Insulin resistance caused by amylin in conscious rats is independent of induced hypocalcemia and fades during long-term exposure

1993 ◽  
Vol 129 (4) ◽  
pp. 360-365 ◽  
Author(s):  
Clemens Fürnsinn ◽  
Peter Nowotny ◽  
Michael Roden ◽  
Madeleine Rohac ◽  
Thomas Pieber ◽  
...  

To compare the effect of short- vs long-term amylin infusion on insulin sensitivity, glucose tolerance and serum calcemia, euglycemic-hyperinsulinemic clamp (26 pmol·kg−1·min−1) and glucose tolerance tests (2.4 mmol/kg over 30 min) were performed in lean Zucker rats. Three infusion protocols were employed: control group: 24 h of iv saline; short-term amylin exposure: 22 h of iv saline followed by 2 h of iv amylin (20 μg/h); long-term amylin exposure: 24 h of iv amylin (20 μg/h). Insulin resistance was induced by short-term amylin infusion during euglycemic clamping, as shown by a 41% decrease in space-corrected glucose infusion rates (μmol·kg−1·min−1; control group, 106.0±15.0; short-term iv amylin, 62.7±15.0; p<0.00 5). After long-term amylin exposure, insulin sensitivity was identical to control values (109.9±6.7). This fading action of amylin was confirmed by data from the glucose tolerance test, demonstrating glucose intolerance after short- but not after long-term amylin exposure. Serum calcium concentration decreased during short-term (2 h) amylin infusion (from 2.52±0.15 to 2.09±0.12 mmol/l; p<0.01) and hypocalcemia of a similar extent also was present after 22 h and 24 h of amylin exposure (2.10±0.09 and 2.04±0.14 mmol/l, respectively). The data demonstrate that short-term amylin infusion induces insulin resistance and glucose intolerance, both of which vanish during long-term (>22 h) amylin exposure, being apparently independent of induced hypocalcemia.

2017 ◽  
Author(s):  
Kevin P. Foley ◽  
Emmanuel Denou ◽  
Brittany M. Duggan ◽  
Rebecca Chan ◽  
Jennifer C. Stearns ◽  
...  

AbstractThe intestinal microbiota and insulin sensitivity are rapidly altered in response to a high fat diet (HFD). It is unclear if gut dysbiosis precedes insulin resistance or vice versa. The initial triggers of diet-induced insulin resistance can differ from mechanisms underlying chronic dysglycemia during prolonged obesity. It is not clear if intestinal dysbiosis contributes to insulin resistance during short-term or long-term HFD-feeding. We found that diet-induced changes in the composition of the fecal microbiome preceded changes in glucose and insulin tolerance at both the onset and removal of a HFD in mice. Dysbiosis occurred after 1-3 days of HFD-feeding, whereas insulin and glucose intolerance manifested by 3-4 days. Antibiotic treatment did not alter glucose tolerance during this short-term HFD period. Conversely, antibiotics improved glucose tolerance in mice with protracted obesity caused by long-term HFD feeding for over 2 months. We also found that microbiota transmissible glucose intolerance only occurred after prolonged diet-induced dysbiosis. Germ-free mice had impaired glucose tolerance when reconstituted with the microbiota from long-term, but not short-term HFD-fed animals. Our results are consistent with intestinal microbiota contributing to chronic insulin resistance and dysglycemia during prolonged obesity, despite rapid diet-induced changes in the taxonomic composition of the fecal microbiota.


2000 ◽  
Vol 279 (4) ◽  
pp. R1334-R1340 ◽  
Author(s):  
Jeffrey S. Thresher ◽  
Deborah A. Podolin ◽  
Yuren Wei ◽  
Robert S. Mazzeo ◽  
Michael J. Pagliassotti

The purpose of the present study was to determine whether fructose is the nutrient mediator of sucrose-induced insulin resistance and glucose intolerance. Toward this end, male rats were fed a purified starch diet (68% of total calories) for a 2-wk baseline period. After this, rats either remained on the starch (ST) diet or were switched to a sucrose (SU, 68% of total calories), fructose/glucose (F/G, 34/34% of total calories), or fructose/starch (F/ST, 34/34% of total calories) diet for 5 wk. Rats then underwent either an intravenous glucose tolerance test ( n = 10/diet) or a euglycemic, hyperinsulinemic clamp ( n = 8 or 9/diet). Incremental glucose and insulin areas under the curve in SU, F/G, and F/ST were on average 61 and 29% greater than ST, respectively, but not significantly different from one another. During clamps, glucose infusion rates (mg · kg−1 · min−1) required to maintain euglycemia were significantly lower ( P< 0.05) in SU, F/G, and F/ST (13.4 ± 0.9, 9.5 ± 1.7, 11.3 ± 1.3, respectively) compared with ST (22.8 ± 1.1). Insulin suppression of glucose appearance (mg · kg−1 · min−1) was significantly lower ( P < 0.05) in SU, F/G, and F/ST (5.6 ± 0.5, 2.2 ± 1.2, and 6.6 ± 0.7, respectively) compared with ST (9.6 ± 0.4). Insulin-stimulated glucose disappearance (mg · kg−1 · min−1) was significantly lower ( P < 0.05) in SU, F/G, and F/ST (17.9 ± 0.6, 16.2 ± 1.3, 15.3 ± 1.8, respectively) compared with ST (24.7 ± 1.2). These data suggest that fructose is the primary nutrient mediator of sucrose-induced insulin resistance and glucose intolerance.


1998 ◽  
Vol 83 (6) ◽  
pp. 1911-1915 ◽  
Author(s):  
Ramin Alemzadeh ◽  
Gina Langley ◽  
Lori Upchurch ◽  
Pam Smith ◽  
Alfred E. Slonim

Hyperinsulinemia, insulin resistance, and increased adipose tissue are hallmarks of the obesity state in both humans and experimental animals. The role of hyperinsulinemia as a possible preceding event in the development of obesity has been proposed. We previously demonstrated that administration of diazoxide (DZ), an inhibitor of insulin secretion, to obese hyperinsulinemic Zucker rats resulted in less weight gain, enhanced insulin sensitivity, and improved glucose tolerance. Assuming that hyperinsulinemia plays a major role in the development of human obesity, then its reversal should have therapeutic potential. To test this hypothesis, we conducted a randomized placebo-controlled trial in 24 hyperinsulinemic adults [body mass index (BMI) &gt; 30 kg/m2]. All subjects were placed on a low-calorie (1260 for females and 1570 for males) Optifast (Sandoz, Minneapolis, MN) diet. After an initial 1-week lead-in period, 12 subjects (mean ± se for age and BMI, 31 ± 1 and 40 ± 2, respectively) received DZ (2 mg/kg BW·day; maximum, 200 mg/day, divided into 3 doses) for 8 weeks; and 12 subjects (mean± se for age and BMI, 28 ± 1 and 43 ± 1, respectively) received placebo. Compared with the placebo group, DZ subjects had greater weight loss (9.5 ± 0.69% vs. 4.6 ± 0.61%, P &lt; 0.001), greater decrease in body fat (P &lt; 0.01), greater increase in fat-free mass to body fat ratio (P &lt; 0.01), and greater attenuation of acute insulin response to glucose (P &lt; 0.01). However, there was no significant difference in insulin sensitivity and glucose effectiveness, as determined by the insulin-modified iv glucose tolerance test (Bergman’s minimal model) and no significant difference in glycohemoglobin values. Conclusion: 8 weeks treatment with DZ had a significant antiobesity effect in hyperinsulinemic obese adults without inducing hyperglycemia.


2014 ◽  
Vol 307 (3) ◽  
pp. R332-R339 ◽  
Author(s):  
Jieyun Yin ◽  
Jian Kuang ◽  
Manisha Chandalia ◽  
Demidmaa Tuvdendorj ◽  
Batbayar Tumurbaatar ◽  
...  

The aim of this study was to investigate effects and mechanisms of electroacupuncture (EA) on blood glucose and insulin sensitivity in mice fed a high-fat diet. Both wild-type (WT) and adipose ectonucleotide pyrophosphate phosphodiesterase (ENPP1) transgenic (TG) mice were fed a high-fat diet for 12 wk; for each mouse, an intraperitoneal glucose tolerance test (IPGTT) and insulin tolerance test (ITT) were performed with or without EA at abdomen or auricular areas. A high-fat diet-induced insulin resistance in both WT and TG mice. In the WT mice, EA at 3 Hz and 15 Hz, but not at 1 Hz or 100 Hz, via CV4+CV12 significantly reduced postprandial glucose levels; EA at 3 Hz was most potent. The glucose level was reduced by 61.7% at 60 min and 74.5% at 120 min with EA at 3 Hz (all P < 0.001 vs. control). Similar hypoglycemic effect was noted in the TG mice. On the contrary, EA at auricular points increased postprandial glucose level ( P < 0.03). 4). EA at 3 Hz via CV4+CV12 significantly enhanced the decrease of blood glucose after insulin injection, suggesting improvement of insulin sensitivity. Plasma free fatty acid was significantly suppressed by 42.5% at 15 min and 50.8% at 30 min with EA ( P < 0.01) in both WT and TG mice. EA improves glucose tolerance in both WT and TG mice fed a high-fat diet, and the effect is associated with stimulation parameters and acupoints and is probably attributed to the reduction of free fatty acid.


1999 ◽  
Vol 162 (1) ◽  
pp. 87-93 ◽  
Author(s):  
T Johansen ◽  
M Deckert ◽  
T Mandrup-Poulsen ◽  
K Malmlof

Growth hormone (GH) can oppose the catabolic effects of glucocorticoids. However, both hormones have adverse effects on carbohydrate metabolism. Here we examined the interactive effects of GH and the glucocorticoid methylprednisolone (MP) on glucose tolerance, insulin resistance and [3H]2,6-deoxyglucose uptake of peripheral tissues in rats. Female Wistar rats received either saline, GH (2.7 mg/kg), MP (5.0 mg/kg) or GH+MP. After 7 days treatment, animals were subjected to an i.v. glucose tolerance test. In a second experiment, animals treated as above were anesthetized and injected with human insulin (0.5 U/kg), [3H]2,6-deoxyglucose (500 microCi/kg), and [14C]mannitol (25 microCi/kg), to estimate insulin resistance and [3H]2,6-deoxyglucose uptake in fat and muscle. Weight gain in controls was 7.6+/-1.7 g, while GH treatment increased the mean body weight by 18.7+/-2.2 g (P<0.0002) and MP inhibited weight gain down to 0.0+/-1.0 g (P<0.004). This drop in weight gain was reversed back to normal when GH was given in combination with MP. After a glucose tolerance test no significant differences in glucose area under the curve were detected when comparing individual groups with the control group, but samples taken just before this test revealed that basal insulin was significantly elevated in the group treated with GH (174+/-27 pM, P<0.008), or GH+MP (209+/-21 pM, P<0.004), when compared with controls (107+/-17 pM). MP alone had no effect (122+/-19, P<0.3). After an i.v. bolus of insulin the group receiving GH+MP had a significantly (P<0.007) higher level of circulating glucose compared with controls (6.5+/-0.3 mM vs 4.4+/-0.7 mM). Despite this, there were no differences in peripheral glucose uptake between the two groups. In conclusion this study shows that a combined administration of GH and MP decreases the potency by which insulin decreases circulating glucose levels, but that peripheral tissues are not primarily involved in this insulin resistance.


Endocrinology ◽  
2010 ◽  
Vol 151 (9) ◽  
pp. 4187-4196 ◽  
Author(s):  
G. Frangioudakis ◽  
J. Garrard ◽  
K. Raddatz ◽  
J. L. Nadler ◽  
T. W. Mitchell ◽  
...  

Lipid-induced insulin resistance is associated with intracellular accumulation of inhibitory intermediates depending on the prevalent fatty acid (FA) species. In cultured myotubes, ceramide and phosphatidic acid (PA) mediate the effects of the saturated FA palmitate and the unsaturated FA linoleate, respectively. We hypothesized that myriocin (MYR), an inhibitor of de novo ceramide synthesis, would protect against glucose intolerance in saturated fat-fed mice, while lisofylline (LSF), a functional inhibitor of PA synthesis, would protect unsaturated fat-fed mice. Mice were fed diets enriched in saturated fat, n-6 polyunsaturated fat, or chow for 6 wk. Saline, LSF (25 mg/kg · d), or MYR (0.3 mg/kg · d) were administered by mini-pumps in the final 4 wk. Glucose homeostasis was examined by glucose tolerance test. Muscle ceramide and PA were analyzed by mass spectrometry. Expression of LASS isoforms (ceramide synthases) was evaluated by immunoblotting. Both saturated and polyunsaturated fat diets increased muscle ceramide and induced glucose intolerance. MYR and LSF reduced ceramide levels in saturated and unsaturated fat-fed mice. Both inhibitors also improved glucose tolerance in unsaturated fat-fed mice, but only LSF was effective in saturated fat-fed mice. The discrepancy between ceramide and glucose tolerance suggests these improvements may not be related directly to changes in muscle ceramide and may involve other insulin-responsive tissues. Changes in the expression of LASS1 were, however, inversely correlated with alterations in glucose tolerance. The demonstration that LSF can ameliorate glucose intolerance in vivo independent of the dietary FA type indicates it may be a novel intervention for the treatment of insulin resistance.


2003 ◽  
Vol 88 (5) ◽  
pp. 2031-2036 ◽  
Author(s):  
Bülent O. Yildiz ◽  
Hakan Yarali ◽  
Havva Oguz ◽  
Miyase Bayraktar

Polycystic ovary syndrome (PCOS) is associated with hyperinsulinemia, insulin resistance (IR), increased risk of glucose intolerance, and type 2 diabetes. Family studies have indicated a genetic susceptibility to PCOS. The aims of this study were 1) to assess glucose tolerance status, gonadotropins, and androgens in first degree relatives of patients with PCOS; and 2) to assess IR in normal glucose tolerant (NGT) family members. One hundred two family members of 52 patients with PCOS [MothersPCOS (n = 34; mean age, 46.5 yr; mean body mass index (BMI), 28.8 kg/m2), FathersPCOS (n = 24; mean age, 50.4 yr; mean BMI, 27.5 kg/m2), SistersPCOS (n = 19; mean age, 25.1 yr; mean BMI, 22.9 kg/m2), and BrothersPCOS (n = 25; mean age, 23.7 yr; mean BMI, 22.5 kg/m2)] and 82 unrelated healthy control subjects without a family history of diabetes or PCOS (4 age- and weight-matched subgroups, i.e. ControlMothersPCOS, ControlFathersPCOS, ControlSistersPCOS, and ControlBrothersPCOS) were studied. Glucose and insulin (at baseline and during a 75-g, 2-h oral glucose tolerance test) were measured. IR was assessed by fasting insulin (FI), fasting glucose to insulin ratio (FGI), homeostatic model assessment (HOMA IR), and area under the curve for insulin during the oral glucose tolerance test (AUCinsulin) in NGT MothersPCOS, FathersPCOS, SistersPCOS, BrothersPCOS, and matched control subgroups. Including the prestudy-diagnosed 3 mothers and 2 fathers with diabetes, diabetes and impaired glucose tolerance (IGT) were noted in 16% and 30% of MothersPCOS and 27% and 31% of FathersPCOS, respectively. There was no diabetes in SistersPCOS and BrothersPCOS. IGT was found in 5% of SistersPCOS. Impaired fasting glucose was found in 3% of MothersPCOS and 4% of BrothersPCOS. The analysis of NGT family members showed that MothersPCOS had higher FI (P &lt; 0.05), HOMA IR (P &lt; 0.05), and AUCinsulin (P &lt; 0.01) and lower FGI (P &lt; 0.05) than ControlMothersPCOS, whereas all IR parameters were comparable between FathersPCOS and their matched control subgroup. SistersPCOS had higher FI (P &lt; 0.05), HOMA IR (P &lt; 0.01), and AUCinsulin (P &lt; 0.05) and lower FGI (P &lt; 0.01), and BrothersPCOS had higher AUCinsulin (P &lt; 0.01) than their matched control subgroups, respectively. MothersPCOS had higher testosterone levels than ControlMothersPCOS (P &lt; 0.01 and P &lt; 0.05 for pre- and postmenopausal women, respectively). SistersPCOS had higher LH (P &lt; 0.01), testosterone (P &lt; 0.001), androstenedione (P &lt; 0.01), and dehydroepiandrosterone sulfate (P &lt; 0.05) levels than ControlSistersPCOS. There was no difference in gonadotropin and androgen levels in FathersPCOS compared with ControlFathersPCOS or in BrothersPCOS compared with ControlBrothersPCOS. Our results suggest that 1) first degree relatives of patients with PCOS may be at high risk for diabetes and glucose intolerance; 2) NGT female family members have insulin resistance; and 3) mothers and sisters of PCOS patients have higher androgen levels than control subjects. We propose that the high risks of these impairments warrant screening in first degree relatives of patients with PCOS.


2021 ◽  
Author(s):  
Lirui Wei ◽  
Xuenan Zhao ◽  
Feng Guo ◽  
Fengjiao Huang ◽  
Yanyan Zhao ◽  
...  

Abstract BackgroundIn modern society, obesity has become a global problem with resulting in metabolic disorders and poses high risk for type 2 diabetes mellitus (T2DM). The glucagon-like peptide-1 (GLP-1) has been taken as an effective drug for the therapy of T2DM and obesity. In the present study, the regulatory roles and molecular mechanisms of miR-425-5p in GLP-1 secretion in high-fat diet (HFD)-induced diabetic mice were explored. MethodsOral glucose tolerance test and insulin tolerance test were performed to assess glucose metabolism and GLP-1 and LPS levels. Quantitative real time polymerase chain reaction (qRT-PCR) was employed to detect the expression of LPS, GLP-1, GLP-1 receptors, miR-425-5p, phosphatase and tensin homology (PTEN), proglucagon, p65 and β-catenin. Western blot was performed to determine the expression of proglucagon, p65, β-catenin and PTEN. ResultsThe results showed that plasma GLP-1 level was negatively correlated with plasma LPS level in HFD-fed mice, and miR-425-5p expression and LPS level were up-regulated in the ileal fluid compared with control groups. LPS injection boosted miR-425-5p expression in ileum. MiR-425-5p ameliorated glucose intolerance and insulin resistance in HFD-fed mice by increasing GLP-1 secretion. Furthermore, p65 protein level in the cytoplasmic and nuclear in the ileum of HFD-fed mice was increased compared with the control group. MiR-425-5p agomir elevated nuclear β-catenin protein level, but reduced PTEN protein level in HFD-fed mice compared with HFD-fed mice treated with the miR-425-5p antagomir. ConclusionsOur results suggest that miR-425-5p promotes GLP-1 secretion and improves glucose tolerance and insulin resistance in high-fat diet-fed mice.


Circulation ◽  
2015 ◽  
Vol 131 (suppl_1) ◽  
Author(s):  
Yoshihiro Kokubo ◽  
Makoto Watanabe ◽  
Aya Higashiyama ◽  
Yoko M Nakao ◽  
Takashi Kobayashi ◽  
...  

Introduction: Glucose intolerance and insulin resistance are known risk factors for cardiovascular disease (CVD). However, few prospective studies were reported the association between combinations of these two factors and incident CVD. We assessed the hypothesis that insulin resistance increased the association between glucose intolerance and CVD in Japanese general population. Methods: We studied 4,638 Japanese individuals (mean age 56.1 years, without CVD) who completed a baseline medical examination and a 75g oral glucose tolerance test in the Suita Study. Glucose categories were defined as follows: diabetes mellitus (DM; fasting plasma glucose levels [FPG] ≥126 mg/dL, 2 hours post-loaded glucose levels [2h-PG] ≥ 200 mg/dL, and/or DM medication); impaired glucose tolerance (IGT; FPG <126 mg/dL and 2h-PG =140-199 mg/dL); impaired fasting glucose (IFG; FPG =100-125 mg/dL and 2h-PG <140 mg/dL); and normal glucose tolerance [NGT]. Insulin resistance was the following formula: HOMA-IR = [FPG] x [fasting insulin] / 405. Insulin resistance was defined as HOMA-IR ≥2.5. Multivariable-adjusted Cox proportional hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated after adjusting for age, sex, body mass index, blood pressure category, hyperlipidemia, smoking, and drinking at the baseline. Results: During the 11.7-year follow-up, we documented 127 cerebral infarctions, 63 hemorrhagic stroke, 12 unclassified strokes, and 143 coronary heart disease events. The adjusted HRs (95% CIs) of subjects with FPG =100-125 mg/dL and ≥126 mg/dL were 1.38 (1.01-1.89) and 2.00 (1.12-3.58) for stroke and 1.47 (0.99-2.19) and 2.73 (1.43-5.22) for cerebral infarction, respectively, compared with the fasting NGT group. On the basis of the subjects with 2h-PG <140 mg/dL group, the adjusted HRs (95% CIs) of subjects with 2h-PG ≥200 mg/dL were 1.71 (1.07-2.72) for stroke and 2.06 (1.20-3.54) for cerebral infarction. Compared to the NGT group, the adjusted HRs (95% CIs) of the subjects with IFG, IGT, and DM were 1.59 (1.10-2.30), 1.34 (0.89-2.00), and 1.86 (1.16-3.00) for stroke and 1.82 (1.13-2.90), 1.55 (0.93-2.56), and 2.43 (1.39-4.26) for cerebral infarction, respectively. Compared to the subjects with HOMA-IR <1.5, the adjusted HRs (95% CIs) of CVD and stroke with HOMA-IR ≥2.5 were 1.45 (1.07-1.96) and 1.61 (1.07-2.42), respectively. Compared to the NGT group without insulin resistance, the IFG and DM groups with insulin resistance were observed the increased risks of stroke (HRs [95% CIs]; 2.05 [1.17-3.57] and 2.11 [1.17-3.83]) and cerebral infarction (HRs [95% CIs]; 2.45 [1.20-5.00] and 3.56 [1.84-6.88]), respectively. Conclusions: Fasting glucose intolerance and insulin resistance are predictive factors for the incidence of stroke and cerebral infarction. Insulin resistance increased the risks of incident stroke and cerebral infarction in general inhabitants with IFG and DM.


Author(s):  
Anwar Borai ◽  
Callum Livingstone ◽  
Gordon A A Ferns

Insulin resistance is a common condition, recognized to be a central feature of the metabolic syndrome, and strongly associated with an increased risk of cardiovascular disease and diabetes. The quantitative assessment of insulin sensitivity is not used for routine clinical purposes, but the emerging importance of insulin resistance has led to its wider application to research studies that have examined its pathogenesis, aetiology and consequences. The gold standard method for the determination of insulin sensitivity is the euglycaemic hyperinsulinaemic clamp from which indices of insulin sensitivity can be derived. The clamp technique is both expensive and complex to undertake and has prompted the use of surrogate methods, notably the insulin tolerance test and frequently sampled intravenous glucose tolerance test. Indices may be derived from these methods and correlate well with those derived from clamp studies. Indices can also be derived from measurements made during a standard oral glucose tolerance test and from one-off fasting specimens (e.g. homeostasis model assessment and quantitative insulin sensitivity check index). These indices lend themselves for use in large population studies where a relatively simple, inexpensive assessment is necessary. However, these tests all suffer from important limitations, including poor precision. Insulin resistance is increasingly being assessed in clinical situations, where relatively simple markers are required. Insulin-like growth factor binding protein-1 is an emerging marker which may be useful in this context.


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