Persistent hypercholesterolemia in child with homozygous autosomal recessive hypercholesterolemia: A decade of lipid management.

Autosomal recessive hypercholesterolemia (ARH) is a rare form of genetic hypercholesterolemia caused by mutations in low density lipoprotein receptor adaptor protein 1 (LDLRAP1). The proband first presented with linear eruptive xanthomas over her ankles, knees and elbows, with low density lipoprotein cholesterol (LDL-C) of 16.0 mmol/L (618.7 mg/dL), at 2.5 years old. Next generation sequencing revealed a novel homozygous mutation in LDLRAP1 exon 5 (c.466delG). In the first year, drug regimens of either cholestyramine or simvastatin, reduced her LDL-C to 10.5 mmol/L (406 mg/dL) and 11.7 mmol/L (452.4 mg/dL), respectively. Combination simvastatin and ezetimibe was the mainstay of therapy from age 5 - 10 years. Her lowest achieved LDL-C was 6.3 mmol/L (243.6 mg/dL). Switching to atorvastatin did not lead to further reduction. Carotid intima-media thickness was 0.47 mm (> 97th percentile) and 0.32 mm (75 - 95th percentile) at ages 8 years and 11 years, respectively. Addition of monthly injections of evolocumab for 3 months, led to an increase in LDL-C, from 7.0 mmol/L (270.7 mg/dL) to a range of [(8.4 - 9.1) mmol/L or (324.8 - 351.9) mg/dL]. In this report, a decade-long lipid management is described in a patient with ARH. Residual activity of LDLRAP1 is a likely determinant of her response. Clinical management remains sub-optimal and options for the paediatric population are limited. Novel classes of cholesterol-lowering medications are needed for this ultra-rare and severe hypercholesterolemia.

Associations of young onset age and genetic risk of beta cell dysfunction with glycaemic progression in individuals with type 2 diabetes.

AIM: To study the relationship between genetic risk of beta cell dysfunction, young onset age and glycaemic progression in individuals with type 2 diabetes (T2D). MATERIALS AND METHODS: 1385 T2D outpatients were included in cross-sectional sub-study and 730 insulin-naïve outpatients were followed for 3 years in prospective sub-study. Genetic risk score (GRS) was derived from 24 beta cell dysfunction-related single nucleotide polymorphisms, with lower and upper 25 percentiles defined as low and high genetic risk. Glycaemic progression was defined as requirement for sustained insulin therapy. RESULTS: 388 participants in cross-sectional and 128 in prospective sub-study experienced glycaemic progression. Young onset age (T2D diagnosis below 40 year-old) was associated with high risk of glycaemic progression as compared to usual-onset counterparts (adjusted OR 1.64 [95% CI 1.14-2.36], and 2.92 [95% CI 1.76-4.87] in cross-sectional and prospective sub-study, respectively). As compared to those with intermediate risk, a low GRS was associated with lower risk for glycaemic progression (adjusted OR 0.72 [95% CI 0.49-1.06], and 0.51 [95% CI 0.29-0.90]) whereas a high GRS was not significantly associated with glycaemic progression. Notably, the association of young-onset T2D with high risk of glycaemic progression was independent of known clinical risk factors and beta cell dysfunction GRS (P interaction > 0.10). CONCLUSION: Young onset age and low genetic risk of beta cell dysfunction are independently associated with risk of glycaemic progression. Our data do not support that genetic risk modulates the risk of glycaemic progression in individuals with young-onset T2D.

Ethnic disparities in risk of cardiovascular disease, end-stage renal disease and all-cause mortality: a prospective study among Asian people with Type 2 diabetes.

AIM: To study prospectively the ethnic-specific risks of cardiovascular disease, end-stage renal disease and all-cause mortality in patients with Type 2 diabetes mellitus among native Asian subpopulations. METHODS: A total of 2337 subjects with Type 2 diabetes (70% Chinese, 17% Malay and 13% Asian Indian) were followed for a median of 4.0 years. Time-to-event analysis was used to study the association of ethnicity with adverse outcomes. RESULTS: Age- and gender-adjusted hazard ratios for cardiovascular disease in ethnic Malay and Asian Indian subjects were 2.01 (1.40-2.88; P<0.0001) and 1.60 (1.07-2.41; P=0.022) as compared with Chinese subjects. Adjustment for conventional cardiovascular disease risk factors, including HbA1c , blood pressure and lipid profile, slightly attenuated the hazards in Malay (1.82, 1.23-2.71; P=0.003) and Asian Indian subjects (1.47, 0.95-2.30; P=0.086); However, further adjustment for baseline renal function (estimated GFR) and albuminuria weakened the cardiovascular disease risks in Malay (1.48, 0.98-2.26; P=0.065) but strengthened that in Asian Indian subjects (1.81, 1.14-2.87; P=0.012). Competing-risk regression showed that the age- and gender-adjusted sub-distribution hazard ratio for end-stage renal disease was 1.87 (1.27-2.73; P=0.001) in Malay and 0.39 (0.18-0.83; P=0.015) in Asian Indian subjects. Notably, the difference in end-stage renal disease risk among the three ethnic groups was abolished after further adjustment for baseline estimated GFR and albuminuria. There was no significant difference in risk of all-cause mortality among the three ethnic groups. CONCLUSIONS: Risks of cardiovascular and end-stage renal diseases in native Asian subjects with Type 2 diabetes vary substantially among different ethnic groups. Differences in prevalence of diabetic kidney disease may partially explain the ethnic disparities.

Elevation of a novel angiogenic factor, leucine-rich-α2-glycoprotein (LRG1), is associated with arterial stiffness, endothelial dysfunction, and peripheral arterial disease in patients with type 2 diabetes.

CONTEXT: Increased arterial stiffness and endothelial dysfunction are associated with peripheral arterial disease (PAD). Leucine-rich-α2-glycoprotein (LRG1) is a proangiogenic factor involved in regulation of the TGFß signaling pathway. OBJECTIVE: This study in patients with type 2 diabetes mellitus explored the associations of plasma LRG1 with arterial stiffness, endothelial function, and PAD. DESIGN: Based on the ankle brachial index (ABI), patients were classified as having PAD (ABI ≤ 0.9) or as being borderline abnormal (ABI, 0.91-0.99) or normal (ABI, 1.00-1.40). LRG1 was measured by immunoassay; arterial stiffness, by carotid-femoral pulse-wave velocity and augmentation index; and endothelial function, by laser Doppler flowmetry. RESULTS: A total of 2058 patients with type 2 diabetes mellitus were recruited. Mean age (1 SD) was 57.4 (0.2) years. Patients with PAD (n = 258) had significantly higher LRG1 compared to patients with borderline ABI and patients without PAD (19.00 [13.50] vs 17.35 [13.30] and 15.28 [10.40] µg/mL, respectively; P < .0001). Multiple regression analysis revealed that female gender (P < .0001), non-Chinese ethnicity (P < .0001), higher waist circumference (P = .017), lower estimated glomerular filtration rate (P < .0001), higher urine albumin-creatinine ratio (P = .009), lower ABI (P < .0001), higher pulse wave velocity (P = .040), and poorer endothelium-dependent vasodilation (P = .007) were independent significant predictors of higher plasma LRG1 levels. A generalized linear model showed that a 1-SD increase in log LRG1 was associated with an odds ratio of 4.072 (95% confidence interval, 1.889-8.777; P < .0001) for prevalence of PAD, after adjustment for traditional risk factors. CONCLUSIONS: Higher LRG1 is a significant predictor for arterial stiffness, endothelial function, and PAD. The pathobiological basis and the temporal relationships of these associations need to be explored by further mechanistic and prospective studies to understand the clinical significance of these findings.

Low-density lipoprotein cholesterol levels in adults with type 2 diabetes: an alternative equation for accurate estimation and improved cardiovascular risk classification.

Low-density lipoprotein cholesterol (LDL-C) is a major risk factor for atherosclerotic disease. Despite its limitations, Friedewald-calculated LDL-C (F-LDL-C) remains widely used for LDL-C determination. In this observational study of 1999 adults with type 2 diabetes mellitus (T2DM), we compare the accuracy of F-LDL-C to directly measured LDL-C (M-LDL-C) and derived and validated a new [SMART2D (Singapore Study of MAcro-angiopathy and Micro-Vascular Reactivity in Type 2 Diabetes)] formula to estimate LDL-C. From 1000 randomly selected patients, M-LDL-C was compared to F-LDL-C. Using multiple linear regression to identify independent predictors for M-LDL-C, the SMART2D equation was derived and subsequently validated in the next 981 patients. F-LDL-C was 0.367 (0.216) mmol/L lower than M-LDL-C. This difference was -0.009 (0.189) for SMART2D-LDL-C. Using F-LDL-C, 27% with M-LDL-C ≥2.6 mmol/L were classified as LDL-C <2.6 mmol/L, reduced to 2.1% when using SMART2D-LDL-C. With F-LDL-C, misclassification was greater when triglycerides were ≥2.2 mmol/L, especially for the lower LDL-C cut-offs (1.8 and 2.6 mmol/L), and this was markedly improved with SMART2D-LDL-C. In conclusion, in T2DM, F-LDL-C underestimates M-LDL-C, with misclassifications that may potentially have an impact on therapeutic decisions in T2DM. The SMART2D equation improves accuracy of estimate, reducing misclassifications. Trials will be needed to ascertain the clinical significance of these findings.

Osteoprotegerin is independently associated with metabolic syndrome and microvascular complications in type 2 diabetes mellitus.

AIMS: Osteoprotegerin (OPG) is a glycoprotein from tumour necrosis factor receptor superfamily, responsible for osteoclastogenesis inhibition and associated with arterial calcification and stiffness. We describe the association between metabolic syndrome (MS) and OPG in type 2 diabetes mellitus patients. METHODOLOGY: We consecutively enrolled 1220 patients from our institution's Diabetes Centre from August 2011. Anthropometric data such as fasting blood/urine were obtained, and OPG was measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: Mean (standard deviation (SD)) of age and diabetes duration was 57.4 (10.9) years and 11.2 (8.9) years, respectively. Prevalence of MS was 64.3% (95% confidence interval (CI): 61.3%-67.2%) and associated with significantly higher OPG (5.44 vs 4.47 pmol/L) and microvascular complications. The presence of microvascular complications was associated with higher OPG: nephropathy (5.54 (2.20) vs 4.65 (1.70) pmol/L, p < 0.0001), neuropathy (6.33 (2.64) vs 5.06 (1.91) pmol/L, p < 0.0001) and retinopathy (6.08 (2.47) vs 5.00 (1.95) pmol/L, p < 0.0001). After adjusting for age, gender, ethnicity, glucose and microvascular complications, OPG remained an independent predictor of MS: (odds ratio (OR) = 1.102 (95% CI: 1.015-1.196), p = 0.021). CONCLUSION: Higher OPG levels were associated with risk of MS and microvascular complications. Studies are needed to test whether OPG could be a useful biomarker identifying patients at risk of vascular complications and whether further exploration of this pathway may lead novel therapeutic options.

High normal albuminuria is independently associated with aortic stiffness in patients with Type 2 diabetes.

BACKGROUND: High normal albuminuria is associated with higher cardiovascular risk in patients with diabetes. Increased aortic stiffness is an established risk factor of vascular events. However, the relationship between albuminuria within the normal range (0-30 mg/g) and aortic stiffness in patients with Type 2 diabetes is unknown. METHODS: A total of 614 normoalbuminuric subjects with Type 2 diabetes with spot urinary albumin:creatinine ratio ≤ 30 mg/g and estimated glomerular filtration rate ≥ 60 ml min⁻¹ 1.73 m⁻² were included in the study. Aortic stiffness was assessed by carotid-femoral pulse wave velocity. RESULTS: Pulse wave velocity increased progressively with the increase of albumin:creatinine ratio within the normoalbuminuric range (0-30 mg/g). Only 2.6% of the subjects with an albumin:creatinine ratio in the lowest quartile (0.7-3.4 mg/g) were classified as having aortic stiffness (pulse wave velocity ≥12 m/s). In contrast, the proportion of subjects with aortic stiffness increased significantly with the increase of albumin:creatinine ratio level (11.0%, 10.4% and 13.6% in albumin:creatinine ratio quartiles 2, 3 and 4, respectively, P = 0.008). A logistic regression model revealed that the odds of having aortic stiffness were increased by 56% with a 1-SD increase of log albumin:creatinine ratio after adjustment for age, gender, duration of diabetes, HbA1c , blood pressure, HDL and LDL cholesterol, estimated glomerular filtration rate, BMI, usage of renin-angiotensin system antagonists, statins and insulin. CONCLUSIONS: High normal albuminuria is associated with aortic stiffness in patients with Type 2 diabetes, which may in part explain their increased cardiovascular risk.

Associations between pigment epithelium-derived factor, insulin resistance and high density lipoprotein.

AIMS: To measure serum pigment epithelium-derived factor in control subjects with normal fasting glucose, and in subjects with impaired fasting glucose and those with newly diagnosed Type 2 diabetes, before treatment initiation, and to measure pigment epithelium-derived factor prospectively in patients being treated with HDL-raising therapy, niacin. METHODS: We enrolled 89 individuals attending an institutional health screen. Biochemical indices including lipids, homeostasis model assessment-insulin resistance, high-sensitivity C-reactive protein and pigment epithelium-derived factor were analysed in fasting blood. To validate the association between HDL and pigment epithelium-derived factor, we analysed samples from a separate study cohort with low HDL, followed up for 12-weeks while on niacin treatment. Secreted pigment epithelium-derived factor from 3T3-L1 adipocytes, after HDL treatment (24-h), was measured using Western blot analysis. RESULTS: Mean (± sd) serum pigment epithelium-derived factor was significantly higher in subjects with impaired fasting glucose [13.99 (± 3.06) µg/ml] and Type 2 diabetes [12.94 (± 2.61)] µg/ml, compared with control subjects [11.83 (± 2.85) µg/ml (P = 0.014)]. In multivariate analyses, serum pigment epithelium-derived factor concentration was associated with BMI (ß = 0.32, 0.007), homeostasis model assessment-insulin resistance (ß = 0.33, P = 0.01) and HDL (ß = -0.24, P = 0.05), after adjustment for age, gender and high-sensitivity C-reactive protein. In the niacin study, on-treatment HDL was an independent determinant of pigment epithelium-derived factor (ß = -0.439, P = 0.033), after adjusting for age, homeostasis model assessment-insulin resistance and treatment. Adipocytes treated with HDL were found to have reduced pigment epithelium-derived factor secretion [24.8% (50 µg/ml), 28.4% (100 µg/ml) HDL; P < 0.05)], compared with the control samples. CONCLUSION: Serum pigment epithelium-derived factor is positively associated with homeostasis model assessment-insulin resistance and negatively associated with HDL. Further studies are needed to understand the mechanism of low HDL and raised pigment epithelium-derived factor and to determine if they are causally related to the pathobiology of insulin resistance.

Elevated undercarboxylated and reduced carboxylated osteocalcin are associated with metabolic syndrome in middle age Asian females.

Accumulating data suggest that bone plays a role in energy metabolism through decarboxylation of osteocalcin. Thus, we aimed to study the association of circulating under--carboxylated osteocalcin (UC-OCN) and car-boxylated osteocalcin (C-OCN) with metabolic syndrome in middle aged Asian population.In this cross-sectional study, 131 middle aged Asian subjects were recruited. Circulating UC-OCN, C-OCN and parameters of metabolic phenotype were measured.Circulating UC-OCN was increased in subjects with metabolic syndrome (8.1±7.2 ng/ml vs. 5.9±4.6 ng/ml, p=0.036). In contrast, C-OCN showed a non-significant trend towards reduction in subjects with metabolic syndrome (3.6±2.2 ng/ml vs. 4.3±1.8 ng/ml, p=0.057). Further analysis revealed that changes in both UC-OCN and C-OCN occurred primarily among females with metabolic syndrome. Interestingly, neither forms of OCN differed significantly between individuals with and without metabolic syndrome in males. Logistic regression revealed that UC-OCN was independently associated with metabolic syndrome after adjusting for multiple covariates. However, association between metabolic syndrome and C-OCN was dependent on gender (i. e., amongst females only) in the fully adjusted regression model.Variation in OCN (including its sub-species) was associated with variation in metabolic parameters amongst Asian adults. Circulating UC-OCN was increased while C-OCN was decreased in treatment-naïve females with metabolic syndrome. Our preliminary observations further supported a potential link between bone and energy metabolism in humans.

Associations between complications and health-related quality of life in individuals with diabetes.

OBJECTIVE: Type 2 diabetes and associated complications adversely affect health-related quality of life (HRQoL). However, it is unclear whether different complications have the same or different associations with HRQoL. We examined associations between retinopathy, nephropathy, peripheral neuropathy (microvascular), coronary heart disease, stroke and peripheral arterial disease (macrovascular) in diabetes and HRQoL. DESIGN: This study was a follow-up examination between 2004 and 2007 of participants from four previous cross-sectional population-based studies in Singapore. METHODS: Health-related quality of life was assessed through self-administered SF-36 health survey version 2. Diabetes and complications status were assessed through self-report, clinical and laboratory examinations. About 2601 individuals, 2205 healthy and 396 with diabetes, were studied. RESULTS: Lower physical component scores (PCS) were associated with microvascular (2.96 points, P < 0.001) and both macro- and microvascular complications (4.67 points, P < 0.001), but not diabetes alone. Coronary heart disease (3.86 points, P = 0.007), peripheral neuropathy (11.46 points, P < 0.001) and severe retinopathy (4.46 points, P < 0.001) were associated with lower PCS. The greatest reduction in scores was seen in peripheral neuropathy. CONCLUSIONS: Quality of life in patients with diabetes is affected mainly by presence of complications, and not diabetes per se. Peripheral neuropathy was associated with the greatest reduction in quality of life. Improved management to prevent or delay onset of complications may reduce the effect on quality of life in patients with diabetes.

Predictors of decrease in ankle-brachial index among patients with diabetes mellitus.

AIM: Screening for peripheral arterial disease, a complication among patients with diabetes, is performed by periodic assessment of ankle-brachial index. We aimed to study the degree of ankle-brachial index change over time and factors associated with significant change. METHOD: We assessed difference between two ankle-brachial index measurements over time in a consecutive series of 82 patients with Type 2 diabetes. All patients had ankle-brachial index > 0.9 but ≤ 1.3 for the first measurement, and significant ankle-brachial index decrease was defined as a decrease of > 0.1 in the follow-up measurement compared with the baseline. RESULTS: The mean follow-up duration was 27.6 (median 30.0) months. Significant ankle-brachial index decrease was seen in 20.7% of patients, including 5% with follow-up ankle-brachial index of ≤ 0.9, consistent with the diagnosis of peripheral arterial disease. After adjusting for age and gender, higher baseline HbA(1c) and serum creatinine levels, increase in follow-up serum LDL cholesterol levels compared with baseline and history of retinopathy were predictors of significant ankle-brachial index decrease. CONCLUSIONS: Our study suggests that, within two years, one in five patients with diabetes and a normal ankle-brachial index may have significant progression of peripheral arterial disease. Annual ankle-brachial index assessment and better control of hyperlipidaemia may thus be required for at-risk patients with poor glycaemic control, renal impairment and retinopathy.

Niacin results in reduced monocyte adhesion in patients with type 2 diabetes mellitus.

BACKGROUND AND AIM: Patients with type 2 diabetes have increased expression of cell adhesion molecules (CAMs). CAMs and monocyte adhesion mediate essential processes in atherogenesis. It remains unclear if monocytes from patients on niacin have reduced adhesion function. METHODS: We studied the variation of monocyte adhesion in patients with type 2 diabetes and low HDL-cholesterol, taking either extended release niacin (Niaspan®, Abbott Laboratories) or controls not on niacin. Biochemical parameters including adiponectin, CAMs and fresh monocytes from whole blood for adhesion assays, were studied at baseline and 12-weeks. RESULTS: Niacin 1500 mg daily raised HDL-cholesterol from 0.8 mmol/l (95% CI: 0.7-0.9) to 0.9 mmol/l (95% CI: 0.8-1.1), p=0.10, and significantly reduced PECAM-1 by 24.9% (95% CI: 10.9-39.0; p<0.05), increased adiponectin by 30.5% (95% CI: 14.1-47.0; p<0.05), with monocyte adhesion reduced by 9.2% (95%CI: 0.7-17.7; p<0.05) in endothelial cells treated in basal conditions, and 7.8% (95% CI: 3.1-12.5; p<0.05) after TNF-α stimulation. CONCLUSIONS: Monocytes isolated from patients on niacin had reduced adhesion to endothelial cells. Our findings suggest niacin has broad range of effects apart from lipid-modification, and these could be important in cardiovascular risk reduction.

Prevalence and risk factors for peripheral artery disease in an Asian population with diabetes mellitus.

We describe the prevalence and risk factors for PAD in Asian Malays with diabetes. A population-based study of 3,280 (78.7% response) Malay persons aged 40-80 years in Singapore was conducted. ABI was measured in all participants with a history of diabetes (N=634). PAD was defined to be present if ABI

Reduced mitochondrial coenzyme Q10 levels in HepG2 cells treated with high-dose simvastatin: a possible role in statin-induced hepatotoxicity?

Lowering of low-density lipoprotein cholesterol is well achieved by 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins). Statins inhibit the conversion of HMG-CoA to mevalonate, a precursor for cholesterol and coenzyme Q10 (CoQ10). In HepG2 cells, simvastatin decreased mitochondrial CoQ10 levels, and at higher concentrations was associated with a moderately higher degree of cell death, increased DNA oxidative damage and a reduction in ATP synthesis. Supplementation of CoQ10, reduced cell death and DNA oxidative stress, and increased ATP synthesis. It is suggested that CoQ10 deficiency plays an important role in statin-induced hepatopathy, and that CoQ10 supplementation protects HepG2 cells from this complication.

Apolipoprotein E genotype affects the response to lipid-lowering therapy in Chinese patients with type 2 diabetes mellitus.

OBJECTIVE: To evaluate the effect of apolipoprotein E (apoE) genotype on baseline lipid levels and the response to hydroxy-methyl glutaryl coenzyme A reductase inhibitors (statins) therapy in Chinese patients with type 2 diabetes mellitus (DM). RESEARCH DESIGN AND METHODS: We consecutively recruited Chinese patients with type 2 DM requiring lipid-lowering therapy according to current guidelines. Patients were started on either simvastatin 10 mg daily or given an equivalent dose of lovastatin 20 mg. After 12 weeks of statin therapy, patients had fasting lipid profiles repeated. ApoE genotyping was performed by restriction fragment length polymorphism (RFLP). RESULTS: Ninety-six patients were studied. The epsilon3/epsilon3 genotype was in 62.5%, epsilon2/epsilon3 and epsilon3/epsilon4, 16.7 and 20.8%, respectively. After adjusting for confounding variables, baseline total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels were significantly higher in those with epsilon3/epsilon4 compared with epsilon2/epsilon3 genotype (6.7 vs. 5.5 mm for TC, 4.5 vs. 3.6 mm for LDL-C; p = 0.015 and p = 0.025, respectively). With statin therapy, epsilon3/epsilon4 patients had significantly greater LDL-C lowering compared with epsilon2/epsilon3 patients (48 vs. 27.7%; p = 0.04). There was no gender difference in baseline lipid parameters or response to statin therapy. CONCLUSIONS: ApoE genotype accounts for interindividual variability of baseline cholesterol levels, and response to statin therapy in Chinese patients with type 2 DM.

Intraepidermal nerve fiber density as a marker of early diabetic neuropathy.

The purpose of the study was to reliably identify an early stage of diabetic polyneuropathy (DPN) by measuring injury to epidermal nerve fibers. We compared intraepidermal nerve fiber density (IENFD) at the ankle and thigh of 29 diabetic subjects who had no clinical or electrophysiological evidence of small- or large-fiber neuropathy to that of 84 healthy controls. The mean ankle IENFD of diabetic subjects was 9.1+/-5.0 mm and that of controls, 13.0+/-4.8 mm (P<0.001). The thigh IENFD did not differ significantly. The IENFD ratio (thigh IENFD divided by ankle IENFD) was 2.39+/-1.30 in diabetic subjects and 1.77+/-0.58 in controls (P<0.001), indicating a length-dependent reduction of IENFD in diabetics. Ankle IENFD remained significantly lower and the IENFD ratio higher in diabetic subjects after adjusting for age. Two subjects had parasympathetic dysfunction, two had retinopathy, and two early nephropathy. Age, height, weight, duration of diabetes, and average HbA1c did not influence IENFD among diabetic subjects. We used receiver operating characteristic (ROC) curves to describe and compare the utility of various threshold values of ankle IENFD and IENFD ratio for the diagnosis of early DPN. The sensitivity and specificity of diagnosing DPN using ankle IENFD of less than 10 mm were 72.4% and 76.2%, respectively. Thus, asymptomatic diabetics have a measurable, length-dependent reduction of distal epidermal nerves. Analogous to microalbuminuria in diabetic nephropathy, reliable identification and quantitation of nascent diabetic neuropathy may have potential therapeutic implications.

Niacin affects cell adhesion molecules and plasminogen activator inhibitor-1 in HepG2 cells.

BACKGROUND: Beyond lipid-modifying actions, niacin lowers the risk of atherothrombotic events by lowering prothrombotic factors like fibrinogen. Plasminogen activator inhibitor type 1 (PAI-1) is a potential factor for atherogenesis and thrombosis, increased in acute myocardial infarctions and restenosis after angioplasty. Cell adhesion molecules (CAM) mediate adhesion, recruitment and migration of white blood cells through vascular surfaces, an essential process in atherogenesis. ICAM-1 is a significant predictor of future coronary events. Whether niacin affects ICAM-1 expression is unknown. We studied the effects of niacin on PAI-1 and CAM using HepG2 cells. METHODS: HepG2 cells were cultured in DMEM until 90% confluent. After serum starvation, cells were exposed to DME/F12 containing niacin. Transforming growth factor-beta (TGF-beta) was added directly to cell media. Cell lysate and conditioned media were collected for measurement of PAI-1 by ELISA. For measurement of ICAM, cells were treated with tumor necrosis factor-alpha (TNF-alpha) instead. The effect of niacin on mRNA expression of ICAM-1 was studied using RT-PCR. RESULTS: Niacin reduced the TGF-beta-induced rise by 30% to 55% (p=0.002). The differences in degree of PAI-1 reduction, between different niacin concentrations, were not statistically significant. Niacin reduced TNF-alpha-induced rise in ICAM-1 levels by 66% to 89% (p<0.0001), but did not significantly affect TNF-alpha-induced rise in PECAM-1. Semiquantitative RT-PCR analysis showed that reduced TNF-alpha-induced rise in ICAM-1 mRNA expression significantly by 17% (p=0.001). CONCLUSIONS: Treatment with niacin suppressed PAI-1 and ICAM-1 levels in HepG2 cells. Further studies to understand the mechanistic pathways of this suppression, could further explain benefits of niacin in prevention of atherosclerotic disease, and offer therapeutic avenues against the rising burden of atherothrombotic disease.

Patients with low levels of high-density lipoprotein cholesterol: to treat or not to treat?

Clinical evidence indicates that a low level of high-density lipoprotein cholesterol (HDL-C) is a major risk of atherosclerosis. Raising HDL-C reduces this risk significantly, making HDL-C levels an important target of treatment for dyslipidaemia, especially in pre-existent atherosclerosis. HDL-C is protective against atherosclerosis, largely due to its function of reverse cholesterol transport. Additionally, some important roles include fibrinolysis, antioxidant functions, and reduction of platelet aggregability. A number of agents potentially modify HDL favourably. Niacin is the most potent HDL-C raising agent currently available in clinical practice, followed by fibrates. CETP inhibitors show greater HDL-C rising, but are still used in trial settings only. HDL mimetic agents are another group of agents that offer much promise. Clinical outcome data are awaited for these newer therapeutic agents.

Niacin noncompetitively inhibits DGAT2 but not DGAT1 activity in HepG2 cells.

Niacin is a widely used lipid-regulating agent in dyslipidemic patients. Previously, we have shown that niacin inhibits triacylglycerol synthesis. In this report, using HepG2 cells, we have examined the effect of niacin on the mRNA expression and microsomal activity of diacylglycerol acyltransferase 1 and 2 (DGAT1 and DGAT2), the last committed but distinctly different enzymes for triglyceride synthesis. Addition of niacin to the DGAT assay reaction mixture dose-dependently (0-3 mM) inhibited DGAT activity by 35-50%, and the IC(50) was found to be 0.1 mM. Enzyme kinetic studies showed apparent K(m) values of 8.3 microM and 100 microM using [(14)C]oleoyl-CoA and sn-1,2-dioleoylglycerol as substrates, respectively. A decrease in apparent V(max) was observed with niacin, whereas the apparent K(m) remained constant. A Lineweaver-Burk plot of DGAT inhibition by niacin showed a noncompetitive type of inhibition. Niacin selectively inhibited DGAT2 but not DGAT1 activity. Niacin inhibited overt DGAT activity. Niacin had no effect on the expression of DGAT1 and DGAT2 mRNA. These data suggest that niacin directly and noncompetitively inhibits DGAT2 but not DGAT1, resulting in decreased triglyceride synthesis and hepatic atherogenic lipoprotein secretion, thus indicating a major target site for its mechanism of action.