Thiamine deficiency in diabetes, obesity and bariatric surgery: Recipes for diabetic ketoacidosis.

Diabetic ketoacidosis (DKA) is a life-threatening condition affecting individuals with diabetes characterised by hyperglycaemia, metabolic acidosis and ketonemia. The incidence and financial burden of DKA is still high. Thiamine deficiency is well documented in patients with DKA and could be associated with cardiac dysfunction in those patients. Thiamine deficiency leads to cardiac dysfunction, neuronal death and worsens the prognosis of DKA. There is an existing metabolic relationship between thiamine deficiency in diabetes, obesity and bariatric surgery. Careful monitoring of thiamine, along with other vitamins, is essential for diabetic patients, obese individuals and postbariatric surgery. Further research and clinical studies are urgently needed to assess the following: (1) Whether diabetes, obesity and bariatric surgery make individuals more prone to have DKA related to thiamine deficiency and (2) Whether supplementation of thiamine can protect diabetic patients, obese subjects and individuals undergoing bariatric surgery from DKA. This review summarises the biochemistry of thiamine and the existing metabolic relationships between thiamine deficiency in DKA, diabetes, obesity and bariatric surgery. Primary and family physicians have an important role in ensuring adequate replacement of thiamine in individuals with diabetes, obesity and bariatric surgery.

The Impact of Clinical Pharmacist Diabetes Education on Medication Adherence in Patients with Type 2 Diabetes Mellitus: An Interventional Study from Khartoum, Sudan.

BACKGROUND: Continuous therapeutic care with good medication adherence is the cornerstone of management of all chronic diseases including diabetes. This study aimed to evaluate the impact of clinical pharmacist intervention on the medication adherence in individuals with type 2 diabetes (T2DM). METHODS: This was a randomized, double-blind, controlled trial conducted at a diabetes clinic located at Omdurman Military Hospital, Sudan. Individuals with T2DM attending the diabetes clinic within 1 year were selected. The sample size was 364 participants (182 control and 182 interventional group). We used a pre-structured standardized questionnaire and checklist to collect the data. Data were analyzed by using the Statistical Package for the Social Sciences (SPSS) (version 28). RESULTS: Majority, 76.4% (n = 278) were females, and they consisted of 80.8% (n = 147) of the interventional group and 72% of the controls. The mean age of the interventional group was 54.5 (±10) years; 31.9% (n = 58) of the interventional group had diabetes for 6-10 years, compared with 26.4% (n = 48) of the control group. Among the control group, the mean adherence score was 6.8 (±1.7) at baseline and it was 6.7 (±1.6) at the end of the study (p < 0.001), while in the interventional group, the mean adherence score was 6.8 (±1.7) at baseline and it was 7.4 (±1.5) at the end of the study (p < 0.001). CONCLUSION: Adherence score among the intervention group was increased significantly from baseline to the end of the study when compared to the control group.

Prevalence of obesity related hypertension among overweight or obese adults in River Nile State in Northern Sudan: a community based cross-sectional study.

Background: Reducing excess body weight is important for control and management of high blood pressure (BP) in adults. Previous studies showed high prevalence of hypertension in River Nile State-north of Sudan, hence this study to establish whether obesity can be among the main risk factors and to study the prevalence of obesity related hypertension among Sudanese adults in River Nile State. Methods: This was a cross sectional community-based study conducted in River Nile State, Northern Sudan from January to June 2021. Obese and overweight, aged 18 years and above and accepted to participate in the study were included in the study. Convenience sampling method was used to select the participants. Data was collected through structured questionnaire filled by the patients after taking informed consent. Anthropometric measurements were taken. Two measurements of BP were obtained. Data was analyzed using SPSS version 23.0 (IBM, Chicago, USA). Chi-square test was used to determine the associations between categorical variables while logistic regression test was used to predict the presence of hypertension among studied population. Results: A total of 1,295 participants were enrolled in this study. Obesity was reported in 1,118 (86.3%) of the participants. The prevalence of hypertension among the participants was 1,027 (79.3%). Central obesity was reported in 951 (92.6%) among hypertensive patients (P<0.001). Moreover, among hypertensive patients 470 (45.8%) were obese class I, 334 (32.5%) overweight, 139 (13.5%) obese class II and 84 (8.2%) obese class III (P<0.001). Obesity, BMI are risk factor of hypertension (P<0.001). Other risk factors were age above 40 years (P<0.001), unemployment (P<0.001), low education level (P<0.001) and being married (P<0.001). Logistic regression analysis showed that increasing age [P<0.001; odds ratio (OR) =1.055; 95% confidence interval (CI): 1.041-1.068], central obesity (P<0.001; OR =5.16; 95% CI: 3.4-7.8) and high body mass index (BMI) (P<0.001; OR =3.7; 95% CI: 1.7-7.9) were associated with uncontrolled hypertension. Conclusions: The study showed that the prevalence of obesity related hypertension was high. Common risk factors were age above 40 years, unemployment, and marriage. Importantly, central obesity, gross obesity and increasing age can be associated with uncontrolled BP management.

Whole body vibration therapy and cognitive functions: a systematic review.

Whole Body Vibration has been found to induce physiological changes in human subjects, improving their neuromuscular, respiratory and cardiovascular functions. Evidence from animal research prove that whole-body vibration appears to induce changes in molecular and cellular levels to alter cognitive functions in mice. There is evolving evidence for a potential value of whole body vibration in improving cognition and preventing the development of age-related cognitive disorders in humans. However, literature on the biological consequences of whole-body vibration on the human brain is scanty. If so, gathering the available evidences would help decide the possibility of designing appropriate whole-body vibration protocols to extend its application to induce neurocognitive enhancement and optimize its effects. Therefore, a systematic review of the literature was performed, consulting the ProQuest, MEDLINE and Scopus bibliographic databases, to summarize the available scientific evidence on the effects of whole-body vibration on cognitive functions in adults. Results of the review suggest that whole-body vibration therapy enhances a wide spectrum of cognitive functions in adults although there isn't enough evidence available yet to be able to design a standardized protocol to achieve optimum cognitive enhancement.

Epidemiological, Clinical, and Histopathological Features of Salivary Gland Tumors among 150 Sudanese Patients: 10 Years' Experience.

Background and Objectives: Salivary gland tumors (SGTs) are serious challenges to pathologists. Herein, we aimed to assess epidemiological and histopathological characteristics of SGTs among Sudanese patients. Materials and Methods: This retrospective descriptive study was undertaken at The pathology department in Khartoum State between 2008 and 2018. Patient records, histopathological reports, and slides were retrieved; and re-examined by two histopathologists. Diagnoses were reclassified according to the 2017 WHO classification of SGTs. Results: Overall, 150 cases of Sudanese patients with SGT were included (90 [60%] males and 60 [40%] females). Among these, 105 were benign (70%) and 45 were malignant (30%). The parotid glands were the most common site for both benign and malignant tumors (77/150; 51%: 59 benign (76.6%) and 18 malignant [23.4%]). The next common site was the submandibular gland (54 [36%]: 38 benign [70.3%] and 16 malignant [29.7%]), followed by minor salivary glands (19 [12.7%]: 8 benign and 11 malignant [57.9%]). Benign gland entities included pleomorphic adenoma (88/105; 83.7%), oncocytoma (5/105; 4.8%), myoepithelioma (4/105; 3.8%), Whartin tumors (3/105; 2.9%), basal cell adenoma (3/105; 2.9%), and sialolipoma (2/105; 1.9%). Malignant gland entities included adenoid cystic carcinoma (12; 26.7%), mucoepidermoid carcinoma (10; 22,2%), acinic cell carcinoma (6; 13.3%), poorly differentiated carcinoma (4; 8.9%), adenocarcinoma NOS (not otherwise specified) (4; 8.9%), basal cell adenocarcinoma (3; 6.7%), carcinoma ex pleomorphic adenoma (3; 6.7%), polymorphous adenocarcinoma (2; 4.4%), salivary duct carcinoma (1; 2.2%), and epithelial-myoepithelial carcinoma (2.2%). Conclusions: SGTs shared several epidemiological and histopathological features, exhibiting high incidence in the parotid and submandibular glands, lower prevalence in minor glands, and greater male predominance.

Knowledge and attitudes toward COVID-19 vaccination in Sudan: A cross-sectional study.

Background: Vaccines are an essential part of public health interventions to mitigate the devastating health and non-health impacts of COVID-19 pandemic. Despite the fact that Sudan launched the COVID-19 vaccination program in March 2021, only 10% of the population received their two primary doses of vaccines by the end of May 2022. This delayed uptake of vaccines obviously warrants investigation. Therefore, we have conducted this study to evaluate the knowledge, attitude and acceptance of the general population in Sudan toward COVID-19 vaccines. Methodology: A descriptive cross-sectional community-based study. The data were collected using an electronic questionnaire from 403 individuals living in Khartoum, Sudan. The data were processed using the Statistical Package for Social Sciences (SPSS), and data analysis was performed using appropriate tests. Results: 51% of the participants were found to have sufficient knowledge about the COVID-19 vaccine, and the knowledge level is higher among those educated beyond the secondary school and those who were employed. Among those unvaccinated, only 47% of the participants expressed their intention to take the vaccine when offered to them. The major reason for not trusting the vaccine is safety concerns expressed by 65.5% of the unvaccinated. Conclusion: Higher education levels and employment were associated with an increase in sufficient knowledge about the vaccine in around half of the participants. However, most of participants had not taken the vaccine at the time of the study, and the trust in vaccines is not high. Effective interventions by the health authorities are needed to address these issues in order to accelerate the COVID-19 vaccination program in Sudan.

Risk factors associated with fasting during Ramadan among individuals with diabetes according to IDF-DAR risk score in Atbara city, Sudan: Cross-sectional hospital-based study.

BACKGROUND: Ramadan is a holy month for Muslims. The aim of this study was to assess risk associated with Ramadan fasting among Sudanese individuals with diabetes (high, moderate, and low risk) according to International Diabetes Federation in collaboration with Diabetes and Ramadan International alliance (IDF-DAR) Practical Guidelines 2021 risk score. METHODS: This was a cross-sectional hospital-based study recruited 300 individuals with diabetes (79% have type 2 diabetes) from diabetes centers in Atbara city, the River Nile state, Sudan. RESULTS: The risk score was distributed as low risk (13.7%), Moderate risk (24%), and High risk (62.3%). T-test showed a significant difference in mean risk score by gender, duration and type of diabetes (p values = 0.004, 0.000, & 0.000, respectively). One-way ANOVA revealed a statistically significant difference in the risk score by age groups (p = 0.000). Logistic regression revealed that the odds of being in the 41-60 years age group had lower probability to be categorized in the moderate risk group of fasting rather than low risk by 4.3 times than being in the age more than 60 years. (p = 0.008), the odds of being in the age group 41-60 years lower probability to be categorized in the high risk of fasting rather than low risk by 8 times than being in the age more than 60 years. (p = 0.000). CONCLUSION: The majority of patients in this study have a high risk for Ramadan fasting. IDF-DAR risk score is of great significance in assessing individuals with diabetes for Ramadan fasting.

Bone Health in People Living with HIV/AIDS: An Update of Where We Are and Potential Future Strategies.

The developments in Human Immunodeficiency Virus (HIV) treatment and in the care of people living with HIV (PLWHIV) and Acquired Immunodeficiency Syndrome (AIDS) over the last three decades has led to a significant increase in life expectancy, on par with HIV-negative individuals. Aside from the fact that bone fractures tend to occur 10 years earlier than in HIV-negative individuals, HIV is, per se, an independent risk factor for bone fractures. A few available antiretroviral therapies (ARVs) are also linked with osteoporosis, particularly those involving tenofovir disoproxil fumarate (TDF). HIV and hepatitis C (HCV) coinfection is associated with a greater risk of osteoporosis and fracture than HIV monoinfection. Both the Fracture Risk Assessment Tool (FRAX) and measurement of bone mineral density (BMD) via a DEXA scan are routinely used in the assessment of fracture risk in individuals living with HIV, as bone loss is thought to start between the ages of 40 and 50 years old. The main treatment for established osteoporosis involves bisphosphonates. Supplementation with calcium and vitamin D is part of clinical practice of most HIV centers globally. Further research is needed to assess (i) the cut-off age for assessment of osteoporosis, (ii) the utility of anti-osteoporotic agents in PLWHIV and (iii) how concomitant viral infections and COVID-19 in PLWHIV can increase risk of osteoporosis.

Safety and effectiveness of newer antidiabetic medications during Ramadan fasting and safety of Ramadan fasting after bariatric surgery.

Background: Fasting during Ramadan is mandatory for all adult healthy Muslims. International studies found that most Muslims with diabetes mellitus fast during Ramadan. The main risk factors are hypoglycemia, Hyperglycemia, diabetic ketoacidosis, and dehydration during fasting. Therefore, stratification of the risks for severe acute diabetes complications needs to be considered for each individual and strategies personalized to advert these complications. The advent of new diabetes medications which are effective yet with a better safety profile and monitoring of blood glucose levels during the day are important to reduce the risk of untoward effects of hypoglycemia and hyperglycemia during Ramadan fasting. Here we review the safety and effectiveness of the newer diabetes medications for Ramadan fasting and whether it is safe to perform fasting after bariatric surgery. Methods: An extensive literature search using PubMed and Google Scholar was done using different search terms. The eligible studies were 48 randomized controlled trials, prospective observational studies, and reviews from January 2008 to June 2022 which were conducted in individuals living with diabetes. Results and Conclusions: The newer diabetes medications such as GLP-1 agonists, DPP-4 inhibitors, SGLT-2 inhibitors, and new Insulin therapy are thought to be safe and effective during fasting of Ramadan. These medications are associated with a reduction in HbA1c, body weight, systolic blood pressure and risk of hypoglycemia during Ramadan fasting. However, further studies with larger sample size are needed to confirm the efficacy and safety of these newer medications during Ramadan fasting. Individuals with Bariatric surgery should seek advice and approval to fast from the bariatric dietician, physician, and surgeon before the beginning of the month of Ramadan.

Correction to: Metabolic syndrome; Definition, Pathogenesis, Elements, and the Effects of medicinal plants on it's elements.

[This corrects the article DOI: 10.1007/s40200-021-00965-2.].

Metabolic syndrome; Definition, Pathogenesis, Elements, and the Effects of medicinal plants on it's elements.

Introduction: Metabolic syndrome (MetS) is a cluster of metabolic risk factors that include central obesity, hypertension, insulin resistance, and atherogenic dyslipidemia and is strongly associated with a greater risk for developing cardiovascular disease and type 2 diabetes mellitus. Methods: A literature search was conducted using the words metabolic syndrome, definition and pathogenesis in Scopus, and PubMed. The search also extended to cover medicinal plants and their role as a potential treatment of the metabolic syndrome. The search based on studies published in the English language from 1st of January 2000 to 30th of May 2021. The abstracts and the articles were then screened. Articles were scanned and read; further relevant references in the reference lists are also included. Results: Both lifestyle factors and genetic factors are involved in the pathogenesis of the metabolic syndrome. Recently, MetS have gained significant attention due to the high prevalence of obesity worldwide. Diagnosis of patients with MetS is important to improve the outcomes of the disease by employing lifestyle and risk factors modifications. Currently, there is a rising interest in medicinal plants and their extracts because the medicinal plants have minimal side effects. Here we review the history, definitions, pathogenesis, management of metabolic syndrome and summarize the beneficial effects of some medicinal plants and their extracts on MetS. Conclusion: Further research and clinical studies are needed to establish whether medicinal plants can be safely given as potential therapy for metabolic syndrome and whether this can be beneficial in low resources setting countries.

Incidental hepatitis B virus in Sudanese patients and relative risk factors: Why more screening is needed in primary care?

Background: Hepatitis B virus (HBV) is considered one of the most paternally transmissible viruses. Therefore, education about its risk factors and transmission is vital in decreasing the prevalence of the disease burden in Sudan. The aim of the present study was to investigate the relative risk factors of HBV and its impact on the society. Materials And Methods: A facility-based, descriptive, cross-sectional study was conducted among those who were incidentally detected with HBV surface antigen (HbsAg) and their contact family members by ICT and enzyme-linked immunosorbent assay (ELISA) in Tropical Diseases Teaching Hospital, Omdurman locality, Khartoum state, Sudan. Results: The study recruited 112 participants, among whom 63 individuals incidentally attended for screening for HBV and this led to contact tracing of 49 individuals (contact relative group). Among 63 patients of the incidental group, there were 83.9% males and 16.1% females. In the contact tracing group consisting of 49 individuals, there were 83.3% males and 16.7% females (odds ratio [OR] = 1.375, 95% confidence interval [CI] = 0.14-13.6; P = 0.000). All the participants were screened for HBsAg. HBV was found to have a significant association with male gender (OR = 1.375, 95% CI = 0.14-13.6; P = 0.000), marital status (OR = 627.084, 95% CI = 48-8195; P = 0.000), working as police officers (OR = 524.2, 95% CI = 43.5-6314; P = 0.000), residing in Khartoum (OR = 520.173, 95% CI = 43-6290; P = 0.000), being illiterate (OR = 558.4, 95% CI = 47.7-6544.7; P = 0.000), vaccination status (OR = 625.4, 95% CI = 48.9-7996.3; P = 0.000), and with some concomitant diseases (OR = 559.193, 95% CI = 47.7-6561.5; P = 0.000). Conclusion: The HBV is still considered a very critical, highly infectious disease; therefore, primary care physicians have an important role in the investigation, prevention, and health education, in order to prevent the viral spread.

Coronavirus disease 2019 morbid pulmonary pathology: What did we learn from autopsy examinations?

BACKGROUND: Despite the rapidly expanding data on clinical, epidemiological and radiological aspects of coronavirus disease 2019 (COVID-19), little is known about the disease's pathological aspects. The scarcity of pathological data on COVID-19 can be explained by the limited autopsy procedures performed on deceased patients. AIM: This work aims to review and summarize the pulmonary pathological findings observed in COIVD-19 deceased individuals based on recent case series reports published in English up to September 2020. METHODS: A search in Google Scholar, PubMedÒ, MEDLINEÒ, and Scopus was performed using the keywords "autopsy and COVID-19," "postmortem and COVID-19," and "pulmonary/lung pathology and COVID-19." RESULTS: Pulmonary autopsy hallmark findings of COVID-19 cases demonstrate the presence of diffuse alveolar damage. The presence of pulmonary thrombi was reported in the majority of patients. Cellular alterations included type 2 pneumocyte hyperplasia, inflammatory cell infiltrates predominantly by lymphocytes, other mononuclear cells, and neutrophils as evident by their specific immunohistochemical markers. Electron microscopy confirmed the presence of virus particles in different cell types, including types 1 and 2 pneumocytes. CONCLUSION: The few emerging autopsy reports have substantially contributed towards our understanding of COVID-19 pulmonary histopathological aspects. COVID-19 caused acute severe respiratory manifestations that are the leading cause of morbidity and mortality in infected patients. More studies and research are needed to understand the inflammatory processes and histopathological changes associated with COVID-19 in African populations. RELEVANCE FOR PATIENTS: Postmortem investigations advance important mechanistic knowledge on COVID-19 pathophysiology and clinical outcomes and could facilitate provisions for targeted therapies.

Nonalcoholic fatty liver disease and COVID-19: An epidemic that begets pandemic.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic, affecting all the individuals across the planet. COVID-19 has gained significant attention due to its high prevalence among individuals with diabetes, nonalcoholic fatty liver disease (NAFLD), and metabolic syndrome. NAFLD is the hepatic manifestation of metabolic syndrome and can be associated with a high risk of developing type 2 diabetes. The association of COVID-19 and NAFLD has also gained more attention because NAFLD is highly associated with the epidemic of obesity. NAFLD is a potential risk factor for SARS-CoV-2 infection and severe COVID-19, independent of metabolic syndrome. Importantly, it is not yet clear whether the epidemics of obesity and NAFLD have perpetuated the current pandemic of COVID-19. Further research is urgently needed to assess the following: (1) Whether NAFLD is a high risk factor for SARS-CoV-2 infection; (2) Whether NAFLD is associated with the severe form of COVID-19; and (3) Whether the presence of NAFLD can explain the racial variation in the morbidity and mortality associated with COVID-19. This review summarizes the interactions between COVID-19 and NAFLD, mechanism of liver injury by COVID-19, and effect of lockdown due to COVID- 19 on patients with NAFLD.

SGK3 Sensitivity of Large-Conductance Ca2+-Activated K+ Channel.

BACKGROUND/AIMS: Large conductance Ca2+-activated K+ channels (maxi K+ channels or BK channels) are rapidly activated by increase of cytosolic Ca2+ activity. The channels participate in the regulation of diverse functions including neuronal excitation and cell volume. The BK channels may be modified by kinases. Channel regulating kinases include the serum & glucocorticoid inducible kinase 3 (SGK3). The present study explored whether SGK3 modifies the activity of BK channels. METHODS: cRNA encoding the Ca2+ insensitive BK channel mutant BKM513I+Δ899-903 was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type SGK3, constitutively active S419DSGK3, or catalytically inactive K191NSGK3. K+ channel activity was measured utilizing dual electrode voltage clamp. RESULTS: BK channel activity in BKM513I+Δ899-903 expressing oocytes was significantly increased by co-expression of SGK3 or active S419DSGK3, but not by coexpression of inactive K191NSGK3. CONCLUSION: SGK3 is a novel positive regulator of BK channels, and thus participates in the regulation of cell volume and excitability.

Up-Regulation of the Large-Conductance Ca2+-Activated K+ Channel by Glycogen Synthase Kinase GSK3ß.

BACKGROUND/AIMS: The pleotropic functions of the large conductance Ca2+-activated K+ channels (maxi K+ channel or BK channels) include regulation of neuronal excitation and cell volume. Kinases participating in those functions include the glycogen synthase kinase GSK3 ß which is under negative control of protein kinase B (PKB/Akt). GSK3ß is inhibited by the antidepressant Lithium. The present study thus explored whether GSK3ß modifies the activity of BK channels. METHODS: cRNA encoding the Ca2+ insensitive BK channel mutant BKM513I+Δ899-903 was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type GSK3ß, inactive K85RGSK3ß, or wild-type GSK3ß with wild-type PKB. K+ channel activity was measured utilizing dual electrode voltage clamp. RESULTS: BK channel activity in BKM513I+Δ899-903 expressing oocytes was significantly increased by co-expression of GSK3ß, but not by co-expression of K85RGSK3ß. The effect of wild type GSK3ß was abrogated by additional co-expression of wild-type PKB and by 24 hours incubation with Lithium (1 mM). Disruption of channel insertion into the cell membrane by brefeldin A (5 µM) was followed by a decline of the current to a similar extent in oocytes expressing BK and GSK3ß and in oocytes expressing BK alone. CONCLUSION: GSK3ß may up-regulate BK channels, an effect disrupted by Lithium or additional expression of PKB and possibly participating in the regulation of cell volume and excitability.

SGK3 Sensitivity of Voltage Gated K+ Channel Kv1.5 (KCNA5).

BACKGROUND: The serum & glucocorticoid inducible kinase isoform SGK3 is a powerful regulator of several transporters, ion channels and the Na+/K+ ATPase. Targets of SGK3 include the ubiquitin ligase Nedd4-2, which is in turn a known regulator of the voltage gated K+ channel Kv1.5 (KCNA5). The present study thus explored whether SGK3 modifies the activity of the voltage gated K+ channel KCNA5, which participates in the regulation of diverse functions including atrial cardiac action potential, activity of vascular smooth muscle cells, insulin release and tumour cell proliferation. METHODS: cRNA encoding KCNA5 was injected into Xenopus oocytes with and without additional injection of cRNA encoding wild-type SGK3, constitutively active S419DSGK3, inactive K191NSGK3 and/or wild type Nedd4-2. Voltage gated K+ channel activity was quantified utilizing dual electrode voltage clamp. RESULTS: Voltage gated current in KCNA5 expressing Xenopus oocytes was significantly enhanced by wild-type SGK3 and S419DSGK3, but not by K191NSGK3. SGK3 was effective in the presence of ouabain (1 mM) and thus did not require Na+/K+ ATPase activity. Coexpression of Nedd4-2 decreased the voltage gated current in KCNA5 expressing Xenopus oocytes, an effect largely reversed by additional coexpression of SGK3. CONCLUSION: SGK3 is a positive regulator of KCNA5, which is at least partially effective by abrogating the effect of Nedd4-2.

SPAK and OSR1 Sensitive Kir2.1 K+ Channels.

BACKGROUND/AIMS: Kir2.1 (KCNJ2) channels are expressed in neurons, skeletal muscle and cardiac tissue and maintain the resting membrane potential. The activity of those channels is regulated by diverse signalling molecules. The present study explored whether Kir2.1 channels are sensitive to the transporter and channels regulating kinases SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1), which are in turn regulated by WNK (with-no-K[Lys]) kinases. METHODS: cRNA encoding Kir2.1 was injected into Xenopus laevis oocytes with or without additional injection of cRNA encoding wild-type SPAK, constitutively active T233E SPAK, WNK insensitive T233A SPAK, catalytically inactive D212A SPAK, wild-type OSR1, constitutively active T185E OSR1, WNK insensitive T185A OSR1 and catalytically inactive D164A OSR1. Inwardly rectifying K+ channel activity was quantified utilizing dual electrode voltage clamp and Kir2.1 channel protein abundance in the cell membrane was measured utilizing chemiluminescence of Kir2.1 containing an extracellular HA-tag epitope. RESULTS: Kir2.1 activity was significantly enhanced by wild-type SPAK and T233E SPAK, but not by T233A SPAK and D212A SPAK, as well as by wild-type OSR1 and T185E OSR1, but not by T185A OSR1 and D164A OSR1. As shown for SPAK, the kinases enhanced Kir2.1 protein abundance in the cell membrane. The difference of current and conductance between oocytes expressing Kir2.1 together with SPAK or OSR1 and oocytes expressing Kir2.1 alone was dissipated following a 24 hours inhibition of channel insertion into the cell membrane by brefeldin A (5 µM). CONCLUSIONS: SPAK and OSR1 are both stimulators of Kir2.1 activity. They are presumably effective by enhancing channel insertion into the cell membrane.

Up-regulation of epithelial Na(+) channel ENaC by human parvovirus B19 capsid protein VP1.

BACKGROUND: Clinical disorders caused by parvovirus B19 (B19V) infection include endothelial dysfunction with cardiac ischemia. The virus is effective in part by lysophosphatidylcholine-producing phospholipase A2 (PLA2) activity of B19V capsid protein VP1. Mechanisms compromising endothelial function include up-regulation of amiloride sensitive epithelial Na(+)-channel ENaC leading to endothelial cell stiffness. Regulators of ENaC include ubiquitin-ligase Nedd4-2. The present study explored whether VP1 modifies ENaC-activity. METHODS: cRNA encoding ENaC was injected into Xenopus oocytes without or with cRNA encoding VP1. Experiments were made with or without coexpression of Nedd4-2. ENaC activity was estimated from amiloride (50 µM) sensitive current. RESULTS: Injection of cRNA encoding ENaC into Xenopus oocytes was followed by appearance of amiloride sensitive current, which was significantly enhanced by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding PLA2-negative VP1 mutant (H153A). The effect of VP1 on ENaC was mimicked by treatment of ENaC expressing oocytes with lysophosphatidylcholine (1 µg/ml). The effect of VP1 and lysophosphatidylcholine was not additive. ENaC activity was downregulated by Nedd4-2, an effect not reversed by VP1. CONCLUSIONS: The B19V capsid protein VP1 up-regulates ENaC, an effect at least partially due to phospholipase A2 (PLA) dependent formation of lysophosphatidylcholine.

SPAK Sensitive Regulation of the Epithelial Na Channel ENaC.

BACKGROUND/AIMS: The WNK-dependent STE20/SPS1-related proline/alanine-rich kinase SPAK participates in the regulation of NaCl and Na(+),K(+),2Cl(-) cotransport and thus renal salt excretion. The present study explored whether SPAK has similarly the potential to regulate the epithelial Na(+) channel (ENaC). METHODS: ENaC was expressed in Xenopus oocytes with or without additional expression of wild type SPAK, constitutively active (T233E)SPAK, WNK insensitive (T233A)SPAK or catalytically inactive (D212A)SPAK, and ENaC activity estimated from amiloride (50 µM) sensitive current (Iamil) in dual electrode voltage clamp experiments. Moreover, Ussing chamber was employed to determine Iamil in colonic tissue from wild type mice (spak(wt/wt)) and from gene targeted mice carrying WNK insensitive SPAK (spak(tg/tg)). RESULTS: Iamil was observed in ENaC-expressing oocytes, but not in water-injected oocytes. In ENaC expressing oocytes Iamil was significantly increased following coexpression of wild-type SPAK and (T233E)SPAK, but not following coexpression of (T233A)SPAK or (D212A)SPAK. Colonic Iamil was significantly higher in spak(wt/wt) than in spak(tg/tg) mice. CONCLUSION: SPAK has the potential to up-regulate ENaC.