Thomas A. Hughes

25-Hydroxyvitamin D, cholesterol, and ultraviolet irradiation

Vitamin D deficiency may have implications for cardiovascular health. The purpose of this study was to determine the relationship of 25-hydroxyvitamin D (25[OH]D) to cholesterol and lipoprotein particles and to determine whether increasing 25(OH)D through ultraviolet (UV) irradiation impacted on these parameters in healthy young men and women. This was a randomized trial of 51 adults exposed to suberythemal doses of whole-body irradiation using UV lamps that emitted UV-A and UV-B radiation, compared with a control group, twice weekly for 12 weeks. 25-Hydroxyvitamin D, cholesterol, and lipoprotein subfractions were measured at baseline and after 12 weeks. There was a significant (P < .03) positive association between 25(OH)D and apolipoprotein A-I (Apo A-I) and lipoprotein A-I (Lp A-I). The ratio of low-density lipoprotein to high-density lipoprotein was significantly (P < or = .044) negatively correlated with 25(OH)D levels. The levels of 25(OH)D increased significantly in the treated compared with control group (P < .05). Overall, there were no significant differences between the treated and control groups in any lipoproteins or apolipoproteins after administration of UV irradiation. Subgroup analysis for Apo A-II confined to those with 25(OH)D insufficiency (25[OH]D <75 nmol/L [30 ng/mL]) revealed decreases in Apo A-II in the treated group and increases in the control group that were statistically significantly different between the groups (P = .026). We found a significant positive correlation between 25(OH)D and Apo A-I and Lp A-I and a significant negative correlation between 25(OH)D and the ratio of low-density lipoprotein to high-density lipoprotein. In those with vitamin D insufficiency, we found small decreases in Apo A-II in the treated relative to the control group. Overall, though, twice weekly exposure to UV radiation resulting in an increase in serum 25(OH)D had no significant impact on lipoprotein composition.

Kidney-pancreas transplantation: The effect of portal versus systemic venous drainage of the pancreas on the lipoprotein composition

We have previously shown that both kidney-alone and combined kidney-pancreas transplantation lower VLDL and IDL apoB while increasing LDL apoB, apoA-I, and HDL free cholesterol (FC). In this report, we analyze the lipoproteins of 31 patients who have undergone combined kidney-pancreas transplantation. Systemic venous drainage of the pancreas was utilized in 20 of these patients while 11 had portal venous drainage. Six lipoprotein subfractions (VLDL, IDL, LDL, HDL-L, HDL-M, HDL-D) were isolated by rapid gradient ultracentrifugation using a fixed-angle rotor. The apolipoprotein (by reverse-phase HPLC) and lipid (by enzymatic assays) composition of each subfraction was determined. After three months, there were few group differences. However, the portal group had substantial reductions in VLDL apoB at both six (-50% vs. +1%) and twelve months (-57% vs. +149%, P = .042) while the systemic group had increases in VLDL apoB. Similar differences were seen in IDL apoB (six months: -38% vs. +13%; twelve months: -61% vs. +56%, P = .008). LDL apoB increased in both groups at six months (portal: +7%; systemic: +30%) but fell in the portal group at twelve months (-17% vs. +41%, P = .0007). IDL triglyceride, cholesterol ester, phospholipids, and free cholesterol also fell by 19% to 47% in the portal group while they rose by 8% to 44% in the systemic patients, six and twelve months after surgery (P < .05). In addition, the VLDL and LDL free cholesterol to phospholipid ratios (FC/PL) fell (improved) by 16% to 26% in the portal patients while they rose by 9% to 28% in the systemic subjects during this time (P < .04). Finally, there were substantial improvements in the LDL composition of the portal patients compared to the systemic patients at six (PL/apoB: +23% vs. -16%, P = .005; CE/apoB: +14% vs. -14%, P = .037) and twelve months (PL/apoB: +39% vs. -13%, P = .011; CE/apoB: +41% vs. -15%, P = .011). These data indicate that portal drainage of the transplanted pancreas reduced the number of VLDL, IDL, and LDL particles, reduced the total mass of IDL (by 35%), and normalized the VLDL and LDL particle composition. These improvements were not seen in the patients who received systemic drainage of their pancreas. HDL-M also improved in the portal patients (TG: -29% vs. +12%, P = .025) (PL: +22% vs. -5%, P = .014) (total mass: +16% vs. +0.2%, P = .044) but not in the systemic patients six months after surgery. These results suggest that portal venous drainage of the pancreas leads to greater improvements in the lipoprotein composition of IDDM patients than does systemic drainage.

Significant Changes in the Lipid-Lipoprotein Status of Premenopausal Morbidly Obese Females following Gastric Bypass Surgery

The morbidly obese premenopausal female may be more dyslipoproteinemic and at greater risk for developing coronary heart disease than her lean or less seriously obese counterparts. The purpose of the present study was to examine the effects of weight loss with Roux-en-Y gastric bypass surgery on the lipid-lipoprotein status of morbidly obese, premenopausal females. Anthropometrics and blood samples for lipid-lipoprotein analyses were obtained before surgery and 6 - 12 months post-operatively. Following surgery, patients lost 30% of their initial body weight, along with a 40% decline (p < 0.01) in total triglyceride and a 20% decrease (p < 0.01) in total cholesterol. Levels of cholesterol in the high density lipoprotein (HDL) fraction were unaffected by weight loss, but there was a significant (p < 0.05) increase in the proportion of HDL in its more buoyant and anti-atherogenic form, i.e. HDL-L. The apolipoprotein B-containing lipoproteins, very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and low density lipoprotein (LDL), were reduced up to 70% following surgery. There were no significant changes in VLDL or IDL particle composition, i.e. cholesterol/triglyceride, cholesterol/protein, but there was a significant (p < 0.01) increase in the ratio of cholesterol/apolipoprotein B in LDL, suggesting a shift from the small, dense atherogenic LDL to a larger, less atherogenic particle. We conclude that weight loss following gastric bypass surgery markedly improves the lipid-lipoprotein status of morbidly obese premenopausal females and, thereby, significantly reduces the risk of coronary disease.

Hypotension During Hemodialysis: Role For Nitric Oxide*

Hypotensive episodes during hemodialysis are a frequent complication in patients with end-stage renal disease. The possibility that nitric oxide (NO), a major regulator of cardiovascular hemodynamics, could be a factor was explored. Pre and postdialysis plasma samples from 17 hemodialysis patients were analyzed for the stable end products of NO,nitrite + nitrate (NO2 + NO3), by the Greiss method. Predialysis NO2 + NO3 levels were significantly higher in end-stage renal disease than in nine age-matched controls (44.08 +/- standard error of mean 5.74 versus 18.67 +/- 3.56 uM, P = 0.017). In more than half of the patients, postdialysis values dropped markedly, whereas in others the value change was far less; several rose above predialysis values. Depending on the nitrite + nitrate reduction ratio (pre minus postdialysis NO2 + NO3 divided by the predialysis value) patients were separated into two groups, A (n = 9 where nitrate + nitrate reduction ratio was > 0.5 and B (n = 8 where nitrate + nitrate reduction ratio was < 0.5). Whereas the mean predialysis NO2 + NO3 values between groups A and B did not differ significantly, postdialysis levels fell from a predialysis mean of 50 uM to 12 uM in group A but rose from 37 uM to 45 uM in group B. The difference between the postdialysis values of group A and group B was significant (P = 0.0264). In group B, mean systolic blood pressure dropped more than in group A, (57.8 mm Hg compared with 21.2 mm Hg, P = 0.0078). When measured by analysis of variance for repeated measures, skin and core temperatures and blood pressures were lower in group B than in group A. The volume of the ultrafiltrate was removed and dialysis duration and mean weight loss did not differ. Thus, in group B, apparently NO formation increased during hemodialysis exceeding the rate of removal or metabolism of the end products, whereas in group A, NO2 + NO3 removal or metabolism was without apparent increase in the formation of NO. The basis for this difference is unknown. Because vasodilation is a major effect of NO, the strong association of severe reduction in blood pressures and increased NO synthesis in subset B suggests a role for NO in hypotensive episodes during hemodialysis.

Lipoprotein composition in insulin-dependent diabetes mellitus with chronic renal failure: Effect of kidney and pancreas transplantation

Chronic renal failure (CRF) in nondiabetics is associated with a number of lipoprotein abnormalities that place these patients at high risk for atherosclerosis. This study compared the lipoprotein composition of nondiabetic controls (n = 68) with that of patients with insulin-dependent diabetes mellitus ([IDDM] n = 13) and of patients with IDDM and CRF ([IDDM + CRF] n = 74). Six lipoprotein subfractions (very-low-density lipoprotein [VLDL], intermediate-density lipoprotein [IDL], low-density lipoprotein [LDL], high-density lipoprotein-light [HDL-L], HDL-medium [HDL-M], and HDL-dense [HDL-D]) were isolated by rapid gradient ultracentrifugation using a fixed-angle rotor. The apolipoprotein (by reverse-phase high-performance liquid chromatography [HPLC]) and lipid (by enzymatic assays) composition of each subfraction was determined. The only abnormalities found in IDDM patients were increases in IDL and HDL-L triglyceride (TG) levels and an increase in the HDL-L free cholesterol (FC) level. The IDDM + CRF group had multiple abnormalities including (1) elevated TG, apolipoprotein (apo) C-II, and apo C-III levels in all lipid subfractions; (2) elevated VLDL and IDL apo B, TG, FC, cholesterol ester (CE), and phospholipid (PL) levels (with an increased CE/TG ratio in VLDL only); (3) decreased HDL-M apo A-I, apo A-II, CE, and PL levels, but an increased HDL-D apo A-I level; and (4) decreased lecithin:cholesterol acyltransferase (LCAT) activity. Twenty-five of the IDDM + CRF patients underwent combined pancreas and kidney (P + K) transplantation, and 12 patients received only a kidney transplant. Lipoprotein composition was determined at 3, 6, and 12 months posttransplant. Both types of transplantation resulted in similar alterations in lipoprotein composition, even though there was essential normalization of blood glucose levels in most of the patients who received a pancreas transplant (hemoglobin A1C [HbA1C], 9.1% +/- 1.1% v 5.7% +/- 0.3% at 12 months, P < .01). These posttransplant changes included (1) no improvement in the elevated TG level in any lipid subfraction even though there was some reduction in apo C-III levels in VLDL; (2) reductions in levels of VLDL and IDL apo B but increases in LDL apo B; (3) increases in HDL apo C-III and FC concentrations despite an increase in LCAT activity; and (4) increases in apo A-I levels in HDL-L and HDL-M. The addition of a pancreas to a kidney transplant had no obvious impact on the lipoproteins.(ABSTRACT TRUNCATED AT 400 WORDS)

A Shift in ApoM/S1P Between HDL-Particles in Women With Type 1 Diabetes Mellitus Is Associated With Impaired Anti-Inflammatory Effects of the ApoM/S1P Complex

Objective— Type 1 diabetes mellitus (T1D) patients have an increased risk of cardiovascular disease despite high levels of high-density lipoproteins (HDL). Apolipoprotein M (apoM) and its ligand sphingosine 1-phospate (S1P) exert many of the anti-inflammatory effects of HDL. We investigated whether apoM and S1P are altered in T1D and whether apoM and S1P are important for HDL functionality in T1D. Approach and Results— ApoM and S1P were quantified in plasma from 42 healthy controls and 89 T1D patients. HDL was isolated from plasma and separated into dense, medium-dense, and light HDL by ultracentrifugation. Primary human aortic endothelial cells were challenged with tumor necrosis factor-&agr; in the presence or absence of isolated HDL. Proinflammatory adhesion molecules E-selectin and vascular cellular adhesion molecule-1 were quantified by flow cytometry. Activation of the S1P1- receptor was evaluated by analyzing downstream signaling targets and receptor internalization. There were no differences in plasma levels of apoM and S1P between controls and T1D patients, but the apoM/S1P complexes were shifted from dense to light HDL particles in T1D. ApoM/S1P in light HDL particles from women were less efficient in inhibiting expression of vascular cellular adhesion molecule-1 than apoM/S1P in denser particles. The light HDL particles were unable to activate Akt, whereas all HDL subfractions were equally efficient in activating Erk and receptor internalization. Conclusions— ApoM/S1P in light HDL particles were inefficient in inhibiting tumor necrosis factor-&agr;–induced vascular cellular adhesion molecule-1 expression in contrast to apoM/S1P in denser HDL particles. T1D patients have a higher proportion of light particles and hence more dysfunctional HDL, which could contribute to the increased cardiovascular disease risk associated with T1D.

Elevated Lipoprotein Lipase Activity Does Not Account for the Association Between Adiponectin and HDL in Type 1 Diabetes

CONTEXT Increased high-density lipoprotein cholesterol (HDL-C) is common in type 1 diabetes (T1D) and is associated both with hyperadiponectinemia and with elevated lipoprotein lipase activity (LPL). Because adiponectin has been shown to increase LPL expression, elevated LPL may link the hyperadiponectinemia in T1D with increased HDL. OBJECTIVE The purpose of this study was to determine whether LPL activity accounts for the association between adiponectin and HDL in T1D. DESIGN, PARTICIPANTS, AND SETTING A cohort of 127 patients with T1D attending the Diabetes Clinic at the University of Miami and 103 healthy control subjects were recruited. MAIN OUTCOME MEASURE HDL-C and adiponectin were measured in the full cohort and in a subgroup, HDL subfractions were obtained by ultracentrifugation, and LPL and hepatic lipase were measured in postheparin plasma. RESULTS Total HDL-C and the lowest density HDL subfraction, apolipoprotein A-I, LPL activity, and adiponectin levels were higher in subjects with T1D than in control subjects (P < .05). Both adiponectin and LPL activity were directly associated with total HDL-C and its lowest density subfraction, but adiponectin and LPL were not correlated (P = 0.13). Adiponectin alone explained 11.6% and adiponectin plus LPL explained 23.8% of the HDL-C variance. In a multivariate model, adiponectin remained an independent predictor of HDL-C along with LPL and serum creatinine, explaining together 27% of HDL-C variance. CONCLUSIONS Adiponectin was strongly associated with HDL-C in T1D, suggesting that hyperadiponectinemia is linked to the elevated HDL-C in this population. However, this relationship is independent of the association between LPL and HDL-C. Thus, elevated adiponectin and LPL activity are independently related to increased HDL-C in T1D.

LIPOPROTEIN COMPOSITIONAL CHANGES WITH COMBINATION HORMONE THERAPY (CONJUGATED ESTROGEN AND MEDROXYPROGESTERONE) IN AFRICAN AMERICAN WOMEN

OBJECTIVE To determine whether combination hormone therapy (HT) significantly alters lipoprotein composition in healthy African American women. METHODS Postmenopausal African American women, 45 to 65 years old, were randomly assigned to receive daily HT (conjugated equine estrogen, 0.625 mg, and medroxyprogesterone, 2.5 mg) or placebo (treated, 44; placebo, 16) for 12 weeks. Lipoproteins were separated by gradient ultracentrifugation into very-low-density, intermediate-density, and low-density lipoproteins (VLDL, IDL, and LDL) and 3 high-density lipoprotein (HDL) subfractions (light, medium, and dense--L, M, and D). Apolipoprotein (apo) A-I, A-II, C-III, C-II, and C-I were measured by high-performance liquid chromatography. Apo B, phospholipids, triglycerides, cholesterol, and free cholesterol were measured by standard assays. RESULTS Total plasma cholesterol, triglycerides, LDL apo B, and total apo B did not change during HT. A small, transient reduction occurred in LDL cholesterol, and a persistent reduction was noted in VLDL apo B, apo C-II, and apo C-III. Total HDL phospholipids, cholesterol, apo A-I, and apo A-II increased, whereas the LDL/HDL ratio and the apo B/apo A-I ratio decreased. Cholesterol ester increased in both HDL-L and HDL-M, but only a transient increase occurred in HDL-L phospholipids. Apo A-I increased in HDL-L, HDL-M, and HDL-D; however, a similar increase occurred in HDL-D apo A-I in the control subjects. Moreover, an increase occurred in apo A-II in HDL-M. A reduction in the apo A-II:A-I ratio in HDL-L but not in HDL-M indicated an increase in HDL-L LpA-I particles. The increase in HDL particles in HDL-M was entirely due to an increase in LpA-I:A-II particles. Apo C-III increased in both HDL-L and HDL-M. The absence of changes in the HDL lipid ratios indicated an unaltered lipid composition of these particles. No changes were found in IDL compositional measurements. In 12 treated patients and 4 control subjects, Lp(a) was detected by ultracentrifugation; no changes were noted in Lp(a) composition or quantity with HT. Total Lp(a) measured by enzyme immunosorbent assay showed a trend toward an increase in treated patients after 12 weeks of HT. CONCLUSION African American women had a beneficial response to HT by increasing the number of LpA-I particles in HDL-L and LpA-I:A-II particles in HDL-M as well as cholesterol esters in both. There was a small reduction in VLDL apo B (and thus particle number) but only a transient reduction in LDL cholesterol. A shift of apo C-III from VLDL to HDL was noted. No detrimental changes occurred in any lipoprotein subfraction (specifically, no increase in triglycerides).

Lipoprotein composition in patients with type 1 diabetes mellitus: Impact of lipases and adipokines

OBJECTIVE High cardiovascular mortality in patients with type 1 diabetes (T1DM) is widely recognized. Paradoxically, these patients have been shown to have elevated HDL-C and reduced apoB-containing lipoproteins. The purpose of this investigation was to further characterize the lipoprotein composition in T1DM and to assess the role that lipases and adipokines may play in these differences. METHODS T1DM patients (89) attending the Diabetes Clinic at the University of Miami and 42 healthy controls were recruited. Clinical characteristics, lipoprotein composition (by ultracentrifugation and HPLC), leptin, and adiponectin were measured in the full cohort, while a subgroup had LPL and hepatic lipase measured. RESULTS Subjects were predominately Caucasian and Hispanic. HgbA1cs were above goal while their mean duration of diabetes was >20 years. LPL was 2-fold elevated in diabetic women versus controls (+107%{p=0.001}) with no difference in men. Hepatic lipase was reduced 50% {p<0.001} in women but increased 50% {p=0.079} in men. Leptin was similar to controls in women but reduced in men (-60%{p<0.001}). Adiponectin was elevated in both genders (men: +55%{p=0.018}; women: +46%{p=0.007}). LDL-C was reduced in both diabetic men (-33%{p<0.001}) and women (-24%{p<0.001}) while HDL-C trended higher only in men (+13%{p=0.064}). Both total apoB (men: -31%{p<0.001}; women: -17%{p=0.016}) and triglycerides (men: -49%{p<0.001}; women: -31%{p=0.011}) were reduced in both genders while total apoA-I was increased in both (men: +31%{p<0.001}; women: +19%{p=0.008}). Both men and women had increases in LpA-I (+66%{p<0.001}; +40%{p=0.001}) which accounted for essentially the entire increase in HDL mass. VLDL lipids (men: -53→70%; women: -31→57%) were lower as was apoB (particle number) in men (-51{p<0.001}) with a similar trend in women (-35%{p=0.066}). Cholesterol esters in the particle core were depleted in both genders relative to both apoB (men: -41%; women: -37%) and triglycerides (men: -38%; women: -34%) (all{p<0.009}). There were similar differences in IDL. HDL-L lipids (except triglycerides) (men: +45→74%; women: +49→77%{p<0.006}), apoA-1 (men: +162%; women: +117%{p<0.001}), and apoA-II (men: +64%{p=0.008}; women: +55%{p=0.014}) were higher in T1DM patients. These differences produced dramatic increases in LpA-I (men: +221%; women +139%{p<0.001}) and total HDL-L mass (men: +85%; women: +78%{p<0.001}). ApoM (men: +190%; women: +149%{p<0.001}) was also dramatically increased. Conversely, HDL-D lipids were lower in both genders (-20%→50%) while apoA-I was not different in either. ApoA-II was lower only in the diabetic women (-25%{p=0.015}). LPL activity correlated primarily with IDL(-), LDL(-), HDL-L(+), and HDL-D(-) only in the women. HL correlated weakly with VLDL(+), LDL(+), HDL-L(-), and HDL-D(+) in women but had much stronger correlations with VLDL(-), IDL(-), and HDL-L(+). Adiponectin correlated with VLDL(-), IDL(-), LDL(-), HDL-L(+), and HDL-D(-) in women but only HDL-L(+) and HDL-D(-) in men. Leptin correlated with very few parameters in women but did correlate weakly with several HDL-L(-) and HDL-M(-) parameters. CONCLUSION Lipoprotein composition and adipokine concentrations in both genders as well as lipase activities in the women would be expected to reduce the atherosclerotic risk in these patients with T1DM. These data suggest that there are functional lipoprotein abnormalities responsible for their CV risk that are not reflected in their plasma concentrations.