Increased endothelin-induced Ca2+ signaling, tyrosine phosphorylation, and coronary artery disease in diabetic dyslipidemic Swine are prevented by atorvastatin

High-throughput screening and investigation of the inhibitory mechanism of α-glucosidase inhibitors in teas using an affinity selection-mass spectrometry method

An affinity selection-mass spectrometry method was applied for high-throughput screening of α-glucosidase (AGH) inhibitors from teas. Fourteen out of nineteen screened AGH inhibitor candidates were clustered as galloylated polyphenols (GPs). "AGH-GPs" interaction studies, including enzyme kinetics, fluorescence spectroscopy, circular dichroism, and molecular docking, jointly suggested that GPs noncompetitively inhibit AGH activity by interacting with amino acid residues near the active site of AGH and inducing changes in AGH secondary structure. Representative GPs and white tea extract (WTE) showed comparable AGH inhibition effects in Caco2 cells and postprandial hypoglycemic efficacy in diabetic mice as acarbose. The area under the curve of oral sucrose tolerance test was lower by 8.16%, 6.17%, and 7.37% than control group in 15 mg/kg EGCG, 15 mg/kg strictinin, and 150 mg/kg WTE group, respectively. Our study presents a high-efficiency approach to discover novel AGH inhibitors and elucidates a potential mechanism by which tea decreases diabetes risks.

Insulin-like growth factor 1 reduces coronary atherosclerosis in pigs with familial hypercholesterolemia

Although murine models of coronary atherosclerotic disease have been used extensively to determine mechanisms, limited new therapeutic options have emerged. Pigs with familial hypercholesterolemia (FH pigs) develop complex coronary atheromas that are almost identical to human lesions. We reported previously that insulin-like growth factor 1 (IGF-1) reduced aortic atherosclerosis and promoted features of stable plaque in a murine model. We administered human recombinant IGF-1 or saline (control) in atherosclerotic FH pigs for 6 months. IGF-1 decreased relative coronary atheroma in vivo (intravascular ultrasound) and reduced lesion cross-sectional area (postmortem histology). IGF-1 increased plaque's fibrous cap thickness, and reduced necrotic core, macrophage content, and cell apoptosis, consistent with promotion of a stable plaque phenotype. IGF-1 reduced circulating triglycerides, markers of systemic oxidative stress, and CXCL12 chemokine levels. We used spatial transcriptomics (ST) to identify global transcriptome changes in advanced plaque compartments and to obtain mechanistic insights into IGF-1 effects. ST analysis showed that IGF-1 suppressed FOS/FOSB factors and gene expression of MMP9 and CXCL14 in plaque macrophages, suggesting possible involvement of these molecules in IGF-1's effect on atherosclerosis. Thus, IGF-1 reduced coronary plaque burden and promoted features of stable plaque in a pig model, providing support for consideration of clinical trials.

Swine Disease Models for Optimal Vascular Engineering

Swine disease models are essential for mimicry of human metabolic and vascular pathophysiology, thereby enabling high-fidelity translation to human medicine. The worldwide epidemic of obesity, metabolic disease, and diabetes has prompted the focus on these diseases in this review. We highlight the remarkable similarity between Ossabaw miniature swine and humans with metabolic syndrome and atherosclerosis. Although the evidence is strongest for swine models of coronary artery disease, findings are generally applicable to any vascular bed. We discuss the major strengths and weaknesses of swine models. The development of vascular imaging is an example of optimal vascular engineering in swine. Although challenges regarding infrastructure and training of engineers in the use of swine models exist, opportunities are ripe for gene editing, studies of molecular mechanisms, and use of swine in coronary artery imaging and testing of devices that can move quickly to human clinical studies.

Alloxan-induced diabetes exacerbates coronary atherosclerosis and calcification in Ossabaw miniature swine with metabolic syndrome

Background

There is a preponderance of evidence implicating diabetes with increased coronary artery disease (CAD) and calcification (CAC) in human patients with metabolic syndrome (MetS), but the effect of diabetes on CAD severity in animal models remains controversial. We investigated whether diabetes exacerbates CAD/CAC and intracellular free calcium ([Ca²⁺]_i) dysregulation in the clinically relevant Ossabaw miniature swine model of MetS.

Methods

Sixteen swine, eight with alloxan-induced diabetes, were fed a hypercaloric, atherogenic diet for 6 months. Alloxan-induced pancreatic beta cell damage was examined by immunohistochemical staining of insulin. The metabolic profile was confirmed by body weight, complete blood panel, intravenous glucose tolerance test (IVGTT), and meal tolerance test. CAD severity was assessed with intravascular ultrasound and histology. [Ca²⁺]_i handling in coronary smooth muscle (CSM) cells was assessed with fura-2 ratiometric imaging.

Results

Fasting and post-prandial blood glucose, total cholesterol, and serum triglycerides were elevated in MetS-diabetic swine. This group also exhibited hypoinsulinemia during IVGTT and less pancreatic beta cell mass when compared to lean and MetS-nondiabetic swine. IVUS analysis revealed that MetS-diabetic swine had greater percent wall coverage, percent plaque burden, and calcium index when compared to lean and MetS-nondiabetic swine. Fura-2 imaging of CSM [Ca²⁺]_i revealed that MetS-nondiabetic swine exhibited increased sarcoplasmic reticulum Ca²⁺ store release and Ca²⁺ influx through voltage-gated Ca²⁺ channels compared to lean swine. MetS-diabetic swine exhibited impaired Ca²⁺ efflux.

Conclusions

Diabetes exacerbates coronary atherosclerosis and calcification in Ossabaw miniature swine with MetS, accompanied by progression of [Ca²⁺]_i dysregulation in advanced CAD/CAC. These results recapitulate increased CAD in humans with diabetes and establish Ossabaw miniature swine as an animal model for future MetS/diabetes comorbidity studies.

Intracellular calcium increases in vascular smooth muscle cells with progression of chronic kidney disease in a rat model

Background

Vascular smooth muscle cells (VSMCs) exhibit phenotypic plasticity, promoting vascular calcification and increasing cardiovascular risk. Changes in VSMC intracellular calcium ([Ca 2+ ] i ) are a major determinant of plasticity, but little is known about changes in [Ca 2+ ] i in chronic kidney disease (CKD). We have previously demonstrated such plasticity in aortas from our rat model of CKD and therefore sought to examine changes in [Ca 2+ ] i during CKD progression.

Materials and Methods

We examined freshly isolated VSMCs from aortas of normal rats, Cy/+ rats (CKD) with early and advanced CKD, and advanced CKD rats treated without and with 3% calcium gluconate (CKD + Ca 2+ ) to lower parathyroid hormone (PTH) levels. [Ca 2+ ] i was measured with fura-2.

Results

Cy/+ rats developed progressive CKD, as assessed by plasma levels of blood urea nitrogen, calcium, phosphorus, parathyroid hormone and fibroblast growth factor 23. VSMCs isolated from rats with CKD demonstrated biphasic alterations in resting [Ca 2+ ] i : VSMCs from rats with early CKD exhibited reduced resting [Ca 2+ ] i , while VSMCs from rats with advanced CKD exhibited elevated resting [Ca 2+ ] i . Caffeine-induced sarcoplasmic reticulum (SR) Ca 2+ store release was modestly increased in early CKD and was more drastically increased in advanced CKD. The advanced CKD elevation in SR Ca 2+ store release was associated with a significant increase in the activity of the sarco-endoplasmic reticulum Ca 2+ ATPase (SERCA); however, SERCA2a protein expression was decreased in advanced CKD. Following SR Ca 2+ store release, recovery of [Ca 2+ ] i in the presence of caffeine and extracellular Ca 2+ was attenuated in VSMCs from rats with advanced CKD. This impairment, together with reductions in expression of the Na + /Ca 2+ exchanger, suggest a reduction in Ca 2+ extrusion capability. Finally, store-operated Ca 2+ entry (SOCE) was assessed following SR Ca 2+ store depletion. Ca 2+ entry during recovery from caffeine-induced SR Ca 2+ store release was elevated in advanced CKD, suggesting a role for exacerbated SOCE with progressing CKD.

Conclusions

With progressive CKD in the Cy/+ rat there is increased resting [Ca 2+ ] i in VSMCs due, in part, to increased SOCE and impaired calcium extrusion from the cell. Such changes may predispose VSMCs to phenotypic changes that are a prerequisite to calcification.

Linking the beneficial effects of current therapeutic approaches in diabetes to the vascular endothelin system

The rising epidemic of diabetes worldwide is of significant concern. Although the ultimate objective is to prevent the development and find a cure for the disease, prevention and treatment of diabetic complications is very important. Vascular complications in diabetes, or diabetic vasculopathy, include macro- and microvascular dysfunction and represent the principal cause of morbidity and mortality in diabetic patients. Endothelial dysfunction plays a pivotal role in the development and progression of diabetic vasculopathy. Endothelin-1 (ET-1), an endothelial cell-derived peptide, is a potent vasoconstrictor with mitogenic, pro-oxidative and pro-inflammatory properties that are particularly relevant to the pathophysiology of diabetic vasculopathy. Overproduction of ET-1 is reported in patients and animal models of diabetes and the functional effects of ET-1 and its receptors are also greatly altered in diabetic conditions. The current therapeutic approaches in diabetes include glucose lowering, sensitization to insulin, reduction of fatty acids and vasculoprotective therapies. However, whether and how these therapeutic approaches affect the ET-1 system remain poorly understood. Accordingly, in the present review, we will focus on experimental and clinical evidence that indicates a role for ET-1 in diabetic vasculopathy and on the effects of current therapeutic approaches in diabetes on the vascular ET-1 system.

Coronary microvascular dysfunction in a porcine model of early atherosclerosis and diabetes

Detailed evaluation of coronary function early in diabetes mellitus (DM)-associated coronary artery disease (CAD) development is difficult in patients. Therefore, we investigated coronary conduit and small artery function in a preatherosclerotic DM porcine model with type 2 characteristics. Streptozotocin-induced DM pigs on a saturated fat/cholesterol (SFC) diet (SFC + DM) were compared with control pigs on SFC and standard (control) diets. SFC + DM pigs showed DM-associated metabolic alterations and early atherosclerosis development in the aorta. Endothelium-dependent vasodilation to bradykinin (BK), with or without blockade of nitric oxide (NO) synthase, endothelium-independent vasodilation to an exogenous NO-donor (S-nitroso-N-acetylpenicillamine), and vasoconstriction to endothelin (ET)-1 with blockade of receptor subtypes, were assessed in vitro. Small coronary arteries, but not conduit vessels, showed functional alterations including impaired BK-induced vasodilatation due to loss of NO (P < 0.01 vs. SFC and control) and reduced vasoconstriction to ET-1 (P < 0.01 vs. SFC and control), due to a decreased ET(A) receptor dominance. Other vasomotor responses were unaltered. In conclusion, this model demonstrates specific coronary microvascular alterations with regard to NO and ET-1 systems in the process of early atherosclerosis in DM. In particular, the altered ET-1 system correlated with hyperglycemia in atherogenic conditions, emphasizing the importance of this system in DM-associated CAD development.

Ca2+ regulatory mechanisms of exercise protection against coronary artery disease in metabolic syndrome and diabetes

Chronic exercise attenuates coronary artery disease (CAD) in humans largely independent of reductions in risk factors; thus major protective mechanisms of exercise are directly within the coronary vasculature. Further, tight control of diabetes, e.g., blood glucose, can be detrimental. Accordingly, knowledge of mechanisms by which exercise attenuates diabetic CAD could catalyze development of molecular therapies. Exercise attenuates CAD (atherosclerosis) and restenosis in miniature swine models, which enable precise control of exercise parameters (intensity, duration, and frequency) and characterization of the metabolic syndrome (MetS) and diabetic milieu. Intracellular Ca(2+) is a pivotal second messenger for coronary smooth muscle (CSM) excitation-contraction and excitation-transcription coupling that modulates CSM proliferation, migration, and calcification. CSM of diabetic dyslipidemic Yucatan swine have impaired Ca(2+) extrusion via the plasmalemma Ca(2+) ATPase (PMCA), downregulation of L-type voltage-gated Ca(2+) channels (VGCC), increased Ca(2+) sequestration by the sarcoplasmic reticulum (SR) Ca(2+) ATPase (SERCA), increased nuclear Ca(2+) localization, and greater activation of K channels by Ca(2+) release from the SR. Endurance exercise training prevents Ca(2+) transport changes with virtually no effect on the diabetic milieu (glucose, lipids). In MetS Ossabaw swine transient receptor potential canonical (TRPC) channels are upregulated and exercise training reverses expression and TRPC-mediated Ca(2+) influx with almost no change in the MetS milieu. Overall, exercise effects on Ca(2+) signaling modulate CSM phenotype. Future studies should 1) selectively target key Ca(2+) transporters to determine definitively their causal role in atherosclerosis and 2) combine mechanistic studies with clinical outcomes, e.g., reduction of myocardial infarction.

Endothelin-1 and diabetic complications: focus on the vasculature

Diabetes is not only an endocrine but also a vascular disease. Cardiovascular complications are the leading cause of morbidity and mortality associated with diabetes. Diabetes affects both large and small vessels and hence diabetic complications are broadly classified as microvascular (retinopathy, nephropathy and neuropathy) and macrovascular (heart disease, stroke and peripheral arterial disease) complications. Endothelial dysfunction, defined as an imbalance of endothelium-derived vasoconstrictor and vasodilator substances, is a common denominator in the pathogenesis and progression of both macro and microvascular complications. While the pathophysiology of diabetic complications is complex, endothelin-1 (ET-1), a potent vasoconstrictor with proliferative, profibrotic, and proinflammatory properties, may contribute to many facets of diabetic vascular disease. This review will focus on the effects of ET-1 on function and structure of microvessels (retina, skin and mesenteric arteries) and macrovessels (coronary and cerebral arteries) and also discuss the relative role(s) of endothelin A (ET(A)) and ET(B) receptors in mediating ET-1 actions.

Short-term exercise training prevents micro- and macrovascular disease following coronary stenting

The purpose of this study was to determine the effects of exercise on coronary blood flow and macrovascular atherosclerosis in response to stent deployment. Male Yucatan swine were placed on a control diet (C); on a high-fat/cholesterol diet (hypercholesterolemic; H); or on a high-fat/cholesterol diet and aerobically exercise trained (HX) starting after 36 wk on the diet. All pigs underwent coronary angiography and intravascular ultrasound (IVUS) guided placement of a bare metal stent in the circumflex coronary artery after 40 wk on diets and 3 wk later pigs underwent repeat angiography and IVUS and coronary blood flow (CBF) measurement. Average peak velocity (APV) was measured under basal conditions and in response to intracoronary application of the endothelium-independent vasodilator adenosine and the endothelium-dependent vasodilator bradykinin. There was a similar approximately 8-fold increase in total cholesterol in H and HX compared with control. Baseline CBF was increased above control and H in HX (P<0.05). At all doses adenosine-induced CBF was impaired in H, but preserved in HX. Similarly, bradykinin-induced CBF was impaired in H vs. control, yet was potentiated in HX. Microvessel density was decreased in H and preserved in HX vs. control. Native atheroma in HX was lower relative to H and control, while in-stent stenosis in HX was not different from H. Hyperlipidemia-induced microvascular dysfunction after stent deployment may be a result of reduction in microvessel density. This is the first report that short-term exercise training near the time of stenting prevents stent-induced microvascular dysfunction and attenuates native atheroma independent of changes in plasma cholesterol in this porcine model.

Altered mechanism of adenosine-induced coronary arteriolar dilation in early-stage metabolic syndrome

Onset of the combined metabolic syndrome (MetS) is a complex progressive process involving numerous cardiovascular risk factors. Although patients with established MetS exhibit reduced coronary flow reserve and individual components of the MetS reduce microvascular vasodilation, little is known concerning the impact of early-stage MetS on the mechanisms of coronary flow control. Therefore, we tested the hypothesis that coronary arteriolar dilation to adenosine is attenuated in early-stage MetS by reduced A2 receptor function and diminished K+ channel involvement. Pigs were fed control or high-fat/cholesterol diet for 9 weeks to induce early-stage MetS. Coronary atheroma was determined in vivo with intravascular ultrasound. In vivo coronary dilation was determined by intracoronary adenosine infusion. Further, apical coronary arterioles were isolated, cannulated and pressurized to 60 cmH2O for in vitro pharmacologic assessment of adenosine dilation. Coronary atheroma was not different between groups, indicating early-stage MetS. Coronary arteriolar dilation to adenosine (in vivo) and 2-chloroadenosine (2-CAD; in vitro) was similar between groups. In control arterioles, 2-CAD-mediated dilation was reduced only by selective A(2A) receptor inhibition, whereas only dual A(2A/2B) inhibition reduced this response in MetS arterioles. Arteriolar A(2B), but not A(2A), receptor protein expression was reduced by MetS. Blockade of voltage-dependent K+ (K(v)) channels reduced arteriolar sensitivity to 2-CAD in both groups, whereas ATP-sensitive K+ (K(ATP)) channel inhibition reduced sensitivity only in control arterioles. Our data indicate that the mechanisms mediating coronary arteriolar dilation to adenosine are altered in early-stage MetS prior to overt decrements in coronary vasodilator reserve.

The non-excitable smooth muscle: calcium signaling and phenotypic switching during vascular disease

Calcium (Ca(2+)) is a highly versatile second messenger that controls vascular smooth muscle cell (VSMC) contraction, proliferation, and migration. By means of Ca(2+) permeable channels, Ca(2+) pumps and channels conducting other ions such as potassium and chloride, VSMC keep intracellular Ca(2+) levels under tight control. In healthy quiescent contractile VSMC, two important components of the Ca(2+) signaling pathways that regulate VSMC contraction are the plasma membrane voltage-operated Ca(2+) channel of the high voltage-activated type (L-type) and the sarcoplasmic reticulum Ca(2+) release channel, Ryanodine Receptor (RyR). Injury to the vessel wall is accompanied by VSMC phenotype switch from a contractile quiescent to a proliferative motile phenotype (synthetic phenotype) and by alteration of many components of VSMC Ca(2+) signaling pathways. Specifically, this switch that culminates in a VSMC phenotype reminiscent of a non-excitable cell is characterized by loss of L-type channels expression and increased expression of the low voltage-activated (T-type) Ca(2+) channels and the canonical transient receptor potential (TRPC) channels. The expression levels of intracellular Ca(2+) release channels, pumps and Ca(2+)-activated proteins are also altered: the proliferative VSMC lose the RyR3 and the sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase isoform 2a pump and reciprocally regulate isoforms of the ca(2+)/calmodulin-dependent protein kinase II. This review focuses on the changes in expression of Ca(2+) signaling proteins associated with VSMC proliferation both in vitro and in vivo. The physiological implications of the altered expression of these Ca(2+) signaling molecules, their contribution to VSMC dysfunction during vascular disease and their potential as targets for drug therapy will be discussed.

Influence of sex, high-fat diet, and exercise training on potassium currents of swine coronary smooth muscle

Potassium channels in vascular smooth muscle (VSM) control vasodilation and are potential regulatory targets. This study evaluated effects of sex differences, exercise training (EX), and high-fat diet (HF) on K(+) currents (I(K)) of coronary VSM cells. Yucatan male and female swine were assigned to either sedentary confinement (SED), 16 wk of EX, 20 wk of HF, or 20 wk of HF with 16 wk of EX (HF-EX). VSM cells of normal-diet SED animals exhibited three components of I(K): 4-aminopyridine-sensitive I(K(KV)), TEA-sensitive I(K(BK)), and 4-aminopyridine + TEA-insensitive I(K). Females exhibited significantly higher basal I(K) than males in the same group. EX increased basal I(K) in males and females. HF reduced I(K) in males and females and nullified effects of EX. Endothelin-1 increased I(K) significantly in males but not in females. In the presence of endothelin-1, 1) I(K(KV)) was similar in SED males and females and EX increased I(K(KV)) to a greater extent in males than in females and 2) I(K(BK)) was greater in SED females than in males and EX increased I(K(BK)) to a greater extent in males, resulting in I(K(BK)) similar to EX females. Importantly, HF nullified effects of EX on I(K(KV)) and I(K(BK)). These data indicate that basal I(K) of SED female swine is inherently greater than that shown in SED males and that males require EX to achieve comparable levels of I(K). Importantly, HF reduced I(K) in males and females and nullified effects of EX, suggesting HF abrogates beneficial effects of EX on coronary smooth muscle.

Exercise training prevents Ca2+ dysregulation in coronary smooth muscle from diabetic dyslipidemic yucatan swine

Aerobic exercise training is known to have profound cardioprotective effects in disease, yet cellular mechanisms remain largely undefined. We tested the hypothesis that increased sarcoplasmic reticulum Ca(2+) buffering and increased voltage-gated Ca(2+) channel density underlie coronary smooth muscle intracellular Ca(2+) (Ca(2+)(i)) dysregulation in diabetic dyslipidemia and that exercise training would prevent these increases. Yucatan swine were maintained in 1) control, 2) alloxan-induced hyperglycemic, 3) high fat/cholesterol fed, 4) hyperglycemic plus high fat/cholesterol fed (diabetic dyslipidemic), and 5) diabetic dyslipidemic plus exercise-trained (treadmill running) conditions. After 20 wk, the heart was removed and smooth muscle cells isolated from the right coronary artery. We utilized fura-2 imaging of Ca(2+)(i) levels to separate the functional role of the sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) from the Na(+)-Ca(2+) exchanger and the plasmalemmal Ca(2+)-ATPase, and whole-cell patch clamp to examine voltage-gated Ca(2+) channel current density (i.e., Ca(2+) influx). Results indicated that diabetic dyslipidemia impaired plasmalemmal Ca(2+) efflux, increased basal Ca(2+)(i) levels, increased SERCA protein and sarcoplasmic reticulum Ca(2+)(i) buffering, and elicited an approximately 50% decrease in voltage-gated Ca(2+) channel current density. Exercise training concurrent with the diabetic dyslipidemic state restored plasmalemmal Ca(2+) efflux, SERCA protein, sarcoplasmic reticulum Ca(2+)(i) buffering, and voltage-gated Ca(2+) channel current density to control levels. Interestingly, basal Ca(2+)(i) levels were significantly lower in the exercise-trained group compared with control. Collectively, these results demonstrate a crucial role for exercise in the prevention of diabetic dyslipidemia-induced Ca(2+)(i) dysregulation.

Impaired endothelin-induced vasoconstriction in coronary arteries of Zucker obese rats is associated with uncoupling of [Ca2+]i signaling

Although insulin resistance (IR) is a major risk factor for coronary artery disease, little is known about the regulation of coronary vascular tone in IR by endothelin-1 (ET-1). We examined ET-1 and PGF(2alpha)-induced vasoconstriction in isolated small coronary arteries (SCAs; approximately 250 microM) of Zucker obese (ZO) rats and control Zucker lean (ZL) rats. ET-1 response was assessed in the absence and presence of endothelin type A (ET(A); BQ-123), type B (ET(B); BQ-788), or both receptor inhibitors. ZO arteries displayed reduced contraction to ET-1 compared with ZL arteries. In contrast, PGF(2alpha) elicited similar vasoconstriction in both groups. ET(A) inhibition diminished the ET-1 response in both groups. ET(B) inhibition alone or in combination with ET(A) blockade, however, restored the ET-1 response in ZO arteries to the level of ZL arteries. Similarly, inhibition of endothelial nitric oxide (NO) synthase with N(omega)-nitro-l-arginine methyl ester (l-NAME) enhanced the contraction to ET-1 and abolished the difference between ZO and ZL arteries. In vascular smooth muscle cells from ZO, ET-1-induced elevation of myoplasmic intracellular free calcium concentration ([Ca2+]i) (measured by fluo-4 AM fluorescence), and maximal contractions were diminished compared with ZL, both in the presence and absence of l-NAME. However, increases in [Ca2+]i elicited similar contractions of the vascular smooth muscle cells in both groups. Analysis of protein and total RNA from SCA of ZO and ZL revealed equal expression of ET-1 and the ET(A) and ET(B) receptors. Thus coronary arteries from ZO rats exhibit reduced ET-1-induced vasoconstriction resulting from increased ET(B)-mediated generation of NO and diminished elevation of myoplasmic [Ca2+]i.

Atorvastatin

Atorvastatin (Lipitor) is an HMG-CoA reductase inhibitor with well documented lipid-lowering effects. It has recently been evaluated for the primary prevention of major cardiovascular events in patients with type 2 diabetes mellitus without elevated serum low-density lipoprotein (LDL)-cholesterol levels. Atorvastatin 10mg daily for 4 years was effective at reducing the risk of a first major cardiovascular event, including stroke, in a large, placebo-controlled, multicentre trial in patients with type 2 diabetes and at least one other coronary heart disease (CHD) risk factor, but without markedly elevated LDL-cholesterol levels. In this trial, known as CARDS (the Collaborative AtoRvastatin Diabetes Study), atorvastatin had a similar tolerability profile to that of placebo. Thus, atorvastatin has a potential role in the primary prevention of cardiovascular events in diabetic patients at risk of CHD, irrespective of pre-treatment LDL-cholesterol levels.

Diabetic dyslipidemia and exercise affect coronary tone and differential regulation of conduit and microvessel K+ current

Spontaneous transient outward K(+) currents (STOCs) elicited by Ca(2+) sparks and steady-state K(+) currents modulate vascular reactivity, but effects of artery size, diabetic dyslipidemia, and exercise on these differentially regulated K(+) currents are unclear. We studied the conduit arteries and microvessels of male Yucatan swine assigned to one of three groups for 20 wk: control (C, n = 7), diabetic dyslipidemic (DD, n = 6), or treadmill-trained DD animals (DDX, n = 7). Circumflex artery blood flow velocity obtained with intracoronary Doppler and lumen diameters obtained by intravascular ultrasound enabled calculation of absolute coronary blood flow (CBF). Ca(2+) sparks were determined in pressurized microvessels, and perforated patch clamp assessed K(+) current in smooth muscle cells isolated from conduits and microvessels. Baseline CBF in DD was decreased versus C. In pressurized microvessels, Ca(2+) spark activity was significantly lower in DD versus C and DDX (P < 0.05 vs. DDX). STOCs were pronounced in microvessel (approximately 35 STOCs/min) in sharp contrast to conduit cells ( approximately 2 STOCs/min). STOCs were decreased by 86% in DD versus C and DDX in microvessels; in contrast, there was no difference in STOCs across groups in conduit cells. Steady-state K(+) current in microvessels was decreased in DD and DDX versus C; in contrast, steady-state K(+) current in conduit cells was decreased in DDX versus DD and C. We conclude that steady-state K(+) current and STOCs are differentially regulated in conduit versus microvessels in health and diabetic dyslipidemia. Exercise prevented diabetic dyslipidemia-induced decreases in baseline CBF, possibly via STOC-regulated basal microvascular tone.

Exercise improves impaired ventricular function and alterations of cardiac myofibrillar proteins in diabetic dyslipidemic pigs

Chronic diabetes is often associated with cardiomyopathy, which may result, in part, from defects in cardiac muscle proteins. We investigated whether a 20-wk porcine model of diabetic dyslipidemia (DD) would impair in vivo myocardial function and yield alterations in cardiac myofibrillar proteins and whether endurance exercise training would improve these changes. Myocardial function was depressed in anesthetized DD pigs (n = 12) compared with sedentary controls (C; n = 13) as evidenced by an approximately 30% decrease in left ventricular fractional shortening and an approximately 35% decrease in +dP/dt measured by noninvasive echocardiography and direct cardiac catheterization, respectively. This depression in myocardial function was improved with chronic exercise as treadmill-trained DD pigs (DDX) (n = 13) had significantly greater fractional shortening and +dP/dt than DD animals. Interestingly, the isoform expression pattern of the myofibrillar regulatory protein, cardiac troponin T (cTnT), was significantly shifted from cTnT1 toward cTnT2 and cTnT3 in DD pigs. Furthermore, this change in cTnT isoform expression pattern was prevented in DDX pigs. Finally, there was a decrease in baseline levels of cAMP-dependent protein kinase-induced phosphorylation of the myofibrillar proteins troponin I and myosin-binding protein-C in DD animals. Overall, these results indicate that 20 wk of DD lead to myocardial dysfunction coincident with significant alterations in myofibrillar proteins, both of which are prevented with endurance exercise training, implying that changes in myofibrillar proteins may contribute, at least in part, to cardiac dysfunction associated with diabetic cardiomyopathy.

Exercise prevents diabetes-induced impairment in superficial buffer barrier in porcine coronary smooth muscle

In healthy coronary smooth muscle cells, the superficial sarcoplasmic reticulum (SR) buffers rise in intracellular Ca2+ levels. In diabetic dyslipidemia, basal Ca2+ levels are increased, yet Ca2+ influx is decreased and SR Ca2+ uptake is increased. Exercise prevents diabetic dyslipidemia-induced increases in basal Ca2+ levels and decreases in Ca2+ influx. We tested the hypothesis that diabetic dyslipidemia impairs Ca2+ extrusion via a decrease in superficial SR and that exercise will prevent these losses. Male Yucatan swine were maintained in four treatment groups: control, hyperlipidemic, diabetic dyslipidemic, and diabetic dyslipidemic plus aerobically exercise trained. Intracellular Ca2+ levels were measured during depolarization-induced Ca2+ influx and caffeine-induced SR Ca2+ release. Na+/Ca2+ exchanger and plasmalemmal Ca2+-ATPase activity were assessed by inhibition with low extracellular Na+ and 5,6-carboxyeosin, respectively. Superficial SR was quantified using the internal membrane dye 3,3′-dihexyloxacarbocyanine iodide (DiOC6) and novel analysis techniques. We found that, in diabetic dyslipidemia, Ca2+ extrusion was impaired and superficial SR was decreased. Exercise prevented the diabetic dyslipidemia-induced decrease in superficial SR and restored plasmalemmal Ca2+ extrusion. On the basis of these results, we conclude exercise attenuates the diabetic dyslipidemia-induced impairment in intracellular Ca2+ regulation.

Altered functional coupling of coronary K+ channels in diabetic dyslipidemic pigs is prevented by exercise

Chronic hyperglycemia and hypercholesterolemia have been shown to alter ionic currents in vascular smooth muscle. We tested the hypothesis that the combined effect of hyperglycemia and hyperlipidemia (diabetic dyslipidemia) would increase the Ca2+-sensitive K+ (KCa) current as a compensatory response to an increase in intracellular Ca2+ concentration. We also hypothesized that exercise training would prevent this elevation in KCa current. Miniature Yucatan swine were randomly assigned to five groups: control, standard pig chow (C, n = 6); hyperlipidemic, high-fat pig chow (H, n = 5); diabetic, standard pig chow (D, n = 7); diabetic, high-fat pig chow ("diabetic dyslipidemic," DD, n = 12); and exercise-trained DD (DDX, n = 9). High-fat chow consisted of standard minipig chow supplemented with cholesterol (2%) and coconut oil. Increased coronary vasoconstriction assessed in vivo and in vitro in DD was prevented by exercise. Patch-clamp experiments performed on right coronary artery smooth muscle cells resulted in greater K+ current densities in the H, D, and DD groups vs. the DDX group between -10 and 40 mV. In fura 2-loaded cells, current activated by caffeine-induced Ca2+ release was greater in H, D, and DD compared with C and DDX (P < 0.05), whereas intracellular Ca2+ concentration was not different across groups. Finally, there were no differences in the KCa or Kv channel protein content between groups. These data indicate that hyperglycemia, hyperlipidemia, and diabetic dyslipidemia lead to elevated whole cell K+ current and increased functional coupling of KCa and Ca2+ release. Endurance exercise prevented increased coupling of Ca2+ release to KCa channel activation in diabetic dyslipidemia.