Takahiko Kawagishi

Inverse relationship between circulating oxidized low density lipoprotein (oxLDL) and anti-oxLDL antibody levels in healthy subjects

Oxidized low density lipoprotein (oxLDL) has been implicated in the pathogenesis of atherosclerosis. Recent studies have shown that immunization of animals with oxLDL results in suppression of atherogenesis. Antibody against oxLDL (oxLDL Ab) is detectable in human sera, although its biological significance is not well established. We examined the relationship between oxLDL Ab titer and circulating oxLDL level in 130 healthy Japanese subjects. OxLDL was measured as apolipoprotein (apo) B-containing lipoproteins carrying oxidized phosphatidylcholines by a sensitive ELISA. IgG class oxLDL Ab titer was measured by ELISA. Plasma oxLDL concentration was very low and it corresponded on average to one to two out of 1000 apoB-containing lipoproteins in plasma. Plasma oxLDL correlated positively with LDL cholesterol and inversely with oxLDL Ab titer. These associations remained significant and independent in multiple regression analysis including age, gender, smoking, and high-density lipoprotein cholesterol. These data indicate that healthy subjects have a very low concentration of oxLDL in the circulation, and that oxLDL Ab titer is in an inverse relationship with plasma oxLDL concentration in this population. Although these results suggest that oxLDL Ab may play a role in maintaining the low level of plasma oxLDL, its role in atherogenesis awaits further studies.

Stiffness indexes beta of the common carotid and femoral arteries are associated with insulin resistance in NIDDM

OBJECTIVE To investigate the association between arterial wall stiffness indexes β of the common carotid artery (CCA) and the femoral artery (FA) and insulin resistance in NIDDM subjects in a cross-sectional study. RESEARCH DESIGN AND METHODS We evaluated the arterial stiffness indexes β of CCA and FA using an ultrasonic phase-locked echo-tracking system in 60 NIDDM subjects attending the diabetes center in Osaka City University Hospital, compared with 120 ageand sex-matched control subjects. Insulin sensitivity indexes were evaluated using a euglycemic-hyperinsulinemic clamp. RESULTS Stiffness indexes β of both CCA and FA were significantly higher in NIDDM subjects than in control subjects (CCA 18.1 ± 0.9 vs. 11.7 ± 0.3, respectively, P < 0.001; FA 35.7 ± 2.3 vs. 23.7 ± 0.8, respectively, P < 0.001). The mean insulin sensitivity index in NIDDM subjects was 4.69 ± 0.29 mg · kg−1 · min−1 · mU−1 · 1. The stiffness indexes β of both CCA and FA were inversely correlated with insulin sensitivity indexes (CCA r = −0.393, P = 0.002; FA r = −0.329, P = 0.010), as well as with age, duration of diabetes, and mean blood pressure. In stepwise multiple regression analyses, insulin sensitivity index and duration of diabetes were identified as significant independent variables for stiffness indexes 3 in both CCA and FA (CCA R2 = 0.249, P = 0.0003; FA R2 = 0.336, P < 0.0001). CONCLUSIONS Arterial stiffness indexes β of CCA and FA were associated with insulin resistance in NIDDM subjects.

Antibodies Against Oxidized LDL and Carotid Artery Intima-Media Thickness in a Healthy Population

Oxidation of LDLs plays an important role in atherosclerosis, and immune response to oxidized LDL (oxLDL) may modulate atherogenesis. Although immunization with oxLDL is shown to suppress atherogenesis in animal models, the role of the immune response to oxLDL is not well established in humans. We investigated the relationship between the titer of anti-oxLDL antibody (oxLDL Ab) and arterial wall thickness in a healthy population with no clinical signs of atherosclerosis. Intima-media thickness of the carotid arteries (CA-IMT) was measured by high-resolution B-mode ultrasonography in 446 healthy subjects. The titer of IgG-class oxLDL Ab was measured by a solid-phase ELISA. In univariate analysis, CA-IMT correlated positively with age, systolic blood pressure, total cholesterol, triglyceride, LDL cholesterol, body mass index, and waist-to-hip ratio, whereas it correlated negatively with HDL cholesterol and oxLDL Ab titer. The inverse association between oxLDL Ab titer and CA-IMT remained significant in multiple regression analysis, which took other confounding variables into account. These results indicate an independent inverse relationship between oxLDL Ab titer and CA-IMT in healthy subjects, supporting the hypothesis that immune response to oxLDL may have a protective role at an early stage of human atherosclerosis.

Atherogenic lipoprotein changes in the absence of hyperlipidemia in patients with chronic renal failure treated by hemodialysis

We compared plasma lipid and lipoprotein parameters between 210 chronic renal failure patients treated by hemodialysis and 223 age- and sex-matched healthy control subjects to examine whether atherogenic lipoprotein changes were present in hemodialysis patients in the absence of hyperlipidemia. The hemodialysis group showed higher levels of plasma triglycerides, very low density lipoprotein (VLDL) cholesterol, and intermediate density lipoprotein (IDL) cholesterol and a lower level of high density lipoprotein (HDL) cholesterol. Low density lipoprotein (LDL) cholesterol of the hemodialysis group was not elevated but their LDL was significantly more triglyceride-enriched than that of controls. Subjects were then divided into five categories according to their plasma triglyceride levels at an interval of 50 mg/dl, and comparison was made between the two groups in the same range of plasma triglycerides. Hemodialysis patients again showed higher levels of VLDL- and IDL-cholesterol, and lower levels of HDL-cholesterol than the control group even in the plasma triglycerides-matched comparisons. Similarly, higher VLDL- and IDL-cholesterol levels in hemodialysis patients were significant in plasma total cholesterol-matched subgroup comparisons. Multiple regression analysis indicated that the relationship between plasma lipid concentrations and individual lipoprotein levels were substantially altered in uremic state. The 95th percentile level of IDL-cholesterol in the nonuremic controls was 15 mg/dl, and 45% of hemodialysis patients exceeded this level. Decreased HDL-cholesterol levels < or = 35 mg/dl were seen in 6% of the control and 38% of the hemodialysis group. Elevated IDL-cholesterol and decreased HDL-cholesterol were persistently found in hemodialysis patients with normal lipid levels. It is concluded that hemodialysis patients exhibited more atherogenic lipoprotein profile than nonuremic subjects with comparable levels of plasma triglycerides and total cholesterol. Especially, increased IDL- and decreased HDL-cholesterol levels in hemodialysis patients persisted even at very low levels of plasma lipids. Since elevated IDL and decreased HDL-cholesterol are implicated in the progression of atherosclerosis, these findings are of clinical importance in the diagnosis of lipoprotein disorder in chronic renal failure.

Angiotensin-Converting Enzyme Gene Polymorphism Is Associated With Carotid Arterial Wall Thickness in Non–Insulin-Dependent Diabetic Patients

BACKGROUND The insertion/deletion (I/D) polymorphism of the ACE gene has been shown to be associated with cardiovascular disease in healthy subjects as well as in patients with non-insulin-dependent diabetes mellitus (NIDDM). We investigated the relationship between the ACE gene polymorphism and the wall thickness of both carotid and femoral arteries in NIDDM patients. METHODS AND RESULTS We measured the intimal plus medial thickness (IMT) of both carotid and femoral arteries using high-resolution B-mode ultrasonography in 288 Japanese NIDDM patients (160 men, 128 women). No significant differences among the three genotypes were found with respect to age, sex, duration of diabetes, body mass index, blood pressure, plasma glucose, hemoglobin AIC, total cholesterol, triglycerides, HDL cholesterol, or cigarette-years. Plasma ACE levels were strongly associated with I/D polymorphism, with an additive effect of the D alleles. The carotid IMT of the patients carrying the D allele (DD+ID genotype) was significantly higher than that of the patients not carrying the D allele (II genotype) (P = .037), whereas the femoral IMT was not affected by the I/D polymorphism. Multiple regression analysis demonstrated that the risk factors for carotid IMT of patients with NIDDM were age, non-HDL cholesterol, and D allele of the ACE gene (R2 = .155, P < .0001). CONCLUSIONS The D allele of the ACE gene may be a risk factor for the development of wall thickening of the carotid but not the femoral artery in NIDDM patients.

Effect of Polymorphism of Apolipoprotein E and Angiotensin-Converting Enzyme Genes on Arterial Wall Thickness

We examined the association between the polymorphism of the apolipoprotein E (apoE) and the ACE genes and the intima-media thickness (IMT) of the carotid and femoral arteries measured using ultrasonography. The values of IMT of each artery were significantly higher in NIDDM patients (n = 356) than in control subjects (n = 235). The E4 allele or the D allele did not affect clinical characteristics, including age, fasting plasma glucose, total cholesterol, HDL cholesterol, LDL cholesterol, or blood pressure, in NIDDM or control subjects. No difference in the carotid IMT value was noted among the apoE genotypes in control or diabetic subjects. The carotid IMT was significantly higher in diabetic patients with the DD genotype (1.200 ± 0.586 mm) than in those with the II genotypes (0.990 ± 0.364 mm). Neither the E4 allele nor the D allele affected the femoral IMT in control or diabetic subjects. Multiple regression analysis demonstrated that the carotid IMT of NIDDM patients was associated with age, the D allele, and LDL cholesterol but not with the E4 allele, whereas that of control subjects was associated with age, sex, systolic blood pressure, LDL cholesterol, and HDL cholesterol, inversely. These results suggested that the E4 allele was not associated with the carotid or femoral IMTs, but that the D allele was statistically associated with carotid IMT in NIDDM patients but not control subjects. However, since the association was weak (2.3% explanatory power), its biological significance remains to be determined.

Poor Glycemic Control Impairs the Response of Biochemical Parameters of Bone Formation and Resorption to Exogenous 1,25-Dihydroxyvitamin D3 in Patients with Type 2 Diabetes

Abstract: Osteoblast deficit plays a principal role in the development of diabetic osteopenia. We have previously reported that high glucose conditions impair the function of osteoblast-like MG-63 cells. This study was performed to assess the sensitivity of osteoblasts to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in patients with type 2 diabetes without insulin deficiency or overt diabetic complications. During stimulation with 1,25(OH)2D3 at 2.0 mg/day for 6 consecutive days in 9 type 2 diabetic patients, serum levels of bone alkaline phosphatase (BALP), osteocalcin (OC) and the carboxyterminal propeptide of type 1 procollagen, and the urinary excretion of pyridinoline and deoxypyridinoline (DPYR), were monitored. As parameters of glycemic control, the mean level of fasting plasma glucose (mFPG) throughout the 1,25(OH)2D3 stimulation test and the level of HbA1C were used. 1,25(OH)2D3 increased serum 1,25(OH)2D significantly by day 2, which was followed by a significant reduction in the serum level of intact parathyroid hormone. The maximal increment of serum OC adjusted for that of 1,25(OH)2D was negatively correlated with both mFPG and HbA1C levels (p50.05). Furthermore, the magnitude of 1,25(OH)2D3-induced bone resorption, as reflected by the maximal increase in urinary DPYR excretion, was negatively correlated with the mFPG level (p50.05). Basal BALP tended to be negatively correlated with HbA1C, although not to a significant extent. In conclusion, our findings would indicate that poor glycemic control impairs the responses of osteoblasts and osteoclasts to 1,25(OH)2D3 in normo-insulinemic type 2 diabetic patients.

Femoral artery wall thickness and stiffness in evaluation of peripheral vascular disease in type 2 diabetes mellitus.

Stiffening and thickening of arterial wall are two important components of atherosclerosis. The purpose of this study was to evaluate the effects of femoral artery wall stiffness on clinical manifestation of peripheral vascular disease (PVD) in type 2 diabetes mellitus. The subjects were 315 patients with type 2 diabetes. Presence of intermittent claudication and/or leg pain at rest and reduced ankle-brachial blood pressure index (ABI<0.9) were used as a subjective and an objective index of PVD, respectively. Femoral artery intima-media thickness (FA-IMT) and stiffness parameter beta (FA-stiffness beta) were measured by ultrasound methods. Symptomatic patients (N=58) showed greater values for both FA-IMT and FA-stiffness beta than those without symptom (N=257). Similarly, patients with reduced ABI (N=56) had greater FA-IMT and FA-stiffness beta than those without (N=259). However, correlation between FA-IMT and FA-stiffness beta was not impressive, especially in the symptomatic patients. To evaluate the effect of FA-stiffness beta on PVD symptoms, the subjects were divided into three subgroups according to FA-IMT, and then FA-stiffness beta was compared between those with and without PVD symptoms in each subgroup. The symptomatic patients had greater FA-stiffness beta values than the asymptomatic subjects in all the three subgroups. Multiple logistic regression analysis indicated that the presence of PVD symptoms was associated more closely with increased FA-stiffness beta than with increased FA-IMT, whereas reduced ABI was associated more closely with FA-IMT than with FA-stiffness beta. These data suggest that stiffening of arterial wall has a significant impact on PVD manifestations, particularly on the leg symptoms, in patients with type 2 diabetes.

Impaired Retinal Artery Blood Flow in IDDM Patients Before Clinical Manifestations of Diabetic Retinopathy

OBJECTIVE To determine whether hemodynamic changes in retinal arteries precede clinical manifestations of diabetic retinopathy and to examine the effects of control of hyperglycemia on retinal artery blood flow. RESEARCH DESIGN AND METHODS We assessed blood flow in bilateral central retinal arteries in 50 insulin-dependent diabetes mellitus (IDDM) patients without retinopathy and 20 sex- and age-matched control subjects using duplex Doppler sonography. We determined the peak systolic velocity (PSV), end-diastolic velocity (EDV), time-averaged velocity (TAV), resistance index (RI), and pulsatility index (PI). RESULTS PSV, EDV, and TAV were significantly lower in IDDM patients than in control subjects (P < 0.05, P < 0.01, and P < 0.01, respectively). The RI was significantly higher in IDDM patients than in control subjects (P < 0.01) and was significantly correlated with plasma levels of glucose in IDDM patients (r = 0.0.310, P = 0.0248). Multiple regression analysis identified the plasma levels of glucose as a significant determination of RI in IDDM patients. After 14 days of intensive insulin therapy in 7 IDDM patients, the RI and plasma levels of glucose showed significant decreases (P = 0.018, P = 0.001, respectively). CONCLUSIONS Our results showed that changes in retinal hemodynamics were present before the clinical detection of overt diabetic retinopathy and suggest that the presence of short-term hyperglycemia partly contributes to impaired retinal circulation.

Renal function and insulin resistance as determinants of plasma leptin levels in patients with NIDDM.

Summary Plasma leptin level is known to correlate with the degree of obesity. To determine the influences of renal fuction and insulin resistance on plasma leptin concentrations, we measured plasma leptin concentrations and performed the euglycaemic hyperinsulinaemic clamp studies in 57 patients with non-insulin-dependent diabetes mellitus with a wide range of renal function. In simple regression analyses, plasma leptin concentration showed significant positive correlations with percentage of body fat measured by dual energy X-ray absorptiometry, body mass index, waist to hip ratio and fasting plasma insulin. Leptin level was higher in females than males. Multiple regression analyses indicated that percent body fat, waist to hip ratio, plasma insulin, gender and renal function (1/creatinine), but not insulin sensitivity, were significant and independent determinants of plasma leptin level. These results suggest that plasma leptin level is regulated or affected by multiple factors including renal function. Insulin resistance appeared to increase leptin levels indirectly by raising plasma insulin. [Diabetologia (1997) 40: 676–679]