Ramesh Saeedi

Metabolic actions of metformin in the heart can occur by AMPK-independent mechanisms

The metabolic actions of the antidiabetic agent metformin reportedly occur via the activation of the AMP-activated protein kinase (AMPK) in the heart and other tissues in the presence or absence of changes in cellular energy status. In this study, we tested the hypothesis that metformin has AMPK-independent effects on metabolism in heart muscle. Fatty acid oxidation and glucose utilization (glycolysis and glucose uptake) were measured in isolated working hearts from halothane-anesthetized male Sprague-Dawley rats and in cultured heart-derived H9c2 cells in the absence or in the presence of metformin (2 mM). Fatty acid oxidation and glucose utilization were significantly altered by metformin in hearts and H9c2 cells. AMPK activity was not measurably altered by metformin in either model system, and no impairment of energetic state was observed in the intact hearts. Furthermore, the inhibition of AMPK by 6-[4-(2-piperidin-1-yl-ethoxy)-phenyl]-3-pyridin-4-yl-pyyrazolo[1,5-a] pyrimidine (Compound C), a well-recognized pharmacological inhibitor of AMPK, or the overexpression of a dominant-negative form of AMPK failed to prevent the metabolic actions of metformin in H9c2 cells. The exposure of H9c2 cells to inhibitors of p38 mitogen-activated protein kinase (p38 MAPK) or protein kinase C (PKC) partially or completely abrogated metformin-induced alterations in metabolism in these cells, respectively. Thus the metabolic actions of metformin in the heart muscle can occur independent of changes in AMPK activity and may be mediated by p38 MAPK- and PKC-dependent mechanisms.

A review on lecithin:cholesterol acyltransferase deficiency.

Lecithin cholesterol acyl transferase (LCAT) is a plasma enzyme which esterifies cholesterol, and plays a key role in the metabolism of high-density lipoprotein cholesterol (HDL-C). Genetic disorders of LCAT are associated with lipoprotein abnormalities including low levels of HDL-C and presence of lipoprotein X, and clinical features mainly corneal opacities, changes in erythrocyte morphology and renal failure. Recombinant LCAT is being developed for the treatment of patients with LCAT deficiency.

Risk stratification of patients with familial hypercholesterolemia in a multi-ethnic cohort

BackgroundHeterozygous Familial hypercholesterolemia (FH) is a common autosomal dominant disorder resulting in in very high blood cholesterol levels and premature cardiovascular disease (CVD). However, there is a wide variation in the occurrence of CVD in these patients. The aim of this study is to determine risk factors that are responsible for the variability of CVD events in FH patients.MethodsThis is a retrospective analysis of a large multiethnic cohort of patients with definite FH attending the Healthy Heart Prevention Clinic in Vancouver, Canada. Cox proportional hazard regression analysis was used to assess the association of the risk factors to the hard cardiovascular outcomes.Results409 patients were identified as having “definite” FH, according to the Dutch Lipid Clinic Network Criteria (DLCNC), with 111 (27%) having evidence of CVD. Male sex, family history of premature CVD, diabetes mellitus, low high density lipoprotein cholesterol (HDL-C) and high lipoprotein (a) (Lp (a)) were significant, independent risk factors for CVD. In men, family history, diabetes and low levels of HDL-C were significant risk factors while in women smoking, diabetes mellitus and high Lp (a) were significant risk factors for CVD. There were no significant differences in risk factors between ethnicities.ConclusionIn conclusion, men and women differ in the impact of the risk factors on the presence of CVD with family history of CVD and low HDL-C being a significant factor in men while smoking and increased Lp (a) were significant factors in women. Diabetes was a significant factor in both men and women.

Gender and post-ischemic recovery of hypertrophied rat hearts.

BackgroundGender influences the cardiac response to prolonged increases in workload, with differences at structural, functional, and molecular levels. However, it is unknown if post-ischemic function or metabolism of female hypertrophied hearts differ from male hypertrophied hearts. Thus, we tested the hypothesis that gender influences post-ischemic function of pressure-overload hypertrophied hearts and determined if the effect of gender on post-ischemic outcome could be explained by differences in metabolism, especially the catabolic fate of glucose.MethodsFunction and metabolism of isolated working hearts from sham-operated and aortic-constricted male and female Sprague-Dawley rats before and after 20 min of no-flow ischemia (N = 17 to 27 per group) were compared. Parallel series of hearts were perfused with Krebs-Henseleit solution containing 5.5 mM [5-3H/U-14C]-glucose, 1.2 mM [1-14C]-palmitate, 0.5 mM [U-14C]-lactate, and 100 mU/L insulin to measure glycolysis and glucose oxidation in one series and oxidation of palmitate and lactate in the second. Statistical analysis was performed using two-way analysis of variance. The sequential rejective Bonferroni procedure was used to correct for multiple comparisons and tests.ResultsFemale gender negatively influenced post-ischemic function of non-hypertrophied hearts, but did not significantly influence function of hypertrophied hearts after ischemia such that mass-corrected hypertrophied heart function did not differ between genders. Before ischemia, glycolysis was accelerated in hypertrophied hearts, but to a greater extent in males, and did not differ between male and female non-hypertrophied hearts. Glycolysis fell in all groups after ischemia, except in non-hypertrophied female hearts, with the reduction in glycolysis after ischemia being greatest in males. Post-ischemic glycolytic rates were, therefore, similarly accelerated in hypertrophied male and female hearts and higher in female than male non-hypertrophied hearts. Glucose oxidation was lower in female than male hearts and was unaffected by hypertrophy or ischemia. Consequently, non-oxidative catabolism of glucose after ischemia was lowest in male non-hypertrophied hearts and comparably elevated in hypertrophied hearts of both sexes. These differences in non-oxidative glucose catabolism were inversely related to post-ischemic functional recovery.ConclusionGender does not significantly influence post-ischemic function of hypertrophied hearts, even though female sex is detrimental to post-ischemic function in non-hypertrophied hearts. Differences in glucose catabolism may contribute to hypertrophy-induced and gender-related differences in post-ischemic function.

AMP-activated protein kinase influences metabolic remodeling in H9c2 cells hypertrophied by arginine vasopressin

Substrate use switches from fatty acids toward glucose in pressure overload-induced cardiac hypertrophy with an acceleration of glycolysis being characteristic. The activation of AMP-activated protein kinase (AMPK) observed in hypertrophied hearts provides one potential mechanism for the acceleration of glycolysis. Here, we directly tested the hypothesis that AMPK causes the acceleration of glycolysis in hypertrophied heart muscle cells. The H9c2 cell line, derived from the embryonic rat heart, was treated with arginine vasopressin (AVP; 1 microM) to induce a cellular model of hypertrophy. Rates of glycolysis and oxidation of glucose and palmitate were measured in nonhypertrophied and hypertrophied H9c2 cells, and the effects of inhibition of AMPK were determined. AMPK activity was inhibited by 6-[4-(2-piperidin-1- yl-ethoxy)-phenyl]-3-pyridin-4-yl-pyrrazolo-[1,5-a]pyrimidine (compound C) or by adenovirus-mediated transfer of dominant negative AMPK. Compared with nonhypertrophied cells, glycolysis was accelerated and palmitate oxidation was reduced with no significant alteration in glucose oxidation in hypertrophied cells, a metabolic profile similar to that of intact hypertrophied hearts. Inhibition of AMPK resulted in the partial reduction of glycolysis in AVP-treated hypertrophied H9c2 cells. Acute exposure of H9c2 cells to AVP also activated AMPK and accelerated glycolysis. These elevated rates of glycolysis were not altered by AMPK inhibition but were blocked by agents that interfere with Ca(2+) signaling, including extracellular EGTA, dantrolene, and 2-aminoethoxydiphenyl borate. We conclude that the acceleration of glycolysis in AVP-treated hypertrophied heart muscle cells is partially dependent on AMPK, whereas the acute glycolytic effects of AVP are AMPK independent and at least partially Ca(2+) dependent.

Marked effects of extreme levels of lipoprotein(a) on estimation of low-density lipoprotein cholesterol

BACKGROUND Low-density lipoprotein cholesterol (LDL-C) is usually calculated using the Friedewald equation. However, this calculation method does not account for the cholesterol associated with lipoprotein(a) [Lp(a)]. Using the Dahlen equation, Li et al. have shown a strong positive correlation between serum Lp(a) levels and overestimation of LDL-C levels. OBJECTIVE To determine how the extreme levels of Lp(a) influence the LDL-C calculation. METHODS We performed a retrospective chart review of the lipid profile and Lp(a) of 223 patients (men and women). LDL-C was calculated using the Friedewald equation. Lp(a) concentrations were measured by an ELISA. Other serum lipids were measured enzymatically by standard methodology. Corrected LDL-C was calculated using the Dahlen equation. RESULTS We found that this overestimation is very significant in individuals with extreme levels of Lp(a) (mean overestimation of 40% at Lp(a) >1200mg/L). CONCLUSIONS Calculated LDL-C is markedly overestimated in patients with extreme levels of Lp(a).

Ankle brachial index screening for occult vascular disease is not useful in HIV-positive patients.

Metabolic complications common to the HIV-positive population may increase the risk for cardiovascular disease. Asymptomatic peripheral arterial disease (PAD) is associated with increased cardiovascular risk. The ankle-brachial pressure index (ABI) is a screening tool commonly used for the detection of asymptomatic PAD. The prevalence of asymptomatic PAD based on ABI in HIV-positive patients is unknown. This study was cross-sectional in design and assessed PAD by measuring the systolic ABI as determined by a handheld 8-MHz Doppler probe with the patient at rest in a supine position. A brief medical history including pertinent risk factors was obtained. One hundred and sixty-seven HIV-positive patients were evaluated (97.6% male; mean age 52.0 years; 31.2% current smokers, 29.4% former smokers, 26.3% diabetes mellitus). Asymptomatic PAD (ABI < or = 0.9) was found in four patients (2.4%, 95% CI: 0.3-4.5%). Smoking was a significant predictor of PAD. Patients with a positive test for PAD had at least two major risk factors for the disease including smoking, a history of disease in another vascular bed, dyslipidemia, diabetes, and hypertension. All patients with a positive test for PAD had a high risk (>20%) for cardiovascular disease according to the Framingham risk score. Three of the four patients with positive tests had previously diagnosed vascular disease (CAD, stroke). Three patients presenting with PAD were evaluated and all had a positive ABI. The prevalence of PAD compared to previous studies on PAD in HIV was low and identified only those patients with high cardiovascular risk based on other features. ABI was not useful in detecting occult vascular disease in HIV-positive patients and offers no additional information to that derived from cardiovascular risk stratification.

Dramatic lowering of very high Lp(a) in response to niacin

We describe a patient with markedly elevated lipoprotein(a) (Lp(a)) without any other lipid abnormalities. After a myocardial infarction, she was treated with combination of extended-release niacin and statin. An 88% reduction in Lp(a) was observed during 5 years of treatment, which is much better response than usually reported.

Lipoprotein (a), an independent cardiovascular risk marker

Epidemiological and genetic studies have identified elevated levels of lipoprotein (a) ((Lp(a)) as a causal and independent risk factor for cardiovascular diseases (CVD). The Lp(a)-induced increased risk of CVD may be mediated by both its proatherogenic and prothrombotic mechanisms. Several guidelines recommend screening of Lp(a) level; however, there are few treatment options for the management of patients with elevated Lp(a). Several new medications for Lp(a) are under development. PCSK9 inhibitors, apolipoprotein (a)-antisense, and apolipoprotein(B-100)-antisense mipomersen have shown promising results. Lp(a) reduction will continue to be an active area of investigation.

Lamivudine, Entecavir, or Tenofovir Treatment of Hepatitis B Infection: Effects on Calcium, Phosphate, FGF23 and Indicators of Bone Metabolism.

BACKGROUND AND AIM The combination of Sofosbuvir (SOF) and Ledipasvir (LDV) has been lead to considerable enhancement of treatment of hepatitis C virus (HCV) genotype 1 infection. A meta-analysis of the currently available studies was undertaken with the aim to evaluate the antiviral efficacy of SOF/LDV therapy for 12 or 24 weeks with or without Ribavirin (RBV) in patients with HCV genotype 1 infection. MATERIAL AND METHODS In this meta-analysis, we searched databases including PubMed, Scopus, Science Direct and Web of Science using appropriate keywords. All papers which evaluated the efficacy of combination therapy of SOF/LDV with or without RBV for 12 or 24 weeks among patients with HCV genotype 1 infection were included. RESULTS The 20 published articles were assessed for eligibility and finally 10 articles pooling 2248 participants were included in this meta-analysis. Pooled SVR12 for four SOF/LDV regimens were 95% (95%CI = 93%-97%) for 12 weeks of treatment with SOF/LDV, 97% (95%CI = 95%-98%) for 24 weeks of treatment with SOF/LDV, 96% (95%CI = 94%-97%) for 12 weeks of treatment with SOF/ LDV/RBV and 98% (95%CI = 97%-99%) for 24 weeks of treatment with SOF/LDV/RBV. Only in treatment regimen of SOF/LDV for 12 weeks, cirrhosis had a significant effect on the SVR12 (OR = 0.21, 95%CI = 0.07-0.66). Furthermore, NS5A resistance-associated substitutions at baseline were associated with decrease in the rate of SVR (OR = 0.31, 95%CI = 0.2-0.5). CONCLUSIONS The Interferon-free regimen of SOF/LDV for 12 or 24 weeks with or without RBV is highly effective for treatment of patients with HCV genotype 1 infection.BACKGROUND Patients with chronic hepatitis B virus (HBV) are often treated with nucleoside/nucleotide antiviral agents and metabolic bone toxicity is a possible concern. OBJECTIVE To determine the relationships between fibroblast growth factor 23 (FGF23), a phosphaturic hormone, bone mineral density (BMD), and bone biochemical abnormalities in these patients. MATERIAL AND METHODS This is a cross-sectional observational study comparing HBV-infected subjects treated for at least one year with tenofovir (TDF), lamuvidine (LVD), entacavir (ETV), or not treated (CON). Patients with abnormalities in either calcium (Ca), phosphate (PO4), intact parathyroid hormone (iPTH) or FGF23 were further evaluated with BMD by DXA. RESULTS No difference in liver enzymes or renal function seen among groups, but hypophosphatemia was seen in all groups with the highest incidence with TDF-treatment (14%). FGF 23 levels were found to be elevated in 11.1% of TDF patients, 2.77% amongst controls. No elevations were found in the LVD or ETV groups. Among a subset of subjects (FGF23, PO4, and/or Ca abnormalities) who underwent further evaluation, 67% had insufficient 25-OH vitamin D, and 30% had elevated 24 h urinary Ca or PO4 excretion. No patients with FGF23 abnormalities had urine abnormalities. 40% had low DXA Z-score (<-2) at spine or hip but there was no difference between control and antiviral treatment groups and the mean FRAX score was 2.33% for major osteoporotic fractures and 0.29% for hip fracture. CONCLUSION Abnormalities in bone metabolism, particularly involving vitamin D insufficiency, in HBV-treated subjects were observed with a small increased likelihood in TDF treated patients.