Prognosis of HIV infected sub-Saharan patients on renal replacement therapy (RRT) in Brussels, Belgium: a single centre retrospective pilot study and review of the literature

BACKGROUND

Few data exist documenting the survival experience of immigrated sub-Saharan patients infected by the human immunodeficiency virus (HIV) on renal replacement therapy (RRT).

METHODS

This retrospective single centre pilot study includes 105 consecutive patients of sub-Saharan origin who started RRT in our unit, between January 1986 and April 2010. The aim was to analyse the characteristics and the survival rate on RRT of these patients.

RESULTS

Out of 105 patients 81/105 (77%) were HIV-negative and 24/105(23%) were HIV-positive. HIV-positive patients were younger than HIV-negative patients and they were more often treated with peritoneal dialysis (PD) (21/24) than with haemodialysis (HD). Dialysis peritonitis was equally distributed between HIV-positive and HIV-negative patients. Because of opportunistic infections, duration of hospitalisation was longer for HIV-positive than for HIV-negative patients. In PD-treated patients, the number of hospitalisations tended to be greater in patients who experienced at least one peritonitis episode and the duration of hospitalisation also tended to be longer. The survival rate was better in patients younger than 50 years and in patients on HD, but was similar for both positive and negative HIV patients.

CONCLUSIONS

To the best of our knowledge, these are the first data concerning patients who have emigrated from sub-Saharan Africa to Belgium, and who are on RTT. Their survival rate is better if they are younger than 50 years and on HD. As the majority of HIV patients were treated by PD in our center, a conclusion regarding survival on different dialysis modalities is not possible for this group of patients. Survival rates were similar for HIV-positive and HIV-negative patients despite longer duration of hospisalization for HIV-positive patients.

Comparative effects of GTPgammaS and insulin on the activation of Rho, phosphatidylinositol 3-kinase, and protein kinase N in rat adipocytes. Relationship to glucose transport

Electroporation of rat adipocytes with guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) elicited sizable insulin-like increases in glucose transport and GLUT4 translocation. Like insulin, GTPgammaS activated membrane phosphatidylinositol (PI) 3-kinase in rat adipocytes, but, unlike insulin, this activation was blocked by Clostridium botulinum C3 transferase, suggesting a requirement for the small G-protein, RhoA. Also suggesting that Rho may operate upstream of PI 3-kinase during GTPgammaS action, the stable overexpression of Rho in 3T3/L1 adipocytes provoked increases in membrane PI 3-kinase activity. As with insulin treatment, GTPgammaS stimulation of glucose transport in rat adipocytes was blocked by C3 transferase, wortmannin, LY294002, and RO 31-8220; accordingly, the activation of glucose transport by GTPgammaS, as well as insulin, appeared to require Rho, PI 3-kinase, and another downstream kinase, e.g. protein kinase C-zeta (PKC-zeta) and/or protein kinase N (PKN). Whereas insulin activated both PKN and PKC-zeta, GTPgammaS activated PKN but not PKC-zeta. In transfection studies in 3T3/L1 cells, stable expression of wild-type Rho and PKN activated glucose transport, and dominant-negative forms of Rho and PKN inhibited insulin-stimulated glucose transport. In transfection studies in rat adipocytes, transient expression of wild-type and constitutive Rho and wild-type PKN provoked increases in the translocation of hemagglutinin (HA)-tagged GLUT4 to the plasma membrane; in contrast, transient expression of dominant-negative forms of Rho and PKN inhibited the effects of both insulin and GTPgammaS on HA-GLUT4 translocation. Our findings suggest that (a) GTPgammaS and insulin activate Rho, PI 3-kinase, and PKN, albeit by different mechanisms; (b) each of these signaling substances appears to be required for, and may contribute to, increases in glucose transport; and (c) PKC-zeta may contribute to increases in glucose transport during insulin, but not GTPgammaS, action.

2-Hydroxypropyl-beta-cyclodextrin enhances phorbol ester effects on glucose transport and/or protein kinase C-beta translocation to the plasma membrane in rat adipocytes and soleus muscles

In rat adipocytes and soleus muscles, 2-hydroxypropyl-beta-cyclodextrin (CD) was found to have a relatively small or no effect on basal or insulin-stimulated hexose uptake, but markedly enhanced hexose uptake effects of phorbol esters and/or diacylglycerol. In rat adipocytes, the CD-induced enhancement of hexose uptake during concurrent phorbol ester treatment was not associated with an increase in GLUT4 glucose transporter translocation to the plasma membrane, which was stimulated comparably by insulin and phorbol esters. Moreover, CD appeared to activate or facilitate the activation of glucose transporters subsequent to their translocation to the plasma membrane during ongoing phorbol ester treatment. In rat adipocytes, CD also enhanced the translocation of protein kinase C (PKC)-beta to the plasma membrane during the action of phorbol esters, which alone had little or no effect on this specific PKC translocation. Although it is uncertain how CD alters the function of plasma membranes to enhance the translocation of PKC-beta to, and the activation of glucose transporters within, this subcellular fraction during phorbol ester treatment, our findings provide direct support for a two-step model in the activation of glucose transport. In addition, it seems clear that, at least in some cell types, simple phorbol ester treatment does not necessarily serve as a ubiquitous activator of all activable PKC pools and all potential PKC-mediated responses.

Effects of insulin on diacylglycerol/protein kinase-C signalling and glucose transport in rat skeletal muscles in vivo and in vitro

Insulin treatment in vivo provoked rapid dose-related increases in diacylglycerol content and/or translocation of protein kinase-C (PKC) from cytosol to membranes in rat soleus and gastrocnemius muscles. These effects were apparent with 1) insulin doses that provoked submaximal and maximal increases in glucose utilization, and 2) glucose-stimulated endogenous insulin secretion. Insulin-stimulated PKC translocation was evident when PKC was assayed by 1) histone or protamine phosphorylation after PKC purification by Mono Q column chromatography, and 2) immunoblotting for PKC beta and PKC epsilon. Dose-related effects of insulin on PKC translocation were also observed in the rat soleus in vitro, and this was associated with increased phosphorylation of 40- and 80-kilodalton proteins, which were also phosphorylated by phorbol ester treatment. A role for diacylglycerol-PKC signalling in insulin-stimulated glucose transport was suggested by studies of [3H]2-deoxyglucose ([3H]2-DOG) uptake in the rat soleus in vitro in that 1) PKC translocation and 2-DOG uptake were correlated; and 2) stimulatory effects of insulin and phorbol esters on 2-DOG uptake were apparently nonadditive.

Sulfonylurea-stimulated glucose transport association with diacylglycerollike activation of protein kinase C in BC3H1 myocytes

The extrapancreatic effects of sulfonylurea drugs include increased glucose uptake by certain peripheral tissues. To study this effect, we used BC3H1 myocytes, which are reported to respond to these drugs. Within 30 min, tolbutamide and glyburide increased [3H]-2-deoxyglucose uptake in a dose-dependent manner. The inactive analogue carboxytolbutamide had no effect on glucose transport. Because increases in glucose transport may be mediated by activation of the diacylglycerol-protein kinase C signaling system, we examined the effects of these drugs on lipid metabolism and protein kinase C activity. Unlike insulin, tolbutamide and glyburide failed to increase [3H]glycerol labeling of diacylglycerol or labeling of phospholipids by 32P. After 30 min of treatment with tolbutamide or glyburide, however, membrane-associated and cytosolic protein kinase C activity were each increased. When cells were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 48 h to deplete certain isoforms of protein kinase C, glyburide, tolbutamide, and acute TPA treatment failed to increase glucose uptake, suggesting that TPA and sulfonylureas operate through activation of a common pathway. The effect of glyburide was additive to TPA in stimulating glucose uptake at low but not high TPA concentrations. As with insulin and TPA, extracellular Ca2+ was not essential for sulfonylurea-stimulated glucose uptake. Staurosporine, a protein kinase C inhibitor, blocked glyburide-, tolbutamide-, and insulin-stimulated glucose uptake. In intact cells, glyburide stimulated the phosphorylation of both 80,000-Mr and 40,000-Mr proteins, which are markers for protein kinase C activation. Addition of sulfonylureas directly to the protein kinase C assay system in vitro provoked dioleinlike effects, in that sensitivity of the enzyme to Ca2+ was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of insulin on diacylglycerol-protein kinase C signaling in rat diaphragm and soleus muscles and relationship to glucose transport

Insulin was found to provoke rapid increases in diacylglycerol (DAG) content and [3H]glycerol incorporation into DAG and other lipids during incubations of rat hemidiaphragms and soleus muscles. Insulin also rapidly increased phosphatidic acid and total glycerolipid labeling by [3H]glycerol, suggesting that insulin increases DAG production at least partly through stimulation of the de novo pathway. Increased DAG production may activate protein kinase C (PKC) as reported previously in the rat diaphragm. We also observed apparent insulin-induced translocation of PKC from cytosol to membrane in the rat soleus muscle. The importance of insulin-induced increases in DAG-PKC signaling in the stimulation of glucose transport in rat diaphragm and soleus muscles was suggested by 1) PKC activators phorbol esters and phospholipase C stimulation of [3H]-2-deoxyglucose (DOG) uptake and 2) PKC inhibitors staurosporine and polymixin B inhibition of insulin effects on [3H]-2-DOG uptake. Although phorbol ester was much less effective than insulin in the diaphragm, phospholipase C provoked increases in [3H]-2-DOG uptake that equaled or exceeded those of insulin. In the soleus muscle, phorbol ester, like phospholipase C, was only slightly but not significantly less effective than insulin. Similar variability in effectiveness of phorbol ester has also been noted previously in rat adipocytes (weak) and BC3H1 myocytes (strong), whereas DAG, added exogenously or generated by phospholipase C treatment, stimulates glucose transport to a degree that is quantitatively more comparable to that of insulin in each of the four tissues. Differences in effectiveness of phorbol ester and DAG could not be readily explained by postulating that the latter acts independently of PKC, because DAG provoked the apparent translocation of the enzyme from cytosol to membranes in rat adipocytes, and effects of DAG on [3H]-2-DOG uptake were blocked by inhibitors of PKC in both rat adipocytes and BC3H1 myocytes. Collectively, our findings provide further support for the hypothesis that insulin increases DAG production and PKC activity, and these processes are important in the stimulation of glucose transport in rat skeletal muscle and other tissues.

Further evidence implicating diacylglycerol generation and protein kinase C activation in agonist-induced increases in glucose uptake. Insulin-like effects of phenylephrine in BC3H-1 myocytes

We have previously suggested that insulin effects on 2-deoxyglucose (2-DOG) uptake in BC3H-1 myocytes are due to increases in de novo phospholipid synthesis, diacylglycerol generation, and protein kinase C activation. To test this hypothesis further, we examined the effects of phenylephrine, an agonist that increases diacylglycerol and protein kinase C activity through phospholipase C activation. As evidence for phospholipase activation in BC3H-1 myocytes, we found that phenylephrine increased acute 32PO4 incorporation into phosphatidic acid and phosphatidylinositol, generation of [3H]inositol phosphates from prelabeled [3H]inositol phospholipids, cytosolic Ca2+, and membrane-bound protein kinase C. Phenylephrine also provoked dose-related increases in [3H]2-DOG uptake that were similar in magnitude and time course to those induced by insulin. As with insulin, phenylephrine effects on 2-DOG uptake were not apparent in myocytes that were maximally stimulated with 12-O-tetradecanoylphorbol-13-acetate, a diacylglycerol analogue that activates protein kinase C. These findings support our hypothesis that diacylglycerol generation and protein kinase C activation may be important in the stimulation of glucose uptake by agents such as phenylephrine and insulin that activate the phosphoinositide cycle.