Insulin resistance is the major determinant for microalbuminuria in severe hypertriglyceridemia: implication for high-risk stratification

Association between Brachial-Ankle Pulse Wave Velocity and Microalbuminuria and to Predict the Risk for the Development of Microalbuminuria Using Brachial-Ankle Pulse Wave Velocity Measurement in Type 2 Diabetes Mellitus Patients

Brachial-ankle pulse wave velocity (baPWV) provides a useful means of assessing cardiovascular events and diabetic complications. However, the nature of associations between baPWV and microalbuminuria (MAU) and its presence in Type 2 diabetes mellitus (Type 2 DM) have rarely been investigated. This study aimed to examine the association between baPWV and MAU coupled with prediction of MAU using baPWV measurement among Type 2 DM patients. In this cross-sectional study, we enrolled 424 Type 2 DM patients who visited the cardiology and endocrinology department at a tertiary level health care facility, Republic of Korea between 1 January 2006 to 31 December 2008. Clinical and laboratory data were collected, and risk factors associated with MAU and prediction of risk for the development of MAU using baPWV measurement. The association between MAU and baPWV was examined using multivariable logistic regression analysis and predicted MAU by using receiver operating characteristic (ROC) curve analysis. Of the 424 Type 2 DM patients, 93 (21.9%) had MAU (20-200 μg/min). baPWV (cm/sec) was found to be significantly correlated with MAU levels (ug/min) (r = 0.791, p < 0.001). Further, baPWV was significantly associated MAU with higher odds ratio (adjusted odds ratio (AOR) 10.899; 95% confidence interval (CI) (4.518-26.292)). Similarly, smoking (AOR 10.899; 95% CI (4.518-26.292)), and low-density lipoprotein (LDL)-cholesterol (mg/dL) (AOR 1.017; 95% CI (1.001-1.033)) were also significantly associated with MAU. The appropriate cut-off value for baPWV to predict MAU 20 μg/min in our study was 1700 cm/sec (area under ROC curve = 0.976). This study shows that baPWV, cigarette smoking, and LDL-cholesterol are associated with MAU in Type 2 DM patients and suggests that a baPWV cut-off of 1700 cm/sec could be used to predict the presence of MAU (20 μg/min) in Type 2 DM patients in the Korean community.

A Randomized, Double-Blind, Placebo-Controlled Clinical Trial to Assess the Efficacy and Safety of Ethyl-Ester Omega-3 Fatty Acid in Taiwanese Hypertriglyceridemic Patients

Aim: Information regarding the effects of omega-3 fatty acid on hypertriglyceridemic patients in Chinese is still limited. This study aimed to investigate the efficacy and safety of Omacor^®, a prescription ethyl-ester omega-3 fatty acid for the treatment of hypertriglyceridemia, administered at doses of 2 g/day and 4 g/day to Taiwanese hypertriglyceridemic patients.

Methods: A multicenter, randomized, double-blind, placebo-controlled, parallel study in adults with hypertriglyceridemia was conducted. After a five-week diet lead in period patients with triglycerides = 200–1000 mg/dL were randomized to receive Omacor^®, a concentrated preparation of omega-3 eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) in a dose of 1 g twice daily (2 g Omacor ^®), 2 g twice daily (4 g Omacor^®) or placebo, for eight weeks. The primary endpoint was the percentage change in triglyceride serum levels from baseline to the end of treatment.

Results: A total of 253 Taiwanese patients were randomized, of which 65.6% (166) were men. At the end of the treatment, the percentage change in triglyceride serum levels in both the Omacor^® 4 g/day (−32.1%) and 2 g/day (−29.7%) groups was larger than in the placebo group (−5.4%) (p < 0.001). The incidence of drug-related adverse events was as follows: 0.0%, 1.2%, and 0.0% in Omacor ^® 4 g/day, Omacor^® 2 g/day, and placebo groups, respectively. No drug-related serious adverse events were reported during the study.

Conclusions: Omacor^® may be a feasible option to treat hypertriglyceridemia in Taiwanese patients.

A cohort study of incident microalbuminuria in relation to HOMA-IR in Korean men

BACKGROUND

Despite the previous studies showing the relationship between microalbuminuria and insulin resistance, longitudinal effect of insulin resistance on development of microalbuminuria is not clearly identified in non-diabetic population.

METHODS

One thousand six hundred three non-diabetic Korean men without microalbuminuria in 2005 had been followed up for the development of microalbuminuria until 2010. Microalbuminuria was evaluated by urine-albumin creatinine ration, and insulin resistance was evaluated by homeostasis model assessment of insulin resistance (HOMA-IR). Cox proportional hazards model was used to estimate the risk for microalbuminuria according to the tertile of HOMA-IR.

RESULTS

During 5465.8 person-y of average follow-up, microalbuminuria developed in 76 (4.7%) participants. Incidence of microalbuminuria increased in proportion to the level of HOMA-IR (tertile 1: 3.0%, tertile 2: 4.1%, tertile 3: 7.1%, P<0.001). When the 1st tertile of HOMA-IR was set as reference, hazard ratios and 95% confidence interval were 1.15 (0.56-2.35) and 2.07 (1.05-4.09) for those in the 2nd and 3rd tertiles of HOMA-IR, even after adjusting multiple covariates, respectively (P for linear trend=0.054).

CONCLUSIONS

Increased insulin resistance was a predictor of microalbuminuria in Korean men.

Maternal inheritance of severe hypertriglyceridemia impairs glucose metabolism in offspring

Maternally inherited familial hypercholesterolemia (FH) impairs glucose metabolism and increases cardiovascular risks in the offspring to a greater degree than paternal inherited FH. However, it remains unknown whether hypertriglyceridemia affects glucose metabolism via inheritance. In this study, we sought to compare the impact of maternally and paternally inherited hypertriglyceridemia on glucose and lipid metabolism in mice. ApoCIII transgenic mice with severe hypertriglyceridemia were mated with non-transgenic control mice to obtain 4 types of offspring: maternal non-transgenic control and maternal transgenic offspring, and paternal control and paternal transgenic offspring. Plasma triglycerides (TG), total cholesterol (TC), fasting plasma glucose (FPG) and fasting insulin (FINS) were measured. ApoCIII overexpression caused severe hypertriglyceridemia, but the transgenic female mice had unaltered fertility with normal pregnancy and birth of pups. The 4 groups of offspring had similar birth weight and growth rate. The plasma TG of maternal and paternal transgenic offspring were nearly 40-fold higher than maternal and paternal control mice, but there was no difference in plasma TG between maternal and paternal transgenic offspring. Although the FPG of the 4 groups of animals had no difference, the maternal transgenic mice showed impaired glucose tolerance, increased FINS levels and higher homeostasis model assessment insulin resistance index (HOMA-IR) than the other 3 groups. In conclusion, maternally inherited hypertriglyceridemia in ApoCIII transgenic mice displayed impaired glucose tolerance, hyperinsulinemia and increased HOMA-R, while paternally inherited hypertriglyceridemia did not have such impacts.

Insulin resistance is associated with the development of albuminuria in Korean subjects without diabetes

Previous studies have shown that insulin resistance is associated with the development of albuminuria. However, most studies are done on a background of diabetes or metabolic syndrome and there is little data from general population. The aim of this study is to define the effect of insulin resistance on the development of albuminuria in healthy individuals without diabetes. We analyzed 60,047 participants without baseline diabetes or chronic kidney disease, who underwent at least two health maintenance visits at a 2-year interval between 2002 and 2009 at a tertiary hospital in Korea. We measured the incidence of albuminuria at the second examination and calculated the odds ratio for the development of albuminuria according to the quintile of the homeostasis model assessment of insulin resistance (HOMA-IR). After 2 years, 880 cases of incident albuminuria were observed. The cumulative incidences of albuminuria were 1.08, 1.50, 1.35, 1.47, and 1.92% for the 1st to 5th quintiles of HOMA-IR. On multivariate logistic analysis, the odds ratios for incident albuminuria compared to those in the 1st quintile were 1.38 (95% CI 1.10-1.73; P=0.006), 1.23 (95% CI 0.97-1.55; P=0.087), 1.32 (95% CI 1.04-1.67; P=0.020), and 1.66 (95% CI 1.31-2.09; P<0.001) in the 2nd, 3rd, 4th, and 5th quintiles, respectively. A high level of insulin resistance assessed with HOMA-IR was associated with the development of albuminuria in relatively healthy subjects without diabetes. Further research is needed to verify the role of insulin resistance in the development of albuminuria and renal injury.

Elevated brachial-ankle pulse wave velocity is independently associated with microalbuminuria in a rural population

Microalbuminuria is a marker of generalized endothelial dysfunction resulting from arterial stiffness or insulin resistance, and brachial-ankle pulse wave velocity (baPWV) is a good measure of arterial stiffness. We aimed to investigate whether elevated baPWV is independently associated with microalbuminuria. This study included 1,648 individuals aged over 40 who participated in the baseline Multi-Rural Cohort Study conducted in Korean rural communities between 2005 and 2006. Participants were classified into less than 30 mg/g as normoalbuminuria or 30-300 mg/g as microalbuminuriausing urinary albumin creatinine ratio (UACR). The median and Q1-Q3 baPWV values were significantly higher in the microalbuminuric group both in men (1,538, 1,370-1,777 cm/s vs. 1,776, 1,552-2,027 cm/s, P < 0.001) and women (1,461, 1,271-1,687 cm/s vs. 1,645, 1,473-1,915 cm/s, P < 0.001). BaPWV was independently associated with microalbuminuria in both genders after adjusting for pulse rate; fasting blood glucose; triglyceride; homeostatic model assessment insulin resistance (HOMAIR) and, history of hypertension and diabetes. Fasting blood sugar and HOMAIR were judged as having nothing to do with multicolinearity (r = 0.532, P < 0.001). Elevated baPWV was independently associated with microalbuminuria regardless of insulin resistance among rural subjects over 40 yr.

Effect of glycine on the cyclooxygenase pathway of the kidney arachidonic acid metabolism in a rat model of metabolic syndrome

The kidneys are organs that can be severely impaired by metabolic syndrome (MS). This is characterized by the association of various pathologies such as hypertension, dyslipidemia, and type-2 diabetes. Glycine, a nonessential amino acid, is known to possess various protective effects in the kidney, such as a decrease in the deterioration of renal function and a reduction of the damage caused by hypoxia. In a rat model of MS, the effect of glycine on the cyclooxygenase (COX) pathway of arachidonic acid (AA) metabolism was studied in isolated perfused kidney. MS was induced in Wistar rats by feeding them a 30% sucrose solution for 16 weeks. The addition of 1% glycine to their drinking water containing 30% sucrose, for 8 weeks, reduced high blood pressure, triglyceride levels, insulin concentration, homeostatis model assessment (HOMA) index, albuminuria, AA concentration in kidney homogenate, renal perfusion pressure, prostaglandin levels, PLA2 expression, and COX isoform expression, compared with MS rats that did not receive the glycine supplement. Glycine receptor expression decreased significantly with MS, but glycine treatment increased it. The results suggest that in the MS model, 1% glycine treatment protects the kidney from damage provoked by the high sucrose consumption, by acting as an anti-inflammatory on the COX pathway of AA metabolism in kidney.

Glucose intolerance and decreased early insulin response in mice with severe hypertriglyceridemia

Hypertriglyceridemia (HTG) is one of the key features of dyslipidemia in type 2 diabetes, caused by the overproduction and/or decreased clearance of triglyceride (TG)-rich lipoproteins, and significantly promotes the development of cardiovascular diseases in diabetes. However, the effect of severe HTG on glucose metabolism has not previously been determined. Lipoprotein lipase (LPL) deficiency results in severe HTG in humans. By using LPL-deficient mice with severe HTG, we assessed the impact of severe HTG on insulin secretion and glucose tolerance in the present study. While young LPL-deficient mice (4 months of age) showed higher fasting blood glucose (7.42 ± 0.84 versus 4.8 ± 0.80 mmol/L, P < 0.01) and lower insulin concentrations (0.16 ± 0.03 versus 0.48 ± 0.14 ng/mL, P < 0.05), old mice (12 months of age) had higher insulin (1.70 ± 0.35 versus 0.77 ± 0.04 ng/mL, P < 0.05) but normal fasting blood glucose concentrations. Both young and old mice had elevated free fatty acid (FFA) concentrations and exhibited decreased early insulin response; however, only old mice showed impaired glucose tolerance, as compared with wild-type mice of a similar age. Morphological assessment showed enlarged islets in old LPL-deficient mice. These findings suggest that different tests for glucose homeostasis may be needed for patients with LPL deficiency and severe HTG, even though their glucose concentrations are normal at initial screening.