Stimulation of NSF ATPase activity by alpha-SNAP is required for SNARE complex disassembly and exocytosis.

N-ethylmaleimide-sensitive fusion protein (NSF) and alpha-SNAP play key roles in vesicular traffic through the secretory pathway. In this study, NH2- and COOH-terminal truncation mutants of alpha-SNAP were assayed for ability to bind NSF and stimulate its ATPase activity. Deletion of up to 160 NH2-terminal amino acids had little effect on the ability of alpha-SNAP to stimulate the ATPase activity of NSF. However, deletion of as few as 10 COOH-terminal amino acids resulted in a marked decrease. Both NH2-terminal (1-160) and COOH-terminal (160-295) fragments of alpha-SNAP were able to bind to NSF, suggesting that alpha-SNAP contains distinct NH2- and COOH-terminal binding sites for NSF. Sequence alignment of known SNAPs revealed only leucine 294 to be conserved in the final 10 amino acids of alpha-SNAP. Mutation of leucine 294 to alanine (alpha-SNAP(L294A)) resulted in a decrease in the ability to stimulate NSF ATPase activity but had no effect on the ability of this mutant to bind NSF. alpha-SNAP (1-285) and alpha-SNAP (L294A) were unable to stimulate Ca2+-dependent exocytosis in permeabilized chromaffin cells. In addition, alpha-SNAP (1-285), and alpha-SNAP (L294A) were able to inhibit the stimulation of exocytosis by exogenous alpha-SNAP. alpha-SNAP, alpha-SNAP (1-285), and alpha-SNAP (L294A) were all able to become incorporated into a 20S complex and recruit NSF. In the presence of MgATP, alpha-SNAP (1-285) and alpha-SNAP (L294A) were unable to fully disassemble the 20S complex and did not allow vesicle-associated membrane protein dissociation to any greater level than seen in control incubations. These findings imply that alpha-SNAP stimulation of NSF ATPase activity may be required for 20S complex disassembly and for the alpha-SNAP stimulation of exocytosis.

Cardiac sarcolemma: compositional adaptation to exercise.

Marked changes were observed in the lipid composition of highly purified plasma membranes isolated from the hearts of rats subjected to daily treadmill running. Compared to sedentary controls, sarcolemmal content of total phospholipid and phosphatidylserine in the trained group was increased 23 and 50 percent, respectively. This observation suggests a mechanism by which cardiac contractility may be enhanced by exercise.

Domains of alpha-SNAP required for the stimulation of exocytosis and for N-ethylmalemide-sensitive fusion protein (NSF) binding and activation.

The binding of alpha-SNAP to the membrane proteins syntaxin, SNAP-25, and synaptobrevin leads to the recruitment of the N-ethylmaleimide-sensitive fusion protein (NSF). ATP hydrolysis by NSF has been suggested to drive conformational changes in one or more of these membrane proteins that are essential for regulated exocytosis. Functional evidence for a role of alpha-SNAP in exocytosis in adrenal chromaffin cells comes from the ability of this protein to stimulate Ca(2+)-dependent exocytosis in digitonin-permeabilized cells. Here we examine the effect of a series of deletion mutants of alpha-SNAP on exocytosis, and on the ability of alpha-SNAP to interact with NSF, to define essential domains involved in protein-protein interactions in exocytosis. Deletion of extreme N- or C-terminal regions of alpha-SNAP produced proteins unable to bind to syntaxin or to stimulate exocytosis, suggesting that these domains participate in essential interactions. Deletion of C-terminal residues abolished the ability of alpha-SNAP to bind NSF. In contrast, deletion of up to 120 N-terminal residues did not prevent the binding of NSF to immobilized alpha-SNAP and such mutants were also able to stimulate the ATPase activity of NSF. These results suggest that the C-terminus, but not the N-terminus, of alpha-SNAP is crucial for interactions with NSF. The involvement of the C-terminus of alpha-SNAP, which contains a predicted coiled-coil domain, in the binding of both syntaxin and NSF would place the latter two proteins in proximity in a ternary complex whereupon the energy derived from ATP hydrolysis by NSF could induce a conformational change in syntaxin required for exocytosis to proceed.

Alpharetrovirus envelope-receptor interactions.

Infection by all enveloped viruses occurs via the fusion of viral and cellular membranes and delivery of the viral nucleocapsid into the cell cytoplasm, after association of the virus with cognate receptors at the cell surface. This process is mediated by viral fusion proteins anchored in the viral envelope and can be defined based on the requirement for low pH to trigger membrane fusion. In viruses that utilize a pH-dependent entry mechanism, such as influenza virus, viral fusion is triggered by the acidic environment of intracellular organelles after uptake of the virus from the cell surface and trafficking to a low-pH compartment. In contrast, in viruses that utilize a pH-independent entry mechanism, such as most retroviruses, membrane fusion is triggered solely by the interaction of the envelope glycoprotein with cognate receptors, often at the cell surface. However, recent work has indicated that the alpharetrovirus, avian sarcoma and leukosis virus (ASLV), utilizes a novel entry mechanism that combines aspects of both pH-independent and pH-dependent entry. In ASLV infection, the interaction of the envelope glycoprotein (Env) with cognate receptors at the cell surface causes an initial conformational change that primes (activates) Env and renders it sensitive to subsequent low-pH triggering from an intracellular compartment. Thus unlike other pH-dependent viruses, ASLV Env is only sensitive to low-pH triggering following interaction with its cognate receptor. In this manuscript we review current research on ASLV Env-receptor interactions and focus on the specific molecular requirements of both the viral fusion protein and cognate receptors for ASLV entry. In addition, we review data pertaining to the novel two-step entry mechanism of ASLV entry and propose a model by which ASLV Env elicits membrane fusion.

Effects of life-style modification on serum lipids.

Life-style modification has been recommended by the National Cholesterol Education Program as the first approach to reduce serum lipid values and the risk for coronary heart disease. Presented are data from 4587 adults who attended a 3-week residential, life-style modification program consisting of a high-complex-carbohydrate, high-fiber, low-fat, and low-cholesterol diet combined with daily aerobic exercise, primarily walking. Total cholesterol values were reduced by 23%, from 6.06 to 4.66 mmol/L (234 to 180 mg/dL). Low-density cholesterol (LDL-C) values were also reduced by 23%, from 3.9 to 3.0 mmol/L (151 to 116 mg/dL), with most of the change occurring during the first 2 weeks. Male subjects showed a greater reduction in total cholesterol (24.4% vs 20.8%) and LDL-C (25% vs 19.4%) values compared with female subjects. Follow-up studies for 18 months on a small group showed that, in most cases, continued compliance with the program maintained total cholesterol values well below 5.18 mmol/L (200 mg/dL), the level recommended by the National Cholesterol Education Program. High-density cholesterol (HDL-C) was reduced by 16%, but the ratio of total cholesterol to HDL-C was reduced by 11%. Female subjects showed a greater drop in HDL-C values than did male subjects (19.4% vs 11.6%). Serum triglyceride values were reduced by 33%, from 2.29 to 1.54 mmol/L (200 to 135 mg/dL); again, male subjects showed a greater reduction than the did female subjects (37.9% vs 22.5%). Body weight was also significantly reduced, 5.5% for male subjects and 4.4% for female subjects. These results show that most adults can significantly reduce serum lipid values and the risk for atherosclerosis and its clinical sequelae through life-style modification consisting of diet and exercise.

Diet and exercise in the treatment of NIDDM. The need for early emphasis.

OBJECTIVE: To investigate the effectiveness of an intensive diet and exercise program for controlling non-insulin-dependent diabetes mellitus (NIDDM) and reducing risk factors associated with macrovascular complications. RESEARCH DESIGN AND METHODS: Medical charts obtained from 4,587 participants in a lifestyle modification program were screened for patients with NIDDM. A total of 652 patients was identified, and their responses to the 3-week program were analyzed. RESULTS: Fasting glucose level was reduced from 10.0 to 8.45 mmol/l, and 71% of 197 subjects taking oral hypoglycemic agents and 39% of 212 taking insulin were able to discontinue their medication. Of the 243 not taking medication, 76% reduced their fasting glucose levels to < or = 7.84 mmol/l. Blood pressure was significantly reduced, and of the 319 initially taking antihypertension drugs, 34% had their medication discontinued. Serum total and low-density lipoprotein cholesterol were reduced by 22% and triglycerides by 33%. The ratio of total to high-density lipoprotein cholesterol was reduced by 13%. CONCLUSIONS: Lifestyle modification consisting of diet combined with aerobic exercise can be effective for controlling NIDDM and reducing risk factors associated with macrovascular complications in both men and women. The program was far more effective in controlling the disease in patients taking no medication or oral agents compared with patients taking insulin. These results stress the need for early emphasis on lifestyle modification in the treatment of NIDDM.

Response of non-insulin-dependent diabetic patients to an intensive program of diet and exercise.

To assess the effectiveness of the Pritikin program of diet and exercise for treating patients with non-insulin-dependent diabetes mellitus (NIDDM), data were obtained from 60 patients who completed the 26-day residential program. Of the 23 patients who were taking oral hypoglycemic agents upon entry, all but 2 were off medication by the end of the program. Of the 17 patients who were taking insulin, all but 4 were off medication at discharge. Two of the four had their insulin reduced by 50% while the remaining two had no major change in their insulin dosage. Fasting blood glucose was reduced from 194.9 +/- 10.1 to 144.6 +/- 7.1 mg/dl. Serum cholesterol was reduced from 225.4 +/- 5.7 to 181.7 +/- 4.9 mg/dl while triglycerides were reduced from 283.7 +/- 28.8 to 186.2 +/- 11.6 mg/dl. The group as a whole lost an average of 4.3 kg/body wt and achieved 40.5% of their desired weight loss. Maximum work capacity increased from 5.6 +/- 0.3 to 7.9 +/- 0.4 METs, while daily walking increased from 11.7 +/- 2.4 to 102.8 +/- 4.8 min/day. The decrease in fasting glucose was not correlated with weight loss (r = 0.24), increase in walking time (r = 0.00), or increase in MET capacity (r = 0.05). We conclude that the total program is an effective means for treating NIDDM patients. We also feel that the high-complex-carbohydrate, high-fiber, low-fat diet is of primary importance.

Long-term use of a high-complex-carbohydrate, high-fiber, low-fat diet and exercise in the treatment of NIDDM patients.

The purpose of this study was to assess the long-term effects of a high-complex-carbohydrate, high-fiber, low-fat diet and exercise on 69 NIDDM patients. During the initial 26-day program, fasting glucose was reduced from 179.5 +/- 10.6 to 133.5 +/- 4.0 mg/dl. This decrease in fasting glucose was achieved along with the discontinuation of oral hypoglycemic agents in 24 of 31 patients and of insulin in 13 of 18 patients; one patient was placed on insulin. Serum cholesterol and triglycerides were reduced by 25% and 27%, respectively. At 2-3 yr of follow-up, fasting glucose was not significantly different from the value observed at the end of the 26-day program. Compared with the end of the 26-day program, seven more patients were taking oral agents and four more were on insulin. Exercise and diet inventories obtained at follow-up indicated good compliance to the program and also indicated that the main difference between those patients who went back on medication at follow-up compared with those remaining off medication was the percent of calories derived from fat.

Exercise capacity of rats remains unaffected by a chronic pressure overload.

OBJECTIVE: The aim was to determine if the adaptive responses of the myocardium to a chronic pressure overload affected cardiovascular performance when evaluated under conditions of increased functional demand. METHODS: Selected female rats were made hypertensive by abdominal aortic constriction. After eight weeks of aortic constriction, cardiovascular responses and work performance were measured during a maximal treadmill exercise bout. RESULTS: Aortic constriction increased mean arterial pressure and the relative quantity of the slow ATPase myosin isoform, V3, relative to untreated controls (p < 0.05). Both groups had similar oxygen consumptions (VO2), heart rates (HR), and oxygen pulses (VO2/HR) at rest and throughout the exercise test. Both groups reached their VO2 max at the same exercise duration and exercise intensity (40.4 m.min-1). Soleus citrate synthase activity was not different between the groups. CONCLUSIONS: These similarities in work capacity, VO2, oxygen pulse, and muscle oxidative capacity suggest (1) that cardiovascular and exercise capacity can both be maintained in spite of the presence of a chronic pressure overload; (2) that after two months of aortic constriction the heart appears to be in a compensated stage of adaptation; and (3) that the cardiac myosin isoenzyme profile may have little direct effect on cardiovascular functional capacity.

Left ventricular O2 requirements of pressure and volume loading in the normal canine heart and inaccuracy of pressure-derived indices of O2 demand.

The purpose of this study was to: 1) re-evaluate the left ventricular O2 requirements (MVO2) of pressure and volume-loading; and b) assess the accuracy of pressure-derived indices of left ventricular (LV) O2 demand under pressure-loading and volume-loading conditions. Using a right heart bypass preparation (heart rate 150 beats . min-1), mean arterial pressure (7.3 to 22.9 kPa) and cardiac output (0.8 to 6.0 litre . min-1) were varied independently. Adequate left ventricular O2 supply was demonstrated by normal transmural distribution of blood flow, normal myocardial lactate metabolism, and intact reactive hyperaemic responses. For equivalent increases in cardiac external work (from 2 to 4 joules . min-1) pressure-loading and volume-loading resulted in similar increases in O2 uptake (59% and 49%, respectively, P = 0.21). MVO2 was consistently greater for volume-loading than for pressure-loading at any SPTI, pressure-rate product, and triple product. The prediction of O2 demands by these indices under these loading conditions collectively was unreliable (r = 30 to 0.42). O2 requirements of the left ventricle with both pressure-loading and volume-loading were highly correlated (r = 0.82 to 0.99) with meridional wall stress. We conclude that: 1) volume-loading conditions have a greater O2 requirement than appreciated previously; 2) pressure loads and volume loads require similar O2 uptake in the normal canine heart for similar external work; 3) currently used pressure-derived indices are unreliable predictors of LV O2 demand when loading conditions are varied; and 4) O2 requirements are more uniformly related to meridional wall stress.

Effects of streptozotocin-induced diabetes on glucose transport in skeletal muscle.

Female Sprague-Dawley rats were injected with streptozotocin (45 mg/kg) to induce mild diabetes (glucose, greater than 13 mM). Half of the animals received daily insulin injections to reduce hyperglycemia. After 10 weeks, sarcolemmal membranes were isolated from hindlimb muscles to study glucose transport, and the number of glucose transporters was assessed by cytochalasin-beta binding. Both glucose transport (19.2 +/- 1.6 vs. 31.93 +/- 3.29 pmol/mg protein.15 sec) and cytochalasin-beta binding (3.06 +/- 0.28 vs. 6.14 +/- 0.59 pmol/mg protein) were significantly (P less than 0.05) reduced in the diabetic untreated rats compared to control values. Daily insulin injections restored both (P less than 0.05) basal transport (33.22 +/- 3.62 pmol/mg protein.15 sec) and cytochalasin-beta binding (5.52 +/- 0.66 pmol/mg protein) to control levels. Maximum insulin stimulation (1 U/kg, iv) significantly increased (P less than 0.05) both glucose transport (30.18 +/- 3.76 vs. 96.48 +/- 4.21 pmol/mg protein.15 sec) and cytochalasin-beta binding (4.38 +/- 0.29 vs. 9.40 +/- 0.42 pmol/mg protein) in the untreated diabetic and control rats. However, the stimulation in the untreated diabetic rats only reached basal control levels, which was significantly (P less than 0.05) below the insulin-stimulated value for the controls. In the rats receiving daily insulin injections, maximum insulin stimulation increased (P less than 0.05) both glucose transport (58.67 +/- 15.24 pmol/mg protein.15 sec) and cytochalasin-beta binding (6.4 +/- 0.7 pmol/mg protein), but both transport and binding were significantly (P less than 0.05) below insulin-stimulated values for the control rats. These data show that insulin deficiency adversely affected the glucose transport system in skeletal muscle. Both basal and maximum insulin-stimulated transport and the number of transport molecules were reduced. Daily insulin treatment corrected some of the defects, but maximum insulin stimulation was still significantly below values for control animals.

Prostate cancer: another aspect of the insulin-resistance syndrome?

Insulin resistance and compensatory hyperinsulinaemia are thought to be the underlying factors in the metabolic or insulin-resistance syndrome and can be controlled by diet and exercise. Hyperinsulinaemia has been shown to have a direct effect on the live, suppressing the production of sex hormone-binding globulin (SHBG) and insulin-like growth factor-binding proteins 1 and 2 (IGFBP-1, -2) while stimulating the production of insulin-like growth factor 1 (IGF-1). These factors have been proposed to be important modulators of hormone-related cancers, such as prostate cancer. Men adopting a low-fat diet and daily exercise reduced their levels of serum insulin and IGF-1, while increasing their levels of IGFBP-1 and sex hormone-binding globulin (SHBG). Cell-culture studies with LNCaP prostate cancer cells showed apoptosis of tumour cells and a reduction in serum-stimulated cell growth in the post diet and exercise serum. These results suggest that prostate cancer may be another aspect of the insulin-resistance syndrome and that adopting a low-fat diet combined with regular exercise may reduce the risk for prostate and other hormone-related cancers. This needs to be tested with prospective studies.

Stimulation of NSF ATPase activity during t-SNARE priming.

N-Ethylmaleimide-sensitive factor (NSF) plays a key role in vesicular traffic by disassembling and priming SNARE proteins for their function in docking and fusion. We demonstrate that the ATPase activity of NSF is activated by alpha-soluble NSF attachment protein (alpha-SNAP) in a complex with syntaxin 1A. In addition, we show that a construct consisting of the H3 domain of syntaxin IA (GST-synt(195-263), which does not support NSF disassembly in the presence of MgATP gave a larger stimulation. NSF ATPase activation was specific and did not occur using mutant alpha-SNAPs unable to bind GST-synt or with mutated C-termini. We suggest that activation of NSF ATPase activity in the SNARE complex may be essential to allow SNARE priming.

Similar effects of alpha- and beta-SNAP on Ca(2+)-regulated exocytosis.

Soluble N-ethylmaleimide-sensitive fusion protein attachment proteins (SNAP) proteins function in Ca(2+)-regulated exocytosis. Recent work (Schiavo et al. (1996) Nature 378, 733-736) based on in vitro protein interactions has raised the possibility that alpha- and beta-SNAPs have distinct roles in exocytosis. We have examined this possibility by comparing the activities of recombinant alpha- and beta-SNAPs. Both of these proteins were able to similarly bind NSF and activate its ATPase activity but to a lesser extent than gamma-SNAP. When introduced into digitoninpermeabilised chromaffin cells, both alpha- and beta-SNAP stimulated Ca(2+)-regulated exocytosis in a MgATP-dependent manner. The dose-response relationships for these proteins were essentially the same and addition of both proteins did not lead to any further increase in exocytosis above that due to each protein alone. We conclude that alpha- and beta-SNAPs are interchangeable isoforms with similar functions in regulated exocytosis.

Peripheral insulin sensitivity as modified by diet and exercise training.

To determine which component of a high-fat sucrose diet (HFS) caused insulin resistance and whether exercise training or fiber could prevent it, six dietary treatments were tested in rats: low-fat complex carbohydrate (LFCC); high-fat complex carbohydrate (HFCC); low-fat sucrose (LFS); high-fat sucrose (HFS); HFS plus fiber (HFS + F); and HFS plus exercise training (HFS + EX). After 10 wk rats were subjected to an intravenous glucose-tolerance test. The HFS and HFS + F groups developed glucose intolerance, as indicated by significantly greater areas under their glucose curves compared with the LFCC group's areas. The LFS, HFS, HFS + F, and HFS + EX groups developed insulin resistance, as indicated by significantly greater areas under their insulin curves compared with the LFCC and HFCC groups' areas. Either the presence of sucrose or the absence of complex carbohydrates, not high fat, was responsible for the insulin resistance and it was not improved by adding fiber to the diet or by exercise training.

Cardiorespiratory, hematological and physical performance responses of anemic subjects to iron treatment.

Twenty-nine adult iron-deficient anemis subjects (13 men and 16 women) with hemoglobin levels of 4.0 to 12.0 g/100 ml blood were divided into either an iron treatment or placebo group. Hematological, cardiorespiratory and performance data were collected before, during, and after treatment and compared with data from a control group of subjects (4 men and 6 women) from the same socioeconomic population. Hemoglobin levels for the iron treatment group improved from 7.7 to 12.4 g for the women and from 7.1 to 14.0 g for the men. Values for the control group were 13.9 g and 14.3 g for the women and men, respectively. The placebo group showed virtually no change over the 80-day period (8.1-8.4 g for women and 7.7-7.4 g for men). Peak exercise heart rates (5 min, 40-cm step test) were significantly reduced after treatment from 155 to 113 for the iron treatment men and 152 to 123 for the women compared with the placebo group which showed no changes. Values for the control group were 119 and 142 for the men and women, respectively. In response to the exercise test, no difference in oxygen consumption was found between the iron treatment and placebo group although 15% more O2 was delivered per pulse in the iron treatment group. Blood lactates were significantly highein the placebo than iron treatment group both at rest, 1.18 versus 0.64 mmole/liter, and 1 min after exercise, 5.30 versus 2.68 mmoles/liter. No changes in handgrip or shoulder adductor strength were observed following treatment. These results clearly support the concept that performance requiring high oxygen delivery is significantly affected by hemoglobin levels.

Evaluation of reactions to food additives: the aspartame experience.

Despite the widespread use of chemical food additives, few criteria exist to evaluate consumer reports of adverse reactions. We analyzed 231 consumer complaints associated with the food additive aspartame. We developed a methodologic approach to evaluate all complaints by adapting general criteria used to investigate adverse reactions to medications. Complaints were ranked according to the effects of cessation and rechallenge. Using this method, we found no clear symptom complex that suggests a widespread public health hazard associated with aspartame use; however, we identified some case reports in which the symptoms may be attributable to aspartame in commonly-consumed amounts. The systematic application of pre-defined review criteria, such as those described here, to monitor consumer complaints related to food additives will help identify products that warrant more focused clinical studies.

Long-term, high-fat-sucrose diet alters rat femoral neck and vertebral morphology, bone mineral content, and mechanical properties.

Short-term exposure to diets high in fat and sucrose can induce hyperinsulinemia, affect calcium and magnesium metabolism, and alter bone mineralization and mechanical properties. The current study focused on the morphological and structural changes that result from long-term exposure to a high-fat sucrose (HFS) diet. Inbred, female Fischer 344 rats were assigned randomly to a low-fat, complex-carbohydrate (LFCC) diet group or a HFS diet for 24 months. At the end of the 2 years, each femoral neck (FN) was tested to failure in cantilever-bending, the sixth lumbar vertebra (L6) was tested in compression, and geometrical characteristics of the bones were determined. Although the HFS rats were significantly fatter and heavier than the LFCC rats, the HFS L6 had a significantly smaller average cross-sectional area. When L6 structural properties were normalised with respect to body mass, the HFS L6 had significantly lower loads, energies, and stiffnesses. The HFS L6 stress and strain energy density values were also significantly less than the LFCC L6. Compared to the LFCC FN, the HFS FN had a smaller cortical shell and larger trabecular core. The HFS FN also had significantly lower mass-normalised loads, energies, and stiffnesses. These results suggest that a long-term HFS diet has a significant adverse effect on rat bone morphology and mechanics.

Dietary regulation of fibrinolytic factors.

W examined the short-term effects of a high-complex carbohydrate, low fat diet on the plasmin-dependent fibrinolytic pathway. A population of 27 adult American Caucasians exposed to the diet for 3 weeks showed highly significant reductions in the levels of plasminogen (P = 0.0001), tissue plasminogen activator (tPA) (P = 0.0001) and plasminogen activator inhibitor (tPAI) (P = 0.0017). Fibrinogen levels also decreased, but the changes did not reach statistical significance (P = 0.07). In contrast, the levels of the Lpa(a) lipoprotein, a potential inhibitor of fibrinolysis, remained remarkably constant despite a marked decrease in the levels of apolipoprotein B, a major constituent of Lp(a). Correlations between the levels of tPA, tPAI and plasma triglyceride were observed among the individuals both before and after the dietary challenge. Although the mechanisms responsible for the effects are unknown, the dramatic responsiveness of the thrombolytic pathway to dietary challenge is likely to be of importance in understanding the etiology of coronary artery disease and other vascular disorders.

Effects of a high-fat, sucrose diet on serum insulin and related atherosclerotic risk factors in rats.

Hyperinsulinemia, hypertension, hypertriglyceridemia and obesity are all risk factors for atherosclerosis. The clustering of these risk factors in the same individual greatly increases the risk for atherosclerosis and has been termed 'Syndrome X' or 'The Deadly Quartet' The purpose of the present study was to investigate the effects of diet on these risk factors in inbred, female Fischer 344 rats. Animals were raised on ad lib diets consisting of high-fat, sucrose (HFS) or low-fat, complex-carbohydrate (LFCC). After 2 years, the HFS rats were obese (38% +/- 1% vs. 15% +/- 1% body fat), hypertensive (140 +/- 3 vs. 123 +/- 3 mmHg), hyperinsulinemic (439 +/- 118 vs. 98 +/- 10 pmol/l), and hypertriglyceridemic (1.1 +/- 0.2 vs. 0.4 +/- 0.07 mmol/l). The HFS rats also exhibited enhanced clotting and impaired fibrinolytic response to streptokinase. All these differences between the two groups were statistically significant (P < 0.05). Insulin was significantly correlated with body weight (r = 0.71), triglycerides (r = 0.48), and systolic blood pressure (r = 0.70). Total cholesterol was slightly, but not significantly higher, in the HFS group (2.8 +/- 0.3 vs 2.2 +/- 0.1 mmol/l) while HDL-cholesterol was unchanged. These results show that many risk factors for atherosclerosis can be induced in inbred rats by feeding a HFS diet. Aggregation of risk factors was found in the HFS group but not in the LFCC group. In fact, most of the rats on the LFCC diet developed no risk factors after 2 years, indicating that the development of risk factors is not an aging phenomenon.