Effect of bromocriptine on maturity onset diabetes

Evidence for dopamine production and distribution of dopamine D2 receptors in the equine gastrointestinal mucosa and pancreas

Insulin dysregulation in horses is characterised by hyperinsulinaemia and/or tissue insulin resistance and is associated with increased risk of laminitis. There is growing evidence in other species that dopamine attenuates insulin release from the pancreas; however, this has yet to be examined in horses. The present study aimed to identify whether there are cells capable of producing or responding to dopamine within the equine gastrointestinal mucosa and pancreas. Tissue samples were collected from the stomach, small and large intestines, and pancreas of six mature horses following euthanasia. Samples of stomach contents and faeces were also collected. Immunohistochemistry was performed to identify tyrosine hydroxylase (TH), the rate-limiting enzyme for dopamine production, and dopamine D2 receptors in tissue sections. Additional immunostaining for glucagon, insulin and chromogranin A was performed to identify α cells, β cells and enteroendocrine cells, respectively. Gastric parietal cells expressed both TH and D2 receptors, indicating that they are capable of both producing and responding to dopamine. Dopamine was quantified in stomach contents and faeces by high-performance liquid chromatography with electrochemical detection, with similar concentrations found at both sites. Dopamine D2 receptors were expressed in duodenal epithelial cells but not more distally. A subset of enteroendocrine cells, located sporadically along the gastrointestinal tract, were found to be immunopositive for the D2 receptor. In pancreatic islets, TH was present in α cells, while D2 receptors were strongly expressed in β cells and variably expressed in α cells. These findings are consistent with studies of other species; however, dynamic studies are required to further elucidate the role of dopamine in the modulation of insulin and glucagon secretion in horses. This descriptive study provides preliminary evidence for a potential role of dopamine to act as a paracrine messenger in the gastrointestinal mucosa and endocrine pancreas of horses.

Development of novel tools for dissection of central versus peripheral dopamine D2-like receptor signaling in dysglycemia

Dopamine (DA) D2-like receptors in both the central nervous system (CNS) and the periphery are key modulators of metabolism. Moreover, disruption of D2-like receptor signaling is implicated in dysglycemia. Yet, the respective metabolic contributions of CNS versus peripheral D2-like receptors including D2 (D2R) and D3 (D3R) receptors remain poorly understood. To address this, we developed new pharmacological tools, D2-like receptor agonists with diminished and delayed blood-brain barrier capability, to selectively manipulate D2R/D3R signaling in the periphery. We designated bromocriptine methiodide (BrMeI), a quaternary methiodide analogue of D2/3R agonist and diabetes drug bromocriptine, as our lead compound based on preservation of D2R/D3R binding and functional efficacy. We then used BrMeI and unmodified bromocriptine to dissect relative contributions of CNS versus peripheral D2R/D3R signaling in treating dysglycemia. Systemic administration of bromocriptine, with unrestricted access to CNS and peripheral targets, significantly improved both insulin sensitivity and glucose tolerance in obese, dysglycemic mice in vivo. In contrast, metabolic improvements were attenuated when access to bromocriptine was restricted either to the CNS through intracerebroventricular administration or delayed access to the CNS via BrMeI. Our findings demonstrate that the coordinated actions of both CNS and peripheral D2-like receptors are required for correcting dysglycemia. Ultimately, the development of a first-generation of drugs designed to selectively target the periphery provides a blueprint for dissecting mechanisms of central versus peripheral DA signaling and paves the way for novel strategies to treat dysglycemia.

Dopamine 2 agonists for the management of type 2 diabetes: a systematic review and meta-analysis

Background

The Dopamine-2 receptor agonists, Bromocriptine and Cabergoline, were originally introduced for prolactinomas, pituitary tumors, and parkinson's disease but have glucose-lowering effects. This paper systematically reviewed the significance of their effects on lowering blood glucose level and conducted a comprehensive systematic search to identify relevant clinical trials of dopamine 2 agonists on glycated hemoglobin (HbA1c) and fasting blood sugar (FBS).

Method

We conducted a systematic review search in the databases (PubMed, Google Scholar, Cochrane Library, Registers, and Citations) until November 30, 2022, using the PRISMA 2020 statement. The Oxford quality score (Jadad score) was used to assess the study's quality. The present study protocol was registered on the PROSPERO database with ID: CRD42023389582. The study included studies with full abstracts, predefined doses, clear interventions, and blood glucose measurements.

Result

Data were synthesized from 23 clinical studies that recruited 6125 study subjects. The pooled effect analysis of the clinical trials revealed that dopamine 2 agonists improved HbA1c [SMD = -1.26; 95% CI (-1.60, -0.93), P < .00001], and FBS [SMD = -1.84; 95% CI (-2.61, -1.07), P < .00001]. Each drug's pooled effect analysis indicates bromocriptine significantly improved HbA1c [SMD = -1.25; 95% CI (-1.64, -0.87), P < .00001] and FBS [SMD = -1.90; 95% CI (-2.79, -1.01), P < .00001] and similarly, cabergoline significantly improved HbA1c [SMD = -1.29; 95% CI (-1.96, -0.62), P < .00001] and FBS [SMD = -1.62; 95% CI (-2.82, -0.41), P < .00001]. The pooled and individual analyses demonstrated that dopamine 2 agonists have a significant ability to lower blood glucose levels in clinical studies.

Conclusion

This study shows that dopamine 2 agonists significantly lowered FBS and HbA1c levels without causing severe negative effects. Even though the results are promising, additional research is necessary to establish the appropriate antihyperglycemic dosage, frequency of daily use, side effects, and potential product interactions when employing dopamine 2 receptor agonists for their antihyperglycemic effect.

Dopamine in the Regulation of Glucose Homeostasis, Pathogenesis of Type 2 Diabetes, and Chronic Conditions of Impaired Dopamine Activity/Metabolism: Implication for Pathophysiological and Therapeutic Purposes

Dopamine regulates several functions, such as voluntary movements, spatial memory, motivation, sleep, arousal, feeding, immune function, maternal behaviors, and lactation. Less clear is the role of dopamine in the pathophysiology of type 2 diabetes mellitus (T2D) and chronic complications and conditions frequently associated with it. This review summarizes recent evidence on the role of dopamine in regulating insular metabolism and activity, the pathophysiology of traditional chronic complications associated with T2D, the pathophysiological interconnection between T2D and chronic neurological and psychiatric disorders characterized by impaired dopamine activity/metabolism, and therapeutic implications. Reinforcing dopamine signaling is therapeutic in T2D, especially in patients with dopamine-related disorders, such as Parkinson's and Huntington's diseases, addictions, and attention-deficit/hyperactivity disorder. On the other hand, although specific trials are probably needed, certain medications approved for T2D (e.g., metformin, pioglitazone, incretin-based therapy, and gliflozins) may have a therapeutic role in such dopamine-related disorders due to anti-inflammatory and anti-oxidative effects, improvement in insulin signaling, neuroinflammation, mitochondrial dysfunction, autophagy, and apoptosis, restoration of striatal dopamine synthesis, and modulation of dopamine signaling associated with reward and hedonic eating. Last, targeting dopamine metabolism could have the potential for diagnostic and therapeutic purposes in chronic diabetes-related complications, such as diabetic retinopathy.

The role of Neurochemicals, Stress Hormones and Immune System in the Positive Feedback Loops between Diabetes, Obesity and Depression

Type 2 diabetes mellitus (T2DM) and depression are significant public health and socioeconomic issues. They commonly co-occur, with T2DM occurring in 11.3% of the US population, while depression has a prevalence of about 9%, with higher rates among youths. Approximately 31% of patients with T2DM suffer from depressive symptoms, with 11.4% having major depressive disorders, which is twice as high as the prevalence of depression in patients without T2DM. Additionally, over 80% of people with T2DM are overweight or obese. This review describes how T2DM and depression can enhance one another, using the same molecular pathways, by synergistically altering the brain's structure and function and reducing the reward obtained from eating. In this article, we reviewed the evidence that eating, especially high-caloric foods, stimulates the limbic system, initiating Reward Deficiency Syndrome. Analogous to other addictive behaviors, neurochemical changes in those with depression and/or T2DM are thought to cause individuals to increase their food intake to obtain the same reward leading to binge eating, weight gain and obesity. Treating the symptoms of T2DM, such as lowering HbA1c, without addressing the underlying pathways has little chance of eliminating the disease. Targeting the immune system, stress circuit, melatonin, and other alterations may be more effective.

Serotonin and Dopamine Mimic Glucose-Induced Reinforcement in C. elegans: Potential Role of NSM Neurons and the Serotonin Subtype 4 Receptor

Food produces powerful reinforcement that can lead to overconsumption and likely contributes to the obesity epidemic. The present studies examined molecular mechanisms mediating food-induced reinforcement in the model system C. elegans. After a 1-h training session during which food (bacteria) is paired with the odorant butanone, odor preference for butanone robustly increased. Glucose mimicked this effect of bacteria. Glucose-induced odor preference was enhanced similarly by prior food withdrawal or blocking glucose metabolism in the presence of food. Food- and glucose-induced odor preference was mimicked by serotonin signaling through the serotonin type-4 (5-HT4) receptor. Dopamine (thought to act primarily through a D1-like receptor) facilitated, whereas the D2 agonist bromocriptine blocked, food- and glucose-induced odor preference. Furthermore, prior food withdrawal similarly influenced reward produced by serotonin, dopamine, or food, implying post-synaptic enhancement of sensitivity to serotonin and dopamine. These results suggest that glucose metabolism plays a key role in mediating both food-induced reinforcement and enhancement of that reinforcement by prior food withdrawal and implicate serotonergic signaling through 5-HT4 receptor in the re-enforcing properties of food.

Bromocriptine as a Potential Glucose-lowering Agent for the Treatment of Prolactinoma with Type 2 Diabetes

A 22-year-old Japanese woman consulted an endocrinologist due to persistent galactorrhea for the past 10 months. She had hyperprolacinemia and had previously been diagnosed with type 2 diabetes mellitus based on her glycohemoglobin level of 11.6%. After two months, she was admitted to our hospital and finally diagnosed with prolactinoma. For the treatment of prolactinoma, bromocriptine 2.5 mg/day was started. After seven days, her post-prandial blood glucose levels, homeostasis model assessment of insulin resistance and plasma C-peptide levels were significantly improved. These results indicate that traditional bromocriptine can be an effective therapeutic alternative in patients with prolactinoma complicated with type 2 diabetes.

Suppression of Prolactin Secretion Partially Explains the Antidiabetic Effect of Bromocriptine in ob/ob Mice

Previous studies have shown that bromocriptine mesylate (Bromo) lowers blood glucose levels in adults with type 2 diabetes mellitus; however, the mechanism of action of the antidiabetic effects of Bromo is unclear. As a dopamine receptor agonist, Bromo can alter brain dopamine activity affecting glucose control, but it also suppresses prolactin (Prl) secretion, and Prl levels modulate glucose homeostasis. Thus, the objective of the current study was to investigate whether Bromo improves insulin sensitivity via inhibition of Prl secretion. Male and female ob/ob animals (a mouse model of obesity and insulin resistance) were treated with Bromo and/or Prl. Bromo-treated ob/ob mice exhibited lower serum Prl concentration, improved glucose and insulin tolerance, and increased insulin sensitivity in the liver and skeletal muscle compared with vehicle-treated mice. Prl replacement in Bromo-treated mice normalized serum Prl concentration without inducing hyperprolactinemia. Importantly, Prl replacement partially reversed the improvements in glucose homeostasis caused by Bromo treatment. The effects of the Prl receptor antagonist G129R-hPrl on glucose homeostasis were also investigated. We found that central G129R-hPrl infusion increased insulin tolerance of male ob/ob mice. In summary, our findings indicate that part of Bromo effects on glucose homeostasis are associated with decrease in serum Prl levels. Because G129R-hPrl treatment also improved the insulin sensitivity of ob/ob mice, pharmacological compounds that inhibit Prl signaling may represent a promising therapeutic approach to control blood glucose levels in individuals with insulin resistance.

Pharmacology and therapeutic implications of current drugs for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a global epidemic that poses a major challenge to health-care systems. Improving metabolic control to approach normal glycaemia (where practical) greatly benefits long-term prognoses and justifies early, effective, sustained and safety-conscious intervention. Improvements in the understanding of the complex pathogenesis of T2DM have underpinned the development of glucose-lowering therapies with complementary mechanisms of action, which have expanded treatment options and facilitated individualized management strategies. Over the past decade, several new classes of glucose-lowering agents have been licensed, including glucagon-like peptide 1 receptor (GLP-1R) agonists, dipeptidyl peptidase 4 (DPP-4) inhibitors and sodium/glucose cotransporter 2 (SGLT2) inhibitors. These agents can be used individually or in combination with well-established treatments such as biguanides, sulfonylureas and thiazolidinediones. Although novel agents have potential advantages including low risk of hypoglycaemia and help with weight control, long-term safety has yet to be established. In this Review, we assess the pharmacokinetics, pharmacodynamics and safety profiles, including cardiovascular safety, of currently available therapies for management of hyperglycaemia in patients with T2DM within the context of disease pathogenesis and natural history. In addition, we briefly describe treatment algorithms for patients with T2DM and lessons from present therapies to inform the development of future therapies.

Glycemic control is impaired in the evening in prediabetes through multiple diurnal rhythms

AIMS

Recent studies suggest that circadian rhythms regulate glucose metabolism, weight loss, and even drug efficacy. Moreover, molecules targeted at the circadian clock show promise in treating metabolic disease. Therefore, this study set out to better characterize interactions among diurnal rhythms in prediabetes.

METHODS

Ten subjects with prediabetes completed oral glucose tolerance tests at 0700h and 1900h on the same day. Lipids and hormones were also measured.

RESULTS

Two-hour and three-hour glucose tolerances were worse in the evening by 40±52mg/dl (p=0.02) and 62±46mg/dl (p=0.001), respectively. These impairments were explained by lower insulin sensitivity (OGIS; 5.14±1.02 vs. 4.74±0.77mg/kg/min; p=0.03) and 2-hour AUC insulin levels (87.4±37.6 vs. 69.8±40.2mU∙hr/l; p=0.02) in the evening. Intriguingly, more insulin resistant subjects had weaker rhythms in insulin sensitivity (r=-0.66; p=0.04) but enhanced rhythms in insulin (r=-0.67; p=0.03) and cortisol (r=-0.78; p=0.008) levels. Importantly, the rhythms in cortisol primarily but also insulin sensitivity drove the declines in evening glucose tolerance (r=0.86; p=0.002).

CONCLUSIONS

Glycemic control is dramatically impaired in the evening in people with prediabetes, particularly when the cortisol rhythm is weak, but is unrelated to the rhythm in insulin levels. Therefore, food intake at dinnertime may need to be curbed in prediabetes.

Adipose tissue macrophages (ATM) of obese patients are releasing increased levels of prolactin during an inflammatory challenge: a role for prolactin in diabesity?

BACKGROUND

Obesity, characterized by low grade inflammation, induces adipose tissue macrophage (ATM) infiltration in white adipose tissue (AT) in both humans and rodents, thus contributing to insulin resistance. Previous studies have shown altered prolactin secretion in obesity, however, studies linking ATM infiltration and prolactin (PRL) secretion to the pathogenesis of the metabolic syndrome, obesity and diabetes are lacking.

METHODS/RESULTS

In vivo, qPCR and Western blot analysis demonstrated that prolactin expression was increased in AT of obese rats and also in human AT from obese, obese pre-diabetic and obese diabetic compared to lean counterparts. Immunohistochemistry of obese rat and human AT sections demonstrated a specific expression of prolactin in macrophages. In vitro, we demonstrated that hyperglycemia and inflammation stimulated macrophages (human THP-1 cell line and sorted rat ATM) to express PRL, when challenged with different glucose concentrations with or without IL1β. In in vivo and in vitro experiments, we assessed the expression of Pit-1 (PRL-specific transcription factor) and found that its expression was parallel to PRL expression.

CONCLUSIONS

In this study, we show that rodent and human macrophages synthesize prolactin in response to inflammation and high glucose concentrations.

GENERAL SIGNIFICANCE

Our data shed new light on the potential role of macrophages in the physiopathology of diabesity via the PRL expression and on its expression mechanism and regulation.

New and Future Medications for the Treatment of Type 2 Diabetes Mellitus

With almost 30 million individuals predicted to be diagnosed by the year 2025, type 2 diabetes mellitus (T2DM) has become one of the most prevalent diseases in the United States. Because of the progressive dysfunction of the pancreatic β-cells and increasing insulin resistance over time, the need for treatments with different mechanisms or addition of medications to a regimen is becoming commonplace. Because of this, developing new medications to treat T2DM has been the focus of a lot of recent research and drug development. Molecular substrates such as glucagon-like peptide-1 (GLP-1), dipeptidyl peptidase-4 (DPP-4), and the sodium glucose transporter-2 (SGLT2) have all become new therapeutic targets. GLP-1 agonists and DPP-4 inhibitors are 2 of the newest classes of Food and Drug Administration–approved medications for diabetes. By increasing GLP-1 to supraphysiologic levels (GLP-1 agonists) and delaying endogenous GLP-1 degradation (DPP-4 inhibitors), these drugs increase insulin secretion and decrease glucagon production. SGLT2 inhibitors, the newest antihyperglycemic class, promote glycosuria by inhibiting sodium and glucose reabsorption in the proximal tubule of the renal nephron. Other novel agents for the treatment of diabetes include the use of the dopamine agonist bromocriptine, the cholesterol medication colesevelam, and a new form of inhaled insulin.

Bromocriptine inhibits adipogenesis and lipogenesis by agonistic action on α2-adrenergic receptor in 3T3-L1 adipocyte cells

The primary goals of the present study were to investigate the inhibitory effects of bromocriptine (BC) on adipogenesis and lipogenesis in 3T3-L1 adipocyte cells as well as to elucidate its molecular mechanism of action. Adipogenic and lipogenic capacity of BC-treated cells was evaluated by oil red-O staining, triglyceride content assay, real-time RT-PCR and immunoblotting. To determine the mechanism responsible for the anti-obesity effect of BC, we applied two methods. Firstly, we knocked down dopamine D2 receptor (D2R) up to 50% using siRNA. Secondly, we blocked the activity of α2-adrenergic receptor (α2-AR) by yohimbine treatment and monitored its effects on adipogenic and lipogenic events in 3T3-L1 cells. BC decreased the expression levels of adipogenic activators, including Pparα, Pparγ, and Cebpα, as well as major lipogenic target genes, including Me1, Acc1, 6Pgd, Fasn, and Prkaa1. Moreover, BC markedly reduced intracellular nitric oxide formation in a dose-dependent manner and expression of pro-inflammatory genes, Tnfα and Il6, which reflects attenuated pro-inflammatory responses. Further, upon treatment with BC, D2R-deficient cells displayed a significant decrease in lipogenic activity compared to control cells, whereas yohimbine-treated cells exhibited no reduction in lipogenic activity. BC can effectively attenuate adipogenesis and lipogenesis in 3T3-L1 cells by downregulating the expression of lipogenic genes and proteins. Our current experimental data collectively establish that the anti-obesity effects of BC are not D2R-dependent but result from the action of α2-AR in 3T3-L1 adipocytes.

Bromocriptine for diabetes mellitus type II

A quick-release formulation of bromocriptine is the latest drug approved by the US Food and Drug Administration for the treatment of type 2 diabetes mellitus. Most interestingly, the development of this drug stems from studies of hibernation in rodents. This article will review the physiology that led to the development of this new drug, as well as its indications, clinical use, benefits, and contraindications.

Management of type 2 diabetes: new and future developments in treatment

The increasing prevalence, variable pathogenesis, progressive natural history, and complications of type 2 diabetes emphasise the urgent need for new treatment strategies. Longacting (eg, once weekly) agonists of the glucagon-like-peptide-1 receptor are advanced in development, and they improve prandial insulin secretion, reduce excess glucagon production, and promote satiety. Trials of inhibitors of dipeptidyl peptidase 4, which enhance the effect of endogenous incretin hormones, are also nearing completion. Novel approaches to glycaemic regulation include use of inhibitors of the sodium-glucose cotransporter 2, which increase renal glucose elimination, and inhibitors of 11β-hydroxysteroid dehydrogenase 1, which reduce the glucocorticoid effects in liver and fat. Insulin-releasing glucokinase activators and pancreatic-G-protein-coupled fatty-acid-receptor agonists, glucagon-receptor antagonists, and metabolic inhibitors of hepatic glucose output are being assessed. Early proof of principle has been shown for compounds that enhance and partly mimic insulin action and replicate some effects of bariatric surgery.

Bromocriptine: old drug, new formulation and new indication

Bromocriptine is an ergot alkaloid dopamine D(2) receptor agonist that has been used extensively in the past to treat hyperprolactinaemia, galactorrhoea and Parkinsonism. It is known that hypothalamic hypodopaminergic states and disturbed circadian rhythm are associated with the development of insulin resistance, obesity and diabetes in animals and humans. When administered in the early morning at the start of the light phase, a new quick release (QR) formulation of bromocriptine appears to act centrally to reset circadian rhythms of hypothalamic dopamine and serotonin and improve insulin resistance and other metabolic abnormalities. Phase II and III clinical studies show that QR-bromocriptine lowers glycated haemoglobin by 0.6-1.2% (7-13 mmol/mol) either as monotherapy or in combination with other antidiabetes medications. Apart from nausea, the drug is well tolerated. The doses used to treat diabetes (up to 4.8 mg daily) are much lower than those used to treat Parkinson's disease and have not been associated with retroperitoneal fibrosis or heart valve abnormalities. QR-bromocriptine (Cycloset™) has recently been approved in the USA for the treatment of type 2 diabetes mellitus (T2DM). Thus, a QR formulation of bromocriptine timed for peak delivery in the early morning may provide a novel neurally mediated approach to the control of hyperglycaemia in T2DM.

Bromocriptine Mesylate for Glycemic Management in Type 2 Diabetes Mellitus

Objective:

To review the pharmacologic characteristics, safety, and efficacy of bromocriptine mesylate for glycemic control in patients with type 2 diabetes mellitus.

Data Sources:

A Scopus and MEDLINE search (1950–June 2010) was conducted using the key words bromocriptine, diabetes, and circadian rhythm. Data were also received from the manufacturer.

Study Selection and Data Extraction:

Available abstracts, studies, and review articles published in English with human data discussing bromocriptine treatment for type 2 diabetes mellitus were reviewed.

Data Synthesis:

Bromocriptine is an ergot derivative available for treatment of type 2 diabetes. The mechanism of action of this agent is unclear; however, activity as a dopamine D2 receptor agonist seems to provide the primary mechanism for utility in resetting the circadian rhythm in patients with type 2 diabetes. Other mechanisms, including α-1 antagonist, α-2 agonist, and serotonin and prolactin modulator, may also help to explain bromocriptine's glucose-lowering effects. Studies with bromocriptine have included 4328 patients with type 2 diabetes. The majority of available trials conducted enrolled patients for a study duration of 6–24 weeks. One trial evaluating the safety and efficacy of bromocriptine concluded after 52 weeks of follow-up. Endpoints of hemoglobin A1c (A1C) reduction and plasma glucose concentrations were the primary focus of all studies, with statistically significant differences found. Bromocriptine use resulted in a mean A1C reduction of 0.27% (range 0.1–0.6), while placebo resulted in a mean A1C increase of 0.48% (range 0.3–1.1), Incidence of adverse effects of nausea, vomiting, headache, and rhinitis was greater than that of placebo in clinical trials. Cardiovascular endpoints did not differ from those of placebo.

Conclusions:

Bromocriptine has demonstrated efficacy as an adjunctive agent in the management of type 2 diabetes. Caution may be warranted in the elderly population or patients at risk for suspected drug-drug interactions. Further studies of longer duration may help to define the role of bromocriptine in the management of diabetes.

Bromocriptine improves glycaemic control and serum lipid profile in obese Type 2 diabetic subjects: a new approach in the treatment of diabetes

Bromocriptine, a potent dopamine D(2) receptor agonist, has been shown to reduce insulin resistance, glucose intolerance and hyperlipidaemia in both numerous animal studies and in Phase II studies. Bromocriptine has been used worldwide for over 20 years to treat Parkinson's disease, macroprolactinoma and other disorders; it has been found to be generally safe. We therefore investigated the possible beneficial effects of Ergoset(R) (Ergo Science Corp.), a new quick release formulation of bromocriptine, on glycaemic control and serum lipid profile in obese Type 2 diabetic subjects in two large Phase III studies. A large, randomised, double-blind placebo-controlled study was conducted in which Ergoset was given once daily at 8 am. (4.8 mg maximum dose) for 24 weeks as adjunctive therapy to sulphonylurea (485 subjects) to obese Type 2 diabetics held on a weight- maintaining diet. Treatment efficacy parameters included change from baseline in glycated haemoglobin A(1c) (HbA(1c)), fasting and post-prandial serum glucose, insulin, triglyceride and free fatty acid levels. Baseline glycated haemoglobin, fasting glucose, insulin, triglyceride and free fatty acid levels did not differ between treatment groups. and on average were 9.4 +/- 0.05%, 222 +/- 2 mg/dl, 24 +/- 1 µU/ml, 248 +/- 11 mg/dl, and 850 +/- 32 µEq/l, respectively. A similarly designed study of Ergoset as monotherapy in Type 2 diabetics (154 subjects) with similar baseline clinical characteristics was conducted. Addition of Ergoset treatment to sulphonylurea reduced percent glycated HbA(1c) by 0.55 (P < 0.0001) (approximately 1.0 for responders, 65% of population), fasting and post-prandial glucose by 23 and 26 mg/dl (P < 0.0002), fasting and post-prandial triglycerides by 72 and 63 mg/dl (P < 0.005) and fasting and post-prandial free fatty acids by 150 and 165 µEq/l (P < 0.05), relative to placebo. Twelve percent of all Ergoset subjects, compared to 3% of placebo subjects, withdrew from the study due to adverse events. The most common events causing withdrawal were nausea, dizziness, asthenia, and rhinitis (representing 4.5, 3.3, 2.0, and 0.8% of the total Ergoset populations, respectively). The incidence of serious adverse events did not differ between Ergoset- (3.4%) and placebo- (4.3%) treated subjects. Ergoset as monotherapy also improved glycaemic control (0.56 HbA(1c) decrease relative to placebo after 24 weeks of treatment; P < 0.02). Once daily Ergoset treatment improves glycaemic control and serum lipid profile and is well-tolerated in obese Type 2 diabetics.

Timed bromocriptine administration reduces body fat stores in obese subjects and hyperglycemia in type II diabetics

Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.

Prolactin secretion and biological activity in females with galactorrhoea and normal circulating prolactin concentrations at rest

Prolactin secretion and biological activity have been investigated in 20 females with persistent idiopathic galactorrhoea who had normal resting serum prolactin levels at presentation. Results were compared with those in 34 normal controls. Hyperprolactinaemia, which was persistent in one and intermittent in the other, developed in two patients over an observation period of 1.5 to 8.5 years. Resting prolactin levels stayed normal in the remaining eighteen who were further investigated. Menstruation was disordered in only six of the 18, while ovulation occurred (serum progesterone greater than 20 nmol/l) in all seven patients who were studied over a 5 week period. Serum prolactin concentrations over 24 h were similar in patients and controls (24 h mean +/- SEM prolactin, 288 +/- 36 mU/l, patients, n = 7; 291 +/- 21 mU/l, controls, n = 9) as were prolactin levels estimated twice weekly for 5 weeks. Prolactin responses to thyrotrophin-releasing hormone, 200 micrograms (at 20 min, 2417 +/- 658 mU/l, patients, n = 7; 2113 +/- 424 mU/l, controls, n = 8), the dopamine antagonist, domperidone, 10 mg (at 30 min, 5949 +/- 536 mU/l, patients, n = 7; 5858 +/- 460 mU/l, controls, n = 8) and insulin-induced hypoglycaemia (at 60 min, 1441 +/- 551 mU/l, patients, n = 7; 1298 +/- 183 mU/l, controls, n = 7) were similar in patients and controls. Two different radioimmunoassays using two different antisera gave similar estimates of serum prolactin levels and prolactin bioactivity in serum was normal in an in-vitro bioassay based on the ability of prolactin to stimulate proliferation of Nb2 node rat lymphoma cells (basal bioassayable prolactin, patients 355 +/- 43 mU/l, n = 10; controls 348 +/- 64 mU/l, n = 7). Metabolic abnormalities similar to those previously noted in hyperprolactinaemia were observed in the patients' 24 h profiles. These included mild hyperglycaemia (24 h mean +/- SEM glucose, 5.47 +/- 0.08 mmol/l, patients; 5.05 +/- 0.14 mmol/l, controls; P less than 0.05) and elevations in circulating lactate, pyruvate and alanine. Blood glycerol was decreased (24 h mean +/- SEM, 0.044 +/- 0.004 versus 0.058 +/- 0.004 mmol/l, P less than 0.05). In the majority of patients with idiopathic galactorrhoea, prolactin concentrations, regulation of secretion and bioactivity in vitro are normal. The galactorrhoea and metabolic abnormalities suggest increased tissue sensitivity to the lactogenic and metabolic actions of prolactin, while ovarian cyclical function is relatively spared.

Effects on growth hormone secretion following intravenous and subcutaneous injections of growth hormone-releasing factor (hGRF-44 NH2): comparison of immunoreactive plasma GRF levels

The effects of subcutaneous administration of three doses of human growth hormone-releasing factor (hGRF-44 NH2 or hGRF) at doses of 100, 300 and 600 micrograms were studied in six normal young men. GH responses obtained with 100 and 300 micrograms were negligible. In contrast, the 600 micrograms dose gave a profile of response comparable in timing and magnitude to that obtained with i.v. hGRF at maximal effect doses (20, 80, 100 micrograms). Plasma immunoreactive hGRF levels (IR-hGRF) were compared after s.c. and i.v. hGRF. Mean maximal plasma concentrations were comparable with s.c. 600 micrograms and i.v. 20 micrograms. Peaks occurred earlier with i.v. hGRF (5 min as opposed to 15 min): however, return to undetectable values was obtained between 90 and 120 min after s.c. or i.v. injections. These data suggest a great loss of the peptide between the subcutaneous space and blood, without delayed absorption. High variability in plasma IR-hGRF concentrations between the subjects after the same s.c. doses was observed.

Mechanism of bromocriptine-induced hyperglycaemia

Results reveal that bromocriptine at a dose of 6 mg/kg. I.P. in mice caused a significant hyperglycaemic effect which was accompanied by a marked increase in liver glycogen. After adrenalectomy, the effect of bromocriptine on serum glucose level was reduced whereas its effect on liver glycogen content was abolished. In rats, administration of bromocriptine (17.5 mg/kg I.P.) induced a significant rise in serum glucose level which was associated with marked reduction in serum insulin activity and increase in serum corticosterone level with no effect on serum triiodothyronine (T3) or thyroxine (T4) levels. It could be concluded that bromocriptine-induced hyperglycaemia might be attributed at least partially to inhibition of insulin release and stimulation of corticosterone secretion.

Hyperprolactinaemia in male diabetics

We recently investigated two patients with diabetes and elevated serum prolactin levels in whom no cause of hyperprolactinaemia could be found. For this reason we measured fasting serum prolactin levels in 72 diabetic males and compared the results with those of 63 healthy males and 90 nondiabetic males attending an Impotence Clinic. The diabetic group had significantly higher serum prolactin levels (13.1 +/- 0.9 ng/ml) than the two control groups (9.9 +/- 0.6 ng/ml for normal males and 7.7 +/- 0.3 ng/ml for the non-diabetic impotent group). Eighteen percent of the diabetics studied had serum prolactin levels above the normal range for males (greater than 20 ng/ml). There was no correlation between serum prolactin levels and duration of diabetes, glycosylated haemoglobin level or presence of clinically apparent retinopathy. The correlation between serum prolactin level and fasting plasma glucose was weak though statistically significant (r = 0.26, P less than 0.05).

The effects of prolonged bromocriptine administration on PRL secretion GH and glycaemic control in stable insulin-dependent diabetes mellitus

Plasma glucose, PRL and GH concentrations were measured at hourly intervals over a 24-h period before and after oral bromocriptine administration in a dosage of 7.5 mg/day for 6 weeks in nine stable insulin-dependent diabetic men. The pattern of PRL secretion was noted to be normal in stable diabetes (with a mean concentration of 205 mu/l +/- 23 SEM) and was effectively suppressed by bromocriptine (to a mean concentration of 51 mu/l +/- 2 SEM). This suppression of PRL secretion caused no major alteration in glycaemic control, mean plasma glucose for the group was 10.6 mmol/l +/- 3.4 SD before and 9.6 mmol/l +/- 3.1 SD after bromocriptine administration. Bromocriptine produced no change in plasma glucose or GH profiles. It is concluded that PRL secretion is not a major influence on carbohydrate metabolism in stable diabetics.