Thiazolidinediones and Edema: Recent Advances in the Pathogenesis of Thiazolidinediones-Induced Renal Sodium Retention

Thiazolidinediones (TZDs) are one of the major classes of antidiabetic drugs that are used widely. TZDs improve insulin resistance by activating peroxisome proliferator-activated receptor gamma (PPARγ) and ameliorate diabetic and other nephropathies, at least, in experimental animals. However, TZDs have side effects, such as edema, congestive heart failure, and bone fracture, and may increase bladder cancer risk. Edema and heart failure, which both probably originate from renal sodium retention, are of great importance because these side effects make it difficult to continue the use of TZDs. However, the pathogenesis of edema remains a matter of controversy. Initially, upregulation of the epithelial sodium channel (ENaC) in the collecting ducts by TZDs was thought to be the primary cause of edema. However, the results of other studies do not support this view. Recent data suggest the involvement of transporters in the proximal tubule, such as sodium-bicarbonate cotransporter and sodium-proton exchanger. Other studies have suggested that sodium-potassium-chloride cotransporter 2 in the thick ascending limb of Henle and aquaporins are also possible targets for TZDs. This paper will discuss the recent advances in the pathogenesis of TZD-induced sodium reabsorption in the renal tubules and edema

Insulin Resistance, Obesity, Hypertension, and Renal Sodium Transport

Sodium transport through various nephron segments is quite important in regulating sodium reabsorption and blood pressure. Among several regulators of this process, insulin acts on almost all the nephron segments and is a strong enhancer of sodium reabsorption. Sodium-proton exchanger type 3 (NHE3) is a main regulator of sodium reabsorption in the luminal side of proximal tubule. In the basolateral side of the proximal tubule, sodium-bicarbonate cotransporter (NBCe1) mediates sodium and bicarbonate exit from tubular cells. In the distal nephron and the connecting tubule, epithelial sodium channel (ENaC) is of great importance to sodium reabsorption. NHE3, NBCe1, and ENaC are all regulated by insulin. Recently with-no-lysine (WNK) kinases, responsible for familial hypertension, stimulating sodium reabsorption in the distal nephron, have been found to be also regulated by insulin. We will discuss the regulation of renal sodium transport by insulin and its roles in the pathogenesis of hypertension in insulin resistance

The impact of patients' social backgrounds assessment on nursing care: Qualitative research

Abstract Background Although nurses are expected to address the social determinants of health (SDH) in clinical settings, the perspectives of front‐line nurses on the integration of SDH into their clinical practice remain unclear. Understanding the dynamism of this integration and its outcomes can yield crucial insights into effective nursing care. This study aims to elucidate the integration and adoption of tool‐based SDH assessment nursing programs and their impacts on daily nursing care. Methods We conducted qualitative research at a small community‐based hospital in Japan, where a tool‐based program characterized by social background interviews and documentation was implemented. Nurses at the hospital were recruited via purposive and snowball sampling. After hypothesis generation, semi‐constructed in‐depth online interviews were conducted. Each interview lasted between 30 and 50 min. The data were analyzed via thematic analysis using the framework approach. Results A total of 16 nurses participated. Participants' incorporation of the novel SDH assessment program was bolstered by prior learning and their recognition of its practical value. Institutional support and collaborative teamwork further facilitated the adoption of this innovation. Enhanced knowledge about the social contexts of their patients contributed to increased respect, empathy, and self‐affirmation among participants, consequently enhancing the quality of nursing care. Conclusion Through team‐based learning, reflection, and support, nurses can integrate a tool‐based SDH assessment program into their daily nursing practice. This program has the potential to empower nurses to deliver more holistic care and redefine their professional identity. Further research is warranted to assess patient‐reported outcomes

Primary care physicians’ perceptions of social determinants of health recommendations: a qualitative study

Background: Several organisations have called for primary care professionals to address social determinants of health (SDoH) in clinical settings. For primary care physicians to fulfill their community health responsibilities, the implications of the SDoH recommendations need to be clarified. Aim: To describe primary care physicians’ views about being asked to address SDoH in clinical settings, from both positive and negative perspectives. Design & setting: A qualitative study in Japan. Twenty-one physicians were purposively recruited. Method: ‘Love and breakup letter’ methodology was used to collect qualitative data that contained both positive and negative feelings. Participants wrote love and breakup letters about being asked to address SDoH in a clinical setting, then undertook an in-depth online interview. Data were analysed via thematic analysis using the framework approach. Results: The following themes were identified: (i) primary care physicians take pride in being expected to address SDoH; (ii) primary care physicians rely on the recommendations as a partner, even in difficult situations; (iii) primary care physicians consider the recommendations to be bothersome, with unreasonable demands and challenges, especially when supportive surroundings are lacking; and (iv) primary care physicians reconstruct the recommendations on the basis of their experience. Conclusion: Primary care physicians felt both sympathy and antipathy towards recommendations asking them to address SDoH in their clinical practice. The recommendations were not followed literally, instead contributing to physicians’ clinical mindlines. Professional organisations that plan to develop and publish recommendations about SDoH should consider how their recommendations might be perceived by their target audience

Residents' learning and behavior about tool‐guided clinical assessment of social determinants of health

Abstract Background The specific dimensions of learners that have been impacted by educational programs related to social determinants of health (SDoH) remain unknown. This study aims to elucidate how learners are affected by postgraduate education (a single 90‐min educational session) regarding tool‐guided clinical assessment of patients' social backgrounds. Methods A pretest‐posttest design was utilized in which residents (postgraduate year (PGY) 1 or 2) and fellows in family medicine (PGY over 3) were recruited. Likert‐type questions were developed based on previous qualitative findings. Participants answered these questions before, immediately after, and 1.5 months after the educational session on tool‐guided clinical SDoH assessment. Paired‐sample t‐tests were used, and effect size was measured using Cohen's d. Results A total of 114 residents and fellows participated. After the session, participants expressed more interest in knowing their patients' social backgrounds when considering how to address their patients and were more open to embracing a pre‐established assessment framework. Participants also considered clinical skills related to SDoH as learnable and improved their attitude toward patients. They reported that they did not perform specific interventions related to SDoH within 1.5 months after the session. Unlike previous qualitative findings, their concern about the implementation of SDoH‐related practices did not increase significantly. Conclusion An educational session on tool‐guided SDoH assessment may have a positive impact on learners' attitudes related to addressing patients' social backgrounds without fostering concerns

Roles of Akt and SGK1 in the Regulation of Renal Tubular Transport

A serine/threonine kinase Akt is a key mediator in various signaling pathways including regulation of renal tubular transport. In proximal tubules, Akt mediates insulin signaling via insulin receptor substrate 2 (IRS2) and stimulates sodium-bicarbonate cotransporter (NBCe1), resulting in increased sodium reabsorption. In insulin resistance, the IRS2 in kidney cortex is exceptionally preserved and may mediate the stimulatory effect of insulin on NBCe1 to cause hypertension in diabetes via sodium retention. Likewise, in distal convoluted tubules and cortical collecting ducts, insulin-induced Akt phosphorylation mediates several hormonal signals to enhance sodium-chloride cotransporter (NCC) and epithelial sodium channel (ENaC) activities, resulting in increased sodium reabsorption. Serum- and glucocorticoid-inducible kinase 1 (SGK1) mediates aldosterone signaling. Insulin can stimulate SGK1 to exert various effects on renal transporters. In renal cortical collecting ducts, SGK1 regulates the expression level of ENaC through inhibition of its degradation. In addition, SGK1 and Akt cooperatively regulate potassium secretion by renal outer medullary potassium channel (ROMK). Moreover, sodium-proton exchanger 3 (NHE3) in proximal tubules is possibly activated by SGK1. This review focuses on recent advances in understanding of the roles of Akt and SGK1 in the regulation of renal tubular transport

Selective Insulin Resistance in the Kidney

Insulin resistance has been characterized as attenuation of insulin sensitivity at target organs and tissues, such as muscle and fat tissues and the liver. The insulin signaling cascade is divided into major pathways such as the PI3K/Akt pathway and the MAPK/MEK pathway. In insulin resistance, however, these pathways are not equally impaired. For example, in the liver, inhibition of gluconeogenesis by the insulin receptor substrate (IRS) 2 pathway is impaired, while lipogenesis by the IRS1 pathway is preserved, thus causing hyperglycemia and hyperlipidemia. It has been recently suggested that selective impairment of insulin signaling cascades in insulin resistance also occurs in the kidney. In the renal proximal tubule, insulin signaling via IRS1 is inhibited, while insulin signaling via IRS2 is preserved. Insulin signaling via IRS2 continues to stimulate sodium reabsorption in the proximal tubule and causes sodium retention, edema, and hypertension. IRS1 signaling deficiency in the proximal tubule may impair IRS1-mediated inhibition of gluconeogenesis, which could induce hyperglycemia by preserving glucose production. In the glomerulus, the impairment of IRS1 signaling deteriorates the structure and function of podocyte and endothelial cells, possibly causing diabetic nephropathy. This paper mainly describes selective insulin resistance in the kidney, focusing on the proximal tubule

Memantine has no effect on KATP channels in pancreatic β cells

Abstract Objective Memantine, a drug for Alzheimer’s disease, is considered to suppress excessive stimulation of N-methyl-d-aspartic acid receptors and to prevent neuronal death. However, a recent report indicated that the neuronal KATP channel also can become a target of memantine. The KATP channel is a key regulator of insulin secretion in pancreatic β cells. Therefore, if memantine could inhibit the KATP channel in pancreatic β cells, it would be an effective drug for both Alzheimer’s disease and diabetes. However, there is no report on the effect of memantine on the KATP channel in pancreatic β cells. Therefore, we investigated whether memantine affect the blood glucose level, insulin secretion and KATP channel activity in pancreatic β cells. Results An intraperitoneal glucose tolerance test was performed with or without memantine (1 mg/kg) injection in intact mice. Insulin secretion from isolated islets was measured under low (2 mM) and high (20 mM) glucose concentrations with or without memantine (1 μM). The effect of memantine (1 μM) on KATP channel currents in isolated pancreatic β cells was recorded using the whole-cell patch-clamp technique. Memantine had no effect on the blood glucose level, insulin secretion from isolated islets or KATP channel current in pancreatic β cells