Adequately adapted insulin secretion and decreased hepatic insulin extraction cause elevated insulin concentrations in insulin resistant non-diabetic adrenal incidentaloma patients

Glucose Alterations, Insulin Resistance, Arterial Hypertension, and Renin are Strictly Associated in Pediatric Obesity

Context

Insulin resistance, glucose alterations, arterial hypertension (HTN), and the renin-angiotensin-aldosterone system (RAAS) are related in adult obesity. This crosstalk is still unexplored in childhood.

Objective

Characterize the relationships of fasting and postload glucose and insulin levels with new American Academy of Pediatrics classification of HTN and RAAS in pediatric obesity.

Methods

This was a retrospective observational study; 799 pediatric outpatients (11.4 ± 3.1 years) at a tertiary center who were overweight or obese and not yet on diet were included. The main outcome measures were mean and correlations among parameters of a complete clinical and metabolic screening (body mass index, blood pressure, and glucose and insulin levels during an oral glucose tolerance test, and renin and aldosterone levels and their ratio).

Results

774 subjects had all the parameters, of whom 87.6% had HTN (5% elevated blood pressure, 29.2% stage I HTN, and 53.4% stage II HTN). Eighty subjects had 1 or more glucose alterations, and more frequently presented HTN. Blood pressure levels were higher in subjects with glucose alterations than in those with normal glucose levels. Fasting and stimulated glucose and insulin levels were directly related to the HTN stages, and insulin sensitivity was lower in HTN than in normal blood pressure. Aldosterone, renin, and aldosterone-renin ratio (ARR) were similar in sexes, whereas aldosterone was higher in prepubertal individuals. Subjects with impaired glucose tolerance (IGT) had higher renin and lower ARR. Renin was positively correlated with postload glucose, and ARR was negatively correlated with the Homeostatic Model Assessment for Insulin Resistance index.

Conclusion

A close relationship exists among insulin resistance, glucose alterations, HTN, and renin in childhood obesity. Specific categories of risk could provide indicators for strict clinical surveillance.

Impairment in insulin secretion without changes in insulin resistance explains hyperglycemia in patients with acromegaly treated with pasireotide LAR

Objective

Pasireotide is a second-generation somatostatin receptor ligand (SRL) used for treating acromegaly. Its clinical use is limited by adverse effects on glucose homeostasis. The aim of this study was to evaluate longitudinal changes in beta-cell function and insulin sensitivity associated with pasireotide in patients not controlled by first-generation SRLs.

Design

We performed a retrospective study.

Methods

The efficacy (growth hormone (GH)/insulin-like growth factor (IGF-1) concentrations; tumor size) and effect on glucose homeostasis were analyzed in 33 patients. Longitudinal data on oral glucose tolerance tests were available before, shortly (mean ± s.d., 6.1 ± 3.8 months) and long term (24.4 ± 11.1 months) after initiation of pasireotide in 14 patients. Insulin secretion (insulinogenic index; disposition index) and insulin sensitivity were calculated by validated indices.

Results

Pasireotide-induced diabetes occurred in 12 patients (36%). It was mediated by impaired insulin secretion, which occurred shortly after initiation of treatment and then remained stable on long term (insulinogenic index, median (min; max), 80 (12; 542) vs 16 (6.4; 101) vs 25 (3.7; 396) pmol/mmol, respectively; P = 0.028; disposition index, 1.45 (0.42; 4.88) vs 0.53 (0.17; 2.63) vs 0.60 (0.22; 1.71), respectively; P = 0.024). No significant changes in insulin sensitivity were observed, despite a marked reduction of GH/IGF-1 concentrations. Older age and a worse glycemic control at baseline were the strongest predictors for hyperglycemia and the need for antidiabetic treatment.

Conclusion

Worsening of glycemic control during pasireotide therapy is caused by an impaired insulin secretion, whereas insulin sensitivity is not affected. These findings might be important for the choice of antidiabetic treatment for pasireotide-induced hyperglycemia.

Significance statement

Pasireotide, a second-generation SRL used for treating acromegaly, may be associated with glucose metabolism impairment. In a retrospective study of 33 patients, we observed that treatment with pasireotide was associated with normalization of serum IGF-1 in almost 60% of patients, but one-third of patients developed diabetes. In the patients who stopped pasireotide because of hyperglycemia, HbA1c promptly decreased. Longitudinal data in 14 patients show that diabetes is mediated by impaired insulin secretion, which occurred shortly and then remained stable on long term, while no significant changes in insulin sensitivity were observed, despite a marked reduction of GH/IGF-1 concentrations. Older age and a worse glycemic control at baseline were the strongest predictors for hyperglycemia.

Nonfunctional adrenal adenomas and impaired glucose metabolism: a systematic review and meta-analysis

PURPOSE

Evidence on nonfunctioning adrenal incidentaloma's (NFAI) associated comorbidities and in particular, glucose disorders, is unclear in contrast to adrenal tumors with mild autonomous cortisol secretion. The current systematic review and meta-analysis aimed to assess the burden of impaired glucose metabolism including diabetes mellitus type 2 (T2DM), fasting blood glucose (FBG), and fasting blood insulin (FBI) levels in patients with NFAI and 1-mg overnight dexamethasone suppression test (ODST) ≤ 1.8 μg/dl across published studies.

METHODS

We searched PubMed, Cochrane, and Scopus databases for identifying studies published between 1956 and March 2021. Twenty-five studies met the selection criteria including prospective, retrospective, and case-control studies. Two reviewers independently extracted studies, participants' characteristics and outcome data in a total pooled sample of 1548 patients.

RESULTS

Patients with NFAI had twofold [(odds ratio (OR) (95% confidence interval (CI)): 2.03 (1.39-2.98)] increased odds to present T2DM as well as higher FBG [weighted mean difference (WMD) (95% CI): 3.85 (1.96-5.74)] and homeostasis model assessment (HOMA) [WMD (95% CI): 0.68 (0.23-1.12)] with respect to controls. On the contrary, the WMD of FBI levels did not differ between the two groups. The incidence of T2DM in a subgroup analysis of patients with NFAI without glucose disorders at baseline was 6% [pooled incidence (95% CI): 0.06 (0.04-0.09)].

CONCLUSIONS

Patients with NFAI and 1-mg ODST ≤ 1.8 μg/dl presented higher odds of T2DM and higher levels of FBG and HOMA index than healthy controls.

Could a nonfunctional adrenal incidentaloma be a risk factor for increased carotid intima-media thickness and metabolic syndrome

BACKGROUND

This study was designed to detect the potential association of a nonfunctional adrenal incidentaloma (NFAI) with insulin resistance and associated metabolic disturbances, with a subsequent increase in cardiovascular risk factors.

METHODS

Eighty-three NFAI patients and 56 volunteers (controls) without any adrenal abnormalities on computed tomography (CT) were included. Fasting blood glucose (FBG), fasting insulin, lipid profiles, uric acid, homocysteine, fibrinogen, high sensitivity C-reactive protein (hs-CRP), and adiponectin levels were measured in both groups. Blood pressure (BP), waist circumference, body mass index (BMI), and carotid intima media thickness (CIMT) were evaluated in both the patients and volunteers.

RESULTS

There were no significant difference between the NFAI and control groups with respect to age, sex, BMI, waist circumference, systolic and diastolic BP, smoking, concomitant disease, and medications. Fasting insulin and glucose levels and homeostasis model of assessment-insulin resistance (HOMA-IR) scores were significantly higher in the NFAI group as compared with those in the control group (p<0.01). The frequency of metabolic syndrome in the NFAI group was higher than that in the control group (p<0.01). All the lipid fractions, except triglyceride (TG), (p<0.05), homocysteine (p=0.01), and fibrinogen levels (p<0.001), were significantly higher in the NFAI group as compared with the levels in the control group. There were no significant differences between the NFAI and control groups in terms of uric acid, hs-CRP, and adiponectin levels. The CIMT values in the NFAI group were significantly higher than those in the control group (0.74±0.14 vs. 0.53±0.09, p<0.001). The mean CIMT value showed a statistically positive correlation with age (r=0.245, p=0.004); the HOMA-IR score (r=0.490, p<0.001); and FBG (r=0.521, p<0.001), fasting insulin (r=0.432, p<0.001), total cholesterol (TC) (r=0.267, p=0.002), and fibrinogen (r=0.398, p<0.001) levels in the NFAI group.

CONCLUSIONS

The results indicated that the NFAI patients had an elevated risk of insulin resistance, with metabolic syndrome and increased CIMT values. Long-term follow-up studies should be designed to evaluate postsurgical alterations in metabolic parameters and cardiovascular risk factors in NFAI patients.

Adrenal Mass: Insight Into Pathogenesis and a Common Link With Insulin Resistance

Adrenal mass (AM) is a common incidental finding detected during radiological investigations with an estimated incidence of 4%. Subjects with AM do not show any physical signs of adrenal hormonal excess, although they are often insulin resistant. Interestingly, apparently nonfunctioning AMs are often associated with a high prevalence of insulin resistance (IR) and metabolic syndrome. However, it is unclear whether AM develops from a primary IR and compensatory hyperinsulinemia or whether IR is only secondary to the slight cortisol hypersecretion by AM. Further, the degree of IR has been directly reported to correlate to the size of AM, thus allowing one to hypothesize that compensatory hyperinsulinemia to IR could be mitogenic on the adrenal cortex acting through the activation of insulin and insulinlike growth factor 1 receptors. Thus, the aim of the present article is to review the current evidence on the link between AM and compensatory hyperinsulinemia to IR.

Hyperinsulinemia caused by dexamethasone treatment is associated with reduced insulin clearance and lower hepatic activity of insulin-degrading enzyme

OBJECTIVES

Glucocorticoid treatment induces insulin resistance (IR), which is counteracted by a compensatory hyperinsulinemia, due to increased pancreatic β-cell function. There is evidence for also reduced hepatic insulin clearance, but whether this correlates with altered activity of insulin-degrading enzyme (IDE) in the liver, is not fully understood. Here, we investigated whether hyperinsulinemia, in glucocorticoid-treated rodents, is associated with any alteration in the insulin clearance and activity of the IDE in the liver.

MATERIALS/METHODS

Adult male Swiss mice and Wistar rats were treated with the synthetic glucocorticoid dexamethasone intraperitoneally [1mg/kg body weight (b.w.)] for 5 consecutive days.

RESULTS

Glucocorticoid treatment induced IR and hyperinsulinemia in both species, but was more impactful in rats that also displayed glucose intolerance and hyperglycemia. Insulin clearance was reduced in glucocorticoid-treated rats and mice, as judged by the reduction of insulin decay rate and increased insulin area-under-the-curve (47% and 87%, respectively). These results were associated with reduced activity (35%) of hepatic IDE in rats and a tendency to reduction (p=0.068) in mice, without alteration in hepatic IDE mRNA content, in both species.

CONCLUSION

In conclusion, the reduced insulin clearance in glucocorticoid-treated rodents was due to the reduction of hepatic IDE activity, at least in rats, which may contributes to the compensatory hyperinsulinemia. These findings corroborate the idea that short-term and/or partial inhibition of IDE activity in the liver could be beneficial for the glycemic control.

Insulin-Mediated Diseases: Adrenal Mass and Polycystic Ovary Syndrome

Adrenal incidentalomas (AIs) and polycystic ovary syndrome (PCOS) have often been associated with compensatory hyperinsulinemia and insulin resistance (IR). The link between these diseases and IR may be changes in hormone secretions that provoke IR and in turn promote the growth of adrenal gland masses and/or ovarian cysts through compensatory hyperinsulinemia.

C-Peptide-based assessment of insulin secretion in the Zucker Fatty rat: a modelistic study

A C-peptide-based assessment of β-cell function was performed here in the Zucker fatty rat, a suitable animal model of human metabolic syndrome. To this aim, a 90-min intravenous glucose tolerance test (IVGTT) was performed in seven Zucker fatty rats (ZFR), 7-to-9week-old, and seven age-matched Zucker lean rats (ZLR). The minimal model of C-peptide (CPMM), originally introduced for humans, was adapted to Zucker rats and then applied to interpret IVGTT data. For a comprehensive evaluation of glucose tolerance in ZFR, CPMM was applied in combination with the minimal model of glucose kinetics (GKMM). Our results showed that the present CPMM-based interpretation of data is able to: 1) provide a suitable fit of C-Peptide data; 2) achieve a satisfactory estimation of parameters of interest 3) quantify both insulin secretion by estimating the time course of pre-hepatic secretion rate, SR(t), and total insulin secretion, TIS, and pancreatic sensitivity by means of three specific indexes of β-cell responsiveness to glucose stimulus (first-phase, Ф₁, second-phase, Ф₂, and steady-state, Ф_ss, never assessed in Zucker rats before; 4) detect the significant enhancement of insulin secretion in the ZFR, in face of a severe insulin-resistant state, previously observed only using a purely experimental approach. Thus, the methodology presented here represents a reliable tool to assess β-cell function in the Zucker rat, and opens new possibilities for the quantification of further processes involved in glucose homeostasis such as the hepatic insulin degradation.

Whole-body insulin sensitivity rather than body-mass-index determines fasting and post-glucose-load growth hormone concentrations

Background

Obese, non-acromegalic persons show lower growth hormone (GH) concentrations at fasting and reduced GH nadir during an oral glucose tolerance test (OGTT). However, this finding has never been studied with regard to whole-body insulin-sensitivity as a possible regulator.

Methods

In this retrospective analysis, non-acromegalic (NonACRO, n = 161) and acromegalic (ACRO, n = 35), non-diabetic subjects were subdivided into insulin-sensitive (IS) and –resistant (IR) groups according to the Clamp-like Index (CLIX)-threshold of 5 mg·kg⁻¹·min⁻¹ from the OGTT.

Results

Non-acromegalic IS (CLIX: 8.8±0.4 mg·kg⁻¹·min⁻¹) persons with similar age and sex distribution, but lower (p<0.001) body-mass-index (BMI = 25±0 kg/m², 84% females, 56±1 years) had 59% and 70%, respectively, higher (p<0.03) fasting GH and OGTT GH area under the curve concentrations than IR (CLIX: 3.5±0.1 mg·kg⁻¹·min⁻¹, p<0.001) subjects (BMI = 29±1 kg/m², 73% females, 58±1 years). When comparing on average overweight non-acromegalic IS and IR with similar anthropometry (IS: BMI: 27±0 kg/m², 82% females, 58±2 years; IR: BMI: 27±0 kg/m², 71% females, 60±1 years), but different CLIX (IS: 8.7±0.9 vs. IR: 3.8±0.1 mg·kg⁻¹·min⁻¹, p<0.001), the results remained almost the same. In addition, when adjusted for OGTT-mediated glucose rise, GH fall was less pronounced in IR. In contrast, in acromegalic subjects, no difference was found between IS and IR patients with regard to fasting and post-glucose-load GH concentrations.

Conclusions

Circulating GH concentrations at fasting and during the OGTT are lower in non-acromegalic insulin-resistant subjects. This study seems the first to demonstrate that insulin sensitivity rather than body-mass modulates fasting and post-glucose-load GH concentrations in non-diabetic non–acromegalic subjects.

Cardiometabolic phenotyping of patients with familial hypocalcuric hypercalcemia

CONTEXT

Heterozygous inactivating mutations of the calcium-sensing receptor (CaSR) gene cause alterations in calcium metabolism [familial hypocalciuric hypercalcemia (FHH)]. In addition, calcium-sensing receptor is expressed in the myocardium and endocrine cells including pancreatic islets, enteroendocrine cells, and adipose tissue.

OBJECTIVE

To discern whether FHH is associated with cardiometabolic alterations of clinical significance, endocrine responses to systemic calcium stimulation and oral glucose tolerance tests were performed. Ectopic lipid deposition and heart function were assessed using magnetic resonance spectroscopy/imaging.

PARTICIPANTS

Eight FHH patients and nine controls matched for anthropometric characteristics (age 45 ± 18 y; body mass index 29 ± 4 vs 29 ± 6 kg/m(2)) were studied to determine cardiac function, ectopic and visceral lipid content, and insulin sensitivity and secretion.

RESULTS

Insulin sensitivity (clamp-like index: 4.5 ± 0.6 vs 4.3 ± 0.4 mg/kg · min), basal (insulin secretion rate: 266 ± 33 vs 218 ± 25 pmol/min), and glucose-stimulated β-cell function (adaptation index: 180.2 ± 12.2 vs 176.2 ± 17.4) as well as calcium-stimulated insulin secretion were comparable between FHH and controls, respectively. Ectopic lipid content in liver [3.75% (1.4%; 34%) vs 4.18% (0.9%; 28%)], soleus muscle (1.07% ± 0.38% vs 1.02% ± 0.56 %), and myocardium (0.39% ± 0.3% vs 0.32% ± 0.1 %), visceral and sc adipose tissue distribution (0.51 ± 0.16 vs 0.47 ± 0.17) as well as heart function (ejection fraction: 71.5% ± 8% vs 72.8% ± 8 %; E to A ratio: 1.4% ± 0.6% vs 1.3% ± 0.7%) were not different between the groups.

CONCLUSION

Despite comprehensive cardiometabolic phenotyping, no alterations in myocardial function, lipid distribution, or glucose metabolism were observed in FHH. Thus, FHH might reflect a laboratory finding without any relevant cardiometabolic alterations.

Insulin-like growth factor 1 predicts post-load hypoglycemia following bariatric surgery: a prospective cohort study

Postprandial hypoglycemia is a complication following gastric bypass surgery, which frequently remains undetected. Severe hypoglycemic episodes, however, put patients at risk, e.g., for syncope. A major cause of hypoglycemia following gastric bypass is hyperinsulinemic nesidioblastosis. Since pancreatic islets in nesidioblastosis overexpress insulin-like growth factor 1 (IGF-1) receptor α and administration of recombinant IGF-1 provokes hypoglycemia, our main objective was to investigate the occurrence of post-load hypoglycemia one year after bariatric surgery and its relation to pre- and post-operative IGF-1 serum concentrations. We evaluated metabolic parameters including 2 h 75 g oral glucose tolerance test (OGTT) and measured IGF-1 serum concentration in thirty-six non-diabetic patients (29 f/7 m), aged 41.3±2.0 y with a median (IQR) BMI of 30.9 kg/m2 (27.5-34.3 kg/m2), who underwent elective bariatric surgery (predominantly gastric bypass, 83%) at our hospital. Post-load hypoglycemia as defined by a 2 h glucose concentration <60 mg/dl was detected in 50% of patients. Serum insulin and C-peptide concentration during the OGTT and HOMA-IR (homeostatic model assessment-insulin resistance) were similar in hypoglycemic and euglycemic patients. Strikingly, pre- and post-operative serum IGF-1 concentrations were significantly higher in hypoglycemic patients (p = 0.012 and p = 0.007 respectively). IGF-1 serum concentration before surgery negatively correlated with 2 h glucose concentration during the OGTT (rho = -0.58, p = 0.0003). Finally, IGF-1 serum concentrations before and after surgery significantly predicted post-load hypoglycemia with odds ratios of 1.28 (95%CI:1.03-1.55, p = 0.029) and 1.18 (95%CI:1.03-1.33, p = 0.015), respectively, for each 10 ng/ml increment. IGF-1 serum concentration could be a valuable biomarker to identify patients at risk for hypoglycemia following bariatric surgery independently of a diagnostic OGTT. Thus, IGF-1 testing could help to prevent a significant complication of gastric bypass surgery.