Contribution of growth hormone and IGF-I to early diabetic nephropathy in type 1 diabetes

In children and adolescents with type 1 diabetes, we have reported an association between duration of puberty and the prevalence of nephromegaly and microalbuminuria (MA), which are early markers of diabetic nephropathy. Growth hormone (GH), IGF-I, testosterone, and prorenin are potential mediators of this effect. This study examined the relationship of these hormonal factors to kidney volume (KV) and MA in 155 subjects (78 males, age 13.2 +/- 3.5 years [mean +/- SD]) with similar diabetes duration (6.83 +/- 1.6 years) but varying pubertal experience (0-10 years). KV (by ultrasound), plasma IGF-I, testosterone, prorenin, and NaLi countertransport, and urinary albumin, urinary GH, and urinary IGF-I from three 24-h collections were measured. Multiple regression analysis showed that BSA (P < 0.0001) and urinary IGF-I (P = 0.001) were significantly associated with KV. MA subjects (albumin excretion rate 15-200 microg/min) had higher urinary IGF-I (P = 0.005) and urinary GH (P = 0.05) compared with normoalbuminuric subjects. Only 9% of the variance in urinary IGF-I could be attributed to plasma IGF-I (r = 0.30, P < 0.0001). Testosterone and prorenin were not associated with MA, but they were associated with KV in univariate analyses. The strong association of urinary IGF-I with KV, a marker for glomerular hypertrophy, and of both urinary IGF-I and urinary GH with MA suggests a role for these growth factors in the development of human diabetic nephropathy. Together, these data support animal studies that have shown that renal GH and IGF-I may contribute significantly to the pathogenesis of early diabetic nephropathy.     

Ischemia causes rapidly progressive nephropathy in the diabetic rat

We examined the influence of renal ischemia in rats with diabetes mellitus (DM). Male Wistar rats were rendered diabetic by streptozotocin treatment. Two weeks later, 30 minutes of complete ischemia was induced in the left kidney of DM and non-DM animals. Both groups were evaluated functionally and morphologically four or eight weeks post-ischemia. In non-DM animals renal function and morphology showed almost complete recovery. In the DM animals, however, this comparatively short period of ischemia caused a substantial loss of renal function. Four weeks post-ischemia inulin clearance in the DM kidneys rendered ischemic was only 20% of that in the corresponding non-DM kidneys, and after eight weeks the DM kidneys were completely anuric. Extensive inflammation and tubulointerstitial fibrosis were evident in DM kidneys four weeks after ischemia and seemed to increase over time. After eight weeks, tubular atrophy was found in the ischemic DM kidneys, resulting in a substantial loss of kidney mass. We conclude that in diabetic rats renal ischemia causes rapidly progressive kidney damage that in several respects resembles diabetic nephropathy in humans. Since advanced renal lesions similar to those seen in human diabetic nephropathy never develop in the rat solely as a result of DM, the present study may provide an experimental model for further studies on renal failure in diabetes mellitus.     

Oral administration of arginine enhances the growth hormone response to growth hormone releasing hormone in short children

We have evaluated the effect of oral administration of arginine chlorhydrate on the growth hormone response to growth hormone releasing hormone in a group of nine short prepubertal children (six boys and four girls). Arginine chlorhydrate 10 g, administered orally 60 min before an i.v. bolus injection of growth hormone releasing hormone 1-29, 1 microgram/kg, significantly enhanced the growth hormone response to the neuropeptide, confirming the results of previous studies which used the i.v. route. Furthermore, our data strengthen the view that the effects of arginine chlorhydrate on growth hormone secretion are mediated by inhibition of endogenous somatostatin release.     

Effect of growth hormone administration on circulating levels of luteinizing hormone, follicle stimulating hormone and testosterone in normal healthy men

A new area of growth hormone (GH) therapy in adults is the treatment of infertility. The aim of this study was to evaluate the effects of pharmacological GH administration on the secretion of pituitary and gonadal hormones in normal men. Eight healthy men, 23-32 years of age (mean 28.1 years), with a normal body mass index were studied in a double-blind, placebo-controlled crossover design. All participants had a normal semen analysis before entering the study. Each participant was treated with placebo and GH (12/IU/day, Norditropin; Novo Nordisk, Denmark) during two different 14-day periods, separated by a 6 week washout period. Administration of GH for 14 days resulted in a significant increase in serum insulin-like growth factor I (IGF-I; P < 0.01) but no changes occurred in IGF-I values during placebo treatment. The concentrations of follicle stimulating hormone and luteinizing hormone displayed no change during the two periods and did not differ between the GH treatment period and the placebo period. The concentration of testosterone was unchanged during the placebo/GH periods and there was no difference between the GH treatment period and the placebo period. We conclude that GH treatment for 14 days in normal healthy men does not affect gonadotrophin or testosterone patterns.     

Effect of timing of growth hormone administration on plasma growth-hormone-binding activity, insulin-like growth factor-I and growth in children with a subnormal spontaneous secretion of growth hormone

Since normal pulsatile growth-hormone (GH) secretion displays a major and consistent surge during sleep, we studied the effect of timing of GH supplementation on plasma GH-binding protein activity (GH-BP), insulin-like growth factor-I (IGF-I) and growth. 34 prepubertal subjects (28 boys, 6 girls) aged 8-11 years, of short stature (< 2 SD for age), with a GH response to provocative test > 10 micrograms/l and a subnormal 24-hour GH secretion (< 3 micrograms/l), were randomly allocated to receive Bio-Tropin (recombinant GH, Bio-Technology, Israel) 0.81 IU/kg/week in 3 equally divided doses. GH was administered either at 8.00-10.00 h (M group), 14.00-16.00 h (AN group) or 19.00-21.00 h (NT group). Height velocity, IGF-I and GH-BP were determined prior to and after 6 and 12 months on GH therapy in the three groups. There was no significant difference between the three groups in the growth response, IGF-I and GH-BP increase, all of which increased significantly during GH therapy. Although GH levels after the injection decline to preinjection levels after 10 h, the changes induced by GH therapy, as reflected in IGF-I and GH-BP, last in the circulation long enough to prevent fluctuations in its action. The similarity of IGF-I and of GH-BP levels in the three treatment groups might explain the similar growth effects of the 3 protocols.     

Effect of chronic administration of Ginkgo biloba extract or Ginkgolide on the hypothalamic-pituitary-adrenal axis in the rat

The hypersecretion of glucocorticoids during exposure to various stressors may induce or worsen pathological states in predisposed subjects. Therefore it is of interest to evaluate drugs able to reduce glucocorticoid secretion. It has recently been shown that chronic administration of a Ginkgo biloba extract (EGb 761) inhibits stress-induced corticosterone hypersecretion through a reduction in the number of adrenal peripheral benzodiazepine receptors. The present study was designed to analyze the effect of EGb 761 and one of its components, Ginkgolide B on the biosynthesis and secretion of CRH and AVP, the hypothalamic neurohormones that regulate the pituitary-adrenal axis. Chronic administration of EGb 761 (50 or 100 mg/kg p.o. daily for 14 days) reduced basal corticosterone secretion and the subsequent increase in CRH and AVP gene expression. Under the same conditions, surgically-induced increase in CRH secretion was attenuated while the activation of CRH gene expression, ACTH and corticosterone secretion following insulin-induced hypoglycemia remained unchanged. Chronic i.p. injection of Ginkgolide B reduced basal corticosterone secretion without alteration in the subsequent CRH and AVP increase. However, the stimulation of CRH gene expression by insulin-induced hypoglycemia was attenuated by Ginkgolide B. These data confirm that the administration of EGb 761 and Ginkgolide B reduces corticosterone secretion. In addition, these substances act also at the hypothalamic level and are able to reduce CRH expression and secretion. However the latter effect appears to be complex and may depend upon both the nature of stress and substance (Ginkgolide B or other compounds of EGb 761).     

Effect of pancreas transplantation on the prevention of nephropathy in alloxan-induced diabetic rats

We studied the effects of pancreas transplantation on kidney lesions of rats with alloxan-induced diabetes. Ninety inbred male Lewis rats were randomly assigned to 3 experimental groups: group NC included 30 non-diabetic control rats, group DC included 30 alloxan-induced diabetic control rats, and group PT included 30 alloxan-induced diabetic rats that received pancreas transplants from normal donor Lewis rats. Each group was further divided into 3 subgroups of 10 rats which were sacrificed at 1, 3, and 6 months of follow-up, respectively. Clinical and laboratory parameters during these periods were documented. The kidneys of 5 rats in each subgroup were studied and 50 glomeruli and tubules from each kidney were analyzed by light microscopy by two different investigators in a double-blind study. There was progressive glomerular basement membrane thickening (GBMT), mesangial enlargement (ME), and Bowman's capsule thickening (BCT) in kidneys of rats in the 3 experimental groups during follow-up. These alterations were significantly higher in DC rats (GBMT: 1.99 +/- 0.31; ME: 2.00 +/- 0.33; BCT: 1.88 +/- 0.27) when compared to NC (GBMT: 1.54 +/- 0.30; ME: 1.56 +/- 0.47; BCT: 1.36 +/- 0.35) and PT rats (GBMT: 1.49 +/- 0.29; ME: 1.57 +/- 0.36; BCT: 1.35 +/- 0.28) at 6 months (P < 0.01). The extent of GBMT, ME, and BCT observed in DC rats at 1 and 3 months was not significantly different from NC and PT rats. The amount of kidney lesions in PT rats was similar to that of NC rats and lower than those of DC rats at 6 months (P < 0.01). In addition, Armanni-Ebstein lesions of the tubules (AE) and tubular lumen protein (PRO) observed in DC rats were not present in NC or PT rats. We conclude that pancreas transplantation in alloxan-induced diabetic rats prevents the development of kidney lesions beginning at 6 months after transplantation.     

Differential effect of insulin-like growth factor-1 and growth hormone on hypothalamic regulation of growth hormone secretion in the rat

Pharmacological administration of either growth hormone (GH) or insulin-like growth factor 1 (IGF-1) were reported to inhibit endogenous GH release in humans and in the laboratory animal. We have evaluated the short-term differential mechanisms whereby the two hormones affect hypothalamic regulation of GH secretion. Wistar male rats (90 days old) were injected i.p. with either GH (recombinant GH NIAMDD, Baltimore, MD, USA), rIGF-1 (Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan) or saline. Animals were sacrificed at 15, 30, 60 and 120 minutes following injection. Hypothalami were dissected and extracted immediately and the levels of growth hormone-releasing hormone (GHRH) and somatostatin were determined using specific antisera. Trunk blood was collected for GH and IGF-1 determination by RIA. Administration of IGF-1 or GH markedly decreased hypothalamic somatostatin stores by 77% and 54% respectively, within 15 minutes. Concomitantly, the wide range of GH levels found in the control group was reduced in the IGF-1 treated group suggesting that the pulsatile pattern of GH secretion was suppressed. Growth hormone administration induced an increase in hypothalamic GHRH stores (60% at 120 minutes). During this period serum IGF-1 levels were not altered. It is suggested that short term modulation of hypothalamic neurohormones by GH and IGF-1 is mediated by rapid stimulation of somatostatin release by both hormones, and inhibition of GHRH release is induced only by GH.     

Prevalence of diabetic nephropathy in adult patients with chronic kidney failure

Diabetic nephropathy is a frequent cause of end-stage renal failure in patients admitted for renal replacement therapy. PURPOSE: To evaluate the prevalence of DN, as the underline disease, in patients with ESRF. METHODS: 1,303 [male (M) = 767 and female (F) = 536] patients with ESRF who were on a waiting list for cadaver kidney transplant at Nephrology Unit-University Hospital (HC-UNICAMP), from August/90 to June/93--group 1--and 193 (M = 112 and F = 81) patients admitted for renal replacement therapy in a year period (April/92 to March/93), in the city of Campinas, State of S?o Paulo, Brazil, were studied. RESULTS: The prevalence of DN was 10.1% in group 1 and 17.6% in group 2 (x2 = 7.15; p = 0.007), being the third cause of ESRF in both groups, and it was preceded by glomerulonephritis and arterial hypertension. In group 1 the reduction of number of patients with increase in duration of dialysis was significantly greater in patients with diabetic nephropathy (x2 = 30.9; p < 0.001). Among patients with DN 35 (26%) in group 1 and 6 (18%) in group 2 had less than 35 years when they were admitted for renal replacement therapy and are likely to be type 1 (insulin-dependent) diabetic patients. CONCLUSION: In our studied groups DN was a frequent cause of ESRF.     

Levodopa-stimulated growth hormone secretion and diabetic retinopathy

Since growth hormone has been implicated as a possible etiologic factor in the development of diabetic retinopathy, we examined growth hormone levels in two groups of growth-onset diabetics matched for age and duration of disease. The experimental group had definite proliferative diabetic retinopathy; the control group of growth-onset diabetics had no significant retinopathy. Basal and levodopa-stimulated levels of growth hormone were determined for each group. Growth hormone response could not be correlated with the presence or absence of diabetic retinopathy (P less than .05).     

Effect of growth hormone therapy on bone metabolism of growth hormone deficient children

The effects of human growth hormone (hGH) therapy on biochemical markers of bone metabolism were studied in 17 children (10 boys and 7 girls, aged 3.7-13.1 years old) with idiopathic GH deficiency, before and 1 and 6 months after GH therapy (0.5 0.7 IU/kg weekly SC). Serum levels of calcium, phosphate, alkaline phosphatase osteocalcin, parathyroid hormone, 1,25 dihydroxyvitamin D, insulin-like growth factor I (IGF-I) and renal phosphate per 100 ml glomerular filtrate (TPO4/GFR) were assessed. During therapy with hGH a significant decrease of serum calcium levels and increases of phosphate, osteocalcin, parathyroid hormone 1,25 dihydroxyvitamin D and IGF-I were observed. TPO4/GFR was also significantly increased. Growth response (increment in HV) was positively related with changes in alkaline phosphatase and IGF-I levels after 6 months of hGH therapy. There was also a significant positive correlation between increment in HV and increment in TPO4/GFR after 1 month of GH therapy, whereas no correlation between HV and changes in osteocalcin levels was found. CONCLUSION: GH treatment significantly influences mineral metabolism and the measurement of TPO4/ GFR after 1 month of GH therapy may serve as a useful predictor of growth response to hGH therapy in GH-deficient children.     

Alcoholism abolishes the growth hormone response to sumatriptan administration in man

To assess the possible influence of alcoholism on serotonergic control of growth hormone (GH) secretion, 6 mg of the 5-HT1D serotonergic receptor agonist, sumatriptan, was injected subcutaneously in a group of nine normal controls (aged 32 to 49 years) and in nine age-matched nondepressed male alcoholic subjects after 10 to 25 days of abstinence from alcohol. During the same period, subjects were also tested with GH-releasing hormone ([GHRH] 1 microgram/kg body weight in an intravenous [i.v.] bolus) and L-arginine, which releases GH from somatostatin inhibition (50 g in 50 mL normal saline over 30 minutes) to determine whether GH secretion in response to alternate secretagogues is preserved in alcoholics. A control test with administration of normal saline instead of drug treatments was also performed. Plasma GH levels were recorded over 2 hours in all tests. Administration of placebo did not change plasma GH levels in any subject. Similar GH responses were observed in normal controls and alcoholic subjects when GHRH or arginine were administered. A significant GH increase was observed in normal controls after sumatriptan injection; in contrast, GH secretion was not modified by sumatriptan administration in alcoholic patients. These data show that alcoholism is associated with an impairment in the serotonergic-stimulatory regulation of GH secretion, whereas GH responses to direct pituitary stimulation with GHRH or to release from somatostatinergic inhibition with arginine appear to be preserved in alcoholics.     

Effect of intensive treatment on diabetic nephropathy in patients with type I diabetes

We evaluated the long-term effect of an intensive treatment of diabetic nephropathy (anti-hypertensive drugs, low protein diet, multiple insulin injections to achieve a good metabolic control) on glomerular filtration rate (GFR) and albumin excretion rate (AER). Fourteen type I diabetic patients (mean age 45 +/- 9.5 years, mean duration of diabetes 23.5 +/- 7.3 years, 8 males/6 females) with glomerular filtration rate < 70 ml/min-1/1.73 m2 and albumin excretion rate > 30 micrograms/min were treated intensively for 36 months. This intensive treatment consisted of multiple insulin injections, antihypertensive therapy with ACE inhibitors and a low-protein diet (0.8 g/kg body wt/day.) Renal function was evaluated as GFR and AER. HbA1c mean value decreased significantly from 8.7 +/- 0.8% to 6.5 +/- 0.5% (P < 0.0002). GFR rose from 58 +/- 12 ml/min-1/1.73 m2 to 84 +/- 11 ml/min-1/1.73 m2 (P < 0.0008). AER decreased from 208 micrograms/min (range: 73 to 500) to 63.8 micrograms/min (range 15 to 180; P < 0.05). Systolic and diastolic blood pressure decreased respectively from 144 +/- 26 mm Hg to 120 +/- 15 mm Hg and from 89 +/- 9 mm Hg to 75 +/- 8 mm Hg (P < 0.01). We obtained a rise of GFR and a reduction of proteinuria after three years of this treatment. We suggest that this intensive treatment in all patients with early stage diabetic nephropathy may be effective in slowing the progression to renal failure.     

Hypothalamic growth hormone secretagogue-receptor (GHS-R) expression is regulated by growth hormone in the rat

Synthetic GH secretagogues (GHSs) act via a receptor (GHS-R) distinct from that for GH-releasing hormone (GHRH). We have studied the hypothalamic expression and regulation of this receptor by in situ hybridization using a homologous riboprobe for rat GHS-R. GHS-R mRNA is prominently expressed in arcuate (ARC) and ventromedial nuclei (VMN) and in hippocampus, but not in the periventricular nucleus. Little or no specific hybridization could be observed in the pituitary under the conditions that gave strong signals in the hypothalamus. No sex difference in GHS-R expression was found in ARC or hippocampus, though expression in VMN was lower in males than in females. Compared with GHRH and neuropeptide Y (NPY), GHS-R was expressed in a distinct region of ventral ARC, and in regions of VMN not expressing GHRH or NPY. GHS-R expression was highly sensitive to GH, being markedly increased in GH-deficient dw/dw dwarf rats, and decreased in dw/dw rats treated with bovine GH (200 microg/day) for 6 days. Similar changes were observed in GHRH expression, whereas NPY expression was reduced in dw/dw rats and increased by bGH treatment. Continuous sc infusion of GHRP-6 in normal female rats did not alter ARC or VMN GHS-R expression. Our data implicate ARC and VMN cells as major hypothalamic targets for direct GHS action. The sensitivity of ARC GHS-R expression to modulation by GH suggests that GHS-Rs may be involved in feedback regulation of GH.     

Experimental diabetic renal growth: role of growth hormone and insulin-like growth factor-I

We have compared the kidneys of two inbred strains of rats (Lewis and Lewis-Dwarf) 7 days after the induction of diabetes mellitus with streptozotocin, in order to examine the influence of a selective growth hormone (GH) deficiency on diabetic renal growth and insulin-like growth factor-I (IGF-I) content of the kidneys. Insulin-like growth factor-I (IGF-I) content of the kidneys. Insulin-like growth factor-I was measured by radioimmunoassay and its distribution within the kidney by immunohistochemical staining. We detected a significant increase in both the wet weight (32.9 +/- 5.3%, P = 0.0085) and dry weight (16.3 +/- 6.3%, P = 0.046) of the kidneys of diabetic Lewis rats but dwarf rats, selectively deficient in GH, did not show a significant increase in either parameter. Extractable IGF-I increased within the kidneys of diabetic rats of both strains but to a lesser extent in the dwarf rats (+105 +/- 28% and +65 +/- 21% respectively, P < 0.01). In diabetic Lewis rats a positive correlation was noted between the severity of glycaemia and kidney IGF-I content (r = 0.604, P < 0.05) but no such correlation was noted in dwarf rats. Inulin-like growth factor-I immunostaining increased in diabetic rats of both strains, mainly within cells of the thick ascending limb of the loop of Henle including damaged and vacuolated cells. However, morphometric analysis of the staining showed that it was significantly less widespread in the diabetic dwarf rats (P = 0.026).(ABSTRACT TRUNCATED AT 250 WORDS)     

The antiproteinuric action of angiotensin-converting enzyme inhibitors in chronic glomerulonephritis and diabetic nephropathy

Antiproteinuria effects of angiotensin-converting enzyme (ACE) inhibitors was studied in 23 patients with chronic nephritis (CN) and 32 patients with diabetic nephropathy (DN). CN patients received Capoten, DN patients were given enalapril. The drugs were also examined for the action on systemic arterial pressure, renal function and intrarenal hemodynamics. Significantly decreased urinary excretion of protein occurred in DN patients on the treatment month 1, in CN subjects on month 3. In both groups ACE inhibitors produced marked hypotensive effect, did not affect renal function, noticeably improved intraglomerular hemodynamics. Hypotensive and antiproteinuria activity of the drugs were unrelated. The mechanism of antiproteinuria action of ACE inhibitors works via normalization of intrarenal hemodynamics. Systemic arterial hypertension seems to be an additional factor aggravating disturbances of intrarenal circulation and provoking proteinuria.