A Dipeptidyl Peptidase-4 Inhibitor but not Incretins Suppresses Abdominal Aortic Aneurysms in Angiotensin II-Infused Apolipoprotein E-Null Mice.

AIM: The main pathophysiology of abdominal aortic aneurysm (AAA) considerably overlaps with that of atherosclerosis. We reported that incretins [glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP)] or a dipeptidyl peptidase-4 inhibitor (DPP-4I) suppressed atherosclerosis in apolipoprotein E-null (Apoe－/－) mice. Here we investigated the effects of incretin-related agents on AAA in a mouse model. METHODS: Apoe－/－ mice maintained on an atherogenic diet were subcutaneously infused with saline, Ang II (2000 ng/kg/min), Ang II, and native GLP-1 (2.16 nmol/kg/day) or Ang II and native GIP (25 nmol/kg/day) for 4 weeks. DPP-4I (MK0626, 6 mg/kg/day) was provided in the diet to the Ang II-infused mice with or without incretin receptor antagonists [(Pro3) GIP and exendin (9-39)]. RESULTS: AAA occurred in 70% of the animals receiving Ang II. DPP-4I reduced this rate to 40% and significantly suppressed AAA dilatation, fibrosis, and thrombosis. In contrast, incretins failed to attenuate AAA. Incretin receptor blockers did not reverse the suppressive effects of DPP-4I on AAA. In the aorta, DPP-4I significantly reduced the expression of Interleukin-1ß and increased that of tissue inhibitor of metalloproteinase (TIMP)-2. In addition, DPP-4I increased the ratio of TIMP-2 to matrix metalloproteinases-9. CONCLUSIONS: DPP-4I, MK0626, but not native incretins has protective effects against AAA in Ang II-infused Apoe－/－ mice via suppression of inflammation, proteolysis, and fibrosis in the aortic wall.

Amelioration of Hyperglycemia with a Sodium-Glucose Cotransporter 2 Inhibitor Prevents Macrophage-Driven Atherosclerosis through Macrophage Foam Cell Formation Suppression in Type 1 and Type 2 Diabetic Mice.

Direct associations between hyperglycemia and atherosclerosis remain unclear. We investigated the association between the amelioration of glycemia by sodium-glucose cotransporter 2 inhibitors (SGLT2is) and macrophage-driven atherosclerosis in diabetic mice. We administered dapagliflozin or ipragliflozin (1.0 mg/kg/day) for 4-weeks to apolipoprotein E-null (Apoe-/-) mice, streptozotocin-induced diabetic Apoe-/- mice, and diabetic db/db mice. We then determined aortic atherosclerosis, oxidized low-density lipoprotein (LDL)-induced foam cell formation, and related gene expression in exudate peritoneal macrophages. Dapagliflozin substantially decreased glycated hemoglobin (HbA1c) and glucose tolerance without affecting body weight, blood pressure, plasma insulin, and lipids in diabetic Apoe-/- mice. Aortic atherosclerotic lesions, atheromatous plaque size, and macrophage infiltration in the aortic root increased in diabetic Apoe-/- mice; dapagliflozin attenuated these changes by 33%, 27%, and 20%, respectively. Atherosclerotic lesions or foam cell formation highly correlated with HbA1c. Dapagliflozin did not affect atherosclerosis or plasma parameters in non-diabetic Apoe-/- mice. In db/db mice, foam cell formation increased by 4-fold compared with C57/BL6 mice, whereas ipragliflozin decreased it by 31%. Foam cell formation exhibited a strong correlation with HbA1c. Gene expression of lectin-like ox-LDL receptor-1 and acyl-coenzyme A:cholesterol acyltransferase 1 was upregulated, whereas that of ATP-binding cassette transporter A1 was downregulated in the peritoneal macrophages of both types of diabetic mice. SGLT2i normalized these gene expressions. Our study is the first to demonstrate that SGLT2i exerts anti-atherogenic effects by pure glucose lowering independent of insulin action in diabetic mice through suppressing macrophage foam cell formation, suggesting that foam cell formation is highly sensitive to glycemia ex vivo.

A glucagon-like peptide-1 analog liraglutide suppresses macrophage foam cell formation and atherosclerosis.

Macrophage foam cell formation, characterized by cholesterol ester accumulation catalyzed by acyl-CoA:cholesterol acyltransferase 1 (ACAT1), is the hallmark of early atherogenesis. We previously demonstrated the suppressive effects of incretins, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), on the development of atherosclerotic lesions in apolipoprotein E-deficient (apoE(-/-)) mice. The present study was performed to evaluate the suppressive effects of these incretins and GLP-1 analogs, such as exendin-4 and liraglutide, on human macrophage foam cell formation in vitro and those of liraglutide on atherosclerotic lesion development in apoE(-/-) mice. We investigated the suppressive effects of GLP-1, GIP, exendin-4, and liraglutide against oxidized low-density lipoprotein (oxLDL)-induced foam cell formation in primary cultured human monocyte-derived macrophages. Seventeen-week-old apoE(-/-) mice were administered a long-acting GLP-1 analog liraglutide by osmotic mini-pumps for 4 weeks. Aortic atherosclerosis, oxLDL-induced foam cell formation, and related gene expression in exudate peritoneal macrophages were determined in vivo and ex vivo. Receptors for GLP-1 and GIP were expressed at high levels in human aortic smooth muscle cells and monocytes, but at relatively low levels in human macrophages and foam cells. GLP-1, GIP, exendin-4, and liraglutide significantly suppressed oxLDL-induced foam cell formation mainly associated with ACAT1 down-regulation in human monocyte-derived macrophages. The infusion of liraglutide into apoE(-/-) mice significantly retarded atherosclerotic lesions with monocyte/macrophage infiltration in the aortic wall and suppressed foam cell formation and ACAT1 expression in macrophages. These findings indicate that liraglutide could prevent the development of atherosclerotic lesions by suppressing macrophage foam cell formation mainly associated with ACAT1 down-regulation.

Preventive effect of dipeptidyl peptidase-4 inhibitor on atherosclerosis is mainly attributable to incretin's actions in nondiabetic and diabetic apolipoprotein E-null mice.

AIM: Several recent reports have revealed that dipeptidyl peptidase (DPP)-4 inhibitors have suppressive effects on atherosclerosis in apolipoprotein E-null (Apoe (-/-)) mice. It remains to be seen, however, whether this effect stems from increased levels of the two active incretins, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). METHODS: Nontreated Apoe (-/-) mice, streptozotocin-induced diabetic Apoe (-/-) mice, and db/db diabetic mice were administered the DPP-4 inhibitor vildagliptin in drinking water and co-infused with either saline, the GLP-1 receptor blocker, exendin(9-39), the GIP receptor blocker, (Pro(3))GIP, or both via osmotic minipumps for 4 weeks. Aortic atherosclerosis and oxidized low-density lipoprotein-induced foam cell formation in exudate peritoneal macrophages were determined. RESULTS: Vildagliptin increased plasma GLP-1 and GIP levels without affecting food intake, body weight, blood pressure, or plasma lipid profile in any of the animals tested, though it reduced HbA1c in the diabetic mice. Diabetic Apoe (-/-) mice exhibited further-progressed atherosclerotic lesions and foam cell formation compared with nondiabetic counterparts. Nondiabetic and diabetic Apoe (-/-) mice showed a comparable response to vildagliptin, namely, remarkable suppression of atherosclerotic lesions with macrophage accumulation and foam cell formation in peritoneal macrophages. Exendin(9-39) or (Pro(3))GIP partially attenuated the vildagliptin-induced suppression of atherosclerosis. The two blockers in combination abolished the anti-atherosclerotic effect of vildagliptin in nondiabetic mice but only partly attenuated it in diabetic mice. Vildagliptin suppressed macrophage foam cell formation in nondiabetic and diabetic mice, and this suppressive effect was abolished by infusions with exendin(9-39)+(Pro(3))GIP. Incubation of DPP-4 or vildagliptin in vitro had no effect on macrophage foam cell formation. CONCLUSIONS: Vildagliptin confers a substantial anti-atherosclerotic effect in both nondiabetic and diabetic mice, mainly via the action of the two incretins. However, the partial attenuation of atherosclerotic lesions by the dual incretin receptor antagonists in diabetic mice implies that vildagliptin confers a partial anti-atherogenic effect beyond that from the incretins.

Increment of C-peptide after glucagon injection determines the progressive nature of Japanese type 2 diabetes: a long-term follow-up study.

Type 2 diabetes (T2D) is characterized by a steady worsening of ß-cell dysfunction as the disease progresses. The objective of this study was to estimate the decline of insulin secretion in Japanese type 2 diabetic patients (T2D-patients) by glucagon injection over an observation period of more than 10 years. Thirty-three T2D-patients were followed for 10.4 ± 1.4 years. Fasting C-peptide immunoreactivity (FCPR), the 6 min value of CPR after glucagon injection (6MCPR), and the increment of CPR (ΔCPR) were measured at baseline and follow-up. FCPR, 6MCPR, ΔCPR were significantly lower at follow-up than at baseline (p<0.05, p<0.005, and p<0.0005, respectively). The annual change of ΔCPR was significantly (p<0.05) greater than the annual change of FCPR (-0.062 ± 0.076 ng/mL/year and -0.025 ± 0.067 ng/mL/year, respectively). In contrast, CPR-index (an index of ß-cell function) and SUIT-index (secretory units of islets in transplantation) calculated based on fasting blood samples were unaltered. The annual changes of FCPR, 6MCPR, and ΔCPR were negatively correlated with the FCPR, 6MCPR, and ΔCPR values at baseline, respectively. Duration of diabetes, BMI, diabetic retinopathy, and secondary sulfonylurea failure at baseline were not correlated with the annual changes of FCPR, 6MCPR, and ΔCPR. In conclusion, our longitudinal observations suggest that ß-cell function progressively declines in Japanese T2D-patients. The annual declines of ΔCPR were more prominent than the annual declines of FCPR. ΔCPR after glucagon injection may be more useful for estimating individual longitudinal insulin secretion than fasting blood samples.

Glucose-dependent insulinotropic polypeptide prevents the progression of macrophage-driven atherosclerosis in diabetic apolipoprotein E-null mice.

AIM: We recently reported that glucose-dependent insulinotropic polypeptide (GIP) prevents the development of atherosclerosis in apolipoprotein E-null (Apoe(-/-)) mice. GIP receptors (GIPRs) are found to be severely down-regulated in diabetic animals. We examined whether GIP can exert anti-atherogenic effects in diabetes. METHODS: Nondiabetic Apoe(-/-) mice, streptozotocin-induced diabetic Apoe(-/-) mice, and db/db mice were administered GIP (25 nmol/kg/day) or saline (vehicle) through osmotic mini-pumps for 4 weeks. The animals were assessed for aortic atherosclerosis and for oxidized low-density lipoprotein-induced foam cell formation in exudate peritoneal macrophages. RESULTS: Diabetic Apoe(-/-) mice of 21 weeks of age exhibited more advanced atherosclerosis than nondiabetic Apoe(-/-) mice of the same age. GIP infusion in diabetic Apoe(-/-) mice increased plasma total GIP levels by 4-fold without improving plasma insulin, glucose, or lipid profiles. GIP infusion significantly suppressed macrophage-driven atherosclerotic lesions, but this effect was abolished by co-infusions with [Pro(3)]GIP, a GIPR antagonist. Foam cell formation was stimulated by 3-fold in diabetic Apoe(-/-) mice compared with their nondiabetic counterparts, but this effect was halved by GIP infusion. GIP infusion also attenuated the foam cell formation in db/db mice. In vitro treatment with GIP (1 nM) reduced foam cell formation by 15% in macrophages from diabetic Apoe(-/-) mice, and this attenuating effect was weaker than that attained by the same treatment of macrophages from nondiabetic counterparts (35%). While GIPR expression was reduced by only about a half in macrophages from diabetic mice, it was reduced much more dramatically in pancreatic islets from the same animals. Incubation with high glucose (500 mg/dl) for 9-10 days markedly reduced GIPR expression in pancreatic islet cells, but not in macrophages. CONCLUSIONS: Long-term infusion of GIP conferred significant anti-atherogenic effects in diabetic mice even though the GIPR expression in macrophages was mildly down-regulated in the diabetic state.

Effects of PKF275-055, a dipeptidyl peptidase-4 inhibitor, on the development of atherosclerotic lesions in apolipoprotein E-null mice.

We recently discovered that glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide can both prevent the development of atherosclerosis in apolipoprotein E-null (Apoe(-/-)) mice. In the present study, we attempted to extend these findings to orally administered dipeptidyl peptidase (DPP)-4 inhibitor. Seventeen-week-old Apoe(-/-) mice fed an atherogenic diet were administered a DPP-4 inhibitor, vildagliptin analogue (PKF275-055 [PKF], 100 µm/[kg d]), in drinking water over a period of 4 weeks. Aortic atherosclerosis and oxidized low-density lipoprotein-induced foam cell formation were determined. Orally administered PKF increased plasma levels of active glucagon-like peptide-1 by 3.5-fold, increased total glucose-dependent insulinotropic polypeptide levels by 2-fold, reduced body weight by 13%, and reduced plasma cholesterol levels by 30%. Compared with drinking water controls, PKF significantly suppressed total aortic atherosclerotic lesions, atheromatous plaque in the aortic root, and macrophage accumulation in the aortic wall by 30% to 40% (P < .001). None of these changes were associated with the PKF-induced reductions in body weight and plasma cholesterol levels. Foam cell formation was suppressed by 40% in the exudate peritoneal macrophages obtained from the PKF-treated mice. The DPP-4 inhibitor prevents the development of atherosclerotic lesions by suppressing macrophage foam cell formation.

The roles of salusins in atherosclerosis and related cardiovascular diseases.

Human salusin-α and -ß are related peptides of 28 and 20 amino acids, respectively, produced from the same precursor, prosalusin. Salusin-ß exerts more potent mitogenic effects on human vascular smooth muscle cells (VSMCs) and fibroblasts than salusin-α. Human macrophage foam cell formation is significantly stimulated by salusin-ß, but suppressed by salusin-α. Chronic salusin-ß infusion into apolipoprotein E-knockout mice enhances atherosclerotic lesions, paralleling increases in foam cell formation and upregulation of scavenger receptors and of acyl-CoA:cholesterol acyltransferase-1 (ACAT1) in macrophages. In contrast, chronic salusin-α infusion reduces atherosclerotic lesions accompanied by significant suppression of foam cell formation owing to ACAT1 downregulation. Salusin-ß is expressed in proliferative neointimal lesions of porcine coronary arteries after stenting. Salusin-α and -ß immunoreactivity has been detected in human coronary atherosclerotic plaques, with dominance of salusin-ß in macrophage foam cells, VSMCs, and fibroblasts. Serum salusin-α levels are markedly decreased in patients with angiographically proven coronary artery disease compared with patients with mild hypertension and healthy volunteers. Furthermore, among patients with acute coronary syndrome, serum salusin-α levels are decreased in accordance with the severity of coronary atherosclerotic lesions. These findings suggest that salusin-ß may contribute to the pathogenesis of atherosclerosis. Decreased levels of salusin-α in circulating blood and vascular tissue are closely linked with human atherosclerosis. Therefore, salusin-α could be a candidate biomarker for atherosclerosis and may be therapeutically useful for prevention of atherosclerotic cardiovascular diseases.

Chronic infusion of salusin-alpha and -beta exerts opposite effects on atherosclerotic lesion development in apolipoprotein E-deficient mice.

OBJECTIVE: Human salusin-alpha and -beta are two-related peptides processed from the same precursor, preprosalusin. Our previous in vitro studies have shown that human macrophage foam cell formation is stimulated by salusin-beta but suppressed by salusin-alpha. Thus we investigated the effects of salusin-alpha and -beta on atherosclerotic plaque formation in vivo in apolipoprotein E-deficient (ApoE-/-) mice. METHODS: Saline (vehicle), salusin-alpha or -beta (0.6 nmol/kg/h) was continuously infused through osmotic mini-pumps into 13-week-old ApoE-/- mice for 8 weeks. Aortic atherosclerosis, oxidized LDL-induced cholesterol ester accumulation (foam cell formation), and its related gene expression in exudate peritoneal macrophages were determined. RESULTS: After 4-week infusion of salusin-beta, atherosclerotic lesions were 2.6 times greater than vehicle controls, which paralleled 1.9-fold increase in foam cell formation and up-regulation of scavenger receptors (CD36, scavenger receptor class A) and acyl-CoA: cholesterol acyltransferase-1 (ACAT1). In contrast, salusin-alpha decreased serum total cholesterol levels by 15% and foam cell formation by 68% associated with ACAT1 down-regulation. After 8-week infusion of salusin-alpha, atherosclerotic lesions were significantly suppressed by 54% compared with vehicle controls. CONCLUSIONS: Our study provided the first evidence that salusin-beta accelerates the development of atherosclerotic lesions associated with up-regulation of scavenger receptors and ACAT1 in ApoE-/- mice. Whilst, salusin-alpha exerts anti-atherosclerotic effects by suppressing serum total cholesterol levels and ACAT1 expression.

Preventive effects of heregulin-beta1 on macrophage foam cell formation and atherosclerosis.

RATIONALE: Human heregulins, neuregulin-1 type I polypeptides that activate proliferation, differentiation, and survival of glial cells, neurons, and myocytes, are expressed in macrophage foam cells within human coronary atherosclerotic lesions. Macrophage foam cell formation, characterized by cholesterol ester accumulation, is modulated by scavenger receptor class A (SR-A), acyl-coenzyme A:cholesterol acyltransferase (ACAT)1, and ATP-binding cassette transporter (ABC)A1. OBJECTIVE: The present study clarified the roles of heregulins in macrophage foam cell formation and atherosclerosis. METHODS AND RESULTS: Plasma heregulin-beta(1) levels were significantly decreased in 31 patients with acute coronary syndrome and 33 patients with effort angina pectoris compared with 34 patients with mild hypertension and 40 healthy volunteers (1.3+/-0.3, 2.0+/-0.4 versus 7.6+/-1.4, 8.2+/-1.2 ng/mL; P<0.01). Among all patients with acute coronary syndrome and effort angina pectoris, plasma heregulin-beta(1) levels were further decreased in accordance with the severity of coronary artery lesions. Expression of heregulin-beta(1) was observed at trace levels in intracoronary atherothrombosis obtained by aspiration thrombectomy from acute coronary syndrome patients. Heregulin-beta(1), but not heregulin-alpha, significantly reduced acetylated low-density lipoprotein-induced cholesterol ester accumulation in primary cultured human monocyte-derived macrophages by reducing SR-A and ACAT1 expression and by increasing ABCA1 expression at both mRNA and protein levels. Heregulin-beta(1) significantly decreased endocytic uptake of [(125)I]acetylated low-density lipoprotein and ACAT activity, and increased cholesterol efflux to apolipoprotein (Apo)A-I from human macrophages. Chronic infusion of heregulin-beta(1) into ApoE(-/-) mice significantly suppressed the development of atherosclerotic lesions. CONCLUSIONS: This study provided the first evidence that heregulin-beta(1) inhibits atherogenesis and suppresses macrophage foam cell formation via SR-A and ACAT1 downregulation and ABCA1 upregulation.

Remnant lipoprotein cholesterol homogenous assay (RemL-C) is closely associated with very-low-density lipoprotein remnants: comparison with the immunoseparation assay.

BACKGROUND: Remnant-like particle-cholesterol (RLP-C) is recognized as a risk factor for cardiovascular disease. As an alternative to the immunoseparation assay widely used for the measurement of RLP-C, a new remnant lipoprotein-C homogenous assay (RemL-C) is available. In light of its homogeneity as an assay method, we speculated that this homogeneous assay (RemL-C) is closely associated with very-low-density lipoprotein(VLDL) remnant including intermediate-density lipoprotein(IDL). We examined the characteristics of the homogeneous assay for reacting with VLDL remnants. METHODS AND RESULTS: VLDL1, VLDL2, and IDL were separated by ultracentrifugation in the fasting serum of subjects including hypertriglyceridemia and uremic patients usually having higher levels of remnants. While RemL-C and RLP-C were mainly recovered in VLDL1 and both assays were strongly correlated with serum TG and VLDL1, the RemL-C assay was more closely correlated with VLDL2 and IDL levels than the RLP-C assay. RemL-C levels were significantly correlated with IDL-C, whereas RLP-C levels had only borderline associations with IDL-C (r= 0.56 Vs. 0.31). CONCLUSIONS: The remnant lipoprotein cholesterol homogenous assay is more closely associated with VLDL2 and IDL than the immunoseparation assay.

Chronic urotensin II infusion enhances macrophage foam cell formation and atherosclerosis in apolipoprotein E-knockout mice.

OBJECTIVE: Our recent studies have indicated that urotensin II, the most potent vasoconstrictor peptide identified to date, potentiates human macrophage foam cell formation and vascular smooth muscle cell proliferation, and its levels are increased in the plasma of hypertensive patients with carotid atherosclerotic plaques. In the present study, we investigated the enhancing effect of urotensin II on atherosclerosis in apolipoprotein E-knockout mice and its suppression by 4-aminoquinoline, an urotensin II receptor-selective antagonist. METHODS: Urotensin II, urotensin II + 4-aminoquinoline, or vehicle was infused for 4 weeks through an osmotic mini-pump into 9-week-old apolipoprotein E-knockout mice on a high-fat diet. Aortic atherosclerosis and foam cell formation in exudate peritoneal macrophages were examined. RESULTS: Atherosclerotic lesions as well as plasma levels of urotensin II, reactive oxygen species, and oxidized low-density lipoprotein and oxidized low-density lipoprotein-induced foam cell formation were significantly greater in urotensin II-infused mice than vehicle-infused controls. Western blotting analysis showed increased expression of scavenger receptors (CD36 and scavenger receptor class A) and acyl-CoA:cholesterol acyltransferase-1 in these macrophages. Increases in these parameters were significantly reduced by addition of 4-aminoquinoline. In apolipoprotein E-knockout mice even without urotensin II infusion, the treatment with 4-aminoquinoline for 8 weeks significantly prevented the development of atherosclerotic lesions. CONCLUSION: Our results provide the first evidence that increased plasma urotensin II level stimulates oxidized low-density lipoprotein and reactive oxygen species production and macrophage foam cell formation via increased expression of CD36, scavenger receptor class A, and acyl-CoA:cholesterol acyltransferase-1, contributing to the development of atherosclerosis in apolipoprotein E-deficient mice. Urotensin II receptor antagonism may be a promising therapeutic strategy against atherosclerosis.

Significant increase of apolipoprotein B48 levels by a standard test meal in type 2 diabetic patients with nephropathy.

AIM: We investigated postprandial changes of apolipoprotein (apo) B48 in type 2 diabetics at different stages of diabetic nephropathy in order to explore non-traditional lipid abnormalities in diabetic nephropathy. METHODS: Twenty-two healthy controls and 56 type 2 diabetics with normoalbuminuria (NA), microalbuminuria (MA), and overt albuminuria (OA) were enrolled. Blood samples were taken at 0, 1, 2, 4, 6 h after the ingestion of Test meal A (460 Kcal, 18 g fat). The maximal increase of triglyceride (TG) was 40% above baseline in controls and 17% above baseline in diabetics. The incremental area under the curve (iAUC) of TG, however, was comparable among controls and diabetics with NA, MA, and OA. The maximal increase of apoB48 was 92% above baseline in controls and 56-88% above baseline in diabetics. Apo B48-iAUC was significantly higher in diabetics than in controls, and diabetics with OA exhibited the highest apoB48-iAUC among the diabetic subgroups. Small dense low-density lipoprotein-cholesterol (LDL-C) was elevated in diabetic nephropathy, and apoB48-iAUC was positively associated with the level of sd-LDL-C. CONCLUSIONS: ApoB48 is a sensitive marker for postprandial lipemia, a condition which is significantly increased in diabetic nephropathy and associated with an increase of potent atherogenic sd- LDL particles.

Serum salusin-alpha levels are decreased and correlated negatively with carotid atherosclerosis in essential hypertensive patients.

Salusin-alpha is a new bioactive peptide with mild hypotensive and bradycardic effects. Our recent study showed that salusin-alpha suppresses foam cell formation in human monocyte-derived macrophages by down-regulating acyl-CoA:cholesterol acyltransferase-1, contributing to its anti-atherosclerotic effect. To clarify the clinical implications of salusin-alpha in hypertension and its complications, we examined the relationship between serum salusin-alpha levels and carotid atherosclerosis in hypertensive patients. The intima-media thickness (IMT) and plaque score in the carotid artery, blood pressure, serum levels of salusin-alpha, and atherosclerotic parameters were determined in 70 patients with essential hypertension and in 20 normotensive controls. There were no significant differences in age, gender, body mass index, fasting plasma glucose level, or serum levels of high-sensitive C-reactive protein, high- or low-density lipoprotein (LDL) cholesterol, small dense LDL, triglycerides, lipoprotein(a), or insulin between the two groups. Serum salusin-alpha levels were significantly lower in hypertensive patients than in normotensive controls. The plasma urotensin-II level, maximal IMT, plaque score, systolic and diastolic blood pressure, and homeostasis model assessment for insulin resistance (HOMA-IR) were significantly greater in hypertensive patients than in normotensive controls. In all subjects, maximal IMT was significantly correlated with age, systolic blood pressure, LDL cholesterol, urotensin-II, salusin-alpha, and HOMA-IR. Forward stepwise multiple linear regression analysis revealed that salusin-alpha levels had a significantly independent and negative association with maximal IMT. Serum salusin-alpha levels were significantly lower in accordance with the severity of plaque score. Our results suggest that the decrease in serum salusin-alpha, an anti-atherogenic peptide, may be associated with carotid atherosclerosis in hypertensive patients.

Chronic insulin infusion normalizes blood pressure and the gene expressions of angiotensin II type 1 receptor in fructose-fed rats.

It remains open to debate whether hyperinsulinemia leads to the development of hypertension. We addressed this issue by investigating the effect of chronic insulin infusion on blood pressure and related parameters in hypertensive fructose-fed rats. Rats were given either normal chow or a fructose-rich diet, and insulin or saline was infused through mini-pumps in the same animals for 14 days. The chronic insulin infusion exerted no effect on the blood pressure of the chow-fed rats. Fructose feeding increased the blood pressure and levels of insulin, triglyceride and fatty acid. Insulin infusion augmented the hyperinsulinemia but normalized the blood pressure and plasma lipids. Plasma angiotensin II was elevated in the fructose-fed rats, while insulin infusion left it unchanged. The expression of angiotensin II type 1 receptor (AT1R) mRNA was doubled in both the aorta and epididymal fat of the fructose-fed rats, while that of angiotensin II type 2 receptor (AT2R) was unaltered. Insulin infusion completely rectified the over-expression of the AT1R gene. Our findings indicate that chronic insulin infusion exacerbates hyperinsulinemia while normalizing blood pressure and the gene expressions of AT1R in insulin-resistant fructose-fed rats, suggesting that endogenous hyperinsulinemia caused by insulin resistance is associated with the development of hypertension, whereas exogenous hyperinsulinemia attenuates hypertension probably due to amelioration of insulin resistance.

Decreased peroxisome proliferator-activated receptor alpha gene expression is associated with dyslipidemia in a rat model of chronic renal failure.

The transcription factor peroxisome proliferator-activated receptor (PPAR) alpha plays an important role in lipid homeostasis. In this study, we examined whether the down-regulation of PPAR-alpha gene expression is associated with dyslipidemia in a rat model of chronic renal failure (CRF). Rats with laboratory-induced uremia by 5/6 nephrectomy were bled at 2 weeks and 10 weeks after the nephrectomy to produce conditions. For the sake of convenience, the rats observed at postoperative week 2 were defined as acute renal failure (ARF) and those observed at week 10 were defined as CRF. Lipids in lipoprotein fractions were measured by high-performance liquid chromatography. The abundance of PPAR-alpha messenger RNA (mRNA) in the liver was measured by reverse transcriptase-polymerase chain reaction. Serum creatinine and blood urea nitrogen levels rose with the progression of renal failure, but the total protein levels remained constant. Serum triglyceride in ARF rats remained unchanged from the level in sham-operated control rats, whereas that in CRF rats was 66% higher than the control level. Serum cholesterol was elevated 1.5-fold in ARF rats and 2-fold in CRF rats compared with the sham-operated counterparts. As with triglyceride, very low-density lipoprotein remained unchanged in ARF rats but rose substantially in CRF rats. All of the major lipoprotein fractions were elevated in CRF rats. These lipid and lipoprotein changes were significantly associated with creatinine and blood urea nitrogen levels. The PPAR-alpha mRNA expression in the liver was unchanged in ARF rats but was 44% lower in CRF rats. The PPAR-alpha mRNA expression was inversely correlated with serum creatinine and lipids in the overall rats. Our results indicate that PPAR-alpha mRNA expression is down-regulated in the liver of CRF rats and that this down-regulation may play a crucial role in the development of dyslipidemia.

The effects of statin and fibrate on lowering small dense LDL- cholesterol in hyperlipidemic patients with type 2 diabetes.

AIM: Small dense (sd)-low-density lipoprotein (LDL) is a potent atherogenic lipoprotein. The overall atherogenicity of this lipoprotein can be precisely assessed by quantifying sd-LDL rather than by measuring the LDL size. We studied the effects of representative lipid-lowering agents (statin and fibrate) on sd-LDL-cholesterol (C) in patients with type 2 diabetes. METHODS: Sd-LDL-C was measured by the precipitation method established by Hirano and Ito. Large buoyant (lb)-LDL-C was calculated by subtracting sd-LDL-C from LDL-C. Type 2 diabetes patients (n=72) were administered lipid-lowering agents for three months: patients with hypercholesterolemia received 1 mg of pitavastatin and those with hypertriglyceridemia received 100 mg of micronized fenofibrate. RESULTS: Pitavastatin reduced LDL-C by 25% and reduced TG by 8%. The statin decreased sd-LDL-C by 26%, and lb-LDL-C by 22%. Fenofibrate reduced TG by 38% and increased HDL-C by 14%. The fibrate decreased sd-LDL-C by 23% without changing LDL-C. The pitavastatin-induced reduction of sd-LDL-C was significantly correlated with the reduction of LDL-C and apo B, whereas the fenofibrate-induced reduction of sd-LDL-C was correlated with the reduction of TG. CONCLUSION: Both statin and fibrate reduce the potency of atherogenic sd-LDL particles, but via different mechanisms: the former decreases total-LDL including sd-LDL, while the latter decreases sd-LDL specifically.