Hypertension and insulin disorders

Comparative risk of new-onset diabetes mellitus for antihypertensive drugs in elderly: A Bayesian network meta-analysis

There is no study to compare different class of antihypertensive drugs on new-onset diabetes mellitus (NOD) in elderly. We aimed to investigate the risk of antihypertensive drugs on NOD in elderly patients. The databases were retrieved in an orderly manner from the dates of their establishment to October, 2018, including Medline, Embase, Clinical Trials, and the Cochrane Database, to collect randomized controlled trials (RCTs) of different antihypertensive drugs in elderly patients (age > 60 years). Then, a network meta-analysis was conducted using R and Stata 12.0 softwares. A total of 14 RCTs involving 74 042 patients were included. The relative risk of NOD mellitus associated with six classes of antihypertensive drugs was analyzed, including placebo, angiotensin-converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), calcium channel blockers (CCBs), diuretics, and β blockers. Patients with ACEIs or ARBs appeared to have significantly reduced risk of NOD compare with placebo: ACEIs (OR = 0.49, 95% CrI 0.28-0.85), ARBs (OR = 0.37, 95% CrI 0.26-0.52), while CCBs, diuretics, and β blockers appeared to have not significantly reduced risk of NOD mellitus compare with placebo: CCBs (OR = 1.10, 95% CrI 0.85-1.60), diuretics (OR = 1.40, 95% CrI 0.92-2.50), β blockers (OR = 1.40, 95% CrI 0.93-2.10). The SUCRA of placebo, ACEIs, ARBs, CCBs, diuretics, and β blockers was, respectively, 65.3%, 69.3%, 92.3%, 44.1%, 12.1%, and 16.5%. According to the evidence, ARBs have an advantage over the other treatments in reducing the risk of NOD in elderly patients.

Prevalence and risk factors of type 2 diabetes in insomnia sufferers: a study on 1311 individuals referred for sleep examinations

BACKGROUND

Several studies have investigated the particular relationship between insomnia and type 2 diabetes. However, few studies have investigated the prevalence and risk factors for type 2 diabetes in insomnia sufferers. The aim of this study was to examine the prevalence and risk factors of type 2 diabetes in a large sample of insomnia sufferers.

METHODS

Data from 1311 insomnia sufferers recruited from the research database of the Erasme Hospital sleep laboratory were analyzed. Only individuals with a diagnosis of type 2 diabetes according to the diagnostic criteria of the American Diabetes Association at admission were included in the diabetes group. Logistic regression analyses were conducted to examine clinical and demographic risk factors of type 2 diabetes in insomnia sufferers.

RESULTS

The prevalence of type 2 diabetes in insomnia sufferers is 21.13%. Multivariate logistic regression analysis revealed that significant risk factors of type 2 diabetes in insomnia sufferers were as follows: being male, Z-drugs use, high blood pressure, hypertriglyceridemia, alcohol consumption of ≥4 units/day, BMI ≥25 & <30 kg/m², BMI ≥30 kg/m², age ≥50 years, C-reactive protein ≥4.5 mg/L, a sleep duration of <6.5 h, apnea-hypopnea index ≥15/hour, periodic limb movements index ≥26/hour, and severe complaints of early morning awakening.

CONCLUSION

Type 2 diabetes is a common pathology in insomnia sufferers. In this subpopulation, most of the risk factors for type 2 diabetes are reversible, which justifies better prevention and management of this pathology in order to avoid its negative consequences.

Resting energy expenditure and systolic blood pressure relationships in women across 4.5 years

Recent studies have reported a strong association between blood pressure (BP) and resting energy expenditure (REE). However, it is not known whether this relationship persists over time. Therefore, the authors examined the temporal relationship between REE and systolic BP. In addition, the impact of sympathetic tone and anthropometric variables on this relationship was examined. All testing was performed on healthy, overweight African American and European American women aged 25 to 45 years over 4.5 years in the University of Alabama at Birmingham General Clinical Research Center. Repeated-measures mixed-models revealed REE as a significant determinant of systolic BP (β=0.0155, P<.0001), independent of catecholamines, leg fat, visceral fat, fat-free mass, fat mass, height, relative skeletal muscle index, and resting heart rate. Observations that REE is predictive of systolic BP across 4.5 years support previous findings that REE may potentially mediate resting BP, independent of anthropometric variables and a marker for sympathetic tone.

Influence of resting energy expenditure on blood pressure is independent of body mass and a marker of sympathetic tone

Two recent examinations reported a strong association between blood pressure (BP) and resting energy expenditure (REE), independent of body mass and body composition. Both reports postulate that neurohumoral processes that contribute to variation in REE may partly mediate the body mass effect on BP. Therefore, we examined the relationship of REE and BP in 108 asymptomatic women (a) to confirm previous findings in a novel population and (b) to examine the impact of a marker of sympathetic tone on this relationship, as this was indicated as a potentially salient intermediary in previous reports. All testing was performed during a 4-day admission to the General Clinical Research Center. Resting energy expenditure was measured by indirect calorimetry, body composition was determined by dual-energy x-ray absorptiometry, and 24-hour fractionated urinary norepinephrine was determined by high-performance liquid chromatography. Multiple linear regression revealed REE as a significant predictor of systolic BP (β = 0.30, P = .04), independent of race (β = 0. 28, P = .01), age (β = -0.02, P = .80), height (β = -0.38, P = .08), fat mass (β = 0.22, P = .20), fat-free mass (β = 0.08, P = .65), and 24-hour fractionated urinary norepinephrine (β = 0.06, P = .57); and the same model using diastolic BP as the dependent variable approached significance (β = 0.24, P = .09). This study affirms previous findings that REE may be a potential mediator in resting BP, independent of many well-cited factors and, additionally, a marker of sympathetic tone.

Menopause, the metabolic syndrome, and mind-body therapies

Cardiovascular disease risk rises sharply with menopause, likely due to the coincident increase in insulin resistance and related atherogenic changes that together comprise the metabolic or insulin resistance syndrome, a cluster of metabolic and hemodynamic abnormalities strongly implicated in the pathogenesis and progression of cardiovascular disease. A growing body of research suggests that traditional mind-body practices such as yoga, tai chi, and qigong may offer safe and cost-effective strategies for reducing insulin resistance syndrome-related risk factors for cardiovascular disease in older populations, including postmenopausal women. Current evidence suggests that these practices may reduce insulin resistance and related physiological risk factors for cardiovascular disease; improve mood, well-being, and sleep; decrease sympathetic activation; and enhance cardiovagal function. However, additional rigorous studies are needed to confirm existing findings and to examine long-term effects on cardiovascular health.

Effect of valsartan addition to amlodipine on insulin sensitivity in overweight-obese hypertensive patients

OBJECTIVE

The aim of the study was to evaluate the effect of valsartan/amlodipine combination on insulin sensitivity in overweight-obese hypertensive patients.

METHODS

After a 4-week placebo period, 58 overweight-obese (BMI >or=25 kg/m(2)) patients, with mild to moderate essential hypertension (DBP >95 and <110 mmHg, SBP >140 mmHg) were treated with amlodipine 5 mg od or valsartan 160 mg od or amlodipine 5 mg plus valsartan 160 mg od for 8 weeks according to a randomized, open-label, blinded end-point, cross-over study. At the end of the placebo period and each treatment period, blood pressure (BP) and insulin sensitivity (IS) (by euglycemic hyperinsulinemic clamp technique) were evaluated. IS was expressed as the amount of glucose infused during the last 30 min (glucose infusion rate, GIR) in mg/kg/min.

RESULTS

Valsartan/amlodipine combination produced a significantly greater decrease in SBP/DBP values (-22.3/16.7 mmHg, p<0.001 vs baseline) than valsartan (-15.2/11.7 mmHg, p<0.01 vs baseline) and amlodipine monotherapy (-16.1/12.6 mmHg, p<0.01 vs baseline). Both valsartan and amlodipine provided a significant increase in GIR (+1.24 mg/kg/min, p=0.036 vs baseline and +1.02 mg/kg/min, p=0.047, respectively), but such an increase was significantly greater with their combination (+1.82 mg/kg/min, p<0.01 vs baseline). These greater changes in IS were not related to BP changes.

CONCLUSION

Valsartan/amlodipine combination improved IS more than respective monotherapy beyond affording greater BP reductions. This strengthens the rationale to use valsartan/amlodipine combination in the treatment of overweight-obese hypertensives.

Metabolic syndrome: treatment of hypertensive patients

Metabolic syndrome (MetSyndr), a constellation of abnormalities [obesity, glucose intolerance, insulin resistance (IR), dyslipidemia (low HDL-cholesterol, high LDL-cholesterol and triglycerides (TG)], and elevated blood pressure (BP)], increases the risk of cardiovascular (CV) disease and premature death. From 10% to 30% of the adult population in industrialized countries has MetSyndr, which effectively predicts the development of type 2 diabetes mellitus (T2D) and CV disease. Because of the complex etiology of MetSyndr, a multi-targeted, integrated therapeutic approach is required to simultaneously treat high BP, obesity, lipid disorders and T2D (if present), to fully protect CV, cerebrovascular and renal systems. If lifestyle modification (weight control, diet, exercise, smoking cessation, moderation of alcohol intake) is ineffective, pharmaco-theraphy should be added to treat simultaneously the lipid- and non-lipid CV risk factors. Patients with HTN and MetSyndr should be started on angiotensin-converting enzyme (ACE) inhibitors, unless contraindicated. The ACE inhibitors and angiotensin receptor blockers (ARBs) reduce the odds of developing new onset T2D and also decrease albuminuria. The ACE inhibitors provide cardioprotective and renoprotective benefits beyond their effect on BP; they also improve IR. The ARBs are renoprotective in addition to being cardioprotective. Long-acting calcium channel blockers are also recommended in hypertensive patients with MetSyndr; these drugs also improve IR. Thiazides (at low doses) and selected ss-blockers can be given to patients with HTN and MetSyndr. Celiprolol in combination with diuretics has a favorable effect on glucose tolerance and IR in patients with HTN and MetSyndr, and spironolactone added to ACE inhibitor or ARB therapy provides additional reno- and CV protective benefits in patients with diabetic nephropathy. Carvedilol, a ss-blocker with vasodilating properties, added to ACE inhibitor or ARB therapy, is effective in preventing worsening of microalbuminuria in patients with HTN and MetSyndr; it also improves IR and glycemic control. Most patients eventually require two or more antihypertensive drugs to reach BP goal. It is recommended that therapy in patients whose BP is more than 20/10 mm Hg above target at diagnosis be initiated with a combination of antihypertensive drugs, administered either as individual drugs or as fixed-dose formulations. Treatment with fixed-dose combinations, such as irbesartan + hydrochlorothiazide provides good BP control in more than two-thirds of hypertensive patients with MetSyndr. Lipid and BP targets are reached in a high percent of patients with HTN and CV disease treated with a combination of amlodipine + atorvastatin. In conclusion, hypertensive patients with the MetSyndr be treated aggressively for each component of the syndrome to provide CV, cerebrovascular and renal protection.

20-Hydroxyeicosatetraenoic acid is not associated with circulating insulin in lean to overweight humans

Hypertension is often associated with insulin resistance or hyperinsulinemia. Metabolism of arachidonic acid by cytochrome P450 to the vasoconstrictor 20-HETE is thought to be involved in the pathogenesis of hypertension, but the relationship of 20-HETE with insulin resistance is not clearly understood. Obesity is a major determinant of insulin resistance, and we have previously demonstrated a positive relationship between BMI and 20-HETE in untreated hypertensive and normotensive individuals. The present analysis sought to determine if this relationship was related to insulin levels or insulin resistance (HOMA). We analysed 24h urinary excretion of 20-HETE, serum insulin levels and insulin resistance in 66 lean to overweight untreated hypertensive and normotensive individuals. There was a significant positive association between 20-HETE and BMI (p<0.001), and serum insulin and BMI (p=0.003). There were no associations between 20-HETE excretion and either serum insulin or insulin resistance, before or after adjustment for age, gender, BMI and BP, or when hypertensive and normotensive individuals were considered separately. The results of the present study suggest that the observed positive association between urinary 20-HETE excretion and BMI may not be related to circulating insulin levels or insulin resistance.

A Positive Association between Leptin and Blood Pressure of Normal Range in Japanese Men

The results of previous studies on the relationship between leptin and blood pressure are discordant. We investigated to what extent the serum leptin level was related to blood pressure independent of the degree of insulin resistance. The subjects were 1916 men aged 34-69 years whose mean body mass index (BMI) was 23.0 kg/m2. Blood pressure was regressed by leptin concentrations with adjustments for age, BMI, insulin resistance, triglyceride, high density lipoprotein cholesterol, low density lipoprotein cholesterol, physical activity, drinking habits and smoking status. Leptin was associated with diastolic blood pressure (DBP) (standardized beta: 0.092, p = 0.003), but not with systolic blood pressure (SBP) (standardized beta: 0.035, p = 0.25), although insulin resistance was positively associated with both SBP and DBP (standardized beta: 0.175 for SBP, p < 0.001 and 0.114 for DBP, p < 0.001) among all subjects. After subjects were divided into those with normal blood pressure (SBP <130 mmHg and DBP <85 mmHg) and those with higher blood pressure, leptin was positively and significantly associated with DBP (standardized beta: 0.106, p = 0.012) independent of the degree of insulin resistance, but not with SBP (standardized beta: 0.064, p = 0.13) among subjects in the normal blood pressure range. Among the subjects with higher blood pressure, however, neither the association of leptin with SBP nor that of leptin with DBP was statistically significant. These findings suggest that leptin may maintain and increase arterial tone, resulting in the elevation of DBP only within normal blood pressure range. It is also likely that leptin is a physiological mediator--or at least a marker--of some degree of DBP elevation in obesity.

Metallothionein alleviates cardiac contractile dysfunction induced by insulin resistance: role of Akt phosphorylation, PTB1B, PPARgamma and c-Jun

AIMS/HYPOTHESIS

Insulin resistance is concomitant with metabolic syndrome, oxidative stress and cardiac contractile dysfunction. However, the causal relationship between oxidative stress and cardiac dysfunction is unknown. This study was designed to determine the impact of overexpression of the cardiac antioxidant metallothionein on cardiac dysfunction induced by insulin resistance in mice.

METHODS

Whole-body insulin resistance was generated in wild-type FVB and metallothionein transgenic mice by feeding them with sucrose for 12 weeks. Contractile and intracellular Ca(2+) properties were evaluated in ventricular myocytes using an IonOptix system. The contractile indices analysed included: peak shortening (PS), time to 90% PS (TPS(90)), time to 90% relengthening (TR(90)), half-width duration, maximal velocity of shortening (+dL/dt) and relengthening (-dL/dt), fura-fluorescence intensity change (DeltaFFI) and decay rate (tau).

RESULTS

The sucrose-fed mice displayed glucose intolerance, enhanced oxidative stress, hyperinsulinaemia, hypertriglyceridaemia and normal body weight. Compared with myocytes in starch-fed mice, those from sucrose-fed mice exhibited depressed PS, +dL/dt, -dL/dt, prolonged TR(90) and decay rate, and reduced DeltaFFI associated with normal TPS(90) and half-width duration. Western blot analysis revealed enhanced basal, but blunted insulin (15 mU/g)-stimulated Akt phosphorylation. It also showed elevated expression of insulin receptor beta, insulin receptor tyrosine phosphorylation, peroxisome proliferator-activated receptor gamma, protein tyrosine phosphatase 1B and phosphorylation of the transcription factor c-Jun, associated with a reduced fold increase of insulin-stimulated insulin receptor tyrosine phosphorylation in sucrose-fed mice. All western blot findings may be attenuated or ablated by metallothionein.

CONCLUSIONS/INTERPRETATION

These data indicate that oxidative stress may play an important role in cardiac contractile dysfunction associated with glucose intolerance and possibly related to alteration in insulin signalling at the receptor and post-receptor levels.

Comparison of the effects of valsartan and felodipine on plasma leptin and insulin sensitivity in hypertensive obese patients

Aim of this study was to compare the effect of valsartan and felodipine on blood pressure (BP), plasma leptin (L), insulin sensitivity and plasma norepinephrine (NE) in obese hypertensive patients. Ninty-six obese patients (body mass index [BMI] > or = 30 kg/m2) with mild to moderate essential hypertension (diastolic blood pressure [DBP] > 90 and < 110 mmHg, as evaluated with an appropriately sized cuff) aged 31-60 years, were randomized to a valsartan (80 mg/day for 16 weeks; n = 48) or felodipine (5 mg/day for 16 weeks; n = 48) treatment group after a 2-week wash-out period. After the first 4 weeks of treatment there was a titration with dose-doubling in non responder patients (DBP > 90 mmHg). At the end of the placebo period and of active treatment period, BP and BMI were evaluated and a venous sample was drawn at the same hour in the morning to evaluate plasma L and NE. Insulin resistance index (HOMA-IR) was calculated. No dietary advice was prescribed. Both valsartan and felodipine significantly decreased BP values (-19.3/15 mmHg and -18.9/13.6 mmHg, respectively p < 0.001 vs. placebo), with no difference between treatments. However, felodipine increased plasma NE (+124 pg/ml, +38.2%, p < 0.05 vs. placebo and < 0.01 vs. valsartan) and had no effect on L, body weight and HOMA-IR index, while valsartan did not modify NE and produced a significant reduction in L (-3.7 ng/ml, -10.1%, p < 0.05 vs. placebo), BMI (-1.7 kg/m2, -4.7%, p < 0.01 vs. placebo) and HOMA-IR index (-1.6, -20%, p < 0.05 vs. placebo). These results suggest that in hypertensive obese subjects, treatment with valsartan might offer an advantage over treatment with felodipine, since valsartan may help to improve obesity-related disorders in addition to lowering BP.

Circadian rhythm of glucose uptake in cultures of skeletal muscle cells and adipocytes in Wistar-Kyoto, Wistar, Goto-Kakizaki, and spontaneously hypertensive rats

Hypertension and noninsulin-dependent diabetes mellitus are usually associated with marked glucose intolerance. Hypertensive and even nonhypertensive diabetic individuals display disturbances of the normal circadian blood pressure rhythm. However, little is known about circadian changes of the glucose uptake in muscle and fat cells, the major glucose utilizing tissues. Therefore, we investigated circadian rhythms of glucose uptake in primary muscle and fat cell cultures of hypertensive and type II diabetic rats and their respective control strains. 2-Deoxy-D-(1-3H)glucose uptake was measured over 48 h after synchronization of cells by means of medium change with and without addition of insulin, phloretine, and/or staurosporine. The circadian changes of glucose uptake were assessed by fitting cosine curves to the uptake values. Insulin stimulation of deoxyglucose uptake was only present in control animals, not in hypertensive and diabetic rats. Deoxyglucose uptake displayed a circadian rhythm in control animals, and was markedly disturbed in hypertensive and diabetic animals. Blocking of glucose transporters by phloretine abolished the circadian pattern of deoxyglucose uptake indicating a role of glucose transporters in its generation. Inhibition of kinases by staurosporine inhibited the insulin-stimulated deoxyglucose uptake, but did not dampen the circadian rhythmicity of basal deoxyglucose uptake. The generation of the circadian rhythm of glucose uptake in muscle and fat cell cultures is therefore probably insulin independent and independent of protein kinases. In summary, our results show for the first time: (a) a circadian rhythm of deoxyglucose uptake in glucose utilizing muscle and fat cells in vitro, (b) a disruption of this rhythm in cells of hypertensive and diabetic rats.

Association Between Blood Pressure and Resting Energy Expenditure Independent of Body Size

Obesity is an important risk factor for hypertension; however, the pathway through which it raises blood pressure (BP) is poorly understood. Body size is also the primary determinant of energy expenditure, and we therefore examined the joint relationship of energy expenditure and body size to blood pressure. Resting energy expenditure (REE) was measured using respiratory gas exchange in population-based samples of 997 Nigerians and 452 African Americans. In a third sample of 118 individuals, nonresting energy expenditure (ie, physical activity) was measured in addition to REE. The univariate correlation between REE and BP ranged from 0.10 to 0.22 in the 3 samples (P<0.001). In multivariate models, adiposity, whether defined by body mass, fat mass, or leptin, was no longer associated with BP, while REE remained highly significant (P<0.001). The REE-BP association also persisted after adjustment for physical activity measured with doubly labeled water. The odds ratio for hypertension among persons in the highest quartile versus the lowest quartile of REE, after adjustment for body size, was 1.7. This relationship was not the result of hypertension among the obese, because it did not vary across the range of BMI and was the same in lean Nigerians as in obese Americans. These data suggest that metabolic processes represented by REE may mediate the effect of body size on BP. The interrelationship of REE with sympathetic tone, transmembrane ion exchange, or other metabolic processes that determine energy costs at rest could provide physiological explanations for this observation.

Contrasting metabolic effects of antihypertensive agents

Hypertension often coexists with hyperlipidemia, insulin resistance, and glucose intolerance, a comorbidity known as metabolic syndrome X. Different antihypertensives have mixed effects on these associated abnormalities. We compared three antihypertensives in the spontaneously hypertensive obese rat model of syndrome X. Moxonidine (4 mg/kg), an imidazoline and alpha2-adrenergic agonist, alpha-methyldopa (200 mg/kg), an alpha2-adrenergic agonist, or the vasodilator hydralazine (10 mg/kg) was given orally for 15 d. All three agents lowered blood pressure equally. Moxonidine significantly reduced fasting plasma insulin, glucagon, cholesterol, triglycerides, and free fatty acids (FFA) compared with untreated controls. In contrast, syndrome X markers were not affected by alpha-methyldopa treatment, and hydralazine reduced only glucagon and FFA. Relative to untreated controls, moxonidine improved glucose tolerance as shown by reduced glucose area under the curve (AUC) (13.6 +/- 2.4 versus 42.5 +/- 9.9 g x min/dl). Insulin AUC was increased (7.4 +/- 0.9 versus 3.9 +/- 1.8 microg x min/ml) as was the plasma C-peptide response to the glucose load. In contrast, alpha-methyldopa and hydralazine worsened glucose tolerance (68 +/- 26 and 110 +/- 21 g x min/ml, respectively) and significantly reduced insulin AUC (2.5 +/- 0.8 and -2.3 +/- 1.0 microg x min/ml, respectively) compared with controls. Moxonidine reduced but alpha-methyldopa and hydralazine elevated glucagon levels after the glucose load. Contrary to the "hemodynamic hypothesis" for the metabolic actions of antihypertensives, which predicts roughly equal benefits, only moxonidine had a positive impact on comorbidities. This unique action suggests a role for direct stimulation of imidazoline receptors.

Peroxisome proliferator-activated receptor γ C161T polymorphisms and survival of Japanese patients with immunoglobulin A nephropathy

Peroxisome proliferator-activated receptor gamma (PPAR gamma) plays an important role in lipid metabolism, insulin sensitivity, atherogenesis, and immune regulation. A genetic polymorphism (C161T) at exon 6 of PPAR gamma gene (PPARG) was reported to be associated with the onset of coronary artery disease. However, there has been no report of an association with renal disease. Genomic DNAs were isolated from 225 Japanese patients with histologically confirmed immunoglobulin A nephropathy (IgAN). The PPARG C161T genotype was determined by polymerase chain reaction-restriction fragment length polymorphism. The association of the polymorphism with renal prognosis in IgAN patients was analyzed using the Kaplan-Meier method and Cox proportional hazard regression model. The PPARG polymorphism was not associated with the renal survival rate. However, when patients were stratified into those either with or without hypertension at the time of diagnosis, the renal survival of the CT/TT genotypes was significantly better in those without hypertension than those with the CC genotype. We report that the PPARG C161T polymorphism is associated with the survival of IgAN patients without hypertension. The T allele of the polymorphism might have a protective effect on the progression of IgAN.

Insulin resistance induces hyperleptinemia, cardiac contractile dysfunction but not cardiac leptin resistance in ventricular myocytes

Insulin resistance is a metabolic syndrome commonly seen in obesity. Leptin, the obese gene product, plays a role in the regulation of cardiac function. Elevated leptin levels have been demonstrated under insulin-resistant states such as obesity and hypertension, although their role in cardiac dysfunction is unknown. This study was designed to determine the impact of prediabetic insulin resistance on leptin levels and leptin-induced cardiac contractile response. Whole-body insulin resistance was generated with a 10-week dietary sucrose feeding. Contractile and intracellular Ca(2+) properties were evaluated in ventricular myocytes using an IonOptix system. The contractile indices analyzed included peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR(90)), maximal velocity of shortening/relengthening (+/-dL/dt), fura-fluorescence intensity change (deltaFFI) and decay rate (tau). Sucrose-fed rats displayed significantly elevated body weight and plasma leptin levels, depressed PS, +/-dL/dt, shortened TPS, prolonged TR(90) and tau, as well as reduced deltaFFI compared to the starch-fed control group. Leptin (1-1000 nM) elicited a concentration-dependent depression of PS and deltaFFI in myocytes from both starch and sucrose groups. Leptin-induced contractile depression was abolished by the nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyle ester, elevation of the extracellular Ca(2+) concentration, the Janus activated kinase 2 inhibitor AG-490 or the mitogen activated protein kinase inhibitor SB203580 in myocytes from both sucrose and starch groups. Moreover, AG-490 and SB203580 unmasked a positive response of PS in myocytes from both groups. These data indicate that insulin resistance directly induces hyperleptinemia and cardiac contractile dysfunction, without affecting leptin-mediated cardiac contractile function at the myocyte level.