Effect of metformin and flutamide on insulin, lipogenic and androgen-estrogen signaling, and cardiometabolic risk in a PCOS-prone metabolic syndrome rodent model.

Polycystic ovary syndrome (PCOS) is highly associated with cardiometabolic risk and the metabolic syndrome (MetS), predisposing women to increased risk of developing type 2 diabetes and cardiovascular disease. Metformin is commonly used to treat insulin resistance-glucose intolerance, and flutamide, an androgen receptor (AR) antagonist, is used to target hyperandrogenemia and dyslipidemia. Currently, the physiological mechanism of action of these treatments on androgen, lipidogenic, and insulin signaling pathways remains unclear in PCOS. The aim of this study was to investigate the effects and mechanisms of action of metformin and flutamide on plasma lipid-apolipoprotein (Apo)B-lipoprotein and insulin-glucose metabolism, and endocrine-reproductive indices in a PCOS-prone MetS rodent model. PCOS-prone rodents were treated with metformin (300 mg/kg body wt), flutamide (30 mg/kg body wt), or metformin + flutamide combination treatment for 6 wk. Metformin was shown to improve fasting insulin and HOMA-IR, whereas flutamide and combination treatment were shown to reduce plasma triglycerides, ApoB48, and ApoB100, and this was associated with decreased intestinal secretion of ApoB48/triglyceride. Flutamide and metformin were shown to reduce plasma androgen indices and to improve ovarian primary and preovulatory follicle frequency. Metformin treatment increased hepatic estrogen receptor (ER)α, and metformin-flutamide decreased intestinal AR and increased ERα mRNA expression. Metformin-flutamide treatment upregulated hepatic and intestinal insulin signaling, including insulin receptor, MAPK1, and AKT2. In conclusion, cardiometabolic risk factors, in particular ApoB-hypertriglyceridemia, are independently modulated via the AR, and understanding the contribution of AR and insulin-signaling pathways further may facilitate the development of targeted interventions in high-risk women with PCOS and MetS.

An apolipoprotein B100 mimotope prevents obesity in mice.

Although apolipoprotein B100 (ApoB100) plays a key role in peripheral fat deposition, it is not considered a suitable therapeutic target in obesity. In the present study we describe a novel ApoB100 mimotope, peptide pB1, and the use of pB1-based vaccine-like formulations (BVFs) against high-fat diet (HFD)-induced obesity. In HFD- compared with chow-fed adolescent mice, BVFs reduced the 3-month body-weight gains attributable to increased dietary fat by 44-65%, and prevented mesenteric fat accumulation and liver steatosis. The body-weight reductions paralleled the titres of pB1-reactive immunoglobulin G (IgG) antibodies, and pB1-reactive antibodies specifically recognized native ApoB100 and a synthetic peptide from the C-terminal half of ApoB100. In cultured 3T3L1 adipocytes, anti-pB1 antibodies increased lipolysis and inhibited low-density lipoprotein (LDL) uptake. In cultured RAW 264.7 macrophages, the same antibodies enhanced LDL uptake (without causing foam cell formation). These findings make ApoB100 a promising target for an immunization strategy against HFD-induced obesity.

Antisense oligonucleotides for the treatment of dyslipidaemia.

Antisense oligonucleotides (ASOs) are short synthetic analogues of natural nucleic acids designed to specifically bind to a target messenger RNA (mRNA) by Watson-Crick hybridization, inducing selective degradation of the mRNA or prohibiting translation of the selected mRNA into protein. Antisense technology has the ability to inhibit unique targets with high specificity and can be used to inhibit synthesis of a wide range of proteins that could influence lipoprotein levels and other targets. A number of different classes of antisense agents are under development. To date, mipomersen, a 2'-O-methoxyethyl phosphorothioate 20-mer ASO, is the most advanced ASO in clinical development. It is a second-generation ASO developed to inhibit the synthesis of apolipoprotein B (apoB)-100 in the liver. In Phase 3 clinical trials, mipomersen has been shown to significantly reduce plasma low-density lipoprotein cholesterol (LDL-c) as well as other atherogenic apoB containing lipoproteins such as lipoprotein (a) [Lp(a)] and small-dense LDL particles. Although concerns have been raised because of an increase in intrahepatic triglyceride content, preliminary data from long-term studies suggest that with continued treatment, liver fat levels tend to stabilize or decline. Further studies are needed to evaluate potential clinical relevance of these changes. Proprotein convertase subtilisin/kexin-9 (PCSK9) is another promising novel target for lowering LDL-c by ASOs. Both second-generation ASOs and ASOs using locked nucleic acid technology have been developed to inhibit PCSK9 and are under clinical development. Other targets currently being addressed include apoC-III and apo(a) or Lp(a). By directly inhibiting the synthesis of specific proteins, ASO technology offers a promising new approach to influence the metabolism of lipids and to control lipoprotein levels. Its application to a wide variety of potential targets can be expected if these agents prove to be clinically safe and effective.

Effects of doxorubicin on myocardial expression of apolipoprotein-B.

OBJECTIVE: Doxorubicin (DOX) is an effective antitumour agent against a variety of human malignancies but is associated with deleterious side effects, including myocardial damage and heart failure. Myocardial apoB-containing lipoprotein (apoB) is upregulated post myocardial infarction and has been shown to be cardioprotective in this setting by unloading excessive lipid. The aim of this study was to investigate whether apoB expression is increased also in DOX-induced heart failure and whether apoB overexpression protects the heart in DOX-induced myocardial injury. DESIGN: Cardiac function and energy metabolism was studied in mice and rats 24 hours after intraperitoneally administered DOX. RESULTS: We found that the content of apoB was decreased in rat myocardium 24 hours after DOX injection. In contrast, apoB content was increased in the infarcted myocardium of rats 24 hours post ischemia-reperfusion. Moreover, transgenic mice overexpressing apoB had better cardiac function and lower intracellular lipid accumulation compared to wild type mice 24 hours post DOX. CONCLUSIONS: Our findings indicate that depression of the myocardial apoB system may contribute to DOX-induced cardiac injury and that overexpression of apoB is protective, not only in ischemically damaged myocardium, but also in DOX-induced heart failure.

The Beneficial Effects of Alpha Lipoic Acid Supplementation on Lp-PLA2 Mass and Its Distribution between HDL and apoB-Containing Lipoproteins in Type 2 Diabetic Patients: A Randomized, Double-Blind, Placebo-Controlled Trial.

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a new specific vascular inflammation biomarker that is carried by the lipoproteins in the blood and plays a prominent role in the pathogenesis of atherosclerosis. Increased Lp-PLA2 levels and impaired Lp-PLA2 distribution across high-density lipoprotein (HDL) and non-HDL lipoproteins have been reported in diabetic patients, which is associated with the increase in cardiovascular disease (CVD) risk. This study is aimed at investigating the effect of alpha lipoic acid (ALA), as an antioxidant with potential cardioprotective properties, on the Lp-PLA2 mass and its distribution in diabetic patients. In a double-blind, randomized, placebo-controlled clinical trial, seventy diabetic patients were randomly allocated to ALA (1200 mg ALA as two 600 mg capsules/day) and placebo (two maltodextrin capsules/day) groups. The serum levels of total Lp-PLA2 mass, HDL-Lp-PLA2, oxidized low-density lipoproteins (ox-LDL), apolipoprotein A1 (apo A1), lipid profiles, fasting blood sugar (FBS), and insulin were measured, and apolipoprotein B- (apoB-) associated Lp-PLA2 and homeostasis model of assessment index (HOMA-IR) were calculated at the baseline and after 8 weeks of intervention. ALA significantly decreased the ox-LDL, total Lp-PLA2 mass, apoB-associated Lp-PLA2, and percent of apoB-associated Lp-PLA2 and triglyceride and increased the percent of HDL-Lp-PLA2 compared with the placebo group but had no significant effect on HDL-Lp-PLA2 mass, apo A1, lipid profiles, and glycemic indices. There was a positive correlation between the reduction in the ox-LDL level and total Lp-PLA2 mass in the ALA group. In conclusion, ALA may decrease the CVD risk by reducing the ox-LDL and Lp-PLA2 mass and improving the Lp-PLA2 distribution among lipoproteins in type 2 diabetic patients.

Comparative effect of tumour necrosis factor inhibitors versus other biological agents on cardiovascular risk-associated biomarkers in patients with rheumatoid arthritis.

Background: To comparatively investigate the differential effect of second-line tumour necrosis factor inhibitors (TNFis) versus other biological agents on cardiovascular disease (CVD) risk-associated biomarkers in patients with rheumatoid arthritis (RA). Methods: We evaluated the serum levels of lipoprotein-associated apoproteins ApoA1 and ApoB100 and lipoprotein(a) (Lp(a)) and the leptin/adiponectin ratio (LAR) as an insulin resistance proxy in patients with RA from the Rotation Or Change (ROC) trial treated with either a second-line TNFi or another biologic (tocilizumab (TCZ), rituximab or abatacept) at baseline and week 24. We compared the changes in biomarker levels in each group and according to the EULAR response. Results: Of the 300 patients enrolled in the ROC trial, 203 were included in the study, including 96 in the second-line TNFi group and 107 in the other biological group. The measured biomarkers did not deteriorate between baseline and week 24 regardless of the group. A greater improvement in the LAR was noted in the other biological group (median (IQR) -0.12 ng/µg (-0.58 to 0.31) vs 0.04 (-0.19 to 0.43), p=0.033), and a greater improvement in the Lp(a) level was observed following treatment with TCZ than with a TNFi (-0.05 g/L (-0.11 to -0.01) vs -0.01 g/L (-0.02 to 0.01), p<0.001). When considering the patients' responses to treatment, improved biomarkers were mainly observed in the EULAR responders in each treatment group. Conclusions: TNFis and non-TNFis were neutral on improved CVD risk-associated biomarkers in patients with RA insufficiently controlled by TNFis. TCZ could be associated with a better improvement concerning Lp(a) and LAR than TNFis. This improvement could be related to a good therapeutic response, thereby supporting the need of good control of RA. Trial registration number: ClinicalTrials.gov Identifier NCT01000441, registered on 22 October 2009.

Secretion of atherogenic risk factor apolipoprotein B-100 is increased by a potential mechanism of JNK/PKC-mediated insulin resistance in liver cells.

Apolipoprotein B-100 (ApoB) is the main protein of the atherogenic lipoproteins and plasma ApoB levels reflect the total numbers of atherogenic lipoproteins. Induction of insulin resistance was accompanied by a considerable rise in the production of hepatic very low density lipoprotein (VLDL) containing ApoB and triglyceride. Increased plasma levels of ApoB and triglyceride in VLDL are common characteristics of the dyslipidemia associated with insulin resistance and type 2 diabetes mellitus. Thus, we investigate whether phorbol 12-myristate-13-acetate (PMA)-induced insulin resistance affects the increase of ApoB secretion. PMA increased ApoB secretion and transcriptional level of microsomal triglyceride transfer protein (MTP). PMA treatment also resulted in increase of insulin receptor substrate 1 (IRS1) serine312 (Ser312) and serine1101 (Ser1101) phosphorylation and induction of IRS1 degradation. Additionally, PMA induced activation of c-jun N-terminal kinase (JNK) and protein kinase C (PKC) isoforms (alpha, betaI, delta, zeta, theta), and reduced AKT8 virus oncogene cellular homolog (AKT) activation in a time dependent manner. PMA-induced ApoB secretion, MTP promoter activities, and IRS1 degradation was significantly decreased by treatment of JNK and PKCs inhibitors. Orthovanadate, a potent tyrosine phosphatase inhibitor, increased tyrosine phosphorylation of IRS1 and decreased ApoB secretion of Chang liver cells although PMA was co-treated. From the results, it was concluded that PMA-induced insulin resistance, through induction of serine phosphorylation of IRS1 mediated by activated JNK and PKCs, increases ApoB secretion in Chang liver cells.

Efficacy and safety of a potent and selective peroxisome proliferator activated receptor alpha agonist in subjects with dyslipidemia and type 2 diabetes mellitus.

The weak peroxisome proliferator activated receptor-alpha (PPAR-alpha) agonists gemfibrozil and fenofibrate achieve only small increases in high-density lipoprotein (HDL) cholesterol. CP-778,875 is a more potent PPAR-alpha agonist developed to produce greater HDL cholesterol increases. This randomized, multicenter, double-blinded, placebo-controlled study evaluated the efficacy and safety of CP-778,875 in subjects with mixed dyslipidemia and type 2 diabetes. Eight-six subjects with low HDL cholesterol (< or =45 mg/dl for men and < or =55 mg/dl for women) and increased triglycerides (150 to 500 mg/dl) who had coexisting type 2 diabetes were randomized. Subjects received CP-778,875 doses of 0.5, 2, or 6 mg/day or placebo for 6 weeks. Any other lipid-altering therapy was stopped at screening. The primary end point was percent change in HDL cholesterol from baseline. The 2-mg/day dose of CP-778,875 significantly increased HDL cholesterol by 14%. The 2-mg dose also increased concentrations of apolipoprotein (apo) A-I, HDL(2) cholesterol, and HDL(3) cholesterol by 13%, 12%, and 19%, respectively. An unusual dose-response pattern was observed in that at 6 mg/day CP-778,875 only increased HDL cholesterol by 3% and decreased HDL(2) cholesterol by 24%. Fasting triglyceride levels were significantly decreased to a similar extent (26%) by all 3 doses of CP-778,875. CP-778,875 significantly increased homocysteine levels. There was no significant relation between change in homocysteine and change in apoA-I or HDL cholesterol. No subjects developed myopathy. In conclusion, CP-778,875 2 mg/day significantly increased HDL cholesterol, significantly lowered fasting triglycerides, and increased apoA-I and HDL subfractions. The clinical relevance of the increase in homocysteine levels is unknown.

Chlordecone, a mixed pregnane X receptor (PXR) and estrogen receptor alpha (ERalpha) agonist, alters cholesterol homeostasis and lipoprotein metabolism in C57BL/6 mice.

Chlordecone (CD) is one of many banned organochlorine (OC) insecticides that are widespread persistent organic pollutants. OC insecticides alter lipid homeostasis in rodents at doses that are not neurotoxic or carcinogenic. Pretreatment of mice or rats with CD altered tissue distribution of a subsequent dose of [(14)C]CD or [(14)C]cholesterol (CH). Nuclear receptors regulate expression of genes important in the homeostasis of CH and other lipids. In this study, we report that CD suppresses in vitro reporter systems for human liver X receptors (LXRs) and activates those for human farnesoid X receptor (FXR), pregnane X receptor (PXR) and estrogen receptor alpha (ERalpha) in a concentration-dependent manner (0-50 muM). Consistent with human PXR activation in vitro, three days after a single dose of CD (15 mg/kg) hepatic microsomal CYP3A11 protein increases in C57BL/6 mice. CD decreases hepatic CH ester content without altering total CH concentration. Apolipoprotein A-I (apoA-I) contents of hepatic lipoprotein-rich and microsomal fractions of CD-treated mice are higher than controls. There is a significant reduction in non-high density lipoprotein CH but not apolipoprotein B-48/100 (apoB-48/100) in plasma from CD-treated mice after a 4 h fast. At 14 days after 15 mg CD/kg apoA-I and apoB-100 proteins but not CYP3A11 protein in hepatic microsomes are similar to controls. This work indicates that altered CH homeostasis is a mode of OC insecticide action of relevance after a single dose. This at least partially explains altered CH tissue distribution in CD-pretreated mice.

Taurine reduces the secretion of apolipoprotein B100 and lipids in HepG2 cells.

BACKGROUND: Higher concentrations of serum lipids and apolipoprotein B100 (apoB) are major individual risk factors of atherosclerosis and coronary heart disease. Therefore ameliorative effects of food components against the diseases are being paid attention in the affluent countries. The present study was undertaken to investigate the effect of taurine on apoB secretion and lipid metabolism in human liver model HepG2 cells. RESULTS: The results demonstrated that an addition of taurine to the culture media reduces triacylglycerol (TG)-mass in the cells and the medium. Similarly, cellular cholesterol-mass was decreased. Taurine inhibited the incorporation of [14C] oleate into cellular and medium TG, suggesting the inhibition of TG synthesis. In addition, taurine reduced the synthesis of cellular cholesterol ester and its secretion, suggesting the inhibition of acyl-coenzyme A:cholesterol acyltransferase activity. Furthermore, taurine reduced the secretion of apoB, which is a major protein component of very low-density lipoprotein. CONCLUSION: This is a first report to demonstrate that taurine inhibits the secretion of apoB from HepG2 cells.

Inhibition of microsomal triglyceride transfer protein expression and atherogenic risk factor apolipoprotein B100 secretion by tanshinone IIA in HepG2 cells.

Salvia miltiorrhiza Bunge is known to be effective for the treatment of cardiovascular diseases. Here, we have isolated tanshinone IIA (T-IIA) from S. miltiorrhiza Bunge. The aim of this study is to address the mechanisms where apolipoprotein B-100 (ApoB) regulation is associated with T-IIA, since T-IIA regulates the lipoprotein metabolism in liver cells. Human HepG2 cells treated with T-IIA for 24 h exerted a dose-dependent inhibitory effect on ApoB secretion together with triglyceride. However, another secretory protein, albumin, was unaffected by T-IIA treatment, indicating that the effect of T-IIA is specific for ApoB secretion. T-IIA decreased the transcription level of microsomal triglyceride transfer protein gene, suggesting that lipoprotein assembly is likely to be involved in the inhibited ApoB secretion. Interestingly, T-IIA inhibited ApoB secretion via a proteasome-dependent pathway. Our results suggest that T-IIA is an influential inhibitor of ApoB secretion and triglyceride secretion in liver cells.

Effect of almond skin polyphenolics and quercetin on human LDL and apolipoprotein B-100 oxidation and conformation.

Almond skin polyphenolics (ASP) and vitamin C (VC) or E (VE) inhibit the Cu(2+)-induced generation of conjugated dienes in human low-density lipoprotein (LDL) in a synergistic manner. However, the mechanism(s) by which this synergy occurs is unknown. As modification of apolipoprotein (apo) B-100 is an early, critical step in LDL oxidation, we examined the effects of combining ASP or quercetin and antioxidant vitamins on the oxidation of this moiety as well as on the alteration of LDL conformation and electronegativity (LDL-). In a dose-dependent manner, ASP (0.12-2.0 micromol/L gallic acid equivalents) decreased tryptophan (Trp) oxidation by 6.7-75.7%, increased the generalized polarity (Gp) of LDL by 21.0-81.5% at 90 min and reduced the ratio of LDL- to total LDL (tLDL) by 38.2-83.8% at 5 h. The actions of ASP on these parameters were generally additive to those of VC and VE. However, a 10-25% synergy of ASP plus VC in protecting apo B-100 Trp against oxidation may result from their synergistic interaction in prolonging the lag time to oxidation. ASP and VE acted in synergy to reduce LDL-/tLDL by 24-43%. Quercetin's actions were similar to ASP, though more effective at inhibiting Trp oxidation. Thus, ASP and quercetin reduce the oxidative modification of apo B-100 and stabilize LDL conformation in a dose-dependent manner, acting in an additive or synergistic fashion with VC and VE.

ω-3 Fatty Acid Ethyl Esters Diminish Postprandial Lipemia in Familial Hypercholesterolemia.

CONTEXT: Impaired postprandial chylomicron metabolism induces hypertriglyceridemia and may increase the risk of atherosclerotic cardiovascular disease. Omega-3 fatty acid ethyl ester (ω-3 FAEE) supplementation decreases plasma triglycerides. However, its effect on postprandial chylomicron metabolism in familial hypercholesterolemia (FH) has not yet been investigated. OBJECTIVE: We aimed to examine the effect of ω-3 FAEE supplementation on postprandial responses in plasma triglycerides, very-low-density lipoprotein (VLDL) apolipoprotein B (apoB)-100, and apoB-48 in FH patients receiving standard cholesterol-lowering treatment. DESIGN, SETTING, AND PATIENTS: We carried out an 8-week open-label, randomized, crossover intervention trial to test the effect of oral supplementation with 4 g/d ω-3 FAEE (46% eicosapentaenoic acid and 38% docosahexaenoic acid) on postprandial triglyceride, VLDL-apoB-100, and apoB-48 responses in FH patients after ingestion of an oral fat load. OUTCOMES MEASURES: Plasma total and incremental triglyceride, VLDL-apoB-100, and apoB-48 0- to 10-hour area under the curve (AUC). RESULTS: ω-3 FAEE supplementation significantly (P < .05 in all) reduced concentrations of fasting plasma triglyceride (-20%), apoB (-8%), VLDL-apoB-100 (-26%), and apoB-48 (-36%); as well as systolic blood pressure (-6%) and diastolic blood pressure (-6%). Postprandial triglyceride and VLDL-apoB-100 total AUCs (-19% and -26%, respectively; P < .01) and incremental AUCs (-18% and -35%, respectively; P < .05), as well as postprandial apoB-48 total AUC (-30%; P < .02) were significantly reduced by ω-3 FAEE supplementation. CONCLUSION: Supplementation with ω-3 FAEEs improves postprandial lipemia in FH patients receiving standard care; this may have implications for further reducing atherosclerotic cardiovascular disease in this high-risk patient group.

Eprotirome in patients with familial hypercholesterolaemia (the AKKA trial): a randomised, double-blind, placebo-controlled phase 3 study.

BACKGROUND: Eprotirome is a liver-selective thyroid hormone receptor agonist that has been shown to lower plasma LDL cholesterol concentrations in previous phase 1 and 2 studies of patients with dyslipidaemia. We aimed to assess the long-term safety and efficacy of 50 µg and 100 µg eprotirome in patients with familial hypercholesterolaemia. METHODS: For this randomised, double-blind, placebo-controlled, parallel-group, phase 3 clinical trial, we enrolled patients between Oct 3, 2011, and Feb 14, 2012, at 53 sites in 11 countries in Europe, Africa, and south Asia. Patients were eligible for enrolment if they were aged 18 years or older, diagnosed with heterozygous familial hypercholesterolaemia, and had not reached target LDL cholesterol concentrations after at least 8 weeks of statin therapy with or without ezetimibe. We used a computer-generated randomisation sequence to allocate patients to one of three groups: 50 µg eprotirome, 100 µg eprotirome, or placebo. This trial was planned for 52-76 weeks, with primary efficacy analysis at 12 weeks, but it was prematurely terminated when another study found that eprotirome causes cartilage damage in dogs. Although it was impossible to meet the predefined study outcomes, we analysed changes in the concentrations of LDL cholesterol and other lipids, liver parameters, thyroid hormone concentrations, and adverse effects of treatment with eprotirome versus placebo at 6 weeks of treatment. Analysis was done in all patients who received 6 weeks of treatment. This study is registered with ClinicalTrials.gov, number NCT01410383. FINDINGS: We enrolled 236 patients, randomly allocating 80 to receive placebo, 79 to receive 50 µg eprotirome, and 77 to receive 100 µg eprotirome. 69 patients reached the 6 week timepoint (23 given placebo, 24 given 50 µg eprotirome, and 22 given 100 µg eprotirome). Mean LDL cholesterol concentrations increased by 9% (95% CI -2 to 20) in the placebo group, decreased by 12% (-28 to 4%; p=0.0677 vs placebo) in the 50 µg eprotirome group, and decreased by 22% (-32 to -13%; p=0.0045 vs placebo) in the 100 µg eprotirome group. We noted statistically significant increases between both eprotirome groups and placebo in aspartate aminotransferase (AST; p<0.0001), alanine aminotransferase (ALT; p<0.0001), conjugated bilirubin (p=0.0006), and gamma-glutamyltranspeptidase (p<0.0001). Four patients had to discontinue or interrupt study treatment before trial termination due to AST increases between the upper limit of normal (ULN) and six times ULN, and ALT concentrations between three and seven times ULN. Although we detected no changes in serum concentrations of thyroid-stimulating hormone or free tri-iodothyronine, free tetra-iodothyronine decreased by 19% (23 to 16) in the 50 µg eprotirome group and 27% (30 to 23) in the 100 µg eprotirome group (p<0.0001 vs placebo for both groups). INTERPRETATION: Our findings show that eprotirome can lower LDL cholesterol concentrations in patients with familial hypercholesterolaemia when added to conventional statin treatment with or without ezetimibe, but that it has the potential to induce liver injury. These findings, along with findings of cartilage damage in dogs, raise serious doubts about selective thyroid hormone mimetics as a therapeutic approach to lower LDL cholesterol concentrations. FUNDING: Karo Bio AB.

Increased glycation and oxidative damage to apolipoprotein B100 of LDL cholesterol in patients with type 2 diabetes and effect of metformin.

OBJECTIVE: The aim of this study was to investigate whether apolipoprotein B100 of LDL suffers increased damage by glycation, oxidation, and nitration in patients with type 2 diabetes, including patients receiving metformin therapy. RESEARCH DESIGN AND METHODS: For this study, 32 type 2 diabetic patients and 21 healthy control subjects were recruited; 13 diabetic patients were receiving metformin therapy (median dose: 1.50 g/day). LDL was isolated from venous plasma by ultracentrifugation, delipidated, digested, and analyzed for protein glycation, oxidation, and nitration adducts by stable isotopic dilution analysis tandem mass spectrometry. RESULTS: Advanced glycation end product (AGE) content of apolipoprotein B100 of LDL from type 2 diabetic patients was higher than from healthy subjects: arginine-derived AGE, 15.8 vs. 5.3 mol% (P < 0.001); and lysine-derived AGE, 2.5 vs. 1.5 mol% (P < 0.05). Oxidative damage, mainly methionine sulfoxide residues, was also increased: 2.5 vs. 1.1 molar equivalents (P < 0.001). 3-Nitrotyrosine content was decreased: 0.04 vs. 0.12 mol% (P < 0.05). In diabetic patients receiving metformin therapy, arginine-derived AGE and methionine sulfoxide were lower than in patients not receiving metformin: 19.3 vs. 8.9 mol% (P < 0.01) and 2.9 vs. 1.9 mol% (P < 0.05), respectively; 3-nitrotyrosine content was higher: 0.10 vs. 0.03 mol% (P < 0.05). Fructosyl-lysine residue content correlated positively with fasting plasma glucose. Arginine-derived AGE residue contents were intercorrelated and also correlated positively with methionine sulfoxide. CONCLUSIONS: Patients with type 2 diabetes had increased arginine-derived AGEs and oxidative damage in apolipoprotein B100 of LDL. This was lower in patients receiving metformin therapy, which may contribute to decreased oxidative damage, atherogenicity, and cardiovascular disease.

L-Carnitine supplementation reduces oxidized LDL cholesterol in patients with diabetes.

BACKGROUND: Patients with type 2 diabetes are under high oxidative stress, and levels of hyperglycemia correlate strongly with levels of LDL oxidation. Carnitine favorably modulates oxidative stress. OBJECTIVE: This objective of this study was to evaluate the efficacy of L-carnitine on the reduction of oxidized LDL cholesterol in patients with type 2 diabetes. DESIGN: Eighty-one patients with diabetes were randomly assigned to 1 of 2 treatment groups for 3 mo. The 2 groups received either 2 g L-carnitine once daily (n = 41) or placebo (n = 40). The following variables were assessed at baseline, after washout, and at 1, 2, and 3 mo of treatment: body mass index, fasting plasma glucose, glycosylated hemoglobin, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, apolipoprotein A1, apolipoprotein B-100, oxidized LDL cholesterol, thiobarbituric acid-reactive substances, and conjugated dienes. RESULTS: At the end of the study period, the L-carnitine-treated patients showed significant improvements compared with the placebo group in the following markers: oxidized LDL levels decreased by 15.1 compared with 3.0 U/L (P < 0.001); LDL cholesterol decreased by 0.45 compared with 0.16 mmol/L (P < 0.05); triglycerides decreased by 1.02 compared with 0.09 mmol/L (P < 0.001); apolipoprotein A1 concentrations decreased by 0.12 compared with 0.03 mg/dL (P < 0.05); apolipoprotein B-100 concentrations decreased by 0.13 compared with 0.04 mg/dL (P < 0.05); thiobarbituric acid-reactive substance concentrations decreased by 1.92 compared with 0.05 (P < 0.001), and conjugated diene concentrations decreased by 0.72 compared with 0.11 in the placebo group (P < 0.001). CONCLUSION: Our study indicates that oral administration of L-carnitine reduces oxidized LDL cholesterol levels in patients with type 2 diabetes.