Abstract-Based on the presence of a functional retinoic acid receptor/retinoid X receptor transcription factor binding sequence (hormone-responsive element) in the renin gene enhancer and on the fact that the peroxisome proliferatoractivated receptors (PPARs) bind to DNA as heterodimers with retinoid X receptors, we speculated that PPARs are involved in the regulation of renin gene expression. To test this hypothesis, we used the human renin-producing cell line CaLu-6. Endogenous or pharmacological PPAR␥ agonists (unsaturated fatty acids and thiazolidinediones, respectively) stimulated renin gene expression. Surprisingly, we found that PPAR␥ targets a palindromic repeat with a 3-bp spacer (Pal3) in the proximal human renin promoter. Thus, renin is the first gene described with a functional Pal3 sequence. PPAR␥ agonists also stimulated renin gene expression in cultured native juxtaglomerular cells, which are the main source of renin in vivo. In summary, PPAR␥ was identified as a novel intracellular mediator involved in the upregulation of renin transcription. Key Words: basic science Ⅲ gene expression/regulation Ⅲ hypertension (kidney), renin Ⅲ cell signaling P lasma renin is aspartyl protease, produced by the juxtaglomerular (JG) cells of the kidney. Renin is the ratelimiting factor of the renin-angiotensin-aldosterone-system, which is of fundamental importance to the regulation of blood pressure. 1 Therefore, the mechanisms involved in the control of the renin gene are extensively characterized. An enhancer sequence, which activates transcription in a position-and orientation-independent manner, was identified in the 5Ј-flanking region of the mouse renin gene. 2 The renin enhancer contains an Ϸ50-bp-long region, which attracts much attention because it is involved in the regulation of renin transcription by virtually all cues tested until now. [2][3][4][5][6][7] A direct repeat 5Ј-AGGTCA-3Ј was identified within the 50-bp enhancer sequence. 7 This direct repeat is principally known as the hormone-responsive element (HRE), because it is the consensus DNA-binding site for the nuclear hormone receptor superfamily. 8 The nuclear hormone receptors represent ligand-activated transcription factors, which are the intracellular docking stations for membrane-permeable bioactive substances, such as corticoids, retinoids, vitamin D3, thyroid hormones, and free fatty acids. Retinoic acid (vitamin A) was found to stimulate renin transcription through retinoic acid receptor-␣ and retinoid X receptor (RXR)-␣. 7 Mice lacking the vitamin D3 receptor have elevated renin mRNA levels, and vitamin D3 inhibits renin promoter activity. 9 Thyroid hormone was also found to regulate renin transcription. 10 On the other hand, aldosterone does not influence renin transcription but stabilizes renin mRNA. 11 Thus, peroxisome proliferator-activated receptors (PPARs) remained as the last nuclear hormone receptor subfamily, which has not been studied for its impact on renin transcription. Such an effect is feasible because PPARs bind to DNA as ...

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BI 425809 is a potent and selective glycine transporter 1 (GlyT1) inhibitor being developed for the treatment of cognitive impairment in Alzheimer disease and schizophrenia. Translational studies evaluated the effects of BI 425809 on glycine levels in rat and human cerebrospinal fluid (CSF). Oral administration of BI 425809 in rats induced a dose‐dependent increase of glycine CSF levels from 30% (0.2 mg/kg, not significant) to 78% (2 mg/kg, P < 0.01), relative to vehicle. Similarly, oral administration of BI 425809 in healthy volunteers resulted in a dose‐dependent increase in glycine CSF levels at steady state, with a mean 50% increase at doses as low as 10 mg. The peak plasma concentration (Cmax) of BI 425809 was achieved earlier in plasma than in CSF (t max 3–5 vs. 5–8 hours, respectively). Generally, BI 425809 was safe and well tolerated. These data provide evidence of functional target engagement of GlyT1 by BI 425809.

Background and objectivesSchizophrenia and Alzheimer’s disease are characterised by glutamatergic pathway abnormalities related to N-methyl-d-aspartate (NMDA) receptor hypofunction and cognitive impairment. Glycine is an NMDA receptor co-agonist; inhibition of glycine transporter 1 (GlyT1) should improve NMDA receptor hypofunction. This study evaluated safety and pharmacokinetic properties of BI 425809—a potent and selective GlyT1 inhibitor.MethodsIn the single-rising dose (SRD) component of this study, subjects were randomised to a single dose of BI 425809 [doses (mg): 0.5, 1, 2, 5, 10, 25, 50, 100 and 150], or placebo. The bioavailability/food effect (BA/FE) component investigated BI 425809 pharmacokinetics following single dosing (25-mg tablet) after overnight fasting or with a high-calorie meal or as solution (25 mg) after overnight fasting.ResultsOverall, 33/83 (39.8%) subjects had ≥ 1 treatment-related adverse event (AE); there were no deaths or serious AEs. Reported SRD part AEs trended towards dose dependency, occurring at the higher doses (mostly central nervous system related). BI 425809 plasma concentration–time profiles were similarly shaped across all doses and plasma exposure increased proportional to dose. In the BA/FE component, geometric mean ratios for the area under the concentration–time curve from time zero to the last measurable concentration and the maximum plasma concentration for tablet fasted versus solution fasted were 80.5 and 50.0%, respectively, and for tablet fed versus fasted were 125.9 and 142.1%, respectively.ConclusionBI 425809 was generally well-tolerated at doses expected to be clinically relevant. The AE profile suggested possible GlyT1-inhibiting effects.Clinical trial identifierNCT02068690.

We recently reported that human renin gene transcription is stimulated by the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-gamma in the renin-producing cell line Calu-6. The effect of PPARgamma was mapped to two sequences in the renin promoter: a direct repeat hormone response element (HRE), which is related to the classical PPAR response element (PPRE) and a nonconsensus palindromic element with a 3-bp spacer (Pal3). We now find that PPARgamma binds to the renin HRE. Neither the human renin HRE nor the consensus PPRE was sufficient to attain the maximal stimulation of renin promoter activity by the PPARgamma agonist rosiglitazone. In contrast, the human renin Pal3 element mediates both the full PPARgamma-dependent activation of transcription and the PPARgamma-driven basal renin gene transcription. The human renin Pal3 sequence was found to selectively bind PPARgamma and the retinoid X receptor-alpha from Calu-6 nuclear extracts. This is in contrast to the consensus PPRE, which can bind other nuclear proteins. PPARgamma knockdown paradoxically did not attenuate the stimulation of the endogenous renin gene expression by rosiglitazone. Similarly, a deficiency of PPARgamma did not attenuate the activation of the minimal human renin promoter, which contains the endogenous Pal3 motif. However, when the human renin Pal3 site was replaced by the consensus PPRE sequence, PPARgamma knockdown abrogated the effect of rosiglitazone on renin promoter activity. Thus, the human renin Pal3 site appears to be critical for the PPARgamma-dependent regulation of gene expression by mediating maximal transcription activation, particularly at the low cellular level of PPARgamma.

Besides of its functional role in the nervous system, the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is involved in the regulation of cardiovascular function. Therefore, PACAP is a potent vasodilator in several vascular beds, including the renal vasculature. Because the kidney expresses both PACAP and PACAP-binding sites, it was speculated that PACAP might regulate cardiovascular function by direct vascular effects and indirectly by regulating renin release from the kidneys. PACAP (1-27) stimulated renin secretion from isolated perfused kidneys of rats 4.9-fold with a half-maximum concentration of 1.9 nmol/L. In addition, PACAP stimulated renin release and enhanced membrane capacitance of isolated juxtaglomerular cells, indicating a direct stimulation of exocytotic events. The effect of PACAP on renin release was mediated by the specific PACAP receptors (PAC1), because PACAP (1-27) applied in concentrations in the physiologic range (10 and 100 pmol/L) did not enhance renin release from isolated kidneys of PAC1 receptor knockout mice (PAC1؊/؊), whereas it stimulated renin release 1.38-and 2.5-fold in kidneys from wild-type mice. Moreover, plasma renin concentration was significantly lower in PAC1؊/؊ compared with their wild-type littermates under control conditions as well as under a lowor high-salt diet and under treatment with the angiotensin-converting enzyme inhibitor ramipril, whereas no differences in plasma renin concentration between the genotypes were detectable after water deprivation. These data show that PACAP acting on PAC1 receptors potently stimulates renin release, serving as a tonic enhancer of the renin system in vivo.

The retina expresses a local renin-angiotensin system (RAS). This study aimed to investigate the influence of systemic modulation of renin synthesis on the expression of renin in the retinal pigment epithelium (RPE), which forms part of the blood/retina barrier. Freshly isolated RPE cells showed expression of renin 1A, which is the secreted isoform of renin. Systemic administration of the angiotensin-converting enzyme inhibitor enalapril in mice increased the renin expression in both the kidney and the retina. Systemic infusion of ANG II led to a decrease in the renin expression in the kidney and in the retina and RPE. The ANG II-dependent down-regulation of renin expression in the RPE was prevented by systemic application of the AT(1) receptor blocker losartan. However, water deprivation lead to an increase of the renin expression in the kidney but unexpectedly to a decrease of the renin expression in the retina. In sections of the mouse retina, the ANG II receptor AT(1) was found in the RPE and localized at the blood side of the epithelium. Short-time cultured RPE cells showed increases in intracellular free Ca(2+) in response to stimulation by ANG II that were sensitive to losartan. In summary, we conclude that the renin expression in cells of the blood/retina barrier is influenced by the systemic RAS. ANG II circulating in the plasma is likely a mediator of this influence.

Aim To report two phase I studies of the novel subcutaneous glucagon‐like peptide‐1 receptor/glucagon receptor (GLP‐1R/GCGR) dual agonist BI 456906 versus placebo in healthy volunteers and people with overweight/obesity. Materials and Methods A phase Ia study (NCT03175211) investigated single rising doses (SRDs) of BI 456906 in 24 males with a body mass index (BMI) of 20–<30 kg/m2. A phase Ib study (NCT03591718) investigated multiple rising doses (MRDs) of BI 456906 (escalated over 6 [Part A] or 16 [Part B] weeks) in 125 adults with a BMI of 27–40 kg/m2. Results In the SRD study (N = 24), mean body weight decreased with increasing BI 456906 dose. In the MRD study, the maximum decreases in placebo‐corrected mean body weight were at week 6 (–5.79%, dosage schedule [DS] 1; Part A) and week 16 (–13.8%, DS7; Part B). BI 456906 reduced plasma amino acids and glucagon, indicating target engagement at GCGRs and GLP‐1Rs. Drug‐related adverse events (AEs) increased with BI 456906 dose. The most frequent drug‐related AE with SRDs was decreased appetite (n = 9, 50.0%), and two subjects (8.3%) did not complete the trial because of AEs (nausea and vomiting). During MRD Part A (N = 80), 10 subjects (12.5%) discontinued BI 456906, most commonly because of a cardiac or vascular AE (n = 6, 7.5%); during Part B (N = 45), eight subjects (17.8%) discontinued BI 456906, mainly because of AEs (n = 6, 13.3%), most commonly gastrointestinal disorders. Conclusions BI 456906 produced a placebo‐corrected body weight loss of 13.8% (week 16), highlighting its potential to promote clinically meaningful body weight loss in people with overweight/obesity.