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Biomedical subjects

R Rabkin

Publications and source records attributed to R Rabkin.

At least 19 recordsLinked to original sources
PubMed2006

Work-induced changes in skeletal muscle IGF-1 and myostatin gene expression in uremia.

Resistance to growth hormone (GH)-induced insulin-like growth factor-1 (IGF-1) gene expression contributes to uremic muscle wasting. Since exercise stimulates muscle IGF-1 expression independent of GH, we tested whether work overload (WO) could increase skeletal muscle IGF-1 expression in uremia and thus bypass the defective GH action. Furthermore, to provide insight into the mechanism of uremic wasting and the response to exercise we examined myostatin expression. Unilateral plantaris muscle WO was initiated in uremic and pairfed (PF) normal rats by ablation of a gastrocnemius tendon and adjoining part of this muscle with the contralateral plantaris as a control. Some rats were GH treated for 7 days. WO led to similar gains in plantaris weight in both groups and corrected the uremic muscle atrophy. GH increased plantaris IGF-1 mRNA >twofold in PF rats but the response in uremia was severely attenuated. WO increased the IGF-1 mRNA levels significantly in both uremic and PF groups, albeit less brisk in uremia; however, after 7 days IGF-1 mRNA levels were elevated similarly, >2-fold, in both groups. In the atrophied uremic plantaris muscle basal myostatin mRNA levels were increased significantly and normalized after an increase in WO suggesting a myostatin role in the wasting process. In the hypertrophied uremic left ventricle the basal myostatin mRNA levels were reduced and likely favor the cardiac hypertrophy. Together the findings provide insight into the mechanisms of skeletal muscle wasting in uremia and the hypertrophic response to exercise, and suggest that alterations in the balance between IGF-1 and myostatin play an important role in these processes.

Animals↗
PubMed2001

Growth factors in the treatment of wasting in kidney failure.

Protein-energy malnutrition is relatively common in patients with advanced renal failure and is associated with an increase in morbidity and mortality. Accordingly, there is a need to develop more effective treatments to enhance the nutritional status of these patients. One such approach is the use of recombinant growth factors and anabolic steroids for malnourished patients refractory to standard nutritional therapy. In this article, we review the current state of our knowledge regarding the potential use of these agents in malnourished renal failure patients and conclude that although the studies performed to date are indeed encouraging, further and more extensive clinical trials are required to firmly establish their efficacy and safety profile and the indications for clinical use.

Anabolic Agents↗
PubMed2001

Expression of insulin-like growth factor-I and transforming growth factor-beta in hypokalemic nephropathy in the rat.

BACKGROUND: Potassium deficiency (KD) in the rat retards body growth but stimulates renal enlargement caused by cellular hypertrophy and hyperplasia, which is most marked in the outer medulla. If hypokalemia persists, interstitial infiltrates appear and eventually fibrosis. Since early in KD insulin-like growth factor-I (IGF-I) levels in the kidney are elevated, suggesting that it may be an early mediator of the exaggerated renal growth, and as transforming growth factor-beta (TGF-beta) promotes cellular hypertrophy and fibrosis, we examined the renal expression of these growth factors in prolonged KD. METHODS: Rats were given a K-deficient diet or were pair fed or ad libitum fed a K-replete diet for 21 days. Growth factor mRNA levels were measured in whole kidney and protein expression localized by immunohistochemistry. RESULTS: KD rats weighed less than pair-fed controls, while the kidneys were 49% larger. Their serum IGF-I and kidney IGF-I protein levels were depressed, as were their IGF-I mRNA levels in liver, kidney, and muscle. These changes can largely be attributed to decreased food intake. In contrast, kidney IGF binding protein-1 (IGFBP-1) mRNA and TGF-beta mRNA levels were increased significantly. Histology of outer medulla revealed marked hypertrophy and adenomatous hyperplasia of the collecting ducts and hypertrophy of the thick ascending limbs of Henle with cellular infiltrates in the interstitium. Both nephron segments immunostained strongly for IGF-I and IGFBP-1, but only the nonhyperplastic enlarged thick ascending Henle limb cells immunostained for TGF-beta, which was strongly positive. Prominent interstitial infiltrates with ED1 immunostained monocytes/macrophages were present. CONCLUSIONS: These findings are consistent with a sustained role for IGF-I in promoting the exaggerated renal growth of KD and appear to be mediated through local trapping of IGF-I by the overexpressed IGFBP-1, which together with IGF-I can promote renal growth. The selective localization of TGF-beta to hypertrophied nonhyperplastic nephron segments containing IGF-I raises the possibility that TGF-beta may be serving to convert the mitogenic action of IGF-I into a hypertrophic response in these segments. It is also conceivable that TGF-beta may be a cause of the tubulointerstitial infiltrate. Finally, the low circulating IGF-I levels likely contribute to the impaired body growth.

Animals↗
PubMed2001

Impaired JAK-STAT signal transduction contributes to growth hormone resistance in chronic uremia.

Chronic renal failure (CRF) is associated with resistance to the growth-promoting and anabolic actions of growth hormone (GH). In rats with CRF induced by partial renal ablation, 7 days of GH treatment had a diminished effect on weight gain and hepatic IGF-1 and IGFBP-1 mRNA levels, compared with sham-operated pair-fed controls. To assess whether GH resistance might be due to altered signal transduction, activation of the JAK-STAT pathway was studied 10 or 15 minutes after intravenous injection of 5 mg/kg GH or vehicle. Hepatic GH receptor (GHR) mRNA levels were significantly decreased in CRF, but GHR protein abundance and GH binding to microsomal and plasma membranes was unaltered. JAK2, STAT1, STAT3, and STAT5 protein abundance was also unchanged. However, GH-induced tyrosine phosphorylation of JAK2, STAT5, and STAT3 was 75% lower in the CRF animals. Phosphorylated STAT5 and STAT3 were also diminished in nuclear extracts. The expression of the suppressor of cytokine signaling-2 (SOCS-2) was increased twofold in GH-treated CRF animals, and SOCS-3 mRNA levels were elevated by 60% in CRF, independent of GH treatment. In conclusion, CRF causes a postreceptor defect in GH signal transduction characterized by impaired phosphorylation and nuclear translocation of GH-activated STAT proteins, which is possibly mediated, at least in part, by overexpression of SOCS proteins.

Animals↗
PubMed2000

A double-blind, placebo-controlled trial of testosterone therapy for HIV-positive men with hypogonadal symptoms.

BACKGROUND: The goal was to evaluate the efficacy of testosterone in alleviation of hypogonadal symptoms (diminished libido, depressed mood, low energy, and depleted muscle mass) in men with symptomatic human immunodeficiency virus illness. METHODS: Seventy-four patients were enrolled in a double-blind, placebo-controlled 6-week trial with bi-weekly testosterone injections, followed by 12 weeks of open-label maintenance treatment. Major outcome measures were Clinical Global Impressions Scale ratings for libido, mood, energy, and erectile function; Hamilton Depression Rating Scale scores, and Chalder Fatigue Scale scores. Body composition changes were assessed with bioelectric impedance analysis. RESULTS: Seventy men completed the 6-week trial. Response rates, defined as much or very much improved libido, were 74% (28/38) for patients randomized to testosterone, and 19% (6/32) for placebo-treated patients (P<.001). Of the 62 completers with fatigue at baseline, 59% (20/34) receiving testosterone and 25% (7/28) receiving placebo reported improved energy (P<.01). Among the 26 completers with an Axis I depressive disorder at baseline, 58% of the testosterone-treated patients reported improved mood compared with 14% of placebo-treated patients (Fisher exact test = .08). With testosterone treatment, average increase in muscle mass over 12 weeks was 1.6 kg for the whole group, and 2.2 kg for the 14 men with wasting at baseline. Improvement on all parameters was maintained during subsequent open-label treatment for up to 18 weeks. CONCLUSION: Testosterone is well tolerated and effective in the short-term treatment of symptoms of clinical hypogonadism in men with symptomatic human immunodeficiency virus illness, restoring libido and energy, alleviating depressed mood, and increasing muscle mass.

Acquired Immunodeficiency Syndrome↗
PubMed2000

DHEA treatment for HIV+ patients: effects on mood, androgenic and anabolic parameters.

The goal of this pilot study was to evaluate the effect of dehydroepiandrosterone (DHEA) on depressed mood and fatigue in HIV+ men and women, unselected for baseline DHEA level. Secondary questions concerned treatment effects on libido and body cell mass, on serum testosterone levels, and elicitation of short-term side effects. Treatment consisted of an open-label 8-week trial using DHEA doses from 200 to 500 mg/day. Mood responders were maintained for another 4 weeks, then randomized to a double blind placebo controlled 4-week discontinuation trial. Forty-five patients, including six women, entered the trial. Of 32 week 8 completers, mood was much improved in 72%, and 81% were rated responders with respect to fatigue. Response on either parameter was unrelated to baseline serum DHEA level. Twenty-one patients entered the double blind discontinuation phase. No differences in relapse rate between placebo and DHEA groups were observed for either mood or fatigue. Body cell mass increased significantly by week 8, and this improvement was maintained throughout the double blind phase for patients in both treatment conditions. Libido increased significantly as well. DHEA therapy did not have an effect on CD4 cell count or on serum testosterone levels in men. In conclusion, DHEA may be a promising treatment for HIV+ patients with depressed mood and fatigue, although persistence of response even in placebo-treated patients during the discontinuation phase leaves unresolved questions. A parallel group double blind clinical trial is indicated as the next step to more clearly identify therapeutic efficacy.

Adult↗
PubMed2000

Effect of metabolic acidosis on the insulin-like growth factor-I system and cathepsins B and L gene expression in the kidney.

Prolonged acidemia causes growth retardation and muscle wasting, in part because of reduced food intake, depressed growth hormone secretion, and low serum insulin-like growth factor-I (IGF-I) levels. Paradoxically, in the rat kidney, protein synthesis increases, cathepsin B and L activities decline, protein degradation falls, and the kidneys enlarge. Because IGF-I has been implicated as a cause of renal hypertrophy in a variety of conditions, we examined whether IGF-I could be playing a role in the renal hypertrophy of acidosis. Rats were gavaged with NH4Cl or water for 4 days. Water-gavaged rats either were pair-fed with the NH4Cl-loaded rats (pH 7.15) or were given free access to food and served as controls. After 2 days, kidney weight and IGF-I mRNA levels did not differ between the groups, but kidney IGF-I protein levels were significantly higher in the acidotic rats. After 4 days the kidneys of the acidotic rats were significantly larger than the kidneys in both control groups but the renal IGF-I levels did not differ between the groups. It is notable that renal cathepsin B and L mRNA levels were reduced by 30% to 50% at both times. Thus the transient increase in renal IGF-I protein levels in acidosis, before the onset of hypertrophy, suggests that IGF-I may play a role in initiating kidney growth. Furthermore, it appears that reduced cathepsin B and L gene expression is a cause of the low renal cathepsin activity seen in acidosis. This likely contributes to the depressed renal proteolysis caused by acidosis.

Acid-Base Equilibrium↗
PubMed2000

Effects of dextroamphetamine on depression and fatigue in men with HIV: a double-blind, placebo-controlled trial.

BACKGROUND: This report documents findings from a small placebo-controlled trial of dextroamphetamine for depression and fatigue in men with the human immunodeficiency virus (HIV). Dextroamphetamine offers the potential for rapid onset of effect and activation properties, both of which are important to persons with medical illness and an uncertain, but limited, life expectancy. METHOD: Primary inclusion criteria included the presence of a DSM-IV depressive disorder, debilitating fatigue, and no history of dependence on stimulants. The study consisted of a 2-week randomized, placebo-controlled trial, with the blind maintained until week 8 for responders, followed by open treatment through the completion of 6 months. RESULTS: Of 23 men who entered the study, 22 completed the 2-week trial. Intent-to-treat analysis indicated that 73% of patients (8/11) randomly assigned to dextroamphetamine reported significant improvement in mood and energy, compared with 25% (3/12) among placebo patients (Fisher exact test, p < .05). Both clinician- and self-administered measures indicated significantly improved mood, energy, and quality of life among patients taking dextroamphetamine. There was no evidence of the development of tolerance of, abuse of, or dependence on the medication. CONCLUSION: These results suggest that dextroamphetamine is a potentially effective, fast-acting antidepressant treatment for HIV patients with depression and debilitating fatigue.

Adult↗
PubMed1999

Response to growth hormone therapy in experimental ischemic acute renal failure.

In acute renal failure (ARF), the gene and peptide expression of insulin-like growth factor-I (IGF-I) falls. Because IGF-I is regulated by growth hormone (GH) and because kidney GH receptor expression is also attenuated in ARF, the impaired IGF-I expression may partly reflect local GH resistance. Because IGF-I treatment accelerates recovery from ARF, we determined whether high-dose GH therapy could overcome this putative GH resistance, stimulate IGF-I production, and enhance recovery. Rats with ARF were given 2.5 mg GH or vehicle (V) over 2 days, beginning 24 hours before the onset of ARF. GH prevented weight loss but did not modify the course of ARF. Next we determined whether the failure of GH to modify kidney recovery could reflect a failure to stimulate renal IGF-I gene expression. Rats were treated with GH or V over an 18-hour period beginning 1 day after the induction of ARF. Hepatic IGF-I mRNA and serum IGF-I peptide levels rose significantly with GH treatment, but the low kidney IGF-I mRNA levels did not respond. We conclude that the failure of GH to enhance recovery from ARF is caused by impaired GH-stimulated renal IGF-I production, while the maintenance of body weight likely reflects the systemic effects of the increase in hepatic IGF-I production.

Acute Kidney Injury↗
PubMed1999

Testosterone therapy for human immunodeficiency virus-positive men with and without hypogonadism.

This study was designed to evaluate the safety and effectiveness of testosterone therapy for clinical symptoms of hypogonadism (low libido, low mood, low energy, loss of appetite/weight) in human immunodeficiency virus-positive men with CD4 cell counts less than 400 cells/mm3 and deficient or low normal serum testosterone levels. The trial consisted of 8 weeks of open treatment with 400 mg of intramuscular testosterone cypionate biweekly. Responders were maintained at this dosage for another 4 weeks and then were randomized in a double-blind, placebo-controlled, 6-week discontinuation trial. Of the 112 men who completed at least 8 weeks of treatment, 102 (91%) were rated as responders on a global assessment of sexual desire/function. Of the 34 study completers with major depressive disorder and/or dysthymia, 79% reported significant improvement in mood at week 8. Average weight change was a gain of 3.7 pounds, with 45% gaining more than 5 pounds. Eighty-four men entered and 77 completed the double-blind phase; of these, 78% of completers randomized to testosterone and 13% randomized to placebo maintained their response. No significant medical or immunologic adverse effects were identified. Testosterone therapy was well tolerated and effective in ameliorating symptoms of clinical hypogonadism, and equally so for men with and without testosterone deficiency. For patients with major depression and/or dysthymia, improvement was equal to that achieved with standard antidepressants.

Adult↗
PubMed1999

Fluoxetine treatment for depression in patients with HIV and AIDS: a randomized, placebo-controlled trial.

OBJECTIVE: The goals of this study were to determine whether fluoxetine is superior to placebo in treating HIV-seropositive patients with major depression or dysthymia or both, whether severity of immunosuppression is associated with treatment response, and whether fluoxetine treatment is associated with change in immune status as measured by CD4 cell count. METHOD: A double-blind, randomized, placebo-controlled 8-week trial of fluoxetine was conducted in a university-affiliated research outpatient clinic. The fluoxetine-placebo randomization was 2:1. All patients were offered 4 months of additional open treatment. Main outcome measures included the Clinical Global Impression, Hamilton Depression Rating Scale, and CD4 cell count. RESULTS: Of 120 patients randomly assigned to fluoxetine or placebo, 87 completed 8 weeks of treatment. In the total group, 51% had AIDS. All but three were men, 35% were nonwhite, and 6% had intravenous drug use as a risk factor. In an intention-to-treat analysis, 57% of fluoxetine patients and 41% of placebo patients were responders. Among patients who completed the study, 74% responded to fluoxetine and 47% to placebo; this difference was statistically significant. Severity of immunosuppression was not related to antidepressant response, attrition, or side effects, and fluoxetine treatment was not associated with change in CD4 cell count. CONCLUSIONS: Fluoxetine is an effective antidepressant in the context of HIV illness. However, both placebo response and attrition were substantial, suggesting both that nonspecific factors may be more salient and that yet another medication (i.e., an antidepressant) may be less acceptable among patients with serious medical illness already requiring multiple concomitant medications.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Intrarenal insulin-like growth factor-1 axis after unilateral nephrectomy in rat.

It has been suggested that insulin-like growth factor-1 (IGF-1) may play a role in early compensatory renal growth. Since IGF-1 action is influenced by IGF binding proteins (IGFBP), this study was conducted to characterize the changes in gene expression not only of IGF-1 and its receptor, but also of IGFBP in the hypertrophying kidney of adult and weanling rats 1 wk after removal of the other kidney. At this time, there were distinct age-dependent changes in the renal IGF-1 axis. In the mature kidney, IGF-1 mRNA levels fell without a change in kidney IGF-1 peptide content. Likewise, although IGFBP-2, -3, and -5 mRNA levels fell, membrane-associated IGFBP did not change. IGF-1 receptor mRNA levels and IGF-1 receptor number both fell. In the weanling kidneys, IGF-1 mRNA and peptide levels and IGF-1 receptor binding were unaltered. However, IGFBP-3, -4, and -5 mRNA levels were increased, as were plasma membrane-associated IGFBP. Although these changes in the intrarenal IGF-1 axis were distinct, it is difficult to conceive how in either the mature or immature rat they could contribute to the ongoing compensatory renal growth that occurs 1 wk after loss of kidney mass unless IGF-1 were acting in a synergistic manner with other growth promoters.

Age Factors↗
PubMed1999

Antidepressant treatment of depression in HIV-seropositive women.

BACKGROUND: This study aimed to assess the effectiveness of fluoxetine and sertraline in treating depressed women who are seropositive for the human immunodeficiency virus (HIV) and to document barriers to study participation. METHOD: Ambulatory HIV-seropositive women with DSM-IV depressive disorders were enrolled in an 8-week, open trial of fluoxetine (N = 21) or sertraline (N = 9) initiated at standard dosages. Outcome measures included the Clinical Global Impressions-Improvement scale (CGI), Hamilton Rating Scale for Depression (HAM-D), Beck Depression Inventory (BDI), physical function ratings, and CD4 count. RESULTS: Thirty-six women were screened for the study and 30 were enrolled. Mean age was 35.5 years and HIV risk was primarily intravenous drug use (N = 16; 53%) or heterosexual contact (N = 12; 40%). Sixteen (53%) were Hispanic, 11 (37%) were African American, and 3 (10%) were white. Mean +/- SD CD4 count was 463+/-312 cells/microL, and 30% had acquired immunodeficiency syndrome (AIDS). Eighteen women (60%) completed the trial (14 fluoxetine: dose range, 10-40 mg/day; 4 sertraline: dose range, 25-100 mg/day). Of completers, 14 (78%) were clinical responders by CGI and reduction in HAM-D > 50%. Statistically significant reductions were seen in HAM-D and BDI scores, but not in measures of physical function or CD4 count. The most frequent adverse effects were anxiety, overstimulation, and insomnia. Reasons for nonparticipation or dropout included refusal to accept antidepressants on account of negative bias, preferring psychotherapy alone, adverse effects, and relapse to illicit drugs. CONCLUSION: While HIV-seropositive women may benefit from antidepressant treatment, multiple barriers to successful treatment exist. Aggressive outreach, education, and attention to the complex psychosocial needs of HIV-seropositive women are essential components of depression treatment in this population.

Ambulatory Care↗
PubMed1998

Testosterone as a treatment for fatigue in HIV+ men.

This study assessed correlates of fatigue and the efficacy of testosterone therapy as a treatment for fatigue in men with symptomatic HIV and clinical hypogonadism. We conducted a 12-week open trial of testosterone for HIV+ men with clinical hypogonadism (low libido plus at least one of the associated symptoms of depressed mood, fatigue, and weight loss), CD4 count below 400 cells/cu.mm, and serum testosterone level below 500 ng/dl. 108 men entered the trial; 50% were nonwhite and 72% had an AIDS diagnosis. Baseline correlates of fatigue, as measured by the self-report Chalder Fatigue Scale (CFS), included elevated laboratory values (hematocrit, hemoglobin), lower overall physical functioning, greater psychological distress, and reduced quality of life. Sixty-six of 72 men who presented with fatigue completed the trial, with 52 (79%) rated as responders (much improved energy level) by the study doctor. Fatigue declined significantly among responders, but not nonresponders.

Adult↗
PubMed1998

Exercise as a mediator of psychological and nutritional effects of testosterone therapy in HIV+ men.

PURPOSE: The purpose of this study was to determine whether exercise mediates the psychological and nutritional effects of testosterone therapy in men with symptomatic HIV illness, low serum testosterone, and clinical symptoms of hypogonadism. METHODS: A 12-wk open trial of biweekly intramuscular testosterone injections was conducted, with 54 men completing the trial and exercise assessments. Most (71%) men were diagnosed with AIDS; 41% had a CD4 < 50. One-third of the men were diagnosed with major depression, and nearly half had some evidence of wasting. Twenty-nine men (54%) engaged in exercise (predominantly resistance training) during the trial. Exercisers did not differ from nonexercisers on any measure of psychological well being or nutritional status at baseline. RESULTS: After 12 wk of testosterone treatment, those who exercised showed significant improvement in mood (Hamilton Rating Scale for Depression; HAM-D) and overall distress (Brief Symptom Inventory; BSI) (P < 0.000 for both), as well as a significant increase in body cell mass (P < 0.01) and lean body mass (mean increase of 2.6 kg; P < 0.000) as measured by bioelectric impedance analysis. In contrast, nonexercisers showed improvement on the HAM-D (P < 0.000), but not the BSI or measures of nutritional status. CONCLUSION: These findings indicate that exercise may be an important adjunct to testosterone therapy in the treatment of psychological distress and wasting symptoms in men with symptomatic HIV illness.

Adult↗
PubMed1998

The insulin-like growth factor-I axis in acute renal failure.

We have examined the response of the renal insulin-like growth factor (IGF-I) axis to acute ischemic injury in the rat Key findings included a decrease in IGF-I mRNA and peptide levels, a decrease in GH receptor gene plus protein expression and a decrease in the IGF binding proteins except for IGF binding protein I. Administration of GH to compensate for the reduced GH receptor binding corrected the IGF-I mRNA levels suggesting a relative GH deficiency. Interestingly, IGF-I receptor mRNA levels were unchanged while plasma membrane IGF-I receptor number increased two fold. This appeared to be due to a redistribution of receptors to a membrane location. IGF-I receptor autophosphorylation and tyrosine kinase activity were intact despite severe uremia for up to 6 days. We propose that this increase of functional IGF-I receptors following acute tubular necrosis will sensitize the kidney to the administration of exogenous IGF-I.

Acute Kidney Injury↗
PubMed1998

Insulin-like growth factor-I treatment to enhance renal function in advanced chronic renal failure.

Because of the potential for IGF-I to enhance renal function in advanced chronic renal failure (CRF) we set out to determine whether IGF-I can induce a sustained increase in renal function in patients with near end-stage renal failure. To this end we first examined the impact of CRF on the pharmacokinetics of IGF-I and then we examined the effect of prolonged IGF-I treatment on the renal function of patients with an average GFR of 17 mL/min/1.73 m2. Interestingly the metabolic clearance rate of IGF-I in CRF subjects was similar to that in normal subjects even though the total serum IGF-I levels rose to higher maximum levels. This increase was due to a reduced volume of IGF-I distribution, a consequence of the elevated serum IGF binding proteins in CRF subjects. Treatment with IGF-I (60 mg/kg twice daily sc) for 31 days resulted in a 14% and 18% increase in the inulin and PAH clearances respectively (n = 6 patients). These parameters returned to basal levels on stopping treatment. Serum immunoreactive IGFBP-3 levels fell and IGFBP-2 and -3 levels rose during IGF-I therapy. Adverse effects were mild, of short duration and easily manageable. Thus IGF-I pharmacokinetics are largely unchanged in CRF and the administration of IGF-I produces a modest improvement in the GFR. These results appear to justify more extensive examination of the therapeutic role of IGF-I in the treatment of CRF.

Adult↗