The interplay between bone and heart health as reflected in medication effects: A narrative review.

There is mounting evidence of an association between osteoporosis and cardiovascular disease that extends beyond shared risk factors for these conditions. In turn, the medications used to treat each of these conditions can have effects that impact the other organ system: medications used in heart disease have the potential to affect bone health, while osteoporosis medications may modify cardiovascular health. While data in this subject area are limited by the paucity of large randomized controlled trials with bone mineral density or fracture risk as primary outcomes, this review explores the data available that can provide some insight into these reciprocal effects of medications on bone and heart health. Data on bone health effects of the loop and thiazide diuretics, beta blockers, calcium channel blockers, statins, warfarin, sodium-glucose cotransporter 2 inhibitors, metformin, and medications impacting the renin-angiotensin-aldosterone system are examined; the cardiovascular effects of osteoporosis therapies and vitamin D are also discussed. Importantly, while most data in this realm are inconclusive, recognizing the parallels between cardiovascular and bone disorders and how this is reflected in medication effects might prompt the clinician to consider the indirect impact of drug regimens when making therapeutic choices for patients with osteoporosis and heart disease.

Discrepancy between DXA and CT-based assessment of spine bone mineral density.

PURPOSE: Adequate bone mineral density (BMD) is necessary for success in spine surgery. Dual-energy X-ray absorptiometry (DXA) is the gold standard in determining BMD but may give spuriously high values. Hounsfield units (HU) from computed tomography (CT) may provide a more accurate depiction of the focal BMD encountered during spine surgery. Our objective is to determine the discrepancy rate between DXA and CT BMD determinations and how often DXA overestimates BMD compared to CT. METHODS: We retrospectively reviewed 93 patients with both DXA and CT within 6 months. DXA lumbar spine and overall T scores were classified as osteoporotic (T Score ≤ - 2.5) or non-osteoporotic (T Score > -2.5). L1 vertebral body HU were classified as osteoporotic or non-osteoporotic using cutoff thresholds of either ≤ 135 HU or ≤ 110 HU. Corresponding DXA and HU classifications were compared to determine disagreement and overestimation rates. RESULTS: Using lumbar T scores, the CT vs DXA disagreement rate was 40-54% depending on the HU threshold. DXA overestimated BMD 97-100% of the time compared to CT. Using overall DXA T scores, the disagreement rate was 33-47% with DXA greater than CT 74-87% of the time. In the sub-cohort of 10 patients with very low HU (HU < 80), DXA overestimated BMD compared to CT in every instance. CONCLUSIONS: There is a large discrepancy between DXA and CT BMD determinations. DXA frequently overestimates regional BMD encountered during spine surgery compared with CT. While DXA remains the gold standard in determining BMD, CT may play an important role in defining the focal BMD pertinent to spine surgery.

Impaired fibrinolysis and risk for cardiovascular disease in the metabolic syndrome and type 2 diabetes.

Patients with the metabolic syndrome are insulin resistant and manifest a cluster of risk factors for cardiovascular disease. Impaired fibrinolysis and increased concentrations in blood of plasminogen activator inhibitor-1 (PAI-1) are related to insulin resistance and abdominal obesity and may contribute to the increased risk for cardiovascular disease in this group. Weight loss, metformin, and thiazolidinediones ameliorate insulin resistance and decrease concentrations of PAI-1. Thus, they may lower risk in patients with the metabolic syndrome.

A recombinant antibody increases cardiac contractility by mimicking phospholamban phosphorylation.

Many cardiovascular disease states end in progressive heart failure. Changes in intracellular calcium handling, including a reduced activity of the sarcoplasmic reticulum calcium pump (SERCA), contribute to this contractile dysfunction. As the regulatory protein phospholamban can inhibit the calcium pump, we evaluated it as a potential target to improve cardiac function. In this study, we describe a recombinant antibody-based protein (PLN-Ab) that binds to the cytoplasmic domain of phospholamban. Fluorescence resonance energy transfer (FRET) studies suggest that PLN-Ab mimics the effects of phospholamban phosphorylation. PLN-Ab accelerated the decay of the calcium transient when expressed in neonatal rat and adult mouse ventricular cardiac myocytes. In addition, direct injection of adenovirus encoding PLN-Ab into the diabetic mouse heart enhanced contractility when measured in vivo by echocardiography and in ex vivo Langendorff perfused hearts. The PLN-Ab provides a novel therapeutic approach to improving contractility through in vivo expression of an antibody inside cardiac myocytes.

Diabetes and the accompanying hyperglycemia impairs cardiomyocyte calcium cycling through increased nuclear O-GlcNAcylation.

Diabetic cardiomyopathy is characterized by impaired cardiac contractility leading to poor myocardial performance. We investigated the role that the hexosamine pathway, and especially altered nuclear O-Glc-NAcylation, plays in the development of diabetic cardiomyopathy. Incubating neonatal rat cardiomyocytes in high glucose (25 mM) resulted in prolonged calcium transients when compared with myocytes incubated in normal glucose (5.5 mM), which is consistent with delayed myocardial relaxation. High glucose-treated myocytes also exhibited reduced sarcoendoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) mRNA and protein expression, decreased SERCA2a promoter activity, and increased O-GlcNAcylation of nuclear proteins compared with myocytes treated with normal glucose. Exposure of myocytes to 8 mM glucosamine or an adenovirus expressing O-GlcNAc-transferase (OGT) resulted in prolonged calcium transient decays and significantly reduced SERCA2a protein levels, whereas treatment with an adenovirus encoding O-GlcNAcase (GCA) resulted in improved calcium transients and SERCA2a protein levels in myocytes exposed to high glucose. Effects of elevated glucose or altered O-GlcNAcylation were also observed on essential transcription factors involved in cardiomyocyte function. High glucose-treated myocytes (with or without OGT adenovirus) exhibited increased levels of O-GlcNAcylated specificity protein 1 compared with control myocytes, whereas infecting high glucose-treated myocytes with GCA adenovirus reduced the degree of specificity protein 1 Glc-NAcylation. Treatment of myocytes with 25 mM glucose, 8 mM glucosamine, or OGT adenovirus also significantly reduced levels of myocytes enhancer factor-2A protein compared with control myocytes, whereas infection with GCA adenovirus resulted in improved myocytes enhancer factor-2 expression. Our results suggest that the hexosamine pathway, and O-GlcNAcylation in particular, is important in impaired cardiac myocyte function and the development of diabetic cardiomyopathy.

Overexpression of the sarcoplasmic reticulum Ca(2+)-ATPase improves myocardial contractility in diabetic cardiomyopathy.

Diabetic cardiomyopathy is characterized by reduced cardiac contractility due to direct changes in heart muscle function independent of vascular disease. An important contributor to contractile dysfunction in the diabetic state is an impaired sarcoplasmic reticulum (SR) function, leading to disturbed intracellular calcium handling. We investigated whether overexpression of the SR calcium pump (SERCA2a) in transgenic mice could reduce the impact of diabetes on the development of cardiomyopathy. Diabetes was induced by streptozotocin injection (200 mg/kg), and left ventricular (LV) function was analyzed in isolated hearts 3 weeks later. In diabetic hearts systolic LV pressure was decreased by 15% and maximum speed of relaxation (-dP/dt) by 34%. Functional changes were also assessed in isolated papillary muscles. Active force was reduced by 61% and maximum speed of relaxation by 65% in the diabetic state. The contractile impairment was accompanied by a 30% decrease in SERCA2a protein in diabetic mice. We investigated whether increased SERCA2a expression in transgenic SERCA2a-overexpressing mice could compensate for the diabetes-induced decrease in cardiac function. Under normal conditions, SERCA2a overexpressors show improved contractile performance relative to wild-type (WT) mice (-dP/dt: 3,169 vs. 2,559 mmHg/s, respectively). Measurement of LV function in hearts from diabetic SERCA2a mice revealed systolic and diastolic functions that were similar to WT control mice and markedly improved relative to diabetic WT mice (-dP/dt: 2,534 vs. 1,690 mmHg/s in diabetic SERCA2a vs. diabetic WT mice, respectively). Similarly, the contractile behavior of isolated papillary muscles from diabetic SERCA2a mice was not different from that of control mice. SERCA2a protein expression was higher (60%) in diabetic SERCA2a mice than WT diabetic mice. These results indicate that overexpression of SERCA2a can protect diabetic hearts from severe contractile dysfunction, presumably by improving the calcium sequestration of the SR.

Diabetic Cardiomyopathy.

Diabetes mellitus is a major risk factor for the development of congestive heart failure (CHF). Diabetic cardiomyopathy has been acknowledged as a distinct disease entity that is an additional risk for diabetic patients to develop CHF, especially when they are affected by hypertension or epicardial coronary artery disease. Moreover, diabetic cardiomyopathy has been documented to lead to CHF even in the absence of other risk factors. As the combination of hypertension and diabetes has shown to be particularly detrimental, aggressive blood pressure control with a goal of less than 130/85 mm Hg is of critical importance. The first choice for pharmacologic treatment is angiotensin-converting enzyme inhibitors. Double- or triple-drug therapy is frequently required for good control. The increased risk of epicardial coronary artery disease in patients with diabetes warrants stringent treatment of dyslipidemia. If dilated cardiomyopathy with low ejection fraction is present, therapy with angiotensin-converting enzyme inhibitors, digoxin, diuretics, beta-blockers, and spironolactone (for patients with New York Heart Association class III to IV functional status) is indicated. If cardiac dysfunction consists predominantly of impaired diastolic function, heart rate control with a beta-blocker or a calcium antagonist is of particular importance. Control of blood glucose should be achieved, with hemoglobin A(1c) levels of less than 7%. Hyperinsulinemia should be avoided when possible; therefore, insulin-sensitizing agents are preferred over insulin-secretion-enhancing agents. Symptoms of CHF and acutely decompensated CHF should be treated no differently than nondiabetic patients. Care for patients with diabetes always includes lifestyle changes consisting of smoking cessation, decreasing obesity, regular exercise, and a heart-healthy diabetic diet.