1. Loss of the Circadian Peak of Dopamine Release at the Biological Clock is Associated with the Onset of Seasonal Insulin Resistance / Glucose Intolerance
Animals on the cusp of Summer-Fall transition
recovery 4 days
Guide cannula inserted at the SCN area
HPLC analysis
24 hour microdialysis of free living animals
Daily Profiles of Dopamine Extracellular Metabolite (HVA) and Serotonin Extracellular Metabolite (5-HIAA) in Hypothalamic Clock (SCN) of Freely Behaving Seasonally Glucose Tolerant (●) and Seasonally Glucose Intolerant (o) Hamsters
Figure 1
Luo S, Luo J, Cincotta AH. Suprachiasmatic nuclei monoamine metabolism of glucose tolerant versus intolerant hamsters. Neuroreport. 1999;10(10):

2. Destruction of Dopaminergic Projections to SCN of Insulin Sensitive Animals Induces Insulin Resistance
Summer animals in the summer condition
Glucose Tolerance Test
recovery 4 days
SCN dopaminergic neuron lesion via neurotoxin
maintain on regular diet for 16 days
Glucose Tolerance Test
Loss of this circadian peak of dopaminergic activity at the SCN induces severe insulin resistance
Figure 2
Luo S, Luo J, Meier AH, Cincotta AH. Dopaminergic neurotoxin administration to the area of the suprachiasmatic nuclei induces insulin resistance. Neuroreport. 1997;8(16):

3. ○ glucose-intolerant, freely moving ● glucose tolerant, freely moving
Norepinephrine (MHPG) and Serotonin (5- HIAA) VMH Extracellular Levels are Elevated in Seasonally Glucose-Intolerant Hamsters
Animals in the Fall-Winter condition
Cannula placement at VMH
Recovery for 4 days
24 hour microdialysis of free living animals
HPLC analysis
○ glucose-intolerant, freely moving
● glucose tolerant, freely moving
Time of Day (hours)
Increased norepinephrine at the VMH elicits the counter-regulatory response to high glycemia
Two-way ANOVA with repeated measures indicates significant difference of 5-HIAA and MHPG between the two groups (p < 0.05).
Beverly JL, de Vries MG, Beverly MF, Arseneau LM. Norepinephrine mediates glucoprivic-induced increase in GABA in the ventromedial hypothalamus of rats. Am J Physiol Regul Integr Comp Physiol. 2000;279(3):R990-6.
Borg WP, Sherwin RS, During MJ, Borg MA, Shulman GI. Local ventromedial hypothalamus glucopenia triggers counterregulatory hormone release. Diabetes 1995;44:180–184.
Borg MA, Sherwin RS, Borg WP, Tamborlane WV, Shulman GI: Local ventromedial hypothalamus glucose perfusion blocks counterregulation during systemic hypoglycemia in awake rats. J Clin Invest 1997;99:361–365.
Steffens AB, Damsma G, van der Gugten J, Luiten PG. Circulating free fatty acids, insulin, and glucose during chemical stimulation of hypothalamus in rats. Am J Physiol. 1984;247(6 Pt 1):E
Steffens AB, Flik G, Kuipers F, Lotter EC, Luiten PG. Hypothalamically-induced insulin release and its potentiation during oral and intravenous glucose loads. Brain Res. 1984;301(2):
Luo S, Meier AH, Cincotta AH. Bromocriptine reduces obesity, glucose intolerance and extracellular monoamine metabolite levels in the ventromedial hypothalamus of Syrian hamsters. Neuroendocrinology Jul;68(1):1-10.
Figure 3

4. Chronic Ventromedial Hypothalamic Infusion of Norepinephrine and Serotonin in Summer Insulin Sensitive Animals Promotes Insulin Resistance and Glucose Intolerance
Animals in Summer condition
surgery to insert VMH cannula and initiate Serotonin and Norepinephrine infusion
Infuse NE and S for 5 weeks
Glucose Tolerance Test
Figure 4
Luo S, Luo J, Cincotta AH. Chronic ventromedial hypothalamic infusion of norepinephrine and serotonin promotes insulin resistance and glucose intolerance. Neuroendocrinology. 1999;70(6):460-5.

5. Chronic Infusion of Norepinephrine into the VMH of Normal Young Insulin Sensitive SD rats Induces the Obese Glucose-Intolerant Hypertensive State
Young insulin sensitive female Sprague-Dawley rats at 10 weeks of age
Surgery to insert VMH cannula and initiation of unilateral Norepinephrine infusion
Infuse for 3-4 weeks
Measure metabolic parameters throughout the infusion period
Plasma Glucose
Plasma Norepinephrine
P<0.01
Plasma Insulin
Plasma Glucagon
Plasma Epinephrine
P<0.05
Plasma Leptin
Increased VMH NE tone is not merely an association of, but rather a contributing factor to, the metabolic syndrome
*P<0.05 and **P<0.01
Cincotta AH, Luo S, Zhang Y, Liang Y, Bina KG, Jetton TL, Scislowski PW. Chronic infusion of norepinephrine into the VMH of normal rats induces the obese glucose-intolerant state. Am J Physiol Regul Integr Comp Physiol Feb;278(2):R Luo S, Ezrokhi M, Trubitsyna Y, Li Y, Cincotta AH. Elevation of Norepinephrine (NE) Activity at the Ventromedial Hypothalamus (VMH) of Normal Rats Induces the Obese Hypertensive Insulin Resistant State without Altering Feeding. Diabetes 2015;64(Suppl1):A540
Figure 5

6. Chronic infusion of norepinephrine into the VMH of normal rats induces the obese glucose-intolerant state
Young insulin sensitive female Sprague-Dawley rats at 10 weeks of age
Surgery to insert VMH cannula and initiation of unilateral Norepinephrine infusion
Infuse for 3-4 weeks
Measure metabolic parameters throughout the infusion period
Effects of unilateral VMH Norepinephrine (NE:) or vehicle (○) infusions
Food Consumption
Body Weight
Retroperitoneal Fat Pad
Whitening of brown fat
Vehicle infusion
Norepinephrine infusion
Glucose tolerance test
Basal Lipolysis
isoproterenol-stimulated lipolysis in isolated adipocytes of rats treated with VMH NE for 4 (■), 9 (▲), or 14 () days or vehicle (○).
Plasma TG
14C=Glucose incorporation into lipid
Respiratory quotient
*P<0.05 and **P<0.01
Increased VMH NE tone is not merely an association of, but rather a contributing factor to, the metabolic syndrome
Figure 6
Cincotta AH, Luo S, Zhang Y, Liang Y, Bina KG, Jetton TL, Scislowski PW. Chronic infusion of norepinephrine into the VMH of normal rats induces the obese glucose-intolerant state. Am J Physiol Regul Integr Comp Physiol Feb;278(2):R

7. Timed Daily Administration of Bromocriptine Reduces (Normalizes) Elevated NE and Serotonin Release at the VMH of Insulin Resistant Syrian Hamsters and SHR Rats
Winter 14 week old male Syrian hamsters
GTT
Separate glucose tolerant from glucose intolerant
Microdialysis on freely moving animals
16 week old male hypertensive insulin resistant SHR rats or normotensive insulin sensitive Wistar rats
Timed daily bromocriptine treatment for 2 weeks at the onset of locomotor activity
Microdialysis on freely moving animals
Time of day (hour)
VMH 5-HIAA
VMH MHPG
Time of day (hour)
VMH 5-HIAA
VMH MHPG
5-HIAA
SHR rats exhibited elevated VMH NE release relative to Wistar normal controls (P < ). Timed daily bromocriptine administration significantly reduced VMH MHPG of SHR rats compared with vehicle treated SHR rats (P < )
In glucose-
tolerant hamsters, the average daily VMH extracellular
levels of 5-HIAA and MHPG were 48 and 44% lower,
respectively, than in glucose-intolerant hamsters
Two-way ANOVA with repeated measures indicates significant difference of 5-HIAA and MHPG between the two groups
(p<0.05)
MHPG
SHR rats exhibited significantly lower extracellular VMH HVA content compared with normal Wistar
rats (p < 0.001)
Daily profiles of 5-HIAA (A), and MHPG (B) in microdialysate samples from VMH of freely moving glucose tolerant
() and glucose-intolerant (○) hamsters
Luo S, Meier AH, Cincotta AH. Bromocriptine reduces obesity, glucose intolerance and extracellular monoamine
metabolite levels in the ventromedial hypothalamus of Syrian hamsters.
Neuroendocrinology Jul;68(1):1-10.
Ezrokhi M, Luo S, Trubitsyna Y, Cincotta AH . Neuroendocrine and metabolic components of dopamine agonist amelioration of metabolic syndrome in SHR rats.
Diabetology & Metabolic Syndrome 2014; 6:104
Figure 7

8. Circadian Timed Bromocriptine Treatment Reduces Free Fatty Acids Mobilization and Plasma Triglycerides in vivo in Winter Obese Insulin Resistant Hamsters
Obese, insulin resistant, hyperinsulinemic Syrian hamsters
Timed daily IP Bromocriptine administration for 9-10 weeks
Lipolysis, plasma TG and FFA measured in vivo
Light period
Figure 8
Cincotta AH, MacEachern TA, Meier AH. Bromocriptine redirects metabolism and prevents seasonal onset of obese hyperinsulinemic state in Syrian hamsters. Am J Physiol. 1993; 264(2 Pt 1):E285-93

9. Circadian Timed Bromocriptine Treatment Increases Whole Body Protein Turnover in Winter Obese Insulin Resistant Syrian Hamsters
Obese, insulin resistant, hyperinsulinemic Syrian hamsters
Timed daily IP Bromocriptine administration for 9-10 weeks
Protein turnover rate measured in vivo
Figure 9
Cincotta AH, MacEachern TA, Meier AH. Bromocriptine redirects metabolism and prevents seasonal onset of obese hyperinsulinemic state in Syrian hamsters. Am J Physiol. 1993; 264(2 Pt 1):E285-93

10. Circadian Timed Bromocriptine Treatment Reduces Plasma Glucose, Insulin, Leptin, Norepinephrine, Systolic and Diastolic Blood Pressure in Hypertensive Insulin Resistant SHR Rats
Hypertensive, obese, insulin resistant male 16 week old SHR rats, healthy Wistar rats as control
Timed daily IP Bromocriptine administration for 2 weeks
Blood pressure, liver enzymes and metabolic parameters measurements
P<0.02
P= P<0.003
P=0.0002
P= P=NS
P=0.001
P<0.0001
P< P<0.001
P<0.001
P< P<0.001
P=0.001
SHR rats treated with vehicle control
SHR rats treated with Timed Daily Bromocriptine
Wistar rats
Figure 10
Ezrokhi M, Luo S, Trubitsyna Y, Cincotta AH. Neuroendocrine and metabolic components of dopamine agonist amelioration of metabolic syndrome in SHR rats. Diabetology & Metabolic Syndrome 2014; 6:104

11. Circadian-Timed BC/SKF Treatment Reduces PVN Levels of NPY and CRH* *
*P<0.05
Figure 11
Bina KG, Cincotta AH. Dopaminergic agonists normalize elevated hypothalamic neuropeptide Y and corticotropin-releasing hormone, body weight gain, and hyperglycemia in ob/ob mice. Neuroendocrinology. 2000;71(1):68-78.

12. Western Diet / Stress / Sleep Wake Alterations Induce A, B, and C
Schematic of Dopamine – Clock Interactions in the Regulation of Peripheral Fuel Metabolism
Western Diet / Stress / Sleep Wake Alterations Induce A, B, and C
Refs. 1, 20, 23, 27, 28
Timed Daily
Dopamine Agonist
Administration Reverses A, B and C A B C
= increases
= decreases
= results in
= stimulates
Abbreviations:
1. CRH: Corticotropin Releasing Hormone
2. eNOS: Endothelial Nitric Oxide Synthase
3. FFA: Free Fatty Acids
4. NPY: Neuropeptide Y
5. PVN: Paraventricular Nucleus
6. SCN: Suprachiasmatic Nucleus
7. SNS: Sympathetic Nervous System
8. TG: Triglycerides
9. VMH: Ventromedial Hypothalamus
Figure 12
Raskin P, Cincotta AH.
Expert Review of Endocrinology & Metabolism 2016;11(2):