Lipoprotein modulation of the intracellular localization of protein kinase C and alteration of phorbol ester-stimulated differentiation in the human monoblastic U937 cell line.

The subcellular localization of protein kinase C and the ability of phorbol esters to alter cell phenotype were examined in the U937 monoblastic cell line. Protein kinase C activity was evaluated using an in vitro assay measuring histone phosphorylation in the cytosolic and detergent extracted particulate fractions obtained after disrupting cells that had been cultured previously under varying conditions. Depriving cells of serum for 2-3 days resulted in a time-dependent decrease in protein kinase C activity of the particulate fraction. The addition of as little as 0.5-1% fetal bovine serum to serum-deprived cells increased protein kinase C in the particulate fraction by up to 2- to 3-fold. In contrast lipoprotein-deficient serum did not mimic the effect of whole serum. However addition of high or low density lipoproteins to cells grown in lipoprotein-deficient serum or serum-free medium produced a concentration-dependent 2- to 3-fold increase in particulate protein C kinase activity. The maximal lipoprotein effect was similar to that observed with 5% fetal bovine serum and the concentrations of lipoproteins needed to increase protein kinase C activity were in the physiological range. Adherence to plastic was used as a marker of the differentiated phenotype. Cells cultured in lipoprotein-deficient serum did not differentiate in response to phorbol ester stimulation as well as cells cultured in 5% fetal bovine serum. These results suggest that serum lipoproteins modulate protein kinase C localization and the response to phorbol ester stimulation in the U937 cell.

High density lipoprotein utilization by dispersed rat luteal cells.

Utilization of lipoproteins by cells prepared by collagenase dispersion of ovaries of immature gonadotropin-primed rats was studied. Human and rat HDL increased basal progestin secretion and incorporation of [14C]oleate into cellular sterol esters 2-fold during a 2 h incubation, with maximal stimulation occurring at a lipoprotein sterol concentration of 125 micrograms/ml. This concentration of HDL cholesterol also increased progestin production by cells stimulated with dibutyryl cyclic AMP. Human LDL or cholesterol-rich lipid dispersions had little effect upon either progestin secretion or sterol esterification at similar sterol concentrations. However, addition of delipidated human HDL apolipoproteins to the cholesterol-rich lipid dispersions markedly enhanced progestin production. Incubation of the dispersed cells in the presence of 25 micro M ML-236B, which blocked cellular de novo sterol synthesis by over 90%, had no effect upon progestin secretion. Specific uptake of human 125I-labeled HDL by the dispersed cells was observed. Analysis fo 125I-labeled HDL uptake as a function of lipoprotein concentration indicated that the uptake process was saturated at HDL levels of 200-400 micrograms protein/ml. The amount of HDL specifically associated with the cells at saturating levels after 1 h of incubation was sufficient to account for the increased progestin synthesis and sterol ester storage observed during this time. During the incubations cell-specific degradation of the 125I-labeled HDL apolipoprotein appeared to be minimal. We conclude that lipoprotein-carried cholesterol is an important substrate for rat luteal cells and that these cells possess a specific mechanism for the uptake of HDL.

Prevalence of valvular-regurgitation associated with dexfenfluramine three to five months after discontinuation of treatment.

OBJECTIVES: The goal of this study was to determine the prevalence of valvular regurgitation and abnormal valve morphology in patients three to five months after discontinuation of dexfenfluramine (Dexfen) therapy. BACKGROUND: We previously reported the results of a randomized, double-blind, placebo-controlled trial of valvular structure and function in 1,073 patients treated either with Dexfen, with an investigational sustained-release dexfenfluramine (Dexfen SR), or with a placebo, with echocardiograms performed approximately one month from the last dose. Using FDA criteria (aortic regurgitation [AR] > or =mild and/or mitral regurgitation [MR] > or =moderate) we found no statistical difference among the groups, but when all degrees of valvular regurgitation were considered and when the two Dexfen groups were combined, there was a higher prevalence of any degree of AR, any degree of MR, and restricted posterior mitral leaflet mobility. However, it was unknown whether these differences in prevalence persisted. METHODS: The double blind was maintained, and all patients were invited to return for a follow-up echocardiogram. Echocardiograms were acquired using a standardized protocol and assessed blindly to determine the degree of valvular regurgitation and valve leaflet thickness and mobility. We had an 80% power to detect a statistically significant change in paired proportions using the McNemar test (alpha = 0.05). RESULTS: Echocardiograms were obtained on 941 patients with a median of 137 days after drug discontinuation. Aortic regurgitation (of any degree) was present in 13.8% of Dexfen (p = 0.41 compared to placebo), 10.7% of Dexfen SR (p = 0.64 compared to placebo), and 11.9% of placebo patients. The minor differences between patients treated with active drug versus placebo, which were found in the previous study, were no longer significant even when the groups were combined (p = 0.83 compared to placebo). Mitral regurgitation (of any degree) was present in 71.5% (p = 0.15 compared to placebo), 69.8% (p = 0.30 compared to placebo), and 70.5%, respectively. This was also not significantly different from placebo when both Dexfen groups were combined (p = 0.16). There was no difference in the prevalence of restricted posterior mitral leaflet mobility among the three groups (p = 0.19). CONCLUSIONS: The small increase in prevalence of minor degrees of AR and MR in patients treated with two to three months of Dexfen previously reported is no longer present three to five months after discontinuation of medication. These data suggest that the degree of regurgitation observed in patients who used Dexfen for a relatively short duration does not progress over time.

Fasting early morning rise in peripheral insulin: evidence of the dawn phenomenon in nondiabetes.

The dawn phenomenon, a tendency for glucose to rise between 0500 and 0800 h in subjects with diabetes, is also reflected as an increase in insulin required to maintain normoglycemia during closed-loop insulin infusion. Individuals without diabetes have minimal or absent rises in early morning glucose. To test the hypothesis that the absence of early morning glucose increases in subjects without diabetes is due to an increase in insulin levels, we measured insulin levels from 2400 to 0800 h in four male and two female volunteers. Subjects were on an unrestricted diet with three main meals and one bedtime snack at 2100 h. Blood samples were collected continuously in hourly pools by a constant-rate withdrawal pump. We observed the following: (1) hourly integrated concentration of glucose was stable from 2400 to 0800 h (range of mean plasma values, 94.5-97.3 mg/dl), and (2) hourly integrated concentration of insulin increased from the 0300-0400 (4.6 microU/ml) to the 0700-0800-h pool (6.2 microU/ml) (P less than 0.05). The observed increase in insulin in the early morning hours despite stable levels of glucose indicates a temporally increased insulin need in nondiabetic individuals similar to that found in individuals with diabetes. The mechanism underlying this increased insulin need may be similar in diabetes and nondiabetes, with the ensuing rise in glucose being dependent on the availability of compensatory insulin.

Insulin-like growth factor type I (somatomedin-C) stimulates high density lipoprotein (HDL) metabolism and HDL-supported progesterone biosynthesis by swine granulosa cells in vitro.

Type I insulin-like growth factor (IGF-I) stimulated high density lipoprotein (HDL)-promoted progesterone production by swine granulosa cells cultured under serum-free conditions in vitro. In the presence of pure human IGF-I (50 ng/ml), the half-maximally effective concentration of swine HDL was 16 micrograms/ml (67% confidence limits; 15-17 micrograms/ml) after 2 days of exposure to this growth factor, 5.4 (2.6-9.8) micrograms/ml after 4 days, and 3.8 (1.2-4.8) micrograms/ml after 6 days. Maximal progesterone production increased approximately 10-fold in the presence of IGF-I and HDL on day 2, 125-fold on day 4, and 330-fold on day 6. The facilitative action of IGF-I on HDL-supported progesterone biosynthesis was accompanied by time-dependent stimulatory effects of IGF-I on trypsin-releasable HDL, trypsin-resistant cell-associated HDL, and degraded HDL (P less than 0.01). Moreover, incubation of swine granulosa cells with [3H]cholesteryl oleate-labeled HDL demonstrated that IGF-I exerted a time-dependent stimulatory effect on [3H]free cholesterol and [3H]cholesteryl ester accumulation in granulosa cells, and significantly augmented the secretion of [3H]progesterone (separated by two-dimensional TLC). In addition to the ability of IGF-I to amplify the cellular acquisition of radiolabeled sterol, this growth factor also increased the total mass of cellular cholesteryl ester and total cellular cholesterol as measured by microfluorometric assay (P less than 0.01). We conclude that IGF-I facilitates the effective delivery of HDL-derived sterol substrate into the steroidogenic pool of ovarian cells. Such observations offer an additional role for the differentiative actions of this somatomedin in the expression of full steroidogenic potential by granulosa-luteal cells.

Estrogen regulates low density lipoprotein metabolism by cultured swine granulosa cells.

To test estrogen's possible regulation of lipoprotein metabolism by granulosa cells, swine granulosa cells were cultured under serum-free conditions in the presence or absence of estradiol. Treatment with estradiol significantly enhanced high affinity, saturable, [125I]iodo-low density lipoprotein (LDL) binding with a median 2.85-fold (range 2.3- to 5.6-fold, n = six experiments) increase in the calculated number of LDL receptors and no change in the apparent dissociation constant (Kd) for LDL binding (Kd = 3.4 +/- 0.92 micrograms/ml in control and 4.0 +/- 0.87 micrograms/ml human LDL in estradiol-treated cultures). Estradiol also significantly increased [125I]iodo-LDL internalization by granulosa cells and augmented the maximal rate of LDL degradation by 2.0 to 2.5-fold without altering the apparent Michaelis-Menten constant (Km) for this process. Estrogen's dose-dependent enhancement of [125I]iodo-LDL binding, internalization, and degradation could be observed at minimum estradiol concentrations of approximately 100 ng/ml and was accompanied by increased progesterone secretion by granulosa cells. Further studies indicated that estrogen's stimulation of LDL internalization and degradation was not simply attributable to increased rates of nonspecific bulk fluid-phase pinocytosis (assessed with [125I]iodo-polyvinylpyrrolidone) or increased steroidogenesis per se (tested by blocking cholesterol side-chain cleavage with aminoglutethimide). We conclude that estradiol amplifies LDL binding by swine granulosa cells by increasing the number of high affinity, saturable LDL receptors with no alteration in their apparent affinity. Moreover, estrogen action is accompanied by enhanced rates of progesterone production in the presence of LDL, and increased rates of LDL internalization and degradation, which could not be accounted for simply by accelerated nonspecific bulk fluid-phase pinocytosis. We suggest that the significant facilitative actions of estradiol on lipoprotein binding and metabolism are likely to assist in preparing granulosa cells for the increased rates of progesterone biosynthesis ultimately required in functional corpora lutea.

Properties of low density lipoprotein binding by cultured swine granulosa cells.

The properties of low density lipoprotein (LDL) binding to ovarian cells were investigated in cultured swine granulosa cells in serum-free monolayer cultures. Swine and human LDL bound with high affinity and specificity, with apparent dissociation constant (Kd) values for swine and human LDL of 1.1 and 3.6 micrograms/ml at 4 C, and 2.7 and 4.8 micrograms/ml at 37 C. In contrast, high density lipoprotein competed sparingly with [125I]iodo-LDL with an apparent half-maximally inhibitory concentration of 650 micrograms/ml. Binding of LDL was dependent upon arginine residues within the apoprotein B moiety, since covalent modification of LDL with 1,2-cyclohexanedione markedly reduced its ability to compete for binding or degradation and to support progesterone biosynthesis. This specific, high affinity saturable binding of LDL to pig granulosa cells exhibited a maximal binding capacity of 0.7 micrograms LDL protein/mg DNA, which corresponds to approximately 5500 LDL receptors per cell. The relative time course of LDL binding, internalization, and degradation by swine granulosa cells was assessed by examining trypsin-releasable (surface-bound) and trypsin-resistant (internalized) [125I]iodo-LDL. At 37 C, granulosa cells exhibited a rapid increase in surface-bound lipoprotein, followed by delayed but subsequently progressive increases in internalized and degraded LDL. LDL degradation by swine granulosa cells was a saturable, temperature- and time-dependent process, with half-maximal degradation occurring at a concentration of 16 micrograms/ml LDL. This correlates closely with the half-maximal concentration of LDL that stimulates progesterone secretion. Degradation of [125I]iodo-LDL was not attributable to bulk fluid-phase pinocytosis, since the cellular ingestion of an impermeant probe, [125I]iodo-polyvinylpyrrolidone, occurred at 1/40 the rate of lipoprotein degradation. In addition, degradation of [125I]iodo-LDL was specifically inhibited by excess unlabeled LDL, decreased by prior exposure of granulosa cells to the soluble sterol, 25-hydroxycholesterol, and antagonized by the lysosomotrophic agent, chloroquine. Moreover, in separate experiments, rates of degradation of LDL were found to be significantly correlated with progesterone one production (r = +0.88, P less than 0.01). In summary, swine granulosa cells exhibit specific, high affinity, saturable, and low capacity receptors for homologous and heterologous LDL. These LDL recognition sites on ovarian cells depend upon cyclohexanedione-sensitive arginine residues with the apoprotein B moiety for effective binding, internalization, and functional (steroidogenic) responses.(ABSTRACT TRUNCATED AT 400 WORDS)

High density lipoprotein3 binding and biological action: high affinity binding is not necessary for stimulation of placental lactogen release from trophoblast cells.

High density lipoprotein (HDL3) binds with high affinity to many types of cells, but controversy exists concerning the nature and biological significance of the binding. We have recently demonstrated that HDL and apoproteins (apo)-AI, -AII, and -CI stimulate a specific and dose-dependent increase in placental lactogen (hPL) release from human trophoblast cells. To examine the possible relationship between HDL3 binding and stimulation of hPL release, we have characterized the binding of [125I]HDL3 to an enriched fraction of hPL-producing trophoblast cells. Binding studies were performed on trophoblast cells isolated by isopycnic centrifugation of collagenase/hyaluronidase-dispersed placental tissue and apo-E free-HDL3 (density, 1.125-1.215 g/ml). Scatchard analysis of binding studies performed at 37 C for 2 h revealed two classes of binding sites: 1) high affinity binding sites with a Kd of 9.7 +/- 2.2 micrograms/ml (1.3 x 10(-7) M) and 9.8 +/- 3.2 x 10(5) binding sites/trophoblast cell, and 2) low affinity binding sites with a Kd of 172.8 +/- 64.8 micrograms/ml (2.3 x 10(-6) M) and an estimated 3.2 x 10(6) sites/cell. As has been found in hepatocytes and other cells, the number of HDL3-binding sites per trophoblast cell (but not the binding affinity) decreased at lower incubation temperatures. In addition, HDL3 binding to trophoblasts cells did not require calcium and was not affected by prior treatment of the cells with pronase or trypsin. HDL3-binding sites on trophoblast cells, however, were not specific for HDL3. Low density lipoprotein (density, 1.063-1.055 g/ml), which does not stimulate hPL release, was nearly as potent on a molar basis as HDL3 in binding to the high and low affinity binding sites on trophoblast cells. Furthermore, nitrated HDL3, which does not compete for high affinity binding to trophoblast cells, stimulated hPL release. Although the characteristics of HDL3 binding to trophoblast cells are similar to those of other cells, these results strongly suggest that the binding of HDL3 to high affinity binding sites is not essential for HDL-mediated hPL release.

Role of estradiol as a biological amplifier of gonadotropin action in the ovary: in vitro studies using swine granulosa cells and homologous lipoproteins.

Swine granulosa cells cultured under serum-free conditions in vitro exhibit significant responsivity to the stimulatory actions of estradiol (E2) and FSH or LH. Under these conditions, granulosa cells harvested from either immature or mature Graafian follicles synthesized significantly increased quantities of progesterone in response to homologous low density lipoprotein (LDL) and, to a lesser degree, homologous high density lipoprotein (HDL) particles. The effects of LDL and HDL were dose dependent and saturable. The stimulatory influence of E2, FSH, or LH alone was significantly enhanced in the presence of pig LDL or HDL. Moreover, the synergism between E2 and FSH or between E2 and LH was significantly augmented by porcine LDL and, to a lesser degree, porcine HDL. To assess the physiological relevance of these observations, the lipoprotein contents of swine blood and follicular fluid were determined by heparin-manganese precipitation and after differential ultracentrifugation. The majority (greater than 70%) of cholesterol in pig blood resided in the LDL fraction, but follicular fluid was essentially devoid of LDL. On the other hand, follicular fluid contained large quantities of a presumptive HDL species with a density between 1.063-1.210. The HDL particle in follicular fluid was further characterized by agarose gel and sodium dodecyl sulfate-polyacrylamide gel electrophoreses, which demonstrated an alpha-migrating species whose major apoprotein exhibited an apparent mol wt of 28,000 and comigrated with human apoprotein A-1. Analytical ultracentrifugation of the pig follicular fluid HDL revealed a sedimentation coefficient (S20,w) of 4.93, similar to that of serum HDL (S20,w = 5.0). The physiological relevance of the HDL particle purified from follicular fluid was further demonstrated by its ability to significantly increase progesterone production by granulosa cells cultured under serum-free conditions in vitro. In summary, we have demonstrated striking responsivity of cultured pig granulosa cells to exogenously supplied LDL and, to a lesser degree, HDL, with further stimulation when cells are treated with estrogen and/or LH and FSH. Although LDL is the predominant lipoprotein in swine blood, it is essentially undetectable in the antral fluid of the intact Graafian follicle. Thus, the unambiguous in vitro responsiveness of granulosa cells to LDL that we observe suggests that the marked increase in availability of blood-borne LDL to granulosa-luteal cells that presumptively occurs at ovulation would contribute significantly to augmented rates of progesterone biosynthesis by luteal tissues in the pig.(ABSTRACT TRUNCATED AT 400 WORDS)

Insulin regulates low density lipoprotein metabolism by swine granulosa cells.

Insulin synergistically amplified the stimulatory effect of low density lipoprotein (LDL) on progesterone biosynthesis by primary cultures of swine granulosa cells. The mechanisms subserving this facilitative interaction included the following: 1) insulin's synergism with LDL was profoundly attenuated by covalent modification of arginine residues in LDL by 1,2-cyclohexanedione treatment; 2) insulin increased by 2- to 6-fold the number of specific high affinity LDL receptors on granulosa cells, with no change in apparent binding affinity; 3) insulin augmented rates of [125I]iodo-LDL internalization and degradation without enhancing nonspecific bulk fluid-phase pinocytosis (assessed with [125I]iodo-polyvinylpyrollidone); 4) insulin increased by 2.5- to 3-fold granulosa cell content of free and esterified cholesterol (measured by fluorometry) in response to treatment with unlabeled LDL; 5) insulin stimulated the intracellular accumulation of free [3H]cholesterol and [3H]cholesteryl ester, and amplified [3H]progesterone secretion by granulosa cells exposed to [3H]cholesteryl linoleate-labeled LDL; and 6) insulin action was specific in that it was not mimicked by desoctapeptide insulin, epidermal growth factor, fibroblast growth factor, or relaxin. We conclude that insulin and LDL synergistically enhance progesterone biosynthesis by swine granulosa cells via specific mechanisms that depend upon 1,2,-cyclohexanedione-sensitive residues within LDL apoprotein. Insulin action results in significantly augmented binding, internalization, and degradation of LDL, which is accompanied by increased effectual delivery of cholesterol substrate into cellular sterol pools that participate in enhanced steroidogenesis.

Effects of caloric restriction and weight loss on glycemic control, insulin release and resistance, and atherosclerotic risk in obese patients with type II diabetes mellitus.

This study was designed to determine: (1) the effectiveness and safety of protein-sparing fast and gastric bypass surgery for achieving weight reduction in obese patients with type II diabetes mellitus (non-insulin-dependent diabetes mellitus); (2) the effects of these interventions on glycemic control; (3) the effects of weight loss on insulin secretion and action; and (4) the effects of treatment on atherosclerotic risk factors. Six patients consumed only a protein supplement (1.4 g/kg ideal body weight) for up to six months until a final weight below 120 percent of ideal body weight was achieved or weight loss ceased. Six patients underwent gastric bypass surgery. Both groups of patients were studied before and after treatment while consuming a balanced weight-maintaining diet. Both protein-sparing fast and gastric bypass surgery were safe and successful in the short term in producing weight loss. Both treatments improved glycemic control. Mean fasting plasma glucose values fell from 287 to 168 mg/dl (p less than 0.01). Mean total glycosylated hemoglobin values declined from 11.9 to 8.2 percent (p less than 0.01) (normal reference interval 5.85 to 8.85 percent). Patients who achieved a final weight below 125 percent of ideal body weight had significantly better post-treatment fasting plasma glucose values (130 versus 196 mg/dl, p less than 0.05) and total glycosylated hemoglobin values (6.8 versus 9.0, p less than 0.02) than those whose weight remained above 125 percent of ideal. In diet-treated patients, improved glycemic control occurred with caloric restriction alone prior to significant weight loss. Improved glycemic control was accompanied by decreased insulin resistance. Mean steady-state plasma glucose values fell from 377 to 208 mg/dl (p less than 0.008), and mean fasting insulin values fell from 31.0 to 17.0 microU/ml (p less than 0.004). Acute-phase insulin release, which was markedly impaired before treatment, did not improve even in patients who had post-treatment fasting plasma glucose values below 130 mg/dl. Significant improvements in atherosclerotic risk factors occurred. Mean high-density lipoprotein cholesterol values increased from 33.8 to 40.5 mg/dl (0.006 less than p less than 0.008), and factor VIII coagulant activity decreased from 194 to 140 percent (p less than 0.005). Serum fibrinogen also decreased (393 to 347 mg/dl, p = 0.08), although the decrease did not reach clinical significance.(ABSTRACT TRUNCATED AT 400 WORDS)

Probucol, high-density lipoprotein metabolism and reverse cholesterol transport.

Accumulation of cholesterol within the arterial wall reflects an imbalance between delivery and efflux. Monocyte-derived macrophages play a major role in arterial wall cholesterol accumulation. Using tracer methodology in a rabbit model, several investigators have estimated the rate of cholesterol delivery and thus the steady-state rate of efflux to be between 0.4 and 2.4 micrograms/cm2/hour. The process responsible for arterial wall cholesterol efflux, "reverse cholesterol transport," can be conceptualized as a sequence of events including (1) loss of cell cholesterol, (2) intravascular cholesterol transport, (3) hepatic cholesterol uptake, and (4) biliary secretion. Work by many investigators has characterized these individual processes.

High-density lipoprotein cholesterol levels as a marker of reverse cholesterol transport.

Dramatic advances have been made over the last decade in understanding the role of low-density lipoprotein (LDL) in atherosclerotic cardiovascular diseases and how to manage elevated levels of LDL cholesterol. Understanding the role of high-density lipoprotein (HDL) and how to intervene therapeutically in HDL action offers the possibility of even greater benefits. Epidemiologic studies have shown a strong inverse relation between HDL cholesterol and the risk of coronary artery disease (CAD). Whereas several subfractions of HDL can be identified, none convincingly offers better predictive value than total HDL cholesterol. Apolipoprotein A-I, the major apolipoprotein of HDL, also is inversely related to atherosclerotic risk. Unfortunately, measurements of HDL cholesterol or apolipoprotein A-I are considerably less precise and less accurate than measurements of total or LDL cholesterol. The biologic phenomena responsible for these epidemiologic relations are not yet clear. Moreover, several apparently contradictory observations and puzzling exceptions to the simplistic inverse relation of HDL cholesterol to CAD suggested by epidemiologic studies have created considerable confusion. The current confusion is not likely to be resolved until HDL metabolism and the cellular and molecular events responsible for the apparent protective effects of HDL are better understood. One current hypothesis that could explain the protective effects of HDL is that it mediates reverse cholesterol transport, the process by which cholesterol is removed from sites of deposition and delivered to the liver for excretion. From the standpoint of current therapy, each intervention that changes HDL cholesterol levels must be evaluated individually, on its own merit, in light of its effect on atherosclerosis and coronary events rather than on alterations in HDL cholesterol levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric bariatric operation in insulin-treated adults.

Gastric bariatric operation has been advocated to ameliorate adult-onset diabetes mellitus in the morbidly obese patient. However, there are few data to support this. In this clinical study we report the cases of 23 insulin-treated, morbidly obese, adult-onset diabetes (type II) patients who underwent gastric bariatric operations for weight reduction. Preoperative insulin requirements ranged from 10 to 230 U/day (mean 74 U/day). After operation, 14 patients discontinued insulin, and seven patients decreased their insulin requirement by 72% (100 to 28 U/day). Two patients were lost to follow-up. Six patients were admitted to the Clinical Research Unit before and after operation to evaluate the effects of surgically induced weight loss on fasting blood glucose levels, hemoglobin A1C insulin resistance, and glucose tolerance. Weight loss at the time of postoperative studies ranged between 22.5 and 49.1 kg (mean 30.6 kg). Fasting blood glucose levels decreased 48% (mean 321 mg/dl before operation to 166 mg/dl after operation). Hemoglobin A1C levels improved from a mean of 11.8% to 7.9%. Insulin resistance assessed in four patients by measurement of glucose clearance during insulin and glucose infusion improved from a mean of 77 ml/min before operation to 228 ml/min after operation. Glucose tolerance was quantitated by determination of glucose disappearance during intravenous glucose tolerance test. The mean glucose disappearance improved from 0.176% to 0.385%/min following operation. This study provides clinical and laboratory evidence indicating significant improvement of insulin-treated diabetes mellitus in morbidly obese patients who have lost weight following gastric bariatric operation.

Binding and degradation of human 125I-HDL by rat adrenocortical cells.

In order to learn more about the mechanism by which high density lipoprotein (HDL) cholesterol is taken up by the adrenal cortex, binding and degradation of human 125I-HDL by suspensions of intact rat adrenal cortical cells have been examined. Cellular accumulation of 125I-HDL was found to occur in two phases. Our results indicate that the initial phase of association results from reversible binding of 125I-HDL to a specific saturable set of membrane binding sites. Binding site affinity appears equal for both rat and human HDL while affinity for human LDL is approximately one order of magnitude less on the basis of apoprotein weight. In addition, isolated rat adrenal cortical cells were found to degrade human 125I-HDL at a rapid rate. Degradation, like binding, can be prevented by addition of excess unlabeled HDL suggesting that binding and degradation are linked. Thus, one mechanism that could account for adrenal uptake of HDL cholesterol is endocytosis, initiated by lipoprotein binding to the HDL specific membrane binding site.