Plasma Insulin Levels in Endocrine Diseases

To determine the relationship between hyperinsulinemia and hypertension in spontaneously hypertensive rats (SHR), the antihyperglycemic agent metformin was administered to SHR and their Wistar-Kyoto (WKY) controls, and its effects on plasma insulin levels and blood pressure were examined. Five-week-old rats were started on oral metformin treatment (350 mg.kg-1.day-1, which was gradually increased to 500 mg.kg-1.day-1 over a 2-wk period). Metformin treatment caused sustained decreases in plasma insulin levels in the SHR (27.1 +/- 2.3 vs. untreated SHR 53.5 +/- 2.7 microU/ml, P < 0.001) without having any effect in the WKY (30.7 +/- 2.2 vs. untreated WKY 37.8 +/- 1.6 microU/ml, P > 0.05). The treatment did not affect the plasma glucose levels in any group. Metformin treatment also attenuated the increase in systolic blood pressure in the SHR (157 +/- 6.0 vs. untreated SHR 196 +/- 9.0 mmHg, P < 0.001) but had no effect in the WKY (134 +/- 3 vs. untreated WKY 136 +/- 4 mmHg, P > 0.05). Furthermore, raising plasma insulin levels in the metformin-treated SHR to levels that existed in the untreated SHR reversed the effect of metformin on blood pressure (189 +/- 3 vs. untreated SHR 208 +/- 5.0 mmHg, P > 0.05). These findings suggest that either hyperinsulinemia may contribute toward the increase in blood pressure in the SHR or that the underlying mechanism is closely associated with the expression of both these disorders.

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Interactions of cold exposure and starvation on glucose tolerance and insulin response

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1983.245.6.e575 ◽

1983 ◽

Vol 245 (6) ◽

pp. E575-E581 ◽

Cited By ~ 3

Author(s):

A. L. Vallerand ◽

J. Lupien ◽

L. J. Bukowiecki

Keyword(s):

Glucose Tolerance ◽

Cold Acclimation ◽

Cold Exposure ◽

Plasma Insulin ◽

Insulin Response ◽

Insulinogenic Index ◽

Intravenous Glucose ◽

Peripheral Tissues ◽

Insulin Levels ◽

Plasma Insulin Levels

The metabolic interactions of cold exposure, cold acclimation, and starvation on glucose tolerance and plasma insulin levels were studied in precannulated, unrestrained, and unanesthetized rats. Cold exposure (48 h at 5 degrees C) significantly reduced the insulin response to intravenous glucose injection (P less than 0.01) while improving glucose tolerance (P less than 0.01). Starvation (48 h at 25 degrees C) also reduced the insulin response (P less than 0.01) but did not significantly alter glucose tolerance. “Accelerated starvation” induced by starving rats for 48 h at 5 degrees C dramatically reduced both basal and glucose-stimulated insulin levels while even improving glucose tolerance, resulting in a 15-fold reduction in the insulinogenic index. Cold acclimation (3 wk at 5 degrees C) induced essentially the same alterations as cold exposure. Approximately reversed changes were observed when cold-acclimated rats were returned to a warm environment for 15–18 h. Results from these studies indicate that 1) cold exposure and starvation, but not cold acclimation, act synergistically in decreasing the sensitivity and/or the capacity of pancreatic islets for secreting insulin in response to glucose stimulation; 2) glucose tolerance and possibly insulin sensitivity of peripheral tissues are enhanced by cold exposure and starvation, although glucose tolerance is improved by cold exposure only, not by starvation; 3) an improved glucose tolerance with barely detectable plasma insulin levels was obtained in cold-starved rats under normal physiological conditions.

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ANF inhibits glucose-stimulated insulin secretion in mouse and rat

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1988.255.5.e579 ◽

1988 ◽

Vol 255 (5) ◽

pp. E579-E582 ◽

Cited By ~ 1

Author(s):

B. Ahren

Keyword(s):

Insulin Secretion ◽

Atrial Natriuretic Factor ◽

Plasma Insulin ◽

Glucagon Secretion ◽

Insulin Levels ◽

Atrial Cells ◽

Insulin And Glucagon Secretion ◽

Plasma Insulin Levels ◽

Glucose Stimulated Insulin Secretion ◽

Dose Levels

Atrial natriuretic factor (ANF) is synthesized in atrial cells and was recently demonstrated to also occur within islet glucagon cells. Therefore, we investigated the possible effects of synthetic rat ANF-(1-28) on basal and stimulated insulin and glucagon secretion in the mouse and on glucose-induced insulin secretion in the rat. We found that ANF did not affect basal levels of insulin, glucagon, or glucose when injected intravenously at dose levels between 0.25 and 4.0 nmol/kg in mice. However, when injected together with glucose (2.8 mmol/kg), ANF (4.0 nmol/kg) inhibited the increase in plasma insulin levels by 40%, from 114 +/- 8 microU/ml in controls to 81 +/- 8 microU/ml (P less than 0.01). Likewise, the increase in plasma insulin levels during an intravenous infusion of glucose in rats (10 mg/min) was significantly reduced by ANF (100 pmol.kg-1.min-1; P less than 0.001). In contrast, the increase in plasma levels of insulin and glucagon after the intravenous injection of the cholinergic agonist carbachol in mice (0.16 mumol/kg) was not significantly affected by ANF. We conclude that ANF inhibits glucose-stimulated insulin secretion in the mouse and the rat. The peptide may therefore be a modulator of insulin secretion.

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Fructose feeding and intermittent hypoxia affect ventilatory responsiveness to hypoxia and hypercapnia in rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00280.2004 ◽

2004 ◽

Vol 97 (4) ◽

pp. 1387-1394 ◽

Cited By ~ 1

Author(s):

Evelyn H. Schlenker ◽

Yijiang Shi ◽

Joni Wipf ◽

Douglas S. Martin ◽

Curtis K. Kost

Keyword(s):

Intermittent Hypoxia ◽

Plasma Insulin ◽

Tap Water ◽

Minute Ventilation ◽

Acute Hypoxia ◽

Male Rats ◽

Control Group ◽

Insulin Levels ◽

Ventilatory Responses ◽

Plasma Insulin Levels

We hypothesized that, in male rats, 10% fructose in drinking water would depress ventilatory responsiveness to acute hypoxia (10% O2 in N2) and hypercapnia (5% CO2 in O2) that would be depressed further by exposure to intermittent hypoxia. Minute ventilation (V̇e) in air and in response to acute hypoxia and hypercapnia was evaluated in 10 rats before fructose feeding (FF), during 6 wk of FF, and after FF was removed for 2 wk. During FF, five rats were exposed to intermittent air and five to intermittent hypoxia for 13 days. Six rats given tap water acted as control and were exposed to intermittent air and subsequently intermittent hypoxia. In FF rats, plasma insulin levels increased threefold in the rats exposed to intermittent hypoxia and during washout returned to levels observed in rats exposed to intermittent air. During FF, ventilatory responsiveness to acute hypoxia was depressed because of decreased tidal volume (Vt) responsiveness. During washout, V̇e decreased as a result of decreased Vt and frequency of breathing, and the ventilatory responsiveness to hypoxia in intermittent hypoxia rats did not recover. In all rats, the ventilatory responses to hypercapnia were decreased during FF and recovered after washout because of an increased Vt responsiveness. In the control group, hypoxic responsiveness was not depressed after intermittent hypoxia and was augmented after washout. Thus FF attenuated the ventilatory responsiveness of conscious rats to hypoxia and hypercapnia. Intermittent hypoxia interacted with FF to increase insulin levels and depress ventilatory responses to acute hypoxia that remained depressed during washout.

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Impact of lifetime marijuana use on fasting plasma insulin levels and HOMA-IR score in obese adults with and without insulin resistance

Acta Diabetologica ◽

10.1007/s00592-019-01390-x ◽

2019 ◽

Vol 57 (2) ◽

pp. 133-140

Author(s):

Gerard Ngueta

Keyword(s):

Insulin Resistance ◽

Plasma Insulin ◽

Marijuana Use ◽

Obese Adults ◽

Insulin Levels ◽

Fasting Plasma ◽

Plasma Insulin Levels ◽

Fasting Plasma Insulin

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Lack of effect of morphine, reserpine, and halothane on oscillation of plasma insulin in M. mulatta

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1981.240.1.e1 ◽

1981 ◽

Vol 240 (1) ◽

pp. E1-E4 ◽

Cited By ~ 2

Author(s):

F. G. Hom ◽

D. J. Koerker ◽

C. J. Goodner

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Rhesus Monkeys ◽

Plasma Insulin ◽

Insulin Levels ◽

Plasma Insulin Levels ◽

The Central Nervous System ◽

Male Rhesus

Oscillating plasma insulin levels, with periods averaging 9 min, in fasting rhesus monkeys have been previously reported by us. To test whether an oscillator in the central nervous system might be driving these oscillations, we subjected five male rhesus monkeys to morphine, reserpine, and halothane, agents known to affect the central nervous system, in an attempt to either disrupt or change the frequency of the oscillations. We could demonstrate no significant effect of any of the three drugs on the oscillations. We conclude, therefore, that the oscillations in plasma insulin are not driven by an oscillator in the central nervous system. Coupled with the results of others, these data suggest that these oscillations are probably due to an intrinsic pancreatic pacemaker.

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