Growth hormone and somatostatin in glomerular injury

Among other neuropeptides and neurohormones, growth hormone (GH) and somatostatin (SRIF) have been shown to modulate the development of glomerular injury in various renal diseases. In particular, GH is implicated in the induction of glomerular hypertrophy and sclerosis in partial nephrectomy and diabetic nephropathy. While GH effects on glomerular hypertrophy are likely mediated by insulin-like growth factor I (IGF-I), GH effects on glomerular sclerosis are independent of IGF-I. Those effects rather require multiple signaling pathways functioning in series, e.g. angiotensin II binding preceding transforming growth factor beta (TGF-beta) release, or pro-inflammatory factor release preceding repair/scarring processes. In contrast with GH, SRIF administration prevents the development of glomerular lesions in experimental diabetes, partial nephrectomy and immune glomerulonephritis. Inhibitory effects of SRIF on glomerular hypotrophy may be through a decrease in GH secretion and/or IGF-I expression or through a direct blockade of glomerular cell proliferation. The mechanisms underlying the anti-inflammatory effects of SRIF are most likely a deactivation of inflammatory cells related in part to an upregulated response of these cells to glucocorticoids. Additional studies will be required to further define the role of GH and SRIF in the development of glomerular injury and, hence, to identify new targets for a therapeutic approach in glomerular diseases.     

Unique glomerular lesion with spontaneous lipid deposition in glomerular capillary lumina in the NON strain of mice

We found a strain of nonobese, nondiabetic (NON) mice which has spontaneous lipid deposition in glomerular capillary lumina. This strain was developed together with a diabetic strain of nonobese diabetic (NOD) mice for the generation of mouse models of diabetes mellitus. In the NON strain, contrary to the name, impaired glucose tolerance (IGT) was observed in about half of the mice. Meanwhile, peculiar glomerular abnormalities which remotely resemble those of diabetic nephropathy were observed in the NON strain. The lesions were characterized by massive lipid accumulation with proteinaceous material within the glomerular capillary lumina. In addition, positive staining for immunoglobulins, especially IgM, was observed by immunofluorescence microscopy. The overall frequency of this lesion was 91%. Mesangiolysis, capillary ballooning with many small lipid vesicles were the striking features by electron microscopy. Histochemical analysis revealed the presence of various lipids in these lesions. However, as far as we examined, these lesions did not correlate with hyperlipidemia or IGT. Lymphoid follicle-like structures were seen around the renal arterioles. The cellular components of these lymphoid follicles reacted with monoclonal antibodies to L3T4. High levels of serum immunoglobulins were observed in this strain. We suppose that the immunological disorders may have some bearing in the evolution of this lesion in NON mice. We believe that this model may be of use in studying the role of lipid derangements in renal diseases.     

Growth hormone promotes healing of tibial fractures in the rat

The effect of administering growth hormone for different periods of time on the mechanical properties of healing rat tibial fractures was investigated after 40 days of healing. Biosynthetic human growth hormone, 2.7 mg/kg body weight/ day, was administered to three groups of rats for 1, 2, or 3 weeks following fracture, whereas isotonic saline was administered to a control group for 3 weeks. The ultimate load values and maximum stiffness of the fractures increased in the groups injected with growth hormone for 2 or 3 weeks; linear regression analysis revealed a high probability of a positive linear relationship. In the intact bones an increase in ultimate load, maximum stiffness, and energy absorption at ultimate load was found in the group injected with growth hormone for 3 weeks, with linear regression analysis again showing a high probability of a positive linear relationship.     

Growth hormone promotes healing of tibial fractures in the rat

The effect of administering growth hormone for different periods of time on the mechanical properties of healing rat tibial fractures was investigated after 40 days of healing. Biosynthetic human growth hormone, 2.7 mg/kg body weight/day, was administered to three groups of rats for 1, 2, or 3 weeks following fracture, whereas isotonic saline was administered to a control group for 3 weeks. The ultimate load values and maximum stiffness of the fractures increased in the groups injected with growth hormone for 2 or 3 weeks; linear regression analysis revealed a high probability of a positive linear relationship. In the intact bones an increase in ultimate load, maximum stiffness, and energy absorption at ultimate load was found in the group injected with growth hormone for 3 weeks, with linear regression analysis again showing a high probability of a positive linear relationship.     

Prednisolone-loaded liposome decreases the accumulation of glomerular extracellular matrix and glomerular injury of immunoglobulin A nephropathy in ddY mice

SUMMARY: Morphometric, immunofluorescent and electron microscopic analyses were performed to determine the glomerular changes of ddY mice after treatment with the prednisolone-loaded liposome (PSL-liposome) in the present study. A morphometric analysis including the extracellular matrix areas (ECMA), number of intraglomerular cell nuclei (NIGCN), and the ratio of glomerular tuft area (GTA) to the whole glomerular area (WGA) (GTA/WGA), or the ratio of glomerular Bowman's space (GBS) to GTA (GBS/GTA) was performed by image analysis using light microscopy. Extracellular matrix case, NIGCN and GTA/WGA of PSL-liposome-treated ddY mice were significantly decreased compared with those of ordinary prednisolone (PSL)-treated and saline control ddY mice. Glomerular Bowman's space/GTA was markedly increased in the PSL-liposome-treated ddY mice. the mean intensity of immunoglobulin (Ig)A, IgG, complement C3 or intercellular adhesion molecule-1 (ICAM-1) staining in glomeruli of the PSL-liposome treated ddY mice was also significantly decreased compared with those of ordinary PSL-treated and saline control ddY mice. Electron dense deposits in glomeruli were decreased after treatment with PSL-liposome in 61-week-old ddY mice. It appears that PSL-liposome therapy might reduce glomerular expansion, and intraglomerular cell proliferation and infiltration in IgA nephropathy of ddY mice.     

Knockout of TRPC6 promotes insulin resistance and exacerbates glomerular injury in Akita mice

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Cyclosporine promotes glomerular endothelin binding in vivo.

It has previously been shown that administration of cyclosporine causes a prompt (within 15 min after infusion) increase in circulating level of endothelin 1 and a pattern of glomerular hypoperfusion and hypofiltration which can be ameliorated with antiendothelin antibody. We now show that 60 min after cyclosporine, serum endothelin 1 level falls to less than 2.55 +/- 0.31 pg/mL (N = 6), a value comparable to that found in normal animals (less than 2 pg/mL). The study presented here also examines whether sustained cyclosporine-induced glomerular dysfunction is associated with altered endothelin receptor characteristics. Saturation and competitive inhibition binding studies in isolated glomerular membranes showed two binding sites. Of these, the density of the low-affinity site was affected by cyclosporine treatment (851 +/- 117 versus 425 +/- 61 fmol/mg of protein; P less than 0.05; N = 6) without a change in equilibrium dissociation constant, KD. The high-affinity site was not affected. The receptor characteristics of another vasoconstrictor, angiotensin II, were not affected by cyclosporine. In addition, there was no difference in endothelin binding sites in hepatic tissue between cyclosporine and control rats. These results raise the intriguing possibility that cyclosporine-induced glomerular dysfunction involves upregulation of endothelin binding sites and that altered endothelin receptors appear specific to the kidney.     

Prolonged inhibition of muscle carnitine palmitoyltransferase-1 promotes intramyocellular lipid accumulation and insulin resistance in rats

Cross-sectional studies in human subjects have used 1H magnetic resonance spectroscopy (HMRS) to demonstrate that insulin resistance correlates more tightly with the intramyocellular lipid (IMCL) concentration than with any other identified risk factor. To further explore the interaction between these two elements in the rat, we used two strategies to promote the storage of lipids in skeletal muscle and then evaluated subsequent changes in insulin-mediated glucose disposal. Normal rats received either a low-fat or a high-fat diet (20% lard oil) for 4 weeks. Two additional groups (lowfat + etoxomir and lard + etoxomir) consumed diets containing 0.01% of the carnitine palmitoyltransferase-1 inhibitor, R-etomoxir, which produced chronic blockade of enzyme activity in liver and skeletal muscle. Both the high-fat diet and drug treatment significantly impaired insulin sensitivity, as measured with the hyperinsulinemic-euglycemic clamp. Insulin-mediated glucose disposal (IMGD) fell from 12.57 +/- 0.72 in the low-fat group to 9.79 +/- 0.59, 8.96 +/- 0.38, and 7.32 +/- 0.28 micromol x min(-1) x 100 g(-1) in the low-fat + etoxomir, lard, and lard + etoxomir groups, respectively. We used HMRS, which distinguishes between fat within the myocytes and fat associated with contaminating adipocytes located in the muscle bed, to assess the IMCL content of isolated soleus muscle. A tight inverse relationship was found between IMGD and IMCL, the correlation (R = 0.96) being much stronger than that seen between IMGD and either fat mass or weight. In conclusion, either a diet rich in saturated fat or prolonged inhibition of fatty acid oxidation impairs IMGD in rats via a mechanism related to the accumulation of IMCL.     

Growth hormone therapy and lipid profile in children on chronic peritoneal dialysis

The aim of the study was to assess the effect of recombinant human growth hormone (rhGH) on serum lipids in children treated with chronic peritoneal dialysis. We studied 26 patients aged 5-18 years, including 13 patients treated with rhGH at a dose of 1-1.1 IU/kg per week for 6 months and a control group of 13 patients. Serum total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), HDL-C, triglycerides (TG), apolipoproteins A-I and B-100 (apoA and apoB), lipoprotein (a) [Lp(a)], total protein, albumin, urea, and creatinine levels were measured in all children at baseline and at 1, 3, and 6 months of follow-up. We found a significant increase in the TG level after 1 month of administration of rhGH in the treatment group compared with both baseline (218.8+/-49.2 mg/dl vs. 175.9+/-71.9 mg/dl, respectively, P<0.05) and the control group at 1 month of follow-up (146.5+/-44.3 mg/dl, P<0.001). We found no change in TC, LDL-C, HDL-C, apoA, and Lp(a) levels during treatment with rhGH. These data suggest that administration of rhGH to children treated with peritoneal dialysis results in only a transient increase of serum TG level and has no effect on TC, LDL-C, HDL-C, apoA, and Lp(a) levels.     

Growth hormone induced rise in glomerular filtration rate is not obliterated by angiotensin-converting enzyme inhibitors.

In 8 healthy normotensive probands with normal glomerular filtration rate, the effect of recombinant human growth hormone (rhGH) on inulin clearance (Cin) was examined in an open study with intraindividual crossover with or without enalapril pretreatment (20 mg/day). rhGH was administered by subcutaneous injection (4.5 U twice daly) for 3 days. On the following day Cin was measured with an enzymatic steady state infusion technique. Systemic hemodynamics and potential metabolic effects of rhGH, i.e., inulin-like growth factors I and II, somatomedin-binding protein, glucagon, C peptide, amino acid pattern, etc., were monitored. On controlled dietary intake of protein, the median Cin rose 72 h after start of rhGh administration from 114 (range 91-158) to 135 (108-167) ml/min/1.73 m2 without enalapril pretreatment (p less than 0.01) and from 111 (88-153) to 131 (100-173 ml/min/1.73 m2 with enalapril pretreatment (p less than 0.02). The results confirm that (1) rhGH increases Cin to a similar extent as extractive GH and (2) further demonstrate that this action is not obliterated by blocking the circulating converting enzyme.     

Growth hormone aggravates glomerular sclerosis in the remnant kidney of 5/6 nephrectomized uremic rats

Background Our study evaluated the influence of short-term growth hormone treatment on the remnant kidney in 5/6 nephrectomized uremic rats Methods Twenty male Sprague-Dawley rats were divided into 4 groups: sham-operated control rats (SC, n=4); sham-operated rats treated with recombinant human growth hormone (SGH, n=4); uremic (5/6 nephrectomized) control rats (UrC, n=6); and uremic rats treated with recombinant human growth hormone (UrGH, n=6). Total food intake, food efficiency, average daily food intake per 100 g body weight, weight gain, increase in body length, creatinine clearance, and kidney weight per 100 g body weight were measured. Glomerular tuft area was determined, and the severity of glomerular sclerosis was scored. Insulin-like growth factor-I was localized in the kidneys by immunostaining. Results Weight gain, increase in body length, food efficiency, and food intake per unit body weight were greatest in the SGH group; in UrGH animals, food efficiency and food intake per unit body weight were significantly higher than those in UrC rats. Creatinine clearance in uremic rats was significantly reduced compared with that in sham-operated animals. There was no difference in the ratio of kidney weight to body weight among the groups. The average glomerular area was greatest, and the glomerular sclerosis index was highest, in the UrGH group. No insulin-like growth factor-I could be identified in the glomeruli. Conclusions Growth-hormone treatment augmented daily food intake, and the more rapid progression to glomerular sclerosis in hormone-treated uremic rats is probably due mainly to increased daily protein intake. This study was partly presented at both the 38th Annual Meeting of the Japanese Society of Nephrology and the Sixth Asian Pacific Congress of Nephrology     

Growth hormone receptor antagonism prevents early renal changes in nonobese diabetic mice.

The growth hormone (GH)/insulin-like growth factor (IGF) axis is involved in diabetic renal disease. The role of a specific GH receptor (GHR) antagonist in the development of early renal changes in nonobese diabetic (NOD) mice was investigated. Female diabetic (nonketotic) NOD mice treated with a polyethylene glycol-treated GHR antagonist (2 mg/kg, every other day) (DA group) or saline (D group) and their nonhyperglycemic age-matched littermates (control animals) were euthanized 3 wk after the onset of diabetes. Body weights at euthanasia were similar among the groups. Serum GH levels were markedly elevated, and serum IGF-I levels were significantly decreased in D and DA animals, compared with controls. The increases in kidney weights and glomerular volumes observed for the D group were absent in the DA group. Albuminuria was increased in the D group but was normalized in the DA group. Extractable renal IGF-I protein levels were increased in the D group but were partially normalized in the DA group. Renal IGF-binding protein 1 mRNA levels were increased in the D group but returned to almost normal levels in the DA animals. Kidney IGF-I and GHR mRNA levels were decreased in both the D and DA groups. Renal GH-binding protein mRNA levels remained unchanged in both diabetic groups. GHR antagonism had a blunting effect on renal/glomerular hypertrophy and albuminuria in diabetic NOD mice. These salutary effects were associated with concomitant inhibition of increased renal IGF-I protein levels and were obtained without affecting either somatic growth or circulating GH and IGF-I levels. Therefore, modulation of GH effects may have beneficial therapeutic implications in diabetic nephropathy.     

t-PA promotes glomerular plasmin generation and matrix degradation in experimental glomerulonephritis

BACKGROUND: In addition to its well-known role in degrading fibrin, recent evidence suggests that plasmin degrades matrix proteins and activates prometalloproteinases. Plasmin is generated from plasminogen by tissue plasminogen activator (t-PA). We hypothesized that t-PA treatment increases plasmin generation in nephritic glomeruli and degrades pathological matrix leading to a therapeutic reduction in matrix accumulation. METHODS: Anti-Thy-1 nephritis was induced by injection of OX-7 antibody. Rats were given twice daily intravenous injections of saline (disease control group) or human recombinant t-PA (rt-PA; 1 mg/kg body weight) on days 3 through 5. Proteinuria, glomerular matrix protein staining, and glomerular mRNA levels for transforming growth factor-beta 1 (TGF-beta 1), fibronectin, and plasminogen activator inhibitor type 1 (PAI-1) were evaluated at day 6. Localization of rt-PA, plasmin generation by glomeruli in vitro, and glomerular production and content of active TGF-beta1 were also investigated. RESULTS: Compared with disease control animals, proteinuria and staining score for periodic acid-Schiff (2.75 +/- 0.17 vs. 1.41 +/- 0.09), fibronectin-EDA+ (19 +/- 2 vs. 14 +/- 1), laminin (35 +/- 2 vs. 25 +/- 2), type I collagen (33 +/- 1 vs. 21 +/- 3), and type IV collagen (27 +/- 2 vs. 23 +/- 1) were significantly reduced in treated rats (P < 0.01). Glomerular TGF-beta 1, fibronectin, and PAI-1 mRNA levels were unchanged. rt-PA colocalized with fibrin along glomerular capillary walls and in the mesangium. Nephritic glomeruli in vitro had decreased plasmin activity, which was elevated by an in vivo presacrifice injection of rt-PA. Glomerular production and content of active TGF-beta 1 were unchanged by the rt-PA injection. CONCLUSIONS:: These results show that injected rt-PA binds to fibrin in nephritic glomeruli, thus increasing plasmin generation and promoting pathological matrix degradation without activating latent TGF-beta. Agents that increase plasmin generation, such as t-PA, may have potential as antifibrotic therapies.     

神经调节蛋白对小鼠睾丸精原细胞增殖作用的研究

目的:研究神经调节蛋白(NRG)对小鼠睾丸精原细胞增殖的影响。方法:将纯化的NRG1β或NRG3的类EGF区域的重组蛋白分别添加到DMEM培养液中,终浓度分别为50、100、200 ng/m l,进行小鼠睾丸断片的器官培养,随后进行B rdU免疫组化染色,检测精原细胞的增殖效应。结果:添加NRG后可以促进精原细胞的增殖活性,与对照组相比具有显著性差异(P<0.05)。按NRG1β50、100、200 ng/m l、NRG3 50、100、200 ng/m l的顺序,精原细胞的增殖活性分别是对照组的1.69、1.55、1.86、1.35、1.54、2.11倍。结论:NRG1β、NRG3能促进小鼠精原细胞的增殖。可以期待NRG应用在男性不育症的治疗上。     

Activation of Galpha q-coupled signaling pathways in glomerular podocytes promotes renal injury

The glomerular podocyte plays a key role in maintaining the integrity of the glomerular filtration barrier. This function may be regulated by activation of cell surface G protein-coupled receptors (GPCR). Studies suggest that podocytes express GPCR that are implicated in the pathogenesis of glomerular diseases. Common to these GPCR systems is activation of phospholipase C through the Gq alpha-subunit (Galpha q). For investigating the role of Galpha q-coupled signaling pathways in promoting renal injury in podocytes, a constitutively active Galpha q subunit (Galpha qQ > L) was expressed in glomerular podocytes using the mouse nephrin promoter. Transgenic (TG) mice demonstrated albuminuria as well as a decrease in both kidney mass and nephron number. By light microscopy, a portion of the TG mice had glomerular abnormalities, including focal to diffuse hypercellularity and segmental sclerosis. Consistent with injury-promoting effects of Galpha qQ > L, there was a significant reduction in podocalyxin mRNA as well as nephrin mRNA and protein levels in glomeruli from TG mice compared with non-TG controls. Expression of the transgene also seemed to increase susceptibility to glomerular injury, because treatment with puromycin aminonucleoside enhanced proteinuria in TG mice compared with non-TG littermate controls (4.2 +/- 1.0 [TG] versus 1.6 +/- 0.3 [non-TG] mg/24 h; P = 0.0161). Thus, activation of Galpha q in glomerular podocytes caused alterations in glomerular histomorphology, albuminuria, decreased nephron mass, and reduced glomerular expression of both nephrin and podocalyxin as well as enhanced susceptibility to glomerular damage induced by puromycin aminonucleoside. It is speculated that Galpha q-coupled signaling cascades may be important effector pathways mediating renal injury.