Glucagon-like peptide-1 receptor agonist and the relation between metabolic effects and cardiovascular outcomes: insight into mechanisms of action

Background

Glucagon-like Peptide-1 receptor agonists (GLP-1RAs) have been shown to lower cardiovascular risk, and they are likely to reduce the incidence of all-cause and cardiovascular mortality in patients with type 2 diabetes. In this study-level analysis we investigated how metabolic and blood pressure changes are related to the reduction of cardiovascular events with GLP-1RAs.

Methods

We included seven randomized, placebo-controlled trials (ELIXA, LEADER, SUSTAIN-6, REWIND, EXSCEL, PIONEER 6, Harmony Outcomes) reporting incidence of one or more of the following outcomes: MACE, stroke, myocardial infarction, cardiovascular death, all-cause death, for a total of 56004 patients. A Pearson correlation analysis between logHR for the occurrence of outcome and placebo-corrected changes in Hb1Ac, systolic blood pressure and weight was performed.

Findings

Reduction of HbA1c level was significantly related to the reduction of MACE, Pearson R 0.86 (p=0.006) and stroke, Pearson R 0.79 (p=0.018). The reduction of weight instead, showed a robust correlation, not only with reduction of MACE, Pearson R 0.75 (p=0.032) and stroke, Pearson R 0.71 (p=0.047), but also with reduction of both cardiovascular death, Pearson R 0.95 (p=0.003; Picture 1) and all-cause death, Pearson R 0.91 (p=0.013). Reduction of SBP was significantly related to the reduction of both cardiovascular death, Pearson R 0.84 (p=0.036) and all-cause death, Pearson R 0.88 (p=0.020), but not of MACE.

Discussion

Mechanism of GLP-1RAs in preventing MACE is not fully understood. Other drugs that improve glycemic control did not showed convincing effect on cardiovascular outcome. Our finding prompts some considerations: both weight loss and control of HbA1c levels could play a role in MACE reduction. On the other hand, GLP1-RAs could act through other mechanisms and the metabolic effect could be a marker of the drug potency and dosage. Based on mechanistic studies, a theorized mechanism of cardiovascular benefit seen with GLP-1 RA is thought to be an anti-atherothrombotic and lipid plaque stabilization effect. This seems particularly convincing seeing the strong relationship of weight change and major events reduction. Notably, reduction in cardiovascular mortality and all-cause mortality was not related to the anti-hyperglycemic effect. Contrarily the body weight and SBP reduction were strongly related to both cardiovascular and all-cause mortality. These features could support the presumption of a hypothetic GLP1-RAs mechanism in modulation of lipidic profile and in RAAS inhibition, which have been already proved as beneficial for primary and secondary cardiovascular prevention.

Conclusion

Cardiovascular protection from GLP1-RAs is not primarily related to HbA1c reduction itself. Our data suggest that GLP-1RAs with the greater metabolic impact, such as liraglutide and semaglutide, should be used to treat diabetic patients to prevent MACE and CV death.

Funding Acknowledgement

Type of funding sources: None.

Carbon dioxide: Global warning for nephrologists

The large prevalence of respiratory acid-base disorders overlapping metabolic acidosis in hemodialysis population should prompt nephrologists to deal with the partial pressure of carbon dioxide (pCO2) complying with the reduced bicarbonate concentration. What the most suitable formula to compute pCO2 is reviewed. Then, the neglected issue of CO2 content in the dialysis fluid is under the spotlight. In fact, a considerable amount of CO2 comes to patients' bloodstream every hemodialysis treatment and "acidosis by dialysate" may occur if lungs do not properly clear away this burden of CO2. Moreover, vascular access recirculation may be easy diagnosed by detecting CO2 in the arterial line of extracorporeal circuit if CO2-enriched blood from the filter reenters arterial needle.

The First Report of Bayés Syndrome in Hemodialysis Patient

A chronic hemodialysis patient-known to have advanced interatrial block (IAB)-had reported symptoms suggesting arrhythmias, hence she underwent hemodialysis treatment while on the cardiac monitor. This allowed us to recognize the occurrence of paroxysmal atrial fibrillation and, in turn, disclose the first case of Bayés syndrome. Even though atrial fibrillation and IAB are very frequent in hemodialysis patients, Bayés syndrome, that comprehends both, has never been described, likely because the IAB is often overlooked and undiagnosed. This case could improve the awareness of IAB and of the Bayés syndrome in hemodialysis population.

Differential cystine and dibasic amino acid handling after loss of function of the amino acid transporter b0,+AT (Slc7a9) in mice

Cystinuria is an autosomal recessive disease caused by mutations in SLC3A1 ( rBAT) and SLC7A9 ( b 0,+ AT). Gene targeting of the catalytic subunit ( Slc7a9) in mice leads to excessive excretion of cystine, lysine, arginine, and ornithine. Here, we studied this non-type I cystinuria mouse model using gene expression analysis, Western blotting, clearance, and brush-border membrane vesicle (BBMV) uptake experiments to further characterize the renal and intestinal consequences of losing Slc7a9 function. The electrogenic and BBMV flux studies in the intestine suggested that arginine and ornithine are transported via other routes apart from system b0,+. No remarkable gene expression changes were observed in other amino acid transporters and the peptide transporters in the intestine and kidney. Furthermore, the glomerular filtration rate (GFR) was reduced by 30% in knockout animals compared with wild-type animals. The fractional excretion of arginine was increased as expected (∼100%), but fractional excretions of lysine (∼35%), ornithine (∼16%), and cystine (∼11%) were less affected. Loss of function of b0,+AT reduced transport of cystine and arginine in renal BBMVs and completely abolished the exchanger activity of dibasic amino acids with neutral amino acids. In conclusion, loss of Slc7a9 function decreases the GFR and increases the excretion of several amino acids to a lesser extent than expected with no clear regulation at the mRNA and protein level of alternative transporters and no increased renal epithelial uptake. These observations indicate that transporters located in distal segments of the kidney and/or metabolic pathways may partially compensate for Slc7a9 loss of function.

Kidney-specific inactivation of Ofd1 leads to renal cystic disease associated with upregulation of the mTOR pathway

The oral-facial-digital type I syndrome (OFDI; MIM 311200) is a rare syndromic form of inherited renal cystic disease. It is transmitted as an X-linked dominant, male lethal disorder and is caused by mutations in the OFD1 gene. Previous studies demonstrated that OFDI belongs to the growing number of disorders ascribed to dysfunction of primary cilia. We generated a conditional inactivation of the mouse Ofd1 gene using the Ksp-Cre transgenic line, which resulted in a viable model characterized by renal cystic disease and progressive impairment of renal function. The study of this model allowed us to demonstrate that primary cilia initially form and then disappear after the development of cysts, suggesting that the absence of primary cilia is a consequence rather than the primary cause of renal cystic disease. Immunofluorescence and western blotting analysis revealed upregulation of the mTOR pathway in both dilated and non-dilated renal structures. Treatment with rapamycin, a specific inhibitor of the mTOR pathway, resulted in a significant reduction in the number and size of renal cysts and a decrease in the cystic index compared with untreated mutant animals, suggesting that dysregulation of this pathway in our model is mTOR-dependent. The animal model we have generated could thus represent a valuable tool to understand the molecular link between mTOR and cyst development, and eventually to the identification of novel drug targets for renal cystic disease.

Female ROMK null mice manifest more severe Bartter II phenotype on renal function and higher PGE2 production

ROMK null mice with a high survival rate and varying severity of hydronephrosis provide a good model to study type II Bartter syndrome pathophysiology (26). During the development of such a colony, we found that more male than female null mice survived, 58.7% vs. 33.3%. To investigate the possible mechanism of this difference, we compared the survival rates, renal functions, degree of hydronephrosis, as well as PGE(2) and TXB(2) production between male and female ROMK wild-type and null mice. We observed that female ROMK Bartter's mice exhibited lower GFR (0.37 vs. 0.54 ml.min(-1).100 g BW(-1), P < 0.05) and higher fractional Na(+) excretion (0.66% vs. 0.48%, P < 0.05) than male Bartter's. No significant differences in acid-base parameters, urinary K(+) excretion, and plasma electrolyte concentrations were observed between sexes. In addition, we assessed the liquid retention rate in the kidney to evaluate the extent of hydronephrosis and observed that 67% of male and 90% of female ROMK null mice were hydronephrotic mice. Urinary PGE(2) excretion was higher in both sexes of ROMK null mice: 1.35 vs. 1.10 ng/24 h in males and 2.90 vs. 0.87 ng/24 h in females. TXB(2) excretion was higher in female mice in both wild-type and ROMK null mice. The increments of urinary PGE(2) and TXB(2) were significantly higher in female null mice than males, 233.33% vs. 22.74% of PGE(2) and 85.67% vs. 20.36% of TXB(2). These data demonstrate a more severe Bartter phenotype in female ROMK null mice, and higher PGE(2) and TXB(2) production may be one of the mechanisms of this manifestation.

Mouse model of type II Bartter's syndrome. I. Upregulation of thiazide-sensitive Na-Cl cotransport activity

ROMK-deficient (Romk(-/-)) mice exhibit polyuria, natriuresis, and kaliuresis similar to individuals with type II Bartter's form of hyperprostaglandin E syndrome (HPS; antenatal Bartter's syndrome). In the present study, we utilized both metabolic and clearance studies to define the contributions of specific distal nephron segments to the renal salt wasting in these mice. The effects of furosemide, hydrochlorothiazide, and benzamil on urinary Na(+) and K(+) excretion in both wild-type (Romk(+/+)) and Romk(-/-) mice were used to assess and compare salt transport by the Na(+)-K(+)-2Cl(-) cotransporter (NKCC2)-expressing thick ascending limb (TAL), the Na(+)-Cl(-) cotransporter (NCC)-expressing distal convoluted tubule (DCT1/DCT2), and the epithelial Na(+) channel (ENaC)-expressing connecting segment (CNT) and collecting duct (CD), respectively. Whole kidney glomerular filtration rate was reduced by 47% in Romk(-/-) mice. Furosemide-induced increments in the fractional excretion rate of Na(+) and K(+) and absolute excretion of Na(+) and K(+) were significantly blunted in Romk(-/-) mice, consistent with a major salt transport defect in the TAL. In contrast, hydrochlorothiazide produced an exaggerated natriuresis in Romk(-/-) mice, indicating upregulation of salt absorption by the DCT. Benzamil resulted in a similar increment in absolute Na excretion in both Romk(-/-) and Romk(+/+), indicating no significant upregulation of Na(+) transport by ENaC in ROMK null mice. Moreover, hydrochlorothiazide increased the fractional K(+) excretion rate in Romk(-/-) mice, confirming our recent observation that maxi-K channels contribute to distal K(+) secretion in the absence of ROMK.

Maxi-K channels contribute to urinary potassium excretion in the ROMK-deficient mouse model of Type II Bartter's syndrome and in adaptation to a high-K diet

Type II Bartter's syndrome is a hereditary hypokalemic renal salt-wasting disorder caused by mutations in the ROMK channel (Kir1.1; Kcnj1), mediating potassium recycling in the thick ascending limb of Henle's loop (TAL) and potassium secretion in the distal tubule and cortical collecting duct (CCT). Newborns with Type II Bartter are transiently hyperkalemic, consistent with loss of ROMK channel function in potassium secretion in distal convoluted tubule and CCT. Yet, these infants rapidly develop persistent hypokalemia owing to increased renal potassium excretion mediated by unknown mechanisms. Here, we used free-flow micropuncture and stationary microperfusion of the late distal tubule to explore the mechanism of renal potassium wasting in the Romk-deficient, Type II Bartter's mouse. We show that potassium absorption in the loop of Henle is reduced in Romk-deficient mice and can account for a significant fraction of renal potassium loss. In addition, we show that iberiotoxin (IBTX)-sensitive, flow-stimulated maxi-K channels account for sustained potassium secretion in the late distal tubule, despite loss of ROMK function. IBTX-sensitive potassium secretion is also increased in high-potassium-adapted wild-type mice. Thus, renal potassium wasting in Type II Bartter is due to both reduced reabsorption in the TAL and K secretion by max-K channels in the late distal tubule.

Acid-base transport in Henle's loop: the effects of reduced renal mass and diabetes

The loop of Henle (LOH) is an important site of renal acidification. Using the in vivo microperfusion technique of LOH combined with quantitative polymerase chain reaction (PCR) performed on isolated thick ascending limbs (TAL), we demonstrated that the Na + -H + exchanger is the main transport mechanism involved, although a small, but significant contribution from the H+-ATPase also occurs. Among the various Na+-H+ exchanger isoforms we have evidenced that NHE3 is expressed and functionally active along the TAL. Since the LOH is exposed to osmotic stress, bicarbonate transport was also measured under medullary hypotonicity conditions, which led to the stimulation of bicarbonate reabsorption. We demonstrated that the LOH can participate in the tubular adaptation to an increased filtered bicarbonate load by increasing net LOH bicarbonate transport. In this setting, at the molecular level, mRNA and protein abundance of NHE3 were also stimulated, and coincided with an increase in NHE3 activity. Finally, NHE3 expression and abundance was highly stimulated in the early phase of diabetes, which is characterized by increased glomerular filtration rate (GFR).

Use of transgenic mice in acid-base balance studies

The kidney is essential in maintaining body acid-base status. Recently, the use of transgenic mice has largely contributed to the understanding of the mechanisms involved. Important issues have been addressed in terms of the function of proteins or their regulation. In the proximal tubule, the role of Na+/HCO3-cotransport has been established, although further studies are needed to understand how its mutations lead to renal disease. Na+/H+ exchange has also been extensively studied, and its role in diuretic and natriuretic responses following an increase in blood pressure has been elucidated. The interaction of other transport proteins, such as the Na+/phosphate cotransporter NaPi II-a, with the Na+/H+ exchanger has also been investigated. In the medullary thick ascending limb of Henle's loop (MTAL), a role for NHE1 in transepithelial HCO3- absorption has been demonstrated: basolateral NHE1 controls the function of apical NHE3. As for the distal nephron, the majority of observations suggest that the regulation of H+-ATPase activity in response to acid-base status is mediated by the trafficking of pumps or pump sub-units, especially for the a4 subunit, rather than changes in subunit expression levels. Furthermore, the function of pendrin, a chloride/anion exchanger, has been assessed in response to changes in acid-base status. Important results have been obtained regarding the regulation of proximal tubule transport by several mechanisms, such as microvilli changes and the inducible and endothelial isoform of nitric oxide synthase (NOS). Finally, the interaction of chloride channels and potassium-chloride cotransporter with proton secretion has been evaluated. These findings highlight the importance of knockout animal models in studying kidney regulation of acid-base balance.

Channels, carriers, and pumps in the pathogenesis of sodium-sensitive hypertension

Sodium-sensitive hypertension is thought to be dependent on primary alterations in renal tubular sodium reabsorption. The major apical plasma membrane Na(+) transporters include the proximal tubular Na(+)-H(+) exchanger, the thick ascending limb Na(+)-K(+)-2Cl(-) cotransport system, the distal tubular Na(+)-Cl(-) cotransporter, and the collecting duct epithelial sodium channel (ENaC). This article explores the role of each transporter in the pathogenesis of hypertension. Although the contribution of the proximal tubule Na(+)-H(+) exchanger is not yet defined completely, more convincing data have been generated about the importance of the Na(+)-K(+)-2Cl(-). Indeed at least 2 forms of hypertension appear to be related to the up-regulation of the transporter: the so-called programmed hypertension induced by low-protein diet during pregnancy and the early phase of hypertension in the Milan strain of rats. With respect to the Na(+)-Cl(-) cotransporter this may be overactive caused by inactivating mutation of WNK4 as in the Gordon syndrome, although it is the main actor for the maintenance phase of the hypertension found in the Milan strain of rats. Finally, the contribution of the ENaC has been established clearly; indeed, in the Liddle syndrome the mutation of the ENaC gene leads to a longer retention of the channel on the cell surface of collecting duct principal cells, thus inducing stronger sodium reabsorption along this segment. All these examples clearly indicate that renal sodium transporters may be responsible for various types of sodium-sensitive hypertension.

[Glomerulo-tubular balance in diabetes mellitus: molecular evidence and clinical consequences]

Diabetes mellitus is fast becoming a world epidemic. About one-third of individuals with diabetes, after 10 yrs, develop diabetic nephropathy, the first cause of end-stage kidney disease. The evolution of diabetic nephropathy can be considered in three stages: glomerular hyperfiltration, microalbuminuria (30-300 mg/24 hr) and proteinuria (>300 mg/24 hr). This study was designed to investigate the tubular basis of glomerular hyperfiltration in early diabetes mellitus. Diabetes was inducted in rats with i.p. streptozotocin (65 mg/kg bw) for 6 days. At the end of the treatment, the glomerular filtration rate (GFR), measured by inulin clearance, had substantially increased in diabetic rats compared with controls. Quantitative polymerase chain reaction (PCR) and Western blot analysis reveal that in diabetic rats compared with controls, mRNA and protein abundance was higher for type 3 sodium/hydrogen exchanger (NHE3) in proximal tubule and ascending limbs of Henle's loop, and higher for bumetanide-sensitive sodium-potassium-2 chloride cotransporter (NKCC2) in ascending limbs of Henle's loop. Western blot analysis confirmed the PCR results. Finally, the abundance of á -ENaC protein was unchanged in diabetic rats compared to controls. These results show that the primary sodium reabsorption increase in proximal tubule reduces salt concentrations at the macula densa. This elicits a tubuloglomerular feedback-dependent increase in single nephron GFR.

[Spontaneous (idiopathic) pneumopericardium. A case report and review of the literature]

Pneumopericardium is a rare entity, but it can occur in a wide variety of clinical situations. The spontaneous cases are very rare and generally can be associated with some predisposing or precipitating conditions. We report a case in which the pathogenesis of pneumopericardium undefined after conventional diagnostic clinical investigation. A concise review of the recent literature is presented, and some practical clinical remarks are made.

Cisplatin-cyclophosphamide-mitomycin combination chemotherapy with supportive care versus supportive care alone for treatment of metastatic non-small-cell lung cancer

BACKGROUND

Patients with TNM stage IV non-small-cell lung cancer have short survival times. Previous controlled studies comparing chemotherapy and supportive care for the treatment of this type of cancer have not given consistent results, have included patients with different disease stages, and have rarely reported drug dose intensity.

PURPOSE

The present trial was designed to assess the safety and the effect on survival of supportive care alone versus chemotherapy with cisplatin, cyclophosphamide, and mitomycin combined with appropriate supportive care in patients with stage IV non-small-cell lung cancer.

METHODS

Patients (n = 102) with stage IV non-small-cell lung cancer were randomly assigned to one of two treatment regimens. The combined modality group (52 patients) received supportive care along with cisplatin (75 mg/m2), cyclophosphamide (400 mg/m2), and mitomycin (10 mg/m2) given intravenously at 3-week intervals. The supportive care group (50 patients) received supportive care alone. Randomization was stratified on the basis of histology (squamous versus nonsquamous cell carcinoma), performance status (Karnofsky), and weight loss (during the 6 months preceding randomization). The two groups were well matched for age and sex. Survival analysis was performed after the last patient died.

RESULTS

The median number of chemotherapy cycles was 3.5 per patient. Mean weekly delivered doses of drugs were as follows: cisplatin, 22.1 mg/m2; cyclophosphamide, 118 mg/m2; and mitomycin, 2.9 mg/m2. Toxic effects due to chemotherapy were generally mild, but peripheral neuropathy and hematologic and renal toxic effects were observed. In the supportive care group, mean survival was 6.1 months (median, 4.0 months); six patients lived at least 12 months and two lived at least 18 months. In the combined modality group, mean survival was 11.3 months (median, 8.5 months); 20 patients lived at least 12 months, 13 lived at least 18 months, and five lived at least 24 months. Difference in survival was statistically significant (P < .0001). Survival was directly related to initial performance status in both groups (P < .01) and was significantly (P < .01) longer for patients with squamous cell carcinoma than for those with nonsquamous cell carcinoma.

CONCLUSIONS

The combination of supportive care and cisplatin-cyclophosphamide-mitomycin therapy offers a survival advantage over supportive care alone in patients with advanced non-small-cell lung cancer.

IMPLICATIONS

Metastatic non-small-cell lung cancer, generally considered to be unresponsive or marginally responsive to chemotherapy, can be treated with chemotherapy, with an expectation of prolonging patient survival. Although the results of the present study are encouraging, clinical research should continue to be directed toward developing more effective treatments for this disease.

[Cyclophosphamide, adriamycin and platinum (CAP) in the preoperative neoadjuvant phase and the therapy phase]

Forty-two patients with metastasized, and 7 patients with locally advanced forms of carcinoma of the breast were treated with a combination of three drugs: CTX 200-400 mg/sq.m. on days 1, 3 and 5, ADM 40 mg/sq.m. on day 1, and DDP 30 mg/sq.m. on days 1, 3 and 5 (CAP), every 21 days. The 42 patients with metastasized carcinoma had already received substantial pre-treatment by surgery and with adjuvant polychemotherapy +/- chemotherapy on recurrence +/- hormonotherapy +/- radiotherapy. The disease sites were: bone (30%), skin (19%), lymph nodes (13.5%), pleura (12.5%), lung (12%) and liver (11%). The 7 patients with locally advanced carcinoma had not been pre-treated; they received the same chemotherapy in the pre-operative neo-adjuvant phase. Positive responses to CAP in the cases with metastasized carcinoma according to individual disease sites (37 pre-treated patients assessable after at least two courses of therapy) were as follows in percentage terms: 24% bone lesions, 56% skin lesions, 77% lymph node lesions, 30% liver lesions, 56% lung lesions, 22% pleural lesions. 3/37 patients (8%) showed complete remission in all disease sites, while 6/37 showed partial remission. This percentage (8 + 16 = 24%) is encouraging, as CAP, in these patients, represents on average the 3rd to 4th line of therapy. Responses to neo-adjuvant CAP therapy (7 patients assessable after at least two courses of therapy) were as follows: 5 patients showed partial remission after 3-6 courses, 1 complete remission, and 1 objective improvement.(ABSTRACT TRUNCATED AT 250 WORDS)

[Variation in weight and food intake of rats exposed to a high-intensity electrical field at 50 Hz]

The effects of exposure to electric fields at 50 Hz of various intensities (100, 25, 10 kV/m) on the food intake and body growth were determined in the rat at various stages of development. The different field intensities were induced between 1.5 by 2 m steel plates. At 100 kV/m, 25 rats were exposed 8 h/d for 48 days. In respect to controls, after 2 weeks of exposure a marked decrease of the growth rate was observed in exposed animals, but not of the food intake. At 25 kV/m 11 animals, 28 days old, were exposed 8 h/d for 35 days. A slight decrease in growth rate, statistically significant only at the 23rd and the 26th day of exposure, was found. No effect was observed on food intake and full recovery of body weight of exposed animals was achieved in 4 weeks after the end of the exposure. At 10 kV/m, in addition to 5 rats 28 days old, exposed 8 h/d for 35 days and to the corresponding controls, 15 "sham exposed" animals were studied. No significant difference in growth rate was found between the exposed animals and the two other groups. Food intake of exposed was for two weeks of treatment the same of control animals. Thereafter, there was tendency toward a higher food intake in the exposed animals being significant during recovery.

Effect of maternal diet on ganglioside distribution in fetal rat brain

Female rats were fed a diet with low protein content or with low and high amount of essential fatty acids (EFA). Ganglioside content and distribution were analyzed in the brain of animals at two different periods of fetal life (15th or 20th day). In the fetuses from mothers fed the diet with low amount of EFA the content of ganglioside is significantly lower than in the control group. The three diets resulted in the modification of ganglioside pattern, mainly for the animals on the 15th day of gestation.

Na+ dependence of phenacetin absorption

Phenacetin in solution at different concentrations of Na+ was orally administered to dogs. Phenacetin absorption is increased by the Na+: a positive correlation was noted between the Na+ concentration in the medium and the plasma levels of phenacetin. Ouabain antagonizes the effect of Na+ on phenacetin absorption.