Acute and 2-week exposure to prednisolone impair different aspects of beta-cell function in healthy men

Anxiety correlates to decreased blood and prefrontal cortex IGF-1 levels in streptozotocin induced diabetes

It is well known that diabetes mellitus may cause neuropsychiatric disorders such as anxiety disorders. Diabetes may also cause reduced IGF-1 (insulin like growth factor-1) levels in brain and blood. The purpose of the present study was to investigate the relationship between diabetes induced anxiety and IGF-1 levels in diabetic rats. The anxiety levels of rats were assessed 2 weeks after intraperitoneal injection of streptozotocin. Diabetic rats had higher levels of anxiety, as they spent more time in closed branches in elevated-plus-maze-test and less time in the center cells of open-field-arena. Prefrontal cortex (PFC) IGF-1 levels and neuron numbers were decreased and apoptosis was increased in diabetic rats. Blood IGF-1 levels decreased in a time dependent fashion following streptozotocin injection while blood corticosterone levels increased. They had higher malondialdehyde levels and lower superoxide dismutase enzyme activity. Oxidative stress may negatively affect blood and PFC tissue IGF-1 levels. Reduction in IGF-1 may cause PFC damage, which may eventually trigger anxiety in diabetic rats. Therapeutic strategies that increase blood and brain tissue IGF-1 levels may be promising to prevent psychiatric sequelae of diabetes mellitus.

Effects of glucocorticoids and exercise on pancreatic β-cell function and diabetes development

Peripheral insulin resistance and pancreatic β-cell dysfunction are hallmark characteristics of type 2 diabetes mellitus (T2DM). Several contributing factors have been proposed to promote these two defects in individuals with T2DM, including physical inactivity and chronic exposure to various psychosocial factors that increase the body's exposure to glucocorticoids, the main stress hormones in humans. Initially, β-cells have been shown to adapt to these stimuli, a phenomenon known as β-cell 'compensation'. However, long-term exposure to these physiologic and psychological stressors induces islet failure. Interestingly, glucocorticoids stimulate β-cell mass growth in parallel with promoting severe insulin resistance, the former being an important adaptive response to the latter. The direct relationship between glucocorticoids and β-cell dysfunction remains a controversial area of research. Elevations in circulating and/or tissue specific glucocorticoids have been associated with the development of obesity and T2DM in human and rodent models; however, the progression from insulin resistance to overt T2DM is highly disputed with respect to the in vivo and in vitro effects of glucocorticoids. Paradoxically, both intermittent physical stress and regular exercise alleviate insulin resistance and help to preserve β-cell mass, potentially by lowering glucocorticoid levels. Recent studies have begun to examine the mechanisms of intermittent and chronic glucocorticoid exposure and regular exercise in altering β-cell function. This review highlights recent discoveries on the physiological regulation of β-cells and diabetes development in conditions of elevated glucocorticoids, regular exercise and intermittent stress.

Glucocorticoid receptor gene polymorphisms are associated with reduced first-phase glucose-stimulated insulin secretion and disposition index in women, but not in men

AIM

Glucocorticoids are efficacious anti-inflammatory agents, but, in susceptible individuals, these drugs may induce glucose intolerance and diabetes by affecting β-cell function and insulin sensitivity. We assessed whether polymorphisms in the glucocorticoid receptor gene NR3C1 associate with measures of β-cell function and insulin sensitivity derived from hyperglycaemic clamps in subjects with normal or impaired glucose tolerance.

METHODS

A cross-sectional cohort study was conducted in four academic medical centres in the Netherlands and Germany. Four hundred and forty-nine volunteers (188 men; 261 women) were recruited with normal glucose tolerance (n=261) and impaired glucose tolerance (n=188). From 2-h hyperglycaemic clamps, first- and second-phase glucose-stimulated insulin secretion, as well as insulin sensitivity index and disposition index, were calculated. All participants were genotyped for the functional NR3C1 polymorphisms N363S (rs6195), BclI (rs41423247), ER22/23EK (rs6189/6190), 9β A/G (rs6198) and ThtIIII (rs10052957). Associations between these polymorphisms and β-cell function parameters were assessed.

RESULTS

In women, but not in men, the N363S polymorphism was associated with reduced disposition index (P=1.06 10(-4) ). Also only in women, the ER22/23EK polymorphism was associated with reduced first-phase glucose-stimulated insulin secretion (P=0.011) and disposition index (P=0.003). The other single-nucleotide polymorphisms were not associated with β-cell function. Finally, none of the polymorphisms was related to insulin sensitivity.

CONCLUSION

The N363S and ER22/23EK polymorphisms of the NR3C1 gene are negatively associated with parameters of β-cell function in women, but not in men.

Chronic prednisolone treatment aggravates hyperglycemia in mice fed a high-fat diet but does not worsen dietary fat-induced insulin resistance

Synthetic glucocorticoids such as prednisolone have potent antiinflammatory actions. Unfortunately, these drugs induce severe adverse effects in patients, many of which resemble features of the metabolic syndrome, such as insulin resistance. In this study, we investigated whether adverse effects of prednisolone on glucose homeostasis are aggravated in mice with compromised insulin sensitivity due to a high-fat diet by applying various methods to analyze changes in insulin sensitivity in mice. C57BL/6J mice were fed a high-fat diet for 6 wk and treated with either prednisolone (10 mg/kg · d) or vehicle for the last 7 d. Insulin sensitivity and blood glucose kinetics were analyzed with state-of-the-art stable isotope procedures in different experimental conditions. Prednisolone treatment aggravated fasting hyperglycemia and hyperinsulinemia caused by high-fat feeding, resulting in a higher homeostatic assessment model of insulin resistance. In addition, prednisolone-treated high-fat diet-fed mice appeared less insulin sensitive by detailed analysis of basal glucose kinetics. Remarkably, using hyperinsulinemic-euglycemic or hyperglycemic clamp techniques, neither hepatic nor peripheral insulin resistance was worsened in the group that was treated with prednisolone. Yet analysis of hepatic glucose metabolism revealed that prednisolone did alter glycogen balance by reducing glycogen synthase flux under hyperinsulinemic as well as hyperglycemic conditions. In addition to elevated insulin levels, prednisolone-treated mice showed a major rise in plasma leptin and fibroblast growth factor 21 levels. Our data indicate that prednisolone-induced adverse effects on glucose metabolism in high-fat diet-fed mice do not reflect impaired insulin sensitivity but may be caused by other changes in the hormonal regulatory network controlling glucose metabolism such as fibroblast growth factor 21 and leptin.

Twenty-four-hour profiles of plasma glucose, insulin, C-peptide and free fatty acid in subjects with varying degrees of glucose tolerance following short-term, medium-dose prednisone (20 mg/day) treatment: evidence for differing effects on insulin secretion and action

OBJECTIVE

To determine the time course and prandial effects of short-term, medium-dose prednisone on 24-h metabolic patterns under standardized conditions.

CONTEXT

Glucocorticoids (GCs) adversely affect glucose homoeostasis but 24-h profiles of glucose, insulin, C-peptide and free fatty acids (FFAs) following short-term, medium-dose prednisone treatment in persons with varying degrees of glucose tolerance are not well defined.

DESIGN

An open-label cross-sectional interventional study.

SUBJECTS

Three groups were prospectively studied: persons with type 2 diabetes (T2DM; n = 7), persons 'at risk' for T2DM (AR; n = 8) and persons with normal glucose tolerance (NGT; n = 5).

METHODS

Before and after 3-day treatment with prednisone 20 mg each morning, subjects underwent 24-h frequent blood sampling. Eucaloric mixed meals were provided at 08:00, 12:00 and 18:00 h. Insulin/glucose ratio provided an estimate of β-cell response to meal stimuli.

MEASUREMENTS

Plasma glucose, insulin, C-peptide, haemoglobin A1c and FFA.

RESULTS

Prednisone induced greater increases in glucose levels from midday (P = 0·001) to midnight (P = 0·02) in the T2DM than the AR and NGT groups. In contrast, insulin (P = 0·03) and C-peptide (P = 0·04) levels decreased postbreakfast in the T2DM group, whereas no changes in the morning but higher C-peptide levels (P = 0·03) from midday to midnight were observed in the AR group. In the T2DM group, insulin/glucose ratio decreased postbreakfast (P = 0·04) and increased postdinner (P = 0·03). Fasting glucose, insulin and C-peptide levels were unchanged in all groups, and FFA levels modestly increased postdinner (P = 0·03) in the NGT group.

CONCLUSION

Short-term, medium-dose prednisone treatment induces postprandial hyperglycaemia in T2DM and AR predominantly from midday to midnight because of suppression of insulin secretion followed by decreased insulin action that dissipates overnight. Effective treatment of prednisone-induced hyperglycaemia should target both rapid onset relative insulin deficiency and a less than 24-h total duration of effect.

Involvement of thioredoxin-interacting protein (TXNIP) in glucocorticoid-mediated beta cell death

AIM/HYPOTHESIS

Glucocorticoid hormones (GCs) are widely used to treat a variety of inflammatory and immune diseases. However, their long-term administration is associated with adverse metabolic effects, including glucose intolerance and diabetes. Our objective was to elucidate the mechanisms by which GCs affect beta cell survival with a specific emphasis on the role of the thioredoxin-interacting protein (TXNIP) in beta cell apoptosis.

METHODS

Human and mouse islets, together with MIN6 beta cells, were exposed to dexamethasone (Dex) and apoptosis was assessed by measuring the percentage of sub-G1 cells, the appearance of cleaved caspase-3 or by using a TUNEL assay. Dex-upregulated expression of Txnip mRNA was analysed by real-time PCR, and GC-modulated production and modification of proteins were determined by western blotting.

RESULTS

We provide evidence that TXNIP, a negative regulator of the antioxidant thioredoxin (TRX), is strongly induced in beta cells by GCs and that its induction is dependent on p38 mitogen-activated protein kinase (MAPK) activation. TXNIP downregulation by RNA interference, overexpression of the radical scavenger TRX1 or elevation of intracellular cAMP levels attenuated the Dex-mediated apoptosis. Dex-induced Txnip expression and beta cell apoptosis are mediated by the glucocorticoid receptor (GR), as the GR antagonist RU486 fully abolishes these effects.

CONCLUSIONS/INTERPRETATION

Altogether, our data suggest TXNIP as a novel mediator of GC-induced apoptosis in beta cells and further contribute to our understanding of beta cell death pathways.

Advances in the epidemiology, pathogenesis, and management of Cushing's syndrome complications

Cushing's syndrome (CS) is a clinical condition resulting from chronic exposure to glucocorticoid excess. As a consequence, hypercortisolism contributes significantly to the early development of systemic disorders by direct and/or indirect effects. Complications such as obesity, hypertension, diabetes, dyslipidemia, and hypercoagulability cause premature atherosclerosis and increase cardiovascular mortality. Impairment of the skeletal system is a relevant cause of morbidity and disability in these patients especially due to the high prevalence of vertebral fractures. In addition, muscle weakness, emotional lability, depression, and impairment of quality of life are very common. Clinical management of these patients is complex and should be particularly careful in identifying global cardiovascular risks and aim at controlling all complications. Although the primary goal in the prevention and treatment of complications is the correction of hypercortisolism, treatment does not completely eliminate these comorbidities. Given that cardiovascular risk and fracture risk can persist after cure, early detection of each morbidity could prevent the development of irreversible damage. In this review we present the various complications of CS and their pathogenetic mechanisms. We also suggest the clinical management of these patients based on our extensive clinical experience and on the available literature.

New-onset diabetes after kidney transplantation-changes and challenges

Despite substantial improvement in short-term results after kidney transplantation, increases in long-term graft survival have been modest. A significant impediment has been the morbidity and mortality attributable to cardiovascular disease (CVD). New-onset diabetes after transplantation (NODAT) is an independent predictor of cardiovascular events. This review examines recent literature surrounding diagnosis, outcomes and management of NODAT. Amongst otherwise heterogeneous studies, a common finding is the relative insensitivity of fasting blood glucose (FBG) as a screening test. Incorporating self-testing of afternoon capillary BG and glycohemoglobin (HbA(1c) ) detects many cases that would otherwise remain undetected without the oral glucose tolerance test (OGTT). Assessing the impact of NODAT on patient and graft survival is complicated by changes to diagnostic criteria, evolution of immunosuppressive regimens and increasing attention to cardiovascular risk management. Although recent studies reinforce a link between NODAT and death with a functioning graft (DWFG), there seems to be little effect on death-censored graft loss. The significance of glycemic control and diabetes resolution for patient outcomes remain notably absent from NODAT literature and treatment is also a neglected area. This review examines new and old therapeutic options, emphasizing the need to assess β-cell pathology in customizing therapy. Finally, areas warranting further research are considered.

Association of hyperglycemia, glucocorticoids, and insulin use with morbidity and mortality in the pediatric intensive care unit

BACKGROUND

Studies of pediatric intensive care unit (PICU) patients have shown a significant association of morbidity and mortality with hyperglycemia. We retrospectively evaluated the degree of hyperglycemia as well as its correlation with glucocorticoid and insulin use and assessed its association with hospital length of stay (LOS) and mortality. This study preceded the initiation of a standard glycemic control protocol.

METHODS

We examined medical records at Kosair Children's Hospital for all PICU admissions from 2008 of patients without diabetes mellitus. Critical illness hyperglycemia (CIH) was defined by having three or more peak glucose values greater than thresholds of 110, 140, 180, and 200 mg/dl. These patients were evaluated for glucocorticoid, insulin use, and outcome measures.

RESULTS

We evaluated the eligible 1173 admissions, where 10.5% of these patients reached the highest threshold (200 mg/dl) of CIH. Glucocorticoids were used in 43% of these patients, with dexamethasone being the most common (58%). There was a significant correlation between glucocorticoids and higher peak glucose values, where 81% of the patients who were above the 200 mg/dl cutoff level were treated with glucocorticoids. Only 36.8% in that group were also treated with insulin. Patients at the 200 mg/dl cutoff had the highest median PICU and total hospital length of stays (4 and 10 days, respectfully). Mortality was associated with increasing glucose levels, reaching 18.7% among patients above the 200 mg/dl cutoff.

CONCLUSION

Hyperglycemia was prevalent in the PICU and was associated with increased morbidity, as characterized by increased LOS and increased mortality. Glucocorticoid use was prevalent among patients exhibiting hyperglycemia. Insulin use was uncommon.

Modulation of pancreatic islets-stress axis by hypothalamic releasing hormones and 11beta-hydroxysteroid dehydrogenase

Corticotropin-releasing hormone (CRH) and growth hormone-releasing hormone (GHRH), primarily characterized as neuroregulators of the hypothalamic-pituitary-adrenal axis, directly influence tissue-specific receptor-systems for CRH and GHRH in the endocrine pancreas. Here, we demonstrate the expression of mRNA for CRH and CRH-receptor type 1 (CRHR1) and of protein for CRHR1 in rat and human pancreatic islets and rat insulinoma cells. Activation of CRHR1 and GHRH-receptor significantly increased cell proliferation and reduced cell apoptosis. CRH stimulated both cellular content and release of insulin in rat islet and insulinoma cells. At the ultrastructural level, CRHR1 stimulation revealed a more active metabolic state with enlarged mitochondria. Moreover, glucocorticoids that promote glucose production are balanced by both 11b-hydroxysteroid dehydrogenase (11β-HSD) isoforms; 11β-HSD-type-1 and 11β-HSD-type-2. We demonstrated expression of mRNA for 11β-HSD-1 and 11β-HSD-2 and protein for 11β-HSD-1 in rat and human pancreatic islets and insulinoma cells. Quantitative real-time PCR revealed that stimulation of CRHR1 and GHRH-receptor affects the metabolism of insulinoma cells by down-regulating 11β-HSD-1 and up-regulating 11β-HSD-2. The 11β-HSD enzyme activity was analyzed by measuring the production of cortisol from cortisone. Similarly, activation of CRHR1 resulted in reduced cortisol levels, indicating either decreased 11β-HSD-1 enzyme activity or increased 11β-HSD-2 enzyme activity; thus, activation of CRHR1 alters the glucocorticoid balance toward the inactive form. These data indicate that functional receptor systems for hypothalamic-releasing hormone agonists exist within the endocrine pancreas and influence synthesis of insulin and the pancreatic glucocorticoid shuttle. Agonists of CRHR1 and GHRH-receptor, therefore, may play an important role as novel therapeutic tools in the treatment of diabetes mellitus.

Low-dose glucocorticoid treatment affects multiple aspects of intermediary metabolism in healthy humans: a randomised controlled trial

AIM/HYPOTHESIS

To assess whether low-dose glucocorticoid treatment induces adverse metabolic effects, as is evident for high glucocorticoid doses.

METHODS

In a randomised placebo-controlled double-blind (participants and the investigators who performed the studies and assessed the outcomes were blinded) dose-response intervention study, 32 healthy men (age 22 ± 3 years; BMI 22.4 ± 1.7 kg/m(2)) were allocated to prednisolone 7.5 mg once daily (n = 12), prednisolone 30 mg once daily (n = 12), or placebo (n = 8) for 2 weeks using block randomisation. Main outcome measures were glucose, lipid and protein metabolism, measured by stable isotopes, before and at 2 weeks of treatment, in the fasted state and during a two-step hyperinsulinaemic clamp conducted in the Clinical Research Unit of the Academic Medical Centre, Amsterdam, the Netherlands

RESULTS

Prednisolone, compared with placebo, dose dependently and significantly increased fasting plasma glucose levels, whereas only prednisolone 30 mg increased fasting insulin levels (29 ± 15 pmol/l). Prednisolone 7.5 mg and prednisolone 30 mg decreased the ability of insulin to suppress endogenous glucose production (by 17 ± 6% and 46 ± 7%, respectively, vs placebo). Peripheral glucose uptake was not reduced by prednisolone 7.5 mg, but was decreased by prednisolone 30 mg by 34 ± 6% (p < 0.0001). Compared with placebo, prednisolone treatment tended to decrease lipolysis in the fasted state (p = 0.062), but both prednisolone 7.5 mg and prednisolone 30 mg decreased insulin-mediated suppression of lipolysis by 11 ± 5% and 34 ± 6%, respectively. Finally, prednisolone treatment increased whole-body proteolysis during hyperinsulinaemia, which tended to be driven by prednisolone 30 mg (5 ± 2%; p = 0.06). No side effects were reported by the study participants. All participants completed the study and were analysed.

CONCLUSIONS/INTERPRETATION

Not only at high doses but also at low doses, glucocorticoid therapy impaired intermediary metabolism by interfering with the metabolic actions of insulin on liver and adipose tissue. These data indicate that even low-dose glucocorticoids may impair glucose tolerance when administered chronically.

TRIAL REGISTRATION

ISRCTN83991850.

Prednisolone-induced changes in gene-expression profiles in healthy volunteers

Background: Prednisolone and other glucocorticoids (GCs) are potent anti-inflammatory and immunosuppressive drugs. However, prolonged use at a medium or high dose is hampered by side effects of which the metabolic side effects are most evident. Relatively little is known about their effect on gene-expression in vivo, the effect on cell subpopulations and the relation to the efficacy and side effects of GCs. Aim: To identify and compare prednisolone-induced gene signatures in CD4+ T lymphocytes and CD14+ monocytes derived from healthy volunteers and to link these signatures to underlying biological pathways involved in metabolic adverse effects. Materials & methods: Whole-genome expression profiling was performed on CD4+ T lymphocytes and CD14+ monocytes derived from healthy volunteers treated with prednisolone. Text-mining analyses was used to link genes to pathways involved in metabolic adverse events. Results: Induction of gene-expression was much stronger in CD4+ T lymphocytes than in CD14+ monocytes with respect to fold changes, but the number of truly cell-specific genes where a strong prednisolone effect in one cell type was accompanied by a total lack of prednisolone effect in the other cell type, was relatively low. Subsequently, a large set of genes was identified with a strong link to metabolic processes, for some of which the association with GCs is novel. Conclusion: The identified gene signatures provide new starting points for further study into GC-induced transcriptional regulation in vivo and the mechanisms underlying GC-mediated metabolic side effects.

Original submitted 5 January 2011; Revision submitted 24 February 2011

Prednisolone-induced beta cell dysfunction is associated with impaired endoplasmic reticulum homeostasis in INS-1E cells

Glucocorticoids (GCs), such as prednisolone (PRED), are widely prescribed anti-inflammatory drugs, but their use may induce glucose intolerance and diabetes. GC-induced beta cell dysfunction contributes to these diabetogenic effects through mechanisms that remain to be elucidated. In this study, we hypothesized that activation of the unfolded protein response (UPR) following endoplasmic reticulum (ER) stress could be one of the underlying mechanisms involved in GC-induced beta cell dysfunction. We report here that PRED did not affect basal insulin release but time-dependently inhibited glucose-stimulated insulin secretion in INS-1E cells. PRED treatment also decreased both PDX1 and insulin expression, leading to a marked reduction in cellular insulin content. These PRED-induced detrimental effects were found to be prevented by prior treatment with the glucocorticoid receptor (GR) antagonist RU486 and associated with activation of two of the three branches of the UPR. Indeed, PRED induced a GR-mediated activation of both ATF6 and IRE1/XBP1 pathways but was found to reduce the phosphorylation of PERK and its downstream substrate eIF2α. These modulations of ER stress pathways were accompanied by upregulation of calpain 10 and increased cleaved caspase 3, indicating that long term exposure to PRED ultimately promotes apoptosis. Taken together, our data suggest that the inhibition of insulin biosynthesis by PRED in the insulin-secreting INS-1E cells results, at least in part, from a GR-mediated impairment in ER homeostasis which may lead to apoptotic cell death.

Glucagon-like peptide-1 receptor agonist treatment prevents glucocorticoid-induced glucose intolerance and islet-cell dysfunction in humans

OBJECTIVE

Glucocorticoids (GCs) are regarded as diabetogenic because they impair insulin sensitivity and islet-cell function. This study assessed whether treatment with the glucagon-like peptide receptor agonist (GLP-1 RA) exenatide (EXE) could prevent GC-induced glucose intolerance.

RESEARCH DESIGN AND METHODS

A randomized, placebo-controlled, double-blind, crossover study in eight healthy men (age: 23.5 [20.0-28.3] years; BMI: 26.4 [24.3-28.0] kg/m(2)) was conducted. Participants received three therapeutic regimens for 2 consecutive days: 1) 80 mg of oral prednisolone (PRED) every day (q.d.) and intravenous (IV) EXE infusion (PRED+EXE); 2) 80 mg of oral PRED q.d. and IV saline infusion (PRED+SAL); and 3) oral placebo-PRED q.d. and intravenous saline infusion (PLB+SAL). On day 1, glucose tolerance was assessed during a meal challenge test. On day 2, participants underwent a clamp procedure to measure insulin secretion and insulin sensitivity.

RESULTS

PRED+SAL treatment increased postprandial glucose levels (vs. PLB+SAL, P = 0.012), which was prevented by concomitant EXE (vs. PLB+SAL, P = NS). EXE reduced PRED-induced hyperglucagonemia during the meal challenge (P = 0.018) and decreased gastric emptying (vs. PRED+SAL, P = 0.028; vs. PLB+SAL, P = 0.046). PRED+SAL decreased first-phase glucose- and arginine-stimulated C-peptide secretion (vs. PLB+SAL, P = 0.017 and P = 0.05, respectively), whereas PRED+EXE improved first- and second-phase glucose- and arginine-stimulated C-peptide secretion (vs. PLB+SAL; P = 0.017, 0.012, and 0.093, respectively).

CONCLUSIONS

The GLP-1 RA EXE prevented PRED-induced glucose intolerance and islet-cell dysfunction in healthy humans. Incretin-based therapies should be explored as a potential strategy to prevent steroid diabetes.

Increased postprandial GIP and glucagon responses, but unaltered GLP-1 response after intervention with steroid hormone, relative physical inactivity, and high-calorie diet in healthy subjects

OBJECTIVE

Increased postprandial glucose-dependent insulinotropic polypeptide (GIP) and glucagon responses and reduced postprandial glucagon-like peptide-1 (GLP-1) responses have been observed in some patients with type 2 diabetes mellitus. The causality of these pathophysiological traits is unknown. We aimed to determine the impact of insulin resistance and reduced glucose tolerance on postprandial GIP, GLP-1, and glucagon responses in healthy subjects.

RESEARCH DESIGN AND METHODS

A 4-h 2200 KJ-liquid meal test was performed in 10 healthy Caucasian males without family history of diabetes [age, 24 ± 3 yr (mean ± sd); body mass index, 24 ± 2 kg/m(2); fasting plasma glucose, 4.9 ± 0.3 mm; hemoglobin A(1)c, 5.4 ± 0.1%] before and after intervention using high-calorie diet, relative physical inactivity, and administration of prednisolone (37.5 mg/d) for 12 d.

RESULTS

The intervention resulted in insulin resistance according to the homeostatic model assessment [1.1 ± 0.3 vs. 2.3 (mean ± SEM) ± 1.3; P = 0.02] and increased postprandial glucose excursions [area under curve (AUC), 51 ± 28 vs. 161 ± 32 mm · 4 h; P = 0.045], fasting plasma insulin (36 ± 3 vs. 61 ± 6 pm; P = 0.02), and postprandial insulin responses (AUC, 22 ± 6 vs. 43 ± 13 nm · 4 h; P = 0.03). This disruption of glucose homeostasis had no impact on postprandial GLP-1 responses (AUC, 1.5 ± 0.7 vs. 2.0 ± 0.5 nm · 4 h; P = 0.56), but resulted in exaggerated postprandial GIP (6.2 ± 1.0 vs. 10.0 ± 1.3 nm · 4 h; P = 0.003) and glucagon responses (1.6 ± 1.5 vs. 2.4 ± 3.2; P = 0.007).

CONCLUSIONS

These data suggest that increased postprandial GIP and glucagon responses may occur as a consequence of insulin resistance and/or reduced glucose tolerance. Our data suggest that acute disruption of glucose homeostasis does not result in reduced postprandial GLP-1 responses as observed in some individuals with type 2 diabetes mellitus.

Reduced glucose tolerance and insulin resistance induced by steroid treatment, relative physical inactivity, and high-calorie diet impairs the incretin effect in healthy subjects

AIMS/HYPOTHESIS

The loss of incretin effect in patients with type 2 diabetes mellitus may be secondary to impaired glucose homeostasis. We investigated whether reduced glucose tolerance and insulin resistance induced by steroid treatment, relative physical inactivity, and high-calorie diet in healthy young males would impair the incretin effect.

METHODS

The incretin effect was measured using 75 g oral glucose tolerance test (OGTT) and isoglycemic iv glucose infusion (IIGI) in 10 healthy Caucasian normal glucose-tolerant male subjects without any family history of diabetes [age 24 + or - 3 yr (mean + or - sd); body mass index 23 + or - 2 kg/m(2); glycosylated hemoglobin 5.4 + or - 0.1%] before and at the end of a 12-d period with oral administration of prednisolone (37.5 mg once daily), high-calorie diet, and relative physical inactivity.

RESULTS

The 12-d intervention period resulted in significant increases in body weight [79 + or - 5 vs. 80 + or - 6 kg (mean + or - sd), P = 0.03] and fasting plasma glucose (5.1 + or - 0.1 vs. 5.6 + or - 0.2 mm, P = 0.016), whereas insulin sensitivity (Matsuda index 17.6 + or - 1.7 vs. 9.2 + or - 1.0, P = 0.0001) decreased. Glucose tolerance [as assessed by the 120-min plasma glucose value after OGTT (4.9 + or - 1.1 vs. 7.8 + or - 2.5 mm, P < 0.0001) and area under curve (AUC) (152 + or - 45 vs. 384 + or - 53 mm.4 h, P = 0.002)] during the OGTT deteriorated. Also, the incretin effect [incretin effect (percent) = 100% x (AUC(insulin,OGTT) - AUC(insulin,IIGI))/AUC(insulin,OGTT))] deteriorated (72 + or - 5 vs. 43 + or - 7%, P = 0.002). An increase in glucose-dependent insulinotropic polypeptide response during OGTT, but no significant changes in glucagon-like peptide-1 or glucagon responses, was observed after glucose homeostatic dysregulation.

CONCLUSIONS/INTERPRETATION

Impairment of the incretin effect can be elicited by a short period of reduced glucose tolerance and insulin resistance in healthy male subjects not disposed for type 2 diabetes.