Robert Fakheri

Ambient temperature as a contributor to kidney stone formation: implications of global warming

Nephrolithiasis is a common disease across the world that is becoming more prevalent. Although the underlying cause for most stones is not known, a body of literature suggests a role of heat and climate as significant risk factors for lithogenesis. Recently, estimates from computer models predicted up to a 10% increase in the prevalence rate in the next half century secondary to the effects of global warming, with a coinciding 25% increase in health-care expenditures. Our aim here is to critically review the medical literature relating stones to ambient temperature. We have categorized the body of evidence by methodology, consisting of comparisons between geographic regions, comparisons over time, and comparisons between people in specialized environments. Although most studies are confounded by other factors like sunlight exposure and regional variation in diet that share some contribution, it appears that heat does play a role in pathogenesis in certain populations. Notably, the role of heat is much greater in men than in women. We also hypothesize that the role of a significant human migration (from rural areas to warmer, urban locales beginning in the last century and projected to continue) may have a greater impact than global warming on the observed worldwide increasing prevalence rate of nephrolithiasis. At this time the limited data available cannot substantiate this proposed mechanism but further studies to investigate this effect are warranted.

Diabetes mellitus as a compelling indication for use of renin angiotensin system blockers: systematic review and meta-analysis of randomized trials

Objective To evaluate the outcomes with use of renin angiotensin system (RAS) blockers compared with other antihypertensive agents in people with diabetes. Design Meta-analysis. Data sources and study selection PubMed, Embase, and the Cochrane central register of controlled trials databases for randomized trials of RAS blockers versus other antihypertensive agents in people with diabetes mellitus. Outcomes were death, cardiovascular death, myocardial infarction, angina, stroke, heart failure, revascularization, and end stage renal disease. Results The search yielded 19 randomized controlled trials that enrolled 25 414 participants with diabetes for a total of 95 910 patient years of follow-up. When compared with other antihypertensive agents, RAS blockers were associated with a similar risk of death (relative risk 0.99, 95% confidence interval 0.93 to 1.05), cardiovascular death (1.02, 0.83 to 1.24), myocardial infarction (0.87, 0.64 to 1.18), angina pectoris (0.80, 0.58 to 1.11), stroke (1.04, 0.92 to 1.17), heart failure (0.90, 0.76 to 1.07), and revascularization (0.97, 0.77 to 1.22). There was also no difference in the hard renal outcome of end stage renal disease (0.99, 0.78 to 1.28) (power of 94% to show a 23% reduction in end stage renal disease). Conclusions In people with diabetes, RAS blockers are not superior to other antihypertensive drug classes such as thiazides, calcium channel blockers, and β blockers at reducing the risk of hard cardiovascular and renal endpoints. These findings support the recommendations of the guidelines of the European Society of Cardiology/European Society of Hypertension and eighth Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure to also use other antihypertensive agents in people with diabetes but without kidney disease.

Angiotensin-Converting Enzyme Inhibitors or Angiotensin Receptor Blockers in Patients Without Heart Failure? Insights From 254,301 Patients From Randomized Trials

OBJECTIVES To compare the efficacy and safety of angiotensin-converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) in patients without heart failure. PATIENTS AND METHODS Meta-analysis of randomized trials identified using PubMed, Embase, and Cochrane Central Register of Controlled Trials searches from January 1, 1980, through April 13, 2015, of ACEis and ARBs compared with placebo or active controls and corroborated with head-to-head trials of ARBs vs ACEis. Outcomes were all-cause mortality, cardiovascular death, myocardial infarction (MI), angina, stroke, heart failure, revascularization, and new-onset diabetes. RESULTS Our search yielded 106 randomized trials that enrolled 254,301 patients. Compared with placebo, ACEis but not ARBs reduced the outcomes of all-cause mortality (ACEis vs placebo: relative risk [RR], 0.89; 95% CI, 0.80-1.00; ARBs vs placebo: RR, 1.01; 95% CI, 0.96-1.06; Pinteraction=.04), cardiovascular death (RR, 0.83; 95% CI, 0.70-0.99 and RR, 1.02; 95% CI, 0.92-1.14; Pinteraction=.05), and MI (RR, 0.83; 95% CI, 0.78-0.90 and RR, 0.93; 95% CI, 0.85-1.03; Pinteraction=.06). The meta-regression analysis revealed that the difference between ACEis and ARBs compared with placebo was due to a higher placebo event rate in the ACEis trials (most of these trials were conducted a decade earlier than the ARB trials) for the outcome of all-cause mortality (P=.001), cardiovascular death (P<.001), and MI (P=.02). Sensitivity analyses restricted to trials published after 2000 revealed similar outcomes with ACEis vs placebo and ARBs vs placebo (Pinteraction>.05). Head-to-head comparison trials of ARBs vs ACEis exhibited no difference in outcomes except for a lower risk of drug withdrawal due to adverse effects with ARBs (RR, 0.72; 95% CI, 0.65-0.81). CONCLUSION In patients without heart failure, evidence from placebo-controlled trials (restricted to trials after 2000), active controlled trials, and head-to-head randomized trials all suggest ARBs to be as efficacious and safe as ACEis, with the added advantage of better tolerability.

27-Hydroxycholesterol, does it exist? On the nomenclature and stereochemistry of 26-hydroxylated sterols.

Significant ambiguity exists in the scientific community with regard to the nomenclature of 26-hydroxylated oxysterols. Oxysterols constitute an important class of compounds that have biological roles in the regulation of cholesterol synthesis and as endogenous selective estrogen receptor modulators (SERMs). The ambiguity is attributable to deviations from clearly stated IUPAC rules and is likely to increase as more biologically active oxysterols are identified. This review provides a uniform approach to the naming of 26-hydroxylated sterols for those of current interest and for those on the horizon such as oxysterols of lanosterol that retain the unsaturation at C-24 and C-25 such as (E)-26-hydroxylanosterol. Using this molecule as a starting point, this review hopes to establish a common language to keep all investigators on the same page.

Renin angiotensin system inhibitors for patients with stable coronary artery disease without heart failure: systematic review and meta-analysis of randomized trials

Objective To critically evaluate the efficacy of renin angiotensin system inhibitors (RASi) in patients with coronary artery disease without heart failure, compared with active controls or placebo. Design Meta-analysis of randomized trials. Data sources PubMed, EMBASE, and CENTRAL databases until 1 May 2016. Eligibility criteria for selecting studies Randomized trials of RASi versus placebo or active controls in patients with stable coronary artery disease without heart failure (defined as left ventricular ejection fraction ≥40% or without clinical heart failure). Each trial had to enroll at least 100 patients with coronary artery disease without heart failure, with at least one year’s follow-up. Studies were excluded if they were redacted or compared use of angiotensin converting enzyme inhibitors with angiotensin receptor blockers. Outcomes were death, cardiovascular death, myocardial infarction, angina, stroke, heart failure, revascularization, incident diabetes, and drug withdrawal due to adverse effects. Results 24 trials with 198 275 patient years of follow-up were included. RASi reduced the risk of all cause mortality (rate ratio 0.84, 95% confidence interval 0.72 to 0.98), cardiovascular mortality (0.74, 0.59 to 0.94), myocardial infarction (0.82, 0.76 to 0.88), stroke (0.79, 0.70 to 0.89), angina, heart failure, and revascularization when compared with placebo but not when compared with active controls (all cause mortality, 1.05, 0.94 to 1.17; Pinteraction=0.006; cardiovascular mortality, 1.08, 0.93 to 1.25, Pinteraction<0.001; myocardial infarction, 0.99, 0.87 to 1.12, Pinteraction=0.01; stroke, 1.10, 0.93 to 1.31; Pinteraction=0.002). Bayesian meta-regression analysis showed that the effect of RASi when compared with placebo on all cause mortality and cardiovascular mortality was dependent on the control event rate, such that RASi was only beneficial in trials with high control event rates (>14.10 deaths and >7.65 cardiovascular deaths per 1000 patient years) but not in those with low control event rates. Conclusions In patients with stable coronary artery disease without heart failure, RASi reduced cardiovascular events and death only when compared with placebo but not when compared with active controls. Even among placebo controlled trials in this study, the benefit of RASi was mainly seen in trials with higher control event rates but not in those with lower control event rates. Evidence does not support a preferred status of RASi over other active controls.

Autoregulation of cholesterol synthesis: Physiologic and pathophysiologic consequences

Autoregulation of cholesterol synthesis focuses on the 19 metabolic steps from lanosterol to cholesterol. Although synchronization of their rates of synthesis in all tissues was the paradigm, a known exception occurs in the ovary where a local increase in a sterol intermediate, FF-MAS (follicular fluid meiosis activating sterol), activates meiosis during oocyte maturation. Mutations in the genes that govern synchronization cause an increase in sterol intermediates that follow an alternate, oxysterol, pathway of metabolism. Experimental models in animals imply that oxysterol metabolites are determinants of the dysmorphism that occurs during fetal development in these genetic diseases. These few examples may portend a much broader role for sterol intermediates and their novel oxysterol metabolites in physiologic and pathophysiologic processes.

Formula for Fresh Frozen Plasma Dosing for Warfarin Reversal

To the Editor: I applaud Drs Rashidi and Tahhan for their excellent work to derive a facile formula for calculating the change in the international normalized ratio (INR) by each unit of fresh frozen plasma (FFP), reported in the March 2013 issue of Mayo Clinic Proceedings. However, calculating the units of FFP needed to reach a goal INR with this formula is still quite cumbersome. Using the formula provided by the authors of DeltaINR after 1 FFP1⁄4 0.57 x PreINR 0.72, where DeltaINR 1⁄4 PreINR PostINR, it is not a simple task to derive a facile formula for calculating the units of FFP needed. The only solution provided by the authors is an iterative approach until the goal INR is reached. However, the problem can be simplified greatly if one accepts that there are 2 goal INRs that are clinically relevant: (1) a goal INR of less than 1.5 for practically total reversal because further FFP will have nil or minimal effect and (2) a goal INR of 2 to 3 for partial reversal in which bleeding risk is reduced but the INR remains in a therapeutic range. Although some clinical indications, like metallic heart valves, normally require INR goals of 2.5 to 3.5, in the context of major bleeding, INR goals of 2 to 3 are likely adequate for a short time until the bleeding is resolved. Thus, with these 2 INR goals, one can tabulate the units of

RENIN ANGIOTENSIN SYSTEM INHIBITORS IN PATIENTS WITH CORONARY ARTERY DISEASE AND PRESERVED LEFT VENTRICULAR FUNCTION

Background: Renin angiotensin system inhibitors (RASi) are recommended (Class I LoE A ) for patients with coronary artery disease (CAD) without heart failure. However, more recent trials with improved background therapy (and lower event rates) failed to show a benefit of RASi over active controls or

The relentless crumbling of the renin-angiotensin system (RAS)-blockade halo.

In 1999 a thorough review article in the New England Journal of Medicine stated that “ Patients with diabetes mellitus may represent a special sub-group for whom calcium antagonist therapy increases the risks of cardiovascular complications (1).” This dictum was met with unanimous approval by the medical community since at that time it was clear beyond any doubt that diabetes was the sole domain of angiotensin converting enzyme (ACE) inhibitors. In fact, in what they called a “consensus approach,” a rather distinguished group of nephrologists and endocrinologists concluded that “ in patients with diabetes… the preferred initial therapy is an ACE-inhibitor, with the dose titrated upward to the moderate or high dose range, as tolerated (2).” So powerful was the marketing machine of Big Pharma at that time that rather solid evidence of benefits of calcium channel blockers (CCB) in diabetes (3), showing that CCB based therapy reduced cardiovascular morbidity and mortality about twice as much in diabetic than in non-diabetic hypertensive patients ( Table 1 ) was completely ignored. The statement of Mancia et al . (4) pertaining to the diabetic subpopulation of the INSIGHT study “ that nifedipine could be considered as first-line therapy for hypertensive diabetics ,” was met with disbelief in the US and considered an aberration.