Corn oil intake favorably impacts lipoprotein cholesterol, apolipoprotein and lipoprotein particle levels compared with extra-virgin olive oil.

BACKGROUND: Corn oil (CO) and extra-virgin olive oil (EVOO) are rich sources of unsaturated fatty acids (UFA), but UFA profiles differ among oils, which may affect lipoprotein levels. OBJECTIVES: The objective of this study was to assess the effects of CO versus EVOO intake on fasting lipoprotein and subfraction cholesterol levels, apolipoprotein (apo) A1, apo B, and low-density lipoprotein particle concentrations in men and women. SUBJECTS/METHODS: As part of a weight maintenance diet, men and women were provided with food items prepared with 54 g per day of CO or EVOO (21-day treatment, 21-day washout) in a randomized, double-blind, controlled-feeding, crossover trial. Fasting lipoprotein cholesterol and related variables were determined with density gradient ultracentrifugation. RESULTS: Among the 54 completers, CO reduced total cholesterol, low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), apo B and LDL particle concentration to a greater extent compared with EVOO intake. Changes in LDL-C and VLDL-C contributed to the larger reduction in non-HDL-C with CO compared with EVOO intake (-0.39 mmol/l vs -0.04 mmol/l; P<0.001). The larger reduction in LDL-C by CO intake was attributable to changes (P<0.05) caused by CO vs EVOO in large LDL1+2-C (-0.22 mmol/l) and intermediate-density lipoprotein cholesterol (-0.12 mmol/l). HDL-C responses did not differ between treatments, but apo A1 increased more with EVOO compared with CO intake (4.6 versus 0.7 mg/dl, respectively, P=0.016). CONCLUSIONS: CO intake reduced atherogenic lipoprotein cholesterol and particle concentrations to a larger extent than did EVOO, which may have implications for cardiovascular disease risk.

Recovery potential of black rockfish, Sebastes melanops Girard, recompressed following barotrauma.

Overfished species of rockfish, Sebastes spp., from the Northeast Pacific experience high bycatch mortality because of 'barotrauma', a condition induced from the rapid change in pressure during capture. Field experiments show that it may be possible for rockfish to recover from barotrauma if quickly recompressed; however, no work has followed the physiological recovery of rockfish after recompression or determined whether it is possible for rockfish to survive barotrauma in the long term. Barotrauma was induced in adult black rockfish, Sebastes melanops Girard, from a simulated depth of 35 m, followed by recompression. Blood and selected tissues (eye, heart ventricle, head kidney, liver, rete mirabile and gonad) were sampled at days 3, 15 and 31 post-recompression to evaluate the tissue- and physiologic-level response during recovery. No mortality from barotrauma occurred during the experiments, and feeding resumed in 80% of both treatment and control fish. The primary injury in treatment fish was the presence of a ruptured swimbladder and/or a ruptured tunica externa (outer layer of swimbladder), which was slow to heal. Blood plasma was analysed for glucose, sodium, chloride, potassium, calcium, phosphorus, insulin-like growth factor-1 and cortisol. Plasma analyses indicated no strong effects because of barotrauma, suggesting overall handling stress outweighed any effect from barotrauma. Rockfish with ruptured swimbladders may face compromised competency in the wild; however, it appears the majority of black rockfish decompressed from 35 m have a high potential for recovery if recompressed immediately after capture. This research suggests recompression could be a valuable bycatch mortality reduction tool for rockfish in recreational fisheries.

Estrogen-induced and TAFII30-mediated gene repression by direct recruitment of the estrogen receptor and co-repressors to the core promoter and its reversal by tamoxifen.

Estradiol (E2) acts through the estrogen receptor (ER) to downregulate many genes, and tamoxifen (Tam) largely reverses this repression but the underlying mechanisms are unclear. Repression of the folate receptor (FR)-alpha P4 core promoter by ER is enhanced by E2 and reversed by Tam. This effect was unaffected by inhibition of new protein synthesis and required the E/F and the DNA-binding domains of ER without direct binding of ER to DNA. The repression by E2/ER was not specific for either Sp1 or TATA elements but was loosely selective for the initiator and flanking sequence. Insertion of a response element or a relatively strong Sp1 cluster to recruit ER upstream of the core promoters caused a switch to activation by E2/ER that was inhibited by Tam. In nuclear extracts, association of ER with a biotinylated core promoter fragment was promoted by E2 but Tam blocked this effect. Repression/de-repression of the P4 promoter and endogenous FR-alpha expression by E2/Tam required SMRT and/or NCoR. ER associated with the chromosomal P4 promoter and SMRT and NCoR associated with it in an ER-dependent manner; these associations were favored by E2 but disrupted by Tam, in the short term, without changes in ER expression. TAFII30 was required for optimal P4 promoter activity and for the repressive association of ER. E2 may thus maintain a low transcriptional status of genes by favoring direct TAFII30-dependent association of ER with the core promoter in a co-repressor complex containing SMRT and/or NCoR; this repression is overridden in target genes containing an upstream element that strongly recruits ER. In addition to suppressing the activation of classical E2 target genes, Tam may upregulate genes by passively dissociating the ER co-repressor complex.

Comparative endocrinology of the insulin-like growth factor-binding protein.

Emerging early in chordate evolution, the IGF-regulatory axis diverged from an insulin-like predecessor into a vertebrate regulatory system specializing in cell growth activation and allied anabolic functions. Essential to the divergence of the IGF and insulin systems was an early presence of soluble IGF-binding proteins (IGFBPs), which bind IGF peptides at much higher affinity than that of the insulin receptor but at comparable affinities to that of the IGF receptor. IGFBPs have no homology with IGF receptors. Instead, IGFBPs are a derived group of proteins within a superfamily of cysteine-rich growth factors, whose members are found throughout the animal taxa. While blocking IGF actions through the insulin receptor is a fundamental role, IGFBPs evolved within the vertebrate line into centralized, 'integrators' of the endocrine growth-regulatory apparatus. IGFBPs have substantial influences on the distribution and bioavailability of IGF peptides in the cellular and physiological environments, but they have a variety of other properties. The six principal mammalian IGFBPs exhibit an array of specialized properties that appear to be derived from a complex evolutionary history (including cell membrane association, interaction with proteins that post-translationally modify them, direct IGF-independent effects on cells, and others) and they are regulated by a diversity of 'outside' factors (e.g. other hormones, metabolic status, stress). Thus, IGFBPs are multifunctional integrators having diverse physiological 'agendas'. Much less is known about IGFBPs and their properties in the other vertebrate taxa. Increasingly, however, it is being recognized that they play equally important endocrine roles, in both conserved and non-conserved ways, when compared with those currently defined in mammals. This review highlights selected 'comparative aspects' in current IGFBP research, in an attempt to view this essential group of endocrine regulators from a wider, biological perspective.

Evidence for segregation of heterologous GPI-anchored proteins into separate lipid rafts within the plasma membrane.

Cholesterol and glycosphingolipid-rich membrane rafts, which are rich in GPI-anchored proteins and are distinct from caveolae, are believed to serve as platforms for signal transduction events and protein recycling. GPI-anchored proteins with diverse functions as well as caveolin may be recovered in a membrane fraction insoluble in cold non-ionic detergent. This study tests for possible heterogeneity in the protein composition of the lipid rafts and detergent-insoluble membrane complexes by examining the two GPI-anchored homologous human folate receptors (FR)-alpha and -beta, the GPI-anchored human placental alkaline phosphatase (PLAP), and caveolin (control) in transfected CHO cells. Both FR and PLAP showed the equal distribution of cell-surface vs. sequestered (recycling) protein typical of GPI-proteins. Quantitative affinity purification of detergent-insoluble complexes using biotinylated folate or specific antibodies demonstrated a strong association of the homologous FR-alpha and FR-beta in the same detergent-insoluble complex and separate complexes containing either PLAP or caveolin. Immunogold localization experiments using antibody crosslinking to produce larger aggregates of GPI-anchored proteins for visualization by electron microscopy also showed a clear separation between FR- and PLAP-rich membrane microdomains. Thus, even though functionally diverse and heterologous GPI-anchored proteins are known to share endocytic and recycling vesicles, they may be segregated in distinct lipid rafts on the basis of their ecto(protein) domains facilitating clustering, compartmentalization and homotypic protein interactions.

Effect of epinephrine on net lactate uptake by contracting skeletal muscle.

The purpose of this study was to determine the effect of epinephrine on net lactate (La(-)) uptake at constant elevated blood La(-) concentration and steady level metabolic rate (O(2) uptake) in the canine gastrocnemius-plantaris muscle in situ. Infusion of La(-)/lactic acid (pH 3.5) established a mean arterial blood La(-) concentration of ~10 mM while normal blood-gas and pH status were maintained as the gastrocnemius-plantaris was stimulated with tetanic trains at a rate of one contraction every 4 s. After steady-state control measures, epinephrine was infused for 35 min at rates that produced a high physiological concentration with (Pro; n = 6) and without (Epi; n = 6) beta-adrenergic-receptor blockade via propranolol. Net La(-) uptake values during the control conditions were not significantly different between trials (Epi: 0.756 +/- 0.043; Pro: 0.703 +/- 0.061 mmol. kg(-1). min(-1)). Steady level O(2) uptake averaged approximately 69.5 ml. kg(-1). min(-1) for both control conditions and did not significantly change over the course of the experiments in either set of trials. Epi experiments resulted in a significantly reduced net La(-) uptake (0.346 +/- 0.088 mmol. kg(-1). min(-1) after 5 min of infusion) compared with control value at all sample times measured. However, net La(-) uptake was not significantly different from control at any time during Pro (0.609 +/- 0.052 mmol. kg(-1). min(-1) after 5 min of infusion). When the change from the respective control values for net La(-) uptake was compared across time for both series of experiments, Epi resulted in a significantly greater change from control than did Pro. This study suggests that epinephrine can have a profound effect on net La(-) uptake by contracting muscle and that these effects are elicited through beta-adrenergic-receptor stimulation.

Serum insulin-like growth factor binding proteins (IGFBPs) as markers for anabolic/catabolic condition in fishes.

In fishes as well as in all vertebrates in which it has been assessed, physiological shifts toward catabolism (e.g. such as during food deprivation) are consistently associated with elevations in the serum levels of at least one (often two in fishes) IGFBP in the < or =31-kDa size range. In mammals, 30-kDa IGFBP-1 is strongly up-regulated under catabolic circumstances, and it plays an important physiological role by sequestering IGF peptides to inhibit energy-expensive growth until conditions are more favorable (e.g. with resumed feeding). Similarly in fishes, it has been found that when the < or =31-kDa IGFBPs are elevated in serum, somatic growth is inhibited, suggesting a similar growth-inhibitory role of these proteins to that of mammalian IGFBP-1. Three different experimentally-induced catabolic states in fishes are compared in this paper: fasting; insulin-dependent diabetes mellitus (IDDM); and stress. A strong relationship between elevated serum cortisol concentrations and the presence of IGFBPs in each case is noted, and the utility of serum IGFBP measurement to serve as an effective indicator (marker) of catabolic condition in fishes is discussed.

Down-regulation in the insulin-like growth factor (IGF) axis during hibernation in the golden-mantled ground squirrel, Spermophilus lateralis: IGF-I and the IGF-binding proteins (IGFBPs).

The golden-mantled ground squirrel, Spermophilus lateralis, undergoes a profound winter hibernation that represents, among other changes, a prolonged period of starvation. In addition to dramatic metabolic and other physiological adaptations during hibernation which serve to reduce fuel energy expenditure, we have hypothesized that there may also be significant changes in the endocrine axis that regulates energetically-expensive somatic growth. As compared with euthermic, non-hibernating controls, hibernating S. lateralis were found to have 75%-reduced serum concentrations of insulin-like growth factor-I (IGF-I; from approximately 625 to approximately 150 ng/ml in both females and males, P < 0.05). While IGFBP-3 was the predominant IGFBP in serum of the euthermic controls, its levels were reduced to a similar degree in serum from the hibernating animals. IGFBP-4 was present at relatively low levels in the euthermic controls, and was reduced to undetectable levels in hibernating animals. Surprisingly, there was no IGFBP detectable in the 30 kDa range in either euthermic or hibernating S. lateralis, suggesting that IGFBP-1 does not play a role in hibernation-related changes in the IGF axis. In accordance with these endocrine changes, when serum from hibernating S. lateralis was added to cartilage explant cultures (at a 5% v/v concentration), it exhibited no ability to alter (35)S-proteoglycan synthetic rate, whereas serum from the euthermic squirrels significantly stimulated synthetic activity by 2-fold. These results suggest that part of hibernation adaptation in S. lateralis includes down-regulation in the growth-regulatory IGF axis. J. Exp. Zool. 289:66-73, 2001.

Role of convective O(2) delivery in determining VO(2) on-kinetics in canine muscle contracting at peak VO(2).

A previous study (Grassi B, Gladden LB, Samaja M, Stary CM, and Hogan MC, J Appl Physiol 85: 1394-1403, 1998) showed that convective O(2) delivery to muscle did not limit O(2) uptake (VO(2)) on-kinetics during transitions from rest to contractions at approximately 60% of peak VO(2). The present study aimed to determine whether this finding is also true for transitions involving contractions of higher metabolic intensities. VO(2) on-kinetics were determined in isolated canine gastrocnemius muscles in situ (n = 5) during transitions from rest to 4 min of electrically stimulated isometric tetanic contractions corresponding to the muscle peak VO(2). Two conditions were compared: 1) spontaneous adjustment of muscle blood flow (Q) (Control) and 2) pump-perfused Q, adjusted approximately 15-30 s before contractions at a constant level corresponding to the steady-state value during contractions in Control (Fast O(2) Delivery). In Fast O(2) Delivery, adenosine was infused intra-arterially. Q was measured continuously in the popliteal vein; arterial and popliteal venous O(2) contents were measured at rest and at 5- to 7-s intervals during the transition. Muscle VO(2) was determined as Q times the arteriovenous blood O(2) content difference. The time to reach 63% of the VO(2) difference between resting baseline and steady-state values during contractions was 24.9 +/- 1.6 (SE) s in Control and 18.5 +/- 1.8 s in Fast O(2) Delivery (P < 0.05). Faster VO(2) on-kinetics in Fast O(2) Delivery was associated with an approximately 30% reduction in the calculated O(2) deficit and with less muscle fatigue. During transitions involving contractions at peak VO(2), convective O(2) delivery to muscle, together with an inertia of oxidative metabolism, contributes in determining the VO(2) on-kinetics.

Diabetogenic role of insulin's counterregulatory hormones in the isletectomized, diabetic goby.

In an experimental model of insulin-dependent diabetes mellitus (IDDM) in the teleost fish, the goby Gillichthys mirabilis, an isletectomy procedure completely removes the pancreatic endocrine tissue without affecting the exocrine acini or other essential tissues. Interestingly, isletectomized (Ix) gobies do not exhibit a significant hyperglycemia until 10-15 d after this procedure, suggesting a lack of initial diabetogenic actions of a pancreatic factor(s). Administering exogenous glucagon in otherwise nonsymptomatic 7-d Ix gobies, however, induces a hyperglycemic state comparable to that in severely diabetic rats or gobies (after 20 d post-Ix). The spontaneously arising hyperglycemia observed between 10 and 15d post-Ix, on the other hand, is significantly correlated with increasing serum cortisol concentrations, with both exhibiting sustained elevated levels (approx 23 mmol/L and >100 ng/mL, respectively) at 20- and 25-d post-Ix. Exogenous cortisol treatment also significantly induced hyperglycemia in nonsymptomatic, 7-d Ix gobies. By contrast, growth hormone (GH) had no detectable diabetogenic effect in 7-d Ix gobies. Serum levels of ammonia, the principal nitrogenous waste in this species, were not affected by glucagon treatment but were reduced slightly by GH treatment (30% reduction; p < 0.05). Cortisol treatment, on the other hand, increased ammonia levels twofold, suggesting that the glucocorticoid induces a negative nitrogen balance. These results indicate that the counterregulatory hormones--glucagon and cortisol--are effective diabetogenic factors in the Ix goby, capable of driving metabolic imbalance in this model of IDDM.

Glucose regulation of the IGF response system in chondrocytes: induction of an IGF-I-resistant state.

Nonresponsiveness to the growth-stimulatory actions of insulin-like growth factor (IGF)-I in chondrocytes has been reported in a number of disease states associated with impaired glucose metabolism. Primary rabbit chondrocytes were investigated for changes in their IGF response system [type-I IGF receptor and IGF-binding protein (IGFBP) expression] and in their ability to mount a synthetic response to IGF-I [as 35S-labeled proteoglycan ([35S]PG) production] in media containing varying ambient glucose concentrations. Whereas basal [35S]PG synthetic rate was unaffected by glucose concentration, synthetic responsiveness to IGF-I was lost in media containing <5 mmol/l glucose or in media containing a "diabetic" glucose concentration (25 mmol/l). IGFBP expression, as measured by Northern analysis of mRNA levels and Western ligand blotting of secreted protein levels, was not significantly altered in the different glucose media, nor were there any differences in the cell surface localization of IGFBPs as assessed by affinity cross-linking with 125I-labeled IGF-I, suggesting that IGFBPs do not induce the IGF-I resistance. The nonresponsiveness to IGF-I in reduced glucose occurred with 25-50% reductions in steady-state levels of IGF type-I receptor mRNA and protein. A significant correlation between IGF receptor mRNA level and synthetic response to IGF-I was observed between 0 and 10 mmol/l glucose concentrations, suggesting that the loss of responsiveness in reduced glucose is manifested at the level of transcription and/or receptor mRNA stability. In contrast, nonresponsiveness to IGF-I in chondrocytes in diabetic glucose concentrations occurred without changes in receptor mRNA and protein levels, suggesting that IGF-I resistance was due to post-ligand-binding receptor defects. It is proposed that IGF-I resistance in chondrocytes subjected to inappropriate glucose levels may constitute an important pathogenic mechanism in degenerative cartilage disorders.

Electrical injury through the eyes of professional electricians.

This paper presents the first results of an attitudinal survey that was conducted among professional electricians in order to explore their knowledge and beliefs related to occupational electrical injury. Four hundred eighty-one out of 1200 questionnaires were returned and analyzed. The presented statistical and qualitative data reflect electricians' personal experiences with electrical injury, their communication patterns around electrical trauma, their understanding of possible electrical injury sequelae, their safety beliefs and attitudes towards occupational dangers, and the reasons for their occupational choice. We expect that the results of this study will enhance our understanding of the psychological profile, environment, and culture of electrical workers. The collected data may also help to identify those at risk for poor outcome after electrical injury and determine a new set of risk factors to be taken into account by medical professionals, social workers, and union/utility training officers.

Management and coordination of postacute medical care for electrical trauma survivors.

The clinical spectrum of electrical injury ranges from the absence of any external physical signs to severe multiple trauma. Reported neuropsychiatric sequelae can vary from vague complaints, which may seem unrelated to the injury in their occurrence over time or by their apparent severity, to sequelae consistent with brain injury accompanying an electrical trauma. In this report, a case study and discussion are presented on the management and coordination of post-acute care of an electrical trauma survivor. Expertise and a multidisciplinary team are essential to cohesive patient care. Patient monitoring for progressive changes and prompt intervention are needed to address the potential difficulties experienced by trauma survivors as they rehabilitate to return to their work and their activities of daily living.

Life after electrical injury. Risk factors for psychiatric sequelae.

Long-term cognitive and emotional deficits have been commonly reported in electrical injury (EI) survivors. However, it remains undetermined what factors may lead to the development of such effects in some patients and not in others. In this study, we hypothesized that certain elements of subjective EI experience may predict specific psychiatric sequelae. A group of 73 post-acute EI patients were included in this retrospective study. Statistical associations were examined between major psychiatric diagnoses (posttraumatic stress disorder and major depression) and such EI descriptors as having experienced "no-let-go" or having been knocked away on contact, as well as loss of consciousness or altered states of consciousness at the scene of the accident (including amnesia for the event). The study results will help physicians determine which patients may be at increased risk of developing psychiatric symptoms and address these issues as part of their total rehabilitation plan.

Neuropsychological symptom presentation after electrical injury.

OBJECTIVE: This study explored the relationship of neuropsychological complaints to accident- and injury-related characteristics, affective state, and work status in a group of electrical injury (EI) patients. METHODS: Sixty-three EI patients and 22 electricians with no history of electrical shock completed the Neuropsychological Symptom Checklist and the Beck Depression Inventory as part of an extensive neuropsychological evaluation. RESULTS: The EI group endorsed significantly more physical, cognitive, and emotional symptoms than did the controls. Symptom complaints were not related to injury parameters or litigation status. Only the time interval between injury and assessment accounted for differences in symptom presentation, with patients in the postacute stages of recovery showing the most cognitive and emotional complaints. CONCLUSION: The neuropsychological syndrome of electrical injury survival includes physical, cognitive, and emotional complaints. Considering that most electrically injured patients are treated within the acute medical setting, greater attention needs to be directed early in the course of treatment toward addressing neuropsychologic and psychiatric issues.

Evidence for insulin-like growth factor (IGF)-independent transcriptional regulation of IGF binding protein-3 by growth hormone in SKHEP-1 human hepatocarcinoma cells.

Insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) is a polypeptide that forms a ternary complex with IGFs and an acid-labile subunit. The hormonal regulation of the components of this complex is highly controversial, and both IGF-I and GH have been shown to mediate the expression/synthesis of IGFBP-3. This study investigates the regulation of IGFBP-3 protein, measured by RIA and Western ligand blot, and messenger RNA (mRNA) expression, measured by Northern analysis and reverse transcriptase-PCR, in SKHEP-1 human hepatocarcinoma cells. SKHEP-1 cells significantly increased the IGFBP-3 concentrations in conditioned medium (CM) when treated with GH (0.1-10 ng/ml), IGF-I (1-100 ng/ml), or Des(1-3)-IGF-I (1-100 ng/ml) in a dose-dependent manner (>3-fold). The increase in IGFBP-3 protein concentrations in CM was accompanied by a corresponding increase in IGFBP-3 mRNA levels. Interestingly, time-course studies showed that the GH-induced increase in IGFBP-3 mRNA preceded the IGF-I-induced increase (6 h for GH-induced IGFBP-3 mRNA; 12 h for IGF-I-induced IGFBP-3 mRNA). The half-life of IGFBP-3 mRNA was evaluated after transcriptional arrest by treatment with a RNA polymerase II inhibitor (5,6-dichloro-1beta-D-ribofuranosylbenzimidazole), and was found to be 14-18 h and unaltered by GH or IGF-I treatment. The induction of IGFBP-3 by GH was not due to the indirect action of locally synthesized IGF-I, because 1) no immunoreactive IGF-I was detected in the CM of control or GH-treated cells; 2) Northern blots revealed no IGF-I mRNA expression in SKHEP-1 cells; 3) reverse transcriptase-PCR did not detect any expression of the IGF-I gene; and 4) time-course studies showed an earlier increase in IGFBP-3 mRNA after GH treatment than after IGF-I treatment. Thus, the results obtained in this study are consistent with an IGF-I-independent regulation of IGFBP-3 gene expression by GH.

Insulin-like growth factor-binding proteins (IGFBPs) and their regulatory dynamics.

The IGFBPs are a family of homologous proteins that have co-evolved with the IGFs and that confer upon the IGF regulatory system both functional and tissue specificity. IGFBPs are not merely carrier proteins for IGFs, but hold a central position in IGF ligand-receptor interactions through influences on both the bioavailability and distribution of IGFs in the extracellular environment. In addition, IGFBPs appear to have intrinsic biological activity independent of IGFs. The current status of research on IGFBPs is reviewed herein. Following a brief introduction to the entire IGF/IGFBP system, separate sections for each of the six cloned mammalian IGFBPs, the most extensive for IGFBP3, cover selected topics that emphasize the dynamics of IGFBPs--that is, their regulation in cells, their functionally important post-translational modifications, and their interactions in the cellular microenvironment--and how these dynamics influence physiological function.

A low-molecular-weight (25-kDa) IGF-binding protein is increased with growth inhibition in the fasting striped bass, Morone saxatilis.

The effect of fasting on circulating IGFBPs in the striped bass was assessed in relation to changes in growth and metabolism. Thirty-day-fasted (30DF) and 60-day-fasted (60DF) fish, and 60DF fish refed for 14 additional days (REFED), were compared with control, fed fish. Growth and metabolic status of each animal were assessed by determining body length (BL) and body weight (BW) changes, hepatosomatic index (HSI), condition factor (CF), and serum glucose concentration, and by assaying for incorporation of [35S]sulfate (proteoglycan synthetic activity) and [3H]thymidine (mitotic activity) in ceratobranchial cartilage explants in vitro. Serum IGFBP concentrations were assessed by a Western ligand blot procedure using 125I-labeled human IGF-I tracer. Both 30DF and 60DF fish exhibited hypoglycemia and reduced HSI and CF, and their BL and BW growth rates were significantly inhibited. Strongly correlated with the inhibited body growth indices were significantly depressed levels of cartilage [35S]sulfate incorporation in both 30DF and 60DF animals. The 60DF group also exhibited reduced [3H]thymidine incorporation. Associated with this growth inhibition was a dramatic increase in the serum levels of a 25-kDa IGFBP (sbIGFBP-1). A 35-kDa IGFBP (sbIGFBP-3), on the other hand, was not significantly altered with fasting. All fasting-induced changes in growth, metabolism, and IGFBP levels were restored in the REFED group. These results demonstrate that an IGFBP of low molecular weight is increased with growth inhibition in the fasting striped bass, suggesting that a teleost fish counterpart to mammalian IGFBP-1 may exist.

Insulin-like growth factor binding protein 3 mediates retinoic acid- and transforming growth factor beta2-induced growth inhibition in human breast cancer cells.

Retinoic acid (RA) is a potent in vitro inhibitor of cell proliferation in various malignant cell lines. The exact mechanisms of its actions, however, are not fully understood. To further elucidate the nature of this inhibition, we investigated the effects of RA in an estrogen receptor-negative human breast cancer cell line, MDA-MB-231. RA (0.01-5 microM) significantly inhibited MDA-MB-231 cell growth by 35-40% as compared with untreated controls. Similar growth inhibitory actions were observed when cells were treated with transforming growth factor beta2 (TGF-beta2), another factor with antiproliferative actions in breast cancer cells. Both RA and TGF-beta2 increased the levels of insulin-like growth factor binding protein (IGFBP) 3 (2-3-fold) and mRNA (1.5-2-fold), whereas IGFBP-4 levels remained essentially unchanged. The direct involvement of IGFBP-3 in cell growth inhibition was further confirmed by its action on cell growth: exogenous IGFBP-3 directly and significantly inhibited MDA-MB-231 cell number by 40%. These results provided circumstantial evidence that IGFBP-3 may mediate RA and TGF-beta2 growth inhibitory actions in human breast cancer cells. To test this hypothesis, we used an antisense IGFBP-3 oligodeoxynucleotide (ODN) which specifically inhibits IGFBP-3 expression. The antisense IGBP-3 ODN dramatically blocked both RA- and TGF-beta2-induced increases in IGFBP-3 protein (90%) and mRNA levels (90%). This effect was not observed when RA- or TGF-beta2-exposed cells were treated with sense IGFBP-3 ODN. Moreover, antisense ODN did not significantly affect IGFBP-4 protein or mRNA levels, strongly supporting the specificity of the antisense IGFBP-3 ODN effect on IGFBP-3 mRNA. This specific effect of antisense IGFBP-3 ODN on IGFBP-3 protein and mRNA levels was accompanied by significant attenuation of the inhibition of cell proliferation attained with RA or TGF-beta2 (approximately 40% of either RA- or TGF-beta2-induced inhibition). The control sense IGFBP-3 ODN did not reduce the growth inhibition observed with either RA or TGF-beta2. These results indicate that IGFBP-3 is an important mediator of RA- and TGF-beta2-induced cell growth inhibition in human breast cancer cells.