Impaired glucose tolerance and indeterminate glycemia in cystic fibrosis

Continuous glucose monitoring and advanced glycation endproducts for prediction of clinical outcomes and development of cystic fibrosis-related diabetes in adults with CF

Introductions

Cystic fibrosis-related diabetes (CFRD) is associated with pulmonary decline, compromised nutritional status, and earlier mortality. Onset is often insidious, so screening for early detection of glycemic abnormalities is important. Continuous glucose monitoring (CGM) has been validated in people with CF and has been shown to detect early glycemic variability otherwise missed on 2-hour oral glucose tolerance testing (OGTT). We previously reported that CGM measures of hyperglycemia and glycemic variability are superior to hemoglobin A1c (HbA1c) in distinguishing those with and without CFRD. However, little is known about the long-term predictive value of CGM measures of glycemia for both the development of CFRD and their effect on key clinical outcomes such as weight maintenance and pulmonary function. In addition, there have been no studies investigating advanced glycation endproducts (AGE) assessed by skin autofluorescence in people with CF.

Methods

In this prospective observational study, CGM and HbA1c were measured at 2 to 3 time points 3 months apart in 77 adults with CF. Participants who did not have CFRD at the time of enrollment underwent OGTT at the baseline visit, and all participants had AGE readings at baseline. Follow up data including anthropometric measures, pulmonary function and CFRD status were collected by review of medical records 1- and 2-years after the baseline visits. We applied multivariable linear regression models correlating glycemic measures to change in key clinical outcomes (weight, BMI, FEV1) accounting for age, gender and elexacaftor/tezacaftor/ivacaftor (ETI) use. We also conducted logistic regression analyses comparing baseline glycemic data to development of CFRD during the 2-year follow up period.

Results

Of the 77 participants, 25 had pre-existing CFRD at the time of enrollment, and six participants were diagnosed with CFRD by the OGTT performed at the baseline visit. When adjusting for age, gender, and ETI use, multiple CGM measures correlated with weight and BMI decline after one year but not after two years. CGM and HbA1c at baseline did not predict decline in FEV1 (p>0.05 for all). In the 46 participants without a diagnosis of CFRD at baseline, two participants were diagnosed with CFRD over the following two years, but CGM measures at baseline did not predict progression to CFRD. Baseline AGE values were higher in individuals with CFRD and correlated with multiple measures of dysglycemia (HbA1c, AG, SD, CV, TIR, % time >140, >180, >250) as well as weight. AGE values also correlated with FEV1 decline at year 1 and weight decline at year 1 and year 2.

Conclusions

Several key CGM measures of hyperglycemia and glycemic variability were predictive of future decline in weight and BMI over one year in this population of adults with CF with and without CFRD. None of the baseline glycemic variables predicted progression to CFRD over 2 years. To our knowledge, this is the first report correlating AGE levels with key clinical and glycemic measures in CF. Limitations of these analyses include the small number of participants who developed CFRD (n=2) during the follow up period and the initiation of ETI by many participants, affecting their trajectory in weight and pulmonary function. These results provide additional data supporting the potential role for CGM in identifying clinically significant dysglycemia in CF. Future studies are needed to investigate CGM as a diagnostic and screening tool for CFRD and to understand the implications of AGE measures in this patient population.

A retrospective study of glucose homeostasis, insulin secretion, sensitivity/resistance in non- transfusion-dependent β-thalassemia patients (NTD- β Thal): reduced β-cell secretion rather than insulin resistance seems to be the dominant defect for glucose dysregulation (GD)

AIMS

Non-transfusion - dependent β-thalassemias (NTD-βThal) can cause iron overload and serious iron-related organ complications as endocrine dysfunction, including glucose dysregulation (GD).

PATIENTS AND METHODS

We retrieved data of all NTD- β Thal patients referred consecutively to a single Outpatient Italian Clinic from October 2010 to April 2023. All patients underwent a standard 3-h oral glucose tolerance test (OGTT) for analysis of glucose homeostasis, insulin secretion and sensitivity/resistance (IR), using conventional surrogate indices derived from the OGTT. The collected data in NTD- β Thal patients were compared to 20 healthy subjects.

RESULTS

Seventeen of 26 (65.3 %) NTD- β Thal patients (aged: 7.8 -35.1 years) had normal glucose tolerance, 1/26 (3.8 %) had impaired fasting glucose (IFG), 5/26 (19.2 %) impaired glucose tolerance (IGT), 1/26 (3.8%) IFG plus IGT and 2/26 (7.6%) plasma glucose (PG) level ≥155 mg/dL 1-h after glucose load. GD was observed exclusively in young adult patients; none of them had diabetes mellitus (DM). These findings were associated with a low insulinogenic index (IGI) and oral disposition index. HOMA-IR and QUICKI were not significantly different compared to controls. Interestingly, in young adult patients, ISI-Matsuda index was statistically higher compared to the control group, suggesting an increased insulin sensitivity.

CONCLUSIONS

This study reported a high prevalence of GD in young adults with NTD- β Thal. The documented reduction of IGI rather than the presence of IR, indicates reduced insulin secretory capacity as the pathophysiological basis of dysglycemia that may represent a novel investigational path for future studies on the mechanism(s) responsible for GD in NTD- β Thal patients.

The effects of excess weight on glucose homeostasis in young adult females with β-thalassemia major (β-TM): a preliminary retrospective study

BACKGROUND

With the rising prevalence of obesity worldwide, it is becoming imperative to detect disturbed glucose metabolism as early as possible in order to prevent type 2 diabetes (T2D) development.

STUDY DESIGN

The present retrospective observational study aimed to evaluate the relationship between BMI and glucose metabolism, insulin secretion and sensitivity indices, derived from glucose tolerance test (OGTT), in β -TM female patients who were overweight (BMI 25-29.9 kg/m2) and follow its outcome over time.

SUBJECTS AND METHODS

Eleven overweight and 11 females with ideal weight and β -TM, matched for age, were recruited. OGTT was undertaken and different indices for β-cell function, insulin sensitivity and insulin secretion were calculated.

RESULTS

At first evaluation, 7 of 11 overweight β -TM patients (63.6%) and 3 of 11 normal weight β-TM patients (27.2%) had glucose dysregulation (GD) during OGTT. Overweight patients with β-TM had increased HOMA-IR and QUICKI indices associated with decreased Matsuda WBISI index. The mean ± SD duration of follow-up was 4.5 ± 1.2 years. At last observation, 2/11 overweight patients had developed T2D (18.1%). In patients with normal weight, GD increased from 3/11 (27.2%) to 5/11 (45.4%), but none developed T2DM. The difference between SF at first and last observation (1,220 ± 702 vs.1,091 ± 454 ng/mL; P: 0.61) was not significant.

CONCLUSION

Overweight seems to be an additional risk factor for the development of GD in β-TM patients. This is particularly important in clinical practice, due to the lack of appropriate guidelines dedicated to this group of patients.

The effects of excess weight on glucose homeostasis in young adult females with β-thalassemia major (β-TM): a preliminary retrospective study

BACKGROUND

With the rising prevalence of obesity worldwide, it is becoming imperative to detect disturbed glucose metabolism as early as possible in order to prevent type 2 diabetes (T2D) development.

STUDY DESIGN

The present retrospective observational study aimed to evaluate the relationship between BMI and glucose metabolism, insulin secretion and sensitivity indices, derived from glucose tolerance test (OGTT), in β -TM female patients who were overweight (BMI 25-29.9 kg/m2) and follow its outcome over time.

SUBJECTS AND METHODS

Eleven overweight and 11 females with ideal weight and β -TM, matched for age, were recruited. OGTT was undertaken and different indices for β-cell function, insulin sensitivity and insulin secretion were calculated.

RESULTS

At first evaluation, 7 of 11 overweight β -TM patients (63.6%) and 3 of 11 normal weight β-TM patients (27.2%) had glucose dysregulation (GD) during OGTT. Overweight patients with β-TM had increased HOMA-IR and QUICKI indices associated with decreased Matsuda WBISI index. The mean ± SD duration of follow-up was 4.5 ± 1.2 years. At last observation, 2/11 overweight patients had developed T2D (18.1%). In patients with normal weight, GD increased from 3/11 (27.2%) to 5/11 (45.4%), but none developed T2DM. The difference between SF at first and last observation (1,220 ± 702 vs.1,091 ± 454 ng/mL; P: 0.61) was not significant.

CONCLUSION

Overweight seems to be an additional risk factor for the development of GD in β-TM patients. This is particularly important in clinical practice, due to the lack of appropriate guidelines dedicated to this group of patients.

Assessment of glucose homeostasis in young adult female β-thalassemia major patients (β-TM) with acquired hypogonadotropic hypogonadism (AHH) never treated with sex steroids compared to eugonadal β-TM patients with spontaneous menstrual cycles

BACKGROUND

Acquired ypogonadotropic hypogonadism (AHH) is the most prevalent endocrine complication in thalassemia major (TM).

STUDY DESIGN

Considering the detrimental effect of estrogen deficiency on glucose metabolism, the ICET-A Network promoted a retrospective study on the long-term effects of estrogen deficiency on glucose homeostasis in female β-TM patients with HH without hormonal replacement therapy (HRT).

PATIENTS AND METHODS

Seventeen β-TM patients with AHH (4 had arrested puberty; Tanners' breast stage 2-3), never treated with sex steroids, and 11 eugonadal β-TM patients with spontaneous menstrual cycles at the time of referral were studied. A standard 3-h OGTT was performed in the morning, after an overnight fast. Six-point plasma glucose and insulin level determinations, indices of insulin secretion and sensitivity, early-phase insulin insulinogenic index (IGI), HOMA-IR and β-cell function (HOMA-β), oral disposition index (oDI), glucose and insulin areas under the OGTT curves were evaluated.

RESULTS

Abnormal glucose tolerance (AGT) or diabetes was observed in 15 (88.2%) of 17 patients with AHH and 6 (54.5%) of 11 patients with eumenorrhea. The difference between the two groups was statistically significant (P: 0.048). However, the group of eugonadal patients was younger compared to AHH patients (26.5 ± 4.8 years vs. 32.6 ± 6.2 years ; P: 0.010). Advanced age,  severity of iron overload, splenectomy, increased ALT levels and reduced IGF-1 levels were the main clinical and laboratory risk factors for glucose dysregulation observed in β-TM with AHH compared to eugonadal β-TM patients with spontaneous menstrual cycles.

CONCLUSION

These data further support the indication for an annual assessment of OGTT in patients with β-TM. We believe that a registry of subjects with hypogonadism is necessary for a better understanding of the long-term consequences of this condition and  refining treatment options.

A provider survey of cystic fibrosis related diabetes screening and management practices at North American CF centers

Background

Cystic Fibrosis Foundation (CFF) Guidelines recommend annual screening for cystic fibrosis related diabetes (CFRD) with an oral glucose tolerance test (OGTT). However, screening rates remain consistently low. We conducted surveys of 1) US CF center directors and 2) Endocrinologists affiliated with the CFF-sponsored EnVision program to characterize CFRD screening practices, describe provider perceived barriers to screening, and identify strategies for improving screening.

Methods

The surveys queried OGTT protocols, alternate screening strategies, and perceived barriers to screening. CF center characteristics and procedures for coordinating OGTTs were compared between centers achieving ≥50% versus <50% OGTT completion. Endocrinologists received additional questions regarding OGTT interpretation and management.

Results

The survey response rate was 18% (51/290) from CF Centers and 63% (25/40) from Endocrinologists. The majority (57%) of CF centers utilized 2 OGTT timepoints (0,120 min). The majority (72%) of Endocrinologists utilized 3 timepoints (0,60,120 min). Four percent of CF centers and 8% of Endocrinologists utilized other timepoints. Forty-nine percent of CF centers reported ≥50% OGTT completion in the past year. Completion of ≥50% OGTT was 5 times more likely when patient reminders were consistently provided (p = 0.017). Both CF Centers and Endocrinologists employed alternative screening strategies including HbA1c (64%, 92%), fasting plasma glucose (49%, 67%), continuous glucose monitoring (30%, 58%), and home fingerstick monitoring (55%, 50%).

Discussion

OGTT is the gold standard screening method for CFRD, but completion rates remain suboptimal, practice variation exists, and many providers utilize alternate screening strategies. Systematic reminders may improve completion rates. Studies to improve our approach to CFRD screening are urgently needed.

Glucose Homeostasis and Assessment of β-Cell Function by 3-hour Oral Glucose Tolerance (OGTT) in Patients with β-Thalassemia Major with Serum Ferritin below 1,000 ng/dL: Results from a Single ICET-A Centre

Aims

The primary aim of this study was to evaluate retrospectively the glucose homeostasis and surrogate indices of insulin sensitivity and resistance, during a 3-hour oral glucose tolerance test (OGTT), in β-thalassemia major patients (β-TM) with serum ferritin (SF) below 1,000 ng/mL.

Patients and methods

The retrospective cohort study evaluated the medical records of 24 β-TM patients from 2010 to 2022. At the year of study the mean age of patients was 31.0 ± 4.1 (20-37.11) years; 13 (54.1%) were females. The most commonly used iron chelator was deferoxamine (DFO: 75%), followed by deferiprone (DFP:12.5%) and deferasirox (DFX: 12.5%). Insulin sensitivity and resistance indices were derived from OGTT. A liver iron concentration (LIC) < 3 mg/g d.w. and a global heart T2* value > 20 ms were considered as conservative cut-off values for insignificant iron overload (IOL).

Results

The mean SF levels in the whole study cohort population at the age of evaluation was 549.6 ± 232.3 ng/mL. Based on the SF levels, two groups were identified: Group A (N = 14) < 500 ng/mL and Group B (N=10) 500-1,000 ng/mL. Normal glucose tolerance (NGT) during OGTT was observed in 4 patients of Group A (28.5 %) and in 5 patients of Group B (50%) (P: 0.29). The remaining 15/24 patients (62.5%) had glucose dysregulation (GD). The mean age at starting iron chelation therapy (ICT) and the mean SF peak in Group A versus Group B were significantly higher in group A. The GD was associated with significantly attenuated IGI (first phase of insulin response) and impaired oral disposition index (oDI). Hypogonadotropic hypogonadism (HH) was the most common associated endocrine complication in both groups of patients.

Conclusions

This study showed that efficient iron chelation monotherapy in patients with β-TM and SF < 1,000 ng/ml did not entirely prevent glucose metabolism disorders, abnormalities of insulin secretion and sensitivity, and development of acquired hypogonadism.

Cystic fibrosis related diabetes (CFRD) in the era of modulators: A scoping review

Cystic fibrosis-related diabetes (CFRD) is a common complication of CF that increases in incidence as patients age. Poor glycemic control has been shown to negatively impact lung function and weight, resulting in higher risk of recurrent pulmonary exacerbations. With the advent of highly effective modulator therapies (HEMT), patients with CF are living longer and healthier lives. Consequently, CFRD and its microvascular complications are rising in prominence, becoming one of the most urgent clinical concerns. As HEMT were developed with the primary focus of improving pulmonary outcomes, it is not clear from the original phase III studies what the short- or long-term benefits of modulators might be on CFRD development and trajectory. In this review, we will examine the pathophysiology of CFRD, summarize and synthesize the available evidence of HEMT impact on CFRD and describe the emerging research needs in this field.