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.

Persistent hypercalcemia mimicking hypophosphatasia after discontinuation of a ketogenic diet: a case report

OBJECTIVES

Hypercalcemia has been reported as an uncommon complication of the ketogenic diet (KD). Here we present a toddler whose hypercalcemia persisted for 2 months after stopping the KD.

CASE PRESENTATION

A 2 year 11-month-old child with global developmental delay, infantile spasms, neuromuscular weakness with limited mobility, tracheostomy and ventilator dependence, and oropharyngeal dysphagia with G-tube dependence presented with hypercalcemia in the setting of recurrent vomiting. At presentation, the patient was adherent to a KD and taking topiramate since infancy for intractable seizures. His laboratory parameters at presentation showed hypercalcemia (11.9 mg/dL), hypercalciuria, acute renal failure, low alkaline phosphatase (76 IU/L [110-302 IU/L]), parathyroid hormone (PTH) <6 pg/mL (18-80 pg/mL), normal thyroid function, cortisol and vitamin D level. The patient's hypercalcemia persisted post-discontinuation of the KD and topiramate. PTH-related protein was mildly elevated at 15.3 pmol/L. Follow-up laboratory and imaging studies ruled out malignancy. He was managed with calcitonin 4 u/kg/dose Q12H × 1 day and 8 u/kg/dose Q8H × 1 day, hydration and low-calcium formula. Post-discontinuation of the KD, normalization of alkaline phosphatase levels preceded the normalization of calcium on day 55 and PTH on day 85.

CONCLUSIONS

Hypercalcemia may persist for an extended period after weaning from a KD; lab parameters may mimic that of hypophosphatasia as previously described in the literature. Normalization of alkaline phosphatase, a marker of bone turnover, indicates recovery from the adynamic state induced by the KD and typically precedes the normalization of calcium and PTH.

The Effect of Control IQ Hybrid Closed Loop Technology on Glycemic Control in Adolescents and Adults with Cystic Fibrosis-Related Diabetes

Background: Cystic fibrosis-related diabetes (CFRD) is associated with pulmonary decline, compromised nutritional status, and earlier mortality. Although diabetes technology is increasingly being used in individuals with CFRD, there is a paucity of data investigating the impact of hybrid closed loop (HCL) technology on glycemia in this patient population. Materials and Methods: In this multicenter retrospective study of 13 adults and adolescents with CFRD, 14 days of continuous glucose monitor data were analyzed at baseline, 1 and 3 months after transition to the Tandem t:slim X2 pump with Control IQ™ technology, a HCL system. Results: Control IQ initiation was associated with a significant increase in % time in target range (70-180 mg/dL), as well as decreases in average glucose, % time in hyperglycemic ranges (% time >180 mg/dL, % time >250 mg/dL), and glycemic variability (standard deviation, coefficient of variation). There was no significant change in % time in hypoglycemia ranges (% time <54 mg/dL, % time <70 mg/dL). Conclusions: To our knowledge, this is the first study to report a beneficial effect of Food and Drug Administration (FDA)-approved HCL technology on glycemia in adults and adolescents with CFRD to date. Future studies are needed to understand the potential long-term glycemic benefits of HCL devices and to explore the impact of this technology on heath-related quality of life, pulmonary function, nutritional status, and mortality.

Continuous Glucose Monitoring and HbA1c in Cystic Fibrosis: Clinical Correlations and Implications for CFRD Diagnosis

CONTEXT

The clinical utility and implications of continuous glucose monitoring (CGM) in cystic fibrosis (CF) are unclear.

OBJECTIVE

We examined the correlation between CGM measures and clinical outcomes in adults with CF, investigated the relationship between hemoglobin A1c (HbA1c) and CGM-derived average glucose (AG), and explored CGM measures that distinguish cystic fibrosis-related diabetes (CFRD) from normal and abnormal glucose tolerance.

METHODS

This prospective observational study included 77 adults with CF who had CGM and HbA1c measured at 2 to 3 time points 3 months apart.

RESULTS

Thirty-one of the 77 participants met American Diabetes Association-recommended diagnostic criteria for CFRD by oral glucose tolerance testing and/or HbA1c. In all participants, CGM measures of hyperglycemia and glycemic variability correlated with nutritional status and pulmonary function. HbA1c was correlated with AG (R2 = 0.71, P < 0.001), with no significant difference between this regression line and that previously established in type 1 and type 2 diabetes and healthy volunteers. Cutoffs of 17.5% time > 140 mg/dL and 3.4% time > 180 mg/dL had sensitivities of 87% and 90%, respectively, and specificities of 95%, for identifying CFRD. Area under the curve and percent of participants correctly classified with CFRD were higher for AG, SD, % time > 140, > 180, and > 250 mg/dL than for HbA1c.

CONCLUSION

CGM measures of hyperglycemia and glycemic variability are superior to HbA1c in distinguishing those with and without CFRD. CGM-derived AG is strongly correlated with HbA1c in adults with CF, with a similar relationship to other diabetes populations. Future studies are needed to investigate CGM as a diagnostic and screening tool for CFRD.

The effect of elexacaftor/tezacaftor/ivacaftor (ETI) on glycemia in adults with cystic fibrosis

BACKGROUND

Cystic fibrosis related diabetes (CFRD) is associated with pulmonary decline and compromised nutritional status. Emerging data suggest that CFTR dysfunction may play a direct role in the pathogenesis of CFRD; however, studies investigating the effect of CFTR modulators on glycemic outcomes in patients with cystic fibrosis (CF) have shown mixed results. The impact of elexacaftor-tezacaftor-ivacaftor (ETI) on glycemic control is currently unknown. Our objective was to investigate the effect of ETI initiation on glycemia in adults with CF using continuous glucose monitoring (CGM).

METHODS

In this prospective observational study, 34 adults with CF and at least one F508del CFTR mutation wore CGM sensors for 14 days prior to starting ETI and again 3-12 months after ETI initiation. Hypoglycemia symptoms were queried at each visit, and most recent anthropometric measures and spirometry data were obtained by chart review.

RESULTS

Twenty-three participants completed the study. Compared to baseline, average glucose (AG), standard deviation (SD), % time >200 mg/dL, and peak sensor glucose decreased with ETI treatment, and % time in target range 70-180 mg/dL increased. Improvements in glycemic parameters were most notable in individuals with CFRD. There was no significant change in CGM-measured or self-reported hypoglycemia before and after ETI initiation.

CONCLUSION

Initiation of ETI in adults with CF was associated with improvement CGM-derived measures of hyperglycemia and glycemic variability with no effect on hypoglycemia. Further studies are needed to investigate underlying etiology of these changes and the long-term impact of ETI on glycemic control in patients with CF.

The Relationship between Body Composition, Dietary Intake, Physical Activity, and Pulmonary Status in Adolescents and Adults with Cystic Fibrosis

Measures of body fat and lean mass may better predict important clinical outcomes in patients with cystic fibrosis (CF) than body mass index (BMI). Little is known about how diet quality and exercise may impact body composition in these patients. Dual X-ray absorptiometry (DXA) body composition, 24-h dietary recall, and physical activity were assessed in a cross-sectional analysis of 38 adolescents and adults with CF and 19 age-, race-, and gender-matched healthy volunteers. Compared with the healthy volunteers, participants with CF had a lower appendicular lean mass index (ALMI), despite no observed difference in BMI, and their diets consisted of higher glycemic index foods with a greater proportion of calories from fat and a lower proportion of calories from protein. In participants with CF, pulmonary function positively correlated with measures of lean mass, particularly ALMI, and negatively correlated with multiple measures of body fat after controlling for age, gender, and BMI. Higher physical activity levels were associated with greater ALMI and lower body fat. In conclusion, body composition measures, particularly ALMI, may better predict key clinical outcomes in individuals with CF than BMI. Future longitudinal studies analyzing the effect of dietary intake and exercise on body composition and CF-specific clinical outcomes are needed.

Acquired growth hormone deficiency in Fanconi-Bickel syndrome

Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disease, resulting from mutations in the SLC2A2 gene, causing impaired glucose transporter 2 protein transporter protein function, impaired glucose and galactose utilisation, hepatorenal glycogen accumulation and organ dysfunction. Clinical features include failure to thrive, hepatomegaly, rickets, short stature and delayed puberty. Therapy includes electrolyte supplementation and uncooked cornstarch. We present a 15-year-old boy diagnosed with FBS in infancy. Growth velocity was normal on standard treatment until age 8.5 years, at which time growth failure led to a diagnosis of acquired growth hormone (GH) deficiency. Initiation of recombinant human GH (rhGH) replacement of 0.25 μg/kg/week resulted in marked improvement in growth velocity and height. While short stature is expected in FBS, growth velocity that falls below the normal range despite adequate therapy should prompt further evaluation. Our case suggests that acquired GH deficiency can arise in FBS and benefits from rhGH therapy.

Efficacy of GLP-1 Agonist Therapy in Autosomal Dominant WFS1-Related Disorder: A Case Report

BACKGROUND

Wolfram syndrome is a rare neurodegenerative disorder, characterized by the presence of diabetes insipidus, diabetes mellitus, optic atrophy, and sensorineural deafness. The majority of cases are due to autosomal recessive biallelic variants in the WFS1 gene; however, pathogenic autosomal dominant (AD) mutations have also been described. Glucagon-like peptide (GLP-1) agonists have been studied in both animal models and humans with classic Wolfram syndrome.

CASE

We present a 15-year-old female with a personal and family history of congenital strabismus, bilateral cataracts, low-frequency sensorineural hearing loss, and diabetes mellitus. Trio whole exome sequencing revealed a previously unknown maternally inherited heterozygous variant in exon 8 of the WFS1 gene c.2605_2616del12 p.Ser869_His872del, leading to the diagnosis of AD WFS1-related disorder. Treatment with a GLP-1 agonist resulted in marked improvement in glycemic control and discontinuation of insulin therapy. This patient's response to a GLP-1 agonist provides suggestive indirect evidence for a role of WFS1 on β-cell endoplasmic reticulum stress and suggests that treatment with a GLP-1 agonist should be considered in patients with dominant forms of WS.

Monogenic Diabetes in a Child with Cystic Fibrosis: A Case Report and Review of the Literature

Cystic fibrosis-related diabetes (CFRD) is associated with worsening pulmonary function, lower body mass index, increased infection frequency, and earlier mortality. While the incidence of CFRD is rising, its development in patients under the age of 10 years is uncommon. We present a 9-year-old girl with cystic fibrosis (CF) who presented with a 5-year history of nonprogressive hyperglycemia, demonstrated by abnormal oral glucose tolerance tests, glycated hemoglobin A1c (HbA1c) levels consistently >6.5%, and negative pancreatic autoantibodies. Subsequent genetic testing revealed a pathogenic heterozygous recessive mutation in the GCK gene at c.667G>A (p.Gly223Ser), consistent with a diagnosis of GCK-MODY. Significant dysglycemia in young children with CF should raise suspicion for alternative etiologies of diabetes and warrants further investigation. The clinical impact of underlying monogenic diabetes in patients with CF is unclear, and close follow-up is warranted. This case also offers unique insight on the impact of hyperglycemia in the absence of insulin deficiency on CF-specific outcomes.

Prediction of pneumonia in a pediatric emergency department

OBJECTIVE

To study the association between historical and physical examination findings and radiographic pneumonia in children who present with suspicion for pneumonia in the emergency department, and to develop a clinical decision rule for the use of chest radiography.

METHODS

We conducted a prospective cohort study in an urban pediatric emergency department of patients younger than 21 who had a chest radiograph performed for suspicion of pneumonia (n = 2574). Pneumonia was categorized into 2 groups on the basis of an attending radiologist interpretation of the chest radiograph: radiographic pneumonia (includes definite and equivocal cases of pneumonia) and definite pneumonia. We estimated a multivariate logistic regression model with pneumonia status as the dependent variable and the historical and physical examination findings as the independent variables. We also performed a recursive partitioning analysis.

RESULTS

Sixteen percent of patients had radiographic pneumonia. History of chest pain, focal rales, duration of fever, and oximetry levels at triage were significant predictors of pneumonia. The presence of tachypnea, retractions, and grunting were not associated with pneumonia. Hypoxia (oxygen saturation ≤92%) was the strongest predictor of pneumonia (odds ratio: 3.6 [95% confidence interval (CI): 2.0-6.8]). Recursive partitioning analysis revealed that among subjects with O₂ saturation >92%, no history of fever, no focal decreased breath sounds, and no focal rales, the rate of radiographic pneumonia was 7.6% (95% CI: 5.3-10.0) and definite pneumonia was 2.9% (95% CI: 1.4-4.4).

CONCLUSION

Historical and physical examination findings can be used to risk stratify children for risk of radiographic pneumonia.

Human propionyl CoA carboxylase: some properties of the partially purified enzyme in fibroblasts from controls and patients with propionic acidemia

We report some properties of propionyl CoA carboxylase (PCC) partially purified from cultured human fibroblasts obtained from controls and several patients with propionic acidemia. A series of steps (Triton X-100 treatment, high speed centrifugation, ammonium sulfate precipitation, and density gradient centrifugation) led to 100- to 300-fold purification of control enzyme. Control PCC had a molecular weight of nearly 700,000, contained biotin, demonstrated a pH optinum at 8.0-8.5, was activated by potassium, and followed Michaelis-Menten kinetics for each of its substrates. It was distinguished from acetyl CoA carboxylase immunologically as well as by differential purification. Each of seven lines from patients with propionic acidemia had clearly detectable PCC activity which was less than 5% of that in control lines. Although yields were poor and purification less extensive than in control lines, mutant PCC was enriched 2- to 40-fold by the same procedures employed for the control enzyme. Mutant enzyme had a pH optimum, ionic requirements, and substrate Km's similar to those of control PCC, but was distinctly more labile to both cold and heat. These findings suggest that the markedly reduced activity of PCC in these patients results from a mutation in the PCC structural gene locus or loci which leads to the synthesis of altered enzyme protein molecules.

Genetic complementation of propionyl-CoA carboxylase deficiency in cultured human fibroblasts

Propionyl-CoA carboxylase (PCC) deficiency is an inherited metabolic disorder showing considerable variability of expression. We have investigated the possibility that there is a genetic basis for the clinical heterogeneity in this disorder by examining complementation in Sendai virus mediated heterokaryons of mutant fibroblast strains. Restoration of PCC activity was monitored in individual multinucleate cells in situ using a radioautographic procedure which detects the incorporation of 14C-propionate into trichloracetic acid precipitable material. Each mutant strain incorporated negligible amounts of radioactivity compared to control strains. Activity was not restored when different mutants were mixed without virus or when homokaryons were produced by self-fusion. Seven mutant strains were fused in all pairwise combinations and examined for increased 14C-propionate incorporation in heterokaryons. Two main complementation groups were revealed. One group was composed of three mutants. The other was a complex group composed of four mutants in which intragroup complementation was demonstrated. Two mutants showing excellent complementation by radioautography were examined for complementation by the direct assay of PCC ACTIVITY. The enzyme activity of virus-treated preparations with 23% multinucleate cells was 183 U (pmol/min/mg protein) compared to 16 U for the untreated mixture (normal range 450-850 u). We conclude that PCC deficiency resulted from mutations of heterogeneous origin, although the classification of mutants into complementation groups did not correlate with patterns of clinical heterogeneity.

Defective leukocyte metabolism in human cobalamin deficiency: impaired propionate oxidation and serine biosynthesis reversible by cyanocobalamin therapy

Biochemical disturbances common to vitamin B12 and folate deficiency were investigated in leukocytes from patients with cobalamin deficiency. The investigations focused on the only two human metabolic pathways known to require vitamin B12. In the propionate pathway, deoxyadenosylcobalamin is required for isomerization of methylmalonyl-CoA to succinyl-CoA. Leukocyte oxidation of 14C-propionate to 14CO2 was markedly decreased in 9 patients with Addisonian cobalamin deficiency and 2 patients with low serum cobalamin associated with folate deficiency, whereas 14C-succinate oxidation was normal. Three of the Addisonian patients had only minimal anemia. Within 4 days after one injection of 1,000 mug of cyanocobalamin, in 7 out of 8 patients studied, leukocyte propionate oxidation increased to normal levels. In folate-mediated one-carbon metabolism, as measured by serine biosynthesis from formate, methylcobalamin is required for conversion of methyl-folate to tetrahydrofolate. Leukocyte formation of 14C-serine from 14C-formate was significantly depressed in 5 patients with low serum cobalamin, little or no anemia, and only marginally low total red cell folate, the low serum cobalamin in 2 of these patients was associated with folate deficiency. After 1,000 mug of cyanocobalamin, in 2 of 3 patients, leukocyte serine biosynthesis increased to the normal range. These observations demonstrated that these two metabolic pathways in leukocytes were sensitive to cobalamin deficiency, and responsive to cobalamin therapy. Although there was no correlation between either of these metabolic activities and the serum cobalamin, red cell folate, or hematocrit, there was a striking correlation between impairment of leukocyte propionate oxidation and of leukocyte serine biosynthesis in 5 patients who were minimally anemic. The remarkably close correspondence between effects of low cobalamin on these two metabolic pathways, in nonanemic patients, must be a direct consequence of their common requirements for a cobalamin co-enzyme. These findings emphasize the importance of cobalamin in folate metabolism, and are consistent with the hypothesis that folate is "trapped" as methyl-folate in cobalamin deficiency, but do not exclude the possibility that this "trapping" is caused by a third metabolic function of cobalamin which might mediate transport of folate into cells.

Inherited propionyl-Coa carboxylase deficiency in "ketotic hyperglycinemia"

Cultured fibroblasts from a young girl with ketotic hyperglycinemia were unable to oxidize propionate-(14)C to (14)CO(2), but oxidized methylmalonate-(14)C and succinate-(14)C normally. This block in propionate catabolism was shown to result from a lack of propionyl-CoA carboxylase activity. The carboxylase deficiency was not due to the presence of an intracellular inhibitor and it was not corrected by biotin, a known cofactor for the enzyme. Both of her parents' fibroblasts had approximately 50% of normal propionyl-CoA carboxylase activity. These results demonstrate that ketotic hyperglycinemia and propionicacidemia are the same disease, caused by a mutation of the propionyl-CoA carboxylase apoenzyme, which is inherited as an autosomal recessive trait. This enzymatic localization provides an explanation for the remarkable clinical and chemical similarity between ketotic hyperglycinemia and methylmalonicaciduria and offers a potential means of antenatal detection of this disorder.