Katya B. Rubinow

Pharmacogenomics of psychiatric disorders

Pharmacogenomics, the utilization of genetic information to predict outcome of drug treatment (therapeutic and side-effects), holds great promise for clinical medicine. The pharmacotherapy of psychiatric disorders exhibits wide variability in therapeutic response with little scientific guidance for treatment on a patient-by-patient basis. The emerging field of pharmacogenomics holds great potential for refining and optimizing psychopharmacology. Key components for future development of the pharmacogenomics of psychiatric disorders include understanding the mechanism of drug action, identification of candidate genes and their variants, and well-conducted clinical trials. In this article, data from recent studies are examined with particular emphasis on methodological requirements and direction for future research.

The effects of sex and hormonal status on restraint-stress-induced working memory impairment

BackgroundRestraint stress has been shown to elicit numerous effects on hippocampal function and neuronal morphology, as well as to induce dendritic remodeling in the prefrontal cortex (PFC). However, the effects of acute restraint stress on PFC cognitive function have not been investigated, despite substantial evidence that the PFC malfunctions in many stress-related disorders.MethodsThe present study examined the effects of restraint stress on PFC function in both male rats and cycling female rats in either the proestrus (high estrogen) or estrus (low estrogen) phase of the estrus cycle. Animals were restrained for 60 or 120 minutes and then tested on spatial delayed alternation, a PFC-mediated task. Performance after stress was compared to performance on a different day under no-stress conditions, and analyzed using analysis of variance (ANOVA).ResultsSixty minutes of restraint impaired only females in proestrus, while 120 minutes of restraint produced significant impairments in all animals. Increases in task completion times did not affect performance.ConclusionThese results demonstrate an interaction between hormonal status and cognitive response to stress in female rats, with high estrogen levels being associated with amplified sensitivity to stress. This effect has been previously observed after administration of a pharmacological stressor (the benzodiazepine inverse agonist FG7142), and results from both studies may be relevant to the increased prevalence of stress-related disorders, such as major depressive disorder, in cycling women. Overall, the results show that restraint stress has important effects on the cognitive functions of the PFC, and that hormonal influences in the PFC are an important area for future research.

ACUTE TESTOSTERONE DEPRIVATION REDUCES INSULIN SENSITIVITY IN MEN

Objective  In men with prostate cancer, androgen deprivation reduces insulin sensitivity; however, the relative roles played by testosterone and estradiol are unknown. To investigate the respective effects of these hormones on insulin sensitivity in men, we employed a model of experimental hypogonadism with or without hormone replacement.

Reexamining metrics for glucose control.

THE HEMOGLOBIN A1C (HBA1C) ASSAY WAS FIRST USED more than 30 years ago as a marker of diabetes control. Despite its availability for 2 decades, HbA1c testing did not assume a central role in diabetes care until the publication of 2 major clinical trials. The Diabetes Control and Complications Trial (DCCT) and the UK Prospective Diabetes Study (UKPDS) demonstrated that HbA1c level strongly predicts risk of microvascular complications associated with type 1 and type 2 diabetes, respectively. Largely consequent to these findings, HbA1c level has become the primary basis for diabetes diagnosis, treatment decisions, and assessment of quality health care. As clinical application of HbA1c measurement expands, so does the need for caution in its interpretation and appreciation of its substantial limitations. The unreliability of HbA1c findings has been recognized in a number of clinical settings. Among the most frequently cited are hematologic conditions, including anemia, hemolysis, variable red blood cell life span, reticulocytosis, and hemoglobinopathies. A variety of less appreciated clinical factors can affect the concordance of HbA1c level with mean blood glucose (MBG) level. These include the use of certain medications (dapsone, erythropoietin), mechanical heart valves, and hypothyroidism. Differential glycation rates also can produce variability in HbA1c values, and rates of protein glycation appear to vary to a much greater extent across individuals than historically has been appreciated. When HbA1c values are compared systematically with MBG values generated by continued glucose monitoring, the range of corresponding MBG for an HbA1c of 8% spans 70 mg/dL; this variability increases even further at higher HbA1c values and may derive substantially from heterogeneity in glycation rates. In a pediatric population of patients with type 1 diabetes, roughly equivalent MBG values corresponded to an HbA1c level of 7.6% among “low glycators” and 9.6% among “high glycators.” These data derive from a study population that simply was divided into tertiles on the basis of differential glycation. Further, differential glycation appears not only a source of HbA1c measurement variability but possibly an independent predictor of diabetes-related microvascular complications. Cohen et al reported that the glycation gap—the difference between glycated fructosamine and glycated hemoglobin—is associated with risk of incident retinopathy in a diabetic population. Differential glycation may have a substantial hereditary basis. The hemoglobin glycation index also has been proposed as an independent predictor of microvascular complications, although this has been refuted on the basis of the strong correlation between HbA1c values and the hemoglobin glycation index. More recently, greater recognition has evolved of the effects of race on HbA1c level, with particular focus on the implications for new diagnosis of diabetes. For comparable MBG values, HbA1c values vary by 0.2% to 0.65% across racial backgrounds. These findings suggest that an HbA1c level of 6.5% may be too sensitive a threshold for diagnosis in some populations and an inadequate threshold in others. The DCCT did not address the possibility that risk of microvascular complications may be conferred at variant HbA1c values across race; it included only patients with type 1 diabetes, a racially homogeneous population. This racial bias was skewed further by the exclusion of study participants with an abnormal hemoglobin electrophoresis and calls into question the fundamental applicability of the DCCT findings to nonwhite patients. The UKPDS similarly lacked racial heterogeneity, as 81% of study participants were white, whereas only 10% were Asian and 8% African Caribbean. The continual identification of sources of variability in HbA1c level has generated interest in the use of alternative, integrative measures of MBG. Expanded use of either fructosamine or glycated albumin, for example, has been advocated for the diagnosis of diabetes and treatment monitoring. Fructosamine offers the advantage of gauging shorterterm glycemic control; however, fructosamine does not correlate strongly with fasting plasma glucose and is a rela-

Acyl-CoA synthetase 1 is induced by Gram-negative bacteria and lipopolysaccharide and is required for phospholipid turnover in stimulated macrophages.

Background: Acyl-CoA synthetase 1 (ACSL1) promotes inflammatory effects in macrophages, but its regulation and biological role remain largely unknown. Results: Multiple inflammatory pathways contribute to ACSL1 induction, and this induction allows for phospholipid turnover in activated macrophages. Conclusion: The regulation and function of ACSL1 differ substantially in macrophages and insulin target tissues. Significance: These findings indicate a novel role for ACSL1 in innate immunity. The enzyme acyl-CoA synthetase 1 (ACSL1) is induced by peroxisome proliferator-activated receptor α (PPARα) and PPARγ in insulin target tissues, such as skeletal muscle and adipose tissue, and plays an important role in β-oxidation in these tissues. In macrophages, however, ACSL1 mediates inflammatory effects without significant effects on β-oxidation. Thus, the function of ACSL1 varies in different tissues. We therefore investigated the signals and signal transduction pathways resulting in ACSL1 induction in macrophages as well as the consequences of ACSL1 deficiency for phospholipid turnover in LPS-activated macrophages. LPS, Gram-negative bacteria, IFN-γ, and TNFα all induce ACSL1 expression in macrophages, whereas PPAR agonists do not. LPS-induced ACSL1 expression is dependent on Toll-like receptor 4 (TLR4) and its adaptor protein TRIF (Toll-like receptor adaptor molecule 1) but does not require the MyD88 (myeloid differentiation primary response gene 88) arm of TLR4 signaling; nor does it require STAT1 (signal transducer and activator of transcription 1) for maximal induction. Furthermore, ACSL1 deletion attenuates phospholipid turnover in LPS-stimulated macrophages. Thus, the regulation and biological function of ACSL1 in macrophages differ markedly from that in insulin target tissues. These results suggest that ACSL1 may have an important role in the innate immune response. Further, these findings illustrate an interesting paradigm in which the same enzyme, ACSL1, confers distinct biological effects in different cell types, and these disparate functions are paralleled by differences in the pathways that regulate its expression.

Testosterone replacement in hypogonadal men alters the HDL proteome but not HDL cholesterol efflux capacity

The effects of androgens on cardiovascular disease (CVD) risk in men remain unclear. To better characterize the relationship between androgens and HDL, we investigated the effects of testosterone replacement on HDL protein composition and serum HDL-mediated cholesterol efflux in hypogonadal men. Twenty-three older hypogonadal men (ages 51–83, baseline testosterone < 280 ng/dl) were administered replacement testosterone therapy (1% transdermal gel) with or without the 5α-reductase inhibitor dutasteride. At baseline and after three months of treatment, we determined fasting lipid concentrations, HDL protein composition, and the cholesterol efflux capacity of serum HDL. Testosterone replacement did not affect HDL cholesterol (HDL-C) concentrations but conferred significant increases in HDL-associated paraoxonase 1 (PON1) and fibrinogen α chain (FGA) (P = 0.022 and P = 0.023, respectively) and a decrease in apolipoprotein A-IV (apoA-IV) (P = 0.016). Exogenous testosterone did not affect the cholesterol efflux capacity of serum HDL. No differences were observed between men who received testosterone alone and those who also received dutasteride. Testosterone replacement in older hypogonadal men alters the protein composition of HDL but does not significantly change serum HDL-mediated cholesterol efflux. These effects appear independent of testosterone conversion to dihydrotestosterone. Further research is needed to determine how changes in HDL protein content affect CVD risk in men.

Acute sex steroid withdrawal increases cholesterol efflux capacity and HDL-associated clusterin in men

Exogenous androgens can lower HDL-cholesterol (HDL-C) concentrations, yet men with low serum testosterone have elevated rates of cardiovascular disease (CVD). HDL function may better predict CVD risk than absolute HDL-C quantity. We evaluated the acute effects of medical castration in men on HDL-C, cholesterol efflux capacity and HDL protein composition. Twenty-one healthy men, ages 18-55, received the GnRH antagonist acyline and one of the following for 28days: Group 1: placebo, Group 2: transdermal testosterone gel and placebo, Group 3: transdermal testosterone gel and an aromatase inhibitor. Sex steroids, fasting lipids, and cholesterol efflux to apoB-depleted serum were measured in all subjects. The HDL proteome was assessed in Group 1 subjects only. In Group 1, serum testosterone concentrations were reduced by >95%, and HDL-C and cholesterol efflux capacity increased (p=0.02 and p=0.03 vs. baseline, respectively). HDL-associated clusterin increased significantly with sex steroid withdrawal (p=0.007 vs. baseline). Testosterone withdrawal in young, healthy men increases HDL-C and cholesterol efflux capacity. Moreover, sex steroid deprivation changes HDL protein composition. Further investigation of the effects of sex steroids on HDL composition and function may help resolve the apparently conflicting data regarding testosterone, HDL-C, and CVD risk.

The short-term and long-term effects of bariatric/metabolic surgery on subcutaneous adipose tissue inflammation in humans

CONTEXT The mechanisms mediating the short- and long-term improvements in glucose homeostasis following bariatric/metabolic surgery remain incompletely understood. OBJECTIVE To investigate whether a reduction in adipose tissue inflammation plays a role in the metabolic improvements seen after bariatric/metabolic surgery, both in the short-term and longer-term. DESIGN Fasting blood and subcutaneous abdominal adipose tissue were obtained before (n=14), at one month (n=9), and 6-12months (n=14) after bariatric/metabolic surgery from individuals with obesity who were not on insulin or anti-diabetes medication. Adipose tissue inflammation was assessed by a combination of whole-tissue gene expression and flow cytometry-based quantification of tissue leukocytes. RESULTS One month after surgery, body weight was reduced by 13.5±4.4kg (p<0.001), with improvements in glucose tolerance reflected by a decrease in area-under-the-curve (AUC) glucose in 3-h oral glucose tolerance tests (-105±98mmol/L * min; p=0.009) and enhanced pancreatic β-cell function (insulinogenic index: +0.8±0.9pmol/mmol; p=0.032), but no change in estimated insulin sensitivity (Matsuda insulin sensitivity index [ISI]; p=0.720). Furthermore, although biomarkers of systemic inflammation and pro-inflammatory gene expression in adipose tissue remained unchanged, the number of neutrophils increased in adipose tissue 15-20 fold (p<0.001), with less substantial increases in other leukocyte populations. By the 6-12month follow-up visit, body weight was reduced by 34.8±10.8kg (p<0.001) relative to baseline, and glucose tolerance was further improved (AUC glucose -276±229; p<0.001) along with estimated insulin sensitivity (Matsuda ISI: +4.6±3.2; p<0.001). In addition, improvements in systemic inflammation were reflected by reductions in circulating C-reactive protein (CRP; -2.0±5.3mg/dL; p=0.002), and increased serum adiponectin (+1358±1406pg/mL; p=0.003). However, leukocyte infiltration of adipose tissue remained elevated relative to baseline, with pro-inflammatory cytokine mRNA expression unchanged, while adiponectin mRNA expression trended downward (p=0.069). CONCLUSION Both the short- and longer-term metabolic improvements following bariatric/metabolic surgery occur without significant reductions in measures of adipose tissue inflammation, as assessed by measuring the expression of genes encoding key mediators of inflammation and by flow cytometric immunophenotyping and quantification of adipose tissue leukocytes.

Stable Intraprostatic Dihydrotestosterone in Healthy Medically Castrate Men Treated With Exogenous Testosterone

CONTEXT Concern exists that T replacement therapy (TRT) might increase the risk of prostate disease. There are limited data regarding the impact of TRT on prostate androgen concentrations. OBJECTIVE Determine the dose-dependent effects of exogenous T administration on intraprostatic androgen concentrations. DESIGN Twelve-week, double-blinded, randomized, placebo-controlled trial. SETTING Academic medical center. PARTICIPANTS Sixty-two healthy eugonadal men, aged 25-55 years. INTERVENTIONS Subjects were randomly assigned to receive injections of acyline, a GnRH antagonist (used to achieve medical castration), every 2 weeks plus transdermal T gel (1.25 g, 2.5 g, 5.0 g, 10 g, or 15 g daily), or placebo injections and transdermal gel for 12 weeks. MAIN OUTCOMES Serum T and dihydrotestosterone (DHT) were measured at baseline and every 2 weeks during treatment. Intraprostatic T and DHT concentrations were assessed from tissue obtained through ultrasound-guided prostate needle biopsies at week 12. Androgens were quantified by liquid chromatography-tandem mass spectrometry. RESULTS 51 men completed the study and were included in the analysis. There were no significant adverse events. Exogenous T resulted in a dose-dependent increase in serum T and DHT concentrations (190-770 and 60-180 ng/dL, respectively). Although intraprostatic T differed among dose groups (P = .01), intraprostatic DHT was comparable regardless of T dose (P = .11) and was 10- to 20-fold greater than intraprostatic T. CONCLUSIONS In healthy, medically castrate men receiving exogenous T, the total intraprostatic androgen concentration (predominantly DHT) remained stable across serum T concentrations within the physiological range. These findings further our knowledge of the relationship between serum and intraprostatic androgens and suggest that physiological serum T achieved by TRT is unlikely to alter the prostate hormonal milieu.

Hematopoietic androgen receptor deficiency promotes visceral fat deposition in male mice without impairing glucose homeostasis.

Androgen deficiency in men increases body fat, but the mechanisms by which testosterone suppresses fat deposition have not been elucidated fully. Adipose tissue macrophages express the androgen receptor (AR) and regulate adipose tissue remodeling. Thus, testosterone signaling in macrophages could alter the paracrine function of these cells and thereby contribute to the metabolic effects of androgens in men. A metabolic phenotyping study was performed to determine whether the loss of AR signaling in hematopoietic cells results in greater fat accumulation in male mice. C57BL/6J male mice (ages 12–14 weeks) underwent bone marrow transplant from either wild‐type (WT) or AR knockout (ARKO) donors (n = 11–13 per group). Mice were fed a high‐fat diet (60% fat) for 16 weeks. At baseline, 8 and 16 weeks, glucose and insulin tolerance tests were performed, and body composition was analyzed with fat‐water imaging by MRI. No differences in body weight were observed between mice transplanted with WT bone marrow [WT(WTbm)] or ARKO bone marrow [WT(ARKObm)] prior to initiation of the high‐fat diet. After 8 weeks of high‐fat feeding, WT(ARKObm) mice exhibited significantly more visceral and total fat mass than WT(WTbm) animals. Despite this, no differences between groups were observed in glucose tolerance, insulin sensitivity, or plasma concentrations of insulin, glucose, leptin, or cholesterol, although WT(ARKObm) mice had higher plasma levels of adiponectin. Resultant data indicate that AR signaling in hematopoietic cells influences body fat distribution in male mice, and the absence of hematopoietic AR plays a permissive role in visceral fat accumulation. These findings demonstrate a metabolic role for AR signaling in marrow‐derived cells and suggest a novel mechanism by which androgen deficiency in men might promote increased adiposity. The relative contributions of AR signaling in macrophages and other marrow‐derived cells require further investigation.