Faculty Bibliography

BACKGROUND: The second best conduit for coronary artery bypass graft surgery (CABG) is unclear. We sought to determine if the use of a second arterial conduit, the radial artery (RA), would improve long-term survival after CABG using the left internal thoracic artery (LITA) and saphenous vein (SV). METHODS: We compared the 14-year outcomes in propensity-matched patients undergoing isolated, primary CABG using the LITA, RA, and SV versus CABG using the LITA and only SV. In all, 826 patients from each group had similar propensity-matched demographics and multiple variables. The primary endpoint was all-cause mortality obtained using the Social Security Death Index. RESULTS: Perioperative outcomes including in hospital mortality (0.1% for the RA patients and 0.2% for the SV patients) were similar. Kaplan-Meier survival at 1, 5, and 10 years was 98.3%, 93.9%, and 83.1% for the RA group versus 97.2%, 88.7%, and 74.3% for the SV group (log rank, p = 0.0011). Cox proportional hazards models showed a lower all-cause mortality in the RA group (hazard ratio 0.72, confidence interval: 0.56 to 0.92, p = 0.0084). Ten-year survivals showed a 52% increased mortality for the SV patients (25.7%) versus the RA patients (16.9%; p = 0.0011). For symptomatic patients, RA patency was 80.7%, which was not different than the LITA patency rate of 86.4% but was superior to the SV patency rate of 46.7% (p < 0.001). CONCLUSIONS: Using the LITA, SV, and a RA conduit for CABG results in significantly improved long-term survival compared with using the LITA and SV. The use of two arterial conduits offers a clear and lasting survival advantage, likely due to the improved patency of RA grafts. We conclude that RA conduits should be more widely utilized during CABG

Dietary fat has been found to alter the incidence of cholesterol gallstones in hamsters: butterfat intensifies while safflower oil reduces lithiasis. WE not report how dietary fat affects bile flow and biliary lipid secretion in this model. Male hamsters were fed one of three experimental diets: a control diet (containing 0.3% cholesterol); control diet + 4.0% butterfat; or control diet + 4.0% safflower oil. After three weeks, bile samples were collected via an external biliary fistula. The endogenous bile acid pool was depleted for 120 min followed by increasing rates of taurocholate infusion for 160 min. Basal secretion of biliary lipids was measured during the bile acid depletion period. Basal bile flow and bile acid output were not significantly different in the three groups. Dietary butterfat increased basal cholesterol output compared to the control diet (0.037 vs. 0.025 mumol/min.kg, respectively); safflower oil did not change cholesterol output (0.027 mumol/min.kg). Hamsters fed butterfat or safflower oil secreted more phospholipid (0.171 and 0.178 mumol/min.kg, respectively) than controls (0.131 mumol/min.kg). The cholesterol/phospholipid output ratio of the butterfat group was higher than the safflower oil group (0.220 vs. 0.153, respectively). Effects of dietary fat on several relationships between file flow and biliary lipid secretion were analyzed by linear regression using the data for the entire bile collection period (bile acid depletion and taurocholate infusion). Butterfat and safflower oil did not change either bile acid dependent or bile acid independent bile flow. Hamsters fed butterfat had a higher linkage coefficient (slope) of cholesterol vs. bile acid output than the safflower oil group (0.023 vs. 0.009, respectively). The linkage coefficient of phospholipid vs. bile acid output of the butterfat group was higher than the controls (0.278 vs. 0.185, respectively). In summary, butterfat induced a high cholesterol and phospholipid secretion with a high cholesterol/phospholipid output ratio; safflower oil induced a high phospholipid secretion with a low cholesterol/phospholipid output ratio. Butterfat and safflower oil have different effects on biliary lipid secretion. These differences in biliary lipid secretion may explain, in part, how butterfat and safflower oil differ in affecting gallstone formation in hamsters.

This study examined the effect of castration and dietary hormonal supplementation on cholesterol cholelithiasis in male hamsters. Animals fed a standard lithogenic diet developed cholesterol gallstones (17%) after 6 wk, while castrated hamsters did not form any stones. Addition of a synthetic androgen, methyltestosterone, to the lithogenic diet induced cholelithiasis in castrated animals (50%). The biles of normal and castrated-hormone supplemented hamsters had cholesterol saturation indices of 1.0 and 1.1, respectively, while the bile of the castrated animals remained unsaturated (0.6). The ratio of cholic acid/chenodeoxycholic acid in bile increased after castration, but returned to normal levels following hormonal supplementation. Biliary cholesterol carriers were separated by ultracentrifugation. Animals in the stone-forming groups (normal and castrated-hormone treated) had a significant proportion of their biliary cholesterol in vesicles (44 and 46%, respectively); castrated hamsters had less cholesterol in vesicle form (9%). The molar ratio of cholesterol/phospholipid in vesicles was reduced after castration (0.93 vs. 0.42) and increased by hormonal supplementation (1.89). In conclusion, when compared to normal male hamsters fed a standard lithogenic diet, castration reduced the cholesterol saturation of bile, lowered the vesicular/micellar ratio in bile, and inhibited cholesterol cholelithiasis. Dietary androgen supplementation increased the lithogenicity of bile, resulting in stone formation in castrated animals.

This study was designed to elucidate the effect of the synthetic androgen, methyltestosterone, on bile flow and biliary lipid secretion in female hamsters. Animals were divided into four groups and fed the following diets: group 1, lithogenic diet for three weeks; group 2, lithogenic diet + 0.05% methyltestosterone for three weeks; group 3, lithogenic diet for six weeks; group 4, lithogenic diet + 0.05% methyltestosterone for six weeks. At the end of each experimental period, the hamsters were operated on to establish external biliary fistulas. During the depletion of the endogenous bile acid pool (for two hours), the basal bile flow of group 4 was significantly smaller than that of group 3. Basal bile acid output was significantly lower in the methyltestosterone-fed groups 2 and 4 than in control groups 1 and 3. In contrast, groups 2 and 4 secreted more cholesterol than groups 1 and 3. Group 4 had a higher ratio of cholesterol output to phospholipid output than group 3. Increasing doses of taurocholate were infused after the bile acid depletion period, and it was found that methyltestosterone did not change the bile acid independent bile flow. The increments in cholesterol or phospholipid output induced per increment of bile acid output (linkage coefficients) were analyzed by linear regression. The methyltestosterone-fed groups (groups 2 and 4) had a higher linkage coefficient of cholesterol output to bile acid output than the control groups (groups 1 and 3). The linkage coefficients of phospholipid output to bile acid output of groups 2 and 4 were also higher compared to groups 1 and 3. The linkage coefficient of cholesterol output to phospholipid output of group 2 was higher than that of group 1. These results suggest that methyltestosterone stimulated the cosecretion mechanism of cholesterol and phospholipid in bile associated with an increasing ratio of cholesterol to phospholipid. In conclusion, the synthetic androgen, methyltestosterone, caused a decrease in basal bile flow and bile acid secretion, and an increase in basal cholesterol secretion and the biliary cholesterol-to-phospholipid ratio. These findings explain, in part, how methyltestosterone intensifies the formation of cholesterol gallstones in female hamsters.

We examined the effect of diet on gallstone incidence and the composition of biliary phosphatidylcholines in methyltestosterone-treated female hamsters. These hamsters were fed a nutritionally adequate purified lithogenic diet containing 2% corn oil, 4% butterfat, 0.3% cholesterol, and 0.05% methyltestosterone, resulting in a cholesterol gallstone incidence of 86%. This incidence was lowered when mono- and polyunsaturated fats or fatty acids were added to the diet: 2.5% oleic acid resulted in total prevention of cholesterol cholelithiasis, 2.5% linoleic acid, and 4% safflower oil (78% linoleic acid content) reduced gallstone incidence to 26 and 8%, respectively. An additional 4% butterfat (29% oleic acid content) produced gallstones in 50% of the animals. At the end of the 6-wk feeding period, the bile of all hamsters was supersaturated with cholesterol. The major biliary phosphatidylcholine species in all groups were (sn-1-sn-2): 16:0-18:2, 16:0-18:1, 18:0-18:2, 16:0-20:4, and 18:2-18:2. The safflower oil- and linoleic acid-fed hamsters exhibited an enrichment of 16:0-18:2 (16-18%); added butterfat or oleic acid increased the proportion of 16:0-18:1 (9 and 25%, respectively). We conclude that the phosphatidylcholine molecular species in female hamster bile can be altered by dietary fats/fatty acids and that mono- and polyunsaturated fatty acids play a role in suppressing the induced cholelithiasis.

The metabolism of 3 alpha,7 alpha-dihydroxy-25,26-bishomo-5 beta-cholane-26-sulfonate (bishomoCDC-sul), the sulfonate analogue of bishomochenodeoxycholic acid, and its effect on biliary bile acid composition were studied during chronic administration in the hamster. After oral administration of radiolabeled bishomoCDC-sul, more than 80% of the radioactivity was excreted into the feces within 7 days, both as the unchanged sulfonate (38.5%) and two more polar metabolites (50.0% and 11.5%). The half time of the fecal excretion was 1.6 days. In gallbladder bile, the unchanged sulfonate and its major metabolite accounted for 19.1% and 19.8% of total bile acids, respectively. In another experiment, hamsters were fed bishomoCDC-sul with antibiotics to evaluate the site of biotransformation. Even when the number of intestinal microorganisms was greatly reduced, the same three metabolites were found in the feces: bishomoCDC-sul (44.0%) and the two polar metabolites (30.8% and 25.1%). The major metabolite was isolated from feces of the hamsters fed bishomoCDC-sul without antibiotics. Its chemical structure was identified by mass spectrometry and nuclear magnetic resonance spectroscopy as the 15 alpha-hydroxylated derivative, namely sodium 3 alpha,7 alpha,15 alpha-trihydroxy-25,26-bishomo-5 beta-cholane-26-sulfonate. These results indicate that after oral administration, the sulfonate analogue of bishomochenodeoxycholic acid underwent enterohepatic circulation like a natural bile acid and was transformed, in part, into the 15 alpha-hydroxylated derivative and another more polar metabolite in the liver of hamsters. There was no evidence that bishomoCDC-sul was dehydroxylated to a lithocholic acid analogue during enterohepatic cycling.

Vesicles and micelles, the major carriers of cholesterol in bile, play a role in the formation of cholesterol gallstones. A simple and rapid ultracentrifugation method was developed to isolate these biliary cholesterol carriers when only microliter amounts of bile were available. The proposed method employs a 46 to 0% sucrose density gradient, a NVT90 near-vertical rotor, and a centrifugation time of one hour. As little as 25 microL of bile can be used with no disruption of the carriers. The method was validated by comparison with gel filtration column chromatography using 6 mM taurocholate in the elution buffer. The sucrose linear density gradient ultracentrifugation procedure described here is simple, fast, and compares favorably with the gel filtration chromatography method for the separation of cholesterol carriers from bile.

The effects of beta-muricholic acid and hyocholic acid on cholesterol cholelithiasis were examined in two animal models. The following experiments were carried out: A) In a gallstone prevention study, prairie dogs were fed the lithogenic diet with or without 0.1% beta-muricholic or 0.1% hyocholic acid for eight weeks. B) In a second prevention study, hamsters were fed the lithogenic diet with or without 0.1% beta-muricholic acid or 0.1% hyocholic acid for six weeks. C) In a gallstone dissolution study, hamsters were fed the lithogenic diet for six weeks to induce stones; stone dissolution was examined during administration of a cholesterol-free purified diet with or without 0.1% beta-muricholic acid or 0.1% hyocholic acid. In the prevention study in prairie dogs (A), both bile acids failed to prevent stone formation, the cholesterol saturation index of bile was 0.89 in the lithogenic controls, remained unchanged with hyocholic acid and increased to 1.52 in the beta-muricholic acid group. In the prevention study in hamsters (B), beta-muricholic acid completely inhibited the cholesterol cholelithiasis (0% stone incidence); the cholesterol saturation index of bile was 1.78 (compared to lithogenic controls, 1.37). Hyocholic acid reduced stone incidence to 16% with a cholesterol saturation index of 0.98. In the dissolution study in hamsters (C), preexisting cholesterol gallstones were not dissolved by either hydrophilic bile acid after feeding these bile acids for an additional six weeks; at the end of the experiment, the cholesterol saturation indices were below unity.(ABSTRACT TRUNCATED AT 250 WORDS)

Male golden Syrian hamsters from Sasco form cholesterol gallstones when fed a lithogenic diet; in contrast, female hamsters are resistant to stones when fed the identical diet. Upon addition of the synthetic androgen, methyl-testosterone, to the diet, the incidence of cholesterol gallstones in female hamsters increased from 0% to 40% after 3 weeks and from 0% to 86% after 6 weeks. Cholesterol cholelithiasis remained high in the males. Biliary cholesterol and phospholipid levels were elevated in the females fed the hormone and approached those of the males. The cholesterol saturation of bile in the females increased from 36% to 75% after 3 weeks and from 54% to 109% after 6 weeks. In addition, an appreciable proportion of the cholesterol in the bile of female hamsters was now present in the form of vesicles. The bile acid composition was significantly altered by methyltestosterone even though the total bile acid concentration did not change; the bile acid composition of the female hamsters approached that of the males. The glycine to taurine ratio of the bile acids was drastically reduced by methyltestosterone in the females and to a lesser extent in males. In summary, in female hamsters the addition of methyltestosterone to the lithogenic diet induced cholesterol gallstones, elevated total biliary phospholipid and cholesterol, altered the bile acid composition, and changed the distribution of cholesterol from micelles to vesicles. The data obtained so far do not enable us to define the precise mechanism of action of methyltestosterone.

The type of dietary fat strongly affects the incidence of gallstones in the hamster model of cholesterol cholelithiasis. The present study was designed to determine whether dietary fats could affect gallstone formation by altering the microstructure (vesicular/micellar ratio) of cholesterol in bile. Golden Syrian hamsters from Sasco (Omaha, NE) or Charles River (Wilmington, MA) were fed nutritionally adequate semipurified diets to which were added: (i) 4.0% butterfat without added cholesterol; (ii) 1.2% palmitic acid plus 0.3% cholesterol; or (iii) 4.0% safflower oil plus 0.3% cholesterol. Gallstone incidence and the percentage of cholesterol in vesicles and micelles were determined after two- or six-week feeding periods. Three out of ten Sasco hamsters fed the 1.2% palmitic acid diet for two weeks had cholesterol stones, while none of the eight Charles River animals had stones. In the Sasco hamsters, a significant proportion of the biliary cholesterol was found in void volume vesicles (28.8%) and small vesicles (17.1%); Charles River hamsters had negligible proportions (1.1%) of cholesterol in void volume vesicles and 15.4% in small vesicles. Cholesterol gallstones were most abundant in Sasco hamsters fed 1.2% palmitic acid for six weeks (nine out of ten animals); the mean cholesterol saturation index of the bile was 1.27. A significant proportion of the biliary cholesterol was eluted in the void volume vesicles (21.4%) and in small vesicles (15.0%). Five of the eight identically treated Charles River hamsters had cholesterol stones; the cholesterol saturation index averaged 1.36, and the biliary cholesterol was present in void volume vesicles (31.3%) and small vesicles (14.3%).(ABSTRACT TRUNCATED AT 250 WORDS)