Genetic variants in the epithelial sodium channel associate with oedema in type 2 diabetic patients receiving the peroxisome proliferator-activated receptor gamma agonist farglitazar

Single Nucleotide Polymorphisms Associated with Metformin and Sulphonylureas' Glycaemic Response among South African Adults with Type 2 Diabetes Mellitus

Aims: To examine the association of polymorphisms belonging to SLC22A1, SP1, PRPF31, NBEA, SCNN1B, CPA6 and CAPN10 genes with glycaemic response to metformin and sulphonylureas (SU) combination therapy among South African adults with diabetes mellitus type 2 (T2DM). Methods: A total of 128 individuals of Swati (n = 22) and Zulu (n = 106) origin attending chronic care for T2DM were recruited. Nine SNPs previously associated with metformin and SUs were selected and genotyped using MassArray. Uncontrolled T2DM was defined as HbA1c > 7%. The association between genotypes, alleles and glycaemic response to treatment was determined using multivariate logistic regression model analysis. Results: About 85.93% (n = 110) of the study participants were female and 77.34% (n = 99) had uncontrolled T2DM (HbA1c > 7%). In the multivariate (adjusted) logistic regression model analysis, the CC genotype of rs2162145 (CPA6), GG and GA genotypes of rs889299 (SCNN1B) were significantly associated with uncontrolled T2DM. On the other hand, the C allele of rs254271 (PRPF31) and the GA genotype of rs3792269 (CAPN10) were associated with controlled T2DM. A significant interaction between rs2162145 and rs889299 in response to metformin and SU combination therapy was observed. Conclusions: In this study, we reported the association of rs2162145 (CC) and rs889299 (GG and GA) with uncontrolled T2DM. We also reported the association of rs254271 (C) and rs3792269 (GA) with controlled T2DM in response to metformin and SU combination therapy. Furthermore, an interaction between rs2162145 and rs889299 was established, where the genotype combination GA (rs889299) and TT (rs2162145) was associated with uncontrolled T2DM.

Clinical laboratory reference values amongst children aged 4 weeks to 17 months in Kilifi, Kenya: A cross sectional observational study

Reference intervals for clinical laboratory parameters are important for assessing eligibility, toxicity grading and management of adverse events in clinical trials. Nonetheless, haematological and biochemical parameters used for clinical trials in sub-Saharan Africa are typically derived from industrialized countries, or from WHO references that are not region-specific. We set out to establish community reference values for haematological and biochemical parameters amongst children aged 4 weeks to 17 months in Kilifi, Kenya. We conducted a cross sectional study nested within phase II and III trials of RTS, S malaria vaccine candidate. We analysed 10 haematological and 2 biochemical parameters from 1,070 and 423 community children without illness prior to experimental vaccine administration. Statistical analysis followed Clinical and Laboratory Standards Institute EP28-A3c guidelines. 95% reference ranges and their respective 90% confidence intervals were determined using non-parametric methods. Findings were compared with published ranges from Tanzania, Europe and The United States. We determined the reference ranges within the following age partitions: 4 weeks to <6 months, 6 months to less than <12 months, and 12 months to 17 months for the haematological parameters; and 4 weeks to 17 months for the biochemical parameters. There were no gender differences for all haematological and biochemical parameters in all age groups. Hb, MCV and platelets 95% reference ranges in infants largely overlapped with those from United States or Europe, except for the lower limit for Hb, Hct and platelets (lower); and upper limit for platelets (higher) and haematocrit(lower). Community norms for common haematological and biochemical parameters differ from developed countries. This reaffirms the need in clinical trials for locally derived reference values to detect deviation from what is usual in typical children in low and middle income countries.

Does Thiazolidinedione therapy exacerbate fluid retention in congestive heart failure?

The ever-growing global burden of congestive heart failure (CHF) and type 2 diabetes mellitus (T2DM) as well as their co-existence necessitate that anti-diabetic pharmacotherapy will modulate the cardiovascular risk inherent to T2DM while complying with the accompanying restrictions imposed by CHF. The thiazolidinedione (TZD) family of peroxisome proliferator-activated receptor γ (PPARγ) agonists initially provided a promising therapeutic option in T2DM owing to anti-diabetic efficacy combined with pleiotropic beneficial cardiovascular effects. However, the utility of TZDs in T2DM has declined in the past decade, largely due to concomitant adverse effects of fluid retention and edema formation attributed to salt-retaining effects of PPARγ activation on the nephron. Presumably, the latter effects are potentially deleterious in the context of pre-existing fluid retention in CHF. However, despite a considerable body of evidence on mechanisms responsible for TZD-induced fluid retention suggesting that this class of drugs is rightfully prohibited from use in CHF patients, there is a paucity of experimental and clinical studies that investigate the effects of TZDs on salt and water homeostasis in the CHF setting. In an attempt to elucidate whether TZDs actually exacerbate the pre-existing fluid retention in CHF, our review summarizes the pathophysiology of fluid retention in CHF. Moreover, we thoroughly review the available data on TZD-induced fluid retention and proposed mechanisms in animals and patients. Finally, we will present recent studies challenging the common notion that TZDs worsen renal salt and water retention in CHF.

Thiazolidinedione-induced fluid retention: recent insights into the molecular mechanisms

Peroxisome proliferator-activated receptor- γ (PPAR γ ) agonists such as rosiglitazone and pioglitazone are used to improve insulin sensitivity in patients with diabetes mellitus. However, thiazolidinediones induce fluid retention, edema, and sometimes precipitate or exacerbate heart failure in a subset of patients. The mechanism through which thiazolidinediones induce fluid retention is controversial. Most studies suggest that this effect results from the increase in tubular sodium and water reabsorption in the kidney, but the role of specific nephron segments and sodium carriers involved is less clear. Some studies suggested that PPAR γ agonist stimulates Na(+) reabsorption in the collecting duct by activating epithelial Na(+) channel (ENaC), either directly or through serum and glucocorticoid-regulated kinase-1 (SGK-1). However, other studies did not confirm this mechanism and even report the suppression of ENaC. Alternative mechanisms in the collecting duct include stimulation of non-ENaC sodium channel or inhibition of chloride secretion to the tubular lumen. In addition, thiazolidinediones may augment sodium reabsorption in the proximal tubule by stimulating the expression and activity of apical Na(+)/H(+) exchanger-3 and basolateral Na(+)-HCO3 (-) cotransporter as well as of Na(+),K(+)-ATPase. These effects are mediated by PPAR γ -induced nongenomic transactivation of the epidermal growth factor receptor and downstream extracellular signal-regulated kinases (ERK).

Genetic predisposition and nongenetic risk factors of thiazolidinedione-related edema in patients with type 2 diabetes

OBJECTIVE

This study aimed to analyze the association of thiazolidinedione (TZD)-related edema with genetic and clinical variables and develop a simple points system to predict the risk of developing TZD-related edema.

METHODS

Fifty-eight (21.6%) of 268 individuals who received TZD for type 2 diabetes developed peripheral edema. Twenty-eight tag single nucleotide polymorphisms (SNPs) from candidate genes involved in sodium and water reabsorption were genotyped. Cox regression and logistic regression models were used to analyze the associations of different genotypes and weighted genotypic scores with TZD-related edema risk.

RESULTS

Individuals with edema were older, predominantly female, and had greater weight gain. The AQP2 rs296766 T allele was associated with TZD-related edema [allelic P=0.0059; odds ratio (OR), 2.89; 95% confidence interval (CI), 1.61-5.17]. The SLC12A rs12904216 G allele had borderline significance (allelic P=0.049), which disappeared after correction for multiple testing. Patients with two SNP-based (AQP2 rs296766 and SLC12A1 rs12904216), who weighted genotypic scores within the top quartile, had a higher risk of developing TZD-related edema (OR, 16.45; 95% CI, 3.05-88.76). Combining the weighted genetic scores of two SNPs or all SNPs with age and sex information significantly improved the predictive power for TZD-related edema. We also developed a simple risk factor-based points system to predict an individual's risk of developing TZD-related edema.

CONCLUSION

A clinically applicable prediction model including age, sex, and genetic information from AQP2 rs296766 and/or SLC12A rs12904216 SNPs can be developed to estimate the risk of TZD-related edema in type 2 diabetes patients.

Variation at the NFATC2 locus increases the risk of thiazolidinedione-induced edema in the Diabetes REduction Assessment with ramipril and rosiglitazone Medication (DREAM) study

OBJECTIVE

Thiazolidinediones are used to treat type 2 diabetes. Their use has been associated with peripheral edema and congestive heart failure-outcomes that may have a genetic etiology.

RESEARCH DESIGN AND METHODS

We genotyped 4,197 participants of the multiethnic DREAM (Diabetes REduction Assessment with ramipril and rosiglitazone Medication) trial with a 50k single nucleotide polymorphisms (SNP) array, which captures ∼2000 cardiovascular, inflammatory, and metabolic genes. We tested 32,088 SNPs for an association with edema among Europeans who received rosiglitazone (n = 965).

RESULTS

One SNP, rs6123045, in NFATC2 was significantly associated with edema (odds ratio 1.89 [95% CI 1.47-2.42]; P = 5.32 × 10(-7), corrected P = 0.017). Homozygous individuals had the highest edema rate (hazard ratio 2.89, P = 4.22 × 10(-4)) when compared with individuals homozygous for the protective allele, with heterozygous individuals having an intermediate risk. The interaction between the SNP and rosiglitazone for edema was significant (P = 7.68 × 10(-3)). Six SNPs in NFATC2 were significant in both Europeans and Latin Americans (P < 0.05).

CONCLUSIONS

Genetic variation at the NFATC2 locus contributes to edema among individuals who receive rosiglitazone.

Pharmacogenetics in diabetes

Genetic variation can impact on efficacy and risk of adverse events to commonly used oral agents in -diabetes. Metformin is not metabolized and its mechanism of action remains debated; however, several cation transporters have been identified. Variation in these pharmacokinetic genes might influence metformin response. Conversely, although the cytochrome P450 system has been implicated in sulfonylurea response in some small studies, to date variants affecting pharmacodynamics, including those in ABCC8 (SUR1) and TCF7L2, are the most promising. For thiazolidinedione response, variants in PPARG or ADIPOQ (adiponectin) have been variably associated with response. With increasing well-phenotyped cohorts and new methods, including genome-wide association studies, the next few years offer great hope to use pharmacogenetics to unravel drug and disease mechanisms, as well as the possibility to individualize therapy by genotype.

Establishment of hypoglycemic agent screening method based on human glucokinase

OBJECTIVE

To establish a reliable platform for screening glucokinase activators (GKAs) in vitro.

METHODS

Pancreatic glucokinase (PGK) protein expressed in a prokaryotic expression system as a histidine-tagged fusion protein from Homo sapiens was produced. Then, response surface methodology (RSM) was used to optimize the microplate-based GKA screening platform. In the first step of optimization with Plackett-Burman design (PBD), initial pH, reaction time and MgCl2 were found to be important factors affecting the activity ratio of GKA (RO-28-1675) significantly. In the second step, a 2(3) full factorial central composite design (CCD) and RSM were applied to the optimal condition determination of each significant variable. A second-order polynomial was determined by a multiple regression analysis of the experimental data.

RESULTS

The following optimal values for the critical factors were obtained: initial pH 0 (7.0), reaction time-0.63 (13.7 min) and MgCl2 0.11 (2.11 mmol/L) with a predicted value of the maximum activity ratio of 34.1%.

CONCLUSION

Under the optimal conditions, the practical activity ratio is 34.8%. The determination coefficient (R2) is 0.9442, ensuring adequate credibility of the model. LLAE3, extracted from Folium nelumbinis in our laboratory, has prominently activated effects on PGK.

Antidepressant-coincident mania in children and adolescents treated with selective serotonin reuptake inhibitors

Several factors have amplified concern about the possibility that antidepressant medication may contribute to induction of pediatric mania. These include the high rate of antidepressant medication prescription, the recent surge in the rate of diagnosis of pediatric bipolar disorder in the USA, and a growing number of case reports and clinical studies showing coincidence of manic symptoms with antidepressant pharmacotherapy in both youths and adults. However, the question of how medications and manic symptoms might be related is complicated, and decisive research studies with rigorous designs for evaluating the issues have not been published. The situation makes it difficult for practitioners to make good, evidence-based decisions. The scientific literature is ambiguous, and the stakes are high. We review the extant literature, offer seven different conceptual models of how medication and mania might be related, and comment on the evidence and clinical implications of each.