Can LDL cholesterol be too low? Possible risks of extremely low levels.

Following the continuous accumulation of evidence supporting the beneficial role of reducing low-density lipoprotein cholesterol (LDL-C) levels in the treatment and prevention of atherosclerotic cardiovascular disease and its complications, therapeutic possibilities now exist to lower LDL-C to very low levels, similar to or even lower than those seen in newborns and nonhuman species. In addition to the important task of evaluating potential side effects of such treatments, the question arises whether extremely low LDL-C levels per se may provoke adverse effects in humans. In this review, we summarize information from studies of human cellular and organ physiology, phenotypic characterization of rare genetic diseases of lipid metabolism, and experience from clinical trials. Specifically, we emphasize the importance of the robustness of the regulatory systems that maintain balanced fluxes and levels of cholesterol at both cellular and organismal levels. Even at extremely low LDL-C levels, critical capacities of steroid hormone and bile acid production are preserved, and the presence of a cholesterol blood-brain barrier protects cells in the central nervous system. Apparent relationships sometimes reported between less pronounced low LDL-C levels and disease states such as cancer, depression, infectious disease and others can generally be explained as secondary phenomena. Drug-related side effects including an increased propensity for development of type 2 diabetes occur during statin treatment, whilst further evaluation of more potent LDL-lowering treatments such as PCSK9 inhibitors is needed. Experience from the recently reported and ongoing large event-driven trials are of great interest, and further evaluation including careful analysis of cognitive functions will be important.

[Clinical importance of HDL cholesterol]. / Klinische Bedeutung des HDL-Cholesterins.

BACKROUND: Each year 16-17 million determinations of high-density lipoprotein cholesterol (HDL-C) are conducted and interpreted in Germany. Recently acquired data have led to a fundamental reassessment of the clinical significance of HDL-C. METHOD: This review article is based on a selective literature search. RESULTS: Low HDL­C levels usually indicate an increased cardiovascular risk, particularly in primary prevention but the epidemiological relationship between HDL­C and the risk is complex. The HDL plays a role in the back transport and excretion of cholesterol; however, the biological functions of HDL are dependent on the protein and lipid composition, which is not reflected by the HDL­C concentration. If the composition of HDL is pathologically altered it can also exert negative vascular effects. CONCLUSION: Compared with low-density lipoprotein cholesterol (LDL-C), HDL­C is of secondary importance for cardiovascular risk stratification and the calculation of the LDL-C:HDL­C ratio is not useful for all patients. Low HDL­C levels should prompt a search for additional metabolic and inflammatory pathologies. An increase in HDL­C through lifestyle changes (e.g. smoking cessation and physical exercise) has positive effects and is recommended; however, HDL­C is currently not a valid target for drug therapy.

Effect of Twice-Yearly Denosumab on Prevention of Bone Mineral Density Loss in De Novo Kidney Transplant Recipients: A Randomized Controlled Trial.

We conducted an open-label, prospective, randomized trial to assess the efficacy and safety of RANKL inhibition with denosumab to prevent the loss of bone mineral density (BMD) in the first year after kidney transplantation. Ninety kidney transplant recipients were randomized 1:1 2 weeks after surgery to receive denosumab (60 mg at baseline and 6 months) or no treatment. After 12 months, total lumbar spine areal BMD (aBMD) increased by 4.6% (95% confidence interval [CI] 3.3-5.9%) in 46 patients in the denosumab group and decreased by -0.5% (95% CI -1.8% to 0.9%) in 44 patients in the control group (between-group difference 5.1% [95% CI 3.1-7.0%], p < 0.0001). Denosumab also increased aBMD at the total hip by 1.9% (95% CI, 0.1-3.7%; p = 0.035) over that in the control group at 12 months. High-resolution peripheral quantitative computed tomography in a subgroup of 24 patients showed that denosumab increased volumetric BMD at the distal tibia and radius (all p < 0.05). Biomarkers of bone turnover (C-terminal telopeptide of type I collagen, procollagen type I N-terminal propeptide) markedly decreased with denosumab (all p < 0.0001). Episodes of cystitis and asymptomatic hypocalcemia occurred more often with denosumab, whereas graft function, rate of rejections, and incidence of opportunistic infections were similar. In conclusion, denosumab increased BMD in the first year after kidney transplantation but was associated with more frequent episodes of urinary tract infection.

Gender-Related Differences in Patients Presenting with Suspected Acute Coronary Syndromes: Clinical Presentation, Biomarkers and Diagnosis.

OBJECTIVES: Gender differences in patients presenting with suspected acute coronary syndromes (ACS) have not yet been fully characterized. The aim of this study was to assess gender-related disparities in clinical profiles, biomarkers and diagnoses of patients with suspected ACS. METHODS: This single-centre, prospective cohort study included 377 consecutive patients presenting with suspected ACS to the emergency department. Suspected ACS was defined as a request for conventional troponin T (c-cTnT) measurements on clinical grounds. RESULTS: Women were older than men (p = 0.004), and had a lower prevalence of known coronary artery and peripheral vascular disease (p < 0.05). c-cTnT was positive in 8% of female and in 14% of male patients (p = 0.16), TIMI risk score and cardiac biomarkers including c-cTnT, hs-cTnT, myoglobin, creatine kinase, N-terminal pro-brain natriuretic peptide, myeloid-related protein 8/14 and pregnancy-associated plasma protein A were lower in women (p < 0.05). Women were less frequently diagnosed with ACS (30 vs. 51%), and were not referred for urgent coronary angiography as often as men (p < 0.001). In multivariate analysis, female gender was associated with a lower referral for coronary angiography (HR 0.41, 95% CI 0.23-0.78, p = 0.006). CONCLUSIONS: In patients with suspected ACS, women presented with different biomarker profiles, and were less often diagnosed with ACS and referred to coronary angiography.

[New AHA and ACC guidelines on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk : Statement of the D•A•CH Society for Prevention of Cardiovascular Diseases, the Austrian Atherosclerosis Society and the Working Group on Lipids and Atherosclerosis (AGLA) of the Swiss Society for Cardiology]. / Neue AHA- und ACC-Leitlinie zur Risikoreduktion von Herz-Kreislauf-Erkrankungen durch Cholesterinsenkung : Stellungnahme der D•A•CH-Gesellschaft Prävention von Herz-Kreislauf-Erkrankungen e. V., der Österreichischen Atherosklerose Gesellschaft und der Arbeitsgruppe Lipide und Atherosklerose (AGLA) der Schweizer Gesellschaft für Kardiologie.

Guidelines for the reduction of cholesterol to prevent atherosclerotic vascular events were recently released by the American Heart Association and the American College of Cardiology. The authors claim to refer entirely to evidence from randomized controlled trials, thereby confining their guidelines to statins as the primary therapeutic option. The guidelines derived from these trials do not specify treatment goals, but refer to the percentage of cholesterol reduction by statin medication with low, moderate, and high intensity. However, these targets are just as little tested in randomized trials as are the cholesterol goals derived from clinical experience. The same applies to the guidelines of the four patient groups which are defined by vascular risk. No major statin trial has included patients on the basis of their global risk; thus the allocation criteria are also arbitrarily chosen. These would actually lead to a significant increase in the number of patients to be treated with high or maximum dosages of statins. Also, adhering to dosage regulations instead of cholesterol goals contradicts the principles of individualized patient care. The option of the new risk score to calculate lifetime risk up to the age of 80 years in addition to the 10-year risk can be appreciated. Unfortunately it is not considered in the therapeutic recommendations provided, despite evidence from population and genetic studies showing that even a moderate lifetime reduction of low-density lipoprotein (LDL) cholesterol or non-HDL cholesterol has a much stronger effect than an aggressive treatment at an advanced age. In respect to secondary prevention, the new American guidelines broadly match the European guidelines. Thus, the involved societies from Germany, Austria and Switzerland recommend continuing according to established standards, such as the EAS/ESC guidelines.

Before and after hip fracture, vitamin D deficiency may not be treated sufficiently.

UNLABELLED: Our findings show that only about 20% of seniors receive vitamin D supplementation prior to their index hip fracture or after the event. We further confirm the high prevalence of severe vitamin D deficiency in this population and show that those who receive supplementation have significantly higher 25-hydroxyvitamin D (25(OH)D) status. INTRODUCTION: The aim of this study is to assess current practice in pre- and post-hip fracture care practice with respect to vitamin D supplementation. METHODS: We surveyed 1,090 acute hip fracture patients age 65 and older admitted to acute care for hip fracture repair; 844 had serum 25-hydroxyvitamin D levels measured upon admission to acute care, and 362 agreed to be followed at 12 month after their hip fracture. Prevalence of vitamin D supplementation was assessed upon admission to acute care (at the time of hip fracture), upon discharge from acute care, and at 6 and 12 months follow-up. RESULTS: Of 1,090 acute hip fracture patients (mean age 85 years, 78% women, 59 % community-dwelling), 19% had received any dose of vitamin D prior to the index hip fracture, 27% (of 854 assessed) at discharge from acute care, 22 % (of 321 assessed) at 6 month, and 21% (of 285 assessed) at 12 month after their hip fracture. At the time of fracture, 45% had 25(OH)D levels below 10 ng/ml, 81% had levels below 20 ng/ml, and 96% had levels below 30 ng/ml. Notably, 25(OH)D levels did not differ by season or gender but were significantly higher among 164 hip fracture patients, with any vitamin D supplementation compared with 680 without supplementation (19.9 versus 10.8 ng/ml; p < 0.0001). CONCLUSION: Only about 20% of seniors receive vitamin D at the time of their fracture and after the event. This is despite the documented 81% prevalence of vitamin D deficiency. Interdisciplinary efforts may be warranted to improve vitamin D supplementation in seniors both before a hip fracture occurs and after.

Assignment of Tangier disease to chromosome 9q31 by a graphical linkage exclusion strategy.

A low level of high density lipoprotein (HDL) cholesterol is a strong predictor of ischaemic heart disease (IHD) and myocardial infarction. One cause of low HDL-cholesterol is Tangier disease (TD), an autosomal codominant inherited condition first described in 1961 in two siblings on Tangier Island in the United States of America. Apart from low HDL-cholesterol levels and an increased incidence of atherosclerosis, TD is characterized by reduced total cholesterol, raised triglycerides, peripheral neuropathy and accumulation of cholesteryl esters in macrophages, which causes enlargement of the liver, spleen and tonsils. In contrast to two other monogenic HDL deficiencies in which defects in the plasma proteins apoA-I and LCAT interfere primarily with the formation of HDL (refs 7-10), TD shows a defect in cell signalling and the mobilization of cellular lipids. The genetic defect in TD is unknown, and identification of the Tangier gene will contribute to the understanding of this intracellular pathway and of HDL metabolism and its link with IHD. We report here the localization of the genetic defect in TD to chromosome 9q31, using a genome-wide graphical linkage exclusion strategy in one pedigree, complemented by classical lod score calculations at this region in a total of three pedigrees (combined lod 10.05 at D9S1784). We also provide evidence that TD may be due to a loss-of-function defect.

Plasma deoxysphingolipids: a novel class of biomarkers for the metabolic syndrome?

AIMS/HYPOTHESIS: Sphingolipid synthesis is typically initiated by the conjugation of L-serine and palmitoyl-CoA, a reaction catalysed by serine palmitoyltransferase (SPT). SPT can also metabolise other acyl-CoAs (C(12) to C(18)) and other amino acids such as L-alanine and glycine, giving rise to a spectrum of atypical sphingolipids. Here, we aimed to identify changes in plasma levels of these atypical sphingolipids to explore their potential as biomarkers in the metabolic syndrome and diabetes. METHODS: We compared the plasma profiles of ten sphingoid bases in healthy individuals with those of patients with the metabolic syndrome but not diabetes, and diabetic patients (n = 25 per group). The results were verified in a streptozotocin (STZ) rat model. Univariate and multivariate statistical analyses were used. RESULTS: Deoxysphingolipids (dSLs) were significantly elevated (p = 5 × 10⁻6) in patients with the metabolic syndrome (0.11 ± 0.04 µmol/l) compared with controls (0.06 ± 0.02 µmol/l) but did not differ between the metabolic syndrome and diabetes groups. Levels of C(16)-sphingosine-based sphingolipids were significantly lowered in diabetic patients but not in patients with the metabolic syndrome but without diabetes (p = 0.008). Significantly elevated dSL levels were also found in the plasma and liver of STZ rats. A principal component analysis revealed a similar or even closer association of dSLs with diabetes and the metabolic syndrome in comparison with the established biomarkers. CONCLUSIONS/INTERPRETATION: We showed that dSLs are significantly elevated in patients with type 2 diabetes mellitus and non-diabetic metabolic syndrome compared with healthy controls. They may, therefore, be useful novel biomarkers to improve risk prediction and therapy monitoring in these patients.

Association of 1-deoxy-sphingolipids with steatosis but not steatohepatitis nor fibrosis in non-alcoholic fatty liver disease.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is the most important cause of chronic liver disease in the western world. Steatosis can be accompanied by inflammation and cell damage (non-alcoholic steatohepatitis, NASH), and even liver fibrosis. Sphingolipids are a heterogeneous class of lipids and essential components of the plasma membrane and plasma lipoproteins. The atypical class of deoxy-sphingolipids has been implicated in the metabolic syndrome and type 2 diabetes. AIM: To determine if circulating (deoxy)sphingolipids are associated with NAFLD and its different entities, steatosis, inflammatory changes (inflammation and ballooning) and fibrosis. METHODS: Sphingolipids were analysed by LC-MS after hydrolysing the N-acyl and O-linked headgroups in plasma of obese adults who underwent a liver biopsy in suspicion of NAFLD. RESULTS: Two-hundred and eighty-eight patients were included. There was no association between typical sphingolipids and NAFLD and its different entities. There was a significant association between the presence of steatosis and the concentrations of deoxy-sphinganine [exp(B) 11.163 with CI (3.432, 36.306) and p < 0.001] and deoxy-sphingosine [exp(B) 8.486 with CI (3.437, 20.949) and p < 0.001]. There was no association between these deoxy-sphingolipids and activity of the steatohepatitis, nor was there any association with fibrosis. Differences in deoxy-sphingolipids also correlated independently with the presence of the metabolic syndrome, but not diabetes. CONCLUSION: Deoxy-sphingolipids are elevated in patients with steatosis compared to those without fatty liver, but not different between the different NAFLD subtypes, suggesting that deoxy-sphingolipid bases might be involved in steatogenesis, but not in the further progression of NAFLD to NASH nor in fibrogenesis.

Effects of the apolipoprotein E polymorphism on uptake and transfer of cell-derived cholesterol in plasma.

The reverse cholesterol transport is initiated by the uptake of cholesterol into minor subfractions of high density lipoproteins (HDL) which contain either apolipoprotein (apo) A-I or apoE as their only apolipoproteins. From these initial acceptors, which are termed prebeta1-LpA-I and gamma-LpE, respectively, cell-derived cholesterol is transferred to LDL via the bulk of HDL termed alpha-LpA-I. In this study we analyzed the effect in plasma of the genetically determined apoE polymorphism on the formation of gamma-LpE, uptake and transfer of cell-derived cholesterol to LDL. Gamma-LpE was immunologically detectable in plasmas of individuals carrying at least one apoE3-allele but not in apoE3-free plasmas. During one minute incubation with [3H]cholesterol-labeled fibroblasts, gamma-LpE of plasmas from apoE3/3 subjects accumulated 7 and 13-fold more radioactivity than the respective fractions in plasmas from apoE2/2- and apoE4/4-subjects, respectively. Totally, 30% less [3H]cholesterol was released into plasmas of apoE2/2 and apoE4/4-individuals as compared with plasmas of apoE3/3-subjects. Moreover, plasmas of apoE3/3 individuals accumulated 50% and 65% more cell-derived [3H]cholesterol in alpha-LpA-I2 than plasmas of apoE4/4 and apoE2/2-subjects, respectively. These results indicate that the apoE-polymorphism is an important determinant of the uptake and transfer of cell-derived cholesterol in plasma.

Apolipoprotein A-I variants. Naturally occurring substitutions of proline residues affect plasma concentration of apolipoprotein A-I.

Six unrelated families with genetically determined structural variants of apo A-I were found in the course of an electrophoretic screening program for apo A-I variants in dried blood samples of newborns. The following structural variations were identified by the combined use of HPLC, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and automated gas phase sequencing: Pro3----Arg (1x), Pro4----Arg (1x), and Pro165----Arg (4x). All variant carriers were heterozygous for their mutant of apo A-I. Subjects heterozygous for apo A-I(Pro165----Arg) (n = 12) were found to exhibit lower mean values for apo A-I (109 +/- 16 mg/dl) and HDL cholesterol (37 +/- 9 mg/dl) than unaffected family members (n = 9): 176 +/- 41 and 64 +/- 18 mg/dl, respectively (P less than 0.001). In 9 of 12 apo A-I(Pro165----Arg) variant carriers the concentrations of apo A-I were below the fifth percentile of sex-matched controls. By two-dimensional immunoelectrophoresis as well as by densitometry the relative concentration of the variant apo A-I in heterozygous carriers of apo A-I(Pro165----Arg) was determined to account for only 30% of the total plasma apo A-I mass instead of the expected 50%. Thus, the observed apo A-I deficiency may be largely a consequence of the decreased concentration of the variant apo A-I. In the case of the apo A-I(Pro3----Arg) mutant, densitometry of HDL apolipoproteins demonstrated a distinctly increased concentration of the variant proapo A-I relative to normal proapo A-I. This phenomenon was not observed in the apo A-I(Pro4----Arg) mutant or in other mutants. This suggests that the interspecies conserved proline residue in position 3 of mature apo A-I is functionally important for the regular enzymatic conversion of proapo A-I to mature apo A-I.

Apolipoprotein C-III(Lys58----Glu). Identification of an apolipoprotein C-III variant in a family with hyperalphalipoproteinemia.

Apolipoprotein C-III is a major protein constituent of triglyceride rich lipoproteins and HDL. It occurs in plasma in three isoforms differing by their sialic acid content. Apo C-III putatively inhibits lipolysis and the apo E mediated hepatic uptake of remnants from triglyceride rich particles. We identified a heterozygous carrier of an apolipoprotein C-III variant by the presence of additional bands after isoelectric focusing (IEF) of VLDL. Structural analysis of the variant protein by HPLC, time-of-flight secondary ion mass spectrometry, and automated gas phase sequencing revealed a lysine to glutamic acid replacement in position 58. The underlying A to G exchange was verified by direct sequencing subsequent to amplification by polymerase chain reaction of exon 4 of the apo C-III gene. Family studies revealed vertical transmission of this defect. The two variant carriers exhibited plasma concentrations of HDL cholesterol and apo A-I above the 95th percentiles of sex matched controls whereas the unaffected father and sister showed normal values. The plasma concentrations of apo C-III in the two variant carriers were decreased by 30-40% compared with those of the two unaffected family members and to random controls. Using two-dimensional immunoelectrophoresis as well as IEF and subsequent scanning densitometry, we found that the low serum concentration of apo C-III was a consequence of diminished concentrations of the variant apo C-III isoproteins in both VLDL (15% of normal) and HDL (25% of normal). Apo C-III(Lys58----Glu) heterozygotes possessed unusual HDL as demonstrated by nondenaturing gradient gel electrophoresis. They consisted mainly of HDL2b and contained a proportion of atypically large particles, enriched in apo E, with a Stokes diameter of 13-18 nm and resembling HDLc. In conclusion, heterozygosity for a structural apo C-III variant--apo C-III(Lys58----Glu)--was identified in two hyperalphalipoproteinemic subjects characterized by the presence of low plasma apo C-III concentrations and atypically large HDL.

Phenotype-dependent differences in apolipoprotein E metabolism and in cholesterol homeostasis in human monocyte-derived macrophages.

In this study, we investigated the impact of the common apoE polymorphism on apoE metabolism and cholesterol homeostasis in monocyte-derived macrophages isolated from E2/2, E3/3, and E4/4 subjects. Unloaded cells of all genotypes contained similar amounts of free cholesterol, cholesteryl ester, and apoE mRNA. E3/3 cells secreted 77 and 30% more apoE than E2/2 or E4/4 cells, respectively. Pulse-chase studies confirmed that the apoE secretion rate was greatest in E3/3 and least in E2/2 cells and showed that a portion of apoE2, but not apoE3 or apoE4, was degraded intracellularly. Surface binding of apoE was greatest in E4/4 cells, as revealed by heparinase treatment. On cholesterol loading with acetylated LDL, apoE mRNA levels and protein secretion rose most in E4/4 and least in E2/2 cells. Cholesterol and cholesteryl ester content, however, rose most in E2/2 and least in E3/3 cells. Incubations with 3H-cholesterol-labeled acetylated LDL revealed that E2/2 cells were most efficient at secreting cholesterol. The greatest reuptake of 3H-cholesterol-rich particles was from E4/4 macrophage- conditioned media. Thus, E2/2 macrophages, despite a low apoE secretion rate, are protected from cholesterol storage by apoE-mediated cholesterol efflux. In E3/3 macrophages, cholesterol accumulation is lessened by a high basal apoE secretion rate. E4/4 macrophages secrete the most apoE but lack effective net cholesterol efflux due to enhanced surface binding and reuptake of cholesterol-rich particles.

A frameshift mutation in the human apolipoprotein A-I gene causes high density lipoprotein deficiency, partial lecithin: cholesterol-acyltransferase deficiency, and corneal opacities.

Epidemiologic data of recent years have identified an important role of HDL deficiency in the etiology of atherosclerosis. Biochemical data suggest that some of these deficiencies may be a consequence of defects in the structural genes of HDL apolipoproteins or of plasma enzymes that modify HDL. We analyzed the genetic defect in a 42-yr-old patient suffering from corneal opacities and complete absence of HDL cholesterol but not of coronary artery disease, thus clinically resembling fish eye disease. The observation of an abnormal immunoblot banding pattern of apolipoprotein A-I (apo A-I) and of reduced lecithin: cholesterol acyltransferase (LCAT) activity in plasma led to sequence analysis of the genes for apo A-I and LCAT in this patient and his family. Direct sequencing of polymerase chain reaction amplified DNA segments containing the exons of the candidate genes, resulted in the identification of a frameshift mutation in apo A-I while the LCAT sequence was identical to the wild type. The apo A-I mutation was predictive for an extensive alteration of the COOH-terminal sequence of the encoded protein. Evidence for the release of this mutant protein into the plasma compartment and for the absence of normal apo A-I was derived from ultraviolet laser desorption/ionization mass spectrometry analysis. Our results suggest that a defective apo A-I is the causative defect in this case of HDL deficiency with corneal opacities.

Genetic and phenotypic heterogeneity in familial lecithin: cholesterol acyltransferase (LCAT) deficiency. Six newly identified defective alleles further contribute to the structural heterogeneity in this disease.

The presence of lecithin:cholesterol acyltransferase (LCAT) deficiency in six probands from five families originating from four different countries was confirmed by the absence or near absence of LCAT activity. Also, other invariate symptoms of LCAT deficiency, a significant increase of unesterified cholesterol in plasma lipoproteins and the reduction of plasma HDL-cholesterol to levels below one-tenth of normal, were present in all probands. In the probands from two families, no mass was detectable, while in others reduced amounts of LCAT mass indicated the presence of a functionally inactive protein. Sequence analysis identified homozygous missense or nonsense mutations in four probands. Two probands from one family both were found to be compound heterozygotes for a missense mutation and for a single base insertion causing a reading frame-shift. Subsequent family analyses were carried out using mutagenic primers for carrier identification. LCAT activity and LCAT mass in 23 genotypic heterozygotes were approximately half normal and clearly distinct from those of 20 unaffected family members. In the homozygous patients no obvious relationship between residual LCAT activity and the clinical phenotype was seen. The observation that the molecular defects in LCAT deficiency are dispersed in different regions of the enzyme suggests the existence of several functionally important structural domains in this enzyme.

Correction: Plasma 1-deoxysphingolipids are early predictors of incident type 2 diabetes mellitus.

[This corrects the article DOI: 10.1371/journal.pone.0175776.].

Plasma 1-deoxysphingolipids are early predictors of incident type 2 diabetes mellitus.

1-Deoxysphingolipids (1-deoxySLs) are atypical sphingolipids, which are formed in a side reaction during sphingolipid de-novo synthesis. Recently, we demonstrated that 1-deoxySLs are biomarkers for the prediction of T2DM in obese, non-diabetic patients. Here we investigated the relevance of 1-deoxySLs as long-term predictive biomarkers for the incidence of T2DM in an asymptomatic population. Here, we analyzed the plasma sphingoid base profile in a nested group of non-diabetic individuals (N = 605) selected from a population-based study including 5 year follow-up data (CoLaus study). 1-DeoxySLs at baseline were significantly elevated in individuals who developed T2DM during the follow-up (p<0.001), together with increased glucose (p<5.11E-14), triglycerides (p<0.001) and HOMA-IR indices (p<0.001). 1-Deoxy-sphinganine (1-deoxySA) and 1-deoxy-sphingosine (1-deoxySO) were predictive for T2DM, even after adjusting for fasting glucose levels in the binary regression analyses. The predictive value of the combined markers 1-deoxySA+glucose were superior to glucose alone in normal-weight subjects (p<0.001) but decreased substantially with increasing BMI. Instead, plasma adiponectin and waist-to-hip ratio appeared to be better risk predictors for obese individuals (BMI>30kg/m2). In conclusion, elevated plasma 1-deoxySL levels are strong and independent risk predictors of future T2DM, especially for non-obese individuals in the general population.

Structural and functional properties of natural and chemical variants of apolipoprotein A-I.

Four isoforms of human apolipoprotein A-I (apo A-I): the normal allele product and the corresponding Lys-107 deletion mutant, and apo A-I with sulfoxidized Met-112 and Met-148 residues and the corresponding reduced form, were investigated in their lipid binding properties, structures, and abilities to activate lecithin-cholesterol acyltransferase. All apo A-I isoforms reacted completely with palmitoyloleoylphosphatidylcholine to give reconstituted high density lipoprotein (rHDL) particles with diameters of 96 A. These particles reacted with low density lipoprotein (LDL) and lecithin-cholesterol acyltransferase (LCAT) equally well, except that the Lys-107 deletion mutant was resistant to structural rearrangements in the presence of LDL. The spectral measurements revealed only minor structural differences among the free apo A-I forms or among their rHDL products, but showed a decreased stability of the Lys-107 deletion mutant and the isoform with reduced Met towards denaturation by guanidine hydrochloride. The results demonstrate that these specific alterations of the apo A-I sequence, which change the helix orientation and hydrophobic moment in one or two putative lipid binding regions, are not sufficient to disrupt the overall properties of the apo A-I complexes with lipid nor to impair significantly their ability to activate LCAT.

Polymorphic site study at codon 347 of apolipoprotein A-IV in a Japanese population.

In a population of Japanese subjects, we surveyed codon 347 of the apolipoprotein (apo) A-IV gene and found that the frequency of a rare allele at this point was extremely low compared to that in western populations. Only one of 850 unrelated samples showed mutation at the enzyme recognition site by agarose gel electrophoresis. However, direct sequencing of the coding region revealed that it did not result from the ACT (Thr) to TCT (Ser) mutation which has been reported in western countries, but from an ACT to ACG (Thr) mutation, which does not affect the primary structure of apo A-IV. Two additional family members showed the same point mutation at codon 347.