scholarly journals Effects of Insulin Treatment without and with Recurrent Hypoglycemia on Hypoglycemic Counterregulation and Adrenal Catecholamine-Synthesizing Enzymes in Diabetic Rats

Endocrinology ◽  
2006 ◽  
Vol 147 (4) ◽  
pp. 1860-1870 ◽  
Author(s):  
Karen E. Inouye ◽  
Jessica T. Y. Yue ◽  
Owen Chan ◽  
Tony Kim ◽  
Eitan M. Akirav ◽  
...  
Keyword(s):  
Tyrosine Hydroxylase ◽  
Insulin Treatment ◽  
Diabetic Rats ◽  
Hyperinsulinemic Hypoglycemia ◽  
Mrna Levels ◽  
Relevant Model ◽  
Counterregulatory Hormones ◽  
Catecholamine Synthesizing Enzymes ◽  
Recurrent Hypoglycemia ◽  
Th Mrna

Untreated diabetic rats show impaired counterregulation against hypoglycemia. The blunted epinephrine responses are associated with reduced adrenomedullary tyrosine hydroxylase (TH) mRNA levels. Recurrent hypoglycemia further impairs epinephrine counterregulation and is also associated with reduced phenylethanolamine N-methyltransferase mRNA. This study investigated the adaptations underlying impaired counterregulation in insulin-treated diabetic rats, a more clinically relevant model. We studied the effects of insulin treatment on counterregulatory hormones and adrenal catecholamine-synthesizing enzymes and adaptations after recurrent hypoglycemia. Groups included: normal; diabetic, insulin-treated for 3 wk (DI); and insulin-treated diabetic exposed to seven episodes (over 4 d) of hyperinsulinemic-hypoglycemia (DI-hypo) or hyperinsulinemic-hyperglycemia (DI-hyper). DI-hyper rats differentiated the effects of hyperinsulinemia from those of hypoglycemia. On d 5, rats from all groups were assessed for adrenal catecholamine-synthesizing enzyme levels or underwent hypoglycemic clamps to examine counterregulatory responses. Despite insulin treatment, fasting corticosterone levels remained increased, and corticosterone responses to hypoglycemia were impaired in DI rats. However, glucagon, epinephrine, norepinephrine, and ACTH counterregulatory defects were prevented. Recurrent hypoglycemia in DI-hypo rats blunted corticosterone but, surprisingly, not epinephrine responses. Norepinephrine and ACTH responses also were not impaired, whereas glucagon counterregulation was reduced due to repeated hyperinsulinemia. Insulin treatment prevented decreases in basal TH protein and increased PNMT and dopamine β-hydroxylase protein. DI-hypo rats showed increases in TH, PNMT, and dopamine β-hydroxylase. We conclude that insulin treatment of diabetic rats protects against most counterregulatory defects but not elevated fasting corticosterone and decreased corticosterone counterregulation. Protection against epinephrine defects, both without and with antecedent hypoglycemia, is associated with enhancement of adrenal catecholamine-synthesizing enzyme levels.

Effects of diabetes and recurrent hypoglycemia on the regulation of the sympathoadrenal system and hypothalamo-pituitary-adrenal axis

2005 ◽  
Vol 288 (2) ◽  
pp. E422-E429 ◽  
Author(s):  
Karen E. Inouye ◽  
Owen Chan ◽  
Jessica T. Y. Yue ◽  
Stephen G. Matthews ◽  
Mladen Vranic
Keyword(s):  
Diabetic Rats ◽  
Hyperinsulinemic Hypoglycemia ◽  
Mrna Levels ◽  
Sympathoadrenal System ◽  
Adrenal Axis ◽  
Basal Expression ◽  
Pomc Mrna ◽  
Recurrent Hypoglycemia ◽  
Pituitary Adrenal Axis ◽  
Th Mrna

Epinephrine, norepinephrine, and corticosterone responses to hypoglycemia are impaired in diabetic rats. Recurrent hypoglycemia further diminishes epinephrine responses. This study examined the sympathoadrenal system and hypothalamo-pituitary-adrenal axis for molecular adaptations underlying these defects. Groups were normal (N) and diabetic (D) rats and diabetic rats exposed to 4 days of 2 episodes/day of hyperinsulinemic hypoglycemia (D-hypo) or hyperinsulinemic hyperglycemia (D-hyper). D-hypo and D-hyper rats differentiated effects of hypoglycemia and hyperinsulinemia. Adrenal tyrosine hydroxylase (TH) mRNA was reduced ( P < 0.05 vs. N) 25% in all diabetic groups. Remarkably, mRNA for phenylethanolamine N-methyltransferase (PNMT), which converts norepinephrine to epinephrine, was reduced ( P < 0.05 vs. all) 40% only in D-hypo rats. Paradoxically, dopamine β-hydroxylase mRNA was elevated ( P < 0.05 vs. D, D-hyper) in D-hypo rats. Hippocampal mineralocorticoid receptor (MR) mRNA was increased ( P < 0.05 vs. N) in all diabetic groups. Hippocampal glucocorticoid receptor (GR), hypothalamic paraventricular nucleus (PVN) GR and corticotropin-releasing hormone (CRH), and pituitary GR and proopiomelanocortin (POMC) mRNA levels did not differ. We conclude that blunted corticosterone responses to hypoglycemia in diabetic rats are not due to altered basal expression of GR, CRH, and POMC in the hippocampus, PVN, and pituitary. The corticosterone defect also does not appear to be due to increased hippocampal MR, since we have reported normalized corticosterone responses in D-hypo and D-hyper rats. Furthermore, impaired epinephrine counterregulation in diabetes is associated with reduced adrenal TH mRNA, whereas the additional epinephrine defect after recurrent hypoglycemia is associated with decreases in both TH and PNMT mRNA.

scholarly journals Regulation of tyrosine hydroxylase mRNA in catecholaminergic cells of embryonic rat: analysis by in situ hybridization.

1989 ◽  
Vol 37 (1) ◽  
pp. 1-5 ◽  
Author(s):  
G M Jonakait ◽  
M Rosenthal ◽  
J I Morrell
Keyword(s):  
In Situ Hybridization ◽  
Tyrosine Hydroxylase ◽  
Messenger Rna ◽  
Sympathetic Ganglia ◽  
Mrna Levels ◽  
Pregnant Rats ◽  
Reserpine Treatment ◽  
Catecholaminergic Cells ◽  
Th Mrna

In situ hybridization was used to examine the appearance of mRNA specific for tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine (CA) biosynthesis, in neural crest derivatives of the rat embryo. These derivatives include sympathetic ganglia and transient catecholaminergic cells of embryonic intestine. Messenger RNA is first detected in sympathetic ganglia at E11.5, the age corresponding to the initial immunocytochemical expression of TH protein. In older embryos increased accumulation of TH-specific mRNA in sympathetic ganglia parallels the increase in TH immunoreactivity. By contrast, mRNA for TH is difficult to detect in embryonic intestines at E11.5 but is found instead in cells clustered at the dorsal boundaries of the pharynx and foregut. Cells expressing TH mRNA are infrequently found in embryonic intestines at any age, even though TH protein is immunohistochemically apparent. Treatment of pregnant rats with doses of reserpine, known to increase circulating levels of glucocorticoid hormones and prolong the expression of TH protein in embryonic gut cells, dramatically but transiently increases the number of gut cells at E12.5 with detectable TH mRNA. After E13.5 TH mRNA is undetectable even in reserpine-treated guts. Reserpine treatment also increases the labeling density in sympathetic ganglia. Taken together, these data are consistent with the hypothesis that the microenvironment of the embryonic intestine affects gene expression directly to alter phenotype. Moreover, although reserpine administration briefly increases TH mRNA levels, the effect is short-lived and does not alter neurotransmitter phenotypic conversion.

Water deprivation and rat adrenal mRNAs for tyrosine hydroxylase and the norepinephrine transporter

1997 ◽  
Vol 272 (6) ◽  
pp. R1897-R1903 ◽  
Author(s):  
V. L. Brooks ◽  
T. A. Huhtala ◽  
T. L. Silliman ◽  
W. C. Engeland
Keyword(s):  
Tyrosine Hydroxylase ◽  
Water Deprivation ◽  
Norepinephrine Transporter ◽  
Ribonuclease Protection Assay ◽  
Mrna Levels ◽  
Total Rna ◽  
Adrenocortical Activity ◽  
Corticosterone Response ◽  
Ribonuclease Protection ◽  
Th Mrna

Experiments were performed in rats to test the hypothesis that adrenal mRNA levels of tyrosine hydroxylase (TH) and the norepinephrine transporter (NET) would be modified by water deprivation via activation of the sympathetic nervous system. TH and NET mRNA levels were measured using the ribonuclease protection assay. Adrenal TH mRNA was higher (P < 0.001) in water-deprived (921 +/- 39 fg/microgram total RNA) compared with the water-replete rats (657 +/- 45 fg/microgram total RNA). In contrast, water deprivation decreased (P < 0.01) adrenal NET mRNA levels (275 +/- 66 vs. 433 +/- 63 fg/microgram total RNA). The dehydration-induced increase in TH mRNA was prevented by prior splanchnicectomy, but the decrease in NET mRNA was produced even in the absence of adrenal nerves. Water deprivation also increased (P < 0.05) plasma adrenocorticotropic hormone (84 +/- 16 vs. 42 +/- 14 pg/ml) and corticosterone (358 +/- 87 vs. 44 +/- 15 ng/ml) levels. Interestingly, the corticosterone response was reduced (P < 0.05) by unilateral adrenal denervation. These results suggest that water deprivation increases both adrenal medullary and adrenocortical activity at least in part by stimulation of sympathetic nerve activity.

scholarly journals Enhanced proteolytic activity directed against the N-terminal of IGF-I in diabetic rats

1999 ◽  
Vol 162 (2) ◽  
pp. 243-250 ◽  
Author(s):  
H Yamamoto ◽  
C Maake ◽  
LJ Murphy
Keyword(s):  
Protease Activity ◽  
Insulin Treatment ◽  
Serum Glucose ◽  
Diabetic Rats ◽  
Acute Administration ◽  
Mrna Levels ◽  
Igf I ◽  
Streptozotocin Diabetic Rats ◽  
Biotin Label

We have recently identified in serum an acid protease which is capable of generating des(1-3)IGF-I from intact IGF-I. Here we have utilized a synthetic substrate with the sequence, biotin-G-P-E-T-L-C-BSA which contains the N-terminal sequence of IGF-I, to investigate the levels of this protease activity in streptozotocin-diabetic rats. Protease activity, quantified in terms of the amount of the biotin label lost, was determined in serum and hepatic extracts from normal control rats, diabetic rats and insulin-treated diabetic rats. Both the serum protease activity and protease activity in hepatic extracts were significantly increased in diabetic rats compared with control rats (P<0.02 and P<0.005). Following acute administration of insulin, a rapid and marked reduction in serum protease activity was observed; with an approximately 50% reduction apparent at 30 min (P<0.001). Chronic insulin treatment of diabetic rats also significantly reduced the serum and hepatic protease activity to the levels seen in control rats. A positive correlation between protease activity and serum glucose level was observed (r=0.58, P<0.005). The abundance of Spi 2.1 mRNA, a serine protease inhibitor, capable of inhibiting the IGF-I protease activity in vitro, was significantly decreased in the liver of diabetic rats and insulin treatment of diabetic rats did not normalize Spi 2.1 mRNA levels. These data suggest that the conversion of IGF-I to the more active des(1-3)IGF-I variant may be enhanced in diabetic animals. Since serum IGF-I levels are reduced in diabetic rats, increased des(1-3)IGF-I-generating protease activity would enhance the functional activity of the circulating IGF-I.

Differential expression of the insulin-like growth factor binding proteins in spontaneously diabetic rats

1992 ◽  
Vol 8 (2) ◽  
pp. 155-163 ◽  
Author(s):  
J. Luo ◽  
L. J. Murphy
Keyword(s):  
Growth Factor ◽  
Binding Proteins ◽  
Insulin Treatment ◽  
Diabetic Rats ◽  
Mrna Levels ◽  
Insulin Like Growth Factor ◽  
Intensive Insulin Treatment ◽  
Igf I ◽  
Spontaneously Diabetic Rats ◽  
Igfbp 3

ABSTRACT Diabetes-induced growth retardation in the rodent is associated with both reduced circulating insulin-like growth factor-I (IGF-I) and enhanced levels of inhibitors of somatomedin activity. IGF-binding proteins (IGFBPs) are present in the circulation and tissue fluids and are believed to modulate the actions of IGF-I. Since elevated concentrations of the IGFBPs may contribute to the enhanced somatomedin-inhibitor activity observed in serum from diabetic animals, we have examined the amounts of hepatic IGFBP-1, -2, -3 and -4 mRNA in the spontaneously diabetic BioBreeding/Worcester rat. The study used two types of diabetic animal: mildly diabetic animals, which received suboptimal insulin treatment (0.5–1 U/day) and diabetic animals, which received intensive insulin treatment (3–6 U/day). A significant increase in the amount of IGFBP-1 and IGFBP-2 mRNA was seen 1 month and 3 months after the onset of diabetes. Intensive insulin treatment for 3 weeks normalized the amount of IGFBP-1 mRNA in diabetic rats and resulted in a decrease in IGFBP-2 mRNA. In contrast to the increase in IGFBP-1 and IGFBP-2 mRNA, a significant decrease in IGFBP-3 mRNA was seen in diabetic rats (54.6% of control, P < 0.0005 and 64.6% of control, P < 0.005 for 1 and 3 months respectively) and intensive insulin treatment for 3 weeks did not restore the IGFBP-3 mRNA level in diabetic rats. No significant difference in IGFBP-4 mRNA levels was seen in diabetic compared with non-diabetic rats. When serum was analysed by ligand blotting the major finding was a reduction in the 39–42kDa binding protein. No increase in 29–30kDa IGFBP in the serum was detected in the diabetic rats. From these studies we conclude that the major change in IGFBPs in mildly hyperglycaemic spontaneously diabetic rats is a decrease in IGFBP-3. The changes in hepatic IGFBP-1 and -2 mRNA do not appear to be of sufficient magnitude to result in an increase in serum concentrations of these binding proteins.

Gene expression of tyrosine hydroxylase and neuropeptide Y in prevertebral ganglia of renal hypertensive rats

1991 ◽  
Vol 261 (6) ◽  
pp. R1455-R1460
Author(s):  
T. L. Krukoff ◽  
Y. Zheng
Keyword(s):  
Gene Expression ◽  
Tyrosine Hydroxylase ◽  
Neuropeptide Y ◽  
Adrenal Glands ◽  
Renal Hypertension ◽  
Male Rats ◽  
Mrna Levels ◽  
Hypertensive Rats ◽  
Prevertebral Ganglia ◽  
Th Mrna

The gene expression of tyrosine hydroxylase (TH) and neuropeptide Y (NPY) was studied in prevertebral ganglia and adrenal glands of adult male rats during the development of renal hypertension (removal of 1 kidney/constriction of other kidney). Only tissues from rats with arterial pressures significantly elevated by day 3 were compared with those from controls. At 4 or 5 days after renal surgery, superior cervical ganglia, celiac-mesenteric plexus, adrenal glands, and stellate ganglia were surgically removed from nonfixed rats for Northern blot analysis or from perfusion-fixed rats for in situ hybridization. In all tissues, levels of TH mRNA were decreased in hypertensive rats; cells with decreased levels were scattered throughout each tissue. In contrast, levels of NPY mRNA were unchanged in hypertensive rats compared with controls. Changes in TH mRNA levels suggest that the developing phase of renal hypertension is associated with a decrease in sympathetic outflow to the periphery. In contrast, the failure of NPY mRNA levels to change suggests a different regulatory mechanism for NPY expression or a different role for NPY in sympathetic neurotransmission.

scholarly journals Effects of recurrent hyperinsulinemia with and without hypoglycemia on counterregulation in diabetic rats

2002 ◽  
Vol 282 (6) ◽  
pp. E1369-E1379 ◽  
Author(s):  
Karen Inouye ◽  
Kathy Shum ◽  
Owen Chan ◽  
Julian Mathoo ◽  
Stephen G. Matthews ◽  
...  
Keyword(s):  
Insulin Sensitivity ◽  
Glucose Production ◽  
Plasma Corticosterone ◽  
Diabetic Rats ◽  
Endocrine Function ◽  
Hyperinsulinemic Hypoglycemia ◽  
Plasma Acth ◽  
Peripheral Insulin Sensitivity ◽  
Basal Plasma ◽  
Recurrent Hypoglycemia

To understand the mechanisms whereby recurrent hypoglycemia increases the risk of subsequent hypoglycemia, it was necessary to differentiate the effects of recurrent hyperinsulinemia from those of hyperinsulinemic hypoglycemia. We examined basal and hypoglycemic endocrine function in normal rats, streptozotocin-diabetic controls, and diabetic rats exposed to 4 days of 2 episodes/day of hyperinsulinemic hypoglycemia (DH) or hyperinsulinemic hyperglycemia (DI). DH and DI rats differentiated the effects of hyperinsulinemia from those of hypoglycemia. In diabetic controls, basal plasma ACTH tended to be increased, and plasma corticosterone, plasma somatostatin, and pancreatic prosomatostatin and proglucagon mRNA were increased ( P < 0.05) vs. normal rats. These parameters were normalized in DH and DI rats. In diabetic controls, glucagon, epinephrine, norepinephrine, corticosterone, and peak glucose production responses to hypoglycemia were reduced ( P < 0.05) vs. normal rats. In DI rats, epinephrine responses were normalized. Conversely, DH rats displayed marked further impairment of epinephrine and glucose production responses and increased peripheral insulin sensitivity ( P < 0.05 vs. diabetic controls). Both insulin regimens partially normalized glucagon and fully normalized norepinephrine and corticosterone responses. In summary, recurrent hyperinsulinemia in diabetic rats normalized most pituitary-adrenal, sympathoadrenal, and pancreatic parameters. However, concurrent hypoglycemia further impaired epinephrine and glucose production responses and increased insulin sensitivity. We conclude that 1) recurrent hypoglycemia may increase the risk of subsequent hypoglycemia by increasing insulin sensitivity, and 2) epinephrine counterregulation is particularly sensitive to impairment by recurrent hypoglycemia.

Growth hormone-releasing factor expression is discordantly regulated in the hypothalamus and testis of streptozotocin-diabetic rats

1996 ◽  
Vol 148 (2) ◽  
pp. 189-192 ◽  
Author(s):  
D Olchovsky ◽  
J F Bruno ◽  
M Berelowitz
Keyword(s):  
Growth Hormone ◽  
Mrna Expression ◽  
Arcuate Nucleus ◽  
Insulin Treatment ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Diabetic Rats ◽  
Male Rats ◽  
Mrna Levels ◽  
Growth Hormone Releasing Factor

Abstract Growth hormone-releasing factor (GRF) mRNA expression in male rats occurs predominantly in the hypothalamus (mainly in the arcuate nucleus), and among extraneural sites primarily in the testis. Hypothalamic GRF is the physiological tropic stimulus to growth hormone secretion. However, the role of GRF in the testis is unknown. We have shown previously that hypothalamic GRF mRNA expression is significantly reduced in streptozotocin (STZ)-diabetic rats. This reduction is confined to the arcuate nucleus and probably accounts for the suppression of growth hormone pulsatility. The present studies were performed to evaluate GRF expression in the testis of streptozotocin (STZ)-diabetic rats. Diabetes was induced by injection of STZ (100 mg/kg i.p.). Seventeen to twenty days later diabetic rats were hyperglycemic compared with vehicle-injected controls and demonstrated growth failure. Insulin treatment reduced the glycemia and increased body weight towards normal. Total RNA was extracted from the hypothalamus and testis, and GRF mRNA levels estimated by solution hybridization/nuclease protection assay. Levels of hypothalamic somatostatin mRNA were measured to serve as control values. GRF mRNA was significantly (P<0·001) decreased in the hypothalamus of STZ-diabetic rats (0·2 ± 0·07 mean relative densitometric units, n=8) compared with controls (1·0 ± 0·19, n=8) with no change in somatostatin mRNA expression. In contrast, testicular GRF mRNA was increased 70% (P<0·05) in STZ-diabetic rats. Insulin treatment resulted in normalization of hypothalamic GRF mRNA levels (1·1 ± 0·17, n=5) with no effect on testicular GRF mRNA expression. In conclusion GRF gene expression is discordantly regulated in tissues of male STZ-diabetic rats. While reduced GRF expression may account for the low growth hormone state in this model, increased testicular GRF mRNA (with the previously reported reduction of insulin-like growth factor-I mRNA) resembles the response seen in growth hormone-sensitive tissue (especially the hypothalamus) to this growth hormone-deficient state. Journal of Endocrinology (1996) 148, 189–192

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