Injection Of Fibroblast Growth Factor 1 Research Articles

1527-P: Anorexia Induced by the Central Action of Fibroblast Growth Factor 1 (FGF1) Is Dependent on Reduced GABA Receptor Activation

Previously, we reported that in multiple rodent models of type 2 diabetes, remission of hyperglycemia lasting for weeks can be induced by a single intracerebroventricular (icv) injection of FGF1. This effect is accompanied by a potent but transient anorexic response that is sufficiently robust as to hinder efforts to translate these findings towards the clinic. To understand the mechanism underlying FGF1-induced anorexia, we considered 1) our recent finding that icv FGF1 induces acute and sustained inhibition of hypothalamic AgRP neurons, and 2) prior work showing that parabrachial nucleus that express calcitonin gene-related peptide (PBNCGRP neurons) are both highly anorexigenic and tonically inhibited by GABAergic projections from AgRP neurons. We therefore hypothesized that FGF1-induced anorexia involves activation PBNCGRPneurons arising from reduced GABAergic input. Consistent with this hypothesis, we report that PBNCGRPneurons are robustly activated following icv FGF1 injection (based on c-Fos staining) via a mechanism that appears to be indirect, since the c-Fos induction is not associated with FGF receptor (FGFR) activation (detected by pERK staining in the PBN). We next asked whether the anorexic response to icv FGF1 administration can be blunted by systemic administration of a GABAA receptor agonist. Consistent with this hypothesis, we found that continuous subcutaneous infusion of the GABAA receptor agonist Bretazenil blunts the anorexic response to icv FGF1 injection by ~50% at a dose that has no effect intake in control mice. Similarly, the effect of FGF1 to induce c-Fos in the PBN was largely blocked by Bretazenil, and our preliminary findings indicate that CGRP neurons are among those in which this effect occurred. Together, these data suggest that FGF1-induced anorexia results from reduced GABAergic inhibition of PBNCGRP neurons. Disclosure J.M.Scarlett: None. K.M.Alonge: None. B.N.Phan: None. G.J.Morton: Research Support; Novo Nordisk A/S. M.W.Schwartz: Consultant; NodThera, Research Support; Novo Nordisk A/S. Funding U.S. Department of Defense (PRMRP W81XWH-21-1-0635); National Institutes of Health (DK083042)

Role of hypothalamic MAPK/ERK signaling and central action of FGF1 in diabetes remission

SummaryThe capacity of the brain to elicit sustained remission of hyperglycemia in rodent models of type 2 diabetes following intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) is well established. Here, we show that following icv FGF1 injection, hypothalamic signaling by extracellular signal-regulated kinases 1 and 2 (ERK1/2), members of the mitogen-activated protein kinase (MAPK) family, is induced for at least 24 h. Further, we show that this prolonged response is required for the sustained antidiabetic action of FGF1 since it is abolished by sustained (but not acute) pharmacologic blockade of hypothalamic MAPK/ERK signaling. We also demonstrate that FGF1 R50E, a FGF1 mutant that activates FGF receptors but induces only transient hypothalamic MAPK/ERK signaling, fails to mimic the sustained glucose lowering induced by FGF1. These data identify sustained activation of hypothalamic MAPK/ERK signaling as playing an essential role in the mechanism underlying diabetes remission induced by icv FGF1 administration.

Role of Hypothalamic MAPK/ERK Signaling in Diabetes Remission Induced by the Central Action of Fibroblast Growth Factor 1

The capacity of the brain to elicit sustained remission of hyperglycemia in rodent models of type 2 diabetes following intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) is well established. Here, we show that following icv FGF1 injection, hypothalamic signaling by extracellular signal-regulated kinases 1 and 2 (ERK1/2), members of the mitogen-activated protein kinase (MAPK) family is induced for at least 24h. Further, we show that in diabetic Lepob/ob mice, this prolonged response is required for the sustained antidiabetic action of FGF1, since it is abolished by sustained (but not acute) pharmacologic blockade of hypothalamic MAPK/ERK signaling. We also demonstrate that FGF1 R50E, a FGF1 mutant that activates FGF receptors but induces only transient hypothalamic MAPK/ERK signaling, fails to mimic the sustained glucose lowering induced by FGF1. These data identify sustained activation of hypothalamic MAPK/ERK signaling as playing an essential role in the mechanism underlying diabetes remission induced by icv FGF1 administration.

Hypothalamic perineuronal net assembly is required for sustained diabetes remission induced by fibroblast growth factor 1 in rats.

We recently showed that perineuronal nets (PNNs) enmesh glucoregulatory neurons in the arcuate nucleus (Arc) of the mediobasal hypothalamus (MBH)1, but whether these PNNs play a role in either the pathogenesis of type 2 diabetes (T2D) or its treatment remains unclear. Here we show that PNN abundance within the Arc is markedly reduced in the Zucker diabetic fatty (ZDF) rat model of T2D, compared with normoglycaemic rats, correlating with altered PNN-associated sulfation patterns of chondroitin sulfate glycosaminoglycans in the MBH. Each of these PNN-associated changes is reversed following a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) at a dose that induces sustained diabetes remission in male ZDF rats. Combined with previous work localizing this FGF1 effect to the Arc area2-4, our finding that enzymatic digestion of Arc PNNs markedly shortens the duration of diabetes remission following icv FGF1 injection in these animals identifies these extracellular matrix structures as previously unrecognized participants in the mechanism underlying diabetes remission induced by the central action of FGF1.

214-OR: Role of Hypothalamic MAPK/ERK Signaling in Diabetes Remission Induced by the Central Action of Fibroblast Growth Factor 1 (FGF1)

The hypothalamic arcuate nucleus-median eminence (ARC-ME) is a target for sustained diabetes remission induced by fibroblast growth factor 1 (FGF1). To identify intracellular signaling cascades underlying this effect, we considered evidence that sustained signal transduction responses engaged by FGF1 are integrin-dependent. To determine if the sustained antidiabetic response of diabetic ob/ob mice to intracerebroventricular (icv) injection of FGF1 is also integrin-dependent, we investigated the response to a mutant FGF1 that is unable to activate integrin receptors (R50E FGF1). We found that although icv injection of R50E FGF1 mimics the transient anorexia, weight loss and blood glucose lowering responses induced by native FGF1 (P<0.001 vs. Veh for each), it fails to elicit sustained diabetes remission. Similarly, MAPK/ERK signaling is induced in the ARC-ME (primarily in tanycytes) for up to 24 h following a single icv FGF1 injection in both wild type and ob/ob mice, but the duration of this response is reduced by∼70% following icv R50E FGF1 injection (P<0.0001 vs. icv FGF1). We therefore hypothesized that owing to its integrin-dependent nature, FGF1-induced remission of diabetic hyperglycemia requires sustained activation of the MAPK/ERK signaling pathway in the ARC-ME. To test this hypothesis, 4 groups of diabetic ob/ob mice were studied. Each group received a single icv injection of either saline vehicle or recombinant FGF1 (3 µg), followed immediately by continuous icv infusion of either the MAPK inhibitor U0126 or its vehicle (DMSO) for 24 h. We report that the duration of the antidiabetic effect induced by icv FGF1 injection is attenuated by pharmacologic blockade of MAPK/ERK signaling. We conclude that the sustained remission of diabetic hyperglycemia induced by the central action of FGF1 depends upon its ability to activate hypothalamic MAPK/ERK signaling in a sustained manner. Disclosure J.M. Brown: None. B.N. Phan: None. H. Wasanwala: None. M.E. Matsen: None. A. Secher: Employee; Spouse/Partner; Gubra. Employee; Self; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. G.J. Morton: Research Support; Self; Novo Nordisk A/S. M.W. Schwartz: Research Support; Self; Novo Nordisk A/S. J. Scarlett: None. Funding National Institutes of Health (K08DK114474, DK101997, DK083042, DK035816, P30DK017047, HL007312); University of Washington

1771-P: Hypothalamic Perineuronal Net Assembly Is Required for Sustained Diabetes Remission Induced by FGF1

Defective glucoregulatory neurocircuit activity within the hypothalamic arcuate nucleus (ARC) is implicated in the pathogenesis of type 2 diabetes (T2D). In the ARC of T2D-Zucker Diabetic Fatty (ZDF) rats, we have identified significant changes in the composition and abundance of extracellular perineuronal nets (PNNs) that enmesh glucoregulatory neurocircuits. Imaging of ARC PNNs, which are comprised of the chondroitin sulfate (CS) proteoglycan aggrecan and attached CS glycosaminoglycans (GAGs), show that T2D-ZDF rats exhibit a 66.4% and 77.3% decrease in aggrecan in the medial and lateral ARC areas, respectively, compared to normoglycemic controls. Distinctive sulfation of the attached CS-GAG isomers (0S-, 4S-, 6S-, 4S6S-, 2S6S-CS) differentially influence the function of PNNs. Using LC-MS/MS, we provide the first description of hypothalamic CS-GAG sulfation patterns and show that in T2D-ZDF rats, levels of the ∆4S- isomer is increased, whereas ∆6S- and ∆2S6S-CS isomers are decreased, differences predicted to disrupt protein-GAG interactions involved in neurite outgrowth and favor tissue stiffening. To determine if ARC PNNs are targets for the antidiabetic effect of fibroblast growth factor 1 (FGF1), we performed intracerebroventricular (icv) injection of FGF1 in ZDF rats and report that both the hypothalamic CS-GAG sulfation patterns and content of ARC PNNs are normalized 24 d after treatment. Western blot analysis shows that the latter effect entails a 1.7-fold increase in aggrecan protein abundance. To assess the functional significance of ARC PNN restoration by FGF1, ZDF rats received an icv FGF1 injection followed by bilateral microinjection of either ChABC, a PNN digesting enzyme, or its vehicle control into the ARC. Our finding that the duration of sustained FGF1-induced blood glucose lowering was shortened following ARC PNN digestion (p<0.05) identifies PNNs as novel participants in the central control of glucose homeostasis and diabetes remission by FGF1. Disclosure K.M. Alonge: Research Support; Self; Novo Nordisk Inc. Z. Mirzadeh: None. J. Scarlett: None. A. Logsdon: None. J.M. Brown: None. E. Cabrales: None. C.K. Chan: None. K. Kaiyala: None. M.A. Bentsen: None. W.A. Banks: None. M. Guttman: None. T.N. Wight: None. G.J. Morton: Research Support; Self; Novo Nordisk A/S. M.W. Schwartz: Research Support; Self; Novo Nordisk A/S. Funding National Institutes of Health (P30DK017047, F32DK122662, R01DK101997, R01DK089056, R01DK083042, K08DK114474, R01GM127579, K12NS080223, P30DK035816); Barrow Neurological Foundation (1800253005); University of Washington; Novo Nordisk (CMS431104); Novo Nordisk Foundation (NNF170C0024328, NNF10CC1016515)

Assembly of Hypothalamic Perineuronal Nets Contributes to Sustained Blood Glucose Lowering by FGF1 Action in the Brain

The mediobasal hypothalamus (MBH) plays a key role in the homeostatic control of blood glucose levels, and defective activity of glucoregulatory neurocircuits in this brain area is implicated in the pathogenesis of type 2 diabetes mellitus (T2DM). We have identified irregularities in the abundance of perineuronal nets (PNNs), specialized extracellular matrix (ECM) lattices that regulate neurocircuit network interactions, surrounding MBH neurons in rodent models of T2DM. Specifically, diabetic Zucker Diabetic Fatty (ZDF) rats exhibit a 56% decrease in aggrecan+ PNN structures in the MBH compared to age‐matched normoglycemic WT controls, suggestive of destabilized glucose‐sensing neurocircuit interactions. To determine whether this effect is associated with changes in the relative abundance of chondroitin sulfate (CS)‐glycosaminoglycan (GAG) isomers (Δ0S‐, Δ4S‐, Δ6S‐, Δ4S6S, Δ2S6S‐CS), which constitute the glycan component of PNNs and influence the function of these matrices, we characterized CS‐GAG sulfation patterns using state‐of‐the‐art LC‐MS/MS + MRM analysis. Here, we report that diabetic ZDF rats exhibit a significant increase in Δ4S‐CS and corresponding decrease in Δ6S‐ and Δ2S6S‐CS isomers within the MBH that are suggestive of altered protein‐GAG interactions, axonal repulsion and ECM stiffening. We next sought to determine if these PNNs are targets for the effect of fibroblast growth factor 1 (FGF1) to induce sustained blood glucose lowering in ZDF rats following intracerebroventricular (icv) administration. We found that in ZDF rats, icv FGF1 injection normalized CS‐GAG composition while inducing a 2.2‐fold increase in aggrecan+ PNN structures. To determine whether this response is required for blood glucose lowering induced by central FGF1 treatment, ZDF rats received an icv injection of FGF1 followed immediately by bilateral microinjection of either vehicle or the CS‐GAG digesting enzyme, Chondroitinase ABC (ChABC), directed to the MBH to disassemble PNNs. Our finding that the duration of blood glucose lowering induced by icv FGF1 injection was markedly shortened by digestion of hypothalamic PNNs identifies PNNs as key targets for the action of FGF1 to induce sustained remission of diabetes. These data identify a key role for MBH PNNs in glucoregulatory neural network interactions involved in the homeostatic control of blood glucose.Support or Funding InformationThis project was supported by the National Institutes of Health Awards DK12266201 (to K.M.A) and DK083042 (to M.W.S). Research support also provided by Novo Nordisk, Inc (CMS‐431104).

The Hypothalamic Arcuate Nucleus-Median Eminence Is a Target for Sustained Diabetes Remission Induced by Fibroblast Growth Factor 1.

In rodent models of type 2 diabetes (T2D), sustained remission of diabetic hyperglycemia can be induced by a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1). To identify the brain areas responsible for this effect, we first used immunohistochemistry to map the hypothalamic distribution of phosphorylated extracellular signal-related kinase 1/2 (pERK1/2), a marker of mitogen-activated protein kinase-ERK signal transduction downstream of FGF receptor activation. Twenty minutes after icv FGF1 injection in adult male Wistar rats, pERK1/2 staining was detected primarily in two hypothalamic areas: the arcuate nucleus-median eminence (ARC-ME) and the paraventricular nucleus (PVN). To determine whether an action of FGF1 localized to either the ARC-ME or the PVN is capable of mimicking the sustained antidiabetic effect elicited by icv FGF1, we microinjected either saline vehicle or a low dose of FGF1 (0.3 µg/side) bilaterally into either the ARC-ME area or PVN of Zucker Diabetic Fatty rats, a model of T2D, and monitored daily food intake, body weight, and blood glucose levels over a 3-week period. Whereas bilateral intra-arcuate microinjection of saline vehicle was without effect, remission of hyperglycemia lasting >3 weeks was observed following bilateral microinjection of FGF1 into the ARC-ME. This antidiabetic effect cannot be attributed to leakage of FGF1 into cerebrospinal fluid and subsequent action on other brain areas, since icv injection of the same total dose was without effect. Combined with our finding that bilateral microinjection of the same dose of FGF1 into the PVN was without effect on glycemia or other parameters, we conclude that the ARC-ME area (but not the PVN) is a target for sustained remission of diabetic hyperglycemia induced by FGF1.

Peripheral Mechanisms Mediating the Sustained Antidiabetic Action of FGF1 in the Brain.

We recently reported that in rodent models of type 2 diabetes (T2D), a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) induces remission of hyperglycemia that is sustained for weeks. To clarify the peripheral mechanisms underlying this effect, we used the Zucker diabetic fatty fa/fa rat model of T2D, which, like human T2D, is characterized by progressive deterioration of pancreatic β-cell function after hyperglycemia onset. We report that although icv FGF1 injection delays the onset of β-cell dysfunction in these animals, it has no effect on either glucose-induced insulin secretion or insulin sensitivity. These observations suggest that FGF1 acts in the brain to stimulate insulin-independent glucose clearance. On the basis of our finding that icv FGF1 treatment increases hepatic glucokinase gene expression, we considered the possibility that increased hepatic glucose uptake (HGU) contributes to the insulin-independent glucose-lowering effect of icv FGF1. Consistent with this possibility, we report that icv FGF1 injection increases liver glucokinase activity by approximately twofold. We conclude that sustained remission of hyperglycemia induced by the central action of FGF1 involves both preservation of β-cell function and stimulation of HGU through increased hepatic glucokinase activity.

A Single-Cell Transcriptomics Roadmap to Investigate Diabetes Remission Induced by the Central Action of Fibroblast Growth Factor-1 (FGF-1)

Recently, lasting remission of hyperglycemia was achieved in rodent models of type 2 diabetes (T2D) by a single intracerebroventricular (icv) injection of FGF-1. While the mechanism underlying this effect is unknown, the lack of association with changes of body fat mass or risk of hypoglycaemia raises the possibility that icv FGF-1 normalizes the defended level of glycemia, rather than simply lowering blood glucose levels. Recent work from our lab has identified gluco-regulatory neurocircuits in the mediobasal hypothalamus (MBH) as targets for this FGF-1 effect. To investigate the mechanism underlying FGF-1 action in this brain area, we used large-scale single cell RNA-sequencing to identify and characterize FGF-1-responsive cells in mouse MBH. Based on >70,000 single cell MBH transcriptomes from diabetic ob/ob mice harvested 5d after a single icv injection of either FGF-1 or vehicle, we identified >20 cell clusters and >900 cell type-specific differentially expressed genes (p<0.01). Among these potential targets of the MBH response to FGF-1 in diabetic mice, we found that FGF-1 treatment robustly increased the proportion of newly formed oligodendrocytes, a response that can be predicted to yield new mature oligodendrocytes and associated myelination of axons. These preliminary results demonstrate that transcriptional identification and characterisation of icv FGF-1-responsive cell clusters may both advance our understanding of brain control of glucose homeostasis and identify novel targets for diabetes prevention and treatment. Disclosure M.A. Bentsen: None. D. Rausch: None. J. Scarlett: None. K.M. Alonge: None. P.N. Timshel: None. Z. Mirzadeh: None. A. Secher: Employee; Self; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. Employee; Spouse/Partner; Gubra. R. Jorgensen: Employee; Self; Novo Nordisk Inc.. T. Pers: None. M.W. Schwartz: Consultant; Self; Novo Nordisk A/S. Research Support; Self; Novo Nordisk A/S.

Sustained Diabetes Remission Induced by the Central Action of Fibroblast Growth Factor-1 (FGF-1) Requires Activation of Integrin Receptor aνß3

The brain is implicated in the antidiabetic effects of members of the fibroblast growth factor (FGF) peptide family. Previously, we reported that a single intracerebroventricular (icv) injection of FGF-1 induces remission of hyperglycemia that is sustained for weeks in rodent models of type 2 diabetes (T2D). The integrin receptor ανβ3 plays a key role in FGF-1 signaling, and crosstalk between ανβ3 and the FGF-1-FGF receptor (FGF-R) complex is necessary for increased DNA synthesis and proliferation in cultured cells. These cellular responses downstream of FGF-1-FGFR-ανβ3 result from sustained (e.g., lasting for 5 hours) activation of the extracellular signal-regulated kinase (ERK) signal transduction pathway. In cultured fibroblasts, prolonged ERK activation induced by FGF-1 is not replicated with a mutant FGF-1 peptide (R50E) that activates FGFR normally, but does not activate ανβ3 signaling. Similarly, we report that whereas icv FGF-1 (3 µg) induces phosphorylation of ERK1/2 at both early (20 minute) and late (5 hr) time points in hypothalamic punches obtained from wild type mice, icv injection of the same dose of R50E elicited this effect only at the early time point. Thus, R50E fails to activate hypothalamic FGF-1-FGFR-ανβ3 signaling in vivo. To investigate whether activation of ανβ3 is required for the prolonged antidiabetic effect of icv FGF-1, diabetic ob/ob mice received a single injection of either vehicle (Veh), recombinant FGF-1 (3 µg), or R50E (3 µg). Whereas R50E mimicked the effect of native FGF-1 to reduce food intake, body weight and blood glucose for the first week after icv injection (P<0.001 vs. Veh), the mutant peptide failed to elicit the sustained diabetes remission observed in animals receiving icv FGF-1. We conclude that signaling by the full FGF-1-FGFR-ανβ3 complex is necessary for the effect of FGF-1 signaling in the brain to elicit sustained remission of diabetic hyperglycemia in rodent models of T2D. Disclosure J. Scarlett: None. J.M. Brown: None. B.N. Phan: None. E.L. Khav: None. M.E. Matsen: None. N.K. Acharya: None. H.T. Nguyen: None. A. Secher: Employee; Self; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. Employee; Spouse/Partner; Gubra. R. Jorgensen: Employee; Self; Novo Nordisk Inc.. G.J. Morton: None. M.W. Schwartz: Consultant; Self; Novo Nordisk A/S. Research Support; Self; Novo Nordisk A/S.

An Action in the Hypothalamic Arcuate Nucleus Is Sufficient to Explain the Sustained Remission of Diabetes Induced by Central Administration of Fibroblast Growth Factor-1 (FGF-1)

Our recent finding that a single intracerebroventricular (icv) injection of FGF-1 elicits sustained diabetes remission in rodent models of type 2 diabetes supports a growing consensus that the brain is a key target for diabetes drug development. The current work was undertaken to pinpoint the brain area responsible for this action of FGF-1. To this end, we considered the following preliminary findings: 1) both FGF Receptor 1 and integrin receptor αvβ3 (known to be involved in sustained FGF-1 signaling) are concentrated in the hypothalamic arcuate nucleus (ARC), 2) neuronal activation and sustained induction of the MAP Kinase / ERK pathway occurs in this brain area following icv FGF-1 injection, and 3) labeled FGF-1 is concentrated in this area following icv injection. We therefore hypothesized that in rodent models of T2D, an action in the ARC (a brain area known to participate in glucose homeostasis) mediates the sustained diabetes remission elicited by icv FGF-1 injection. To test this hypothesis, we investigated whether a single microinjection of a low dose of FGF-1 into the ARC (0.3 µg bilaterally, for a total of 0.6 µg) can mimic the response elicited by icv injection of a higher dose (3.0 µg). We report that in Zucker Diabetic Fatty rats, a single microinjection of FGF-1 bilaterally into the ARC (via an indwelling dual guide cannula) induced remission of hyperglycemia lasting >3 week, whereas intra-arcuate microinjection of saline vehicle was without effect (P<0.vs. Veh). Since icv injection of the same FGF-1 dose (0.6 µg) had no significant effect on glycemia, sustained diabetes remission induced by intra-ARC microinjection of FGF-1 cannot be explained by leakage into ventricular cerebrospinal fluid. We conclude that an action in the ARC is sufficient to explain the effect of FGF-1 to induce sustained diabetes remission. Disclosure J.M. Brown: None. J. Scarlett: None. M.E. Matsen: None. A. Secher: Employee; Self; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. Employee; Spouse/Partner; Gubra. R. Jorgensen: Employee; Self; Novo Nordisk Inc.. G.J. Morton: None. M.W. Schwartz: Consultant; Self; Novo Nordisk A/S. Research Support; Self; Novo Nordisk A/S.

FGF1 - a new weapon to control type 2 diabetes mellitus.

A hypercaloric diet combined with a sedentary lifestyle is a major risk factor for the development of insulin resistance, type 2 diabetes mellitus (T2DM) and associated comorbidities. Standard treatment for T2DM begins with lifestyle modification, and includes oral medications and insulin therapy to compensate for progressive β-cell failure. However, current pharmaceutical options for T2DM are limited in that they do not maintain stable, durable glucose control without the need for treatment intensification. Furthermore, each medication is associated with adverse effects, which range from hypoglycaemia to weight gain or bone loss. Unexpectedly, fibroblast growth factor 1 (FGF1) and its low mitogenic variants have emerged as potentially safe candidates for restoring euglycaemia, without causing overt adverse effects. In particular, a single peripheral injection of FGF1 can lower glucose to normal levels within hours, without the risk of hypoglycaemia. Similarly, a single intracerebroventricular injection of FGF1 can induce long-lasting remission of the diabetic phenotype. This Review discusses potential mechanisms by which centrally administered FGF1 improves central glucose-sensing and peripheral glucose uptake in a sustained manner. Specifically, we explore the potential crosstalk between FGF1 and glucose-sensing neuronal circuits, hypothalamic neural stem cells and synaptic plasticity. Finally, we highlight therapeutic considerations of FGF1 and compare its metabolic actions with FGF15 (rodents), FGF19 (humans) and FGF21.

Sustained delivery of FGF-1 increases vascular density in comparison to bolus administration

The use of growth factors for the therapeutic stimulation of neovascularization in regenerative medicine has been extensively investigated, but the inability to control their temporal delivery may limit clinical success. A strategy that delivers continuous therapeutic concentrations of growth factors may increase the protein's efficacy. The present study investigates the ability of sustained delivery of fibroblast growth factor-1 (FGF-1), to induce neovascularization in vivo. Alginate microbeads were synthesized to release active FGF-1 for three weeks. Microbeads loaded with FGF-1 (total amount 150 ng) were implanted into a surgically created omentum pouch in rats and were compared to control empty microbead implants and a single bolus injection of 150 ng of FGF-1 with empty microbead implant. Animals were sacrificed at either 3 or 6 weeks post implantation and omenta were analyzed for vascular density and mural cell interactions. Vascular area for bolus FGF-1 and FGF-1 loaded microbeads was higher than control at 3 weeks. At 6 weeks, vascular density in the group with FGF-1 loaded microbeads was significantly higher than the group with bolus administration of FGF-1, primarily due to an increase in the number of vessels less than 20 µm in diameter. Vascular density in omenta of the group receiving the bolus FGF-1 returned to control levels by 6 weeks. Staining for smooth muscle actin showed that 50% of vessels had associated mural cells. There was a trend of increased mural cell staining at 6 weeks for the FGF-1 loaded beads compared to bolus FGF-1 and control levels. Results in these studies suggest that sustained release of FGF-1 increases the duration of the vascular response in contrast to a bolus injection of FGF-1.