/L) by exercise at a mean heart rate of about 135 bpm, which is equivalent to 50% VO2max for 30 minutes x 3 times/week. 4) In nutritional trends, the mean energy intake in 52 postwar years averaged 2,116+/-84 kcal with no marked changes according to nutritional surveys. However, the percentage of fat in total energy intake was lowest at 7% in 1946, increased thereafter until it exceeded 20% in 1973, and surpassed 25% in 1988. The mean total cholesterol level of the Japanese increased by 28 mg/dl (0.72 mmol/L) in the past 30 years and reached 204 mg/dl (5.28 mmol/L) in a survey in 1990. 5) Concerning dietary habits, total cholesterol was lower by a mean of 13 mg/dl (0.34 mmol/L), triglycerides lower by 40 mg/dl (0.45 mmol/L), and HDL-cholesterol higher by 5 mg/dl (0.13 mmol/L) in the group who ate 7 or more Japanese-style meals in the 9 meals during 3 days than in the group who ate 3 or less Japanese-style meals in the 9 meals. When serum lipids were compared among individuals living in cities (8 groups; 3,613 subjects; mean age 51 years), agricultural villages (13 groups; 5,364 subjects; mean age 51 years), and fishing villages (9 groups; 1,071 subjects; mean age 52 years). Total cholesterol was lower by a mean of 10 mg/dl (0.26 mmol/L) in fishing villages than in cities, and triglycerides lower by a mean of 15 mg/dl (0.17 mmol/L) in fishing villages than in cities and agricultural villages. HDL-cholesterol was 5 mg/dl (0.13 mmol/L) higher in agricultural villages and 3 mg/dl (0.08 mmol/L) higher in fishing villages than in cities. 6) The effects of dietary therapy or guidance were evaluated in 585 subjects (mean age, 53 years) in 12 papers. Total cholesterol was reduced by 20 mg/dl (0.52 mmol/L), triglycerides by a mean of 40 mg/dl (0.45 mmol/L), and HDL-cholesterol was increased by 5 mg/dl (0.13 mmol/L) by restriction of fat intake or restriction of the intake of saturated fat and dietary cholesterol. The results of these meta-analyses are considered to indicate the extent to which abnormalities of serum lipids are caused by a distorted life-style and the extent to which they are improved by correction of the life-style and exercise or dietary therapy. Correction of the life-style as a non-drug therapy may clearly improve hyperlipidemias or hypo-HDL-cholesterolemia so that this approach should be aggressively employed as part of the prevention and treatment for hyperlipidemias.

Impact of body weight and weight loss on cardiovascular risk factors

Overwieght and obesity are classified as a major risk for cardiovascular disease (CVD). An increase in the body mass index is associated with adverse changes in the plasma lipid and lipoprotein profile resulting in elevated total cholesterol, low-density lipoprotein-cholesterol, and triglyceride levels and a decrease in high-density lipoprotein levels. An android pattern of obesity is associated with a more deleterious plasma lipoprotein profile as well as hypertension and insulin resistance, resulting in an even greater increase in CVD risk. Weight loss through caloric restriction improves the plasma lipoprotein profile. A Step-1 diet plus exercise confer even greater benefits.

Effects of hypocaloric dietary treatment enriched in oleic acid on LDL and HDL subclass distribution in mildly obese women

OBJECTIVE

To study the effects of a carbohydrate-enriched (HiCarbo) or olive-oil-enriched (HiMUFA) hypocaloric diet on plasma lipoprotein levels and physical properties.

DESIGN

A six-month follow-up dietary intervention study with a HiCarbo diet providing 60% of total calories as complex carbohydrates, 15% as proteins and 25% as fats [10% saturated (SFA); 7% monounsaturated (MUFA); 8% polyunsaturated fatty acids (PUFA)]; or a HiMUFA diet with 40% complex carbohydrates, 15% proteins and 45% fats (10% SFA; 27% MUFA; 8% PUFA).

SUBJECTS

Twenty consecutive, mildly obese, normolipidemic premenopausal women (11 on HiCarbo and nine on HiMUFA diets) and 14 age- and sex-matched, lean controls.

MEASUREMENTS

Body mass index (BMI), waist/hip ratio, plasma lipoproteins, apolipoprotein (apo) AI and B, LDL and HDL density distribution, and phospholipid fatty acid composition at baseline, and after 3 and 6 months on dietary treatment.

RESULTS

Body weight progressively decreased during the first 3 months and then it stabilized during the following 3 months (-11% vs. baseline in both groups; P < 0.01). LDL-Cholesterol decreased significantly in both groups. HDL-Cholesterol increased significantly in the HiMUFA group, whereas a decreased level was observed in the HiCarbo group. At baseline the obese women had higher very low density lipoprotein (VLDL) and dense LDL-Cholesterol, and lower HDL2 cholesterol levels than the controls; these abnormalities persisted in the HiCarbo diet, whilst a significant decrease in the dense LDL associated with an increase in the HDL2 cholesterol was seen in the HiMUFA diet. HDL3 was not affected by either diet. The LDL/HDL-Cholesterol ratio was not affected by the HiCarbo diet, whilst it was significantly reduced after 6 months of HiMUFA diet as compared with baseline. Apo AI increased in the HiMUFA group, and decreased in the HiCarbo group.

CONCLUSIONS

Both diets were effective in decreasing body weight. At steady weight conditions, only the HiMUFA diet improved LDL and HDL subclass distribution abnormalities present in mildly obese normolipidemic women.

Hypercholesterolaemia of prolonged fasting and cholesterol lowering of re-feeding in lean human subjects

Serum cholesterol and triglycerides were determined in 36 lean, healthy adults (mean body mass index = 24.3 +/- 0.4 kg m-2) during a period of fasting of 7-21 days. Fasting for 1 week resulted in significant elevation of serum cholesterol (mean increase 25%, range 0-68) and triglycerides (mean increase 24%). No correlation was observed between pre-fast cholesterol level and fasting-induced hypercholesterolaemia. Continued fasting for up to 21 days resulted in lowering of both cholesterol and triglycerides to pre-fast levels. One week of hypocaloric re-feeding resulted in significantly lower than pre-fast cholesterol (mean decrease 13%) and significantly higher than prefast triglycerides (mean increase 86%). The net change in serum cholesterol observed as a result of fasting and re-feeding correlated with prefast cholesterol (r = -0.6901, p = 0.0001). No significant change in the ratio of unesterified cholesterol to total cholesterol was observed during fasting. Fasting for 3 weeks followed by 1 week of hypocaloric re-feeding, however, resulted in a significant (p = 0.05) increase in this ratio from 0.27 +/- 0.0057 to 0.34 +/- 0.01. Fasting for 1 or 2 weeks followed by re-feeding also resulted in a similar increase in the ratio of unesterified cholesterol to total cholesterol. Cholesterol in the HDL fraction remained within normal range throughout the fasting and re-feeding period, with no significant changes between time points.

Reduced HDL2 cholesterol subspecies and elevated postheparin hepatic lipase activity in older men with abdominal obesity and asymptomatic myocardial ischemia

Silent myocardial ischemia (SI), an asymptomatic manifestation of coronary artery disease (CAD), was identified in 10% of apparently healthy nonsmoking, nondiabetic older (60 +/- 7 years, mean +/- SD) men with normal plasma cholesterol levels. We hypothesized that in the absence of other major risk factors for CAD, the men with SI would have reduced plasma levels of high density lipoprotein (HDL) and HDL2 subspecies due to an upper-body fat distribution (waist-to-hip ratio [WHR]), hyperinsulinemia, and abnormal postheparin plasma lipoprotein lipase (LPL) and hepatic lipase (HL) activities. Compared with 47 normal control subjects of similar age, obesity, and maximal aerobic capacity, the 18 men with SI had higher plasma triglyceride (TG) (162 +/- 71 versus 102 +/- 39 mg/dl, p less than 0.001) and lower HDL-C (33 +/- 6 versus 37 +/- 7 mg/dl, p less than 0.02) levels with no difference in low density lipoprotein cholesterol level. The HDL2b and HDL2a subspecies measured by gradient gel electrophoresis were also lower in the men with SI (p less than 0.01). The plasma glucose and insulin responses during an oral glucose tolerance test were the same in both groups. Postheparin plasma HL activity was significantly higher in 12 men with SI than in 41 control subjects (34 +/- 8 versus 27 +/- 10 mumol/ml.hr-1, p less than 0.03) and was correlated with log insulin area (r = 0.36, p less than 0.05) and WHR (r = 0.32, p less than 0.05) in the control subjects but not in the men with SI. In the control group, the percent HDL2b subspecies was correlated inversely with postheparin plasma HL activity (r = -0.46, p less than 0.01, n = 41) as well as WHR (r = -0.49, p less than 0.001, n = 47) and log insulin area (r = -0.37, p less than 0.05, n = 47) but not in the men with SI. Postheparin LPL activity was the same in both groups of men and did not correlate with HDL, WHR, insulin, or plasma TG levels. As the control subjects and men with SI had comparable degrees of abdominal obesity and hyperinsulinemia, these results suggest that the reduced HDL-C levels in men with SI may be related to elevations in HL activity. Thus, abdominal obesity, hyperinsulinemia, elevated TG levels, and low HDL-C and HDL2 subspecies levels may predispose these older men to atherosclerosis.

The effects of weight loss on the activity and expression of adipose-tissue lipoprotein lipase in very obese humans

Lipoprotein lipase is an enzyme in adipose tissue that hydrolyzes circulating triglycerides and thereby generates the fatty acids used in the synthesis of triglyceride in fat cells. To determine whether the activity and expression of lipoprotein lipase are affected by weight loss, we studied lipoprotein lipase in the adipose tissue of nine very obese subjects before and after a program of weight reduction. The subjects' mean (+/- SEM) initial weight was 136 +/- 7.3 kg, and the body-mass index (weight in kilograms divided by the square of the height in meters) ranged from 33.3 to 52.8 (mean, 43.0 +/- 2.5). Biopsies of adipose tissue were performed before weight loss and after it, when weight had been stable for three months. The weight reduction was achieved by a very-low-calorie diet (mean weight loss, 42.5 +/- 6.8 kg). After weight loss, the level of heparin-releasable lipoprotein lipase activity increased in all patients, from 3.8 +/- 1.1 to 7.1 +/- 1.6 neq of free fatty acid released per minute per 10(6) cells (P less than 0.05). In addition, the amount of lipoprotein lipase immunoreactive protein increased from 6.3 +/- 1.7 to 24.4 +/- 6.9 ng per 10(6) cells (P less than 0.05), and there was also an increase in the level of lipoprotein lipase messenger RNA as measured by Northern blotting. There was a strongly positive correlation between the initial body-mass index and the magnitude of the increase in lipoprotein lipase activity (r = 0.80, P less than 0.01) and immunoreactive protein (r = 0.92, P less than 0.01). We conclude that weight loss in very obese subjects leads to the increased activity and expression of lipoprotein lipase, thereby potentially enhancing lipid storage and making further weight loss more difficult.

Changes in lipoprotein subfractions during diet-induced and exercise-induced weight loss in moderately overweight men

We studied separately the effects of weight loss by calorie restriction (dieting) and by calorie expenditure (primarily, running) on lipoprotein subfraction concentrations in sedentary, moderately overweight men assigned at random into three groups as follows: exercise without calorie restriction (n = 46), calorie restriction without exercise (n = 42), and control (n = 42). Plasma lipoprotein mass concentrations were measured by analytic ultracentrifugation for flotation rates (F0(1.20), S0f) within high density lipoprotein (HDL) (F0(1.20) 0-9), low density lipoprotein (LDL) (S0f 0-12), intermediate density lipoprotein (IDL) (S0f 12-20), and very low density lipoprotein (VLDL) (S0f 20-400) particle distributions. Particle diameter and flotation rate of the most abundant LDL species were determined by nondenaturing polyacrylamide gradient gel electrophoresis and analytic ultracentrifugation, respectively. During the 1-year trial, the exercisers ran (mean +/- SD) 15.6 +/- 9.1 km/wk, and the dieters ate 340 +/- 71 fewer kilocalories per day than at baseline. Total body weight was reduced significantly more in dieters (-7.2 +/- 4.1 kg) and exercisers (-4.0 +/- 3.9 kg) than controls (0.6 +/- 3.7 kg). As compared with mean changes in controls, the exercisers and dieters significantly increased HDL2 mass (48.6% and 47.1%, respectively), decreased VLDL mass (-23.9% and -25.5%), and increased LDL peak particle diameter (2.4 and 3.2 A). When adjusted to an equivalent change in body mass index by analysis of covariance, 1) exercise-induced and diet-induced weight loss produced comparable mean changes in the mass of small LDL and VLDL, and in LDL peak particle diameter; 2) the exercisers versus control group difference in HDL2 was attributed to the exercisers' reduced body mass index; and 3) HDL2 increased significantly less in dieters than in exercisers. In dieters, low calorie intake might mitigate the effects of weight loss on HDL2.

Levels of plasma and aortic lipids in young exercised rats with a diminished weight gain

Young exercised rats with a diminished weight gain had a decrease in high density lipoprotein (HDL) cholesterol and phospholipid levels in the plasma and augmented free cholesterol and phosphatide in the aorta. When the weight gain in the trained rats paralleled the gain in non-exercised animals, the values of these lipids were not altered. The levels of aortic free cholesterol in the non-exercised and exercised groups were inversely associated with concentrations of HDL-cholesterol, but were not related to the activities of lecithin cholesterol acyltransferase. In addition, the total cholesterol and phospholipid contents in the aorta negatively correlated with HDL-cholesterol concentrations. We propose that in young exercised rats with a diminished weight gain, the removal of aortic lipids is hampered due to a reduction in HDL-cholesterol.

Elevated adipose tissue lipoprotein lipase activity in craniopharyngioma patients

The activity of lipoprotein lipase (LPL) was measured in adipose tissue (AT-LPL) and postheparin plasma (PH-LPL) of 13 obese patients (aged 11 to 31 years) who had surgery for craniopharyngioma 1 to 13 years earlier. AT-LPL activity (mean +/- SEM) was higher in them than in subjects matched with respect to age, sex, and relative body weight (4.6 +/- 1.1 v 2.1 +/- 0.4 mumol free fatty acids (FFA).h-1.g-1, P less than .05). The activity was also higher when expressed per fat cell.

Weight reduction increases adipose tissue lipoprotein lipase responsiveness in obese women

Lipoprotein lipase was measured in gluteal adipose tissue from nine obese (90.6 +/- 2.7 kg) women fasting and after the intravenous infusion of insulin and glucose before, immediately after, and 3 mo subsequent to a 14.0 +/- 1.8% (mean +/- SEM) weight reduction. Fasting adipose tissue lipoprotein lipase activity (ATLPL) decreased from 5.3 to 2.3 nEq FFA/10(6) cells per min (P less than 0.02) immediately after weight reduction, yet after weight maintenance, higher levels were again found (6.1 nEq FFA/10(6) cells per min). Although responsiveness of ATLPL to 40 mU/m2 per min of insulin infusion over 6 h was absent before weight loss, increases were seen immediately after weight loss (delta 0.8, P = 0.05) and more so (delta 7.7, P less than 0.01) after 3 mo. Moreover, whereas before weight loss the ATLPL response to ingested mixed meals (delta 0.9) was minimal, in the maintained reduced-obese state a marked increase was seen (delta 12.6, P = 0.02). Thus, because ATLPL is important to lipid filling in adipose tissue, the maintenance of high levels of fasting ATLPL and the increase in enzyme responsiveness in the reduced-obese state could play an important role in the resumption of the obese state, which so commonly follows weight reduction.

Basal and postprandial lipoprotein lipase activity in adipose tissue during caloric restriction and refeeding

The effect of a ten-day caloric restriction period and of subsequent refeeding on adipose tissue lipoprotein lipase (LPL) activity was studied in 14 moderately obese women. The enzyme assays were made from subcutaneous fat taken from three separate regions (gluteal, femoral, and abdominal) after overnight fasting and from one region also after a standard meal. There was a close correlation between the activities measured from the different subcutaneous sites. The caloric restriction was followed by a decrease of the basal LPL activity to one fifth of the value recorded during the isocaloric diet. However, the relative postprandial increase of LPL activity was greater during the low-calorie diet than during the isocaloric diet. During refeeding the basal LPL activity rose but remained at a lower level than before the caloric restriction. The postprandial LPL response was markedly exaggerated after ten days of refeeding (21% increase before dieting and 250% after refeeding). The changes of LPL during caloric restriction and subsequent refeeding were not correlated to plasma insulin levels. The mechanism of the exaggerated LPL response to meal during refeeding remains obscure.

Effects of a low-energy diet associated with egg supplementation on plasma cholesterol and lipoprotein levels in normal subjects: results of a cross-over study

1. The influence of a low-energy diet when associated with high-cholesterol intake was investigated in seventeen normal men during an 8-week cross-over study. The subjects were given a daily supplement of two whole eggs and two egg yolks (approximately 1 g cholesterol) either with their usual diet for 4 weeks or with a low-energy diet for 4 weeks. Each subject took part randomly in both dietary periods. 2. During the first part of the study, no changes occurred in the plasma cholesterol of the subjects with egg supplementation of the usual diet. 3. In contrast, the low-energy diet and associated weight loss markedly decreased tolerance to high-cholesterol intake resulting in increased plasma cholesterol. The mean rise was 22.7% but with wide individual variations in the response. This was almost completely normalized when the subjects returned to their usual energy intake indicating the involvement of weight reduction in the increase observed. 4. Changes in low-density-lipoprotein (LDL) cholesterol were parallel to those of total plasma cholesterol with an increase following the low-energy diet and normalization after body-weight recovery. 5. The opposite effect was shown with the low-energy diet after previous adaptation to the consumption of four eggs per day. This dietary regimen resulted in a decrease in plasma cholesterol although it was not significant. Moreover, the lipoprotein profile was improved with a decrease in very-low-density-lipoprotein (VLDL) cholesterol and an increase in high-density-lipoprotein (HDL) cholesterol. 6. High-cholesterol intake induced significant changes in lipoprotein composition whatever the energy ration. LDL and HDL were enriched in cholesterol esters as early as the 1st month of egg supplementation of the diet. 7. Taken together, the results emphasize the possible adverse effect of slimming diets when associated with high-cholesterol intake. The existence of 'high-responders' to these dietary conditions calls for special attention to be paid to the cholesterol content of restricted diets.

Comparison of clofibrate and caloric restriction on kinetics of very low density lipoprotein triglycerides

This study of 12 patients with mild-to-moderate hypertriglyceridemia compares the mechanisms of triglyceride (TG) lowering by caloric restriction and by clofibrate. Turnover rates of very low density lipoprotein triglycerides (VLDL-TG) were determined by using 3H-glycerol as a precursor. Radioactivity-time curves of VLDL-TG were analyzed with a multicompartmental model. Hypertriglyceridemia in these patients was due mainly to overproduction of VLDL-TG. Clofibrate therapy for 1 month had a variable effect on VLDL-TG levels. A group of relatively poor responders to the drug had a mild increase in the fractional catabolic rate (FCR) of VLDL-TG, but no change in production rates. The remaining patients were relatively good responders; they had increased FCR and modest reductions in synthetic rates of VLDL-TG. However, clofibrate largely failed to correct the primary defect in this group of patients, namely, the overproduction of VLDL-TG. Almost all patients responded to 1 month of caloric restriction (1000 cal/day) with marked reductions in VLDL-TG levels. The major response to reduced caloric intake was a decrease in production of VLDL-TG, although FCR was also increased to some extent. Despite these differences in mechanisms for VLDL-TG lowering, both regimens tended to raise levels of LDL and HDL.

Serum lipoprotein and lipoprotein lipase in overweight, type II diabetics during and after supplemented fasting

Poorly controlled, obese, Type II diabetics were studied before, during, and 3 months after a weight reduction program that used supplemented fasting (200 kcal or 0.9 MJ/day). During fasting, the very low density lipoprotein (VLDL) triglycerides (TG) decreased, as did the adipose tissue lipoprotein lipase (AT-LPLA) and skeletal muscle lipoprotein lipase (SM-LPLA) activities. Three months later VLDL TG remained low (-59%), while high density lipoprotein cholesterol was higher (+11%) and blood glucose control improved compared with values on admission. The fractional removal rate (K2) at the i.v. fat tolerance test (IVFTT) and the SM-LPLA were unchanged, while AT-LPLA (expressed per gram of wet weight, but not as whole-body AT-LPLA) increased by 25%. There were no significant correlations between AT-LPLA and the lipoprotein TG concentrations or K2-IVFTT, although there were significant positive correlations between SM-LPLA and K2-IVFtt, both on admission and after body weight stabilization. This may indicate that SM-LPLA is more directly related to the capacity to remove lipoprotein TG, at least in obese diabetic patients. K2-IVFTT was inversely correlated to the VLDL TG and cholesterol concentrations both before and 3 months after fasting. Because both SM-LPLA and K2-IVFTT were unchanged after body weight reduction, the change in VLDL TG may be mainly due to a reduced rate of lipoprotein synthesis.

Changes in lipoprotein metabolism during a supplemented fast and an ensuing vegetarian diet period

The effect on lipoprotein metabolism of a 2-week modified fast and an immediately ensuing 3-week period on a vegetarian diet was studied under metabolic ward conditions in 21 non-obese female and 6 male patients. The very low calorie diet induced reductions of the cholesterol concentration in all serum lipoprotein classes. In the female patients, who were all normolipoproteinaemic, the triglycerides in serum showed a slight increase during the fast, reflecting small changes in very low (VLDL) and low density lipoprotein triglycerides. This may probably be explained partly by simultaneous significant reductions of both the adipose tissue and skeletal muscle tissue lipoprotein lipase activities (LPLA). In contrast, in the male patients who had a higher VLDL level at admission, the VLDL triglycerides decreased without significant changes of high density lipoprotein (HDL) cholesterol and of LPLA in muscle. The female patients, whose weights were stable during the vegetarian diet, ended up with a lower HDL cholesterol than at the start of the trial. This effect was probably partly due to the high content of polyunsaturated fatty acids in the vegetarian diet. It is concluded that the changes of lipoprotein metabolism during supplemented fasting are quantitatively and qualitatively different in several respects in females and males.

Regulation of lipoprotein lipase in primary cultures of isolated human adipocytes

To study the regulation of adipose tissue lipoprotein lipase (LPL) in human adipocytes, omental adipose tissue was obtained from healthy subjects and digested in collagenase. The isolated adipocytes thus obtained were suspended in Medium 199 and cultured at 37 degrees C. Cell viability was demonstrated in adipocytes cultured for up to 72 h by constancy of cell number, cell size, trypan-blue exclusion, and specific 125I-insulin binding. In addition, chloroquine induced an increase in cell-associated 125I-insulin at 24, 48, and 72 h after preparation. Thus, isolated adipocytes retained their ability to bind, internalize, and degrade insulin. LPL was measured as activity secreted into the culture medium (CM), released from cells by heparin (HR), and extracted from cell digests. A broad range of heparin concentrations produced a prompt release of LPL from a rapidly replenishable pool of cellular activity. When cells were cultured in medium containing 10% fetal bovine serum, there was a marked stimulation of CM and HR. The secretory response to serum (CM) correlated strongly with HR 24 h after preparation (rs = 0.731, P less than 0.001). In addition, HR was found to correlate logarithmically and inversely with body mass index (r = -0.731, P less than 0.001). Insulin, at 400 ng/ml only, increased HR by 36 +/- 10%, an effect simulated by lower concentrations of insulin-like growth factor-1 (IGF1). Thus, LPL is produced and regulated in isolated human adipocytes. The degree of adiposity and serum are important regulators of HR activity, whereas insulin is stimulatory only at a pharmacologic concentration. This effect of insulin may be mediated through the IGF1 receptor. Isolated human adipocytes represent a novel and useful system for the study of LPL and lipid metabolism as well as for other aspects of adipocyte biology.

Metabolic changes induced by combined prolonged exercise and low-calorie intake in man

Thirteen middle-aged women and 10 men walked 344 km during 7 days. The daily walking distances were 57, 53, 67, 53, 41, 36, and 37 km at an average speed of 3.5 km X h-1. During the hike the subjects drank water, mineral drinks, and juices ad libitum. Except for some natural products, no food intake was allowed. During the hike the body weight and serum protein concentration of the subjects decreased by about 7%, on average. Serum triglyceride and total cholesterol decreased drastically, about 30-40% during the hike, but HDL-cholesterol showed a tendency to increase, giving a 40% increment in HDL/total cholesterol ratio. Serum free fatty acids rose 1.5-2 times above the starting level. Serum glucose and evening insulin levels decreased significantly during the hike. Serum cortisol in evening samples after the daily walking and plasma norepinephrine concentrations were significantly increased, reflecting the immediate daily response to the combined fasting and walking. Serum testosterone levels decreased in men but not in women, indicating the involvement of the LH-testis pathway in the decrease obtained. Serum ASAT activity rose to about three times the starting level during the hike, whereas gamma-GT activity gradually decreased. These marked metabolic changes caused by combined fasting and several days exercise were in many respects (as in cholesterol, HDL/total cholesterol ratio or testosterone levels) more pronounced than those earlier reported to be caused by exercise or fasting alone.

Response of adipose tissue lipoprotein lipase activity and serum lipoproteins to acute hyperinsulinaemia in man

In order to assess the short-term effects of hyperinsulinaemia and hyperglycaemia on adipose tissue lipoprotein lipase activity and on serum lipoproteins, we measured these variables in ten normal subjects during euglycaemic and hyperglycaemic hyperinsulinaemic clamps. The mean steady-state plasma glucose and insulin concentrations, respectively, were 4.7 mmol/l and 101 mU/l during euglycaemic moderate-insulin clamp, 4.9 mmol/l and 565 mU/l during euglycaemic high-insulin clamp, and 8.8 mmol/l and 148 mU/l during hyperglycaemic clamp. Saline infusion was used as control. The adipose tissue lipoprotein lipase activity rose significantly over 5 h during high-insulin clamp (p less than 0.01) and during hyperglycaemic clamp (p less than 0.05), but did not change during the moderate-insulin clamp. The magnitude of change of lipoprotein lipase activity from baseline (either rise or fall) was inversely related to the preclamp activity during euglycaemic moderate-insulin clamp (r = -0.67), during hyperglycaemic clamp (r = -0.68) and during infusion of saline (r = -0.75, p less than 0.05). Total serum triglyceride concentration decreased significantly during all clamp studies compared with the control experiment. This change was mainly accounted for by a decrease of VLDL triglyceride. The LDL cholesterol level fell by an average of 5% (p less than 0.05) during the high-insulin clamp and by 10% (p less than 0.05) during the hyperglycaemic clamp. The HDL cholesterol level did not change significantly. It is concluded that adipose tissue lipoprotein lipase activity in man is increased by physiological insulin levels during hyperglycaemia and also by supraphysiological insulin levels during euglycaemia, but is not influenced by physiological hyperinsulinaemia without hyperglycaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary fiber and lipoprotein metabolism in the genetically obese Zucker rat

The present investigation was designed to examine the influence of dietary fibers with differing soluble fiber compositions upon the metabolism of lipids in a hyperlipemic animal model, the Zucker fatty rat. The response to fiber was examined using a diet supplemented with cellulose, oat bran, or pectin which have a soluble/insoluble fiber ratio of 0:100, 33:66, and 100:0, respectively. These fibers provided 10% of the total diet weight; the control diet contained no fiber. A rapid increase in plasma triglyceride concentration was observed in all animals given fiber-supplemented diets in correlation with the increased carbohydrate content of the defined diets relative to the prestudy diets. This increase in plasma triglyceride was due to increased production of triglycerides with no change in the rates of clearance. The plasma total cholesterol levels were relatively constant on all diets. However, after 7 weeks on the pectin-supplemented diet, rats showed a 39% elevation in HDL and a 44% reduction in LDL concentration. This diet also resulted in reduced weight gain, in spite of a caloric intake equivalent to the control diets. Our data suggest that the ability of dietary fiber to alter plasma lipoproteins might be predictable from the soluble fiber composition or the pectin content of a given dietary fiber in this model of genetic endogenous hyperlipemia.

Increases in hyperlipoproteinemia, disturbances in cholesterol metabolism and atherosclerosis induced by dietary restriction in rabbits fed a cholesterol-rich diet

The influence of dietary restriction on cholesterol transport and metabolism was investigated in rabbits given standard or cholesterol-rich diets (0.2 g cholesterol/kg body weight daily) either ad libitum or with 50% caloric ration. Dietary restriction which has only a slight influence in control rabbits markedly aggravated the disturbances induced by exogenous cholesterol. With limited feeding, control rabbits presented a moderate increase in plasma cholesterol, whereas marked aggravation of hypercholesterolemia was observed in cholesterol-fed rabbits. Analysis of the lipoprotein profile showed that the excess of plasma cholesterol with the restricted cholesterol-rich diet corresponded to an increase in the concentration of very low density lipoprotein (VLDL) and low density lipoproteins (LDL) without any additional changes in the composition of these lipoproteins. No significant change appeared in the high density lipoprotein (HDL) concentration. The parameters of cholesterol metabolism were determined, from the curves of [3H]cholesterol radioactivity decrease, using a two-pool model. The increase in cholesterol turnover rate induced by the cholesterol-rich diet was accentuated by dietary restriction, whereas rabbits on standard restricted diet showed a slight decrease. The large increase in the size of both pools A and B in cholesterol-fed rabbits was even more pronounced with limited feeding. Dietary restriction induced additional accumulation of cholesterol in the aortic wall and the grade of the lesions was also aggravated.

Exercise, diet, or physical characteristics as determinants of HDL-levels in endurance athletes

Serum lipids, lipoproteins, apolipoproteins, physical characteristics, and 10-day dietary records of 20 male distance runners (aged 20-42 years) were compared with those of 14 sedentary controls (aged 23-34 years). Runners had significantly greater levels (mean +/- SD) of high density lipoproteins (HDL) whether estimated as HDL-cholesterol (66 +/- 12 vs 46 +/- 10 mg/dl) or as the major HDL apolipoproteins, apoA-I (170 +/- 36 vs 124 +/- 27 mg/dl) or apoA-II (39 +/- 5 vs 34 +/- 4 mg/dl). Runners were leaner with considerably less body fat (8.3 +/- 1.7 vs 16.2 +/- 3.9%) than the sedentary men despite consuming 20% more calories. Moreover, the additional calories consumed were largely carbohydrate. This comparison illustrates that high absolute quantities of dietary carbohydrate do not depress HDL levels in lean individuals engaged in exercise training. Furthermore, the results suggest that dietary factors may be as important as exercise itself in producing the lipoprotein pattern characteristic of endurance athletes.

Changes in the activities of lipoprotein lipase and the lipogenic enzymes in tumor-bearing rats

The effects of tumor growth on lipid metabolism were investigated by evaluating serum lipids, lipoprotein lipase activity (LPLA), the lipogenic enzymes, urinary catecholamines along with serum insulin and glucagon levels. We injected 1.5 X 10(6) cells of rat mammary tumor, AC33, and killed the rats on the 18th day. Serum triglycerides and free fatty acids of the tumor-bearing (TB) rats increased 4 and 5 times, respectively, more than the control (C) rats. Total liver lipids were not significantly different between the two groups. Tumor growth produced a 70% decrease in total epididymal fat pad LPLA; there were no changes in soleus muscle LPLA. Serum insulin levels of the TB rats were 49% less than the C rats. The TB rats had significantly lighter epididymal fat pads and lower activities of adipose fatty acid synthetase and citrate cleavage enzyme. Urinary catecholamines of the TB rats were reduced over 30% compared with the C rats. These results show that the hypertriglyceridemia of the TB rats may be due, in part, to a deficiency of adipose tissue LPLA. The data also suggest that the effects of the tumor on lipid metabolism may be mediated through insulin.

Dietary determinants of plasma cholesterol change in the recruitment phase of the Lipid Research Clinics Coronary Primary Prevention Trial

We have investigated the relationship of diet to plasma lipid and lipoprotein levels in 6494 hypercholesterolemic (Type IIA) men who were instructed in an isocaloric, 400 mg cholesterol, 0.8 polyunsaturated-to-saturated fat ratio diet in the course of recruitment for the Lipid Research Clinics Coronary Primary Prevention Trial. Single 24-hour dietary recalls, plasma total and high density lipoprotein cholesterol, and total triglyceride determinations were obtained approximately 1 month before and 1 month after dietary instruction. Cross-sectional correlation analysis disclosed no significant association between diet and plasma cholesterol at entry. However, when diet-associated changes were similarly analyzed, weight loss, decreased intakes of saturated fat and cholesterol, and increased intake of polyunsaturated fat were all significantly and independently predictive of falls in plasma cholesterol, mainly in its low density lipoprotein fraction. The multiple correlation coefficient for the resultant four-variable regression model was 0.29. Diet-associated changes in plasma very low density lipoprotein cholesterol were less marked but in the same direction. These dietary changes were also weakly associated with a lowering of plasma high density lipoprotein cholesterol, while weight loss had an opposite effect of similar strength. When one takes into account the variability of dietary recall data, the observed diet-associated changes in plasma cholesterol were compatible with the findings of metabolic ward studies.

Characterization of lipase activities in obese Pima indians. Decreases with weight reduction

Adipose tissue and muscle lipoprotein lipase and postheparin hepatic and lipoprotein lipase activities have been measured in a group of 21 Pima Indian males over a wide range of body weight to determine the relationship between obesity and these lipase activities. There was a significant positive correlation between adipose tissue lipoprotein lipase and obesity; muscle and postheparin lipoprotein lipase and hepatic lipase were not related to degree of obesity. Fasting insulin levels were not related to any of the measurements of lipase activity. There were racial differences in adipose and postheparin lipoprotein lipase activities; both were significantly lower in the Pimas as compared with a group of weight-matched Caucasian males. Lipase activities were remeasured in eight subjects after a period of weight reduction including several weeks of stabilization at the reduced weights. After the period of weight reduction adipose tissue lipoprotein lipase declined in all subjects. Hepatic lipase also declined in all but two patients. Muscle and postheparin lipolytic activities were not affected by weight loss. The data indicate that (a) there are racial differences in adipose tissue lipoprotein lipase; and (b) the elevated adipose lipoprotein lipase associated with obesity, like many other biochemical variables in the obese state, returns toward normal after weight reduction.

Regulation of high density lipoprotein levels

Current concepts of the structure and metabolism of high density lipoproteins are presented and factors that influence their levels in human beings are surveyed.

Lipoprotein lipase activity and serum lipoproteins in untreated type 2 (insulin-independent) diabetes associated with obesity

Serum lipoproteins and the heparin-releasable lipoprotein lipase (LPL) activity of adipose tissue and skeletal muscle were measured in 36 untreated obese patients with Type 2 (insulin-independent) diabetes and the values were compared with those of non-diabetic subjects of similar age, sex and relative body weight. In diabetic men, the LPL activity of adipose tissue was significantly reduced when expressed per tissue weight or per fat cell (p less than 0.01). Diabetic females had slightly but not significantly lower LPL activity in adipose tissue than the non-diabetic females. The muscle LPL activity was similar in diabetic and non-diabetic subjects of both sexes. When the diabetic men were classified according to fasting blood glucose, the patients with high glucose levels had lower adipose tissue LPL activity than those with moderate hyperglycemia. In both diabetic and non-diabetic subjects, there was a significant positive correlation between HDL cholesterol concentrations and adipose tissue LPL activity. It is concluded that Type 2 diabetes influences adipose tissue LPL activity and plasma lipoprotein concentrations and that this effect is superimposed on the similar changes produced by obesity alone.

Increase of adipose tissue lipoprotein lipase activity with weight loss

Obese subjects have elevated adipose tissue lipoprotein lipase activity per fat cell when compared with lean control subjects. This enzyme, which is rate limiting for the uptake and storage of lipoprotein triglyceride in adipose tissue, has been shown to be further elevated in a group of previously obese subjects who had been weight stable at a reduced weight for 4-28 mo. In the present prospective study of eight obese subjects, adipose tissue lipoprotein lipase activity was demonstrated to increase after weight stabilization at a reduced weight (0.33 mU/10(6) cells). In three subjects who lost weight and subsequently regained their lost weight, the enzyme activity increased after weight loss and then returned toward the original basal level with weight gain. One subject who maintained his weight loss for 10 mo. continued to have an elevated level of enzyme activity. Because adipose tissue lipoprotein lipase activity does not "normalize" after weight loss, we hypothesize that this enzyme may play a counterregulatory role in resisting deviation from a "set point" for fat mass or fat cell size and thereby predispose to reattainment of the original obese state.

Lipoprotein lipase activity in adipose tissue and skeletal muscle of human diabetics during insulin deprivation and restoration

Twelve insulin-dependent diabetic patients were deprived of insulin for 12 h, and thereafter given an 8-h i.v. infusion of insulin. Lipoprotein lipase (LPL) activity was determined from heparin eluates of adipose tissue and skeletal muscle before and after insulin infusion. In spite of development of marked hyperglycemia and hyperketonaemia during the insulin deprivation the LPL activity of the two tissues remained mostly within normal range. During the subsequent insulin administration the LPL activity of adipose tissue increased by 36% (p less than 0.05) whereas the skeletal muscle LPL remained unchanged. The result is compatible with the view that human adipose tissue LPL is more sensitive to insulin than the corresponding enzyme of muscle.