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Yanto TA, Budiputri CL, Muljono MP, Chandra S. Efficacy and Safety of Bromocriptine-QR as an Adjunctive Therapy on Glycemic Control in Subjects with Uncontrolled Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis. J ASEAN Fed Endocr Soc 2024; 39:95-105. [PMID: 38863918 PMCID: PMC11163318 DOI: 10.15605/jafes.039.01.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 09/03/2023] [Indexed: 06/13/2024] Open
Abstract
Introduction There has been an increasing awareness of the effects of combining bromocriptine-QR with other medications for diabetes mellitus type 2. This study aimed to assess the efficacy and safety of bromocriptine-QR as an adjunctive therapy for patients with uncontrolled type 2 diabetes mellitus. Methodology This systematic review is registered at the International Prospective Register of Systematic Reviews (CRD42022360326). Literature search was done via MEDLINE, NCBI, Google Scholar, Science Direct, Europe PMC and Cochrane Library databases. We included randomized controlled trials with participants 18 years old and above with uncontrolled type 2 diabetes mellitus. The primary outcome of interest is the efficacy and safety of bromocriptine-QR as an adjunctive therapy for glycemic control. Case reports, case series, reviews and animal studies were excluded. The risk of bias was reviewed using the Cochrane Risk of Bias tool. Meta-analysis was performed using Review Manager 5.4 and presented as a weighted mean difference and 95% confidence interval for changes from the baseline level. Results Nine studies were included in the systematic review with a total of 2709 participants. The baseline HbA1c in the bromocriptine-QR group was 7.42% and 7.51% in the control group. The bromocriptine-QR group was favoured, outperforming the control group in terms of reducing hemoglobin A1c(HbA1c), with a statistically significant difference (weighted mean difference -0.6%; 95% CI [-0.83,-0.36]; p<0.00001). The most common side effects were nausea (33.75% vs 6.92%), fatigue (13.11% vs 5.94%), and headache (11.17% vs 6.87%). Conclusion Administration of bromocriptine-QR at a dose range of 1.6 to 4.8 mg/day as an adjunctive therapy reduced HbA1c and FBG in patients with uncontrolled type 2 diabetes mellitus (T2DM). However, there were also statistically greater odds of the occurrence of adverse events such as nausea, vomiting, and headache compared to controls.
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Affiliation(s)
- Theo Audi Yanto
- Department of Internal Medicine, Faculty of Medicine, Universitas Pelita Harapan, Karawaci, Tangerang, Banten, Indonesia
| | - Charista Lydia Budiputri
- Department of Internal Medicine, Faculty of Medicine, Universitas Pelita Harapan, Karawaci, Tangerang, Banten, Indonesia
| | - Michelle Patricia Muljono
- Department of Internal Medicine, Faculty of Medicine, Universitas Pelita Harapan, Karawaci, Tangerang, Banten, Indonesia
| | - Shally Chandra
- Department of Internal Medicine, Faculty of Medicine, Universitas Pelita Harapan, Karawaci, Tangerang, Banten, Indonesia
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Kutikuppala LVS, Sharma S, Chavan M, Rangari G, Misra AK, Innamuri SR, Vijayakumar T, Varshitha G. Bromocriptine: does this drug of Parkinson's disease have a role in managing cardiovascular diseases? Ann Med Surg (Lond) 2024; 86:926-929. [PMID: 38333315 PMCID: PMC10849299 DOI: 10.1097/ms9.0000000000001642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Accepted: 12/11/2023] [Indexed: 02/10/2024] Open
Abstract
Cardiovascular disease (CVD) is the most common cause of morbidity and mortality worldwide. Bromocriptine is a partial antagonist for D1 dopamine receptors while also serving as a selective agonist on D2 dopamine receptors as a dopamine receptor agonist. Apart from prolactin inhibiting action, bromocriptine has some beneficial effects on the blood pressure, plasma norepinephrine levels and vascular resistance. Dopamine D2 receptor activation of bromocriptine is associated with the antihypertensive effect, which lowers blood pressure via inhibiting sympathetic nerve activity and Na/K ATPase activity. Plasma levels of the pro-inflammatory cytokines such as interleukin (IL)-1B and IL-18, chemokine CCL2/ MCP-1/, and the pro-inflammatory hormone prolactin, all of which are elevated and linked to accelerated cardiometabolic illness, were decreased because of bromocriptine therapy. The most common side effects of Bromocriptine use are dizziness, nausea, headache, vomiting and hypotension. Bromocriptine is mainly contraindicated in patients with syncope with hypotension, psychosis, and type I diabetes mellitus. The authors suggest that developing therapies directed to increase D2 receptor expression and function by drugs like Bromocriptine can provide practical and novelistic approaches to prevent and manage myocardial and renal injury in the cardiovascular disease patients.
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Affiliation(s)
| | - Sushil Sharma
- Department of Pharamacology, All India Institute of Medical Sciences (AIIMS), Mangalagiri, Andhra Pradesh, India
| | - Madhavrao Chavan
- Department of Pharamacology, All India Institute of Medical Sciences (AIIMS), Mangalagiri, Andhra Pradesh, India
| | - Gaurav Rangari
- Department of Pharamacology, All India Institute of Medical Sciences (AIIMS), Mangalagiri, Andhra Pradesh, India
| | - Arup Kumar Misra
- Department of Pharamacology, All India Institute of Medical Sciences (AIIMS), Mangalagiri, Andhra Pradesh, India
| | - Sai Ram Innamuri
- Department of Pharamacology, All India Institute of Medical Sciences (AIIMS), Mangalagiri, Andhra Pradesh, India
| | - Tejus Vijayakumar
- Department of Pharamacology, All India Institute of Medical Sciences (AIIMS), Mangalagiri, Andhra Pradesh, India
| | - Golla Varshitha
- Department of General Medicine, International School of Medicine (ISM), Bishkek, Kyrgyzstan
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Cincotta AH. Brain Dopamine-Clock Interactions Regulate Cardiometabolic Physiology: Mechanisms of the Observed Cardioprotective Effects of Circadian-Timed Bromocriptine-QR Therapy in Type 2 Diabetes Subjects. Int J Mol Sci 2023; 24:13255. [PMID: 37686060 PMCID: PMC10487918 DOI: 10.3390/ijms241713255] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/19/2023] [Accepted: 07/27/2023] [Indexed: 09/10/2023] Open
Abstract
Despite enormous global efforts within clinical research and medical practice to reduce cardiovascular disease(s) (CVD), it still remains the leading cause of death worldwide. While genetic factors clearly contribute to CVD etiology, the preponderance of epidemiological data indicate that a major common denominator among diverse ethnic populations from around the world contributing to CVD is the composite of Western lifestyle cofactors, particularly Western diets (high saturated fat/simple sugar [particularly high fructose and sucrose and to a lesser extent glucose] diets), psychosocial stress, depression, and altered sleep/wake architecture. Such Western lifestyle cofactors are potent drivers for the increased risk of metabolic syndrome and its attendant downstream CVD. The central nervous system (CNS) evolved to respond to and anticipate changes in the external (and internal) environment to adapt survival mechanisms to perceived stresses (challenges to normal biological function), including the aforementioned Western lifestyle cofactors. Within the CNS of vertebrates in the wild, the biological clock circuitry surveils the environment and has evolved mechanisms for the induction of the obese, insulin-resistant state as a survival mechanism against an anticipated ensuing season of low/no food availability. The peripheral tissues utilize fat as an energy source under muscle insulin resistance, while increased hepatic insulin resistance more readily supplies glucose to the brain. This neural clock function also orchestrates the reversal of the obese, insulin-resistant condition when the low food availability season ends. The circadian neural network that produces these seasonal shifts in metabolism is also responsive to Western lifestyle stressors that drive the CNS clock into survival mode. A major component of this natural or Western lifestyle stressor-induced CNS clock neurophysiological shift potentiating the obese, insulin-resistant state is a diminution of the circadian peak of dopaminergic input activity to the pacemaker clock center, suprachiasmatic nucleus. Pharmacologically preventing this loss of circadian peak dopaminergic activity both prevents and reverses existing metabolic syndrome in a wide variety of animal models of the disorder, including high fat-fed animals. Clinically, across a variety of different study designs, circadian-timed bromocriptine-QR (quick release) (a unique formulation of micronized bromocriptine-a dopamine D2 receptor agonist) therapy of type 2 diabetes subjects improved hyperglycemia, hyperlipidemia, hypertension, immune sterile inflammation, and/or adverse cardiovascular event rate. The present review details the seminal circadian science investigations delineating important roles for CNS circadian peak dopaminergic activity in the regulation of peripheral fuel metabolism and cardiovascular biology and also summarizes the clinical study findings of bromocriptine-QR therapy on cardiometabolic outcomes in type 2 diabetes subjects.
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Tavares G, Rosendo-Silva D, Simões F, Eickhoff H, Marques D, Sacramento JF, Capucho AM, Seiça R, Conde SV, Matafome P. Circulating Dopamine Is Regulated by Dietary Glucose and Controls Glucagon-like 1 Peptide Action in White Adipose Tissue. Int J Mol Sci 2023; 24:ijms24032464. [PMID: 36768789 PMCID: PMC9916853 DOI: 10.3390/ijms24032464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/21/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023] Open
Abstract
Dopamine directly acts in the liver and white adipose tissue (WAT) to regulate insulin signaling, glucose uptake, and catabolic activity. Given that dopamine is secreted by the gut and regulates insulin secretion in the pancreas, we aimed to determine its regulation by nutritional cues and its role in regulating glucagon-like peptide 1 (GLP-1) action in WAT. Solutions with different nutrients were administered to Wistar rats and postprandial dopamine levels showed elevations following a mixed meal and glucose intake. In high-fat diet-fed diabetic Goto-Kakizaki rats, sleeve gastrectomy upregulated dopaminergic machinery, showing the role of the gut in dopamine signaling in WAT. Bromocriptine treatment in the same model increased GLP-1R in WAT, showing the role of dopamine in regulating GLP-1R. By contrast, treatment with the GLP-1 receptor agonist Liraglutide had no impact on dopamine receptors. GLP-1 and dopamine crosstalk was shown in rat WAT explants, since dopamine upregulated GLP-1-induced AMPK activity in mesenteric WAT in the presence of the D2R and D3R inhibitor Domperidone. In human WAT, dopamine receptor 1 (D1DR) and GLP-1R expression were correlated. Our results point out a dietary and gut regulation of plasma dopamine, acting in the WAT to regulate GLP-1 action. Together with the known dopamine action in the pancreas, such results may identify new therapeutic opportunities to improve metabolic control in metabolic disorders.
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Affiliation(s)
- Gabriela Tavares
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Center for Innovative Biomedicine and Biotechnology (CIBB), University of Coimbra, 3000-548 Coimbra, Portugal
- Clinical-Academic Center of Coimbra, 3004-531 Coimbra, Portugal
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Daniela Rosendo-Silva
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Center for Innovative Biomedicine and Biotechnology (CIBB), University of Coimbra, 3000-548 Coimbra, Portugal
- Clinical-Academic Center of Coimbra, 3004-531 Coimbra, Portugal
| | - Flávia Simões
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Hans Eickhoff
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Daniela Marques
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Joana F. Sacramento
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Adriana M. Capucho
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Raquel Seiça
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Clinical-Academic Center of Coimbra, 3004-531 Coimbra, Portugal
| | - Sílvia V. Conde
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Paulo Matafome
- Institute of Physiology and Institute of Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
- Center for Innovative Biomedicine and Biotechnology (CIBB), University of Coimbra, 3000-548 Coimbra, Portugal
- Clinical-Academic Center of Coimbra, 3004-531 Coimbra, Portugal
- Instituto Politécnico de Coimbra, Coimbra Health School, 3046-854 Coimbra, Portugal
- Correspondence:
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Cincotta AH, Cersosimo E, Alatrach M, Ezrokhi M, Agyin C, Adams J, Chilton R, Triplitt C, Chamarthi B, Cominos N, DeFronzo RA. Bromocriptine-QR Therapy Reduces Sympathetic Tone and Ameliorates a Pro-Oxidative/Pro-Inflammatory Phenotype in Peripheral Blood Mononuclear Cells and Plasma of Type 2 Diabetes Subjects. Int J Mol Sci 2022; 23:ijms23168851. [PMID: 36012132 PMCID: PMC9407769 DOI: 10.3390/ijms23168851] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/16/2022] Open
Abstract
Bromocriptine-QR is a sympatholytic dopamine D2 agonist for the treatment of type 2 diabetes that has demonstrated rapid (within 1 year) substantial reductions in adverse cardiovascular events in this population by as yet incompletely delineated mechanisms. However, a chronic state of elevated sympathetic nervous system activity and central hypodopaminergic function has been demonstrated to potentiate an immune system pro-oxidative/pro-inflammatory condition and this immune phenotype is known to contribute significantly to the advancement of cardiovascular disease (CVD). Therefore, the possibility exists that bromocriptine-QR therapy may reduce adverse cardiovascular events in type 2 diabetes subjects via attenuation of this underlying chronic pro-oxidative/pro-inflammatory state. The present study was undertaken to assess the impact of bromocriptine-QR on a wide range of immune pro-oxidative/pro-inflammatory biochemical pathways and genes known to be operative in the genesis and progression of CVD. Inflammatory peripheral blood mononuclear cell biology is both a significant contributor to cardiovascular disease and also a marker of the body’s systemic pro-inflammatory status. Therefore, this study investigated the effects of 4-month circadian-timed (within 2 h of waking in the morning) bromocriptine-QR therapy (3.2 mg/day) in type 2 diabetes subjects whose glycemia was not optimally controlled on the glucagon-like peptide 1 receptor agonist on (i) gene expression status (via qPCR) of a wide array of mononuclear cell pro-oxidative/pro-inflammatory genes known to participate in the genesis and progression of CVD (OXR1, NRF2, NQO1, SOD1, SOD2, CAT, GSR, GPX1, GPX4, GCH1, HMOX1, BiP, EIF2α, ATF4, PERK, XBP1, ATF6, CHOP, GSK3β, NFkB, TXNIP, PIN1, BECN1, TLR2, TLR4, TLR10, MAPK8, NLRP3, CCR2, GCR, L-selectin, VCAM1, ICAM1) and (ii) humoral measures of sympathetic tone (norepinephrine and normetanephrine), whole-body oxidative stress (nitrotyrosine, TBARS), and pro-inflammatory factors (IL-1β, IL-6, IL-18, MCP-1, prolactin, C-reactive protein [CRP]). Relative to pre-treatment status, 4 months of bromocriptine-QR therapy resulted in significant reductions of mRNA levels in PBMC endoplasmic reticulum stress-unfolded protein response effectors [GRP78/BiP (34%), EIF2α (32%), ATF4 (29%), XBP1 (25%), PIN1 (14%), BECN1 (23%)], oxidative stress response proteins [OXR1 (31%), NRF2 (32%), NQO1 (39%), SOD1 (52%), CAT (26%), GPX1 (33%), GPX4 (31%), GCH1 (30%), HMOX1 (40%)], mRNA levels of TLR pro-inflammatory pathway proteins [TLR2 (46%), TLR4 (20%), GSK3β (19%), NFkB (33%), TXNIP (18%), NLRP3 (32%), CCR2 (24%), GCR (28%)], mRNA levels of pro-inflammatory cellular receptor proteins CCR2 and GCR by 24% and 28%, and adhesion molecule proteins L-selectin (35%) and VCAM1 (24%). Relative to baseline, bromocriptine-QR therapy also significantly reduced plasma levels of norepinephrine and normetanephrine by 33% and 22%, respectively, plasma pro-oxidative markers nitrotyrosine and TBARS by 13% and 10%, respectively, and pro-inflammatory factors IL-18, MCP1, IL-1β, prolactin, and CRP by 21%,13%, 12%, 42%, and 45%, respectively. These findings suggest a unique role for circadian-timed bromocriptine-QR sympatholytic dopamine agonist therapy in reducing systemic low-grade sterile inflammation to thereby reduce cardiovascular disease risk.
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Affiliation(s)
- Anthony H. Cincotta
- VeroScience LLC, Tiverton, RI 02878, USA
- Correspondence: ; Tel.: +1-401-816-0525
| | - Eugenio Cersosimo
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Mariam Alatrach
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | | | - Christina Agyin
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - John Adams
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Robert Chilton
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Curtis Triplitt
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | | | | | - Ralph A. DeFronzo
- Texas Diabetes Institute, University Health System, San Antonio, TX 78207, USA
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Naz F, Malik A, Riaz M, Mahmood Q, Mehmood MH, Rasool G, Mahmood Z, Abbas M. Bromocriptine Therapy: Review of mechanism of action, safety and tolerability. Clin Exp Pharmacol Physiol 2022; 49:903-922. [DOI: 10.1111/1440-1681.13678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 11/28/2022]
Affiliation(s)
- Faiza Naz
- Punjab University College of Pharmacy University of the Punjab Lahore Pakistan
| | - Abdul Malik
- College of Pharmacy University of Sargodha Sargodha Pakistan
| | - Muhammad Riaz
- Department of Allied Health Sciences University of Sargodha Sargodha Pakistan
| | - Qaisar Mahmood
- College of Pharmacy University of Sargodha Sargodha Pakistan
| | - Malik Hassan Mehmood
- Department of Pharmacology, Faculty of Pharmaceutical Sciences Government College University Faisalabad Pakistan
| | - Ghulam Rasool
- Department of Allied Health Sciences University of Sargodha Sargodha Pakistan
| | - Zahed Mahmood
- Department of Biochemistry Government College University Faisalabad Pakistan
| | - Mazhar Abbas
- Department of Biochemistry College of Veterinary and Animal Sciences, University of Veterinary and Animal Sciences (Jhang Campus) Lahore Pakistan
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Siamashvili M, Davis S. Late phase completed clinical trials investigating bromocriptine mesylate quick release as treatment of type 2 diabetes mellitus. Expert Opin Pharmacother 2020; 22:241-247. [PMID: 33030357 DOI: 10.1080/14656566.2020.1825683] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Bromocriptine mesylate quick release (QR) is a dopamine D2 receptor agonist and is the only oral, primarily centrally acting drug that can be used for the treatment of adults with type 2 diabetes. AREAS COVERED The authors describe current recommendations on the use of bromocriptine mesylate QR. Major efficacy and safety parameters of the late phase trials, including The Cycloset Safety Trial, have been identified and presented. EXPERT OPINION Efficacy of bromocriptine mesylate QR monotherapy appears to be low but is compensated by favorable safety profile: low risk of hypoglycemia and no weight gain. The latter makes the drug an acceptable choice for obese individuals with type 2 diabetes. As a valuable additional benefit, bromocriptine is associated with significant cardiovascular risk reduction. Current recommendations include bromocriptine mesylate QR as part of dual or triple antihyperglycemic therapy especially in individuals with type 2 diabetes who are hesitant to add injectable treatment options and/or have cardiovascular disease.
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Affiliation(s)
- Maka Siamashvili
- School of Medicine, University of Maryland , Baltimore 21201, USA
| | - Stephen Davis
- School of Medicine, University of Maryland , Baltimore 21201, USA
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Stoelzel CR, Zhang Y, Cincotta AH. Circadian-timed dopamine agonist treatment reverses high-fat diet-induced diabetogenic shift in ventromedial hypothalamic glucose sensing. Endocrinol Diabetes Metab 2020; 3:e00139. [PMID: 32704560 PMCID: PMC7375120 DOI: 10.1002/edm2.139] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 03/28/2020] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION Within the ventromedial hypothalamus (VMH), glucose inhibitory (GI) neurons sense hypoglycaemia while glucose excitatory (GE) neurons sense hyperglycaemia to initiate counter control mechanisms under normal conditions. However, potential electrophysiological alterations of these two neuronal types in vivo in insulin-resistant states have never been simultaneously fully documented. Further, the anti-diabetic effect of dopamine agonism on this VMH system under insulin resistance has not been studied. METHODS This study examined the impact of a high-fat diet (HFD) on in vivo electrophysiological recordings from VMH GE and GI neurons and the ability of circadian-timed dopamine agonist therapy to reverse any adverse effect of the HFD on such VMH activities and peripheral glucose metabolism. RESULTS HFD significantly inhibited VMH GE neuronal electrophysiological response to local hyperglycaemia (36.3%) and augmented GI neuronal excitation response to local hypoglycaemia (47.0%). Bromocriptine (dopamine agonist) administration at onset of daily activity (but not during the daily sleep phase) completely reversed both VMH GE and GI neuronal aberrations induced by HFD. Such timed treatment also normalized glucose intolerance and insulin resistance. These VMH and peripheral glucose metabolism effects of circadian-timed bromocriptine may involve its known effect to reduce elevated VMH noradrenergic activity in insulin-resistant states as local VMH administration of norepinephrine was observed to significantly inhibit VMH GE neuronal sensing of local hyperglycaemia in insulin-sensitive animals on regular chow diet (52.4%). CONCLUSIONS HFD alters VMH glucose sensing in a manner that potentiates hyperglycaemia and this effect on the VMH can be reversed by appropriately circadian-timed dopamine agonist administration.
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