23 research outputs found
Characterization of iodothyronine sulfotransferase activity in rat liver
Sulfation is an important pathway in the metabolism of thyroid hormone
because it strongly facilitates the degradation of the hormone by the type
I iodothyronine deiodinase. However, little is known about the properties
and possible regulation of the sulfotransferase(s) involved in the
sulfation of thyroid hormone. We have developed a convenient method for
the analysis of iodothyronine sulfotransferase activity in tissue
cytosolic fractions, using radioiodinated 3,3'-diiodothyronine (3,3'-T2)
as the preferred substrate, unlabeled
3'-phosphoadenosine-5'-phosphosulfate (PAPS) as the sulfate donor, and
Sephadex LH-20 minicolomns for separation of the products. We found that
iodothyronine sulfotransferase activity in rat liver cytosol is 1) higher
in male than in female rats; 2) optimal at pH 8.0; 3) characterized (at 50
microM PAPS and pH 7.2) by apparent Michaelis-Menton (Km) values for
3,3'-T2 of 1.77 and 4.19 microM, and Vmax values of 1.94 and 1.45 nmol/min
per mg protein in male and female rats, respectively; 4) characterized (at
1 microM 3,3'-T2 and pH 7.2) by apparent Km values for PAPS of 4.92 and
3.80 microM and Vmax values of 0.72 and 0.31 nmol/min per mg protein, in
males and females, respectively; 5) little affected by hyperthyroidism in
both male and female rats, but significantly decreased by hypothyroidism
in males but not in females; and 6) not affected by short-term (3 days)
fasting in both male and female rats, but significantly decreased by
long-term (3 weeks) food restriction to one-third of normal intake in
males but not in females. It is suggested that the higher hepatic
iodothyronine sulfotransferase activity in male vs. female rats, as well
as the decreases induced in males by hypothyroidism and long-term food
restriction, represents differences in the expression of the male-dominant
isoenzyme rSULT1C1
Neural differentiation of the human neuroblastoma cell line IMR32 induces production of a thyrotropin-releasing hormone-like peptide
The human neuroblastoma cell line IMR32 produces and secretes substantial amounts of TRH-immunoreactivity (TRH-IR) as measured with radioimmunoassay (RIA) using the nonspecific antiserum 4319. It was found that synthesis of TRH-IR is dependent on neural differentiation: under serum-free conditions these cells exhibit neural characteristics as defined by morphological and biochemical standards. After culture for 2–5 days in serum-free medium cells grew large neural processes and expressed neuron-specific markers whereas glial-specific markers were absent. TRH-IR became detectable after 4–8 days serum-free conditions. Northern blot and chromatographic analysis, however, failed to detect proTRH mRNA and authentic TRH in these cells. Moreover, TRH-IR was undetectable in the RIA using TRH-specific antiserum 8880. TRH-IR produced by differentiated cells was retained on a QAE Sephadex A-25 anion-exchange column and thus negatively charged. HPLC analysis showed coelution with the synthetic peptide pGlu-Glu-ProNH2. Study of the mechanisms regulating production of this novel peptide in these cells should further elucidate the role differentation plays in the synthesis of neuropeptides
Effects of thyroid status and thyrostatic drugs on hepatic glucuronidation of lodothyronines and other substrates in rats - Induction of phenol UDP-glucuronyltransferase by methimazole
Glucuronidation of iodothyronines in rat liver is catalyzed by at least three UDP-glucuronyltransferases (UGTs): bilirubin UGT, phenol UGT, and androsterone UGT. Bilirubin and phenol UGT activities are regulated by thyroid hormone, but the effect of thyroid status on hepatic glucuronidation of iodothyronines is unknown. We examined the effects of hypothyroidism induced by treatment of rats with propylthiouracil (PTU) or methimazole (MMI) or by thyroidectomy as well as the effects of T4-induced hyperthyroidism on the hepatic UGT activities for T4, T3, bilirubin, p-nitrophenol (PNP), and androsterone. Bilirubin UGT activity was increased in MMI- or PTU-induced hypothyroid and thyroidectomized rats, and decreased in hyperthyroid animals. T4 and, to a lesser extent, T3 UGT activities were increased in MMI- or PTU-induced hypothyroid rats, and T4 but not T3 glucuronidation also showed a significant increase in thyroidectomized rats. T4 but not T3 UGT activity was slightly decreased in hyperthyroid rats. While PNP UGT activity was decreased in thyroidectomized rats and increased in hyperthyroid animals, it was also markedly increased by MMI and slightly increased by PTU-induced hypothyroidism. In T4-substituted rats, MMI did not affect T4, T3, bilirubin and androsterone UGT activities but again strongly induced PNP UGT activity, indicating that this represented a direct induction of PNP UGT by the drug independent of its thyrostatic action. Androsterone UGT activity was hardly affected by thyroid status. Our results suggest a modest, negative control of the hepatic glucuronidation of thyroid hormone by thyroid status, which may be mediated by changes in bilirubin UGT activity. To our knowledge, this is the first report of the marked induction of a hepatic enzyme by MMI, which is not mediated by its thyroid hormone-lowering effect
Evidence that the TRH-like peptide pyroglutamyl-glutamyl-prolineamide in human serum may not be secreted by the pituitary gland
Recent studies have revealed that TRH-like immunoreactivity (TRH-LI) in
human serum is predominantly pGlu-Glu-ProNH2 (< EEP-NH2), a peptide
previously found in, among others tissues, the pituitary gland of various
mammalian species. In the rat pituitary, < EEP-NH2 is present in
gonadotrophs and its pituitary content is regulated by gonadal steroids
and gonadotrophin-releasing hormone (GnRH). Hence, we reasoned that <
EEP-NH2 in human serum may also arise, at least in part, from the
pituitary, and that its secretion may correlate with that of
gonadotrophins. Therefore, blood was simultaneously sampled from both
inferior petrosal sinuses, which are major sites of the venous drainage of
the pituitary gland, and a peripheral vein from seven patients with
suspected adrenocorticotrophin-secreting pituitary tumours. In addition,
in six postmenopausal and six cyclic women, peripheral vein blood was
collected at 10-min intervals for 6 h, then a standard 100 micrograms GnRH
test was performed. In the sera, TRH-LI was estimated by RIA with
antiserum 4319, which binds most tripeptides that share the N- and
C-terminal amino acids with TRH (pGlu-His-ProNH2). In addition, LH and FSH
were measured in these sera b
Hepatic lipase gene expression is transiently induced by gonadotropic hormones in rat ovaries
Hepatic lipase (HL) gene expression was studied in rat ovaries. A transcript lacking exons 1 and 2 could be detected by reverse transcription-polymerase chain reaction (RT-PCR) in the ovaries of mature cyclic females and of immature rats treated with pregnant mare serum followed by human chorionic gonadotropin (hCG) to induce superovulation. By competitive RT-PCR the HL transcript was quantified. Low levels of HL mRNA were detected in ovaries of mature cyclic females and of immature rats. During superovulation HL mRNA was several fold higher than in mature cyclic rats and transiently increased to a maximum at 2 days after hCG treatment. Pulse-labelling of ovarian cells and ovarian slices with [35S]methionine followed by immunoprecipitation with polyclonal anti-HL IgGs showed de novo synthesis of a 47 kDa HL-related protein. Expression of the protein was transiently induced by gonadotropins with a peak at 2 days after hCG treatment. Induction of liver-type lipase activity occurred only after HL mRNA and synthesis of the HL-related protein had returned to pre-stimulatory levels. We conclude that in rat ovaries the HL gene is expressed into a variant mRNA and a 47 kDa protein. The expression of the HL gene in ovaries is inducible and precedes the expression of the mature, enzymatically active liver-type lipase
Renal clearance of the thyrotropin-releasing hormone-like peptide pyroglutamyl-glutamyl-prolineamide in humans
TRH-like peptides have been identified that differ from TRH
(pGlu-His-ProNH2) in the middle amino acid. We have estimated TRH-like
immunoreactivity (TRH-LI) in human serum and urine by RIA with
TRH-specific antiserum 8880 or with antiserum 4319, which binds most
peptides with the structure pGlu-X-ProNH2. TRH was undetectable in serum
(< 25 pg/mL), but TRH-LI was detected with antiserum 4319 in serum of 27
normal subjects, 21 control patients, and 12 patients with carcinoid
tumors (range 17-45, 5-79, and 18-16,600 pg/mL, respectively). Because
serum was kept for at least 2 h at room temperature, which causes
degradation of TRH, pGlu-Phe-ProNH2, and pGlu-Tyr-ProNH2, serum TRH-LI is
not caused by these peptides. On high-performance liquid chromatography,
serum TRH-LI coeluted with pGlu-Glu-ProNH2 (< EEP-NH2), a peptide produced
in, among others, the prostate. Urine of normals and control patients also
contained TRH-LI (range 1.14-4.97 and 0.24-5.51 ng/mL, respectively), with
similar levels in males and females. TRH represented only 2% of urinary
TRH-LI, and anion-exchange chromatography and high-performance liquid
chromatography revealed that most TRH-LI in urine was < EEP-NH2. In
patients with carcinoid tumors, increased urinary TRH-LI levels were noted
(range 1.35-962.4 ng/mL). Urinary TRH-LI correlated positively with
urinary creatinine, and the urinary clearance rate of TRH-LI was similar
to the glomerular filtration rate. In addition, serum TRH-LI was increased
in 17 hemodialysis patients (43-373 pg/mL). This suggests that serum <
EEP-NH2 is cleared by glomerular filtration wit
Renal clearance of the thyrotropin-releasing hormone-like peptide pyroglutamyl-glutamyl-prolineamide in humans
TRH-like peptides have been identified that differ from TRH
(pGlu-His-ProNH2) in the middle amino acid. We have estimated TRH-like
immunoreactivity (TRH-LI) in human serum and urine by RIA with
TRH-specific antiserum 8880 or with antiserum 4319, which binds most
peptides with the structure pGlu-X-ProNH2. TRH was undetectable in serum
(< 25 pg/mL), but TRH-LI was detected with antiserum 4319 in serum of 27
normal subjects, 21 control patients, and 12 patients with carcinoid
tumors (range 17-45, 5-79, and 18-16,600 pg/mL, respectively). Because
serum was kept for at least 2 h at room temperature, which causes
degradation of TRH, pGlu-Phe-ProNH2, and pGlu-Tyr-ProNH2, serum TRH-LI is
not caused by these peptides. On high-performance liquid chromatography,
serum TRH-LI coeluted with pGlu-Glu-ProNH2 (< EEP-NH2), a peptide produced
in, among others, the prostate. Urine of normals and control patients also
contained TRH-LI (range 1.14-4.97 and 0.24-5.51 ng/mL, respectively), with
similar levels in males and females. TRH represented only 2% of urinary
TRH-LI, and anion-exchange chromatography and high-performance liquid
chromatography revealed that most TRH-LI in urine was < EEP-NH2. In
patients with carcinoid tumors, increased urinary TRH-LI levels were noted
(range 1.35-962.4 ng/mL). Urinary TRH-LI correlated positively with
urinary creatinine, and the urinary clearance rate of TRH-LI was similar
to the glomerular filtration rate. In addition, serum TRH-LI was increased
in 17 hemodialysis patients (43-373 pg/mL). This suggests that serum <
EEP-NH2 is cleared by glomerular filtration with little tubular
resorption. The possible role of the prostate as a source of urinary
TRH-LI was evaluated in 11 men with prostate cancer, showing a 25%
decrease in urinary TRH-LI excretion after prostatectomy (0.19 +/- 0.02
vs. 0.15 +/- 0.01 ng/mumol creatinine, mean +/- SEM). However, TRH-LI was
similar in spontaneously voided urine and in urine obtained through a
nephrostomy cannula from 16 patients with unilateral urinary tract
obstruction (0.15 +/- 0.01 vs. 0.14 +/- 0.01 ng/mumol creatinine). These
data indicate that: 1) TRH-LI in human serum represents largely < EEP-NH2,
which is cleared by renal excretion; 2) part of urinary < EEP-NH2 is
derived from prostatic secretion into the blood and not directly into
urine; and 3) urinary < EEP-NH2 can be used as marker for carcinoid
tumors
Different effects of continuous infusion of interleukin-1 and interleukin-6 on the hypothalamic-hypophysial-thyroid axis
The cytokines interleukin-1 (IL-1) and IL-6 are thought to be important
mediators in the suppression of thyroid function during nonthyroidal
illness. In this study we compared the effects of IL-1 and IL-6 infusion
on the hypothalamus-pituitary-thyroid axis in rats. Cytokines were
administered by continuous ip infusion of 4 micrograms IL-1 alpha/day for
1, 2, or 7 days or of 15 micrograms IL-6/day for 7 days. Body weight and
temperature, food and water intake, and plasma TSH, T4, free T4 (FT4), T3,
and corticosterone levels were measured daily, and hypothalamic pro-TRH
messenger RNA (mRNA) and hypophysial TSH beta mRNA were determined after
termination of the experiments. Compared with saline-treated controls,
infusion of IL-1, but not of IL-6, produced a transient decrease in food
and water intake, a transient increase in body temperature, and a
prolonged decrease in body weight. Both cytokines caused transient
decreases in plasma TSH and T4, which were greater and more prolonged with
IL-1 than with IL-6, whereas they effected similar transient increases in
the plasma FT4 fraction. Infusion with IL-1, but not IL-6, also induced
transient decreases in plasma FT4 and T3 and a transient increase in
plasma corticosterone. Hypothalamic pro-TRH mRNA was significantly
decreased (-73%) after 7 days, but not after 1 or 2 days, of IL-1 infusion
and was unaffected by IL-6 infusion. Hypophysial TSH beta mRNA was
significantly decreased after 2 (-62%) and 7 (-62%) days, but not after 1
day, of IL-1 infusion and was unaffected by IL-6 infusion. These results
are in agreement with previous findings that IL-1, more so than IL-6,
directly inhibits thyroid hormone production. They also indicate that IL-1
and IL-6 both decrease plasma T4 binding. Furthermore, both cytokines
induce an acute and dramatic decrease in plasma TSH before (IL-1) or even
without (IL-6) a decrease in hypothalamic pro-TRH mRNA or hypophysial TSH
beta mRNA, suggesting that the acute decrease in TSH secretion is not
caused by decreased pro-TRH and TSH beta gene expression. The
TSH-suppressive effect of IL-6, either administered as such or induced by
IL-1 infusion, may be due to a direct effect on the thyrotroph, whereas
additional effects of IL-1 may involve changes in the hypothalamic release
of somatostatin or TRH.(ABSTRACT TRUNCATED AT 400 WORDS
The Effect of Body Mass Index on Outcome after Endovascular Treatment in Acute Ischemic Stroke Patients: A Post Hoc Analysis of the MR
Background: Though obesity is a well-known risk factor for vascular disease, the impact of obesity on stroke outcome has been disputed. Several studies have shown that obesity is associated with better functional outcome after stroke. Whether obesity influences the benefit of endovascular treatment (EVT) in stroke patients is unknown. We evaluated the association between body mass index (BMI) and outcome in acute ischemic stroke patients with large vessel-occlusion (LVO), and assessed whether BMI affects the-benefit of EVT. Methods: This is a post hoc analysis of the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands trial (-ISRCTN10888758). BMI was used as a continuous and categorical variable, distinguishing underweight and normal weight (BMI <25), overweight (BMI 25-30), and obesity (BMI ≥30). We used multivariable ordinal logistic regression analysis to estimate the association of BMI with functional outcome (shift analysis), assessed with modified Rankin Scale (mRs) at 90 days. The impact of BMI on EVT effect was tested by the use of a multiplicative interaction term. Results: Of 366 patients, 160 (44%) were underweight or normal weight, 145 (40%) overweight, and 61 (17%) were obese. In multivariable analysis with BMI as a continuous variable, we found a shift toward better functional outcome with higher BMI (mRS adjusted common OR 1.04; 95% CI 1.0-1.09), and mortality was inversely related to BMI (aOR 0.92; 95% CI 0.85-0.99). Safety analysis showed that higher BMI was associated with lower risk of stroke progression (aOR 0.92, 95% CI 0.87-0.99). Additional analysis showed no interaction between BMI and EVT effect on functional outcome, mortality, and other safety outcomes. Conclusion: Our study confirms the effect of obesity on outcome in acute ischemic stroke patients with LVO, meaning better functional outcome, lower mortality, and lower risk of stroke progression for patients with higher BMI. As we found no interaction between BMI and EVT effect, all BMI classes may expect the same benefit from EVT