Regulation of Glucose Transporter Messenger RNA Levels in Rat Adipose Tissue by Insulin

The ob gene, specifically expressed in fat cells, encodes leptin, a hormone that induces satiety and increases energy expenditure. In this study, we investigated the interactions between glucocorticoids and insulin on ob gene expression in cultured explants of rat adipose tissue. Only low levels of ob mRNA were detected when adipose tissue from fasted rats was cultured for 12–24 h in minimal essential medium. However, the addition of dexamethasone to the medium increased ob gene expression in a concentration-dependent manner (EC50 10 nM). With 1 μM dexamethasone, ob mRNA levels were similar to those in fresh fat pads from fed rats, reaching a maximum after 12 h. The effect of dexamethasone was blocked by actinomycin D, which indicates an action on transcription. This effect was increased when a minimum amount of fuel (glucose or a mixture of lactate and pyruvate) was supplied in the medium. Unlike dexamethasone, insulin, even when combined with high glucose concentrations, did not induce ob expression, although it strongly increased the accumulation of mRNA species for fatty acid synthase (FAS), the insulin-sensitive glucose transporter GLUT4 and the γ isoform of peroxisome proliferator-activated receptor (PPARγ). Unexpectedly, insulin dose-dependently inhibited dexamethasone-induced ob mRNA accumulation. This effect was observed at low concentrations of insulin (IC50 1 nM) and was delayed in onset, beginning after 6–9 h of culture. It was mimicked by insulin-like growth factor 1 (IGF-1) (100 nM). The inhibition by insulin was only detectable when fuels were present and/or when a critical level of ob expression was reached. As this inhibitory effect was reversed by cycloheximide, this suggests that it required ongoing protein synthesis. In conclusion, unlike dexamethasone, insulin had no direct stimulatory effect on ob gene expression. On the other hand, insulin (and IGF-1) even inhibited the dexamethasone-induced accumulation of ob mRNA. The underlying mechanism involved ongoing synthesis of an inhibitory protein by insulin, which is in keeping with its delayed effect. Moreover, the expression of genes for FAS, GLUT4 and PPARγ may be inversely related to that of ob.

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Differential effects of dietary saturated and trans-fatty acids on expression of genes associated with insulin sensitivity in rat adipose tissue

Acta Endocrinologica ◽

10.1530/eje.1.01946 ◽

2005 ◽

Vol 153 (1) ◽

pp. 159-165 ◽

Cited By ~ 75

Author(s):

Natarajan Saravanan ◽

Abdul Haseeb ◽

Nasreen Z Ehtesham ◽

Keyword(s):

Fatty Acids ◽

Adipose Tissue ◽

Insulin Sensitivity ◽

Glucose Transporter ◽

Control Diet ◽

Saturated Fatty Acids ◽

Partial Hydrogenation ◽

Mrna Levels ◽

Expression Of Genes ◽

Rat Adipose Tissue

Objective: Trans-fatty acids (TFAs) are formed during partial hydrogenation of vegetable oils and are shown to be more atherogenic than saturated fatty acids (SFAs). Our previous study showed that dietary TFAs decrease adipose tissue insulin sensitivity to a greater extent than SFAs in rats. We hypothesized that the effects of these fatty acids on insulin sensitivity could be mediated through an alteration in gene expression. In the current study we have investigated the effects of dietary TFAs or SFAs on expression of genes associated with insulin sensitivity in rat adipose tissue. Design and methods: Male weanling Wistar/NIN rats were divided into four groups and fed one of the following diets containing 10% fat (g/100 g diet) differing only in the fatty acid composition for 3 months: control diet (3.7% linoleic acid (LA)), SFA diet (5% SFA), TFA diet 1 (1.5% TFA + 1% LA) and TFA diet 2 (1.5% TFA + 2% LA). The mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ), lipoprotein lipase (LPL), glucose transporter-4 (GLUT4), resistin and adiponectin was analyzed in epididymal fat using RT-PCR. The effects of TFA were studied at two levels of LA to understand the beneficial effects of LA over the effects of TFA. Results: Both dietary SFA and TFA upregulated the mRNA levels of resistin. Dietary SFA downregulated adiponectin and GLUT4 and upregulated LPL, while TFA downregulated PPARγ and LPL. The effects of dietary TFA on PPARγ and resistin were not counteracted by increased LA (TFA diet 2). Conclusion: The effects of SFAs on the aforementioned genes except PPARγ could be extrapolated towards decreased insulin sensitivity, while only the alteration in the mRNA levels of PPARγ and resistin could be associated with insulin resistance in TFA-fed rats. These findings suggest that dietary SFAs and TFAs alter the expression of different genes associated with insulin sensitivity in adipose tissue.

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Amino acid incorporation by a cell-free preparation from rat adipose tissue. Effects of fasting

Canadian Journal of Biochemistry ◽

10.1139/o70-018 ◽

1970 ◽

Vol 48 (1) ◽

pp. 113-121 ◽

Cited By ~ 2

Author(s):

A. H. Shlossberg ◽

C. H. Hollenberg

Keyword(s):

Adipose Tissue ◽

Ribosomal Rna ◽

Messenger Rna ◽

Gradient Analysis ◽

Sucrose Density Gradient ◽

Supernatant Fraction ◽

Progressive Reduction ◽

A Cell ◽

Rat Adipose Tissue ◽

Kinetics Of

Ribosomes were isolated from a postmitochondrial, detergent-treated supernatant fraction prepared either from adipose tissue passed through a tissue press, or from a collection of free fat cells. Optimum conditions for incorporation were established and the kinetics of the system denned with and without artificial messenger RNA. Studies were performed on ribosomes isolated from fed, 24-h fasted, and 48-h fasted animals. There was a progressive reduction in yield and activity (per milligram ribosomal RNA) of ribosomal material recovered from animals fasted up to 48 h. In the presence of poly-U, incorporation by ribosomes from fasted animals returned towards but did not reach the fed level. This return was less complete with ribosomes from 48-h than from 24-h fasted groups although as fasting proceeded, the percentage stimulation produced by poly-U progressively increased. Sucrose density gradient analysis revealed a greater proportion of light ribosome species and a smaller proportion of polysomes in fasted than in fed animals. These results suggest that fasting, in addition to producing a progressive reduction in ribosomal yield, also caused an early loss of messenger RNA or messenger function and later an alteration of ribosome function. The effect of fasting on messenger function could not be explained by alterations in ribonuclease activity.

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Duodenal Sodium/Glucose Cotransporter 1 Expression Under Fasting Conditions Is Associated With Postload Hyperglycemia

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2017-00348 ◽

2017 ◽

Vol 102 (11) ◽

pp. 3979-3989 ◽

Cited By ~ 11

Author(s):

Teresa Vanessa Fiorentino ◽

Evelina Suraci ◽

Gaetano Paride Arcidiacono ◽

Antonio Cimellaro ◽

Chiara Mignogna ◽

...

Keyword(s):

Glucose Tolerance ◽

Messenger Rna ◽

Glucose Transporter ◽

Normal Glucose Tolerance ◽

Upper Gastrointestinal Endoscopy ◽

Cross Sectional ◽

Glucose Levels ◽

Glucose Transporter 2 ◽

Sodium Glucose Cotransporter ◽

Rna Levels

Abstract Context Type 2 diabetes (T2DM) is associated with a higher intestinal expression of the glucose transporters sodium/glucose cotransporter 1 (SGLT-1) and glucose transporter 2 (GLUT-2). It is currently unsettled whether prediabetes conditions characterized by postprandial hyperglycemia, such as impaired glucose tolerance (IGT) and normal glucose tolerance (NGT) with 1-hour postload glucose ≥155 mg/dL (8.6 mmol/L) (NGT-1h-high) are associated with increased expression of these glucose carriers in the intestine. Objective We evaluated whether duodenal abundance of SGLT-1 and GLUT-2 is augmented in subjects with IGT and NGT-1h-high, in comparison with subjects with NGT and 1-hour postload glucose ˂155 mg/dL (NGT-1h-low). Design Cross-sectional. Patients A total of 54 individuals underwent an upper gastrointestinal endoscopy. Main Outcome Measures Duodenal SGLT-1 and GLUT-2 protein and messenger RNA levels were assessed by Western blot and reverse transcription polymerase chain reaction, respectively. Results Of the 54 subjects examined, 18 had NGT-1h-low, 12 had NGT-1h-high, 12 had IGT, and 12 had T2DM. Duodenal SGLT-1 protein and messenger RNA levels were significantly higher in individuals with NGT-1h-high, IGT, or T2DM in comparison with NGT-1h-low subjects. GLUT-2 abundance was higher in individuals with T2DM in comparison with NGT-1h-low subjects; no substantial increase in GLUT-2 expression was observed in NGT-1h-high or IGT individuals. Univariate correlations showed that duodenal SGLT-1 abundance was positively correlated with 1-hour postload plasma glucose levels (r = 0.44; P = 0.003) but not with fasting or 2-hour postload glucose levels. Conclusions Duodenal SGLT-1 expression is increased in individuals with 1-hour postload hyperglycemia or IGT, as well as in subjects with T2DM, and it positively correlates with early postload glucose excursion.

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