Insights into the diverse mechanisms and effects of variant CUL3-induced familial hyperkalemic hypertension.

Familial hyperkalemic hypertension (FHHt), also known as Pseudohypoaldosteronism type II (PHAII) or Gordon syndrome is a rare Mendelian disease classically characterized by hyperkalemia, hyperchloremic metabolic acidosis, and high systolic blood pressure. The most severe form of the disease is caused by autosomal dominant variants in CUL3 (Cullin 3), a critical subunit of the multimeric CUL3-RING ubiquitin ligase complex. The recent identification of a novel FHHt disease variant of CUL3 revealed intricacies within the underlying disease mechanism. When combined with studies on canonical CUL3 variant-induced FHHt, these findings further support CUL3's role in regulating renal electrolyte transport and maintaining systemic vascular tone. However, the pathophysiological effects of CUL3 variants are often accompanied by diverse systemic disturbances in addition to classical FHHt symptoms. Recent global proteomic analyses provide a rationale for these systemic disturbances, paving the way for future mechanistic studies to reveal how CUL3 variants dysregulate processes outside of the renovascular axis. Video Abstract.

Novel CUL3 Variant Causing Familial Hyperkalemic Hypertension Impairs Regulation and Function of Ubiquitin Ligase Activity.

Familial hyperkalemic hypertension is caused by pathogenic variants in genes of the CUL3 (cullin-3)-KLHL3 (kelch-like-family-member-3)-WNK (with no-lysine [K] kinase) pathway, manifesting clinically as hyperkalemia, metabolic acidosis, and high systolic blood pressure. The ubiquitin E3 ligase CUL3-KLHL3 targets WNK kinases for degradation to limit activation of the thiazide-sensitive NCC (Na-Cl cotransporter). All known variants in CUL3 lead to exon 9 skipping (CUL3Δ9) and typically result in severe familial hyperkalemic hypertension and growth disturbances in patients. Whether other variants in CUL3 cause familial hyperkalemic hypertension is unknown. Here, we identify a novel de novo heterozygous CUL3 variant (CUL3Δ474-477) in a pediatric familial hyperkalemic hypertension patient with multiple congenital anomalies and reveal molecular mechanisms by which CUL3Δ474-477 leads to dysregulation of the CUL3-KLHL3-WNK signaling axis. Using patient-derived urinary extracellular vesicles and dermal fibroblasts, in vitro assays, and cultured kidney cells, we demonstrate that CUL3Δ474-477 causes reduced total CUL3 levels due to increased autoubiquitination. The CUL3Δ474-477 that escapes autodegradation shows enhanced modification with NEDD8 (neural precursor cell expressed developmentally down-regulated protein 8) and increased formation of CUL3-KLHL3 complexes that are impaired in ubiquitinating WNK4. Proteomic analysis of CUL3 complexes revealed that, in addition to increased KLHL3 binding, the CUL3Δ474-477 variant also exhibits increased interactions with other BTB (Bric-a-brac, Tramtrack, and Broad complex) substrate adaptors, providing a rationale for the patient's diverse phenotypes. We conclude that the pathophysiological effects of CUL3Δ474-477 are caused by reduced CUL3 levels and formation of catalytically impaired CUL3 ligase complexes.

Undiagnosed Hypertension and Undiagnosed Type 2 Diabetes among Overweight and Obese Marshallese Participants in a Diabetes Prevention Program.

Hypertension and type 2 diabetes (T2D) are major public health issues that disproportionately affect minority communities, including Native Hawaiians and Pacific Islanders (NHPI). Minority communities are also more likely to have undiagnosed hypertension and T2D. Marshallese Pacific Islanders have been shown to have high proportions of diagnosed and undiagnosed hypertension and T2D. Using survey and biometric data collected from 378 overweight/obese Marshallese Pacific Islander adults, this study documents the prevalence of hypertension and T2D, as well as the prevalence of undiagnosed hypertension and T2D. The study also examines associations between undiagnosed hypertension and undiagnosed T2D and age group, sex, health care access (defined by foregone care due to cost and health insurance status), and body mass index (BMI). Among participants with blood pressure readings indicative of hypertension, 68.4% were undiagnosed, and among participants with HbA1c indicative of T2D, 31.6% were undiagnosed. A quarter of participants (24.5%) had blood pressure and HbA1c measures indicative of both undiagnosed hypertension and undiagnosed T2D. Undiagnosed hypertension was significantly associated with age group (p's<0.0001) and sex (p=0.028). Undiagnosed T2D was significantly associated with age group (p's<0.05), forgone care due to cost (p=0.018), health insurance status (p=0.035), and BMI (p=0.001). Participants in this study had high proportions of undiagnosed hypertension and undiagnosed T2D. These findings will be immediately useful for those working to address hypertension and T2D disparities among Marshallese and other NHPI populations.

Examining elevated blood pressure and the effects of diabetes self-management education on blood pressure among a sample of Marshallese with type 2 diabetes in Arkansas.

INTRODUCTION: Hypertension is a leading risk factor for heart attack and stroke. Undiagnosed hypertension increases the risk of heart attack and stroke. The risk of hypertension is increased for those with type 2 diabetes mellitus (T2DM). Diabetes self-management education (DSME) has been shown to be effective at improving clinical outcomes, including reducing blood pressure, but few studies have evaluated the effects of DSME for Native Hawaiians and Pacific Islanders. METHODS: This study examined the baseline prevalence of diagnosed hypertension and undiagnosed high blood pressure and differences in health care access between those with diagnosed hypertension versus undiagnosed high blood pressure. The sample consisted of 221 Marshallese adults with T2DM participating in a DSME randomized controlled trial in northwest Arkansas. The study also examined the effects of DSME interventions on participants' blood pressure, comparing an Adapted-Family DSME with a Standard DSME. RESULTS: Nearly two-thirds of participants had blood pressure readings indicative of hypertension, and of those, over one-third were previously undiagnosed. The frequency of doctor visits was significantly lower for those with undiagnosed high blood pressure. There were no differences in health insurance coverage or forgone medical care between those with undiagnosed high blood pressure versus diagnosed hypertension. Across all participants, a significant reduction in systolic blood pressure occurred between baseline and post intervention, and a significant reduction in diastolic blood pressure occurred between baseline and post-intervention, 6 months, and 12 months post-intervention. No differences were observed by study arm. CONCLUSION: This study is the first to document the prevalence of diagnosed hypertension and undiagnosed high blood pressure, as well as the effects of DSME on blood pressure among a sample of Marshallese adults with T2DM.

First Do No Harm: Ethical Concerns of Health Researchers That Discourage the Sharing of Results With Research Participants.

Background: Health researchers and health research participants support the sharing of research results; however, results are typically only shared through peer-reviewed publications. Few studies have investigated researchers' ethical concerns related to sharing results with research participants. Methods: An explanatory approach was used to explore the ethical concerns researchers may have with returning aggregate results to research participants. Researchers (N = 414) responded to an online survey of open-ended questions that allowed researchers to provide in-depth explanations regarding their responses to closed-ended questions. Results: Across researchers, the mean percentage of studies for which ethical concerns were reported as a barrier to results sharing was 38.5% (SD= 30.7). Researchers' primary ethical concerns with returning results were articulated as an overarching desire to prevent harm to participants. Three broad ethical concerns emerged, each with underlying subthemes: 1) distress, 2) understanding, and 3) privacy. Conclusions: This is the first study to broadly explore researchers' ethical concerns with sharing aggregate research results with participants and reveals that researchers' ethical concerns are closely tied to the ethical obligation to do no harm. In order to increase results sharing, steps must be taken to help researchers understand how to minimize potential harm when sharing results.